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/-
Copyright (c) 2020 Johan Commelin. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johan Commelin, Jujian Zhang, Yongle Hu
-/
import Mathlib.Algebra.Colimit.TensorProduct
import Mathlib.Algebra.DirectSum.Finsupp
import Mathlib.Algebra.DirectSum.Module
import Mathlib.Algebra.Exact
import Mathlib.Algebra.Module.CharacterModule
import Mathlib.Algebra.Module.Injective
import Mathlib.Algebra.Module.Projective
import Mathlib.LinearAlgebra.DirectSum.TensorProduct
import Mathlib.LinearAlgebra.FreeModule.Basic
import Mathlib.LinearAlgebra.TensorProduct.RightExactness
import Mathlib.RingTheory.Finiteness.Small
import Mathlib.RingTheory.TensorProduct.Finite
/-!
# Flat modules
A module `M` over a commutative semiring `R` is *mono-flat* if for all monomorphisms of modules
(i.e., injective linear maps) `N →ₗ[R] P`, the canonical map `N ⊗ M → P ⊗ M` is injective
(cf. [Katsov2004], [KatsovNam2011]).
To show a module is mono-flat, it suffices to check inclusions of finitely generated
submodules `N` into finitely generated modules `P`, and `P` can be further assumed to lie in
the same universe as `R`.
`M` is flat if `· ⊗ M` preserves finite limits (equivalently, pullbacks, or equalizers).
If `R` is a ring, an `R`-module `M` is flat if and only if it is mono-flat, and to show
a module is flat, it suffices to check inclusions of finitely generated ideals into `R`.
See <https://stacks.math.columbia.edu/tag/00HD>.
Currently, `Module.Flat` is defined to be equivalent to mono-flatness over a semiring.
It is left as a TODO item to introduce the genuine flatness over semirings and rename
the current `Module.Flat` to `Module.MonoFlat`.
## Main declaration
* `Module.Flat`: the predicate asserting that an `R`-module `M` is flat.
## Main theorems
* `Module.Flat.of_retract`: retracts of flat modules are flat
* `Module.Flat.of_linearEquiv`: modules linearly equivalent to a flat modules are flat
* `Module.Flat.directSum`: arbitrary direct sums of flat modules are flat
* `Module.Flat.of_free`: free modules are flat
* `Module.Flat.of_projective`: projective modules are flat
* `Module.Flat.preserves_injective_linearMap`: If `M` is a flat module then tensoring with `M`
preserves injectivity of linear maps. This lemma is fully universally polymorphic in all
arguments, i.e. `R`, `M` and linear maps `N → N'` can all have different universe levels.
* `Module.Flat.iff_rTensor_preserves_injective_linearMap`: a module is flat iff tensoring modules
in the higher universe preserves injectivity .
* `Module.Flat.lTensor_exact`: If `M` is a flat module then tensoring with `M` is an exact
functor. This lemma is fully universally polymorphic in all arguments, i.e.
`R`, `M` and linear maps `N → N' → N''` can all have different universe levels.
* `Module.Flat.iff_lTensor_exact`: a module is flat iff tensoring modules
in the higher universe is an exact functor.
## TODO
* Generalize flatness to noncommutative semirings.
-/
universe v' u v w
open TensorProduct
namespace Module
open Function (Surjective)
open LinearMap Submodule DirectSum
section Semiring
/-! ### Flatness over a semiring -/
variable {R : Type u} {M : Type v} {N P Q : Type*} [CommSemiring R] [AddCommMonoid M] [Module R M]
[AddCommMonoid N] [Module R N] [AddCommMonoid P] [Module R P] [AddCommMonoid Q] [Module R Q]
theorem _root_.LinearMap.rTensor_injective_of_fg {f : N →ₗ[R] P}
(h : ∀ (N' : Submodule R N) (P' : Submodule R P),
N'.FG → P'.FG → ∀ h : N' ≤ P'.comap f, Function.Injective ((f.restrict h).rTensor M)) :
Function.Injective (f.rTensor M) := fun x y eq ↦ by
have ⟨N', Nfg, sub⟩ := Submodule.exists_fg_le_subset_range_rTensor_subtype {x, y} (by simp)
obtain ⟨x, rfl⟩ := sub (.inl rfl)
obtain ⟨y, rfl⟩ := sub (.inr rfl)
simp_rw [← rTensor_comp_apply, show f ∘ₗ N'.subtype = (N'.map f).subtype ∘ₗ f.submoduleMap N'
from rfl, rTensor_comp_apply] at eq
have ⟨P', Pfg, le, eq⟩ := (Nfg.map _).exists_rTensor_fg_inclusion_eq eq
simp_rw [← rTensor_comp_apply] at eq
rw [h _ _ Nfg Pfg (map_le_iff_le_comap.mp le) eq]
lemma _root_.LinearMap.rTensor_injective_iff_subtype {f : N →ₗ[R] P} (hf : Function.Injective f)
(e : P ≃ₗ[R] Q) : Function.Injective (f.rTensor M) ↔
| Function.Injective ((range <| e.toLinearMap ∘ₗ f).subtype.rTensor M) := by
simp_rw [← EquivLike.injective_comp <| (LinearEquiv.ofInjective (e.toLinearMap ∘ₗ f)
(e.injective.comp hf)).rTensor M, ← EquivLike.comp_injective _ (e.rTensor M),
← LinearEquiv.coe_coe, ← coe_comp, LinearEquiv.coe_rTensor, ← rTensor_comp]
rfl
variable (R M) in
/-- An `R`-module `M` is flat if for every finitely generated submodule `N` of every
finitely generated `R`-module `P` in the same universe as `R`,
| Mathlib/RingTheory/Flat/Basic.lean | 98 | 106 |
/-
Copyright (c) 2022 Yury Kudryashov. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yury Kudryashov
-/
import Mathlib.Data.Set.Image
import Mathlib.Order.Interval.Set.Basic
import Mathlib.Order.WithBot
/-!
# Intervals in `WithTop α` and `WithBot α`
In this file we prove various lemmas about `Set.image`s and `Set.preimage`s of intervals under
`some : α → WithTop α` and `some : α → WithBot α`.
-/
open Set
variable {α : Type*}
/-! ### `WithTop` -/
namespace WithTop
@[simp]
theorem preimage_coe_top : (some : α → WithTop α) ⁻¹' {⊤} = (∅ : Set α) :=
eq_empty_of_subset_empty fun _ => coe_ne_top
variable [Preorder α] {a b : α}
theorem range_coe : range (some : α → WithTop α) = Iio ⊤ := by
ext x
rw [mem_Iio, WithTop.lt_top_iff_ne_top, mem_range, ne_top_iff_exists]
@[simp]
theorem preimage_coe_Ioi : (some : α → WithTop α) ⁻¹' Ioi a = Ioi a :=
ext fun _ => coe_lt_coe
@[simp]
theorem preimage_coe_Ici : (some : α → WithTop α) ⁻¹' Ici a = Ici a :=
ext fun _ => coe_le_coe
@[simp]
theorem preimage_coe_Iio : (some : α → WithTop α) ⁻¹' Iio a = Iio a :=
ext fun _ => coe_lt_coe
@[simp]
theorem preimage_coe_Iic : (some : α → WithTop α) ⁻¹' Iic a = Iic a :=
ext fun _ => coe_le_coe
@[simp]
theorem preimage_coe_Icc : (some : α → WithTop α) ⁻¹' Icc a b = Icc a b := by simp [← Ici_inter_Iic]
@[simp]
theorem preimage_coe_Ico : (some : α → WithTop α) ⁻¹' Ico a b = Ico a b := by simp [← Ici_inter_Iio]
@[simp]
theorem preimage_coe_Ioc : (some : α → WithTop α) ⁻¹' Ioc a b = Ioc a b := by simp [← Ioi_inter_Iic]
@[simp]
theorem preimage_coe_Ioo : (some : α → WithTop α) ⁻¹' Ioo a b = Ioo a b := by simp [← Ioi_inter_Iio]
@[simp]
theorem preimage_coe_Iio_top : (some : α → WithTop α) ⁻¹' Iio ⊤ = univ := by
rw [← range_coe, preimage_range]
@[simp]
theorem preimage_coe_Ico_top : (some : α → WithTop α) ⁻¹' Ico a ⊤ = Ici a := by
simp [← Ici_inter_Iio]
@[simp]
theorem preimage_coe_Ioo_top : (some : α → WithTop α) ⁻¹' Ioo a ⊤ = Ioi a := by
simp [← Ioi_inter_Iio]
theorem image_coe_Ioi : (some : α → WithTop α) '' Ioi a = Ioo (a : WithTop α) ⊤ := by
rw [← preimage_coe_Ioi, image_preimage_eq_inter_range, range_coe, Ioi_inter_Iio]
theorem image_coe_Ici : (some : α → WithTop α) '' Ici a = Ico (a : WithTop α) ⊤ := by
rw [← preimage_coe_Ici, image_preimage_eq_inter_range, range_coe, Ici_inter_Iio]
theorem image_coe_Iio : (some : α → WithTop α) '' Iio a = Iio (a : WithTop α) := by
rw [← preimage_coe_Iio, image_preimage_eq_inter_range, range_coe,
inter_eq_self_of_subset_left (Iio_subset_Iio le_top)]
theorem image_coe_Iic : (some : α → WithTop α) '' Iic a = Iic (a : WithTop α) := by
rw [← preimage_coe_Iic, image_preimage_eq_inter_range, range_coe,
inter_eq_self_of_subset_left (Iic_subset_Iio.2 <| coe_lt_top a)]
theorem image_coe_Icc : (some : α → WithTop α) '' Icc a b = Icc (a : WithTop α) b := by
rw [← preimage_coe_Icc, image_preimage_eq_inter_range, range_coe,
inter_eq_self_of_subset_left
(Subset.trans Icc_subset_Iic_self <| Iic_subset_Iio.2 <| coe_lt_top b)]
theorem image_coe_Ico : (some : α → WithTop α) '' Ico a b = Ico (a : WithTop α) b := by
rw [← preimage_coe_Ico, image_preimage_eq_inter_range, range_coe,
inter_eq_self_of_subset_left (Subset.trans Ico_subset_Iio_self <| Iio_subset_Iio le_top)]
theorem image_coe_Ioc : (some : α → WithTop α) '' Ioc a b = Ioc (a : WithTop α) b := by
rw [← preimage_coe_Ioc, image_preimage_eq_inter_range, range_coe,
inter_eq_self_of_subset_left
(Subset.trans Ioc_subset_Iic_self <| Iic_subset_Iio.2 <| coe_lt_top b)]
theorem image_coe_Ioo : (some : α → WithTop α) '' Ioo a b = Ioo (a : WithTop α) b := by
rw [← preimage_coe_Ioo, image_preimage_eq_inter_range, range_coe,
inter_eq_self_of_subset_left (Subset.trans Ioo_subset_Iio_self <| Iio_subset_Iio le_top)]
end WithTop
/-! ### `WithBot` -/
namespace WithBot
@[simp]
theorem preimage_coe_bot : (some : α → WithBot α) ⁻¹' {⊥} = (∅ : Set α) :=
@WithTop.preimage_coe_top αᵒᵈ
variable [Preorder α] {a b : α}
theorem range_coe : range (some : α → WithBot α) = Ioi ⊥ :=
@WithTop.range_coe αᵒᵈ _
@[simp]
theorem preimage_coe_Ioi : (some : α → WithBot α) ⁻¹' Ioi a = Ioi a :=
ext fun _ => coe_lt_coe
@[simp]
theorem preimage_coe_Ici : (some : α → WithBot α) ⁻¹' Ici a = Ici a :=
ext fun _ => coe_le_coe
@[simp]
theorem preimage_coe_Iio : (some : α → WithBot α) ⁻¹' Iio a = Iio a :=
ext fun _ => coe_lt_coe
@[simp]
theorem preimage_coe_Iic : (some : α → WithBot α) ⁻¹' Iic a = Iic a :=
ext fun _ => coe_le_coe
@[simp]
theorem preimage_coe_Icc : (some : α → WithBot α) ⁻¹' Icc a b = Icc a b := by simp [← Ici_inter_Iic]
@[simp]
theorem preimage_coe_Ico : (some : α → WithBot α) ⁻¹' Ico a b = Ico a b := by simp [← Ici_inter_Iio]
@[simp]
theorem preimage_coe_Ioc : (some : α → WithBot α) ⁻¹' Ioc a b = Ioc a b := by simp [← Ioi_inter_Iic]
@[simp]
theorem preimage_coe_Ioo : (some : α → WithBot α) ⁻¹' Ioo a b = Ioo a b := by simp [← Ioi_inter_Iio]
@[simp]
theorem preimage_coe_Ioi_bot : (some : α → WithBot α) ⁻¹' Ioi ⊥ = univ := by
rw [← range_coe, preimage_range]
@[simp]
theorem preimage_coe_Ioc_bot : (some : α → WithBot α) ⁻¹' Ioc ⊥ a = Iic a := by
simp [← Ioi_inter_Iic]
@[simp]
theorem preimage_coe_Ioo_bot : (some : α → WithBot α) ⁻¹' Ioo ⊥ a = Iio a := by
simp [← Ioi_inter_Iio]
theorem image_coe_Iio : (some : α → WithBot α) '' Iio a = Ioo (⊥ : WithBot α) a := by
rw [← preimage_coe_Iio, image_preimage_eq_inter_range, range_coe, inter_comm, Ioi_inter_Iio]
theorem image_coe_Iic : (some : α → WithBot α) '' Iic a = Ioc (⊥ : WithBot α) a := by
rw [← preimage_coe_Iic, image_preimage_eq_inter_range, range_coe, inter_comm, Ioi_inter_Iic]
theorem image_coe_Ioi : (some : α → WithBot α) '' Ioi a = Ioi (a : WithBot α) := by
rw [← preimage_coe_Ioi, image_preimage_eq_inter_range, range_coe,
inter_eq_self_of_subset_left (Ioi_subset_Ioi bot_le)]
theorem image_coe_Ici : (some : α → WithBot α) '' Ici a = Ici (a : WithBot α) := by
rw [← preimage_coe_Ici, image_preimage_eq_inter_range, range_coe,
inter_eq_self_of_subset_left (Ici_subset_Ioi.2 <| bot_lt_coe a)]
theorem image_coe_Icc : (some : α → WithBot α) '' Icc a b = Icc (a : WithBot α) b := by
rw [← preimage_coe_Icc, image_preimage_eq_inter_range, range_coe,
inter_eq_self_of_subset_left
(Subset.trans Icc_subset_Ici_self <| Ici_subset_Ioi.2 <| bot_lt_coe a)]
theorem image_coe_Ioc : (some : α → WithBot α) '' Ioc a b = Ioc (a : WithBot α) b := by
rw [← preimage_coe_Ioc, image_preimage_eq_inter_range, range_coe,
inter_eq_self_of_subset_left (Subset.trans Ioc_subset_Ioi_self <| Ioi_subset_Ioi bot_le)]
theorem image_coe_Ico : (some : α → WithBot α) '' Ico a b = Ico (a : WithBot α) b := by
rw [← preimage_coe_Ico, image_preimage_eq_inter_range, range_coe,
inter_eq_self_of_subset_left
(Subset.trans Ico_subset_Ici_self <| Ici_subset_Ioi.2 <| bot_lt_coe a)]
theorem image_coe_Ioo : (some : α → WithBot α) '' Ioo a b = Ioo (a : WithBot α) b := by
rw [← preimage_coe_Ioo, image_preimage_eq_inter_range, range_coe,
inter_eq_self_of_subset_left (Subset.trans Ioo_subset_Ioi_self <| Ioi_subset_Ioi bot_le)]
end WithBot
| Mathlib/Order/Interval/Set/WithBotTop.lean | 221 | 223 | |
/-
Copyright (c) 2018 Ellen Arlt. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Ellen Arlt, Blair Shi, Sean Leather, Mario Carneiro, Johan Commelin
-/
import Mathlib.Data.Matrix.Basic
import Mathlib.Data.Matrix.Composition
import Mathlib.Data.Matrix.ConjTranspose
/-!
# Block Matrices
## Main definitions
* `Matrix.fromBlocks`: build a block matrix out of 4 blocks
* `Matrix.toBlocks₁₁`, `Matrix.toBlocks₁₂`, `Matrix.toBlocks₂₁`, `Matrix.toBlocks₂₂`:
extract each of the four blocks from `Matrix.fromBlocks`.
* `Matrix.blockDiagonal`: block diagonal of equally sized blocks. On square blocks, this is a
ring homomorphisms, `Matrix.blockDiagonalRingHom`.
* `Matrix.blockDiag`: extract the blocks from the diagonal of a block diagonal matrix.
* `Matrix.blockDiagonal'`: block diagonal of unequally sized blocks. On square blocks, this is a
ring homomorphisms, `Matrix.blockDiagonal'RingHom`.
* `Matrix.blockDiag'`: extract the blocks from the diagonal of a block diagonal matrix.
-/
variable {l m n o p q : Type*} {m' n' p' : o → Type*}
variable {R : Type*} {S : Type*} {α : Type*} {β : Type*}
open Matrix
namespace Matrix
theorem dotProduct_block [Fintype m] [Fintype n] [Mul α] [AddCommMonoid α] (v w : m ⊕ n → α) :
v ⬝ᵥ w = v ∘ Sum.inl ⬝ᵥ w ∘ Sum.inl + v ∘ Sum.inr ⬝ᵥ w ∘ Sum.inr :=
Fintype.sum_sum_type _
section BlockMatrices
/-- We can form a single large matrix by flattening smaller 'block' matrices of compatible
dimensions. -/
@[pp_nodot]
def fromBlocks (A : Matrix n l α) (B : Matrix n m α) (C : Matrix o l α) (D : Matrix o m α) :
Matrix (n ⊕ o) (l ⊕ m) α :=
of <| Sum.elim (fun i => Sum.elim (A i) (B i)) (fun j => Sum.elim (C j) (D j))
@[simp]
theorem fromBlocks_apply₁₁ (A : Matrix n l α) (B : Matrix n m α) (C : Matrix o l α)
(D : Matrix o m α) (i : n) (j : l) : fromBlocks A B C D (Sum.inl i) (Sum.inl j) = A i j :=
rfl
@[simp]
theorem fromBlocks_apply₁₂ (A : Matrix n l α) (B : Matrix n m α) (C : Matrix o l α)
(D : Matrix o m α) (i : n) (j : m) : fromBlocks A B C D (Sum.inl i) (Sum.inr j) = B i j :=
rfl
@[simp]
theorem fromBlocks_apply₂₁ (A : Matrix n l α) (B : Matrix n m α) (C : Matrix o l α)
(D : Matrix o m α) (i : o) (j : l) : fromBlocks A B C D (Sum.inr i) (Sum.inl j) = C i j :=
rfl
@[simp]
theorem fromBlocks_apply₂₂ (A : Matrix n l α) (B : Matrix n m α) (C : Matrix o l α)
(D : Matrix o m α) (i : o) (j : m) : fromBlocks A B C D (Sum.inr i) (Sum.inr j) = D i j :=
rfl
/-- Given a matrix whose row and column indexes are sum types, we can extract the corresponding
"top left" submatrix. -/
def toBlocks₁₁ (M : Matrix (n ⊕ o) (l ⊕ m) α) : Matrix n l α :=
of fun i j => M (Sum.inl i) (Sum.inl j)
/-- Given a matrix whose row and column indexes are sum types, we can extract the corresponding
"top right" submatrix. -/
def toBlocks₁₂ (M : Matrix (n ⊕ o) (l ⊕ m) α) : Matrix n m α :=
of fun i j => M (Sum.inl i) (Sum.inr j)
/-- Given a matrix whose row and column indexes are sum types, we can extract the corresponding
"bottom left" submatrix. -/
def toBlocks₂₁ (M : Matrix (n ⊕ o) (l ⊕ m) α) : Matrix o l α :=
of fun i j => M (Sum.inr i) (Sum.inl j)
/-- Given a matrix whose row and column indexes are sum types, we can extract the corresponding
"bottom right" submatrix. -/
def toBlocks₂₂ (M : Matrix (n ⊕ o) (l ⊕ m) α) : Matrix o m α :=
of fun i j => M (Sum.inr i) (Sum.inr j)
theorem fromBlocks_toBlocks (M : Matrix (n ⊕ o) (l ⊕ m) α) :
fromBlocks M.toBlocks₁₁ M.toBlocks₁₂ M.toBlocks₂₁ M.toBlocks₂₂ = M := by
ext i j
rcases i with ⟨⟩ <;> rcases j with ⟨⟩ <;> rfl
@[simp]
theorem toBlocks_fromBlocks₁₁ (A : Matrix n l α) (B : Matrix n m α) (C : Matrix o l α)
(D : Matrix o m α) : (fromBlocks A B C D).toBlocks₁₁ = A :=
rfl
@[simp]
theorem toBlocks_fromBlocks₁₂ (A : Matrix n l α) (B : Matrix n m α) (C : Matrix o l α)
(D : Matrix o m α) : (fromBlocks A B C D).toBlocks₁₂ = B :=
rfl
@[simp]
theorem toBlocks_fromBlocks₂₁ (A : Matrix n l α) (B : Matrix n m α) (C : Matrix o l α)
(D : Matrix o m α) : (fromBlocks A B C D).toBlocks₂₁ = C :=
rfl
@[simp]
theorem toBlocks_fromBlocks₂₂ (A : Matrix n l α) (B : Matrix n m α) (C : Matrix o l α)
(D : Matrix o m α) : (fromBlocks A B C D).toBlocks₂₂ = D :=
rfl
/-- Two block matrices are equal if their blocks are equal. -/
theorem ext_iff_blocks {A B : Matrix (n ⊕ o) (l ⊕ m) α} :
A = B ↔
A.toBlocks₁₁ = B.toBlocks₁₁ ∧
A.toBlocks₁₂ = B.toBlocks₁₂ ∧ A.toBlocks₂₁ = B.toBlocks₂₁ ∧ A.toBlocks₂₂ = B.toBlocks₂₂ :=
⟨fun h => h ▸ ⟨rfl, rfl, rfl, rfl⟩, fun ⟨h₁₁, h₁₂, h₂₁, h₂₂⟩ => by
rw [← fromBlocks_toBlocks A, ← fromBlocks_toBlocks B, h₁₁, h₁₂, h₂₁, h₂₂]⟩
@[simp]
theorem fromBlocks_inj {A : Matrix n l α} {B : Matrix n m α} {C : Matrix o l α} {D : Matrix o m α}
{A' : Matrix n l α} {B' : Matrix n m α} {C' : Matrix o l α} {D' : Matrix o m α} :
fromBlocks A B C D = fromBlocks A' B' C' D' ↔ A = A' ∧ B = B' ∧ C = C' ∧ D = D' :=
ext_iff_blocks
theorem fromBlocks_map (A : Matrix n l α) (B : Matrix n m α) (C : Matrix o l α) (D : Matrix o m α)
(f : α → β) : (fromBlocks A B C D).map f =
fromBlocks (A.map f) (B.map f) (C.map f) (D.map f) := by
ext i j; rcases i with ⟨⟩ <;> rcases j with ⟨⟩ <;> simp [fromBlocks]
theorem fromBlocks_transpose (A : Matrix n l α) (B : Matrix n m α) (C : Matrix o l α)
(D : Matrix o m α) : (fromBlocks A B C D)ᵀ = fromBlocks Aᵀ Cᵀ Bᵀ Dᵀ := by
ext i j
rcases i with ⟨⟩ <;> rcases j with ⟨⟩ <;> simp [fromBlocks]
theorem fromBlocks_conjTranspose [Star α] (A : Matrix n l α) (B : Matrix n m α) (C : Matrix o l α)
(D : Matrix o m α) : (fromBlocks A B C D)ᴴ = fromBlocks Aᴴ Cᴴ Bᴴ Dᴴ := by
simp only [conjTranspose, fromBlocks_transpose, fromBlocks_map]
@[simp]
theorem fromBlocks_submatrix_sum_swap_left (A : Matrix n l α) (B : Matrix n m α) (C : Matrix o l α)
(D : Matrix o m α) (f : p → l ⊕ m) :
(fromBlocks A B C D).submatrix Sum.swap f = (fromBlocks C D A B).submatrix id f := by
ext i j
cases i <;> dsimp <;> cases f j <;> rfl
@[simp]
theorem fromBlocks_submatrix_sum_swap_right (A : Matrix n l α) (B : Matrix n m α) (C : Matrix o l α)
(D : Matrix o m α) (f : p → n ⊕ o) :
(fromBlocks A B C D).submatrix f Sum.swap = (fromBlocks B A D C).submatrix f id := by
ext i j
cases j <;> dsimp <;> cases f i <;> rfl
theorem fromBlocks_submatrix_sum_swap_sum_swap {l m n o α : Type*} (A : Matrix n l α)
(B : Matrix n m α) (C : Matrix o l α) (D : Matrix o m α) :
(fromBlocks A B C D).submatrix Sum.swap Sum.swap = fromBlocks D C B A := by simp
/-- A 2x2 block matrix is block diagonal if the blocks outside of the diagonal vanish -/
def IsTwoBlockDiagonal [Zero α] (A : Matrix (n ⊕ o) (l ⊕ m) α) : Prop :=
toBlocks₁₂ A = 0 ∧ toBlocks₂₁ A = 0
/-- Let `p` pick out certain rows and `q` pick out certain columns of a matrix `M`. Then
`toBlock M p q` is the corresponding block matrix. -/
def toBlock (M : Matrix m n α) (p : m → Prop) (q : n → Prop) : Matrix { a // p a } { a // q a } α :=
M.submatrix (↑) (↑)
@[simp]
theorem toBlock_apply (M : Matrix m n α) (p : m → Prop) (q : n → Prop) (i : { a // p a })
(j : { a // q a }) : toBlock M p q i j = M ↑i ↑j :=
rfl
/-- Let `p` pick out certain rows and columns of a square matrix `M`. Then
`toSquareBlockProp M p` is the corresponding block matrix. -/
def toSquareBlockProp (M : Matrix m m α) (p : m → Prop) : Matrix { a // p a } { a // p a } α :=
toBlock M _ _
theorem toSquareBlockProp_def (M : Matrix m m α) (p : m → Prop) :
toSquareBlockProp M p = of (fun i j : { a // p a } => M ↑i ↑j) :=
rfl
/-- Let `b` map rows and columns of a square matrix `M` to blocks. Then
`toSquareBlock M b k` is the block `k` matrix. -/
def toSquareBlock (M : Matrix m m α) (b : m → β) (k : β) :
Matrix { a // b a = k } { a // b a = k } α :=
toSquareBlockProp M _
theorem toSquareBlock_def (M : Matrix m m α) (b : m → β) (k : β) :
toSquareBlock M b k = of (fun i j : { a // b a = k } => M ↑i ↑j) :=
rfl
theorem fromBlocks_smul [SMul R α] (x : R) (A : Matrix n l α) (B : Matrix n m α) (C : Matrix o l α)
(D : Matrix o m α) : x • fromBlocks A B C D = fromBlocks (x • A) (x • B) (x • C) (x • D) := by
ext i j; rcases i with ⟨⟩ <;> rcases j with ⟨⟩ <;> simp [fromBlocks]
theorem fromBlocks_neg [Neg R] (A : Matrix n l R) (B : Matrix n m R) (C : Matrix o l R)
(D : Matrix o m R) : -fromBlocks A B C D = fromBlocks (-A) (-B) (-C) (-D) := by
ext i j
cases i <;> cases j <;> simp [fromBlocks]
@[simp]
theorem fromBlocks_zero [Zero α] : fromBlocks (0 : Matrix n l α) 0 0 (0 : Matrix o m α) = 0 := by
ext i j
rcases i with ⟨⟩ <;> rcases j with ⟨⟩ <;> rfl
theorem fromBlocks_add [Add α] (A : Matrix n l α) (B : Matrix n m α) (C : Matrix o l α)
(D : Matrix o m α) (A' : Matrix n l α) (B' : Matrix n m α) (C' : Matrix o l α)
(D' : Matrix o m α) : fromBlocks A B C D + fromBlocks A' B' C' D' =
fromBlocks (A + A') (B + B') (C + C') (D + D') := by
ext i j; rcases i with ⟨⟩ <;> rcases j with ⟨⟩ <;> rfl
theorem fromBlocks_multiply [Fintype l] [Fintype m] [NonUnitalNonAssocSemiring α] (A : Matrix n l α)
(B : Matrix n m α) (C : Matrix o l α) (D : Matrix o m α) (A' : Matrix l p α) (B' : Matrix l q α)
(C' : Matrix m p α) (D' : Matrix m q α) :
fromBlocks A B C D * fromBlocks A' B' C' D' =
fromBlocks (A * A' + B * C') (A * B' + B * D') (C * A' + D * C') (C * B' + D * D') := by
ext i j
rcases i with ⟨⟩ <;> rcases j with ⟨⟩ <;> simp only [fromBlocks, mul_apply, of_apply,
Sum.elim_inr, Fintype.sum_sum_type, Sum.elim_inl, add_apply]
theorem fromBlocks_mulVec [Fintype l] [Fintype m] [NonUnitalNonAssocSemiring α] (A : Matrix n l α)
(B : Matrix n m α) (C : Matrix o l α) (D : Matrix o m α) (x : l ⊕ m → α) :
(fromBlocks A B C D) *ᵥ x =
Sum.elim (A *ᵥ (x ∘ Sum.inl) + B *ᵥ (x ∘ Sum.inr))
(C *ᵥ (x ∘ Sum.inl) + D *ᵥ (x ∘ Sum.inr)) := by
ext i
cases i <;> simp [mulVec, dotProduct]
theorem vecMul_fromBlocks [Fintype n] [Fintype o] [NonUnitalNonAssocSemiring α] (A : Matrix n l α)
(B : Matrix n m α) (C : Matrix o l α) (D : Matrix o m α) (x : n ⊕ o → α) :
x ᵥ* fromBlocks A B C D =
Sum.elim ((x ∘ Sum.inl) ᵥ* A + (x ∘ Sum.inr) ᵥ* C)
((x ∘ Sum.inl) ᵥ* B + (x ∘ Sum.inr) ᵥ* D) := by
ext i
cases i <;> simp [vecMul, dotProduct]
variable [DecidableEq l] [DecidableEq m]
section Zero
variable [Zero α]
theorem toBlock_diagonal_self (d : m → α) (p : m → Prop) :
Matrix.toBlock (diagonal d) p p = diagonal fun i : Subtype p => d ↑i := by
ext i j
by_cases h : i = j
· simp [h]
· simp [One.one, h, Subtype.val_injective.ne h]
theorem toBlock_diagonal_disjoint (d : m → α) {p q : m → Prop} (hpq : Disjoint p q) :
Matrix.toBlock (diagonal d) p q = 0 := by
ext ⟨i, hi⟩ ⟨j, hj⟩
have : i ≠ j := fun heq => hpq.le_bot i ⟨hi, heq.symm ▸ hj⟩
simp [diagonal_apply_ne d this]
@[simp]
theorem fromBlocks_diagonal (d₁ : l → α) (d₂ : m → α) :
fromBlocks (diagonal d₁) 0 0 (diagonal d₂) = diagonal (Sum.elim d₁ d₂) := by
ext i j
rcases i with ⟨⟩ <;> rcases j with ⟨⟩ <;> simp [diagonal]
@[simp]
lemma toBlocks₁₁_diagonal (v : l ⊕ m → α) :
toBlocks₁₁ (diagonal v) = diagonal (fun i => v (Sum.inl i)) := by
unfold toBlocks₁₁
funext i j
simp only [ne_eq, Sum.inl.injEq, of_apply, diagonal_apply]
@[simp]
lemma toBlocks₂₂_diagonal (v : l ⊕ m → α) :
toBlocks₂₂ (diagonal v) = diagonal (fun i => v (Sum.inr i)) := by
unfold toBlocks₂₂
funext i j
simp only [ne_eq, Sum.inr.injEq, of_apply, diagonal_apply]
@[simp]
lemma toBlocks₁₂_diagonal (v : l ⊕ m → α) : toBlocks₁₂ (diagonal v) = 0 := rfl
@[simp]
lemma toBlocks₂₁_diagonal (v : l ⊕ m → α) : toBlocks₂₁ (diagonal v) = 0 := rfl
end Zero
section HasZeroHasOne
variable [Zero α] [One α]
@[simp]
theorem fromBlocks_one : fromBlocks (1 : Matrix l l α) 0 0 (1 : Matrix m m α) = 1 := by
ext i j
rcases i with ⟨⟩ <;> rcases j with ⟨⟩ <;> simp [one_apply]
@[simp]
theorem toBlock_one_self (p : m → Prop) : Matrix.toBlock (1 : Matrix m m α) p p = 1 :=
toBlock_diagonal_self _ p
theorem toBlock_one_disjoint {p q : m → Prop} (hpq : Disjoint p q) :
Matrix.toBlock (1 : Matrix m m α) p q = 0 :=
toBlock_diagonal_disjoint _ hpq
end HasZeroHasOne
end BlockMatrices
section BlockDiagonal
variable [DecidableEq o]
section Zero
variable [Zero α] [Zero β]
/-- `Matrix.blockDiagonal M` turns a homogeneously-indexed collection of matrices
`M : o → Matrix m n α'` into an `m × o`-by-`n × o` block matrix which has the entries of `M` along
the diagonal and zero elsewhere.
See also `Matrix.blockDiagonal'` if the matrices may not have the same size everywhere.
-/
def blockDiagonal (M : o → Matrix m n α) : Matrix (m × o) (n × o) α :=
of <| (fun ⟨i, k⟩ ⟨j, k'⟩ => if k = k' then M k i j else 0 : m × o → n × o → α)
-- TODO: set as an equation lemma for `blockDiagonal`, see https://github.com/leanprover-community/mathlib4/pull/3024
theorem blockDiagonal_apply' (M : o → Matrix m n α) (i k j k') :
blockDiagonal M ⟨i, k⟩ ⟨j, k'⟩ = if k = k' then M k i j else 0 :=
rfl
theorem blockDiagonal_apply (M : o → Matrix m n α) (ik jk) :
blockDiagonal M ik jk = if ik.2 = jk.2 then M ik.2 ik.1 jk.1 else 0 := by
cases ik
cases jk
rfl
@[simp]
theorem blockDiagonal_apply_eq (M : o → Matrix m n α) (i j k) :
blockDiagonal M (i, k) (j, k) = M k i j :=
if_pos rfl
theorem blockDiagonal_apply_ne (M : o → Matrix m n α) (i j) {k k'} (h : k ≠ k') :
blockDiagonal M (i, k) (j, k') = 0 :=
if_neg h
theorem blockDiagonal_map (M : o → Matrix m n α) (f : α → β) (hf : f 0 = 0) :
(blockDiagonal M).map f = blockDiagonal fun k => (M k).map f := by
ext
simp only [map_apply, blockDiagonal_apply, eq_comm]
rw [apply_ite f, hf]
@[simp]
theorem blockDiagonal_transpose (M : o → Matrix m n α) :
(blockDiagonal M)ᵀ = blockDiagonal fun k => (M k)ᵀ := by
ext
simp only [transpose_apply, blockDiagonal_apply, eq_comm]
split_ifs with h
· rw [h]
· rfl
@[simp]
theorem blockDiagonal_conjTranspose {α : Type*} [AddMonoid α] [StarAddMonoid α]
(M : o → Matrix m n α) : (blockDiagonal M)ᴴ = blockDiagonal fun k => (M k)ᴴ := by
simp only [conjTranspose, blockDiagonal_transpose]
rw [blockDiagonal_map _ star (star_zero α)]
@[simp]
theorem blockDiagonal_zero : blockDiagonal (0 : o → Matrix m n α) = 0 := by
ext
simp [blockDiagonal_apply]
@[simp]
theorem blockDiagonal_diagonal [DecidableEq m] (d : o → m → α) :
(blockDiagonal fun k => diagonal (d k)) = diagonal fun ik => d ik.2 ik.1 := by
ext ⟨i, k⟩ ⟨j, k'⟩
simp only [blockDiagonal_apply, diagonal_apply, Prod.mk_inj, ← ite_and]
congr 1
rw [and_comm]
@[simp]
theorem blockDiagonal_one [DecidableEq m] [One α] : blockDiagonal (1 : o → Matrix m m α) = 1 :=
show (blockDiagonal fun _ : o => diagonal fun _ : m => (1 : α)) = diagonal fun _ => 1 by
rw [blockDiagonal_diagonal]
end Zero
@[simp]
theorem blockDiagonal_add [AddZeroClass α] (M N : o → Matrix m n α) :
blockDiagonal (M + N) = blockDiagonal M + blockDiagonal N := by
ext
simp only [blockDiagonal_apply, Pi.add_apply, add_apply]
split_ifs <;> simp
section
variable (o m n α)
/-- `Matrix.blockDiagonal` as an `AddMonoidHom`. -/
@[simps]
def blockDiagonalAddMonoidHom [AddZeroClass α] :
(o → Matrix m n α) →+ Matrix (m × o) (n × o) α where
toFun := blockDiagonal
map_zero' := blockDiagonal_zero
map_add' := blockDiagonal_add
end
@[simp]
theorem blockDiagonal_neg [AddGroup α] (M : o → Matrix m n α) :
blockDiagonal (-M) = -blockDiagonal M :=
map_neg (blockDiagonalAddMonoidHom m n o α) M
@[simp]
theorem blockDiagonal_sub [AddGroup α] (M N : o → Matrix m n α) :
blockDiagonal (M - N) = blockDiagonal M - blockDiagonal N :=
map_sub (blockDiagonalAddMonoidHom m n o α) M N
@[simp]
theorem blockDiagonal_mul [Fintype n] [Fintype o] [NonUnitalNonAssocSemiring α]
(M : o → Matrix m n α) (N : o → Matrix n p α) :
(blockDiagonal fun k => M k * N k) = blockDiagonal M * blockDiagonal N := by
ext ⟨i, k⟩ ⟨j, k'⟩
simp only [blockDiagonal_apply, mul_apply, ← Finset.univ_product_univ, Finset.sum_product]
split_ifs with h <;> simp [h]
section
variable (α m o)
/-- `Matrix.blockDiagonal` as a `RingHom`. -/
@[simps]
def blockDiagonalRingHom [DecidableEq m] [Fintype o] [Fintype m] [NonAssocSemiring α] :
(o → Matrix m m α) →+* Matrix (m × o) (m × o) α :=
{ blockDiagonalAddMonoidHom m m o α with
toFun := blockDiagonal
map_one' := blockDiagonal_one
map_mul' := blockDiagonal_mul }
end
@[simp]
theorem blockDiagonal_pow [DecidableEq m] [Fintype o] [Fintype m] [Semiring α]
(M : o → Matrix m m α) (n : ℕ) : blockDiagonal (M ^ n) = blockDiagonal M ^ n :=
map_pow (blockDiagonalRingHom m o α) M n
@[simp]
theorem blockDiagonal_smul {R : Type*} [Zero α] [SMulZeroClass R α] (x : R)
(M : o → Matrix m n α) : blockDiagonal (x • M) = x • blockDiagonal M := by
ext
simp only [blockDiagonal_apply, Pi.smul_apply, smul_apply]
split_ifs <;> simp
end BlockDiagonal
section BlockDiag
/-- Extract a block from the diagonal of a block diagonal matrix.
This is the block form of `Matrix.diag`, and the left-inverse of `Matrix.blockDiagonal`. -/
def blockDiag (M : Matrix (m × o) (n × o) α) (k : o) : Matrix m n α :=
of fun i j => M (i, k) (j, k)
-- TODO: set as an equation lemma for `blockDiag`, see https://github.com/leanprover-community/mathlib4/pull/3024
theorem blockDiag_apply (M : Matrix (m × o) (n × o) α) (k : o) (i j) :
blockDiag M k i j = M (i, k) (j, k) :=
rfl
theorem blockDiag_map (M : Matrix (m × o) (n × o) α) (f : α → β) :
blockDiag (M.map f) = fun k => (blockDiag M k).map f :=
rfl
@[simp]
theorem blockDiag_transpose (M : Matrix (m × o) (n × o) α) (k : o) :
blockDiag Mᵀ k = (blockDiag M k)ᵀ :=
ext fun _ _ => rfl
@[simp]
theorem blockDiag_conjTranspose {α : Type*} [Star α]
(M : Matrix (m × o) (n × o) α) (k : o) : blockDiag Mᴴ k = (blockDiag M k)ᴴ :=
ext fun _ _ => rfl
section Zero
variable [Zero α] [Zero β]
@[simp]
theorem blockDiag_zero : blockDiag (0 : Matrix (m × o) (n × o) α) = 0 :=
rfl
@[simp]
theorem blockDiag_diagonal [DecidableEq o] [DecidableEq m] (d : m × o → α) (k : o) :
blockDiag (diagonal d) k = diagonal fun i => d (i, k) :=
ext fun i j => by
obtain rfl | hij := Decidable.eq_or_ne i j
· rw [blockDiag_apply, diagonal_apply_eq, diagonal_apply_eq]
· rw [blockDiag_apply, diagonal_apply_ne _ hij, diagonal_apply_ne _ (mt _ hij)]
exact Prod.fst_eq_iff.mpr
@[simp]
theorem blockDiag_blockDiagonal [DecidableEq o] (M : o → Matrix m n α) :
blockDiag (blockDiagonal M) = M :=
funext fun _ => ext fun i j => blockDiagonal_apply_eq M i j _
theorem blockDiagonal_injective [DecidableEq o] :
Function.Injective (blockDiagonal : (o → Matrix m n α) → Matrix _ _ α) :=
Function.LeftInverse.injective blockDiag_blockDiagonal
@[simp]
theorem blockDiagonal_inj [DecidableEq o] {M N : o → Matrix m n α} :
blockDiagonal M = blockDiagonal N ↔ M = N :=
blockDiagonal_injective.eq_iff
@[simp]
theorem blockDiag_one [DecidableEq o] [DecidableEq m] [One α] :
blockDiag (1 : Matrix (m × o) (m × o) α) = 1 :=
funext <| blockDiag_diagonal _
end Zero
@[simp]
theorem blockDiag_add [Add α] (M N : Matrix (m × o) (n × o) α) :
blockDiag (M + N) = blockDiag M + blockDiag N :=
rfl
section
variable (o m n α)
/-- `Matrix.blockDiag` as an `AddMonoidHom`. -/
@[simps]
def blockDiagAddMonoidHom [AddZeroClass α] : Matrix (m × o) (n × o) α →+ o → Matrix m n α where
toFun := blockDiag
map_zero' := blockDiag_zero
map_add' := blockDiag_add
end
@[simp]
theorem blockDiag_neg [AddGroup α] (M : Matrix (m × o) (n × o) α) : blockDiag (-M) = -blockDiag M :=
map_neg (blockDiagAddMonoidHom m n o α) M
@[simp]
theorem blockDiag_sub [AddGroup α] (M N : Matrix (m × o) (n × o) α) :
blockDiag (M - N) = blockDiag M - blockDiag N :=
map_sub (blockDiagAddMonoidHom m n o α) M N
@[simp]
theorem blockDiag_smul {R : Type*} [SMul R α] (x : R)
(M : Matrix (m × o) (n × o) α) : blockDiag (x • M) = x • blockDiag M :=
rfl
end BlockDiag
section BlockDiagonal'
variable [DecidableEq o]
section Zero
variable [Zero α] [Zero β]
/-- `Matrix.blockDiagonal' M` turns `M : Π i, Matrix (m i) (n i) α` into a
`Σ i, m i`-by-`Σ i, n i` block matrix which has the entries of `M` along the diagonal
and zero elsewhere.
This is the dependently-typed version of `Matrix.blockDiagonal`. -/
def blockDiagonal' (M : ∀ i, Matrix (m' i) (n' i) α) : Matrix (Σ i, m' i) (Σ i, n' i) α :=
of <|
(fun ⟨k, i⟩ ⟨k', j⟩ => if h : k = k' then M k i (cast (congr_arg n' h.symm) j) else 0 :
(Σ i, m' i) → (Σ i, n' i) → α)
-- TODO: set as an equation lemma for `blockDiagonal'`, see https://github.com/leanprover-community/mathlib4/pull/3024
theorem blockDiagonal'_apply' (M : ∀ i, Matrix (m' i) (n' i) α) (k i k' j) :
blockDiagonal' M ⟨k, i⟩ ⟨k', j⟩ =
if h : k = k' then M k i (cast (congr_arg n' h.symm) j) else 0 :=
rfl
theorem blockDiagonal'_eq_blockDiagonal (M : o → Matrix m n α) {k k'} (i j) :
blockDiagonal M (i, k) (j, k') = blockDiagonal' M ⟨k, i⟩ ⟨k', j⟩ :=
rfl
theorem blockDiagonal'_submatrix_eq_blockDiagonal (M : o → Matrix m n α) :
(blockDiagonal' M).submatrix (Prod.toSigma ∘ Prod.swap) (Prod.toSigma ∘ Prod.swap) =
blockDiagonal M :=
Matrix.ext fun ⟨_, _⟩ ⟨_, _⟩ => rfl
theorem blockDiagonal'_apply (M : ∀ i, Matrix (m' i) (n' i) α) (ik jk) :
blockDiagonal' M ik jk =
if h : ik.1 = jk.1 then M ik.1 ik.2 (cast (congr_arg n' h.symm) jk.2) else 0 := by
cases ik
cases jk
rfl
@[simp]
theorem blockDiagonal'_apply_eq (M : ∀ i, Matrix (m' i) (n' i) α) (k i j) :
blockDiagonal' M ⟨k, i⟩ ⟨k, j⟩ = M k i j :=
dif_pos rfl
theorem blockDiagonal'_apply_ne (M : ∀ i, Matrix (m' i) (n' i) α) {k k'} (i j) (h : k ≠ k') :
blockDiagonal' M ⟨k, i⟩ ⟨k', j⟩ = 0 :=
dif_neg h
theorem blockDiagonal'_map (M : ∀ i, Matrix (m' i) (n' i) α) (f : α → β) (hf : f 0 = 0) :
(blockDiagonal' M).map f = blockDiagonal' fun k => (M k).map f := by
ext
simp only [map_apply, blockDiagonal'_apply, eq_comm]
rw [apply_dite f, hf]
@[simp]
theorem blockDiagonal'_transpose (M : ∀ i, Matrix (m' i) (n' i) α) :
(blockDiagonal' M)ᵀ = blockDiagonal' fun k => (M k)ᵀ := by
ext ⟨ii, ix⟩ ⟨ji, jx⟩
simp only [transpose_apply, blockDiagonal'_apply]
split_ifs <;> cc
@[simp]
theorem blockDiagonal'_conjTranspose {α} [AddMonoid α] [StarAddMonoid α]
(M : ∀ i, Matrix (m' i) (n' i) α) : (blockDiagonal' M)ᴴ = blockDiagonal' fun k => (M k)ᴴ := by
simp only [conjTranspose, blockDiagonal'_transpose]
exact blockDiagonal'_map _ star (star_zero α)
@[simp]
theorem blockDiagonal'_zero : blockDiagonal' (0 : ∀ i, Matrix (m' i) (n' i) α) = 0 := by
ext
simp [blockDiagonal'_apply]
@[simp]
theorem blockDiagonal'_diagonal [∀ i, DecidableEq (m' i)] (d : ∀ i, m' i → α) :
(blockDiagonal' fun k => diagonal (d k)) = diagonal fun ik => d ik.1 ik.2 := by
ext ⟨i, k⟩ ⟨j, k'⟩
simp only [blockDiagonal'_apply, diagonal]
obtain rfl | hij := Decidable.eq_or_ne i j
· simp
· simp [hij]
@[simp]
theorem blockDiagonal'_one [∀ i, DecidableEq (m' i)] [One α] :
blockDiagonal' (1 : ∀ i, Matrix (m' i) (m' i) α) = 1 :=
show (blockDiagonal' fun i : o => diagonal fun _ : m' i => (1 : α)) = diagonal fun _ => 1 by
rw [blockDiagonal'_diagonal]
end Zero
@[simp]
theorem blockDiagonal'_add [AddZeroClass α] (M N : ∀ i, Matrix (m' i) (n' i) α) :
blockDiagonal' (M + N) = blockDiagonal' M + blockDiagonal' N := by
ext
simp only [blockDiagonal'_apply, Pi.add_apply, add_apply]
split_ifs <;> simp
section
variable (m' n' α)
/-- `Matrix.blockDiagonal'` as an `AddMonoidHom`. -/
@[simps]
def blockDiagonal'AddMonoidHom [AddZeroClass α] :
(∀ i, Matrix (m' i) (n' i) α) →+ Matrix (Σ i, m' i) (Σ i, n' i) α where
toFun := blockDiagonal'
map_zero' := blockDiagonal'_zero
map_add' := blockDiagonal'_add
end
@[simp]
theorem blockDiagonal'_neg [AddGroup α] (M : ∀ i, Matrix (m' i) (n' i) α) :
blockDiagonal' (-M) = -blockDiagonal' M :=
map_neg (blockDiagonal'AddMonoidHom m' n' α) M
@[simp]
theorem blockDiagonal'_sub [AddGroup α] (M N : ∀ i, Matrix (m' i) (n' i) α) :
blockDiagonal' (M - N) = blockDiagonal' M - blockDiagonal' N :=
map_sub (blockDiagonal'AddMonoidHom m' n' α) M N
@[simp]
theorem blockDiagonal'_mul [NonUnitalNonAssocSemiring α] [∀ i, Fintype (n' i)] [Fintype o]
(M : ∀ i, Matrix (m' i) (n' i) α) (N : ∀ i, Matrix (n' i) (p' i) α) :
(blockDiagonal' fun k => M k * N k) = blockDiagonal' M * blockDiagonal' N := by
ext ⟨k, i⟩ ⟨k', j⟩
simp only [blockDiagonal'_apply, mul_apply, ← Finset.univ_sigma_univ, Finset.sum_sigma]
rw [Fintype.sum_eq_single k]
· simp only [if_pos, dif_pos]
split_ifs <;> simp
· intro j' hj'
exact Finset.sum_eq_zero fun _ _ => by rw [dif_neg hj'.symm, zero_mul]
section
variable (α m')
/-- `Matrix.blockDiagonal'` as a `RingHom`. -/
@[simps]
def blockDiagonal'RingHom [∀ i, DecidableEq (m' i)] [Fintype o] [∀ i, Fintype (m' i)]
[NonAssocSemiring α] : (∀ i, Matrix (m' i) (m' i) α) →+* Matrix (Σ i, m' i) (Σ i, m' i) α :=
{ blockDiagonal'AddMonoidHom m' m' α with
toFun := blockDiagonal'
map_one' := blockDiagonal'_one
map_mul' := blockDiagonal'_mul }
end
@[simp]
theorem blockDiagonal'_pow [∀ i, DecidableEq (m' i)] [Fintype o] [∀ i, Fintype (m' i)] [Semiring α]
(M : ∀ i, Matrix (m' i) (m' i) α) (n : ℕ) : blockDiagonal' (M ^ n) = blockDiagonal' M ^ n :=
map_pow (blockDiagonal'RingHom m' α) M n
@[simp]
theorem blockDiagonal'_smul {R : Type*} [Zero α] [SMulZeroClass R α] (x : R)
(M : ∀ i, Matrix (m' i) (n' i) α) : blockDiagonal' (x • M) = x • blockDiagonal' M := by
ext
simp only [blockDiagonal'_apply, Pi.smul_apply, smul_apply]
split_ifs <;> simp
end BlockDiagonal'
section BlockDiag'
/-- Extract a block from the diagonal of a block diagonal matrix.
This is the block form of `Matrix.diag`, and the left-inverse of `Matrix.blockDiagonal'`. -/
def blockDiag' (M : Matrix (Σ i, m' i) (Σ i, n' i) α) (k : o) : Matrix (m' k) (n' k) α :=
of fun i j => M ⟨k, i⟩ ⟨k, j⟩
-- TODO: set as an equation lemma for `blockDiag'`, see https://github.com/leanprover-community/mathlib4/pull/3024
theorem blockDiag'_apply (M : Matrix (Σ i, m' i) (Σ i, n' i) α) (k : o) (i j) :
blockDiag' M k i j = M ⟨k, i⟩ ⟨k, j⟩ :=
rfl
theorem blockDiag'_map (M : Matrix (Σ i, m' i) (Σ i, n' i) α) (f : α → β) :
blockDiag' (M.map f) = fun k => (blockDiag' M k).map f :=
rfl
@[simp]
theorem blockDiag'_transpose (M : Matrix (Σ i, m' i) (Σ i, n' i) α) (k : o) :
blockDiag' Mᵀ k = (blockDiag' M k)ᵀ :=
ext fun _ _ => rfl
@[simp]
theorem blockDiag'_conjTranspose {α : Type*} [Star α]
(M : Matrix (Σ i, m' i) (Σ i, n' i) α) (k : o) : blockDiag' Mᴴ k = (blockDiag' M k)ᴴ :=
ext fun _ _ => rfl
section Zero
variable [Zero α] [Zero β]
@[simp]
theorem blockDiag'_zero : blockDiag' (0 : Matrix (Σ i, m' i) (Σ i, n' i) α) = 0 :=
rfl
@[simp]
theorem blockDiag'_diagonal
[DecidableEq o] [∀ i, DecidableEq (m' i)] (d : (Σ i, m' i) → α) (k : o) :
blockDiag' (diagonal d) k = diagonal fun i => d ⟨k, i⟩ :=
ext fun i j => by
obtain rfl | hij := Decidable.eq_or_ne i j
· rw [blockDiag'_apply, diagonal_apply_eq, diagonal_apply_eq]
· rw [blockDiag'_apply, diagonal_apply_ne _ hij, diagonal_apply_ne _ (mt (fun h => ?_) hij)]
cases h
rfl
@[simp]
theorem blockDiag'_blockDiagonal' [DecidableEq o] (M : ∀ i, Matrix (m' i) (n' i) α) :
blockDiag' (blockDiagonal' M) = M :=
funext fun _ => ext fun _ _ => blockDiagonal'_apply_eq M _ _ _
theorem blockDiagonal'_injective [DecidableEq o] :
Function.Injective (blockDiagonal' : (∀ i, Matrix (m' i) (n' i) α) → Matrix _ _ α) :=
Function.LeftInverse.injective blockDiag'_blockDiagonal'
@[simp]
theorem blockDiagonal'_inj [DecidableEq o] {M N : ∀ i, Matrix (m' i) (n' i) α} :
blockDiagonal' M = blockDiagonal' N ↔ M = N :=
blockDiagonal'_injective.eq_iff
@[simp]
theorem blockDiag'_one [DecidableEq o] [∀ i, DecidableEq (m' i)] [One α] :
blockDiag' (1 : Matrix (Σ i, m' i) (Σ i, m' i) α) = 1 :=
funext <| blockDiag'_diagonal _
end Zero
@[simp]
theorem blockDiag'_add [Add α] (M N : Matrix (Σ i, m' i) (Σ i, n' i) α) :
blockDiag' (M + N) = blockDiag' M + blockDiag' N :=
rfl
section
variable (m' n' α)
/-- `Matrix.blockDiag'` as an `AddMonoidHom`. -/
@[simps]
def blockDiag'AddMonoidHom [AddZeroClass α] :
Matrix (Σ i, m' i) (Σ i, n' i) α →+ ∀ i, Matrix (m' i) (n' i) α where
toFun := blockDiag'
map_zero' := blockDiag'_zero
map_add' := blockDiag'_add
end
@[simp]
theorem blockDiag'_neg [AddGroup α] (M : Matrix (Σ i, m' i) (Σ i, n' i) α) :
blockDiag' (-M) = -blockDiag' M :=
map_neg (blockDiag'AddMonoidHom m' n' α) M
@[simp]
theorem blockDiag'_sub [AddGroup α] (M N : Matrix (Σ i, m' i) (Σ i, n' i) α) :
| blockDiag' (M - N) = blockDiag' M - blockDiag' N :=
map_sub (blockDiag'AddMonoidHom m' n' α) M N
@[simp]
theorem blockDiag'_smul {R : Type*} [SMul R α] (x : R)
| Mathlib/Data/Matrix/Block.lean | 803 | 807 |
/-
Copyright (c) 2018 Mario Carneiro. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Mario Carneiro, Johannes Hölzl
-/
import Mathlib.MeasureTheory.Integral.Lebesgue.Basic
import Mathlib.MeasureTheory.Integral.Lebesgue.Countable
import Mathlib.MeasureTheory.Integral.Lebesgue.MeasurePreserving
import Mathlib.MeasureTheory.Integral.Lebesgue.Norm
deprecated_module (since := "2025-04-13")
| Mathlib/MeasureTheory/Integral/Lebesgue.lean | 969 | 982 | |
/-
Copyright (c) 2019 Zhouhang Zhou. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Zhouhang Zhou, Sébastien Gouëzel, Frédéric Dupuis
-/
import Mathlib.Algebra.BigOperators.Field
import Mathlib.Analysis.Complex.Basic
import Mathlib.Analysis.InnerProductSpace.Defs
import Mathlib.GroupTheory.MonoidLocalization.Basic
/-!
# Properties of inner product spaces
This file proves many basic properties of inner product spaces (real or complex).
## Main results
- `inner_mul_inner_self_le`: the Cauchy-Schwartz inequality (one of many variants).
- `norm_inner_eq_norm_iff`: the equality criteion in the Cauchy-Schwartz inequality (also in many
variants).
- `inner_eq_sum_norm_sq_div_four`: the polarization identity.
## Tags
inner product space, Hilbert space, norm
-/
noncomputable section
open RCLike Real Filter Topology ComplexConjugate Finsupp
open LinearMap (BilinForm)
variable {𝕜 E F : Type*} [RCLike 𝕜]
section BasicProperties_Seminormed
open scoped InnerProductSpace
variable [SeminormedAddCommGroup E] [InnerProductSpace 𝕜 E]
variable [SeminormedAddCommGroup F] [InnerProductSpace ℝ F]
local notation "⟪" x ", " y "⟫" => @inner 𝕜 _ _ x y
local postfix:90 "†" => starRingEnd _
export InnerProductSpace (norm_sq_eq_re_inner)
@[simp]
theorem inner_conj_symm (x y : E) : ⟪y, x⟫† = ⟪x, y⟫ :=
InnerProductSpace.conj_inner_symm _ _
theorem real_inner_comm (x y : F) : ⟪y, x⟫_ℝ = ⟪x, y⟫_ℝ :=
@inner_conj_symm ℝ _ _ _ _ x y
theorem inner_eq_zero_symm {x y : E} : ⟪x, y⟫ = 0 ↔ ⟪y, x⟫ = 0 := by
rw [← inner_conj_symm]
exact star_eq_zero
@[simp]
theorem inner_self_im (x : E) : im ⟪x, x⟫ = 0 := by rw [← @ofReal_inj 𝕜, im_eq_conj_sub]; simp
theorem inner_add_left (x y z : E) : ⟪x + y, z⟫ = ⟪x, z⟫ + ⟪y, z⟫ :=
InnerProductSpace.add_left _ _ _
theorem inner_add_right (x y z : E) : ⟪x, y + z⟫ = ⟪x, y⟫ + ⟪x, z⟫ := by
rw [← inner_conj_symm, inner_add_left, RingHom.map_add]
simp only [inner_conj_symm]
theorem inner_re_symm (x y : E) : re ⟪x, y⟫ = re ⟪y, x⟫ := by rw [← inner_conj_symm, conj_re]
theorem inner_im_symm (x y : E) : im ⟪x, y⟫ = -im ⟪y, x⟫ := by rw [← inner_conj_symm, conj_im]
section Algebra
variable {𝕝 : Type*} [CommSemiring 𝕝] [StarRing 𝕝] [Algebra 𝕝 𝕜] [Module 𝕝 E]
[IsScalarTower 𝕝 𝕜 E] [StarModule 𝕝 𝕜]
/-- See `inner_smul_left` for the common special when `𝕜 = 𝕝`. -/
lemma inner_smul_left_eq_star_smul (x y : E) (r : 𝕝) : ⟪r • x, y⟫ = r† • ⟪x, y⟫ := by
rw [← algebraMap_smul 𝕜 r, InnerProductSpace.smul_left, starRingEnd_apply, starRingEnd_apply,
← algebraMap_star_comm, ← smul_eq_mul, algebraMap_smul]
/-- Special case of `inner_smul_left_eq_star_smul` when the acting ring has a trivial star
(eg `ℕ`, `ℤ`, `ℚ≥0`, `ℚ`, `ℝ`). -/
lemma inner_smul_left_eq_smul [TrivialStar 𝕝] (x y : E) (r : 𝕝) : ⟪r • x, y⟫ = r • ⟪x, y⟫ := by
rw [inner_smul_left_eq_star_smul, starRingEnd_apply, star_trivial]
/-- See `inner_smul_right` for the common special when `𝕜 = 𝕝`. -/
lemma inner_smul_right_eq_smul (x y : E) (r : 𝕝) : ⟪x, r • y⟫ = r • ⟪x, y⟫ := by
rw [← inner_conj_symm, inner_smul_left_eq_star_smul, starRingEnd_apply, starRingEnd_apply,
star_smul, star_star, ← starRingEnd_apply, inner_conj_symm]
end Algebra
/-- See `inner_smul_left_eq_star_smul` for the case of a general algebra action. -/
theorem inner_smul_left (x y : E) (r : 𝕜) : ⟪r • x, y⟫ = r† * ⟪x, y⟫ :=
inner_smul_left_eq_star_smul ..
theorem real_inner_smul_left (x y : F) (r : ℝ) : ⟪r • x, y⟫_ℝ = r * ⟪x, y⟫_ℝ :=
inner_smul_left _ _ _
theorem inner_smul_real_left (x y : E) (r : ℝ) : ⟪(r : 𝕜) • x, y⟫ = r • ⟪x, y⟫ := by
rw [inner_smul_left, conj_ofReal, Algebra.smul_def]
/-- See `inner_smul_right_eq_smul` for the case of a general algebra action. -/
theorem inner_smul_right (x y : E) (r : 𝕜) : ⟪x, r • y⟫ = r * ⟪x, y⟫ :=
inner_smul_right_eq_smul ..
theorem real_inner_smul_right (x y : F) (r : ℝ) : ⟪x, r • y⟫_ℝ = r * ⟪x, y⟫_ℝ :=
inner_smul_right _ _ _
theorem inner_smul_real_right (x y : E) (r : ℝ) : ⟪x, (r : 𝕜) • y⟫ = r • ⟪x, y⟫ := by
rw [inner_smul_right, Algebra.smul_def]
/-- The inner product as a sesquilinear form.
Note that in the case `𝕜 = ℝ` this is a bilinear form. -/
@[simps!]
def sesqFormOfInner : E →ₗ[𝕜] E →ₗ⋆[𝕜] 𝕜 :=
LinearMap.mk₂'ₛₗ (RingHom.id 𝕜) (starRingEnd _) (fun x y => ⟪y, x⟫)
(fun _x _y _z => inner_add_right _ _ _) (fun _r _x _y => inner_smul_right _ _ _)
(fun _x _y _z => inner_add_left _ _ _) fun _r _x _y => inner_smul_left _ _ _
/-- The real inner product as a bilinear form.
Note that unlike `sesqFormOfInner`, this does not reverse the order of the arguments. -/
@[simps!]
def bilinFormOfRealInner : BilinForm ℝ F := sesqFormOfInner.flip
/-- An inner product with a sum on the left. -/
theorem sum_inner {ι : Type*} (s : Finset ι) (f : ι → E) (x : E) :
⟪∑ i ∈ s, f i, x⟫ = ∑ i ∈ s, ⟪f i, x⟫ :=
map_sum (sesqFormOfInner (𝕜 := 𝕜) (E := E) x) _ _
/-- An inner product with a sum on the right. -/
theorem inner_sum {ι : Type*} (s : Finset ι) (f : ι → E) (x : E) :
⟪x, ∑ i ∈ s, f i⟫ = ∑ i ∈ s, ⟪x, f i⟫ :=
map_sum (LinearMap.flip sesqFormOfInner x) _ _
/-- An inner product with a sum on the left, `Finsupp` version. -/
protected theorem Finsupp.sum_inner {ι : Type*} (l : ι →₀ 𝕜) (v : ι → E) (x : E) :
⟪l.sum fun (i : ι) (a : 𝕜) => a • v i, x⟫ = l.sum fun (i : ι) (a : 𝕜) => conj a • ⟪v i, x⟫ := by
convert sum_inner (𝕜 := 𝕜) l.support (fun a => l a • v a) x
simp only [inner_smul_left, Finsupp.sum, smul_eq_mul]
/-- An inner product with a sum on the right, `Finsupp` version. -/
protected theorem Finsupp.inner_sum {ι : Type*} (l : ι →₀ 𝕜) (v : ι → E) (x : E) :
⟪x, l.sum fun (i : ι) (a : 𝕜) => a • v i⟫ = l.sum fun (i : ι) (a : 𝕜) => a • ⟪x, v i⟫ := by
convert inner_sum (𝕜 := 𝕜) l.support (fun a => l a • v a) x
simp only [inner_smul_right, Finsupp.sum, smul_eq_mul]
protected theorem DFinsupp.sum_inner {ι : Type*} [DecidableEq ι] {α : ι → Type*}
[∀ i, AddZeroClass (α i)] [∀ (i) (x : α i), Decidable (x ≠ 0)] (f : ∀ i, α i → E)
(l : Π₀ i, α i) (x : E) : ⟪l.sum f, x⟫ = l.sum fun i a => ⟪f i a, x⟫ := by
simp +contextual only [DFinsupp.sum, sum_inner, smul_eq_mul]
protected theorem DFinsupp.inner_sum {ι : Type*} [DecidableEq ι] {α : ι → Type*}
[∀ i, AddZeroClass (α i)] [∀ (i) (x : α i), Decidable (x ≠ 0)] (f : ∀ i, α i → E)
(l : Π₀ i, α i) (x : E) : ⟪x, l.sum f⟫ = l.sum fun i a => ⟪x, f i a⟫ := by
simp +contextual only [DFinsupp.sum, inner_sum, smul_eq_mul]
@[simp]
theorem inner_zero_left (x : E) : ⟪0, x⟫ = 0 := by
rw [← zero_smul 𝕜 (0 : E), inner_smul_left, RingHom.map_zero, zero_mul]
theorem inner_re_zero_left (x : E) : re ⟪0, x⟫ = 0 := by
simp only [inner_zero_left, AddMonoidHom.map_zero]
@[simp]
theorem inner_zero_right (x : E) : ⟪x, 0⟫ = 0 := by
rw [← inner_conj_symm, inner_zero_left, RingHom.map_zero]
theorem inner_re_zero_right (x : E) : re ⟪x, 0⟫ = 0 := by
simp only [inner_zero_right, AddMonoidHom.map_zero]
theorem inner_self_nonneg {x : E} : 0 ≤ re ⟪x, x⟫ :=
PreInnerProductSpace.toCore.re_inner_nonneg x
theorem real_inner_self_nonneg {x : F} : 0 ≤ ⟪x, x⟫_ℝ :=
@inner_self_nonneg ℝ F _ _ _ x
@[simp]
theorem inner_self_ofReal_re (x : E) : (re ⟪x, x⟫ : 𝕜) = ⟪x, x⟫ :=
((RCLike.is_real_TFAE (⟪x, x⟫ : 𝕜)).out 2 3).2 (inner_self_im (𝕜 := 𝕜) x)
theorem inner_self_eq_norm_sq_to_K (x : E) : ⟪x, x⟫ = (‖x‖ : 𝕜) ^ 2 := by
rw [← inner_self_ofReal_re, ← norm_sq_eq_re_inner, ofReal_pow]
theorem inner_self_re_eq_norm (x : E) : re ⟪x, x⟫ = ‖⟪x, x⟫‖ := by
conv_rhs => rw [← inner_self_ofReal_re]
symm
exact norm_of_nonneg inner_self_nonneg
theorem inner_self_ofReal_norm (x : E) : (‖⟪x, x⟫‖ : 𝕜) = ⟪x, x⟫ := by
rw [← inner_self_re_eq_norm]
exact inner_self_ofReal_re _
theorem real_inner_self_abs (x : F) : |⟪x, x⟫_ℝ| = ⟪x, x⟫_ℝ :=
@inner_self_ofReal_norm ℝ F _ _ _ x
theorem norm_inner_symm (x y : E) : ‖⟪x, y⟫‖ = ‖⟪y, x⟫‖ := by rw [← inner_conj_symm, norm_conj]
@[simp]
theorem inner_neg_left (x y : E) : ⟪-x, y⟫ = -⟪x, y⟫ := by
rw [← neg_one_smul 𝕜 x, inner_smul_left]
simp
@[simp]
theorem inner_neg_right (x y : E) : ⟪x, -y⟫ = -⟪x, y⟫ := by
rw [← inner_conj_symm, inner_neg_left]; simp only [RingHom.map_neg, inner_conj_symm]
theorem inner_neg_neg (x y : E) : ⟪-x, -y⟫ = ⟪x, y⟫ := by simp
theorem inner_self_conj (x : E) : ⟪x, x⟫† = ⟪x, x⟫ := inner_conj_symm _ _
theorem inner_sub_left (x y z : E) : ⟪x - y, z⟫ = ⟪x, z⟫ - ⟪y, z⟫ := by
simp [sub_eq_add_neg, inner_add_left]
theorem inner_sub_right (x y z : E) : ⟪x, y - z⟫ = ⟪x, y⟫ - ⟪x, z⟫ := by
simp [sub_eq_add_neg, inner_add_right]
theorem inner_mul_symm_re_eq_norm (x y : E) : re (⟪x, y⟫ * ⟪y, x⟫) = ‖⟪x, y⟫ * ⟪y, x⟫‖ := by
rw [← inner_conj_symm, mul_comm]
exact re_eq_norm_of_mul_conj (inner y x)
/-- Expand `⟪x + y, x + y⟫` -/
theorem inner_add_add_self (x y : E) : ⟪x + y, x + y⟫ = ⟪x, x⟫ + ⟪x, y⟫ + ⟪y, x⟫ + ⟪y, y⟫ := by
simp only [inner_add_left, inner_add_right]; ring
/-- Expand `⟪x + y, x + y⟫_ℝ` -/
theorem real_inner_add_add_self (x y : F) :
⟪x + y, x + y⟫_ℝ = ⟪x, x⟫_ℝ + 2 * ⟪x, y⟫_ℝ + ⟪y, y⟫_ℝ := by
have : ⟪y, x⟫_ℝ = ⟪x, y⟫_ℝ := by rw [← inner_conj_symm]; rfl
simp only [inner_add_add_self, this, add_left_inj]
ring
-- Expand `⟪x - y, x - y⟫`
theorem inner_sub_sub_self (x y : E) : ⟪x - y, x - y⟫ = ⟪x, x⟫ - ⟪x, y⟫ - ⟪y, x⟫ + ⟪y, y⟫ := by
simp only [inner_sub_left, inner_sub_right]; ring
/-- Expand `⟪x - y, x - y⟫_ℝ` -/
theorem real_inner_sub_sub_self (x y : F) :
⟪x - y, x - y⟫_ℝ = ⟪x, x⟫_ℝ - 2 * ⟪x, y⟫_ℝ + ⟪y, y⟫_ℝ := by
have : ⟪y, x⟫_ℝ = ⟪x, y⟫_ℝ := by rw [← inner_conj_symm]; rfl
simp only [inner_sub_sub_self, this, add_left_inj]
ring
/-- Parallelogram law -/
theorem parallelogram_law {x y : E} : ⟪x + y, x + y⟫ + ⟪x - y, x - y⟫ = 2 * (⟪x, x⟫ + ⟪y, y⟫) := by
simp only [inner_add_add_self, inner_sub_sub_self]
ring
/-- **Cauchy–Schwarz inequality**. -/
theorem inner_mul_inner_self_le (x y : E) : ‖⟪x, y⟫‖ * ‖⟪y, x⟫‖ ≤ re ⟪x, x⟫ * re ⟪y, y⟫ :=
letI cd : PreInnerProductSpace.Core 𝕜 E := PreInnerProductSpace.toCore
InnerProductSpace.Core.inner_mul_inner_self_le x y
/-- Cauchy–Schwarz inequality for real inner products. -/
theorem real_inner_mul_inner_self_le (x y : F) : ⟪x, y⟫_ℝ * ⟪x, y⟫_ℝ ≤ ⟪x, x⟫_ℝ * ⟪y, y⟫_ℝ :=
calc
⟪x, y⟫_ℝ * ⟪x, y⟫_ℝ ≤ ‖⟪x, y⟫_ℝ‖ * ‖⟪y, x⟫_ℝ‖ := by
rw [real_inner_comm y, ← norm_mul]
exact le_abs_self _
_ ≤ ⟪x, x⟫_ℝ * ⟪y, y⟫_ℝ := @inner_mul_inner_self_le ℝ _ _ _ _ x y
end BasicProperties_Seminormed
section BasicProperties
variable [NormedAddCommGroup E] [InnerProductSpace 𝕜 E]
variable [NormedAddCommGroup F] [InnerProductSpace ℝ F]
local notation "⟪" x ", " y "⟫" => @inner 𝕜 _ _ x y
export InnerProductSpace (norm_sq_eq_re_inner)
@[simp]
theorem inner_self_eq_zero {x : E} : ⟪x, x⟫ = 0 ↔ x = 0 := by
rw [inner_self_eq_norm_sq_to_K, sq_eq_zero_iff, ofReal_eq_zero, norm_eq_zero]
theorem inner_self_ne_zero {x : E} : ⟪x, x⟫ ≠ 0 ↔ x ≠ 0 :=
inner_self_eq_zero.not
variable (𝕜)
theorem ext_inner_left {x y : E} (h : ∀ v, ⟪v, x⟫ = ⟪v, y⟫) : x = y := by
rw [← sub_eq_zero, ← @inner_self_eq_zero 𝕜, inner_sub_right, sub_eq_zero, h (x - y)]
theorem ext_inner_right {x y : E} (h : ∀ v, ⟪x, v⟫ = ⟪y, v⟫) : x = y := by
rw [← sub_eq_zero, ← @inner_self_eq_zero 𝕜, inner_sub_left, sub_eq_zero, h (x - y)]
variable {𝕜}
@[simp]
theorem re_inner_self_nonpos {x : E} : re ⟪x, x⟫ ≤ 0 ↔ x = 0 := by
rw [← norm_sq_eq_re_inner, (sq_nonneg _).le_iff_eq, sq_eq_zero_iff, norm_eq_zero]
@[simp]
lemma re_inner_self_pos {x : E} : 0 < re ⟪x, x⟫ ↔ x ≠ 0 := by
simpa [-re_inner_self_nonpos] using re_inner_self_nonpos (𝕜 := 𝕜) (x := x).not
@[deprecated (since := "2025-04-22")] alias inner_self_nonpos := re_inner_self_nonpos
@[deprecated (since := "2025-04-22")] alias inner_self_pos := re_inner_self_pos
open scoped InnerProductSpace in
theorem real_inner_self_nonpos {x : F} : ⟪x, x⟫_ℝ ≤ 0 ↔ x = 0 := re_inner_self_nonpos (𝕜 := ℝ)
open scoped InnerProductSpace in
theorem real_inner_self_pos {x : F} : 0 < ⟪x, x⟫_ℝ ↔ x ≠ 0 := re_inner_self_pos (𝕜 := ℝ)
/-- A family of vectors is linearly independent if they are nonzero
and orthogonal. -/
theorem linearIndependent_of_ne_zero_of_inner_eq_zero {ι : Type*} {v : ι → E} (hz : ∀ i, v i ≠ 0)
(ho : Pairwise fun i j => ⟪v i, v j⟫ = 0) : LinearIndependent 𝕜 v := by
rw [linearIndependent_iff']
intro s g hg i hi
have h' : g i * inner (v i) (v i) = inner (v i) (∑ j ∈ s, g j • v j) := by
rw [inner_sum]
symm
convert Finset.sum_eq_single (M := 𝕜) i ?_ ?_
· rw [inner_smul_right]
· intro j _hj hji
rw [inner_smul_right, ho hji.symm, mul_zero]
· exact fun h => False.elim (h hi)
simpa [hg, hz] using h'
end BasicProperties
section Norm_Seminormed
open scoped InnerProductSpace
variable [SeminormedAddCommGroup E] [InnerProductSpace 𝕜 E]
variable [SeminormedAddCommGroup F] [InnerProductSpace ℝ F]
local notation "⟪" x ", " y "⟫" => @inner 𝕜 _ _ x y
local notation "IK" => @RCLike.I 𝕜 _
theorem norm_eq_sqrt_re_inner (x : E) : ‖x‖ = √(re ⟪x, x⟫) :=
calc
‖x‖ = √(‖x‖ ^ 2) := (sqrt_sq (norm_nonneg _)).symm
_ = √(re ⟪x, x⟫) := congr_arg _ (norm_sq_eq_re_inner _)
@[deprecated (since := "2025-04-22")] alias norm_eq_sqrt_inner := norm_eq_sqrt_re_inner
theorem norm_eq_sqrt_real_inner (x : F) : ‖x‖ = √⟪x, x⟫_ℝ :=
@norm_eq_sqrt_re_inner ℝ _ _ _ _ x
theorem inner_self_eq_norm_mul_norm (x : E) : re ⟪x, x⟫ = ‖x‖ * ‖x‖ := by
rw [@norm_eq_sqrt_re_inner 𝕜, ← sqrt_mul inner_self_nonneg (re ⟪x, x⟫),
sqrt_mul_self inner_self_nonneg]
theorem inner_self_eq_norm_sq (x : E) : re ⟪x, x⟫ = ‖x‖ ^ 2 := by
rw [pow_two, inner_self_eq_norm_mul_norm]
theorem real_inner_self_eq_norm_mul_norm (x : F) : ⟪x, x⟫_ℝ = ‖x‖ * ‖x‖ := by
have h := @inner_self_eq_norm_mul_norm ℝ F _ _ _ x
simpa using h
theorem real_inner_self_eq_norm_sq (x : F) : ⟪x, x⟫_ℝ = ‖x‖ ^ 2 := by
rw [pow_two, real_inner_self_eq_norm_mul_norm]
/-- Expand the square -/
theorem norm_add_sq (x y : E) : ‖x + y‖ ^ 2 = ‖x‖ ^ 2 + 2 * re ⟪x, y⟫ + ‖y‖ ^ 2 := by
repeat' rw [sq (M := ℝ), ← @inner_self_eq_norm_mul_norm 𝕜]
rw [inner_add_add_self, two_mul]
simp only [add_assoc, add_left_inj, add_right_inj, AddMonoidHom.map_add]
rw [← inner_conj_symm, conj_re]
alias norm_add_pow_two := norm_add_sq
/-- Expand the square -/
theorem norm_add_sq_real (x y : F) : ‖x + y‖ ^ 2 = ‖x‖ ^ 2 + 2 * ⟪x, y⟫_ℝ + ‖y‖ ^ 2 := by
have h := @norm_add_sq ℝ _ _ _ _ x y
simpa using h
alias norm_add_pow_two_real := norm_add_sq_real
/-- Expand the square -/
theorem norm_add_mul_self (x y : E) :
‖x + y‖ * ‖x + y‖ = ‖x‖ * ‖x‖ + 2 * re ⟪x, y⟫ + ‖y‖ * ‖y‖ := by
repeat' rw [← sq (M := ℝ)]
exact norm_add_sq _ _
/-- Expand the square -/
theorem norm_add_mul_self_real (x y : F) :
‖x + y‖ * ‖x + y‖ = ‖x‖ * ‖x‖ + 2 * ⟪x, y⟫_ℝ + ‖y‖ * ‖y‖ := by
have h := @norm_add_mul_self ℝ _ _ _ _ x y
simpa using h
/-- Expand the square -/
theorem norm_sub_sq (x y : E) : ‖x - y‖ ^ 2 = ‖x‖ ^ 2 - 2 * re ⟪x, y⟫ + ‖y‖ ^ 2 := by
rw [sub_eq_add_neg, @norm_add_sq 𝕜 _ _ _ _ x (-y), norm_neg, inner_neg_right, map_neg, mul_neg,
sub_eq_add_neg]
alias norm_sub_pow_two := norm_sub_sq
/-- Expand the square -/
theorem norm_sub_sq_real (x y : F) : ‖x - y‖ ^ 2 = ‖x‖ ^ 2 - 2 * ⟪x, y⟫_ℝ + ‖y‖ ^ 2 :=
@norm_sub_sq ℝ _ _ _ _ _ _
alias norm_sub_pow_two_real := norm_sub_sq_real
/-- Expand the square -/
theorem norm_sub_mul_self (x y : E) :
‖x - y‖ * ‖x - y‖ = ‖x‖ * ‖x‖ - 2 * re ⟪x, y⟫ + ‖y‖ * ‖y‖ := by
repeat' rw [← sq (M := ℝ)]
exact norm_sub_sq _ _
/-- Expand the square -/
theorem norm_sub_mul_self_real (x y : F) :
‖x - y‖ * ‖x - y‖ = ‖x‖ * ‖x‖ - 2 * ⟪x, y⟫_ℝ + ‖y‖ * ‖y‖ := by
have h := @norm_sub_mul_self ℝ _ _ _ _ x y
simpa using h
/-- Cauchy–Schwarz inequality with norm -/
theorem norm_inner_le_norm (x y : E) : ‖⟪x, y⟫‖ ≤ ‖x‖ * ‖y‖ := by
rw [norm_eq_sqrt_re_inner (𝕜 := 𝕜) x, norm_eq_sqrt_re_inner (𝕜 := 𝕜) y]
letI : PreInnerProductSpace.Core 𝕜 E := PreInnerProductSpace.toCore
exact InnerProductSpace.Core.norm_inner_le_norm x y
theorem nnnorm_inner_le_nnnorm (x y : E) : ‖⟪x, y⟫‖₊ ≤ ‖x‖₊ * ‖y‖₊ :=
norm_inner_le_norm x y
theorem re_inner_le_norm (x y : E) : re ⟪x, y⟫ ≤ ‖x‖ * ‖y‖ :=
le_trans (re_le_norm (inner x y)) (norm_inner_le_norm x y)
/-- Cauchy–Schwarz inequality with norm -/
theorem abs_real_inner_le_norm (x y : F) : |⟪x, y⟫_ℝ| ≤ ‖x‖ * ‖y‖ :=
(Real.norm_eq_abs _).ge.trans (norm_inner_le_norm x y)
/-- Cauchy–Schwarz inequality with norm -/
theorem real_inner_le_norm (x y : F) : ⟪x, y⟫_ℝ ≤ ‖x‖ * ‖y‖ :=
le_trans (le_abs_self _) (abs_real_inner_le_norm _ _)
lemma inner_eq_zero_of_left {x : E} (y : E) (h : ‖x‖ = 0) : ⟪x, y⟫_𝕜 = 0 := by
rw [← norm_eq_zero]
refine le_antisymm ?_ (by positivity)
exact norm_inner_le_norm _ _ |>.trans <| by simp [h]
lemma inner_eq_zero_of_right (x : E) {y : E} (h : ‖y‖ = 0) : ⟪x, y⟫_𝕜 = 0 := by
rw [inner_eq_zero_symm, inner_eq_zero_of_left _ h]
variable (𝕜)
include 𝕜 in
theorem parallelogram_law_with_norm (x y : E) :
‖x + y‖ * ‖x + y‖ + ‖x - y‖ * ‖x - y‖ = 2 * (‖x‖ * ‖x‖ + ‖y‖ * ‖y‖) := by
simp only [← @inner_self_eq_norm_mul_norm 𝕜]
rw [← re.map_add, parallelogram_law, two_mul, two_mul]
simp only [re.map_add]
include 𝕜 in
theorem parallelogram_law_with_nnnorm (x y : E) :
‖x + y‖₊ * ‖x + y‖₊ + ‖x - y‖₊ * ‖x - y‖₊ = 2 * (‖x‖₊ * ‖x‖₊ + ‖y‖₊ * ‖y‖₊) :=
Subtype.ext <| parallelogram_law_with_norm 𝕜 x y
variable {𝕜}
/-- Polarization identity: The real part of the inner product, in terms of the norm. -/
theorem re_inner_eq_norm_add_mul_self_sub_norm_mul_self_sub_norm_mul_self_div_two (x y : E) :
re ⟪x, y⟫ = (‖x + y‖ * ‖x + y‖ - ‖x‖ * ‖x‖ - ‖y‖ * ‖y‖) / 2 := by
rw [@norm_add_mul_self 𝕜]
ring
/-- Polarization identity: The real part of the inner product, in terms of the norm. -/
theorem re_inner_eq_norm_mul_self_add_norm_mul_self_sub_norm_sub_mul_self_div_two (x y : E) :
re ⟪x, y⟫ = (‖x‖ * ‖x‖ + ‖y‖ * ‖y‖ - ‖x - y‖ * ‖x - y‖) / 2 := by
rw [@norm_sub_mul_self 𝕜]
ring
/-- Polarization identity: The real part of the inner product, in terms of the norm. -/
theorem re_inner_eq_norm_add_mul_self_sub_norm_sub_mul_self_div_four (x y : E) :
re ⟪x, y⟫ = (‖x + y‖ * ‖x + y‖ - ‖x - y‖ * ‖x - y‖) / 4 := by
rw [@norm_add_mul_self 𝕜, @norm_sub_mul_self 𝕜]
ring
/-- Polarization identity: The imaginary part of the inner product, in terms of the norm. -/
theorem im_inner_eq_norm_sub_i_smul_mul_self_sub_norm_add_i_smul_mul_self_div_four (x y : E) :
im ⟪x, y⟫ = (‖x - IK • y‖ * ‖x - IK • y‖ - ‖x + IK • y‖ * ‖x + IK • y‖) / 4 := by
simp only [@norm_add_mul_self 𝕜, @norm_sub_mul_self 𝕜, inner_smul_right, I_mul_re]
ring
/-- Polarization identity: The inner product, in terms of the norm. -/
theorem inner_eq_sum_norm_sq_div_four (x y : E) :
⟪x, y⟫ = ((‖x + y‖ : 𝕜) ^ 2 - (‖x - y‖ : 𝕜) ^ 2 +
((‖x - IK • y‖ : 𝕜) ^ 2 - (‖x + IK • y‖ : 𝕜) ^ 2) * IK) / 4 := by
rw [← re_add_im ⟪x, y⟫, re_inner_eq_norm_add_mul_self_sub_norm_sub_mul_self_div_four,
im_inner_eq_norm_sub_i_smul_mul_self_sub_norm_add_i_smul_mul_self_div_four]
push_cast
simp only [sq, ← mul_div_right_comm, ← add_div]
/-- Polarization identity: The real inner product, in terms of the norm. -/
theorem real_inner_eq_norm_add_mul_self_sub_norm_mul_self_sub_norm_mul_self_div_two (x y : F) :
⟪x, y⟫_ℝ = (‖x + y‖ * ‖x + y‖ - ‖x‖ * ‖x‖ - ‖y‖ * ‖y‖) / 2 :=
re_to_real.symm.trans <|
re_inner_eq_norm_add_mul_self_sub_norm_mul_self_sub_norm_mul_self_div_two x y
/-- Polarization identity: The real inner product, in terms of the norm. -/
theorem real_inner_eq_norm_mul_self_add_norm_mul_self_sub_norm_sub_mul_self_div_two (x y : F) :
⟪x, y⟫_ℝ = (‖x‖ * ‖x‖ + ‖y‖ * ‖y‖ - ‖x - y‖ * ‖x - y‖) / 2 :=
re_to_real.symm.trans <|
re_inner_eq_norm_mul_self_add_norm_mul_self_sub_norm_sub_mul_self_div_two x y
/-- Pythagorean theorem, if-and-only-if vector inner product form. -/
theorem norm_add_sq_eq_norm_sq_add_norm_sq_iff_real_inner_eq_zero (x y : F) :
‖x + y‖ * ‖x + y‖ = ‖x‖ * ‖x‖ + ‖y‖ * ‖y‖ ↔ ⟪x, y⟫_ℝ = 0 := by
rw [@norm_add_mul_self ℝ, add_right_cancel_iff, add_eq_left, mul_eq_zero]
norm_num
/-- Pythagorean theorem, if-and-if vector inner product form using square roots. -/
theorem norm_add_eq_sqrt_iff_real_inner_eq_zero {x y : F} :
‖x + y‖ = √(‖x‖ * ‖x‖ + ‖y‖ * ‖y‖) ↔ ⟪x, y⟫_ℝ = 0 := by
rw [← norm_add_sq_eq_norm_sq_add_norm_sq_iff_real_inner_eq_zero, eq_comm, sqrt_eq_iff_mul_self_eq,
eq_comm] <;> positivity
/-- Pythagorean theorem, vector inner product form. -/
theorem norm_add_sq_eq_norm_sq_add_norm_sq_of_inner_eq_zero (x y : E) (h : ⟪x, y⟫ = 0) :
‖x + y‖ * ‖x + y‖ = ‖x‖ * ‖x‖ + ‖y‖ * ‖y‖ := by
rw [@norm_add_mul_self 𝕜, add_right_cancel_iff, add_eq_left, mul_eq_zero]
apply Or.inr
simp only [h, zero_re']
/-- Pythagorean theorem, vector inner product form. -/
theorem norm_add_sq_eq_norm_sq_add_norm_sq_real {x y : F} (h : ⟪x, y⟫_ℝ = 0) :
‖x + y‖ * ‖x + y‖ = ‖x‖ * ‖x‖ + ‖y‖ * ‖y‖ :=
(norm_add_sq_eq_norm_sq_add_norm_sq_iff_real_inner_eq_zero x y).2 h
/-- Pythagorean theorem, subtracting vectors, if-and-only-if vector
inner product form. -/
theorem norm_sub_sq_eq_norm_sq_add_norm_sq_iff_real_inner_eq_zero (x y : F) :
‖x - y‖ * ‖x - y‖ = ‖x‖ * ‖x‖ + ‖y‖ * ‖y‖ ↔ ⟪x, y⟫_ℝ = 0 := by
rw [@norm_sub_mul_self ℝ, add_right_cancel_iff, sub_eq_add_neg, add_eq_left, neg_eq_zero,
mul_eq_zero]
norm_num
/-- Pythagorean theorem, subtracting vectors, if-and-if vector inner product form using square
roots. -/
theorem norm_sub_eq_sqrt_iff_real_inner_eq_zero {x y : F} :
‖x - y‖ = √(‖x‖ * ‖x‖ + ‖y‖ * ‖y‖) ↔ ⟪x, y⟫_ℝ = 0 := by
rw [← norm_sub_sq_eq_norm_sq_add_norm_sq_iff_real_inner_eq_zero, eq_comm, sqrt_eq_iff_mul_self_eq,
eq_comm] <;> positivity
/-- Pythagorean theorem, subtracting vectors, vector inner product
form. -/
theorem norm_sub_sq_eq_norm_sq_add_norm_sq_real {x y : F} (h : ⟪x, y⟫_ℝ = 0) :
‖x - y‖ * ‖x - y‖ = ‖x‖ * ‖x‖ + ‖y‖ * ‖y‖ :=
(norm_sub_sq_eq_norm_sq_add_norm_sq_iff_real_inner_eq_zero x y).2 h
/-- The sum and difference of two vectors are orthogonal if and only
if they have the same norm. -/
theorem real_inner_add_sub_eq_zero_iff (x y : F) : ⟪x + y, x - y⟫_ℝ = 0 ↔ ‖x‖ = ‖y‖ := by
conv_rhs => rw [← mul_self_inj_of_nonneg (norm_nonneg _) (norm_nonneg _)]
simp only [← @inner_self_eq_norm_mul_norm ℝ, inner_add_left, inner_sub_right, real_inner_comm y x,
sub_eq_zero, re_to_real]
constructor
· intro h
rw [add_comm] at h
linarith
· intro h
linarith
/-- Given two orthogonal vectors, their sum and difference have equal norms. -/
theorem norm_sub_eq_norm_add {v w : E} (h : ⟪v, w⟫ = 0) : ‖w - v‖ = ‖w + v‖ := by
rw [← mul_self_inj_of_nonneg (norm_nonneg _) (norm_nonneg _)]
simp only [h, ← @inner_self_eq_norm_mul_norm 𝕜, sub_neg_eq_add, sub_zero, map_sub, zero_re',
zero_sub, add_zero, map_add, inner_add_right, inner_sub_left, inner_sub_right, inner_re_symm,
zero_add]
/-- The real inner product of two vectors, divided by the product of their
norms, has absolute value at most 1. -/
theorem abs_real_inner_div_norm_mul_norm_le_one (x y : F) : |⟪x, y⟫_ℝ / (‖x‖ * ‖y‖)| ≤ 1 := by
rw [abs_div, abs_mul, abs_norm, abs_norm]
exact div_le_one_of_le₀ (abs_real_inner_le_norm x y) (by positivity)
/-- The inner product of a vector with a multiple of itself. -/
theorem real_inner_smul_self_left (x : F) (r : ℝ) : ⟪r • x, x⟫_ℝ = r * (‖x‖ * ‖x‖) := by
rw [real_inner_smul_left, ← real_inner_self_eq_norm_mul_norm]
/-- The inner product of a vector with a multiple of itself. -/
theorem real_inner_smul_self_right (x : F) (r : ℝ) : ⟪x, r • x⟫_ℝ = r * (‖x‖ * ‖x‖) := by
rw [inner_smul_right, ← real_inner_self_eq_norm_mul_norm]
/-- The inner product of two weighted sums, where the weights in each
sum add to 0, in terms of the norms of pairwise differences. -/
theorem inner_sum_smul_sum_smul_of_sum_eq_zero {ι₁ : Type*} {s₁ : Finset ι₁} {w₁ : ι₁ → ℝ}
(v₁ : ι₁ → F) (h₁ : ∑ i ∈ s₁, w₁ i = 0) {ι₂ : Type*} {s₂ : Finset ι₂} {w₂ : ι₂ → ℝ}
(v₂ : ι₂ → F) (h₂ : ∑ i ∈ s₂, w₂ i = 0) :
⟪∑ i₁ ∈ s₁, w₁ i₁ • v₁ i₁, ∑ i₂ ∈ s₂, w₂ i₂ • v₂ i₂⟫_ℝ =
(-∑ i₁ ∈ s₁, ∑ i₂ ∈ s₂, w₁ i₁ * w₂ i₂ * (‖v₁ i₁ - v₂ i₂‖ * ‖v₁ i₁ - v₂ i₂‖)) / 2 := by
simp_rw [sum_inner, inner_sum, real_inner_smul_left, real_inner_smul_right,
real_inner_eq_norm_mul_self_add_norm_mul_self_sub_norm_sub_mul_self_div_two, ← div_sub_div_same,
← div_add_div_same, mul_sub_left_distrib, left_distrib, Finset.sum_sub_distrib,
Finset.sum_add_distrib, ← Finset.mul_sum, ← Finset.sum_mul, h₁, h₂, zero_mul,
mul_zero, Finset.sum_const_zero, zero_add, zero_sub, Finset.mul_sum, neg_div,
Finset.sum_div, mul_div_assoc, mul_assoc]
end Norm_Seminormed
section Norm
open scoped InnerProductSpace
variable [NormedAddCommGroup E] [InnerProductSpace 𝕜 E]
variable [NormedAddCommGroup F] [InnerProductSpace ℝ F]
variable {ι : Type*}
local notation "⟪" x ", " y "⟫" => @inner 𝕜 _ _ x y
/-- Formula for the distance between the images of two nonzero points under an inversion with center
zero. See also `EuclideanGeometry.dist_inversion_inversion` for inversions around a general
point. -/
theorem dist_div_norm_sq_smul {x y : F} (hx : x ≠ 0) (hy : y ≠ 0) (R : ℝ) :
dist ((R / ‖x‖) ^ 2 • x) ((R / ‖y‖) ^ 2 • y) = R ^ 2 / (‖x‖ * ‖y‖) * dist x y :=
calc
dist ((R / ‖x‖) ^ 2 • x) ((R / ‖y‖) ^ 2 • y) =
√(‖(R / ‖x‖) ^ 2 • x - (R / ‖y‖) ^ 2 • y‖ ^ 2) := by
rw [dist_eq_norm, sqrt_sq (norm_nonneg _)]
_ = √((R ^ 2 / (‖x‖ * ‖y‖)) ^ 2 * ‖x - y‖ ^ 2) :=
congr_arg sqrt <| by
field_simp [sq, norm_sub_mul_self_real, norm_smul, real_inner_smul_left, inner_smul_right,
Real.norm_of_nonneg (mul_self_nonneg _)]
ring
_ = R ^ 2 / (‖x‖ * ‖y‖) * dist x y := by
rw [sqrt_mul, sqrt_sq, sqrt_sq, dist_eq_norm] <;> positivity
/-- The inner product of a nonzero vector with a nonzero multiple of
itself, divided by the product of their norms, has absolute value
1. -/
theorem norm_inner_div_norm_mul_norm_eq_one_of_ne_zero_of_ne_zero_mul {x : E} {r : 𝕜} (hx : x ≠ 0)
(hr : r ≠ 0) : ‖⟪x, r • x⟫‖ / (‖x‖ * ‖r • x‖) = 1 := by
have hx' : ‖x‖ ≠ 0 := by simp [hx]
have hr' : ‖r‖ ≠ 0 := by simp [hr]
rw [inner_smul_right, norm_mul, ← inner_self_re_eq_norm, inner_self_eq_norm_mul_norm, norm_smul]
rw [← mul_assoc, ← div_div, mul_div_cancel_right₀ _ hx', ← div_div, mul_comm,
mul_div_cancel_right₀ _ hr', div_self hx']
/-- The inner product of a nonzero vector with a nonzero multiple of
itself, divided by the product of their norms, has absolute value
1. -/
theorem abs_real_inner_div_norm_mul_norm_eq_one_of_ne_zero_of_ne_zero_mul {x : F} {r : ℝ}
(hx : x ≠ 0) (hr : r ≠ 0) : |⟪x, r • x⟫_ℝ| / (‖x‖ * ‖r • x‖) = 1 :=
norm_inner_div_norm_mul_norm_eq_one_of_ne_zero_of_ne_zero_mul hx hr
/-- The inner product of a nonzero vector with a positive multiple of
itself, divided by the product of their norms, has value 1. -/
theorem real_inner_div_norm_mul_norm_eq_one_of_ne_zero_of_pos_mul {x : F} {r : ℝ} (hx : x ≠ 0)
(hr : 0 < r) : ⟪x, r • x⟫_ℝ / (‖x‖ * ‖r • x‖) = 1 := by
rw [real_inner_smul_self_right, norm_smul, Real.norm_eq_abs, ← mul_assoc ‖x‖, mul_comm _ |r|,
mul_assoc, abs_of_nonneg hr.le, div_self]
exact mul_ne_zero hr.ne' (mul_self_ne_zero.2 (norm_ne_zero_iff.2 hx))
/-- The inner product of a nonzero vector with a negative multiple of
itself, divided by the product of their norms, has value -1. -/
theorem real_inner_div_norm_mul_norm_eq_neg_one_of_ne_zero_of_neg_mul {x : F} {r : ℝ} (hx : x ≠ 0)
(hr : r < 0) : ⟪x, r • x⟫_ℝ / (‖x‖ * ‖r • x‖) = -1 := by
rw [real_inner_smul_self_right, norm_smul, Real.norm_eq_abs, ← mul_assoc ‖x‖, mul_comm _ |r|,
mul_assoc, abs_of_neg hr, neg_mul, div_neg_eq_neg_div, div_self]
exact mul_ne_zero hr.ne (mul_self_ne_zero.2 (norm_ne_zero_iff.2 hx))
theorem norm_inner_eq_norm_tfae (x y : E) :
List.TFAE [‖⟪x, y⟫‖ = ‖x‖ * ‖y‖,
x = 0 ∨ y = (⟪x, y⟫ / ⟪x, x⟫) • x,
x = 0 ∨ ∃ r : 𝕜, y = r • x,
x = 0 ∨ y ∈ 𝕜 ∙ x] := by
tfae_have 1 → 2 := by
refine fun h => or_iff_not_imp_left.2 fun hx₀ => ?_
have : ‖x‖ ^ 2 ≠ 0 := pow_ne_zero _ (norm_ne_zero_iff.2 hx₀)
rw [← sq_eq_sq₀, mul_pow, ← mul_right_inj' this, eq_comm, ← sub_eq_zero, ← mul_sub] at h <;>
try positivity
simp only [@norm_sq_eq_re_inner 𝕜] at h
letI : InnerProductSpace.Core 𝕜 E := InnerProductSpace.toCore
erw [← InnerProductSpace.Core.cauchy_schwarz_aux (𝕜 := 𝕜) (F := E)] at h
rw [InnerProductSpace.Core.normSq_eq_zero, sub_eq_zero] at h
rw [div_eq_inv_mul, mul_smul, h, inv_smul_smul₀]
rwa [inner_self_ne_zero]
tfae_have 2 → 3 := fun h => h.imp_right fun h' => ⟨_, h'⟩
tfae_have 3 → 1 := by
rintro (rfl | ⟨r, rfl⟩) <;>
simp [inner_smul_right, norm_smul, inner_self_eq_norm_sq_to_K, inner_self_eq_norm_mul_norm,
sq, mul_left_comm]
tfae_have 3 ↔ 4 := by simp only [Submodule.mem_span_singleton, eq_comm]
tfae_finish
/-- If the inner product of two vectors is equal to the product of their norms, then the two vectors
are multiples of each other. One form of the equality case for Cauchy-Schwarz.
Compare `inner_eq_norm_mul_iff`, which takes the stronger hypothesis `⟪x, y⟫ = ‖x‖ * ‖y‖`. -/
theorem norm_inner_eq_norm_iff {x y : E} (hx₀ : x ≠ 0) (hy₀ : y ≠ 0) :
‖⟪x, y⟫‖ = ‖x‖ * ‖y‖ ↔ ∃ r : 𝕜, r ≠ 0 ∧ y = r • x :=
calc
‖⟪x, y⟫‖ = ‖x‖ * ‖y‖ ↔ x = 0 ∨ ∃ r : 𝕜, y = r • x :=
(@norm_inner_eq_norm_tfae 𝕜 _ _ _ _ x y).out 0 2
_ ↔ ∃ r : 𝕜, y = r • x := or_iff_right hx₀
_ ↔ ∃ r : 𝕜, r ≠ 0 ∧ y = r • x :=
⟨fun ⟨r, h⟩ => ⟨r, fun hr₀ => hy₀ <| h.symm ▸ smul_eq_zero.2 <| Or.inl hr₀, h⟩,
fun ⟨r, _hr₀, h⟩ => ⟨r, h⟩⟩
/-- The inner product of two vectors, divided by the product of their
norms, has absolute value 1 if and only if they are nonzero and one is
a multiple of the other. One form of equality case for Cauchy-Schwarz. -/
theorem norm_inner_div_norm_mul_norm_eq_one_iff (x y : E) :
‖⟪x, y⟫ / (‖x‖ * ‖y‖)‖ = 1 ↔ x ≠ 0 ∧ ∃ r : 𝕜, r ≠ 0 ∧ y = r • x := by
constructor
· intro h
have hx₀ : x ≠ 0 := fun h₀ => by simp [h₀] at h
have hy₀ : y ≠ 0 := fun h₀ => by simp [h₀] at h
refine ⟨hx₀, (norm_inner_eq_norm_iff hx₀ hy₀).1 <| eq_of_div_eq_one ?_⟩
simpa using h
· rintro ⟨hx, ⟨r, ⟨hr, rfl⟩⟩⟩
simp only [norm_div, norm_mul, norm_ofReal, abs_norm]
exact norm_inner_div_norm_mul_norm_eq_one_of_ne_zero_of_ne_zero_mul hx hr
/-- The inner product of two vectors, divided by the product of their
norms, has absolute value 1 if and only if they are nonzero and one is
a multiple of the other. One form of equality case for Cauchy-Schwarz. -/
theorem abs_real_inner_div_norm_mul_norm_eq_one_iff (x y : F) :
|⟪x, y⟫_ℝ / (‖x‖ * ‖y‖)| = 1 ↔ x ≠ 0 ∧ ∃ r : ℝ, r ≠ 0 ∧ y = r • x :=
@norm_inner_div_norm_mul_norm_eq_one_iff ℝ F _ _ _ x y
theorem inner_eq_norm_mul_iff_div {x y : E} (h₀ : x ≠ 0) :
⟪x, y⟫ = (‖x‖ : 𝕜) * ‖y‖ ↔ (‖y‖ / ‖x‖ : 𝕜) • x = y := by
have h₀' := h₀
rw [← norm_ne_zero_iff, Ne, ← @ofReal_eq_zero 𝕜] at h₀'
constructor <;> intro h
· have : x = 0 ∨ y = (⟪x, y⟫ / ⟪x, x⟫ : 𝕜) • x :=
((@norm_inner_eq_norm_tfae 𝕜 _ _ _ _ x y).out 0 1).1 (by simp [h])
rw [this.resolve_left h₀, h]
simp [norm_smul, inner_self_ofReal_norm, mul_div_cancel_right₀ _ h₀']
· conv_lhs => rw [← h, inner_smul_right, inner_self_eq_norm_sq_to_K]
field_simp [sq, mul_left_comm]
/-- If the inner product of two vectors is equal to the product of their norms (i.e.,
`⟪x, y⟫ = ‖x‖ * ‖y‖`), then the two vectors are nonnegative real multiples of each other. One form
of the equality case for Cauchy-Schwarz.
Compare `norm_inner_eq_norm_iff`, which takes the weaker hypothesis `abs ⟪x, y⟫ = ‖x‖ * ‖y‖`. -/
theorem inner_eq_norm_mul_iff {x y : E} :
⟪x, y⟫ = (‖x‖ : 𝕜) * ‖y‖ ↔ (‖y‖ : 𝕜) • x = (‖x‖ : 𝕜) • y := by
rcases eq_or_ne x 0 with (rfl | h₀)
· simp
· rw [inner_eq_norm_mul_iff_div h₀, div_eq_inv_mul, mul_smul, inv_smul_eq_iff₀]
rwa [Ne, ofReal_eq_zero, norm_eq_zero]
/-- If the inner product of two vectors is equal to the product of their norms (i.e.,
`⟪x, y⟫ = ‖x‖ * ‖y‖`), then the two vectors are nonnegative real multiples of each other. One form
of the equality case for Cauchy-Schwarz.
Compare `norm_inner_eq_norm_iff`, which takes the weaker hypothesis `abs ⟪x, y⟫ = ‖x‖ * ‖y‖`. -/
theorem inner_eq_norm_mul_iff_real {x y : F} : ⟪x, y⟫_ℝ = ‖x‖ * ‖y‖ ↔ ‖y‖ • x = ‖x‖ • y :=
inner_eq_norm_mul_iff
/-- The inner product of two vectors, divided by the product of their
norms, has value 1 if and only if they are nonzero and one is
a positive multiple of the other. -/
theorem real_inner_div_norm_mul_norm_eq_one_iff (x y : F) :
⟪x, y⟫_ℝ / (‖x‖ * ‖y‖) = 1 ↔ x ≠ 0 ∧ ∃ r : ℝ, 0 < r ∧ y = r • x := by
constructor
· intro h
have hx₀ : x ≠ 0 := fun h₀ => by simp [h₀] at h
have hy₀ : y ≠ 0 := fun h₀ => by simp [h₀] at h
refine ⟨hx₀, ‖y‖ / ‖x‖, div_pos (norm_pos_iff.2 hy₀) (norm_pos_iff.2 hx₀), ?_⟩
exact ((inner_eq_norm_mul_iff_div hx₀).1 (eq_of_div_eq_one h)).symm
· rintro ⟨hx, ⟨r, ⟨hr, rfl⟩⟩⟩
exact real_inner_div_norm_mul_norm_eq_one_of_ne_zero_of_pos_mul hx hr
/-- The inner product of two vectors, divided by the product of their
norms, has value -1 if and only if they are nonzero and one is
a negative multiple of the other. -/
theorem real_inner_div_norm_mul_norm_eq_neg_one_iff (x y : F) :
⟪x, y⟫_ℝ / (‖x‖ * ‖y‖) = -1 ↔ x ≠ 0 ∧ ∃ r : ℝ, r < 0 ∧ y = r • x := by
rw [← neg_eq_iff_eq_neg, ← neg_div, ← inner_neg_right, ← norm_neg y,
real_inner_div_norm_mul_norm_eq_one_iff, (@neg_surjective ℝ _).exists]
refine Iff.rfl.and (exists_congr fun r => ?_)
rw [neg_pos, neg_smul, neg_inj]
/-- If the inner product of two unit vectors is `1`, then the two vectors are equal. One form of
the equality case for Cauchy-Schwarz. -/
theorem inner_eq_one_iff_of_norm_one {x y : E} (hx : ‖x‖ = 1) (hy : ‖y‖ = 1) :
⟪x, y⟫ = 1 ↔ x = y := by
convert inner_eq_norm_mul_iff (𝕜 := 𝕜) (E := E) using 2 <;> simp [hx, hy]
theorem inner_lt_norm_mul_iff_real {x y : F} : ⟪x, y⟫_ℝ < ‖x‖ * ‖y‖ ↔ ‖y‖ • x ≠ ‖x‖ • y :=
calc
⟪x, y⟫_ℝ < ‖x‖ * ‖y‖ ↔ ⟪x, y⟫_ℝ ≠ ‖x‖ * ‖y‖ :=
⟨ne_of_lt, lt_of_le_of_ne (real_inner_le_norm _ _)⟩
_ ↔ ‖y‖ • x ≠ ‖x‖ • y := not_congr inner_eq_norm_mul_iff_real
/-- If the inner product of two unit vectors is strictly less than `1`, then the two vectors are
distinct. One form of the equality case for Cauchy-Schwarz. -/
theorem inner_lt_one_iff_real_of_norm_one {x y : F} (hx : ‖x‖ = 1) (hy : ‖y‖ = 1) :
⟪x, y⟫_ℝ < 1 ↔ x ≠ y := by convert inner_lt_norm_mul_iff_real (F := F) <;> simp [hx, hy]
/-- The sphere of radius `r = ‖y‖` is tangent to the plane `⟪x, y⟫ = ‖y‖ ^ 2` at `x = y`. -/
theorem eq_of_norm_le_re_inner_eq_norm_sq {x y : E} (hle : ‖x‖ ≤ ‖y‖) (h : re ⟪x, y⟫ = ‖y‖ ^ 2) :
x = y := by
suffices H : re ⟪x - y, x - y⟫ ≤ 0 by rwa [re_inner_self_nonpos, sub_eq_zero] at H
have H₁ : ‖x‖ ^ 2 ≤ ‖y‖ ^ 2 := by gcongr
have H₂ : re ⟪y, x⟫ = ‖y‖ ^ 2 := by rwa [← inner_conj_symm, conj_re]
simpa [inner_sub_left, inner_sub_right, ← norm_sq_eq_re_inner, h, H₂] using H₁
end Norm
section RCLike
local notation "⟪" x ", " y "⟫" => @inner 𝕜 _ _ x y
/-- A field `𝕜` satisfying `RCLike` is itself a `𝕜`-inner product space. -/
instance RCLike.innerProductSpace : InnerProductSpace 𝕜 𝕜 where
inner x y := y * conj x
norm_sq_eq_re_inner x := by simp only [inner, mul_conj, ← ofReal_pow, ofReal_re]
conj_inner_symm x y := by simp only [mul_comm, map_mul, starRingEnd_self_apply]
add_left x y z := by simp only [mul_add, map_add]
smul_left x y z := by simp only [mul_comm (conj z), mul_assoc, smul_eq_mul, map_mul]
@[simp]
theorem RCLike.inner_apply (x y : 𝕜) : ⟪x, y⟫ = y * conj x :=
rfl
/-- A version of `RCLike.inner_apply` that swaps the order of multiplication. -/
theorem RCLike.inner_apply' (x y : 𝕜) : ⟪x, y⟫ = conj x * y := mul_comm _ _
end RCLike
section RCLikeToReal
open scoped InnerProductSpace
variable {G : Type*}
variable (𝕜 E)
variable [SeminormedAddCommGroup E] [InnerProductSpace 𝕜 E]
local notation "⟪" x ", " y "⟫" => @inner 𝕜 _ _ x y
/-- A general inner product implies a real inner product. This is not registered as an instance
since `𝕜` does not appear in the return type `Inner ℝ E`. -/
def Inner.rclikeToReal : Inner ℝ E where inner x y := re ⟪x, y⟫
/-- A general inner product space structure implies a real inner product structure.
This is not registered as an instance since
* `𝕜` does not appear in the return type `InnerProductSpace ℝ E`,
* It is likely to create instance diamonds, as it builds upon the diamond-prone
`NormedSpace.restrictScalars`.
However, it can be used in a proof to obtain a real inner product space structure from a given
`𝕜`-inner product space structure. -/
-- See note [reducible non instances]
abbrev InnerProductSpace.rclikeToReal : InnerProductSpace ℝ E :=
{ Inner.rclikeToReal 𝕜 E,
NormedSpace.restrictScalars ℝ 𝕜
E with
norm_sq_eq_re_inner := norm_sq_eq_re_inner
conj_inner_symm := fun _ _ => inner_re_symm _ _
add_left := fun x y z => by
change re ⟪x + y, z⟫ = re ⟪x, z⟫ + re ⟪y, z⟫
simp only [inner_add_left, map_add]
smul_left := fun x y r => by
change re ⟪(r : 𝕜) • x, y⟫ = r * re ⟪x, y⟫
simp only [inner_smul_left, conj_ofReal, re_ofReal_mul] }
variable {E}
theorem real_inner_eq_re_inner (x y : E) :
@Inner.inner ℝ E (Inner.rclikeToReal 𝕜 E) x y = re ⟪x, y⟫ :=
rfl
theorem real_inner_I_smul_self (x : E) :
@Inner.inner ℝ E (Inner.rclikeToReal 𝕜 E) x ((I : 𝕜) • x) = 0 := by
simp [real_inner_eq_re_inner 𝕜, inner_smul_right]
/-- A complex inner product implies a real inner product. This cannot be an instance since it
creates a diamond with `PiLp.innerProductSpace` because `re (sum i, inner (x i) (y i))` and
`sum i, re (inner (x i) (y i))` are not defeq. -/
def InnerProductSpace.complexToReal [SeminormedAddCommGroup G] [InnerProductSpace ℂ G] :
InnerProductSpace ℝ G :=
InnerProductSpace.rclikeToReal ℂ G
instance : InnerProductSpace ℝ ℂ := InnerProductSpace.complexToReal
@[simp]
protected theorem Complex.inner (w z : ℂ) : ⟪w, z⟫_ℝ = (z * conj w).re :=
rfl
end RCLikeToReal
/-- An `RCLike` field is a real inner product space. -/
noncomputable instance RCLike.toInnerProductSpaceReal : InnerProductSpace ℝ 𝕜 where
__ := Inner.rclikeToReal 𝕜 𝕜
norm_sq_eq_re_inner := norm_sq_eq_re_inner
conj_inner_symm x y := inner_re_symm ..
add_left x y z :=
show re (_ * _) = re (_ * _) + re (_ * _) by simp only [map_add, mul_re, conj_re, conj_im]; ring
smul_left x y r :=
show re (_ * _) = _ * re (_ * _) by
simp only [mul_re, conj_re, conj_im, conj_trivial, smul_re, smul_im]; ring
-- The instance above does not create diamonds for concrete `𝕜`:
example : (innerProductSpace : InnerProductSpace ℝ ℝ) = RCLike.toInnerProductSpaceReal := rfl
example :
(instInnerProductSpaceRealComplex : InnerProductSpace ℝ ℂ) = RCLike.toInnerProductSpaceReal := rfl
| Mathlib/Analysis/InnerProductSpace/Basic.lean | 1,914 | 1,917 | |
/-
Copyright (c) 2020 Yury Kudryashov. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yury Kudryashov
-/
import Mathlib.Algebra.Group.Pi.Basic
import Mathlib.Data.Set.BooleanAlgebra
import Mathlib.Data.Set.Piecewise
import Mathlib.Order.Interval.Set.Basic
import Mathlib.Order.Interval.Set.UnorderedInterval
/-!
# Intervals in `pi`-space
In this we prove various simple lemmas about intervals in `Π i, α i`. Closed intervals (`Ici x`,
`Iic x`, `Icc x y`) are equal to products of their projections to `α i`, while (semi-)open intervals
usually include the corresponding products as proper subsets.
-/
-- Porting note: Added, since dot notation no longer works on `Function.update`
open Function
variable {ι : Type*} {α : ι → Type*}
namespace Set
section PiPreorder
variable [∀ i, Preorder (α i)] (x y : ∀ i, α i)
@[simp]
theorem pi_univ_Ici : (pi univ fun i ↦ Ici (x i)) = Ici x :=
ext fun y ↦ by simp [Pi.le_def]
@[simp]
theorem pi_univ_Iic : (pi univ fun i ↦ Iic (x i)) = Iic x :=
ext fun y ↦ by simp [Pi.le_def]
@[simp]
theorem pi_univ_Icc : (pi univ fun i ↦ Icc (x i) (y i)) = Icc x y :=
ext fun y ↦ by simp [Pi.le_def, forall_and]
theorem piecewise_mem_Icc {s : Set ι} [∀ j, Decidable (j ∈ s)] {f₁ f₂ g₁ g₂ : ∀ i, α i}
(h₁ : ∀ i ∈ s, f₁ i ∈ Icc (g₁ i) (g₂ i)) (h₂ : ∀ i ∉ s, f₂ i ∈ Icc (g₁ i) (g₂ i)) :
s.piecewise f₁ f₂ ∈ Icc g₁ g₂ :=
⟨le_piecewise (fun i hi ↦ (h₁ i hi).1) fun i hi ↦ (h₂ i hi).1,
piecewise_le (fun i hi ↦ (h₁ i hi).2) fun i hi ↦ (h₂ i hi).2⟩
theorem piecewise_mem_Icc' {s : Set ι} [∀ j, Decidable (j ∈ s)] {f₁ f₂ g₁ g₂ : ∀ i, α i}
(h₁ : f₁ ∈ Icc g₁ g₂) (h₂ : f₂ ∈ Icc g₁ g₂) : s.piecewise f₁ f₂ ∈ Icc g₁ g₂ :=
piecewise_mem_Icc (fun _ _ ↦ ⟨h₁.1 _, h₁.2 _⟩) fun _ _ ↦ ⟨h₂.1 _, h₂.2 _⟩
section Nonempty
theorem pi_univ_Ioi_subset [Nonempty ι]: (pi univ fun i ↦ Ioi (x i)) ⊆ Ioi x := fun _ hz ↦
⟨fun i ↦ le_of_lt <| hz i trivial, fun h ↦
(‹Nonempty ι›.elim) fun i ↦ not_lt_of_le (h i) (hz i trivial)⟩
theorem pi_univ_Iio_subset [Nonempty ι]: (pi univ fun i ↦ Iio (x i)) ⊆ Iio x :=
pi_univ_Ioi_subset (α := fun i ↦ (α i)ᵒᵈ) x
theorem pi_univ_Ioo_subset [Nonempty ι]: (pi univ fun i ↦ Ioo (x i) (y i)) ⊆ Ioo x y := fun _ hx ↦
⟨(pi_univ_Ioi_subset _) fun i hi ↦ (hx i hi).1, (pi_univ_Iio_subset _) fun i hi ↦ (hx i hi).2⟩
theorem pi_univ_Ioc_subset [Nonempty ι]: (pi univ fun i ↦ Ioc (x i) (y i)) ⊆ Ioc x y := fun _ hx ↦
⟨(pi_univ_Ioi_subset _) fun i hi ↦ (hx i hi).1, fun i ↦ (hx i trivial).2⟩
theorem pi_univ_Ico_subset [Nonempty ι]: (pi univ fun i ↦ Ico (x i) (y i)) ⊆ Ico x y := fun _ hx ↦
⟨fun i ↦ (hx i trivial).1, (pi_univ_Iio_subset _) fun i hi ↦ (hx i hi).2⟩
end Nonempty
variable [DecidableEq ι]
open Function (update)
theorem pi_univ_Ioc_update_left {x y : ∀ i, α i} {i₀ : ι} {m : α i₀} (hm : x i₀ ≤ m) :
(pi univ fun i ↦ Ioc (update x i₀ m i) (y i)) =
{ z | m < z i₀ } ∩ pi univ fun i ↦ Ioc (x i) (y i) := by
have : Ioc m (y i₀) = Ioi m ∩ Ioc (x i₀) (y i₀) := by
rw [← Ioi_inter_Iic, ← Ioi_inter_Iic, ← inter_assoc,
inter_eq_self_of_subset_left (Ioi_subset_Ioi hm)]
simp_rw [univ_pi_update i₀ _ _ fun i z ↦ Ioc z (y i), ← pi_inter_compl ({i₀} : Set ι),
singleton_pi', ← inter_assoc, this]
rfl
theorem pi_univ_Ioc_update_right {x y : ∀ i, α i} {i₀ : ι} {m : α i₀} (hm : m ≤ y i₀) :
(pi univ fun i ↦ Ioc (x i) (update y i₀ m i)) =
{ z | z i₀ ≤ m } ∩ pi univ fun i ↦ Ioc (x i) (y i) := by
have : Ioc (x i₀) m = Iic m ∩ Ioc (x i₀) (y i₀) := by
rw [← Ioi_inter_Iic, ← Ioi_inter_Iic, inter_left_comm,
inter_eq_self_of_subset_left (Iic_subset_Iic.2 hm)]
simp_rw [univ_pi_update i₀ y m fun i z ↦ Ioc (x i) z, ← pi_inter_compl ({i₀} : Set ι),
singleton_pi', ← inter_assoc, this]
rfl
theorem disjoint_pi_univ_Ioc_update_left_right {x y : ∀ i, α i} {i₀ : ι} {m : α i₀} :
Disjoint (pi univ fun i ↦ Ioc (x i) (update y i₀ m i))
(pi univ fun i ↦ Ioc (update x i₀ m i) (y i)) := by
rw [disjoint_left]
rintro z h₁ h₂
refine (h₁ i₀ (mem_univ _)).2.not_lt ?_
simpa only [Function.update_self] using (h₂ i₀ (mem_univ _)).1
end PiPreorder
section PiPartialOrder
variable [DecidableEq ι] [∀ i, PartialOrder (α i)]
-- Porting note: Dot notation on `Function.update` broke
theorem image_update_Icc (f : ∀ i, α i) (i : ι) (a b : α i) :
update f i '' Icc a b = Icc (update f i a) (update f i b) := by
ext x
rw [← Set.pi_univ_Icc]
refine ⟨?_, fun h => ⟨x i, ?_, ?_⟩⟩
· rintro ⟨c, hc, rfl⟩
simpa [update_le_update_iff]
· simpa only [Function.update_self] using h i (mem_univ i)
· ext j
obtain rfl | hij := eq_or_ne i j
· exact Function.update_self ..
· simpa only [Function.update_of_ne hij.symm, le_antisymm_iff] using h j (mem_univ j)
theorem image_update_Ico (f : ∀ i, α i) (i : ι) (a b : α i) :
update f i '' Ico a b = Ico (update f i a) (update f i b) := by
rw [← Icc_diff_right, ← Icc_diff_right, image_diff (update_injective _ _), image_singleton,
image_update_Icc]
theorem image_update_Ioc (f : ∀ i, α i) (i : ι) (a b : α i) :
update f i '' Ioc a b = Ioc (update f i a) (update f i b) := by
rw [← Icc_diff_left, ← Icc_diff_left, image_diff (update_injective _ _), image_singleton,
image_update_Icc]
theorem image_update_Ioo (f : ∀ i, α i) (i : ι) (a b : α i) :
update f i '' Ioo a b = Ioo (update f i a) (update f i b) := by
rw [← Ico_diff_left, ← Ico_diff_left, image_diff (update_injective _ _), image_singleton,
image_update_Ico]
theorem image_update_Icc_left (f : ∀ i, α i) (i : ι) (a : α i) :
update f i '' Icc a (f i) = Icc (update f i a) f := by simpa using image_update_Icc f i a (f i)
theorem image_update_Ico_left (f : ∀ i, α i) (i : ι) (a : α i) :
update f i '' Ico a (f i) = Ico (update f i a) f := by simpa using image_update_Ico f i a (f i)
theorem image_update_Ioc_left (f : ∀ i, α i) (i : ι) (a : α i) :
update f i '' Ioc a (f i) = Ioc (update f i a) f := by simpa using image_update_Ioc f i a (f i)
theorem image_update_Ioo_left (f : ∀ i, α i) (i : ι) (a : α i) :
update f i '' Ioo a (f i) = Ioo (update f i a) f := by simpa using image_update_Ioo f i a (f i)
theorem image_update_Icc_right (f : ∀ i, α i) (i : ι) (b : α i) :
update f i '' Icc (f i) b = Icc f (update f i b) := by simpa using image_update_Icc f i (f i) b
theorem image_update_Ico_right (f : ∀ i, α i) (i : ι) (b : α i) :
update f i '' Ico (f i) b = Ico f (update f i b) := by simpa using image_update_Ico f i (f i) b
theorem image_update_Ioc_right (f : ∀ i, α i) (i : ι) (b : α i) :
update f i '' Ioc (f i) b = Ioc f (update f i b) := by simpa using image_update_Ioc f i (f i) b
theorem image_update_Ioo_right (f : ∀ i, α i) (i : ι) (b : α i) :
update f i '' Ioo (f i) b = Ioo f (update f i b) := by simpa using image_update_Ioo f i (f i) b
| variable [∀ i, One (α i)]
| Mathlib/Order/Interval/Set/Pi.lean | 164 | 165 |
/-
Copyright (c) 2017 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl
-/
import Mathlib.SetTheory.Cardinal.Finite
import Mathlib.Topology.Algebra.InfiniteSum.Basic
import Mathlib.Topology.UniformSpace.Cauchy
import Mathlib.Topology.Algebra.IsUniformGroup.Defs
import Mathlib.Topology.Algebra.Group.Pointwise
/-!
# Infinite sums and products in topological groups
Lemmas on topological sums in groups (as opposed to monoids).
-/
noncomputable section
open Filter Finset Function
open scoped Topology
variable {α β γ : Type*}
section IsTopologicalGroup
variable [CommGroup α] [TopologicalSpace α] [IsTopologicalGroup α]
variable {f g : β → α} {a a₁ a₂ : α}
-- `by simpa using` speeds up elaboration. Why?
@[to_additive]
theorem HasProd.inv (h : HasProd f a) : HasProd (fun b ↦ (f b)⁻¹) a⁻¹ := by
simpa only using h.map (MonoidHom.id α)⁻¹ continuous_inv
@[to_additive]
theorem Multipliable.inv (hf : Multipliable f) : Multipliable fun b ↦ (f b)⁻¹ :=
hf.hasProd.inv.multipliable
@[to_additive]
theorem Multipliable.of_inv (hf : Multipliable fun b ↦ (f b)⁻¹) : Multipliable f := by
simpa only [inv_inv] using hf.inv
@[to_additive]
theorem multipliable_inv_iff : (Multipliable fun b ↦ (f b)⁻¹) ↔ Multipliable f :=
⟨Multipliable.of_inv, Multipliable.inv⟩
@[to_additive]
theorem HasProd.div (hf : HasProd f a₁) (hg : HasProd g a₂) :
HasProd (fun b ↦ f b / g b) (a₁ / a₂) := by
simp only [div_eq_mul_inv]
exact hf.mul hg.inv
@[to_additive]
theorem Multipliable.div (hf : Multipliable f) (hg : Multipliable g) :
Multipliable fun b ↦ f b / g b :=
(hf.hasProd.div hg.hasProd).multipliable
@[to_additive]
theorem Multipliable.trans_div (hg : Multipliable g) (hfg : Multipliable fun b ↦ f b / g b) :
Multipliable f := by
simpa only [div_mul_cancel] using hfg.mul hg
@[to_additive]
theorem multipliable_iff_of_multipliable_div (hfg : Multipliable fun b ↦ f b / g b) :
Multipliable f ↔ Multipliable g :=
⟨fun hf ↦ hf.trans_div <| by simpa only [inv_div] using hfg.inv, fun hg ↦ hg.trans_div hfg⟩
@[to_additive]
theorem HasProd.update (hf : HasProd f a₁) (b : β) [DecidableEq β] (a : α) :
HasProd (update f b a) (a / f b * a₁) := by
convert (hasProd_ite_eq b (a / f b)).mul hf with b'
by_cases h : b' = b
· rw [h, update_self]
simp [eq_self_iff_true, if_true, sub_add_cancel]
· simp only [h, update_of_ne, if_false, Ne, one_mul, not_false_iff]
@[to_additive]
theorem Multipliable.update (hf : Multipliable f) (b : β) [DecidableEq β] (a : α) :
Multipliable (update f b a) :=
(hf.hasProd.update b a).multipliable
@[to_additive]
theorem HasProd.hasProd_compl_iff {s : Set β} (hf : HasProd (f ∘ (↑) : s → α) a₁) :
HasProd (f ∘ (↑) : ↑sᶜ → α) a₂ ↔ HasProd f (a₁ * a₂) := by
refine ⟨fun h ↦ hf.mul_compl h, fun h ↦ ?_⟩
rw [hasProd_subtype_iff_mulIndicator] at hf ⊢
rw [Set.mulIndicator_compl]
simpa only [div_eq_mul_inv, mul_inv_cancel_comm] using h.div hf
@[to_additive]
theorem HasProd.hasProd_iff_compl {s : Set β} (hf : HasProd (f ∘ (↑) : s → α) a₁) :
HasProd f a₂ ↔ HasProd (f ∘ (↑) : ↑sᶜ → α) (a₂ / a₁) :=
Iff.symm <| hf.hasProd_compl_iff.trans <| by rw [mul_div_cancel]
@[to_additive]
theorem Multipliable.multipliable_compl_iff {s : Set β} (hf : Multipliable (f ∘ (↑) : s → α)) :
Multipliable (f ∘ (↑) : ↑sᶜ → α) ↔ Multipliable f where
mp := fun ⟨_, ha⟩ ↦ (hf.hasProd.hasProd_compl_iff.1 ha).multipliable
mpr := fun ⟨_, ha⟩ ↦ (hf.hasProd.hasProd_iff_compl.1 ha).multipliable
@[to_additive]
protected theorem Finset.hasProd_compl_iff (s : Finset β) :
HasProd (fun x : { x // x ∉ s } ↦ f x) a ↔ HasProd f (a * ∏ i ∈ s, f i) :=
(s.hasProd f).hasProd_compl_iff.trans <| by rw [mul_comm]
@[to_additive]
protected theorem Finset.hasProd_iff_compl (s : Finset β) :
HasProd f a ↔ HasProd (fun x : { x // x ∉ s } ↦ f x) (a / ∏ i ∈ s, f i) :=
(s.hasProd f).hasProd_iff_compl
@[to_additive]
protected theorem Finset.multipliable_compl_iff (s : Finset β) :
(Multipliable fun x : { x // x ∉ s } ↦ f x) ↔ Multipliable f :=
(s.multipliable f).multipliable_compl_iff
@[to_additive]
theorem Set.Finite.multipliable_compl_iff {s : Set β} (hs : s.Finite) :
Multipliable (f ∘ (↑) : ↑sᶜ → α) ↔ Multipliable f :=
(hs.multipliable f).multipliable_compl_iff
@[to_additive]
theorem hasProd_ite_div_hasProd [DecidableEq β] (hf : HasProd f a) (b : β) :
HasProd (fun n ↦ ite (n = b) 1 (f n)) (a / f b) := by
convert hf.update b 1 using 1
· ext n
rw [Function.update_apply]
· rw [div_mul_eq_mul_div, one_mul]
/-- A more general version of `Multipliable.congr`, allowing the functions to
disagree on a finite set.
Note that this requires the target to be a group, and hence fails for products valued
in a ring. See `Multipliable.congr_cofinite₀` for a version applying in this case,
with an additional non-vanishing hypothesis.
-/
@[to_additive "A more general version of `Summable.congr`, allowing the functions to
disagree on a finite set."]
theorem Multipliable.congr_cofinite (hf : Multipliable f) (hfg : f =ᶠ[cofinite] g) :
Multipliable g :=
hfg.multipliable_compl_iff.mp <| (hfg.multipliable_compl_iff.mpr hf).congr (by simp)
/-- A more general version of `multipliable_congr`, allowing the functions to
disagree on a finite set. -/
@[to_additive "A more general version of `summable_congr`, allowing the functions to
disagree on a finite set."]
theorem multipliable_congr_cofinite (hfg : f =ᶠ[cofinite] g) :
Multipliable f ↔ Multipliable g :=
⟨fun h ↦ h.congr_cofinite hfg, fun h ↦ h.congr_cofinite (hfg.mono fun _ h' ↦ h'.symm)⟩
|
@[to_additive]
theorem Multipliable.congr_atTop {f₁ g₁ : ℕ → α} (hf : Multipliable f₁) (hfg : f₁ =ᶠ[atTop] g₁) :
Multipliable g₁ := hf.congr_cofinite (Nat.cofinite_eq_atTop ▸ hfg)
| Mathlib/Topology/Algebra/InfiniteSum/Group.lean | 150 | 154 |
/-
Copyright (c) 2022 Yaël Dillies. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yaël Dillies
-/
import Mathlib.Order.PropInstances
import Mathlib.Order.GaloisConnection.Defs
/-!
# Heyting algebras
This file defines Heyting, co-Heyting and bi-Heyting algebras.
A Heyting algebra is a bounded distributive lattice with an implication operation `⇨` such that
`a ≤ b ⇨ c ↔ a ⊓ b ≤ c`. It also comes with a pseudo-complement `ᶜ`, such that `aᶜ = a ⇨ ⊥`.
Co-Heyting algebras are dual to Heyting algebras. They have a difference `\` and a negation `￢`
such that `a \ b ≤ c ↔ a ≤ b ⊔ c` and `￢a = ⊤ \ a`.
Bi-Heyting algebras are Heyting algebras that are also co-Heyting algebras.
From a logic standpoint, Heyting algebras precisely model intuitionistic logic, whereas boolean
algebras model classical logic.
Heyting algebras are the order theoretic equivalent of cartesian-closed categories.
## Main declarations
* `GeneralizedHeytingAlgebra`: Heyting algebra without a top element (nor negation).
* `GeneralizedCoheytingAlgebra`: Co-Heyting algebra without a bottom element (nor complement).
* `HeytingAlgebra`: Heyting algebra.
* `CoheytingAlgebra`: Co-Heyting algebra.
* `BiheytingAlgebra`: bi-Heyting algebra.
## References
* [Francis Borceux, *Handbook of Categorical Algebra III*][borceux-vol3]
## Tags
Heyting, Brouwer, algebra, implication, negation, intuitionistic
-/
assert_not_exists RelIso
open Function OrderDual
universe u
variable {ι α β : Type*}
/-! ### Notation -/
section
variable (α β)
instance Prod.instHImp [HImp α] [HImp β] : HImp (α × β) :=
⟨fun a b => (a.1 ⇨ b.1, a.2 ⇨ b.2)⟩
instance Prod.instHNot [HNot α] [HNot β] : HNot (α × β) :=
⟨fun a => (￢a.1, ￢a.2)⟩
instance Prod.instSDiff [SDiff α] [SDiff β] : SDiff (α × β) :=
⟨fun a b => (a.1 \ b.1, a.2 \ b.2)⟩
instance Prod.instHasCompl [HasCompl α] [HasCompl β] : HasCompl (α × β) :=
⟨fun a => (a.1ᶜ, a.2ᶜ)⟩
end
@[simp]
theorem fst_himp [HImp α] [HImp β] (a b : α × β) : (a ⇨ b).1 = a.1 ⇨ b.1 :=
rfl
@[simp]
theorem snd_himp [HImp α] [HImp β] (a b : α × β) : (a ⇨ b).2 = a.2 ⇨ b.2 :=
rfl
@[simp]
theorem fst_hnot [HNot α] [HNot β] (a : α × β) : (￢a).1 = ￢a.1 :=
rfl
@[simp]
theorem snd_hnot [HNot α] [HNot β] (a : α × β) : (￢a).2 = ￢a.2 :=
rfl
@[simp]
theorem fst_sdiff [SDiff α] [SDiff β] (a b : α × β) : (a \ b).1 = a.1 \ b.1 :=
rfl
@[simp]
theorem snd_sdiff [SDiff α] [SDiff β] (a b : α × β) : (a \ b).2 = a.2 \ b.2 :=
rfl
@[simp]
theorem fst_compl [HasCompl α] [HasCompl β] (a : α × β) : aᶜ.1 = a.1ᶜ :=
rfl
@[simp]
theorem snd_compl [HasCompl α] [HasCompl β] (a : α × β) : aᶜ.2 = a.2ᶜ :=
rfl
namespace Pi
variable {π : ι → Type*}
instance [∀ i, HImp (π i)] : HImp (∀ i, π i) :=
⟨fun a b i => a i ⇨ b i⟩
instance [∀ i, HNot (π i)] : HNot (∀ i, π i) :=
⟨fun a i => ￢a i⟩
theorem himp_def [∀ i, HImp (π i)] (a b : ∀ i, π i) : a ⇨ b = fun i => a i ⇨ b i :=
rfl
theorem hnot_def [∀ i, HNot (π i)] (a : ∀ i, π i) : ￢a = fun i => ￢a i :=
rfl
@[simp]
theorem himp_apply [∀ i, HImp (π i)] (a b : ∀ i, π i) (i : ι) : (a ⇨ b) i = a i ⇨ b i :=
rfl
@[simp]
theorem hnot_apply [∀ i, HNot (π i)] (a : ∀ i, π i) (i : ι) : (￢a) i = ￢a i :=
rfl
end Pi
/-- A generalized Heyting algebra is a lattice with an additional binary operation `⇨` called
Heyting implication such that `(a ⇨ ·)` is right adjoint to `(a ⊓ ·)`.
This generalizes `HeytingAlgebra` by not requiring a bottom element. -/
class GeneralizedHeytingAlgebra (α : Type*) extends Lattice α, OrderTop α, HImp α where
/-- `(a ⇨ ·)` is right adjoint to `(a ⊓ ·)` -/
le_himp_iff (a b c : α) : a ≤ b ⇨ c ↔ a ⊓ b ≤ c
/-- A generalized co-Heyting algebra is a lattice with an additional binary
difference operation `\` such that `(· \ a)` is left adjoint to `(· ⊔ a)`.
This generalizes `CoheytingAlgebra` by not requiring a top element. -/
class GeneralizedCoheytingAlgebra (α : Type*) extends Lattice α, OrderBot α, SDiff α where
/-- `(· \ a)` is left adjoint to `(· ⊔ a)` -/
sdiff_le_iff (a b c : α) : a \ b ≤ c ↔ a ≤ b ⊔ c
/-- A Heyting algebra is a bounded lattice with an additional binary operation `⇨` called Heyting
implication such that `(a ⇨ ·)` is right adjoint to `(a ⊓ ·)`. -/
class HeytingAlgebra (α : Type*) extends GeneralizedHeytingAlgebra α, OrderBot α, HasCompl α where
/-- `aᶜ` is defined as `a ⇨ ⊥` -/
himp_bot (a : α) : a ⇨ ⊥ = aᶜ
/-- A co-Heyting algebra is a bounded lattice with an additional binary difference operation `\`
such that `(· \ a)` is left adjoint to `(· ⊔ a)`. -/
class CoheytingAlgebra (α : Type*) extends GeneralizedCoheytingAlgebra α, OrderTop α, HNot α where
/-- `⊤ \ a` is `￢a` -/
top_sdiff (a : α) : ⊤ \ a = ￢a
/-- A bi-Heyting algebra is a Heyting algebra that is also a co-Heyting algebra. -/
class BiheytingAlgebra (α : Type*) extends HeytingAlgebra α, SDiff α, HNot α where
/-- `(· \ a)` is left adjoint to `(· ⊔ a)` -/
sdiff_le_iff (a b c : α) : a \ b ≤ c ↔ a ≤ b ⊔ c
/-- `⊤ \ a` is `￢a` -/
top_sdiff (a : α) : ⊤ \ a = ￢a
-- See note [lower instance priority]
attribute [instance 100] GeneralizedHeytingAlgebra.toOrderTop
attribute [instance 100] GeneralizedCoheytingAlgebra.toOrderBot
-- See note [lower instance priority]
instance (priority := 100) HeytingAlgebra.toBoundedOrder [HeytingAlgebra α] : BoundedOrder α :=
{ bot_le := ‹HeytingAlgebra α›.bot_le }
-- See note [lower instance priority]
instance (priority := 100) CoheytingAlgebra.toBoundedOrder [CoheytingAlgebra α] : BoundedOrder α :=
{ ‹CoheytingAlgebra α› with }
-- See note [lower instance priority]
instance (priority := 100) BiheytingAlgebra.toCoheytingAlgebra [BiheytingAlgebra α] :
CoheytingAlgebra α :=
{ ‹BiheytingAlgebra α› with }
-- See note [reducible non-instances]
/-- Construct a Heyting algebra from the lattice structure and Heyting implication alone. -/
abbrev HeytingAlgebra.ofHImp [DistribLattice α] [BoundedOrder α] (himp : α → α → α)
(le_himp_iff : ∀ a b c, a ≤ himp b c ↔ a ⊓ b ≤ c) : HeytingAlgebra α :=
{ ‹DistribLattice α›, ‹BoundedOrder α› with
himp,
compl := fun a => himp a ⊥,
le_himp_iff,
himp_bot := fun _ => rfl }
-- See note [reducible non-instances]
/-- Construct a Heyting algebra from the lattice structure and complement operator alone. -/
abbrev HeytingAlgebra.ofCompl [DistribLattice α] [BoundedOrder α] (compl : α → α)
(le_himp_iff : ∀ a b c, a ≤ compl b ⊔ c ↔ a ⊓ b ≤ c) : HeytingAlgebra α where
himp := (compl · ⊔ ·)
compl := compl
le_himp_iff := le_himp_iff
himp_bot _ := sup_bot_eq _
-- See note [reducible non-instances]
/-- Construct a co-Heyting algebra from the lattice structure and the difference alone. -/
abbrev CoheytingAlgebra.ofSDiff [DistribLattice α] [BoundedOrder α] (sdiff : α → α → α)
(sdiff_le_iff : ∀ a b c, sdiff a b ≤ c ↔ a ≤ b ⊔ c) : CoheytingAlgebra α :=
{ ‹DistribLattice α›, ‹BoundedOrder α› with
sdiff,
hnot := fun a => sdiff ⊤ a,
sdiff_le_iff,
top_sdiff := fun _ => rfl }
-- See note [reducible non-instances]
/-- Construct a co-Heyting algebra from the difference and Heyting negation alone. -/
abbrev CoheytingAlgebra.ofHNot [DistribLattice α] [BoundedOrder α] (hnot : α → α)
(sdiff_le_iff : ∀ a b c, a ⊓ hnot b ≤ c ↔ a ≤ b ⊔ c) : CoheytingAlgebra α where
sdiff a b := a ⊓ hnot b
hnot := hnot
sdiff_le_iff := sdiff_le_iff
top_sdiff _ := top_inf_eq _
/-! In this section, we'll give interpretations of these results in the Heyting algebra model of
intuitionistic logic,- where `≤` can be interpreted as "validates", `⇨` as "implies", `⊓` as "and",
`⊔` as "or", `⊥` as "false" and `⊤` as "true". Note that we confuse `→` and `⊢` because those are
the same in this logic.
See also `Prop.heytingAlgebra`. -/
section GeneralizedHeytingAlgebra
variable [GeneralizedHeytingAlgebra α] {a b c d : α}
/-- `p → q → r ↔ p ∧ q → r` -/
@[simp]
theorem le_himp_iff : a ≤ b ⇨ c ↔ a ⊓ b ≤ c :=
GeneralizedHeytingAlgebra.le_himp_iff _ _ _
/-- `p → q → r ↔ q ∧ p → r` -/
theorem le_himp_iff' : a ≤ b ⇨ c ↔ b ⊓ a ≤ c := by rw [le_himp_iff, inf_comm]
/-- `p → q → r ↔ q → p → r` -/
theorem le_himp_comm : a ≤ b ⇨ c ↔ b ≤ a ⇨ c := by rw [le_himp_iff, le_himp_iff']
/-- `p → q → p` -/
theorem le_himp : a ≤ b ⇨ a :=
le_himp_iff.2 inf_le_left
/-- `p → p → q ↔ p → q` -/
theorem le_himp_iff_left : a ≤ a ⇨ b ↔ a ≤ b := by rw [le_himp_iff, inf_idem]
/-- `p → p` -/
@[simp]
theorem himp_self : a ⇨ a = ⊤ :=
top_le_iff.1 <| le_himp_iff.2 inf_le_right
/-- `(p → q) ∧ p → q` -/
theorem himp_inf_le : (a ⇨ b) ⊓ a ≤ b :=
le_himp_iff.1 le_rfl
/-- `p ∧ (p → q) → q` -/
theorem inf_himp_le : a ⊓ (a ⇨ b) ≤ b := by rw [inf_comm, ← le_himp_iff]
/-- `p ∧ (p → q) ↔ p ∧ q` -/
@[simp]
theorem inf_himp (a b : α) : a ⊓ (a ⇨ b) = a ⊓ b :=
le_antisymm (le_inf inf_le_left <| by rw [inf_comm, ← le_himp_iff]) <| inf_le_inf_left _ le_himp
/-- `(p → q) ∧ p ↔ q ∧ p` -/
@[simp]
theorem himp_inf_self (a b : α) : (a ⇨ b) ⊓ a = b ⊓ a := by rw [inf_comm, inf_himp, inf_comm]
/-- The **deduction theorem** in the Heyting algebra model of intuitionistic logic:
an implication holds iff the conclusion follows from the hypothesis. -/
@[simp]
theorem himp_eq_top_iff : a ⇨ b = ⊤ ↔ a ≤ b := by rw [← top_le_iff, le_himp_iff, top_inf_eq]
/-- `p → true`, `true → p ↔ p` -/
@[simp]
theorem himp_top : a ⇨ ⊤ = ⊤ :=
himp_eq_top_iff.2 le_top
@[simp]
theorem top_himp : ⊤ ⇨ a = a :=
eq_of_forall_le_iff fun b => by rw [le_himp_iff, inf_top_eq]
/-- `p → q → r ↔ p ∧ q → r` -/
theorem himp_himp (a b c : α) : a ⇨ b ⇨ c = a ⊓ b ⇨ c :=
eq_of_forall_le_iff fun d => by simp_rw [le_himp_iff, inf_assoc]
/-- `(q → r) → (p → q) → q → r` -/
theorem himp_le_himp_himp_himp : b ⇨ c ≤ (a ⇨ b) ⇨ a ⇨ c := by
rw [le_himp_iff, le_himp_iff, inf_assoc, himp_inf_self, ← inf_assoc, himp_inf_self, inf_assoc]
exact inf_le_left
@[simp]
theorem himp_inf_himp_inf_le : (b ⇨ c) ⊓ (a ⇨ b) ⊓ a ≤ c := by
simpa using @himp_le_himp_himp_himp
/-- `p → q → r ↔ q → p → r` -/
theorem himp_left_comm (a b c : α) : a ⇨ b ⇨ c = b ⇨ a ⇨ c := by simp_rw [himp_himp, inf_comm]
@[simp]
theorem himp_idem : b ⇨ b ⇨ a = b ⇨ a := by rw [himp_himp, inf_idem]
theorem himp_inf_distrib (a b c : α) : a ⇨ b ⊓ c = (a ⇨ b) ⊓ (a ⇨ c) :=
eq_of_forall_le_iff fun d => by simp_rw [le_himp_iff, le_inf_iff, le_himp_iff]
theorem sup_himp_distrib (a b c : α) : a ⊔ b ⇨ c = (a ⇨ c) ⊓ (b ⇨ c) :=
eq_of_forall_le_iff fun d => by
rw [le_inf_iff, le_himp_comm, sup_le_iff]
simp_rw [le_himp_comm]
theorem himp_le_himp_left (h : a ≤ b) : c ⇨ a ≤ c ⇨ b :=
le_himp_iff.2 <| himp_inf_le.trans h
theorem himp_le_himp_right (h : a ≤ b) : b ⇨ c ≤ a ⇨ c :=
le_himp_iff.2 <| (inf_le_inf_left _ h).trans himp_inf_le
theorem himp_le_himp (hab : a ≤ b) (hcd : c ≤ d) : b ⇨ c ≤ a ⇨ d :=
(himp_le_himp_right hab).trans <| himp_le_himp_left hcd
@[simp]
theorem sup_himp_self_left (a b : α) : a ⊔ b ⇨ a = b ⇨ a := by
rw [sup_himp_distrib, himp_self, top_inf_eq]
@[simp]
theorem sup_himp_self_right (a b : α) : a ⊔ b ⇨ b = a ⇨ b := by
rw [sup_himp_distrib, himp_self, inf_top_eq]
theorem Codisjoint.himp_eq_right (h : Codisjoint a b) : b ⇨ a = a := by
conv_rhs => rw [← @top_himp _ _ a]
rw [← h.eq_top, sup_himp_self_left]
theorem Codisjoint.himp_eq_left (h : Codisjoint a b) : a ⇨ b = b :=
h.symm.himp_eq_right
theorem Codisjoint.himp_inf_cancel_right (h : Codisjoint a b) : a ⇨ a ⊓ b = b := by
rw [himp_inf_distrib, himp_self, top_inf_eq, h.himp_eq_left]
theorem Codisjoint.himp_inf_cancel_left (h : Codisjoint a b) : b ⇨ a ⊓ b = a := by
rw [himp_inf_distrib, himp_self, inf_top_eq, h.himp_eq_right]
/-- See `himp_le` for a stronger version in Boolean algebras. -/
theorem Codisjoint.himp_le_of_right_le (hac : Codisjoint a c) (hba : b ≤ a) : c ⇨ b ≤ a :=
(himp_le_himp_left hba).trans_eq hac.himp_eq_right
theorem le_himp_himp : a ≤ (a ⇨ b) ⇨ b :=
le_himp_iff.2 inf_himp_le
@[simp] lemma himp_eq_himp_iff : b ⇨ a = a ⇨ b ↔ a = b := by simp [le_antisymm_iff]
lemma himp_ne_himp_iff : b ⇨ a ≠ a ⇨ b ↔ a ≠ b := himp_eq_himp_iff.not
theorem himp_triangle (a b c : α) : (a ⇨ b) ⊓ (b ⇨ c) ≤ a ⇨ c := by
rw [le_himp_iff, inf_right_comm, ← le_himp_iff]
exact himp_inf_le.trans le_himp_himp
theorem himp_inf_himp_cancel (hba : b ≤ a) (hcb : c ≤ b) : (a ⇨ b) ⊓ (b ⇨ c) = a ⇨ c :=
(himp_triangle _ _ _).antisymm <| le_inf (himp_le_himp_left hcb) (himp_le_himp_right hba)
theorem gc_inf_himp : GaloisConnection (a ⊓ ·) (a ⇨ ·) :=
fun _ _ ↦ Iff.symm le_himp_iff'
-- See note [lower instance priority]
instance (priority := 100) GeneralizedHeytingAlgebra.toDistribLattice : DistribLattice α :=
DistribLattice.ofInfSupLe fun a b c => by
simp_rw [inf_comm a, ← le_himp_iff, sup_le_iff, le_himp_iff, ← sup_le_iff]; rfl
instance OrderDual.instGeneralizedCoheytingAlgebra : GeneralizedCoheytingAlgebra αᵒᵈ where
sdiff a b := toDual (ofDual b ⇨ ofDual a)
sdiff_le_iff a b c := by rw [sup_comm]; exact le_himp_iff
instance Prod.instGeneralizedHeytingAlgebra [GeneralizedHeytingAlgebra β] :
GeneralizedHeytingAlgebra (α × β) where
le_himp_iff _ _ _ := and_congr le_himp_iff le_himp_iff
instance Pi.instGeneralizedHeytingAlgebra {α : ι → Type*} [∀ i, GeneralizedHeytingAlgebra (α i)] :
GeneralizedHeytingAlgebra (∀ i, α i) where
le_himp_iff i := by simp [le_def]
end GeneralizedHeytingAlgebra
section GeneralizedCoheytingAlgebra
variable [GeneralizedCoheytingAlgebra α] {a b c d : α}
@[simp]
theorem sdiff_le_iff : a \ b ≤ c ↔ a ≤ b ⊔ c :=
GeneralizedCoheytingAlgebra.sdiff_le_iff _ _ _
theorem sdiff_le_iff' : a \ b ≤ c ↔ a ≤ c ⊔ b := by rw [sdiff_le_iff, sup_comm]
theorem sdiff_le_comm : a \ b ≤ c ↔ a \ c ≤ b := by rw [sdiff_le_iff, sdiff_le_iff']
theorem sdiff_le : a \ b ≤ a :=
sdiff_le_iff.2 le_sup_right
theorem Disjoint.disjoint_sdiff_left (h : Disjoint a b) : Disjoint (a \ c) b :=
h.mono_left sdiff_le
theorem Disjoint.disjoint_sdiff_right (h : Disjoint a b) : Disjoint a (b \ c) :=
h.mono_right sdiff_le
theorem sdiff_le_iff_left : a \ b ≤ b ↔ a ≤ b := by rw [sdiff_le_iff, sup_idem]
@[simp]
theorem sdiff_self : a \ a = ⊥ :=
le_bot_iff.1 <| sdiff_le_iff.2 le_sup_left
theorem le_sup_sdiff : a ≤ b ⊔ a \ b :=
sdiff_le_iff.1 le_rfl
theorem le_sdiff_sup : a ≤ a \ b ⊔ b := by rw [sup_comm, ← sdiff_le_iff]
theorem sup_sdiff_left : a ⊔ a \ b = a :=
sup_of_le_left sdiff_le
theorem sup_sdiff_right : a \ b ⊔ a = a :=
sup_of_le_right sdiff_le
theorem inf_sdiff_left : a \ b ⊓ a = a \ b :=
inf_of_le_left sdiff_le
theorem inf_sdiff_right : a ⊓ a \ b = a \ b :=
inf_of_le_right sdiff_le
@[simp]
theorem sup_sdiff_self (a b : α) : a ⊔ b \ a = a ⊔ b :=
le_antisymm (sup_le_sup_left sdiff_le _) (sup_le le_sup_left le_sup_sdiff)
@[simp]
theorem sdiff_sup_self (a b : α) : b \ a ⊔ a = b ⊔ a := by rw [sup_comm, sup_sdiff_self, sup_comm]
alias sup_sdiff_self_left := sdiff_sup_self
alias sup_sdiff_self_right := sup_sdiff_self
theorem sup_sdiff_eq_sup (h : c ≤ a) : a ⊔ b \ c = a ⊔ b :=
sup_congr_left (sdiff_le.trans le_sup_right) <| le_sup_sdiff.trans <| sup_le_sup_right h _
-- cf. `Set.union_diff_cancel'`
theorem sup_sdiff_cancel' (hab : a ≤ b) (hbc : b ≤ c) : b ⊔ c \ a = c := by
rw [sup_sdiff_eq_sup hab, sup_of_le_right hbc]
theorem sup_sdiff_cancel_right (h : a ≤ b) : a ⊔ b \ a = b :=
sup_sdiff_cancel' le_rfl h
theorem sdiff_sup_cancel (h : b ≤ a) : a \ b ⊔ b = a := by rw [sup_comm, sup_sdiff_cancel_right h]
theorem sup_le_of_le_sdiff_left (h : b ≤ c \ a) (hac : a ≤ c) : a ⊔ b ≤ c :=
sup_le hac <| h.trans sdiff_le
theorem sup_le_of_le_sdiff_right (h : a ≤ c \ b) (hbc : b ≤ c) : a ⊔ b ≤ c :=
sup_le (h.trans sdiff_le) hbc
@[simp]
theorem sdiff_eq_bot_iff : a \ b = ⊥ ↔ a ≤ b := by rw [← le_bot_iff, sdiff_le_iff, sup_bot_eq]
@[simp]
theorem sdiff_bot : a \ ⊥ = a :=
eq_of_forall_ge_iff fun b => by rw [sdiff_le_iff, bot_sup_eq]
@[simp]
theorem bot_sdiff : ⊥ \ a = ⊥ :=
sdiff_eq_bot_iff.2 bot_le
theorem sdiff_sdiff_sdiff_le_sdiff : (a \ b) \ (a \ c) ≤ c \ b := by
rw [sdiff_le_iff, sdiff_le_iff, sup_left_comm, sup_sdiff_self, sup_left_comm, sdiff_sup_self,
sup_left_comm]
exact le_sup_left
@[simp]
theorem le_sup_sdiff_sup_sdiff : a ≤ b ⊔ (a \ c ⊔ c \ b) := by
simpa using @sdiff_sdiff_sdiff_le_sdiff
theorem sdiff_sdiff (a b c : α) : (a \ b) \ c = a \ (b ⊔ c) :=
eq_of_forall_ge_iff fun d => by simp_rw [sdiff_le_iff, sup_assoc]
theorem sdiff_sdiff_left : (a \ b) \ c = a \ (b ⊔ c) :=
sdiff_sdiff _ _ _
theorem sdiff_right_comm (a b c : α) : (a \ b) \ c = (a \ c) \ b := by
simp_rw [sdiff_sdiff, sup_comm]
theorem sdiff_sdiff_comm : (a \ b) \ c = (a \ c) \ b :=
sdiff_right_comm _ _ _
@[simp]
theorem sdiff_idem : (a \ b) \ b = a \ b := by rw [sdiff_sdiff_left, sup_idem]
@[simp]
theorem sdiff_sdiff_self : (a \ b) \ a = ⊥ := by rw [sdiff_sdiff_comm, sdiff_self, bot_sdiff]
theorem sup_sdiff_distrib (a b c : α) : (a ⊔ b) \ c = a \ c ⊔ b \ c :=
eq_of_forall_ge_iff fun d => by simp_rw [sdiff_le_iff, sup_le_iff, sdiff_le_iff]
theorem sdiff_inf_distrib (a b c : α) : a \ (b ⊓ c) = a \ b ⊔ a \ c :=
eq_of_forall_ge_iff fun d => by
rw [sup_le_iff, sdiff_le_comm, le_inf_iff]
simp_rw [sdiff_le_comm]
theorem sup_sdiff : (a ⊔ b) \ c = a \ c ⊔ b \ c :=
sup_sdiff_distrib _ _ _
@[simp]
theorem sup_sdiff_right_self : (a ⊔ b) \ b = a \ b := by rw [sup_sdiff, sdiff_self, sup_bot_eq]
@[simp]
theorem sup_sdiff_left_self : (a ⊔ b) \ a = b \ a := by rw [sup_comm, sup_sdiff_right_self]
@[gcongr]
theorem sdiff_le_sdiff_right (h : a ≤ b) : a \ c ≤ b \ c :=
sdiff_le_iff.2 <| h.trans <| le_sup_sdiff
@[gcongr]
theorem sdiff_le_sdiff_left (h : a ≤ b) : c \ b ≤ c \ a :=
sdiff_le_iff.2 <| le_sup_sdiff.trans <| sup_le_sup_right h _
@[gcongr]
theorem sdiff_le_sdiff (hab : a ≤ b) (hcd : c ≤ d) : a \ d ≤ b \ c :=
(sdiff_le_sdiff_right hab).trans <| sdiff_le_sdiff_left hcd
-- cf. `IsCompl.inf_sup`
theorem sdiff_inf : a \ (b ⊓ c) = a \ b ⊔ a \ c :=
sdiff_inf_distrib _ _ _
@[simp]
theorem sdiff_inf_self_left (a b : α) : a \ (a ⊓ b) = a \ b := by
rw [sdiff_inf, sdiff_self, bot_sup_eq]
@[simp]
theorem sdiff_inf_self_right (a b : α) : b \ (a ⊓ b) = b \ a := by
rw [sdiff_inf, sdiff_self, sup_bot_eq]
theorem Disjoint.sdiff_eq_left (h : Disjoint a b) : a \ b = a := by
conv_rhs => rw [← @sdiff_bot _ _ a]
rw [← h.eq_bot, sdiff_inf_self_left]
theorem Disjoint.sdiff_eq_right (h : Disjoint a b) : b \ a = b :=
h.symm.sdiff_eq_left
theorem Disjoint.sup_sdiff_cancel_left (h : Disjoint a b) : (a ⊔ b) \ a = b := by
rw [sup_sdiff, sdiff_self, bot_sup_eq, h.sdiff_eq_right]
theorem Disjoint.sup_sdiff_cancel_right (h : Disjoint a b) : (a ⊔ b) \ b = a := by
rw [sup_sdiff, sdiff_self, sup_bot_eq, h.sdiff_eq_left]
/-- See `le_sdiff` for a stronger version in generalised Boolean algebras. -/
theorem Disjoint.le_sdiff_of_le_left (hac : Disjoint a c) (hab : a ≤ b) : a ≤ b \ c :=
hac.sdiff_eq_left.ge.trans <| sdiff_le_sdiff_right hab
theorem sdiff_sdiff_le : a \ (a \ b) ≤ b :=
sdiff_le_iff.2 le_sdiff_sup
@[simp] lemma sdiff_eq_sdiff_iff : a \ b = b \ a ↔ a = b := by simp [le_antisymm_iff]
lemma sdiff_ne_sdiff_iff : a \ b ≠ b \ a ↔ a ≠ b := sdiff_eq_sdiff_iff.not
theorem sdiff_triangle (a b c : α) : a \ c ≤ a \ b ⊔ b \ c := by
rw [sdiff_le_iff, sup_left_comm, ← sdiff_le_iff]
exact sdiff_sdiff_le.trans le_sup_sdiff
theorem sdiff_sup_sdiff_cancel (hba : b ≤ a) (hcb : c ≤ b) : a \ b ⊔ b \ c = a \ c :=
(sdiff_triangle _ _ _).antisymm' <| sup_le (sdiff_le_sdiff_left hcb) (sdiff_le_sdiff_right hba)
/-- a version of `sdiff_sup_sdiff_cancel` with more general hypotheses. -/
theorem sdiff_sup_sdiff_cancel' (hinf : a ⊓ c ≤ b) (hsup : b ≤ a ⊔ c) :
a \ b ⊔ b \ c = a \ c := by
refine (sdiff_triangle ..).antisymm' <| sup_le ?_ <| by simpa [sup_comm]
rw [← sdiff_inf_self_left (b := c)]
exact sdiff_le_sdiff_left hinf
theorem sdiff_le_sdiff_of_sup_le_sup_left (h : c ⊔ a ≤ c ⊔ b) : a \ c ≤ b \ c := by
rw [← sup_sdiff_left_self, ← @sup_sdiff_left_self _ _ _ b]
exact sdiff_le_sdiff_right h
theorem sdiff_le_sdiff_of_sup_le_sup_right (h : a ⊔ c ≤ b ⊔ c) : a \ c ≤ b \ c := by
rw [← sup_sdiff_right_self, ← @sup_sdiff_right_self _ _ b]
exact sdiff_le_sdiff_right h
@[simp]
theorem inf_sdiff_sup_left : a \ c ⊓ (a ⊔ b) = a \ c :=
inf_of_le_left <| sdiff_le.trans le_sup_left
@[simp]
theorem inf_sdiff_sup_right : a \ c ⊓ (b ⊔ a) = a \ c :=
inf_of_le_left <| sdiff_le.trans le_sup_right
theorem gc_sdiff_sup : GaloisConnection (· \ a) (a ⊔ ·) :=
fun _ _ ↦ sdiff_le_iff
-- See note [lower instance priority]
instance (priority := 100) GeneralizedCoheytingAlgebra.toDistribLattice : DistribLattice α :=
{ ‹GeneralizedCoheytingAlgebra α› with
le_sup_inf :=
fun a b c => by simp_rw [← sdiff_le_iff, le_inf_iff, sdiff_le_iff, ← le_inf_iff]; rfl }
instance OrderDual.instGeneralizedHeytingAlgebra : GeneralizedHeytingAlgebra αᵒᵈ where
himp := fun a b => toDual (ofDual b \ ofDual a)
le_himp_iff := fun a b c => by rw [inf_comm]; exact sdiff_le_iff
instance Prod.instGeneralizedCoheytingAlgebra [GeneralizedCoheytingAlgebra β] :
GeneralizedCoheytingAlgebra (α × β) where
sdiff_le_iff _ _ _ := and_congr sdiff_le_iff sdiff_le_iff
instance Pi.instGeneralizedCoheytingAlgebra {α : ι → Type*}
[∀ i, GeneralizedCoheytingAlgebra (α i)] : GeneralizedCoheytingAlgebra (∀ i, α i) where
sdiff_le_iff i := by simp [le_def]
end GeneralizedCoheytingAlgebra
section HeytingAlgebra
variable [HeytingAlgebra α] {a b : α}
@[simp]
theorem himp_bot (a : α) : a ⇨ ⊥ = aᶜ :=
HeytingAlgebra.himp_bot _
@[simp]
theorem bot_himp (a : α) : ⊥ ⇨ a = ⊤ :=
himp_eq_top_iff.2 bot_le
theorem compl_sup_distrib (a b : α) : (a ⊔ b)ᶜ = aᶜ ⊓ bᶜ := by
simp_rw [← himp_bot, sup_himp_distrib]
@[simp]
theorem compl_sup : (a ⊔ b)ᶜ = aᶜ ⊓ bᶜ :=
compl_sup_distrib _ _
theorem compl_le_himp : aᶜ ≤ a ⇨ b :=
(himp_bot _).ge.trans <| himp_le_himp_left bot_le
theorem compl_sup_le_himp : aᶜ ⊔ b ≤ a ⇨ b :=
sup_le compl_le_himp le_himp
theorem sup_compl_le_himp : b ⊔ aᶜ ≤ a ⇨ b :=
sup_le le_himp compl_le_himp
-- `p → ¬ p ↔ ¬ p`
@[simp]
theorem himp_compl (a : α) : a ⇨ aᶜ = aᶜ := by rw [← himp_bot, himp_himp, inf_idem]
-- `p → ¬ q ↔ q → ¬ p`
theorem himp_compl_comm (a b : α) : a ⇨ bᶜ = b ⇨ aᶜ := by simp_rw [← himp_bot, himp_left_comm]
theorem le_compl_iff_disjoint_right : a ≤ bᶜ ↔ Disjoint a b := by
rw [← himp_bot, le_himp_iff, disjoint_iff_inf_le]
theorem le_compl_iff_disjoint_left : a ≤ bᶜ ↔ Disjoint b a :=
| le_compl_iff_disjoint_right.trans disjoint_comm
| Mathlib/Order/Heyting/Basic.lean | 645 | 646 |
/-
Copyright (c) 2024 Lean FRO. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kim Morrison
-/
import Mathlib.Data.List.InsertIdx
/-!
This is a stub file for importing `Mathlib.Data.List.InsertNth`,
which has been renamed to `Mathlib.Data.List.InsertIdx`.
This file can be removed once the deprecation for `List.insertNth` is removed.
-/
| Mathlib/Data/List/InsertNth.lean | 213 | 217 | |
/-
Copyright (c) 2018 Mario Carneiro. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Mario Carneiro, Kevin Kappelmann
-/
import Mathlib.Algebra.Order.Floor.Defs
import Mathlib.Algebra.Order.Floor.Ring
import Mathlib.Algebra.Order.Floor.Semiring
deprecated_module (since := "2025-04-13")
| Mathlib/Algebra/Order/Floor.lean | 1,281 | 1,283 | |
/-
Copyright (c) 2020 Kenny Lau. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kenny Lau, Ken Lee, Chris Hughes
-/
import Mathlib.Algebra.Group.Action.Units
import Mathlib.Algebra.Group.Nat.Units
import Mathlib.Algebra.GroupWithZero.Divisibility
import Mathlib.Algebra.Ring.Divisibility.Basic
import Mathlib.Algebra.Ring.Hom.Defs
import Mathlib.Logic.Basic
import Mathlib.Tactic.Ring
/-!
# Coprime elements of a ring or monoid
## Main definition
* `IsCoprime x y`: that `x` and `y` are coprime, defined to be the existence of `a` and `b` such
that `a * x + b * y = 1`. Note that elements with no common divisors (`IsRelPrime`) are not
necessarily coprime, e.g., the multivariate polynomials `x₁` and `x₂` are not coprime.
The two notions are equivalent in Bézout rings, see `isRelPrime_iff_isCoprime`.
This file also contains lemmas about `IsRelPrime` parallel to `IsCoprime`.
See also `RingTheory.Coprime.Lemmas` for further development of coprime elements.
-/
universe u v
section CommSemiring
variable {R : Type u} [CommSemiring R] (x y z : R)
/-- The proposition that `x` and `y` are coprime, defined to be the existence of `a` and `b` such
that `a * x + b * y = 1`. Note that elements with no common divisors are not necessarily coprime,
e.g., the multivariate polynomials `x₁` and `x₂` are not coprime. -/
def IsCoprime : Prop :=
∃ a b, a * x + b * y = 1
variable {x y z}
@[symm]
theorem IsCoprime.symm (H : IsCoprime x y) : IsCoprime y x :=
let ⟨a, b, H⟩ := H
⟨b, a, by rw [add_comm, H]⟩
theorem isCoprime_comm : IsCoprime x y ↔ IsCoprime y x :=
⟨IsCoprime.symm, IsCoprime.symm⟩
theorem isCoprime_self : IsCoprime x x ↔ IsUnit x :=
⟨fun ⟨a, b, h⟩ => isUnit_of_mul_eq_one x (a + b) <| by rwa [mul_comm, add_mul], fun h =>
let ⟨b, hb⟩ := isUnit_iff_exists_inv'.1 h
⟨b, 0, by rwa [zero_mul, add_zero]⟩⟩
theorem isCoprime_zero_left : IsCoprime 0 x ↔ IsUnit x :=
⟨fun ⟨a, b, H⟩ => isUnit_of_mul_eq_one x b <| by rwa [mul_zero, zero_add, mul_comm] at H, fun H =>
let ⟨b, hb⟩ := isUnit_iff_exists_inv'.1 H
⟨1, b, by rwa [one_mul, zero_add]⟩⟩
theorem isCoprime_zero_right : IsCoprime x 0 ↔ IsUnit x :=
isCoprime_comm.trans isCoprime_zero_left
theorem not_isCoprime_zero_zero [Nontrivial R] : ¬IsCoprime (0 : R) 0 :=
mt isCoprime_zero_right.mp not_isUnit_zero
lemma IsCoprime.intCast {R : Type*} [CommRing R] {a b : ℤ} (h : IsCoprime a b) :
IsCoprime (a : R) (b : R) := by
rcases h with ⟨u, v, H⟩
use u, v
rw_mod_cast [H]
exact Int.cast_one
/-- If a 2-vector `p` satisfies `IsCoprime (p 0) (p 1)`, then `p ≠ 0`. -/
theorem IsCoprime.ne_zero [Nontrivial R] {p : Fin 2 → R} (h : IsCoprime (p 0) (p 1)) : p ≠ 0 := by
rintro rfl
exact not_isCoprime_zero_zero h
theorem IsCoprime.ne_zero_or_ne_zero [Nontrivial R] (h : IsCoprime x y) : x ≠ 0 ∨ y ≠ 0 := by
apply not_or_of_imp
rintro rfl rfl
exact not_isCoprime_zero_zero h
theorem isCoprime_one_left : IsCoprime 1 x :=
⟨1, 0, by rw [one_mul, zero_mul, add_zero]⟩
theorem isCoprime_one_right : IsCoprime x 1 :=
⟨0, 1, by rw [one_mul, zero_mul, zero_add]⟩
theorem IsCoprime.dvd_of_dvd_mul_right (H1 : IsCoprime x z) (H2 : x ∣ y * z) : x ∣ y := by
let ⟨a, b, H⟩ := H1
rw [← mul_one y, ← H, mul_add, ← mul_assoc, mul_left_comm]
exact dvd_add (dvd_mul_left _ _) (H2.mul_left _)
theorem IsCoprime.dvd_of_dvd_mul_left (H1 : IsCoprime x y) (H2 : x ∣ y * z) : x ∣ z := by
let ⟨a, b, H⟩ := H1
rw [← one_mul z, ← H, add_mul, mul_right_comm, mul_assoc b]
exact dvd_add (dvd_mul_left _ _) (H2.mul_left _)
theorem IsCoprime.mul_left (H1 : IsCoprime x z) (H2 : IsCoprime y z) : IsCoprime (x * y) z :=
let ⟨a, b, h1⟩ := H1
let ⟨c, d, h2⟩ := H2
⟨a * c, a * x * d + b * c * y + b * d * z,
calc a * c * (x * y) + (a * x * d + b * c * y + b * d * z) * z
_ = (a * x + b * z) * (c * y + d * z) := by ring
_ = 1 := by rw [h1, h2, mul_one]
⟩
theorem IsCoprime.mul_right (H1 : IsCoprime x y) (H2 : IsCoprime x z) : IsCoprime x (y * z) := by
rw [isCoprime_comm] at H1 H2 ⊢
exact H1.mul_left H2
| theorem IsCoprime.mul_dvd (H : IsCoprime x y) (H1 : x ∣ z) (H2 : y ∣ z) : x * y ∣ z := by
obtain ⟨a, b, h⟩ := H
rw [← mul_one z, ← h, mul_add]
apply dvd_add
· rw [mul_comm z, mul_assoc]
exact (mul_dvd_mul_left _ H2).mul_left _
· rw [mul_comm b, ← mul_assoc]
exact (mul_dvd_mul_right H1 _).mul_right _
| Mathlib/RingTheory/Coprime/Basic.lean | 114 | 121 |
/-
Copyright (c) 2021 Kim Morrison. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johan Commelin, Kim Morrison
-/
import Mathlib.Algebra.Homology.ComplexShape
import Mathlib.CategoryTheory.Subobject.Limits
import Mathlib.CategoryTheory.GradedObject
import Mathlib.Algebra.Homology.ShortComplex.Basic
/-!
# Homological complexes.
A `HomologicalComplex V c` with a "shape" controlled by `c : ComplexShape ι`
has chain groups `X i` (objects in `V`) indexed by `i : ι`,
and a differential `d i j` whenever `c.Rel i j`.
We in fact ask for differentials `d i j` for all `i j : ι`,
but have a field `shape` requiring that these are zero when not allowed by `c`.
This avoids a lot of dependent type theory hell!
The composite of any two differentials `d i j ≫ d j k` must be zero.
We provide `ChainComplex V α` for
`α`-indexed chain complexes in which `d i j ≠ 0` only if `j + 1 = i`,
and similarly `CochainComplex V α`, with `i = j + 1`.
There is a category structure, where morphisms are chain maps.
For `C : HomologicalComplex V c`, we define `C.xNext i`, which is either `C.X j` for some
arbitrarily chosen `j` such that `c.r i j`, or `C.X i` if there is no such `j`.
Similarly we have `C.xPrev j`.
Defined in terms of these we have `C.dFrom i : C.X i ⟶ C.xNext i` and
`C.dTo j : C.xPrev j ⟶ C.X j`, which are either defined as `C.d i j`, or zero, as needed.
-/
universe v u
open CategoryTheory CategoryTheory.Category CategoryTheory.Limits
variable {ι : Type*}
variable (V : Type u) [Category.{v} V] [HasZeroMorphisms V]
/-- A `HomologicalComplex V c` with a "shape" controlled by `c : ComplexShape ι`
has chain groups `X i` (objects in `V`) indexed by `i : ι`,
and a differential `d i j` whenever `c.Rel i j`.
We in fact ask for differentials `d i j` for all `i j : ι`,
but have a field `shape` requiring that these are zero when not allowed by `c`.
This avoids a lot of dependent type theory hell!
The composite of any two differentials `d i j ≫ d j k` must be zero.
-/
structure HomologicalComplex (c : ComplexShape ι) where
X : ι → V
d : ∀ i j, X i ⟶ X j
shape : ∀ i j, ¬c.Rel i j → d i j = 0 := by aesop_cat
d_comp_d' : ∀ i j k, c.Rel i j → c.Rel j k → d i j ≫ d j k = 0 := by aesop_cat
namespace HomologicalComplex
attribute [simp] shape
variable {V} {c : ComplexShape ι}
@[reassoc (attr := simp)]
theorem d_comp_d (C : HomologicalComplex V c) (i j k : ι) : C.d i j ≫ C.d j k = 0 := by
by_cases hij : c.Rel i j
· by_cases hjk : c.Rel j k
· exact C.d_comp_d' i j k hij hjk
· rw [C.shape j k hjk, comp_zero]
· rw [C.shape i j hij, zero_comp]
theorem ext {C₁ C₂ : HomologicalComplex V c} (h_X : C₁.X = C₂.X)
(h_d :
∀ i j : ι,
c.Rel i j → C₁.d i j ≫ eqToHom (congr_fun h_X j) = eqToHom (congr_fun h_X i) ≫ C₂.d i j) :
C₁ = C₂ := by
obtain ⟨X₁, d₁, s₁, h₁⟩ := C₁
obtain ⟨X₂, d₂, s₂, h₂⟩ := C₂
dsimp at h_X
subst h_X
simp only [mk.injEq, heq_eq_eq, true_and]
ext i j
by_cases hij : c.Rel i j
· simpa only [comp_id, id_comp, eqToHom_refl] using h_d i j hij
· rw [s₁ i j hij, s₂ i j hij]
/-- The obvious isomorphism `K.X p ≅ K.X q` when `p = q`. -/
def XIsoOfEq (K : HomologicalComplex V c) {p q : ι} (h : p = q) : K.X p ≅ K.X q :=
eqToIso (by rw [h])
@[simp]
lemma XIsoOfEq_rfl (K : HomologicalComplex V c) (p : ι) :
K.XIsoOfEq (rfl : p = p) = Iso.refl _ := rfl
@[reassoc (attr := simp)]
lemma XIsoOfEq_hom_comp_XIsoOfEq_hom (K : HomologicalComplex V c) {p₁ p₂ p₃ : ι}
(h₁₂ : p₁ = p₂) (h₂₃ : p₂ = p₃) :
(K.XIsoOfEq h₁₂).hom ≫ (K.XIsoOfEq h₂₃).hom = (K.XIsoOfEq (h₁₂.trans h₂₃)).hom := by
dsimp [XIsoOfEq]
simp only [eqToHom_trans]
@[reassoc (attr := simp)]
lemma XIsoOfEq_hom_comp_XIsoOfEq_inv (K : HomologicalComplex V c) {p₁ p₂ p₃ : ι}
(h₁₂ : p₁ = p₂) (h₃₂ : p₃ = p₂) :
(K.XIsoOfEq h₁₂).hom ≫ (K.XIsoOfEq h₃₂).inv = (K.XIsoOfEq (h₁₂.trans h₃₂.symm)).hom := by
dsimp [XIsoOfEq]
simp only [eqToHom_trans]
@[reassoc (attr := simp)]
lemma XIsoOfEq_inv_comp_XIsoOfEq_hom (K : HomologicalComplex V c) {p₁ p₂ p₃ : ι}
(h₂₁ : p₂ = p₁) (h₂₃ : p₂ = p₃) :
(K.XIsoOfEq h₂₁).inv ≫ (K.XIsoOfEq h₂₃).hom = (K.XIsoOfEq (h₂₁.symm.trans h₂₃)).hom := by
dsimp [XIsoOfEq]
simp only [eqToHom_trans]
@[reassoc (attr := simp)]
lemma XIsoOfEq_inv_comp_XIsoOfEq_inv (K : HomologicalComplex V c) {p₁ p₂ p₃ : ι}
(h₂₁ : p₂ = p₁) (h₃₂ : p₃ = p₂) :
(K.XIsoOfEq h₂₁).inv ≫ (K.XIsoOfEq h₃₂).inv = (K.XIsoOfEq (h₃₂.trans h₂₁).symm).hom := by
dsimp [XIsoOfEq]
simp only [eqToHom_trans]
@[reassoc (attr := simp)]
lemma XIsoOfEq_hom_comp_d (K : HomologicalComplex V c) {p₁ p₂ : ι} (h : p₁ = p₂) (p₃ : ι) :
(K.XIsoOfEq h).hom ≫ K.d p₂ p₃ = K.d p₁ p₃ := by subst h; simp
@[reassoc (attr := simp)]
lemma XIsoOfEq_inv_comp_d (K : HomologicalComplex V c) {p₂ p₁ : ι} (h : p₂ = p₁) (p₃ : ι) :
(K.XIsoOfEq h).inv ≫ K.d p₂ p₃ = K.d p₁ p₃ := by subst h; simp
@[reassoc (attr := simp)]
lemma d_comp_XIsoOfEq_hom (K : HomologicalComplex V c) {p₂ p₃ : ι} (h : p₂ = p₃) (p₁ : ι) :
K.d p₁ p₂ ≫ (K.XIsoOfEq h).hom = K.d p₁ p₃ := by subst h; simp
@[reassoc (attr := simp)]
lemma d_comp_XIsoOfEq_inv (K : HomologicalComplex V c) {p₂ p₃ : ι} (h : p₃ = p₂) (p₁ : ι) :
K.d p₁ p₂ ≫ (K.XIsoOfEq h).inv = K.d p₁ p₃ := by subst h; simp
end HomologicalComplex
/-- An `α`-indexed chain complex is a `HomologicalComplex`
in which `d i j ≠ 0` only if `j + 1 = i`.
-/
abbrev ChainComplex (α : Type*) [AddRightCancelSemigroup α] [One α] : Type _ :=
HomologicalComplex V (ComplexShape.down α)
/-- An `α`-indexed cochain complex is a `HomologicalComplex`
in which `d i j ≠ 0` only if `i + 1 = j`.
-/
abbrev CochainComplex (α : Type*) [AddRightCancelSemigroup α] [One α] : Type _ :=
HomologicalComplex V (ComplexShape.up α)
namespace ChainComplex
@[simp]
theorem prev (α : Type*) [AddRightCancelSemigroup α] [One α] (i : α) :
(ComplexShape.down α).prev i = i + 1 :=
(ComplexShape.down α).prev_eq' rfl
@[simp]
theorem next (α : Type*) [AddGroup α] [One α] (i : α) : (ComplexShape.down α).next i = i - 1 :=
(ComplexShape.down α).next_eq' <| sub_add_cancel _ _
@[simp]
theorem next_nat_zero : (ComplexShape.down ℕ).next 0 = 0 := by
classical
refine dif_neg ?_
push_neg
intro
apply Nat.noConfusion
@[simp]
theorem next_nat_succ (i : ℕ) : (ComplexShape.down ℕ).next (i + 1) = i :=
(ComplexShape.down ℕ).next_eq' rfl
end ChainComplex
namespace CochainComplex
@[simp]
theorem prev (α : Type*) [AddGroup α] [One α] (i : α) : (ComplexShape.up α).prev i = i - 1 :=
(ComplexShape.up α).prev_eq' <| sub_add_cancel _ _
@[simp]
theorem next (α : Type*) [AddRightCancelSemigroup α] [One α] (i : α) :
(ComplexShape.up α).next i = i + 1 :=
(ComplexShape.up α).next_eq' rfl
@[simp]
theorem prev_nat_zero : (ComplexShape.up ℕ).prev 0 = 0 := by
classical
refine dif_neg ?_
push_neg
intro
apply Nat.noConfusion
@[simp]
theorem prev_nat_succ (i : ℕ) : (ComplexShape.up ℕ).prev (i + 1) = i :=
(ComplexShape.up ℕ).prev_eq' rfl
end CochainComplex
namespace HomologicalComplex
variable {V}
variable {c : ComplexShape ι} (C : HomologicalComplex V c)
/-- A morphism of homological complexes consists of maps between the chain groups,
commuting with the differentials.
-/
@[ext]
structure Hom (A B : HomologicalComplex V c) where
f : ∀ i, A.X i ⟶ B.X i
comm' : ∀ i j, c.Rel i j → f i ≫ B.d i j = A.d i j ≫ f j := by aesop_cat
@[reassoc (attr := simp)]
theorem Hom.comm {A B : HomologicalComplex V c} (f : A.Hom B) (i j : ι) :
f.f i ≫ B.d i j = A.d i j ≫ f.f j := by
by_cases hij : c.Rel i j
· exact f.comm' i j hij
· rw [A.shape i j hij, B.shape i j hij, comp_zero, zero_comp]
instance (A B : HomologicalComplex V c) : Inhabited (Hom A B) :=
⟨{ f := fun _ => 0 }⟩
/-- Identity chain map. -/
def id (A : HomologicalComplex V c) : Hom A A where f _ := 𝟙 _
/-- Composition of chain maps. -/
def comp (A B C : HomologicalComplex V c) (φ : Hom A B) (ψ : Hom B C) : Hom A C where
f i := φ.f i ≫ ψ.f i
section
attribute [local simp] id comp
instance : Category (HomologicalComplex V c) where
Hom := Hom
id := id
comp := comp _ _ _
end
@[ext]
lemma hom_ext {C D : HomologicalComplex V c} (f g : C ⟶ D)
(h : ∀ i, f.f i = g.f i) : f = g := by
apply Hom.ext
funext
apply h
@[simp]
theorem id_f (C : HomologicalComplex V c) (i : ι) : Hom.f (𝟙 C) i = 𝟙 (C.X i) :=
rfl
@[simp, reassoc]
theorem comp_f {C₁ C₂ C₃ : HomologicalComplex V c} (f : C₁ ⟶ C₂) (g : C₂ ⟶ C₃) (i : ι) :
(f ≫ g).f i = f.f i ≫ g.f i :=
rfl
@[simp]
theorem eqToHom_f {C₁ C₂ : HomologicalComplex V c} (h : C₁ = C₂) (n : ι) :
HomologicalComplex.Hom.f (eqToHom h) n =
eqToHom (congr_fun (congr_arg HomologicalComplex.X h) n) := by
subst h
rfl
-- We'll use this later to show that `HomologicalComplex V c` is preadditive when `V` is.
theorem hom_f_injective {C₁ C₂ : HomologicalComplex V c} :
Function.Injective fun f : Hom C₁ C₂ => f.f := by aesop_cat
instance (X Y : HomologicalComplex V c) : Zero (X ⟶ Y) :=
⟨{ f := fun _ => 0}⟩
@[simp]
theorem zero_f (C D : HomologicalComplex V c) (i : ι) : (0 : C ⟶ D).f i = 0 :=
rfl
instance : HasZeroMorphisms (HomologicalComplex V c) where
open ZeroObject
/-- The zero complex -/
noncomputable def zero [HasZeroObject V] : HomologicalComplex V c where
X _ := 0
d _ _ := 0
theorem isZero_zero [HasZeroObject V] : IsZero (zero : HomologicalComplex V c) := by
refine ⟨fun X => ⟨⟨⟨0⟩, fun f => ?_⟩⟩, fun X => ⟨⟨⟨0⟩, fun f => ?_⟩⟩⟩
all_goals
ext
dsimp only [zero]
subsingleton
instance [HasZeroObject V] : HasZeroObject (HomologicalComplex V c) :=
⟨⟨zero, isZero_zero⟩⟩
noncomputable instance [HasZeroObject V] : Inhabited (HomologicalComplex V c) :=
⟨zero⟩
theorem congr_hom {C D : HomologicalComplex V c} {f g : C ⟶ D} (w : f = g) (i : ι) :
f.f i = g.f i :=
congr_fun (congr_arg Hom.f w) i
lemma mono_of_mono_f {K L : HomologicalComplex V c} (φ : K ⟶ L)
(hφ : ∀ i, Mono (φ.f i)) : Mono φ where
right_cancellation g h eq := by
ext i
rw [← cancel_mono (φ.f i)]
exact congr_hom eq i
lemma epi_of_epi_f {K L : HomologicalComplex V c} (φ : K ⟶ L)
(hφ : ∀ i, Epi (φ.f i)) : Epi φ where
left_cancellation g h eq := by
ext i
rw [← cancel_epi (φ.f i)]
exact congr_hom eq i
section
variable (V c)
/-- The functor picking out the `i`-th object of a complex. -/
@[simps]
def eval (i : ι) : HomologicalComplex V c ⥤ V where
obj C := C.X i
map f := f.f i
instance (i : ι) : (eval V c i).PreservesZeroMorphisms where
/-- The functor forgetting the differential in a complex, obtaining a graded object. -/
@[simps]
def forget : HomologicalComplex V c ⥤ GradedObject ι V where
obj C := C.X
map f := f.f
instance : (forget V c).Faithful where
map_injective h := by
ext i
exact congr_fun h i
/-- Forgetting the differentials than picking out the `i`-th object is the same as
just picking out the `i`-th object. -/
@[simps!]
def forgetEval (i : ι) : forget V c ⋙ GradedObject.eval i ≅ eval V c i :=
NatIso.ofComponents fun _ => Iso.refl _
end
noncomputable section
@[reassoc]
lemma XIsoOfEq_hom_naturality {K L : HomologicalComplex V c} (φ : K ⟶ L) {n n' : ι} (h : n = n') :
φ.f n ≫ (L.XIsoOfEq h).hom = (K.XIsoOfEq h).hom ≫ φ.f n' := by subst h; simp
@[reassoc]
lemma XIsoOfEq_inv_naturality {K L : HomologicalComplex V c} (φ : K ⟶ L) {n n' : ι} (h : n = n') :
φ.f n' ≫ (L.XIsoOfEq h).inv = (K.XIsoOfEq h).inv ≫ φ.f n := by subst h; simp
-- Porting note: removed @[simp] as the linter complained
/-- If `C.d i j` and `C.d i j'` are both allowed, then we must have `j = j'`,
and so the differentials only differ by an `eqToHom`.
-/
theorem d_comp_eqToHom {i j j' : ι} (rij : c.Rel i j) (rij' : c.Rel i j') :
C.d i j' ≫ eqToHom (congr_arg C.X (c.next_eq rij' rij)) = C.d i j := by
obtain rfl := c.next_eq rij rij'
simp only [eqToHom_refl, comp_id]
-- Porting note: removed @[simp] as the linter complained
/-- If `C.d i j` and `C.d i' j` are both allowed, then we must have `i = i'`,
and so the differentials only differ by an `eqToHom`.
-/
theorem eqToHom_comp_d {i i' j : ι} (rij : c.Rel i j) (rij' : c.Rel i' j) :
eqToHom (congr_arg C.X (c.prev_eq rij rij')) ≫ C.d i' j = C.d i j := by
obtain rfl := c.prev_eq rij rij'
simp only [eqToHom_refl, id_comp]
theorem kernel_eq_kernel [HasKernels V] {i j j' : ι} (r : c.Rel i j) (r' : c.Rel i j') :
kernelSubobject (C.d i j) = kernelSubobject (C.d i j') := by
rw [← d_comp_eqToHom C r r']
apply kernelSubobject_comp_mono
theorem image_eq_image [HasImages V] [HasEqualizers V] {i i' j : ι} (r : c.Rel i j)
(r' : c.Rel i' j) : imageSubobject (C.d i j) = imageSubobject (C.d i' j) := by
rw [← eqToHom_comp_d C r r']
apply imageSubobject_iso_comp
section
/-- Either `C.X i`, if there is some `i` with `c.Rel i j`, or `C.X j`. -/
abbrev xPrev (j : ι) : V :=
C.X (c.prev j)
/-- If `c.Rel i j`, then `C.xPrev j` is isomorphic to `C.X i`. -/
def xPrevIso {i j : ι} (r : c.Rel i j) : C.xPrev j ≅ C.X i :=
eqToIso <| by rw [← c.prev_eq' r]
/-- If there is no `i` so `c.Rel i j`, then `C.xPrev j` is isomorphic to `C.X j`. -/
def xPrevIsoSelf {j : ι} (h : ¬c.Rel (c.prev j) j) : C.xPrev j ≅ C.X j :=
eqToIso <|
congr_arg C.X
(by
dsimp [ComplexShape.prev]
rw [dif_neg]
push_neg; intro i hi
have : c.prev j = i := c.prev_eq' hi
rw [this] at h; contradiction)
/-- Either `C.X j`, if there is some `j` with `c.rel i j`, or `C.X i`. -/
abbrev xNext (i : ι) : V :=
C.X (c.next i)
/-- If `c.Rel i j`, then `C.xNext i` is isomorphic to `C.X j`. -/
def xNextIso {i j : ι} (r : c.Rel i j) : C.xNext i ≅ C.X j :=
eqToIso <| by rw [← c.next_eq' r]
/-- If there is no `j` so `c.Rel i j`, then `C.xNext i` is isomorphic to `C.X i`. -/
def xNextIsoSelf {i : ι} (h : ¬c.Rel i (c.next i)) : C.xNext i ≅ C.X i :=
eqToIso <|
congr_arg C.X
(by
dsimp [ComplexShape.next]
rw [dif_neg]; rintro ⟨j, hj⟩
have : c.next i = j := c.next_eq' hj
rw [this] at h; contradiction)
/-- The differential mapping into `C.X j`, or zero if there isn't one.
-/
abbrev dTo (j : ι) : C.xPrev j ⟶ C.X j :=
C.d (c.prev j) j
/-- The differential mapping out of `C.X i`, or zero if there isn't one.
-/
abbrev dFrom (i : ι) : C.X i ⟶ C.xNext i :=
C.d i (c.next i)
theorem dTo_eq {i j : ι} (r : c.Rel i j) : C.dTo j = (C.xPrevIso r).hom ≫ C.d i j := by
obtain rfl := c.prev_eq' r
exact (Category.id_comp _).symm
@[simp]
theorem dTo_eq_zero {j : ι} (h : ¬c.Rel (c.prev j) j) : C.dTo j = 0 :=
C.shape _ _ h
theorem dFrom_eq {i j : ι} (r : c.Rel i j) : C.dFrom i = C.d i j ≫ (C.xNextIso r).inv := by
obtain rfl := c.next_eq' r
exact (Category.comp_id _).symm
@[simp]
theorem dFrom_eq_zero {i : ι} (h : ¬c.Rel i (c.next i)) : C.dFrom i = 0 :=
C.shape _ _ h
@[reassoc (attr := simp)]
theorem xPrevIso_comp_dTo {i j : ι} (r : c.Rel i j) : (C.xPrevIso r).inv ≫ C.dTo j = C.d i j := by
simp [C.dTo_eq r]
@[reassoc (attr := simp)]
theorem xPrevIsoSelf_comp_dTo {j : ι} (h : ¬c.Rel (c.prev j) j) :
(C.xPrevIsoSelf h).inv ≫ C.dTo j = 0 := by simp [h]
@[reassoc (attr := simp)]
theorem dFrom_comp_xNextIso {i j : ι} (r : c.Rel i j) :
C.dFrom i ≫ (C.xNextIso r).hom = C.d i j := by
simp [C.dFrom_eq r]
@[reassoc (attr := simp)]
theorem dFrom_comp_xNextIsoSelf {i : ι} (h : ¬c.Rel i (c.next i)) :
C.dFrom i ≫ (C.xNextIsoSelf h).hom = 0 := by simp [h]
-- This is not a simp lemma; the LHS already simplifies.
theorem dTo_comp_dFrom (j : ι) : C.dTo j ≫ C.dFrom j = 0 :=
C.d_comp_d _ _ _
theorem kernel_from_eq_kernel [HasKernels V] {i j : ι} (r : c.Rel i j) :
kernelSubobject (C.dFrom i) = kernelSubobject (C.d i j) := by
rw [C.dFrom_eq r]
apply kernelSubobject_comp_mono
theorem image_to_eq_image [HasImages V] [HasEqualizers V] {i j : ι} (r : c.Rel i j) :
imageSubobject (C.dTo j) = imageSubobject (C.d i j) := by
rw [C.dTo_eq r]
apply imageSubobject_iso_comp
end
namespace Hom
variable {C₁ C₂ C₃ : HomologicalComplex V c}
/-- The `i`-th component of an isomorphism of chain complexes. -/
@[simps!]
def isoApp (f : C₁ ≅ C₂) (i : ι) : C₁.X i ≅ C₂.X i :=
(eval V c i).mapIso f
/-- Construct an isomorphism of chain complexes from isomorphism of the objects
which commute with the differentials. -/
@[simps]
def isoOfComponents (f : ∀ i, C₁.X i ≅ C₂.X i)
(hf : ∀ i j, c.Rel i j → (f i).hom ≫ C₂.d i j = C₁.d i j ≫ (f j).hom := by aesop_cat) :
C₁ ≅ C₂ where
hom :=
{ f := fun i => (f i).hom
comm' := hf }
inv :=
{ f := fun i => (f i).inv
comm' := fun i j hij =>
calc
(f i).inv ≫ C₁.d i j = (f i).inv ≫ (C₁.d i j ≫ (f j).hom) ≫ (f j).inv := by simp
_ = (f i).inv ≫ ((f i).hom ≫ C₂.d i j) ≫ (f j).inv := by rw [hf i j hij]
_ = C₂.d i j ≫ (f j).inv := by simp }
hom_inv_id := by
ext i
exact (f i).hom_inv_id
inv_hom_id := by
ext i
exact (f i).inv_hom_id
@[simp]
theorem isoOfComponents_app (f : ∀ i, C₁.X i ≅ C₂.X i)
(hf : ∀ i j, c.Rel i j → (f i).hom ≫ C₂.d i j = C₁.d i j ≫ (f j).hom) (i : ι) :
isoApp (isoOfComponents f hf) i = f i := by
ext
simp
|
theorem isIso_of_components (f : C₁ ⟶ C₂) [∀ n : ι, IsIso (f.f n)] : IsIso f :=
| Mathlib/Algebra/Homology/HomologicalComplex.lean | 526 | 527 |
/-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.Field.NegOnePow
import Mathlib.Algebra.Field.Periodic
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.SpecialFunctions.Exp
/-!
# Trigonometric functions
## Main definitions
This file contains the definition of `π`.
See also `Analysis.SpecialFunctions.Trigonometric.Inverse` and
`Analysis.SpecialFunctions.Trigonometric.Arctan` for the inverse trigonometric functions.
See also `Analysis.SpecialFunctions.Complex.Arg` and
`Analysis.SpecialFunctions.Complex.Log` for the complex argument function
and the complex logarithm.
## Main statements
Many basic inequalities on the real trigonometric functions are established.
The continuity of the usual trigonometric functions is proved.
Several facts about the real trigonometric functions have the proofs deferred to
`Analysis.SpecialFunctions.Trigonometric.Complex`,
as they are most easily proved by appealing to the corresponding fact for
complex trigonometric functions.
See also `Analysis.SpecialFunctions.Trigonometric.Chebyshev` for the multiple angle formulas
in terms of Chebyshev polynomials.
## Tags
sin, cos, tan, angle
-/
noncomputable section
open Topology Filter Set
namespace Complex
@[continuity, fun_prop]
theorem continuous_sin : Continuous sin := by
change Continuous fun z => (exp (-z * I) - exp (z * I)) * I / 2
fun_prop
@[fun_prop]
theorem continuousOn_sin {s : Set ℂ} : ContinuousOn sin s :=
continuous_sin.continuousOn
@[continuity, fun_prop]
theorem continuous_cos : Continuous cos := by
change Continuous fun z => (exp (z * I) + exp (-z * I)) / 2
fun_prop
@[fun_prop]
theorem continuousOn_cos {s : Set ℂ} : ContinuousOn cos s :=
continuous_cos.continuousOn
@[continuity, fun_prop]
theorem continuous_sinh : Continuous sinh := by
change Continuous fun z => (exp z - exp (-z)) / 2
fun_prop
@[continuity, fun_prop]
theorem continuous_cosh : Continuous cosh := by
change Continuous fun z => (exp z + exp (-z)) / 2
fun_prop
end Complex
namespace Real
variable {x y z : ℝ}
@[continuity, fun_prop]
theorem continuous_sin : Continuous sin :=
Complex.continuous_re.comp (Complex.continuous_sin.comp Complex.continuous_ofReal)
@[fun_prop]
theorem continuousOn_sin {s} : ContinuousOn sin s :=
continuous_sin.continuousOn
@[continuity, fun_prop]
theorem continuous_cos : Continuous cos :=
Complex.continuous_re.comp (Complex.continuous_cos.comp Complex.continuous_ofReal)
@[fun_prop]
theorem continuousOn_cos {s} : ContinuousOn cos s :=
continuous_cos.continuousOn
@[continuity, fun_prop]
theorem continuous_sinh : Continuous sinh :=
Complex.continuous_re.comp (Complex.continuous_sinh.comp Complex.continuous_ofReal)
@[continuity, fun_prop]
theorem continuous_cosh : Continuous cosh :=
Complex.continuous_re.comp (Complex.continuous_cosh.comp Complex.continuous_ofReal)
end Real
namespace Real
theorem exists_cos_eq_zero : 0 ∈ cos '' Icc (1 : ℝ) 2 :=
intermediate_value_Icc' (by norm_num) continuousOn_cos
⟨le_of_lt cos_two_neg, le_of_lt cos_one_pos⟩
/-- The number π = 3.14159265... Defined here using choice as twice a zero of cos in [1,2], from
which one can derive all its properties. For explicit bounds on π, see `Data.Real.Pi.Bounds`.
Denoted `π`, once the `Real` namespace is opened. -/
protected noncomputable def pi : ℝ :=
2 * Classical.choose exists_cos_eq_zero
@[inherit_doc]
scoped notation "π" => Real.pi
@[simp]
theorem cos_pi_div_two : cos (π / 2) = 0 := by
rw [Real.pi, mul_div_cancel_left₀ _ (two_ne_zero' ℝ)]
exact (Classical.choose_spec exists_cos_eq_zero).2
theorem one_le_pi_div_two : (1 : ℝ) ≤ π / 2 := by
rw [Real.pi, mul_div_cancel_left₀ _ (two_ne_zero' ℝ)]
exact (Classical.choose_spec exists_cos_eq_zero).1.1
theorem pi_div_two_le_two : π / 2 ≤ 2 := by
rw [Real.pi, mul_div_cancel_left₀ _ (two_ne_zero' ℝ)]
exact (Classical.choose_spec exists_cos_eq_zero).1.2
theorem two_le_pi : (2 : ℝ) ≤ π :=
(div_le_div_iff_of_pos_right (show (0 : ℝ) < 2 by norm_num)).1
(by rw [div_self (two_ne_zero' ℝ)]; exact one_le_pi_div_two)
theorem pi_le_four : π ≤ 4 :=
(div_le_div_iff_of_pos_right (show (0 : ℝ) < 2 by norm_num)).1
(calc
π / 2 ≤ 2 := pi_div_two_le_two
_ = 4 / 2 := by norm_num)
@[bound]
theorem pi_pos : 0 < π :=
lt_of_lt_of_le (by norm_num) two_le_pi
@[bound]
theorem pi_nonneg : 0 ≤ π :=
pi_pos.le
theorem pi_ne_zero : π ≠ 0 :=
pi_pos.ne'
theorem pi_div_two_pos : 0 < π / 2 :=
half_pos pi_pos
theorem two_pi_pos : 0 < 2 * π := by linarith [pi_pos]
end Real
namespace Mathlib.Meta.Positivity
open Lean.Meta Qq
/-- Extension for the `positivity` tactic: `π` is always positive. -/
@[positivity Real.pi]
def evalRealPi : PositivityExt where eval {u α} _zα _pα e := do
match u, α, e with
| 0, ~q(ℝ), ~q(Real.pi) =>
assertInstancesCommute
pure (.positive q(Real.pi_pos))
| _, _, _ => throwError "not Real.pi"
end Mathlib.Meta.Positivity
namespace NNReal
open Real
open Real NNReal
/-- `π` considered as a nonnegative real. -/
noncomputable def pi : ℝ≥0 :=
⟨π, Real.pi_pos.le⟩
@[simp]
theorem coe_real_pi : (pi : ℝ) = π :=
rfl
theorem pi_pos : 0 < pi := mod_cast Real.pi_pos
theorem pi_ne_zero : pi ≠ 0 :=
pi_pos.ne'
end NNReal
namespace Real
@[simp]
theorem sin_pi : sin π = 0 := by
rw [← mul_div_cancel_left₀ π (two_ne_zero' ℝ), two_mul, add_div, sin_add, cos_pi_div_two]; simp
@[simp]
theorem cos_pi : cos π = -1 := by
rw [← mul_div_cancel_left₀ π (two_ne_zero' ℝ), mul_div_assoc, cos_two_mul, cos_pi_div_two]
norm_num
@[simp]
theorem sin_two_pi : sin (2 * π) = 0 := by simp [two_mul, sin_add]
@[simp]
theorem cos_two_pi : cos (2 * π) = 1 := by simp [two_mul, cos_add]
theorem sin_antiperiodic : Function.Antiperiodic sin π := by simp [sin_add]
theorem sin_periodic : Function.Periodic sin (2 * π) :=
sin_antiperiodic.periodic_two_mul
@[simp]
theorem sin_add_pi (x : ℝ) : sin (x + π) = -sin x :=
sin_antiperiodic x
@[simp]
theorem sin_add_two_pi (x : ℝ) : sin (x + 2 * π) = sin x :=
sin_periodic x
@[simp]
theorem sin_sub_pi (x : ℝ) : sin (x - π) = -sin x :=
sin_antiperiodic.sub_eq x
@[simp]
theorem sin_sub_two_pi (x : ℝ) : sin (x - 2 * π) = sin x :=
sin_periodic.sub_eq x
@[simp]
theorem sin_pi_sub (x : ℝ) : sin (π - x) = sin x :=
neg_neg (sin x) ▸ sin_neg x ▸ sin_antiperiodic.sub_eq'
@[simp]
theorem sin_two_pi_sub (x : ℝ) : sin (2 * π - x) = -sin x :=
sin_neg x ▸ sin_periodic.sub_eq'
@[simp]
theorem sin_nat_mul_pi (n : ℕ) : sin (n * π) = 0 :=
sin_antiperiodic.nat_mul_eq_of_eq_zero sin_zero n
@[simp]
theorem sin_int_mul_pi (n : ℤ) : sin (n * π) = 0 :=
sin_antiperiodic.int_mul_eq_of_eq_zero sin_zero n
@[simp]
theorem sin_add_nat_mul_two_pi (x : ℝ) (n : ℕ) : sin (x + n * (2 * π)) = sin x :=
sin_periodic.nat_mul n x
@[simp]
theorem sin_add_int_mul_two_pi (x : ℝ) (n : ℤ) : sin (x + n * (2 * π)) = sin x :=
sin_periodic.int_mul n x
@[simp]
theorem sin_sub_nat_mul_two_pi (x : ℝ) (n : ℕ) : sin (x - n * (2 * π)) = sin x :=
sin_periodic.sub_nat_mul_eq n
@[simp]
theorem sin_sub_int_mul_two_pi (x : ℝ) (n : ℤ) : sin (x - n * (2 * π)) = sin x :=
sin_periodic.sub_int_mul_eq n
@[simp]
theorem sin_nat_mul_two_pi_sub (x : ℝ) (n : ℕ) : sin (n * (2 * π) - x) = -sin x :=
sin_neg x ▸ sin_periodic.nat_mul_sub_eq n
@[simp]
theorem sin_int_mul_two_pi_sub (x : ℝ) (n : ℤ) : sin (n * (2 * π) - x) = -sin x :=
sin_neg x ▸ sin_periodic.int_mul_sub_eq n
theorem sin_add_int_mul_pi (x : ℝ) (n : ℤ) : sin (x + n * π) = (-1) ^ n * sin x :=
n.cast_negOnePow ℝ ▸ sin_antiperiodic.add_int_mul_eq n
theorem sin_add_nat_mul_pi (x : ℝ) (n : ℕ) : sin (x + n * π) = (-1) ^ n * sin x :=
sin_antiperiodic.add_nat_mul_eq n
theorem sin_sub_int_mul_pi (x : ℝ) (n : ℤ) : sin (x - n * π) = (-1) ^ n * sin x :=
n.cast_negOnePow ℝ ▸ sin_antiperiodic.sub_int_mul_eq n
theorem sin_sub_nat_mul_pi (x : ℝ) (n : ℕ) : sin (x - n * π) = (-1) ^ n * sin x :=
sin_antiperiodic.sub_nat_mul_eq n
theorem sin_int_mul_pi_sub (x : ℝ) (n : ℤ) : sin (n * π - x) = -((-1) ^ n * sin x) := by
simpa only [sin_neg, mul_neg, Int.cast_negOnePow] using sin_antiperiodic.int_mul_sub_eq n
theorem sin_nat_mul_pi_sub (x : ℝ) (n : ℕ) : sin (n * π - x) = -((-1) ^ n * sin x) := by
simpa only [sin_neg, mul_neg] using sin_antiperiodic.nat_mul_sub_eq n
theorem cos_antiperiodic : Function.Antiperiodic cos π := by simp [cos_add]
theorem cos_periodic : Function.Periodic cos (2 * π) :=
cos_antiperiodic.periodic_two_mul
@[simp]
theorem abs_cos_int_mul_pi (k : ℤ) : |cos (k * π)| = 1 := by
simp [abs_cos_eq_sqrt_one_sub_sin_sq]
@[simp]
theorem cos_add_pi (x : ℝ) : cos (x + π) = -cos x :=
cos_antiperiodic x
@[simp]
theorem cos_add_two_pi (x : ℝ) : cos (x + 2 * π) = cos x :=
cos_periodic x
@[simp]
theorem cos_sub_pi (x : ℝ) : cos (x - π) = -cos x :=
cos_antiperiodic.sub_eq x
@[simp]
theorem cos_sub_two_pi (x : ℝ) : cos (x - 2 * π) = cos x :=
cos_periodic.sub_eq x
@[simp]
theorem cos_pi_sub (x : ℝ) : cos (π - x) = -cos x :=
cos_neg x ▸ cos_antiperiodic.sub_eq'
@[simp]
theorem cos_two_pi_sub (x : ℝ) : cos (2 * π - x) = cos x :=
cos_neg x ▸ cos_periodic.sub_eq'
@[simp]
theorem cos_nat_mul_two_pi (n : ℕ) : cos (n * (2 * π)) = 1 :=
(cos_periodic.nat_mul_eq n).trans cos_zero
@[simp]
theorem cos_int_mul_two_pi (n : ℤ) : cos (n * (2 * π)) = 1 :=
(cos_periodic.int_mul_eq n).trans cos_zero
@[simp]
theorem cos_add_nat_mul_two_pi (x : ℝ) (n : ℕ) : cos (x + n * (2 * π)) = cos x :=
cos_periodic.nat_mul n x
@[simp]
theorem cos_add_int_mul_two_pi (x : ℝ) (n : ℤ) : cos (x + n * (2 * π)) = cos x :=
cos_periodic.int_mul n x
@[simp]
theorem cos_sub_nat_mul_two_pi (x : ℝ) (n : ℕ) : cos (x - n * (2 * π)) = cos x :=
cos_periodic.sub_nat_mul_eq n
@[simp]
theorem cos_sub_int_mul_two_pi (x : ℝ) (n : ℤ) : cos (x - n * (2 * π)) = cos x :=
cos_periodic.sub_int_mul_eq n
@[simp]
theorem cos_nat_mul_two_pi_sub (x : ℝ) (n : ℕ) : cos (n * (2 * π) - x) = cos x :=
cos_neg x ▸ cos_periodic.nat_mul_sub_eq n
@[simp]
theorem cos_int_mul_two_pi_sub (x : ℝ) (n : ℤ) : cos (n * (2 * π) - x) = cos x :=
cos_neg x ▸ cos_periodic.int_mul_sub_eq n
theorem cos_add_int_mul_pi (x : ℝ) (n : ℤ) : cos (x + n * π) = (-1) ^ n * cos x :=
n.cast_negOnePow ℝ ▸ cos_antiperiodic.add_int_mul_eq n
theorem cos_add_nat_mul_pi (x : ℝ) (n : ℕ) : cos (x + n * π) = (-1) ^ n * cos x :=
cos_antiperiodic.add_nat_mul_eq n
theorem cos_sub_int_mul_pi (x : ℝ) (n : ℤ) : cos (x - n * π) = (-1) ^ n * cos x :=
n.cast_negOnePow ℝ ▸ cos_antiperiodic.sub_int_mul_eq n
theorem cos_sub_nat_mul_pi (x : ℝ) (n : ℕ) : cos (x - n * π) = (-1) ^ n * cos x :=
cos_antiperiodic.sub_nat_mul_eq n
theorem cos_int_mul_pi_sub (x : ℝ) (n : ℤ) : cos (n * π - x) = (-1) ^ n * cos x :=
n.cast_negOnePow ℝ ▸ cos_neg x ▸ cos_antiperiodic.int_mul_sub_eq n
theorem cos_nat_mul_pi_sub (x : ℝ) (n : ℕ) : cos (n * π - x) = (-1) ^ n * cos x :=
cos_neg x ▸ cos_antiperiodic.nat_mul_sub_eq n
theorem cos_nat_mul_two_pi_add_pi (n : ℕ) : cos (n * (2 * π) + π) = -1 := by
simpa only [cos_zero] using (cos_periodic.nat_mul n).add_antiperiod_eq cos_antiperiodic
theorem cos_int_mul_two_pi_add_pi (n : ℤ) : cos (n * (2 * π) + π) = -1 := by
simpa only [cos_zero] using (cos_periodic.int_mul n).add_antiperiod_eq cos_antiperiodic
theorem cos_nat_mul_two_pi_sub_pi (n : ℕ) : cos (n * (2 * π) - π) = -1 := by
simpa only [cos_zero] using (cos_periodic.nat_mul n).sub_antiperiod_eq cos_antiperiodic
theorem cos_int_mul_two_pi_sub_pi (n : ℤ) : cos (n * (2 * π) - π) = -1 := by
simpa only [cos_zero] using (cos_periodic.int_mul n).sub_antiperiod_eq cos_antiperiodic
theorem sin_pos_of_pos_of_lt_pi {x : ℝ} (h0x : 0 < x) (hxp : x < π) : 0 < sin x :=
if hx2 : x ≤ 2 then sin_pos_of_pos_of_le_two h0x hx2
else
have : (2 : ℝ) + 2 = 4 := by norm_num
have : π - x ≤ 2 :=
sub_le_iff_le_add.2 (le_trans pi_le_four (this ▸ add_le_add_left (le_of_not_ge hx2) _))
sin_pi_sub x ▸ sin_pos_of_pos_of_le_two (sub_pos.2 hxp) this
theorem sin_pos_of_mem_Ioo {x : ℝ} (hx : x ∈ Ioo 0 π) : 0 < sin x :=
sin_pos_of_pos_of_lt_pi hx.1 hx.2
theorem sin_nonneg_of_mem_Icc {x : ℝ} (hx : x ∈ Icc 0 π) : 0 ≤ sin x := by
rw [← closure_Ioo pi_ne_zero.symm] at hx
exact
closure_lt_subset_le continuous_const continuous_sin
(closure_mono (fun y => sin_pos_of_mem_Ioo) hx)
theorem sin_nonneg_of_nonneg_of_le_pi {x : ℝ} (h0x : 0 ≤ x) (hxp : x ≤ π) : 0 ≤ sin x :=
sin_nonneg_of_mem_Icc ⟨h0x, hxp⟩
theorem sin_neg_of_neg_of_neg_pi_lt {x : ℝ} (hx0 : x < 0) (hpx : -π < x) : sin x < 0 :=
neg_pos.1 <| sin_neg x ▸ sin_pos_of_pos_of_lt_pi (neg_pos.2 hx0) (neg_lt.1 hpx)
theorem sin_nonpos_of_nonnpos_of_neg_pi_le {x : ℝ} (hx0 : x ≤ 0) (hpx : -π ≤ x) : sin x ≤ 0 :=
neg_nonneg.1 <| sin_neg x ▸ sin_nonneg_of_nonneg_of_le_pi (neg_nonneg.2 hx0) (neg_le.1 hpx)
@[simp]
theorem sin_pi_div_two : sin (π / 2) = 1 :=
have : sin (π / 2) = 1 ∨ sin (π / 2) = -1 := by
simpa [sq, mul_self_eq_one_iff] using sin_sq_add_cos_sq (π / 2)
this.resolve_right fun h =>
show ¬(0 : ℝ) < -1 by norm_num <|
h ▸ sin_pos_of_pos_of_lt_pi pi_div_two_pos (half_lt_self pi_pos)
theorem sin_add_pi_div_two (x : ℝ) : sin (x + π / 2) = cos x := by simp [sin_add]
theorem sin_sub_pi_div_two (x : ℝ) : sin (x - π / 2) = -cos x := by simp [sub_eq_add_neg, sin_add]
theorem sin_pi_div_two_sub (x : ℝ) : sin (π / 2 - x) = cos x := by simp [sub_eq_add_neg, sin_add]
theorem cos_add_pi_div_two (x : ℝ) : cos (x + π / 2) = -sin x := by simp [cos_add]
theorem cos_sub_pi_div_two (x : ℝ) : cos (x - π / 2) = sin x := by simp [sub_eq_add_neg, cos_add]
theorem cos_pi_div_two_sub (x : ℝ) : cos (π / 2 - x) = sin x := by
rw [← cos_neg, neg_sub, cos_sub_pi_div_two]
theorem cos_pos_of_mem_Ioo {x : ℝ} (hx : x ∈ Ioo (-(π / 2)) (π / 2)) : 0 < cos x :=
sin_add_pi_div_two x ▸ sin_pos_of_mem_Ioo ⟨by linarith [hx.1], by linarith [hx.2]⟩
theorem cos_nonneg_of_mem_Icc {x : ℝ} (hx : x ∈ Icc (-(π / 2)) (π / 2)) : 0 ≤ cos x :=
sin_add_pi_div_two x ▸ sin_nonneg_of_mem_Icc ⟨by linarith [hx.1], by linarith [hx.2]⟩
theorem cos_nonneg_of_neg_pi_div_two_le_of_le {x : ℝ} (hl : -(π / 2) ≤ x) (hu : x ≤ π / 2) :
0 ≤ cos x :=
cos_nonneg_of_mem_Icc ⟨hl, hu⟩
theorem cos_neg_of_pi_div_two_lt_of_lt {x : ℝ} (hx₁ : π / 2 < x) (hx₂ : x < π + π / 2) :
cos x < 0 :=
neg_pos.1 <| cos_pi_sub x ▸ cos_pos_of_mem_Ioo ⟨by linarith, by linarith⟩
theorem cos_nonpos_of_pi_div_two_le_of_le {x : ℝ} (hx₁ : π / 2 ≤ x) (hx₂ : x ≤ π + π / 2) :
cos x ≤ 0 :=
neg_nonneg.1 <| cos_pi_sub x ▸ cos_nonneg_of_mem_Icc ⟨by linarith, by linarith⟩
theorem sin_eq_sqrt_one_sub_cos_sq {x : ℝ} (hl : 0 ≤ x) (hu : x ≤ π) :
sin x = √(1 - cos x ^ 2) := by
rw [← abs_sin_eq_sqrt_one_sub_cos_sq, abs_of_nonneg (sin_nonneg_of_nonneg_of_le_pi hl hu)]
theorem cos_eq_sqrt_one_sub_sin_sq {x : ℝ} (hl : -(π / 2) ≤ x) (hu : x ≤ π / 2) :
cos x = √(1 - sin x ^ 2) := by
rw [← abs_cos_eq_sqrt_one_sub_sin_sq, abs_of_nonneg (cos_nonneg_of_mem_Icc ⟨hl, hu⟩)]
lemma cos_half {x : ℝ} (hl : -π ≤ x) (hr : x ≤ π) : cos (x / 2) = sqrt ((1 + cos x) / 2) := by
have : 0 ≤ cos (x / 2) := cos_nonneg_of_mem_Icc <| by constructor <;> linarith
rw [← sqrt_sq this, cos_sq, add_div, two_mul, add_halves]
lemma abs_sin_half (x : ℝ) : |sin (x / 2)| = sqrt ((1 - cos x) / 2) := by
rw [← sqrt_sq_eq_abs, sin_sq_eq_half_sub, two_mul, add_halves, sub_div]
lemma sin_half_eq_sqrt {x : ℝ} (hl : 0 ≤ x) (hr : x ≤ 2 * π) :
sin (x / 2) = sqrt ((1 - cos x) / 2) := by
rw [← abs_sin_half, abs_of_nonneg]
apply sin_nonneg_of_nonneg_of_le_pi <;> linarith
lemma sin_half_eq_neg_sqrt {x : ℝ} (hl : -(2 * π) ≤ x) (hr : x ≤ 0) :
sin (x / 2) = -sqrt ((1 - cos x) / 2) := by
rw [← abs_sin_half, abs_of_nonpos, neg_neg]
apply sin_nonpos_of_nonnpos_of_neg_pi_le <;> linarith
theorem sin_eq_zero_iff_of_lt_of_lt {x : ℝ} (hx₁ : -π < x) (hx₂ : x < π) : sin x = 0 ↔ x = 0 :=
⟨fun h => by
contrapose! h
cases h.lt_or_lt with
| inl h0 => exact (sin_neg_of_neg_of_neg_pi_lt h0 hx₁).ne
| inr h0 => exact (sin_pos_of_pos_of_lt_pi h0 hx₂).ne',
fun h => by simp [h]⟩
theorem sin_eq_zero_iff {x : ℝ} : sin x = 0 ↔ ∃ n : ℤ, (n : ℝ) * π = x :=
⟨fun h =>
⟨⌊x / π⌋,
le_antisymm (sub_nonneg.1 (Int.sub_floor_div_mul_nonneg _ pi_pos))
(sub_nonpos.1 <|
le_of_not_gt fun h₃ =>
(sin_pos_of_pos_of_lt_pi h₃ (Int.sub_floor_div_mul_lt _ pi_pos)).ne
(by simp [sub_eq_add_neg, sin_add, h, sin_int_mul_pi]))⟩,
fun ⟨_, hn⟩ => hn ▸ sin_int_mul_pi _⟩
theorem sin_ne_zero_iff {x : ℝ} : sin x ≠ 0 ↔ ∀ n : ℤ, (n : ℝ) * π ≠ x := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
theorem sin_eq_zero_iff_cos_eq {x : ℝ} : sin x = 0 ↔ cos x = 1 ∨ cos x = -1 := by
rw [← mul_self_eq_one_iff, ← sin_sq_add_cos_sq x, sq, sq, ← sub_eq_iff_eq_add, sub_self]
exact ⟨fun h => by rw [h, mul_zero], eq_zero_of_mul_self_eq_zero ∘ Eq.symm⟩
theorem cos_eq_one_iff (x : ℝ) : cos x = 1 ↔ ∃ n : ℤ, (n : ℝ) * (2 * π) = x :=
⟨fun h =>
let ⟨n, hn⟩ := sin_eq_zero_iff.1 (sin_eq_zero_iff_cos_eq.2 (Or.inl h))
⟨n / 2,
(Int.emod_two_eq_zero_or_one n).elim
(fun hn0 => by
rwa [← mul_assoc, ← @Int.cast_two ℝ, ← Int.cast_mul,
Int.ediv_mul_cancel (Int.dvd_iff_emod_eq_zero.2 hn0)])
fun hn1 => by
rw [← Int.emod_add_ediv n 2, hn1, Int.cast_add, Int.cast_one, add_mul, one_mul, add_comm,
mul_comm (2 : ℤ), Int.cast_mul, mul_assoc, Int.cast_two] at hn
rw [← hn, cos_int_mul_two_pi_add_pi] at h
exact absurd h (by norm_num)⟩,
fun ⟨_, hn⟩ => hn ▸ cos_int_mul_two_pi _⟩
theorem cos_eq_one_iff_of_lt_of_lt {x : ℝ} (hx₁ : -(2 * π) < x) (hx₂ : x < 2 * π) :
cos x = 1 ↔ x = 0 :=
⟨fun h => by
rcases (cos_eq_one_iff _).1 h with ⟨n, rfl⟩
rw [mul_lt_iff_lt_one_left two_pi_pos] at hx₂
rw [neg_lt, neg_mul_eq_neg_mul, mul_lt_iff_lt_one_left two_pi_pos] at hx₁
norm_cast at hx₁ hx₂
obtain rfl : n = 0 := le_antisymm (by omega) (by omega)
simp, fun h => by simp [h]⟩
theorem sin_lt_sin_of_lt_of_le_pi_div_two {x y : ℝ} (hx₁ : -(π / 2) ≤ x) (hy₂ : y ≤ π / 2)
(hxy : x < y) : sin x < sin y := by
rw [← sub_pos, sin_sub_sin]
have : 0 < sin ((y - x) / 2) := by apply sin_pos_of_pos_of_lt_pi <;> linarith
have : 0 < cos ((y + x) / 2) := by refine cos_pos_of_mem_Ioo ⟨?_, ?_⟩ <;> linarith
positivity
theorem strictMonoOn_sin : StrictMonoOn sin (Icc (-(π / 2)) (π / 2)) := fun _ hx _ hy hxy =>
sin_lt_sin_of_lt_of_le_pi_div_two hx.1 hy.2 hxy
theorem cos_lt_cos_of_nonneg_of_le_pi {x y : ℝ} (hx₁ : 0 ≤ x) (hy₂ : y ≤ π) (hxy : x < y) :
cos y < cos x := by
rw [← sin_pi_div_two_sub, ← sin_pi_div_two_sub]
apply sin_lt_sin_of_lt_of_le_pi_div_two <;> linarith
theorem cos_lt_cos_of_nonneg_of_le_pi_div_two {x y : ℝ} (hx₁ : 0 ≤ x) (hy₂ : y ≤ π / 2)
(hxy : x < y) : cos y < cos x :=
cos_lt_cos_of_nonneg_of_le_pi hx₁ (hy₂.trans (by linarith)) hxy
theorem strictAntiOn_cos : StrictAntiOn cos (Icc 0 π) := fun _ hx _ hy hxy =>
cos_lt_cos_of_nonneg_of_le_pi hx.1 hy.2 hxy
theorem cos_le_cos_of_nonneg_of_le_pi {x y : ℝ} (hx₁ : 0 ≤ x) (hy₂ : y ≤ π) (hxy : x ≤ y) :
cos y ≤ cos x :=
(strictAntiOn_cos.le_iff_le ⟨hx₁.trans hxy, hy₂⟩ ⟨hx₁, hxy.trans hy₂⟩).2 hxy
theorem sin_le_sin_of_le_of_le_pi_div_two {x y : ℝ} (hx₁ : -(π / 2) ≤ x) (hy₂ : y ≤ π / 2)
(hxy : x ≤ y) : sin x ≤ sin y :=
(strictMonoOn_sin.le_iff_le ⟨hx₁, hxy.trans hy₂⟩ ⟨hx₁.trans hxy, hy₂⟩).2 hxy
theorem injOn_sin : InjOn sin (Icc (-(π / 2)) (π / 2)) :=
strictMonoOn_sin.injOn
theorem injOn_cos : InjOn cos (Icc 0 π) :=
strictAntiOn_cos.injOn
theorem surjOn_sin : SurjOn sin (Icc (-(π / 2)) (π / 2)) (Icc (-1) 1) := by
simpa only [sin_neg, sin_pi_div_two] using
intermediate_value_Icc (neg_le_self pi_div_two_pos.le) continuous_sin.continuousOn
theorem surjOn_cos : SurjOn cos (Icc 0 π) (Icc (-1) 1) := by
simpa only [cos_zero, cos_pi] using intermediate_value_Icc' pi_pos.le continuous_cos.continuousOn
theorem sin_mem_Icc (x : ℝ) : sin x ∈ Icc (-1 : ℝ) 1 :=
⟨neg_one_le_sin x, sin_le_one x⟩
theorem cos_mem_Icc (x : ℝ) : cos x ∈ Icc (-1 : ℝ) 1 :=
⟨neg_one_le_cos x, cos_le_one x⟩
theorem mapsTo_sin (s : Set ℝ) : MapsTo sin s (Icc (-1 : ℝ) 1) := fun x _ => sin_mem_Icc x
theorem mapsTo_cos (s : Set ℝ) : MapsTo cos s (Icc (-1 : ℝ) 1) := fun x _ => cos_mem_Icc x
theorem bijOn_sin : BijOn sin (Icc (-(π / 2)) (π / 2)) (Icc (-1) 1) :=
⟨mapsTo_sin _, injOn_sin, surjOn_sin⟩
theorem bijOn_cos : BijOn cos (Icc 0 π) (Icc (-1) 1) :=
⟨mapsTo_cos _, injOn_cos, surjOn_cos⟩
@[simp]
theorem range_cos : range cos = (Icc (-1) 1 : Set ℝ) :=
Subset.antisymm (range_subset_iff.2 cos_mem_Icc) surjOn_cos.subset_range
@[simp]
theorem range_sin : range sin = (Icc (-1) 1 : Set ℝ) :=
Subset.antisymm (range_subset_iff.2 sin_mem_Icc) surjOn_sin.subset_range
theorem range_cos_infinite : (range Real.cos).Infinite := by
rw [Real.range_cos]
exact Icc_infinite (by norm_num)
theorem range_sin_infinite : (range Real.sin).Infinite := by
rw [Real.range_sin]
exact Icc_infinite (by norm_num)
section CosDivSq
variable (x : ℝ)
/-- the series `sqrtTwoAddSeries x n` is `sqrt(2 + sqrt(2 + ... ))` with `n` square roots,
starting with `x`. We define it here because `cos (pi / 2 ^ (n+1)) = sqrtTwoAddSeries 0 n / 2`
-/
@[simp]
noncomputable def sqrtTwoAddSeries (x : ℝ) : ℕ → ℝ
| 0 => x
| n + 1 => √(2 + sqrtTwoAddSeries x n)
theorem sqrtTwoAddSeries_zero : sqrtTwoAddSeries x 0 = x := by simp
theorem sqrtTwoAddSeries_one : sqrtTwoAddSeries 0 1 = √2 := by simp
theorem sqrtTwoAddSeries_two : sqrtTwoAddSeries 0 2 = √(2 + √2) := by simp
theorem sqrtTwoAddSeries_zero_nonneg : ∀ n : ℕ, 0 ≤ sqrtTwoAddSeries 0 n
| 0 => le_refl 0
| _ + 1 => sqrt_nonneg _
theorem sqrtTwoAddSeries_nonneg {x : ℝ} (h : 0 ≤ x) : ∀ n : ℕ, 0 ≤ sqrtTwoAddSeries x n
| 0 => h
| _ + 1 => sqrt_nonneg _
theorem sqrtTwoAddSeries_lt_two : ∀ n : ℕ, sqrtTwoAddSeries 0 n < 2
| 0 => by norm_num
| n + 1 => by
refine lt_of_lt_of_le ?_ (sqrt_sq zero_lt_two.le).le
rw [sqrtTwoAddSeries, sqrt_lt_sqrt_iff, ← lt_sub_iff_add_lt']
· refine (sqrtTwoAddSeries_lt_two n).trans_le ?_
norm_num
· exact add_nonneg zero_le_two (sqrtTwoAddSeries_zero_nonneg n)
theorem sqrtTwoAddSeries_succ (x : ℝ) :
| ∀ n : ℕ, sqrtTwoAddSeries x (n + 1) = sqrtTwoAddSeries (√(2 + x)) n
| 0 => rfl
| n + 1 => by rw [sqrtTwoAddSeries, sqrtTwoAddSeries_succ _ _, sqrtTwoAddSeries]
| Mathlib/Analysis/SpecialFunctions/Trigonometric/Basic.lean | 645 | 647 |
/-
Copyright (c) 2022 Sebastian Monnet. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Sebastian Monnet
-/
import Mathlib.FieldTheory.Galois.Basic
import Mathlib.Topology.Algebra.FilterBasis
import Mathlib.Topology.Algebra.OpenSubgroup
import Mathlib.Tactic.ByContra
/-!
# Krull topology
We define the Krull topology on `L ≃ₐ[K] L` for an arbitrary field extension `L/K`. In order to do
this, we first define a `GroupFilterBasis` on `L ≃ₐ[K] L`, whose sets are `E.fixingSubgroup` for
all intermediate fields `E` with `E/K` finite dimensional.
## Main Definitions
- `finiteExts K L`. Given a field extension `L/K`, this is the set of intermediate fields that are
finite-dimensional over `K`.
- `fixedByFinite K L`. Given a field extension `L/K`, `fixedByFinite K L` is the set of
subsets `Gal(L/E)` of `Gal(L/K)`, where `E/K` is finite
- `galBasis K L`. Given a field extension `L/K`, this is the filter basis on `L ≃ₐ[K] L` whose
sets are `Gal(L/E)` for intermediate fields `E` with `E/K` finite.
- `galGroupBasis K L`. This is the same as `galBasis K L`, but with the added structure
that it is a group filter basis on `L ≃ₐ[K] L`, rather than just a filter basis.
- `krullTopology K L`. Given a field extension `L/K`, this is the topology on `L ≃ₐ[K] L`, induced
by the group filter basis `galGroupBasis K L`.
## Main Results
- `krullTopology_t2 K L`. For an integral field extension `L/K`, the topology `krullTopology K L`
is Hausdorff.
- `krullTopology_totallyDisconnected K L`. For an integral field extension `L/K`, the topology
`krullTopology K L` is totally disconnected.
- `IntermediateField.finrank_eq_fixingSubgroup_index`: given a Galois extension `K/k` and an
intermediate field `L`, the `[L : k]` as a natural number is equal to the index of the
fixing subgroup of `L`.
## Notations
- In docstrings, we will write `Gal(L/E)` to denote the fixing subgroup of an intermediate field
`E`. That is, `Gal(L/E)` is the subgroup of `L ≃ₐ[K] L` consisting of automorphisms that fix
every element of `E`. In particular, we distinguish between `L ≃ₐ[E] L` and `Gal(L/E)`, since the
former is defined to be a subgroup of `L ≃ₐ[K] L`, while the latter is a group in its own right.
## Implementation Notes
- `krullTopology K L` is defined as an instance for type class inference.
-/
open scoped Pointwise
/-- Mapping intermediate fields along the identity does not change them -/
theorem IntermediateField.map_id {K L : Type*} [Field K] [Field L] [Algebra K L]
(E : IntermediateField K L) : E.map (AlgHom.id K L) = E :=
SetLike.coe_injective <| Set.image_id _
/-- Mapping a finite dimensional intermediate field along an algebra equivalence gives
a finite-dimensional intermediate field. -/
instance im_finiteDimensional {K L : Type*} [Field K] [Field L] [Algebra K L]
{E : IntermediateField K L} (σ : L ≃ₐ[K] L) [FiniteDimensional K E] :
FiniteDimensional K (E.map σ.toAlgHom) :=
LinearEquiv.finiteDimensional (IntermediateField.intermediateFieldMap σ E).toLinearEquiv
/-- Given a field extension `L/K`, `finiteExts K L` is the set of
intermediate field extensions `L/E/K` such that `E/K` is finite -/
def finiteExts (K : Type*) [Field K] (L : Type*) [Field L] [Algebra K L] :
Set (IntermediateField K L) :=
{E | FiniteDimensional K E}
/-- Given a field extension `L/K`, `fixedByFinite K L` is the set of
subsets `Gal(L/E)` of `L ≃ₐ[K] L`, where `E/K` is finite -/
def fixedByFinite (K L : Type*) [Field K] [Field L] [Algebra K L] : Set (Subgroup (L ≃ₐ[K] L)) :=
IntermediateField.fixingSubgroup '' finiteExts K L
/-- For a field extension `L/K`, the intermediate field `K` is finite-dimensional over `K` -/
theorem IntermediateField.finiteDimensional_bot (K L : Type*) [Field K] [Field L] [Algebra K L] :
FiniteDimensional K (⊥ : IntermediateField K L) :=
.of_rank_eq_one IntermediateField.rank_bot
/-- This lemma says that `Gal(L/K) = L ≃ₐ[K] L` -/
theorem IntermediateField.fixingSubgroup.bot {K L : Type*} [Field K] [Field L] [Algebra K L] :
IntermediateField.fixingSubgroup (⊥ : IntermediateField K L) = ⊤ := by
ext f
refine ⟨fun _ => Subgroup.mem_top _, fun _ => ?_⟩
rintro ⟨x, hx : x ∈ (⊥ : IntermediateField K L)⟩
rw [IntermediateField.mem_bot] at hx
rcases hx with ⟨y, rfl⟩
exact f.commutes y
/-- If `L/K` is a field extension, then we have `Gal(L/K) ∈ fixedByFinite K L` -/
theorem top_fixedByFinite {K L : Type*} [Field K] [Field L] [Algebra K L] :
⊤ ∈ fixedByFinite K L :=
⟨⊥, IntermediateField.finiteDimensional_bot K L, IntermediateField.fixingSubgroup.bot⟩
/-- If `E1` and `E2` are finite-dimensional intermediate fields, then so is their compositum.
This rephrases a result already in mathlib so that it is compatible with our type classes -/
theorem finiteDimensional_sup {K L : Type*} [Field K] [Field L] [Algebra K L]
(E1 E2 : IntermediateField K L) (_ : FiniteDimensional K E1) (_ : FiniteDimensional K E2) :
FiniteDimensional K (↥(E1 ⊔ E2)) :=
IntermediateField.finiteDimensional_sup E1 E2
/-- An element of `L ≃ₐ[K] L` is in `Gal(L/E)` if and only if it fixes every element of `E`. -/
theorem IntermediateField.mem_fixingSubgroup_iff {K L : Type*} [Field K] [Field L] [Algebra K L]
(E : IntermediateField K L) (σ : L ≃ₐ[K] L) : σ ∈ E.fixingSubgroup ↔ ∀ x : L, x ∈ E → σ x = x :=
⟨fun hσ x hx => hσ ⟨x, hx⟩, fun h ⟨x, hx⟩ => h x hx⟩
/-- The map `E ↦ Gal(L/E)` is inclusion-reversing -/
theorem IntermediateField.fixingSubgroup.antimono {K L : Type*} [Field K] [Field L] [Algebra K L]
{E1 E2 : IntermediateField K L} (h12 : E1 ≤ E2) : E2.fixingSubgroup ≤ E1.fixingSubgroup := by
rintro σ hσ ⟨x, hx⟩
exact hσ ⟨x, h12 hx⟩
/-- Given a field extension `L/K`, `galBasis K L` is the filter basis on `L ≃ₐ[K] L` whose sets
are `Gal(L/E)` for intermediate fields `E` with `E/K` finite dimensional -/
def galBasis (K L : Type*) [Field K] [Field L] [Algebra K L] : FilterBasis (L ≃ₐ[K] L) where
sets := (fun g => g.carrier) '' fixedByFinite K L
nonempty := ⟨⊤, ⊤, top_fixedByFinite, rfl⟩
inter_sets := by
rintro X Y ⟨H1, ⟨E1, h_E1, rfl⟩, rfl⟩ ⟨H2, ⟨E2, h_E2, rfl⟩, rfl⟩
use (IntermediateField.fixingSubgroup (E1 ⊔ E2)).carrier
refine ⟨⟨_, ⟨_, finiteDimensional_sup E1 E2 h_E1 h_E2, rfl⟩, rfl⟩, ?_⟩
rw [Set.subset_inter_iff]
exact
⟨IntermediateField.fixingSubgroup.antimono le_sup_left,
IntermediateField.fixingSubgroup.antimono le_sup_right⟩
/-- A subset of `L ≃ₐ[K] L` is a member of `galBasis K L` if and only if it is the underlying set
of `Gal(L/E)` for some finite subextension `E/K`. -/
theorem mem_galBasis_iff (K L : Type*) [Field K] [Field L] [Algebra K L] (U : Set (L ≃ₐ[K] L)) :
U ∈ galBasis K L ↔ U ∈ (fun g => g.carrier) '' fixedByFinite K L :=
Iff.rfl
/-- For a field extension `L/K`, `galGroupBasis K L` is the group filter basis on `L ≃ₐ[K] L`
whose sets are `Gal(L/E)` for finite subextensions `E/K` -/
def galGroupBasis (K L : Type*) [Field K] [Field L] [Algebra K L] :
GroupFilterBasis (L ≃ₐ[K] L) where
toFilterBasis := galBasis K L
one' := fun ⟨H, _, h2⟩ => h2 ▸ H.one_mem
mul' {U} hU :=
⟨U, hU, by
rcases hU with ⟨H, _, rfl⟩
rintro x ⟨a, haH, b, hbH, rfl⟩
exact H.mul_mem haH hbH⟩
inv' {U} hU :=
⟨U, hU, by
rcases hU with ⟨H, _, rfl⟩
exact fun _ => H.inv_mem'⟩
conj' := by
rintro σ U ⟨H, ⟨E, hE, rfl⟩, rfl⟩
let F : IntermediateField K L := E.map σ.symm.toAlgHom
refine ⟨F.fixingSubgroup.carrier, ⟨⟨F.fixingSubgroup, ⟨F, ?_, rfl⟩, rfl⟩, fun g hg => ?_⟩⟩
· have : FiniteDimensional K E := hE
apply im_finiteDimensional σ.symm
change σ * g * σ⁻¹ ∈ E.fixingSubgroup
rw [IntermediateField.mem_fixingSubgroup_iff]
intro x hx
change σ (g (σ⁻¹ x)) = x
have h_in_F : σ⁻¹ x ∈ F := ⟨x, hx, by dsimp; rw [← AlgEquiv.invFun_eq_symm]; rfl⟩
have h_g_fix : g (σ⁻¹ x) = σ⁻¹ x := by
rw [Subgroup.mem_carrier, IntermediateField.mem_fixingSubgroup_iff F g] at hg
exact hg (σ⁻¹ x) h_in_F
rw [h_g_fix]
change σ (σ⁻¹ x) = x
exact AlgEquiv.apply_symm_apply σ x
/-- For a field extension `L/K`, `krullTopology K L` is the topological space structure on
`L ≃ₐ[K] L` induced by the group filter basis `galGroupBasis K L` -/
instance krullTopology (K L : Type*) [Field K] [Field L] [Algebra K L] :
TopologicalSpace (L ≃ₐ[K] L) :=
GroupFilterBasis.topology (galGroupBasis K L)
/-- For a field extension `L/K`, the Krull topology on `L ≃ₐ[K] L` makes it a topological group. -/
@[stacks 0BMJ "We define Krull topology directly without proving the universal property"]
instance (K L : Type*) [Field K] [Field L] [Algebra K L] : IsTopologicalGroup (L ≃ₐ[K] L) :=
GroupFilterBasis.isTopologicalGroup (galGroupBasis K L)
open scoped Topology in
lemma krullTopology_mem_nhds_one_iff (K L : Type*) [Field K] [Field L] [Algebra K L]
(s : Set (L ≃ₐ[K] L)) : s ∈ 𝓝 1 ↔ ∃ E : IntermediateField K L,
FiniteDimensional K E ∧ (E.fixingSubgroup : Set (L ≃ₐ[K] L)) ⊆ s := by
rw [GroupFilterBasis.nhds_one_eq]
constructor
· rintro ⟨-, ⟨-, ⟨E, fin, rfl⟩, rfl⟩, hE⟩
exact ⟨E, fin, hE⟩
· rintro ⟨E, fin, hE⟩
exact ⟨E.fixingSubgroup, ⟨E.fixingSubgroup, ⟨E, fin, rfl⟩, rfl⟩, hE⟩
open scoped Topology in
lemma krullTopology_mem_nhds_one_iff_of_normal (K L : Type*) [Field K] [Field L] [Algebra K L]
[Normal K L] (s : Set (L ≃ₐ[K] L)) : s ∈ 𝓝 1 ↔ ∃ E : IntermediateField K L,
FiniteDimensional K E ∧ Normal K E ∧ (E.fixingSubgroup : Set (L ≃ₐ[K] L)) ⊆ s := by
rw [krullTopology_mem_nhds_one_iff]
refine ⟨fun ⟨E, _, hE⟩ ↦ ?_, fun ⟨E, hE⟩ ↦ ⟨E, hE.1, hE.2.2⟩⟩
| use (IntermediateField.normalClosure K E L)
simp only [normalClosure.is_finiteDimensional K E L, normalClosure.normal K E L, true_and]
exact le_trans (E.fixingSubgroup_anti E.le_normalClosure) hE
section KrullT2
open scoped Topology Filter
| Mathlib/FieldTheory/KrullTopology.lean | 203 | 209 |
/-
Copyright (c) 2021 Yaël Dillies. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yaël Dillies
-/
import Mathlib.Algebra.Order.Ring.Int
import Mathlib.Data.Nat.SuccPred
/-!
# Successors and predecessors of integers
In this file, we show that `ℤ` is both an archimedean `SuccOrder` and an archimedean `PredOrder`.
-/
open Function Order
namespace Int
-- so that Lean reads `Int.succ` through `SuccOrder.succ`
@[instance] abbrev instSuccOrder : SuccOrder ℤ :=
{ SuccOrder.ofSuccLeIff succ fun {_ _} => Iff.rfl with succ := succ }
instance instSuccAddOrder : SuccAddOrder ℤ := ⟨fun _ => rfl⟩
-- so that Lean reads `Int.pred` through `PredOrder.pred`
@[instance] abbrev instPredOrder : PredOrder ℤ where
pred := pred
pred_le _ := (sub_one_lt_of_le le_rfl).le
min_of_le_pred ha := ((sub_one_lt_of_le le_rfl).not_le ha).elim
le_pred_of_lt {_ _} := le_sub_one_of_lt
instance instPredSubOrder : PredSubOrder ℤ := ⟨fun _ => rfl⟩
@[simp]
theorem succ_eq_succ : Order.succ = succ :=
rfl
@[simp]
theorem pred_eq_pred : Order.pred = pred :=
rfl
instance : IsSuccArchimedean ℤ :=
⟨fun {a b} h =>
⟨(b - a).toNat, by rw [succ_iterate, toNat_sub_of_le h, ← add_sub_assoc, add_sub_cancel_left]⟩⟩
instance : IsPredArchimedean ℤ :=
| ⟨fun {a b} h =>
⟨(b - a).toNat, by rw [pred_iterate, toNat_sub_of_le h, sub_sub_cancel]⟩⟩
/-! ### Covering relation -/
| Mathlib/Data/Int/SuccPred.lean | 48 | 52 |
/-
Copyright (c) 2023 Peter Nelson. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Peter Nelson
-/
import Mathlib.Data.Finite.Prod
import Mathlib.Data.Matroid.Init
import Mathlib.Data.Set.Card
import Mathlib.Data.Set.Finite.Powerset
import Mathlib.Order.UpperLower.Closure
/-!
# Matroids
A `Matroid` is a structure that combinatorially abstracts
the notion of linear independence and dependence;
matroids have connections with graph theory, discrete optimization,
additive combinatorics and algebraic geometry.
Mathematically, a matroid `M` is a structure on a set `E` comprising a
collection of subsets of `E` called the bases of `M`,
where the bases are required to obey certain axioms.
This file gives a definition of a matroid `M` in terms of its bases,
and some API relating independent sets (subsets of bases) and the notion of a
basis of a set `X` (a maximal independent subset of `X`).
## Main definitions
* a `Matroid α` on a type `α` is a structure comprising a 'ground set'
and a suitably behaved 'base' predicate.
Given `M : Matroid α` ...
* `M.E` denotes the ground set of `M`, which has type `Set α`
* For `B : Set α`, `M.IsBase B` means that `B` is a base of `M`.
* For `I : Set α`, `M.Indep I` means that `I` is independent in `M`
(that is, `I` is contained in a base of `M`).
* For `D : Set α`, `M.Dep D` means that `D` is contained in the ground set of `M`
but isn't independent.
* For `I : Set α` and `X : Set α`, `M.IsBasis I X` means that `I` is a maximal independent
subset of `X`.
* `M.Finite` means that `M` has finite ground set.
* `M.Nonempty` means that the ground set of `M` is nonempty.
* `RankFinite M` means that the bases of `M` are finite.
* `RankInfinite M` means that the bases of `M` are infinite.
* `RankPos M` means that the bases of `M` are nonempty.
* `Finitary M` means that a set is independent if and only if all its finite subsets are
independent.
* `aesop_mat` : a tactic designed to prove `X ⊆ M.E` for some set `X` and matroid `M`.
## Implementation details
There are a few design decisions worth discussing.
### Finiteness
The first is that our matroids are allowed to be infinite.
Unlike with many mathematical structures, this isn't such an obvious choice.
Finite matroids have been studied since the 1930's,
and there was never controversy as to what is and isn't an example of a finite matroid -
in fact, surprisingly many apparently different definitions of a matroid
give rise to the same class of objects.
However, generalizing different definitions of a finite matroid
to the infinite in the obvious way (i.e. by simply allowing the ground set to be infinite)
gives a number of different notions of 'infinite matroid' that disagree with each other,
and that all lack nice properties.
Many different competing notions of infinite matroid were studied through the years;
in fact, the problem of which definition is the best was only really solved in 2013,
when Bruhn et al. [2] showed that there is a unique 'reasonable' notion of an infinite matroid
(these objects had previously defined by Higgs under the name 'B-matroid').
These are defined by adding one carefully chosen axiom to the standard set,
and adapting existing axioms to not mention set cardinalities;
they enjoy nearly all the nice properties of standard finite matroids.
Even though at least 90% of the literature is on finite matroids,
B-matroids are the definition we use, because they allow for additional generality,
nearly all theorems are still true and just as easy to state,
and (hopefully) the more general definition will prevent the need for a costly future refactor.
The disadvantage is that developing API for the finite case is harder work
(for instance, it is harder to prove that something is a matroid in the first place,
and one must deal with `ℕ∞` rather than `ℕ`).
For serious work on finite matroids, we provide the typeclasses
`[M.Finite]` and `[RankFinite M]` and associated API.
### Cardinality
Just as with bases of a vector space,
all bases of a finite matroid `M` are finite and have the same cardinality;
this cardinality is an important invariant known as the 'rank' of `M`.
For infinite matroids, bases are not in general equicardinal;
in fact the equicardinality of bases of infinite matroids is independent of ZFC [3].
What is still true is that either all bases are finite and equicardinal,
or all bases are infinite. This means that the natural notion of 'size'
for a set in matroid theory is given by the function `Set.encard`, which
is the cardinality as a term in `ℕ∞`. We use this function extensively
in building the API; it is preferable to both `Set.ncard` and `Finset.card`
because it allows infinite sets to be handled without splitting into cases.
### The ground `Set`
A last place where we make a consequential choice is making the ground set of a matroid
a structure field of type `Set α` (where `α` is the type of 'possible matroid elements')
rather than just having a type `α` of all the matroid elements.
This is because of how common it is to simultaneously consider
a number of matroids on different but related ground sets.
For example, a matroid `M` on ground set `E` can have its structure
'restricted' to some subset `R ⊆ E` to give a smaller matroid `M ↾ R` with ground set `R`.
A statement like `(M ↾ R₁) ↾ R₂ = M ↾ R₂` is mathematically obvious.
But if the ground set of a matroid is a type, this doesn't typecheck,
and is only true up to canonical isomorphism.
Restriction is just the tip of the iceberg here;
one can also 'contract' and 'delete' elements and sets of elements
in a matroid to give a smaller matroid,
and in practice it is common to make statements like `M₁.E = M₂.E ∩ M₃.E` and
`((M ⟋ e) ↾ R) ⟋ C = M ⟋ (C ∪ {e}) ↾ R`.
Such things are a nightmare to work with unless `=` is actually propositional equality
(especially because the relevant coercions are usually between sets and not just elements).
So the solution is that the ground set `M.E` has type `Set α`,
and there are elements of type `α` that aren't in the matroid.
The tradeoff is that for many statements, one now has to add
hypotheses of the form `X ⊆ M.E` to make sure than `X` is actually 'in the matroid',
rather than letting a 'type of matroid elements' take care of this invisibly.
It still seems that this is worth it.
The tactic `aesop_mat` exists specifically to discharge such goals
with minimal fuss (using default values).
The tactic works fairly well, but has room for improvement.
A related decision is to not have matroids themselves be a typeclass.
This would make things be notationally simpler
(having `Base` in the presence of `[Matroid α]` rather than `M.Base` for a term `M : Matroid α`)
but is again just too awkward when one has multiple matroids on the same type.
In fact, in regular written mathematics,
it is normal to explicitly indicate which matroid something is happening in,
so our notation mirrors common practice.
### Notation
We use a few nonstandard conventions in theorem names that are related to the above.
First, we mirror common informal practice by referring explicitly to the `ground` set rather
than the notation `E`. (Writing `ground` everywhere in a proof term would be unwieldy, and
writing `E` in theorem names would be unnatural to read.)
Second, because we are typically interested in subsets of the ground set `M.E`,
using `Set.compl` is inconvenient, since `Xᶜ ⊆ M.E` is typically false for `X ⊆ M.E`.
On the other hand (especially when duals arise), it is common to complement
a set `X ⊆ M.E` *within* the ground set, giving `M.E \ X`.
For this reason, we use the term `compl` in theorem names to refer to taking a set difference
with respect to the ground set, rather than a complement within a type. The lemma
`compl_isBase_dual` is one of the many examples of this.
Finally, in theorem names, matroid predicates that apply to sets
(such as `Base`, `Indep`, `IsBasis`) are typically used as suffixes rather than prefixes.
For instance, we have `ground_indep_iff_isBase` rather than `indep_ground_iff_isBase`.
## References
* [J. Oxley, Matroid Theory][oxley2011]
* [H. Bruhn, R. Diestel, M. Kriesell, R. Pendavingh, P. Wollan, Axioms for infinite matroids,
Adv. Math 239 (2013), 18-46][bruhnDiestelKriesselPendavinghWollan2013]
* [N. Bowler, S. Geschke, Self-dual uniform matroids on infinite sets,
Proc. Amer. Math. Soc. 144 (2016), 459-471][bowlerGeschke2015]
-/
assert_not_exists Field
open Set
/-- A predicate `P` on sets satisfies the **exchange property** if,
for all `X` and `Y` satisfying `P` and all `a ∈ X \ Y`, there exists `b ∈ Y \ X` so that
swapping `a` for `b` in `X` maintains `P`. -/
def Matroid.ExchangeProperty {α : Type*} (P : Set α → Prop) : Prop :=
∀ X Y, P X → P Y → ∀ a ∈ X \ Y, ∃ b ∈ Y \ X, P (insert b (X \ {a}))
/-- A set `X` has the maximal subset property for a predicate `P` if every subset of `X` satisfying
`P` is contained in a maximal subset of `X` satisfying `P`. -/
def Matroid.ExistsMaximalSubsetProperty {α : Type*} (P : Set α → Prop) (X : Set α) : Prop :=
∀ I, P I → I ⊆ X → ∃ J, I ⊆ J ∧ Maximal (fun K ↦ P K ∧ K ⊆ X) J
/-- A `Matroid α` is a ground set `E` of type `Set α`, and a nonempty collection of its subsets
satisfying the exchange property and the maximal subset property. Each such set is called a
`Base` of `M`. An `Indep`endent set is just a set contained in a base, but we include this
predicate as a structure field for better definitional properties.
In most cases, using this definition directly is not the best way to construct a matroid,
since it requires specifying both the bases and independent sets. If the bases are known,
use `Matroid.ofBase` or a variant. If just the independent sets are known,
define an `IndepMatroid`, and then use `IndepMatroid.matroid`.
-/
structure Matroid (α : Type*) where
/-- `M` has a ground set `E`. -/
(E : Set α)
/-- `M` has a predicate `Base` defining its bases. -/
(IsBase : Set α → Prop)
/-- `M` has a predicate `Indep` defining its independent sets. -/
(Indep : Set α → Prop)
/-- The `Indep`endent sets are those contained in `Base`s. -/
(indep_iff' : ∀ ⦃I⦄, Indep I ↔ ∃ B, IsBase B ∧ I ⊆ B)
/-- There is at least one `Base`. -/
(exists_isBase : ∃ B, IsBase B)
/-- For any bases `B`, `B'` and `e ∈ B \ B'`, there is some `f ∈ B' \ B` for which `B-e+f`
is a base. -/
(isBase_exchange : Matroid.ExchangeProperty IsBase)
/-- Every independent subset `I` of a set `X` for is contained in a maximal independent
subset of `X`. -/
(maximality : ∀ X, X ⊆ E → Matroid.ExistsMaximalSubsetProperty Indep X)
/-- Every base is contained in the ground set. -/
(subset_ground : ∀ B, IsBase B → B ⊆ E)
attribute [local ext] Matroid
namespace Matroid
variable {α : Type*} {M : Matroid α}
@[deprecated (since := "2025-02-14")] alias Base := IsBase
instance (M : Matroid α) : Nonempty {B // M.IsBase B} :=
nonempty_subtype.2 M.exists_isBase
/-- Typeclass for a matroid having finite ground set. Just a wrapper for `M.E.Finite`. -/
@[mk_iff] protected class Finite (M : Matroid α) : Prop where
/-- The ground set is finite -/
(ground_finite : M.E.Finite)
/-- Typeclass for a matroid having nonempty ground set. Just a wrapper for `M.E.Nonempty`. -/
protected class Nonempty (M : Matroid α) : Prop where
/-- The ground set is nonempty -/
(ground_nonempty : M.E.Nonempty)
theorem ground_nonempty (M : Matroid α) [M.Nonempty] : M.E.Nonempty :=
Nonempty.ground_nonempty
theorem ground_nonempty_iff (M : Matroid α) : M.E.Nonempty ↔ M.Nonempty :=
⟨fun h ↦ ⟨h⟩, fun ⟨h⟩ ↦ h⟩
lemma nonempty_type (M : Matroid α) [h : M.Nonempty] : Nonempty α :=
⟨M.ground_nonempty.some⟩
theorem ground_finite (M : Matroid α) [M.Finite] : M.E.Finite :=
Finite.ground_finite
theorem set_finite (M : Matroid α) [M.Finite] (X : Set α) (hX : X ⊆ M.E := by aesop) : X.Finite :=
M.ground_finite.subset hX
instance finite_of_finite [Finite α] {M : Matroid α} : M.Finite :=
⟨Set.toFinite _⟩
/-- A `RankFinite` matroid is one whose bases are finite -/
@[mk_iff] class RankFinite (M : Matroid α) : Prop where
/-- There is a finite base -/
exists_finite_isBase : ∃ B, M.IsBase B ∧ B.Finite
@[deprecated (since := "2025-02-09")] alias FiniteRk := RankFinite
instance rankFinite_of_finite (M : Matroid α) [M.Finite] : RankFinite M :=
⟨M.exists_isBase.imp (fun B hB ↦ ⟨hB, M.set_finite B (M.subset_ground _ hB)⟩)⟩
/-- An `RankInfinite` matroid is one whose bases are infinite. -/
@[mk_iff] class RankInfinite (M : Matroid α) : Prop where
/-- There is an infinite base -/
exists_infinite_isBase : ∃ B, M.IsBase B ∧ B.Infinite
@[deprecated (since := "2025-02-09")] alias InfiniteRk := RankInfinite
/-- A `RankPos` matroid is one whose bases are nonempty. -/
@[mk_iff] class RankPos (M : Matroid α) : Prop where
/-- The empty set isn't a base -/
empty_not_isBase : ¬M.IsBase ∅
@[deprecated (since := "2025-02-09")] alias RkPos := RankPos
instance rankPos_nonempty {M : Matroid α} [M.RankPos] : M.Nonempty := by
obtain ⟨B, hB⟩ := M.exists_isBase
obtain rfl | ⟨e, heB⟩ := B.eq_empty_or_nonempty
· exact False.elim <| RankPos.empty_not_isBase hB
exact ⟨e, M.subset_ground B hB heB ⟩
@[deprecated (since := "2025-01-20")] alias rkPos_iff_empty_not_base := rankPos_iff
section exchange
namespace ExchangeProperty
variable {IsBase : Set α → Prop} {B B' : Set α}
/-- A family of sets with the exchange property is an antichain. -/
theorem antichain (exch : ExchangeProperty IsBase) (hB : IsBase B) (hB' : IsBase B') (h : B ⊆ B') :
B = B' :=
h.antisymm (fun x hx ↦ by_contra
(fun hxB ↦ let ⟨_, hy, _⟩ := exch B' B hB' hB x ⟨hx, hxB⟩; hy.2 <| h hy.1))
theorem encard_diff_le_aux {B₁ B₂ : Set α}
(exch : ExchangeProperty IsBase) (hB₁ : IsBase B₁) (hB₂ : IsBase B₂) :
(B₁ \ B₂).encard ≤ (B₂ \ B₁).encard := by
obtain (he | hinf | ⟨e, he, hcard⟩) :=
(B₂ \ B₁).eq_empty_or_encard_eq_top_or_encard_diff_singleton_lt
· rw [exch.antichain hB₂ hB₁ (diff_eq_empty.mp he)]
· exact le_top.trans_eq hinf.symm
obtain ⟨f, hf, hB'⟩ := exch B₂ B₁ hB₂ hB₁ e he
have : encard (insert f (B₂ \ {e}) \ B₁) < encard (B₂ \ B₁) := by
rw [insert_diff_of_mem _ hf.1, diff_diff_comm]; exact hcard
have hencard := encard_diff_le_aux exch hB₁ hB'
rw [insert_diff_of_mem _ hf.1, diff_diff_comm, ← union_singleton, ← diff_diff, diff_diff_right,
inter_singleton_eq_empty.mpr he.2, union_empty] at hencard
rw [← encard_diff_singleton_add_one he, ← encard_diff_singleton_add_one hf]
exact add_le_add_right hencard 1
termination_by (B₂ \ B₁).encard
variable {B₁ B₂ : Set α}
/-- For any two sets `B₁`, `B₂` in a family with the exchange property, the differences `B₁ \ B₂`
and `B₂ \ B₁` have the same `ℕ∞`-cardinality. -/
theorem encard_diff_eq (exch : ExchangeProperty IsBase) (hB₁ : IsBase B₁) (hB₂ : IsBase B₂) :
(B₁ \ B₂).encard = (B₂ \ B₁).encard :=
(encard_diff_le_aux exch hB₁ hB₂).antisymm (encard_diff_le_aux exch hB₂ hB₁)
/-- Any two sets `B₁`, `B₂` in a family with the exchange property have the same
`ℕ∞`-cardinality. -/
theorem encard_isBase_eq (exch : ExchangeProperty IsBase) (hB₁ : IsBase B₁) (hB₂ : IsBase B₂) :
B₁.encard = B₂.encard := by
rw [← encard_diff_add_encard_inter B₁ B₂, exch.encard_diff_eq hB₁ hB₂, inter_comm,
encard_diff_add_encard_inter]
end ExchangeProperty
end exchange
section aesop
/-- The `aesop_mat` tactic attempts to prove a set is contained in the ground set of a matroid.
It uses a `[Matroid]` ruleset, and is allowed to fail. -/
macro (name := aesop_mat) "aesop_mat" c:Aesop.tactic_clause* : tactic =>
`(tactic|
aesop $c* (config := { terminal := true })
(rule_sets := [$(Lean.mkIdent `Matroid):ident]))
/- We add a number of trivial lemmas (deliberately specialized to statements in terms of the
ground set of a matroid) to the ruleset `Matroid` for `aesop`. -/
variable {X Y : Set α} {e : α}
@[aesop unsafe 5% (rule_sets := [Matroid])]
private theorem inter_right_subset_ground (hX : X ⊆ M.E) :
X ∩ Y ⊆ M.E := inter_subset_left.trans hX
@[aesop unsafe 5% (rule_sets := [Matroid])]
private theorem inter_left_subset_ground (hX : X ⊆ M.E) :
Y ∩ X ⊆ M.E := inter_subset_right.trans hX
@[aesop unsafe 5% (rule_sets := [Matroid])]
private theorem diff_subset_ground (hX : X ⊆ M.E) : X \ Y ⊆ M.E :=
diff_subset.trans hX
@[aesop unsafe 10% (rule_sets := [Matroid])]
private theorem ground_diff_subset_ground : M.E \ X ⊆ M.E :=
diff_subset_ground rfl.subset
@[aesop unsafe 10% (rule_sets := [Matroid])]
private theorem singleton_subset_ground (he : e ∈ M.E) : {e} ⊆ M.E :=
singleton_subset_iff.mpr he
@[aesop unsafe 5% (rule_sets := [Matroid])]
private theorem subset_ground_of_subset (hXY : X ⊆ Y) (hY : Y ⊆ M.E) : X ⊆ M.E :=
hXY.trans hY
@[aesop unsafe 5% (rule_sets := [Matroid])]
private theorem mem_ground_of_mem_of_subset (hX : X ⊆ M.E) (heX : e ∈ X) : e ∈ M.E :=
hX heX
@[aesop safe (rule_sets := [Matroid])]
private theorem insert_subset_ground {e : α} {X : Set α} {M : Matroid α}
(he : e ∈ M.E) (hX : X ⊆ M.E) : insert e X ⊆ M.E :=
insert_subset he hX
@[aesop safe (rule_sets := [Matroid])]
private theorem ground_subset_ground {M : Matroid α} : M.E ⊆ M.E :=
rfl.subset
attribute [aesop safe (rule_sets := [Matroid])] empty_subset union_subset iUnion_subset
end aesop
section IsBase
variable {B B₁ B₂ : Set α}
@[aesop unsafe 10% (rule_sets := [Matroid])]
theorem IsBase.subset_ground (hB : M.IsBase B) : B ⊆ M.E :=
M.subset_ground B hB
theorem IsBase.exchange {e : α} (hB₁ : M.IsBase B₁) (hB₂ : M.IsBase B₂) (hx : e ∈ B₁ \ B₂) :
∃ y ∈ B₂ \ B₁, M.IsBase (insert y (B₁ \ {e})) :=
M.isBase_exchange B₁ B₂ hB₁ hB₂ _ hx
theorem IsBase.exchange_mem {e : α}
(hB₁ : M.IsBase B₁) (hB₂ : M.IsBase B₂) (hxB₁ : e ∈ B₁) (hxB₂ : e ∉ B₂) :
∃ y, (y ∈ B₂ ∧ y ∉ B₁) ∧ M.IsBase (insert y (B₁ \ {e})) := by
simpa using hB₁.exchange hB₂ ⟨hxB₁, hxB₂⟩
theorem IsBase.eq_of_subset_isBase (hB₁ : M.IsBase B₁) (hB₂ : M.IsBase B₂) (hB₁B₂ : B₁ ⊆ B₂) :
B₁ = B₂ :=
M.isBase_exchange.antichain hB₁ hB₂ hB₁B₂
theorem IsBase.not_isBase_of_ssubset {X : Set α} (hB : M.IsBase B) (hX : X ⊂ B) : ¬ M.IsBase X :=
fun h ↦ hX.ne (h.eq_of_subset_isBase hB hX.subset)
theorem IsBase.insert_not_isBase {e : α} (hB : M.IsBase B) (heB : e ∉ B) :
¬ M.IsBase (insert e B) :=
fun h ↦ h.not_isBase_of_ssubset (ssubset_insert heB) hB
theorem IsBase.encard_diff_comm (hB₁ : M.IsBase B₁) (hB₂ : M.IsBase B₂) :
(B₁ \ B₂).encard = (B₂ \ B₁).encard :=
M.isBase_exchange.encard_diff_eq hB₁ hB₂
theorem IsBase.ncard_diff_comm (hB₁ : M.IsBase B₁) (hB₂ : M.IsBase B₂) :
(B₁ \ B₂).ncard = (B₂ \ B₁).ncard := by
rw [ncard_def, hB₁.encard_diff_comm hB₂, ← ncard_def]
theorem IsBase.encard_eq_encard_of_isBase (hB₁ : M.IsBase B₁) (hB₂ : M.IsBase B₂) :
B₁.encard = B₂.encard := by
rw [M.isBase_exchange.encard_isBase_eq hB₁ hB₂]
theorem IsBase.ncard_eq_ncard_of_isBase (hB₁ : M.IsBase B₁) (hB₂ : M.IsBase B₂) :
B₁.ncard = B₂.ncard := by
rw [ncard_def B₁, hB₁.encard_eq_encard_of_isBase hB₂, ← ncard_def]
theorem IsBase.finite_of_finite {B' : Set α}
(hB : M.IsBase B) (h : B.Finite) (hB' : M.IsBase B') : B'.Finite :=
(finite_iff_finite_of_encard_eq_encard (hB.encard_eq_encard_of_isBase hB')).mp h
theorem IsBase.infinite_of_infinite (hB : M.IsBase B) (h : B.Infinite) (hB₁ : M.IsBase B₁) :
B₁.Infinite :=
by_contra (fun hB_inf ↦ (hB₁.finite_of_finite (not_infinite.mp hB_inf) hB).not_infinite h)
theorem IsBase.finite [RankFinite M] (hB : M.IsBase B) : B.Finite :=
let ⟨_,hB₀⟩ := ‹RankFinite M›.exists_finite_isBase
hB₀.1.finite_of_finite hB₀.2 hB
theorem IsBase.infinite [RankInfinite M] (hB : M.IsBase B) : B.Infinite :=
let ⟨_,hB₀⟩ := ‹RankInfinite M›.exists_infinite_isBase
hB₀.1.infinite_of_infinite hB₀.2 hB
theorem empty_not_isBase [h : RankPos M] : ¬M.IsBase ∅ :=
h.empty_not_isBase
theorem IsBase.nonempty [RankPos M] (hB : M.IsBase B) : B.Nonempty := by
rw [nonempty_iff_ne_empty]; rintro rfl; exact M.empty_not_isBase hB
theorem IsBase.rankPos_of_nonempty (hB : M.IsBase B) (h : B.Nonempty) : M.RankPos := by
rw [rankPos_iff]
intro he
obtain rfl := he.eq_of_subset_isBase hB (empty_subset B)
simp at h
theorem IsBase.rankFinite_of_finite (hB : M.IsBase B) (hfin : B.Finite) : RankFinite M :=
⟨⟨B, hB, hfin⟩⟩
theorem IsBase.rankInfinite_of_infinite (hB : M.IsBase B) (h : B.Infinite) : RankInfinite M :=
⟨⟨B, hB, h⟩⟩
theorem not_rankFinite (M : Matroid α) [RankInfinite M] : ¬ RankFinite M := by
intro h; obtain ⟨B,hB⟩ := M.exists_isBase; exact hB.infinite hB.finite
theorem not_rankInfinite (M : Matroid α) [RankFinite M] : ¬ RankInfinite M := by
intro h; obtain ⟨B,hB⟩ := M.exists_isBase; exact hB.infinite hB.finite
theorem rankFinite_or_rankInfinite (M : Matroid α) : RankFinite M ∨ RankInfinite M :=
let ⟨B, hB⟩ := M.exists_isBase
B.finite_or_infinite.imp hB.rankFinite_of_finite hB.rankInfinite_of_infinite
@[deprecated (since := "2025-03-27")] alias finite_or_rankInfinite := rankFinite_or_rankInfinite
@[simp]
theorem not_rankFinite_iff (M : Matroid α) : ¬ RankFinite M ↔ RankInfinite M :=
M.rankFinite_or_rankInfinite.elim (fun h ↦ iff_of_false (by simpa) M.not_rankInfinite)
fun h ↦ iff_of_true M.not_rankFinite h
@[simp]
theorem not_rankInfinite_iff (M : Matroid α) : ¬ RankInfinite M ↔ RankFinite M := by
rw [← not_rankFinite_iff, not_not]
theorem IsBase.diff_finite_comm (hB₁ : M.IsBase B₁) (hB₂ : M.IsBase B₂) :
(B₁ \ B₂).Finite ↔ (B₂ \ B₁).Finite :=
finite_iff_finite_of_encard_eq_encard (hB₁.encard_diff_comm hB₂)
theorem IsBase.diff_infinite_comm (hB₁ : M.IsBase B₁) (hB₂ : M.IsBase B₂) :
(B₁ \ B₂).Infinite ↔ (B₂ \ B₁).Infinite :=
infinite_iff_infinite_of_encard_eq_encard (hB₁.encard_diff_comm hB₂)
theorem ext_isBase {M₁ M₂ : Matroid α} (hE : M₁.E = M₂.E)
(h : ∀ ⦃B⦄, B ⊆ M₁.E → (M₁.IsBase B ↔ M₂.IsBase B)) : M₁ = M₂ := by
have h' : ∀ B, M₁.IsBase B ↔ M₂.IsBase B :=
fun B ↦ ⟨fun hB ↦ (h hB.subset_ground).1 hB,
fun hB ↦ (h <| hB.subset_ground.trans_eq hE.symm).2 hB⟩
ext <;> simp [hE, M₁.indep_iff', M₂.indep_iff', h']
@[deprecated (since := "2024-12-25")] alias eq_of_isBase_iff_isBase_forall := ext_isBase
theorem ext_iff_isBase {M₁ M₂ : Matroid α} :
M₁ = M₂ ↔ M₁.E = M₂.E ∧ ∀ ⦃B⦄, B ⊆ M₁.E → (M₁.IsBase B ↔ M₂.IsBase B) :=
⟨fun h ↦ by simp [h], fun ⟨hE, h⟩ ↦ ext_isBase hE h⟩
theorem isBase_compl_iff_maximal_disjoint_isBase (hB : B ⊆ M.E := by aesop_mat) :
M.IsBase (M.E \ B) ↔ Maximal (fun I ↦ I ⊆ M.E ∧ ∃ B, M.IsBase B ∧ Disjoint I B) B := by
simp_rw [maximal_iff, and_iff_right hB, and_imp, forall_exists_index]
refine ⟨fun h ↦ ⟨⟨_, h, disjoint_sdiff_right⟩,
fun I hI B' ⟨hB', hIB'⟩ hBI ↦ hBI.antisymm ?_⟩, fun ⟨⟨B', hB', hBB'⟩,h⟩ ↦ ?_⟩
· rw [hB'.eq_of_subset_isBase h, ← subset_compl_iff_disjoint_right, diff_eq, compl_inter,
compl_compl] at hIB'
· exact fun e he ↦ (hIB' he).elim (fun h' ↦ (h' (hI he)).elim) id
rw [subset_diff, and_iff_right hB'.subset_ground, disjoint_comm]
exact disjoint_of_subset_left hBI hIB'
rw [h diff_subset B' ⟨hB', disjoint_sdiff_left⟩]
· simpa [hB'.subset_ground]
simp [subset_diff, hB, hBB']
end IsBase
section dep_indep
/-- A subset of `M.E` is `Dep`endent if it is not `Indep`endent . -/
def Dep (M : Matroid α) (D : Set α) : Prop := ¬M.Indep D ∧ D ⊆ M.E
variable {B B' I J D X : Set α} {e f : α}
theorem indep_iff : M.Indep I ↔ ∃ B, M.IsBase B ∧ I ⊆ B :=
M.indep_iff' (I := I)
theorem setOf_indep_eq (M : Matroid α) : {I | M.Indep I} = lowerClosure ({B | M.IsBase B}) := by
simp_rw [indep_iff, lowerClosure, LowerSet.coe_mk, mem_setOf, le_eq_subset]
theorem Indep.exists_isBase_superset (hI : M.Indep I) : ∃ B, M.IsBase B ∧ I ⊆ B :=
indep_iff.1 hI
theorem dep_iff : M.Dep D ↔ ¬M.Indep D ∧ D ⊆ M.E := Iff.rfl
theorem setOf_dep_eq (M : Matroid α) : {D | M.Dep D} = {I | M.Indep I}ᶜ ∩ Iic M.E := rfl
@[aesop unsafe 30% (rule_sets := [Matroid])]
theorem Indep.subset_ground (hI : M.Indep I) : I ⊆ M.E := by
obtain ⟨B, hB, hIB⟩ := hI.exists_isBase_superset
exact hIB.trans hB.subset_ground
@[aesop unsafe 20% (rule_sets := [Matroid])]
theorem Dep.subset_ground (hD : M.Dep D) : D ⊆ M.E :=
hD.2
theorem indep_or_dep (hX : X ⊆ M.E := by aesop_mat) : M.Indep X ∨ M.Dep X := by
rw [Dep, and_iff_left hX]
apply em
theorem Indep.not_dep (hI : M.Indep I) : ¬ M.Dep I :=
fun h ↦ h.1 hI
theorem Dep.not_indep (hD : M.Dep D) : ¬ M.Indep D :=
hD.1
theorem dep_of_not_indep (hD : ¬ M.Indep D) (hDE : D ⊆ M.E := by aesop_mat) : M.Dep D :=
⟨hD, hDE⟩
theorem indep_of_not_dep (hI : ¬ M.Dep I) (hIE : I ⊆ M.E := by aesop_mat) : M.Indep I :=
by_contra (fun h ↦ hI ⟨h, hIE⟩)
@[simp] theorem not_dep_iff (hX : X ⊆ M.E := by aesop_mat) : ¬ M.Dep X ↔ M.Indep X := by
rw [Dep, and_iff_left hX, not_not]
@[simp] theorem not_indep_iff (hX : X ⊆ M.E := by aesop_mat) : ¬ M.Indep X ↔ M.Dep X := by
rw [Dep, and_iff_left hX]
theorem indep_iff_not_dep : M.Indep I ↔ ¬M.Dep I ∧ I ⊆ M.E := by
rw [dep_iff, not_and, not_imp_not]
exact ⟨fun h ↦ ⟨fun _ ↦ h, h.subset_ground⟩, fun h ↦ h.1 h.2⟩
theorem Indep.subset (hJ : M.Indep J) (hIJ : I ⊆ J) : M.Indep I := by
obtain ⟨B, hB, hJB⟩ := hJ.exists_isBase_superset
exact indep_iff.2 ⟨B, hB, hIJ.trans hJB⟩
theorem Dep.superset (hD : M.Dep D) (hDX : D ⊆ X) (hXE : X ⊆ M.E := by aesop_mat) : M.Dep X :=
dep_of_not_indep (fun hI ↦ (hI.subset hDX).not_dep hD)
theorem IsBase.indep (hB : M.IsBase B) : M.Indep B :=
indep_iff.2 ⟨B, hB, subset_rfl⟩
@[simp] theorem empty_indep (M : Matroid α) : M.Indep ∅ :=
Exists.elim M.exists_isBase (fun _ hB ↦ hB.indep.subset (empty_subset _))
theorem Dep.nonempty (hD : M.Dep D) : D.Nonempty := by
rw [nonempty_iff_ne_empty]; rintro rfl; exact hD.not_indep M.empty_indep
theorem Indep.finite [RankFinite M] (hI : M.Indep I) : I.Finite :=
let ⟨_, hB, hIB⟩ := hI.exists_isBase_superset
hB.finite.subset hIB
theorem Indep.rankPos_of_nonempty (hI : M.Indep I) (hne : I.Nonempty) : M.RankPos := by
obtain ⟨B, hB, hIB⟩ := hI.exists_isBase_superset
exact hB.rankPos_of_nonempty (hne.mono hIB)
theorem Indep.inter_right (hI : M.Indep I) (X : Set α) : M.Indep (I ∩ X) :=
hI.subset inter_subset_left
theorem Indep.inter_left (hI : M.Indep I) (X : Set α) : M.Indep (X ∩ I) :=
hI.subset inter_subset_right
theorem Indep.diff (hI : M.Indep I) (X : Set α) : M.Indep (I \ X) :=
hI.subset diff_subset
theorem IsBase.eq_of_subset_indep (hB : M.IsBase B) (hI : M.Indep I) (hBI : B ⊆ I) : B = I :=
let ⟨B', hB', hB'I⟩ := hI.exists_isBase_superset
hBI.antisymm (by rwa [hB.eq_of_subset_isBase hB' (hBI.trans hB'I)])
theorem isBase_iff_maximal_indep : M.IsBase B ↔ Maximal M.Indep B := by
rw [maximal_subset_iff]
refine ⟨fun h ↦ ⟨h.indep, fun _ ↦ h.eq_of_subset_indep⟩, fun ⟨h, h'⟩ ↦ ?_⟩
obtain ⟨B', hB', hBB'⟩ := h.exists_isBase_superset
rwa [h' hB'.indep hBB']
theorem Indep.isBase_of_maximal (hI : M.Indep I) (h : ∀ ⦃J⦄, M.Indep J → I ⊆ J → I = J) :
M.IsBase I := by
rwa [isBase_iff_maximal_indep, maximal_subset_iff, and_iff_right hI]
theorem IsBase.dep_of_ssubset (hB : M.IsBase B) (h : B ⊂ X) (hX : X ⊆ M.E := by aesop_mat) :
M.Dep X :=
⟨fun hX ↦ h.ne (hB.eq_of_subset_indep hX h.subset), hX⟩
theorem IsBase.dep_of_insert (hB : M.IsBase B) (heB : e ∉ B) (he : e ∈ M.E := by aesop_mat) :
M.Dep (insert e B) := hB.dep_of_ssubset (ssubset_insert heB) (insert_subset he hB.subset_ground)
theorem IsBase.mem_of_insert_indep (hB : M.IsBase B) (heB : M.Indep (insert e B)) : e ∈ B :=
by_contra fun he ↦ (hB.dep_of_insert he (heB.subset_ground (mem_insert _ _))).not_indep heB
/-- If the difference of two IsBases is a singleton, then they differ by an insertion/removal -/
theorem IsBase.eq_exchange_of_diff_eq_singleton (hB : M.IsBase B) (hB' : M.IsBase B')
(h : B \ B' = {e}) : ∃ f ∈ B' \ B, B' = (insert f B) \ {e} := by
obtain ⟨f, hf, hb⟩ := hB.exchange hB' (h.symm.subset (mem_singleton e))
have hne : f ≠ e := by rintro rfl; exact hf.2 (h.symm.subset (mem_singleton f)).1
rw [insert_diff_singleton_comm hne] at hb
refine ⟨f, hf, (hb.eq_of_subset_isBase hB' ?_).symm⟩
rw [diff_subset_iff, insert_subset_iff, union_comm, ← diff_subset_iff, h, and_iff_left rfl.subset]
exact Or.inl hf.1
theorem IsBase.exchange_isBase_of_indep (hB : M.IsBase B) (hf : f ∉ B)
(hI : M.Indep (insert f (B \ {e}))) : M.IsBase (insert f (B \ {e})) := by
obtain ⟨B', hB', hIB'⟩ := hI.exists_isBase_superset
have hcard := hB'.encard_diff_comm hB
rw [insert_subset_iff, ← diff_eq_empty, diff_diff_comm, diff_eq_empty, subset_singleton_iff_eq]
at hIB'
obtain ⟨hfB, (h | h)⟩ := hIB'
· rw [h, encard_empty, encard_eq_zero, eq_empty_iff_forall_not_mem] at hcard
exact (hcard f ⟨hfB, hf⟩).elim
rw [h, encard_singleton, encard_eq_one] at hcard
obtain ⟨x, hx⟩ := hcard
obtain (rfl : f = x) := hx.subset ⟨hfB, hf⟩
simp_rw [← h, ← singleton_union, ← hx, sdiff_sdiff_right_self, inf_eq_inter, inter_comm B,
diff_union_inter]
exact hB'
theorem IsBase.exchange_isBase_of_indep' (hB : M.IsBase B) (he : e ∈ B) (hf : f ∉ B)
(hI : M.Indep (insert f B \ {e})) : M.IsBase (insert f B \ {e}) := by
have hfe : f ≠ e := ne_of_mem_of_not_mem he hf |>.symm
rw [← insert_diff_singleton_comm hfe] at *
exact hB.exchange_isBase_of_indep hf hI
lemma insert_isBase_of_insert_indep {M : Matroid α} {I : Set α} {e f : α}
(he : e ∉ I) (hf : f ∉ I) (heI : M.IsBase (insert e I)) (hfI : M.Indep (insert f I)) :
M.IsBase (insert f I) := by
obtain rfl | hef := eq_or_ne e f
· assumption
simpa [diff_singleton_eq_self he, hfI]
using heI.exchange_isBase_of_indep (e := e) (f := f) (by simp [hef.symm, hf])
theorem IsBase.insert_dep (hB : M.IsBase B) (h : e ∈ M.E \ B) : M.Dep (insert e B) := by
rw [← not_indep_iff (insert_subset h.1 hB.subset_ground)]
exact h.2 ∘ (fun hi ↦ insert_eq_self.mp (hB.eq_of_subset_indep hi (subset_insert e B)).symm)
theorem Indep.exists_insert_of_not_isBase (hI : M.Indep I) (hI' : ¬M.IsBase I) (hB : M.IsBase B) :
∃ e ∈ B \ I, M.Indep (insert e I) := by
obtain ⟨B', hB', hIB'⟩ := hI.exists_isBase_superset
obtain ⟨x, hxB', hx⟩ := exists_of_ssubset (hIB'.ssubset_of_ne (by (rintro rfl; exact hI' hB')))
by_cases hxB : x ∈ B
· exact ⟨x, ⟨hxB, hx⟩, hB'.indep.subset (insert_subset hxB' hIB')⟩
obtain ⟨e,he, hBase⟩ := hB'.exchange hB ⟨hxB',hxB⟩
exact ⟨e, ⟨he.1, not_mem_subset hIB' he.2⟩,
indep_iff.2 ⟨_, hBase, insert_subset_insert (subset_diff_singleton hIB' hx)⟩⟩
/-- This is the same as `Indep.exists_insert_of_not_isBase`, but phrased so that
it is defeq to the augmentation axiom for independent sets. -/
theorem Indep.exists_insert_of_not_maximal (M : Matroid α) ⦃I B : Set α⦄ (hI : M.Indep I)
(hInotmax : ¬ Maximal M.Indep I) (hB : Maximal M.Indep B) :
∃ x ∈ B \ I, M.Indep (insert x I) := by
simp only [maximal_subset_iff, hI, not_and, not_forall, exists_prop, true_imp_iff] at hB hInotmax
refine hI.exists_insert_of_not_isBase (fun hIb ↦ ?_) ?_
· obtain ⟨I', hII', hI', hne⟩ := hInotmax
exact hne <| hIb.eq_of_subset_indep hII' hI'
exact hB.1.isBase_of_maximal fun J hJ hBJ ↦ hB.2 hJ hBJ
theorem Indep.isBase_of_forall_insert (hB : M.Indep B)
(hBmax : ∀ e ∈ M.E \ B, ¬ M.Indep (insert e B)) : M.IsBase B := by
refine by_contra fun hnb ↦ ?_
obtain ⟨B', hB'⟩ := M.exists_isBase
obtain ⟨e, he, h⟩ := hB.exists_insert_of_not_isBase hnb hB'
exact hBmax e ⟨hB'.subset_ground he.1, he.2⟩ h
theorem ground_indep_iff_isBase : M.Indep M.E ↔ M.IsBase M.E :=
⟨fun h ↦ h.isBase_of_maximal (fun _ hJ hEJ ↦ hEJ.antisymm hJ.subset_ground), IsBase.indep⟩
theorem IsBase.exists_insert_of_ssubset (hB : M.IsBase B) (hIB : I ⊂ B) (hB' : M.IsBase B') :
∃ e ∈ B' \ I, M.Indep (insert e I) :=
(hB.indep.subset hIB.subset).exists_insert_of_not_isBase
(fun hI ↦ hIB.ne (hI.eq_of_subset_isBase hB hIB.subset)) hB'
@[ext] theorem ext_indep {M₁ M₂ : Matroid α} (hE : M₁.E = M₂.E)
(h : ∀ ⦃I⦄, I ⊆ M₁.E → (M₁.Indep I ↔ M₂.Indep I)) : M₁ = M₂ :=
have h' : M₁.Indep = M₂.Indep := by
ext I
by_cases hI : I ⊆ M₁.E
· rwa [h]
exact iff_of_false (fun hi ↦ hI hi.subset_ground)
(fun hi ↦ hI (hi.subset_ground.trans_eq hE.symm))
ext_isBase hE (fun B _ ↦ by simp_rw [isBase_iff_maximal_indep, h'])
@[deprecated (since := "2024-12-25")] alias eq_of_indep_iff_indep_forall := ext_indep
theorem ext_iff_indep {M₁ M₂ : Matroid α} :
M₁ = M₂ ↔ (M₁.E = M₂.E) ∧ ∀ ⦃I⦄, I ⊆ M₁.E → (M₁.Indep I ↔ M₂.Indep I) :=
⟨fun h ↦ by (subst h; simp), fun h ↦ ext_indep h.1 h.2⟩
@[deprecated (since := "2024-12-25")] alias eq_iff_indep_iff_indep_forall := ext_iff_indep
/-- If every base of `M₁` is independent in `M₂` and vice versa, then `M₁ = M₂`. -/
lemma ext_isBase_indep {M₁ M₂ : Matroid α} (hE : M₁.E = M₂.E)
(hM₁ : ∀ ⦃B⦄, M₁.IsBase B → M₂.Indep B) (hM₂ : ∀ ⦃B⦄, M₂.IsBase B → M₁.Indep B) : M₁ = M₂ := by
refine ext_indep hE fun I hIE ↦ ⟨fun hI ↦ ?_, fun hI ↦ ?_⟩
· obtain ⟨B, hB, hIB⟩ := hI.exists_isBase_superset
exact (hM₁ hB).subset hIB
obtain ⟨B, hB, hIB⟩ := hI.exists_isBase_superset
exact (hM₂ hB).subset hIB
/-- A `Finitary` matroid is one where a set is independent if and only if it all
its finite subsets are independent, or equivalently a matroid whose circuits are finite. -/
@[mk_iff] class Finitary (M : Matroid α) : Prop where
/-- `I` is independent if all its finite subsets are independent. -/
indep_of_forall_finite : ∀ I, (∀ J, J ⊆ I → J.Finite → M.Indep J) → M.Indep I
theorem indep_of_forall_finite_subset_indep {M : Matroid α} [Finitary M] (I : Set α)
(h : ∀ J, J ⊆ I → J.Finite → M.Indep J) : M.Indep I :=
Finitary.indep_of_forall_finite I h
theorem indep_iff_forall_finite_subset_indep {M : Matroid α} [Finitary M] :
M.Indep I ↔ ∀ J, J ⊆ I → J.Finite → M.Indep J :=
⟨fun h _ hJI _ ↦ h.subset hJI, Finitary.indep_of_forall_finite I⟩
instance finitary_of_rankFinite {M : Matroid α} [RankFinite M] : Finitary M where
indep_of_forall_finite I hI := by
refine I.finite_or_infinite.elim (hI _ Subset.rfl) (fun h ↦ False.elim ?_)
obtain ⟨B, hB⟩ := M.exists_isBase
obtain ⟨I₀, hI₀I, hI₀fin, hI₀card⟩ := h.exists_subset_ncard_eq (B.ncard + 1)
obtain ⟨B', hB', hI₀B'⟩ := (hI _ hI₀I hI₀fin).exists_isBase_superset
have hle := ncard_le_ncard hI₀B' hB'.finite
rw [hI₀card, hB'.ncard_eq_ncard_of_isBase hB, Nat.add_one_le_iff] at hle
exact hle.ne rfl
/-- Matroids obey the maximality axiom -/
theorem existsMaximalSubsetProperty_indep (M : Matroid α) :
∀ X, X ⊆ M.E → ExistsMaximalSubsetProperty M.Indep X :=
M.maximality
end dep_indep
section copy
/-- create a copy of `M : Matroid α` with independence and base predicates and ground set defeq
to supplied arguments that are provably equal to those of `M`. -/
@[simps] def copy (M : Matroid α) (E : Set α) (IsBase Indep : Set α → Prop) (hE : E = M.E)
(hB : ∀ B, IsBase B ↔ M.IsBase B) (hI : ∀ I, Indep I ↔ M.Indep I) : Matroid α where
E := E
IsBase := IsBase
Indep := Indep
indep_iff' _ := by simp_rw [hI, hB, M.indep_iff]
exists_isBase := by
simp_rw [hB]
exact M.exists_isBase
isBase_exchange := by
simp_rw [show IsBase = M.IsBase from funext (by simp [hB])]
exact M.isBase_exchange
maximality := by
simp_rw [hE, show Indep = M.Indep from funext (by simp [hI])]
exact M.maximality
subset_ground := by
simp_rw [hE, hB]
exact M.subset_ground
/-- create a copy of `M : Matroid α` with an independence predicate and ground set defeq
to supplied arguments that are provably equal to those of `M`. -/
@[simps!] def copyIndep (M : Matroid α) (E : Set α) (Indep : Set α → Prop)
(hE : E = M.E) (h : ∀ I, Indep I ↔ M.Indep I) : Matroid α :=
M.copy E M.IsBase Indep hE (fun _ ↦ Iff.rfl) h
/-- create a copy of `M : Matroid α` with a base predicate and ground set defeq
to supplied arguments that are provably equal to those of `M`. -/
@[simps!] def copyBase (M : Matroid α) (E : Set α) (IsBase : Set α → Prop)
(hE : E = M.E) (h : ∀ B, IsBase B ↔ M.IsBase B) : Matroid α :=
M.copy E IsBase M.Indep hE h (fun _ ↦ Iff.rfl)
end copy
| section IsBasis
/-- A Basis for a set `X ⊆ M.E` is a maximal independent subset of `X`
(Often in the literature, the word 'Basis' is used to refer to what we call a 'Base'). -/
| Mathlib/Data/Matroid/Basic.lean | 807 | 810 |
/-
Copyright (c) 2023 Joël Riou. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Joël Riou
-/
import Mathlib.Algebra.Homology.HomologicalComplexBiprod
import Mathlib.Algebra.Homology.Homotopy
import Mathlib.CategoryTheory.MorphismProperty.IsInvertedBy
/-! The homotopy cofiber of a morphism of homological complexes
In this file, we construct the homotopy cofiber of a morphism `φ : F ⟶ G`
between homological complexes in `HomologicalComplex C c`. In degree `i`,
it is isomorphic to `(F.X j) ⊞ (G.X i)` if there is a `j` such that `c.Rel i j`,
and `G.X i` otherwise. (This is also known as the mapping cone of `φ`. Under
the name `CochainComplex.mappingCone`, a specific API shall be developed
for the case of cochain complexes indexed by `ℤ`.)
When we assume `hc : ∀ j, ∃ i, c.Rel i j` (which holds in the case of chain complexes,
or cochain complexes indexed by `ℤ`), then for any homological complex `K`,
there is a bijection `HomologicalComplex.homotopyCofiber.descEquiv φ K hc`
between `homotopyCofiber φ ⟶ K` and the tuples `(α, hα)` with
`α : G ⟶ K` and `hα : Homotopy (φ ≫ α) 0`.
We shall also study the cylinder of a homological complex `K`: this is the
homotopy cofiber of the morphism `biprod.lift (𝟙 K) (-𝟙 K) : K ⟶ K ⊞ K`.
Then, a morphism `K.cylinder ⟶ M` is determined by the data of two
morphisms `φ₀ φ₁ : K ⟶ M` and a homotopy `h : Homotopy φ₀ φ₁`,
see `cylinder.desc`. There is also a homotopy equivalence
`cylinder.homotopyEquiv K : HomotopyEquiv K.cylinder K`. From the construction of
the cylinder, we deduce the lemma `Homotopy.map_eq_of_inverts_homotopyEquivalences`
which assert that if a functor inverts homotopy equivalences, then the image of
two homotopic maps are equal.
-/
open CategoryTheory Category Limits Preadditive
variable {C : Type*} [Category C] [Preadditive C]
namespace HomologicalComplex
variable {ι : Type*} {c : ComplexShape ι} {F G K : HomologicalComplex C c} (φ : F ⟶ G)
/-- A morphism of homological complexes `φ : F ⟶ G` has a homotopy cofiber if for all
indices `i` and `j` such that `c.Rel i j`, the binary biproduct `F.X j ⊞ G.X i` exists. -/
class HasHomotopyCofiber (φ : F ⟶ G) : Prop where
hasBinaryBiproduct (i j : ι) (hij : c.Rel i j) : HasBinaryBiproduct (F.X j) (G.X i)
instance [HasBinaryBiproducts C] : HasHomotopyCofiber φ where
hasBinaryBiproduct _ _ _ := inferInstance
variable [HasHomotopyCofiber φ] [DecidableRel c.Rel]
namespace homotopyCofiber
/-- The `X` field of the homological complex `homotopyCofiber φ`. -/
noncomputable def X (i : ι) : C :=
if hi : c.Rel i (c.next i)
then
haveI := HasHomotopyCofiber.hasBinaryBiproduct φ _ _ hi
(F.X (c.next i)) ⊞ (G.X i)
else G.X i
/-- The canonical isomorphism `(homotopyCofiber φ).X i ≅ F.X j ⊞ G.X i` when `c.Rel i j`. -/
noncomputable def XIsoBiprod (i j : ι) (hij : c.Rel i j) [HasBinaryBiproduct (F.X j) (G.X i)] :
X φ i ≅ F.X j ⊞ G.X i :=
eqToIso (by
obtain rfl := c.next_eq' hij
apply dif_pos hij)
/-- The canonical isomorphism `(homotopyCofiber φ).X i ≅ G.X i` when `¬ c.Rel i (c.next i)`. -/
noncomputable def XIso (i : ι) (hi : ¬ c.Rel i (c.next i)) :
X φ i ≅ G.X i :=
eqToIso (dif_neg hi)
/-- The second projection `(homotopyCofiber φ).X i ⟶ G.X i`. -/
noncomputable def sndX (i : ι) : X φ i ⟶ G.X i :=
if hi : c.Rel i (c.next i)
then
haveI := HasHomotopyCofiber.hasBinaryBiproduct φ _ _ hi
(XIsoBiprod φ _ _ hi).hom ≫ biprod.snd
else
(XIso φ i hi).hom
/-- The right inclusion `G.X i ⟶ (homotopyCofiber φ).X i`. -/
noncomputable def inrX (i : ι) : G.X i ⟶ X φ i :=
if hi : c.Rel i (c.next i)
then
haveI := HasHomotopyCofiber.hasBinaryBiproduct φ _ _ hi
biprod.inr ≫ (XIsoBiprod φ _ _ hi).inv
else
(XIso φ i hi).inv
@[reassoc (attr := simp)]
lemma inrX_sndX (i : ι) : inrX φ i ≫ sndX φ i = 𝟙 _ := by
dsimp [sndX, inrX]
split_ifs with hi <;> simp
@[reassoc]
lemma sndX_inrX (i : ι) (hi : ¬ c.Rel i (c.next i)) :
sndX φ i ≫ inrX φ i = 𝟙 _ := by
dsimp [sndX, inrX]
simp only [dif_neg hi, Iso.hom_inv_id]
/-- The first projection `(homotopyCofiber φ).X i ⟶ F.X j` when `c.Rel i j`. -/
noncomputable def fstX (i j : ι) (hij : c.Rel i j) : X φ i ⟶ F.X j :=
haveI := HasHomotopyCofiber.hasBinaryBiproduct φ _ _ hij
(XIsoBiprod φ i j hij).hom ≫ biprod.fst
/-- The left inclusion `F.X i ⟶ (homotopyCofiber φ).X j` when `c.Rel j i`. -/
noncomputable def inlX (i j : ι) (hij : c.Rel j i) : F.X i ⟶ X φ j :=
haveI := HasHomotopyCofiber.hasBinaryBiproduct φ _ _ hij
biprod.inl ≫ (XIsoBiprod φ j i hij).inv
@[reassoc (attr := simp)]
lemma inlX_fstX (i j : ι ) (hij : c.Rel j i) :
inlX φ i j hij ≫ fstX φ j i hij = 𝟙 _ := by
simp [inlX, fstX]
@[reassoc (attr := simp)]
lemma inlX_sndX (i j : ι) (hij : c.Rel j i) :
inlX φ i j hij ≫ sndX φ j = 0 := by
obtain rfl := c.next_eq' hij
simp [inlX, sndX, dif_pos hij]
@[reassoc (attr := simp)]
lemma inrX_fstX (i j : ι) (hij : c.Rel i j) :
inrX φ i ≫ fstX φ i j hij = 0 := by
obtain rfl := c.next_eq' hij
simp [inrX, fstX, dif_pos hij]
/-- The `d` field of the homological complex `homotopyCofiber φ`. -/
noncomputable def d (i j : ι) : X φ i ⟶ X φ j :=
if hij : c.Rel i j
then
(if hj : c.Rel j (c.next j) then -fstX φ i j hij ≫ F.d _ _ ≫ inlX φ _ _ hj else 0) +
fstX φ i j hij ≫ φ.f j ≫ inrX φ j + sndX φ i ≫ G.d i j ≫ inrX φ j
else
0
lemma ext_to_X (i j : ι) (hij : c.Rel i j) {A : C} {f g : A ⟶ X φ i}
(h₁ : f ≫ fstX φ i j hij = g ≫ fstX φ i j hij) (h₂ : f ≫ sndX φ i = g ≫ sndX φ i) :
f = g := by
haveI := HasHomotopyCofiber.hasBinaryBiproduct φ _ _ hij
rw [← cancel_mono (XIsoBiprod φ i j hij).hom]
apply biprod.hom_ext
· simpa using h₁
· obtain rfl := c.next_eq' hij
simpa [sndX, dif_pos hij] using h₂
lemma ext_to_X' (i : ι) (hi : ¬ c.Rel i (c.next i)) {A : C} {f g : A ⟶ X φ i}
(h : f ≫ sndX φ i = g ≫ sndX φ i) : f = g := by
rw [← cancel_mono (XIso φ i hi).hom]
simpa only [sndX, dif_neg hi] using h
lemma ext_from_X (i j : ι) (hij : c.Rel j i) {A : C} {f g : X φ j ⟶ A}
(h₁ : inlX φ i j hij ≫ f = inlX φ i j hij ≫ g) (h₂ : inrX φ j ≫ f = inrX φ j ≫ g) :
f = g := by
haveI := HasHomotopyCofiber.hasBinaryBiproduct φ _ _ hij
rw [← cancel_epi (XIsoBiprod φ j i hij).inv]
apply biprod.hom_ext'
· simpa [inlX] using h₁
· obtain rfl := c.next_eq' hij
simpa [inrX, dif_pos hij] using h₂
lemma ext_from_X' (i : ι) (hi : ¬ c.Rel i (c.next i)) {A : C} {f g : X φ i ⟶ A}
(h : inrX φ i ≫ f = inrX φ i ≫ g) : f = g := by
rw [← cancel_epi (XIso φ i hi).inv]
simpa only [inrX, dif_neg hi] using h
@[reassoc]
lemma d_fstX (i j k : ι) (hij : c.Rel i j) (hjk : c.Rel j k) :
d φ i j ≫ fstX φ j k hjk = -fstX φ i j hij ≫ F.d j k := by
obtain rfl := c.next_eq' hjk
simp [d, dif_pos hij, dif_pos hjk]
@[reassoc]
lemma d_sndX (i j : ι) (hij : c.Rel i j) :
d φ i j ≫ sndX φ j = fstX φ i j hij ≫ φ.f j + sndX φ i ≫ G.d i j := by
dsimp [d]
split_ifs with hij <;> simp
@[reassoc]
lemma inlX_d (i j k : ι) (hij : c.Rel i j) (hjk : c.Rel j k) :
inlX φ j i hij ≫ d φ i j = -F.d j k ≫ inlX φ k j hjk + φ.f j ≫ inrX φ j := by
apply ext_to_X φ j k hjk
· dsimp
simp [d_fstX φ _ _ _ hij hjk]
· simp [d_sndX φ _ _ hij]
| @[reassoc]
lemma inlX_d' (i j : ι) (hij : c.Rel i j) (hj : ¬ c.Rel j (c.next j)) :
inlX φ j i hij ≫ d φ i j = φ.f j ≫ inrX φ j := by
apply ext_to_X' _ _ hj
simp [d_sndX φ i j hij]
| Mathlib/Algebra/Homology/HomotopyCofiber.lean | 193 | 197 |
/-
Copyright (c) 2014 Robert Y. Lewis. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Robert Y. Lewis, Leonardo de Moura, Mario Carneiro, Floris van Doorn
-/
import Mathlib.Algebra.Field.Basic
import Mathlib.Algebra.GroupWithZero.Units.Lemmas
import Mathlib.Algebra.Order.Ring.Abs
import Mathlib.Order.Bounds.Basic
import Mathlib.Order.Bounds.OrderIso
import Mathlib.Tactic.Positivity.Core
/-!
# Lemmas about linear ordered (semi)fields
-/
open Function OrderDual
variable {ι α β : Type*}
section LinearOrderedSemifield
variable [Semifield α] [LinearOrder α] [IsStrictOrderedRing α] {a b c d e : α} {m n : ℤ}
/-!
### Relating two divisions.
-/
@[deprecated div_le_div_iff_of_pos_right (since := "2024-11-12")]
theorem div_le_div_right (hc : 0 < c) : a / c ≤ b / c ↔ a ≤ b := div_le_div_iff_of_pos_right hc
@[deprecated div_lt_div_iff_of_pos_right (since := "2024-11-12")]
theorem div_lt_div_right (hc : 0 < c) : a / c < b / c ↔ a < b := div_lt_div_iff_of_pos_right hc
@[deprecated div_lt_div_iff_of_pos_left (since := "2024-11-13")]
theorem div_lt_div_left (ha : 0 < a) (hb : 0 < b) (hc : 0 < c) : a / b < a / c ↔ c < b :=
div_lt_div_iff_of_pos_left ha hb hc
@[deprecated div_le_div_iff_of_pos_left (since := "2024-11-12")]
theorem div_le_div_left (ha : 0 < a) (hb : 0 < b) (hc : 0 < c) : a / b ≤ a / c ↔ c ≤ b :=
div_le_div_iff_of_pos_left ha hb hc
@[deprecated div_lt_div_iff₀ (since := "2024-11-12")]
theorem div_lt_div_iff (b0 : 0 < b) (d0 : 0 < d) : a / b < c / d ↔ a * d < c * b :=
div_lt_div_iff₀ b0 d0
@[deprecated div_le_div_iff₀ (since := "2024-11-12")]
theorem div_le_div_iff (b0 : 0 < b) (d0 : 0 < d) : a / b ≤ c / d ↔ a * d ≤ c * b :=
div_le_div_iff₀ b0 d0
@[deprecated div_le_div₀ (since := "2024-11-12")]
theorem div_le_div (hc : 0 ≤ c) (hac : a ≤ c) (hd : 0 < d) (hbd : d ≤ b) : a / b ≤ c / d :=
div_le_div₀ hc hac hd hbd
@[deprecated div_lt_div₀ (since := "2024-11-12")]
theorem div_lt_div (hac : a < c) (hbd : d ≤ b) (c0 : 0 ≤ c) (d0 : 0 < d) : a / b < c / d :=
div_lt_div₀ hac hbd c0 d0
@[deprecated div_lt_div₀' (since := "2024-11-12")]
theorem div_lt_div' (hac : a ≤ c) (hbd : d < b) (c0 : 0 < c) (d0 : 0 < d) : a / b < c / d :=
div_lt_div₀' hac hbd c0 d0
/-!
### Relating one division and involving `1`
-/
@[bound]
theorem div_le_self (ha : 0 ≤ a) (hb : 1 ≤ b) : a / b ≤ a := by
simpa only [div_one] using div_le_div_of_nonneg_left ha zero_lt_one hb
@[bound]
theorem div_lt_self (ha : 0 < a) (hb : 1 < b) : a / b < a := by
simpa only [div_one] using div_lt_div_of_pos_left ha zero_lt_one hb
@[bound]
theorem le_div_self (ha : 0 ≤ a) (hb₀ : 0 < b) (hb₁ : b ≤ 1) : a ≤ a / b := by
simpa only [div_one] using div_le_div_of_nonneg_left ha hb₀ hb₁
theorem one_le_div (hb : 0 < b) : 1 ≤ a / b ↔ b ≤ a := by rw [le_div_iff₀ hb, one_mul]
theorem div_le_one (hb : 0 < b) : a / b ≤ 1 ↔ a ≤ b := by rw [div_le_iff₀ hb, one_mul]
theorem one_lt_div (hb : 0 < b) : 1 < a / b ↔ b < a := by rw [lt_div_iff₀ hb, one_mul]
theorem div_lt_one (hb : 0 < b) : a / b < 1 ↔ a < b := by rw [div_lt_iff₀ hb, one_mul]
theorem one_div_le (ha : 0 < a) (hb : 0 < b) : 1 / a ≤ b ↔ 1 / b ≤ a := by
simpa using inv_le_comm₀ ha hb
theorem one_div_lt (ha : 0 < a) (hb : 0 < b) : 1 / a < b ↔ 1 / b < a := by
simpa using inv_lt_comm₀ ha hb
theorem le_one_div (ha : 0 < a) (hb : 0 < b) : a ≤ 1 / b ↔ b ≤ 1 / a := by
simpa using le_inv_comm₀ ha hb
theorem lt_one_div (ha : 0 < a) (hb : 0 < b) : a < 1 / b ↔ b < 1 / a := by
simpa using lt_inv_comm₀ ha hb
@[bound] lemma Bound.one_lt_div_of_pos_of_lt (b0 : 0 < b) : b < a → 1 < a / b := (one_lt_div b0).mpr
@[bound] lemma Bound.div_lt_one_of_pos_of_lt (b0 : 0 < b) : a < b → a / b < 1 := (div_lt_one b0).mpr
/-!
### Relating two divisions, involving `1`
-/
theorem one_div_le_one_div_of_le (ha : 0 < a) (h : a ≤ b) : 1 / b ≤ 1 / a := by
simpa using inv_anti₀ ha h
theorem one_div_lt_one_div_of_lt (ha : 0 < a) (h : a < b) : 1 / b < 1 / a := by
rwa [lt_div_iff₀' ha, ← div_eq_mul_one_div, div_lt_one (ha.trans h)]
theorem le_of_one_div_le_one_div (ha : 0 < a) (h : 1 / a ≤ 1 / b) : b ≤ a :=
le_imp_le_of_lt_imp_lt (one_div_lt_one_div_of_lt ha) h
theorem lt_of_one_div_lt_one_div (ha : 0 < a) (h : 1 / a < 1 / b) : b < a :=
lt_imp_lt_of_le_imp_le (one_div_le_one_div_of_le ha) h
/-- For the single implications with fewer assumptions, see `one_div_le_one_div_of_le` and
`le_of_one_div_le_one_div` -/
theorem one_div_le_one_div (ha : 0 < a) (hb : 0 < b) : 1 / a ≤ 1 / b ↔ b ≤ a :=
div_le_div_iff_of_pos_left zero_lt_one ha hb
/-- For the single implications with fewer assumptions, see `one_div_lt_one_div_of_lt` and
`lt_of_one_div_lt_one_div` -/
theorem one_div_lt_one_div (ha : 0 < a) (hb : 0 < b) : 1 / a < 1 / b ↔ b < a :=
div_lt_div_iff_of_pos_left zero_lt_one ha hb
theorem one_lt_one_div (h1 : 0 < a) (h2 : a < 1) : 1 < 1 / a := by
rwa [lt_one_div (@zero_lt_one α _ _ _ _ _) h1, one_div_one]
theorem one_le_one_div (h1 : 0 < a) (h2 : a ≤ 1) : 1 ≤ 1 / a := by
rwa [le_one_div (@zero_lt_one α _ _ _ _ _) h1, one_div_one]
/-!
### Results about halving.
The equalities also hold in semifields of characteristic `0`.
-/
theorem half_pos (h : 0 < a) : 0 < a / 2 :=
div_pos h zero_lt_two
theorem one_half_pos : (0 : α) < 1 / 2 :=
half_pos zero_lt_one
@[simp]
theorem half_le_self_iff : a / 2 ≤ a ↔ 0 ≤ a := by
rw [div_le_iff₀ (zero_lt_two' α), mul_two, le_add_iff_nonneg_left]
@[simp]
theorem half_lt_self_iff : a / 2 < a ↔ 0 < a := by
rw [div_lt_iff₀ (zero_lt_two' α), mul_two, lt_add_iff_pos_left]
alias ⟨_, half_le_self⟩ := half_le_self_iff
alias ⟨_, half_lt_self⟩ := half_lt_self_iff
alias div_two_lt_of_pos := half_lt_self
theorem one_half_lt_one : (1 / 2 : α) < 1 :=
half_lt_self zero_lt_one
theorem two_inv_lt_one : (2⁻¹ : α) < 1 :=
(one_div _).symm.trans_lt one_half_lt_one
theorem left_lt_add_div_two : a < (a + b) / 2 ↔ a < b := by simp [lt_div_iff₀, mul_two]
theorem add_div_two_lt_right : (a + b) / 2 < b ↔ a < b := by simp [div_lt_iff₀, mul_two]
theorem add_thirds (a : α) : a / 3 + a / 3 + a / 3 = a := by
rw [div_add_div_same, div_add_div_same, ← two_mul, ← add_one_mul 2 a, two_add_one_eq_three,
mul_div_cancel_left₀ a three_ne_zero]
/-!
### Miscellaneous lemmas
-/
@[simp] lemma div_pos_iff_of_pos_left (ha : 0 < a) : 0 < a / b ↔ 0 < b := by
simp only [div_eq_mul_inv, mul_pos_iff_of_pos_left ha, inv_pos]
@[simp] lemma div_pos_iff_of_pos_right (hb : 0 < b) : 0 < a / b ↔ 0 < a := by
simp only [div_eq_mul_inv, mul_pos_iff_of_pos_right (inv_pos.2 hb)]
theorem mul_le_mul_of_mul_div_le (h : a * (b / c) ≤ d) (hc : 0 < c) : b * a ≤ d * c := by
rw [← mul_div_assoc] at h
rwa [mul_comm b, ← div_le_iff₀ hc]
theorem div_mul_le_div_mul_of_div_le_div (h : a / b ≤ c / d) (he : 0 ≤ e) :
a / (b * e) ≤ c / (d * e) := by
rw [div_mul_eq_div_mul_one_div, div_mul_eq_div_mul_one_div]
exact mul_le_mul_of_nonneg_right h (one_div_nonneg.2 he)
theorem exists_pos_mul_lt {a : α} (h : 0 < a) (b : α) : ∃ c : α, 0 < c ∧ b * c < a := by
have : 0 < a / max (b + 1) 1 := div_pos h (lt_max_iff.2 (Or.inr zero_lt_one))
refine ⟨a / max (b + 1) 1, this, ?_⟩
rw [← lt_div_iff₀ this, div_div_cancel₀ h.ne']
exact lt_max_iff.2 (Or.inl <| lt_add_one _)
theorem exists_pos_lt_mul {a : α} (h : 0 < a) (b : α) : ∃ c : α, 0 < c ∧ b < c * a :=
let ⟨c, hc₀, hc⟩ := exists_pos_mul_lt h b;
⟨c⁻¹, inv_pos.2 hc₀, by rwa [← div_eq_inv_mul, lt_div_iff₀ hc₀]⟩
lemma monotone_div_right_of_nonneg (ha : 0 ≤ a) : Monotone (· / a) :=
fun _b _c hbc ↦ div_le_div_of_nonneg_right hbc ha
lemma strictMono_div_right_of_pos (ha : 0 < a) : StrictMono (· / a) :=
fun _b _c hbc ↦ div_lt_div_of_pos_right hbc ha
theorem Monotone.div_const {β : Type*} [Preorder β] {f : β → α} (hf : Monotone f) {c : α}
(hc : 0 ≤ c) : Monotone fun x => f x / c := (monotone_div_right_of_nonneg hc).comp hf
theorem StrictMono.div_const {β : Type*} [Preorder β] {f : β → α} (hf : StrictMono f) {c : α}
(hc : 0 < c) : StrictMono fun x => f x / c := by
simpa only [div_eq_mul_inv] using hf.mul_const (inv_pos.2 hc)
-- see Note [lower instance priority]
instance (priority := 100) LinearOrderedSemiField.toDenselyOrdered : DenselyOrdered α where
dense a₁ a₂ h :=
⟨(a₁ + a₂) / 2,
calc
a₁ = (a₁ + a₁) / 2 := (add_self_div_two a₁).symm
_ < (a₁ + a₂) / 2 := div_lt_div_of_pos_right (add_lt_add_left h _) zero_lt_two
,
calc
(a₁ + a₂) / 2 < (a₂ + a₂) / 2 := div_lt_div_of_pos_right (add_lt_add_right h _) zero_lt_two
_ = a₂ := add_self_div_two a₂
⟩
theorem min_div_div_right {c : α} (hc : 0 ≤ c) (a b : α) : min (a / c) (b / c) = min a b / c :=
(monotone_div_right_of_nonneg hc).map_min.symm
theorem max_div_div_right {c : α} (hc : 0 ≤ c) (a b : α) : max (a / c) (b / c) = max a b / c :=
(monotone_div_right_of_nonneg hc).map_max.symm
theorem one_div_strictAntiOn : StrictAntiOn (fun x : α => 1 / x) (Set.Ioi 0) :=
fun _ x1 _ y1 xy => (one_div_lt_one_div (Set.mem_Ioi.mp y1) (Set.mem_Ioi.mp x1)).mpr xy
theorem one_div_pow_le_one_div_pow_of_le (a1 : 1 ≤ a) {m n : ℕ} (mn : m ≤ n) :
1 / a ^ n ≤ 1 / a ^ m := by
refine (one_div_le_one_div ?_ ?_).mpr (pow_right_mono₀ a1 mn) <;>
exact pow_pos (zero_lt_one.trans_le a1) _
theorem one_div_pow_lt_one_div_pow_of_lt (a1 : 1 < a) {m n : ℕ} (mn : m < n) :
1 / a ^ n < 1 / a ^ m := by
refine (one_div_lt_one_div ?_ ?_).2 (pow_lt_pow_right₀ a1 mn) <;>
exact pow_pos (zero_lt_one.trans a1) _
theorem one_div_pow_anti (a1 : 1 ≤ a) : Antitone fun n : ℕ => 1 / a ^ n := fun _ _ =>
one_div_pow_le_one_div_pow_of_le a1
theorem one_div_pow_strictAnti (a1 : 1 < a) : StrictAnti fun n : ℕ => 1 / a ^ n := fun _ _ =>
one_div_pow_lt_one_div_pow_of_lt a1
theorem inv_strictAntiOn : StrictAntiOn (fun x : α => x⁻¹) (Set.Ioi 0) := fun _ hx _ hy xy =>
(inv_lt_inv₀ hy hx).2 xy
theorem inv_pow_le_inv_pow_of_le (a1 : 1 ≤ a) {m n : ℕ} (mn : m ≤ n) : (a ^ n)⁻¹ ≤ (a ^ m)⁻¹ := by
convert one_div_pow_le_one_div_pow_of_le a1 mn using 1 <;> simp
theorem inv_pow_lt_inv_pow_of_lt (a1 : 1 < a) {m n : ℕ} (mn : m < n) : (a ^ n)⁻¹ < (a ^ m)⁻¹ := by
convert one_div_pow_lt_one_div_pow_of_lt a1 mn using 1 <;> simp
theorem inv_pow_anti (a1 : 1 ≤ a) : Antitone fun n : ℕ => (a ^ n)⁻¹ := fun _ _ =>
inv_pow_le_inv_pow_of_le a1
theorem inv_pow_strictAnti (a1 : 1 < a) : StrictAnti fun n : ℕ => (a ^ n)⁻¹ := fun _ _ =>
inv_pow_lt_inv_pow_of_lt a1
theorem le_iff_forall_one_lt_le_mul₀ {α : Type*}
[Semifield α] [LinearOrder α] [IsStrictOrderedRing α]
{a b : α} (hb : 0 ≤ b) : a ≤ b ↔ ∀ ε, 1 < ε → a ≤ b * ε := by
refine ⟨fun h _ hε ↦ h.trans <| le_mul_of_one_le_right hb hε.le, fun h ↦ ?_⟩
obtain rfl|hb := hb.eq_or_lt
· simp_rw [zero_mul] at h
exact h 2 one_lt_two
refine le_of_forall_gt_imp_ge_of_dense fun x hbx => ?_
convert h (x / b) ((one_lt_div hb).mpr hbx)
rw [mul_div_cancel₀ _ hb.ne']
/-! ### Results about `IsGLB` -/
theorem IsGLB.mul_left {s : Set α} (ha : 0 ≤ a) (hs : IsGLB s b) :
IsGLB ((fun b => a * b) '' s) (a * b) := by
rcases lt_or_eq_of_le ha with (ha | rfl)
· exact (OrderIso.mulLeft₀ _ ha).isGLB_image'.2 hs
· simp_rw [zero_mul]
rw [hs.nonempty.image_const]
exact isGLB_singleton
theorem IsGLB.mul_right {s : Set α} (ha : 0 ≤ a) (hs : IsGLB s b) :
IsGLB ((fun b => b * a) '' s) (b * a) := by simpa [mul_comm] using hs.mul_left ha
end LinearOrderedSemifield
section
variable [Field α] [LinearOrder α] [IsStrictOrderedRing α] {a b c d : α} {n : ℤ}
/-! ### Lemmas about pos, nonneg, nonpos, neg -/
theorem div_pos_iff : 0 < a / b ↔ 0 < a ∧ 0 < b ∨ a < 0 ∧ b < 0 := by
simp only [division_def, mul_pos_iff, inv_pos, inv_lt_zero]
theorem div_neg_iff : a / b < 0 ↔ 0 < a ∧ b < 0 ∨ a < 0 ∧ 0 < b := by
simp [division_def, mul_neg_iff]
theorem div_nonneg_iff : 0 ≤ a / b ↔ 0 ≤ a ∧ 0 ≤ b ∨ a ≤ 0 ∧ b ≤ 0 := by
simp [division_def, mul_nonneg_iff]
theorem div_nonpos_iff : a / b ≤ 0 ↔ 0 ≤ a ∧ b ≤ 0 ∨ a ≤ 0 ∧ 0 ≤ b := by
simp [division_def, mul_nonpos_iff]
theorem div_nonneg_of_nonpos (ha : a ≤ 0) (hb : b ≤ 0) : 0 ≤ a / b :=
div_nonneg_iff.2 <| Or.inr ⟨ha, hb⟩
theorem div_pos_of_neg_of_neg (ha : a < 0) (hb : b < 0) : 0 < a / b :=
div_pos_iff.2 <| Or.inr ⟨ha, hb⟩
theorem div_neg_of_neg_of_pos (ha : a < 0) (hb : 0 < b) : a / b < 0 :=
div_neg_iff.2 <| Or.inr ⟨ha, hb⟩
theorem div_neg_of_pos_of_neg (ha : 0 < a) (hb : b < 0) : a / b < 0 :=
div_neg_iff.2 <| Or.inl ⟨ha, hb⟩
/-! ### Relating one division with another term -/
theorem div_le_iff_of_neg (hc : c < 0) : b / c ≤ a ↔ a * c ≤ b :=
⟨fun h => div_mul_cancel₀ b (ne_of_lt hc) ▸ mul_le_mul_of_nonpos_right h hc.le, fun h =>
calc
a = a * c * (1 / c) := mul_mul_div a (ne_of_lt hc)
_ ≥ b * (1 / c) := mul_le_mul_of_nonpos_right h (one_div_neg.2 hc).le
_ = b / c := (div_eq_mul_one_div b c).symm
⟩
theorem div_le_iff_of_neg' (hc : c < 0) : b / c ≤ a ↔ c * a ≤ b := by
rw [mul_comm, div_le_iff_of_neg hc]
theorem le_div_iff_of_neg (hc : c < 0) : a ≤ b / c ↔ b ≤ a * c := by
rw [← neg_neg c, mul_neg, div_neg, le_neg, div_le_iff₀ (neg_pos.2 hc), neg_mul]
theorem le_div_iff_of_neg' (hc : c < 0) : a ≤ b / c ↔ b ≤ c * a := by
rw [mul_comm, le_div_iff_of_neg hc]
theorem div_lt_iff_of_neg (hc : c < 0) : b / c < a ↔ a * c < b :=
lt_iff_lt_of_le_iff_le <| le_div_iff_of_neg hc
theorem div_lt_iff_of_neg' (hc : c < 0) : b / c < a ↔ c * a < b := by
rw [mul_comm, div_lt_iff_of_neg hc]
theorem lt_div_iff_of_neg (hc : c < 0) : a < b / c ↔ b < a * c :=
lt_iff_lt_of_le_iff_le <| div_le_iff_of_neg hc
theorem lt_div_iff_of_neg' (hc : c < 0) : a < b / c ↔ b < c * a := by
rw [mul_comm, lt_div_iff_of_neg hc]
theorem div_le_one_of_ge (h : b ≤ a) (hb : b ≤ 0) : a / b ≤ 1 := by
simpa only [neg_div_neg_eq] using div_le_one_of_le₀ (neg_le_neg h) (neg_nonneg_of_nonpos hb)
/-! ### Bi-implications of inequalities using inversions -/
theorem inv_le_inv_of_neg (ha : a < 0) (hb : b < 0) : a⁻¹ ≤ b⁻¹ ↔ b ≤ a := by
rw [← one_div, div_le_iff_of_neg ha, ← div_eq_inv_mul, div_le_iff_of_neg hb, one_mul]
theorem inv_le_of_neg (ha : a < 0) (hb : b < 0) : a⁻¹ ≤ b ↔ b⁻¹ ≤ a := by
rw [← inv_le_inv_of_neg hb (inv_lt_zero.2 ha), inv_inv]
theorem le_inv_of_neg (ha : a < 0) (hb : b < 0) : a ≤ b⁻¹ ↔ b ≤ a⁻¹ := by
rw [← inv_le_inv_of_neg (inv_lt_zero.2 hb) ha, inv_inv]
theorem inv_lt_inv_of_neg (ha : a < 0) (hb : b < 0) : a⁻¹ < b⁻¹ ↔ b < a :=
lt_iff_lt_of_le_iff_le (inv_le_inv_of_neg hb ha)
theorem inv_lt_of_neg (ha : a < 0) (hb : b < 0) : a⁻¹ < b ↔ b⁻¹ < a :=
| lt_iff_lt_of_le_iff_le (le_inv_of_neg hb ha)
| Mathlib/Algebra/Order/Field/Basic.lean | 381 | 381 |
/-
Copyright (c) 2019 Abhimanyu Pallavi Sudhir. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Abhimanyu Pallavi Sudhir, Yury Kudryashov
-/
import Mathlib.Algebra.Field.Defs
import Mathlib.Algebra.Order.Group.Unbundled.Abs
import Mathlib.Order.Filter.Ring
import Mathlib.Order.Filter.Ultrafilter.Defs
/-!
# Ultraproducts
If `φ` is an ultrafilter, then the space of germs of functions `f : α → β` at `φ` is called
the *ultraproduct*. In this file we prove properties of ultraproducts that rely on `φ` being an
ultrafilter. Definitions and properties that work for any filter should go to `Order.Filter.Germ`.
## Tags
ultrafilter, ultraproduct
-/
universe u v
variable {α : Type u} {β : Type v} {φ : Ultrafilter α}
namespace Filter
local notation3 "∀* "(...)", "r:(scoped p => Filter.Eventually p (Ultrafilter.toFilter φ)) => r
namespace Germ
open Ultrafilter
local notation "β*" => Germ (φ : Filter α) β
instance instGroupWithZero [GroupWithZero β] : GroupWithZero β* where
__ := instDivInvMonoid
__ := instMonoidWithZero
mul_inv_cancel f := inductionOn f fun f hf ↦ coe_eq.2 <| (φ.em fun y ↦ f y = 0).elim
(fun H ↦ (hf <| coe_eq.2 H).elim) fun H ↦ H.mono fun _ ↦ mul_inv_cancel₀
inv_zero := coe_eq.2 <| by simp only [Function.comp_def, inv_zero, EventuallyEq.rfl]
instance instDivisionSemiring [DivisionSemiring β] : DivisionSemiring β* where
toSemiring := instSemiring
__ := instGroupWithZero
nnqsmul := _
nnqsmul_def := fun _ _ => rfl
instance instDivisionRing [DivisionRing β] : DivisionRing β* where
__ := instRing
__ := instDivisionSemiring
qsmul := _
qsmul_def := fun _ _ => rfl
instance instSemifield [Semifield β] : Semifield β* where
__ := instCommSemiring
__ := instDivisionSemiring
instance instField [Field β] : Field β* where
__ := instCommRing
__ := instDivisionRing
theorem coe_lt [Preorder β] {f g : α → β} : (f : β*) < g ↔ ∀* x, f x < g x := by
simp only [lt_iff_le_not_le, eventually_and, coe_le, eventually_not, EventuallyLE]
theorem coe_pos [Preorder β] [Zero β] {f : α → β} : 0 < (f : β*) ↔ ∀* x, 0 < f x :=
coe_lt
theorem const_lt [Preorder β] {x y : β} : x < y → (↑x : β*) < ↑y :=
coe_lt.mpr ∘ liftRel_const
@[simp, norm_cast]
theorem const_lt_iff [Preorder β] {x y : β} : (↑x : β*) < ↑y ↔ x < y :=
coe_lt.trans liftRel_const_iff
theorem lt_def [Preorder β] : ((· < ·) : β* → β* → Prop) = LiftRel (· < ·) := by
ext ⟨f⟩ ⟨g⟩
exact coe_lt
instance isTotal [LE β] [IsTotal β (· ≤ ·)] : IsTotal β* (· ≤ ·) :=
⟨fun f g =>
inductionOn₂ f g fun _f _g => eventually_or.1 <| Eventually.of_forall fun _x => total_of _ _ _⟩
open Classical in
/-- If `φ` is an ultrafilter then the ultraproduct is a linear order. -/
noncomputable instance instLinearOrder [LinearOrder β] : LinearOrder β* :=
Lattice.toLinearOrder _
instance instIsStrictOrderedRing [Semiring β] [PartialOrder β] [IsStrictOrderedRing β] :
IsStrictOrderedRing β* where
mul_lt_mul_of_pos_left x y z := inductionOn₃ x y z fun _f _g _h hfg hh ↦
coe_lt.2 <| (coe_lt.1 hh).mp <| (coe_lt.1 hfg).mono fun _a ↦ mul_lt_mul_of_pos_left
mul_lt_mul_of_pos_right x y z := inductionOn₃ x y z fun _f _g _h hfg hh ↦
coe_lt.2 <| (coe_lt.1 hh).mp <| (coe_lt.1 hfg).mono fun _a ↦ mul_lt_mul_of_pos_right
theorem max_def [LinearOrder β] (x y : β*) : max x y = map₂ max x y :=
inductionOn₂ x y fun a b => by
rcases le_total (a : β*) b with h | h
· rw [max_eq_right h, map₂_coe, coe_eq]
exact h.mono fun i hi => (max_eq_right hi).symm
· rw [max_eq_left h, map₂_coe, coe_eq]
exact h.mono fun i hi => (max_eq_left hi).symm
theorem min_def [K : LinearOrder β] (x y : β*) : min x y = map₂ min x y :=
inductionOn₂ x y fun a b => by
rcases le_total (a : β*) b with h | h
· rw [min_eq_left h, map₂_coe, coe_eq]
exact h.mono fun i hi => (min_eq_left hi).symm
· rw [min_eq_right h, map₂_coe, coe_eq]
exact h.mono fun i hi => (min_eq_right hi).symm
theorem abs_def [AddCommGroup β] [LinearOrder β] (x : β*) :
|x| = map abs x :=
inductionOn x fun _a => rfl
@[simp]
theorem const_max [LinearOrder β] (x y : β) : (↑(max x y : β) : β*) = max ↑x ↑y := by
rw [max_def, map₂_const]
@[simp]
theorem const_min [LinearOrder β] (x y : β) : (↑(min x y : β) : β*) = min ↑x ↑y := by
rw [min_def, map₂_const]
@[simp]
theorem const_abs [AddCommGroup β] [LinearOrder β] (x : β) :
(↑|x| : β*) = |↑x| := by
rw [abs_def, map_const]
end Germ
end Filter
| Mathlib/Order/Filter/FilterProduct.lean | 166 | 167 | |
/-
Copyright (c) 2018 Louis Carlin. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Louis Carlin, Mario Carneiro
-/
import Mathlib.Algebra.EuclideanDomain.Defs
import Mathlib.Algebra.Ring.Divisibility.Basic
import Mathlib.Algebra.Ring.Regular
import Mathlib.Algebra.GroupWithZero.Divisibility
import Mathlib.Algebra.Ring.Basic
/-!
# Lemmas about Euclidean domains
## Main statements
* `gcd_eq_gcd_ab`: states Bézout's lemma for Euclidean domains.
-/
universe u
namespace EuclideanDomain
variable {R : Type u}
variable [EuclideanDomain R]
/-- The well founded relation in a Euclidean Domain satisfying `a % b ≺ b` for `b ≠ 0` -/
local infixl:50 " ≺ " => EuclideanDomain.r
-- See note [lower instance priority]
instance (priority := 100) toMulDivCancelClass : MulDivCancelClass R where
mul_div_cancel a b hb := by
refine (eq_of_sub_eq_zero ?_).symm
by_contra h
have := mul_right_not_lt b h
rw [sub_mul, mul_comm (_ / _), sub_eq_iff_eq_add'.2 (div_add_mod (a * b) b).symm] at this
exact this (mod_lt _ hb)
theorem mod_eq_sub_mul_div {R : Type*} [EuclideanDomain R] (a b : R) : a % b = a - b * (a / b) :=
calc
a % b = b * (a / b) + a % b - b * (a / b) := (add_sub_cancel_left _ _).symm
_ = a - b * (a / b) := by rw [div_add_mod]
theorem val_dvd_le : ∀ a b : R, b ∣ a → a ≠ 0 → ¬a ≺ b
| _, b, ⟨d, rfl⟩, ha => mul_left_not_lt b (mt (by rintro rfl; exact mul_zero _) ha)
@[simp]
theorem mod_eq_zero {a b : R} : a % b = 0 ↔ b ∣ a :=
⟨fun h => by
rw [← div_add_mod a b, h, add_zero]
exact dvd_mul_right _ _, fun ⟨c, e⟩ => by
rw [e, ← add_left_cancel_iff, div_add_mod, add_zero]
haveI := Classical.dec
by_cases b0 : b = 0
· simp only [b0, zero_mul]
· rw [mul_div_cancel_left₀ _ b0]⟩
@[simp]
theorem mod_self (a : R) : a % a = 0 :=
mod_eq_zero.2 dvd_rfl
theorem dvd_mod_iff {a b c : R} (h : c ∣ b) : c ∣ a % b ↔ c ∣ a := by
rw [← dvd_add_right (h.mul_right _), div_add_mod]
@[simp]
theorem mod_one (a : R) : a % 1 = 0 :=
mod_eq_zero.2 (one_dvd _)
@[simp]
theorem zero_mod (b : R) : 0 % b = 0 :=
mod_eq_zero.2 (dvd_zero _)
@[simp]
theorem zero_div {a : R} : 0 / a = 0 :=
by_cases (fun a0 : a = 0 => a0.symm ▸ div_zero 0) fun a0 => by
| simpa only [zero_mul] using mul_div_cancel_right₀ 0 a0
@[simp]
| Mathlib/Algebra/EuclideanDomain/Basic.lean | 78 | 80 |
/-
Copyright (c) 2019 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl, Mario Carneiro
-/
import Mathlib.Algebra.Field.Basic
import Mathlib.Algebra.Field.Rat
import Mathlib.Algebra.Group.Commute.Basic
import Mathlib.Algebra.GroupWithZero.Units.Lemmas
import Mathlib.Data.Int.Cast.Lemmas
import Mathlib.Data.Rat.Lemmas
import Mathlib.Order.Nat
/-!
# Casts for Rational Numbers
## Summary
We define the canonical injection from ℚ into an arbitrary division ring and prove various
casting lemmas showing the well-behavedness of this injection.
## Tags
rat, rationals, field, ℚ, numerator, denominator, num, denom, cast, coercion, casting
-/
assert_not_exists MulAction OrderedAddCommMonoid
variable {F ι α β : Type*}
namespace NNRat
variable [DivisionSemiring α] {q r : ℚ≥0}
@[simp, norm_cast] lemma cast_natCast (n : ℕ) : ((n : ℚ≥0) : α) = n := by simp [cast_def]
@[simp, norm_cast] lemma cast_ofNat (n : ℕ) [n.AtLeastTwo] :
(ofNat(n) : ℚ≥0) = (ofNat(n) : α) := cast_natCast _
@[simp, norm_cast] lemma cast_zero : ((0 : ℚ≥0) : α) = 0 := (cast_natCast _).trans Nat.cast_zero
@[simp, norm_cast] lemma cast_one : ((1 : ℚ≥0) : α) = 1 := (cast_natCast _).trans Nat.cast_one
lemma cast_commute (q : ℚ≥0) (a : α) : Commute (↑q) a := by
simpa only [cast_def] using (q.num.cast_commute a).div_left (q.den.cast_commute a)
lemma commute_cast (a : α) (q : ℚ≥0) : Commute a q := (cast_commute ..).symm
lemma cast_comm (q : ℚ≥0) (a : α) : q * a = a * q := cast_commute _ _
@[norm_cast] lemma cast_divNat_of_ne_zero (a : ℕ) {b : ℕ} (hb : (b : α) ≠ 0) :
divNat a b = (a / b : α) := by
rcases e : divNat a b with ⟨⟨n, d, h, c⟩, hn⟩
rw [← Rat.num_nonneg] at hn
lift n to ℕ using hn
have hd : (d : α) ≠ 0 := by
refine fun hd ↦ hb ?_
have : Rat.divInt a b = _ := congr_arg NNRat.cast e
obtain ⟨k, rfl⟩ : d ∣ b := by simpa [Int.natCast_dvd_natCast, this] using Rat.den_dvd a b
simp [*]
have hb' : b ≠ 0 := by rintro rfl; exact hb Nat.cast_zero
have hd' : d ≠ 0 := by rintro rfl; exact hd Nat.cast_zero
simp_rw [Rat.mk'_eq_divInt, mk_divInt, divNat_inj hb' hd'] at e
rw [cast_def]
dsimp
rw [Commute.div_eq_div_iff _ hd hb]
· norm_cast
rw [e]
exact b.commute_cast _
@[norm_cast]
lemma cast_add_of_ne_zero (hq : (q.den : α) ≠ 0) (hr : (r.den : α) ≠ 0) :
↑(q + r) = (q + r : α) := by
rw [add_def, cast_divNat_of_ne_zero, cast_def, cast_def, mul_comm _ q.den,
(Nat.commute_cast _ _).div_add_div (Nat.commute_cast _ _) hq hr]
· push_cast
rfl
· push_cast
exact mul_ne_zero hq hr
@[norm_cast]
lemma cast_mul_of_ne_zero (hq : (q.den : α) ≠ 0) (hr : (r.den : α) ≠ 0) :
↑(q * r) = (q * r : α) := by
rw [mul_def, cast_divNat_of_ne_zero, cast_def, cast_def,
(Nat.commute_cast _ _).div_mul_div_comm (Nat.commute_cast _ _)]
· push_cast
rfl
· push_cast
exact mul_ne_zero hq hr
@[norm_cast]
lemma cast_inv_of_ne_zero (hq : (q.num : α) ≠ 0) : (q⁻¹ : ℚ≥0) = (q⁻¹ : α) := by
rw [inv_def, cast_divNat_of_ne_zero _ hq, cast_def, inv_div]
@[norm_cast]
| lemma cast_div_of_ne_zero (hq : (q.den : α) ≠ 0) (hr : (r.num : α) ≠ 0) :
↑(q / r) = (q / r : α) := by
rw [div_def, cast_divNat_of_ne_zero, cast_def, cast_def, div_eq_mul_inv (_ / _),
| Mathlib/Data/Rat/Cast/Defs.lean | 94 | 96 |
/-
Copyright (c) 2017 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Mario Carneiro
-/
import Mathlib.Data.WSeq.Basic
import Mathlib.Data.WSeq.Defs
import Mathlib.Data.WSeq.Productive
import Mathlib.Data.WSeq.Relation
deprecated_module (since := "2025-04-13")
| Mathlib/Data/Seq/WSeq.lean | 1,550 | 1,563 | |
/-
Copyright (c) 2021 Benjamin Davidson. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Benjamin Davidson, Yury Kudryashov
-/
import Mathlib.Analysis.Calculus.LocalExtr.Rolle
import Mathlib.Analysis.Calculus.Deriv.Polynomial
import Mathlib.Topology.Algebra.Polynomial
/-!
# Rolle's Theorem for polynomials
In this file we use Rolle's Theorem
to relate the number of real roots of a real polynomial and its derivative.
Namely, we prove the following facts.
* `Polynomial.card_roots_toFinset_le_card_roots_derivative_diff_roots_succ`:
the number of roots of a real polynomial `p` is at most the number of roots of its derivative
that are not roots of `p` plus one.
* `Polynomial.card_roots_toFinset_le_derivative`, `Polynomial.card_rootSet_le_derivative`:
the number of roots of a real polynomial
is at most the number of roots of its derivative plus one.
* `Polynomial.card_roots_le_derivative`: same, but the roots are counted with multiplicities.
## Keywords
polynomial, Rolle's Theorem, root
-/
namespace Polynomial
/-- The number of roots of a real polynomial `p` is at most the number of roots of its derivative
that are not roots of `p` plus one. -/
theorem card_roots_toFinset_le_card_roots_derivative_diff_roots_succ (p : ℝ[X]) :
p.roots.toFinset.card ≤ (p.derivative.roots.toFinset \ p.roots.toFinset).card + 1 := by
rcases eq_or_ne (derivative p) 0 with hp' | hp'
| · rw [eq_C_of_derivative_eq_zero hp', roots_C, Multiset.toFinset_zero, Finset.card_empty]
exact zero_le _
have hp : p ≠ 0 := ne_of_apply_ne derivative (by rwa [derivative_zero])
refine Finset.card_le_diff_of_interleaved fun x hx y hy hxy hxy' => ?_
rw [Multiset.mem_toFinset, mem_roots hp] at hx hy
obtain ⟨z, hz1, hz2⟩ := exists_deriv_eq_zero hxy p.continuousOn (hx.trans hy.symm)
refine ⟨z, ?_, hz1⟩
rwa [Multiset.mem_toFinset, mem_roots hp', IsRoot, ← p.deriv]
/-- The number of roots of a real polynomial is at most the number of roots of its derivative plus
one. -/
| Mathlib/Analysis/Calculus/LocalExtr/Polynomial.lean | 37 | 47 |
/-
Copyright (c) 2022 Eric Wieser. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Eric Wieser
-/
import Mathlib.Algebra.Order.Floor.Semiring
import Mathlib.Data.Nat.Log
/-!
# Integer logarithms in a field with respect to a natural base
This file defines two `ℤ`-valued analogs of the logarithm of `r : R` with base `b : ℕ`:
* `Int.log b r`: Lower logarithm, or floor **log**. Greatest `k` such that `↑b^k ≤ r`.
* `Int.clog b r`: Upper logarithm, or **c**eil **log**. Least `k` such that `r ≤ ↑b^k`.
Note that `Int.log` gives the position of the left-most non-zero digit:
```lean
#eval (Int.log 10 (0.09 : ℚ), Int.log 10 (0.10 : ℚ), Int.log 10 (0.11 : ℚ))
-- (-2, -1, -1)
#eval (Int.log 10 (9 : ℚ), Int.log 10 (10 : ℚ), Int.log 10 (11 : ℚ))
-- (0, 1, 1)
```
which means it can be used for computing digit expansions
```lean
import Data.Fin.VecNotation
import Mathlib.Data.Rat.Floor
def digits (b : ℕ) (q : ℚ) (n : ℕ) : ℕ :=
⌊q * ((b : ℚ) ^ (n - Int.log b q))⌋₊ % b
#eval digits 10 (1/7) ∘ ((↑) : Fin 8 → ℕ)
-- ![1, 4, 2, 8, 5, 7, 1, 4]
```
## Main results
* For `Int.log`:
* `Int.zpow_log_le_self`, `Int.lt_zpow_succ_log_self`: the bounds formed by `Int.log`,
`(b : R) ^ log b r ≤ r < (b : R) ^ (log b r + 1)`.
* `Int.zpow_log_gi`: the galois coinsertion between `zpow` and `Int.log`.
* For `Int.clog`:
* `Int.zpow_pred_clog_lt_self`, `Int.self_le_zpow_clog`: the bounds formed by `Int.clog`,
`(b : R) ^ (clog b r - 1) < r ≤ (b : R) ^ clog b r`.
* `Int.clog_zpow_gi`: the galois insertion between `Int.clog` and `zpow`.
* `Int.neg_log_inv_eq_clog`, `Int.neg_clog_inv_eq_log`: the link between the two definitions.
-/
assert_not_exists Finset
variable {R : Type*} [Semifield R] [LinearOrder R] [IsStrictOrderedRing R] [FloorSemiring R]
namespace Int
/-- The greatest power of `b` such that `b ^ log b r ≤ r`. -/
def log (b : ℕ) (r : R) : ℤ :=
if 1 ≤ r then Nat.log b ⌊r⌋₊ else -Nat.clog b ⌈r⁻¹⌉₊
omit [IsStrictOrderedRing R] in
theorem log_of_one_le_right (b : ℕ) {r : R} (hr : 1 ≤ r) : log b r = Nat.log b ⌊r⌋₊ :=
if_pos hr
theorem log_of_right_le_one (b : ℕ) {r : R} (hr : r ≤ 1) : log b r = -Nat.clog b ⌈r⁻¹⌉₊ := by
obtain rfl | hr := hr.eq_or_lt
· rw [log, if_pos hr, inv_one, Nat.ceil_one, Nat.floor_one, Nat.log_one_right, Nat.clog_one_right,
Int.ofNat_zero, neg_zero]
· exact if_neg hr.not_le
@[simp, norm_cast]
theorem log_natCast (b : ℕ) (n : ℕ) : log b (n : R) = Nat.log b n := by
cases n
· simp [log_of_right_le_one]
· rw [log_of_one_le_right, Nat.floor_natCast]
simp
@[simp]
theorem log_ofNat (b : ℕ) (n : ℕ) [n.AtLeastTwo] :
log b (ofNat(n) : R) = Nat.log b ofNat(n) :=
log_natCast b n
theorem log_of_left_le_one {b : ℕ} (hb : b ≤ 1) (r : R) : log b r = 0 := by
rcases le_total 1 r with h | h
· rw [log_of_one_le_right _ h, Nat.log_of_left_le_one hb, Int.ofNat_zero]
· rw [log_of_right_le_one _ h, Nat.clog_of_left_le_one hb, Int.ofNat_zero, neg_zero]
theorem log_of_right_le_zero (b : ℕ) {r : R} (hr : r ≤ 0) : log b r = 0 := by
rw [log_of_right_le_one _ (hr.trans zero_le_one),
Nat.clog_of_right_le_one ((Nat.ceil_eq_zero.mpr <| inv_nonpos.2 hr).trans_le zero_le_one),
Int.ofNat_zero, neg_zero]
theorem zpow_log_le_self {b : ℕ} {r : R} (hb : 1 < b) (hr : 0 < r) : (b : R) ^ log b r ≤ r := by
rcases le_total 1 r with hr1 | hr1
· rw [log_of_one_le_right _ hr1]
rw [zpow_natCast, ← Nat.cast_pow, ← Nat.le_floor_iff hr.le]
exact Nat.pow_log_le_self b (Nat.floor_pos.mpr hr1).ne'
· rw [log_of_right_le_one _ hr1, zpow_neg, zpow_natCast, ← Nat.cast_pow]
exact inv_le_of_inv_le₀ hr (Nat.ceil_le.1 <| Nat.le_pow_clog hb _)
theorem lt_zpow_succ_log_self {b : ℕ} (hb : 1 < b) (r : R) : r < (b : R) ^ (log b r + 1) := by
rcases le_or_lt r 0 with hr | hr
· rw [log_of_right_le_zero _ hr, zero_add, zpow_one]
exact hr.trans_lt (zero_lt_one.trans_le <| mod_cast hb.le)
rcases le_or_lt 1 r with hr1 | hr1
· rw [log_of_one_le_right _ hr1]
rw [Int.ofNat_add_one_out, zpow_natCast, ← Nat.cast_pow]
apply Nat.lt_of_floor_lt
exact Nat.lt_pow_succ_log_self hb _
| · rw [log_of_right_le_one _ hr1.le]
have hcri : 1 < r⁻¹ := (one_lt_inv₀ hr).2 hr1
have : 1 ≤ Nat.clog b ⌈r⁻¹⌉₊ :=
Nat.succ_le_of_lt (Nat.clog_pos hb <| Nat.one_lt_cast.1 <| hcri.trans_le (Nat.le_ceil _))
rw [neg_add_eq_sub, ← neg_sub, ← Int.ofNat_one, ← Int.ofNat_sub this, zpow_neg, zpow_natCast,
lt_inv_comm₀ hr (pow_pos (Nat.cast_pos.mpr <| zero_lt_one.trans hb) _), ← Nat.cast_pow]
refine Nat.lt_ceil.1 ?_
exact Nat.pow_pred_clog_lt_self hb <| Nat.one_lt_cast.1 <| hcri.trans_le <| Nat.le_ceil _
@[simp]
theorem log_zero_right (b : ℕ) : log b (0 : R) = 0 :=
log_of_right_le_zero b le_rfl
@[simp]
theorem log_one_right (b : ℕ) : log b (1 : R) = 0 := by
rw [log_of_one_le_right _ le_rfl, Nat.floor_one, Nat.log_one_right, Int.ofNat_zero]
| Mathlib/Data/Int/Log.lean | 108 | 124 |
/-
Copyright (c) 2014 Parikshit Khanna. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Parikshit Khanna, Jeremy Avigad, Leonardo de Moura, Floris van Doorn, Mario Carneiro
-/
import Mathlib.Control.Basic
import Mathlib.Data.Nat.Basic
import Mathlib.Data.Option.Basic
import Mathlib.Data.List.Defs
import Mathlib.Data.List.Monad
import Mathlib.Logic.OpClass
import Mathlib.Logic.Unique
import Mathlib.Order.Basic
import Mathlib.Tactic.Common
/-!
# Basic properties of lists
-/
assert_not_exists GroupWithZero
assert_not_exists Lattice
assert_not_exists Prod.swap_eq_iff_eq_swap
assert_not_exists Ring
assert_not_exists Set.range
open Function
open Nat hiding one_pos
namespace List
universe u v w
variable {ι : Type*} {α : Type u} {β : Type v} {γ : Type w} {l₁ l₂ : List α}
/-- There is only one list of an empty type -/
instance uniqueOfIsEmpty [IsEmpty α] : Unique (List α) :=
{ instInhabitedList with
uniq := fun l =>
match l with
| [] => rfl
| a :: _ => isEmptyElim a }
instance : Std.LawfulIdentity (α := List α) Append.append [] where
left_id := nil_append
right_id := append_nil
instance : Std.Associative (α := List α) Append.append where
assoc := append_assoc
@[simp] theorem cons_injective {a : α} : Injective (cons a) := fun _ _ => tail_eq_of_cons_eq
theorem singleton_injective : Injective fun a : α => [a] := fun _ _ h => (cons_eq_cons.1 h).1
theorem set_of_mem_cons (l : List α) (a : α) : { x | x ∈ a :: l } = insert a { x | x ∈ l } :=
Set.ext fun _ => mem_cons
/-! ### mem -/
theorem _root_.Decidable.List.eq_or_ne_mem_of_mem [DecidableEq α]
{a b : α} {l : List α} (h : a ∈ b :: l) : a = b ∨ a ≠ b ∧ a ∈ l := by
by_cases hab : a = b
· exact Or.inl hab
· exact ((List.mem_cons.1 h).elim Or.inl (fun h => Or.inr ⟨hab, h⟩))
lemma mem_pair {a b c : α} : a ∈ [b, c] ↔ a = b ∨ a = c := by
rw [mem_cons, mem_singleton]
-- The simpNF linter says that the LHS can be simplified via `List.mem_map`.
-- However this is a higher priority lemma.
-- It seems the side condition `hf` is not applied by `simpNF`.
-- https://github.com/leanprover/std4/issues/207
@[simp 1100, nolint simpNF]
theorem mem_map_of_injective {f : α → β} (H : Injective f) {a : α} {l : List α} :
f a ∈ map f l ↔ a ∈ l :=
⟨fun m => let ⟨_, m', e⟩ := exists_of_mem_map m; H e ▸ m', mem_map_of_mem⟩
@[simp]
theorem _root_.Function.Involutive.exists_mem_and_apply_eq_iff {f : α → α}
(hf : Function.Involutive f) (x : α) (l : List α) : (∃ y : α, y ∈ l ∧ f y = x) ↔ f x ∈ l :=
⟨by rintro ⟨y, h, rfl⟩; rwa [hf y], fun h => ⟨f x, h, hf _⟩⟩
theorem mem_map_of_involutive {f : α → α} (hf : Involutive f) {a : α} {l : List α} :
a ∈ map f l ↔ f a ∈ l := by rw [mem_map, hf.exists_mem_and_apply_eq_iff]
/-! ### length -/
alias ⟨_, length_pos_of_ne_nil⟩ := length_pos_iff
theorem length_pos_iff_ne_nil {l : List α} : 0 < length l ↔ l ≠ [] :=
⟨ne_nil_of_length_pos, length_pos_of_ne_nil⟩
theorem exists_of_length_succ {n} : ∀ l : List α, l.length = n + 1 → ∃ h t, l = h :: t
| [], H => absurd H.symm <| succ_ne_zero n
| h :: t, _ => ⟨h, t, rfl⟩
@[simp] lemma length_injective_iff : Injective (List.length : List α → ℕ) ↔ Subsingleton α := by
constructor
· intro h; refine ⟨fun x y => ?_⟩; (suffices [x] = [y] by simpa using this); apply h; rfl
· intros hα l1 l2 hl
induction l1 generalizing l2 <;> cases l2
· rfl
· cases hl
· cases hl
· next ih _ _ =>
congr
· subsingleton
· apply ih; simpa using hl
@[simp default+1] -- Raise priority above `length_injective_iff`.
lemma length_injective [Subsingleton α] : Injective (length : List α → ℕ) :=
length_injective_iff.mpr inferInstance
theorem length_eq_two {l : List α} : l.length = 2 ↔ ∃ a b, l = [a, b] :=
⟨fun _ => let [a, b] := l; ⟨a, b, rfl⟩, fun ⟨_, _, e⟩ => e ▸ rfl⟩
theorem length_eq_three {l : List α} : l.length = 3 ↔ ∃ a b c, l = [a, b, c] :=
⟨fun _ => let [a, b, c] := l; ⟨a, b, c, rfl⟩, fun ⟨_, _, _, e⟩ => e ▸ rfl⟩
/-! ### set-theoretic notation of lists -/
instance instSingletonList : Singleton α (List α) := ⟨fun x => [x]⟩
instance [DecidableEq α] : Insert α (List α) := ⟨List.insert⟩
instance [DecidableEq α] : LawfulSingleton α (List α) :=
{ insert_empty_eq := fun x =>
show (if x ∈ ([] : List α) then [] else [x]) = [x] from if_neg not_mem_nil }
theorem singleton_eq (x : α) : ({x} : List α) = [x] :=
rfl
theorem insert_neg [DecidableEq α] {x : α} {l : List α} (h : x ∉ l) :
Insert.insert x l = x :: l :=
insert_of_not_mem h
theorem insert_pos [DecidableEq α] {x : α} {l : List α} (h : x ∈ l) : Insert.insert x l = l :=
insert_of_mem h
theorem doubleton_eq [DecidableEq α] {x y : α} (h : x ≠ y) : ({x, y} : List α) = [x, y] := by
rw [insert_neg, singleton_eq]
rwa [singleton_eq, mem_singleton]
/-! ### bounded quantifiers over lists -/
theorem forall_mem_of_forall_mem_cons {p : α → Prop} {a : α} {l : List α} (h : ∀ x ∈ a :: l, p x) :
∀ x ∈ l, p x := (forall_mem_cons.1 h).2
theorem exists_mem_cons_of {p : α → Prop} {a : α} (l : List α) (h : p a) : ∃ x ∈ a :: l, p x :=
⟨a, mem_cons_self, h⟩
theorem exists_mem_cons_of_exists {p : α → Prop} {a : α} {l : List α} : (∃ x ∈ l, p x) →
∃ x ∈ a :: l, p x :=
fun ⟨x, xl, px⟩ => ⟨x, mem_cons_of_mem _ xl, px⟩
theorem or_exists_of_exists_mem_cons {p : α → Prop} {a : α} {l : List α} : (∃ x ∈ a :: l, p x) →
p a ∨ ∃ x ∈ l, p x :=
fun ⟨x, xal, px⟩ =>
Or.elim (eq_or_mem_of_mem_cons xal) (fun h : x = a => by rw [← h]; left; exact px)
fun h : x ∈ l => Or.inr ⟨x, h, px⟩
theorem exists_mem_cons_iff (p : α → Prop) (a : α) (l : List α) :
(∃ x ∈ a :: l, p x) ↔ p a ∨ ∃ x ∈ l, p x :=
Iff.intro or_exists_of_exists_mem_cons fun h =>
Or.elim h (exists_mem_cons_of l) exists_mem_cons_of_exists
/-! ### list subset -/
theorem cons_subset_of_subset_of_mem {a : α} {l m : List α}
(ainm : a ∈ m) (lsubm : l ⊆ m) : a::l ⊆ m :=
cons_subset.2 ⟨ainm, lsubm⟩
theorem append_subset_of_subset_of_subset {l₁ l₂ l : List α} (l₁subl : l₁ ⊆ l) (l₂subl : l₂ ⊆ l) :
l₁ ++ l₂ ⊆ l :=
fun _ h ↦ (mem_append.1 h).elim (@l₁subl _) (@l₂subl _)
theorem map_subset_iff {l₁ l₂ : List α} (f : α → β) (h : Injective f) :
map f l₁ ⊆ map f l₂ ↔ l₁ ⊆ l₂ := by
refine ⟨?_, map_subset f⟩; intro h2 x hx
rcases mem_map.1 (h2 (mem_map_of_mem hx)) with ⟨x', hx', hxx'⟩
cases h hxx'; exact hx'
/-! ### append -/
theorem append_eq_has_append {L₁ L₂ : List α} : List.append L₁ L₂ = L₁ ++ L₂ :=
rfl
theorem append_right_injective (s : List α) : Injective fun t ↦ s ++ t :=
fun _ _ ↦ append_cancel_left
theorem append_left_injective (t : List α) : Injective fun s ↦ s ++ t :=
fun _ _ ↦ append_cancel_right
/-! ### replicate -/
theorem eq_replicate_length {a : α} : ∀ {l : List α}, l = replicate l.length a ↔ ∀ b ∈ l, b = a
| [] => by simp
| (b :: l) => by simp [eq_replicate_length, replicate_succ]
theorem replicate_add (m n) (a : α) : replicate (m + n) a = replicate m a ++ replicate n a := by
rw [replicate_append_replicate]
theorem replicate_subset_singleton (n) (a : α) : replicate n a ⊆ [a] := fun _ h =>
mem_singleton.2 (eq_of_mem_replicate h)
theorem subset_singleton_iff {a : α} {L : List α} : L ⊆ [a] ↔ ∃ n, L = replicate n a := by
simp only [eq_replicate_iff, subset_def, mem_singleton, exists_eq_left']
theorem replicate_right_injective {n : ℕ} (hn : n ≠ 0) : Injective (@replicate α n) :=
fun _ _ h => (eq_replicate_iff.1 h).2 _ <| mem_replicate.2 ⟨hn, rfl⟩
theorem replicate_right_inj {a b : α} {n : ℕ} (hn : n ≠ 0) :
replicate n a = replicate n b ↔ a = b :=
(replicate_right_injective hn).eq_iff
theorem replicate_right_inj' {a b : α} : ∀ {n},
replicate n a = replicate n b ↔ n = 0 ∨ a = b
| 0 => by simp
| n + 1 => (replicate_right_inj n.succ_ne_zero).trans <| by simp only [n.succ_ne_zero, false_or]
theorem replicate_left_injective (a : α) : Injective (replicate · a) :=
LeftInverse.injective (length_replicate (n := ·))
theorem replicate_left_inj {a : α} {n m : ℕ} : replicate n a = replicate m a ↔ n = m :=
(replicate_left_injective a).eq_iff
@[simp]
theorem head?_flatten_replicate {n : ℕ} (h : n ≠ 0) (l : List α) :
(List.replicate n l).flatten.head? = l.head? := by
obtain ⟨n, rfl⟩ := Nat.exists_eq_succ_of_ne_zero h
induction l <;> simp [replicate]
@[simp]
theorem getLast?_flatten_replicate {n : ℕ} (h : n ≠ 0) (l : List α) :
(List.replicate n l).flatten.getLast? = l.getLast? := by
rw [← List.head?_reverse, ← List.head?_reverse, List.reverse_flatten, List.map_replicate,
List.reverse_replicate, head?_flatten_replicate h]
/-! ### pure -/
theorem mem_pure (x y : α) : x ∈ (pure y : List α) ↔ x = y := by simp
/-! ### bind -/
@[simp]
theorem bind_eq_flatMap {α β} (f : α → List β) (l : List α) : l >>= f = l.flatMap f :=
rfl
/-! ### concat -/
/-! ### reverse -/
theorem reverse_cons' (a : α) (l : List α) : reverse (a :: l) = concat (reverse l) a := by
simp only [reverse_cons, concat_eq_append]
theorem reverse_concat' (l : List α) (a : α) : (l ++ [a]).reverse = a :: l.reverse := by
rw [reverse_append]; rfl
@[simp]
theorem reverse_singleton (a : α) : reverse [a] = [a] :=
rfl
@[simp]
theorem reverse_involutive : Involutive (@reverse α) :=
reverse_reverse
@[simp]
theorem reverse_injective : Injective (@reverse α) :=
reverse_involutive.injective
theorem reverse_surjective : Surjective (@reverse α) :=
reverse_involutive.surjective
theorem reverse_bijective : Bijective (@reverse α) :=
reverse_involutive.bijective
theorem concat_eq_reverse_cons (a : α) (l : List α) : concat l a = reverse (a :: reverse l) := by
simp only [concat_eq_append, reverse_cons, reverse_reverse]
theorem map_reverseAux (f : α → β) (l₁ l₂ : List α) :
map f (reverseAux l₁ l₂) = reverseAux (map f l₁) (map f l₂) := by
simp only [reverseAux_eq, map_append, map_reverse]
-- TODO: Rename `List.reverse_perm` to `List.reverse_perm_self`
@[simp] lemma reverse_perm' : l₁.reverse ~ l₂ ↔ l₁ ~ l₂ where
mp := l₁.reverse_perm.symm.trans
mpr := l₁.reverse_perm.trans
@[simp] lemma perm_reverse : l₁ ~ l₂.reverse ↔ l₁ ~ l₂ where
mp hl := hl.trans l₂.reverse_perm
mpr hl := hl.trans l₂.reverse_perm.symm
/-! ### getLast -/
attribute [simp] getLast_cons
theorem getLast_append_singleton {a : α} (l : List α) :
getLast (l ++ [a]) (append_ne_nil_of_right_ne_nil l (cons_ne_nil a _)) = a := by
simp [getLast_append]
theorem getLast_append_of_right_ne_nil (l₁ l₂ : List α) (h : l₂ ≠ []) :
getLast (l₁ ++ l₂) (append_ne_nil_of_right_ne_nil l₁ h) = getLast l₂ h := by
induction l₁ with
| nil => simp
| cons _ _ ih => simp only [cons_append]; rw [List.getLast_cons]; exact ih
@[deprecated (since := "2025-02-06")]
alias getLast_append' := getLast_append_of_right_ne_nil
theorem getLast_concat' {a : α} (l : List α) : getLast (concat l a) (by simp) = a := by
simp
@[simp]
theorem getLast_singleton' (a : α) : getLast [a] (cons_ne_nil a []) = a := rfl
@[simp]
theorem getLast_cons_cons (a₁ a₂ : α) (l : List α) :
getLast (a₁ :: a₂ :: l) (cons_ne_nil _ _) = getLast (a₂ :: l) (cons_ne_nil a₂ l) :=
rfl
theorem dropLast_append_getLast : ∀ {l : List α} (h : l ≠ []), dropLast l ++ [getLast l h] = l
| [], h => absurd rfl h
| [_], _ => rfl
| a :: b :: l, h => by
rw [dropLast_cons₂, cons_append, getLast_cons (cons_ne_nil _ _)]
congr
exact dropLast_append_getLast (cons_ne_nil b l)
theorem getLast_congr {l₁ l₂ : List α} (h₁ : l₁ ≠ []) (h₂ : l₂ ≠ []) (h₃ : l₁ = l₂) :
getLast l₁ h₁ = getLast l₂ h₂ := by subst l₁; rfl
theorem getLast_replicate_succ (m : ℕ) (a : α) :
(replicate (m + 1) a).getLast (ne_nil_of_length_eq_add_one length_replicate) = a := by
simp only [replicate_succ']
exact getLast_append_singleton _
@[deprecated (since := "2025-02-07")]
alias getLast_filter' := getLast_filter_of_pos
/-! ### getLast? -/
theorem mem_getLast?_eq_getLast : ∀ {l : List α} {x : α}, x ∈ l.getLast? → ∃ h, x = getLast l h
| [], x, hx => False.elim <| by simp at hx
| [a], x, hx =>
have : a = x := by simpa using hx
this ▸ ⟨cons_ne_nil a [], rfl⟩
| a :: b :: l, x, hx => by
rw [getLast?_cons_cons] at hx
rcases mem_getLast?_eq_getLast hx with ⟨_, h₂⟩
use cons_ne_nil _ _
assumption
theorem getLast?_eq_getLast_of_ne_nil : ∀ {l : List α} (h : l ≠ []), l.getLast? = some (l.getLast h)
| [], h => (h rfl).elim
| [_], _ => rfl
| _ :: b :: l, _ => @getLast?_eq_getLast_of_ne_nil (b :: l) (cons_ne_nil _ _)
theorem mem_getLast?_cons {x y : α} : ∀ {l : List α}, x ∈ l.getLast? → x ∈ (y :: l).getLast?
| [], _ => by contradiction
| _ :: _, h => h
theorem dropLast_append_getLast? : ∀ {l : List α}, ∀ a ∈ l.getLast?, dropLast l ++ [a] = l
| [], a, ha => (Option.not_mem_none a ha).elim
| [a], _, rfl => rfl
| a :: b :: l, c, hc => by
rw [getLast?_cons_cons] at hc
rw [dropLast_cons₂, cons_append, dropLast_append_getLast? _ hc]
theorem getLastI_eq_getLast? [Inhabited α] : ∀ l : List α, l.getLastI = l.getLast?.iget
| [] => by simp [getLastI, Inhabited.default]
| [_] => rfl
| [_, _] => rfl
| [_, _, _] => rfl
| _ :: _ :: c :: l => by simp [getLastI, getLastI_eq_getLast? (c :: l)]
theorem getLast?_append_cons :
∀ (l₁ : List α) (a : α) (l₂ : List α), getLast? (l₁ ++ a :: l₂) = getLast? (a :: l₂)
| [], _, _ => rfl
| [_], _, _ => rfl
| b :: c :: l₁, a, l₂ => by rw [cons_append, cons_append, getLast?_cons_cons,
← cons_append, getLast?_append_cons (c :: l₁)]
theorem getLast?_append_of_ne_nil (l₁ : List α) :
∀ {l₂ : List α} (_ : l₂ ≠ []), getLast? (l₁ ++ l₂) = getLast? l₂
| [], hl₂ => by contradiction
| b :: l₂, _ => getLast?_append_cons l₁ b l₂
theorem mem_getLast?_append_of_mem_getLast? {l₁ l₂ : List α} {x : α} (h : x ∈ l₂.getLast?) :
x ∈ (l₁ ++ l₂).getLast? := by
cases l₂
· contradiction
· rw [List.getLast?_append_cons]
exact h
/-! ### head(!?) and tail -/
@[simp]
theorem head!_nil [Inhabited α] : ([] : List α).head! = default := rfl
@[simp] theorem head_cons_tail (x : List α) (h : x ≠ []) : x.head h :: x.tail = x := by
cases x <;> simp at h ⊢
theorem head_eq_getElem_zero {l : List α} (hl : l ≠ []) :
l.head hl = l[0]'(length_pos_iff.2 hl) :=
(getElem_zero _).symm
theorem head!_eq_head? [Inhabited α] (l : List α) : head! l = (head? l).iget := by cases l <;> rfl
theorem surjective_head! [Inhabited α] : Surjective (@head! α _) := fun x => ⟨[x], rfl⟩
theorem surjective_head? : Surjective (@head? α) :=
Option.forall.2 ⟨⟨[], rfl⟩, fun x => ⟨[x], rfl⟩⟩
theorem surjective_tail : Surjective (@tail α)
| [] => ⟨[], rfl⟩
| a :: l => ⟨a :: a :: l, rfl⟩
theorem eq_cons_of_mem_head? {x : α} : ∀ {l : List α}, x ∈ l.head? → l = x :: tail l
| [], h => (Option.not_mem_none _ h).elim
| a :: l, h => by
simp only [head?, Option.mem_def, Option.some_inj] at h
exact h ▸ rfl
@[simp] theorem head!_cons [Inhabited α] (a : α) (l : List α) : head! (a :: l) = a := rfl
@[simp]
theorem head!_append [Inhabited α] (t : List α) {s : List α} (h : s ≠ []) :
head! (s ++ t) = head! s := by
induction s
· contradiction
· rfl
theorem mem_head?_append_of_mem_head? {s t : List α} {x : α} (h : x ∈ s.head?) :
x ∈ (s ++ t).head? := by
cases s
· contradiction
· exact h
theorem head?_append_of_ne_nil :
∀ (l₁ : List α) {l₂ : List α} (_ : l₁ ≠ []), head? (l₁ ++ l₂) = head? l₁
| _ :: _, _, _ => rfl
theorem tail_append_singleton_of_ne_nil {a : α} {l : List α} (h : l ≠ nil) :
tail (l ++ [a]) = tail l ++ [a] := by
induction l
· contradiction
· rw [tail, cons_append, tail]
theorem cons_head?_tail : ∀ {l : List α} {a : α}, a ∈ head? l → a :: tail l = l
| [], a, h => by contradiction
| b :: l, a, h => by
simp? at h says simp only [head?_cons, Option.mem_def, Option.some.injEq] at h
simp [h]
theorem head!_mem_head? [Inhabited α] : ∀ {l : List α}, l ≠ [] → head! l ∈ head? l
| [], h => by contradiction
| _ :: _, _ => rfl
theorem cons_head!_tail [Inhabited α] {l : List α} (h : l ≠ []) : head! l :: tail l = l :=
cons_head?_tail (head!_mem_head? h)
theorem head!_mem_self [Inhabited α] {l : List α} (h : l ≠ nil) : l.head! ∈ l := by
have h' : l.head! ∈ l.head! :: l.tail := mem_cons_self
rwa [cons_head!_tail h] at h'
theorem get_eq_getElem? (l : List α) (i : Fin l.length) :
l.get i = l[i]?.get (by simp [getElem?_eq_getElem]) := by
simp
@[deprecated (since := "2025-02-15")] alias get_eq_get? := get_eq_getElem?
theorem exists_mem_iff_getElem {l : List α} {p : α → Prop} :
(∃ x ∈ l, p x) ↔ ∃ (i : ℕ) (_ : i < l.length), p l[i] := by
simp only [mem_iff_getElem]
exact ⟨fun ⟨_x, ⟨i, hi, hix⟩, hxp⟩ ↦ ⟨i, hi, hix ▸ hxp⟩, fun ⟨i, hi, hp⟩ ↦ ⟨_, ⟨i, hi, rfl⟩, hp⟩⟩
theorem forall_mem_iff_getElem {l : List α} {p : α → Prop} :
(∀ x ∈ l, p x) ↔ ∀ (i : ℕ) (_ : i < l.length), p l[i] := by
simp [mem_iff_getElem, @forall_swap α]
theorem get_tail (l : List α) (i) (h : i < l.tail.length)
(h' : i + 1 < l.length := (by simp only [length_tail] at h; omega)) :
l.tail.get ⟨i, h⟩ = l.get ⟨i + 1, h'⟩ := by
cases l <;> [cases h; rfl]
/-! ### sublists -/
attribute [refl] List.Sublist.refl
theorem Sublist.cons_cons {l₁ l₂ : List α} (a : α) (s : l₁ <+ l₂) : a :: l₁ <+ a :: l₂ :=
Sublist.cons₂ _ s
lemma cons_sublist_cons' {a b : α} : a :: l₁ <+ b :: l₂ ↔ a :: l₁ <+ l₂ ∨ a = b ∧ l₁ <+ l₂ := by
constructor
· rintro (_ | _)
· exact Or.inl ‹_›
· exact Or.inr ⟨rfl, ‹_›⟩
· rintro (h | ⟨rfl, h⟩)
· exact h.cons _
· rwa [cons_sublist_cons]
theorem sublist_cons_of_sublist (a : α) (h : l₁ <+ l₂) : l₁ <+ a :: l₂ := h.cons _
@[deprecated (since := "2025-02-07")]
alias sublist_nil_iff_eq_nil := sublist_nil
@[simp] lemma sublist_singleton {l : List α} {a : α} : l <+ [a] ↔ l = [] ∨ l = [a] := by
constructor <;> rintro (_ | _) <;> aesop
theorem Sublist.antisymm (s₁ : l₁ <+ l₂) (s₂ : l₂ <+ l₁) : l₁ = l₂ :=
s₁.eq_of_length_le s₂.length_le
/-- If the first element of two lists are different, then a sublist relation can be reduced. -/
theorem Sublist.of_cons_of_ne {a b} (h₁ : a ≠ b) (h₂ : a :: l₁ <+ b :: l₂) : a :: l₁ <+ l₂ :=
match h₁, h₂ with
| _, .cons _ h => h
/-! ### indexOf -/
section IndexOf
variable [DecidableEq α]
theorem idxOf_cons_eq {a b : α} (l : List α) : b = a → idxOf a (b :: l) = 0
| e => by rw [← e]; exact idxOf_cons_self
@[deprecated (since := "2025-01-30")] alias indexOf_cons_eq := idxOf_cons_eq
@[simp]
theorem idxOf_cons_ne {a b : α} (l : List α) : b ≠ a → idxOf a (b :: l) = succ (idxOf a l)
| h => by simp only [idxOf_cons, Bool.cond_eq_ite, beq_iff_eq, if_neg h]
@[deprecated (since := "2025-01-30")] alias indexOf_cons_ne := idxOf_cons_ne
theorem idxOf_eq_length_iff {a : α} {l : List α} : idxOf a l = length l ↔ a ∉ l := by
induction l with
| nil => exact iff_of_true rfl not_mem_nil
| cons b l ih =>
simp only [length, mem_cons, idxOf_cons, eq_comm]
rw [cond_eq_if]
split_ifs with h <;> simp at h
· exact iff_of_false (by rintro ⟨⟩) fun H => H <| Or.inl h.symm
· simp only [Ne.symm h, false_or]
rw [← ih]
exact succ_inj
@[simp]
theorem idxOf_of_not_mem {l : List α} {a : α} : a ∉ l → idxOf a l = length l :=
idxOf_eq_length_iff.2
@[deprecated (since := "2025-01-30")] alias indexOf_of_not_mem := idxOf_of_not_mem
theorem idxOf_le_length {a : α} {l : List α} : idxOf a l ≤ length l := by
induction l with | nil => rfl | cons b l ih => ?_
simp only [length, idxOf_cons, cond_eq_if, beq_iff_eq]
by_cases h : b = a
· rw [if_pos h]; exact Nat.zero_le _
· rw [if_neg h]; exact succ_le_succ ih
@[deprecated (since := "2025-01-30")] alias indexOf_le_length := idxOf_le_length
theorem idxOf_lt_length_iff {a} {l : List α} : idxOf a l < length l ↔ a ∈ l :=
⟨fun h => Decidable.byContradiction fun al => Nat.ne_of_lt h <| idxOf_eq_length_iff.2 al,
fun al => (lt_of_le_of_ne idxOf_le_length) fun h => idxOf_eq_length_iff.1 h al⟩
@[deprecated (since := "2025-01-30")] alias indexOf_lt_length_iff := idxOf_lt_length_iff
theorem idxOf_append_of_mem {a : α} (h : a ∈ l₁) : idxOf a (l₁ ++ l₂) = idxOf a l₁ := by
induction l₁ with
| nil =>
exfalso
exact not_mem_nil h
| cons d₁ t₁ ih =>
rw [List.cons_append]
by_cases hh : d₁ = a
· iterate 2 rw [idxOf_cons_eq _ hh]
rw [idxOf_cons_ne _ hh, idxOf_cons_ne _ hh, ih (mem_of_ne_of_mem (Ne.symm hh) h)]
@[deprecated (since := "2025-01-30")] alias indexOf_append_of_mem := idxOf_append_of_mem
theorem idxOf_append_of_not_mem {a : α} (h : a ∉ l₁) :
idxOf a (l₁ ++ l₂) = l₁.length + idxOf a l₂ := by
induction l₁ with
| nil => rw [List.nil_append, List.length, Nat.zero_add]
| cons d₁ t₁ ih =>
rw [List.cons_append, idxOf_cons_ne _ (ne_of_not_mem_cons h).symm, List.length,
ih (not_mem_of_not_mem_cons h), Nat.succ_add]
@[deprecated (since := "2025-01-30")] alias indexOf_append_of_not_mem := idxOf_append_of_not_mem
end IndexOf
/-! ### nth element -/
section deprecated
@[simp]
theorem getElem?_length (l : List α) : l[l.length]? = none := getElem?_eq_none le_rfl
/-- A version of `getElem_map` that can be used for rewriting. -/
theorem getElem_map_rev (f : α → β) {l} {n : Nat} {h : n < l.length} :
f l[n] = (map f l)[n]'((l.length_map f).symm ▸ h) := Eq.symm (getElem_map _)
theorem get_length_sub_one {l : List α} (h : l.length - 1 < l.length) :
l.get ⟨l.length - 1, h⟩ = l.getLast (by rintro rfl; exact Nat.lt_irrefl 0 h) :=
(getLast_eq_getElem _).symm
theorem take_one_drop_eq_of_lt_length {l : List α} {n : ℕ} (h : n < l.length) :
(l.drop n).take 1 = [l.get ⟨n, h⟩] := by
rw [drop_eq_getElem_cons h, take, take]
simp
theorem ext_getElem?' {l₁ l₂ : List α} (h' : ∀ n < max l₁.length l₂.length, l₁[n]? = l₂[n]?) :
l₁ = l₂ := by
apply ext_getElem?
intro n
rcases Nat.lt_or_ge n <| max l₁.length l₂.length with hn | hn
· exact h' n hn
· simp_all [Nat.max_le, getElem?_eq_none]
@[deprecated (since := "2025-02-15")] alias ext_get?' := ext_getElem?'
@[deprecated (since := "2025-02-15")] alias ext_get?_iff := List.ext_getElem?_iff
theorem ext_get_iff {l₁ l₂ : List α} :
l₁ = l₂ ↔ l₁.length = l₂.length ∧ ∀ n h₁ h₂, get l₁ ⟨n, h₁⟩ = get l₂ ⟨n, h₂⟩ := by
constructor
· rintro rfl
exact ⟨rfl, fun _ _ _ ↦ rfl⟩
· intro ⟨h₁, h₂⟩
exact ext_get h₁ h₂
theorem ext_getElem?_iff' {l₁ l₂ : List α} : l₁ = l₂ ↔
∀ n < max l₁.length l₂.length, l₁[n]? = l₂[n]? :=
⟨by rintro rfl _ _; rfl, ext_getElem?'⟩
@[deprecated (since := "2025-02-15")] alias ext_get?_iff' := ext_getElem?_iff'
/-- If two lists `l₁` and `l₂` are the same length and `l₁[n]! = l₂[n]!` for all `n`,
then the lists are equal. -/
theorem ext_getElem! [Inhabited α] (hl : length l₁ = length l₂) (h : ∀ n : ℕ, l₁[n]! = l₂[n]!) :
l₁ = l₂ :=
ext_getElem hl fun n h₁ h₂ ↦ by simpa only [← getElem!_pos] using h n
@[simp]
theorem getElem_idxOf [DecidableEq α] {a : α} : ∀ {l : List α} (h : idxOf a l < l.length),
l[idxOf a l] = a
| b :: l, h => by
by_cases h' : b = a <;>
simp [h', if_pos, if_false, getElem_idxOf]
@[deprecated (since := "2025-01-30")] alias getElem_indexOf := getElem_idxOf
-- This is incorrectly named and should be `get_idxOf`;
-- this already exists, so will require a deprecation dance.
theorem idxOf_get [DecidableEq α] {a : α} {l : List α} (h) : get l ⟨idxOf a l, h⟩ = a := by
simp
@[deprecated (since := "2025-01-30")] alias indexOf_get := idxOf_get
@[simp]
theorem getElem?_idxOf [DecidableEq α] {a : α} {l : List α} (h : a ∈ l) :
l[idxOf a l]? = some a := by
rw [getElem?_eq_getElem, getElem_idxOf (idxOf_lt_length_iff.2 h)]
@[deprecated (since := "2025-01-30")] alias getElem?_indexOf := getElem?_idxOf
@[deprecated (since := "2025-02-15")] alias idxOf_get? := getElem?_idxOf
@[deprecated (since := "2025-01-30")] alias indexOf_get? := getElem?_idxOf
theorem idxOf_inj [DecidableEq α] {l : List α} {x y : α} (hx : x ∈ l) (hy : y ∈ l) :
idxOf x l = idxOf y l ↔ x = y :=
⟨fun h => by
have x_eq_y :
get l ⟨idxOf x l, idxOf_lt_length_iff.2 hx⟩ =
get l ⟨idxOf y l, idxOf_lt_length_iff.2 hy⟩ := by
simp only [h]
simp only [idxOf_get] at x_eq_y; exact x_eq_y, fun h => by subst h; rfl⟩
@[deprecated (since := "2025-01-30")] alias indexOf_inj := idxOf_inj
theorem get_reverse' (l : List α) (n) (hn') :
l.reverse.get n = l.get ⟨l.length - 1 - n, hn'⟩ := by
simp
theorem eq_cons_of_length_one {l : List α} (h : l.length = 1) : l = [l.get ⟨0, by omega⟩] := by
refine ext_get (by convert h) fun n h₁ h₂ => ?_
simp
congr
omega
end deprecated
@[simp]
theorem getElem_set_of_ne {l : List α} {i j : ℕ} (h : i ≠ j) (a : α)
(hj : j < (l.set i a).length) :
(l.set i a)[j] = l[j]'(by simpa using hj) := by
rw [← Option.some_inj, ← List.getElem?_eq_getElem, List.getElem?_set_ne h,
List.getElem?_eq_getElem]
/-! ### map -/
-- `List.map_const` (the version with `Function.const` instead of a lambda) is already tagged
-- `simp` in Core
-- TODO: Upstream the tagging to Core?
attribute [simp] map_const'
theorem flatMap_pure_eq_map (f : α → β) (l : List α) : l.flatMap (pure ∘ f) = map f l :=
.symm <| map_eq_flatMap ..
theorem flatMap_congr {l : List α} {f g : α → List β} (h : ∀ x ∈ l, f x = g x) :
l.flatMap f = l.flatMap g :=
(congr_arg List.flatten <| map_congr_left h :)
theorem infix_flatMap_of_mem {a : α} {as : List α} (h : a ∈ as) (f : α → List α) :
f a <:+: as.flatMap f :=
infix_of_mem_flatten (mem_map_of_mem h)
@[simp]
theorem map_eq_map {α β} (f : α → β) (l : List α) : f <$> l = map f l :=
rfl
/-- A single `List.map` of a composition of functions is equal to
composing a `List.map` with another `List.map`, fully applied.
This is the reverse direction of `List.map_map`.
-/
theorem comp_map (h : β → γ) (g : α → β) (l : List α) : map (h ∘ g) l = map h (map g l) :=
map_map.symm
/-- Composing a `List.map` with another `List.map` is equal to
a single `List.map` of composed functions.
-/
@[simp]
theorem map_comp_map (g : β → γ) (f : α → β) : map g ∘ map f = map (g ∘ f) := by
ext l; rw [comp_map, Function.comp_apply]
section map_bijectivity
theorem _root_.Function.LeftInverse.list_map {f : α → β} {g : β → α} (h : LeftInverse f g) :
LeftInverse (map f) (map g)
| [] => by simp_rw [map_nil]
| x :: xs => by simp_rw [map_cons, h x, h.list_map xs]
nonrec theorem _root_.Function.RightInverse.list_map {f : α → β} {g : β → α}
(h : RightInverse f g) : RightInverse (map f) (map g) :=
h.list_map
nonrec theorem _root_.Function.Involutive.list_map {f : α → α}
(h : Involutive f) : Involutive (map f) :=
Function.LeftInverse.list_map h
@[simp]
theorem map_leftInverse_iff {f : α → β} {g : β → α} :
LeftInverse (map f) (map g) ↔ LeftInverse f g :=
⟨fun h x => by injection h [x], (·.list_map)⟩
@[simp]
theorem map_rightInverse_iff {f : α → β} {g : β → α} :
RightInverse (map f) (map g) ↔ RightInverse f g := map_leftInverse_iff
@[simp]
theorem map_involutive_iff {f : α → α} :
Involutive (map f) ↔ Involutive f := map_leftInverse_iff
theorem _root_.Function.Injective.list_map {f : α → β} (h : Injective f) :
Injective (map f)
| [], [], _ => rfl
| x :: xs, y :: ys, hxy => by
injection hxy with hxy hxys
rw [h hxy, h.list_map hxys]
@[simp]
theorem map_injective_iff {f : α → β} : Injective (map f) ↔ Injective f := by
refine ⟨fun h x y hxy => ?_, (·.list_map)⟩
suffices [x] = [y] by simpa using this
apply h
simp [hxy]
theorem _root_.Function.Surjective.list_map {f : α → β} (h : Surjective f) :
Surjective (map f) :=
let ⟨_, h⟩ := h.hasRightInverse; h.list_map.surjective
@[simp]
theorem map_surjective_iff {f : α → β} : Surjective (map f) ↔ Surjective f := by
refine ⟨fun h x => ?_, (·.list_map)⟩
let ⟨[y], hxy⟩ := h [x]
exact ⟨_, List.singleton_injective hxy⟩
theorem _root_.Function.Bijective.list_map {f : α → β} (h : Bijective f) : Bijective (map f) :=
⟨h.1.list_map, h.2.list_map⟩
@[simp]
theorem map_bijective_iff {f : α → β} : Bijective (map f) ↔ Bijective f := by
simp_rw [Function.Bijective, map_injective_iff, map_surjective_iff]
end map_bijectivity
theorem eq_of_mem_map_const {b₁ b₂ : β} {l : List α} (h : b₁ ∈ map (const α b₂) l) :
b₁ = b₂ := by rw [map_const] at h; exact eq_of_mem_replicate h
/-- `eq_nil_or_concat` in simp normal form -/
lemma eq_nil_or_concat' (l : List α) : l = [] ∨ ∃ L b, l = L ++ [b] := by
simpa using l.eq_nil_or_concat
/-! ### foldl, foldr -/
theorem foldl_ext (f g : α → β → α) (a : α) {l : List β} (H : ∀ a : α, ∀ b ∈ l, f a b = g a b) :
foldl f a l = foldl g a l := by
induction l generalizing a with
| nil => rfl
| cons hd tl ih =>
unfold foldl
rw [ih _ fun a b bin => H a b <| mem_cons_of_mem _ bin, H a hd mem_cons_self]
theorem foldr_ext (f g : α → β → β) (b : β) {l : List α} (H : ∀ a ∈ l, ∀ b : β, f a b = g a b) :
foldr f b l = foldr g b l := by
induction l with | nil => rfl | cons hd tl ih => ?_
simp only [mem_cons, or_imp, forall_and, forall_eq] at H
simp only [foldr, ih H.2, H.1]
theorem foldl_concat
(f : β → α → β) (b : β) (x : α) (xs : List α) :
List.foldl f b (xs ++ [x]) = f (List.foldl f b xs) x := by
simp only [List.foldl_append, List.foldl]
theorem foldr_concat
(f : α → β → β) (b : β) (x : α) (xs : List α) :
List.foldr f b (xs ++ [x]) = (List.foldr f (f x b) xs) := by
simp only [List.foldr_append, List.foldr]
theorem foldl_fixed' {f : α → β → α} {a : α} (hf : ∀ b, f a b = a) : ∀ l : List β, foldl f a l = a
| [] => rfl
| b :: l => by rw [foldl_cons, hf b, foldl_fixed' hf l]
theorem foldr_fixed' {f : α → β → β} {b : β} (hf : ∀ a, f a b = b) : ∀ l : List α, foldr f b l = b
| [] => rfl
| a :: l => by rw [foldr_cons, foldr_fixed' hf l, hf a]
@[simp]
theorem foldl_fixed {a : α} : ∀ l : List β, foldl (fun a _ => a) a l = a :=
foldl_fixed' fun _ => rfl
@[simp]
theorem foldr_fixed {b : β} : ∀ l : List α, foldr (fun _ b => b) b l = b :=
foldr_fixed' fun _ => rfl
@[deprecated foldr_cons_nil (since := "2025-02-10")]
theorem foldr_eta (l : List α) : foldr cons [] l = l := foldr_cons_nil
theorem reverse_foldl {l : List α} : reverse (foldl (fun t h => h :: t) [] l) = l := by
simp
theorem foldl_hom₂ (l : List ι) (f : α → β → γ) (op₁ : α → ι → α) (op₂ : β → ι → β)
(op₃ : γ → ι → γ) (a : α) (b : β) (h : ∀ a b i, f (op₁ a i) (op₂ b i) = op₃ (f a b) i) :
foldl op₃ (f a b) l = f (foldl op₁ a l) (foldl op₂ b l) :=
Eq.symm <| by
revert a b
induction l <;> intros <;> [rfl; simp only [*, foldl]]
theorem foldr_hom₂ (l : List ι) (f : α → β → γ) (op₁ : ι → α → α) (op₂ : ι → β → β)
(op₃ : ι → γ → γ) (a : α) (b : β) (h : ∀ a b i, f (op₁ i a) (op₂ i b) = op₃ i (f a b)) :
foldr op₃ (f a b) l = f (foldr op₁ a l) (foldr op₂ b l) := by
revert a
induction l <;> intros <;> [rfl; simp only [*, foldr]]
theorem injective_foldl_comp {l : List (α → α)} {f : α → α}
(hl : ∀ f ∈ l, Function.Injective f) (hf : Function.Injective f) :
Function.Injective (@List.foldl (α → α) (α → α) Function.comp f l) := by
induction l generalizing f with
| nil => exact hf
| cons lh lt l_ih =>
apply l_ih fun _ h => hl _ (List.mem_cons_of_mem _ h)
apply Function.Injective.comp hf
apply hl _ mem_cons_self
/-- Consider two lists `l₁` and `l₂` with designated elements `a₁` and `a₂` somewhere in them:
`l₁ = x₁ ++ [a₁] ++ z₁` and `l₂ = x₂ ++ [a₂] ++ z₂`.
Assume the designated element `a₂` is present in neither `x₁` nor `z₁`.
We conclude that the lists are equal (`l₁ = l₂`) if and only if their respective parts are equal
(`x₁ = x₂ ∧ a₁ = a₂ ∧ z₁ = z₂`). -/
lemma append_cons_inj_of_not_mem {x₁ x₂ z₁ z₂ : List α} {a₁ a₂ : α}
(notin_x : a₂ ∉ x₁) (notin_z : a₂ ∉ z₁) :
x₁ ++ a₁ :: z₁ = x₂ ++ a₂ :: z₂ ↔ x₁ = x₂ ∧ a₁ = a₂ ∧ z₁ = z₂ := by
constructor
· simp only [append_eq_append_iff, cons_eq_append_iff, cons_eq_cons]
rintro (⟨c, rfl, ⟨rfl, rfl, rfl⟩ | ⟨d, rfl, rfl⟩⟩ |
⟨c, rfl, ⟨rfl, rfl, rfl⟩ | ⟨d, rfl, rfl⟩⟩) <;> simp_all
· rintro ⟨rfl, rfl, rfl⟩
rfl
section FoldlEqFoldr
-- foldl and foldr coincide when f is commutative and associative
variable {f : α → α → α}
theorem foldl1_eq_foldr1 [hassoc : Std.Associative f] :
∀ a b l, foldl f a (l ++ [b]) = foldr f b (a :: l)
| _, _, nil => rfl
| a, b, c :: l => by
simp only [cons_append, foldl_cons, foldr_cons, foldl1_eq_foldr1 _ _ l]
rw [hassoc.assoc]
theorem foldl_eq_of_comm_of_assoc [hcomm : Std.Commutative f] [hassoc : Std.Associative f] :
∀ a b l, foldl f a (b :: l) = f b (foldl f a l)
| a, b, nil => hcomm.comm a b
| a, b, c :: l => by
simp only [foldl_cons]
have : RightCommutative f := inferInstance
rw [← foldl_eq_of_comm_of_assoc .., this.right_comm, foldl_cons]
theorem foldl_eq_foldr [Std.Commutative f] [Std.Associative f] :
∀ a l, foldl f a l = foldr f a l
| _, nil => rfl
| a, b :: l => by
simp only [foldr_cons, foldl_eq_of_comm_of_assoc]
rw [foldl_eq_foldr a l]
end FoldlEqFoldr
section FoldlEqFoldlr'
variable {f : α → β → α}
variable (hf : ∀ a b c, f (f a b) c = f (f a c) b)
include hf
theorem foldl_eq_of_comm' : ∀ a b l, foldl f a (b :: l) = f (foldl f a l) b
| _, _, [] => rfl
| a, b, c :: l => by rw [foldl, foldl, foldl, ← foldl_eq_of_comm' .., foldl, hf]
theorem foldl_eq_foldr' : ∀ a l, foldl f a l = foldr (flip f) a l
| _, [] => rfl
| a, b :: l => by rw [foldl_eq_of_comm' hf, foldr, foldl_eq_foldr' ..]; rfl
end FoldlEqFoldlr'
section FoldlEqFoldlr'
variable {f : α → β → β}
theorem foldr_eq_of_comm' (hf : ∀ a b c, f a (f b c) = f b (f a c)) :
∀ a b l, foldr f a (b :: l) = foldr f (f b a) l
| _, _, [] => rfl
| a, b, c :: l => by rw [foldr, foldr, foldr, hf, ← foldr_eq_of_comm' hf ..]; rfl
end FoldlEqFoldlr'
section
variable {op : α → α → α} [ha : Std.Associative op]
/-- Notation for `op a b`. -/
local notation a " ⋆ " b => op a b
/-- Notation for `foldl op a l`. -/
local notation l " <*> " a => foldl op a l
theorem foldl_op_eq_op_foldr_assoc :
∀ {l : List α} {a₁ a₂}, ((l <*> a₁) ⋆ a₂) = a₁ ⋆ l.foldr (· ⋆ ·) a₂
| [], _, _ => rfl
| a :: l, a₁, a₂ => by
simp only [foldl_cons, foldr_cons, foldl_assoc, ha.assoc]; rw [foldl_op_eq_op_foldr_assoc]
variable [hc : Std.Commutative op]
theorem foldl_assoc_comm_cons {l : List α} {a₁ a₂} : ((a₁ :: l) <*> a₂) = a₁ ⋆ l <*> a₂ := by
rw [foldl_cons, hc.comm, foldl_assoc]
end
/-! ### foldlM, foldrM, mapM -/
section FoldlMFoldrM
variable {m : Type v → Type w} [Monad m]
variable [LawfulMonad m]
theorem foldrM_eq_foldr (f : α → β → m β) (b l) :
foldrM f b l = foldr (fun a mb => mb >>= f a) (pure b) l := by induction l <;> simp [*]
theorem foldlM_eq_foldl (f : β → α → m β) (b l) :
List.foldlM f b l = foldl (fun mb a => mb >>= fun b => f b a) (pure b) l := by
suffices h :
∀ mb : m β, (mb >>= fun b => List.foldlM f b l) = foldl (fun mb a => mb >>= fun b => f b a) mb l
by simp [← h (pure b)]
induction l with
| nil => intro; simp
| cons _ _ l_ih => intro; simp only [List.foldlM, foldl, ← l_ih, functor_norm]
end FoldlMFoldrM
/-! ### intersperse -/
@[deprecated (since := "2025-02-07")] alias intersperse_singleton := intersperse_single
@[deprecated (since := "2025-02-07")] alias intersperse_cons_cons := intersperse_cons₂
/-! ### map for partial functions -/
@[deprecated "Deprecated without replacement." (since := "2025-02-07")]
theorem sizeOf_lt_sizeOf_of_mem [SizeOf α] {x : α} {l : List α} (hx : x ∈ l) :
SizeOf.sizeOf x < SizeOf.sizeOf l := by
induction l with | nil => ?_ | cons h t ih => ?_ <;> cases hx <;> rw [cons.sizeOf_spec]
· omega
· specialize ih ‹_›
omega
/-! ### filter -/
theorem length_eq_length_filter_add {l : List (α)} (f : α → Bool) :
l.length = (l.filter f).length + (l.filter (! f ·)).length := by
simp_rw [← List.countP_eq_length_filter, l.length_eq_countP_add_countP f, Bool.not_eq_true,
Bool.decide_eq_false]
/-! ### filterMap -/
theorem filterMap_eq_flatMap_toList (f : α → Option β) (l : List α) :
l.filterMap f = l.flatMap fun a ↦ (f a).toList := by
induction l with | nil => ?_ | cons a l ih => ?_ <;> simp [filterMap_cons]
rcases f a <;> simp [ih]
theorem filterMap_congr {f g : α → Option β} {l : List α}
(h : ∀ x ∈ l, f x = g x) : l.filterMap f = l.filterMap g := by
induction l <;> simp_all [filterMap_cons]
theorem filterMap_eq_map_iff_forall_eq_some {f : α → Option β} {g : α → β} {l : List α} :
l.filterMap f = l.map g ↔ ∀ x ∈ l, f x = some (g x) where
mp := by
induction l with | nil => simp | cons a l ih => ?_
rcases ha : f a with - | b <;> simp [ha, filterMap_cons]
· intro h
simpa [show (filterMap f l).length = l.length + 1 from by simp[h], Nat.add_one_le_iff]
using List.length_filterMap_le f l
· rintro rfl h
exact ⟨rfl, ih h⟩
mpr h := Eq.trans (filterMap_congr <| by simpa) (congr_fun filterMap_eq_map _)
/-! ### filter -/
section Filter
variable {p : α → Bool}
theorem filter_singleton {a : α} : [a].filter p = bif p a then [a] else [] :=
rfl
theorem filter_eq_foldr (p : α → Bool) (l : List α) :
filter p l = foldr (fun a out => bif p a then a :: out else out) [] l := by
induction l <;> simp [*, filter]; rfl
#adaptation_note /-- nightly-2024-07-27
This has to be temporarily renamed to avoid an unintentional collision.
The prime should be removed at nightly-2024-07-27. -/
@[simp]
theorem filter_subset' (l : List α) : filter p l ⊆ l :=
filter_sublist.subset
theorem of_mem_filter {a : α} {l} (h : a ∈ filter p l) : p a := (mem_filter.1 h).2
theorem mem_of_mem_filter {a : α} {l} (h : a ∈ filter p l) : a ∈ l :=
filter_subset' l h
theorem mem_filter_of_mem {a : α} {l} (h₁ : a ∈ l) (h₂ : p a) : a ∈ filter p l :=
mem_filter.2 ⟨h₁, h₂⟩
@[deprecated (since := "2025-02-07")] alias monotone_filter_left := filter_subset
variable (p)
theorem monotone_filter_right (l : List α) ⦃p q : α → Bool⦄
(h : ∀ a, p a → q a) : l.filter p <+ l.filter q := by
induction l with
| nil => rfl
| cons hd tl IH =>
by_cases hp : p hd
· rw [filter_cons_of_pos hp, filter_cons_of_pos (h _ hp)]
exact IH.cons_cons hd
· rw [filter_cons_of_neg hp]
by_cases hq : q hd
· rw [filter_cons_of_pos hq]
exact sublist_cons_of_sublist hd IH
· rw [filter_cons_of_neg hq]
exact IH
lemma map_filter {f : α → β} (hf : Injective f) (l : List α)
[DecidablePred fun b => ∃ a, p a ∧ f a = b] :
(l.filter p).map f = (l.map f).filter fun b => ∃ a, p a ∧ f a = b := by
simp [comp_def, filter_map, hf.eq_iff]
@[deprecated (since := "2025-02-07")] alias map_filter' := map_filter
lemma filter_attach' (l : List α) (p : {a // a ∈ l} → Bool) [DecidableEq α] :
l.attach.filter p =
(l.filter fun x => ∃ h, p ⟨x, h⟩).attach.map (Subtype.map id fun _ => mem_of_mem_filter) := by
classical
refine map_injective_iff.2 Subtype.coe_injective ?_
simp [comp_def, map_filter _ Subtype.coe_injective]
lemma filter_attach (l : List α) (p : α → Bool) :
(l.attach.filter fun x => p x : List {x // x ∈ l}) =
(l.filter p).attach.map (Subtype.map id fun _ => mem_of_mem_filter) :=
map_injective_iff.2 Subtype.coe_injective <| by
simp_rw [map_map, comp_def, Subtype.map, id, ← Function.comp_apply (g := Subtype.val),
← filter_map, attach_map_subtype_val]
lemma filter_comm (q) (l : List α) : filter p (filter q l) = filter q (filter p l) := by
simp [Bool.and_comm]
@[simp]
theorem filter_true (l : List α) :
filter (fun _ => true) l = l := by induction l <;> simp [*, filter]
@[simp]
theorem filter_false (l : List α) :
filter (fun _ => false) l = [] := by induction l <;> simp [*, filter]
end Filter
/-! ### eraseP -/
section eraseP
variable {p : α → Bool}
@[simp]
theorem length_eraseP_add_one {l : List α} {a} (al : a ∈ l) (pa : p a) :
(l.eraseP p).length + 1 = l.length := by
let ⟨_, l₁, l₂, _, _, h₁, h₂⟩ := exists_of_eraseP al pa
rw [h₂, h₁, length_append, length_append]
rfl
end eraseP
/-! ### erase -/
section Erase
variable [DecidableEq α]
@[simp] theorem length_erase_add_one {a : α} {l : List α} (h : a ∈ l) :
(l.erase a).length + 1 = l.length := by
rw [erase_eq_eraseP, length_eraseP_add_one h (decide_eq_true rfl)]
theorem map_erase [DecidableEq β] {f : α → β} (finj : Injective f) {a : α} (l : List α) :
map f (l.erase a) = (map f l).erase (f a) := by
have this : (a == ·) = (f a == f ·) := by ext b; simp [beq_eq_decide, finj.eq_iff]
rw [erase_eq_eraseP, erase_eq_eraseP, eraseP_map, this]; rfl
theorem map_foldl_erase [DecidableEq β] {f : α → β} (finj : Injective f) {l₁ l₂ : List α} :
map f (foldl List.erase l₁ l₂) = foldl (fun l a => l.erase (f a)) (map f l₁) l₂ := by
induction l₂ generalizing l₁ <;> [rfl; simp only [foldl_cons, map_erase finj, *]]
theorem erase_getElem [DecidableEq ι] {l : List ι} {i : ℕ} (hi : i < l.length) :
Perm (l.erase l[i]) (l.eraseIdx i) := by
induction l generalizing i with
| nil => simp
| cons a l IH =>
cases i with
| zero => simp
| succ i =>
have hi' : i < l.length := by simpa using hi
if ha : a = l[i] then
simpa [ha] using .trans (perm_cons_erase (getElem_mem _)) (.cons _ (IH hi'))
else
simpa [ha] using IH hi'
theorem length_eraseIdx_add_one {l : List ι} {i : ℕ} (h : i < l.length) :
(l.eraseIdx i).length + 1 = l.length := by
rw [length_eraseIdx]
split <;> omega
end Erase
/-! ### diff -/
section Diff
variable [DecidableEq α]
@[simp]
theorem map_diff [DecidableEq β] {f : α → β} (finj : Injective f) {l₁ l₂ : List α} :
map f (l₁.diff l₂) = (map f l₁).diff (map f l₂) := by
simp only [diff_eq_foldl, foldl_map, map_foldl_erase finj]
@[deprecated (since := "2025-04-10")]
alias erase_diff_erase_sublist_of_sublist := Sublist.erase_diff_erase_sublist
end Diff
section Choose
variable (p : α → Prop) [DecidablePred p] (l : List α)
theorem choose_spec (hp : ∃ a, a ∈ l ∧ p a) : choose p l hp ∈ l ∧ p (choose p l hp) :=
(chooseX p l hp).property
theorem choose_mem (hp : ∃ a, a ∈ l ∧ p a) : choose p l hp ∈ l :=
(choose_spec _ _ _).1
theorem choose_property (hp : ∃ a, a ∈ l ∧ p a) : p (choose p l hp) :=
(choose_spec _ _ _).2
end Choose
/-! ### Forall -/
section Forall
variable {p q : α → Prop} {l : List α}
@[simp]
theorem forall_cons (p : α → Prop) (x : α) : ∀ l : List α, Forall p (x :: l) ↔ p x ∧ Forall p l
| [] => (and_iff_left_of_imp fun _ ↦ trivial).symm
| _ :: _ => Iff.rfl
@[simp]
theorem forall_append {p : α → Prop} : ∀ {xs ys : List α},
Forall p (xs ++ ys) ↔ Forall p xs ∧ Forall p ys
| [] => by simp
| _ :: _ => by simp [forall_append, and_assoc]
theorem forall_iff_forall_mem : ∀ {l : List α}, Forall p l ↔ ∀ x ∈ l, p x
| [] => (iff_true_intro <| forall_mem_nil _).symm
| x :: l => by rw [forall_mem_cons, forall_cons, forall_iff_forall_mem]
theorem Forall.imp (h : ∀ x, p x → q x) : ∀ {l : List α}, Forall p l → Forall q l
| [] => id
| x :: l => by
simp only [forall_cons, and_imp]
rw [← and_imp]
exact And.imp (h x) (Forall.imp h)
@[simp]
theorem forall_map_iff {p : β → Prop} (f : α → β) : Forall p (l.map f) ↔ Forall (p ∘ f) l := by
induction l <;> simp [*]
instance (p : α → Prop) [DecidablePred p] : DecidablePred (Forall p) := fun _ =>
decidable_of_iff' _ forall_iff_forall_mem
end Forall
/-! ### Miscellaneous lemmas -/
theorem get_attach (l : List α) (i) :
(l.attach.get i).1 = l.get ⟨i, length_attach (l := l) ▸ i.2⟩ := by simp
section Disjoint
/-- The images of disjoint lists under a partially defined map are disjoint -/
theorem disjoint_pmap {p : α → Prop} {f : ∀ a : α, p a → β} {s t : List α}
(hs : ∀ a ∈ s, p a) (ht : ∀ a ∈ t, p a)
(hf : ∀ (a a' : α) (ha : p a) (ha' : p a'), f a ha = f a' ha' → a = a')
(h : Disjoint s t) :
Disjoint (s.pmap f hs) (t.pmap f ht) := by
simp only [Disjoint, mem_pmap]
rintro b ⟨a, ha, rfl⟩ ⟨a', ha', ha''⟩
apply h ha
rwa [hf a a' (hs a ha) (ht a' ha') ha''.symm]
/-- The images of disjoint lists under an injective map are disjoint -/
theorem disjoint_map {f : α → β} {s t : List α} (hf : Function.Injective f)
(h : Disjoint s t) : Disjoint (s.map f) (t.map f) := by
rw [← pmap_eq_map (fun _ _ ↦ trivial), ← pmap_eq_map (fun _ _ ↦ trivial)]
exact disjoint_pmap _ _ (fun _ _ _ _ h' ↦ hf h') h
alias Disjoint.map := disjoint_map
theorem Disjoint.of_map {f : α → β} {s t : List α} (h : Disjoint (s.map f) (t.map f)) :
Disjoint s t := fun _a has hat ↦
h (mem_map_of_mem has) (mem_map_of_mem hat)
theorem Disjoint.map_iff {f : α → β} {s t : List α} (hf : Function.Injective f) :
Disjoint (s.map f) (t.map f) ↔ Disjoint s t :=
⟨fun h ↦ h.of_map, fun h ↦ h.map hf⟩
theorem Perm.disjoint_left {l₁ l₂ l : List α} (p : List.Perm l₁ l₂) :
Disjoint l₁ l ↔ Disjoint l₂ l := by
simp_rw [List.disjoint_left, p.mem_iff]
theorem Perm.disjoint_right {l₁ l₂ l : List α} (p : List.Perm l₁ l₂) :
Disjoint l l₁ ↔ Disjoint l l₂ := by
simp_rw [List.disjoint_right, p.mem_iff]
@[simp]
theorem disjoint_reverse_left {l₁ l₂ : List α} : Disjoint l₁.reverse l₂ ↔ Disjoint l₁ l₂ :=
reverse_perm _ |>.disjoint_left
@[simp]
theorem disjoint_reverse_right {l₁ l₂ : List α} : Disjoint l₁ l₂.reverse ↔ Disjoint l₁ l₂ :=
reverse_perm _ |>.disjoint_right
end Disjoint
section lookup
variable [BEq α] [LawfulBEq α]
lemma lookup_graph (f : α → β) {a : α} {as : List α} (h : a ∈ as) :
lookup a (as.map fun x => (x, f x)) = some (f a) := by
induction as with
| nil => exact (not_mem_nil h).elim
| cons a' as ih =>
by_cases ha : a = a'
· simp [ha, lookup_cons]
· simpa [lookup_cons, beq_false_of_ne ha] using ih (List.mem_of_ne_of_mem ha h)
end lookup
section range'
@[simp]
lemma range'_0 (a b : ℕ) :
range' a b 0 = replicate b a := by
induction b with
| zero => simp
| succ b ih => simp [range'_succ, ih, replicate_succ]
lemma left_le_of_mem_range' {a b s x : ℕ}
(hx : x ∈ List.range' a b s) : a ≤ x := by
obtain ⟨i, _, rfl⟩ := List.mem_range'.mp hx
exact le_add_right a (s * i)
end range'
end List
| Mathlib/Data/List/Basic.lean | 3,148 | 3,156 | |
/-
Copyright (c) 2021 Yaël Dillies. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yaël Dillies
-/
import Mathlib.Analysis.Convex.Basic
import Mathlib.Topology.Algebra.Group.Pointwise
import Mathlib.Topology.Order.Basic
/-!
# Strictly convex sets
This file defines strictly convex sets.
A set is strictly convex if the open segment between any two distinct points lies in its interior.
-/
open Set
open Convex Pointwise
variable {𝕜 𝕝 E F β : Type*}
open Function Set
open Convex
section OrderedSemiring
/-- A set is strictly convex if the open segment between any two distinct points lies is in its
interior. This basically means "convex and not flat on the boundary". -/
def StrictConvex (𝕜 : Type*) {E : Type*} [Semiring 𝕜] [PartialOrder 𝕜] [TopologicalSpace E]
[AddCommMonoid E] [SMul 𝕜 E] (s : Set E) : Prop :=
s.Pairwise fun x y => ∀ ⦃a b : 𝕜⦄, 0 < a → 0 < b → a + b = 1 → a • x + b • y ∈ interior s
variable [Semiring 𝕜] [PartialOrder 𝕜] [TopologicalSpace E] [TopologicalSpace F]
section AddCommMonoid
variable [AddCommMonoid E] [AddCommMonoid F]
section SMul
variable [SMul 𝕜 E] [SMul 𝕜 F] (s : Set E)
variable {s}
variable {x y : E} {a b : 𝕜}
theorem strictConvex_iff_openSegment_subset :
StrictConvex 𝕜 s ↔ s.Pairwise fun x y => openSegment 𝕜 x y ⊆ interior s :=
forall₅_congr fun _ _ _ _ _ => (openSegment_subset_iff 𝕜).symm
theorem StrictConvex.openSegment_subset (hs : StrictConvex 𝕜 s) (hx : x ∈ s) (hy : y ∈ s)
(h : x ≠ y) : openSegment 𝕜 x y ⊆ interior s :=
strictConvex_iff_openSegment_subset.1 hs hx hy h
theorem strictConvex_empty : StrictConvex 𝕜 (∅ : Set E) :=
pairwise_empty _
theorem strictConvex_univ : StrictConvex 𝕜 (univ : Set E) := by
intro x _ y _ _ a b _ _ _
rw [interior_univ]
exact mem_univ _
protected nonrec theorem StrictConvex.eq (hs : StrictConvex 𝕜 s) (hx : x ∈ s) (hy : y ∈ s)
(ha : 0 < a) (hb : 0 < b) (hab : a + b = 1) (h : a • x + b • y ∉ interior s) : x = y :=
hs.eq hx hy fun H => h <| H ha hb hab
protected theorem StrictConvex.inter {t : Set E} (hs : StrictConvex 𝕜 s) (ht : StrictConvex 𝕜 t) :
StrictConvex 𝕜 (s ∩ t) := by
intro x hx y hy hxy a b ha hb hab
rw [interior_inter]
exact ⟨hs hx.1 hy.1 hxy ha hb hab, ht hx.2 hy.2 hxy ha hb hab⟩
theorem Directed.strictConvex_iUnion {ι : Sort*} {s : ι → Set E} (hdir : Directed (· ⊆ ·) s)
(hs : ∀ ⦃i : ι⦄, StrictConvex 𝕜 (s i)) : StrictConvex 𝕜 (⋃ i, s i) := by
rintro x hx y hy hxy a b ha hb hab
rw [mem_iUnion] at hx hy
obtain ⟨i, hx⟩ := hx
obtain ⟨j, hy⟩ := hy
obtain ⟨k, hik, hjk⟩ := hdir i j
exact interior_mono (subset_iUnion s k) (hs (hik hx) (hjk hy) hxy ha hb hab)
theorem DirectedOn.strictConvex_sUnion {S : Set (Set E)} (hdir : DirectedOn (· ⊆ ·) S)
(hS : ∀ s ∈ S, StrictConvex 𝕜 s) : StrictConvex 𝕜 (⋃₀ S) := by
rw [sUnion_eq_iUnion]
exact (directedOn_iff_directed.1 hdir).strictConvex_iUnion fun s => hS _ s.2
end SMul
section Module
variable [Module 𝕜 E] [Module 𝕜 F] {s : Set E}
protected theorem StrictConvex.convex (hs : StrictConvex 𝕜 s) : Convex 𝕜 s :=
convex_iff_pairwise_pos.2 fun _ hx _ hy hxy _ _ ha hb hab =>
interior_subset <| hs hx hy hxy ha hb hab
/-- An open convex set is strictly convex. -/
protected theorem Convex.strictConvex_of_isOpen (h : IsOpen s) (hs : Convex 𝕜 s) :
StrictConvex 𝕜 s :=
fun _ hx _ hy _ _ _ ha hb hab => h.interior_eq.symm ▸ hs hx hy ha.le hb.le hab
theorem IsOpen.strictConvex_iff (h : IsOpen s) : StrictConvex 𝕜 s ↔ Convex 𝕜 s :=
⟨StrictConvex.convex, Convex.strictConvex_of_isOpen h⟩
theorem strictConvex_singleton (c : E) : StrictConvex 𝕜 ({c} : Set E) :=
pairwise_singleton _ _
theorem Set.Subsingleton.strictConvex (hs : s.Subsingleton) : StrictConvex 𝕜 s :=
hs.pairwise _
theorem StrictConvex.linear_image [Semiring 𝕝] [Module 𝕝 E] [Module 𝕝 F]
[LinearMap.CompatibleSMul E F 𝕜 𝕝] (hs : StrictConvex 𝕜 s) (f : E →ₗ[𝕝] F) (hf : IsOpenMap f) :
StrictConvex 𝕜 (f '' s) := by
rintro _ ⟨x, hx, rfl⟩ _ ⟨y, hy, rfl⟩ hxy a b ha hb hab
refine hf.image_interior_subset _ ⟨a • x + b • y, hs hx hy (ne_of_apply_ne _ hxy) ha hb hab, ?_⟩
rw [map_add, f.map_smul_of_tower a, f.map_smul_of_tower b]
theorem StrictConvex.is_linear_image (hs : StrictConvex 𝕜 s) {f : E → F} (h : IsLinearMap 𝕜 f)
(hf : IsOpenMap f) : StrictConvex 𝕜 (f '' s) :=
hs.linear_image (h.mk' f) hf
theorem StrictConvex.linear_preimage {s : Set F} (hs : StrictConvex 𝕜 s) (f : E →ₗ[𝕜] F)
(hf : Continuous f) (hfinj : Injective f) : StrictConvex 𝕜 (s.preimage f) := by
intro x hx y hy hxy a b ha hb hab
refine preimage_interior_subset_interior_preimage hf ?_
rw [mem_preimage, f.map_add, f.map_smul, f.map_smul]
exact hs hx hy (hfinj.ne hxy) ha hb hab
theorem StrictConvex.is_linear_preimage {s : Set F} (hs : StrictConvex 𝕜 s) {f : E → F}
(h : IsLinearMap 𝕜 f) (hf : Continuous f) (hfinj : Injective f) :
StrictConvex 𝕜 (s.preimage f) :=
hs.linear_preimage (h.mk' f) hf hfinj
section LinearOrderedCancelAddCommMonoid
variable [TopologicalSpace β] [AddCommMonoid β] [LinearOrder β] [IsOrderedCancelAddMonoid β]
[OrderTopology β] [Module 𝕜 β] [OrderedSMul 𝕜 β]
protected theorem Set.OrdConnected.strictConvex {s : Set β} (hs : OrdConnected s) :
StrictConvex 𝕜 s := by
refine strictConvex_iff_openSegment_subset.2 fun x hx y hy hxy => ?_
rcases hxy.lt_or_lt with hlt | hlt <;> [skip; rw [openSegment_symm]] <;>
exact
(openSegment_subset_Ioo hlt).trans
(isOpen_Ioo.subset_interior_iff.2 <| Ioo_subset_Icc_self.trans <| hs.out ‹_› ‹_›)
theorem strictConvex_Iic (r : β) : StrictConvex 𝕜 (Iic r) :=
ordConnected_Iic.strictConvex
theorem strictConvex_Ici (r : β) : StrictConvex 𝕜 (Ici r) :=
ordConnected_Ici.strictConvex
theorem strictConvex_Iio (r : β) : StrictConvex 𝕜 (Iio r) :=
ordConnected_Iio.strictConvex
theorem strictConvex_Ioi (r : β) : StrictConvex 𝕜 (Ioi r) :=
ordConnected_Ioi.strictConvex
theorem strictConvex_Icc (r s : β) : StrictConvex 𝕜 (Icc r s) :=
ordConnected_Icc.strictConvex
theorem strictConvex_Ioo (r s : β) : StrictConvex 𝕜 (Ioo r s) :=
ordConnected_Ioo.strictConvex
theorem strictConvex_Ico (r s : β) : StrictConvex 𝕜 (Ico r s) :=
ordConnected_Ico.strictConvex
theorem strictConvex_Ioc (r s : β) : StrictConvex 𝕜 (Ioc r s) :=
ordConnected_Ioc.strictConvex
theorem strictConvex_uIcc (r s : β) : StrictConvex 𝕜 (uIcc r s) :=
strictConvex_Icc _ _
theorem strictConvex_uIoc (r s : β) : StrictConvex 𝕜 (uIoc r s) :=
strictConvex_Ioc _ _
end LinearOrderedCancelAddCommMonoid
end Module
end AddCommMonoid
section AddCancelCommMonoid
variable [AddCancelCommMonoid E] [ContinuousAdd E] [Module 𝕜 E] {s : Set E}
/-- The translation of a strictly convex set is also strictly convex. -/
theorem StrictConvex.preimage_add_right (hs : StrictConvex 𝕜 s) (z : E) :
StrictConvex 𝕜 ((fun x => z + x) ⁻¹' s) := by
intro x hx y hy hxy a b ha hb hab
refine preimage_interior_subset_interior_preimage (continuous_add_left _) ?_
have h := hs hx hy ((add_right_injective _).ne hxy) ha hb hab
rwa [smul_add, smul_add, add_add_add_comm, ← _root_.add_smul, hab, one_smul] at h
/-- The translation of a strictly convex set is also strictly convex. -/
theorem StrictConvex.preimage_add_left (hs : StrictConvex 𝕜 s) (z : E) :
StrictConvex 𝕜 ((fun x => x + z) ⁻¹' s) := by
simpa only [add_comm] using hs.preimage_add_right z
end AddCancelCommMonoid
section AddCommGroup
variable [AddCommGroup E] [AddCommGroup F] [Module 𝕜 E] [Module 𝕜 F]
section continuous_add
variable [ContinuousAdd E] {s t : Set E}
theorem StrictConvex.add (hs : StrictConvex 𝕜 s) (ht : StrictConvex 𝕜 t) :
StrictConvex 𝕜 (s + t) := by
rintro _ ⟨v, hv, w, hw, rfl⟩ _ ⟨x, hx, y, hy, rfl⟩ h a b ha hb hab
rw [smul_add, smul_add, add_add_add_comm]
obtain rfl | hvx := eq_or_ne v x
· refine interior_mono (add_subset_add (singleton_subset_iff.2 hv) Subset.rfl) ?_
rw [Convex.combo_self hab, singleton_add]
exact
(isOpenMap_add_left _).image_interior_subset _
(mem_image_of_mem _ <| ht hw hy (ne_of_apply_ne _ h) ha hb hab)
exact
subset_interior_add_left
(add_mem_add (hs hv hx hvx ha hb hab) <| ht.convex hw hy ha.le hb.le hab)
theorem StrictConvex.add_left (hs : StrictConvex 𝕜 s) (z : E) :
StrictConvex 𝕜 ((fun x => z + x) '' s) := by
simpa only [singleton_add] using (strictConvex_singleton z).add hs
theorem StrictConvex.add_right (hs : StrictConvex 𝕜 s) (z : E) :
StrictConvex 𝕜 ((fun x => x + z) '' s) := by simpa only [add_comm] using hs.add_left z
/-- The translation of a strictly convex set is also strictly convex. -/
theorem StrictConvex.vadd (hs : StrictConvex 𝕜 s) (x : E) : StrictConvex 𝕜 (x +ᵥ s) :=
hs.add_left x
end continuous_add
section ContinuousSMul
variable [Field 𝕝] [Module 𝕝 E] [ContinuousConstSMul 𝕝 E]
[LinearMap.CompatibleSMul E E 𝕜 𝕝] {s : Set E} {x : E}
theorem StrictConvex.smul (hs : StrictConvex 𝕜 s) (c : 𝕝) : StrictConvex 𝕜 (c • s) := by
obtain rfl | hc := eq_or_ne c 0
· exact (subsingleton_zero_smul_set _).strictConvex
· exact hs.linear_image (LinearMap.lsmul _ _ c) (isOpenMap_smul₀ hc)
theorem StrictConvex.affinity [ContinuousAdd E] (hs : StrictConvex 𝕜 s) (z : E) (c : 𝕝) :
StrictConvex 𝕜 (z +ᵥ c • s) :=
(hs.smul c).vadd z
end ContinuousSMul
end AddCommGroup
end OrderedSemiring
section CommSemiring
variable [CommSemiring 𝕜] [PartialOrder 𝕜] [TopologicalSpace E]
section AddCommGroup
variable [AddCommGroup E] [Module 𝕜 E] [NoZeroSMulDivisors 𝕜 E] [ContinuousConstSMul 𝕜 E]
{s : Set E}
theorem StrictConvex.preimage_smul (hs : StrictConvex 𝕜 s) (c : 𝕜) :
StrictConvex 𝕜 ((fun z => c • z) ⁻¹' s) := by
classical
obtain rfl | hc := eq_or_ne c 0
· simp_rw [zero_smul, preimage_const]
split_ifs
· exact strictConvex_univ
· exact strictConvex_empty
refine hs.linear_preimage (LinearMap.lsmul _ _ c) ?_ (smul_right_injective E hc)
unfold LinearMap.lsmul LinearMap.mk₂ LinearMap.mk₂' LinearMap.mk₂'ₛₗ
exact continuous_const_smul _
end AddCommGroup
end CommSemiring
section OrderedRing
variable [Ring 𝕜] [PartialOrder 𝕜] [TopologicalSpace E] [TopologicalSpace F]
section AddCommGroup
variable [AddCommGroup E] [AddCommGroup F] [Module 𝕜 E] [Module 𝕜 F] {s t : Set E} {x y : E}
theorem StrictConvex.eq_of_openSegment_subset_frontier
[IsOrderedRing 𝕜] [Nontrivial 𝕜] [DenselyOrdered 𝕜]
(hs : StrictConvex 𝕜 s) (hx : x ∈ s) (hy : y ∈ s) (h : openSegment 𝕜 x y ⊆ frontier s) :
x = y := by
obtain ⟨a, ha₀, ha₁⟩ := DenselyOrdered.dense (0 : 𝕜) 1 zero_lt_one
classical
by_contra hxy
exact
(h ⟨a, 1 - a, ha₀, sub_pos_of_lt ha₁, add_sub_cancel _ _, rfl⟩).2
(hs hx hy hxy ha₀ (sub_pos_of_lt ha₁) <| add_sub_cancel _ _)
theorem StrictConvex.add_smul_mem [AddRightStrictMono 𝕜]
(hs : StrictConvex 𝕜 s) (hx : x ∈ s) (hxy : x + y ∈ s)
(hy : y ≠ 0) {t : 𝕜} (ht₀ : 0 < t) (ht₁ : t < 1) : x + t • y ∈ interior s := by
have h : x + t • y = (1 - t) • x + t • (x + y) := by match_scalars <;> field_simp
rw [h]
exact hs hx hxy (fun h => hy <| add_left_cancel (a := x) (by rw [← h, add_zero]))
(sub_pos_of_lt ht₁) ht₀ (sub_add_cancel 1 t)
theorem StrictConvex.smul_mem_of_zero_mem [AddRightStrictMono 𝕜]
(hs : StrictConvex 𝕜 s) (zero_mem : (0 : E) ∈ s)
(hx : x ∈ s) (hx₀ : x ≠ 0) {t : 𝕜} (ht₀ : 0 < t) (ht₁ : t < 1) : t • x ∈ interior s := by
simpa using hs.add_smul_mem zero_mem (by simpa using hx) hx₀ ht₀ ht₁
theorem StrictConvex.add_smul_sub_mem [AddRightMono 𝕜]
(h : StrictConvex 𝕜 s) (hx : x ∈ s) (hy : y ∈ s) (hxy : x ≠ y)
{t : 𝕜} (ht₀ : 0 < t) (ht₁ : t < 1) : x + t • (y - x) ∈ interior s := by
apply h.openSegment_subset hx hy hxy
rw [openSegment_eq_image']
exact mem_image_of_mem _ ⟨ht₀, ht₁⟩
/-- The preimage of a strictly convex set under an affine map is strictly convex. -/
theorem StrictConvex.affine_preimage {s : Set F} (hs : StrictConvex 𝕜 s) {f : E →ᵃ[𝕜] F}
(hf : Continuous f) (hfinj : Injective f) : StrictConvex 𝕜 (f ⁻¹' s) := by
intro x hx y hy hxy a b ha hb hab
refine preimage_interior_subset_interior_preimage hf ?_
rw [mem_preimage, Convex.combo_affine_apply hab]
exact hs hx hy (hfinj.ne hxy) ha hb hab
/-- The image of a strictly convex set under an affine map is strictly convex. -/
theorem StrictConvex.affine_image (hs : StrictConvex 𝕜 s) {f : E →ᵃ[𝕜] F} (hf : IsOpenMap f) :
StrictConvex 𝕜 (f '' s) := by
rintro _ ⟨x, hx, rfl⟩ _ ⟨y, hy, rfl⟩ hxy a b ha hb hab
exact
hf.image_interior_subset _
⟨a • x + b • y, ⟨hs hx hy (ne_of_apply_ne _ hxy) ha hb hab, Convex.combo_affine_apply hab⟩⟩
variable [IsTopologicalAddGroup E]
theorem StrictConvex.neg (hs : StrictConvex 𝕜 s) : StrictConvex 𝕜 (-s) :=
hs.is_linear_preimage IsLinearMap.isLinearMap_neg continuous_id.neg neg_injective
theorem StrictConvex.sub (hs : StrictConvex 𝕜 s) (ht : StrictConvex 𝕜 t) : StrictConvex 𝕜 (s - t) :=
(sub_eq_add_neg s t).symm ▸ hs.add ht.neg
end AddCommGroup
end OrderedRing
section LinearOrderedField
variable [Field 𝕜] [LinearOrder 𝕜] [IsStrictOrderedRing 𝕜] [TopologicalSpace E]
section AddCommGroup
variable [AddCommGroup E] [AddCommGroup F] [Module 𝕜 E] [Module 𝕜 F] {s : Set E} {x : E}
/-- Alternative definition of set strict convexity, using division. -/
theorem strictConvex_iff_div :
StrictConvex 𝕜 s ↔
s.Pairwise fun x y =>
∀ ⦃a b : 𝕜⦄, 0 < a → 0 < b → (a / (a + b)) • x + (b / (a + b)) • y ∈ interior s :=
⟨fun h x hx y hy hxy a b ha hb ↦ h hx hy hxy (by positivity) (by positivity) (by field_simp),
fun h x hx y hy hxy a b ha hb hab ↦ by
convert h hx hy hxy ha hb <;> rw [hab, div_one]⟩
theorem StrictConvex.mem_smul_of_zero_mem (hs : StrictConvex 𝕜 s) (zero_mem : (0 : E) ∈ s)
(hx : x ∈ s) (hx₀ : x ≠ 0) {t : 𝕜} (ht : 1 < t) : x ∈ t • interior s := by
rw [mem_smul_set_iff_inv_smul_mem₀ (by positivity)]
exact hs.smul_mem_of_zero_mem zero_mem hx hx₀ (by positivity) (inv_lt_one_of_one_lt₀ ht)
end AddCommGroup
end LinearOrderedField
/-!
#### Convex sets in an ordered space
Relates `Convex` and `Set.OrdConnected`.
-/
section
variable [Field 𝕜] [LinearOrder 𝕜] [IsStrictOrderedRing 𝕜] [TopologicalSpace 𝕜] [OrderTopology 𝕜]
{s : Set 𝕜}
/-- A set in a linear ordered field is strictly convex if and only if it is convex. -/
@[simp]
theorem strictConvex_iff_convex : StrictConvex 𝕜 s ↔ Convex 𝕜 s :=
⟨StrictConvex.convex, fun hs => hs.ordConnected.strictConvex⟩
theorem strictConvex_iff_ordConnected : StrictConvex 𝕜 s ↔ s.OrdConnected :=
strictConvex_iff_convex.trans convex_iff_ordConnected
alias ⟨StrictConvex.ordConnected, _⟩ := strictConvex_iff_ordConnected
end
| Mathlib/Analysis/Convex/Strict.lean | 417 | 420 | |
/-
Copyright (c) 2019 Kevin Buzzard. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kevin Buzzard
-/
import Mathlib.Data.EReal.Basic
deprecated_module (since := "2025-04-13")
| Mathlib/Data/Real/EReal.lean | 1,141 | 1,143 | |
/-
Copyright (c) 2017 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl, Mario Carneiro, Patrick Massot
-/
import Mathlib.Order.Filter.SmallSets
import Mathlib.Topology.UniformSpace.Defs
import Mathlib.Topology.ContinuousOn
/-!
# Basic results on uniform spaces
Uniform spaces are a generalization of metric spaces and topological groups.
## Main definitions
In this file we define a complete lattice structure on the type `UniformSpace X`
of uniform structures on `X`, as well as the pullback (`UniformSpace.comap`) of uniform structures
coming from the pullback of filters.
Like distance functions, uniform structures cannot be pushed forward in general.
## Notations
Localized in `Uniformity`, we have the notation `𝓤 X` for the uniformity on a uniform space `X`,
and `○` for composition of relations, seen as terms with type `Set (X × X)`.
## References
The formalization uses the books:
* [N. Bourbaki, *General Topology*][bourbaki1966]
* [I. M. James, *Topologies and Uniformities*][james1999]
But it makes a more systematic use of the filter library.
-/
open Set Filter Topology
universe u v ua ub uc ud
/-!
### Relations, seen as `Set (α × α)`
-/
variable {α : Type ua} {β : Type ub} {γ : Type uc} {δ : Type ud} {ι : Sort*}
open Uniformity
section UniformSpace
variable [UniformSpace α]
/-- If `s ∈ 𝓤 α`, then for any natural `n`, for a subset `t` of a sufficiently small set in `𝓤 α`,
we have `t ○ t ○ ... ○ t ⊆ s` (`n` compositions). -/
theorem eventually_uniformity_iterate_comp_subset {s : Set (α × α)} (hs : s ∈ 𝓤 α) (n : ℕ) :
∀ᶠ t in (𝓤 α).smallSets, (t ○ ·)^[n] t ⊆ s := by
suffices ∀ᶠ t in (𝓤 α).smallSets, t ⊆ s ∧ (t ○ ·)^[n] t ⊆ s from (eventually_and.1 this).2
induction n generalizing s with
| zero => simpa
| succ _ ihn =>
rcases comp_mem_uniformity_sets hs with ⟨t, htU, hts⟩
refine (ihn htU).mono fun U hU => ?_
rw [Function.iterate_succ_apply']
exact
⟨hU.1.trans <| (subset_comp_self <| refl_le_uniformity htU).trans hts,
(compRel_mono hU.1 hU.2).trans hts⟩
/-- If `s ∈ 𝓤 α`, then for a subset `t` of a sufficiently small set in `𝓤 α`,
we have `t ○ t ⊆ s`. -/
theorem eventually_uniformity_comp_subset {s : Set (α × α)} (hs : s ∈ 𝓤 α) :
∀ᶠ t in (𝓤 α).smallSets, t ○ t ⊆ s :=
eventually_uniformity_iterate_comp_subset hs 1
/-!
### Balls in uniform spaces
-/
namespace UniformSpace
open UniformSpace (ball)
lemma isOpen_ball (x : α) {V : Set (α × α)} (hV : IsOpen V) : IsOpen (ball x V) :=
hV.preimage <| .prodMk_right _
lemma isClosed_ball (x : α) {V : Set (α × α)} (hV : IsClosed V) : IsClosed (ball x V) :=
hV.preimage <| .prodMk_right _
/-!
### Neighborhoods in uniform spaces
-/
theorem hasBasis_nhds_prod (x y : α) :
HasBasis (𝓝 (x, y)) (fun s => s ∈ 𝓤 α ∧ IsSymmetricRel s) fun s => ball x s ×ˢ ball y s := by
rw [nhds_prod_eq]
apply (hasBasis_nhds x).prod_same_index (hasBasis_nhds y)
rintro U V ⟨U_in, U_symm⟩ ⟨V_in, V_symm⟩
exact
⟨U ∩ V, ⟨(𝓤 α).inter_sets U_in V_in, U_symm.inter V_symm⟩, ball_inter_left x U V,
ball_inter_right y U V⟩
end UniformSpace
open UniformSpace
theorem nhds_eq_uniformity_prod {a b : α} :
𝓝 (a, b) =
(𝓤 α).lift' fun s : Set (α × α) => { y : α | (y, a) ∈ s } ×ˢ { y : α | (b, y) ∈ s } := by
rw [nhds_prod_eq, nhds_nhds_eq_uniformity_uniformity_prod, lift_lift'_same_eq_lift']
· exact fun s => monotone_const.set_prod monotone_preimage
· refine fun t => Monotone.set_prod ?_ monotone_const
exact monotone_preimage (f := fun y => (y, a))
theorem nhdset_of_mem_uniformity {d : Set (α × α)} (s : Set (α × α)) (hd : d ∈ 𝓤 α) :
∃ t : Set (α × α), IsOpen t ∧ s ⊆ t ∧
t ⊆ { p | ∃ x y, (p.1, x) ∈ d ∧ (x, y) ∈ s ∧ (y, p.2) ∈ d } := by
let cl_d := { p : α × α | ∃ x y, (p.1, x) ∈ d ∧ (x, y) ∈ s ∧ (y, p.2) ∈ d }
have : ∀ p ∈ s, ∃ t, t ⊆ cl_d ∧ IsOpen t ∧ p ∈ t := fun ⟨x, y⟩ hp =>
mem_nhds_iff.mp <|
show cl_d ∈ 𝓝 (x, y) by
rw [nhds_eq_uniformity_prod, mem_lift'_sets]
· exact ⟨d, hd, fun ⟨a, b⟩ ⟨ha, hb⟩ => ⟨x, y, ha, hp, hb⟩⟩
· exact fun _ _ h _ h' => ⟨h h'.1, h h'.2⟩
choose t ht using this
exact ⟨(⋃ p : α × α, ⋃ h : p ∈ s, t p h : Set (α × α)),
isOpen_iUnion fun p : α × α => isOpen_iUnion fun hp => (ht p hp).right.left,
fun ⟨a, b⟩ hp => by
simp only [mem_iUnion, Prod.exists]; exact ⟨a, b, hp, (ht (a, b) hp).right.right⟩,
iUnion_subset fun p => iUnion_subset fun hp => (ht p hp).left⟩
/-- Entourages are neighborhoods of the diagonal. -/
theorem nhds_le_uniformity (x : α) : 𝓝 (x, x) ≤ 𝓤 α := by
intro V V_in
rcases comp_symm_mem_uniformity_sets V_in with ⟨w, w_in, w_symm, w_sub⟩
have : ball x w ×ˢ ball x w ∈ 𝓝 (x, x) := by
rw [nhds_prod_eq]
exact prod_mem_prod (ball_mem_nhds x w_in) (ball_mem_nhds x w_in)
apply mem_of_superset this
rintro ⟨u, v⟩ ⟨u_in, v_in⟩
exact w_sub (mem_comp_of_mem_ball w_symm u_in v_in)
/-- Entourages are neighborhoods of the diagonal. -/
theorem iSup_nhds_le_uniformity : ⨆ x : α, 𝓝 (x, x) ≤ 𝓤 α :=
iSup_le nhds_le_uniformity
/-- Entourages are neighborhoods of the diagonal. -/
theorem nhdsSet_diagonal_le_uniformity : 𝓝ˢ (diagonal α) ≤ 𝓤 α :=
(nhdsSet_diagonal α).trans_le iSup_nhds_le_uniformity
section
variable (α)
theorem UniformSpace.has_seq_basis [IsCountablyGenerated <| 𝓤 α] :
∃ V : ℕ → Set (α × α), HasAntitoneBasis (𝓤 α) V ∧ ∀ n, IsSymmetricRel (V n) :=
let ⟨U, hsym, hbasis⟩ := (@UniformSpace.hasBasis_symmetric α _).exists_antitone_subbasis
⟨U, hbasis, fun n => (hsym n).2⟩
end
/-!
### Closure and interior in uniform spaces
-/
theorem closure_eq_uniformity (s : Set <| α × α) :
closure s = ⋂ V ∈ { V | V ∈ 𝓤 α ∧ IsSymmetricRel V }, V ○ s ○ V := by
ext ⟨x, y⟩
simp +contextual only
[mem_closure_iff_nhds_basis (UniformSpace.hasBasis_nhds_prod x y), mem_iInter, mem_setOf_eq,
and_imp, mem_comp_comp, exists_prop, ← mem_inter_iff, inter_comm, Set.Nonempty]
theorem uniformity_hasBasis_closed :
HasBasis (𝓤 α) (fun V : Set (α × α) => V ∈ 𝓤 α ∧ IsClosed V) id := by
refine Filter.hasBasis_self.2 fun t h => ?_
rcases comp_comp_symm_mem_uniformity_sets h with ⟨w, w_in, w_symm, r⟩
refine ⟨closure w, mem_of_superset w_in subset_closure, isClosed_closure, ?_⟩
refine Subset.trans ?_ r
rw [closure_eq_uniformity]
apply iInter_subset_of_subset
apply iInter_subset
exact ⟨w_in, w_symm⟩
theorem uniformity_eq_uniformity_closure : 𝓤 α = (𝓤 α).lift' closure :=
Eq.symm <| uniformity_hasBasis_closed.lift'_closure_eq_self fun _ => And.right
theorem Filter.HasBasis.uniformity_closure {p : ι → Prop} {U : ι → Set (α × α)}
(h : (𝓤 α).HasBasis p U) : (𝓤 α).HasBasis p fun i => closure (U i) :=
(@uniformity_eq_uniformity_closure α _).symm ▸ h.lift'_closure
/-- Closed entourages form a basis of the uniformity filter. -/
theorem uniformity_hasBasis_closure : HasBasis (𝓤 α) (fun V : Set (α × α) => V ∈ 𝓤 α) closure :=
(𝓤 α).basis_sets.uniformity_closure
theorem closure_eq_inter_uniformity {t : Set (α × α)} : closure t = ⋂ d ∈ 𝓤 α, d ○ (t ○ d) :=
calc
closure t = ⋂ (V) (_ : V ∈ 𝓤 α ∧ IsSymmetricRel V), V ○ t ○ V := closure_eq_uniformity t
_ = ⋂ V ∈ 𝓤 α, V ○ t ○ V :=
Eq.symm <|
UniformSpace.hasBasis_symmetric.biInter_mem fun _ _ hV =>
compRel_mono (compRel_mono hV Subset.rfl) hV
_ = ⋂ V ∈ 𝓤 α, V ○ (t ○ V) := by simp only [compRel_assoc]
theorem uniformity_eq_uniformity_interior : 𝓤 α = (𝓤 α).lift' interior :=
le_antisymm
(le_iInf₂ fun d hd => by
let ⟨s, hs, hs_comp⟩ := comp3_mem_uniformity hd
let ⟨t, ht, hst, ht_comp⟩ := nhdset_of_mem_uniformity s hs
have : s ⊆ interior d :=
calc
s ⊆ t := hst
_ ⊆ interior d :=
ht.subset_interior_iff.mpr fun x (hx : x ∈ t) =>
let ⟨x, y, h₁, h₂, h₃⟩ := ht_comp hx
hs_comp ⟨x, h₁, y, h₂, h₃⟩
have : interior d ∈ 𝓤 α := by filter_upwards [hs] using this
simp [this])
fun _ hs => ((𝓤 α).lift' interior).sets_of_superset (mem_lift' hs) interior_subset
theorem interior_mem_uniformity {s : Set (α × α)} (hs : s ∈ 𝓤 α) : interior s ∈ 𝓤 α := by
rw [uniformity_eq_uniformity_interior]; exact mem_lift' hs
theorem mem_uniformity_isClosed {s : Set (α × α)} (h : s ∈ 𝓤 α) : ∃ t ∈ 𝓤 α, IsClosed t ∧ t ⊆ s :=
let ⟨t, ⟨ht_mem, htc⟩, hts⟩ := uniformity_hasBasis_closed.mem_iff.1 h
⟨t, ht_mem, htc, hts⟩
theorem isOpen_iff_isOpen_ball_subset {s : Set α} :
IsOpen s ↔ ∀ x ∈ s, ∃ V ∈ 𝓤 α, IsOpen V ∧ ball x V ⊆ s := by
rw [isOpen_iff_ball_subset]
constructor <;> intro h x hx
· obtain ⟨V, hV, hV'⟩ := h x hx
exact
⟨interior V, interior_mem_uniformity hV, isOpen_interior,
(ball_mono interior_subset x).trans hV'⟩
· obtain ⟨V, hV, -, hV'⟩ := h x hx
exact ⟨V, hV, hV'⟩
@[deprecated (since := "2024-11-18")] alias
isOpen_iff_open_ball_subset := isOpen_iff_isOpen_ball_subset
/-- The uniform neighborhoods of all points of a dense set cover the whole space. -/
theorem Dense.biUnion_uniformity_ball {s : Set α} {U : Set (α × α)} (hs : Dense s) (hU : U ∈ 𝓤 α) :
⋃ x ∈ s, ball x U = univ := by
refine iUnion₂_eq_univ_iff.2 fun y => ?_
rcases hs.inter_nhds_nonempty (mem_nhds_right y hU) with ⟨x, hxs, hxy : (x, y) ∈ U⟩
exact ⟨x, hxs, hxy⟩
/-- The uniform neighborhoods of all points of a dense indexed collection cover the whole space. -/
lemma DenseRange.iUnion_uniformity_ball {ι : Type*} {xs : ι → α}
(xs_dense : DenseRange xs) {U : Set (α × α)} (hU : U ∈ uniformity α) :
⋃ i, UniformSpace.ball (xs i) U = univ := by
rw [← biUnion_range (f := xs) (g := fun x ↦ UniformSpace.ball x U)]
exact Dense.biUnion_uniformity_ball xs_dense hU
/-!
### Uniformity bases
-/
/-- Open elements of `𝓤 α` form a basis of `𝓤 α`. -/
theorem uniformity_hasBasis_open : HasBasis (𝓤 α) (fun V : Set (α × α) => V ∈ 𝓤 α ∧ IsOpen V) id :=
hasBasis_self.2 fun s hs =>
⟨interior s, interior_mem_uniformity hs, isOpen_interior, interior_subset⟩
theorem Filter.HasBasis.mem_uniformity_iff {p : β → Prop} {s : β → Set (α × α)}
(h : (𝓤 α).HasBasis p s) {t : Set (α × α)} :
t ∈ 𝓤 α ↔ ∃ i, p i ∧ ∀ a b, (a, b) ∈ s i → (a, b) ∈ t :=
h.mem_iff.trans <| by simp only [Prod.forall, subset_def]
/-- Open elements `s : Set (α × α)` of `𝓤 α` such that `(x, y) ∈ s ↔ (y, x) ∈ s` form a basis
of `𝓤 α`. -/
theorem uniformity_hasBasis_open_symmetric :
HasBasis (𝓤 α) (fun V : Set (α × α) => V ∈ 𝓤 α ∧ IsOpen V ∧ IsSymmetricRel V) id := by
simp only [← and_assoc]
refine uniformity_hasBasis_open.restrict fun s hs => ⟨symmetrizeRel s, ?_⟩
exact
⟨⟨symmetrize_mem_uniformity hs.1, IsOpen.inter hs.2 (hs.2.preimage continuous_swap)⟩,
symmetric_symmetrizeRel s, symmetrizeRel_subset_self s⟩
theorem comp_open_symm_mem_uniformity_sets {s : Set (α × α)} (hs : s ∈ 𝓤 α) :
∃ t ∈ 𝓤 α, IsOpen t ∧ IsSymmetricRel t ∧ t ○ t ⊆ s := by
obtain ⟨t, ht₁, ht₂⟩ := comp_mem_uniformity_sets hs
obtain ⟨u, ⟨hu₁, hu₂, hu₃⟩, hu₄ : u ⊆ t⟩ := uniformity_hasBasis_open_symmetric.mem_iff.mp ht₁
exact ⟨u, hu₁, hu₂, hu₃, (compRel_mono hu₄ hu₄).trans ht₂⟩
end UniformSpace
open uniformity
section Constructions
instance : PartialOrder (UniformSpace α) :=
PartialOrder.lift (fun u => 𝓤[u]) fun _ _ => UniformSpace.ext
protected theorem UniformSpace.le_def {u₁ u₂ : UniformSpace α} : u₁ ≤ u₂ ↔ 𝓤[u₁] ≤ 𝓤[u₂] := Iff.rfl
instance : InfSet (UniformSpace α) :=
⟨fun s =>
UniformSpace.ofCore
{ uniformity := ⨅ u ∈ s, 𝓤[u]
refl := le_iInf fun u => le_iInf fun _ => u.toCore.refl
symm := le_iInf₂ fun u hu =>
le_trans (map_mono <| iInf_le_of_le _ <| iInf_le _ hu) u.symm
comp := le_iInf₂ fun u hu =>
le_trans (lift'_mono (iInf_le_of_le _ <| iInf_le _ hu) <| le_rfl) u.comp }⟩
protected theorem UniformSpace.sInf_le {tt : Set (UniformSpace α)} {t : UniformSpace α}
(h : t ∈ tt) : sInf tt ≤ t :=
show ⨅ u ∈ tt, 𝓤[u] ≤ 𝓤[t] from iInf₂_le t h
protected theorem UniformSpace.le_sInf {tt : Set (UniformSpace α)} {t : UniformSpace α}
(h : ∀ t' ∈ tt, t ≤ t') : t ≤ sInf tt :=
show 𝓤[t] ≤ ⨅ u ∈ tt, 𝓤[u] from le_iInf₂ h
instance : Top (UniformSpace α) :=
⟨@UniformSpace.mk α ⊤ ⊤ le_top le_top fun x ↦ by simp only [nhds_top, comap_top]⟩
instance : Bot (UniformSpace α) :=
⟨{ toTopologicalSpace := ⊥
uniformity := 𝓟 idRel
symm := by simp [Tendsto]
comp := lift'_le (mem_principal_self _) <| principal_mono.2 id_compRel.subset
nhds_eq_comap_uniformity := fun s => by
let _ : TopologicalSpace α := ⊥; have := discreteTopology_bot α
simp [idRel] }⟩
instance : Min (UniformSpace α) :=
⟨fun u₁ u₂ =>
{ uniformity := 𝓤[u₁] ⊓ 𝓤[u₂]
symm := u₁.symm.inf u₂.symm
comp := (lift'_inf_le _ _ _).trans <| inf_le_inf u₁.comp u₂.comp
toTopologicalSpace := u₁.toTopologicalSpace ⊓ u₂.toTopologicalSpace
nhds_eq_comap_uniformity := fun _ ↦ by
rw [@nhds_inf _ u₁.toTopologicalSpace _, @nhds_eq_comap_uniformity _ u₁,
@nhds_eq_comap_uniformity _ u₂, comap_inf] }⟩
instance : CompleteLattice (UniformSpace α) :=
{ inferInstanceAs (PartialOrder (UniformSpace α)) with
sup := fun a b => sInf { x | a ≤ x ∧ b ≤ x }
le_sup_left := fun _ _ => UniformSpace.le_sInf fun _ ⟨h, _⟩ => h
le_sup_right := fun _ _ => UniformSpace.le_sInf fun _ ⟨_, h⟩ => h
sup_le := fun _ _ _ h₁ h₂ => UniformSpace.sInf_le ⟨h₁, h₂⟩
inf := (· ⊓ ·)
le_inf := fun a _ _ h₁ h₂ => show a.uniformity ≤ _ from le_inf h₁ h₂
inf_le_left := fun a _ => show _ ≤ a.uniformity from inf_le_left
inf_le_right := fun _ b => show _ ≤ b.uniformity from inf_le_right
top := ⊤
le_top := fun a => show a.uniformity ≤ ⊤ from le_top
bot := ⊥
bot_le := fun u => u.toCore.refl
sSup := fun tt => sInf { t | ∀ t' ∈ tt, t' ≤ t }
le_sSup := fun _ _ h => UniformSpace.le_sInf fun _ h' => h' _ h
sSup_le := fun _ _ h => UniformSpace.sInf_le h
sInf := sInf
le_sInf := fun _ _ hs => UniformSpace.le_sInf hs
sInf_le := fun _ _ ha => UniformSpace.sInf_le ha }
theorem iInf_uniformity {ι : Sort*} {u : ι → UniformSpace α} : 𝓤[iInf u] = ⨅ i, 𝓤[u i] :=
iInf_range
theorem inf_uniformity {u v : UniformSpace α} : 𝓤[u ⊓ v] = 𝓤[u] ⊓ 𝓤[v] := rfl
lemma bot_uniformity : 𝓤[(⊥ : UniformSpace α)] = 𝓟 idRel := rfl
lemma top_uniformity : 𝓤[(⊤ : UniformSpace α)] = ⊤ := rfl
instance inhabitedUniformSpace : Inhabited (UniformSpace α) :=
⟨⊥⟩
instance inhabitedUniformSpaceCore : Inhabited (UniformSpace.Core α) :=
⟨@UniformSpace.toCore _ default⟩
instance [Subsingleton α] : Unique (UniformSpace α) where
uniq u := bot_unique <| le_principal_iff.2 <| by
rw [idRel, ← diagonal, diagonal_eq_univ]; exact univ_mem
/-- Given `f : α → β` and a uniformity `u` on `β`, the inverse image of `u` under `f`
is the inverse image in the filter sense of the induced function `α × α → β × β`.
See note [reducible non-instances]. -/
abbrev UniformSpace.comap (f : α → β) (u : UniformSpace β) : UniformSpace α where
uniformity := 𝓤[u].comap fun p : α × α => (f p.1, f p.2)
symm := by
simp only [tendsto_comap_iff, Prod.swap, (· ∘ ·)]
exact tendsto_swap_uniformity.comp tendsto_comap
comp := le_trans
(by
rw [comap_lift'_eq, comap_lift'_eq2]
· exact lift'_mono' fun s _ ⟨a₁, a₂⟩ ⟨x, h₁, h₂⟩ => ⟨f x, h₁, h₂⟩
· exact monotone_id.compRel monotone_id)
(comap_mono u.comp)
toTopologicalSpace := u.toTopologicalSpace.induced f
nhds_eq_comap_uniformity x := by
simp only [nhds_induced, nhds_eq_comap_uniformity, comap_comap, Function.comp_def]
theorem uniformity_comap {_ : UniformSpace β} (f : α → β) :
𝓤[UniformSpace.comap f ‹_›] = comap (Prod.map f f) (𝓤 β) :=
rfl
lemma ball_preimage {f : α → β} {U : Set (β × β)} {x : α} :
UniformSpace.ball x (Prod.map f f ⁻¹' U) = f ⁻¹' UniformSpace.ball (f x) U := by
ext : 1
simp only [UniformSpace.ball, mem_preimage, Prod.map_apply]
@[simp]
theorem uniformSpace_comap_id {α : Type*} : UniformSpace.comap (id : α → α) = id := by
ext : 2
rw [uniformity_comap, Prod.map_id, comap_id]
theorem UniformSpace.comap_comap {α β γ} {uγ : UniformSpace γ} {f : α → β} {g : β → γ} :
UniformSpace.comap (g ∘ f) uγ = UniformSpace.comap f (UniformSpace.comap g uγ) := by
ext1
simp only [uniformity_comap, Filter.comap_comap, Prod.map_comp_map]
theorem UniformSpace.comap_inf {α γ} {u₁ u₂ : UniformSpace γ} {f : α → γ} :
(u₁ ⊓ u₂).comap f = u₁.comap f ⊓ u₂.comap f :=
UniformSpace.ext Filter.comap_inf
theorem UniformSpace.comap_iInf {ι α γ} {u : ι → UniformSpace γ} {f : α → γ} :
(⨅ i, u i).comap f = ⨅ i, (u i).comap f := by
ext : 1
simp [uniformity_comap, iInf_uniformity]
theorem UniformSpace.comap_mono {α γ} {f : α → γ} :
Monotone fun u : UniformSpace γ => u.comap f := fun _ _ hu =>
Filter.comap_mono hu
theorem uniformContinuous_iff {α β} {uα : UniformSpace α} {uβ : UniformSpace β} {f : α → β} :
UniformContinuous f ↔ uα ≤ uβ.comap f :=
Filter.map_le_iff_le_comap
theorem le_iff_uniformContinuous_id {u v : UniformSpace α} :
u ≤ v ↔ @UniformContinuous _ _ u v id := by
rw [uniformContinuous_iff, uniformSpace_comap_id, id]
theorem uniformContinuous_comap {f : α → β} [u : UniformSpace β] :
@UniformContinuous α β (UniformSpace.comap f u) u f :=
tendsto_comap
theorem uniformContinuous_comap' {f : γ → β} {g : α → γ} [v : UniformSpace β] [u : UniformSpace α]
(h : UniformContinuous (f ∘ g)) : @UniformContinuous α γ u (UniformSpace.comap f v) g :=
tendsto_comap_iff.2 h
namespace UniformSpace
theorem to_nhds_mono {u₁ u₂ : UniformSpace α} (h : u₁ ≤ u₂) (a : α) :
@nhds _ (@UniformSpace.toTopologicalSpace _ u₁) a ≤
@nhds _ (@UniformSpace.toTopologicalSpace _ u₂) a := by
rw [@nhds_eq_uniformity α u₁ a, @nhds_eq_uniformity α u₂ a]; exact lift'_mono h le_rfl
theorem toTopologicalSpace_mono {u₁ u₂ : UniformSpace α} (h : u₁ ≤ u₂) :
@UniformSpace.toTopologicalSpace _ u₁ ≤ @UniformSpace.toTopologicalSpace _ u₂ :=
le_of_nhds_le_nhds <| to_nhds_mono h
theorem toTopologicalSpace_comap {f : α → β} {u : UniformSpace β} :
@UniformSpace.toTopologicalSpace _ (UniformSpace.comap f u) =
TopologicalSpace.induced f (@UniformSpace.toTopologicalSpace β u) :=
rfl
lemma uniformSpace_eq_bot {u : UniformSpace α} : u = ⊥ ↔ idRel ∈ 𝓤[u] :=
le_bot_iff.symm.trans le_principal_iff
protected lemma _root_.Filter.HasBasis.uniformSpace_eq_bot {ι p} {s : ι → Set (α × α)}
{u : UniformSpace α} (h : 𝓤[u].HasBasis p s) :
u = ⊥ ↔ ∃ i, p i ∧ Pairwise fun x y : α ↦ (x, y) ∉ s i := by
simp [uniformSpace_eq_bot, h.mem_iff, subset_def, Pairwise, not_imp_not]
theorem toTopologicalSpace_bot : @UniformSpace.toTopologicalSpace α ⊥ = ⊥ := rfl
theorem toTopologicalSpace_top : @UniformSpace.toTopologicalSpace α ⊤ = ⊤ := rfl
theorem toTopologicalSpace_iInf {ι : Sort*} {u : ι → UniformSpace α} :
(iInf u).toTopologicalSpace = ⨅ i, (u i).toTopologicalSpace :=
TopologicalSpace.ext_nhds fun a ↦ by simp only [@nhds_eq_comap_uniformity _ (iInf u), nhds_iInf,
iInf_uniformity, @nhds_eq_comap_uniformity _ (u _), Filter.comap_iInf]
theorem toTopologicalSpace_sInf {s : Set (UniformSpace α)} :
(sInf s).toTopologicalSpace = ⨅ i ∈ s, @UniformSpace.toTopologicalSpace α i := by
rw [sInf_eq_iInf]
simp only [← toTopologicalSpace_iInf]
theorem toTopologicalSpace_inf {u v : UniformSpace α} :
(u ⊓ v).toTopologicalSpace = u.toTopologicalSpace ⊓ v.toTopologicalSpace :=
rfl
end UniformSpace
theorem UniformContinuous.continuous [UniformSpace α] [UniformSpace β] {f : α → β}
(hf : UniformContinuous f) : Continuous f :=
continuous_iff_le_induced.mpr <| UniformSpace.toTopologicalSpace_mono <|
uniformContinuous_iff.1 hf
/-- Uniform space structure on `ULift α`. -/
instance ULift.uniformSpace [UniformSpace α] : UniformSpace (ULift α) :=
UniformSpace.comap ULift.down ‹_›
/-- Uniform space structure on `αᵒᵈ`. -/
instance OrderDual.instUniformSpace [UniformSpace α] : UniformSpace (αᵒᵈ) :=
‹UniformSpace α›
section UniformContinuousInfi
-- TODO: add an `iff` lemma?
theorem UniformContinuous.inf_rng {f : α → β} {u₁ : UniformSpace α} {u₂ u₃ : UniformSpace β}
(h₁ : UniformContinuous[u₁, u₂] f) (h₂ : UniformContinuous[u₁, u₃] f) :
UniformContinuous[u₁, u₂ ⊓ u₃] f :=
tendsto_inf.mpr ⟨h₁, h₂⟩
theorem UniformContinuous.inf_dom_left {f : α → β} {u₁ u₂ : UniformSpace α} {u₃ : UniformSpace β}
(hf : UniformContinuous[u₁, u₃] f) : UniformContinuous[u₁ ⊓ u₂, u₃] f :=
tendsto_inf_left hf
theorem UniformContinuous.inf_dom_right {f : α → β} {u₁ u₂ : UniformSpace α} {u₃ : UniformSpace β}
(hf : UniformContinuous[u₂, u₃] f) : UniformContinuous[u₁ ⊓ u₂, u₃] f :=
tendsto_inf_right hf
theorem uniformContinuous_sInf_dom {f : α → β} {u₁ : Set (UniformSpace α)} {u₂ : UniformSpace β}
{u : UniformSpace α} (h₁ : u ∈ u₁) (hf : UniformContinuous[u, u₂] f) :
UniformContinuous[sInf u₁, u₂] f := by
delta UniformContinuous
rw [sInf_eq_iInf', iInf_uniformity]
exact tendsto_iInf' ⟨u, h₁⟩ hf
theorem uniformContinuous_sInf_rng {f : α → β} {u₁ : UniformSpace α} {u₂ : Set (UniformSpace β)} :
UniformContinuous[u₁, sInf u₂] f ↔ ∀ u ∈ u₂, UniformContinuous[u₁, u] f := by
delta UniformContinuous
rw [sInf_eq_iInf', iInf_uniformity, tendsto_iInf, SetCoe.forall]
theorem uniformContinuous_iInf_dom {f : α → β} {u₁ : ι → UniformSpace α} {u₂ : UniformSpace β}
{i : ι} (hf : UniformContinuous[u₁ i, u₂] f) : UniformContinuous[iInf u₁, u₂] f := by
delta UniformContinuous
rw [iInf_uniformity]
exact tendsto_iInf' i hf
theorem uniformContinuous_iInf_rng {f : α → β} {u₁ : UniformSpace α} {u₂ : ι → UniformSpace β} :
UniformContinuous[u₁, iInf u₂] f ↔ ∀ i, UniformContinuous[u₁, u₂ i] f := by
delta UniformContinuous
rw [iInf_uniformity, tendsto_iInf]
end UniformContinuousInfi
/-- A uniform space with the discrete uniformity has the discrete topology. -/
theorem discreteTopology_of_discrete_uniformity [hα : UniformSpace α] (h : uniformity α = 𝓟 idRel) :
DiscreteTopology α :=
⟨(UniformSpace.ext h.symm : ⊥ = hα) ▸ rfl⟩
instance : UniformSpace Empty := ⊥
instance : UniformSpace PUnit := ⊥
instance : UniformSpace Bool := ⊥
instance : UniformSpace ℕ := ⊥
instance : UniformSpace ℤ := ⊥
section
variable [UniformSpace α]
open Additive Multiplicative
instance : UniformSpace (Additive α) := ‹UniformSpace α›
instance : UniformSpace (Multiplicative α) := ‹UniformSpace α›
theorem uniformContinuous_ofMul : UniformContinuous (ofMul : α → Additive α) :=
uniformContinuous_id
theorem uniformContinuous_toMul : UniformContinuous (toMul : Additive α → α) :=
uniformContinuous_id
theorem uniformContinuous_ofAdd : UniformContinuous (ofAdd : α → Multiplicative α) :=
uniformContinuous_id
theorem uniformContinuous_toAdd : UniformContinuous (toAdd : Multiplicative α → α) :=
uniformContinuous_id
theorem uniformity_additive : 𝓤 (Additive α) = (𝓤 α).map (Prod.map ofMul ofMul) := rfl
theorem uniformity_multiplicative : 𝓤 (Multiplicative α) = (𝓤 α).map (Prod.map ofAdd ofAdd) := rfl
end
instance instUniformSpaceSubtype {p : α → Prop} [t : UniformSpace α] : UniformSpace (Subtype p) :=
UniformSpace.comap Subtype.val t
theorem uniformity_subtype {p : α → Prop} [UniformSpace α] :
𝓤 (Subtype p) = comap (fun q : Subtype p × Subtype p => (q.1.1, q.2.1)) (𝓤 α) :=
rfl
theorem uniformity_setCoe {s : Set α} [UniformSpace α] :
𝓤 s = comap (Prod.map ((↑) : s → α) ((↑) : s → α)) (𝓤 α) :=
rfl
theorem map_uniformity_set_coe {s : Set α} [UniformSpace α] :
map (Prod.map (↑) (↑)) (𝓤 s) = 𝓤 α ⊓ 𝓟 (s ×ˢ s) := by
rw [uniformity_setCoe, map_comap, range_prodMap, Subtype.range_val]
theorem uniformContinuous_subtype_val {p : α → Prop} [UniformSpace α] :
UniformContinuous (Subtype.val : { a : α // p a } → α) :=
uniformContinuous_comap
theorem UniformContinuous.subtype_mk {p : α → Prop} [UniformSpace α] [UniformSpace β] {f : β → α}
(hf : UniformContinuous f) (h : ∀ x, p (f x)) :
UniformContinuous (fun x => ⟨f x, h x⟩ : β → Subtype p) :=
uniformContinuous_comap' hf
theorem uniformContinuousOn_iff_restrict [UniformSpace α] [UniformSpace β] {f : α → β} {s : Set α} :
UniformContinuousOn f s ↔ UniformContinuous (s.restrict f) := by
delta UniformContinuousOn UniformContinuous
rw [← map_uniformity_set_coe, tendsto_map'_iff]; rfl
theorem tendsto_of_uniformContinuous_subtype [UniformSpace α] [UniformSpace β] {f : α → β}
{s : Set α} {a : α} (hf : UniformContinuous fun x : s => f x.val) (ha : s ∈ 𝓝 a) :
Tendsto f (𝓝 a) (𝓝 (f a)) := by
rw [(@map_nhds_subtype_coe_eq_nhds α _ s a (mem_of_mem_nhds ha) ha).symm]
exact tendsto_map' hf.continuous.continuousAt
theorem UniformContinuousOn.continuousOn [UniformSpace α] [UniformSpace β] {f : α → β} {s : Set α}
(h : UniformContinuousOn f s) : ContinuousOn f s := by
rw [uniformContinuousOn_iff_restrict] at h
rw [continuousOn_iff_continuous_restrict]
exact h.continuous
@[to_additive]
instance [UniformSpace α] : UniformSpace αᵐᵒᵖ :=
UniformSpace.comap MulOpposite.unop ‹_›
@[to_additive]
theorem uniformity_mulOpposite [UniformSpace α] :
𝓤 αᵐᵒᵖ = comap (fun q : αᵐᵒᵖ × αᵐᵒᵖ => (q.1.unop, q.2.unop)) (𝓤 α) :=
rfl
@[to_additive (attr := simp)]
theorem comap_uniformity_mulOpposite [UniformSpace α] :
comap (fun p : α × α => (MulOpposite.op p.1, MulOpposite.op p.2)) (𝓤 αᵐᵒᵖ) = 𝓤 α := by
simpa [uniformity_mulOpposite, comap_comap, (· ∘ ·)] using comap_id
namespace MulOpposite
@[to_additive]
theorem uniformContinuous_unop [UniformSpace α] : UniformContinuous (unop : αᵐᵒᵖ → α) :=
uniformContinuous_comap
@[to_additive]
theorem uniformContinuous_op [UniformSpace α] : UniformContinuous (op : α → αᵐᵒᵖ) :=
uniformContinuous_comap' uniformContinuous_id
end MulOpposite
section Prod
open UniformSpace
/- a similar product space is possible on the function space (uniformity of pointwise convergence),
but we want to have the uniformity of uniform convergence on function spaces -/
instance instUniformSpaceProd [u₁ : UniformSpace α] [u₂ : UniformSpace β] : UniformSpace (α × β) :=
u₁.comap Prod.fst ⊓ u₂.comap Prod.snd
-- check the above produces no diamond for `simp` and typeclass search
example [UniformSpace α] [UniformSpace β] :
(instTopologicalSpaceProd : TopologicalSpace (α × β)) = UniformSpace.toTopologicalSpace := by
with_reducible_and_instances rfl
theorem uniformity_prod [UniformSpace α] [UniformSpace β] :
𝓤 (α × β) =
((𝓤 α).comap fun p : (α × β) × α × β => (p.1.1, p.2.1)) ⊓
(𝓤 β).comap fun p : (α × β) × α × β => (p.1.2, p.2.2) :=
rfl
instance [UniformSpace α] [IsCountablyGenerated (𝓤 α)]
[UniformSpace β] [IsCountablyGenerated (𝓤 β)] : IsCountablyGenerated (𝓤 (α × β)) := by
rw [uniformity_prod]
infer_instance
theorem uniformity_prod_eq_comap_prod [UniformSpace α] [UniformSpace β] :
𝓤 (α × β) =
comap (fun p : (α × β) × α × β => ((p.1.1, p.2.1), (p.1.2, p.2.2))) (𝓤 α ×ˢ 𝓤 β) := by
simp_rw [uniformity_prod, prod_eq_inf, Filter.comap_inf, Filter.comap_comap, Function.comp_def]
theorem uniformity_prod_eq_prod [UniformSpace α] [UniformSpace β] :
𝓤 (α × β) = map (fun p : (α × α) × β × β => ((p.1.1, p.2.1), (p.1.2, p.2.2))) (𝓤 α ×ˢ 𝓤 β) := by
rw [map_swap4_eq_comap, uniformity_prod_eq_comap_prod]
theorem mem_uniformity_of_uniformContinuous_invariant [UniformSpace α] [UniformSpace β]
{s : Set (β × β)} {f : α → α → β} (hf : UniformContinuous fun p : α × α => f p.1 p.2)
(hs : s ∈ 𝓤 β) : ∃ u ∈ 𝓤 α, ∀ a b c, (a, b) ∈ u → (f a c, f b c) ∈ s := by
rw [UniformContinuous, uniformity_prod_eq_prod, tendsto_map'_iff] at hf
rcases mem_prod_iff.1 (mem_map.1 <| hf hs) with ⟨u, hu, v, hv, huvt⟩
exact ⟨u, hu, fun a b c hab => @huvt ((_, _), (_, _)) ⟨hab, refl_mem_uniformity hv⟩⟩
/-- An entourage of the diagonal in `α` and an entourage in `β` yield an entourage in `α × β`
once we permute coordinates. -/
def entourageProd (u : Set (α × α)) (v : Set (β × β)) : Set ((α × β) × α × β) :=
{((a₁, b₁),(a₂, b₂)) | (a₁, a₂) ∈ u ∧ (b₁, b₂) ∈ v}
theorem mem_entourageProd {u : Set (α × α)} {v : Set (β × β)} {p : (α × β) × α × β} :
p ∈ entourageProd u v ↔ (p.1.1, p.2.1) ∈ u ∧ (p.1.2, p.2.2) ∈ v := Iff.rfl
theorem entourageProd_mem_uniformity [t₁ : UniformSpace α] [t₂ : UniformSpace β] {u : Set (α × α)}
{v : Set (β × β)} (hu : u ∈ 𝓤 α) (hv : v ∈ 𝓤 β) :
entourageProd u v ∈ 𝓤 (α × β) := by
rw [uniformity_prod]; exact inter_mem_inf (preimage_mem_comap hu) (preimage_mem_comap hv)
theorem ball_entourageProd (u : Set (α × α)) (v : Set (β × β)) (x : α × β) :
ball x (entourageProd u v) = ball x.1 u ×ˢ ball x.2 v := by
ext p; simp only [ball, entourageProd, Set.mem_setOf_eq, Set.mem_prod, Set.mem_preimage]
lemma IsSymmetricRel.entourageProd {u : Set (α × α)} {v : Set (β × β)}
(hu : IsSymmetricRel u) (hv : IsSymmetricRel v) :
IsSymmetricRel (entourageProd u v) :=
Set.ext fun _ ↦ and_congr hu.mk_mem_comm hv.mk_mem_comm
theorem Filter.HasBasis.uniformity_prod {ιa ιb : Type*} [UniformSpace α] [UniformSpace β]
{pa : ιa → Prop} {pb : ιb → Prop} {sa : ιa → Set (α × α)} {sb : ιb → Set (β × β)}
(ha : (𝓤 α).HasBasis pa sa) (hb : (𝓤 β).HasBasis pb sb) :
(𝓤 (α × β)).HasBasis (fun i : ιa × ιb ↦ pa i.1 ∧ pb i.2)
(fun i ↦ entourageProd (sa i.1) (sb i.2)) :=
(ha.comap _).inf (hb.comap _)
theorem entourageProd_subset [UniformSpace α] [UniformSpace β]
{s : Set ((α × β) × α × β)} (h : s ∈ 𝓤 (α × β)) :
∃ u ∈ 𝓤 α, ∃ v ∈ 𝓤 β, entourageProd u v ⊆ s := by
rcases (((𝓤 α).basis_sets.uniformity_prod (𝓤 β).basis_sets).mem_iff' s).1 h with ⟨w, hw⟩
use w.1, hw.1.1, w.2, hw.1.2, hw.2
theorem tendsto_prod_uniformity_fst [UniformSpace α] [UniformSpace β] :
Tendsto (fun p : (α × β) × α × β => (p.1.1, p.2.1)) (𝓤 (α × β)) (𝓤 α) :=
le_trans (map_mono inf_le_left) map_comap_le
theorem tendsto_prod_uniformity_snd [UniformSpace α] [UniformSpace β] :
Tendsto (fun p : (α × β) × α × β => (p.1.2, p.2.2)) (𝓤 (α × β)) (𝓤 β) :=
le_trans (map_mono inf_le_right) map_comap_le
theorem uniformContinuous_fst [UniformSpace α] [UniformSpace β] :
UniformContinuous fun p : α × β => p.1 :=
tendsto_prod_uniformity_fst
theorem uniformContinuous_snd [UniformSpace α] [UniformSpace β] :
UniformContinuous fun p : α × β => p.2 :=
tendsto_prod_uniformity_snd
variable [UniformSpace α] [UniformSpace β] [UniformSpace γ]
theorem UniformContinuous.prodMk {f₁ : α → β} {f₂ : α → γ} (h₁ : UniformContinuous f₁)
(h₂ : UniformContinuous f₂) : UniformContinuous fun a => (f₁ a, f₂ a) := by
rw [UniformContinuous, uniformity_prod]
exact tendsto_inf.2 ⟨tendsto_comap_iff.2 h₁, tendsto_comap_iff.2 h₂⟩
@[deprecated (since := "2025-03-10")]
alias UniformContinuous.prod_mk := UniformContinuous.prodMk
theorem UniformContinuous.prodMk_left {f : α × β → γ} (h : UniformContinuous f) (b) :
UniformContinuous fun a => f (a, b) :=
h.comp (uniformContinuous_id.prodMk uniformContinuous_const)
@[deprecated (since := "2025-03-10")]
alias UniformContinuous.prod_mk_left := UniformContinuous.prodMk_left
theorem UniformContinuous.prodMk_right {f : α × β → γ} (h : UniformContinuous f) (a) :
UniformContinuous fun b => f (a, b) :=
h.comp (uniformContinuous_const.prodMk uniformContinuous_id)
@[deprecated (since := "2025-03-10")]
alias UniformContinuous.prod_mk_right := UniformContinuous.prodMk_right
theorem UniformContinuous.prodMap [UniformSpace δ] {f : α → γ} {g : β → δ}
(hf : UniformContinuous f) (hg : UniformContinuous g) : UniformContinuous (Prod.map f g) :=
(hf.comp uniformContinuous_fst).prodMk (hg.comp uniformContinuous_snd)
theorem toTopologicalSpace_prod {α} {β} [u : UniformSpace α] [v : UniformSpace β] :
@UniformSpace.toTopologicalSpace (α × β) instUniformSpaceProd =
@instTopologicalSpaceProd α β u.toTopologicalSpace v.toTopologicalSpace :=
rfl
/-- A version of `UniformContinuous.inf_dom_left` for binary functions -/
theorem uniformContinuous_inf_dom_left₂ {α β γ} {f : α → β → γ} {ua1 ua2 : UniformSpace α}
{ub1 ub2 : UniformSpace β} {uc1 : UniformSpace γ}
(h : by haveI := ua1; haveI := ub1; exact UniformContinuous fun p : α × β => f p.1 p.2) : by
haveI := ua1 ⊓ ua2; haveI := ub1 ⊓ ub2
exact UniformContinuous fun p : α × β => f p.1 p.2 := by
-- proof essentially copied from `continuous_inf_dom_left₂`
have ha := @UniformContinuous.inf_dom_left _ _ id ua1 ua2 ua1 (@uniformContinuous_id _ (id _))
have hb := @UniformContinuous.inf_dom_left _ _ id ub1 ub2 ub1 (@uniformContinuous_id _ (id _))
have h_unif_cont_id :=
@UniformContinuous.prodMap _ _ _ _ (ua1 ⊓ ua2) (ub1 ⊓ ub2) ua1 ub1 _ _ ha hb
exact @UniformContinuous.comp _ _ _ (id _) (id _) _ _ _ h h_unif_cont_id
/-- A version of `UniformContinuous.inf_dom_right` for binary functions -/
theorem uniformContinuous_inf_dom_right₂ {α β γ} {f : α → β → γ} {ua1 ua2 : UniformSpace α}
{ub1 ub2 : UniformSpace β} {uc1 : UniformSpace γ}
(h : by haveI := ua2; haveI := ub2; exact UniformContinuous fun p : α × β => f p.1 p.2) : by
haveI := ua1 ⊓ ua2; haveI := ub1 ⊓ ub2
exact UniformContinuous fun p : α × β => f p.1 p.2 := by
-- proof essentially copied from `continuous_inf_dom_right₂`
have ha := @UniformContinuous.inf_dom_right _ _ id ua1 ua2 ua2 (@uniformContinuous_id _ (id _))
have hb := @UniformContinuous.inf_dom_right _ _ id ub1 ub2 ub2 (@uniformContinuous_id _ (id _))
have h_unif_cont_id :=
@UniformContinuous.prodMap _ _ _ _ (ua1 ⊓ ua2) (ub1 ⊓ ub2) ua2 ub2 _ _ ha hb
exact @UniformContinuous.comp _ _ _ (id _) (id _) _ _ _ h h_unif_cont_id
/-- A version of `uniformContinuous_sInf_dom` for binary functions -/
theorem uniformContinuous_sInf_dom₂ {α β γ} {f : α → β → γ} {uas : Set (UniformSpace α)}
{ubs : Set (UniformSpace β)} {ua : UniformSpace α} {ub : UniformSpace β} {uc : UniformSpace γ}
(ha : ua ∈ uas) (hb : ub ∈ ubs) (hf : UniformContinuous fun p : α × β => f p.1 p.2) : by
haveI := sInf uas; haveI := sInf ubs
exact @UniformContinuous _ _ _ uc fun p : α × β => f p.1 p.2 := by
-- proof essentially copied from `continuous_sInf_dom`
let _ : UniformSpace (α × β) := instUniformSpaceProd
have ha := uniformContinuous_sInf_dom ha uniformContinuous_id
have hb := uniformContinuous_sInf_dom hb uniformContinuous_id
have h_unif_cont_id := @UniformContinuous.prodMap _ _ _ _ (sInf uas) (sInf ubs) ua ub _ _ ha hb
exact @UniformContinuous.comp _ _ _ (id _) (id _) _ _ _ hf h_unif_cont_id
end Prod
section
open UniformSpace Function
variable {δ' : Type*} [UniformSpace α] [UniformSpace β] [UniformSpace γ] [UniformSpace δ]
[UniformSpace δ']
local notation f " ∘₂ " g => Function.bicompr f g
/-- Uniform continuity for functions of two variables. -/
def UniformContinuous₂ (f : α → β → γ) :=
UniformContinuous (uncurry f)
theorem uniformContinuous₂_def (f : α → β → γ) :
UniformContinuous₂ f ↔ UniformContinuous (uncurry f) :=
Iff.rfl
theorem UniformContinuous₂.uniformContinuous {f : α → β → γ} (h : UniformContinuous₂ f) :
UniformContinuous (uncurry f) :=
h
theorem uniformContinuous₂_curry (f : α × β → γ) :
UniformContinuous₂ (Function.curry f) ↔ UniformContinuous f := by
rw [UniformContinuous₂, uncurry_curry]
theorem UniformContinuous₂.comp {f : α → β → γ} {g : γ → δ} (hg : UniformContinuous g)
(hf : UniformContinuous₂ f) : UniformContinuous₂ (g ∘₂ f) :=
hg.comp hf
theorem UniformContinuous₂.bicompl {f : α → β → γ} {ga : δ → α} {gb : δ' → β}
(hf : UniformContinuous₂ f) (hga : UniformContinuous ga) (hgb : UniformContinuous gb) :
UniformContinuous₂ (bicompl f ga gb) :=
hf.uniformContinuous.comp (hga.prodMap hgb)
end
theorem toTopologicalSpace_subtype [u : UniformSpace α] {p : α → Prop} :
@UniformSpace.toTopologicalSpace (Subtype p) instUniformSpaceSubtype =
@instTopologicalSpaceSubtype α p u.toTopologicalSpace :=
rfl
section Sum
variable [UniformSpace α] [UniformSpace β]
open Sum
-- Obsolete auxiliary definitions and lemmas
/-- Uniformity on a disjoint union. Entourages of the diagonal in the union are obtained
by taking independently an entourage of the diagonal in the first part, and an entourage of
the diagonal in the second part. -/
instance Sum.instUniformSpace : UniformSpace (α ⊕ β) where
uniformity := map (fun p : α × α => (inl p.1, inl p.2)) (𝓤 α) ⊔
map (fun p : β × β => (inr p.1, inr p.2)) (𝓤 β)
symm := fun _ hs ↦ ⟨symm_le_uniformity hs.1, symm_le_uniformity hs.2⟩
comp := fun s hs ↦ by
rcases comp_mem_uniformity_sets hs.1 with ⟨tα, htα, Htα⟩
rcases comp_mem_uniformity_sets hs.2 with ⟨tβ, htβ, Htβ⟩
filter_upwards [mem_lift' (union_mem_sup (image_mem_map htα) (image_mem_map htβ))]
rintro ⟨_, _⟩ ⟨z, ⟨⟨a, b⟩, hab, ⟨⟩⟩ | ⟨⟨a, b⟩, hab, ⟨⟩⟩, ⟨⟨_, c⟩, hbc, ⟨⟩⟩ | ⟨⟨_, c⟩, hbc, ⟨⟩⟩⟩
exacts [@Htα (_, _) ⟨b, hab, hbc⟩, @Htβ (_, _) ⟨b, hab, hbc⟩]
nhds_eq_comap_uniformity x := by
ext
cases x <;> simp [mem_comap', -mem_comap, nhds_inl, nhds_inr, nhds_eq_comap_uniformity,
Prod.ext_iff]
/-- The union of an entourage of the diagonal in each set of a disjoint union is again an entourage
of the diagonal. -/
theorem union_mem_uniformity_sum {a : Set (α × α)} (ha : a ∈ 𝓤 α) {b : Set (β × β)} (hb : b ∈ 𝓤 β) :
Prod.map inl inl '' a ∪ Prod.map inr inr '' b ∈ 𝓤 (α ⊕ β) :=
union_mem_sup (image_mem_map ha) (image_mem_map hb)
theorem Sum.uniformity : 𝓤 (α ⊕ β) = map (Prod.map inl inl) (𝓤 α) ⊔ map (Prod.map inr inr) (𝓤 β) :=
rfl
lemma uniformContinuous_inl : UniformContinuous (Sum.inl : α → α ⊕ β) := le_sup_left
lemma uniformContinuous_inr : UniformContinuous (Sum.inr : β → α ⊕ β) := le_sup_right
instance [IsCountablyGenerated (𝓤 α)] [IsCountablyGenerated (𝓤 β)] :
IsCountablyGenerated (𝓤 (α ⊕ β)) := by
rw [Sum.uniformity]
infer_instance
end Sum
end Constructions
/-!
### Expressing continuity properties in uniform spaces
We reformulate the various continuity properties of functions taking values in a uniform space
in terms of the uniformity in the target. Since the same lemmas (essentially with the same names)
also exist for metric spaces and emetric spaces (reformulating things in terms of the distance or
the edistance in the target), we put them in a namespace `Uniform` here.
In the metric and emetric space setting, there are also similar lemmas where one assumes that
both the source and the target are metric spaces, reformulating things in terms of the distance
on both sides. These lemmas are generally written without primes, and the versions where only
the target is a metric space is primed. We follow the same convention here, thus giving lemmas
with primes.
-/
namespace Uniform
variable [UniformSpace α]
theorem tendsto_nhds_right {f : Filter β} {u : β → α} {a : α} :
Tendsto u f (𝓝 a) ↔ Tendsto (fun x => (a, u x)) f (𝓤 α) := by
rw [nhds_eq_comap_uniformity, tendsto_comap_iff]; rfl
theorem tendsto_nhds_left {f : Filter β} {u : β → α} {a : α} :
Tendsto u f (𝓝 a) ↔ Tendsto (fun x => (u x, a)) f (𝓤 α) := by
rw [nhds_eq_comap_uniformity', tendsto_comap_iff]; rfl
theorem continuousAt_iff'_right [TopologicalSpace β] {f : β → α} {b : β} :
ContinuousAt f b ↔ Tendsto (fun x => (f b, f x)) (𝓝 b) (𝓤 α) := by
rw [ContinuousAt, tendsto_nhds_right]
theorem continuousAt_iff'_left [TopologicalSpace β] {f : β → α} {b : β} :
ContinuousAt f b ↔ Tendsto (fun x => (f x, f b)) (𝓝 b) (𝓤 α) := by
rw [ContinuousAt, tendsto_nhds_left]
theorem continuousAt_iff_prod [TopologicalSpace β] {f : β → α} {b : β} :
ContinuousAt f b ↔ Tendsto (fun x : β × β => (f x.1, f x.2)) (𝓝 (b, b)) (𝓤 α) :=
⟨fun H => le_trans (H.prodMap' H) (nhds_le_uniformity _), fun H =>
continuousAt_iff'_left.2 <| H.comp <| tendsto_id.prodMk_nhds tendsto_const_nhds⟩
theorem continuousWithinAt_iff'_right [TopologicalSpace β] {f : β → α} {b : β} {s : Set β} :
ContinuousWithinAt f s b ↔ Tendsto (fun x => (f b, f x)) (𝓝[s] b) (𝓤 α) := by
rw [ContinuousWithinAt, tendsto_nhds_right]
theorem continuousWithinAt_iff'_left [TopologicalSpace β] {f : β → α} {b : β} {s : Set β} :
ContinuousWithinAt f s b ↔ Tendsto (fun x => (f x, f b)) (𝓝[s] b) (𝓤 α) := by
rw [ContinuousWithinAt, tendsto_nhds_left]
theorem continuousOn_iff'_right [TopologicalSpace β] {f : β → α} {s : Set β} :
ContinuousOn f s ↔ ∀ b ∈ s, Tendsto (fun x => (f b, f x)) (𝓝[s] b) (𝓤 α) := by
simp [ContinuousOn, continuousWithinAt_iff'_right]
theorem continuousOn_iff'_left [TopologicalSpace β] {f : β → α} {s : Set β} :
ContinuousOn f s ↔ ∀ b ∈ s, Tendsto (fun x => (f x, f b)) (𝓝[s] b) (𝓤 α) := by
simp [ContinuousOn, continuousWithinAt_iff'_left]
theorem continuous_iff'_right [TopologicalSpace β] {f : β → α} :
Continuous f ↔ ∀ b, Tendsto (fun x => (f b, f x)) (𝓝 b) (𝓤 α) :=
continuous_iff_continuousAt.trans <| forall_congr' fun _ => tendsto_nhds_right
theorem continuous_iff'_left [TopologicalSpace β] {f : β → α} :
Continuous f ↔ ∀ b, Tendsto (fun x => (f x, f b)) (𝓝 b) (𝓤 α) :=
continuous_iff_continuousAt.trans <| forall_congr' fun _ => tendsto_nhds_left
/-- Consider two functions `f` and `g` which coincide on a set `s` and are continuous there.
Then there is an open neighborhood of `s` on which `f` and `g` are uniformly close. -/
lemma exists_is_open_mem_uniformity_of_forall_mem_eq
[TopologicalSpace β] {r : Set (α × α)} {s : Set β}
{f g : β → α} (hf : ∀ x ∈ s, ContinuousAt f x) (hg : ∀ x ∈ s, ContinuousAt g x)
(hfg : s.EqOn f g) (hr : r ∈ 𝓤 α) :
∃ t, IsOpen t ∧ s ⊆ t ∧ ∀ x ∈ t, (f x, g x) ∈ r := by
have A : ∀ x ∈ s, ∃ t, IsOpen t ∧ x ∈ t ∧ ∀ z ∈ t, (f z, g z) ∈ r := by
intro x hx
obtain ⟨t, ht, htsymm, htr⟩ := comp_symm_mem_uniformity_sets hr
have A : {z | (f x, f z) ∈ t} ∈ 𝓝 x := (hf x hx).preimage_mem_nhds (mem_nhds_left (f x) ht)
have B : {z | (g x, g z) ∈ t} ∈ 𝓝 x := (hg x hx).preimage_mem_nhds (mem_nhds_left (g x) ht)
rcases _root_.mem_nhds_iff.1 (inter_mem A B) with ⟨u, hu, u_open, xu⟩
refine ⟨u, u_open, xu, fun y hy ↦ ?_⟩
have I1 : (f y, f x) ∈ t := (htsymm.mk_mem_comm).2 (hu hy).1
have I2 : (g x, g y) ∈ t := (hu hy).2
rw [hfg hx] at I1
exact htr (prodMk_mem_compRel I1 I2)
choose! t t_open xt ht using A
refine ⟨⋃ x ∈ s, t x, isOpen_biUnion t_open, fun x hx ↦ mem_biUnion hx (xt x hx), ?_⟩
rintro x hx
simp only [mem_iUnion, exists_prop] at hx
rcases hx with ⟨y, ys, hy⟩
exact ht y ys x hy
end Uniform
theorem Filter.Tendsto.congr_uniformity {α β} [UniformSpace β] {f g : α → β} {l : Filter α} {b : β}
(hf : Tendsto f l (𝓝 b)) (hg : Tendsto (fun x => (f x, g x)) l (𝓤 β)) : Tendsto g l (𝓝 b) :=
Uniform.tendsto_nhds_right.2 <| (Uniform.tendsto_nhds_right.1 hf).uniformity_trans hg
theorem Uniform.tendsto_congr {α β} [UniformSpace β] {f g : α → β} {l : Filter α} {b : β}
(hfg : Tendsto (fun x => (f x, g x)) l (𝓤 β)) : Tendsto f l (𝓝 b) ↔ Tendsto g l (𝓝 b) :=
⟨fun h => h.congr_uniformity hfg, fun h => h.congr_uniformity hfg.uniformity_symm⟩
| Mathlib/Topology/UniformSpace/Basic.lean | 1,593 | 1,598 | |
/-
Copyright (c) 2023 Kyle Miller, Rémi Bottinelli. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kyle Miller, Rémi Bottinelli
-/
import Mathlib.Combinatorics.SimpleGraph.Path
import Mathlib.Data.Set.Card
/-!
# Connectivity of subgraphs and induced graphs
## Main definitions
* `SimpleGraph.Subgraph.Preconnected` and `SimpleGraph.Subgraph.Connected` give subgraphs
connectivity predicates via `SimpleGraph.subgraph.coe`.
-/
namespace SimpleGraph
universe u v
variable {V : Type u} {V' : Type v} {G : SimpleGraph V} {G' : SimpleGraph V'}
namespace Subgraph
/-- A subgraph is preconnected if it is preconnected when coerced to be a simple graph.
Note: This is a structure to make it so one can be precise about how dot notation resolves. -/
protected structure Preconnected (H : G.Subgraph) : Prop where
protected coe : H.coe.Preconnected
instance {H : G.Subgraph} : Coe H.Preconnected H.coe.Preconnected := ⟨Preconnected.coe⟩
instance {H : G.Subgraph} : CoeFun H.Preconnected (fun _ => ∀ u v : H.verts, H.coe.Reachable u v) :=
⟨fun h => h.coe⟩
protected lemma preconnected_iff {H : G.Subgraph} :
H.Preconnected ↔ H.coe.Preconnected := ⟨fun ⟨h⟩ => h, .mk⟩
/-- A subgraph is connected if it is connected when coerced to be a simple graph.
Note: This is a structure to make it so one can be precise about how dot notation resolves. -/
protected structure Connected (H : G.Subgraph) : Prop where
protected coe : H.coe.Connected
instance {H : G.Subgraph} : Coe H.Connected H.coe.Connected := ⟨Connected.coe⟩
instance {H : G.Subgraph} : CoeFun H.Connected (fun _ => ∀ u v : H.verts, H.coe.Reachable u v) :=
⟨fun h => h.coe⟩
protected lemma connected_iff' {H : G.Subgraph} :
H.Connected ↔ H.coe.Connected := ⟨fun ⟨h⟩ => h, .mk⟩
protected lemma connected_iff {H : G.Subgraph} :
H.Connected ↔ H.Preconnected ∧ H.verts.Nonempty := by
rw [H.connected_iff', connected_iff, H.preconnected_iff, Set.nonempty_coe_sort]
| protected lemma Connected.preconnected {H : G.Subgraph} (h : H.Connected) : H.Preconnected := by
rw [H.connected_iff] at h; exact h.1
| Mathlib/Combinatorics/SimpleGraph/Connectivity/Subgraph.lean | 58 | 59 |
/-
Copyright (c) 2014 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Mario Carneiro
-/
import Mathlib.Algebra.Order.Ring.Nat
import Mathlib.Algebra.Ring.Int.Defs
import Mathlib.Data.Nat.Bitwise
import Mathlib.Data.Nat.Cast.Order.Basic
import Mathlib.Data.Nat.PSub
import Mathlib.Data.Nat.Size
import Mathlib.Data.Num.Bitwise
/-!
# Properties of the binary representation of integers
-/
open Int
attribute [local simp] add_assoc
namespace PosNum
variable {α : Type*}
@[simp, norm_cast]
theorem cast_one [One α] [Add α] : ((1 : PosNum) : α) = 1 :=
rfl
@[simp]
theorem cast_one' [One α] [Add α] : (PosNum.one : α) = 1 :=
rfl
@[simp, norm_cast]
theorem cast_bit0 [One α] [Add α] (n : PosNum) : (n.bit0 : α) = (n : α) + n :=
rfl
@[simp, norm_cast]
theorem cast_bit1 [One α] [Add α] (n : PosNum) : (n.bit1 : α) = ((n : α) + n) + 1 :=
rfl
@[simp, norm_cast]
theorem cast_to_nat [AddMonoidWithOne α] : ∀ n : PosNum, ((n : ℕ) : α) = n
| 1 => Nat.cast_one
| bit0 p => by dsimp; rw [Nat.cast_add, p.cast_to_nat]
| bit1 p => by dsimp; rw [Nat.cast_add, Nat.cast_add, Nat.cast_one, p.cast_to_nat]
@[norm_cast]
theorem to_nat_to_int (n : PosNum) : ((n : ℕ) : ℤ) = n :=
cast_to_nat _
@[simp, norm_cast]
theorem cast_to_int [AddGroupWithOne α] (n : PosNum) : ((n : ℤ) : α) = n := by
rw [← to_nat_to_int, Int.cast_natCast, cast_to_nat]
theorem succ_to_nat : ∀ n, (succ n : ℕ) = n + 1
| 1 => rfl
| bit0 _ => rfl
| bit1 p =>
(congr_arg (fun n ↦ n + n) (succ_to_nat p)).trans <|
show ↑p + 1 + ↑p + 1 = ↑p + ↑p + 1 + 1 by simp [add_left_comm]
theorem one_add (n : PosNum) : 1 + n = succ n := by cases n <;> rfl
theorem add_one (n : PosNum) : n + 1 = succ n := by cases n <;> rfl
@[norm_cast]
theorem add_to_nat : ∀ m n, ((m + n : PosNum) : ℕ) = m + n
| 1, b => by rw [one_add b, succ_to_nat, add_comm, cast_one]
| a, 1 => by rw [add_one a, succ_to_nat, cast_one]
| bit0 a, bit0 b => (congr_arg (fun n ↦ n + n) (add_to_nat a b)).trans <| add_add_add_comm _ _ _ _
| bit0 a, bit1 b =>
(congr_arg (fun n ↦ (n + n) + 1) (add_to_nat a b)).trans <|
show (a + b + (a + b) + 1 : ℕ) = a + a + (b + b + 1) by simp [add_left_comm]
| bit1 a, bit0 b =>
(congr_arg (fun n ↦ (n + n) + 1) (add_to_nat a b)).trans <|
show (a + b + (a + b) + 1 : ℕ) = a + a + 1 + (b + b) by simp [add_comm, add_left_comm]
| bit1 a, bit1 b =>
show (succ (a + b) + succ (a + b) : ℕ) = a + a + 1 + (b + b + 1) by
rw [succ_to_nat, add_to_nat a b]; simp [add_left_comm]
theorem add_succ : ∀ m n : PosNum, m + succ n = succ (m + n)
| 1, b => by simp [one_add]
| bit0 a, 1 => congr_arg bit0 (add_one a)
| bit1 a, 1 => congr_arg bit1 (add_one a)
| bit0 _, bit0 _ => rfl
| bit0 a, bit1 b => congr_arg bit0 (add_succ a b)
| bit1 _, bit0 _ => rfl
| bit1 a, bit1 b => congr_arg bit1 (add_succ a b)
theorem bit0_of_bit0 : ∀ n, n + n = bit0 n
| 1 => rfl
| bit0 p => congr_arg bit0 (bit0_of_bit0 p)
| bit1 p => show bit0 (succ (p + p)) = _ by rw [bit0_of_bit0 p, succ]
theorem bit1_of_bit1 (n : PosNum) : (n + n) + 1 = bit1 n :=
show (n + n) + 1 = bit1 n by rw [add_one, bit0_of_bit0, succ]
@[norm_cast]
theorem mul_to_nat (m) : ∀ n, ((m * n : PosNum) : ℕ) = m * n
| 1 => (mul_one _).symm
| bit0 p => show (↑(m * p) + ↑(m * p) : ℕ) = ↑m * (p + p) by rw [mul_to_nat m p, left_distrib]
| bit1 p =>
(add_to_nat (bit0 (m * p)) m).trans <|
show (↑(m * p) + ↑(m * p) + ↑m : ℕ) = ↑m * (p + p) + m by rw [mul_to_nat m p, left_distrib]
theorem to_nat_pos : ∀ n : PosNum, 0 < (n : ℕ)
| 1 => Nat.zero_lt_one
| bit0 p =>
let h := to_nat_pos p
add_pos h h
| bit1 _p => Nat.succ_pos _
theorem cmp_to_nat_lemma {m n : PosNum} : (m : ℕ) < n → (bit1 m : ℕ) < bit0 n :=
show (m : ℕ) < n → (m + m + 1 + 1 : ℕ) ≤ n + n by
intro h; rw [Nat.add_right_comm m m 1, add_assoc]; exact Nat.add_le_add h h
theorem cmp_swap (m) : ∀ n, (cmp m n).swap = cmp n m := by
induction' m with m IH m IH <;> intro n <;> obtain - | n | n := n <;> unfold cmp <;>
try { rfl } <;> rw [← IH] <;> cases cmp m n <;> rfl
theorem cmp_to_nat : ∀ m n, (Ordering.casesOn (cmp m n) ((m : ℕ) < n) (m = n) ((n : ℕ) < m) : Prop)
| 1, 1 => rfl
| bit0 a, 1 =>
let h : (1 : ℕ) ≤ a := to_nat_pos a
Nat.add_le_add h h
| bit1 a, 1 => Nat.succ_lt_succ <| to_nat_pos <| bit0 a
| 1, bit0 b =>
let h : (1 : ℕ) ≤ b := to_nat_pos b
Nat.add_le_add h h
| 1, bit1 b => Nat.succ_lt_succ <| to_nat_pos <| bit0 b
| bit0 a, bit0 b => by
dsimp [cmp]
have := cmp_to_nat a b; revert this; cases cmp a b <;> dsimp <;> intro this
· exact Nat.add_lt_add this this
· rw [this]
· exact Nat.add_lt_add this this
| bit0 a, bit1 b => by
dsimp [cmp]
have := cmp_to_nat a b; revert this; cases cmp a b <;> dsimp <;> intro this
· exact Nat.le_succ_of_le (Nat.add_lt_add this this)
· rw [this]
apply Nat.lt_succ_self
· exact cmp_to_nat_lemma this
| bit1 a, bit0 b => by
dsimp [cmp]
have := cmp_to_nat a b; revert this; cases cmp a b <;> dsimp <;> intro this
· exact cmp_to_nat_lemma this
· rw [this]
apply Nat.lt_succ_self
· exact Nat.le_succ_of_le (Nat.add_lt_add this this)
| bit1 a, bit1 b => by
dsimp [cmp]
have := cmp_to_nat a b; revert this; cases cmp a b <;> dsimp <;> intro this
· exact Nat.succ_lt_succ (Nat.add_lt_add this this)
· rw [this]
· exact Nat.succ_lt_succ (Nat.add_lt_add this this)
@[norm_cast]
theorem lt_to_nat {m n : PosNum} : (m : ℕ) < n ↔ m < n :=
show (m : ℕ) < n ↔ cmp m n = Ordering.lt from
match cmp m n, cmp_to_nat m n with
| Ordering.lt, h => by simp only at h; simp [h]
| Ordering.eq, h => by simp only at h; simp [h, lt_irrefl]
| Ordering.gt, h => by simp [not_lt_of_gt h]
@[norm_cast]
theorem le_to_nat {m n : PosNum} : (m : ℕ) ≤ n ↔ m ≤ n := by
rw [← not_lt]; exact not_congr lt_to_nat
end PosNum
namespace Num
variable {α : Type*}
open PosNum
theorem add_zero (n : Num) : n + 0 = n := by cases n <;> rfl
theorem zero_add (n : Num) : 0 + n = n := by cases n <;> rfl
theorem add_one : ∀ n : Num, n + 1 = succ n
| 0 => rfl
| pos p => by cases p <;> rfl
theorem add_succ : ∀ m n : Num, m + succ n = succ (m + n)
| 0, n => by simp [zero_add]
| pos p, 0 => show pos (p + 1) = succ (pos p + 0) by rw [PosNum.add_one, add_zero, succ, succ']
| pos _, pos _ => congr_arg pos (PosNum.add_succ _ _)
theorem bit0_of_bit0 : ∀ n : Num, n + n = n.bit0
| 0 => rfl
| pos p => congr_arg pos p.bit0_of_bit0
theorem bit1_of_bit1 : ∀ n : Num, (n + n) + 1 = n.bit1
| 0 => rfl
| pos p => congr_arg pos p.bit1_of_bit1
@[simp]
theorem ofNat'_zero : Num.ofNat' 0 = 0 := by simp [Num.ofNat']
theorem ofNat'_bit (b n) : ofNat' (Nat.bit b n) = cond b Num.bit1 Num.bit0 (ofNat' n) :=
Nat.binaryRec_eq _ _ (.inl rfl)
@[simp]
theorem ofNat'_one : Num.ofNat' 1 = 1 := by erw [ofNat'_bit true 0, cond, ofNat'_zero]; rfl
theorem bit1_succ : ∀ n : Num, n.bit1.succ = n.succ.bit0
| 0 => rfl
| pos _n => rfl
theorem ofNat'_succ : ∀ {n}, ofNat' (n + 1) = ofNat' n + 1 :=
@(Nat.binaryRec (by simp [zero_add]) fun b n ih => by
cases b
· erw [ofNat'_bit true n, ofNat'_bit]
simp only [← bit1_of_bit1, ← bit0_of_bit0, cond]
· rw [show n.bit true + 1 = (n + 1).bit false by simp [Nat.bit, mul_add],
ofNat'_bit, ofNat'_bit, ih]
simp only [cond, add_one, bit1_succ])
@[simp]
theorem add_ofNat' (m n) : Num.ofNat' (m + n) = Num.ofNat' m + Num.ofNat' n := by
induction n
· simp only [Nat.add_zero, ofNat'_zero, add_zero]
· simp only [Nat.add_succ, Nat.add_zero, ofNat'_succ, add_one, add_succ, *]
@[simp, norm_cast]
theorem cast_zero [Zero α] [One α] [Add α] : ((0 : Num) : α) = 0 :=
rfl
@[simp]
theorem cast_zero' [Zero α] [One α] [Add α] : (Num.zero : α) = 0 :=
rfl
@[simp, norm_cast]
theorem cast_one [Zero α] [One α] [Add α] : ((1 : Num) : α) = 1 :=
rfl
@[simp]
theorem cast_pos [Zero α] [One α] [Add α] (n : PosNum) : (Num.pos n : α) = n :=
rfl
theorem succ'_to_nat : ∀ n, (succ' n : ℕ) = n + 1
| 0 => (Nat.zero_add _).symm
| pos _p => PosNum.succ_to_nat _
theorem succ_to_nat (n) : (succ n : ℕ) = n + 1 :=
succ'_to_nat n
@[simp, norm_cast]
theorem cast_to_nat [AddMonoidWithOne α] : ∀ n : Num, ((n : ℕ) : α) = n
| 0 => Nat.cast_zero
| pos p => p.cast_to_nat
@[norm_cast]
theorem add_to_nat : ∀ m n, ((m + n : Num) : ℕ) = m + n
| 0, 0 => rfl
| 0, pos _q => (Nat.zero_add _).symm
| pos _p, 0 => rfl
| pos _p, pos _q => PosNum.add_to_nat _ _
@[norm_cast]
theorem mul_to_nat : ∀ m n, ((m * n : Num) : ℕ) = m * n
| 0, 0 => rfl
| 0, pos _q => (zero_mul _).symm
| pos _p, 0 => rfl
| pos _p, pos _q => PosNum.mul_to_nat _ _
theorem cmp_to_nat : ∀ m n, (Ordering.casesOn (cmp m n) ((m : ℕ) < n) (m = n) ((n : ℕ) < m) : Prop)
| 0, 0 => rfl
| 0, pos _ => to_nat_pos _
| pos _, 0 => to_nat_pos _
| pos a, pos b => by
have := PosNum.cmp_to_nat a b; revert this; dsimp [cmp]; cases PosNum.cmp a b
exacts [id, congr_arg pos, id]
@[norm_cast]
theorem lt_to_nat {m n : Num} : (m : ℕ) < n ↔ m < n :=
show (m : ℕ) < n ↔ cmp m n = Ordering.lt from
match cmp m n, cmp_to_nat m n with
| Ordering.lt, h => by simp only at h; simp [h]
| Ordering.eq, h => by simp only at h; simp [h, lt_irrefl]
| Ordering.gt, h => by simp [not_lt_of_gt h]
@[norm_cast]
theorem le_to_nat {m n : Num} : (m : ℕ) ≤ n ↔ m ≤ n := by
rw [← not_lt]; exact not_congr lt_to_nat
end Num
namespace PosNum
@[simp]
theorem of_to_nat' : ∀ n : PosNum, Num.ofNat' (n : ℕ) = Num.pos n
| 1 => by erw [@Num.ofNat'_bit true 0, Num.ofNat'_zero]; rfl
| bit0 p => by
simpa only [Nat.bit_false, cond_false, two_mul, of_to_nat' p] using Num.ofNat'_bit false p
| bit1 p => by
simpa only [Nat.bit_true, cond_true, two_mul, of_to_nat' p] using Num.ofNat'_bit true p
end PosNum
namespace Num
@[simp, norm_cast]
theorem of_to_nat' : ∀ n : Num, Num.ofNat' (n : ℕ) = n
| 0 => ofNat'_zero
| pos p => p.of_to_nat'
lemma toNat_injective : Function.Injective (castNum : Num → ℕ) :=
Function.LeftInverse.injective of_to_nat'
@[norm_cast]
theorem to_nat_inj {m n : Num} : (m : ℕ) = n ↔ m = n := toNat_injective.eq_iff
/-- This tactic tries to turn an (in)equality about `Num`s to one about `Nat`s by rewriting.
```lean
example (n : Num) (m : Num) : n ≤ n + m := by
transfer_rw
exact Nat.le_add_right _ _
```
-/
scoped macro (name := transfer_rw) "transfer_rw" : tactic => `(tactic|
(repeat first | rw [← to_nat_inj] | rw [← lt_to_nat] | rw [← le_to_nat]
repeat first | rw [add_to_nat] | rw [mul_to_nat] | rw [cast_one] | rw [cast_zero]))
/--
This tactic tries to prove (in)equalities about `Num`s by transferring them to the `Nat` world and
then trying to call `simp`.
```lean
example (n : Num) (m : Num) : n ≤ n + m := by transfer
```
-/
scoped macro (name := transfer) "transfer" : tactic => `(tactic|
(intros; transfer_rw; try simp))
instance addMonoid : AddMonoid Num where
add := (· + ·)
zero := 0
zero_add := zero_add
add_zero := add_zero
add_assoc := by transfer
nsmul := nsmulRec
instance addMonoidWithOne : AddMonoidWithOne Num :=
{ Num.addMonoid with
natCast := Num.ofNat'
one := 1
natCast_zero := ofNat'_zero
natCast_succ := fun _ => ofNat'_succ }
instance commSemiring : CommSemiring Num where
__ := Num.addMonoid
__ := Num.addMonoidWithOne
mul := (· * ·)
npow := @npowRec Num ⟨1⟩ ⟨(· * ·)⟩
mul_zero _ := by rw [← to_nat_inj, mul_to_nat, cast_zero, mul_zero]
zero_mul _ := by rw [← to_nat_inj, mul_to_nat, cast_zero, zero_mul]
mul_one _ := by rw [← to_nat_inj, mul_to_nat, cast_one, mul_one]
one_mul _ := by rw [← to_nat_inj, mul_to_nat, cast_one, one_mul]
add_comm _ _ := by simp_rw [← to_nat_inj, add_to_nat, add_comm]
mul_comm _ _ := by simp_rw [← to_nat_inj, mul_to_nat, mul_comm]
mul_assoc _ _ _ := by simp_rw [← to_nat_inj, mul_to_nat, mul_assoc]
left_distrib _ _ _ := by simp only [← to_nat_inj, mul_to_nat, add_to_nat, mul_add]
right_distrib _ _ _ := by simp only [← to_nat_inj, mul_to_nat, add_to_nat, add_mul]
instance partialOrder : PartialOrder Num where
lt_iff_le_not_le a b := by simp only [← lt_to_nat, ← le_to_nat, lt_iff_le_not_le]
le_refl := by transfer
le_trans a b c := by transfer_rw; apply le_trans
le_antisymm a b := by transfer_rw; apply le_antisymm
instance isOrderedCancelAddMonoid : IsOrderedCancelAddMonoid Num where
add_le_add_left a b h c := by revert h; transfer_rw; exact fun h => add_le_add_left h c
le_of_add_le_add_left a b c :=
show a + b ≤ a + c → b ≤ c by transfer_rw; apply le_of_add_le_add_left
instance linearOrder : LinearOrder Num :=
{ le_total := by
intro a b
transfer_rw
apply le_total
toDecidableLT := Num.decidableLT
toDecidableLE := Num.decidableLE
-- This is relying on an automatically generated instance name,
-- generated in a `deriving` handler.
-- See https://github.com/leanprover/lean4/issues/2343
toDecidableEq := instDecidableEqNum }
instance isStrictOrderedRing : IsStrictOrderedRing Num :=
{ zero_le_one := by decide
mul_lt_mul_of_pos_left := by
intro a b c
transfer_rw
apply mul_lt_mul_of_pos_left
mul_lt_mul_of_pos_right := by
intro a b c
transfer_rw
apply mul_lt_mul_of_pos_right
exists_pair_ne := ⟨0, 1, by decide⟩ }
@[norm_cast]
theorem add_of_nat (m n) : ((m + n : ℕ) : Num) = m + n :=
add_ofNat' _ _
@[norm_cast]
theorem to_nat_to_int (n : Num) : ((n : ℕ) : ℤ) = n :=
cast_to_nat _
@[simp, norm_cast]
theorem cast_to_int {α} [AddGroupWithOne α] (n : Num) : ((n : ℤ) : α) = n := by
rw [← to_nat_to_int, Int.cast_natCast, cast_to_nat]
theorem to_of_nat : ∀ n : ℕ, ((n : Num) : ℕ) = n
| 0 => by rw [Nat.cast_zero, cast_zero]
| n + 1 => by rw [Nat.cast_succ, add_one, succ_to_nat, to_of_nat n]
@[simp, norm_cast]
theorem of_natCast {α} [AddMonoidWithOne α] (n : ℕ) : ((n : Num) : α) = n := by
rw [← cast_to_nat, to_of_nat]
@[norm_cast]
theorem of_nat_inj {m n : ℕ} : (m : Num) = n ↔ m = n :=
⟨fun h => Function.LeftInverse.injective to_of_nat h, congr_arg _⟩
-- The priority should be `high`er than `cast_to_nat`.
@[simp high, norm_cast]
theorem of_to_nat : ∀ n : Num, ((n : ℕ) : Num) = n :=
of_to_nat'
@[norm_cast]
theorem dvd_to_nat (m n : Num) : (m : ℕ) ∣ n ↔ m ∣ n :=
⟨fun ⟨k, e⟩ => ⟨k, by rw [← of_to_nat n, e]; simp⟩, fun ⟨k, e⟩ => ⟨k, by simp [e, mul_to_nat]⟩⟩
end Num
namespace PosNum
variable {α : Type*}
open Num
-- The priority should be `high`er than `cast_to_nat`.
@[simp high, norm_cast]
theorem of_to_nat : ∀ n : PosNum, ((n : ℕ) : Num) = Num.pos n :=
of_to_nat'
@[norm_cast]
theorem to_nat_inj {m n : PosNum} : (m : ℕ) = n ↔ m = n :=
⟨fun h => Num.pos.inj <| by rw [← PosNum.of_to_nat, ← PosNum.of_to_nat, h], congr_arg _⟩
theorem pred'_to_nat : ∀ n, (pred' n : ℕ) = Nat.pred n
| 1 => rfl
| bit0 n =>
have : Nat.succ ↑(pred' n) = ↑n := by
rw [pred'_to_nat n, Nat.succ_pred_eq_of_pos (to_nat_pos n)]
match (motive :=
∀ k : Num, Nat.succ ↑k = ↑n → ↑(Num.casesOn k 1 bit1 : PosNum) = Nat.pred (n + n))
pred' n, this with
| 0, (h : ((1 : Num) : ℕ) = n) => by rw [← to_nat_inj.1 h]; rfl
| Num.pos p, (h : Nat.succ ↑p = n) => by rw [← h]; exact (Nat.succ_add p p).symm
| bit1 _ => rfl
@[simp]
theorem pred'_succ' (n) : pred' (succ' n) = n :=
Num.to_nat_inj.1 <| by rw [pred'_to_nat, succ'_to_nat, Nat.add_one, Nat.pred_succ]
@[simp]
theorem succ'_pred' (n) : succ' (pred' n) = n :=
to_nat_inj.1 <| by
rw [succ'_to_nat, pred'_to_nat, Nat.add_one, Nat.succ_pred_eq_of_pos (to_nat_pos _)]
instance dvd : Dvd PosNum :=
⟨fun m n => pos m ∣ pos n⟩
@[norm_cast]
theorem dvd_to_nat {m n : PosNum} : (m : ℕ) ∣ n ↔ m ∣ n :=
Num.dvd_to_nat (pos m) (pos n)
theorem size_to_nat : ∀ n, (size n : ℕ) = Nat.size n
| 1 => Nat.size_one.symm
| bit0 n => by
rw [size, succ_to_nat, size_to_nat n, cast_bit0, ← two_mul]
erw [@Nat.size_bit false n]
have := to_nat_pos n
dsimp [Nat.bit]; omega
| bit1 n => by
rw [size, succ_to_nat, size_to_nat n, cast_bit1, ← two_mul]
erw [@Nat.size_bit true n]
dsimp [Nat.bit]; omega
theorem size_eq_natSize : ∀ n, (size n : ℕ) = natSize n
| 1 => rfl
| bit0 n => by rw [size, succ_to_nat, natSize, size_eq_natSize n]
| bit1 n => by rw [size, succ_to_nat, natSize, size_eq_natSize n]
theorem natSize_to_nat (n) : natSize n = Nat.size n := by rw [← size_eq_natSize, size_to_nat]
theorem natSize_pos (n) : 0 < natSize n := by cases n <;> apply Nat.succ_pos
/-- This tactic tries to turn an (in)equality about `PosNum`s to one about `Nat`s by rewriting.
```lean
example (n : PosNum) (m : PosNum) : n ≤ n + m := by
transfer_rw
exact Nat.le_add_right _ _
```
-/
scoped macro (name := transfer_rw) "transfer_rw" : tactic => `(tactic|
(repeat first | rw [← to_nat_inj] | rw [← lt_to_nat] | rw [← le_to_nat]
repeat first | rw [add_to_nat] | rw [mul_to_nat] | rw [cast_one] | rw [cast_zero]))
/--
This tactic tries to prove (in)equalities about `PosNum`s by transferring them to the `Nat` world
and then trying to call `simp`.
```lean
example (n : PosNum) (m : PosNum) : n ≤ n + m := by transfer
```
-/
scoped macro (name := transfer) "transfer" : tactic => `(tactic|
(intros; transfer_rw; try simp [add_comm, add_left_comm, mul_comm, mul_left_comm]))
instance addCommSemigroup : AddCommSemigroup PosNum where
add := (· + ·)
add_assoc := by transfer
add_comm := by transfer
instance commMonoid : CommMonoid PosNum where
mul := (· * ·)
one := (1 : PosNum)
npow := @npowRec PosNum ⟨1⟩ ⟨(· * ·)⟩
mul_assoc := by transfer
one_mul := by transfer
mul_one := by transfer
mul_comm := by transfer
instance distrib : Distrib PosNum where
add := (· + ·)
mul := (· * ·)
left_distrib := by transfer; simp [mul_add]
right_distrib := by transfer; simp [mul_add, mul_comm]
instance linearOrder : LinearOrder PosNum where
lt := (· < ·)
lt_iff_le_not_le := by
intro a b
transfer_rw
apply lt_iff_le_not_le
le := (· ≤ ·)
le_refl := by transfer
le_trans := by
intro a b c
transfer_rw
apply le_trans
le_antisymm := by
intro a b
transfer_rw
apply le_antisymm
le_total := by
intro a b
transfer_rw
apply le_total
toDecidableLT := by infer_instance
toDecidableLE := by infer_instance
toDecidableEq := by infer_instance
@[simp]
theorem cast_to_num (n : PosNum) : ↑n = Num.pos n := by rw [← cast_to_nat, ← of_to_nat n]
@[simp, norm_cast]
theorem bit_to_nat (b n) : (bit b n : ℕ) = Nat.bit b n := by cases b <;> simp [bit, two_mul]
@[simp, norm_cast]
theorem cast_add [AddMonoidWithOne α] (m n) : ((m + n : PosNum) : α) = m + n := by
rw [← cast_to_nat, add_to_nat, Nat.cast_add, cast_to_nat, cast_to_nat]
@[simp 500, norm_cast]
theorem cast_succ [AddMonoidWithOne α] (n : PosNum) : (succ n : α) = n + 1 := by
rw [← add_one, cast_add, cast_one]
@[simp, norm_cast]
theorem cast_inj [AddMonoidWithOne α] [CharZero α] {m n : PosNum} : (m : α) = n ↔ m = n := by
rw [← cast_to_nat m, ← cast_to_nat n, Nat.cast_inj, to_nat_inj]
@[simp]
theorem one_le_cast [Semiring α] [PartialOrder α] [IsStrictOrderedRing α] (n : PosNum) :
(1 : α) ≤ n := by
rw [← cast_to_nat, ← Nat.cast_one, Nat.cast_le (α := α)]; apply to_nat_pos
@[simp]
theorem cast_pos [Semiring α] [PartialOrder α] [IsStrictOrderedRing α] (n : PosNum) : 0 < (n : α) :=
lt_of_lt_of_le zero_lt_one (one_le_cast n)
@[simp, norm_cast]
theorem cast_mul [NonAssocSemiring α] (m n) : ((m * n : PosNum) : α) = m * n := by
rw [← cast_to_nat, mul_to_nat, Nat.cast_mul, cast_to_nat, cast_to_nat]
@[simp]
theorem cmp_eq (m n) : cmp m n = Ordering.eq ↔ m = n := by
have := cmp_to_nat m n
-- Porting note: `cases` didn't rewrite at `this`, so `revert` & `intro` are required.
revert this; cases cmp m n <;> intro this <;> simp at this ⊢ <;> try { exact this } <;>
simp [show m ≠ n from fun e => by rw [e] at this;exact lt_irrefl _ this]
@[simp, norm_cast]
theorem cast_lt [Semiring α] [PartialOrder α] [IsStrictOrderedRing α] {m n : PosNum} :
(m : α) < n ↔ m < n := by
rw [← cast_to_nat m, ← cast_to_nat n, Nat.cast_lt (α := α), lt_to_nat]
@[simp, norm_cast]
theorem cast_le [Semiring α] [LinearOrder α] [IsStrictOrderedRing α] {m n : PosNum} :
(m : α) ≤ n ↔ m ≤ n := by
rw [← not_lt]; exact not_congr cast_lt
end PosNum
namespace Num
variable {α : Type*}
open PosNum
theorem bit_to_nat (b n) : (bit b n : ℕ) = Nat.bit b n := by
cases b <;> cases n <;> simp [bit, two_mul] <;> rfl
theorem cast_succ' [AddMonoidWithOne α] (n) : (succ' n : α) = n + 1 := by
rw [← PosNum.cast_to_nat, succ'_to_nat, Nat.cast_add_one, cast_to_nat]
theorem cast_succ [AddMonoidWithOne α] (n) : (succ n : α) = n + 1 :=
cast_succ' n
@[simp, norm_cast]
theorem cast_add [AddMonoidWithOne α] (m n) : ((m + n : Num) : α) = m + n := by
rw [← cast_to_nat, add_to_nat, Nat.cast_add, cast_to_nat, cast_to_nat]
@[simp, norm_cast]
theorem cast_bit0 [NonAssocSemiring α] (n : Num) : (n.bit0 : α) = 2 * (n : α) := by
rw [← bit0_of_bit0, two_mul, cast_add]
@[simp, norm_cast]
theorem cast_bit1 [NonAssocSemiring α] (n : Num) : (n.bit1 : α) = 2 * (n : α) + 1 := by
rw [← bit1_of_bit1, bit0_of_bit0, cast_add, cast_bit0]; rfl
@[simp, norm_cast]
theorem cast_mul [NonAssocSemiring α] : ∀ m n, ((m * n : Num) : α) = m * n
| 0, 0 => (zero_mul _).symm
| 0, pos _q => (zero_mul _).symm
| pos _p, 0 => (mul_zero _).symm
| pos _p, pos _q => PosNum.cast_mul _ _
theorem size_to_nat : ∀ n, (size n : ℕ) = Nat.size n
| 0 => Nat.size_zero.symm
| pos p => p.size_to_nat
theorem size_eq_natSize : ∀ n, (size n : ℕ) = natSize n
| 0 => rfl
| pos p => p.size_eq_natSize
theorem natSize_to_nat (n) : natSize n = Nat.size n := by rw [← size_eq_natSize, size_to_nat]
| @[simp 999]
theorem ofNat'_eq : ∀ n, Num.ofNat' n = n :=
| Mathlib/Data/Num/Lemmas.lean | 661 | 662 |
/-
Copyright (c) 2019 Zhouhang Zhou. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Zhouhang Zhou, Frédéric Dupuis, Heather Macbeth
-/
import Mathlib.Analysis.Convex.Basic
import Mathlib.Analysis.InnerProductSpace.Orthogonal
import Mathlib.Analysis.InnerProductSpace.Symmetric
import Mathlib.Analysis.NormedSpace.RCLike
import Mathlib.Analysis.RCLike.Lemmas
import Mathlib.Algebra.DirectSum.Decomposition
/-!
# The orthogonal projection
Given a nonempty complete subspace `K` of an inner product space `E`, this file constructs
`K.orthogonalProjection : E →L[𝕜] K`, the orthogonal projection of `E` onto `K`. This map
satisfies: for any point `u` in `E`, the point `v = K.orthogonalProjection u` in `K` minimizes the
distance `‖u - v‖` to `u`.
Also a linear isometry equivalence `K.reflection : E ≃ₗᵢ[𝕜] E` is constructed, by choosing, for
each `u : E`, the point `K.reflection u` to satisfy
`u + (K.reflection u) = 2 • K.orthogonalProjection u`.
Basic API for `orthogonalProjection` and `reflection` is developed.
Next, the orthogonal projection is used to prove a series of more subtle lemmas about the
orthogonal complement of complete subspaces of `E` (the orthogonal complement itself was
defined in `Analysis.InnerProductSpace.Orthogonal`); the lemma
`Submodule.sup_orthogonal_of_completeSpace`, stating that for a complete subspace `K` of `E` we have
`K ⊔ Kᗮ = ⊤`, is a typical example.
## References
The orthogonal projection construction is adapted from
* [Clément & Martin, *The Lax-Milgram Theorem. A detailed proof to be formalized in Coq*]
* [Clément & Martin, *A Coq formal proof of the Lax–Milgram theorem*]
The Coq code is available at the following address: <http://www.lri.fr/~sboldo/elfic/index.html>
-/
noncomputable section
open InnerProductSpace
open RCLike Real Filter
open LinearMap (ker range)
open Topology Finsupp
variable {𝕜 E F : Type*} [RCLike 𝕜]
variable [NormedAddCommGroup E] [NormedAddCommGroup F]
variable [InnerProductSpace 𝕜 E] [InnerProductSpace ℝ F]
local notation "⟪" x ", " y "⟫" => @inner 𝕜 _ _ x y
local notation "absR" => abs
/-! ### Orthogonal projection in inner product spaces -/
-- FIXME this monolithic proof causes a deterministic timeout with `-T50000`
-- It should be broken in a sequence of more manageable pieces,
-- perhaps with individual statements for the three steps below.
/-- **Existence of minimizers**, aka the **Hilbert projection theorem**.
Let `u` be a point in a real inner product space, and let `K` be a nonempty complete convex subset.
Then there exists a (unique) `v` in `K` that minimizes the distance `‖u - v‖` to `u`. -/
theorem exists_norm_eq_iInf_of_complete_convex {K : Set F} (ne : K.Nonempty) (h₁ : IsComplete K)
(h₂ : Convex ℝ K) : ∀ u : F, ∃ v ∈ K, ‖u - v‖ = ⨅ w : K, ‖u - w‖ := fun u => by
let δ := ⨅ w : K, ‖u - w‖
letI : Nonempty K := ne.to_subtype
have zero_le_δ : 0 ≤ δ := le_ciInf fun _ => norm_nonneg _
have δ_le : ∀ w : K, δ ≤ ‖u - w‖ := ciInf_le ⟨0, Set.forall_mem_range.2 fun _ => norm_nonneg _⟩
have δ_le' : ∀ w ∈ K, δ ≤ ‖u - w‖ := fun w hw => δ_le ⟨w, hw⟩
-- Step 1: since `δ` is the infimum, can find a sequence `w : ℕ → K` in `K`
-- such that `‖u - w n‖ < δ + 1 / (n + 1)` (which implies `‖u - w n‖ --> δ`);
-- maybe this should be a separate lemma
have exists_seq : ∃ w : ℕ → K, ∀ n, ‖u - w n‖ < δ + 1 / (n + 1) := by
have hδ : ∀ n : ℕ, δ < δ + 1 / (n + 1) := fun n =>
lt_add_of_le_of_pos le_rfl Nat.one_div_pos_of_nat
have h := fun n => exists_lt_of_ciInf_lt (hδ n)
let w : ℕ → K := fun n => Classical.choose (h n)
exact ⟨w, fun n => Classical.choose_spec (h n)⟩
rcases exists_seq with ⟨w, hw⟩
have norm_tendsto : Tendsto (fun n => ‖u - w n‖) atTop (𝓝 δ) := by
have h : Tendsto (fun _ : ℕ => δ) atTop (𝓝 δ) := tendsto_const_nhds
have h' : Tendsto (fun n : ℕ => δ + 1 / (n + 1)) atTop (𝓝 δ) := by
convert h.add tendsto_one_div_add_atTop_nhds_zero_nat
simp only [add_zero]
exact tendsto_of_tendsto_of_tendsto_of_le_of_le h h' (fun x => δ_le _) fun x => le_of_lt (hw _)
-- Step 2: Prove that the sequence `w : ℕ → K` is a Cauchy sequence
have seq_is_cauchy : CauchySeq fun n => (w n : F) := by
rw [cauchySeq_iff_le_tendsto_0]
-- splits into three goals
let b := fun n : ℕ => 8 * δ * (1 / (n + 1)) + 4 * (1 / (n + 1)) * (1 / (n + 1))
use fun n => √(b n)
constructor
-- first goal : `∀ (n : ℕ), 0 ≤ √(b n)`
· intro n
exact sqrt_nonneg _
constructor
-- second goal : `∀ (n m N : ℕ), N ≤ n → N ≤ m → dist ↑(w n) ↑(w m) ≤ √(b N)`
· intro p q N hp hq
let wp := (w p : F)
let wq := (w q : F)
let a := u - wq
let b := u - wp
let half := 1 / (2 : ℝ)
let div := 1 / ((N : ℝ) + 1)
have :
4 * ‖u - half • (wq + wp)‖ * ‖u - half • (wq + wp)‖ + ‖wp - wq‖ * ‖wp - wq‖ =
2 * (‖a‖ * ‖a‖ + ‖b‖ * ‖b‖) :=
calc
4 * ‖u - half • (wq + wp)‖ * ‖u - half • (wq + wp)‖ + ‖wp - wq‖ * ‖wp - wq‖ =
2 * ‖u - half • (wq + wp)‖ * (2 * ‖u - half • (wq + wp)‖) + ‖wp - wq‖ * ‖wp - wq‖ :=
by ring
_ =
absR (2 : ℝ) * ‖u - half • (wq + wp)‖ * (absR (2 : ℝ) * ‖u - half • (wq + wp)‖) +
‖wp - wq‖ * ‖wp - wq‖ := by
rw [abs_of_nonneg]
exact zero_le_two
_ =
‖(2 : ℝ) • (u - half • (wq + wp))‖ * ‖(2 : ℝ) • (u - half • (wq + wp))‖ +
‖wp - wq‖ * ‖wp - wq‖ := by simp [norm_smul]
_ = ‖a + b‖ * ‖a + b‖ + ‖a - b‖ * ‖a - b‖ := by
rw [smul_sub, smul_smul, mul_one_div_cancel (_root_.two_ne_zero : (2 : ℝ) ≠ 0), ←
one_add_one_eq_two, add_smul]
simp only [one_smul]
have eq₁ : wp - wq = a - b := (sub_sub_sub_cancel_left _ _ _).symm
have eq₂ : u + u - (wq + wp) = a + b := by
show u + u - (wq + wp) = u - wq + (u - wp)
abel
rw [eq₁, eq₂]
_ = 2 * (‖a‖ * ‖a‖ + ‖b‖ * ‖b‖) := parallelogram_law_with_norm ℝ _ _
have eq : δ ≤ ‖u - half • (wq + wp)‖ := by
rw [smul_add]
apply δ_le'
apply h₂
repeat' exact Subtype.mem _
repeat' exact le_of_lt one_half_pos
exact add_halves 1
have eq₁ : 4 * δ * δ ≤ 4 * ‖u - half • (wq + wp)‖ * ‖u - half • (wq + wp)‖ := by
simp_rw [mul_assoc]
gcongr
have eq₂ : ‖a‖ ≤ δ + div :=
le_trans (le_of_lt <| hw q) (add_le_add_left (Nat.one_div_le_one_div hq) _)
have eq₂' : ‖b‖ ≤ δ + div :=
le_trans (le_of_lt <| hw p) (add_le_add_left (Nat.one_div_le_one_div hp) _)
rw [dist_eq_norm]
apply nonneg_le_nonneg_of_sq_le_sq
· exact sqrt_nonneg _
rw [mul_self_sqrt]
· calc
‖wp - wq‖ * ‖wp - wq‖ =
2 * (‖a‖ * ‖a‖ + ‖b‖ * ‖b‖) - 4 * ‖u - half • (wq + wp)‖ * ‖u - half • (wq + wp)‖ := by
simp [← this]
_ ≤ 2 * (‖a‖ * ‖a‖ + ‖b‖ * ‖b‖) - 4 * δ * δ := by gcongr
_ ≤ 2 * ((δ + div) * (δ + div) + (δ + div) * (δ + div)) - 4 * δ * δ := by gcongr
_ = 8 * δ * div + 4 * div * div := by ring
positivity
-- third goal : `Tendsto (fun (n : ℕ) => √(b n)) atTop (𝓝 0)`
suffices Tendsto (fun x ↦ √(8 * δ * x + 4 * x * x) : ℝ → ℝ) (𝓝 0) (𝓝 0)
from this.comp tendsto_one_div_add_atTop_nhds_zero_nat
exact Continuous.tendsto' (by fun_prop) _ _ (by simp)
-- Step 3: By completeness of `K`, let `w : ℕ → K` converge to some `v : K`.
-- Prove that it satisfies all requirements.
rcases cauchySeq_tendsto_of_isComplete h₁ (fun n => Subtype.mem _) seq_is_cauchy with
⟨v, hv, w_tendsto⟩
use v
use hv
have h_cont : Continuous fun v => ‖u - v‖ :=
Continuous.comp continuous_norm (Continuous.sub continuous_const continuous_id)
have : Tendsto (fun n => ‖u - w n‖) atTop (𝓝 ‖u - v‖) := by
convert Tendsto.comp h_cont.continuousAt w_tendsto
exact tendsto_nhds_unique this norm_tendsto
/-- Characterization of minimizers for the projection on a convex set in a real inner product
space. -/
theorem norm_eq_iInf_iff_real_inner_le_zero {K : Set F} (h : Convex ℝ K) {u : F} {v : F}
(hv : v ∈ K) : (‖u - v‖ = ⨅ w : K, ‖u - w‖) ↔ ∀ w ∈ K, ⟪u - v, w - v⟫_ℝ ≤ 0 := by
letI : Nonempty K := ⟨⟨v, hv⟩⟩
constructor
· intro eq w hw
let δ := ⨅ w : K, ‖u - w‖
let p := ⟪u - v, w - v⟫_ℝ
let q := ‖w - v‖ ^ 2
have δ_le (w : K) : δ ≤ ‖u - w‖ := ciInf_le ⟨0, fun _ ⟨_, h⟩ => h ▸ norm_nonneg _⟩ _
have δ_le' (w) (hw : w ∈ K) : δ ≤ ‖u - w‖ := δ_le ⟨w, hw⟩
have (θ : ℝ) (hθ₁ : 0 < θ) (hθ₂ : θ ≤ 1) : 2 * p ≤ θ * q := by
have : ‖u - v‖ ^ 2 ≤ ‖u - v‖ ^ 2 - 2 * θ * ⟪u - v, w - v⟫_ℝ + θ * θ * ‖w - v‖ ^ 2 :=
calc ‖u - v‖ ^ 2
_ ≤ ‖u - (θ • w + (1 - θ) • v)‖ ^ 2 := by
simp only [sq]; apply mul_self_le_mul_self (norm_nonneg _)
rw [eq]; apply δ_le'
apply h hw hv
exacts [le_of_lt hθ₁, sub_nonneg.2 hθ₂, add_sub_cancel _ _]
_ = ‖u - v - θ • (w - v)‖ ^ 2 := by
have : u - (θ • w + (1 - θ) • v) = u - v - θ • (w - v) := by
rw [smul_sub, sub_smul, one_smul]
simp only [sub_eq_add_neg, add_comm, add_left_comm, add_assoc, neg_add_rev]
rw [this]
_ = ‖u - v‖ ^ 2 - 2 * θ * inner (u - v) (w - v) + θ * θ * ‖w - v‖ ^ 2 := by
rw [@norm_sub_sq ℝ, inner_smul_right, norm_smul]
simp only [sq]
show
‖u - v‖ * ‖u - v‖ - 2 * (θ * inner (u - v) (w - v)) +
absR θ * ‖w - v‖ * (absR θ * ‖w - v‖) =
‖u - v‖ * ‖u - v‖ - 2 * θ * inner (u - v) (w - v) + θ * θ * (‖w - v‖ * ‖w - v‖)
rw [abs_of_pos hθ₁]; ring
have eq₁ :
‖u - v‖ ^ 2 - 2 * θ * inner (u - v) (w - v) + θ * θ * ‖w - v‖ ^ 2 =
‖u - v‖ ^ 2 + (θ * θ * ‖w - v‖ ^ 2 - 2 * θ * inner (u - v) (w - v)) := by
abel
rw [eq₁, le_add_iff_nonneg_right] at this
have eq₂ :
θ * θ * ‖w - v‖ ^ 2 - 2 * θ * inner (u - v) (w - v) =
θ * (θ * ‖w - v‖ ^ 2 - 2 * inner (u - v) (w - v)) := by ring
rw [eq₂] at this
exact le_of_sub_nonneg (nonneg_of_mul_nonneg_right this hθ₁)
by_cases hq : q = 0
· rw [hq] at this
have : p ≤ 0 := by
have := this (1 : ℝ) (by norm_num) (by norm_num)
linarith
exact this
· have q_pos : 0 < q := lt_of_le_of_ne (sq_nonneg _) fun h ↦ hq h.symm
by_contra hp
rw [not_le] at hp
let θ := min (1 : ℝ) (p / q)
have eq₁ : θ * q ≤ p :=
calc
θ * q ≤ p / q * q := mul_le_mul_of_nonneg_right (min_le_right _ _) (sq_nonneg _)
_ = p := div_mul_cancel₀ _ hq
have : 2 * p ≤ p :=
calc
2 * p ≤ θ * q := by
exact this θ (lt_min (by norm_num) (div_pos hp q_pos)) (by norm_num [θ])
_ ≤ p := eq₁
linarith
· intro h
apply le_antisymm
· apply le_ciInf
intro w
apply nonneg_le_nonneg_of_sq_le_sq (norm_nonneg _)
have := h w w.2
calc
‖u - v‖ * ‖u - v‖ ≤ ‖u - v‖ * ‖u - v‖ - 2 * inner (u - v) ((w : F) - v) := by linarith
_ ≤ ‖u - v‖ ^ 2 - 2 * inner (u - v) ((w : F) - v) + ‖(w : F) - v‖ ^ 2 := by
rw [sq]
refine le_add_of_nonneg_right ?_
exact sq_nonneg _
_ = ‖u - v - (w - v)‖ ^ 2 := (@norm_sub_sq ℝ _ _ _ _ _ _).symm
_ = ‖u - w‖ * ‖u - w‖ := by
have : u - v - (w - v) = u - w := by abel
rw [this, sq]
· show ⨅ w : K, ‖u - w‖ ≤ (fun w : K => ‖u - w‖) ⟨v, hv⟩
apply ciInf_le
use 0
rintro y ⟨z, rfl⟩
exact norm_nonneg _
variable (K : Submodule 𝕜 E)
namespace Submodule
/-- Existence of projections on complete subspaces.
Let `u` be a point in an inner product space, and let `K` be a nonempty complete subspace.
Then there exists a (unique) `v` in `K` that minimizes the distance `‖u - v‖` to `u`.
This point `v` is usually called the orthogonal projection of `u` onto `K`.
-/
theorem exists_norm_eq_iInf_of_complete_subspace (h : IsComplete (↑K : Set E)) :
∀ u : E, ∃ v ∈ K, ‖u - v‖ = ⨅ w : (K : Set E), ‖u - w‖ := by
letI : InnerProductSpace ℝ E := InnerProductSpace.rclikeToReal 𝕜 E
letI : Module ℝ E := RestrictScalars.module ℝ 𝕜 E
let K' : Submodule ℝ E := Submodule.restrictScalars ℝ K
exact exists_norm_eq_iInf_of_complete_convex ⟨0, K'.zero_mem⟩ h K'.convex
/-- Characterization of minimizers in the projection on a subspace, in the real case.
Let `u` be a point in a real inner product space, and let `K` be a nonempty subspace.
Then point `v` minimizes the distance `‖u - v‖` over points in `K` if and only if
for all `w ∈ K`, `⟪u - v, w⟫ = 0` (i.e., `u - v` is orthogonal to the subspace `K`).
This is superseded by `norm_eq_iInf_iff_inner_eq_zero` that gives the same conclusion over
any `RCLike` field.
-/
theorem norm_eq_iInf_iff_real_inner_eq_zero (K : Submodule ℝ F) {u : F} {v : F} (hv : v ∈ K) :
(‖u - v‖ = ⨅ w : (↑K : Set F), ‖u - w‖) ↔ ∀ w ∈ K, ⟪u - v, w⟫_ℝ = 0 :=
Iff.intro
(by
intro h
have h : ∀ w ∈ K, ⟪u - v, w - v⟫_ℝ ≤ 0 := by
rwa [norm_eq_iInf_iff_real_inner_le_zero] at h
exacts [K.convex, hv]
intro w hw
have le : ⟪u - v, w⟫_ℝ ≤ 0 := by
let w' := w + v
have : w' ∈ K := Submodule.add_mem _ hw hv
have h₁ := h w' this
have h₂ : w' - v = w := by
simp only [w', add_neg_cancel_right, sub_eq_add_neg]
rw [h₂] at h₁
exact h₁
have ge : ⟪u - v, w⟫_ℝ ≥ 0 := by
let w'' := -w + v
have : w'' ∈ K := Submodule.add_mem _ (Submodule.neg_mem _ hw) hv
have h₁ := h w'' this
have h₂ : w'' - v = -w := by
simp only [w'', neg_inj, add_neg_cancel_right, sub_eq_add_neg]
rw [h₂, inner_neg_right] at h₁
linarith
exact le_antisymm le ge)
(by
intro h
have : ∀ w ∈ K, ⟪u - v, w - v⟫_ℝ ≤ 0 := by
intro w hw
let w' := w - v
have : w' ∈ K := Submodule.sub_mem _ hw hv
have h₁ := h w' this
exact le_of_eq h₁
rwa [norm_eq_iInf_iff_real_inner_le_zero]
exacts [Submodule.convex _, hv])
/-- Characterization of minimizers in the projection on a subspace.
Let `u` be a point in an inner product space, and let `K` be a nonempty subspace.
Then point `v` minimizes the distance `‖u - v‖` over points in `K` if and only if
for all `w ∈ K`, `⟪u - v, w⟫ = 0` (i.e., `u - v` is orthogonal to the subspace `K`)
-/
theorem norm_eq_iInf_iff_inner_eq_zero {u : E} {v : E} (hv : v ∈ K) :
(‖u - v‖ = ⨅ w : K, ‖u - w‖) ↔ ∀ w ∈ K, ⟪u - v, w⟫ = 0 := by
letI : InnerProductSpace ℝ E := InnerProductSpace.rclikeToReal 𝕜 E
letI : Module ℝ E := RestrictScalars.module ℝ 𝕜 E
let K' : Submodule ℝ E := K.restrictScalars ℝ
constructor
· intro H
have A : ∀ w ∈ K, re ⟪u - v, w⟫ = 0 := (K'.norm_eq_iInf_iff_real_inner_eq_zero hv).1 H
intro w hw
apply RCLike.ext
· simp [A w hw]
· symm
calc
im (0 : 𝕜) = 0 := im.map_zero
_ = re ⟪u - v, (-I : 𝕜) • w⟫ := (A _ (K.smul_mem (-I) hw)).symm
_ = re (-I * ⟪u - v, w⟫) := by rw [inner_smul_right]
_ = im ⟪u - v, w⟫ := by simp
· intro H
have : ∀ w ∈ K', ⟪u - v, w⟫_ℝ = 0 := by
intro w hw
rw [real_inner_eq_re_inner, H w hw]
exact zero_re'
exact (K'.norm_eq_iInf_iff_real_inner_eq_zero hv).2 this
/-- A subspace `K : Submodule 𝕜 E` has an orthogonal projection if every vector `v : E` admits an
orthogonal projection to `K`. -/
class HasOrthogonalProjection (K : Submodule 𝕜 E) : Prop where
exists_orthogonal (v : E) : ∃ w ∈ K, v - w ∈ Kᗮ
instance (priority := 100) HasOrthogonalProjection.ofCompleteSpace [CompleteSpace K] :
K.HasOrthogonalProjection where
exists_orthogonal v := by
rcases K.exists_norm_eq_iInf_of_complete_subspace (completeSpace_coe_iff_isComplete.mp ‹_›) v
with ⟨w, hwK, hw⟩
refine ⟨w, hwK, (K.mem_orthogonal' _).2 ?_⟩
rwa [← K.norm_eq_iInf_iff_inner_eq_zero hwK]
instance [K.HasOrthogonalProjection] : Kᗮ.HasOrthogonalProjection where
exists_orthogonal v := by
rcases HasOrthogonalProjection.exists_orthogonal (K := K) v with ⟨w, hwK, hw⟩
refine ⟨_, hw, ?_⟩
rw [sub_sub_cancel]
exact K.le_orthogonal_orthogonal hwK
instance HasOrthogonalProjection.map_linearIsometryEquiv [K.HasOrthogonalProjection]
{E' : Type*} [NormedAddCommGroup E'] [InnerProductSpace 𝕜 E'] (f : E ≃ₗᵢ[𝕜] E') :
(K.map (f.toLinearEquiv : E →ₗ[𝕜] E')).HasOrthogonalProjection where
exists_orthogonal v := by
rcases HasOrthogonalProjection.exists_orthogonal (K := K) (f.symm v) with ⟨w, hwK, hw⟩
refine ⟨f w, Submodule.mem_map_of_mem hwK, Set.forall_mem_image.2 fun u hu ↦ ?_⟩
erw [← f.symm.inner_map_map, f.symm_apply_apply, map_sub, f.symm_apply_apply, hw u hu]
instance HasOrthogonalProjection.map_linearIsometryEquiv' [K.HasOrthogonalProjection]
{E' : Type*} [NormedAddCommGroup E'] [InnerProductSpace 𝕜 E'] (f : E ≃ₗᵢ[𝕜] E') :
(K.map f.toLinearIsometry).HasOrthogonalProjection :=
HasOrthogonalProjection.map_linearIsometryEquiv K f
instance : (⊤ : Submodule 𝕜 E).HasOrthogonalProjection := ⟨fun v ↦ ⟨v, trivial, by simp⟩⟩
section orthogonalProjection
variable [K.HasOrthogonalProjection]
/-- The orthogonal projection onto a complete subspace, as an
unbundled function. This definition is only intended for use in
setting up the bundled version `orthogonalProjection` and should not
be used once that is defined. -/
def orthogonalProjectionFn (v : E) :=
(HasOrthogonalProjection.exists_orthogonal (K := K) v).choose
variable {K}
/-- The unbundled orthogonal projection is in the given subspace.
This lemma is only intended for use in setting up the bundled version
and should not be used once that is defined. -/
theorem orthogonalProjectionFn_mem (v : E) : K.orthogonalProjectionFn v ∈ K :=
(HasOrthogonalProjection.exists_orthogonal (K := K) v).choose_spec.left
/-- The characterization of the unbundled orthogonal projection. This
lemma is only intended for use in setting up the bundled version
and should not be used once that is defined. -/
theorem orthogonalProjectionFn_inner_eq_zero (v : E) :
∀ w ∈ K, ⟪v - K.orthogonalProjectionFn v, w⟫ = 0 :=
(K.mem_orthogonal' _).1 (HasOrthogonalProjection.exists_orthogonal (K := K) v).choose_spec.right
/-- The unbundled orthogonal projection is the unique point in `K`
with the orthogonality property. This lemma is only intended for use
in setting up the bundled version and should not be used once that is
defined. -/
theorem eq_orthogonalProjectionFn_of_mem_of_inner_eq_zero {u v : E} (hvm : v ∈ K)
(hvo : ∀ w ∈ K, ⟪u - v, w⟫ = 0) : K.orthogonalProjectionFn u = v := by
rw [← sub_eq_zero, ← @inner_self_eq_zero 𝕜]
have hvs : K.orthogonalProjectionFn u - v ∈ K :=
Submodule.sub_mem K (orthogonalProjectionFn_mem u) hvm
have huo : ⟪u - K.orthogonalProjectionFn u, K.orthogonalProjectionFn u - v⟫ = 0 :=
orthogonalProjectionFn_inner_eq_zero u _ hvs
have huv : ⟪u - v, K.orthogonalProjectionFn u - v⟫ = 0 := hvo _ hvs
have houv : ⟪u - v - (u - K.orthogonalProjectionFn u), K.orthogonalProjectionFn u - v⟫ = 0 := by
rw [inner_sub_left, huo, huv, sub_zero]
rwa [sub_sub_sub_cancel_left] at houv
variable (K)
theorem orthogonalProjectionFn_norm_sq (v : E) :
‖v‖ * ‖v‖ =
‖v - K.orthogonalProjectionFn v‖ * ‖v - K.orthogonalProjectionFn v‖ +
‖K.orthogonalProjectionFn v‖ * ‖K.orthogonalProjectionFn v‖ := by
set p := K.orthogonalProjectionFn v
have h' : ⟪v - p, p⟫ = 0 :=
orthogonalProjectionFn_inner_eq_zero _ _ (orthogonalProjectionFn_mem v)
convert norm_add_sq_eq_norm_sq_add_norm_sq_of_inner_eq_zero (v - p) p h' using 2 <;> simp
/-- The orthogonal projection onto a complete subspace. -/
def orthogonalProjection : E →L[𝕜] K :=
LinearMap.mkContinuous
{ toFun := fun v => ⟨K.orthogonalProjectionFn v, orthogonalProjectionFn_mem v⟩
map_add' := fun x y => by
have hm : K.orthogonalProjectionFn x + K.orthogonalProjectionFn y ∈ K :=
Submodule.add_mem K (orthogonalProjectionFn_mem x) (orthogonalProjectionFn_mem y)
have ho :
∀ w ∈ K, ⟪x + y - (K.orthogonalProjectionFn x + K.orthogonalProjectionFn y), w⟫ = 0 := by
intro w hw
rw [add_sub_add_comm, inner_add_left, orthogonalProjectionFn_inner_eq_zero _ w hw,
orthogonalProjectionFn_inner_eq_zero _ w hw, add_zero]
ext
simp [eq_orthogonalProjectionFn_of_mem_of_inner_eq_zero hm ho]
map_smul' := fun c x => by
have hm : c • K.orthogonalProjectionFn x ∈ K :=
Submodule.smul_mem K _ (orthogonalProjectionFn_mem x)
have ho : ∀ w ∈ K, ⟪c • x - c • K.orthogonalProjectionFn x, w⟫ = 0 := by
intro w hw
rw [← smul_sub, inner_smul_left, orthogonalProjectionFn_inner_eq_zero _ w hw,
mul_zero]
ext
simp [eq_orthogonalProjectionFn_of_mem_of_inner_eq_zero hm ho] }
1 fun x => by
simp only [one_mul, LinearMap.coe_mk]
refine le_of_pow_le_pow_left₀ two_ne_zero (norm_nonneg _) ?_
change ‖K.orthogonalProjectionFn x‖ ^ 2 ≤ ‖x‖ ^ 2
nlinarith [K.orthogonalProjectionFn_norm_sq x]
variable {K}
@[simp]
theorem orthogonalProjectionFn_eq (v : E) :
K.orthogonalProjectionFn v = (K.orthogonalProjection v : E) :=
rfl
/-- The characterization of the orthogonal projection. -/
@[simp]
theorem orthogonalProjection_inner_eq_zero (v : E) :
∀ w ∈ K, ⟪v - K.orthogonalProjection v, w⟫ = 0 :=
orthogonalProjectionFn_inner_eq_zero v
/-- The difference of `v` from its orthogonal projection onto `K` is in `Kᗮ`. -/
@[simp]
theorem sub_orthogonalProjection_mem_orthogonal (v : E) : v - K.orthogonalProjection v ∈ Kᗮ := by
intro w hw
rw [inner_eq_zero_symm]
exact orthogonalProjection_inner_eq_zero _ _ hw
/-- The orthogonal projection is the unique point in `K` with the
orthogonality property. -/
theorem eq_orthogonalProjection_of_mem_of_inner_eq_zero {u v : E} (hvm : v ∈ K)
(hvo : ∀ w ∈ K, ⟪u - v, w⟫ = 0) : (K.orthogonalProjection u : E) = v :=
eq_orthogonalProjectionFn_of_mem_of_inner_eq_zero hvm hvo
/-- A point in `K` with the orthogonality property (here characterized in terms of `Kᗮ`) must be the
orthogonal projection. -/
theorem eq_orthogonalProjection_of_mem_orthogonal {u v : E} (hv : v ∈ K)
(hvo : u - v ∈ Kᗮ) : (K.orthogonalProjection u : E) = v :=
eq_orthogonalProjectionFn_of_mem_of_inner_eq_zero hv <| (Submodule.mem_orthogonal' _ _).1 hvo
/-- A point in `K` with the orthogonality property (here characterized in terms of `Kᗮ`) must be the
orthogonal projection. -/
theorem eq_orthogonalProjection_of_mem_orthogonal' {u v z : E}
(hv : v ∈ K) (hz : z ∈ Kᗮ) (hu : u = v + z) : (K.orthogonalProjection u : E) = v :=
eq_orthogonalProjection_of_mem_orthogonal hv (by simpa [hu] )
@[simp]
theorem orthogonalProjection_orthogonal_val (u : E) :
(Kᗮ.orthogonalProjection u : E) = u - K.orthogonalProjection u :=
eq_orthogonalProjection_of_mem_orthogonal' (sub_orthogonalProjection_mem_orthogonal _)
(K.le_orthogonal_orthogonal (K.orthogonalProjection u).2) <| by simp
theorem orthogonalProjection_orthogonal (u : E) :
Kᗮ.orthogonalProjection u =
⟨u - K.orthogonalProjection u, sub_orthogonalProjection_mem_orthogonal _⟩ :=
Subtype.eq <| orthogonalProjection_orthogonal_val _
/-- The orthogonal projection of `y` on `U` minimizes the distance `‖y - x‖` for `x ∈ U`. -/
theorem orthogonalProjection_minimal {U : Submodule 𝕜 E} [U.HasOrthogonalProjection] (y : E) :
‖y - U.orthogonalProjection y‖ = ⨅ x : U, ‖y - x‖ := by
rw [U.norm_eq_iInf_iff_inner_eq_zero (Submodule.coe_mem _)]
exact orthogonalProjection_inner_eq_zero _
/-- The orthogonal projections onto equal subspaces are coerced back to the same point in `E`. -/
theorem eq_orthogonalProjection_of_eq_submodule {K' : Submodule 𝕜 E} [K'.HasOrthogonalProjection]
(h : K = K') (u : E) : (K.orthogonalProjection u : E) = (K'.orthogonalProjection u : E) := by
subst h; rfl
/-- The orthogonal projection sends elements of `K` to themselves. -/
@[simp]
theorem orthogonalProjection_mem_subspace_eq_self (v : K) : K.orthogonalProjection v = v := by
ext
apply eq_orthogonalProjection_of_mem_of_inner_eq_zero <;> simp
/-- A point equals its orthogonal projection if and only if it lies in the subspace. -/
theorem orthogonalProjection_eq_self_iff {v : E} : (K.orthogonalProjection v : E) = v ↔ v ∈ K := by
refine ⟨fun h => ?_, fun h => eq_orthogonalProjection_of_mem_of_inner_eq_zero h ?_⟩
· rw [← h]
simp
· simp
@[simp]
theorem orthogonalProjection_eq_zero_iff {v : E} : K.orthogonalProjection v = 0 ↔ v ∈ Kᗮ := by
refine ⟨fun h ↦ ?_, fun h ↦ Subtype.eq <| eq_orthogonalProjection_of_mem_orthogonal
(zero_mem _) ?_⟩
· simpa [h] using sub_orthogonalProjection_mem_orthogonal (K := K) v
· simpa
@[simp]
theorem ker_orthogonalProjection : LinearMap.ker K.orthogonalProjection = Kᗮ := by
ext; exact orthogonalProjection_eq_zero_iff
theorem _root_.LinearIsometry.map_orthogonalProjection {E E' : Type*} [NormedAddCommGroup E]
[NormedAddCommGroup E'] [InnerProductSpace 𝕜 E] [InnerProductSpace 𝕜 E'] (f : E →ₗᵢ[𝕜] E')
(p : Submodule 𝕜 E) [p.HasOrthogonalProjection] [(p.map f.toLinearMap).HasOrthogonalProjection]
(x : E) : f (p.orthogonalProjection x) = (p.map f.toLinearMap).orthogonalProjection (f x) := by
refine (eq_orthogonalProjection_of_mem_of_inner_eq_zero ?_ fun y hy => ?_).symm
· refine Submodule.apply_coe_mem_map _ _
rcases hy with ⟨x', hx', rfl : f x' = y⟩
rw [← f.map_sub, f.inner_map_map, orthogonalProjection_inner_eq_zero x x' hx']
theorem _root_.LinearIsometry.map_orthogonalProjection' {E E' : Type*} [NormedAddCommGroup E]
[NormedAddCommGroup E'] [InnerProductSpace 𝕜 E] [InnerProductSpace 𝕜 E'] (f : E →ₗᵢ[𝕜] E')
(p : Submodule 𝕜 E) [p.HasOrthogonalProjection] [(p.map f).HasOrthogonalProjection] (x : E) :
f (p.orthogonalProjection x) = (p.map f).orthogonalProjection (f x) :=
have : (p.map f.toLinearMap).HasOrthogonalProjection := ‹_›
f.map_orthogonalProjection p x
/-- Orthogonal projection onto the `Submodule.map` of a subspace. -/
theorem orthogonalProjection_map_apply {E E' : Type*} [NormedAddCommGroup E]
[NormedAddCommGroup E'] [InnerProductSpace 𝕜 E] [InnerProductSpace 𝕜 E'] (f : E ≃ₗᵢ[𝕜] E')
(p : Submodule 𝕜 E) [p.HasOrthogonalProjection] (x : E') :
((p.map (f.toLinearEquiv : E →ₗ[𝕜] E')).orthogonalProjection x : E') =
f (p.orthogonalProjection (f.symm x)) := by
simpa only [f.coe_toLinearIsometry, f.apply_symm_apply] using
(f.toLinearIsometry.map_orthogonalProjection' p (f.symm x)).symm
/-- The orthogonal projection onto the trivial submodule is the zero map. -/
@[simp]
theorem orthogonalProjection_bot : (⊥ : Submodule 𝕜 E).orthogonalProjection = 0 := by ext
variable (K)
/-- The orthogonal projection has norm `≤ 1`. -/
theorem orthogonalProjection_norm_le : ‖K.orthogonalProjection‖ ≤ 1 :=
LinearMap.mkContinuous_norm_le _ (by norm_num) _
variable (𝕜)
theorem smul_orthogonalProjection_singleton {v : E} (w : E) :
((‖v‖ ^ 2 : ℝ) : 𝕜) • ((𝕜 ∙ v).orthogonalProjection w : E) = ⟪v, w⟫ • v := by
suffices (((𝕜 ∙ v).orthogonalProjection (((‖v‖ : 𝕜) ^ 2) • w)) : E) = ⟪v, w⟫ • v by
simpa using this
apply eq_orthogonalProjection_of_mem_of_inner_eq_zero
· rw [Submodule.mem_span_singleton]
use ⟪v, w⟫
· rw [← Submodule.mem_orthogonal', Submodule.mem_orthogonal_singleton_iff_inner_left]
simp [inner_sub_left, inner_smul_left, inner_self_eq_norm_sq_to_K, mul_comm]
/-- Formula for orthogonal projection onto a single vector. -/
theorem orthogonalProjection_singleton {v : E} (w : E) :
((𝕜 ∙ v).orthogonalProjection w : E) = (⟪v, w⟫ / ((‖v‖ ^ 2 : ℝ) : 𝕜)) • v := by
by_cases hv : v = 0
· rw [hv, eq_orthogonalProjection_of_eq_submodule (Submodule.span_zero_singleton 𝕜)]
simp
have hv' : ‖v‖ ≠ 0 := ne_of_gt (norm_pos_iff.mpr hv)
have key :
(((‖v‖ ^ 2 : ℝ) : 𝕜)⁻¹ * ((‖v‖ ^ 2 : ℝ) : 𝕜)) • (((𝕜 ∙ v).orthogonalProjection w) : E) =
(((‖v‖ ^ 2 : ℝ) : 𝕜)⁻¹ * ⟪v, w⟫) • v := by
simp [mul_smul, smul_orthogonalProjection_singleton 𝕜 w, -map_pow]
convert key using 1 <;> field_simp [hv']
/-- Formula for orthogonal projection onto a single unit vector. -/
theorem orthogonalProjection_unit_singleton {v : E} (hv : ‖v‖ = 1) (w : E) :
((𝕜 ∙ v).orthogonalProjection w : E) = ⟪v, w⟫ • v := by
rw [← smul_orthogonalProjection_singleton 𝕜 w]
simp [hv]
end orthogonalProjection
section reflection
variable [K.HasOrthogonalProjection]
/-- Auxiliary definition for `reflection`: the reflection as a linear equivalence. -/
def reflectionLinearEquiv : E ≃ₗ[𝕜] E :=
LinearEquiv.ofInvolutive
(2 • (K.subtype.comp K.orthogonalProjection.toLinearMap) - LinearMap.id) fun x => by
simp [two_smul]
/-- Reflection in a complete subspace of an inner product space. The word "reflection" is
sometimes understood to mean specifically reflection in a codimension-one subspace, and sometimes
more generally to cover operations such as reflection in a point. The definition here, of
reflection in a subspace, is a more general sense of the word that includes both those common
cases. -/
def reflection : E ≃ₗᵢ[𝕜] E :=
{ K.reflectionLinearEquiv with
norm_map' := by
intro x
let w : K := K.orthogonalProjection x
let v := x - w
have : ⟪v, w⟫ = 0 := orthogonalProjection_inner_eq_zero x w w.2
convert norm_sub_eq_norm_add this using 2
· rw [LinearEquiv.coe_mk, reflectionLinearEquiv, LinearEquiv.toFun_eq_coe,
LinearEquiv.coe_ofInvolutive, LinearMap.sub_apply, LinearMap.id_apply, two_smul,
LinearMap.add_apply, LinearMap.comp_apply, Submodule.subtype_apply,
ContinuousLinearMap.coe_coe]
dsimp [v]
abel
· simp only [v, add_sub_cancel, eq_self_iff_true] }
variable {K}
/-- The result of reflecting. -/
theorem reflection_apply (p : E) : K.reflection p = 2 • (K.orthogonalProjection p : E) - p :=
rfl
/-- Reflection is its own inverse. -/
@[simp]
theorem reflection_symm : K.reflection.symm = K.reflection :=
rfl
/-- Reflection is its own inverse. -/
@[simp]
theorem reflection_inv : K.reflection⁻¹ = K.reflection :=
rfl
variable (K)
/-- Reflecting twice in the same subspace. -/
@[simp]
theorem reflection_reflection (p : E) : K.reflection (K.reflection p) = p :=
K.reflection.left_inv p
/-- Reflection is involutive. -/
theorem reflection_involutive : Function.Involutive K.reflection :=
K.reflection_reflection
/-- Reflection is involutive. -/
@[simp]
theorem reflection_trans_reflection :
K.reflection.trans K.reflection = LinearIsometryEquiv.refl 𝕜 E :=
LinearIsometryEquiv.ext <| reflection_involutive K
/-- Reflection is involutive. -/
@[simp]
theorem reflection_mul_reflection : K.reflection * K.reflection = 1 :=
reflection_trans_reflection _
theorem reflection_orthogonal_apply (v : E) : Kᗮ.reflection v = -K.reflection v := by
simp [reflection_apply]; abel
theorem reflection_orthogonal : Kᗮ.reflection = .trans K.reflection (.neg _) := by
ext; apply reflection_orthogonal_apply
variable {K}
theorem reflection_singleton_apply (u v : E) :
reflection (𝕜 ∙ u) v = 2 • (⟪u, v⟫ / ((‖u‖ : 𝕜) ^ 2)) • u - v := by
rw [reflection_apply, orthogonalProjection_singleton, ofReal_pow]
/-- A point is its own reflection if and only if it is in the subspace. -/
theorem reflection_eq_self_iff (x : E) : K.reflection x = x ↔ x ∈ K := by
rw [← orthogonalProjection_eq_self_iff, reflection_apply, sub_eq_iff_eq_add', ← two_smul 𝕜,
two_smul ℕ, ← two_smul 𝕜]
refine (smul_right_injective E ?_).eq_iff
exact two_ne_zero
theorem reflection_mem_subspace_eq_self {x : E} (hx : x ∈ K) : K.reflection x = x :=
(reflection_eq_self_iff x).mpr hx
/-- Reflection in the `Submodule.map` of a subspace. -/
theorem reflection_map_apply {E E' : Type*} [NormedAddCommGroup E] [NormedAddCommGroup E']
[InnerProductSpace 𝕜 E] [InnerProductSpace 𝕜 E'] (f : E ≃ₗᵢ[𝕜] E') (K : Submodule 𝕜 E)
[K.HasOrthogonalProjection] (x : E') :
reflection (K.map (f.toLinearEquiv : E →ₗ[𝕜] E')) x = f (K.reflection (f.symm x)) := by
simp [two_smul, reflection_apply, orthogonalProjection_map_apply f K x]
/-- Reflection in the `Submodule.map` of a subspace. -/
theorem reflection_map {E E' : Type*} [NormedAddCommGroup E] [NormedAddCommGroup E']
[InnerProductSpace 𝕜 E] [InnerProductSpace 𝕜 E'] (f : E ≃ₗᵢ[𝕜] E') (K : Submodule 𝕜 E)
[K.HasOrthogonalProjection] :
reflection (K.map (f.toLinearEquiv : E →ₗ[𝕜] E')) = f.symm.trans (K.reflection.trans f) :=
LinearIsometryEquiv.ext <| reflection_map_apply f K
/-- Reflection through the trivial subspace {0} is just negation. -/
@[simp]
theorem reflection_bot : reflection (⊥ : Submodule 𝕜 E) = LinearIsometryEquiv.neg 𝕜 := by
ext; simp [reflection_apply]
end reflection
end Submodule
section Orthogonal
namespace Submodule
/-- If `K₁` is complete and contained in `K₂`, `K₁` and `K₁ᗮ ⊓ K₂` span `K₂`. -/
theorem sup_orthogonal_inf_of_completeSpace {K₁ K₂ : Submodule 𝕜 E} (h : K₁ ≤ K₂)
[K₁.HasOrthogonalProjection] : K₁ ⊔ K₁ᗮ ⊓ K₂ = K₂ := by
ext x
rw [Submodule.mem_sup]
let v : K₁ := orthogonalProjection K₁ x
have hvm : x - v ∈ K₁ᗮ := sub_orthogonalProjection_mem_orthogonal x
constructor
· rintro ⟨y, hy, z, hz, rfl⟩
exact K₂.add_mem (h hy) hz.2
· exact fun hx => ⟨v, v.prop, x - v, ⟨hvm, K₂.sub_mem hx (h v.prop)⟩, add_sub_cancel _ _⟩
variable {K} in
/-- If `K` is complete, `K` and `Kᗮ` span the whole space. -/
theorem sup_orthogonal_of_completeSpace [K.HasOrthogonalProjection] : K ⊔ Kᗮ = ⊤ := by
convert Submodule.sup_orthogonal_inf_of_completeSpace (le_top : K ≤ ⊤) using 2
simp
/-- If `K` is complete, any `v` in `E` can be expressed as a sum of elements of `K` and `Kᗮ`. -/
theorem exists_add_mem_mem_orthogonal [K.HasOrthogonalProjection] (v : E) :
∃ y ∈ K, ∃ z ∈ Kᗮ, v = y + z :=
⟨K.orthogonalProjection v, Subtype.coe_prop _, v - K.orthogonalProjection v,
sub_orthogonalProjection_mem_orthogonal _, by simp⟩
/-- If `K` admits an orthogonal projection, then the orthogonal complement of its orthogonal
complement is itself. -/
@[simp]
theorem orthogonal_orthogonal [K.HasOrthogonalProjection] : Kᗮᗮ = K := by
ext v
constructor
· obtain ⟨y, hy, z, hz, rfl⟩ := K.exists_add_mem_mem_orthogonal v
intro hv
have hz' : z = 0 := by
have hyz : ⟪z, y⟫ = 0 := by simp [hz y hy, inner_eq_zero_symm]
simpa [inner_add_right, hyz] using hv z hz
simp [hy, hz']
· intro hv w hw
rw [inner_eq_zero_symm]
exact hw v hv
/-- In a Hilbert space, the orthogonal complement of the orthogonal complement of a subspace `K`
is the topological closure of `K`.
Note that the completeness assumption is necessary. Let `E` be the space `ℕ →₀ ℝ` with inner space
structure inherited from `PiLp 2 (fun _ : ℕ ↦ ℝ)`. Let `K` be the subspace of sequences with the sum
of all elements equal to zero. Then `Kᗮ = ⊥`, `Kᗮᗮ = ⊤`. -/
theorem orthogonal_orthogonal_eq_closure [CompleteSpace E] :
Kᗮᗮ = K.topologicalClosure := by
refine le_antisymm ?_ ?_
· convert Submodule.orthogonal_orthogonal_monotone K.le_topologicalClosure using 1
rw [K.topologicalClosure.orthogonal_orthogonal]
· exact K.topologicalClosure_minimal K.le_orthogonal_orthogonal Kᗮ.isClosed_orthogonal
variable {K}
/-- If `K` admits an orthogonal projection, `K` and `Kᗮ` are complements of each other. -/
theorem isCompl_orthogonal_of_completeSpace [K.HasOrthogonalProjection] : IsCompl K Kᗮ :=
⟨K.orthogonal_disjoint, codisjoint_iff.2 Submodule.sup_orthogonal_of_completeSpace⟩
@[simp]
theorem orthogonalComplement_eq_orthogonalComplement {L : Submodule 𝕜 E} [K.HasOrthogonalProjection]
[L.HasOrthogonalProjection] : Kᗮ = Lᗮ ↔ K = L :=
⟨fun h ↦ by simpa using congr(Submodule.orthogonal $(h)),
fun h ↦ congr(Submodule.orthogonal $(h))⟩
@[simp]
theorem orthogonal_eq_bot_iff [K.HasOrthogonalProjection] : Kᗮ = ⊥ ↔ K = ⊤ := by
refine ⟨?_, fun h => by rw [h, Submodule.top_orthogonal_eq_bot]⟩
intro h
have : K ⊔ Kᗮ = ⊤ := Submodule.sup_orthogonal_of_completeSpace
rwa [h, sup_comm, bot_sup_eq] at this
/-- The orthogonal projection onto `K` of an element of `Kᗮ` is zero. -/
theorem orthogonalProjection_mem_subspace_orthogonalComplement_eq_zero [K.HasOrthogonalProjection]
{v : E} (hv : v ∈ Kᗮ) : K.orthogonalProjection v = 0 := by
ext
convert eq_orthogonalProjection_of_mem_orthogonal (K := K) _ _ <;> simp [hv]
/-- The projection into `U` from an orthogonal submodule `V` is the zero map. -/
theorem IsOrtho.orthogonalProjection_comp_subtypeL {U V : Submodule 𝕜 E}
[U.HasOrthogonalProjection] (h : U ⟂ V) : U.orthogonalProjection ∘L V.subtypeL = 0 :=
ContinuousLinearMap.ext fun v =>
orthogonalProjection_mem_subspace_orthogonalComplement_eq_zero <| h.symm v.prop
/-- The projection into `U` from `V` is the zero map if and only if `U` and `V` are orthogonal. -/
theorem orthogonalProjection_comp_subtypeL_eq_zero_iff {U V : Submodule 𝕜 E}
[U.HasOrthogonalProjection] : U.orthogonalProjection ∘L V.subtypeL = 0 ↔ U ⟂ V :=
⟨fun h u hu v hv => by
convert orthogonalProjection_inner_eq_zero v u hu using 2
have : U.orthogonalProjection v = 0 := DFunLike.congr_fun h (⟨_, hv⟩ : V)
rw [this, Submodule.coe_zero, sub_zero], Submodule.IsOrtho.orthogonalProjection_comp_subtypeL⟩
theorem orthogonalProjection_eq_linear_proj [K.HasOrthogonalProjection] (x : E) :
K.orthogonalProjection x =
K.linearProjOfIsCompl _ Submodule.isCompl_orthogonal_of_completeSpace x := by
have : IsCompl K Kᗮ := Submodule.isCompl_orthogonal_of_completeSpace
conv_lhs => rw [← Submodule.linear_proj_add_linearProjOfIsCompl_eq_self this x]
rw [map_add, orthogonalProjection_mem_subspace_eq_self,
orthogonalProjection_mem_subspace_orthogonalComplement_eq_zero (Submodule.coe_mem _), add_zero]
theorem orthogonalProjection_coe_linearMap_eq_linearProj [K.HasOrthogonalProjection] :
(K.orthogonalProjection : E →ₗ[𝕜] K) =
K.linearProjOfIsCompl _ Submodule.isCompl_orthogonal_of_completeSpace :=
LinearMap.ext <| orthogonalProjection_eq_linear_proj
/-- The reflection in `K` of an element of `Kᗮ` is its negation. -/
theorem reflection_mem_subspace_orthogonalComplement_eq_neg [K.HasOrthogonalProjection] {v : E}
(hv : v ∈ Kᗮ) : K.reflection v = -v := by
simp [reflection_apply, orthogonalProjection_mem_subspace_orthogonalComplement_eq_zero hv]
/-- The orthogonal projection onto `Kᗮ` of an element of `K` is zero. -/
theorem orthogonalProjection_mem_subspace_orthogonal_precomplement_eq_zero
[Kᗮ.HasOrthogonalProjection] {v : E} (hv : v ∈ K) : Kᗮ.orthogonalProjection v = 0 :=
orthogonalProjection_mem_subspace_orthogonalComplement_eq_zero (K.le_orthogonal_orthogonal hv)
/-- If `U ≤ V`, then projecting on `V` and then on `U` is the same as projecting on `U`. -/
theorem orthogonalProjection_orthogonalProjection_of_le {U V : Submodule 𝕜 E}
[U.HasOrthogonalProjection] [V.HasOrthogonalProjection] (h : U ≤ V) (x : E) :
U.orthogonalProjection (V.orthogonalProjection x) = U.orthogonalProjection x :=
Eq.symm <| by
simpa only [sub_eq_zero, map_sub] using
orthogonalProjection_mem_subspace_orthogonalComplement_eq_zero
(Submodule.orthogonal_le h (sub_orthogonalProjection_mem_orthogonal x))
/-- Given a monotone family `U` of complete submodules of `E` and a fixed `x : E`,
the orthogonal projection of `x` on `U i` tends to the orthogonal projection of `x` on
`(⨆ i, U i).topologicalClosure` along `atTop`. -/
theorem orthogonalProjection_tendsto_closure_iSup {ι : Type*} [Preorder ι]
(U : ι → Submodule 𝕜 E) [∀ i, (U i).HasOrthogonalProjection]
[(⨆ i, U i).topologicalClosure.HasOrthogonalProjection] (hU : Monotone U) (x : E) :
Filter.Tendsto (fun i => ((U i).orthogonalProjection x : E)) atTop
(𝓝 ((⨆ i, U i).topologicalClosure.orthogonalProjection x : E)) := by
refine .of_neBot_imp fun h ↦ ?_
cases atTop_neBot_iff.mp h
let y := ((⨆ i, U i).topologicalClosure.orthogonalProjection x : E)
have proj_x : ∀ i, (U i).orthogonalProjection x = (U i).orthogonalProjection y := fun i =>
(orthogonalProjection_orthogonalProjection_of_le
((le_iSup U i).trans (iSup U).le_topologicalClosure) _).symm
suffices ∀ ε > 0, ∃ I, ∀ i ≥ I, ‖((U i).orthogonalProjection y : E) - y‖ < ε by
simpa only [proj_x, NormedAddCommGroup.tendsto_atTop] using this
intro ε hε
obtain ⟨a, ha, hay⟩ : ∃ a ∈ ⨆ i, U i, dist y a < ε := by
have y_mem : y ∈ (⨆ i, U i).topologicalClosure := Submodule.coe_mem _
rw [← SetLike.mem_coe, Submodule.topologicalClosure_coe, Metric.mem_closure_iff] at y_mem
exact y_mem ε hε
rw [dist_eq_norm] at hay
obtain ⟨I, hI⟩ : ∃ I, a ∈ U I := by rwa [Submodule.mem_iSup_of_directed _ hU.directed_le] at ha
refine ⟨I, fun i (hi : I ≤ i) => ?_⟩
rw [norm_sub_rev, orthogonalProjection_minimal]
refine lt_of_le_of_lt ?_ hay
change _ ≤ ‖y - (⟨a, hU hi hI⟩ : U i)‖
exact ciInf_le ⟨0, Set.forall_mem_range.mpr fun _ => norm_nonneg _⟩ _
/-- Given a monotone family `U` of complete submodules of `E` with dense span supremum,
and a fixed `x : E`, the orthogonal projection of `x` on `U i` tends to `x` along `at_top`. -/
theorem orthogonalProjection_tendsto_self {ι : Type*} [Preorder ι]
(U : ι → Submodule 𝕜 E) [∀ t, (U t).HasOrthogonalProjection] (hU : Monotone U) (x : E)
(hU' : ⊤ ≤ (⨆ t, U t).topologicalClosure) :
Filter.Tendsto (fun t => ((U t).orthogonalProjection x : E)) atTop (𝓝 x) := by
have : (⨆ i, U i).topologicalClosure.HasOrthogonalProjection := by
rw [top_unique hU']
infer_instance
convert orthogonalProjection_tendsto_closure_iSup U hU x
rw [eq_comm, orthogonalProjection_eq_self_iff, top_unique hU']
trivial
/-- The orthogonal complement satisfies `Kᗮᗮᗮ = Kᗮ`. -/
theorem triorthogonal_eq_orthogonal [CompleteSpace E] : Kᗮᗮᗮ = Kᗮ := by
rw [Kᗮ.orthogonal_orthogonal_eq_closure]
exact K.isClosed_orthogonal.submodule_topologicalClosure_eq
/-- The closure of `K` is the full space iff `Kᗮ` is trivial. -/
theorem topologicalClosure_eq_top_iff [CompleteSpace E] :
K.topologicalClosure = ⊤ ↔ Kᗮ = ⊥ := by
rw [← K.orthogonal_orthogonal_eq_closure]
constructor <;> intro h
· rw [← Submodule.triorthogonal_eq_orthogonal, h, Submodule.top_orthogonal_eq_bot]
· rw [h, Submodule.bot_orthogonal_eq_top]
end Submodule
namespace Dense
/- TODO: Move to another file? -/
open Submodule
variable {K} {x y : E}
theorem eq_zero_of_inner_left (hK : Dense (K : Set E)) (h : ∀ v : K, ⟪x, v⟫ = 0) : x = 0 := by
have : (⟪x, ·⟫) = 0 := (continuous_const.inner continuous_id).ext_on
hK continuous_const (Subtype.forall.1 h)
simpa using congr_fun this x
theorem eq_zero_of_mem_orthogonal (hK : Dense (K : Set E)) (h : x ∈ Kᗮ) : x = 0 :=
eq_zero_of_inner_left hK fun v ↦ (mem_orthogonal' _ _).1 h _ v.2
/-- If `S` is dense and `x - y ∈ Kᗮ`, then `x = y`. -/
theorem eq_of_sub_mem_orthogonal (hK : Dense (K : Set E)) (h : x - y ∈ Kᗮ) : x = y :=
sub_eq_zero.1 <| eq_zero_of_mem_orthogonal hK h
theorem eq_of_inner_left (hK : Dense (K : Set E)) (h : ∀ v : K, ⟪x, v⟫ = ⟪y, v⟫) : x = y :=
hK.eq_of_sub_mem_orthogonal (Submodule.sub_mem_orthogonal_of_inner_left h)
theorem eq_of_inner_right (hK : Dense (K : Set E)) (h : ∀ v : K, ⟪(v : E), x⟫ = ⟪(v : E), y⟫) :
x = y :=
hK.eq_of_sub_mem_orthogonal (Submodule.sub_mem_orthogonal_of_inner_right h)
theorem eq_zero_of_inner_right (hK : Dense (K : Set E)) (h : ∀ v : K, ⟪(v : E), x⟫ = 0) : x = 0 :=
hK.eq_of_inner_right fun v => by rw [inner_zero_right, h v]
end Dense
namespace Submodule
variable {K}
/-- The reflection in `Kᗮ` of an element of `K` is its negation. -/
theorem reflection_mem_subspace_orthogonal_precomplement_eq_neg [K.HasOrthogonalProjection] {v : E}
(hv : v ∈ K) : Kᗮ.reflection v = -v :=
reflection_mem_subspace_orthogonalComplement_eq_neg (K.le_orthogonal_orthogonal hv)
/-- The orthogonal projection onto `(𝕜 ∙ v)ᗮ` of `v` is zero. -/
theorem orthogonalProjection_orthogonalComplement_singleton_eq_zero (v : E) :
(𝕜 ∙ v)ᗮ.orthogonalProjection v = 0 :=
orthogonalProjection_mem_subspace_orthogonal_precomplement_eq_zero
(Submodule.mem_span_singleton_self v)
/-- The reflection in `(𝕜 ∙ v)ᗮ` of `v` is `-v`. -/
theorem reflection_orthogonalComplement_singleton_eq_neg (v : E) : reflection (𝕜 ∙ v)ᗮ v = -v :=
reflection_mem_subspace_orthogonal_precomplement_eq_neg (Submodule.mem_span_singleton_self v)
theorem reflection_sub {v w : F} (h : ‖v‖ = ‖w‖) : reflection (ℝ ∙ (v - w))ᗮ v = w := by
set R : F ≃ₗᵢ[ℝ] F := reflection (ℝ ∙ v - w)ᗮ
suffices R v + R v = w + w by
apply smul_right_injective F (by norm_num : (2 : ℝ) ≠ 0)
simpa [two_smul] using this
have h₁ : R (v - w) = -(v - w) := reflection_orthogonalComplement_singleton_eq_neg (v - w)
have h₂ : R (v + w) = v + w := by
apply reflection_mem_subspace_eq_self
rw [Submodule.mem_orthogonal_singleton_iff_inner_left]
rw [real_inner_add_sub_eq_zero_iff]
exact h
convert congr_arg₂ (· + ·) h₂ h₁ using 1
· simp
· abel
variable (K)
section FiniteDimensional
open Module
variable [FiniteDimensional 𝕜 K]
@[simp]
theorem det_reflection : LinearMap.det K.reflection.toLinearMap = (-1) ^ finrank 𝕜 Kᗮ := by
by_cases hK : FiniteDimensional 𝕜 Kᗮ
swap
· rw [finrank_of_infinite_dimensional hK, pow_zero, LinearMap.det_eq_one_of_finrank_eq_zero]
exact finrank_of_infinite_dimensional fun h ↦ hK (h.finiteDimensional_submodule _)
let e := K.prodEquivOfIsCompl _ K.isCompl_orthogonal_of_completeSpace
let b := (finBasis 𝕜 K).prod (finBasis 𝕜 Kᗮ)
have : LinearMap.toMatrix b b (e.symm ∘ₗ K.reflection.toLinearMap ∘ₗ e.symm.symm) =
Matrix.fromBlocks 1 0 0 (-1) := by
ext (_ | _) (_ | _) <;>
simp [LinearMap.toMatrix_apply, b, Matrix.one_apply, Finsupp.single_apply, e, eq_comm,
reflection_mem_subspace_eq_self, reflection_mem_subspace_orthogonalComplement_eq_neg]
rw [← LinearMap.det_conj _ e.symm, ← LinearMap.det_toMatrix b, this, Matrix.det_fromBlocks_zero₂₁,
Matrix.det_one, one_mul, Matrix.det_neg, Fintype.card_fin, Matrix.det_one, mul_one]
@[simp]
theorem linearEquiv_det_reflection : K.reflection.det = (-1) ^ finrank 𝕜 Kᗮ := by
ext
rw [LinearEquiv.coe_det, Units.val_pow_eq_pow_val]
exact K.det_reflection
end FiniteDimensional
/-- If the orthogonal projection to `K` is well-defined, then a vector splits as the sum of its
orthogonal projections onto a complete submodule `K` and onto the orthogonal complement of `K`. -/
theorem orthogonalProjection_add_orthogonalProjection_orthogonal [K.HasOrthogonalProjection]
(w : E) : (K.orthogonalProjection w : E) + (Kᗮ.orthogonalProjection w : E) = w := by
simp
/-- The Pythagorean theorem, for an orthogonal projection. -/
theorem norm_sq_eq_add_norm_sq_projection (x : E) (S : Submodule 𝕜 E) [S.HasOrthogonalProjection] :
‖x‖ ^ 2 = ‖S.orthogonalProjection x‖ ^ 2 + ‖Sᗮ.orthogonalProjection x‖ ^ 2 :=
calc
‖x‖ ^ 2 = ‖(S.orthogonalProjection x : E) + Sᗮ.orthogonalProjection x‖ ^ 2 := by
rw [orthogonalProjection_add_orthogonalProjection_orthogonal]
_ = ‖S.orthogonalProjection x‖ ^ 2 + ‖Sᗮ.orthogonalProjection x‖ ^ 2 := by
simp only [sq]
exact norm_add_sq_eq_norm_sq_add_norm_sq_of_inner_eq_zero _ _ <|
(S.mem_orthogonal _).1 (Sᗮ.orthogonalProjection x).2 _ (S.orthogonalProjection x).2
/-- In a complete space `E`, the projection maps onto a complete subspace `K` and its orthogonal
complement sum to the identity. -/
theorem id_eq_sum_orthogonalProjection_self_orthogonalComplement [K.HasOrthogonalProjection] :
ContinuousLinearMap.id 𝕜 E =
K.subtypeL.comp K.orthogonalProjection + Kᗮ.subtypeL.comp Kᗮ.orthogonalProjection := by
ext w
exact (K.orthogonalProjection_add_orthogonalProjection_orthogonal w).symm
-- Porting note: The priority should be higher than `Submodule.coe_inner`.
@[simp high]
theorem inner_orthogonalProjection_eq_of_mem_right [K.HasOrthogonalProjection] (u : K) (v : E) :
⟪K.orthogonalProjection v, u⟫ = ⟪v, u⟫ :=
calc
⟪K.orthogonalProjection v, u⟫ = ⟪(K.orthogonalProjection v : E), u⟫ := K.coe_inner _ _
_ = ⟪(K.orthogonalProjection v : E), u⟫ + ⟪v - K.orthogonalProjection v, u⟫ := by
rw [orthogonalProjection_inner_eq_zero _ _ (Submodule.coe_mem _), add_zero]
_ = ⟪v, u⟫ := by rw [← inner_add_left, add_sub_cancel]
| -- Porting note: The priority should be higher than `Submodule.coe_inner`.
@[simp high]
theorem inner_orthogonalProjection_eq_of_mem_left [K.HasOrthogonalProjection] (u : K) (v : E) :
| Mathlib/Analysis/InnerProductSpace/Projection.lean | 1,052 | 1,054 |
/-
Copyright (c) 2015 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Leonardo de Moura
-/
import Mathlib.Data.Stream.Defs
import Mathlib.Logic.Function.Basic
import Mathlib.Data.List.Defs
import Mathlib.Data.Nat.Basic
import Mathlib.Tactic.Common
/-!
# Streams a.k.a. infinite lists a.k.a. infinite sequences
-/
open Nat Function Option
namespace Stream'
universe u v w
variable {α : Type u} {β : Type v} {δ : Type w}
variable (m n : ℕ) (x y : List α) (a b : Stream' α)
instance [Inhabited α] : Inhabited (Stream' α) :=
⟨Stream'.const default⟩
@[simp] protected theorem eta (s : Stream' α) : head s :: tail s = s :=
funext fun i => by cases i <;> rfl
/-- Alias for `Stream'.eta` to match `List` API. -/
alias cons_head_tail := Stream'.eta
@[ext]
protected theorem ext {s₁ s₂ : Stream' α} : (∀ n, get s₁ n = get s₂ n) → s₁ = s₂ :=
fun h => funext h
@[simp]
theorem get_zero_cons (a : α) (s : Stream' α) : get (a::s) 0 = a :=
rfl
@[simp]
theorem head_cons (a : α) (s : Stream' α) : head (a::s) = a :=
rfl
@[simp]
theorem tail_cons (a : α) (s : Stream' α) : tail (a::s) = s :=
rfl
@[simp]
theorem get_drop (n m : ℕ) (s : Stream' α) : get (drop m s) n = get s (m + n) := by
rw [Nat.add_comm]
rfl
theorem tail_eq_drop (s : Stream' α) : tail s = drop 1 s :=
rfl
@[simp]
theorem drop_drop (n m : ℕ) (s : Stream' α) : drop n (drop m s) = drop (m + n) s := by
ext; simp [Nat.add_assoc]
@[simp] theorem get_tail {n : ℕ} {s : Stream' α} : s.tail.get n = s.get (n + 1) := rfl
@[simp] theorem tail_drop' {i : ℕ} {s : Stream' α} : tail (drop i s) = s.drop (i + 1) := by
ext; simp [Nat.add_comm, Nat.add_assoc, Nat.add_left_comm]
@[simp] theorem drop_tail' {i : ℕ} {s : Stream' α} : drop i (tail s) = s.drop (i + 1) := rfl
theorem tail_drop (n : ℕ) (s : Stream' α) : tail (drop n s) = drop n (tail s) := by simp
theorem get_succ (n : ℕ) (s : Stream' α) : get s (succ n) = get (tail s) n :=
rfl
@[simp]
theorem get_succ_cons (n : ℕ) (s : Stream' α) (x : α) : get (x :: s) n.succ = get s n :=
rfl
@[simp] lemma get_cons_append_zero {a : α} {x : List α} {s : Stream' α} :
(a :: x ++ₛ s).get 0 = a := rfl
@[simp] lemma append_eq_cons {a : α} {as : Stream' α} : [a] ++ₛ as = a :: as := by rfl
@[simp] theorem drop_zero {s : Stream' α} : s.drop 0 = s := rfl
theorem drop_succ (n : ℕ) (s : Stream' α) : drop (succ n) s = drop n (tail s) :=
rfl
theorem head_drop (a : Stream' α) (n : ℕ) : (a.drop n).head = a.get n := by simp
theorem cons_injective2 : Function.Injective2 (cons : α → Stream' α → Stream' α) := fun x y s t h =>
⟨by rw [← get_zero_cons x s, h, get_zero_cons],
Stream'.ext fun n => by rw [← get_succ_cons n _ x, h, get_succ_cons]⟩
theorem cons_injective_left (s : Stream' α) : Function.Injective fun x => cons x s :=
cons_injective2.left _
theorem cons_injective_right (x : α) : Function.Injective (cons x) :=
cons_injective2.right _
theorem all_def (p : α → Prop) (s : Stream' α) : All p s = ∀ n, p (get s n) :=
rfl
theorem any_def (p : α → Prop) (s : Stream' α) : Any p s = ∃ n, p (get s n) :=
rfl
@[simp]
theorem mem_cons (a : α) (s : Stream' α) : a ∈ a::s :=
Exists.intro 0 rfl
theorem mem_cons_of_mem {a : α} {s : Stream' α} (b : α) : a ∈ s → a ∈ b::s := fun ⟨n, h⟩ =>
Exists.intro (succ n) (by rw [get_succ, tail_cons, h])
theorem eq_or_mem_of_mem_cons {a b : α} {s : Stream' α} : (a ∈ b::s) → a = b ∨ a ∈ s :=
fun ⟨n, h⟩ => by
rcases n with - | n'
· left
exact h
· right
rw [get_succ, tail_cons] at h
exact ⟨n', h⟩
theorem mem_of_get_eq {n : ℕ} {s : Stream' α} {a : α} : a = get s n → a ∈ s := fun h =>
Exists.intro n h
section Map
variable (f : α → β)
theorem drop_map (n : ℕ) (s : Stream' α) : drop n (map f s) = map f (drop n s) :=
Stream'.ext fun _ => rfl
@[simp]
theorem get_map (n : ℕ) (s : Stream' α) : get (map f s) n = f (get s n) :=
rfl
theorem tail_map (s : Stream' α) : tail (map f s) = map f (tail s) := rfl
@[simp]
theorem head_map (s : Stream' α) : head (map f s) = f (head s) :=
rfl
theorem map_eq (s : Stream' α) : map f s = f (head s)::map f (tail s) := by
rw [← Stream'.eta (map f s), tail_map, head_map]
theorem map_cons (a : α) (s : Stream' α) : map f (a::s) = f a::map f s := by
rw [← Stream'.eta (map f (a::s)), map_eq]; rfl
@[simp]
theorem map_id (s : Stream' α) : map id s = s :=
rfl
@[simp]
theorem map_map (g : β → δ) (f : α → β) (s : Stream' α) : map g (map f s) = map (g ∘ f) s :=
rfl
@[simp]
theorem map_tail (s : Stream' α) : map f (tail s) = tail (map f s) :=
rfl
theorem mem_map {a : α} {s : Stream' α} : a ∈ s → f a ∈ map f s := fun ⟨n, h⟩ =>
Exists.intro n (by rw [get_map, h])
theorem exists_of_mem_map {f} {b : β} {s : Stream' α} : b ∈ map f s → ∃ a, a ∈ s ∧ f a = b :=
fun ⟨n, h⟩ => ⟨get s n, ⟨n, rfl⟩, h.symm⟩
end Map
section Zip
variable (f : α → β → δ)
theorem drop_zip (n : ℕ) (s₁ : Stream' α) (s₂ : Stream' β) :
drop n (zip f s₁ s₂) = zip f (drop n s₁) (drop n s₂) :=
Stream'.ext fun _ => rfl
@[simp]
theorem get_zip (n : ℕ) (s₁ : Stream' α) (s₂ : Stream' β) :
get (zip f s₁ s₂) n = f (get s₁ n) (get s₂ n) :=
rfl
theorem head_zip (s₁ : Stream' α) (s₂ : Stream' β) : head (zip f s₁ s₂) = f (head s₁) (head s₂) :=
rfl
theorem tail_zip (s₁ : Stream' α) (s₂ : Stream' β) :
tail (zip f s₁ s₂) = zip f (tail s₁) (tail s₂) :=
rfl
theorem zip_eq (s₁ : Stream' α) (s₂ : Stream' β) :
zip f s₁ s₂ = f (head s₁) (head s₂)::zip f (tail s₁) (tail s₂) := by
rw [← Stream'.eta (zip f s₁ s₂)]; rfl
@[simp]
theorem get_enum (s : Stream' α) (n : ℕ) : get (enum s) n = (n, s.get n) :=
rfl
theorem enum_eq_zip (s : Stream' α) : enum s = zip Prod.mk nats s :=
rfl
end Zip
@[simp]
theorem mem_const (a : α) : a ∈ const a :=
Exists.intro 0 rfl
theorem const_eq (a : α) : const a = a::const a := by
apply Stream'.ext; intro n
cases n <;> rfl
@[simp]
theorem tail_const (a : α) : tail (const a) = const a :=
suffices tail (a::const a) = const a by rwa [← const_eq] at this
rfl
@[simp]
theorem map_const (f : α → β) (a : α) : map f (const a) = const (f a) :=
rfl
@[simp]
theorem get_const (n : ℕ) (a : α) : get (const a) n = a :=
rfl
@[simp]
theorem drop_const (n : ℕ) (a : α) : drop n (const a) = const a :=
Stream'.ext fun _ => rfl
@[simp]
theorem head_iterate (f : α → α) (a : α) : head (iterate f a) = a :=
rfl
theorem get_succ_iterate' (n : ℕ) (f : α → α) (a : α) :
get (iterate f a) (succ n) = f (get (iterate f a) n) := rfl
theorem tail_iterate (f : α → α) (a : α) : tail (iterate f a) = iterate f (f a) := by
ext n
rw [get_tail]
induction' n with n' ih
· rfl
· rw [get_succ_iterate', ih, get_succ_iterate']
theorem iterate_eq (f : α → α) (a : α) : iterate f a = a::iterate f (f a) := by
rw [← Stream'.eta (iterate f a)]
rw [tail_iterate]; rfl
@[simp]
theorem get_zero_iterate (f : α → α) (a : α) : get (iterate f a) 0 = a :=
rfl
theorem get_succ_iterate (n : ℕ) (f : α → α) (a : α) :
get (iterate f a) (succ n) = get (iterate f (f a)) n := by rw [get_succ, tail_iterate]
section Bisim
variable (R : Stream' α → Stream' α → Prop)
/-- equivalence relation -/
local infixl:50 " ~ " => R
/-- Streams `s₁` and `s₂` are defined to be bisimulations if
their heads are equal and tails are bisimulations. -/
def IsBisimulation :=
∀ ⦃s₁ s₂⦄, s₁ ~ s₂ →
head s₁ = head s₂ ∧ tail s₁ ~ tail s₂
theorem get_of_bisim (bisim : IsBisimulation R) {s₁ s₂} :
∀ n, s₁ ~ s₂ → get s₁ n = get s₂ n ∧ drop (n + 1) s₁ ~ drop (n + 1) s₂
| 0, h => bisim h
| n + 1, h =>
match bisim h with
| ⟨_, trel⟩ => get_of_bisim bisim n trel
-- If two streams are bisimilar, then they are equal
theorem eq_of_bisim (bisim : IsBisimulation R) {s₁ s₂} : s₁ ~ s₂ → s₁ = s₂ := fun r =>
Stream'.ext fun n => And.left (get_of_bisim R bisim n r)
end Bisim
theorem bisim_simple (s₁ s₂ : Stream' α) :
head s₁ = head s₂ → s₁ = tail s₁ → s₂ = tail s₂ → s₁ = s₂ := fun hh ht₁ ht₂ =>
eq_of_bisim (fun s₁ s₂ => head s₁ = head s₂ ∧ s₁ = tail s₁ ∧ s₂ = tail s₂)
(fun s₁ s₂ ⟨h₁, h₂, h₃⟩ => by
constructor
· exact h₁
| rw [← h₂, ← h₃]
(repeat' constructor) <;> assumption)
(And.intro hh (And.intro ht₁ ht₂))
| Mathlib/Data/Stream/Init.lean | 282 | 284 |
/-
Copyright (c) 2020 Yury Kudryashov. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yury Kudryashov, Patrick Massot
-/
import Mathlib.Data.Set.Function
import Mathlib.Order.Interval.Set.OrdConnected
/-!
# Projection of a line onto a closed interval
Given a linearly ordered type `α`, in this file we define
* `Set.projIci (a : α)` to be the map `α → [a, ∞)` sending `(-∞, a]` to `a`, and each point
`x ∈ [a, ∞)` to itself;
* `Set.projIic (b : α)` to be the map `α → (-∞, b[` sending `[b, ∞)` to `b`, and each point
`x ∈ (-∞, b]` to itself;
* `Set.projIcc (a b : α) (h : a ≤ b)` to be the map `α → [a, b]` sending `(-∞, a]` to `a`, `[b, ∞)`
to `b`, and each point `x ∈ [a, b]` to itself;
* `Set.IccExtend {a b : α} (h : a ≤ b) (f : Icc a b → β)` to be the extension of `f` to `α` defined
as `f ∘ projIcc a b h`.
* `Set.IciExtend {a : α} (f : Ici a → β)` to be the extension of `f` to `α` defined
as `f ∘ projIci a`.
* `Set.IicExtend {b : α} (f : Iic b → β)` to be the extension of `f` to `α` defined
as `f ∘ projIic b`.
We also prove some trivial properties of these maps.
-/
variable {α β : Type*} [LinearOrder α]
open Function
namespace Set
/-- Projection of `α` to the closed interval `[a, ∞)`. -/
def projIci (a x : α) : Ici a := ⟨max a x, le_max_left _ _⟩
/-- Projection of `α` to the closed interval `(-∞, b]`. -/
def projIic (b x : α) : Iic b := ⟨min b x, min_le_left _ _⟩
/-- Projection of `α` to the closed interval `[a, b]`. -/
def projIcc (a b : α) (h : a ≤ b) (x : α) : Icc a b :=
⟨max a (min b x), le_max_left _ _, max_le h (min_le_left _ _)⟩
variable {a b : α} (h : a ≤ b) {x : α}
@[norm_cast]
theorem coe_projIci (a x : α) : (projIci a x : α) = max a x := rfl
@[norm_cast]
theorem coe_projIic (b x : α) : (projIic b x : α) = min b x := rfl
@[norm_cast]
theorem coe_projIcc (a b : α) (h : a ≤ b) (x : α) : (projIcc a b h x : α) = max a (min b x) := rfl
theorem projIci_of_le (hx : x ≤ a) : projIci a x = ⟨a, le_rfl⟩ := Subtype.ext <| max_eq_left hx
theorem projIic_of_le (hx : b ≤ x) : projIic b x = ⟨b, le_rfl⟩ := Subtype.ext <| min_eq_left hx
theorem projIcc_of_le_left (hx : x ≤ a) : projIcc a b h x = ⟨a, left_mem_Icc.2 h⟩ := by
simp [projIcc, hx, hx.trans h]
theorem projIcc_of_right_le (hx : b ≤ x) : projIcc a b h x = ⟨b, right_mem_Icc.2 h⟩ := by
simp [projIcc, hx, h]
@[simp]
theorem projIci_self (a : α) : projIci a a = ⟨a, le_rfl⟩ := projIci_of_le le_rfl
@[simp]
theorem projIic_self (b : α) : projIic b b = ⟨b, le_rfl⟩ := projIic_of_le le_rfl
@[simp]
theorem projIcc_left : projIcc a b h a = ⟨a, left_mem_Icc.2 h⟩ :=
projIcc_of_le_left h le_rfl
@[simp]
theorem projIcc_right : projIcc a b h b = ⟨b, right_mem_Icc.2 h⟩ :=
projIcc_of_right_le h le_rfl
theorem projIci_eq_self : projIci a x = ⟨a, le_rfl⟩ ↔ x ≤ a := by simp [projIci, Subtype.ext_iff]
theorem projIic_eq_self : projIic b x = ⟨b, le_rfl⟩ ↔ b ≤ x := by simp [projIic, Subtype.ext_iff]
theorem projIcc_eq_left (h : a < b) : projIcc a b h.le x = ⟨a, left_mem_Icc.mpr h.le⟩ ↔ x ≤ a := by
simp [projIcc, Subtype.ext_iff, h.not_le]
theorem projIcc_eq_right (h : a < b) : projIcc a b h.le x = ⟨b, right_mem_Icc.2 h.le⟩ ↔ b ≤ x := by
simp [projIcc, Subtype.ext_iff, max_min_distrib_left, h.le, h.not_le]
theorem projIci_of_mem (hx : x ∈ Ici a) : projIci a x = ⟨x, hx⟩ := by simpa [projIci]
theorem projIic_of_mem (hx : x ∈ Iic b) : projIic b x = ⟨x, hx⟩ := by simpa [projIic]
theorem projIcc_of_mem (hx : x ∈ Icc a b) : projIcc a b h x = ⟨x, hx⟩ := by
simp [projIcc, hx.1, hx.2]
@[simp]
theorem projIci_coe (x : Ici a) : projIci a x = x := by cases x; apply projIci_of_mem
@[simp]
theorem projIic_coe (x : Iic b) : projIic b x = x := by cases x; apply projIic_of_mem
@[simp]
theorem projIcc_val (x : Icc a b) : projIcc a b h x = x := by
cases x
apply projIcc_of_mem
theorem projIci_surjOn : SurjOn (projIci a) (Ici a) univ := fun x _ => ⟨x, x.2, projIci_coe x⟩
theorem projIic_surjOn : SurjOn (projIic b) (Iic b) univ := fun x _ => ⟨x, x.2, projIic_coe x⟩
theorem projIcc_surjOn : SurjOn (projIcc a b h) (Icc a b) univ := fun x _ =>
⟨x, x.2, projIcc_val h x⟩
theorem projIci_surjective : Surjective (projIci a) := fun x => ⟨x, projIci_coe x⟩
theorem projIic_surjective : Surjective (projIic b) := fun x => ⟨x, projIic_coe x⟩
theorem projIcc_surjective : Surjective (projIcc a b h) := fun x => ⟨x, projIcc_val h x⟩
@[simp]
theorem range_projIci : range (projIci a) = univ := projIci_surjective.range_eq
@[simp]
theorem range_projIic : range (projIic a) = univ := projIic_surjective.range_eq
@[simp]
theorem range_projIcc : range (projIcc a b h) = univ :=
(projIcc_surjective h).range_eq
theorem monotone_projIci : Monotone (projIci a) := fun _ _ => max_le_max le_rfl
theorem monotone_projIic : Monotone (projIic a) := fun _ _ => min_le_min le_rfl
theorem monotone_projIcc : Monotone (projIcc a b h) := fun _ _ hxy =>
max_le_max le_rfl <| min_le_min le_rfl hxy
theorem strictMonoOn_projIci : StrictMonoOn (projIci a) (Ici a) := fun x hx y hy hxy => by
simpa only [projIci_of_mem, hx, hy]
theorem strictMonoOn_projIic : StrictMonoOn (projIic b) (Iic b) := fun x hx y hy hxy => by
simpa only [projIic_of_mem, hx, hy]
theorem strictMonoOn_projIcc : StrictMonoOn (projIcc a b h) (Icc a b) := fun x hx y hy hxy => by
simpa only [projIcc_of_mem, hx, hy]
/-- Extend a function `[a, ∞) → β` to a map `α → β`. -/
def IciExtend (f : Ici a → β) : α → β :=
f ∘ projIci a
/-- Extend a function `(-∞, b] → β` to a map `α → β`. -/
def IicExtend (f : Iic b → β) : α → β :=
f ∘ projIic b
/-- Extend a function `[a, b] → β` to a map `α → β`. -/
def IccExtend {a b : α} (h : a ≤ b) (f : Icc a b → β) : α → β :=
f ∘ projIcc a b h
theorem IciExtend_apply (f : Ici a → β) (x : α) : IciExtend f x = f ⟨max a x, le_max_left _ _⟩ :=
rfl
theorem IicExtend_apply (f : Iic b → β) (x : α) : IicExtend f x = f ⟨min b x, min_le_left _ _⟩ :=
rfl
theorem IccExtend_apply (h : a ≤ b) (f : Icc a b → β) (x : α) :
IccExtend h f x = f ⟨max a (min b x), le_max_left _ _, max_le h (min_le_left _ _)⟩ := rfl
@[simp]
theorem range_IciExtend (f : Ici a → β) : range (IciExtend f) = range f := by
simp only [IciExtend, range_comp f, range_projIci, range_id', image_univ]
@[simp]
theorem range_IicExtend (f : Iic b → β) : range (IicExtend f) = range f := by
simp only [IicExtend, range_comp f, range_projIic, range_id', image_univ]
@[simp]
theorem IccExtend_range (f : Icc a b → β) : range (IccExtend h f) = range f := by
simp only [IccExtend, range_comp f, range_projIcc, image_univ]
theorem IciExtend_of_le (f : Ici a → β) (hx : x ≤ a) : IciExtend f x = f ⟨a, le_rfl⟩ :=
congr_arg f <| projIci_of_le hx
theorem IicExtend_of_le (f : Iic b → β) (hx : b ≤ x) : IicExtend f x = f ⟨b, le_rfl⟩ :=
congr_arg f <| projIic_of_le hx
|
theorem IccExtend_of_le_left (f : Icc a b → β) (hx : x ≤ a) :
| Mathlib/Order/Interval/Set/ProjIcc.lean | 187 | 188 |
/-
Copyright (c) 2022 Xavier Roblot. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Alex J. Best, Xavier Roblot
-/
import Mathlib.Algebra.Algebra.Hom.Rat
import Mathlib.Analysis.Complex.Polynomial.Basic
import Mathlib.NumberTheory.NumberField.Norm
import Mathlib.RingTheory.RootsOfUnity.PrimitiveRoots
import Mathlib.Topology.Instances.Complex
/-!
# Embeddings of number fields
This file defines the embeddings of a number field into an algebraic closed field.
## Main Definitions and Results
* `NumberField.Embeddings.range_eval_eq_rootSet_minpoly`: let `x ∈ K` with `K` number field and
let `A` be an algebraic closed field of char. 0, then the images of `x` by the embeddings of `K`
in `A` are exactly the roots in `A` of the minimal polynomial of `x` over `ℚ`.
* `NumberField.Embeddings.pow_eq_one_of_norm_eq_one`: an algebraic integer whose conjugates are
all of norm one is a root of unity.
* `NumberField.InfinitePlace`: the type of infinite places of a number field `K`.
* `NumberField.InfinitePlace.mk_eq_iff`: two complex embeddings define the same infinite place iff
they are equal or complex conjugates.
* `NumberField.InfinitePlace.prod_eq_abs_norm`: the infinite part of the product formula, that is
for `x ∈ K`, we have `Π_w ‖x‖_w = |norm(x)|` where the product is over the infinite place `w` and
`‖·‖_w` is the normalized absolute value for `w`.
## Tags
number field, embeddings, places, infinite places
-/
open scoped Finset
namespace NumberField.Embeddings
section Fintype
open Module
variable (K : Type*) [Field K] [NumberField K]
variable (A : Type*) [Field A] [CharZero A]
/-- There are finitely many embeddings of a number field. -/
noncomputable instance : Fintype (K →+* A) :=
Fintype.ofEquiv (K →ₐ[ℚ] A) RingHom.equivRatAlgHom.symm
variable [IsAlgClosed A]
/-- The number of embeddings of a number field is equal to its finrank. -/
theorem card : Fintype.card (K →+* A) = finrank ℚ K := by
rw [Fintype.ofEquiv_card RingHom.equivRatAlgHom.symm, AlgHom.card]
instance : Nonempty (K →+* A) := by
rw [← Fintype.card_pos_iff, NumberField.Embeddings.card K A]
exact Module.finrank_pos
end Fintype
section Roots
open Set Polynomial
variable (K A : Type*) [Field K] [NumberField K] [Field A] [Algebra ℚ A] [IsAlgClosed A] (x : K)
/-- Let `A` be an algebraically closed field and let `x ∈ K`, with `K` a number field.
The images of `x` by the embeddings of `K` in `A` are exactly the roots in `A` of
the minimal polynomial of `x` over `ℚ`. -/
theorem range_eval_eq_rootSet_minpoly :
(range fun φ : K →+* A => φ x) = (minpoly ℚ x).rootSet A := by
convert (NumberField.isAlgebraic K).range_eval_eq_rootSet_minpoly A x using 1
ext a
exact ⟨fun ⟨φ, hφ⟩ => ⟨φ.toRatAlgHom, hφ⟩, fun ⟨φ, hφ⟩ => ⟨φ.toRingHom, hφ⟩⟩
end Roots
section Bounded
open Module Polynomial Set
variable {K : Type*} [Field K] [NumberField K]
variable {A : Type*} [NormedField A] [IsAlgClosed A] [NormedAlgebra ℚ A]
theorem coeff_bdd_of_norm_le {B : ℝ} {x : K} (h : ∀ φ : K →+* A, ‖φ x‖ ≤ B) (i : ℕ) :
‖(minpoly ℚ x).coeff i‖ ≤ max B 1 ^ finrank ℚ K * (finrank ℚ K).choose (finrank ℚ K / 2) := by
have hx := Algebra.IsSeparable.isIntegral ℚ x
rw [← norm_algebraMap' A, ← coeff_map (algebraMap ℚ A)]
refine coeff_bdd_of_roots_le _ (minpoly.monic hx)
(IsAlgClosed.splits_codomain _) (minpoly.natDegree_le x) (fun z hz => ?_) i
classical
rw [← Multiset.mem_toFinset] at hz
obtain ⟨φ, rfl⟩ := (range_eval_eq_rootSet_minpoly K A x).symm.subset hz
exact h φ
variable (K A)
/-- Let `B` be a real number. The set of algebraic integers in `K` whose conjugates are all
smaller in norm than `B` is finite. -/
theorem finite_of_norm_le (B : ℝ) : {x : K | IsIntegral ℤ x ∧ ∀ φ : K →+* A, ‖φ x‖ ≤ B}.Finite := by
classical
let C := Nat.ceil (max B 1 ^ finrank ℚ K * (finrank ℚ K).choose (finrank ℚ K / 2))
have := bUnion_roots_finite (algebraMap ℤ K) (finrank ℚ K) (finite_Icc (-C : ℤ) C)
refine this.subset fun x hx => ?_; simp_rw [mem_iUnion]
have h_map_ℚ_minpoly := minpoly.isIntegrallyClosed_eq_field_fractions' ℚ hx.1
refine ⟨_, ⟨?_, fun i => ?_⟩, mem_rootSet.2 ⟨minpoly.ne_zero hx.1, minpoly.aeval ℤ x⟩⟩
· rw [← (minpoly.monic hx.1).natDegree_map (algebraMap ℤ ℚ), ← h_map_ℚ_minpoly]
exact minpoly.natDegree_le x
rw [mem_Icc, ← abs_le, ← @Int.cast_le ℝ]
refine (Eq.trans_le ?_ <| coeff_bdd_of_norm_le hx.2 i).trans (Nat.le_ceil _)
rw [h_map_ℚ_minpoly, coeff_map, eq_intCast, Int.norm_cast_rat, Int.norm_eq_abs, Int.cast_abs]
/-- An algebraic integer whose conjugates are all of norm one is a root of unity. -/
theorem pow_eq_one_of_norm_eq_one {x : K} (hxi : IsIntegral ℤ x) (hx : ∀ φ : K →+* A, ‖φ x‖ = 1) :
∃ (n : ℕ) (_ : 0 < n), x ^ n = 1 := by
obtain ⟨a, -, b, -, habne, h⟩ :=
@Set.Infinite.exists_ne_map_eq_of_mapsTo _ _ _ _ (x ^ · : ℕ → K) Set.infinite_univ
(by exact fun a _ => ⟨hxi.pow a, fun φ => by simp [hx φ]⟩) (finite_of_norm_le K A (1 : ℝ))
wlog hlt : b < a
· exact this K A hxi hx b a habne.symm h.symm (habne.lt_or_lt.resolve_right hlt)
refine ⟨a - b, tsub_pos_of_lt hlt, ?_⟩
rw [← Nat.sub_add_cancel hlt.le, pow_add, mul_left_eq_self₀] at h
refine h.resolve_right fun hp => ?_
specialize hx (IsAlgClosed.lift (R := ℚ)).toRingHom
rw [pow_eq_zero hp, map_zero, norm_zero] at hx; norm_num at hx
end Bounded
end NumberField.Embeddings
section Place
variable {K : Type*} [Field K] {A : Type*} [NormedDivisionRing A] [Nontrivial A] (φ : K →+* A)
/-- An embedding into a normed division ring defines a place of `K` -/
def NumberField.place : AbsoluteValue K ℝ :=
(IsAbsoluteValue.toAbsoluteValue (norm : A → ℝ)).comp φ.injective
@[simp]
theorem NumberField.place_apply (x : K) : (NumberField.place φ) x = norm (φ x) := rfl
end Place
namespace NumberField.ComplexEmbedding
open Complex NumberField
open scoped ComplexConjugate
variable {K : Type*} [Field K] {k : Type*} [Field k]
variable (K) in
/--
A (random) lift of the complex embedding `φ : k →+* ℂ` to an extension `K` of `k`.
-/
noncomputable def lift [Algebra k K] [Algebra.IsAlgebraic k K] (φ : k →+* ℂ) : K →+* ℂ := by
letI := φ.toAlgebra
exact (IsAlgClosed.lift (R := k)).toRingHom
@[simp]
theorem lift_comp_algebraMap [Algebra k K] [Algebra.IsAlgebraic k K] (φ : k →+* ℂ) :
(lift K φ).comp (algebraMap k K) = φ := by
unfold lift
letI := φ.toAlgebra
rw [AlgHom.toRingHom_eq_coe, AlgHom.comp_algebraMap_of_tower, RingHom.algebraMap_toAlgebra']
@[simp]
theorem lift_algebraMap_apply [Algebra k K] [Algebra.IsAlgebraic k K] (φ : k →+* ℂ) (x : k) :
lift K φ (algebraMap k K x) = φ x :=
RingHom.congr_fun (lift_comp_algebraMap φ) x
/-- The conjugate of a complex embedding as a complex embedding. -/
abbrev conjugate (φ : K →+* ℂ) : K →+* ℂ := star φ
@[simp]
theorem conjugate_coe_eq (φ : K →+* ℂ) (x : K) : (conjugate φ) x = conj (φ x) := rfl
theorem place_conjugate (φ : K →+* ℂ) : place (conjugate φ) = place φ := by
ext; simp only [place_apply, norm_conj, conjugate_coe_eq]
/-- An embedding into `ℂ` is real if it is fixed by complex conjugation. -/
abbrev IsReal (φ : K →+* ℂ) : Prop := IsSelfAdjoint φ
theorem isReal_iff {φ : K →+* ℂ} : IsReal φ ↔ conjugate φ = φ := isSelfAdjoint_iff
theorem isReal_conjugate_iff {φ : K →+* ℂ} : IsReal (conjugate φ) ↔ IsReal φ :=
IsSelfAdjoint.star_iff
/-- A real embedding as a ring homomorphism from `K` to `ℝ` . -/
def IsReal.embedding {φ : K →+* ℂ} (hφ : IsReal φ) : K →+* ℝ where
toFun x := (φ x).re
map_one' := by simp only [map_one, one_re]
map_mul' := by
simp only [Complex.conj_eq_iff_im.mp (RingHom.congr_fun hφ _), map_mul, mul_re,
mul_zero, tsub_zero, eq_self_iff_true, forall_const]
map_zero' := by simp only [map_zero, zero_re]
map_add' := by simp only [map_add, add_re, eq_self_iff_true, forall_const]
@[simp]
theorem IsReal.coe_embedding_apply {φ : K →+* ℂ} (hφ : IsReal φ) (x : K) :
(hφ.embedding x : ℂ) = φ x := by
apply Complex.ext
· rfl
· rw [ofReal_im, eq_comm, ← Complex.conj_eq_iff_im]
exact RingHom.congr_fun hφ x
lemma IsReal.comp (f : k →+* K) {φ : K →+* ℂ} (hφ : IsReal φ) :
IsReal (φ.comp f) := by ext1 x; simpa using RingHom.congr_fun hφ (f x)
lemma isReal_comp_iff {f : k ≃+* K} {φ : K →+* ℂ} :
IsReal (φ.comp (f : k →+* K)) ↔ IsReal φ :=
⟨fun H ↦ by convert H.comp f.symm.toRingHom; ext1; simp, IsReal.comp _⟩
lemma exists_comp_symm_eq_of_comp_eq [Algebra k K] [IsGalois k K] (φ ψ : K →+* ℂ)
(h : φ.comp (algebraMap k K) = ψ.comp (algebraMap k K)) :
∃ σ : K ≃ₐ[k] K, φ.comp σ.symm = ψ := by
letI := (φ.comp (algebraMap k K)).toAlgebra
letI := φ.toAlgebra
have : IsScalarTower k K ℂ := IsScalarTower.of_algebraMap_eq' rfl
let ψ' : K →ₐ[k] ℂ := { ψ with commutes' := fun r ↦ (RingHom.congr_fun h r).symm }
use (AlgHom.restrictNormal' ψ' K).symm
ext1 x
exact AlgHom.restrictNormal_commutes ψ' K x
variable [Algebra k K] (φ : K →+* ℂ) (σ : K ≃ₐ[k] K)
/--
`IsConj φ σ` states that `σ : K ≃ₐ[k] K` is the conjugation under the embedding `φ : K →+* ℂ`.
-/
def IsConj : Prop := conjugate φ = φ.comp σ
variable {φ σ}
lemma IsConj.eq (h : IsConj φ σ) (x) : φ (σ x) = star (φ x) := RingHom.congr_fun h.symm x
lemma IsConj.ext {σ₁ σ₂ : K ≃ₐ[k] K} (h₁ : IsConj φ σ₁) (h₂ : IsConj φ σ₂) : σ₁ = σ₂ :=
AlgEquiv.ext fun x ↦ φ.injective ((h₁.eq x).trans (h₂.eq x).symm)
lemma IsConj.ext_iff {σ₁ σ₂ : K ≃ₐ[k] K} (h₁ : IsConj φ σ₁) : σ₁ = σ₂ ↔ IsConj φ σ₂ :=
⟨fun e ↦ e ▸ h₁, h₁.ext⟩
lemma IsConj.isReal_comp (h : IsConj φ σ) : IsReal (φ.comp (algebraMap k K)) := by
ext1 x
simp only [conjugate_coe_eq, RingHom.coe_comp, Function.comp_apply, ← h.eq,
starRingEnd_apply, AlgEquiv.commutes]
lemma isConj_one_iff : IsConj φ (1 : K ≃ₐ[k] K) ↔ IsReal φ := Iff.rfl
alias ⟨_, IsReal.isConjGal_one⟩ := ComplexEmbedding.isConj_one_iff
lemma IsConj.symm (hσ : IsConj φ σ) :
IsConj φ σ.symm := RingHom.ext fun x ↦ by simpa using congr_arg star (hσ.eq (σ.symm x))
lemma isConj_symm : IsConj φ σ.symm ↔ IsConj φ σ :=
⟨IsConj.symm, IsConj.symm⟩
end NumberField.ComplexEmbedding
section InfinitePlace
open NumberField
variable {k : Type*} [Field k] (K : Type*) [Field K] {F : Type*} [Field F]
/-- An infinite place of a number field `K` is a place associated to a complex embedding. -/
def NumberField.InfinitePlace := { w : AbsoluteValue K ℝ // ∃ φ : K →+* ℂ, place φ = w }
instance [NumberField K] : Nonempty (NumberField.InfinitePlace K) := Set.instNonemptyRange _
variable {K}
/-- Return the infinite place defined by a complex embedding `φ`. -/
noncomputable def NumberField.InfinitePlace.mk (φ : K →+* ℂ) : NumberField.InfinitePlace K :=
⟨place φ, ⟨φ, rfl⟩⟩
namespace NumberField.InfinitePlace
open NumberField
instance {K : Type*} [Field K] : FunLike (InfinitePlace K) K ℝ where
coe w x := w.1 x
coe_injective' _ _ h := Subtype.eq (AbsoluteValue.ext fun x => congr_fun h x)
lemma coe_apply {K : Type*} [Field K] (v : InfinitePlace K) (x : K) :
v x = v.1 x := rfl
@[ext]
lemma ext {K : Type*} [Field K] (v₁ v₂ : InfinitePlace K) (h : ∀ k, v₁ k = v₂ k) : v₁ = v₂ :=
Subtype.ext <| AbsoluteValue.ext h
instance : MonoidWithZeroHomClass (InfinitePlace K) K ℝ where
map_mul w _ _ := w.1.map_mul _ _
map_one w := w.1.map_one
map_zero w := w.1.map_zero
instance : NonnegHomClass (InfinitePlace K) K ℝ where
apply_nonneg w _ := w.1.nonneg _
@[simp]
theorem apply (φ : K →+* ℂ) (x : K) : (mk φ) x = ‖φ x‖ := rfl
/-- For an infinite place `w`, return an embedding `φ` such that `w = infinite_place φ` . -/
noncomputable def embedding (w : InfinitePlace K) : K →+* ℂ := w.2.choose
@[simp]
theorem mk_embedding (w : InfinitePlace K) : mk (embedding w) = w := Subtype.ext w.2.choose_spec
@[simp]
theorem mk_conjugate_eq (φ : K →+* ℂ) : mk (ComplexEmbedding.conjugate φ) = mk φ := by
refine DFunLike.ext _ _ (fun x => ?_)
rw [apply, apply, ComplexEmbedding.conjugate_coe_eq, Complex.norm_conj]
theorem norm_embedding_eq (w : InfinitePlace K) (x : K) :
‖(embedding w) x‖ = w x := by
nth_rewrite 2 [← mk_embedding w]
rfl
theorem eq_iff_eq (x : K) (r : ℝ) : (∀ w : InfinitePlace K, w x = r) ↔ ∀ φ : K →+* ℂ, ‖φ x‖ = r :=
⟨fun hw φ => hw (mk φ), by rintro hφ ⟨w, ⟨φ, rfl⟩⟩; exact hφ φ⟩
theorem le_iff_le (x : K) (r : ℝ) : (∀ w : InfinitePlace K, w x ≤ r) ↔ ∀ φ : K →+* ℂ, ‖φ x‖ ≤ r :=
⟨fun hw φ => hw (mk φ), by rintro hφ ⟨w, ⟨φ, rfl⟩⟩; exact hφ φ⟩
theorem pos_iff {w : InfinitePlace K} {x : K} : 0 < w x ↔ x ≠ 0 := AbsoluteValue.pos_iff w.1
@[simp]
theorem mk_eq_iff {φ ψ : K →+* ℂ} : mk φ = mk ψ ↔ φ = ψ ∨ ComplexEmbedding.conjugate φ = ψ := by
constructor
· -- We prove that the map ψ ∘ φ⁻¹ between φ(K) and ℂ is uniform continuous, thus it is either the
-- inclusion or the complex conjugation using `Complex.uniformContinuous_ringHom_eq_id_or_conj`
intro h₀
obtain ⟨j, hiφ⟩ := (φ.injective).hasLeftInverse
let ι := RingEquiv.ofLeftInverse hiφ
have hlip : LipschitzWith 1 (RingHom.comp ψ ι.symm.toRingHom) := by
change LipschitzWith 1 (ψ ∘ ι.symm)
apply LipschitzWith.of_dist_le_mul
intro x y
rw [NNReal.coe_one, one_mul, NormedField.dist_eq, Function.comp_apply, Function.comp_apply,
← map_sub, ← map_sub]
apply le_of_eq
suffices ‖φ (ι.symm (x - y))‖ = ‖ψ (ι.symm (x - y))‖ by
rw [← this, ← RingEquiv.ofLeftInverse_apply hiφ _, RingEquiv.apply_symm_apply ι _]
rfl
exact congrFun (congrArg (↑) h₀) _
cases
Complex.uniformContinuous_ringHom_eq_id_or_conj φ.fieldRange hlip.uniformContinuous with
| inl h =>
left; ext1 x
conv_rhs => rw [← hiφ x]
exact (congrFun h (ι x)).symm
| inr h =>
right; ext1 x
conv_rhs => rw [← hiφ x]
exact (congrFun h (ι x)).symm
· rintro (⟨h⟩ | ⟨h⟩)
· exact congr_arg mk h
· rw [← mk_conjugate_eq]
exact congr_arg mk h
/-- An infinite place is real if it is defined by a real embedding. -/
def IsReal (w : InfinitePlace K) : Prop := ∃ φ : K →+* ℂ, ComplexEmbedding.IsReal φ ∧ mk φ = w
/-- An infinite place is complex if it is defined by a complex (ie. not real) embedding. -/
def IsComplex (w : InfinitePlace K) : Prop := ∃ φ : K →+* ℂ, ¬ComplexEmbedding.IsReal φ ∧ mk φ = w
theorem embedding_mk_eq (φ : K →+* ℂ) :
embedding (mk φ) = φ ∨ embedding (mk φ) = ComplexEmbedding.conjugate φ := by
rw [@eq_comm _ _ φ, @eq_comm _ _ (ComplexEmbedding.conjugate φ), ← mk_eq_iff, mk_embedding]
@[simp]
theorem embedding_mk_eq_of_isReal {φ : K →+* ℂ} (h : ComplexEmbedding.IsReal φ) :
embedding (mk φ) = φ := by
have := embedding_mk_eq φ
rwa [ComplexEmbedding.isReal_iff.mp h, or_self] at this
theorem isReal_iff {w : InfinitePlace K} :
IsReal w ↔ ComplexEmbedding.IsReal (embedding w) := by
refine ⟨?_, fun h => ⟨embedding w, h, mk_embedding w⟩⟩
rintro ⟨φ, ⟨hφ, rfl⟩⟩
rwa [embedding_mk_eq_of_isReal hφ]
theorem isComplex_iff {w : InfinitePlace K} :
IsComplex w ↔ ¬ComplexEmbedding.IsReal (embedding w) := by
refine ⟨?_, fun h => ⟨embedding w, h, mk_embedding w⟩⟩
rintro ⟨φ, ⟨hφ, rfl⟩⟩
contrapose! hφ
cases mk_eq_iff.mp (mk_embedding (mk φ)) with
| inl h => rwa [h] at hφ
| inr h => rwa [← ComplexEmbedding.isReal_conjugate_iff, h] at hφ
@[simp]
theorem conjugate_embedding_eq_of_isReal {w : InfinitePlace K} (h : IsReal w) :
ComplexEmbedding.conjugate (embedding w) = embedding w :=
ComplexEmbedding.isReal_iff.mpr (isReal_iff.mp h)
@[simp]
theorem not_isReal_iff_isComplex {w : InfinitePlace K} : ¬IsReal w ↔ IsComplex w := by
rw [isComplex_iff, isReal_iff]
@[simp]
theorem not_isComplex_iff_isReal {w : InfinitePlace K} : ¬IsComplex w ↔ IsReal w := by
rw [isComplex_iff, isReal_iff, not_not]
theorem isReal_or_isComplex (w : InfinitePlace K) : IsReal w ∨ IsComplex w := by
rw [← not_isReal_iff_isComplex]; exact em _
theorem ne_of_isReal_isComplex {w w' : InfinitePlace K} (h : IsReal w) (h' : IsComplex w') :
w ≠ w' := fun h_eq ↦ not_isReal_iff_isComplex.mpr h' (h_eq ▸ h)
variable (K) in
theorem disjoint_isReal_isComplex :
Disjoint {(w : InfinitePlace K) | IsReal w} {(w : InfinitePlace K) | IsComplex w} :=
Set.disjoint_iff.2 <| fun _ hw ↦ not_isReal_iff_isComplex.2 hw.2 hw.1
/-- The real embedding associated to a real infinite place. -/
noncomputable def embedding_of_isReal {w : InfinitePlace K} (hw : IsReal w) : K →+* ℝ :=
ComplexEmbedding.IsReal.embedding (isReal_iff.mp hw)
@[simp]
theorem embedding_of_isReal_apply {w : InfinitePlace K} (hw : IsReal w) (x : K) :
((embedding_of_isReal hw) x : ℂ) = (embedding w) x :=
ComplexEmbedding.IsReal.coe_embedding_apply (isReal_iff.mp hw) x
theorem norm_embedding_of_isReal {w : InfinitePlace K} (hw : IsReal w) (x : K) :
‖embedding_of_isReal hw x‖ = w x := by
rw [← norm_embedding_eq, ← embedding_of_isReal_apply hw, Complex.norm_real]
@[simp]
theorem isReal_of_mk_isReal {φ : K →+* ℂ} (h : IsReal (mk φ)) :
ComplexEmbedding.IsReal φ := by
contrapose! h
rw [not_isReal_iff_isComplex]
exact ⟨φ, h, rfl⟩
lemma isReal_mk_iff {φ : K →+* ℂ} :
IsReal (mk φ) ↔ ComplexEmbedding.IsReal φ :=
⟨isReal_of_mk_isReal, fun H ↦ ⟨_, H, rfl⟩⟩
lemma isComplex_mk_iff {φ : K →+* ℂ} :
IsComplex (mk φ) ↔ ¬ ComplexEmbedding.IsReal φ :=
not_isReal_iff_isComplex.symm.trans isReal_mk_iff.not
@[simp]
theorem not_isReal_of_mk_isComplex {φ : K →+* ℂ} (h : IsComplex (mk φ)) :
¬ ComplexEmbedding.IsReal φ := by rwa [← isComplex_mk_iff]
open scoped Classical in
/-- The multiplicity of an infinite place, that is the number of distinct complex embeddings that
define it, see `card_filter_mk_eq`. -/
noncomputable def mult (w : InfinitePlace K) : ℕ := if (IsReal w) then 1 else 2
@[simp]
theorem mult_isReal (w : {w : InfinitePlace K // IsReal w}) :
mult w.1 = 1 := by
rw [mult, if_pos w.prop]
@[simp]
theorem mult_isComplex (w : {w : InfinitePlace K // IsComplex w}) :
mult w.1 = 2 := by
rw [mult, if_neg (not_isReal_iff_isComplex.mpr w.prop)]
theorem mult_pos {w : InfinitePlace K} : 0 < mult w := by
rw [mult]
split_ifs <;> norm_num
@[simp]
theorem mult_ne_zero {w : InfinitePlace K} : mult w ≠ 0 := ne_of_gt mult_pos
theorem mult_coe_ne_zero {w : InfinitePlace K} : (mult w : ℝ) ≠ 0 :=
Nat.cast_ne_zero.mpr mult_ne_zero
theorem one_le_mult {w : InfinitePlace K} : (1 : ℝ) ≤ mult w := by
rw [← Nat.cast_one, Nat.cast_le]
exact mult_pos
open scoped Classical in
theorem card_filter_mk_eq [NumberField K] (w : InfinitePlace K) : #{φ | mk φ = w} = mult w := by
conv_lhs =>
congr; congr; ext
rw [← mk_embedding w, mk_eq_iff, ComplexEmbedding.conjugate, star_involutive.eq_iff]
simp_rw [Finset.filter_or, Finset.filter_eq' _ (embedding w),
Finset.filter_eq' _ (ComplexEmbedding.conjugate (embedding w)),
Finset.mem_univ, ite_true, mult]
split_ifs with hw
· rw [ComplexEmbedding.isReal_iff.mp (isReal_iff.mp hw), Finset.union_idempotent,
Finset.card_singleton]
· refine Finset.card_pair ?_
| rwa [Ne, eq_comm, ← ComplexEmbedding.isReal_iff, ← isReal_iff]
open scoped Classical in
noncomputable instance NumberField.InfinitePlace.fintype [NumberField K] :
Fintype (InfinitePlace K) := Set.fintypeRange _
| Mathlib/NumberTheory/NumberField/Embeddings.lean | 487 | 492 |
/-
Copyright (c) 2023 Dagur Asgeirsson. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Dagur Asgeirsson
-/
import Mathlib.Topology.Category.Profinite.Nobeling.Basic
import Mathlib.Topology.Category.Profinite.Nobeling.Induction
import Mathlib.Topology.Category.Profinite.Nobeling.Span
import Mathlib.Topology.Category.Profinite.Nobeling.Successor
import Mathlib.Topology.Category.Profinite.Nobeling.ZeroLimit
deprecated_module (since := "2025-04-13")
| Mathlib/Topology/Category/Profinite/Nobeling.lean | 740 | 748 | |
/-
Copyright (c) 2021 Junyan Xu. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Junyan Xu
-/
import Mathlib.AlgebraicGeometry.Restrict
import Mathlib.CategoryTheory.Adjunction.Limits
import Mathlib.CategoryTheory.Adjunction.Reflective
/-!
# Adjunction between `Γ` and `Spec`
We define the adjunction `ΓSpec.adjunction : Γ ⊣ Spec` by defining the unit (`toΓSpec`,
in multiple steps in this file) and counit (done in `Spec.lean`) and checking that they satisfy
the left and right triangle identities. The constructions and proofs make use of
maps and lemmas defined and proved in structure_sheaf.lean extensively.
Notice that since the adjunction is between contravariant functors, you get to choose
one of the two categories to have arrows reversed, and it is equally valid to present
the adjunction as `Spec ⊣ Γ` (`Spec.to_LocallyRingedSpace.right_op ⊣ Γ`), in which
case the unit and the counit would switch to each other.
## Main definition
* `AlgebraicGeometry.identityToΓSpec` : The natural transformation `𝟭 _ ⟶ Γ ⋙ Spec`.
* `AlgebraicGeometry.ΓSpec.locallyRingedSpaceAdjunction` : The adjunction `Γ ⊣ Spec` from
`CommRingᵒᵖ` to `LocallyRingedSpace`.
* `AlgebraicGeometry.ΓSpec.adjunction` : The adjunction `Γ ⊣ Spec` from
`CommRingᵒᵖ` to `Scheme`.
-/
-- Explicit universe annotations were used in this file to improve performance https://github.com/leanprover-community/mathlib4/issues/12737
noncomputable section
universe u
open PrimeSpectrum
namespace AlgebraicGeometry
open Opposite
open CategoryTheory
open StructureSheaf
open Spec (structureSheaf)
open TopologicalSpace
open AlgebraicGeometry.LocallyRingedSpace
open TopCat.Presheaf
open TopCat.Presheaf.SheafCondition
namespace LocallyRingedSpace
variable (X : LocallyRingedSpace.{u})
/-- The canonical map from the underlying set to the prime spectrum of `Γ(X)`. -/
def toΓSpecFun : X → PrimeSpectrum (Γ.obj (op X)) := fun x =>
comap (X.presheaf.Γgerm x).hom (IsLocalRing.closedPoint (X.presheaf.stalk x))
theorem not_mem_prime_iff_unit_in_stalk (r : Γ.obj (op X)) (x : X) :
r ∉ (X.toΓSpecFun x).asIdeal ↔ IsUnit (X.presheaf.Γgerm x r) := by
simp [toΓSpecFun, IsLocalRing.closedPoint]
/-- The preimage of a basic open in `Spec Γ(X)` under the unit is the basic
open in `X` defined by the same element (they are equal as sets). -/
theorem toΓSpec_preimage_basicOpen_eq (r : Γ.obj (op X)) :
X.toΓSpecFun ⁻¹' basicOpen r = SetLike.coe (X.toRingedSpace.basicOpen r) := by
ext
dsimp
simp only [Set.mem_preimage, SetLike.mem_coe]
rw [X.toRingedSpace.mem_top_basicOpen]
exact not_mem_prime_iff_unit_in_stalk ..
/-- `toΓSpecFun` is continuous. -/
theorem toΓSpec_continuous : Continuous X.toΓSpecFun := by
rw [isTopologicalBasis_basic_opens.continuous_iff]
rintro _ ⟨r, rfl⟩
rw [X.toΓSpec_preimage_basicOpen_eq r]
exact (X.toRingedSpace.basicOpen r).2
/-- The canonical (bundled) continuous map from the underlying topological
space of `X` to the prime spectrum of its global sections. -/
def toΓSpecBase : X.toTopCat ⟶ Spec.topObj (Γ.obj (op X)) :=
TopCat.ofHom
{ toFun := X.toΓSpecFun
continuous_toFun := X.toΓSpec_continuous }
variable (r : Γ.obj (op X))
/-- The preimage in `X` of a basic open in `Spec Γ(X)` (as an open set). -/
abbrev toΓSpecMapBasicOpen : Opens X :=
(Opens.map X.toΓSpecBase).obj (basicOpen r)
/-- The preimage is the basic open in `X` defined by the same element `r`. -/
theorem toΓSpecMapBasicOpen_eq : X.toΓSpecMapBasicOpen r = X.toRingedSpace.basicOpen r :=
Opens.ext (X.toΓSpec_preimage_basicOpen_eq r)
/-- The map from the global sections `Γ(X)` to the sections on the (preimage of) a basic open. -/
abbrev toToΓSpecMapBasicOpen :
X.presheaf.obj (op ⊤) ⟶ X.presheaf.obj (op <| X.toΓSpecMapBasicOpen r) :=
X.presheaf.map (X.toΓSpecMapBasicOpen r).leTop.op
/-- `r` is a unit as a section on the basic open defined by `r`. -/
theorem isUnit_res_toΓSpecMapBasicOpen : IsUnit (X.toToΓSpecMapBasicOpen r r) := by
convert
(X.presheaf.map <| (eqToHom <| X.toΓSpecMapBasicOpen_eq r).op).hom.isUnit_map
(X.toRingedSpace.isUnit_res_basicOpen r)
rw [← CommRingCat.comp_apply, ← Functor.map_comp]
congr
/-- Define the sheaf hom on individual basic opens for the unit. -/
def toΓSpecCApp :
(structureSheaf <| Γ.obj <| op X).val.obj (op <| basicOpen r) ⟶
X.presheaf.obj (op <| X.toΓSpecMapBasicOpen r) :=
-- note: the explicit type annotations were not needed before
-- https://github.com/leanprover-community/mathlib4/pull/19757
CommRingCat.ofHom <|
IsLocalization.Away.lift
(R := Γ.obj (op X))
(S := (structureSheaf ↑(Γ.obj (op X))).val.obj (op (basicOpen r)))
r
(isUnit_res_toΓSpecMapBasicOpen _ r)
/-- Characterization of the sheaf hom on basic opens,
direction ← (next lemma) is used at various places, but → is not used in this file. -/
theorem toΓSpecCApp_iff
(f :
(structureSheaf <| Γ.obj <| op X).val.obj (op <| basicOpen r) ⟶
X.presheaf.obj (op <| X.toΓSpecMapBasicOpen r)) :
toOpen _ (basicOpen r) ≫ f = X.toToΓSpecMapBasicOpen r ↔ f = X.toΓSpecCApp r := by
-- Porting Note: Type class problem got stuck in `IsLocalization.Away.AwayMap.lift_comp`
-- created instance manually. This replaces the `pick_goal` tactics
have loc_inst := IsLocalization.to_basicOpen (Γ.obj (op X)) r
refine ConcreteCategory.ext_iff.trans ?_
rw [← @IsLocalization.Away.lift_comp _ _ _ _ _ _ _ r loc_inst _
(X.isUnit_res_toΓSpecMapBasicOpen r)]
--pick_goal 5; exact is_localization.to_basic_open _ r
constructor
· intro h
ext : 1
exact IsLocalization.ringHom_ext (Submonoid.powers r) h
apply congr_arg
theorem toΓSpecCApp_spec : toOpen _ (basicOpen r) ≫ X.toΓSpecCApp r = X.toToΓSpecMapBasicOpen r :=
(X.toΓSpecCApp_iff r _).2 rfl
/-- The sheaf hom on all basic opens, commuting with restrictions. -/
@[simps app]
def toΓSpecCBasicOpens :
(inducedFunctor basicOpen).op ⋙ (structureSheaf (Γ.obj (op X))).1 ⟶
(inducedFunctor basicOpen).op ⋙ ((TopCat.Sheaf.pushforward _ X.toΓSpecBase).obj X.𝒪).1 where
app r := X.toΓSpecCApp r.unop
naturality r s f := by
apply (StructureSheaf.to_basicOpen_epi (Γ.obj (op X)) r.unop).1
simp only [← Category.assoc]
rw [X.toΓSpecCApp_spec r.unop]
convert X.toΓSpecCApp_spec s.unop
symm
apply X.presheaf.map_comp
/-- The canonical morphism of sheafed spaces from `X` to the spectrum of its global sections. -/
@[simps]
def toΓSpecSheafedSpace : X.toSheafedSpace ⟶ Spec.toSheafedSpace.obj (op (Γ.obj (op X))) where
base := X.toΓSpecBase
c :=
TopCat.Sheaf.restrictHomEquivHom (structureSheaf (Γ.obj (op X))).1 _ isBasis_basic_opens
X.toΓSpecCBasicOpens
theorem toΓSpecSheafedSpace_app_eq :
X.toΓSpecSheafedSpace.c.app (op (basicOpen r)) = X.toΓSpecCApp r := by
apply TopCat.Sheaf.extend_hom_app _ _ _
-- Porting note: need a helper lemma `toΓSpecSheafedSpace_app_spec_assoc` to help compile
-- `toStalk_stalkMap_to_Γ_Spec`
@[reassoc] theorem toΓSpecSheafedSpace_app_spec (r : Γ.obj (op X)) :
toOpen (Γ.obj (op X)) (basicOpen r) ≫ X.toΓSpecSheafedSpace.c.app (op (basicOpen r)) =
X.toToΓSpecMapBasicOpen r :=
(X.toΓSpecSheafedSpace_app_eq r).symm ▸ X.toΓSpecCApp_spec r
/-- The map on stalks induced by the unit commutes with maps from `Γ(X)` to
stalks (in `Spec Γ(X)` and in `X`). -/
theorem toStalk_stalkMap_toΓSpec (x : X) :
toStalk _ _ ≫ X.toΓSpecSheafedSpace.stalkMap x = X.presheaf.Γgerm x := by
rw [PresheafedSpace.Hom.stalkMap,
← toOpen_germ _ (basicOpen (1 : Γ.obj (op X))) _ (by rw [basicOpen_one]; trivial),
← Category.assoc, Category.assoc (toOpen _ _), stalkFunctor_map_germ, ← Category.assoc,
toΓSpecSheafedSpace_app_spec, Γgerm]
erw [← stalkPushforward_germ _ _ X.presheaf ⊤]
congr 1
exact (X.toΓSpecBase _* X.presheaf).germ_res le_top.hom _ _
/-- The canonical morphism from `X` to the spectrum of its global sections. -/
@[simps! base]
def toΓSpec : X ⟶ Spec.locallyRingedSpaceObj (Γ.obj (op X)) where
__ := X.toΓSpecSheafedSpace
prop := by
intro x
let p : PrimeSpectrum (Γ.obj (op X)) := X.toΓSpecFun x
constructor
-- show stalk map is local hom ↓
let S := (structureSheaf _).presheaf.stalk p
rintro (t : S) ht
obtain ⟨⟨r, s⟩, he⟩ := IsLocalization.surj p.asIdeal.primeCompl t
dsimp at he
set t' := _
change t * t' = _ at he
apply isUnit_of_mul_isUnit_left (y := t')
rw [he]
refine IsLocalization.map_units S (⟨r, ?_⟩ : p.asIdeal.primeCompl)
apply (not_mem_prime_iff_unit_in_stalk _ _ _).mpr
rw [← toStalk_stalkMap_toΓSpec, CommRingCat.comp_apply]
erw [← he]
rw [RingHom.map_mul]
exact ht.mul <| (IsLocalization.map_units (R := Γ.obj (op X)) S s).map _
/-- On a locally ringed space `X`, the preimage of the zero locus of the prime spectrum
of `Γ(X, ⊤)` under `toΓSpec` agrees with the associated zero locus on `X`. -/
lemma toΓSpec_preimage_zeroLocus_eq {X : LocallyRingedSpace.{u}}
(s : Set (X.presheaf.obj (op ⊤))) :
X.toΓSpec.base ⁻¹' PrimeSpectrum.zeroLocus s = X.toRingedSpace.zeroLocus s := by
simp only [RingedSpace.zeroLocus]
have (i : LocallyRingedSpace.Γ.obj (op X)) (_ : i ∈ s) :
(SetLike.coe (X.toRingedSpace.basicOpen i))ᶜ =
X.toΓSpec.base ⁻¹' ((PrimeSpectrum.basicOpen i).carrier)ᶜ := by
symm
rw [Set.preimage_compl, Opens.carrier_eq_coe]
erw [X.toΓSpec_preimage_basicOpen_eq i]
erw [Set.iInter₂_congr this]
simp_rw [← Set.preimage_iInter₂, Opens.carrier_eq_coe, PrimeSpectrum.basicOpen_eq_zeroLocus_compl,
compl_compl]
rw [← PrimeSpectrum.zeroLocus_iUnion₂]
simp
theorem comp_ring_hom_ext {X : LocallyRingedSpace.{u}} {R : CommRingCat.{u}} {f : R ⟶ Γ.obj (op X)}
{β : X ⟶ Spec.locallyRingedSpaceObj R}
(w : X.toΓSpec.base ≫ (Spec.locallyRingedSpaceMap f).base = β.base)
(h :
∀ r : R,
f ≫ X.presheaf.map (homOfLE le_top : (Opens.map β.base).obj (basicOpen r) ⟶ _).op =
toOpen R (basicOpen r) ≫ β.c.app (op (basicOpen r))) :
X.toΓSpec ≫ Spec.locallyRingedSpaceMap f = β := by
ext1
refine Spec.basicOpen_hom_ext w ?_
intro r U
rw [LocallyRingedSpace.comp_c_app]
erw [toOpen_comp_comap_assoc]
rw [Category.assoc]
erw [toΓSpecSheafedSpace_app_spec, ← X.presheaf.map_comp]
exact h r
/-- `toSpecΓ _` is an isomorphism so these are mutually two-sided inverses. -/
theorem Γ_Spec_left_triangle : toSpecΓ (Γ.obj (op X)) ≫ X.toΓSpec.c.app (op ⊤) = 𝟙 _ := by
unfold toSpecΓ
rw [← toOpen_res _ (basicOpen (1 : Γ.obj (op X))) ⊤ (eqToHom basicOpen_one.symm),
Category.assoc, NatTrans.naturality, ← Category.assoc]
erw [X.toΓSpecSheafedSpace_app_spec 1, ← Functor.map_comp]
convert eqToHom_map X.presheaf _; rfl
end LocallyRingedSpace
/-- The unit as a natural transformation. -/
def identityToΓSpec : 𝟭 LocallyRingedSpace.{u} ⟶ Γ.rightOp ⋙ Spec.toLocallyRingedSpace where
app := LocallyRingedSpace.toΓSpec
naturality X Y f := by
symm
apply LocallyRingedSpace.comp_ring_hom_ext
· ext1 x
dsimp
show PrimeSpectrum.comap (f.c.app (op ⊤)).hom (X.toΓSpecFun x) = Y.toΓSpecFun (f.base x)
dsimp [toΓSpecFun]
rw [← IsLocalRing.comap_closedPoint (f.stalkMap x).hom, ←
PrimeSpectrum.comap_comp_apply, ← PrimeSpectrum.comap_comp_apply,
← CommRingCat.hom_comp, ← CommRingCat.hom_comp]
congr 3
exact (PresheafedSpace.stalkMap_germ f.1 ⊤ x trivial).symm
· intro r
rw [LocallyRingedSpace.comp_c_app, ← Category.assoc]
erw [Y.toΓSpecSheafedSpace_app_spec, f.c.naturality]
rfl
namespace ΓSpec
theorem left_triangle (X : LocallyRingedSpace) :
SpecΓIdentity.inv.app (Γ.obj (op X)) ≫ (identityToΓSpec.app X).c.app (op ⊤) = 𝟙 _ :=
X.Γ_Spec_left_triangle
/-- `SpecΓIdentity` is iso so these are mutually two-sided inverses. -/
theorem right_triangle (R : CommRingCat) :
identityToΓSpec.app (Spec.toLocallyRingedSpace.obj <| op R) ≫
Spec.toLocallyRingedSpace.map (SpecΓIdentity.inv.app R).op =
𝟙 _ := by
apply LocallyRingedSpace.comp_ring_hom_ext
· ext (p : PrimeSpectrum R)
dsimp
refine PrimeSpectrum.ext (Ideal.ext fun x => ?_)
rw [← IsLocalization.AtPrime.to_map_mem_maximal_iff ((structureSheaf R).presheaf.stalk p)
p.asIdeal x]
rfl
· intro r; apply toOpen_res
/-- The adjunction `Γ ⊣ Spec` from `CommRingᵒᵖ` to `LocallyRingedSpace`. -/
-- Porting note: `simps` generates lemmas not in `simp` normal form, so `unit` and `counit` have to
-- be added manually
def locallyRingedSpaceAdjunction : Γ.rightOp ⊣ Spec.toLocallyRingedSpace.{u} where
unit := identityToΓSpec
counit := (NatIso.op SpecΓIdentity).inv
left_triangle_components X := by
simp only [Functor.id_obj, Functor.rightOp_obj, Γ_obj, Functor.comp_obj,
Spec.toLocallyRingedSpace_obj, Spec.locallyRingedSpaceObj_toSheafedSpace,
Spec.sheafedSpaceObj_carrier, Spec.sheafedSpaceObj_presheaf, Functor.rightOp_map, Γ_map,
Quiver.Hom.unop_op, NatIso.op_inv, NatTrans.op_app, SpecΓIdentity_inv_app]
exact congr_arg Quiver.Hom.op (left_triangle X)
right_triangle_components R := by
simp only [Spec.toLocallyRingedSpace_obj, Functor.id_obj, Functor.comp_obj, Functor.rightOp_obj,
Γ_obj, Spec.locallyRingedSpaceObj_toSheafedSpace, Spec.sheafedSpaceObj_carrier,
Spec.sheafedSpaceObj_presheaf, NatIso.op_inv, NatTrans.op_app, op_unop, SpecΓIdentity_inv_app,
Spec.toLocallyRingedSpace_map, Quiver.Hom.unop_op]
exact right_triangle R.unop
| lemma locallyRingedSpaceAdjunction_unit :
locallyRingedSpaceAdjunction.unit = identityToΓSpec := rfl
lemma locallyRingedSpaceAdjunction_counit :
locallyRingedSpaceAdjunction.counit = (NatIso.op SpecΓIdentity.{u}).inv := rfl
@[simp]
lemma locallyRingedSpaceAdjunction_counit_app (R : CommRingCatᵒᵖ) :
locallyRingedSpaceAdjunction.counit.app R =
(toOpen R.unop ⊤).op := rfl
@[simp]
| Mathlib/AlgebraicGeometry/GammaSpecAdjunction.lean | 328 | 339 |
/-
Copyright (c) 2017 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl, Jeremy Avigad
-/
import Mathlib.Algebra.Group.Basic
import Mathlib.Algebra.Notation.Pi
import Mathlib.Data.Set.Lattice
import Mathlib.Order.Filter.Defs
/-!
# Theory of filters on sets
A *filter* on a type `α` is a collection of sets of `α` which contains the whole `α`,
is upwards-closed, and is stable under intersection. They are mostly used to
abstract two related kinds of ideas:
* *limits*, including finite or infinite limits of sequences, finite or infinite limits of functions
at a point or at infinity, etc...
* *things happening eventually*, including things happening for large enough `n : ℕ`, or near enough
a point `x`, or for close enough pairs of points, or things happening almost everywhere in the
sense of measure theory. Dually, filters can also express the idea of *things happening often*:
for arbitrarily large `n`, or at a point in any neighborhood of given a point etc...
## Main definitions
In this file, we endow `Filter α` it with a complete lattice structure.
This structure is lifted from the lattice structure on `Set (Set X)` using the Galois
insertion which maps a filter to its elements in one direction, and an arbitrary set of sets to
the smallest filter containing it in the other direction.
We also prove `Filter` is a monadic functor, with a push-forward operation
`Filter.map` and a pull-back operation `Filter.comap` that form a Galois connections for the
order on filters.
The examples of filters appearing in the description of the two motivating ideas are:
* `(Filter.atTop : Filter ℕ)` : made of sets of `ℕ` containing `{n | n ≥ N}` for some `N`
* `𝓝 x` : made of neighborhoods of `x` in a topological space (defined in topology.basic)
* `𝓤 X` : made of entourages of a uniform space (those space are generalizations of metric spaces
defined in `Mathlib/Topology/UniformSpace/Basic.lean`)
* `MeasureTheory.ae` : made of sets whose complement has zero measure with respect to `μ`
(defined in `Mathlib/MeasureTheory/OuterMeasure/AE`)
The predicate "happening eventually" is `Filter.Eventually`, and "happening often" is
`Filter.Frequently`, whose definitions are immediate after `Filter` is defined (but they come
rather late in this file in order to immediately relate them to the lattice structure).
## Notations
* `∀ᶠ x in f, p x` : `f.Eventually p`;
* `∃ᶠ x in f, p x` : `f.Frequently p`;
* `f =ᶠ[l] g` : `∀ᶠ x in l, f x = g x`;
* `f ≤ᶠ[l] g` : `∀ᶠ x in l, f x ≤ g x`;
* `𝓟 s` : `Filter.Principal s`, localized in `Filter`.
## References
* [N. Bourbaki, *General Topology*][bourbaki1966]
Important note: Bourbaki requires that a filter on `X` cannot contain all sets of `X`, which
we do *not* require. This gives `Filter X` better formal properties, in particular a bottom element
`⊥` for its lattice structure, at the cost of including the assumption
`[NeBot f]` in a number of lemmas and definitions.
-/
assert_not_exists OrderedSemiring Fintype
open Function Set Order
open scoped symmDiff
universe u v w x y
namespace Filter
variable {α : Type u} {f g : Filter α} {s t : Set α}
instance inhabitedMem : Inhabited { s : Set α // s ∈ f } :=
⟨⟨univ, f.univ_sets⟩⟩
theorem filter_eq_iff : f = g ↔ f.sets = g.sets :=
⟨congr_arg _, filter_eq⟩
@[simp] theorem sets_subset_sets : f.sets ⊆ g.sets ↔ g ≤ f := .rfl
@[simp] theorem sets_ssubset_sets : f.sets ⊂ g.sets ↔ g < f := .rfl
/-- An extensionality lemma that is useful for filters with good lemmas about `sᶜ ∈ f` (e.g.,
`Filter.comap`, `Filter.coprod`, `Filter.Coprod`, `Filter.cofinite`). -/
protected theorem coext (h : ∀ s, sᶜ ∈ f ↔ sᶜ ∈ g) : f = g :=
Filter.ext <| compl_surjective.forall.2 h
instance : Trans (· ⊇ ·) ((· ∈ ·) : Set α → Filter α → Prop) (· ∈ ·) where
trans h₁ h₂ := mem_of_superset h₂ h₁
instance : Trans Membership.mem (· ⊆ ·) (Membership.mem : Filter α → Set α → Prop) where
trans h₁ h₂ := mem_of_superset h₁ h₂
@[simp]
theorem inter_mem_iff {s t : Set α} : s ∩ t ∈ f ↔ s ∈ f ∧ t ∈ f :=
⟨fun h => ⟨mem_of_superset h inter_subset_left, mem_of_superset h inter_subset_right⟩,
and_imp.2 inter_mem⟩
theorem diff_mem {s t : Set α} (hs : s ∈ f) (ht : tᶜ ∈ f) : s \ t ∈ f :=
inter_mem hs ht
theorem congr_sets (h : { x | x ∈ s ↔ x ∈ t } ∈ f) : s ∈ f ↔ t ∈ f :=
⟨fun hs => mp_mem hs (mem_of_superset h fun _ => Iff.mp), fun hs =>
mp_mem hs (mem_of_superset h fun _ => Iff.mpr)⟩
lemma copy_eq {S} (hmem : ∀ s, s ∈ S ↔ s ∈ f) : f.copy S hmem = f := Filter.ext hmem
/-- Weaker version of `Filter.biInter_mem` that assumes `Subsingleton β` rather than `Finite β`. -/
theorem biInter_mem' {β : Type v} {s : β → Set α} {is : Set β} (hf : is.Subsingleton) :
(⋂ i ∈ is, s i) ∈ f ↔ ∀ i ∈ is, s i ∈ f := by
apply Subsingleton.induction_on hf <;> simp
/-- Weaker version of `Filter.iInter_mem` that assumes `Subsingleton β` rather than `Finite β`. -/
theorem iInter_mem' {β : Sort v} {s : β → Set α} [Subsingleton β] :
(⋂ i, s i) ∈ f ↔ ∀ i, s i ∈ f := by
rw [← sInter_range, sInter_eq_biInter, biInter_mem' (subsingleton_range s), forall_mem_range]
theorem exists_mem_subset_iff : (∃ t ∈ f, t ⊆ s) ↔ s ∈ f :=
⟨fun ⟨_, ht, ts⟩ => mem_of_superset ht ts, fun hs => ⟨s, hs, Subset.rfl⟩⟩
theorem monotone_mem {f : Filter α} : Monotone fun s => s ∈ f := fun _ _ hst h =>
mem_of_superset h hst
theorem exists_mem_and_iff {P : Set α → Prop} {Q : Set α → Prop} (hP : Antitone P)
(hQ : Antitone Q) : ((∃ u ∈ f, P u) ∧ ∃ u ∈ f, Q u) ↔ ∃ u ∈ f, P u ∧ Q u := by
constructor
· rintro ⟨⟨u, huf, hPu⟩, v, hvf, hQv⟩
exact
⟨u ∩ v, inter_mem huf hvf, hP inter_subset_left hPu, hQ inter_subset_right hQv⟩
· rintro ⟨u, huf, hPu, hQu⟩
exact ⟨⟨u, huf, hPu⟩, u, huf, hQu⟩
theorem forall_in_swap {β : Type*} {p : Set α → β → Prop} :
(∀ a ∈ f, ∀ (b), p a b) ↔ ∀ (b), ∀ a ∈ f, p a b :=
Set.forall_in_swap
end Filter
namespace Filter
variable {α : Type u} {β : Type v} {γ : Type w} {δ : Type*} {ι : Sort x}
theorem mem_principal_self (s : Set α) : s ∈ 𝓟 s := Subset.rfl
section Lattice
variable {f g : Filter α} {s t : Set α}
protected theorem not_le : ¬f ≤ g ↔ ∃ s ∈ g, s ∉ f := by simp_rw [le_def, not_forall, exists_prop]
/-- `GenerateSets g s`: `s` is in the filter closure of `g`. -/
inductive GenerateSets (g : Set (Set α)) : Set α → Prop
| basic {s : Set α} : s ∈ g → GenerateSets g s
| univ : GenerateSets g univ
| superset {s t : Set α} : GenerateSets g s → s ⊆ t → GenerateSets g t
| inter {s t : Set α} : GenerateSets g s → GenerateSets g t → GenerateSets g (s ∩ t)
/-- `generate g` is the largest filter containing the sets `g`. -/
def generate (g : Set (Set α)) : Filter α where
sets := {s | GenerateSets g s}
univ_sets := GenerateSets.univ
sets_of_superset := GenerateSets.superset
inter_sets := GenerateSets.inter
lemma mem_generate_of_mem {s : Set <| Set α} {U : Set α} (h : U ∈ s) :
U ∈ generate s := GenerateSets.basic h
theorem le_generate_iff {s : Set (Set α)} {f : Filter α} : f ≤ generate s ↔ s ⊆ f.sets :=
Iff.intro (fun h _ hu => h <| GenerateSets.basic <| hu) fun h _ hu =>
hu.recOn (fun h' => h h') univ_mem (fun _ hxy hx => mem_of_superset hx hxy) fun _ _ hx hy =>
inter_mem hx hy
@[simp] lemma generate_singleton (s : Set α) : generate {s} = 𝓟 s :=
le_antisymm (fun _t ht ↦ mem_of_superset (mem_generate_of_mem <| mem_singleton _) ht) <|
le_generate_iff.2 <| singleton_subset_iff.2 Subset.rfl
/-- `mkOfClosure s hs` constructs a filter on `α` whose elements set is exactly
`s : Set (Set α)`, provided one gives the assumption `hs : (generate s).sets = s`. -/
protected def mkOfClosure (s : Set (Set α)) (hs : (generate s).sets = s) : Filter α where
sets := s
univ_sets := hs ▸ univ_mem
sets_of_superset := hs ▸ mem_of_superset
inter_sets := hs ▸ inter_mem
theorem mkOfClosure_sets {s : Set (Set α)} {hs : (generate s).sets = s} :
Filter.mkOfClosure s hs = generate s :=
Filter.ext fun u =>
show u ∈ (Filter.mkOfClosure s hs).sets ↔ u ∈ (generate s).sets from hs.symm ▸ Iff.rfl
/-- Galois insertion from sets of sets into filters. -/
def giGenerate (α : Type*) :
@GaloisInsertion (Set (Set α)) (Filter α)ᵒᵈ _ _ Filter.generate Filter.sets where
gc _ _ := le_generate_iff
le_l_u _ _ h := GenerateSets.basic h
choice s hs := Filter.mkOfClosure s (le_antisymm hs <| le_generate_iff.1 <| le_rfl)
choice_eq _ _ := mkOfClosure_sets
theorem mem_inf_iff {f g : Filter α} {s : Set α} : s ∈ f ⊓ g ↔ ∃ t₁ ∈ f, ∃ t₂ ∈ g, s = t₁ ∩ t₂ :=
Iff.rfl
theorem mem_inf_of_left {f g : Filter α} {s : Set α} (h : s ∈ f) : s ∈ f ⊓ g :=
⟨s, h, univ, univ_mem, (inter_univ s).symm⟩
theorem mem_inf_of_right {f g : Filter α} {s : Set α} (h : s ∈ g) : s ∈ f ⊓ g :=
⟨univ, univ_mem, s, h, (univ_inter s).symm⟩
theorem inter_mem_inf {α : Type u} {f g : Filter α} {s t : Set α} (hs : s ∈ f) (ht : t ∈ g) :
s ∩ t ∈ f ⊓ g :=
⟨s, hs, t, ht, rfl⟩
theorem mem_inf_of_inter {f g : Filter α} {s t u : Set α} (hs : s ∈ f) (ht : t ∈ g)
(h : s ∩ t ⊆ u) : u ∈ f ⊓ g :=
mem_of_superset (inter_mem_inf hs ht) h
theorem mem_inf_iff_superset {f g : Filter α} {s : Set α} :
s ∈ f ⊓ g ↔ ∃ t₁ ∈ f, ∃ t₂ ∈ g, t₁ ∩ t₂ ⊆ s :=
⟨fun ⟨t₁, h₁, t₂, h₂, Eq⟩ => ⟨t₁, h₁, t₂, h₂, Eq ▸ Subset.rfl⟩, fun ⟨_, h₁, _, h₂, sub⟩ =>
mem_inf_of_inter h₁ h₂ sub⟩
section CompleteLattice
/-- Complete lattice structure on `Filter α`. -/
instance instCompleteLatticeFilter : CompleteLattice (Filter α) where
inf a b := min a b
sup a b := max a b
le_sup_left _ _ _ h := h.1
le_sup_right _ _ _ h := h.2
sup_le _ _ _ h₁ h₂ _ h := ⟨h₁ h, h₂ h⟩
inf_le_left _ _ _ := mem_inf_of_left
inf_le_right _ _ _ := mem_inf_of_right
le_inf := fun _ _ _ h₁ h₂ _s ⟨_a, ha, _b, hb, hs⟩ => hs.symm ▸ inter_mem (h₁ ha) (h₂ hb)
le_sSup _ _ h₁ _ h₂ := h₂ h₁
sSup_le _ _ h₁ _ h₂ _ h₃ := h₁ _ h₃ h₂
sInf_le _ _ h₁ _ h₂ := by rw [← Filter.sSup_lowerBounds]; exact fun _ h₃ ↦ h₃ h₁ h₂
le_sInf _ _ h₁ _ h₂ := by rw [← Filter.sSup_lowerBounds] at h₂; exact h₂ h₁
le_top _ _ := univ_mem'
bot_le _ _ _ := trivial
instance : Inhabited (Filter α) := ⟨⊥⟩
end CompleteLattice
theorem NeBot.ne {f : Filter α} (hf : NeBot f) : f ≠ ⊥ := hf.ne'
@[simp] theorem not_neBot {f : Filter α} : ¬f.NeBot ↔ f = ⊥ := neBot_iff.not_left
theorem NeBot.mono {f g : Filter α} (hf : NeBot f) (hg : f ≤ g) : NeBot g :=
⟨ne_bot_of_le_ne_bot hf.1 hg⟩
theorem neBot_of_le {f g : Filter α} [hf : NeBot f] (hg : f ≤ g) : NeBot g :=
hf.mono hg
@[simp] theorem sup_neBot {f g : Filter α} : NeBot (f ⊔ g) ↔ NeBot f ∨ NeBot g := by
simp only [neBot_iff, not_and_or, Ne, sup_eq_bot_iff]
theorem not_disjoint_self_iff : ¬Disjoint f f ↔ f.NeBot := by rw [disjoint_self, neBot_iff]
theorem bot_sets_eq : (⊥ : Filter α).sets = univ := rfl
/-- Either `f = ⊥` or `Filter.NeBot f`. This is a version of `eq_or_ne` that uses `Filter.NeBot`
as the second alternative, to be used as an instance. -/
theorem eq_or_neBot (f : Filter α) : f = ⊥ ∨ NeBot f := (eq_or_ne f ⊥).imp_right NeBot.mk
theorem sup_sets_eq {f g : Filter α} : (f ⊔ g).sets = f.sets ∩ g.sets :=
(giGenerate α).gc.u_inf
theorem sSup_sets_eq {s : Set (Filter α)} : (sSup s).sets = ⋂ f ∈ s, (f : Filter α).sets :=
(giGenerate α).gc.u_sInf
theorem iSup_sets_eq {f : ι → Filter α} : (iSup f).sets = ⋂ i, (f i).sets :=
(giGenerate α).gc.u_iInf
theorem generate_empty : Filter.generate ∅ = (⊤ : Filter α) :=
(giGenerate α).gc.l_bot
theorem generate_univ : Filter.generate univ = (⊥ : Filter α) :=
bot_unique fun _ _ => GenerateSets.basic (mem_univ _)
theorem generate_union {s t : Set (Set α)} :
Filter.generate (s ∪ t) = Filter.generate s ⊓ Filter.generate t :=
(giGenerate α).gc.l_sup
theorem generate_iUnion {s : ι → Set (Set α)} :
Filter.generate (⋃ i, s i) = ⨅ i, Filter.generate (s i) :=
(giGenerate α).gc.l_iSup
@[simp]
theorem mem_sup {f g : Filter α} {s : Set α} : s ∈ f ⊔ g ↔ s ∈ f ∧ s ∈ g :=
Iff.rfl
theorem union_mem_sup {f g : Filter α} {s t : Set α} (hs : s ∈ f) (ht : t ∈ g) : s ∪ t ∈ f ⊔ g :=
⟨mem_of_superset hs subset_union_left, mem_of_superset ht subset_union_right⟩
@[simp]
theorem mem_iSup {x : Set α} {f : ι → Filter α} : x ∈ iSup f ↔ ∀ i, x ∈ f i := by
simp only [← Filter.mem_sets, iSup_sets_eq, mem_iInter]
@[simp]
theorem iSup_neBot {f : ι → Filter α} : (⨆ i, f i).NeBot ↔ ∃ i, (f i).NeBot := by
simp [neBot_iff]
theorem iInf_eq_generate (s : ι → Filter α) : iInf s = generate (⋃ i, (s i).sets) :=
eq_of_forall_le_iff fun _ ↦ by simp [le_generate_iff]
theorem mem_iInf_of_mem {f : ι → Filter α} (i : ι) {s} (hs : s ∈ f i) : s ∈ ⨅ i, f i :=
iInf_le f i hs
@[simp]
theorem le_principal_iff {s : Set α} {f : Filter α} : f ≤ 𝓟 s ↔ s ∈ f :=
⟨fun h => h Subset.rfl, fun hs _ ht => mem_of_superset hs ht⟩
theorem Iic_principal (s : Set α) : Iic (𝓟 s) = { l | s ∈ l } :=
Set.ext fun _ => le_principal_iff
theorem principal_mono {s t : Set α} : 𝓟 s ≤ 𝓟 t ↔ s ⊆ t := by
simp only [le_principal_iff, mem_principal]
@[gcongr] alias ⟨_, _root_.GCongr.filter_principal_mono⟩ := principal_mono
@[mono]
theorem monotone_principal : Monotone (𝓟 : Set α → Filter α) := fun _ _ => principal_mono.2
@[simp] theorem principal_eq_iff_eq {s t : Set α} : 𝓟 s = 𝓟 t ↔ s = t := by
simp only [le_antisymm_iff, le_principal_iff, mem_principal]; rfl
@[simp] theorem join_principal_eq_sSup {s : Set (Filter α)} : join (𝓟 s) = sSup s := rfl
@[simp] theorem principal_univ : 𝓟 (univ : Set α) = ⊤ :=
top_unique <| by simp only [le_principal_iff, mem_top, eq_self_iff_true]
@[simp]
theorem principal_empty : 𝓟 (∅ : Set α) = ⊥ :=
bot_unique fun _ _ => empty_subset _
theorem generate_eq_biInf (S : Set (Set α)) : generate S = ⨅ s ∈ S, 𝓟 s :=
eq_of_forall_le_iff fun f => by simp [le_generate_iff, le_principal_iff, subset_def]
/-! ### Lattice equations -/
theorem empty_mem_iff_bot {f : Filter α} : ∅ ∈ f ↔ f = ⊥ :=
⟨fun h => bot_unique fun s _ => mem_of_superset h (empty_subset s), fun h => h.symm ▸ mem_bot⟩
theorem nonempty_of_mem {f : Filter α} [hf : NeBot f] {s : Set α} (hs : s ∈ f) : s.Nonempty :=
s.eq_empty_or_nonempty.elim (fun h => absurd hs (h.symm ▸ mt empty_mem_iff_bot.mp hf.1)) id
theorem NeBot.nonempty_of_mem {f : Filter α} (hf : NeBot f) {s : Set α} (hs : s ∈ f) : s.Nonempty :=
@Filter.nonempty_of_mem α f hf s hs
@[simp]
theorem empty_not_mem (f : Filter α) [NeBot f] : ¬∅ ∈ f := fun h => (nonempty_of_mem h).ne_empty rfl
theorem nonempty_of_neBot (f : Filter α) [NeBot f] : Nonempty α :=
nonempty_of_exists <| nonempty_of_mem (univ_mem : univ ∈ f)
theorem compl_not_mem {f : Filter α} {s : Set α} [NeBot f] (h : s ∈ f) : sᶜ ∉ f := fun hsc =>
(nonempty_of_mem (inter_mem h hsc)).ne_empty <| inter_compl_self s
theorem filter_eq_bot_of_isEmpty [IsEmpty α] (f : Filter α) : f = ⊥ :=
empty_mem_iff_bot.mp <| univ_mem' isEmptyElim
protected lemma disjoint_iff {f g : Filter α} : Disjoint f g ↔ ∃ s ∈ f, ∃ t ∈ g, Disjoint s t := by
simp only [disjoint_iff, ← empty_mem_iff_bot, mem_inf_iff, inf_eq_inter, bot_eq_empty,
@eq_comm _ ∅]
theorem disjoint_of_disjoint_of_mem {f g : Filter α} {s t : Set α} (h : Disjoint s t) (hs : s ∈ f)
(ht : t ∈ g) : Disjoint f g :=
Filter.disjoint_iff.mpr ⟨s, hs, t, ht, h⟩
theorem NeBot.not_disjoint (hf : f.NeBot) (hs : s ∈ f) (ht : t ∈ f) : ¬Disjoint s t := fun h =>
not_disjoint_self_iff.2 hf <| Filter.disjoint_iff.2 ⟨s, hs, t, ht, h⟩
theorem inf_eq_bot_iff {f g : Filter α} : f ⊓ g = ⊥ ↔ ∃ U ∈ f, ∃ V ∈ g, U ∩ V = ∅ := by
simp only [← disjoint_iff, Filter.disjoint_iff, Set.disjoint_iff_inter_eq_empty]
/-- There is exactly one filter on an empty type. -/
instance unique [IsEmpty α] : Unique (Filter α) where
default := ⊥
uniq := filter_eq_bot_of_isEmpty
theorem NeBot.nonempty (f : Filter α) [hf : f.NeBot] : Nonempty α :=
not_isEmpty_iff.mp fun _ ↦ hf.ne (Subsingleton.elim _ _)
/-- There are only two filters on a `Subsingleton`: `⊥` and `⊤`. If the type is empty, then they are
equal. -/
theorem eq_top_of_neBot [Subsingleton α] (l : Filter α) [NeBot l] : l = ⊤ := by
refine top_unique fun s hs => ?_
obtain rfl : s = univ := Subsingleton.eq_univ_of_nonempty (nonempty_of_mem hs)
exact univ_mem
theorem forall_mem_nonempty_iff_neBot {f : Filter α} :
(∀ s : Set α, s ∈ f → s.Nonempty) ↔ NeBot f :=
⟨fun h => ⟨fun hf => not_nonempty_empty (h ∅ <| hf.symm ▸ mem_bot)⟩, @nonempty_of_mem _ _⟩
instance instNeBotTop [Nonempty α] : NeBot (⊤ : Filter α) :=
forall_mem_nonempty_iff_neBot.1 fun s hs => by rwa [mem_top.1 hs, ← nonempty_iff_univ_nonempty]
instance instNontrivialFilter [Nonempty α] : Nontrivial (Filter α) :=
⟨⟨⊤, ⊥, instNeBotTop.ne⟩⟩
theorem nontrivial_iff_nonempty : Nontrivial (Filter α) ↔ Nonempty α :=
⟨fun _ =>
by_contra fun h' =>
haveI := not_nonempty_iff.1 h'
not_subsingleton (Filter α) inferInstance,
@Filter.instNontrivialFilter α⟩
theorem eq_sInf_of_mem_iff_exists_mem {S : Set (Filter α)} {l : Filter α}
(h : ∀ {s}, s ∈ l ↔ ∃ f ∈ S, s ∈ f) : l = sInf S :=
le_antisymm (le_sInf fun f hf _ hs => h.2 ⟨f, hf, hs⟩)
fun _ hs => let ⟨_, hf, hs⟩ := h.1 hs; (sInf_le hf) hs
theorem eq_iInf_of_mem_iff_exists_mem {f : ι → Filter α} {l : Filter α}
(h : ∀ {s}, s ∈ l ↔ ∃ i, s ∈ f i) : l = iInf f :=
eq_sInf_of_mem_iff_exists_mem <| h.trans (exists_range_iff (p := (_ ∈ ·))).symm
theorem eq_biInf_of_mem_iff_exists_mem {f : ι → Filter α} {p : ι → Prop} {l : Filter α}
(h : ∀ {s}, s ∈ l ↔ ∃ i, p i ∧ s ∈ f i) : l = ⨅ (i) (_ : p i), f i := by
rw [iInf_subtype']
exact eq_iInf_of_mem_iff_exists_mem fun {_} => by simp only [Subtype.exists, h, exists_prop]
theorem iInf_sets_eq {f : ι → Filter α} (h : Directed (· ≥ ·) f) [ne : Nonempty ι] :
(iInf f).sets = ⋃ i, (f i).sets :=
let ⟨i⟩ := ne
let u :=
{ sets := ⋃ i, (f i).sets
univ_sets := mem_iUnion.2 ⟨i, univ_mem⟩
sets_of_superset := by
simp only [mem_iUnion, exists_imp]
exact fun i hx hxy => ⟨i, mem_of_superset hx hxy⟩
inter_sets := by
simp only [mem_iUnion, exists_imp]
intro x y a hx b hy
rcases h a b with ⟨c, ha, hb⟩
exact ⟨c, inter_mem (ha hx) (hb hy)⟩ }
have : u = iInf f := eq_iInf_of_mem_iff_exists_mem mem_iUnion
congr_arg Filter.sets this.symm
theorem mem_iInf_of_directed {f : ι → Filter α} (h : Directed (· ≥ ·) f) [Nonempty ι] (s) :
s ∈ iInf f ↔ ∃ i, s ∈ f i := by
simp only [← Filter.mem_sets, iInf_sets_eq h, mem_iUnion]
theorem mem_biInf_of_directed {f : β → Filter α} {s : Set β} (h : DirectedOn (f ⁻¹'o (· ≥ ·)) s)
(ne : s.Nonempty) {t : Set α} : (t ∈ ⨅ i ∈ s, f i) ↔ ∃ i ∈ s, t ∈ f i := by
haveI := ne.to_subtype
simp_rw [iInf_subtype', mem_iInf_of_directed h.directed_val, Subtype.exists, exists_prop]
theorem biInf_sets_eq {f : β → Filter α} {s : Set β} (h : DirectedOn (f ⁻¹'o (· ≥ ·)) s)
(ne : s.Nonempty) : (⨅ i ∈ s, f i).sets = ⋃ i ∈ s, (f i).sets :=
ext fun t => by simp [mem_biInf_of_directed h ne]
@[simp]
theorem sup_join {f₁ f₂ : Filter (Filter α)} : join f₁ ⊔ join f₂ = join (f₁ ⊔ f₂) :=
Filter.ext fun x => by simp only [mem_sup, mem_join]
@[simp]
theorem iSup_join {ι : Sort w} {f : ι → Filter (Filter α)} : ⨆ x, join (f x) = join (⨆ x, f x) :=
Filter.ext fun x => by simp only [mem_iSup, mem_join]
instance : DistribLattice (Filter α) :=
{ Filter.instCompleteLatticeFilter with
le_sup_inf := by
intro x y z s
simp only [and_assoc, mem_inf_iff, mem_sup, exists_prop, exists_imp, and_imp]
rintro hs t₁ ht₁ t₂ ht₂ rfl
exact
⟨t₁, x.sets_of_superset hs inter_subset_left, ht₁, t₂,
x.sets_of_superset hs inter_subset_right, ht₂, rfl⟩ }
/-- If `f : ι → Filter α` is directed, `ι` is not empty, and `∀ i, f i ≠ ⊥`, then `iInf f ≠ ⊥`.
See also `iInf_neBot_of_directed` for a version assuming `Nonempty α` instead of `Nonempty ι`. -/
theorem iInf_neBot_of_directed' {f : ι → Filter α} [Nonempty ι] (hd : Directed (· ≥ ·) f) :
(∀ i, NeBot (f i)) → NeBot (iInf f) :=
not_imp_not.1 <| by simpa only [not_forall, not_neBot, ← empty_mem_iff_bot,
mem_iInf_of_directed hd] using id
/-- If `f : ι → Filter α` is directed, `α` is not empty, and `∀ i, f i ≠ ⊥`, then `iInf f ≠ ⊥`.
See also `iInf_neBot_of_directed'` for a version assuming `Nonempty ι` instead of `Nonempty α`. -/
theorem iInf_neBot_of_directed {f : ι → Filter α} [hn : Nonempty α] (hd : Directed (· ≥ ·) f)
(hb : ∀ i, NeBot (f i)) : NeBot (iInf f) := by
cases isEmpty_or_nonempty ι
· constructor
simp [iInf_of_empty f, top_ne_bot]
· exact iInf_neBot_of_directed' hd hb
theorem sInf_neBot_of_directed' {s : Set (Filter α)} (hne : s.Nonempty) (hd : DirectedOn (· ≥ ·) s)
(hbot : ⊥ ∉ s) : NeBot (sInf s) :=
(sInf_eq_iInf' s).symm ▸
@iInf_neBot_of_directed' _ _ _ hne.to_subtype hd.directed_val fun ⟨_, hf⟩ =>
⟨ne_of_mem_of_not_mem hf hbot⟩
theorem sInf_neBot_of_directed [Nonempty α] {s : Set (Filter α)} (hd : DirectedOn (· ≥ ·) s)
(hbot : ⊥ ∉ s) : NeBot (sInf s) :=
(sInf_eq_iInf' s).symm ▸
iInf_neBot_of_directed hd.directed_val fun ⟨_, hf⟩ => ⟨ne_of_mem_of_not_mem hf hbot⟩
theorem iInf_neBot_iff_of_directed' {f : ι → Filter α} [Nonempty ι] (hd : Directed (· ≥ ·) f) :
NeBot (iInf f) ↔ ∀ i, NeBot (f i) :=
⟨fun H i => H.mono (iInf_le _ i), iInf_neBot_of_directed' hd⟩
theorem iInf_neBot_iff_of_directed {f : ι → Filter α} [Nonempty α] (hd : Directed (· ≥ ·) f) :
NeBot (iInf f) ↔ ∀ i, NeBot (f i) :=
⟨fun H i => H.mono (iInf_le _ i), iInf_neBot_of_directed hd⟩
/-! #### `principal` equations -/
@[simp]
theorem inf_principal {s t : Set α} : 𝓟 s ⊓ 𝓟 t = 𝓟 (s ∩ t) :=
le_antisymm
(by simp only [le_principal_iff, mem_inf_iff]; exact ⟨s, Subset.rfl, t, Subset.rfl, rfl⟩)
(by simp [le_inf_iff, inter_subset_left, inter_subset_right])
@[simp]
theorem sup_principal {s t : Set α} : 𝓟 s ⊔ 𝓟 t = 𝓟 (s ∪ t) :=
Filter.ext fun u => by simp only [union_subset_iff, mem_sup, mem_principal]
@[simp]
theorem iSup_principal {ι : Sort w} {s : ι → Set α} : ⨆ x, 𝓟 (s x) = 𝓟 (⋃ i, s i) :=
Filter.ext fun x => by simp only [mem_iSup, mem_principal, iUnion_subset_iff]
@[simp]
theorem principal_eq_bot_iff {s : Set α} : 𝓟 s = ⊥ ↔ s = ∅ :=
empty_mem_iff_bot.symm.trans <| mem_principal.trans subset_empty_iff
@[simp]
theorem principal_neBot_iff {s : Set α} : NeBot (𝓟 s) ↔ s.Nonempty :=
neBot_iff.trans <| (not_congr principal_eq_bot_iff).trans nonempty_iff_ne_empty.symm
alias ⟨_, _root_.Set.Nonempty.principal_neBot⟩ := principal_neBot_iff
theorem isCompl_principal (s : Set α) : IsCompl (𝓟 s) (𝓟 sᶜ) :=
IsCompl.of_eq (by rw [inf_principal, inter_compl_self, principal_empty]) <| by
rw [sup_principal, union_compl_self, principal_univ]
theorem mem_inf_principal' {f : Filter α} {s t : Set α} : s ∈ f ⊓ 𝓟 t ↔ tᶜ ∪ s ∈ f := by
simp only [← le_principal_iff, (isCompl_principal s).le_left_iff, disjoint_assoc, inf_principal,
← (isCompl_principal (t ∩ sᶜ)).le_right_iff, compl_inter, compl_compl]
lemma mem_inf_principal {f : Filter α} {s t : Set α} : s ∈ f ⊓ 𝓟 t ↔ { x | x ∈ t → x ∈ s } ∈ f := by
simp only [mem_inf_principal', imp_iff_not_or, setOf_or, compl_def, setOf_mem_eq]
lemma iSup_inf_principal (f : ι → Filter α) (s : Set α) : ⨆ i, f i ⊓ 𝓟 s = (⨆ i, f i) ⊓ 𝓟 s := by
ext
simp only [mem_iSup, mem_inf_principal]
theorem inf_principal_eq_bot {f : Filter α} {s : Set α} : f ⊓ 𝓟 s = ⊥ ↔ sᶜ ∈ f := by
rw [← empty_mem_iff_bot, mem_inf_principal]
simp only [mem_empty_iff_false, imp_false, compl_def]
theorem mem_of_eq_bot {f : Filter α} {s : Set α} (h : f ⊓ 𝓟 sᶜ = ⊥) : s ∈ f := by
rwa [inf_principal_eq_bot, compl_compl] at h
theorem diff_mem_inf_principal_compl {f : Filter α} {s : Set α} (hs : s ∈ f) (t : Set α) :
s \ t ∈ f ⊓ 𝓟 tᶜ :=
inter_mem_inf hs <| mem_principal_self tᶜ
theorem principal_le_iff {s : Set α} {f : Filter α} : 𝓟 s ≤ f ↔ ∀ V ∈ f, s ⊆ V := by
simp_rw [le_def, mem_principal]
end Lattice
@[mono, gcongr]
theorem join_mono {f₁ f₂ : Filter (Filter α)} (h : f₁ ≤ f₂) : join f₁ ≤ join f₂ := fun _ hs => h hs
/-! ### Eventually -/
theorem eventually_iff {f : Filter α} {P : α → Prop} : (∀ᶠ x in f, P x) ↔ { x | P x } ∈ f :=
Iff.rfl
@[simp]
theorem eventually_mem_set {s : Set α} {l : Filter α} : (∀ᶠ x in l, x ∈ s) ↔ s ∈ l :=
Iff.rfl
protected theorem ext' {f₁ f₂ : Filter α}
(h : ∀ p : α → Prop, (∀ᶠ x in f₁, p x) ↔ ∀ᶠ x in f₂, p x) : f₁ = f₂ :=
Filter.ext h
theorem Eventually.filter_mono {f₁ f₂ : Filter α} (h : f₁ ≤ f₂) {p : α → Prop}
(hp : ∀ᶠ x in f₂, p x) : ∀ᶠ x in f₁, p x :=
h hp
theorem eventually_of_mem {f : Filter α} {P : α → Prop} {U : Set α} (hU : U ∈ f)
(h : ∀ x ∈ U, P x) : ∀ᶠ x in f, P x :=
mem_of_superset hU h
protected theorem Eventually.and {p q : α → Prop} {f : Filter α} :
f.Eventually p → f.Eventually q → ∀ᶠ x in f, p x ∧ q x :=
inter_mem
@[simp] theorem eventually_true (f : Filter α) : ∀ᶠ _ in f, True := univ_mem
theorem Eventually.of_forall {p : α → Prop} {f : Filter α} (hp : ∀ x, p x) : ∀ᶠ x in f, p x :=
univ_mem' hp
@[simp]
theorem eventually_false_iff_eq_bot {f : Filter α} : (∀ᶠ _ in f, False) ↔ f = ⊥ :=
empty_mem_iff_bot
@[simp]
theorem eventually_const {f : Filter α} [t : NeBot f] {p : Prop} : (∀ᶠ _ in f, p) ↔ p := by
by_cases h : p <;> simp [h, t.ne]
theorem eventually_iff_exists_mem {p : α → Prop} {f : Filter α} :
(∀ᶠ x in f, p x) ↔ ∃ v ∈ f, ∀ y ∈ v, p y :=
exists_mem_subset_iff.symm
theorem Eventually.exists_mem {p : α → Prop} {f : Filter α} (hp : ∀ᶠ x in f, p x) :
∃ v ∈ f, ∀ y ∈ v, p y :=
eventually_iff_exists_mem.1 hp
theorem Eventually.mp {p q : α → Prop} {f : Filter α} (hp : ∀ᶠ x in f, p x)
(hq : ∀ᶠ x in f, p x → q x) : ∀ᶠ x in f, q x :=
mp_mem hp hq
theorem Eventually.mono {p q : α → Prop} {f : Filter α} (hp : ∀ᶠ x in f, p x)
(hq : ∀ x, p x → q x) : ∀ᶠ x in f, q x :=
hp.mp (Eventually.of_forall hq)
theorem forall_eventually_of_eventually_forall {f : Filter α} {p : α → β → Prop}
(h : ∀ᶠ x in f, ∀ y, p x y) : ∀ y, ∀ᶠ x in f, p x y :=
fun y => h.mono fun _ h => h y
@[simp]
theorem eventually_and {p q : α → Prop} {f : Filter α} :
(∀ᶠ x in f, p x ∧ q x) ↔ (∀ᶠ x in f, p x) ∧ ∀ᶠ x in f, q x :=
inter_mem_iff
theorem Eventually.congr {f : Filter α} {p q : α → Prop} (h' : ∀ᶠ x in f, p x)
(h : ∀ᶠ x in f, p x ↔ q x) : ∀ᶠ x in f, q x :=
h'.mp (h.mono fun _ hx => hx.mp)
theorem eventually_congr {f : Filter α} {p q : α → Prop} (h : ∀ᶠ x in f, p x ↔ q x) :
(∀ᶠ x in f, p x) ↔ ∀ᶠ x in f, q x :=
⟨fun hp => hp.congr h, fun hq => hq.congr <| by simpa only [Iff.comm] using h⟩
@[simp]
theorem eventually_or_distrib_left {f : Filter α} {p : Prop} {q : α → Prop} :
(∀ᶠ x in f, p ∨ q x) ↔ p ∨ ∀ᶠ x in f, q x :=
by_cases (fun h : p => by simp [h]) fun h => by simp [h]
@[simp]
theorem eventually_or_distrib_right {f : Filter α} {p : α → Prop} {q : Prop} :
(∀ᶠ x in f, p x ∨ q) ↔ (∀ᶠ x in f, p x) ∨ q := by
simp only [@or_comm _ q, eventually_or_distrib_left]
theorem eventually_imp_distrib_left {f : Filter α} {p : Prop} {q : α → Prop} :
(∀ᶠ x in f, p → q x) ↔ p → ∀ᶠ x in f, q x := by
simp only [imp_iff_not_or, eventually_or_distrib_left]
@[simp]
theorem eventually_bot {p : α → Prop} : ∀ᶠ x in ⊥, p x :=
⟨⟩
@[simp]
theorem eventually_top {p : α → Prop} : (∀ᶠ x in ⊤, p x) ↔ ∀ x, p x :=
Iff.rfl
@[simp]
theorem eventually_sup {p : α → Prop} {f g : Filter α} :
(∀ᶠ x in f ⊔ g, p x) ↔ (∀ᶠ x in f, p x) ∧ ∀ᶠ x in g, p x :=
Iff.rfl
@[simp]
theorem eventually_sSup {p : α → Prop} {fs : Set (Filter α)} :
(∀ᶠ x in sSup fs, p x) ↔ ∀ f ∈ fs, ∀ᶠ x in f, p x :=
Iff.rfl
@[simp]
theorem eventually_iSup {p : α → Prop} {fs : ι → Filter α} :
(∀ᶠ x in ⨆ b, fs b, p x) ↔ ∀ b, ∀ᶠ x in fs b, p x :=
mem_iSup
@[simp]
theorem eventually_principal {a : Set α} {p : α → Prop} : (∀ᶠ x in 𝓟 a, p x) ↔ ∀ x ∈ a, p x :=
Iff.rfl
theorem Eventually.forall_mem {α : Type*} {f : Filter α} {s : Set α} {P : α → Prop}
(hP : ∀ᶠ x in f, P x) (hf : 𝓟 s ≤ f) : ∀ x ∈ s, P x :=
Filter.eventually_principal.mp (hP.filter_mono hf)
theorem eventually_inf {f g : Filter α} {p : α → Prop} :
(∀ᶠ x in f ⊓ g, p x) ↔ ∃ s ∈ f, ∃ t ∈ g, ∀ x ∈ s ∩ t, p x :=
mem_inf_iff_superset
theorem eventually_inf_principal {f : Filter α} {p : α → Prop} {s : Set α} :
(∀ᶠ x in f ⊓ 𝓟 s, p x) ↔ ∀ᶠ x in f, x ∈ s → p x :=
mem_inf_principal
theorem eventually_iff_all_subsets {f : Filter α} {p : α → Prop} :
(∀ᶠ x in f, p x) ↔ ∀ (s : Set α), ∀ᶠ x in f, x ∈ s → p x where
mp h _ := by filter_upwards [h] with _ pa _ using pa
mpr h := by filter_upwards [h univ] with _ pa using pa (by simp)
/-! ### Frequently -/
theorem Eventually.frequently {f : Filter α} [NeBot f] {p : α → Prop} (h : ∀ᶠ x in f, p x) :
∃ᶠ x in f, p x :=
compl_not_mem h
theorem Frequently.of_forall {f : Filter α} [NeBot f] {p : α → Prop} (h : ∀ x, p x) :
∃ᶠ x in f, p x :=
Eventually.frequently (Eventually.of_forall h)
theorem Frequently.mp {p q : α → Prop} {f : Filter α} (h : ∃ᶠ x in f, p x)
(hpq : ∀ᶠ x in f, p x → q x) : ∃ᶠ x in f, q x :=
mt (fun hq => hq.mp <| hpq.mono fun _ => mt) h
lemma frequently_congr {p q : α → Prop} {f : Filter α} (h : ∀ᶠ x in f, p x ↔ q x) :
(∃ᶠ x in f, p x) ↔ ∃ᶠ x in f, q x :=
⟨fun h' ↦ h'.mp (h.mono fun _ ↦ Iff.mp), fun h' ↦ h'.mp (h.mono fun _ ↦ Iff.mpr)⟩
theorem Frequently.filter_mono {p : α → Prop} {f g : Filter α} (h : ∃ᶠ x in f, p x) (hle : f ≤ g) :
∃ᶠ x in g, p x :=
mt (fun h' => h'.filter_mono hle) h
theorem Frequently.mono {p q : α → Prop} {f : Filter α} (h : ∃ᶠ x in f, p x)
(hpq : ∀ x, p x → q x) : ∃ᶠ x in f, q x :=
h.mp (Eventually.of_forall hpq)
theorem Frequently.and_eventually {p q : α → Prop} {f : Filter α} (hp : ∃ᶠ x in f, p x)
(hq : ∀ᶠ x in f, q x) : ∃ᶠ x in f, p x ∧ q x := by
refine mt (fun h => hq.mp <| h.mono ?_) hp
exact fun x hpq hq hp => hpq ⟨hp, hq⟩
theorem Eventually.and_frequently {p q : α → Prop} {f : Filter α} (hp : ∀ᶠ x in f, p x)
(hq : ∃ᶠ x in f, q x) : ∃ᶠ x in f, p x ∧ q x := by
simpa only [and_comm] using hq.and_eventually hp
theorem Frequently.exists {p : α → Prop} {f : Filter α} (hp : ∃ᶠ x in f, p x) : ∃ x, p x := by
by_contra H
replace H : ∀ᶠ x in f, ¬p x := Eventually.of_forall (not_exists.1 H)
exact hp H
theorem Eventually.exists {p : α → Prop} {f : Filter α} [NeBot f] (hp : ∀ᶠ x in f, p x) :
∃ x, p x :=
hp.frequently.exists
lemma frequently_iff_neBot {l : Filter α} {p : α → Prop} :
(∃ᶠ x in l, p x) ↔ NeBot (l ⊓ 𝓟 {x | p x}) := by
rw [neBot_iff, Ne, inf_principal_eq_bot]; rfl
lemma frequently_mem_iff_neBot {l : Filter α} {s : Set α} : (∃ᶠ x in l, x ∈ s) ↔ NeBot (l ⊓ 𝓟 s) :=
frequently_iff_neBot
theorem frequently_iff_forall_eventually_exists_and {p : α → Prop} {f : Filter α} :
(∃ᶠ x in f, p x) ↔ ∀ {q : α → Prop}, (∀ᶠ x in f, q x) → ∃ x, p x ∧ q x :=
⟨fun hp _ hq => (hp.and_eventually hq).exists, fun H hp => by
simpa only [and_not_self_iff, exists_false] using H hp⟩
theorem frequently_iff {f : Filter α} {P : α → Prop} :
(∃ᶠ x in f, P x) ↔ ∀ {U}, U ∈ f → ∃ x ∈ U, P x := by
simp only [frequently_iff_forall_eventually_exists_and, @and_comm (P _)]
rfl
@[simp]
theorem not_eventually {p : α → Prop} {f : Filter α} : (¬∀ᶠ x in f, p x) ↔ ∃ᶠ x in f, ¬p x := by
simp [Filter.Frequently]
@[simp]
theorem not_frequently {p : α → Prop} {f : Filter α} : (¬∃ᶠ x in f, p x) ↔ ∀ᶠ x in f, ¬p x := by
simp only [Filter.Frequently, not_not]
@[simp]
theorem frequently_true_iff_neBot (f : Filter α) : (∃ᶠ _ in f, True) ↔ NeBot f := by
simp [frequently_iff_neBot]
@[simp]
theorem frequently_false (f : Filter α) : ¬∃ᶠ _ in f, False := by simp
@[simp]
theorem frequently_const {f : Filter α} [NeBot f] {p : Prop} : (∃ᶠ _ in f, p) ↔ p := by
by_cases p <;> simp [*]
@[simp]
theorem frequently_or_distrib {f : Filter α} {p q : α → Prop} :
(∃ᶠ x in f, p x ∨ q x) ↔ (∃ᶠ x in f, p x) ∨ ∃ᶠ x in f, q x := by
simp only [Filter.Frequently, ← not_and_or, not_or, eventually_and]
theorem frequently_or_distrib_left {f : Filter α} [NeBot f] {p : Prop} {q : α → Prop} :
(∃ᶠ x in f, p ∨ q x) ↔ p ∨ ∃ᶠ x in f, q x := by simp
theorem frequently_or_distrib_right {f : Filter α} [NeBot f] {p : α → Prop} {q : Prop} :
(∃ᶠ x in f, p x ∨ q) ↔ (∃ᶠ x in f, p x) ∨ q := by simp
theorem frequently_imp_distrib {f : Filter α} {p q : α → Prop} :
(∃ᶠ x in f, p x → q x) ↔ (∀ᶠ x in f, p x) → ∃ᶠ x in f, q x := by
simp [imp_iff_not_or]
theorem frequently_imp_distrib_left {f : Filter α} [NeBot f] {p : Prop} {q : α → Prop} :
(∃ᶠ x in f, p → q x) ↔ p → ∃ᶠ x in f, q x := by simp [frequently_imp_distrib]
theorem frequently_imp_distrib_right {f : Filter α} [NeBot f] {p : α → Prop} {q : Prop} :
(∃ᶠ x in f, p x → q) ↔ (∀ᶠ x in f, p x) → q := by
simp only [frequently_imp_distrib, frequently_const]
theorem eventually_imp_distrib_right {f : Filter α} {p : α → Prop} {q : Prop} :
(∀ᶠ x in f, p x → q) ↔ (∃ᶠ x in f, p x) → q := by
simp only [imp_iff_not_or, eventually_or_distrib_right, not_frequently]
@[simp]
theorem frequently_and_distrib_left {f : Filter α} {p : Prop} {q : α → Prop} :
(∃ᶠ x in f, p ∧ q x) ↔ p ∧ ∃ᶠ x in f, q x := by
simp only [Filter.Frequently, not_and, eventually_imp_distrib_left, Classical.not_imp]
@[simp]
theorem frequently_and_distrib_right {f : Filter α} {p : α → Prop} {q : Prop} :
(∃ᶠ x in f, p x ∧ q) ↔ (∃ᶠ x in f, p x) ∧ q := by
simp only [@and_comm _ q, frequently_and_distrib_left]
@[simp]
theorem frequently_bot {p : α → Prop} : ¬∃ᶠ x in ⊥, p x := by simp
@[simp]
theorem frequently_top {p : α → Prop} : (∃ᶠ x in ⊤, p x) ↔ ∃ x, p x := by simp [Filter.Frequently]
@[simp]
theorem frequently_principal {a : Set α} {p : α → Prop} : (∃ᶠ x in 𝓟 a, p x) ↔ ∃ x ∈ a, p x := by
simp [Filter.Frequently, not_forall]
theorem frequently_inf_principal {f : Filter α} {s : Set α} {p : α → Prop} :
(∃ᶠ x in f ⊓ 𝓟 s, p x) ↔ ∃ᶠ x in f, x ∈ s ∧ p x := by
simp only [Filter.Frequently, eventually_inf_principal, not_and]
alias ⟨Frequently.of_inf_principal, Frequently.inf_principal⟩ := frequently_inf_principal
theorem frequently_sup {p : α → Prop} {f g : Filter α} :
(∃ᶠ x in f ⊔ g, p x) ↔ (∃ᶠ x in f, p x) ∨ ∃ᶠ x in g, p x := by
simp only [Filter.Frequently, eventually_sup, not_and_or]
@[simp]
theorem frequently_sSup {p : α → Prop} {fs : Set (Filter α)} :
(∃ᶠ x in sSup fs, p x) ↔ ∃ f ∈ fs, ∃ᶠ x in f, p x := by
simp only [Filter.Frequently, not_forall, eventually_sSup, exists_prop]
@[simp]
theorem frequently_iSup {p : α → Prop} {fs : β → Filter α} :
(∃ᶠ x in ⨆ b, fs b, p x) ↔ ∃ b, ∃ᶠ x in fs b, p x := by
simp only [Filter.Frequently, eventually_iSup, not_forall]
theorem Eventually.choice {r : α → β → Prop} {l : Filter α} [l.NeBot] (h : ∀ᶠ x in l, ∃ y, r x y) :
∃ f : α → β, ∀ᶠ x in l, r x (f x) := by
haveI : Nonempty β := let ⟨_, hx⟩ := h.exists; hx.nonempty
choose! f hf using fun x (hx : ∃ y, r x y) => hx
exact ⟨f, h.mono hf⟩
lemma skolem {ι : Type*} {α : ι → Type*} [∀ i, Nonempty (α i)]
{P : ∀ i : ι, α i → Prop} {F : Filter ι} :
(∀ᶠ i in F, ∃ b, P i b) ↔ ∃ b : (Π i, α i), ∀ᶠ i in F, P i (b i) := by
classical
refine ⟨fun H ↦ ?_, fun ⟨b, hb⟩ ↦ hb.mp (.of_forall fun x a ↦ ⟨_, a⟩)⟩
refine ⟨fun i ↦ if h : ∃ b, P i b then h.choose else Nonempty.some inferInstance, ?_⟩
filter_upwards [H] with i hi
exact dif_pos hi ▸ hi.choose_spec
/-!
### Relation “eventually equal”
-/
section EventuallyEq
variable {l : Filter α} {f g : α → β}
theorem EventuallyEq.eventually (h : f =ᶠ[l] g) : ∀ᶠ x in l, f x = g x := h
@[simp] lemma eventuallyEq_top : f =ᶠ[⊤] g ↔ f = g := by simp [EventuallyEq, funext_iff]
theorem EventuallyEq.rw {l : Filter α} {f g : α → β} (h : f =ᶠ[l] g) (p : α → β → Prop)
(hf : ∀ᶠ x in l, p x (f x)) : ∀ᶠ x in l, p x (g x) :=
hf.congr <| h.mono fun _ hx => hx ▸ Iff.rfl
theorem eventuallyEq_set {s t : Set α} {l : Filter α} : s =ᶠ[l] t ↔ ∀ᶠ x in l, x ∈ s ↔ x ∈ t :=
eventually_congr <| Eventually.of_forall fun _ ↦ eq_iff_iff
alias ⟨EventuallyEq.mem_iff, Eventually.set_eq⟩ := eventuallyEq_set
@[simp]
theorem eventuallyEq_univ {s : Set α} {l : Filter α} : s =ᶠ[l] univ ↔ s ∈ l := by
simp [eventuallyEq_set]
theorem EventuallyEq.exists_mem {l : Filter α} {f g : α → β} (h : f =ᶠ[l] g) :
∃ s ∈ l, EqOn f g s :=
Eventually.exists_mem h
theorem eventuallyEq_of_mem {l : Filter α} {f g : α → β} {s : Set α} (hs : s ∈ l) (h : EqOn f g s) :
f =ᶠ[l] g :=
eventually_of_mem hs h
theorem eventuallyEq_iff_exists_mem {l : Filter α} {f g : α → β} :
f =ᶠ[l] g ↔ ∃ s ∈ l, EqOn f g s :=
eventually_iff_exists_mem
theorem EventuallyEq.filter_mono {l l' : Filter α} {f g : α → β} (h₁ : f =ᶠ[l] g) (h₂ : l' ≤ l) :
f =ᶠ[l'] g :=
h₂ h₁
@[refl, simp]
theorem EventuallyEq.refl (l : Filter α) (f : α → β) : f =ᶠ[l] f :=
Eventually.of_forall fun _ => rfl
protected theorem EventuallyEq.rfl {l : Filter α} {f : α → β} : f =ᶠ[l] f :=
EventuallyEq.refl l f
theorem EventuallyEq.of_eq {l : Filter α} {f g : α → β} (h : f = g) : f =ᶠ[l] g := h ▸ .rfl
alias _root_.Eq.eventuallyEq := EventuallyEq.of_eq
@[symm]
theorem EventuallyEq.symm {f g : α → β} {l : Filter α} (H : f =ᶠ[l] g) : g =ᶠ[l] f :=
H.mono fun _ => Eq.symm
lemma eventuallyEq_comm {f g : α → β} {l : Filter α} : f =ᶠ[l] g ↔ g =ᶠ[l] f := ⟨.symm, .symm⟩
@[trans]
theorem EventuallyEq.trans {l : Filter α} {f g h : α → β} (H₁ : f =ᶠ[l] g) (H₂ : g =ᶠ[l] h) :
f =ᶠ[l] h :=
H₂.rw (fun x y => f x = y) H₁
theorem EventuallyEq.congr_left {l : Filter α} {f g h : α → β} (H : f =ᶠ[l] g) :
f =ᶠ[l] h ↔ g =ᶠ[l] h :=
⟨H.symm.trans, H.trans⟩
theorem EventuallyEq.congr_right {l : Filter α} {f g h : α → β} (H : g =ᶠ[l] h) :
f =ᶠ[l] g ↔ f =ᶠ[l] h :=
⟨(·.trans H), (·.trans H.symm)⟩
instance {l : Filter α} :
Trans ((· =ᶠ[l] ·) : (α → β) → (α → β) → Prop) (· =ᶠ[l] ·) (· =ᶠ[l] ·) where
trans := EventuallyEq.trans
theorem EventuallyEq.prodMk {l} {f f' : α → β} (hf : f =ᶠ[l] f') {g g' : α → γ} (hg : g =ᶠ[l] g') :
(fun x => (f x, g x)) =ᶠ[l] fun x => (f' x, g' x) :=
hf.mp <|
hg.mono <| by
intros
simp only [*]
@[deprecated (since := "2025-03-10")]
alias EventuallyEq.prod_mk := EventuallyEq.prodMk
-- See `EventuallyEq.comp_tendsto` further below for a similar statement w.r.t.
-- composition on the right.
theorem EventuallyEq.fun_comp {f g : α → β} {l : Filter α} (H : f =ᶠ[l] g) (h : β → γ) :
h ∘ f =ᶠ[l] h ∘ g :=
H.mono fun _ hx => congr_arg h hx
theorem EventuallyEq.comp₂ {δ} {f f' : α → β} {g g' : α → γ} {l} (Hf : f =ᶠ[l] f') (h : β → γ → δ)
(Hg : g =ᶠ[l] g') : (fun x => h (f x) (g x)) =ᶠ[l] fun x => h (f' x) (g' x) :=
(Hf.prodMk Hg).fun_comp (uncurry h)
@[to_additive]
theorem EventuallyEq.mul [Mul β] {f f' g g' : α → β} {l : Filter α} (h : f =ᶠ[l] g)
(h' : f' =ᶠ[l] g') : (fun x => f x * f' x) =ᶠ[l] fun x => g x * g' x :=
h.comp₂ (· * ·) h'
@[to_additive const_smul]
theorem EventuallyEq.pow_const {γ} [Pow β γ] {f g : α → β} {l : Filter α} (h : f =ᶠ[l] g) (c : γ) :
(fun x => f x ^ c) =ᶠ[l] fun x => g x ^ c :=
h.fun_comp (· ^ c)
@[to_additive]
theorem EventuallyEq.inv [Inv β] {f g : α → β} {l : Filter α} (h : f =ᶠ[l] g) :
(fun x => (f x)⁻¹) =ᶠ[l] fun x => (g x)⁻¹ :=
h.fun_comp Inv.inv
@[to_additive]
theorem EventuallyEq.div [Div β] {f f' g g' : α → β} {l : Filter α} (h : f =ᶠ[l] g)
(h' : f' =ᶠ[l] g') : (fun x => f x / f' x) =ᶠ[l] fun x => g x / g' x :=
h.comp₂ (· / ·) h'
attribute [to_additive] EventuallyEq.const_smul
@[to_additive]
theorem EventuallyEq.smul {𝕜} [SMul 𝕜 β] {l : Filter α} {f f' : α → 𝕜} {g g' : α → β}
(hf : f =ᶠ[l] f') (hg : g =ᶠ[l] g') : (fun x => f x • g x) =ᶠ[l] fun x => f' x • g' x :=
hf.comp₂ (· • ·) hg
theorem EventuallyEq.sup [Max β] {l : Filter α} {f f' g g' : α → β} (hf : f =ᶠ[l] f')
(hg : g =ᶠ[l] g') : (fun x => f x ⊔ g x) =ᶠ[l] fun x => f' x ⊔ g' x :=
hf.comp₂ (· ⊔ ·) hg
theorem EventuallyEq.inf [Min β] {l : Filter α} {f f' g g' : α → β} (hf : f =ᶠ[l] f')
(hg : g =ᶠ[l] g') : (fun x => f x ⊓ g x) =ᶠ[l] fun x => f' x ⊓ g' x :=
hf.comp₂ (· ⊓ ·) hg
theorem EventuallyEq.preimage {l : Filter α} {f g : α → β} (h : f =ᶠ[l] g) (s : Set β) :
f ⁻¹' s =ᶠ[l] g ⁻¹' s :=
h.fun_comp s
theorem EventuallyEq.inter {s t s' t' : Set α} {l : Filter α} (h : s =ᶠ[l] t) (h' : s' =ᶠ[l] t') :
(s ∩ s' : Set α) =ᶠ[l] (t ∩ t' : Set α) :=
h.comp₂ (· ∧ ·) h'
theorem EventuallyEq.union {s t s' t' : Set α} {l : Filter α} (h : s =ᶠ[l] t) (h' : s' =ᶠ[l] t') :
(s ∪ s' : Set α) =ᶠ[l] (t ∪ t' : Set α) :=
h.comp₂ (· ∨ ·) h'
theorem EventuallyEq.compl {s t : Set α} {l : Filter α} (h : s =ᶠ[l] t) :
(sᶜ : Set α) =ᶠ[l] (tᶜ : Set α) :=
h.fun_comp Not
theorem EventuallyEq.diff {s t s' t' : Set α} {l : Filter α} (h : s =ᶠ[l] t) (h' : s' =ᶠ[l] t') :
(s \ s' : Set α) =ᶠ[l] (t \ t' : Set α) :=
h.inter h'.compl
protected theorem EventuallyEq.symmDiff {s t s' t' : Set α} {l : Filter α}
(h : s =ᶠ[l] t) (h' : s' =ᶠ[l] t') : (s ∆ s' : Set α) =ᶠ[l] (t ∆ t' : Set α) :=
(h.diff h').union (h'.diff h)
theorem eventuallyEq_empty {s : Set α} {l : Filter α} : s =ᶠ[l] (∅ : Set α) ↔ ∀ᶠ x in l, x ∉ s :=
eventuallyEq_set.trans <| by simp
theorem inter_eventuallyEq_left {s t : Set α} {l : Filter α} :
(s ∩ t : Set α) =ᶠ[l] s ↔ ∀ᶠ x in l, x ∈ s → x ∈ t := by
simp only [eventuallyEq_set, mem_inter_iff, and_iff_left_iff_imp]
theorem inter_eventuallyEq_right {s t : Set α} {l : Filter α} :
(s ∩ t : Set α) =ᶠ[l] t ↔ ∀ᶠ x in l, x ∈ t → x ∈ s := by
rw [inter_comm, inter_eventuallyEq_left]
@[simp]
theorem eventuallyEq_principal {s : Set α} {f g : α → β} : f =ᶠ[𝓟 s] g ↔ EqOn f g s :=
Iff.rfl
theorem eventuallyEq_inf_principal_iff {F : Filter α} {s : Set α} {f g : α → β} :
f =ᶠ[F ⊓ 𝓟 s] g ↔ ∀ᶠ x in F, x ∈ s → f x = g x :=
eventually_inf_principal
theorem EventuallyEq.sub_eq [AddGroup β] {f g : α → β} {l : Filter α} (h : f =ᶠ[l] g) :
f - g =ᶠ[l] 0 := by simpa using ((EventuallyEq.refl l f).sub h).symm
theorem eventuallyEq_iff_sub [AddGroup β] {f g : α → β} {l : Filter α} :
f =ᶠ[l] g ↔ f - g =ᶠ[l] 0 :=
⟨fun h => h.sub_eq, fun h => by simpa using h.add (EventuallyEq.refl l g)⟩
theorem eventuallyEq_iff_all_subsets {f g : α → β} {l : Filter α} :
f =ᶠ[l] g ↔ ∀ s : Set α, ∀ᶠ x in l, x ∈ s → f x = g x :=
eventually_iff_all_subsets
section LE
variable [LE β] {l : Filter α}
theorem EventuallyLE.congr {f f' g g' : α → β} (H : f ≤ᶠ[l] g) (hf : f =ᶠ[l] f') (hg : g =ᶠ[l] g') :
f' ≤ᶠ[l] g' :=
H.mp <| hg.mp <| hf.mono fun x hf hg H => by rwa [hf, hg] at H
theorem eventuallyLE_congr {f f' g g' : α → β} (hf : f =ᶠ[l] f') (hg : g =ᶠ[l] g') :
f ≤ᶠ[l] g ↔ f' ≤ᶠ[l] g' :=
⟨fun H => H.congr hf hg, fun H => H.congr hf.symm hg.symm⟩
theorem eventuallyLE_iff_all_subsets {f g : α → β} {l : Filter α} :
f ≤ᶠ[l] g ↔ ∀ s : Set α, ∀ᶠ x in l, x ∈ s → f x ≤ g x :=
eventually_iff_all_subsets
end LE
section Preorder
variable [Preorder β] {l : Filter α} {f g h : α → β}
theorem EventuallyEq.le (h : f =ᶠ[l] g) : f ≤ᶠ[l] g :=
h.mono fun _ => le_of_eq
@[refl]
theorem EventuallyLE.refl (l : Filter α) (f : α → β) : f ≤ᶠ[l] f :=
EventuallyEq.rfl.le
theorem EventuallyLE.rfl : f ≤ᶠ[l] f :=
EventuallyLE.refl l f
@[trans]
theorem EventuallyLE.trans (H₁ : f ≤ᶠ[l] g) (H₂ : g ≤ᶠ[l] h) : f ≤ᶠ[l] h :=
H₂.mp <| H₁.mono fun _ => le_trans
instance : Trans ((· ≤ᶠ[l] ·) : (α → β) → (α → β) → Prop) (· ≤ᶠ[l] ·) (· ≤ᶠ[l] ·) where
trans := EventuallyLE.trans
@[trans]
theorem EventuallyEq.trans_le (H₁ : f =ᶠ[l] g) (H₂ : g ≤ᶠ[l] h) : f ≤ᶠ[l] h :=
H₁.le.trans H₂
instance : Trans ((· =ᶠ[l] ·) : (α → β) → (α → β) → Prop) (· ≤ᶠ[l] ·) (· ≤ᶠ[l] ·) where
trans := EventuallyEq.trans_le
@[trans]
theorem EventuallyLE.trans_eq (H₁ : f ≤ᶠ[l] g) (H₂ : g =ᶠ[l] h) : f ≤ᶠ[l] h :=
H₁.trans H₂.le
instance : Trans ((· ≤ᶠ[l] ·) : (α → β) → (α → β) → Prop) (· =ᶠ[l] ·) (· ≤ᶠ[l] ·) where
trans := EventuallyLE.trans_eq
end Preorder
variable {l : Filter α}
theorem EventuallyLE.antisymm [PartialOrder β] {l : Filter α} {f g : α → β} (h₁ : f ≤ᶠ[l] g)
(h₂ : g ≤ᶠ[l] f) : f =ᶠ[l] g :=
h₂.mp <| h₁.mono fun _ => le_antisymm
theorem eventuallyLE_antisymm_iff [PartialOrder β] {l : Filter α} {f g : α → β} :
f =ᶠ[l] g ↔ f ≤ᶠ[l] g ∧ g ≤ᶠ[l] f := by
simp only [EventuallyEq, EventuallyLE, le_antisymm_iff, eventually_and]
theorem EventuallyLE.le_iff_eq [PartialOrder β] {l : Filter α} {f g : α → β} (h : f ≤ᶠ[l] g) :
g ≤ᶠ[l] f ↔ g =ᶠ[l] f :=
⟨fun h' => h'.antisymm h, EventuallyEq.le⟩
theorem Eventually.ne_of_lt [Preorder β] {l : Filter α} {f g : α → β} (h : ∀ᶠ x in l, f x < g x) :
∀ᶠ x in l, f x ≠ g x :=
h.mono fun _ hx => hx.ne
theorem Eventually.ne_top_of_lt [Preorder β] [OrderTop β] {l : Filter α} {f g : α → β}
(h : ∀ᶠ x in l, f x < g x) : ∀ᶠ x in l, f x ≠ ⊤ :=
h.mono fun _ hx => hx.ne_top
theorem Eventually.lt_top_of_ne [PartialOrder β] [OrderTop β] {l : Filter α} {f : α → β}
(h : ∀ᶠ x in l, f x ≠ ⊤) : ∀ᶠ x in l, f x < ⊤ :=
h.mono fun _ hx => hx.lt_top
theorem Eventually.lt_top_iff_ne_top [PartialOrder β] [OrderTop β] {l : Filter α} {f : α → β} :
(∀ᶠ x in l, f x < ⊤) ↔ ∀ᶠ x in l, f x ≠ ⊤ :=
⟨Eventually.ne_of_lt, Eventually.lt_top_of_ne⟩
@[mono]
theorem EventuallyLE.inter {s t s' t' : Set α} {l : Filter α} (h : s ≤ᶠ[l] t) (h' : s' ≤ᶠ[l] t') :
(s ∩ s' : Set α) ≤ᶠ[l] (t ∩ t' : Set α) :=
h'.mp <| h.mono fun _ => And.imp
@[mono]
theorem EventuallyLE.union {s t s' t' : Set α} {l : Filter α} (h : s ≤ᶠ[l] t) (h' : s' ≤ᶠ[l] t') :
(s ∪ s' : Set α) ≤ᶠ[l] (t ∪ t' : Set α) :=
h'.mp <| h.mono fun _ => Or.imp
@[mono]
theorem EventuallyLE.compl {s t : Set α} {l : Filter α} (h : s ≤ᶠ[l] t) :
(tᶜ : Set α) ≤ᶠ[l] (sᶜ : Set α) :=
h.mono fun _ => mt
@[mono]
theorem EventuallyLE.diff {s t s' t' : Set α} {l : Filter α} (h : s ≤ᶠ[l] t) (h' : t' ≤ᶠ[l] s') :
(s \ s' : Set α) ≤ᶠ[l] (t \ t' : Set α) :=
h.inter h'.compl
theorem set_eventuallyLE_iff_mem_inf_principal {s t : Set α} {l : Filter α} :
s ≤ᶠ[l] t ↔ t ∈ l ⊓ 𝓟 s :=
eventually_inf_principal.symm
theorem set_eventuallyLE_iff_inf_principal_le {s t : Set α} {l : Filter α} :
s ≤ᶠ[l] t ↔ l ⊓ 𝓟 s ≤ l ⊓ 𝓟 t :=
set_eventuallyLE_iff_mem_inf_principal.trans <| by
simp only [le_inf_iff, inf_le_left, true_and, le_principal_iff]
theorem set_eventuallyEq_iff_inf_principal {s t : Set α} {l : Filter α} :
s =ᶠ[l] t ↔ l ⊓ 𝓟 s = l ⊓ 𝓟 t := by
simp only [eventuallyLE_antisymm_iff, le_antisymm_iff, set_eventuallyLE_iff_inf_principal_le]
theorem EventuallyLE.sup [SemilatticeSup β] {l : Filter α} {f₁ f₂ g₁ g₂ : α → β} (hf : f₁ ≤ᶠ[l] f₂)
(hg : g₁ ≤ᶠ[l] g₂) : f₁ ⊔ g₁ ≤ᶠ[l] f₂ ⊔ g₂ := by
filter_upwards [hf, hg] with x hfx hgx using sup_le_sup hfx hgx
theorem EventuallyLE.sup_le [SemilatticeSup β] {l : Filter α} {f g h : α → β} (hf : f ≤ᶠ[l] h)
(hg : g ≤ᶠ[l] h) : f ⊔ g ≤ᶠ[l] h := by
filter_upwards [hf, hg] with x hfx hgx using _root_.sup_le hfx hgx
theorem EventuallyLE.le_sup_of_le_left [SemilatticeSup β] {l : Filter α} {f g h : α → β}
(hf : h ≤ᶠ[l] f) : h ≤ᶠ[l] f ⊔ g :=
hf.mono fun _ => _root_.le_sup_of_le_left
theorem EventuallyLE.le_sup_of_le_right [SemilatticeSup β] {l : Filter α} {f g h : α → β}
(hg : h ≤ᶠ[l] g) : h ≤ᶠ[l] f ⊔ g :=
hg.mono fun _ => _root_.le_sup_of_le_right
theorem join_le {f : Filter (Filter α)} {l : Filter α} (h : ∀ᶠ m in f, m ≤ l) : join f ≤ l :=
fun _ hs => h.mono fun _ hm => hm hs
end EventuallyEq
end Filter
open Filter
theorem Set.EqOn.eventuallyEq {α β} {s : Set α} {f g : α → β} (h : EqOn f g s) : f =ᶠ[𝓟 s] g :=
h
theorem Set.EqOn.eventuallyEq_of_mem {α β} {s : Set α} {l : Filter α} {f g : α → β} (h : EqOn f g s)
(hl : s ∈ l) : f =ᶠ[l] g :=
h.eventuallyEq.filter_mono <| Filter.le_principal_iff.2 hl
theorem HasSubset.Subset.eventuallyLE {α} {l : Filter α} {s t : Set α} (h : s ⊆ t) : s ≤ᶠ[l] t :=
Filter.Eventually.of_forall h
variable {α β : Type*} {F : Filter α} {G : Filter β}
namespace Filter
lemma compl_mem_comk {p : Set α → Prop} {he hmono hunion s} :
sᶜ ∈ comk p he hmono hunion ↔ p s := by
simp
end Filter
| Mathlib/Order/Filter/Basic.lean | 1,640 | 1,642 | |
/-
Copyright (c) 2022 Joël Riou. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Joël Riou
-/
import Mathlib.AlgebraicTopology.DoldKan.FunctorGamma
import Mathlib.AlgebraicTopology.DoldKan.SplitSimplicialObject
import Mathlib.CategoryTheory.Idempotents.HomologicalComplex
import Mathlib.Tactic.SuppressCompilation
/-! The counit isomorphism of the Dold-Kan equivalence
The purpose of this file is to construct natural isomorphisms
`N₁Γ₀ : Γ₀ ⋙ N₁ ≅ toKaroubi (ChainComplex C ℕ)`
and `N₂Γ₂ : Γ₂ ⋙ N₂ ≅ 𝟭 (Karoubi (ChainComplex C ℕ))`.
(See `Equivalence.lean` for the general strategy of proof of the Dold-Kan equivalence.)
-/
suppress_compilation
noncomputable section
open CategoryTheory CategoryTheory.Category CategoryTheory.Limits
CategoryTheory.Idempotents Opposite SimplicialObject Simplicial
namespace AlgebraicTopology
namespace DoldKan
variable {C : Type*} [Category C] [Preadditive C] [HasFiniteCoproducts C]
/-- The isomorphism `(Γ₀.splitting K).nondegComplex ≅ K` for all `K : ChainComplex C ℕ`. -/
@[simps!]
def Γ₀NondegComplexIso (K : ChainComplex C ℕ) : (Γ₀.splitting K).nondegComplex ≅ K :=
HomologicalComplex.Hom.isoOfComponents (fun _ => Iso.refl _)
(by
rintro _ n (rfl : n + 1 = _)
dsimp
simp only [id_comp, comp_id, AlternatingFaceMapComplex.obj_d_eq, Preadditive.sum_comp,
Preadditive.comp_sum]
rw [Fintype.sum_eq_single (0 : Fin (n + 2))]
· simp only [Fin.val_zero, pow_zero, one_zsmul]
rw [δ, Γ₀.Obj.mapMono_on_summand_id_assoc, Γ₀.Obj.Termwise.mapMono_δ₀,
Splitting.cofan_inj_πSummand_eq_id]
dsimp only [Γ₀.splitting, Splitting.summand.eq_1, Splitting.IndexSet.id_fst]
rw [comp_id]
· intro i hi
dsimp
simp only [Preadditive.zsmul_comp, Preadditive.comp_zsmul, assoc]
rw [δ, Γ₀.Obj.mapMono_on_summand_id_assoc, Γ₀.Obj.Termwise.mapMono_eq_zero, zero_comp,
zsmul_zero]
· intro h
replace h := congr_arg SimplexCategory.len h
change n + 1 = n at h
omega
· simpa only [Isδ₀.iff] using hi)
/-- The natural isomorphism `(Γ₀.splitting K).nondegComplex ≅ K` for `K : ChainComplex C ℕ`. -/
def Γ₀'CompNondegComplexFunctor : Γ₀' ⋙ Split.nondegComplexFunctor ≅ 𝟭 (ChainComplex C ℕ) :=
NatIso.ofComponents Γ₀NondegComplexIso
/-- The natural isomorphism `Γ₀ ⋙ N₁ ≅ toKaroubi (ChainComplex C ℕ)`. -/
def N₁Γ₀ : Γ₀ ⋙ N₁ ≅ toKaroubi (ChainComplex C ℕ) :=
calc
Γ₀ ⋙ N₁ ≅ Γ₀' ⋙ Split.forget C ⋙ N₁ := Functor.associator _ _ _
_ ≅ Γ₀' ⋙ Split.nondegComplexFunctor ⋙ toKaroubi _ :=
(isoWhiskerLeft Γ₀' Split.toKaroubiNondegComplexFunctorIsoN₁.symm)
_ ≅ (Γ₀' ⋙ Split.nondegComplexFunctor) ⋙ toKaroubi _ := (Functor.associator _ _ _).symm
_ ≅ 𝟭 _ ⋙ toKaroubi (ChainComplex C ℕ) := isoWhiskerRight Γ₀'CompNondegComplexFunctor _
_ ≅ toKaroubi (ChainComplex C ℕ) := Functor.leftUnitor _
theorem N₁Γ₀_app (K : ChainComplex C ℕ) :
N₁Γ₀.app K = (Γ₀.splitting K).toKaroubiNondegComplexIsoN₁.symm ≪≫
(toKaroubi _).mapIso (Γ₀NondegComplexIso K) := by
ext1
dsimp [N₁Γ₀]
erw [id_comp, comp_id, comp_id]
rfl
theorem N₁Γ₀_hom_app (K : ChainComplex C ℕ) :
N₁Γ₀.hom.app K = (Γ₀.splitting K).toKaroubiNondegComplexIsoN₁.inv ≫
(toKaroubi _).map (Γ₀NondegComplexIso K).hom := by
change (N₁Γ₀.app K).hom = _
simp only [N₁Γ₀_app]
rfl
theorem N₁Γ₀_inv_app (K : ChainComplex C ℕ) :
N₁Γ₀.inv.app K = (toKaroubi _).map (Γ₀NondegComplexIso K).inv ≫
(Γ₀.splitting K).toKaroubiNondegComplexIsoN₁.hom := by
change (N₁Γ₀.app K).inv = _
simp only [N₁Γ₀_app]
rfl
@[simp]
theorem N₁Γ₀_hom_app_f_f (K : ChainComplex C ℕ) (n : ℕ) :
(N₁Γ₀.hom.app K).f.f n = (Γ₀.splitting K).toKaroubiNondegComplexIsoN₁.inv.f.f n := by
rw [N₁Γ₀_hom_app]
apply comp_id
@[simp]
theorem N₁Γ₀_inv_app_f_f (K : ChainComplex C ℕ) (n : ℕ) :
(N₁Γ₀.inv.app K).f.f n = (Γ₀.splitting K).toKaroubiNondegComplexIsoN₁.hom.f.f n := by
rw [N₁Γ₀_inv_app]
apply id_comp
/-- Compatibility isomorphism between `toKaroubi _ ⋙ Γ₂ ⋙ N₂` and `Γ₀ ⋙ N₁` which
are functors `ChainComplex C ℕ ⥤ Karoubi (ChainComplex C ℕ)`. -/
def N₂Γ₂ToKaroubiIso : toKaroubi (ChainComplex C ℕ) ⋙ Γ₂ ⋙ N₂ ≅ Γ₀ ⋙ N₁ :=
calc
toKaroubi (ChainComplex C ℕ) ⋙ Γ₂ ⋙ N₂ ≅
toKaroubi (ChainComplex C ℕ) ⋙ (Γ₂ ⋙ N₂) := (Functor.associator _ _ _).symm
_ ≅ (Γ₀ ⋙ toKaroubi (SimplicialObject C)) ⋙ N₂ :=
isoWhiskerRight ((functorExtension₂CompWhiskeringLeftToKaroubiIso _ _).app Γ₀) N₂
_ ≅ Γ₀ ⋙ toKaroubi (SimplicialObject C) ⋙ N₂ := Functor.associator _ _ _
_ ≅ Γ₀ ⋙ N₁ :=
isoWhiskerLeft Γ₀ ((functorExtension₁CompWhiskeringLeftToKaroubiIso _ _).app N₁)
@[simp]
lemma N₂Γ₂ToKaroubiIso_hom_app (X : ChainComplex C ℕ) :
(N₂Γ₂ToKaroubiIso.hom.app X).f = PInfty := by
ext n
dsimp [N₂Γ₂ToKaroubiIso]
simp only [comp_id, assoc, PInfty_f_idem]
conv_rhs =>
rw [← PInfty_f_idem]
congr 1
apply (Γ₀.splitting X).hom_ext'
intro A
rw [Splitting.ι_desc_assoc, assoc]
apply id_comp
@[simp]
lemma N₂Γ₂ToKaroubiIso_inv_app (X : ChainComplex C ℕ) :
(N₂Γ₂ToKaroubiIso.inv.app X).f = PInfty := by
ext n
dsimp [N₂Γ₂ToKaroubiIso]
simp only [comp_id, PInfty_f_idem_assoc, AlternatingFaceMapComplex.obj_X, Γ₀_obj_obj]
convert comp_id _
apply (Γ₀.splitting X).hom_ext'
intro A
rw [Splitting.ι_desc]
erw [comp_id, id_comp]
/-- The counit isomorphism of the Dold-Kan equivalence for additive categories. -/
def N₂Γ₂ : Γ₂ ⋙ N₂ ≅ 𝟭 (Karoubi (ChainComplex C ℕ)) :=
((whiskeringLeft _ _ _).obj (toKaroubi (ChainComplex C ℕ))).preimageIso
(N₂Γ₂ToKaroubiIso ≪≫ N₁Γ₀)
@[simp]
theorem N₂Γ₂_inv_app_f_f (X : Karoubi (ChainComplex C ℕ)) (n : ℕ) :
(N₂Γ₂.inv.app X).f.f n =
X.p.f n ≫ ((Γ₀.splitting X.X).cofan _).inj (Splitting.IndexSet.id (op ⦋n⦌)) := by
dsimp [N₂Γ₂]
simp only [whiskeringLeft_obj_preimage_app, NatTrans.comp_app, Functor.comp_map,
Karoubi.comp_f, N₂Γ₂ToKaroubiIso_inv_app, HomologicalComplex.comp_f,
N₁Γ₀_inv_app_f_f, toKaroubi_obj_X, Splitting.toKaroubiNondegComplexIsoN₁_hom_f_f,
Γ₀.obj_obj, PInfty_on_Γ₀_splitting_summand_eq_self, N₂_map_f_f,
Γ₂_map_f_app, unop_op, Karoubi.decompId_p_f, PInfty_f_idem_assoc,
PInfty_on_Γ₀_splitting_summand_eq_self_assoc, Splitting.IndexSet.id_fst, SimplexCategory.len_mk,
Splitting.ι_desc]
apply Karoubi.HomologicalComplex.p_idem_assoc
lemma whiskerLeft_toKaroubi_N₂Γ₂_hom :
whiskerLeft (toKaroubi (ChainComplex C ℕ)) N₂Γ₂.hom = N₂Γ₂ToKaroubiIso.hom ≫ N₁Γ₀.hom := by
let e : _ ≅ toKaroubi (ChainComplex C ℕ) ⋙ 𝟭 _ := N₂Γ₂ToKaroubiIso ≪≫ N₁Γ₀
have h := ((whiskeringLeft _ _ (Karoubi (ChainComplex C ℕ))).obj
(toKaroubi (ChainComplex C ℕ))).map_preimage e.hom
dsimp only [whiskeringLeft, N₂Γ₂, Functor.preimageIso] at h ⊢
exact h
theorem N₂Γ₂_compatible_with_N₁Γ₀ (K : ChainComplex C ℕ) :
| N₂Γ₂.hom.app ((toKaroubi _).obj K) = N₂Γ₂ToKaroubiIso.hom.app K ≫ N₁Γ₀.hom.app K :=
congr_app whiskerLeft_toKaroubi_N₂Γ₂_hom K
end DoldKan
end AlgebraicTopology
| Mathlib/AlgebraicTopology/DoldKan/GammaCompN.lean | 174 | 185 |
/-
Copyright (c) 2019 Calle Sönne. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Calle Sönne
-/
import Mathlib.Analysis.SpecialFunctions.Trigonometric.Basic
import Mathlib.Analysis.Normed.Group.AddCircle
import Mathlib.Algebra.CharZero.Quotient
import Mathlib.Topology.Instances.Sign
/-!
# The type of angles
In this file we define `Real.Angle` to be the quotient group `ℝ/2πℤ` and prove a few simple lemmas
about trigonometric functions and angles.
-/
open Real
noncomputable section
namespace Real
/-- The type of angles -/
def Angle : Type :=
AddCircle (2 * π)
-- The `NormedAddCommGroup, Inhabited` instances should be constructed by a deriving handler.
-- https://github.com/leanprover-community/mathlib4/issues/380
namespace Angle
instance : NormedAddCommGroup Angle :=
inferInstanceAs (NormedAddCommGroup (AddCircle (2 * π)))
instance : Inhabited Angle :=
inferInstanceAs (Inhabited (AddCircle (2 * π)))
/-- The canonical map from `ℝ` to the quotient `Angle`. -/
@[coe]
protected def coe (r : ℝ) : Angle := QuotientAddGroup.mk r
instance : Coe ℝ Angle := ⟨Angle.coe⟩
instance : CircularOrder Real.Angle :=
QuotientAddGroup.circularOrder (hp' := ⟨by norm_num [pi_pos]⟩)
@[continuity]
theorem continuous_coe : Continuous ((↑) : ℝ → Angle) :=
continuous_quotient_mk'
/-- Coercion `ℝ → Angle` as an additive homomorphism. -/
def coeHom : ℝ →+ Angle :=
QuotientAddGroup.mk' _
@[simp]
theorem coe_coeHom : (coeHom : ℝ → Angle) = ((↑) : ℝ → Angle) :=
rfl
/-- An induction principle to deduce results for `Angle` from those for `ℝ`, used with
`induction θ using Real.Angle.induction_on`. -/
@[elab_as_elim]
protected theorem induction_on {p : Angle → Prop} (θ : Angle) (h : ∀ x : ℝ, p x) : p θ :=
Quotient.inductionOn' θ h
@[simp]
theorem coe_zero : ↑(0 : ℝ) = (0 : Angle) :=
rfl
@[simp]
theorem coe_add (x y : ℝ) : ↑(x + y : ℝ) = (↑x + ↑y : Angle) :=
rfl
@[simp]
theorem coe_neg (x : ℝ) : ↑(-x : ℝ) = -(↑x : Angle) :=
rfl
@[simp]
theorem coe_sub (x y : ℝ) : ↑(x - y : ℝ) = (↑x - ↑y : Angle) :=
rfl
theorem coe_nsmul (n : ℕ) (x : ℝ) : ↑(n • x : ℝ) = n • (↑x : Angle) :=
rfl
theorem coe_zsmul (z : ℤ) (x : ℝ) : ↑(z • x : ℝ) = z • (↑x : Angle) :=
rfl
theorem coe_eq_zero_iff {x : ℝ} : (x : Angle) = 0 ↔ ∃ n : ℤ, n • (2 * π) = x :=
AddCircle.coe_eq_zero_iff (2 * π)
@[simp, norm_cast]
theorem natCast_mul_eq_nsmul (x : ℝ) (n : ℕ) : ↑((n : ℝ) * x) = n • (↑x : Angle) := by
simpa only [nsmul_eq_mul] using coeHom.map_nsmul x n
@[simp, norm_cast]
theorem intCast_mul_eq_zsmul (x : ℝ) (n : ℤ) : ↑((n : ℝ) * x : ℝ) = n • (↑x : Angle) := by
simpa only [zsmul_eq_mul] using coeHom.map_zsmul x n
theorem angle_eq_iff_two_pi_dvd_sub {ψ θ : ℝ} : (θ : Angle) = ψ ↔ ∃ k : ℤ, θ - ψ = 2 * π * k := by
simp only [QuotientAddGroup.eq, AddSubgroup.zmultiples_eq_closure,
AddSubgroup.mem_closure_singleton, zsmul_eq_mul', (sub_eq_neg_add _ _).symm, eq_comm]
rw [Angle.coe, Angle.coe, QuotientAddGroup.eq]
simp only [AddSubgroup.zmultiples_eq_closure,
AddSubgroup.mem_closure_singleton, zsmul_eq_mul', (sub_eq_neg_add _ _).symm, eq_comm]
@[simp]
theorem coe_two_pi : ↑(2 * π : ℝ) = (0 : Angle) :=
angle_eq_iff_two_pi_dvd_sub.2 ⟨1, by rw [sub_zero, Int.cast_one, mul_one]⟩
@[simp]
theorem neg_coe_pi : -(π : Angle) = π := by
rw [← coe_neg, angle_eq_iff_two_pi_dvd_sub]
use -1
simp [two_mul, sub_eq_add_neg]
@[simp]
theorem two_nsmul_coe_div_two (θ : ℝ) : (2 : ℕ) • (↑(θ / 2) : Angle) = θ := by
rw [← coe_nsmul, two_nsmul, add_halves]
@[simp]
theorem two_zsmul_coe_div_two (θ : ℝ) : (2 : ℤ) • (↑(θ / 2) : Angle) = θ := by
rw [← coe_zsmul, two_zsmul, add_halves]
theorem two_nsmul_neg_pi_div_two : (2 : ℕ) • (↑(-π / 2) : Angle) = π := by
rw [two_nsmul_coe_div_two, coe_neg, neg_coe_pi]
theorem two_zsmul_neg_pi_div_two : (2 : ℤ) • (↑(-π / 2) : Angle) = π := by
rw [two_zsmul, ← two_nsmul, two_nsmul_neg_pi_div_two]
theorem sub_coe_pi_eq_add_coe_pi (θ : Angle) : θ - π = θ + π := by
rw [sub_eq_add_neg, neg_coe_pi]
@[simp]
theorem two_nsmul_coe_pi : (2 : ℕ) • (π : Angle) = 0 := by simp [← natCast_mul_eq_nsmul]
@[simp]
theorem two_zsmul_coe_pi : (2 : ℤ) • (π : Angle) = 0 := by simp [← intCast_mul_eq_zsmul]
@[simp]
theorem coe_pi_add_coe_pi : (π : Real.Angle) + π = 0 := by rw [← two_nsmul, two_nsmul_coe_pi]
theorem zsmul_eq_iff {ψ θ : Angle} {z : ℤ} (hz : z ≠ 0) :
z • ψ = z • θ ↔ ∃ k : Fin z.natAbs, ψ = θ + (k : ℕ) • (2 * π / z : ℝ) :=
QuotientAddGroup.zmultiples_zsmul_eq_zsmul_iff hz
theorem nsmul_eq_iff {ψ θ : Angle} {n : ℕ} (hz : n ≠ 0) :
n • ψ = n • θ ↔ ∃ k : Fin n, ψ = θ + (k : ℕ) • (2 * π / n : ℝ) :=
QuotientAddGroup.zmultiples_nsmul_eq_nsmul_iff hz
theorem two_zsmul_eq_iff {ψ θ : Angle} : (2 : ℤ) • ψ = (2 : ℤ) • θ ↔ ψ = θ ∨ ψ = θ + ↑π := by
have : Int.natAbs 2 = 2 := rfl
rw [zsmul_eq_iff two_ne_zero, this, Fin.exists_fin_two, Fin.val_zero,
Fin.val_one, zero_smul, add_zero, one_smul, Int.cast_two,
mul_div_cancel_left₀ (_ : ℝ) two_ne_zero]
theorem two_nsmul_eq_iff {ψ θ : Angle} : (2 : ℕ) • ψ = (2 : ℕ) • θ ↔ ψ = θ ∨ ψ = θ + ↑π := by
simp_rw [← natCast_zsmul, Nat.cast_ofNat, two_zsmul_eq_iff]
| theorem two_nsmul_eq_zero_iff {θ : Angle} : (2 : ℕ) • θ = 0 ↔ θ = 0 ∨ θ = π := by
convert two_nsmul_eq_iff <;> simp
| Mathlib/Analysis/SpecialFunctions/Trigonometric/Angle.lean | 160 | 161 |
/-
Copyright (c) 2021 Yakov Pechersky. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yakov Pechersky
-/
import Mathlib.Algebra.GroupWithZero.Action.Defs
import Mathlib.Algebra.Order.AddGroupWithTop
import Mathlib.Algebra.Order.Monoid.Unbundled.MinMax
import Mathlib.Algebra.Order.Monoid.Unbundled.Pow
import Mathlib.Algebra.Order.Monoid.Unbundled.WithTop
import Mathlib.Algebra.Ring.Defs
import Mathlib.Order.Hom.Basic
/-!
# Tropical algebraic structures
This file defines algebraic structures of the (min-)tropical numbers, up to the tropical semiring.
Some basic lemmas about conversion from the base type `R` to `Tropical R` are provided, as
well as the expected implementations of tropical addition and tropical multiplication.
## Main declarations
* `Tropical R`: The type synonym of the tropical interpretation of `R`.
If `[LinearOrder R]`, then addition on `R` is via `min`.
* `Semiring (Tropical R)`: A `LinearOrderedAddCommMonoidWithTop R`
induces a `Semiring (Tropical R)`. If one solely has `[LinearOrderedAddCommMonoid R]`,
then the "tropicalization of `R`" would be `Tropical (WithTop R)`.
## Implementation notes
The tropical structure relies on `Top` and `min`. For the max-tropical numbers, use
`OrderDual R`.
Inspiration was drawn from the implementation of `Additive`/`Multiplicative`/`Opposite`,
where a type synonym is created with some barebones API, and quickly made irreducible.
Algebraic structures are provided with as few typeclass assumptions as possible, even though
most references rely on `Semiring (Tropical R)` for building up the whole theory.
## References followed
* https://arxiv.org/pdf/math/0408099.pdf
* https://www.mathenjeans.fr/sites/default/files/sujets/tropical_geometry_-_casagrande.pdf
-/
assert_not_exists Nat.instMulOneClass
universe u v
variable (R : Type u)
/-- The tropicalization of a type `R`. -/
def Tropical : Type u :=
R
variable {R}
namespace Tropical
/-- Reinterpret `x : R` as an element of `Tropical R`.
See `Tropical.tropEquiv` for the equivalence.
-/
def trop : R → Tropical R :=
id
/-- Reinterpret `x : Tropical R` as an element of `R`.
See `Tropical.tropEquiv` for the equivalence. -/
@[pp_nodot]
def untrop : Tropical R → R :=
id
theorem trop_injective : Function.Injective (trop : R → Tropical R) := fun _ _ => id
theorem untrop_injective : Function.Injective (untrop : Tropical R → R) := fun _ _ => id
@[simp]
theorem trop_inj_iff (x y : R) : trop x = trop y ↔ x = y :=
Iff.rfl
@[simp]
theorem untrop_inj_iff (x y : Tropical R) : untrop x = untrop y ↔ x = y :=
Iff.rfl
@[simp]
theorem trop_untrop (x : Tropical R) : trop (untrop x) = x :=
rfl
@[simp]
theorem untrop_trop (x : R) : untrop (trop x) = x :=
rfl
attribute [irreducible] Tropical
theorem leftInverse_trop : Function.LeftInverse (trop : R → Tropical R) untrop :=
trop_untrop
theorem rightInverse_trop : Function.RightInverse (trop : R → Tropical R) untrop :=
untrop_trop
/-- Reinterpret `x : R` as an element of `Tropical R`.
See `Tropical.tropOrderIso` for the order-preserving equivalence. -/
def tropEquiv : R ≃ Tropical R where
toFun := trop
invFun := untrop
left_inv := untrop_trop
right_inv := trop_untrop
@[simp]
theorem tropEquiv_coe_fn : (tropEquiv : R → Tropical R) = trop :=
rfl
@[simp]
theorem tropEquiv_symm_coe_fn : (tropEquiv.symm : Tropical R → R) = untrop :=
rfl
theorem trop_eq_iff_eq_untrop {x : R} {y} : trop x = y ↔ x = untrop y :=
tropEquiv.apply_eq_iff_eq_symm_apply
theorem untrop_eq_iff_eq_trop {x} {y : R} : untrop x = y ↔ x = trop y :=
tropEquiv.symm.apply_eq_iff_eq_symm_apply
theorem injective_trop : Function.Injective (trop : R → Tropical R) :=
tropEquiv.injective
theorem injective_untrop : Function.Injective (untrop : Tropical R → R) :=
tropEquiv.symm.injective
theorem surjective_trop : Function.Surjective (trop : R → Tropical R) :=
tropEquiv.surjective
theorem surjective_untrop : Function.Surjective (untrop : Tropical R → R) :=
tropEquiv.symm.surjective
instance [Inhabited R] : Inhabited (Tropical R) :=
⟨trop default⟩
/-- Recursing on an `x' : Tropical R` is the same as recursing on an `x : R` reinterpreted
as a term of `Tropical R` via `trop x`. -/
@[simp]
def tropRec {F : Tropical R → Sort v} (h : ∀ X, F (trop X)) : ∀ X, F X := fun X => h (untrop X)
instance [DecidableEq R] : DecidableEq (Tropical R) := fun _ _ =>
decidable_of_iff _ injective_untrop.eq_iff
section Order
instance instLETropical [LE R] : LE (Tropical R) where le x y := untrop x ≤ untrop y
@[simp]
theorem untrop_le_iff [LE R] {x y : Tropical R} : untrop x ≤ untrop y ↔ x ≤ y :=
Iff.rfl
instance decidableLE [LE R] [DecidableLE R] : DecidableLE (Tropical R) := fun x y =>
‹DecidableLE R› (untrop x) (untrop y)
instance instLTTropical [LT R] : LT (Tropical R) where lt x y := untrop x < untrop y
@[simp]
theorem untrop_lt_iff [LT R] {x y : Tropical R} : untrop x < untrop y ↔ x < y :=
Iff.rfl
instance decidableLT [LT R] [DecidableLT R] : DecidableLT (Tropical R) := fun x y =>
‹DecidableLT R› (untrop x) (untrop y)
instance instPreorderTropical [Preorder R] : Preorder (Tropical R) :=
{ instLETropical, instLTTropical with
le_refl := fun x => le_refl (untrop x)
le_trans := fun _ _ _ h h' => le_trans (α := R) h h'
lt_iff_le_not_le := fun _ _ => lt_iff_le_not_le (α := R) }
/-- Reinterpret `x : R` as an element of `Tropical R`, preserving the order. -/
def tropOrderIso [Preorder R] : R ≃o Tropical R :=
{ tropEquiv with map_rel_iff' := untrop_le_iff }
@[simp]
theorem tropOrderIso_coe_fn [Preorder R] : (tropOrderIso : R → Tropical R) = trop :=
rfl
@[simp]
theorem tropOrderIso_symm_coe_fn [Preorder R] : (tropOrderIso.symm : Tropical R → R) = untrop :=
rfl
theorem trop_monotone [Preorder R] : Monotone (trop : R → Tropical R) := fun _ _ => id
theorem untrop_monotone [Preorder R] : Monotone (untrop : Tropical R → R) := fun _ _ => id
instance instPartialOrderTropical [PartialOrder R] : PartialOrder (Tropical R) :=
{ instPreorderTropical with le_antisymm := fun _ _ h h' => untrop_injective (le_antisymm h h') }
instance instZeroTropical [Top R] : Zero (Tropical R) :=
⟨trop ⊤⟩
instance instTopTropical [Top R] : Top (Tropical R) :=
⟨0⟩
@[simp]
theorem untrop_zero [Top R] : untrop (0 : Tropical R) = ⊤ :=
rfl
@[simp]
theorem trop_top [Top R] : trop (⊤ : R) = 0 :=
rfl
@[simp]
theorem trop_coe_ne_zero (x : R) : trop (x : WithTop R) ≠ 0 :=
nofun
@[simp]
theorem zero_ne_trop_coe (x : R) : (0 : Tropical (WithTop R)) ≠ trop x :=
nofun
@[simp]
theorem le_zero [LE R] [OrderTop R] (x : Tropical R) : x ≤ 0 :=
le_top (α := R)
instance [LE R] [OrderTop R] : OrderTop (Tropical R) :=
{ instTopTropical with le_top := fun _ => le_top (α := R) }
variable [LinearOrder R]
/-- Tropical addition is the minimum of two underlying elements of `R`. -/
instance : Add (Tropical R) :=
⟨fun x y => trop (min (untrop x) (untrop y))⟩
instance instAddCommSemigroupTropical : AddCommSemigroup (Tropical R) where
add := (· + ·)
add_assoc _ _ _ := untrop_injective (min_assoc _ _ _)
add_comm _ _ := untrop_injective (min_comm _ _)
@[simp]
theorem untrop_add (x y : Tropical R) : untrop (x + y) = min (untrop x) (untrop y) :=
rfl
@[simp]
theorem trop_min (x y : R) : trop (min x y) = trop x + trop y :=
rfl
@[simp]
theorem trop_inf (x y : R) : trop (x ⊓ y) = trop x + trop y :=
rfl
theorem trop_add_def (x y : Tropical R) : x + y = trop (min (untrop x) (untrop y)) :=
rfl
instance instLinearOrderTropical : LinearOrder (Tropical R) :=
{ instPartialOrderTropical with
le_total := fun a b => le_total (untrop a) (untrop b)
toDecidableLE := Tropical.decidableLE
toDecidableEq := Tropical.instDecidableEq
toDecidableLT := Tropical.decidableLT
max := fun a b => trop (max (untrop a) (untrop b))
max_def := fun a b => untrop_injective (by
simp only [max_def, untrop_le_iff, untrop_trop]; split_ifs <;> simp)
min := (· + ·)
min_def := fun a b => untrop_injective (by
simp only [untrop_add, min_def, untrop_le_iff]; split_ifs <;> simp) }
@[simp]
theorem untrop_sup (x y : Tropical R) : untrop (x ⊔ y) = untrop x ⊔ untrop y :=
rfl
@[simp]
theorem untrop_max (x y : Tropical R) : untrop (max x y) = max (untrop x) (untrop y) :=
rfl
@[simp]
theorem min_eq_add : (min : Tropical R → Tropical R → Tropical R) = (· + ·) :=
rfl
@[simp]
theorem inf_eq_add : ((· ⊓ ·) : Tropical R → Tropical R → Tropical R) = (· + ·) :=
rfl
theorem trop_max_def (x y : Tropical R) : max x y = trop (max (untrop x) (untrop y)) :=
rfl
theorem trop_sup_def (x y : Tropical R) : x ⊔ y = trop (untrop x ⊔ untrop y) :=
rfl
@[simp]
theorem add_eq_left ⦃x y : Tropical R⦄ (h : x ≤ y) : x + y = x :=
untrop_injective (by simpa using h)
@[simp]
theorem add_eq_right ⦃x y : Tropical R⦄ (h : y ≤ x) : x + y = y :=
untrop_injective (by simpa using h)
theorem add_eq_left_iff {x y : Tropical R} : x + y = x ↔ x ≤ y := by
rw [trop_add_def, trop_eq_iff_eq_untrop, ← untrop_le_iff, min_eq_left_iff]
theorem add_eq_right_iff {x y : Tropical R} : x + y = y ↔ y ≤ x := by
rw [trop_add_def, trop_eq_iff_eq_untrop, ← untrop_le_iff, min_eq_right_iff]
theorem add_self (x : Tropical R) : x + x = x :=
untrop_injective (min_eq_right le_rfl)
theorem add_eq_iff {x y z : Tropical R} : x + y = z ↔ x = z ∧ x ≤ y ∨ y = z ∧ y ≤ x := by
rw [trop_add_def, trop_eq_iff_eq_untrop]
simp [min_eq_iff]
@[simp]
theorem add_eq_zero_iff {a b : Tropical (WithTop R)} : a + b = 0 ↔ a = 0 ∧ b = 0 := by
rw [add_eq_iff]
constructor
· rintro (⟨rfl, h⟩ | ⟨rfl, h⟩)
· exact ⟨rfl, le_antisymm (le_zero _) h⟩
· exact ⟨le_antisymm (le_zero _) h, rfl⟩
· rintro ⟨rfl, rfl⟩
simp
instance instAddCommMonoidTropical [OrderTop R] : AddCommMonoid (Tropical R) :=
{ instZeroTropical, instAddCommSemigroupTropical with
zero_add := fun _ => untrop_injective (min_top_left _)
add_zero := fun _ => untrop_injective (min_top_right _)
nsmul := nsmulRec }
end Order
section Monoid
/-- Tropical multiplication is the addition in the underlying `R`. -/
instance [Add R] : Mul (Tropical R) :=
⟨fun x y => trop (untrop x + untrop y)⟩
@[simp]
theorem trop_add [Add R] (x y : R) : trop (x + y) = trop x * trop y :=
rfl
@[simp]
theorem untrop_mul [Add R] (x y : Tropical R) : untrop (x * y) = untrop x + untrop y :=
rfl
theorem trop_mul_def [Add R] (x y : Tropical R) : x * y = trop (untrop x + untrop y) :=
rfl
instance instOneTropical [Zero R] : One (Tropical R) :=
⟨trop 0⟩
@[simp]
theorem trop_zero [Zero R] : trop (0 : R) = 1 :=
rfl
@[simp]
theorem untrop_one [Zero R] : untrop (1 : Tropical R) = 0 :=
rfl
instance instAddMonoidWithOneTropical [LinearOrder R] [OrderTop R] [Zero R] :
AddMonoidWithOne (Tropical R) :=
{ instOneTropical, instAddCommMonoidTropical with
natCast := fun n => if n = 0 then 0 else 1
natCast_zero := rfl
natCast_succ := fun n => (untrop_inj_iff _ _).1 (by cases n <;> simp [Nat.cast]) }
| instance [Zero R] : Nontrivial (Tropical (WithTop R)) :=
⟨⟨0, 1, trop_injective.ne WithTop.top_ne_coe⟩⟩
| Mathlib/Algebra/Tropical/Basic.lean | 356 | 358 |
/-
Copyright (c) 2017 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl, Yury Kudryashov
-/
import Mathlib.MeasureTheory.Constructions.BorelSpace.Order
import Mathlib.MeasureTheory.MeasurableSpace.Prod
import Mathlib.MeasureTheory.Measure.Typeclasses.NoAtoms
import Mathlib.Topology.Instances.Real.Lemmas
/-!
# Borel (measurable) spaces ℝ, ℝ≥0, ℝ≥0∞
## Main statements
* `borel_eq_generateFrom_Ixx_rat` (where Ixx is one of {Ioo, Ioi, Iio, Ici, Iic):
the Borel sigma algebra on ℝ is generated by intervals with rational endpoints;
* `isPiSystem_Ixx_rat` (where Ixx is one of {Ioo, Ioi, Iio, Ici, Iic):
intervals with rational endpoints form a pi system on ℝ;
* `measurable_real_toNNReal`, `measurable_coe_nnreal_real`, `measurable_coe_nnreal_ennreal`,
`ENNReal.measurable_ofReal`, `ENNReal.measurable_toReal`:
measurability of various coercions between ℝ, ℝ≥0, and ℝ≥0∞;
* `Measurable.real_toNNReal`, `Measurable.coe_nnreal_real`, `Measurable.coe_nnreal_ennreal`,
`Measurable.ennreal_ofReal`, `Measurable.ennreal_toNNReal`, `Measurable.ennreal_toReal`:
measurability of functions composed with various coercions between ℝ, ℝ≥0, and ℝ≥0∞
(also similar results for a.e.-measurability);
* `Measurable.ennreal*` : measurability of special cases for arithmetic operations on `ℝ≥0∞`.
-/
open Set Filter MeasureTheory MeasurableSpace
open scoped Topology NNReal ENNReal
universe u v w x y
variable {α β γ δ : Type*} {ι : Sort y} {s t u : Set α}
namespace Real
theorem borel_eq_generateFrom_Ioo_rat :
borel ℝ = .generateFrom (⋃ (a : ℚ) (b : ℚ) (_ : a < b), {Ioo (a : ℝ) (b : ℝ)}) :=
isTopologicalBasis_Ioo_rat.borel_eq_generateFrom
theorem borel_eq_generateFrom_Iio_rat : borel ℝ = .generateFrom (⋃ a : ℚ, {Iio (a : ℝ)}) := by
rw [borel_eq_generateFrom_Iio]
refine le_antisymm
(generateFrom_le ?_)
(generateFrom_mono <| iUnion_subset fun q ↦ singleton_subset_iff.mpr <| mem_range_self _)
rintro _ ⟨a, rfl⟩
have : IsLUB (range ((↑) : ℚ → ℝ) ∩ Iio a) a := by
simp [isLUB_iff_le_iff, mem_upperBounds, ← le_iff_forall_rat_lt_imp_le]
rw [← this.biUnion_Iio_eq, ← image_univ, ← image_inter_preimage, univ_inter, biUnion_image]
exact MeasurableSet.biUnion (to_countable _)
fun b _ => GenerateMeasurable.basic (Iio (b : ℝ)) (by simp)
theorem borel_eq_generateFrom_Ioi_rat : borel ℝ = .generateFrom (⋃ a : ℚ, {Ioi (a : ℝ)}) := by
rw [borel_eq_generateFrom_Ioi]
refine le_antisymm
(generateFrom_le ?_)
(generateFrom_mono <| iUnion_subset fun q ↦ singleton_subset_iff.mpr <| mem_range_self _)
rintro _ ⟨a, rfl⟩
have : IsGLB (range ((↑) : ℚ → ℝ) ∩ Ioi a) a := by
simp [isGLB_iff_le_iff, mem_lowerBounds, ← le_iff_forall_lt_rat_imp_le]
rw [← this.biUnion_Ioi_eq, ← image_univ, ← image_inter_preimage, univ_inter, biUnion_image]
exact MeasurableSet.biUnion (to_countable _)
fun b _ => GenerateMeasurable.basic (Ioi (b : ℝ)) (by simp)
theorem borel_eq_generateFrom_Iic_rat : borel ℝ = .generateFrom (⋃ a : ℚ, {Iic (a : ℝ)}) := by
rw [borel_eq_generateFrom_Ioi_rat, iUnion_singleton_eq_range, iUnion_singleton_eq_range]
refine le_antisymm (generateFrom_le ?_) (generateFrom_le ?_) <;>
rintro _ ⟨q, rfl⟩ <;>
dsimp only <;>
[rw [← compl_Iic]; rw [← compl_Ioi]] <;>
exact MeasurableSet.compl (GenerateMeasurable.basic _ (mem_range_self q))
| theorem borel_eq_generateFrom_Ici_rat : borel ℝ = .generateFrom (⋃ a : ℚ, {Ici (a : ℝ)}) := by
rw [borel_eq_generateFrom_Iio_rat, iUnion_singleton_eq_range, iUnion_singleton_eq_range]
refine le_antisymm (generateFrom_le ?_) (generateFrom_le ?_) <;>
rintro _ ⟨q, rfl⟩ <;>
dsimp only <;>
[rw [← compl_Ici]; rw [← compl_Iio]] <;>
exact MeasurableSet.compl (GenerateMeasurable.basic _ (mem_range_self q))
| Mathlib/MeasureTheory/Constructions/BorelSpace/Real.lean | 76 | 82 |
/-
Copyright (c) 2023 Antoine Labelle. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Antoine Labelle
-/
import Mathlib.Combinatorics.Quiver.Cast
import Mathlib.Combinatorics.Quiver.Symmetric
/-!
# Single-object quiver
Single object quiver with a given arrows type.
## Main definitions
Given a type `α`, `SingleObj α` is the `Unit` type, whose single object is called `star α`, with
`Quiver` structure such that `star α ⟶ star α` is the type `α`.
An element `x : α` can be reinterpreted as an element of `star α ⟶ star α` using
`toHom`.
More generally, a list of elements of `a` can be reinterpreted as a path from `star α` to
itself using `pathEquivList`.
-/
namespace Quiver
/-- Type tag on `Unit` used to define single-object quivers. -/
@[nolint unusedArguments]
def SingleObj (_ : Type*) : Type :=
Unit
-- The `Unique` instance should be constructed by a deriving handler.
-- https://github.com/leanprover-community/mathlib4/issues/380
instance {α : Type*} : Unique (SingleObj α) where
default := ⟨⟩
uniq := fun _ => rfl
namespace SingleObj
variable (α β γ : Type*)
instance : Quiver (SingleObj α) :=
⟨fun _ _ => α⟩
/-- The single object in `SingleObj α`. -/
def star : SingleObj α :=
Unit.unit
instance : Inhabited (SingleObj α) :=
⟨star α⟩
variable {α β γ}
lemma ext {x y : SingleObj α} : x = y := Unit.ext x y
-- See note [reducible non-instances]
/-- Equip `SingleObj α` with a reverse operation. -/
abbrev hasReverse (rev : α → α) : HasReverse (SingleObj α) := ⟨rev⟩
-- See note [reducible non-instances]
/-- Equip `SingleObj α` with an involutive reverse operation. -/
abbrev hasInvolutiveReverse (rev : α → α) (h : Function.Involutive rev) :
HasInvolutiveReverse (SingleObj α) where
toHasReverse := hasReverse rev
inv' := h
/-- The type of arrows from `star α` to itself is equivalent to the original type `α`. -/
@[simps!]
def toHom : α ≃ (star α ⟶ star α) :=
Equiv.refl _
/-- Prefunctors between two `SingleObj` quivers correspond to functions between the corresponding
arrows types.
-/
@[simps]
def toPrefunctor : (α → β) ≃ SingleObj α ⥤q SingleObj β where
toFun f := ⟨id, f⟩
invFun f a := f.map (toHom a)
left_inv _ := rfl
right_inv _ := rfl
theorem toPrefunctor_id : toPrefunctor id = 𝟭q (SingleObj α) :=
rfl
@[simp]
theorem toPrefunctor_symm_id : toPrefunctor.symm (𝟭q (SingleObj α)) = id :=
rfl
theorem toPrefunctor_comp (f : α → β) (g : β → γ) :
toPrefunctor (g ∘ f) = toPrefunctor f ⋙q toPrefunctor g :=
rfl
@[simp]
theorem toPrefunctor_symm_comp (f : SingleObj α ⥤q SingleObj β) (g : SingleObj β ⥤q SingleObj γ) :
toPrefunctor.symm (f ⋙q g) = toPrefunctor.symm g ∘ toPrefunctor.symm f := by
simp only [Equiv.symm_apply_eq, toPrefunctor_comp, Equiv.apply_symm_apply]
/-- Auxiliary definition for `quiver.SingleObj.pathEquivList`.
Converts a path in the quiver `single_obj α` into a list of elements of type `a`.
-/
def pathToList : ∀ {x : SingleObj α}, Path (star α) x → List α
| _, Path.nil => []
| _, Path.cons p a => a :: pathToList p
/-- Auxiliary definition for `quiver.SingleObj.pathEquivList`.
Converts a list of elements of type `α` into a path in the quiver `SingleObj α`.
-/
@[simp]
def listToPath : List α → Path (star α) (star α)
| [] => Path.nil
| | a :: l => (listToPath l).cons a
theorem listToPath_pathToList {x : SingleObj α} (p : Path (star α) x) :
| Mathlib/Combinatorics/Quiver/SingleObj.lean | 110 | 112 |
/-
Copyright (c) 2020 Kevin Kappelmann. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kevin Kappelmann
-/
import Mathlib.Algebra.ContinuedFractions.Translations
/-!
# Stabilisation of gcf Computations Under Termination
## Summary
We show that the continuants and convergents of a gcf stabilise once the gcf terminates.
-/
namespace GenContFract
variable {K : Type*} {g : GenContFract K} {n m : ℕ}
/-- If a gcf terminated at position `n`, it also terminated at `m ≥ n`. -/
theorem terminated_stable (n_le_m : n ≤ m) (terminatedAt_n : g.TerminatedAt n) :
g.TerminatedAt m :=
g.s.terminated_stable n_le_m terminatedAt_n
variable [DivisionRing K]
theorem contsAux_stable_step_of_terminated (terminatedAt_n : g.TerminatedAt n) :
g.contsAux (n + 2) = g.contsAux (n + 1) := by
rw [terminatedAt_iff_s_none] at terminatedAt_n
simp only [contsAux, Nat.add_eq, Nat.add_zero, terminatedAt_n]
theorem contsAux_stable_of_terminated (n_lt_m : n < m) (terminatedAt_n : g.TerminatedAt n) :
g.contsAux m = g.contsAux (n + 1) := by
refine Nat.le_induction rfl (fun k hnk hk => ?_) _ n_lt_m
rcases Nat.exists_eq_add_of_lt hnk with ⟨k, rfl⟩
refine (contsAux_stable_step_of_terminated ?_).trans hk
exact terminated_stable (Nat.le_add_right _ _) terminatedAt_n
theorem convs'Aux_stable_step_of_terminated {s : Stream'.Seq <| Pair K}
(terminatedAt_n : s.TerminatedAt n) : convs'Aux s (n + 1) = convs'Aux s n := by
change s.get? n = none at terminatedAt_n
induction n generalizing s with
| zero => simp only [convs'Aux, terminatedAt_n, Stream'.Seq.head]
| succ n IH =>
cases s_head_eq : s.head with
| none => simp only [convs'Aux, s_head_eq]
| some gp_head =>
have : s.tail.TerminatedAt n := by
simp only [Stream'.Seq.TerminatedAt, s.get?_tail, terminatedAt_n]
have := IH this
rw [convs'Aux] at this
simp [this, Nat.add_eq, add_zero, convs'Aux, s_head_eq]
theorem convs'Aux_stable_of_terminated {s : Stream'.Seq <| Pair K} (n_le_m : n ≤ m)
(terminatedAt_n : s.TerminatedAt n) : convs'Aux s m = convs'Aux s n := by
induction n_le_m with
| refl => rfl
| step n_le_m IH =>
refine (convs'Aux_stable_step_of_terminated (?_)).trans IH
exact s.terminated_stable n_le_m terminatedAt_n
theorem conts_stable_of_terminated (n_le_m : n ≤ m) (terminatedAt_n : g.TerminatedAt n) :
g.conts m = g.conts n := by
simp only [nth_cont_eq_succ_nth_contAux,
contsAux_stable_of_terminated (Nat.pred_le_iff.mp n_le_m) terminatedAt_n]
theorem nums_stable_of_terminated (n_le_m : n ≤ m) (terminatedAt_n : g.TerminatedAt n) :
g.nums m = g.nums n := by
simp only [num_eq_conts_a, conts_stable_of_terminated n_le_m terminatedAt_n]
theorem dens_stable_of_terminated (n_le_m : n ≤ m) (terminatedAt_n : g.TerminatedAt n) :
g.dens m = g.dens n := by
simp only [den_eq_conts_b, conts_stable_of_terminated n_le_m terminatedAt_n]
|
theorem convs_stable_of_terminated (n_le_m : n ≤ m) (terminatedAt_n : g.TerminatedAt n) :
g.convs m = g.convs n := by
| Mathlib/Algebra/ContinuedFractions/TerminatedStable.lean | 75 | 77 |
/-
Copyright (c) 2014 Jeremy Avigad. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Jeremy Avigad, Leonardo de Moura, Johannes Hölzl, Mario Carneiro
-/
import Mathlib.Logic.Pairwise
import Mathlib.Data.Set.BooleanAlgebra
/-!
# The set lattice
This file is a collection of results on the complete atomic boolean algebra structure of `Set α`.
Notation for the complete lattice operations can be found in `Mathlib.Order.SetNotation`.
## Main declarations
* `Set.sInter_eq_biInter`, `Set.sUnion_eq_biInter`: Shows that `⋂₀ s = ⋂ x ∈ s, x` and
`⋃₀ s = ⋃ x ∈ s, x`.
* `Set.completeAtomicBooleanAlgebra`: `Set α` is a `CompleteAtomicBooleanAlgebra` with `≤ = ⊆`,
`< = ⊂`, `⊓ = ∩`, `⊔ = ∪`, `⨅ = ⋂`, `⨆ = ⋃` and `\` as the set difference.
See `Set.instBooleanAlgebra`.
* `Set.unionEqSigmaOfDisjoint`: Equivalence between `⋃ i, t i` and `Σ i, t i`, where `t` is an
indexed family of disjoint sets.
## Naming convention
In lemma names,
* `⋃ i, s i` is called `iUnion`
* `⋂ i, s i` is called `iInter`
* `⋃ i j, s i j` is called `iUnion₂`. This is an `iUnion` inside an `iUnion`.
* `⋂ i j, s i j` is called `iInter₂`. This is an `iInter` inside an `iInter`.
* `⋃ i ∈ s, t i` is called `biUnion` for "bounded `iUnion`". This is the special case of `iUnion₂`
where `j : i ∈ s`.
* `⋂ i ∈ s, t i` is called `biInter` for "bounded `iInter`". This is the special case of `iInter₂`
where `j : i ∈ s`.
## Notation
* `⋃`: `Set.iUnion`
* `⋂`: `Set.iInter`
* `⋃₀`: `Set.sUnion`
* `⋂₀`: `Set.sInter`
-/
open Function Set
universe u
variable {α β γ δ : Type*} {ι ι' ι₂ : Sort*} {κ κ₁ κ₂ : ι → Sort*} {κ' : ι' → Sort*}
namespace Set
/-! ### Complete lattice and complete Boolean algebra instances -/
theorem mem_iUnion₂ {x : γ} {s : ∀ i, κ i → Set γ} : (x ∈ ⋃ (i) (j), s i j) ↔ ∃ i j, x ∈ s i j := by
simp_rw [mem_iUnion]
theorem mem_iInter₂ {x : γ} {s : ∀ i, κ i → Set γ} : (x ∈ ⋂ (i) (j), s i j) ↔ ∀ i j, x ∈ s i j := by
simp_rw [mem_iInter]
theorem mem_iUnion_of_mem {s : ι → Set α} {a : α} (i : ι) (ha : a ∈ s i) : a ∈ ⋃ i, s i :=
mem_iUnion.2 ⟨i, ha⟩
theorem mem_iUnion₂_of_mem {s : ∀ i, κ i → Set α} {a : α} {i : ι} (j : κ i) (ha : a ∈ s i j) :
a ∈ ⋃ (i) (j), s i j :=
mem_iUnion₂.2 ⟨i, j, ha⟩
theorem mem_iInter_of_mem {s : ι → Set α} {a : α} (h : ∀ i, a ∈ s i) : a ∈ ⋂ i, s i :=
mem_iInter.2 h
theorem mem_iInter₂_of_mem {s : ∀ i, κ i → Set α} {a : α} (h : ∀ i j, a ∈ s i j) :
a ∈ ⋂ (i) (j), s i j :=
mem_iInter₂.2 h
/-! ### Union and intersection over an indexed family of sets -/
@[congr]
theorem iUnion_congr_Prop {p q : Prop} {f₁ : p → Set α} {f₂ : q → Set α} (pq : p ↔ q)
(f : ∀ x, f₁ (pq.mpr x) = f₂ x) : iUnion f₁ = iUnion f₂ :=
iSup_congr_Prop pq f
@[congr]
theorem iInter_congr_Prop {p q : Prop} {f₁ : p → Set α} {f₂ : q → Set α} (pq : p ↔ q)
(f : ∀ x, f₁ (pq.mpr x) = f₂ x) : iInter f₁ = iInter f₂ :=
iInf_congr_Prop pq f
theorem iUnion_plift_up (f : PLift ι → Set α) : ⋃ i, f (PLift.up i) = ⋃ i, f i :=
iSup_plift_up _
theorem iUnion_plift_down (f : ι → Set α) : ⋃ i, f (PLift.down i) = ⋃ i, f i :=
iSup_plift_down _
theorem iInter_plift_up (f : PLift ι → Set α) : ⋂ i, f (PLift.up i) = ⋂ i, f i :=
iInf_plift_up _
theorem iInter_plift_down (f : ι → Set α) : ⋂ i, f (PLift.down i) = ⋂ i, f i :=
iInf_plift_down _
theorem iUnion_eq_if {p : Prop} [Decidable p] (s : Set α) : ⋃ _ : p, s = if p then s else ∅ :=
iSup_eq_if _
theorem iUnion_eq_dif {p : Prop} [Decidable p] (s : p → Set α) :
⋃ h : p, s h = if h : p then s h else ∅ :=
iSup_eq_dif _
theorem iInter_eq_if {p : Prop} [Decidable p] (s : Set α) : ⋂ _ : p, s = if p then s else univ :=
iInf_eq_if _
theorem iInf_eq_dif {p : Prop} [Decidable p] (s : p → Set α) :
⋂ h : p, s h = if h : p then s h else univ :=
_root_.iInf_eq_dif _
theorem exists_set_mem_of_union_eq_top {ι : Type*} (t : Set ι) (s : ι → Set β)
(w : ⋃ i ∈ t, s i = ⊤) (x : β) : ∃ i ∈ t, x ∈ s i := by
have p : x ∈ ⊤ := Set.mem_univ x
rw [← w, Set.mem_iUnion] at p
simpa using p
theorem nonempty_of_union_eq_top_of_nonempty {ι : Type*} (t : Set ι) (s : ι → Set α)
(H : Nonempty α) (w : ⋃ i ∈ t, s i = ⊤) : t.Nonempty := by
obtain ⟨x, m, -⟩ := exists_set_mem_of_union_eq_top t s w H.some
exact ⟨x, m⟩
theorem nonempty_of_nonempty_iUnion
{s : ι → Set α} (h_Union : (⋃ i, s i).Nonempty) : Nonempty ι := by
obtain ⟨x, hx⟩ := h_Union
exact ⟨Classical.choose <| mem_iUnion.mp hx⟩
theorem nonempty_of_nonempty_iUnion_eq_univ
{s : ι → Set α} [Nonempty α] (h_Union : ⋃ i, s i = univ) : Nonempty ι :=
nonempty_of_nonempty_iUnion (s := s) (by simpa only [h_Union] using univ_nonempty)
theorem setOf_exists (p : ι → β → Prop) : { x | ∃ i, p i x } = ⋃ i, { x | p i x } :=
ext fun _ => mem_iUnion.symm
theorem setOf_forall (p : ι → β → Prop) : { x | ∀ i, p i x } = ⋂ i, { x | p i x } :=
ext fun _ => mem_iInter.symm
theorem iUnion_subset {s : ι → Set α} {t : Set α} (h : ∀ i, s i ⊆ t) : ⋃ i, s i ⊆ t :=
iSup_le h
theorem iUnion₂_subset {s : ∀ i, κ i → Set α} {t : Set α} (h : ∀ i j, s i j ⊆ t) :
⋃ (i) (j), s i j ⊆ t :=
iUnion_subset fun x => iUnion_subset (h x)
theorem subset_iInter {t : Set β} {s : ι → Set β} (h : ∀ i, t ⊆ s i) : t ⊆ ⋂ i, s i :=
le_iInf h
theorem subset_iInter₂ {s : Set α} {t : ∀ i, κ i → Set α} (h : ∀ i j, s ⊆ t i j) :
s ⊆ ⋂ (i) (j), t i j :=
subset_iInter fun x => subset_iInter <| h x
@[simp]
theorem iUnion_subset_iff {s : ι → Set α} {t : Set α} : ⋃ i, s i ⊆ t ↔ ∀ i, s i ⊆ t :=
⟨fun h _ => Subset.trans (le_iSup s _) h, iUnion_subset⟩
theorem iUnion₂_subset_iff {s : ∀ i, κ i → Set α} {t : Set α} :
⋃ (i) (j), s i j ⊆ t ↔ ∀ i j, s i j ⊆ t := by simp_rw [iUnion_subset_iff]
@[simp]
theorem subset_iInter_iff {s : Set α} {t : ι → Set α} : (s ⊆ ⋂ i, t i) ↔ ∀ i, s ⊆ t i :=
le_iInf_iff
theorem subset_iInter₂_iff {s : Set α} {t : ∀ i, κ i → Set α} :
(s ⊆ ⋂ (i) (j), t i j) ↔ ∀ i j, s ⊆ t i j := by simp_rw [subset_iInter_iff]
theorem subset_iUnion : ∀ (s : ι → Set β) (i : ι), s i ⊆ ⋃ i, s i :=
le_iSup
theorem iInter_subset : ∀ (s : ι → Set β) (i : ι), ⋂ i, s i ⊆ s i :=
iInf_le
lemma iInter_subset_iUnion [Nonempty ι] {s : ι → Set α} : ⋂ i, s i ⊆ ⋃ i, s i := iInf_le_iSup
theorem subset_iUnion₂ {s : ∀ i, κ i → Set α} (i : ι) (j : κ i) : s i j ⊆ ⋃ (i') (j'), s i' j' :=
le_iSup₂ i j
theorem iInter₂_subset {s : ∀ i, κ i → Set α} (i : ι) (j : κ i) : ⋂ (i) (j), s i j ⊆ s i j :=
iInf₂_le i j
/-- This rather trivial consequence of `subset_iUnion`is convenient with `apply`, and has `i`
explicit for this purpose. -/
theorem subset_iUnion_of_subset {s : Set α} {t : ι → Set α} (i : ι) (h : s ⊆ t i) : s ⊆ ⋃ i, t i :=
le_iSup_of_le i h
/-- This rather trivial consequence of `iInter_subset`is convenient with `apply`, and has `i`
explicit for this purpose. -/
theorem iInter_subset_of_subset {s : ι → Set α} {t : Set α} (i : ι) (h : s i ⊆ t) :
⋂ i, s i ⊆ t :=
iInf_le_of_le i h
/-- This rather trivial consequence of `subset_iUnion₂` is convenient with `apply`, and has `i` and
`j` explicit for this purpose. -/
theorem subset_iUnion₂_of_subset {s : Set α} {t : ∀ i, κ i → Set α} (i : ι) (j : κ i)
(h : s ⊆ t i j) : s ⊆ ⋃ (i) (j), t i j :=
le_iSup₂_of_le i j h
/-- This rather trivial consequence of `iInter₂_subset` is convenient with `apply`, and has `i` and
`j` explicit for this purpose. -/
theorem iInter₂_subset_of_subset {s : ∀ i, κ i → Set α} {t : Set α} (i : ι) (j : κ i)
(h : s i j ⊆ t) : ⋂ (i) (j), s i j ⊆ t :=
iInf₂_le_of_le i j h
theorem iUnion_mono {s t : ι → Set α} (h : ∀ i, s i ⊆ t i) : ⋃ i, s i ⊆ ⋃ i, t i :=
iSup_mono h
@[gcongr]
theorem iUnion_mono'' {s t : ι → Set α} (h : ∀ i, s i ⊆ t i) : iUnion s ⊆ iUnion t :=
iSup_mono h
theorem iUnion₂_mono {s t : ∀ i, κ i → Set α} (h : ∀ i j, s i j ⊆ t i j) :
⋃ (i) (j), s i j ⊆ ⋃ (i) (j), t i j :=
iSup₂_mono h
theorem iInter_mono {s t : ι → Set α} (h : ∀ i, s i ⊆ t i) : ⋂ i, s i ⊆ ⋂ i, t i :=
iInf_mono h
@[gcongr]
theorem iInter_mono'' {s t : ι → Set α} (h : ∀ i, s i ⊆ t i) : iInter s ⊆ iInter t :=
iInf_mono h
theorem iInter₂_mono {s t : ∀ i, κ i → Set α} (h : ∀ i j, s i j ⊆ t i j) :
⋂ (i) (j), s i j ⊆ ⋂ (i) (j), t i j :=
iInf₂_mono h
theorem iUnion_mono' {s : ι → Set α} {t : ι₂ → Set α} (h : ∀ i, ∃ j, s i ⊆ t j) :
⋃ i, s i ⊆ ⋃ i, t i :=
iSup_mono' h
theorem iUnion₂_mono' {s : ∀ i, κ i → Set α} {t : ∀ i', κ' i' → Set α}
(h : ∀ i j, ∃ i' j', s i j ⊆ t i' j') : ⋃ (i) (j), s i j ⊆ ⋃ (i') (j'), t i' j' :=
iSup₂_mono' h
theorem iInter_mono' {s : ι → Set α} {t : ι' → Set α} (h : ∀ j, ∃ i, s i ⊆ t j) :
⋂ i, s i ⊆ ⋂ j, t j :=
Set.subset_iInter fun j =>
let ⟨i, hi⟩ := h j
iInter_subset_of_subset i hi
theorem iInter₂_mono' {s : ∀ i, κ i → Set α} {t : ∀ i', κ' i' → Set α}
(h : ∀ i' j', ∃ i j, s i j ⊆ t i' j') : ⋂ (i) (j), s i j ⊆ ⋂ (i') (j'), t i' j' :=
subset_iInter₂_iff.2 fun i' j' =>
let ⟨_, _, hst⟩ := h i' j'
(iInter₂_subset _ _).trans hst
theorem iUnion₂_subset_iUnion (κ : ι → Sort*) (s : ι → Set α) :
⋃ (i) (_ : κ i), s i ⊆ ⋃ i, s i :=
iUnion_mono fun _ => iUnion_subset fun _ => Subset.rfl
theorem iInter_subset_iInter₂ (κ : ι → Sort*) (s : ι → Set α) :
⋂ i, s i ⊆ ⋂ (i) (_ : κ i), s i :=
iInter_mono fun _ => subset_iInter fun _ => Subset.rfl
theorem iUnion_setOf (P : ι → α → Prop) : ⋃ i, { x : α | P i x } = { x : α | ∃ i, P i x } := by
ext
exact mem_iUnion
theorem iInter_setOf (P : ι → α → Prop) : ⋂ i, { x : α | P i x } = { x : α | ∀ i, P i x } := by
ext
exact mem_iInter
theorem iUnion_congr_of_surjective {f : ι → Set α} {g : ι₂ → Set α} (h : ι → ι₂) (h1 : Surjective h)
(h2 : ∀ x, g (h x) = f x) : ⋃ x, f x = ⋃ y, g y :=
h1.iSup_congr h h2
theorem iInter_congr_of_surjective {f : ι → Set α} {g : ι₂ → Set α} (h : ι → ι₂) (h1 : Surjective h)
(h2 : ∀ x, g (h x) = f x) : ⋂ x, f x = ⋂ y, g y :=
h1.iInf_congr h h2
lemma iUnion_congr {s t : ι → Set α} (h : ∀ i, s i = t i) : ⋃ i, s i = ⋃ i, t i := iSup_congr h
lemma iInter_congr {s t : ι → Set α} (h : ∀ i, s i = t i) : ⋂ i, s i = ⋂ i, t i := iInf_congr h
lemma iUnion₂_congr {s t : ∀ i, κ i → Set α} (h : ∀ i j, s i j = t i j) :
⋃ (i) (j), s i j = ⋃ (i) (j), t i j :=
iUnion_congr fun i => iUnion_congr <| h i
lemma iInter₂_congr {s t : ∀ i, κ i → Set α} (h : ∀ i j, s i j = t i j) :
⋂ (i) (j), s i j = ⋂ (i) (j), t i j :=
iInter_congr fun i => iInter_congr <| h i
section Nonempty
variable [Nonempty ι] {f : ι → Set α} {s : Set α}
lemma iUnion_const (s : Set β) : ⋃ _ : ι, s = s := iSup_const
lemma iInter_const (s : Set β) : ⋂ _ : ι, s = s := iInf_const
lemma iUnion_eq_const (hf : ∀ i, f i = s) : ⋃ i, f i = s :=
(iUnion_congr hf).trans <| iUnion_const _
lemma iInter_eq_const (hf : ∀ i, f i = s) : ⋂ i, f i = s :=
(iInter_congr hf).trans <| iInter_const _
end Nonempty
@[simp]
theorem compl_iUnion (s : ι → Set β) : (⋃ i, s i)ᶜ = ⋂ i, (s i)ᶜ :=
compl_iSup
theorem compl_iUnion₂ (s : ∀ i, κ i → Set α) : (⋃ (i) (j), s i j)ᶜ = ⋂ (i) (j), (s i j)ᶜ := by
simp_rw [compl_iUnion]
@[simp]
theorem compl_iInter (s : ι → Set β) : (⋂ i, s i)ᶜ = ⋃ i, (s i)ᶜ :=
compl_iInf
theorem compl_iInter₂ (s : ∀ i, κ i → Set α) : (⋂ (i) (j), s i j)ᶜ = ⋃ (i) (j), (s i j)ᶜ := by
simp_rw [compl_iInter]
-- classical -- complete_boolean_algebra
theorem iUnion_eq_compl_iInter_compl (s : ι → Set β) : ⋃ i, s i = (⋂ i, (s i)ᶜ)ᶜ := by
simp only [compl_iInter, compl_compl]
-- classical -- complete_boolean_algebra
theorem iInter_eq_compl_iUnion_compl (s : ι → Set β) : ⋂ i, s i = (⋃ i, (s i)ᶜ)ᶜ := by
simp only [compl_iUnion, compl_compl]
theorem inter_iUnion (s : Set β) (t : ι → Set β) : (s ∩ ⋃ i, t i) = ⋃ i, s ∩ t i :=
inf_iSup_eq _ _
theorem iUnion_inter (s : Set β) (t : ι → Set β) : (⋃ i, t i) ∩ s = ⋃ i, t i ∩ s :=
iSup_inf_eq _ _
theorem iUnion_union_distrib (s : ι → Set β) (t : ι → Set β) :
⋃ i, s i ∪ t i = (⋃ i, s i) ∪ ⋃ i, t i :=
iSup_sup_eq
theorem iInter_inter_distrib (s : ι → Set β) (t : ι → Set β) :
⋂ i, s i ∩ t i = (⋂ i, s i) ∩ ⋂ i, t i :=
iInf_inf_eq
theorem union_iUnion [Nonempty ι] (s : Set β) (t : ι → Set β) : (s ∪ ⋃ i, t i) = ⋃ i, s ∪ t i :=
sup_iSup
theorem iUnion_union [Nonempty ι] (s : Set β) (t : ι → Set β) : (⋃ i, t i) ∪ s = ⋃ i, t i ∪ s :=
iSup_sup
theorem inter_iInter [Nonempty ι] (s : Set β) (t : ι → Set β) : (s ∩ ⋂ i, t i) = ⋂ i, s ∩ t i :=
inf_iInf
theorem iInter_inter [Nonempty ι] (s : Set β) (t : ι → Set β) : (⋂ i, t i) ∩ s = ⋂ i, t i ∩ s :=
iInf_inf
theorem insert_iUnion [Nonempty ι] (x : β) (t : ι → Set β) :
insert x (⋃ i, t i) = ⋃ i, insert x (t i) := by
simp_rw [← union_singleton, iUnion_union]
-- classical
theorem union_iInter (s : Set β) (t : ι → Set β) : (s ∪ ⋂ i, t i) = ⋂ i, s ∪ t i :=
sup_iInf_eq _ _
theorem iInter_union (s : ι → Set β) (t : Set β) : (⋂ i, s i) ∪ t = ⋂ i, s i ∪ t :=
iInf_sup_eq _ _
theorem insert_iInter (x : β) (t : ι → Set β) : insert x (⋂ i, t i) = ⋂ i, insert x (t i) := by
simp_rw [← union_singleton, iInter_union]
theorem iUnion_diff (s : Set β) (t : ι → Set β) : (⋃ i, t i) \ s = ⋃ i, t i \ s :=
iUnion_inter _ _
theorem diff_iUnion [Nonempty ι] (s : Set β) (t : ι → Set β) : (s \ ⋃ i, t i) = ⋂ i, s \ t i := by
rw [diff_eq, compl_iUnion, inter_iInter]; rfl
theorem diff_iInter (s : Set β) (t : ι → Set β) : (s \ ⋂ i, t i) = ⋃ i, s \ t i := by
rw [diff_eq, compl_iInter, inter_iUnion]; rfl
theorem iUnion_inter_subset {ι α} {s t : ι → Set α} : ⋃ i, s i ∩ t i ⊆ (⋃ i, s i) ∩ ⋃ i, t i :=
le_iSup_inf_iSup s t
theorem iUnion_inter_of_monotone {ι α} [Preorder ι] [IsDirected ι (· ≤ ·)] {s t : ι → Set α}
(hs : Monotone s) (ht : Monotone t) : ⋃ i, s i ∩ t i = (⋃ i, s i) ∩ ⋃ i, t i :=
iSup_inf_of_monotone hs ht
theorem iUnion_inter_of_antitone {ι α} [Preorder ι] [IsDirected ι (swap (· ≤ ·))] {s t : ι → Set α}
(hs : Antitone s) (ht : Antitone t) : ⋃ i, s i ∩ t i = (⋃ i, s i) ∩ ⋃ i, t i :=
iSup_inf_of_antitone hs ht
theorem iInter_union_of_monotone {ι α} [Preorder ι] [IsDirected ι (swap (· ≤ ·))] {s t : ι → Set α}
(hs : Monotone s) (ht : Monotone t) : ⋂ i, s i ∪ t i = (⋂ i, s i) ∪ ⋂ i, t i :=
iInf_sup_of_monotone hs ht
theorem iInter_union_of_antitone {ι α} [Preorder ι] [IsDirected ι (· ≤ ·)] {s t : ι → Set α}
(hs : Antitone s) (ht : Antitone t) : ⋂ i, s i ∪ t i = (⋂ i, s i) ∪ ⋂ i, t i :=
iInf_sup_of_antitone hs ht
/-- An equality version of this lemma is `iUnion_iInter_of_monotone` in `Data.Set.Finite`. -/
theorem iUnion_iInter_subset {s : ι → ι' → Set α} : (⋃ j, ⋂ i, s i j) ⊆ ⋂ i, ⋃ j, s i j :=
iSup_iInf_le_iInf_iSup (flip s)
theorem iUnion_option {ι} (s : Option ι → Set α) : ⋃ o, s o = s none ∪ ⋃ i, s (some i) :=
iSup_option s
theorem iInter_option {ι} (s : Option ι → Set α) : ⋂ o, s o = s none ∩ ⋂ i, s (some i) :=
iInf_option s
section
variable (p : ι → Prop) [DecidablePred p]
theorem iUnion_dite (f : ∀ i, p i → Set α) (g : ∀ i, ¬p i → Set α) :
⋃ i, (if h : p i then f i h else g i h) = (⋃ (i) (h : p i), f i h) ∪ ⋃ (i) (h : ¬p i), g i h :=
iSup_dite _ _ _
theorem iUnion_ite (f g : ι → Set α) :
⋃ i, (if p i then f i else g i) = (⋃ (i) (_ : p i), f i) ∪ ⋃ (i) (_ : ¬p i), g i :=
iUnion_dite _ _ _
theorem iInter_dite (f : ∀ i, p i → Set α) (g : ∀ i, ¬p i → Set α) :
⋂ i, (if h : p i then f i h else g i h) = (⋂ (i) (h : p i), f i h) ∩ ⋂ (i) (h : ¬p i), g i h :=
iInf_dite _ _ _
theorem iInter_ite (f g : ι → Set α) :
⋂ i, (if p i then f i else g i) = (⋂ (i) (_ : p i), f i) ∩ ⋂ (i) (_ : ¬p i), g i :=
iInter_dite _ _ _
end
/-! ### Unions and intersections indexed by `Prop` -/
theorem iInter_false {s : False → Set α} : iInter s = univ :=
iInf_false
theorem iUnion_false {s : False → Set α} : iUnion s = ∅ :=
iSup_false
@[simp]
theorem iInter_true {s : True → Set α} : iInter s = s trivial :=
iInf_true
@[simp]
theorem iUnion_true {s : True → Set α} : iUnion s = s trivial :=
iSup_true
@[simp]
theorem iInter_exists {p : ι → Prop} {f : Exists p → Set α} :
⋂ x, f x = ⋂ (i) (h : p i), f ⟨i, h⟩ :=
iInf_exists
@[simp]
theorem iUnion_exists {p : ι → Prop} {f : Exists p → Set α} :
⋃ x, f x = ⋃ (i) (h : p i), f ⟨i, h⟩ :=
iSup_exists
@[simp]
theorem iUnion_empty : (⋃ _ : ι, ∅ : Set α) = ∅ :=
iSup_bot
@[simp]
theorem iInter_univ : (⋂ _ : ι, univ : Set α) = univ :=
iInf_top
section
variable {s : ι → Set α}
@[simp]
theorem iUnion_eq_empty : ⋃ i, s i = ∅ ↔ ∀ i, s i = ∅ :=
iSup_eq_bot
@[simp]
theorem iInter_eq_univ : ⋂ i, s i = univ ↔ ∀ i, s i = univ :=
iInf_eq_top
@[simp]
theorem nonempty_iUnion : (⋃ i, s i).Nonempty ↔ ∃ i, (s i).Nonempty := by
simp [nonempty_iff_ne_empty]
theorem nonempty_biUnion {t : Set α} {s : α → Set β} :
(⋃ i ∈ t, s i).Nonempty ↔ ∃ i ∈ t, (s i).Nonempty := by simp
theorem iUnion_nonempty_index (s : Set α) (t : s.Nonempty → Set β) :
⋃ h, t h = ⋃ x ∈ s, t ⟨x, ‹_›⟩ :=
iSup_exists
end
@[simp]
theorem iInter_iInter_eq_left {b : β} {s : ∀ x : β, x = b → Set α} :
⋂ (x) (h : x = b), s x h = s b rfl :=
iInf_iInf_eq_left
@[simp]
theorem iInter_iInter_eq_right {b : β} {s : ∀ x : β, b = x → Set α} :
⋂ (x) (h : b = x), s x h = s b rfl :=
iInf_iInf_eq_right
@[simp]
theorem iUnion_iUnion_eq_left {b : β} {s : ∀ x : β, x = b → Set α} :
⋃ (x) (h : x = b), s x h = s b rfl :=
iSup_iSup_eq_left
@[simp]
theorem iUnion_iUnion_eq_right {b : β} {s : ∀ x : β, b = x → Set α} :
⋃ (x) (h : b = x), s x h = s b rfl :=
iSup_iSup_eq_right
theorem iInter_or {p q : Prop} (s : p ∨ q → Set α) :
⋂ h, s h = (⋂ h : p, s (Or.inl h)) ∩ ⋂ h : q, s (Or.inr h) :=
iInf_or
theorem iUnion_or {p q : Prop} (s : p ∨ q → Set α) :
⋃ h, s h = (⋃ i, s (Or.inl i)) ∪ ⋃ j, s (Or.inr j) :=
iSup_or
theorem iUnion_and {p q : Prop} (s : p ∧ q → Set α) : ⋃ h, s h = ⋃ (hp) (hq), s ⟨hp, hq⟩ :=
iSup_and
theorem iInter_and {p q : Prop} (s : p ∧ q → Set α) : ⋂ h, s h = ⋂ (hp) (hq), s ⟨hp, hq⟩ :=
iInf_and
theorem iUnion_comm (s : ι → ι' → Set α) : ⋃ (i) (i'), s i i' = ⋃ (i') (i), s i i' :=
iSup_comm
theorem iInter_comm (s : ι → ι' → Set α) : ⋂ (i) (i'), s i i' = ⋂ (i') (i), s i i' :=
iInf_comm
theorem iUnion_sigma {γ : α → Type*} (s : Sigma γ → Set β) : ⋃ ia, s ia = ⋃ i, ⋃ a, s ⟨i, a⟩ :=
iSup_sigma
theorem iUnion_sigma' {γ : α → Type*} (s : ∀ i, γ i → Set β) :
⋃ i, ⋃ a, s i a = ⋃ ia : Sigma γ, s ia.1 ia.2 :=
iSup_sigma' _
theorem iInter_sigma {γ : α → Type*} (s : Sigma γ → Set β) : ⋂ ia, s ia = ⋂ i, ⋂ a, s ⟨i, a⟩ :=
iInf_sigma
theorem iInter_sigma' {γ : α → Type*} (s : ∀ i, γ i → Set β) :
⋂ i, ⋂ a, s i a = ⋂ ia : Sigma γ, s ia.1 ia.2 :=
iInf_sigma' _
theorem iUnion₂_comm (s : ∀ i₁, κ₁ i₁ → ∀ i₂, κ₂ i₂ → Set α) :
⋃ (i₁) (j₁) (i₂) (j₂), s i₁ j₁ i₂ j₂ = ⋃ (i₂) (j₂) (i₁) (j₁), s i₁ j₁ i₂ j₂ :=
iSup₂_comm _
theorem iInter₂_comm (s : ∀ i₁, κ₁ i₁ → ∀ i₂, κ₂ i₂ → Set α) :
⋂ (i₁) (j₁) (i₂) (j₂), s i₁ j₁ i₂ j₂ = ⋂ (i₂) (j₂) (i₁) (j₁), s i₁ j₁ i₂ j₂ :=
iInf₂_comm _
@[simp]
theorem biUnion_and (p : ι → Prop) (q : ι → ι' → Prop) (s : ∀ x y, p x ∧ q x y → Set α) :
⋃ (x : ι) (y : ι') (h : p x ∧ q x y), s x y h =
⋃ (x : ι) (hx : p x) (y : ι') (hy : q x y), s x y ⟨hx, hy⟩ := by
simp only [iUnion_and, @iUnion_comm _ ι']
@[simp]
theorem biUnion_and' (p : ι' → Prop) (q : ι → ι' → Prop) (s : ∀ x y, p y ∧ q x y → Set α) :
⋃ (x : ι) (y : ι') (h : p y ∧ q x y), s x y h =
⋃ (y : ι') (hy : p y) (x : ι) (hx : q x y), s x y ⟨hy, hx⟩ := by
simp only [iUnion_and, @iUnion_comm _ ι]
@[simp]
theorem biInter_and (p : ι → Prop) (q : ι → ι' → Prop) (s : ∀ x y, p x ∧ q x y → Set α) :
⋂ (x : ι) (y : ι') (h : p x ∧ q x y), s x y h =
⋂ (x : ι) (hx : p x) (y : ι') (hy : q x y), s x y ⟨hx, hy⟩ := by
simp only [iInter_and, @iInter_comm _ ι']
@[simp]
theorem biInter_and' (p : ι' → Prop) (q : ι → ι' → Prop) (s : ∀ x y, p y ∧ q x y → Set α) :
⋂ (x : ι) (y : ι') (h : p y ∧ q x y), s x y h =
⋂ (y : ι') (hy : p y) (x : ι) (hx : q x y), s x y ⟨hy, hx⟩ := by
simp only [iInter_and, @iInter_comm _ ι]
@[simp]
theorem iUnion_iUnion_eq_or_left {b : β} {p : β → Prop} {s : ∀ x : β, x = b ∨ p x → Set α} :
⋃ (x) (h), s x h = s b (Or.inl rfl) ∪ ⋃ (x) (h : p x), s x (Or.inr h) := by
simp only [iUnion_or, iUnion_union_distrib, iUnion_iUnion_eq_left]
@[simp]
theorem iInter_iInter_eq_or_left {b : β} {p : β → Prop} {s : ∀ x : β, x = b ∨ p x → Set α} :
⋂ (x) (h), s x h = s b (Or.inl rfl) ∩ ⋂ (x) (h : p x), s x (Or.inr h) := by
simp only [iInter_or, iInter_inter_distrib, iInter_iInter_eq_left]
lemma iUnion_sum {s : α ⊕ β → Set γ} : ⋃ x, s x = (⋃ x, s (.inl x)) ∪ ⋃ x, s (.inr x) := iSup_sum
lemma iInter_sum {s : α ⊕ β → Set γ} : ⋂ x, s x = (⋂ x, s (.inl x)) ∩ ⋂ x, s (.inr x) := iInf_sum
theorem iUnion_psigma {γ : α → Type*} (s : PSigma γ → Set β) : ⋃ ia, s ia = ⋃ i, ⋃ a, s ⟨i, a⟩ :=
iSup_psigma _
/-- A reversed version of `iUnion_psigma` with a curried map. -/
theorem iUnion_psigma' {γ : α → Type*} (s : ∀ i, γ i → Set β) :
⋃ i, ⋃ a, s i a = ⋃ ia : PSigma γ, s ia.1 ia.2 :=
iSup_psigma' _
theorem iInter_psigma {γ : α → Type*} (s : PSigma γ → Set β) : ⋂ ia, s ia = ⋂ i, ⋂ a, s ⟨i, a⟩ :=
iInf_psigma _
/-- A reversed version of `iInter_psigma` with a curried map. -/
theorem iInter_psigma' {γ : α → Type*} (s : ∀ i, γ i → Set β) :
⋂ i, ⋂ a, s i a = ⋂ ia : PSigma γ, s ia.1 ia.2 :=
iInf_psigma' _
/-! ### Bounded unions and intersections -/
/-- A specialization of `mem_iUnion₂`. -/
theorem mem_biUnion {s : Set α} {t : α → Set β} {x : α} {y : β} (xs : x ∈ s) (ytx : y ∈ t x) :
y ∈ ⋃ x ∈ s, t x :=
mem_iUnion₂_of_mem xs ytx
/-- A specialization of `mem_iInter₂`. -/
theorem mem_biInter {s : Set α} {t : α → Set β} {y : β} (h : ∀ x ∈ s, y ∈ t x) :
y ∈ ⋂ x ∈ s, t x :=
mem_iInter₂_of_mem h
/-- A specialization of `subset_iUnion₂`. -/
theorem subset_biUnion_of_mem {s : Set α} {u : α → Set β} {x : α} (xs : x ∈ s) :
u x ⊆ ⋃ x ∈ s, u x :=
subset_iUnion₂ (s := fun i _ => u i) x xs
/-- A specialization of `iInter₂_subset`. -/
theorem biInter_subset_of_mem {s : Set α} {t : α → Set β} {x : α} (xs : x ∈ s) :
⋂ x ∈ s, t x ⊆ t x :=
iInter₂_subset x xs
lemma biInter_subset_biUnion {s : Set α} (hs : s.Nonempty) {t : α → Set β} :
⋂ x ∈ s, t x ⊆ ⋃ x ∈ s, t x := biInf_le_biSup hs
theorem biUnion_subset_biUnion_left {s s' : Set α} {t : α → Set β} (h : s ⊆ s') :
⋃ x ∈ s, t x ⊆ ⋃ x ∈ s', t x :=
iUnion₂_subset fun _ hx => subset_biUnion_of_mem <| h hx
theorem biInter_subset_biInter_left {s s' : Set α} {t : α → Set β} (h : s' ⊆ s) :
⋂ x ∈ s, t x ⊆ ⋂ x ∈ s', t x :=
subset_iInter₂ fun _ hx => biInter_subset_of_mem <| h hx
theorem biUnion_mono {s s' : Set α} {t t' : α → Set β} (hs : s' ⊆ s) (h : ∀ x ∈ s, t x ⊆ t' x) :
⋃ x ∈ s', t x ⊆ ⋃ x ∈ s, t' x :=
(biUnion_subset_biUnion_left hs).trans <| iUnion₂_mono h
theorem biInter_mono {s s' : Set α} {t t' : α → Set β} (hs : s ⊆ s') (h : ∀ x ∈ s, t x ⊆ t' x) :
⋂ x ∈ s', t x ⊆ ⋂ x ∈ s, t' x :=
(biInter_subset_biInter_left hs).trans <| iInter₂_mono h
theorem biUnion_eq_iUnion (s : Set α) (t : ∀ x ∈ s, Set β) :
⋃ x ∈ s, t x ‹_› = ⋃ x : s, t x x.2 :=
iSup_subtype'
theorem biInter_eq_iInter (s : Set α) (t : ∀ x ∈ s, Set β) :
⋂ x ∈ s, t x ‹_› = ⋂ x : s, t x x.2 :=
iInf_subtype'
@[simp] lemma biUnion_const {s : Set α} (hs : s.Nonempty) (t : Set β) : ⋃ a ∈ s, t = t :=
biSup_const hs
@[simp] lemma biInter_const {s : Set α} (hs : s.Nonempty) (t : Set β) : ⋂ a ∈ s, t = t :=
biInf_const hs
theorem iUnion_subtype (p : α → Prop) (s : { x // p x } → Set β) :
⋃ x : { x // p x }, s x = ⋃ (x) (hx : p x), s ⟨x, hx⟩ :=
iSup_subtype
theorem iInter_subtype (p : α → Prop) (s : { x // p x } → Set β) :
⋂ x : { x // p x }, s x = ⋂ (x) (hx : p x), s ⟨x, hx⟩ :=
iInf_subtype
theorem biInter_empty (u : α → Set β) : ⋂ x ∈ (∅ : Set α), u x = univ :=
iInf_emptyset
theorem biInter_univ (u : α → Set β) : ⋂ x ∈ @univ α, u x = ⋂ x, u x :=
iInf_univ
@[simp]
theorem biUnion_self (s : Set α) : ⋃ x ∈ s, s = s :=
Subset.antisymm (iUnion₂_subset fun _ _ => Subset.refl s) fun _ hx => mem_biUnion hx hx
@[simp]
theorem iUnion_nonempty_self (s : Set α) : ⋃ _ : s.Nonempty, s = s := by
rw [iUnion_nonempty_index, biUnion_self]
theorem biInter_singleton (a : α) (s : α → Set β) : ⋂ x ∈ ({a} : Set α), s x = s a :=
iInf_singleton
theorem biInter_union (s t : Set α) (u : α → Set β) :
⋂ x ∈ s ∪ t, u x = (⋂ x ∈ s, u x) ∩ ⋂ x ∈ t, u x :=
iInf_union
theorem biInter_insert (a : α) (s : Set α) (t : α → Set β) :
⋂ x ∈ insert a s, t x = t a ∩ ⋂ x ∈ s, t x := by simp
theorem biInter_pair (a b : α) (s : α → Set β) : ⋂ x ∈ ({a, b} : Set α), s x = s a ∩ s b := by
rw [biInter_insert, biInter_singleton]
theorem biInter_inter {ι α : Type*} {s : Set ι} (hs : s.Nonempty) (f : ι → Set α) (t : Set α) :
⋂ i ∈ s, f i ∩ t = (⋂ i ∈ s, f i) ∩ t := by
haveI : Nonempty s := hs.to_subtype
simp [biInter_eq_iInter, ← iInter_inter]
theorem inter_biInter {ι α : Type*} {s : Set ι} (hs : s.Nonempty) (f : ι → Set α) (t : Set α) :
⋂ i ∈ s, t ∩ f i = t ∩ ⋂ i ∈ s, f i := by
rw [inter_comm, ← biInter_inter hs]
simp [inter_comm]
theorem biUnion_empty (s : α → Set β) : ⋃ x ∈ (∅ : Set α), s x = ∅ :=
iSup_emptyset
theorem biUnion_univ (s : α → Set β) : ⋃ x ∈ @univ α, s x = ⋃ x, s x :=
iSup_univ
theorem biUnion_singleton (a : α) (s : α → Set β) : ⋃ x ∈ ({a} : Set α), s x = s a :=
iSup_singleton
@[simp]
theorem biUnion_of_singleton (s : Set α) : ⋃ x ∈ s, {x} = s :=
ext <| by simp
theorem biUnion_union (s t : Set α) (u : α → Set β) :
⋃ x ∈ s ∪ t, u x = (⋃ x ∈ s, u x) ∪ ⋃ x ∈ t, u x :=
iSup_union
@[simp]
theorem iUnion_coe_set {α β : Type*} (s : Set α) (f : s → Set β) :
⋃ i, f i = ⋃ i ∈ s, f ⟨i, ‹i ∈ s›⟩ :=
iUnion_subtype _ _
@[simp]
theorem iInter_coe_set {α β : Type*} (s : Set α) (f : s → Set β) :
⋂ i, f i = ⋂ i ∈ s, f ⟨i, ‹i ∈ s›⟩ :=
iInter_subtype _ _
theorem biUnion_insert (a : α) (s : Set α) (t : α → Set β) :
⋃ x ∈ insert a s, t x = t a ∪ ⋃ x ∈ s, t x := by simp
theorem biUnion_pair (a b : α) (s : α → Set β) : ⋃ x ∈ ({a, b} : Set α), s x = s a ∪ s b := by
simp
theorem inter_iUnion₂ (s : Set α) (t : ∀ i, κ i → Set α) :
(s ∩ ⋃ (i) (j), t i j) = ⋃ (i) (j), s ∩ t i j := by simp only [inter_iUnion]
theorem iUnion₂_inter (s : ∀ i, κ i → Set α) (t : Set α) :
(⋃ (i) (j), s i j) ∩ t = ⋃ (i) (j), s i j ∩ t := by simp_rw [iUnion_inter]
theorem union_iInter₂ (s : Set α) (t : ∀ i, κ i → Set α) :
(s ∪ ⋂ (i) (j), t i j) = ⋂ (i) (j), s ∪ t i j := by simp_rw [union_iInter]
theorem iInter₂_union (s : ∀ i, κ i → Set α) (t : Set α) :
(⋂ (i) (j), s i j) ∪ t = ⋂ (i) (j), s i j ∪ t := by simp_rw [iInter_union]
theorem mem_sUnion_of_mem {x : α} {t : Set α} {S : Set (Set α)} (hx : x ∈ t) (ht : t ∈ S) :
x ∈ ⋃₀ S :=
⟨t, ht, hx⟩
-- is this theorem really necessary?
theorem not_mem_of_not_mem_sUnion {x : α} {t : Set α} {S : Set (Set α)} (hx : x ∉ ⋃₀ S)
(ht : t ∈ S) : x ∉ t := fun h => hx ⟨t, ht, h⟩
theorem sInter_subset_of_mem {S : Set (Set α)} {t : Set α} (tS : t ∈ S) : ⋂₀ S ⊆ t :=
sInf_le tS
theorem subset_sUnion_of_mem {S : Set (Set α)} {t : Set α} (tS : t ∈ S) : t ⊆ ⋃₀ S :=
le_sSup tS
theorem subset_sUnion_of_subset {s : Set α} (t : Set (Set α)) (u : Set α) (h₁ : s ⊆ u)
(h₂ : u ∈ t) : s ⊆ ⋃₀ t :=
Subset.trans h₁ (subset_sUnion_of_mem h₂)
theorem sUnion_subset {S : Set (Set α)} {t : Set α} (h : ∀ t' ∈ S, t' ⊆ t) : ⋃₀ S ⊆ t :=
sSup_le h
@[simp]
theorem sUnion_subset_iff {s : Set (Set α)} {t : Set α} : ⋃₀ s ⊆ t ↔ ∀ t' ∈ s, t' ⊆ t :=
sSup_le_iff
/-- `sUnion` is monotone under taking a subset of each set. -/
lemma sUnion_mono_subsets {s : Set (Set α)} {f : Set α → Set α} (hf : ∀ t : Set α, t ⊆ f t) :
⋃₀ s ⊆ ⋃₀ (f '' s) :=
fun _ ⟨t, htx, hxt⟩ ↦ ⟨f t, mem_image_of_mem f htx, hf t hxt⟩
/-- `sUnion` is monotone under taking a superset of each set. -/
lemma sUnion_mono_supsets {s : Set (Set α)} {f : Set α → Set α} (hf : ∀ t : Set α, f t ⊆ t) :
⋃₀ (f '' s) ⊆ ⋃₀ s :=
-- If t ∈ f '' s is arbitrary; t = f u for some u : Set α.
fun _ ⟨_, ⟨u, hus, hut⟩, hxt⟩ ↦ ⟨u, hus, (hut ▸ hf u) hxt⟩
theorem subset_sInter {S : Set (Set α)} {t : Set α} (h : ∀ t' ∈ S, t ⊆ t') : t ⊆ ⋂₀ S :=
le_sInf h
@[simp]
theorem subset_sInter_iff {S : Set (Set α)} {t : Set α} : t ⊆ ⋂₀ S ↔ ∀ t' ∈ S, t ⊆ t' :=
le_sInf_iff
@[gcongr]
theorem sUnion_subset_sUnion {S T : Set (Set α)} (h : S ⊆ T) : ⋃₀ S ⊆ ⋃₀ T :=
sUnion_subset fun _ hs => subset_sUnion_of_mem (h hs)
@[gcongr]
theorem sInter_subset_sInter {S T : Set (Set α)} (h : S ⊆ T) : ⋂₀ T ⊆ ⋂₀ S :=
subset_sInter fun _ hs => sInter_subset_of_mem (h hs)
@[simp]
theorem sUnion_empty : ⋃₀ ∅ = (∅ : Set α) :=
sSup_empty
@[simp]
theorem sInter_empty : ⋂₀ ∅ = (univ : Set α) :=
sInf_empty
@[simp]
theorem sUnion_singleton (s : Set α) : ⋃₀ {s} = s :=
sSup_singleton
@[simp]
theorem sInter_singleton (s : Set α) : ⋂₀ {s} = s :=
sInf_singleton
@[simp]
theorem sUnion_eq_empty {S : Set (Set α)} : ⋃₀ S = ∅ ↔ ∀ s ∈ S, s = ∅ :=
sSup_eq_bot
@[simp]
theorem sInter_eq_univ {S : Set (Set α)} : ⋂₀ S = univ ↔ ∀ s ∈ S, s = univ :=
sInf_eq_top
theorem subset_powerset_iff {s : Set (Set α)} {t : Set α} : s ⊆ 𝒫 t ↔ ⋃₀ s ⊆ t :=
sUnion_subset_iff.symm
/-- `⋃₀` and `𝒫` form a Galois connection. -/
theorem sUnion_powerset_gc :
GaloisConnection (⋃₀ · : Set (Set α) → Set α) (𝒫 · : Set α → Set (Set α)) :=
gc_sSup_Iic
/-- `⋃₀` and `𝒫` form a Galois insertion. -/
def sUnionPowersetGI :
GaloisInsertion (⋃₀ · : Set (Set α) → Set α) (𝒫 · : Set α → Set (Set α)) :=
gi_sSup_Iic
@[deprecated (since := "2024-12-07")] alias sUnion_powerset_gi := sUnionPowersetGI
/-- If all sets in a collection are either `∅` or `Set.univ`, then so is their union. -/
theorem sUnion_mem_empty_univ {S : Set (Set α)} (h : S ⊆ {∅, univ}) :
⋃₀ S ∈ ({∅, univ} : Set (Set α)) := by
simp only [mem_insert_iff, mem_singleton_iff, or_iff_not_imp_left, sUnion_eq_empty, not_forall]
rintro ⟨s, hs, hne⟩
obtain rfl : s = univ := (h hs).resolve_left hne
exact univ_subset_iff.1 <| subset_sUnion_of_mem hs
@[simp]
theorem nonempty_sUnion {S : Set (Set α)} : (⋃₀ S).Nonempty ↔ ∃ s ∈ S, Set.Nonempty s := by
simp [nonempty_iff_ne_empty]
theorem Nonempty.of_sUnion {s : Set (Set α)} (h : (⋃₀ s).Nonempty) : s.Nonempty :=
let ⟨s, hs, _⟩ := nonempty_sUnion.1 h
⟨s, hs⟩
theorem Nonempty.of_sUnion_eq_univ [Nonempty α] {s : Set (Set α)} (h : ⋃₀ s = univ) : s.Nonempty :=
Nonempty.of_sUnion <| h.symm ▸ univ_nonempty
theorem sUnion_union (S T : Set (Set α)) : ⋃₀ (S ∪ T) = ⋃₀ S ∪ ⋃₀ T :=
sSup_union
theorem sInter_union (S T : Set (Set α)) : ⋂₀ (S ∪ T) = ⋂₀ S ∩ ⋂₀ T :=
sInf_union
@[simp]
theorem sUnion_insert (s : Set α) (T : Set (Set α)) : ⋃₀ insert s T = s ∪ ⋃₀ T :=
sSup_insert
@[simp]
theorem sInter_insert (s : Set α) (T : Set (Set α)) : ⋂₀ insert s T = s ∩ ⋂₀ T :=
sInf_insert
@[simp]
theorem sUnion_diff_singleton_empty (s : Set (Set α)) : ⋃₀ (s \ {∅}) = ⋃₀ s :=
sSup_diff_singleton_bot s
@[simp]
theorem sInter_diff_singleton_univ (s : Set (Set α)) : ⋂₀ (s \ {univ}) = ⋂₀ s :=
sInf_diff_singleton_top s
theorem sUnion_pair (s t : Set α) : ⋃₀ {s, t} = s ∪ t :=
sSup_pair
theorem sInter_pair (s t : Set α) : ⋂₀ {s, t} = s ∩ t :=
sInf_pair
@[simp]
theorem sUnion_image (f : α → Set β) (s : Set α) : ⋃₀ (f '' s) = ⋃ a ∈ s, f a :=
sSup_image
@[simp]
theorem sInter_image (f : α → Set β) (s : Set α) : ⋂₀ (f '' s) = ⋂ a ∈ s, f a :=
sInf_image
@[simp]
lemma sUnion_image2 (f : α → β → Set γ) (s : Set α) (t : Set β) :
⋃₀ (image2 f s t) = ⋃ (a ∈ s) (b ∈ t), f a b := sSup_image2
@[simp]
lemma sInter_image2 (f : α → β → Set γ) (s : Set α) (t : Set β) :
⋂₀ (image2 f s t) = ⋂ (a ∈ s) (b ∈ t), f a b := sInf_image2
@[simp]
theorem sUnion_range (f : ι → Set β) : ⋃₀ range f = ⋃ x, f x :=
rfl
@[simp]
theorem sInter_range (f : ι → Set β) : ⋂₀ range f = ⋂ x, f x :=
rfl
theorem iUnion_eq_univ_iff {f : ι → Set α} : ⋃ i, f i = univ ↔ ∀ x, ∃ i, x ∈ f i := by
simp only [eq_univ_iff_forall, mem_iUnion]
theorem iUnion₂_eq_univ_iff {s : ∀ i, κ i → Set α} :
⋃ (i) (j), s i j = univ ↔ ∀ a, ∃ i j, a ∈ s i j := by
simp only [iUnion_eq_univ_iff, mem_iUnion]
theorem sUnion_eq_univ_iff {c : Set (Set α)} : ⋃₀ c = univ ↔ ∀ a, ∃ b ∈ c, a ∈ b := by
simp only [eq_univ_iff_forall, mem_sUnion]
-- classical
theorem iInter_eq_empty_iff {f : ι → Set α} : ⋂ i, f i = ∅ ↔ ∀ x, ∃ i, x ∉ f i := by
simp [Set.eq_empty_iff_forall_not_mem]
-- classical
theorem iInter₂_eq_empty_iff {s : ∀ i, κ i → Set α} :
⋂ (i) (j), s i j = ∅ ↔ ∀ a, ∃ i j, a ∉ s i j := by
simp only [eq_empty_iff_forall_not_mem, mem_iInter, not_forall]
-- classical
theorem sInter_eq_empty_iff {c : Set (Set α)} : ⋂₀ c = ∅ ↔ ∀ a, ∃ b ∈ c, a ∉ b := by
simp [Set.eq_empty_iff_forall_not_mem]
-- classical
@[simp]
theorem nonempty_iInter {f : ι → Set α} : (⋂ i, f i).Nonempty ↔ ∃ x, ∀ i, x ∈ f i := by
simp [nonempty_iff_ne_empty, iInter_eq_empty_iff]
-- classical
theorem nonempty_iInter₂ {s : ∀ i, κ i → Set α} :
(⋂ (i) (j), s i j).Nonempty ↔ ∃ a, ∀ i j, a ∈ s i j := by
simp
-- classical
@[simp]
theorem nonempty_sInter {c : Set (Set α)} : (⋂₀ c).Nonempty ↔ ∃ a, ∀ b ∈ c, a ∈ b := by
simp [nonempty_iff_ne_empty, sInter_eq_empty_iff]
-- classical
theorem compl_sUnion (S : Set (Set α)) : (⋃₀ S)ᶜ = ⋂₀ (compl '' S) :=
ext fun x => by simp
-- classical
theorem sUnion_eq_compl_sInter_compl (S : Set (Set α)) : ⋃₀ S = (⋂₀ (compl '' S))ᶜ := by
rw [← compl_compl (⋃₀ S), compl_sUnion]
-- classical
theorem compl_sInter (S : Set (Set α)) : (⋂₀ S)ᶜ = ⋃₀ (compl '' S) := by
rw [sUnion_eq_compl_sInter_compl, compl_compl_image]
-- classical
theorem sInter_eq_compl_sUnion_compl (S : Set (Set α)) : ⋂₀ S = (⋃₀ (compl '' S))ᶜ := by
rw [← compl_compl (⋂₀ S), compl_sInter]
theorem inter_empty_of_inter_sUnion_empty {s t : Set α} {S : Set (Set α)} (hs : t ∈ S)
(h : s ∩ ⋃₀ S = ∅) : s ∩ t = ∅ :=
eq_empty_of_subset_empty <| by
rw [← h]; exact inter_subset_inter_right _ (subset_sUnion_of_mem hs)
theorem range_sigma_eq_iUnion_range {γ : α → Type*} (f : Sigma γ → β) :
range f = ⋃ a, range fun b => f ⟨a, b⟩ :=
Set.ext <| by simp
theorem iUnion_eq_range_sigma (s : α → Set β) : ⋃ i, s i = range fun a : Σi, s i => a.2 := by
simp [Set.ext_iff]
theorem iUnion_eq_range_psigma (s : ι → Set β) : ⋃ i, s i = range fun a : Σ'i, s i => a.2 := by
simp [Set.ext_iff]
theorem iUnion_image_preimage_sigma_mk_eq_self {ι : Type*} {σ : ι → Type*} (s : Set (Sigma σ)) :
⋃ i, Sigma.mk i '' (Sigma.mk i ⁻¹' s) = s := by
ext x
simp only [mem_iUnion, mem_image, mem_preimage]
constructor
· rintro ⟨i, a, h, rfl⟩
exact h
· intro h
obtain ⟨i, a⟩ := x
exact ⟨i, a, h, rfl⟩
theorem Sigma.univ (X : α → Type*) : (Set.univ : Set (Σa, X a)) = ⋃ a, range (Sigma.mk a) :=
Set.ext fun x =>
iff_of_true trivial ⟨range (Sigma.mk x.1), Set.mem_range_self _, x.2, Sigma.eta x⟩
alias sUnion_mono := sUnion_subset_sUnion
alias sInter_mono := sInter_subset_sInter
theorem iUnion_subset_iUnion_const {s : Set α} (h : ι → ι₂) : ⋃ _ : ι, s ⊆ ⋃ _ : ι₂, s :=
iSup_const_mono (α := Set α) h
@[simp]
theorem iUnion_singleton_eq_range (f : α → β) : ⋃ x : α, {f x} = range f := by
ext x
simp [@eq_comm _ x]
theorem iUnion_insert_eq_range_union_iUnion {ι : Type*} (x : ι → β) (t : ι → Set β) :
⋃ i, insert (x i) (t i) = range x ∪ ⋃ i, t i := by
simp_rw [← union_singleton, iUnion_union_distrib, union_comm, iUnion_singleton_eq_range]
theorem iUnion_of_singleton (α : Type*) : (⋃ x, {x} : Set α) = univ := by simp [Set.ext_iff]
theorem iUnion_of_singleton_coe (s : Set α) : ⋃ i : s, ({(i : α)} : Set α) = s := by simp
theorem sUnion_eq_biUnion {s : Set (Set α)} : ⋃₀ s = ⋃ (i : Set α) (_ : i ∈ s), i := by
rw [← sUnion_image, image_id']
theorem sInter_eq_biInter {s : Set (Set α)} : ⋂₀ s = ⋂ (i : Set α) (_ : i ∈ s), i := by
rw [← sInter_image, image_id']
theorem sUnion_eq_iUnion {s : Set (Set α)} : ⋃₀ s = ⋃ i : s, i := by
simp only [← sUnion_range, Subtype.range_coe]
theorem sInter_eq_iInter {s : Set (Set α)} : ⋂₀ s = ⋂ i : s, i := by
simp only [← sInter_range, Subtype.range_coe]
@[simp]
theorem iUnion_of_empty [IsEmpty ι] (s : ι → Set α) : ⋃ i, s i = ∅ :=
iSup_of_empty _
@[simp]
theorem iInter_of_empty [IsEmpty ι] (s : ι → Set α) : ⋂ i, s i = univ :=
iInf_of_empty _
theorem union_eq_iUnion {s₁ s₂ : Set α} : s₁ ∪ s₂ = ⋃ b : Bool, cond b s₁ s₂ :=
sup_eq_iSup s₁ s₂
theorem inter_eq_iInter {s₁ s₂ : Set α} : s₁ ∩ s₂ = ⋂ b : Bool, cond b s₁ s₂ :=
inf_eq_iInf s₁ s₂
theorem sInter_union_sInter {S T : Set (Set α)} :
⋂₀ S ∪ ⋂₀ T = ⋂ p ∈ S ×ˢ T, (p : Set α × Set α).1 ∪ p.2 :=
sInf_sup_sInf
theorem sUnion_inter_sUnion {s t : Set (Set α)} :
⋃₀ s ∩ ⋃₀ t = ⋃ p ∈ s ×ˢ t, (p : Set α × Set α).1 ∩ p.2 :=
sSup_inf_sSup
theorem biUnion_iUnion (s : ι → Set α) (t : α → Set β) :
⋃ x ∈ ⋃ i, s i, t x = ⋃ (i) (x ∈ s i), t x := by simp [@iUnion_comm _ ι]
theorem biInter_iUnion (s : ι → Set α) (t : α → Set β) :
⋂ x ∈ ⋃ i, s i, t x = ⋂ (i) (x ∈ s i), t x := by simp [@iInter_comm _ ι]
theorem sUnion_iUnion (s : ι → Set (Set α)) : ⋃₀ ⋃ i, s i = ⋃ i, ⋃₀ s i := by
simp only [sUnion_eq_biUnion, biUnion_iUnion]
theorem sInter_iUnion (s : ι → Set (Set α)) : ⋂₀ ⋃ i, s i = ⋂ i, ⋂₀ s i := by
simp only [sInter_eq_biInter, biInter_iUnion]
theorem iUnion_range_eq_sUnion {α β : Type*} (C : Set (Set α)) {f : ∀ s : C, β → (s : Type _)}
(hf : ∀ s : C, Surjective (f s)) : ⋃ y : β, range (fun s : C => (f s y).val) = ⋃₀ C := by
ext x; constructor
· rintro ⟨s, ⟨y, rfl⟩, ⟨s, hs⟩, rfl⟩
refine ⟨_, hs, ?_⟩
exact (f ⟨s, hs⟩ y).2
· rintro ⟨s, hs, hx⟩
obtain ⟨y, hy⟩ := hf ⟨s, hs⟩ ⟨x, hx⟩
refine ⟨_, ⟨y, rfl⟩, ⟨s, hs⟩, ?_⟩
exact congr_arg Subtype.val hy
theorem iUnion_range_eq_iUnion (C : ι → Set α) {f : ∀ x : ι, β → C x}
(hf : ∀ x : ι, Surjective (f x)) : ⋃ y : β, range (fun x : ι => (f x y).val) = ⋃ x, C x := by
ext x; rw [mem_iUnion, mem_iUnion]; constructor
· rintro ⟨y, i, rfl⟩
exact ⟨i, (f i y).2⟩
· rintro ⟨i, hx⟩
obtain ⟨y, hy⟩ := hf i ⟨x, hx⟩
exact ⟨y, i, congr_arg Subtype.val hy⟩
theorem union_distrib_iInter_left (s : ι → Set α) (t : Set α) : (t ∪ ⋂ i, s i) = ⋂ i, t ∪ s i :=
sup_iInf_eq _ _
theorem union_distrib_iInter₂_left (s : Set α) (t : ∀ i, κ i → Set α) :
(s ∪ ⋂ (i) (j), t i j) = ⋂ (i) (j), s ∪ t i j := by simp_rw [union_distrib_iInter_left]
theorem union_distrib_iInter_right (s : ι → Set α) (t : Set α) : (⋂ i, s i) ∪ t = ⋂ i, s i ∪ t :=
iInf_sup_eq _ _
theorem union_distrib_iInter₂_right (s : ∀ i, κ i → Set α) (t : Set α) :
(⋂ (i) (j), s i j) ∪ t = ⋂ (i) (j), s i j ∪ t := by simp_rw [union_distrib_iInter_right]
lemma biUnion_lt_eq_iUnion [LT α] [NoMaxOrder α] {s : α → Set β} :
⋃ (n) (m < n), s m = ⋃ n, s n := biSup_lt_eq_iSup
lemma biUnion_le_eq_iUnion [Preorder α] {s : α → Set β} :
⋃ (n) (m ≤ n), s m = ⋃ n, s n := biSup_le_eq_iSup
lemma biInter_lt_eq_iInter [LT α] [NoMaxOrder α] {s : α → Set β} :
⋂ (n) (m < n), s m = ⋂ (n), s n := biInf_lt_eq_iInf
lemma biInter_le_eq_iInter [Preorder α] {s : α → Set β} :
⋂ (n) (m ≤ n), s m = ⋂ (n), s n := biInf_le_eq_iInf
lemma biUnion_gt_eq_iUnion [LT α] [NoMinOrder α] {s : α → Set β} :
⋃ (n) (m > n), s m = ⋃ n, s n := biSup_gt_eq_iSup
lemma biUnion_ge_eq_iUnion [Preorder α] {s : α → Set β} :
⋃ (n) (m ≥ n), s m = ⋃ n, s n := biSup_ge_eq_iSup
lemma biInter_gt_eq_iInf [LT α] [NoMinOrder α] {s : α → Set β} :
⋂ (n) (m > n), s m = ⋂ n, s n := biInf_gt_eq_iInf
lemma biInter_ge_eq_iInf [Preorder α] {s : α → Set β} :
⋂ (n) (m ≥ n), s m = ⋂ n, s n := biInf_ge_eq_iInf
section le
variable {ι : Type*} [PartialOrder ι] (s : ι → Set α) (i : ι)
theorem biUnion_le : (⋃ j ≤ i, s j) = (⋃ j < i, s j) ∪ s i :=
biSup_le_eq_sup s i
theorem biInter_le : (⋂ j ≤ i, s j) = (⋂ j < i, s j) ∩ s i :=
biInf_le_eq_inf s i
theorem biUnion_ge : (⋃ j ≥ i, s j) = s i ∪ ⋃ j > i, s j :=
biSup_ge_eq_sup s i
theorem biInter_ge : (⋂ j ≥ i, s j) = s i ∩ ⋂ j > i, s j :=
biInf_ge_eq_inf s i
end le
section Pi
variable {π : α → Type*}
theorem pi_def (i : Set α) (s : ∀ a, Set (π a)) : pi i s = ⋂ a ∈ i, eval a ⁻¹' s a := by
ext
simp
theorem univ_pi_eq_iInter (t : ∀ i, Set (π i)) : pi univ t = ⋂ i, eval i ⁻¹' t i := by
simp only [pi_def, iInter_true, mem_univ]
theorem pi_diff_pi_subset (i : Set α) (s t : ∀ a, Set (π a)) :
pi i s \ pi i t ⊆ ⋃ a ∈ i, eval a ⁻¹' (s a \ t a) := by
refine diff_subset_comm.2 fun x hx a ha => ?_
simp only [mem_diff, mem_pi, mem_iUnion, not_exists, mem_preimage, not_and, not_not,
eval_apply] at hx
exact hx.2 _ ha (hx.1 _ ha)
theorem iUnion_univ_pi {ι : α → Type*} (t : (a : α) → ι a → Set (π a)) :
⋃ x : (a : α) → ι a, pi univ (fun a => t a (x a)) = pi univ fun a => ⋃ j : ι a, t a j := by
ext
simp [Classical.skolem]
end Pi
section Directed
theorem directedOn_iUnion {r} {f : ι → Set α} (hd : Directed (· ⊆ ·) f)
(h : ∀ x, DirectedOn r (f x)) : DirectedOn r (⋃ x, f x) := by
simp only [DirectedOn, exists_prop, mem_iUnion, exists_imp]
exact fun a₁ b₁ fb₁ a₂ b₂ fb₂ =>
let ⟨z, zb₁, zb₂⟩ := hd b₁ b₂
let ⟨x, xf, xa₁, xa₂⟩ := h z a₁ (zb₁ fb₁) a₂ (zb₂ fb₂)
⟨x, ⟨z, xf⟩, xa₁, xa₂⟩
theorem directedOn_sUnion {r} {S : Set (Set α)} (hd : DirectedOn (· ⊆ ·) S)
(h : ∀ x ∈ S, DirectedOn r x) : DirectedOn r (⋃₀ S) := by
rw [sUnion_eq_iUnion]
exact directedOn_iUnion (directedOn_iff_directed.mp hd) (fun i ↦ h i.1 i.2)
theorem pairwise_iUnion₂ {S : Set (Set α)} (hd : DirectedOn (· ⊆ ·) S)
(r : α → α → Prop) (h : ∀ s ∈ S, s.Pairwise r) : (⋃ s ∈ S, s).Pairwise r := by
simp only [Set.Pairwise, Set.mem_iUnion, exists_prop, forall_exists_index, and_imp]
intro x S hS hx y T hT hy hne
obtain ⟨U, hU, hSU, hTU⟩ := hd S hS T hT
exact h U hU (hSU hx) (hTU hy) hne
end Directed
end Set
namespace Function
namespace Surjective
theorem iUnion_comp {f : ι → ι₂} (hf : Surjective f) (g : ι₂ → Set α) : ⋃ x, g (f x) = ⋃ y, g y :=
hf.iSup_comp g
theorem iInter_comp {f : ι → ι₂} (hf : Surjective f) (g : ι₂ → Set α) : ⋂ x, g (f x) = ⋂ y, g y :=
hf.iInf_comp g
end Surjective
end Function
/-!
### Disjoint sets
-/
section Disjoint
variable {s t : Set α}
namespace Set
@[simp]
theorem disjoint_iUnion_left {ι : Sort*} {s : ι → Set α} :
Disjoint (⋃ i, s i) t ↔ ∀ i, Disjoint (s i) t :=
iSup_disjoint_iff
@[simp]
theorem disjoint_iUnion_right {ι : Sort*} {s : ι → Set α} :
Disjoint t (⋃ i, s i) ↔ ∀ i, Disjoint t (s i) :=
disjoint_iSup_iff
theorem disjoint_iUnion₂_left {s : ∀ i, κ i → Set α} {t : Set α} :
Disjoint (⋃ (i) (j), s i j) t ↔ ∀ i j, Disjoint (s i j) t :=
iSup₂_disjoint_iff
theorem disjoint_iUnion₂_right {s : Set α} {t : ∀ i, κ i → Set α} :
Disjoint s (⋃ (i) (j), t i j) ↔ ∀ i j, Disjoint s (t i j) :=
disjoint_iSup₂_iff
@[simp]
theorem disjoint_sUnion_left {S : Set (Set α)} {t : Set α} :
Disjoint (⋃₀ S) t ↔ ∀ s ∈ S, Disjoint s t :=
sSup_disjoint_iff
@[simp]
theorem disjoint_sUnion_right {s : Set α} {S : Set (Set α)} :
Disjoint s (⋃₀ S) ↔ ∀ t ∈ S, Disjoint s t :=
disjoint_sSup_iff
lemma biUnion_compl_eq_of_pairwise_disjoint_of_iUnion_eq_univ {ι : Type*} {Es : ι → Set α}
(Es_union : ⋃ i, Es i = univ) (Es_disj : Pairwise fun i j ↦ Disjoint (Es i) (Es j))
(I : Set ι) :
(⋃ i ∈ I, Es i)ᶜ = ⋃ i ∈ Iᶜ, Es i := by
ext x
obtain ⟨i, hix⟩ : ∃ i, x ∈ Es i := by simp [← mem_iUnion, Es_union]
have obs : ∀ (J : Set ι), x ∈ ⋃ j ∈ J, Es j ↔ i ∈ J := by
refine fun J ↦ ⟨?_, fun i_in_J ↦ by simpa only [mem_iUnion, exists_prop] using ⟨i, i_in_J, hix⟩⟩
intro x_in_U
simp only [mem_iUnion, exists_prop] at x_in_U
obtain ⟨j, j_in_J, hjx⟩ := x_in_U
rwa [show i = j by by_contra i_ne_j; exact Disjoint.ne_of_mem (Es_disj i_ne_j) hix hjx rfl]
have obs' : ∀ (J : Set ι), x ∈ (⋃ j ∈ J, Es j)ᶜ ↔ i ∉ J :=
fun J ↦ by simpa only [mem_compl_iff, not_iff_not] using obs J
rw [obs, obs', mem_compl_iff]
end Set
end Disjoint
/-! ### Intervals -/
namespace Set
lemma nonempty_iInter_Iic_iff [Preorder α] {f : ι → α} :
(⋂ i, Iic (f i)).Nonempty ↔ BddBelow (range f) := by
have : (⋂ (i : ι), Iic (f i)) = lowerBounds (range f) := by
ext c; simp [lowerBounds]
simp [this, BddBelow]
lemma nonempty_iInter_Ici_iff [Preorder α] {f : ι → α} :
(⋂ i, Ici (f i)).Nonempty ↔ BddAbove (range f) :=
nonempty_iInter_Iic_iff (α := αᵒᵈ)
variable [CompleteLattice α]
theorem Ici_iSup (f : ι → α) : Ici (⨆ i, f i) = ⋂ i, Ici (f i) :=
ext fun _ => by simp only [mem_Ici, iSup_le_iff, mem_iInter]
theorem Iic_iInf (f : ι → α) : Iic (⨅ i, f i) = ⋂ i, Iic (f i) :=
ext fun _ => by simp only [mem_Iic, le_iInf_iff, mem_iInter]
theorem Ici_iSup₂ (f : ∀ i, κ i → α) : Ici (⨆ (i) (j), f i j) = ⋂ (i) (j), Ici (f i j) := by
simp_rw [Ici_iSup]
theorem Iic_iInf₂ (f : ∀ i, κ i → α) : Iic (⨅ (i) (j), f i j) = ⋂ (i) (j), Iic (f i j) := by
simp_rw [Iic_iInf]
theorem Ici_sSup (s : Set α) : Ici (sSup s) = ⋂ a ∈ s, Ici a := by rw [sSup_eq_iSup, Ici_iSup₂]
theorem Iic_sInf (s : Set α) : Iic (sInf s) = ⋂ a ∈ s, Iic a := by rw [sInf_eq_iInf, Iic_iInf₂]
end Set
namespace Set
variable (t : α → Set β)
theorem biUnion_diff_biUnion_subset (s₁ s₂ : Set α) :
((⋃ x ∈ s₁, t x) \ ⋃ x ∈ s₂, t x) ⊆ ⋃ x ∈ s₁ \ s₂, t x := by
simp only [diff_subset_iff, ← biUnion_union]
apply biUnion_subset_biUnion_left
rw [union_diff_self]
apply subset_union_right
/-- If `t` is an indexed family of sets, then there is a natural map from `Σ i, t i` to `⋃ i, t i`
sending `⟨i, x⟩` to `x`. -/
def sigmaToiUnion (x : Σi, t i) : ⋃ i, t i :=
⟨x.2, mem_iUnion.2 ⟨x.1, x.2.2⟩⟩
theorem sigmaToiUnion_surjective : Surjective (sigmaToiUnion t)
| ⟨b, hb⟩ =>
have : ∃ a, b ∈ t a := by simpa using hb
let ⟨a, hb⟩ := this
⟨⟨a, b, hb⟩, rfl⟩
theorem sigmaToiUnion_injective (h : Pairwise (Disjoint on t)) :
Injective (sigmaToiUnion t)
| ⟨a₁, b₁, h₁⟩, ⟨a₂, b₂, h₂⟩, eq =>
have b_eq : b₁ = b₂ := congr_arg Subtype.val eq
have a_eq : a₁ = a₂ :=
by_contradiction fun ne =>
have : b₁ ∈ t a₁ ∩ t a₂ := ⟨h₁, b_eq.symm ▸ h₂⟩
(h ne).le_bot this
Sigma.eq a_eq <| Subtype.eq <| by subst b_eq; subst a_eq; rfl
theorem sigmaToiUnion_bijective (h : Pairwise (Disjoint on t)) :
Bijective (sigmaToiUnion t) :=
⟨sigmaToiUnion_injective t h, sigmaToiUnion_surjective t⟩
/-- Equivalence from the disjoint union of a family of sets forming a partition of `β`, to `β`
itself. -/
noncomputable def sigmaEquiv (s : α → Set β) (hs : ∀ b, ∃! i, b ∈ s i) :
(Σ i, s i) ≃ β where
toFun | ⟨_, b⟩ => b
invFun b := ⟨(hs b).choose, b, (hs b).choose_spec.1⟩
left_inv | ⟨i, b, hb⟩ => Sigma.subtype_ext ((hs b).choose_spec.2 i hb).symm rfl
right_inv _ := rfl
/-- Equivalence between a disjoint union and a dependent sum. -/
noncomputable def unionEqSigmaOfDisjoint {t : α → Set β}
(h : Pairwise (Disjoint on t)) :
(⋃ i, t i) ≃ Σi, t i :=
(Equiv.ofBijective _ <| sigmaToiUnion_bijective t h).symm
theorem iUnion_ge_eq_iUnion_nat_add (u : ℕ → Set α) (n : ℕ) : ⋃ i ≥ n, u i = ⋃ i, u (i + n) :=
iSup_ge_eq_iSup_nat_add u n
theorem iInter_ge_eq_iInter_nat_add (u : ℕ → Set α) (n : ℕ) : ⋂ i ≥ n, u i = ⋂ i, u (i + n) :=
iInf_ge_eq_iInf_nat_add u n
theorem _root_.Monotone.iUnion_nat_add {f : ℕ → Set α} (hf : Monotone f) (k : ℕ) :
⋃ n, f (n + k) = ⋃ n, f n :=
hf.iSup_nat_add k
theorem _root_.Antitone.iInter_nat_add {f : ℕ → Set α} (hf : Antitone f) (k : ℕ) :
⋂ n, f (n + k) = ⋂ n, f n :=
hf.iInf_nat_add k
@[simp]
theorem iUnion_iInter_ge_nat_add (f : ℕ → Set α) (k : ℕ) :
⋃ n, ⋂ i ≥ n, f (i + k) = ⋃ n, ⋂ i ≥ n, f i :=
iSup_iInf_ge_nat_add f k
theorem union_iUnion_nat_succ (u : ℕ → Set α) : (u 0 ∪ ⋃ i, u (i + 1)) = ⋃ i, u i :=
sup_iSup_nat_succ u
theorem inter_iInter_nat_succ (u : ℕ → Set α) : (u 0 ∩ ⋂ i, u (i + 1)) = ⋂ i, u i :=
inf_iInf_nat_succ u
end Set
open Set
variable [CompleteLattice β]
theorem iSup_iUnion (s : ι → Set α) (f : α → β) : ⨆ a ∈ ⋃ i, s i, f a = ⨆ (i) (a ∈ s i), f a := by
rw [iSup_comm]
simp_rw [mem_iUnion, iSup_exists]
theorem iInf_iUnion (s : ι → Set α) (f : α → β) : ⨅ a ∈ ⋃ i, s i, f a = ⨅ (i) (a ∈ s i), f a :=
iSup_iUnion (β := βᵒᵈ) s f
theorem sSup_iUnion (t : ι → Set β) : sSup (⋃ i, t i) = ⨆ i, sSup (t i) := by
simp_rw [sSup_eq_iSup, iSup_iUnion]
theorem sSup_sUnion (s : Set (Set β)) : sSup (⋃₀ s) = ⨆ t ∈ s, sSup t := by
simp only [sUnion_eq_biUnion, sSup_eq_iSup, iSup_iUnion]
theorem sInf_sUnion (s : Set (Set β)) : sInf (⋃₀ s) = ⨅ t ∈ s, sInf t :=
sSup_sUnion (β := βᵒᵈ) s
lemma iSup_sUnion (S : Set (Set α)) (f : α → β) :
(⨆ x ∈ ⋃₀ S, f x) = ⨆ (s ∈ S) (x ∈ s), f x := by
rw [sUnion_eq_iUnion, iSup_iUnion, ← iSup_subtype'']
lemma iInf_sUnion (S : Set (Set α)) (f : α → β) :
(⨅ x ∈ ⋃₀ S, f x) = ⨅ (s ∈ S) (x ∈ s), f x := by
rw [sUnion_eq_iUnion, iInf_iUnion, ← iInf_subtype'']
lemma forall_sUnion {S : Set (Set α)} {p : α → Prop} :
(∀ x ∈ ⋃₀ S, p x) ↔ ∀ s ∈ S, ∀ x ∈ s, p x := by
simp_rw [← iInf_Prop_eq, iInf_sUnion]
lemma exists_sUnion {S : Set (Set α)} {p : α → Prop} :
(∃ x ∈ ⋃₀ S, p x) ↔ ∃ s ∈ S, ∃ x ∈ s, p x := by
simp_rw [← exists_prop, ← iSup_Prop_eq, iSup_sUnion]
| Mathlib/Data/Set/Lattice.lean | 1,753 | 1,754 | |
/-
Copyright (c) 2022 Alexander Bentkamp. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Alexander Bentkamp
-/
import Mathlib.Analysis.InnerProductSpace.Spectrum
import Mathlib.Data.Matrix.Rank
import Mathlib.LinearAlgebra.Matrix.Diagonal
import Mathlib.LinearAlgebra.Matrix.Hermitian
import Mathlib.Topology.Algebra.Module.FiniteDimension
/-! # Spectral theory of hermitian matrices
This file proves the spectral theorem for matrices. The proof of the spectral theorem is based on
the spectral theorem for linear maps (`LinearMap.IsSymmetric.eigenvectorBasis_apply_self_apply`).
## Tags
spectral theorem, diagonalization theorem -/
namespace Matrix
variable {𝕜 : Type*} [RCLike 𝕜] {n : Type*} [Fintype n]
variable {A : Matrix n n 𝕜}
namespace IsHermitian
section DecidableEq
variable [DecidableEq n]
variable (hA : A.IsHermitian)
/-- The eigenvalues of a hermitian matrix, indexed by `Fin (Fintype.card n)` where `n` is the index
type of the matrix. -/
noncomputable def eigenvalues₀ : Fin (Fintype.card n) → ℝ :=
(isHermitian_iff_isSymmetric.1 hA).eigenvalues finrank_euclideanSpace
/-- The eigenvalues of a hermitian matrix, reusing the index `n` of the matrix entries. -/
noncomputable def eigenvalues : n → ℝ := fun i =>
hA.eigenvalues₀ <| (Fintype.equivOfCardEq (Fintype.card_fin _)).symm i
/-- A choice of an orthonormal basis of eigenvectors of a hermitian matrix. -/
noncomputable def eigenvectorBasis : OrthonormalBasis n 𝕜 (EuclideanSpace 𝕜 n) :=
((isHermitian_iff_isSymmetric.1 hA).eigenvectorBasis finrank_euclideanSpace).reindex
(Fintype.equivOfCardEq (Fintype.card_fin _))
lemma mulVec_eigenvectorBasis (j : n) :
A *ᵥ ⇑(hA.eigenvectorBasis j) = (hA.eigenvalues j) • ⇑(hA.eigenvectorBasis j) := by
simpa only [eigenvectorBasis, OrthonormalBasis.reindex_apply, toEuclideanLin_apply,
RCLike.real_smul_eq_coe_smul (K := 𝕜)] using
congr(⇑$((isHermitian_iff_isSymmetric.1 hA).apply_eigenvectorBasis
finrank_euclideanSpace ((Fintype.equivOfCardEq (Fintype.card_fin _)).symm j)))
/-- The spectrum of a Hermitian matrix `A` coincides with the spectrum of `toEuclideanLin A`. -/
theorem spectrum_toEuclideanLin : spectrum 𝕜 (toEuclideanLin A) = spectrum 𝕜 A :=
AlgEquiv.spectrum_eq (Matrix.toLinAlgEquiv (PiLp.basisFun 2 𝕜 n)) _
/-- Eigenvalues of a hermitian matrix A are in the ℝ spectrum of A. -/
theorem eigenvalues_mem_spectrum_real (i : n) : hA.eigenvalues i ∈ spectrum ℝ A := by
apply spectrum.of_algebraMap_mem 𝕜
rw [← spectrum_toEuclideanLin]
exact LinearMap.IsSymmetric.hasEigenvalue_eigenvalues _ _ _ |>.mem_spectrum
/-- Unitary matrix whose columns are `Matrix.IsHermitian.eigenvectorBasis`. -/
noncomputable def eigenvectorUnitary {𝕜 : Type*} [RCLike 𝕜] {n : Type*}
[Fintype n] {A : Matrix n n 𝕜} [DecidableEq n] (hA : Matrix.IsHermitian A) :
Matrix.unitaryGroup n 𝕜 :=
⟨(EuclideanSpace.basisFun n 𝕜).toBasis.toMatrix (hA.eigenvectorBasis).toBasis,
(EuclideanSpace.basisFun n 𝕜).toMatrix_orthonormalBasis_mem_unitary (eigenvectorBasis hA)⟩
lemma eigenvectorUnitary_coe {𝕜 : Type*} [RCLike 𝕜] {n : Type*} [Fintype n]
{A : Matrix n n 𝕜} [DecidableEq n] (hA : Matrix.IsHermitian A) :
eigenvectorUnitary hA =
(EuclideanSpace.basisFun n 𝕜).toBasis.toMatrix (hA.eigenvectorBasis).toBasis :=
rfl
@[simp]
theorem eigenvectorUnitary_transpose_apply (j : n) :
(eigenvectorUnitary hA)ᵀ j = ⇑(hA.eigenvectorBasis j) :=
rfl
@[simp]
theorem eigenvectorUnitary_apply (i j : n) :
eigenvectorUnitary hA i j = ⇑(hA.eigenvectorBasis j) i :=
rfl
theorem eigenvectorUnitary_mulVec (j : n) :
eigenvectorUnitary hA *ᵥ Pi.single j 1 = ⇑(hA.eigenvectorBasis j) := by
simp_rw [mulVec_single_one, eigenvectorUnitary_transpose_apply]
theorem star_eigenvectorUnitary_mulVec (j : n) :
(star (eigenvectorUnitary hA : Matrix n n 𝕜)) *ᵥ ⇑(hA.eigenvectorBasis j) = Pi.single j 1 := by
rw [← eigenvectorUnitary_mulVec, mulVec_mulVec, unitary.coe_star_mul_self, one_mulVec]
| /-- Unitary diagonalization of a Hermitian matrix. -/
theorem star_mul_self_mul_eq_diagonal :
(star (eigenvectorUnitary hA : Matrix n n 𝕜)) * A * (eigenvectorUnitary hA : Matrix n n 𝕜)
| Mathlib/LinearAlgebra/Matrix/Spectrum.lean | 95 | 97 |
/-
Copyright (c) 2022 Hanting Zhang. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Hanting Zhang
-/
import Mathlib.Topology.MetricSpace.Antilipschitz
import Mathlib.Topology.MetricSpace.Isometry
import Mathlib.Topology.MetricSpace.Lipschitz
import Mathlib.Data.FunLike.Basic
/-!
# Dilations
We define dilations, i.e., maps between emetric spaces that satisfy
`edist (f x) (f y) = r * edist x y` for some `r ∉ {0, ∞}`.
The value `r = 0` is not allowed because we want dilations of (e)metric spaces to be automatically
injective. The value `r = ∞` is not allowed because this way we can define `Dilation.ratio f : ℝ≥0`,
not `Dilation.ratio f : ℝ≥0∞`. Also, we do not often need maps sending distinct points to points at
infinite distance.
## Main definitions
* `Dilation.ratio f : ℝ≥0`: the value of `r` in the relation above, defaulting to 1 in the case
where it is not well-defined.
## Notation
- `α →ᵈ β`: notation for `Dilation α β`.
## Implementation notes
The type of dilations defined in this file are also referred to as "similarities" or "similitudes"
by other authors. The name `Dilation` was chosen to match the Wikipedia name.
Since a lot of elementary properties don't require `eq_of_dist_eq_zero` we start setting up the
theory for `PseudoEMetricSpace` and we specialize to `PseudoMetricSpace` and `MetricSpace` when
needed.
## TODO
- Introduce dilation equivs.
- Refactor the `Isometry` API to match the `*HomClass` API below.
## References
- https://en.wikipedia.org/wiki/Dilation_(metric_space)
- [Marcel Berger, *Geometry*][berger1987]
-/
noncomputable section
open Bornology Function Set Topology
open scoped ENNReal NNReal
section Defs
variable (α : Type*) (β : Type*) [PseudoEMetricSpace α] [PseudoEMetricSpace β]
/-- A dilation is a map that uniformly scales the edistance between any two points. -/
structure Dilation where
toFun : α → β
edist_eq' : ∃ r : ℝ≥0, r ≠ 0 ∧ ∀ x y : α, edist (toFun x) (toFun y) = r * edist x y
@[inherit_doc] infixl:25 " →ᵈ " => Dilation
/-- `DilationClass F α β r` states that `F` is a type of `r`-dilations.
You should extend this typeclass when you extend `Dilation`. -/
class DilationClass (F : Type*) (α β : outParam Type*) [PseudoEMetricSpace α] [PseudoEMetricSpace β]
[FunLike F α β] : Prop where
edist_eq' : ∀ f : F, ∃ r : ℝ≥0, r ≠ 0 ∧ ∀ x y : α, edist (f x) (f y) = r * edist x y
end Defs
namespace Dilation
variable {α : Type*} {β : Type*} {γ : Type*} {F : Type*}
section Setup
variable [PseudoEMetricSpace α] [PseudoEMetricSpace β]
instance funLike : FunLike (α →ᵈ β) α β where
coe := toFun
coe_injective' f g h := by cases f; cases g; congr
instance toDilationClass : DilationClass (α →ᵈ β) α β where
edist_eq' f := edist_eq' f
@[simp]
theorem toFun_eq_coe {f : α →ᵈ β} : f.toFun = (f : α → β) :=
rfl
@[simp]
theorem coe_mk (f : α → β) (h) : ⇑(⟨f, h⟩ : α →ᵈ β) = f :=
rfl
protected theorem congr_fun {f g : α →ᵈ β} (h : f = g) (x : α) : f x = g x :=
DFunLike.congr_fun h x
protected theorem congr_arg (f : α →ᵈ β) {x y : α} (h : x = y) : f x = f y :=
DFunLike.congr_arg f h
@[ext]
theorem ext {f g : α →ᵈ β} (h : ∀ x, f x = g x) : f = g :=
DFunLike.ext f g h
@[simp]
theorem mk_coe (f : α →ᵈ β) (h) : Dilation.mk f h = f :=
ext fun _ => rfl
/-- Copy of a `Dilation` with a new `toFun` equal to the old one. Useful to fix definitional
equalities. -/
@[simps -fullyApplied]
protected def copy (f : α →ᵈ β) (f' : α → β) (h : f' = ⇑f) : α →ᵈ β where
toFun := f'
edist_eq' := h.symm ▸ f.edist_eq'
theorem copy_eq_self (f : α →ᵈ β) {f' : α → β} (h : f' = f) : f.copy f' h = f :=
DFunLike.ext' h
variable [FunLike F α β]
open Classical in
/-- The ratio of a dilation `f`. If the ratio is undefined (i.e., the distance between any two
points in `α` is either zero or infinity), then we choose one as the ratio. -/
def ratio [DilationClass F α β] (f : F) : ℝ≥0 :=
if ∀ x y : α, edist x y = 0 ∨ edist x y = ⊤ then 1 else (DilationClass.edist_eq' f).choose
theorem ratio_of_trivial [DilationClass F α β] (f : F)
(h : ∀ x y : α, edist x y = 0 ∨ edist x y = ∞) : ratio f = 1 :=
if_pos h
@[nontriviality]
theorem ratio_of_subsingleton [Subsingleton α] [DilationClass F α β] (f : F) : ratio f = 1 :=
if_pos fun x y ↦ by simp [Subsingleton.elim x y]
theorem ratio_ne_zero [DilationClass F α β] (f : F) : ratio f ≠ 0 := by
rw [ratio]; split_ifs
· exact one_ne_zero
exact (DilationClass.edist_eq' f).choose_spec.1
theorem ratio_pos [DilationClass F α β] (f : F) : 0 < ratio f :=
(ratio_ne_zero f).bot_lt
@[simp]
theorem edist_eq [DilationClass F α β] (f : F) (x y : α) :
edist (f x) (f y) = ratio f * edist x y := by
rw [ratio]; split_ifs with key
· rcases DilationClass.edist_eq' f with ⟨r, hne, hr⟩
replace hr := hr x y
rcases key x y with h | h
· simp only [hr, h, mul_zero]
· simp [hr, h, hne]
exact (DilationClass.edist_eq' f).choose_spec.2 x y
| @[simp]
theorem nndist_eq {α β F : Type*} [PseudoMetricSpace α] [PseudoMetricSpace β] [FunLike F α β]
| Mathlib/Topology/MetricSpace/Dilation.lean | 157 | 158 |
/-
Copyright (c) 2018 Kenny Lau. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kenny Lau, Mario Carneiro
-/
import Mathlib.Algebra.Module.Submodule.Bilinear
import Mathlib.Algebra.Module.Equiv.Basic
import Mathlib.GroupTheory.Congruence.Hom
import Mathlib.Tactic.Abel
import Mathlib.Tactic.SuppressCompilation
/-!
# Tensor product of modules over commutative semirings.
This file constructs the tensor product of modules over commutative semirings. Given a semiring `R`
and modules over it `M` and `N`, the standard construction of the tensor product is
`TensorProduct R M N`. It is also a module over `R`.
It comes with a canonical bilinear map
`TensorProduct.mk R M N : M →ₗ[R] N →ₗ[R] TensorProduct R M N`.
Given any bilinear map `f : M →ₗ[R] N →ₗ[R] P`, there is a unique linear map
`TensorProduct.lift f : TensorProduct R M N →ₗ[R] P` whose composition with the canonical bilinear
map `TensorProduct.mk` is the given bilinear map `f`. Uniqueness is shown in the theorem
`TensorProduct.lift.unique`.
## Notation
* This file introduces the notation `M ⊗ N` and `M ⊗[R] N` for the tensor product space
`TensorProduct R M N`.
* It introduces the notation `m ⊗ₜ n` and `m ⊗ₜ[R] n` for the tensor product of two elements,
otherwise written as `TensorProduct.tmul R m n`.
## Tags
bilinear, tensor, tensor product
-/
suppress_compilation
section Semiring
variable {R : Type*} [CommSemiring R]
variable {R' : Type*} [Monoid R']
variable {R'' : Type*} [Semiring R'']
variable {A M N P Q S T : Type*}
variable [AddCommMonoid M] [AddCommMonoid N] [AddCommMonoid P]
variable [AddCommMonoid Q] [AddCommMonoid S] [AddCommMonoid T]
variable [Module R M] [Module R N] [Module R Q] [Module R S] [Module R T]
variable [DistribMulAction R' M]
variable [Module R'' M]
variable (M N)
namespace TensorProduct
section
variable (R)
/-- The relation on `FreeAddMonoid (M × N)` that generates a congruence whose quotient is
the tensor product. -/
inductive Eqv : FreeAddMonoid (M × N) → FreeAddMonoid (M × N) → Prop
| of_zero_left : ∀ n : N, Eqv (.of (0, n)) 0
| of_zero_right : ∀ m : M, Eqv (.of (m, 0)) 0
| of_add_left : ∀ (m₁ m₂ : M) (n : N), Eqv (.of (m₁, n) + .of (m₂, n)) (.of (m₁ + m₂, n))
| of_add_right : ∀ (m : M) (n₁ n₂ : N), Eqv (.of (m, n₁) + .of (m, n₂)) (.of (m, n₁ + n₂))
| of_smul : ∀ (r : R) (m : M) (n : N), Eqv (.of (r • m, n)) (.of (m, r • n))
| add_comm : ∀ x y, Eqv (x + y) (y + x)
end
end TensorProduct
variable (R) in
/-- The tensor product of two modules `M` and `N` over the same commutative semiring `R`.
The localized notations are `M ⊗ N` and `M ⊗[R] N`, accessed by `open scoped TensorProduct`. -/
def TensorProduct : Type _ :=
(addConGen (TensorProduct.Eqv R M N)).Quotient
set_option quotPrecheck false in
@[inherit_doc TensorProduct] scoped[TensorProduct] infixl:100 " ⊗ " => TensorProduct _
@[inherit_doc] scoped[TensorProduct] notation:100 M " ⊗[" R "] " N:100 => TensorProduct R M N
namespace TensorProduct
section Module
protected instance zero : Zero (M ⊗[R] N) :=
(addConGen (TensorProduct.Eqv R M N)).zero
protected instance add : Add (M ⊗[R] N) :=
(addConGen (TensorProduct.Eqv R M N)).hasAdd
instance addZeroClass : AddZeroClass (M ⊗[R] N) :=
{ (addConGen (TensorProduct.Eqv R M N)).addMonoid with
/- The `toAdd` field is given explicitly as `TensorProduct.add` for performance reasons.
This avoids any need to unfold `Con.addMonoid` when the type checker is checking
that instance diagrams commute -/
toAdd := TensorProduct.add _ _
toZero := TensorProduct.zero _ _ }
instance addSemigroup : AddSemigroup (M ⊗[R] N) :=
{ (addConGen (TensorProduct.Eqv R M N)).addMonoid with
toAdd := TensorProduct.add _ _ }
instance addCommSemigroup : AddCommSemigroup (M ⊗[R] N) :=
{ (addConGen (TensorProduct.Eqv R M N)).addMonoid with
toAddSemigroup := TensorProduct.addSemigroup _ _
add_comm := fun x y =>
AddCon.induction_on₂ x y fun _ _ =>
Quotient.sound' <| AddConGen.Rel.of _ _ <| Eqv.add_comm _ _ }
instance : Inhabited (M ⊗[R] N) :=
⟨0⟩
variable {M N}
variable (R) in
/-- The canonical function `M → N → M ⊗ N`. The localized notations are `m ⊗ₜ n` and `m ⊗ₜ[R] n`,
accessed by `open scoped TensorProduct`. -/
def tmul (m : M) (n : N) : M ⊗[R] N :=
AddCon.mk' _ <| FreeAddMonoid.of (m, n)
/-- The canonical function `M → N → M ⊗ N`. -/
infixl:100 " ⊗ₜ " => tmul _
/-- The canonical function `M → N → M ⊗ N`. -/
notation:100 x " ⊗ₜ[" R "] " y:100 => tmul R x y
@[elab_as_elim, induction_eliminator]
protected theorem induction_on {motive : M ⊗[R] N → Prop} (z : M ⊗[R] N)
(zero : motive 0)
(tmul : ∀ x y, motive <| x ⊗ₜ[R] y)
(add : ∀ x y, motive x → motive y → motive (x + y)) : motive z :=
AddCon.induction_on z fun x =>
FreeAddMonoid.recOn x zero fun ⟨m, n⟩ y ih => by
rw [AddCon.coe_add]
exact add _ _ (tmul ..) ih
/-- Lift an `R`-balanced map to the tensor product.
A map `f : M →+ N →+ P` additive in both components is `R`-balanced, or middle linear with respect
to `R`, if scalar multiplication in either argument is equivalent, `f (r • m) n = f m (r • n)`.
Note that strictly the first action should be a right-action by `R`, but for now `R` is commutative
so it doesn't matter. -/
-- TODO: use this to implement `lift` and `SMul.aux`. For now we do not do this as it causes
-- performance issues elsewhere.
def liftAddHom (f : M →+ N →+ P)
(hf : ∀ (r : R) (m : M) (n : N), f (r • m) n = f m (r • n)) :
M ⊗[R] N →+ P :=
(addConGen (TensorProduct.Eqv R M N)).lift (FreeAddMonoid.lift (fun mn : M × N => f mn.1 mn.2)) <|
AddCon.addConGen_le fun x y hxy =>
match x, y, hxy with
| _, _, .of_zero_left n =>
(AddCon.ker_rel _).2 <| by simp_rw [map_zero, FreeAddMonoid.lift_eval_of, map_zero,
AddMonoidHom.zero_apply]
| _, _, .of_zero_right m =>
(AddCon.ker_rel _).2 <| by simp_rw [map_zero, FreeAddMonoid.lift_eval_of, map_zero]
| _, _, .of_add_left m₁ m₂ n =>
(AddCon.ker_rel _).2 <| by simp_rw [map_add, FreeAddMonoid.lift_eval_of, map_add,
AddMonoidHom.add_apply]
| _, _, .of_add_right m n₁ n₂ =>
(AddCon.ker_rel _).2 <| by simp_rw [map_add, FreeAddMonoid.lift_eval_of, map_add]
| _, _, .of_smul s m n =>
(AddCon.ker_rel _).2 <| by rw [FreeAddMonoid.lift_eval_of, FreeAddMonoid.lift_eval_of, hf]
| _, _, .add_comm x y =>
(AddCon.ker_rel _).2 <| by simp_rw [map_add, add_comm]
@[simp]
theorem liftAddHom_tmul (f : M →+ N →+ P)
(hf : ∀ (r : R) (m : M) (n : N), f (r • m) n = f m (r • n)) (m : M) (n : N) :
liftAddHom f hf (m ⊗ₜ n) = f m n :=
rfl
variable (M) in
@[simp]
theorem zero_tmul (n : N) : (0 : M) ⊗ₜ[R] n = 0 :=
Quotient.sound' <| AddConGen.Rel.of _ _ <| Eqv.of_zero_left _
theorem add_tmul (m₁ m₂ : M) (n : N) : (m₁ + m₂) ⊗ₜ n = m₁ ⊗ₜ n + m₂ ⊗ₜ[R] n :=
Eq.symm <| Quotient.sound' <| AddConGen.Rel.of _ _ <| Eqv.of_add_left _ _ _
variable (N) in
@[simp]
theorem tmul_zero (m : M) : m ⊗ₜ[R] (0 : N) = 0 :=
Quotient.sound' <| AddConGen.Rel.of _ _ <| Eqv.of_zero_right _
theorem tmul_add (m : M) (n₁ n₂ : N) : m ⊗ₜ (n₁ + n₂) = m ⊗ₜ n₁ + m ⊗ₜ[R] n₂ :=
Eq.symm <| Quotient.sound' <| AddConGen.Rel.of _ _ <| Eqv.of_add_right _ _ _
instance uniqueLeft [Subsingleton M] : Unique (M ⊗[R] N) where
default := 0
uniq z := z.induction_on rfl (fun x y ↦ by rw [Subsingleton.elim x 0, zero_tmul]) <| by
rintro _ _ rfl rfl; apply add_zero
instance uniqueRight [Subsingleton N] : Unique (M ⊗[R] N) where
default := 0
uniq z := z.induction_on rfl (fun x y ↦ by rw [Subsingleton.elim y 0, tmul_zero]) <| by
rintro _ _ rfl rfl; apply add_zero
section
variable (R R' M N)
/-- A typeclass for `SMul` structures which can be moved across a tensor product.
This typeclass is generated automatically from an `IsScalarTower` instance, but exists so that
we can also add an instance for `AddCommGroup.toIntModule`, allowing `z •` to be moved even if
`R` does not support negation.
Note that `Module R' (M ⊗[R] N)` is available even without this typeclass on `R'`; it's only
needed if `TensorProduct.smul_tmul`, `TensorProduct.smul_tmul'`, or `TensorProduct.tmul_smul` is
used.
-/
class CompatibleSMul [DistribMulAction R' N] : Prop where
smul_tmul : ∀ (r : R') (m : M) (n : N), (r • m) ⊗ₜ n = m ⊗ₜ[R] (r • n)
end
/-- Note that this provides the default `CompatibleSMul R R M N` instance through
`IsScalarTower.left`. -/
instance (priority := 100) CompatibleSMul.isScalarTower [SMul R' R] [IsScalarTower R' R M]
[DistribMulAction R' N] [IsScalarTower R' R N] : CompatibleSMul R R' M N :=
⟨fun r m n => by
conv_lhs => rw [← one_smul R m]
conv_rhs => rw [← one_smul R n]
rw [← smul_assoc, ← smul_assoc]
exact Quotient.sound' <| AddConGen.Rel.of _ _ <| Eqv.of_smul _ _ _⟩
/-- `smul` can be moved from one side of the product to the other . -/
theorem smul_tmul [DistribMulAction R' N] [CompatibleSMul R R' M N] (r : R') (m : M) (n : N) :
(r • m) ⊗ₜ n = m ⊗ₜ[R] (r • n) :=
CompatibleSMul.smul_tmul _ _ _
private def addMonoidWithWrongNSMul : AddMonoid (M ⊗[R] N) :=
{ (addConGen (TensorProduct.Eqv R M N)).addMonoid with }
attribute [local instance] addMonoidWithWrongNSMul in
/-- Auxiliary function to defining scalar multiplication on tensor product. -/
def SMul.aux {R' : Type*} [SMul R' M] (r : R') : FreeAddMonoid (M × N) →+ M ⊗[R] N :=
FreeAddMonoid.lift fun p : M × N => (r • p.1) ⊗ₜ p.2
theorem SMul.aux_of {R' : Type*} [SMul R' M] (r : R') (m : M) (n : N) :
SMul.aux r (.of (m, n)) = (r • m) ⊗ₜ[R] n :=
rfl
variable [SMulCommClass R R' M] [SMulCommClass R R'' M]
/-- Given two modules over a commutative semiring `R`, if one of the factors carries a
(distributive) action of a second type of scalars `R'`, which commutes with the action of `R`, then
the tensor product (over `R`) carries an action of `R'`.
This instance defines this `R'` action in the case that it is the left module which has the `R'`
action. Two natural ways in which this situation arises are:
* Extension of scalars
* A tensor product of a group representation with a module not carrying an action
Note that in the special case that `R = R'`, since `R` is commutative, we just get the usual scalar
action on a tensor product of two modules. This special case is important enough that, for
performance reasons, we define it explicitly below. -/
instance leftHasSMul : SMul R' (M ⊗[R] N) :=
⟨fun r =>
(addConGen (TensorProduct.Eqv R M N)).lift (SMul.aux r : _ →+ M ⊗[R] N) <|
AddCon.addConGen_le fun x y hxy =>
match x, y, hxy with
| _, _, .of_zero_left n =>
(AddCon.ker_rel _).2 <| by simp_rw [map_zero, SMul.aux_of, smul_zero, zero_tmul]
| _, _, .of_zero_right m =>
(AddCon.ker_rel _).2 <| by simp_rw [map_zero, SMul.aux_of, tmul_zero]
| _, _, .of_add_left m₁ m₂ n =>
(AddCon.ker_rel _).2 <| by simp_rw [map_add, SMul.aux_of, smul_add, add_tmul]
| _, _, .of_add_right m n₁ n₂ =>
(AddCon.ker_rel _).2 <| by simp_rw [map_add, SMul.aux_of, tmul_add]
| _, _, .of_smul s m n =>
(AddCon.ker_rel _).2 <| by rw [SMul.aux_of, SMul.aux_of, ← smul_comm, smul_tmul]
| _, _, .add_comm x y =>
(AddCon.ker_rel _).2 <| by simp_rw [map_add, add_comm]⟩
instance : SMul R (M ⊗[R] N) :=
TensorProduct.leftHasSMul
protected theorem smul_zero (r : R') : r • (0 : M ⊗[R] N) = 0 :=
AddMonoidHom.map_zero _
protected theorem smul_add (r : R') (x y : M ⊗[R] N) : r • (x + y) = r • x + r • y :=
AddMonoidHom.map_add _ _ _
protected theorem zero_smul (x : M ⊗[R] N) : (0 : R'') • x = 0 :=
have : ∀ (r : R'') (m : M) (n : N), r • m ⊗ₜ[R] n = (r • m) ⊗ₜ n := fun _ _ _ => rfl
x.induction_on (by rw [TensorProduct.smul_zero])
(fun m n => by rw [this, zero_smul, zero_tmul]) fun x y ihx ihy => by
rw [TensorProduct.smul_add, ihx, ihy, add_zero]
protected theorem one_smul (x : M ⊗[R] N) : (1 : R') • x = x :=
have : ∀ (r : R') (m : M) (n : N), r • m ⊗ₜ[R] n = (r • m) ⊗ₜ n := fun _ _ _ => rfl
x.induction_on (by rw [TensorProduct.smul_zero])
(fun m n => by rw [this, one_smul])
fun x y ihx ihy => by rw [TensorProduct.smul_add, ihx, ihy]
protected theorem add_smul (r s : R'') (x : M ⊗[R] N) : (r + s) • x = r • x + s • x :=
have : ∀ (r : R'') (m : M) (n : N), r • m ⊗ₜ[R] n = (r • m) ⊗ₜ n := fun _ _ _ => rfl
x.induction_on (by simp_rw [TensorProduct.smul_zero, add_zero])
(fun m n => by simp_rw [this, add_smul, add_tmul]) fun x y ihx ihy => by
simp_rw [TensorProduct.smul_add]
rw [ihx, ihy, add_add_add_comm]
instance addMonoid : AddMonoid (M ⊗[R] N) :=
{ TensorProduct.addZeroClass _ _ with
toAddSemigroup := TensorProduct.addSemigroup _ _
toZero := TensorProduct.zero _ _
nsmul := fun n v => n • v
nsmul_zero := by simp [TensorProduct.zero_smul]
nsmul_succ := by simp only [TensorProduct.one_smul, TensorProduct.add_smul, add_comm,
forall_const] }
instance addCommMonoid : AddCommMonoid (M ⊗[R] N) :=
{ TensorProduct.addCommSemigroup _ _ with
toAddMonoid := TensorProduct.addMonoid }
instance leftDistribMulAction : DistribMulAction R' (M ⊗[R] N) :=
have : ∀ (r : R') (m : M) (n : N), r • m ⊗ₜ[R] n = (r • m) ⊗ₜ n := fun _ _ _ => rfl
{ smul_add := fun r x y => TensorProduct.smul_add r x y
mul_smul := fun r s x =>
x.induction_on (by simp_rw [TensorProduct.smul_zero])
(fun m n => by simp_rw [this, mul_smul]) fun x y ihx ihy => by
simp_rw [TensorProduct.smul_add]
rw [ihx, ihy]
one_smul := TensorProduct.one_smul
smul_zero := TensorProduct.smul_zero }
instance : DistribMulAction R (M ⊗[R] N) :=
TensorProduct.leftDistribMulAction
theorem smul_tmul' (r : R') (m : M) (n : N) : r • m ⊗ₜ[R] n = (r • m) ⊗ₜ n :=
rfl
@[simp]
theorem tmul_smul [DistribMulAction R' N] [CompatibleSMul R R' M N] (r : R') (x : M) (y : N) :
x ⊗ₜ (r • y) = r • x ⊗ₜ[R] y :=
(smul_tmul _ _ _).symm
theorem smul_tmul_smul (r s : R) (m : M) (n : N) : (r • m) ⊗ₜ[R] (s • n) = (r * s) • m ⊗ₜ[R] n := by
simp_rw [smul_tmul, tmul_smul, mul_smul]
instance leftModule : Module R'' (M ⊗[R] N) :=
{ add_smul := TensorProduct.add_smul
zero_smul := TensorProduct.zero_smul }
instance : Module R (M ⊗[R] N) :=
TensorProduct.leftModule
instance [Module R''ᵐᵒᵖ M] [IsCentralScalar R'' M] : IsCentralScalar R'' (M ⊗[R] N) where
op_smul_eq_smul r x :=
x.induction_on (by rw [smul_zero, smul_zero])
(fun x y => by rw [smul_tmul', smul_tmul', op_smul_eq_smul]) fun x y hx hy => by
rw [smul_add, smul_add, hx, hy]
section
-- Like `R'`, `R'₂` provides a `DistribMulAction R'₂ (M ⊗[R] N)`
variable {R'₂ : Type*} [Monoid R'₂] [DistribMulAction R'₂ M]
variable [SMulCommClass R R'₂ M]
/-- `SMulCommClass R' R'₂ M` implies `SMulCommClass R' R'₂ (M ⊗[R] N)` -/
instance smulCommClass_left [SMulCommClass R' R'₂ M] : SMulCommClass R' R'₂ (M ⊗[R] N) where
smul_comm r' r'₂ x :=
TensorProduct.induction_on x (by simp_rw [TensorProduct.smul_zero])
(fun m n => by simp_rw [smul_tmul', smul_comm]) fun x y ihx ihy => by
simp_rw [TensorProduct.smul_add]; rw [ihx, ihy]
variable [SMul R'₂ R']
/-- `IsScalarTower R'₂ R' M` implies `IsScalarTower R'₂ R' (M ⊗[R] N)` -/
instance isScalarTower_left [IsScalarTower R'₂ R' M] : IsScalarTower R'₂ R' (M ⊗[R] N) :=
⟨fun s r x =>
x.induction_on (by simp)
(fun m n => by rw [smul_tmul', smul_tmul', smul_tmul', smul_assoc]) fun x y ihx ihy => by
rw [smul_add, smul_add, smul_add, ihx, ihy]⟩
variable [DistribMulAction R'₂ N] [DistribMulAction R' N]
variable [CompatibleSMul R R'₂ M N] [CompatibleSMul R R' M N]
/-- `IsScalarTower R'₂ R' N` implies `IsScalarTower R'₂ R' (M ⊗[R] N)` -/
instance isScalarTower_right [IsScalarTower R'₂ R' N] : IsScalarTower R'₂ R' (M ⊗[R] N) :=
⟨fun s r x =>
x.induction_on (by simp)
(fun m n => by rw [← tmul_smul, ← tmul_smul, ← tmul_smul, smul_assoc]) fun x y ihx ihy => by
rw [smul_add, smul_add, smul_add, ihx, ihy]⟩
end
/-- A short-cut instance for the common case, where the requirements for the `compatible_smul`
instances are sufficient. -/
instance isScalarTower [SMul R' R] [IsScalarTower R' R M] : IsScalarTower R' R (M ⊗[R] N) :=
TensorProduct.isScalarTower_left
-- or right
variable (R M N) in
/-- The canonical bilinear map `M → N → M ⊗[R] N`. -/
def mk : M →ₗ[R] N →ₗ[R] M ⊗[R] N :=
LinearMap.mk₂ R (· ⊗ₜ ·) add_tmul (fun c m n => by simp_rw [smul_tmul, tmul_smul])
tmul_add tmul_smul
@[simp]
theorem mk_apply (m : M) (n : N) : mk R M N m n = m ⊗ₜ n :=
rfl
theorem ite_tmul (x₁ : M) (x₂ : N) (P : Prop) [Decidable P] :
(if P then x₁ else 0) ⊗ₜ[R] x₂ = if P then x₁ ⊗ₜ x₂ else 0 := by split_ifs <;> simp
theorem tmul_ite (x₁ : M) (x₂ : N) (P : Prop) [Decidable P] :
(x₁ ⊗ₜ[R] if P then x₂ else 0) = if P then x₁ ⊗ₜ x₂ else 0 := by split_ifs <;> simp
lemma tmul_single {ι : Type*} [DecidableEq ι] {M : ι → Type*} [∀ i, AddCommMonoid (M i)]
[∀ i, Module R (M i)] (i : ι) (x : N) (m : M i) (j : ι) :
x ⊗ₜ[R] Pi.single i m j = (Pi.single i (x ⊗ₜ[R] m) : ∀ i, N ⊗[R] M i) j := by
by_cases h : i = j <;> aesop
lemma single_tmul {ι : Type*} [DecidableEq ι] {M : ι → Type*} [∀ i, AddCommMonoid (M i)]
[∀ i, Module R (M i)] (i : ι) (x : N) (m : M i) (j : ι) :
Pi.single i m j ⊗ₜ[R] x = (Pi.single i (m ⊗ₜ[R] x) : ∀ i, M i ⊗[R] N) j := by
by_cases h : i = j <;> aesop
section
theorem sum_tmul {α : Type*} (s : Finset α) (m : α → M) (n : N) :
(∑ a ∈ s, m a) ⊗ₜ[R] n = ∑ a ∈ s, m a ⊗ₜ[R] n := by
classical
induction s using Finset.induction with
| empty => simp
| insert _ _ has ih => simp [Finset.sum_insert has, add_tmul, ih]
theorem tmul_sum (m : M) {α : Type*} (s : Finset α) (n : α → N) :
(m ⊗ₜ[R] ∑ a ∈ s, n a) = ∑ a ∈ s, m ⊗ₜ[R] n a := by
classical
induction s using Finset.induction with
| empty => simp
| insert _ _ has ih => simp [Finset.sum_insert has, tmul_add, ih]
end
variable (R M N)
/-- The simple (aka pure) elements span the tensor product. -/
theorem span_tmul_eq_top : Submodule.span R { t : M ⊗[R] N | ∃ m n, m ⊗ₜ n = t } = ⊤ := by
ext t; simp only [Submodule.mem_top, iff_true]
refine t.induction_on ?_ ?_ ?_
· exact Submodule.zero_mem _
· intro m n
apply Submodule.subset_span
use m, n
· intro t₁ t₂ ht₁ ht₂
exact Submodule.add_mem _ ht₁ ht₂
@[simp]
theorem map₂_mk_top_top_eq_top : Submodule.map₂ (mk R M N) ⊤ ⊤ = ⊤ := by
rw [← top_le_iff, ← span_tmul_eq_top, Submodule.map₂_eq_span_image2]
exact Submodule.span_mono fun _ ⟨m, n, h⟩ => ⟨m, trivial, n, trivial, h⟩
theorem exists_eq_tmul_of_forall (x : TensorProduct R M N)
(h : ∀ (m₁ m₂ : M) (n₁ n₂ : N), ∃ m n, m₁ ⊗ₜ n₁ + m₂ ⊗ₜ n₂ = m ⊗ₜ[R] n) :
∃ m n, x = m ⊗ₜ n := by
induction x with
| zero =>
use 0, 0
rw [TensorProduct.zero_tmul]
| tmul m n => use m, n
| add x y h₁ h₂ =>
obtain ⟨m₁, n₁, rfl⟩ := h₁
obtain ⟨m₂, n₂, rfl⟩ := h₂
apply h
end Module
variable [Module R P]
section UniversalProperty
variable {M N}
variable (f : M →ₗ[R] N →ₗ[R] P)
/-- Auxiliary function to constructing a linear map `M ⊗ N → P` given a bilinear map `M → N → P`
with the property that its composition with the canonical bilinear map `M → N → M ⊗ N` is
the given bilinear map `M → N → P`. -/
def liftAux : M ⊗[R] N →+ P :=
liftAddHom (LinearMap.toAddMonoidHom'.comp <| f.toAddMonoidHom)
fun r m n => by dsimp; rw [LinearMap.map_smul₂, map_smul]
theorem liftAux_tmul (m n) : liftAux f (m ⊗ₜ n) = f m n :=
rfl
variable {f}
@[simp]
theorem liftAux.smul (r : R) (x) : liftAux f (r • x) = r • liftAux f x :=
TensorProduct.induction_on x (smul_zero _).symm
(fun p q => by simp_rw [← tmul_smul, liftAux_tmul, (f p).map_smul])
fun p q ih1 ih2 => by simp_rw [smul_add, (liftAux f).map_add, ih1, ih2, smul_add]
variable (f) in
/-- Constructing a linear map `M ⊗ N → P` given a bilinear map `M → N → P` with the property that
its composition with the canonical bilinear map `M → N → M ⊗ N` is
the given bilinear map `M → N → P`. -/
def lift : M ⊗[R] N →ₗ[R] P :=
{ liftAux f with map_smul' := liftAux.smul }
@[simp]
theorem lift.tmul (x y) : lift f (x ⊗ₜ y) = f x y :=
rfl
@[simp]
theorem lift.tmul' (x y) : (lift f).1 (x ⊗ₜ y) = f x y :=
rfl
theorem ext' {g h : M ⊗[R] N →ₗ[R] P} (H : ∀ x y, g (x ⊗ₜ y) = h (x ⊗ₜ y)) : g = h :=
LinearMap.ext fun z =>
TensorProduct.induction_on z (by simp_rw [LinearMap.map_zero]) H fun x y ihx ihy => by
rw [g.map_add, h.map_add, ihx, ihy]
theorem lift.unique {g : M ⊗[R] N →ₗ[R] P} (H : ∀ x y, g (x ⊗ₜ y) = f x y) : g = lift f :=
ext' fun m n => by rw [H, lift.tmul]
theorem lift_mk : lift (mk R M N) = LinearMap.id :=
Eq.symm <| lift.unique fun _ _ => rfl
theorem lift_compr₂ (g : P →ₗ[R] Q) : lift (f.compr₂ g) = g.comp (lift f) :=
Eq.symm <| lift.unique fun _ _ => by simp
theorem lift_mk_compr₂ (f : M ⊗ N →ₗ[R] P) : lift ((mk R M N).compr₂ f) = f := by
rw [lift_compr₂ f, lift_mk, LinearMap.comp_id]
/-- This used to be an `@[ext]` lemma, but it fails very slowly when the `ext` tactic tries to apply
it in some cases, notably when one wants to show equality of two linear maps. The `@[ext]`
attribute is now added locally where it is needed. Using this as the `@[ext]` lemma instead of
`TensorProduct.ext'` allows `ext` to apply lemmas specific to `M →ₗ _` and `N →ₗ _`.
See note [partially-applied ext lemmas]. -/
theorem ext {g h : M ⊗ N →ₗ[R] P} (H : (mk R M N).compr₂ g = (mk R M N).compr₂ h) : g = h := by
rw [← lift_mk_compr₂ g, H, lift_mk_compr₂]
attribute [local ext high] ext
example : M → N → (M → N → P) → P := fun m => flip fun f => f m
variable (R M N P) in
/-- Linearly constructing a linear map `M ⊗ N → P` given a bilinear map `M → N → P`
with the property that its composition with the canonical bilinear map `M → N → M ⊗ N` is
the given bilinear map `M → N → P`. -/
def uncurry : (M →ₗ[R] N →ₗ[R] P) →ₗ[R] M ⊗[R] N →ₗ[R] P :=
LinearMap.flip <| lift <| LinearMap.lflip.comp (LinearMap.flip LinearMap.id)
@[simp]
theorem uncurry_apply (f : M →ₗ[R] N →ₗ[R] P) (m : M) (n : N) :
uncurry R M N P f (m ⊗ₜ n) = f m n := by rw [uncurry, LinearMap.flip_apply, lift.tmul]; rfl
variable (R M N P)
/-- A linear equivalence constructing a linear map `M ⊗ N → P` given a bilinear map `M → N → P`
with the property that its composition with the canonical bilinear map `M → N → M ⊗ N` is
the given bilinear map `M → N → P`. -/
def lift.equiv : (M →ₗ[R] N →ₗ[R] P) ≃ₗ[R] M ⊗[R] N →ₗ[R] P :=
{ uncurry R M N P with
invFun := fun f => (mk R M N).compr₂ f
left_inv := fun _ => LinearMap.ext₂ fun _ _ => lift.tmul _ _
right_inv := fun _ => ext' fun _ _ => lift.tmul _ _ }
@[simp]
theorem lift.equiv_apply (f : M →ₗ[R] N →ₗ[R] P) (m : M) (n : N) :
lift.equiv R M N P f (m ⊗ₜ n) = f m n :=
uncurry_apply f m n
@[simp]
theorem lift.equiv_symm_apply (f : M ⊗[R] N →ₗ[R] P) (m : M) (n : N) :
(lift.equiv R M N P).symm f m n = f (m ⊗ₜ n) :=
rfl
/-- Given a linear map `M ⊗ N → P`, compose it with the canonical bilinear map `M → N → M ⊗ N` to
form a bilinear map `M → N → P`. -/
def lcurry : (M ⊗[R] N →ₗ[R] P) →ₗ[R] M →ₗ[R] N →ₗ[R] P :=
(lift.equiv R M N P).symm
variable {R M N P}
@[simp]
theorem lcurry_apply (f : M ⊗[R] N →ₗ[R] P) (m : M) (n : N) : lcurry R M N P f m n = f (m ⊗ₜ n) :=
rfl
/-- Given a linear map `M ⊗ N → P`, compose it with the canonical bilinear map `M → N → M ⊗ N` to
form a bilinear map `M → N → P`. -/
def curry (f : M ⊗[R] N →ₗ[R] P) : M →ₗ[R] N →ₗ[R] P :=
lcurry R M N P f
@[simp]
theorem curry_apply (f : M ⊗ N →ₗ[R] P) (m : M) (n : N) : curry f m n = f (m ⊗ₜ n) :=
rfl
theorem curry_injective : Function.Injective (curry : (M ⊗[R] N →ₗ[R] P) → M →ₗ[R] N →ₗ[R] P) :=
fun _ _ H => ext H
theorem ext_threefold {g h : (M ⊗[R] N) ⊗[R] P →ₗ[R] Q}
(H : ∀ x y z, g (x ⊗ₜ y ⊗ₜ z) = h (x ⊗ₜ y ⊗ₜ z)) : g = h := by
ext x y z
exact H x y z
-- We'll need this one for checking the pentagon identity!
theorem ext_fourfold {g h : ((M ⊗[R] N) ⊗[R] P) ⊗[R] Q →ₗ[R] S}
(H : ∀ w x y z, g (w ⊗ₜ x ⊗ₜ y ⊗ₜ z) = h (w ⊗ₜ x ⊗ₜ y ⊗ₜ z)) : g = h := by
ext w x y z
exact H w x y z
/-- Two linear maps (M ⊗ N) ⊗ (P ⊗ Q) → S which agree on all elements of the
form (m ⊗ₜ n) ⊗ₜ (p ⊗ₜ q) are equal. -/
theorem ext_fourfold' {φ ψ : (M ⊗[R] N) ⊗[R] P ⊗[R] Q →ₗ[R] S}
(H : ∀ w x y z, φ (w ⊗ₜ x ⊗ₜ (y ⊗ₜ z)) = ψ (w ⊗ₜ x ⊗ₜ (y ⊗ₜ z))) : φ = ψ := by
ext m n p q
exact H m n p q
end UniversalProperty
variable {M N}
section
variable (R M N)
/-- The tensor product of modules is commutative, up to linear equivalence.
-/
protected def comm : M ⊗[R] N ≃ₗ[R] N ⊗[R] M :=
LinearEquiv.ofLinear (lift (mk R N M).flip) (lift (mk R M N).flip) (ext' fun _ _ => rfl)
(ext' fun _ _ => rfl)
@[simp]
theorem comm_tmul (m : M) (n : N) : (TensorProduct.comm R M N) (m ⊗ₜ n) = n ⊗ₜ m :=
rfl
@[simp]
theorem comm_symm_tmul (m : M) (n : N) : (TensorProduct.comm R M N).symm (n ⊗ₜ m) = m ⊗ₜ n :=
rfl
lemma lift_comp_comm_eq (f : M →ₗ[R] N →ₗ[R] P) :
lift f ∘ₗ TensorProduct.comm R N M = lift f.flip :=
ext rfl
end
section CompatibleSMul
variable (R A M N) [CommSemiring A] [Module A M] [Module A N] [SMulCommClass R A M]
[CompatibleSMul R A M N]
/-- If M and N are both R- and A-modules and their actions on them commute,
and if the A-action on `M ⊗[R] N` can switch between the two factors, then there is a
canonical A-linear map from `M ⊗[A] N` to `M ⊗[R] N`. -/
def mapOfCompatibleSMul : M ⊗[A] N →ₗ[A] M ⊗[R] N :=
lift
{ toFun := fun m ↦
{ __ := mk R M N m
map_smul' := fun _ _ ↦ (smul_tmul _ _ _).symm }
map_add' := fun _ _ ↦ LinearMap.ext <| by simp
map_smul' := fun _ _ ↦ rfl }
@[simp] theorem mapOfCompatibleSMul_tmul (m n) : mapOfCompatibleSMul R A M N (m ⊗ₜ n) = m ⊗ₜ n :=
rfl
theorem mapOfCompatibleSMul_surjective : Function.Surjective (mapOfCompatibleSMul R A M N) :=
fun x ↦ x.induction_on (⟨0, map_zero _⟩) (fun m n ↦ ⟨_, mapOfCompatibleSMul_tmul ..⟩)
fun _ _ ⟨x, hx⟩ ⟨y, hy⟩ ↦ ⟨x + y, by simpa using congr($hx + $hy)⟩
attribute [local instance] SMulCommClass.symm
/-- `mapOfCompatibleSMul R A M N` is also R-linear. -/
def mapOfCompatibleSMul' : M ⊗[A] N →ₗ[R] M ⊗[R] N where
__ := mapOfCompatibleSMul R A M N
map_smul' _ x := x.induction_on (map_zero _) (fun _ _ ↦ by simp [smul_tmul'])
fun _ _ h h' ↦ by simpa using congr($h + $h')
/-- If the R- and A-actions on M and N satisfy `CompatibleSMul` both ways,
then `M ⊗[A] N` is canonically isomorphic to `M ⊗[R] N`. -/
def equivOfCompatibleSMul [CompatibleSMul A R M N] : M ⊗[A] N ≃ₗ[A] M ⊗[R] N where
__ := mapOfCompatibleSMul R A M N
invFun := mapOfCompatibleSMul A R M N
left_inv x := x.induction_on (map_zero _) (fun _ _ ↦ rfl)
fun _ _ h h' ↦ by simpa using congr($h + $h')
right_inv x := x.induction_on (map_zero _) (fun _ _ ↦ rfl)
fun _ _ h h' ↦ by simpa using congr($h + $h')
omit [SMulCommClass R A M]
end CompatibleSMul
open LinearMap
/-- The tensor product of a pair of linear maps between modules. -/
def map (f : M →ₗ[R] P) (g : N →ₗ[R] Q) : M ⊗[R] N →ₗ[R] P ⊗[R] Q :=
lift <| comp (compl₂ (mk _ _ _) g) f
@[simp]
theorem map_tmul (f : M →ₗ[R] P) (g : N →ₗ[R] Q) (m : M) (n : N) : map f g (m ⊗ₜ n) = f m ⊗ₜ g n :=
rfl
/-- Given linear maps `f : M → P`, `g : N → Q`, if we identify `M ⊗ N` with `N ⊗ M` and `P ⊗ Q`
with `Q ⊗ P`, then this lemma states that `f ⊗ g = g ⊗ f`. -/
lemma map_comp_comm_eq (f : M →ₗ[R] P) (g : N →ₗ[R] Q) :
map f g ∘ₗ TensorProduct.comm R N M = TensorProduct.comm R Q P ∘ₗ map g f :=
ext rfl
lemma map_comm (f : M →ₗ[R] P) (g : N →ₗ[R] Q) (x : N ⊗[R] M) :
map f g (TensorProduct.comm R N M x) = TensorProduct.comm R Q P (map g f x) :=
DFunLike.congr_fun (map_comp_comm_eq _ _) _
theorem map_range_eq_span_tmul (f : M →ₗ[R] P) (g : N →ₗ[R] Q) :
range (map f g) = Submodule.span R { t | ∃ m n, f m ⊗ₜ g n = t } := by
simp only [← Submodule.map_top, ← span_tmul_eq_top, Submodule.map_span, Set.mem_image,
Set.mem_setOf_eq]
congr; ext t
constructor
· rintro ⟨_, ⟨⟨m, n, rfl⟩, rfl⟩⟩
use m, n
simp only [map_tmul]
· rintro ⟨m, n, rfl⟩
refine ⟨_, ⟨⟨m, n, rfl⟩, ?_⟩⟩
simp only [map_tmul]
/-- Given submodules `p ⊆ P` and `q ⊆ Q`, this is the natural map: `p ⊗ q → P ⊗ Q`. -/
@[simp]
def mapIncl (p : Submodule R P) (q : Submodule R Q) : p ⊗[R] q →ₗ[R] P ⊗[R] Q :=
map p.subtype q.subtype
lemma range_mapIncl (p : Submodule R P) (q : Submodule R Q) :
LinearMap.range (mapIncl p q) = Submodule.span R (Set.image2 (· ⊗ₜ ·) p q) := by
rw [mapIncl, map_range_eq_span_tmul]
congr; ext; simp
theorem map₂_eq_range_lift_comp_mapIncl (f : P →ₗ[R] Q →ₗ[R] M)
(p : Submodule R P) (q : Submodule R Q) :
Submodule.map₂ f p q = LinearMap.range (lift f ∘ₗ mapIncl p q) := by
simp_rw [LinearMap.range_comp, range_mapIncl, Submodule.map_span,
Set.image_image2, Submodule.map₂_eq_span_image2, lift.tmul]
section
variable {P' Q' : Type*}
variable [AddCommMonoid P'] [Module R P']
variable [AddCommMonoid Q'] [Module R Q']
theorem map_comp (f₂ : P →ₗ[R] P') (f₁ : M →ₗ[R] P) (g₂ : Q →ₗ[R] Q') (g₁ : N →ₗ[R] Q) :
map (f₂.comp f₁) (g₂.comp g₁) = (map f₂ g₂).comp (map f₁ g₁) :=
ext' fun _ _ => rfl
lemma range_mapIncl_mono {p p' : Submodule R P} {q q' : Submodule R Q} (hp : p ≤ p') (hq : q ≤ q') :
LinearMap.range (mapIncl p q) ≤ LinearMap.range (mapIncl p' q') := by
simp_rw [range_mapIncl]
exact Submodule.span_mono (Set.image2_subset hp hq)
theorem lift_comp_map (i : P →ₗ[R] Q →ₗ[R] Q') (f : M →ₗ[R] P) (g : N →ₗ[R] Q) :
(lift i).comp (map f g) = lift ((i.comp f).compl₂ g) :=
ext' fun _ _ => rfl
attribute [local ext high] ext
@[simp]
theorem map_id : map (id : M →ₗ[R] M) (id : N →ₗ[R] N) = .id := by
ext
simp only [mk_apply, id_coe, compr₂_apply, _root_.id, map_tmul]
@[simp]
protected theorem map_one : map (1 : M →ₗ[R] M) (1 : N →ₗ[R] N) = 1 :=
map_id
protected theorem map_mul (f₁ f₂ : M →ₗ[R] M) (g₁ g₂ : N →ₗ[R] N) :
map (f₁ * f₂) (g₁ * g₂) = map f₁ g₁ * map f₂ g₂ :=
map_comp f₁ f₂ g₁ g₂
@[simp]
protected theorem map_pow (f : M →ₗ[R] M) (g : N →ₗ[R] N) (n : ℕ) :
map f g ^ n = map (f ^ n) (g ^ n) := by
induction n with
| zero => simp only [pow_zero, TensorProduct.map_one]
| succ n ih => simp only [pow_succ', ih, TensorProduct.map_mul]
theorem map_add_left (f₁ f₂ : M →ₗ[R] P) (g : N →ₗ[R] Q) :
map (f₁ + f₂) g = map f₁ g + map f₂ g := by
ext
simp only [add_tmul, compr₂_apply, mk_apply, map_tmul, add_apply]
theorem map_add_right (f : M →ₗ[R] P) (g₁ g₂ : N →ₗ[R] Q) :
map f (g₁ + g₂) = map f g₁ + map f g₂ := by
ext
simp only [tmul_add, compr₂_apply, mk_apply, map_tmul, add_apply]
theorem map_smul_left (r : R) (f : M →ₗ[R] P) (g : N →ₗ[R] Q) : map (r • f) g = r • map f g := by
ext
simp only [smul_tmul, compr₂_apply, mk_apply, map_tmul, smul_apply, tmul_smul]
theorem map_smul_right (r : R) (f : M →ₗ[R] P) (g : N →ₗ[R] Q) : map f (r • g) = r • map f g := by
ext
simp only [smul_tmul, compr₂_apply, mk_apply, map_tmul, smul_apply, tmul_smul]
variable (R M N P Q)
/-- The tensor product of a pair of linear maps between modules, bilinear in both maps. -/
def mapBilinear : (M →ₗ[R] P) →ₗ[R] (N →ₗ[R] Q) →ₗ[R] M ⊗[R] N →ₗ[R] P ⊗[R] Q :=
LinearMap.mk₂ R map map_add_left map_smul_left map_add_right map_smul_right
/-- The canonical linear map from `P ⊗[R] (M →ₗ[R] Q)` to `(M →ₗ[R] P ⊗[R] Q)` -/
def lTensorHomToHomLTensor : P ⊗[R] (M →ₗ[R] Q) →ₗ[R] M →ₗ[R] P ⊗[R] Q :=
TensorProduct.lift (llcomp R M Q _ ∘ₗ mk R P Q)
/-- The canonical linear map from `(M →ₗ[R] P) ⊗[R] Q` to `(M →ₗ[R] P ⊗[R] Q)` -/
def rTensorHomToHomRTensor : (M →ₗ[R] P) ⊗[R] Q →ₗ[R] M →ₗ[R] P ⊗[R] Q :=
TensorProduct.lift (llcomp R M P _ ∘ₗ (mk R P Q).flip).flip
/-- The linear map from `(M →ₗ P) ⊗ (N →ₗ Q)` to `(M ⊗ N →ₗ P ⊗ Q)` sending `f ⊗ₜ g` to
the `TensorProduct.map f g`, the tensor product of the two maps. -/
def homTensorHomMap : (M →ₗ[R] P) ⊗[R] (N →ₗ[R] Q) →ₗ[R] M ⊗[R] N →ₗ[R] P ⊗[R] Q :=
lift (mapBilinear R M N P Q)
variable {R M N P Q}
/--
This is a binary version of `TensorProduct.map`: Given a bilinear map `f : M ⟶ P ⟶ Q` and a
bilinear map `g : N ⟶ S ⟶ T`, if we think `f` and `g` as linear maps with two inputs, then
`map₂ f g` is a bilinear map taking two inputs `M ⊗ N → P ⊗ S → Q ⊗ S` defined by
`map₂ f g (m ⊗ n) (p ⊗ s) = f m p ⊗ g n s`.
Mathematically, `TensorProduct.map₂` is defined as the composition
`M ⊗ N -map→ Hom(P, Q) ⊗ Hom(S, T) -homTensorHomMap→ Hom(P ⊗ S, Q ⊗ T)`.
-/
def map₂ (f : M →ₗ[R] P →ₗ[R] Q) (g : N →ₗ[R] S →ₗ[R] T) :
M ⊗[R] N →ₗ[R] P ⊗[R] S →ₗ[R] Q ⊗[R] T :=
homTensorHomMap R _ _ _ _ ∘ₗ map f g
@[simp]
theorem mapBilinear_apply (f : M →ₗ[R] P) (g : N →ₗ[R] Q) : mapBilinear R M N P Q f g = map f g :=
rfl
@[simp]
theorem lTensorHomToHomLTensor_apply (p : P) (f : M →ₗ[R] Q) (m : M) :
lTensorHomToHomLTensor R M P Q (p ⊗ₜ f) m = p ⊗ₜ f m :=
rfl
@[simp]
theorem rTensorHomToHomRTensor_apply (f : M →ₗ[R] P) (q : Q) (m : M) :
rTensorHomToHomRTensor R M P Q (f ⊗ₜ q) m = f m ⊗ₜ q :=
rfl
@[simp]
theorem homTensorHomMap_apply (f : M →ₗ[R] P) (g : N →ₗ[R] Q) :
homTensorHomMap R M N P Q (f ⊗ₜ g) = map f g :=
rfl
@[simp]
theorem map₂_apply_tmul (f : M →ₗ[R] P →ₗ[R] Q) (g : N →ₗ[R] S →ₗ[R] T) (m : M) (n : N) :
map₂ f g (m ⊗ₜ n) = map (f m) (g n) := rfl
@[simp]
theorem map_zero_left (g : N →ₗ[R] Q) : map (0 : M →ₗ[R] P) g = 0 :=
(mapBilinear R M N P Q).map_zero₂ _
@[simp]
theorem map_zero_right (f : M →ₗ[R] P) : map f (0 : N →ₗ[R] Q) = 0 :=
(mapBilinear R M N P Q _).map_zero
end
/-- If `M` and `P` are linearly equivalent and `N` and `Q` are linearly equivalent
then `M ⊗ N` and `P ⊗ Q` are linearly equivalent. -/
def congr (f : M ≃ₗ[R] P) (g : N ≃ₗ[R] Q) : M ⊗[R] N ≃ₗ[R] P ⊗[R] Q :=
LinearEquiv.ofLinear (map f g) (map f.symm g.symm)
(ext' fun m n => by simp)
(ext' fun m n => by simp)
@[simp]
theorem congr_tmul (f : M ≃ₗ[R] P) (g : N ≃ₗ[R] Q) (m : M) (n : N) :
congr f g (m ⊗ₜ n) = f m ⊗ₜ g n :=
rfl
@[simp]
theorem congr_symm_tmul (f : M ≃ₗ[R] P) (g : N ≃ₗ[R] Q) (p : P) (q : Q) :
(congr f g).symm (p ⊗ₜ q) = f.symm p ⊗ₜ g.symm q :=
rfl
theorem congr_symm (f : M ≃ₗ[R] P) (g : N ≃ₗ[R] Q) : (congr f g).symm = congr f.symm g.symm := rfl
@[simp] theorem congr_refl_refl : congr (.refl R M) (.refl R N) = .refl R _ :=
LinearEquiv.toLinearMap_injective <| ext' fun _ _ ↦ rfl
theorem congr_trans (f : M ≃ₗ[R] P) (g : N ≃ₗ[R] Q) (f' : P ≃ₗ[R] S) (g' : Q ≃ₗ[R] T) :
congr (f ≪≫ₗ f') (g ≪≫ₗ g') = congr f g ≪≫ₗ congr f' g' :=
LinearEquiv.toLinearMap_injective <| map_comp _ _ _ _
theorem congr_mul (f : M ≃ₗ[R] M) (g : N ≃ₗ[R] N) (f' : M ≃ₗ[R] M) (g' : N ≃ₗ[R] N) :
congr (f * f') (g * g') = congr f g * congr f' g' := congr_trans _ _ _ _
@[simp] theorem congr_pow (f : M ≃ₗ[R] M) (g : N ≃ₗ[R] N) (n : ℕ) :
congr f g ^ n = congr (f ^ n) (g ^ n) := by
induction n with
| zero => exact congr_refl_refl.symm
| succ n ih => simp_rw [pow_succ, ih, congr_mul]
@[simp] theorem congr_zpow (f : M ≃ₗ[R] M) (g : N ≃ₗ[R] N) (n : ℤ) :
congr f g ^ n = congr (f ^ n) (g ^ n) := by
cases n with
| ofNat n => exact congr_pow _ _ _
| negSucc n => simp_rw [zpow_negSucc, congr_pow]; exact congr_symm _ _
end TensorProduct
open scoped TensorProduct
variable [Module R P]
namespace LinearMap
variable {N}
/-- `LinearMap.lTensor M f : M ⊗ N →ₗ M ⊗ P` is the natural linear map
induced by `f : N →ₗ P`. -/
def lTensor (f : N →ₗ[R] P) : M ⊗[R] N →ₗ[R] M ⊗[R] P :=
TensorProduct.map id f
/-- `LinearMap.rTensor M f : N₁ ⊗ M →ₗ N₂ ⊗ M` is the natural linear map
induced by `f : N₁ →ₗ N₂`. -/
def rTensor (f : N →ₗ[R] P) : N ⊗[R] M →ₗ[R] P ⊗[R] M :=
TensorProduct.map f id
variable (g : P →ₗ[R] Q) (f : N →ₗ[R] P)
theorem lTensor_def : f.lTensor M = TensorProduct.map LinearMap.id f := rfl
theorem rTensor_def : f.rTensor M = TensorProduct.map f LinearMap.id := rfl
@[simp]
theorem lTensor_tmul (m : M) (n : N) : f.lTensor M (m ⊗ₜ n) = m ⊗ₜ f n :=
rfl
@[simp]
theorem rTensor_tmul (m : M) (n : N) : f.rTensor M (n ⊗ₜ m) = f n ⊗ₜ m :=
rfl
@[simp]
theorem lTensor_comp_mk (m : M) :
f.lTensor M ∘ₗ TensorProduct.mk R M N m = TensorProduct.mk R M P m ∘ₗ f :=
rfl
@[simp]
theorem rTensor_comp_flip_mk (m : M) :
f.rTensor M ∘ₗ (TensorProduct.mk R N M).flip m = (TensorProduct.mk R P M).flip m ∘ₗ f :=
rfl
lemma comm_comp_rTensor_comp_comm_eq (g : N →ₗ[R] P) :
TensorProduct.comm R P Q ∘ₗ rTensor Q g ∘ₗ TensorProduct.comm R Q N =
lTensor Q g :=
TensorProduct.ext rfl
lemma comm_comp_lTensor_comp_comm_eq (g : N →ₗ[R] P) :
TensorProduct.comm R Q P ∘ₗ lTensor Q g ∘ₗ TensorProduct.comm R N Q =
rTensor Q g :=
TensorProduct.ext rfl
/-- Given a linear map `f : N → P`, `f ⊗ M` is injective if and only if `M ⊗ f` is injective. -/
theorem lTensor_inj_iff_rTensor_inj :
Function.Injective (lTensor M f) ↔ Function.Injective (rTensor M f) := by
simp [← comm_comp_rTensor_comp_comm_eq]
/-- Given a linear map `f : N → P`, `f ⊗ M` is surjective if and only if `M ⊗ f` is surjective. -/
theorem lTensor_surj_iff_rTensor_surj :
Function.Surjective (lTensor M f) ↔ Function.Surjective (rTensor M f) := by
simp [← comm_comp_rTensor_comp_comm_eq]
/-- Given a linear map `f : N → P`, `f ⊗ M` is bijective if and only if `M ⊗ f` is bijective. -/
theorem lTensor_bij_iff_rTensor_bij :
Function.Bijective (lTensor M f) ↔ Function.Bijective (rTensor M f) := by
simp [← comm_comp_rTensor_comp_comm_eq]
open TensorProduct
attribute [local ext high] TensorProduct.ext
/-- `lTensorHom M` is the natural linear map that sends a linear map `f : N →ₗ P` to `M ⊗ f`.
See also `Module.End.lTensorAlgHom`. -/
def lTensorHom : (N →ₗ[R] P) →ₗ[R] M ⊗[R] N →ₗ[R] M ⊗[R] P where
toFun := lTensor M
map_add' f g := by
ext x y
simp only [compr₂_apply, mk_apply, add_apply, lTensor_tmul, tmul_add]
map_smul' r f := by
dsimp
ext x y
simp only [compr₂_apply, mk_apply, tmul_smul, smul_apply, lTensor_tmul]
/-- `rTensorHom M` is the natural linear map that sends a linear map `f : N →ₗ P` to `f ⊗ M`.
See also `Module.End.rTensorAlgHom`. -/
def rTensorHom : (N →ₗ[R] P) →ₗ[R] N ⊗[R] M →ₗ[R] P ⊗[R] M where
toFun f := f.rTensor M
map_add' f g := by
ext x y
simp only [compr₂_apply, mk_apply, add_apply, rTensor_tmul, add_tmul]
map_smul' r f := by
dsimp
ext x y
simp only [compr₂_apply, mk_apply, smul_tmul, tmul_smul, smul_apply, rTensor_tmul]
@[simp]
theorem coe_lTensorHom : (lTensorHom M : (N →ₗ[R] P) → M ⊗[R] N →ₗ[R] M ⊗[R] P) = lTensor M :=
rfl
@[simp]
theorem coe_rTensorHom : (rTensorHom M : (N →ₗ[R] P) → N ⊗[R] M →ₗ[R] P ⊗[R] M) = rTensor M :=
rfl
@[simp]
theorem lTensor_add (f g : N →ₗ[R] P) : (f + g).lTensor M = f.lTensor M + g.lTensor M :=
(lTensorHom M).map_add f g
@[simp]
theorem rTensor_add (f g : N →ₗ[R] P) : (f + g).rTensor M = f.rTensor M + g.rTensor M :=
(rTensorHom M).map_add f g
@[simp]
theorem lTensor_zero : lTensor M (0 : N →ₗ[R] P) = 0 :=
(lTensorHom M).map_zero
@[simp]
theorem rTensor_zero : rTensor M (0 : N →ₗ[R] P) = 0 :=
(rTensorHom M).map_zero
@[simp]
theorem lTensor_smul (r : R) (f : N →ₗ[R] P) : (r • f).lTensor M = r • f.lTensor M :=
(lTensorHom M).map_smul r f
@[simp]
theorem rTensor_smul (r : R) (f : N →ₗ[R] P) : (r • f).rTensor M = r • f.rTensor M :=
(rTensorHom M).map_smul r f
theorem lTensor_comp : (g.comp f).lTensor M = (g.lTensor M).comp (f.lTensor M) := by
ext m n
simp only [compr₂_apply, mk_apply, comp_apply, lTensor_tmul]
theorem lTensor_comp_apply (x : M ⊗[R] N) :
(g.comp f).lTensor M x = (g.lTensor M) ((f.lTensor M) x) := by rw [lTensor_comp, coe_comp]; rfl
theorem rTensor_comp : (g.comp f).rTensor M = (g.rTensor M).comp (f.rTensor M) := by
ext m n
simp only [compr₂_apply, mk_apply, comp_apply, rTensor_tmul]
theorem rTensor_comp_apply (x : N ⊗[R] M) :
(g.comp f).rTensor M x = (g.rTensor M) ((f.rTensor M) x) := by rw [rTensor_comp, coe_comp]; rfl
theorem lTensor_mul (f g : Module.End R N) : (f * g).lTensor M = f.lTensor M * g.lTensor M :=
lTensor_comp M f g
theorem rTensor_mul (f g : Module.End R N) : (f * g).rTensor M = f.rTensor M * g.rTensor M :=
rTensor_comp M f g
variable (N)
@[simp]
theorem lTensor_id : (id : N →ₗ[R] N).lTensor M = id :=
map_id
-- `simp` can prove this.
theorem lTensor_id_apply (x : M ⊗[R] N) : (LinearMap.id : N →ₗ[R] N).lTensor M x = x := by
rw [lTensor_id, id_coe, _root_.id]
@[simp]
theorem rTensor_id : (id : N →ₗ[R] N).rTensor M = id :=
map_id
-- `simp` can prove this.
theorem rTensor_id_apply (x : N ⊗[R] M) : (LinearMap.id : N →ₗ[R] N).rTensor M x = x := by
rw [rTensor_id, id_coe, _root_.id]
@[simp]
theorem lTensor_smul_action (r : R) :
(DistribMulAction.toLinearMap R N r).lTensor M =
DistribMulAction.toLinearMap R (M ⊗[R] N) r :=
(lTensor_smul M r LinearMap.id).trans (congrArg _ (lTensor_id M N))
@[simp]
theorem rTensor_smul_action (r : R) :
(DistribMulAction.toLinearMap R N r).rTensor M =
DistribMulAction.toLinearMap R (N ⊗[R] M) r :=
(rTensor_smul M r LinearMap.id).trans (congrArg _ (rTensor_id M N))
variable {N}
@[simp]
theorem lTensor_comp_rTensor (f : M →ₗ[R] P) (g : N →ₗ[R] Q) :
(g.lTensor P).comp (f.rTensor N) = map f g := by
simp only [lTensor, rTensor, ← map_comp, id_comp, comp_id]
@[simp]
theorem rTensor_comp_lTensor (f : M →ₗ[R] P) (g : N →ₗ[R] Q) :
(f.rTensor Q).comp (g.lTensor M) = map f g := by
simp only [lTensor, rTensor, ← map_comp, id_comp, comp_id]
@[simp]
theorem map_comp_rTensor (f : M →ₗ[R] P) (g : N →ₗ[R] Q) (f' : S →ₗ[R] M) :
(map f g).comp (f'.rTensor _) = map (f.comp f') g := by
simp only [lTensor, rTensor, ← map_comp, id_comp, comp_id]
@[simp]
theorem map_comp_lTensor (f : M →ₗ[R] P) (g : N →ₗ[R] Q) (g' : S →ₗ[R] N) :
(map f g).comp (g'.lTensor _) = map f (g.comp g') := by
simp only [lTensor, rTensor, ← map_comp, id_comp, comp_id]
@[simp]
theorem rTensor_comp_map (f' : P →ₗ[R] S) (f : M →ₗ[R] P) (g : N →ₗ[R] Q) :
(f'.rTensor _).comp (map f g) = map (f'.comp f) g := by
simp only [lTensor, rTensor, ← map_comp, id_comp, comp_id]
@[simp]
theorem lTensor_comp_map (g' : Q →ₗ[R] S) (f : M →ₗ[R] P) (g : N →ₗ[R] Q) :
(g'.lTensor _).comp (map f g) = map f (g'.comp g) := by
simp only [lTensor, rTensor, ← map_comp, id_comp, comp_id]
variable {M}
@[simp]
theorem rTensor_pow (f : M →ₗ[R] M) (n : ℕ) : f.rTensor N ^ n = (f ^ n).rTensor N := by
have h := TensorProduct.map_pow f (id : N →ₗ[R] N) n
rwa [Module.End.id_pow] at h
@[simp]
theorem lTensor_pow (f : N →ₗ[R] N) (n : ℕ) : f.lTensor M ^ n = (f ^ n).lTensor M := by
have h := TensorProduct.map_pow (id : M →ₗ[R] M) f n
rwa [Module.End.id_pow] at h
end LinearMap
namespace LinearEquiv
variable {N}
/-- `LinearEquiv.lTensor M f : M ⊗ N ≃ₗ M ⊗ P` is the natural linear equivalence
induced by `f : N ≃ₗ P`. -/
def lTensor (f : N ≃ₗ[R] P) : M ⊗[R] N ≃ₗ[R] M ⊗[R] P := TensorProduct.congr (refl R M) f
/-- `LinearEquiv.rTensor M f : N₁ ⊗ M ≃ₗ N₂ ⊗ M` is the natural linear equivalence
induced by `f : N₁ ≃ₗ N₂`. -/
def rTensor (f : N ≃ₗ[R] P) : N ⊗[R] M ≃ₗ[R] P ⊗[R] M := TensorProduct.congr f (refl R M)
variable (g : P ≃ₗ[R] Q) (f : N ≃ₗ[R] P) (m : M) (n : N) (p : P) (x : M ⊗[R] N) (y : N ⊗[R] M)
@[simp] theorem coe_lTensor : lTensor M f = (f : N →ₗ[R] P).lTensor M := rfl
@[simp] theorem coe_lTensor_symm : (lTensor M f).symm = (f.symm : P →ₗ[R] N).lTensor M := rfl
@[simp] theorem coe_rTensor : rTensor M f = (f : N →ₗ[R] P).rTensor M := rfl
@[simp] theorem coe_rTensor_symm : (rTensor M f).symm = (f.symm : P →ₗ[R] N).rTensor M := rfl
@[simp] theorem lTensor_tmul : f.lTensor M (m ⊗ₜ n) = m ⊗ₜ f n := rfl
@[simp] theorem lTensor_symm_tmul : (f.lTensor M).symm (m ⊗ₜ p) = m ⊗ₜ f.symm p := rfl
@[simp] theorem rTensor_tmul : f.rTensor M (n ⊗ₜ m) = f n ⊗ₜ m := rfl
@[simp] theorem rTensor_symm_tmul : (f.rTensor M).symm (p ⊗ₜ m) = f.symm p ⊗ₜ m := rfl
lemma comm_trans_rTensor_trans_comm_eq (g : N ≃ₗ[R] P) :
TensorProduct.comm R Q N ≪≫ₗ rTensor Q g ≪≫ₗ TensorProduct.comm R P Q = lTensor Q g :=
toLinearMap_injective <| TensorProduct.ext rfl
lemma comm_trans_lTensor_trans_comm_eq (g : N ≃ₗ[R] P) :
TensorProduct.comm R N Q ≪≫ₗ lTensor Q g ≪≫ₗ TensorProduct.comm R Q P = rTensor Q g :=
toLinearMap_injective <| TensorProduct.ext rfl
theorem lTensor_trans : (f ≪≫ₗ g).lTensor M = f.lTensor M ≪≫ₗ g.lTensor M :=
toLinearMap_injective <| LinearMap.lTensor_comp M _ _
theorem lTensor_trans_apply : (f ≪≫ₗ g).lTensor M x = g.lTensor M (f.lTensor M x) :=
LinearMap.lTensor_comp_apply M _ _ x
theorem rTensor_trans : (f ≪≫ₗ g).rTensor M = f.rTensor M ≪≫ₗ g.rTensor M :=
toLinearMap_injective <| LinearMap.rTensor_comp M _ _
theorem rTensor_trans_apply : (f ≪≫ₗ g).rTensor M y = g.rTensor M (f.rTensor M y) :=
LinearMap.rTensor_comp_apply M _ _ y
theorem lTensor_mul (f g : N ≃ₗ[R] N) : (f * g).lTensor M = f.lTensor M * g.lTensor M :=
lTensor_trans M f g
theorem rTensor_mul (f g : N ≃ₗ[R] N) : (f * g).rTensor M = f.rTensor M * g.rTensor M :=
rTensor_trans M f g
variable (N)
@[simp] theorem lTensor_refl : (refl R N).lTensor M = refl R _ := TensorProduct.congr_refl_refl
theorem lTensor_refl_apply : (refl R N).lTensor M x = x := by rw [lTensor_refl, refl_apply]
@[simp] theorem rTensor_refl : (refl R N).rTensor M = refl R _ := TensorProduct.congr_refl_refl
theorem rTensor_refl_apply : (refl R N).rTensor M y = y := by rw [rTensor_refl, refl_apply]
variable {N}
@[simp] theorem rTensor_trans_lTensor (f : M ≃ₗ[R] P) (g : N ≃ₗ[R] Q) :
f.rTensor N ≪≫ₗ g.lTensor P = TensorProduct.congr f g :=
toLinearMap_injective <| LinearMap.lTensor_comp_rTensor M _ _
@[simp] theorem lTensor_trans_rTensor (f : M ≃ₗ[R] P) (g : N ≃ₗ[R] Q) :
g.lTensor M ≪≫ₗ f.rTensor Q = TensorProduct.congr f g :=
toLinearMap_injective <| LinearMap.rTensor_comp_lTensor M _ _
@[simp] theorem rTensor_trans_congr (f : M ≃ₗ[R] P) (g : N ≃ₗ[R] Q) (f' : S ≃ₗ[R] M) :
f'.rTensor _ ≪≫ₗ TensorProduct.congr f g = TensorProduct.congr (f' ≪≫ₗ f) g :=
toLinearMap_injective <| LinearMap.map_comp_rTensor M _ _ _
@[simp] theorem lTensor_trans_congr (f : M ≃ₗ[R] P) (g : N ≃ₗ[R] Q) (g' : S ≃ₗ[R] N) :
g'.lTensor _ ≪≫ₗ TensorProduct.congr f g = TensorProduct.congr f (g' ≪≫ₗ g) :=
toLinearMap_injective <| LinearMap.map_comp_lTensor M _ _ _
@[simp] theorem congr_trans_rTensor (f' : P ≃ₗ[R] S) (f : M ≃ₗ[R] P) (g : N ≃ₗ[R] Q) :
TensorProduct.congr f g ≪≫ₗ f'.rTensor _ = TensorProduct.congr (f ≪≫ₗ f') g :=
toLinearMap_injective <| LinearMap.rTensor_comp_map M _ _ _
@[simp] theorem congr_trans_lTensor (g' : Q ≃ₗ[R] S) (f : M ≃ₗ[R] P) (g : N ≃ₗ[R] Q) :
TensorProduct.congr f g ≪≫ₗ g'.lTensor _ = TensorProduct.congr f (g ≪≫ₗ g') :=
toLinearMap_injective <| LinearMap.lTensor_comp_map M _ _ _
variable {M}
@[simp] theorem rTensor_pow (f : M ≃ₗ[R] M) (n : ℕ) : f.rTensor N ^ n = (f ^ n).rTensor N := by
simpa only [one_pow] using TensorProduct.congr_pow f (1 : N ≃ₗ[R] N) n
@[simp] theorem rTensor_zpow (f : M ≃ₗ[R] M) (n : ℤ) : f.rTensor N ^ n = (f ^ n).rTensor N := by
simpa only [one_zpow] using TensorProduct.congr_zpow f (1 : N ≃ₗ[R] N) n
@[simp] theorem lTensor_pow (f : N ≃ₗ[R] N) (n : ℕ) : f.lTensor M ^ n = (f ^ n).lTensor M := by
simpa only [one_pow] using TensorProduct.congr_pow (1 : M ≃ₗ[R] M) f n
@[simp] theorem lTensor_zpow (f : N ≃ₗ[R] N) (n : ℤ) : f.lTensor M ^ n = (f ^ n).lTensor M := by
simpa only [one_zpow] using TensorProduct.congr_zpow (1 : M ≃ₗ[R] M) f n
end LinearEquiv
end Semiring
section Ring
variable {R : Type*} [CommSemiring R]
variable {M : Type*} {N : Type*} {P : Type*} {Q : Type*} {S : Type*}
variable [AddCommGroup M] [AddCommGroup N] [AddCommGroup P] [AddCommGroup Q] [AddCommGroup S]
variable [Module R M] [Module R N] [Module R P] [Module R Q] [Module R S]
namespace TensorProduct
open TensorProduct
open LinearMap
variable (R) in
/-- Auxiliary function to defining negation multiplication on tensor product. -/
def Neg.aux : M ⊗[R] N →ₗ[R] M ⊗[R] N :=
lift <| (mk R M N).comp (-LinearMap.id)
instance neg : Neg (M ⊗[R] N) where
neg := Neg.aux R
protected theorem neg_add_cancel (x : M ⊗[R] N) : -x + x = 0 :=
x.induction_on
(by rw [add_zero]; apply (Neg.aux R).map_zero)
(fun x y => by convert (add_tmul (R := R) (-x) x y).symm; rw [neg_add_cancel, zero_tmul])
fun x y hx hy => by
suffices -x + x + (-y + y) = 0 by
rw [← this]
unfold Neg.neg neg
simp only
rw [map_add]
abel
rw [hx, hy, add_zero]
instance addCommGroup : AddCommGroup (M ⊗[R] N) :=
{ TensorProduct.addCommMonoid with
neg := Neg.neg
sub := _
sub_eq_add_neg := fun _ _ => rfl
neg_add_cancel := fun x => TensorProduct.neg_add_cancel x
zsmul := fun n v => n • v
zsmul_zero' := by simp [TensorProduct.zero_smul]
| zsmul_succ' := by simp [add_comm, TensorProduct.one_smul, TensorProduct.add_smul]
zsmul_neg' := fun n x => by
change (-n.succ : ℤ) • x = -(((n : ℤ) + 1) • x)
| Mathlib/LinearAlgebra/TensorProduct/Basic.lean | 1,288 | 1,290 |
/-
Copyright (c) 2015 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Leonardo de Moura
-/
import Mathlib.Data.Stream.Defs
import Mathlib.Logic.Function.Basic
import Mathlib.Data.List.Defs
import Mathlib.Data.Nat.Basic
import Mathlib.Tactic.Common
/-!
# Streams a.k.a. infinite lists a.k.a. infinite sequences
-/
open Nat Function Option
namespace Stream'
universe u v w
variable {α : Type u} {β : Type v} {δ : Type w}
variable (m n : ℕ) (x y : List α) (a b : Stream' α)
instance [Inhabited α] : Inhabited (Stream' α) :=
⟨Stream'.const default⟩
@[simp] protected theorem eta (s : Stream' α) : head s :: tail s = s :=
funext fun i => by cases i <;> rfl
/-- Alias for `Stream'.eta` to match `List` API. -/
alias cons_head_tail := Stream'.eta
@[ext]
protected theorem ext {s₁ s₂ : Stream' α} : (∀ n, get s₁ n = get s₂ n) → s₁ = s₂ :=
fun h => funext h
@[simp]
theorem get_zero_cons (a : α) (s : Stream' α) : get (a::s) 0 = a :=
rfl
@[simp]
theorem head_cons (a : α) (s : Stream' α) : head (a::s) = a :=
rfl
@[simp]
theorem tail_cons (a : α) (s : Stream' α) : tail (a::s) = s :=
rfl
@[simp]
theorem get_drop (n m : ℕ) (s : Stream' α) : get (drop m s) n = get s (m + n) := by
rw [Nat.add_comm]
rfl
theorem tail_eq_drop (s : Stream' α) : tail s = drop 1 s :=
rfl
@[simp]
theorem drop_drop (n m : ℕ) (s : Stream' α) : drop n (drop m s) = drop (m + n) s := by
ext; simp [Nat.add_assoc]
@[simp] theorem get_tail {n : ℕ} {s : Stream' α} : s.tail.get n = s.get (n + 1) := rfl
@[simp] theorem tail_drop' {i : ℕ} {s : Stream' α} : tail (drop i s) = s.drop (i + 1) := by
ext; simp [Nat.add_comm, Nat.add_assoc, Nat.add_left_comm]
@[simp] theorem drop_tail' {i : ℕ} {s : Stream' α} : drop i (tail s) = s.drop (i + 1) := rfl
theorem tail_drop (n : ℕ) (s : Stream' α) : tail (drop n s) = drop n (tail s) := by simp
theorem get_succ (n : ℕ) (s : Stream' α) : get s (succ n) = get (tail s) n :=
rfl
@[simp]
theorem get_succ_cons (n : ℕ) (s : Stream' α) (x : α) : get (x :: s) n.succ = get s n :=
rfl
@[simp] lemma get_cons_append_zero {a : α} {x : List α} {s : Stream' α} :
(a :: x ++ₛ s).get 0 = a := rfl
@[simp] lemma append_eq_cons {a : α} {as : Stream' α} : [a] ++ₛ as = a :: as := by rfl
@[simp] theorem drop_zero {s : Stream' α} : s.drop 0 = s := rfl
theorem drop_succ (n : ℕ) (s : Stream' α) : drop (succ n) s = drop n (tail s) :=
rfl
theorem head_drop (a : Stream' α) (n : ℕ) : (a.drop n).head = a.get n := by simp
theorem cons_injective2 : Function.Injective2 (cons : α → Stream' α → Stream' α) := fun x y s t h =>
⟨by rw [← get_zero_cons x s, h, get_zero_cons],
Stream'.ext fun n => by rw [← get_succ_cons n _ x, h, get_succ_cons]⟩
theorem cons_injective_left (s : Stream' α) : Function.Injective fun x => cons x s :=
cons_injective2.left _
theorem cons_injective_right (x : α) : Function.Injective (cons x) :=
cons_injective2.right _
theorem all_def (p : α → Prop) (s : Stream' α) : All p s = ∀ n, p (get s n) :=
rfl
theorem any_def (p : α → Prop) (s : Stream' α) : Any p s = ∃ n, p (get s n) :=
rfl
@[simp]
theorem mem_cons (a : α) (s : Stream' α) : a ∈ a::s :=
Exists.intro 0 rfl
theorem mem_cons_of_mem {a : α} {s : Stream' α} (b : α) : a ∈ s → a ∈ b::s := fun ⟨n, h⟩ =>
Exists.intro (succ n) (by rw [get_succ, tail_cons, h])
theorem eq_or_mem_of_mem_cons {a b : α} {s : Stream' α} : (a ∈ b::s) → a = b ∨ a ∈ s :=
fun ⟨n, h⟩ => by
rcases n with - | n'
· left
exact h
· right
rw [get_succ, tail_cons] at h
exact ⟨n', h⟩
theorem mem_of_get_eq {n : ℕ} {s : Stream' α} {a : α} : a = get s n → a ∈ s := fun h =>
Exists.intro n h
section Map
variable (f : α → β)
theorem drop_map (n : ℕ) (s : Stream' α) : drop n (map f s) = map f (drop n s) :=
Stream'.ext fun _ => rfl
@[simp]
theorem get_map (n : ℕ) (s : Stream' α) : get (map f s) n = f (get s n) :=
rfl
theorem tail_map (s : Stream' α) : tail (map f s) = map f (tail s) := rfl
@[simp]
theorem head_map (s : Stream' α) : head (map f s) = f (head s) :=
rfl
theorem map_eq (s : Stream' α) : map f s = f (head s)::map f (tail s) := by
rw [← Stream'.eta (map f s), tail_map, head_map]
theorem map_cons (a : α) (s : Stream' α) : map f (a::s) = f a::map f s := by
rw [← Stream'.eta (map f (a::s)), map_eq]; rfl
@[simp]
theorem map_id (s : Stream' α) : map id s = s :=
rfl
@[simp]
theorem map_map (g : β → δ) (f : α → β) (s : Stream' α) : map g (map f s) = map (g ∘ f) s :=
rfl
@[simp]
theorem map_tail (s : Stream' α) : map f (tail s) = tail (map f s) :=
rfl
theorem mem_map {a : α} {s : Stream' α} : a ∈ s → f a ∈ map f s := fun ⟨n, h⟩ =>
Exists.intro n (by rw [get_map, h])
theorem exists_of_mem_map {f} {b : β} {s : Stream' α} : b ∈ map f s → ∃ a, a ∈ s ∧ f a = b :=
fun ⟨n, h⟩ => ⟨get s n, ⟨n, rfl⟩, h.symm⟩
end Map
section Zip
variable (f : α → β → δ)
theorem drop_zip (n : ℕ) (s₁ : Stream' α) (s₂ : Stream' β) :
drop n (zip f s₁ s₂) = zip f (drop n s₁) (drop n s₂) :=
Stream'.ext fun _ => rfl
@[simp]
theorem get_zip (n : ℕ) (s₁ : Stream' α) (s₂ : Stream' β) :
get (zip f s₁ s₂) n = f (get s₁ n) (get s₂ n) :=
rfl
theorem head_zip (s₁ : Stream' α) (s₂ : Stream' β) : head (zip f s₁ s₂) = f (head s₁) (head s₂) :=
rfl
theorem tail_zip (s₁ : Stream' α) (s₂ : Stream' β) :
tail (zip f s₁ s₂) = zip f (tail s₁) (tail s₂) :=
rfl
theorem zip_eq (s₁ : Stream' α) (s₂ : Stream' β) :
zip f s₁ s₂ = f (head s₁) (head s₂)::zip f (tail s₁) (tail s₂) := by
rw [← Stream'.eta (zip f s₁ s₂)]; rfl
@[simp]
theorem get_enum (s : Stream' α) (n : ℕ) : get (enum s) n = (n, s.get n) :=
rfl
theorem enum_eq_zip (s : Stream' α) : enum s = zip Prod.mk nats s :=
rfl
end Zip
@[simp]
theorem mem_const (a : α) : a ∈ const a :=
Exists.intro 0 rfl
theorem const_eq (a : α) : const a = a::const a := by
apply Stream'.ext; intro n
cases n <;> rfl
@[simp]
theorem tail_const (a : α) : tail (const a) = const a :=
suffices tail (a::const a) = const a by rwa [← const_eq] at this
rfl
@[simp]
theorem map_const (f : α → β) (a : α) : map f (const a) = const (f a) :=
rfl
@[simp]
theorem get_const (n : ℕ) (a : α) : get (const a) n = a :=
rfl
@[simp]
theorem drop_const (n : ℕ) (a : α) : drop n (const a) = const a :=
Stream'.ext fun _ => rfl
@[simp]
theorem head_iterate (f : α → α) (a : α) : head (iterate f a) = a :=
rfl
theorem get_succ_iterate' (n : ℕ) (f : α → α) (a : α) :
get (iterate f a) (succ n) = f (get (iterate f a) n) := rfl
theorem tail_iterate (f : α → α) (a : α) : tail (iterate f a) = iterate f (f a) := by
ext n
rw [get_tail]
induction' n with n' ih
· rfl
· rw [get_succ_iterate', ih, get_succ_iterate']
theorem iterate_eq (f : α → α) (a : α) : iterate f a = a::iterate f (f a) := by
rw [← Stream'.eta (iterate f a)]
rw [tail_iterate]; rfl
@[simp]
theorem get_zero_iterate (f : α → α) (a : α) : get (iterate f a) 0 = a :=
rfl
theorem get_succ_iterate (n : ℕ) (f : α → α) (a : α) :
get (iterate f a) (succ n) = get (iterate f (f a)) n := by rw [get_succ, tail_iterate]
section Bisim
variable (R : Stream' α → Stream' α → Prop)
/-- equivalence relation -/
local infixl:50 " ~ " => R
/-- Streams `s₁` and `s₂` are defined to be bisimulations if
their heads are equal and tails are bisimulations. -/
def IsBisimulation :=
∀ ⦃s₁ s₂⦄, s₁ ~ s₂ →
head s₁ = head s₂ ∧ tail s₁ ~ tail s₂
theorem get_of_bisim (bisim : IsBisimulation R) {s₁ s₂} :
∀ n, s₁ ~ s₂ → get s₁ n = get s₂ n ∧ drop (n + 1) s₁ ~ drop (n + 1) s₂
| 0, h => bisim h
| n + 1, h =>
match bisim h with
| ⟨_, trel⟩ => get_of_bisim bisim n trel
-- If two streams are bisimilar, then they are equal
theorem eq_of_bisim (bisim : IsBisimulation R) {s₁ s₂} : s₁ ~ s₂ → s₁ = s₂ := fun r =>
Stream'.ext fun n => And.left (get_of_bisim R bisim n r)
end Bisim
theorem bisim_simple (s₁ s₂ : Stream' α) :
head s₁ = head s₂ → s₁ = tail s₁ → s₂ = tail s₂ → s₁ = s₂ := fun hh ht₁ ht₂ =>
eq_of_bisim (fun s₁ s₂ => head s₁ = head s₂ ∧ s₁ = tail s₁ ∧ s₂ = tail s₂)
(fun s₁ s₂ ⟨h₁, h₂, h₃⟩ => by
constructor
· exact h₁
rw [← h₂, ← h₃]
(repeat' constructor) <;> assumption)
(And.intro hh (And.intro ht₁ ht₂))
theorem coinduction {s₁ s₂ : Stream' α} :
head s₁ = head s₂ →
(∀ (β : Type u) (fr : Stream' α → β),
fr s₁ = fr s₂ → fr (tail s₁) = fr (tail s₂)) → s₁ = s₂ :=
fun hh ht =>
eq_of_bisim
(fun s₁ s₂ =>
head s₁ = head s₂ ∧
∀ (β : Type u) (fr : Stream' α → β), fr s₁ = fr s₂ → fr (tail s₁) = fr (tail s₂))
(fun s₁ s₂ h =>
have h₁ : head s₁ = head s₂ := And.left h
have h₂ : head (tail s₁) = head (tail s₂) := And.right h α (@head α) h₁
have h₃ :
∀ (β : Type u) (fr : Stream' α → β),
fr (tail s₁) = fr (tail s₂) → fr (tail (tail s₁)) = fr (tail (tail s₂)) :=
fun β fr => And.right h β fun s => fr (tail s)
And.intro h₁ (And.intro h₂ h₃))
(And.intro hh ht)
@[simp]
theorem iterate_id (a : α) : iterate id a = const a :=
coinduction rfl fun β fr ch => by rw [tail_iterate, tail_const]; exact ch
theorem map_iterate (f : α → α) (a : α) : iterate f (f a) = map f (iterate f a) := by
funext n
induction' n with n' ih
· rfl
· unfold map iterate get
rw [map, get] at ih
rw [iterate]
exact congrArg f ih
section Corec
theorem corec_def (f : α → β) (g : α → α) (a : α) : corec f g a = map f (iterate g a) :=
rfl
theorem corec_eq (f : α → β) (g : α → α) (a : α) : corec f g a = f a :: corec f g (g a) := by
rw [corec_def, map_eq, head_iterate, tail_iterate]; rfl
theorem corec_id_id_eq_const (a : α) : corec id id a = const a := by
rw [corec_def, map_id, iterate_id]
theorem corec_id_f_eq_iterate (f : α → α) (a : α) : corec id f a = iterate f a :=
rfl
end Corec
section Corec'
theorem corec'_eq (f : α → β × α) (a : α) : corec' f a = (f a).1 :: corec' f (f a).2 :=
corec_eq _ _ _
end Corec'
theorem unfolds_eq (g : α → β) (f : α → α) (a : α) : unfolds g f a = g a :: unfolds g f (f a) := by
unfold unfolds; rw [corec_eq]
theorem get_unfolds_head_tail : ∀ (n : ℕ) (s : Stream' α),
get (unfolds head tail s) n = get s n := by
intro n; induction' n with n' ih
· intro s
rfl
· intro s
rw [get_succ, get_succ, unfolds_eq, tail_cons, ih]
theorem unfolds_head_eq : ∀ s : Stream' α, unfolds head tail s = s := fun s =>
Stream'.ext fun n => get_unfolds_head_tail n s
theorem interleave_eq (s₁ s₂ : Stream' α) : s₁ ⋈ s₂ = head s₁::head s₂::(tail s₁ ⋈ tail s₂) := by
let t := tail s₁ ⋈ tail s₂
show s₁ ⋈ s₂ = head s₁::head s₂::t
unfold interleave; unfold corecOn; rw [corec_eq]; dsimp; rw [corec_eq]; rfl
theorem tail_interleave (s₁ s₂ : Stream' α) : tail (s₁ ⋈ s₂) = s₂ ⋈ tail s₁ := by
unfold interleave corecOn; rw [corec_eq]; rfl
theorem interleave_tail_tail (s₁ s₂ : Stream' α) : tail s₁ ⋈ tail s₂ = tail (tail (s₁ ⋈ s₂)) := by
rw [interleave_eq s₁ s₂]; rfl
theorem get_interleave_left : ∀ (n : ℕ) (s₁ s₂ : Stream' α),
get (s₁ ⋈ s₂) (2 * n) = get s₁ n
| 0, _, _ => rfl
| n + 1, s₁, s₂ => by
change get (s₁ ⋈ s₂) (succ (succ (2 * n))) = get s₁ (succ n)
rw [get_succ, get_succ, interleave_eq, tail_cons, tail_cons]
rw [get_interleave_left n (tail s₁) (tail s₂)]
rfl
theorem get_interleave_right : ∀ (n : ℕ) (s₁ s₂ : Stream' α),
get (s₁ ⋈ s₂) (2 * n + 1) = get s₂ n
| 0, _, _ => rfl
| n + 1, s₁, s₂ => by
change get (s₁ ⋈ s₂) (succ (succ (2 * n + 1))) = get s₂ (succ n)
rw [get_succ, get_succ, interleave_eq, tail_cons, tail_cons,
get_interleave_right n (tail s₁) (tail s₂)]
rfl
theorem mem_interleave_left {a : α} {s₁ : Stream' α} (s₂ : Stream' α) : a ∈ s₁ → a ∈ s₁ ⋈ s₂ :=
fun ⟨n, h⟩ => Exists.intro (2 * n) (by rw [h, get_interleave_left])
theorem mem_interleave_right {a : α} {s₁ : Stream' α} (s₂ : Stream' α) : a ∈ s₂ → a ∈ s₁ ⋈ s₂ :=
fun ⟨n, h⟩ => Exists.intro (2 * n + 1) (by rw [h, get_interleave_right])
theorem odd_eq (s : Stream' α) : odd s = even (tail s) :=
rfl
@[simp]
theorem head_even (s : Stream' α) : head (even s) = head s :=
rfl
theorem tail_even (s : Stream' α) : tail (even s) = even (tail (tail s)) := by
unfold even
rw [corec_eq]
rfl
theorem even_cons_cons (a₁ a₂ : α) (s : Stream' α) : even (a₁::a₂::s) = a₁::even s := by
unfold even
rw [corec_eq]; rfl
theorem even_tail (s : Stream' α) : even (tail s) = odd s :=
rfl
theorem even_interleave (s₁ s₂ : Stream' α) : even (s₁ ⋈ s₂) = s₁ :=
eq_of_bisim (fun s₁' s₁ => ∃ s₂, s₁' = even (s₁ ⋈ s₂))
(fun s₁' s₁ ⟨s₂, h₁⟩ => by
rw [h₁]
constructor
· rfl
· exact ⟨tail s₂, by rw [interleave_eq, even_cons_cons, tail_cons]⟩)
(Exists.intro s₂ rfl)
theorem interleave_even_odd (s₁ : Stream' α) : even s₁ ⋈ odd s₁ = s₁ :=
eq_of_bisim (fun s' s => s' = even s ⋈ odd s)
(fun s' s (h : s' = even s ⋈ odd s) => by
rw [h]; constructor
· rfl
· simp [odd_eq, odd_eq, tail_interleave, tail_even])
rfl
theorem get_even : ∀ (n : ℕ) (s : Stream' α), get (even s) n = get s (2 * n)
| 0, _ => rfl
| succ n, s => by
change get (even s) (succ n) = get s (succ (succ (2 * n)))
rw [get_succ, get_succ, tail_even, get_even n]; rfl
theorem get_odd : ∀ (n : ℕ) (s : Stream' α), get (odd s) n = get s (2 * n + 1) := fun n s => by
rw [odd_eq, get_even]; rfl
theorem mem_of_mem_even (a : α) (s : Stream' α) : a ∈ even s → a ∈ s := fun ⟨n, h⟩ =>
Exists.intro (2 * n) (by rw [h, get_even])
theorem mem_of_mem_odd (a : α) (s : Stream' α) : a ∈ odd s → a ∈ s := fun ⟨n, h⟩ =>
Exists.intro (2 * n + 1) (by rw [h, get_odd])
@[simp] theorem nil_append_stream (s : Stream' α) : appendStream' [] s = s :=
rfl
theorem cons_append_stream (a : α) (l : List α) (s : Stream' α) :
appendStream' (a::l) s = a::appendStream' l s :=
rfl
@[simp] theorem append_append_stream : ∀ (l₁ l₂ : List α) (s : Stream' α),
l₁ ++ l₂ ++ₛ s = l₁ ++ₛ (l₂ ++ₛ s)
| [], _, _ => rfl
| List.cons a l₁, l₂, s => by
rw [List.cons_append, cons_append_stream, cons_append_stream, append_append_stream l₁]
lemma get_append_left (h : n < x.length) : (x ++ₛ a).get n = x[n] := by
induction' x with b x ih generalizing n
· simp at h
· rcases n with (_ | n)
· simp
· simp [ih n (by simpa using h), cons_append_stream]
@[simp] lemma get_append_right : (x ++ₛ a).get (x.length + n) = a.get n := by
induction' x <;> simp [Nat.succ_add, *, cons_append_stream]
@[simp] lemma get_append_length : (x ++ₛ a).get x.length = a.get 0 := get_append_right 0 x a
lemma append_right_injective (h : x ++ₛ a = x ++ₛ b) : a = b := by
ext n; replace h := congr_arg (fun a ↦ a.get (x.length + n)) h; simpa using h
@[simp] lemma append_right_inj : x ++ₛ a = x ++ₛ b ↔ a = b :=
⟨append_right_injective x a b, by simp +contextual⟩
lemma append_left_injective (h : x ++ₛ a = y ++ₛ b) (hl : x.length = y.length) : x = y := by
apply List.ext_getElem hl
intros
rw [← get_append_left, ← get_append_left, h]
theorem map_append_stream (f : α → β) :
∀ (l : List α) (s : Stream' α), map f (l ++ₛ s) = List.map f l ++ₛ map f s
| [], _ => rfl
| List.cons a l, s => by
rw [cons_append_stream, List.map_cons, map_cons, cons_append_stream, map_append_stream f l]
theorem drop_append_stream : ∀ (l : List α) (s : Stream' α), drop l.length (l ++ₛ s) = s
| [], s => by rfl
| List.cons a l, s => by
rw [List.length_cons, drop_succ, cons_append_stream, tail_cons, drop_append_stream l s]
theorem append_stream_head_tail (s : Stream' α) : [head s] ++ₛ tail s = s := by
simp
theorem mem_append_stream_right : ∀ {a : α} (l : List α) {s : Stream' α}, a ∈ s → a ∈ l ++ₛ s
| _, [], _, h => h
| a, List.cons _ l, s, h =>
have ih : a ∈ l ++ₛ s := mem_append_stream_right l h
mem_cons_of_mem _ ih
theorem mem_append_stream_left : ∀ {a : α} {l : List α} (s : Stream' α), a ∈ l → a ∈ l ++ₛ s
| _, [], _, h => absurd h List.not_mem_nil
| a, List.cons b l, s, h =>
Or.elim (List.eq_or_mem_of_mem_cons h) (fun aeqb : a = b => Exists.intro 0 aeqb)
fun ainl : a ∈ l => mem_cons_of_mem b (mem_append_stream_left s ainl)
@[simp]
theorem take_zero (s : Stream' α) : take 0 s = [] :=
rfl
-- This lemma used to be simp, but we removed it from the simp set because:
| -- 1) It duplicates the (often large) `s` term, resulting in large tactic states.
-- 2) It conflicts with the very useful `dropLast_take` lemma below (causing nonconfluence).
| Mathlib/Data/Stream/Init.lean | 508 | 509 |
/-
Copyright (c) 2023 Joël Riou. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Joël Riou
-/
import Mathlib.Algebra.Homology.ShortComplex.LeftHomology
import Mathlib.CategoryTheory.Limits.Opposites
/-!
# Right Homology of short complexes
In this file, we define the dual notions to those defined in
`Algebra.Homology.ShortComplex.LeftHomology`. In particular, if `S : ShortComplex C` is
a short complex consisting of two composable maps `f : X₁ ⟶ X₂` and `g : X₂ ⟶ X₃` such
that `f ≫ g = 0`, we define `h : S.RightHomologyData` to be the datum of morphisms
`p : X₂ ⟶ Q` and `ι : H ⟶ Q` such that `Q` identifies to the cokernel of `f` and `H`
to the kernel of the induced map `g' : Q ⟶ X₃`.
When such a `S.RightHomologyData` exists, we shall say that `[S.HasRightHomology]`
and we define `S.rightHomology` to be the `H` field of a chosen right homology data.
Similarly, we define `S.opcycles` to be the `Q` field.
In `Homology.lean`, when `S` has two compatible left and right homology data
(i.e. they give the same `H` up to a canonical isomorphism), we shall define
`[S.HasHomology]` and `S.homology`.
-/
namespace CategoryTheory
open Category Limits
namespace ShortComplex
variable {C : Type*} [Category C] [HasZeroMorphisms C]
(S : ShortComplex C) {S₁ S₂ S₃ : ShortComplex C}
/-- A right homology data for a short complex `S` consists of morphisms `p : S.X₂ ⟶ Q` and
`ι : H ⟶ Q` such that `p` identifies `Q` to the kernel of `f : S.X₁ ⟶ S.X₂`,
and that `ι` identifies `H` to the kernel of the induced map `g' : Q ⟶ S.X₃` -/
structure RightHomologyData where
/-- a choice of cokernel of `S.f : S.X₁ ⟶ S.X₂` -/
Q : C
/-- a choice of kernel of the induced morphism `S.g' : S.Q ⟶ X₃` -/
H : C
/-- the projection from `S.X₂` -/
p : S.X₂ ⟶ Q
/-- the inclusion of the (right) homology in the chosen cokernel of `S.f` -/
ι : H ⟶ Q
/-- the cokernel condition for `p` -/
wp : S.f ≫ p = 0
/-- `p : S.X₂ ⟶ Q` is a cokernel of `S.f : S.X₁ ⟶ S.X₂` -/
hp : IsColimit (CokernelCofork.ofπ p wp)
/-- the kernel condition for `ι` -/
wι : ι ≫ hp.desc (CokernelCofork.ofπ _ S.zero) = 0
/-- `ι : H ⟶ Q` is a kernel of `S.g' : Q ⟶ S.X₃` -/
hι : IsLimit (KernelFork.ofι ι wι)
initialize_simps_projections RightHomologyData (-hp, -hι)
namespace RightHomologyData
/-- The chosen cokernels and kernels of the limits API give a `RightHomologyData` -/
@[simps]
noncomputable def ofHasCokernelOfHasKernel
[HasCokernel S.f] [HasKernel (cokernel.desc S.f S.g S.zero)] :
S.RightHomologyData :=
{ Q := cokernel S.f,
H := kernel (cokernel.desc S.f S.g S.zero),
p := cokernel.π _,
ι := kernel.ι _,
wp := cokernel.condition _,
hp := cokernelIsCokernel _,
wι := kernel.condition _,
hι := kernelIsKernel _, }
attribute [reassoc (attr := simp)] wp wι
variable {S}
variable (h : S.RightHomologyData) {A : C}
instance : Epi h.p := ⟨fun _ _ => Cofork.IsColimit.hom_ext h.hp⟩
instance : Mono h.ι := ⟨fun _ _ => Fork.IsLimit.hom_ext h.hι⟩
/-- Any morphism `k : S.X₂ ⟶ A` such that `S.f ≫ k = 0` descends
to a morphism `Q ⟶ A` -/
def descQ (k : S.X₂ ⟶ A) (hk : S.f ≫ k = 0) : h.Q ⟶ A :=
h.hp.desc (CokernelCofork.ofπ k hk)
@[reassoc (attr := simp)]
lemma p_descQ (k : S.X₂ ⟶ A) (hk : S.f ≫ k = 0) : h.p ≫ h.descQ k hk = k :=
h.hp.fac _ WalkingParallelPair.one
/-- The morphism from the (right) homology attached to a morphism
`k : S.X₂ ⟶ A` such that `S.f ≫ k = 0`. -/
@[simp]
def descH (k : S.X₂ ⟶ A) (hk : S.f ≫ k = 0) : h.H ⟶ A :=
h.ι ≫ h.descQ k hk
/-- The morphism `h.Q ⟶ S.X₃` induced by `S.g : S.X₂ ⟶ S.X₃` and the fact that
`h.Q` is a cokernel of `S.f : S.X₁ ⟶ S.X₂`. -/
def g' : h.Q ⟶ S.X₃ := h.descQ S.g S.zero
@[reassoc (attr := simp)] lemma p_g' : h.p ≫ h.g' = S.g := p_descQ _ _ _
@[reassoc (attr := simp)] lemma ι_g' : h.ι ≫ h.g' = 0 := h.wι
@[reassoc]
lemma ι_descQ_eq_zero_of_boundary (k : S.X₂ ⟶ A) (x : S.X₃ ⟶ A) (hx : k = S.g ≫ x) :
h.ι ≫ h.descQ k (by rw [hx, S.zero_assoc, zero_comp]) = 0 := by
rw [show 0 = h.ι ≫ h.g' ≫ x by simp]
congr 1
simp only [← cancel_epi h.p, hx, p_descQ, p_g'_assoc]
/-- For `h : S.RightHomologyData`, this is a restatement of `h.hι`, saying that
`ι : h.H ⟶ h.Q` is a kernel of `h.g' : h.Q ⟶ S.X₃`. -/
def hι' : IsLimit (KernelFork.ofι h.ι h.ι_g') := h.hι
/-- The morphism `A ⟶ H` induced by a morphism `k : A ⟶ Q` such that `k ≫ g' = 0` -/
def liftH (k : A ⟶ h.Q) (hk : k ≫ h.g' = 0) : A ⟶ h.H :=
h.hι.lift (KernelFork.ofι k hk)
@[reassoc (attr := simp)]
lemma liftH_ι (k : A ⟶ h.Q) (hk : k ≫ h.g' = 0) : h.liftH k hk ≫ h.ι = k :=
h.hι.fac (KernelFork.ofι k hk) WalkingParallelPair.zero
lemma isIso_p (hf : S.f = 0) : IsIso h.p :=
⟨h.descQ (𝟙 S.X₂) (by rw [hf, comp_id]), p_descQ _ _ _, by
simp only [← cancel_epi h.p, p_descQ_assoc, id_comp, comp_id]⟩
lemma isIso_ι (hg : S.g = 0) : IsIso h.ι := by
have ⟨φ, hφ⟩ := KernelFork.IsLimit.lift' h.hι' (𝟙 _)
(by rw [← cancel_epi h.p, id_comp, p_g', comp_zero, hg])
dsimp at hφ
exact ⟨φ, by rw [← cancel_mono h.ι, assoc, hφ, comp_id, id_comp], hφ⟩
variable (S)
/-- When the first map `S.f` is zero, this is the right homology data on `S` given
by any limit kernel fork of `S.g` -/
@[simps]
def ofIsLimitKernelFork (hf : S.f = 0) (c : KernelFork S.g) (hc : IsLimit c) :
S.RightHomologyData where
Q := S.X₂
H := c.pt
p := 𝟙 _
ι := c.ι
wp := by rw [comp_id, hf]
hp := CokernelCofork.IsColimit.ofId _ hf
wι := KernelFork.condition _
hι := IsLimit.ofIsoLimit hc (Fork.ext (Iso.refl _) (by simp))
@[simp] lemma ofIsLimitKernelFork_g' (hf : S.f = 0) (c : KernelFork S.g)
(hc : IsLimit c) : (ofIsLimitKernelFork S hf c hc).g' = S.g := by
rw [← cancel_epi (ofIsLimitKernelFork S hf c hc).p, p_g',
ofIsLimitKernelFork_p, id_comp]
/-- When the first map `S.f` is zero, this is the right homology data on `S` given by
the chosen `kernel S.g` -/
@[simps!]
noncomputable def ofHasKernel [HasKernel S.g] (hf : S.f = 0) : S.RightHomologyData :=
ofIsLimitKernelFork S hf _ (kernelIsKernel _)
/-- When the second map `S.g` is zero, this is the right homology data on `S` given
by any colimit cokernel cofork of `S.g` -/
@[simps]
def ofIsColimitCokernelCofork (hg : S.g = 0) (c : CokernelCofork S.f) (hc : IsColimit c) :
S.RightHomologyData where
Q := c.pt
H := c.pt
p := c.π
ι := 𝟙 _
wp := CokernelCofork.condition _
hp := IsColimit.ofIsoColimit hc (Cofork.ext (Iso.refl _) (by simp))
wι := Cofork.IsColimit.hom_ext hc (by simp [hg])
hι := KernelFork.IsLimit.ofId _ (Cofork.IsColimit.hom_ext hc (by simp [hg]))
@[simp] lemma ofIsColimitCokernelCofork_g' (hg : S.g = 0) (c : CokernelCofork S.f)
(hc : IsColimit c) : (ofIsColimitCokernelCofork S hg c hc).g' = 0 := by
rw [← cancel_epi (ofIsColimitCokernelCofork S hg c hc).p, p_g', hg, comp_zero]
/-- When the second map `S.g` is zero, this is the right homology data on `S` given
by the chosen `cokernel S.f` -/
@[simp]
noncomputable def ofHasCokernel [HasCokernel S.f] (hg : S.g = 0) : S.RightHomologyData :=
ofIsColimitCokernelCofork S hg _ (cokernelIsCokernel _)
/-- When both `S.f` and `S.g` are zero, the middle object `S.X₂`
gives a right homology data on S -/
@[simps]
def ofZeros (hf : S.f = 0) (hg : S.g = 0) : S.RightHomologyData where
Q := S.X₂
H := S.X₂
p := 𝟙 _
ι := 𝟙 _
wp := by rw [comp_id, hf]
hp := CokernelCofork.IsColimit.ofId _ hf
wι := by
change 𝟙 _ ≫ S.g = 0
simp only [hg, comp_zero]
hι := KernelFork.IsLimit.ofId _ hg
@[simp]
lemma ofZeros_g' (hf : S.f = 0) (hg : S.g = 0) :
(ofZeros S hf hg).g' = 0 := by
rw [← cancel_epi ((ofZeros S hf hg).p), comp_zero, p_g', hg]
end RightHomologyData
/-- A short complex `S` has right homology when there exists a `S.RightHomologyData` -/
class HasRightHomology : Prop where
condition : Nonempty S.RightHomologyData
/-- A chosen `S.RightHomologyData` for a short complex `S` that has right homology -/
noncomputable def rightHomologyData [HasRightHomology S] :
S.RightHomologyData := HasRightHomology.condition.some
variable {S}
namespace HasRightHomology
lemma mk' (h : S.RightHomologyData) : HasRightHomology S := ⟨Nonempty.intro h⟩
instance of_hasCokernel_of_hasKernel
[HasCokernel S.f] [HasKernel (cokernel.desc S.f S.g S.zero)] :
S.HasRightHomology := HasRightHomology.mk' (RightHomologyData.ofHasCokernelOfHasKernel S)
instance of_hasKernel {Y Z : C} (g : Y ⟶ Z) (X : C) [HasKernel g] :
(ShortComplex.mk (0 : X ⟶ Y) g zero_comp).HasRightHomology :=
HasRightHomology.mk' (RightHomologyData.ofHasKernel _ rfl)
instance of_hasCokernel {X Y : C} (f : X ⟶ Y) (Z : C) [HasCokernel f] :
(ShortComplex.mk f (0 : Y ⟶ Z) comp_zero).HasRightHomology :=
HasRightHomology.mk' (RightHomologyData.ofHasCokernel _ rfl)
instance of_zeros (X Y Z : C) :
(ShortComplex.mk (0 : X ⟶ Y) (0 : Y ⟶ Z) zero_comp).HasRightHomology :=
HasRightHomology.mk' (RightHomologyData.ofZeros _ rfl rfl)
end HasRightHomology
namespace RightHomologyData
/-- A right homology data for a short complex `S` induces a left homology data for `S.op`. -/
@[simps]
def op (h : S.RightHomologyData) : S.op.LeftHomologyData where
K := Opposite.op h.Q
H := Opposite.op h.H
i := h.p.op
π := h.ι.op
wi := Quiver.Hom.unop_inj h.wp
hi := CokernelCofork.IsColimit.ofπOp _ _ h.hp
wπ := Quiver.Hom.unop_inj h.wι
hπ := KernelFork.IsLimit.ofιOp _ _ h.hι
@[simp] lemma op_f' (h : S.RightHomologyData) :
h.op.f' = h.g'.op := rfl
/-- A right homology data for a short complex `S` in the opposite category
induces a left homology data for `S.unop`. -/
@[simps]
def unop {S : ShortComplex Cᵒᵖ} (h : S.RightHomologyData) : S.unop.LeftHomologyData where
K := Opposite.unop h.Q
H := Opposite.unop h.H
i := h.p.unop
π := h.ι.unop
wi := Quiver.Hom.op_inj h.wp
hi := CokernelCofork.IsColimit.ofπUnop _ _ h.hp
wπ := Quiver.Hom.op_inj h.wι
hπ := KernelFork.IsLimit.ofιUnop _ _ h.hι
@[simp] lemma unop_f' {S : ShortComplex Cᵒᵖ} (h : S.RightHomologyData) :
h.unop.f' = h.g'.unop := rfl
end RightHomologyData
namespace LeftHomologyData
/-- A left homology data for a short complex `S` induces a right homology data for `S.op`. -/
@[simps]
def op (h : S.LeftHomologyData) : S.op.RightHomologyData where
Q := Opposite.op h.K
H := Opposite.op h.H
p := h.i.op
ι := h.π.op
wp := Quiver.Hom.unop_inj h.wi
hp := KernelFork.IsLimit.ofιOp _ _ h.hi
wι := Quiver.Hom.unop_inj h.wπ
hι := CokernelCofork.IsColimit.ofπOp _ _ h.hπ
@[simp] lemma op_g' (h : S.LeftHomologyData) :
h.op.g' = h.f'.op := rfl
/-- A left homology data for a short complex `S` in the opposite category
induces a right homology data for `S.unop`. -/
@[simps]
def unop {S : ShortComplex Cᵒᵖ} (h : S.LeftHomologyData) : S.unop.RightHomologyData where
Q := Opposite.unop h.K
H := Opposite.unop h.H
p := h.i.unop
ι := h.π.unop
wp := Quiver.Hom.op_inj h.wi
hp := KernelFork.IsLimit.ofιUnop _ _ h.hi
wι := Quiver.Hom.op_inj h.wπ
hι := CokernelCofork.IsColimit.ofπUnop _ _ h.hπ
@[simp] lemma unop_g' {S : ShortComplex Cᵒᵖ} (h : S.LeftHomologyData) :
h.unop.g' = h.f'.unop := rfl
end LeftHomologyData
instance [S.HasLeftHomology] : HasRightHomology S.op :=
HasRightHomology.mk' S.leftHomologyData.op
instance [S.HasRightHomology] : HasLeftHomology S.op :=
HasLeftHomology.mk' S.rightHomologyData.op
lemma hasLeftHomology_iff_op (S : ShortComplex C) :
S.HasLeftHomology ↔ S.op.HasRightHomology :=
⟨fun _ => inferInstance, fun _ => HasLeftHomology.mk' S.op.rightHomologyData.unop⟩
lemma hasRightHomology_iff_op (S : ShortComplex C) :
S.HasRightHomology ↔ S.op.HasLeftHomology :=
⟨fun _ => inferInstance, fun _ => HasRightHomology.mk' S.op.leftHomologyData.unop⟩
lemma hasLeftHomology_iff_unop (S : ShortComplex Cᵒᵖ) :
S.HasLeftHomology ↔ S.unop.HasRightHomology :=
S.unop.hasRightHomology_iff_op.symm
lemma hasRightHomology_iff_unop (S : ShortComplex Cᵒᵖ) :
S.HasRightHomology ↔ S.unop.HasLeftHomology :=
S.unop.hasLeftHomology_iff_op.symm
section
variable (φ : S₁ ⟶ S₂) (h₁ : S₁.RightHomologyData) (h₂ : S₂.RightHomologyData)
/-- Given right homology data `h₁` and `h₂` for two short complexes `S₁` and `S₂`,
a `RightHomologyMapData` for a morphism `φ : S₁ ⟶ S₂`
consists of a description of the induced morphisms on the `Q` (opcycles)
and `H` (right homology) fields of `h₁` and `h₂`. -/
structure RightHomologyMapData where
/-- the induced map on opcycles -/
φQ : h₁.Q ⟶ h₂.Q
/-- the induced map on right homology -/
φH : h₁.H ⟶ h₂.H
/-- commutation with `p` -/
commp : h₁.p ≫ φQ = φ.τ₂ ≫ h₂.p := by aesop_cat
/-- commutation with `g'` -/
commg' : φQ ≫ h₂.g' = h₁.g' ≫ φ.τ₃ := by aesop_cat
/-- commutation with `ι` -/
commι : φH ≫ h₂.ι = h₁.ι ≫ φQ := by aesop_cat
namespace RightHomologyMapData
attribute [reassoc (attr := simp)] commp commg' commι
/-- The right homology map data associated to the zero morphism between two short complexes. -/
@[simps]
def zero (h₁ : S₁.RightHomologyData) (h₂ : S₂.RightHomologyData) :
RightHomologyMapData 0 h₁ h₂ where
φQ := 0
φH := 0
/-- The right homology map data associated to the identity morphism of a short complex. -/
@[simps]
def id (h : S.RightHomologyData) : RightHomologyMapData (𝟙 S) h h where
φQ := 𝟙 _
φH := 𝟙 _
/-- The composition of right homology map data. -/
@[simps]
def comp {φ : S₁ ⟶ S₂} {φ' : S₂ ⟶ S₃} {h₁ : S₁.RightHomologyData}
{h₂ : S₂.RightHomologyData} {h₃ : S₃.RightHomologyData}
(ψ : RightHomologyMapData φ h₁ h₂) (ψ' : RightHomologyMapData φ' h₂ h₃) :
RightHomologyMapData (φ ≫ φ') h₁ h₃ where
φQ := ψ.φQ ≫ ψ'.φQ
φH := ψ.φH ≫ ψ'.φH
instance : Subsingleton (RightHomologyMapData φ h₁ h₂) :=
⟨fun ψ₁ ψ₂ => by
have hQ : ψ₁.φQ = ψ₂.φQ := by rw [← cancel_epi h₁.p, commp, commp]
have hH : ψ₁.φH = ψ₂.φH := by rw [← cancel_mono h₂.ι, commι, commι, hQ]
cases ψ₁
cases ψ₂
congr⟩
instance : Inhabited (RightHomologyMapData φ h₁ h₂) := ⟨by
let φQ : h₁.Q ⟶ h₂.Q := h₁.descQ (φ.τ₂ ≫ h₂.p) (by rw [← φ.comm₁₂_assoc, h₂.wp, comp_zero])
have commg' : φQ ≫ h₂.g' = h₁.g' ≫ φ.τ₃ := by
rw [← cancel_epi h₁.p, RightHomologyData.p_descQ_assoc, assoc,
RightHomologyData.p_g', φ.comm₂₃, RightHomologyData.p_g'_assoc]
let φH : h₁.H ⟶ h₂.H := h₂.liftH (h₁.ι ≫ φQ)
(by rw [assoc, commg', RightHomologyData.ι_g'_assoc, zero_comp])
exact ⟨φQ, φH, by simp [φQ], commg', by simp [φH]⟩⟩
instance : Unique (RightHomologyMapData φ h₁ h₂) := Unique.mk' _
variable {φ h₁ h₂}
lemma congr_φH {γ₁ γ₂ : RightHomologyMapData φ h₁ h₂} (eq : γ₁ = γ₂) : γ₁.φH = γ₂.φH := by rw [eq]
| lemma congr_φQ {γ₁ γ₂ : RightHomologyMapData φ h₁ h₂} (eq : γ₁ = γ₂) : γ₁.φQ = γ₂.φQ := by rw [eq]
| Mathlib/Algebra/Homology/ShortComplex/RightHomology.lean | 404 | 404 |
/-
Copyright (c) 2022 Yaël Dillies. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yaël Dillies
-/
import Batteries.Tactic.Init
import Mathlib.Logic.Function.Defs
/-!
# Binary map of options
This file defines the binary map of `Option`. This is mostly useful to define pointwise operations
on intervals.
## Main declarations
* `Option.map₂`: Binary map of options.
## Notes
This file is very similar to the n-ary section of `Mathlib.Data.Set.Basic`, to
`Mathlib.Data.Finset.NAry` and to `Mathlib.Order.Filter.NAry`. Please keep them in sync.
We do not define `Option.map₃` as its only purpose so far would be to prove properties of
`Option.map₂` and casing already fulfills this task.
-/
universe u
open Function
namespace Option
variable {α β γ δ : Type*} {f : α → β → γ} {a : Option α} {b : Option β} {c : Option γ}
/-- The image of a binary function `f : α → β → γ` as a function `Option α → Option β → Option γ`.
Mathematically this should be thought of as the image of the corresponding function `α × β → γ`. -/
def map₂ (f : α → β → γ) (a : Option α) (b : Option β) : Option γ :=
a.bind fun a => b.map <| f a
/-- `Option.map₂` in terms of monadic operations. Note that this can't be taken as the definition
because of the lack of universe polymorphism. -/
theorem map₂_def {α β γ : Type u} (f : α → β → γ) (a : Option α) (b : Option β) :
map₂ f a b = f <$> a <*> b := by
cases a <;> rfl
@[simp]
theorem map₂_some_some (f : α → β → γ) (a : α) (b : β) : map₂ f (some a) (some b) = f a b := rfl
theorem map₂_coe_coe (f : α → β → γ) (a : α) (b : β) : map₂ f a b = f a b := rfl
@[simp]
theorem map₂_none_left (f : α → β → γ) (b : Option β) : map₂ f none b = none := rfl
@[simp]
theorem map₂_none_right (f : α → β → γ) (a : Option α) : map₂ f a none = none := by cases a <;> rfl
@[simp]
theorem map₂_coe_left (f : α → β → γ) (a : α) (b : Option β) : map₂ f a b = b.map fun b => f a b :=
rfl
-- Porting note: This proof was `rfl` in Lean3, but now is not.
@[simp]
theorem map₂_coe_right (f : α → β → γ) (a : Option α) (b : β) :
map₂ f a b = a.map fun a => f a b := by cases a <;> rfl
theorem mem_map₂_iff {c : γ} : c ∈ map₂ f a b ↔ ∃ a' b', a' ∈ a ∧ b' ∈ b ∧ f a' b' = c := by
simp [map₂, bind_eq_some]
/-- `simp`-normal form of `mem_map₂_iff`. -/
@[simp]
theorem map₂_eq_some_iff {c : γ} :
map₂ f a b = some c ↔ ∃ a' b', a' ∈ a ∧ b' ∈ b ∧ f a' b' = c := by
simp [map₂, bind_eq_some]
@[simp]
theorem map₂_eq_none_iff : map₂ f a b = none ↔ a = none ∨ b = none := by
cases a <;> cases b <;> simp
theorem map₂_swap (f : α → β → γ) (a : Option α) (b : Option β) :
map₂ f a b = map₂ (fun a b => f b a) b a := by cases a <;> cases b <;> rfl
theorem map_map₂ (f : α → β → γ) (g : γ → δ) :
(map₂ f a b).map g = map₂ (fun a b => g (f a b)) a b := by cases a <;> cases b <;> rfl
theorem map₂_map_left (f : γ → β → δ) (g : α → γ) :
map₂ f (a.map g) b = map₂ (fun a b => f (g a) b) a b := by cases a <;> rfl
theorem map₂_map_right (f : α → γ → δ) (g : β → γ) :
map₂ f a (b.map g) = map₂ (fun a b => f a (g b)) a b := by cases b <;> rfl
@[simp]
theorem map₂_curry (f : α × β → γ) (a : Option α) (b : Option β) :
map₂ (curry f) a b = Option.map f (map₂ Prod.mk a b) := (map_map₂ _ _).symm
@[simp]
theorem map_uncurry (f : α → β → γ) (x : Option (α × β)) :
x.map (uncurry f) = map₂ f (x.map Prod.fst) (x.map Prod.snd) := by cases x <;> rfl
/-!
### Algebraic replacement rules
A collection of lemmas to transfer associativity, commutativity, distributivity, ... of operations
to the associativity, commutativity, distributivity, ... of `Option.map₂` of those operations.
The proof pattern is `map₂_lemma operation_lemma`. For example, `map₂_comm mul_comm` proves that
`map₂ (*) a b = map₂ (*) g f` in a `CommSemigroup`.
-/
variable {α' β' δ' ε ε' : Type*}
theorem map₂_assoc {f : δ → γ → ε} {g : α → β → δ} {f' : α → ε' → ε} {g' : β → γ → ε'}
(h_assoc : ∀ a b c, f (g a b) c = f' a (g' b c)) :
map₂ f (map₂ g a b) c = map₂ f' a (map₂ g' b c) := by
cases a <;> cases b <;> cases c <;> simp [h_assoc]
theorem map₂_comm {g : β → α → γ} (h_comm : ∀ a b, f a b = g b a) : map₂ f a b = map₂ g b a := by
cases a <;> cases b <;> simp [h_comm]
theorem map₂_left_comm {f : α → δ → ε} {g : β → γ → δ} {f' : α → γ → δ'} {g' : β → δ' → ε}
(h_left_comm : ∀ a b c, f a (g b c) = g' b (f' a c)) :
map₂ f a (map₂ g b c) = map₂ g' b (map₂ f' a c) := by
cases a <;> cases b <;> cases c <;> simp [h_left_comm]
theorem map₂_right_comm {f : δ → γ → ε} {g : α → β → δ} {f' : α → γ → δ'} {g' : δ' → β → ε}
(h_right_comm : ∀ a b c, f (g a b) c = g' (f' a c) b) :
map₂ f (map₂ g a b) c = map₂ g' (map₂ f' a c) b := by
cases a <;> cases b <;> cases c <;> simp [h_right_comm]
theorem map_map₂_distrib {g : γ → δ} {f' : α' → β' → δ} {g₁ : α → α'} {g₂ : β → β'}
(h_distrib : ∀ a b, g (f a b) = f' (g₁ a) (g₂ b)) :
(map₂ f a b).map g = map₂ f' (a.map g₁) (b.map g₂) := by
cases a <;> cases b <;> simp [h_distrib]
/-!
The following symmetric restatement are needed because unification has a hard time figuring all the
functions if you symmetrize on the spot. This is also how the other n-ary APIs do it.
-/
/-- Symmetric statement to `Option.map₂_map_left_comm`. -/
theorem map_map₂_distrib_left {g : γ → δ} {f' : α' → β → δ} {g' : α → α'}
(h_distrib : ∀ a b, g (f a b) = f' (g' a) b) :
(map₂ f a b).map g = map₂ f' (a.map g') b := by cases a <;> cases b <;> simp [h_distrib]
/-- Symmetric statement to `Option.map_map₂_right_comm`. -/
theorem map_map₂_distrib_right {g : γ → δ} {f' : α → β' → δ} {g' : β → β'}
(h_distrib : ∀ a b, g (f a b) = f' a (g' b)) : (map₂ f a b).map g = map₂ f' a (b.map g') := by
cases a <;> cases b <;> simp [h_distrib]
/-- Symmetric statement to `Option.map_map₂_distrib_left`. -/
theorem map₂_map_left_comm {f : α' → β → γ} {g : α → α'} {f' : α → β → δ} {g' : δ → γ}
(h_left_comm : ∀ a b, f (g a) b = g' (f' a b)) : map₂ f (a.map g) b = (map₂ f' a b).map g' := by
cases a <;> cases b <;> simp [h_left_comm]
/-- Symmetric statement to `Option.map_map₂_distrib_right`. -/
theorem map_map₂_right_comm {f : α → β' → γ} {g : β → β'} {f' : α → β → δ} {g' : δ → γ}
(h_right_comm : ∀ a b, f a (g b) = g' (f' a b)) :
map₂ f a (b.map g) = (map₂ f' a b).map g' := by cases a <;> cases b <;> simp [h_right_comm]
theorem map_map₂_antidistrib {g : γ → δ} {f' : β' → α' → δ} {g₁ : β → β'} {g₂ : α → α'}
(h_antidistrib : ∀ a b, g (f a b) = f' (g₁ b) (g₂ a)) :
(map₂ f a b).map g = map₂ f' (b.map g₁) (a.map g₂) := by
cases a <;> cases b <;> simp [h_antidistrib]
/-- Symmetric statement to `Option.map₂_map_left_anticomm`. -/
theorem map_map₂_antidistrib_left {g : γ → δ} {f' : β' → α → δ} {g' : β → β'}
(h_antidistrib : ∀ a b, g (f a b) = f' (g' b) a) :
(map₂ f a b).map g = map₂ f' (b.map g') a := by
cases a <;> cases b <;> simp [h_antidistrib]
/-- Symmetric statement to `Option.map_map₂_right_anticomm`. -/
theorem map_map₂_antidistrib_right {g : γ → δ} {f' : β → α' → δ} {g' : α → α'}
(h_antidistrib : ∀ a b, g (f a b) = f' b (g' a)) :
(map₂ f a b).map g = map₂ f' b (a.map g') := by cases a <;> cases b <;> simp [h_antidistrib]
/-- Symmetric statement to `Option.map_map₂_antidistrib_left`. -/
theorem map₂_map_left_anticomm {f : α' → β → γ} {g : α → α'} {f' : β → α → δ} {g' : δ → γ}
(h_left_anticomm : ∀ a b, f (g a) b = g' (f' b a)) :
map₂ f (a.map g) b = (map₂ f' b a).map g' := by cases a <;> cases b <;> simp [h_left_anticomm]
/-- Symmetric statement to `Option.map_map₂_antidistrib_right`. -/
theorem map_map₂_right_anticomm {f : α → β' → γ} {g : β → β'} {f' : β → α → δ} {g' : δ → γ}
(h_right_anticomm : ∀ a b, f a (g b) = g' (f' b a)) :
map₂ f a (b.map g) = (map₂ f' b a).map g' := by cases a <;> cases b <;> simp [h_right_anticomm]
/-- If `a` is a left identity for a binary operation `f`, then `some a` is a left identity for
`Option.map₂ f`. -/
lemma map₂_left_identity {f : α → β → β} {a : α} (h : ∀ b, f a b = b) (o : Option β) :
map₂ f (some a) o = o := by
cases o; exacts [rfl, congr_arg some (h _)]
/-- If `b` is a right identity for a binary operation `f`, then `some b` is a right identity for
`Option.map₂ f`. -/
lemma map₂_right_identity {f : α → β → α} {b : β} (h : ∀ a, f a b = a) (o : Option α) :
map₂ f o (some b) = o := by
simp [h, map₂]
end Option
| Mathlib/Data/Option/NAry.lean | 201 | 203 | |
/-
Copyright (c) 2017 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl, Johan Commelin, Mario Carneiro
-/
import Mathlib.Algebra.MonoidAlgebra.Degree
import Mathlib.Algebra.MvPolynomial.Rename
/-!
# Degrees of polynomials
This file establishes many results about the degree of a multivariate polynomial.
The *degree set* of a polynomial $P \in R[X]$ is a `Multiset` containing, for each $x$ in the
variable set, $n$ copies of $x$, where $n$ is the maximum number of copies of $x$ appearing in a
monomial of $P$.
## Main declarations
* `MvPolynomial.degrees p` : the multiset of variables representing the union of the multisets
corresponding to each non-zero monomial in `p`.
For example if `7 ≠ 0` in `R` and `p = x²y+7y³` then `degrees p = {x, x, y, y, y}`
* `MvPolynomial.degreeOf n p : ℕ` : the total degree of `p` with respect to the variable `n`.
For example if `p = x⁴y+yz` then `degreeOf y p = 1`.
* `MvPolynomial.totalDegree p : ℕ` :
the max of the sizes of the multisets `s` whose monomials `X^s` occur in `p`.
For example if `p = x⁴y+yz` then `totalDegree p = 5`.
## Notation
As in other polynomial files, we typically use the notation:
+ `σ τ : Type*` (indexing the variables)
+ `R : Type*` `[CommSemiring R]` (the coefficients)
+ `s : σ →₀ ℕ`, a function from `σ` to `ℕ` which is zero away from a finite set.
This will give rise to a monomial in `MvPolynomial σ R` which mathematicians might call `X^s`
+ `r : R`
+ `i : σ`, with corresponding monomial `X i`, often denoted `X_i` by mathematicians
+ `p : MvPolynomial σ R`
-/
noncomputable section
open Set Function Finsupp AddMonoidAlgebra
universe u v w
variable {R : Type u} {S : Type v}
namespace MvPolynomial
variable {σ τ : Type*} {r : R} {e : ℕ} {n m : σ} {s : σ →₀ ℕ}
section CommSemiring
variable [CommSemiring R] {p q : MvPolynomial σ R}
section Degrees
/-! ### `degrees` -/
/-- The maximal degrees of each variable in a multi-variable polynomial, expressed as a multiset.
(For example, `degrees (x^2 * y + y^3)` would be `{x, x, y, y, y}`.)
-/
def degrees (p : MvPolynomial σ R) : Multiset σ :=
letI := Classical.decEq σ
p.support.sup fun s : σ →₀ ℕ => toMultiset s
theorem degrees_def [DecidableEq σ] (p : MvPolynomial σ R) :
p.degrees = p.support.sup fun s : σ →₀ ℕ => Finsupp.toMultiset s := by rw [degrees]; convert rfl
theorem degrees_monomial (s : σ →₀ ℕ) (a : R) : degrees (monomial s a) ≤ toMultiset s := by
classical
refine (supDegree_single s a).trans_le ?_
split_ifs
exacts [bot_le, le_rfl]
theorem degrees_monomial_eq (s : σ →₀ ℕ) (a : R) (ha : a ≠ 0) :
degrees (monomial s a) = toMultiset s := by
classical
exact (supDegree_single s a).trans (if_neg ha)
theorem degrees_C (a : R) : degrees (C a : MvPolynomial σ R) = 0 :=
Multiset.le_zero.1 <| degrees_monomial _ _
theorem degrees_X' (n : σ) : degrees (X n : MvPolynomial σ R) ≤ {n} :=
le_trans (degrees_monomial _ _) <| le_of_eq <| toMultiset_single _ _
@[simp]
theorem degrees_X [Nontrivial R] (n : σ) : degrees (X n : MvPolynomial σ R) = {n} :=
(degrees_monomial_eq _ (1 : R) one_ne_zero).trans (toMultiset_single _ _)
@[simp]
theorem degrees_zero : degrees (0 : MvPolynomial σ R) = 0 := by
rw [← C_0]
exact degrees_C 0
@[simp]
theorem degrees_one : degrees (1 : MvPolynomial σ R) = 0 :=
degrees_C 1
theorem degrees_add_le [DecidableEq σ] {p q : MvPolynomial σ R} :
(p + q).degrees ≤ p.degrees ⊔ q.degrees := by
simp_rw [degrees_def]; exact supDegree_add_le
theorem degrees_sum_le {ι : Type*} [DecidableEq σ] (s : Finset ι) (f : ι → MvPolynomial σ R) :
(∑ i ∈ s, f i).degrees ≤ s.sup fun i => (f i).degrees := by
simp_rw [degrees_def]; exact supDegree_sum_le
theorem degrees_mul_le {p q : MvPolynomial σ R} : (p * q).degrees ≤ p.degrees + q.degrees := by
classical
simp_rw [degrees_def]
exact supDegree_mul_le (map_add _)
theorem degrees_prod_le {ι : Type*} {s : Finset ι} {f : ι → MvPolynomial σ R} :
(∏ i ∈ s, f i).degrees ≤ ∑ i ∈ s, (f i).degrees := by
classical exact supDegree_prod_le (map_zero _) (map_add _)
theorem degrees_pow_le {p : MvPolynomial σ R} {n : ℕ} : (p ^ n).degrees ≤ n • p.degrees := by
simpa using degrees_prod_le (s := .range n) (f := fun _ ↦ p)
| @[deprecated (since := "2024-12-28")] alias degrees_add := degrees_add_le
@[deprecated (since := "2024-12-28")] alias degrees_sum := degrees_sum_le
@[deprecated (since := "2024-12-28")] alias degrees_mul := degrees_mul_le
| Mathlib/Algebra/MvPolynomial/Degrees.lean | 133 | 135 |
/-
Copyright (c) 2018 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl, Julian Kuelshammer
-/
import Mathlib.Algebra.CharP.Defs
import Mathlib.Algebra.Group.Commute.Basic
import Mathlib.Algebra.Group.Pointwise.Set.Finite
import Mathlib.Algebra.Group.Subgroup.Finite
import Mathlib.Algebra.Module.NatInt
import Mathlib.Algebra.Order.Group.Action
import Mathlib.Algebra.Order.Ring.Abs
import Mathlib.Data.Int.ModEq
import Mathlib.Dynamics.PeriodicPts.Lemmas
import Mathlib.GroupTheory.Index
import Mathlib.NumberTheory.Divisors
import Mathlib.Order.Interval.Set.Infinite
/-!
# Order of an element
This file defines the order of an element of a finite group. For a finite group `G` the order of
`x ∈ G` is the minimal `n ≥ 1` such that `x ^ n = 1`.
## Main definitions
* `IsOfFinOrder` is a predicate on an element `x` of a monoid `G` saying that `x` is of finite
order.
* `IsOfFinAddOrder` is the additive analogue of `IsOfFinOrder`.
* `orderOf x` defines the order of an element `x` of a monoid `G`, by convention its value is `0`
if `x` has infinite order.
* `addOrderOf` is the additive analogue of `orderOf`.
## Tags
order of an element
-/
assert_not_exists Field
open Function Fintype Nat Pointwise Subgroup Submonoid
open scoped Finset
variable {G H A α β : Type*}
section Monoid
variable [Monoid G] {a b x y : G} {n m : ℕ}
section IsOfFinOrder
-- Porting note (https://github.com/leanprover-community/mathlib4/issues/12129): additional beta reduction needed
@[to_additive]
theorem isPeriodicPt_mul_iff_pow_eq_one (x : G) : IsPeriodicPt (x * ·) n 1 ↔ x ^ n = 1 := by
rw [IsPeriodicPt, IsFixedPt, mul_left_iterate]; beta_reduce; rw [mul_one]
/-- `IsOfFinOrder` is a predicate on an element `x` of a monoid to be of finite order, i.e. there
exists `n ≥ 1` such that `x ^ n = 1`. -/
@[to_additive "`IsOfFinAddOrder` is a predicate on an element `a` of an
additive monoid to be of finite order, i.e. there exists `n ≥ 1` such that `n • a = 0`."]
def IsOfFinOrder (x : G) : Prop :=
(1 : G) ∈ periodicPts (x * ·)
theorem isOfFinAddOrder_ofMul_iff : IsOfFinAddOrder (Additive.ofMul x) ↔ IsOfFinOrder x :=
Iff.rfl
theorem isOfFinOrder_ofAdd_iff {α : Type*} [AddMonoid α] {x : α} :
IsOfFinOrder (Multiplicative.ofAdd x) ↔ IsOfFinAddOrder x := Iff.rfl
@[to_additive]
theorem isOfFinOrder_iff_pow_eq_one : IsOfFinOrder x ↔ ∃ n, 0 < n ∧ x ^ n = 1 := by
simp [IsOfFinOrder, mem_periodicPts, isPeriodicPt_mul_iff_pow_eq_one]
@[to_additive] alias ⟨IsOfFinOrder.exists_pow_eq_one, _⟩ := isOfFinOrder_iff_pow_eq_one
@[to_additive]
lemma isOfFinOrder_iff_zpow_eq_one {G} [DivisionMonoid G] {x : G} :
IsOfFinOrder x ↔ ∃ (n : ℤ), n ≠ 0 ∧ x ^ n = 1 := by
rw [isOfFinOrder_iff_pow_eq_one]
refine ⟨fun ⟨n, hn, hn'⟩ ↦ ⟨n, Int.natCast_ne_zero_iff_pos.mpr hn, zpow_natCast x n ▸ hn'⟩,
fun ⟨n, hn, hn'⟩ ↦ ⟨n.natAbs, Int.natAbs_pos.mpr hn, ?_⟩⟩
rcases (Int.natAbs_eq_iff (a := n)).mp rfl with h | h
· rwa [h, zpow_natCast] at hn'
· rwa [h, zpow_neg, inv_eq_one, zpow_natCast] at hn'
/-- See also `injective_pow_iff_not_isOfFinOrder`. -/
@[to_additive "See also `injective_nsmul_iff_not_isOfFinAddOrder`."]
theorem not_isOfFinOrder_of_injective_pow {x : G} (h : Injective fun n : ℕ => x ^ n) :
¬IsOfFinOrder x := by
simp_rw [isOfFinOrder_iff_pow_eq_one, not_exists, not_and]
intro n hn_pos hnx
rw [← pow_zero x] at hnx
rw [h hnx] at hn_pos
exact irrefl 0 hn_pos
/-- 1 is of finite order in any monoid. -/
@[to_additive (attr := simp) "0 is of finite order in any additive monoid."]
theorem IsOfFinOrder.one : IsOfFinOrder (1 : G) :=
isOfFinOrder_iff_pow_eq_one.mpr ⟨1, Nat.one_pos, one_pow 1⟩
@[to_additive]
lemma IsOfFinOrder.pow {n : ℕ} : IsOfFinOrder a → IsOfFinOrder (a ^ n) := by
simp_rw [isOfFinOrder_iff_pow_eq_one]
rintro ⟨m, hm, ha⟩
exact ⟨m, hm, by simp [pow_right_comm _ n, ha]⟩
@[to_additive]
lemma IsOfFinOrder.of_pow {n : ℕ} (h : IsOfFinOrder (a ^ n)) (hn : n ≠ 0) : IsOfFinOrder a := by
rw [isOfFinOrder_iff_pow_eq_one] at *
rcases h with ⟨m, hm, ha⟩
exact ⟨n * m, mul_pos hn.bot_lt hm, by rwa [pow_mul]⟩
@[to_additive (attr := simp)]
lemma isOfFinOrder_pow {n : ℕ} : IsOfFinOrder (a ^ n) ↔ IsOfFinOrder a ∨ n = 0 := by
rcases Decidable.eq_or_ne n 0 with rfl | hn
· simp
· exact ⟨fun h ↦ .inl <| h.of_pow hn, fun h ↦ (h.resolve_right hn).pow⟩
/-- Elements of finite order are of finite order in submonoids. -/
@[to_additive "Elements of finite order are of finite order in submonoids."]
theorem Submonoid.isOfFinOrder_coe {H : Submonoid G} {x : H} :
IsOfFinOrder (x : G) ↔ IsOfFinOrder x := by
rw [isOfFinOrder_iff_pow_eq_one, isOfFinOrder_iff_pow_eq_one]
norm_cast
theorem IsConj.isOfFinOrder (h : IsConj x y) : IsOfFinOrder x → IsOfFinOrder y := by
simp_rw [isOfFinOrder_iff_pow_eq_one]
rintro ⟨n, n_gt_0, eq'⟩
exact ⟨n, n_gt_0, by rw [← isConj_one_right, ← eq']; exact h.pow n⟩
/-- The image of an element of finite order has finite order. -/
@[to_additive "The image of an element of finite additive order has finite additive order."]
theorem MonoidHom.isOfFinOrder [Monoid H] (f : G →* H) {x : G} (h : IsOfFinOrder x) :
IsOfFinOrder <| f x :=
isOfFinOrder_iff_pow_eq_one.mpr <| by
obtain ⟨n, npos, hn⟩ := h.exists_pow_eq_one
exact ⟨n, npos, by rw [← f.map_pow, hn, f.map_one]⟩
/-- If a direct product has finite order then so does each component. -/
@[to_additive "If a direct product has finite additive order then so does each component."]
theorem IsOfFinOrder.apply {η : Type*} {Gs : η → Type*} [∀ i, Monoid (Gs i)] {x : ∀ i, Gs i}
(h : IsOfFinOrder x) : ∀ i, IsOfFinOrder (x i) := by
obtain ⟨n, npos, hn⟩ := h.exists_pow_eq_one
exact fun _ => isOfFinOrder_iff_pow_eq_one.mpr ⟨n, npos, (congr_fun hn.symm _).symm⟩
/-- The submonoid generated by an element is a group if that element has finite order. -/
@[to_additive "The additive submonoid generated by an element is
an additive group if that element has finite order."]
noncomputable abbrev IsOfFinOrder.groupPowers (hx : IsOfFinOrder x) :
Group (Submonoid.powers x) := by
obtain ⟨hpos, hx⟩ := hx.exists_pow_eq_one.choose_spec
exact Submonoid.groupPowers hpos hx
end IsOfFinOrder
/-- `orderOf x` is the order of the element `x`, i.e. the `n ≥ 1`, s.t. `x ^ n = 1` if it exists.
Otherwise, i.e. if `x` is of infinite order, then `orderOf x` is `0` by convention. -/
@[to_additive
"`addOrderOf a` is the order of the element `a`, i.e. the `n ≥ 1`, s.t. `n • a = 0` if it
exists. Otherwise, i.e. if `a` is of infinite order, then `addOrderOf a` is `0` by convention."]
noncomputable def orderOf (x : G) : ℕ :=
minimalPeriod (x * ·) 1
@[simp]
theorem addOrderOf_ofMul_eq_orderOf (x : G) : addOrderOf (Additive.ofMul x) = orderOf x :=
rfl
@[simp]
lemma orderOf_ofAdd_eq_addOrderOf {α : Type*} [AddMonoid α] (a : α) :
orderOf (Multiplicative.ofAdd a) = addOrderOf a := rfl
@[to_additive]
protected lemma IsOfFinOrder.orderOf_pos (h : IsOfFinOrder x) : 0 < orderOf x :=
minimalPeriod_pos_of_mem_periodicPts h
@[to_additive addOrderOf_nsmul_eq_zero]
theorem pow_orderOf_eq_one (x : G) : x ^ orderOf x = 1 := by
convert Eq.trans _ (isPeriodicPt_minimalPeriod (x * ·) 1)
-- Porting note (https://github.com/leanprover-community/mathlib4/issues/12129): additional beta reduction needed in the middle of the rewrite
rw [orderOf, mul_left_iterate]; beta_reduce; rw [mul_one]
@[to_additive]
theorem orderOf_eq_zero (h : ¬IsOfFinOrder x) : orderOf x = 0 := by
rwa [orderOf, minimalPeriod, dif_neg]
@[to_additive]
theorem orderOf_eq_zero_iff : orderOf x = 0 ↔ ¬IsOfFinOrder x :=
⟨fun h H ↦ H.orderOf_pos.ne' h, orderOf_eq_zero⟩
@[to_additive]
theorem orderOf_eq_zero_iff' : orderOf x = 0 ↔ ∀ n : ℕ, 0 < n → x ^ n ≠ 1 := by
simp_rw [orderOf_eq_zero_iff, isOfFinOrder_iff_pow_eq_one, not_exists, not_and]
@[to_additive]
theorem orderOf_eq_iff {n} (h : 0 < n) :
orderOf x = n ↔ x ^ n = 1 ∧ ∀ m, m < n → 0 < m → x ^ m ≠ 1 := by
simp_rw [Ne, ← isPeriodicPt_mul_iff_pow_eq_one, orderOf, minimalPeriod]
split_ifs with h1
· classical
rw [find_eq_iff]
simp only [h, true_and]
push_neg
rfl
· rw [iff_false_left h.ne]
| rintro ⟨h', -⟩
exact h1 ⟨n, h, h'⟩
/-- A group element has finite order iff its order is positive. -/
@[to_additive
"A group element has finite additive order iff its order is positive."]
theorem orderOf_pos_iff : 0 < orderOf x ↔ IsOfFinOrder x := by
rw [iff_not_comm.mp orderOf_eq_zero_iff, pos_iff_ne_zero]
@[to_additive]
theorem IsOfFinOrder.mono [Monoid β] {y : β} (hx : IsOfFinOrder x) (h : orderOf y ∣ orderOf x) :
IsOfFinOrder y := by rw [← orderOf_pos_iff] at hx ⊢; exact Nat.pos_of_dvd_of_pos h hx
| Mathlib/GroupTheory/OrderOfElement.lean | 203 | 214 |
/-
Copyright (c) 2020 Kenny Lau. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kenny Lau, Eric Wieser
-/
import Mathlib.Algebra.BigOperators.GroupWithZero.Action
import Mathlib.Algebra.GroupWithZero.Invertible
import Mathlib.LinearAlgebra.Prod
/-!
# Trivial Square-Zero Extension
Given a ring `R` together with an `(R, R)`-bimodule `M`, the trivial square-zero extension of `M`
over `R` is defined to be the `R`-algebra `R ⊕ M` with multiplication given by
`(r₁ + m₁) * (r₂ + m₂) = r₁ r₂ + r₁ m₂ + m₁ r₂`.
It is a square-zero extension because `M^2 = 0`.
Note that expressing this requires bimodules; we write these in general for a
not-necessarily-commutative `R` as:
```lean
variable {R M : Type*} [Semiring R] [AddCommMonoid M]
variable [Module R M] [Module Rᵐᵒᵖ M] [SMulCommClass R Rᵐᵒᵖ M]
```
If we instead work with a commutative `R'` acting symmetrically on `M`, we write
```lean
variable {R' M : Type*} [CommSemiring R'] [AddCommMonoid M]
variable [Module R' M] [Module R'ᵐᵒᵖ M] [IsCentralScalar R' M]
```
noting that in this context `IsCentralScalar R' M` implies `SMulCommClass R' R'ᵐᵒᵖ M`.
Many of the later results in this file are only stated for the commutative `R'` for simplicity.
## Main definitions
* `TrivSqZeroExt.inl`, `TrivSqZeroExt.inr`: the canonical inclusions into
`TrivSqZeroExt R M`.
* `TrivSqZeroExt.fst`, `TrivSqZeroExt.snd`: the canonical projections from
`TrivSqZeroExt R M`.
* `triv_sq_zero_ext.algebra`: the associated `R`-algebra structure.
* `TrivSqZeroExt.lift`: the universal property of the trivial square-zero extension; algebra
morphisms `TrivSqZeroExt R M →ₐ[S] A` are uniquely defined by an algebra morphism `f : R →ₐ[S] A`
on `R` and a linear map `g : M →ₗ[S] A` on `M` such that:
* `g x * g y = 0`: the elements of `M` continue to square to zero.
* `g (r •> x) = f r * g x` and `g (x <• r) = g x * f r`: left and right actions are preserved by
`g`.
* `TrivSqZeroExt.lift`: the universal property of the trivial square-zero extension; algebra
morphisms `TrivSqZeroExt R M →ₐ[R] A` are uniquely defined by linear maps `M →ₗ[R] A` for
which the product of any two elements in the range is zero.
-/
universe u v w
/-- "Trivial Square-Zero Extension".
Given a module `M` over a ring `R`, the trivial square-zero extension of `M` over `R` is defined
to be the `R`-algebra `R × M` with multiplication given by
`(r₁ + m₁) * (r₂ + m₂) = r₁ r₂ + r₁ m₂ + r₂ m₁`.
It is a square-zero extension because `M^2 = 0`.
-/
def TrivSqZeroExt (R : Type u) (M : Type v) :=
R × M
local notation "tsze" => TrivSqZeroExt
open scoped RightActions
namespace TrivSqZeroExt
open MulOpposite
section Basic
variable {R : Type u} {M : Type v}
/-- The canonical inclusion `R → TrivSqZeroExt R M`. -/
def inl [Zero M] (r : R) : tsze R M :=
(r, 0)
/-- The canonical inclusion `M → TrivSqZeroExt R M`. -/
def inr [Zero R] (m : M) : tsze R M :=
(0, m)
/-- The canonical projection `TrivSqZeroExt R M → R`. -/
def fst (x : tsze R M) : R :=
x.1
/-- The canonical projection `TrivSqZeroExt R M → M`. -/
def snd (x : tsze R M) : M :=
x.2
@[simp]
theorem fst_mk (r : R) (m : M) : fst (r, m) = r :=
rfl
@[simp]
theorem snd_mk (r : R) (m : M) : snd (r, m) = m :=
rfl
@[ext]
theorem ext {x y : tsze R M} (h1 : x.fst = y.fst) (h2 : x.snd = y.snd) : x = y :=
Prod.ext h1 h2
section
variable (M)
@[simp]
theorem fst_inl [Zero M] (r : R) : (inl r : tsze R M).fst = r :=
rfl
@[simp]
theorem snd_inl [Zero M] (r : R) : (inl r : tsze R M).snd = 0 :=
rfl
@[simp]
theorem fst_comp_inl [Zero M] : fst ∘ (inl : R → tsze R M) = id :=
rfl
@[simp]
theorem snd_comp_inl [Zero M] : snd ∘ (inl : R → tsze R M) = 0 :=
rfl
end
section
variable (R)
@[simp]
theorem fst_inr [Zero R] (m : M) : (inr m : tsze R M).fst = 0 :=
rfl
@[simp]
theorem snd_inr [Zero R] (m : M) : (inr m : tsze R M).snd = m :=
rfl
@[simp]
theorem fst_comp_inr [Zero R] : fst ∘ (inr : M → tsze R M) = 0 :=
rfl
@[simp]
theorem snd_comp_inr [Zero R] : snd ∘ (inr : M → tsze R M) = id :=
rfl
end
theorem fst_surjective [Nonempty M] : Function.Surjective (fst : tsze R M → R) :=
Prod.fst_surjective
theorem snd_surjective [Nonempty R] : Function.Surjective (snd : tsze R M → M) :=
Prod.snd_surjective
theorem inl_injective [Zero M] : Function.Injective (inl : R → tsze R M) :=
Function.LeftInverse.injective <| fst_inl _
theorem inr_injective [Zero R] : Function.Injective (inr : M → tsze R M) :=
Function.LeftInverse.injective <| snd_inr _
end Basic
/-! ### Structures inherited from `Prod`
Additive operators and scalar multiplication operate elementwise. -/
section Additive
variable {T : Type*} {S : Type*} {R : Type u} {M : Type v}
instance inhabited [Inhabited R] [Inhabited M] : Inhabited (tsze R M) :=
instInhabitedProd
instance zero [Zero R] [Zero M] : Zero (tsze R M) :=
Prod.instZero
instance add [Add R] [Add M] : Add (tsze R M) :=
Prod.instAdd
instance sub [Sub R] [Sub M] : Sub (tsze R M) :=
Prod.instSub
instance neg [Neg R] [Neg M] : Neg (tsze R M) :=
Prod.instNeg
instance addSemigroup [AddSemigroup R] [AddSemigroup M] : AddSemigroup (tsze R M) :=
Prod.instAddSemigroup
instance addZeroClass [AddZeroClass R] [AddZeroClass M] : AddZeroClass (tsze R M) :=
Prod.instAddZeroClass
instance addMonoid [AddMonoid R] [AddMonoid M] : AddMonoid (tsze R M) :=
Prod.instAddMonoid
instance addGroup [AddGroup R] [AddGroup M] : AddGroup (tsze R M) :=
Prod.instAddGroup
instance addCommSemigroup [AddCommSemigroup R] [AddCommSemigroup M] : AddCommSemigroup (tsze R M) :=
Prod.instAddCommSemigroup
instance addCommMonoid [AddCommMonoid R] [AddCommMonoid M] : AddCommMonoid (tsze R M) :=
Prod.instAddCommMonoid
instance addCommGroup [AddCommGroup R] [AddCommGroup M] : AddCommGroup (tsze R M) :=
Prod.instAddCommGroup
instance smul [SMul S R] [SMul S M] : SMul S (tsze R M) :=
Prod.instSMul
instance isScalarTower [SMul T R] [SMul T M] [SMul S R] [SMul S M] [SMul T S]
[IsScalarTower T S R] [IsScalarTower T S M] : IsScalarTower T S (tsze R M) :=
Prod.isScalarTower
instance smulCommClass [SMul T R] [SMul T M] [SMul S R] [SMul S M]
[SMulCommClass T S R] [SMulCommClass T S M] : SMulCommClass T S (tsze R M) :=
Prod.smulCommClass
instance isCentralScalar [SMul S R] [SMul S M] [SMul Sᵐᵒᵖ R] [SMul Sᵐᵒᵖ M] [IsCentralScalar S R]
[IsCentralScalar S M] : IsCentralScalar S (tsze R M) :=
Prod.isCentralScalar
instance mulAction [Monoid S] [MulAction S R] [MulAction S M] : MulAction S (tsze R M) :=
Prod.mulAction
instance distribMulAction [Monoid S] [AddMonoid R] [AddMonoid M]
[DistribMulAction S R] [DistribMulAction S M] : DistribMulAction S (tsze R M) :=
Prod.distribMulAction
instance module [Semiring S] [AddCommMonoid R] [AddCommMonoid M] [Module S R] [Module S M] :
Module S (tsze R M) :=
Prod.instModule
/-- The trivial square-zero extension is nontrivial if it is over a nontrivial ring. -/
instance instNontrivial_of_left {R M : Type*} [Nontrivial R] [Nonempty M] :
Nontrivial (TrivSqZeroExt R M) :=
fst_surjective.nontrivial
/-- The trivial square-zero extension is nontrivial if it is over a nontrivial module. -/
instance instNontrivial_of_right {R M : Type*} [Nonempty R] [Nontrivial M] :
Nontrivial (TrivSqZeroExt R M) :=
snd_surjective.nontrivial
@[simp]
theorem fst_zero [Zero R] [Zero M] : (0 : tsze R M).fst = 0 :=
rfl
@[simp]
theorem snd_zero [Zero R] [Zero M] : (0 : tsze R M).snd = 0 :=
rfl
@[simp]
theorem fst_add [Add R] [Add M] (x₁ x₂ : tsze R M) : (x₁ + x₂).fst = x₁.fst + x₂.fst :=
rfl
@[simp]
theorem snd_add [Add R] [Add M] (x₁ x₂ : tsze R M) : (x₁ + x₂).snd = x₁.snd + x₂.snd :=
rfl
@[simp]
theorem fst_neg [Neg R] [Neg M] (x : tsze R M) : (-x).fst = -x.fst :=
rfl
@[simp]
theorem snd_neg [Neg R] [Neg M] (x : tsze R M) : (-x).snd = -x.snd :=
rfl
@[simp]
theorem fst_sub [Sub R] [Sub M] (x₁ x₂ : tsze R M) : (x₁ - x₂).fst = x₁.fst - x₂.fst :=
rfl
@[simp]
theorem snd_sub [Sub R] [Sub M] (x₁ x₂ : tsze R M) : (x₁ - x₂).snd = x₁.snd - x₂.snd :=
rfl
@[simp]
theorem fst_smul [SMul S R] [SMul S M] (s : S) (x : tsze R M) : (s • x).fst = s • x.fst :=
rfl
@[simp]
theorem snd_smul [SMul S R] [SMul S M] (s : S) (x : tsze R M) : (s • x).snd = s • x.snd :=
rfl
theorem fst_sum {ι} [AddCommMonoid R] [AddCommMonoid M] (s : Finset ι) (f : ι → tsze R M) :
(∑ i ∈ s, f i).fst = ∑ i ∈ s, (f i).fst :=
Prod.fst_sum
theorem snd_sum {ι} [AddCommMonoid R] [AddCommMonoid M] (s : Finset ι) (f : ι → tsze R M) :
(∑ i ∈ s, f i).snd = ∑ i ∈ s, (f i).snd :=
Prod.snd_sum
section
variable (M)
@[simp]
theorem inl_zero [Zero R] [Zero M] : (inl 0 : tsze R M) = 0 :=
rfl
@[simp]
theorem inl_add [Add R] [AddZeroClass M] (r₁ r₂ : R) :
(inl (r₁ + r₂) : tsze R M) = inl r₁ + inl r₂ :=
ext rfl (add_zero 0).symm
@[simp]
theorem inl_neg [Neg R] [NegZeroClass M] (r : R) : (inl (-r) : tsze R M) = -inl r :=
ext rfl neg_zero.symm
@[simp]
theorem inl_sub [Sub R] [SubNegZeroMonoid M] (r₁ r₂ : R) :
(inl (r₁ - r₂) : tsze R M) = inl r₁ - inl r₂ :=
ext rfl (sub_zero _).symm
@[simp]
theorem inl_smul [Monoid S] [AddMonoid M] [SMul S R] [DistribMulAction S M] (s : S) (r : R) :
(inl (s • r) : tsze R M) = s • inl r :=
ext rfl (smul_zero s).symm
theorem inl_sum {ι} [AddCommMonoid R] [AddCommMonoid M] (s : Finset ι) (f : ι → R) :
(inl (∑ i ∈ s, f i) : tsze R M) = ∑ i ∈ s, inl (f i) :=
map_sum (LinearMap.inl ℕ _ _) _ _
end
section
variable (R)
@[simp]
theorem inr_zero [Zero R] [Zero M] : (inr 0 : tsze R M) = 0 :=
rfl
@[simp]
theorem inr_add [AddZeroClass R] [Add M] (m₁ m₂ : M) :
(inr (m₁ + m₂) : tsze R M) = inr m₁ + inr m₂ :=
ext (add_zero 0).symm rfl
@[simp]
theorem inr_neg [NegZeroClass R] [Neg M] (m : M) : (inr (-m) : tsze R M) = -inr m :=
ext neg_zero.symm rfl
@[simp]
theorem inr_sub [SubNegZeroMonoid R] [Sub M] (m₁ m₂ : M) :
(inr (m₁ - m₂) : tsze R M) = inr m₁ - inr m₂ :=
ext (sub_zero _).symm rfl
@[simp]
theorem inr_smul [Zero R] [SMulZeroClass S R] [SMul S M] (r : S) (m : M) :
(inr (r • m) : tsze R M) = r • inr m :=
ext (smul_zero _).symm rfl
theorem inr_sum {ι} [AddCommMonoid R] [AddCommMonoid M] (s : Finset ι) (f : ι → M) :
(inr (∑ i ∈ s, f i) : tsze R M) = ∑ i ∈ s, inr (f i) :=
map_sum (LinearMap.inr ℕ _ _) _ _
end
theorem inl_fst_add_inr_snd_eq [AddZeroClass R] [AddZeroClass M] (x : tsze R M) :
inl x.fst + inr x.snd = x :=
ext (add_zero x.1) (zero_add x.2)
/-- To show a property hold on all `TrivSqZeroExt R M` it suffices to show it holds
on terms of the form `inl r + inr m`. -/
@[elab_as_elim, induction_eliminator, cases_eliminator]
theorem ind {R M} [AddZeroClass R] [AddZeroClass M] {P : TrivSqZeroExt R M → Prop}
(inl_add_inr : ∀ r m, P (inl r + inr m)) (x) : P x :=
inl_fst_add_inr_snd_eq x ▸ inl_add_inr x.1 x.2
/-- This cannot be marked `@[ext]` as it ends up being used instead of `LinearMap.prod_ext` when
working with `R × M`. -/
theorem linearMap_ext {N} [Semiring S] [AddCommMonoid R] [AddCommMonoid M] [AddCommMonoid N]
[Module S R] [Module S M] [Module S N] ⦃f g : tsze R M →ₗ[S] N⦄
(hl : ∀ r, f (inl r) = g (inl r)) (hr : ∀ m, f (inr m) = g (inr m)) : f = g :=
LinearMap.prod_ext (LinearMap.ext hl) (LinearMap.ext hr)
variable (R M)
/-- The canonical `R`-linear inclusion `M → TrivSqZeroExt R M`. -/
@[simps apply]
def inrHom [Semiring R] [AddCommMonoid M] [Module R M] : M →ₗ[R] tsze R M :=
{ LinearMap.inr R R M with toFun := inr }
/-- The canonical `R`-linear projection `TrivSqZeroExt R M → M`. -/
@[simps apply]
def sndHom [Semiring R] [AddCommMonoid M] [Module R M] : tsze R M →ₗ[R] M :=
{ LinearMap.snd _ _ _ with toFun := snd }
end Additive
/-! ### Multiplicative structure -/
section Mul
variable {R : Type u} {M : Type v}
instance one [One R] [Zero M] : One (tsze R M) :=
⟨(1, 0)⟩
instance mul [Mul R] [Add M] [SMul R M] [SMul Rᵐᵒᵖ M] : Mul (tsze R M) :=
⟨fun x y => (x.1 * y.1, x.1 •> y.2 + x.2 <• y.1)⟩
@[simp]
theorem fst_one [One R] [Zero M] : (1 : tsze R M).fst = 1 :=
rfl
@[simp]
theorem snd_one [One R] [Zero M] : (1 : tsze R M).snd = 0 :=
rfl
@[simp]
theorem fst_mul [Mul R] [Add M] [SMul R M] [SMul Rᵐᵒᵖ M] (x₁ x₂ : tsze R M) :
(x₁ * x₂).fst = x₁.fst * x₂.fst :=
rfl
@[simp]
theorem snd_mul [Mul R] [Add M] [SMul R M] [SMul Rᵐᵒᵖ M] (x₁ x₂ : tsze R M) :
(x₁ * x₂).snd = x₁.fst •> x₂.snd + x₁.snd <• x₂.fst :=
rfl
section
variable (M)
@[simp]
theorem inl_one [One R] [Zero M] : (inl 1 : tsze R M) = 1 :=
rfl
@[simp]
theorem inl_mul [Monoid R] [AddMonoid M] [DistribMulAction R M] [DistribMulAction Rᵐᵒᵖ M]
(r₁ r₂ : R) : (inl (r₁ * r₂) : tsze R M) = inl r₁ * inl r₂ :=
ext rfl <| show (0 : M) = r₁ •> (0 : M) + (0 : M) <• r₂ by rw [smul_zero, zero_add, smul_zero]
theorem inl_mul_inl [Monoid R] [AddMonoid M] [DistribMulAction R M] [DistribMulAction Rᵐᵒᵖ M]
(r₁ r₂ : R) : (inl r₁ * inl r₂ : tsze R M) = inl (r₁ * r₂) :=
(inl_mul M r₁ r₂).symm
end
section
variable (R)
@[simp]
theorem inr_mul_inr [Semiring R] [AddCommMonoid M] [Module R M] [Module Rᵐᵒᵖ M] (m₁ m₂ : M) :
(inr m₁ * inr m₂ : tsze R M) = 0 :=
ext (mul_zero _) <|
show (0 : R) •> m₂ + m₁ <• (0 : R) = 0 by rw [zero_smul, zero_add, op_zero, zero_smul]
end
theorem inl_mul_inr [MonoidWithZero R] [AddMonoid M] [DistribMulAction R M]
[DistribMulAction Rᵐᵒᵖ M] (r : R) (m : M) : (inl r * inr m : tsze R M) = inr (r • m) :=
ext (mul_zero r) <|
show r • m + (0 : Rᵐᵒᵖ) • (0 : M) = r • m by rw [smul_zero, add_zero]
theorem inr_mul_inl [MonoidWithZero R] [AddMonoid M] [DistribMulAction R M]
[DistribMulAction Rᵐᵒᵖ M] (r : R) (m : M) : (inr m * inl r : tsze R M) = inr (m <• r) :=
ext (zero_mul r) <|
show (0 : R) •> (0 : M) + m <• r = m <• r by rw [smul_zero, zero_add]
theorem inl_mul_eq_smul [Monoid R] [AddMonoid M] [DistribMulAction R M] [DistribMulAction Rᵐᵒᵖ M]
(r : R) (x : tsze R M) :
inl r * x = r •> x :=
ext rfl (by dsimp; rw [smul_zero, add_zero])
theorem mul_inl_eq_op_smul [Monoid R] [AddMonoid M] [DistribMulAction R M] [DistribMulAction Rᵐᵒᵖ M]
(x : tsze R M) (r : R) :
x * inl r = x <• r :=
ext rfl (by dsimp; rw [smul_zero, zero_add])
instance mulOneClass [Monoid R] [AddMonoid M] [DistribMulAction R M] [DistribMulAction Rᵐᵒᵖ M] :
MulOneClass (tsze R M) :=
{ TrivSqZeroExt.one, TrivSqZeroExt.mul with
one_mul := fun x =>
ext (one_mul x.1) <|
show (1 : R) •> x.2 + (0 : M) <• x.1 = x.2 by rw [one_smul, smul_zero, add_zero]
mul_one := fun x =>
ext (mul_one x.1) <|
show x.1 • (0 : M) + x.2 <• (1 : R) = x.2 by rw [smul_zero, zero_add, op_one, one_smul] }
instance addMonoidWithOne [AddMonoidWithOne R] [AddMonoid M] : AddMonoidWithOne (tsze R M) :=
{ TrivSqZeroExt.addMonoid, TrivSqZeroExt.one with
natCast := fun n => inl n
| natCast_zero := by simp [Nat.cast]
natCast_succ := fun _ => by ext <;> simp [Nat.cast] }
@[simp]
| Mathlib/Algebra/TrivSqZeroExt.lean | 486 | 489 |
/-
Copyright (c) 2020 Anne Baanen. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Anne Baanen, Devon Tuma
-/
import Mathlib.Algebra.GroupWithZero.NonZeroDivisors
import Mathlib.Algebra.Polynomial.AlgebraMap
import Mathlib.RingTheory.Coprime.Basic
import Mathlib.Tactic.AdaptationNote
/-!
# Scaling the roots of a polynomial
This file defines `scaleRoots p s` for a polynomial `p` in one variable and a ring element `s` to
be the polynomial with root `r * s` for each root `r` of `p` and proves some basic results about it.
-/
variable {R S A K : Type*}
namespace Polynomial
section Semiring
variable [Semiring R] [Semiring S]
/-- `scaleRoots p s` is a polynomial with root `r * s` for each root `r` of `p`. -/
noncomputable def scaleRoots (p : R[X]) (s : R) : R[X] :=
∑ i ∈ p.support, monomial i (p.coeff i * s ^ (p.natDegree - i))
@[simp]
theorem coeff_scaleRoots (p : R[X]) (s : R) (i : ℕ) :
(scaleRoots p s).coeff i = coeff p i * s ^ (p.natDegree - i) := by
simp +contextual [scaleRoots, coeff_monomial]
theorem coeff_scaleRoots_natDegree (p : R[X]) (s : R) :
(scaleRoots p s).coeff p.natDegree = p.leadingCoeff := by
rw [leadingCoeff, coeff_scaleRoots, tsub_self, pow_zero, mul_one]
@[simp]
theorem zero_scaleRoots (s : R) : scaleRoots 0 s = 0 := by
ext
simp
theorem scaleRoots_ne_zero {p : R[X]} (hp : p ≠ 0) (s : R) : scaleRoots p s ≠ 0 := by
intro h
have : p.coeff p.natDegree ≠ 0 := mt leadingCoeff_eq_zero.mp hp
have : (scaleRoots p s).coeff p.natDegree = 0 :=
congr_fun (congr_arg (coeff : R[X] → ℕ → R) h) p.natDegree
rw [coeff_scaleRoots_natDegree] at this
contradiction
theorem support_scaleRoots_le (p : R[X]) (s : R) : (scaleRoots p s).support ≤ p.support := by
intro
simpa using left_ne_zero_of_mul
theorem support_scaleRoots_eq (p : R[X]) {s : R} (hs : s ∈ nonZeroDivisors R) :
(scaleRoots p s).support = p.support :=
le_antisymm (support_scaleRoots_le p s)
(by intro i
simp only [coeff_scaleRoots, Polynomial.mem_support_iff]
intro p_ne_zero ps_zero
have := pow_mem hs (p.natDegree - i) _ ps_zero
contradiction)
@[simp]
theorem degree_scaleRoots (p : R[X]) {s : R} : degree (scaleRoots p s) = degree p := by
haveI := Classical.propDecidable
by_cases hp : p = 0
· rw [hp, zero_scaleRoots]
refine le_antisymm (Finset.sup_mono (support_scaleRoots_le p s)) (degree_le_degree ?_)
rw [coeff_scaleRoots_natDegree]
intro h
have := leadingCoeff_eq_zero.mp h
contradiction
@[simp]
theorem natDegree_scaleRoots (p : R[X]) (s : R) : natDegree (scaleRoots p s) = natDegree p := by
simp only [natDegree, degree_scaleRoots]
theorem monic_scaleRoots_iff {p : R[X]} (s : R) : Monic (scaleRoots p s) ↔ Monic p := by
simp only [Monic, leadingCoeff, natDegree_scaleRoots, coeff_scaleRoots_natDegree]
theorem map_scaleRoots (p : R[X]) (x : R) (f : R →+* S) (h : f p.leadingCoeff ≠ 0) :
(p.scaleRoots x).map f = (p.map f).scaleRoots (f x) := by
ext
simp [Polynomial.natDegree_map_of_leadingCoeff_ne_zero _ h]
@[simp]
lemma scaleRoots_C (r c : R) : (C c).scaleRoots r = C c := by
ext; simp
@[simp]
lemma scaleRoots_one (p : R[X]) :
p.scaleRoots 1 = p := by ext; simp
@[simp]
lemma scaleRoots_zero (p : R[X]) :
p.scaleRoots 0 = p.leadingCoeff • X ^ p.natDegree := by
ext n
simp only [coeff_scaleRoots, ne_eq, tsub_eq_zero_iff_le, not_le, zero_pow_eq, mul_ite,
mul_one, mul_zero, coeff_smul, coeff_X_pow, smul_eq_mul]
split_ifs with h₁ h₂ h₂
· subst h₂; rfl
· exact coeff_eq_zero_of_natDegree_lt (lt_of_le_of_ne h₁ (Ne.symm h₂))
· exact (h₁ h₂.ge).elim
· rfl
@[simp]
lemma one_scaleRoots (r : R) :
(1 : R[X]).scaleRoots r = 1 := by ext; simp
end Semiring
section CommSemiring
variable [Semiring S] [CommSemiring R] [Semiring A] [Field K]
theorem scaleRoots_eval₂_mul_of_commute {p : S[X]} (f : S →+* A) (a : A) (s : S)
(hsa : Commute (f s) a) (hf : ∀ s₁ s₂, Commute (f s₁) (f s₂)) :
eval₂ f (f s * a) (scaleRoots p s) = f s ^ p.natDegree * eval₂ f a p := by
calc
_ = (scaleRoots p s).support.sum fun i =>
f (coeff p i * s ^ (p.natDegree - i)) * (f s * a) ^ i := by
simp [eval₂_eq_sum, sum_def]
_ = p.support.sum fun i => f (coeff p i * s ^ (p.natDegree - i)) * (f s * a) ^ i :=
(Finset.sum_subset (support_scaleRoots_le p s) fun i _hi hi' => by
let this : coeff p i * s ^ (p.natDegree - i) = 0 := by simpa using hi'
simp [this])
_ = p.support.sum fun i : ℕ => f (p.coeff i) * f s ^ (p.natDegree - i + i) * a ^ i :=
(Finset.sum_congr rfl fun i _hi => by
simp_rw [f.map_mul, f.map_pow, pow_add, hsa.mul_pow, mul_assoc])
_ = p.support.sum fun i : ℕ => f s ^ p.natDegree * (f (p.coeff i) * a ^ i) :=
Finset.sum_congr rfl fun i hi => by
rw [mul_assoc, ← map_pow, (hf _ _).left_comm, map_pow, tsub_add_cancel_of_le]
exact le_natDegree_of_ne_zero (Polynomial.mem_support_iff.mp hi)
_ = f s ^ p.natDegree * eval₂ f a p := by simp [← Finset.mul_sum, eval₂_eq_sum, sum_def]
theorem scaleRoots_eval₂_mul {p : S[X]} (f : S →+* R) (r : R) (s : S) :
eval₂ f (f s * r) (scaleRoots p s) = f s ^ p.natDegree * eval₂ f r p :=
scaleRoots_eval₂_mul_of_commute f r s (mul_comm _ _) fun _ _ ↦ mul_comm _ _
theorem scaleRoots_eval₂_eq_zero {p : S[X]} (f : S →+* R) {r : R} {s : S} (hr : eval₂ f r p = 0) :
eval₂ f (f s * r) (scaleRoots p s) = 0 := by rw [scaleRoots_eval₂_mul, hr, mul_zero]
theorem scaleRoots_aeval_eq_zero [Algebra R A] {p : R[X]} {a : A} {r : R} (ha : aeval a p = 0) :
aeval (algebraMap R A r * a) (scaleRoots p r) = 0 := by
rw [aeval_def, scaleRoots_eval₂_mul_of_commute, ← aeval_def, ha, mul_zero]
· apply Algebra.commutes
· intros; rw [Commute, SemiconjBy, ← map_mul, ← map_mul, mul_comm]
theorem scaleRoots_eval₂_eq_zero_of_eval₂_div_eq_zero {p : S[X]} {f : S →+* K}
(hf : Function.Injective f) {r s : S} (hr : eval₂ f (f r / f s) p = 0)
(hs : s ∈ nonZeroDivisors S) : eval₂ f (f r) (scaleRoots p s) = 0 := by
-- if we don't specify the type with `(_ : S)`, the proof is much slower
nontriviality S using Subsingleton.eq_zero (_ : S)
convert @scaleRoots_eval₂_eq_zero _ _ _ _ p f _ s hr
rw [← mul_div_assoc, mul_comm, mul_div_cancel_right₀]
exact map_ne_zero_of_mem_nonZeroDivisors _ hf hs
theorem scaleRoots_aeval_eq_zero_of_aeval_div_eq_zero [Algebra R K]
(inj : Function.Injective (algebraMap R K)) {p : R[X]} {r s : R}
(hr : aeval (algebraMap R K r / algebraMap R K s) p = 0) (hs : s ∈ nonZeroDivisors R) :
aeval (algebraMap R K r) (scaleRoots p s) = 0 :=
scaleRoots_eval₂_eq_zero_of_eval₂_div_eq_zero inj hr hs
@[simp]
lemma scaleRoots_mul (p : R[X]) (r s) :
p.scaleRoots (r * s) = (p.scaleRoots r).scaleRoots s := by
ext; simp [mul_pow, mul_assoc]
/-- Multiplication and `scaleRoots` commute up to a power of `r`. The factor disappears if we
assume that the product of the leading coeffs does not vanish. See `Polynomial.mul_scaleRoots'`. -/
lemma mul_scaleRoots (p q : R[X]) (r : R) :
r ^ (natDegree p + natDegree q - natDegree (p * q)) • (p * q).scaleRoots r =
p.scaleRoots r * q.scaleRoots r := by
ext n; simp only [coeff_scaleRoots, coeff_smul, smul_eq_mul]
trans (∑ x ∈ Finset.antidiagonal n, coeff p x.1 * coeff q x.2) *
r ^ (natDegree p + natDegree q - n)
· rw [← coeff_mul]
cases lt_or_le (natDegree (p * q)) n with
| inl h => simp only [coeff_eq_zero_of_natDegree_lt h, zero_mul, mul_zero]
| inr h =>
rw [mul_comm, mul_assoc, ← pow_add, add_comm, tsub_add_tsub_cancel natDegree_mul_le h]
· rw [coeff_mul, Finset.sum_mul]
apply Finset.sum_congr rfl
simp only [Finset.mem_antidiagonal, coeff_scaleRoots, Prod.forall]
intros a b e
cases lt_or_le (natDegree p) a with
| inl h => simp only [coeff_eq_zero_of_natDegree_lt h, zero_mul, mul_zero]
| inr ha =>
cases lt_or_le (natDegree q) b with
| inl h => simp only [coeff_eq_zero_of_natDegree_lt h, zero_mul, mul_zero]
| inr hb =>
simp only [← e, mul_assoc, mul_comm (r ^ (_ - a)), ← pow_add]
rw [add_comm (_ - _), tsub_add_tsub_comm ha hb]
lemma mul_scaleRoots' (p q : R[X]) (r : R) (h : leadingCoeff p * leadingCoeff q ≠ 0) :
(p * q).scaleRoots r = p.scaleRoots r * q.scaleRoots r := by
rw [← mul_scaleRoots, natDegree_mul' h, tsub_self, pow_zero, one_smul]
lemma mul_scaleRoots_of_noZeroDivisors (p q : R[X]) (r : R) [NoZeroDivisors R] :
(p * q).scaleRoots r = p.scaleRoots r * q.scaleRoots r := by
by_cases hp : p = 0; · simp [hp]
by_cases hq : q = 0; · simp [hq]
apply mul_scaleRoots'
simp only [ne_eq, mul_eq_zero, leadingCoeff_eq_zero, hp, hq, or_self, not_false_eq_true]
lemma add_scaleRoots_of_natDegree_eq (p q : R[X]) (r : R) (h : natDegree p = natDegree q) :
r ^ (natDegree p - natDegree (p + q)) • (p + q).scaleRoots r =
p.scaleRoots r + q.scaleRoots r := by
ext n; simp only [coeff_smul, coeff_scaleRoots, coeff_add, smul_eq_mul,
mul_comm (r ^ _), ← pow_add, ← h, ← add_mul, add_comm (_ - n)]
#adaptation_note /-- v4.7.0-rc1
Previously `mul_assoc` was part of the `simp only` above, and this `rw` was not needed.
but this now causes a max rec depth error. -/
rw [mul_assoc, ← pow_add]
cases lt_or_le (natDegree (p + q)) n with
| inl hn => simp only [← coeff_add, coeff_eq_zero_of_natDegree_lt hn, zero_mul]
| inr hn =>
rw [add_comm (_ - n), tsub_add_tsub_cancel (natDegree_add_le_of_degree_le le_rfl h.ge) hn]
lemma scaleRoots_dvd' (p q : R[X]) {r : R} (hr : IsUnit r)
(hpq : p ∣ q) : p.scaleRoots r ∣ q.scaleRoots r := by
obtain ⟨a, rfl⟩ := hpq
rw [← ((hr.pow (natDegree p + natDegree a - natDegree (p * a))).map
(algebraMap R R[X])).dvd_mul_left, ← Algebra.smul_def, mul_scaleRoots]
exact dvd_mul_right (scaleRoots p r) (scaleRoots a r)
lemma scaleRoots_dvd (p q : R[X]) {r : R} [NoZeroDivisors R] (hpq : p ∣ q) :
p.scaleRoots r ∣ q.scaleRoots r := by
obtain ⟨a, rfl⟩ := hpq
rw [mul_scaleRoots_of_noZeroDivisors]
exact dvd_mul_right (scaleRoots p r) (scaleRoots a r)
alias _root_.Dvd.dvd.scaleRoots := scaleRoots_dvd
lemma scaleRoots_dvd_iff (p q : R[X]) {r : R} (hr : IsUnit r) :
p.scaleRoots r ∣ q.scaleRoots r ↔ p ∣ q := by
refine ⟨?_ ∘ scaleRoots_dvd' _ _ (hr.unit⁻¹).isUnit, scaleRoots_dvd' p q hr⟩
simp [← scaleRoots_mul, scaleRoots_one]
alias _root_.IsUnit.scaleRoots_dvd_iff := scaleRoots_dvd_iff
lemma isCoprime_scaleRoots (p q : R[X]) (r : R) (hr : IsUnit r) (h : IsCoprime p q) :
| IsCoprime (p.scaleRoots r) (q.scaleRoots r) := by
obtain ⟨a, b, e⟩ := h
let s : R := ↑hr.unit⁻¹
have : natDegree (a * p) = natDegree (b * q) := by
apply natDegree_eq_of_natDegree_add_eq_zero
rw [e, natDegree_one]
| Mathlib/RingTheory/Polynomial/ScaleRoots.lean | 244 | 249 |
/-
Copyright (c) 2014 Parikshit Khanna. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Parikshit Khanna, Jeremy Avigad, Leonardo de Moura, Floris van Doorn, Mario Carneiro
-/
import Mathlib.Control.Basic
import Mathlib.Data.Nat.Basic
import Mathlib.Data.Option.Basic
import Mathlib.Data.List.Defs
import Mathlib.Data.List.Monad
import Mathlib.Logic.OpClass
import Mathlib.Logic.Unique
import Mathlib.Order.Basic
import Mathlib.Tactic.Common
/-!
# Basic properties of lists
-/
assert_not_exists GroupWithZero
assert_not_exists Lattice
assert_not_exists Prod.swap_eq_iff_eq_swap
assert_not_exists Ring
assert_not_exists Set.range
open Function
open Nat hiding one_pos
namespace List
universe u v w
variable {ι : Type*} {α : Type u} {β : Type v} {γ : Type w} {l₁ l₂ : List α}
/-- There is only one list of an empty type -/
instance uniqueOfIsEmpty [IsEmpty α] : Unique (List α) :=
{ instInhabitedList with
uniq := fun l =>
match l with
| [] => rfl
| a :: _ => isEmptyElim a }
instance : Std.LawfulIdentity (α := List α) Append.append [] where
left_id := nil_append
right_id := append_nil
instance : Std.Associative (α := List α) Append.append where
assoc := append_assoc
@[simp] theorem cons_injective {a : α} : Injective (cons a) := fun _ _ => tail_eq_of_cons_eq
theorem singleton_injective : Injective fun a : α => [a] := fun _ _ h => (cons_eq_cons.1 h).1
theorem set_of_mem_cons (l : List α) (a : α) : { x | x ∈ a :: l } = insert a { x | x ∈ l } :=
Set.ext fun _ => mem_cons
/-! ### mem -/
theorem _root_.Decidable.List.eq_or_ne_mem_of_mem [DecidableEq α]
{a b : α} {l : List α} (h : a ∈ b :: l) : a = b ∨ a ≠ b ∧ a ∈ l := by
by_cases hab : a = b
· exact Or.inl hab
· exact ((List.mem_cons.1 h).elim Or.inl (fun h => Or.inr ⟨hab, h⟩))
lemma mem_pair {a b c : α} : a ∈ [b, c] ↔ a = b ∨ a = c := by
rw [mem_cons, mem_singleton]
-- The simpNF linter says that the LHS can be simplified via `List.mem_map`.
-- However this is a higher priority lemma.
-- It seems the side condition `hf` is not applied by `simpNF`.
-- https://github.com/leanprover/std4/issues/207
@[simp 1100, nolint simpNF]
theorem mem_map_of_injective {f : α → β} (H : Injective f) {a : α} {l : List α} :
f a ∈ map f l ↔ a ∈ l :=
⟨fun m => let ⟨_, m', e⟩ := exists_of_mem_map m; H e ▸ m', mem_map_of_mem⟩
@[simp]
theorem _root_.Function.Involutive.exists_mem_and_apply_eq_iff {f : α → α}
(hf : Function.Involutive f) (x : α) (l : List α) : (∃ y : α, y ∈ l ∧ f y = x) ↔ f x ∈ l :=
⟨by rintro ⟨y, h, rfl⟩; rwa [hf y], fun h => ⟨f x, h, hf _⟩⟩
theorem mem_map_of_involutive {f : α → α} (hf : Involutive f) {a : α} {l : List α} :
a ∈ map f l ↔ f a ∈ l := by rw [mem_map, hf.exists_mem_and_apply_eq_iff]
/-! ### length -/
alias ⟨_, length_pos_of_ne_nil⟩ := length_pos_iff
theorem length_pos_iff_ne_nil {l : List α} : 0 < length l ↔ l ≠ [] :=
⟨ne_nil_of_length_pos, length_pos_of_ne_nil⟩
theorem exists_of_length_succ {n} : ∀ l : List α, l.length = n + 1 → ∃ h t, l = h :: t
| [], H => absurd H.symm <| succ_ne_zero n
| h :: t, _ => ⟨h, t, rfl⟩
@[simp] lemma length_injective_iff : Injective (List.length : List α → ℕ) ↔ Subsingleton α := by
constructor
· intro h; refine ⟨fun x y => ?_⟩; (suffices [x] = [y] by simpa using this); apply h; rfl
· intros hα l1 l2 hl
induction l1 generalizing l2 <;> cases l2
· rfl
· cases hl
· cases hl
· next ih _ _ =>
congr
· subsingleton
· apply ih; simpa using hl
@[simp default+1] -- Raise priority above `length_injective_iff`.
lemma length_injective [Subsingleton α] : Injective (length : List α → ℕ) :=
length_injective_iff.mpr inferInstance
theorem length_eq_two {l : List α} : l.length = 2 ↔ ∃ a b, l = [a, b] :=
⟨fun _ => let [a, b] := l; ⟨a, b, rfl⟩, fun ⟨_, _, e⟩ => e ▸ rfl⟩
theorem length_eq_three {l : List α} : l.length = 3 ↔ ∃ a b c, l = [a, b, c] :=
⟨fun _ => let [a, b, c] := l; ⟨a, b, c, rfl⟩, fun ⟨_, _, _, e⟩ => e ▸ rfl⟩
/-! ### set-theoretic notation of lists -/
instance instSingletonList : Singleton α (List α) := ⟨fun x => [x]⟩
instance [DecidableEq α] : Insert α (List α) := ⟨List.insert⟩
instance [DecidableEq α] : LawfulSingleton α (List α) :=
{ insert_empty_eq := fun x =>
show (if x ∈ ([] : List α) then [] else [x]) = [x] from if_neg not_mem_nil }
theorem singleton_eq (x : α) : ({x} : List α) = [x] :=
rfl
theorem insert_neg [DecidableEq α] {x : α} {l : List α} (h : x ∉ l) :
Insert.insert x l = x :: l :=
insert_of_not_mem h
theorem insert_pos [DecidableEq α] {x : α} {l : List α} (h : x ∈ l) : Insert.insert x l = l :=
insert_of_mem h
theorem doubleton_eq [DecidableEq α] {x y : α} (h : x ≠ y) : ({x, y} : List α) = [x, y] := by
rw [insert_neg, singleton_eq]
rwa [singleton_eq, mem_singleton]
/-! ### bounded quantifiers over lists -/
theorem forall_mem_of_forall_mem_cons {p : α → Prop} {a : α} {l : List α} (h : ∀ x ∈ a :: l, p x) :
∀ x ∈ l, p x := (forall_mem_cons.1 h).2
theorem exists_mem_cons_of {p : α → Prop} {a : α} (l : List α) (h : p a) : ∃ x ∈ a :: l, p x :=
⟨a, mem_cons_self, h⟩
theorem exists_mem_cons_of_exists {p : α → Prop} {a : α} {l : List α} : (∃ x ∈ l, p x) →
∃ x ∈ a :: l, p x :=
fun ⟨x, xl, px⟩ => ⟨x, mem_cons_of_mem _ xl, px⟩
theorem or_exists_of_exists_mem_cons {p : α → Prop} {a : α} {l : List α} : (∃ x ∈ a :: l, p x) →
p a ∨ ∃ x ∈ l, p x :=
fun ⟨x, xal, px⟩ =>
Or.elim (eq_or_mem_of_mem_cons xal) (fun h : x = a => by rw [← h]; left; exact px)
fun h : x ∈ l => Or.inr ⟨x, h, px⟩
theorem exists_mem_cons_iff (p : α → Prop) (a : α) (l : List α) :
(∃ x ∈ a :: l, p x) ↔ p a ∨ ∃ x ∈ l, p x :=
Iff.intro or_exists_of_exists_mem_cons fun h =>
Or.elim h (exists_mem_cons_of l) exists_mem_cons_of_exists
/-! ### list subset -/
theorem cons_subset_of_subset_of_mem {a : α} {l m : List α}
(ainm : a ∈ m) (lsubm : l ⊆ m) : a::l ⊆ m :=
cons_subset.2 ⟨ainm, lsubm⟩
theorem append_subset_of_subset_of_subset {l₁ l₂ l : List α} (l₁subl : l₁ ⊆ l) (l₂subl : l₂ ⊆ l) :
l₁ ++ l₂ ⊆ l :=
fun _ h ↦ (mem_append.1 h).elim (@l₁subl _) (@l₂subl _)
theorem map_subset_iff {l₁ l₂ : List α} (f : α → β) (h : Injective f) :
map f l₁ ⊆ map f l₂ ↔ l₁ ⊆ l₂ := by
refine ⟨?_, map_subset f⟩; intro h2 x hx
rcases mem_map.1 (h2 (mem_map_of_mem hx)) with ⟨x', hx', hxx'⟩
cases h hxx'; exact hx'
/-! ### append -/
theorem append_eq_has_append {L₁ L₂ : List α} : List.append L₁ L₂ = L₁ ++ L₂ :=
rfl
theorem append_right_injective (s : List α) : Injective fun t ↦ s ++ t :=
fun _ _ ↦ append_cancel_left
theorem append_left_injective (t : List α) : Injective fun s ↦ s ++ t :=
fun _ _ ↦ append_cancel_right
/-! ### replicate -/
theorem eq_replicate_length {a : α} : ∀ {l : List α}, l = replicate l.length a ↔ ∀ b ∈ l, b = a
| [] => by simp
| (b :: l) => by simp [eq_replicate_length, replicate_succ]
theorem replicate_add (m n) (a : α) : replicate (m + n) a = replicate m a ++ replicate n a := by
rw [replicate_append_replicate]
theorem replicate_subset_singleton (n) (a : α) : replicate n a ⊆ [a] := fun _ h =>
mem_singleton.2 (eq_of_mem_replicate h)
theorem subset_singleton_iff {a : α} {L : List α} : L ⊆ [a] ↔ ∃ n, L = replicate n a := by
simp only [eq_replicate_iff, subset_def, mem_singleton, exists_eq_left']
theorem replicate_right_injective {n : ℕ} (hn : n ≠ 0) : Injective (@replicate α n) :=
fun _ _ h => (eq_replicate_iff.1 h).2 _ <| mem_replicate.2 ⟨hn, rfl⟩
theorem replicate_right_inj {a b : α} {n : ℕ} (hn : n ≠ 0) :
replicate n a = replicate n b ↔ a = b :=
(replicate_right_injective hn).eq_iff
theorem replicate_right_inj' {a b : α} : ∀ {n},
replicate n a = replicate n b ↔ n = 0 ∨ a = b
| 0 => by simp
| n + 1 => (replicate_right_inj n.succ_ne_zero).trans <| by simp only [n.succ_ne_zero, false_or]
theorem replicate_left_injective (a : α) : Injective (replicate · a) :=
LeftInverse.injective (length_replicate (n := ·))
theorem replicate_left_inj {a : α} {n m : ℕ} : replicate n a = replicate m a ↔ n = m :=
(replicate_left_injective a).eq_iff
@[simp]
theorem head?_flatten_replicate {n : ℕ} (h : n ≠ 0) (l : List α) :
(List.replicate n l).flatten.head? = l.head? := by
obtain ⟨n, rfl⟩ := Nat.exists_eq_succ_of_ne_zero h
induction l <;> simp [replicate]
@[simp]
theorem getLast?_flatten_replicate {n : ℕ} (h : n ≠ 0) (l : List α) :
(List.replicate n l).flatten.getLast? = l.getLast? := by
rw [← List.head?_reverse, ← List.head?_reverse, List.reverse_flatten, List.map_replicate,
List.reverse_replicate, head?_flatten_replicate h]
/-! ### pure -/
theorem mem_pure (x y : α) : x ∈ (pure y : List α) ↔ x = y := by simp
/-! ### bind -/
@[simp]
theorem bind_eq_flatMap {α β} (f : α → List β) (l : List α) : l >>= f = l.flatMap f :=
rfl
/-! ### concat -/
/-! ### reverse -/
theorem reverse_cons' (a : α) (l : List α) : reverse (a :: l) = concat (reverse l) a := by
simp only [reverse_cons, concat_eq_append]
theorem reverse_concat' (l : List α) (a : α) : (l ++ [a]).reverse = a :: l.reverse := by
rw [reverse_append]; rfl
@[simp]
theorem reverse_singleton (a : α) : reverse [a] = [a] :=
rfl
@[simp]
theorem reverse_involutive : Involutive (@reverse α) :=
reverse_reverse
@[simp]
theorem reverse_injective : Injective (@reverse α) :=
reverse_involutive.injective
theorem reverse_surjective : Surjective (@reverse α) :=
reverse_involutive.surjective
theorem reverse_bijective : Bijective (@reverse α) :=
reverse_involutive.bijective
theorem concat_eq_reverse_cons (a : α) (l : List α) : concat l a = reverse (a :: reverse l) := by
simp only [concat_eq_append, reverse_cons, reverse_reverse]
theorem map_reverseAux (f : α → β) (l₁ l₂ : List α) :
map f (reverseAux l₁ l₂) = reverseAux (map f l₁) (map f l₂) := by
simp only [reverseAux_eq, map_append, map_reverse]
-- TODO: Rename `List.reverse_perm` to `List.reverse_perm_self`
@[simp] lemma reverse_perm' : l₁.reverse ~ l₂ ↔ l₁ ~ l₂ where
mp := l₁.reverse_perm.symm.trans
mpr := l₁.reverse_perm.trans
@[simp] lemma perm_reverse : l₁ ~ l₂.reverse ↔ l₁ ~ l₂ where
mp hl := hl.trans l₂.reverse_perm
mpr hl := hl.trans l₂.reverse_perm.symm
/-! ### getLast -/
attribute [simp] getLast_cons
theorem getLast_append_singleton {a : α} (l : List α) :
getLast (l ++ [a]) (append_ne_nil_of_right_ne_nil l (cons_ne_nil a _)) = a := by
simp [getLast_append]
theorem getLast_append_of_right_ne_nil (l₁ l₂ : List α) (h : l₂ ≠ []) :
getLast (l₁ ++ l₂) (append_ne_nil_of_right_ne_nil l₁ h) = getLast l₂ h := by
induction l₁ with
| nil => simp
| cons _ _ ih => simp only [cons_append]; rw [List.getLast_cons]; exact ih
@[deprecated (since := "2025-02-06")]
alias getLast_append' := getLast_append_of_right_ne_nil
theorem getLast_concat' {a : α} (l : List α) : getLast (concat l a) (by simp) = a := by
simp
@[simp]
theorem getLast_singleton' (a : α) : getLast [a] (cons_ne_nil a []) = a := rfl
@[simp]
theorem getLast_cons_cons (a₁ a₂ : α) (l : List α) :
getLast (a₁ :: a₂ :: l) (cons_ne_nil _ _) = getLast (a₂ :: l) (cons_ne_nil a₂ l) :=
rfl
theorem dropLast_append_getLast : ∀ {l : List α} (h : l ≠ []), dropLast l ++ [getLast l h] = l
| [], h => absurd rfl h
| [_], _ => rfl
| a :: b :: l, h => by
rw [dropLast_cons₂, cons_append, getLast_cons (cons_ne_nil _ _)]
congr
exact dropLast_append_getLast (cons_ne_nil b l)
theorem getLast_congr {l₁ l₂ : List α} (h₁ : l₁ ≠ []) (h₂ : l₂ ≠ []) (h₃ : l₁ = l₂) :
getLast l₁ h₁ = getLast l₂ h₂ := by subst l₁; rfl
theorem getLast_replicate_succ (m : ℕ) (a : α) :
(replicate (m + 1) a).getLast (ne_nil_of_length_eq_add_one length_replicate) = a := by
simp only [replicate_succ']
exact getLast_append_singleton _
@[deprecated (since := "2025-02-07")]
alias getLast_filter' := getLast_filter_of_pos
/-! ### getLast? -/
theorem mem_getLast?_eq_getLast : ∀ {l : List α} {x : α}, x ∈ l.getLast? → ∃ h, x = getLast l h
| [], x, hx => False.elim <| by simp at hx
| [a], x, hx =>
have : a = x := by simpa using hx
this ▸ ⟨cons_ne_nil a [], rfl⟩
| a :: b :: l, x, hx => by
rw [getLast?_cons_cons] at hx
rcases mem_getLast?_eq_getLast hx with ⟨_, h₂⟩
use cons_ne_nil _ _
assumption
theorem getLast?_eq_getLast_of_ne_nil : ∀ {l : List α} (h : l ≠ []), l.getLast? = some (l.getLast h)
| [], h => (h rfl).elim
| [_], _ => rfl
| _ :: b :: l, _ => @getLast?_eq_getLast_of_ne_nil (b :: l) (cons_ne_nil _ _)
theorem mem_getLast?_cons {x y : α} : ∀ {l : List α}, x ∈ l.getLast? → x ∈ (y :: l).getLast?
| [], _ => by contradiction
| _ :: _, h => h
theorem dropLast_append_getLast? : ∀ {l : List α}, ∀ a ∈ l.getLast?, dropLast l ++ [a] = l
| [], a, ha => (Option.not_mem_none a ha).elim
| [a], _, rfl => rfl
| a :: b :: l, c, hc => by
rw [getLast?_cons_cons] at hc
rw [dropLast_cons₂, cons_append, dropLast_append_getLast? _ hc]
theorem getLastI_eq_getLast? [Inhabited α] : ∀ l : List α, l.getLastI = l.getLast?.iget
| [] => by simp [getLastI, Inhabited.default]
| [_] => rfl
| [_, _] => rfl
| [_, _, _] => rfl
| _ :: _ :: c :: l => by simp [getLastI, getLastI_eq_getLast? (c :: l)]
theorem getLast?_append_cons :
∀ (l₁ : List α) (a : α) (l₂ : List α), getLast? (l₁ ++ a :: l₂) = getLast? (a :: l₂)
| [], _, _ => rfl
| [_], _, _ => rfl
| b :: c :: l₁, a, l₂ => by rw [cons_append, cons_append, getLast?_cons_cons,
← cons_append, getLast?_append_cons (c :: l₁)]
theorem getLast?_append_of_ne_nil (l₁ : List α) :
∀ {l₂ : List α} (_ : l₂ ≠ []), getLast? (l₁ ++ l₂) = getLast? l₂
| [], hl₂ => by contradiction
| b :: l₂, _ => getLast?_append_cons l₁ b l₂
theorem mem_getLast?_append_of_mem_getLast? {l₁ l₂ : List α} {x : α} (h : x ∈ l₂.getLast?) :
x ∈ (l₁ ++ l₂).getLast? := by
cases l₂
· contradiction
· rw [List.getLast?_append_cons]
exact h
/-! ### head(!?) and tail -/
@[simp]
theorem head!_nil [Inhabited α] : ([] : List α).head! = default := rfl
@[simp] theorem head_cons_tail (x : List α) (h : x ≠ []) : x.head h :: x.tail = x := by
cases x <;> simp at h ⊢
theorem head_eq_getElem_zero {l : List α} (hl : l ≠ []) :
l.head hl = l[0]'(length_pos_iff.2 hl) :=
(getElem_zero _).symm
theorem head!_eq_head? [Inhabited α] (l : List α) : head! l = (head? l).iget := by cases l <;> rfl
theorem surjective_head! [Inhabited α] : Surjective (@head! α _) := fun x => ⟨[x], rfl⟩
theorem surjective_head? : Surjective (@head? α) :=
Option.forall.2 ⟨⟨[], rfl⟩, fun x => ⟨[x], rfl⟩⟩
theorem surjective_tail : Surjective (@tail α)
| [] => ⟨[], rfl⟩
| a :: l => ⟨a :: a :: l, rfl⟩
theorem eq_cons_of_mem_head? {x : α} : ∀ {l : List α}, x ∈ l.head? → l = x :: tail l
| [], h => (Option.not_mem_none _ h).elim
| a :: l, h => by
simp only [head?, Option.mem_def, Option.some_inj] at h
exact h ▸ rfl
@[simp] theorem head!_cons [Inhabited α] (a : α) (l : List α) : head! (a :: l) = a := rfl
@[simp]
theorem head!_append [Inhabited α] (t : List α) {s : List α} (h : s ≠ []) :
head! (s ++ t) = head! s := by
induction s
· contradiction
· rfl
theorem mem_head?_append_of_mem_head? {s t : List α} {x : α} (h : x ∈ s.head?) :
x ∈ (s ++ t).head? := by
cases s
· contradiction
· exact h
theorem head?_append_of_ne_nil :
∀ (l₁ : List α) {l₂ : List α} (_ : l₁ ≠ []), head? (l₁ ++ l₂) = head? l₁
| _ :: _, _, _ => rfl
theorem tail_append_singleton_of_ne_nil {a : α} {l : List α} (h : l ≠ nil) :
tail (l ++ [a]) = tail l ++ [a] := by
induction l
· contradiction
· rw [tail, cons_append, tail]
theorem cons_head?_tail : ∀ {l : List α} {a : α}, a ∈ head? l → a :: tail l = l
| [], a, h => by contradiction
| b :: l, a, h => by
simp? at h says simp only [head?_cons, Option.mem_def, Option.some.injEq] at h
simp [h]
theorem head!_mem_head? [Inhabited α] : ∀ {l : List α}, l ≠ [] → head! l ∈ head? l
| [], h => by contradiction
| _ :: _, _ => rfl
theorem cons_head!_tail [Inhabited α] {l : List α} (h : l ≠ []) : head! l :: tail l = l :=
cons_head?_tail (head!_mem_head? h)
theorem head!_mem_self [Inhabited α] {l : List α} (h : l ≠ nil) : l.head! ∈ l := by
have h' : l.head! ∈ l.head! :: l.tail := mem_cons_self
rwa [cons_head!_tail h] at h'
theorem get_eq_getElem? (l : List α) (i : Fin l.length) :
l.get i = l[i]?.get (by simp [getElem?_eq_getElem]) := by
simp
@[deprecated (since := "2025-02-15")] alias get_eq_get? := get_eq_getElem?
theorem exists_mem_iff_getElem {l : List α} {p : α → Prop} :
(∃ x ∈ l, p x) ↔ ∃ (i : ℕ) (_ : i < l.length), p l[i] := by
simp only [mem_iff_getElem]
exact ⟨fun ⟨_x, ⟨i, hi, hix⟩, hxp⟩ ↦ ⟨i, hi, hix ▸ hxp⟩, fun ⟨i, hi, hp⟩ ↦ ⟨_, ⟨i, hi, rfl⟩, hp⟩⟩
theorem forall_mem_iff_getElem {l : List α} {p : α → Prop} :
(∀ x ∈ l, p x) ↔ ∀ (i : ℕ) (_ : i < l.length), p l[i] := by
simp [mem_iff_getElem, @forall_swap α]
theorem get_tail (l : List α) (i) (h : i < l.tail.length)
(h' : i + 1 < l.length := (by simp only [length_tail] at h; omega)) :
l.tail.get ⟨i, h⟩ = l.get ⟨i + 1, h'⟩ := by
cases l <;> [cases h; rfl]
/-! ### sublists -/
attribute [refl] List.Sublist.refl
theorem Sublist.cons_cons {l₁ l₂ : List α} (a : α) (s : l₁ <+ l₂) : a :: l₁ <+ a :: l₂ :=
Sublist.cons₂ _ s
lemma cons_sublist_cons' {a b : α} : a :: l₁ <+ b :: l₂ ↔ a :: l₁ <+ l₂ ∨ a = b ∧ l₁ <+ l₂ := by
constructor
· rintro (_ | _)
· exact Or.inl ‹_›
· exact Or.inr ⟨rfl, ‹_›⟩
· rintro (h | ⟨rfl, h⟩)
· exact h.cons _
· rwa [cons_sublist_cons]
theorem sublist_cons_of_sublist (a : α) (h : l₁ <+ l₂) : l₁ <+ a :: l₂ := h.cons _
@[deprecated (since := "2025-02-07")]
alias sublist_nil_iff_eq_nil := sublist_nil
@[simp] lemma sublist_singleton {l : List α} {a : α} : l <+ [a] ↔ l = [] ∨ l = [a] := by
constructor <;> rintro (_ | _) <;> aesop
theorem Sublist.antisymm (s₁ : l₁ <+ l₂) (s₂ : l₂ <+ l₁) : l₁ = l₂ :=
s₁.eq_of_length_le s₂.length_le
/-- If the first element of two lists are different, then a sublist relation can be reduced. -/
theorem Sublist.of_cons_of_ne {a b} (h₁ : a ≠ b) (h₂ : a :: l₁ <+ b :: l₂) : a :: l₁ <+ l₂ :=
match h₁, h₂ with
| _, .cons _ h => h
/-! ### indexOf -/
section IndexOf
variable [DecidableEq α]
theorem idxOf_cons_eq {a b : α} (l : List α) : b = a → idxOf a (b :: l) = 0
| e => by rw [← e]; exact idxOf_cons_self
@[deprecated (since := "2025-01-30")] alias indexOf_cons_eq := idxOf_cons_eq
@[simp]
theorem idxOf_cons_ne {a b : α} (l : List α) : b ≠ a → idxOf a (b :: l) = succ (idxOf a l)
| h => by simp only [idxOf_cons, Bool.cond_eq_ite, beq_iff_eq, if_neg h]
@[deprecated (since := "2025-01-30")] alias indexOf_cons_ne := idxOf_cons_ne
theorem idxOf_eq_length_iff {a : α} {l : List α} : idxOf a l = length l ↔ a ∉ l := by
induction l with
| nil => exact iff_of_true rfl not_mem_nil
| cons b l ih =>
simp only [length, mem_cons, idxOf_cons, eq_comm]
rw [cond_eq_if]
split_ifs with h <;> simp at h
· exact iff_of_false (by rintro ⟨⟩) fun H => H <| Or.inl h.symm
· simp only [Ne.symm h, false_or]
rw [← ih]
exact succ_inj
@[simp]
theorem idxOf_of_not_mem {l : List α} {a : α} : a ∉ l → idxOf a l = length l :=
idxOf_eq_length_iff.2
@[deprecated (since := "2025-01-30")] alias indexOf_of_not_mem := idxOf_of_not_mem
theorem idxOf_le_length {a : α} {l : List α} : idxOf a l ≤ length l := by
induction l with | nil => rfl | cons b l ih => ?_
simp only [length, idxOf_cons, cond_eq_if, beq_iff_eq]
by_cases h : b = a
· rw [if_pos h]; exact Nat.zero_le _
· rw [if_neg h]; exact succ_le_succ ih
@[deprecated (since := "2025-01-30")] alias indexOf_le_length := idxOf_le_length
theorem idxOf_lt_length_iff {a} {l : List α} : idxOf a l < length l ↔ a ∈ l :=
⟨fun h => Decidable.byContradiction fun al => Nat.ne_of_lt h <| idxOf_eq_length_iff.2 al,
fun al => (lt_of_le_of_ne idxOf_le_length) fun h => idxOf_eq_length_iff.1 h al⟩
@[deprecated (since := "2025-01-30")] alias indexOf_lt_length_iff := idxOf_lt_length_iff
theorem idxOf_append_of_mem {a : α} (h : a ∈ l₁) : idxOf a (l₁ ++ l₂) = idxOf a l₁ := by
induction l₁ with
| nil =>
exfalso
exact not_mem_nil h
| cons d₁ t₁ ih =>
rw [List.cons_append]
by_cases hh : d₁ = a
· iterate 2 rw [idxOf_cons_eq _ hh]
rw [idxOf_cons_ne _ hh, idxOf_cons_ne _ hh, ih (mem_of_ne_of_mem (Ne.symm hh) h)]
@[deprecated (since := "2025-01-30")] alias indexOf_append_of_mem := idxOf_append_of_mem
theorem idxOf_append_of_not_mem {a : α} (h : a ∉ l₁) :
idxOf a (l₁ ++ l₂) = l₁.length + idxOf a l₂ := by
induction l₁ with
| nil => rw [List.nil_append, List.length, Nat.zero_add]
| cons d₁ t₁ ih =>
rw [List.cons_append, idxOf_cons_ne _ (ne_of_not_mem_cons h).symm, List.length,
ih (not_mem_of_not_mem_cons h), Nat.succ_add]
@[deprecated (since := "2025-01-30")] alias indexOf_append_of_not_mem := idxOf_append_of_not_mem
end IndexOf
/-! ### nth element -/
section deprecated
@[simp]
theorem getElem?_length (l : List α) : l[l.length]? = none := getElem?_eq_none le_rfl
/-- A version of `getElem_map` that can be used for rewriting. -/
theorem getElem_map_rev (f : α → β) {l} {n : Nat} {h : n < l.length} :
f l[n] = (map f l)[n]'((l.length_map f).symm ▸ h) := Eq.symm (getElem_map _)
theorem get_length_sub_one {l : List α} (h : l.length - 1 < l.length) :
l.get ⟨l.length - 1, h⟩ = l.getLast (by rintro rfl; exact Nat.lt_irrefl 0 h) :=
(getLast_eq_getElem _).symm
|
theorem take_one_drop_eq_of_lt_length {l : List α} {n : ℕ} (h : n < l.length) :
(l.drop n).take 1 = [l.get ⟨n, h⟩] := by
rw [drop_eq_getElem_cons h, take, take]
simp
theorem ext_getElem?' {l₁ l₂ : List α} (h' : ∀ n < max l₁.length l₂.length, l₁[n]? = l₂[n]?) :
| Mathlib/Data/List/Basic.lean | 608 | 614 |
/-
Copyright (c) 2022 Andrew Yang. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Andrew Yang
-/
import Mathlib.CategoryTheory.Comma.Arrow
import Mathlib.Order.CompleteBooleanAlgebra
/-!
# Properties of morphisms
We provide the basic framework for talking about properties of morphisms.
The following meta-property is defined
* `RespectsLeft P Q`: `P` respects the property `Q` on the left if `P f → P (i ≫ f)` where
`i` satisfies `Q`.
* `RespectsRight P Q`: `P` respects the property `Q` on the right if `P f → P (f ≫ i)` where
`i` satisfies `Q`.
* `Respects`: `P` respects `Q` if `P` respects `Q` both on the left and on the right.
-/
universe w v v' u u'
open CategoryTheory Opposite
noncomputable section
namespace CategoryTheory
variable (C : Type u) [Category.{v} C] {D : Type*} [Category D]
/-- A `MorphismProperty C` is a class of morphisms between objects in `C`. -/
def MorphismProperty :=
∀ ⦃X Y : C⦄ (_ : X ⟶ Y), Prop
instance : CompleteBooleanAlgebra (MorphismProperty C) where
le P₁ P₂ := ∀ ⦃X Y : C⦄ (f : X ⟶ Y), P₁ f → P₂ f
__ := inferInstanceAs (CompleteBooleanAlgebra (∀ ⦃X Y : C⦄ (_ : X ⟶ Y), Prop))
lemma MorphismProperty.le_def {P Q : MorphismProperty C} :
P ≤ Q ↔ ∀ {X Y : C} (f : X ⟶ Y), P f → Q f := Iff.rfl
instance : Inhabited (MorphismProperty C) :=
⟨⊤⟩
lemma MorphismProperty.top_eq : (⊤ : MorphismProperty C) = fun _ _ _ => True := rfl
variable {C}
namespace MorphismProperty
@[ext]
lemma ext (W W' : MorphismProperty C) (h : ∀ ⦃X Y : C⦄ (f : X ⟶ Y), W f ↔ W' f) :
W = W' := by
funext X Y f
rw [h]
@[simp]
lemma top_apply {X Y : C} (f : X ⟶ Y) : (⊤ : MorphismProperty C) f := by
simp only [top_eq]
lemma of_eq_top {P : MorphismProperty C} (h : P = ⊤) {X Y : C} (f : X ⟶ Y) : P f := by
simp [h]
@[simp]
lemma sSup_iff (S : Set (MorphismProperty C)) {X Y : C} (f : X ⟶ Y) :
sSup S f ↔ ∃ (W : S), W.1 f := by
dsimp [sSup, iSup]
constructor
· rintro ⟨_, ⟨⟨_, ⟨⟨_, ⟨_, h⟩, rfl⟩, rfl⟩⟩, rfl⟩, hf⟩
exact ⟨⟨_, h⟩, hf⟩
· rintro ⟨⟨W, hW⟩, hf⟩
exact ⟨_, ⟨⟨_, ⟨_, ⟨⟨W, hW⟩, rfl⟩⟩, rfl⟩, rfl⟩, hf⟩
@[simp]
lemma iSup_iff {ι : Sort*} (W : ι → MorphismProperty C) {X Y : C} (f : X ⟶ Y) :
iSup W f ↔ ∃ i, W i f := by
apply (sSup_iff (Set.range W) f).trans
constructor
· rintro ⟨⟨_, i, rfl⟩, hf⟩
exact ⟨i, hf⟩
· rintro ⟨i, hf⟩
exact ⟨⟨_, i, rfl⟩, hf⟩
/-- The morphism property in `Cᵒᵖ` associated to a morphism property in `C` -/
@[simp]
def op (P : MorphismProperty C) : MorphismProperty Cᵒᵖ := fun _ _ f => P f.unop
/-- The morphism property in `C` associated to a morphism property in `Cᵒᵖ` -/
@[simp]
def unop (P : MorphismProperty Cᵒᵖ) : MorphismProperty C := fun _ _ f => P f.op
theorem unop_op (P : MorphismProperty C) : P.op.unop = P :=
rfl
theorem op_unop (P : MorphismProperty Cᵒᵖ) : P.unop.op = P :=
rfl
/-- The inverse image of a `MorphismProperty D` by a functor `C ⥤ D` -/
def inverseImage (P : MorphismProperty D) (F : C ⥤ D) : MorphismProperty C := fun _ _ f =>
P (F.map f)
@[simp]
lemma inverseImage_iff (P : MorphismProperty D) (F : C ⥤ D) {X Y : C} (f : X ⟶ Y) :
P.inverseImage F f ↔ P (F.map f) := by rfl
/-- The image (up to isomorphisms) of a `MorphismProperty C` by a functor `C ⥤ D` -/
def map (P : MorphismProperty C) (F : C ⥤ D) : MorphismProperty D := fun _ _ f =>
∃ (X' Y' : C) (f' : X' ⟶ Y') (_ : P f'), Nonempty (Arrow.mk (F.map f') ≅ Arrow.mk f)
lemma map_mem_map (P : MorphismProperty C) (F : C ⥤ D) {X Y : C} (f : X ⟶ Y) (hf : P f) :
(P.map F) (F.map f) := ⟨X, Y, f, hf, ⟨Iso.refl _⟩⟩
lemma monotone_map (F : C ⥤ D) :
Monotone (map · F) := by
intro P Q h X Y f ⟨X', Y', f', hf', ⟨e⟩⟩
exact ⟨X', Y', f', h _ hf', ⟨e⟩⟩
section
variable (P : MorphismProperty C)
/-- The set in `Set (Arrow C)` which corresponds to `P : MorphismProperty C`. -/
def toSet : Set (Arrow C) := setOf (fun f ↦ P f.hom)
/-- The family of morphisms indexed by `P.toSet` which corresponds
to `P : MorphismProperty C`, see `MorphismProperty.ofHoms_homFamily`. -/
def homFamily (f : P.toSet) : f.1.left ⟶ f.1.right := f.1.hom
lemma homFamily_apply (f : P.toSet) : P.homFamily f = f.1.hom := rfl
@[simp]
lemma homFamily_arrow_mk {X Y : C} (f : X ⟶ Y) (hf : P f) :
P.homFamily ⟨Arrow.mk f, hf⟩ = f := rfl
@[simp]
lemma arrow_mk_mem_toSet_iff {X Y : C} (f : X ⟶ Y) : Arrow.mk f ∈ P.toSet ↔ P f := Iff.rfl
lemma of_eq {X Y : C} {f : X ⟶ Y} (hf : P f)
{X' Y' : C} {f' : X' ⟶ Y'}
(hX : X = X') (hY : Y = Y') (h : f' = eqToHom hX.symm ≫ f ≫ eqToHom hY) :
P f' := by
rw [← P.arrow_mk_mem_toSet_iff] at hf ⊢
rwa [(Arrow.mk_eq_mk_iff f' f).2 ⟨hX.symm, hY.symm, h⟩]
end
/-- The class of morphisms given by a family of morphisms `f i : X i ⟶ Y i`. -/
inductive ofHoms {ι : Type*} {X Y : ι → C} (f : ∀ i, X i ⟶ Y i) : MorphismProperty C
| mk (i : ι) : ofHoms f (f i)
lemma ofHoms_iff {ι : Type*} {X Y : ι → C} (f : ∀ i, X i ⟶ Y i) {A B : C} (g : A ⟶ B) :
ofHoms f g ↔ ∃ i, Arrow.mk g = Arrow.mk (f i) := by
constructor
· rintro ⟨i⟩
exact ⟨i, rfl⟩
· rintro ⟨i, h⟩
rw [← (ofHoms f).arrow_mk_mem_toSet_iff, h, arrow_mk_mem_toSet_iff]
constructor
@[simp]
lemma ofHoms_homFamily (P : MorphismProperty C) : ofHoms P.homFamily = P := by
ext _ _ f
constructor
· intro hf
rw [ofHoms_iff] at hf
obtain ⟨⟨f, hf⟩, ⟨_, _⟩⟩ := hf
exact hf
· intro hf
exact ⟨(⟨f, hf⟩ : P.toSet)⟩
/-- A morphism property `P` satisfies `P.RespectsRight Q` if it is stable under post-composition
with morphisms satisfying `Q`, i.e. whenever `P` holds for `f` and `Q` holds for `i` then `P`
holds for `f ≫ i`. -/
class RespectsRight (P Q : MorphismProperty C) : Prop where
postcomp {X Y Z : C} (i : Y ⟶ Z) (hi : Q i) (f : X ⟶ Y) (hf : P f) : P (f ≫ i)
/-- A morphism property `P` satisfies `P.RespectsLeft Q` if it is stable under
pre-composition with morphisms satisfying `Q`, i.e. whenever `P` holds for `f`
and `Q` holds for `i` then `P` holds for `i ≫ f`. -/
class RespectsLeft (P Q : MorphismProperty C) : Prop where
precomp {X Y Z : C} (i : X ⟶ Y) (hi : Q i) (f : Y ⟶ Z) (hf : P f) : P (i ≫ f)
/-- A morphism property `P` satisfies `P.Respects Q` if it is stable under composition on the
left and right by morphisms satisfying `Q`. -/
class Respects (P Q : MorphismProperty C) : Prop extends P.RespectsLeft Q, P.RespectsRight Q where
instance (P Q : MorphismProperty C) [P.RespectsLeft Q] [P.RespectsRight Q] : P.Respects Q where
instance (P Q : MorphismProperty C) [P.RespectsLeft Q] : P.op.RespectsRight Q.op where
postcomp i hi f hf := RespectsLeft.precomp (Q := Q) i.unop hi f.unop hf
instance (P Q : MorphismProperty C) [P.RespectsRight Q] : P.op.RespectsLeft Q.op where
precomp i hi f hf := RespectsRight.postcomp (Q := Q) i.unop hi f.unop hf
| instance RespectsLeft.inf (P₁ P₂ Q : MorphismProperty C) [P₁.RespectsLeft Q]
[P₂.RespectsLeft Q] : (P₁ ⊓ P₂).RespectsLeft Q where
precomp i hi f hf := ⟨precomp i hi f hf.left, precomp i hi f hf.right⟩
instance RespectsRight.inf (P₁ P₂ Q : MorphismProperty C) [P₁.RespectsRight Q]
[P₂.RespectsRight Q] : (P₁ ⊓ P₂).RespectsRight Q where
postcomp i hi f hf := ⟨postcomp i hi f hf.left, postcomp i hi f hf.right⟩
| Mathlib/CategoryTheory/MorphismProperty/Basic.lean | 198 | 205 |
/-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Johannes Hölzl, Kim Morrison, Jens Wagemaker
-/
import Mathlib.Algebra.MonoidAlgebra.Degree
import Mathlib.Algebra.Order.Ring.WithTop
import Mathlib.Algebra.Polynomial.Basic
import Mathlib.Data.Nat.Cast.WithTop
import Mathlib.Data.Nat.SuccPred
import Mathlib.Order.SuccPred.WithBot
/-!
# Degree of univariate polynomials
## Main definitions
* `Polynomial.degree`: the degree of a polynomial, where `0` has degree `⊥`
* `Polynomial.natDegree`: the degree of a polynomial, where `0` has degree `0`
* `Polynomial.leadingCoeff`: the leading coefficient of a polynomial
* `Polynomial.Monic`: a polynomial is monic if its leading coefficient is 0
* `Polynomial.nextCoeff`: the next coefficient after the leading coefficient
## Main results
* `Polynomial.degree_eq_natDegree`: the degree and natDegree coincide for nonzero polynomials
-/
noncomputable section
open Finsupp Finset
open Polynomial
namespace Polynomial
universe u v
variable {R : Type u} {S : Type v} {a b c d : R} {n m : ℕ}
section Semiring
variable [Semiring R] {p q r : R[X]}
/-- `degree p` is the degree of the polynomial `p`, i.e. the largest `X`-exponent in `p`.
`degree p = some n` when `p ≠ 0` and `n` is the highest power of `X` that appears in `p`, otherwise
`degree 0 = ⊥`. -/
def degree (p : R[X]) : WithBot ℕ :=
p.support.max
/-- `natDegree p` forces `degree p` to ℕ, by defining `natDegree 0 = 0`. -/
def natDegree (p : R[X]) : ℕ :=
(degree p).unbotD 0
/-- `leadingCoeff p` gives the coefficient of the highest power of `X` in `p`. -/
def leadingCoeff (p : R[X]) : R :=
coeff p (natDegree p)
/-- a polynomial is `Monic` if its leading coefficient is 1 -/
def Monic (p : R[X]) :=
leadingCoeff p = (1 : R)
theorem Monic.def : Monic p ↔ leadingCoeff p = 1 :=
Iff.rfl
instance Monic.decidable [DecidableEq R] : Decidable (Monic p) := by unfold Monic; infer_instance
@[simp]
theorem Monic.leadingCoeff {p : R[X]} (hp : p.Monic) : leadingCoeff p = 1 :=
hp
theorem Monic.coeff_natDegree {p : R[X]} (hp : p.Monic) : p.coeff p.natDegree = 1 :=
hp
@[simp]
theorem degree_zero : degree (0 : R[X]) = ⊥ :=
rfl
@[simp]
theorem natDegree_zero : natDegree (0 : R[X]) = 0 :=
rfl
@[simp]
theorem coeff_natDegree : coeff p (natDegree p) = leadingCoeff p :=
rfl
@[simp]
theorem degree_eq_bot : degree p = ⊥ ↔ p = 0 :=
⟨fun h => support_eq_empty.1 (Finset.max_eq_bot.1 h), fun h => h.symm ▸ rfl⟩
theorem degree_ne_bot : degree p ≠ ⊥ ↔ p ≠ 0 := degree_eq_bot.not
theorem degree_eq_natDegree (hp : p ≠ 0) : degree p = (natDegree p : WithBot ℕ) := by
let ⟨n, hn⟩ := not_forall.1 (mt Option.eq_none_iff_forall_not_mem.2 (mt degree_eq_bot.1 hp))
have hn : degree p = some n := Classical.not_not.1 hn
rw [natDegree, hn]; rfl
theorem degree_eq_iff_natDegree_eq {p : R[X]} {n : ℕ} (hp : p ≠ 0) :
p.degree = n ↔ p.natDegree = n := by rw [degree_eq_natDegree hp]; exact WithBot.coe_eq_coe
theorem degree_eq_iff_natDegree_eq_of_pos {p : R[X]} {n : ℕ} (hn : 0 < n) :
p.degree = n ↔ p.natDegree = n := by
obtain rfl|h := eq_or_ne p 0
· simp [hn.ne]
· exact degree_eq_iff_natDegree_eq h
theorem natDegree_eq_of_degree_eq_some {p : R[X]} {n : ℕ} (h : degree p = n) : natDegree p = n := by
rw [natDegree, h, Nat.cast_withBot, WithBot.unbotD_coe]
theorem degree_ne_of_natDegree_ne {n : ℕ} : p.natDegree ≠ n → degree p ≠ n :=
mt natDegree_eq_of_degree_eq_some
@[simp]
theorem degree_le_natDegree : degree p ≤ natDegree p :=
WithBot.giUnbotDBot.gc.le_u_l _
theorem natDegree_eq_of_degree_eq [Semiring S] {q : S[X]} (h : degree p = degree q) :
natDegree p = natDegree q := by unfold natDegree; rw [h]
theorem le_degree_of_ne_zero (h : coeff p n ≠ 0) : (n : WithBot ℕ) ≤ degree p := by
rw [Nat.cast_withBot]
exact Finset.le_sup (mem_support_iff.2 h)
theorem degree_mono [Semiring S] {f : R[X]} {g : S[X]} (h : f.support ⊆ g.support) :
f.degree ≤ g.degree :=
Finset.sup_mono h
theorem degree_le_degree (h : coeff q (natDegree p) ≠ 0) : degree p ≤ degree q := by
by_cases hp : p = 0
· rw [hp, degree_zero]
exact bot_le
· rw [degree_eq_natDegree hp]
exact le_degree_of_ne_zero h
theorem natDegree_le_iff_degree_le {n : ℕ} : natDegree p ≤ n ↔ degree p ≤ n :=
WithBot.unbotD_le_iff (fun _ ↦ bot_le)
theorem natDegree_lt_iff_degree_lt (hp : p ≠ 0) : p.natDegree < n ↔ p.degree < ↑n :=
WithBot.unbotD_lt_iff (absurd · (degree_eq_bot.not.mpr hp))
alias ⟨degree_le_of_natDegree_le, natDegree_le_of_degree_le⟩ := natDegree_le_iff_degree_le
theorem natDegree_le_natDegree [Semiring S] {q : S[X]} (hpq : p.degree ≤ q.degree) :
p.natDegree ≤ q.natDegree :=
WithBot.giUnbotDBot.gc.monotone_l hpq
@[simp]
theorem degree_C (ha : a ≠ 0) : degree (C a) = (0 : WithBot ℕ) := by
rw [degree, ← monomial_zero_left, support_monomial 0 ha, max_eq_sup_coe, sup_singleton,
WithBot.coe_zero]
theorem degree_C_le : degree (C a) ≤ 0 := by
by_cases h : a = 0
· rw [h, C_0]
exact bot_le
· rw [degree_C h]
theorem degree_C_lt : degree (C a) < 1 :=
degree_C_le.trans_lt <| WithBot.coe_lt_coe.mpr zero_lt_one
theorem degree_one_le : degree (1 : R[X]) ≤ (0 : WithBot ℕ) := by rw [← C_1]; exact degree_C_le
@[simp]
theorem natDegree_C (a : R) : natDegree (C a) = 0 := by
by_cases ha : a = 0
· have : C a = 0 := by rw [ha, C_0]
rw [natDegree, degree_eq_bot.2 this, WithBot.unbotD_bot]
· rw [natDegree, degree_C ha, WithBot.unbotD_zero]
@[simp]
theorem natDegree_one : natDegree (1 : R[X]) = 0 :=
natDegree_C 1
@[simp]
theorem natDegree_natCast (n : ℕ) : natDegree (n : R[X]) = 0 := by
simp only [← C_eq_natCast, natDegree_C]
@[simp]
theorem natDegree_ofNat (n : ℕ) [Nat.AtLeastTwo n] :
natDegree (ofNat(n) : R[X]) = 0 :=
natDegree_natCast _
theorem degree_natCast_le (n : ℕ) : degree (n : R[X]) ≤ 0 := degree_le_of_natDegree_le (by simp)
@[simp]
theorem degree_monomial (n : ℕ) (ha : a ≠ 0) : degree (monomial n a) = n := by
rw [degree, support_monomial n ha, max_singleton, Nat.cast_withBot]
@[simp]
theorem degree_C_mul_X_pow (n : ℕ) (ha : a ≠ 0) : degree (C a * X ^ n) = n := by
rw [C_mul_X_pow_eq_monomial, degree_monomial n ha]
theorem degree_C_mul_X (ha : a ≠ 0) : degree (C a * X) = 1 := by
simpa only [pow_one] using degree_C_mul_X_pow 1 ha
theorem degree_monomial_le (n : ℕ) (a : R) : degree (monomial n a) ≤ n :=
letI := Classical.decEq R
if h : a = 0 then by rw [h, (monomial n).map_zero, degree_zero]; exact bot_le
else le_of_eq (degree_monomial n h)
theorem degree_C_mul_X_pow_le (n : ℕ) (a : R) : degree (C a * X ^ n) ≤ n := by
rw [C_mul_X_pow_eq_monomial]
apply degree_monomial_le
theorem degree_C_mul_X_le (a : R) : degree (C a * X) ≤ 1 := by
simpa only [pow_one] using degree_C_mul_X_pow_le 1 a
@[simp]
theorem natDegree_C_mul_X_pow (n : ℕ) (a : R) (ha : a ≠ 0) : natDegree (C a * X ^ n) = n :=
natDegree_eq_of_degree_eq_some (degree_C_mul_X_pow n ha)
@[simp]
theorem natDegree_C_mul_X (a : R) (ha : a ≠ 0) : natDegree (C a * X) = 1 := by
simpa only [pow_one] using natDegree_C_mul_X_pow 1 a ha
@[simp]
theorem natDegree_monomial [DecidableEq R] (i : ℕ) (r : R) :
natDegree (monomial i r) = if r = 0 then 0 else i := by
split_ifs with hr
· simp [hr]
· rw [← C_mul_X_pow_eq_monomial, natDegree_C_mul_X_pow i r hr]
theorem natDegree_monomial_le (a : R) {m : ℕ} : (monomial m a).natDegree ≤ m := by
classical
rw [Polynomial.natDegree_monomial]
split_ifs
exacts [Nat.zero_le _, le_rfl]
theorem natDegree_monomial_eq (i : ℕ) {r : R} (r0 : r ≠ 0) : (monomial i r).natDegree = i :=
letI := Classical.decEq R
Eq.trans (natDegree_monomial _ _) (if_neg r0)
theorem coeff_ne_zero_of_eq_degree (hn : degree p = n) : coeff p n ≠ 0 := fun h =>
mem_support_iff.mp (mem_of_max hn) h
theorem degree_X_pow_le (n : ℕ) : degree (X ^ n : R[X]) ≤ n := by
simpa only [C_1, one_mul] using degree_C_mul_X_pow_le n (1 : R)
theorem degree_X_le : degree (X : R[X]) ≤ 1 :=
degree_monomial_le _ _
theorem natDegree_X_le : (X : R[X]).natDegree ≤ 1 :=
natDegree_le_of_degree_le degree_X_le
theorem withBotSucc_degree_eq_natDegree_add_one (h : p ≠ 0) : p.degree.succ = p.natDegree + 1 := by
rw [degree_eq_natDegree h]
exact WithBot.succ_coe p.natDegree
end Semiring
section NonzeroSemiring
variable [Semiring R] [Nontrivial R] {p q : R[X]}
@[simp]
theorem degree_one : degree (1 : R[X]) = (0 : WithBot ℕ) :=
degree_C one_ne_zero
@[simp]
theorem degree_X : degree (X : R[X]) = 1 :=
degree_monomial _ one_ne_zero
@[simp]
theorem natDegree_X : (X : R[X]).natDegree = 1 :=
natDegree_eq_of_degree_eq_some degree_X
end NonzeroSemiring
section Ring
variable [Ring R]
@[simp]
theorem degree_neg (p : R[X]) : degree (-p) = degree p := by unfold degree; rw [support_neg]
theorem degree_neg_le_of_le {a : WithBot ℕ} {p : R[X]} (hp : degree p ≤ a) : degree (-p) ≤ a :=
p.degree_neg.le.trans hp
@[simp]
theorem natDegree_neg (p : R[X]) : natDegree (-p) = natDegree p := by simp [natDegree]
theorem natDegree_neg_le_of_le {p : R[X]} (hp : natDegree p ≤ m) : natDegree (-p) ≤ m :=
(natDegree_neg p).le.trans hp
@[simp]
theorem natDegree_intCast (n : ℤ) : natDegree (n : R[X]) = 0 := by
rw [← C_eq_intCast, natDegree_C]
theorem degree_intCast_le (n : ℤ) : degree (n : R[X]) ≤ 0 := degree_le_of_natDegree_le (by simp)
@[simp]
theorem leadingCoeff_neg (p : R[X]) : (-p).leadingCoeff = -p.leadingCoeff := by
rw [leadingCoeff, leadingCoeff, natDegree_neg, coeff_neg]
end Ring
section Semiring
variable [Semiring R] {p : R[X]}
/-- The second-highest coefficient, or 0 for constants -/
def nextCoeff (p : R[X]) : R :=
if p.natDegree = 0 then 0 else p.coeff (p.natDegree - 1)
lemma nextCoeff_eq_zero :
p.nextCoeff = 0 ↔ p.natDegree = 0 ∨ 0 < p.natDegree ∧ p.coeff (p.natDegree - 1) = 0 := by
simp [nextCoeff, or_iff_not_imp_left, pos_iff_ne_zero]; aesop
lemma nextCoeff_ne_zero : p.nextCoeff ≠ 0 ↔ p.natDegree ≠ 0 ∧ p.coeff (p.natDegree - 1) ≠ 0 := by
simp [nextCoeff]
@[simp]
theorem nextCoeff_C_eq_zero (c : R) : nextCoeff (C c) = 0 := by
rw [nextCoeff]
simp
theorem nextCoeff_of_natDegree_pos (hp : 0 < p.natDegree) :
nextCoeff p = p.coeff (p.natDegree - 1) := by
rw [nextCoeff, if_neg]
contrapose! hp
simpa
variable {p q : R[X]} {ι : Type*}
theorem degree_add_le (p q : R[X]) : degree (p + q) ≤ max (degree p) (degree q) := by
simpa only [degree, ← support_toFinsupp, toFinsupp_add]
using AddMonoidAlgebra.sup_support_add_le _ _ _
theorem degree_add_le_of_degree_le {p q : R[X]} {n : ℕ} (hp : degree p ≤ n) (hq : degree q ≤ n) :
degree (p + q) ≤ n :=
(degree_add_le p q).trans <| max_le hp hq
theorem degree_add_le_of_le {a b : WithBot ℕ} (hp : degree p ≤ a) (hq : degree q ≤ b) :
degree (p + q) ≤ max a b :=
(p.degree_add_le q).trans <| max_le_max ‹_› ‹_›
theorem natDegree_add_le (p q : R[X]) : natDegree (p + q) ≤ max (natDegree p) (natDegree q) := by
rcases le_max_iff.1 (degree_add_le p q) with h | h <;> simp [natDegree_le_natDegree h]
theorem natDegree_add_le_of_degree_le {p q : R[X]} {n : ℕ} (hp : natDegree p ≤ n)
(hq : natDegree q ≤ n) : natDegree (p + q) ≤ n :=
(natDegree_add_le p q).trans <| max_le hp hq
theorem natDegree_add_le_of_le (hp : natDegree p ≤ m) (hq : natDegree q ≤ n) :
natDegree (p + q) ≤ max m n :=
(p.natDegree_add_le q).trans <| max_le_max ‹_› ‹_›
@[simp]
theorem leadingCoeff_zero : leadingCoeff (0 : R[X]) = 0 :=
rfl
@[simp]
theorem leadingCoeff_eq_zero : leadingCoeff p = 0 ↔ p = 0 :=
⟨fun h =>
Classical.by_contradiction fun hp =>
mt mem_support_iff.1 (Classical.not_not.2 h) (mem_of_max (degree_eq_natDegree hp)),
fun h => h.symm ▸ leadingCoeff_zero⟩
theorem leadingCoeff_ne_zero : leadingCoeff p ≠ 0 ↔ p ≠ 0 := by rw [Ne, leadingCoeff_eq_zero]
theorem leadingCoeff_eq_zero_iff_deg_eq_bot : leadingCoeff p = 0 ↔ degree p = ⊥ := by
rw [leadingCoeff_eq_zero, degree_eq_bot]
theorem natDegree_C_mul_X_pow_le (a : R) (n : ℕ) : natDegree (C a * X ^ n) ≤ n :=
natDegree_le_iff_degree_le.2 <| degree_C_mul_X_pow_le _ _
theorem degree_erase_le (p : R[X]) (n : ℕ) : degree (p.erase n) ≤ degree p := by
rcases p with ⟨p⟩
simp only [erase_def, degree, coeff, support]
apply sup_mono
rw [Finsupp.support_erase]
apply Finset.erase_subset
theorem degree_erase_lt (hp : p ≠ 0) : degree (p.erase (natDegree p)) < degree p := by
apply lt_of_le_of_ne (degree_erase_le _ _)
rw [degree_eq_natDegree hp, degree, support_erase]
exact fun h => not_mem_erase _ _ (mem_of_max h)
theorem degree_update_le (p : R[X]) (n : ℕ) (a : R) : degree (p.update n a) ≤ max (degree p) n := by
classical
rw [degree, support_update]
split_ifs
· exact (Finset.max_mono (erase_subset _ _)).trans (le_max_left _ _)
· rw [max_insert, max_comm]
exact le_rfl
theorem degree_sum_le (s : Finset ι) (f : ι → R[X]) :
degree (∑ i ∈ s, f i) ≤ s.sup fun b => degree (f b) :=
Finset.cons_induction_on s (by simp only [sum_empty, sup_empty, degree_zero, le_refl])
fun a s has ih =>
calc
degree (∑ i ∈ cons a s has, f i) ≤ max (degree (f a)) (degree (∑ i ∈ s, f i)) := by
rw [Finset.sum_cons]; exact degree_add_le _ _
_ ≤ _ := by rw [sup_cons]; exact max_le_max le_rfl ih
theorem degree_mul_le (p q : R[X]) : degree (p * q) ≤ degree p + degree q := by
simpa only [degree, ← support_toFinsupp, toFinsupp_mul]
using AddMonoidAlgebra.sup_support_mul_le (WithBot.coe_add _ _).le _ _
theorem degree_mul_le_of_le {a b : WithBot ℕ} (hp : degree p ≤ a) (hq : degree q ≤ b) :
degree (p * q) ≤ a + b :=
(p.degree_mul_le _).trans <| add_le_add ‹_› ‹_›
theorem degree_pow_le (p : R[X]) : ∀ n : ℕ, degree (p ^ n) ≤ n • degree p
| 0 => by rw [pow_zero, zero_nsmul]; exact degree_one_le
| n + 1 =>
calc
degree (p ^ (n + 1)) ≤ degree (p ^ n) + degree p := by
rw [pow_succ]; exact degree_mul_le _ _
_ ≤ _ := by rw [succ_nsmul]; exact add_le_add_right (degree_pow_le _ _) _
theorem degree_pow_le_of_le {a : WithBot ℕ} (b : ℕ) (hp : degree p ≤ a) :
degree (p ^ b) ≤ b * a := by
induction b with
| zero => simp [degree_one_le]
| succ n hn =>
rw [Nat.cast_succ, add_mul, one_mul, pow_succ]
exact degree_mul_le_of_le hn hp
@[simp]
theorem leadingCoeff_monomial (a : R) (n : ℕ) : leadingCoeff (monomial n a) = a := by
classical
by_cases ha : a = 0
· simp only [ha, (monomial n).map_zero, leadingCoeff_zero]
· rw [leadingCoeff, natDegree_monomial, if_neg ha, coeff_monomial]
simp
theorem leadingCoeff_C_mul_X_pow (a : R) (n : ℕ) : leadingCoeff (C a * X ^ n) = a := by
rw [C_mul_X_pow_eq_monomial, leadingCoeff_monomial]
theorem leadingCoeff_C_mul_X (a : R) : leadingCoeff (C a * X) = a := by
simpa only [pow_one] using leadingCoeff_C_mul_X_pow a 1
@[simp]
theorem leadingCoeff_C (a : R) : leadingCoeff (C a) = a :=
leadingCoeff_monomial a 0
theorem leadingCoeff_X_pow (n : ℕ) : leadingCoeff ((X : R[X]) ^ n) = 1 := by
simpa only [C_1, one_mul] using leadingCoeff_C_mul_X_pow (1 : R) n
theorem leadingCoeff_X : leadingCoeff (X : R[X]) = 1 := by
simpa only [pow_one] using @leadingCoeff_X_pow R _ 1
@[simp]
theorem monic_X_pow (n : ℕ) : Monic (X ^ n : R[X]) :=
leadingCoeff_X_pow n
@[simp]
theorem monic_X : Monic (X : R[X]) :=
leadingCoeff_X
theorem leadingCoeff_one : leadingCoeff (1 : R[X]) = 1 :=
leadingCoeff_C 1
@[simp]
theorem monic_one : Monic (1 : R[X]) :=
leadingCoeff_C _
theorem Monic.ne_zero {R : Type*} [Semiring R] [Nontrivial R] {p : R[X]} (hp : p.Monic) :
p ≠ 0 := by
rintro rfl
simp [Monic] at hp
theorem Monic.ne_zero_of_ne (h : (0 : R) ≠ 1) {p : R[X]} (hp : p.Monic) : p ≠ 0 := by
nontriviality R
exact hp.ne_zero
theorem Monic.ne_zero_of_polynomial_ne {r} (hp : Monic p) (hne : q ≠ r) : p ≠ 0 :=
haveI := Nontrivial.of_polynomial_ne hne
hp.ne_zero
theorem natDegree_mul_le {p q : R[X]} : natDegree (p * q) ≤ natDegree p + natDegree q := by
apply natDegree_le_of_degree_le
apply le_trans (degree_mul_le p q)
rw [Nat.cast_add]
apply add_le_add <;> apply degree_le_natDegree
theorem natDegree_mul_le_of_le (hp : natDegree p ≤ m) (hg : natDegree q ≤ n) :
natDegree (p * q) ≤ m + n :=
natDegree_mul_le.trans <| add_le_add ‹_› ‹_›
theorem natDegree_pow_le {p : R[X]} {n : ℕ} : (p ^ n).natDegree ≤ n * p.natDegree := by
induction n with
| zero => simp
| succ i hi =>
rw [pow_succ, Nat.succ_mul]
apply le_trans natDegree_mul_le (add_le_add_right hi _)
theorem natDegree_pow_le_of_le (n : ℕ) (hp : natDegree p ≤ m) :
natDegree (p ^ n) ≤ n * m :=
natDegree_pow_le.trans (Nat.mul_le_mul le_rfl ‹_›)
theorem natDegree_eq_zero_iff_degree_le_zero : p.natDegree = 0 ↔ p.degree ≤ 0 := by
rw [← nonpos_iff_eq_zero, natDegree_le_iff_degree_le, Nat.cast_zero]
theorem degree_zero_le : degree (0 : R[X]) ≤ 0 := natDegree_eq_zero_iff_degree_le_zero.mp rfl
theorem degree_le_iff_coeff_zero (f : R[X]) (n : WithBot ℕ) :
degree f ≤ n ↔ ∀ m : ℕ, n < m → coeff f m = 0 := by
simp only [degree, Finset.max, Finset.sup_le_iff, mem_support_iff, Ne, ← not_le,
not_imp_comm, Nat.cast_withBot]
theorem degree_lt_iff_coeff_zero (f : R[X]) (n : ℕ) :
degree f < n ↔ ∀ m : ℕ, n ≤ m → coeff f m = 0 := by
simp only [degree, Finset.sup_lt_iff (WithBot.bot_lt_coe n), mem_support_iff,
WithBot.coe_lt_coe, ← @not_le ℕ, max_eq_sup_coe, Nat.cast_withBot, Ne, not_imp_not]
theorem natDegree_pos_iff_degree_pos : 0 < natDegree p ↔ 0 < degree p :=
lt_iff_lt_of_le_iff_le natDegree_le_iff_degree_le
end Semiring
section NontrivialSemiring
variable [Semiring R] [Nontrivial R] {p q : R[X]} (n : ℕ)
@[simp]
theorem degree_X_pow : degree ((X : R[X]) ^ n) = n := by
rw [X_pow_eq_monomial, degree_monomial _ (one_ne_zero' R)]
@[simp]
theorem natDegree_X_pow : natDegree ((X : R[X]) ^ n) = n :=
natDegree_eq_of_degree_eq_some (degree_X_pow n)
end NontrivialSemiring
section Ring
variable [Ring R] {p q : R[X]}
theorem degree_sub_le (p q : R[X]) : degree (p - q) ≤ max (degree p) (degree q) := by
simpa only [degree_neg q] using degree_add_le p (-q)
theorem degree_sub_le_of_le {a b : WithBot ℕ} (hp : degree p ≤ a) (hq : degree q ≤ b) :
degree (p - q) ≤ max a b :=
(p.degree_sub_le q).trans <| max_le_max ‹_› ‹_›
theorem natDegree_sub_le (p q : R[X]) : natDegree (p - q) ≤ max (natDegree p) (natDegree q) := by
simpa only [← natDegree_neg q] using natDegree_add_le p (-q)
theorem natDegree_sub_le_of_le (hp : natDegree p ≤ m) (hq : natDegree q ≤ n) :
natDegree (p - q) ≤ max m n :=
(p.natDegree_sub_le q).trans <| max_le_max ‹_› ‹_›
theorem degree_sub_lt (hd : degree p = degree q) (hp0 : p ≠ 0)
(hlc : leadingCoeff p = leadingCoeff q) : degree (p - q) < degree p :=
have hp : monomial (natDegree p) (leadingCoeff p) + p.erase (natDegree p) = p :=
monomial_add_erase _ _
have hq : monomial (natDegree q) (leadingCoeff q) + q.erase (natDegree q) = q :=
monomial_add_erase _ _
have hd' : natDegree p = natDegree q := by unfold natDegree; rw [hd]
have hq0 : q ≠ 0 := mt degree_eq_bot.2 (hd ▸ mt degree_eq_bot.1 hp0)
calc
degree (p - q) = degree (erase (natDegree q) p + -erase (natDegree q) q) := by
conv =>
lhs
rw [← hp, ← hq, hlc, hd', add_sub_add_left_eq_sub, sub_eq_add_neg]
_ ≤ max (degree (erase (natDegree q) p)) (degree (erase (natDegree q) q)) :=
(degree_neg (erase (natDegree q) q) ▸ degree_add_le _ _)
_ < degree p := max_lt_iff.2 ⟨hd' ▸ degree_erase_lt hp0, hd.symm ▸ degree_erase_lt hq0⟩
theorem degree_X_sub_C_le (r : R) : (X - C r).degree ≤ 1 :=
(degree_sub_le _ _).trans (max_le degree_X_le (degree_C_le.trans zero_le_one))
theorem natDegree_X_sub_C_le (r : R) : (X - C r).natDegree ≤ 1 :=
natDegree_le_iff_degree_le.2 <| degree_X_sub_C_le r
end Ring
end Polynomial
| Mathlib/Algebra/Polynomial/Degree/Definitions.lean | 584 | 586 | |
/-
Copyright (c) 2020 Anne Baanen. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Anne Baanen, Yongle Hu
-/
import Mathlib.Algebra.Algebra.Tower
import Mathlib.Algebra.Group.Subgroup.Actions
import Mathlib.RingTheory.Ideal.Pointwise
import Mathlib.RingTheory.Ideal.Quotient.Operations
/-!
# Ideals over/under ideals
This file concerns ideals lying over other ideals.
Let `f : R →+* S` be a ring homomorphism (typically a ring extension), `I` an ideal of `R` and
`J` an ideal of `S`. We say `J` lies over `I` (and `I` under `J`) if `I` is the `f`-preimage of `J`.
This is expressed here by writing `I = J.comap f`.
-/
-- for going-up results about integral extensions, see `Mathlib.RingTheory.Ideal.GoingUp`
assert_not_exists Algebra.IsIntegral
-- for results about finiteness, see `Mathlib.RingTheory.Finiteness.Quotient`
assert_not_exists Module.Finite
variable {R : Type*} [CommRing R]
namespace Ideal
open Submodule
open scoped Pointwise
section CommRing
variable {S : Type*} [CommRing S] {f : R →+* S} {I J : Ideal S}
variable {p : Ideal R} {P : Ideal S}
/-- If there is an injective map `R/p → S/P` such that following diagram commutes:
```
R → S
↓ ↓
R/p → S/P
```
then `P` lies over `p`.
-/
theorem comap_eq_of_scalar_tower_quotient [Algebra R S] [Algebra (R ⧸ p) (S ⧸ P)]
[IsScalarTower R (R ⧸ p) (S ⧸ P)] (h : Function.Injective (algebraMap (R ⧸ p) (S ⧸ P))) :
comap (algebraMap R S) P = p := by
ext x
rw [mem_comap, ← Quotient.eq_zero_iff_mem, ← Quotient.eq_zero_iff_mem, Quotient.mk_algebraMap,
IsScalarTower.algebraMap_apply R (R ⧸ p) (S ⧸ P), Quotient.algebraMap_eq]
constructor
· intro hx
exact (injective_iff_map_eq_zero (algebraMap (R ⧸ p) (S ⧸ P))).mp h _ hx
· intro hx
rw [hx, RingHom.map_zero]
variable [Algebra R S]
/-- `R / p` has a canonical map to `S / pS`. -/
instance Quotient.algebraQuotientMapQuotient : Algebra (R ⧸ p) (S ⧸ map (algebraMap R S) p) :=
Ideal.Quotient.algebraQuotientOfLEComap le_comap_map
@[simp]
theorem Quotient.algebraMap_quotient_map_quotient (x : R) :
letI f := algebraMap R S
algebraMap (R ⧸ p) (S ⧸ map f p) (Ideal.Quotient.mk p x) =
Ideal.Quotient.mk (map f p) (f x) :=
rfl
@[simp]
theorem Quotient.mk_smul_mk_quotient_map_quotient (x : R) (y : S) :
letI f := algebraMap R S
Quotient.mk p x • Quotient.mk (map f p) y = Quotient.mk (map f p) (f x * y) :=
Algebra.smul_def _ _
instance Quotient.tower_quotient_map_quotient [Algebra R S] :
IsScalarTower R (R ⧸ p) (S ⧸ map (algebraMap R S) p) :=
IsScalarTower.of_algebraMap_eq fun x => by
rw [Quotient.algebraMap_eq, Quotient.algebraMap_quotient_map_quotient,
Quotient.mk_algebraMap]
end CommRing
section ideal_liesOver
section Semiring
variable (A : Type*) [CommSemiring A] {B C : Type*} [Semiring B] [Semiring C] [Algebra A B]
[Algebra A C] (P : Ideal B) {Q : Ideal C} (p : Ideal A)
/-- The ideal obtained by pulling back the ideal `P` from `B` to `A`. -/
abbrev under : Ideal A := Ideal.comap (algebraMap A B) P
theorem under_def : P.under A = Ideal.comap (algebraMap A B) P := rfl
instance IsPrime.under [hP : P.IsPrime] : (P.under A).IsPrime :=
hP.comap (algebraMap A B)
@[simp]
lemma under_smul {G : Type*} [Group G] [MulSemiringAction G B] [SMulCommClass G A B] (g : G) :
(g • P : Ideal B).under A = P.under A := by
ext a
rw [mem_comap, mem_comap, mem_pointwise_smul_iff_inv_smul_mem, smul_algebraMap]
variable (B) in
theorem under_top : under A (⊤ : Ideal B) = ⊤ := comap_top
variable {A}
/-- `P` lies over `p` if `p` is the preimage of `P` of the `algebraMap`. -/
class LiesOver : Prop where
over : p = P.under A
instance over_under : P.LiesOver (P.under A) where over := rfl
theorem over_def [P.LiesOver p] : p = P.under A := LiesOver.over
theorem mem_of_liesOver [P.LiesOver p] (x : A) : x ∈ p ↔ algebraMap A B x ∈ P := by
rw [P.over_def p]
rfl
variable (A B) in
instance top_liesOver_top : (⊤ : Ideal B).LiesOver (⊤ : Ideal A) where
over := (under_top A B).symm
theorem eq_top_iff_of_liesOver [P.LiesOver p] : P = ⊤ ↔ p = ⊤ := by
rw [P.over_def p]
exact comap_eq_top_iff.symm
variable {P}
theorem LiesOver.of_eq_comap [Q.LiesOver p] {F : Type*} [FunLike F B C]
[AlgHomClass F A B C] (f : F) (h : P = Q.comap f) : P.LiesOver p where
over := by
rw [h]
exact (over_def Q p).trans <|
congrFun (congrFun (congrArg comap ((f : B →ₐ[A] C).comp_algebraMap.symm)) _) Q
theorem LiesOver.of_eq_map_equiv [P.LiesOver p] {E : Type*} [EquivLike E B C]
[AlgEquivClass E A B C] (σ : E) (h : Q = P.map σ) : Q.LiesOver p := by
rw [← show _ = P.map σ from comap_symm (σ : B ≃+* C)] at h
exact of_eq_comap p (σ : B ≃ₐ[A] C).symm h
variable (P) (Q)
instance comap_liesOver [Q.LiesOver p] {F : Type*} [FunLike F B C] [AlgHomClass F A B C]
(f : F) : (Q.comap f).LiesOver p :=
LiesOver.of_eq_comap p f rfl
instance map_equiv_liesOver [P.LiesOver p] {E : Type*} [EquivLike E B C] [AlgEquivClass E A B C]
(σ : E) : (P.map σ).LiesOver p :=
LiesOver.of_eq_map_equiv p σ rfl
end Semiring
section CommSemiring
variable {A : Type*} [CommSemiring A] {B : Type*} [CommSemiring B] {C : Type*} [Semiring C]
[Algebra A B] [Algebra B C] [Algebra A C] [IsScalarTower A B C]
(𝔓 : Ideal C) (P : Ideal B) (p : Ideal A)
@[simp]
theorem under_under : (𝔓.under B).under A = 𝔓.under A := by
simp_rw [comap_comap, ← IsScalarTower.algebraMap_eq]
theorem LiesOver.trans [𝔓.LiesOver P] [P.LiesOver p] : 𝔓.LiesOver p where
over := by rw [P.over_def p, 𝔓.over_def P, under_under]
theorem LiesOver.tower_bot [hp : 𝔓.LiesOver p] [hP : 𝔓.LiesOver P] : P.LiesOver p where
over := by rw [𝔓.over_def p, 𝔓.over_def P, under_under]
variable (B)
instance under_liesOver_of_liesOver [𝔓.LiesOver p] : (𝔓.under B).LiesOver p :=
LiesOver.tower_bot 𝔓 (𝔓.under B) p
end CommSemiring
section CommRing
variable (A : Type*) [CommRing A] (B : Type*) [Ring B] [Nontrivial B]
[Algebra A B] [NoZeroSMulDivisors A B] {p : Ideal A}
@[simp]
theorem under_bot : under A (⊥ : Ideal B) = ⊥ :=
comap_bot_of_injective (algebraMap A B) (FaithfulSMul.algebraMap_injective A B)
instance bot_liesOver_bot : (⊥ : Ideal B).LiesOver (⊥ : Ideal A) where
over := (under_bot A B).symm
variable {A B} in
theorem ne_bot_of_liesOver_of_ne_bot (hp : p ≠ ⊥) (P : Ideal B) [P.LiesOver p] : P ≠ ⊥ := by
contrapose! hp
rw [over_def P p, hp, under_bot]
end CommRing
namespace Quotient
variable (R : Type*) [CommSemiring R] {A B C : Type*} [CommRing A] [CommRing B] [CommRing C]
[Algebra A B] [Algebra A C] [Algebra R A] [Algebra R B] [IsScalarTower R A B]
(P : Ideal B) {Q : Ideal C} (p : Ideal A) [Q.LiesOver p] [P.LiesOver p]
(G : Type*) [Group G] [MulSemiringAction G B] [SMulCommClass G A B]
/-- If `P` lies over `p`, then canonically `B ⧸ P` is a `A ⧸ p`-algebra. -/
instance algebraOfLiesOver : Algebra (A ⧸ p) (B ⧸ P) :=
algebraQuotientOfLEComap (le_of_eq (P.over_def p))
instance isScalarTower_of_liesOver : IsScalarTower R (A ⧸ p) (B ⧸ P) :=
IsScalarTower.of_algebraMap_eq' <|
congrArg (algebraMap B (B ⧸ P)).comp (IsScalarTower.algebraMap_eq R A B)
instance instFaithfulSMul : FaithfulSMul (A ⧸ p) (B ⧸ P) := by
rw [faithfulSMul_iff_algebraMap_injective]
rintro ⟨a⟩ ⟨b⟩ hab
apply Quotient.eq.mpr ((mem_of_liesOver P p (a - b)).mpr _)
rw [RingHom.map_sub]
exact Quotient.eq.mp hab
@[deprecated (since := "2025-01-31")]
alias algebraMap_injective_of_liesOver := instFaithfulSMul
variable {p} in
theorem nontrivial_of_liesOver_of_ne_top (hp : p ≠ ⊤) : Nontrivial (B ⧸ P) :=
Quotient.nontrivial ((eq_top_iff_of_liesOver P p).mp.mt hp)
theorem nontrivial_of_liesOver_of_isPrime [hp : p.IsPrime] : Nontrivial (B ⧸ P) :=
nontrivial_of_liesOver_of_ne_top P hp.ne_top
section algEquiv
variable {P} {E : Type*} [EquivLike E B C] [AlgEquivClass E A B C] (σ : E)
/-- An `A ⧸ p`-algebra isomorphism between `B ⧸ P` and `C ⧸ Q` induced by an `A`-algebra
isomorphism between `B` and `C`, where `Q = σ P`. -/
def algEquivOfEqMap (h : Q = P.map σ) : (B ⧸ P) ≃ₐ[A ⧸ p] (C ⧸ Q) where
__ := quotientEquiv P Q σ h
commutes' := by
rintro ⟨x⟩
exact congrArg (Ideal.Quotient.mk Q) (AlgHomClass.commutes σ x)
@[simp]
theorem algEquivOfEqMap_apply (h : Q = P.map σ) (x : B) : algEquivOfEqMap p σ h x = σ x :=
rfl
/-- An `A ⧸ p`-algebra isomorphism between `B ⧸ P` and `C ⧸ Q` induced by an `A`-algebra
isomorphism between `B` and `C`, where `P = σ⁻¹ Q`. -/
def algEquivOfEqComap (h : P = Q.comap σ) : (B ⧸ P) ≃ₐ[A ⧸ p] (C ⧸ Q) :=
algEquivOfEqMap p σ ((congrArg (map σ) h).trans (Q.map_comap_eq_self_of_equiv σ)).symm
@[simp]
theorem algEquivOfEqComap_apply (h : P = Q.comap σ) (x : B) : algEquivOfEqComap p σ h x = σ x :=
rfl
end algEquiv
/-- If `P` lies over `p`, then the stabilizer of `P` acts on the extension `(B ⧸ P) / (A ⧸ p)`. -/
def stabilizerHom : MulAction.stabilizer G P →* ((B ⧸ P) ≃ₐ[A ⧸ p] (B ⧸ P)) where
toFun g := algEquivOfEqMap p (MulSemiringAction.toAlgEquiv A B g) g.2.symm
map_one' := by
ext ⟨x⟩
exact congrArg (Ideal.Quotient.mk P) (one_smul G x)
map_mul' g h := by
ext ⟨x⟩
exact congrArg (Ideal.Quotient.mk P) (mul_smul g h x)
@[simp] theorem stabilizerHom_apply (g : MulAction.stabilizer G P) (b : B) :
stabilizerHom P p G g b = ↑(g • b) :=
rfl
end Quotient
end ideal_liesOver
section primesOver
variable {A : Type*} [CommSemiring A] (p : Ideal A) (B : Type*) [Semiring B] [Algebra A B]
/-- The set of all prime ideals in `B` that lie over an ideal `p` of `A`. -/
def primesOver : Set (Ideal B) :=
{ P : Ideal B | P.IsPrime ∧ P.LiesOver p }
variable {B}
instance primesOver.isPrime (Q : primesOver p B) : Q.1.IsPrime :=
Q.2.1
instance primesOver.liesOver (Q : primesOver p B) : Q.1.LiesOver p :=
Q.2.2
/-- If an ideal `P` of `B` is prime and lying over `p`, then it is in `primesOver p B`. -/
abbrev primesOver.mk (P : Ideal B) [hPp : P.IsPrime] [hp : P.LiesOver p] : primesOver p B :=
⟨P, ⟨hPp, hp⟩⟩
end primesOver
end Ideal
| Mathlib/RingTheory/Ideal/Over.lean | 410 | 430 | |
/-
Copyright (c) 2022 Yaël Dillies, Sara Rousta. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yaël Dillies, Sara Rousta
-/
import Mathlib.Logic.Equiv.Set
import Mathlib.Order.Interval.Set.OrderEmbedding
import Mathlib.Order.SetNotation
/-!
# Properties of unbundled upper/lower sets
This file proves results on `IsUpperSet` and `IsLowerSet`, including their interactions with
set operations, images, preimages and order duals, and properties that reflect stronger assumptions
on the underlying order (such as `PartialOrder` and `LinearOrder`).
## TODO
* Lattice structure on antichains.
* Order equivalence between upper/lower sets and antichains.
-/
open OrderDual Set
variable {α β : Type*} {ι : Sort*} {κ : ι → Sort*}
attribute [aesop norm unfold] IsUpperSet IsLowerSet
section LE
variable [LE α] {s t : Set α} {a : α}
theorem isUpperSet_empty : IsUpperSet (∅ : Set α) := fun _ _ _ => id
theorem isLowerSet_empty : IsLowerSet (∅ : Set α) := fun _ _ _ => id
theorem isUpperSet_univ : IsUpperSet (univ : Set α) := fun _ _ _ => id
theorem isLowerSet_univ : IsLowerSet (univ : Set α) := fun _ _ _ => id
theorem IsUpperSet.compl (hs : IsUpperSet s) : IsLowerSet sᶜ := fun _a _b h hb ha => hb <| hs h ha
theorem IsLowerSet.compl (hs : IsLowerSet s) : IsUpperSet sᶜ := fun _a _b h hb ha => hb <| hs h ha
@[simp]
theorem isUpperSet_compl : IsUpperSet sᶜ ↔ IsLowerSet s :=
⟨fun h => by
convert h.compl
rw [compl_compl], IsLowerSet.compl⟩
@[simp]
theorem isLowerSet_compl : IsLowerSet sᶜ ↔ IsUpperSet s :=
⟨fun h => by
convert h.compl
rw [compl_compl], IsUpperSet.compl⟩
theorem IsUpperSet.union (hs : IsUpperSet s) (ht : IsUpperSet t) : IsUpperSet (s ∪ t) :=
fun _ _ h => Or.imp (hs h) (ht h)
theorem IsLowerSet.union (hs : IsLowerSet s) (ht : IsLowerSet t) : IsLowerSet (s ∪ t) :=
fun _ _ h => Or.imp (hs h) (ht h)
theorem IsUpperSet.inter (hs : IsUpperSet s) (ht : IsUpperSet t) : IsUpperSet (s ∩ t) :=
fun _ _ h => And.imp (hs h) (ht h)
theorem IsLowerSet.inter (hs : IsLowerSet s) (ht : IsLowerSet t) : IsLowerSet (s ∩ t) :=
fun _ _ h => And.imp (hs h) (ht h)
theorem isUpperSet_sUnion {S : Set (Set α)} (hf : ∀ s ∈ S, IsUpperSet s) : IsUpperSet (⋃₀ S) :=
fun _ _ h => Exists.imp fun _ hs => ⟨hs.1, hf _ hs.1 h hs.2⟩
theorem isLowerSet_sUnion {S : Set (Set α)} (hf : ∀ s ∈ S, IsLowerSet s) : IsLowerSet (⋃₀ S) :=
fun _ _ h => Exists.imp fun _ hs => ⟨hs.1, hf _ hs.1 h hs.2⟩
theorem isUpperSet_iUnion {f : ι → Set α} (hf : ∀ i, IsUpperSet (f i)) : IsUpperSet (⋃ i, f i) :=
isUpperSet_sUnion <| forall_mem_range.2 hf
theorem isLowerSet_iUnion {f : ι → Set α} (hf : ∀ i, IsLowerSet (f i)) : IsLowerSet (⋃ i, f i) :=
isLowerSet_sUnion <| forall_mem_range.2 hf
theorem isUpperSet_iUnion₂ {f : ∀ i, κ i → Set α} (hf : ∀ i j, IsUpperSet (f i j)) :
IsUpperSet (⋃ (i) (j), f i j) :=
isUpperSet_iUnion fun i => isUpperSet_iUnion <| hf i
theorem isLowerSet_iUnion₂ {f : ∀ i, κ i → Set α} (hf : ∀ i j, IsLowerSet (f i j)) :
IsLowerSet (⋃ (i) (j), f i j) :=
isLowerSet_iUnion fun i => isLowerSet_iUnion <| hf i
theorem isUpperSet_sInter {S : Set (Set α)} (hf : ∀ s ∈ S, IsUpperSet s) : IsUpperSet (⋂₀ S) :=
fun _ _ h => forall₂_imp fun s hs => hf s hs h
theorem isLowerSet_sInter {S : Set (Set α)} (hf : ∀ s ∈ S, IsLowerSet s) : IsLowerSet (⋂₀ S) :=
fun _ _ h => forall₂_imp fun s hs => hf s hs h
theorem isUpperSet_iInter {f : ι → Set α} (hf : ∀ i, IsUpperSet (f i)) : IsUpperSet (⋂ i, f i) :=
isUpperSet_sInter <| forall_mem_range.2 hf
theorem isLowerSet_iInter {f : ι → Set α} (hf : ∀ i, IsLowerSet (f i)) : IsLowerSet (⋂ i, f i) :=
isLowerSet_sInter <| forall_mem_range.2 hf
theorem isUpperSet_iInter₂ {f : ∀ i, κ i → Set α} (hf : ∀ i j, IsUpperSet (f i j)) :
IsUpperSet (⋂ (i) (j), f i j) :=
isUpperSet_iInter fun i => isUpperSet_iInter <| hf i
theorem isLowerSet_iInter₂ {f : ∀ i, κ i → Set α} (hf : ∀ i j, IsLowerSet (f i j)) :
IsLowerSet (⋂ (i) (j), f i j) :=
isLowerSet_iInter fun i => isLowerSet_iInter <| hf i
@[simp]
theorem isLowerSet_preimage_ofDual_iff : IsLowerSet (ofDual ⁻¹' s) ↔ IsUpperSet s :=
Iff.rfl
@[simp]
theorem isUpperSet_preimage_ofDual_iff : IsUpperSet (ofDual ⁻¹' s) ↔ IsLowerSet s :=
Iff.rfl
@[simp]
theorem isLowerSet_preimage_toDual_iff {s : Set αᵒᵈ} : IsLowerSet (toDual ⁻¹' s) ↔ IsUpperSet s :=
Iff.rfl
@[simp]
theorem isUpperSet_preimage_toDual_iff {s : Set αᵒᵈ} : IsUpperSet (toDual ⁻¹' s) ↔ IsLowerSet s :=
Iff.rfl
alias ⟨_, IsUpperSet.toDual⟩ := isLowerSet_preimage_ofDual_iff
alias ⟨_, IsLowerSet.toDual⟩ := isUpperSet_preimage_ofDual_iff
alias ⟨_, IsUpperSet.ofDual⟩ := isLowerSet_preimage_toDual_iff
alias ⟨_, IsLowerSet.ofDual⟩ := isUpperSet_preimage_toDual_iff
lemma IsUpperSet.isLowerSet_preimage_coe (hs : IsUpperSet s) :
IsLowerSet ((↑) ⁻¹' t : Set s) ↔ ∀ b ∈ s, ∀ c ∈ t, b ≤ c → b ∈ t := by aesop
lemma IsLowerSet.isUpperSet_preimage_coe (hs : IsLowerSet s) :
IsUpperSet ((↑) ⁻¹' t : Set s) ↔ ∀ b ∈ s, ∀ c ∈ t, c ≤ b → b ∈ t := by aesop
lemma IsUpperSet.sdiff (hs : IsUpperSet s) (ht : ∀ b ∈ s, ∀ c ∈ t, b ≤ c → b ∈ t) :
IsUpperSet (s \ t) :=
fun _b _c hbc hb ↦ ⟨hs hbc hb.1, fun hc ↦ hb.2 <| ht _ hb.1 _ hc hbc⟩
lemma IsLowerSet.sdiff (hs : IsLowerSet s) (ht : ∀ b ∈ s, ∀ c ∈ t, c ≤ b → b ∈ t) :
IsLowerSet (s \ t) :=
fun _b _c hcb hb ↦ ⟨hs hcb hb.1, fun hc ↦ hb.2 <| ht _ hb.1 _ hc hcb⟩
lemma IsUpperSet.sdiff_of_isLowerSet (hs : IsUpperSet s) (ht : IsLowerSet t) : IsUpperSet (s \ t) :=
hs.sdiff <| by aesop
lemma IsLowerSet.sdiff_of_isUpperSet (hs : IsLowerSet s) (ht : IsUpperSet t) : IsLowerSet (s \ t) :=
hs.sdiff <| by aesop
lemma IsUpperSet.erase (hs : IsUpperSet s) (has : ∀ b ∈ s, b ≤ a → b = a) : IsUpperSet (s \ {a}) :=
hs.sdiff <| by simpa using has
lemma IsLowerSet.erase (hs : IsLowerSet s) (has : ∀ b ∈ s, a ≤ b → b = a) : IsLowerSet (s \ {a}) :=
hs.sdiff <| by simpa using has
end LE
section Preorder
variable [Preorder α] [Preorder β] {s : Set α} {p : α → Prop} (a : α)
theorem isUpperSet_Ici : IsUpperSet (Ici a) := fun _ _ => ge_trans
theorem isLowerSet_Iic : IsLowerSet (Iic a) := fun _ _ => le_trans
theorem isUpperSet_Ioi : IsUpperSet (Ioi a) := fun _ _ => flip lt_of_lt_of_le
theorem isLowerSet_Iio : IsLowerSet (Iio a) := fun _ _ => lt_of_le_of_lt
theorem isUpperSet_iff_Ici_subset : IsUpperSet s ↔ ∀ ⦃a⦄, a ∈ s → Ici a ⊆ s := by
simp [IsUpperSet, subset_def, @forall_swap (_ ∈ s)]
theorem isLowerSet_iff_Iic_subset : IsLowerSet s ↔ ∀ ⦃a⦄, a ∈ s → Iic a ⊆ s := by
simp [IsLowerSet, subset_def, @forall_swap (_ ∈ s)]
alias ⟨IsUpperSet.Ici_subset, _⟩ := isUpperSet_iff_Ici_subset
alias ⟨IsLowerSet.Iic_subset, _⟩ := isLowerSet_iff_Iic_subset
theorem IsUpperSet.Ioi_subset (h : IsUpperSet s) ⦃a⦄ (ha : a ∈ s) : Ioi a ⊆ s :=
Ioi_subset_Ici_self.trans <| h.Ici_subset ha
theorem IsLowerSet.Iio_subset (h : IsLowerSet s) ⦃a⦄ (ha : a ∈ s) : Iio a ⊆ s :=
h.toDual.Ioi_subset ha
theorem IsUpperSet.ordConnected (h : IsUpperSet s) : s.OrdConnected :=
⟨fun _ ha _ _ => Icc_subset_Ici_self.trans <| h.Ici_subset ha⟩
theorem IsLowerSet.ordConnected (h : IsLowerSet s) : s.OrdConnected :=
⟨fun _ _ _ hb => Icc_subset_Iic_self.trans <| h.Iic_subset hb⟩
theorem IsUpperSet.preimage (hs : IsUpperSet s) {f : β → α} (hf : Monotone f) :
IsUpperSet (f ⁻¹' s : Set β) := fun _ _ h => hs <| hf h
theorem IsLowerSet.preimage (hs : IsLowerSet s) {f : β → α} (hf : Monotone f) :
IsLowerSet (f ⁻¹' s : Set β) := fun _ _ h => hs <| hf h
theorem IsUpperSet.image (hs : IsUpperSet s) (f : α ≃o β) : IsUpperSet (f '' s : Set β) := by
change IsUpperSet ((f : α ≃ β) '' s)
rw [Set.image_equiv_eq_preimage_symm]
exact hs.preimage f.symm.monotone
theorem IsLowerSet.image (hs : IsLowerSet s) (f : α ≃o β) : IsLowerSet (f '' s : Set β) := by
change IsLowerSet ((f : α ≃ β) '' s)
rw [Set.image_equiv_eq_preimage_symm]
exact hs.preimage f.symm.monotone
theorem OrderEmbedding.image_Ici (e : α ↪o β) (he : IsUpperSet (range e)) (a : α) :
e '' Ici a = Ici (e a) := by
rw [← e.preimage_Ici, image_preimage_eq_inter_range,
inter_eq_left.2 <| he.Ici_subset (mem_range_self _)]
theorem OrderEmbedding.image_Iic (e : α ↪o β) (he : IsLowerSet (range e)) (a : α) :
e '' Iic a = Iic (e a) :=
e.dual.image_Ici he a
theorem OrderEmbedding.image_Ioi (e : α ↪o β) (he : IsUpperSet (range e)) (a : α) :
e '' Ioi a = Ioi (e a) := by
rw [← e.preimage_Ioi, image_preimage_eq_inter_range,
inter_eq_left.2 <| he.Ioi_subset (mem_range_self _)]
theorem OrderEmbedding.image_Iio (e : α ↪o β) (he : IsLowerSet (range e)) (a : α) :
e '' Iio a = Iio (e a) :=
e.dual.image_Ioi he a
@[simp]
theorem Set.monotone_mem : Monotone (· ∈ s) ↔ IsUpperSet s :=
Iff.rfl
@[simp]
theorem Set.antitone_mem : Antitone (· ∈ s) ↔ IsLowerSet s :=
forall_swap
@[simp]
theorem isUpperSet_setOf : IsUpperSet { a | p a } ↔ Monotone p :=
Iff.rfl
@[simp]
theorem isLowerSet_setOf : IsLowerSet { a | p a } ↔ Antitone p :=
forall_swap
lemma IsUpperSet.upperBounds_subset (hs : IsUpperSet s) : s.Nonempty → upperBounds s ⊆ s :=
fun ⟨_a, ha⟩ _b hb ↦ hs (hb ha) ha
lemma IsLowerSet.lowerBounds_subset (hs : IsLowerSet s) : s.Nonempty → lowerBounds s ⊆ s :=
fun ⟨_a, ha⟩ _b hb ↦ hs (hb ha) ha
section OrderTop
variable [OrderTop α]
theorem IsLowerSet.top_mem (hs : IsLowerSet s) : ⊤ ∈ s ↔ s = univ :=
⟨fun h => eq_univ_of_forall fun _ => hs le_top h, fun h => h.symm ▸ mem_univ _⟩
theorem IsUpperSet.top_mem (hs : IsUpperSet s) : ⊤ ∈ s ↔ s.Nonempty :=
⟨fun h => ⟨_, h⟩, fun ⟨_a, ha⟩ => hs le_top ha⟩
theorem IsUpperSet.not_top_mem (hs : IsUpperSet s) : ⊤ ∉ s ↔ s = ∅ :=
hs.top_mem.not.trans not_nonempty_iff_eq_empty
end OrderTop
section OrderBot
variable [OrderBot α]
theorem IsUpperSet.bot_mem (hs : IsUpperSet s) : ⊥ ∈ s ↔ s = univ :=
⟨fun h => eq_univ_of_forall fun _ => hs bot_le h, fun h => h.symm ▸ mem_univ _⟩
theorem IsLowerSet.bot_mem (hs : IsLowerSet s) : ⊥ ∈ s ↔ s.Nonempty :=
⟨fun h => ⟨_, h⟩, fun ⟨_a, ha⟩ => hs bot_le ha⟩
theorem IsLowerSet.not_bot_mem (hs : IsLowerSet s) : ⊥ ∉ s ↔ s = ∅ :=
hs.bot_mem.not.trans not_nonempty_iff_eq_empty
end OrderBot
section NoMaxOrder
variable [NoMaxOrder α]
theorem IsUpperSet.not_bddAbove (hs : IsUpperSet s) : s.Nonempty → ¬BddAbove s := by
| rintro ⟨a, ha⟩ ⟨b, hb⟩
obtain ⟨c, hc⟩ := exists_gt b
exact hc.not_le (hb <| hs ((hb ha).trans hc.le) ha)
| Mathlib/Order/UpperLower/Basic.lean | 286 | 289 |
/-
Copyright (c) 2015 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Leonardo de Moura, Jeremy Avigad, Minchao Wu, Mario Carneiro
-/
import Mathlib.Data.Finset.Attach
import Mathlib.Data.Finset.Disjoint
import Mathlib.Data.Finset.Erase
import Mathlib.Data.Finset.Filter
import Mathlib.Data.Finset.Range
import Mathlib.Data.Finset.SDiff
import Mathlib.Data.Multiset.Basic
import Mathlib.Logic.Equiv.Set
import Mathlib.Order.Directed
import Mathlib.Order.Interval.Set.Defs
import Mathlib.Data.Set.SymmDiff
/-!
# Basic lemmas on finite sets
This file contains lemmas on the interaction of various definitions on the `Finset` type.
For an explanation of `Finset` design decisions, please see `Mathlib/Data/Finset/Defs.lean`.
## Main declarations
### Main definitions
* `Finset.choose`: Given a proof `h` of existence and uniqueness of a certain element
satisfying a predicate, `choose s h` returns the element of `s` satisfying that predicate.
### Equivalences between finsets
* The `Mathlib/Logic/Equiv/Defs.lean` file describes a general type of equivalence, so look in there
for any lemmas. There is some API for rewriting sums and products from `s` to `t` given that
`s ≃ t`.
TODO: examples
## Tags
finite sets, finset
-/
-- Assert that we define `Finset` without the material on `List.sublists`.
-- Note that we cannot use `List.sublists` itself as that is defined very early.
assert_not_exists List.sublistsLen Multiset.powerset CompleteLattice Monoid
open Multiset Subtype Function
universe u
variable {α : Type*} {β : Type*} {γ : Type*}
namespace Finset
-- TODO: these should be global attributes, but this will require fixing other files
attribute [local trans] Subset.trans Superset.trans
set_option linter.deprecated false in
@[deprecated "Deprecated without replacement." (since := "2025-02-07")]
theorem sizeOf_lt_sizeOf_of_mem [SizeOf α] {x : α} {s : Finset α} (hx : x ∈ s) :
SizeOf.sizeOf x < SizeOf.sizeOf s := by
cases s
dsimp [SizeOf.sizeOf, SizeOf.sizeOf, Multiset.sizeOf]
rw [Nat.add_comm]
refine lt_trans ?_ (Nat.lt_succ_self _)
exact Multiset.sizeOf_lt_sizeOf_of_mem hx
/-! ### Lattice structure -/
section Lattice
variable [DecidableEq α] {s s₁ s₂ t t₁ t₂ u v : Finset α} {a b : α}
/-! #### union -/
@[simp]
theorem disjUnion_eq_union (s t h) : @disjUnion α s t h = s ∪ t :=
ext fun a => by simp
@[simp]
theorem disjoint_union_left : Disjoint (s ∪ t) u ↔ Disjoint s u ∧ Disjoint t u := by
simp only [disjoint_left, mem_union, or_imp, forall_and]
@[simp]
theorem disjoint_union_right : Disjoint s (t ∪ u) ↔ Disjoint s t ∧ Disjoint s u := by
simp only [disjoint_right, mem_union, or_imp, forall_and]
/-! #### inter -/
theorem not_disjoint_iff_nonempty_inter : ¬Disjoint s t ↔ (s ∩ t).Nonempty :=
not_disjoint_iff.trans <| by simp [Finset.Nonempty]
alias ⟨_, Nonempty.not_disjoint⟩ := not_disjoint_iff_nonempty_inter
theorem disjoint_or_nonempty_inter (s t : Finset α) : Disjoint s t ∨ (s ∩ t).Nonempty := by
rw [← not_disjoint_iff_nonempty_inter]
exact em _
omit [DecidableEq α] in
theorem disjoint_of_subset_iff_left_eq_empty (h : s ⊆ t) :
Disjoint s t ↔ s = ∅ :=
disjoint_of_le_iff_left_eq_bot h
lemma pairwiseDisjoint_iff {ι : Type*} {s : Set ι} {f : ι → Finset α} :
s.PairwiseDisjoint f ↔ ∀ ⦃i⦄, i ∈ s → ∀ ⦃j⦄, j ∈ s → (f i ∩ f j).Nonempty → i = j := by
simp [Set.PairwiseDisjoint, Set.Pairwise, Function.onFun, not_imp_comm (a := _ = _),
not_disjoint_iff_nonempty_inter]
end Lattice
instance isDirected_le : IsDirected (Finset α) (· ≤ ·) := by classical infer_instance
instance isDirected_subset : IsDirected (Finset α) (· ⊆ ·) := isDirected_le
/-! ### erase -/
section Erase
variable [DecidableEq α] {s t u v : Finset α} {a b : α}
@[simp]
theorem erase_empty (a : α) : erase ∅ a = ∅ :=
rfl
protected lemma Nontrivial.erase_nonempty (hs : s.Nontrivial) : (s.erase a).Nonempty :=
(hs.exists_ne a).imp <| by aesop
@[simp] lemma erase_nonempty (ha : a ∈ s) : (s.erase a).Nonempty ↔ s.Nontrivial := by
simp only [Finset.Nonempty, mem_erase, and_comm (b := _ ∈ _)]
refine ⟨?_, fun hs ↦ hs.exists_ne a⟩
rintro ⟨b, hb, hba⟩
exact ⟨_, hb, _, ha, hba⟩
@[simp]
theorem erase_singleton (a : α) : ({a} : Finset α).erase a = ∅ := by
ext x
simp
@[simp]
theorem erase_insert_eq_erase (s : Finset α) (a : α) : (insert a s).erase a = s.erase a :=
ext fun x => by
simp +contextual only [mem_erase, mem_insert, and_congr_right_iff,
false_or, iff_self, imp_true_iff]
theorem erase_insert {a : α} {s : Finset α} (h : a ∉ s) : erase (insert a s) a = s := by
rw [erase_insert_eq_erase, erase_eq_of_not_mem h]
theorem erase_insert_of_ne {a b : α} {s : Finset α} (h : a ≠ b) :
erase (insert a s) b = insert a (erase s b) :=
ext fun x => by
have : x ≠ b ∧ x = a ↔ x = a := and_iff_right_of_imp fun hx => hx.symm ▸ h
simp only [mem_erase, mem_insert, and_or_left, this]
theorem erase_cons_of_ne {a b : α} {s : Finset α} (ha : a ∉ s) (hb : a ≠ b) :
erase (cons a s ha) b = cons a (erase s b) fun h => ha <| erase_subset _ _ h := by
simp only [cons_eq_insert, erase_insert_of_ne hb]
@[simp] theorem insert_erase (h : a ∈ s) : insert a (erase s a) = s :=
ext fun x => by
simp only [mem_insert, mem_erase, or_and_left, dec_em, true_and]
apply or_iff_right_of_imp
rintro rfl
exact h
lemma erase_eq_iff_eq_insert (hs : a ∈ s) (ht : a ∉ t) : erase s a = t ↔ s = insert a t := by
aesop
lemma insert_erase_invOn :
Set.InvOn (insert a) (fun s ↦ erase s a) {s : Finset α | a ∈ s} {s : Finset α | a ∉ s} :=
⟨fun _s ↦ insert_erase, fun _s ↦ erase_insert⟩
theorem erase_ssubset {a : α} {s : Finset α} (h : a ∈ s) : s.erase a ⊂ s :=
calc
s.erase a ⊂ insert a (s.erase a) := ssubset_insert <| not_mem_erase _ _
_ = _ := insert_erase h
theorem ssubset_iff_exists_subset_erase {s t : Finset α} : s ⊂ t ↔ ∃ a ∈ t, s ⊆ t.erase a := by
refine ⟨fun h => ?_, fun ⟨a, ha, h⟩ => ssubset_of_subset_of_ssubset h <| erase_ssubset ha⟩
obtain ⟨a, ht, hs⟩ := not_subset.1 h.2
exact ⟨a, ht, subset_erase.2 ⟨h.1, hs⟩⟩
theorem erase_ssubset_insert (s : Finset α) (a : α) : s.erase a ⊂ insert a s :=
ssubset_iff_exists_subset_erase.2
⟨a, mem_insert_self _ _, erase_subset_erase _ <| subset_insert _ _⟩
theorem erase_cons {s : Finset α} {a : α} (h : a ∉ s) : (s.cons a h).erase a = s := by
rw [cons_eq_insert, erase_insert_eq_erase, erase_eq_of_not_mem h]
theorem subset_insert_iff {a : α} {s t : Finset α} : s ⊆ insert a t ↔ erase s a ⊆ t := by
simp only [subset_iff, or_iff_not_imp_left, mem_erase, mem_insert, and_imp]
exact forall_congr' fun x => forall_swap
theorem erase_insert_subset (a : α) (s : Finset α) : erase (insert a s) a ⊆ s :=
subset_insert_iff.1 <| Subset.rfl
theorem insert_erase_subset (a : α) (s : Finset α) : s ⊆ insert a (erase s a) :=
subset_insert_iff.2 <| Subset.rfl
theorem subset_insert_iff_of_not_mem (h : a ∉ s) : s ⊆ insert a t ↔ s ⊆ t := by
rw [subset_insert_iff, erase_eq_of_not_mem h]
theorem erase_subset_iff_of_mem (h : a ∈ t) : s.erase a ⊆ t ↔ s ⊆ t := by
rw [← subset_insert_iff, insert_eq_of_mem h]
theorem erase_injOn' (a : α) : { s : Finset α | a ∈ s }.InjOn fun s => erase s a :=
fun s hs t ht (h : s.erase a = _) => by rw [← insert_erase hs, ← insert_erase ht, h]
end Erase
lemma Nontrivial.exists_cons_eq {s : Finset α} (hs : s.Nontrivial) :
∃ t a ha b hb hab, (cons b t hb).cons a (mem_cons.not.2 <| not_or_intro hab ha) = s := by
classical
obtain ⟨a, ha, b, hb, hab⟩ := hs
have : b ∈ s.erase a := mem_erase.2 ⟨hab.symm, hb⟩
refine ⟨(s.erase a).erase b, a, ?_, b, ?_, ?_, ?_⟩ <;>
simp [insert_erase this, insert_erase ha, *]
/-! ### sdiff -/
section Sdiff
variable [DecidableEq α] {s t u v : Finset α} {a b : α}
lemma erase_sdiff_erase (hab : a ≠ b) (hb : b ∈ s) : s.erase a \ s.erase b = {b} := by
ext; aesop
-- TODO: Do we want to delete this lemma and `Finset.disjUnion_singleton`,
-- or instead add `Finset.union_singleton`/`Finset.singleton_union`?
theorem sdiff_singleton_eq_erase (a : α) (s : Finset α) : s \ {a} = erase s a := by
ext
rw [mem_erase, mem_sdiff, mem_singleton, and_comm]
-- This lemma matches `Finset.insert_eq` in functionality.
theorem erase_eq (s : Finset α) (a : α) : s.erase a = s \ {a} :=
(sdiff_singleton_eq_erase _ _).symm
theorem disjoint_erase_comm : Disjoint (s.erase a) t ↔ Disjoint s (t.erase a) := by
simp_rw [erase_eq, disjoint_sdiff_comm]
lemma disjoint_insert_erase (ha : a ∉ t) : Disjoint (s.erase a) (insert a t) ↔ Disjoint s t := by
rw [disjoint_erase_comm, erase_insert ha]
lemma disjoint_erase_insert (ha : a ∉ s) : Disjoint (insert a s) (t.erase a) ↔ Disjoint s t := by
rw [← disjoint_erase_comm, erase_insert ha]
theorem disjoint_of_erase_left (ha : a ∉ t) (hst : Disjoint (s.erase a) t) : Disjoint s t := by
rw [← erase_insert ha, ← disjoint_erase_comm, disjoint_insert_right]
exact ⟨not_mem_erase _ _, hst⟩
theorem disjoint_of_erase_right (ha : a ∉ s) (hst : Disjoint s (t.erase a)) : Disjoint s t := by
rw [← erase_insert ha, disjoint_erase_comm, disjoint_insert_left]
exact ⟨not_mem_erase _ _, hst⟩
theorem inter_erase (a : α) (s t : Finset α) : s ∩ t.erase a = (s ∩ t).erase a := by
simp only [erase_eq, inter_sdiff_assoc]
@[simp]
theorem erase_inter (a : α) (s t : Finset α) : s.erase a ∩ t = (s ∩ t).erase a := by
simpa only [inter_comm t] using inter_erase a t s
theorem erase_sdiff_comm (s t : Finset α) (a : α) : s.erase a \ t = (s \ t).erase a := by
simp_rw [erase_eq, sdiff_right_comm]
theorem erase_inter_comm (s t : Finset α) (a : α) : s.erase a ∩ t = s ∩ t.erase a := by
rw [erase_inter, inter_erase]
theorem erase_union_distrib (s t : Finset α) (a : α) : (s ∪ t).erase a = s.erase a ∪ t.erase a := by
simp_rw [erase_eq, union_sdiff_distrib]
theorem insert_inter_distrib (s t : Finset α) (a : α) :
insert a (s ∩ t) = insert a s ∩ insert a t := by simp_rw [insert_eq, union_inter_distrib_left]
theorem erase_sdiff_distrib (s t : Finset α) (a : α) : (s \ t).erase a = s.erase a \ t.erase a := by
simp_rw [erase_eq, sdiff_sdiff, sup_sdiff_eq_sup le_rfl, sup_comm]
theorem erase_union_of_mem (ha : a ∈ t) (s : Finset α) : s.erase a ∪ t = s ∪ t := by
rw [← insert_erase (mem_union_right s ha), erase_union_distrib, ← union_insert, insert_erase ha]
theorem union_erase_of_mem (ha : a ∈ s) (t : Finset α) : s ∪ t.erase a = s ∪ t := by
rw [← insert_erase (mem_union_left t ha), erase_union_distrib, ← insert_union, insert_erase ha]
theorem sdiff_union_erase_cancel (hts : t ⊆ s) (ha : a ∈ t) : s \ t ∪ t.erase a = s.erase a := by
simp_rw [erase_eq, sdiff_union_sdiff_cancel hts (singleton_subset_iff.2 ha)]
theorem sdiff_insert (s t : Finset α) (x : α) : s \ insert x t = (s \ t).erase x := by
simp_rw [← sdiff_singleton_eq_erase, insert_eq, sdiff_sdiff_left', sdiff_union_distrib,
inter_comm]
theorem sdiff_insert_insert_of_mem_of_not_mem {s t : Finset α} {x : α} (hxs : x ∈ s) (hxt : x ∉ t) :
insert x (s \ insert x t) = s \ t := by
rw [sdiff_insert, insert_erase (mem_sdiff.mpr ⟨hxs, hxt⟩)]
theorem sdiff_erase (h : a ∈ s) : s \ t.erase a = insert a (s \ t) := by
rw [← sdiff_singleton_eq_erase, sdiff_sdiff_eq_sdiff_union (singleton_subset_iff.2 h), insert_eq,
union_comm]
theorem sdiff_erase_self (ha : a ∈ s) : s \ s.erase a = {a} := by
rw [sdiff_erase ha, Finset.sdiff_self, insert_empty_eq]
theorem erase_eq_empty_iff (s : Finset α) (a : α) : s.erase a = ∅ ↔ s = ∅ ∨ s = {a} := by
rw [← sdiff_singleton_eq_erase, sdiff_eq_empty_iff_subset, subset_singleton_iff]
--TODO@Yaël: Kill lemmas duplicate with `BooleanAlgebra`
theorem sdiff_disjoint : Disjoint (t \ s) s :=
disjoint_left.2 fun _a ha => (mem_sdiff.1 ha).2
theorem disjoint_sdiff : Disjoint s (t \ s) :=
sdiff_disjoint.symm
theorem disjoint_sdiff_inter (s t : Finset α) : Disjoint (s \ t) (s ∩ t) :=
disjoint_of_subset_right inter_subset_right sdiff_disjoint
end Sdiff
/-! ### attach -/
@[simp]
theorem attach_empty : attach (∅ : Finset α) = ∅ :=
rfl
@[simp]
theorem attach_nonempty_iff {s : Finset α} : s.attach.Nonempty ↔ s.Nonempty := by
simp [Finset.Nonempty]
@[aesop safe apply (rule_sets := [finsetNonempty])]
protected alias ⟨_, Nonempty.attach⟩ := attach_nonempty_iff
@[simp]
theorem attach_eq_empty_iff {s : Finset α} : s.attach = ∅ ↔ s = ∅ := by
simp [eq_empty_iff_forall_not_mem]
/-! ### filter -/
section Filter
variable (p q : α → Prop) [DecidablePred p] [DecidablePred q] {s t : Finset α}
theorem filter_singleton (a : α) : filter p {a} = if p a then {a} else ∅ := by
classical
ext x
simp only [mem_singleton, forall_eq, mem_filter]
split_ifs with h <;> by_cases h' : x = a <;> simp [h, h']
theorem filter_cons_of_pos (a : α) (s : Finset α) (ha : a ∉ s) (hp : p a) :
filter p (cons a s ha) = cons a (filter p s) ((mem_of_mem_filter _).mt ha) :=
eq_of_veq <| Multiset.filter_cons_of_pos s.val hp
theorem filter_cons_of_neg (a : α) (s : Finset α) (ha : a ∉ s) (hp : ¬p a) :
filter p (cons a s ha) = filter p s :=
eq_of_veq <| Multiset.filter_cons_of_neg s.val hp
theorem disjoint_filter {s : Finset α} {p q : α → Prop} [DecidablePred p] [DecidablePred q] :
Disjoint (s.filter p) (s.filter q) ↔ ∀ x ∈ s, p x → ¬q x := by
constructor <;> simp +contextual [disjoint_left]
theorem disjoint_filter_filter' (s t : Finset α)
{p q : α → Prop} [DecidablePred p] [DecidablePred q] (h : Disjoint p q) :
Disjoint (s.filter p) (t.filter q) := by
simp_rw [disjoint_left, mem_filter]
rintro a ⟨_, hp⟩ ⟨_, hq⟩
rw [Pi.disjoint_iff] at h
simpa [hp, hq] using h a
theorem disjoint_filter_filter_neg (s t : Finset α) (p : α → Prop)
[DecidablePred p] [∀ x, Decidable (¬p x)] :
Disjoint (s.filter p) (t.filter fun a => ¬p a) :=
disjoint_filter_filter' s t disjoint_compl_right
theorem filter_disj_union (s : Finset α) (t : Finset α) (h : Disjoint s t) :
filter p (disjUnion s t h) = (filter p s).disjUnion (filter p t) (disjoint_filter_filter h) :=
eq_of_veq <| Multiset.filter_add _ _ _
theorem filter_cons {a : α} (s : Finset α) (ha : a ∉ s) :
filter p (cons a s ha) =
if p a then cons a (filter p s) ((mem_of_mem_filter _).mt ha) else filter p s := by
split_ifs with h
· rw [filter_cons_of_pos _ _ _ ha h]
· rw [filter_cons_of_neg _ _ _ ha h]
section
variable [DecidableEq α]
theorem filter_union (s₁ s₂ : Finset α) : (s₁ ∪ s₂).filter p = s₁.filter p ∪ s₂.filter p :=
ext fun _ => by simp only [mem_filter, mem_union, or_and_right]
theorem filter_union_right (s : Finset α) : s.filter p ∪ s.filter q = s.filter fun x => p x ∨ q x :=
ext fun x => by simp [mem_filter, mem_union, ← and_or_left]
theorem filter_mem_eq_inter {s t : Finset α} [∀ i, Decidable (i ∈ t)] :
(s.filter fun i => i ∈ t) = s ∩ t :=
ext fun i => by simp [mem_filter, mem_inter]
theorem filter_inter_distrib (s t : Finset α) : (s ∩ t).filter p = s.filter p ∩ t.filter p := by
ext
simp [mem_filter, mem_inter, and_assoc]
theorem filter_inter (s t : Finset α) : filter p s ∩ t = filter p (s ∩ t) := by
ext
simp only [mem_inter, mem_filter, and_right_comm]
theorem inter_filter (s t : Finset α) : s ∩ filter p t = filter p (s ∩ t) := by
rw [inter_comm, filter_inter, inter_comm]
theorem filter_insert (a : α) (s : Finset α) :
filter p (insert a s) = if p a then insert a (filter p s) else filter p s := by
ext x
split_ifs with h <;> by_cases h' : x = a <;> simp [h, h']
theorem filter_erase (a : α) (s : Finset α) : filter p (erase s a) = erase (filter p s) a := by
ext x
simp only [and_assoc, mem_filter, iff_self, mem_erase]
theorem filter_or (s : Finset α) : (s.filter fun a => p a ∨ q a) = s.filter p ∪ s.filter q :=
ext fun _ => by simp [mem_filter, mem_union, and_or_left]
theorem filter_and (s : Finset α) : (s.filter fun a => p a ∧ q a) = s.filter p ∩ s.filter q :=
ext fun _ => by simp [mem_filter, mem_inter, and_comm, and_left_comm, and_self_iff, and_assoc]
theorem filter_not (s : Finset α) : (s.filter fun a => ¬p a) = s \ s.filter p :=
ext fun a => by
simp only [Bool.decide_coe, Bool.not_eq_true', mem_filter, and_comm, mem_sdiff, not_and_or,
Bool.not_eq_true, and_or_left, and_not_self, or_false]
lemma filter_and_not (s : Finset α) (p q : α → Prop) [DecidablePred p] [DecidablePred q] :
s.filter (fun a ↦ p a ∧ ¬ q a) = s.filter p \ s.filter q := by
rw [filter_and, filter_not, ← inter_sdiff_assoc, inter_eq_left.2 (filter_subset _ _)]
theorem sdiff_eq_filter (s₁ s₂ : Finset α) : s₁ \ s₂ = filter (· ∉ s₂) s₁ :=
ext fun _ => by simp [mem_sdiff, mem_filter]
theorem subset_union_elim {s : Finset α} {t₁ t₂ : Set α} (h : ↑s ⊆ t₁ ∪ t₂) :
∃ s₁ s₂ : Finset α, s₁ ∪ s₂ = s ∧ ↑s₁ ⊆ t₁ ∧ ↑s₂ ⊆ t₂ \ t₁ := by
classical
refine ⟨s.filter (· ∈ t₁), s.filter (· ∉ t₁), ?_, ?_, ?_⟩
· simp [filter_union_right, em]
· intro x
simp
· intro x
simp only [not_not, coe_filter, Set.mem_setOf_eq, Set.mem_diff, and_imp]
intro hx hx₂
exact ⟨Or.resolve_left (h hx) hx₂, hx₂⟩
-- This is not a good simp lemma, as it would prevent `Finset.mem_filter` from firing
-- on, e.g. `x ∈ s.filter (Eq b)`.
/-- After filtering out everything that does not equal a given value, at most that value remains.
This is equivalent to `filter_eq'` with the equality the other way.
-/
theorem filter_eq [DecidableEq β] (s : Finset β) (b : β) :
s.filter (Eq b) = ite (b ∈ s) {b} ∅ := by
split_ifs with h
· ext
simp only [mem_filter, mem_singleton, decide_eq_true_eq]
refine ⟨fun h => h.2.symm, ?_⟩
rintro rfl
exact ⟨h, rfl⟩
· ext
simp only [mem_filter, not_and, iff_false, not_mem_empty, decide_eq_true_eq]
rintro m rfl
exact h m
/-- After filtering out everything that does not equal a given value, at most that value remains.
This is equivalent to `filter_eq` with the equality the other way.
-/
theorem filter_eq' [DecidableEq β] (s : Finset β) (b : β) :
(s.filter fun a => a = b) = ite (b ∈ s) {b} ∅ :=
_root_.trans (filter_congr fun _ _ => by simp_rw [@eq_comm _ b]) (filter_eq s b)
theorem filter_ne [DecidableEq β] (s : Finset β) (b : β) :
(s.filter fun a => b ≠ a) = s.erase b := by
ext
simp only [mem_filter, mem_erase, Ne, decide_not, Bool.not_eq_true', decide_eq_false_iff_not]
tauto
theorem filter_ne' [DecidableEq β] (s : Finset β) (b : β) : (s.filter fun a => a ≠ b) = s.erase b :=
_root_.trans (filter_congr fun _ _ => by simp_rw [@ne_comm _ b]) (filter_ne s b)
theorem filter_union_filter_of_codisjoint (s : Finset α) (h : Codisjoint p q) :
s.filter p ∪ s.filter q = s :=
(filter_or _ _ _).symm.trans <| filter_true_of_mem fun x _ => h.top_le x trivial
theorem filter_union_filter_neg_eq [∀ x, Decidable (¬p x)] (s : Finset α) :
(s.filter p ∪ s.filter fun a => ¬p a) = s :=
filter_union_filter_of_codisjoint _ _ _ <| @codisjoint_hnot_right _ _ p
end
end Filter
/-! ### range -/
section Range
open Nat
variable {n m l : ℕ}
@[simp]
theorem range_filter_eq {n m : ℕ} : (range n).filter (· = m) = if m < n then {m} else ∅ := by
convert filter_eq (range n) m using 2
· ext
rw [eq_comm]
· simp
end Range
end Finset
/-! ### dedup on list and multiset -/
namespace Multiset
variable [DecidableEq α] {s t : Multiset α}
@[simp]
theorem toFinset_add (s t : Multiset α) : toFinset (s + t) = toFinset s ∪ toFinset t :=
Finset.ext <| by simp
@[simp]
theorem toFinset_inter (s t : Multiset α) : toFinset (s ∩ t) = toFinset s ∩ toFinset t :=
Finset.ext <| by simp
@[simp]
theorem toFinset_union (s t : Multiset α) : (s ∪ t).toFinset = s.toFinset ∪ t.toFinset := by
ext; simp
@[simp]
theorem toFinset_eq_empty {m : Multiset α} : m.toFinset = ∅ ↔ m = 0 :=
Finset.val_inj.symm.trans Multiset.dedup_eq_zero
@[simp]
theorem toFinset_nonempty : s.toFinset.Nonempty ↔ s ≠ 0 := by
simp only [toFinset_eq_empty, Ne, Finset.nonempty_iff_ne_empty]
@[aesop safe apply (rule_sets := [finsetNonempty])]
protected alias ⟨_, Aesop.toFinset_nonempty_of_ne⟩ := toFinset_nonempty
@[simp]
theorem toFinset_filter (s : Multiset α) (p : α → Prop) [DecidablePred p] :
Multiset.toFinset (s.filter p) = s.toFinset.filter p := by
ext; simp
end Multiset
namespace List
variable [DecidableEq α] {l l' : List α} {a : α} {f : α → β}
{s : Finset α} {t : Set β} {t' : Finset β}
@[simp]
theorem toFinset_union (l l' : List α) : (l ∪ l').toFinset = l.toFinset ∪ l'.toFinset := by
ext
simp
@[simp]
theorem toFinset_inter (l l' : List α) : (l ∩ l').toFinset = l.toFinset ∩ l'.toFinset := by
ext
simp
@[aesop safe apply (rule_sets := [finsetNonempty])]
alias ⟨_, Aesop.toFinset_nonempty_of_ne⟩ := toFinset_nonempty_iff
@[simp]
theorem toFinset_filter (s : List α) (p : α → Bool) :
(s.filter p).toFinset = s.toFinset.filter (p ·) := by
ext; simp [List.mem_filter]
end List
namespace Finset
section ToList
@[simp]
theorem toList_eq_nil {s : Finset α} : s.toList = [] ↔ s = ∅ :=
Multiset.toList_eq_nil.trans val_eq_zero
theorem empty_toList {s : Finset α} : s.toList.isEmpty ↔ s = ∅ := by simp
@[simp]
theorem toList_empty : (∅ : Finset α).toList = [] :=
toList_eq_nil.mpr rfl
theorem Nonempty.toList_ne_nil {s : Finset α} (hs : s.Nonempty) : s.toList ≠ [] :=
mt toList_eq_nil.mp hs.ne_empty
theorem Nonempty.not_empty_toList {s : Finset α} (hs : s.Nonempty) : ¬s.toList.isEmpty :=
mt empty_toList.mp hs.ne_empty
end ToList
/-! ### choose -/
section Choose
variable (p : α → Prop) [DecidablePred p] (l : Finset α)
/-- Given a finset `l` and a predicate `p`, associate to a proof that there is a unique element of
`l` satisfying `p` this unique element, as an element of the corresponding subtype. -/
def chooseX (hp : ∃! a, a ∈ l ∧ p a) : { a // a ∈ l ∧ p a } :=
Multiset.chooseX p l.val hp
/-- Given a finset `l` and a predicate `p`, associate to a proof that there is a unique element of
`l` satisfying `p` this unique element, as an element of the ambient type. -/
def choose (hp : ∃! a, a ∈ l ∧ p a) : α :=
chooseX p l hp
theorem choose_spec (hp : ∃! a, a ∈ l ∧ p a) : choose p l hp ∈ l ∧ p (choose p l hp) :=
(chooseX p l hp).property
theorem choose_mem (hp : ∃! a, a ∈ l ∧ p a) : choose p l hp ∈ l :=
(choose_spec _ _ _).1
theorem choose_property (hp : ∃! a, a ∈ l ∧ p a) : p (choose p l hp) :=
(choose_spec _ _ _).2
end Choose
end Finset
namespace Equiv
variable [DecidableEq α] {s t : Finset α}
open Finset
/-- The disjoint union of finsets is a sum -/
def Finset.union (s t : Finset α) (h : Disjoint s t) :
s ⊕ t ≃ (s ∪ t : Finset α) :=
Equiv.setCongr (coe_union _ _) |>.trans (Equiv.Set.union (disjoint_coe.mpr h)) |>.symm
@[simp]
theorem Finset.union_symm_inl (h : Disjoint s t) (x : s) :
Equiv.Finset.union s t h (Sum.inl x) = ⟨x, Finset.mem_union.mpr <| Or.inl x.2⟩ :=
rfl
@[simp]
theorem Finset.union_symm_inr (h : Disjoint s t) (y : t) :
Equiv.Finset.union s t h (Sum.inr y) = ⟨y, Finset.mem_union.mpr <| Or.inr y.2⟩ :=
rfl
/-- The type of dependent functions on the disjoint union of finsets `s ∪ t` is equivalent to the
type of pairs of functions on `s` and on `t`. This is similar to `Equiv.sumPiEquivProdPi`. -/
def piFinsetUnion {ι} [DecidableEq ι] (α : ι → Type*) {s t : Finset ι} (h : Disjoint s t) :
((∀ i : s, α i) × ∀ i : t, α i) ≃ ∀ i : (s ∪ t : Finset ι), α i :=
let e := Equiv.Finset.union s t h
sumPiEquivProdPi (fun b ↦ α (e b)) |>.symm.trans (.piCongrLeft (fun i : ↥(s ∪ t) ↦ α i) e)
/-- A finset is equivalent to its coercion as a set. -/
def _root_.Finset.equivToSet (s : Finset α) : s ≃ s.toSet where
toFun a := ⟨a.1, mem_coe.2 a.2⟩
invFun a := ⟨a.1, mem_coe.1 a.2⟩
left_inv := fun _ ↦ rfl
right_inv := fun _ ↦ rfl
end Equiv
namespace Multiset
variable [DecidableEq α]
@[simp]
lemma toFinset_replicate (n : ℕ) (a : α) :
(replicate n a).toFinset = if n = 0 then ∅ else {a} := by
ext x
simp only [mem_toFinset, Finset.mem_singleton, mem_replicate]
split_ifs with hn <;> simp [hn]
end Multiset
| Mathlib/Data/Finset/Basic.lean | 743 | 749 | |
/-
Copyright (c) 2017 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl, Mario Carneiro, Patrick Massot
-/
import Mathlib.Algebra.Group.TypeTags.Basic
import Mathlib.Data.Fin.VecNotation
import Mathlib.Data.Finset.Piecewise
import Mathlib.Order.Filter.Cofinite
import Mathlib.Order.Filter.Curry
import Mathlib.Topology.Constructions.SumProd
import Mathlib.Topology.NhdsSet
/-!
# Constructions of new topological spaces from old ones
This file constructs pi types, subtypes and quotients of topological spaces
and sets up their basic theory, such as criteria for maps into or out of these
constructions to be continuous; descriptions of the open sets, neighborhood filters,
and generators of these constructions; and their behavior with respect to embeddings
and other specific classes of maps.
## Implementation note
The constructed topologies are defined using induced and coinduced topologies
along with the complete lattice structure on topologies. Their universal properties
(for example, a map `X → Y × Z` is continuous if and only if both projections
`X → Y`, `X → Z` are) follow easily using order-theoretic descriptions of
continuity. With more work we can also extract descriptions of the open sets,
neighborhood filters and so on.
## Tags
product, subspace, quotient space
-/
noncomputable section
open Topology TopologicalSpace Set Filter Function
open scoped Set.Notation
universe u v u' v'
variable {X : Type u} {Y : Type v} {Z W ε ζ : Type*}
section Constructions
instance {r : X → X → Prop} [t : TopologicalSpace X] : TopologicalSpace (Quot r) :=
coinduced (Quot.mk r) t
instance instTopologicalSpaceQuotient {s : Setoid X} [t : TopologicalSpace X] :
TopologicalSpace (Quotient s) :=
coinduced Quotient.mk' t
instance instTopologicalSpaceSigma {ι : Type*} {X : ι → Type v} [t₂ : ∀ i, TopologicalSpace (X i)] :
TopologicalSpace (Sigma X) :=
⨆ i, coinduced (Sigma.mk i) (t₂ i)
instance Pi.topologicalSpace {ι : Type*} {Y : ι → Type v} [t₂ : (i : ι) → TopologicalSpace (Y i)] :
TopologicalSpace ((i : ι) → Y i) :=
⨅ i, induced (fun f => f i) (t₂ i)
instance ULift.topologicalSpace [t : TopologicalSpace X] : TopologicalSpace (ULift.{v, u} X) :=
t.induced ULift.down
/-!
### `Additive`, `Multiplicative`
The topology on those type synonyms is inherited without change.
-/
section
variable [TopologicalSpace X]
open Additive Multiplicative
instance : TopologicalSpace (Additive X) := ‹TopologicalSpace X›
instance : TopologicalSpace (Multiplicative X) := ‹TopologicalSpace X›
instance [DiscreteTopology X] : DiscreteTopology (Additive X) := ‹DiscreteTopology X›
instance [DiscreteTopology X] : DiscreteTopology (Multiplicative X) := ‹DiscreteTopology X›
theorem continuous_ofMul : Continuous (ofMul : X → Additive X) := continuous_id
theorem continuous_toMul : Continuous (toMul : Additive X → X) := continuous_id
theorem continuous_ofAdd : Continuous (ofAdd : X → Multiplicative X) := continuous_id
theorem continuous_toAdd : Continuous (toAdd : Multiplicative X → X) := continuous_id
theorem isOpenMap_ofMul : IsOpenMap (ofMul : X → Additive X) := IsOpenMap.id
theorem isOpenMap_toMul : IsOpenMap (toMul : Additive X → X) := IsOpenMap.id
theorem isOpenMap_ofAdd : IsOpenMap (ofAdd : X → Multiplicative X) := IsOpenMap.id
theorem isOpenMap_toAdd : IsOpenMap (toAdd : Multiplicative X → X) := IsOpenMap.id
theorem isClosedMap_ofMul : IsClosedMap (ofMul : X → Additive X) := IsClosedMap.id
theorem isClosedMap_toMul : IsClosedMap (toMul : Additive X → X) := IsClosedMap.id
theorem isClosedMap_ofAdd : IsClosedMap (ofAdd : X → Multiplicative X) := IsClosedMap.id
theorem isClosedMap_toAdd : IsClosedMap (toAdd : Multiplicative X → X) := IsClosedMap.id
theorem nhds_ofMul (x : X) : 𝓝 (ofMul x) = map ofMul (𝓝 x) := rfl
theorem nhds_ofAdd (x : X) : 𝓝 (ofAdd x) = map ofAdd (𝓝 x) := rfl
theorem nhds_toMul (x : Additive X) : 𝓝 x.toMul = map toMul (𝓝 x) := rfl
theorem nhds_toAdd (x : Multiplicative X) : 𝓝 x.toAdd = map toAdd (𝓝 x) := rfl
end
/-!
### Order dual
The topology on this type synonym is inherited without change.
-/
section
variable [TopologicalSpace X]
open OrderDual
instance OrderDual.instTopologicalSpace : TopologicalSpace Xᵒᵈ := ‹_›
instance OrderDual.instDiscreteTopology [DiscreteTopology X] : DiscreteTopology Xᵒᵈ := ‹_›
theorem continuous_toDual : Continuous (toDual : X → Xᵒᵈ) := continuous_id
theorem continuous_ofDual : Continuous (ofDual : Xᵒᵈ → X) := continuous_id
theorem isOpenMap_toDual : IsOpenMap (toDual : X → Xᵒᵈ) := IsOpenMap.id
theorem isOpenMap_ofDual : IsOpenMap (ofDual : Xᵒᵈ → X) := IsOpenMap.id
theorem isClosedMap_toDual : IsClosedMap (toDual : X → Xᵒᵈ) := IsClosedMap.id
theorem isClosedMap_ofDual : IsClosedMap (ofDual : Xᵒᵈ → X) := IsClosedMap.id
theorem nhds_toDual (x : X) : 𝓝 (toDual x) = map toDual (𝓝 x) := rfl
theorem nhds_ofDual (x : X) : 𝓝 (ofDual x) = map ofDual (𝓝 x) := rfl
variable [Preorder X] {x : X}
instance OrderDual.instNeBotNhdsWithinIoi [(𝓝[<] x).NeBot] : (𝓝[>] toDual x).NeBot := ‹_›
instance OrderDual.instNeBotNhdsWithinIio [(𝓝[>] x).NeBot] : (𝓝[<] toDual x).NeBot := ‹_›
end
theorem Quotient.preimage_mem_nhds [TopologicalSpace X] [s : Setoid X] {V : Set <| Quotient s}
{x : X} (hs : V ∈ 𝓝 (Quotient.mk' x)) : Quotient.mk' ⁻¹' V ∈ 𝓝 x :=
preimage_nhds_coinduced hs
/-- The image of a dense set under `Quotient.mk'` is a dense set. -/
theorem Dense.quotient [Setoid X] [TopologicalSpace X] {s : Set X} (H : Dense s) :
Dense (Quotient.mk' '' s) :=
Quotient.mk''_surjective.denseRange.dense_image continuous_coinduced_rng H
/-- The composition of `Quotient.mk'` and a function with dense range has dense range. -/
theorem DenseRange.quotient [Setoid X] [TopologicalSpace X] {f : Y → X} (hf : DenseRange f) :
DenseRange (Quotient.mk' ∘ f) :=
Quotient.mk''_surjective.denseRange.comp hf continuous_coinduced_rng
theorem continuous_map_of_le {α : Type*} [TopologicalSpace α]
{s t : Setoid α} (h : s ≤ t) : Continuous (Setoid.map_of_le h) :=
continuous_coinduced_rng
theorem continuous_map_sInf {α : Type*} [TopologicalSpace α]
{S : Set (Setoid α)} {s : Setoid α} (h : s ∈ S) : Continuous (Setoid.map_sInf h) :=
continuous_coinduced_rng
instance {p : X → Prop} [TopologicalSpace X] [DiscreteTopology X] : DiscreteTopology (Subtype p) :=
⟨bot_unique fun s _ => ⟨(↑) '' s, isOpen_discrete _, preimage_image_eq _ Subtype.val_injective⟩⟩
instance Sum.discreteTopology [TopologicalSpace X] [TopologicalSpace Y] [h : DiscreteTopology X]
[hY : DiscreteTopology Y] : DiscreteTopology (X ⊕ Y) :=
⟨sup_eq_bot_iff.2 <| by simp [h.eq_bot, hY.eq_bot]⟩
instance Sigma.discreteTopology {ι : Type*} {Y : ι → Type v} [∀ i, TopologicalSpace (Y i)]
[h : ∀ i, DiscreteTopology (Y i)] : DiscreteTopology (Sigma Y) :=
⟨iSup_eq_bot.2 fun _ => by simp only [(h _).eq_bot, coinduced_bot]⟩
@[simp] lemma comap_nhdsWithin_range {α β} [TopologicalSpace β] (f : α → β) (y : β) :
comap f (𝓝[range f] y) = comap f (𝓝 y) := comap_inf_principal_range
section Top
variable [TopologicalSpace X]
/-
The 𝓝 filter and the subspace topology.
-/
theorem mem_nhds_subtype (s : Set X) (x : { x // x ∈ s }) (t : Set { x // x ∈ s }) :
t ∈ 𝓝 x ↔ ∃ u ∈ 𝓝 (x : X), Subtype.val ⁻¹' u ⊆ t :=
mem_nhds_induced _ x t
theorem nhds_subtype (s : Set X) (x : { x // x ∈ s }) : 𝓝 x = comap (↑) (𝓝 (x : X)) :=
nhds_induced _ x
lemma nhds_subtype_eq_comap_nhdsWithin (s : Set X) (x : { x // x ∈ s }) :
𝓝 x = comap (↑) (𝓝[s] (x : X)) := by
rw [nhds_subtype, ← comap_nhdsWithin_range, Subtype.range_val]
theorem nhdsWithin_subtype_eq_bot_iff {s t : Set X} {x : s} :
𝓝[((↑) : s → X) ⁻¹' t] x = ⊥ ↔ 𝓝[t] (x : X) ⊓ 𝓟 s = ⊥ := by
rw [inf_principal_eq_bot_iff_comap, nhdsWithin, nhdsWithin, comap_inf, comap_principal,
nhds_induced]
theorem nhds_ne_subtype_eq_bot_iff {S : Set X} {x : S} :
𝓝[≠] x = ⊥ ↔ 𝓝[≠] (x : X) ⊓ 𝓟 S = ⊥ := by
rw [← nhdsWithin_subtype_eq_bot_iff, preimage_compl, ← image_singleton,
Subtype.coe_injective.preimage_image]
theorem nhds_ne_subtype_neBot_iff {S : Set X} {x : S} :
(𝓝[≠] x).NeBot ↔ (𝓝[≠] (x : X) ⊓ 𝓟 S).NeBot := by
rw [neBot_iff, neBot_iff, not_iff_not, nhds_ne_subtype_eq_bot_iff]
theorem discreteTopology_subtype_iff {S : Set X} :
DiscreteTopology S ↔ ∀ x ∈ S, 𝓝[≠] x ⊓ 𝓟 S = ⊥ := by
simp_rw [discreteTopology_iff_nhds_ne, SetCoe.forall', nhds_ne_subtype_eq_bot_iff]
end Top
/-- A type synonym equipped with the topology whose open sets are the empty set and the sets with
finite complements. -/
def CofiniteTopology (X : Type*) := X
namespace CofiniteTopology
/-- The identity equivalence between `` and `CofiniteTopology `. -/
def of : X ≃ CofiniteTopology X :=
Equiv.refl X
instance [Inhabited X] : Inhabited (CofiniteTopology X) where default := of default
instance : TopologicalSpace (CofiniteTopology X) where
IsOpen s := s.Nonempty → Set.Finite sᶜ
isOpen_univ := by simp
isOpen_inter s t := by
rintro hs ht ⟨x, hxs, hxt⟩
rw [compl_inter]
exact (hs ⟨x, hxs⟩).union (ht ⟨x, hxt⟩)
isOpen_sUnion := by
rintro s h ⟨x, t, hts, hzt⟩
rw [compl_sUnion]
exact Finite.sInter (mem_image_of_mem _ hts) (h t hts ⟨x, hzt⟩)
theorem isOpen_iff {s : Set (CofiniteTopology X)} : IsOpen s ↔ s.Nonempty → sᶜ.Finite :=
Iff.rfl
theorem isOpen_iff' {s : Set (CofiniteTopology X)} : IsOpen s ↔ s = ∅ ∨ sᶜ.Finite := by
simp only [isOpen_iff, nonempty_iff_ne_empty, or_iff_not_imp_left]
theorem isClosed_iff {s : Set (CofiniteTopology X)} : IsClosed s ↔ s = univ ∨ s.Finite := by
simp only [← isOpen_compl_iff, isOpen_iff', compl_compl, compl_empty_iff]
theorem nhds_eq (x : CofiniteTopology X) : 𝓝 x = pure x ⊔ cofinite := by
ext U
rw [mem_nhds_iff]
constructor
· rintro ⟨V, hVU, V_op, haV⟩
exact mem_sup.mpr ⟨hVU haV, mem_of_superset (V_op ⟨_, haV⟩) hVU⟩
· rintro ⟨hU : x ∈ U, hU' : Uᶜ.Finite⟩
exact ⟨U, Subset.rfl, fun _ => hU', hU⟩
theorem mem_nhds_iff {x : CofiniteTopology X} {s : Set (CofiniteTopology X)} :
s ∈ 𝓝 x ↔ x ∈ s ∧ sᶜ.Finite := by simp [nhds_eq]
end CofiniteTopology
end Constructions
section Prod
variable [TopologicalSpace X] [TopologicalSpace Y]
theorem MapClusterPt.curry_prodMap {α β : Type*}
{f : α → X} {g : β → Y} {la : Filter α} {lb : Filter β} {x : X} {y : Y}
(hf : MapClusterPt x la f) (hg : MapClusterPt y lb g) :
MapClusterPt (x, y) (la.curry lb) (.map f g) := by
rw [mapClusterPt_iff_frequently] at hf hg
rw [((𝓝 x).basis_sets.prod_nhds (𝓝 y).basis_sets).mapClusterPt_iff_frequently]
rintro ⟨s, t⟩ ⟨hs, ht⟩
rw [frequently_curry_iff]
exact (hf s hs).mono fun x hx ↦ (hg t ht).mono fun y hy ↦ ⟨hx, hy⟩
theorem MapClusterPt.prodMap {α β : Type*}
{f : α → X} {g : β → Y} {la : Filter α} {lb : Filter β} {x : X} {y : Y}
(hf : MapClusterPt x la f) (hg : MapClusterPt y lb g) :
MapClusterPt (x, y) (la ×ˢ lb) (.map f g) :=
(hf.curry_prodMap hg).mono <| map_mono curry_le_prod
end Prod
section Bool
lemma continuous_bool_rng [TopologicalSpace X] {f : X → Bool} (b : Bool) :
Continuous f ↔ IsClopen (f ⁻¹' {b}) := by
rw [continuous_discrete_rng, Bool.forall_bool' b, IsClopen, ← isOpen_compl_iff, ← preimage_compl,
Bool.compl_singleton, and_comm]
end Bool
section Subtype
variable [TopologicalSpace X] [TopologicalSpace Y] {p : X → Prop}
lemma Topology.IsInducing.subtypeVal {t : Set Y} : IsInducing ((↑) : t → Y) := ⟨rfl⟩
@[deprecated (since := "2024-10-28")] alias inducing_subtype_val := IsInducing.subtypeVal
lemma Topology.IsInducing.of_codRestrict {f : X → Y} {t : Set Y} (ht : ∀ x, f x ∈ t)
(h : IsInducing (t.codRestrict f ht)) : IsInducing f := subtypeVal.comp h
@[deprecated (since := "2024-10-28")] alias Inducing.of_codRestrict := IsInducing.of_codRestrict
lemma Topology.IsEmbedding.subtypeVal : IsEmbedding ((↑) : Subtype p → X) :=
⟨.subtypeVal, Subtype.coe_injective⟩
@[deprecated (since := "2024-10-26")] alias embedding_subtype_val := IsEmbedding.subtypeVal
theorem Topology.IsClosedEmbedding.subtypeVal (h : IsClosed {a | p a}) :
IsClosedEmbedding ((↑) : Subtype p → X) :=
⟨.subtypeVal, by rwa [Subtype.range_coe_subtype]⟩
@[continuity, fun_prop]
theorem continuous_subtype_val : Continuous (@Subtype.val X p) :=
continuous_induced_dom
theorem Continuous.subtype_val {f : Y → Subtype p} (hf : Continuous f) :
Continuous fun x => (f x : X) :=
continuous_subtype_val.comp hf
theorem IsOpen.isOpenEmbedding_subtypeVal {s : Set X} (hs : IsOpen s) :
IsOpenEmbedding ((↑) : s → X) :=
⟨.subtypeVal, (@Subtype.range_coe _ s).symm ▸ hs⟩
theorem IsOpen.isOpenMap_subtype_val {s : Set X} (hs : IsOpen s) : IsOpenMap ((↑) : s → X) :=
hs.isOpenEmbedding_subtypeVal.isOpenMap
theorem IsOpenMap.restrict {f : X → Y} (hf : IsOpenMap f) {s : Set X} (hs : IsOpen s) :
IsOpenMap (s.restrict f) :=
hf.comp hs.isOpenMap_subtype_val
lemma IsClosed.isClosedEmbedding_subtypeVal {s : Set X} (hs : IsClosed s) :
IsClosedEmbedding ((↑) : s → X) := .subtypeVal hs
theorem IsClosed.isClosedMap_subtype_val {s : Set X} (hs : IsClosed s) :
IsClosedMap ((↑) : s → X) :=
hs.isClosedEmbedding_subtypeVal.isClosedMap
@[continuity, fun_prop]
theorem Continuous.subtype_mk {f : Y → X} (h : Continuous f) (hp : ∀ x, p (f x)) :
Continuous fun x => (⟨f x, hp x⟩ : Subtype p) :=
continuous_induced_rng.2 h
theorem Continuous.subtype_map {f : X → Y} (h : Continuous f) {q : Y → Prop}
(hpq : ∀ x, p x → q (f x)) : Continuous (Subtype.map f hpq) :=
(h.comp continuous_subtype_val).subtype_mk _
theorem continuous_inclusion {s t : Set X} (h : s ⊆ t) : Continuous (inclusion h) :=
continuous_id.subtype_map h
theorem continuousAt_subtype_val {p : X → Prop} {x : Subtype p} :
ContinuousAt ((↑) : Subtype p → X) x :=
continuous_subtype_val.continuousAt
theorem Subtype.dense_iff {s : Set X} {t : Set s} : Dense t ↔ s ⊆ closure ((↑) '' t) := by
rw [IsInducing.subtypeVal.dense_iff, SetCoe.forall]
rfl
theorem map_nhds_subtype_val {s : Set X} (x : s) : map ((↑) : s → X) (𝓝 x) = 𝓝[s] ↑x := by
rw [IsInducing.subtypeVal.map_nhds_eq, Subtype.range_val]
theorem map_nhds_subtype_coe_eq_nhds {x : X} (hx : p x) (h : ∀ᶠ x in 𝓝 x, p x) :
map ((↑) : Subtype p → X) (𝓝 ⟨x, hx⟩) = 𝓝 x :=
map_nhds_induced_of_mem <| by rw [Subtype.range_val]; exact h
theorem nhds_subtype_eq_comap {x : X} {h : p x} : 𝓝 (⟨x, h⟩ : Subtype p) = comap (↑) (𝓝 x) :=
nhds_induced _ _
theorem tendsto_subtype_rng {Y : Type*} {p : X → Prop} {l : Filter Y} {f : Y → Subtype p} :
∀ {x : Subtype p}, Tendsto f l (𝓝 x) ↔ Tendsto (fun x => (f x : X)) l (𝓝 (x : X))
| ⟨a, ha⟩ => by rw [nhds_subtype_eq_comap, tendsto_comap_iff]; rfl
theorem closure_subtype {x : { a // p a }} {s : Set { a // p a }} :
x ∈ closure s ↔ (x : X) ∈ closure (((↑) : _ → X) '' s) :=
closure_induced
@[simp]
theorem continuousAt_codRestrict_iff {f : X → Y} {t : Set Y} (h1 : ∀ x, f x ∈ t) {x : X} :
ContinuousAt (codRestrict f t h1) x ↔ ContinuousAt f x :=
IsInducing.subtypeVal.continuousAt_iff
alias ⟨_, ContinuousAt.codRestrict⟩ := continuousAt_codRestrict_iff
theorem ContinuousAt.restrict {f : X → Y} {s : Set X} {t : Set Y} (h1 : MapsTo f s t) {x : s}
(h2 : ContinuousAt f x) : ContinuousAt (h1.restrict f s t) x :=
(h2.comp continuousAt_subtype_val).codRestrict _
theorem ContinuousAt.restrictPreimage {f : X → Y} {s : Set Y} {x : f ⁻¹' s} (h : ContinuousAt f x) :
ContinuousAt (s.restrictPreimage f) x :=
h.restrict _
@[continuity, fun_prop]
theorem Continuous.codRestrict {f : X → Y} {s : Set Y} (hf : Continuous f) (hs : ∀ a, f a ∈ s) :
Continuous (s.codRestrict f hs) :=
hf.subtype_mk hs
@[continuity, fun_prop]
theorem Continuous.restrict {f : X → Y} {s : Set X} {t : Set Y} (h1 : MapsTo f s t)
(h2 : Continuous f) : Continuous (h1.restrict f s t) :=
(h2.comp continuous_subtype_val).codRestrict _
@[continuity, fun_prop]
theorem Continuous.restrictPreimage {f : X → Y} {s : Set Y} (h : Continuous f) :
Continuous (s.restrictPreimage f) :=
h.restrict _
lemma Topology.IsEmbedding.restrict {f : X → Y}
(hf : IsEmbedding f) {s : Set X} {t : Set Y} (H : s.MapsTo f t) :
IsEmbedding H.restrict :=
.of_comp (hf.continuous.restrict H) continuous_subtype_val (hf.comp .subtypeVal)
lemma Topology.IsOpenEmbedding.restrict {f : X → Y}
(hf : IsOpenEmbedding f) {s : Set X} {t : Set Y} (H : s.MapsTo f t) (hs : IsOpen s) :
IsOpenEmbedding H.restrict :=
⟨hf.isEmbedding.restrict H, (by
rw [MapsTo.range_restrict]
exact continuous_subtype_val.1 _ (hf.isOpenMap _ hs))⟩
theorem Topology.IsInducing.codRestrict {e : X → Y} (he : IsInducing e) {s : Set Y}
(hs : ∀ x, e x ∈ s) : IsInducing (codRestrict e s hs) :=
he.of_comp (he.continuous.codRestrict hs) continuous_subtype_val
@[deprecated (since := "2024-10-28")] alias Inducing.codRestrict := IsInducing.codRestrict
protected lemma Topology.IsEmbedding.codRestrict {e : X → Y} (he : IsEmbedding e) (s : Set Y)
(hs : ∀ x, e x ∈ s) : IsEmbedding (codRestrict e s hs) :=
he.of_comp (he.continuous.codRestrict hs) continuous_subtype_val
@[deprecated (since := "2024-10-26")]
alias Embedding.codRestrict := IsEmbedding.codRestrict
variable {s t : Set X}
protected lemma Topology.IsEmbedding.inclusion (h : s ⊆ t) :
IsEmbedding (inclusion h) := IsEmbedding.subtypeVal.codRestrict _ _
protected lemma Topology.IsOpenEmbedding.inclusion (hst : s ⊆ t) (hs : IsOpen (t ↓∩ s)) :
IsOpenEmbedding (inclusion hst) where
toIsEmbedding := .inclusion _
isOpen_range := by rwa [range_inclusion]
protected lemma Topology.IsClosedEmbedding.inclusion (hst : s ⊆ t) (hs : IsClosed (t ↓∩ s)) :
IsClosedEmbedding (inclusion hst) where
toIsEmbedding := .inclusion _
isClosed_range := by rwa [range_inclusion]
@[deprecated (since := "2024-10-26")]
alias embedding_inclusion := IsEmbedding.inclusion
/-- Let `s, t ⊆ X` be two subsets of a topological space `X`. If `t ⊆ s` and the topology induced
by `X`on `s` is discrete, then also the topology induces on `t` is discrete. -/
theorem DiscreteTopology.of_subset {X : Type*} [TopologicalSpace X] {s t : Set X}
(_ : DiscreteTopology s) (ts : t ⊆ s) : DiscreteTopology t :=
(IsEmbedding.inclusion ts).discreteTopology
/-- Let `s` be a discrete subset of a topological space. Then the preimage of `s` by
a continuous injective map is also discrete. -/
theorem DiscreteTopology.preimage_of_continuous_injective {X Y : Type*} [TopologicalSpace X]
[TopologicalSpace Y] (s : Set Y) [DiscreteTopology s] {f : X → Y} (hc : Continuous f)
(hinj : Function.Injective f) : DiscreteTopology (f ⁻¹' s) :=
DiscreteTopology.of_continuous_injective (β := s) (Continuous.restrict
(by exact fun _ x ↦ x) hc) ((MapsTo.restrict_inj _).mpr hinj.injOn)
/-- If `f : X → Y` is a quotient map,
then its restriction to the preimage of an open set is a quotient map too. -/
theorem Topology.IsQuotientMap.restrictPreimage_isOpen {f : X → Y} (hf : IsQuotientMap f)
{s : Set Y} (hs : IsOpen s) : IsQuotientMap (s.restrictPreimage f) := by
refine isQuotientMap_iff.2 ⟨hf.surjective.restrictPreimage _, fun U ↦ ?_⟩
rw [hs.isOpenEmbedding_subtypeVal.isOpen_iff_image_isOpen, ← hf.isOpen_preimage,
(hs.preimage hf.continuous).isOpenEmbedding_subtypeVal.isOpen_iff_image_isOpen,
image_val_preimage_restrictPreimage]
@[deprecated (since := "2024-10-22")]
alias QuotientMap.restrictPreimage_isOpen := IsQuotientMap.restrictPreimage_isOpen
open scoped Set.Notation in
lemma isClosed_preimage_val {s t : Set X} : IsClosed (s ↓∩ t) ↔ s ∩ closure (s ∩ t) ⊆ t := by
rw [← closure_eq_iff_isClosed, IsEmbedding.subtypeVal.closure_eq_preimage_closure_image,
← Subtype.val_injective.image_injective.eq_iff, Subtype.image_preimage_coe,
Subtype.image_preimage_coe, subset_antisymm_iff, and_iff_left, Set.subset_inter_iff,
and_iff_right]
exacts [Set.inter_subset_left, Set.subset_inter Set.inter_subset_left subset_closure]
theorem frontier_inter_open_inter {s t : Set X} (ht : IsOpen t) :
frontier (s ∩ t) ∩ t = frontier s ∩ t := by
simp only [Set.inter_comm _ t, ← Subtype.preimage_coe_eq_preimage_coe_iff,
ht.isOpenMap_subtype_val.preimage_frontier_eq_frontier_preimage continuous_subtype_val,
Subtype.preimage_coe_self_inter]
section SetNotation
open scoped Set.Notation
lemma IsOpen.preimage_val {s t : Set X} (ht : IsOpen t) : IsOpen (s ↓∩ t) :=
ht.preimage continuous_subtype_val
lemma IsClosed.preimage_val {s t : Set X} (ht : IsClosed t) : IsClosed (s ↓∩ t) :=
ht.preimage continuous_subtype_val
@[simp] lemma IsOpen.inter_preimage_val_iff {s t : Set X} (hs : IsOpen s) :
IsOpen (s ↓∩ t) ↔ IsOpen (s ∩ t) :=
⟨fun h ↦ by simpa using hs.isOpenMap_subtype_val _ h,
fun h ↦ (Subtype.preimage_coe_self_inter _ _).symm ▸ h.preimage_val⟩
@[simp] lemma IsClosed.inter_preimage_val_iff {s t : Set X} (hs : IsClosed s) :
IsClosed (s ↓∩ t) ↔ IsClosed (s ∩ t) :=
⟨fun h ↦ by simpa using hs.isClosedMap_subtype_val _ h,
fun h ↦ (Subtype.preimage_coe_self_inter _ _).symm ▸ h.preimage_val⟩
end SetNotation
end Subtype
section Quotient
variable [TopologicalSpace X] [TopologicalSpace Y]
variable {r : X → X → Prop} {s : Setoid X}
theorem isQuotientMap_quot_mk : IsQuotientMap (@Quot.mk X r) :=
⟨Quot.exists_rep, rfl⟩
@[deprecated (since := "2024-10-22")]
alias quotientMap_quot_mk := isQuotientMap_quot_mk
@[continuity, fun_prop]
theorem continuous_quot_mk : Continuous (@Quot.mk X r) :=
continuous_coinduced_rng
@[continuity, fun_prop]
theorem continuous_quot_lift {f : X → Y} (hr : ∀ a b, r a b → f a = f b) (h : Continuous f) :
Continuous (Quot.lift f hr : Quot r → Y) :=
continuous_coinduced_dom.2 h
theorem isQuotientMap_quotient_mk' : IsQuotientMap (@Quotient.mk' X s) :=
isQuotientMap_quot_mk
@[deprecated (since := "2024-10-22")]
alias quotientMap_quotient_mk' := isQuotientMap_quotient_mk'
theorem continuous_quotient_mk' : Continuous (@Quotient.mk' X s) :=
continuous_coinduced_rng
theorem Continuous.quotient_lift {f : X → Y} (h : Continuous f) (hs : ∀ a b, a ≈ b → f a = f b) :
Continuous (Quotient.lift f hs : Quotient s → Y) :=
continuous_coinduced_dom.2 h
theorem Continuous.quotient_liftOn' {f : X → Y} (h : Continuous f)
(hs : ∀ a b, s a b → f a = f b) :
Continuous (fun x => Quotient.liftOn' x f hs : Quotient s → Y) :=
h.quotient_lift hs
open scoped Relator in
@[continuity, fun_prop]
theorem Continuous.quotient_map' {t : Setoid Y} {f : X → Y} (hf : Continuous f)
(H : (s.r ⇒ t.r) f f) : Continuous (Quotient.map' f H) :=
(continuous_quotient_mk'.comp hf).quotient_lift _
end Quotient
section Pi
variable {ι : Type*} {π : ι → Type*} {κ : Type*} [TopologicalSpace X]
[T : ∀ i, TopologicalSpace (π i)] {f : X → ∀ i : ι, π i}
theorem continuous_pi_iff : Continuous f ↔ ∀ i, Continuous fun a => f a i := by
simp only [continuous_iInf_rng, continuous_induced_rng, comp_def]
@[continuity, fun_prop]
theorem continuous_pi (h : ∀ i, Continuous fun a => f a i) : Continuous f :=
continuous_pi_iff.2 h
@[continuity, fun_prop]
theorem continuous_apply (i : ι) : Continuous fun p : ∀ i, π i => p i :=
continuous_iInf_dom continuous_induced_dom
@[continuity]
theorem continuous_apply_apply {ρ : κ → ι → Type*} [∀ j i, TopologicalSpace (ρ j i)] (j : κ)
(i : ι) : Continuous fun p : ∀ j, ∀ i, ρ j i => p j i :=
(continuous_apply i).comp (continuous_apply j)
theorem continuousAt_apply (i : ι) (x : ∀ i, π i) : ContinuousAt (fun p : ∀ i, π i => p i) x :=
(continuous_apply i).continuousAt
theorem Filter.Tendsto.apply_nhds {l : Filter Y} {f : Y → ∀ i, π i} {x : ∀ i, π i}
(h : Tendsto f l (𝓝 x)) (i : ι) : Tendsto (fun a => f a i) l (𝓝 <| x i) :=
(continuousAt_apply i _).tendsto.comp h
@[fun_prop]
protected theorem Continuous.piMap {Y : ι → Type*} [∀ i, TopologicalSpace (Y i)]
{f : ∀ i, π i → Y i} (hf : ∀ i, Continuous (f i)) : Continuous (Pi.map f) :=
continuous_pi fun i ↦ (hf i).comp (continuous_apply i)
theorem nhds_pi {a : ∀ i, π i} : 𝓝 a = pi fun i => 𝓝 (a i) := by
simp only [nhds_iInf, nhds_induced, Filter.pi]
protected theorem IsOpenMap.piMap {Y : ι → Type*} [∀ i, TopologicalSpace (Y i)] {f : ∀ i, π i → Y i}
(hfo : ∀ i, IsOpenMap (f i)) (hsurj : ∀ᶠ i in cofinite, Surjective (f i)) :
IsOpenMap (Pi.map f) := by
refine IsOpenMap.of_nhds_le fun x ↦ ?_
rw [nhds_pi, nhds_pi, map_piMap_pi hsurj]
exact Filter.pi_mono fun i ↦ (hfo i).nhds_le _
protected theorem IsOpenQuotientMap.piMap {Y : ι → Type*} [∀ i, TopologicalSpace (Y i)]
{f : ∀ i, π i → Y i} (hf : ∀ i, IsOpenQuotientMap (f i)) : IsOpenQuotientMap (Pi.map f) :=
⟨.piMap fun i ↦ (hf i).1, .piMap fun i ↦ (hf i).2, .piMap (fun i ↦ (hf i).3) <|
.of_forall fun i ↦ (hf i).1⟩
theorem tendsto_pi_nhds {f : Y → ∀ i, π i} {g : ∀ i, π i} {u : Filter Y} :
Tendsto f u (𝓝 g) ↔ ∀ x, Tendsto (fun i => f i x) u (𝓝 (g x)) := by
rw [nhds_pi, Filter.tendsto_pi]
theorem continuousAt_pi {f : X → ∀ i, π i} {x : X} :
ContinuousAt f x ↔ ∀ i, ContinuousAt (fun y => f y i) x :=
tendsto_pi_nhds
@[fun_prop]
theorem continuousAt_pi' {f : X → ∀ i, π i} {x : X} (hf : ∀ i, ContinuousAt (fun y => f y i) x) :
ContinuousAt f x :=
continuousAt_pi.2 hf
@[fun_prop]
protected theorem ContinuousAt.piMap {Y : ι → Type*} [∀ i, TopologicalSpace (Y i)]
{f : ∀ i, π i → Y i} {x : ∀ i, π i} (hf : ∀ i, ContinuousAt (f i) (x i)) :
ContinuousAt (Pi.map f) x :=
continuousAt_pi.2 fun i ↦ (hf i).comp (continuousAt_apply i x)
theorem Pi.continuous_precomp' {ι' : Type*} (φ : ι' → ι) :
Continuous (fun (f : (∀ i, π i)) (j : ι') ↦ f (φ j)) :=
continuous_pi fun j ↦ continuous_apply (φ j)
theorem Pi.continuous_precomp {ι' : Type*} (φ : ι' → ι) :
Continuous (· ∘ φ : (ι → X) → (ι' → X)) :=
Pi.continuous_precomp' φ
theorem Pi.continuous_postcomp' {X : ι → Type*} [∀ i, TopologicalSpace (X i)]
{g : ∀ i, π i → X i} (hg : ∀ i, Continuous (g i)) :
Continuous (fun (f : (∀ i, π i)) (i : ι) ↦ g i (f i)) :=
continuous_pi fun i ↦ (hg i).comp <| continuous_apply i
theorem Pi.continuous_postcomp [TopologicalSpace Y] {g : X → Y} (hg : Continuous g) :
Continuous (g ∘ · : (ι → X) → (ι → Y)) :=
Pi.continuous_postcomp' fun _ ↦ hg
lemma Pi.induced_precomp' {ι' : Type*} (φ : ι' → ι) :
induced (fun (f : (∀ i, π i)) (j : ι') ↦ f (φ j)) Pi.topologicalSpace =
⨅ i', induced (eval (φ i')) (T (φ i')) := by
simp [Pi.topologicalSpace, induced_iInf, induced_compose, comp_def]
lemma Pi.induced_precomp [TopologicalSpace Y] {ι' : Type*} (φ : ι' → ι) :
induced (· ∘ φ) Pi.topologicalSpace =
⨅ i', induced (eval (φ i')) ‹TopologicalSpace Y› :=
induced_precomp' φ
@[continuity, fun_prop]
lemma Pi.continuous_restrict (S : Set ι) :
Continuous (S.restrict : (∀ i : ι, π i) → (∀ i : S, π i)) :=
Pi.continuous_precomp' ((↑) : S → ι)
@[continuity, fun_prop]
lemma Pi.continuous_restrict₂ {s t : Set ι} (hst : s ⊆ t) : Continuous (restrict₂ (π := π) hst) :=
continuous_pi fun _ ↦ continuous_apply _
@[continuity, fun_prop]
theorem Finset.continuous_restrict (s : Finset ι) : Continuous (s.restrict (π := π)) :=
continuous_pi fun _ ↦ continuous_apply _
@[continuity, fun_prop]
theorem Finset.continuous_restrict₂ {s t : Finset ι} (hst : s ⊆ t) :
Continuous (Finset.restrict₂ (π := π) hst) :=
continuous_pi fun _ ↦ continuous_apply _
variable [TopologicalSpace Z]
@[continuity, fun_prop]
theorem Pi.continuous_restrict_apply (s : Set X) {f : X → Z} (hf : Continuous f) :
Continuous (s.restrict f) := hf.comp continuous_subtype_val
@[continuity, fun_prop]
theorem Pi.continuous_restrict₂_apply {s t : Set X} (hst : s ⊆ t)
{f : t → Z} (hf : Continuous f) :
Continuous (restrict₂ (π := fun _ ↦ Z) hst f) := hf.comp (continuous_inclusion hst)
@[continuity, fun_prop]
theorem Finset.continuous_restrict_apply (s : Finset X) {f : X → Z} (hf : Continuous f) :
Continuous (s.restrict f) := hf.comp continuous_subtype_val
@[continuity, fun_prop]
theorem Finset.continuous_restrict₂_apply {s t : Finset X} (hst : s ⊆ t)
{f : t → Z} (hf : Continuous f) :
Continuous (restrict₂ (π := fun _ ↦ Z) hst f) := hf.comp (continuous_inclusion hst)
lemma Pi.induced_restrict (S : Set ι) :
induced (S.restrict) Pi.topologicalSpace =
⨅ i ∈ S, induced (eval i) (T i) := by
simp +unfoldPartialApp [← iInf_subtype'', ← induced_precomp' ((↑) : S → ι),
restrict]
lemma Pi.induced_restrict_sUnion (𝔖 : Set (Set ι)) :
induced (⋃₀ 𝔖).restrict (Pi.topologicalSpace (Y := fun i : (⋃₀ 𝔖) ↦ π i)) =
⨅ S ∈ 𝔖, induced S.restrict Pi.topologicalSpace := by
simp_rw [Pi.induced_restrict, iInf_sUnion]
theorem Filter.Tendsto.update [DecidableEq ι] {l : Filter Y} {f : Y → ∀ i, π i} {x : ∀ i, π i}
(hf : Tendsto f l (𝓝 x)) (i : ι) {g : Y → π i} {xi : π i} (hg : Tendsto g l (𝓝 xi)) :
Tendsto (fun a => update (f a) i (g a)) l (𝓝 <| update x i xi) :=
tendsto_pi_nhds.2 fun j => by rcases eq_or_ne j i with (rfl | hj) <;> simp [*, hf.apply_nhds]
theorem ContinuousAt.update [DecidableEq ι] {x : X} (hf : ContinuousAt f x) (i : ι) {g : X → π i}
(hg : ContinuousAt g x) : ContinuousAt (fun a => update (f a) i (g a)) x :=
hf.tendsto.update i hg
theorem Continuous.update [DecidableEq ι] (hf : Continuous f) (i : ι) {g : X → π i}
(hg : Continuous g) : Continuous fun a => update (f a) i (g a) :=
continuous_iff_continuousAt.2 fun _ => hf.continuousAt.update i hg.continuousAt
/-- `Function.update f i x` is continuous in `(f, x)`. -/
@[continuity, fun_prop]
theorem continuous_update [DecidableEq ι] (i : ι) :
Continuous fun f : (∀ j, π j) × π i => update f.1 i f.2 :=
continuous_fst.update i continuous_snd
/-- `Pi.mulSingle i x` is continuous in `x`. -/
@[to_additive (attr := continuity) "`Pi.single i x` is continuous in `x`."]
theorem continuous_mulSingle [∀ i, One (π i)] [DecidableEq ι] (i : ι) :
Continuous fun x => (Pi.mulSingle i x : ∀ i, π i) :=
continuous_const.update _ continuous_id
section Fin
variable {n : ℕ} {π : Fin (n + 1) → Type*} [∀ i, TopologicalSpace (π i)]
theorem Filter.Tendsto.finCons
{f : Y → π 0} {g : Y → ∀ j : Fin n, π j.succ} {l : Filter Y} {x : π 0} {y : ∀ j, π (Fin.succ j)}
(hf : Tendsto f l (𝓝 x)) (hg : Tendsto g l (𝓝 y)) :
Tendsto (fun a => Fin.cons (f a) (g a)) l (𝓝 <| Fin.cons x y) :=
tendsto_pi_nhds.2 fun j => Fin.cases (by simpa) (by simpa using tendsto_pi_nhds.1 hg) j
theorem ContinuousAt.finCons {f : X → π 0} {g : X → ∀ j : Fin n, π (Fin.succ j)} {x : X}
(hf : ContinuousAt f x) (hg : ContinuousAt g x) :
ContinuousAt (fun a => Fin.cons (f a) (g a)) x :=
hf.tendsto.finCons hg
theorem Continuous.finCons {f : X → π 0} {g : X → ∀ j : Fin n, π (Fin.succ j)}
(hf : Continuous f) (hg : Continuous g) : Continuous fun a => Fin.cons (f a) (g a) :=
continuous_iff_continuousAt.2 fun _ => hf.continuousAt.finCons hg.continuousAt
theorem Filter.Tendsto.matrixVecCons
{f : Y → Z} {g : Y → Fin n → Z} {l : Filter Y} {x : Z} {y : Fin n → Z}
(hf : Tendsto f l (𝓝 x)) (hg : Tendsto g l (𝓝 y)) :
Tendsto (fun a => Matrix.vecCons (f a) (g a)) l (𝓝 <| Matrix.vecCons x y) :=
hf.finCons hg
theorem ContinuousAt.matrixVecCons
{f : X → Z} {g : X → Fin n → Z} {x : X} (hf : ContinuousAt f x) (hg : ContinuousAt g x) :
ContinuousAt (fun a => Matrix.vecCons (f a) (g a)) x :=
hf.finCons hg
theorem Continuous.matrixVecCons
{f : X → Z} {g : X → Fin n → Z} (hf : Continuous f) (hg : Continuous g) :
Continuous fun a => Matrix.vecCons (f a) (g a) :=
hf.finCons hg
theorem Filter.Tendsto.finSnoc
{f : Y → ∀ j : Fin n, π j.castSucc} {g : Y → π (Fin.last _)}
{l : Filter Y} {x : ∀ j, π (Fin.castSucc j)} {y : π (Fin.last _)}
(hf : Tendsto f l (𝓝 x)) (hg : Tendsto g l (𝓝 y)) :
Tendsto (fun a => Fin.snoc (f a) (g a)) l (𝓝 <| Fin.snoc x y) :=
tendsto_pi_nhds.2 fun j => Fin.lastCases (by simpa) (by simpa using tendsto_pi_nhds.1 hf) j
theorem ContinuousAt.finSnoc {f : X → ∀ j : Fin n, π j.castSucc} {g : X → π (Fin.last _)} {x : X}
(hf : ContinuousAt f x) (hg : ContinuousAt g x) :
ContinuousAt (fun a => Fin.snoc (f a) (g a)) x :=
hf.tendsto.finSnoc hg
theorem Continuous.finSnoc {f : X → ∀ j : Fin n, π j.castSucc} {g : X → π (Fin.last _)}
(hf : Continuous f) (hg : Continuous g) : Continuous fun a => Fin.snoc (f a) (g a) :=
continuous_iff_continuousAt.2 fun _ => hf.continuousAt.finSnoc hg.continuousAt
theorem Filter.Tendsto.finInsertNth
(i : Fin (n + 1)) {f : Y → π i} {g : Y → ∀ j : Fin n, π (i.succAbove j)} {l : Filter Y}
{x : π i} {y : ∀ j, π (i.succAbove j)} (hf : Tendsto f l (𝓝 x)) (hg : Tendsto g l (𝓝 y)) :
Tendsto (fun a => i.insertNth (f a) (g a)) l (𝓝 <| i.insertNth x y) :=
tendsto_pi_nhds.2 fun j => Fin.succAboveCases i (by simpa) (by simpa using tendsto_pi_nhds.1 hg) j
@[deprecated (since := "2025-01-02")]
alias Filter.Tendsto.fin_insertNth := Filter.Tendsto.finInsertNth
theorem ContinuousAt.finInsertNth
(i : Fin (n + 1)) {f : X → π i} {g : X → ∀ j : Fin n, π (i.succAbove j)} {x : X}
(hf : ContinuousAt f x) (hg : ContinuousAt g x) :
ContinuousAt (fun a => i.insertNth (f a) (g a)) x :=
hf.tendsto.finInsertNth i hg
@[deprecated (since := "2025-01-02")]
alias ContinuousAt.fin_insertNth := ContinuousAt.finInsertNth
theorem Continuous.finInsertNth
(i : Fin (n + 1)) {f : X → π i} {g : X → ∀ j : Fin n, π (i.succAbove j)}
(hf : Continuous f) (hg : Continuous g) : Continuous fun a => i.insertNth (f a) (g a) :=
continuous_iff_continuousAt.2 fun _ => hf.continuousAt.finInsertNth i hg.continuousAt
@[deprecated (since := "2025-01-02")]
alias Continuous.fin_insertNth := Continuous.finInsertNth
theorem Filter.Tendsto.finInit {f : Y → ∀ j : Fin (n + 1), π j} {l : Filter Y} {x : ∀ j, π j}
(hg : Tendsto f l (𝓝 x)) : Tendsto (fun a ↦ Fin.init (f a)) l (𝓝 <| Fin.init x) :=
tendsto_pi_nhds.2 fun j ↦ apply_nhds hg j.castSucc
@[fun_prop]
theorem ContinuousAt.finInit {f : X → ∀ j : Fin (n + 1), π j} {x : X}
(hf : ContinuousAt f x) : ContinuousAt (fun a ↦ Fin.init (f a)) x :=
hf.tendsto.finInit
@[fun_prop]
theorem Continuous.finInit {f : X → ∀ j : Fin (n + 1), π j} (hf : Continuous f) :
Continuous fun a ↦ Fin.init (f a) :=
continuous_iff_continuousAt.2 fun _ ↦ hf.continuousAt.finInit
theorem Filter.Tendsto.finTail {f : Y → ∀ j : Fin (n + 1), π j} {l : Filter Y} {x : ∀ j, π j}
(hg : Tendsto f l (𝓝 x)) : Tendsto (fun a ↦ Fin.tail (f a)) l (𝓝 <| Fin.tail x) :=
tendsto_pi_nhds.2 fun j ↦ apply_nhds hg j.succ
@[fun_prop]
theorem ContinuousAt.finTail {f : X → ∀ j : Fin (n + 1), π j} {x : X}
(hf : ContinuousAt f x) : ContinuousAt (fun a ↦ Fin.tail (f a)) x :=
hf.tendsto.finTail
@[fun_prop]
theorem Continuous.finTail {f : X → ∀ j : Fin (n + 1), π j} (hf : Continuous f) :
Continuous fun a ↦ Fin.tail (f a) :=
continuous_iff_continuousAt.2 fun _ ↦ hf.continuousAt.finTail
end Fin
theorem isOpen_set_pi {i : Set ι} {s : ∀ a, Set (π a)} (hi : i.Finite)
(hs : ∀ a ∈ i, IsOpen (s a)) : IsOpen (pi i s) := by
rw [pi_def]; exact hi.isOpen_biInter fun a ha => (hs _ ha).preimage (continuous_apply _)
|
theorem isOpen_pi_iff {s : Set (∀ a, π a)} :
IsOpen s ↔
| Mathlib/Topology/Constructions.lean | 858 | 860 |
/-
Copyright (c) 2022 Yaël Dillies, George Shakan. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yaël Dillies, George Shakan
-/
import Mathlib.Algebra.Order.Field.Rat
import Mathlib.Combinatorics.Enumerative.DoubleCounting
import Mathlib.Tactic.FieldSimp
import Mathlib.Tactic.GCongr
import Mathlib.Tactic.Positivity
import Mathlib.Tactic.Ring
import Mathlib.Algebra.Group.Pointwise.Finset.Basic
/-!
# The Plünnecke-Ruzsa inequality
This file proves Ruzsa's triangle inequality, the Plünnecke-Petridis lemma, and the Plünnecke-Ruzsa
inequality.
## Main declarations
* `Finset.ruzsa_triangle_inequality_sub_sub_sub`: The Ruzsa triangle inequality, difference version.
* `Finset.ruzsa_triangle_inequality_add_add_add`: The Ruzsa triangle inequality, sum version.
* `Finset.pluennecke_petridis_inequality_add`: The Plünnecke-Petridis inequality.
* `Finset.pluennecke_ruzsa_inequality_nsmul_sub_nsmul_add`: The Plünnecke-Ruzsa inequality.
## References
* [Giorgis Petridis, *The Plünnecke-Ruzsa inequality: an overview*][petridis2014]
* [Terrence Tao, Van Vu, *Additive Combinatorics][tao-vu]
## See also
In general non-abelian groups, small doubling doesn't imply small powers anymore, but small tripling
does. See `Mathlib.Combinatorics.Additive.SmallTripling`.
-/
open MulOpposite Nat
open scoped Pointwise
namespace Finset
variable {G : Type*} [DecidableEq G]
section Group
variable [Group G] {A B C : Finset G}
/-! ### Noncommutative Ruzsa triangle inequality -/
/-- **Ruzsa's triangle inequality**. Division version. -/
@[to_additive "**Ruzsa's triangle inequality**. Subtraction version."]
theorem ruzsa_triangle_inequality_div_div_div (A B C : Finset G) :
#(A / C) * #B ≤ #(A / B) * #(C / B) := by
rw [← card_product (A / B), ← mul_one #((A / B) ×ˢ (C / B))]
refine card_mul_le_card_mul (fun b (a, c) ↦ a / c = b) (fun x hx ↦ ?_)
fun x _ ↦ card_le_one_iff.2 fun hu hv ↦
((mem_bipartiteBelow _).1 hu).2.symm.trans ?_
· obtain ⟨a, ha, c, hc, rfl⟩ := mem_div.1 hx
refine card_le_card_of_injOn (fun b ↦ (a / b, c / b)) (fun b hb ↦ ?_) fun b₁ _ b₂ _ h ↦ ?_
· rw [mem_bipartiteAbove]
exact ⟨mk_mem_product (div_mem_div ha hb) (div_mem_div hc hb), div_div_div_cancel_right ..⟩
· exact div_right_injective (Prod.ext_iff.1 h).1
· exact ((mem_bipartiteBelow _).1 hv).2
/-- **Ruzsa's triangle inequality**. Mulinv-mulinv-mulinv version. -/
@[to_additive "**Ruzsa's triangle inequality**. Addneg-addneg-addneg version."]
theorem ruzsa_triangle_inequality_mulInv_mulInv_mulInv (A B C : Finset G) :
#(A * C⁻¹) * #B ≤ #(A * B⁻¹) * #(C * B⁻¹) := by
simpa [div_eq_mul_inv] using ruzsa_triangle_inequality_div_div_div A B C
/-- **Ruzsa's triangle inequality**. Invmul-invmul-invmul version. -/
@[to_additive "**Ruzsa's triangle inequality**. Negadd-negadd-negadd version."]
theorem ruzsa_triangle_inequality_invMul_invMul_invMul (A B C : Finset G) :
#B * #(A⁻¹ * C) ≤ #(B⁻¹ * A) * #(B⁻¹ * C) := by
simpa [mul_comm, div_eq_mul_inv, ← map_op_mul, ← map_op_inv] using
ruzsa_triangle_inequality_div_div_div (G := Gᵐᵒᵖ) (C.map opEquiv.toEmbedding)
(B.map opEquiv.toEmbedding) (A.map opEquiv.toEmbedding)
/-- **Ruzsa's triangle inequality**. Div-mul-mul version. -/
@[to_additive "**Ruzsa's triangle inequality**. Sub-add-add version."]
theorem ruzsa_triangle_inequality_div_mul_mul (A B C : Finset G) :
#(A / C) * #B ≤ #(A * B) * #(C * B) := by
simpa using ruzsa_triangle_inequality_div_div_div A B⁻¹ C
/-- **Ruzsa's triangle inequality**. Mulinv-mul-mul version. -/
@[to_additive "**Ruzsa's triangle inequality**. Addneg-add-add version."]
theorem ruzsa_triangle_inequality_mulInv_mul_mul (A B C : Finset G) :
#(A * C⁻¹) * #B ≤ #(A * B) * #(C * B) := by
simpa using ruzsa_triangle_inequality_mulInv_mulInv_mulInv A B⁻¹ C
/-- **Ruzsa's triangle inequality**. Invmul-mul-mul version. -/
@[to_additive "**Ruzsa's triangle inequality**. Negadd-add-add version."]
theorem ruzsa_triangle_inequality_invMul_mul_mul (A B C : Finset G) :
#B * #(A⁻¹ * C) ≤ #(B * A) * #(B * C) := by
simpa using ruzsa_triangle_inequality_invMul_invMul_invMul A B⁻¹ C
/-- **Ruzsa's triangle inequality**. Mul-div-mul version. -/
@[to_additive "**Ruzsa's triangle inequality**. Add-sub-add version."]
theorem ruzsa_triangle_inequality_mul_div_mul (A B C : Finset G) :
#B * #(A * C) ≤ #(B / A) * #(B * C) := by
simpa [div_eq_mul_inv] using ruzsa_triangle_inequality_invMul_mul_mul A⁻¹ B C
/-- **Ruzsa's triangle inequality**. Mul-mulinv-mul version. -/
@[to_additive "**Ruzsa's triangle inequality**. Add-addneg-add version."]
theorem ruzsa_triangle_inequality_mul_mulInv_mul (A B C : Finset G) :
#B * #(A * C) ≤ #(B * A⁻¹) * #(B * C) := by
simpa [div_eq_mul_inv] using ruzsa_triangle_inequality_mul_div_mul A B C
/-- **Ruzsa's triangle inequality**. Mul-mul-invmul version. -/
@[to_additive "**Ruzsa's triangle inequality**. Add-add-negadd version."]
theorem ruzsa_triangle_inequality_mul_mul_invMul (A B C : Finset G) :
#(A * C) * #B ≤ #(A * B) * #(C⁻¹ * B) := by
simpa using ruzsa_triangle_inequality_mulInv_mul_mul A B C⁻¹
/-! ### Plünnecke-Petridis inequality -/
@[to_additive]
theorem pluennecke_petridis_inequality_mul (C : Finset G)
(hA : ∀ A' ⊆ A, #(A * B) * #A' ≤ #(A' * B) * #A) :
#(C * A * B) * #A ≤ #(A * B) * #(C * A) := by
induction C using Finset.induction_on with
| empty => simp
| insert x C _ ih =>
set A' := A ∩ ({x}⁻¹ * C * A) with hA'
set C' := insert x C with hC'
| have h₀ : {x} * A' = {x} * A ∩ (C * A) := by
rw [hA', mul_assoc, singleton_mul_inter, (isUnit_singleton x).mul_inv_cancel_left]
have h₁ : C' * A * B = C * A * B ∪ ({x} * A * B) \ ({x} * A' * B) := by
rw [hC', insert_eq, union_comm, union_mul, union_mul]
refine (sup_sdiff_eq_sup ?_).symm
rw [h₀]
gcongr
exact inter_subset_right
have h₂ : {x} * A' * B ⊆ {x} * A * B := by gcongr; exact inter_subset_left
have h₃ : #(C' * A * B) ≤ #(C * A * B) + #(A * B) - #(A' * B) := by
rw [h₁]
| Mathlib/Combinatorics/Additive/PluenneckeRuzsa.lean | 126 | 136 |
/-
Copyright (c) 2021 Yury Kudryashov. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yury Kudryashov
-/
import Mathlib.Analysis.Calculus.FDeriv.Prod
import Mathlib.Analysis.Calculus.InverseFunctionTheorem.FDeriv
import Mathlib.GroupTheory.MonoidLocalization.Basic
import Mathlib.LinearAlgebra.Dual.Defs
/-!
# Lagrange multipliers
In this file we formalize the
[Lagrange multipliers](https://en.wikipedia.org/wiki/Lagrange_multiplier) method of solving
conditional extremum problems: if a function `φ` has a local extremum at `x₀` on the set
`f ⁻¹' {f x₀}`, `f x = (f₀ x, ..., fₙ₋₁ x)`, then the differentials of `fₖ` and `φ` are linearly
dependent. First we formulate a geometric version of this theorem which does not rely on the
target space being `ℝⁿ`, then restate it in terms of coordinates.
## TODO
Formalize Karush-Kuhn-Tucker theorem
## Tags
lagrange multiplier, local extremum
-/
open Filter Set
open scoped Topology Filter
variable {E F : Type*} [NormedAddCommGroup E] [NormedSpace ℝ E] [CompleteSpace E]
[NormedAddCommGroup F] [NormedSpace ℝ F] [CompleteSpace F] {f : E → F} {φ : E → ℝ} {x₀ : E}
{f' : E →L[ℝ] F} {φ' : E →L[ℝ] ℝ}
/-- Lagrange multipliers theorem: if `φ : E → ℝ` has a local extremum on the set `{x | f x = f x₀}`
at `x₀`, both `f : E → F` and `φ` are strictly differentiable at `x₀`, and the codomain of `f` is
a complete space, then the linear map `x ↦ (f' x, φ' x)` is not surjective. -/
theorem IsLocalExtrOn.range_ne_top_of_hasStrictFDerivAt
| (hextr : IsLocalExtrOn φ {x | f x = f x₀} x₀) (hf' : HasStrictFDerivAt f f' x₀)
(hφ' : HasStrictFDerivAt φ φ' x₀) : LinearMap.range (f'.prod φ') ≠ ⊤ := by
intro htop
set fφ := fun x => (f x, φ x)
have A : map φ (𝓝[f ⁻¹' {f x₀}] x₀) = 𝓝 (φ x₀) := by
change map (Prod.snd ∘ fφ) (𝓝[fφ ⁻¹' {p | p.1 = f x₀}] x₀) = 𝓝 (φ x₀)
rw [← map_map, nhdsWithin, map_inf_principal_preimage,
(hf'.prodMk hφ').map_nhds_eq_of_surj htop]
exact map_snd_nhdsWithin _
exact hextr.not_nhds_le_map A.ge
| Mathlib/Analysis/Calculus/LagrangeMultipliers.lean | 44 | 53 |
/-
Copyright (c) 2023 Eric Wieser. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Eric Wieser, Ahmad Alkhalawi
-/
import Mathlib.Data.Matrix.ConjTranspose
import Mathlib.Tactic.Abel
/-! # Extra lemmas about invertible matrices
A few of the `Invertible` lemmas generalize to multiplication of rectangular matrices.
For lemmas about the matrix inverse in terms of the determinant and adjugate, see `Matrix.inv`
in `LinearAlgebra/Matrix/NonsingularInverse.lean`.
## Main results
* `Matrix.invertibleConjTranspose`
* `Matrix.invertibleTranspose`
* `Matrix.isUnit_conjTranspose`
* `Matrix.isUnit_transpose`
-/
open scoped Matrix
variable {m n : Type*} {α : Type*}
variable [Fintype n] [DecidableEq n]
namespace Matrix
section Semiring
variable [Semiring α]
/-- A copy of `invOf_mul_cancel_left` for rectangular matrices. -/
protected theorem invOf_mul_cancel_left (A : Matrix n n α) (B : Matrix n m α) [Invertible A] :
⅟ A * (A * B) = B := by rw [← Matrix.mul_assoc, invOf_mul_self, Matrix.one_mul]
/-- A copy of `mul_invOf_cancel_left` for rectangular matrices. -/
protected theorem mul_invOf_cancel_left (A : Matrix n n α) (B : Matrix n m α) [Invertible A] :
A * (⅟ A * B) = B := by rw [← Matrix.mul_assoc, mul_invOf_self, Matrix.one_mul]
/-- A copy of `invOf_mul_cancel_right` for rectangular matrices. -/
protected theorem invOf_mul_cancel_right (A : Matrix m n α) (B : Matrix n n α) [Invertible B] :
A * ⅟ B * B = A := by rw [Matrix.mul_assoc, invOf_mul_self, Matrix.mul_one]
/-- A copy of `mul_invOf_cancel_right` for rectangular matrices. -/
protected theorem mul_invOf_cancel_right (A : Matrix m n α) (B : Matrix n n α) [Invertible B] :
A * B * ⅟ B = A := by rw [Matrix.mul_assoc, mul_invOf_self, Matrix.mul_one]
section ConjTranspose
variable [StarRing α] (A : Matrix n n α)
/-- The conjugate transpose of an invertible matrix is invertible. -/
| instance invertibleConjTranspose [Invertible A] : Invertible Aᴴ := Invertible.star _
| Mathlib/Data/Matrix/Invertible.lean | 55 | 56 |
/-
Copyright (c) 2022 Yaël Dillies. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yaël Dillies
-/
import Mathlib.Order.PropInstances
import Mathlib.Order.GaloisConnection.Defs
/-!
# Heyting algebras
This file defines Heyting, co-Heyting and bi-Heyting algebras.
A Heyting algebra is a bounded distributive lattice with an implication operation `⇨` such that
`a ≤ b ⇨ c ↔ a ⊓ b ≤ c`. It also comes with a pseudo-complement `ᶜ`, such that `aᶜ = a ⇨ ⊥`.
Co-Heyting algebras are dual to Heyting algebras. They have a difference `\` and a negation `￢`
such that `a \ b ≤ c ↔ a ≤ b ⊔ c` and `￢a = ⊤ \ a`.
Bi-Heyting algebras are Heyting algebras that are also co-Heyting algebras.
From a logic standpoint, Heyting algebras precisely model intuitionistic logic, whereas boolean
algebras model classical logic.
Heyting algebras are the order theoretic equivalent of cartesian-closed categories.
## Main declarations
* `GeneralizedHeytingAlgebra`: Heyting algebra without a top element (nor negation).
* `GeneralizedCoheytingAlgebra`: Co-Heyting algebra without a bottom element (nor complement).
* `HeytingAlgebra`: Heyting algebra.
* `CoheytingAlgebra`: Co-Heyting algebra.
* `BiheytingAlgebra`: bi-Heyting algebra.
## References
* [Francis Borceux, *Handbook of Categorical Algebra III*][borceux-vol3]
## Tags
Heyting, Brouwer, algebra, implication, negation, intuitionistic
-/
assert_not_exists RelIso
open Function OrderDual
universe u
variable {ι α β : Type*}
/-! ### Notation -/
section
variable (α β)
instance Prod.instHImp [HImp α] [HImp β] : HImp (α × β) :=
⟨fun a b => (a.1 ⇨ b.1, a.2 ⇨ b.2)⟩
instance Prod.instHNot [HNot α] [HNot β] : HNot (α × β) :=
⟨fun a => (￢a.1, ￢a.2)⟩
instance Prod.instSDiff [SDiff α] [SDiff β] : SDiff (α × β) :=
⟨fun a b => (a.1 \ b.1, a.2 \ b.2)⟩
instance Prod.instHasCompl [HasCompl α] [HasCompl β] : HasCompl (α × β) :=
⟨fun a => (a.1ᶜ, a.2ᶜ)⟩
end
@[simp]
theorem fst_himp [HImp α] [HImp β] (a b : α × β) : (a ⇨ b).1 = a.1 ⇨ b.1 :=
rfl
@[simp]
theorem snd_himp [HImp α] [HImp β] (a b : α × β) : (a ⇨ b).2 = a.2 ⇨ b.2 :=
rfl
@[simp]
theorem fst_hnot [HNot α] [HNot β] (a : α × β) : (￢a).1 = ￢a.1 :=
rfl
@[simp]
theorem snd_hnot [HNot α] [HNot β] (a : α × β) : (￢a).2 = ￢a.2 :=
rfl
@[simp]
theorem fst_sdiff [SDiff α] [SDiff β] (a b : α × β) : (a \ b).1 = a.1 \ b.1 :=
rfl
@[simp]
theorem snd_sdiff [SDiff α] [SDiff β] (a b : α × β) : (a \ b).2 = a.2 \ b.2 :=
rfl
@[simp]
theorem fst_compl [HasCompl α] [HasCompl β] (a : α × β) : aᶜ.1 = a.1ᶜ :=
rfl
@[simp]
theorem snd_compl [HasCompl α] [HasCompl β] (a : α × β) : aᶜ.2 = a.2ᶜ :=
rfl
namespace Pi
variable {π : ι → Type*}
instance [∀ i, HImp (π i)] : HImp (∀ i, π i) :=
⟨fun a b i => a i ⇨ b i⟩
instance [∀ i, HNot (π i)] : HNot (∀ i, π i) :=
⟨fun a i => ￢a i⟩
theorem himp_def [∀ i, HImp (π i)] (a b : ∀ i, π i) : a ⇨ b = fun i => a i ⇨ b i :=
rfl
theorem hnot_def [∀ i, HNot (π i)] (a : ∀ i, π i) : ￢a = fun i => ￢a i :=
rfl
@[simp]
theorem himp_apply [∀ i, HImp (π i)] (a b : ∀ i, π i) (i : ι) : (a ⇨ b) i = a i ⇨ b i :=
rfl
@[simp]
theorem hnot_apply [∀ i, HNot (π i)] (a : ∀ i, π i) (i : ι) : (￢a) i = ￢a i :=
rfl
end Pi
/-- A generalized Heyting algebra is a lattice with an additional binary operation `⇨` called
Heyting implication such that `(a ⇨ ·)` is right adjoint to `(a ⊓ ·)`.
This generalizes `HeytingAlgebra` by not requiring a bottom element. -/
class GeneralizedHeytingAlgebra (α : Type*) extends Lattice α, OrderTop α, HImp α where
/-- `(a ⇨ ·)` is right adjoint to `(a ⊓ ·)` -/
le_himp_iff (a b c : α) : a ≤ b ⇨ c ↔ a ⊓ b ≤ c
/-- A generalized co-Heyting algebra is a lattice with an additional binary
difference operation `\` such that `(· \ a)` is left adjoint to `(· ⊔ a)`.
This generalizes `CoheytingAlgebra` by not requiring a top element. -/
class GeneralizedCoheytingAlgebra (α : Type*) extends Lattice α, OrderBot α, SDiff α where
/-- `(· \ a)` is left adjoint to `(· ⊔ a)` -/
sdiff_le_iff (a b c : α) : a \ b ≤ c ↔ a ≤ b ⊔ c
/-- A Heyting algebra is a bounded lattice with an additional binary operation `⇨` called Heyting
implication such that `(a ⇨ ·)` is right adjoint to `(a ⊓ ·)`. -/
class HeytingAlgebra (α : Type*) extends GeneralizedHeytingAlgebra α, OrderBot α, HasCompl α where
/-- `aᶜ` is defined as `a ⇨ ⊥` -/
himp_bot (a : α) : a ⇨ ⊥ = aᶜ
/-- A co-Heyting algebra is a bounded lattice with an additional binary difference operation `\`
such that `(· \ a)` is left adjoint to `(· ⊔ a)`. -/
class CoheytingAlgebra (α : Type*) extends GeneralizedCoheytingAlgebra α, OrderTop α, HNot α where
/-- `⊤ \ a` is `￢a` -/
top_sdiff (a : α) : ⊤ \ a = ￢a
/-- A bi-Heyting algebra is a Heyting algebra that is also a co-Heyting algebra. -/
class BiheytingAlgebra (α : Type*) extends HeytingAlgebra α, SDiff α, HNot α where
/-- `(· \ a)` is left adjoint to `(· ⊔ a)` -/
sdiff_le_iff (a b c : α) : a \ b ≤ c ↔ a ≤ b ⊔ c
/-- `⊤ \ a` is `￢a` -/
top_sdiff (a : α) : ⊤ \ a = ￢a
-- See note [lower instance priority]
attribute [instance 100] GeneralizedHeytingAlgebra.toOrderTop
attribute [instance 100] GeneralizedCoheytingAlgebra.toOrderBot
-- See note [lower instance priority]
instance (priority := 100) HeytingAlgebra.toBoundedOrder [HeytingAlgebra α] : BoundedOrder α :=
{ bot_le := ‹HeytingAlgebra α›.bot_le }
-- See note [lower instance priority]
instance (priority := 100) CoheytingAlgebra.toBoundedOrder [CoheytingAlgebra α] : BoundedOrder α :=
{ ‹CoheytingAlgebra α› with }
-- See note [lower instance priority]
instance (priority := 100) BiheytingAlgebra.toCoheytingAlgebra [BiheytingAlgebra α] :
CoheytingAlgebra α :=
{ ‹BiheytingAlgebra α› with }
-- See note [reducible non-instances]
/-- Construct a Heyting algebra from the lattice structure and Heyting implication alone. -/
abbrev HeytingAlgebra.ofHImp [DistribLattice α] [BoundedOrder α] (himp : α → α → α)
(le_himp_iff : ∀ a b c, a ≤ himp b c ↔ a ⊓ b ≤ c) : HeytingAlgebra α :=
{ ‹DistribLattice α›, ‹BoundedOrder α› with
himp,
compl := fun a => himp a ⊥,
le_himp_iff,
himp_bot := fun _ => rfl }
-- See note [reducible non-instances]
/-- Construct a Heyting algebra from the lattice structure and complement operator alone. -/
abbrev HeytingAlgebra.ofCompl [DistribLattice α] [BoundedOrder α] (compl : α → α)
(le_himp_iff : ∀ a b c, a ≤ compl b ⊔ c ↔ a ⊓ b ≤ c) : HeytingAlgebra α where
himp := (compl · ⊔ ·)
compl := compl
le_himp_iff := le_himp_iff
himp_bot _ := sup_bot_eq _
-- See note [reducible non-instances]
/-- Construct a co-Heyting algebra from the lattice structure and the difference alone. -/
abbrev CoheytingAlgebra.ofSDiff [DistribLattice α] [BoundedOrder α] (sdiff : α → α → α)
(sdiff_le_iff : ∀ a b c, sdiff a b ≤ c ↔ a ≤ b ⊔ c) : CoheytingAlgebra α :=
{ ‹DistribLattice α›, ‹BoundedOrder α› with
sdiff,
hnot := fun a => sdiff ⊤ a,
sdiff_le_iff,
top_sdiff := fun _ => rfl }
-- See note [reducible non-instances]
/-- Construct a co-Heyting algebra from the difference and Heyting negation alone. -/
abbrev CoheytingAlgebra.ofHNot [DistribLattice α] [BoundedOrder α] (hnot : α → α)
(sdiff_le_iff : ∀ a b c, a ⊓ hnot b ≤ c ↔ a ≤ b ⊔ c) : CoheytingAlgebra α where
sdiff a b := a ⊓ hnot b
hnot := hnot
sdiff_le_iff := sdiff_le_iff
top_sdiff _ := top_inf_eq _
/-! In this section, we'll give interpretations of these results in the Heyting algebra model of
intuitionistic logic,- where `≤` can be interpreted as "validates", `⇨` as "implies", `⊓` as "and",
`⊔` as "or", `⊥` as "false" and `⊤` as "true". Note that we confuse `→` and `⊢` because those are
the same in this logic.
See also `Prop.heytingAlgebra`. -/
section GeneralizedHeytingAlgebra
variable [GeneralizedHeytingAlgebra α] {a b c d : α}
/-- `p → q → r ↔ p ∧ q → r` -/
@[simp]
theorem le_himp_iff : a ≤ b ⇨ c ↔ a ⊓ b ≤ c :=
GeneralizedHeytingAlgebra.le_himp_iff _ _ _
/-- `p → q → r ↔ q ∧ p → r` -/
theorem le_himp_iff' : a ≤ b ⇨ c ↔ b ⊓ a ≤ c := by rw [le_himp_iff, inf_comm]
/-- `p → q → r ↔ q → p → r` -/
theorem le_himp_comm : a ≤ b ⇨ c ↔ b ≤ a ⇨ c := by rw [le_himp_iff, le_himp_iff']
/-- `p → q → p` -/
theorem le_himp : a ≤ b ⇨ a :=
le_himp_iff.2 inf_le_left
/-- `p → p → q ↔ p → q` -/
theorem le_himp_iff_left : a ≤ a ⇨ b ↔ a ≤ b := by rw [le_himp_iff, inf_idem]
/-- `p → p` -/
@[simp]
theorem himp_self : a ⇨ a = ⊤ :=
top_le_iff.1 <| le_himp_iff.2 inf_le_right
/-- `(p → q) ∧ p → q` -/
theorem himp_inf_le : (a ⇨ b) ⊓ a ≤ b :=
le_himp_iff.1 le_rfl
/-- `p ∧ (p → q) → q` -/
theorem inf_himp_le : a ⊓ (a ⇨ b) ≤ b := by rw [inf_comm, ← le_himp_iff]
/-- `p ∧ (p → q) ↔ p ∧ q` -/
@[simp]
theorem inf_himp (a b : α) : a ⊓ (a ⇨ b) = a ⊓ b :=
le_antisymm (le_inf inf_le_left <| by rw [inf_comm, ← le_himp_iff]) <| inf_le_inf_left _ le_himp
/-- `(p → q) ∧ p ↔ q ∧ p` -/
@[simp]
theorem himp_inf_self (a b : α) : (a ⇨ b) ⊓ a = b ⊓ a := by rw [inf_comm, inf_himp, inf_comm]
/-- The **deduction theorem** in the Heyting algebra model of intuitionistic logic:
an implication holds iff the conclusion follows from the hypothesis. -/
@[simp]
theorem himp_eq_top_iff : a ⇨ b = ⊤ ↔ a ≤ b := by rw [← top_le_iff, le_himp_iff, top_inf_eq]
/-- `p → true`, `true → p ↔ p` -/
@[simp]
theorem himp_top : a ⇨ ⊤ = ⊤ :=
himp_eq_top_iff.2 le_top
@[simp]
theorem top_himp : ⊤ ⇨ a = a :=
eq_of_forall_le_iff fun b => by rw [le_himp_iff, inf_top_eq]
/-- `p → q → r ↔ p ∧ q → r` -/
theorem himp_himp (a b c : α) : a ⇨ b ⇨ c = a ⊓ b ⇨ c :=
eq_of_forall_le_iff fun d => by simp_rw [le_himp_iff, inf_assoc]
/-- `(q → r) → (p → q) → q → r` -/
theorem himp_le_himp_himp_himp : b ⇨ c ≤ (a ⇨ b) ⇨ a ⇨ c := by
rw [le_himp_iff, le_himp_iff, inf_assoc, himp_inf_self, ← inf_assoc, himp_inf_self, inf_assoc]
exact inf_le_left
@[simp]
theorem himp_inf_himp_inf_le : (b ⇨ c) ⊓ (a ⇨ b) ⊓ a ≤ c := by
simpa using @himp_le_himp_himp_himp
/-- `p → q → r ↔ q → p → r` -/
theorem himp_left_comm (a b c : α) : a ⇨ b ⇨ c = b ⇨ a ⇨ c := by simp_rw [himp_himp, inf_comm]
@[simp]
theorem himp_idem : b ⇨ b ⇨ a = b ⇨ a := by rw [himp_himp, inf_idem]
theorem himp_inf_distrib (a b c : α) : a ⇨ b ⊓ c = (a ⇨ b) ⊓ (a ⇨ c) :=
eq_of_forall_le_iff fun d => by simp_rw [le_himp_iff, le_inf_iff, le_himp_iff]
theorem sup_himp_distrib (a b c : α) : a ⊔ b ⇨ c = (a ⇨ c) ⊓ (b ⇨ c) :=
eq_of_forall_le_iff fun d => by
rw [le_inf_iff, le_himp_comm, sup_le_iff]
simp_rw [le_himp_comm]
theorem himp_le_himp_left (h : a ≤ b) : c ⇨ a ≤ c ⇨ b :=
le_himp_iff.2 <| himp_inf_le.trans h
theorem himp_le_himp_right (h : a ≤ b) : b ⇨ c ≤ a ⇨ c :=
le_himp_iff.2 <| (inf_le_inf_left _ h).trans himp_inf_le
theorem himp_le_himp (hab : a ≤ b) (hcd : c ≤ d) : b ⇨ c ≤ a ⇨ d :=
(himp_le_himp_right hab).trans <| himp_le_himp_left hcd
@[simp]
theorem sup_himp_self_left (a b : α) : a ⊔ b ⇨ a = b ⇨ a := by
rw [sup_himp_distrib, himp_self, top_inf_eq]
@[simp]
theorem sup_himp_self_right (a b : α) : a ⊔ b ⇨ b = a ⇨ b := by
rw [sup_himp_distrib, himp_self, inf_top_eq]
theorem Codisjoint.himp_eq_right (h : Codisjoint a b) : b ⇨ a = a := by
conv_rhs => rw [← @top_himp _ _ a]
rw [← h.eq_top, sup_himp_self_left]
theorem Codisjoint.himp_eq_left (h : Codisjoint a b) : a ⇨ b = b :=
h.symm.himp_eq_right
theorem Codisjoint.himp_inf_cancel_right (h : Codisjoint a b) : a ⇨ a ⊓ b = b := by
rw [himp_inf_distrib, himp_self, top_inf_eq, h.himp_eq_left]
theorem Codisjoint.himp_inf_cancel_left (h : Codisjoint a b) : b ⇨ a ⊓ b = a := by
rw [himp_inf_distrib, himp_self, inf_top_eq, h.himp_eq_right]
/-- See `himp_le` for a stronger version in Boolean algebras. -/
theorem Codisjoint.himp_le_of_right_le (hac : Codisjoint a c) (hba : b ≤ a) : c ⇨ b ≤ a :=
(himp_le_himp_left hba).trans_eq hac.himp_eq_right
theorem le_himp_himp : a ≤ (a ⇨ b) ⇨ b :=
le_himp_iff.2 inf_himp_le
@[simp] lemma himp_eq_himp_iff : b ⇨ a = a ⇨ b ↔ a = b := by simp [le_antisymm_iff]
lemma himp_ne_himp_iff : b ⇨ a ≠ a ⇨ b ↔ a ≠ b := himp_eq_himp_iff.not
theorem himp_triangle (a b c : α) : (a ⇨ b) ⊓ (b ⇨ c) ≤ a ⇨ c := by
rw [le_himp_iff, inf_right_comm, ← le_himp_iff]
exact himp_inf_le.trans le_himp_himp
theorem himp_inf_himp_cancel (hba : b ≤ a) (hcb : c ≤ b) : (a ⇨ b) ⊓ (b ⇨ c) = a ⇨ c :=
(himp_triangle _ _ _).antisymm <| le_inf (himp_le_himp_left hcb) (himp_le_himp_right hba)
theorem gc_inf_himp : GaloisConnection (a ⊓ ·) (a ⇨ ·) :=
fun _ _ ↦ Iff.symm le_himp_iff'
-- See note [lower instance priority]
instance (priority := 100) GeneralizedHeytingAlgebra.toDistribLattice : DistribLattice α :=
DistribLattice.ofInfSupLe fun a b c => by
simp_rw [inf_comm a, ← le_himp_iff, sup_le_iff, le_himp_iff, ← sup_le_iff]; rfl
instance OrderDual.instGeneralizedCoheytingAlgebra : GeneralizedCoheytingAlgebra αᵒᵈ where
sdiff a b := toDual (ofDual b ⇨ ofDual a)
sdiff_le_iff a b c := by rw [sup_comm]; exact le_himp_iff
instance Prod.instGeneralizedHeytingAlgebra [GeneralizedHeytingAlgebra β] :
GeneralizedHeytingAlgebra (α × β) where
le_himp_iff _ _ _ := and_congr le_himp_iff le_himp_iff
instance Pi.instGeneralizedHeytingAlgebra {α : ι → Type*} [∀ i, GeneralizedHeytingAlgebra (α i)] :
GeneralizedHeytingAlgebra (∀ i, α i) where
le_himp_iff i := by simp [le_def]
end GeneralizedHeytingAlgebra
section GeneralizedCoheytingAlgebra
variable [GeneralizedCoheytingAlgebra α] {a b c d : α}
@[simp]
theorem sdiff_le_iff : a \ b ≤ c ↔ a ≤ b ⊔ c :=
GeneralizedCoheytingAlgebra.sdiff_le_iff _ _ _
theorem sdiff_le_iff' : a \ b ≤ c ↔ a ≤ c ⊔ b := by rw [sdiff_le_iff, sup_comm]
theorem sdiff_le_comm : a \ b ≤ c ↔ a \ c ≤ b := by rw [sdiff_le_iff, sdiff_le_iff']
theorem sdiff_le : a \ b ≤ a :=
sdiff_le_iff.2 le_sup_right
theorem Disjoint.disjoint_sdiff_left (h : Disjoint a b) : Disjoint (a \ c) b :=
h.mono_left sdiff_le
theorem Disjoint.disjoint_sdiff_right (h : Disjoint a b) : Disjoint a (b \ c) :=
h.mono_right sdiff_le
theorem sdiff_le_iff_left : a \ b ≤ b ↔ a ≤ b := by rw [sdiff_le_iff, sup_idem]
@[simp]
theorem sdiff_self : a \ a = ⊥ :=
le_bot_iff.1 <| sdiff_le_iff.2 le_sup_left
theorem le_sup_sdiff : a ≤ b ⊔ a \ b :=
sdiff_le_iff.1 le_rfl
theorem le_sdiff_sup : a ≤ a \ b ⊔ b := by rw [sup_comm, ← sdiff_le_iff]
theorem sup_sdiff_left : a ⊔ a \ b = a :=
sup_of_le_left sdiff_le
theorem sup_sdiff_right : a \ b ⊔ a = a :=
sup_of_le_right sdiff_le
theorem inf_sdiff_left : a \ b ⊓ a = a \ b :=
inf_of_le_left sdiff_le
theorem inf_sdiff_right : a ⊓ a \ b = a \ b :=
inf_of_le_right sdiff_le
@[simp]
theorem sup_sdiff_self (a b : α) : a ⊔ b \ a = a ⊔ b :=
le_antisymm (sup_le_sup_left sdiff_le _) (sup_le le_sup_left le_sup_sdiff)
@[simp]
theorem sdiff_sup_self (a b : α) : b \ a ⊔ a = b ⊔ a := by rw [sup_comm, sup_sdiff_self, sup_comm]
alias sup_sdiff_self_left := sdiff_sup_self
alias sup_sdiff_self_right := sup_sdiff_self
theorem sup_sdiff_eq_sup (h : c ≤ a) : a ⊔ b \ c = a ⊔ b :=
sup_congr_left (sdiff_le.trans le_sup_right) <| le_sup_sdiff.trans <| sup_le_sup_right h _
-- cf. `Set.union_diff_cancel'`
theorem sup_sdiff_cancel' (hab : a ≤ b) (hbc : b ≤ c) : b ⊔ c \ a = c := by
rw [sup_sdiff_eq_sup hab, sup_of_le_right hbc]
theorem sup_sdiff_cancel_right (h : a ≤ b) : a ⊔ b \ a = b :=
sup_sdiff_cancel' le_rfl h
theorem sdiff_sup_cancel (h : b ≤ a) : a \ b ⊔ b = a := by rw [sup_comm, sup_sdiff_cancel_right h]
theorem sup_le_of_le_sdiff_left (h : b ≤ c \ a) (hac : a ≤ c) : a ⊔ b ≤ c :=
sup_le hac <| h.trans sdiff_le
theorem sup_le_of_le_sdiff_right (h : a ≤ c \ b) (hbc : b ≤ c) : a ⊔ b ≤ c :=
sup_le (h.trans sdiff_le) hbc
@[simp]
theorem sdiff_eq_bot_iff : a \ b = ⊥ ↔ a ≤ b := by rw [← le_bot_iff, sdiff_le_iff, sup_bot_eq]
@[simp]
theorem sdiff_bot : a \ ⊥ = a :=
eq_of_forall_ge_iff fun b => by rw [sdiff_le_iff, bot_sup_eq]
@[simp]
theorem bot_sdiff : ⊥ \ a = ⊥ :=
sdiff_eq_bot_iff.2 bot_le
theorem sdiff_sdiff_sdiff_le_sdiff : (a \ b) \ (a \ c) ≤ c \ b := by
rw [sdiff_le_iff, sdiff_le_iff, sup_left_comm, sup_sdiff_self, sup_left_comm, sdiff_sup_self,
sup_left_comm]
exact le_sup_left
@[simp]
theorem le_sup_sdiff_sup_sdiff : a ≤ b ⊔ (a \ c ⊔ c \ b) := by
simpa using @sdiff_sdiff_sdiff_le_sdiff
theorem sdiff_sdiff (a b c : α) : (a \ b) \ c = a \ (b ⊔ c) :=
eq_of_forall_ge_iff fun d => by simp_rw [sdiff_le_iff, sup_assoc]
theorem sdiff_sdiff_left : (a \ b) \ c = a \ (b ⊔ c) :=
sdiff_sdiff _ _ _
theorem sdiff_right_comm (a b c : α) : (a \ b) \ c = (a \ c) \ b := by
simp_rw [sdiff_sdiff, sup_comm]
theorem sdiff_sdiff_comm : (a \ b) \ c = (a \ c) \ b :=
sdiff_right_comm _ _ _
@[simp]
theorem sdiff_idem : (a \ b) \ b = a \ b := by rw [sdiff_sdiff_left, sup_idem]
@[simp]
theorem sdiff_sdiff_self : (a \ b) \ a = ⊥ := by rw [sdiff_sdiff_comm, sdiff_self, bot_sdiff]
theorem sup_sdiff_distrib (a b c : α) : (a ⊔ b) \ c = a \ c ⊔ b \ c :=
eq_of_forall_ge_iff fun d => by simp_rw [sdiff_le_iff, sup_le_iff, sdiff_le_iff]
theorem sdiff_inf_distrib (a b c : α) : a \ (b ⊓ c) = a \ b ⊔ a \ c :=
eq_of_forall_ge_iff fun d => by
rw [sup_le_iff, sdiff_le_comm, le_inf_iff]
simp_rw [sdiff_le_comm]
theorem sup_sdiff : (a ⊔ b) \ c = a \ c ⊔ b \ c :=
sup_sdiff_distrib _ _ _
@[simp]
theorem sup_sdiff_right_self : (a ⊔ b) \ b = a \ b := by rw [sup_sdiff, sdiff_self, sup_bot_eq]
@[simp]
theorem sup_sdiff_left_self : (a ⊔ b) \ a = b \ a := by rw [sup_comm, sup_sdiff_right_self]
@[gcongr]
theorem sdiff_le_sdiff_right (h : a ≤ b) : a \ c ≤ b \ c :=
sdiff_le_iff.2 <| h.trans <| le_sup_sdiff
@[gcongr]
theorem sdiff_le_sdiff_left (h : a ≤ b) : c \ b ≤ c \ a :=
sdiff_le_iff.2 <| le_sup_sdiff.trans <| sup_le_sup_right h _
@[gcongr]
theorem sdiff_le_sdiff (hab : a ≤ b) (hcd : c ≤ d) : a \ d ≤ b \ c :=
(sdiff_le_sdiff_right hab).trans <| sdiff_le_sdiff_left hcd
-- cf. `IsCompl.inf_sup`
theorem sdiff_inf : a \ (b ⊓ c) = a \ b ⊔ a \ c :=
sdiff_inf_distrib _ _ _
@[simp]
theorem sdiff_inf_self_left (a b : α) : a \ (a ⊓ b) = a \ b := by
rw [sdiff_inf, sdiff_self, bot_sup_eq]
@[simp]
theorem sdiff_inf_self_right (a b : α) : b \ (a ⊓ b) = b \ a := by
rw [sdiff_inf, sdiff_self, sup_bot_eq]
theorem Disjoint.sdiff_eq_left (h : Disjoint a b) : a \ b = a := by
conv_rhs => rw [← @sdiff_bot _ _ a]
rw [← h.eq_bot, sdiff_inf_self_left]
theorem Disjoint.sdiff_eq_right (h : Disjoint a b) : b \ a = b :=
h.symm.sdiff_eq_left
theorem Disjoint.sup_sdiff_cancel_left (h : Disjoint a b) : (a ⊔ b) \ a = b := by
rw [sup_sdiff, sdiff_self, bot_sup_eq, h.sdiff_eq_right]
theorem Disjoint.sup_sdiff_cancel_right (h : Disjoint a b) : (a ⊔ b) \ b = a := by
rw [sup_sdiff, sdiff_self, sup_bot_eq, h.sdiff_eq_left]
/-- See `le_sdiff` for a stronger version in generalised Boolean algebras. -/
theorem Disjoint.le_sdiff_of_le_left (hac : Disjoint a c) (hab : a ≤ b) : a ≤ b \ c :=
hac.sdiff_eq_left.ge.trans <| sdiff_le_sdiff_right hab
theorem sdiff_sdiff_le : a \ (a \ b) ≤ b :=
sdiff_le_iff.2 le_sdiff_sup
@[simp] lemma sdiff_eq_sdiff_iff : a \ b = b \ a ↔ a = b := by simp [le_antisymm_iff]
lemma sdiff_ne_sdiff_iff : a \ b ≠ b \ a ↔ a ≠ b := sdiff_eq_sdiff_iff.not
theorem sdiff_triangle (a b c : α) : a \ c ≤ a \ b ⊔ b \ c := by
rw [sdiff_le_iff, sup_left_comm, ← sdiff_le_iff]
exact sdiff_sdiff_le.trans le_sup_sdiff
theorem sdiff_sup_sdiff_cancel (hba : b ≤ a) (hcb : c ≤ b) : a \ b ⊔ b \ c = a \ c :=
(sdiff_triangle _ _ _).antisymm' <| sup_le (sdiff_le_sdiff_left hcb) (sdiff_le_sdiff_right hba)
/-- a version of `sdiff_sup_sdiff_cancel` with more general hypotheses. -/
theorem sdiff_sup_sdiff_cancel' (hinf : a ⊓ c ≤ b) (hsup : b ≤ a ⊔ c) :
a \ b ⊔ b \ c = a \ c := by
refine (sdiff_triangle ..).antisymm' <| sup_le ?_ <| by simpa [sup_comm]
rw [← sdiff_inf_self_left (b := c)]
exact sdiff_le_sdiff_left hinf
theorem sdiff_le_sdiff_of_sup_le_sup_left (h : c ⊔ a ≤ c ⊔ b) : a \ c ≤ b \ c := by
rw [← sup_sdiff_left_self, ← @sup_sdiff_left_self _ _ _ b]
exact sdiff_le_sdiff_right h
theorem sdiff_le_sdiff_of_sup_le_sup_right (h : a ⊔ c ≤ b ⊔ c) : a \ c ≤ b \ c := by
rw [← sup_sdiff_right_self, ← @sup_sdiff_right_self _ _ b]
exact sdiff_le_sdiff_right h
@[simp]
theorem inf_sdiff_sup_left : a \ c ⊓ (a ⊔ b) = a \ c :=
inf_of_le_left <| sdiff_le.trans le_sup_left
@[simp]
theorem inf_sdiff_sup_right : a \ c ⊓ (b ⊔ a) = a \ c :=
inf_of_le_left <| sdiff_le.trans le_sup_right
theorem gc_sdiff_sup : GaloisConnection (· \ a) (a ⊔ ·) :=
fun _ _ ↦ sdiff_le_iff
-- See note [lower instance priority]
instance (priority := 100) GeneralizedCoheytingAlgebra.toDistribLattice : DistribLattice α :=
{ ‹GeneralizedCoheytingAlgebra α› with
le_sup_inf :=
fun a b c => by simp_rw [← sdiff_le_iff, le_inf_iff, sdiff_le_iff, ← le_inf_iff]; rfl }
instance OrderDual.instGeneralizedHeytingAlgebra : GeneralizedHeytingAlgebra αᵒᵈ where
himp := fun a b => toDual (ofDual b \ ofDual a)
le_himp_iff := fun a b c => by rw [inf_comm]; exact sdiff_le_iff
instance Prod.instGeneralizedCoheytingAlgebra [GeneralizedCoheytingAlgebra β] :
GeneralizedCoheytingAlgebra (α × β) where
sdiff_le_iff _ _ _ := and_congr sdiff_le_iff sdiff_le_iff
instance Pi.instGeneralizedCoheytingAlgebra {α : ι → Type*}
[∀ i, GeneralizedCoheytingAlgebra (α i)] : GeneralizedCoheytingAlgebra (∀ i, α i) where
sdiff_le_iff i := by simp [le_def]
end GeneralizedCoheytingAlgebra
section HeytingAlgebra
variable [HeytingAlgebra α] {a b : α}
@[simp]
theorem himp_bot (a : α) : a ⇨ ⊥ = aᶜ :=
HeytingAlgebra.himp_bot _
@[simp]
theorem bot_himp (a : α) : ⊥ ⇨ a = ⊤ :=
himp_eq_top_iff.2 bot_le
theorem compl_sup_distrib (a b : α) : (a ⊔ b)ᶜ = aᶜ ⊓ bᶜ := by
simp_rw [← himp_bot, sup_himp_distrib]
@[simp]
theorem compl_sup : (a ⊔ b)ᶜ = aᶜ ⊓ bᶜ :=
compl_sup_distrib _ _
theorem compl_le_himp : aᶜ ≤ a ⇨ b :=
(himp_bot _).ge.trans <| himp_le_himp_left bot_le
theorem compl_sup_le_himp : aᶜ ⊔ b ≤ a ⇨ b :=
sup_le compl_le_himp le_himp
theorem sup_compl_le_himp : b ⊔ aᶜ ≤ a ⇨ b :=
sup_le le_himp compl_le_himp
-- `p → ¬ p ↔ ¬ p`
@[simp]
theorem himp_compl (a : α) : a ⇨ aᶜ = aᶜ := by rw [← himp_bot, himp_himp, inf_idem]
-- `p → ¬ q ↔ q → ¬ p`
theorem himp_compl_comm (a b : α) : a ⇨ bᶜ = b ⇨ aᶜ := by simp_rw [← himp_bot, himp_left_comm]
theorem le_compl_iff_disjoint_right : a ≤ bᶜ ↔ Disjoint a b := by
rw [← himp_bot, le_himp_iff, disjoint_iff_inf_le]
theorem le_compl_iff_disjoint_left : a ≤ bᶜ ↔ Disjoint b a :=
le_compl_iff_disjoint_right.trans disjoint_comm
theorem le_compl_comm : a ≤ bᶜ ↔ b ≤ aᶜ := by
rw [le_compl_iff_disjoint_right, le_compl_iff_disjoint_left]
alias ⟨_, Disjoint.le_compl_right⟩ := le_compl_iff_disjoint_right
alias ⟨_, Disjoint.le_compl_left⟩ := le_compl_iff_disjoint_left
alias le_compl_iff_le_compl := le_compl_comm
alias ⟨le_compl_of_le_compl, _⟩ := le_compl_comm
theorem disjoint_compl_left : Disjoint aᶜ a :=
disjoint_iff_inf_le.mpr <| le_himp_iff.1 (himp_bot _).ge
theorem disjoint_compl_right : Disjoint a aᶜ :=
disjoint_compl_left.symm
theorem LE.le.disjoint_compl_left (h : b ≤ a) : Disjoint aᶜ b :=
_root_.disjoint_compl_left.mono_right h
theorem LE.le.disjoint_compl_right (h : a ≤ b) : Disjoint a bᶜ :=
_root_.disjoint_compl_right.mono_left h
theorem IsCompl.compl_eq (h : IsCompl a b) : aᶜ = b :=
h.1.le_compl_left.antisymm' <| Disjoint.le_of_codisjoint disjoint_compl_left h.2
theorem IsCompl.eq_compl (h : IsCompl a b) : a = bᶜ :=
h.1.le_compl_right.antisymm <| Disjoint.le_of_codisjoint disjoint_compl_left h.2.symm
|
theorem compl_unique (h₀ : a ⊓ b = ⊥) (h₁ : a ⊔ b = ⊤) : aᶜ = b :=
(IsCompl.of_eq h₀ h₁).compl_eq
| Mathlib/Order/Heyting/Basic.lean | 675 | 677 |
/-
Copyright (c) 2018 Mario Carneiro. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Mario Carneiro, Johannes Hölzl, Sander Dahmen, Kim Morrison, Chris Hughes, Anne Baanen
-/
import Mathlib.Algebra.Algebra.Subalgebra.Lattice
import Mathlib.LinearAlgebra.Basis.Prod
import Mathlib.LinearAlgebra.Dimension.Free
import Mathlib.LinearAlgebra.TensorProduct.Basis
/-!
# Rank of various constructions
## Main statements
- `rank_quotient_add_rank_le` : `rank M/N + rank N ≤ rank M`.
- `lift_rank_add_lift_rank_le_rank_prod`: `rank M × N ≤ rank M + rank N`.
- `rank_span_le_of_finite`: `rank (span s) ≤ #s` for finite `s`.
For free modules, we have
- `rank_prod` : `rank M × N = rank M + rank N`.
- `rank_finsupp` : `rank (ι →₀ M) = #ι * rank M`
- `rank_directSum`: `rank (⨁ Mᵢ) = ∑ rank Mᵢ`
- `rank_tensorProduct`: `rank (M ⊗ N) = rank M * rank N`.
Lemmas for ranks of submodules and subalgebras are also provided.
We have finrank variants for most lemmas as well.
-/
noncomputable section
universe u u' v v' u₁' w w'
variable {R : Type u} {S : Type u'} {M : Type v} {M' : Type v'} {M₁ : Type v}
variable {ι : Type w} {ι' : Type w'} {η : Type u₁'} {φ : η → Type*}
open Basis Cardinal DirectSum Function Module Set Submodule
section Quotient
variable [Ring R] [CommRing S] [AddCommGroup M] [AddCommGroup M'] [AddCommGroup M₁]
variable [Module R M]
theorem LinearIndependent.sumElim_of_quotient
{M' : Submodule R M} {ι₁ ι₂} {f : ι₁ → M'} (hf : LinearIndependent R f) (g : ι₂ → M)
(hg : LinearIndependent R (Submodule.Quotient.mk (p := M') ∘ g)) :
LinearIndependent R (Sum.elim (f · : ι₁ → M) g) := by
refine .sum_type (hf.map' M'.subtype M'.ker_subtype) (.of_comp M'.mkQ hg) ?_
refine disjoint_def.mpr fun x h₁ h₂ ↦ ?_
have : x ∈ M' := span_le.mpr (Set.range_subset_iff.mpr fun i ↦ (f i).prop) h₁
obtain ⟨c, rfl⟩ := Finsupp.mem_span_range_iff_exists_finsupp.mp h₂
simp_rw [← Quotient.mk_eq_zero, ← mkQ_apply, map_finsuppSum, map_smul, mkQ_apply] at this
rw [linearIndependent_iff.mp hg _ this, Finsupp.sum_zero_index]
@[deprecated (since := "2025-02-21")]
alias LinearIndependent.sum_elim_of_quotient := LinearIndependent.sumElim_of_quotient
theorem LinearIndepOn.union_of_quotient {s t : Set ι} {f : ι → M} (hs : LinearIndepOn R f s)
(ht : LinearIndepOn R (mkQ (span R (f '' s)) ∘ f) t) : LinearIndepOn R f (s ∪ t) := by
apply hs.union ht.of_comp
convert (Submodule.range_ker_disjoint ht).symm
· simp
aesop
theorem LinearIndepOn.union_id_of_quotient {M' : Submodule R M}
{s : Set M} (hs : s ⊆ M') (hs' : LinearIndepOn R id s) {t : Set M}
(ht : LinearIndepOn R (mkQ M') t) : LinearIndepOn R id (s ∪ t) :=
hs'.union_of_quotient <| by
rw [image_id]
exact ht.of_comp ((span R s).mapQ M' (LinearMap.id) (span_le.2 hs))
@[deprecated (since := "2025-02-16")] alias LinearIndependent.union_of_quotient :=
LinearIndepOn.union_id_of_quotient
theorem linearIndepOn_union_iff_quotient {s t : Set ι} {f : ι → M} (hst : Disjoint s t) :
LinearIndepOn R f (s ∪ t) ↔
LinearIndepOn R f s ∧ LinearIndepOn R (mkQ (span R (f '' s)) ∘ f) t := by
refine ⟨fun h ↦ ⟨?_, ?_⟩, fun h ↦ h.1.union_of_quotient h.2⟩
· exact h.mono subset_union_left
apply (h.mono subset_union_right).map
simpa [← image_eq_range] using ((linearIndepOn_union_iff hst).1 h).2.2.symm
theorem LinearIndepOn.quotient_iff_union {s t : Set ι} {f : ι → M} (hs : LinearIndepOn R f s)
(hst : Disjoint s t) :
LinearIndepOn R (mkQ (span R (f '' s)) ∘ f) t ↔ LinearIndepOn R f (s ∪ t) := by
rw [linearIndepOn_union_iff_quotient hst, and_iff_right hs]
theorem rank_quotient_add_rank_le [Nontrivial R] (M' : Submodule R M) :
Module.rank R (M ⧸ M') + Module.rank R M' ≤ Module.rank R M := by
conv_lhs => simp only [Module.rank_def]
have := nonempty_linearIndependent_set R (M ⧸ M')
have := nonempty_linearIndependent_set R M'
rw [Cardinal.ciSup_add_ciSup _ (bddAbove_range _) _ (bddAbove_range _)]
refine ciSup_le fun ⟨s, hs⟩ ↦ ciSup_le fun ⟨t, ht⟩ ↦ ?_
choose f hf using Submodule.Quotient.mk_surjective M'
simpa [add_comm] using (LinearIndependent.sumElim_of_quotient ht (fun (i : s) ↦ f i)
(by simpa [Function.comp_def, hf] using hs)).cardinal_le_rank
theorem rank_quotient_le (p : Submodule R M) : Module.rank R (M ⧸ p) ≤ Module.rank R M :=
(mkQ p).rank_le_of_surjective Quot.mk_surjective
/-- The dimension of a quotient is bounded by the dimension of the ambient space. -/
theorem Submodule.finrank_quotient_le [StrongRankCondition R] [Module.Finite R M]
(s : Submodule R M) : finrank R (M ⧸ s) ≤ finrank R M :=
toNat_le_toNat ((Submodule.mkQ s).rank_le_of_surjective Quot.mk_surjective)
(rank_lt_aleph0 _ _)
end Quotient
variable [Semiring R] [CommSemiring S] [AddCommMonoid M] [AddCommMonoid M'] [AddCommMonoid M₁]
variable [Module R M]
section ULift
@[simp]
theorem rank_ulift : Module.rank R (ULift.{w} M) = Cardinal.lift.{w} (Module.rank R M) :=
Cardinal.lift_injective.{v} <| Eq.symm <| (lift_lift _).trans ULift.moduleEquiv.symm.lift_rank_eq
@[simp]
theorem finrank_ulift : finrank R (ULift M) = finrank R M := by
simp_rw [finrank, rank_ulift, toNat_lift]
end ULift
section Prod
variable (R M M')
variable [Module R M₁] [Module R M']
theorem rank_add_rank_le_rank_prod [Nontrivial R] :
Module.rank R M + Module.rank R M₁ ≤ Module.rank R (M × M₁) := by
conv_lhs => simp only [Module.rank_def]
have := nonempty_linearIndependent_set R M
have := nonempty_linearIndependent_set R M₁
rw [Cardinal.ciSup_add_ciSup _ (bddAbove_range _) _ (bddAbove_range _)]
exact ciSup_le fun ⟨s, hs⟩ ↦ ciSup_le fun ⟨t, ht⟩ ↦
(linearIndependent_inl_union_inr' hs ht).cardinal_le_rank
theorem lift_rank_add_lift_rank_le_rank_prod [Nontrivial R] :
lift.{v'} (Module.rank R M) + lift.{v} (Module.rank R M') ≤ Module.rank R (M × M') := by
rw [← rank_ulift, ← rank_ulift]
exact (rank_add_rank_le_rank_prod R _).trans_eq
(ULift.moduleEquiv.prodCongr ULift.moduleEquiv).rank_eq
variable {R M M'}
variable [StrongRankCondition R] [Module.Free R M] [Module.Free R M'] [Module.Free R M₁]
open Module.Free
/-- If `M` and `M'` are free, then the rank of `M × M'` is
`(Module.rank R M).lift + (Module.rank R M').lift`. -/
@[simp]
theorem rank_prod : Module.rank R (M × M') =
Cardinal.lift.{v'} (Module.rank R M) + Cardinal.lift.{v, v'} (Module.rank R M') := by
simpa [rank_eq_card_chooseBasisIndex R M, rank_eq_card_chooseBasisIndex R M', lift_umax]
using ((chooseBasis R M).prod (chooseBasis R M')).mk_eq_rank.symm
/-- If `M` and `M'` are free (and lie in the same universe), the rank of `M × M'` is
`(Module.rank R M) + (Module.rank R M')`. -/
theorem rank_prod' : Module.rank R (M × M₁) = Module.rank R M + Module.rank R M₁ := by simp
/-- The finrank of `M × M'` is `(finrank R M) + (finrank R M')`. -/
@[simp]
theorem Module.finrank_prod [Module.Finite R M] [Module.Finite R M'] :
finrank R (M × M') = finrank R M + finrank R M' := by
simp [finrank, rank_lt_aleph0 R M, rank_lt_aleph0 R M']
end Prod
section Finsupp
variable (R M M')
variable [StrongRankCondition R] [Module.Free R M] [Module R M'] [Module.Free R M']
open Module.Free
@[simp]
theorem rank_finsupp (ι : Type w) :
Module.rank R (ι →₀ M) = Cardinal.lift.{v} #ι * Cardinal.lift.{w} (Module.rank R M) := by
obtain ⟨⟨_, bs⟩⟩ := Module.Free.exists_basis (R := R) (M := M)
rw [← bs.mk_eq_rank'', ← (Finsupp.basis fun _ : ι => bs).mk_eq_rank'', Cardinal.mk_sigma,
Cardinal.sum_const]
theorem rank_finsupp' (ι : Type v) : Module.rank R (ι →₀ M) = #ι * Module.rank R M := by
simp [rank_finsupp]
/-- The rank of `(ι →₀ R)` is `(#ι).lift`. -/
theorem rank_finsupp_self (ι : Type w) : Module.rank R (ι →₀ R) = Cardinal.lift.{u} #ι := by
simp
/-- If `R` and `ι` lie in the same universe, the rank of `(ι →₀ R)` is `# ι`. -/
theorem rank_finsupp_self' {ι : Type u} : Module.rank R (ι →₀ R) = #ι := by simp
/-- The rank of the direct sum is the sum of the ranks. -/
@[simp]
theorem rank_directSum {ι : Type v} (M : ι → Type w) [∀ i : ι, AddCommMonoid (M i)]
[∀ i : ι, Module R (M i)] [∀ i : ι, Module.Free R (M i)] :
Module.rank R (⨁ i, M i) = Cardinal.sum fun i => Module.rank R (M i) := by
let B i := chooseBasis R (M i)
let b : Basis _ R (⨁ i, M i) := DFinsupp.basis fun i => B i
simp [← b.mk_eq_rank'', fun i => (B i).mk_eq_rank'']
/-- If `m` and `n` are finite, the rank of `m × n` matrices over a module `M` is
`(#m).lift * (#n).lift * rank R M`. -/
@[simp]
theorem rank_matrix_module (m : Type w) (n : Type w') [Finite m] [Finite n] :
Module.rank R (Matrix m n M) =
lift.{max v w'} #m * lift.{max v w} #n * lift.{max w w'} (Module.rank R M) := by
cases nonempty_fintype m
cases nonempty_fintype n
obtain ⟨I, b⟩ := Module.Free.exists_basis (R := R) (M := M)
rw [← (b.matrix m n).mk_eq_rank'']
simp only [mk_prod, lift_mul, lift_lift, ← mul_assoc, b.mk_eq_rank'']
/-- If `m` and `n` are finite and lie in the same universe, the rank of `m × n` matrices over a
module `M` is `(#m * #n).lift * rank R M`. -/
@[simp high]
theorem rank_matrix_module' (m n : Type w) [Finite m] [Finite n] :
Module.rank R (Matrix m n M) =
lift.{max v} (#m * #n) * lift.{w} (Module.rank R M) := by
rw [rank_matrix_module, lift_mul, lift_umax.{w, v}]
/-- If `m` and `n` are finite, the rank of `m × n` matrices is `(#m).lift * (#n).lift`. -/
theorem rank_matrix (m : Type v) (n : Type w) [Finite m] [Finite n] :
Module.rank R (Matrix m n R) =
Cardinal.lift.{max v w u, v} #m * Cardinal.lift.{max v w u, w} #n := by
rw [rank_matrix_module, rank_self, lift_one, mul_one, ← lift_lift.{v, max u w}, lift_id,
← lift_lift.{w, max u v}, lift_id]
/-- If `m` and `n` are finite and lie in the same universe, the rank of `m × n` matrices is
`(#n * #m).lift`. -/
theorem rank_matrix' (m n : Type v) [Finite m] [Finite n] :
Module.rank R (Matrix m n R) = Cardinal.lift.{u} (#m * #n) := by
rw [rank_matrix, lift_mul, lift_umax.{v, u}]
/-- If `m` and `n` are finite and lie in the same universe as `R`, the rank of `m × n` matrices
is `# m * # n`. -/
theorem rank_matrix'' (m n : Type u) [Finite m] [Finite n] :
Module.rank R (Matrix m n R) = #m * #n := by simp
open Fintype
namespace Module
@[simp]
theorem finrank_finsupp {ι : Type v} [Fintype ι] : finrank R (ι →₀ M) = card ι * finrank R M := by
rw [finrank, finrank, rank_finsupp, ← mk_toNat_eq_card, toNat_mul, toNat_lift, toNat_lift]
/-- The finrank of `(ι →₀ R)` is `Fintype.card ι`. -/
@[simp]
theorem finrank_finsupp_self {ι : Type v} [Fintype ι] : finrank R (ι →₀ R) = card ι := by
rw [finrank, rank_finsupp_self, ← mk_toNat_eq_card, toNat_lift]
/-- The finrank of the direct sum is the sum of the finranks. -/
@[simp]
theorem finrank_directSum {ι : Type v} [Fintype ι] (M : ι → Type w) [∀ i : ι, AddCommMonoid (M i)]
[∀ i : ι, Module R (M i)] [∀ i : ι, Module.Free R (M i)] [∀ i : ι, Module.Finite R (M i)] :
finrank R (⨁ i, M i) = ∑ i, finrank R (M i) := by
letI := nontrivial_of_invariantBasisNumber R
simp only [finrank, fun i => rank_eq_card_chooseBasisIndex R (M i), rank_directSum, ← mk_sigma,
mk_toNat_eq_card, card_sigma]
/-- If `m` and `n` are `Fintype`, the finrank of `m × n` matrices over a module `M` is
`(Fintype.card m) * (Fintype.card n) * finrank R M`. -/
theorem finrank_matrix (m n : Type*) [Fintype m] [Fintype n] :
finrank R (Matrix m n M) = card m * card n * finrank R M := by simp [finrank]
end Module
end Finsupp
section Pi
variable [StrongRankCondition R] [Module.Free R M]
variable [∀ i, AddCommMonoid (φ i)] [∀ i, Module R (φ i)] [∀ i, Module.Free R (φ i)]
open Module.Free
open LinearMap
/-- The rank of a finite product of free modules is the sum of the ranks. -/
-- this result is not true without the freeness assumption
@[simp]
theorem rank_pi [Finite η] : Module.rank R (∀ i, φ i) =
Cardinal.sum fun i => Module.rank R (φ i) := by
cases nonempty_fintype η
let B i := chooseBasis R (φ i)
let b : Basis _ R (∀ i, φ i) := Pi.basis fun i => B i
simp [← b.mk_eq_rank'', fun i => (B i).mk_eq_rank'']
variable (R)
/-- The finrank of `(ι → R)` is `Fintype.card ι`. -/
theorem Module.finrank_pi {ι : Type v} [Fintype ι] :
finrank R (ι → R) = Fintype.card ι := by
simp [finrank]
--TODO: this should follow from `LinearEquiv.finrank_eq`, that is over a field.
/-- The finrank of a finite product is the sum of the finranks. -/
theorem Module.finrank_pi_fintype
{ι : Type v} [Fintype ι] {M : ι → Type w} [∀ i : ι, AddCommMonoid (M i)]
[∀ i : ι, Module R (M i)] [∀ i : ι, Module.Free R (M i)] [∀ i : ι, Module.Finite R (M i)] :
finrank R (∀ i, M i) = ∑ i, finrank R (M i) := by
letI := nontrivial_of_invariantBasisNumber R
simp only [finrank, fun i => rank_eq_card_chooseBasisIndex R (M i), rank_pi, ← mk_sigma,
mk_toNat_eq_card, Fintype.card_sigma]
variable {R}
variable [Fintype η]
theorem rank_fun {M η : Type u} [Fintype η] [AddCommMonoid M] [Module R M] [Module.Free R M] :
Module.rank R (η → M) = Fintype.card η * Module.rank R M := by
rw [rank_pi, Cardinal.sum_const', Cardinal.mk_fintype]
theorem rank_fun_eq_lift_mul : Module.rank R (η → M) =
(Fintype.card η : Cardinal.{max u₁' v}) * Cardinal.lift.{u₁'} (Module.rank R M) := by
rw [rank_pi, Cardinal.sum_const, Cardinal.mk_fintype, Cardinal.lift_natCast]
theorem rank_fun' : Module.rank R (η → R) = Fintype.card η := by
rw [rank_fun_eq_lift_mul, rank_self, Cardinal.lift_one, mul_one]
theorem rank_fin_fun (n : ℕ) : Module.rank R (Fin n → R) = n := by simp [rank_fun']
variable (R)
/-- The vector space of functions on a `Fintype ι` has finrank equal to the cardinality of `ι`. -/
@[simp]
theorem Module.finrank_fintype_fun_eq_card : finrank R (η → R) = Fintype.card η :=
finrank_eq_of_rank_eq rank_fun'
/-- The vector space of functions on `Fin n` has finrank equal to `n`. -/
theorem Module.finrank_fin_fun {n : ℕ} : finrank R (Fin n → R) = n := by simp
variable {R}
-- TODO: merge with the `Finrank` content
/-- An `n`-dimensional `R`-vector space is equivalent to `Fin n → R`. -/
def finDimVectorspaceEquiv (n : ℕ) (hn : Module.rank R M = n) : M ≃ₗ[R] Fin n → R := by
haveI := nontrivial_of_invariantBasisNumber R
have : Cardinal.lift.{u} (n : Cardinal.{v}) = Cardinal.lift.{v} (n : Cardinal.{u}) := by simp
have hn := Cardinal.lift_inj.{v, u}.2 hn
rw [this] at hn
rw [← @rank_fin_fun R _ _ n] at hn
haveI : Module.Free R (Fin n → R) := Module.Free.pi _ _
exact Classical.choice (nonempty_linearEquiv_of_lift_rank_eq hn)
end Pi
section TensorProduct
open TensorProduct
variable [StrongRankCondition R] [StrongRankCondition S]
variable [Module S M] [Module S M'] [Module.Free S M']
variable [Module S M₁] [Module.Free S M₁]
variable [Algebra S R] [IsScalarTower S R M] [Module.Free R M]
open Module.Free
/-- The `S`-rank of `M ⊗[R] M'` is `(Module.rank S M).lift * (Module.rank R M').lift`. -/
@[simp]
theorem rank_tensorProduct :
Module.rank R (M ⊗[S] M') =
Cardinal.lift.{v'} (Module.rank R M) * Cardinal.lift.{v} (Module.rank S M') := by
obtain ⟨⟨_, bM⟩⟩ := Module.Free.exists_basis (R := R) (M := M)
obtain ⟨⟨_, bN⟩⟩ := Module.Free.exists_basis (R := S) (M := M')
rw [← bM.mk_eq_rank'', ← bN.mk_eq_rank'', ← (bM.tensorProduct bN).mk_eq_rank'', Cardinal.mk_prod]
/-- If `M` and `M'` lie in the same universe, the `S`-rank of `M ⊗[R] M'` is
`(Module.rank S M) * (Module.rank R M')`. -/
theorem rank_tensorProduct' :
Module.rank R (M ⊗[S] M₁) = Module.rank R M * Module.rank S M₁ := by simp
theorem Module.rank_baseChange :
Module.rank R (R ⊗[S] M') = Cardinal.lift.{u} (Module.rank S M') := by simp
/-- The `S`-finrank of `M ⊗[R] M'` is `(finrank S M) * (finrank R M')`. -/
@[simp]
theorem Module.finrank_tensorProduct :
finrank R (M ⊗[S] M') = finrank R M * finrank S M' := by simp [finrank]
theorem Module.finrank_baseChange : finrank R (R ⊗[S] M') = finrank S M' := by simp
end TensorProduct
section SubmoduleRank
section
open Module
namespace Submodule
theorem lt_of_le_of_finrank_lt_finrank {s t : Submodule R M} (le : s ≤ t)
(lt : finrank R s < finrank R t) : s < t :=
lt_of_le_of_ne le fun h => ne_of_lt lt (by rw [h])
theorem lt_top_of_finrank_lt_finrank {s : Submodule R M} (lt : finrank R s < finrank R M) :
s < ⊤ := by
rw [← finrank_top R M] at lt
exact lt_of_le_of_finrank_lt_finrank le_top lt
end Submodule
variable [StrongRankCondition R]
/-- The dimension of a submodule is bounded by the dimension of the ambient space. -/
theorem Submodule.finrank_le [Module.Finite R M] (s : Submodule R M) :
finrank R s ≤ finrank R M :=
toNat_le_toNat (Submodule.rank_le s) (rank_lt_aleph0 _ _)
/-- Pushforwards of finite submodules have a smaller finrank. -/
theorem Submodule.finrank_map_le
[Module R M'] (f : M →ₗ[R] M') (p : Submodule R M) [Module.Finite R p] :
finrank R (p.map f) ≤ finrank R p :=
finrank_le_finrank_of_rank_le_rank (lift_rank_map_le _ _) (rank_lt_aleph0 _ _)
theorem Submodule.finrank_mono {s t : Submodule R M} [Module.Finite R t] (hst : s ≤ t) :
finrank R s ≤ finrank R t :=
Cardinal.toNat_le_toNat (Submodule.rank_mono hst) (rank_lt_aleph0 R ↥t)
end
end SubmoduleRank
section Span
variable [StrongRankCondition R]
theorem rank_span_le (s : Set M) : Module.rank R (span R s) ≤ #s := by
rw [Finsupp.span_eq_range_linearCombination, ← lift_strictMono.le_iff_le]
refine (lift_rank_range_le _).trans ?_
rw [rank_finsupp_self]
simp only [lift_lift, le_refl]
theorem rank_span_finset_le (s : Finset M) : Module.rank R (span R (s : Set M)) ≤ s.card := by
simpa using rank_span_le s.toSet
theorem rank_span_of_finset (s : Finset M) : Module.rank R (span R (s : Set M)) < ℵ₀ :=
(rank_span_finset_le s).trans_lt (Cardinal.nat_lt_aleph0 _)
open Submodule Module
variable (R) in
/-- The rank of a set of vectors as a natural number. -/
protected noncomputable def Set.finrank (s : Set M) : ℕ :=
finrank R (span R s)
theorem finrank_span_le_card (s : Set M) [Fintype s] : finrank R (span R s) ≤ s.toFinset.card :=
finrank_le_of_rank_le (by simpa using rank_span_le (R := R) s)
theorem finrank_span_finset_le_card (s : Finset M) : (s : Set M).finrank R ≤ s.card :=
calc
(s : Set M).finrank R ≤ (s : Set M).toFinset.card := finrank_span_le_card (M := M) s
_ = s.card := by simp
theorem finrank_range_le_card {ι : Type*} [Fintype ι] (b : ι → M) :
(Set.range b).finrank R ≤ Fintype.card ι := by
classical
refine (finrank_span_le_card _).trans ?_
rw [Set.toFinset_range]
exact Finset.card_image_le
theorem finrank_span_eq_card [Nontrivial R] {ι : Type*} [Fintype ι] {b : ι → M}
| (hb : LinearIndependent R b) :
finrank R (span R (Set.range b)) = Fintype.card ι :=
finrank_eq_of_rank_eq
(by
| Mathlib/LinearAlgebra/Dimension/Constructions.lean | 469 | 472 |
/-
Copyright (c) 2014 Jeremy Avigad. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Jeremy Avigad, Andrew Zipperer, Haitao Zhang, Minchao Wu, Yury Kudryashov
-/
import Mathlib.Data.Set.Prod
import Mathlib.Data.Set.Restrict
/-!
# Functions over sets
This file contains basic results on the following predicates of functions and sets:
* `Set.EqOn f₁ f₂ s` : functions `f₁` and `f₂` are equal at every point of `s`;
* `Set.MapsTo f s t` : `f` sends every point of `s` to a point of `t`;
* `Set.InjOn f s` : restriction of `f` to `s` is injective;
* `Set.SurjOn f s t` : every point in `s` has a preimage in `s`;
* `Set.BijOn f s t` : `f` is a bijection between `s` and `t`;
* `Set.LeftInvOn f' f s` : for every `x ∈ s` we have `f' (f x) = x`;
* `Set.RightInvOn f' f t` : for every `y ∈ t` we have `f (f' y) = y`;
* `Set.InvOn f' f s t` : `f'` is a two-side inverse of `f` on `s` and `t`, i.e.
we have `Set.LeftInvOn f' f s` and `Set.RightInvOn f' f t`.
-/
variable {α β γ δ : Type*} {ι : Sort*} {π : α → Type*}
open Equiv Equiv.Perm Function
namespace Set
/-! ### Equality on a set -/
section equality
variable {s s₁ s₂ : Set α} {f₁ f₂ f₃ : α → β} {g : β → γ} {a : α}
/-- This lemma exists for use by `aesop` as a forward rule. -/
@[aesop safe forward]
lemma EqOn.eq_of_mem (h : s.EqOn f₁ f₂) (ha : a ∈ s) : f₁ a = f₂ a :=
h ha
@[simp]
theorem eqOn_empty (f₁ f₂ : α → β) : EqOn f₁ f₂ ∅ := fun _ => False.elim
@[simp]
theorem eqOn_singleton : Set.EqOn f₁ f₂ {a} ↔ f₁ a = f₂ a := by
simp [Set.EqOn]
@[simp]
theorem eqOn_univ (f₁ f₂ : α → β) : EqOn f₁ f₂ univ ↔ f₁ = f₂ := by
simp [EqOn, funext_iff]
@[symm]
theorem EqOn.symm (h : EqOn f₁ f₂ s) : EqOn f₂ f₁ s := fun _ hx => (h hx).symm
theorem eqOn_comm : EqOn f₁ f₂ s ↔ EqOn f₂ f₁ s :=
⟨EqOn.symm, EqOn.symm⟩
-- This can not be tagged as `@[refl]` with the current argument order.
-- See note below at `EqOn.trans`.
theorem eqOn_refl (f : α → β) (s : Set α) : EqOn f f s := fun _ _ => rfl
-- Note: this was formerly tagged with `@[trans]`, and although the `trans` attribute accepted it
-- the `trans` tactic could not use it.
-- An update to the trans tactic coming in https://github.com/leanprover-community/mathlib4/pull/7014 will reject this attribute.
-- It can be restored by changing the argument order from `EqOn f₁ f₂ s` to `EqOn s f₁ f₂`.
-- This change will be made separately: [zulip](https://leanprover.zulipchat.com/#narrow/stream/287929-mathlib4/topic/Reordering.20arguments.20of.20.60Set.2EEqOn.60/near/390467581).
theorem EqOn.trans (h₁ : EqOn f₁ f₂ s) (h₂ : EqOn f₂ f₃ s) : EqOn f₁ f₃ s := fun _ hx =>
(h₁ hx).trans (h₂ hx)
theorem EqOn.image_eq (heq : EqOn f₁ f₂ s) : f₁ '' s = f₂ '' s :=
image_congr heq
/-- Variant of `EqOn.image_eq`, for one function being the identity. -/
theorem EqOn.image_eq_self {f : α → α} (h : Set.EqOn f id s) : f '' s = s := by
rw [h.image_eq, image_id]
theorem EqOn.inter_preimage_eq (heq : EqOn f₁ f₂ s) (t : Set β) : s ∩ f₁ ⁻¹' t = s ∩ f₂ ⁻¹' t :=
ext fun x => and_congr_right_iff.2 fun hx => by rw [mem_preimage, mem_preimage, heq hx]
theorem EqOn.mono (hs : s₁ ⊆ s₂) (hf : EqOn f₁ f₂ s₂) : EqOn f₁ f₂ s₁ := fun _ hx => hf (hs hx)
@[simp]
theorem eqOn_union : EqOn f₁ f₂ (s₁ ∪ s₂) ↔ EqOn f₁ f₂ s₁ ∧ EqOn f₁ f₂ s₂ :=
forall₂_or_left
theorem EqOn.union (h₁ : EqOn f₁ f₂ s₁) (h₂ : EqOn f₁ f₂ s₂) : EqOn f₁ f₂ (s₁ ∪ s₂) :=
eqOn_union.2 ⟨h₁, h₂⟩
theorem EqOn.comp_left (h : s.EqOn f₁ f₂) : s.EqOn (g ∘ f₁) (g ∘ f₂) := fun _ ha =>
congr_arg _ <| h ha
@[simp]
theorem eqOn_range {ι : Sort*} {f : ι → α} {g₁ g₂ : α → β} :
EqOn g₁ g₂ (range f) ↔ g₁ ∘ f = g₂ ∘ f :=
forall_mem_range.trans <| funext_iff.symm
alias ⟨EqOn.comp_eq, _⟩ := eqOn_range
end equality
variable {s s₁ s₂ : Set α} {t t₁ t₂ : Set β} {p : Set γ} {f f₁ f₂ : α → β} {g g₁ g₂ : β → γ}
{f' f₁' f₂' : β → α} {g' : γ → β} {a : α} {b : β}
section MapsTo
theorem mapsTo' : MapsTo f s t ↔ f '' s ⊆ t :=
image_subset_iff.symm
theorem mapsTo_prodMap_diagonal : MapsTo (Prod.map f f) (diagonal α) (diagonal β) :=
diagonal_subset_iff.2 fun _ => rfl
@[deprecated (since := "2025-04-18")]
alias mapsTo_prod_map_diagonal := mapsTo_prodMap_diagonal
theorem MapsTo.subset_preimage (hf : MapsTo f s t) : s ⊆ f ⁻¹' t := hf
theorem mapsTo_iff_subset_preimage : MapsTo f s t ↔ s ⊆ f ⁻¹' t := Iff.rfl
@[simp]
theorem mapsTo_singleton {x : α} : MapsTo f {x} t ↔ f x ∈ t :=
singleton_subset_iff
theorem mapsTo_empty (f : α → β) (t : Set β) : MapsTo f ∅ t :=
empty_subset _
@[simp] theorem mapsTo_empty_iff : MapsTo f s ∅ ↔ s = ∅ := by
simp [mapsTo', subset_empty_iff]
/-- If `f` maps `s` to `t` and `s` is non-empty, `t` is non-empty. -/
theorem MapsTo.nonempty (h : MapsTo f s t) (hs : s.Nonempty) : t.Nonempty :=
(hs.image f).mono (mapsTo'.mp h)
theorem MapsTo.image_subset (h : MapsTo f s t) : f '' s ⊆ t :=
mapsTo'.1 h
theorem MapsTo.congr (h₁ : MapsTo f₁ s t) (h : EqOn f₁ f₂ s) : MapsTo f₂ s t := fun _ hx =>
h hx ▸ h₁ hx
theorem EqOn.comp_right (hg : t.EqOn g₁ g₂) (hf : s.MapsTo f t) : s.EqOn (g₁ ∘ f) (g₂ ∘ f) :=
fun _ ha => hg <| hf ha
theorem EqOn.mapsTo_iff (H : EqOn f₁ f₂ s) : MapsTo f₁ s t ↔ MapsTo f₂ s t :=
⟨fun h => h.congr H, fun h => h.congr H.symm⟩
theorem MapsTo.comp (h₁ : MapsTo g t p) (h₂ : MapsTo f s t) : MapsTo (g ∘ f) s p := fun _ h =>
h₁ (h₂ h)
theorem mapsTo_id (s : Set α) : MapsTo id s s := fun _ => id
theorem MapsTo.iterate {f : α → α} {s : Set α} (h : MapsTo f s s) : ∀ n, MapsTo f^[n] s s
| 0 => fun _ => id
| n + 1 => (MapsTo.iterate h n).comp h
theorem MapsTo.iterate_restrict {f : α → α} {s : Set α} (h : MapsTo f s s) (n : ℕ) :
(h.restrict f s s)^[n] = (h.iterate n).restrict _ _ _ := by
funext x
rw [Subtype.ext_iff, MapsTo.val_restrict_apply]
induction n generalizing x with
| zero => rfl
| succ n ihn => simp [Nat.iterate, ihn]
lemma mapsTo_of_subsingleton' [Subsingleton β] (f : α → β) (h : s.Nonempty → t.Nonempty) :
MapsTo f s t :=
fun a ha ↦ Subsingleton.mem_iff_nonempty.2 <| h ⟨a, ha⟩
lemma mapsTo_of_subsingleton [Subsingleton α] (f : α → α) (s : Set α) : MapsTo f s s :=
mapsTo_of_subsingleton' _ id
theorem MapsTo.mono (hf : MapsTo f s₁ t₁) (hs : s₂ ⊆ s₁) (ht : t₁ ⊆ t₂) : MapsTo f s₂ t₂ :=
fun _ hx => ht (hf <| hs hx)
theorem MapsTo.mono_left (hf : MapsTo f s₁ t) (hs : s₂ ⊆ s₁) : MapsTo f s₂ t := fun _ hx =>
hf (hs hx)
theorem MapsTo.mono_right (hf : MapsTo f s t₁) (ht : t₁ ⊆ t₂) : MapsTo f s t₂ := fun _ hx =>
ht (hf hx)
theorem MapsTo.union_union (h₁ : MapsTo f s₁ t₁) (h₂ : MapsTo f s₂ t₂) :
MapsTo f (s₁ ∪ s₂) (t₁ ∪ t₂) := fun _ hx =>
hx.elim (fun hx => Or.inl <| h₁ hx) fun hx => Or.inr <| h₂ hx
theorem MapsTo.union (h₁ : MapsTo f s₁ t) (h₂ : MapsTo f s₂ t) : MapsTo f (s₁ ∪ s₂) t :=
union_self t ▸ h₁.union_union h₂
@[simp]
theorem mapsTo_union : MapsTo f (s₁ ∪ s₂) t ↔ MapsTo f s₁ t ∧ MapsTo f s₂ t :=
⟨fun h =>
⟨h.mono subset_union_left (Subset.refl t),
h.mono subset_union_right (Subset.refl t)⟩,
fun h => h.1.union h.2⟩
theorem MapsTo.inter (h₁ : MapsTo f s t₁) (h₂ : MapsTo f s t₂) : MapsTo f s (t₁ ∩ t₂) := fun _ hx =>
⟨h₁ hx, h₂ hx⟩
lemma MapsTo.insert (h : MapsTo f s t) (x : α) : MapsTo f (insert x s) (insert (f x) t) := by
simpa [← singleton_union] using h.mono_right subset_union_right
theorem MapsTo.inter_inter (h₁ : MapsTo f s₁ t₁) (h₂ : MapsTo f s₂ t₂) :
MapsTo f (s₁ ∩ s₂) (t₁ ∩ t₂) := fun _ hx => ⟨h₁ hx.1, h₂ hx.2⟩
@[simp]
theorem mapsTo_inter : MapsTo f s (t₁ ∩ t₂) ↔ MapsTo f s t₁ ∧ MapsTo f s t₂ :=
⟨fun h =>
⟨h.mono (Subset.refl s) inter_subset_left,
h.mono (Subset.refl s) inter_subset_right⟩,
fun h => h.1.inter h.2⟩
theorem mapsTo_univ (f : α → β) (s : Set α) : MapsTo f s univ := fun _ _ => trivial
theorem mapsTo_range (f : α → β) (s : Set α) : MapsTo f s (range f) :=
(mapsTo_image f s).mono (Subset.refl s) (image_subset_range _ _)
@[simp]
theorem mapsTo_image_iff {f : α → β} {g : γ → α} {s : Set γ} {t : Set β} :
MapsTo f (g '' s) t ↔ MapsTo (f ∘ g) s t :=
⟨fun h c hc => h ⟨c, hc, rfl⟩, fun h _ ⟨_, hc⟩ => hc.2 ▸ h hc.1⟩
lemma MapsTo.comp_left (g : β → γ) (hf : MapsTo f s t) : MapsTo (g ∘ f) s (g '' t) :=
fun x hx ↦ ⟨f x, hf hx, rfl⟩
lemma MapsTo.comp_right {s : Set β} {t : Set γ} (hg : MapsTo g s t) (f : α → β) :
MapsTo (g ∘ f) (f ⁻¹' s) t := fun _ hx ↦ hg hx
@[simp]
lemma mapsTo_univ_iff : MapsTo f univ t ↔ ∀ x, f x ∈ t :=
⟨fun h _ => h (mem_univ _), fun h x _ => h x⟩
@[simp]
lemma mapsTo_range_iff {g : ι → α} : MapsTo f (range g) t ↔ ∀ i, f (g i) ∈ t :=
forall_mem_range
theorem MapsTo.mem_iff (h : MapsTo f s t) (hc : MapsTo f sᶜ tᶜ) {x} : f x ∈ t ↔ x ∈ s :=
⟨fun ht => by_contra fun hs => hc hs ht, fun hx => h hx⟩
end MapsTo
/-! ### Injectivity on a set -/
section injOn
theorem Subsingleton.injOn (hs : s.Subsingleton) (f : α → β) : InjOn f s := fun _ hx _ hy _ =>
hs hx hy
@[simp]
theorem injOn_empty (f : α → β) : InjOn f ∅ :=
subsingleton_empty.injOn f
@[simp]
theorem injOn_singleton (f : α → β) (a : α) : InjOn f {a} :=
subsingleton_singleton.injOn f
@[simp] lemma injOn_pair {b : α} : InjOn f {a, b} ↔ f a = f b → a = b := by unfold InjOn; aesop
theorem InjOn.eq_iff {x y} (h : InjOn f s) (hx : x ∈ s) (hy : y ∈ s) : f x = f y ↔ x = y :=
⟨h hx hy, fun h => h ▸ rfl⟩
theorem InjOn.ne_iff {x y} (h : InjOn f s) (hx : x ∈ s) (hy : y ∈ s) : f x ≠ f y ↔ x ≠ y :=
(h.eq_iff hx hy).not
alias ⟨_, InjOn.ne⟩ := InjOn.ne_iff
theorem InjOn.congr (h₁ : InjOn f₁ s) (h : EqOn f₁ f₂ s) : InjOn f₂ s := fun _ hx _ hy =>
h hx ▸ h hy ▸ h₁ hx hy
theorem EqOn.injOn_iff (H : EqOn f₁ f₂ s) : InjOn f₁ s ↔ InjOn f₂ s :=
⟨fun h => h.congr H, fun h => h.congr H.symm⟩
theorem InjOn.mono (h : s₁ ⊆ s₂) (ht : InjOn f s₂) : InjOn f s₁ := fun _ hx _ hy H =>
ht (h hx) (h hy) H
theorem injOn_union (h : Disjoint s₁ s₂) :
InjOn f (s₁ ∪ s₂) ↔ InjOn f s₁ ∧ InjOn f s₂ ∧ ∀ x ∈ s₁, ∀ y ∈ s₂, f x ≠ f y := by
refine ⟨fun H => ⟨H.mono subset_union_left, H.mono subset_union_right, ?_⟩, ?_⟩
· intro x hx y hy hxy
obtain rfl : x = y := H (Or.inl hx) (Or.inr hy) hxy
exact h.le_bot ⟨hx, hy⟩
· rintro ⟨h₁, h₂, h₁₂⟩
rintro x (hx | hx) y (hy | hy) hxy
exacts [h₁ hx hy hxy, (h₁₂ _ hx _ hy hxy).elim, (h₁₂ _ hy _ hx hxy.symm).elim, h₂ hx hy hxy]
theorem injOn_insert {f : α → β} {s : Set α} {a : α} (has : a ∉ s) :
Set.InjOn f (insert a s) ↔ Set.InjOn f s ∧ f a ∉ f '' s := by
rw [← union_singleton, injOn_union (disjoint_singleton_right.2 has)]
simp
theorem injective_iff_injOn_univ : Injective f ↔ InjOn f univ :=
⟨fun h _ _ _ _ hxy => h hxy, fun h _ _ heq => h trivial trivial heq⟩
theorem injOn_of_injective (h : Injective f) {s : Set α} : InjOn f s := fun _ _ _ _ hxy => h hxy
alias _root_.Function.Injective.injOn := injOn_of_injective
-- A specialization of `injOn_of_injective` for `Subtype.val`.
theorem injOn_subtype_val {s : Set { x // p x }} : Set.InjOn Subtype.val s :=
Subtype.coe_injective.injOn
lemma injOn_id (s : Set α) : InjOn id s := injective_id.injOn
theorem InjOn.comp (hg : InjOn g t) (hf : InjOn f s) (h : MapsTo f s t) : InjOn (g ∘ f) s :=
fun _ hx _ hy heq => hf hx hy <| hg (h hx) (h hy) heq
lemma InjOn.of_comp (h : InjOn (g ∘ f) s) : InjOn f s :=
fun _ hx _ hy heq ↦ h hx hy (by simp [heq])
lemma InjOn.image_of_comp (h : InjOn (g ∘ f) s) : InjOn g (f '' s) :=
forall_mem_image.2 fun _x hx ↦ forall_mem_image.2 fun _y hy heq ↦ congr_arg f <| h hx hy heq
lemma InjOn.comp_iff (hf : InjOn f s) : InjOn (g ∘ f) s ↔ InjOn g (f '' s) :=
⟨image_of_comp, fun h ↦ InjOn.comp h hf <| mapsTo_image f s⟩
lemma InjOn.iterate {f : α → α} {s : Set α} (h : InjOn f s) (hf : MapsTo f s s) :
∀ n, InjOn f^[n] s
| 0 => injOn_id _
| (n + 1) => (h.iterate hf n).comp h hf
lemma injOn_of_subsingleton [Subsingleton α] (f : α → β) (s : Set α) : InjOn f s :=
(injective_of_subsingleton _).injOn
theorem _root_.Function.Injective.injOn_range (h : Injective (g ∘ f)) : InjOn g (range f) := by
rintro _ ⟨x, rfl⟩ _ ⟨y, rfl⟩ H
exact congr_arg f (h H)
theorem _root_.Set.InjOn.injective_iff (s : Set β) (h : InjOn g s) (hs : range f ⊆ s) :
Injective (g ∘ f) ↔ Injective f :=
⟨(·.of_comp), fun h _ ↦ by aesop⟩
theorem exists_injOn_iff_injective [Nonempty β] :
(∃ f : α → β, InjOn f s) ↔ ∃ f : s → β, Injective f :=
⟨fun ⟨_, hf⟩ => ⟨_, hf.injective⟩,
fun ⟨f, hf⟩ => by
lift f to α → β using trivial
exact ⟨f, injOn_iff_injective.2 hf⟩⟩
theorem injOn_preimage {B : Set (Set β)} (hB : B ⊆ 𝒫 range f) : InjOn (preimage f) B :=
fun _ hs _ ht hst => (preimage_eq_preimage' (hB hs) (hB ht)).1 hst
theorem InjOn.mem_of_mem_image {x} (hf : InjOn f s) (hs : s₁ ⊆ s) (h : x ∈ s) (h₁ : f x ∈ f '' s₁) :
x ∈ s₁ :=
let ⟨_, h', Eq⟩ := h₁
hf (hs h') h Eq ▸ h'
theorem InjOn.mem_image_iff {x} (hf : InjOn f s) (hs : s₁ ⊆ s) (hx : x ∈ s) :
f x ∈ f '' s₁ ↔ x ∈ s₁ :=
⟨hf.mem_of_mem_image hs hx, mem_image_of_mem f⟩
theorem InjOn.preimage_image_inter (hf : InjOn f s) (hs : s₁ ⊆ s) : f ⁻¹' (f '' s₁) ∩ s = s₁ :=
ext fun _ => ⟨fun ⟨h₁, h₂⟩ => hf.mem_of_mem_image hs h₂ h₁, fun h => ⟨mem_image_of_mem _ h, hs h⟩⟩
theorem EqOn.cancel_left (h : s.EqOn (g ∘ f₁) (g ∘ f₂)) (hg : t.InjOn g) (hf₁ : s.MapsTo f₁ t)
(hf₂ : s.MapsTo f₂ t) : s.EqOn f₁ f₂ := fun _ ha => hg (hf₁ ha) (hf₂ ha) (h ha)
theorem InjOn.cancel_left (hg : t.InjOn g) (hf₁ : s.MapsTo f₁ t) (hf₂ : s.MapsTo f₂ t) :
s.EqOn (g ∘ f₁) (g ∘ f₂) ↔ s.EqOn f₁ f₂ :=
⟨fun h => h.cancel_left hg hf₁ hf₂, EqOn.comp_left⟩
lemma InjOn.image_inter {s t u : Set α} (hf : u.InjOn f) (hs : s ⊆ u) (ht : t ⊆ u) :
f '' (s ∩ t) = f '' s ∩ f '' t := by
apply Subset.antisymm (image_inter_subset _ _ _)
intro x ⟨⟨y, ys, hy⟩, ⟨z, zt, hz⟩⟩
have : y = z := by
apply hf (hs ys) (ht zt)
rwa [← hz] at hy
rw [← this] at zt
exact ⟨y, ⟨ys, zt⟩, hy⟩
lemma InjOn.image (h : s.InjOn f) : s.powerset.InjOn (image f) :=
fun s₁ hs₁ s₂ hs₂ h' ↦ by rw [← h.preimage_image_inter hs₁, h', h.preimage_image_inter hs₂]
theorem InjOn.image_eq_image_iff (h : s.InjOn f) (h₁ : s₁ ⊆ s) (h₂ : s₂ ⊆ s) :
f '' s₁ = f '' s₂ ↔ s₁ = s₂ :=
h.image.eq_iff h₁ h₂
lemma InjOn.image_subset_image_iff (h : s.InjOn f) (h₁ : s₁ ⊆ s) (h₂ : s₂ ⊆ s) :
f '' s₁ ⊆ f '' s₂ ↔ s₁ ⊆ s₂ := by
refine ⟨fun h' ↦ ?_, image_subset _⟩
rw [← h.preimage_image_inter h₁, ← h.preimage_image_inter h₂]
exact inter_subset_inter_left _ (preimage_mono h')
lemma InjOn.image_ssubset_image_iff (h : s.InjOn f) (h₁ : s₁ ⊆ s) (h₂ : s₂ ⊆ s) :
f '' s₁ ⊂ f '' s₂ ↔ s₁ ⊂ s₂ := by
simp_rw [ssubset_def, h.image_subset_image_iff h₁ h₂, h.image_subset_image_iff h₂ h₁]
-- TODO: can this move to a better place?
theorem _root_.Disjoint.image {s t u : Set α} {f : α → β} (h : Disjoint s t) (hf : u.InjOn f)
(hs : s ⊆ u) (ht : t ⊆ u) : Disjoint (f '' s) (f '' t) := by
rw [disjoint_iff_inter_eq_empty] at h ⊢
rw [← hf.image_inter hs ht, h, image_empty]
lemma InjOn.image_diff {t : Set α} (h : s.InjOn f) : f '' (s \ t) = f '' s \ f '' (s ∩ t) := by
refine subset_antisymm (subset_diff.2 ⟨image_subset f diff_subset, ?_⟩)
(diff_subset_iff.2 (by rw [← image_union, inter_union_diff]))
exact Disjoint.image disjoint_sdiff_inter h diff_subset inter_subset_left
lemma InjOn.image_diff_subset {f : α → β} {t : Set α} (h : InjOn f s) (hst : t ⊆ s) :
f '' (s \ t) = f '' s \ f '' t := by
rw [h.image_diff, inter_eq_self_of_subset_right hst]
alias image_diff_of_injOn := InjOn.image_diff_subset
theorem InjOn.imageFactorization_injective (h : InjOn f s) :
Injective (s.imageFactorization f) :=
fun ⟨x, hx⟩ ⟨y, hy⟩ h' ↦ by simpa [imageFactorization, h.eq_iff hx hy] using h'
@[simp] theorem imageFactorization_injective_iff : Injective (s.imageFactorization f) ↔ InjOn f s :=
⟨fun h x hx y hy _ ↦ by simpa using @h ⟨x, hx⟩ ⟨y, hy⟩ (by simpa [imageFactorization]),
InjOn.imageFactorization_injective⟩
end injOn
section graphOn
variable {x : α × β}
lemma graphOn_univ_inj {g : α → β} : univ.graphOn f = univ.graphOn g ↔ f = g := by simp
lemma graphOn_univ_injective : Injective (univ.graphOn : (α → β) → Set (α × β)) :=
fun _f _g ↦ graphOn_univ_inj.1
lemma exists_eq_graphOn_image_fst [Nonempty β] {s : Set (α × β)} :
(∃ f : α → β, s = graphOn f (Prod.fst '' s)) ↔ InjOn Prod.fst s := by
refine ⟨?_, fun h ↦ ?_⟩
· rintro ⟨f, hf⟩
rw [hf]
exact InjOn.image_of_comp <| injOn_id _
· have : ∀ x ∈ Prod.fst '' s, ∃ y, (x, y) ∈ s := forall_mem_image.2 fun (x, y) h ↦ ⟨y, h⟩
choose! f hf using this
rw [forall_mem_image] at hf
use f
rw [graphOn, image_image, EqOn.image_eq_self]
exact fun x hx ↦ h (hf hx) hx rfl
lemma exists_eq_graphOn [Nonempty β] {s : Set (α × β)} :
(∃ f t, s = graphOn f t) ↔ InjOn Prod.fst s :=
.trans ⟨fun ⟨f, t, hs⟩ ↦ ⟨f, by rw [hs, image_fst_graphOn]⟩, fun ⟨f, hf⟩ ↦ ⟨f, _, hf⟩⟩
exists_eq_graphOn_image_fst
end graphOn
/-! ### Surjectivity on a set -/
section surjOn
theorem SurjOn.subset_range (h : SurjOn f s t) : t ⊆ range f :=
Subset.trans h <| image_subset_range f s
theorem surjOn_iff_exists_map_subtype :
SurjOn f s t ↔ ∃ (t' : Set β) (g : s → t'), t ⊆ t' ∧ Surjective g ∧ ∀ x : s, f x = g x :=
⟨fun h =>
⟨_, (mapsTo_image f s).restrict f s _, h, surjective_mapsTo_image_restrict _ _, fun _ => rfl⟩,
fun ⟨t', g, htt', hg, hfg⟩ y hy =>
let ⟨x, hx⟩ := hg ⟨y, htt' hy⟩
⟨x, x.2, by rw [hfg, hx, Subtype.coe_mk]⟩⟩
theorem surjOn_empty (f : α → β) (s : Set α) : SurjOn f s ∅ :=
empty_subset _
@[simp] theorem surjOn_empty_iff : SurjOn f ∅ t ↔ t = ∅ := by
simp [SurjOn, subset_empty_iff]
@[simp] lemma surjOn_singleton : SurjOn f s {b} ↔ b ∈ f '' s := singleton_subset_iff
theorem surjOn_image (f : α → β) (s : Set α) : SurjOn f s (f '' s) :=
Subset.rfl
theorem SurjOn.comap_nonempty (h : SurjOn f s t) (ht : t.Nonempty) : s.Nonempty :=
(ht.mono h).of_image
theorem SurjOn.congr (h : SurjOn f₁ s t) (H : EqOn f₁ f₂ s) : SurjOn f₂ s t := by
rwa [SurjOn, ← H.image_eq]
theorem EqOn.surjOn_iff (h : EqOn f₁ f₂ s) : SurjOn f₁ s t ↔ SurjOn f₂ s t :=
⟨fun H => H.congr h, fun H => H.congr h.symm⟩
theorem SurjOn.mono (hs : s₁ ⊆ s₂) (ht : t₁ ⊆ t₂) (hf : SurjOn f s₁ t₂) : SurjOn f s₂ t₁ :=
Subset.trans ht <| Subset.trans hf <| image_subset _ hs
theorem SurjOn.union (h₁ : SurjOn f s t₁) (h₂ : SurjOn f s t₂) : SurjOn f s (t₁ ∪ t₂) := fun _ hx =>
hx.elim (fun hx => h₁ hx) fun hx => h₂ hx
theorem SurjOn.union_union (h₁ : SurjOn f s₁ t₁) (h₂ : SurjOn f s₂ t₂) :
SurjOn f (s₁ ∪ s₂) (t₁ ∪ t₂) :=
(h₁.mono subset_union_left (Subset.refl _)).union
(h₂.mono subset_union_right (Subset.refl _))
theorem SurjOn.inter_inter (h₁ : SurjOn f s₁ t₁) (h₂ : SurjOn f s₂ t₂) (h : InjOn f (s₁ ∪ s₂)) :
SurjOn f (s₁ ∩ s₂) (t₁ ∩ t₂) := by
intro y hy
rcases h₁ hy.1 with ⟨x₁, hx₁, rfl⟩
rcases h₂ hy.2 with ⟨x₂, hx₂, heq⟩
obtain rfl : x₁ = x₂ := h (Or.inl hx₁) (Or.inr hx₂) heq.symm
exact mem_image_of_mem f ⟨hx₁, hx₂⟩
theorem SurjOn.inter (h₁ : SurjOn f s₁ t) (h₂ : SurjOn f s₂ t) (h : InjOn f (s₁ ∪ s₂)) :
SurjOn f (s₁ ∩ s₂) t :=
inter_self t ▸ h₁.inter_inter h₂ h
lemma surjOn_id (s : Set α) : SurjOn id s s := by simp [SurjOn]
theorem SurjOn.comp (hg : SurjOn g t p) (hf : SurjOn f s t) : SurjOn (g ∘ f) s p :=
Subset.trans hg <| Subset.trans (image_subset g hf) <| image_comp g f s ▸ Subset.refl _
lemma SurjOn.of_comp (h : SurjOn (g ∘ f) s p) (hr : MapsTo f s t) : SurjOn g t p := by
intro z hz
obtain ⟨x, hx, rfl⟩ := h hz
exact ⟨f x, hr hx, rfl⟩
lemma surjOn_comp_iff : SurjOn (g ∘ f) s p ↔ SurjOn g (f '' s) p :=
⟨fun h ↦ h.of_comp <| mapsTo_image f s, fun h ↦ h.comp <| surjOn_image _ _⟩
lemma SurjOn.iterate {f : α → α} {s : Set α} (h : SurjOn f s s) : ∀ n, SurjOn f^[n] s s
| 0 => surjOn_id _
| (n + 1) => (h.iterate n).comp h
lemma SurjOn.comp_left (hf : SurjOn f s t) (g : β → γ) : SurjOn (g ∘ f) s (g '' t) := by
rw [SurjOn, image_comp g f]; exact image_subset _ hf
lemma SurjOn.comp_right {s : Set β} {t : Set γ} (hf : Surjective f) (hg : SurjOn g s t) :
SurjOn (g ∘ f) (f ⁻¹' s) t := by
rwa [SurjOn, image_comp g f, image_preimage_eq _ hf]
lemma surjOn_of_subsingleton' [Subsingleton β] (f : α → β) (h : t.Nonempty → s.Nonempty) :
SurjOn f s t :=
fun _ ha ↦ Subsingleton.mem_iff_nonempty.2 <| (h ⟨_, ha⟩).image _
lemma surjOn_of_subsingleton [Subsingleton α] (f : α → α) (s : Set α) : SurjOn f s s :=
surjOn_of_subsingleton' _ id
theorem surjective_iff_surjOn_univ : Surjective f ↔ SurjOn f univ univ := by
simp [Surjective, SurjOn, subset_def]
theorem SurjOn.image_eq_of_mapsTo (h₁ : SurjOn f s t) (h₂ : MapsTo f s t) : f '' s = t :=
eq_of_subset_of_subset h₂.image_subset h₁
theorem image_eq_iff_surjOn_mapsTo : f '' s = t ↔ s.SurjOn f t ∧ s.MapsTo f t := by
refine ⟨?_, fun h => h.1.image_eq_of_mapsTo h.2⟩
rintro rfl
exact ⟨s.surjOn_image f, s.mapsTo_image f⟩
lemma SurjOn.image_preimage (h : Set.SurjOn f s t) (ht : t₁ ⊆ t) : f '' (f ⁻¹' t₁) = t₁ :=
image_preimage_eq_iff.2 fun _ hx ↦ mem_range_of_mem_image f s <| h <| ht hx
theorem SurjOn.mapsTo_compl (h : SurjOn f s t) (h' : Injective f) : MapsTo f sᶜ tᶜ :=
fun _ hs ht =>
let ⟨_, hx', HEq⟩ := h ht
hs <| h' HEq ▸ hx'
theorem MapsTo.surjOn_compl (h : MapsTo f s t) (h' : Surjective f) : SurjOn f sᶜ tᶜ :=
h'.forall.2 fun _ ht => (mem_image_of_mem _) fun hs => ht (h hs)
theorem EqOn.cancel_right (hf : s.EqOn (g₁ ∘ f) (g₂ ∘ f)) (hf' : s.SurjOn f t) : t.EqOn g₁ g₂ := by
intro b hb
obtain ⟨a, ha, rfl⟩ := hf' hb
exact hf ha
theorem SurjOn.cancel_right (hf : s.SurjOn f t) (hf' : s.MapsTo f t) :
s.EqOn (g₁ ∘ f) (g₂ ∘ f) ↔ t.EqOn g₁ g₂ :=
⟨fun h => h.cancel_right hf, fun h => h.comp_right hf'⟩
theorem eqOn_comp_right_iff : s.EqOn (g₁ ∘ f) (g₂ ∘ f) ↔ (f '' s).EqOn g₁ g₂ :=
(s.surjOn_image f).cancel_right <| s.mapsTo_image f
theorem SurjOn.forall {p : β → Prop} (hf : s.SurjOn f t) (hf' : s.MapsTo f t) :
(∀ y ∈ t, p y) ↔ (∀ x ∈ s, p (f x)) :=
⟨fun H x hx ↦ H (f x) (hf' hx), fun H _y hy ↦ let ⟨x, hx, hxy⟩ := hf hy; hxy ▸ H x hx⟩
end surjOn
/-! ### Bijectivity -/
section bijOn
theorem BijOn.mapsTo (h : BijOn f s t) : MapsTo f s t :=
h.left
theorem BijOn.injOn (h : BijOn f s t) : InjOn f s :=
h.right.left
theorem BijOn.surjOn (h : BijOn f s t) : SurjOn f s t :=
h.right.right
theorem BijOn.mk (h₁ : MapsTo f s t) (h₂ : InjOn f s) (h₃ : SurjOn f s t) : BijOn f s t :=
⟨h₁, h₂, h₃⟩
theorem bijOn_empty (f : α → β) : BijOn f ∅ ∅ :=
⟨mapsTo_empty f ∅, injOn_empty f, surjOn_empty f ∅⟩
@[simp] theorem bijOn_empty_iff_left : BijOn f s ∅ ↔ s = ∅ :=
⟨fun h ↦ by simpa using h.mapsTo, by rintro rfl; exact bijOn_empty f⟩
@[simp] theorem bijOn_empty_iff_right : BijOn f ∅ t ↔ t = ∅ :=
⟨fun h ↦ by simpa using h.surjOn, by rintro rfl; exact bijOn_empty f⟩
@[simp] lemma bijOn_singleton : BijOn f {a} {b} ↔ f a = b := by simp [BijOn, eq_comm]
theorem BijOn.inter_mapsTo (h₁ : BijOn f s₁ t₁) (h₂ : MapsTo f s₂ t₂) (h₃ : s₁ ∩ f ⁻¹' t₂ ⊆ s₂) :
BijOn f (s₁ ∩ s₂) (t₁ ∩ t₂) :=
⟨h₁.mapsTo.inter_inter h₂, h₁.injOn.mono inter_subset_left, fun _ hy =>
let ⟨x, hx, hxy⟩ := h₁.surjOn hy.1
⟨x, ⟨hx, h₃ ⟨hx, hxy.symm.subst hy.2⟩⟩, hxy⟩⟩
theorem MapsTo.inter_bijOn (h₁ : MapsTo f s₁ t₁) (h₂ : BijOn f s₂ t₂) (h₃ : s₂ ∩ f ⁻¹' t₁ ⊆ s₁) :
BijOn f (s₁ ∩ s₂) (t₁ ∩ t₂) :=
inter_comm s₂ s₁ ▸ inter_comm t₂ t₁ ▸ h₂.inter_mapsTo h₁ h₃
theorem BijOn.inter (h₁ : BijOn f s₁ t₁) (h₂ : BijOn f s₂ t₂) (h : InjOn f (s₁ ∪ s₂)) :
BijOn f (s₁ ∩ s₂) (t₁ ∩ t₂) :=
⟨h₁.mapsTo.inter_inter h₂.mapsTo, h₁.injOn.mono inter_subset_left,
h₁.surjOn.inter_inter h₂.surjOn h⟩
theorem BijOn.union (h₁ : BijOn f s₁ t₁) (h₂ : BijOn f s₂ t₂) (h : InjOn f (s₁ ∪ s₂)) :
BijOn f (s₁ ∪ s₂) (t₁ ∪ t₂) :=
⟨h₁.mapsTo.union_union h₂.mapsTo, h, h₁.surjOn.union_union h₂.surjOn⟩
theorem BijOn.subset_range (h : BijOn f s t) : t ⊆ range f :=
h.surjOn.subset_range
theorem InjOn.bijOn_image (h : InjOn f s) : BijOn f s (f '' s) :=
BijOn.mk (mapsTo_image f s) h (Subset.refl _)
theorem BijOn.congr (h₁ : BijOn f₁ s t) (h : EqOn f₁ f₂ s) : BijOn f₂ s t :=
BijOn.mk (h₁.mapsTo.congr h) (h₁.injOn.congr h) (h₁.surjOn.congr h)
theorem EqOn.bijOn_iff (H : EqOn f₁ f₂ s) : BijOn f₁ s t ↔ BijOn f₂ s t :=
⟨fun h => h.congr H, fun h => h.congr H.symm⟩
theorem BijOn.image_eq (h : BijOn f s t) : f '' s = t :=
h.surjOn.image_eq_of_mapsTo h.mapsTo
lemma BijOn.forall {p : β → Prop} (hf : BijOn f s t) : (∀ b ∈ t, p b) ↔ ∀ a ∈ s, p (f a) where
mp h _ ha := h _ <| hf.mapsTo ha
mpr h b hb := by obtain ⟨a, ha, rfl⟩ := hf.surjOn hb; exact h _ ha
lemma BijOn.exists {p : β → Prop} (hf : BijOn f s t) : (∃ b ∈ t, p b) ↔ ∃ a ∈ s, p (f a) where
mp := by rintro ⟨b, hb, h⟩; obtain ⟨a, ha, rfl⟩ := hf.surjOn hb; exact ⟨a, ha, h⟩
mpr := by rintro ⟨a, ha, h⟩; exact ⟨f a, hf.mapsTo ha, h⟩
lemma _root_.Equiv.image_eq_iff_bijOn (e : α ≃ β) : e '' s = t ↔ BijOn e s t :=
⟨fun h ↦ ⟨(mapsTo_image e s).mono_right h.subset, e.injective.injOn, h ▸ surjOn_image e s⟩,
BijOn.image_eq⟩
lemma bijOn_id (s : Set α) : BijOn id s s := ⟨s.mapsTo_id, s.injOn_id, s.surjOn_id⟩
theorem BijOn.comp (hg : BijOn g t p) (hf : BijOn f s t) : BijOn (g ∘ f) s p :=
BijOn.mk (hg.mapsTo.comp hf.mapsTo) (hg.injOn.comp hf.injOn hf.mapsTo) (hg.surjOn.comp hf.surjOn)
/-- If `f : α → β` and `g : β → γ` and if `f` is injective on `s`, then `f ∘ g` is a bijection
on `s` iff `g` is a bijection on `f '' s`. -/
theorem bijOn_comp_iff (hf : InjOn f s) : BijOn (g ∘ f) s p ↔ BijOn g (f '' s) p := by
simp only [BijOn, InjOn.comp_iff, surjOn_comp_iff, mapsTo_image_iff, hf]
/--
If we have a commutative square
```
α --f--> β
| |
p₁ p₂
| |
\/ \/
γ --g--> δ
```
and `f` induces a bijection from `s : Set α` to `t : Set β`, then `g`
induces a bijection from the image of `s` to the image of `t`, as long as `g` is
is injective on the image of `s`.
-/
theorem bijOn_image_image {p₁ : α → γ} {p₂ : β → δ} {g : γ → δ} (comm : ∀ a, p₂ (f a) = g (p₁ a))
(hbij : BijOn f s t) (hinj: InjOn g (p₁ '' s)) : BijOn g (p₁ '' s) (p₂ '' t) := by
obtain ⟨h1, h2, h3⟩ := hbij
refine ⟨?_, hinj, ?_⟩
· rintro _ ⟨a, ha, rfl⟩
exact ⟨f a, h1 ha, by rw [comm a]⟩
· rintro _ ⟨b, hb, rfl⟩
obtain ⟨a, ha, rfl⟩ := h3 hb
rw [← image_comp, comm]
exact ⟨a, ha, rfl⟩
lemma BijOn.iterate {f : α → α} {s : Set α} (h : BijOn f s s) : ∀ n, BijOn f^[n] s s
| 0 => s.bijOn_id
| (n + 1) => (h.iterate n).comp h
lemma bijOn_of_subsingleton' [Subsingleton α] [Subsingleton β] (f : α → β)
(h : s.Nonempty ↔ t.Nonempty) : BijOn f s t :=
⟨mapsTo_of_subsingleton' _ h.1, injOn_of_subsingleton _ _, surjOn_of_subsingleton' _ h.2⟩
lemma bijOn_of_subsingleton [Subsingleton α] (f : α → α) (s : Set α) : BijOn f s s :=
bijOn_of_subsingleton' _ Iff.rfl
theorem BijOn.bijective (h : BijOn f s t) : Bijective (h.mapsTo.restrict f s t) :=
⟨fun x y h' => Subtype.ext <| h.injOn x.2 y.2 <| Subtype.ext_iff.1 h', fun ⟨_, hy⟩ =>
let ⟨x, hx, hxy⟩ := h.surjOn hy
⟨⟨x, hx⟩, Subtype.eq hxy⟩⟩
theorem bijective_iff_bijOn_univ : Bijective f ↔ BijOn f univ univ :=
Iff.intro
(fun h =>
let ⟨inj, surj⟩ := h
⟨mapsTo_univ f _, inj.injOn, Iff.mp surjective_iff_surjOn_univ surj⟩)
fun h =>
let ⟨_map, inj, surj⟩ := h
⟨Iff.mpr injective_iff_injOn_univ inj, Iff.mpr surjective_iff_surjOn_univ surj⟩
alias ⟨_root_.Function.Bijective.bijOn_univ, _⟩ := bijective_iff_bijOn_univ
theorem BijOn.compl (hst : BijOn f s t) (hf : Bijective f) : BijOn f sᶜ tᶜ :=
⟨hst.surjOn.mapsTo_compl hf.1, hf.1.injOn, hst.mapsTo.surjOn_compl hf.2⟩
theorem BijOn.subset_right {r : Set β} (hf : BijOn f s t) (hrt : r ⊆ t) :
BijOn f (s ∩ f ⁻¹' r) r := by
refine ⟨inter_subset_right, hf.injOn.mono inter_subset_left, fun x hx ↦ ?_⟩
obtain ⟨y, hy, rfl⟩ := hf.surjOn (hrt hx)
exact ⟨y, ⟨hy, hx⟩, rfl⟩
theorem BijOn.subset_left {r : Set α} (hf : BijOn f s t) (hrs : r ⊆ s) :
BijOn f r (f '' r) :=
(hf.injOn.mono hrs).bijOn_image
theorem BijOn.insert_iff (ha : a ∉ s) (hfa : f a ∉ t) :
BijOn f (insert a s) (insert (f a) t) ↔ BijOn f s t where
mp h := by
have := congrArg (· \ {f a}) (image_insert_eq ▸ h.image_eq)
simp only [mem_singleton_iff, insert_diff_of_mem] at this
rw [diff_singleton_eq_self hfa, diff_singleton_eq_self] at this
· exact ⟨by simp [← this, mapsTo'], h.injOn.mono (subset_insert ..),
by simp [← this, surjOn_image]⟩
simp only [mem_image, not_exists, not_and]
intro x hx
rw [h.injOn.eq_iff (by simp [hx]) (by simp)]
exact ha ∘ (· ▸ hx)
mpr h := by
repeat rw [insert_eq]
refine (bijOn_singleton.mpr rfl).union h ?_
simp only [singleton_union, injOn_insert fun x ↦ (hfa (h.mapsTo x)), h.injOn, mem_image,
not_exists, not_and, true_and]
exact fun _ hx h₂ ↦ hfa (h₂ ▸ h.mapsTo hx)
theorem BijOn.insert (h₁ : BijOn f s t) (h₂ : f a ∉ t) :
BijOn f (insert a s) (insert (f a) t) :=
(insert_iff (h₂ <| h₁.mapsTo ·) h₂).mpr h₁
theorem BijOn.sdiff_singleton (h₁ : BijOn f s t) (h₂ : a ∈ s) :
BijOn f (s \ {a}) (t \ {f a}) := by
convert h₁.subset_left diff_subset
simp [h₁.injOn.image_diff, h₁.image_eq, h₂, inter_eq_self_of_subset_right]
end bijOn
/-! ### left inverse -/
namespace LeftInvOn
theorem eqOn (h : LeftInvOn f' f s) : EqOn (f' ∘ f) id s :=
h
theorem eq (h : LeftInvOn f' f s) {x} (hx : x ∈ s) : f' (f x) = x :=
h hx
theorem congr_left (h₁ : LeftInvOn f₁' f s) {t : Set β} (h₁' : MapsTo f s t)
(heq : EqOn f₁' f₂' t) : LeftInvOn f₂' f s := fun _ hx => heq (h₁' hx) ▸ h₁ hx
theorem congr_right (h₁ : LeftInvOn f₁' f₁ s) (heq : EqOn f₁ f₂ s) : LeftInvOn f₁' f₂ s :=
fun _ hx => heq hx ▸ h₁ hx
theorem injOn (h : LeftInvOn f₁' f s) : InjOn f s := fun x₁ h₁ x₂ h₂ heq =>
calc
x₁ = f₁' (f x₁) := Eq.symm <| h h₁
_ = f₁' (f x₂) := congr_arg f₁' heq
_ = x₂ := h h₂
theorem surjOn (h : LeftInvOn f' f s) (hf : MapsTo f s t) : SurjOn f' t s := fun x hx =>
⟨f x, hf hx, h hx⟩
|
theorem mapsTo (h : LeftInvOn f' f s) (hf : SurjOn f s t) :
| Mathlib/Data/Set/Function.lean | 766 | 767 |
/-
Copyright (c) 2019 Kim Morrison. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kim Morrison, Jakob von Raumer
-/
import Mathlib.CategoryTheory.Limits.Shapes.FiniteProducts
import Mathlib.CategoryTheory.Limits.Shapes.Kernels
/-!
# Biproducts and binary biproducts
We introduce the notion of (finite) biproducts.
Binary biproducts are defined in `CategoryTheory.Limits.Shapes.BinaryBiproducts`.
These are slightly unusual relative to the other shapes in the library,
as they are simultaneously limits and colimits.
(Zero objects are similar; they are "biterminal".)
For results about biproducts in preadditive categories see
`CategoryTheory.Preadditive.Biproducts`.
For biproducts indexed by a `Fintype J`, a `bicone` consists of a cone point `X`
and morphisms `π j : X ⟶ F j` and `ι j : F j ⟶ X` for each `j`,
such that `ι j ≫ π j'` is the identity when `j = j'` and zero otherwise.
## Notation
As `⊕` is already taken for the sum of types, we introduce the notation `X ⊞ Y` for
a binary biproduct. We introduce `⨁ f` for the indexed biproduct.
## Implementation notes
Prior to https://github.com/leanprover-community/mathlib3/pull/14046,
`HasFiniteBiproducts` required a `DecidableEq` instance on the indexing type.
As this had no pay-off (everything about limits is non-constructive in mathlib),
and occasional cost
(constructing decidability instances appropriate for constructions involving the indexing type),
we made everything classical.
-/
noncomputable section
universe w w' v u
open CategoryTheory Functor
namespace CategoryTheory.Limits
variable {J : Type w}
universe uC' uC uD' uD
variable {C : Type uC} [Category.{uC'} C] [HasZeroMorphisms C]
variable {D : Type uD} [Category.{uD'} D] [HasZeroMorphisms D]
open scoped Classical in
/-- A `c : Bicone F` is:
* an object `c.pt` and
* morphisms `π j : pt ⟶ F j` and `ι j : F j ⟶ pt` for each `j`,
* such that `ι j ≫ π j'` is the identity when `j = j'` and zero otherwise.
-/
structure Bicone (F : J → C) where
pt : C
π : ∀ j, pt ⟶ F j
ι : ∀ j, F j ⟶ pt
ι_π : ∀ j j', ι j ≫ π j' =
if h : j = j' then eqToHom (congrArg F h) else 0 := by aesop
attribute [inherit_doc Bicone] Bicone.pt Bicone.π Bicone.ι Bicone.ι_π
@[reassoc (attr := simp)]
theorem bicone_ι_π_self {F : J → C} (B : Bicone F) (j : J) : B.ι j ≫ B.π j = 𝟙 (F j) := by
simpa using B.ι_π j j
@[reassoc (attr := simp)]
theorem bicone_ι_π_ne {F : J → C} (B : Bicone F) {j j' : J} (h : j ≠ j') : B.ι j ≫ B.π j' = 0 := by
simpa [h] using B.ι_π j j'
variable {F : J → C}
/-- A bicone morphism between two bicones for the same diagram is a morphism of the bicone points
which commutes with the cone and cocone legs. -/
structure BiconeMorphism {F : J → C} (A B : Bicone F) where
/-- A morphism between the two vertex objects of the bicones -/
hom : A.pt ⟶ B.pt
/-- The triangle consisting of the two natural transformations and `hom` commutes -/
wπ : ∀ j : J, hom ≫ B.π j = A.π j := by aesop_cat
/-- The triangle consisting of the two natural transformations and `hom` commutes -/
wι : ∀ j : J, A.ι j ≫ hom = B.ι j := by aesop_cat
attribute [reassoc (attr := simp)] BiconeMorphism.wι BiconeMorphism.wπ
/-- The category of bicones on a given diagram. -/
@[simps]
instance Bicone.category : Category (Bicone F) where
Hom A B := BiconeMorphism A B
comp f g := { hom := f.hom ≫ g.hom }
id B := { hom := 𝟙 B.pt }
-- Porting note: if we do not have `simps` automatically generate the lemma for simplifying
-- the `hom` field of a category, we need to write the `ext` lemma in terms of the categorical
-- morphism, rather than the underlying structure.
@[ext]
theorem BiconeMorphism.ext {c c' : Bicone F} (f g : c ⟶ c') (w : f.hom = g.hom) : f = g := by
cases f
cases g
congr
namespace Bicones
/-- To give an isomorphism between cocones, it suffices to give an
isomorphism between their vertices which commutes with the cocone
maps. -/
@[aesop apply safe (rule_sets := [CategoryTheory]), simps]
def ext {c c' : Bicone F} (φ : c.pt ≅ c'.pt)
(wι : ∀ j, c.ι j ≫ φ.hom = c'.ι j := by aesop_cat)
(wπ : ∀ j, φ.hom ≫ c'.π j = c.π j := by aesop_cat) : c ≅ c' where
hom := { hom := φ.hom }
inv :=
{ hom := φ.inv
wι := fun j => φ.comp_inv_eq.mpr (wι j).symm
wπ := fun j => φ.inv_comp_eq.mpr (wπ j).symm }
variable (F) in
/-- A functor `G : C ⥤ D` sends bicones over `F` to bicones over `G.obj ∘ F` functorially. -/
@[simps]
def functoriality (G : C ⥤ D) [Functor.PreservesZeroMorphisms G] :
Bicone F ⥤ Bicone (G.obj ∘ F) where
obj A :=
{ pt := G.obj A.pt
π := fun j => G.map (A.π j)
ι := fun j => G.map (A.ι j)
ι_π := fun i j => (Functor.map_comp _ _ _).symm.trans <| by
rw [A.ι_π]
aesop_cat }
map f :=
{ hom := G.map f.hom
wπ := fun j => by simp [-BiconeMorphism.wπ, ← f.wπ j]
wι := fun j => by simp [-BiconeMorphism.wι, ← f.wι j] }
variable (G : C ⥤ D)
instance functoriality_full [G.PreservesZeroMorphisms] [G.Full] [G.Faithful] :
(functoriality F G).Full where
map_surjective t :=
⟨{ hom := G.preimage t.hom
wι := fun j => G.map_injective (by simpa using t.wι j)
wπ := fun j => G.map_injective (by simpa using t.wπ j) }, by aesop_cat⟩
instance functoriality_faithful [G.PreservesZeroMorphisms] [G.Faithful] :
(functoriality F G).Faithful where
map_injective {_X} {_Y} f g h :=
BiconeMorphism.ext f g <| G.map_injective <| congr_arg BiconeMorphism.hom h
end Bicones
namespace Bicone
attribute [local aesop safe tactic (rule_sets := [CategoryTheory])]
CategoryTheory.Discrete.discreteCases
-- Porting note: would it be okay to use this more generally?
attribute [local aesop safe cases (rule_sets := [CategoryTheory])] Eq
/-- Extract the cone from a bicone. -/
def toConeFunctor : Bicone F ⥤ Cone (Discrete.functor F) where
obj B := { pt := B.pt, π := { app := fun j => B.π j.as } }
map {_ _} F := { hom := F.hom, w := fun _ => F.wπ _ }
/-- A shorthand for `toConeFunctor.obj` -/
abbrev toCone (B : Bicone F) : Cone (Discrete.functor F) := toConeFunctor.obj B
-- TODO Consider changing this API to `toFan (B : Bicone F) : Fan F`.
@[simp] theorem toCone_pt (B : Bicone F) : B.toCone.pt = B.pt := rfl
@[simp] theorem toCone_π_app (B : Bicone F) (j : Discrete J) : B.toCone.π.app j = B.π j.as := rfl
theorem toCone_π_app_mk (B : Bicone F) (j : J) : B.toCone.π.app ⟨j⟩ = B.π j := rfl
@[simp] theorem toCone_proj (B : Bicone F) (j : J) : Fan.proj B.toCone j = B.π j := rfl
/-- Extract the cocone from a bicone. -/
def toCoconeFunctor : Bicone F ⥤ Cocone (Discrete.functor F) where
obj B := { pt := B.pt, ι := { app := fun j => B.ι j.as } }
map {_ _} F := { hom := F.hom, w := fun _ => F.wι _ }
/-- A shorthand for `toCoconeFunctor.obj` -/
abbrev toCocone (B : Bicone F) : Cocone (Discrete.functor F) := toCoconeFunctor.obj B
@[simp] theorem toCocone_pt (B : Bicone F) : B.toCocone.pt = B.pt := rfl
@[simp]
theorem toCocone_ι_app (B : Bicone F) (j : Discrete J) : B.toCocone.ι.app j = B.ι j.as := rfl
@[simp] theorem toCocone_inj (B : Bicone F) (j : J) : Cofan.inj B.toCocone j = B.ι j := rfl
theorem toCocone_ι_app_mk (B : Bicone F) (j : J) : B.toCocone.ι.app ⟨j⟩ = B.ι j := rfl
open scoped Classical in
/-- We can turn any limit cone over a discrete collection of objects into a bicone. -/
@[simps]
def ofLimitCone {f : J → C} {t : Cone (Discrete.functor f)} (ht : IsLimit t) : Bicone f where
pt := t.pt
π j := t.π.app ⟨j⟩
ι j := ht.lift (Fan.mk _ fun j' => if h : j = j' then eqToHom (congr_arg f h) else 0)
ι_π j j' := by simp
open scoped Classical in
theorem ι_of_isLimit {f : J → C} {t : Bicone f} (ht : IsLimit t.toCone) (j : J) :
t.ι j = ht.lift (Fan.mk _ fun j' => if h : j = j' then eqToHom (congr_arg f h) else 0) :=
ht.hom_ext fun j' => by
rw [ht.fac]
simp [t.ι_π]
open scoped Classical in
/-- We can turn any colimit cocone over a discrete collection of objects into a bicone. -/
@[simps]
def ofColimitCocone {f : J → C} {t : Cocone (Discrete.functor f)} (ht : IsColimit t) :
Bicone f where
pt := t.pt
π j := ht.desc (Cofan.mk _ fun j' => if h : j' = j then eqToHom (congr_arg f h) else 0)
ι j := t.ι.app ⟨j⟩
ι_π j j' := by simp
open scoped Classical in
theorem π_of_isColimit {f : J → C} {t : Bicone f} (ht : IsColimit t.toCocone) (j : J) :
t.π j = ht.desc (Cofan.mk _ fun j' => if h : j' = j then eqToHom (congr_arg f h) else 0) :=
ht.hom_ext fun j' => by
rw [ht.fac]
simp [t.ι_π]
/-- Structure witnessing that a bicone is both a limit cone and a colimit cocone. -/
structure IsBilimit {F : J → C} (B : Bicone F) where
isLimit : IsLimit B.toCone
isColimit : IsColimit B.toCocone
attribute [inherit_doc IsBilimit] IsBilimit.isLimit IsBilimit.isColimit
attribute [simp] IsBilimit.mk.injEq
attribute [local ext] Bicone.IsBilimit
instance subsingleton_isBilimit {f : J → C} {c : Bicone f} : Subsingleton c.IsBilimit :=
⟨fun _ _ => Bicone.IsBilimit.ext (Subsingleton.elim _ _) (Subsingleton.elim _ _)⟩
section Whisker
variable {K : Type w'}
/-- Whisker a bicone with an equivalence between the indexing types. -/
@[simps]
def whisker {f : J → C} (c : Bicone f) (g : K ≃ J) : Bicone (f ∘ g) where
pt := c.pt
π k := c.π (g k)
ι k := c.ι (g k)
ι_π k k' := by
simp only [c.ι_π]
split_ifs with h h' h' <;> simp [Equiv.apply_eq_iff_eq g] at h h' <;> tauto
/-- Taking the cone of a whiskered bicone results in a cone isomorphic to one gained
by whiskering the cone and postcomposing with a suitable isomorphism. -/
| def whiskerToCone {f : J → C} (c : Bicone f) (g : K ≃ J) :
(c.whisker g).toCone ≅
(Cones.postcompose (Discrete.functorComp f g).inv).obj
(c.toCone.whisker (Discrete.functor (Discrete.mk ∘ g))) :=
Cones.ext (Iso.refl _) (by simp)
| Mathlib/CategoryTheory/Limits/Shapes/Biproducts.lean | 259 | 263 |
/-
Copyright (c) 2022 Andrew Yang. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Andrew Yang
-/
import Mathlib.CategoryTheory.Limits.Shapes.Pullback.CommSq
import Mathlib.CategoryTheory.Limits.Shapes.StrictInitial
import Mathlib.CategoryTheory.Limits.Types.Shapes
import Mathlib.Topology.Category.TopCat.Limits.Pullbacks
import Mathlib.CategoryTheory.Limits.FunctorCategory.Basic
import Mathlib.CategoryTheory.Limits.Constructions.FiniteProductsOfBinaryProducts
import Mathlib.CategoryTheory.Limits.VanKampen
/-!
# Extensive categories
## Main definitions
- `CategoryTheory.FinitaryExtensive`: A category is (finitary) extensive if it has finite
coproducts, and binary coproducts are van Kampen.
## Main Results
- `CategoryTheory.hasStrictInitialObjects_of_finitaryExtensive`: The initial object
in extensive categories is strict.
- `CategoryTheory.FinitaryExtensive.mono_inr_of_isColimit`: Coproduct injections are monic in
extensive categories.
- `CategoryTheory.BinaryCofan.isPullback_initial_to_of_isVanKampen`: In extensive categories,
sums are disjoint, i.e. the pullback of `X ⟶ X ⨿ Y` and `Y ⟶ X ⨿ Y` is the initial object.
- `CategoryTheory.types.finitaryExtensive`: The category of types is extensive.
- `CategoryTheory.FinitaryExtensive_TopCat`:
The category `Top` is extensive.
- `CategoryTheory.FinitaryExtensive_functor`: The category `C ⥤ D` is extensive if `D`
has all pullbacks and is extensive.
- `CategoryTheory.FinitaryExtensive.isVanKampen_finiteCoproducts`: Finite coproducts in a
finitary extensive category are van Kampen.
## TODO
Show that the following are finitary extensive:
- `Scheme`
- `AffineScheme` (`CommRingᵒᵖ`)
## References
- https://ncatlab.org/nlab/show/extensive+category
- [Carboni et al, Introduction to extensive and distributive categories][CARBONI1993145]
-/
open CategoryTheory.Limits Topology
namespace CategoryTheory
universe v' u' v u v'' u''
variable {J : Type v'} [Category.{u'} J] {C : Type u} [Category.{v} C]
variable {D : Type u''} [Category.{v''} D]
section Extensive
variable {X Y : C}
/-- A category has pullback of inclusions if it has all pullbacks along coproduct injections. -/
class HasPullbacksOfInclusions (C : Type u) [Category.{v} C] [HasBinaryCoproducts C] : Prop where
[hasPullbackInl : ∀ {X Y Z : C} (f : Z ⟶ X ⨿ Y), HasPullback coprod.inl f]
attribute [instance] HasPullbacksOfInclusions.hasPullbackInl
/--
A functor preserves pullback of inclusions if it preserves all pullbacks along coproduct injections.
-/
class PreservesPullbacksOfInclusions {C : Type*} [Category C] {D : Type*} [Category D]
(F : C ⥤ D) [HasBinaryCoproducts C] where
[preservesPullbackInl : ∀ {X Y Z : C} (f : Z ⟶ X ⨿ Y), PreservesLimit (cospan coprod.inl f) F]
attribute [instance] PreservesPullbacksOfInclusions.preservesPullbackInl
/-- A category is (finitary) pre-extensive if it has finite coproducts,
and binary coproducts are universal. -/
class FinitaryPreExtensive (C : Type u) [Category.{v} C] : Prop where
[hasFiniteCoproducts : HasFiniteCoproducts C]
[hasPullbacksOfInclusions : HasPullbacksOfInclusions C]
/-- In a finitary extensive category, all coproducts are van Kampen -/
universal' : ∀ {X Y : C} (c : BinaryCofan X Y), IsColimit c → IsUniversalColimit c
attribute [instance] FinitaryPreExtensive.hasFiniteCoproducts
attribute [instance] FinitaryPreExtensive.hasPullbacksOfInclusions
/-- A category is (finitary) extensive if it has finite coproducts,
and binary coproducts are van Kampen. -/
class FinitaryExtensive (C : Type u) [Category.{v} C] : Prop where
[hasFiniteCoproducts : HasFiniteCoproducts C]
[hasPullbacksOfInclusions : HasPullbacksOfInclusions C]
/-- In a finitary extensive category, all coproducts are van Kampen -/
van_kampen' : ∀ {X Y : C} (c : BinaryCofan X Y), IsColimit c → IsVanKampenColimit c
attribute [instance] FinitaryExtensive.hasFiniteCoproducts
attribute [instance] FinitaryExtensive.hasPullbacksOfInclusions
theorem FinitaryExtensive.vanKampen [FinitaryExtensive C] {F : Discrete WalkingPair ⥤ C}
(c : Cocone F) (hc : IsColimit c) : IsVanKampenColimit c := by
let X := F.obj ⟨WalkingPair.left⟩
let Y := F.obj ⟨WalkingPair.right⟩
| have : F = pair X Y := by
apply Functor.hext
· rintro ⟨⟨⟩⟩ <;> rfl
· rintro ⟨⟨⟩⟩ ⟨j⟩ ⟨⟨rfl : _ = j⟩⟩ <;> simp [X, Y]
clear_value X Y
subst this
exact FinitaryExtensive.van_kampen' c hc
namespace HasPullbacksOfInclusions
instance (priority := 100) [HasBinaryCoproducts C] [HasPullbacks C] :
| Mathlib/CategoryTheory/Extensive.lean | 102 | 112 |
/-
Copyright (c) 2024 Dagur Asgeirsson. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Dagur Asgeirsson
-/
import Mathlib.CategoryTheory.Sites.Coherent.SheafComparison
import Mathlib.CategoryTheory.Sites.Equivalence
/-!
# Coherence and equivalence of categories
This file proves that the coherent and regular topologies transfer nicely along equivalences of
categories.
-/
namespace CategoryTheory
variable {C : Type*} [Category C]
open GrothendieckTopology
namespace Equivalence
variable {D : Type*} [Category D]
section Coherent
variable [Precoherent C]
/-- `Precoherent` is preserved by equivalence of categories. -/
theorem precoherent (e : C ≌ D) : Precoherent D := e.inverse.reflects_precoherent
instance [EssentiallySmall C] :
Precoherent (SmallModel C) := (equivSmallModel C).precoherent
instance (e : C ≌ D) : haveI := precoherent e
e.inverse.IsDenseSubsite (coherentTopology D) (coherentTopology C) where
functorPushforward_mem_iff := by
rw [coherentTopology.eq_induced e.inverse]
simp only [Functor.mem_inducedTopology_sieves_iff, implies_true]
variable (A : Type*) [Category A]
/--
Equivalent precoherent categories give equivalent coherent toposes.
-/
@[simps!]
def sheafCongrPrecoherent (e : C ≌ D) : haveI := e.precoherent
Sheaf (coherentTopology C) A ≌ Sheaf (coherentTopology D) A := e.sheafCongr _ _ _
open Presheaf
/--
The coherent sheaf condition can be checked after precomposing with the equivalence.
| -/
theorem precoherent_isSheaf_iff (e : C ≌ D) (F : Cᵒᵖ ⥤ A) : haveI := e.precoherent
IsSheaf (coherentTopology C) F ↔ IsSheaf (coherentTopology D) (e.inverse.op ⋙ F) := by
refine ⟨fun hF ↦ ((e.sheafCongrPrecoherent A).functor.obj ⟨F, hF⟩).cond, fun hF ↦ ?_⟩
rw [isSheaf_of_iso_iff (P' := e.functor.op ⋙ e.inverse.op ⋙ F)]
· exact (e.sheafCongrPrecoherent A).inverse.obj ⟨e.inverse.op ⋙ F, hF⟩ |>.cond
| Mathlib/CategoryTheory/Sites/Coherent/Equivalence.lean | 55 | 60 |
/-
Copyright (c) 2019 Kevin Kappelmann. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kevin Kappelmann, Kyle Miller, Mario Carneiro
-/
import Mathlib.Data.Finset.NatAntidiagonal
import Mathlib.Data.Nat.GCD.Basic
import Mathlib.Data.Nat.BinaryRec
import Mathlib.Logic.Function.Iterate
import Mathlib.Tactic.Ring
import Mathlib.Tactic.Zify
import Mathlib.Data.Nat.Choose.Basic
import Mathlib.Algebra.BigOperators.Group.Finset.Basic
/-!
# Fibonacci Numbers
This file defines the fibonacci series, proves results about it and introduces
methods to compute it quickly.
-/
/-!
# The Fibonacci Sequence
## Summary
Definition of the Fibonacci sequence `F₀ = 0, F₁ = 1, Fₙ₊₂ = Fₙ + Fₙ₊₁`.
## Main Definitions
- `Nat.fib` returns the stream of Fibonacci numbers.
## Main Statements
- `Nat.fib_add_two`: shows that `fib` indeed satisfies the Fibonacci recurrence `Fₙ₊₂ = Fₙ + Fₙ₊₁.`.
- `Nat.fib_gcd`: `fib n` is a strong divisibility sequence.
- `Nat.fib_succ_eq_sum_choose`: `fib` is given by the sum of `Nat.choose` along an antidiagonal.
- `Nat.fib_succ_eq_succ_sum`: shows that `F₀ + F₁ + ⋯ + Fₙ = Fₙ₊₂ - 1`.
- `Nat.fib_two_mul` and `Nat.fib_two_mul_add_one` are the basis for an efficient algorithm to
compute `fib` (see `Nat.fastFib`).
## Implementation Notes
For efficiency purposes, the sequence is defined using `Stream.iterate`.
## Tags
fib, fibonacci
-/
namespace Nat
/-- Implementation of the fibonacci sequence satisfying
`fib 0 = 0, fib 1 = 1, fib (n + 2) = fib n + fib (n + 1)`.
*Note:* We use a stream iterator for better performance when compared to the naive recursive
implementation.
-/
@[pp_nodot]
def fib (n : ℕ) : ℕ :=
((fun p : ℕ × ℕ => (p.snd, p.fst + p.snd))^[n] (0, 1)).fst
@[simp]
theorem fib_zero : fib 0 = 0 :=
rfl
@[simp]
theorem fib_one : fib 1 = 1 :=
rfl
@[simp]
theorem fib_two : fib 2 = 1 :=
rfl
/-- Shows that `fib` indeed satisfies the Fibonacci recurrence `Fₙ₊₂ = Fₙ + Fₙ₊₁.` -/
theorem fib_add_two {n : ℕ} : fib (n + 2) = fib n + fib (n + 1) := by
simp [fib, Function.iterate_succ_apply']
lemma fib_add_one : ∀ {n}, n ≠ 0 → fib (n + 1) = fib (n - 1) + fib n
| _n + 1, _ => fib_add_two
theorem fib_le_fib_succ {n : ℕ} : fib n ≤ fib (n + 1) := by cases n <;> simp [fib_add_two]
@[mono]
theorem fib_mono : Monotone fib :=
monotone_nat_of_le_succ fun _ => fib_le_fib_succ
@[simp] lemma fib_eq_zero : ∀ {n}, fib n = 0 ↔ n = 0
| 0 => Iff.rfl
| | 1 => Iff.rfl
| Mathlib/Data/Nat/Fib/Basic.lean | 93 | 93 |
/-
Copyright (c) 2020 Kyle Miller. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kyle Miller
-/
import Mathlib.Algebra.Group.Action.Pi
import Mathlib.Data.Finset.Prod
import Mathlib.Data.SetLike.Basic
import Mathlib.Data.Sym.Basic
import Mathlib.Data.Sym.Sym2.Init
/-!
# The symmetric square
This file defines the symmetric square, which is `α × α` modulo
swapping. This is also known as the type of unordered pairs.
More generally, the symmetric square is the second symmetric power
(see `Data.Sym.Basic`). The equivalence is `Sym2.equivSym`.
From the point of view that an unordered pair is equivalent to a
multiset of cardinality two (see `Sym2.equivMultiset`), there is a
`Mem` instance `Sym2.Mem`, which is a `Prop`-valued membership
test. Given `h : a ∈ z` for `z : Sym2 α`, then `Mem.other h` is the other
element of the pair, defined using `Classical.choice`. If `α` has
decidable equality, then `h.other'` computably gives the other element.
The universal property of `Sym2` is provided as `Sym2.lift`, which
states that functions from `Sym2 α` are equivalent to symmetric
two-argument functions from `α`.
Recall that an undirected graph (allowing self loops, but no multiple
edges) is equivalent to a symmetric relation on the vertex type `α`.
Given a symmetric relation on `α`, the corresponding edge set is
constructed by `Sym2.fromRel` which is a special case of `Sym2.lift`.
## Notation
The element `Sym2.mk (a, b)` can be written as `s(a, b)` for short.
## Tags
symmetric square, unordered pairs, symmetric powers
-/
assert_not_exists MonoidWithZero
open List (Vector)
open Finset Function Sym
universe u
variable {α β γ : Type*}
namespace Sym2
/-- This is the relation capturing the notion of pairs equivalent up to permutations. -/
@[aesop (rule_sets := [Sym2]) [safe [constructors, cases], norm]]
inductive Rel (α : Type u) : α × α → α × α → Prop
| refl (x y : α) : Rel _ (x, y) (x, y)
| swap (x y : α) : Rel _ (x, y) (y, x)
attribute [refl] Rel.refl
@[symm]
theorem Rel.symm {x y : α × α} : Rel α x y → Rel α y x := by aesop (rule_sets := [Sym2])
@[trans]
theorem Rel.trans {x y z : α × α} (a : Rel α x y) (b : Rel α y z) : Rel α x z := by
aesop (rule_sets := [Sym2])
theorem Rel.is_equivalence : Equivalence (Rel α) :=
{ refl := fun (x, y) ↦ Rel.refl x y, symm := Rel.symm, trans := Rel.trans }
/-- One can use `attribute [local instance] Sym2.Rel.setoid` to temporarily
make `Quotient` functionality work for `α × α`. -/
def Rel.setoid (α : Type u) : Setoid (α × α) :=
⟨Rel α, Rel.is_equivalence⟩
@[simp]
theorem rel_iff' {p q : α × α} : Rel α p q ↔ p = q ∨ p = q.swap := by
aesop (rule_sets := [Sym2])
theorem rel_iff {x y z w : α} : Rel α (x, y) (z, w) ↔ x = z ∧ y = w ∨ x = w ∧ y = z := by
simp
end Sym2
/-- `Sym2 α` is the symmetric square of `α`, which, in other words, is the
type of unordered pairs.
It is equivalent in a natural way to multisets of cardinality 2 (see
`Sym2.equivMultiset`).
-/
abbrev Sym2 (α : Type u) := Quot (Sym2.Rel α)
/-- Constructor for `Sym2`. This is the quotient map `α × α → Sym2 α`. -/
protected abbrev Sym2.mk {α : Type*} (p : α × α) : Sym2 α := Quot.mk (Sym2.Rel α) p
/-- `s(x, y)` is an unordered pair,
which is to say a pair modulo the action of the symmetric group.
It is equal to `Sym2.mk (x, y)`. -/
notation3 "s(" x ", " y ")" => Sym2.mk (x, y)
namespace Sym2
protected theorem sound {p p' : α × α} (h : Sym2.Rel α p p') : Sym2.mk p = Sym2.mk p' :=
Quot.sound h
protected theorem exact {p p' : α × α} (h : Sym2.mk p = Sym2.mk p') : Sym2.Rel α p p' :=
Quotient.exact (s := Sym2.Rel.setoid α) h
@[simp]
protected theorem eq {p p' : α × α} : Sym2.mk p = Sym2.mk p' ↔ Sym2.Rel α p p' :=
Quotient.eq' (s₁ := Sym2.Rel.setoid α)
@[elab_as_elim, cases_eliminator, induction_eliminator]
protected theorem ind {f : Sym2 α → Prop} (h : ∀ x y, f s(x, y)) : ∀ i, f i :=
Quot.ind <| Prod.rec <| h
@[elab_as_elim]
protected theorem inductionOn {f : Sym2 α → Prop} (i : Sym2 α) (hf : ∀ x y, f s(x, y)) : f i :=
i.ind hf
@[elab_as_elim]
protected theorem inductionOn₂ {f : Sym2 α → Sym2 β → Prop} (i : Sym2 α) (j : Sym2 β)
(hf : ∀ a₁ a₂ b₁ b₂, f s(a₁, a₂) s(b₁, b₂)) : f i j :=
Quot.induction_on₂ i j <| by
intro ⟨a₁, a₂⟩ ⟨b₁, b₂⟩
exact hf _ _ _ _
/-- Dependent recursion principal for `Sym2`. See `Quot.rec`. -/
@[elab_as_elim]
protected def rec {motive : Sym2 α → Sort*}
(f : (p : α × α) → motive (Sym2.mk p))
(h : (p q : α × α) → (h : Sym2.Rel α p q) → Eq.ndrec (f p) (Sym2.sound h) = f q)
(z : Sym2 α) : motive z :=
Quot.rec f h z
/-- Dependent recursion principal for `Sym2` when the target is a `Subsingleton` type.
See `Quot.recOnSubsingleton`. -/
@[elab_as_elim]
protected abbrev recOnSubsingleton {motive : Sym2 α → Sort*}
[(p : α × α) → Subsingleton (motive (Sym2.mk p))]
(z : Sym2 α) (f : (p : α × α) → motive (Sym2.mk p)) : motive z :=
Quot.recOnSubsingleton z f
protected theorem «exists» {α : Sort _} {f : Sym2 α → Prop} :
(∃ x : Sym2 α, f x) ↔ ∃ x y, f s(x, y) :=
Quot.mk_surjective.exists.trans Prod.exists
protected theorem «forall» {α : Sort _} {f : Sym2 α → Prop} :
(∀ x : Sym2 α, f x) ↔ ∀ x y, f s(x, y) :=
Quot.mk_surjective.forall.trans Prod.forall
theorem eq_swap {a b : α} : s(a, b) = s(b, a) := Quot.sound (Rel.swap _ _)
@[simp]
theorem mk_prod_swap_eq {p : α × α} : Sym2.mk p.swap = Sym2.mk p := by
cases p
exact eq_swap
theorem congr_right {a b c : α} : s(a, b) = s(a, c) ↔ b = c := by
simp +contextual
theorem congr_left {a b c : α} : s(b, a) = s(c, a) ↔ b = c := by
simp +contextual
theorem eq_iff {x y z w : α} : s(x, y) = s(z, w) ↔ x = z ∧ y = w ∨ x = w ∧ y = z := by
simp
theorem mk_eq_mk_iff {p q : α × α} : Sym2.mk p = Sym2.mk q ↔ p = q ∨ p = q.swap := by
cases p
cases q
simp only [eq_iff, Prod.mk_inj, Prod.swap_prod_mk]
/-- The universal property of `Sym2`; symmetric functions of two arguments are equivalent to
functions from `Sym2`. Note that when `β` is `Prop`, it can sometimes be more convenient to use
`Sym2.fromRel` instead. -/
def lift : { f : α → α → β // ∀ a₁ a₂, f a₁ a₂ = f a₂ a₁ } ≃ (Sym2 α → β) where
toFun f :=
Quot.lift (uncurry ↑f) <| by
rintro _ _ ⟨⟩
exacts [rfl, f.prop _ _]
invFun F := ⟨curry (F ∘ Sym2.mk), fun _ _ => congr_arg F eq_swap⟩
left_inv _ := Subtype.ext rfl
right_inv _ := funext <| Sym2.ind fun _ _ => rfl
@[simp]
theorem lift_mk (f : { f : α → α → β // ∀ a₁ a₂, f a₁ a₂ = f a₂ a₁ }) (a₁ a₂ : α) :
lift f s(a₁, a₂) = (f : α → α → β) a₁ a₂ :=
rfl
@[simp]
theorem coe_lift_symm_apply (F : Sym2 α → β) (a₁ a₂ : α) :
(lift.symm F : α → α → β) a₁ a₂ = F s(a₁, a₂) :=
rfl
/-- A two-argument version of `Sym2.lift`. -/
def lift₂ :
{ f : α → α → β → β → γ //
∀ a₁ a₂ b₁ b₂, f a₁ a₂ b₁ b₂ = f a₂ a₁ b₁ b₂ ∧ f a₁ a₂ b₁ b₂ = f a₁ a₂ b₂ b₁ } ≃
(Sym2 α → Sym2 β → γ) where
toFun f :=
Quotient.lift₂ (s₁ := Sym2.Rel.setoid α) (s₂ := Sym2.Rel.setoid β)
(fun (a : α × α) (b : β × β) => f.1 a.1 a.2 b.1 b.2)
(by
rintro _ _ _ _ ⟨⟩ ⟨⟩
exacts [rfl, (f.2 _ _ _ _).2, (f.2 _ _ _ _).1, (f.2 _ _ _ _).1.trans (f.2 _ _ _ _).2])
invFun F :=
⟨fun a₁ a₂ b₁ b₂ => F s(a₁, a₂) s(b₁, b₂), fun a₁ a₂ b₁ b₂ => by
constructor
exacts [congr_arg₂ F eq_swap rfl, congr_arg₂ F rfl eq_swap]⟩
left_inv _ := Subtype.ext rfl
right_inv _ := funext₂ fun a b => Sym2.inductionOn₂ a b fun _ _ _ _ => rfl
@[simp]
theorem lift₂_mk
(f :
{ f : α → α → β → β → γ //
∀ a₁ a₂ b₁ b₂, f a₁ a₂ b₁ b₂ = f a₂ a₁ b₁ b₂ ∧ f a₁ a₂ b₁ b₂ = f a₁ a₂ b₂ b₁ })
(a₁ a₂ : α) (b₁ b₂ : β) : lift₂ f s(a₁, a₂) s(b₁, b₂) = (f : α → α → β → β → γ) a₁ a₂ b₁ b₂ :=
rfl
@[simp]
theorem coe_lift₂_symm_apply (F : Sym2 α → Sym2 β → γ) (a₁ a₂ : α) (b₁ b₂ : β) :
(lift₂.symm F : α → α → β → β → γ) a₁ a₂ b₁ b₂ = F s(a₁, a₂) s(b₁, b₂) :=
rfl
/-- The functor `Sym2` is functorial, and this function constructs the induced maps.
-/
def map (f : α → β) : Sym2 α → Sym2 β :=
Quot.map (Prod.map f f)
(by intro _ _ h; cases h <;> constructor)
@[simp]
theorem map_id : map (@id α) = id := by
ext ⟨⟨x, y⟩⟩
rfl
theorem map_comp {g : β → γ} {f : α → β} : Sym2.map (g ∘ f) = Sym2.map g ∘ Sym2.map f := by
ext ⟨⟨x, y⟩⟩
rfl
theorem map_map {g : β → γ} {f : α → β} (x : Sym2 α) : map g (map f x) = map (g ∘ f) x := by
induction x; aesop
@[simp]
theorem map_pair_eq (f : α → β) (x y : α) : map f s(x, y) = s(f x, f y) :=
rfl
theorem map.injective {f : α → β} (hinj : Injective f) : Injective (map f) := by
intro z z'
refine Sym2.inductionOn₂ z z' (fun x y x' y' => ?_)
simp [hinj.eq_iff]
/-- `mk a` as an embedding. This is the symmetric version of `Function.Embedding.sectL`. -/
@[simps]
def mkEmbedding (a : α) : α ↪ Sym2 α where
toFun b := s(a, b)
inj' b₁ b₁ h := by
simp only [Sym2.eq, Sym2.rel_iff', Prod.mk.injEq, true_and, Prod.swap_prod_mk] at h
obtain rfl | ⟨rfl, rfl⟩ := h <;> rfl
/-- `Sym2.map` as an embedding. -/
@[simps]
def _root_.Function.Embedding.sym2Map (f : α ↪ β) : Sym2 α ↪ Sym2 β where
toFun := map f
inj' := map.injective f.injective
lemma lift_comp_map {g : γ → α} (f : {f : α → α → β // ∀ a₁ a₂, f a₁ a₂ = f a₂ a₁}) :
lift f ∘ map g = lift ⟨fun (c₁ c₂ : γ) => f.val (g c₁) (g c₂), fun _ _ => f.prop _ _⟩ :=
lift.symm_apply_eq.mp rfl
lemma lift_map_apply {g : γ → α} (f : {f : α → α → β // ∀ a₁ a₂, f a₁ a₂ = f a₂ a₁}) (p : Sym2 γ) :
lift f (map g p) = lift ⟨fun (c₁ c₂ : γ) => f.val (g c₁) (g c₂), fun _ _ => f.prop _ _⟩ p := by
conv_rhs => rw [← lift_comp_map, comp_apply]
section Membership
/-! ### Membership and set coercion -/
/-- This is a predicate that determines whether a given term is a member of a term of the
symmetric square. From this point of view, the symmetric square is the subtype of
cardinality-two multisets on `α`.
-/
protected def Mem (x : α) (z : Sym2 α) : Prop :=
∃ y : α, z = s(x, y)
@[aesop norm (rule_sets := [Sym2])]
theorem mem_iff' {a b c : α} : Sym2.Mem a s(b, c) ↔ a = b ∨ a = c :=
{ mp := by
rintro ⟨_, h⟩
rw [eq_iff] at h
aesop
mpr := by
rintro (rfl | rfl)
· exact ⟨_, rfl⟩
rw [eq_swap]
exact ⟨_, rfl⟩ }
instance : SetLike (Sym2 α) α where
coe z := { x | z.Mem x }
coe_injective' z z' h := by
simp only [Set.ext_iff, Set.mem_setOf_eq] at h
obtain ⟨x, y⟩ := z
obtain ⟨x', y'⟩ := z'
have hx := h x; have hy := h y; have hx' := h x'; have hy' := h y'
simp only [mem_iff', eq_self_iff_true] at hx hy hx' hy'
aesop
@[simp]
theorem mem_iff_mem {x : α} {z : Sym2 α} : Sym2.Mem x z ↔ x ∈ z :=
Iff.rfl
theorem mem_iff_exists {x : α} {z : Sym2 α} : x ∈ z ↔ ∃ y : α, z = s(x, y) :=
Iff.rfl
@[ext]
theorem ext {p q : Sym2 α} (h : ∀ x, x ∈ p ↔ x ∈ q) : p = q :=
SetLike.ext h
theorem mem_mk_left (x y : α) : x ∈ s(x, y) :=
⟨y, rfl⟩
theorem mem_mk_right (x y : α) : y ∈ s(x, y) :=
eq_swap ▸ mem_mk_left y x
@[simp, aesop norm (rule_sets := [Sym2])]
theorem mem_iff {a b c : α} : a ∈ s(b, c) ↔ a = b ∨ a = c :=
mem_iff'
theorem out_fst_mem (e : Sym2 α) : e.out.1 ∈ e :=
⟨e.out.2, by rw [Sym2.mk, e.out_eq]⟩
theorem out_snd_mem (e : Sym2 α) : e.out.2 ∈ e :=
⟨e.out.1, by rw [eq_swap, Sym2.mk, e.out_eq]⟩
theorem ball {p : α → Prop} {a b : α} : (∀ c ∈ s(a, b), p c) ↔ p a ∧ p b := by
refine ⟨fun h => ⟨h _ <| mem_mk_left _ _, h _ <| mem_mk_right _ _⟩, fun h c hc => ?_⟩
obtain rfl | rfl := Sym2.mem_iff.1 hc
· exact h.1
· exact h.2
/-- Given an element of the unordered pair, give the other element using `Classical.choose`.
See also `Mem.other'` for the computable version.
-/
noncomputable def Mem.other {a : α} {z : Sym2 α} (h : a ∈ z) : α :=
Classical.choose h
@[simp]
theorem other_spec {a : α} {z : Sym2 α} (h : a ∈ z) : s(a, Mem.other h) = z := by
erw [← Classical.choose_spec h]
theorem other_mem {a : α} {z : Sym2 α} (h : a ∈ z) : Mem.other h ∈ z := by
convert mem_mk_right a <| Mem.other h
rw [other_spec h]
theorem mem_and_mem_iff {x y : α} {z : Sym2 α} (hne : x ≠ y) : x ∈ z ∧ y ∈ z ↔ z = s(x, y) := by
constructor
· cases z
rw [mem_iff, mem_iff]
aesop
· rintro rfl
simp
theorem eq_of_ne_mem {x y : α} {z z' : Sym2 α} (h : x ≠ y) (h1 : x ∈ z) (h2 : y ∈ z) (h3 : x ∈ z')
(h4 : y ∈ z') : z = z' :=
((mem_and_mem_iff h).mp ⟨h1, h2⟩).trans ((mem_and_mem_iff h).mp ⟨h3, h4⟩).symm
instance Mem.decidable [DecidableEq α] (x : α) (z : Sym2 α) : Decidable (x ∈ z) :=
z.recOnSubsingleton fun ⟨_, _⟩ => decidable_of_iff' _ mem_iff
end Membership
@[simp]
theorem mem_map {f : α → β} {b : β} {z : Sym2 α} : b ∈ Sym2.map f z ↔ ∃ a, a ∈ z ∧ f a = b := by
cases z
simp only [map_pair_eq, mem_iff, exists_eq_or_imp, exists_eq_left]
aesop
@[congr]
theorem map_congr {f g : α → β} {s : Sym2 α} (h : ∀ x ∈ s, f x = g x) : map f s = map g s := by
ext y
simp only [mem_map]
constructor <;>
· rintro ⟨w, hw, rfl⟩
exact ⟨w, hw, by simp [hw, h]⟩
/-- Note: `Sym2.map_id` will not simplify `Sym2.map id z` due to `Sym2.map_congr`. -/
@[simp]
theorem map_id' : (map fun x : α => x) = id :=
map_id
/--
Partial map. If `f : ∀ a, p a → β` is a partial function defined on `a : α` satisfying `p`,
then `pmap f s h` is essentially the same as `map f s` but is defined only when all members of `s`
satisfy `p`, using the proof to apply `f`.
-/
def pmap {P : α → Prop} (f : ∀ a, P a → β) (s : Sym2 α) : (∀ a ∈ s, P a) → Sym2 β :=
let g (p : α × α) (H : ∀ a ∈ Sym2.mk p, P a) : Sym2 β :=
s(f p.1 (H p.1 <| mem_mk_left _ _), f p.2 (H p.2 <| mem_mk_right _ _))
Quot.recOn s g fun p q hpq => funext fun Hq => by
rw [rel_iff'] at hpq
have Hp : ∀ a ∈ Sym2.mk p, P a := fun a hmem =>
Hq a (Sym2.mk_eq_mk_iff.2 hpq ▸ hmem : a ∈ Sym2.mk q)
have h : ∀ {s₂ e H}, Eq.ndrec (motive := fun s => (∀ a ∈ s, P a) → Sym2 β) (g p) (b := s₂) e H =
g p Hp := by
rintro s₂ rfl _
rfl
refine h.trans (Quot.sound ?_)
rw [rel_iff', Prod.mk.injEq, Prod.swap_prod_mk]
apply hpq.imp <;> rintro rfl <;> simp
theorem forall_mem_pair {P : α → Prop} {a b : α} : (∀ x ∈ s(a, b), P x) ↔ P a ∧ P b := by
simp only [mem_iff, forall_eq_or_imp, forall_eq]
lemma pair_eq_pmap {P : α → Prop} (f : ∀ a, P a → β) (a b : α) (h : P a) (h' : P b) :
s(f a h, f b h') = pmap f s(a, b) (forall_mem_pair.mpr ⟨h, h'⟩) := rfl
lemma pmap_pair {P : α → Prop} (f : ∀ a, P a → β) (a b : α) (h : ∀ x ∈ s(a, b), P x) :
pmap f s(a, b) h = s(f a (h a (mem_mk_left a b)), f b (h b (mem_mk_right a b))) := rfl
@[simp]
lemma mem_pmap_iff {P : α → Prop} (f : ∀ a, P a → β) (z : Sym2 α) (h : ∀ a ∈ z, P a) (b : β) :
b ∈ z.pmap f h ↔ ∃ (a : α) (ha : a ∈ z), b = f a (h a ha) := by
obtain ⟨x, y⟩ := z
rw [pmap_pair f x y h]
aesop
lemma pmap_eq_map {P : α → Prop} (f : α → β) (z : Sym2 α) (h : ∀ a ∈ z, P a) :
z.pmap (fun a _ => f a) h = z.map f := by
cases z; rfl
lemma map_pmap {Q : β → Prop} (f : α → β) (g : ∀ b, Q b → γ) (z : Sym2 α) (h : ∀ b ∈ z.map f, Q b):
(z.map f).pmap g h =
z.pmap (fun a ha => g (f a) (h (f a) (mem_map.mpr ⟨a, ha, rfl⟩))) (fun _ ha => ha) := by
cases z; rfl
lemma pmap_map {P : α → Prop} {Q : β → Prop} (f : ∀ a, P a → β) (g : β → γ)
(z : Sym2 α) (h : ∀ a ∈ z, P a) (h' : ∀ b ∈ z.pmap f h, Q b) :
(z.pmap f h).map g = z.pmap (fun a ha => g (f a (h a ha))) (fun _ ha ↦ ha) := by
cases z; rfl
lemma pmap_pmap {P : α → Prop} {Q : β → Prop} (f : ∀ a, P a → β) (g : ∀ b, Q b → γ)
(z : Sym2 α) (h : ∀ a ∈ z, P a) (h' : ∀ b ∈ z.pmap f h, Q b) :
(z.pmap f h).pmap g h' = z.pmap (fun a ha => g (f a (h a ha))
(h' _ ((mem_pmap_iff f z h _).mpr ⟨a, ha, rfl⟩))) (fun _ ha ↦ ha) := by
cases z; rfl
@[simp]
lemma pmap_subtype_map_subtypeVal {P : α → Prop} (s : Sym2 α) (h : ∀ a ∈ s, P a) :
(s.pmap Subtype.mk h).map Subtype.val = s := by
cases s; rfl
/--
"Attach" a proof `P a` that holds for all the elements of `s` to produce a new Sym2 object
with the same elements but in the type `{x // P x}`.
-/
def attachWith {P : α → Prop} (s : Sym2 α) (h : ∀ a ∈ s, P a) : Sym2 {a // P a} :=
pmap Subtype.mk s h
@[simp]
lemma attachWith_map_subtypeVal {s : Sym2 α} {P : α → Prop} (h : ∀ a ∈ s, P a) :
(s.attachWith h).map Subtype.val = s := by
cases s; rfl
/-! ### Diagonal -/
variable {e : Sym2 α} {f : α → β}
/-- A type `α` is naturally included in the diagonal of `α × α`, and this function gives the image
of this diagonal in `Sym2 α`.
-/
def diag (x : α) : Sym2 α := s(x, x)
theorem diag_injective : Function.Injective (Sym2.diag : α → Sym2 α) := fun x y h => by
cases Sym2.exact h <;> rfl
/-- A predicate for testing whether an element of `Sym2 α` is on the diagonal.
-/
def IsDiag : Sym2 α → Prop :=
lift ⟨Eq, fun _ _ => propext eq_comm⟩
theorem mk_isDiag_iff {x y : α} : IsDiag s(x, y) ↔ x = y :=
Iff.rfl
@[simp]
theorem isDiag_iff_proj_eq (z : α × α) : IsDiag (Sym2.mk z) ↔ z.1 = z.2 :=
Prod.recOn z fun _ _ => mk_isDiag_iff
protected lemma IsDiag.map : e.IsDiag → (e.map f).IsDiag := Sym2.ind (fun _ _ ↦ congr_arg f) e
lemma isDiag_map (hf : Injective f) : (e.map f).IsDiag ↔ e.IsDiag :=
Sym2.ind (fun _ _ ↦ hf.eq_iff) e
@[simp]
theorem diag_isDiag (a : α) : IsDiag (diag a) :=
Eq.refl a
theorem IsDiag.mem_range_diag {z : Sym2 α} : IsDiag z → z ∈ Set.range (@diag α) := by
obtain ⟨x, y⟩ := z
rintro (rfl : x = y)
exact ⟨_, rfl⟩
theorem isDiag_iff_mem_range_diag (z : Sym2 α) : IsDiag z ↔ z ∈ Set.range (@diag α) :=
⟨IsDiag.mem_range_diag, fun ⟨i, hi⟩ => hi ▸ diag_isDiag i⟩
instance IsDiag.decidablePred (α : Type u) [DecidableEq α] : DecidablePred (@IsDiag α) :=
fun z => z.recOnSubsingleton fun a => decidable_of_iff' _ (isDiag_iff_proj_eq a)
theorem other_ne {a : α} {z : Sym2 α} (hd : ¬IsDiag z) (h : a ∈ z) : Mem.other h ≠ a := by
contrapose! hd
have h' := Sym2.other_spec h
rw [hd] at h'
rw [← h']
simp
section Relations
/-! ### Declarations about symmetric relations -/
variable {r : α → α → Prop}
|
/-- Symmetric relations define a set on `Sym2 α` by taking all those pairs
of elements that are related.
-/
| Mathlib/Data/Sym/Sym2.lean | 527 | 530 |
/-
Copyright (c) 2021 Yakov Pechersky. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yakov Pechersky
-/
import Mathlib.Data.Fintype.EquivFin
import Mathlib.Data.Fintype.Inv
/-! # Equivalence between fintypes
This file contains some basic results on equivalences where one or both
sides of the equivalence are `Fintype`s.
# Main definitions
- `Function.Embedding.toEquivRange`: computably turn an embedding of a
fintype into an `Equiv` of the domain to its range
- `Equiv.Perm.viaFintypeEmbedding : Perm α → (α ↪ β) → Perm β` extends the domain of
a permutation, fixing everything outside the range of the embedding
# Implementation details
- `Function.Embedding.toEquivRange` uses a computable inverse, but one that has poor
computational performance, since it operates by exhaustive search over the input `Fintype`s.
-/
assert_not_exists Equiv.Perm.sign
section Fintype
variable {α β : Type*} [Fintype α] [DecidableEq β] (e : Equiv.Perm α) (f : α ↪ β)
/-- Computably turn an embedding `f : α ↪ β` into an equiv `α ≃ Set.range f`,
if `α` is a `Fintype`. Has poor computational performance, due to exhaustive searching in
constructed inverse. When a better inverse is known, use `Equiv.ofLeftInverse'` or
`Equiv.ofLeftInverse` instead. This is the computable version of `Equiv.ofInjective`.
-/
def Function.Embedding.toEquivRange : α ≃ Set.range f :=
⟨fun a => ⟨f a, Set.mem_range_self a⟩, f.invOfMemRange, fun _ => by simp, fun _ => by simp⟩
@[simp]
theorem Function.Embedding.toEquivRange_apply (a : α) :
f.toEquivRange a = ⟨f a, Set.mem_range_self a⟩ :=
rfl
@[simp]
theorem Function.Embedding.toEquivRange_symm_apply_self (a : α) :
f.toEquivRange.symm ⟨f a, Set.mem_range_self a⟩ = a := by simp [Equiv.symm_apply_eq]
theorem Function.Embedding.toEquivRange_eq_ofInjective :
f.toEquivRange = Equiv.ofInjective f f.injective := by
ext
simp
/-- Extend the domain of `e : Equiv.Perm α`, mapping it through `f : α ↪ β`.
Everything outside of `Set.range f` is kept fixed. Has poor computational performance,
due to exhaustive searching in constructed inverse due to using `Function.Embedding.toEquivRange`.
When a better `α ≃ Set.range f` is known, use `Equiv.Perm.viaSetRange`.
When `[Fintype α]` is not available, a noncomputable version is available as
`Equiv.Perm.viaEmbedding`.
-/
def Equiv.Perm.viaFintypeEmbedding : Equiv.Perm β :=
e.extendDomain f.toEquivRange
@[simp]
theorem Equiv.Perm.viaFintypeEmbedding_apply_image (a : α) :
e.viaFintypeEmbedding f (f a) = f (e a) := by
rw [Equiv.Perm.viaFintypeEmbedding]
convert Equiv.Perm.extendDomain_apply_image e (Function.Embedding.toEquivRange f) a
theorem Equiv.Perm.viaFintypeEmbedding_apply_mem_range {b : β} (h : b ∈ Set.range f) :
| e.viaFintypeEmbedding f b = f (e (f.invOfMemRange ⟨b, h⟩)) := by
simp only [viaFintypeEmbedding, Function.Embedding.invOfMemRange]
rw [Equiv.Perm.extendDomain_apply_subtype]
congr
| Mathlib/Logic/Equiv/Fintype.lean | 72 | 75 |
/-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne
-/
import Mathlib.Analysis.SpecialFunctions.Exp
import Mathlib.Data.Nat.Factorization.Defs
import Mathlib.Analysis.NormedSpace.Real
import Mathlib.Data.Rat.Cast.CharZero
/-!
# Real logarithm
In this file we define `Real.log` to be the logarithm of a real number. As usual, we extend it from
its domain `(0, +∞)` to a globally defined function. We choose to do it so that `log 0 = 0` and
`log (-x) = log x`.
We prove some basic properties of this function and show that it is continuous.
## Tags
logarithm, continuity
-/
open Set Filter Function
open Topology
noncomputable section
namespace Real
variable {x y : ℝ}
/-- The real logarithm function, equal to the inverse of the exponential for `x > 0`,
to `log |x|` for `x < 0`, and to `0` for `0`. We use this unconventional extension to
`(-∞, 0]` as it gives the formula `log (x * y) = log x + log y` for all nonzero `x` and `y`, and
the derivative of `log` is `1/x` away from `0`. -/
@[pp_nodot]
noncomputable def log (x : ℝ) : ℝ :=
if hx : x = 0 then 0 else expOrderIso.symm ⟨|x|, abs_pos.2 hx⟩
theorem log_of_ne_zero (hx : x ≠ 0) : log x = expOrderIso.symm ⟨|x|, abs_pos.2 hx⟩ :=
dif_neg hx
theorem log_of_pos (hx : 0 < x) : log x = expOrderIso.symm ⟨x, hx⟩ := by
rw [log_of_ne_zero hx.ne']
congr
exact abs_of_pos hx
theorem exp_log_eq_abs (hx : x ≠ 0) : exp (log x) = |x| := by
rw [log_of_ne_zero hx, ← coe_expOrderIso_apply, OrderIso.apply_symm_apply, Subtype.coe_mk]
theorem exp_log (hx : 0 < x) : exp (log x) = x := by
rw [exp_log_eq_abs hx.ne']
exact abs_of_pos hx
theorem exp_log_of_neg (hx : x < 0) : exp (log x) = -x := by
rw [exp_log_eq_abs (ne_of_lt hx)]
exact abs_of_neg hx
theorem le_exp_log (x : ℝ) : x ≤ exp (log x) := by
by_cases h_zero : x = 0
· rw [h_zero, log, dif_pos rfl, exp_zero]
exact zero_le_one
· rw [exp_log_eq_abs h_zero]
exact le_abs_self _
@[simp]
theorem log_exp (x : ℝ) : log (exp x) = x :=
exp_injective <| exp_log (exp_pos x)
theorem exp_one_mul_le_exp {x : ℝ} : exp 1 * x ≤ exp x := by
by_cases hx0 : x ≤ 0
· apply le_trans (mul_nonpos_of_nonneg_of_nonpos (exp_pos 1).le hx0) (exp_nonneg x)
· have h := add_one_le_exp (log x)
rwa [← exp_le_exp, exp_add, exp_log (lt_of_not_le hx0), mul_comm] at h
theorem two_mul_le_exp {x : ℝ} : 2 * x ≤ exp x := by
by_cases hx0 : x < 0
· exact le_trans (mul_nonpos_of_nonneg_of_nonpos (by simp only [Nat.ofNat_nonneg]) hx0.le)
(exp_nonneg x)
· apply le_trans (mul_le_mul_of_nonneg_right _ (le_of_not_lt hx0)) exp_one_mul_le_exp
have := Real.add_one_le_exp 1
rwa [one_add_one_eq_two] at this
theorem surjOn_log : SurjOn log (Ioi 0) univ := fun x _ => ⟨exp x, exp_pos x, log_exp x⟩
theorem log_surjective : Surjective log := fun x => ⟨exp x, log_exp x⟩
@[simp]
theorem range_log : range log = univ :=
log_surjective.range_eq
@[simp]
theorem log_zero : log 0 = 0 :=
dif_pos rfl
@[simp]
theorem log_one : log 1 = 0 :=
exp_injective <| by rw [exp_log zero_lt_one, exp_zero]
/-- This holds true for all `x : ℝ` because of the junk values `0 / 0 = 0` and `log 0 = 0`. -/
@[simp] lemma log_div_self (x : ℝ) : log (x / x) = 0 := by
obtain rfl | hx := eq_or_ne x 0 <;> simp [*]
@[simp]
theorem log_abs (x : ℝ) : log |x| = log x := by
by_cases h : x = 0
· simp [h]
· rw [← exp_eq_exp, exp_log_eq_abs h, exp_log_eq_abs (abs_pos.2 h).ne', abs_abs]
@[simp]
theorem log_neg_eq_log (x : ℝ) : log (-x) = log x := by rw [← log_abs x, ← log_abs (-x), abs_neg]
theorem sinh_log {x : ℝ} (hx : 0 < x) : sinh (log x) = (x - x⁻¹) / 2 := by
rw [sinh_eq, exp_neg, exp_log hx]
theorem cosh_log {x : ℝ} (hx : 0 < x) : cosh (log x) = (x + x⁻¹) / 2 := by
rw [cosh_eq, exp_neg, exp_log hx]
theorem surjOn_log' : SurjOn log (Iio 0) univ := fun x _ =>
⟨-exp x, neg_lt_zero.2 <| exp_pos x, by rw [log_neg_eq_log, log_exp]⟩
theorem log_mul (hx : x ≠ 0) (hy : y ≠ 0) : log (x * y) = log x + log y :=
exp_injective <| by
rw [exp_log_eq_abs (mul_ne_zero hx hy), exp_add, exp_log_eq_abs hx, exp_log_eq_abs hy, abs_mul]
theorem log_div (hx : x ≠ 0) (hy : y ≠ 0) : log (x / y) = log x - log y :=
exp_injective <| by
rw [exp_log_eq_abs (div_ne_zero hx hy), exp_sub, exp_log_eq_abs hx, exp_log_eq_abs hy, abs_div]
@[simp]
theorem log_inv (x : ℝ) : log x⁻¹ = -log x := by
by_cases hx : x = 0; · simp [hx]
rw [← exp_eq_exp, exp_log_eq_abs (inv_ne_zero hx), exp_neg, exp_log_eq_abs hx, abs_inv]
theorem log_le_log_iff (h : 0 < x) (h₁ : 0 < y) : log x ≤ log y ↔ x ≤ y := by
rw [← exp_le_exp, exp_log h, exp_log h₁]
@[gcongr, bound]
lemma log_le_log (hx : 0 < x) (hxy : x ≤ y) : log x ≤ log y :=
(log_le_log_iff hx (hx.trans_le hxy)).2 hxy
@[gcongr, bound]
theorem log_lt_log (hx : 0 < x) (h : x < y) : log x < log y := by
rwa [← exp_lt_exp, exp_log hx, exp_log (lt_trans hx h)]
theorem log_lt_log_iff (hx : 0 < x) (hy : 0 < y) : log x < log y ↔ x < y := by
rw [← exp_lt_exp, exp_log hx, exp_log hy]
theorem log_le_iff_le_exp (hx : 0 < x) : log x ≤ y ↔ x ≤ exp y := by rw [← exp_le_exp, exp_log hx]
theorem log_lt_iff_lt_exp (hx : 0 < x) : log x < y ↔ x < exp y := by rw [← exp_lt_exp, exp_log hx]
theorem le_log_iff_exp_le (hy : 0 < y) : x ≤ log y ↔ exp x ≤ y := by rw [← exp_le_exp, exp_log hy]
theorem lt_log_iff_exp_lt (hy : 0 < y) : x < log y ↔ exp x < y := by rw [← exp_lt_exp, exp_log hy]
theorem log_pos_iff (hx : 0 ≤ x) : 0 < log x ↔ 1 < x := by
rcases hx.eq_or_lt with (rfl | hx)
· simp [le_refl, zero_le_one]
rw [← log_one]
exact log_lt_log_iff zero_lt_one hx
@[bound]
theorem log_pos (hx : 1 < x) : 0 < log x :=
(log_pos_iff (lt_trans zero_lt_one hx).le).2 hx
theorem log_pos_of_lt_neg_one (hx : x < -1) : 0 < log x := by
rw [← neg_neg x, log_neg_eq_log]
have : 1 < -x := by linarith
exact log_pos this
theorem log_neg_iff (h : 0 < x) : log x < 0 ↔ x < 1 := by
rw [← log_one]
exact log_lt_log_iff h zero_lt_one
@[bound]
theorem log_neg (h0 : 0 < x) (h1 : x < 1) : log x < 0 :=
(log_neg_iff h0).2 h1
theorem log_neg_of_lt_zero (h0 : x < 0) (h1 : -1 < x) : log x < 0 := by
rw [← neg_neg x, log_neg_eq_log]
have h0' : 0 < -x := by linarith
have h1' : -x < 1 := by linarith
exact log_neg h0' h1'
theorem log_nonneg_iff (hx : 0 < x) : 0 ≤ log x ↔ 1 ≤ x := by rw [← not_lt, log_neg_iff hx, not_lt]
@[bound]
theorem log_nonneg (hx : 1 ≤ x) : 0 ≤ log x :=
(log_nonneg_iff (zero_lt_one.trans_le hx)).2 hx
theorem log_nonpos_iff (hx : 0 ≤ x) : log x ≤ 0 ↔ x ≤ 1 := by
rcases hx.eq_or_lt with (rfl | hx)
· simp [le_refl, zero_le_one]
rw [← not_lt, log_pos_iff hx.le, not_lt]
@[deprecated (since := "2025-01-16")]
alias log_nonpos_iff' := log_nonpos_iff
@[bound]
theorem log_nonpos (hx : 0 ≤ x) (h'x : x ≤ 1) : log x ≤ 0 :=
(log_nonpos_iff hx).2 h'x
theorem log_natCast_nonneg (n : ℕ) : 0 ≤ log n := by
if hn : n = 0 then
simp [hn]
else
have : (1 : ℝ) ≤ n := mod_cast Nat.one_le_of_lt <| Nat.pos_of_ne_zero hn
exact log_nonneg this
theorem log_neg_natCast_nonneg (n : ℕ) : 0 ≤ log (-n) := by
rw [← log_neg_eq_log, neg_neg]
exact log_natCast_nonneg _
theorem log_intCast_nonneg (n : ℤ) : 0 ≤ log n := by
cases lt_trichotomy 0 n with
| inl hn =>
have : (1 : ℝ) ≤ n := mod_cast hn
exact log_nonneg this
| inr hn =>
cases hn with
| inl hn => simp [hn.symm]
| inr hn =>
have : (1 : ℝ) ≤ -n := by rw [← neg_zero, ← lt_neg] at hn; exact mod_cast hn
rw [← log_neg_eq_log]
exact log_nonneg this
theorem strictMonoOn_log : StrictMonoOn log (Set.Ioi 0) := fun _ hx _ _ hxy => log_lt_log hx hxy
theorem strictAntiOn_log : StrictAntiOn log (Set.Iio 0) := by
rintro x (hx : x < 0) y (hy : y < 0) hxy
rw [← log_abs y, ← log_abs x]
refine log_lt_log (abs_pos.2 hy.ne) ?_
rwa [abs_of_neg hy, abs_of_neg hx, neg_lt_neg_iff]
theorem log_injOn_pos : Set.InjOn log (Set.Ioi 0) :=
strictMonoOn_log.injOn
theorem log_lt_sub_one_of_pos (hx1 : 0 < x) (hx2 : x ≠ 1) : log x < x - 1 := by
have h : log x ≠ 0 := by
rwa [← log_one, log_injOn_pos.ne_iff hx1]
exact mem_Ioi.mpr zero_lt_one
linarith [add_one_lt_exp h, exp_log hx1]
theorem eq_one_of_pos_of_log_eq_zero {x : ℝ} (h₁ : 0 < x) (h₂ : log x = 0) : x = 1 :=
log_injOn_pos (Set.mem_Ioi.2 h₁) (Set.mem_Ioi.2 zero_lt_one) (h₂.trans Real.log_one.symm)
theorem log_ne_zero_of_pos_of_ne_one {x : ℝ} (hx_pos : 0 < x) (hx : x ≠ 1) : log x ≠ 0 :=
mt (eq_one_of_pos_of_log_eq_zero hx_pos) hx
@[simp]
theorem log_eq_zero {x : ℝ} : log x = 0 ↔ x = 0 ∨ x = 1 ∨ x = -1 := by
constructor
· intro h
rcases lt_trichotomy x 0 with (x_lt_zero | rfl | x_gt_zero)
· refine Or.inr (Or.inr (neg_eq_iff_eq_neg.mp ?_))
rw [← log_neg_eq_log x] at h
exact eq_one_of_pos_of_log_eq_zero (neg_pos.mpr x_lt_zero) h
· exact Or.inl rfl
· exact Or.inr (Or.inl (eq_one_of_pos_of_log_eq_zero x_gt_zero h))
· rintro (rfl | rfl | rfl) <;> simp only [log_one, log_zero, log_neg_eq_log]
theorem log_ne_zero {x : ℝ} : log x ≠ 0 ↔ x ≠ 0 ∧ x ≠ 1 ∧ x ≠ -1 := by
simpa only [not_or] using log_eq_zero.not
@[simp]
theorem log_pow (x : ℝ) (n : ℕ) : log (x ^ n) = n * log x := by
induction n with
| zero => simp
| succ n ih =>
rcases eq_or_ne x 0 with (rfl | hx)
· simp
· rw [pow_succ, log_mul (pow_ne_zero _ hx) hx, ih, Nat.cast_succ, add_mul, one_mul]
@[simp]
theorem log_zpow (x : ℝ) (n : ℤ) : log (x ^ n) = n * log x := by
cases n
· rw [Int.ofNat_eq_coe, zpow_natCast, log_pow, Int.cast_natCast]
· rw [zpow_negSucc, log_inv, log_pow, Int.cast_negSucc, Nat.cast_add_one, neg_mul_eq_neg_mul]
theorem log_sqrt {x : ℝ} (hx : 0 ≤ x) : log (√x) = log x / 2 := by
rw [eq_div_iff, mul_comm, ← Nat.cast_two, ← log_pow, sq_sqrt hx]
exact two_ne_zero
theorem log_le_sub_one_of_pos {x : ℝ} (hx : 0 < x) : log x ≤ x - 1 := by
rw [le_sub_iff_add_le]
convert add_one_le_exp (log x)
rw [exp_log hx]
lemma one_sub_inv_le_log_of_pos (hx : 0 < x) : 1 - x⁻¹ ≤ log x := by
simpa [add_comm] using log_le_sub_one_of_pos (inv_pos.2 hx)
/-- See `Real.log_le_sub_one_of_pos` for the stronger version when `x ≠ 0`. -/
lemma log_le_self (hx : 0 ≤ x) : log x ≤ x := by
obtain rfl | hx := hx.eq_or_lt
· simp
· exact (log_le_sub_one_of_pos hx).trans (by linarith)
/-- See `Real.one_sub_inv_le_log_of_pos` for the stronger version when `x ≠ 0`. -/
lemma neg_inv_le_log (hx : 0 ≤ x) : -x⁻¹ ≤ log x := by
rw [neg_le, ← log_inv]; exact log_le_self <| inv_nonneg.2 hx
/-- Bound for `|log x * x|` in the interval `(0, 1]`. -/
theorem abs_log_mul_self_lt (x : ℝ) (h1 : 0 < x) (h2 : x ≤ 1) : |log x * x| < 1 := by
have : 0 < 1 / x := by simpa only [one_div, inv_pos] using h1
replace := log_le_sub_one_of_pos this
replace : log (1 / x) < 1 / x := by linarith
rw [log_div one_ne_zero h1.ne', log_one, zero_sub, lt_div_iff₀ h1] at this
have aux : 0 ≤ -log x * x := by
refine mul_nonneg ?_ h1.le
rw [← log_inv]
apply log_nonneg
rw [← le_inv_comm₀ h1 zero_lt_one, inv_one]
exact h2
rw [← abs_of_nonneg aux, neg_mul, abs_neg] at this
exact this
/-- The real logarithm function tends to `+∞` at `+∞`. -/
theorem tendsto_log_atTop : Tendsto log atTop atTop :=
tendsto_comp_exp_atTop.1 <| by simpa only [log_exp] using tendsto_id
lemma tendsto_log_nhdsGT_zero : Tendsto log (𝓝[>] 0) atBot := by
simpa [← tendsto_comp_exp_atBot] using tendsto_id
@[deprecated (since := "2025-03-18")]
alias tendsto_log_nhdsWithin_zero_right := tendsto_log_nhdsGT_zero
theorem tendsto_log_nhdsNE_zero : Tendsto log (𝓝[≠] 0) atBot := by
simpa [comp_def] using tendsto_log_nhdsGT_zero.comp tendsto_abs_nhdsNE_zero
@[deprecated (since := "2025-03-18")]
alias tendsto_log_nhdsWithin_zero := tendsto_log_nhdsNE_zero
lemma tendsto_log_nhdsLT_zero : Tendsto log (𝓝[<] 0) atBot :=
tendsto_log_nhdsNE_zero.mono_left <| nhdsWithin_mono _ fun _ h ↦ ne_of_lt h
@[deprecated (since := "2025-03-18")]
alias tendsto_log_nhdsWithin_zero_left := tendsto_log_nhdsLT_zero
theorem continuousOn_log : ContinuousOn log {0}ᶜ := by
simp +unfoldPartialApp only [continuousOn_iff_continuous_restrict,
restrict]
conv in log _ => rw [log_of_ne_zero (show (x : ℝ) ≠ 0 from x.2)]
exact expOrderIso.symm.continuous.comp (continuous_subtype_val.norm.subtype_mk _)
/-- The real logarithm is continuous as a function from nonzero reals. -/
@[fun_prop]
theorem continuous_log : Continuous fun x : { x : ℝ // x ≠ 0 } => log x :=
continuousOn_iff_continuous_restrict.1 <| continuousOn_log.mono fun _ => id
/-- The real logarithm is continuous as a function from positive reals. -/
@[fun_prop]
theorem continuous_log' : Continuous fun x : { x : ℝ // 0 < x } => log x :=
continuousOn_iff_continuous_restrict.1 <| continuousOn_log.mono fun _ hx => ne_of_gt hx
theorem continuousAt_log (hx : x ≠ 0) : ContinuousAt log x :=
(continuousOn_log x hx).continuousAt <| isOpen_compl_singleton.mem_nhds hx
@[simp]
theorem continuousAt_log_iff : ContinuousAt log x ↔ x ≠ 0 := by
refine ⟨?_, continuousAt_log⟩
rintro h rfl
exact not_tendsto_nhds_of_tendsto_atBot tendsto_log_nhdsNE_zero _ <|
h.tendsto.mono_left nhdsWithin_le_nhds
theorem log_prod {α : Type*} (s : Finset α) (f : α → ℝ) (hf : ∀ x ∈ s, f x ≠ 0) :
log (∏ i ∈ s, f i) = ∑ i ∈ s, log (f i) := by
induction' s using Finset.cons_induction_on with a s ha ih
· simp
· rw [Finset.forall_mem_cons] at hf
simp [ih hf.2, log_mul hf.1 (Finset.prod_ne_zero_iff.2 hf.2)]
protected theorem _root_.Finsupp.log_prod {α β : Type*} [Zero β] (f : α →₀ β) (g : α → β → ℝ)
(hg : ∀ a, g a (f a) = 0 → f a = 0) : log (f.prod g) = f.sum fun a b ↦ log (g a b) :=
log_prod _ _ fun _x hx h₀ ↦ Finsupp.mem_support_iff.1 hx <| hg _ h₀
theorem log_nat_eq_sum_factorization (n : ℕ) :
log n = n.factorization.sum fun p t => t * log p := by
rcases eq_or_ne n 0 with (rfl | hn)
· simp -- relies on junk values of `log` and `Nat.factorization`
· simp only [← log_pow, ← Nat.cast_pow]
rw [← Finsupp.log_prod, ← Nat.cast_finsuppProd, Nat.factorization_prod_pow_eq_self hn]
intro p hp
rw [pow_eq_zero (Nat.cast_eq_zero.1 hp), Nat.factorization_zero_right]
theorem tendsto_pow_log_div_mul_add_atTop (a b : ℝ) (n : ℕ) (ha : a ≠ 0) :
Tendsto (fun x => log x ^ n / (a * x + b)) atTop (𝓝 0) :=
((tendsto_div_pow_mul_exp_add_atTop a b n ha.symm).comp tendsto_log_atTop).congr' <| by
filter_upwards [eventually_gt_atTop (0 : ℝ)] with x hx using by simp [exp_log hx]
theorem isLittleO_pow_log_id_atTop {n : ℕ} : (fun x => log x ^ n) =o[atTop] id := by
rw [Asymptotics.isLittleO_iff_tendsto']
· simpa using tendsto_pow_log_div_mul_add_atTop 1 0 n one_ne_zero
filter_upwards [eventually_ne_atTop (0 : ℝ)] with x h₁ h₂ using (h₁ h₂).elim
theorem isLittleO_log_id_atTop : log =o[atTop] id :=
isLittleO_pow_log_id_atTop.congr_left fun _ => pow_one _
theorem isLittleO_const_log_atTop {c : ℝ} : (fun _ => c) =o[atTop] log := by
refine Asymptotics.isLittleO_of_tendsto' ?_
<| Tendsto.div_atTop (a := c) (by simp) tendsto_log_atTop
filter_upwards [eventually_gt_atTop 1] with x hx
aesop (add safe forward log_pos)
/-- `Real.exp` as a `PartialHomeomorph` with `source = univ` and `target = {z | 0 < z}`. -/
@[simps] noncomputable def expPartialHomeomorph : PartialHomeomorph ℝ ℝ where
toFun := Real.exp
invFun := Real.log
source := univ
target := Ioi (0 : ℝ)
map_source' x _ := exp_pos x
map_target' _ _ := mem_univ _
left_inv' _ _ := by simp
right_inv' _ hx := exp_log hx
open_source := isOpen_univ
open_target := isOpen_Ioi
continuousOn_toFun := continuousOn_exp
continuousOn_invFun x hx := (continuousAt_log (ne_of_gt hx)).continuousWithinAt
end Real
section Continuity
open Real
variable {α : Type*}
theorem Filter.Tendsto.log {f : α → ℝ} {l : Filter α} {x : ℝ} (h : Tendsto f l (𝓝 x)) (hx : x ≠ 0) :
Tendsto (fun x => log (f x)) l (𝓝 (log x)) :=
(continuousAt_log hx).tendsto.comp h
variable [TopologicalSpace α] {f : α → ℝ} {s : Set α} {a : α}
@[fun_prop]
theorem Continuous.log (hf : Continuous f) (h₀ : ∀ x, f x ≠ 0) : Continuous fun x => log (f x) :=
continuousOn_log.comp_continuous hf h₀
@[fun_prop]
nonrec theorem ContinuousAt.log (hf : ContinuousAt f a) (h₀ : f a ≠ 0) :
ContinuousAt (fun x => log (f x)) a :=
hf.log h₀
nonrec theorem ContinuousWithinAt.log (hf : ContinuousWithinAt f s a) (h₀ : f a ≠ 0) :
ContinuousWithinAt (fun x => log (f x)) s a :=
hf.log h₀
@[fun_prop]
theorem ContinuousOn.log (hf : ContinuousOn f s) (h₀ : ∀ x ∈ s, f x ≠ 0) :
ContinuousOn (fun x => log (f x)) s := fun x hx => (hf x hx).log (h₀ x hx)
end Continuity
section TendstoCompAddSub
open Filter
namespace Real
theorem tendsto_log_comp_add_sub_log (y : ℝ) :
Tendsto (fun x : ℝ => log (x + y) - log x) atTop (𝓝 0) := by
have : Tendsto (fun x ↦ 1 + y / x) atTop (𝓝 (1 + 0)) :=
tendsto_const_nhds.add (tendsto_const_nhds.div_atTop tendsto_id)
rw [← comap_exp_nhds_exp, exp_zero, tendsto_comap_iff, ← add_zero (1 : ℝ)]
refine this.congr' ?_
filter_upwards [eventually_gt_atTop (0 : ℝ), eventually_gt_atTop (-y)] with x hx₀ hxy
rw [comp_apply, exp_sub, exp_log, exp_log, one_add_div] <;> linarith
theorem tendsto_log_nat_add_one_sub_log : Tendsto (fun k : ℕ => log (k + 1) - log k) atTop (𝓝 0) :=
(tendsto_log_comp_add_sub_log 1).comp tendsto_natCast_atTop_atTop
end Real
end TendstoCompAddSub
namespace Mathlib.Meta.Positivity
open Lean.Meta Qq
variable {e : ℝ} {d : ℕ}
lemma log_nonneg_of_isNat {n : ℕ} (h : NormNum.IsNat e n) : 0 ≤ Real.log (e : ℝ) := by
rw [NormNum.IsNat.to_eq h rfl]
exact Real.log_natCast_nonneg _
lemma log_pos_of_isNat {n : ℕ} (h : NormNum.IsNat e n) (w : Nat.blt 1 n = true) :
0 < Real.log (e : ℝ) := by
rw [NormNum.IsNat.to_eq h rfl]
apply Real.log_pos
simpa using w
lemma log_nonneg_of_isNegNat {n : ℕ} (h : NormNum.IsInt e (.negOfNat n)) :
0 ≤ Real.log (e : ℝ) := by
rw [NormNum.IsInt.neg_to_eq h rfl]
exact Real.log_neg_natCast_nonneg _
lemma log_pos_of_isNegNat {n : ℕ} (h : NormNum.IsInt e (.negOfNat n)) (w : Nat.blt 1 n = true) :
0 < Real.log (e : ℝ) := by
rw [NormNum.IsInt.neg_to_eq h rfl]
rw [Real.log_neg_eq_log]
apply Real.log_pos
simpa using w
lemma log_pos_of_isRat {n : ℤ} :
| (NormNum.IsRat e n d) → (decide ((1 : ℚ) < n / d)) → (0 < Real.log (e : ℝ))
| ⟨inv, eq⟩, h => by
rw [eq, invOf_eq_inv, ← div_eq_mul_inv]
have : 1 < (n : ℝ) / d := by exact_mod_cast of_decide_eq_true h
| Mathlib/Analysis/SpecialFunctions/Log/Basic.lean | 506 | 509 |
/-
Copyright (c) 2020 Kim Morrison. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kim Morrison
-/
import Mathlib.CategoryTheory.Monoidal.Discrete
import Mathlib.CategoryTheory.Monoidal.NaturalTransformation
import Mathlib.CategoryTheory.Monoidal.Opposite
import Mathlib.Tactic.CategoryTheory.Monoidal.Basic
import Mathlib.CategoryTheory.CommSq
/-!
# Braided and symmetric monoidal categories
The basic definitions of braided monoidal categories, and symmetric monoidal categories,
as well as braided functors.
## Implementation note
We make `BraidedCategory` another typeclass, but then have `SymmetricCategory` extend this.
The rationale is that we are not carrying any additional data, just requiring a property.
## Future work
* Construct the Drinfeld center of a monoidal category as a braided monoidal category.
* Say something about pseudo-natural transformations.
## References
* [Pavel Etingof, Shlomo Gelaki, Dmitri Nikshych, Victor Ostrik, *Tensor categories*][egno15]
-/
universe v v₁ v₂ v₃ u u₁ u₂ u₃
namespace CategoryTheory
open Category MonoidalCategory Functor.LaxMonoidal Functor.OplaxMonoidal Functor.Monoidal
/-- A braided monoidal category is a monoidal category equipped with a braiding isomorphism
`β_ X Y : X ⊗ Y ≅ Y ⊗ X`
which is natural in both arguments,
and also satisfies the two hexagon identities.
-/
class BraidedCategory (C : Type u) [Category.{v} C] [MonoidalCategory.{v} C] where
/-- The braiding natural isomorphism. -/
braiding : ∀ X Y : C, X ⊗ Y ≅ Y ⊗ X
braiding_naturality_right :
∀ (X : C) {Y Z : C} (f : Y ⟶ Z),
X ◁ f ≫ (braiding X Z).hom = (braiding X Y).hom ≫ f ▷ X := by
aesop_cat
braiding_naturality_left :
∀ {X Y : C} (f : X ⟶ Y) (Z : C),
f ▷ Z ≫ (braiding Y Z).hom = (braiding X Z).hom ≫ Z ◁ f := by
aesop_cat
/-- The first hexagon identity. -/
hexagon_forward :
∀ X Y Z : C,
(α_ X Y Z).hom ≫ (braiding X (Y ⊗ Z)).hom ≫ (α_ Y Z X).hom =
((braiding X Y).hom ▷ Z) ≫ (α_ Y X Z).hom ≫ (Y ◁ (braiding X Z).hom) := by
aesop_cat
/-- The second hexagon identity. -/
hexagon_reverse :
∀ X Y Z : C,
(α_ X Y Z).inv ≫ (braiding (X ⊗ Y) Z).hom ≫ (α_ Z X Y).inv =
(X ◁ (braiding Y Z).hom) ≫ (α_ X Z Y).inv ≫ ((braiding X Z).hom ▷ Y) := by
aesop_cat
attribute [reassoc (attr := simp)]
BraidedCategory.braiding_naturality_left
BraidedCategory.braiding_naturality_right
attribute [reassoc] BraidedCategory.hexagon_forward BraidedCategory.hexagon_reverse
open BraidedCategory
@[inherit_doc]
notation "β_" => BraidedCategory.braiding
namespace BraidedCategory
variable {C : Type u} [Category.{v} C] [MonoidalCategory.{v} C] [BraidedCategory.{v} C]
@[simp, reassoc]
theorem braiding_tensor_left (X Y Z : C) :
(β_ (X ⊗ Y) Z).hom =
(α_ X Y Z).hom ≫ X ◁ (β_ Y Z).hom ≫ (α_ X Z Y).inv ≫
(β_ X Z).hom ▷ Y ≫ (α_ Z X Y).hom := by
apply (cancel_epi (α_ X Y Z).inv).1
apply (cancel_mono (α_ Z X Y).inv).1
simp [hexagon_reverse]
@[simp, reassoc]
theorem braiding_tensor_right (X Y Z : C) :
(β_ X (Y ⊗ Z)).hom =
(α_ X Y Z).inv ≫ (β_ X Y).hom ▷ Z ≫ (α_ Y X Z).hom ≫
Y ◁ (β_ X Z).hom ≫ (α_ Y Z X).inv := by
apply (cancel_epi (α_ X Y Z).hom).1
apply (cancel_mono (α_ Y Z X).hom).1
simp [hexagon_forward]
@[simp, reassoc]
theorem braiding_inv_tensor_left (X Y Z : C) :
(β_ (X ⊗ Y) Z).inv =
(α_ Z X Y).inv ≫ (β_ X Z).inv ▷ Y ≫ (α_ X Z Y).hom ≫
X ◁ (β_ Y Z).inv ≫ (α_ X Y Z).inv :=
eq_of_inv_eq_inv (by simp)
@[simp, reassoc]
theorem braiding_inv_tensor_right (X Y Z : C) :
(β_ X (Y ⊗ Z)).inv =
(α_ Y Z X).hom ≫ Y ◁ (β_ X Z).inv ≫ (α_ Y X Z).inv ≫
(β_ X Y).inv ▷ Z ≫ (α_ X Y Z).hom :=
eq_of_inv_eq_inv (by simp)
@[reassoc (attr := simp)]
theorem braiding_naturality {X X' Y Y' : C} (f : X ⟶ Y) (g : X' ⟶ Y') :
(f ⊗ g) ≫ (braiding Y Y').hom = (braiding X X').hom ≫ (g ⊗ f) := by
rw [tensorHom_def' f g, tensorHom_def g f]
simp_rw [Category.assoc, braiding_naturality_left, braiding_naturality_right_assoc]
@[reassoc (attr := simp)]
theorem braiding_inv_naturality_right (X : C) {Y Z : C} (f : Y ⟶ Z) :
X ◁ f ≫ (β_ Z X).inv = (β_ Y X).inv ≫ f ▷ X :=
CommSq.w <| .vert_inv <| .mk <| braiding_naturality_left f X
@[reassoc (attr := simp)]
theorem braiding_inv_naturality_left {X Y : C} (f : X ⟶ Y) (Z : C) :
f ▷ Z ≫ (β_ Z Y).inv = (β_ Z X).inv ≫ Z ◁ f :=
CommSq.w <| .vert_inv <| .mk <| braiding_naturality_right Z f
@[reassoc (attr := simp)]
theorem braiding_inv_naturality {X X' Y Y' : C} (f : X ⟶ Y) (g : X' ⟶ Y') :
(f ⊗ g) ≫ (β_ Y' Y).inv = (β_ X' X).inv ≫ (g ⊗ f) :=
CommSq.w <| .vert_inv <| .mk <| braiding_naturality g f
/-- In a braided monoidal category, the functors `tensorLeft X` and
`tensorRight X` are isomorphic. -/
@[simps]
def tensorLeftIsoTensorRight (X : C) :
tensorLeft X ≅ tensorRight X where
hom := { app Y := (β_ X Y).hom }
inv := { app Y := (β_ X Y).inv }
@[reassoc]
theorem yang_baxter (X Y Z : C) :
(α_ X Y Z).inv ≫ (β_ X Y).hom ▷ Z ≫ (α_ Y X Z).hom ≫
Y ◁ (β_ X Z).hom ≫ (α_ Y Z X).inv ≫ (β_ Y Z).hom ▷ X ≫ (α_ Z Y X).hom =
X ◁ (β_ Y Z).hom ≫ (α_ X Z Y).inv ≫ (β_ X Z).hom ▷ Y ≫
(α_ Z X Y).hom ≫ Z ◁ (β_ X Y).hom := by
rw [← braiding_tensor_right_assoc X Y Z, ← cancel_mono (α_ Z Y X).inv]
repeat rw [assoc]
rw [Iso.hom_inv_id, comp_id, ← braiding_naturality_right, braiding_tensor_right]
theorem yang_baxter' (X Y Z : C) :
(β_ X Y).hom ▷ Z ⊗≫ Y ◁ (β_ X Z).hom ⊗≫ (β_ Y Z).hom ▷ X =
𝟙 _ ⊗≫ (X ◁ (β_ Y Z).hom ⊗≫ (β_ X Z).hom ▷ Y ⊗≫ Z ◁ (β_ X Y).hom) ⊗≫ 𝟙 _ := by
rw [← cancel_epi (α_ X Y Z).inv, ← cancel_mono (α_ Z Y X).hom]
convert yang_baxter X Y Z using 1
all_goals monoidal
theorem yang_baxter_iso (X Y Z : C) :
(α_ X Y Z).symm ≪≫ whiskerRightIso (β_ X Y) Z ≪≫ α_ Y X Z ≪≫
whiskerLeftIso Y (β_ X Z) ≪≫ (α_ Y Z X).symm ≪≫
whiskerRightIso (β_ Y Z) X ≪≫ (α_ Z Y X) =
whiskerLeftIso X (β_ Y Z) ≪≫ (α_ X Z Y).symm ≪≫
whiskerRightIso (β_ X Z) Y ≪≫ α_ Z X Y ≪≫
whiskerLeftIso Z (β_ X Y) := Iso.ext (yang_baxter X Y Z)
theorem hexagon_forward_iso (X Y Z : C) :
α_ X Y Z ≪≫ β_ X (Y ⊗ Z) ≪≫ α_ Y Z X =
whiskerRightIso (β_ X Y) Z ≪≫ α_ Y X Z ≪≫ whiskerLeftIso Y (β_ X Z) :=
Iso.ext (hexagon_forward X Y Z)
theorem hexagon_reverse_iso (X Y Z : C) :
(α_ X Y Z).symm ≪≫ β_ (X ⊗ Y) Z ≪≫ (α_ Z X Y).symm =
whiskerLeftIso X (β_ Y Z) ≪≫ (α_ X Z Y).symm ≪≫ whiskerRightIso (β_ X Z) Y :=
Iso.ext (hexagon_reverse X Y Z)
@[reassoc]
theorem hexagon_forward_inv (X Y Z : C) :
(α_ Y Z X).inv ≫ (β_ X (Y ⊗ Z)).inv ≫ (α_ X Y Z).inv =
Y ◁ (β_ X Z).inv ≫ (α_ Y X Z).inv ≫ (β_ X Y).inv ▷ Z := by
simp
@[reassoc]
theorem hexagon_reverse_inv (X Y Z : C) :
(α_ Z X Y).hom ≫ (β_ (X ⊗ Y) Z).inv ≫ (α_ X Y Z).hom =
(β_ X Z).inv ▷ Y ≫ (α_ X Z Y).hom ≫ X ◁ (β_ Y Z).inv := by
simp
end BraidedCategory
/--
Verifying the axioms for a braiding by checking that the candidate braiding is sent to a braiding
by a faithful monoidal functor.
-/
def braidedCategoryOfFaithful {C D : Type*} [Category C] [Category D] [MonoidalCategory C]
[MonoidalCategory D] (F : C ⥤ D) [F.Monoidal] [F.Faithful] [BraidedCategory D]
(β : ∀ X Y : C, X ⊗ Y ≅ Y ⊗ X)
(w : ∀ X Y, μ F _ _ ≫ F.map (β X Y).hom = (β_ _ _).hom ≫ μ F _ _) : BraidedCategory C where
braiding := β
braiding_naturality_left := by
intros
apply F.map_injective
refine (cancel_epi (μ F ?_ ?_)).1 ?_
rw [Functor.map_comp, ← μ_natural_left_assoc, w, Functor.map_comp,
reassoc_of% w, braiding_naturality_left_assoc, μ_natural_right]
braiding_naturality_right := by
intros
apply F.map_injective
refine (cancel_epi (μ F ?_ ?_)).1 ?_
rw [Functor.map_comp, ← μ_natural_right_assoc, w, Functor.map_comp,
reassoc_of% w, braiding_naturality_right_assoc, μ_natural_left]
hexagon_forward := by
intros
apply F.map_injective
refine (cancel_epi (μ F _ _)).1 ?_
refine (cancel_epi (μ F _ _ ▷ _)).1 ?_
rw [Functor.map_comp, Functor.map_comp, Functor.map_comp, Functor.map_comp, ←
μ_natural_left_assoc, ← comp_whiskerRight_assoc, w,
comp_whiskerRight_assoc, Functor.LaxMonoidal.associativity_assoc,
Functor.LaxMonoidal.associativity_assoc, ← μ_natural_right, ←
MonoidalCategory.whiskerLeft_comp_assoc, w, MonoidalCategory.whiskerLeft_comp_assoc,
reassoc_of% w, braiding_naturality_right_assoc,
Functor.LaxMonoidal.associativity, hexagon_forward_assoc]
hexagon_reverse := by
intros
apply F.map_injective
refine (cancel_epi (μ F _ _)).1 ?_
refine (cancel_epi (_ ◁ μ F _ _)).1 ?_
rw [Functor.map_comp, Functor.map_comp, Functor.map_comp, Functor.map_comp, ←
μ_natural_right_assoc, ← MonoidalCategory.whiskerLeft_comp_assoc, w,
MonoidalCategory.whiskerLeft_comp_assoc, Functor.LaxMonoidal.associativity_inv_assoc,
Functor.LaxMonoidal.associativity_inv_assoc, ← μ_natural_left,
← comp_whiskerRight_assoc, w, comp_whiskerRight_assoc, reassoc_of% w,
braiding_naturality_left_assoc, Functor.LaxMonoidal.associativity_inv, hexagon_reverse_assoc]
/-- Pull back a braiding along a fully faithful monoidal functor. -/
noncomputable def braidedCategoryOfFullyFaithful {C D : Type*} [Category C] [Category D]
[MonoidalCategory C] [MonoidalCategory D] (F : C ⥤ D) [F.Monoidal] [F.Full]
[F.Faithful] [BraidedCategory D] : BraidedCategory C :=
braidedCategoryOfFaithful F
(fun X Y => F.preimageIso
((μIso F _ _).symm ≪≫ β_ (F.obj X) (F.obj Y) ≪≫ (μIso F _ _)))
(by simp)
section
/-!
We now establish how the braiding interacts with the unitors.
I couldn't find a detailed proof in print, but this is discussed in:
* Proposition 1 of André Joyal and Ross Street,
"Braided monoidal categories", Macquarie Math Reports 860081 (1986).
* Proposition 2.1 of André Joyal and Ross Street,
"Braided tensor categories" , Adv. Math. 102 (1993), 20–78.
* Exercise 8.1.6 of Etingof, Gelaki, Nikshych, Ostrik,
"Tensor categories", vol 25, Mathematical Surveys and Monographs (2015), AMS.
-/
variable {C : Type u₁} [Category.{v₁} C] [MonoidalCategory C] [BraidedCategory C]
theorem braiding_leftUnitor_aux₁ (X : C) :
| (α_ (𝟙_ C) (𝟙_ C) X).hom ≫
(𝟙_ C ◁ (β_ X (𝟙_ C)).inv) ≫ (α_ _ X _).inv ≫ ((λ_ X).hom ▷ _) =
((λ_ _).hom ▷ X) ≫ (β_ X (𝟙_ C)).inv := by
monoidal
| Mathlib/CategoryTheory/Monoidal/Braided/Basic.lean | 267 | 271 |
/-
Copyright (c) 2015, 2017 Jeremy Avigad. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Jeremy Avigad, Robert Y. Lewis, Johannes Hölzl, Mario Carneiro, Sébastien Gouëzel
-/
import Mathlib.Data.ENNReal.Real
import Mathlib.Tactic.Bound.Attribute
import Mathlib.Topology.Bornology.Basic
import Mathlib.Topology.EMetricSpace.Defs
import Mathlib.Topology.UniformSpace.Basic
/-!
## Pseudo-metric spaces
This file defines pseudo-metric spaces: these differ from metric spaces by not imposing the
condition `dist x y = 0 → x = y`.
Many definitions and theorems expected on (pseudo-)metric spaces are already introduced on uniform
spaces and topological spaces. For example: open and closed sets, compactness, completeness,
continuity and uniform continuity.
## Main definitions
* `Dist α`: Endows a space `α` with a function `dist a b`.
* `PseudoMetricSpace α`: A space endowed with a distance function, which can
be zero even if the two elements are non-equal.
* `Metric.ball x ε`: The set of all points `y` with `dist y x < ε`.
* `Metric.Bounded s`: Whether a subset of a `PseudoMetricSpace` is bounded.
* `MetricSpace α`: A `PseudoMetricSpace` with the guarantee `dist x y = 0 → x = y`.
Additional useful definitions:
* `nndist a b`: `dist` as a function to the non-negative reals.
* `Metric.closedBall x ε`: The set of all points `y` with `dist y x ≤ ε`.
* `Metric.sphere x ε`: The set of all points `y` with `dist y x = ε`.
TODO (anyone): Add "Main results" section.
## Tags
pseudo_metric, dist
-/
assert_not_exists compactSpace_uniformity
open Set Filter TopologicalSpace Bornology
open scoped ENNReal NNReal Uniformity Topology
universe u v w
variable {α : Type u} {β : Type v} {X ι : Type*}
theorem UniformSpace.ofDist_aux (ε : ℝ) (hε : 0 < ε) : ∃ δ > (0 : ℝ), ∀ x < δ, ∀ y < δ, x + y < ε :=
⟨ε / 2, half_pos hε, fun _x hx _y hy => add_halves ε ▸ add_lt_add hx hy⟩
/-- Construct a uniform structure from a distance function and metric space axioms -/
def UniformSpace.ofDist (dist : α → α → ℝ) (dist_self : ∀ x : α, dist x x = 0)
(dist_comm : ∀ x y : α, dist x y = dist y x)
(dist_triangle : ∀ x y z : α, dist x z ≤ dist x y + dist y z) : UniformSpace α :=
.ofFun dist dist_self dist_comm dist_triangle ofDist_aux
/-- Construct a bornology from a distance function and metric space axioms. -/
abbrev Bornology.ofDist {α : Type*} (dist : α → α → ℝ) (dist_comm : ∀ x y, dist x y = dist y x)
(dist_triangle : ∀ x y z, dist x z ≤ dist x y + dist y z) : Bornology α :=
Bornology.ofBounded { s : Set α | ∃ C, ∀ ⦃x⦄, x ∈ s → ∀ ⦃y⦄, y ∈ s → dist x y ≤ C }
⟨0, fun _ hx _ => hx.elim⟩ (fun _ ⟨c, hc⟩ _ h => ⟨c, fun _ hx _ hy => hc (h hx) (h hy)⟩)
(fun s hs t ht => by
rcases s.eq_empty_or_nonempty with rfl | ⟨x, hx⟩
· rwa [empty_union]
rcases t.eq_empty_or_nonempty with rfl | ⟨y, hy⟩
· rwa [union_empty]
rsuffices ⟨C, hC⟩ : ∃ C, ∀ z ∈ s ∪ t, dist x z ≤ C
· refine ⟨C + C, fun a ha b hb => (dist_triangle a x b).trans ?_⟩
simpa only [dist_comm] using add_le_add (hC _ ha) (hC _ hb)
rcases hs with ⟨Cs, hs⟩; rcases ht with ⟨Ct, ht⟩
refine ⟨max Cs (dist x y + Ct), fun z hz => hz.elim
(fun hz => (hs hx hz).trans (le_max_left _ _))
(fun hz => (dist_triangle x y z).trans <|
(add_le_add le_rfl (ht hy hz)).trans (le_max_right _ _))⟩)
fun z => ⟨dist z z, forall_eq.2 <| forall_eq.2 le_rfl⟩
/-- The distance function (given an ambient metric space on `α`), which returns
a nonnegative real number `dist x y` given `x y : α`. -/
@[ext]
class Dist (α : Type*) where
/-- Distance between two points -/
dist : α → α → ℝ
export Dist (dist)
-- the uniform structure and the emetric space structure are embedded in the metric space structure
-- to avoid instance diamond issues. See Note [forgetful inheritance].
/-- This is an internal lemma used inside the default of `PseudoMetricSpace.edist`. -/
private theorem dist_nonneg' {α} {x y : α} (dist : α → α → ℝ)
(dist_self : ∀ x : α, dist x x = 0) (dist_comm : ∀ x y : α, dist x y = dist y x)
(dist_triangle : ∀ x y z : α, dist x z ≤ dist x y + dist y z) : 0 ≤ dist x y :=
have : 0 ≤ 2 * dist x y :=
calc 0 = dist x x := (dist_self _).symm
_ ≤ dist x y + dist y x := dist_triangle _ _ _
_ = 2 * dist x y := by rw [two_mul, dist_comm]
nonneg_of_mul_nonneg_right this two_pos
/-- A pseudometric space is a type endowed with a `ℝ`-valued distance `dist` satisfying
reflexivity `dist x x = 0`, commutativity `dist x y = dist y x`, and the triangle inequality
`dist x z ≤ dist x y + dist y z`.
Note that we do not require `dist x y = 0 → x = y`. See metric spaces (`MetricSpace`) for the
similar class with that stronger assumption.
Any pseudometric space is a topological space and a uniform space (see `TopologicalSpace`,
`UniformSpace`), where the topology and uniformity come from the metric.
Note that a T1 pseudometric space is just a metric space.
We make the uniformity/topology part of the data instead of deriving it from the metric. This eg
ensures that we do not get a diamond when doing
`[PseudoMetricSpace α] [PseudoMetricSpace β] : TopologicalSpace (α × β)`:
The product metric and product topology agree, but not definitionally so.
See Note [forgetful inheritance]. -/
class PseudoMetricSpace (α : Type u) : Type u extends Dist α where
dist_self : ∀ x : α, dist x x = 0
dist_comm : ∀ x y : α, dist x y = dist y x
dist_triangle : ∀ x y z : α, dist x z ≤ dist x y + dist y z
/-- Extended distance between two points -/
edist : α → α → ℝ≥0∞ := fun x y => ENNReal.ofNNReal ⟨dist x y, dist_nonneg' _ ‹_› ‹_› ‹_›⟩
edist_dist : ∀ x y : α, edist x y = ENNReal.ofReal (dist x y) := by
intros x y; exact ENNReal.coe_nnreal_eq _
toUniformSpace : UniformSpace α := .ofDist dist dist_self dist_comm dist_triangle
uniformity_dist : 𝓤 α = ⨅ ε > 0, 𝓟 { p : α × α | dist p.1 p.2 < ε } := by intros; rfl
toBornology : Bornology α := Bornology.ofDist dist dist_comm dist_triangle
cobounded_sets : (Bornology.cobounded α).sets =
{ s | ∃ C : ℝ, ∀ x ∈ sᶜ, ∀ y ∈ sᶜ, dist x y ≤ C } := by intros; rfl
/-- Two pseudo metric space structures with the same distance function coincide. -/
@[ext]
theorem PseudoMetricSpace.ext {α : Type*} {m m' : PseudoMetricSpace α}
(h : m.toDist = m'.toDist) : m = m' := by
let d := m.toDist
obtain ⟨_, _, _, _, hed, _, hU, _, hB⟩ := m
let d' := m'.toDist
obtain ⟨_, _, _, _, hed', _, hU', _, hB'⟩ := m'
obtain rfl : d = d' := h
congr
· ext x y : 2
rw [hed, hed']
· exact UniformSpace.ext (hU.trans hU'.symm)
· ext : 2
rw [← Filter.mem_sets, ← Filter.mem_sets, hB, hB']
variable [PseudoMetricSpace α]
attribute [instance] PseudoMetricSpace.toUniformSpace PseudoMetricSpace.toBornology
-- see Note [lower instance priority]
instance (priority := 200) PseudoMetricSpace.toEDist : EDist α :=
⟨PseudoMetricSpace.edist⟩
/-- Construct a pseudo-metric space structure whose underlying topological space structure
(definitionally) agrees which a pre-existing topology which is compatible with a given distance
function. -/
def PseudoMetricSpace.ofDistTopology {α : Type u} [TopologicalSpace α] (dist : α → α → ℝ)
(dist_self : ∀ x : α, dist x x = 0) (dist_comm : ∀ x y : α, dist x y = dist y x)
(dist_triangle : ∀ x y z : α, dist x z ≤ dist x y + dist y z)
(H : ∀ s : Set α, IsOpen s ↔ ∀ x ∈ s, ∃ ε > 0, ∀ y, dist x y < ε → y ∈ s) :
PseudoMetricSpace α :=
{ dist := dist
dist_self := dist_self
dist_comm := dist_comm
dist_triangle := dist_triangle
toUniformSpace :=
(UniformSpace.ofDist dist dist_self dist_comm dist_triangle).replaceTopology <|
TopologicalSpace.ext_iff.2 fun s ↦ (H s).trans <| forall₂_congr fun x _ ↦
((UniformSpace.hasBasis_ofFun (exists_gt (0 : ℝ)) dist dist_self dist_comm dist_triangle
UniformSpace.ofDist_aux).comap (Prod.mk x)).mem_iff.symm
uniformity_dist := rfl
toBornology := Bornology.ofDist dist dist_comm dist_triangle
cobounded_sets := rfl }
@[simp]
theorem dist_self (x : α) : dist x x = 0 :=
PseudoMetricSpace.dist_self x
theorem dist_comm (x y : α) : dist x y = dist y x :=
PseudoMetricSpace.dist_comm x y
theorem edist_dist (x y : α) : edist x y = ENNReal.ofReal (dist x y) :=
PseudoMetricSpace.edist_dist x y
@[bound]
theorem dist_triangle (x y z : α) : dist x z ≤ dist x y + dist y z :=
PseudoMetricSpace.dist_triangle x y z
theorem dist_triangle_left (x y z : α) : dist x y ≤ dist z x + dist z y := by
rw [dist_comm z]; apply dist_triangle
theorem dist_triangle_right (x y z : α) : dist x y ≤ dist x z + dist y z := by
rw [dist_comm y]; apply dist_triangle
theorem dist_triangle4 (x y z w : α) : dist x w ≤ dist x y + dist y z + dist z w :=
calc
dist x w ≤ dist x z + dist z w := dist_triangle x z w
_ ≤ dist x y + dist y z + dist z w := add_le_add_right (dist_triangle x y z) _
theorem dist_triangle4_left (x₁ y₁ x₂ y₂ : α) :
dist x₂ y₂ ≤ dist x₁ y₁ + (dist x₁ x₂ + dist y₁ y₂) := by
rw [add_left_comm, dist_comm x₁, ← add_assoc]
apply dist_triangle4
theorem dist_triangle4_right (x₁ y₁ x₂ y₂ : α) :
dist x₁ y₁ ≤ dist x₁ x₂ + dist y₁ y₂ + dist x₂ y₂ := by
rw [add_right_comm, dist_comm y₁]
apply dist_triangle4
theorem dist_triangle8 (a b c d e f g h : α) : dist a h ≤ dist a b + dist b c + dist c d
+ dist d e + dist e f + dist f g + dist g h := by
apply le_trans (dist_triangle4 a f g h)
apply add_le_add_right (add_le_add_right _ (dist f g)) (dist g h)
apply le_trans (dist_triangle4 a d e f)
apply add_le_add_right (add_le_add_right _ (dist d e)) (dist e f)
exact dist_triangle4 a b c d
theorem swap_dist : Function.swap (@dist α _) = dist := by funext x y; exact dist_comm _ _
theorem abs_dist_sub_le (x y z : α) : |dist x z - dist y z| ≤ dist x y :=
abs_sub_le_iff.2
⟨sub_le_iff_le_add.2 (dist_triangle _ _ _), sub_le_iff_le_add.2 (dist_triangle_left _ _ _)⟩
@[bound]
theorem dist_nonneg {x y : α} : 0 ≤ dist x y :=
dist_nonneg' dist dist_self dist_comm dist_triangle
namespace Mathlib.Meta.Positivity
open Lean Meta Qq Function
/-- Extension for the `positivity` tactic: distances are nonnegative. -/
@[positivity Dist.dist _ _]
def evalDist : PositivityExt where eval {u α} _zα _pα e := do
match u, α, e with
| 0, ~q(ℝ), ~q(@Dist.dist $β $inst $a $b) =>
let _inst ← synthInstanceQ q(PseudoMetricSpace $β)
assertInstancesCommute
pure (.nonnegative q(dist_nonneg))
| _, _, _ => throwError "not dist"
end Mathlib.Meta.Positivity
example {x y : α} : 0 ≤ dist x y := by positivity
@[simp] theorem abs_dist {a b : α} : |dist a b| = dist a b := abs_of_nonneg dist_nonneg
/-- A version of `Dist` that takes value in `ℝ≥0`. -/
class NNDist (α : Type*) where
/-- Nonnegative distance between two points -/
nndist : α → α → ℝ≥0
export NNDist (nndist)
-- see Note [lower instance priority]
/-- Distance as a nonnegative real number. -/
instance (priority := 100) PseudoMetricSpace.toNNDist : NNDist α :=
⟨fun a b => ⟨dist a b, dist_nonneg⟩⟩
/-- Express `dist` in terms of `nndist` -/
theorem dist_nndist (x y : α) : dist x y = nndist x y := rfl
@[simp, norm_cast]
theorem coe_nndist (x y : α) : ↑(nndist x y) = dist x y := rfl
/-- Express `edist` in terms of `nndist` -/
theorem edist_nndist (x y : α) : edist x y = nndist x y := by
rw [edist_dist, dist_nndist, ENNReal.ofReal_coe_nnreal]
/-- Express `nndist` in terms of `edist` -/
theorem nndist_edist (x y : α) : nndist x y = (edist x y).toNNReal := by
simp [edist_nndist]
@[simp, norm_cast]
theorem coe_nnreal_ennreal_nndist (x y : α) : ↑(nndist x y) = edist x y :=
(edist_nndist x y).symm
@[simp, norm_cast]
theorem edist_lt_coe {x y : α} {c : ℝ≥0} : edist x y < c ↔ nndist x y < c := by
rw [edist_nndist, ENNReal.coe_lt_coe]
@[simp, norm_cast]
theorem edist_le_coe {x y : α} {c : ℝ≥0} : edist x y ≤ c ↔ nndist x y ≤ c := by
rw [edist_nndist, ENNReal.coe_le_coe]
/-- In a pseudometric space, the extended distance is always finite -/
theorem edist_lt_top {α : Type*} [PseudoMetricSpace α] (x y : α) : edist x y < ⊤ :=
(edist_dist x y).symm ▸ ENNReal.ofReal_lt_top
/-- In a pseudometric space, the extended distance is always finite -/
theorem edist_ne_top (x y : α) : edist x y ≠ ⊤ :=
(edist_lt_top x y).ne
/-- `nndist x x` vanishes -/
@[simp] theorem nndist_self (a : α) : nndist a a = 0 := NNReal.coe_eq_zero.1 (dist_self a)
@[simp, norm_cast]
theorem dist_lt_coe {x y : α} {c : ℝ≥0} : dist x y < c ↔ nndist x y < c :=
Iff.rfl
@[simp, norm_cast]
theorem dist_le_coe {x y : α} {c : ℝ≥0} : dist x y ≤ c ↔ nndist x y ≤ c :=
Iff.rfl
@[simp]
theorem edist_lt_ofReal {x y : α} {r : ℝ} : edist x y < ENNReal.ofReal r ↔ dist x y < r := by
rw [edist_dist, ENNReal.ofReal_lt_ofReal_iff_of_nonneg dist_nonneg]
@[simp]
theorem edist_le_ofReal {x y : α} {r : ℝ} (hr : 0 ≤ r) :
edist x y ≤ ENNReal.ofReal r ↔ dist x y ≤ r := by
rw [edist_dist, ENNReal.ofReal_le_ofReal_iff hr]
/-- Express `nndist` in terms of `dist` -/
theorem nndist_dist (x y : α) : nndist x y = Real.toNNReal (dist x y) := by
rw [dist_nndist, Real.toNNReal_coe]
theorem nndist_comm (x y : α) : nndist x y = nndist y x := NNReal.eq <| dist_comm x y
/-- Triangle inequality for the nonnegative distance -/
theorem nndist_triangle (x y z : α) : nndist x z ≤ nndist x y + nndist y z :=
dist_triangle _ _ _
theorem nndist_triangle_left (x y z : α) : nndist x y ≤ nndist z x + nndist z y :=
dist_triangle_left _ _ _
theorem nndist_triangle_right (x y z : α) : nndist x y ≤ nndist x z + nndist y z :=
dist_triangle_right _ _ _
/-- Express `dist` in terms of `edist` -/
theorem dist_edist (x y : α) : dist x y = (edist x y).toReal := by
rw [edist_dist, ENNReal.toReal_ofReal dist_nonneg]
namespace Metric
-- instantiate pseudometric space as a topology
variable {x y z : α} {δ ε ε₁ ε₂ : ℝ} {s : Set α}
/-- `ball x ε` is the set of all points `y` with `dist y x < ε` -/
def ball (x : α) (ε : ℝ) : Set α :=
{ y | dist y x < ε }
@[simp]
theorem mem_ball : y ∈ ball x ε ↔ dist y x < ε :=
Iff.rfl
theorem mem_ball' : y ∈ ball x ε ↔ dist x y < ε := by rw [dist_comm, mem_ball]
theorem pos_of_mem_ball (hy : y ∈ ball x ε) : 0 < ε :=
dist_nonneg.trans_lt hy
theorem mem_ball_self (h : 0 < ε) : x ∈ ball x ε := by
rwa [mem_ball, dist_self]
@[simp]
theorem nonempty_ball : (ball x ε).Nonempty ↔ 0 < ε :=
⟨fun ⟨_x, hx⟩ => pos_of_mem_ball hx, fun h => ⟨x, mem_ball_self h⟩⟩
@[simp]
theorem ball_eq_empty : ball x ε = ∅ ↔ ε ≤ 0 := by
rw [← not_nonempty_iff_eq_empty, nonempty_ball, not_lt]
@[simp]
theorem ball_zero : ball x 0 = ∅ := by rw [ball_eq_empty]
/-- If a point belongs to an open ball, then there is a strictly smaller radius whose ball also
contains it.
See also `exists_lt_subset_ball`. -/
theorem exists_lt_mem_ball_of_mem_ball (h : x ∈ ball y ε) : ∃ ε' < ε, x ∈ ball y ε' := by
simp only [mem_ball] at h ⊢
exact ⟨(dist x y + ε) / 2, by linarith, by linarith⟩
theorem ball_eq_ball (ε : ℝ) (x : α) :
UniformSpace.ball x { p | dist p.2 p.1 < ε } = Metric.ball x ε :=
rfl
theorem ball_eq_ball' (ε : ℝ) (x : α) :
UniformSpace.ball x { p | dist p.1 p.2 < ε } = Metric.ball x ε := by
ext
simp [dist_comm, UniformSpace.ball]
@[simp]
theorem iUnion_ball_nat (x : α) : ⋃ n : ℕ, ball x n = univ :=
iUnion_eq_univ_iff.2 fun y => exists_nat_gt (dist y x)
@[simp]
theorem iUnion_ball_nat_succ (x : α) : ⋃ n : ℕ, ball x (n + 1) = univ :=
iUnion_eq_univ_iff.2 fun y => (exists_nat_gt (dist y x)).imp fun _ h => h.trans (lt_add_one _)
/-- `closedBall x ε` is the set of all points `y` with `dist y x ≤ ε` -/
def closedBall (x : α) (ε : ℝ) :=
{ y | dist y x ≤ ε }
@[simp] theorem mem_closedBall : y ∈ closedBall x ε ↔ dist y x ≤ ε := Iff.rfl
theorem mem_closedBall' : y ∈ closedBall x ε ↔ dist x y ≤ ε := by rw [dist_comm, mem_closedBall]
/-- `sphere x ε` is the set of all points `y` with `dist y x = ε` -/
def sphere (x : α) (ε : ℝ) := { y | dist y x = ε }
@[simp] theorem mem_sphere : y ∈ sphere x ε ↔ dist y x = ε := Iff.rfl
theorem mem_sphere' : y ∈ sphere x ε ↔ dist x y = ε := by rw [dist_comm, mem_sphere]
theorem ne_of_mem_sphere (h : y ∈ sphere x ε) (hε : ε ≠ 0) : y ≠ x :=
ne_of_mem_of_not_mem h <| by simpa using hε.symm
theorem nonneg_of_mem_sphere (hy : y ∈ sphere x ε) : 0 ≤ ε :=
dist_nonneg.trans_eq hy
@[simp]
theorem sphere_eq_empty_of_neg (hε : ε < 0) : sphere x ε = ∅ :=
Set.eq_empty_iff_forall_not_mem.mpr fun _y hy => (nonneg_of_mem_sphere hy).not_lt hε
theorem sphere_eq_empty_of_subsingleton [Subsingleton α] (hε : ε ≠ 0) : sphere x ε = ∅ :=
Set.eq_empty_iff_forall_not_mem.mpr fun _ h => ne_of_mem_sphere h hε (Subsingleton.elim _ _)
instance sphere_isEmpty_of_subsingleton [Subsingleton α] [NeZero ε] : IsEmpty (sphere x ε) := by
rw [sphere_eq_empty_of_subsingleton (NeZero.ne ε)]; infer_instance
theorem closedBall_eq_singleton_of_subsingleton [Subsingleton α] (h : 0 ≤ ε) :
closedBall x ε = {x} := by
ext x'
simpa [Subsingleton.allEq x x']
theorem ball_eq_singleton_of_subsingleton [Subsingleton α] (h : 0 < ε) : ball x ε = {x} := by
ext x'
simpa [Subsingleton.allEq x x']
theorem mem_closedBall_self (h : 0 ≤ ε) : x ∈ closedBall x ε := by
rwa [mem_closedBall, dist_self]
@[simp]
theorem nonempty_closedBall : (closedBall x ε).Nonempty ↔ 0 ≤ ε :=
⟨fun ⟨_x, hx⟩ => dist_nonneg.trans hx, fun h => ⟨x, mem_closedBall_self h⟩⟩
@[simp]
theorem closedBall_eq_empty : closedBall x ε = ∅ ↔ ε < 0 := by
rw [← not_nonempty_iff_eq_empty, nonempty_closedBall, not_le]
/-- Closed balls and spheres coincide when the radius is non-positive -/
theorem closedBall_eq_sphere_of_nonpos (hε : ε ≤ 0) : closedBall x ε = sphere x ε :=
Set.ext fun _ => (hε.trans dist_nonneg).le_iff_eq
theorem ball_subset_closedBall : ball x ε ⊆ closedBall x ε := fun _y hy =>
mem_closedBall.2 (le_of_lt hy)
theorem sphere_subset_closedBall : sphere x ε ⊆ closedBall x ε := fun _ => le_of_eq
lemma sphere_subset_ball {r R : ℝ} (h : r < R) : sphere x r ⊆ ball x R := fun _x hx ↦
(mem_sphere.1 hx).trans_lt h
theorem closedBall_disjoint_ball (h : δ + ε ≤ dist x y) : Disjoint (closedBall x δ) (ball y ε) :=
Set.disjoint_left.mpr fun _a ha1 ha2 =>
(h.trans <| dist_triangle_left _ _ _).not_lt <| add_lt_add_of_le_of_lt ha1 ha2
theorem ball_disjoint_closedBall (h : δ + ε ≤ dist x y) : Disjoint (ball x δ) (closedBall y ε) :=
(closedBall_disjoint_ball <| by rwa [add_comm, dist_comm]).symm
theorem ball_disjoint_ball (h : δ + ε ≤ dist x y) : Disjoint (ball x δ) (ball y ε) :=
(closedBall_disjoint_ball h).mono_left ball_subset_closedBall
theorem closedBall_disjoint_closedBall (h : δ + ε < dist x y) :
Disjoint (closedBall x δ) (closedBall y ε) :=
Set.disjoint_left.mpr fun _a ha1 ha2 =>
h.not_le <| (dist_triangle_left _ _ _).trans <| add_le_add ha1 ha2
theorem sphere_disjoint_ball : Disjoint (sphere x ε) (ball x ε) :=
Set.disjoint_left.mpr fun _y hy₁ hy₂ => absurd hy₁ <| ne_of_lt hy₂
@[simp]
theorem ball_union_sphere : ball x ε ∪ sphere x ε = closedBall x ε :=
Set.ext fun _y => (@le_iff_lt_or_eq ℝ _ _ _).symm
@[simp]
theorem sphere_union_ball : sphere x ε ∪ ball x ε = closedBall x ε := by
rw [union_comm, ball_union_sphere]
@[simp]
theorem closedBall_diff_sphere : closedBall x ε \ sphere x ε = ball x ε := by
rw [← ball_union_sphere, Set.union_diff_cancel_right sphere_disjoint_ball.symm.le_bot]
@[simp]
theorem closedBall_diff_ball : closedBall x ε \ ball x ε = sphere x ε := by
rw [← ball_union_sphere, Set.union_diff_cancel_left sphere_disjoint_ball.symm.le_bot]
theorem mem_ball_comm : x ∈ ball y ε ↔ y ∈ ball x ε := by rw [mem_ball', mem_ball]
theorem mem_closedBall_comm : x ∈ closedBall y ε ↔ y ∈ closedBall x ε := by
rw [mem_closedBall', mem_closedBall]
theorem mem_sphere_comm : x ∈ sphere y ε ↔ y ∈ sphere x ε := by rw [mem_sphere', mem_sphere]
@[gcongr]
theorem ball_subset_ball (h : ε₁ ≤ ε₂) : ball x ε₁ ⊆ ball x ε₂ := fun _y yx =>
lt_of_lt_of_le (mem_ball.1 yx) h
theorem closedBall_eq_bInter_ball : closedBall x ε = ⋂ δ > ε, ball x δ := by
ext y; rw [mem_closedBall, ← forall_lt_iff_le', mem_iInter₂]; rfl
theorem ball_subset_ball' (h : ε₁ + dist x y ≤ ε₂) : ball x ε₁ ⊆ ball y ε₂ := fun z hz =>
calc
dist z y ≤ dist z x + dist x y := dist_triangle _ _ _
_ < ε₁ + dist x y := add_lt_add_right (mem_ball.1 hz) _
_ ≤ ε₂ := h
@[gcongr]
theorem closedBall_subset_closedBall (h : ε₁ ≤ ε₂) : closedBall x ε₁ ⊆ closedBall x ε₂ :=
fun _y (yx : _ ≤ ε₁) => le_trans yx h
theorem closedBall_subset_closedBall' (h : ε₁ + dist x y ≤ ε₂) :
closedBall x ε₁ ⊆ closedBall y ε₂ := fun z hz =>
calc
dist z y ≤ dist z x + dist x y := dist_triangle _ _ _
_ ≤ ε₁ + dist x y := add_le_add_right (mem_closedBall.1 hz) _
_ ≤ ε₂ := h
theorem closedBall_subset_ball (h : ε₁ < ε₂) : closedBall x ε₁ ⊆ ball x ε₂ :=
fun y (yh : dist y x ≤ ε₁) => lt_of_le_of_lt yh h
theorem closedBall_subset_ball' (h : ε₁ + dist x y < ε₂) :
closedBall x ε₁ ⊆ ball y ε₂ := fun z hz =>
calc
dist z y ≤ dist z x + dist x y := dist_triangle _ _ _
_ ≤ ε₁ + dist x y := add_le_add_right (mem_closedBall.1 hz) _
_ < ε₂ := h
theorem dist_le_add_of_nonempty_closedBall_inter_closedBall
(h : (closedBall x ε₁ ∩ closedBall y ε₂).Nonempty) : dist x y ≤ ε₁ + ε₂ :=
let ⟨z, hz⟩ := h
calc
dist x y ≤ dist z x + dist z y := dist_triangle_left _ _ _
_ ≤ ε₁ + ε₂ := add_le_add hz.1 hz.2
theorem dist_lt_add_of_nonempty_closedBall_inter_ball (h : (closedBall x ε₁ ∩ ball y ε₂).Nonempty) :
dist x y < ε₁ + ε₂ :=
let ⟨z, hz⟩ := h
calc
dist x y ≤ dist z x + dist z y := dist_triangle_left _ _ _
_ < ε₁ + ε₂ := add_lt_add_of_le_of_lt hz.1 hz.2
theorem dist_lt_add_of_nonempty_ball_inter_closedBall (h : (ball x ε₁ ∩ closedBall y ε₂).Nonempty) :
dist x y < ε₁ + ε₂ := by
rw [inter_comm] at h
rw [add_comm, dist_comm]
exact dist_lt_add_of_nonempty_closedBall_inter_ball h
theorem dist_lt_add_of_nonempty_ball_inter_ball (h : (ball x ε₁ ∩ ball y ε₂).Nonempty) :
dist x y < ε₁ + ε₂ :=
dist_lt_add_of_nonempty_closedBall_inter_ball <|
h.mono (inter_subset_inter ball_subset_closedBall Subset.rfl)
@[simp]
theorem iUnion_closedBall_nat (x : α) : ⋃ n : ℕ, closedBall x n = univ :=
iUnion_eq_univ_iff.2 fun y => exists_nat_ge (dist y x)
theorem iUnion_inter_closedBall_nat (s : Set α) (x : α) : ⋃ n : ℕ, s ∩ closedBall x n = s := by
rw [← inter_iUnion, iUnion_closedBall_nat, inter_univ]
theorem ball_subset (h : dist x y ≤ ε₂ - ε₁) : ball x ε₁ ⊆ ball y ε₂ := fun z zx => by
rw [← add_sub_cancel ε₁ ε₂]
exact lt_of_le_of_lt (dist_triangle z x y) (add_lt_add_of_lt_of_le zx h)
theorem ball_half_subset (y) (h : y ∈ ball x (ε / 2)) : ball y (ε / 2) ⊆ ball x ε :=
ball_subset <| by rw [sub_self_div_two]; exact le_of_lt h
theorem exists_ball_subset_ball (h : y ∈ ball x ε) : ∃ ε' > 0, ball y ε' ⊆ ball x ε :=
⟨_, sub_pos.2 h, ball_subset <| by rw [sub_sub_self]⟩
/-- If a property holds for all points in closed balls of arbitrarily large radii, then it holds for
all points. -/
theorem forall_of_forall_mem_closedBall (p : α → Prop) (x : α)
(H : ∃ᶠ R : ℝ in atTop, ∀ y ∈ closedBall x R, p y) (y : α) : p y := by
obtain ⟨R, hR, h⟩ : ∃ R ≥ dist y x, ∀ z : α, z ∈ closedBall x R → p z :=
frequently_iff.1 H (Ici_mem_atTop (dist y x))
exact h _ hR
/-- If a property holds for all points in balls of arbitrarily large radii, then it holds for all
points. -/
theorem forall_of_forall_mem_ball (p : α → Prop) (x : α)
(H : ∃ᶠ R : ℝ in atTop, ∀ y ∈ ball x R, p y) (y : α) : p y := by
obtain ⟨R, hR, h⟩ : ∃ R > dist y x, ∀ z : α, z ∈ ball x R → p z :=
frequently_iff.1 H (Ioi_mem_atTop (dist y x))
exact h _ hR
theorem isBounded_iff {s : Set α} :
IsBounded s ↔ ∃ C : ℝ, ∀ ⦃x⦄, x ∈ s → ∀ ⦃y⦄, y ∈ s → dist x y ≤ C := by
rw [isBounded_def, ← Filter.mem_sets, @PseudoMetricSpace.cobounded_sets α, mem_setOf_eq,
compl_compl]
theorem isBounded_iff_eventually {s : Set α} :
IsBounded s ↔ ∀ᶠ C in atTop, ∀ ⦃x⦄, x ∈ s → ∀ ⦃y⦄, y ∈ s → dist x y ≤ C :=
isBounded_iff.trans
⟨fun ⟨C, h⟩ => eventually_atTop.2 ⟨C, fun _C' hC' _x hx _y hy => (h hx hy).trans hC'⟩,
Eventually.exists⟩
theorem isBounded_iff_exists_ge {s : Set α} (c : ℝ) :
IsBounded s ↔ ∃ C, c ≤ C ∧ ∀ ⦃x⦄, x ∈ s → ∀ ⦃y⦄, y ∈ s → dist x y ≤ C :=
⟨fun h => ((eventually_ge_atTop c).and (isBounded_iff_eventually.1 h)).exists, fun h =>
isBounded_iff.2 <| h.imp fun _ => And.right⟩
theorem isBounded_iff_nndist {s : Set α} :
IsBounded s ↔ ∃ C : ℝ≥0, ∀ ⦃x⦄, x ∈ s → ∀ ⦃y⦄, y ∈ s → nndist x y ≤ C := by
simp only [isBounded_iff_exists_ge 0, NNReal.exists, ← NNReal.coe_le_coe, ← dist_nndist,
NNReal.coe_mk, exists_prop]
theorem toUniformSpace_eq :
‹PseudoMetricSpace α›.toUniformSpace = .ofDist dist dist_self dist_comm dist_triangle :=
UniformSpace.ext PseudoMetricSpace.uniformity_dist
theorem uniformity_basis_dist :
(𝓤 α).HasBasis (fun ε : ℝ => 0 < ε) fun ε => { p : α × α | dist p.1 p.2 < ε } := by
rw [toUniformSpace_eq]
exact UniformSpace.hasBasis_ofFun (exists_gt _) _ _ _ _ _
/-- Given `f : β → ℝ`, if `f` sends `{i | p i}` to a set of positive numbers
accumulating to zero, then `f i`-neighborhoods of the diagonal form a basis of `𝓤 α`.
For specific bases see `uniformity_basis_dist`, `uniformity_basis_dist_inv_nat_succ`,
and `uniformity_basis_dist_inv_nat_pos`. -/
protected theorem mk_uniformity_basis {β : Type*} {p : β → Prop} {f : β → ℝ}
(hf₀ : ∀ i, p i → 0 < f i) (hf : ∀ ⦃ε⦄, 0 < ε → ∃ i, p i ∧ f i ≤ ε) :
(𝓤 α).HasBasis p fun i => { p : α × α | dist p.1 p.2 < f i } := by
refine ⟨fun s => uniformity_basis_dist.mem_iff.trans ?_⟩
constructor
· rintro ⟨ε, ε₀, hε⟩
rcases hf ε₀ with ⟨i, hi, H⟩
exact ⟨i, hi, fun x (hx : _ < _) => hε <| lt_of_lt_of_le hx H⟩
· exact fun ⟨i, hi, H⟩ => ⟨f i, hf₀ i hi, H⟩
theorem uniformity_basis_dist_rat :
(𝓤 α).HasBasis (fun r : ℚ => 0 < r) fun r => { p : α × α | dist p.1 p.2 < r } :=
Metric.mk_uniformity_basis (fun _ => Rat.cast_pos.2) fun _ε hε =>
let ⟨r, hr0, hrε⟩ := exists_rat_btwn hε
⟨r, Rat.cast_pos.1 hr0, hrε.le⟩
theorem uniformity_basis_dist_inv_nat_succ :
(𝓤 α).HasBasis (fun _ => True) fun n : ℕ => { p : α × α | dist p.1 p.2 < 1 / (↑n + 1) } :=
Metric.mk_uniformity_basis (fun n _ => div_pos zero_lt_one <| Nat.cast_add_one_pos n) fun _ε ε0 =>
(exists_nat_one_div_lt ε0).imp fun _n hn => ⟨trivial, le_of_lt hn⟩
theorem uniformity_basis_dist_inv_nat_pos :
(𝓤 α).HasBasis (fun n : ℕ => 0 < n) fun n : ℕ => { p : α × α | dist p.1 p.2 < 1 / ↑n } :=
Metric.mk_uniformity_basis (fun _ hn => div_pos zero_lt_one <| Nat.cast_pos.2 hn) fun _ ε0 =>
let ⟨n, hn⟩ := exists_nat_one_div_lt ε0
⟨n + 1, Nat.succ_pos n, mod_cast hn.le⟩
theorem uniformity_basis_dist_pow {r : ℝ} (h0 : 0 < r) (h1 : r < 1) :
(𝓤 α).HasBasis (fun _ : ℕ => True) fun n : ℕ => { p : α × α | dist p.1 p.2 < r ^ n } :=
Metric.mk_uniformity_basis (fun _ _ => pow_pos h0 _) fun _ε ε0 =>
let ⟨n, hn⟩ := exists_pow_lt_of_lt_one ε0 h1
⟨n, trivial, hn.le⟩
theorem uniformity_basis_dist_lt {R : ℝ} (hR : 0 < R) :
(𝓤 α).HasBasis (fun r : ℝ => 0 < r ∧ r < R) fun r => { p : α × α | dist p.1 p.2 < r } :=
Metric.mk_uniformity_basis (fun _ => And.left) fun r hr =>
⟨min r (R / 2), ⟨lt_min hr (half_pos hR), min_lt_iff.2 <| Or.inr (half_lt_self hR)⟩,
min_le_left _ _⟩
/-- Given `f : β → ℝ`, if `f` sends `{i | p i}` to a set of positive numbers
accumulating to zero, then closed neighborhoods of the diagonal of sizes `{f i | p i}`
form a basis of `𝓤 α`.
Currently we have only one specific basis `uniformity_basis_dist_le` based on this constructor.
More can be easily added if needed in the future. -/
protected theorem mk_uniformity_basis_le {β : Type*} {p : β → Prop} {f : β → ℝ}
(hf₀ : ∀ x, p x → 0 < f x) (hf : ∀ ε, 0 < ε → ∃ x, p x ∧ f x ≤ ε) :
(𝓤 α).HasBasis p fun x => { p : α × α | dist p.1 p.2 ≤ f x } := by
refine ⟨fun s => uniformity_basis_dist.mem_iff.trans ?_⟩
constructor
· rintro ⟨ε, ε₀, hε⟩
| rcases exists_between ε₀ with ⟨ε', hε'⟩
rcases hf ε' hε'.1 with ⟨i, hi, H⟩
| Mathlib/Topology/MetricSpace/Pseudo/Defs.lean | 675 | 676 |
/-
Copyright (c) 2018 Jeremy Avigad. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Jeremy Avigad, Mario Carneiro, Simon Hudon
-/
import Mathlib.Data.Fin.Fin2
import Mathlib.Logic.Function.Basic
import Mathlib.Tactic.Common
/-!
# Tuples of types, and their categorical structure.
## Features
* `TypeVec n` - n-tuples of types
* `α ⟹ β` - n-tuples of maps
* `f ⊚ g` - composition
Also, support functions for operating with n-tuples of types, such as:
* `append1 α β` - append type `β` to n-tuple `α` to obtain an (n+1)-tuple
* `drop α` - drops the last element of an (n+1)-tuple
* `last α` - returns the last element of an (n+1)-tuple
* `appendFun f g` - appends a function g to an n-tuple of functions
* `dropFun f` - drops the last function from an n+1-tuple
* `lastFun f` - returns the last function of a tuple.
Since e.g. `append1 α.drop α.last` is propositionally equal to `α` but not definitionally equal
to it, we need support functions and lemmas to mediate between constructions.
-/
universe u v w
/-- n-tuples of types, as a category -/
@[pp_with_univ]
def TypeVec (n : ℕ) :=
Fin2 n → Type*
instance {n} : Inhabited (TypeVec.{u} n) :=
⟨fun _ => PUnit⟩
namespace TypeVec
variable {n : ℕ}
/-- arrow in the category of `TypeVec` -/
def Arrow (α β : TypeVec n) :=
∀ i : Fin2 n, α i → β i
@[inherit_doc] scoped[MvFunctor] infixl:40 " ⟹ " => TypeVec.Arrow
open MvFunctor
/-- Extensionality for arrows -/
@[ext]
theorem Arrow.ext {α β : TypeVec n} (f g : α ⟹ β) :
(∀ i, f i = g i) → f = g := by
intro h; funext i; apply h
instance Arrow.inhabited (α β : TypeVec n) [∀ i, Inhabited (β i)] : Inhabited (α ⟹ β) :=
⟨fun _ _ => default⟩
/-- identity of arrow composition -/
def id {α : TypeVec n} : α ⟹ α := fun _ x => x
/-- arrow composition in the category of `TypeVec` -/
def comp {α β γ : TypeVec n} (g : β ⟹ γ) (f : α ⟹ β) : α ⟹ γ := fun i x => g i (f i x)
@[inherit_doc] scoped[MvFunctor] infixr:80 " ⊚ " => TypeVec.comp -- type as \oo
@[simp]
theorem id_comp {α β : TypeVec n} (f : α ⟹ β) : id ⊚ f = f :=
rfl
@[simp]
theorem comp_id {α β : TypeVec n} (f : α ⟹ β) : f ⊚ id = f :=
rfl
theorem comp_assoc {α β γ δ : TypeVec n} (h : γ ⟹ δ) (g : β ⟹ γ) (f : α ⟹ β) :
(h ⊚ g) ⊚ f = h ⊚ g ⊚ f :=
rfl
/-- Support for extending a `TypeVec` by one element. -/
def append1 (α : TypeVec n) (β : Type*) : TypeVec (n + 1)
| Fin2.fs i => α i
| Fin2.fz => β
@[inherit_doc] infixl:67 " ::: " => append1
/-- retain only a `n-length` prefix of the argument -/
def drop (α : TypeVec.{u} (n + 1)) : TypeVec n := fun i => α i.fs
/-- take the last value of a `(n+1)-length` vector -/
def last (α : TypeVec.{u} (n + 1)) : Type _ :=
α Fin2.fz
instance last.inhabited (α : TypeVec (n + 1)) [Inhabited (α Fin2.fz)] : Inhabited (last α) :=
⟨show α Fin2.fz from default⟩
theorem drop_append1 {α : TypeVec n} {β : Type*} {i : Fin2 n} : drop (append1 α β) i = α i :=
rfl
theorem drop_append1' {α : TypeVec n} {β : Type*} : drop (append1 α β) = α :=
funext fun _ => drop_append1
theorem last_append1 {α : TypeVec n} {β : Type*} : last (append1 α β) = β :=
rfl
@[simp]
theorem append1_drop_last (α : TypeVec (n + 1)) : append1 (drop α) (last α) = α :=
funext fun i => by cases i <;> rfl
/-- cases on `(n+1)-length` vectors -/
@[elab_as_elim]
def append1Cases {C : TypeVec (n + 1) → Sort u} (H : ∀ α β, C (append1 α β)) (γ) : C γ := by
rw [← @append1_drop_last _ γ]; apply H
@[simp]
theorem append1_cases_append1 {C : TypeVec (n + 1) → Sort u} (H : ∀ α β, C (append1 α β)) (α β) :
@append1Cases _ C H (append1 α β) = H α β :=
rfl
/-- append an arrow and a function for arbitrary source and target type vectors -/
def splitFun {α α' : TypeVec (n + 1)} (f : drop α ⟹ drop α') (g : last α → last α') : α ⟹ α'
| Fin2.fs i => f i
| Fin2.fz => g
/-- append an arrow and a function as well as their respective source and target types / typevecs -/
def appendFun {α α' : TypeVec n} {β β' : Type*} (f : α ⟹ α') (g : β → β') :
append1 α β ⟹ append1 α' β' :=
splitFun f g
@[inherit_doc] infixl:0 " ::: " => appendFun
/-- split off the prefix of an arrow -/
def dropFun {α β : TypeVec (n + 1)} (f : α ⟹ β) : drop α ⟹ drop β := fun i => f i.fs
/-- split off the last function of an arrow -/
def lastFun {α β : TypeVec (n + 1)} (f : α ⟹ β) : last α → last β :=
f Fin2.fz
/-- arrow in the category of `0-length` vectors -/
def nilFun {α : TypeVec 0} {β : TypeVec 0} : α ⟹ β := fun i => by apply Fin2.elim0 i
theorem eq_of_drop_last_eq {α β : TypeVec (n + 1)} {f g : α ⟹ β} (h₀ : dropFun f = dropFun g)
(h₁ : lastFun f = lastFun g) : f = g := by
refine funext (fun x => ?_)
cases x
· apply h₁
· apply congr_fun h₀
@[simp]
theorem dropFun_splitFun {α α' : TypeVec (n + 1)} (f : drop α ⟹ drop α') (g : last α → last α') :
dropFun (splitFun f g) = f :=
rfl
/-- turn an equality into an arrow -/
def Arrow.mp {α β : TypeVec n} (h : α = β) : α ⟹ β
| _ => Eq.mp (congr_fun h _)
/-- turn an equality into an arrow, with reverse direction -/
def Arrow.mpr {α β : TypeVec n} (h : α = β) : β ⟹ α
| _ => Eq.mpr (congr_fun h _)
/-- decompose a vector into its prefix appended with its last element -/
def toAppend1DropLast {α : TypeVec (n + 1)} : α ⟹ (drop α ::: last α) :=
Arrow.mpr (append1_drop_last _)
/-- stitch two bits of a vector back together -/
def fromAppend1DropLast {α : TypeVec (n + 1)} : (drop α ::: last α) ⟹ α :=
Arrow.mp (append1_drop_last _)
@[simp]
theorem lastFun_splitFun {α α' : TypeVec (n + 1)} (f : drop α ⟹ drop α') (g : last α → last α') :
lastFun (splitFun f g) = g :=
rfl
@[simp]
theorem dropFun_appendFun {α α' : TypeVec n} {β β' : Type*} (f : α ⟹ α') (g : β → β') :
dropFun (f ::: g) = f :=
rfl
@[simp]
theorem lastFun_appendFun {α α' : TypeVec n} {β β' : Type*} (f : α ⟹ α') (g : β → β') :
lastFun (f ::: g) = g :=
rfl
theorem split_dropFun_lastFun {α α' : TypeVec (n + 1)} (f : α ⟹ α') :
splitFun (dropFun f) (lastFun f) = f :=
eq_of_drop_last_eq rfl rfl
theorem splitFun_inj {α α' : TypeVec (n + 1)} {f f' : drop α ⟹ drop α'} {g g' : last α → last α'}
(H : splitFun f g = splitFun f' g') : f = f' ∧ g = g' := by
rw [← dropFun_splitFun f g, H, ← lastFun_splitFun f g, H]; simp
theorem appendFun_inj {α α' : TypeVec n} {β β' : Type*} {f f' : α ⟹ α'} {g g' : β → β'} :
(f ::: g : (α ::: β) ⟹ _) = (f' ::: g' : (α ::: β) ⟹ _)
→ f = f' ∧ g = g' :=
splitFun_inj
theorem splitFun_comp {α₀ α₁ α₂ : TypeVec (n + 1)} (f₀ : drop α₀ ⟹ drop α₁)
(f₁ : drop α₁ ⟹ drop α₂) (g₀ : last α₀ → last α₁) (g₁ : last α₁ → last α₂) :
splitFun (f₁ ⊚ f₀) (g₁ ∘ g₀) = splitFun f₁ g₁ ⊚ splitFun f₀ g₀ :=
eq_of_drop_last_eq rfl rfl
theorem appendFun_comp_splitFun {α γ : TypeVec n} {β δ : Type*} {ε : TypeVec (n + 1)}
(f₀ : drop ε ⟹ α) (f₁ : α ⟹ γ) (g₀ : last ε → β) (g₁ : β → δ) :
appendFun f₁ g₁ ⊚ splitFun f₀ g₀ = splitFun (α' := γ.append1 δ) (f₁ ⊚ f₀) (g₁ ∘ g₀) :=
(splitFun_comp _ _ _ _).symm
theorem appendFun_comp {α₀ α₁ α₂ : TypeVec n}
{β₀ β₁ β₂ : Type*}
(f₀ : α₀ ⟹ α₁) (f₁ : α₁ ⟹ α₂)
(g₀ : β₀ → β₁) (g₁ : β₁ → β₂) :
(f₁ ⊚ f₀ ::: g₁ ∘ g₀) = (f₁ ::: g₁) ⊚ (f₀ ::: g₀) :=
eq_of_drop_last_eq rfl rfl
theorem appendFun_comp' {α₀ α₁ α₂ : TypeVec n} {β₀ β₁ β₂ : Type*}
(f₀ : α₀ ⟹ α₁) (f₁ : α₁ ⟹ α₂) (g₀ : β₀ → β₁) (g₁ : β₁ → β₂) :
(f₁ ::: g₁) ⊚ (f₀ ::: g₀) = (f₁ ⊚ f₀ ::: g₁ ∘ g₀) :=
eq_of_drop_last_eq rfl rfl
theorem nilFun_comp {α₀ : TypeVec 0} (f₀ : α₀ ⟹ Fin2.elim0) : nilFun ⊚ f₀ = f₀ :=
funext Fin2.elim0
theorem appendFun_comp_id {α : TypeVec n} {β₀ β₁ β₂ : Type u} (g₀ : β₀ → β₁) (g₁ : β₁ → β₂) :
(@id _ α ::: g₁ ∘ g₀) = (id ::: g₁) ⊚ (id ::: g₀) :=
eq_of_drop_last_eq rfl rfl
@[simp]
theorem dropFun_comp {α₀ α₁ α₂ : TypeVec (n + 1)} (f₀ : α₀ ⟹ α₁) (f₁ : α₁ ⟹ α₂) :
dropFun (f₁ ⊚ f₀) = dropFun f₁ ⊚ dropFun f₀ :=
rfl
@[simp]
theorem lastFun_comp {α₀ α₁ α₂ : TypeVec (n + 1)} (f₀ : α₀ ⟹ α₁) (f₁ : α₁ ⟹ α₂) :
lastFun (f₁ ⊚ f₀) = lastFun f₁ ∘ lastFun f₀ :=
rfl
theorem appendFun_aux {α α' : TypeVec n} {β β' : Type*} (f : (α ::: β) ⟹ (α' ::: β')) :
(dropFun f ::: lastFun f) = f :=
eq_of_drop_last_eq rfl rfl
theorem appendFun_id_id {α : TypeVec n} {β : Type*} :
(@TypeVec.id n α ::: @_root_.id β) = TypeVec.id :=
eq_of_drop_last_eq rfl rfl
instance subsingleton0 : Subsingleton (TypeVec 0) :=
⟨fun _ _ => funext Fin2.elim0⟩
-- See `Mathlib.Tactic.Attr.Register` for `register_simp_attr typevec`
/-- cases distinction for 0-length type vector -/
protected def casesNil {β : TypeVec 0 → Sort*} (f : β Fin2.elim0) : ∀ v, β v :=
fun v => cast (by congr; funext i; cases i) f
/-- cases distinction for (n+1)-length type vector -/
protected def casesCons (n : ℕ) {β : TypeVec (n + 1) → Sort*}
(f : ∀ (t) (v : TypeVec n), β (v ::: t)) :
∀ v, β v :=
fun v : TypeVec (n + 1) => cast (by simp) (f v.last v.drop)
protected theorem casesNil_append1 {β : TypeVec 0 → Sort*} (f : β Fin2.elim0) :
TypeVec.casesNil f Fin2.elim0 = f :=
rfl
protected theorem casesCons_append1 (n : ℕ) {β : TypeVec (n + 1) → Sort*}
(f : ∀ (t) (v : TypeVec n), β (v ::: t)) (v : TypeVec n) (α) :
TypeVec.casesCons n f (v ::: α) = f α v :=
rfl
/-- cases distinction for an arrow in the category of 0-length type vectors -/
def typevecCasesNil₃ {β : ∀ v v' : TypeVec 0, v ⟹ v' → Sort*}
(f : β Fin2.elim0 Fin2.elim0 nilFun) :
∀ v v' fs, β v v' fs := fun v v' fs => by
refine cast ?_ f
have eq₁ : v = Fin2.elim0 := by funext i; contradiction
have eq₂ : v' = Fin2.elim0 := by funext i; contradiction
have eq₃ : fs = nilFun := by funext i; contradiction
cases eq₁; cases eq₂; cases eq₃; rfl
/-- cases distinction for an arrow in the category of (n+1)-length type vectors -/
def typevecCasesCons₃ (n : ℕ) {β : ∀ v v' : TypeVec (n + 1), v ⟹ v' → Sort*}
(F : ∀ (t t') (f : t → t') (v v' : TypeVec n) (fs : v ⟹ v'),
β (v ::: t) (v' ::: t') (fs ::: f)) :
∀ v v' fs, β v v' fs := by
intro v v'
rw [← append1_drop_last v, ← append1_drop_last v']
intro fs
rw [← split_dropFun_lastFun fs]
apply F
/-- specialized cases distinction for an arrow in the category of 0-length type vectors -/
def typevecCasesNil₂ {β : Fin2.elim0 ⟹ Fin2.elim0 → Sort*} (f : β nilFun) : ∀ f, β f := by
intro g
suffices g = nilFun by rwa [this]
ext ⟨⟩
/-- specialized cases distinction for an arrow in the category of (n+1)-length type vectors -/
def typevecCasesCons₂ (n : ℕ) (t t' : Type*) (v v' : TypeVec n)
{β : (v ::: t) ⟹ (v' ::: t') → Sort*}
(F : ∀ (f : t → t') (fs : v ⟹ v'), β (fs ::: f)) : ∀ fs, β fs := by
intro fs
rw [← split_dropFun_lastFun fs]
apply F
theorem typevecCasesNil₂_appendFun {β : Fin2.elim0 ⟹ Fin2.elim0 → Sort*} (f : β nilFun) :
typevecCasesNil₂ f nilFun = f :=
rfl
theorem typevecCasesCons₂_appendFun (n : ℕ) (t t' : Type*) (v v' : TypeVec n)
{β : (v ::: t) ⟹ (v' ::: t') → Sort*}
(F : ∀ (f : t → t') (fs : v ⟹ v'), β (fs ::: f))
(f fs) :
typevecCasesCons₂ n t t' v v' F (fs ::: f) = F f fs :=
rfl
-- for lifting predicates and relations
/-- `PredLast α p x` predicates `p` of the last element of `x : α.append1 β`. -/
def PredLast (α : TypeVec n) {β : Type*} (p : β → Prop) : ∀ ⦃i⦄, (α.append1 β) i → Prop
| Fin2.fs _ => fun _ => True
| Fin2.fz => p
/-- `RelLast α r x y` says that `p` the last elements of `x y : α.append1 β` are related by `r` and
all the other elements are equal. -/
def RelLast (α : TypeVec n) {β γ : Type u} (r : β → γ → Prop) :
∀ ⦃i⦄, (α.append1 β) i → (α.append1 γ) i → Prop
| Fin2.fs _ => Eq
| Fin2.fz => r
section Liftp'
open Nat
/-- `repeat n t` is a `n-length` type vector that contains `n` occurrences of `t` -/
def «repeat» : ∀ (n : ℕ), Sort _ → TypeVec n
| 0, _ => Fin2.elim0
| Nat.succ i, t => append1 («repeat» i t) t
/-- `prod α β` is the pointwise product of the components of `α` and `β` -/
def prod : ∀ {n}, TypeVec.{u} n → TypeVec.{u} n → TypeVec n
| 0, _, _ => Fin2.elim0
| n + 1, α, β => (@prod n (drop α) (drop β)) ::: (last α × last β)
@[inherit_doc] scoped[MvFunctor] infixl:45 " ⊗ " => TypeVec.prod
/-- `const x α` is an arrow that ignores its source and constructs a `TypeVec` that
contains nothing but `x` -/
protected def const {β} (x : β) : ∀ {n} (α : TypeVec n), α ⟹ «repeat» _ β
| succ _, α, Fin2.fs _ => TypeVec.const x (drop α) _
| succ _, _, Fin2.fz => fun _ => x
open Function (uncurry)
/-- vector of equality on a product of vectors -/
def repeatEq : ∀ {n} (α : TypeVec n), (α ⊗ α) ⟹ «repeat» _ Prop
| 0, _ => nilFun
| succ _, α => repeatEq (drop α) ::: uncurry Eq
theorem const_append1 {β γ} (x : γ) {n} (α : TypeVec n) :
TypeVec.const x (α ::: β) = appendFun (TypeVec.const x α) fun _ => x := by
ext i : 1; cases i <;> rfl
theorem eq_nilFun {α β : TypeVec 0} (f : α ⟹ β) : f = nilFun := by
ext x; cases x
theorem id_eq_nilFun {α : TypeVec 0} : @id _ α = nilFun := by
ext x; cases x
theorem const_nil {β} (x : β) (α : TypeVec 0) : TypeVec.const x α = nilFun := by
ext i : 1; cases i
@[typevec]
theorem repeat_eq_append1 {β} {n} (α : TypeVec n) :
repeatEq (α ::: β) = splitFun (α := (α ⊗ α) ::: _)
(α' := («repeat» n Prop) ::: _) (repeatEq α) (uncurry Eq) := by
induction n <;> rfl
@[typevec]
theorem repeat_eq_nil (α : TypeVec 0) : repeatEq α = nilFun := by ext i; cases i
/-- predicate on a type vector to constrain only the last object -/
def PredLast' (α : TypeVec n) {β : Type*} (p : β → Prop) :
(α ::: β) ⟹ «repeat» (n + 1) Prop :=
splitFun (TypeVec.const True α) p
/-- predicate on the product of two type vectors to constrain only their last object -/
def RelLast' (α : TypeVec n) {β : Type*} (p : β → β → Prop) :
(α ::: β) ⊗ (α ::: β) ⟹ «repeat» (n + 1) Prop :=
splitFun (repeatEq α) (uncurry p)
/-- given `F : TypeVec.{u} (n+1) → Type u`, `curry F : Type u → TypeVec.{u} → Type u`,
i.e. its first argument can be fed in separately from the rest of the vector of arguments -/
def Curry (F : TypeVec.{u} (n + 1) → Type*) (α : Type u) (β : TypeVec.{u} n) : Type _ :=
F (β ::: α)
instance Curry.inhabited (F : TypeVec.{u} (n + 1) → Type*) (α : Type u) (β : TypeVec.{u} n)
[I : Inhabited (F <| (β ::: α))] : Inhabited (Curry F α β) :=
I
/-- arrow to remove one element of a `repeat` vector -/
def dropRepeat (α : Type*) : ∀ {n}, drop («repeat» (succ n) α) ⟹ «repeat» n α
| succ _, Fin2.fs i => dropRepeat α i
| succ _, Fin2.fz => fun (a : α) => a
/-- projection for a repeat vector -/
def ofRepeat {α : Sort _} : ∀ {n i}, «repeat» n α i → α
| _, Fin2.fz => fun (a : α) => a
| _, Fin2.fs i => @ofRepeat _ _ i
theorem const_iff_true {α : TypeVec n} {i x p} : ofRepeat (TypeVec.const p α i x) ↔ p := by
induction i with
| fz => rfl
| fs _ ih =>
rw [TypeVec.const]
exact ih
section
variable {α β : TypeVec.{u} n}
variable (p : α ⟹ «repeat» n Prop)
/-- left projection of a `prod` vector -/
def prod.fst : ∀ {n} {α β : TypeVec.{u} n}, α ⊗ β ⟹ α
| succ _, α, β, Fin2.fs i => @prod.fst _ (drop α) (drop β) i
| succ _, _, _, Fin2.fz => Prod.fst
/-- right projection of a `prod` vector -/
def prod.snd : ∀ {n} {α β : TypeVec.{u} n}, α ⊗ β ⟹ β
| succ _, α, β, Fin2.fs i => @prod.snd _ (drop α) (drop β) i
| succ _, _, _, Fin2.fz => Prod.snd
/-- introduce a product where both components are the same -/
def prod.diag : ∀ {n} {α : TypeVec.{u} n}, α ⟹ α ⊗ α
| succ _, α, Fin2.fs _, x => @prod.diag _ (drop α) _ x
| succ _, _, Fin2.fz, x => (x, x)
/-- constructor for `prod` -/
def prod.mk : ∀ {n} {α β : TypeVec.{u} n} (i : Fin2 n), α i → β i → (α ⊗ β) i
| succ _, α, β, Fin2.fs i => mk (α := fun i => α i.fs) (β := fun i => β i.fs) i
| succ _, _, _, Fin2.fz => Prod.mk
end
| @[simp]
theorem prod_fst_mk {α β : TypeVec n} (i : Fin2 n) (a : α i) (b : β i) :
TypeVec.prod.fst i (prod.mk i a b) = a := by
induction i with
| Mathlib/Data/TypeVec.lean | 446 | 449 |
/-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.Field.NegOnePow
import Mathlib.Algebra.Field.Periodic
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.SpecialFunctions.Exp
/-!
# Trigonometric functions
## Main definitions
This file contains the definition of `π`.
See also `Analysis.SpecialFunctions.Trigonometric.Inverse` and
`Analysis.SpecialFunctions.Trigonometric.Arctan` for the inverse trigonometric functions.
See also `Analysis.SpecialFunctions.Complex.Arg` and
`Analysis.SpecialFunctions.Complex.Log` for the complex argument function
and the complex logarithm.
## Main statements
Many basic inequalities on the real trigonometric functions are established.
The continuity of the usual trigonometric functions is proved.
Several facts about the real trigonometric functions have the proofs deferred to
`Analysis.SpecialFunctions.Trigonometric.Complex`,
as they are most easily proved by appealing to the corresponding fact for
complex trigonometric functions.
See also `Analysis.SpecialFunctions.Trigonometric.Chebyshev` for the multiple angle formulas
in terms of Chebyshev polynomials.
## Tags
sin, cos, tan, angle
-/
noncomputable section
open Topology Filter Set
namespace Complex
@[continuity, fun_prop]
theorem continuous_sin : Continuous sin := by
change Continuous fun z => (exp (-z * I) - exp (z * I)) * I / 2
fun_prop
@[fun_prop]
theorem continuousOn_sin {s : Set ℂ} : ContinuousOn sin s :=
continuous_sin.continuousOn
@[continuity, fun_prop]
theorem continuous_cos : Continuous cos := by
change Continuous fun z => (exp (z * I) + exp (-z * I)) / 2
fun_prop
@[fun_prop]
theorem continuousOn_cos {s : Set ℂ} : ContinuousOn cos s :=
continuous_cos.continuousOn
@[continuity, fun_prop]
theorem continuous_sinh : Continuous sinh := by
change Continuous fun z => (exp z - exp (-z)) / 2
fun_prop
@[continuity, fun_prop]
theorem continuous_cosh : Continuous cosh := by
change Continuous fun z => (exp z + exp (-z)) / 2
fun_prop
end Complex
namespace Real
variable {x y z : ℝ}
@[continuity, fun_prop]
theorem continuous_sin : Continuous sin :=
Complex.continuous_re.comp (Complex.continuous_sin.comp Complex.continuous_ofReal)
@[fun_prop]
theorem continuousOn_sin {s} : ContinuousOn sin s :=
continuous_sin.continuousOn
@[continuity, fun_prop]
theorem continuous_cos : Continuous cos :=
Complex.continuous_re.comp (Complex.continuous_cos.comp Complex.continuous_ofReal)
@[fun_prop]
theorem continuousOn_cos {s} : ContinuousOn cos s :=
continuous_cos.continuousOn
@[continuity, fun_prop]
theorem continuous_sinh : Continuous sinh :=
Complex.continuous_re.comp (Complex.continuous_sinh.comp Complex.continuous_ofReal)
@[continuity, fun_prop]
theorem continuous_cosh : Continuous cosh :=
Complex.continuous_re.comp (Complex.continuous_cosh.comp Complex.continuous_ofReal)
end Real
namespace Real
theorem exists_cos_eq_zero : 0 ∈ cos '' Icc (1 : ℝ) 2 :=
intermediate_value_Icc' (by norm_num) continuousOn_cos
⟨le_of_lt cos_two_neg, le_of_lt cos_one_pos⟩
/-- The number π = 3.14159265... Defined here using choice as twice a zero of cos in [1,2], from
which one can derive all its properties. For explicit bounds on π, see `Data.Real.Pi.Bounds`.
Denoted `π`, once the `Real` namespace is opened. -/
protected noncomputable def pi : ℝ :=
2 * Classical.choose exists_cos_eq_zero
@[inherit_doc]
scoped notation "π" => Real.pi
@[simp]
theorem cos_pi_div_two : cos (π / 2) = 0 := by
rw [Real.pi, mul_div_cancel_left₀ _ (two_ne_zero' ℝ)]
exact (Classical.choose_spec exists_cos_eq_zero).2
theorem one_le_pi_div_two : (1 : ℝ) ≤ π / 2 := by
rw [Real.pi, mul_div_cancel_left₀ _ (two_ne_zero' ℝ)]
exact (Classical.choose_spec exists_cos_eq_zero).1.1
theorem pi_div_two_le_two : π / 2 ≤ 2 := by
rw [Real.pi, mul_div_cancel_left₀ _ (two_ne_zero' ℝ)]
exact (Classical.choose_spec exists_cos_eq_zero).1.2
theorem two_le_pi : (2 : ℝ) ≤ π :=
(div_le_div_iff_of_pos_right (show (0 : ℝ) < 2 by norm_num)).1
(by rw [div_self (two_ne_zero' ℝ)]; exact one_le_pi_div_two)
theorem pi_le_four : π ≤ 4 :=
(div_le_div_iff_of_pos_right (show (0 : ℝ) < 2 by norm_num)).1
(calc
π / 2 ≤ 2 := pi_div_two_le_two
_ = 4 / 2 := by norm_num)
@[bound]
theorem pi_pos : 0 < π :=
lt_of_lt_of_le (by norm_num) two_le_pi
@[bound]
theorem pi_nonneg : 0 ≤ π :=
pi_pos.le
theorem pi_ne_zero : π ≠ 0 :=
pi_pos.ne'
theorem pi_div_two_pos : 0 < π / 2 :=
half_pos pi_pos
theorem two_pi_pos : 0 < 2 * π := by linarith [pi_pos]
end Real
namespace Mathlib.Meta.Positivity
open Lean.Meta Qq
/-- Extension for the `positivity` tactic: `π` is always positive. -/
@[positivity Real.pi]
def evalRealPi : PositivityExt where eval {u α} _zα _pα e := do
match u, α, e with
| 0, ~q(ℝ), ~q(Real.pi) =>
assertInstancesCommute
pure (.positive q(Real.pi_pos))
| _, _, _ => throwError "not Real.pi"
end Mathlib.Meta.Positivity
namespace NNReal
open Real
open Real NNReal
/-- `π` considered as a nonnegative real. -/
noncomputable def pi : ℝ≥0 :=
⟨π, Real.pi_pos.le⟩
@[simp]
theorem coe_real_pi : (pi : ℝ) = π :=
rfl
theorem pi_pos : 0 < pi := mod_cast Real.pi_pos
theorem pi_ne_zero : pi ≠ 0 :=
pi_pos.ne'
end NNReal
namespace Real
@[simp]
theorem sin_pi : sin π = 0 := by
rw [← mul_div_cancel_left₀ π (two_ne_zero' ℝ), two_mul, add_div, sin_add, cos_pi_div_two]; simp
@[simp]
theorem cos_pi : cos π = -1 := by
rw [← mul_div_cancel_left₀ π (two_ne_zero' ℝ), mul_div_assoc, cos_two_mul, cos_pi_div_two]
norm_num
@[simp]
theorem sin_two_pi : sin (2 * π) = 0 := by simp [two_mul, sin_add]
@[simp]
theorem cos_two_pi : cos (2 * π) = 1 := by simp [two_mul, cos_add]
theorem sin_antiperiodic : Function.Antiperiodic sin π := by simp [sin_add]
theorem sin_periodic : Function.Periodic sin (2 * π) :=
sin_antiperiodic.periodic_two_mul
@[simp]
theorem sin_add_pi (x : ℝ) : sin (x + π) = -sin x :=
sin_antiperiodic x
@[simp]
theorem sin_add_two_pi (x : ℝ) : sin (x + 2 * π) = sin x :=
sin_periodic x
@[simp]
theorem sin_sub_pi (x : ℝ) : sin (x - π) = -sin x :=
sin_antiperiodic.sub_eq x
@[simp]
theorem sin_sub_two_pi (x : ℝ) : sin (x - 2 * π) = sin x :=
sin_periodic.sub_eq x
@[simp]
theorem sin_pi_sub (x : ℝ) : sin (π - x) = sin x :=
neg_neg (sin x) ▸ sin_neg x ▸ sin_antiperiodic.sub_eq'
@[simp]
theorem sin_two_pi_sub (x : ℝ) : sin (2 * π - x) = -sin x :=
sin_neg x ▸ sin_periodic.sub_eq'
@[simp]
theorem sin_nat_mul_pi (n : ℕ) : sin (n * π) = 0 :=
sin_antiperiodic.nat_mul_eq_of_eq_zero sin_zero n
@[simp]
theorem sin_int_mul_pi (n : ℤ) : sin (n * π) = 0 :=
sin_antiperiodic.int_mul_eq_of_eq_zero sin_zero n
@[simp]
theorem sin_add_nat_mul_two_pi (x : ℝ) (n : ℕ) : sin (x + n * (2 * π)) = sin x :=
sin_periodic.nat_mul n x
@[simp]
theorem sin_add_int_mul_two_pi (x : ℝ) (n : ℤ) : sin (x + n * (2 * π)) = sin x :=
sin_periodic.int_mul n x
@[simp]
theorem sin_sub_nat_mul_two_pi (x : ℝ) (n : ℕ) : sin (x - n * (2 * π)) = sin x :=
sin_periodic.sub_nat_mul_eq n
@[simp]
theorem sin_sub_int_mul_two_pi (x : ℝ) (n : ℤ) : sin (x - n * (2 * π)) = sin x :=
sin_periodic.sub_int_mul_eq n
@[simp]
theorem sin_nat_mul_two_pi_sub (x : ℝ) (n : ℕ) : sin (n * (2 * π) - x) = -sin x :=
sin_neg x ▸ sin_periodic.nat_mul_sub_eq n
@[simp]
theorem sin_int_mul_two_pi_sub (x : ℝ) (n : ℤ) : sin (n * (2 * π) - x) = -sin x :=
sin_neg x ▸ sin_periodic.int_mul_sub_eq n
theorem sin_add_int_mul_pi (x : ℝ) (n : ℤ) : sin (x + n * π) = (-1) ^ n * sin x :=
n.cast_negOnePow ℝ ▸ sin_antiperiodic.add_int_mul_eq n
theorem sin_add_nat_mul_pi (x : ℝ) (n : ℕ) : sin (x + n * π) = (-1) ^ n * sin x :=
sin_antiperiodic.add_nat_mul_eq n
theorem sin_sub_int_mul_pi (x : ℝ) (n : ℤ) : sin (x - n * π) = (-1) ^ n * sin x :=
n.cast_negOnePow ℝ ▸ sin_antiperiodic.sub_int_mul_eq n
theorem sin_sub_nat_mul_pi (x : ℝ) (n : ℕ) : sin (x - n * π) = (-1) ^ n * sin x :=
sin_antiperiodic.sub_nat_mul_eq n
theorem sin_int_mul_pi_sub (x : ℝ) (n : ℤ) : sin (n * π - x) = -((-1) ^ n * sin x) := by
simpa only [sin_neg, mul_neg, Int.cast_negOnePow] using sin_antiperiodic.int_mul_sub_eq n
theorem sin_nat_mul_pi_sub (x : ℝ) (n : ℕ) : sin (n * π - x) = -((-1) ^ n * sin x) := by
simpa only [sin_neg, mul_neg] using sin_antiperiodic.nat_mul_sub_eq n
theorem cos_antiperiodic : Function.Antiperiodic cos π := by simp [cos_add]
theorem cos_periodic : Function.Periodic cos (2 * π) :=
cos_antiperiodic.periodic_two_mul
@[simp]
theorem abs_cos_int_mul_pi (k : ℤ) : |cos (k * π)| = 1 := by
simp [abs_cos_eq_sqrt_one_sub_sin_sq]
@[simp]
theorem cos_add_pi (x : ℝ) : cos (x + π) = -cos x :=
cos_antiperiodic x
@[simp]
theorem cos_add_two_pi (x : ℝ) : cos (x + 2 * π) = cos x :=
cos_periodic x
@[simp]
theorem cos_sub_pi (x : ℝ) : cos (x - π) = -cos x :=
cos_antiperiodic.sub_eq x
@[simp]
theorem cos_sub_two_pi (x : ℝ) : cos (x - 2 * π) = cos x :=
cos_periodic.sub_eq x
@[simp]
theorem cos_pi_sub (x : ℝ) : cos (π - x) = -cos x :=
cos_neg x ▸ cos_antiperiodic.sub_eq'
@[simp]
theorem cos_two_pi_sub (x : ℝ) : cos (2 * π - x) = cos x :=
cos_neg x ▸ cos_periodic.sub_eq'
@[simp]
theorem cos_nat_mul_two_pi (n : ℕ) : cos (n * (2 * π)) = 1 :=
(cos_periodic.nat_mul_eq n).trans cos_zero
@[simp]
theorem cos_int_mul_two_pi (n : ℤ) : cos (n * (2 * π)) = 1 :=
(cos_periodic.int_mul_eq n).trans cos_zero
@[simp]
theorem cos_add_nat_mul_two_pi (x : ℝ) (n : ℕ) : cos (x + n * (2 * π)) = cos x :=
cos_periodic.nat_mul n x
@[simp]
theorem cos_add_int_mul_two_pi (x : ℝ) (n : ℤ) : cos (x + n * (2 * π)) = cos x :=
cos_periodic.int_mul n x
@[simp]
theorem cos_sub_nat_mul_two_pi (x : ℝ) (n : ℕ) : cos (x - n * (2 * π)) = cos x :=
cos_periodic.sub_nat_mul_eq n
@[simp]
theorem cos_sub_int_mul_two_pi (x : ℝ) (n : ℤ) : cos (x - n * (2 * π)) = cos x :=
cos_periodic.sub_int_mul_eq n
@[simp]
theorem cos_nat_mul_two_pi_sub (x : ℝ) (n : ℕ) : cos (n * (2 * π) - x) = cos x :=
cos_neg x ▸ cos_periodic.nat_mul_sub_eq n
@[simp]
theorem cos_int_mul_two_pi_sub (x : ℝ) (n : ℤ) : cos (n * (2 * π) - x) = cos x :=
cos_neg x ▸ cos_periodic.int_mul_sub_eq n
theorem cos_add_int_mul_pi (x : ℝ) (n : ℤ) : cos (x + n * π) = (-1) ^ n * cos x :=
n.cast_negOnePow ℝ ▸ cos_antiperiodic.add_int_mul_eq n
theorem cos_add_nat_mul_pi (x : ℝ) (n : ℕ) : cos (x + n * π) = (-1) ^ n * cos x :=
cos_antiperiodic.add_nat_mul_eq n
theorem cos_sub_int_mul_pi (x : ℝ) (n : ℤ) : cos (x - n * π) = (-1) ^ n * cos x :=
n.cast_negOnePow ℝ ▸ cos_antiperiodic.sub_int_mul_eq n
theorem cos_sub_nat_mul_pi (x : ℝ) (n : ℕ) : cos (x - n * π) = (-1) ^ n * cos x :=
cos_antiperiodic.sub_nat_mul_eq n
theorem cos_int_mul_pi_sub (x : ℝ) (n : ℤ) : cos (n * π - x) = (-1) ^ n * cos x :=
n.cast_negOnePow ℝ ▸ cos_neg x ▸ cos_antiperiodic.int_mul_sub_eq n
theorem cos_nat_mul_pi_sub (x : ℝ) (n : ℕ) : cos (n * π - x) = (-1) ^ n * cos x :=
cos_neg x ▸ cos_antiperiodic.nat_mul_sub_eq n
theorem cos_nat_mul_two_pi_add_pi (n : ℕ) : cos (n * (2 * π) + π) = -1 := by
simpa only [cos_zero] using (cos_periodic.nat_mul n).add_antiperiod_eq cos_antiperiodic
theorem cos_int_mul_two_pi_add_pi (n : ℤ) : cos (n * (2 * π) + π) = -1 := by
simpa only [cos_zero] using (cos_periodic.int_mul n).add_antiperiod_eq cos_antiperiodic
theorem cos_nat_mul_two_pi_sub_pi (n : ℕ) : cos (n * (2 * π) - π) = -1 := by
simpa only [cos_zero] using (cos_periodic.nat_mul n).sub_antiperiod_eq cos_antiperiodic
theorem cos_int_mul_two_pi_sub_pi (n : ℤ) : cos (n * (2 * π) - π) = -1 := by
simpa only [cos_zero] using (cos_periodic.int_mul n).sub_antiperiod_eq cos_antiperiodic
theorem sin_pos_of_pos_of_lt_pi {x : ℝ} (h0x : 0 < x) (hxp : x < π) : 0 < sin x :=
if hx2 : x ≤ 2 then sin_pos_of_pos_of_le_two h0x hx2
else
have : (2 : ℝ) + 2 = 4 := by norm_num
have : π - x ≤ 2 :=
sub_le_iff_le_add.2 (le_trans pi_le_four (this ▸ add_le_add_left (le_of_not_ge hx2) _))
sin_pi_sub x ▸ sin_pos_of_pos_of_le_two (sub_pos.2 hxp) this
theorem sin_pos_of_mem_Ioo {x : ℝ} (hx : x ∈ Ioo 0 π) : 0 < sin x :=
sin_pos_of_pos_of_lt_pi hx.1 hx.2
theorem sin_nonneg_of_mem_Icc {x : ℝ} (hx : x ∈ Icc 0 π) : 0 ≤ sin x := by
rw [← closure_Ioo pi_ne_zero.symm] at hx
exact
closure_lt_subset_le continuous_const continuous_sin
(closure_mono (fun y => sin_pos_of_mem_Ioo) hx)
theorem sin_nonneg_of_nonneg_of_le_pi {x : ℝ} (h0x : 0 ≤ x) (hxp : x ≤ π) : 0 ≤ sin x :=
sin_nonneg_of_mem_Icc ⟨h0x, hxp⟩
theorem sin_neg_of_neg_of_neg_pi_lt {x : ℝ} (hx0 : x < 0) (hpx : -π < x) : sin x < 0 :=
neg_pos.1 <| sin_neg x ▸ sin_pos_of_pos_of_lt_pi (neg_pos.2 hx0) (neg_lt.1 hpx)
theorem sin_nonpos_of_nonnpos_of_neg_pi_le {x : ℝ} (hx0 : x ≤ 0) (hpx : -π ≤ x) : sin x ≤ 0 :=
neg_nonneg.1 <| sin_neg x ▸ sin_nonneg_of_nonneg_of_le_pi (neg_nonneg.2 hx0) (neg_le.1 hpx)
@[simp]
theorem sin_pi_div_two : sin (π / 2) = 1 :=
have : sin (π / 2) = 1 ∨ sin (π / 2) = -1 := by
simpa [sq, mul_self_eq_one_iff] using sin_sq_add_cos_sq (π / 2)
this.resolve_right fun h =>
show ¬(0 : ℝ) < -1 by norm_num <|
h ▸ sin_pos_of_pos_of_lt_pi pi_div_two_pos (half_lt_self pi_pos)
theorem sin_add_pi_div_two (x : ℝ) : sin (x + π / 2) = cos x := by simp [sin_add]
theorem sin_sub_pi_div_two (x : ℝ) : sin (x - π / 2) = -cos x := by simp [sub_eq_add_neg, sin_add]
theorem sin_pi_div_two_sub (x : ℝ) : sin (π / 2 - x) = cos x := by simp [sub_eq_add_neg, sin_add]
theorem cos_add_pi_div_two (x : ℝ) : cos (x + π / 2) = -sin x := by simp [cos_add]
theorem cos_sub_pi_div_two (x : ℝ) : cos (x - π / 2) = sin x := by simp [sub_eq_add_neg, cos_add]
theorem cos_pi_div_two_sub (x : ℝ) : cos (π / 2 - x) = sin x := by
rw [← cos_neg, neg_sub, cos_sub_pi_div_two]
theorem cos_pos_of_mem_Ioo {x : ℝ} (hx : x ∈ Ioo (-(π / 2)) (π / 2)) : 0 < cos x :=
sin_add_pi_div_two x ▸ sin_pos_of_mem_Ioo ⟨by linarith [hx.1], by linarith [hx.2]⟩
theorem cos_nonneg_of_mem_Icc {x : ℝ} (hx : x ∈ Icc (-(π / 2)) (π / 2)) : 0 ≤ cos x :=
sin_add_pi_div_two x ▸ sin_nonneg_of_mem_Icc ⟨by linarith [hx.1], by linarith [hx.2]⟩
theorem cos_nonneg_of_neg_pi_div_two_le_of_le {x : ℝ} (hl : -(π / 2) ≤ x) (hu : x ≤ π / 2) :
0 ≤ cos x :=
cos_nonneg_of_mem_Icc ⟨hl, hu⟩
theorem cos_neg_of_pi_div_two_lt_of_lt {x : ℝ} (hx₁ : π / 2 < x) (hx₂ : x < π + π / 2) :
cos x < 0 :=
neg_pos.1 <| cos_pi_sub x ▸ cos_pos_of_mem_Ioo ⟨by linarith, by linarith⟩
theorem cos_nonpos_of_pi_div_two_le_of_le {x : ℝ} (hx₁ : π / 2 ≤ x) (hx₂ : x ≤ π + π / 2) :
cos x ≤ 0 :=
neg_nonneg.1 <| cos_pi_sub x ▸ cos_nonneg_of_mem_Icc ⟨by linarith, by linarith⟩
theorem sin_eq_sqrt_one_sub_cos_sq {x : ℝ} (hl : 0 ≤ x) (hu : x ≤ π) :
sin x = √(1 - cos x ^ 2) := by
rw [← abs_sin_eq_sqrt_one_sub_cos_sq, abs_of_nonneg (sin_nonneg_of_nonneg_of_le_pi hl hu)]
theorem cos_eq_sqrt_one_sub_sin_sq {x : ℝ} (hl : -(π / 2) ≤ x) (hu : x ≤ π / 2) :
cos x = √(1 - sin x ^ 2) := by
rw [← abs_cos_eq_sqrt_one_sub_sin_sq, abs_of_nonneg (cos_nonneg_of_mem_Icc ⟨hl, hu⟩)]
lemma cos_half {x : ℝ} (hl : -π ≤ x) (hr : x ≤ π) : cos (x / 2) = sqrt ((1 + cos x) / 2) := by
have : 0 ≤ cos (x / 2) := cos_nonneg_of_mem_Icc <| by constructor <;> linarith
rw [← sqrt_sq this, cos_sq, add_div, two_mul, add_halves]
lemma abs_sin_half (x : ℝ) : |sin (x / 2)| = sqrt ((1 - cos x) / 2) := by
rw [← sqrt_sq_eq_abs, sin_sq_eq_half_sub, two_mul, add_halves, sub_div]
lemma sin_half_eq_sqrt {x : ℝ} (hl : 0 ≤ x) (hr : x ≤ 2 * π) :
sin (x / 2) = sqrt ((1 - cos x) / 2) := by
rw [← abs_sin_half, abs_of_nonneg]
apply sin_nonneg_of_nonneg_of_le_pi <;> linarith
lemma sin_half_eq_neg_sqrt {x : ℝ} (hl : -(2 * π) ≤ x) (hr : x ≤ 0) :
sin (x / 2) = -sqrt ((1 - cos x) / 2) := by
rw [← abs_sin_half, abs_of_nonpos, neg_neg]
apply sin_nonpos_of_nonnpos_of_neg_pi_le <;> linarith
theorem sin_eq_zero_iff_of_lt_of_lt {x : ℝ} (hx₁ : -π < x) (hx₂ : x < π) : sin x = 0 ↔ x = 0 :=
⟨fun h => by
contrapose! h
cases h.lt_or_lt with
| inl h0 => exact (sin_neg_of_neg_of_neg_pi_lt h0 hx₁).ne
| inr h0 => exact (sin_pos_of_pos_of_lt_pi h0 hx₂).ne',
fun h => by simp [h]⟩
theorem sin_eq_zero_iff {x : ℝ} : sin x = 0 ↔ ∃ n : ℤ, (n : ℝ) * π = x :=
⟨fun h =>
⟨⌊x / π⌋,
le_antisymm (sub_nonneg.1 (Int.sub_floor_div_mul_nonneg _ pi_pos))
(sub_nonpos.1 <|
le_of_not_gt fun h₃ =>
(sin_pos_of_pos_of_lt_pi h₃ (Int.sub_floor_div_mul_lt _ pi_pos)).ne
(by simp [sub_eq_add_neg, sin_add, h, sin_int_mul_pi]))⟩,
fun ⟨_, hn⟩ => hn ▸ sin_int_mul_pi _⟩
theorem sin_ne_zero_iff {x : ℝ} : sin x ≠ 0 ↔ ∀ n : ℤ, (n : ℝ) * π ≠ x := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
theorem sin_eq_zero_iff_cos_eq {x : ℝ} : sin x = 0 ↔ cos x = 1 ∨ cos x = -1 := by
rw [← mul_self_eq_one_iff, ← sin_sq_add_cos_sq x, sq, sq, ← sub_eq_iff_eq_add, sub_self]
exact ⟨fun h => by rw [h, mul_zero], eq_zero_of_mul_self_eq_zero ∘ Eq.symm⟩
theorem cos_eq_one_iff (x : ℝ) : cos x = 1 ↔ ∃ n : ℤ, (n : ℝ) * (2 * π) = x :=
⟨fun h =>
let ⟨n, hn⟩ := sin_eq_zero_iff.1 (sin_eq_zero_iff_cos_eq.2 (Or.inl h))
⟨n / 2,
(Int.emod_two_eq_zero_or_one n).elim
(fun hn0 => by
rwa [← mul_assoc, ← @Int.cast_two ℝ, ← Int.cast_mul,
Int.ediv_mul_cancel (Int.dvd_iff_emod_eq_zero.2 hn0)])
fun hn1 => by
rw [← Int.emod_add_ediv n 2, hn1, Int.cast_add, Int.cast_one, add_mul, one_mul, add_comm,
mul_comm (2 : ℤ), Int.cast_mul, mul_assoc, Int.cast_two] at hn
rw [← hn, cos_int_mul_two_pi_add_pi] at h
exact absurd h (by norm_num)⟩,
fun ⟨_, hn⟩ => hn ▸ cos_int_mul_two_pi _⟩
theorem cos_eq_one_iff_of_lt_of_lt {x : ℝ} (hx₁ : -(2 * π) < x) (hx₂ : x < 2 * π) :
cos x = 1 ↔ x = 0 :=
⟨fun h => by
rcases (cos_eq_one_iff _).1 h with ⟨n, rfl⟩
rw [mul_lt_iff_lt_one_left two_pi_pos] at hx₂
rw [neg_lt, neg_mul_eq_neg_mul, mul_lt_iff_lt_one_left two_pi_pos] at hx₁
norm_cast at hx₁ hx₂
obtain rfl : n = 0 := le_antisymm (by omega) (by omega)
simp, fun h => by simp [h]⟩
| theorem sin_lt_sin_of_lt_of_le_pi_div_two {x y : ℝ} (hx₁ : -(π / 2) ≤ x) (hy₂ : y ≤ π / 2)
(hxy : x < y) : sin x < sin y := by
rw [← sub_pos, sin_sub_sin]
| Mathlib/Analysis/SpecialFunctions/Trigonometric/Basic.lean | 534 | 536 |
/-
Copyright (c) 2017 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl, Mario Carneiro, Patrick Massot, Yury Kudryashov, Rémy Degenne
-/
import Mathlib.Data.Set.Subsingleton
import Mathlib.Order.Interval.Set.Defs
/-!
# Intervals
In any preorder, we define intervals (which on each side can be either infinite, open or closed)
using the following naming conventions:
- `i`: infinite
- `o`: open
- `c`: closed
Each interval has the name `I` + letter for left side + letter for right side.
For instance, `Ioc a b` denotes the interval `(a, b]`.
The definitions can be found in `Mathlib.Order.Interval.Set.Defs`.
This file contains basic facts on inclusion of and set operations on intervals
(where the precise statements depend on the order's properties;
statements requiring `LinearOrder` are in `Mathlib.Order.Interval.Set.LinearOrder`).
TODO: This is just the beginning; a lot of rules are missing
-/
assert_not_exists RelIso
open Function
open OrderDual (toDual ofDual)
variable {α : Type*}
namespace Set
section Preorder
variable [Preorder α] {a a₁ a₂ b b₁ b₂ c x : α}
instance decidableMemIoo [Decidable (a < x ∧ x < b)] : Decidable (x ∈ Ioo a b) := by assumption
instance decidableMemIco [Decidable (a ≤ x ∧ x < b)] : Decidable (x ∈ Ico a b) := by assumption
instance decidableMemIio [Decidable (x < b)] : Decidable (x ∈ Iio b) := by assumption
instance decidableMemIcc [Decidable (a ≤ x ∧ x ≤ b)] : Decidable (x ∈ Icc a b) := by assumption
instance decidableMemIic [Decidable (x ≤ b)] : Decidable (x ∈ Iic b) := by assumption
instance decidableMemIoc [Decidable (a < x ∧ x ≤ b)] : Decidable (x ∈ Ioc a b) := by assumption
instance decidableMemIci [Decidable (a ≤ x)] : Decidable (x ∈ Ici a) := by assumption
instance decidableMemIoi [Decidable (a < x)] : Decidable (x ∈ Ioi a) := by assumption
theorem left_mem_Ioo : a ∈ Ioo a b ↔ False := by simp [lt_irrefl]
theorem left_mem_Ico : a ∈ Ico a b ↔ a < b := by simp [le_refl]
theorem left_mem_Icc : a ∈ Icc a b ↔ a ≤ b := by simp [le_refl]
theorem left_mem_Ioc : a ∈ Ioc a b ↔ False := by simp [lt_irrefl]
theorem left_mem_Ici : a ∈ Ici a := by simp
theorem right_mem_Ioo : b ∈ Ioo a b ↔ False := by simp [lt_irrefl]
theorem right_mem_Ico : b ∈ Ico a b ↔ False := by simp [lt_irrefl]
theorem right_mem_Icc : b ∈ Icc a b ↔ a ≤ b := by simp [le_refl]
theorem right_mem_Ioc : b ∈ Ioc a b ↔ a < b := by simp [le_refl]
theorem right_mem_Iic : a ∈ Iic a := by simp
@[simp]
theorem Ici_toDual : Ici (toDual a) = ofDual ⁻¹' Iic a :=
rfl
@[deprecated (since := "2025-03-20")]
alias dual_Ici := Ici_toDual
@[simp]
theorem Iic_toDual : Iic (toDual a) = ofDual ⁻¹' Ici a :=
rfl
@[deprecated (since := "2025-03-20")]
alias dual_Iic := Iic_toDual
@[simp]
theorem Ioi_toDual : Ioi (toDual a) = ofDual ⁻¹' Iio a :=
rfl
@[deprecated (since := "2025-03-20")]
alias dual_Ioi := Ioi_toDual
@[simp]
theorem Iio_toDual : Iio (toDual a) = ofDual ⁻¹' Ioi a :=
rfl
@[deprecated (since := "2025-03-20")]
alias dual_Iio := Iio_toDual
@[simp]
theorem Icc_toDual : Icc (toDual a) (toDual b) = ofDual ⁻¹' Icc b a :=
Set.ext fun _ => and_comm
@[deprecated (since := "2025-03-20")]
alias dual_Icc := Icc_toDual
@[simp]
theorem Ioc_toDual : Ioc (toDual a) (toDual b) = ofDual ⁻¹' Ico b a :=
Set.ext fun _ => and_comm
@[deprecated (since := "2025-03-20")]
alias dual_Ioc := Ioc_toDual
@[simp]
theorem Ico_toDual : Ico (toDual a) (toDual b) = ofDual ⁻¹' Ioc b a :=
Set.ext fun _ => and_comm
@[deprecated (since := "2025-03-20")]
alias dual_Ico := Ico_toDual
@[simp]
theorem Ioo_toDual : Ioo (toDual a) (toDual b) = ofDual ⁻¹' Ioo b a :=
Set.ext fun _ => and_comm
@[deprecated (since := "2025-03-20")]
alias dual_Ioo := Ioo_toDual
@[simp]
theorem Ici_ofDual {x : αᵒᵈ} : Ici (ofDual x) = toDual ⁻¹' Iic x :=
rfl
@[simp]
theorem Iic_ofDual {x : αᵒᵈ} : Iic (ofDual x) = toDual ⁻¹' Ici x :=
rfl
@[simp]
theorem Ioi_ofDual {x : αᵒᵈ} : Ioi (ofDual x) = toDual ⁻¹' Iio x :=
rfl
@[simp]
theorem Iio_ofDual {x : αᵒᵈ} : Iio (ofDual x) = toDual ⁻¹' Ioi x :=
rfl
@[simp]
theorem Icc_ofDual {x y : αᵒᵈ} : Icc (ofDual y) (ofDual x) = toDual ⁻¹' Icc x y :=
Set.ext fun _ => and_comm
@[simp]
theorem Ico_ofDual {x y : αᵒᵈ} : Ico (ofDual y) (ofDual x) = toDual ⁻¹' Ioc x y :=
Set.ext fun _ => and_comm
@[simp]
theorem Ioc_ofDual {x y : αᵒᵈ} : Ioc (ofDual y) (ofDual x) = toDual ⁻¹' Ico x y :=
Set.ext fun _ => and_comm
@[simp]
theorem Ioo_ofDual {x y : αᵒᵈ} : Ioo (ofDual y) (ofDual x) = toDual ⁻¹' Ioo x y :=
Set.ext fun _ => and_comm
@[simp]
theorem nonempty_Icc : (Icc a b).Nonempty ↔ a ≤ b :=
⟨fun ⟨_, hx⟩ => hx.1.trans hx.2, fun h => ⟨a, left_mem_Icc.2 h⟩⟩
@[simp]
theorem nonempty_Ico : (Ico a b).Nonempty ↔ a < b :=
⟨fun ⟨_, hx⟩ => hx.1.trans_lt hx.2, fun h => ⟨a, left_mem_Ico.2 h⟩⟩
@[simp]
theorem nonempty_Ioc : (Ioc a b).Nonempty ↔ a < b :=
⟨fun ⟨_, hx⟩ => hx.1.trans_le hx.2, fun h => ⟨b, right_mem_Ioc.2 h⟩⟩
@[simp]
theorem nonempty_Ici : (Ici a).Nonempty :=
⟨a, left_mem_Ici⟩
@[simp]
theorem nonempty_Iic : (Iic a).Nonempty :=
⟨a, right_mem_Iic⟩
@[simp]
theorem nonempty_Ioo [DenselyOrdered α] : (Ioo a b).Nonempty ↔ a < b :=
⟨fun ⟨_, ha, hb⟩ => ha.trans hb, exists_between⟩
@[simp]
theorem nonempty_Ioi [NoMaxOrder α] : (Ioi a).Nonempty :=
exists_gt a
@[simp]
theorem nonempty_Iio [NoMinOrder α] : (Iio a).Nonempty :=
exists_lt a
theorem nonempty_Icc_subtype (h : a ≤ b) : Nonempty (Icc a b) :=
Nonempty.to_subtype (nonempty_Icc.mpr h)
theorem nonempty_Ico_subtype (h : a < b) : Nonempty (Ico a b) :=
Nonempty.to_subtype (nonempty_Ico.mpr h)
theorem nonempty_Ioc_subtype (h : a < b) : Nonempty (Ioc a b) :=
Nonempty.to_subtype (nonempty_Ioc.mpr h)
/-- An interval `Ici a` is nonempty. -/
instance nonempty_Ici_subtype : Nonempty (Ici a) :=
Nonempty.to_subtype nonempty_Ici
/-- An interval `Iic a` is nonempty. -/
instance nonempty_Iic_subtype : Nonempty (Iic a) :=
Nonempty.to_subtype nonempty_Iic
theorem nonempty_Ioo_subtype [DenselyOrdered α] (h : a < b) : Nonempty (Ioo a b) :=
Nonempty.to_subtype (nonempty_Ioo.mpr h)
/-- In an order without maximal elements, the intervals `Ioi` are nonempty. -/
instance nonempty_Ioi_subtype [NoMaxOrder α] : Nonempty (Ioi a) :=
Nonempty.to_subtype nonempty_Ioi
/-- In an order without minimal elements, the intervals `Iio` are nonempty. -/
instance nonempty_Iio_subtype [NoMinOrder α] : Nonempty (Iio a) :=
Nonempty.to_subtype nonempty_Iio
instance [NoMinOrder α] : NoMinOrder (Iio a) :=
⟨fun a =>
let ⟨b, hb⟩ := exists_lt (a : α)
⟨⟨b, lt_trans hb a.2⟩, hb⟩⟩
instance [NoMinOrder α] : NoMinOrder (Iic a) :=
⟨fun a =>
let ⟨b, hb⟩ := exists_lt (a : α)
⟨⟨b, hb.le.trans a.2⟩, hb⟩⟩
instance [NoMaxOrder α] : NoMaxOrder (Ioi a) :=
OrderDual.noMaxOrder (α := Iio (toDual a))
instance [NoMaxOrder α] : NoMaxOrder (Ici a) :=
OrderDual.noMaxOrder (α := Iic (toDual a))
@[simp]
theorem Icc_eq_empty (h : ¬a ≤ b) : Icc a b = ∅ :=
eq_empty_iff_forall_not_mem.2 fun _ ⟨ha, hb⟩ => h (ha.trans hb)
@[simp]
theorem Ico_eq_empty (h : ¬a < b) : Ico a b = ∅ :=
eq_empty_iff_forall_not_mem.2 fun _ ⟨ha, hb⟩ => h (ha.trans_lt hb)
@[simp]
theorem Ioc_eq_empty (h : ¬a < b) : Ioc a b = ∅ :=
eq_empty_iff_forall_not_mem.2 fun _ ⟨ha, hb⟩ => h (ha.trans_le hb)
@[simp]
theorem Ioo_eq_empty (h : ¬a < b) : Ioo a b = ∅ :=
eq_empty_iff_forall_not_mem.2 fun _ ⟨ha, hb⟩ => h (ha.trans hb)
@[simp]
theorem Icc_eq_empty_of_lt (h : b < a) : Icc a b = ∅ :=
Icc_eq_empty h.not_le
@[simp]
theorem Ico_eq_empty_of_le (h : b ≤ a) : Ico a b = ∅ :=
Ico_eq_empty h.not_lt
@[simp]
theorem Ioc_eq_empty_of_le (h : b ≤ a) : Ioc a b = ∅ :=
Ioc_eq_empty h.not_lt
@[simp]
theorem Ioo_eq_empty_of_le (h : b ≤ a) : Ioo a b = ∅ :=
Ioo_eq_empty h.not_lt
theorem Ico_self (a : α) : Ico a a = ∅ :=
Ico_eq_empty <| lt_irrefl _
theorem Ioc_self (a : α) : Ioc a a = ∅ :=
Ioc_eq_empty <| lt_irrefl _
theorem Ioo_self (a : α) : Ioo a a = ∅ :=
Ioo_eq_empty <| lt_irrefl _
@[simp]
theorem Ici_subset_Ici : Ici a ⊆ Ici b ↔ b ≤ a :=
⟨fun h => h <| left_mem_Ici, fun h _ hx => h.trans hx⟩
@[gcongr] alias ⟨_, _root_.GCongr.Ici_subset_Ici_of_le⟩ := Ici_subset_Ici
@[simp]
theorem Ici_ssubset_Ici : Ici a ⊂ Ici b ↔ b < a where
mp h := by
obtain ⟨ab, c, cb, ac⟩ := ssubset_iff_exists.mp h
exact lt_of_le_not_le (Ici_subset_Ici.mp ab) (fun h' ↦ ac (h'.trans cb))
mpr h := (ssubset_iff_of_subset (Ici_subset_Ici.mpr h.le)).mpr
⟨b, right_mem_Iic, fun h' => h.not_le h'⟩
@[gcongr] alias ⟨_, _root_.GCongr.Ici_ssubset_Ici_of_le⟩ := Ici_ssubset_Ici
@[simp]
theorem Iic_subset_Iic : Iic a ⊆ Iic b ↔ a ≤ b :=
@Ici_subset_Ici αᵒᵈ _ _ _
@[gcongr] alias ⟨_, _root_.GCongr.Iic_subset_Iic_of_le⟩ := Iic_subset_Iic
@[simp]
theorem Iic_ssubset_Iic : Iic a ⊂ Iic b ↔ a < b :=
@Ici_ssubset_Ici αᵒᵈ _ _ _
@[gcongr] alias ⟨_, _root_.GCongr.Iic_ssubset_Iic_of_le⟩ := Iic_ssubset_Iic
@[simp]
theorem Ici_subset_Ioi : Ici a ⊆ Ioi b ↔ b < a :=
⟨fun h => h left_mem_Ici, fun h _ hx => h.trans_le hx⟩
@[simp]
theorem Iic_subset_Iio : Iic a ⊆ Iio b ↔ a < b :=
⟨fun h => h right_mem_Iic, fun h _ hx => lt_of_le_of_lt hx h⟩
@[gcongr]
theorem Ioo_subset_Ioo (h₁ : a₂ ≤ a₁) (h₂ : b₁ ≤ b₂) : Ioo a₁ b₁ ⊆ Ioo a₂ b₂ := fun _ ⟨hx₁, hx₂⟩ =>
⟨h₁.trans_lt hx₁, hx₂.trans_le h₂⟩
@[gcongr]
theorem Ioo_subset_Ioo_left (h : a₁ ≤ a₂) : Ioo a₂ b ⊆ Ioo a₁ b :=
Ioo_subset_Ioo h le_rfl
@[gcongr]
theorem Ioo_subset_Ioo_right (h : b₁ ≤ b₂) : Ioo a b₁ ⊆ Ioo a b₂ :=
Ioo_subset_Ioo le_rfl h
@[gcongr]
theorem Ico_subset_Ico (h₁ : a₂ ≤ a₁) (h₂ : b₁ ≤ b₂) : Ico a₁ b₁ ⊆ Ico a₂ b₂ := fun _ ⟨hx₁, hx₂⟩ =>
⟨h₁.trans hx₁, hx₂.trans_le h₂⟩
@[gcongr]
theorem Ico_subset_Ico_left (h : a₁ ≤ a₂) : Ico a₂ b ⊆ Ico a₁ b :=
Ico_subset_Ico h le_rfl
@[gcongr]
theorem Ico_subset_Ico_right (h : b₁ ≤ b₂) : Ico a b₁ ⊆ Ico a b₂ :=
Ico_subset_Ico le_rfl h
@[gcongr]
theorem Icc_subset_Icc (h₁ : a₂ ≤ a₁) (h₂ : b₁ ≤ b₂) : Icc a₁ b₁ ⊆ Icc a₂ b₂ := fun _ ⟨hx₁, hx₂⟩ =>
⟨h₁.trans hx₁, le_trans hx₂ h₂⟩
@[gcongr]
theorem Icc_subset_Icc_left (h : a₁ ≤ a₂) : Icc a₂ b ⊆ Icc a₁ b :=
Icc_subset_Icc h le_rfl
@[gcongr]
theorem Icc_subset_Icc_right (h : b₁ ≤ b₂) : Icc a b₁ ⊆ Icc a b₂ :=
Icc_subset_Icc le_rfl h
theorem Icc_subset_Ioo (ha : a₂ < a₁) (hb : b₁ < b₂) : Icc a₁ b₁ ⊆ Ioo a₂ b₂ := fun _ hx =>
⟨ha.trans_le hx.1, hx.2.trans_lt hb⟩
theorem Icc_subset_Ici_self : Icc a b ⊆ Ici a := fun _ => And.left
theorem Icc_subset_Iic_self : Icc a b ⊆ Iic b := fun _ => And.right
theorem Ioc_subset_Iic_self : Ioc a b ⊆ Iic b := fun _ => And.right
@[gcongr]
theorem Ioc_subset_Ioc (h₁ : a₂ ≤ a₁) (h₂ : b₁ ≤ b₂) : Ioc a₁ b₁ ⊆ Ioc a₂ b₂ := fun _ ⟨hx₁, hx₂⟩ =>
⟨h₁.trans_lt hx₁, hx₂.trans h₂⟩
@[gcongr]
theorem Ioc_subset_Ioc_left (h : a₁ ≤ a₂) : Ioc a₂ b ⊆ Ioc a₁ b :=
Ioc_subset_Ioc h le_rfl
@[gcongr]
theorem Ioc_subset_Ioc_right (h : b₁ ≤ b₂) : Ioc a b₁ ⊆ Ioc a b₂ :=
Ioc_subset_Ioc le_rfl h
theorem Ico_subset_Ioo_left (h₁ : a₁ < a₂) : Ico a₂ b ⊆ Ioo a₁ b := fun _ =>
And.imp_left h₁.trans_le
theorem Ioc_subset_Ioo_right (h : b₁ < b₂) : Ioc a b₁ ⊆ Ioo a b₂ := fun _ =>
And.imp_right fun h' => h'.trans_lt h
theorem Icc_subset_Ico_right (h₁ : b₁ < b₂) : Icc a b₁ ⊆ Ico a b₂ := fun _ =>
And.imp_right fun h₂ => h₂.trans_lt h₁
theorem Ioo_subset_Ico_self : Ioo a b ⊆ Ico a b := fun _ => And.imp_left le_of_lt
theorem Ioo_subset_Ioc_self : Ioo a b ⊆ Ioc a b := fun _ => And.imp_right le_of_lt
theorem Ico_subset_Icc_self : Ico a b ⊆ Icc a b := fun _ => And.imp_right le_of_lt
theorem Ioc_subset_Icc_self : Ioc a b ⊆ Icc a b := fun _ => And.imp_left le_of_lt
theorem Ioo_subset_Icc_self : Ioo a b ⊆ Icc a b :=
Subset.trans Ioo_subset_Ico_self Ico_subset_Icc_self
theorem Ico_subset_Iio_self : Ico a b ⊆ Iio b := fun _ => And.right
theorem Ioo_subset_Iio_self : Ioo a b ⊆ Iio b := fun _ => And.right
theorem Ioc_subset_Ioi_self : Ioc a b ⊆ Ioi a := fun _ => And.left
theorem Ioo_subset_Ioi_self : Ioo a b ⊆ Ioi a := fun _ => And.left
theorem Ioi_subset_Ici_self : Ioi a ⊆ Ici a := fun _ hx => le_of_lt hx
theorem Iio_subset_Iic_self : Iio a ⊆ Iic a := fun _ hx => le_of_lt hx
theorem Ico_subset_Ici_self : Ico a b ⊆ Ici a := fun _ => And.left
theorem Ioi_ssubset_Ici_self : Ioi a ⊂ Ici a :=
⟨Ioi_subset_Ici_self, fun h => lt_irrefl a (h le_rfl)⟩
theorem Iio_ssubset_Iic_self : Iio a ⊂ Iic a :=
@Ioi_ssubset_Ici_self αᵒᵈ _ _
theorem Icc_subset_Icc_iff (h₁ : a₁ ≤ b₁) : Icc a₁ b₁ ⊆ Icc a₂ b₂ ↔ a₂ ≤ a₁ ∧ b₁ ≤ b₂ :=
⟨fun h => ⟨(h ⟨le_rfl, h₁⟩).1, (h ⟨h₁, le_rfl⟩).2⟩, fun ⟨h, h'⟩ _ ⟨hx, hx'⟩ =>
⟨h.trans hx, hx'.trans h'⟩⟩
theorem Icc_subset_Ioo_iff (h₁ : a₁ ≤ b₁) : Icc a₁ b₁ ⊆ Ioo a₂ b₂ ↔ a₂ < a₁ ∧ b₁ < b₂ :=
⟨fun h => ⟨(h ⟨le_rfl, h₁⟩).1, (h ⟨h₁, le_rfl⟩).2⟩, fun ⟨h, h'⟩ _ ⟨hx, hx'⟩ =>
⟨h.trans_le hx, hx'.trans_lt h'⟩⟩
theorem Icc_subset_Ico_iff (h₁ : a₁ ≤ b₁) : Icc a₁ b₁ ⊆ Ico a₂ b₂ ↔ a₂ ≤ a₁ ∧ b₁ < b₂ :=
⟨fun h => ⟨(h ⟨le_rfl, h₁⟩).1, (h ⟨h₁, le_rfl⟩).2⟩, fun ⟨h, h'⟩ _ ⟨hx, hx'⟩ =>
⟨h.trans hx, hx'.trans_lt h'⟩⟩
theorem Icc_subset_Ioc_iff (h₁ : a₁ ≤ b₁) : Icc a₁ b₁ ⊆ Ioc a₂ b₂ ↔ a₂ < a₁ ∧ b₁ ≤ b₂ :=
⟨fun h => ⟨(h ⟨le_rfl, h₁⟩).1, (h ⟨h₁, le_rfl⟩).2⟩, fun ⟨h, h'⟩ _ ⟨hx, hx'⟩ =>
⟨h.trans_le hx, hx'.trans h'⟩⟩
theorem Icc_subset_Iio_iff (h₁ : a₁ ≤ b₁) : Icc a₁ b₁ ⊆ Iio b₂ ↔ b₁ < b₂ :=
⟨fun h => h ⟨h₁, le_rfl⟩, fun h _ ⟨_, hx'⟩ => hx'.trans_lt h⟩
theorem Icc_subset_Ioi_iff (h₁ : a₁ ≤ b₁) : Icc a₁ b₁ ⊆ Ioi a₂ ↔ a₂ < a₁ :=
⟨fun h => h ⟨le_rfl, h₁⟩, fun h _ ⟨hx, _⟩ => h.trans_le hx⟩
theorem Icc_subset_Iic_iff (h₁ : a₁ ≤ b₁) : Icc a₁ b₁ ⊆ Iic b₂ ↔ b₁ ≤ b₂ :=
⟨fun h => h ⟨h₁, le_rfl⟩, fun h _ ⟨_, hx'⟩ => hx'.trans h⟩
theorem Icc_subset_Ici_iff (h₁ : a₁ ≤ b₁) : Icc a₁ b₁ ⊆ Ici a₂ ↔ a₂ ≤ a₁ :=
⟨fun h => h ⟨le_rfl, h₁⟩, fun h _ ⟨hx, _⟩ => h.trans hx⟩
theorem Icc_ssubset_Icc_left (hI : a₂ ≤ b₂) (ha : a₂ < a₁) (hb : b₁ ≤ b₂) : Icc a₁ b₁ ⊂ Icc a₂ b₂ :=
(ssubset_iff_of_subset (Icc_subset_Icc (le_of_lt ha) hb)).mpr
⟨a₂, left_mem_Icc.mpr hI, not_and.mpr fun f _ => lt_irrefl a₂ (ha.trans_le f)⟩
theorem Icc_ssubset_Icc_right (hI : a₂ ≤ b₂) (ha : a₂ ≤ a₁) (hb : b₁ < b₂) :
Icc a₁ b₁ ⊂ Icc a₂ b₂ :=
(ssubset_iff_of_subset (Icc_subset_Icc ha (le_of_lt hb))).mpr
⟨b₂, right_mem_Icc.mpr hI, fun f => lt_irrefl b₁ (hb.trans_le f.2)⟩
/-- If `a ≤ b`, then `(b, +∞) ⊆ (a, +∞)`. In preorders, this is just an implication. If you need
the equivalence in linear orders, use `Ioi_subset_Ioi_iff`. -/
@[gcongr]
theorem Ioi_subset_Ioi (h : a ≤ b) : Ioi b ⊆ Ioi a := fun _ hx => h.trans_lt hx
/-- If `a < b`, then `(b, +∞) ⊂ (a, +∞)`. In preorders, this is just an implication. If you need
the equivalence in linear orders, use `Ioi_ssubset_Ioi_iff`. -/
@[gcongr]
theorem Ioi_ssubset_Ioi (h : a < b) : Ioi b ⊂ Ioi a :=
(ssubset_iff_of_subset (Ioi_subset_Ioi h.le)).mpr ⟨b, h, lt_irrefl b⟩
/-- If `a ≤ b`, then `(b, +∞) ⊆ [a, +∞)`. In preorders, this is just an implication. If you need
the equivalence in dense linear orders, use `Ioi_subset_Ici_iff`. -/
theorem Ioi_subset_Ici (h : a ≤ b) : Ioi b ⊆ Ici a :=
Subset.trans (Ioi_subset_Ioi h) Ioi_subset_Ici_self
/-- If `a ≤ b`, then `(-∞, a) ⊆ (-∞, b)`. In preorders, this is just an implication. If you need
the equivalence in linear orders, use `Iio_subset_Iio_iff`. -/
@[gcongr]
theorem Iio_subset_Iio (h : a ≤ b) : Iio a ⊆ Iio b := fun _ hx => lt_of_lt_of_le hx h
/-- If `a < b`, then `(-∞, a) ⊂ (-∞, b)`. In preorders, this is just an implication. If you need
the equivalence in linear orders, use `Iio_ssubset_Iio_iff`. -/
@[gcongr]
theorem Iio_ssubset_Iio (h : a < b) : Iio a ⊂ Iio b :=
(ssubset_iff_of_subset (Iio_subset_Iio h.le)).mpr ⟨a, h, lt_irrefl a⟩
/-- If `a ≤ b`, then `(-∞, a) ⊆ (-∞, b]`. In preorders, this is just an implication. If you need
the equivalence in dense linear orders, use `Iio_subset_Iic_iff`. -/
theorem Iio_subset_Iic (h : a ≤ b) : Iio a ⊆ Iic b :=
Subset.trans (Iio_subset_Iio h) Iio_subset_Iic_self
theorem Ici_inter_Iic : Ici a ∩ Iic b = Icc a b :=
rfl
theorem Ici_inter_Iio : Ici a ∩ Iio b = Ico a b :=
rfl
theorem Ioi_inter_Iic : Ioi a ∩ Iic b = Ioc a b :=
rfl
theorem Ioi_inter_Iio : Ioi a ∩ Iio b = Ioo a b :=
rfl
theorem Iic_inter_Ici : Iic a ∩ Ici b = Icc b a :=
inter_comm _ _
theorem Iio_inter_Ici : Iio a ∩ Ici b = Ico b a :=
inter_comm _ _
theorem Iic_inter_Ioi : Iic a ∩ Ioi b = Ioc b a :=
inter_comm _ _
theorem Iio_inter_Ioi : Iio a ∩ Ioi b = Ioo b a :=
inter_comm _ _
theorem mem_Icc_of_Ioo (h : x ∈ Ioo a b) : x ∈ Icc a b :=
Ioo_subset_Icc_self h
theorem mem_Ico_of_Ioo (h : x ∈ Ioo a b) : x ∈ Ico a b :=
Ioo_subset_Ico_self h
theorem mem_Ioc_of_Ioo (h : x ∈ Ioo a b) : x ∈ Ioc a b :=
Ioo_subset_Ioc_self h
theorem mem_Icc_of_Ico (h : x ∈ Ico a b) : x ∈ Icc a b :=
Ico_subset_Icc_self h
theorem mem_Icc_of_Ioc (h : x ∈ Ioc a b) : x ∈ Icc a b :=
Ioc_subset_Icc_self h
theorem mem_Ici_of_Ioi (h : x ∈ Ioi a) : x ∈ Ici a :=
Ioi_subset_Ici_self h
theorem mem_Iic_of_Iio (h : x ∈ Iio a) : x ∈ Iic a :=
Iio_subset_Iic_self h
theorem Icc_eq_empty_iff : Icc a b = ∅ ↔ ¬a ≤ b := by
rw [← not_nonempty_iff_eq_empty, not_iff_not, nonempty_Icc]
theorem Ico_eq_empty_iff : Ico a b = ∅ ↔ ¬a < b := by
rw [← not_nonempty_iff_eq_empty, not_iff_not, nonempty_Ico]
theorem Ioc_eq_empty_iff : Ioc a b = ∅ ↔ ¬a < b := by
rw [← not_nonempty_iff_eq_empty, not_iff_not, nonempty_Ioc]
theorem Ioo_eq_empty_iff [DenselyOrdered α] : Ioo a b = ∅ ↔ ¬a < b := by
rw [← not_nonempty_iff_eq_empty, not_iff_not, nonempty_Ioo]
theorem _root_.IsTop.Iic_eq (h : IsTop a) : Iic a = univ :=
eq_univ_of_forall h
theorem _root_.IsBot.Ici_eq (h : IsBot a) : Ici a = univ :=
eq_univ_of_forall h
@[simp] theorem Ioi_eq_empty_iff : Ioi a = ∅ ↔ IsMax a := by
simp only [isMax_iff_forall_not_lt, eq_empty_iff_forall_not_mem, mem_Ioi]
@[simp] theorem Iio_eq_empty_iff : Iio a = ∅ ↔ IsMin a := Ioi_eq_empty_iff (α := αᵒᵈ)
@[simp] alias ⟨_, _root_.IsMax.Ioi_eq⟩ := Ioi_eq_empty_iff
@[simp] alias ⟨_, _root_.IsMin.Iio_eq⟩ := Iio_eq_empty_iff
@[simp] lemma Iio_nonempty : (Iio a).Nonempty ↔ ¬ IsMin a := by simp [nonempty_iff_ne_empty]
@[simp] lemma Ioi_nonempty : (Ioi a).Nonempty ↔ ¬ IsMax a := by simp [nonempty_iff_ne_empty]
theorem Iic_inter_Ioc_of_le (h : a ≤ c) : Iic a ∩ Ioc b c = Ioc b a :=
ext fun _ => ⟨fun H => ⟨H.2.1, H.1⟩, fun H => ⟨H.2, H.1, H.2.trans h⟩⟩
theorem not_mem_Icc_of_lt (ha : c < a) : c ∉ Icc a b := fun h => ha.not_le h.1
theorem not_mem_Icc_of_gt (hb : b < c) : c ∉ Icc a b := fun h => hb.not_le h.2
theorem not_mem_Ico_of_lt (ha : c < a) : c ∉ Ico a b := fun h => ha.not_le h.1
theorem not_mem_Ioc_of_gt (hb : b < c) : c ∉ Ioc a b := fun h => hb.not_le h.2
theorem not_mem_Ioi_self : a ∉ Ioi a := lt_irrefl _
theorem not_mem_Iio_self : b ∉ Iio b := lt_irrefl _
theorem not_mem_Ioc_of_le (ha : c ≤ a) : c ∉ Ioc a b := fun h => lt_irrefl _ <| h.1.trans_le ha
theorem not_mem_Ico_of_ge (hb : b ≤ c) : c ∉ Ico a b := fun h => lt_irrefl _ <| h.2.trans_le hb
theorem not_mem_Ioo_of_le (ha : c ≤ a) : c ∉ Ioo a b := fun h => lt_irrefl _ <| h.1.trans_le ha
theorem not_mem_Ioo_of_ge (hb : b ≤ c) : c ∉ Ioo a b := fun h => lt_irrefl _ <| h.2.trans_le hb
section matched_intervals
@[simp] theorem Icc_eq_Ioc_same_iff : Icc a b = Ioc a b ↔ ¬a ≤ b where
mp h := by simpa using Set.ext_iff.mp h a
mpr h := by rw [Icc_eq_empty h, Ioc_eq_empty (mt le_of_lt h)]
@[simp] theorem Icc_eq_Ico_same_iff : Icc a b = Ico a b ↔ ¬a ≤ b where
mp h := by simpa using Set.ext_iff.mp h b
mpr h := by rw [Icc_eq_empty h, Ico_eq_empty (mt le_of_lt h)]
@[simp] theorem Icc_eq_Ioo_same_iff : Icc a b = Ioo a b ↔ ¬a ≤ b where
mp h := by simpa using Set.ext_iff.mp h b
mpr h := by rw [Icc_eq_empty h, Ioo_eq_empty (mt le_of_lt h)]
@[simp] theorem Ioc_eq_Ico_same_iff : Ioc a b = Ico a b ↔ ¬a < b where
mp h := by simpa using Set.ext_iff.mp h a
mpr h := by rw [Ioc_eq_empty h, Ico_eq_empty h]
@[simp] theorem Ioo_eq_Ioc_same_iff : Ioo a b = Ioc a b ↔ ¬a < b where
mp h := by simpa using Set.ext_iff.mp h b
mpr h := by rw [Ioo_eq_empty h, Ioc_eq_empty h]
@[simp] theorem Ioo_eq_Ico_same_iff : Ioo a b = Ico a b ↔ ¬a < b where
mp h := by simpa using Set.ext_iff.mp h a
mpr h := by rw [Ioo_eq_empty h, Ico_eq_empty h]
-- Mirrored versions of the above for `simp`.
@[simp] theorem Ioc_eq_Icc_same_iff : Ioc a b = Icc a b ↔ ¬a ≤ b :=
eq_comm.trans Icc_eq_Ioc_same_iff
@[simp] theorem Ico_eq_Icc_same_iff : Ico a b = Icc a b ↔ ¬a ≤ b :=
eq_comm.trans Icc_eq_Ico_same_iff
@[simp] theorem Ioo_eq_Icc_same_iff : Ioo a b = Icc a b ↔ ¬a ≤ b :=
eq_comm.trans Icc_eq_Ioo_same_iff
@[simp] theorem Ico_eq_Ioc_same_iff : Ico a b = Ioc a b ↔ ¬a < b :=
eq_comm.trans Ioc_eq_Ico_same_iff
@[simp] theorem Ioc_eq_Ioo_same_iff : Ioc a b = Ioo a b ↔ ¬a < b :=
eq_comm.trans Ioo_eq_Ioc_same_iff
@[simp] theorem Ico_eq_Ioo_same_iff : Ico a b = Ioo a b ↔ ¬a < b :=
eq_comm.trans Ioo_eq_Ico_same_iff
end matched_intervals
end Preorder
section PartialOrder
variable [PartialOrder α] {a b c : α}
@[simp]
theorem Icc_self (a : α) : Icc a a = {a} :=
Set.ext <| by simp [Icc, le_antisymm_iff, and_comm]
instance instIccUnique : Unique (Set.Icc a a) where
default := ⟨a, by simp⟩
uniq y := Subtype.ext <| by simpa using y.2
@[simp]
theorem Icc_eq_singleton_iff : Icc a b = {c} ↔ a = c ∧ b = c := by
refine ⟨fun h => ?_, ?_⟩
· have hab : a ≤ b := nonempty_Icc.1 (h.symm.subst <| singleton_nonempty c)
exact
⟨eq_of_mem_singleton <| h ▸ left_mem_Icc.2 hab,
eq_of_mem_singleton <| h ▸ right_mem_Icc.2 hab⟩
· rintro ⟨rfl, rfl⟩
exact Icc_self _
lemma subsingleton_Icc_of_ge (hba : b ≤ a) : Set.Subsingleton (Icc a b) :=
fun _x ⟨hax, hxb⟩ _y ⟨hay, hyb⟩ ↦ le_antisymm
(le_implies_le_of_le_of_le hxb hay hba) (le_implies_le_of_le_of_le hyb hax hba)
@[simp] lemma subsingleton_Icc_iff {α : Type*} [LinearOrder α] {a b : α} :
Set.Subsingleton (Icc a b) ↔ b ≤ a := by
refine ⟨fun h ↦ ?_, subsingleton_Icc_of_ge⟩
contrapose! h
simp only [gt_iff_lt, not_subsingleton_iff]
exact ⟨a, ⟨le_refl _, h.le⟩, b, ⟨h.le, le_refl _⟩, h.ne⟩
@[simp]
theorem Icc_diff_left : Icc a b \ {a} = Ioc a b :=
ext fun x => by simp [lt_iff_le_and_ne, eq_comm, and_right_comm]
@[simp]
theorem Icc_diff_right : Icc a b \ {b} = Ico a b :=
ext fun x => by simp [lt_iff_le_and_ne, and_assoc]
@[simp]
theorem Ico_diff_left : Ico a b \ {a} = Ioo a b :=
ext fun x => by simp [and_right_comm, ← lt_iff_le_and_ne, eq_comm]
@[simp]
theorem Ioc_diff_right : Ioc a b \ {b} = Ioo a b :=
ext fun x => by simp [and_assoc, ← lt_iff_le_and_ne]
@[simp]
theorem Icc_diff_both : Icc a b \ {a, b} = Ioo a b := by
rw [insert_eq, ← diff_diff, Icc_diff_left, Ioc_diff_right]
@[simp]
theorem Ici_diff_left : Ici a \ {a} = Ioi a :=
ext fun x => by simp [lt_iff_le_and_ne, eq_comm]
@[simp]
theorem Iic_diff_right : Iic a \ {a} = Iio a :=
ext fun x => by simp [lt_iff_le_and_ne]
@[simp]
theorem Ico_diff_Ioo_same (h : a < b) : Ico a b \ Ioo a b = {a} := by
rw [← Ico_diff_left, diff_diff_cancel_left (singleton_subset_iff.2 <| left_mem_Ico.2 h)]
@[simp]
theorem Ioc_diff_Ioo_same (h : a < b) : Ioc a b \ Ioo a b = {b} := by
rw [← Ioc_diff_right, diff_diff_cancel_left (singleton_subset_iff.2 <| right_mem_Ioc.2 h)]
@[simp]
theorem Icc_diff_Ico_same (h : a ≤ b) : Icc a b \ Ico a b = {b} := by
rw [← Icc_diff_right, diff_diff_cancel_left (singleton_subset_iff.2 <| right_mem_Icc.2 h)]
@[simp]
theorem Icc_diff_Ioc_same (h : a ≤ b) : Icc a b \ Ioc a b = {a} := by
rw [← Icc_diff_left, diff_diff_cancel_left (singleton_subset_iff.2 <| left_mem_Icc.2 h)]
@[simp]
theorem Icc_diff_Ioo_same (h : a ≤ b) : Icc a b \ Ioo a b = {a, b} := by
rw [← Icc_diff_both, diff_diff_cancel_left]
simp [insert_subset_iff, h]
@[simp]
theorem Ici_diff_Ioi_same : Ici a \ Ioi a = {a} := by
rw [← Ici_diff_left, diff_diff_cancel_left (singleton_subset_iff.2 left_mem_Ici)]
@[simp]
theorem Iic_diff_Iio_same : Iic a \ Iio a = {a} := by
rw [← Iic_diff_right, diff_diff_cancel_left (singleton_subset_iff.2 right_mem_Iic)]
theorem Ioi_union_left : Ioi a ∪ {a} = Ici a :=
ext fun x => by simp [eq_comm, le_iff_eq_or_lt]
theorem Iio_union_right : Iio a ∪ {a} = Iic a :=
ext fun _ => le_iff_lt_or_eq.symm
theorem Ioo_union_left (hab : a < b) : Ioo a b ∪ {a} = Ico a b := by
rw [← Ico_diff_left, diff_union_self,
union_eq_self_of_subset_right (singleton_subset_iff.2 <| left_mem_Ico.2 hab)]
theorem Ioo_union_right (hab : a < b) : Ioo a b ∪ {b} = Ioc a b := by
simpa only [Ioo_toDual, Ico_toDual] using Ioo_union_left hab.dual
theorem Ioo_union_both (h : a ≤ b) : Ioo a b ∪ {a, b} = Icc a b := by
have : (Icc a b \ {a, b}) ∪ {a, b} = Icc a b := diff_union_of_subset fun
| x, .inl rfl => left_mem_Icc.mpr h
| x, .inr rfl => right_mem_Icc.mpr h
rw [← this, Icc_diff_both]
theorem Ioc_union_left (hab : a ≤ b) : Ioc a b ∪ {a} = Icc a b := by
rw [← Icc_diff_left, diff_union_self,
union_eq_self_of_subset_right (singleton_subset_iff.2 <| left_mem_Icc.2 hab)]
theorem Ico_union_right (hab : a ≤ b) : Ico a b ∪ {b} = Icc a b := by
simpa only [Ioc_toDual, Icc_toDual] using Ioc_union_left hab.dual
@[simp]
theorem Ico_insert_right (h : a ≤ b) : insert b (Ico a b) = Icc a b := by
rw [insert_eq, union_comm, Ico_union_right h]
@[simp]
theorem Ioc_insert_left (h : a ≤ b) : insert a (Ioc a b) = Icc a b := by
rw [insert_eq, union_comm, Ioc_union_left h]
@[simp]
theorem Ioo_insert_left (h : a < b) : insert a (Ioo a b) = Ico a b := by
rw [insert_eq, union_comm, Ioo_union_left h]
@[simp]
theorem Ioo_insert_right (h : a < b) : insert b (Ioo a b) = Ioc a b := by
rw [insert_eq, union_comm, Ioo_union_right h]
@[simp]
theorem Iio_insert : insert a (Iio a) = Iic a :=
ext fun _ => le_iff_eq_or_lt.symm
@[simp]
theorem Ioi_insert : insert a (Ioi a) = Ici a :=
ext fun _ => (or_congr_left eq_comm).trans le_iff_eq_or_lt.symm
theorem mem_Ici_Ioi_of_subset_of_subset {s : Set α} (ho : Ioi a ⊆ s) (hc : s ⊆ Ici a) :
s ∈ ({Ici a, Ioi a} : Set (Set α)) :=
by_cases
(fun h : a ∈ s =>
Or.inl <| Subset.antisymm hc <| by rw [← Ioi_union_left, union_subset_iff]; simp [*])
fun h =>
Or.inr <| Subset.antisymm (fun _ hx => lt_of_le_of_ne (hc hx) fun heq => h <| heq.symm ▸ hx) ho
theorem mem_Iic_Iio_of_subset_of_subset {s : Set α} (ho : Iio a ⊆ s) (hc : s ⊆ Iic a) :
s ∈ ({Iic a, Iio a} : Set (Set α)) :=
@mem_Ici_Ioi_of_subset_of_subset αᵒᵈ _ a s ho hc
theorem mem_Icc_Ico_Ioc_Ioo_of_subset_of_subset {s : Set α} (ho : Ioo a b ⊆ s) (hc : s ⊆ Icc a b) :
s ∈ ({Icc a b, Ico a b, Ioc a b, Ioo a b} : Set (Set α)) := by
classical
by_cases ha : a ∈ s <;> by_cases hb : b ∈ s
· refine Or.inl (Subset.antisymm hc ?_)
rwa [← Ico_diff_left, diff_singleton_subset_iff, insert_eq_of_mem ha, ← Icc_diff_right,
diff_singleton_subset_iff, insert_eq_of_mem hb] at ho
· refine Or.inr <| Or.inl <| Subset.antisymm ?_ ?_
· rw [← Icc_diff_right]
exact subset_diff_singleton hc hb
· rwa [← Ico_diff_left, diff_singleton_subset_iff, insert_eq_of_mem ha] at ho
· refine Or.inr <| Or.inr <| Or.inl <| Subset.antisymm ?_ ?_
· rw [← Icc_diff_left]
exact subset_diff_singleton hc ha
· rwa [← Ioc_diff_right, diff_singleton_subset_iff, insert_eq_of_mem hb] at ho
· refine Or.inr <| Or.inr <| Or.inr <| Subset.antisymm ?_ ho
rw [← Ico_diff_left, ← Icc_diff_right]
apply_rules [subset_diff_singleton]
theorem eq_left_or_mem_Ioo_of_mem_Ico {x : α} (hmem : x ∈ Ico a b) : x = a ∨ x ∈ Ioo a b :=
hmem.1.eq_or_gt.imp_right fun h => ⟨h, hmem.2⟩
theorem eq_right_or_mem_Ioo_of_mem_Ioc {x : α} (hmem : x ∈ Ioc a b) : x = b ∨ x ∈ Ioo a b :=
hmem.2.eq_or_lt.imp_right <| And.intro hmem.1
theorem eq_endpoints_or_mem_Ioo_of_mem_Icc {x : α} (hmem : x ∈ Icc a b) :
x = a ∨ x = b ∨ x ∈ Ioo a b :=
hmem.1.eq_or_gt.imp_right fun h => eq_right_or_mem_Ioo_of_mem_Ioc ⟨h, hmem.2⟩
theorem _root_.IsMax.Ici_eq (h : IsMax a) : Ici a = {a} :=
eq_singleton_iff_unique_mem.2 ⟨left_mem_Ici, fun _ => h.eq_of_ge⟩
theorem _root_.IsMin.Iic_eq (h : IsMin a) : Iic a = {a} :=
h.toDual.Ici_eq
theorem Ici_injective : Injective (Ici : α → Set α) := fun _ _ =>
eq_of_forall_ge_iff ∘ Set.ext_iff.1
theorem Iic_injective : Injective (Iic : α → Set α) := fun _ _ =>
eq_of_forall_le_iff ∘ Set.ext_iff.1
theorem Ici_inj : Ici a = Ici b ↔ a = b :=
Ici_injective.eq_iff
theorem Iic_inj : Iic a = Iic b ↔ a = b :=
Iic_injective.eq_iff
@[simp]
theorem Icc_inter_Icc_eq_singleton (hab : a ≤ b) (hbc : b ≤ c) : Icc a b ∩ Icc b c = {b} := by
rw [← Ici_inter_Iic, ← Iic_inter_Ici, inter_inter_inter_comm, Iic_inter_Ici]
simp [hab, hbc]
lemma Icc_eq_Icc_iff {d : α} (h : a ≤ b) :
Icc a b = Icc c d ↔ a = c ∧ b = d := by
refine ⟨fun heq ↦ ?_, by rintro ⟨rfl, rfl⟩; rfl⟩
have h' : c ≤ d := by
by_contra contra; rw [Icc_eq_empty_iff.mpr contra, Icc_eq_empty_iff] at heq; contradiction
simp only [Set.ext_iff, mem_Icc] at heq
obtain ⟨-, h₁⟩ := (heq b).mp ⟨h, le_refl _⟩
obtain ⟨h₂, -⟩ := (heq a).mp ⟨le_refl _, h⟩
obtain ⟨h₃, -⟩ := (heq c).mpr ⟨le_refl _, h'⟩
obtain ⟨-, h₄⟩ := (heq d).mpr ⟨h', le_refl _⟩
exact ⟨le_antisymm h₃ h₂, le_antisymm h₁ h₄⟩
end PartialOrder
section OrderTop
@[simp]
theorem Ici_top [PartialOrder α] [OrderTop α] : Ici (⊤ : α) = {⊤} :=
isMax_top.Ici_eq
variable [Preorder α] [OrderTop α] {a : α}
theorem Ioi_top : Ioi (⊤ : α) = ∅ :=
isMax_top.Ioi_eq
@[simp]
theorem Iic_top : Iic (⊤ : α) = univ :=
isTop_top.Iic_eq
@[simp]
theorem Icc_top : Icc a ⊤ = Ici a := by simp [← Ici_inter_Iic]
@[simp]
theorem Ioc_top : Ioc a ⊤ = Ioi a := by simp [← Ioi_inter_Iic]
end OrderTop
section OrderBot
@[simp]
theorem Iic_bot [PartialOrder α] [OrderBot α] : Iic (⊥ : α) = {⊥} :=
isMin_bot.Iic_eq
variable [Preorder α] [OrderBot α] {a : α}
theorem Iio_bot : Iio (⊥ : α) = ∅ :=
isMin_bot.Iio_eq
@[simp]
theorem Ici_bot : Ici (⊥ : α) = univ :=
isBot_bot.Ici_eq
@[simp]
theorem Icc_bot : Icc ⊥ a = Iic a := by simp [← Ici_inter_Iic]
@[simp]
theorem Ico_bot : Ico ⊥ a = Iio a := by simp [← Ici_inter_Iio]
end OrderBot
theorem Icc_bot_top [Preorder α] [BoundedOrder α] : Icc (⊥ : α) ⊤ = univ := by simp
section Lattice
section Inf
variable [SemilatticeInf α]
@[simp]
theorem Iic_inter_Iic {a b : α} : Iic a ∩ Iic b = Iic (a ⊓ b) := by
ext x
simp [Iic]
@[simp]
theorem Ioc_inter_Iic (a b c : α) : Ioc a b ∩ Iic c = Ioc a (b ⊓ c) := by
rw [← Ioi_inter_Iic, ← Ioi_inter_Iic, inter_assoc, Iic_inter_Iic]
end Inf
section Sup
variable [SemilatticeSup α]
@[simp]
theorem Ici_inter_Ici {a b : α} : Ici a ∩ Ici b = Ici (a ⊔ b) := by
ext x
simp [Ici]
@[simp]
theorem Ico_inter_Ici (a b c : α) : Ico a b ∩ Ici c = Ico (a ⊔ c) b := by
rw [← Ici_inter_Iio, ← Ici_inter_Iio, ← Ici_inter_Ici, inter_right_comm]
end Sup
section Both
variable [Lattice α] {a b c a₁ a₂ b₁ b₂ : α}
theorem Icc_inter_Icc : Icc a₁ b₁ ∩ Icc a₂ b₂ = Icc (a₁ ⊔ a₂) (b₁ ⊓ b₂) := by
simp only [Ici_inter_Iic.symm, Ici_inter_Ici.symm, Iic_inter_Iic.symm]; ac_rfl
end Both
end Lattice
/-! ### Closed intervals in `α × β` -/
section Prod
variable {β : Type*} [Preorder α] [Preorder β]
@[simp]
theorem Iic_prod_Iic (a : α) (b : β) : Iic a ×ˢ Iic b = Iic (a, b) :=
rfl
@[simp]
theorem Ici_prod_Ici (a : α) (b : β) : Ici a ×ˢ Ici b = Ici (a, b) :=
rfl
theorem Ici_prod_eq (a : α × β) : Ici a = Ici a.1 ×ˢ Ici a.2 :=
rfl
theorem Iic_prod_eq (a : α × β) : Iic a = Iic a.1 ×ˢ Iic a.2 :=
rfl
@[simp]
theorem Icc_prod_Icc (a₁ a₂ : α) (b₁ b₂ : β) : Icc a₁ a₂ ×ˢ Icc b₁ b₂ = Icc (a₁, b₁) (a₂, b₂) := by
ext ⟨x, y⟩
simp [and_assoc, and_comm, and_left_comm]
theorem Icc_prod_eq (a b : α × β) : Icc a b = Icc a.1 b.1 ×ˢ Icc a.2 b.2 := by simp
end Prod
end Set
/-! ### Lemmas about intervals in dense orders -/
section Dense
variable (α) [Preorder α] [DenselyOrdered α] {x y : α}
instance : NoMinOrder (Set.Ioo x y) :=
⟨fun ⟨a, ha₁, ha₂⟩ => by
rcases exists_between ha₁ with ⟨b, hb₁, hb₂⟩
exact ⟨⟨b, hb₁, hb₂.trans ha₂⟩, hb₂⟩⟩
instance : NoMinOrder (Set.Ioc x y) :=
⟨fun ⟨a, ha₁, ha₂⟩ => by
rcases exists_between ha₁ with ⟨b, hb₁, hb₂⟩
exact ⟨⟨b, hb₁, hb₂.le.trans ha₂⟩, hb₂⟩⟩
instance : NoMinOrder (Set.Ioi x) :=
⟨fun ⟨a, ha⟩ => by
rcases exists_between ha with ⟨b, hb₁, hb₂⟩
exact ⟨⟨b, hb₁⟩, hb₂⟩⟩
instance : NoMaxOrder (Set.Ioo x y) :=
⟨fun ⟨a, ha₁, ha₂⟩ => by
rcases exists_between ha₂ with ⟨b, hb₁, hb₂⟩
exact ⟨⟨b, ha₁.trans hb₁, hb₂⟩, hb₁⟩⟩
instance : NoMaxOrder (Set.Ico x y) :=
⟨fun ⟨a, ha₁, ha₂⟩ => by
rcases exists_between ha₂ with ⟨b, hb₁, hb₂⟩
exact ⟨⟨b, ha₁.trans hb₁.le, hb₂⟩, hb₁⟩⟩
instance : NoMaxOrder (Set.Iio x) :=
⟨fun ⟨a, ha⟩ => by
rcases exists_between ha with ⟨b, hb₁, hb₂⟩
exact ⟨⟨b, hb₂⟩, hb₁⟩⟩
end Dense
/-! ### Intervals in `Prop` -/
namespace Set
@[simp] lemma Iic_False : Iic False = {False} := by aesop
@[simp] lemma Iic_True : Iic True = univ := by aesop
@[simp] lemma Ici_False : Ici False = univ := by aesop
@[simp] lemma Ici_True : Ici True = {True} := by aesop
lemma Iio_False : Iio False = ∅ := by aesop
@[simp] lemma Iio_True : Iio True = {False} := by aesop (add simp [Ioi, lt_iff_le_not_le])
@[simp] lemma Ioi_False : Ioi False = {True} := by aesop (add simp [Ioi, lt_iff_le_not_le])
lemma Ioi_True : Ioi True = ∅ := by aesop
end Set
| Mathlib/Order/Interval/Set/Basic.lean | 1,293 | 1,297 | |
/-
Copyright (c) 2023 Kalle Kytölä. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kalle Kytölä
-/
import Mathlib.MeasureTheory.Measure.Portmanteau
import Mathlib.MeasureTheory.Integral.DominatedConvergence
import Mathlib.MeasureTheory.Integral.Layercake
import Mathlib.MeasureTheory.Integral.BoundedContinuousFunction
/-!
# The Lévy-Prokhorov distance on spaces of finite measures and probability measures
## Main definitions
* `MeasureTheory.levyProkhorovEDist`: The Lévy-Prokhorov edistance between two measures.
* `MeasureTheory.levyProkhorovDist`: The Lévy-Prokhorov distance between two finite measures.
## Main results
* `levyProkhorovDist_pseudoMetricSpace_finiteMeasure`: The Lévy-Prokhorov distance is a
pseudoemetric on the space of finite measures.
* `levyProkhorovDist_pseudoMetricSpace_probabilityMeasure`: The Lévy-Prokhorov distance is a
pseudoemetric on the space of probability measures.
* `levyProkhorov_le_convergenceInDistribution`: The topology of the Lévy-Prokhorov metric on
probability measures is always at least as fine as the topology of convergence in distribution.
* `levyProkhorov_eq_convergenceInDistribution`: The topology of the Lévy-Prokhorov metric on
probability measures on a separable space coincides with the topology of convergence in
distribution, and in particular convergence in distribution is then pseudometrizable.
## Tags
finite measure, probability measure, weak convergence, convergence in distribution, metrizability
-/
open Topology Metric Filter Set ENNReal NNReal
namespace MeasureTheory
open scoped Topology ENNReal NNReal BoundedContinuousFunction
section Levy_Prokhorov
/-! ### Lévy-Prokhorov metric -/
variable {Ω : Type*} [MeasurableSpace Ω] [PseudoEMetricSpace Ω]
/-- The Lévy-Prokhorov edistance between measures:
`d(μ,ν) = inf {r ≥ 0 | ∀ B, μ B ≤ ν Bᵣ + r ∧ ν B ≤ μ Bᵣ + r}`. -/
noncomputable def levyProkhorovEDist (μ ν : Measure Ω) : ℝ≥0∞ :=
sInf {ε | ∀ B, MeasurableSet B →
μ B ≤ ν (thickening ε.toReal B) + ε ∧ ν B ≤ μ (thickening ε.toReal B) + ε}
/- This result is not placed in earlier more generic files, since it is rather specialized;
it mixes measure and metric in a very particular way. -/
lemma meas_le_of_le_of_forall_le_meas_thickening_add {ε₁ ε₂ : ℝ≥0∞} (μ ν : Measure Ω)
(h_le : ε₁ ≤ ε₂) {B : Set Ω} (hε₁ : μ B ≤ ν (thickening ε₁.toReal B) + ε₁) :
μ B ≤ ν (thickening ε₂.toReal B) + ε₂ := by
by_cases ε_top : ε₂ = ∞
· simp only [ne_eq, FiniteMeasure.ennreal_coeFn_eq_coeFn_toMeasure, ε_top, toReal_top,
add_top, le_top]
apply hε₁.trans (add_le_add ?_ h_le)
exact measure_mono (μ := ν) (thickening_mono (toReal_mono ε_top h_le) B)
lemma left_measure_le_of_levyProkhorovEDist_lt {μ ν : Measure Ω} {c : ℝ≥0∞}
(h : levyProkhorovEDist μ ν < c) {B : Set Ω} (B_mble : MeasurableSet B) :
μ B ≤ ν (thickening c.toReal B) + c := by
obtain ⟨c', ⟨hc', lt_c⟩⟩ := sInf_lt_iff.mp h
exact meas_le_of_le_of_forall_le_meas_thickening_add μ ν lt_c.le (hc' B B_mble).1
lemma right_measure_le_of_levyProkhorovEDist_lt {μ ν : Measure Ω} {c : ℝ≥0∞}
(h : levyProkhorovEDist μ ν < c) {B : Set Ω} (B_mble : MeasurableSet B) :
ν B ≤ μ (thickening c.toReal B) + c := by
obtain ⟨c', ⟨hc', lt_c⟩⟩ := sInf_lt_iff.mp h
exact meas_le_of_le_of_forall_le_meas_thickening_add ν μ lt_c.le (hc' B B_mble).2
/-- A general sufficient condition for bounding `levyProkhorovEDist` from above. -/
lemma levyProkhorovEDist_le_of_forall_add_pos_le (μ ν : Measure Ω) (δ : ℝ≥0∞)
(h : ∀ ε B, 0 < ε → ε < ∞ → MeasurableSet B →
μ B ≤ ν (thickening (δ + ε).toReal B) + δ + ε ∧
ν B ≤ μ (thickening (δ + ε).toReal B) + δ + ε) :
levyProkhorovEDist μ ν ≤ δ := by
apply ENNReal.le_of_forall_pos_le_add
intro ε hε _
by_cases ε_top : ε = ∞
· simp only [ε_top, add_top, le_top]
apply sInf_le
intro B B_mble
simpa only [add_assoc] using h ε B (coe_pos.mpr hε) coe_lt_top B_mble
/-- A simple general sufficient condition for bounding `levyProkhorovEDist` from above. -/
lemma levyProkhorovEDist_le_of_forall (μ ν : Measure Ω) (δ : ℝ≥0∞)
(h : ∀ ε B, δ < ε → ε < ∞ → MeasurableSet B →
μ B ≤ ν (thickening ε.toReal B) + ε ∧ ν B ≤ μ (thickening ε.toReal B) + ε) :
levyProkhorovEDist μ ν ≤ δ := by
by_cases δ_top : δ = ∞
· simp only [δ_top, add_top, le_top]
apply levyProkhorovEDist_le_of_forall_add_pos_le
intro x B x_pos x_lt_top B_mble
simpa only [← add_assoc] using h (δ + x) B (ENNReal.lt_add_right δ_top x_pos.ne.symm)
(by simp only [add_lt_top, Ne.lt_top δ_top, x_lt_top, and_self]) B_mble
lemma levyProkhorovEDist_le_max_measure_univ (μ ν : Measure Ω) :
levyProkhorovEDist μ ν ≤ max (μ univ) (ν univ) := by
refine sInf_le fun B _ ↦ ⟨?_, ?_⟩ <;> apply le_add_left <;> simp [measure_mono]
lemma levyProkhorovEDist_lt_top (μ ν : Measure Ω) [IsFiniteMeasure μ] [IsFiniteMeasure ν] :
levyProkhorovEDist μ ν < ∞ :=
(levyProkhorovEDist_le_max_measure_univ μ ν).trans_lt <| by simp [measure_lt_top]
lemma levyProkhorovEDist_ne_top (μ ν : Measure Ω) [IsFiniteMeasure μ] [IsFiniteMeasure ν] :
levyProkhorovEDist μ ν ≠ ∞ := (levyProkhorovEDist_lt_top μ ν).ne
lemma levyProkhorovEDist_self (μ : Measure Ω) :
levyProkhorovEDist μ μ = 0 := by
rw [← nonpos_iff_eq_zero, ← csInf_Ioo zero_lt_top]
refine sInf_le_sInf fun ε ⟨hε₀, hε_top⟩ B _ ↦ and_self_iff.2 ?_
refine le_add_right <| measure_mono <| self_subset_thickening ?_ _
exact ENNReal.toReal_pos hε₀.ne' hε_top.ne
lemma levyProkhorovEDist_comm (μ ν : Measure Ω) :
levyProkhorovEDist μ ν = levyProkhorovEDist ν μ := by
simp only [levyProkhorovEDist, and_comm]
lemma levyProkhorovEDist_triangle [OpensMeasurableSpace Ω] (μ ν κ : Measure Ω) :
levyProkhorovEDist μ κ ≤ levyProkhorovEDist μ ν + levyProkhorovEDist ν κ := by
by_cases LPμν_finite : levyProkhorovEDist μ ν = ∞
· simp [LPμν_finite]
by_cases LPνκ_finite : levyProkhorovEDist ν κ = ∞
· simp [LPνκ_finite]
apply levyProkhorovEDist_le_of_forall_add_pos_le
intro ε B ε_pos ε_lt_top B_mble
have half_ε_pos : 0 < ε / 2 := ENNReal.div_pos ε_pos.ne' ofNat_ne_top
have half_ε_lt_top : ε / 2 < ∞ := ENNReal.div_lt_top ε_lt_top.ne two_ne_zero
let r := levyProkhorovEDist μ ν + ε / 2
let s := levyProkhorovEDist ν κ + ε / 2
have lt_r : levyProkhorovEDist μ ν < r := lt_add_right LPμν_finite half_ε_pos.ne'
have lt_s : levyProkhorovEDist ν κ < s := lt_add_right LPνκ_finite half_ε_pos.ne'
have hs_add_r : s + r = levyProkhorovEDist μ ν + levyProkhorovEDist ν κ + ε := by
simp_rw [s, r, add_assoc, add_comm (ε / 2), add_assoc, ENNReal.add_halves, ← add_assoc,
add_comm (levyProkhorovEDist μ ν)]
have hs_add_r' : s.toReal + r.toReal
= (levyProkhorovEDist μ ν + levyProkhorovEDist ν κ + ε).toReal := by
rw [← hs_add_r, ← ENNReal.toReal_add]
· exact ENNReal.add_ne_top.mpr ⟨LPνκ_finite, half_ε_lt_top.ne⟩
· exact ENNReal.add_ne_top.mpr ⟨LPμν_finite, half_ε_lt_top.ne⟩
rw [← hs_add_r', add_assoc, ← hs_add_r, add_assoc _ _ ε, ← hs_add_r]
refine ⟨?_, ?_⟩
· calc μ B ≤ ν (thickening r.toReal B) + r :=
left_measure_le_of_levyProkhorovEDist_lt lt_r B_mble
_ ≤ κ (thickening s.toReal (thickening r.toReal B)) + s + r :=
add_le_add_right
(left_measure_le_of_levyProkhorovEDist_lt lt_s isOpen_thickening.measurableSet) _
_ = κ (thickening s.toReal (thickening r.toReal B)) + (s + r) := add_assoc _ _ _
_ ≤ κ (thickening (s.toReal + r.toReal) B) + (s + r) :=
add_le_add_right (measure_mono (thickening_thickening_subset _ _ _)) _
· calc κ B ≤ ν (thickening s.toReal B) + s :=
right_measure_le_of_levyProkhorovEDist_lt lt_s B_mble
_ ≤ μ (thickening r.toReal (thickening s.toReal B)) + r + s :=
add_le_add_right
(right_measure_le_of_levyProkhorovEDist_lt lt_r isOpen_thickening.measurableSet) s
_ = μ (thickening r.toReal (thickening s.toReal B)) + (s + r) := by rw [add_assoc, add_comm r]
_ ≤ μ (thickening (r.toReal + s.toReal) B) + (s + r) :=
add_le_add_right (measure_mono (thickening_thickening_subset _ _ _)) _
_ = μ (thickening (s.toReal + r.toReal) B) + (s + r) := by rw [add_comm r.toReal]
/-- The Lévy-Prokhorov distance between finite measures:
`d(μ,ν) = inf {r ≥ 0 | ∀ B, μ B ≤ ν Bᵣ + r ∧ ν B ≤ μ Bᵣ + r}`. -/
noncomputable def levyProkhorovDist (μ ν : Measure Ω) : ℝ :=
(levyProkhorovEDist μ ν).toReal
lemma levyProkhorovDist_self (μ : Measure Ω) :
levyProkhorovDist μ μ = 0 := by
simp only [levyProkhorovDist, levyProkhorovEDist_self, toReal_zero]
lemma levyProkhorovDist_comm (μ ν : Measure Ω) :
levyProkhorovDist μ ν = levyProkhorovDist ν μ := by
simp only [levyProkhorovDist, levyProkhorovEDist_comm]
lemma levyProkhorovDist_triangle [OpensMeasurableSpace Ω] (μ ν κ : Measure Ω)
[IsFiniteMeasure μ] [IsFiniteMeasure ν] [IsFiniteMeasure κ] :
levyProkhorovDist μ κ ≤ levyProkhorovDist μ ν + levyProkhorovDist ν κ := by
have dμν_finite := (levyProkhorovEDist_lt_top μ ν).ne
have dνκ_finite := (levyProkhorovEDist_lt_top ν κ).ne
convert ENNReal.toReal_mono ?_ <| levyProkhorovEDist_triangle μ ν κ
· simp only [levyProkhorovDist, ENNReal.toReal_add dμν_finite dνκ_finite]
· exact ENNReal.add_ne_top.mpr ⟨dμν_finite, dνκ_finite⟩
/-- A type synonym, to be used for `Measure α`, `FiniteMeasure α`, or `ProbabilityMeasure α`,
when they are to be equipped with the Lévy-Prokhorov distance. -/
def LevyProkhorov (α : Type*) := α
/-- The "identity" equivalence between the type synonym `LevyProkhorov α` and `α`. -/
def LevyProkhorov.equiv (α : Type*) : LevyProkhorov α ≃ α := Equiv.refl _
variable [OpensMeasurableSpace Ω]
/-- The Lévy-Prokhorov distance `levyProkhorovEDist` makes `Measure Ω` a pseudoemetric
space. The instance is recorded on the type synonym `LevyProkhorov (Measure Ω) := Measure Ω`. -/
noncomputable instance : PseudoEMetricSpace (LevyProkhorov (Measure Ω)) where
edist := levyProkhorovEDist
edist_self := levyProkhorovEDist_self
edist_comm := levyProkhorovEDist_comm
edist_triangle := levyProkhorovEDist_triangle
/-- The Lévy-Prokhorov distance `levyProkhorovDist` makes `FiniteMeasure Ω` a pseudometric
space. The instance is recorded on the type synonym
`LevyProkhorov (FiniteMeasure Ω) := FiniteMeasure Ω`. -/
noncomputable instance levyProkhorovDist_pseudoMetricSpace_finiteMeasure :
PseudoMetricSpace (LevyProkhorov (FiniteMeasure Ω)) where
dist μ ν := levyProkhorovDist μ.toMeasure ν.toMeasure
dist_self _ := levyProkhorovDist_self _
dist_comm _ _ := levyProkhorovDist_comm _ _
dist_triangle _ _ _ := levyProkhorovDist_triangle _ _ _
edist_dist μ ν := by simp [← ENNReal.ofReal_coe_nnreal]
lemma measure_le_measure_closure_of_levyProkhorovEDist_eq_zero {μ ν : Measure Ω}
(hLP : levyProkhorovEDist μ ν = 0) {s : Set Ω} (s_mble : MeasurableSet s)
(h_finite : ∃ δ > 0, ν (thickening δ s) ≠ ∞) :
μ s ≤ ν (closure s) := by
have key : Tendsto (fun ε ↦ ν (thickening ε.toReal s)) (𝓝[>] (0 : ℝ≥0∞)) (𝓝 (ν (closure s))) := by
have aux : Tendsto ENNReal.toReal (𝓝[>] 0) (𝓝[>] 0) := by
apply tendsto_nhdsWithin_of_tendsto_nhds_of_eventually_within (s := Ioi 0) ENNReal.toReal
· exact tendsto_nhdsWithin_of_tendsto_nhds (continuousAt_toReal zero_ne_top).tendsto
· filter_upwards [Ioo_mem_nhdsGT zero_lt_one] with x hx
exact toReal_pos hx.1.ne.symm <| ne_top_of_lt hx.2
exact (tendsto_measure_thickening h_finite).comp aux
have obs := Tendsto.add key (tendsto_nhdsWithin_of_tendsto_nhds tendsto_id)
simp only [id_eq, add_zero] at obs
apply ge_of_tendsto (b := μ s) obs
filter_upwards [self_mem_nhdsWithin] with ε ε_pos
exact left_measure_le_of_levyProkhorovEDist_lt (B_mble := s_mble) (hLP ▸ ε_pos)
/-- Two measures at vanishing Lévy-Prokhorov distance from each other assign the same values to all
closed sets. -/
lemma measure_eq_measure_of_levyProkhorovEDist_eq_zero_of_isClosed {μ ν : Measure Ω}
(hLP : levyProkhorovEDist μ ν = 0) {s : Set Ω} (s_closed : IsClosed s)
(hμs : ∃ δ > 0, μ (thickening δ s) ≠ ∞) (hνs : ∃ δ > 0, ν (thickening δ s) ≠ ∞) :
μ s = ν s := by
apply le_antisymm
· exact measure_le_measure_closure_of_levyProkhorovEDist_eq_zero
hLP s_closed.measurableSet hνs |>.trans <|
le_of_eq (congr_arg _ s_closed.closure_eq)
· exact measure_le_measure_closure_of_levyProkhorovEDist_eq_zero
(levyProkhorovEDist_comm μ ν ▸ hLP) s_closed.measurableSet hμs |>.trans <|
le_of_eq (congr_arg _ s_closed.closure_eq)
/-- The Lévy-Prokhorov distance `levyProkhorovDist` makes `ProbabilityMeasure Ω` a pseudometric
space. The instance is recorded on the type synonym
`LevyProkhorov (ProbabilityMeasure Ω) := ProbabilityMeasure Ω`.
Note: For this pseudometric to give the topology of convergence in distribution, one must
furthermore assume that `Ω` is separable. -/
noncomputable instance levyProkhorovDist_pseudoMetricSpace_probabilityMeasure :
PseudoMetricSpace (LevyProkhorov (ProbabilityMeasure Ω)) where
dist μ ν := levyProkhorovDist μ.toMeasure ν.toMeasure
dist_self _ := levyProkhorovDist_self _
dist_comm _ _ := levyProkhorovDist_comm _ _
dist_triangle _ _ _ := levyProkhorovDist_triangle _ _ _
edist_dist μ ν := by simp [← ENNReal.ofReal_coe_nnreal]
lemma LevyProkhorov.dist_def (μ ν : LevyProkhorov (ProbabilityMeasure Ω)) :
dist μ ν = levyProkhorovDist μ.toMeasure ν.toMeasure := rfl
/-- If `Ω` is a Borel space, then the Lévy-Prokhorov distance `levyProkhorovDist` makes
`ProbabilityMeasure Ω` a metric space. The instance is recorded on the type synonym
`LevyProkhorov (ProbabilityMeasure Ω) := ProbabilityMeasure Ω`.
Note: For this metric to give the topology of convergence in distribution, one must
furthermore assume that `Ω` is separable. -/
noncomputable instance levyProkhorovDist_metricSpace_probabilityMeasure [BorelSpace Ω] :
MetricSpace (LevyProkhorov (ProbabilityMeasure Ω)) where
eq_of_dist_eq_zero := by
intro μ ν h
apply (LevyProkhorov.equiv _).injective
apply ProbabilityMeasure.toMeasure_injective
apply ext_of_generate_finite _ ?_ isPiSystem_isClosed ?_ (by simp)
· rw [BorelSpace.measurable_eq (α := Ω), borel_eq_generateFrom_isClosed]
· intro A A_closed
apply measure_eq_measure_of_levyProkhorovEDist_eq_zero_of_isClosed
· simpa only [levyProkhorovEDist_ne_top μ.toMeasure ν.toMeasure, mem_setOf_eq,
or_false, ne_eq, zero_ne_top, not_false_eq_true, toReal_zero]
using (toReal_eq_zero_iff _).mp h
· exact A_closed
· exact ⟨1, Real.zero_lt_one, measure_ne_top _ _⟩
· exact ⟨1, Real.zero_lt_one, measure_ne_top _ _⟩
/-- A simple sufficient condition for bounding `levyProkhorovEDist` between probability measures
from above. The condition involves only one of two natural bounds, the other bound is for free. -/
lemma levyProkhorovEDist_le_of_forall_le
(μ ν : Measure Ω) [IsProbabilityMeasure μ] [IsProbabilityMeasure ν] (δ : ℝ≥0∞)
(h : ∀ ε B, δ < ε → ε < ∞ → MeasurableSet B → μ B ≤ ν (thickening ε.toReal B) + ε) :
levyProkhorovEDist μ ν ≤ δ := by
apply levyProkhorovEDist_le_of_forall μ ν δ
intro ε B ε_gt ε_lt_top B_mble
refine ⟨h ε B ε_gt ε_lt_top B_mble, ?_⟩
have B_subset := subset_compl_thickening_compl_thickening_self ε.toReal B
apply (measure_mono (μ := ν) B_subset).trans
rw [prob_compl_eq_one_sub isOpen_thickening.measurableSet]
have Tc_mble := (isOpen_thickening (δ := ε.toReal) (E := B)).isClosed_compl.measurableSet
specialize h ε (thickening ε.toReal B)ᶜ ε_gt ε_lt_top Tc_mble
rw [prob_compl_eq_one_sub isOpen_thickening.measurableSet] at h
have almost := add_le_add (c := μ (thickening ε.toReal B)) h rfl.le
rw [tsub_add_cancel_of_le prob_le_one, add_assoc] at almost
apply (tsub_le_tsub_right almost _).trans
rw [ENNReal.add_sub_cancel_left (measure_ne_top ν _), add_comm ε]
/-- A simple sufficient condition for bounding `levyProkhorovDist` between probability measures
from above. The condition involves only one of two natural bounds, the other bound is for free. -/
lemma levyProkhorovDist_le_of_forall_le
(μ ν : Measure Ω) [IsProbabilityMeasure μ] [IsProbabilityMeasure ν] {δ : ℝ} (δ_nn : 0 ≤ δ)
(h : ∀ ε B, δ < ε → MeasurableSet B → μ B ≤ ν (thickening ε B) + ENNReal.ofReal ε) :
levyProkhorovDist μ ν ≤ δ := by
apply toReal_le_of_le_ofReal δ_nn
apply levyProkhorovEDist_le_of_forall_le
intro ε B ε_gt ε_lt_top B_mble
have ε_gt' : δ < ε.toReal := by
refine (ofReal_lt_ofReal_iff ?_).mp ?_
· exact ENNReal.toReal_pos (ne_zero_of_lt ε_gt) ε_lt_top.ne
· simpa [ofReal_toReal_eq_iff.mpr ε_lt_top.ne] using ε_gt
convert h ε.toReal B ε_gt' B_mble
exact (ENNReal.ofReal_toReal ε_lt_top.ne).symm
end Levy_Prokhorov --section
section Levy_Prokhorov_is_finer
/-! ### The Lévy-Prokhorov topology is at least as fine as convergence in distribution -/
open BoundedContinuousFunction
variable {Ω : Type*} [MeasurableSpace Ω]
variable [PseudoMetricSpace Ω] [OpensMeasurableSpace Ω]
/-- A version of the layer cake formula for bounded continuous functions which have finite integral:
∫ f dμ = ∫ t in (0, ‖f‖], μ {x | f(x) ≥ t} dt. -/
lemma BoundedContinuousFunction.integral_eq_integral_meas_le_of_hasFiniteIntegral
{α : Type*} [MeasurableSpace α] [TopologicalSpace α] [OpensMeasurableSpace α]
(f : α →ᵇ ℝ) (μ : Measure α) (f_nn : 0 ≤ᵐ[μ] f) (hf : HasFiniteIntegral f μ) :
∫ ω, f ω ∂μ = ∫ t in Ioc 0 ‖f‖, μ.real {a : α | t ≤ f a} := by
rw [Integrable.integral_eq_integral_Ioc_meas_le (M := ‖f‖) ?_ f_nn ?_]
· exact ⟨f.continuous.measurable.aestronglyMeasurable, hf⟩
· exact Eventually.of_forall (fun x ↦ BoundedContinuousFunction.apply_le_norm f x)
/-- A version of the layer cake formula for bounded continuous functions and finite measures:
∫ f dμ = ∫ t in (0, ‖f‖], μ {x | f(x) ≥ t} dt. -/
lemma BoundedContinuousFunction.integral_eq_integral_meas_le
{α : Type*} [MeasurableSpace α] [TopologicalSpace α] [OpensMeasurableSpace α]
(f : α →ᵇ ℝ) (μ : Measure α) [IsFiniteMeasure μ] (f_nn : 0 ≤ᵐ[μ] f) :
∫ ω, f ω ∂μ = ∫ t in Ioc 0 ‖f‖, μ.real {a : α | t ≤ f a} :=
integral_eq_integral_meas_le_of_hasFiniteIntegral _ _ f_nn (f.integrable μ).2
/-- Assuming `levyProkhorovEDist μ ν < ε`, we can bound `∫ f ∂μ` in terms of
`∫ t in (0, ‖f‖], ν (thickening ε {x | f(x) ≥ t}) dt` and `‖f‖`. -/
lemma BoundedContinuousFunction.integral_le_of_levyProkhorovEDist_lt (μ ν : Measure Ω)
[IsFiniteMeasure μ] [IsFiniteMeasure ν] {ε : ℝ} (ε_pos : 0 < ε)
(hμν : levyProkhorovEDist μ ν < ENNReal.ofReal ε) (f : Ω →ᵇ ℝ) (f_nn : 0 ≤ᵐ[μ] f) :
∫ ω, f ω ∂μ
≤ (∫ t in Ioc 0 ‖f‖, ν.real (thickening ε {a | t ≤ f a})) + ε * ‖f‖ := by
rw [BoundedContinuousFunction.integral_eq_integral_meas_le f μ f_nn]
have key : (fun (t : ℝ) ↦ μ.real {a | t ≤ f a})
≤ (fun (t : ℝ) ↦ ν.real (thickening ε {a | t ≤ f a}) + ε) := by
intro t
simp only [measureReal_def]
convert ENNReal.toReal_mono ?_ <| left_measure_le_of_levyProkhorovEDist_lt hμν
(B := {a | t ≤ f a}) (f.continuous.measurable measurableSet_Ici)
· rw [ENNReal.toReal_add (measure_ne_top ν _) ofReal_ne_top, ENNReal.toReal_ofReal ε_pos.le]
· exact ENNReal.add_ne_top.mpr ⟨measure_ne_top ν _, ofReal_ne_top⟩
have intble₁ : IntegrableOn (fun t ↦ μ.real {a | t ≤ f a}) (Ioc 0 ‖f‖) := by
apply Measure.integrableOn_of_bounded (M := μ.real univ) measure_Ioc_lt_top.ne
· apply (Measurable.ennreal_toReal (Antitone.measurable ?_)).aestronglyMeasurable
exact fun _ _ hst ↦ measure_mono (fun _ h ↦ hst.trans h)
· apply Eventually.of_forall <| fun t ↦ ?_
simp only [Real.norm_eq_abs, abs_of_nonneg measureReal_nonneg]
exact measureReal_mono (subset_univ _)
have intble₂ : IntegrableOn (fun t ↦ ν.real (thickening ε {a | t ≤ f a})) (Ioc 0 ‖f‖) := by
apply Measure.integrableOn_of_bounded (M := ν.real univ) measure_Ioc_lt_top.ne
· apply (Measurable.ennreal_toReal (Antitone.measurable ?_)).aestronglyMeasurable
exact fun _ _ hst ↦ measure_mono <| thickening_subset_of_subset ε (fun _ h ↦ hst.trans h)
· apply Eventually.of_forall <| fun t ↦ ?_
simp only [Real.norm_eq_abs, abs_of_nonneg measureReal_nonneg]
exact ENNReal.toReal_mono (measure_ne_top _ _) <| measure_mono (subset_univ _)
apply le_trans (setIntegral_mono (s := Ioc 0 ‖f‖) ?_ ?_ key)
· rw [integral_add]
· apply add_le_add_left
simp [(mul_comm _ ε).le]
· exact intble₂
· exact integrable_const ε
· exact intble₁
· exact intble₂.add <| integrable_const ε
/-- A monotone decreasing convergence lemma for integrals of measures of thickenings:
`∫ t in (0, ‖f‖], μ (thickening ε {x | f(x) ≥ t}) dt` tends to
`∫ t in (0, ‖f‖], μ {x | f(x) ≥ t} dt` as `ε → 0`. -/
lemma tendsto_integral_meas_thickening_le (f : Ω →ᵇ ℝ)
{A : Set ℝ} (A_finmeas : volume A ≠ ∞) (μ : ProbabilityMeasure Ω) :
Tendsto (fun ε ↦ ∫ t in A, (Measure.real μ (thickening ε {a | t ≤ f a}))) (𝓝[>] (0 : ℝ))
(𝓝 (∫ t in A, (Measure.real μ {a | t ≤ f a}))) := by
apply tendsto_integral_filter_of_dominated_convergence (G := ℝ) (μ := volume.restrict A)
(F := fun ε t ↦ (μ (thickening ε {a | t ≤ f a}))) (f := fun t ↦ (μ {a | t ≤ f a})) 1
· apply Eventually.of_forall fun n ↦ Measurable.aestronglyMeasurable ?_
simp only [measurable_coe_nnreal_real_iff]
apply measurable_toNNReal.comp <| Antitone.measurable (fun s t hst ↦ ?_)
exact measure_mono <| thickening_subset_of_subset _ <| fun ω h ↦ hst.trans h
· apply Eventually.of_forall (fun i ↦ ?_)
apply Eventually.of_forall (fun t ↦ ?_)
simp only [Real.norm_eq_abs, NNReal.abs_eq, Pi.one_apply]
exact ENNReal.toReal_mono one_ne_top prob_le_one
· have aux : IsFiniteMeasure (volume.restrict A) := ⟨by simp [lt_top_iff_ne_top, A_finmeas]⟩
apply integrable_const
· apply Eventually.of_forall (fun t ↦ ?_)
simp only [NNReal.tendsto_coe]
apply (ENNReal.tendsto_toNNReal _).comp
· apply tendsto_measure_thickening_of_isClosed ?_ ?_
· exact ⟨1, ⟨Real.zero_lt_one, measure_ne_top _ _⟩⟩
· exact isClosed_le continuous_const f.continuous
· exact measure_ne_top _ _
/-- The identity map `LevyProkhorov (ProbabilityMeasure Ω) → ProbabilityMeasure Ω` is continuous. -/
lemma LevyProkhorov.continuous_equiv_probabilityMeasure :
Continuous (LevyProkhorov.equiv (α := ProbabilityMeasure Ω)) := by
refine SeqContinuous.continuous ?_
intro μs ν hμs
set P := LevyProkhorov.equiv _ ν -- more palatable notation
set Ps := fun n ↦ LevyProkhorov.equiv _ (μs n) -- more palatable notation
rw [ProbabilityMeasure.tendsto_iff_forall_integral_tendsto]
refine fun f ↦ tendsto_integral_of_forall_limsup_integral_le_integral ?_ f
intro f f_nn
by_cases f_zero : ‖f‖ = 0
· simp only [norm_eq_zero] at f_zero
simp [f_zero, limsup_const]
have norm_f_pos : 0 < ‖f‖ := lt_of_le_of_ne (norm_nonneg _) (fun a => f_zero a.symm)
apply _root_.le_of_forall_pos_le_add
intro δ δ_pos
apply limsup_le_of_le ?_
· obtain ⟨εs, ⟨_, ⟨εs_pos, εs_lim⟩⟩⟩ := exists_seq_strictAnti_tendsto (0 : ℝ)
have ε_of_room := Tendsto.add (tendsto_iff_dist_tendsto_zero.mp hμs) εs_lim
have ε_of_room' : Tendsto (fun n ↦ dist (μs n) ν + εs n) atTop (𝓝[>] 0) := by
rw [tendsto_nhdsWithin_iff]
refine ⟨by simpa using ε_of_room, Eventually.of_forall fun n ↦ ?_⟩
· rw [mem_Ioi]
linarith [εs_pos n, dist_nonneg (x := μs n) (y := ν)]
rw [add_zero] at ε_of_room
have key := (tendsto_integral_meas_thickening_le f (A := Ioc 0 ‖f‖) (by simp) P).comp ε_of_room'
have aux : ∀ (z : ℝ), Iio (z + δ/2) ∈ 𝓝 z := fun z ↦ Iio_mem_nhds (by linarith)
filter_upwards [key (aux _), ε_of_room <| Iio_mem_nhds <| half_pos <|
mul_pos (inv_pos.mpr norm_f_pos) δ_pos]
with n hn hn'
simp only [mem_preimage, mem_Iio] at *
specialize εs_pos n
have bound := BoundedContinuousFunction.integral_le_of_levyProkhorovEDist_lt
(Ps n) P (ε := dist (μs n) ν + εs n) ?_ ?_ f ?_
· refine bound.trans ?_
apply (add_le_add_right hn.le _).trans
rw [BoundedContinuousFunction.integral_eq_integral_meas_le]
· rw [add_assoc, mul_comm]
gcongr
calc
δ / 2 + ‖f‖ * (dist (μs n) ν + εs n)
_ ≤ δ / 2 + ‖f‖ * (‖f‖⁻¹ * δ / 2) := by gcongr
_ = δ := by field_simp; ring
· exact Eventually.of_forall f_nn
· positivity
· rw [ENNReal.ofReal_add (by positivity) (by positivity), ← add_zero (levyProkhorovEDist _ _)]
apply ENNReal.add_lt_add_of_le_of_lt (levyProkhorovEDist_ne_top _ _)
(le_of_eq ?_) (ofReal_pos.mpr εs_pos)
rw [LevyProkhorov.dist_def, levyProkhorovDist, ofReal_toReal (levyProkhorovEDist_ne_top _ _)]
rfl
· exact Eventually.of_forall f_nn
· simp only [IsCoboundedUnder, IsCobounded, eventually_map, eventually_atTop,
forall_exists_index]
refine ⟨0, fun a i hia ↦ le_trans (integral_nonneg f_nn) (hia i le_rfl)⟩
/-- The topology of the Lévy-Prokhorov metric is at least as fine as the topology of convergence in
distribution. -/
theorem levyProkhorov_le_convergenceInDistribution :
TopologicalSpace.coinduced (LevyProkhorov.equiv (α := ProbabilityMeasure Ω)) inferInstance
≤ (inferInstance : TopologicalSpace (ProbabilityMeasure Ω)) :=
(LevyProkhorov.continuous_equiv_probabilityMeasure).coinduced_le
end Levy_Prokhorov_is_finer
section Levy_Prokhorov_metrizes_convergence_in_distribution
/-! ### On separable spaces the Lévy-Prokhorov distance metrizes convergence in distribution -/
open BoundedContinuousFunction TopologicalSpace
variable {Ω : Type*} [PseudoMetricSpace Ω]
variable [MeasurableSpace Ω] [OpensMeasurableSpace Ω]
lemma ProbabilityMeasure.toMeasure_add_pos_gt_mem_nhds (P : ProbabilityMeasure Ω)
{G : Set Ω} (G_open : IsOpen G) {ε : ℝ≥0∞} (ε_pos : 0 < ε) :
{Q | P.toMeasure G < Q.toMeasure G + ε} ∈ 𝓝 P := by
by_cases easy : P.toMeasure G < ε
| · exact Eventually.of_forall (fun _ ↦ lt_of_lt_of_le easy le_add_self)
by_cases ε_top : ε = ∞
· simp [ε_top, measure_lt_top]
simp only [not_lt] at easy
have aux : P.toMeasure G - ε < liminf (fun Q ↦ Q.toMeasure G) (𝓝 P) := by
apply lt_of_lt_of_le (ENNReal.sub_lt_self (measure_lt_top _ _).ne _ _)
<| ProbabilityMeasure.le_liminf_measure_open_of_tendsto tendsto_id G_open
· exact (lt_of_lt_of_le ε_pos easy).ne.symm
· exact ε_pos.ne.symm
filter_upwards [gt_mem_sets_of_limsInf_gt (α := ℝ≥0∞) isBounded_ge_of_bot
(show P.toMeasure G - ε < limsInf ((𝓝 P).map (fun Q ↦ Q.toMeasure G)) from aux)] with Q hQ
simp only [preimage_setOf_eq, mem_setOf_eq] at hQ
convert ENNReal.add_lt_add_right ε_top hQ
exact (tsub_add_cancel_of_le easy).symm
variable [SeparableSpace Ω]
variable (Ω) in
| Mathlib/MeasureTheory/Measure/LevyProkhorovMetric.lean | 497 | 514 |
/-
Copyright (c) 2021 Jireh Loreaux. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Jireh Loreaux
-/
import Mathlib.Algebra.Algebra.Spectrum.Basic
import Mathlib.FieldTheory.IsAlgClosed.Basic
/-!
# Spectrum mapping theorem
This file develops proves the spectral mapping theorem for polynomials over algebraically closed
fields. In particular, if `a` is an element of a `𝕜`-algebra `A` where `𝕜` is a field, and
`p : 𝕜[X]` is a polynomial, then the spectrum of `Polynomial.aeval a p` contains the image of the
spectrum of `a` under `(fun k ↦ Polynomial.eval k p)`. When `𝕜` is algebraically closed,
these are in fact equal (assuming either that the spectrum of `a` is nonempty or the polynomial
has positive degree), which is the **spectral mapping theorem**.
In addition, this file contains the fact that every element of a finite dimensional nontrivial
algebra over an algebraically closed field has nonempty spectrum. In particular, this is used in
`Module.End.exists_eigenvalue` to show that every linear map from a vector space to itself has an
eigenvalue.
## Main statements
* `spectrum.subset_polynomial_aeval`, `spectrum.map_polynomial_aeval_of_degree_pos`,
`spectrum.map_polynomial_aeval_of_nonempty`: variations on the **spectral mapping theorem**.
* `spectrum.nonempty_of_isAlgClosed_of_finiteDimensional`: the spectrum is nonempty for any
element of a nontrivial finite dimensional algebra over an algebraically closed field.
## Notations
* `σ a` : `spectrum R a` of `a : A`
-/
namespace spectrum
open Set Polynomial
open scoped Pointwise Polynomial
universe u v
section ScalarRing
variable {R : Type u} {A : Type v}
variable [CommRing R] [Ring A] [Algebra R A]
local notation "σ" => spectrum R
local notation "↑ₐ" => algebraMap R A
theorem exists_mem_of_not_isUnit_aeval_prod [IsDomain R] {p : R[X]} {a : A}
(h : ¬IsUnit (aeval a (Multiset.map (fun x : R => X - C x) p.roots).prod)) :
∃ k : R, k ∈ σ a ∧ eval k p = 0 := by
rw [← Multiset.prod_toList, map_list_prod] at h
replace h := mt List.prod_isUnit h
simp only [not_forall, exists_prop, aeval_C, Multiset.mem_toList, List.mem_map, aeval_X,
exists_exists_and_eq_and, Multiset.mem_map, map_sub] at h
rcases h with ⟨r, r_mem, r_nu⟩
exact ⟨r, by rwa [mem_iff, ← IsUnit.sub_iff], (mem_roots'.1 r_mem).2⟩
end ScalarRing
section ScalarField
variable {𝕜 : Type u} {A : Type v}
variable [Field 𝕜] [Ring A] [Algebra 𝕜 A]
local notation "σ" => spectrum 𝕜
local notation "↑ₐ" => algebraMap 𝕜 A
open Polynomial
/-- Half of the spectral mapping theorem for polynomials. We prove it separately
because it holds over any field, whereas `spectrum.map_polynomial_aeval_of_degree_pos` and
`spectrum.map_polynomial_aeval_of_nonempty` need the field to be algebraically closed. -/
theorem subset_polynomial_aeval (a : A) (p : 𝕜[X]) : (eval · p) '' σ a ⊆ σ (aeval a p) := by
rintro _ ⟨k, hk, rfl⟩
let q := C (eval k p) - p
have hroot : IsRoot q k := by simp only [q, eval_C, eval_sub, sub_self, IsRoot.def]
rw [← mul_div_eq_iff_isRoot, ← neg_mul_neg, neg_sub] at hroot
have aeval_q_eq : ↑ₐ (eval k p) - aeval a p = aeval a q := by
simp only [q, aeval_C, map_sub, sub_left_inj]
rw [mem_iff, aeval_q_eq, ← hroot, aeval_mul]
have hcomm := (Commute.all (C k - X) (-(q / (X - C k)))).map (aeval a : 𝕜[X] →ₐ[𝕜] A)
apply mt fun h => (hcomm.isUnit_mul_iff.mp h).1
simpa only [aeval_X, aeval_C, map_sub] using hk
/-- The *spectral mapping theorem* for polynomials. Note: the assumption `degree p > 0`
is necessary in case `σ a = ∅`, for then the left-hand side is `∅` and the right-hand side,
assuming `[Nontrivial A]`, is `{k}` where `p = Polynomial.C k`. -/
theorem map_polynomial_aeval_of_degree_pos [IsAlgClosed 𝕜] (a : A) (p : 𝕜[X])
(hdeg : 0 < degree p) : σ (aeval a p) = (eval · p) '' σ a := by
-- handle the easy direction via `spectrum.subset_polynomial_aeval`
refine Set.eq_of_subset_of_subset (fun k hk => ?_) (subset_polynomial_aeval a p)
-- write `C k - p` product of linear factors and a constant; show `C k - p ≠ 0`.
have hprod := eq_prod_roots_of_splits_id (IsAlgClosed.splits (C k - p))
have h_ne : C k - p ≠ 0 := ne_zero_of_degree_gt <| by
rwa [degree_sub_eq_right_of_degree_lt (lt_of_le_of_lt degree_C_le hdeg)]
have lead_ne := leadingCoeff_ne_zero.mpr h_ne
have lead_unit := (Units.map ↑ₐ.toMonoidHom (Units.mk0 _ lead_ne)).isUnit
/- leading coefficient is a unit so product of linear factors is not a unit;
apply `exists_mem_of_not_is_unit_aeval_prod`. -/
have p_a_eq : aeval a (C k - p) = ↑ₐ k - aeval a p := by
simp only [aeval_C, map_sub, sub_left_inj]
rw [mem_iff, ← p_a_eq, hprod, aeval_mul,
((Commute.all _ _).map (aeval a : 𝕜[X] →ₐ[𝕜] A)).isUnit_mul_iff, aeval_C] at hk
replace hk := exists_mem_of_not_isUnit_aeval_prod (not_and.mp hk lead_unit)
rcases hk with ⟨r, r_mem, r_ev⟩
exact ⟨r, r_mem, symm (by simpa [eval_sub, eval_C, sub_eq_zero] using r_ev)⟩
/-- In this version of the spectral mapping theorem, we assume the spectrum
is nonempty instead of assuming the degree of the polynomial is positive. -/
theorem map_polynomial_aeval_of_nonempty [IsAlgClosed 𝕜] (a : A) (p : 𝕜[X])
(hnon : (σ a).Nonempty) : σ (aeval a p) = (fun k => eval k p) '' σ a := by
nontriviality A
refine Or.elim (le_or_gt (degree p) 0) (fun h => ?_) (map_polynomial_aeval_of_degree_pos a p)
rw [eq_C_of_degree_le_zero h]
simp only [Set.image_congr, eval_C, aeval_C, scalar_eq, Set.Nonempty.image_const hnon]
/-- A specialization of `spectrum.subset_polynomial_aeval` to monic monomials for convenience. -/
theorem pow_image_subset (a : A) (n : ℕ) : (fun x => x ^ n) '' σ a ⊆ σ (a ^ n) := by
simpa only [eval_pow, eval_X, aeval_X_pow] using subset_polynomial_aeval a (X ^ n : 𝕜[X])
/-- A specialization of `spectrum.map_polynomial_aeval_of_nonempty` to monic monomials for
convenience. -/
theorem map_pow_of_pos [IsAlgClosed 𝕜] (a : A) {n : ℕ} (hn : 0 < n) :
σ (a ^ n) = (· ^ n) '' σ a := by
simpa only [aeval_X_pow, eval_pow, eval_X]
using map_polynomial_aeval_of_degree_pos a (X ^ n : 𝕜[X]) (by rwa [degree_X_pow, Nat.cast_pos])
/-- A specialization of `spectrum.map_polynomial_aeval_of_nonempty` to monic monomials for
convenience. -/
theorem map_pow_of_nonempty [IsAlgClosed 𝕜] {a : A} (ha : (σ a).Nonempty) (n : ℕ) :
| σ (a ^ n) = (· ^ n) '' σ a := by
simpa only [aeval_X_pow, eval_pow, eval_X] using map_polynomial_aeval_of_nonempty a (X ^ n) ha
variable (𝕜)
| Mathlib/FieldTheory/IsAlgClosed/Spectrum.lean | 135 | 138 |
/-
Copyright (c) 2023 Yaël Dillies. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yaël Dillies
-/
import Mathlib.Order.BooleanAlgebra
import Mathlib.Order.Hom.Lattice
/-!
# Adding complements to a generalized Boolean algebra
This file embeds any generalized Boolean algebra into a Boolean algebra.
This concretely proves that any equation holding true in the theory of Boolean algebras that does
not reference `ᶜ` also holds true in the theory of generalized Boolean algebras. Put another way,
one does not need the existence of complements to prove something which does not talk about
complements.
## Main declarations
* `Booleanisation`: Boolean algebra containing a given generalised Boolean algebra as a sublattice.
* `Booleanisation.liftLatticeHom`: Boolean algebra containing a given generalised Boolean algebra as
a sublattice.
## Future work
If mathlib ever acquires `GenBoolAlg`, the category of generalised Boolean algebras, then one could
show that `Booleanisation` is the free functor from `GenBoolAlg` to `BoolAlg`.
-/
open Function
variable {α : Type*}
/-- Boolean algebra containing a given generalised Boolean algebra `α` as a sublattice.
This should be thought of as made of a copy of `α` (representing elements of `α`) living under
another copy of `α` (representing complements of elements of `α`). -/
def Booleanisation (α : Type*) := α ⊕ α
namespace Booleanisation
instance instDecidableEq [DecidableEq α] : DecidableEq (Booleanisation α) :=
inferInstanceAs <| DecidableEq (α ⊕ α)
/-- The natural inclusion `a ↦ a` from a generalized Boolean algebra to its generated Boolean
algebra. -/
@[match_pattern] def lift : α → Booleanisation α := Sum.inl
/-- The inclusion `a ↦ aᶜ from a generalized Boolean algebra to its generated Boolean algebra. -/
@[match_pattern] def comp : α → Booleanisation α := Sum.inr
/-- The complement operator on `Booleanisation α` sends `a` to `aᶜ` and `aᶜ` to `a`, for `a : α`. -/
instance instCompl : HasCompl (Booleanisation α) where
compl
| lift a => comp a
| comp a => lift a
@[simp] lemma compl_lift (a : α) : (lift a)ᶜ = comp a := rfl
@[simp] lemma compl_comp (a : α) : (comp a)ᶜ = lift a := rfl
variable [GeneralizedBooleanAlgebra α] {a b : α}
/-- The order on `Booleanisation α` is as follows: For `a b : α`,
* `a ≤ b` iff `a ≤ b` in `α`
* `a ≤ bᶜ` iff `a` and `b` are disjoint in `α`
* `aᶜ ≤ bᶜ` iff `b ≤ a` in `α`
* `¬ aᶜ ≤ b` -/
protected inductive LE : Booleanisation α → Booleanisation α → Prop
| protected lift {a b} : a ≤ b → Booleanisation.LE (lift a) (lift b)
| protected comp {a b} : a ≤ b → Booleanisation.LE (comp b) (comp a)
| protected sep {a b} : Disjoint a b → Booleanisation.LE (lift a) (comp b)
/-- The order on `Booleanisation α` is as follows: For `a b : α`,
* `a < b` iff `a < b` in `α`
* `a < bᶜ` iff `a` and `b` are disjoint in `α`
* `aᶜ < bᶜ` iff `b < a` in `α`
* `¬ aᶜ < b` -/
protected inductive LT : Booleanisation α → Booleanisation α → Prop
| protected lift {a b} : a < b → Booleanisation.LT (lift a) (lift b)
| protected comp {a b} : a < b → Booleanisation.LT (comp b) (comp a)
| protected sep {a b} : Disjoint a b → Booleanisation.LT (lift a) (comp b)
@[inherit_doc Booleanisation.LE]
instance instLE : LE (Booleanisation α) where
le := Booleanisation.LE
@[inherit_doc Booleanisation.LT]
instance instLT : LT (Booleanisation α) where
lt := Booleanisation.LT
/-- The supremum on `Booleanisation α` is as follows: For `a b : α`,
* `a ⊔ b` is `a ⊔ b`
* `a ⊔ bᶜ` is `(b \ a)ᶜ`
* `aᶜ ⊔ b` is `(a \ b)ᶜ`
* `aᶜ ⊔ bᶜ` is `(a ⊓ b)ᶜ` -/
instance instSup : Max (Booleanisation α) where
max
| lift a, lift b => lift (a ⊔ b)
| lift a, comp b => comp (b \ a)
| comp a, lift b => comp (a \ b)
| comp a, comp b => comp (a ⊓ b)
/-- The infimum on `Booleanisation α` is as follows: For `a b : α`,
* `a ⊓ b` is `a ⊓ b`
* `a ⊓ bᶜ` is `a \ b`
* `aᶜ ⊓ b` is `b \ a`
* `aᶜ ⊓ bᶜ` is `(a ⊔ b)ᶜ` -/
instance instInf : Min (Booleanisation α) where
min
| lift a, lift b => lift (a ⊓ b)
| lift a, comp b => lift (a \ b)
| comp a, lift b => lift (b \ a)
| comp a, comp b => comp (a ⊔ b)
/-- The bottom element of `Booleanisation α` is the bottom element of `α`. -/
instance instBot : Bot (Booleanisation α) where
bot := lift ⊥
/-- The top element of `Booleanisation α` is the complement of the bottom element of `α`. -/
instance instTop : Top (Booleanisation α) where
top := comp ⊥
/-- The difference operator on `Booleanisation α` is as follows: For `a b : α`,
* `a \ b` is `a \ b`
* `a \ bᶜ` is `a ⊓ b`
* `aᶜ \ b` is `(a ⊔ b)ᶜ`
* `aᶜ \ bᶜ` is `b \ a` -/
instance instSDiff : SDiff (Booleanisation α) where
sdiff
| lift a, lift b => lift (a \ b)
| lift a, comp b => lift (a ⊓ b)
| comp a, lift b => comp (a ⊔ b)
| | comp a, comp b => lift (b \ a)
| Mathlib/Order/Booleanisation.lean | 134 | 134 |
/-
Copyright (c) 2018 Patrick Massot. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Patrick Massot, Johannes Hölzl
-/
import Mathlib.Algebra.Field.Subfield.Defs
import Mathlib.Algebra.Order.Group.Pointwise.Interval
import Mathlib.Analysis.Normed.Ring.Basic
/-!
# Normed division rings and fields
In this file we define normed fields, and (more generally) normed division rings. We also prove
some theorems about these definitions.
Some useful results that relate the topology of the normed field to the discrete topology include:
* `norm_eq_one_iff_ne_zero_of_discrete`
Methods for constructing a normed field instance from a given real absolute value on a field are
given in:
* AbsoluteValue.toNormedField
-/
-- Guard against import creep.
assert_not_exists AddChar comap_norm_atTop DilationEquiv Finset.sup_mul_le_mul_sup_of_nonneg
IsOfFinOrder Isometry.norm_map_of_map_one NNReal.isOpen_Ico_zero Rat.norm_cast_real
RestrictScalars
variable {G α β ι : Type*}
open Filter
open scoped Topology NNReal ENNReal
/-- A normed division ring is a division ring endowed with a seminorm which satisfies the equality
`‖x y‖ = ‖x‖ ‖y‖`. -/
class NormedDivisionRing (α : Type*) extends Norm α, DivisionRing α, MetricSpace α where
/-- The distance is induced by the norm. -/
dist_eq : ∀ x y, dist x y = norm (x - y)
/-- The norm is multiplicative. -/
protected norm_mul : ∀ a b, norm (a * b) = norm a * norm b
-- see Note [lower instance priority]
/-- A normed division ring is a normed ring. -/
instance (priority := 100) NormedDivisionRing.toNormedRing [β : NormedDivisionRing α] :
NormedRing α :=
{ β with norm_mul_le a b := (NormedDivisionRing.norm_mul a b).le }
-- see Note [lower instance priority]
/-- The norm on a normed division ring is strictly multiplicative. -/
instance (priority := 100) NormedDivisionRing.toNormMulClass [NormedDivisionRing α] :
NormMulClass α where
norm_mul := NormedDivisionRing.norm_mul
section NormedDivisionRing
variable [NormedDivisionRing α] {a b : α}
instance (priority := 900) NormedDivisionRing.to_normOneClass : NormOneClass α :=
⟨mul_left_cancel₀ (mt norm_eq_zero.1 (one_ne_zero' α)) <| by rw [← norm_mul, mul_one, mul_one]⟩
@[simp]
theorem norm_div (a b : α) : ‖a / b‖ = ‖a‖ / ‖b‖ :=
map_div₀ (normHom : α →*₀ ℝ) a b
@[simp]
theorem nnnorm_div (a b : α) : ‖a / b‖₊ = ‖a‖₊ / ‖b‖₊ :=
map_div₀ (nnnormHom : α →*₀ ℝ≥0) a b
@[simp]
theorem norm_inv (a : α) : ‖a⁻¹‖ = ‖a‖⁻¹ :=
map_inv₀ (normHom : α →*₀ ℝ) a
@[simp]
theorem nnnorm_inv (a : α) : ‖a⁻¹‖₊ = ‖a‖₊⁻¹ :=
NNReal.eq <| by simp
@[simp]
lemma enorm_inv {a : α} (ha : a ≠ 0) : ‖a⁻¹‖ₑ = ‖a‖ₑ⁻¹ := by simp [enorm, ENNReal.coe_inv, ha]
@[simp]
theorem norm_zpow : ∀ (a : α) (n : ℤ), ‖a ^ n‖ = ‖a‖ ^ n :=
map_zpow₀ (normHom : α →*₀ ℝ)
@[simp]
theorem nnnorm_zpow : ∀ (a : α) (n : ℤ), ‖a ^ n‖₊ = ‖a‖₊ ^ n :=
map_zpow₀ (nnnormHom : α →*₀ ℝ≥0)
theorem dist_inv_inv₀ {z w : α} (hz : z ≠ 0) (hw : w ≠ 0) :
dist z⁻¹ w⁻¹ = dist z w / (‖z‖ * ‖w‖) := by
rw [dist_eq_norm, inv_sub_inv' hz hw, norm_mul, norm_mul, norm_inv, norm_inv, mul_comm ‖z‖⁻¹,
mul_assoc, dist_eq_norm', div_eq_mul_inv, mul_inv]
theorem nndist_inv_inv₀ {z w : α} (hz : z ≠ 0) (hw : w ≠ 0) :
nndist z⁻¹ w⁻¹ = nndist z w / (‖z‖₊ * ‖w‖₊) :=
NNReal.eq <| dist_inv_inv₀ hz hw
lemma norm_commutator_sub_one_le (ha : a ≠ 0) (hb : b ≠ 0) :
‖a * b * a⁻¹ * b⁻¹ - 1‖ ≤ 2 * ‖a‖⁻¹ * ‖b‖⁻¹ * ‖a - 1‖ * ‖b - 1‖ := by
simpa using norm_commutator_units_sub_one_le (.mk0 a ha) (.mk0 b hb)
lemma nnnorm_commutator_sub_one_le (ha : a ≠ 0) (hb : b ≠ 0) :
‖a * b * a⁻¹ * b⁻¹ - 1‖₊ ≤ 2 * ‖a‖₊⁻¹ * ‖b‖₊⁻¹ * ‖a - 1‖₊ * ‖b - 1‖₊ := by
simpa using nnnorm_commutator_units_sub_one_le (.mk0 a ha) (.mk0 b hb)
namespace NormedDivisionRing
section Discrete
variable {𝕜 : Type*} [NormedDivisionRing 𝕜] [DiscreteTopology 𝕜]
lemma norm_eq_one_iff_ne_zero_of_discrete {x : 𝕜} : ‖x‖ = 1 ↔ x ≠ 0 := by
constructor <;> intro hx
· contrapose! hx
simp [hx]
· have : IsOpen {(0 : 𝕜)} := isOpen_discrete {0}
simp_rw [Metric.isOpen_singleton_iff, dist_eq_norm, sub_zero] at this
obtain ⟨ε, εpos, h'⟩ := this
wlog h : ‖x‖ < 1 generalizing 𝕜 with H
· push_neg at h
rcases h.eq_or_lt with h|h
· rw [h]
replace h := norm_inv x ▸ inv_lt_one_of_one_lt₀ h
rw [← inv_inj, inv_one, ← norm_inv]
exact H (by simpa) h' h
obtain ⟨k, hk⟩ : ∃ k : ℕ, ‖x‖ ^ k < ε := exists_pow_lt_of_lt_one εpos h
rw [← norm_pow] at hk
specialize h' _ hk
simp [hx] at h'
@[simp]
lemma norm_le_one_of_discrete
(x : 𝕜) : ‖x‖ ≤ 1 := by
rcases eq_or_ne x 0 with rfl|hx
· simp
· simp [norm_eq_one_iff_ne_zero_of_discrete.mpr hx]
lemma unitClosedBall_eq_univ_of_discrete : (Metric.closedBall 0 1 : Set 𝕜) = Set.univ := by
ext
simp
@[deprecated (since := "2024-12-01")]
alias discreteTopology_unit_closedBall_eq_univ := unitClosedBall_eq_univ_of_discrete
end Discrete
end NormedDivisionRing
end NormedDivisionRing
/-- A normed field is a field with a norm satisfying ‖x y‖ = ‖x‖ ‖y‖. -/
class NormedField (α : Type*) extends Norm α, Field α, MetricSpace α where
/-- The distance is induced by the norm. -/
dist_eq : ∀ x y, dist x y = norm (x - y)
/-- The norm is multiplicative. -/
protected norm_mul : ∀ a b, norm (a * b) = norm a * norm b
/-- A nontrivially normed field is a normed field in which there is an element of norm different
from `0` and `1`. This makes it possible to bring any element arbitrarily close to `0` by
multiplication by the powers of any element, and thus to relate algebra and topology. -/
class NontriviallyNormedField (α : Type*) extends NormedField α where
/-- The norm attains a value exceeding 1. -/
non_trivial : ∃ x : α, 1 < ‖x‖
/-- A densely normed field is a normed field for which the image of the norm is dense in `ℝ≥0`,
which means it is also nontrivially normed. However, not all nontrivally normed fields are densely
normed; in particular, the `Padic`s exhibit this fact. -/
class DenselyNormedField (α : Type*) extends NormedField α where
/-- The range of the norm is dense in the collection of nonnegative real numbers. -/
lt_norm_lt : ∀ x y : ℝ, 0 ≤ x → x < y → ∃ a : α, x < ‖a‖ ∧ ‖a‖ < y
section NormedField
/-- A densely normed field is always a nontrivially normed field.
See note [lower instance priority]. -/
instance (priority := 100) DenselyNormedField.toNontriviallyNormedField [DenselyNormedField α] :
NontriviallyNormedField α where
non_trivial :=
let ⟨a, h, _⟩ := DenselyNormedField.lt_norm_lt 1 2 zero_le_one one_lt_two
⟨a, h⟩
variable [NormedField α]
-- see Note [lower instance priority]
instance (priority := 100) NormedField.toNormedDivisionRing : NormedDivisionRing α :=
{ ‹NormedField α› with }
-- see Note [lower instance priority]
instance (priority := 100) NormedField.toNormedCommRing : NormedCommRing α :=
{ ‹NormedField α› with norm_mul_le a b := (norm_mul a b).le }
end NormedField
namespace NormedField
section Nontrivially
variable (α) [NontriviallyNormedField α]
theorem exists_one_lt_norm : ∃ x : α, 1 < ‖x‖ :=
‹NontriviallyNormedField α›.non_trivial
theorem exists_one_lt_nnnorm : ∃ x : α, 1 < ‖x‖₊ := exists_one_lt_norm α
theorem exists_one_lt_enorm : ∃ x : α, 1 < ‖x‖ₑ :=
exists_one_lt_nnnorm α |>.imp fun _ => ENNReal.coe_lt_coe.mpr
theorem exists_lt_norm (r : ℝ) : ∃ x : α, r < ‖x‖ :=
let ⟨w, hw⟩ := exists_one_lt_norm α
let ⟨n, hn⟩ := pow_unbounded_of_one_lt r hw
⟨w ^ n, by rwa [norm_pow]⟩
theorem exists_lt_nnnorm (r : ℝ≥0) : ∃ x : α, r < ‖x‖₊ := exists_lt_norm α r
theorem exists_lt_enorm {r : ℝ≥0∞} (hr : r ≠ ∞) : ∃ x : α, r < ‖x‖ₑ := by
lift r to ℝ≥0 using hr
exact mod_cast exists_lt_nnnorm α r
theorem exists_norm_lt {r : ℝ} (hr : 0 < r) : ∃ x : α, 0 < ‖x‖ ∧ ‖x‖ < r :=
let ⟨w, hw⟩ := exists_lt_norm α r⁻¹
⟨w⁻¹, by rwa [← Set.mem_Ioo, norm_inv, ← Set.mem_inv, Set.inv_Ioo_0_left hr]⟩
theorem exists_nnnorm_lt {r : ℝ≥0} (hr : 0 < r) : ∃ x : α, 0 < ‖x‖₊ ∧ ‖x‖₊ < r :=
exists_norm_lt α hr
/-- TODO: merge with `_root_.exists_enorm_lt`. -/
theorem exists_enorm_lt {r : ℝ≥0∞} (hr : 0 < r) : ∃ x : α, 0 < ‖x‖ₑ ∧ ‖x‖ₑ < r :=
match r with
| ∞ => exists_one_lt_enorm α |>.imp fun _ hx => ⟨zero_le_one.trans_lt hx, ENNReal.coe_lt_top⟩
| (r : ℝ≥0) => exists_nnnorm_lt α (ENNReal.coe_pos.mp hr) |>.imp fun _ =>
And.imp ENNReal.coe_pos.mpr ENNReal.coe_lt_coe.mpr
theorem exists_norm_lt_one : ∃ x : α, 0 < ‖x‖ ∧ ‖x‖ < 1 :=
exists_norm_lt α one_pos
theorem exists_nnnorm_lt_one : ∃ x : α, 0 < ‖x‖₊ ∧ ‖x‖₊ < 1 := exists_norm_lt_one _
theorem exists_enorm_lt_one : ∃ x : α, 0 < ‖x‖ₑ ∧ ‖x‖ₑ < 1 := exists_enorm_lt _ one_pos
variable {α}
@[instance]
theorem nhdsNE_neBot (x : α) : NeBot (𝓝[≠] x) := by
rw [← mem_closure_iff_nhdsWithin_neBot, Metric.mem_closure_iff]
rintro ε ε0
rcases exists_norm_lt α ε0 with ⟨b, hb0, hbε⟩
refine ⟨x + b, mt (Set.mem_singleton_iff.trans add_eq_left).1 <| norm_pos_iff.1 hb0, ?_⟩
rwa [dist_comm, dist_eq_norm, add_sub_cancel_left]
@[deprecated (since := "2025-03-02")]
alias punctured_nhds_neBot := nhdsNE_neBot
@[instance]
theorem nhdsWithin_isUnit_neBot : NeBot (𝓝[{ x : α | IsUnit x }] 0) := by
simpa only [isUnit_iff_ne_zero] using nhdsNE_neBot (0 : α)
end Nontrivially
section Densely
variable (α) [DenselyNormedField α]
theorem exists_lt_norm_lt {r₁ r₂ : ℝ} (h₀ : 0 ≤ r₁) (h : r₁ < r₂) : ∃ x : α, r₁ < ‖x‖ ∧ ‖x‖ < r₂ :=
DenselyNormedField.lt_norm_lt r₁ r₂ h₀ h
theorem exists_lt_nnnorm_lt {r₁ r₂ : ℝ≥0} (h : r₁ < r₂) : ∃ x : α, r₁ < ‖x‖₊ ∧ ‖x‖₊ < r₂ :=
mod_cast exists_lt_norm_lt α r₁.prop h
instance denselyOrdered_range_norm : DenselyOrdered (Set.range (norm : α → ℝ)) where
dense := by
rintro ⟨-, x, rfl⟩ ⟨-, y, rfl⟩ hxy
let ⟨z, h⟩ := exists_lt_norm_lt α (norm_nonneg _) hxy
exact ⟨⟨‖z‖, z, rfl⟩, h⟩
instance denselyOrdered_range_nnnorm : DenselyOrdered (Set.range (nnnorm : α → ℝ≥0)) where
dense := by
rintro ⟨-, x, rfl⟩ ⟨-, y, rfl⟩ hxy
let ⟨z, h⟩ := exists_lt_nnnorm_lt α hxy
exact ⟨⟨‖z‖₊, z, rfl⟩, h⟩
end Densely
end NormedField
/-- A normed field is nontrivially normed
provided that the norm of some nonzero element is not one. -/
def NontriviallyNormedField.ofNormNeOne {𝕜 : Type*} [h' : NormedField 𝕜]
(h : ∃ x : 𝕜, x ≠ 0 ∧ ‖x‖ ≠ 1) : NontriviallyNormedField 𝕜 where
toNormedField := h'
non_trivial := by
rcases h with ⟨x, hx, hx1⟩
rcases hx1.lt_or_lt with hlt | hlt
· use x⁻¹
rw [norm_inv]
exact (one_lt_inv₀ (norm_pos_iff.2 hx)).2 hlt
· exact ⟨x, hlt⟩
noncomputable instance Real.normedField : NormedField ℝ :=
{ Real.normedAddCommGroup, Real.field with
norm_mul := abs_mul }
noncomputable instance Real.denselyNormedField : DenselyNormedField ℝ where
lt_norm_lt _ _ h₀ hr :=
let ⟨x, h⟩ := exists_between hr
⟨x, by rwa [Real.norm_eq_abs, abs_of_nonneg (h₀.trans h.1.le)]⟩
namespace Real
theorem toNNReal_mul_nnnorm {x : ℝ} (y : ℝ) (hx : 0 ≤ x) : x.toNNReal * ‖y‖₊ = ‖x * y‖₊ := by
ext
simp only [NNReal.coe_mul, nnnorm_mul, coe_nnnorm, Real.toNNReal_of_nonneg, norm_of_nonneg, hx,
NNReal.coe_mk]
theorem nnnorm_mul_toNNReal (x : ℝ) {y : ℝ} (hy : 0 ≤ y) : ‖x‖₊ * y.toNNReal = ‖x * y‖₊ := by
rw [mul_comm, mul_comm x, toNNReal_mul_nnnorm x hy]
end Real
/-! ### Induced normed structures -/
section Induced
variable {F : Type*} (R S : Type*) [FunLike F R S]
/-- An injective non-unital ring homomorphism from a `DivisionRing` to a `NormedRing` induces a
`NormedDivisionRing` structure on the domain.
See note [reducible non-instances] -/
abbrev NormedDivisionRing.induced [DivisionRing R] [NormedDivisionRing S]
[NonUnitalRingHomClass F R S] (f : F) (hf : Function.Injective f) : NormedDivisionRing R :=
{ NormedAddCommGroup.induced R S f hf, ‹DivisionRing R› with
norm_mul x y := show ‖f _‖ = _ from (map_mul f x y).symm ▸ norm_mul (f x) (f y) }
/-- An injective non-unital ring homomorphism from a `Field` to a `NormedRing` induces a
`NormedField` structure on the domain.
See note [reducible non-instances] -/
abbrev NormedField.induced [Field R] [NormedField S] [NonUnitalRingHomClass F R S] (f : F)
(hf : Function.Injective f) : NormedField R :=
{ NormedDivisionRing.induced R S f hf with
mul_comm := mul_comm }
end Induced
namespace SubfieldClass
variable {S F : Type*} [SetLike S F]
/--
If `s` is a subfield of a normed field `F`, then `s` is equipped with an induced normed
field structure.
-/
instance toNormedField [NormedField F] [SubfieldClass S F] (s : S) : NormedField s :=
NormedField.induced s F (SubringClass.subtype s) Subtype.val_injective
end SubfieldClass
namespace AbsoluteValue
/-- A real absolute value on a field determines a `NormedField` structure. -/
noncomputable def toNormedField {K : Type*} [Field K] (v : AbsoluteValue K ℝ) : NormedField K where
toField := inferInstanceAs (Field K)
__ := v.toNormedRing
norm_mul := v.map_mul
end AbsoluteValue
| Mathlib/Analysis/Normed/Field/Basic.lean | 398 | 401 | |
/-
Copyright (c) 2015 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Leonardo de Moura, Jeremy Avigad, Minchao Wu, Mario Carneiro
-/
import Mathlib.Data.Finset.Attach
import Mathlib.Data.Finset.Disjoint
import Mathlib.Data.Finset.Erase
import Mathlib.Data.Finset.Filter
import Mathlib.Data.Finset.Range
import Mathlib.Data.Finset.SDiff
import Mathlib.Data.Multiset.Basic
import Mathlib.Logic.Equiv.Set
import Mathlib.Order.Directed
import Mathlib.Order.Interval.Set.Defs
import Mathlib.Data.Set.SymmDiff
/-!
# Basic lemmas on finite sets
This file contains lemmas on the interaction of various definitions on the `Finset` type.
For an explanation of `Finset` design decisions, please see `Mathlib/Data/Finset/Defs.lean`.
## Main declarations
### Main definitions
* `Finset.choose`: Given a proof `h` of existence and uniqueness of a certain element
satisfying a predicate, `choose s h` returns the element of `s` satisfying that predicate.
### Equivalences between finsets
* The `Mathlib/Logic/Equiv/Defs.lean` file describes a general type of equivalence, so look in there
for any lemmas. There is some API for rewriting sums and products from `s` to `t` given that
`s ≃ t`.
TODO: examples
## Tags
finite sets, finset
-/
-- Assert that we define `Finset` without the material on `List.sublists`.
-- Note that we cannot use `List.sublists` itself as that is defined very early.
assert_not_exists List.sublistsLen Multiset.powerset CompleteLattice Monoid
open Multiset Subtype Function
universe u
variable {α : Type*} {β : Type*} {γ : Type*}
namespace Finset
-- TODO: these should be global attributes, but this will require fixing other files
attribute [local trans] Subset.trans Superset.trans
set_option linter.deprecated false in
@[deprecated "Deprecated without replacement." (since := "2025-02-07")]
theorem sizeOf_lt_sizeOf_of_mem [SizeOf α] {x : α} {s : Finset α} (hx : x ∈ s) :
SizeOf.sizeOf x < SizeOf.sizeOf s := by
cases s
dsimp [SizeOf.sizeOf, SizeOf.sizeOf, Multiset.sizeOf]
rw [Nat.add_comm]
refine lt_trans ?_ (Nat.lt_succ_self _)
exact Multiset.sizeOf_lt_sizeOf_of_mem hx
/-! ### Lattice structure -/
section Lattice
variable [DecidableEq α] {s s₁ s₂ t t₁ t₂ u v : Finset α} {a b : α}
/-! #### union -/
@[simp]
theorem disjUnion_eq_union (s t h) : @disjUnion α s t h = s ∪ t :=
ext fun a => by simp
@[simp]
theorem disjoint_union_left : Disjoint (s ∪ t) u ↔ Disjoint s u ∧ Disjoint t u := by
simp only [disjoint_left, mem_union, or_imp, forall_and]
@[simp]
theorem disjoint_union_right : Disjoint s (t ∪ u) ↔ Disjoint s t ∧ Disjoint s u := by
simp only [disjoint_right, mem_union, or_imp, forall_and]
/-! #### inter -/
theorem not_disjoint_iff_nonempty_inter : ¬Disjoint s t ↔ (s ∩ t).Nonempty :=
not_disjoint_iff.trans <| by simp [Finset.Nonempty]
alias ⟨_, Nonempty.not_disjoint⟩ := not_disjoint_iff_nonempty_inter
theorem disjoint_or_nonempty_inter (s t : Finset α) : Disjoint s t ∨ (s ∩ t).Nonempty := by
rw [← not_disjoint_iff_nonempty_inter]
exact em _
omit [DecidableEq α] in
theorem disjoint_of_subset_iff_left_eq_empty (h : s ⊆ t) :
Disjoint s t ↔ s = ∅ :=
disjoint_of_le_iff_left_eq_bot h
lemma pairwiseDisjoint_iff {ι : Type*} {s : Set ι} {f : ι → Finset α} :
s.PairwiseDisjoint f ↔ ∀ ⦃i⦄, i ∈ s → ∀ ⦃j⦄, j ∈ s → (f i ∩ f j).Nonempty → i = j := by
simp [Set.PairwiseDisjoint, Set.Pairwise, Function.onFun, not_imp_comm (a := _ = _),
not_disjoint_iff_nonempty_inter]
end Lattice
instance isDirected_le : IsDirected (Finset α) (· ≤ ·) := by classical infer_instance
instance isDirected_subset : IsDirected (Finset α) (· ⊆ ·) := isDirected_le
/-! ### erase -/
section Erase
variable [DecidableEq α] {s t u v : Finset α} {a b : α}
@[simp]
theorem erase_empty (a : α) : erase ∅ a = ∅ :=
rfl
protected lemma Nontrivial.erase_nonempty (hs : s.Nontrivial) : (s.erase a).Nonempty :=
(hs.exists_ne a).imp <| by aesop
@[simp] lemma erase_nonempty (ha : a ∈ s) : (s.erase a).Nonempty ↔ s.Nontrivial := by
simp only [Finset.Nonempty, mem_erase, and_comm (b := _ ∈ _)]
refine ⟨?_, fun hs ↦ hs.exists_ne a⟩
rintro ⟨b, hb, hba⟩
exact ⟨_, hb, _, ha, hba⟩
@[simp]
theorem erase_singleton (a : α) : ({a} : Finset α).erase a = ∅ := by
ext x
simp
@[simp]
theorem erase_insert_eq_erase (s : Finset α) (a : α) : (insert a s).erase a = s.erase a :=
ext fun x => by
simp +contextual only [mem_erase, mem_insert, and_congr_right_iff,
false_or, iff_self, imp_true_iff]
theorem erase_insert {a : α} {s : Finset α} (h : a ∉ s) : erase (insert a s) a = s := by
rw [erase_insert_eq_erase, erase_eq_of_not_mem h]
theorem erase_insert_of_ne {a b : α} {s : Finset α} (h : a ≠ b) :
erase (insert a s) b = insert a (erase s b) :=
ext fun x => by
have : x ≠ b ∧ x = a ↔ x = a := and_iff_right_of_imp fun hx => hx.symm ▸ h
simp only [mem_erase, mem_insert, and_or_left, this]
theorem erase_cons_of_ne {a b : α} {s : Finset α} (ha : a ∉ s) (hb : a ≠ b) :
erase (cons a s ha) b = cons a (erase s b) fun h => ha <| erase_subset _ _ h := by
simp only [cons_eq_insert, erase_insert_of_ne hb]
@[simp] theorem insert_erase (h : a ∈ s) : insert a (erase s a) = s :=
ext fun x => by
simp only [mem_insert, mem_erase, or_and_left, dec_em, true_and]
apply or_iff_right_of_imp
rintro rfl
exact h
lemma erase_eq_iff_eq_insert (hs : a ∈ s) (ht : a ∉ t) : erase s a = t ↔ s = insert a t := by
aesop
lemma insert_erase_invOn :
Set.InvOn (insert a) (fun s ↦ erase s a) {s : Finset α | a ∈ s} {s : Finset α | a ∉ s} :=
⟨fun _s ↦ insert_erase, fun _s ↦ erase_insert⟩
theorem erase_ssubset {a : α} {s : Finset α} (h : a ∈ s) : s.erase a ⊂ s :=
calc
s.erase a ⊂ insert a (s.erase a) := ssubset_insert <| not_mem_erase _ _
_ = _ := insert_erase h
theorem ssubset_iff_exists_subset_erase {s t : Finset α} : s ⊂ t ↔ ∃ a ∈ t, s ⊆ t.erase a := by
refine ⟨fun h => ?_, fun ⟨a, ha, h⟩ => ssubset_of_subset_of_ssubset h <| erase_ssubset ha⟩
obtain ⟨a, ht, hs⟩ := not_subset.1 h.2
exact ⟨a, ht, subset_erase.2 ⟨h.1, hs⟩⟩
theorem erase_ssubset_insert (s : Finset α) (a : α) : s.erase a ⊂ insert a s :=
ssubset_iff_exists_subset_erase.2
⟨a, mem_insert_self _ _, erase_subset_erase _ <| subset_insert _ _⟩
theorem erase_cons {s : Finset α} {a : α} (h : a ∉ s) : (s.cons a h).erase a = s := by
rw [cons_eq_insert, erase_insert_eq_erase, erase_eq_of_not_mem h]
theorem subset_insert_iff {a : α} {s t : Finset α} : s ⊆ insert a t ↔ erase s a ⊆ t := by
simp only [subset_iff, or_iff_not_imp_left, mem_erase, mem_insert, and_imp]
exact forall_congr' fun x => forall_swap
theorem erase_insert_subset (a : α) (s : Finset α) : erase (insert a s) a ⊆ s :=
subset_insert_iff.1 <| Subset.rfl
theorem insert_erase_subset (a : α) (s : Finset α) : s ⊆ insert a (erase s a) :=
subset_insert_iff.2 <| Subset.rfl
theorem subset_insert_iff_of_not_mem (h : a ∉ s) : s ⊆ insert a t ↔ s ⊆ t := by
rw [subset_insert_iff, erase_eq_of_not_mem h]
theorem erase_subset_iff_of_mem (h : a ∈ t) : s.erase a ⊆ t ↔ s ⊆ t := by
rw [← subset_insert_iff, insert_eq_of_mem h]
theorem erase_injOn' (a : α) : { s : Finset α | a ∈ s }.InjOn fun s => erase s a :=
fun s hs t ht (h : s.erase a = _) => by rw [← insert_erase hs, ← insert_erase ht, h]
end Erase
lemma Nontrivial.exists_cons_eq {s : Finset α} (hs : s.Nontrivial) :
∃ t a ha b hb hab, (cons b t hb).cons a (mem_cons.not.2 <| not_or_intro hab ha) = s := by
classical
obtain ⟨a, ha, b, hb, hab⟩ := hs
have : b ∈ s.erase a := mem_erase.2 ⟨hab.symm, hb⟩
refine ⟨(s.erase a).erase b, a, ?_, b, ?_, ?_, ?_⟩ <;>
simp [insert_erase this, insert_erase ha, *]
/-! ### sdiff -/
section Sdiff
variable [DecidableEq α] {s t u v : Finset α} {a b : α}
lemma erase_sdiff_erase (hab : a ≠ b) (hb : b ∈ s) : s.erase a \ s.erase b = {b} := by
ext; aesop
-- TODO: Do we want to delete this lemma and `Finset.disjUnion_singleton`,
-- or instead add `Finset.union_singleton`/`Finset.singleton_union`?
theorem sdiff_singleton_eq_erase (a : α) (s : Finset α) : s \ {a} = erase s a := by
ext
rw [mem_erase, mem_sdiff, mem_singleton, and_comm]
-- This lemma matches `Finset.insert_eq` in functionality.
theorem erase_eq (s : Finset α) (a : α) : s.erase a = s \ {a} :=
(sdiff_singleton_eq_erase _ _).symm
theorem disjoint_erase_comm : Disjoint (s.erase a) t ↔ Disjoint s (t.erase a) := by
simp_rw [erase_eq, disjoint_sdiff_comm]
lemma disjoint_insert_erase (ha : a ∉ t) : Disjoint (s.erase a) (insert a t) ↔ Disjoint s t := by
rw [disjoint_erase_comm, erase_insert ha]
lemma disjoint_erase_insert (ha : a ∉ s) : Disjoint (insert a s) (t.erase a) ↔ Disjoint s t := by
rw [← disjoint_erase_comm, erase_insert ha]
theorem disjoint_of_erase_left (ha : a ∉ t) (hst : Disjoint (s.erase a) t) : Disjoint s t := by
rw [← erase_insert ha, ← disjoint_erase_comm, disjoint_insert_right]
exact ⟨not_mem_erase _ _, hst⟩
theorem disjoint_of_erase_right (ha : a ∉ s) (hst : Disjoint s (t.erase a)) : Disjoint s t := by
rw [← erase_insert ha, disjoint_erase_comm, disjoint_insert_left]
exact ⟨not_mem_erase _ _, hst⟩
theorem inter_erase (a : α) (s t : Finset α) : s ∩ t.erase a = (s ∩ t).erase a := by
simp only [erase_eq, inter_sdiff_assoc]
@[simp]
theorem erase_inter (a : α) (s t : Finset α) : s.erase a ∩ t = (s ∩ t).erase a := by
simpa only [inter_comm t] using inter_erase a t s
theorem erase_sdiff_comm (s t : Finset α) (a : α) : s.erase a \ t = (s \ t).erase a := by
simp_rw [erase_eq, sdiff_right_comm]
theorem erase_inter_comm (s t : Finset α) (a : α) : s.erase a ∩ t = s ∩ t.erase a := by
rw [erase_inter, inter_erase]
theorem erase_union_distrib (s t : Finset α) (a : α) : (s ∪ t).erase a = s.erase a ∪ t.erase a := by
simp_rw [erase_eq, union_sdiff_distrib]
theorem insert_inter_distrib (s t : Finset α) (a : α) :
insert a (s ∩ t) = insert a s ∩ insert a t := by simp_rw [insert_eq, union_inter_distrib_left]
theorem erase_sdiff_distrib (s t : Finset α) (a : α) : (s \ t).erase a = s.erase a \ t.erase a := by
simp_rw [erase_eq, sdiff_sdiff, sup_sdiff_eq_sup le_rfl, sup_comm]
theorem erase_union_of_mem (ha : a ∈ t) (s : Finset α) : s.erase a ∪ t = s ∪ t := by
rw [← insert_erase (mem_union_right s ha), erase_union_distrib, ← union_insert, insert_erase ha]
theorem union_erase_of_mem (ha : a ∈ s) (t : Finset α) : s ∪ t.erase a = s ∪ t := by
rw [← insert_erase (mem_union_left t ha), erase_union_distrib, ← insert_union, insert_erase ha]
theorem sdiff_union_erase_cancel (hts : t ⊆ s) (ha : a ∈ t) : s \ t ∪ t.erase a = s.erase a := by
simp_rw [erase_eq, sdiff_union_sdiff_cancel hts (singleton_subset_iff.2 ha)]
theorem sdiff_insert (s t : Finset α) (x : α) : s \ insert x t = (s \ t).erase x := by
simp_rw [← sdiff_singleton_eq_erase, insert_eq, sdiff_sdiff_left', sdiff_union_distrib,
inter_comm]
theorem sdiff_insert_insert_of_mem_of_not_mem {s t : Finset α} {x : α} (hxs : x ∈ s) (hxt : x ∉ t) :
insert x (s \ insert x t) = s \ t := by
rw [sdiff_insert, insert_erase (mem_sdiff.mpr ⟨hxs, hxt⟩)]
theorem sdiff_erase (h : a ∈ s) : s \ t.erase a = insert a (s \ t) := by
rw [← sdiff_singleton_eq_erase, sdiff_sdiff_eq_sdiff_union (singleton_subset_iff.2 h), insert_eq,
union_comm]
theorem sdiff_erase_self (ha : a ∈ s) : s \ s.erase a = {a} := by
rw [sdiff_erase ha, Finset.sdiff_self, insert_empty_eq]
theorem erase_eq_empty_iff (s : Finset α) (a : α) : s.erase a = ∅ ↔ s = ∅ ∨ s = {a} := by
rw [← sdiff_singleton_eq_erase, sdiff_eq_empty_iff_subset, subset_singleton_iff]
--TODO@Yaël: Kill lemmas duplicate with `BooleanAlgebra`
theorem sdiff_disjoint : Disjoint (t \ s) s :=
disjoint_left.2 fun _a ha => (mem_sdiff.1 ha).2
theorem disjoint_sdiff : Disjoint s (t \ s) :=
sdiff_disjoint.symm
theorem disjoint_sdiff_inter (s t : Finset α) : Disjoint (s \ t) (s ∩ t) :=
disjoint_of_subset_right inter_subset_right sdiff_disjoint
end Sdiff
/-! ### attach -/
@[simp]
theorem attach_empty : attach (∅ : Finset α) = ∅ :=
rfl
@[simp]
theorem attach_nonempty_iff {s : Finset α} : s.attach.Nonempty ↔ s.Nonempty := by
simp [Finset.Nonempty]
@[aesop safe apply (rule_sets := [finsetNonempty])]
protected alias ⟨_, Nonempty.attach⟩ := attach_nonempty_iff
@[simp]
theorem attach_eq_empty_iff {s : Finset α} : s.attach = ∅ ↔ s = ∅ := by
simp [eq_empty_iff_forall_not_mem]
/-! ### filter -/
section Filter
variable (p q : α → Prop) [DecidablePred p] [DecidablePred q] {s t : Finset α}
theorem filter_singleton (a : α) : filter p {a} = if p a then {a} else ∅ := by
classical
ext x
simp only [mem_singleton, forall_eq, mem_filter]
split_ifs with h <;> by_cases h' : x = a <;> simp [h, h']
theorem filter_cons_of_pos (a : α) (s : Finset α) (ha : a ∉ s) (hp : p a) :
filter p (cons a s ha) = cons a (filter p s) ((mem_of_mem_filter _).mt ha) :=
eq_of_veq <| Multiset.filter_cons_of_pos s.val hp
theorem filter_cons_of_neg (a : α) (s : Finset α) (ha : a ∉ s) (hp : ¬p a) :
filter p (cons a s ha) = filter p s :=
eq_of_veq <| Multiset.filter_cons_of_neg s.val hp
theorem disjoint_filter {s : Finset α} {p q : α → Prop} [DecidablePred p] [DecidablePred q] :
Disjoint (s.filter p) (s.filter q) ↔ ∀ x ∈ s, p x → ¬q x := by
constructor <;> simp +contextual [disjoint_left]
theorem disjoint_filter_filter' (s t : Finset α)
{p q : α → Prop} [DecidablePred p] [DecidablePred q] (h : Disjoint p q) :
Disjoint (s.filter p) (t.filter q) := by
simp_rw [disjoint_left, mem_filter]
rintro a ⟨_, hp⟩ ⟨_, hq⟩
rw [Pi.disjoint_iff] at h
simpa [hp, hq] using h a
theorem disjoint_filter_filter_neg (s t : Finset α) (p : α → Prop)
[DecidablePred p] [∀ x, Decidable (¬p x)] :
Disjoint (s.filter p) (t.filter fun a => ¬p a) :=
disjoint_filter_filter' s t disjoint_compl_right
theorem filter_disj_union (s : Finset α) (t : Finset α) (h : Disjoint s t) :
filter p (disjUnion s t h) = (filter p s).disjUnion (filter p t) (disjoint_filter_filter h) :=
eq_of_veq <| Multiset.filter_add _ _ _
theorem filter_cons {a : α} (s : Finset α) (ha : a ∉ s) :
filter p (cons a s ha) =
if p a then cons a (filter p s) ((mem_of_mem_filter _).mt ha) else filter p s := by
split_ifs with h
· rw [filter_cons_of_pos _ _ _ ha h]
· rw [filter_cons_of_neg _ _ _ ha h]
section
variable [DecidableEq α]
theorem filter_union (s₁ s₂ : Finset α) : (s₁ ∪ s₂).filter p = s₁.filter p ∪ s₂.filter p :=
ext fun _ => by simp only [mem_filter, mem_union, or_and_right]
theorem filter_union_right (s : Finset α) : s.filter p ∪ s.filter q = s.filter fun x => p x ∨ q x :=
ext fun x => by simp [mem_filter, mem_union, ← and_or_left]
theorem filter_mem_eq_inter {s t : Finset α} [∀ i, Decidable (i ∈ t)] :
(s.filter fun i => i ∈ t) = s ∩ t :=
ext fun i => by simp [mem_filter, mem_inter]
theorem filter_inter_distrib (s t : Finset α) : (s ∩ t).filter p = s.filter p ∩ t.filter p := by
ext
simp [mem_filter, mem_inter, and_assoc]
theorem filter_inter (s t : Finset α) : filter p s ∩ t = filter p (s ∩ t) := by
ext
simp only [mem_inter, mem_filter, and_right_comm]
theorem inter_filter (s t : Finset α) : s ∩ filter p t = filter p (s ∩ t) := by
rw [inter_comm, filter_inter, inter_comm]
theorem filter_insert (a : α) (s : Finset α) :
filter p (insert a s) = if p a then insert a (filter p s) else filter p s := by
ext x
split_ifs with h <;> by_cases h' : x = a <;> simp [h, h']
theorem filter_erase (a : α) (s : Finset α) : filter p (erase s a) = erase (filter p s) a := by
ext x
simp only [and_assoc, mem_filter, iff_self, mem_erase]
theorem filter_or (s : Finset α) : (s.filter fun a => p a ∨ q a) = s.filter p ∪ s.filter q :=
ext fun _ => by simp [mem_filter, mem_union, and_or_left]
theorem filter_and (s : Finset α) : (s.filter fun a => p a ∧ q a) = s.filter p ∩ s.filter q :=
ext fun _ => by simp [mem_filter, mem_inter, and_comm, and_left_comm, and_self_iff, and_assoc]
theorem filter_not (s : Finset α) : (s.filter fun a => ¬p a) = s \ s.filter p :=
ext fun a => by
simp only [Bool.decide_coe, Bool.not_eq_true', mem_filter, and_comm, mem_sdiff, not_and_or,
Bool.not_eq_true, and_or_left, and_not_self, or_false]
lemma filter_and_not (s : Finset α) (p q : α → Prop) [DecidablePred p] [DecidablePred q] :
s.filter (fun a ↦ p a ∧ ¬ q a) = s.filter p \ s.filter q := by
rw [filter_and, filter_not, ← inter_sdiff_assoc, inter_eq_left.2 (filter_subset _ _)]
theorem sdiff_eq_filter (s₁ s₂ : Finset α) : s₁ \ s₂ = filter (· ∉ s₂) s₁ :=
ext fun _ => by simp [mem_sdiff, mem_filter]
theorem subset_union_elim {s : Finset α} {t₁ t₂ : Set α} (h : ↑s ⊆ t₁ ∪ t₂) :
∃ s₁ s₂ : Finset α, s₁ ∪ s₂ = s ∧ ↑s₁ ⊆ t₁ ∧ ↑s₂ ⊆ t₂ \ t₁ := by
classical
refine ⟨s.filter (· ∈ t₁), s.filter (· ∉ t₁), ?_, ?_, ?_⟩
· simp [filter_union_right, em]
· intro x
simp
· intro x
simp only [not_not, coe_filter, Set.mem_setOf_eq, Set.mem_diff, and_imp]
intro hx hx₂
exact ⟨Or.resolve_left (h hx) hx₂, hx₂⟩
-- This is not a good simp lemma, as it would prevent `Finset.mem_filter` from firing
-- on, e.g. `x ∈ s.filter (Eq b)`.
/-- After filtering out everything that does not equal a given value, at most that value remains.
This is equivalent to `filter_eq'` with the equality the other way.
-/
theorem filter_eq [DecidableEq β] (s : Finset β) (b : β) :
s.filter (Eq b) = ite (b ∈ s) {b} ∅ := by
split_ifs with h
· ext
simp only [mem_filter, mem_singleton, decide_eq_true_eq]
refine ⟨fun h => h.2.symm, ?_⟩
rintro rfl
exact ⟨h, rfl⟩
· ext
simp only [mem_filter, not_and, iff_false, not_mem_empty, decide_eq_true_eq]
rintro m rfl
exact h m
/-- After filtering out everything that does not equal a given value, at most that value remains.
This is equivalent to `filter_eq` with the equality the other way.
-/
theorem filter_eq' [DecidableEq β] (s : Finset β) (b : β) :
(s.filter fun a => a = b) = ite (b ∈ s) {b} ∅ :=
_root_.trans (filter_congr fun _ _ => by simp_rw [@eq_comm _ b]) (filter_eq s b)
theorem filter_ne [DecidableEq β] (s : Finset β) (b : β) :
(s.filter fun a => b ≠ a) = s.erase b := by
ext
simp only [mem_filter, mem_erase, Ne, decide_not, Bool.not_eq_true', decide_eq_false_iff_not]
tauto
theorem filter_ne' [DecidableEq β] (s : Finset β) (b : β) : (s.filter fun a => a ≠ b) = s.erase b :=
_root_.trans (filter_congr fun _ _ => by simp_rw [@ne_comm _ b]) (filter_ne s b)
theorem filter_union_filter_of_codisjoint (s : Finset α) (h : Codisjoint p q) :
s.filter p ∪ s.filter q = s :=
(filter_or _ _ _).symm.trans <| filter_true_of_mem fun x _ => h.top_le x trivial
theorem filter_union_filter_neg_eq [∀ x, Decidable (¬p x)] (s : Finset α) :
(s.filter p ∪ s.filter fun a => ¬p a) = s :=
filter_union_filter_of_codisjoint _ _ _ <| @codisjoint_hnot_right _ _ p
end
end Filter
/-! ### range -/
section Range
open Nat
variable {n m l : ℕ}
@[simp]
theorem range_filter_eq {n m : ℕ} : (range n).filter (· = m) = if m < n then {m} else ∅ := by
convert filter_eq (range n) m using 2
· ext
rw [eq_comm]
· simp
end Range
end Finset
/-! ### dedup on list and multiset -/
namespace Multiset
variable [DecidableEq α] {s t : Multiset α}
@[simp]
theorem toFinset_add (s t : Multiset α) : toFinset (s + t) = toFinset s ∪ toFinset t :=
Finset.ext <| by simp
@[simp]
theorem toFinset_inter (s t : Multiset α) : toFinset (s ∩ t) = toFinset s ∩ toFinset t :=
Finset.ext <| by simp
@[simp]
theorem toFinset_union (s t : Multiset α) : (s ∪ t).toFinset = s.toFinset ∪ t.toFinset := by
ext; simp
@[simp]
theorem toFinset_eq_empty {m : Multiset α} : m.toFinset = ∅ ↔ m = 0 :=
Finset.val_inj.symm.trans Multiset.dedup_eq_zero
@[simp]
theorem toFinset_nonempty : s.toFinset.Nonempty ↔ s ≠ 0 := by
simp only [toFinset_eq_empty, Ne, Finset.nonempty_iff_ne_empty]
@[aesop safe apply (rule_sets := [finsetNonempty])]
protected alias ⟨_, Aesop.toFinset_nonempty_of_ne⟩ := toFinset_nonempty
@[simp]
theorem toFinset_filter (s : Multiset α) (p : α → Prop) [DecidablePred p] :
Multiset.toFinset (s.filter p) = s.toFinset.filter p := by
ext; simp
end Multiset
namespace List
variable [DecidableEq α] {l l' : List α} {a : α} {f : α → β}
{s : Finset α} {t : Set β} {t' : Finset β}
@[simp]
theorem toFinset_union (l l' : List α) : (l ∪ l').toFinset = l.toFinset ∪ l'.toFinset := by
ext
simp
@[simp]
theorem toFinset_inter (l l' : List α) : (l ∩ l').toFinset = l.toFinset ∩ l'.toFinset := by
ext
simp
@[aesop safe apply (rule_sets := [finsetNonempty])]
alias ⟨_, Aesop.toFinset_nonempty_of_ne⟩ := toFinset_nonempty_iff
@[simp]
theorem toFinset_filter (s : List α) (p : α → Bool) :
(s.filter p).toFinset = s.toFinset.filter (p ·) := by
ext; simp [List.mem_filter]
end List
namespace Finset
section ToList
@[simp]
theorem toList_eq_nil {s : Finset α} : s.toList = [] ↔ s = ∅ :=
Multiset.toList_eq_nil.trans val_eq_zero
theorem empty_toList {s : Finset α} : s.toList.isEmpty ↔ s = ∅ := by simp
@[simp]
theorem toList_empty : (∅ : Finset α).toList = [] :=
toList_eq_nil.mpr rfl
theorem Nonempty.toList_ne_nil {s : Finset α} (hs : s.Nonempty) : s.toList ≠ [] :=
mt toList_eq_nil.mp hs.ne_empty
theorem Nonempty.not_empty_toList {s : Finset α} (hs : s.Nonempty) : ¬s.toList.isEmpty :=
mt empty_toList.mp hs.ne_empty
end ToList
/-! ### choose -/
section Choose
variable (p : α → Prop) [DecidablePred p] (l : Finset α)
/-- Given a finset `l` and a predicate `p`, associate to a proof that there is a unique element of
`l` satisfying `p` this unique element, as an element of the corresponding subtype. -/
def chooseX (hp : ∃! a, a ∈ l ∧ p a) : { a // a ∈ l ∧ p a } :=
Multiset.chooseX p l.val hp
/-- Given a finset `l` and a predicate `p`, associate to a proof that there is a unique element of
`l` satisfying `p` this unique element, as an element of the ambient type. -/
def choose (hp : ∃! a, a ∈ l ∧ p a) : α :=
chooseX p l hp
theorem choose_spec (hp : ∃! a, a ∈ l ∧ p a) : choose p l hp ∈ l ∧ p (choose p l hp) :=
(chooseX p l hp).property
theorem choose_mem (hp : ∃! a, a ∈ l ∧ p a) : choose p l hp ∈ l :=
(choose_spec _ _ _).1
theorem choose_property (hp : ∃! a, a ∈ l ∧ p a) : p (choose p l hp) :=
(choose_spec _ _ _).2
end Choose
end Finset
namespace Equiv
variable [DecidableEq α] {s t : Finset α}
open Finset
/-- The disjoint union of finsets is a sum -/
def Finset.union (s t : Finset α) (h : Disjoint s t) :
s ⊕ t ≃ (s ∪ t : Finset α) :=
Equiv.setCongr (coe_union _ _) |>.trans (Equiv.Set.union (disjoint_coe.mpr h)) |>.symm
@[simp]
theorem Finset.union_symm_inl (h : Disjoint s t) (x : s) :
Equiv.Finset.union s t h (Sum.inl x) = ⟨x, Finset.mem_union.mpr <| Or.inl x.2⟩ :=
rfl
@[simp]
theorem Finset.union_symm_inr (h : Disjoint s t) (y : t) :
Equiv.Finset.union s t h (Sum.inr y) = ⟨y, Finset.mem_union.mpr <| Or.inr y.2⟩ :=
rfl
/-- The type of dependent functions on the disjoint union of finsets `s ∪ t` is equivalent to the
type of pairs of functions on `s` and on `t`. This is similar to `Equiv.sumPiEquivProdPi`. -/
def piFinsetUnion {ι} [DecidableEq ι] (α : ι → Type*) {s t : Finset ι} (h : Disjoint s t) :
((∀ i : s, α i) × ∀ i : t, α i) ≃ ∀ i : (s ∪ t : Finset ι), α i :=
let e := Equiv.Finset.union s t h
sumPiEquivProdPi (fun b ↦ α (e b)) |>.symm.trans (.piCongrLeft (fun i : ↥(s ∪ t) ↦ α i) e)
/-- A finset is equivalent to its coercion as a set. -/
def _root_.Finset.equivToSet (s : Finset α) : s ≃ s.toSet where
toFun a := ⟨a.1, mem_coe.2 a.2⟩
invFun a := ⟨a.1, mem_coe.1 a.2⟩
left_inv := fun _ ↦ rfl
right_inv := fun _ ↦ rfl
end Equiv
namespace Multiset
variable [DecidableEq α]
@[simp]
lemma toFinset_replicate (n : ℕ) (a : α) :
(replicate n a).toFinset = if n = 0 then ∅ else {a} := by
ext x
simp only [mem_toFinset, Finset.mem_singleton, mem_replicate]
split_ifs with hn <;> simp [hn]
end Multiset
| Mathlib/Data/Finset/Basic.lean | 3,068 | 3,070 | |
/-
Copyright (c) 2016 Jeremy Avigad. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Jeremy Avigad, Leonardo de Moura, Mario Carneiro, Johannes Hölzl
-/
import Mathlib.Algebra.Order.Group.Unbundled.Basic
import Mathlib.Algebra.Order.Monoid.Defs
import Mathlib.Algebra.Order.Sub.Defs
import Mathlib.Util.AssertExists
/-!
# Ordered groups
This file defines bundled ordered groups and develops a few basic results.
## Implementation details
Unfortunately, the number of `'` appended to lemmas in this file
may differ between the multiplicative and the additive version of a lemma.
The reason is that we did not want to change existing names in the library.
-/
/-
`NeZero` theory should not be needed at this point in the ordered algebraic hierarchy.
-/
assert_not_imported Mathlib.Algebra.NeZero
open Function
universe u
variable {α : Type u}
/-- An ordered additive commutative group is an additive commutative group
with a partial order in which addition is strictly monotone. -/
@[deprecated "Use `[AddCommGroup α] [PartialOrder α] [IsOrderedAddMonoid α]` instead."
(since := "2025-04-10")]
structure OrderedAddCommGroup (α : Type u) extends AddCommGroup α, PartialOrder α where
/-- Addition is monotone in an ordered additive commutative group. -/
protected add_le_add_left : ∀ a b : α, a ≤ b → ∀ c : α, c + a ≤ c + b
set_option linter.existingAttributeWarning false in
/-- An ordered commutative group is a commutative group
with a partial order in which multiplication is strictly monotone. -/
@[to_additive,
deprecated "Use `[CommGroup α] [PartialOrder α] [IsOrderedMonoid α]` instead."
(since := "2025-04-10")]
structure OrderedCommGroup (α : Type u) extends CommGroup α, PartialOrder α where
/-- Multiplication is monotone in an ordered commutative group. -/
protected mul_le_mul_left : ∀ a b : α, a ≤ b → ∀ c : α, c * a ≤ c * b
alias OrderedCommGroup.mul_lt_mul_left' := mul_lt_mul_left'
attribute [to_additive OrderedAddCommGroup.add_lt_add_left] OrderedCommGroup.mul_lt_mul_left'
alias OrderedCommGroup.le_of_mul_le_mul_left := le_of_mul_le_mul_left'
attribute [to_additive] OrderedCommGroup.le_of_mul_le_mul_left
alias OrderedCommGroup.lt_of_mul_lt_mul_left := lt_of_mul_lt_mul_left'
attribute [to_additive] OrderedCommGroup.lt_of_mul_lt_mul_left
-- See note [lower instance priority]
@[to_additive IsOrderedAddMonoid.toIsOrderedCancelAddMonoid]
instance (priority := 100) IsOrderedMonoid.toIsOrderedCancelMonoid
[CommGroup α] [PartialOrder α] [IsOrderedMonoid α] : IsOrderedCancelMonoid α where
le_of_mul_le_mul_left a b c bc := by simpa using mul_le_mul_left' bc a⁻¹
le_of_mul_le_mul_right a b c bc := by simpa using mul_le_mul_left' bc a⁻¹
/-!
### Linearly ordered commutative groups
-/
set_option linter.deprecated false in
/-- A linearly ordered additive commutative group is an
additive commutative group with a linear order in which
addition is monotone. -/
@[deprecated "Use `[AddCommGroup α] [LinearOrder α] [IsOrderedAddMonoid α]` instead."
(since := "2025-04-10")]
structure LinearOrderedAddCommGroup (α : Type u) extends OrderedAddCommGroup α, LinearOrder α
set_option linter.existingAttributeWarning false in
set_option linter.deprecated false in
/-- A linearly ordered commutative group is a
commutative group with a linear order in which
multiplication is monotone. -/
@[to_additive,
deprecated "Use `[CommGroup α] [LinearOrder α] [IsOrderedMonoid α]` instead."
(since := "2025-04-10")]
structure LinearOrderedCommGroup (α : Type u) extends OrderedCommGroup α, LinearOrder α
attribute [nolint docBlame]
LinearOrderedCommGroup.toLinearOrder LinearOrderedAddCommGroup.toLinearOrder
section LinearOrderedCommGroup
variable [CommGroup α] [LinearOrder α] [IsOrderedMonoid α] {a : α}
@[to_additive LinearOrderedAddCommGroup.add_lt_add_left]
theorem LinearOrderedCommGroup.mul_lt_mul_left' (a b : α) (h : a < b) (c : α) : c * a < c * b :=
_root_.mul_lt_mul_left' h c
@[to_additive eq_zero_of_neg_eq]
theorem eq_one_of_inv_eq' (h : a⁻¹ = a) : a = 1 :=
match lt_trichotomy a 1 with
| Or.inl h₁ =>
have : 1 < a := h ▸ one_lt_inv_of_inv h₁
absurd h₁ this.asymm
| Or.inr (Or.inl h₁) => h₁
| Or.inr (Or.inr h₁) =>
have : a < 1 := h ▸ inv_lt_one'.mpr h₁
absurd h₁ this.asymm
@[to_additive exists_zero_lt]
theorem exists_one_lt' [Nontrivial α] : ∃ a : α, 1 < a := by
obtain ⟨y, hy⟩ := Decidable.exists_ne (1 : α)
obtain h|h := hy.lt_or_lt
· exact ⟨y⁻¹, one_lt_inv'.mpr h⟩
· exact ⟨y, h⟩
-- see Note [lower instance priority]
@[to_additive]
instance (priority := 100) LinearOrderedCommGroup.to_noMaxOrder [Nontrivial α] : NoMaxOrder α :=
⟨by
obtain ⟨y, hy⟩ : ∃ a : α, 1 < a := exists_one_lt'
exact fun a => ⟨a * y, lt_mul_of_one_lt_right' a hy⟩⟩
-- see Note [lower instance priority]
@[to_additive]
instance (priority := 100) LinearOrderedCommGroup.to_noMinOrder [Nontrivial α] : NoMinOrder α :=
⟨by
obtain ⟨y, hy⟩ : ∃ a : α, 1 < a := exists_one_lt'
exact fun a => ⟨a / y, (div_lt_self_iff a).mpr hy⟩⟩
@[to_additive (attr := simp)]
theorem inv_le_self_iff : a⁻¹ ≤ a ↔ 1 ≤ a := by simp [inv_le_iff_one_le_mul']
@[to_additive (attr := simp)]
theorem inv_lt_self_iff : a⁻¹ < a ↔ 1 < a := by simp [inv_lt_iff_one_lt_mul]
@[to_additive (attr := simp)]
theorem le_inv_self_iff : a ≤ a⁻¹ ↔ a ≤ 1 := by simp [← not_iff_not]
@[to_additive (attr := simp)]
theorem lt_inv_self_iff : a < a⁻¹ ↔ a < 1 := by simp [← not_iff_not]
end LinearOrderedCommGroup
section NormNumLemmas
/- The following lemmas are stated so that the `norm_num` tactic can use them with the
expected signatures. -/
variable [CommGroup α] [PartialOrder α] [IsOrderedMonoid α] {a b : α}
@[to_additive (attr := gcongr) neg_le_neg]
theorem inv_le_inv' : a ≤ b → b⁻¹ ≤ a⁻¹ :=
inv_le_inv_iff.mpr
@[to_additive (attr := gcongr) neg_lt_neg]
theorem inv_lt_inv' : a < b → b⁻¹ < a⁻¹ :=
inv_lt_inv_iff.mpr
-- The additive version is also a `linarith` lemma.
@[to_additive]
theorem inv_lt_one_of_one_lt : 1 < a → a⁻¹ < 1 :=
inv_lt_one_iff_one_lt.mpr
-- The additive version is also a `linarith` lemma.
@[to_additive]
theorem inv_le_one_of_one_le : 1 ≤ a → a⁻¹ ≤ 1 :=
inv_le_one'.mpr
@[to_additive neg_nonneg_of_nonpos]
theorem one_le_inv_of_le_one : a ≤ 1 → 1 ≤ a⁻¹ :=
one_le_inv'.mpr
end NormNumLemmas
| Mathlib/Algebra/Order/Group/Defs.lean | 875 | 876 | |
/-
Copyright (c) 2021 Kalle Kytölä. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kalle Kytölä
-/
import Mathlib.MeasureTheory.Integral.Bochner.ContinuousLinearMap
import Mathlib.MeasureTheory.Measure.HasOuterApproxClosed
import Mathlib.MeasureTheory.Measure.Prod
import Mathlib.Topology.Algebra.Module.WeakDual
/-!
# Finite measures
This file defines the type of finite measures on a given measurable space. When the underlying
space has a topology and the measurable space structure (sigma algebra) is finer than the Borel
sigma algebra, then the type of finite measures is equipped with the topology of weak convergence
of measures. The topology of weak convergence is the coarsest topology w.r.t. which
for every bounded continuous `ℝ≥0`-valued function `f`, the integration of `f` against the
measure is continuous.
## Main definitions
The main definitions are
* `MeasureTheory.FiniteMeasure Ω`: The type of finite measures on `Ω` with the topology of weak
convergence of measures.
* `MeasureTheory.FiniteMeasure.toWeakDualBCNN : FiniteMeasure Ω → (WeakDual ℝ≥0 (Ω →ᵇ ℝ≥0))`:
Interpret a finite measure as a continuous linear functional on the space of
bounded continuous nonnegative functions on `Ω`. This is used for the definition of the
topology of weak convergence.
* `MeasureTheory.FiniteMeasure.map`: The push-forward `f* μ` of a finite measure `μ` on `Ω`
along a measurable function `f : Ω → Ω'`.
* `MeasureTheory.FiniteMeasure.mapCLM`: The push-forward along a given continuous `f : Ω → Ω'`
as a continuous linear map `f* : FiniteMeasure Ω →L[ℝ≥0] FiniteMeasure Ω'`.
## Main results
* Finite measures `μ` on `Ω` give rise to continuous linear functionals on the space of
bounded continuous nonnegative functions on `Ω` via integration:
`MeasureTheory.FiniteMeasure.toWeakDualBCNN : FiniteMeasure Ω → (WeakDual ℝ≥0 (Ω →ᵇ ℝ≥0))`
* `MeasureTheory.FiniteMeasure.tendsto_iff_forall_integral_tendsto`: Convergence of finite
measures is characterized by the convergence of integrals of all bounded continuous functions.
This shows that the chosen definition of topology coincides with the common textbook definition
of weak convergence of measures. A similar characterization by the convergence of integrals (in
the `MeasureTheory.lintegral` sense) of all bounded continuous nonnegative functions is
`MeasureTheory.FiniteMeasure.tendsto_iff_forall_lintegral_tendsto`.
* `MeasureTheory.FiniteMeasure.continuous_map`: For a continuous function `f : Ω → Ω'`, the
push-forward of finite measures `f* : FiniteMeasure Ω → FiniteMeasure Ω'` is continuous.
* `MeasureTheory.FiniteMeasure.t2Space`: The topology of weak convergence of finite Borel measures
is Hausdorff on spaces where indicators of closed sets have continuous decreasing approximating
sequences (in particular on any pseudo-metrizable spaces).
## Implementation notes
The topology of weak convergence of finite Borel measures is defined using a mapping from
`MeasureTheory.FiniteMeasure Ω` to `WeakDual ℝ≥0 (Ω →ᵇ ℝ≥0)`, inheriting the topology from the
latter.
The implementation of `MeasureTheory.FiniteMeasure Ω` and is directly as a subtype of
`MeasureTheory.Measure Ω`, and the coercion to a function is the composition `ENNReal.toNNReal`
and the coercion to function of `MeasureTheory.Measure Ω`. Another alternative would have been to
use a bijection with `MeasureTheory.VectorMeasure Ω ℝ≥0` as an intermediate step. Some
considerations:
* Potential advantages of using the `NNReal`-valued vector measure alternative:
* The coercion to function would avoid need to compose with `ENNReal.toNNReal`, the
`NNReal`-valued API could be more directly available.
* Potential drawbacks of the vector measure alternative:
* The coercion to function would lose monotonicity, as non-measurable sets would be defined to
have measure 0.
* No integration theory directly. E.g., the topology definition requires
`MeasureTheory.lintegral` w.r.t. a coercion to `MeasureTheory.Measure Ω` in any case.
## References
* [Billingsley, *Convergence of probability measures*][billingsley1999]
## Tags
weak convergence of measures, finite measure
-/
noncomputable section
open BoundedContinuousFunction Filter MeasureTheory Set Topology
open scoped ENNReal NNReal
namespace MeasureTheory
namespace FiniteMeasure
section FiniteMeasure
/-! ### Finite measures
In this section we define the `Type` of `MeasureTheory.FiniteMeasure Ω`, when `Ω` is a measurable
space. Finite measures on `Ω` are a module over `ℝ≥0`.
If `Ω` is moreover a topological space and the sigma algebra on `Ω` is finer than the Borel sigma
algebra (i.e. `[OpensMeasurableSpace Ω]`), then `MeasureTheory.FiniteMeasure Ω` is equipped with
the topology of weak convergence of measures. This is implemented by defining a pairing of finite
measures `μ` on `Ω` with continuous bounded nonnegative functions `f : Ω →ᵇ ℝ≥0` via integration,
and using the associated weak topology (essentially the weak-star topology on the dual of
`Ω →ᵇ ℝ≥0`).
-/
variable {Ω : Type*} [MeasurableSpace Ω]
/-- Finite measures are defined as the subtype of measures that have the property of being finite
measures (i.e., their total mass is finite). -/
def _root_.MeasureTheory.FiniteMeasure (Ω : Type*) [MeasurableSpace Ω] : Type _ :=
{ μ : Measure Ω // IsFiniteMeasure μ }
/-- Coercion from `MeasureTheory.FiniteMeasure Ω` to `MeasureTheory.Measure Ω`. -/
@[coe]
def toMeasure : FiniteMeasure Ω → Measure Ω := Subtype.val
/-- A finite measure can be interpreted as a measure. -/
instance instCoe : Coe (FiniteMeasure Ω) (MeasureTheory.Measure Ω) := { coe := toMeasure }
instance isFiniteMeasure (μ : FiniteMeasure Ω) : IsFiniteMeasure (μ : Measure Ω) := μ.prop
@[simp]
theorem val_eq_toMeasure (ν : FiniteMeasure Ω) : ν.val = (ν : Measure Ω) := rfl
theorem toMeasure_injective : Function.Injective ((↑) : FiniteMeasure Ω → Measure Ω) :=
Subtype.coe_injective
instance instFunLike : FunLike (FiniteMeasure Ω) (Set Ω) ℝ≥0 where
coe μ s := ((μ : Measure Ω) s).toNNReal
coe_injective' μ ν h := toMeasure_injective <| Measure.ext fun s _ ↦ by
simpa [ENNReal.toNNReal_eq_toNNReal_iff, measure_ne_top] using congr_fun h s
lemma coeFn_def (μ : FiniteMeasure Ω) : μ = fun s ↦ ((μ : Measure Ω) s).toNNReal := rfl
lemma coeFn_mk (μ : Measure Ω) (hμ) :
DFunLike.coe (F := FiniteMeasure Ω) ⟨μ, hμ⟩ = fun s ↦ (μ s).toNNReal := rfl
@[simp, norm_cast]
lemma mk_apply (μ : Measure Ω) (hμ) (s : Set Ω) :
DFunLike.coe (F := FiniteMeasure Ω) ⟨μ, hμ⟩ s = (μ s).toNNReal := rfl
@[simp]
theorem ennreal_coeFn_eq_coeFn_toMeasure (ν : FiniteMeasure Ω) (s : Set Ω) :
(ν s : ℝ≥0∞) = (ν : Measure Ω) s :=
ENNReal.coe_toNNReal (measure_lt_top (↑ν) s).ne
@[simp]
theorem null_iff_toMeasure_null (ν : FiniteMeasure Ω) (s : Set Ω) :
ν s = 0 ↔ (ν : Measure Ω) s = 0 :=
⟨fun h ↦ by rw [← ennreal_coeFn_eq_coeFn_toMeasure, h, ENNReal.coe_zero],
fun h ↦ congrArg ENNReal.toNNReal h⟩
theorem apply_mono (μ : FiniteMeasure Ω) {s₁ s₂ : Set Ω} (h : s₁ ⊆ s₂) : μ s₁ ≤ μ s₂ :=
ENNReal.toNNReal_mono (measure_ne_top _ s₂) ((μ : Measure Ω).mono h)
/-- Continuity from below: the measure of the union of a sequence of (not necessarily measurable)
sets is the limit of the measures of the partial unions. -/
protected lemma tendsto_measure_iUnion_accumulate {ι : Type*} [Preorder ι]
[IsCountablyGenerated (atTop : Filter ι)] {μ : FiniteMeasure Ω} {f : ι → Set Ω} :
Tendsto (fun i ↦ μ (Accumulate f i)) atTop (𝓝 (μ (⋃ i, f i))) := by
simpa [← ennreal_coeFn_eq_coeFn_toMeasure]
using tendsto_measure_iUnion_accumulate (μ := μ.toMeasure) (ι := ι)
/-- The (total) mass of a finite measure `μ` is `μ univ`, i.e., the cast to `NNReal` of
`(μ : measure Ω) univ`. -/
def mass (μ : FiniteMeasure Ω) : ℝ≥0 := μ univ
@[simp] theorem apply_le_mass (μ : FiniteMeasure Ω) (s : Set Ω) : μ s ≤ μ.mass := by
simpa using apply_mono μ (subset_univ s)
@[simp]
theorem ennreal_mass {μ : FiniteMeasure Ω} : (μ.mass : ℝ≥0∞) = (μ : Measure Ω) univ :=
ennreal_coeFn_eq_coeFn_toMeasure μ Set.univ
instance instZero : Zero (FiniteMeasure Ω) where zero := ⟨0, MeasureTheory.isFiniteMeasureZero⟩
@[simp, norm_cast] lemma coeFn_zero : ⇑(0 : FiniteMeasure Ω) = 0 := rfl
@[simp]
theorem zero_mass : (0 : FiniteMeasure Ω).mass = 0 := rfl
@[simp]
theorem mass_zero_iff (μ : FiniteMeasure Ω) : μ.mass = 0 ↔ μ = 0 := by
refine ⟨fun μ_mass => ?_, fun hμ => by simp only [hμ, zero_mass]⟩
apply toMeasure_injective
apply Measure.measure_univ_eq_zero.mp
rwa [← ennreal_mass, ENNReal.coe_eq_zero]
theorem mass_nonzero_iff (μ : FiniteMeasure Ω) : μ.mass ≠ 0 ↔ μ ≠ 0 :=
not_iff_not.mpr <| FiniteMeasure.mass_zero_iff μ
@[ext]
theorem eq_of_forall_toMeasure_apply_eq (μ ν : FiniteMeasure Ω)
(h : ∀ s : Set Ω, MeasurableSet s → (μ : Measure Ω) s = (ν : Measure Ω) s) : μ = ν := by
apply Subtype.ext
ext1 s s_mble
exact h s s_mble
theorem eq_of_forall_apply_eq (μ ν : FiniteMeasure Ω)
(h : ∀ s : Set Ω, MeasurableSet s → μ s = ν s) : μ = ν := by
ext1 s s_mble
simpa [ennreal_coeFn_eq_coeFn_toMeasure] using congr_arg ((↑) : ℝ≥0 → ℝ≥0∞) (h s s_mble)
instance instInhabited : Inhabited (FiniteMeasure Ω) := ⟨0⟩
instance instAdd : Add (FiniteMeasure Ω) where add μ ν := ⟨μ + ν, MeasureTheory.isFiniteMeasureAdd⟩
variable {R : Type*} [SMul R ℝ≥0] [SMul R ℝ≥0∞] [IsScalarTower R ℝ≥0 ℝ≥0∞]
[IsScalarTower R ℝ≥0∞ ℝ≥0∞]
instance instSMul : SMul R (FiniteMeasure Ω) where
smul (c : R) μ := ⟨c • (μ : Measure Ω), MeasureTheory.isFiniteMeasureSMulOfNNRealTower⟩
@[simp, norm_cast]
theorem toMeasure_zero : ((↑) : FiniteMeasure Ω → Measure Ω) 0 = 0 := rfl
@[norm_cast]
theorem toMeasure_add (μ ν : FiniteMeasure Ω) : ↑(μ + ν) = (↑μ + ↑ν : Measure Ω) := rfl
@[simp, norm_cast]
theorem toMeasure_smul (c : R) (μ : FiniteMeasure Ω) : ↑(c • μ) = c • (μ : Measure Ω) :=
rfl
@[simp, norm_cast]
theorem coeFn_add (μ ν : FiniteMeasure Ω) : (⇑(μ + ν) : Set Ω → ℝ≥0) = (⇑μ + ⇑ν : Set Ω → ℝ≥0) := by
funext
simp only [Pi.add_apply, ← ENNReal.coe_inj, ne_eq, ennreal_coeFn_eq_coeFn_toMeasure,
ENNReal.coe_add]
norm_cast
@[simp, norm_cast]
theorem coeFn_smul [IsScalarTower R ℝ≥0 ℝ≥0] (c : R) (μ : FiniteMeasure Ω) :
(⇑(c • μ) : Set Ω → ℝ≥0) = c • (⇑μ : Set Ω → ℝ≥0) := by
funext; simp [← ENNReal.coe_inj, ENNReal.coe_smul]
instance instAddCommMonoid : AddCommMonoid (FiniteMeasure Ω) :=
toMeasure_injective.addCommMonoid _ toMeasure_zero toMeasure_add fun _ _ ↦ toMeasure_smul _ _
/-- Coercion is an `AddMonoidHom`. -/
@[simps]
def toMeasureAddMonoidHom : FiniteMeasure Ω →+ Measure Ω where
toFun := (↑)
map_zero' := toMeasure_zero
map_add' := toMeasure_add
instance {Ω : Type*} [MeasurableSpace Ω] : Module ℝ≥0 (FiniteMeasure Ω) :=
Function.Injective.module _ toMeasureAddMonoidHom toMeasure_injective toMeasure_smul
@[simp]
theorem smul_apply [IsScalarTower R ℝ≥0 ℝ≥0] (c : R) (μ : FiniteMeasure Ω) (s : Set Ω) :
(c • μ) s = c • μ s := by
rw [coeFn_smul, Pi.smul_apply]
/-- Restrict a finite measure μ to a set A. -/
def restrict (μ : FiniteMeasure Ω) (A : Set Ω) : FiniteMeasure Ω where
val := (μ : Measure Ω).restrict A
property := MeasureTheory.isFiniteMeasureRestrict (μ : Measure Ω) A
theorem restrict_measure_eq (μ : FiniteMeasure Ω) (A : Set Ω) :
(μ.restrict A : Measure Ω) = (μ : Measure Ω).restrict A := rfl
theorem restrict_apply_measure (μ : FiniteMeasure Ω) (A : Set Ω) {s : Set Ω}
(s_mble : MeasurableSet s) : (μ.restrict A : Measure Ω) s = (μ : Measure Ω) (s ∩ A) :=
Measure.restrict_apply s_mble
theorem restrict_apply (μ : FiniteMeasure Ω) (A : Set Ω) {s : Set Ω} (s_mble : MeasurableSet s) :
(μ.restrict A) s = μ (s ∩ A) := by
apply congr_arg ENNReal.toNNReal
exact Measure.restrict_apply s_mble
theorem restrict_mass (μ : FiniteMeasure Ω) (A : Set Ω) : (μ.restrict A).mass = μ A := by
simp only [mass, restrict_apply μ A MeasurableSet.univ, univ_inter]
theorem restrict_eq_zero_iff (μ : FiniteMeasure Ω) (A : Set Ω) : μ.restrict A = 0 ↔ μ A = 0 := by
rw [← mass_zero_iff, restrict_mass]
theorem restrict_nonzero_iff (μ : FiniteMeasure Ω) (A : Set Ω) : μ.restrict A ≠ 0 ↔ μ A ≠ 0 := by
rw [← mass_nonzero_iff, restrict_mass]
/-- The type of finite measures is a measurable space when equipped with the Giry monad. -/
instance : MeasurableSpace (FiniteMeasure Ω) := Subtype.instMeasurableSpace
/-- The set of all finite measures is a measurable set in the Giry monad. -/
lemma measurableSet_isFiniteMeasure : MeasurableSet { μ : Measure Ω | IsFiniteMeasure μ } := by
suffices { μ : Measure Ω | IsFiniteMeasure μ } = (fun μ => μ univ) ⁻¹' (Set.Ico 0 ∞) by
rw [this]
exact Measure.measurable_coe MeasurableSet.univ measurableSet_Ico
ext μ
simp only [mem_setOf_eq, mem_iUnion, mem_preimage, mem_Ico, zero_le, true_and, exists_const]
exact isFiniteMeasure_iff μ
/-- The monoidal product is a measurabule function from the product of finite measures over
`α` and `β` into the type of finite measures over `α × β`. -/
theorem measurable_prod {α β : Type*} [MeasurableSpace α] [MeasurableSpace β] :
Measurable (fun (μ : FiniteMeasure α × FiniteMeasure β)
↦ μ.1.toMeasure.prod μ.2.toMeasure) := by
have Heval {u v} (Hu : MeasurableSet u) (Hv : MeasurableSet v):
Measurable fun a : (FiniteMeasure α × FiniteMeasure β) ↦
a.1.toMeasure u * a.2.toMeasure v :=
Measurable.mul
((Measure.measurable_coe Hu).comp (measurable_subtype_coe.comp measurable_fst))
((Measure.measurable_coe Hv).comp (measurable_subtype_coe.comp measurable_snd))
apply Measurable.measure_of_isPiSystem generateFrom_prod.symm isPiSystem_prod _
· simp_rw [← Set.univ_prod_univ, Measure.prod_prod, Heval MeasurableSet.univ MeasurableSet.univ]
simp only [mem_image2, mem_setOf_eq, forall_exists_index, and_imp]
intros _ _ Hu _ Hv Heq
simp_rw [← Heq, Measure.prod_prod, Heval Hu Hv]
variable [TopologicalSpace Ω]
/-- Two finite Borel measures are equal if the integrals of all non-negative bounded continuous
functions with respect to both agree. -/
theorem ext_of_forall_lintegral_eq [HasOuterApproxClosed Ω] [BorelSpace Ω]
{μ ν : FiniteMeasure Ω} (h : ∀ (f : Ω →ᵇ ℝ≥0), ∫⁻ x, f x ∂μ = ∫⁻ x, f x ∂ν) :
μ = ν := by
apply Subtype.ext
change (μ : Measure Ω) = (ν : Measure Ω)
exact ext_of_forall_lintegral_eq_of_IsFiniteMeasure h
/-- Two finite Borel measures are equal if the integrals of all bounded continuous functions with
respect to both agree. -/
theorem ext_of_forall_integral_eq [HasOuterApproxClosed Ω] [BorelSpace Ω]
{μ ν : FiniteMeasure Ω} (h : ∀ (f : Ω →ᵇ ℝ), ∫ x, f x ∂μ = ∫ x, f x ∂ν) :
μ = ν := by
apply ext_of_forall_lintegral_eq
intro f
apply (ENNReal.toReal_eq_toReal_iff' (lintegral_lt_top_of_nnreal μ f).ne
(lintegral_lt_top_of_nnreal ν f).ne).mp
rw [toReal_lintegral_coe_eq_integral f μ, toReal_lintegral_coe_eq_integral f ν]
exact h ⟨⟨fun x => (f x).toReal, Continuous.comp' NNReal.continuous_coe f.continuous⟩,
f.map_bounded'⟩
/-- The pairing of a finite (Borel) measure `μ` with a nonnegative bounded continuous
function is obtained by (Lebesgue) integrating the (test) function against the measure.
This is `MeasureTheory.FiniteMeasure.testAgainstNN`. -/
def testAgainstNN (μ : FiniteMeasure Ω) (f : Ω →ᵇ ℝ≥0) : ℝ≥0 :=
(∫⁻ ω, f ω ∂(μ : Measure Ω)).toNNReal
@[simp]
theorem testAgainstNN_coe_eq {μ : FiniteMeasure Ω} {f : Ω →ᵇ ℝ≥0} :
(μ.testAgainstNN f : ℝ≥0∞) = ∫⁻ ω, f ω ∂(μ : Measure Ω) :=
ENNReal.coe_toNNReal (f.lintegral_lt_top_of_nnreal _).ne
theorem testAgainstNN_const (μ : FiniteMeasure Ω) (c : ℝ≥0) :
μ.testAgainstNN (BoundedContinuousFunction.const Ω c) = c * μ.mass := by
simp [← ENNReal.coe_inj]
theorem testAgainstNN_mono (μ : FiniteMeasure Ω) {f g : Ω →ᵇ ℝ≥0} (f_le_g : (f : Ω → ℝ≥0) ≤ g) :
μ.testAgainstNN f ≤ μ.testAgainstNN g := by
simp only [← ENNReal.coe_le_coe, testAgainstNN_coe_eq]
gcongr
apply f_le_g
@[simp]
theorem testAgainstNN_zero (μ : FiniteMeasure Ω) : μ.testAgainstNN 0 = 0 := by
simpa only [zero_mul] using μ.testAgainstNN_const 0
@[simp]
theorem testAgainstNN_one (μ : FiniteMeasure Ω) : μ.testAgainstNN 1 = μ.mass := by
simp only [testAgainstNN, coe_one, Pi.one_apply, ENNReal.coe_one, lintegral_one]
rfl
@[simp]
theorem zero_testAgainstNN_apply (f : Ω →ᵇ ℝ≥0) : (0 : FiniteMeasure Ω).testAgainstNN f = 0 := by
simp only [testAgainstNN, toMeasure_zero, lintegral_zero_measure, ENNReal.toNNReal_zero]
theorem zero_testAgainstNN : (0 : FiniteMeasure Ω).testAgainstNN = 0 := by
funext
simp only [zero_testAgainstNN_apply, Pi.zero_apply]
| @[simp]
theorem smul_testAgainstNN_apply (c : ℝ≥0) (μ : FiniteMeasure Ω) (f : Ω →ᵇ ℝ≥0) :
(c • μ).testAgainstNN f = c • μ.testAgainstNN f := by
| Mathlib/MeasureTheory/Measure/FiniteMeasure.lean | 373 | 375 |
/-
Copyright (c) 2021 Bryan Gin-ge Chen. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Adam Topaz, Bryan Gin-ge Chen, Yaël Dillies
-/
import Mathlib.Order.BooleanAlgebra
import Mathlib.Logic.Equiv.Basic
/-!
# Symmetric difference and bi-implication
This file defines the symmetric difference and bi-implication operators in (co-)Heyting algebras.
## Examples
Some examples are
* The symmetric difference of two sets is the set of elements that are in either but not both.
* The symmetric difference on propositions is `Xor'`.
* The symmetric difference on `Bool` is `Bool.xor`.
* The equivalence of propositions. Two propositions are equivalent if they imply each other.
* The symmetric difference translates to addition when considering a Boolean algebra as a Boolean
ring.
## Main declarations
* `symmDiff`: The symmetric difference operator, defined as `(a \ b) ⊔ (b \ a)`
* `bihimp`: The bi-implication operator, defined as `(b ⇨ a) ⊓ (a ⇨ b)`
In generalized Boolean algebras, the symmetric difference operator is:
* `symmDiff_comm`: commutative, and
* `symmDiff_assoc`: associative.
## Notations
* `a ∆ b`: `symmDiff a b`
* `a ⇔ b`: `bihimp a b`
## References
The proof of associativity follows the note "Associativity of the Symmetric Difference of Sets: A
Proof from the Book" by John McCuan:
* <https://people.math.gatech.edu/~mccuan/courses/4317/symmetricdifference.pdf>
## Tags
boolean ring, generalized boolean algebra, boolean algebra, symmetric difference, bi-implication,
Heyting
-/
assert_not_exists RelIso
open Function OrderDual
variable {ι α β : Type*} {π : ι → Type*}
/-- The symmetric difference operator on a type with `⊔` and `\` is `(A \ B) ⊔ (B \ A)`. -/
def symmDiff [Max α] [SDiff α] (a b : α) : α :=
a \ b ⊔ b \ a
/-- The Heyting bi-implication is `(b ⇨ a) ⊓ (a ⇨ b)`. This generalizes equivalence of
propositions. -/
def bihimp [Min α] [HImp α] (a b : α) : α :=
(b ⇨ a) ⊓ (a ⇨ b)
/-- Notation for symmDiff -/
scoped[symmDiff] infixl:100 " ∆ " => symmDiff
/-- Notation for bihimp -/
scoped[symmDiff] infixl:100 " ⇔ " => bihimp
open scoped symmDiff
theorem symmDiff_def [Max α] [SDiff α] (a b : α) : a ∆ b = a \ b ⊔ b \ a :=
rfl
theorem bihimp_def [Min α] [HImp α] (a b : α) : a ⇔ b = (b ⇨ a) ⊓ (a ⇨ b) :=
rfl
theorem symmDiff_eq_Xor' (p q : Prop) : p ∆ q = Xor' p q :=
rfl
@[simp]
theorem bihimp_iff_iff {p q : Prop} : p ⇔ q ↔ (p ↔ q) :=
iff_iff_implies_and_implies.symm.trans Iff.comm
@[simp]
theorem Bool.symmDiff_eq_xor : ∀ p q : Bool, p ∆ q = xor p q := by decide
section GeneralizedCoheytingAlgebra
variable [GeneralizedCoheytingAlgebra α] (a b c : α)
@[simp]
theorem toDual_symmDiff : toDual (a ∆ b) = toDual a ⇔ toDual b :=
rfl
@[simp]
theorem ofDual_bihimp (a b : αᵒᵈ) : ofDual (a ⇔ b) = ofDual a ∆ ofDual b :=
rfl
theorem symmDiff_comm : a ∆ b = b ∆ a := by simp only [symmDiff, sup_comm]
instance symmDiff_isCommutative : Std.Commutative (α := α) (· ∆ ·) :=
⟨symmDiff_comm⟩
@[simp]
theorem symmDiff_self : a ∆ a = ⊥ := by rw [symmDiff, sup_idem, sdiff_self]
@[simp]
theorem symmDiff_bot : a ∆ ⊥ = a := by rw [symmDiff, sdiff_bot, bot_sdiff, sup_bot_eq]
@[simp]
theorem bot_symmDiff : ⊥ ∆ a = a := by rw [symmDiff_comm, symmDiff_bot]
@[simp]
theorem symmDiff_eq_bot {a b : α} : a ∆ b = ⊥ ↔ a = b := by
simp_rw [symmDiff, sup_eq_bot_iff, sdiff_eq_bot_iff, le_antisymm_iff]
theorem symmDiff_of_le {a b : α} (h : a ≤ b) : a ∆ b = b \ a := by
rw [symmDiff, sdiff_eq_bot_iff.2 h, bot_sup_eq]
theorem symmDiff_of_ge {a b : α} (h : b ≤ a) : a ∆ b = a \ b := by
rw [symmDiff, sdiff_eq_bot_iff.2 h, sup_bot_eq]
theorem symmDiff_le {a b c : α} (ha : a ≤ b ⊔ c) (hb : b ≤ a ⊔ c) : a ∆ b ≤ c :=
sup_le (sdiff_le_iff.2 ha) <| sdiff_le_iff.2 hb
theorem symmDiff_le_iff {a b c : α} : a ∆ b ≤ c ↔ a ≤ b ⊔ c ∧ b ≤ a ⊔ c := by
simp_rw [symmDiff, sup_le_iff, sdiff_le_iff]
@[simp]
theorem symmDiff_le_sup {a b : α} : a ∆ b ≤ a ⊔ b :=
sup_le_sup sdiff_le sdiff_le
theorem symmDiff_eq_sup_sdiff_inf : a ∆ b = (a ⊔ b) \ (a ⊓ b) := by simp [sup_sdiff, symmDiff]
theorem Disjoint.symmDiff_eq_sup {a b : α} (h : Disjoint a b) : a ∆ b = a ⊔ b := by
rw [symmDiff, h.sdiff_eq_left, h.sdiff_eq_right]
theorem symmDiff_sdiff : a ∆ b \ c = a \ (b ⊔ c) ⊔ b \ (a ⊔ c) := by
rw [symmDiff, sup_sdiff_distrib, sdiff_sdiff_left, sdiff_sdiff_left]
@[simp]
theorem symmDiff_sdiff_inf : a ∆ b \ (a ⊓ b) = a ∆ b := by
rw [symmDiff_sdiff]
simp [symmDiff]
@[simp]
theorem symmDiff_sdiff_eq_sup : a ∆ (b \ a) = a ⊔ b := by
rw [symmDiff, sdiff_idem]
exact
le_antisymm (sup_le_sup sdiff_le sdiff_le)
(sup_le le_sdiff_sup <| le_sdiff_sup.trans <| sup_le le_sup_right le_sdiff_sup)
@[simp]
theorem sdiff_symmDiff_eq_sup : (a \ b) ∆ b = a ⊔ b := by
rw [symmDiff_comm, symmDiff_sdiff_eq_sup, sup_comm]
@[simp]
theorem symmDiff_sup_inf : a ∆ b ⊔ a ⊓ b = a ⊔ b := by
refine le_antisymm (sup_le symmDiff_le_sup inf_le_sup) ?_
rw [sup_inf_left, symmDiff]
refine sup_le (le_inf le_sup_right ?_) (le_inf ?_ le_sup_right)
· rw [sup_right_comm]
exact le_sup_of_le_left le_sdiff_sup
· rw [sup_assoc]
exact le_sup_of_le_right le_sdiff_sup
@[simp]
theorem inf_sup_symmDiff : a ⊓ b ⊔ a ∆ b = a ⊔ b := by rw [sup_comm, symmDiff_sup_inf]
@[simp]
theorem symmDiff_symmDiff_inf : a ∆ b ∆ (a ⊓ b) = a ⊔ b := by
rw [← symmDiff_sdiff_inf a, sdiff_symmDiff_eq_sup, symmDiff_sup_inf]
@[simp]
theorem inf_symmDiff_symmDiff : (a ⊓ b) ∆ (a ∆ b) = a ⊔ b := by
rw [symmDiff_comm, symmDiff_symmDiff_inf]
theorem symmDiff_triangle : a ∆ c ≤ a ∆ b ⊔ b ∆ c := by
refine (sup_le_sup (sdiff_triangle a b c) <| sdiff_triangle _ b _).trans_eq ?_
rw [sup_comm (c \ b), sup_sup_sup_comm, symmDiff, symmDiff]
theorem le_symmDiff_sup_right (a b : α) : a ≤ (a ∆ b) ⊔ b := by
convert symmDiff_triangle a b ⊥ <;> rw [symmDiff_bot]
theorem le_symmDiff_sup_left (a b : α) : b ≤ (a ∆ b) ⊔ a :=
symmDiff_comm a b ▸ le_symmDiff_sup_right ..
end GeneralizedCoheytingAlgebra
section GeneralizedHeytingAlgebra
variable [GeneralizedHeytingAlgebra α] (a b c : α)
@[simp]
theorem toDual_bihimp : toDual (a ⇔ b) = toDual a ∆ toDual b :=
rfl
@[simp]
theorem ofDual_symmDiff (a b : αᵒᵈ) : ofDual (a ∆ b) = ofDual a ⇔ ofDual b :=
rfl
theorem bihimp_comm : a ⇔ b = b ⇔ a := by simp only [(· ⇔ ·), inf_comm]
instance bihimp_isCommutative : Std.Commutative (α := α) (· ⇔ ·) :=
⟨bihimp_comm⟩
@[simp]
theorem bihimp_self : a ⇔ a = ⊤ := by rw [bihimp, inf_idem, himp_self]
@[simp]
theorem bihimp_top : a ⇔ ⊤ = a := by rw [bihimp, himp_top, top_himp, inf_top_eq]
@[simp]
theorem top_bihimp : ⊤ ⇔ a = a := by rw [bihimp_comm, bihimp_top]
@[simp]
theorem bihimp_eq_top {a b : α} : a ⇔ b = ⊤ ↔ a = b :=
@symmDiff_eq_bot αᵒᵈ _ _ _
theorem bihimp_of_le {a b : α} (h : a ≤ b) : a ⇔ b = b ⇨ a := by
rw [bihimp, himp_eq_top_iff.2 h, inf_top_eq]
theorem bihimp_of_ge {a b : α} (h : b ≤ a) : a ⇔ b = a ⇨ b := by
rw [bihimp, himp_eq_top_iff.2 h, top_inf_eq]
theorem le_bihimp {a b c : α} (hb : a ⊓ b ≤ c) (hc : a ⊓ c ≤ b) : a ≤ b ⇔ c :=
le_inf (le_himp_iff.2 hc) <| le_himp_iff.2 hb
theorem le_bihimp_iff {a b c : α} : a ≤ b ⇔ c ↔ a ⊓ b ≤ c ∧ a ⊓ c ≤ b := by
simp_rw [bihimp, le_inf_iff, le_himp_iff, and_comm]
@[simp]
theorem inf_le_bihimp {a b : α} : a ⊓ b ≤ a ⇔ b :=
inf_le_inf le_himp le_himp
theorem bihimp_eq_inf_himp_inf : a ⇔ b = a ⊔ b ⇨ a ⊓ b := by simp [himp_inf_distrib, bihimp]
theorem Codisjoint.bihimp_eq_inf {a b : α} (h : Codisjoint a b) : a ⇔ b = a ⊓ b := by
rw [bihimp, h.himp_eq_left, h.himp_eq_right]
theorem himp_bihimp : a ⇨ b ⇔ c = (a ⊓ c ⇨ b) ⊓ (a ⊓ b ⇨ c) := by
rw [bihimp, himp_inf_distrib, himp_himp, himp_himp]
@[simp]
theorem sup_himp_bihimp : a ⊔ b ⇨ a ⇔ b = a ⇔ b := by
rw [himp_bihimp]
simp [bihimp]
@[simp]
theorem bihimp_himp_eq_inf : a ⇔ (a ⇨ b) = a ⊓ b :=
@symmDiff_sdiff_eq_sup αᵒᵈ _ _ _
@[simp]
theorem himp_bihimp_eq_inf : (b ⇨ a) ⇔ b = a ⊓ b :=
@sdiff_symmDiff_eq_sup αᵒᵈ _ _ _
@[simp]
theorem bihimp_inf_sup : a ⇔ b ⊓ (a ⊔ b) = a ⊓ b :=
@symmDiff_sup_inf αᵒᵈ _ _ _
@[simp]
theorem sup_inf_bihimp : (a ⊔ b) ⊓ a ⇔ b = a ⊓ b :=
@inf_sup_symmDiff αᵒᵈ _ _ _
@[simp]
theorem bihimp_bihimp_sup : a ⇔ b ⇔ (a ⊔ b) = a ⊓ b :=
@symmDiff_symmDiff_inf αᵒᵈ _ _ _
@[simp]
theorem sup_bihimp_bihimp : (a ⊔ b) ⇔ (a ⇔ b) = a ⊓ b :=
@inf_symmDiff_symmDiff αᵒᵈ _ _ _
theorem bihimp_triangle : a ⇔ b ⊓ b ⇔ c ≤ a ⇔ c :=
@symmDiff_triangle αᵒᵈ _ _ _ _
end GeneralizedHeytingAlgebra
section CoheytingAlgebra
variable [CoheytingAlgebra α] (a : α)
@[simp]
theorem symmDiff_top' : a ∆ ⊤ = ￢a := by simp [symmDiff]
@[simp]
theorem top_symmDiff' : ⊤ ∆ a = ￢a := by simp [symmDiff]
@[simp]
theorem hnot_symmDiff_self : (￢a) ∆ a = ⊤ := by
rw [eq_top_iff, symmDiff, hnot_sdiff, sup_sdiff_self]
exact Codisjoint.top_le codisjoint_hnot_left
@[simp]
theorem symmDiff_hnot_self : a ∆ (￢a) = ⊤ := by rw [symmDiff_comm, hnot_symmDiff_self]
theorem IsCompl.symmDiff_eq_top {a b : α} (h : IsCompl a b) : a ∆ b = ⊤ := by
rw [h.eq_hnot, hnot_symmDiff_self]
end CoheytingAlgebra
section HeytingAlgebra
variable [HeytingAlgebra α] (a : α)
@[simp]
theorem bihimp_bot : a ⇔ ⊥ = aᶜ := by simp [bihimp]
@[simp]
theorem bot_bihimp : ⊥ ⇔ a = aᶜ := by simp [bihimp]
@[simp]
theorem compl_bihimp_self : aᶜ ⇔ a = ⊥ :=
@hnot_symmDiff_self αᵒᵈ _ _
@[simp]
theorem bihimp_hnot_self : a ⇔ aᶜ = ⊥ :=
@symmDiff_hnot_self αᵒᵈ _ _
theorem IsCompl.bihimp_eq_bot {a b : α} (h : IsCompl a b) : a ⇔ b = ⊥ := by
rw [h.eq_compl, compl_bihimp_self]
end HeytingAlgebra
section GeneralizedBooleanAlgebra
variable [GeneralizedBooleanAlgebra α] (a b c d : α)
@[simp]
theorem sup_sdiff_symmDiff : (a ⊔ b) \ a ∆ b = a ⊓ b :=
sdiff_eq_symm inf_le_sup (by rw [symmDiff_eq_sup_sdiff_inf])
theorem disjoint_symmDiff_inf : Disjoint (a ∆ b) (a ⊓ b) := by
rw [symmDiff_eq_sup_sdiff_inf]
exact disjoint_sdiff_self_left
theorem inf_symmDiff_distrib_left : a ⊓ b ∆ c = (a ⊓ b) ∆ (a ⊓ c) := by
rw [symmDiff_eq_sup_sdiff_inf, inf_sdiff_distrib_left, inf_sup_left, inf_inf_distrib_left,
symmDiff_eq_sup_sdiff_inf]
theorem inf_symmDiff_distrib_right : a ∆ b ⊓ c = (a ⊓ c) ∆ (b ⊓ c) := by
simp_rw [inf_comm _ c, inf_symmDiff_distrib_left]
| theorem sdiff_symmDiff : c \ a ∆ b = c ⊓ a ⊓ b ⊔ c \ a ⊓ c \ b := by
| Mathlib/Order/SymmDiff.lean | 347 | 347 |
/-
Copyright (c) 2020 Sébastien Gouëzel. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Sébastien Gouëzel, Floris van Doorn
-/
import Mathlib.Geometry.Manifold.MFDeriv.Defs
import Mathlib.Geometry.Manifold.ContMDiff.Defs
/-!
# Basic properties of the manifold Fréchet derivative
In this file, we show various properties of the manifold Fréchet derivative,
mimicking the API for Fréchet derivatives.
- basic properties of unique differentiability sets
- various general lemmas about the manifold Fréchet derivative
- deducing differentiability from smoothness,
- deriving continuity from differentiability on manifolds,
- congruence lemmas for derivatives on manifolds
- composition lemmas and the chain rule
-/
noncomputable section
assert_not_exists tangentBundleCore
open scoped Topology Manifold
open Set Bundle ChartedSpace
section DerivativesProperties
/-! ### Unique differentiability sets in manifolds -/
variable
{𝕜 : Type*} [NontriviallyNormedField 𝕜]
{E : Type*} [NormedAddCommGroup E] [NormedSpace 𝕜 E]
{H : Type*} [TopologicalSpace H] (I : ModelWithCorners 𝕜 E H)
{M : Type*} [TopologicalSpace M] [ChartedSpace H M]
{E' : Type*} [NormedAddCommGroup E'] [NormedSpace 𝕜 E']
{H' : Type*} [TopologicalSpace H'] {I' : ModelWithCorners 𝕜 E' H'}
{M' : Type*} [TopologicalSpace M'] [ChartedSpace H' M']
{E'' : Type*} [NormedAddCommGroup E''] [NormedSpace 𝕜 E'']
{H'' : Type*} [TopologicalSpace H''] {I'' : ModelWithCorners 𝕜 E'' H''}
{M'' : Type*} [TopologicalSpace M''] [ChartedSpace H'' M'']
{f f₁ : M → M'} {x : M} {s t : Set M} {g : M' → M''} {u : Set M'}
theorem uniqueMDiffWithinAt_univ : UniqueMDiffWithinAt I univ x := by
unfold UniqueMDiffWithinAt
simp only [preimage_univ, univ_inter]
exact I.uniqueDiffOn _ (mem_range_self _)
variable {I}
theorem uniqueMDiffWithinAt_iff_inter_range {s : Set M} {x : M} :
UniqueMDiffWithinAt I s x ↔
UniqueDiffWithinAt 𝕜 ((extChartAt I x).symm ⁻¹' s ∩ range I)
((extChartAt I x) x) := Iff.rfl
theorem uniqueMDiffWithinAt_iff {s : Set M} {x : M} :
UniqueMDiffWithinAt I s x ↔
UniqueDiffWithinAt 𝕜 ((extChartAt I x).symm ⁻¹' s ∩ (extChartAt I x).target)
((extChartAt I x) x) := by
apply uniqueDiffWithinAt_congr
rw [nhdsWithin_inter, nhdsWithin_inter, nhdsWithin_extChartAt_target_eq]
nonrec theorem UniqueMDiffWithinAt.mono_nhds {s t : Set M} {x : M} (hs : UniqueMDiffWithinAt I s x)
(ht : 𝓝[s] x ≤ 𝓝[t] x) : UniqueMDiffWithinAt I t x :=
hs.mono_nhds <| by simpa only [← map_extChartAt_nhdsWithin] using Filter.map_mono ht
theorem UniqueMDiffWithinAt.mono_of_mem_nhdsWithin {s t : Set M} {x : M}
(hs : UniqueMDiffWithinAt I s x) (ht : t ∈ 𝓝[s] x) : UniqueMDiffWithinAt I t x :=
hs.mono_nhds (nhdsWithin_le_iff.2 ht)
@[deprecated (since := "2024-10-31")]
alias UniqueMDiffWithinAt.mono_of_mem := UniqueMDiffWithinAt.mono_of_mem_nhdsWithin
theorem UniqueMDiffWithinAt.mono (h : UniqueMDiffWithinAt I s x) (st : s ⊆ t) :
UniqueMDiffWithinAt I t x :=
UniqueDiffWithinAt.mono h <| inter_subset_inter (preimage_mono st) (Subset.refl _)
theorem UniqueMDiffWithinAt.inter' (hs : UniqueMDiffWithinAt I s x) (ht : t ∈ 𝓝[s] x) :
UniqueMDiffWithinAt I (s ∩ t) x :=
hs.mono_of_mem_nhdsWithin (Filter.inter_mem self_mem_nhdsWithin ht)
theorem UniqueMDiffWithinAt.inter (hs : UniqueMDiffWithinAt I s x) (ht : t ∈ 𝓝 x) :
UniqueMDiffWithinAt I (s ∩ t) x :=
hs.inter' (nhdsWithin_le_nhds ht)
theorem IsOpen.uniqueMDiffWithinAt (hs : IsOpen s) (xs : x ∈ s) : UniqueMDiffWithinAt I s x :=
(uniqueMDiffWithinAt_univ I).mono_of_mem_nhdsWithin <| nhdsWithin_le_nhds <| hs.mem_nhds xs
theorem UniqueMDiffOn.inter (hs : UniqueMDiffOn I s) (ht : IsOpen t) : UniqueMDiffOn I (s ∩ t) :=
fun _x hx => UniqueMDiffWithinAt.inter (hs _ hx.1) (ht.mem_nhds hx.2)
theorem IsOpen.uniqueMDiffOn (hs : IsOpen s) : UniqueMDiffOn I s :=
fun _x hx => hs.uniqueMDiffWithinAt hx
theorem uniqueMDiffOn_univ : UniqueMDiffOn I (univ : Set M) :=
isOpen_univ.uniqueMDiffOn
nonrec theorem UniqueMDiffWithinAt.prod {x : M} {y : M'} {s t} (hs : UniqueMDiffWithinAt I s x)
(ht : UniqueMDiffWithinAt I' t y) : UniqueMDiffWithinAt (I.prod I') (s ×ˢ t) (x, y) := by
refine (hs.prod ht).mono ?_
rw [ModelWithCorners.range_prod, ← prod_inter_prod]
rfl
theorem UniqueMDiffOn.prod {s : Set M} {t : Set M'} (hs : UniqueMDiffOn I s)
(ht : UniqueMDiffOn I' t) : UniqueMDiffOn (I.prod I') (s ×ˢ t) := fun x h ↦
(hs x.1 h.1).prod (ht x.2 h.2)
theorem MDifferentiableWithinAt.mono (hst : s ⊆ t) (h : MDifferentiableWithinAt I I' f t x) :
MDifferentiableWithinAt I I' f s x :=
⟨ContinuousWithinAt.mono h.1 hst, DifferentiableWithinAt.mono
h.differentiableWithinAt_writtenInExtChartAt
(inter_subset_inter_left _ (preimage_mono hst))⟩
theorem mdifferentiableWithinAt_univ :
MDifferentiableWithinAt I I' f univ x ↔ MDifferentiableAt I I' f x := by
simp_rw [MDifferentiableWithinAt, MDifferentiableAt, ChartedSpace.LiftPropAt]
theorem mdifferentiableWithinAt_inter (ht : t ∈ 𝓝 x) :
MDifferentiableWithinAt I I' f (s ∩ t) x ↔ MDifferentiableWithinAt I I' f s x := by
rw [MDifferentiableWithinAt, MDifferentiableWithinAt,
differentiableWithinAt_localInvariantProp.liftPropWithinAt_inter ht]
theorem mdifferentiableWithinAt_inter' (ht : t ∈ 𝓝[s] x) :
MDifferentiableWithinAt I I' f (s ∩ t) x ↔ MDifferentiableWithinAt I I' f s x := by
rw [MDifferentiableWithinAt, MDifferentiableWithinAt,
differentiableWithinAt_localInvariantProp.liftPropWithinAt_inter' ht]
theorem MDifferentiableAt.mdifferentiableWithinAt (h : MDifferentiableAt I I' f x) :
MDifferentiableWithinAt I I' f s x :=
MDifferentiableWithinAt.mono (subset_univ _) (mdifferentiableWithinAt_univ.2 h)
theorem MDifferentiableWithinAt.mdifferentiableAt (h : MDifferentiableWithinAt I I' f s x)
(hs : s ∈ 𝓝 x) : MDifferentiableAt I I' f x := by
have : s = univ ∩ s := by rw [univ_inter]
rwa [this, mdifferentiableWithinAt_inter hs, mdifferentiableWithinAt_univ] at h
theorem MDifferentiableOn.mono (h : MDifferentiableOn I I' f t) (st : s ⊆ t) :
MDifferentiableOn I I' f s := fun x hx => (h x (st hx)).mono st
theorem mdifferentiableOn_univ : MDifferentiableOn I I' f univ ↔ MDifferentiable I I' f := by
simp only [MDifferentiableOn, mdifferentiableWithinAt_univ, mfld_simps]; rfl
theorem MDifferentiableOn.mdifferentiableAt (h : MDifferentiableOn I I' f s) (hx : s ∈ 𝓝 x) :
MDifferentiableAt I I' f x :=
(h x (mem_of_mem_nhds hx)).mdifferentiableAt hx
theorem MDifferentiable.mdifferentiableOn (h : MDifferentiable I I' f) :
MDifferentiableOn I I' f s :=
(mdifferentiableOn_univ.2 h).mono (subset_univ _)
theorem mdifferentiableOn_of_locally_mdifferentiableOn
(h : ∀ x ∈ s, ∃ u, IsOpen u ∧ x ∈ u ∧ MDifferentiableOn I I' f (s ∩ u)) :
MDifferentiableOn I I' f s := by
intro x xs
rcases h x xs with ⟨t, t_open, xt, ht⟩
exact (mdifferentiableWithinAt_inter (t_open.mem_nhds xt)).1 (ht x ⟨xs, xt⟩)
theorem MDifferentiable.mdifferentiableAt (hf : MDifferentiable I I' f) :
MDifferentiableAt I I' f x :=
hf x
/-!
### Relating differentiability in a manifold and differentiability in the model space
through extended charts
-/
theorem mdifferentiableWithinAt_iff_target_inter {f : M → M'} {s : Set M} {x : M} :
MDifferentiableWithinAt I I' f s x ↔
ContinuousWithinAt f s x ∧
DifferentiableWithinAt 𝕜 (writtenInExtChartAt I I' x f)
((extChartAt I x).target ∩ (extChartAt I x).symm ⁻¹' s) ((extChartAt I x) x) := by
rw [mdifferentiableWithinAt_iff']
refine and_congr Iff.rfl (exists_congr fun f' => ?_)
rw [inter_comm]
simp only [HasFDerivWithinAt, nhdsWithin_inter, nhdsWithin_extChartAt_target_eq]
/-- One can reformulate smoothness within a set at a point as continuity within this set at this
point, and smoothness in the corresponding extended chart. -/
theorem mdifferentiableWithinAt_iff :
MDifferentiableWithinAt I I' f s x ↔
ContinuousWithinAt f s x ∧
DifferentiableWithinAt 𝕜 (extChartAt I' (f x) ∘ f ∘ (extChartAt I x).symm)
((extChartAt I x).symm ⁻¹' s ∩ range I) (extChartAt I x x) := by
simp_rw [MDifferentiableWithinAt, ChartedSpace.liftPropWithinAt_iff']; rfl
/-- One can reformulate smoothness within a set at a point as continuity within this set at this
point, and smoothness in the corresponding extended chart. This form states smoothness of `f`
written in such a way that the set is restricted to lie within the domain/codomain of the
corresponding charts.
Even though this expression is more complicated than the one in `mdifferentiableWithinAt_iff`, it is
a smaller set, but their germs at `extChartAt I x x` are equal. It is sometimes useful to rewrite
using this in the goal.
-/
theorem mdifferentiableWithinAt_iff_target_inter' :
MDifferentiableWithinAt I I' f s x ↔
ContinuousWithinAt f s x ∧
DifferentiableWithinAt 𝕜 (extChartAt I' (f x) ∘ f ∘ (extChartAt I x).symm)
((extChartAt I x).target ∩
(extChartAt I x).symm ⁻¹' (s ∩ f ⁻¹' (extChartAt I' (f x)).source))
(extChartAt I x x) := by
simp only [MDifferentiableWithinAt, liftPropWithinAt_iff']
exact and_congr_right fun hc => differentiableWithinAt_congr_nhds <|
hc.nhdsWithin_extChartAt_symm_preimage_inter_range
/-- One can reformulate smoothness within a set at a point as continuity within this set at this
point, and smoothness in the corresponding extended chart in the target. -/
theorem mdifferentiableWithinAt_iff_target :
MDifferentiableWithinAt I I' f s x ↔
ContinuousWithinAt f s x ∧
MDifferentiableWithinAt I 𝓘(𝕜, E') (extChartAt I' (f x) ∘ f) s x := by
simp_rw [MDifferentiableWithinAt, liftPropWithinAt_iff', ← and_assoc]
have cont :
ContinuousWithinAt f s x ∧ ContinuousWithinAt (extChartAt I' (f x) ∘ f) s x ↔
ContinuousWithinAt f s x :=
and_iff_left_of_imp <| (continuousAt_extChartAt _).comp_continuousWithinAt
simp_rw [cont, DifferentiableWithinAtProp, extChartAt, PartialHomeomorph.extend,
PartialEquiv.coe_trans,
ModelWithCorners.toPartialEquiv_coe, PartialHomeomorph.coe_coe, modelWithCornersSelf_coe,
chartAt_self_eq, PartialHomeomorph.refl_apply]
rfl
theorem mdifferentiableAt_iff_target {x : M} :
MDifferentiableAt I I' f x ↔
ContinuousAt f x ∧ MDifferentiableAt I 𝓘(𝕜, E') (extChartAt I' (f x) ∘ f) x := by
rw [← mdifferentiableWithinAt_univ, ← mdifferentiableWithinAt_univ,
mdifferentiableWithinAt_iff_target, continuousWithinAt_univ]
section IsManifold
variable {e : PartialHomeomorph M H} {e' : PartialHomeomorph M' H'}
open IsManifold
theorem mdifferentiableWithinAt_iff_source_of_mem_maximalAtlas
[IsManifold I 1 M] (he : e ∈ maximalAtlas I 1 M) (hx : x ∈ e.source) :
MDifferentiableWithinAt I I' f s x ↔
MDifferentiableWithinAt 𝓘(𝕜, E) I' (f ∘ (e.extend I).symm) ((e.extend I).symm ⁻¹' s ∩ range I)
(e.extend I x) := by
have h2x := hx; rw [← e.extend_source (I := I)] at h2x
simp_rw [MDifferentiableWithinAt,
differentiableWithinAt_localInvariantProp.liftPropWithinAt_indep_chart_source he hx,
StructureGroupoid.liftPropWithinAt_self_source,
e.extend_symm_continuousWithinAt_comp_right_iff, differentiableWithinAtProp_self_source,
DifferentiableWithinAtProp, Function.comp, e.left_inv hx, (e.extend I).left_inv h2x]
rfl
theorem mdifferentiableWithinAt_iff_source_of_mem_source
[IsManifold I 1 M] {x' : M} (hx' : x' ∈ (chartAt H x).source) :
MDifferentiableWithinAt I I' f s x' ↔
MDifferentiableWithinAt 𝓘(𝕜, E) I' (f ∘ (extChartAt I x).symm)
((extChartAt I x).symm ⁻¹' s ∩ range I) (extChartAt I x x') :=
mdifferentiableWithinAt_iff_source_of_mem_maximalAtlas (chart_mem_maximalAtlas x) hx'
theorem mdifferentiableAt_iff_source_of_mem_source
[IsManifold I 1 M] {x' : M} (hx' : x' ∈ (chartAt H x).source) :
MDifferentiableAt I I' f x' ↔
MDifferentiableWithinAt 𝓘(𝕜, E) I' (f ∘ (extChartAt I x).symm) (range I)
(extChartAt I x x') := by
simp_rw [← mdifferentiableWithinAt_univ, mdifferentiableWithinAt_iff_source_of_mem_source hx',
preimage_univ, univ_inter]
theorem mdifferentiableWithinAt_iff_target_of_mem_source
[IsManifold I' 1 M'] {x : M} {y : M'} (hy : f x ∈ (chartAt H' y).source) :
MDifferentiableWithinAt I I' f s x ↔
ContinuousWithinAt f s x ∧ MDifferentiableWithinAt I 𝓘(𝕜, E') (extChartAt I' y ∘ f) s x := by
simp_rw [MDifferentiableWithinAt]
rw [differentiableWithinAt_localInvariantProp.liftPropWithinAt_indep_chart_target
(chart_mem_maximalAtlas y) hy,
and_congr_right]
intro hf
simp_rw [StructureGroupoid.liftPropWithinAt_self_target]
simp_rw [((chartAt H' y).continuousAt hy).comp_continuousWithinAt hf]
rw [← extChartAt_source I'] at hy
simp_rw [(continuousAt_extChartAt' hy).comp_continuousWithinAt hf]
rfl
theorem mdifferentiableAt_iff_target_of_mem_source
[IsManifold I' 1 M'] {x : M} {y : M'} (hy : f x ∈ (chartAt H' y).source) :
MDifferentiableAt I I' f x ↔
ContinuousAt f x ∧ MDifferentiableAt I 𝓘(𝕜, E') (extChartAt I' y ∘ f) x := by
rw [← mdifferentiableWithinAt_univ, mdifferentiableWithinAt_iff_target_of_mem_source hy,
continuousWithinAt_univ, ← mdifferentiableWithinAt_univ]
variable [IsManifold I 1 M] [IsManifold I' 1 M']
theorem mdifferentiableWithinAt_iff_of_mem_maximalAtlas {x : M} (he : e ∈ maximalAtlas I 1 M)
(he' : e' ∈ maximalAtlas I' 1 M') (hx : x ∈ e.source) (hy : f x ∈ e'.source) :
MDifferentiableWithinAt I I' f s x ↔
ContinuousWithinAt f s x ∧
DifferentiableWithinAt 𝕜 (e'.extend I' ∘ f ∘ (e.extend I).symm)
((e.extend I).symm ⁻¹' s ∩ range I) (e.extend I x) :=
differentiableWithinAt_localInvariantProp.liftPropWithinAt_indep_chart he hx he' hy
/-- An alternative formulation of `mdifferentiableWithinAt_iff_of_mem_maximalAtlas`
if the set if `s` lies in `e.source`. -/
theorem mdifferentiableWithinAt_iff_image {x : M} (he : e ∈ maximalAtlas I 1 M)
(he' : e' ∈ maximalAtlas I' 1 M') (hs : s ⊆ e.source) (hx : x ∈ e.source)
(hy : f x ∈ e'.source) :
MDifferentiableWithinAt I I' f s x ↔
ContinuousWithinAt f s x ∧
DifferentiableWithinAt 𝕜 (e'.extend I' ∘ f ∘ (e.extend I).symm) (e.extend I '' s)
(e.extend I x) := by
rw [mdifferentiableWithinAt_iff_of_mem_maximalAtlas he he' hx hy, and_congr_right_iff]
refine fun _ => differentiableWithinAt_congr_nhds ?_
simp_rw [nhdsWithin_eq_iff_eventuallyEq, e.extend_symm_preimage_inter_range_eventuallyEq hs hx]
/-- One can reformulate smoothness within a set at a point as continuity within this set at this
point, and smoothness in any chart containing that point. -/
theorem mdifferentiableWithinAt_iff_of_mem_source {x' : M} {y : M'} (hx : x' ∈ (chartAt H x).source)
(hy : f x' ∈ (chartAt H' y).source) :
MDifferentiableWithinAt I I' f s x' ↔
ContinuousWithinAt f s x' ∧
DifferentiableWithinAt 𝕜 (extChartAt I' y ∘ f ∘ (extChartAt I x).symm)
((extChartAt I x).symm ⁻¹' s ∩ range I) (extChartAt I x x') :=
mdifferentiableWithinAt_iff_of_mem_maximalAtlas (chart_mem_maximalAtlas x)
(chart_mem_maximalAtlas y) hx hy
/-- One can reformulate smoothness within a set at a point as continuity within this set at this
point, and smoothness in any chart containing that point. Version requiring differentiability
in the target instead of `range I`. -/
theorem mdifferentiableWithinAt_iff_of_mem_source' {x' : M} {y : M'}
(hx : x' ∈ (chartAt H x).source) (hy : f x' ∈ (chartAt H' y).source) :
MDifferentiableWithinAt I I' f s x' ↔
ContinuousWithinAt f s x' ∧
DifferentiableWithinAt 𝕜 (extChartAt I' y ∘ f ∘ (extChartAt I x).symm)
((extChartAt I x).target ∩ (extChartAt I x).symm ⁻¹' (s ∩ f ⁻¹' (extChartAt I' y).source))
(extChartAt I x x') := by
refine (mdifferentiableWithinAt_iff_of_mem_source hx hy).trans ?_
rw [← extChartAt_source I] at hx
rw [← extChartAt_source I'] at hy
rw [and_congr_right_iff]
set e := extChartAt I x; set e' := extChartAt I' (f x)
refine fun hc => differentiableWithinAt_congr_nhds ?_
rw [← e.image_source_inter_eq', ← map_extChartAt_nhdsWithin_eq_image' hx,
← map_extChartAt_nhdsWithin' hx, inter_comm, nhdsWithin_inter_of_mem]
exact hc (extChartAt_source_mem_nhds' hy)
theorem mdifferentiableAt_iff_of_mem_source {x' : M} {y : M'} (hx : x' ∈ (chartAt H x).source)
(hy : f x' ∈ (chartAt H' y).source) :
MDifferentiableAt I I' f x' ↔
ContinuousAt f x' ∧
DifferentiableWithinAt 𝕜 (extChartAt I' y ∘ f ∘ (extChartAt I x).symm) (range I)
(extChartAt I x x') :=
(mdifferentiableWithinAt_iff_of_mem_source hx hy).trans <| by
rw [continuousWithinAt_univ, preimage_univ, univ_inter]
theorem mdifferentiableOn_iff_of_mem_maximalAtlas (he : e ∈ maximalAtlas I 1 M)
(he' : e' ∈ maximalAtlas I' 1 M') (hs : s ⊆ e.source) (h2s : MapsTo f s e'.source) :
MDifferentiableOn I I' f s ↔
ContinuousOn f s ∧
DifferentiableOn 𝕜 (e'.extend I' ∘ f ∘ (e.extend I).symm) (e.extend I '' s) := by
simp_rw [ContinuousOn, DifferentiableOn, Set.forall_mem_image, ← forall_and, MDifferentiableOn]
exact forall₂_congr fun x hx => mdifferentiableWithinAt_iff_image he he' hs (hs hx) (h2s hx)
/-- Differentiability on a set is equivalent to differentiability in the extended charts. -/
theorem mdifferentiableOn_iff_of_mem_maximalAtlas' (he : e ∈ maximalAtlas I 1 M)
(he' : e' ∈ maximalAtlas I' 1 M') (hs : s ⊆ e.source) (h2s : MapsTo f s e'.source) :
MDifferentiableOn I I' f s ↔
DifferentiableOn 𝕜 (e'.extend I' ∘ f ∘ (e.extend I).symm) (e.extend I '' s) :=
(mdifferentiableOn_iff_of_mem_maximalAtlas he he' hs h2s).trans <| and_iff_right_of_imp fun h ↦
(e.continuousOn_writtenInExtend_iff hs h2s).1 h.continuousOn
/-- If the set where you want `f` to be smooth lies entirely in a single chart, and `f` maps it
into a single chart, the smoothness of `f` on that set can be expressed by purely looking in
these charts.
Note: this lemma uses `extChartAt I x '' s` instead of `(extChartAt I x).symm ⁻¹' s` to ensure
that this set lies in `(extChartAt I x).target`. -/
theorem mdifferentiableOn_iff_of_subset_source {x : M} {y : M'} (hs : s ⊆ (chartAt H x).source)
(h2s : MapsTo f s (chartAt H' y).source) :
MDifferentiableOn I I' f s ↔
ContinuousOn f s ∧
DifferentiableOn 𝕜 (extChartAt I' y ∘ f ∘ (extChartAt I x).symm) (extChartAt I x '' s) :=
mdifferentiableOn_iff_of_mem_maximalAtlas (chart_mem_maximalAtlas x)
(chart_mem_maximalAtlas y) hs h2s
/-- If the set where you want `f` to be smooth lies entirely in a single chart, and `f` maps it
into a single chart, the smoothness of `f` on that set can be expressed by purely looking in
these charts.
Note: this lemma uses `extChartAt I x '' s` instead of `(extChartAt I x).symm ⁻¹' s` to ensure
that this set lies in `(extChartAt I x).target`. -/
theorem mdifferentiableOn_iff_of_subset_source' {x : M} {y : M'} (hs : s ⊆ (extChartAt I x).source)
(h2s : MapsTo f s (extChartAt I' y).source) :
MDifferentiableOn I I' f s ↔
DifferentiableOn 𝕜 (extChartAt I' y ∘ f ∘ (extChartAt I x).symm) (extChartAt I x '' s) := by
rw [extChartAt_source] at hs h2s
exact mdifferentiableOn_iff_of_mem_maximalAtlas' (chart_mem_maximalAtlas x)
(chart_mem_maximalAtlas y) hs h2s
/-- One can reformulate smoothness on a set as continuity on this set, and smoothness in any
extended chart. -/
theorem mdifferentiableOn_iff :
MDifferentiableOn I I' f s ↔
ContinuousOn f s ∧
∀ (x : M) (y : M'),
DifferentiableOn 𝕜 (extChartAt I' y ∘ f ∘ (extChartAt I x).symm)
((extChartAt I x).target ∩
(extChartAt I x).symm ⁻¹' (s ∩ f ⁻¹' (extChartAt I' y).source)) := by
constructor
· intro h
refine ⟨fun x hx => (h x hx).1, fun x y z hz => ?_⟩
simp only [mfld_simps] at hz
let w := (extChartAt I x).symm z
have : w ∈ s := by simp only [w, hz, mfld_simps]
specialize h w this
have w1 : w ∈ (chartAt H x).source := by simp only [w, hz, mfld_simps]
have w2 : f w ∈ (chartAt H' y).source := by simp only [w, hz, mfld_simps]
convert ((mdifferentiableWithinAt_iff_of_mem_source w1 w2).mp h).2.mono _
· simp only [w, hz, mfld_simps]
· mfld_set_tac
· rintro ⟨hcont, hdiff⟩ x hx
refine differentiableWithinAt_localInvariantProp.liftPropWithinAt_iff.mpr ?_
refine ⟨hcont x hx, ?_⟩
dsimp [DifferentiableWithinAtProp]
convert hdiff x (f x) (extChartAt I x x) (by simp only [hx, mfld_simps]) using 1
mfld_set_tac
/-- One can reformulate smoothness on a set as continuity on this set, and smoothness in any
extended chart in the target. -/
theorem mdifferentiableOn_iff_target :
MDifferentiableOn I I' f s ↔
ContinuousOn f s ∧
∀ y : M', MDifferentiableOn I 𝓘(𝕜, E') (extChartAt I' y ∘ f)
(s ∩ f ⁻¹' (extChartAt I' y).source) := by
simp only [mdifferentiableOn_iff, ModelWithCorners.source_eq, chartAt_self_eq,
PartialHomeomorph.refl_partialEquiv, PartialEquiv.refl_trans, extChartAt,
PartialHomeomorph.extend, Set.preimage_univ, Set.inter_univ, and_congr_right_iff]
intro h
constructor
· refine fun h' y => ⟨?_, fun x _ => h' x y⟩
have h'' : ContinuousOn _ univ := (ModelWithCorners.continuous I').continuousOn
convert (h''.comp_inter (chartAt H' y).continuousOn_toFun).comp_inter h
simp
· exact fun h' x y => (h' y).2 x 0
/-- One can reformulate smoothness as continuity and smoothness in any extended chart. -/
theorem mdifferentiable_iff :
MDifferentiable I I' f ↔
Continuous f ∧
∀ (x : M) (y : M'),
DifferentiableOn 𝕜 (extChartAt I' y ∘ f ∘ (extChartAt I x).symm)
((extChartAt I x).target ∩
(extChartAt I x).symm ⁻¹' (f ⁻¹' (extChartAt I' y).source)) := by
simp [← mdifferentiableOn_univ, mdifferentiableOn_iff, continuous_iff_continuousOn_univ]
/-- One can reformulate smoothness as continuity and smoothness in any extended chart in the
target. -/
theorem mdifferentiable_iff_target :
MDifferentiable I I' f ↔
Continuous f ∧ ∀ y : M',
MDifferentiableOn I 𝓘(𝕜, E') (extChartAt I' y ∘ f) (f ⁻¹' (extChartAt I' y).source) := by
rw [← mdifferentiableOn_univ, mdifferentiableOn_iff_target]
simp [continuous_iff_continuousOn_univ]
end IsManifold
/-! ### Deducing differentiability from smoothness -/
variable {n : WithTop ℕ∞}
theorem ContMDiffWithinAt.mdifferentiableWithinAt (hf : ContMDiffWithinAt I I' n f s x)
(hn : 1 ≤ n) : MDifferentiableWithinAt I I' f s x := by
suffices h : MDifferentiableWithinAt I I' f (s ∩ f ⁻¹' (extChartAt I' (f x)).source) x by
rwa [mdifferentiableWithinAt_inter'] at h
apply hf.1.preimage_mem_nhdsWithin
exact extChartAt_source_mem_nhds (f x)
rw [mdifferentiableWithinAt_iff]
exact ⟨hf.1.mono inter_subset_left, (hf.2.differentiableWithinAt (mod_cast hn)).mono
(by mfld_set_tac)⟩
theorem ContMDiffAt.mdifferentiableAt (hf : ContMDiffAt I I' n f x) (hn : 1 ≤ n) :
MDifferentiableAt I I' f x :=
mdifferentiableWithinAt_univ.1 <| ContMDiffWithinAt.mdifferentiableWithinAt hf hn
theorem ContMDiff.mdifferentiableAt (hf : ContMDiff I I' n f) (hn : 1 ≤ n) :
MDifferentiableAt I I' f x :=
hf.contMDiffAt.mdifferentiableAt hn
theorem ContMDiff.mdifferentiableWithinAt (hf : ContMDiff I I' n f) (hn : 1 ≤ n) :
MDifferentiableWithinAt I I' f s x :=
(hf.contMDiffAt.mdifferentiableAt hn).mdifferentiableWithinAt
theorem ContMDiffOn.mdifferentiableOn (hf : ContMDiffOn I I' n f s) (hn : 1 ≤ n) :
MDifferentiableOn I I' f s := fun x hx => (hf x hx).mdifferentiableWithinAt hn
@[deprecated (since := "2024-11-20")]
alias SmoothWithinAt.mdifferentiableWithinAt := ContMDiffWithinAt.mdifferentiableWithinAt
theorem ContMDiff.mdifferentiable (hf : ContMDiff I I' n f) (hn : 1 ≤ n) : MDifferentiable I I' f :=
fun x => (hf x).mdifferentiableAt hn
@[deprecated (since := "2024-11-20")]
alias SmoothAt.mdifferentiableAt := ContMDiffAt.mdifferentiableAt
@[deprecated (since := "2024-11-20")]
alias SmoothOn.mdifferentiableOn := ContMDiffOn.mdifferentiableOn
@[deprecated (since := "2024-11-20")]
alias Smooth.mdifferentiable := ContMDiff.mdifferentiable
@[deprecated (since := "2024-11-20")]
alias Smooth.mdifferentiableAt := ContMDiff.mdifferentiableAt
theorem MDifferentiableOn.continuousOn (h : MDifferentiableOn I I' f s) : ContinuousOn f s :=
fun x hx => (h x hx).continuousWithinAt
theorem MDifferentiable.continuous (h : MDifferentiable I I' f) : Continuous f :=
continuous_iff_continuousAt.2 fun x => (h x).continuousAt
@[deprecated (since := "2024-11-20")]
alias Smooth.mdifferentiableWithinAt := ContMDiff.mdifferentiableWithinAt
/-! ### Deriving continuity from differentiability on manifolds -/
theorem MDifferentiableWithinAt.prodMk {f : M → M'} {g : M → M''}
(hf : MDifferentiableWithinAt I I' f s x) (hg : MDifferentiableWithinAt I I'' g s x) :
MDifferentiableWithinAt I (I'.prod I'') (fun x => (f x, g x)) s x :=
⟨hf.1.prodMk hg.1, hf.2.prodMk hg.2⟩
@[deprecated (since := "2025-03-08")]
alias MDifferentiableWithinAt.prod_mk := MDifferentiableWithinAt.prodMk
theorem MDifferentiableAt.prodMk {f : M → M'} {g : M → M''} (hf : MDifferentiableAt I I' f x)
(hg : MDifferentiableAt I I'' g x) :
MDifferentiableAt I (I'.prod I'') (fun x => (f x, g x)) x :=
⟨hf.1.prodMk hg.1, hf.2.prodMk hg.2⟩
@[deprecated (since := "2025-03-08")]
alias MDifferentiableAt.prod_mk := MDifferentiableAt.prodMk
theorem MDifferentiableWithinAt.prodMk_space {f : M → E'} {g : M → E''}
(hf : MDifferentiableWithinAt I 𝓘(𝕜, E') f s x)
(hg : MDifferentiableWithinAt I 𝓘(𝕜, E'') g s x) :
MDifferentiableWithinAt I 𝓘(𝕜, E' × E'') (fun x => (f x, g x)) s x :=
⟨hf.1.prodMk hg.1, hf.2.prodMk hg.2⟩
@[deprecated (since := "2025-03-08")]
alias MDifferentiableWithinAt.prod_mk_space := MDifferentiableWithinAt.prodMk_space
theorem MDifferentiableAt.prodMk_space {f : M → E'} {g : M → E''}
(hf : MDifferentiableAt I 𝓘(𝕜, E') f x) (hg : MDifferentiableAt I 𝓘(𝕜, E'') g x) :
MDifferentiableAt I 𝓘(𝕜, E' × E'') (fun x => (f x, g x)) x :=
⟨hf.1.prodMk hg.1, hf.2.prodMk hg.2⟩
@[deprecated (since := "2025-03-08")]
alias MDifferentiableAt.prod_mk_space := MDifferentiableAt.prodMk_space
theorem MDifferentiableOn.prodMk {f : M → M'} {g : M → M''} (hf : MDifferentiableOn I I' f s)
(hg : MDifferentiableOn I I'' g s) :
MDifferentiableOn I (I'.prod I'') (fun x => (f x, g x)) s := fun x hx =>
(hf x hx).prodMk (hg x hx)
@[deprecated (since := "2025-03-08")]
alias MDifferentiableOn.prod_mk := MDifferentiableOn.prodMk
theorem MDifferentiable.prodMk {f : M → M'} {g : M → M''} (hf : MDifferentiable I I' f)
(hg : MDifferentiable I I'' g) : MDifferentiable I (I'.prod I'') fun x => (f x, g x) := fun x =>
(hf x).prodMk (hg x)
@[deprecated (since := "2025-03-08")]
alias MDifferentiable.prod_mk := MDifferentiable.prodMk
theorem MDifferentiableOn.prodMk_space {f : M → E'} {g : M → E''}
(hf : MDifferentiableOn I 𝓘(𝕜, E') f s) (hg : MDifferentiableOn I 𝓘(𝕜, E'') g s) :
MDifferentiableOn I 𝓘(𝕜, E' × E'') (fun x => (f x, g x)) s := fun x hx =>
(hf x hx).prodMk_space (hg x hx)
@[deprecated (since := "2025-03-08")]
alias MDifferentiableOn.prod_mk_space := MDifferentiableOn.prodMk_space
theorem MDifferentiable.prodMk_space {f : M → E'} {g : M → E''} (hf : MDifferentiable I 𝓘(𝕜, E') f)
(hg : MDifferentiable I 𝓘(𝕜, E'') g) : MDifferentiable I 𝓘(𝕜, E' × E'') fun x => (f x, g x) :=
fun x => (hf x).prodMk_space (hg x)
@[deprecated (since := "2025-03-08")]
alias MDifferentiable.prod_mk_space := MDifferentiable.prodMk_space
theorem writtenInExtChartAt_comp (h : ContinuousWithinAt f s x) :
{y | writtenInExtChartAt I I'' x (g ∘ f) y =
(writtenInExtChartAt I' I'' (f x) g ∘ writtenInExtChartAt I I' x f) y} ∈
𝓝[(extChartAt I x).symm ⁻¹' s ∩ range I] (extChartAt I x) x := by
apply
@Filter.mem_of_superset _ _ (f ∘ (extChartAt I x).symm ⁻¹' (extChartAt I' (f x)).source) _
(extChartAt_preimage_mem_nhdsWithin
(h.preimage_mem_nhdsWithin (extChartAt_source_mem_nhds _)))
mfld_set_tac
variable {f' f₀' f₁' : TangentSpace I x →L[𝕜] TangentSpace I' (f x)}
{g' : TangentSpace I' (f x) →L[𝕜] TangentSpace I'' (g (f x))}
/-- `UniqueMDiffWithinAt` achieves its goal: it implies the uniqueness of the derivative. -/
protected nonrec theorem UniqueMDiffWithinAt.eq (U : UniqueMDiffWithinAt I s x)
(h : HasMFDerivWithinAt I I' f s x f') (h₁ : HasMFDerivWithinAt I I' f s x f₁') : f' = f₁' := by
-- Porting note: didn't need `convert` because of finding instances by unification
convert U.eq h.2 h₁.2
protected theorem UniqueMDiffOn.eq (U : UniqueMDiffOn I s) (hx : x ∈ s)
(h : HasMFDerivWithinAt I I' f s x f') (h₁ : HasMFDerivWithinAt I I' f s x f₁') : f' = f₁' :=
UniqueMDiffWithinAt.eq (U _ hx) h h₁
/-!
### General lemmas on derivatives of functions between manifolds
We mimic the API for functions between vector spaces
-/
@[simp, mfld_simps]
theorem mfderivWithin_univ : mfderivWithin I I' f univ = mfderiv I I' f := by
ext x : 1
simp only [mfderivWithin, mfderiv, mfld_simps]
rw [mdifferentiableWithinAt_univ]
theorem mfderivWithin_zero_of_not_mdifferentiableWithinAt
(h : ¬MDifferentiableWithinAt I I' f s x) : mfderivWithin I I' f s x = 0 := by
simp only [mfderivWithin, h, if_neg, not_false_iff]
theorem mfderiv_zero_of_not_mdifferentiableAt (h : ¬MDifferentiableAt I I' f x) :
mfderiv I I' f x = 0 := by simp only [mfderiv, h, if_neg, not_false_iff]
theorem mdifferentiable_of_subsingleton [Subsingleton E] : MDifferentiable I I' f := by
intro x
have : Subsingleton H := I.injective.subsingleton
have : DiscreteTopology M := discreteTopology H M
simp only [mdifferentiableAt_iff, continuous_of_discreteTopology.continuousAt, true_and]
exact (hasFDerivAt_of_subsingleton _ _).differentiableAt.differentiableWithinAt
theorem mdifferentiableWithinAt_of_isInvertible_mfderivWithin
(hf : (mfderivWithin I I' f s x).IsInvertible) : MDifferentiableWithinAt I I' f s x := by
contrapose hf
rw [mfderivWithin_zero_of_not_mdifferentiableWithinAt hf]
contrapose! hf
rcases ContinuousLinearMap.isInvertible_zero_iff.1 hf with ⟨hE, hF⟩
have : Subsingleton E := hE
exact mdifferentiable_of_subsingleton.mdifferentiableAt.mdifferentiableWithinAt
theorem mdifferentiableAt_of_isInvertible_mfderiv
(hf : (mfderiv I I' f x).IsInvertible) : MDifferentiableAt I I' f x := by
simp only [← mdifferentiableWithinAt_univ, ← mfderivWithin_univ] at hf ⊢
exact mdifferentiableWithinAt_of_isInvertible_mfderivWithin hf
theorem HasMFDerivWithinAt.mono (h : HasMFDerivWithinAt I I' f t x f') (hst : s ⊆ t) :
HasMFDerivWithinAt I I' f s x f' :=
⟨ContinuousWithinAt.mono h.1 hst,
HasFDerivWithinAt.mono h.2 (inter_subset_inter (preimage_mono hst) (Subset.refl _))⟩
theorem HasMFDerivAt.hasMFDerivWithinAt (h : HasMFDerivAt I I' f x f') :
HasMFDerivWithinAt I I' f s x f' :=
⟨ContinuousAt.continuousWithinAt h.1, HasFDerivWithinAt.mono h.2 inter_subset_right⟩
theorem HasMFDerivWithinAt.mdifferentiableWithinAt (h : HasMFDerivWithinAt I I' f s x f') :
MDifferentiableWithinAt I I' f s x :=
⟨h.1, ⟨f', h.2⟩⟩
| theorem HasMFDerivAt.mdifferentiableAt (h : HasMFDerivAt I I' f x f') :
MDifferentiableAt I I' f x := by
rw [mdifferentiableAt_iff]
exact ⟨h.1, ⟨f', h.2⟩⟩
@[simp, mfld_simps]
theorem hasMFDerivWithinAt_univ :
HasMFDerivWithinAt I I' f univ x f' ↔ HasMFDerivAt I I' f x f' := by
simp only [HasMFDerivWithinAt, HasMFDerivAt, continuousWithinAt_univ, mfld_simps]
| Mathlib/Geometry/Manifold/MFDeriv/Basic.lean | 657 | 665 |
/-
Copyright (c) 2014 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Mario Carneiro
-/
import Mathlib.Algebra.Order.Ring.Nat
import Mathlib.Algebra.Ring.Int.Defs
import Mathlib.Data.Nat.Bitwise
import Mathlib.Data.Nat.Cast.Order.Basic
import Mathlib.Data.Nat.PSub
import Mathlib.Data.Nat.Size
import Mathlib.Data.Num.Bitwise
/-!
# Properties of the binary representation of integers
-/
open Int
attribute [local simp] add_assoc
namespace PosNum
variable {α : Type*}
@[simp, norm_cast]
theorem cast_one [One α] [Add α] : ((1 : PosNum) : α) = 1 :=
rfl
@[simp]
theorem cast_one' [One α] [Add α] : (PosNum.one : α) = 1 :=
rfl
@[simp, norm_cast]
theorem cast_bit0 [One α] [Add α] (n : PosNum) : (n.bit0 : α) = (n : α) + n :=
rfl
@[simp, norm_cast]
theorem cast_bit1 [One α] [Add α] (n : PosNum) : (n.bit1 : α) = ((n : α) + n) + 1 :=
rfl
@[simp, norm_cast]
theorem cast_to_nat [AddMonoidWithOne α] : ∀ n : PosNum, ((n : ℕ) : α) = n
| 1 => Nat.cast_one
| bit0 p => by dsimp; rw [Nat.cast_add, p.cast_to_nat]
| bit1 p => by dsimp; rw [Nat.cast_add, Nat.cast_add, Nat.cast_one, p.cast_to_nat]
@[norm_cast]
theorem to_nat_to_int (n : PosNum) : ((n : ℕ) : ℤ) = n :=
cast_to_nat _
@[simp, norm_cast]
theorem cast_to_int [AddGroupWithOne α] (n : PosNum) : ((n : ℤ) : α) = n := by
rw [← to_nat_to_int, Int.cast_natCast, cast_to_nat]
theorem succ_to_nat : ∀ n, (succ n : ℕ) = n + 1
| 1 => rfl
| bit0 _ => rfl
| bit1 p =>
(congr_arg (fun n ↦ n + n) (succ_to_nat p)).trans <|
show ↑p + 1 + ↑p + 1 = ↑p + ↑p + 1 + 1 by simp [add_left_comm]
theorem one_add (n : PosNum) : 1 + n = succ n := by cases n <;> rfl
theorem add_one (n : PosNum) : n + 1 = succ n := by cases n <;> rfl
@[norm_cast]
theorem add_to_nat : ∀ m n, ((m + n : PosNum) : ℕ) = m + n
| 1, b => by rw [one_add b, succ_to_nat, add_comm, cast_one]
| a, 1 => by rw [add_one a, succ_to_nat, cast_one]
| bit0 a, bit0 b => (congr_arg (fun n ↦ n + n) (add_to_nat a b)).trans <| add_add_add_comm _ _ _ _
| bit0 a, bit1 b =>
(congr_arg (fun n ↦ (n + n) + 1) (add_to_nat a b)).trans <|
show (a + b + (a + b) + 1 : ℕ) = a + a + (b + b + 1) by simp [add_left_comm]
| bit1 a, bit0 b =>
(congr_arg (fun n ↦ (n + n) + 1) (add_to_nat a b)).trans <|
show (a + b + (a + b) + 1 : ℕ) = a + a + 1 + (b + b) by simp [add_comm, add_left_comm]
| bit1 a, bit1 b =>
show (succ (a + b) + succ (a + b) : ℕ) = a + a + 1 + (b + b + 1) by
rw [succ_to_nat, add_to_nat a b]; simp [add_left_comm]
theorem add_succ : ∀ m n : PosNum, m + succ n = succ (m + n)
| 1, b => by simp [one_add]
| bit0 a, 1 => congr_arg bit0 (add_one a)
| bit1 a, 1 => congr_arg bit1 (add_one a)
| bit0 _, bit0 _ => rfl
| bit0 a, bit1 b => congr_arg bit0 (add_succ a b)
| bit1 _, bit0 _ => rfl
| bit1 a, bit1 b => congr_arg bit1 (add_succ a b)
theorem bit0_of_bit0 : ∀ n, n + n = bit0 n
| 1 => rfl
| bit0 p => congr_arg bit0 (bit0_of_bit0 p)
| bit1 p => show bit0 (succ (p + p)) = _ by rw [bit0_of_bit0 p, succ]
theorem bit1_of_bit1 (n : PosNum) : (n + n) + 1 = bit1 n :=
show (n + n) + 1 = bit1 n by rw [add_one, bit0_of_bit0, succ]
@[norm_cast]
theorem mul_to_nat (m) : ∀ n, ((m * n : PosNum) : ℕ) = m * n
| 1 => (mul_one _).symm
| bit0 p => show (↑(m * p) + ↑(m * p) : ℕ) = ↑m * (p + p) by rw [mul_to_nat m p, left_distrib]
| | bit1 p =>
(add_to_nat (bit0 (m * p)) m).trans <|
show (↑(m * p) + ↑(m * p) + ↑m : ℕ) = ↑m * (p + p) + m by rw [mul_to_nat m p, left_distrib]
theorem to_nat_pos : ∀ n : PosNum, 0 < (n : ℕ)
| 1 => Nat.zero_lt_one
| bit0 p =>
let h := to_nat_pos p
| Mathlib/Data/Num/Lemmas.lean | 103 | 110 |
/-
Copyright (c) 2024 Rémy Degenne. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Rémy Degenne
-/
import Mathlib.LinearAlgebra.FreeModule.Basic
import Mathlib.MeasureTheory.Measure.Decomposition.Exhaustion
import Mathlib.Probability.ConditionalProbability
/-!
# s-finite measures can be written as `withDensity` of a finite measure
If `μ` is an s-finite measure, then there exists a finite measure `μ.toFinite`
such that a set is `μ`-null iff it is `μ.toFinite`-null.
In particular, `MeasureTheory.ae μ.toFinite = MeasureTheory.ae μ` and `μ.toFinite = 0` iff `μ = 0`.
As a corollary, `μ` can be represented as `μ.toFinite.withDensity (μ.rnDeriv μ.toFinite)`.
Our definition of `MeasureTheory.Measure.toFinite` ensures some extra properties:
- if `μ` is a finite measure, then `μ.toFinite = μ[|univ] = (μ univ)⁻¹ • μ`;
- in particular, `μ.toFinite = μ` for a probability measure;
- if `μ ≠ 0`, then `μ.toFinite` is a probability measure.
## Main definitions
In these definitions and the results below, `μ` is an s-finite measure (`SFinite μ`).
* `MeasureTheory.Measure.toFinite`: a finite measure with `μ ≪ μ.toFinite` and `μ.toFinite ≪ μ`.
If `μ ≠ 0`, this is a probability measure.
* `MeasureTheory.Measure.densityToFinite` (deprecated, use `MeasureTheory.Measure.rnDeriv`):
the Radon-Nikodym derivative of `μ.toFinite` with respect to `μ`.
## Main statements
* `absolutelyContinuous_toFinite`: `μ ≪ μ.toFinite`.
* `toFinite_absolutelyContinuous`: `μ.toFinite ≪ μ`.
* `ae_toFinite`: `ae μ.toFinite = ae μ`.
-/
open Set
open scoped ENNReal ProbabilityTheory
namespace MeasureTheory
variable {α : Type*} {mα : MeasurableSpace α} {μ : Measure α}
/-- Auxiliary definition for `MeasureTheory.Measure.toFinite`. -/
noncomputable def Measure.toFiniteAux (μ : Measure α) [SFinite μ] : Measure α :=
letI := Classical.dec
if IsFiniteMeasure μ then μ else (exists_isFiniteMeasure_absolutelyContinuous μ).choose
/-- A finite measure obtained from an s-finite measure `μ`, such that
`μ = μ.toFinite.withDensity μ.densityToFinite` (see `withDensity_densitytoFinite`).
If `μ` is non-zero, this is a probability measure. -/
noncomputable def Measure.toFinite (μ : Measure α) [SFinite μ] : Measure α :=
μ.toFiniteAux[|univ]
@[local simp]
lemma ae_toFiniteAux [SFinite μ] : ae μ.toFiniteAux = ae μ := by
rw [Measure.toFiniteAux]
split_ifs
· simp
· obtain ⟨_, h₁, h₂⟩ := (exists_isFiniteMeasure_absolutelyContinuous μ).choose_spec
exact h₂.ae_le.antisymm h₁.ae_le
@[local instance]
theorem isFiniteMeasure_toFiniteAux [SFinite μ] : IsFiniteMeasure μ.toFiniteAux := by
rw [Measure.toFiniteAux]
split_ifs
· assumption
| · exact (exists_isFiniteMeasure_absolutelyContinuous μ).choose_spec.1
@[simp]
| Mathlib/MeasureTheory/Measure/WithDensityFinite.lean | 72 | 74 |
/-
Copyright (c) 2022 Joseph Myers. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Joseph Myers, Heather Macbeth
-/
import Mathlib.Analysis.SpecialFunctions.Complex.Circle
import Mathlib.Geometry.Euclidean.Angle.Oriented.Basic
/-!
# Rotations by oriented angles.
This file defines rotations by oriented angles in real inner product spaces.
## Main definitions
* `Orientation.rotation` is the rotation by an oriented angle with respect to an orientation.
-/
noncomputable section
open Module Complex
open scoped Real RealInnerProductSpace ComplexConjugate
namespace Orientation
attribute [local instance] Complex.finrank_real_complex_fact
variable {V V' : Type*}
variable [NormedAddCommGroup V] [NormedAddCommGroup V']
variable [InnerProductSpace ℝ V] [InnerProductSpace ℝ V']
variable [Fact (finrank ℝ V = 2)] [Fact (finrank ℝ V' = 2)] (o : Orientation ℝ V (Fin 2))
local notation "J" => o.rightAngleRotation
/-- Auxiliary construction to build a rotation by the oriented angle `θ`. -/
def rotationAux (θ : Real.Angle) : V →ₗᵢ[ℝ] V :=
LinearMap.isometryOfInner
(Real.Angle.cos θ • LinearMap.id +
Real.Angle.sin θ • (LinearIsometryEquiv.toLinearEquiv J).toLinearMap)
(by
intro x y
simp only [RCLike.conj_to_real, id, LinearMap.smul_apply, LinearMap.add_apply,
LinearMap.id_coe, LinearEquiv.coe_coe, LinearIsometryEquiv.coe_toLinearEquiv,
Orientation.areaForm_rightAngleRotation_left, Orientation.inner_rightAngleRotation_left,
Orientation.inner_rightAngleRotation_right, inner_add_left, inner_smul_left,
inner_add_right, inner_smul_right]
linear_combination inner (𝕜 := ℝ) x y * θ.cos_sq_add_sin_sq)
@[simp]
theorem rotationAux_apply (θ : Real.Angle) (x : V) :
o.rotationAux θ x = Real.Angle.cos θ • x + Real.Angle.sin θ • J x :=
rfl
/-- A rotation by the oriented angle `θ`. -/
def rotation (θ : Real.Angle) : V ≃ₗᵢ[ℝ] V :=
LinearIsometryEquiv.ofLinearIsometry (o.rotationAux θ)
(Real.Angle.cos θ • LinearMap.id -
Real.Angle.sin θ • (LinearIsometryEquiv.toLinearEquiv J).toLinearMap)
(by
ext x
convert congr_arg (fun t : ℝ => t • x) θ.cos_sq_add_sin_sq using 1
· simp only [o.rightAngleRotation_rightAngleRotation, o.rotationAux_apply,
Function.comp_apply, id, LinearEquiv.coe_coe, LinearIsometry.coe_toLinearMap,
LinearIsometryEquiv.coe_toLinearEquiv, map_smul, map_sub, LinearMap.coe_comp,
LinearMap.id_coe, LinearMap.smul_apply, LinearMap.sub_apply]
module
· simp)
(by
ext x
convert congr_arg (fun t : ℝ => t • x) θ.cos_sq_add_sin_sq using 1
· simp only [o.rightAngleRotation_rightAngleRotation, o.rotationAux_apply,
Function.comp_apply, id, LinearEquiv.coe_coe, LinearIsometry.coe_toLinearMap,
LinearIsometryEquiv.coe_toLinearEquiv, map_add, map_smul, LinearMap.coe_comp,
LinearMap.id_coe, LinearMap.smul_apply, LinearMap.sub_apply]
module
· simp)
theorem rotation_apply (θ : Real.Angle) (x : V) :
o.rotation θ x = Real.Angle.cos θ • x + Real.Angle.sin θ • J x :=
rfl
theorem rotation_symm_apply (θ : Real.Angle) (x : V) :
(o.rotation θ).symm x = Real.Angle.cos θ • x - Real.Angle.sin θ • J x :=
rfl
theorem rotation_eq_matrix_toLin (θ : Real.Angle) {x : V} (hx : x ≠ 0) :
(o.rotation θ).toLinearMap =
Matrix.toLin (o.basisRightAngleRotation x hx) (o.basisRightAngleRotation x hx)
!![θ.cos, -θ.sin; θ.sin, θ.cos] := by
apply (o.basisRightAngleRotation x hx).ext
intro i
fin_cases i
· rw [Matrix.toLin_self]
simp [rotation_apply, Fin.sum_univ_succ]
· rw [Matrix.toLin_self]
simp [rotation_apply, Fin.sum_univ_succ, add_comm]
/-- The determinant of `rotation` (as a linear map) is equal to `1`. -/
@[simp]
theorem det_rotation (θ : Real.Angle) : LinearMap.det (o.rotation θ).toLinearMap = 1 := by
haveI : Nontrivial V := nontrivial_of_finrank_eq_succ (@Fact.out (finrank ℝ V = 2) _)
obtain ⟨x, hx⟩ : ∃ x, x ≠ (0 : V) := exists_ne (0 : V)
rw [o.rotation_eq_matrix_toLin θ hx]
simpa [sq] using θ.cos_sq_add_sin_sq
/-- The determinant of `rotation` (as a linear equiv) is equal to `1`. -/
@[simp]
theorem linearEquiv_det_rotation (θ : Real.Angle) :
LinearEquiv.det (o.rotation θ).toLinearEquiv = 1 :=
Units.ext <| by
-- Porting note: Lean can't see through `LinearEquiv.coe_det` and needed the rewrite
-- in mathlib3 this was just `units.ext <| o.det_rotation θ`
simpa only [LinearEquiv.coe_det, Units.val_one] using o.det_rotation θ
/-- The inverse of `rotation` is rotation by the negation of the angle. -/
@[simp]
theorem rotation_symm (θ : Real.Angle) : (o.rotation θ).symm = o.rotation (-θ) := by
ext; simp [o.rotation_apply, o.rotation_symm_apply, sub_eq_add_neg]
/-- Rotation by 0 is the identity. -/
@[simp]
theorem rotation_zero : o.rotation 0 = LinearIsometryEquiv.refl ℝ V := by ext; simp [rotation]
/-- Rotation by π is negation. -/
@[simp]
theorem rotation_pi : o.rotation π = LinearIsometryEquiv.neg ℝ := by
ext x
simp [rotation]
/-- Rotation by π is negation. -/
theorem rotation_pi_apply (x : V) : o.rotation π x = -x := by simp
/-- Rotation by π / 2 is the "right-angle-rotation" map `J`. -/
theorem rotation_pi_div_two : o.rotation (π / 2 : ℝ) = J := by
ext x
simp [rotation]
/-- Rotating twice is equivalent to rotating by the sum of the angles. -/
@[simp]
theorem rotation_rotation (θ₁ θ₂ : Real.Angle) (x : V) :
o.rotation θ₁ (o.rotation θ₂ x) = o.rotation (θ₁ + θ₂) x := by
simp only [o.rotation_apply, Real.Angle.cos_add, Real.Angle.sin_add, LinearIsometryEquiv.map_add,
LinearIsometryEquiv.trans_apply, map_smul, rightAngleRotation_rightAngleRotation]
module
/-- Rotating twice is equivalent to rotating by the sum of the angles. -/
@[simp]
theorem rotation_trans (θ₁ θ₂ : Real.Angle) :
(o.rotation θ₁).trans (o.rotation θ₂) = o.rotation (θ₂ + θ₁) :=
LinearIsometryEquiv.ext fun _ => by rw [← rotation_rotation, LinearIsometryEquiv.trans_apply]
/-- Rotating the first of two vectors by `θ` scales their Kahler form by `cos θ - sin θ * I`. -/
@[simp]
theorem kahler_rotation_left (x y : V) (θ : Real.Angle) :
o.kahler (o.rotation θ x) y = conj (θ.toCircle : ℂ) * o.kahler x y := by
-- Porting note: this needed the `Complex.conj_ofReal` instead of `RCLike.conj_ofReal`;
-- I believe this is because the respective coercions are no longer defeq, and
-- `Real.Angle.coe_toCircle` uses the `Complex` version.
simp only [o.rotation_apply, map_add, map_mul, LinearMap.map_smulₛₗ, RingHom.id_apply,
LinearMap.add_apply, LinearMap.smul_apply, real_smul, kahler_rightAngleRotation_left,
Real.Angle.coe_toCircle, Complex.conj_ofReal, conj_I]
ring
/-- Negating a rotation is equivalent to rotation by π plus the angle. -/
theorem neg_rotation (θ : Real.Angle) (x : V) : -o.rotation θ x = o.rotation (π + θ) x := by
rw [← o.rotation_pi_apply, rotation_rotation]
/-- Negating a rotation by -π / 2 is equivalent to rotation by π / 2. -/
@[simp]
theorem neg_rotation_neg_pi_div_two (x : V) :
-o.rotation (-π / 2 : ℝ) x = o.rotation (π / 2 : ℝ) x := by
rw [neg_rotation, ← Real.Angle.coe_add, neg_div, ← sub_eq_add_neg, sub_half]
/-- Negating a rotation by π / 2 is equivalent to rotation by -π / 2. -/
theorem neg_rotation_pi_div_two (x : V) : -o.rotation (π / 2 : ℝ) x = o.rotation (-π / 2 : ℝ) x :=
(neg_eq_iff_eq_neg.mp <| o.neg_rotation_neg_pi_div_two _).symm
/-- Rotating the first of two vectors by `θ` scales their Kahler form by `cos (-θ) + sin (-θ) * I`.
-/
theorem kahler_rotation_left' (x y : V) (θ : Real.Angle) :
o.kahler (o.rotation θ x) y = (-θ).toCircle * o.kahler x y := by
simp only [Real.Angle.toCircle_neg, Circle.coe_inv_eq_conj, kahler_rotation_left]
/-- Rotating the second of two vectors by `θ` scales their Kahler form by `cos θ + sin θ * I`. -/
@[simp]
theorem kahler_rotation_right (x y : V) (θ : Real.Angle) :
o.kahler x (o.rotation θ y) = θ.toCircle * o.kahler x y := by
simp only [o.rotation_apply, map_add, LinearMap.map_smulₛₗ, RingHom.id_apply, real_smul,
kahler_rightAngleRotation_right, Real.Angle.coe_toCircle]
ring
/-- Rotating the first vector by `θ` subtracts `θ` from the angle between two vectors. -/
@[simp]
theorem oangle_rotation_left {x y : V} (hx : x ≠ 0) (hy : y ≠ 0) (θ : Real.Angle) :
o.oangle (o.rotation θ x) y = o.oangle x y - θ := by
simp only [oangle, o.kahler_rotation_left']
rw [Complex.arg_mul_coe_angle, Real.Angle.arg_toCircle]
· abel
· exact Circle.coe_ne_zero _
· exact o.kahler_ne_zero hx hy
/-- Rotating the second vector by `θ` adds `θ` to the angle between two vectors. -/
@[simp]
theorem oangle_rotation_right {x y : V} (hx : x ≠ 0) (hy : y ≠ 0) (θ : Real.Angle) :
o.oangle x (o.rotation θ y) = o.oangle x y + θ := by
simp only [oangle, o.kahler_rotation_right]
rw [Complex.arg_mul_coe_angle, Real.Angle.arg_toCircle]
· abel
· exact Circle.coe_ne_zero _
· exact o.kahler_ne_zero hx hy
/-- The rotation of a vector by `θ` has an angle of `-θ` from that vector. -/
@[simp]
theorem oangle_rotation_self_left {x : V} (hx : x ≠ 0) (θ : Real.Angle) :
o.oangle (o.rotation θ x) x = -θ := by simp [hx]
/-- A vector has an angle of `θ` from the rotation of that vector by `θ`. -/
@[simp]
theorem oangle_rotation_self_right {x : V} (hx : x ≠ 0) (θ : Real.Angle) :
o.oangle x (o.rotation θ x) = θ := by simp [hx]
/-- Rotating the first vector by the angle between the two vectors results in an angle of 0. -/
@[simp]
theorem oangle_rotation_oangle_left (x y : V) : o.oangle (o.rotation (o.oangle x y) x) y = 0 := by
by_cases hx : x = 0
· simp [hx]
· by_cases hy : y = 0
· simp [hy]
· simp [hx, hy]
/-- Rotating the first vector by the angle between the two vectors and swapping the vectors
results in an angle of 0. -/
@[simp]
theorem oangle_rotation_oangle_right (x y : V) : o.oangle y (o.rotation (o.oangle x y) x) = 0 := by
rw [oangle_rev]
simp
/-- Rotating both vectors by the same angle does not change the angle between those vectors. -/
@[simp]
theorem oangle_rotation (x y : V) (θ : Real.Angle) :
o.oangle (o.rotation θ x) (o.rotation θ y) = o.oangle x y := by
by_cases hx : x = 0 <;> by_cases hy : y = 0 <;> simp [hx, hy]
/-- A rotation of a nonzero vector equals that vector if and only if the angle is zero. -/
@[simp]
theorem rotation_eq_self_iff_angle_eq_zero {x : V} (hx : x ≠ 0) (θ : Real.Angle) :
o.rotation θ x = x ↔ θ = 0 := by
constructor
· intro h
rw [eq_comm]
simpa [hx, h] using o.oangle_rotation_right hx hx θ
· intro h
simp [h]
/-- A nonzero vector equals a rotation of that vector if and only if the angle is zero. -/
@[simp]
theorem eq_rotation_self_iff_angle_eq_zero {x : V} (hx : x ≠ 0) (θ : Real.Angle) :
x = o.rotation θ x ↔ θ = 0 := by rw [← o.rotation_eq_self_iff_angle_eq_zero hx, eq_comm]
/-- A rotation of a vector equals that vector if and only if the vector or the angle is zero. -/
theorem rotation_eq_self_iff (x : V) (θ : Real.Angle) : o.rotation θ x = x ↔ x = 0 ∨ θ = 0 := by
by_cases h : x = 0 <;> simp [h]
/-- A vector equals a rotation of that vector if and only if the vector or the angle is zero. -/
theorem eq_rotation_self_iff (x : V) (θ : Real.Angle) : x = o.rotation θ x ↔ x = 0 ∨ θ = 0 := by
rw [← rotation_eq_self_iff, eq_comm]
/-- Rotating a vector by the angle to another vector gives the second vector if and only if the
norms are equal. -/
@[simp]
theorem rotation_oangle_eq_iff_norm_eq (x y : V) : o.rotation (o.oangle x y) x = y ↔ ‖x‖ = ‖y‖ := by
constructor
· intro h
rw [← h, LinearIsometryEquiv.norm_map]
· intro h
rw [o.eq_iff_oangle_eq_zero_of_norm_eq] <;> simp [h]
/-- The angle between two nonzero vectors is `θ` if and only if the second vector is the first
rotated by `θ` and scaled by the ratio of the norms. -/
theorem oangle_eq_iff_eq_norm_div_norm_smul_rotation_of_ne_zero {x y : V} (hx : x ≠ 0) (hy : y ≠ 0)
(θ : Real.Angle) : o.oangle x y = θ ↔ y = (‖y‖ / ‖x‖) • o.rotation θ x := by
have hp := div_pos (norm_pos_iff.2 hy) (norm_pos_iff.2 hx)
constructor
· rintro rfl
rw [← LinearIsometryEquiv.map_smul, ← o.oangle_smul_left_of_pos x y hp, eq_comm,
rotation_oangle_eq_iff_norm_eq, norm_smul, Real.norm_of_nonneg hp.le,
div_mul_cancel₀ _ (norm_ne_zero_iff.2 hx)]
· intro hye
rw [hye, o.oangle_smul_right_of_pos _ _ hp, o.oangle_rotation_self_right hx]
/-- The angle between two nonzero vectors is `θ` if and only if the second vector is the first
rotated by `θ` and scaled by a positive real. -/
theorem oangle_eq_iff_eq_pos_smul_rotation_of_ne_zero {x y : V} (hx : x ≠ 0) (hy : y ≠ 0)
(θ : Real.Angle) : o.oangle x y = θ ↔ ∃ r : ℝ, 0 < r ∧ y = r • o.rotation θ x := by
constructor
· intro h
rw [o.oangle_eq_iff_eq_norm_div_norm_smul_rotation_of_ne_zero hx hy] at h
exact ⟨‖y‖ / ‖x‖, div_pos (norm_pos_iff.2 hy) (norm_pos_iff.2 hx), h⟩
· rintro ⟨r, hr, rfl⟩
rw [o.oangle_smul_right_of_pos _ _ hr, o.oangle_rotation_self_right hx]
/-- The angle between two vectors is `θ` if and only if they are nonzero and the second vector
is the first rotated by `θ` and scaled by the ratio of the norms, or `θ` and at least one of the
vectors are zero. -/
theorem oangle_eq_iff_eq_norm_div_norm_smul_rotation_or_eq_zero {x y : V} (θ : Real.Angle) :
o.oangle x y = θ ↔
x ≠ 0 ∧ y ≠ 0 ∧ y = (‖y‖ / ‖x‖) • o.rotation θ x ∨ θ = 0 ∧ (x = 0 ∨ y = 0) := by
by_cases hx : x = 0
· simp [hx, eq_comm]
· by_cases hy : y = 0
· simp [hy, eq_comm]
· rw [o.oangle_eq_iff_eq_norm_div_norm_smul_rotation_of_ne_zero hx hy]
simp [hx, hy]
/-- The angle between two vectors is `θ` if and only if they are nonzero and the second vector
is the first rotated by `θ` and scaled by a positive real, or `θ` and at least one of the
vectors are zero. -/
theorem oangle_eq_iff_eq_pos_smul_rotation_or_eq_zero {x y : V} (θ : Real.Angle) :
o.oangle x y = θ ↔
(x ≠ 0 ∧ y ≠ 0 ∧ ∃ r : ℝ, 0 < r ∧ y = r • o.rotation θ x) ∨ θ = 0 ∧ (x = 0 ∨ y = 0) := by
by_cases hx : x = 0
· simp [hx, eq_comm]
· by_cases hy : y = 0
· simp [hy, eq_comm]
· rw [o.oangle_eq_iff_eq_pos_smul_rotation_of_ne_zero hx hy]
simp [hx, hy]
/-- Any linear isometric equivalence in `V` with positive determinant is `rotation`. -/
theorem exists_linearIsometryEquiv_eq_of_det_pos {f : V ≃ₗᵢ[ℝ] V}
(hd : 0 < LinearMap.det (f.toLinearEquiv : V →ₗ[ℝ] V)) :
∃ θ : Real.Angle, f = o.rotation θ := by
haveI : Nontrivial V := nontrivial_of_finrank_eq_succ (@Fact.out (finrank ℝ V = 2) _)
obtain ⟨x, hx⟩ : ∃ x, x ≠ (0 : V) := exists_ne (0 : V)
use o.oangle x (f x)
apply LinearIsometryEquiv.toLinearEquiv_injective
apply LinearEquiv.toLinearMap_injective
apply (o.basisRightAngleRotation x hx).ext
intro i
symm
fin_cases i
· simp
have : o.oangle (J x) (f (J x)) = o.oangle x (f x) := by
simp only [oangle, o.linearIsometryEquiv_comp_rightAngleRotation f hd,
o.kahler_comp_rightAngleRotation]
simp [← this]
theorem rotation_map (θ : Real.Angle) (f : V ≃ₗᵢ[ℝ] V') (x : V') :
(Orientation.map (Fin 2) f.toLinearEquiv o).rotation θ x = f (o.rotation θ (f.symm x)) := by
simp [rotation_apply, o.rightAngleRotation_map]
@[simp]
protected theorem _root_.Complex.rotation (θ : Real.Angle) (z : ℂ) :
Complex.orientation.rotation θ z = θ.toCircle * z := by
simp only [rotation_apply, Complex.rightAngleRotation, Real.Angle.coe_toCircle, real_smul]
ring
/-- Rotation in an oriented real inner product space of dimension 2 can be evaluated in terms of a
complex-number representation of the space. -/
theorem rotation_map_complex (θ : Real.Angle) (f : V ≃ₗᵢ[ℝ] ℂ)
(hf : Orientation.map (Fin 2) f.toLinearEquiv o = Complex.orientation) (x : V) :
f (o.rotation θ x) = θ.toCircle * f x := by
rw [← Complex.rotation, ← hf, o.rotation_map, LinearIsometryEquiv.symm_apply_apply]
/-- Negating the orientation negates the angle in `rotation`. -/
theorem rotation_neg_orientation_eq_neg (θ : Real.Angle) : (-o).rotation θ = o.rotation (-θ) :=
LinearIsometryEquiv.ext <| by simp [rotation_apply]
/-- The inner product between a `π / 2` rotation of a vector and that vector is zero. -/
@[simp]
theorem inner_rotation_pi_div_two_left (x : V) : ⟪o.rotation (π / 2 : ℝ) x, x⟫ = 0 := by
rw [rotation_pi_div_two, inner_rightAngleRotation_self]
/-- The inner product between a vector and a `π / 2` rotation of that vector is zero. -/
@[simp]
theorem inner_rotation_pi_div_two_right (x : V) : ⟪x, o.rotation (π / 2 : ℝ) x⟫ = 0 := by
rw [real_inner_comm, inner_rotation_pi_div_two_left]
/-- The inner product between a multiple of a `π / 2` rotation of a vector and that vector is
zero. -/
@[simp]
theorem inner_smul_rotation_pi_div_two_left (x : V) (r : ℝ) :
⟪r • o.rotation (π / 2 : ℝ) x, x⟫ = 0 := by
rw [inner_smul_left, inner_rotation_pi_div_two_left, mul_zero]
/-- The inner product between a vector and a multiple of a `π / 2` rotation of that vector is
zero. -/
@[simp]
theorem inner_smul_rotation_pi_div_two_right (x : V) (r : ℝ) :
⟪x, r • o.rotation (π / 2 : ℝ) x⟫ = 0 := by
rw [real_inner_comm, inner_smul_rotation_pi_div_two_left]
/-- The inner product between a `π / 2` rotation of a vector and a multiple of that vector is
zero. -/
@[simp]
theorem inner_rotation_pi_div_two_left_smul (x : V) (r : ℝ) :
⟪o.rotation (π / 2 : ℝ) x, r • x⟫ = 0 := by
rw [inner_smul_right, inner_rotation_pi_div_two_left, mul_zero]
/-- The inner product between a multiple of a vector and a `π / 2` rotation of that vector is
zero. -/
@[simp]
theorem inner_rotation_pi_div_two_right_smul (x : V) (r : ℝ) :
⟪r • x, o.rotation (π / 2 : ℝ) x⟫ = 0 := by
rw [real_inner_comm, inner_rotation_pi_div_two_left_smul]
/-- The inner product between a multiple of a `π / 2` rotation of a vector and a multiple of
that vector is zero. -/
@[simp]
theorem inner_smul_rotation_pi_div_two_smul_left (x : V) (r₁ r₂ : ℝ) :
⟪r₁ • o.rotation (π / 2 : ℝ) x, r₂ • x⟫ = 0 := by
rw [inner_smul_right, inner_smul_rotation_pi_div_two_left, mul_zero]
/-- The inner product between a multiple of a vector and a multiple of a `π / 2` rotation of
that vector is zero. -/
@[simp]
theorem inner_smul_rotation_pi_div_two_smul_right (x : V) (r₁ r₂ : ℝ) :
⟪r₂ • x, r₁ • o.rotation (π / 2 : ℝ) x⟫ = 0 := by
rw [real_inner_comm, inner_smul_rotation_pi_div_two_smul_left]
/-- The inner product between two vectors is zero if and only if the first vector is zero or
the second is a multiple of a `π / 2` rotation of that vector. -/
theorem inner_eq_zero_iff_eq_zero_or_eq_smul_rotation_pi_div_two {x y : V} :
⟪x, y⟫ = 0 ↔ x = 0 ∨ ∃ r : ℝ, r • o.rotation (π / 2 : ℝ) x = y := by
rw [← o.eq_zero_or_oangle_eq_iff_inner_eq_zero]
refine ⟨fun h => ?_, fun h => ?_⟩
· rcases h with (rfl | rfl | h | h)
· exact Or.inl rfl
· exact Or.inr ⟨0, zero_smul _ _⟩
· obtain ⟨r, _, rfl⟩ :=
(o.oangle_eq_iff_eq_pos_smul_rotation_of_ne_zero (o.left_ne_zero_of_oangle_eq_pi_div_two h)
(o.right_ne_zero_of_oangle_eq_pi_div_two h) _).1 h
exact Or.inr ⟨r, rfl⟩
· obtain ⟨r, _, rfl⟩ :=
(o.oangle_eq_iff_eq_pos_smul_rotation_of_ne_zero
(o.left_ne_zero_of_oangle_eq_neg_pi_div_two h)
(o.right_ne_zero_of_oangle_eq_neg_pi_div_two h) _).1 h
refine Or.inr ⟨-r, ?_⟩
rw [neg_smul, ← smul_neg, o.neg_rotation_pi_div_two]
· rcases h with (rfl | ⟨r, rfl⟩)
· exact Or.inl rfl
· by_cases hx : x = 0; · exact Or.inl hx
rcases lt_trichotomy r 0 with (hr | rfl | hr)
· refine Or.inr (Or.inr (Or.inr ?_))
rw [o.oangle_smul_right_of_neg _ _ hr, o.neg_rotation_pi_div_two,
o.oangle_rotation_self_right hx]
· exact Or.inr (Or.inl (zero_smul _ _))
· refine Or.inr (Or.inr (Or.inl ?_))
rw [o.oangle_smul_right_of_pos _ _ hr, o.oangle_rotation_self_right hx]
| end Orientation
| Mathlib/Geometry/Euclidean/Angle/Oriented/Rotation.lean | 453 | 455 |
/-
Copyright (c) 2022 Jujian Zhang. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Jujian Zhang, Andrew Yang
-/
import Mathlib.AlgebraicGeometry.ProjectiveSpectrum.StructureSheaf
import Mathlib.AlgebraicGeometry.GammaSpecAdjunction
import Mathlib.RingTheory.GradedAlgebra.Radical
/-!
# Proj as a scheme
This file is to prove that `Proj` is a scheme.
## Notation
* `Proj` : `Proj` as a locally ringed space
* `Proj.T` : the underlying topological space of `Proj`
* `Proj| U` : `Proj` restricted to some open set `U`
* `Proj.T| U` : the underlying topological space of `Proj` restricted to open set `U`
* `pbo f` : basic open set at `f` in `Proj`
* `Spec` : `Spec` as a locally ringed space
* `Spec.T` : the underlying topological space of `Spec`
* `sbo g` : basic open set at `g` in `Spec`
* `A⁰_x` : the degree zero part of localized ring `Aₓ`
## Implementation
In `AlgebraicGeometry/ProjectiveSpectrum/StructureSheaf.lean`, we have given `Proj` a
structure sheaf so that `Proj` is a locally ringed space. In this file we will prove that `Proj`
equipped with this structure sheaf is a scheme. We achieve this by using an affine cover by basic
open sets in `Proj`, more specifically:
1. We prove that `Proj` can be covered by basic open sets at homogeneous element of positive degree.
2. We prove that for any homogeneous element `f : A` of positive degree `m`, `Proj.T | (pbo f)` is
homeomorphic to `Spec.T A⁰_f`:
- forward direction `toSpec`:
for any `x : pbo f`, i.e. a relevant homogeneous prime ideal `x`, send it to
`A⁰_f ∩ span {g / 1 | g ∈ x}` (see `ProjIsoSpecTopComponent.IoSpec.carrier`). This ideal is
prime, the proof is in `ProjIsoSpecTopComponent.ToSpec.toFun`. The fact that this function
is continuous is found in `ProjIsoSpecTopComponent.toSpec`
- backward direction `fromSpec`:
for any `q : Spec A⁰_f`, we send it to `{a | ∀ i, aᵢᵐ/fⁱ ∈ q}`; we need this to be a
homogeneous prime ideal that is relevant.
* This is in fact an ideal, the proof can be found in
`ProjIsoSpecTopComponent.FromSpec.carrier.asIdeal`;
* This ideal is also homogeneous, the proof can be found in
`ProjIsoSpecTopComponent.FromSpec.carrier.asIdeal.homogeneous`;
* This ideal is relevant, the proof can be found in
`ProjIsoSpecTopComponent.FromSpec.carrier.relevant`;
* This ideal is prime, the proof can be found in
`ProjIsoSpecTopComponent.FromSpec.carrier.asIdeal.prime`.
Hence we have a well defined function `Spec.T A⁰_f → Proj.T | (pbo f)`, this function is called
`ProjIsoSpecTopComponent.FromSpec.toFun`. But to prove the continuity of this function, we need
to prove `fromSpec ∘ toSpec` and `toSpec ∘ fromSpec` are both identities; these are achieved in
`ProjIsoSpecTopComponent.fromSpec_toSpec` and `ProjIsoSpecTopComponent.toSpec_fromSpec`.
3. Then we construct a morphism of locally ringed spaces `α : Proj| (pbo f) ⟶ Spec.T A⁰_f` as the
following: by the Gamma-Spec adjunction, it is sufficient to construct a ring map
`A⁰_f → Γ(Proj, pbo f)` from the ring of homogeneous localization of `A` away from `f` to the
local sections of structure sheaf of projective spectrum on the basic open set around `f`.
The map `A⁰_f → Γ(Proj, pbo f)` is constructed in `awayToΓ` and is defined by sending
`s ∈ A⁰_f` to the section `x ↦ s` on `pbo f`.
## Main Definitions and Statements
For a homogeneous element `f` of degree `m`
* `ProjIsoSpecTopComponent.toSpec`: the continuous map between `Proj.T| pbo f` and `Spec.T A⁰_f`
defined by sending `x : Proj| (pbo f)` to `A⁰_f ∩ span {g / 1 | g ∈ x}`. We also denote this map
as `ψ`.
* `ProjIsoSpecTopComponent.ToSpec.preimage_eq`: for any `a: A`, if `a/f^m` has degree zero,
then the preimage of `sbo a/f^m` under `toSpec f` is `pbo f ∩ pbo a`.
If we further assume `m` is positive
* `ProjIsoSpecTopComponent.fromSpec`: the continuous map between `Spec.T A⁰_f` and `Proj.T| pbo f`
defined by sending `q` to `{a | aᵢᵐ/fⁱ ∈ q}` where `aᵢ` is the `i`-th coordinate of `a`.
We also denote this map as `φ`
* `projIsoSpecTopComponent`: the homeomorphism `Proj.T| pbo f ≅ Spec.T A⁰_f` obtained by `φ` and
`ψ`.
* `ProjectiveSpectrum.Proj.toSpec`: the morphism of locally ringed spaces between `Proj| pbo f`
and `Spec A⁰_f` corresponding to the ring map `A⁰_f → Γ(Proj, pbo f)` under the Gamma-Spec
adjunction defined by sending `s` to the section `x ↦ s` on `pbo f`.
Finally,
* `AlgebraicGeometry.Proj`: for any `ℕ`-graded ring `A`, `Proj A` is locally affine, hence is a
scheme.
## Reference
* [Robin Hartshorne, *Algebraic Geometry*][Har77]: Chapter II.2 Proposition 2.5
-/
noncomputable section
namespace AlgebraicGeometry
open scoped DirectSum Pointwise
open DirectSum SetLike.GradedMonoid Localization
open Finset hiding mk_zero
variable {R A : Type*}
variable [CommRing R] [CommRing A] [Algebra R A]
variable (𝒜 : ℕ → Submodule R A)
variable [GradedAlgebra 𝒜]
open TopCat TopologicalSpace
open CategoryTheory Opposite
open ProjectiveSpectrum.StructureSheaf
-- Porting note: currently require lack of hygiene to use in variable declarations
-- maybe all make into notation3?
set_option hygiene false
/-- `Proj` as a locally ringed space -/
local notation3 "Proj" => Proj.toLocallyRingedSpace 𝒜
/-- The underlying topological space of `Proj` -/
local notation3 "Proj.T" => PresheafedSpace.carrier <| SheafedSpace.toPresheafedSpace
<| LocallyRingedSpace.toSheafedSpace <| Proj.toLocallyRingedSpace 𝒜
/-- `Proj` restrict to some open set -/
macro "Proj| " U:term : term =>
`((Proj.toLocallyRingedSpace 𝒜).restrict
(Opens.isOpenEmbedding (X := Proj.T) ($U : Opens Proj.T)))
/-- the underlying topological space of `Proj` restricted to some open set -/
local notation "Proj.T| " U => PresheafedSpace.carrier <| SheafedSpace.toPresheafedSpace
<| LocallyRingedSpace.toSheafedSpace
<| (LocallyRingedSpace.restrict Proj (Opens.isOpenEmbedding (X := Proj.T) (U : Opens Proj.T)))
/-- basic open sets in `Proj` -/
local notation "pbo " x => ProjectiveSpectrum.basicOpen 𝒜 x
/-- basic open sets in `Spec` -/
local notation "sbo " f => PrimeSpectrum.basicOpen f
/-- `Spec` as a locally ringed space -/
local notation3 "Spec " ring => Spec.locallyRingedSpaceObj (CommRingCat.of ring)
/-- the underlying topological space of `Spec` -/
local notation "Spec.T " ring =>
(Spec.locallyRingedSpaceObj (CommRingCat.of ring)).toSheafedSpace.toPresheafedSpace.1
local notation3 "A⁰_ " f => HomogeneousLocalization.Away 𝒜 f
namespace ProjIsoSpecTopComponent
/-
This section is to construct the homeomorphism between `Proj` restricted at basic open set at
a homogeneous element `x` and `Spec A⁰ₓ` where `A⁰ₓ` is the degree zero part of the localized
ring `Aₓ`.
-/
namespace ToSpec
open Ideal
-- This section is to construct the forward direction :
-- So for any `x` in `Proj| (pbo f)`, we need some point in `Spec A⁰_f`, i.e. a prime ideal,
-- and we need this correspondence to be continuous in their Zariski topology.
variable {𝒜}
variable {f : A} {m : ℕ} (x : Proj| (pbo f))
/--
For any `x` in `Proj| (pbo f)`, the corresponding ideal in `Spec A⁰_f`. This fact that this ideal
is prime is proven in `TopComponent.Forward.toFun`. -/
def carrier : Ideal (A⁰_ f) :=
Ideal.comap (algebraMap (A⁰_ f) (Away f))
(x.val.asHomogeneousIdeal.toIdeal.map (algebraMap A (Away f)))
@[simp]
theorem mk_mem_carrier (z : HomogeneousLocalization.NumDenSameDeg 𝒜 (.powers f)) :
HomogeneousLocalization.mk z ∈ carrier x ↔ z.num.1 ∈ x.1.asHomogeneousIdeal := by
rw [carrier, Ideal.mem_comap, HomogeneousLocalization.algebraMap_apply,
HomogeneousLocalization.val_mk, Localization.mk_eq_mk', IsLocalization.mk'_eq_mul_mk'_one,
mul_comm, Ideal.unit_mul_mem_iff_mem, ← Ideal.mem_comap,
IsLocalization.comap_map_of_isPrime_disjoint (.powers f)]
· rfl
· infer_instance
· exact (disjoint_powers_iff_not_mem _ (Ideal.IsPrime.isRadical inferInstance)).mpr x.2
· exact isUnit_of_invertible _
theorem isPrime_carrier : Ideal.IsPrime (carrier x) := by
refine Ideal.IsPrime.comap _ (hK := ?_)
exact IsLocalization.isPrime_of_isPrime_disjoint
(Submonoid.powers f) _ _ inferInstance
((disjoint_powers_iff_not_mem _ (Ideal.IsPrime.isRadical inferInstance)).mpr x.2)
variable (f)
/-- The function between the basic open set `D(f)` in `Proj` to the corresponding basic open set in
`Spec A⁰_f`. This is bundled into a continuous map in `TopComponent.forward`.
-/
@[simps -isSimp]
def toFun (x : Proj.T| pbo f) : Spec.T A⁰_ f :=
⟨carrier x, isPrime_carrier x⟩
/-
The preimage of basic open set `D(a/f^n)` in `Spec A⁰_f` under the forward map from `Proj A` to
`Spec A⁰_f` is the basic open set `D(a) ∩ D(f)` in `Proj A`. This lemma is used to prove that the
forward map is continuous.
-/
theorem preimage_basicOpen (z : HomogeneousLocalization.NumDenSameDeg 𝒜 (.powers f)) :
toFun f ⁻¹' (sbo (HomogeneousLocalization.mk z) : Set (PrimeSpectrum (A⁰_ f))) =
Subtype.val ⁻¹' (pbo z.num.1 : Set (ProjectiveSpectrum 𝒜)) :=
Set.ext fun y ↦ (mk_mem_carrier y z).not
end ToSpec
section
/-- The continuous function from the basic open set `D(f)` in `Proj`
to the corresponding basic open set in `Spec A⁰_f`. -/
@[simps! -isSimp hom_apply_asIdeal]
def toSpec (f : A) : (Proj.T| pbo f) ⟶ Spec.T A⁰_ f :=
TopCat.ofHom
{ toFun := ToSpec.toFun f
continuous_toFun := by
rw [PrimeSpectrum.isTopologicalBasis_basic_opens.continuous_iff]
rintro _ ⟨x, rfl⟩
obtain ⟨x, rfl⟩ := Quotient.mk''_surjective x
rw [ToSpec.preimage_basicOpen]
exact (pbo x.num).2.preimage continuous_subtype_val }
variable {𝒜} in
lemma toSpec_preimage_basicOpen {f} (z : HomogeneousLocalization.NumDenSameDeg 𝒜 (.powers f)) :
toSpec 𝒜 f ⁻¹' (sbo (HomogeneousLocalization.mk z) : Set (PrimeSpectrum (A⁰_ f))) =
Subtype.val ⁻¹' (pbo z.num.1 : Set (ProjectiveSpectrum 𝒜)) :=
ToSpec.preimage_basicOpen f z
end
namespace FromSpec
open GradedAlgebra SetLike
open Finset hiding mk_zero
open HomogeneousLocalization
variable {𝒜}
variable {f : A} {m : ℕ} (f_deg : f ∈ 𝒜 m)
open Lean Meta Elab Tactic
macro "mem_tac_aux" : tactic =>
`(tactic| first | exact pow_mem_graded _ (Submodule.coe_mem _) | exact natCast_mem_graded _ _ |
exact pow_mem_graded _ f_deg)
macro "mem_tac" : tactic =>
`(tactic| first | mem_tac_aux |
repeat (all_goals (apply SetLike.GradedMonoid.toGradedMul.mul_mem)); mem_tac_aux)
/-- The function from `Spec A⁰_f` to `Proj|D(f)` is defined by `q ↦ {a | aᵢᵐ/fⁱ ∈ q}`, i.e. sending
`q` a prime ideal in `A⁰_f` to the homogeneous prime relevant ideal containing only and all the
elements `a : A` such that for every `i`, the degree 0 element formed by dividing the `m`-th power
of the `i`-th projection of `a` by the `i`-th power of the degree-`m` homogeneous element `f`,
lies in `q`.
The set `{a | aᵢᵐ/fⁱ ∈ q}`
* is an ideal, as proved in `carrier.asIdeal`;
* is homogeneous, as proved in `carrier.asHomogeneousIdeal`;
* is prime, as proved in `carrier.asIdeal.prime`;
* is relevant, as proved in `carrier.relevant`.
-/
def carrier (f_deg : f ∈ 𝒜 m) (q : Spec.T A⁰_ f) : Set A :=
{a | ∀ i, (HomogeneousLocalization.mk ⟨m * i, ⟨proj 𝒜 i a ^ m, by rw [← smul_eq_mul]; mem_tac⟩,
⟨f ^ i, by rw [mul_comm]; mem_tac⟩, ⟨_, rfl⟩⟩ : A⁰_ f) ∈ q.1}
theorem mem_carrier_iff (q : Spec.T A⁰_ f) (a : A) :
a ∈ carrier f_deg q ↔ ∀ i, (HomogeneousLocalization.mk ⟨m * i, ⟨proj 𝒜 i a ^ m, by
rw [← smul_eq_mul]; mem_tac⟩,
⟨f ^ i, by rw [mul_comm]; mem_tac⟩, ⟨_, rfl⟩⟩ : A⁰_ f) ∈ q.1 :=
Iff.rfl
theorem mem_carrier_iff' (q : Spec.T A⁰_ f) (a : A) :
a ∈ carrier f_deg q ↔
∀ i, (Localization.mk (proj 𝒜 i a ^ m) ⟨f ^ i, ⟨i, rfl⟩⟩ : Localization.Away f) ∈
algebraMap (HomogeneousLocalization.Away 𝒜 f) (Localization.Away f) '' { s | s ∈ q.1 } :=
(mem_carrier_iff f_deg q a).trans
(by
constructor <;> intro h i <;> specialize h i
· rw [Set.mem_image]; refine ⟨_, h, rfl⟩
· rw [Set.mem_image] at h; rcases h with ⟨x, h, hx⟩
change x ∈ q.asIdeal at h
convert h
rw [HomogeneousLocalization.ext_iff_val, HomogeneousLocalization.val_mk]
dsimp only [Subtype.coe_mk]; rw [← hx]; rfl)
theorem mem_carrier_iff_of_mem (hm : 0 < m) (q : Spec.T A⁰_ f) (a : A) {n} (hn : a ∈ 𝒜 n) :
a ∈ carrier f_deg q ↔
(HomogeneousLocalization.mk ⟨m * n, ⟨a ^ m, pow_mem_graded m hn⟩,
⟨f ^ n, by rw [mul_comm]; mem_tac⟩, ⟨_, rfl⟩⟩ : A⁰_ f) ∈ q.asIdeal := by
trans (HomogeneousLocalization.mk ⟨m * n, ⟨proj 𝒜 n a ^ m, by rw [← smul_eq_mul]; mem_tac⟩,
⟨f ^ n, by rw [mul_comm]; mem_tac⟩, ⟨_, rfl⟩⟩ : A⁰_ f) ∈ q.asIdeal
· refine ⟨fun h ↦ h n, fun h i ↦ if hi : i = n then hi ▸ h else ?_⟩
convert zero_mem q.asIdeal
apply HomogeneousLocalization.val_injective
simp only [proj_apply, decompose_of_mem_ne _ hn (Ne.symm hi), zero_pow hm.ne',
HomogeneousLocalization.val_mk, Localization.mk_zero, HomogeneousLocalization.val_zero]
· simp only [proj_apply, decompose_of_mem_same _ hn]
theorem mem_carrier_iff_of_mem_mul (hm : 0 < m)
(q : Spec.T A⁰_ f) (a : A) {n} (hn : a ∈ 𝒜 (n * m)) :
a ∈ carrier f_deg q ↔ (HomogeneousLocalization.mk ⟨m * n, ⟨a, mul_comm n m ▸ hn⟩,
⟨f ^ n, by rw [mul_comm]; mem_tac⟩, ⟨_, rfl⟩⟩ : A⁰_ f) ∈ q.asIdeal := by
rw [mem_carrier_iff_of_mem f_deg hm q a hn, iff_iff_eq, eq_comm,
← Ideal.IsPrime.pow_mem_iff_mem (α := A⁰_ f) inferInstance m hm]
congr 1
apply HomogeneousLocalization.val_injective
simp only [HomogeneousLocalization.val_mk, HomogeneousLocalization.val_pow,
Localization.mk_pow, pow_mul]
rfl
theorem num_mem_carrier_iff (hm : 0 < m) (q : Spec.T A⁰_ f)
(z : HomogeneousLocalization.NumDenSameDeg 𝒜 (.powers f)) :
z.num.1 ∈ carrier f_deg q ↔ HomogeneousLocalization.mk z ∈ q.asIdeal := by
obtain ⟨n, hn : f ^ n = _⟩ := z.den_mem
have : f ^ n ≠ 0 := fun e ↦ by
have := HomogeneousLocalization.subsingleton 𝒜 (x := .powers f) ⟨n, e⟩
exact IsEmpty.elim (inferInstanceAs (IsEmpty (PrimeSpectrum (A⁰_ f)))) q
convert mem_carrier_iff_of_mem_mul f_deg hm q z.num.1 (n := n) ?_ using 2
· apply HomogeneousLocalization.val_injective; simp only [hn, HomogeneousLocalization.val_mk]
· have := degree_eq_of_mem_mem 𝒜 (SetLike.pow_mem_graded n f_deg) (hn.symm ▸ z.den.2) this
rw [← smul_eq_mul, this]; exact z.num.2
theorem carrier.add_mem (q : Spec.T A⁰_ f) {a b : A} (ha : a ∈ carrier f_deg q)
(hb : b ∈ carrier f_deg q) : a + b ∈ carrier f_deg q := by
refine fun i => (q.2.mem_or_mem ?_).elim id id
change (HomogeneousLocalization.mk ⟨_, _, _, _⟩ : A⁰_ f) ∈ q.1; dsimp only [Subtype.coe_mk]
simp_rw [← pow_add, map_add, add_pow, mul_comm, ← nsmul_eq_mul]
let g : ℕ → A⁰_ f := fun j => (m + m).choose j •
if h2 : m + m < j then (0 : A⁰_ f)
else
-- Porting note: inlining `l`, `r` causes a "can't synth HMul A⁰_ f A⁰_ f ?" error
if h1 : j ≤ m then
letI l : A⁰_ f := HomogeneousLocalization.mk
⟨m * i, ⟨proj 𝒜 i a ^ j * proj 𝒜 i b ^ (m - j), ?_⟩,
⟨_, by rw [mul_comm]; mem_tac⟩, ⟨i, rfl⟩⟩
letI r : A⁰_ f := (HomogeneousLocalization.mk
⟨m * i, ⟨proj 𝒜 i b ^ m, by rw [← smul_eq_mul]; mem_tac⟩,
⟨_, by rw [mul_comm]; mem_tac⟩, ⟨i, rfl⟩⟩)
l * r
else
letI l : A⁰_ f := HomogeneousLocalization.mk
⟨m * i, ⟨proj 𝒜 i a ^ m, by rw [← smul_eq_mul]; mem_tac⟩,
⟨_, by rw [mul_comm]; mem_tac⟩, ⟨i, rfl⟩⟩
letI r : A⁰_ f := HomogeneousLocalization.mk
⟨m * i, ⟨proj 𝒜 i a ^ (j - m) * proj 𝒜 i b ^ (m + m - j), ?_⟩,
⟨_, by rw [mul_comm]; mem_tac⟩, ⟨i, rfl⟩⟩
l * r
rotate_left
· rw [(_ : m * i = _)]
apply GradedMonoid.toGradedMul.mul_mem <;> mem_tac_aux
rw [← add_smul, Nat.add_sub_of_le h1]; rfl
· rw [(_ : m * i = _)]
apply GradedMonoid.toGradedMul.mul_mem (i := (j-m) • i) (j := (m + m - j) • i) <;> mem_tac_aux
rw [← add_smul]; congr; zify [le_of_not_lt h2, le_of_not_le h1]; abel
convert_to ∑ i ∈ range (m + m + 1), g i ∈ q.1; swap
· refine q.1.sum_mem fun j _ => nsmul_mem ?_ _; split_ifs
exacts [q.1.zero_mem, q.1.mul_mem_left _ (hb i), q.1.mul_mem_right _ (ha i)]
rw [HomogeneousLocalization.ext_iff_val, HomogeneousLocalization.val_mk]
change _ = (algebraMap (HomogeneousLocalization.Away 𝒜 f) (Localization.Away f)) _
dsimp only [Subtype.coe_mk]; rw [map_sum, mk_sum]
apply Finset.sum_congr rfl fun j hj => _
intro j hj
change _ = HomogeneousLocalization.val _
rw [HomogeneousLocalization.val_smul]
split_ifs with h2 h1
· exact ((Finset.mem_range.1 hj).not_le h2).elim
all_goals simp only [HomogeneousLocalization.val_mul, HomogeneousLocalization.val_zero,
HomogeneousLocalization.val_mk, Subtype.coe_mk, Localization.mk_mul, ← smul_mk]; congr 2
· dsimp; rw [mul_assoc, ← pow_add, add_comm (m - j), Nat.add_sub_assoc h1]
· simp_rw [pow_add]; rfl
· dsimp; rw [← mul_assoc, ← pow_add, Nat.add_sub_of_le (le_of_not_le h1)]
· simp_rw [pow_add]; rfl
variable (hm : 0 < m) (q : Spec.T A⁰_ f)
include hm
theorem carrier.zero_mem : (0 : A) ∈ carrier f_deg q := fun i => by
convert Submodule.zero_mem q.1 using 1
rw [HomogeneousLocalization.ext_iff_val, HomogeneousLocalization.val_mk,
HomogeneousLocalization.val_zero]; simp_rw [map_zero, zero_pow hm.ne']
convert Localization.mk_zero (S := Submonoid.powers f) _ using 1
theorem carrier.smul_mem (c x : A) (hx : x ∈ carrier f_deg q) : c • x ∈ carrier f_deg q := by
revert c
refine DirectSum.Decomposition.inductionOn 𝒜 ?_ ?_ ?_
· rw [zero_smul]; exact carrier.zero_mem f_deg hm _
· rintro n ⟨a, ha⟩ i
simp_rw [proj_apply, smul_eq_mul, coe_decompose_mul_of_left_mem 𝒜 i ha]
let product : A⁰_ f :=
(HomogeneousLocalization.mk
⟨_, ⟨a ^ m, pow_mem_graded m ha⟩, ⟨_, ?_⟩, ⟨n, rfl⟩⟩ : A⁰_ f) *
(HomogeneousLocalization.mk
⟨_, ⟨proj 𝒜 (i - n) x ^ m, by mem_tac⟩, ⟨_, ?_⟩, ⟨i - n, rfl⟩⟩ : A⁰_ f)
· split_ifs with h
· convert_to product ∈ q.1
· dsimp [product]
rw [HomogeneousLocalization.ext_iff_val, HomogeneousLocalization.val_mk,
HomogeneousLocalization.val_mul, HomogeneousLocalization.val_mk,
HomogeneousLocalization.val_mk]
· simp_rw [mul_pow]; rw [Localization.mk_mul]
· congr; rw [← pow_add, Nat.add_sub_of_le h]
· apply Ideal.mul_mem_left (α := A⁰_ f) _ _ (hx _)
rw [(_ : m • n = _)]
· mem_tac
· simp only [smul_eq_mul, mul_comm]
· simpa only [map_zero, zero_pow hm.ne'] using zero_mem f_deg hm q i
rw [(_ : m • (i - n) = _)]
· mem_tac
· simp only [smul_eq_mul, mul_comm]
· simp_rw [add_smul]; exact fun _ _ => carrier.add_mem f_deg q
/-- For a prime ideal `q` in `A⁰_f`, the set `{a | aᵢᵐ/fⁱ ∈ q}` as an ideal.
-/
def carrier.asIdeal : Ideal A where
carrier := carrier f_deg q
zero_mem' := carrier.zero_mem f_deg hm q
add_mem' := carrier.add_mem f_deg q
smul_mem' := carrier.smul_mem f_deg hm q
theorem carrier.asIdeal.homogeneous : (carrier.asIdeal f_deg hm q).IsHomogeneous 𝒜 :=
fun i a ha j =>
(em (i = j)).elim (fun h => h ▸ by simpa only [proj_apply, decompose_coe, of_eq_same] using ha _)
fun h => by
simpa only [proj_apply, decompose_of_mem_ne 𝒜 (Submodule.coe_mem (decompose 𝒜 a i)) h,
zero_pow hm.ne', map_zero] using carrier.zero_mem f_deg hm q j
/-- For a prime ideal `q` in `A⁰_f`, the set `{a | aᵢᵐ/fⁱ ∈ q}` as a homogeneous ideal.
-/
def carrier.asHomogeneousIdeal : HomogeneousIdeal 𝒜 :=
⟨carrier.asIdeal f_deg hm q, carrier.asIdeal.homogeneous f_deg hm q⟩
theorem carrier.denom_not_mem : f ∉ carrier.asIdeal f_deg hm q := fun rid =>
q.isPrime.ne_top <|
(Ideal.eq_top_iff_one _).mpr
(by
convert rid m
rw [HomogeneousLocalization.ext_iff_val, HomogeneousLocalization.val_one,
HomogeneousLocalization.val_mk]
dsimp
simp_rw [decompose_of_mem_same _ f_deg]
simp only [mk_eq_monoidOf_mk', Submonoid.LocalizationMap.mk'_self])
theorem carrier.relevant : ¬HomogeneousIdeal.irrelevant 𝒜 ≤ carrier.asHomogeneousIdeal f_deg hm q :=
fun rid => carrier.denom_not_mem f_deg hm q <| rid <| DirectSum.decompose_of_mem_ne 𝒜 f_deg hm.ne'
theorem carrier.asIdeal.ne_top : carrier.asIdeal f_deg hm q ≠ ⊤ := fun rid =>
carrier.denom_not_mem f_deg hm q (rid.symm ▸ Submodule.mem_top)
theorem carrier.asIdeal.prime : (carrier.asIdeal f_deg hm q).IsPrime :=
(carrier.asIdeal.homogeneous f_deg hm q).isPrime_of_homogeneous_mem_or_mem
(carrier.asIdeal.ne_top f_deg hm q) fun {x y} ⟨nx, hnx⟩ ⟨ny, hny⟩ hxy =>
show (∀ _, _ ∈ _) ∨ ∀ _, _ ∈ _ by
rw [← and_forall_ne nx, and_iff_left, ← and_forall_ne ny, and_iff_left]
· apply q.2.mem_or_mem; convert hxy (nx + ny) using 1
dsimp
simp_rw [decompose_of_mem_same 𝒜 hnx, decompose_of_mem_same 𝒜 hny,
decompose_of_mem_same 𝒜 (SetLike.GradedMonoid.toGradedMul.mul_mem hnx hny),
mul_pow, pow_add]
simp only [HomogeneousLocalization.ext_iff_val, HomogeneousLocalization.val_mk,
HomogeneousLocalization.val_mul, Localization.mk_mul]
simp only [Submonoid.mk_mul_mk, mk_eq_monoidOf_mk']
all_goals
intro n hn; convert q.1.zero_mem using 1
rw [HomogeneousLocalization.ext_iff_val, HomogeneousLocalization.val_mk,
HomogeneousLocalization.val_zero]; simp_rw [proj_apply]
convert mk_zero (S := Submonoid.powers f) _
rw [decompose_of_mem_ne 𝒜 _ hn.symm, zero_pow hm.ne']
· first | exact hnx | exact hny
/-- The function `Spec A⁰_f → Proj|D(f)` sending `q` to `{a | aᵢᵐ/fⁱ ∈ q}`. -/
def toFun : (Spec.T A⁰_ f) → Proj.T| pbo f := fun q =>
⟨⟨carrier.asHomogeneousIdeal f_deg hm q, carrier.asIdeal.prime f_deg hm q,
carrier.relevant f_deg hm q⟩,
(ProjectiveSpectrum.mem_basicOpen _ f _).mp <| carrier.denom_not_mem f_deg hm q⟩
end FromSpec
section toSpecFromSpec
lemma toSpec_fromSpec {f : A} {m : ℕ} (f_deg : f ∈ 𝒜 m) (hm : 0 < m) (x : Spec.T (A⁰_ f)) :
toSpec 𝒜 f (FromSpec.toFun f_deg hm x) = x := by
apply PrimeSpectrum.ext
ext z
obtain ⟨z, rfl⟩ := HomogeneousLocalization.mk_surjective z
rw [← FromSpec.num_mem_carrier_iff f_deg hm x]
exact ToSpec.mk_mem_carrier _ z
end toSpecFromSpec
section fromSpecToSpec
lemma fromSpec_toSpec {f : A} {m : ℕ} (f_deg : f ∈ 𝒜 m) (hm : 0 < m) (x : Proj.T| pbo f) :
FromSpec.toFun f_deg hm (toSpec 𝒜 f x) = x := by
refine Subtype.ext <| ProjectiveSpectrum.ext <| HomogeneousIdeal.ext' ?_
intros i z hzi
refine (FromSpec.mem_carrier_iff_of_mem f_deg hm _ _ hzi).trans ?_
exact (ToSpec.mk_mem_carrier _ _).trans (x.1.2.pow_mem_iff_mem m hm)
|
lemma toSpec_injective {f : A} {m : ℕ} (f_deg : f ∈ 𝒜 m) (hm : 0 < m) :
Function.Injective (toSpec 𝒜 f) := by
intro x₁ x₂ h
have := congr_arg (FromSpec.toFun f_deg hm) h
rwa [fromSpec_toSpec, fromSpec_toSpec] at this
| Mathlib/AlgebraicGeometry/ProjectiveSpectrum/Scheme.lean | 505 | 511 |
/-
Copyright (c) 2021 Anne Baanen. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Anne Baanen, Ashvni Narayanan
-/
import Mathlib.FieldTheory.RatFunc.Degree
import Mathlib.RingTheory.DedekindDomain.IntegralClosure
import Mathlib.RingTheory.IntegralClosure.IntegrallyClosed
import Mathlib.Topology.Algebra.Valued.ValuedField
/-!
# Function fields
This file defines a function field and the ring of integers corresponding to it.
## Main definitions
- `FunctionField Fq F` states that `F` is a function field over the (finite) field `Fq`,
i.e. it is a finite extension of the field of rational functions in one variable over `Fq`.
- `FunctionField.ringOfIntegers` defines the ring of integers corresponding to a function field
as the integral closure of `Fq[X]` in the function field.
- `FunctionField.inftyValuation` : The place at infinity on `Fq(t)` is the nonarchimedean
valuation on `Fq(t)` with uniformizer `1/t`.
- `FunctionField.FqtInfty` : The completion `Fq((t⁻¹))` of `Fq(t)` with respect to the
valuation at infinity.
## Implementation notes
The definitions that involve a field of fractions choose a canonical field of fractions,
but are independent of that choice. We also omit assumptions like `Finite Fq` or
`IsScalarTower Fq[X] (FractionRing Fq[X]) F` in definitions,
adding them back in lemmas when they are needed.
## References
* [D. Marcus, *Number Fields*][marcus1977number]
* [J.W.S. Cassels, A. Fröhlich, *Algebraic Number Theory*][cassels1967algebraic]
* [P. Samuel, *Algebraic Theory of Numbers*][samuel1967]
## Tags
function field, ring of integers
-/
noncomputable section
open scoped nonZeroDivisors Polynomial Multiplicative
variable (Fq F : Type*) [Field Fq] [Field F]
/-- `F` is a function field over the finite field `Fq` if it is a finite
extension of the field of rational functions in one variable over `Fq`.
Note that `F` can be a function field over multiple, non-isomorphic, `Fq`.
-/
abbrev FunctionField [Algebra (RatFunc Fq) F] : Prop :=
FiniteDimensional (RatFunc Fq) F
/-- `F` is a function field over `Fq` iff it is a finite extension of `Fq(t)`. -/
theorem functionField_iff (Fqt : Type*) [Field Fqt] [Algebra Fq[X] Fqt]
[IsFractionRing Fq[X] Fqt] [Algebra (RatFunc Fq) F] [Algebra Fqt F] [Algebra Fq[X] F]
[IsScalarTower Fq[X] Fqt F] [IsScalarTower Fq[X] (RatFunc Fq) F] :
FunctionField Fq F ↔ FiniteDimensional Fqt F := by
let e := IsLocalization.algEquiv Fq[X]⁰ (RatFunc Fq) Fqt
have : ∀ (c) (x : F), e c • x = c • x := by
intro c x
rw [Algebra.smul_def, Algebra.smul_def]
congr
refine congr_fun (f := fun c => algebraMap Fqt F (e c)) ?_ c
refine IsLocalization.ext (nonZeroDivisors Fq[X]) _ _ ?_ ?_ ?_ ?_ ?_ <;> intros <;>
simp only [map_one, map_mul, AlgEquiv.commutes, ← IsScalarTower.algebraMap_apply]
constructor <;> intro h
· let b := Module.finBasis (RatFunc Fq) F
exact FiniteDimensional.of_fintype_basis (b.mapCoeffs e this)
· let b := Module.finBasis Fqt F
refine FiniteDimensional.of_fintype_basis (b.mapCoeffs e.symm ?_)
intro c x; convert (this (e.symm c) x).symm; simp only [e.apply_symm_apply]
namespace FunctionField
theorem algebraMap_injective [Algebra Fq[X] F] [Algebra (RatFunc Fq) F]
[IsScalarTower Fq[X] (RatFunc Fq) F] : Function.Injective (⇑(algebraMap Fq[X] F)) := by
rw [IsScalarTower.algebraMap_eq Fq[X] (RatFunc Fq) F]
exact (algebraMap (RatFunc Fq) F).injective.comp (IsFractionRing.injective Fq[X] (RatFunc Fq))
@[deprecated (since := "2025-03-03")]
alias _root_.algebraMap_injective := FunctionField.algebraMap_injective
/-- The function field analogue of `NumberField.ringOfIntegers`:
`FunctionField.ringOfIntegers Fq Fqt F` is the integral closure of `Fq[t]` in `F`.
We don't actually assume `F` is a function field over `Fq` in the definition,
only when proving its properties.
-/
def ringOfIntegers [Algebra Fq[X] F] :=
integralClosure Fq[X] F
namespace ringOfIntegers
variable [Algebra Fq[X] F]
instance : IsDomain (ringOfIntegers Fq F) :=
(ringOfIntegers Fq F).isDomain
instance : IsIntegralClosure (ringOfIntegers Fq F) Fq[X] F :=
integralClosure.isIntegralClosure _ _
variable [Algebra (RatFunc Fq) F] [IsScalarTower Fq[X] (RatFunc Fq) F]
theorem algebraMap_injective : Function.Injective (⇑(algebraMap Fq[X] (ringOfIntegers Fq F))) := by
have hinj : Function.Injective (⇑(algebraMap Fq[X] F)) := by
rw [IsScalarTower.algebraMap_eq Fq[X] (RatFunc Fq) F]
exact (algebraMap (RatFunc Fq) F).injective.comp (IsFractionRing.injective Fq[X] (RatFunc Fq))
rw [injective_iff_map_eq_zero (algebraMap Fq[X] (↥(ringOfIntegers Fq F)))]
intro p hp
rw [← Subtype.coe_inj, Subalgebra.coe_zero] at hp
rw [injective_iff_map_eq_zero (algebraMap Fq[X] F)] at hinj
exact hinj p hp
theorem not_isField : ¬IsField (ringOfIntegers Fq F) := by
simpa [← (IsIntegralClosure.isIntegral_algebra Fq[X] F).isField_iff_isField
(algebraMap_injective Fq F)] using
Polynomial.not_isField Fq
variable [FunctionField Fq F]
instance : IsFractionRing (ringOfIntegers Fq F) F :=
integralClosure.isFractionRing_of_finite_extension (RatFunc Fq) F
instance : IsIntegrallyClosed (ringOfIntegers Fq F) :=
integralClosure.isIntegrallyClosedOfFiniteExtension (RatFunc Fq)
instance [Algebra.IsSeparable (RatFunc Fq) F] : IsNoetherian Fq[X] (ringOfIntegers Fq F) :=
IsIntegralClosure.isNoetherian _ (RatFunc Fq) F _
instance [Algebra.IsSeparable (RatFunc Fq) F] : IsDedekindDomain (ringOfIntegers Fq F) :=
IsIntegralClosure.isDedekindDomain Fq[X] (RatFunc Fq) F _
end ringOfIntegers
/-! ### The place at infinity on Fq(t) -/
section InftyValuation
variable [DecidableEq (RatFunc Fq)]
/-- The valuation at infinity is the nonarchimedean valuation on `Fq(t)` with uniformizer `1/t`.
Explicitly, if `f/g ∈ Fq(t)` is a nonzero quotient of polynomials, its valuation at infinity is
`Multiplicative.ofAdd(degree(f) - degree(g))`. -/
def inftyValuationDef (r : RatFunc Fq) : ℤₘ₀ :=
if r = 0 then 0 else ↑(Multiplicative.ofAdd r.intDegree)
theorem InftyValuation.map_zero' : inftyValuationDef Fq 0 = 0 :=
if_pos rfl
theorem InftyValuation.map_one' : inftyValuationDef Fq 1 = 1 :=
(if_neg one_ne_zero).trans <| by rw [RatFunc.intDegree_one, ofAdd_zero, WithZero.coe_one]
theorem InftyValuation.map_mul' (x y : RatFunc Fq) :
inftyValuationDef Fq (x * y) = inftyValuationDef Fq x * inftyValuationDef Fq y := by
rw [inftyValuationDef, inftyValuationDef, inftyValuationDef]
by_cases hx : x = 0
· rw [hx, zero_mul, if_pos (Eq.refl _), zero_mul]
· by_cases hy : y = 0
· rw [hy, mul_zero, if_pos (Eq.refl _), mul_zero]
· rw [if_neg hx, if_neg hy, if_neg (mul_ne_zero hx hy), ← WithZero.coe_mul, WithZero.coe_inj,
← ofAdd_add, RatFunc.intDegree_mul hx hy]
theorem InftyValuation.map_add_le_max' (x y : RatFunc Fq) :
inftyValuationDef Fq (x + y) ≤ max (inftyValuationDef Fq x) (inftyValuationDef Fq y) := by
by_cases hx : x = 0
· rw [hx, zero_add]
conv_rhs => rw [inftyValuationDef, if_pos (Eq.refl _)]
rw [max_eq_right (WithZero.zero_le (inftyValuationDef Fq y))]
· by_cases hy : y = 0
· rw [hy, add_zero]
conv_rhs => rw [max_comm, inftyValuationDef, if_pos (Eq.refl _)]
rw [max_eq_right (WithZero.zero_le (inftyValuationDef Fq x))]
· by_cases hxy : x + y = 0
· rw [inftyValuationDef, if_pos hxy]; exact zero_le'
· rw [inftyValuationDef, inftyValuationDef, inftyValuationDef, if_neg hx, if_neg hy,
if_neg hxy]
rw [le_max_iff, WithZero.coe_le_coe, Multiplicative.ofAdd_le, WithZero.coe_le_coe,
Multiplicative.ofAdd_le, ← le_max_iff]
exact RatFunc.intDegree_add_le hy hxy
@[simp]
theorem inftyValuation_of_nonzero {x : RatFunc Fq} (hx : x ≠ 0) :
inftyValuationDef Fq x = Multiplicative.ofAdd x.intDegree := by
rw [inftyValuationDef, if_neg hx]
/-- The valuation at infinity on `Fq(t)`. -/
def inftyValuation : Valuation (RatFunc Fq) ℤₘ₀ where
toFun := inftyValuationDef Fq
map_zero' := InftyValuation.map_zero' Fq
map_one' := InftyValuation.map_one' Fq
map_mul' := InftyValuation.map_mul' Fq
map_add_le_max' := InftyValuation.map_add_le_max' Fq
@[simp]
theorem inftyValuation_apply {x : RatFunc Fq} : inftyValuation Fq x = inftyValuationDef Fq x :=
rfl
@[simp]
theorem inftyValuation.C {k : Fq} (hk : k ≠ 0) :
inftyValuationDef Fq (RatFunc.C k) = Multiplicative.ofAdd (0 : ℤ) := by
have hCk : RatFunc.C k ≠ 0 := (map_ne_zero _).mpr hk
rw [inftyValuationDef, if_neg hCk, RatFunc.intDegree_C]
@[simp]
theorem inftyValuation.X : inftyValuationDef Fq RatFunc.X = Multiplicative.ofAdd (1 : ℤ) := by
rw [inftyValuationDef, if_neg RatFunc.X_ne_zero, RatFunc.intDegree_X]
-- Dropped attribute `@[simp]` due to issue described here:
-- https://leanprover.zulipchat.com/#narrow/channel/287929-mathlib4/topic/.60synthInstance.2EmaxHeartbeats.60.20error.20but.20only.20in.20.60simpNF.60
theorem inftyValuation.polynomial {p : Fq[X]} (hp : p ≠ 0) :
inftyValuationDef Fq (algebraMap Fq[X] (RatFunc Fq) p) =
Multiplicative.ofAdd (p.natDegree : ℤ) := by
have hp' : algebraMap Fq[X] (RatFunc Fq) p ≠ 0 := by simpa
rw [inftyValuationDef, if_neg hp', RatFunc.intDegree_polynomial]
/-- The valued field `Fq(t)` with the valuation at infinity. -/
def inftyValuedFqt : Valued (RatFunc Fq) ℤₘ₀ :=
Valued.mk' <| inftyValuation Fq
theorem inftyValuedFqt.def {x : RatFunc Fq} :
@Valued.v (RatFunc Fq) _ _ _ (inftyValuedFqt Fq) x = inftyValuationDef Fq x :=
| rfl
| Mathlib/NumberTheory/FunctionField.lean | 226 | 227 |
/-
Copyright (c) 2021 Yaël Dillies. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yaël Dillies
-/
import Mathlib.Algebra.GroupWithZero.Action.Pointwise.Set
import Mathlib.Algebra.Module.LinearMap.Prod
import Mathlib.Algebra.Order.Module.Synonym
import Mathlib.Analysis.Convex.Segment
import Mathlib.Tactic.GCongr
import Mathlib.Tactic.Module
/-!
# Star-convex sets
This files defines star-convex sets (aka star domains, star-shaped set, radially convex set).
A set is star-convex at `x` if every segment from `x` to a point in the set is contained in the set.
This is the prototypical example of a contractible set in homotopy theory (by scaling every point
towards `x`), but has wider uses.
Note that this has nothing to do with star rings, `Star` and co.
## Main declarations
* `StarConvex 𝕜 x s`: `s` is star-convex at `x` with scalars `𝕜`.
## Implementation notes
Instead of saying that a set is star-convex, we say a set is star-convex *at a point*. This has the
advantage of allowing us to talk about convexity as being "everywhere star-convexity" and of making
the union of star-convex sets be star-convex.
Incidentally, this choice means we don't need to assume a set is nonempty for it to be star-convex.
Concretely, the empty set is star-convex at every point.
## TODO
Balanced sets are star-convex.
The closure of a star-convex set is star-convex.
Star-convex sets are contractible.
A nonempty open star-convex set in `ℝ^n` is diffeomorphic to the entire space.
-/
open Set
open Convex Pointwise
variable {𝕜 E F : Type*}
section OrderedSemiring
variable [Semiring 𝕜] [PartialOrder 𝕜]
section AddCommMonoid
variable [AddCommMonoid E] [AddCommMonoid F]
section SMul
variable (𝕜) [SMul 𝕜 E] [SMul 𝕜 F] (x : E) (s : Set E)
/-- Star-convexity of sets. `s` is star-convex at `x` if every segment from `x` to a point in `s` is
contained in `s`. -/
def StarConvex (𝕜 : Type*) {E : Type*} [Semiring 𝕜] [PartialOrder 𝕜]
[AddCommMonoid E] [SMul 𝕜 E] (x : E) (s : Set E) : Prop :=
∀ ⦃y : E⦄, y ∈ s → ∀ ⦃a b : 𝕜⦄, 0 ≤ a → 0 ≤ b → a + b = 1 → a • x + b • y ∈ s
variable {𝕜 x s} {t : Set E}
theorem starConvex_iff_segment_subset : StarConvex 𝕜 x s ↔ ∀ ⦃y⦄, y ∈ s → [x -[𝕜] y] ⊆ s := by
constructor
· rintro h y hy z ⟨a, b, ha, hb, hab, rfl⟩
exact h hy ha hb hab
· rintro h y hy a b ha hb hab
exact h hy ⟨a, b, ha, hb, hab, rfl⟩
theorem StarConvex.segment_subset (h : StarConvex 𝕜 x s) {y : E} (hy : y ∈ s) : [x -[𝕜] y] ⊆ s :=
starConvex_iff_segment_subset.1 h hy
theorem StarConvex.openSegment_subset (h : StarConvex 𝕜 x s) {y : E} (hy : y ∈ s) :
openSegment 𝕜 x y ⊆ s :=
(openSegment_subset_segment 𝕜 x y).trans (h.segment_subset hy)
/-- Alternative definition of star-convexity, in terms of pointwise set operations. -/
theorem starConvex_iff_pointwise_add_subset :
StarConvex 𝕜 x s ↔ ∀ ⦃a b : 𝕜⦄, 0 ≤ a → 0 ≤ b → a + b = 1 → a • {x} + b • s ⊆ s := by
refine
⟨?_, fun h y hy a b ha hb hab =>
h ha hb hab (add_mem_add (smul_mem_smul_set <| mem_singleton _) ⟨_, hy, rfl⟩)⟩
rintro hA a b ha hb hab w ⟨au, ⟨u, rfl : u = x, rfl⟩, bv, ⟨v, hv, rfl⟩, rfl⟩
exact hA hv ha hb hab
theorem starConvex_empty (x : E) : StarConvex 𝕜 x ∅ := fun _ hy => hy.elim
theorem starConvex_univ (x : E) : StarConvex 𝕜 x univ := fun _ _ _ _ _ _ _ => trivial
theorem StarConvex.inter (hs : StarConvex 𝕜 x s) (ht : StarConvex 𝕜 x t) : StarConvex 𝕜 x (s ∩ t) :=
fun _ hy _ _ ha hb hab => ⟨hs hy.left ha hb hab, ht hy.right ha hb hab⟩
theorem starConvex_sInter {S : Set (Set E)} (h : ∀ s ∈ S, StarConvex 𝕜 x s) :
StarConvex 𝕜 x (⋂₀ S) := fun _ hy _ _ ha hb hab s hs => h s hs (hy s hs) ha hb hab
theorem starConvex_iInter {ι : Sort*} {s : ι → Set E} (h : ∀ i, StarConvex 𝕜 x (s i)) :
StarConvex 𝕜 x (⋂ i, s i) :=
sInter_range s ▸ starConvex_sInter <| forall_mem_range.2 h
theorem starConvex_iInter₂ {ι : Sort*} {κ : ι → Sort*} {s : (i : ι) → κ i → Set E}
(h : ∀ i j, StarConvex 𝕜 x (s i j)) : StarConvex 𝕜 x (⋂ (i) (j), s i j) :=
starConvex_iInter fun i => starConvex_iInter (h i)
theorem StarConvex.union (hs : StarConvex 𝕜 x s) (ht : StarConvex 𝕜 x t) :
StarConvex 𝕜 x (s ∪ t) := by
rintro y (hy | hy) a b ha hb hab
· exact Or.inl (hs hy ha hb hab)
· exact Or.inr (ht hy ha hb hab)
theorem starConvex_iUnion {ι : Sort*} {s : ι → Set E} (hs : ∀ i, StarConvex 𝕜 x (s i)) :
StarConvex 𝕜 x (⋃ i, s i) := by
rintro y hy a b ha hb hab
rw [mem_iUnion] at hy ⊢
obtain ⟨i, hy⟩ := hy
exact ⟨i, hs i hy ha hb hab⟩
theorem starConvex_iUnion₂ {ι : Sort*} {κ : ι → Sort*} {s : (i : ι) → κ i → Set E}
(h : ∀ i j, StarConvex 𝕜 x (s i j)) : StarConvex 𝕜 x (⋃ (i) (j), s i j) :=
starConvex_iUnion fun i => starConvex_iUnion (h i)
theorem starConvex_sUnion {S : Set (Set E)} (hS : ∀ s ∈ S, StarConvex 𝕜 x s) :
StarConvex 𝕜 x (⋃₀ S) := by
rw [sUnion_eq_iUnion]
exact starConvex_iUnion fun s => hS _ s.2
theorem StarConvex.prod {y : F} {s : Set E} {t : Set F} (hs : StarConvex 𝕜 x s)
(ht : StarConvex 𝕜 y t) : StarConvex 𝕜 (x, y) (s ×ˢ t) := fun _ hy _ _ ha hb hab =>
⟨hs hy.1 ha hb hab, ht hy.2 ha hb hab⟩
theorem starConvex_pi {ι : Type*} {E : ι → Type*} [∀ i, AddCommMonoid (E i)] [∀ i, SMul 𝕜 (E i)]
{x : ∀ i, E i} {s : Set ι} {t : ∀ i, Set (E i)} (ht : ∀ ⦃i⦄, i ∈ s → StarConvex 𝕜 (x i) (t i)) :
StarConvex 𝕜 x (s.pi t) := fun _ hy _ _ ha hb hab i hi => ht hi (hy i hi) ha hb hab
end SMul
section Module
variable [Module 𝕜 E] [Module 𝕜 F] {x y z : E} {s : Set E}
theorem StarConvex.mem [ZeroLEOneClass 𝕜] (hs : StarConvex 𝕜 x s) (h : s.Nonempty) : x ∈ s := by
obtain ⟨y, hy⟩ := h
convert hs hy zero_le_one le_rfl (add_zero 1)
rw [one_smul, zero_smul, add_zero]
theorem starConvex_iff_forall_pos (hx : x ∈ s) : StarConvex 𝕜 x s ↔
| ∀ ⦃y⦄, y ∈ s → ∀ ⦃a b : 𝕜⦄, 0 < a → 0 < b → a + b = 1 → a • x + b • y ∈ s := by
refine ⟨fun h y hy a b ha hb hab => h hy ha.le hb.le hab, ?_⟩
intro h y hy a b ha hb hab
obtain rfl | ha := ha.eq_or_lt
| Mathlib/Analysis/Convex/Star.lean | 159 | 162 |
/-
Copyright (c) 2023 Yaël Dillies, Bhavik Mehta. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yaël Dillies, Bhavik Mehta
-/
import Mathlib.Combinatorics.SimpleGraph.Triangle.Basic
/-!
# Construct a tripartite graph from its triangles
This file contains the construction of a simple graph on `α ⊕ β ⊕ γ` from a list of triangles
`(a, b, c)` (with `a` in the first component, `b` in the second, `c` in the third).
We call
* `t : Finset (α × β × γ)` the set of *triangle indices* (its elements are not triangles within the
graph but instead index them).
* *explicit* a triangle of the constructed graph coming from a triangle index.
* *accidental* a triangle of the constructed graph not coming from a triangle index.
The two important properties of this construction are:
* `SimpleGraph.TripartiteFromTriangles.ExplicitDisjoint`: Whether the explicit triangles are
edge-disjoint.
* `SimpleGraph.TripartiteFromTriangles.NoAccidental`: Whether all triangles are explicit.
This construction shows up unrelatedly twice in the theory of Roth numbers:
* The lower bound of the Ruzsa-Szemerédi problem: From a set `s` in a finite abelian group `G` of
odd order, we construct a tripartite graph on `G ⊕ G ⊕ G`. The triangle indices are
`(x, x + a, x + 2 * a)` for `x` any element and `a ∈ s`. The explicit triangles are always
edge-disjoint and there is no accidental triangle if `s` is 3AP-free.
* The proof of the corners theorem from the triangle removal lemma: For a set `s` in a finite
abelian group `G`, we construct a tripartite graph on `G ⊕ G ⊕ G`, whose vertices correspond to
the horizontal, vertical and diagonal lines in `G × G`. The explicit triangles are `(h, v, d)`
where `h`, `v`, `d` are horizontal, vertical, diagonal lines that intersect in an element of `s`.
The explicit triangles are always edge-disjoint and there is no accidental triangle if `s` is
corner-free.
-/
open Finset Function Sum3
variable {α β γ 𝕜 : Type*} [Field 𝕜] [LinearOrder 𝕜] [IsStrictOrderedRing 𝕜]
{t : Finset (α × β × γ)} {a a' : α} {b b' : β} {c c' : γ} {x : α × β × γ}
namespace SimpleGraph
namespace TripartiteFromTriangles
/-- The underlying relation of the tripartite-from-triangles graph.
Two vertices are related iff there exists a triangle index containing them both. -/
@[mk_iff] inductive Rel (t : Finset (α × β × γ)) : α ⊕ β ⊕ γ → α ⊕ β ⊕ γ → Prop
| in₀₁ ⦃a b c⦄ : (a, b, c) ∈ t → Rel t (in₀ a) (in₁ b)
| in₁₀ ⦃a b c⦄ : (a, b, c) ∈ t → Rel t (in₁ b) (in₀ a)
| in₀₂ ⦃a b c⦄ : (a, b, c) ∈ t → Rel t (in₀ a) (in₂ c)
| in₂₀ ⦃a b c⦄ : (a, b, c) ∈ t → Rel t (in₂ c) (in₀ a)
| in₁₂ ⦃a b c⦄ : (a, b, c) ∈ t → Rel t (in₁ b) (in₂ c)
| in₂₁ ⦃a b c⦄ : (a, b, c) ∈ t → Rel t (in₂ c) (in₁ b)
open Rel
lemma rel_irrefl : ∀ x, ¬ Rel t x x := fun _x hx ↦ nomatch hx
lemma rel_symm : Symmetric (Rel t) := fun x y h ↦ by cases h <;> constructor <;> assumption
/-- The tripartite-from-triangles graph. Two vertices are related iff there exists a triangle index
containing them both. -/
def graph (t : Finset (α × β × γ)) : SimpleGraph (α ⊕ β ⊕ γ) := ⟨Rel t, rel_symm, rel_irrefl⟩
namespace Graph
@[simp] lemma not_in₀₀ : ¬ (graph t).Adj (in₀ a) (in₀ a') := fun h ↦ nomatch h
@[simp] lemma not_in₁₁ : ¬ (graph t).Adj (in₁ b) (in₁ b') := fun h ↦ nomatch h
@[simp] lemma not_in₂₂ : ¬ (graph t).Adj (in₂ c) (in₂ c') := fun h ↦ nomatch h
@[simp] lemma in₀₁_iff : (graph t).Adj (in₀ a) (in₁ b) ↔ ∃ c, (a, b, c) ∈ t :=
⟨by rintro ⟨⟩; exact ⟨_, ‹_›⟩, fun ⟨_, h⟩ ↦ in₀₁ h⟩
@[simp] lemma in₁₀_iff : (graph t).Adj (in₁ b) (in₀ a) ↔ ∃ c, (a, b, c) ∈ t :=
⟨by rintro ⟨⟩; exact ⟨_, ‹_›⟩, fun ⟨_, h⟩ ↦ in₁₀ h⟩
| @[simp] lemma in₀₂_iff : (graph t).Adj (in₀ a) (in₂ c) ↔ ∃ b, (a, b, c) ∈ t :=
⟨by rintro ⟨⟩; exact ⟨_, ‹_›⟩, fun ⟨_, h⟩ ↦ in₀₂ h⟩
| Mathlib/Combinatorics/SimpleGraph/Triangle/Tripartite.lean | 76 | 77 |
/-
Copyright (c) 2018 Patrick Massot. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Patrick Massot, Johannes Hölzl
-/
import Mathlib.Topology.UniformSpace.AbstractCompletion
/-!
# Hausdorff completions of uniform spaces
The goal is to construct a left-adjoint to the inclusion of complete Hausdorff uniform spaces
into all uniform spaces. Any uniform space `α` gets a completion `Completion α` and a morphism
(ie. uniformly continuous map) `(↑) : α → Completion α` which solves the universal
mapping problem of factorizing morphisms from `α` to any complete Hausdorff uniform space `β`.
It means any uniformly continuous `f : α → β` gives rise to a unique morphism
`Completion.extension f : Completion α → β` such that `f = Completion.extension f ∘ (↑)`.
Actually `Completion.extension f` is defined for all maps from `α` to `β` but it has the desired
properties only if `f` is uniformly continuous.
Beware that `(↑)` is not injective if `α` is not Hausdorff. But its image is always
dense. The adjoint functor acting on morphisms is then constructed by the usual abstract nonsense.
For every uniform spaces `α` and `β`, it turns `f : α → β` into a morphism
`Completion.map f : Completion α → Completion β`
such that
`(↑) ∘ f = (Completion.map f) ∘ (↑)`
provided `f` is uniformly continuous. This construction is compatible with composition.
In this file we introduce the following concepts:
* `CauchyFilter α` the uniform completion of the uniform space `α` (using Cauchy filters).
These are not minimal filters.
* `Completion α := Quotient (separationSetoid (CauchyFilter α))` the Hausdorff completion.
## References
This formalization is mostly based on
N. Bourbaki: General Topology
I. M. James: Topologies and Uniformities
From a slightly different perspective in order to reuse material in `Topology.UniformSpace.Basic`.
-/
noncomputable section
open Filter Set
universe u v w x
open Uniformity Topology Filter
/-- Space of Cauchy filters
This is essentially the completion of a uniform space. The embeddings are the neighbourhood filters.
This space is not minimal, the separated uniform space (i.e. quotiented on the intersection of all
entourages) is necessary for this.
-/
def CauchyFilter (α : Type u) [UniformSpace α] : Type u :=
{ f : Filter α // Cauchy f }
namespace CauchyFilter
section
variable {α : Type u} [UniformSpace α]
variable {β : Type v} {γ : Type w}
variable [UniformSpace β] [UniformSpace γ]
instance (f : CauchyFilter α) : NeBot f.1 := f.2.1
/-- The pairs of Cauchy filters generated by a set. -/
def gen (s : Set (α × α)) : Set (CauchyFilter α × CauchyFilter α) :=
{ p | s ∈ p.1.val ×ˢ p.2.val }
theorem monotone_gen : Monotone (gen : Set (α × α) → _) :=
monotone_setOf fun p => @Filter.monotone_mem _ (p.1.val ×ˢ p.2.val)
-- Porting note: this was a calc proof, but I could not make it work
private theorem symm_gen : map Prod.swap ((𝓤 α).lift' gen) ≤ (𝓤 α).lift' gen := by
let f := fun s : Set (α × α) =>
{ p : CauchyFilter α × CauchyFilter α | s ∈ (p.2.val ×ˢ p.1.val : Filter (α × α)) }
have h₁ : map Prod.swap ((𝓤 α).lift' gen) = (𝓤 α).lift' f := by
delta gen
simp [f, map_lift'_eq, monotone_setOf, Filter.monotone_mem, Function.comp_def,
image_swap_eq_preimage_swap]
have h₂ : (𝓤 α).lift' f ≤ (𝓤 α).lift' gen :=
uniformity_lift_le_swap
(monotone_principal.comp
(monotone_setOf fun p => @Filter.monotone_mem _ (p.2.val ×ˢ p.1.val)))
(by
have h := fun p : CauchyFilter α × CauchyFilter α => @Filter.prod_comm _ _ p.2.val p.1.val
simp only [Function.comp, h, mem_map, f]
exact le_rfl)
exact h₁.trans_le h₂
private theorem compRel_gen_gen_subset_gen_compRel {s t : Set (α × α)} :
compRel (gen s) (gen t) ⊆ (gen (compRel s t) : Set (CauchyFilter α × CauchyFilter α)) :=
fun ⟨f, g⟩ ⟨h, h₁, h₂⟩ =>
let ⟨t₁, (ht₁ : t₁ ∈ f.val), t₂, (ht₂ : t₂ ∈ h.val), (h₁ : t₁ ×ˢ t₂ ⊆ s)⟩ := mem_prod_iff.mp h₁
let ⟨t₃, (ht₃ : t₃ ∈ h.val), t₄, (ht₄ : t₄ ∈ g.val), (h₂ : t₃ ×ˢ t₄ ⊆ t)⟩ := mem_prod_iff.mp h₂
have : t₂ ∩ t₃ ∈ h.val := inter_mem ht₂ ht₃
let ⟨x, xt₂, xt₃⟩ := h.property.left.nonempty_of_mem this
(f.val ×ˢ g.val).sets_of_superset (prod_mem_prod ht₁ ht₄)
fun ⟨a, b⟩ ⟨(ha : a ∈ t₁), (hb : b ∈ t₄)⟩ =>
⟨x, h₁ (show (a, x) ∈ t₁ ×ˢ t₂ from ⟨ha, xt₂⟩), h₂ (show (x, b) ∈ t₃ ×ˢ t₄ from ⟨xt₃, hb⟩)⟩
private theorem comp_gen : (((𝓤 α).lift' gen).lift' fun s => compRel s s) ≤ (𝓤 α).lift' gen :=
calc
(((𝓤 α).lift' gen).lift' fun s => compRel s s) =
(𝓤 α).lift' fun s => compRel (gen s) (gen s) := by
rw [lift'_lift'_assoc]
· exact monotone_gen
· exact monotone_id.compRel monotone_id
_ ≤ (𝓤 α).lift' fun s => gen <| compRel s s :=
lift'_mono' fun _ _hs => compRel_gen_gen_subset_gen_compRel
_ = ((𝓤 α).lift' fun s : Set (α × α) => compRel s s).lift' gen := by
rw [lift'_lift'_assoc]
· exact monotone_id.compRel monotone_id
· exact monotone_gen
_ ≤ (𝓤 α).lift' gen := lift'_mono comp_le_uniformity le_rfl
instance : UniformSpace (CauchyFilter α) :=
UniformSpace.ofCore
{ uniformity := (𝓤 α).lift' gen
refl := principal_le_lift'.2 fun _s hs ⟨a, b⟩ =>
fun (a_eq_b : a = b) => a_eq_b ▸ a.property.right hs
symm := symm_gen
comp := comp_gen }
theorem mem_uniformity {s : Set (CauchyFilter α × CauchyFilter α)} :
s ∈ 𝓤 (CauchyFilter α) ↔ ∃ t ∈ 𝓤 α, gen t ⊆ s :=
mem_lift'_sets monotone_gen
theorem basis_uniformity {ι : Sort*} {p : ι → Prop} {s : ι → Set (α × α)} (h : (𝓤 α).HasBasis p s) :
(𝓤 (CauchyFilter α)).HasBasis p (gen ∘ s) :=
h.lift' monotone_gen
theorem mem_uniformity' {s : Set (CauchyFilter α × CauchyFilter α)} :
s ∈ 𝓤 (CauchyFilter α) ↔ ∃ t ∈ 𝓤 α, ∀ f g : CauchyFilter α, t ∈ f.1 ×ˢ g.1 → (f, g) ∈ s := by
refine mem_uniformity.trans (exists_congr (fun t => and_congr_right_iff.mpr (fun _h => ?_)))
exact ⟨fun h _f _g ht => h ht, fun h _p hp => h _ _ hp⟩
/-- Embedding of `α` into its completion `CauchyFilter α` -/
def pureCauchy (a : α) : CauchyFilter α :=
⟨pure a, cauchy_pure⟩
theorem isUniformInducing_pureCauchy : IsUniformInducing (pureCauchy : α → CauchyFilter α) :=
⟨have : (preimage fun x : α × α => (pureCauchy x.fst, pureCauchy x.snd)) ∘ gen = id :=
funext fun s =>
Set.ext fun ⟨a₁, a₂⟩ => by simp [preimage, gen, pureCauchy, prod_principal_principal]
calc
comap (fun x : α × α => (pureCauchy x.fst, pureCauchy x.snd)) ((𝓤 α).lift' gen) =
(𝓤 α).lift' ((preimage fun x : α × α => (pureCauchy x.fst, pureCauchy x.snd)) ∘ gen) :=
comap_lift'_eq
_ = 𝓤 α := by simp [this]
⟩
theorem isUniformEmbedding_pureCauchy : IsUniformEmbedding (pureCauchy : α → CauchyFilter α) where
__ := isUniformInducing_pureCauchy
injective _a₁ _a₂ h := pure_injective <| Subtype.ext_iff_val.1 h
theorem denseRange_pureCauchy : DenseRange (pureCauchy : α → CauchyFilter α) := fun f => by
have h_ex : ∀ s ∈ 𝓤 (CauchyFilter α), ∃ y : α, (f, pureCauchy y) ∈ s := fun s hs =>
let ⟨t'', ht''₁, (ht''₂ : gen t'' ⊆ s)⟩ := (mem_lift'_sets monotone_gen).mp hs
let ⟨t', ht'₁, ht'₂⟩ := comp_mem_uniformity_sets ht''₁
have : t' ∈ f.val ×ˢ f.val := f.property.right ht'₁
let ⟨t, ht, (h : t ×ˢ t ⊆ t')⟩ := mem_prod_same_iff.mp this
let ⟨x, (hx : x ∈ t)⟩ := f.property.left.nonempty_of_mem ht
have : t'' ∈ f.val ×ˢ pure x :=
mem_prod_iff.mpr
⟨t, ht, { y : α | (x, y) ∈ t' }, h <| mk_mem_prod hx hx,
fun ⟨a, b⟩ ⟨(h₁ : a ∈ t), (h₂ : (x, b) ∈ t')⟩ =>
ht'₂ <| prodMk_mem_compRel (@h (a, x) ⟨h₁, hx⟩) h₂⟩
⟨x, ht''₂ <| by dsimp [gen]; exact this⟩
simp only [closure_eq_cluster_pts, ClusterPt, nhds_eq_uniformity, lift'_inf_principal_eq,
Set.inter_comm _ (range pureCauchy), mem_setOf_eq]
refine (lift'_neBot_iff ?_).mpr (fun s hs => ?_)
· exact monotone_const.inter monotone_preimage
· let ⟨y, hy⟩ := h_ex s hs
have : pureCauchy y ∈ range pureCauchy ∩ { y : CauchyFilter α | (f, y) ∈ s } :=
⟨mem_range_self y, hy⟩
exact ⟨_, this⟩
theorem isDenseInducing_pureCauchy : IsDenseInducing (pureCauchy : α → CauchyFilter α) :=
isUniformInducing_pureCauchy.isDenseInducing denseRange_pureCauchy
theorem isDenseEmbedding_pureCauchy : IsDenseEmbedding (pureCauchy : α → CauchyFilter α) :=
isUniformEmbedding_pureCauchy.isDenseEmbedding denseRange_pureCauchy
theorem nonempty_cauchyFilter_iff : Nonempty (CauchyFilter α) ↔ Nonempty α := by
constructor <;> rintro ⟨c⟩
· have := eq_univ_iff_forall.1 isDenseEmbedding_pureCauchy.isDenseInducing.closure_range c
obtain ⟨_, ⟨_, a, _⟩⟩ := mem_closure_iff.1 this _ isOpen_univ trivial
exact ⟨a⟩
· exact ⟨pureCauchy c⟩
section
instance : CompleteSpace (CauchyFilter α) :=
completeSpace_extension isUniformInducing_pureCauchy denseRange_pureCauchy fun f hf =>
let f' : CauchyFilter α := ⟨f, hf⟩
have : map pureCauchy f ≤ (𝓤 <| CauchyFilter α).lift' (preimage (Prod.mk f')) :=
le_lift'.2 fun _ hs =>
let ⟨t, ht₁, ht₂⟩ := (mem_lift'_sets monotone_gen).mp hs
let ⟨t', ht', (h : t' ×ˢ t' ⊆ t)⟩ := mem_prod_same_iff.mp (hf.right ht₁)
have : t' ⊆ { y : α | (f', pureCauchy y) ∈ gen t } := fun x hx =>
(f ×ˢ pure x).sets_of_superset (prod_mem_prod ht' hx) h
f.sets_of_superset ht' <| Subset.trans this (preimage_mono ht₂)
⟨f', by simpa [nhds_eq_uniformity]⟩
end
instance [Inhabited α] : Inhabited (CauchyFilter α) :=
⟨pureCauchy default⟩
instance [h : Nonempty α] : Nonempty (CauchyFilter α) :=
h.recOn fun a => Nonempty.intro <| CauchyFilter.pureCauchy a
section Extend
open Classical in
/-- Extend a uniformly continuous function `α → β` to a function `CauchyFilter α → β`.
Outputs junk when `f` is not uniformly continuous. -/
def extend (f : α → β) : CauchyFilter α → β :=
if UniformContinuous f then isDenseInducing_pureCauchy.extend f
else fun x => f (nonempty_cauchyFilter_iff.1 ⟨x⟩).some
section T0Space
variable [T0Space β]
theorem extend_pureCauchy {f : α → β} (hf : UniformContinuous f) (a : α) :
extend f (pureCauchy a) = f a := by
rw [extend, if_pos hf]
exact uniformly_extend_of_ind isUniformInducing_pureCauchy denseRange_pureCauchy hf _
end T0Space
variable [CompleteSpace β]
theorem uniformContinuous_extend {f : α → β} : UniformContinuous (extend f) := by
by_cases hf : UniformContinuous f
· rw [extend, if_pos hf]
exact uniformContinuous_uniformly_extend isUniformInducing_pureCauchy denseRange_pureCauchy hf
· rw [extend, if_neg hf]
exact uniformContinuous_of_const fun a _b => by congr
end Extend
theorem inseparable_iff {f g : CauchyFilter α} : Inseparable f g ↔ f.1 ×ˢ g.1 ≤ 𝓤 α :=
(basis_uniformity (basis_sets _)).inseparable_iff_uniformity
theorem inseparable_iff_of_le_nhds {f g : CauchyFilter α} {a b : α}
(ha : f.1 ≤ 𝓝 a) (hb : g.1 ≤ 𝓝 b) : Inseparable a b ↔ Inseparable f g := by
rw [← tendsto_id'] at ha hb
rw [inseparable_iff, (ha.comp tendsto_fst).inseparable_iff_uniformity (hb.comp tendsto_snd)]
simp only [Function.comp_apply, id_eq, Prod.mk.eta, ← Function.id_def, tendsto_id']
theorem inseparable_lim_iff [CompleteSpace α] {f g : CauchyFilter α} :
haveI := f.2.1.nonempty; Inseparable (lim f.1) (lim g.1) ↔ Inseparable f g :=
inseparable_iff_of_le_nhds f.2.le_nhds_lim g.2.le_nhds_lim
end
theorem cauchyFilter_eq {α : Type*} [UniformSpace α] [CompleteSpace α] [T0Space α]
{f g : CauchyFilter α} :
haveI := f.2.1.nonempty; lim f.1 = lim g.1 ↔ Inseparable f g := by
rw [← inseparable_iff_eq, inseparable_lim_iff]
section
theorem separated_pureCauchy_injective {α : Type*} [UniformSpace α] [T0Space α] :
Function.Injective fun a : α => SeparationQuotient.mk (pureCauchy a) := fun a b h ↦
Inseparable.eq <| (inseparable_iff_of_le_nhds (pure_le_nhds a) (pure_le_nhds b)).2 <|
SeparationQuotient.mk_eq_mk.1 h
end
end CauchyFilter
open CauchyFilter Set
namespace UniformSpace
variable (α : Type*) [UniformSpace α]
variable {β : Type*} [UniformSpace β]
variable {γ : Type*} [UniformSpace γ]
| /-- Hausdorff completion of `α` -/
def Completion := SeparationQuotient (CauchyFilter α)
namespace Completion
| Mathlib/Topology/UniformSpace/Completion.lean | 288 | 292 |
/-
Copyright (c) 2022 Moritz Doll. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Moritz Doll, Mario Carneiro, Robert Y. Lewis
-/
import Mathlib.Algebra.Order.Ring.Cast
import Mathlib.Data.Int.Cast.Lemmas
import Mathlib.Data.NNRat.Defs
import Mathlib.Tactic.Basic
import Mathlib.Tactic.Zify
/-!
# `qify` tactic
The `qify` tactic is used to shift propositions from `ℕ` or `ℤ` to `ℚ`.
This is often useful since `ℚ` has well-behaved division.
```
example (a b c x y z : ℕ) (h : ¬ x*y*z < 0) : c < a + 3*b := by
qify
qify at h
/-
h : ¬↑x * ↑y * ↑z < 0
⊢ ↑c < ↑a + 3 * ↑b
-/
sorry
```
-/
namespace Mathlib.Tactic.Qify
open Lean
open Lean.Meta
open Lean.Parser.Tactic
open Lean.Elab.Tactic
/--
The `qify` tactic is used to shift propositions from `ℕ` or `ℤ` to `ℚ`.
This is often useful since `ℚ` has well-behaved division.
```
example (a b c x y z : ℕ) (h : ¬ x*y*z < 0) : c < a + 3*b := by
qify
qify at h
/-
h : ¬↑x * ↑y * ↑z < 0
⊢ ↑c < ↑a + 3 * ↑b
-/
sorry
```
`qify` can be given extra lemmas to use in simplification. This is especially useful in the
presence of nat subtraction: passing `≤` arguments will allow `push_cast` to do more work.
```
example (a b c : ℤ) (h : a / b = c) (hab : b ∣ a) (hb : b ≠ 0) : a = c * b := by
qify [hab] at h hb ⊢
exact (div_eq_iff hb).1 h
```
`qify` makes use of the `@[zify_simps]` and `@[qify_simps]` attributes to move propositions,
and the `push_cast` tactic to simplify the `ℚ`-valued expressions. -/
syntax (name := qify) "qify" (simpArgs)? (location)? : tactic
macro_rules
| `(tactic| qify $[[$simpArgs,*]]? $[at $location]?) =>
let args := simpArgs.map (·.getElems) |>.getD #[]
`(tactic|
simp -decide only [zify_simps, qify_simps, push_cast, $args,*]
$[at $location]?)
@[qify_simps] lemma intCast_eq (a b : ℤ) : a = b ↔ (a : ℚ) = (b : ℚ) := by simp only [Int.cast_inj]
@[qify_simps] lemma intCast_le (a b : ℤ) : a ≤ b ↔ (a : ℚ) ≤ (b : ℚ) := Int.cast_le.symm
@[qify_simps] lemma intCast_lt (a b : ℤ) : a < b ↔ (a : ℚ) < (b : ℚ) := Int.cast_lt.symm
| @[qify_simps] lemma intCast_ne (a b : ℤ) : a ≠ b ↔ (a : ℚ) ≠ (b : ℚ) := by
simp only [ne_eq, Int.cast_inj]
| Mathlib/Tactic/Qify.lean | 70 | 71 |
/-
Copyright (c) 2020 Kenny Lau. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kenny Lau, Wrenna Robson
-/
import Mathlib.Algebra.BigOperators.Group.Finset.Pi
import Mathlib.Algebra.Polynomial.FieldDivision
import Mathlib.LinearAlgebra.Vandermonde
import Mathlib.RingTheory.Polynomial.Basic
/-!
# Lagrange interpolation
## Main definitions
* In everything that follows, `s : Finset ι` is a finite set of indexes, with `v : ι → F` an
indexing of the field over some type. We call the image of v on s the interpolation nodes,
though strictly unique nodes are only defined when v is injective on s.
* `Lagrange.basisDivisor x y`, with `x y : F`. These are the normalised irreducible factors of
the Lagrange basis polynomials. They evaluate to `1` at `x` and `0` at `y` when `x` and `y`
are distinct.
* `Lagrange.basis v i` with `i : ι`: the Lagrange basis polynomial that evaluates to `1` at `v i`
and `0` at `v j` for `i ≠ j`.
* `Lagrange.interpolate v r` where `r : ι → F` is a function from the fintype to the field: the
Lagrange interpolant that evaluates to `r i` at `x i` for all `i : ι`. The `r i` are the _values_
associated with the _nodes_`x i`.
-/
open Polynomial
section PolynomialDetermination
namespace Polynomial
variable {R : Type*} [CommRing R] [IsDomain R] {f g : R[X]}
section Finset
open Function Fintype
open scoped Finset
variable (s : Finset R)
theorem eq_zero_of_degree_lt_of_eval_finset_eq_zero (degree_f_lt : f.degree < #s)
(eval_f : ∀ x ∈ s, f.eval x = 0) : f = 0 := by
rw [← mem_degreeLT] at degree_f_lt
simp_rw [eval_eq_sum_degreeLTEquiv degree_f_lt] at eval_f
rw [← degreeLTEquiv_eq_zero_iff_eq_zero degree_f_lt]
exact
Matrix.eq_zero_of_forall_index_sum_mul_pow_eq_zero
(Injective.comp (Embedding.subtype _).inj' (equivFinOfCardEq (card_coe _)).symm.injective)
fun _ => eval_f _ (Finset.coe_mem _)
theorem eq_of_degree_sub_lt_of_eval_finset_eq (degree_fg_lt : (f - g).degree < #s)
(eval_fg : ∀ x ∈ s, f.eval x = g.eval x) : f = g := by
rw [← sub_eq_zero]
refine eq_zero_of_degree_lt_of_eval_finset_eq_zero _ degree_fg_lt ?_
simp_rw [eval_sub, sub_eq_zero]
exact eval_fg
theorem eq_of_degrees_lt_of_eval_finset_eq (degree_f_lt : f.degree < #s)
(degree_g_lt : g.degree < #s) (eval_fg : ∀ x ∈ s, f.eval x = g.eval x) : f = g := by
rw [← mem_degreeLT] at degree_f_lt degree_g_lt
refine eq_of_degree_sub_lt_of_eval_finset_eq _ ?_ eval_fg
rw [← mem_degreeLT]; exact Submodule.sub_mem _ degree_f_lt degree_g_lt
/--
Two polynomials, with the same degree and leading coefficient, which have the same evaluation
on a set of distinct values with cardinality equal to the degree, are equal.
-/
theorem eq_of_degree_le_of_eval_finset_eq
(h_deg_le : f.degree ≤ #s)
(h_deg_eq : f.degree = g.degree)
(hlc : f.leadingCoeff = g.leadingCoeff)
(h_eval : ∀ x ∈ s, f.eval x = g.eval x) :
f = g := by
rcases eq_or_ne f 0 with rfl | hf
· rwa [degree_zero, eq_comm, degree_eq_bot, eq_comm] at h_deg_eq
· exact eq_of_degree_sub_lt_of_eval_finset_eq s
(lt_of_lt_of_le (degree_sub_lt h_deg_eq hf hlc) h_deg_le) h_eval
end Finset
section Indexed
open Finset
variable {ι : Type*} {v : ι → R} (s : Finset ι)
theorem eq_zero_of_degree_lt_of_eval_index_eq_zero (hvs : Set.InjOn v s)
(degree_f_lt : f.degree < #s) (eval_f : ∀ i ∈ s, f.eval (v i) = 0) : f = 0 := by
classical
rw [← card_image_of_injOn hvs] at degree_f_lt
refine eq_zero_of_degree_lt_of_eval_finset_eq_zero _ degree_f_lt ?_
intro x hx
rcases mem_image.mp hx with ⟨_, hj, rfl⟩
exact eval_f _ hj
theorem eq_of_degree_sub_lt_of_eval_index_eq (hvs : Set.InjOn v s)
(degree_fg_lt : (f - g).degree < #s) (eval_fg : ∀ i ∈ s, f.eval (v i) = g.eval (v i)) :
f = g := by
rw [← sub_eq_zero]
refine eq_zero_of_degree_lt_of_eval_index_eq_zero _ hvs degree_fg_lt ?_
simp_rw [eval_sub, sub_eq_zero]
exact eval_fg
theorem eq_of_degrees_lt_of_eval_index_eq (hvs : Set.InjOn v s) (degree_f_lt : f.degree < #s)
(degree_g_lt : g.degree < #s) (eval_fg : ∀ i ∈ s, f.eval (v i) = g.eval (v i)) : f = g := by
refine eq_of_degree_sub_lt_of_eval_index_eq _ hvs ?_ eval_fg
rw [← mem_degreeLT] at degree_f_lt degree_g_lt ⊢
exact Submodule.sub_mem _ degree_f_lt degree_g_lt
theorem eq_of_degree_le_of_eval_index_eq (hvs : Set.InjOn v s)
(h_deg_le : f.degree ≤ #s)
(h_deg_eq : f.degree = g.degree)
(hlc : f.leadingCoeff = g.leadingCoeff)
(h_eval : ∀ i ∈ s, f.eval (v i) = g.eval (v i)) : f = g := by
rcases eq_or_ne f 0 with rfl | hf
· rwa [degree_zero, eq_comm, degree_eq_bot, eq_comm] at h_deg_eq
· exact eq_of_degree_sub_lt_of_eval_index_eq s hvs
(lt_of_lt_of_le (degree_sub_lt h_deg_eq hf hlc) h_deg_le)
h_eval
end Indexed
end Polynomial
end PolynomialDetermination
noncomputable section
namespace Lagrange
open Polynomial
section BasisDivisor
variable {F : Type*} [Field F]
variable {x y : F}
/-- `basisDivisor x y` is the unique linear or constant polynomial such that
when evaluated at `x` it gives `1` and `y` it gives `0` (where when `x = y` it is identically `0`).
Such polynomials are the building blocks for the Lagrange interpolants. -/
def basisDivisor (x y : F) : F[X] :=
C (x - y)⁻¹ * (X - C y)
theorem basisDivisor_self : basisDivisor x x = 0 := by
simp only [basisDivisor, sub_self, inv_zero, map_zero, zero_mul]
theorem basisDivisor_inj (hxy : basisDivisor x y = 0) : x = y := by
simp_rw [basisDivisor, mul_eq_zero, X_sub_C_ne_zero, or_false, C_eq_zero, inv_eq_zero,
sub_eq_zero] at hxy
exact hxy
@[simp]
theorem basisDivisor_eq_zero_iff : basisDivisor x y = 0 ↔ x = y :=
⟨basisDivisor_inj, fun H => H ▸ basisDivisor_self⟩
theorem basisDivisor_ne_zero_iff : basisDivisor x y ≠ 0 ↔ x ≠ y := by
rw [Ne, basisDivisor_eq_zero_iff]
theorem degree_basisDivisor_of_ne (hxy : x ≠ y) : (basisDivisor x y).degree = 1 := by
rw [basisDivisor, degree_mul, degree_X_sub_C, degree_C, zero_add]
exact inv_ne_zero (sub_ne_zero_of_ne hxy)
@[simp]
theorem degree_basisDivisor_self : (basisDivisor x x).degree = ⊥ := by
rw [basisDivisor_self, degree_zero]
theorem natDegree_basisDivisor_self : (basisDivisor x x).natDegree = 0 := by
rw [basisDivisor_self, natDegree_zero]
theorem natDegree_basisDivisor_of_ne (hxy : x ≠ y) : (basisDivisor x y).natDegree = 1 :=
natDegree_eq_of_degree_eq_some (degree_basisDivisor_of_ne hxy)
@[simp]
theorem eval_basisDivisor_right : eval y (basisDivisor x y) = 0 := by
simp only [basisDivisor, eval_mul, eval_C, eval_sub, eval_X, sub_self, mul_zero]
theorem eval_basisDivisor_left_of_ne (hxy : x ≠ y) : eval x (basisDivisor x y) = 1 := by
simp only [basisDivisor, eval_mul, eval_C, eval_sub, eval_X]
exact inv_mul_cancel₀ (sub_ne_zero_of_ne hxy)
end BasisDivisor
section Basis
variable {F : Type*} [Field F] {ι : Type*} [DecidableEq ι]
variable {s : Finset ι} {v : ι → F} {i j : ι}
open Finset
/-- Lagrange basis polynomials indexed by `s : Finset ι`, defined at nodes `v i` for a
map `v : ι → F`. For `i, j ∈ s`, `basis s v i` evaluates to 0 at `v j` for `i ≠ j`. When
`v` is injective on `s`, `basis s v i` evaluates to 1 at `v i`. -/
protected def basis (s : Finset ι) (v : ι → F) (i : ι) : F[X] :=
∏ j ∈ s.erase i, basisDivisor (v i) (v j)
@[simp]
theorem basis_empty : Lagrange.basis ∅ v i = 1 :=
rfl
@[simp]
theorem basis_singleton (i : ι) : Lagrange.basis {i} v i = 1 := by
rw [Lagrange.basis, erase_singleton, prod_empty]
@[simp]
theorem basis_pair_left (hij : i ≠ j) : Lagrange.basis {i, j} v i = basisDivisor (v i) (v j) := by
simp only [Lagrange.basis, hij, erase_insert_eq_erase, erase_eq_of_not_mem, mem_singleton,
not_false_iff, prod_singleton]
@[simp]
theorem basis_pair_right (hij : i ≠ j) : Lagrange.basis {i, j} v j = basisDivisor (v j) (v i) := by
rw [pair_comm]
exact basis_pair_left hij.symm
theorem basis_ne_zero (hvs : Set.InjOn v s) (hi : i ∈ s) : Lagrange.basis s v i ≠ 0 := by
simp_rw [Lagrange.basis, prod_ne_zero_iff, Ne, mem_erase]
rintro j ⟨hij, hj⟩
rw [basisDivisor_eq_zero_iff, hvs.eq_iff hi hj]
exact hij.symm
@[simp]
theorem eval_basis_self (hvs : Set.InjOn v s) (hi : i ∈ s) :
(Lagrange.basis s v i).eval (v i) = 1 := by
rw [Lagrange.basis, eval_prod]
refine prod_eq_one fun j H => ?_
rw [eval_basisDivisor_left_of_ne]
rcases mem_erase.mp H with ⟨hij, hj⟩
exact mt (hvs hi hj) hij.symm
@[simp]
theorem eval_basis_of_ne (hij : i ≠ j) (hj : j ∈ s) : (Lagrange.basis s v i).eval (v j) = 0 := by
simp_rw [Lagrange.basis, eval_prod, prod_eq_zero_iff]
exact ⟨j, ⟨mem_erase.mpr ⟨hij.symm, hj⟩, eval_basisDivisor_right⟩⟩
@[simp]
theorem natDegree_basis (hvs : Set.InjOn v s) (hi : i ∈ s) :
(Lagrange.basis s v i).natDegree = #s - 1 := by
have H : ∀ j, j ∈ s.erase i → basisDivisor (v i) (v j) ≠ 0 := by
simp_rw [Ne, mem_erase, basisDivisor_eq_zero_iff]
exact fun j ⟨hij₁, hj⟩ hij₂ => hij₁ (hvs hj hi hij₂.symm)
rw [← card_erase_of_mem hi, card_eq_sum_ones]
convert natDegree_prod _ _ H using 1
refine sum_congr rfl fun j hj => (natDegree_basisDivisor_of_ne ?_).symm
rw [Ne, ← basisDivisor_eq_zero_iff]
exact H _ hj
theorem degree_basis (hvs : Set.InjOn v s) (hi : i ∈ s) :
(Lagrange.basis s v i).degree = ↑(#s - 1) := by
rw [degree_eq_natDegree (basis_ne_zero hvs hi), natDegree_basis hvs hi]
theorem sum_basis (hvs : Set.InjOn v s) (hs : s.Nonempty) :
∑ j ∈ s, Lagrange.basis s v j = 1 := by
refine eq_of_degrees_lt_of_eval_index_eq s hvs (lt_of_le_of_lt (degree_sum_le _ _) ?_) ?_ ?_
· rw [Nat.cast_withBot, Finset.sup_lt_iff (WithBot.bot_lt_coe #s)]
intro i hi
rw [degree_basis hvs hi, Nat.cast_withBot, WithBot.coe_lt_coe]
exact Nat.pred_lt (card_ne_zero_of_mem hi)
· rw [degree_one, ← WithBot.coe_zero, Nat.cast_withBot, WithBot.coe_lt_coe]
exact Nonempty.card_pos hs
· intro i hi
rw [eval_finset_sum, eval_one, ← add_sum_erase _ _ hi, eval_basis_self hvs hi,
add_eq_left]
refine sum_eq_zero fun j hj => ?_
rcases mem_erase.mp hj with ⟨hij, _⟩
rw [eval_basis_of_ne hij hi]
theorem basisDivisor_add_symm {x y : F} (hxy : x ≠ y) :
basisDivisor x y + basisDivisor y x = 1 := by
classical
rw [← sum_basis Function.injective_id.injOn ⟨x, mem_insert_self _ {y}⟩,
sum_insert (not_mem_singleton.mpr hxy), sum_singleton, basis_pair_left hxy,
basis_pair_right hxy, id, id]
end Basis
section Interpolate
variable {F : Type*} [Field F] {ι : Type*} [DecidableEq ι]
variable {s t : Finset ι} {i j : ι} {v : ι → F} (r r' : ι → F)
open Finset
/-- Lagrange interpolation: given a finset `s : Finset ι`, a nodal map `v : ι → F` injective on
`s` and a value function `r : ι → F`, `interpolate s v r` is the unique
polynomial of degree `< #s` that takes value `r i` on `v i` for all `i` in `s`. -/
@[simps]
def interpolate (s : Finset ι) (v : ι → F) : (ι → F) →ₗ[F] F[X] where
toFun r := ∑ i ∈ s, C (r i) * Lagrange.basis s v i
map_add' f g := by
simp_rw [← Finset.sum_add_distrib]
have h : (fun x => C (f x) * Lagrange.basis s v x + C (g x) * Lagrange.basis s v x) =
(fun x => C ((f + g) x) * Lagrange.basis s v x) := by
simp_rw [← add_mul, ← C_add, Pi.add_apply]
rw [h]
map_smul' c f := by
simp_rw [Finset.smul_sum, C_mul', smul_smul, Pi.smul_apply, RingHom.id_apply, smul_eq_mul]
theorem interpolate_empty : interpolate ∅ v r = 0 := by rw [interpolate_apply, sum_empty]
theorem interpolate_singleton : interpolate {i} v r = C (r i) := by
rw [interpolate_apply, sum_singleton, basis_singleton, mul_one]
theorem interpolate_one (hvs : Set.InjOn v s) (hs : s.Nonempty) : interpolate s v 1 = 1 := by
simp_rw [interpolate_apply, Pi.one_apply, map_one, one_mul]
exact sum_basis hvs hs
theorem eval_interpolate_at_node (hvs : Set.InjOn v s) (hi : i ∈ s) :
eval (v i) (interpolate s v r) = r i := by
rw [interpolate_apply, eval_finset_sum, ← add_sum_erase _ _ hi]
simp_rw [eval_mul, eval_C, eval_basis_self hvs hi, mul_one, add_eq_left]
refine sum_eq_zero fun j H => ?_
rw [eval_basis_of_ne (mem_erase.mp H).1 hi, mul_zero]
theorem degree_interpolate_le (hvs : Set.InjOn v s) :
(interpolate s v r).degree ≤ ↑(#s - 1) := by
refine (degree_sum_le _ _).trans ?_
rw [Finset.sup_le_iff]
intro i hi
rw [degree_mul, degree_basis hvs hi]
by_cases hr : r i = 0
· simpa only [hr, map_zero, degree_zero, WithBot.bot_add] using bot_le
· rw [degree_C hr, zero_add]
theorem degree_interpolate_lt (hvs : Set.InjOn v s) : (interpolate s v r).degree < #s := by
rw [Nat.cast_withBot]
rcases eq_empty_or_nonempty s with (rfl | h)
· rw [interpolate_empty, degree_zero, card_empty]
exact WithBot.bot_lt_coe _
· refine lt_of_le_of_lt (degree_interpolate_le _ hvs) ?_
rw [Nat.cast_withBot, WithBot.coe_lt_coe]
exact Nat.sub_lt (Nonempty.card_pos h) zero_lt_one
theorem degree_interpolate_erase_lt (hvs : Set.InjOn v s) (hi : i ∈ s) :
(interpolate (s.erase i) v r).degree < ↑(#s - 1) := by
rw [← Finset.card_erase_of_mem hi]
exact degree_interpolate_lt _ (Set.InjOn.mono (coe_subset.mpr (erase_subset _ _)) hvs)
theorem values_eq_on_of_interpolate_eq (hvs : Set.InjOn v s)
(hrr' : interpolate s v r = interpolate s v r') : ∀ i ∈ s, r i = r' i := fun _ hi => by
rw [← eval_interpolate_at_node r hvs hi, hrr', eval_interpolate_at_node r' hvs hi]
theorem interpolate_eq_of_values_eq_on (hrr' : ∀ i ∈ s, r i = r' i) :
interpolate s v r = interpolate s v r' :=
sum_congr rfl fun i hi => by rw [hrr' _ hi]
theorem interpolate_eq_iff_values_eq_on (hvs : Set.InjOn v s) :
interpolate s v r = interpolate s v r' ↔ ∀ i ∈ s, r i = r' i :=
⟨values_eq_on_of_interpolate_eq _ _ hvs, interpolate_eq_of_values_eq_on _ _⟩
theorem eq_interpolate {f : F[X]} (hvs : Set.InjOn v s) (degree_f_lt : f.degree < #s) :
f = interpolate s v fun i => f.eval (v i) :=
eq_of_degrees_lt_of_eval_index_eq _ hvs degree_f_lt (degree_interpolate_lt _ hvs) fun _ hi =>
(eval_interpolate_at_node (fun x ↦ eval (v x) f) hvs hi).symm
theorem eq_interpolate_of_eval_eq {f : F[X]} (hvs : Set.InjOn v s) (degree_f_lt : f.degree < #s)
(eval_f : ∀ i ∈ s, f.eval (v i) = r i) : f = interpolate s v r := by
rw [eq_interpolate hvs degree_f_lt]
exact interpolate_eq_of_values_eq_on _ _ eval_f
/-- This is the characteristic property of the interpolation: the interpolation is the
unique polynomial of `degree < Fintype.card ι` which takes the value of the `r i` on the `v i`.
-/
theorem eq_interpolate_iff {f : F[X]} (hvs : Set.InjOn v s) :
(f.degree < #s ∧ ∀ i ∈ s, eval (v i) f = r i) ↔ f = interpolate s v r := by
constructor <;> intro h
· exact eq_interpolate_of_eval_eq _ hvs h.1 h.2
· rw [h]
exact ⟨degree_interpolate_lt _ hvs, fun _ hi => eval_interpolate_at_node _ hvs hi⟩
/-- Lagrange interpolation induces isomorphism between functions from `s`
and polynomials of degree less than `Fintype.card ι`. -/
def funEquivDegreeLT (hvs : Set.InjOn v s) : degreeLT F #s ≃ₗ[F] s → F where
toFun f i := f.1.eval (v i)
map_add' _ _ := funext fun _ => eval_add
map_smul' c f := funext <| by simp
invFun r :=
⟨interpolate s v fun x => if hx : x ∈ s then r ⟨x, hx⟩ else 0,
mem_degreeLT.2 <| degree_interpolate_lt _ hvs⟩
left_inv := by
rintro ⟨f, hf⟩
simp only [Subtype.mk_eq_mk, Subtype.coe_mk, dite_eq_ite]
rw [mem_degreeLT] at hf
conv => rhs; rw [eq_interpolate hvs hf]
exact interpolate_eq_of_values_eq_on _ _ fun _ hi => if_pos hi
right_inv := by
intro f
ext ⟨i, hi⟩
simp only [Subtype.coe_mk, eval_interpolate_at_node _ hvs hi]
exact dif_pos hi
theorem interpolate_eq_sum_interpolate_insert_sdiff (hvt : Set.InjOn v t) (hs : s.Nonempty)
(hst : s ⊆ t) :
interpolate t v r = ∑ i ∈ s, interpolate (insert i (t \ s)) v r * Lagrange.basis s v i := by
symm
refine eq_interpolate_of_eval_eq _ hvt (lt_of_le_of_lt (degree_sum_le _ _) ?_) fun i hi => ?_
· simp_rw [Nat.cast_withBot, Finset.sup_lt_iff (WithBot.bot_lt_coe #t), degree_mul]
intro i hi
have hs : 1 ≤ #s := Nonempty.card_pos ⟨_, hi⟩
have hst' : #s ≤ #t := card_le_card hst
have H : #t = 1 + (#t - #s) + (#s - 1) := by
rw [add_assoc, tsub_add_tsub_cancel hst' hs, ← add_tsub_assoc_of_le (hs.trans hst'),
Nat.succ_add_sub_one, zero_add]
rw [degree_basis (Set.InjOn.mono hst hvt) hi, H, WithBot.coe_add, Nat.cast_withBot,
WithBot.add_lt_add_iff_right (@WithBot.coe_ne_bot _ (#s - 1))]
convert degree_interpolate_lt _
(hvt.mono (coe_subset.mpr (insert_subset_iff.mpr ⟨hst hi, sdiff_subset⟩)))
rw [card_insert_of_not_mem (not_mem_sdiff_of_mem_right hi), card_sdiff hst, add_comm]
· simp_rw [eval_finset_sum, eval_mul]
by_cases hi' : i ∈ s
· rw [← add_sum_erase _ _ hi', eval_basis_self (hvt.mono hst) hi',
eval_interpolate_at_node _
(hvt.mono (coe_subset.mpr (insert_subset_iff.mpr ⟨hi, sdiff_subset⟩)))
(mem_insert_self _ _),
mul_one, add_eq_left]
refine sum_eq_zero fun j hj => ?_
rcases mem_erase.mp hj with ⟨hij, _⟩
rw [eval_basis_of_ne hij hi', mul_zero]
· have H : (∑ j ∈ s, eval (v i) (Lagrange.basis s v j)) = 1 := by
rw [← eval_finset_sum, sum_basis (hvt.mono hst) hs, eval_one]
rw [← mul_one (r i), ← H, mul_sum]
refine sum_congr rfl fun j hj => ?_
congr
exact
eval_interpolate_at_node _ (hvt.mono (insert_subset_iff.mpr ⟨hst hj, sdiff_subset⟩))
(mem_insert.mpr (Or.inr (mem_sdiff.mpr ⟨hi, hi'⟩)))
theorem interpolate_eq_add_interpolate_erase (hvs : Set.InjOn v s) (hi : i ∈ s) (hj : j ∈ s)
(hij : i ≠ j) :
interpolate s v r =
interpolate (s.erase j) v r * basisDivisor (v i) (v j) +
interpolate (s.erase i) v r * basisDivisor (v j) (v i) := by
rw [interpolate_eq_sum_interpolate_insert_sdiff _ hvs ⟨i, mem_insert_self i {j}⟩ _,
sum_insert (not_mem_singleton.mpr hij), sum_singleton, basis_pair_left hij,
basis_pair_right hij, sdiff_insert_insert_of_mem_of_not_mem hi (not_mem_singleton.mpr hij),
sdiff_singleton_eq_erase, pair_comm,
sdiff_insert_insert_of_mem_of_not_mem hj (not_mem_singleton.mpr hij.symm),
sdiff_singleton_eq_erase]
exact insert_subset_iff.mpr ⟨hi, singleton_subset_iff.mpr hj⟩
end Interpolate
section Nodal
variable {R : Type*} [CommRing R] {ι : Type*}
variable {s : Finset ι} {v : ι → R}
open Finset Polynomial
/-- `nodal s v` is the unique monic polynomial whose roots are the nodes defined by `v` and `s`.
That is, the roots of `nodal s v` are exactly the image of `v` on `s`,
with appropriate multiplicity.
We can use `nodal` to define the barycentric forms of the evaluated interpolant.
-/
def nodal (s : Finset ι) (v : ι → R) : R[X] :=
∏ i ∈ s, (X - C (v i))
theorem nodal_eq (s : Finset ι) (v : ι → R) : nodal s v = ∏ i ∈ s, (X - C (v i)) :=
rfl
@[simp]
theorem nodal_empty : nodal ∅ v = 1 := by
rfl
@[simp]
theorem natDegree_nodal [Nontrivial R] : (nodal s v).natDegree = #s := by
simp_rw [nodal, natDegree_prod_of_monic (h := fun i _ => monic_X_sub_C (v i)),
natDegree_X_sub_C, sum_const, smul_eq_mul, mul_one]
theorem nodal_ne_zero [Nontrivial R] : nodal s v ≠ 0 := by
rcases s.eq_empty_or_nonempty with (rfl | h)
· exact one_ne_zero
· apply ne_zero_of_natDegree_gt (n := 0)
simp only [natDegree_nodal, h.card_pos]
@[simp]
theorem degree_nodal [Nontrivial R] : (nodal s v).degree = #s := by
simp_rw [degree_eq_natDegree nodal_ne_zero, natDegree_nodal]
theorem nodal_monic : (nodal s v).Monic :=
monic_prod_of_monic s (fun i ↦ X - C (v i)) fun i _ ↦ monic_X_sub_C (v i)
theorem eval_nodal {x : R} : (nodal s v).eval x = ∏ i ∈ s, (x - v i) := by
simp_rw [nodal, eval_prod, eval_sub, eval_X, eval_C]
theorem eval_nodal_at_node {i : ι} (hi : i ∈ s) : eval (v i) (nodal s v) = 0 := by
rw [eval_nodal]
exact s.prod_eq_zero hi (sub_self (v i))
theorem eval_nodal_not_at_node [Nontrivial R] [NoZeroDivisors R] {x : R}
(hx : ∀ i ∈ s, x ≠ v i) : eval x (nodal s v) ≠ 0 := by
simp_rw [nodal, eval_prod, prod_ne_zero_iff, eval_sub, eval_X, eval_C, sub_ne_zero]
exact hx
theorem nodal_eq_mul_nodal_erase [DecidableEq ι] {i : ι} (hi : i ∈ s) :
nodal s v = (X - C (v i)) * nodal (s.erase i) v := by
simp_rw [nodal, Finset.mul_prod_erase _ (fun x => X - C (v x)) hi]
theorem X_sub_C_dvd_nodal (v : ι → R) {i : ι} (hi : i ∈ s) : X - C (v i) ∣ nodal s v := by
classical
exact ⟨nodal (s.erase i) v, nodal_eq_mul_nodal_erase hi⟩
theorem nodal_insert_eq_nodal [DecidableEq ι] {i : ι} (hi : i ∉ s) :
nodal (insert i s) v = (X - C (v i)) * nodal s v := by
simp_rw [nodal, prod_insert hi]
theorem derivative_nodal [DecidableEq ι] :
derivative (nodal s v) = ∑ i ∈ s, nodal (s.erase i) v := by
refine s.induction_on ?_ fun i t hit IH => ?_
· rw [nodal_empty, derivative_one, sum_empty]
· rw [nodal_insert_eq_nodal hit, derivative_mul, IH, derivative_sub, derivative_X, derivative_C,
sub_zero, one_mul, sum_insert hit, mul_sum, erase_insert hit, add_right_inj]
refine sum_congr rfl fun j hjt => ?_
rw [t.erase_insert_of_ne (ne_of_mem_of_not_mem hjt hit).symm,
nodal_insert_eq_nodal (mem_of_mem_erase.mt hit)]
theorem eval_nodal_derivative_eval_node_eq [DecidableEq ι] {i : ι} (hi : i ∈ s) :
eval (v i) (derivative (nodal s v)) = eval (v i) (nodal (s.erase i) v) := by
rw [derivative_nodal, eval_finset_sum, ← add_sum_erase _ _ hi, add_eq_left]
exact sum_eq_zero fun j hj => (eval_nodal_at_node (mem_erase.mpr ⟨(mem_erase.mp hj).1.symm, hi⟩))
/-- The vanishing polynomial on a multiplicative subgroup is of the form X ^ n - 1. -/
@[simp] theorem nodal_subgroup_eq_X_pow_card_sub_one [IsDomain R]
(G : Subgroup Rˣ) [Fintype G] :
nodal (G : Set Rˣ).toFinset ((↑) : Rˣ → R) = X ^ (Fintype.card G) - 1 := by
have h : degree (1 : R[X]) < degree ((X : R[X]) ^ Fintype.card G) := by simp [Fintype.card_pos]
apply eq_of_degree_le_of_eval_index_eq (v := ((↑) : Rˣ → R)) (G : Set Rˣ).toFinset
· exact Set.injOn_of_injective Units.ext
· simp
· rw [degree_sub_eq_left_of_degree_lt h, degree_nodal, Set.toFinset_card, degree_pow, degree_X,
nsmul_eq_mul, mul_one, Nat.cast_inj]
exact rfl
· rw [nodal_monic, leadingCoeff_sub_of_degree_lt h, monic_X_pow]
· intros i hi
rw [eval_nodal_at_node hi]
replace hi : i ∈ G := by simpa using hi
obtain ⟨g, rfl⟩ : ∃ g : G, g.val = i := ⟨⟨i, hi⟩, rfl⟩
simp [← Units.val_pow_eq_pow_val, ← Subgroup.coe_pow G]
end Nodal
section NodalWeight
variable {F : Type*} [Field F] {ι : Type*} [DecidableEq ι]
variable {s : Finset ι} {v : ι → F} {i : ι}
open Finset
/-- This defines the nodal weight for a given set of node indexes and node mapping function `v`. -/
def nodalWeight (s : Finset ι) (v : ι → F) (i : ι) :=
∏ j ∈ s.erase i, (v i - v j)⁻¹
theorem nodalWeight_eq_eval_nodal_erase_inv :
nodalWeight s v i = (eval (v i) (nodal (s.erase i) v))⁻¹ := by
rw [eval_nodal, nodalWeight, prod_inv_distrib]
theorem nodal_erase_eq_nodal_div (hi : i ∈ s) :
nodal (s.erase i) v = nodal s v / (X - C (v i)) := by
rw [nodal_eq_mul_nodal_erase hi, mul_div_cancel_left₀]
exact X_sub_C_ne_zero _
theorem nodalWeight_eq_eval_nodal_derative (hi : i ∈ s) :
nodalWeight s v i = (eval (v i) (Polynomial.derivative (nodal s v)))⁻¹ := by
rw [eval_nodal_derivative_eval_node_eq hi, nodalWeight_eq_eval_nodal_erase_inv]
theorem nodalWeight_ne_zero (hvs : Set.InjOn v s) (hi : i ∈ s) : nodalWeight s v i ≠ 0 := by
rw [nodalWeight, prod_ne_zero_iff]
intro j hj
rcases mem_erase.mp hj with ⟨hij, hj⟩
exact inv_ne_zero (sub_ne_zero_of_ne (mt (hvs.eq_iff hi hj).mp hij.symm))
end NodalWeight
section LagrangeBarycentric
variable {F : Type*} [Field F] {ι : Type*} [DecidableEq ι]
variable {s : Finset ι} {v : ι → F} (r : ι → F) {i : ι} {x : F}
open Finset
theorem basis_eq_prod_sub_inv_mul_nodal_div (hi : i ∈ s) :
Lagrange.basis s v i = C (nodalWeight s v i) * (nodal s v / (X - C (v i))) := by
simp_rw [Lagrange.basis, basisDivisor, nodalWeight, prod_mul_distrib, map_prod, ←
nodal_erase_eq_nodal_div hi, nodal]
theorem eval_basis_not_at_node (hi : i ∈ s) (hxi : x ≠ v i) :
eval x (Lagrange.basis s v i) = eval x (nodal s v) * (nodalWeight s v i * (x - v i)⁻¹) := by
rw [mul_comm, basis_eq_prod_sub_inv_mul_nodal_div hi, eval_mul, eval_C, ←
nodal_erase_eq_nodal_div hi, eval_nodal, eval_nodal, mul_assoc, ← mul_prod_erase _ _ hi, ←
mul_assoc (x - v i)⁻¹, inv_mul_cancel₀ (sub_ne_zero_of_ne hxi), one_mul]
theorem interpolate_eq_nodalWeight_mul_nodal_div_X_sub_C :
interpolate s v r = ∑ i ∈ s, C (nodalWeight s v i) * (nodal s v / (X - C (v i))) * C (r i) :=
sum_congr rfl fun j hj => by rw [mul_comm, basis_eq_prod_sub_inv_mul_nodal_div hj]
/-- This is the first barycentric form of the Lagrange interpolant. -/
theorem eval_interpolate_not_at_node (hx : ∀ i ∈ s, x ≠ v i) :
eval x (interpolate s v r) =
eval x (nodal s v) * ∑ i ∈ s, nodalWeight s v i * (x - v i)⁻¹ * r i := by
simp_rw [interpolate_apply, mul_sum, eval_finset_sum, eval_mul, eval_C]
refine sum_congr rfl fun i hi => ?_
rw [← mul_assoc, mul_comm, eval_basis_not_at_node hi (hx _ hi)]
theorem sum_nodalWeight_mul_inv_sub_ne_zero (hvs : Set.InjOn v s) (hx : ∀ i ∈ s, x ≠ v i)
(hs : s.Nonempty) : (∑ i ∈ s, nodalWeight s v i * (x - v i)⁻¹) ≠ 0 :=
@right_ne_zero_of_mul_eq_one _ _ _ (eval x (nodal s v)) _ <| by
simpa only [Pi.one_apply, interpolate_one hvs hs, eval_one, mul_one] using
(eval_interpolate_not_at_node 1 hx).symm
/-- This is the second barycentric form of the Lagrange interpolant. -/
theorem eval_interpolate_not_at_node' (hvs : Set.InjOn v s) (hs : s.Nonempty)
(hx : ∀ i ∈ s, x ≠ v i) :
eval x (interpolate s v r) =
(∑ i ∈ s, nodalWeight s v i * (x - v i)⁻¹ * r i) /
∑ i ∈ s, nodalWeight s v i * (x - v i)⁻¹ := by
rw [← div_one (eval x (interpolate s v r)), ← @eval_one _ _ x, ← interpolate_one hvs hs,
eval_interpolate_not_at_node r hx, eval_interpolate_not_at_node 1 hx]
simp only [mul_div_mul_left _ _ (eval_nodal_not_at_node hx), Pi.one_apply, mul_one]
end LagrangeBarycentric
end Lagrange
| Mathlib/LinearAlgebra/Lagrange.lean | 668 | 670 | |
/-
Copyright (c) 2020 Joseph Myers. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Joseph Myers
-/
import Mathlib.Algebra.Order.Group.Pointwise.Interval
import Mathlib.LinearAlgebra.BilinearMap
import Mathlib.LinearAlgebra.Pi
import Mathlib.LinearAlgebra.Prod
import Mathlib.Tactic.Abel
import Mathlib.Algebra.AddTorsor.Basic
import Mathlib.LinearAlgebra.AffineSpace.Defs
/-!
# Affine maps
This file defines affine maps.
## Main definitions
* `AffineMap` is the type of affine maps between two affine spaces with the same ring `k`. Various
basic examples of affine maps are defined, including `const`, `id`, `lineMap` and `homothety`.
## Notations
* `P1 →ᵃ[k] P2` is a notation for `AffineMap k P1 P2`;
* `AffineSpace V P`: a localized notation for `AddTorsor V P` defined in
`LinearAlgebra.AffineSpace.Basic`.
## Implementation notes
`outParam` is used in the definition of `[AddTorsor V P]` to make `V` an implicit argument
(deduced from `P`) in most cases. As for modules, `k` is an explicit argument rather than implied by
`P` or `V`.
This file only provides purely algebraic definitions and results. Those depending on analysis or
topology are defined elsewhere; see `Analysis.Normed.Affine.AddTorsor` and
`Topology.Algebra.Affine`.
## References
* https://en.wikipedia.org/wiki/Affine_space
* https://en.wikipedia.org/wiki/Principal_homogeneous_space
-/
open Affine
/-- An `AffineMap k P1 P2` (notation: `P1 →ᵃ[k] P2`) is a map from `P1` to `P2` that
induces a corresponding linear map from `V1` to `V2`. -/
structure AffineMap (k : Type*) {V1 : Type*} (P1 : Type*) {V2 : Type*} (P2 : Type*) [Ring k]
[AddCommGroup V1] [Module k V1] [AffineSpace V1 P1] [AddCommGroup V2] [Module k V2]
[AffineSpace V2 P2] where
toFun : P1 → P2
linear : V1 →ₗ[k] V2
map_vadd' : ∀ (p : P1) (v : V1), toFun (v +ᵥ p) = linear v +ᵥ toFun p
/-- An `AffineMap k P1 P2` (notation: `P1 →ᵃ[k] P2`) is a map from `P1` to `P2` that
induces a corresponding linear map from `V1` to `V2`. -/
notation:25 P1 " →ᵃ[" k:25 "] " P2:0 => AffineMap k P1 P2
instance AffineMap.instFunLike (k : Type*) {V1 : Type*} (P1 : Type*) {V2 : Type*} (P2 : Type*)
[Ring k] [AddCommGroup V1] [Module k V1] [AffineSpace V1 P1] [AddCommGroup V2] [Module k V2]
[AffineSpace V2 P2] : FunLike (P1 →ᵃ[k] P2) P1 P2 where
coe := AffineMap.toFun
coe_injective' := fun ⟨f, f_linear, f_add⟩ ⟨g, g_linear, g_add⟩ => fun (h : f = g) => by
obtain ⟨p⟩ := (AddTorsor.nonempty : Nonempty P1)
congr with v
apply vadd_right_cancel (f p)
rw [← f_add, h, ← g_add]
namespace LinearMap
variable {k : Type*} {V₁ : Type*} {V₂ : Type*} [Ring k] [AddCommGroup V₁] [Module k V₁]
[AddCommGroup V₂] [Module k V₂] (f : V₁ →ₗ[k] V₂)
/-- Reinterpret a linear map as an affine map. -/
def toAffineMap : V₁ →ᵃ[k] V₂ where
toFun := f
linear := f
map_vadd' p v := f.map_add v p
@[simp]
theorem coe_toAffineMap : ⇑f.toAffineMap = f :=
rfl
@[simp]
theorem toAffineMap_linear : f.toAffineMap.linear = f :=
rfl
end LinearMap
namespace AffineMap
variable {k : Type*} {V1 : Type*} {P1 : Type*} {V2 : Type*} {P2 : Type*} {V3 : Type*}
{P3 : Type*} {V4 : Type*} {P4 : Type*} [Ring k] [AddCommGroup V1] [Module k V1]
[AffineSpace V1 P1] [AddCommGroup V2] [Module k V2] [AffineSpace V2 P2] [AddCommGroup V3]
[Module k V3] [AffineSpace V3 P3] [AddCommGroup V4] [Module k V4] [AffineSpace V4 P4]
/-- Constructing an affine map and coercing back to a function
produces the same map. -/
@[simp]
theorem coe_mk (f : P1 → P2) (linear add) : ((mk f linear add : P1 →ᵃ[k] P2) : P1 → P2) = f :=
rfl
/-- `toFun` is the same as the result of coercing to a function. -/
@[simp]
theorem toFun_eq_coe (f : P1 →ᵃ[k] P2) : f.toFun = ⇑f :=
rfl
/-- An affine map on the result of adding a vector to a point produces
the same result as the linear map applied to that vector, added to the
affine map applied to that point. -/
@[simp]
theorem map_vadd (f : P1 →ᵃ[k] P2) (p : P1) (v : V1) : f (v +ᵥ p) = f.linear v +ᵥ f p :=
f.map_vadd' p v
/-- The linear map on the result of subtracting two points is the
result of subtracting the result of the affine map on those two
points. -/
@[simp]
theorem linearMap_vsub (f : P1 →ᵃ[k] P2) (p1 p2 : P1) : f.linear (p1 -ᵥ p2) = f p1 -ᵥ f p2 := by
conv_rhs => rw [← vsub_vadd p1 p2, map_vadd, vadd_vsub]
/-- Two affine maps are equal if they coerce to the same function. -/
@[ext]
theorem ext {f g : P1 →ᵃ[k] P2} (h : ∀ p, f p = g p) : f = g :=
DFunLike.ext _ _ h
theorem coeFn_injective : @Function.Injective (P1 →ᵃ[k] P2) (P1 → P2) (⇑) :=
DFunLike.coe_injective
protected theorem congr_arg (f : P1 →ᵃ[k] P2) {x y : P1} (h : x = y) : f x = f y :=
congr_arg _ h
protected theorem congr_fun {f g : P1 →ᵃ[k] P2} (h : f = g) (x : P1) : f x = g x :=
h ▸ rfl
/-- Two affine maps are equal if they have equal linear maps and are equal at some point. -/
theorem ext_linear {f g : P1 →ᵃ[k] P2} (h₁ : f.linear = g.linear) {p : P1} (h₂ : f p = g p) :
f = g := by
ext q
have hgl : g.linear (q -ᵥ p) = toFun g ((q -ᵥ p) +ᵥ q) -ᵥ toFun g q := by simp
have := f.map_vadd' q (q -ᵥ p)
rw [h₁, hgl, toFun_eq_coe, map_vadd, linearMap_vsub, h₂] at this
simpa
/-- Two affine maps are equal if they have equal linear maps and are equal at some point. -/
theorem ext_linear_iff {f g : P1 →ᵃ[k] P2} : f = g ↔ (f.linear = g.linear) ∧ (∃ p, f p = g p) :=
⟨fun h ↦ ⟨congrArg _ h, by inhabit P1; exact default, by rw [h]⟩,
fun h ↦ Exists.casesOn h.2 fun _ hp ↦ ext_linear h.1 hp⟩
variable (k P1)
/-- The constant function as an `AffineMap`. -/
def const (p : P2) : P1 →ᵃ[k] P2 where
toFun := Function.const P1 p
linear := 0
map_vadd' _ _ :=
letI : AddAction V2 P2 := inferInstance
by simp
@[simp]
theorem coe_const (p : P2) : ⇑(const k P1 p) = Function.const P1 p :=
| rfl
@[simp]
theorem const_apply (p : P2) (q : P1) : (const k P1 p) q = p := rfl
@[simp]
theorem const_linear (p : P2) : (const k P1 p).linear = 0 :=
| Mathlib/LinearAlgebra/AffineSpace/AffineMap.lean | 163 | 169 |
/-
Copyright (c) 2020 Nicolò Cavalleri. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Nicolò Cavalleri, Sébastien Gouëzel, Heather Macbeth, Patrick Massot, Floris van Doorn
-/
import Mathlib.Analysis.Normed.Operator.BoundedLinearMaps
import Mathlib.Topology.FiberBundle.Basic
/-!
# Vector bundles
In this file we define (topological) vector bundles.
Let `B` be the base space, let `F` be a normed space over a normed field `R`, and let
`E : B → Type*` be a `FiberBundle` with fiber `F`, in which, for each `x`, the fiber `E x` is a
topological vector space over `R`.
To have a vector bundle structure on `Bundle.TotalSpace F E`, one should additionally have the
following properties:
* The bundle trivializations in the trivialization atlas should be continuous linear equivs in the
fibers;
* For any two trivializations `e`, `e'` in the atlas the transition function considered as a map
from `B` into `F →L[R] F` is continuous on `e.baseSet ∩ e'.baseSet` with respect to the operator
norm topology on `F →L[R] F`.
If these conditions are satisfied, we register the typeclass `VectorBundle R F E`.
We define constructions on vector bundles like pullbacks and direct sums in other files.
## Main Definitions
* `Trivialization.IsLinear`: a class stating that a trivialization is fiberwise linear on its base
set.
* `Trivialization.linearEquivAt` and `Trivialization.continuousLinearMapAt` are the
(continuous) linear fiberwise equivalences a trivialization induces.
* They have forward maps `Trivialization.linearMapAt` / `Trivialization.continuousLinearMapAt`
and inverses `Trivialization.symmₗ` / `Trivialization.symmL`. Note that these are all defined
everywhere, since they are extended using the zero function.
* `Trivialization.coordChangeL` is the coordinate change induced by two trivializations. It only
makes sense on the intersection of their base sets, but is extended outside it using the identity.
* Given a continuous (semi)linear map between `E x` and `E' y` where `E` and `E'` are bundles over
possibly different base sets, `ContinuousLinearMap.inCoordinates` turns this into a continuous
(semi)linear map between the chosen fibers of those bundles.
## Implementation notes
The implementation choices in the vector bundle definition are discussed in the "Implementation
notes" section of `Mathlib.Topology.FiberBundle.Basic`.
## Tags
Vector bundle
-/
noncomputable section
open Bundle Set Topology
variable (R : Type*) {B : Type*} (F : Type*) (E : B → Type*)
section TopologicalVectorSpace
variable {F E}
variable [Semiring R] [TopologicalSpace F] [TopologicalSpace B]
/-- A mixin class for `Pretrivialization`, stating that a pretrivialization is fiberwise linear with
respect to given module structures on its fibers and the model fiber. -/
protected class Pretrivialization.IsLinear [AddCommMonoid F] [Module R F] [∀ x, AddCommMonoid (E x)]
[∀ x, Module R (E x)] (e : Pretrivialization F (π F E)) : Prop where
linear : ∀ b ∈ e.baseSet, IsLinearMap R fun x : E b => (e ⟨b, x⟩).2
namespace Pretrivialization
variable (e : Pretrivialization F (π F E)) {x : TotalSpace F E} {b : B} {y : E b}
theorem linear [AddCommMonoid F] [Module R F] [∀ x, AddCommMonoid (E x)] [∀ x, Module R (E x)]
[e.IsLinear R] {b : B} (hb : b ∈ e.baseSet) :
IsLinearMap R fun x : E b => (e ⟨b, x⟩).2 :=
Pretrivialization.IsLinear.linear b hb
variable [AddCommMonoid F] [Module R F] [∀ x, AddCommMonoid (E x)] [∀ x, Module R (E x)]
/-- A fiberwise linear inverse to `e`. -/
@[simps!]
protected def symmₗ (e : Pretrivialization F (π F E)) [e.IsLinear R] (b : B) : F →ₗ[R] E b := by
refine IsLinearMap.mk' (e.symm b) ?_
by_cases hb : b ∈ e.baseSet
· exact (((e.linear R hb).mk' _).inverse (e.symm b) (e.symm_apply_apply_mk hb) fun v ↦
congr_arg Prod.snd <| e.apply_mk_symm hb v).isLinear
· rw [e.coe_symm_of_not_mem hb]
exact (0 : F →ₗ[R] E b).isLinear
/-- A pretrivialization for a vector bundle defines linear equivalences between the
fibers and the model space. -/
@[simps -fullyApplied]
def linearEquivAt (e : Pretrivialization F (π F E)) [e.IsLinear R] (b : B) (hb : b ∈ e.baseSet) :
E b ≃ₗ[R] F where
toFun y := (e ⟨b, y⟩).2
invFun := e.symm b
left_inv := e.symm_apply_apply_mk hb
right_inv v := by simp_rw [e.apply_mk_symm hb v]
map_add' v w := (e.linear R hb).map_add v w
map_smul' c v := (e.linear R hb).map_smul c v
open Classical in
/-- A fiberwise linear map equal to `e` on `e.baseSet`. -/
protected def linearMapAt (e : Pretrivialization F (π F E)) [e.IsLinear R] (b : B) : E b →ₗ[R] F :=
if hb : b ∈ e.baseSet then e.linearEquivAt R b hb else 0
variable {R}
open Classical in
theorem coe_linearMapAt (e : Pretrivialization F (π F E)) [e.IsLinear R] (b : B) :
⇑(e.linearMapAt R b) = fun y => if b ∈ e.baseSet then (e ⟨b, y⟩).2 else 0 := by
rw [Pretrivialization.linearMapAt]
split_ifs <;> rfl
theorem coe_linearMapAt_of_mem (e : Pretrivialization F (π F E)) [e.IsLinear R] {b : B}
(hb : b ∈ e.baseSet) : ⇑(e.linearMapAt R b) = fun y => (e ⟨b, y⟩).2 := by
simp_rw [coe_linearMapAt, if_pos hb]
open Classical in
theorem linearMapAt_apply (e : Pretrivialization F (π F E)) [e.IsLinear R] {b : B} (y : E b) :
e.linearMapAt R b y = if b ∈ e.baseSet then (e ⟨b, y⟩).2 else 0 := by
rw [coe_linearMapAt]
theorem linearMapAt_def_of_mem (e : Pretrivialization F (π F E)) [e.IsLinear R] {b : B}
(hb : b ∈ e.baseSet) : e.linearMapAt R b = e.linearEquivAt R b hb :=
dif_pos hb
theorem linearMapAt_def_of_not_mem (e : Pretrivialization F (π F E)) [e.IsLinear R] {b : B}
(hb : b ∉ e.baseSet) : e.linearMapAt R b = 0 :=
dif_neg hb
theorem linearMapAt_eq_zero (e : Pretrivialization F (π F E)) [e.IsLinear R] {b : B}
(hb : b ∉ e.baseSet) : e.linearMapAt R b = 0 :=
dif_neg hb
theorem symmₗ_linearMapAt (e : Pretrivialization F (π F E)) [e.IsLinear R] {b : B}
(hb : b ∈ e.baseSet) (y : E b) : e.symmₗ R b (e.linearMapAt R b y) = y := by
rw [e.linearMapAt_def_of_mem hb]
exact (e.linearEquivAt R b hb).left_inv y
theorem linearMapAt_symmₗ (e : Pretrivialization F (π F E)) [e.IsLinear R] {b : B}
(hb : b ∈ e.baseSet) (y : F) : e.linearMapAt R b (e.symmₗ R b y) = y := by
rw [e.linearMapAt_def_of_mem hb]
exact (e.linearEquivAt R b hb).right_inv y
end Pretrivialization
variable [TopologicalSpace (TotalSpace F E)]
/-- A mixin class for `Trivialization`, stating that a trivialization is fiberwise linear with
respect to given module structures on its fibers and the model fiber. -/
protected class Trivialization.IsLinear [AddCommMonoid F] [Module R F] [∀ x, AddCommMonoid (E x)]
[∀ x, Module R (E x)] (e : Trivialization F (π F E)) : Prop where
linear : ∀ b ∈ e.baseSet, IsLinearMap R fun x : E b => (e ⟨b, x⟩).2
namespace Trivialization
variable (e : Trivialization F (π F E)) {x : TotalSpace F E} {b : B} {y : E b}
protected theorem linear [AddCommMonoid F] [Module R F] [∀ x, AddCommMonoid (E x)]
[∀ x, Module R (E x)] [e.IsLinear R] {b : B} (hb : b ∈ e.baseSet) :
IsLinearMap R fun y : E b => (e ⟨b, y⟩).2 :=
Trivialization.IsLinear.linear b hb
instance toPretrivialization.isLinear [AddCommMonoid F] [Module R F] [∀ x, AddCommMonoid (E x)]
[∀ x, Module R (E x)] [e.IsLinear R] : e.toPretrivialization.IsLinear R :=
{ (‹_› : e.IsLinear R) with }
variable [AddCommMonoid F] [Module R F] [∀ x, AddCommMonoid (E x)] [∀ x, Module R (E x)]
/-- A trivialization for a vector bundle defines linear equivalences between the
fibers and the model space. -/
def linearEquivAt (e : Trivialization F (π F E)) [e.IsLinear R] (b : B) (hb : b ∈ e.baseSet) :
E b ≃ₗ[R] F :=
e.toPretrivialization.linearEquivAt R b hb
variable {R}
@[simp]
theorem linearEquivAt_apply (e : Trivialization F (π F E)) [e.IsLinear R] (b : B)
(hb : b ∈ e.baseSet) (v : E b) : e.linearEquivAt R b hb v = (e ⟨b, v⟩).2 :=
rfl
@[simp]
theorem linearEquivAt_symm_apply (e : Trivialization F (π F E)) [e.IsLinear R] (b : B)
(hb : b ∈ e.baseSet) (v : F) : (e.linearEquivAt R b hb).symm v = e.symm b v :=
rfl
variable (R) in
/-- A fiberwise linear inverse to `e`. -/
protected def symmₗ (e : Trivialization F (π F E)) [e.IsLinear R] (b : B) : F →ₗ[R] E b :=
e.toPretrivialization.symmₗ R b
theorem coe_symmₗ (e : Trivialization F (π F E)) [e.IsLinear R] (b : B) :
⇑(e.symmₗ R b) = e.symm b :=
rfl
variable (R) in
/-- A fiberwise linear map equal to `e` on `e.baseSet`. -/
protected def linearMapAt (e : Trivialization F (π F E)) [e.IsLinear R] (b : B) : E b →ₗ[R] F :=
e.toPretrivialization.linearMapAt R b
open Classical in
theorem coe_linearMapAt (e : Trivialization F (π F E)) [e.IsLinear R] (b : B) :
⇑(e.linearMapAt R b) = fun y => if b ∈ e.baseSet then (e ⟨b, y⟩).2 else 0 :=
e.toPretrivialization.coe_linearMapAt b
theorem coe_linearMapAt_of_mem (e : Trivialization F (π F E)) [e.IsLinear R] {b : B}
(hb : b ∈ e.baseSet) : ⇑(e.linearMapAt R b) = fun y => (e ⟨b, y⟩).2 := by
simp_rw [coe_linearMapAt, if_pos hb]
open Classical in
theorem linearMapAt_apply (e : Trivialization F (π F E)) [e.IsLinear R] {b : B} (y : E b) :
e.linearMapAt R b y = if b ∈ e.baseSet then (e ⟨b, y⟩).2 else 0 := by
rw [coe_linearMapAt]
theorem linearMapAt_def_of_mem (e : Trivialization F (π F E)) [e.IsLinear R] {b : B}
(hb : b ∈ e.baseSet) : e.linearMapAt R b = e.linearEquivAt R b hb :=
dif_pos hb
theorem linearMapAt_def_of_not_mem (e : Trivialization F (π F E)) [e.IsLinear R] {b : B}
(hb : b ∉ e.baseSet) : e.linearMapAt R b = 0 :=
dif_neg hb
theorem symmₗ_linearMapAt (e : Trivialization F (π F E)) [e.IsLinear R] {b : B} (hb : b ∈ e.baseSet)
(y : E b) : e.symmₗ R b (e.linearMapAt R b y) = y :=
e.toPretrivialization.symmₗ_linearMapAt hb y
theorem linearMapAt_symmₗ (e : Trivialization F (π F E)) [e.IsLinear R] {b : B} (hb : b ∈ e.baseSet)
(y : F) : e.linearMapAt R b (e.symmₗ R b y) = y :=
e.toPretrivialization.linearMapAt_symmₗ hb y
variable (R) in
open Classical in
/-- A coordinate change function between two trivializations, as a continuous linear equivalence.
Defined to be the identity when `b` does not lie in the base set of both trivializations. -/
def coordChangeL (e e' : Trivialization F (π F E)) [e.IsLinear R] [e'.IsLinear R] (b : B) :
F ≃L[R] F :=
{ toLinearEquiv := if hb : b ∈ e.baseSet ∩ e'.baseSet
then (e.linearEquivAt R b (hb.1 :)).symm.trans (e'.linearEquivAt R b hb.2)
else LinearEquiv.refl R F
continuous_toFun := by
by_cases hb : b ∈ e.baseSet ∩ e'.baseSet
· rw [dif_pos hb]
refine (e'.continuousOn.comp_continuous ?_ ?_).snd
· exact e.continuousOn_symm.comp_continuous (Continuous.prodMk_right b) fun y =>
mk_mem_prod hb.1 (mem_univ y)
· exact fun y => e'.mem_source.mpr hb.2
· rw [dif_neg hb]
exact continuous_id
continuous_invFun := by
by_cases hb : b ∈ e.baseSet ∩ e'.baseSet
· rw [dif_pos hb]
refine (e.continuousOn.comp_continuous ?_ ?_).snd
· exact e'.continuousOn_symm.comp_continuous (Continuous.prodMk_right b) fun y =>
mk_mem_prod hb.2 (mem_univ y)
exact fun y => e.mem_source.mpr hb.1
· rw [dif_neg hb]
exact continuous_id }
theorem coe_coordChangeL (e e' : Trivialization F (π F E)) [e.IsLinear R] [e'.IsLinear R] {b : B}
(hb : b ∈ e.baseSet ∩ e'.baseSet) :
⇑(coordChangeL R e e' b) = (e.linearEquivAt R b hb.1).symm.trans (e'.linearEquivAt R b hb.2) :=
congr_arg (fun f : F ≃ₗ[R] F ↦ ⇑f) (dif_pos hb)
theorem coe_coordChangeL' (e e' : Trivialization F (π F E)) [e.IsLinear R] [e'.IsLinear R] {b : B}
(hb : b ∈ e.baseSet ∩ e'.baseSet) :
(coordChangeL R e e' b).toLinearEquiv =
(e.linearEquivAt R b hb.1).symm.trans (e'.linearEquivAt R b hb.2) :=
LinearEquiv.coe_injective (coe_coordChangeL _ _ hb)
theorem symm_coordChangeL (e e' : Trivialization F (π F E)) [e.IsLinear R] [e'.IsLinear R] {b : B}
(hb : b ∈ e'.baseSet ∩ e.baseSet) : (e.coordChangeL R e' b).symm = e'.coordChangeL R e b := by
apply ContinuousLinearEquiv.toLinearEquiv_injective
rw [coe_coordChangeL' e' e hb, (coordChangeL R e e' b).symm_toLinearEquiv,
coe_coordChangeL' e e' hb.symm, LinearEquiv.trans_symm, LinearEquiv.symm_symm]
theorem coordChangeL_apply (e e' : Trivialization F (π F E)) [e.IsLinear R] [e'.IsLinear R] {b : B}
(hb : b ∈ e.baseSet ∩ e'.baseSet) (y : F) :
coordChangeL R e e' b y = (e' ⟨b, e.symm b y⟩).2 :=
congr_fun (coe_coordChangeL e e' hb) y
theorem mk_coordChangeL (e e' : Trivialization F (π F E)) [e.IsLinear R] [e'.IsLinear R] {b : B}
(hb : b ∈ e.baseSet ∩ e'.baseSet) (y : F) :
(b, coordChangeL R e e' b y) = e' ⟨b, e.symm b y⟩ := by
ext
· rw [e.mk_symm hb.1 y, e'.coe_fst', e.proj_symm_apply' hb.1]
rw [e.proj_symm_apply' hb.1]
exact hb.2
· exact e.coordChangeL_apply e' hb y
theorem apply_symm_apply_eq_coordChangeL (e e' : Trivialization F (π F E)) [e.IsLinear R]
[e'.IsLinear R] {b : B} (hb : b ∈ e.baseSet ∩ e'.baseSet) (v : F) :
e' (e.toPartialHomeomorph.symm (b, v)) = (b, e.coordChangeL R e' b v) := by
rw [e.mk_coordChangeL e' hb, e.mk_symm hb.1]
/-- A version of `Trivialization.coordChangeL_apply` that fully unfolds `coordChange`. The
right-hand side is ugly, but has good definitional properties for specifically defined
trivializations. -/
theorem coordChangeL_apply' (e e' : Trivialization F (π F E)) [e.IsLinear R] [e'.IsLinear R] {b : B}
(hb : b ∈ e.baseSet ∩ e'.baseSet) (y : F) :
coordChangeL R e e' b y = (e' (e.toPartialHomeomorph.symm (b, y))).2 := by
rw [e.coordChangeL_apply e' hb, e.mk_symm hb.1]
theorem coordChangeL_symm_apply (e e' : Trivialization F (π F E)) [e.IsLinear R] [e'.IsLinear R]
{b : B} (hb : b ∈ e.baseSet ∩ e'.baseSet) :
⇑(coordChangeL R e e' b).symm =
(e'.linearEquivAt R b hb.2).symm.trans (e.linearEquivAt R b hb.1) :=
congr_arg LinearEquiv.invFun (dif_pos hb)
end Trivialization
end TopologicalVectorSpace
section
namespace Bundle
/-- The zero section of a vector bundle -/
def zeroSection [∀ x, Zero (E x)] : B → TotalSpace F E := (⟨·, 0⟩)
@[simp, mfld_simps]
theorem zeroSection_proj [∀ x, Zero (E x)] (x : B) : (zeroSection F E x).proj = x :=
rfl
@[simp, mfld_simps]
theorem zeroSection_snd [∀ x, Zero (E x)] (x : B) : (zeroSection F E x).2 = 0 :=
rfl
| end Bundle
open Bundle
variable [NontriviallyNormedField R] [∀ x, AddCommMonoid (E x)] [∀ x, Module R (E x)]
[NormedAddCommGroup F] [NormedSpace R F] [TopologicalSpace B] [TopologicalSpace (TotalSpace F E)]
[∀ x, TopologicalSpace (E x)] [FiberBundle F E]
| Mathlib/Topology/VectorBundle/Basic.lean | 333 | 340 |
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