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36851d6561a38a689c8792edc4efc7f8349212a9 | 8cae430f0a71442d02dbb1cbb14073b31048e4b0 | /src/category_theory/sites/types.lean | 1c5d7b81c911c9a7532e5c4b89f3e9fa32e92b45 | [
"Apache-2.0"
] | permissive | leanprover-community/mathlib | 56a2cadd17ac88caf4ece0a775932fa26327ba0e | 442a83d738cb208d3600056c489be16900ba701d | refs/heads/master | 1,693,584,102,358 | 1,693,471,902,000 | 1,693,471,902,000 | 97,922,418 | 1,595 | 352 | Apache-2.0 | 1,694,693,445,000 | 1,500,624,130,000 | Lean | UTF-8 | Lean | false | false | 7,734 | lean | /-
Copyright (c) 2020 Kenny Lau. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kenny Lau
-/
import category_theory.sites.canonical
/-!
# Grothendieck Topology and Sheaves on the Category of Types
> THIS FILE IS SYNCHRONIZED WITH MATHLIB4.
> Any changes to this file require a corresponding PR to mathlib4.
In this file we define a Grothendieck topology on the category of types,
and construct the canonical functor that sends a type to a sheaf over
the category of types, and make this an equivalence of categories.
Then we prove that the topology defined is the canonical topology.
-/
universe u
namespace category_theory
open_locale category_theory.Type
/-- A Grothendieck topology associated to the category of all types.
A sieve is a covering iff it is jointly surjective. -/
def types_grothendieck_topology : grothendieck_topology (Type u) :=
{ sieves := λ α S, ∀ x : α, S (λ _ : punit, x),
top_mem' := λ α x, trivial,
pullback_stable' := λ α β S f hs x, hs (f x),
transitive' := λ α S hs R hr x, hr (hs x) punit.star }
/-- The discrete sieve on a type, which only includes arrows whose image is a subsingleton. -/
@[simps] def discrete_sieve (α : Type u) : sieve α :=
{ arrows := λ β f, ∃ x, ∀ y, f y = x,
downward_closed' := λ β γ f ⟨x, hx⟩ g, ⟨x, λ y, hx $ g y⟩ }
lemma discrete_sieve_mem (α : Type u) : discrete_sieve α ∈ types_grothendieck_topology α :=
λ x, ⟨x, λ y, rfl⟩
/-- The discrete presieve on a type, which only includes arrows whose domain is a singleton. -/
def discrete_presieve (α : Type u) : presieve α :=
λ β f, ∃ x : β, ∀ y : β, y = x
lemma generate_discrete_presieve_mem (α : Type u) :
sieve.generate (discrete_presieve α) ∈ types_grothendieck_topology α :=
λ x, ⟨punit, id, λ _, x, ⟨punit.star, λ _, subsingleton.elim _ _⟩, rfl⟩
open presieve
theorem is_sheaf_yoneda' {α : Type u} : is_sheaf types_grothendieck_topology (yoneda.obj α) :=
λ β S hs x hx, ⟨λ y, x _ (hs y) punit.star,
λ γ f h, funext $ λ z,
have _ := congr_fun (hx (𝟙 _) (λ _, z) (hs $ f z) h rfl) punit.star,
by { convert this, exact rfl },
λ f hf, funext $ λ y, by convert congr_fun (hf _ (hs y)) punit.star⟩
/-- The yoneda functor that sends a type to a sheaf over the category of types -/
@[simps] def yoneda' : Type u ⥤ SheafOfTypes types_grothendieck_topology :=
{ obj := λ α, ⟨yoneda.obj α, is_sheaf_yoneda'⟩,
map := λ α β f, ⟨yoneda.map f⟩ }
@[simp] lemma yoneda'_comp : yoneda'.{u} ⋙ SheafOfTypes_to_presheaf _ = yoneda := rfl
open opposite
/-- Given a presheaf `P` on the category of types, construct
a map `P(α) → (α → P(*))` for all type `α`. -/
def eval (P : (Type u)ᵒᵖ ⥤ Type u) (α : Type u) (s : P.obj (op α)) (x : α) : P.obj (op punit) :=
P.map (↾λ _, x).op s
/-- Given a sheaf `S` on the category of types, construct a map
`(α → S(*)) → S(α)` that is inverse to `eval`. -/
noncomputable def types_glue (S : (Type u)ᵒᵖ ⥤ Type u)
(hs : is_sheaf types_grothendieck_topology S)
(α : Type u) (f : α → S.obj (op punit)) : S.obj (op α) :=
(hs.is_sheaf_for _ _ (generate_discrete_presieve_mem α)).amalgamate
(λ β g hg, S.map (↾λ x, punit.star).op $ f $ g $ classical.some hg)
(λ β γ δ g₁ g₂ f₁ f₂ hf₁ hf₂ h,
(hs.is_sheaf_for _ _ (generate_discrete_presieve_mem δ)).is_separated_for.ext $
λ ε g ⟨x, hx⟩, have f₁ (classical.some hf₁) = f₂ (classical.some hf₂),
from classical.some_spec hf₁ (g₁ $ g x) ▸ classical.some_spec hf₂ (g₂ $ g x) ▸ congr_fun h _,
by { simp_rw [← functor_to_types.map_comp_apply, this, ← op_comp], refl })
lemma eval_types_glue {S hs α} (f) : eval.{u} S α (types_glue S hs α f) = f :=
funext $ λ x, (is_sheaf_for.valid_glue _ _ _ $
by exact ⟨punit.star, λ _, subsingleton.elim _ _⟩).trans $
by { convert functor_to_types.map_id_apply _ _, rw ← op_id, congr }
lemma types_glue_eval {S hs α} (s) : types_glue.{u} S hs α (eval S α s) = s :=
(hs.is_sheaf_for _ _ (generate_discrete_presieve_mem α)).is_separated_for.ext $ λ β f hf,
(is_sheaf_for.valid_glue _ _ _ hf).trans $ (functor_to_types.map_comp_apply _ _ _ _).symm.trans $
by { rw ← op_comp, congr' 2, exact funext (λ x, congr_arg f (classical.some_spec hf x).symm) }
/-- Given a sheaf `S`, construct an equivalence `S(α) ≃ (α → S(*))`. -/
@[simps] noncomputable def eval_equiv (S : (Type u)ᵒᵖ ⥤ Type u)
(hs : is_sheaf types_grothendieck_topology S)
(α : Type u) : S.obj (op α) ≃ (α → S.obj (op punit)) :=
{ to_fun := eval S α,
inv_fun := types_glue S hs α,
left_inv := types_glue_eval,
right_inv := eval_types_glue }
lemma eval_map (S : (Type u)ᵒᵖ ⥤ Type u) (α β) (f : β ⟶ α) (s x) :
eval S β (S.map f.op s) x = eval S α s (f x) :=
by { simp_rw [eval, ← functor_to_types.map_comp_apply, ← op_comp], refl }
/-- Given a sheaf `S`, construct an isomorphism `S ≅ [-, S(*)]`. -/
@[simps] noncomputable def equiv_yoneda (S : (Type u)ᵒᵖ ⥤ Type u)
(hs : is_sheaf types_grothendieck_topology S) :
S ≅ yoneda.obj (S.obj (op punit)) :=
nat_iso.of_components (λ α, equiv.to_iso $ eval_equiv S hs $ unop α) $ λ α β f,
funext $ λ s, funext $ λ x, eval_map S (unop α) (unop β) f.unop _ _
/-- Given a sheaf `S`, construct an isomorphism `S ≅ [-, S(*)]`. -/
@[simps] noncomputable def equiv_yoneda'
(S : SheafOfTypes types_grothendieck_topology) :
S ≅ yoneda'.obj (S.1.obj (op punit)) :=
{ hom := ⟨(equiv_yoneda S.1 S.2).hom⟩,
inv := ⟨(equiv_yoneda S.1 S.2).inv⟩,
hom_inv_id' := by { ext1, apply (equiv_yoneda S.1 S.2).hom_inv_id },
inv_hom_id' := by { ext1, apply (equiv_yoneda S.1 S.2).inv_hom_id } }
lemma eval_app (S₁ S₂ : SheafOfTypes.{u} types_grothendieck_topology)
(f : S₁ ⟶ S₂) (α : Type u) (s : S₁.1.obj (op α)) (x : α) :
eval S₂.1 α (f.val.app (op α) s) x = f.val.app (op punit) (eval S₁.1 α s x) :=
(congr_fun (f.val.naturality (↾λ _ : punit, x).op) s).symm
/-- `yoneda'` induces an equivalence of category between `Type u` and
`Sheaf types_grothendieck_topology`. -/
@[simps] noncomputable def type_equiv :
Type u ≌ SheafOfTypes types_grothendieck_topology :=
equivalence.mk
yoneda'
(SheafOfTypes_to_presheaf _ ⋙ (evaluation _ _).obj (op punit))
(nat_iso.of_components
(λ α, /- α ≅ punit ⟶ α -/
{ hom := λ x _, x,
inv := λ f, f punit.star,
hom_inv_id' := funext $ λ x, rfl,
inv_hom_id' := funext $ λ f, funext $ λ y, punit.cases_on y rfl })
(λ α β f, rfl))
(iso.symm $ nat_iso.of_components
(λ S, equiv_yoneda' S)
(λ S₁ S₂ f, SheafOfTypes.hom.ext _ _ $
nat_trans.ext _ _ $ funext $ λ α, funext $ λ s, funext $ λ x,
eval_app S₁ S₂ f (unop α) s x))
lemma subcanonical_types_grothendieck_topology :
sheaf.subcanonical types_grothendieck_topology.{u} :=
sheaf.subcanonical.of_yoneda_is_sheaf _ (λ X, is_sheaf_yoneda')
lemma types_grothendieck_topology_eq_canonical :
types_grothendieck_topology.{u} = sheaf.canonical_topology (Type u) :=
le_antisymm subcanonical_types_grothendieck_topology $ Inf_le ⟨yoneda.obj (ulift bool), ⟨_, rfl⟩,
grothendieck_topology.ext $ funext $ λ α, set.ext $ λ S,
⟨λ hs x, classical.by_contradiction $ λ hsx,
have (λ _, ulift.up tt : (yoneda.obj (ulift bool)).obj (op punit)) = λ _, ulift.up ff :=
(hs punit (λ _, x)).is_separated_for.ext $ λ β f hf, funext $ λ y, hsx.elim $ S.2 hf $ λ _, y,
bool.no_confusion $ ulift.up.inj $ (congr_fun this punit.star : _),
λ hs β f, is_sheaf_yoneda' _ $ λ y, hs _⟩⟩
end category_theory
|
d8b10242eb6e6642c7e96db81da4eb1f695a0139 | 97f752b44fd85ec3f635078a2dd125ddae7a82b6 | /library/theories/measure_theory/sigma_algebra.lean | 1c23d8cb847e9a13185d276a2710da0f0c896617 | [
"Apache-2.0"
] | permissive | tectronics/lean | ab977ba6be0fcd46047ddbb3c8e16e7c26710701 | f38af35e0616f89c6e9d7e3eb1d48e47ee666efe | refs/heads/master | 1,532,358,526,384 | 1,456,276,623,000 | 1,456,276,623,000 | null | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 9,383 | lean | /-
Copyright (c) 2016 Jacob Gross. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Jacob Gross, Jeremy Avigad
Sigma algebras.
-/
import data.set data.nat theories.topology.basic
open eq.ops set nat
structure sigma_algebra [class] (X : Type) :=
(sets : set (set X))
(univ_mem_sets : univ ∈ sets)
(comp_mem_sets : ∀ {s : set X}, s ∈ sets → (-s ∈ sets))
(cUnion_mem_sets : ∀ {s : ℕ → set X}, (∀ i, s i ∈ sets) → (⋃ i, s i) ∈ sets)
/- Closure properties -/
namespace measure_theory
open sigma_algebra
variables {X : Type} [sigma_algebra X]
definition measurable (t : set X) : Prop := t ∈ sets X
theorem measurable_univ : measurable (@univ X) :=
univ_mem_sets X
theorem measurable_compl {s : set X} (H : measurable s) : measurable (-s) :=
comp_mem_sets H
theorem measurable_of_measurable_compl {s : set X} (H : measurable (-s)) : measurable s :=
!compl_compl ▸ measurable_compl H
theorem measurable_empty : measurable (∅ : set X) :=
compl_univ ▸ measurable_compl measurable_univ
theorem measurable_cUnion {s : ℕ → set X} (H : ∀ i, measurable (s i)) :
measurable (⋃ i, s i) :=
cUnion_mem_sets H
theorem measurable_cInter {s : ℕ → set X} (H : ∀ i, measurable (s i)) :
measurable (⋂ i, s i) :=
have ∀ i, measurable (-(s i)), from take i, measurable_compl (H i),
have measurable (-(⋃ i, -(s i))), from measurable_compl (measurable_cUnion this),
show measurable (⋂ i, s i), using this, by rewrite Inter_eq_comp_Union_comp; apply this
theorem measurable_union {s t : set X} (Hs : measurable s) (Ht : measurable t) :
measurable (s ∪ t) :=
have ∀ i, measurable (bin_ext s t i), by intro i; cases i; exact Hs; exact Ht,
show measurable (s ∪ t), using this, by rewrite -Union_bin_ext; exact measurable_cUnion this
theorem measurable_inter {s t : set X} (Hs : measurable s) (Ht : measurable t) :
measurable (s ∩ t) :=
have ∀ i, measurable (bin_ext s t i), by intro i; cases i; exact Hs; exact Ht,
show measurable (s ∩ t), using this, by rewrite -Inter_bin_ext; exact measurable_cInter this
theorem measurable_diff {s t : set X} (Hs : measurable s) (Ht : measurable t) :
measurable (s \ t) :=
measurable_inter Hs (measurable_compl Ht)
theorem measurable_insert {x : X} {s : set X} (Hx : measurable '{x}) (Hs : measurable s) :
measurable (insert x s) :=
!insert_eq⁻¹ ▸ measurable_union Hx Hs
end measure_theory
/-
-- Properties of sigma algebras
-/
namespace sigma_algebra
open measure_theory
variable {X : Type}
protected theorem eq {M N : sigma_algebra X} (H : @sets X M = @sets X N) :
M = N :=
by cases M; cases N; cases H; apply rfl
/- sigma algebra generated by a set -/
inductive sets_generated_by (G : set (set X)) : set X → Prop :=
| generators_mem : ∀ ⦃s : set X⦄, s ∈ G → sets_generated_by G s
| univ_mem : sets_generated_by G univ
| comp_mem : ∀ ⦃s : set X⦄, sets_generated_by G s → sets_generated_by G (-s)
| cUnion_mem : ∀ ⦃s : ℕ → set X⦄, (∀ i, sets_generated_by G (s i)) →
sets_generated_by G (⋃ i, s i)
protected definition generated_by {X : Type} (G : set (set X)) : sigma_algebra X :=
⦃sigma_algebra,
sets := sets_generated_by G,
univ_mem_sets := sets_generated_by.univ_mem G,
comp_mem_sets := sets_generated_by.comp_mem ,
cUnion_mem_sets := sets_generated_by.cUnion_mem ⦄
theorem sets_generated_by_initial {G : set (set X)} {M : sigma_algebra X} (H : G ⊆ @sets _ M) :
sets_generated_by G ⊆ @sets _ M :=
begin
intro s Hs,
induction Hs with s sG s Hs ssX s Hs sisX,
{exact H sG},
{exact measurable_univ},
{exact measurable_compl ssX},
exact measurable_cUnion sisX
end
theorem measurable_generated_by {G : set (set X)} :
∀₀ s ∈ G, @measurable _ (sigma_algebra.generated_by G) s :=
λ s H, sets_generated_by.generators_mem H
/- The collection of sigma algebras forms a complete lattice. -/
protected definition le (M N : sigma_algebra X) : Prop := @sets _ M ⊆ @sets _ N
definition sigma_algebra_has_le [reducible] [instance] :
has_le (sigma_algebra X) :=
has_le.mk sigma_algebra.le
protected theorem le_refl (M : sigma_algebra X) : M ≤ M := subset.refl (@sets _ M)
protected theorem le_trans (M N L : sigma_algebra X) : M ≤ N → N ≤ L → M ≤ L :=
assume H1, assume H2,
subset.trans H1 H2
protected theorem le_antisymm (M N : sigma_algebra X) : M ≤ N → N ≤ M → M = N :=
assume H1, assume H2,
sigma_algebra.eq (subset.antisymm H1 H2)
protected theorem generated_by_initial {G : set (set X)} {M : sigma_algebra X} (H : G ⊆ @sets X M) :
sigma_algebra.generated_by G ≤ M :=
sets_generated_by_initial H
protected definition inf (M N : sigma_algebra X) : sigma_algebra X :=
⦃sigma_algebra,
sets := @sets X M ∩ @sets X N,
univ_mem_sets := abstract and.intro (@measurable_univ X M) (@measurable_univ X N) end,
comp_mem_sets := abstract take s, assume Hs, and.intro
(@measurable_compl X M s (and.elim_left Hs))
(@measurable_compl X N s (and.elim_right Hs)) end,
cUnion_mem_sets := abstract take s, assume Hs, and.intro
(@measurable_cUnion X M s (λ i, and.elim_left (Hs i)))
(@measurable_cUnion X N s (λ i, and.elim_right (Hs i))) end⦄
protected theorem inf_le_left (M N : sigma_algebra X) : sigma_algebra.inf M N ≤ M :=
λ s, !inter_subset_left
protected theorem inf_le_right (M N : sigma_algebra X) : sigma_algebra.inf M N ≤ N :=
λ s, !inter_subset_right
protected theorem le_inf (M N L : sigma_algebra X) (H1 : L ≤ M) (H2 : L ≤ N) :
L ≤ sigma_algebra.inf M N :=
λ s H, and.intro (H1 s H) (H2 s H)
protected definition Inf (MS : set (sigma_algebra X)) : sigma_algebra X :=
⦃sigma_algebra,
sets := ⋂ M ∈ MS, @sets _ M,
univ_mem_sets := abstract take M, assume HM, @measurable_univ X M end,
comp_mem_sets := abstract take s, assume Hs, take M, assume HM,
measurable_compl (Hs M HM) end,
cUnion_mem_sets := abstract take s, assume Hs, take M, assume HM,
measurable_cUnion (λ i, Hs i M HM) end
⦄
protected theorem Inf_le {M : sigma_algebra X} {MS : set (sigma_algebra X)} (MMS : M ∈ MS) :
sigma_algebra.Inf MS ≤ M :=
bInter_subset_of_mem MMS
protected theorem le_Inf {M : sigma_algebra X} {MS : set (sigma_algebra X)} (H : ∀₀ N ∈ MS, M ≤ N) :
M ≤ sigma_algebra.Inf MS :=
take s, assume Hs : s ∈ @sets _ M,
take N, assume NMS : N ∈ MS,
show s ∈ @sets _ N, from H NMS s Hs
protected definition sup (M N : sigma_algebra X) : sigma_algebra X :=
sigma_algebra.generated_by (@sets _ M ∪ @sets _ N)
protected theorem le_sup_left (M N : sigma_algebra X) : M ≤ sigma_algebra.sup M N :=
take s, assume Hs : s ∈ @sets _ M,
measurable_generated_by (or.inl Hs)
protected theorem le_sup_right (M N : sigma_algebra X) : N ≤ sigma_algebra.sup M N :=
take s, assume Hs : s ∈ @sets _ N,
measurable_generated_by (or.inr Hs)
protected theorem sup_le {M N L : sigma_algebra X} (H1 : M ≤ L) (H2 : N ≤ L) :
sigma_algebra.sup M N ≤ L :=
have @sets _ M ∪ @sets _ N ⊆ @sets _ L, from union_subset H1 H2,
sets_generated_by_initial this
protected definition Sup (MS : set (sigma_algebra X)) : sigma_algebra X :=
sigma_algebra.generated_by (⋃ M ∈ MS, @sets _ M)
protected theorem le_Sup {M : sigma_algebra X} {MS : set (sigma_algebra X)} (MMS : M ∈ MS) :
M ≤ sigma_algebra.Sup MS :=
take s, assume Hs : s ∈ @sets _ M,
measurable_generated_by (mem_bUnion MMS Hs)
protected theorem Sup_le {N : sigma_algebra X} {MS : set (sigma_algebra X)} (H : ∀₀ M ∈ MS, M ≤ N) :
sigma_algebra.Sup MS ≤ N :=
have (⋃ M ∈ MS, @sets _ M) ⊆ @sets _ N, from bUnion_subset H,
sets_generated_by_initial this
protected definition complete_lattice [reducible] [trans_instance] :
complete_lattice (sigma_algebra X) :=
⦃complete_lattice,
le := sigma_algebra.le,
le_refl := sigma_algebra.le_refl,
le_trans := sigma_algebra.le_trans,
le_antisymm := sigma_algebra.le_antisymm,
inf := sigma_algebra.inf,
sup := sigma_algebra.sup,
inf_le_left := sigma_algebra.inf_le_left,
inf_le_right := sigma_algebra.inf_le_right,
le_inf := sigma_algebra.le_inf,
le_sup_left := sigma_algebra.le_sup_left,
le_sup_right := sigma_algebra.le_sup_right,
sup_le := @sigma_algebra.sup_le X,
Inf := sigma_algebra.Inf,
Sup := sigma_algebra.Sup,
Inf_le := @sigma_algebra.Inf_le X,
le_Inf := @sigma_algebra.le_Inf X,
le_Sup := @sigma_algebra.le_Sup X,
Sup_le := @sigma_algebra.Sup_le X⦄
end sigma_algebra
/- Borel sets -/
namespace measure_theory
section
open topology
variables (X : Type) [topology X]
definition borel_algebra : sigma_algebra X :=
sigma_algebra.generated_by (opens X)
variable {X}
definition borel (s : set X) : Prop := @measurable _ (borel_algebra X) s
theorem borel_of_open {s : set X} (H : Open s) : borel s :=
sigma_algebra.measurable_generated_by H
theorem borel_of_closed {s : set X} (H : closed s) : borel s :=
have borel (-s), from borel_of_open H,
@measurable_of_measurable_compl _ (borel_algebra X) _ this
end
end measure_theory
|
ff70d13f08ac59efa91f3ccdbfbcdfa630bdb35d | a9d0fb7b0e4f802bd3857b803e6c5c23d87fef91 | /tests/lean/run/class11.lean | e45990c6837167635c23d0d202488d91070b5285 | [
"Apache-2.0"
] | permissive | soonhokong/lean-osx | 4a954262c780e404c1369d6c06516161d07fcb40 | 3670278342d2f4faa49d95b46d86642d7875b47c | refs/heads/master | 1,611,410,334,552 | 1,474,425,686,000 | 1,474,425,686,000 | 12,043,103 | 5 | 1 | null | null | null | null | UTF-8 | Lean | false | false | 185 | lean | inductive [class] C {A : Type} : A → Prop
constant f {A : Type} (a : A) [H : C a] : Prop
noncomputable definition g {A : Type} (a b : A) {H1 : C a} {H2 : C b} : Prop :=
f a ∧ f b
|
67f69819fe007404266ba27eec6fdb14bd75e219 | 05b503addd423dd68145d68b8cde5cd595d74365 | /src/measure_theory/borel_space.lean | c9e81e65ff066613d10aab6947c808fa3d5e3457 | [
"Apache-2.0"
] | permissive | aestriplex/mathlib | 77513ff2b176d74a3bec114f33b519069788811d | e2fa8b2b1b732d7c25119229e3cdfba8370cb00f | refs/heads/master | 1,621,969,960,692 | 1,586,279,279,000 | 1,586,279,279,000 | null | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 29,534 | lean | /-
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 measure_theory.measurable_space topology.instances.ennreal analysis.normed_space.basic
/-!
# Borel (measurable) space
## Main definitions
* `borel α` : the least `σ`-algebra that contains all open sets;
* `class borel_space` : a space with `topological_space` and `measurable_space` structures
such that `‹measurable_space α› = borel α`;
* `class opens_measurable_space` : a space with `topological_space` and `measurable_space` structures
such that all open sets are measurable; equivalently, `borel α ≤ ‹measurable_space α›`.
* `borel_space` instances on `empty`, `unit`, `bool`, `nat`, `int`, `rat`;
* `measurable` and `borel_space` instances on `ℝ`, `ℝ≥0`, `ennreal`.
## Main statements
* `is_open.is_measurable`, `is_closed.is_measurable`: open and closed sets are measurable;
* `continuous.measurable` : a continuous function is measurable;
* `continuous.measurable2` : if `f : α → β` and `g : α → γ` are measurable and `op : β × γ → δ`
is continuous, then `λ x, op (f x, g y)` is measurable;
* `measurable.add` etc : dot notation for arithmetic operations on `measurable` predicates,
and similarly for `dist` and `edist`;
* `measurable.ennreal*` : special cases for arithmetic operations on `ennreal`s.
-/
noncomputable theory
open classical set
open_locale classical
universes u v w x y
variables {α : Type u} {β : Type v} {γ : Type w} {δ : Type x} {ι : Sort y} {s t u : set α}
open measurable_space topological_space
/-- `measurable_space` structure generated by `topological_space`. -/
def borel (α : Type u) [topological_space α] : measurable_space α :=
generate_from {s : set α | is_open s}
lemma borel_eq_top_of_discrete [topological_space α] [discrete_topology α] :
borel α = ⊤ :=
top_le_iff.1 $ λ s hs, generate_measurable.basic s (is_open_discrete s)
lemma borel_eq_top_of_encodable [topological_space α] [t1_space α] [encodable α] :
borel α = ⊤ :=
begin
refine (top_le_iff.1 $ λ s hs, bUnion_of_singleton s ▸ _),
apply is_measurable.bUnion s.countable_encodable,
intros x hx,
apply is_measurable.of_compl,
apply generate_measurable.basic,
exact is_closed_singleton
end
lemma borel_eq_generate_from_of_subbasis {s : set (set α)}
[t : topological_space α] [second_countable_topology α] (hs : t = generate_from s) :
borel α = generate_from s :=
le_antisymm
(generate_from_le $ assume u (hu : t.is_open u),
begin
rw [hs] at hu,
induction hu,
case generate_open.basic : u hu
{ exact generate_measurable.basic u hu },
case generate_open.univ
{ exact @is_measurable.univ α (generate_from s) },
case generate_open.inter : s₁ s₂ _ _ hs₁ hs₂
{ exact @is_measurable.inter α (generate_from s) _ _ hs₁ hs₂ },
case generate_open.sUnion : f hf ih {
rcases is_open_sUnion_countable f (by rwa hs) with ⟨v, hv, vf, vu⟩,
rw ← vu,
exact @is_measurable.sUnion α (generate_from s) _ hv
(λ x xv, ih _ (vf xv)) }
end)
(generate_from_le $ assume u hu, generate_measurable.basic _ $
show t.is_open u, by rw [hs]; exact generate_open.basic _ hu)
lemma borel_eq_generate_Iio (α)
[topological_space α] [second_countable_topology α]
[linear_order α] [order_topology α] :
borel α = generate_from (range Iio) :=
begin
refine le_antisymm _ (generate_from_le _),
{ rw borel_eq_generate_from_of_subbasis (order_topology.topology_eq_generate_intervals α),
have H : ∀ a:α, is_measurable (measurable_space.generate_from (range Iio)) (Iio a) :=
λ a, generate_measurable.basic _ ⟨_, rfl⟩,
refine generate_from_le _, rintro _ ⟨a, rfl | rfl⟩; [skip, apply H],
by_cases h : ∃ a', ∀ b, a < b ↔ a' ≤ b,
{ rcases h with ⟨a', ha'⟩,
rw (_ : Ioi a = -Iio a'), {exact (H _).compl _},
simp [set.ext_iff, ha'] },
{ rcases is_open_Union_countable
(λ a' : {a' : α // a < a'}, {b | a'.1 < b})
(λ a', is_open_lt' _) with ⟨v, ⟨hv⟩, vu⟩,
simp [set.ext_iff] at vu,
have : Ioi a = ⋃ x : v, -Iio x.1.1,
{ simp [set.ext_iff],
refine λ x, ⟨λ ax, _, λ ⟨a', ⟨h, av⟩, ax⟩, lt_of_lt_of_le h ax⟩,
rcases (vu x).2 _ with ⟨a', h₁, h₂⟩,
{ exact ⟨a', h₁, le_of_lt h₂⟩ },
refine not_imp_comm.1 (λ h, _) h,
exact ⟨x, λ b, ⟨λ ab, le_of_not_lt (λ h', h ⟨b, ab, h'⟩),
lt_of_lt_of_le ax⟩⟩ },
rw this, resetI,
apply is_measurable.Union,
exact λ _, (H _).compl _ } },
{ simp, rintro _ a rfl,
exact generate_measurable.basic _ is_open_Iio }
end
lemma borel_eq_generate_Ioi (α)
[topological_space α] [second_countable_topology α]
[linear_order α] [order_topology α] :
borel α = generate_from (range Ioi) :=
begin
refine le_antisymm _ (generate_from_le _),
{ rw borel_eq_generate_from_of_subbasis (order_topology.topology_eq_generate_intervals α),
have H : ∀ a:α, is_measurable (measurable_space.generate_from (range (λ a, {x | a < x}))) {x | a < x} :=
λ a, generate_measurable.basic _ ⟨_, rfl⟩,
refine generate_from_le _, rintro _ ⟨a, rfl | rfl⟩, {apply H},
by_cases h : ∃ a', ∀ b, b < a ↔ b ≤ a',
{ rcases h with ⟨a', ha'⟩,
rw (_ : Iio a = -Ioi a'), {exact (H _).compl _},
simp [set.ext_iff, ha'] },
{ rcases is_open_Union_countable
(λ a' : {a' : α // a' < a}, {b | b < a'.1})
(λ a', is_open_gt' _) with ⟨v, ⟨hv⟩, vu⟩,
simp [set.ext_iff] at vu,
have : Iio a = ⋃ x : v, -Ioi x.1.1,
{ simp [set.ext_iff],
refine λ x, ⟨λ ax, _, λ ⟨a', ⟨h, av⟩, ax⟩, lt_of_le_of_lt ax h⟩,
rcases (vu x).2 _ with ⟨a', h₁, h₂⟩,
{ exact ⟨a', h₁, le_of_lt h₂⟩ },
refine not_imp_comm.1 (λ h, _) h,
exact ⟨x, λ b, ⟨λ ab, le_of_not_lt (λ h', h ⟨b, ab, h'⟩),
λ h, lt_of_le_of_lt h ax⟩⟩ },
rw this, resetI,
apply is_measurable.Union,
exact λ _, (H _).compl _ } },
{ simp, rintro _ a rfl,
exact generate_measurable.basic _ (is_open_lt' _) }
end
lemma borel_comap {f : α → β} {t : topological_space β} :
@borel α (t.induced f) = (@borel β t).comap f :=
comap_generate_from.symm
lemma continuous.borel_measurable [topological_space α] [topological_space β]
{f : α → β} (hf : continuous f) :
@measurable α β (borel α) (borel β) f :=
generate_from_le $ λ s hs, generate_measurable.basic (f ⁻¹' s) (hf s hs)
/-- A space with `measurable_space` and `topological_space` structures such that
all open sets are measurable. -/
class opens_measurable_space (α : Type*) [topological_space α] [h : measurable_space α] : Prop :=
(borel_le : borel α ≤ h)
/-- A space with `measurable_space` and `topological_space` structures such that
the `σ`-algebra of measurable sets is exactly the `σ`-algebra generated by open sets. -/
class borel_space (α : Type*) [topological_space α] [measurable_space α] : Prop :=
(measurable_eq : ‹measurable_space α› = borel α)
/-- In a `borel_space` all open sets are measurable. -/
@[priority 100]
instance borel_space.opens_measurable {α : Type*} [topological_space α] [measurable_space α]
[borel_space α] : opens_measurable_space α :=
⟨ge_of_eq $ borel_space.measurable_eq α⟩
instance subtype.borel_space {α : Type*} [topological_space α] [measurable_space α]
[hα : borel_space α] (s : set α) :
borel_space s :=
⟨by { rw [hα.1, subtype.measurable_space, ← borel_comap], refl }⟩
instance subtype.opens_measurable_space {α : Type*} [topological_space α] [measurable_space α]
[h : opens_measurable_space α] (s : set α) :
opens_measurable_space s :=
⟨by { rw [borel_comap], exact comap_mono h.1 }⟩
section
variables [topological_space α] [measurable_space α] [opens_measurable_space α]
[topological_space β] [measurable_space β] [opens_measurable_space β]
[topological_space γ] [measurable_space γ] [borel_space γ]
[measurable_space δ]
lemma is_open.is_measurable (h : is_open s) : is_measurable s :=
opens_measurable_space.borel_le α _ $ generate_measurable.basic _ h
lemma is_measurable_interior : is_measurable (interior s) := is_open_interior.is_measurable
lemma is_closed.is_measurable (h : is_closed s) : is_measurable s :=
is_measurable.compl_iff.1 $ h.is_measurable
lemma is_measurable_singleton [t1_space α] {x : α} : is_measurable ({x} : set α) :=
is_closed_singleton.is_measurable
-- TODO (Lean 3.8): this will become `= is_measurable_singleton`
lemma is_measurable_eq [t1_space α] {a : α} : is_measurable {x | x = a} :=
by { convert is_measurable_singleton; try { apply_instance }, ext x, exact mem_singleton_iff.symm }
lemma is_measurable_closure : is_measurable (closure s) :=
is_closed_closure.is_measurable
section order_closed_topology
variables [preorder α] [order_closed_topology α] {a b : α}
lemma is_measurable_Ici : is_measurable (Ici a) := is_closed_Ici.is_measurable
lemma is_measurable_Iic : is_measurable (Iic a) := is_closed_Iic.is_measurable
lemma is_measurable_Icc : is_measurable (Icc a b) := is_closed_Icc.is_measurable
end order_closed_topology
section order_closed_topology
variables [linear_order α] [order_closed_topology α] {a b : α}
lemma is_measurable_Iio : is_measurable (Iio a) := is_open_Iio.is_measurable
lemma is_measurable_Ioi : is_measurable (Ioi a) := is_open_Ioi.is_measurable
lemma is_measurable_Ioo : is_measurable (Ioo a b) := is_open_Ioo.is_measurable
lemma is_measurable_Ioc : is_measurable (Ioc a b) := is_measurable_Ioi.inter is_measurable_Iic
lemma is_measurable_Ico : is_measurable (Ico a b) := is_measurable_Ici.inter is_measurable_Iio
end order_closed_topology
lemma is_measurable_interval [decidable_linear_order α] [order_closed_topology α] {a b : α} :
is_measurable (interval a b) :=
is_measurable_Icc
instance prod.opens_measurable_space [second_countable_topology α] [second_countable_topology β] :
opens_measurable_space (α × β) :=
begin
refine ⟨_⟩,
rcases is_open_generated_countable_inter α with ⟨a, ha₁, ha₂, ha₃, ha₄, ha₅⟩,
rcases is_open_generated_countable_inter β with ⟨b, hb₁, hb₂, hb₃, hb₄, hb₅⟩,
have : prod.topological_space = generate_from {g | ∃u∈a, ∃v∈b, g = set.prod u v},
{ rw [ha₅, hb₅], exact prod_generate_from_generate_from_eq ha₄ hb₄ },
rw [borel_eq_generate_from_of_subbasis this],
apply generate_from_le,
rintros _ ⟨u, hu, v, hv, rfl⟩,
have hu : is_open u, by { rw [ha₅], exact generate_open.basic _ hu },
have hv : is_open v, by { rw [hb₅], exact generate_open.basic _ hv },
exact hu.is_measurable.prod hv.is_measurable
end
/-- A continuous function from an `opens_measurable_space` to a `borel_space`
is measurable. -/
lemma continuous.measurable {f : α → γ} (hf : continuous f) :
measurable f :=
hf.borel_measurable.mono (opens_measurable_space.borel_le _)
(le_of_eq $ borel_space.measurable_eq _)
/-- A homeomorphism between two Borel spaces is a measurable equivalence.-/
def homeomorph.to_measurable_equiv {α : Type*} {β : Type*} [topological_space α]
[measurable_space α] [borel_space α] [topological_space β] [measurable_space β]
[borel_space β] (h : α ≃ₜ β) :
measurable_equiv α β :=
{ measurable_to_fun := h.continuous_to_fun.measurable,
measurable_inv_fun := h.continuous_inv_fun.measurable,
.. h }
lemma measurable_of_continuous_on_compl_singleton [t1_space α] {f : α → γ} (a : α)
(hf : continuous_on f {x | x ≠ a}) :
measurable f :=
measurable_of_measurable_on_compl_singleton a is_measurable_singleton
(continuous_on_iff_continuous_restrict.1 hf).measurable
lemma continuous.measurable2 [second_countable_topology α] [second_countable_topology β]
{f : δ → α} {g : δ → β} {c : α → β → γ}
(h : continuous (λp:α×β, c p.1 p.2)) (hf : measurable f) (hg : measurable g) :
measurable (λa, c (f a) (g a)) :=
h.measurable.comp (hf.prod_mk hg)
lemma measurable.smul [semiring α] [second_countable_topology α]
[add_comm_monoid γ] [second_countable_topology γ]
[semimodule α γ] [topological_semimodule α γ]
{f : δ → α} {g : δ → γ} (hf : measurable f) (hg : measurable g) :
measurable (λ c, f c • g c) :=
continuous_smul.measurable2 hf hg
lemma measurable.const_smul {α : Type*} [topological_space α] [semiring α]
[add_comm_monoid γ] [semimodule α γ] [topological_semimodule α γ]
{f : δ → γ} (hf : measurable f) (c : α) :
measurable (λ x, c • f x) :=
(continuous_const.smul continuous_id).measurable.comp hf
lemma measurable_const_smul_iff {α : Type*} [topological_space α]
[division_ring α] [add_comm_monoid γ]
[semimodule α γ] [topological_semimodule α γ]
{f : δ → γ} {c : α} (hc : c ≠ 0) :
measurable (λ x, c • f x) ↔ measurable f :=
⟨λ h, by simpa only [smul_smul, inv_mul_cancel hc, one_smul] using h.const_smul c⁻¹,
λ h, h.const_smul c⟩
lemma is_measurable_le' [partial_order α] [order_closed_topology α] [second_countable_topology α] :
is_measurable {p : α × α | p.1 ≤ p.2} :=
(order_closed_topology.is_closed_le' _).is_measurable
lemma is_measurable_le [partial_order α] [order_closed_topology α] [second_countable_topology α]
{f g : δ → α} (hf : measurable f) (hg : measurable g) :
is_measurable {a | f a ≤ g a} :=
(hf.prod_mk hg).preimage is_measurable_le'
lemma measurable.max [decidable_linear_order α] [order_closed_topology α] [second_countable_topology α]
{f g : δ → α} (hf : measurable f) (hg : measurable g) :
measurable (λa, max (f a) (g a)) :=
measurable.if (is_measurable_le hf hg) hg hf
lemma measurable.min [decidable_linear_order α] [order_closed_topology α] [second_countable_topology α]
{f g : δ → α} (hf : measurable f) (hg : measurable g) :
measurable (λa, min (f a) (g a)) :=
measurable.if (is_measurable_le hf hg) hf hg
end
section borel_space
variables [topological_space α] [measurable_space α] [borel_space α]
[topological_space β] [measurable_space β] [borel_space β]
[topological_space γ] [measurable_space γ] [borel_space γ]
[measurable_space δ]
lemma prod_le_borel_prod : prod.measurable_space ≤ borel (α × β) :=
begin
rw [‹borel_space α›.measurable_eq, ‹borel_space β›.measurable_eq],
refine sup_le _ _,
{ exact comap_le_iff_le_map.mpr continuous_fst.borel_measurable },
{ exact comap_le_iff_le_map.mpr continuous_snd.borel_measurable }
end
instance prod.borel_space [second_countable_topology α] [second_countable_topology β] :
borel_space (α × β) :=
⟨le_antisymm prod_le_borel_prod (opens_measurable_space.borel_le (α × β))⟩
@[to_additive]
lemma measurable_mul [monoid α] [topological_monoid α] [second_countable_topology α] :
measurable (λ p : α × α, p.1 * p.2) :=
continuous_mul.measurable
@[to_additive]
lemma measurable.mul [monoid α] [topological_monoid α] [second_countable_topology α]
{f : δ → α} {g : δ → α} : measurable f → measurable g → measurable (λa, f a * g a) :=
continuous_mul.measurable2
@[to_additive]
lemma finset.measurable_prod {ι : Type*} [comm_monoid α] [topological_monoid α]
[second_countable_topology α] {f : ι → δ → α} (s : finset ι) (hf : ∀i, measurable (f i)) :
measurable (λa, s.prod (λi, f i a)) :=
finset.induction_on s
(by simp only [finset.prod_empty, measurable_const])
(assume i s his ih, by simpa [his] using (hf i).mul ih)
@[to_additive]
lemma measurable_inv [group α] [topological_group α] : measurable (has_inv.inv : α → α) :=
continuous_inv.measurable
@[to_additive]
lemma measurable.inv [group α] [topological_group α] {f : δ → α} (hf : measurable f) :
measurable (λa, (f a)⁻¹) :=
measurable_inv.comp hf
lemma measurable_inv' {α : Type*} [normed_field α] [measurable_space α] [borel_space α] :
measurable (has_inv.inv : α → α) :=
measurable_of_continuous_on_compl_singleton 0 normed_field.continuous_on_inv
lemma measurable.inv' {α : Type*} [normed_field α] [measurable_space α] [borel_space α]
{f : δ → α} (hf : measurable f) :
measurable (λa, (f a)⁻¹) :=
measurable_inv'.comp hf
@[to_additive]
lemma measurable.of_inv [group α] [topological_group α] {f : δ → α}
(hf : measurable (λ a, (f a)⁻¹)) : measurable f :=
by simpa only [inv_inv] using hf.inv
@[to_additive]
lemma measurable_inv_iff [group α] [topological_group α] {f : δ → α} :
measurable (λ a, (f a)⁻¹) ↔ measurable f :=
⟨measurable.of_inv, measurable.inv⟩
lemma measurable.sub [add_group α] [topological_add_group α] [second_countable_topology α]
{f g : δ → α} (hf : measurable f) (hg : measurable g) :
measurable (λ x, f x - g x) :=
hf.add hg.neg
lemma measurable.is_lub [linear_order α] [order_topology α] [second_countable_topology α]
{ι} [encodable ι] {f : ι → δ → α} {g : δ → α} (hf : ∀ i, measurable (f i))
(hg : ∀ b, is_lub {a | ∃ i, f i b = a} (g b)) :
measurable g :=
begin
change ∀ b, is_lub (range $ λ i, f i b) (g b) at hg,
rw [‹borel_space α›.measurable_eq, borel_eq_generate_Ioi α],
apply measurable_generate_from,
rintro _ ⟨a, rfl⟩,
simp only [set.preimage, mem_Ioi, lt_is_lub_iff (hg _), exists_range_iff, set_of_exists],
exact is_measurable.Union (λ i, hf i _ (is_open_lt' _).is_measurable)
end
lemma measurable.is_glb [linear_order α] [order_topology α] [second_countable_topology α]
{ι} [encodable ι] {f : ι → δ → α} {g : δ → α} (hf : ∀ i, measurable (f i))
(hg : ∀ b, is_glb {a | ∃ i, f i b = a} (g b)) :
measurable g :=
begin
change ∀ b, is_glb (range $ λ i, f i b) (g b) at hg,
rw [‹borel_space α›.measurable_eq, borel_eq_generate_Iio α],
apply measurable_generate_from,
rintro _ ⟨a, rfl⟩,
simp only [set.preimage, mem_Iio, is_glb_lt_iff (hg _), exists_range_iff, set_of_exists],
exact is_measurable.Union (λ i, hf i _ (is_open_gt' _).is_measurable)
end
lemma measurable_supr [complete_linear_order α] [order_topology α] [second_countable_topology α]
{ι} [encodable ι] {f : ι → δ → α} (hf : ∀ i, measurable (f i)) :
measurable (λ b, ⨆ i, f i b) :=
measurable.is_lub hf $ λ b, is_lub_supr
lemma measurable_infi [complete_linear_order α] [order_topology α] [second_countable_topology α]
{ι} [encodable ι] {f : ι → δ → α} (hf : ∀ i, measurable (f i)) :
measurable (λ b, ⨅ i, f i b) :=
measurable.is_glb hf $ λ b, is_glb_infi
lemma measurable.supr_Prop {α} [measurable_space α] [complete_lattice α]
(p : Prop) {f : δ → α} (hf : measurable f) :
measurable (λ b, ⨆ h : p, f b) :=
classical.by_cases
(assume h : p, begin convert hf, funext, exact supr_pos h end)
(assume h : ¬p, begin convert measurable_const, funext, exact supr_neg h end)
lemma measurable.infi_Prop {α} [measurable_space α] [complete_lattice α]
(p : Prop) {f : δ → α} (hf : measurable f) :
measurable (λ b, ⨅ h : p, f b) :=
classical.by_cases
(assume h : p, begin convert hf, funext, exact infi_pos h end )
(assume h : ¬p, begin convert measurable_const, funext, exact infi_neg h end)
lemma measurable_bsupr [complete_linear_order α] [order_topology α] [second_countable_topology α]
{ι} [encodable ι] (p : ι → Prop) {f : ι → δ → α} (hf : ∀ i, measurable (f i)) :
measurable (λ b, ⨆ i (hi : p i), f i b) :=
measurable_supr $ λ i, (hf i).supr_Prop (p i)
lemma measurable_binfi [complete_linear_order α] [order_topology α] [second_countable_topology α]
{ι} [encodable ι] (p : ι → Prop) {f : ι → δ → α} (hf : ∀ i, measurable (f i)) :
measurable (λ b, ⨅ i (hi : p i), f i b) :=
measurable_infi $ λ i, (hf i).infi_Prop (p i)
/-- Convert a `homeomorph` to a `measurable_equiv`. -/
def homemorph.to_measurable_equiv (h : α ≃ₜ β) :
measurable_equiv α β :=
{ to_equiv := h.to_equiv,
measurable_to_fun := h.continuous_to_fun.measurable,
measurable_inv_fun := h.continuous_inv_fun.measurable }
end borel_space
instance empty.borel_space : borel_space empty := ⟨borel_eq_top_of_discrete.symm⟩
instance unit.borel_space : borel_space unit := ⟨borel_eq_top_of_discrete.symm⟩
instance bool.borel_space : borel_space bool := ⟨borel_eq_top_of_discrete.symm⟩
instance nat.borel_space : borel_space ℕ := ⟨borel_eq_top_of_discrete.symm⟩
instance int.borel_space : borel_space ℤ := ⟨borel_eq_top_of_discrete.symm⟩
instance rat.borel_space : borel_space ℚ := ⟨borel_eq_top_of_encodable.symm⟩
instance real.measurable_space : measurable_space ℝ := borel ℝ
instance real.borel_space : borel_space ℝ := ⟨rfl⟩
instance nnreal.measurable_space : measurable_space nnreal := borel nnreal
instance nnreal.borel_space : borel_space nnreal := ⟨rfl⟩
instance ennreal.measurable_space : measurable_space ennreal := borel ennreal
instance ennreal.borel_space : borel_space ennreal := ⟨rfl⟩
section metric_space
variables [metric_space α] [measurable_space α] [opens_measurable_space α] {x : α} {ε : ℝ}
lemma is_measurable_ball : is_measurable (metric.ball x ε) :=
metric.is_open_ball.is_measurable
lemma is_measurable_closed_ball : is_measurable (metric.closed_ball x ε) :=
metric.is_closed_ball.is_measurable
lemma measurable_dist [second_countable_topology α] :
measurable (λp:α×α, dist p.1 p.2) :=
continuous_dist.measurable
lemma measurable.dist [second_countable_topology α] [measurable_space β] {f g : β → α}
(hf : measurable f) (hg : measurable g) : measurable (λ b, dist (f b) (g b)) :=
continuous_dist.measurable2 hf hg
lemma measurable_nndist [second_countable_topology α] : measurable (λp:α×α, nndist p.1 p.2) :=
continuous_nndist.measurable
lemma measurable.nndist [second_countable_topology α] [measurable_space β] {f g : β → α} :
measurable f → measurable g → measurable (λ b, nndist (f b) (g b)) :=
continuous_nndist.measurable2
end metric_space
section emetric_space
variables [emetric_space α] [measurable_space α] [opens_measurable_space α] {x : α} {ε : ennreal}
lemma is_measurable_eball : is_measurable (emetric.ball x ε) :=
emetric.is_open_ball.is_measurable
lemma measurable_edist [second_countable_topology α] :
measurable (λp:α×α, edist p.1 p.2) :=
continuous_edist.measurable
lemma measurable.edist [second_countable_topology α] [measurable_space β] {f g : β → α} :
measurable f → measurable g → measurable (λ b, edist (f b) (g b)) :=
continuous_edist.measurable2
end emetric_space
namespace real
open measurable_space
lemma borel_eq_generate_from_Ioo_rat :
borel ℝ = generate_from (⋃(a b : ℚ) (h : a < b), {Ioo a b}) :=
borel_eq_generate_from_of_subbasis is_topological_basis_Ioo_rat.2.2
lemma borel_eq_generate_from_Iio_rat :
borel ℝ = generate_from (⋃a:ℚ, {Iio a}) :=
begin
let g, swap,
apply le_antisymm (_ : _ ≤ g) (measurable_space.generate_from_le (λ t, _)),
{ rw borel_eq_generate_from_Ioo_rat,
refine generate_from_le (λ t, _),
simp only [mem_Union], rintro ⟨a, b, h, rfl|⟨⟨⟩⟩⟩,
rw (set.ext (λ x, _) : Ioo (a:ℝ) b = (⋃c>a, - Iio c) ∩ Iio b),
{ have hg : ∀q:ℚ, g.is_measurable (Iio q) :=
λ q, generate_measurable.basic _ (by simp; exact ⟨_, rfl⟩),
refine @is_measurable.inter _ g _ _ _ (hg _),
refine @is_measurable.bUnion _ _ g _ _ (countable_encodable _) (λ c h, _),
exact @is_measurable.compl _ _ g (hg _) },
{ simp [Ioo, Iio],
refine and_congr _ iff.rfl,
exact ⟨λ h,
let ⟨c, ac, cx⟩ := exists_rat_btwn h in
⟨c, rat.cast_lt.1 ac, le_of_lt cx⟩,
λ ⟨c, ac, cx⟩, lt_of_lt_of_le (rat.cast_lt.2 ac) cx⟩ } },
{ simp, rintro r rfl,
exact is_open_Iio.is_measurable }
end
end real
lemma measurable.sub_nnreal [measurable_space α] {f g : α → nnreal} :
measurable f → measurable g → measurable (λ a, f a - g a) :=
nnreal.continuous_sub.measurable2
lemma measurable.nnreal_of_real [measurable_space α] {f : α → ℝ} (hf : measurable f) :
measurable (λ x, nnreal.of_real (f x)) :=
nnreal.continuous_of_real.measurable.comp hf
lemma measurable.nnreal_coe [measurable_space α] {f : α → nnreal} (hf : measurable f) :
measurable (λ x, (f x : ℝ)) :=
nnreal.continuous_coe.measurable.comp hf
lemma measurable.ennreal_coe [measurable_space α] {f : α → nnreal} (hf : measurable f) :
measurable (λ x, (f x : ennreal)) :=
(ennreal.continuous_coe.2 continuous_id).measurable.comp hf
lemma measurable.ennreal_of_real [measurable_space α] {f : α → ℝ} (hf : measurable f) :
measurable (λ x, ennreal.of_real (f x)) :=
ennreal.continuous_of_real.measurable.comp hf
/-- The set of finite `ennreal` numbers is `measurable_equiv` to `nnreal`. -/
def measurable_equiv.ennreal_equiv_nnreal : measurable_equiv {r : ennreal | r ≠ ⊤} nnreal :=
ennreal.ne_top_homeomorph_nnreal.to_measurable_equiv
namespace ennreal
open filter
lemma measurable_coe : measurable (coe : nnreal → ennreal) :=
measurable_id.ennreal_coe
lemma measurable_of_measurable_nnreal [measurable_space α] {f : ennreal → α}
(h : measurable (λp:nnreal, f p)) : measurable f :=
measurable_of_measurable_on_compl_singleton ⊤ is_measurable_singleton
(measurable_equiv.ennreal_equiv_nnreal.symm.measurable_coe_iff.1 h)
/-- `ennreal` is `measurable_equiv` to `nnreal ⊕ unit`. -/
def ennreal_equiv_sum :
measurable_equiv ennreal (nnreal ⊕ unit) :=
{ measurable_to_fun := measurable_of_measurable_nnreal measurable_inl,
measurable_inv_fun := measurable_sum measurable_coe (@measurable_const ennreal unit _ _ ⊤),
.. equiv.option_equiv_sum_punit nnreal }
lemma measurable_of_measurable_nnreal_nnreal [measurable_space α] [measurable_space β]
(f : ennreal → ennreal → β) {g : α → ennreal} {h : α → ennreal}
(h₁ : measurable (λp:nnreal × nnreal, f p.1 p.2))
(h₂ : measurable (λr:nnreal, f ⊤ r))
(h₃ : measurable (λr:nnreal, f r ⊤))
(hg : measurable g) (hh : measurable h) : measurable (λa, f (g a) (h a)) :=
let e : measurable_equiv (ennreal × ennreal)
(((nnreal × nnreal) ⊕ (nnreal × unit)) ⊕ ((unit × nnreal) ⊕ (unit × unit))) :=
(measurable_equiv.prod_congr ennreal_equiv_sum ennreal_equiv_sum).trans
(measurable_equiv.sum_prod_sum _ _ _ _) in
have measurable (λp:ennreal×ennreal, f p.1 p.2),
begin
refine e.symm.measurable_coe_iff.1 (measurable_sum (measurable_sum _ _) (measurable_sum _ _)),
{ show measurable (λp:nnreal × nnreal, f p.1 p.2),
exact h₁ },
{ show measurable (λp:nnreal × unit, f p.1 ⊤),
exact h₃.comp (measurable.fst measurable_id) },
{ show measurable ((λp:nnreal, f ⊤ p) ∘ (λp:unit × nnreal, p.2)),
exact h₂.comp (measurable.snd measurable_id) },
{ show measurable (λp:unit × unit, f ⊤ ⊤),
exact measurable_const }
end,
this.comp (measurable.prod_mk hg hh)
lemma measurable_of_real : measurable ennreal.of_real :=
ennreal.continuous_of_real.measurable
end ennreal
lemma measurable.ennreal_mul {α : Type*} [measurable_space α] {f g : α → ennreal} :
measurable f → measurable g → measurable (λa, f a * g a) :=
begin
refine ennreal.measurable_of_measurable_nnreal_nnreal (*) _ _ _,
{ simp only [ennreal.coe_mul.symm],
exact ennreal.measurable_coe.comp measurable_mul },
{ simp [ennreal.top_mul],
exact measurable.if
(is_closed_eq continuous_id continuous_const).is_measurable
measurable_const
measurable_const },
{ simp [ennreal.mul_top],
exact measurable.if
(is_closed_eq continuous_id continuous_const).is_measurable
measurable_const
measurable_const }
end
lemma measurable.ennreal_add {α : Type*} [measurable_space α] {f g : α → ennreal} :
measurable f → measurable g → measurable (λa, f a + g a) :=
begin
refine ennreal.measurable_of_measurable_nnreal_nnreal (+) _ _ _,
{ simp only [ennreal.coe_add.symm],
exact ennreal.measurable_coe.comp measurable_add },
{ simp [measurable_const] },
{ simp [measurable_const] }
end
lemma measurable.ennreal_sub {α : Type*} [measurable_space α] {f g : α → ennreal} :
measurable f → measurable g → measurable (λa, f a - g a) :=
begin
refine ennreal.measurable_of_measurable_nnreal_nnreal (has_sub.sub) _ _ _,
{ simp only [ennreal.coe_sub.symm],
exact ennreal.measurable_coe.comp nnreal.continuous_sub.measurable },
{ simp [measurable_const] },
{ simp [measurable_const] }
end
section normed_group
variables [measurable_space α] [normed_group α] [opens_measurable_space α] [measurable_space β]
lemma measurable_norm : measurable (norm : α → ℝ) :=
continuous_norm.measurable
lemma measurable.norm {f : β → α} (hf : measurable f) : measurable (λa, norm (f a)) :=
measurable_norm.comp hf
lemma measurable_nnnorm : measurable (nnnorm : α → nnreal) :=
continuous_nnnorm.measurable
lemma measurable.nnnorm {f : β → α} (hf : measurable f) : measurable (λa, nnnorm (f a)) :=
measurable_nnnorm.comp hf
lemma measurable.ennnorm {f : β → α} (hf : measurable f) :
measurable (λa, (nnnorm (f a) : ennreal)) :=
hf.nnnorm.ennreal_coe
end normed_group
|
77ff98901c1c4a3b2566c0fd5529a4aeae0d4a3e | fa02ed5a3c9c0adee3c26887a16855e7841c668b | /src/data/rel.lean | 00ce75a8d0fa2ec89bc417b6458e5df43c833992 | [
"Apache-2.0"
] | permissive | jjgarzella/mathlib | 96a345378c4e0bf26cf604aed84f90329e4896a2 | 395d8716c3ad03747059d482090e2bb97db612c8 | refs/heads/master | 1,686,480,124,379 | 1,625,163,323,000 | 1,625,163,323,000 | 281,190,421 | 2 | 0 | Apache-2.0 | 1,595,268,170,000 | 1,595,268,169,000 | null | UTF-8 | Lean | false | false | 6,431 | lean | /-
Copyright (c) 2018 Jeremy Avigad. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Jeremy Avigad
Operations on set-valued functions, aka partial multifunctions, aka relations.
-/
import data.set.lattice
variables {α : Type*} {β : Type*} {γ : Type*}
/-- A relation on `α` and `β`, aka a set-valued function, aka a partial multifunction --/
@[derive complete_lattice, derive inhabited]
def rel (α : Type*) (β : Type*) := α → β → Prop
namespace rel
variables {δ : Type*} (r : rel α β)
/-- The inverse relation : `r.inv x y ↔ r y x`. Note that this is *not* a groupoid inverse. -/
def inv : rel β α := flip r
lemma inv_def (x : α) (y : β) : r.inv y x ↔ r x y := iff.rfl
lemma inv_inv : inv (inv r) = r := by { ext x y, reflexivity }
/-- Domain of a relation -/
def dom := {x | ∃ y, r x y}
/-- Codomain aka range of a relation-/
def codom := {y | ∃ x, r x y}
lemma codom_inv : r.inv.codom = r.dom := by { ext x y, reflexivity }
lemma dom_inv : r.inv.dom = r.codom := by { ext x y, reflexivity}
/-- Composition of relation; note that it follows the `category_theory/` order of arguments. -/
def comp (r : rel α β) (s : rel β γ) : rel α γ :=
λ x z, ∃ y, r x y ∧ s y z
local infixr ` ∘ ` :=rel.comp
lemma comp_assoc (r : rel α β) (s : rel β γ) (t : rel γ δ) :
(r ∘ s) ∘ t = r ∘ s ∘ t :=
begin
unfold comp, ext x w, split,
{ rintros ⟨z, ⟨y, rxy, syz⟩, tzw⟩, exact ⟨y, rxy, z, syz, tzw⟩ },
rintros ⟨y, rxy, z, syz, tzw⟩, exact ⟨z, ⟨y, rxy, syz⟩, tzw⟩
end
@[simp]
lemma comp_right_id (r : rel α β) : r ∘ @eq β = r :=
by { unfold comp, ext y, simp }
@[simp]
lemma comp_left_id (r : rel α β) : @eq α ∘ r = r :=
by { unfold comp, ext x, simp }
lemma inv_id : inv (@eq α) = @eq α :=
by { ext x y, split; apply eq.symm }
lemma inv_comp (r : rel α β) (s : rel β γ) : inv (r ∘ s) = inv s ∘ inv r :=
by { ext x z, simp [comp, inv, flip, and.comm] }
/-- Image of a set under a relation -/
def image (s : set α) : set β := {y | ∃ x ∈ s, r x y}
lemma mem_image (y : β) (s : set α) : y ∈ image r s ↔ ∃ x ∈ s, r x y :=
iff.rfl
lemma image_subset : ((⊆) ⇒ (⊆)) r.image r.image :=
assume s t h y ⟨x, xs, rxy⟩, ⟨x, h xs, rxy⟩
lemma image_mono : monotone r.image := r.image_subset
lemma image_inter (s t : set α) : r.image (s ∩ t) ⊆ r.image s ∩ r.image t :=
r.image_mono.map_inf_le s t
lemma image_union (s t : set α) : r.image (s ∪ t) = r.image s ∪ r.image t :=
le_antisymm
(λ y ⟨x, xst, rxy⟩, xst.elim (λ xs, or.inl ⟨x, ⟨xs, rxy⟩⟩) (λ xt, or.inr ⟨x, ⟨xt, rxy⟩⟩))
(r.image_mono.le_map_sup s t)
@[simp]
lemma image_id (s : set α) : image (@eq α) s = s :=
by { ext x, simp [mem_image] }
lemma image_comp (s : rel β γ) (t : set α) : image (r ∘ s) t = image s (image r t) :=
begin
ext z, simp only [mem_image, comp], split,
{ rintros ⟨x, xt, y, rxy, syz⟩, exact ⟨y, ⟨x, xt, rxy⟩, syz⟩ },
rintros ⟨y, ⟨x, xt, rxy⟩, syz⟩, exact ⟨x, xt, y, rxy, syz⟩
end
lemma image_univ : r.image set.univ = r.codom := by { ext y, simp [mem_image, codom] }
/-- Preimage of a set under a relation `r`. Same as the image of `s` under `r.inv` -/
def preimage (s : set β) : set α := image (inv r) s
lemma mem_preimage (x : α) (s : set β) : x ∈ preimage r s ↔ ∃ y ∈ s, r x y :=
iff.rfl
lemma preimage_def (s : set β) : preimage r s = {x | ∃ y ∈ s, r x y} :=
set.ext $ λ x, mem_preimage _ _ _
lemma preimage_mono {s t : set β} (h : s ⊆ t) : r.preimage s ⊆ r.preimage t :=
image_mono _ h
lemma preimage_inter (s t : set β) : r.preimage (s ∩ t) ⊆ r.preimage s ∩ r.preimage t :=
image_inter _ s t
lemma preimage_union (s t : set β) : r.preimage (s ∪ t) = r.preimage s ∪ r.preimage t :=
image_union _ s t
lemma preimage_id (s : set α) : preimage (@eq α) s = s :=
by simp only [preimage, inv_id, image_id]
lemma preimage_comp (s : rel β γ) (t : set γ) :
preimage (r ∘ s) t = preimage r (preimage s t) :=
by simp only [preimage, inv_comp, image_comp]
lemma preimage_univ : r.preimage set.univ = r.dom :=
by { rw [preimage, image_univ, codom_inv] }
/-- Core of a set `s : set β` w.r.t `r : rel α β` is the set of `x : α` that are related *only*
to elements of `s`. -/
def core (s : set β) := {x | ∀ y, r x y → y ∈ s}
lemma mem_core (x : α) (s : set β) : x ∈ core r s ↔ ∀ y, r x y → y ∈ s :=
iff.rfl
lemma core_subset : ((⊆) ⇒ (⊆)) r.core r.core :=
assume s t h x h' y rxy, h (h' y rxy)
lemma core_mono : monotone r.core := r.core_subset
lemma core_inter (s t : set β) : r.core (s ∩ t) = r.core s ∩ r.core t :=
set.ext (by simp [mem_core, imp_and_distrib, forall_and_distrib])
lemma core_union (s t : set β) : r.core s ∪ r.core t ⊆ r.core (s ∪ t) :=
r.core_mono.le_map_sup s t
@[simp] lemma core_univ : r.core set.univ = set.univ := set.ext (by simp [mem_core])
lemma core_id (s : set α) : core (@eq α) s = s :=
by simp [core]
lemma core_comp (s : rel β γ) (t : set γ) :
core (r ∘ s) t = core r (core s t) :=
begin
ext x, simp [core, comp], split,
{ intros h y rxy z syz, exact h z y rxy syz },
intros h z y rzy syz, exact h y rzy z syz
end
/-- Restrict the domain of a relation to a subtype. -/
def restrict_domain (s : set α) : rel {x // x ∈ s} β :=
λ x y, r x.val y
theorem image_subset_iff (s : set α) (t : set β) : image r s ⊆ t ↔ s ⊆ core r t :=
iff.intro
(λ h x xs y rxy, h ⟨x, xs, rxy⟩)
(λ h y ⟨x, xs, rxy⟩, h xs y rxy)
theorem core_preimage_gc : galois_connection (image r) (core r) :=
image_subset_iff _
end rel
namespace function
/-- The graph of a function as a relation. -/
def graph (f : α → β) : rel α β := λ x y, f x = y
end function
namespace set
-- TODO: if image were defined with bounded quantification in corelib, the next two would
-- be definitional
lemma image_eq (f : α → β) (s : set α) : f '' s = (function.graph f).image s :=
by simp [set.image, function.graph, rel.image]
lemma preimage_eq (f : α → β) (s : set β) :
f ⁻¹' s = (function.graph f).preimage s :=
by simp [set.preimage, function.graph, rel.preimage, rel.inv, flip, rel.image]
lemma preimage_eq_core (f : α → β) (s : set β) :
f ⁻¹' s = (function.graph f).core s :=
by simp [set.preimage, function.graph, rel.core]
end set
|
3d5e267790225c4b9e3d6b07db67cf6d9135afcc | 35677d2df3f081738fa6b08138e03ee36bc33cad | /src/tactic/wlog.lean | e17096f710494469abb8a957d80229b6b3bfbf72 | [
"Apache-2.0"
] | permissive | gebner/mathlib | eab0150cc4f79ec45d2016a8c21750244a2e7ff0 | cc6a6edc397c55118df62831e23bfbd6e6c6b4ab | refs/heads/master | 1,625,574,853,976 | 1,586,712,827,000 | 1,586,712,827,000 | 99,101,412 | 1 | 0 | Apache-2.0 | 1,586,716,389,000 | 1,501,667,958,000 | Lean | UTF-8 | Lean | false | false | 9,314 | lean | /-
Copyright (c) 2018 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl
Without loss of generality tactic.
-/
import tactic.tauto tactic.core data.list.perm
open expr tactic lean lean.parser
local postfix `?`:9001 := optional
local postfix *:9001 := many
namespace tactic
private meta def update_pp_name : expr → name → expr
| (local_const n _ bi d) pp := local_const n pp bi d
| e n := e
private meta def elim_or : ℕ → expr → tactic (list expr)
| 0 h := fail "zero cases"
| 1 h := return [h]
| (n + 1) h := do
[(_, [hl], []), (_, [hr], [])] ← induction h, -- there should be no dependent terms
[gl, gr] ← get_goals,
set_goals [gr],
hsr ← elim_or n hr,
gsr ← get_goals,
set_goals (gl :: gsr),
return (hl :: hsr)
private meta def dest_or : expr → tactic (list expr) | e := do
`(%%a ∨ %%b) ← whnf e | return [e],
lb ← dest_or b,
return (a :: lb)
private meta def match_perms (pat : pattern) : expr → tactic (list $ list expr) | t :=
(do
m ← match_pattern pat t,
guard (m.2.all expr.is_local_constant),
return [m.2]) <|>
(do
`(%%l ∨ %%r) ← whnf t,
m ← match_pattern pat l,
rs ← match_perms r,
return (m.2 :: rs))
private meta def update_type : expr → expr → expr
| (local_const n pp bi d) t := local_const n pp bi t
| e t := e
private meta def intron' : ℕ → tactic (list expr)
| 0 := return []
| (i + 1) := do
n ← intro1,
ls ← intron' i,
return (n :: ls)
meta def wlog (vars' : list expr) (h_cases fst_case : expr) (perms : list (list expr)) :
tactic unit := do
guard h_cases.is_local_constant,
-- reorder s.t. context is Γ ⬝ vars ⬝ cases ⊢ ∀deps, …
nr ← revert_lst (vars' ++ [h_cases]),
vars ← intron' vars'.length,
h_cases ← intro h_cases.local_pp_name,
cases ← infer_type h_cases,
h_fst_case ←
mk_local_def h_cases.local_pp_name
(fst_case.instantiate_locals $ (vars'.zip vars).map $ λ⟨o, n⟩, (o.local_uniq_name, n)),
((), pr) ← solve_aux cases (repeat $ exact h_fst_case <|> left >> skip),
t ← target,
fixed_vars ← vars.mmap (λv, do t ← infer_type v, return (update_type v t) ),
let t' := (instantiate_local h_cases.local_uniq_name pr t).pis (fixed_vars ++ [h_fst_case]),
(h, [g]) ← local_proof `this t' (do
clear h_cases,
vars.mmap clear,
intron nr),
h₀ :: hs ← elim_or perms.length h_cases,
solve1 (do
exact (h.mk_app $ vars ++ [h₀])),
focus ((hs.zip perms.tail).map $ λ⟨h_case, perm⟩, do
let p_v := (vars'.zip vars).map (λ⟨p, v⟩, (p.local_uniq_name, v)),
let p := perm.map (λp, p.instantiate_locals p_v),
note `this none (h.mk_app $ p ++ [h_case]),
clear h,
return ()),
gs ← get_goals,
set_goals (g :: gs)
namespace interactive
open interactive interactive.types expr
private meta def parse_permutations : option (list (list name)) → tactic (list (list expr))
| none := return []
| (some []) := return []
| (some perms@(p₀ :: ps)) := do
(guard p₀.nodup <|>
fail "No permutation `xs_i` in `using [xs_1, …, xs_n]` should contain the same variable twice."),
(guard (perms.all $ λp, p.perm p₀) <|>
fail "The permutations `xs_i` in `using [xs_1, …, xs_n]` must be permutations of the same variables."),
perms.mmap (λp, p.mmap get_local)
/-- Without loss of generality: reduces to one goal under variables permutations.
Given a goal of the form `g xs`, a predicate `p` over a set of variables, as well as variable
permutations `xs_i`. Then `wlog` produces goals of the form
The case goal, i.e. the permutation `xs_i` covers all possible cases:
`⊢ p xs_0 ∨ ⋯ ∨ p xs_n`
The main goal, i.e. the goal reduced to `xs_0`:
`(h : p xs_0) ⊢ g xs_0`
The invariant goals, i.e. `g` is invariant under `xs_i`:
`(h : p xs_i) (this : g xs_0) ⊢ gs xs_i`
Either the permutation is provided, or a proof of the disjunction is provided to compute the
permutation. The disjunction need to be in assoc normal form, e.g. `p₀ ∨ (p₁ ∨ p₂)`. In many cases
the invariant goals can be solved by AC rewriting using `cc` etc.
Example:
On a state `(n m : ℕ) ⊢ p n m` the tactic `wlog h : n ≤ m using [n m, m n]` produces the following
states:
`(n m : ℕ) ⊢ n ≤ m ∨ m ≤ n`
`(n m : ℕ) (h : n ≤ m) ⊢ p n m`
`(n m : ℕ) (h : m ≤ n) (this : p n m) ⊢ p m n`
`wlog` supports different calling conventions. The name `h` is used to give a name to the introduced
case hypothesis. If the name is avoided, the default will be `case`.
(1) `wlog : p xs0 using [xs0, …, xsn]`
Results in the case goal `p xs0 ∨ ⋯ ∨ ps xsn`, the main goal `(case : p xs0) ⊢ g xs0` and the
invariance goals `(case : p xsi) (this : g xs0) ⊢ g xsi`.
(2) `wlog : p xs0 := r using xs0`
The expression `r` is a proof of the shape `p xs0 ∨ ⋯ ∨ p xsi`, it is also used to compute the
variable permutations.
(3) `wlog := r using xs0`
The expression `r` is a proof of the shape `p xs0 ∨ ⋯ ∨ p xsi`, it is also used to compute the
variable permutations. This is not as stable as (2), for example `p` cannot be a disjunction.
(4) `wlog : R x y using x y` and `wlog : R x y`
Produces the case `R x y ∨ R y x`. If `R` is ≤, then the disjunction discharged using linearity.
If `using x y` is avoided then `x` and `y` are the last two variables appearing in the
expression `R x y`. -/
meta def wlog
(h : parse ident?)
(pat : parse (tk ":" *> texpr)?)
(cases : parse (tk ":=" *> texpr)?)
(perms : parse (tk "using" *> (list_of (ident*) <|> (λx, [x]) <$> ident*))?)
(discharger : tactic unit :=
(tactic.solve_by_elim <|> tactic.tautology tt <|> using_smt (smt_tactic.intros >> smt_tactic.solve_goals))) :
tactic unit := do
perms ← parse_permutations perms,
(pat, cases_pr, cases_goal, vars, perms) ← (match cases with
| some r := do
vars::_ ← return perms |
fail "At least one set of variables expected, i.e. `using x y` or `using [x y, y x]`.",
cases_pr ← to_expr r,
cases_pr ← (if cases_pr.is_local_constant
then return $ match h with some n := update_pp_name cases_pr n | none := cases_pr end
else do
note (h.get_or_else `case) none cases_pr),
cases ← infer_type cases_pr,
(pat, perms') ← match pat with
| some pat := do
pat ← to_expr pat,
let vars' := vars.filter $ λv, v.occurs pat,
case_pat ← mk_pattern [] vars' pat [] vars',
perms' ← match_perms case_pat cases,
return (pat, perms')
| none := do
(p :: ps) ← dest_or cases,
let vars' := vars.filter $ λv, v.occurs p,
case_pat ← mk_pattern [] vars' p [] vars',
perms' ← (p :: ps).mmap (λp, do m ← match_pattern case_pat p, return m.2),
return (p, perms')
end,
let vars_name := vars.map local_uniq_name,
guard (perms'.all $ λp, p.all $ λv, v.is_local_constant ∧ v.local_uniq_name ∈ vars_name) <|>
fail "Cases contains variables not declared in `using x y z`",
perms ← (if perms.length = 1
then do
return (perms'.map $ λp, p ++ vars.filter (λv, p.all (λv', v'.local_uniq_name ≠ v.local_uniq_name)))
else do
guard (perms.length = perms'.length) <|>
fail "The provided permutation list has a different length then the provided cases.",
return perms),
return (pat, cases_pr, @none expr, vars, perms)
| none := do
let name_h := h.get_or_else `case,
some pat ← return pat | fail "Either specify cases or a pattern with permutations",
pat ← to_expr pat,
(do
[x, y] ← match perms with
| [] := return pat.list_local_consts
| [l] := return l
| _ := failed
end,
let cases := mk_or_lst [pat, pat.instantiate_locals [(x.local_uniq_name, y), (y.local_uniq_name, x)]],
(do
`(%%x' ≤ %%y') ← return pat,
(cases_pr, []) ← local_proof name_h cases (exact ``(le_total %%x' %%y')),
return (pat, cases_pr, none, [x, y], [[x, y], [y, x]]))
<|>
(do
(cases_pr, [g]) ← local_proof name_h cases skip,
return (pat, cases_pr, some g, [x, y], [[x, y], [y, x]]))) <|>
(do
guard (perms.length ≥ 2) <|>
fail ("To generate cases at least two permutations are required, i.e. `using [x y, y x]`" ++
" or exactly 0 or 2 variables"),
(vars :: perms') ← return perms,
let names := vars.map local_uniq_name,
let cases := mk_or_lst (pat :: perms'.map (λp, pat.instantiate_locals (names.zip p))),
(cases_pr, [g]) ← local_proof name_h cases skip,
return (pat, cases_pr, some g, vars, perms))
end),
let name_fn :=
(if perms.length = 2 then λi, `invariant else λi, mk_simple_name ("invariant_" ++ to_string (i + 1))),
with_enable_tags $ tactic.focus1 $ do
t ← get_main_tag,
tactic.wlog vars cases_pr pat perms,
tactic.focus (set_main_tag (mk_num_name `_case 0 :: `main :: t) ::
(list.range (perms.length - 1)).map (λi, do
set_main_tag (mk_num_name `_case 0 :: name_fn i :: t),
try discharger)),
match cases_goal with
| some g := do
set_tag g (mk_num_name `_case 0 :: `cases :: t),
gs ← get_goals,
set_goals (g :: gs)
| none := skip
end
end interactive
end tactic
|
3dd32e35b6c60c27788dd5f924a94821df88b230 | 6e41ee3ac9b96e8980a16295cc21f131e731884f | /library/data/bool.lean | 36f1b16e72cc38a12c1bbe99690b7baf120c06e1 | [
"Apache-2.0"
] | permissive | EgbertRijke/lean | 3426cfa0e5b3d35d12fc3fd7318b35574cb67dc3 | 4f2e0c6d7fc9274d953cfa1c37ab2f3e799ab183 | refs/heads/master | 1,610,834,871,476 | 1,422,159,801,000 | 1,422,159,801,000 | null | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 3,583 | lean | /-
Copyright (c) 2014 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Module: data.bool
Author: Leonardo de Moura
-/
import logic.eq
open eq eq.ops decidable
namespace bool
attribute bor [reducible]
attribute band [reducible]
theorem dichotomy (b : bool) : b = ff ∨ b = tt :=
cases_on b (or.inl rfl) (or.inr rfl)
theorem cond.ff {A : Type} (t e : A) : cond ff t e = e :=
rfl
theorem cond.tt {A : Type} (t e : A) : cond tt t e = t :=
rfl
theorem ff_ne_tt : ¬ ff = tt :=
assume H : ff = tt, absurd
(calc true = cond tt true false : !cond.tt⁻¹
... = cond ff true false : {H⁻¹}
... = false : cond.ff)
true_ne_false
theorem bor.tt_left (a : bool) : bor tt a = tt :=
rfl
notation a || b := bor a b
theorem bor.tt_right (a : bool) : a || tt = tt :=
cases_on a rfl rfl
theorem bor.ff_left (a : bool) : ff || a = a :=
cases_on a rfl rfl
theorem bor.ff_right (a : bool) : a || ff = a :=
cases_on a rfl rfl
theorem bor.id (a : bool) : a || a = a :=
cases_on a rfl rfl
theorem bor.comm (a b : bool) : a || b = b || a :=
cases_on a
(cases_on b rfl rfl)
(cases_on b rfl rfl)
theorem bor.assoc (a b c : bool) : (a || b) || c = a || (b || c) :=
cases_on a
(calc (ff || b) || c = b || c : {!bor.ff_left}
... = ff || (b || c) : !bor.ff_left⁻¹)
(calc (tt || b) || c = tt || c : {!bor.tt_left}
... = tt : !bor.tt_left
... = tt || (b || c) : !bor.tt_left⁻¹)
theorem bor.to_or {a b : bool} : a || b = tt → a = tt ∨ b = tt :=
rec_on a
(assume H : ff || b = tt,
have Hb : b = tt, from !bor.ff_left ▸ H,
or.inr Hb)
(assume H, or.inl rfl)
theorem band.ff_left (a : bool) : ff && a = ff :=
rfl
theorem band.tt_left (a : bool) : tt && a = a :=
cases_on a rfl rfl
theorem band.ff_right (a : bool) : a && ff = ff :=
cases_on a rfl rfl
theorem band.tt_right (a : bool) : a && tt = a :=
cases_on a rfl rfl
theorem band.id (a : bool) : a && a = a :=
cases_on a rfl rfl
theorem band.comm (a b : bool) : a && b = b && a :=
cases_on a
(cases_on b rfl rfl)
(cases_on b rfl rfl)
theorem band.assoc (a b c : bool) : (a && b) && c = a && (b && c) :=
cases_on a
(calc (ff && b) && c = ff && c : {!band.ff_left}
... = ff : !band.ff_left
... = ff && (b && c) : !band.ff_left⁻¹)
(calc (tt && b) && c = b && c : {!band.tt_left}
... = tt && (b && c) : !band.tt_left⁻¹)
theorem band.eq_tt_elim_left {a b : bool} (H : a && b = tt) : a = tt :=
or.elim (dichotomy a)
(assume H0 : a = ff,
absurd
(calc ff = ff && b : !band.ff_left⁻¹
... = a && b : {H0⁻¹}
... = tt : H)
ff_ne_tt)
(assume H1 : a = tt, H1)
theorem band.eq_tt_elim_right {a b : bool} (H : a && b = tt) : b = tt :=
band.eq_tt_elim_left (!band.comm ⬝ H)
theorem bnot.bnot (a : bool) : bnot (bnot a) = a :=
cases_on a rfl rfl
theorem bnot.false : bnot ff = tt :=
rfl
theorem bnot.true : bnot tt = ff :=
rfl
protected definition is_inhabited [instance] : inhabited bool :=
inhabited.mk ff
protected definition has_decidable_eq [instance] : decidable_eq bool :=
take a b : bool,
rec_on a
(rec_on b (inl rfl) (inr ff_ne_tt))
(rec_on b (inr (ne.symm ff_ne_tt)) (inl rfl))
end bool
|
0cffc8cfa8570b35f005cde5dd26bb7655954819 | 46125763b4dbf50619e8846a1371029346f4c3db | /src/tactic/converter/binders.lean | 6f31530dca1317965f836be5c31a5880b051c9d1 | [
"Apache-2.0"
] | permissive | thjread/mathlib | a9d97612cedc2c3101060737233df15abcdb9eb1 | 7cffe2520a5518bba19227a107078d83fa725ddc | refs/heads/master | 1,615,637,696,376 | 1,583,953,063,000 | 1,583,953,063,000 | 246,680,271 | 0 | 0 | Apache-2.0 | 1,583,960,875,000 | 1,583,960,875,000 | null | UTF-8 | Lean | false | false | 7,777 | lean | /-
Copyright (c) 2017 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl
Binder elimination
-/
import order tactic.converter.old_conv
namespace old_conv
open tactic monad
meta instance : monad_fail old_conv :=
{ fail := λ α s, (λr e, tactic.fail (to_fmt s) : old_conv α), ..old_conv.monad }
meta instance : has_monad_lift tactic old_conv :=
⟨λα, lift_tactic⟩
meta instance (α : Type) : has_coe (tactic α) (old_conv α) :=
⟨monad_lift⟩
meta def current_relation : old_conv name := λr lhs, return ⟨r, lhs, none⟩
meta def head_beta : old_conv unit :=
λ r e, do n ← tactic.head_beta e, return ⟨(), n, none⟩
/- congr should forward data! -/
meta def congr_arg : old_conv unit → old_conv unit := congr_core (return ())
meta def congr_fun : old_conv unit → old_conv unit := λc, congr_core c (return ())
meta def congr_rule (congr : expr) (cs : list (list expr → old_conv unit)) : old_conv unit := λr lhs, do
meta_rhs ← infer_type lhs >>= mk_meta_var, -- is maybe overly restricted for `heq`
t ← mk_app r [lhs, meta_rhs],
((), meta_pr) ← solve_aux t (do
apply congr,
focus $ cs.map $ λc, (do
xs ← intros,
conversion (head_beta >> c xs)),
done),
rhs ← instantiate_mvars meta_rhs,
pr ← instantiate_mvars meta_pr,
return ⟨(), rhs, some pr⟩
meta def congr_binder (congr : name) (cs : expr → old_conv unit) : old_conv unit := do
e ← mk_const congr,
congr_rule e [λbs, do [b] ← return bs, cs b]
meta def funext' : (expr → old_conv unit) → old_conv unit := congr_binder ``_root_.funext
meta def propext' {α : Type} (c : old_conv α) : old_conv α := λr lhs, (do
guard (r = `iff),
c r lhs)
<|> (do
guard (r = `eq),
⟨res, rhs, pr⟩ ← c `iff lhs,
match pr with
| some pr := return ⟨res, rhs, (expr.const `propext [] : expr) lhs rhs pr⟩
| none := return ⟨res, rhs, none⟩
end)
meta def apply (pr : expr) : old_conv unit :=
λ r e, do
sl ← simp_lemmas.mk.add pr,
apply_lemmas sl r e
meta def applyc (n : name) : old_conv unit :=
λ r e, do
sl ← simp_lemmas.mk.add_simp n,
apply_lemmas sl r e
meta def apply' (n : name) : old_conv unit := do
e ← mk_const n,
congr_rule e []
end old_conv
open expr tactic old_conv
/- Binder elimination:
We assume a binder `B : p → Π (α : Sort u), (α → t) → t`, where `t` is a type depending on `p`.
Examples:
∃: there is no `p` and `t` is `Prop`.
⨅, ⨆: here p is `β` and `[complete_lattice β]`, `p` is `β`
Problem: ∀x, _ should be a binder, but is not a constant!
Provide a mechanism to rewrite:
B (x : α) ..x.. (h : x = t), p x = B ..x/t.., p t
Here ..x.. are binders, maybe also some constants which provide commutativity rules with `B`.
-/
meta structure binder_eq_elim :=
(match_binder : expr → tactic (expr × expr)) -- returns the bound type and body
(adapt_rel : old_conv unit → old_conv unit) -- optionally adapt `eq` to `iff`
(apply_comm : old_conv unit) -- apply commutativity rule
(apply_congr : (expr → old_conv unit) → old_conv unit) -- apply congruence rule
(apply_elim_eq : old_conv unit) -- (B (x : β) (h : x = t), s x) = s t
meta def binder_eq_elim.check_eq (b : binder_eq_elim) (x : expr) : expr → tactic unit
| `(@eq %%β %%l %%r) := guard ((l = x ∧ ¬ x.occurs r) ∨ (r = x ∧ ¬ x.occurs l))
| _ := fail "no match"
meta def binder_eq_elim.pull (b : binder_eq_elim) (x : expr) : old_conv unit := do
(β, f) ← lhs >>= (lift_tactic ∘ b.match_binder),
guard (¬ x.occurs β)
<|> b.check_eq x β
<|> (do
b.apply_congr $ λx, binder_eq_elim.pull,
b.apply_comm)
meta def binder_eq_elim.push (b : binder_eq_elim) : old_conv unit :=
b.apply_elim_eq
<|> (do
b.apply_comm,
b.apply_congr $ λx, binder_eq_elim.push)
<|> (do
b.apply_congr $ b.pull,
binder_eq_elim.push)
meta def binder_eq_elim.check (b : binder_eq_elim) (x : expr) : expr → tactic unit
| e := do
(β, f) ← b.match_binder e,
b.check_eq x β
<|> (do
(lam n bi d bd) ← return f,
x ← mk_local' n bi d,
binder_eq_elim.check $ bd.instantiate_var x)
meta def binder_eq_elim.old_conv (b : binder_eq_elim) : old_conv unit := do
(β, f) ← lhs >>= (lift_tactic ∘ b.match_binder),
(lam n bi d bd) ← return f,
x ← mk_local' n bi d,
b.check x (bd.instantiate_var x),
b.adapt_rel b.push
theorem {u v} exists_comm {α : Sort u} {β : Sort v} (p : α → β → Prop) :
(∃a b, p a b) ↔ (∃b a, p a b) :=
⟨λ⟨a, ⟨b, h⟩⟩, ⟨b, ⟨a, h⟩⟩, λ⟨a, ⟨b, h⟩⟩, ⟨b, ⟨a, h⟩⟩⟩
theorem {u v} exists_elim_eq_left {α : Sort u} (a : α) (p : Π(a':α), a' = a → Prop) :
(∃(a':α)(h : a' = a), p a' h) ↔ p a rfl :=
⟨λ⟨a', ⟨h, p_h⟩⟩, match a', h, p_h with ._, rfl, h := h end, λh, ⟨a, rfl, h⟩⟩
theorem {u v} exists_elim_eq_right {α : Sort u} (a : α) (p : Π(a':α), a = a' → Prop) :
(∃(a':α)(h : a = a'), p a' h) ↔ p a rfl :=
⟨λ⟨a', ⟨h, p_h⟩⟩, match a', h, p_h with ._, rfl, h := h end, λh, ⟨a, rfl, h⟩⟩
meta def exists_eq_elim : binder_eq_elim :=
{ match_binder := λe, (do `(@Exists %%β %%f) ← return e, return (β, f)),
adapt_rel := propext',
apply_comm := applyc ``exists_comm,
apply_congr := congr_binder ``exists_congr,
apply_elim_eq := apply' ``exists_elim_eq_left <|> apply' ``exists_elim_eq_right }
theorem {u v} forall_comm {α : Sort u} {β : Sort v} (p : α → β → Prop) :
(∀a b, p a b) ↔ (∀b a, p a b) :=
⟨assume h b a, h a b, assume h b a, h a b⟩
theorem {u v} forall_elim_eq_left {α : Sort u} (a : α) (p : Π(a':α), a' = a → Prop) :
(∀(a':α)(h : a' = a), p a' h) ↔ p a rfl :=
⟨λh, h a rfl, λh a' h_eq, match a', h_eq with ._, rfl := h end⟩
theorem {u v} forall_elim_eq_right {α : Sort u} (a : α) (p : Π(a':α), a = a' → Prop) :
(∀(a':α)(h : a = a'), p a' h) ↔ p a rfl :=
⟨λh, h a rfl, λh a' h_eq, match a', h_eq with ._, rfl := h end⟩
meta def forall_eq_elim : binder_eq_elim :=
{ match_binder := λe, (do (expr.pi n bi d bd) ← return e, return (d, expr.lam n bi d bd)),
adapt_rel := propext',
apply_comm := applyc ``forall_comm,
apply_congr := congr_binder ``forall_congr,
apply_elim_eq := apply' ``forall_elim_eq_left <|> apply' ``forall_elim_eq_right }
meta def supr_eq_elim : binder_eq_elim :=
{ match_binder := λe, (do `(@lattice.supr %%α %%β %%cl %%f) ← return e, return (β, f)),
adapt_rel := λc, (do r ← current_relation, guard (r = `eq), c),
apply_comm := applyc ``lattice.supr_comm,
apply_congr := congr_arg ∘ funext',
apply_elim_eq := applyc ``lattice.supr_supr_eq_left <|> applyc ``lattice.supr_supr_eq_right }
meta def infi_eq_elim : binder_eq_elim :=
{ match_binder := λe, (do `(@lattice.infi %%α %%β %%cl %%f) ← return e, return (β, f)),
adapt_rel := λc, (do r ← current_relation, guard (r = `eq), c),
apply_comm := applyc ``lattice.infi_comm,
apply_congr := congr_arg ∘ funext',
apply_elim_eq := applyc ``lattice.infi_infi_eq_left <|> applyc ``lattice.infi_infi_eq_right }
universes u v w w₂
variables {α : Type u} {β : Type v} {ι : Sort w} {ι₂ : Sort w₂} {s t : set α} {a : α}
section
open lattice
variables [complete_lattice α]
theorem Inf_image {s : set β} {f : β → α} : Inf (set.image f s) = (⨅ a ∈ s, f a) :=
begin
simp [Inf_eq_infi, infi_and],
conversion infi_eq_elim.old_conv,
end
theorem Sup_image {s : set β} {f : β → α} : Sup (set.image f s) = (⨆ a ∈ s, f a) :=
begin
simp [Sup_eq_supr, supr_and],
conversion supr_eq_elim.old_conv,
end
end
|
151a4f0ca0a990c56a0c29b379889faf20a8dd2b | e9dbaaae490bc072444e3021634bf73664003760 | /src/Problems/2006/IMO_2006_P1.lean | a9eef6c5121879641e4e9494a6d4b1b184965a87 | [
"Apache-2.0"
] | permissive | liaofei1128/geometry | 566d8bfe095ce0c0113d36df90635306c60e975b | 3dd128e4eec8008764bb94e18b932f9ffd66e6b3 | refs/heads/master | 1,678,996,510,399 | 1,581,454,543,000 | 1,583,337,839,000 | null | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 354 | lean | import Geo.Geo.Core
namespace Geo
open Seg Triangle
def IMO_2006_P1 : Prop :=
∀ (A B C P : Point),
let I := incenter ⟨A, B, C⟩;
inside P (Triangle.mk A B C) →
uangle ⟨P, B, A⟩ + uangle ⟨P, C, A⟩ = uangle ⟨P, B, C⟩ + uangle ⟨P, C, B⟩ →
ulen (Seg.mk A P) ≥ ulen (Seg.mk A I) →
cong ⟨A, P⟩ ⟨A, I⟩ ↔ P = I
end Geo
|
fdfbb6e410b47cb4737d563934391aa63c6cf010 | 74addaa0e41490cbaf2abd313a764c96df57b05d | /Mathlib/data/pfunctor/multivariate/W_auto.lean | d0e85b72f2051e8b881f4844ef7a7727524d69b7 | [] | no_license | AurelienSaue/Mathlib4_auto | f538cfd0980f65a6361eadea39e6fc639e9dae14 | 590df64109b08190abe22358fabc3eae000943f2 | refs/heads/master | 1,683,906,849,776 | 1,622,564,669,000 | 1,622,564,669,000 | 371,723,747 | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 12,362 | lean | /-
Copyright (c) 2018 Jeremy Avigad. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Author: Jeremy Avigad, Simon Hudon
-/
import Mathlib.PrePort
import Mathlib.Lean3Lib.init.default
import Mathlib.data.pfunctor.multivariate.basic
import Mathlib.PostPort
universes u l u_1 u_2
namespace Mathlib
/-!
# The W construction as a multivariate polynomial functor.
W types are well-founded tree-like structures. They are defined
as the least fixpoint of a polynomial functor.
## Main definitions
* `W_mk` - constructor
* `W_dest - destructor
* `W_rec` - recursor: basis for defining functions by structural recursion on `P.W α`
* `W_rec_eq` - defining equation for `W_rec`
* `W_ind` - induction principle for `P.W α`
## Implementation notes
Three views of M-types:
* `Wp`: polynomial functor
* `W`: data type inductively defined by a triple: shape of the root, data in the root and children of the root
* `W`: least fixed point of a polynomial functor
Specifically, we define the polynomial functor `Wp` as:
* A := a tree-like structure without information in the nodes
* B := given the tree-like structure `t`, `B t` is a valid path
(specified inductively by `W_path`) from the root of `t` to any given node.
As a result `Wp.obj α` is made of a dataless tree and a function from
its valid paths to values of `α`
## Reference
* [Jeremy Avigad, Mario M. Carneiro and Simon Hudon, *Data Types as Quotients of Polynomial Functors*][avigad-carneiro-hudon2019]
-/
namespace mvpfunctor
/-- A path from the root of a tree to one of its node -/
inductive W_path {n : ℕ} (P : mvpfunctor (n + 1)) : pfunctor.W (last P) → fin2 n → Type u where
| root :
(a : A P) →
(f : pfunctor.B (last P) a → pfunctor.W (last P)) →
(i : fin2 n) → B (drop P) a i → W_path P (W_type.mk a f) i
| child :
(a : A P) →
(f : pfunctor.B (last P) a → pfunctor.W (last P)) →
(i : fin2 n) → (j : pfunctor.B (last P) a) → W_path P (f j) i → W_path P (W_type.mk a f) i
protected instance W_path.inhabited {n : ℕ} (P : mvpfunctor (n + 1)) (x : pfunctor.W (last P))
{i : fin2 n} [I : Inhabited (B (drop P) (pfunctor.W.head x) i)] : Inhabited (W_path P x i) :=
{ default := sorry }
/-- Specialized destructor on `W_path` -/
def W_path_cases_on {n : ℕ} (P : mvpfunctor (n + 1)) {α : typevec n} {a : A P}
{f : pfunctor.B (last P) a → pfunctor.W (last P)} (g' : typevec.arrow (B (drop P) a) α)
(g : (j : pfunctor.B (last P) a) → typevec.arrow (W_path P (f j)) α) :
typevec.arrow (W_path P (W_type.mk a f)) α :=
sorry
/-- Specialized destructor on `W_path` -/
def W_path_dest_left {n : ℕ} (P : mvpfunctor (n + 1)) {α : typevec n} {a : A P}
{f : pfunctor.B (last P) a → pfunctor.W (last P)}
(h : typevec.arrow (W_path P (W_type.mk a f)) α) : typevec.arrow (B (drop P) a) α :=
fun (i : fin2 n) (c : B (drop P) a i) => h i (W_path.root a f i c)
/-- Specialized destructor on `W_path` -/
def W_path_dest_right {n : ℕ} (P : mvpfunctor (n + 1)) {α : typevec n} {a : A P}
{f : pfunctor.B (last P) a → pfunctor.W (last P)}
(h : typevec.arrow (W_path P (W_type.mk a f)) α) (j : pfunctor.B (last P) a) :
typevec.arrow (W_path P (f j)) α :=
fun (i : fin2 n) (c : W_path P (f j) i) => h i (W_path.child a f i j c)
theorem W_path_dest_left_W_path_cases_on {n : ℕ} (P : mvpfunctor (n + 1)) {α : typevec n} {a : A P}
{f : pfunctor.B (last P) a → pfunctor.W (last P)} (g' : typevec.arrow (B (drop P) a) α)
(g : (j : pfunctor.B (last P) a) → typevec.arrow (W_path P (f j)) α) :
W_path_dest_left P (W_path_cases_on P g' g) = g' :=
rfl
theorem W_path_dest_right_W_path_cases_on {n : ℕ} (P : mvpfunctor (n + 1)) {α : typevec n} {a : A P}
{f : pfunctor.B (last P) a → pfunctor.W (last P)} (g' : typevec.arrow (B (drop P) a) α)
(g : (j : pfunctor.B (last P) a) → typevec.arrow (W_path P (f j)) α) :
W_path_dest_right P (W_path_cases_on P g' g) = g :=
rfl
theorem W_path_cases_on_eta {n : ℕ} (P : mvpfunctor (n + 1)) {α : typevec n} {a : A P}
{f : pfunctor.B (last P) a → pfunctor.W (last P)}
(h : typevec.arrow (W_path P (W_type.mk a f)) α) :
W_path_cases_on P (W_path_dest_left P h) (W_path_dest_right P h) = h :=
sorry
theorem comp_W_path_cases_on {n : ℕ} (P : mvpfunctor (n + 1)) {α : typevec n} {β : typevec n}
(h : typevec.arrow α β) {a : A P} {f : pfunctor.B (last P) a → pfunctor.W (last P)}
(g' : typevec.arrow (B (drop P) a) α)
(g : (j : pfunctor.B (last P) a) → typevec.arrow (W_path P (f j)) α) :
typevec.comp h (W_path_cases_on P g' g) =
W_path_cases_on P (typevec.comp h g')
fun (i : pfunctor.B (last P) a) => typevec.comp h (g i) :=
sorry
/-- Polynomial functor for the W-type of `P`. `A` is a data-less well-founded
tree whereas, for a given `a : A`, `B a` is a valid path in tree `a` so
that `Wp.obj α` is made of a tree and a function from its valid paths to
the values it contains -/
def Wp {n : ℕ} (P : mvpfunctor (n + 1)) : mvpfunctor n := mk (pfunctor.W (last P)) (W_path P)
/-- W-type of `P` -/
def W {n : ℕ} (P : mvpfunctor (n + 1)) (α : typevec n) := obj (Wp P) α
protected instance mvfunctor_W {n : ℕ} (P : mvpfunctor (n + 1)) : mvfunctor (W P) :=
id (obj.mvfunctor (Wp P))
/-!
First, describe operations on `W` as a polynomial functor.
-/
/-- Constructor for `Wp` -/
def Wp_mk {n : ℕ} (P : mvpfunctor (n + 1)) {α : typevec n} (a : A P)
(f : pfunctor.B (last P) a → pfunctor.W (last P))
(f' : typevec.arrow (W_path P (W_type.mk a f)) α) : W P α :=
sigma.mk (W_type.mk a f) f'
/-- Recursor for `Wp` -/
def Wp_rec {n : ℕ} (P : mvpfunctor (n + 1)) {α : typevec n} {C : Type u_2}
(g :
(a : A P) →
(f : pfunctor.B (last P) a → pfunctor.W (last P)) →
typevec.arrow (W_path P (W_type.mk a f)) α → (pfunctor.B (last P) a → C) → C)
(x : pfunctor.W (last P)) (f' : typevec.arrow (W_path P x) α) : C :=
sorry
theorem Wp_rec_eq {n : ℕ} (P : mvpfunctor (n + 1)) {α : typevec n} {C : Type u_2}
(g :
(a : A P) →
(f : pfunctor.B (last P) a → pfunctor.W (last P)) →
typevec.arrow (W_path P (W_type.mk a f)) α → (pfunctor.B (last P) a → C) → C)
(a : A P) (f : pfunctor.B (last P) a → pfunctor.W (last P))
(f' : typevec.arrow (W_path P (W_type.mk a f)) α) :
Wp_rec P g (W_type.mk a f) f' =
g a f f' fun (i : pfunctor.B (last P) a) => Wp_rec P g (f i) (W_path_dest_right P f' i) :=
rfl
-- Note: we could replace Prop by Type* and obtain a dependent recursor
theorem Wp_ind {n : ℕ} (P : mvpfunctor (n + 1)) {α : typevec n}
{C : (x : pfunctor.W (last P)) → typevec.arrow (W_path P x) α → Prop}
(ih :
∀ (a : A P) (f : pfunctor.B (last P) a → pfunctor.W (last P))
(f' : typevec.arrow (W_path P (W_type.mk a f)) α),
(∀ (i : pfunctor.B (last P) a), C (f i) (W_path_dest_right P f' i)) → C (W_type.mk a f) f')
(x : pfunctor.W (last P)) (f' : typevec.arrow (W_path P x) α) : C x f' :=
sorry
/-!
Now think of W as defined inductively by the data ⟨a, f', f⟩ where
- `a : P.A` is the shape of the top node
- `f' : P.drop.B a ⟹ α` is the contents of the top node
- `f : P.last.B a → P.last.W` are the subtrees
-/
/-- Constructor for `W` -/
def W_mk {n : ℕ} (P : mvpfunctor (n + 1)) {α : typevec n} (a : A P)
(f' : typevec.arrow (B (drop P) a) α) (f : pfunctor.B (last P) a → W P α) : W P α :=
let g : pfunctor.B (last P) a → pfunctor.W (last P) :=
fun (i : pfunctor.B (last P) a) => sigma.fst (f i);
let g' : typevec.arrow (W_path P (W_type.mk a g)) α :=
W_path_cases_on P f' fun (i : pfunctor.B (last P) a) => sigma.snd (f i);
sigma.mk (W_type.mk a g) g'
/-- Recursor for `W` -/
def W_rec {n : ℕ} (P : mvpfunctor (n + 1)) {α : typevec n} {C : Type u_1}
(g :
(a : A P) →
typevec.arrow (B (drop P) a) α →
(pfunctor.B (last P) a → W P α) → (pfunctor.B (last P) a → C) → C) :
W P α → C :=
sorry
/-- Defining equation for the recursor of `W` -/
theorem W_rec_eq {n : ℕ} (P : mvpfunctor (n + 1)) {α : typevec n} {C : Type u_1}
(g :
(a : A P) →
typevec.arrow (B (drop P) a) α →
(pfunctor.B (last P) a → W P α) → (pfunctor.B (last P) a → C) → C)
(a : A P) (f' : typevec.arrow (B (drop P) a) α) (f : pfunctor.B (last P) a → W P α) :
W_rec P g (W_mk P a f' f) = g a f' f fun (i : pfunctor.B (last P) a) => W_rec P g (f i) :=
sorry
/-- Induction principle for `W` -/
theorem W_ind {n : ℕ} (P : mvpfunctor (n + 1)) {α : typevec n} {C : W P α → Prop}
(ih :
∀ (a : A P) (f' : typevec.arrow (B (drop P) a) α) (f : pfunctor.B (last P) a → W P α),
(∀ (i : pfunctor.B (last P) a), C (f i)) → C (W_mk P a f' f))
(x : W P α) : C x :=
sorry
theorem W_cases {n : ℕ} (P : mvpfunctor (n + 1)) {α : typevec n} {C : W P α → Prop}
(ih :
∀ (a : A P) (f' : typevec.arrow (B (drop P) a) α) (f : pfunctor.B (last P) a → W P α),
C (W_mk P a f' f))
(x : W P α) : C x :=
W_ind P
fun (a : A P) (f' : typevec.arrow (B (drop P) a) α) (f : pfunctor.B (last P) a → W P α)
(ih' : ∀ (i : pfunctor.B (last P) a), C (f i)) => ih a f' f
/-- W-types are functorial -/
def W_map {n : ℕ} (P : mvpfunctor (n + 1)) {α : typevec n} {β : typevec n} (g : typevec.arrow α β) :
W P α → W P β :=
fun (x : W P α) => mvfunctor.map g x
theorem W_mk_eq {n : ℕ} (P : mvpfunctor (n + 1)) {α : typevec n} (a : A P)
(f : pfunctor.B (last P) a → pfunctor.W (last P)) (g' : typevec.arrow (B (drop P) a) α)
(g : (j : pfunctor.B (last P) a) → typevec.arrow (W_path P (f j)) α) :
(W_mk P a g' fun (i : pfunctor.B (last P) a) => sigma.mk (f i) (g i)) =
sigma.mk (W_type.mk a f) (W_path_cases_on P g' g) :=
rfl
theorem W_map_W_mk {n : ℕ} (P : mvpfunctor (n + 1)) {α : typevec n} {β : typevec n}
(g : typevec.arrow α β) (a : A P) (f' : typevec.arrow (B (drop P) a) α)
(f : pfunctor.B (last P) a → W P α) :
mvfunctor.map g (W_mk P a f' f) =
W_mk P a (typevec.comp g f') fun (i : pfunctor.B (last P) a) => mvfunctor.map g (f i) :=
sorry
-- TODO: this technical theorem is used in one place in constructing the initial algebra.
-- Can it be avoided?
/-- Constructor of a value of `P.obj (α ::: β)` from components.
Useful to avoid complicated type annotation -/
def obj_append1 {n : ℕ} (P : mvpfunctor (n + 1)) {α : typevec n} {β : Type u} (a : A P)
(f' : typevec.arrow (B (drop P) a) α) (f : pfunctor.B (last P) a → β) : obj P (α ::: β) :=
sigma.mk a (typevec.split_fun f' f)
theorem map_obj_append1 {n : ℕ} (P : mvpfunctor (n + 1)) {α : typevec n} {γ : typevec n}
(g : typevec.arrow α γ) (a : A P) (f' : typevec.arrow (B (drop P) a) α)
(f : pfunctor.B (last P) a → W P α) :
mvfunctor.map (g ::: W_map P g) (obj_append1 P a f' f) =
obj_append1 P a (typevec.comp g f') fun (x : pfunctor.B (last P) a) => W_map P g (f x) :=
sorry
/-!
Yet another view of the W type: as a fixed point for a multivariate polynomial functor.
These are needed to use the W-construction to construct a fixed point of a qpf, since
the qpf axioms are expressed in terms of `map` on `P`.
-/
/-- Constructor for the W-type of `P` -/
def W_mk' {n : ℕ} (P : mvpfunctor (n + 1)) {α : typevec n} : obj P (α ::: W P α) → W P α := sorry
/-- Destructor for the W-type of `P` -/
def W_dest' {n : ℕ} (P : mvpfunctor (n + 1)) {α : typevec n} : W P α → obj P (α ::: W P α) :=
W_rec P
fun (a : A P) (f' : typevec.arrow (B (drop P) a) α) (f : pfunctor.B (last P) a → W P α)
(_x : pfunctor.B (last P) a → obj P (α ::: W P α)) => sigma.mk a (typevec.split_fun f' f)
theorem W_dest'_W_mk {n : ℕ} (P : mvpfunctor (n + 1)) {α : typevec n} (a : A P)
(f' : typevec.arrow (B (drop P) a) α) (f : pfunctor.B (last P) a → W P α) :
W_dest' P (W_mk P a f' f) = sigma.mk a (typevec.split_fun f' f) :=
sorry
theorem W_dest'_W_mk' {n : ℕ} (P : mvpfunctor (n + 1)) {α : typevec n} (x : obj P (α ::: W P α)) :
W_dest' P (W_mk' P x) = x :=
sorry
end Mathlib |
6e8b7ad058c9541e18a67a9559e814501f3e7f63 | 63abd62053d479eae5abf4951554e1064a4c45b4 | /src/category_theory/monoidal/internal/Module.lean | ffe881f0ea08955ca408020923e448b1e7436b40 | [
"Apache-2.0"
] | permissive | Lix0120/mathlib | 0020745240315ed0e517cbf32e738d8f9811dd80 | e14c37827456fc6707f31b4d1d16f1f3a3205e91 | refs/heads/master | 1,673,102,855,024 | 1,604,151,044,000 | 1,604,151,044,000 | 308,930,245 | 0 | 0 | Apache-2.0 | 1,604,164,710,000 | 1,604,163,547,000 | null | UTF-8 | Lean | false | false | 5,229 | lean | /-
Copyright (c) 2020 Scott Morrison. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Scott Morrison
-/
import algebra.category.Module.monoidal
import algebra.category.Algebra.basic
import category_theory.monoidal.Mon_
/-!
# `Mon_ (Module R) ≌ Algebra R`
The category of internal monoid objects in `Module R`
is equivalent to the category of "native" bundled `R`-algebras.
Moreover, this equivalence is compatible with the forgetful functors to `Module R`.
-/
universes v u
open category_theory
open linear_map
open_locale tensor_product
namespace Module
variables {R : Type u} [comm_ring R]
namespace Mon_Module_equivalence_Algebra
@[simps]
instance (A : Mon_ (Module.{u} R)) : ring A.X :=
{ one := A.one (1 : R),
mul := λ x y, A.mul (x ⊗ₜ y),
one_mul := λ x, by { convert linear_map.congr_fun A.one_mul ((1 : R) ⊗ₜ x), simp, },
mul_one := λ x, by { convert linear_map.congr_fun A.mul_one (x ⊗ₜ (1 : R)), simp, },
mul_assoc := λ x y z, by convert linear_map.congr_fun A.mul_assoc ((x ⊗ₜ y) ⊗ₜ z),
left_distrib := λ x y z,
begin
convert A.mul.map_add (x ⊗ₜ y) (x ⊗ₜ z),
rw ←tensor_product.tmul_add,
refl,
end,
right_distrib := λ x y z,
begin
convert A.mul.map_add (x ⊗ₜ z) (y ⊗ₜ z),
rw ←tensor_product.add_tmul,
refl,
end,
..(by apply_instance : add_comm_group A.X) }
instance (A : Mon_ (Module.{u} R)) : algebra R A.X :=
{ map_zero' := A.one.map_zero,
map_one' := rfl,
map_mul' := λ x y,
begin
have h := linear_map.congr_fun A.one_mul.symm (x ⊗ₜ (A.one y)),
rwa [monoidal_category.left_unitor_hom_apply, ←A.one.map_smul] at h,
end,
commutes' := λ r a,
begin dsimp,
have h₁ := linear_map.congr_fun A.one_mul (r ⊗ₜ a),
have h₂ := linear_map.congr_fun A.mul_one (a ⊗ₜ r),
exact h₁.trans h₂.symm,
end,
smul_def' := λ r a, by { convert (linear_map.congr_fun A.one_mul (r ⊗ₜ a)).symm, simp, },
..A.one }
@[simp] lemma algebra_map (A : Mon_ (Module.{u} R)) (r : R) : algebra_map R A.X r = A.one r := rfl
/--
Converting a monoid object in `Module R` to a bundled algebra.
-/
@[simps]
def functor : Mon_ (Module.{u} R) ⥤ Algebra R :=
{ obj := λ A, Algebra.of R A.X,
map := λ A B f,
{ to_fun := f.hom,
map_one' := linear_map.congr_fun f.one_hom (1 : R),
map_mul' := λ x y, linear_map.congr_fun f.mul_hom (x ⊗ₜ y),
commutes' := λ r, linear_map.congr_fun f.one_hom r,
..(f.hom.to_add_monoid_hom) }, }.
/--
Converting a bundled algebra to a monoid object in `Module R`.
-/
@[simps]
def inverse_obj (A : Algebra.{u} R) : Mon_ (Module.{u} R) :=
{ X := Module.of R A,
one := algebra.linear_map R A,
mul := @algebra.lmul' R A _ _ _,
one_mul' :=
begin
ext x,
dsimp,
rw [algebra.lmul'_apply, monoidal_category.left_unitor_hom_apply, algebra.smul_def],
refl,
end,
mul_one' :=
begin
ext x,
dsimp,
rw [algebra.lmul'_apply, monoidal_category.right_unitor_hom_apply,
←algebra.commutes, algebra.smul_def],
refl,
end,
mul_assoc' :=
begin
ext xy z,
dsimp,
apply tensor_product.induction_on xy,
{ simp only [linear_map.map_zero, tensor_product.zero_tmul], },
{ intros x y, dsimp, simp only [mul_assoc, algebra.lmul'_apply], },
{ intros x y hx hy, dsimp,
simp only [tensor_product.add_tmul, hx, hy, map_add], },
end }
/--
Converting a bundled algebra to a monoid object in `Module R`.
-/
@[simps]
def inverse : Algebra.{u} R ⥤ Mon_ (Module.{u} R) :=
{ obj := inverse_obj,
map := λ A B f,
{ hom := f.to_linear_map, }, }.
end Mon_Module_equivalence_Algebra
open Mon_Module_equivalence_Algebra
/--
The category of internal monoid objects in `Module R`
is equivalent to the category of "native" bundled `R`-algebras.
-/
def Mon_Module_equivalence_Algebra : Mon_ (Module.{u} R) ≌ Algebra R :=
{ functor := functor,
inverse := inverse,
unit_iso := nat_iso.of_components
(λ A,
{ hom := { hom := { to_fun := id, map_add' := λ x y, rfl, map_smul' := λ r a, rfl, } },
inv := { hom := { to_fun := id, map_add' := λ x y, rfl, map_smul' := λ r a, rfl, } } })
(by tidy),
counit_iso := nat_iso.of_components (λ A,
{ hom :=
{ to_fun := id,
map_zero' := rfl,
map_add' := λ x y, rfl,
map_one' := (algebra_map R A).map_one,
map_mul' := λ x y, algebra.lmul'_apply,
commutes' := λ r, rfl, },
inv :=
{ to_fun := id,
map_zero' := rfl,
map_add' := λ x y, rfl,
map_one' := (algebra_map R A).map_one.symm,
map_mul' := λ x y, algebra.lmul'_apply.symm,
commutes' := λ r, rfl } }) (by tidy), }.
/--
The equivalence `Mon_ (Module R) ≌ Algebra R`
is naturally compatible with the forgetful functors to `Module R`.
-/
def Mon_Module_equivalence_Algebra_forget :
Mon_Module_equivalence_Algebra.functor ⋙ forget₂ (Algebra.{u} R) (Module.{u} R) ≅
Mon_.forget (Module.{u} R):=
nat_iso.of_components (λ A,
{ hom :=
{ to_fun := id,
map_add' := λ x y, rfl,
map_smul' := λ c x, rfl },
inv :=
{ to_fun := id,
map_add' := λ x y, rfl,
map_smul' := λ c x, rfl }, }) (by tidy)
end Module
|
5f66860675f2d99d962f621cd0c16ce22ec5da30 | d29d82a0af640c937e499f6be79fc552eae0aa13 | /src/ring_theory/integral_closure.lean | 670e90734b5eb9bf7ea515844039d52cab1a1c9a | [
"Apache-2.0"
] | permissive | AbdulMajeedkhurasani/mathlib | 835f8a5c5cf3075b250b3737172043ab4fa1edf6 | 79bc7323b164aebd000524ebafd198eb0e17f956 | refs/heads/master | 1,688,003,895,660 | 1,627,788,521,000 | 1,627,788,521,000 | null | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 25,830 | lean | /-
Copyright (c) 2019 Kenny Lau. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kenny Lau
-/
import ring_theory.adjoin.basic
import ring_theory.polynomial.scale_roots
import ring_theory.polynomial.tower
/-!
# Integral closure of a subring.
If A is an R-algebra then `a : A` is integral over R if it is a root of a monic polynomial
with coefficients in R. Enough theory is developed to prove that integral elements
form a sub-R-algebra of A.
## Main definitions
Let `R` be a `comm_ring` and let `A` be an R-algebra.
* `ring_hom.is_integral_elem (f : R →+* A) (x : A)` : `x` is integral with respect to the map `f`,
* `is_integral (x : A)` : `x` is integral over `R`, i.e., is a root of a monic polynomial with
coefficients in `R`.
* `integral_closure R A` : the integral closure of `R` in `A`, regarded as a sub-`R`-algebra of `A`.
-/
open_locale classical
open_locale big_operators
open polynomial submodule
section ring
variables {R S A : Type*}
variables [comm_ring R] [ring A] [ring S] (f : R →+* S)
/-- An element `x` of `A` is said to be integral over `R` with respect to `f`
if it is a root of a monic polynomial `p : polynomial R` evaluated under `f` -/
def ring_hom.is_integral_elem (f : R →+* A) (x : A) :=
∃ p : polynomial R, monic p ∧ eval₂ f x p = 0
/-- A ring homomorphism `f : R →+* A` is said to be integral
if every element `A` is integral with respect to the map `f` -/
def ring_hom.is_integral (f : R →+* A) :=
∀ x : A, f.is_integral_elem x
variables [algebra R A] (R)
/-- An element `x` of an algebra `A` over a commutative ring `R` is said to be *integral*,
if it is a root of some monic polynomial `p : polynomial R`.
Equivalently, the element is integral over `R` with respect to the induced `algebra_map` -/
def is_integral (x : A) : Prop :=
(algebra_map R A).is_integral_elem x
variable (A)
/-- An algebra is integral if every element of the extension is integral over the base ring -/
def algebra.is_integral : Prop :=
(algebra_map R A).is_integral
variables {R A}
lemma ring_hom.is_integral_map {x : R} : f.is_integral_elem (f x) :=
⟨X - C x, monic_X_sub_C _, by simp⟩
theorem is_integral_algebra_map {x : R} : is_integral R (algebra_map R A x) :=
(algebra_map R A).is_integral_map
theorem is_integral_of_noetherian (H : is_noetherian R A) (x : A) :
is_integral R x :=
begin
let leval : @linear_map R (polynomial R) A _ _ _ _ _ := (aeval x).to_linear_map,
let D : ℕ → submodule R A := λ n, (degree_le R n).map leval,
let M := well_founded.min (is_noetherian_iff_well_founded.1 H)
(set.range D) ⟨_, ⟨0, rfl⟩⟩,
have HM : M ∈ set.range D := well_founded.min_mem _ _ _,
cases HM with N HN,
have HM : ¬M < D (N+1) := well_founded.not_lt_min
(is_noetherian_iff_well_founded.1 H) (set.range D) _ ⟨N+1, rfl⟩,
rw ← HN at HM,
have HN2 : D (N+1) ≤ D N := classical.by_contradiction (λ H, HM
(lt_of_le_not_le (map_mono (degree_le_mono
(with_bot.coe_le_coe.2 (nat.le_succ N)))) H)),
have HN3 : leval (X^(N+1)) ∈ D N,
{ exact HN2 (mem_map_of_mem (mem_degree_le.2 (degree_X_pow_le _))) },
rcases HN3 with ⟨p, hdp, hpe⟩,
refine ⟨X^(N+1) - p, monic_X_pow_sub (mem_degree_le.1 hdp), _⟩,
show leval (X ^ (N + 1) - p) = 0,
rw [linear_map.map_sub, hpe, sub_self]
end
theorem is_integral_of_submodule_noetherian (S : subalgebra R A)
(H : is_noetherian R S.to_submodule) (x : A) (hx : x ∈ S) :
is_integral R x :=
begin
suffices : is_integral R (show S, from ⟨x, hx⟩),
{ rcases this with ⟨p, hpm, hpx⟩,
replace hpx := congr_arg S.val hpx,
refine ⟨p, hpm, eq.trans _ hpx⟩,
simp only [aeval_def, eval₂, sum_def],
rw S.val.map_sum,
refine finset.sum_congr rfl (λ n hn, _),
rw [S.val.map_mul, S.val.map_pow, S.val.commutes, S.val_apply, subtype.coe_mk], },
refine is_integral_of_noetherian H ⟨x, hx⟩
end
end ring
section
variables {R A B S : Type*}
variables [comm_ring R] [comm_ring A] [comm_ring B] [comm_ring S]
variables [algebra R A] [algebra R B] (f : R →+* S)
theorem is_integral_alg_hom (f : A →ₐ[R] B) {x : A} (hx : is_integral R x) : is_integral R (f x) :=
let ⟨p, hp, hpx⟩ :=
hx in ⟨p, hp, by rw [← aeval_def, aeval_alg_hom_apply, aeval_def, hpx, f.map_zero]⟩
theorem is_integral_of_is_scalar_tower [algebra A B] [is_scalar_tower R A B]
(x : B) (hx : is_integral R x) : is_integral A x :=
let ⟨p, hp, hpx⟩ := hx in
⟨p.map $ algebra_map R A, monic_map _ hp,
by rw [← aeval_def, ← is_scalar_tower.aeval_apply, aeval_def, hpx]⟩
section
local attribute [instance] subset.comm_ring algebra.of_is_subring
theorem is_integral_of_subring {x : A} (T : set R) [is_subring T]
(hx : is_integral T x) : is_integral R x :=
is_integral_of_is_scalar_tower x hx
lemma is_integral_algebra_map_iff [algebra A B] [is_scalar_tower R A B]
{x : A} (hAB : function.injective (algebra_map A B)) :
is_integral R (algebra_map A B x) ↔ is_integral R x :=
begin
split; rintros ⟨f, hf, hx⟩; use [f, hf],
{ exact is_scalar_tower.aeval_eq_zero_of_aeval_algebra_map_eq_zero R A B hAB hx },
{ rw [is_scalar_tower.algebra_map_eq R A B, ← hom_eval₂, hx, ring_hom.map_zero] }
end
theorem is_integral_iff_is_integral_closure_finite {r : A} :
is_integral R r ↔ ∃ s : set R, s.finite ∧ is_integral (ring.closure s) r :=
begin
split; intro hr,
{ rcases hr with ⟨p, hmp, hpr⟩,
refine ⟨_, set.finite_mem_finset _, p.restriction, monic_restriction.2 hmp, _⟩,
erw [← aeval_def, is_scalar_tower.aeval_apply _ R, map_restriction, aeval_def, hpr] },
rcases hr with ⟨s, hs, hsr⟩,
exact is_integral_of_subring _ hsr
end
end
theorem fg_adjoin_singleton_of_integral (x : A) (hx : is_integral R x) :
(algebra.adjoin R ({x} : set A)).to_submodule.fg :=
begin
rcases hx with ⟨f, hfm, hfx⟩,
existsi finset.image ((^) x) (finset.range (nat_degree f + 1)),
apply le_antisymm,
{ rw span_le, intros s hs, rw finset.mem_coe at hs,
rcases finset.mem_image.1 hs with ⟨k, hk, rfl⟩, clear hk,
exact is_submonoid.pow_mem (algebra.subset_adjoin (set.mem_singleton _)) },
intros r hr, change r ∈ algebra.adjoin R ({x} : set A) at hr,
rw algebra.adjoin_singleton_eq_range at hr,
rcases (aeval x).mem_range.mp hr with ⟨p, rfl⟩,
rw ← mod_by_monic_add_div p hfm,
rw ← aeval_def at hfx,
rw [alg_hom.map_add, alg_hom.map_mul, hfx, zero_mul, add_zero],
have : degree (p %ₘ f) ≤ degree f := degree_mod_by_monic_le p hfm,
generalize_hyp : p %ₘ f = q at this ⊢,
rw [← sum_C_mul_X_eq q, aeval_def, eval₂_sum, sum_def],
refine sum_mem _ (λ k hkq, _),
rw [eval₂_mul, eval₂_C, eval₂_pow, eval₂_X, ← algebra.smul_def],
refine smul_mem _ _ (subset_span _),
rw finset.mem_coe, refine finset.mem_image.2 ⟨_, _, rfl⟩,
rw [finset.mem_range, nat.lt_succ_iff], refine le_of_not_lt (λ hk, _),
rw [degree_le_iff_coeff_zero] at this,
rw [mem_support_iff] at hkq, apply hkq, apply this,
exact lt_of_le_of_lt degree_le_nat_degree (with_bot.coe_lt_coe.2 hk)
end
theorem fg_adjoin_of_finite {s : set A} (hfs : s.finite)
(his : ∀ x ∈ s, is_integral R x) : (algebra.adjoin R s).to_submodule.fg :=
set.finite.induction_on hfs (λ _, ⟨{1}, submodule.ext $ λ x,
by { erw [algebra.adjoin_empty, finset.coe_singleton, ← one_eq_span, one_eq_range,
linear_map.mem_range, algebra.mem_bot], refl }⟩)
(λ a s has hs ih his, by rw [← set.union_singleton, algebra.adjoin_union_coe_submodule]; exact
fg_mul _ _ (ih $ λ i hi, his i $ set.mem_insert_of_mem a hi)
(fg_adjoin_singleton_of_integral _ $ his a $ set.mem_insert a s)) his
theorem is_integral_of_mem_of_fg (S : subalgebra R A)
(HS : S.to_submodule.fg) (x : A) (hx : x ∈ S) : is_integral R x :=
begin
cases HS with y hy,
obtain ⟨lx, hlx1, hlx2⟩ :
∃ (l : A →₀ R) (H : l ∈ finsupp.supported R R ↑y), (finsupp.total A A R id) l = x,
{ rwa [←(@finsupp.mem_span_image_iff_total A A R _ _ _ id ↑y x), set.image_id ↑y, hy] },
have hyS : ∀ {p}, p ∈ y → p ∈ S := λ p hp, show p ∈ S.to_submodule,
by { rw ← hy, exact subset_span hp },
have : ∀ (jk : (↑(y.product y) : set (A × A))), jk.1.1 * jk.1.2 ∈ S.to_submodule :=
λ jk, S.mul_mem (hyS (finset.mem_product.1 jk.2).1) (hyS (finset.mem_product.1 jk.2).2),
rw [← hy, ← set.image_id ↑y] at this, simp only [finsupp.mem_span_image_iff_total] at this,
choose ly hly1 hly2,
let S₀ : set R := ring.closure ↑(lx.frange ∪ finset.bUnion finset.univ (finsupp.frange ∘ ly)),
refine is_integral_of_subring S₀ _,
letI : comm_ring S₀ := @subtype.comm_ring _ _ _ ring.closure.is_subring,
letI : algebra S₀ A := algebra.of_is_subring _,
have :
span S₀ (insert 1 ↑y : set A) * span S₀ (insert 1 ↑y : set A) ≤ span S₀ (insert 1 ↑y : set A),
{ rw span_mul_span, refine span_le.2 (λ z hz, _),
rcases set.mem_mul.1 hz with ⟨p, q, rfl | hp, hq, rfl⟩,
{ rw one_mul, exact subset_span hq },
rcases hq with rfl | hq,
{ rw mul_one, exact subset_span (or.inr hp) },
erw ← hly2 ⟨(p, q), finset.mem_product.2 ⟨hp, hq⟩⟩,
rw [finsupp.total_apply, finsupp.sum],
refine (span S₀ (insert 1 ↑y : set A)).sum_mem (λ t ht, _),
have : ly ⟨(p, q), finset.mem_product.2 ⟨hp, hq⟩⟩ t ∈ S₀ :=
ring.subset_closure (finset.mem_union_right _ $ finset.mem_bUnion.2
⟨⟨(p, q), finset.mem_product.2 ⟨hp, hq⟩⟩, finset.mem_univ _,
finsupp.mem_frange.2 ⟨finsupp.mem_support_iff.1 ht, _, rfl⟩⟩),
change (⟨_, this⟩ : S₀) • t ∈ _, exact smul_mem _ _ (subset_span $ or.inr $ hly1 _ ht) },
haveI : is_subring (span S₀ (insert 1 ↑y : set A) : set A) :=
{ one_mem := subset_span $ or.inl rfl,
mul_mem := λ p q hp hq, this $ mul_mem_mul hp hq,
zero_mem := (span S₀ (insert 1 ↑y : set A)).zero_mem,
add_mem := λ _ _, (span S₀ (insert 1 ↑y : set A)).add_mem,
neg_mem := λ _, (span S₀ (insert 1 ↑y : set A)).neg_mem },
have : span S₀ (insert 1 ↑y : set A) = (algebra.adjoin S₀ (↑y : set A)).to_submodule,
{ refine le_antisymm (span_le.2 $ set.insert_subset.2
⟨(algebra.adjoin S₀ ↑y).one_mem, algebra.subset_adjoin⟩) (λ z hz, _),
rw [subalgebra.mem_to_submodule, algebra.mem_adjoin_iff] at hz, rw ← set_like.mem_coe,
refine ring.closure_subset (set.union_subset (set.range_subset_iff.2 $ λ t, _)
(λ t ht, subset_span $ or.inr ht)) hz,
rw algebra.algebra_map_eq_smul_one,
exact smul_mem (span S₀ (insert 1 ↑y : set A)) _ (subset_span $ or.inl rfl) },
haveI : is_noetherian_ring ↥S₀ := is_noetherian_ring_closure _ (finset.finite_to_set _),
refine is_integral_of_submodule_noetherian (algebra.adjoin S₀ ↑y)
(is_noetherian_of_fg_of_noetherian _ ⟨insert 1 y, by rw [finset.coe_insert, this]⟩) _ _,
rw [← hlx2, finsupp.total_apply, finsupp.sum], refine subalgebra.sum_mem _ (λ r hr, _),
have : lx r ∈ S₀ := ring.subset_closure (finset.mem_union_left _ (finset.mem_image_of_mem _ hr)),
change (⟨_, this⟩ : S₀) • r ∈ _,
rw finsupp.mem_supported at hlx1,
exact subalgebra.smul_mem _ (algebra.subset_adjoin $ hlx1 hr) _
end
lemma ring_hom.is_integral_of_mem_closure {x y z : S}
(hx : f.is_integral_elem x) (hy : f.is_integral_elem y)
(hz : z ∈ ring.closure ({x, y} : set S)) :
f.is_integral_elem z :=
begin
letI : algebra R S := f.to_algebra,
have := fg_mul _ _ (fg_adjoin_singleton_of_integral x hx) (fg_adjoin_singleton_of_integral y hy),
rw [← algebra.adjoin_union_coe_submodule, set.singleton_union] at this,
exact is_integral_of_mem_of_fg (algebra.adjoin R {x, y}) this z
(algebra.mem_adjoin_iff.2 $ ring.closure_mono (set.subset_union_right _ _) hz),
end
theorem is_integral_of_mem_closure {x y z : A}
(hx : is_integral R x) (hy : is_integral R y)
(hz : z ∈ ring.closure ({x, y} : set A)) :
is_integral R z :=
(algebra_map R A).is_integral_of_mem_closure hx hy hz
lemma ring_hom.is_integral_zero : f.is_integral_elem 0 :=
f.map_zero ▸ f.is_integral_map
theorem is_integral_zero : is_integral R (0:A) :=
(algebra_map R A).is_integral_zero
lemma ring_hom.is_integral_one : f.is_integral_elem 1 :=
f.map_one ▸ f.is_integral_map
theorem is_integral_one : is_integral R (1:A) :=
(algebra_map R A).is_integral_one
lemma ring_hom.is_integral_add {x y : S}
(hx : f.is_integral_elem x) (hy : f.is_integral_elem y) :
f.is_integral_elem (x + y) :=
f.is_integral_of_mem_closure hx hy (is_add_submonoid.add_mem
(ring.subset_closure (or.inl rfl)) (ring.subset_closure (or.inr rfl)))
theorem is_integral_add {x y : A}
(hx : is_integral R x) (hy : is_integral R y) :
is_integral R (x + y) :=
(algebra_map R A).is_integral_add hx hy
lemma ring_hom.is_integral_neg {x : S}
(hx : f.is_integral_elem x) : f.is_integral_elem (-x) :=
f.is_integral_of_mem_closure hx hx (is_add_subgroup.neg_mem
(ring.subset_closure (or.inl rfl)))
theorem is_integral_neg {x : A}
(hx : is_integral R x) : is_integral R (-x) :=
(algebra_map R A).is_integral_neg hx
lemma ring_hom.is_integral_sub {x y : S}
(hx : f.is_integral_elem x) (hy : f.is_integral_elem y) : f.is_integral_elem (x - y) :=
by simpa only [sub_eq_add_neg] using f.is_integral_add hx (f.is_integral_neg hy)
theorem is_integral_sub {x y : A}
(hx : is_integral R x) (hy : is_integral R y) : is_integral R (x - y) :=
(algebra_map R A).is_integral_sub hx hy
lemma ring_hom.is_integral_mul {x y : S}
(hx : f.is_integral_elem x) (hy : f.is_integral_elem y) : f.is_integral_elem (x * y) :=
f.is_integral_of_mem_closure hx hy (is_submonoid.mul_mem
(ring.subset_closure (or.inl rfl)) (ring.subset_closure (or.inr rfl)))
theorem is_integral_mul {x y : A}
(hx : is_integral R x) (hy : is_integral R y) : is_integral R (x * y) :=
(algebra_map R A).is_integral_mul hx hy
variables (R A)
/-- The integral closure of R in an R-algebra A. -/
def integral_closure : subalgebra R A :=
{ carrier := { r | is_integral R r },
zero_mem' := is_integral_zero,
one_mem' := is_integral_one,
add_mem' := λ _ _, is_integral_add,
mul_mem' := λ _ _, is_integral_mul,
algebra_map_mem' := λ x, is_integral_algebra_map }
theorem mem_integral_closure_iff_mem_fg {r : A} :
r ∈ integral_closure R A ↔ ∃ M : subalgebra R A, M.to_submodule.fg ∧ r ∈ M :=
⟨λ hr, ⟨algebra.adjoin R {r}, fg_adjoin_singleton_of_integral _ hr, algebra.subset_adjoin rfl⟩,
λ ⟨M, Hf, hrM⟩, is_integral_of_mem_of_fg M Hf _ hrM⟩
variables {R} {A}
/-- Mapping an integral closure along an `alg_equiv` gives the integral closure. -/
lemma integral_closure_map_alg_equiv (f : A ≃ₐ[R] B) :
(integral_closure R A).map (f : A →ₐ[R] B) = integral_closure R B :=
begin
ext y,
rw subalgebra.mem_map,
split,
{ rintros ⟨x, hx, rfl⟩,
exact is_integral_alg_hom f hx },
{ intro hy,
use [f.symm y, is_integral_alg_hom (f.symm : B →ₐ[R] A) hy],
simp }
end
lemma integral_closure.is_integral (x : integral_closure R A) : is_integral R x :=
let ⟨p, hpm, hpx⟩ := x.2 in ⟨p, hpm, subtype.eq $
by rwa [← aeval_def, subtype.val_eq_coe, ← subalgebra.val_apply, aeval_alg_hom_apply] at hpx⟩
lemma ring_hom.is_integral_of_is_integral_mul_unit (x y : S) (r : R) (hr : f r * y = 1)
(hx : f.is_integral_elem (x * y)) : f.is_integral_elem x :=
begin
obtain ⟨p, ⟨p_monic, hp⟩⟩ := hx,
refine ⟨scale_roots p r, ⟨(monic_scale_roots_iff r).2 p_monic, _⟩⟩,
convert scale_roots_eval₂_eq_zero f hp,
rw [mul_comm x y, ← mul_assoc, hr, one_mul],
end
theorem is_integral_of_is_integral_mul_unit {x y : A} {r : R} (hr : algebra_map R A r * y = 1)
(hx : is_integral R (x * y)) : is_integral R x :=
(algebra_map R A).is_integral_of_is_integral_mul_unit x y r hr hx
/-- Generalization of `is_integral_of_mem_closure` bootstrapped up from that lemma -/
lemma is_integral_of_mem_closure' (G : set A) (hG : ∀ x ∈ G, is_integral R x) :
∀ x ∈ (subring.closure G), is_integral R x :=
λ x hx, subring.closure_induction hx hG is_integral_zero is_integral_one
(λ _ _, is_integral_add) (λ _, is_integral_neg) (λ _ _, is_integral_mul)
lemma is_integral_of_mem_closure'' {S : Type*} [comm_ring S] {f : R →+* S} (G : set S)
(hG : ∀ x ∈ G, f.is_integral_elem x) : ∀ x ∈ (subring.closure G), f.is_integral_elem x :=
λ x hx, @is_integral_of_mem_closure' R S _ _ f.to_algebra G hG x hx
end
section algebra
open algebra
variables {R A B S T : Type*}
variables [comm_ring R] [comm_ring A] [comm_ring B] [comm_ring S] [comm_ring T]
variables [algebra A B] [algebra R B] (f : R →+* S) (g : S →+* T)
lemma is_integral_trans_aux (x : B) {p : polynomial A} (pmonic : monic p) (hp : aeval x p = 0) :
is_integral (adjoin R (↑(p.map $ algebra_map A B).frange : set B)) x :=
begin
generalize hS : (↑(p.map $ algebra_map A B).frange : set B) = S,
have coeffs_mem : ∀ i, (p.map $ algebra_map A B).coeff i ∈ adjoin R S,
{ intro i, by_cases hi : (p.map $ algebra_map A B).coeff i = 0,
{ rw hi, exact subalgebra.zero_mem _ },
rw ← hS,
exact subset_adjoin (coeff_mem_frange _ _ hi) },
obtain ⟨q, hq⟩ : ∃ q : polynomial (adjoin R S), q.map (algebra_map (adjoin R S) B) =
(p.map $ algebra_map A B),
{ rw ← set.mem_range, exact (polynomial.mem_map_range _).2 (λ i, ⟨⟨_, coeffs_mem i⟩, rfl⟩) },
use q,
split,
{ suffices h : (q.map (algebra_map (adjoin R S) B)).monic,
{ refine monic_of_injective _ h,
exact subtype.val_injective },
{ rw hq, exact monic_map _ pmonic } },
{ convert hp using 1,
replace hq := congr_arg (eval x) hq,
convert hq using 1; symmetry; apply eval_map },
end
variables [algebra R A] [is_scalar_tower R A B]
/-- If A is an R-algebra all of whose elements are integral over R,
and x is an element of an A-algebra that is integral over A, then x is integral over R.-/
lemma is_integral_trans (A_int : is_integral R A) (x : B) (hx : is_integral A x) :
is_integral R x :=
begin
rcases hx with ⟨p, pmonic, hp⟩,
let S : set B := ↑(p.map $ algebra_map A B).frange,
refine is_integral_of_mem_of_fg (adjoin R (S ∪ {x})) _ _ (subset_adjoin $ or.inr rfl),
refine fg_trans (fg_adjoin_of_finite (finset.finite_to_set _) (λ x hx, _)) _,
{ rw [finset.mem_coe, frange, finset.mem_image] at hx,
rcases hx with ⟨i, _, rfl⟩,
rw coeff_map,
exact is_integral_alg_hom (is_scalar_tower.to_alg_hom R A B) (A_int _) },
{ apply fg_adjoin_singleton_of_integral,
exact is_integral_trans_aux _ pmonic hp }
end
/-- If A is an R-algebra all of whose elements are integral over R,
and B is an A-algebra all of whose elements are integral over A,
then all elements of B are integral over R.-/
lemma algebra.is_integral_trans (hA : is_integral R A) (hB : is_integral A B) : is_integral R B :=
λ x, is_integral_trans hA x (hB x)
lemma ring_hom.is_integral_trans (hf : f.is_integral) (hg : g.is_integral) :
(g.comp f).is_integral :=
@algebra.is_integral_trans R S T _ _ _ g.to_algebra (g.comp f).to_algebra f.to_algebra
(@is_scalar_tower.of_algebra_map_eq R S T _ _ _ f.to_algebra g.to_algebra (g.comp f).to_algebra
(ring_hom.comp_apply g f)) hf hg
lemma ring_hom.is_integral_of_surjective (hf : function.surjective f) : f.is_integral :=
λ x, (hf x).rec_on (λ y hy, (hy ▸ f.is_integral_map : f.is_integral_elem x))
lemma is_integral_of_surjective (h : function.surjective (algebra_map R A)) : is_integral R A :=
(algebra_map R A).is_integral_of_surjective h
/-- If `R → A → B` is an algebra tower with `A → B` injective,
then if the entire tower is an integral extension so is `R → A` -/
lemma is_integral_tower_bot_of_is_integral (H : function.injective (algebra_map A B))
{x : A} (h : is_integral R (algebra_map A B x)) : is_integral R x :=
begin
rcases h with ⟨p, ⟨hp, hp'⟩⟩,
refine ⟨p, ⟨hp, _⟩⟩,
rw [is_scalar_tower.algebra_map_eq R A B, ← eval₂_map,
eval₂_hom, ← ring_hom.map_zero (algebra_map A B)] at hp',
rw [eval₂_eq_eval_map],
exact H hp',
end
lemma ring_hom.is_integral_tower_bot_of_is_integral (hg : function.injective g)
(hfg : (g.comp f).is_integral) : f.is_integral :=
λ x,
@is_integral_tower_bot_of_is_integral R S T _ _ _ g.to_algebra (g.comp f).to_algebra f.to_algebra
(@is_scalar_tower.of_algebra_map_eq R S T _ _ _ f.to_algebra g.to_algebra (g.comp f).to_algebra
(ring_hom.comp_apply g f)) hg x (hfg (g x))
lemma is_integral_tower_bot_of_is_integral_field {R A B : Type*} [comm_ring R] [field A]
[comm_ring B] [nontrivial B] [algebra R A] [algebra A B] [algebra R B] [is_scalar_tower R A B]
{x : A} (h : is_integral R (algebra_map A B x)) : is_integral R x :=
is_integral_tower_bot_of_is_integral (algebra_map A B).injective h
lemma ring_hom.is_integral_elem_of_is_integral_elem_comp {x : T}
(h : (g.comp f).is_integral_elem x) : g.is_integral_elem x :=
let ⟨p, ⟨hp, hp'⟩⟩ := h in ⟨p.map f, monic_map f hp, by rwa ← eval₂_map at hp'⟩
lemma ring_hom.is_integral_tower_top_of_is_integral (h : (g.comp f).is_integral) : g.is_integral :=
λ x, ring_hom.is_integral_elem_of_is_integral_elem_comp f g (h x)
/-- If `R → A → B` is an algebra tower,
then if the entire tower is an integral extension so is `A → B`. -/
lemma is_integral_tower_top_of_is_integral {x : B} (h : is_integral R x) : is_integral A x :=
begin
rcases h with ⟨p, ⟨hp, hp'⟩⟩,
refine ⟨p.map (algebra_map R A), ⟨monic_map (algebra_map R A) hp, _⟩⟩,
rw [is_scalar_tower.algebra_map_eq R A B, ← eval₂_map] at hp',
exact hp',
end
lemma ring_hom.is_integral_quotient_of_is_integral {I : ideal S} (hf : f.is_integral) :
(ideal.quotient_map I f le_rfl).is_integral :=
begin
rintros ⟨x⟩,
obtain ⟨p, ⟨p_monic, hpx⟩⟩ := hf x,
refine ⟨p.map (ideal.quotient.mk _), ⟨monic_map _ p_monic, _⟩⟩,
simpa only [hom_eval₂, eval₂_map] using congr_arg (ideal.quotient.mk I) hpx
end
lemma is_integral_quotient_of_is_integral {I : ideal A} (hRA : is_integral R A) :
is_integral (I.comap (algebra_map R A)).quotient I.quotient :=
(algebra_map R A).is_integral_quotient_of_is_integral hRA
lemma is_integral_quotient_map_iff {I : ideal S} :
(ideal.quotient_map I f le_rfl).is_integral ↔
((ideal.quotient.mk I).comp f : R →+* I.quotient).is_integral :=
begin
let g := ideal.quotient.mk (I.comap f),
have := ideal.quotient_map_comp_mk le_rfl,
refine ⟨λ h, _, λ h, ring_hom.is_integral_tower_top_of_is_integral g _ (this ▸ h)⟩,
refine this ▸ ring_hom.is_integral_trans g (ideal.quotient_map I f le_rfl) _ h,
exact ring_hom.is_integral_of_surjective g ideal.quotient.mk_surjective,
end
/-- If the integral extension `R → S` is injective, and `S` is a field, then `R` is also a field. -/
lemma is_field_of_is_integral_of_is_field {R S : Type*} [integral_domain R] [integral_domain S]
[algebra R S] (H : is_integral R S) (hRS : function.injective (algebra_map R S))
(hS : is_field S) : is_field R :=
begin
refine ⟨⟨0, 1, zero_ne_one⟩, mul_comm, λ a ha, _⟩,
-- Let `a_inv` be the inverse of `algebra_map R S a`,
-- then we need to show that `a_inv` is of the form `algebra_map R S b`.
obtain ⟨a_inv, ha_inv⟩ := hS.mul_inv_cancel (λ h, ha (hRS (trans h (ring_hom.map_zero _).symm))),
-- Let `p : polynomial R` be monic with root `a_inv`,
-- and `q` be `p` with coefficients reversed (so `q(a) = q'(a) * a + 1`).
-- We claim that `q(a) = 0`, so `-q'(a)` is the inverse of `a`.
obtain ⟨p, p_monic, hp⟩ := H a_inv,
use -∑ (i : ℕ) in finset.range p.nat_degree, (p.coeff i) * a ^ (p.nat_degree - i - 1),
-- `q(a) = 0`, because multiplying everything with `a_inv^n` gives `p(a_inv) = 0`.
-- TODO: this could be a lemma for `polynomial.reverse`.
have hq : ∑ (i : ℕ) in finset.range (p.nat_degree + 1), (p.coeff i) * a ^ (p.nat_degree - i) = 0,
{ apply (algebra_map R S).injective_iff.mp hRS,
have a_inv_ne_zero : a_inv ≠ 0 := right_ne_zero_of_mul (mt ha_inv.symm.trans one_ne_zero),
refine (mul_eq_zero.mp _).resolve_right (pow_ne_zero p.nat_degree a_inv_ne_zero),
rw [eval₂_eq_sum_range] at hp,
rw [ring_hom.map_sum, finset.sum_mul],
refine (finset.sum_congr rfl (λ i hi, _)).trans hp,
rw [ring_hom.map_mul, mul_assoc],
congr,
have : a_inv ^ p.nat_degree = a_inv ^ (p.nat_degree - i) * a_inv ^ i,
{ rw [← pow_add a_inv, nat.sub_add_cancel (nat.le_of_lt_succ (finset.mem_range.mp hi))] },
rw [ring_hom.map_pow, this, ← mul_assoc, ← mul_pow, ha_inv, one_pow, one_mul] },
-- Since `q(a) = 0` and `q(a) = q'(a) * a + 1`, we have `a * -q'(a) = 1`.
-- TODO: we could use a lemma for `polynomial.div_X` here.
rw [finset.sum_range_succ_comm, p_monic.coeff_nat_degree, one_mul, nat.sub_self, pow_zero,
add_eq_zero_iff_eq_neg, eq_comm] at hq,
rw [mul_comm, ← neg_mul_eq_neg_mul, finset.sum_mul],
convert hq using 2,
refine finset.sum_congr rfl (λ i hi, _),
have : 1 ≤ p.nat_degree - i := nat.le_sub_left_of_add_le (finset.mem_range.mp hi),
rw [mul_assoc, ← pow_succ', nat.sub_add_cancel this]
end
end algebra
section
local attribute [instance] subset.comm_ring algebra.of_is_subring
theorem integral_closure_idem {R : Type*} {A : Type*} [comm_ring R] [comm_ring A] [algebra R A] :
integral_closure (integral_closure R A : set A) A = ⊥ :=
eq_bot_iff.2 $ λ x hx, algebra.mem_bot.2
⟨⟨x, @is_integral_trans _ _ _ _ _ _ _ _ (integral_closure R A).algebra
_ integral_closure.is_integral x hx⟩, rfl⟩
end
section integral_domain
variables {R S : Type*} [comm_ring R] [integral_domain S] [algebra R S]
instance : integral_domain (integral_closure R S) :=
infer_instance
end integral_domain
|
509307a7292af9d242b6d69711012607a6950571 | d1a52c3f208fa42c41df8278c3d280f075eb020c | /tests/leanpkg/cyclic/Cyclic/A/B.lean | 41c84985d2a232f841b90aa4306f44b57431b12f | [
"Apache-2.0",
"LLVM-exception",
"NCSA",
"LGPL-3.0-only",
"LicenseRef-scancode-inner-net-2.0",
"BSD-3-Clause",
"LGPL-2.0-or-later",
"Spencer-94",
"LGPL-2.1-or-later",
"HPND",
"LicenseRef-scancode-pcre",
"ISC",
"LGPL-2.1-only",
"LicenseRef-scancode-other-permissive",
"SunPro",
"CMU-Mach"... | permissive | cipher1024/lean4 | 6e1f98bb58e7a92b28f5364eb38a14c8d0aae393 | 69114d3b50806264ef35b57394391c3e738a9822 | refs/heads/master | 1,642,227,983,603 | 1,642,011,696,000 | 1,642,011,696,000 | 228,607,691 | 0 | 0 | Apache-2.0 | 1,576,584,269,000 | 1,576,584,268,000 | null | UTF-8 | Lean | false | false | 14 | lean | import Cyclic
|
275b6a68bff13b96d4a329a67d6112898354e4d7 | 624f6f2ae8b3b1adc5f8f67a365c51d5126be45a | /tests/compiler/partial.lean | b061a0f177a6b4e5a56ea6d9726b57d1adcccccd | [
"Apache-2.0"
] | permissive | mhuisi/lean4 | 28d35a4febc2e251c7f05492e13f3b05d6f9b7af | dda44bc47f3e5d024508060dac2bcb59fd12e4c0 | refs/heads/master | 1,621,225,489,283 | 1,585,142,689,000 | 1,585,142,689,000 | 250,590,438 | 0 | 2 | Apache-2.0 | 1,602,443,220,000 | 1,585,327,814,000 | C | UTF-8 | Lean | false | false | 373 | lean | set_option pp.implicit true
set_option pp.binder_types false
-- set_option trace.compiler.boxed true
partial def contains : String → Char → Nat → Bool
| s, c, i =>
if s.atEnd i then false
else if s.get i == c then true
else contains s c (s.next i)
def main : IO Unit :=
let s1 := "hello";
IO.println (contains s1 'a' 0) *>
IO.println (contains s1 'o' 0)
|
62cd94be6bfb7d96a0f5e3888f29a570d8737f28 | a047a4718edfa935d17231e9e6ecec8c7b701e05 | /src/analysis/analytic/composition.lean | a12a57d57a242b106fb079486566ad72de805ef2 | [
"Apache-2.0"
] | permissive | utensil-contrib/mathlib | bae0c9fafe5e2bdb516efc89d6f8c1502ecc9767 | b91909e77e219098a2f8cc031f89d595fe274bd2 | refs/heads/master | 1,668,048,976,965 | 1,592,442,701,000 | 1,592,442,701,000 | 273,197,855 | 0 | 0 | null | 1,592,472,812,000 | 1,592,472,811,000 | null | UTF-8 | Lean | false | false | 56,619 | lean | /-
Copyright (c) 2020 Sébastien Gouëzel. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Sébastien Gouëzel, Johan Commelin
-/
import analysis.analytic.basic
import combinatorics.composition
/-!
# Composition of analytic functions
in this file we prove that the composition of analytic functions is analytic.
The argument is the following. Assume `g z = ∑' qₙ (z, ..., z)` and `f y = ∑' pₖ (y, ..., y)`. Then
`g (f y) = ∑' qₙ (∑' pₖ (y, ..., y), ..., ∑' pₖ (y, ..., y))
= ∑' qₙ (p_{i₁} (y, ..., y), ..., p_{iₙ} (y, ..., y))`.
For each `n` and `i₁, ..., iₙ`, define a `i₁ + ... + iₙ` multilinear function mapping
`(y₀, ..., y_{i₁ + ... + iₙ - 1})` to
`qₙ (p_{i₁} (y₀, ..., y_{i₁-1}), p_{i₂} (y_{i₁}, ..., y_{i₁ + i₂ - 1}), ..., p_{iₙ} (....)))`.
Then `g ∘ f` is obtained by summing all these multilinear functions.
To formalize this, we use compositions of an integer `N`, i.e., its decompositions into
a sum `i₁ + ... + iₙ` of positive integers. Given such a composition `c` and two formal
multilinear series `q` and `p`, let `q.comp_along_composition p c` be the above multilinear
function. Then the `N`-th coefficient in the power series expansion of `g ∘ f` is the sum of these
terms over all `c : composition N`.
To complete the proof, we need to show that this power series has a positive radius of convergence.
This follows from the fact that `composition N` has cardinality `2^(N-1)` and estimates on
the norm of `qₙ` and `pₖ`, which give summability. We also need to show that it indeed converges to
`g ∘ f`. For this, we note that the composition of partial sums converges to `g ∘ f`, and that it
corresponds to a part of the whole sum, on a subset that increases to the whole space. By
summability of the norms, this implies the overall convergence.
## Main results
* `q.comp p` is the formal composition of the formal multilinear series `q` and `p`.
* `has_fpower_series_at.comp` states that if two functions `g` and `f` admit power series expansions
`q` and `p`, then `g ∘ f` admits a power series expansion given by `q.comp p`.
* `analytic_at.comp` states that the composition of analytic functions is analytic.
* `formal_multilinear_series.comp_assoc` states that composition is associative on formal
multilinear series.
## Implementation details
The main technical difficulty is to write down things. In particular, we need to define precisely
`q.comp_along_composition p c` and to show that it is indeed a continuous multilinear
function. This requires a whole interface built on the class `composition`. Once this is set,
the main difficulty is to reorder the sums, writing the composition of the partial sums as a sum
over some subset of `Σ n, composition n`. We need to check that the reordering is a bijection,
running over difficulties due to the dependent nature of the types under consideration, that are
controlled thanks to the interface for `composition`.
The associativity of composition on formal multilinear series is a nontrivial result: it does not
follow from the associativity of composition of analytic functions, as there is no uniqueness for
the formal multilinear series representing a function (and also, it holds even when the radius of
convergence of the series is `0`). Instead, we give a direct proof, which amounts to reordering
double sums in a careful way. The change of variables is a canonical (combinatorial) bijection
`composition.sigma_equiv_sigma_pi` between `(Σ (a : composition n), composition a.length)` and
`(Σ (c : composition n), Π (i : fin c.length), composition (c.blocks_fun i))`, and is described
in more details below in the paragraph on associativity.
-/
noncomputable theory
variables {𝕜 : Type*} [nondiscrete_normed_field 𝕜]
{E : Type*} [normed_group E] [normed_space 𝕜 E]
{F : Type*} [normed_group F] [normed_space 𝕜 F]
{G : Type*} [normed_group G] [normed_space 𝕜 G]
{H : Type*} [normed_group H] [normed_space 𝕜 H]
open filter list
open_locale topological_space big_operators classical
/-! ### Composing formal multilinear series -/
namespace formal_multilinear_series
/-!
In this paragraph, we define the composition of formal multilinear series, by summing over all
possible compositions of `n`.
-/
/-- Given a formal multilinear series `p`, a composition `c` of `n` and the index `i` of a
block of `c`, we may define a function on `fin n → E` by picking the variables in the `i`-th block
of `n`, and applying the corresponding coefficient of `p` to these variables. This function is
called `p.apply_composition c v i` for `v : fin n → E` and `i : fin c.length`. -/
def apply_composition
(p : formal_multilinear_series 𝕜 E F) {n : ℕ} (c : composition n) :
(fin n → E) → (fin (c.length) → F) :=
λ v i, p (c.blocks_fun i) (v ∘ (c.embedding i))
lemma apply_composition_ones (p : formal_multilinear_series 𝕜 E F) (n : ℕ) :
apply_composition p (composition.ones n) =
λ v i, p 1 (λ _, v (i.cast_le (composition.length_le _))) :=
begin
funext v i,
apply p.congr (composition.ones_blocks_fun _ _),
intros j hjn hj1,
obtain rfl : j = 0, { linarith },
refine congr_arg v _,
rw [fin.ext_iff, fin.cast_le_val, composition.ones_embedding],
end
/-- Technical lemma stating how `p.apply_composition` commutes with updating variables. This
will be the key point to show that functions constructed from `apply_composition` retain
multilinearity. -/
lemma apply_composition_update
(p : formal_multilinear_series 𝕜 E F) {n : ℕ} (c : composition n)
(j : fin n) (v : fin n → E) (z : E) :
p.apply_composition c (function.update v j z) =
function.update (p.apply_composition c v) (c.index j)
(p (c.blocks_fun (c.index j))
(function.update (v ∘ (c.embedding (c.index j))) (c.inv_embedding j) z)) :=
begin
ext k,
by_cases h : k = c.index j,
{ rw h,
let r : fin (c.blocks_fun (c.index j)) → fin n := c.embedding (c.index j),
simp only [function.update_same],
change p (c.blocks_fun (c.index j)) ((function.update v j z) ∘ r) = _,
let j' := c.inv_embedding j,
suffices B : (function.update v j z) ∘ r = function.update (v ∘ r) j' z,
by rw B,
suffices C : (function.update v (r j') z) ∘ r = function.update (v ∘ r) j' z,
by { convert C, exact (c.embedding_comp_inv j).symm },
exact function.update_comp_eq_of_injective _ (c.embedding_inj _) _ _ },
{ simp only [h, function.update_eq_self, function.update_noteq, ne.def, not_false_iff],
let r : fin (c.blocks_fun k) → fin n := c.embedding k,
change p (c.blocks_fun k) ((function.update v j z) ∘ r) = p (c.blocks_fun k) (v ∘ r),
suffices B : (function.update v j z) ∘ r = v ∘ r, by rw B,
apply function.update_comp_eq_of_not_mem_range,
rwa c.mem_range_embedding_iff' }
end
/-- Given two formal multilinear series `q` and `p` and a composition `c` of `n`, one may
form a multilinear map in `n` variables by applying the right coefficient of `p` to each block of
the composition, and then applying `q c.length` to the resulting vector. It is called
`q.comp_along_composition_multilinear p c`. This function admits a version as a continuous
multilinear map, called `q.comp_along_composition p c` below. -/
def comp_along_composition_multilinear {n : ℕ}
(q : formal_multilinear_series 𝕜 F G) (p : formal_multilinear_series 𝕜 E F)
(c : composition n) : multilinear_map 𝕜 (λ i : fin n, E) G :=
{ to_fun := λ v, q c.length (p.apply_composition c v),
map_add' := λ v i x y, by simp only [apply_composition_update,
continuous_multilinear_map.map_add],
map_smul' := λ v i c x, by simp only [apply_composition_update,
continuous_multilinear_map.map_smul] }
/-- The norm of `q.comp_along_composition_multilinear p c` is controlled by the product of
the norms of the relevant bits of `q` and `p`. -/
lemma comp_along_composition_multilinear_bound {n : ℕ}
(q : formal_multilinear_series 𝕜 F G) (p : formal_multilinear_series 𝕜 E F)
(c : composition n) (v : fin n → E) :
∥q.comp_along_composition_multilinear p c v∥ ≤
∥q c.length∥ * (∏ i, ∥p (c.blocks_fun i)∥) * (∏ i : fin n, ∥v i∥) :=
calc ∥q.comp_along_composition_multilinear p c v∥ = ∥q c.length (p.apply_composition c v)∥ : rfl
... ≤ ∥q c.length∥ * ∏ i, ∥p.apply_composition c v i∥ : continuous_multilinear_map.le_op_norm _ _
... ≤ ∥q c.length∥ * ∏ i, ∥p (c.blocks_fun i)∥ * ∏ j : fin (c.blocks_fun i), ∥(v ∘ (c.embedding i)) j∥ :
begin
apply mul_le_mul_of_nonneg_left _ (norm_nonneg _),
refine finset.prod_le_prod (λ i hi, norm_nonneg _) (λ i hi, _),
apply continuous_multilinear_map.le_op_norm,
end
... = ∥q c.length∥ * (∏ i, ∥p (c.blocks_fun i)∥) *
∏ i (j : fin (c.blocks_fun i)), ∥(v ∘ (c.embedding i)) j∥ :
by rw [finset.prod_mul_distrib, mul_assoc]
... = ∥q c.length∥ * (∏ i, ∥p (c.blocks_fun i)∥) * (∏ i : fin n, ∥v i∥) :
by { rw [← finset.prod_equiv c.blocks_fin_equiv, ← finset.univ_sigma_univ, finset.prod_sigma],
congr }
/-- Given two formal multilinear series `q` and `p` and a composition `c` of `n`, one may
form a continuous multilinear map in `n` variables by applying the right coefficient of `p` to each
block of the composition, and then applying `q c.length` to the resulting vector. It is
called `q.comp_along_composition p c`. It is constructed from the analogous multilinear
function `q.comp_along_composition_multilinear p c`, together with a norm control to get
the continuity. -/
def comp_along_composition {n : ℕ}
(q : formal_multilinear_series 𝕜 F G) (p : formal_multilinear_series 𝕜 E F)
(c : composition n) : continuous_multilinear_map 𝕜 (λ i : fin n, E) G :=
(q.comp_along_composition_multilinear p c).mk_continuous _
(q.comp_along_composition_multilinear_bound p c)
@[simp] lemma comp_along_composition_apply {n : ℕ}
(q : formal_multilinear_series 𝕜 F G) (p : formal_multilinear_series 𝕜 E F)
(c : composition n) (v : fin n → E) :
(q.comp_along_composition p c) v = q c.length (p.apply_composition c v) := rfl
/-- The norm of `q.comp_along_composition p c` is controlled by the product of
the norms of the relevant bits of `q` and `p`. -/
lemma comp_along_composition_norm {n : ℕ}
(q : formal_multilinear_series 𝕜 F G) (p : formal_multilinear_series 𝕜 E F)
(c : composition n) :
∥q.comp_along_composition p c∥ ≤ ∥q c.length∥ * ∏ i, ∥p (c.blocks_fun i)∥ :=
multilinear_map.mk_continuous_norm_le _
(mul_nonneg (norm_nonneg _) (finset.prod_nonneg (λ i hi, norm_nonneg _))) _
lemma comp_along_composition_nnnorm {n : ℕ}
(q : formal_multilinear_series 𝕜 F G) (p : formal_multilinear_series 𝕜 E F)
(c : composition n) :
nnnorm (q.comp_along_composition p c) ≤ nnnorm (q c.length) * ∏ i, nnnorm (p (c.blocks_fun i)) :=
by simpa only [← nnreal.coe_le_coe, coe_nnnorm, nnreal.coe_mul, coe_nnnorm, nnreal.coe_prod, coe_nnnorm]
using q.comp_along_composition_norm p c
/-- Formal composition of two formal multilinear series. The `n`-th coefficient in the composition
is defined to be the sum of `q.comp_along_composition p c` over all compositions of
`n`. In other words, this term (as a multilinear function applied to `v_0, ..., v_{n-1}`) is
`∑'_{k} ∑'_{i₁ + ... + iₖ = n} pₖ (q_{i_1} (...), ..., q_{i_k} (...))`, where one puts all variables
`v_0, ..., v_{n-1}` in increasing order in the dots.-/
protected def comp (q : formal_multilinear_series 𝕜 F G) (p : formal_multilinear_series 𝕜 E F) :
formal_multilinear_series 𝕜 E G :=
λ n, ∑ c : composition n, q.comp_along_composition p c
/-- The `0`-th coefficient of `q.comp p` is `q 0`. Since these maps are multilinear maps in zero
variables, but on different spaces, we can not state this directly, so we state it when applied to
arbitrary vectors (which have to be the zero vector). -/
lemma comp_coeff_zero (q : formal_multilinear_series 𝕜 F G) (p : formal_multilinear_series 𝕜 E F)
(v : fin 0 → E) (v' : fin 0 → F) :
(q.comp p) 0 v = q 0 v' :=
begin
let c : composition 0 := composition.ones 0,
dsimp [formal_multilinear_series.comp],
have : {c} = (finset.univ : finset (composition 0)),
{ apply finset.eq_of_subset_of_card_le; simp [finset.card_univ, composition_card 0] },
rw ← this,
simp only [finset.sum_singleton, continuous_multilinear_map.sum_apply],
change q c.length (p.apply_composition c v) = q 0 v',
congr,
ext i,
simp only [composition.ones_length] at i,
exact fin_zero_elim i
end
@[simp] lemma comp_coeff_zero'
(q : formal_multilinear_series 𝕜 F G) (p : formal_multilinear_series 𝕜 E F) (v : fin 0 → E) :
(q.comp p) 0 v = q 0 (λ i, 0) :=
q.comp_coeff_zero p v _
/-- The `0`-th coefficient of `q.comp p` is `q 0`. When `p` goes from `E` to `E`, this can be
expressed as a direct equality -/
lemma comp_coeff_zero'' (q : formal_multilinear_series 𝕜 E F) (p : formal_multilinear_series 𝕜 E E) :
(q.comp p) 0 = q 0 :=
by { ext v, exact q.comp_coeff_zero p _ _ }
/-!
### The identity formal power series
We will now define the identity power series, and show that it is a neutral element for left and
right composition.
-/
section
variables (𝕜 E)
/-- The identity formal multilinear series, with all coefficients equal to `0` except for `n = 1`
where it is (the continuous multilinear version of) the identity. -/
def id : formal_multilinear_series 𝕜 E E
| 0 := 0
| 1 := (continuous_multilinear_curry_fin1 𝕜 E E).symm (continuous_linear_map.id 𝕜 E)
| _ := 0
/-- The first coefficient of `id 𝕜 E` is the identity. -/
@[simp] lemma id_apply_one (v : fin 1 → E) : (formal_multilinear_series.id 𝕜 E) 1 v = v 0 := rfl
/-- The `n`th coefficient of `id 𝕜 E` is the identity when `n = 1`. We state this in a dependent
way, as it will often appear in this form. -/
lemma id_apply_one' {n : ℕ} (h : n = 1) (v : fin n → E) :
(id 𝕜 E) n v = v ⟨0, h.symm ▸ zero_lt_one⟩ :=
begin
let w : fin 1 → E := λ i, v ⟨i.1, h.symm ▸ i.2⟩,
have : v ⟨0, h.symm ▸ zero_lt_one⟩ = w 0 := rfl,
rw [this, ← id_apply_one 𝕜 E w],
apply congr _ h,
intros,
obtain rfl : i = 0, { linarith },
exact this,
end
/-- For `n ≠ 1`, the `n`-th coefficient of `id 𝕜 E` is zero, by definition. -/
@[simp] lemma id_apply_ne_one {n : ℕ} (h : n ≠ 1) : (formal_multilinear_series.id 𝕜 E) n = 0 :=
by { cases n, { refl }, cases n, { contradiction }, refl }
end
@[simp] theorem comp_id (p : formal_multilinear_series 𝕜 E F) : p.comp (id 𝕜 E) = p :=
begin
ext1 n,
dsimp [formal_multilinear_series.comp],
rw finset.sum_eq_single (composition.ones n),
show comp_along_composition p (id 𝕜 E) (composition.ones n) = p n,
{ ext v,
rw comp_along_composition_apply,
apply p.congr (composition.ones_length n),
intros,
rw apply_composition_ones,
refine congr_arg v _,
rw [fin.ext_iff, fin.cast_le_val], },
show ∀ (b : composition n),
b ∈ finset.univ → b ≠ composition.ones n → comp_along_composition p (id 𝕜 E) b = 0,
{ assume b _ hb,
obtain ⟨k, hk, lt_k⟩ : ∃ (k : ℕ) (H : k ∈ composition.blocks b), 1 < k :=
composition.ne_ones_iff.1 hb,
obtain ⟨i, i_lt, hi⟩ : ∃ (i : ℕ) (h : i < b.blocks.length), b.blocks.nth_le i h = k :=
nth_le_of_mem hk,
let j : fin b.length := ⟨i, b.blocks_length ▸ i_lt⟩,
have A : 1 < b.blocks_fun j := by convert lt_k,
ext v,
rw [comp_along_composition_apply, continuous_multilinear_map.zero_apply],
apply continuous_multilinear_map.map_coord_zero _ j,
dsimp [apply_composition],
rw id_apply_ne_one _ _ (ne_of_gt A),
refl },
{ simp }
end
theorem id_comp (p : formal_multilinear_series 𝕜 E F) (h : p 0 = 0) : (id 𝕜 F).comp p = p :=
begin
ext1 n,
by_cases hn : n = 0,
{ rw [hn, h],
ext v,
rw [comp_coeff_zero', id_apply_ne_one _ _ zero_ne_one],
refl },
{ dsimp [formal_multilinear_series.comp],
have n_pos : 0 < n := bot_lt_iff_ne_bot.mpr hn,
rw finset.sum_eq_single (composition.single n n_pos),
show comp_along_composition (id 𝕜 F) p (composition.single n n_pos) = p n,
{ ext v,
rw [comp_along_composition_apply, id_apply_one' _ _ (composition.single_length n_pos)],
dsimp [apply_composition],
apply p.congr rfl,
intros,
rw [function.comp_app, composition.single_embedding] },
show ∀ (b : composition n),
b ∈ finset.univ → b ≠ composition.single n n_pos → comp_along_composition (id 𝕜 F) p b = 0,
{ assume b _ hb,
have A : b.length ≠ 1, by simpa [composition.eq_single_iff] using hb,
ext v,
rw [comp_along_composition_apply, id_apply_ne_one _ _ A],
refl },
{ simp } }
end
/-! ### Summability properties of the composition of formal power series-/
/-- If two formal multilinear series have positive radius of convergence, then the terms appearing
in the definition of their composition are also summable (when multiplied by a suitable positive
geometric term). -/
theorem comp_summable_nnreal
(q : formal_multilinear_series 𝕜 F G) (p : formal_multilinear_series 𝕜 E F)
(hq : 0 < q.radius) (hp : 0 < p.radius) :
∃ (r : nnreal), 0 < r ∧ summable (λ i, nnnorm (q.comp_along_composition p i.2) * r ^ i.1 :
(Σ n, composition n) → nnreal) :=
begin
/- This follows from the fact that the growth rate of `∥qₙ∥` and `∥pₙ∥` is at most geometric,
giving a geometric bound on each `∥q.comp_along_composition p op∥`, together with the
fact that there are `2^(n-1)` compositions of `n`, giving at most a geometric loss. -/
rcases ennreal.lt_iff_exists_nnreal_btwn.1 hq with ⟨rq, rq_pos, hrq⟩,
rcases ennreal.lt_iff_exists_nnreal_btwn.1 hp with ⟨rp, rp_pos, hrp⟩,
obtain ⟨Cq, hCq⟩ : ∃ (Cq : nnreal), ∀ n, nnnorm (q n) * rq^n ≤ Cq := q.bound_of_lt_radius hrq,
obtain ⟨Cp, hCp⟩ : ∃ (Cp : nnreal), ∀ n, nnnorm (p n) * rp^n ≤ Cp := p.bound_of_lt_radius hrp,
let r0 : nnreal := (4 * max Cp 1)⁻¹,
set r := min rp 1 * min rq 1 * r0,
have r_pos : 0 < r,
{ apply mul_pos (mul_pos _ _),
{ rw [nnreal.inv_pos],
apply mul_pos,
{ norm_num },
{ exact lt_of_lt_of_le zero_lt_one (le_max_right _ _) } },
{ rw ennreal.coe_pos at rp_pos, simp [rp_pos, zero_lt_one] },
{ rw ennreal.coe_pos at rq_pos, simp [rq_pos, zero_lt_one] } },
let a : ennreal := ((4 : nnreal) ⁻¹ : nnreal),
have two_a : 2 * a < 1,
{ change ((2 : nnreal) : ennreal) * ((4 : nnreal) ⁻¹ : nnreal) < (1 : nnreal),
rw [← ennreal.coe_mul, ennreal.coe_lt_coe, ← nnreal.coe_lt_coe, nnreal.coe_mul],
change (2 : ℝ) * (4 : ℝ)⁻¹ < 1,
norm_num },
have I : ∀ (i : Σ (n : ℕ), composition n),
↑(nnnorm (q.comp_along_composition p i.2) * r ^ i.1) ≤ (Cq : ennreal) * a ^ i.1,
{ rintros ⟨n, c⟩,
rw [← ennreal.coe_pow, ← ennreal.coe_mul, ennreal.coe_le_coe],
calc nnnorm (q.comp_along_composition p c) * r ^ n
≤ (nnnorm (q c.length) * ∏ i, nnnorm (p (c.blocks_fun i))) * r ^ n :
mul_le_mul_of_nonneg_right (q.comp_along_composition_nnnorm p c) (bot_le)
... = (nnnorm (q c.length) * (min rq 1)^n) *
((∏ i, nnnorm (p (c.blocks_fun i))) * (min rp 1) ^ n) *
r0 ^ n : by { dsimp [r], ring_exp }
... ≤ (nnnorm (q c.length) * (min rq 1) ^ c.length) *
(∏ i, nnnorm (p (c.blocks_fun i)) * (min rp 1) ^ (c.blocks_fun i)) * r0 ^ n :
begin
apply_rules [mul_le_mul, bot_le, le_refl, pow_le_pow_of_le_one, min_le_right, c.length_le],
apply le_of_eq,
rw finset.prod_mul_distrib,
congr' 1,
conv_lhs { rw [← c.sum_blocks_fun, ← finset.prod_pow_eq_pow_sum] },
end
... ≤ Cq * (∏ i : fin c.length, Cp) * r0 ^ n :
begin
apply_rules [mul_le_mul, bot_le, le_trans _ (hCq c.length), le_refl, finset.prod_le_prod'],
{ assume i hi,
refine le_trans (mul_le_mul (le_refl _) _ bot_le bot_le) (hCp (c.blocks_fun i)),
exact pow_le_pow_of_le_left bot_le (min_le_left _ _) _ },
{ refine mul_le_mul (le_refl _) _ bot_le bot_le,
exact pow_le_pow_of_le_left bot_le (min_le_left _ _) _ }
end
... ≤ Cq * (max Cp 1) ^ n * r0 ^ n :
begin
apply_rules [mul_le_mul, bot_le, le_refl],
simp only [finset.card_fin, finset.prod_const],
refine le_trans (pow_le_pow_of_le_left bot_le (le_max_left Cp 1) c.length) _,
apply pow_le_pow (le_max_right Cp 1) c.length_le,
end
... = Cq * 4⁻¹ ^ n :
begin
dsimp [r0],
have A : (4 : nnreal) ≠ 0, by norm_num,
have B : max Cp 1 ≠ 0 :=
ne_of_gt (lt_of_lt_of_le zero_lt_one (le_max_right Cp 1)),
field_simp [A, B],
ring_exp
end },
refine ⟨r, r_pos, _⟩,
rw [← ennreal.tsum_coe_ne_top_iff_summable],
apply ne_of_lt,
calc (∑' (i : Σ (n : ℕ), composition n), ↑(nnnorm (q.comp_along_composition p i.2) * r ^ i.1))
≤ (∑' (i : Σ (n : ℕ), composition n), (Cq : ennreal) * a ^ i.1) : ennreal.tsum_le_tsum I
... = (∑' (n : ℕ), (∑' (c : composition n), (Cq : ennreal) * a ^ n)) : ennreal.tsum_sigma' _
... = (∑' (n : ℕ), ↑(fintype.card (composition n)) * (Cq : ennreal) * a ^ n) :
begin
congr' 1,
ext1 n,
rw [tsum_fintype, finset.sum_const, nsmul_eq_mul, finset.card_univ, mul_assoc]
end
... ≤ (∑' (n : ℕ), (2 : ennreal) ^ n * (Cq : ennreal) * a ^ n) :
begin
apply ennreal.tsum_le_tsum (λ n, _),
apply ennreal.mul_le_mul (ennreal.mul_le_mul _ (le_refl _)) (le_refl _),
rw composition_card,
simp only [nat.cast_bit0, nat.cast_one, nat.cast_pow],
apply ennreal.pow_le_pow _ (nat.sub_le n 1),
have : (1 : nnreal) ≤ (2 : nnreal), by norm_num,
rw ← ennreal.coe_le_coe at this,
exact this
end
... = (∑' (n : ℕ), (Cq : ennreal) * (2 * a) ^ n) : by { congr' 1, ext1 n, rw mul_pow, ring }
... = (Cq : ennreal) * (1 - 2 * a) ⁻¹ : by rw [ennreal.tsum_mul_left, ennreal.tsum_geometric]
... < ⊤ : by simp [lt_top_iff_ne_top, ennreal.mul_eq_top, two_a]
end
/-- Bounding below the radius of the composition of two formal multilinear series assuming
summability over all compositions. -/
theorem le_comp_radius_of_summable
(q : formal_multilinear_series 𝕜 F G) (p : formal_multilinear_series 𝕜 E F) (r : nnreal)
(hr : summable (λ i, nnnorm (q.comp_along_composition p i.2) * r ^ i.1 :
(Σ n, composition n) → nnreal)) :
(r : ennreal) ≤ (q.comp p).radius :=
begin
apply le_radius_of_bound _ (tsum (λ (i : Σ (n : ℕ), composition n),
(nnnorm (comp_along_composition q p i.snd) * r ^ i.fst))),
assume n,
calc nnnorm (formal_multilinear_series.comp q p n) * r ^ n ≤
∑' (c : composition n), nnnorm (comp_along_composition q p c) * r ^ n :
begin
rw [tsum_fintype, ← finset.sum_mul],
exact mul_le_mul_of_nonneg_right (nnnorm_sum_le _ _) bot_le
end
... ≤ ∑' (i : Σ (n : ℕ), composition n),
nnnorm (comp_along_composition q p i.snd) * r ^ i.fst :
begin
let f : composition n → (Σ (n : ℕ), composition n) := λ c, ⟨n, c⟩,
have : function.injective f, by tidy,
convert nnreal.tsum_comp_le_tsum_of_inj hr this
end
end
/-!
### Composing analytic functions
Now, we will prove that the composition of the partial sums of `q` and `p` up to order `N` is
given by a sum over some large subset of `Σ n, composition n` of `q.comp_along_composition p`, to
deduce that the series for `q.comp p` indeed converges to `g ∘ f` when `q` is a power series for
`g` and `p` is a power series for `f`.
This proof is a big reindexing argument of a sum. Since it is a bit involved, we define first
the source of the change of variables (`comp_partial_source`), its target
(`comp_partial_target`) and the change of variables itself (`comp_change_of_variables`) before
giving the main statement in `comp_partial_sum`. -/
/-- Source set in the change of variables to compute the composition of partial sums of formal
power series.
See also `comp_partial_sum`. -/
def comp_partial_sum_source (N : ℕ) : finset (Σ n, (fin n) → ℕ) :=
finset.sigma (finset.range N) (λ (n : ℕ), fintype.pi_finset (λ (i : fin n), finset.Ico 1 N) : _)
@[simp] lemma mem_comp_partial_sum_source_iff (N : ℕ) (i : Σ n, (fin n) → ℕ) :
i ∈ comp_partial_sum_source N ↔ i.1 < N ∧ ∀ (a : fin i.1), 1 ≤ i.2 a ∧ i.2 a < N :=
by simp only [comp_partial_sum_source, finset.Ico.mem,
fintype.mem_pi_finset, finset.mem_sigma, finset.mem_range]
/-- Change of variables appearing to compute the composition of partial sums of formal
power series -/
def comp_change_of_variables (N : ℕ) (i : Σ n, (fin n) → ℕ) (hi : i ∈ comp_partial_sum_source N) :
(Σ n, composition n) :=
begin
rcases i with ⟨n, f⟩,
rw mem_comp_partial_sum_source_iff at hi,
refine ⟨∑ j, f j, of_fn (λ a, f a), λ i hi', _, by simp [sum_of_fn]⟩,
obtain ⟨j, rfl⟩ : ∃ (j : fin n), f j = i, by rwa [mem_of_fn, set.mem_range] at hi',
exact (hi.2 j).1
end
@[simp] lemma comp_change_of_variables_length
(N : ℕ) {i : Σ n, (fin n) → ℕ} (hi : i ∈ comp_partial_sum_source N) :
composition.length (comp_change_of_variables N i hi).2 = i.1 :=
begin
rcases i with ⟨k, blocks_fun⟩,
dsimp [comp_change_of_variables],
simp only [composition.length, map_of_fn, length_of_fn]
end
lemma comp_change_of_variables_blocks_fun
(N : ℕ) {i : Σ n, (fin n) → ℕ} (hi : i ∈ comp_partial_sum_source N) (j : fin i.1) :
(comp_change_of_variables N i hi).2.blocks_fun
⟨j.val, (comp_change_of_variables_length N hi).symm ▸ j.2⟩ = i.2 j :=
begin
rcases i with ⟨n, f⟩,
dsimp [composition.blocks_fun, composition.blocks, comp_change_of_variables],
simp only [map_of_fn, nth_le_of_fn', function.comp_app],
apply congr_arg,
rw fin.ext_iff
end
/-- Target set in the change of variables to compute the composition of partial sums of formal
power series, here given a a set. -/
def comp_partial_sum_target_set (N : ℕ) : set (Σ n, composition n) :=
{i | (i.2.length < N) ∧ (∀ (j : fin i.2.length), i.2.blocks_fun j < N)}
lemma comp_partial_sum_target_subset_image_comp_partial_sum_source
(N : ℕ) (i : Σ n, composition n) (hi : i ∈ comp_partial_sum_target_set N) :
∃ j (hj : j ∈ comp_partial_sum_source N), i = comp_change_of_variables N j hj :=
begin
rcases i with ⟨n, c⟩,
refine ⟨⟨c.length, c.blocks_fun⟩, _, _⟩,
{ simp only [comp_partial_sum_target_set, set.mem_set_of_eq] at hi,
simp only [mem_comp_partial_sum_source_iff, hi.left, hi.right, true_and, and_true],
exact λ a, c.one_le_blocks' _ },
{ dsimp [comp_change_of_variables],
rw composition.sigma_eq_iff_blocks_eq,
simp only [composition.blocks_fun, composition.blocks, subtype.coe_eta, nth_le_map'],
conv_lhs { rw ← of_fn_nth_le c.blocks } }
end
/-- Target set in the change of variables to compute the composition of partial sums of formal
power series, here given a a finset.
See also `comp_partial_sum`. -/
def comp_partial_sum_target (N : ℕ) : finset (Σ n, composition n) :=
set.finite.to_finset $ set.finite_dependent_image (finset.finite_to_set _)
(comp_partial_sum_target_subset_image_comp_partial_sum_source N)
@[simp] lemma mem_comp_partial_sum_target_iff {N : ℕ} {a : Σ n, composition n} :
a ∈ comp_partial_sum_target N ↔ a.2.length < N ∧ (∀ (j : fin a.2.length), a.2.blocks_fun j < N) :=
by simp [comp_partial_sum_target, comp_partial_sum_target_set]
/-- The auxiliary set corresponding to the composition of partial sums asymptotically contains
all possible compositions. -/
lemma comp_partial_sum_target_tendsto_at_top :
tendsto comp_partial_sum_target at_top at_top :=
begin
apply monotone.tendsto_at_top_finset,
{ assume m n hmn a ha,
have : ∀ i, i < m → i < n := λ i hi, lt_of_lt_of_le hi hmn,
tidy },
{ rintros ⟨n, c⟩,
simp only [mem_comp_partial_sum_target_iff],
obtain ⟨n, hn⟩ : bdd_above ↑(finset.univ.image (λ (i : fin c.length), c.blocks_fun i)) :=
finset.bdd_above _,
refine ⟨max n c.length + 1, lt_of_le_of_lt (le_max_right n c.length) (lt_add_one _),
λ j, lt_of_le_of_lt (le_trans _ (le_max_left _ _)) (lt_add_one _)⟩,
apply hn,
simp only [finset.mem_image_of_mem, finset.mem_coe, finset.mem_univ] }
end
/-- Composing the partial sums of two multilinear series coincides with the sum over all
compositions in `comp_partial_sum_target N`. This is precisely the motivation for the definition of
`comp_partial_sum_target N`. -/
lemma comp_partial_sum
(q : formal_multilinear_series 𝕜 F G) (p : formal_multilinear_series 𝕜 E F) (N : ℕ) (z : E) :
q.partial_sum N (∑ i in finset.Ico 1 N, p i (λ j, z)) =
∑ i in comp_partial_sum_target N, q.comp_along_composition_multilinear p i.2 (λ j, z) :=
begin
-- we expand the composition, using the multilinearity of `q` to expand along each coordinate.
suffices H : ∑ n in finset.range N, ∑ r in fintype.pi_finset (λ (i : fin n), finset.Ico 1 N),
q n (λ (i : fin n), p (r i) (λ j, z)) =
∑ i in comp_partial_sum_target N, q.comp_along_composition_multilinear p i.2 (λ j, z),
by simpa only [formal_multilinear_series.partial_sum,
continuous_multilinear_map.map_sum_finset] using H,
-- rewrite the first sum as a big sum over a sigma type
rw ← @finset.sum_sigma _ _ _ _
(finset.range N) (λ (n : ℕ), (fintype.pi_finset (λ (i : fin n), finset.Ico 1 N)) : _)
(λ i, q i.1 (λ (j : fin i.1), p (i.2 j) (λ (k : fin (i.2 j)), z))),
show ∑ i in comp_partial_sum_source N,
q i.1 (λ (j : fin i.1), p (i.2 j) (λ (k : fin (i.2 j)), z)) =
∑ i in comp_partial_sum_target N, q.comp_along_composition_multilinear p i.2 (λ j, z),
-- show that the two sums correspond to each other by reindexing the variables.
apply finset.sum_bij (comp_change_of_variables N),
-- To conclude, we should show that the correspondance we have set up is indeed a bijection
-- between the index sets of the two sums.
-- 1 - show that the image belongs to `comp_partial_sum_target N`
{ rintros ⟨k, blocks_fun⟩ H,
rw mem_comp_partial_sum_source_iff at H,
simp only [mem_comp_partial_sum_target_iff, composition.length, composition.blocks, H.left,
map_of_fn, length_of_fn, true_and, comp_change_of_variables],
assume j,
simp only [composition.blocks_fun, (H.right _).right, nth_le_of_fn'] },
-- 2 - show that the composition gives the `comp_along_composition` application
{ rintros ⟨k, blocks_fun⟩ H,
apply congr _ (comp_change_of_variables_length N H).symm,
intros,
rw ← comp_change_of_variables_blocks_fun N H,
refl },
-- 3 - show that the map is injective
{ rintros ⟨k, blocks_fun⟩ ⟨k', blocks_fun'⟩ H H' heq,
obtain rfl : k = k',
{ have := (comp_change_of_variables_length N H).symm,
rwa [heq, comp_change_of_variables_length] at this, },
congr,
funext i,
calc blocks_fun i = (comp_change_of_variables N _ H).2.blocks_fun _ :
(comp_change_of_variables_blocks_fun N H i).symm
... = (comp_change_of_variables N _ H').2.blocks_fun _ :
begin
apply composition.blocks_fun_congr; try { rw heq },
refl
end
... = blocks_fun' i : comp_change_of_variables_blocks_fun N H' i },
-- 4 - show that the map is surjective
{ assume i hi,
apply comp_partial_sum_target_subset_image_comp_partial_sum_source N i,
simpa [comp_partial_sum_target] using hi }
end
end formal_multilinear_series
open formal_multilinear_series
/-- If two functions `g` and `f` have power series `q` and `p` respectively at `f x` and `x`, then
`g ∘ f` admits the power series `q.comp p` at `x`. -/
theorem has_fpower_series_at.comp {g : F → G} {f : E → F}
{q : formal_multilinear_series 𝕜 F G} {p : formal_multilinear_series 𝕜 E F} {x : E}
(hg : has_fpower_series_at g q (f x)) (hf : has_fpower_series_at f p x) :
has_fpower_series_at (g ∘ f) (q.comp p) x :=
begin
/- Consider `rf` and `rg` such that `f` and `g` have power series expansion on the disks
of radius `rf` and `rg`. -/
rcases hg with ⟨rg, Hg⟩,
rcases hf with ⟨rf, Hf⟩,
/- The terms defining `q.comp p` are geometrically summable in a disk of some radius `r`. -/
rcases q.comp_summable_nnreal p Hg.radius_pos Hf.radius_pos with ⟨r, r_pos, hr⟩,
/- We will consider `y` which is smaller than `r` and `rf`, and also small enough that
`f (x + y)` is close enough to `f x` to be in the disk where `g` is well behaved. Let
`min (r, rf, δ)` be this new radius.-/
have : continuous_at f x := Hf.analytic_at.continuous_at,
obtain ⟨δ, δpos, hδ⟩ : ∃ (δ : ennreal) (H : 0 < δ),
∀ {z : E}, z ∈ emetric.ball x δ → f z ∈ emetric.ball (f x) rg,
{ have : emetric.ball (f x) rg ∈ 𝓝 (f x) := emetric.ball_mem_nhds _ Hg.r_pos,
rcases emetric.mem_nhds_iff.1 (Hf.analytic_at.continuous_at this) with ⟨δ, δpos, Hδ⟩,
exact ⟨δ, δpos, λ z hz, Hδ hz⟩ },
let rf' := min rf δ,
have min_pos : 0 < min rf' r,
by simp only [r_pos, Hf.r_pos, δpos, lt_min_iff, ennreal.coe_pos, and_self],
/- We will show that `g ∘ f` admits the power series `q.comp p` in the disk of
radius `min (r, rf', δ)`. -/
refine ⟨min rf' r, _⟩,
refine ⟨le_trans (min_le_right rf' r)
(formal_multilinear_series.le_comp_radius_of_summable q p r hr), min_pos, λ y hy, _⟩,
/- Let `y` satisfy `∥y∥ < min (r, rf', δ)`. We want to show that `g (f (x + y))` is the sum of
`q.comp p` applied to `y`. -/
-- First, check that `y` is small enough so that estimates for `f` and `g` apply.
have y_mem : y ∈ emetric.ball (0 : E) rf :=
(emetric.ball_subset_ball (le_trans (min_le_left _ _) (min_le_left _ _))) hy,
have fy_mem : f (x + y) ∈ emetric.ball (f x) rg,
{ apply hδ,
have : y ∈ emetric.ball (0 : E) δ :=
(emetric.ball_subset_ball (le_trans (min_le_left _ _) (min_le_right _ _))) hy,
simpa [edist_eq_coe_nnnorm_sub, edist_eq_coe_nnnorm] },
/- Now the proof starts. To show that the sum of `q.comp p` at `y` is `g (f (x + y))`, we will
write `q.comp p` applied to `y` as a big sum over all compositions. Since the sum is
summable, to get its convergence it suffices to get the convergence along some increasing sequence
of sets. We will use the sequence of sets `comp_partial_sum_target n`, along which the sum is
exactly the composition of the partial sums of `q` and `p`, by design. To show that it converges
to `g (f (x + y))`, pointwise convergence would not be enough, but we have uniform convergence
to save the day. -/
-- First step: the partial sum of `p` converges to `f (x + y)`.
have A : tendsto (λ n, ∑ a in finset.Ico 1 n, p a (λ b, y)) at_top (𝓝 (f (x + y) - f x)),
{ have L : ∀ᶠ n in at_top, ∑ a in finset.range n, p a (λ b, y) - f x =
∑ a in finset.Ico 1 n, p a (λ b, y),
{ rw eventually_at_top,
refine ⟨1, λ n hn, _⟩,
symmetry,
rw [eq_sub_iff_add_eq', finset.range_eq_Ico, ← Hf.coeff_zero (λi, y),
finset.sum_eq_sum_Ico_succ_bot hn] },
have : tendsto (λ n, ∑ a in finset.range n, p a (λ b, y) - f x) at_top (𝓝 (f (x + y) - f x)) :=
(Hf.has_sum y_mem).tendsto_sum_nat.sub tendsto_const_nhds,
exact tendsto.congr' L this },
-- Second step: the composition of the partial sums of `q` and `p` converges to `g (f (x + y))`.
have B : tendsto (λ n, q.partial_sum n (∑ a in finset.Ico 1 n, p a (λ b, y)))
at_top (𝓝 (g (f (x + y)))),
{ -- we use the fact that the partial sums of `q` converge locally uniformly to `g`, and that
-- composition passes to the limit under locally uniform convergence.
have B₁ : continuous_at (λ (z : F), g (f x + z)) (f (x + y) - f x),
{ refine continuous_at.comp _ (continuous_const.add continuous_id).continuous_at,
simp only [add_sub_cancel'_right, id.def],
exact Hg.continuous_on.continuous_at (mem_nhds_sets (emetric.is_open_ball) fy_mem) },
have B₂ : f (x + y) - f x ∈ emetric.ball (0 : F) rg,
by simpa [edist_eq_coe_nnnorm, edist_eq_coe_nnnorm_sub] using fy_mem,
rw [← nhds_within_eq_of_open B₂ emetric.is_open_ball] at A,
convert Hg.tendsto_locally_uniformly_on.tendsto_comp B₁.continuous_within_at B₂ A,
simp only [add_sub_cancel'_right] },
-- Third step: the sum over all compositions in `comp_partial_sum_target n` converges to
-- `g (f (x + y))`. As this sum is exactly the composition of the partial sum, this is a direct
-- consequence of the second step
have C : tendsto (λ n,
∑ i in comp_partial_sum_target n, q.comp_along_composition_multilinear p i.2 (λ j, y))
at_top (𝓝 (g (f (x + y)))),
by simpa [comp_partial_sum] using B,
-- Fourth step: the sum over all compositions is `g (f (x + y))`. This follows from the
-- convergence along a subsequence proved in the third step, and the fact that the sum is Cauchy
-- thanks to the summability properties.
have D : has_sum (λ i : (Σ n, composition n),
q.comp_along_composition_multilinear p i.2 (λ j, y)) (g (f (x + y))),
{ have cau : cauchy_seq (λ (s : finset (Σ n, composition n)),
∑ i in s, q.comp_along_composition_multilinear p i.2 (λ j, y)),
{ apply cauchy_seq_finset_of_norm_bounded _ (nnreal.summable_coe.2 hr) _,
simp only [coe_nnnorm, nnreal.coe_mul, nnreal.coe_pow],
rintros ⟨n, c⟩,
calc ∥(comp_along_composition q p c) (λ (j : fin n), y)∥
≤ ∥comp_along_composition q p c∥ * ∏ j : fin n, ∥y∥ :
by apply continuous_multilinear_map.le_op_norm
... ≤ ∥comp_along_composition q p c∥ * (r : ℝ) ^ n :
begin
apply mul_le_mul_of_nonneg_left _ (norm_nonneg _),
rw [finset.prod_const, finset.card_fin],
apply pow_le_pow_of_le_left (norm_nonneg _),
rw [emetric.mem_ball, edist_eq_coe_nnnorm] at hy,
have := (le_trans (le_of_lt hy) (min_le_right _ _)),
rwa [ennreal.coe_le_coe, ← nnreal.coe_le_coe, coe_nnnorm] at this
end },
exact tendsto_nhds_of_cauchy_seq_of_subseq cau at_top_ne_bot
comp_partial_sum_target_tendsto_at_top C },
-- Fifth step: the sum over `n` of `q.comp p n` can be expressed as a particular resummation of
-- the sum over all compositions, by grouping together the compositions of the same
-- integer `n`. The convergence of the whole sum therefore implies the converence of the sum
-- of `q.comp p n`
have E : has_sum (λ n, (q.comp p) n (λ j, y)) (g (f (x + y))),
{ apply D.sigma,
assume n,
dsimp [formal_multilinear_series.comp],
convert has_sum_fintype _,
simp only [continuous_multilinear_map.sum_apply],
refl },
exact E
end
/-- If two functions `g` and `f` are analytic respectively at `f x` and `x`, then `g ∘ f` is
analytic at `x`. -/
theorem analytic_at.comp {g : F → G} {f : E → F} {x : E}
(hg : analytic_at 𝕜 g (f x)) (hf : analytic_at 𝕜 f x) : analytic_at 𝕜 (g ∘ f) x :=
let ⟨q, hq⟩ := hg, ⟨p, hp⟩ := hf in (hq.comp hp).analytic_at
/-!
### Associativity of the composition of formal multilinear series
In this paragraph, we us prove the associativity of the composition of formal power series.
By definition,
```
(r.comp q).comp p n v
= ∑_{i₁ + ... + iₖ = n} (r.comp q)ₖ (p_{i₁} (v₀, ..., v_{i₁ -1}), p_{i₂} (...), ..., p_{iₖ}(...))
= ∑_{a : composition n} (r.comp q) a.length (apply_composition p a v)
```
decomposing `r.comp q` in the same way, we get
```
(r.comp q).comp p n v
= ∑_{a : composition n} ∑_{b : composition a.length}
r b.length (apply_composition q b (apply_composition p a v))
```
On the other hand,
```
r.comp (q.comp p) n v = ∑_{c : composition n} r c.length (apply_composition (q.comp p) c v)
```
Here, `apply_composition (q.comp p) c v` is a vector of length `c.length`, whose `i`-th term is
given by `(q.comp p) (c.blocks_fun i) (v_l, v_{l+1}, ..., v_{m-1})` where `{l, ..., m-1}` is the
`i`-th block in the composition `c`, of length `c.blocks_fun i` by definition. To compute this term,
we expand it as `∑_{dᵢ : composition (c.blocks_fun i)} q dᵢ.length (apply_composition p dᵢ v')`,
where `v' = (v_l, v_{l+1}, ..., v_{m-1})`. Therefore, we get
```
r.comp (q.comp p) n v =
∑_{c : composition n} ∑_{d₀ : composition (c.blocks_fun 0),
..., d_{c.length - 1} : composition (c.blocks_fun (c.length - 1))}
r c.length (λ i, q dᵢ.length (apply_composition p dᵢ v'ᵢ))
```
To show that these terms coincide, we need to explain how to reindex the sums to put them in
bijection (and then the terms we are summing will correspond to each other). Suppose we have a
composition `a` of `n`, and a composition `b` of `a.length`. Then `b` indicates how to group
together some blocks of `a`, giving altogether `b.length` blocks of blocks. These blocks of blocks
can be called `d₀, ..., d_{a.length - 1}`, and one obtains a composition `c` of `n` by saying that
each `dᵢ` is one single block. Conversely, if one starts from `c` and the `dᵢ`s, one can concatenate
the `dᵢ`s to obtain a composition `a` of `n`, and register the lengths of the `dᵢ`s in a composition
`b` of `a.length`.
An example might be enlightening. Suppose `a = [2, 2, 3, 4, 2]`. It is a composition of
length 5 of 13. The content of the blocks may be represented as `0011222333344`.
Now take `b = [2, 3]` as a composition of `a.length = 5`. It says that the first 2 blocks of `a`
should be merged, and the last 3 blocks of `a` should be merged, giving a new composition of `13`
made of two blocks of length `4` and `9`, i.e., `c = [4, 9]`. But one can also remember that
the new first block was initially made of two blocks of size `2`, so `d₀ = [2, 2]`, and the new
second block was initially made of three blocks of size `3`, `4` and `2`, so `d₁ = [3, 4, 2]`.
This equivalence is called `composition.sigma_equiv_sigma_pi n` below.
We start with preliminary results on compositions, of a very specialized nature, then define the
equivalence `composition.sigma_equiv_sigma_pi n`, and we deduce finally the associativity of
composition of formal multilinear series in `formal_multilinear_series.comp_assoc`.
-/
namespace composition
variable {n : ℕ}
/-- Rewriting equality in the dependent type `Σ (a : composition n), composition a.length)` in
non-dependent terms with lists, requiring that the blocks coincide. -/
lemma sigma_composition_eq_iff (i j : Σ (a : composition n), composition a.length) :
i = j ↔ i.1.blocks = j.1.blocks ∧ i.2.blocks = j.2.blocks :=
begin
refine ⟨by rintro rfl; exact ⟨rfl, rfl⟩, _⟩,
rcases i with ⟨a, b⟩,
rcases j with ⟨a', b'⟩,
rintros ⟨h, h'⟩,
have H : a = a', by { ext1, exact h },
induction H,
congr,
ext1,
exact h'
end
/-- Rewriting equality in the dependent type
`Σ (c : composition n), Π (i : fin c.length), composition (c.blocks_fun i)` in
non-dependent terms with lists, requiring that the lists of blocks coincide. -/
lemma sigma_pi_composition_eq_iff
(u v : Σ (c : composition n), Π (i : fin c.length), composition (c.blocks_fun i)) :
u = v ↔ of_fn (λ i, (u.2 i).blocks) = of_fn (λ i, (v.2 i).blocks) :=
begin
refine ⟨λ H, by rw H, λ H, _⟩,
rcases u with ⟨a, b⟩,
rcases v with ⟨a', b'⟩,
dsimp at H,
have h : a = a',
{ ext1,
have : map list.sum (of_fn (λ (i : fin (composition.length a)), (b i).blocks)) =
map list.sum (of_fn (λ (i : fin (composition.length a')), (b' i).blocks)), by rw H,
simp only [map_of_fn] at this,
change of_fn (λ (i : fin (composition.length a)), (b i).blocks.sum) =
of_fn (λ (i : fin (composition.length a')), (b' i).blocks.sum) at this,
simpa [composition.blocks_sum, composition.of_fn_blocks_fun] using this },
induction h,
simp only [true_and, eq_self_iff_true, heq_iff_eq],
ext i : 2,
have : nth_le (of_fn (λ (i : fin (composition.length a)), (b i).blocks)) i.1 (by simp [i.2]) =
nth_le (of_fn (λ (i : fin (composition.length a)), (b' i).blocks)) i.1 (by simp [i.2]) :=
nth_le_of_eq H _,
rwa [nth_le_of_fn, nth_le_of_fn] at this
end
/-- When `a` is a composition of `n` and `b` is a composition of `a.length`, `a.gather b` is the
composition of `n` obtained by gathering all the blocks of `a` corresponding to a block of `b`.
For instance, if `a = [6, 5, 3, 5, 2]` and `b = [2, 3]`, one should gather together
the first two blocks of `a` and its last three blocks, giving `a.gather b = [11, 10]`. -/
def gather (a : composition n) (b : composition a.length) : composition n :=
{ blocks := (a.blocks.split_wrt_composition b).map sum,
blocks_pos :=
begin
rw forall_mem_map_iff,
intros j hj,
suffices H : ∀ i ∈ j, 1 ≤ i, from
calc 0 < j.length : length_pos_of_mem_split_wrt_composition hj
... ≤ j.sum : length_le_sum_of_one_le _ H,
intros i hi,
apply a.one_le_blocks,
rw ← a.blocks.join_split_wrt_composition b,
exact mem_join_of_mem hj hi,
end,
blocks_sum := by { rw [← sum_join, join_split_wrt_composition, a.blocks_sum] } }
lemma length_gather (a : composition n) (b : composition a.length) :
length (a.gather b) = b.length :=
show (map list.sum (a.blocks.split_wrt_composition b)).length = b.blocks.length,
by rw [length_map, length_split_wrt_composition]
/-- An auxiliary function used in the definition of `sigma_equiv_sigma_pi` below, associating to
two compositions `a` of `n` and `b` of `a.length`, and an index `i` bounded by the length of
`a.gather b`, the subcomposition of `a` made of those blocks belonging to the `i`-th block of
`a.gather b`. -/
def sigma_composition_aux (a : composition n) (b : composition a.length)
(i : fin (a.gather b).length) :
composition ((a.gather b).blocks_fun i) :=
{ blocks := nth_le (a.blocks.split_wrt_composition b) i.val
(by { rw [length_split_wrt_composition, ← length_gather], exact i.2 }),
blocks_pos := assume i hi, a.blocks_pos
(by { rw ← a.blocks.join_split_wrt_composition b, exact mem_join_of_mem (nth_le_mem _ _ _) hi }),
blocks_sum := by simp only [composition.blocks_fun, nth_le_map', composition.gather] }
lemma length_sigma_composition_aux (a : composition n) (b : composition a.length) (i : fin b.length) :
composition.length (composition.sigma_composition_aux a b ⟨i.val, (length_gather a b).symm ▸ i.2⟩) =
composition.blocks_fun b i :=
show list.length (nth_le (split_wrt_composition a.blocks b) i.val _) = blocks_fun b i,
by { rw [nth_le_map_rev list.length, nth_le_of_eq (map_length_split_wrt_composition _ _)], refl }
lemma blocks_fun_sigma_composition_aux (a : composition n) (b : composition a.length)
(i : fin b.length) (j : fin (blocks_fun b i)) :
blocks_fun (sigma_composition_aux a b ⟨i.val, (length_gather a b).symm ▸ i.2⟩)
⟨j.val, (length_sigma_composition_aux a b i).symm ▸ j.2⟩ = blocks_fun a (embedding b i j) :=
show nth_le (nth_le _ _ _) _ _ = nth_le a.blocks _ _,
by { rw [nth_le_of_eq (nth_le_split_wrt_composition _ _ _), nth_le_drop', nth_le_take'], refl }
/-- Auxiliary lemma to prove that the composition of formal multilinear series is associative.
Consider a composition `a` of `n` and a composition `b` of `a.length`. Grouping together some
blocks of `a` according to `b` as in `a.gather b`, one can compute the total size of the blocks
of `a` up to an index `size_up_to b i + j` (where the `j` corresponds to a set of blocks of `a`
that do not fill a whole block of `a.gather b`). The first part corresponds to a sum of blocks
in `a.gather b`, and the second one to a sum of blocks in the next block of
`sigma_composition_aux a b`. This is the content of this lemma. -/
lemma size_up_to_size_up_to_add (a : composition n) (b : composition a.length)
{i j : ℕ} (hi : i < b.length) (hj : j < blocks_fun b ⟨i, hi⟩) :
size_up_to a (size_up_to b i + j) = size_up_to (a.gather b) i +
(size_up_to (sigma_composition_aux a b ⟨i, (length_gather a b).symm ▸ hi⟩) j) :=
begin
induction j with j IHj,
{ show sum (take ((b.blocks.take i).sum) a.blocks) =
sum (take i (map sum (split_wrt_composition a.blocks b))),
induction i with i IH,
{ refl },
{ have A : i < b.length := nat.lt_of_succ_lt hi,
have B : i < list.length (map list.sum (split_wrt_composition a.blocks b)), by simp [A],
have C : 0 < blocks_fun b ⟨i, A⟩ := composition.blocks_pos' _ _ _,
rw [sum_take_succ _ _ B, ← IH A C],
have : take (sum (take i b.blocks)) a.blocks =
take (sum (take i b.blocks)) (take (sum (take (i+1) b.blocks)) a.blocks),
{ rw [take_take, min_eq_left],
apply monotone_sum_take _ (nat.le_succ _) },
rw [this, nth_le_map', nth_le_split_wrt_composition,
← take_append_drop (sum (take i b.blocks)) ((take (sum (take (nat.succ i) b.blocks)) a.blocks)),
sum_append],
congr,
rw [take_append_drop] } },
{ have A : j < blocks_fun b ⟨i, hi⟩ := lt_trans (lt_add_one j) hj,
have B : j < length (sigma_composition_aux a b ⟨i, (length_gather a b).symm ▸ hi⟩),
by { convert A, rw ← length_sigma_composition_aux },
have C : size_up_to b i + j < size_up_to b (i + 1),
{ simp only [size_up_to_succ b hi, add_lt_add_iff_left],
exact A },
have D : size_up_to b i + j < length a := lt_of_lt_of_le C (b.size_up_to_le _),
have : size_up_to b i + nat.succ j = (size_up_to b i + j).succ := rfl,
rw [this, size_up_to_succ _ D, IHj A, size_up_to_succ _ B],
simp only [sigma_composition_aux, add_assoc, add_left_inj],
rw [nth_le_of_eq (nth_le_split_wrt_composition _ _ _), nth_le_drop', nth_le_take _ _ C] }
end
/--
Natural equivalence between `(Σ (a : composition n), composition a.length)` and
`(Σ (c : composition n), Π (i : fin c.length), composition (c.blocks_fun i))`, that shows up as a
change of variables in the proof that composition of formal multilinear series is associative.
Consider a composition `a` of `n` and a composition `b` of `a.length`. Then `b` indicates how to
group together some blocks of `a`, giving altogether `b.length` blocks of blocks. These blocks of
blocks can be called `d₀, ..., d_{a.length - 1}`, and one obtains a composition `c` of `n` by
saying that each `dᵢ` is one single block. The map `⟨a, b⟩ → ⟨c, (d₀, ..., d_{a.length - 1})⟩` is
the direct map in the equiv.
Conversely, if one starts from `c` and the `dᵢ`s, one can join the `dᵢ`s to obtain a composition
`a` of `n`, and register the lengths of the `dᵢ`s in a composition `b` of `a.length`. This is the
inverse map of the equiv.
-/
def sigma_equiv_sigma_pi (n : ℕ) :
(Σ (a : composition n), composition a.length) ≃
(Σ (c : composition n), Π (i : fin c.length), composition (c.blocks_fun i)) :=
{ to_fun := λ i, ⟨i.1.gather i.2, i.1.sigma_composition_aux i.2⟩,
inv_fun := λ i, ⟨
{ blocks := (of_fn (λ j, (i.2 j).blocks)).join,
blocks_pos :=
begin
simp only [and_imp, mem_join, exists_imp_distrib, forall_mem_of_fn_iff],
exact λ i j hj, composition.blocks_pos _ hj
end,
blocks_sum := by simp [sum_of_fn, composition.blocks_sum, composition.sum_blocks_fun] },
{ blocks := of_fn (λ j, (i.2 j).length),
blocks_pos := forall_mem_of_fn_iff.2
(λ j, composition.length_pos_of_pos _ (composition.blocks_pos' _ _ _)),
blocks_sum := by { dsimp only [composition.length], simp [sum_of_fn] } }⟩,
left_inv :=
begin
-- the fact that we have a left inverse is essentially `join_split_wrt_composition`,
-- but we need to massage it to take care of the dependent setting.
rintros ⟨a, b⟩,
rw sigma_composition_eq_iff,
dsimp,
split,
{ have A := length_map list.sum (split_wrt_composition a.blocks b),
conv_rhs { rw [← join_split_wrt_composition a.blocks b,
← of_fn_nth_le (split_wrt_composition a.blocks b)] },
congr,
{ exact A },
{ exact (fin.heq_fun_iff A).2 (λ i, rfl) } },
{ have B : composition.length (composition.gather a b) = list.length b.blocks :=
composition.length_gather _ _,
conv_rhs { rw [← of_fn_nth_le b.blocks] },
congr' 1,
{ exact B },
{ apply (fin.heq_fun_iff B).2 (λ i, _),
rw [sigma_composition_aux, composition.length, nth_le_map_rev list.length,
nth_le_of_eq (map_length_split_wrt_composition _ _)] } }
end,
right_inv :=
begin
-- the fact that we have a right inverse is essentially `split_wrt_composition_join`,
-- but we need to massage it to take care of the dependent setting.
rintros ⟨c, d⟩,
have : map list.sum (of_fn (λ (i : fin (composition.length c)), (d i).blocks)) = c.blocks,
by simp [map_of_fn, (∘), composition.blocks_sum, composition.of_fn_blocks_fun],
rw sigma_pi_composition_eq_iff,
dsimp,
congr,
{ ext1,
dsimp [composition.gather],
rwa split_wrt_composition_join,
simp only [map_of_fn] },
{ rw fin.heq_fun_iff,
{ assume i,
dsimp [composition.sigma_composition_aux],
rw [nth_le_of_eq (split_wrt_composition_join _ _ _)],
{ simp only [nth_le_of_fn'] },
{ simp only [map_of_fn] } },
{ congr,
ext1,
dsimp [composition.gather],
rwa split_wrt_composition_join,
simp only [map_of_fn] } }
end }
end composition
namespace formal_multilinear_series
open composition
theorem comp_assoc (r : formal_multilinear_series 𝕜 G H) (q : formal_multilinear_series 𝕜 F G)
(p : formal_multilinear_series 𝕜 E F) :
(r.comp q).comp p = r.comp (q.comp p) :=
begin
ext n v,
/- First, rewrite the two compositions appearing in the theorem as two sums over complicated
sigma types, as in the description of the proof above. -/
let f : (Σ (a : composition n), composition a.length) → H :=
λ ⟨a, b⟩, r b.length (apply_composition q b (apply_composition p a v)),
let g : (Σ (c : composition n), Π (i : fin c.length), composition (c.blocks_fun i)) → H :=
λ ⟨c, d⟩, r c.length
(λ (i : fin c.length), q (d i).length (apply_composition p (d i) (v ∘ c.embedding i))),
suffices A : ∑ c, f c = ∑ c, g c,
{ dsimp [formal_multilinear_series.comp],
simp only [continuous_multilinear_map.sum_apply, comp_along_composition_apply],
rw ← @finset.sum_sigma _ _ _ _ (finset.univ : finset (composition n)) _ f,
dsimp [apply_composition],
simp only [continuous_multilinear_map.sum_apply, comp_along_composition_apply,
continuous_multilinear_map.map_sum],
rw ← @finset.sum_sigma _ _ _ _ (finset.univ : finset (composition n)) _ g,
exact A },
/- Now, we use `composition.sigma_equiv_sigma_pi n` to change
variables in the second sum, and check that we get exactly the same sums. -/
rw ← finset.sum_equiv (sigma_equiv_sigma_pi n),
/- To check that we have the same terms, we should check that we apply the same component of
`r`, and the same component of `q`, and the same component of `p`, to the same coordinate of
`v`. This is true by definition, but at each step one needs to convince Lean that the types
one considers are the same, using a suitable congruence lemma to avoid dependent type issues.
This dance has to be done three times, one for `r`, one for `q` and one for `p`.-/
apply finset.sum_congr rfl,
rintros ⟨a, b⟩ _,
dsimp [f, g, sigma_equiv_sigma_pi],
-- check that the `r` components are the same. Based on `composition.length_gather`
apply r.congr (composition.length_gather a b).symm,
intros i hi1 hi2,
-- check that the `q` components are the same. Based on `length_sigma_composition_aux`
apply q.congr (length_sigma_composition_aux a b _).symm,
intros j hj1 hj2,
-- check that the `p` components are the same. Based on `blocks_fun_sigma_composition_aux`
apply p.congr (blocks_fun_sigma_composition_aux a b _ _).symm,
intros k hk1 hk2,
-- finally, check that the coordinates of `v` one is using are the same. Based on
-- `size_up_to_size_up_to_add`.
refine congr_arg v (fin.eq_of_veq _),
dsimp [composition.embedding],
rw [size_up_to_size_up_to_add _ _ hi1 hj1, add_assoc],
end
end formal_multilinear_series
|
617b9461e131467f138a887430052fc4823aceac | 8cae430f0a71442d02dbb1cbb14073b31048e4b0 | /src/category_theory/limits/shapes/binary_products.lean | 3a6301e637bd0753bbc6b8a03388aa2be4a06ef4 | [
"Apache-2.0"
] | permissive | leanprover-community/mathlib | 56a2cadd17ac88caf4ece0a775932fa26327ba0e | 442a83d738cb208d3600056c489be16900ba701d | refs/heads/master | 1,693,584,102,358 | 1,693,471,902,000 | 1,693,471,902,000 | 97,922,418 | 1,595 | 352 | Apache-2.0 | 1,694,693,445,000 | 1,500,624,130,000 | Lean | UTF-8 | Lean | false | false | 48,266 | lean | /-
Copyright (c) 2019 Scott Morrison. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Scott Morrison, Bhavik Mehta
-/
import category_theory.limits.shapes.terminal
import category_theory.discrete_category
import category_theory.epi_mono
import category_theory.over
/-!
# Binary (co)products
> THIS FILE IS SYNCHRONIZED WITH MATHLIB4.
> Any changes to this file require a corresponding PR to mathlib4.
We define a category `walking_pair`, which is the index category
for a binary (co)product diagram. A convenience method `pair X Y`
constructs the functor from the walking pair, hitting the given objects.
We define `prod X Y` and `coprod X Y` as limits and colimits of such functors.
Typeclasses `has_binary_products` and `has_binary_coproducts` assert the existence
of (co)limits shaped as walking pairs.
We include lemmas for simplifying equations involving projections and coprojections, and define
braiding and associating isomorphisms, and the product comparison morphism.
## References
* [Stacks: Products of pairs](https://stacks.math.columbia.edu/tag/001R)
* [Stacks: coproducts of pairs](https://stacks.math.columbia.edu/tag/04AN)
-/
noncomputable theory
universes v u u₂
open category_theory
namespace category_theory.limits
/-- The type of objects for the diagram indexing a binary (co)product. -/
@[derive decidable_eq, derive inhabited]
inductive walking_pair : Type
| left | right
open walking_pair
/--
The equivalence swapping left and right.
-/
def walking_pair.swap : walking_pair ≃ walking_pair :=
{ to_fun := λ j, walking_pair.rec_on j right left,
inv_fun := λ j, walking_pair.rec_on j right left,
left_inv := λ j, by { cases j; refl, },
right_inv := λ j, by { cases j; refl, }, }
@[simp] lemma walking_pair.swap_apply_left : walking_pair.swap left = right := rfl
@[simp] lemma walking_pair.swap_apply_right : walking_pair.swap right = left := rfl
@[simp] lemma walking_pair.swap_symm_apply_tt : walking_pair.swap.symm left = right := rfl
@[simp] lemma walking_pair.swap_symm_apply_ff : walking_pair.swap.symm right = left := rfl
/--
An equivalence from `walking_pair` to `bool`, sometimes useful when reindexing limits.
-/
def walking_pair.equiv_bool : walking_pair ≃ bool :=
{ to_fun := λ j, walking_pair.rec_on j tt ff, -- to match equiv.sum_equiv_sigma_bool
inv_fun := λ b, bool.rec_on b right left,
left_inv := λ j, by { cases j; refl, },
right_inv := λ b, by { cases b; refl, }, }
@[simp] lemma walking_pair.equiv_bool_apply_left : walking_pair.equiv_bool left = tt := rfl
@[simp] lemma walking_pair.equiv_bool_apply_right : walking_pair.equiv_bool right = ff := rfl
@[simp] lemma walking_pair.equiv_bool_symm_apply_tt : walking_pair.equiv_bool.symm tt = left := rfl
@[simp] lemma walking_pair.equiv_bool_symm_apply_ff : walking_pair.equiv_bool.symm ff = right := rfl
variables {C : Type u}
/-- The function on the walking pair, sending the two points to `X` and `Y`. -/
def pair_function (X Y : C) : walking_pair → C := λ j, walking_pair.cases_on j X Y
@[simp] lemma pair_function_left (X Y : C) : pair_function X Y left = X := rfl
@[simp] lemma pair_function_right (X Y : C) : pair_function X Y right = Y := rfl
variables [category.{v} C]
/-- The diagram on the walking pair, sending the two points to `X` and `Y`. -/
def pair (X Y : C) : discrete walking_pair ⥤ C :=
discrete.functor (λ j, walking_pair.cases_on j X Y)
@[simp] lemma pair_obj_left (X Y : C) : (pair X Y).obj ⟨left⟩ = X := rfl
@[simp] lemma pair_obj_right (X Y : C) : (pair X Y).obj ⟨right⟩ = Y := rfl
section
variables {F G : discrete walking_pair ⥤ C} (f : F.obj ⟨left⟩ ⟶ G.obj ⟨left⟩)
(g : F.obj ⟨right⟩ ⟶ G.obj ⟨right⟩)
local attribute [tidy] tactic.discrete_cases
/-- The natural transformation between two functors out of the
walking pair, specified by its
components. -/
def map_pair : F ⟶ G := { app := λ j, discrete.rec_on j (λ j, walking_pair.cases_on j f g) }
@[simp] lemma map_pair_left : (map_pair f g).app ⟨left⟩ = f := rfl
@[simp] lemma map_pair_right : (map_pair f g).app ⟨right⟩ = g := rfl
/-- The natural isomorphism between two functors out of the walking pair, specified by its
components. -/
@[simps]
def map_pair_iso (f : F.obj ⟨left⟩ ≅ G.obj ⟨left⟩) (g : F.obj ⟨right⟩ ≅ G.obj ⟨right⟩) : F ≅ G :=
nat_iso.of_components (λ j, discrete.rec_on j (λ j, walking_pair.cases_on j f g)) (by tidy)
end
/-- Every functor out of the walking pair is naturally isomorphic (actually, equal) to a `pair` -/
@[simps]
def diagram_iso_pair (F : discrete walking_pair ⥤ C) :
F ≅ pair (F.obj ⟨walking_pair.left⟩) (F.obj ⟨walking_pair.right⟩) :=
map_pair_iso (iso.refl _) (iso.refl _)
section
variables {D : Type u} [category.{v} D]
/-- The natural isomorphism between `pair X Y ⋙ F` and `pair (F.obj X) (F.obj Y)`. -/
def pair_comp (X Y : C) (F : C ⥤ D) : pair X Y ⋙ F ≅ pair (F.obj X) (F.obj Y) :=
diagram_iso_pair _
end
/-- A binary fan is just a cone on a diagram indexing a product. -/
abbreviation binary_fan (X Y : C) := cone (pair X Y)
/-- The first projection of a binary fan. -/
abbreviation binary_fan.fst {X Y : C} (s : binary_fan X Y) := s.π.app ⟨walking_pair.left⟩
/-- The second projection of a binary fan. -/
abbreviation binary_fan.snd {X Y : C} (s : binary_fan X Y) := s.π.app ⟨walking_pair.right⟩
@[simp] lemma binary_fan.π_app_left {X Y : C} (s : binary_fan X Y) :
s.π.app ⟨walking_pair.left⟩ = s.fst := rfl
@[simp] lemma binary_fan.π_app_right {X Y : C} (s : binary_fan X Y) :
s.π.app ⟨walking_pair.right⟩ = s.snd := rfl
/-- A convenient way to show that a binary fan is a limit. -/
def binary_fan.is_limit.mk {X Y : C} (s : binary_fan X Y)
(lift : Π {T : C} (f : T ⟶ X) (g : T ⟶ Y), T ⟶ s.X)
(hl₁ : ∀ {T : C} (f : T ⟶ X) (g : T ⟶ Y), lift f g ≫ s.fst = f)
(hl₂ : ∀ {T : C} (f : T ⟶ X) (g : T ⟶ Y), lift f g ≫ s.snd = g)
(uniq : ∀ {T : C} (f : T ⟶ X) (g : T ⟶ Y) (m : T ⟶ s.X) (h₁ : m ≫ s.fst = f)
(h₂ : m ≫ s.snd = g), m = lift f g) : is_limit s := is_limit.mk
(λ t, lift (binary_fan.fst t) (binary_fan.snd t))
(by { rintros t (rfl|rfl), { exact hl₁ _ _ }, { exact hl₂ _ _ } })
(λ t m h, uniq _ _ _ (h ⟨walking_pair.left⟩) (h ⟨walking_pair.right⟩))
lemma binary_fan.is_limit.hom_ext {W X Y : C} {s : binary_fan X Y} (h : is_limit s)
{f g : W ⟶ s.X} (h₁ : f ≫ s.fst = g ≫ s.fst) (h₂ : f ≫ s.snd = g ≫ s.snd) : f = g :=
h.hom_ext $ λ j, discrete.rec_on j (λ j, walking_pair.cases_on j h₁ h₂)
/-- A binary cofan is just a cocone on a diagram indexing a coproduct. -/
abbreviation binary_cofan (X Y : C) := cocone (pair X Y)
/-- The first inclusion of a binary cofan. -/
abbreviation binary_cofan.inl {X Y : C} (s : binary_cofan X Y) := s.ι.app ⟨walking_pair.left⟩
/-- The second inclusion of a binary cofan. -/
abbreviation binary_cofan.inr {X Y : C} (s : binary_cofan X Y) := s.ι.app ⟨walking_pair.right⟩
@[simp] lemma binary_cofan.ι_app_left {X Y : C} (s : binary_cofan X Y) :
s.ι.app ⟨walking_pair.left⟩ = s.inl := rfl
@[simp] lemma binary_cofan.ι_app_right {X Y : C} (s : binary_cofan X Y) :
s.ι.app ⟨walking_pair.right⟩ = s.inr := rfl
/-- A convenient way to show that a binary cofan is a colimit. -/
def binary_cofan.is_colimit.mk {X Y : C} (s : binary_cofan X Y)
(desc : Π {T : C} (f : X ⟶ T) (g : Y ⟶ T), s.X ⟶ T)
(hd₁ : ∀ {T : C} (f : X ⟶ T) (g : Y ⟶ T), s.inl ≫ desc f g = f)
(hd₂ : ∀ {T : C} (f : X ⟶ T) (g : Y ⟶ T), s.inr ≫ desc f g = g)
(uniq : ∀ {T : C} (f : X ⟶ T) (g : Y ⟶ T) (m : s.X ⟶ T) (h₁ : s.inl ≫ m = f)
(h₂ : s.inr ≫ m = g), m = desc f g) : is_colimit s := is_colimit.mk
(λ t, desc (binary_cofan.inl t) (binary_cofan.inr t))
(by { rintros t (rfl|rfl), { exact hd₁ _ _ }, { exact hd₂ _ _ }})
(λ t m h, uniq _ _ _ (h ⟨walking_pair.left⟩) (h ⟨walking_pair.right⟩))
lemma binary_cofan.is_colimit.hom_ext {W X Y : C} {s : binary_cofan X Y} (h : is_colimit s)
{f g : s.X ⟶ W} (h₁ : s.inl ≫ f = s.inl ≫ g) (h₂ : s.inr ≫ f = s.inr ≫ g) : f = g :=
h.hom_ext $ λ j, discrete.rec_on j (λ j, walking_pair.cases_on j h₁ h₂)
variables {X Y : C}
section
local attribute [tidy] tactic.discrete_cases
/-- A binary fan with vertex `P` consists of the two projections `π₁ : P ⟶ X` and `π₂ : P ⟶ Y`. -/
@[simps X]
def binary_fan.mk {P : C} (π₁ : P ⟶ X) (π₂ : P ⟶ Y) : binary_fan X Y :=
{ X := P,
π := { app := λ j, discrete.rec_on j (λ j, walking_pair.cases_on j π₁ π₂) }}
/-- A binary cofan with vertex `P` consists of the two inclusions `ι₁ : X ⟶ P` and `ι₂ : Y ⟶ P`. -/
@[simps X]
def binary_cofan.mk {P : C} (ι₁ : X ⟶ P) (ι₂ : Y ⟶ P) : binary_cofan X Y :=
{ X := P,
ι := { app := λ j, discrete.rec_on j (λ j, walking_pair.cases_on j ι₁ ι₂) }}
end
@[simp] lemma binary_fan.mk_fst {P : C} (π₁ : P ⟶ X) (π₂ : P ⟶ Y) :
(binary_fan.mk π₁ π₂).fst = π₁ := rfl
@[simp] lemma binary_fan.mk_snd {P : C} (π₁ : P ⟶ X) (π₂ : P ⟶ Y) :
(binary_fan.mk π₁ π₂).snd = π₂ := rfl
@[simp] lemma binary_cofan.mk_inl {P : C} (ι₁ : X ⟶ P) (ι₂ : Y ⟶ P) :
(binary_cofan.mk ι₁ ι₂).inl = ι₁ := rfl
@[simp] lemma binary_cofan.mk_inr {P : C} (ι₁ : X ⟶ P) (ι₂ : Y ⟶ P) :
(binary_cofan.mk ι₁ ι₂).inr = ι₂ := rfl
/-- Every `binary_fan` is isomorphic to an application of `binary_fan.mk`. -/
def iso_binary_fan_mk {X Y : C} (c : binary_fan X Y) : c ≅ binary_fan.mk c.fst c.snd :=
cones.ext (iso.refl _) (λ j, by discrete_cases; cases j; tidy)
/-- Every `binary_fan` is isomorphic to an application of `binary_fan.mk`. -/
def iso_binary_cofan_mk {X Y : C} (c : binary_cofan X Y) : c ≅ binary_cofan.mk c.inl c.inr :=
cocones.ext (iso.refl _) (λ j, by discrete_cases; cases j; tidy)
/--
This is a more convenient formulation to show that a `binary_fan` constructed using
`binary_fan.mk` is a limit cone.
-/
def binary_fan.is_limit_mk {W : C} {fst : W ⟶ X} {snd : W ⟶ Y}
(lift : Π (s : binary_fan X Y), s.X ⟶ W)
(fac_left : ∀ (s : binary_fan X Y), lift s ≫ fst = s.fst)
(fac_right : ∀ (s : binary_fan X Y), lift s ≫ snd = s.snd)
(uniq : ∀ (s : binary_fan X Y) (m : s.X ⟶ W)
(w_fst : m ≫ fst = s.fst) (w_snd : m ≫ snd = s.snd), m = lift s) :
is_limit (binary_fan.mk fst snd) :=
{ lift := lift,
fac' := λ s j, by { rcases j with ⟨⟨⟩⟩, exacts [fac_left s, fac_right s], },
uniq' := λ s m w, uniq s m (w ⟨walking_pair.left⟩) (w ⟨walking_pair.right⟩) }
/--
This is a more convenient formulation to show that a `binary_cofan` constructed using
`binary_cofan.mk` is a colimit cocone.
-/
def binary_cofan.is_colimit_mk {W : C} {inl : X ⟶ W} {inr : Y ⟶ W}
(desc : Π (s : binary_cofan X Y), W ⟶ s.X)
(fac_left : ∀ (s : binary_cofan X Y), inl ≫ desc s = s.inl)
(fac_right : ∀ (s : binary_cofan X Y), inr ≫ desc s = s.inr)
(uniq : ∀ (s : binary_cofan X Y) (m : W ⟶ s.X)
(w_inl : inl ≫ m = s.inl) (w_inr : inr ≫ m = s.inr), m = desc s) :
is_colimit (binary_cofan.mk inl inr) :=
{ desc := desc,
fac' := λ s j, by { rcases j with ⟨⟨⟩⟩, exacts [fac_left s, fac_right s], },
uniq' := λ s m w, uniq s m (w ⟨walking_pair.left⟩) (w ⟨walking_pair.right⟩) }
/-- If `s` is a limit binary fan over `X` and `Y`, then every pair of morphisms `f : W ⟶ X` and
`g : W ⟶ Y` induces a morphism `l : W ⟶ s.X` satisfying `l ≫ s.fst = f` and `l ≫ s.snd = g`.
-/
@[simps]
def binary_fan.is_limit.lift' {W X Y : C} {s : binary_fan X Y} (h : is_limit s) (f : W ⟶ X)
(g : W ⟶ Y) : {l : W ⟶ s.X // l ≫ s.fst = f ∧ l ≫ s.snd = g} :=
⟨h.lift $ binary_fan.mk f g, h.fac _ _, h.fac _ _⟩
/-- If `s` is a colimit binary cofan over `X` and `Y`,, then every pair of morphisms `f : X ⟶ W` and
`g : Y ⟶ W` induces a morphism `l : s.X ⟶ W` satisfying `s.inl ≫ l = f` and `s.inr ≫ l = g`.
-/
@[simps]
def binary_cofan.is_colimit.desc' {W X Y : C} {s : binary_cofan X Y} (h : is_colimit s) (f : X ⟶ W)
(g : Y ⟶ W) : {l : s.X ⟶ W // s.inl ≫ l = f ∧ s.inr ≫ l = g} :=
⟨h.desc $ binary_cofan.mk f g, h.fac _ _, h.fac _ _⟩
/-- Binary products are symmetric. -/
def binary_fan.is_limit_flip {X Y : C} {c : binary_fan X Y} (hc : is_limit c) :
is_limit (binary_fan.mk c.snd c.fst) :=
binary_fan.is_limit_mk (λ s, hc.lift (binary_fan.mk s.snd s.fst))
(λ s, hc.fac _ _) (λ s, hc.fac _ _)
(λ s m e₁ e₂, binary_fan.is_limit.hom_ext hc
(e₂.trans (hc.fac (binary_fan.mk s.snd s.fst) ⟨walking_pair.left⟩).symm)
(e₁.trans (hc.fac (binary_fan.mk s.snd s.fst) ⟨walking_pair.right⟩).symm))
lemma binary_fan.is_limit_iff_is_iso_fst {X Y : C} (h : is_terminal Y) (c : binary_fan X Y) :
nonempty (is_limit c) ↔ is_iso c.fst :=
begin
split,
{ rintro ⟨H⟩,
obtain ⟨l, hl, -⟩ := binary_fan.is_limit.lift' H (𝟙 X) (h.from X),
exact ⟨⟨l, binary_fan.is_limit.hom_ext H
(by simpa [hl, -category.comp_id] using category.comp_id _) (h.hom_ext _ _), hl⟩⟩ },
{ introI,
exact ⟨binary_fan.is_limit.mk _ (λ _ f _, f ≫ inv c.fst)
(λ _ _ _, by simp) (λ _ _ _, h.hom_ext _ _)
(λ _ _ _ _ e _, by simp [← e])⟩ }
end
lemma binary_fan.is_limit_iff_is_iso_snd {X Y : C} (h : is_terminal X) (c : binary_fan X Y) :
nonempty (is_limit c) ↔ is_iso c.snd :=
begin
refine iff.trans _ (binary_fan.is_limit_iff_is_iso_fst h (binary_fan.mk c.snd c.fst)),
exact ⟨λ h, ⟨binary_fan.is_limit_flip h.some⟩,
λ h, ⟨(binary_fan.is_limit_flip h.some).of_iso_limit (iso_binary_fan_mk c).symm⟩⟩,
end
/-- If `X' ≅ X`, then `X × Y` also is the product of `X'` and `Y`. -/
noncomputable
def binary_fan.is_limit_comp_left_iso {X Y X' : C} (c : binary_fan X Y) (f : X ⟶ X')
[is_iso f] (h : is_limit c) : is_limit (binary_fan.mk (c.fst ≫ f) c.snd) :=
begin
fapply binary_fan.is_limit_mk,
{ exact λ s, h.lift (binary_fan.mk (s.fst ≫ inv f) s.snd) },
{ intro s, simp },
{ intro s, simp },
{ intros s m e₁ e₂, apply binary_fan.is_limit.hom_ext h; simpa }
end
/-- If `Y' ≅ Y`, then `X x Y` also is the product of `X` and `Y'`. -/
noncomputable
def binary_fan.is_limit_comp_right_iso {X Y Y' : C} (c : binary_fan X Y) (f : Y ⟶ Y')
[is_iso f] (h : is_limit c) : is_limit (binary_fan.mk c.fst (c.snd ≫ f)) :=
binary_fan.is_limit_flip $ binary_fan.is_limit_comp_left_iso _ f (binary_fan.is_limit_flip h)
/-- Binary coproducts are symmetric. -/
def binary_cofan.is_colimit_flip {X Y : C} {c : binary_cofan X Y} (hc : is_colimit c) :
is_colimit (binary_cofan.mk c.inr c.inl) :=
binary_cofan.is_colimit_mk (λ s, hc.desc (binary_cofan.mk s.inr s.inl))
(λ s, hc.fac _ _) (λ s, hc.fac _ _)
(λ s m e₁ e₂, binary_cofan.is_colimit.hom_ext hc
(e₂.trans (hc.fac (binary_cofan.mk s.inr s.inl) ⟨walking_pair.left⟩).symm)
(e₁.trans (hc.fac (binary_cofan.mk s.inr s.inl) ⟨walking_pair.right⟩).symm))
lemma binary_cofan.is_colimit_iff_is_iso_inl {X Y : C} (h : is_initial Y) (c : binary_cofan X Y) :
nonempty (is_colimit c) ↔ is_iso c.inl :=
begin
split,
{ rintro ⟨H⟩,
obtain ⟨l, hl, -⟩ := binary_cofan.is_colimit.desc' H (𝟙 X) (h.to X),
exact ⟨⟨l, hl, binary_cofan.is_colimit.hom_ext H (by simp [reassoc_of hl]) (h.hom_ext _ _)⟩⟩ },
{ introI,
exact ⟨binary_cofan.is_colimit.mk _ (λ _ f _, inv c.inl ≫ f)
(λ _ _ _, is_iso.hom_inv_id_assoc _ _) (λ _ _ _, h.hom_ext _ _)
(λ _ _ _ _ e _, (is_iso.eq_inv_comp _).mpr e)⟩ }
end
lemma binary_cofan.is_colimit_iff_is_iso_inr {X Y : C} (h : is_initial X) (c : binary_cofan X Y) :
nonempty (is_colimit c) ↔ is_iso c.inr :=
begin
refine iff.trans _ (binary_cofan.is_colimit_iff_is_iso_inl h (binary_cofan.mk c.inr c.inl)),
exact ⟨λ h, ⟨binary_cofan.is_colimit_flip h.some⟩,
λ h, ⟨(binary_cofan.is_colimit_flip h.some).of_iso_colimit (iso_binary_cofan_mk c).symm⟩⟩,
end
/-- If `X' ≅ X`, then `X ⨿ Y` also is the coproduct of `X'` and `Y`. -/
noncomputable
def binary_cofan.is_colimit_comp_left_iso {X Y X' : C} (c : binary_cofan X Y) (f : X' ⟶ X)
[is_iso f] (h : is_colimit c) : is_colimit (binary_cofan.mk (f ≫ c.inl) c.inr) :=
begin
fapply binary_cofan.is_colimit_mk,
{ exact λ s, h.desc (binary_cofan.mk (inv f ≫ s.inl) s.inr) },
{ intro s, simp },
{ intro s, simp },
{ intros s m e₁ e₂,
apply binary_cofan.is_colimit.hom_ext h,
{ rw ← cancel_epi f, simpa using e₁ },
{ simpa } }
end
/-- If `Y' ≅ Y`, then `X ⨿ Y` also is the coproduct of `X` and `Y'`. -/
noncomputable
def binary_cofan.is_colimit_comp_right_iso {X Y Y' : C} (c : binary_cofan X Y) (f : Y' ⟶ Y)
[is_iso f] (h : is_colimit c) : is_colimit (binary_cofan.mk c.inl (f ≫ c.inr)) :=
binary_cofan.is_colimit_flip $
binary_cofan.is_colimit_comp_left_iso _ f (binary_cofan.is_colimit_flip h)
/-- An abbreviation for `has_limit (pair X Y)`. -/
abbreviation has_binary_product (X Y : C) := has_limit (pair X Y)
/-- An abbreviation for `has_colimit (pair X Y)`. -/
abbreviation has_binary_coproduct (X Y : C) := has_colimit (pair X Y)
/-- If we have a product of `X` and `Y`, we can access it using `prod X Y` or
`X ⨯ Y`. -/
abbreviation prod (X Y : C) [has_binary_product X Y] := limit (pair X Y)
/-- If we have a coproduct of `X` and `Y`, we can access it using `coprod X Y ` or
`X ⨿ Y`. -/
abbreviation coprod (X Y : C) [has_binary_coproduct X Y] := colimit (pair X Y)
notation X ` ⨯ `:20 Y:20 := prod X Y
notation X ` ⨿ `:20 Y:20 := coprod X Y
/-- The projection map to the first component of the product. -/
abbreviation prod.fst {X Y : C} [has_binary_product X Y] : X ⨯ Y ⟶ X :=
limit.π (pair X Y) ⟨walking_pair.left⟩
/-- The projecton map to the second component of the product. -/
abbreviation prod.snd {X Y : C} [has_binary_product X Y] : X ⨯ Y ⟶ Y :=
limit.π (pair X Y) ⟨walking_pair.right⟩
/-- The inclusion map from the first component of the coproduct. -/
abbreviation coprod.inl {X Y : C} [has_binary_coproduct X Y] : X ⟶ X ⨿ Y :=
colimit.ι (pair X Y) ⟨walking_pair.left⟩
/-- The inclusion map from the second component of the coproduct. -/
abbreviation coprod.inr {X Y : C} [has_binary_coproduct X Y] : Y ⟶ X ⨿ Y :=
colimit.ι (pair X Y) ⟨walking_pair.right⟩
/-- The binary fan constructed from the projection maps is a limit. -/
def prod_is_prod (X Y : C) [has_binary_product X Y] :
is_limit (binary_fan.mk (prod.fst : X ⨯ Y ⟶ X) prod.snd) :=
(limit.is_limit _).of_iso_limit (cones.ext (iso.refl _) (by { rintro (_ | _), tidy }))
/-- The binary cofan constructed from the coprojection maps is a colimit. -/
def coprod_is_coprod (X Y : C) [has_binary_coproduct X Y] :
is_colimit (binary_cofan.mk (coprod.inl : X ⟶ X ⨿ Y) coprod.inr) :=
(colimit.is_colimit _).of_iso_colimit (cocones.ext (iso.refl _) (by { rintro (_ | _), tidy }))
@[ext] lemma prod.hom_ext {W X Y : C} [has_binary_product X Y] {f g : W ⟶ X ⨯ Y}
(h₁ : f ≫ prod.fst = g ≫ prod.fst) (h₂ : f ≫ prod.snd = g ≫ prod.snd) : f = g :=
binary_fan.is_limit.hom_ext (limit.is_limit _) h₁ h₂
@[ext] lemma coprod.hom_ext {W X Y : C} [has_binary_coproduct X Y] {f g : X ⨿ Y ⟶ W}
(h₁ : coprod.inl ≫ f = coprod.inl ≫ g) (h₂ : coprod.inr ≫ f = coprod.inr ≫ g) : f = g :=
binary_cofan.is_colimit.hom_ext (colimit.is_colimit _) h₁ h₂
/-- If the product of `X` and `Y` exists, then every pair of morphisms `f : W ⟶ X` and `g : W ⟶ Y`
induces a morphism `prod.lift f g : W ⟶ X ⨯ Y`. -/
abbreviation prod.lift {W X Y : C} [has_binary_product X Y] (f : W ⟶ X) (g : W ⟶ Y) : W ⟶ X ⨯ Y :=
limit.lift _ (binary_fan.mk f g)
/-- diagonal arrow of the binary product in the category `fam I` -/
abbreviation diag (X : C) [has_binary_product X X] : X ⟶ X ⨯ X :=
prod.lift (𝟙 _) (𝟙 _)
/-- If the coproduct of `X` and `Y` exists, then every pair of morphisms `f : X ⟶ W` and
`g : Y ⟶ W` induces a morphism `coprod.desc f g : X ⨿ Y ⟶ W`. -/
abbreviation coprod.desc {W X Y : C} [has_binary_coproduct X Y] (f : X ⟶ W) (g : Y ⟶ W) :
X ⨿ Y ⟶ W :=
colimit.desc _ (binary_cofan.mk f g)
/-- codiagonal arrow of the binary coproduct -/
abbreviation codiag (X : C) [has_binary_coproduct X X] : X ⨿ X ⟶ X :=
coprod.desc (𝟙 _) (𝟙 _)
@[simp, reassoc]
lemma prod.lift_fst {W X Y : C} [has_binary_product X Y] (f : W ⟶ X) (g : W ⟶ Y) :
prod.lift f g ≫ prod.fst = f :=
limit.lift_π _ _
@[simp, reassoc]
lemma prod.lift_snd {W X Y : C} [has_binary_product X Y] (f : W ⟶ X) (g : W ⟶ Y) :
prod.lift f g ≫ prod.snd = g :=
limit.lift_π _ _
-- The simp linter says simp can prove the reassoc version of this lemma.
@[reassoc, simp]
lemma coprod.inl_desc {W X Y : C} [has_binary_coproduct X Y] (f : X ⟶ W) (g : Y ⟶ W) :
coprod.inl ≫ coprod.desc f g = f :=
colimit.ι_desc _ _
-- The simp linter says simp can prove the reassoc version of this lemma.
@[reassoc, simp]
lemma coprod.inr_desc {W X Y : C} [has_binary_coproduct X Y] (f : X ⟶ W) (g : Y ⟶ W) :
coprod.inr ≫ coprod.desc f g = g :=
colimit.ι_desc _ _
instance prod.mono_lift_of_mono_left {W X Y : C} [has_binary_product X Y] (f : W ⟶ X) (g : W ⟶ Y)
[mono f] : mono (prod.lift f g) :=
mono_of_mono_fac $ prod.lift_fst _ _
instance prod.mono_lift_of_mono_right {W X Y : C} [has_binary_product X Y] (f : W ⟶ X) (g : W ⟶ Y)
[mono g] : mono (prod.lift f g) :=
mono_of_mono_fac $ prod.lift_snd _ _
instance coprod.epi_desc_of_epi_left {W X Y : C} [has_binary_coproduct X Y] (f : X ⟶ W) (g : Y ⟶ W)
[epi f] : epi (coprod.desc f g) :=
epi_of_epi_fac $ coprod.inl_desc _ _
instance coprod.epi_desc_of_epi_right {W X Y : C} [has_binary_coproduct X Y] (f : X ⟶ W) (g : Y ⟶ W)
[epi g] : epi (coprod.desc f g) :=
epi_of_epi_fac $ coprod.inr_desc _ _
/-- If the product of `X` and `Y` exists, then every pair of morphisms `f : W ⟶ X` and `g : W ⟶ Y`
induces a morphism `l : W ⟶ X ⨯ Y` satisfying `l ≫ prod.fst = f` and `l ≫ prod.snd = g`. -/
def prod.lift' {W X Y : C} [has_binary_product X Y] (f : W ⟶ X) (g : W ⟶ Y) :
{l : W ⟶ X ⨯ Y // l ≫ prod.fst = f ∧ l ≫ prod.snd = g} :=
⟨prod.lift f g, prod.lift_fst _ _, prod.lift_snd _ _⟩
/-- If the coproduct of `X` and `Y` exists, then every pair of morphisms `f : X ⟶ W` and
`g : Y ⟶ W` induces a morphism `l : X ⨿ Y ⟶ W` satisfying `coprod.inl ≫ l = f` and
`coprod.inr ≫ l = g`. -/
def coprod.desc' {W X Y : C} [has_binary_coproduct X Y] (f : X ⟶ W) (g : Y ⟶ W) :
{l : X ⨿ Y ⟶ W // coprod.inl ≫ l = f ∧ coprod.inr ≫ l = g} :=
⟨coprod.desc f g, coprod.inl_desc _ _, coprod.inr_desc _ _⟩
/-- If the products `W ⨯ X` and `Y ⨯ Z` exist, then every pair of morphisms `f : W ⟶ Y` and
`g : X ⟶ Z` induces a morphism `prod.map f g : W ⨯ X ⟶ Y ⨯ Z`. -/
def prod.map {W X Y Z : C} [has_binary_product W X] [has_binary_product Y Z]
(f : W ⟶ Y) (g : X ⟶ Z) : W ⨯ X ⟶ Y ⨯ Z :=
lim_map (map_pair f g)
/-- If the coproducts `W ⨿ X` and `Y ⨿ Z` exist, then every pair of morphisms `f : W ⟶ Y` and
`g : W ⟶ Z` induces a morphism `coprod.map f g : W ⨿ X ⟶ Y ⨿ Z`. -/
def coprod.map {W X Y Z : C} [has_binary_coproduct W X] [has_binary_coproduct Y Z]
(f : W ⟶ Y) (g : X ⟶ Z) : W ⨿ X ⟶ Y ⨿ Z :=
colim_map (map_pair f g)
section prod_lemmas
-- Making the reassoc version of this a simp lemma seems to be more harmful than helpful.
@[reassoc, simp]
lemma prod.comp_lift {V W X Y : C} [has_binary_product X Y] (f : V ⟶ W) (g : W ⟶ X) (h : W ⟶ Y) :
f ≫ prod.lift g h = prod.lift (f ≫ g) (f ≫ h) :=
by { ext; simp }
lemma prod.comp_diag {X Y : C} [has_binary_product Y Y] (f : X ⟶ Y) :
f ≫ diag Y = prod.lift f f :=
by simp
@[simp, reassoc]
lemma prod.map_fst {W X Y Z : C} [has_binary_product W X] [has_binary_product Y Z]
(f : W ⟶ Y) (g : X ⟶ Z) : prod.map f g ≫ prod.fst = prod.fst ≫ f :=
lim_map_π _ _
@[simp, reassoc]
lemma prod.map_snd {W X Y Z : C} [has_binary_product W X] [has_binary_product Y Z]
(f : W ⟶ Y) (g : X ⟶ Z) : prod.map f g ≫ prod.snd = prod.snd ≫ g :=
lim_map_π _ _
@[simp] lemma prod.map_id_id {X Y : C} [has_binary_product X Y] :
prod.map (𝟙 X) (𝟙 Y) = 𝟙 _ :=
by { ext; simp }
@[simp] lemma prod.lift_fst_snd {X Y : C} [has_binary_product X Y] :
prod.lift prod.fst prod.snd = 𝟙 (X ⨯ Y) :=
by { ext; simp }
@[simp, reassoc] lemma prod.lift_map {V W X Y Z : C} [has_binary_product W X]
[has_binary_product Y Z] (f : V ⟶ W) (g : V ⟶ X) (h : W ⟶ Y) (k : X ⟶ Z) :
prod.lift f g ≫ prod.map h k = prod.lift (f ≫ h) (g ≫ k) :=
by { ext; simp }
@[simp] lemma prod.lift_fst_comp_snd_comp {W X Y Z : C} [has_binary_product W Y]
[has_binary_product X Z] (g : W ⟶ X) (g' : Y ⟶ Z) :
prod.lift (prod.fst ≫ g) (prod.snd ≫ g') = prod.map g g' :=
by { rw ← prod.lift_map, simp }
-- We take the right hand side here to be simp normal form, as this way composition lemmas for
-- `f ≫ h` and `g ≫ k` can fire (eg `id_comp`) , while `map_fst` and `map_snd` can still work just
-- as well.
@[simp, reassoc]
lemma prod.map_map {A₁ A₂ A₃ B₁ B₂ B₃ : C}
[has_binary_product A₁ B₁] [has_binary_product A₂ B₂] [has_binary_product A₃ B₃]
(f : A₁ ⟶ A₂) (g : B₁ ⟶ B₂) (h : A₂ ⟶ A₃) (k : B₂ ⟶ B₃) :
prod.map f g ≫ prod.map h k = prod.map (f ≫ h) (g ≫ k) :=
by { ext; simp }
-- TODO: is it necessary to weaken the assumption here?
@[reassoc]
lemma prod.map_swap {A B X Y : C} (f : A ⟶ B) (g : X ⟶ Y)
[has_limits_of_shape (discrete walking_pair) C] :
prod.map (𝟙 X) f ≫ prod.map g (𝟙 B) = prod.map g (𝟙 A) ≫ prod.map (𝟙 Y) f :=
by simp
@[reassoc] lemma prod.map_comp_id {X Y Z W : C} (f : X ⟶ Y) (g : Y ⟶ Z)
[has_binary_product X W] [has_binary_product Z W] [has_binary_product Y W] :
prod.map (f ≫ g) (𝟙 W) = prod.map f (𝟙 W) ≫ prod.map g (𝟙 W) :=
by simp
@[reassoc] lemma prod.map_id_comp {X Y Z W : C} (f : X ⟶ Y) (g : Y ⟶ Z)
[has_binary_product W X] [has_binary_product W Y] [has_binary_product W Z] :
prod.map (𝟙 W) (f ≫ g) = prod.map (𝟙 W) f ≫ prod.map (𝟙 W) g :=
by simp
/-- If the products `W ⨯ X` and `Y ⨯ Z` exist, then every pair of isomorphisms `f : W ≅ Y` and
`g : X ≅ Z` induces an isomorphism `prod.map_iso f g : W ⨯ X ≅ Y ⨯ Z`. -/
@[simps]
def prod.map_iso {W X Y Z : C} [has_binary_product W X] [has_binary_product Y Z]
(f : W ≅ Y) (g : X ≅ Z) : W ⨯ X ≅ Y ⨯ Z :=
{ hom := prod.map f.hom g.hom,
inv := prod.map f.inv g.inv }
instance is_iso_prod {W X Y Z : C} [has_binary_product W X] [has_binary_product Y Z]
(f : W ⟶ Y) (g : X ⟶ Z) [is_iso f] [is_iso g] : is_iso (prod.map f g) :=
is_iso.of_iso (prod.map_iso (as_iso f) (as_iso g))
instance prod.map_mono {C : Type*} [category C] {W X Y Z : C} (f : W ⟶ Y) (g : X ⟶ Z) [mono f]
[mono g] [has_binary_product W X] [has_binary_product Y Z] : mono (prod.map f g) :=
⟨λ A i₁ i₂ h, begin
ext,
{ rw ← cancel_mono f, simpa using congr_arg (λ f, f ≫ prod.fst) h },
{ rw ← cancel_mono g, simpa using congr_arg (λ f, f ≫ prod.snd) h }
end⟩
@[simp, reassoc]
lemma prod.diag_map {X Y : C} (f : X ⟶ Y) [has_binary_product X X] [has_binary_product Y Y] :
diag X ≫ prod.map f f = f ≫ diag Y :=
by simp
@[simp, reassoc]
lemma prod.diag_map_fst_snd {X Y : C} [has_binary_product X Y]
[has_binary_product (X ⨯ Y) (X ⨯ Y)] :
diag (X ⨯ Y) ≫ prod.map prod.fst prod.snd = 𝟙 (X ⨯ Y) :=
by simp
@[simp, reassoc]
lemma prod.diag_map_fst_snd_comp [has_limits_of_shape (discrete walking_pair) C]
{X X' Y Y' : C} (g : X ⟶ Y) (g' : X' ⟶ Y') :
diag (X ⨯ X') ≫ prod.map (prod.fst ≫ g) (prod.snd ≫ g') = prod.map g g' :=
by simp
instance {X : C} [has_binary_product X X] : is_split_mono (diag X) :=
is_split_mono.mk' { retraction := prod.fst }
end prod_lemmas
section coprod_lemmas
@[simp, reassoc]
lemma coprod.desc_comp {V W X Y : C} [has_binary_coproduct X Y] (f : V ⟶ W) (g : X ⟶ V)
(h : Y ⟶ V) :
coprod.desc g h ≫ f = coprod.desc (g ≫ f) (h ≫ f) :=
by { ext; simp }
lemma coprod.diag_comp {X Y : C} [has_binary_coproduct X X] (f : X ⟶ Y) :
codiag X ≫ f = coprod.desc f f :=
by simp
@[simp, reassoc]
lemma coprod.inl_map {W X Y Z : C} [has_binary_coproduct W X] [has_binary_coproduct Y Z]
(f : W ⟶ Y) (g : X ⟶ Z) : coprod.inl ≫ coprod.map f g = f ≫ coprod.inl :=
ι_colim_map _ _
@[simp, reassoc]
lemma coprod.inr_map {W X Y Z : C} [has_binary_coproduct W X] [has_binary_coproduct Y Z]
(f : W ⟶ Y) (g : X ⟶ Z) : coprod.inr ≫ coprod.map f g = g ≫ coprod.inr :=
ι_colim_map _ _
@[simp]
lemma coprod.map_id_id {X Y : C} [has_binary_coproduct X Y] :
coprod.map (𝟙 X) (𝟙 Y) = 𝟙 _ :=
by { ext; simp }
@[simp]
lemma coprod.desc_inl_inr {X Y : C} [has_binary_coproduct X Y] :
coprod.desc coprod.inl coprod.inr = 𝟙 (X ⨿ Y) :=
by { ext; simp }
-- The simp linter says simp can prove the reassoc version of this lemma.
@[reassoc, simp]
lemma coprod.map_desc {S T U V W : C} [has_binary_coproduct U W] [has_binary_coproduct T V]
(f : U ⟶ S) (g : W ⟶ S) (h : T ⟶ U) (k : V ⟶ W) :
coprod.map h k ≫ coprod.desc f g = coprod.desc (h ≫ f) (k ≫ g) :=
by { ext; simp }
@[simp]
lemma coprod.desc_comp_inl_comp_inr {W X Y Z : C}
[has_binary_coproduct W Y] [has_binary_coproduct X Z]
(g : W ⟶ X) (g' : Y ⟶ Z) :
coprod.desc (g ≫ coprod.inl) (g' ≫ coprod.inr) = coprod.map g g' :=
by { rw ← coprod.map_desc, simp }
-- We take the right hand side here to be simp normal form, as this way composition lemmas for
-- `f ≫ h` and `g ≫ k` can fire (eg `id_comp`) , while `inl_map` and `inr_map` can still work just
-- as well.
@[simp, reassoc]
lemma coprod.map_map {A₁ A₂ A₃ B₁ B₂ B₃ : C}
[has_binary_coproduct A₁ B₁] [has_binary_coproduct A₂ B₂] [has_binary_coproduct A₃ B₃]
(f : A₁ ⟶ A₂) (g : B₁ ⟶ B₂) (h : A₂ ⟶ A₃) (k : B₂ ⟶ B₃) :
coprod.map f g ≫ coprod.map h k = coprod.map (f ≫ h) (g ≫ k) :=
by { ext; simp }
-- I don't think it's a good idea to make any of the following three simp lemmas.
@[reassoc]
lemma coprod.map_swap {A B X Y : C} (f : A ⟶ B) (g : X ⟶ Y)
[has_colimits_of_shape (discrete walking_pair) C] :
coprod.map (𝟙 X) f ≫ coprod.map g (𝟙 B) = coprod.map g (𝟙 A) ≫ coprod.map (𝟙 Y) f :=
by simp
@[reassoc] lemma coprod.map_comp_id {X Y Z W : C} (f : X ⟶ Y) (g : Y ⟶ Z)
[has_binary_coproduct Z W] [has_binary_coproduct Y W] [has_binary_coproduct X W] :
coprod.map (f ≫ g) (𝟙 W) = coprod.map f (𝟙 W) ≫ coprod.map g (𝟙 W) :=
by simp
@[reassoc] lemma coprod.map_id_comp {X Y Z W : C} (f : X ⟶ Y) (g : Y ⟶ Z)
[has_binary_coproduct W X] [has_binary_coproduct W Y] [has_binary_coproduct W Z] :
coprod.map (𝟙 W) (f ≫ g) = coprod.map (𝟙 W) f ≫ coprod.map (𝟙 W) g :=
by simp
/-- If the coproducts `W ⨿ X` and `Y ⨿ Z` exist, then every pair of isomorphisms `f : W ≅ Y` and
`g : W ≅ Z` induces a isomorphism `coprod.map_iso f g : W ⨿ X ≅ Y ⨿ Z`. -/
@[simps]
def coprod.map_iso {W X Y Z : C} [has_binary_coproduct W X] [has_binary_coproduct Y Z]
(f : W ≅ Y) (g : X ≅ Z) : W ⨿ X ≅ Y ⨿ Z :=
{ hom := coprod.map f.hom g.hom,
inv := coprod.map f.inv g.inv }
instance is_iso_coprod {W X Y Z : C} [has_binary_coproduct W X] [has_binary_coproduct Y Z]
(f : W ⟶ Y) (g : X ⟶ Z) [is_iso f] [is_iso g] : is_iso (coprod.map f g) :=
is_iso.of_iso (coprod.map_iso (as_iso f) (as_iso g))
instance coprod.map_epi {C : Type*} [category C] {W X Y Z : C} (f : W ⟶ Y) (g : X ⟶ Z) [epi f]
[epi g] [has_binary_coproduct W X] [has_binary_coproduct Y Z] : epi (coprod.map f g) :=
⟨λ A i₁ i₂ h, begin
ext,
{ rw ← cancel_epi f, simpa using congr_arg (λ f, coprod.inl ≫ f) h },
{ rw ← cancel_epi g, simpa using congr_arg (λ f, coprod.inr ≫ f) h }
end⟩
-- The simp linter says simp can prove the reassoc version of this lemma.
@[reassoc, simp]
lemma coprod.map_codiag {X Y : C} (f : X ⟶ Y) [has_binary_coproduct X X]
[has_binary_coproduct Y Y] :
coprod.map f f ≫ codiag Y = codiag X ≫ f :=
by simp
-- The simp linter says simp can prove the reassoc version of this lemma.
@[reassoc, simp]
lemma coprod.map_inl_inr_codiag {X Y : C} [has_binary_coproduct X Y]
[has_binary_coproduct (X ⨿ Y) (X ⨿ Y)] :
coprod.map coprod.inl coprod.inr ≫ codiag (X ⨿ Y) = 𝟙 (X ⨿ Y) :=
by simp
-- The simp linter says simp can prove the reassoc version of this lemma.
@[reassoc, simp]
lemma coprod.map_comp_inl_inr_codiag [has_colimits_of_shape (discrete walking_pair) C]
{X X' Y Y' : C} (g : X ⟶ Y) (g' : X' ⟶ Y') :
coprod.map (g ≫ coprod.inl) (g' ≫ coprod.inr) ≫ codiag (Y ⨿ Y') = coprod.map g g' :=
by simp
end coprod_lemmas
variables (C)
/--
`has_binary_products` represents a choice of product for every pair of objects.
See <https://stacks.math.columbia.edu/tag/001T>.
-/
abbreviation has_binary_products := has_limits_of_shape (discrete walking_pair) C
/--
`has_binary_coproducts` represents a choice of coproduct for every pair of objects.
See <https://stacks.math.columbia.edu/tag/04AP>.
-/
abbreviation has_binary_coproducts := has_colimits_of_shape (discrete walking_pair) C
/-- If `C` has all limits of diagrams `pair X Y`, then it has all binary products -/
lemma has_binary_products_of_has_limit_pair [Π {X Y : C}, has_limit (pair X Y)] :
has_binary_products C :=
{ has_limit := λ F, has_limit_of_iso (diagram_iso_pair F).symm }
/-- If `C` has all colimits of diagrams `pair X Y`, then it has all binary coproducts -/
lemma has_binary_coproducts_of_has_colimit_pair [Π {X Y : C}, has_colimit (pair X Y)] :
has_binary_coproducts C :=
{ has_colimit := λ F, has_colimit_of_iso (diagram_iso_pair F) }
section
variables {C}
/-- The braiding isomorphism which swaps a binary product. -/
@[simps] def prod.braiding (P Q : C) [has_binary_product P Q] [has_binary_product Q P] :
P ⨯ Q ≅ Q ⨯ P :=
{ hom := prod.lift prod.snd prod.fst,
inv := prod.lift prod.snd prod.fst }
/-- The braiding isomorphism can be passed through a map by swapping the order. -/
@[reassoc] lemma braid_natural [has_binary_products C] {W X Y Z : C} (f : X ⟶ Y) (g : Z ⟶ W) :
prod.map f g ≫ (prod.braiding _ _).hom = (prod.braiding _ _).hom ≫ prod.map g f :=
by simp
@[reassoc] lemma prod.symmetry' (P Q : C) [has_binary_product P Q] [has_binary_product Q P] :
prod.lift prod.snd prod.fst ≫ prod.lift prod.snd prod.fst = 𝟙 (P ⨯ Q) :=
(prod.braiding _ _).hom_inv_id
/-- The braiding isomorphism is symmetric. -/
@[reassoc] lemma prod.symmetry (P Q : C) [has_binary_product P Q] [has_binary_product Q P] :
(prod.braiding P Q).hom ≫ (prod.braiding Q P).hom = 𝟙 _ :=
(prod.braiding _ _).hom_inv_id
/-- The associator isomorphism for binary products. -/
@[simps] def prod.associator [has_binary_products C] (P Q R : C) :
(P ⨯ Q) ⨯ R ≅ P ⨯ (Q ⨯ R) :=
{ hom :=
prod.lift
(prod.fst ≫ prod.fst)
(prod.lift (prod.fst ≫ prod.snd) prod.snd),
inv :=
prod.lift
(prod.lift prod.fst (prod.snd ≫ prod.fst))
(prod.snd ≫ prod.snd) }
@[reassoc]
lemma prod.pentagon [has_binary_products C] (W X Y Z : C) :
prod.map ((prod.associator W X Y).hom) (𝟙 Z) ≫
(prod.associator W (X ⨯ Y) Z).hom ≫ prod.map (𝟙 W) ((prod.associator X Y Z).hom) =
(prod.associator (W ⨯ X) Y Z).hom ≫ (prod.associator W X (Y ⨯ Z)).hom :=
by simp
@[reassoc]
lemma prod.associator_naturality [has_binary_products C] {X₁ X₂ X₃ Y₁ Y₂ Y₃ : C}
(f₁ : X₁ ⟶ Y₁) (f₂ : X₂ ⟶ Y₂) (f₃ : X₃ ⟶ Y₃) :
prod.map (prod.map f₁ f₂) f₃ ≫ (prod.associator Y₁ Y₂ Y₃).hom =
(prod.associator X₁ X₂ X₃).hom ≫ prod.map f₁ (prod.map f₂ f₃) :=
by simp
variables [has_terminal C]
/-- The left unitor isomorphism for binary products with the terminal object. -/
@[simps] def prod.left_unitor (P : C) [has_binary_product (⊤_ C) P] :
⊤_ C ⨯ P ≅ P :=
{ hom := prod.snd,
inv := prod.lift (terminal.from P) (𝟙 _) }
/-- The right unitor isomorphism for binary products with the terminal object. -/
@[simps] def prod.right_unitor (P : C) [has_binary_product P (⊤_ C)] :
P ⨯ ⊤_ C ≅ P :=
{ hom := prod.fst,
inv := prod.lift (𝟙 _) (terminal.from P) }
@[reassoc]
lemma prod.left_unitor_hom_naturality [has_binary_products C] (f : X ⟶ Y) :
prod.map (𝟙 _) f ≫ (prod.left_unitor Y).hom = (prod.left_unitor X).hom ≫ f :=
prod.map_snd _ _
@[reassoc]
lemma prod.left_unitor_inv_naturality [has_binary_products C] (f : X ⟶ Y) :
(prod.left_unitor X).inv ≫ prod.map (𝟙 _) f = f ≫ (prod.left_unitor Y).inv :=
by rw [iso.inv_comp_eq, ← category.assoc, iso.eq_comp_inv, prod.left_unitor_hom_naturality]
@[reassoc]
lemma prod.right_unitor_hom_naturality [has_binary_products C] (f : X ⟶ Y) :
prod.map f (𝟙 _) ≫ (prod.right_unitor Y).hom = (prod.right_unitor X).hom ≫ f :=
prod.map_fst _ _
@[reassoc]
lemma prod_right_unitor_inv_naturality [has_binary_products C] (f : X ⟶ Y) :
(prod.right_unitor X).inv ≫ prod.map f (𝟙 _) = f ≫ (prod.right_unitor Y).inv :=
by rw [iso.inv_comp_eq, ← category.assoc, iso.eq_comp_inv, prod.right_unitor_hom_naturality]
lemma prod.triangle [has_binary_products C] (X Y : C) :
(prod.associator X (⊤_ C) Y).hom ≫ prod.map (𝟙 X) ((prod.left_unitor Y).hom) =
prod.map ((prod.right_unitor X).hom) (𝟙 Y) :=
by tidy
end
section
variables {C} [has_binary_coproducts C]
/-- The braiding isomorphism which swaps a binary coproduct. -/
@[simps] def coprod.braiding (P Q : C) : P ⨿ Q ≅ Q ⨿ P :=
{ hom := coprod.desc coprod.inr coprod.inl,
inv := coprod.desc coprod.inr coprod.inl }
@[reassoc] lemma coprod.symmetry' (P Q : C) :
coprod.desc coprod.inr coprod.inl ≫ coprod.desc coprod.inr coprod.inl = 𝟙 (P ⨿ Q) :=
(coprod.braiding _ _).hom_inv_id
/-- The braiding isomorphism is symmetric. -/
lemma coprod.symmetry (P Q : C) :
(coprod.braiding P Q).hom ≫ (coprod.braiding Q P).hom = 𝟙 _ :=
coprod.symmetry' _ _
/-- The associator isomorphism for binary coproducts. -/
@[simps] def coprod.associator
(P Q R : C) : (P ⨿ Q) ⨿ R ≅ P ⨿ (Q ⨿ R) :=
{ hom :=
coprod.desc
(coprod.desc coprod.inl (coprod.inl ≫ coprod.inr))
(coprod.inr ≫ coprod.inr),
inv :=
coprod.desc
(coprod.inl ≫ coprod.inl)
(coprod.desc (coprod.inr ≫ coprod.inl) coprod.inr) }
lemma coprod.pentagon (W X Y Z : C) :
coprod.map ((coprod.associator W X Y).hom) (𝟙 Z) ≫
(coprod.associator W (X ⨿ Y) Z).hom ≫ coprod.map (𝟙 W) ((coprod.associator X Y Z).hom) =
(coprod.associator (W ⨿ X) Y Z).hom ≫ (coprod.associator W X (Y ⨿ Z)).hom :=
by simp
lemma coprod.associator_naturality {X₁ X₂ X₃ Y₁ Y₂ Y₃ : C} (f₁ : X₁ ⟶ Y₁) (f₂ : X₂ ⟶ Y₂)
(f₃ : X₃ ⟶ Y₃) :
coprod.map (coprod.map f₁ f₂) f₃ ≫ (coprod.associator Y₁ Y₂ Y₃).hom =
(coprod.associator X₁ X₂ X₃).hom ≫ coprod.map f₁ (coprod.map f₂ f₃) :=
by simp
variables [has_initial C]
/-- The left unitor isomorphism for binary coproducts with the initial object. -/
@[simps] def coprod.left_unitor
(P : C) : ⊥_ C ⨿ P ≅ P :=
{ hom := coprod.desc (initial.to P) (𝟙 _),
inv := coprod.inr }
/-- The right unitor isomorphism for binary coproducts with the initial object. -/
@[simps] def coprod.right_unitor
(P : C) : P ⨿ ⊥_ C ≅ P :=
{ hom := coprod.desc (𝟙 _) (initial.to P),
inv := coprod.inl }
lemma coprod.triangle (X Y : C) :
(coprod.associator X (⊥_ C) Y).hom ≫ coprod.map (𝟙 X) ((coprod.left_unitor Y).hom) =
coprod.map ((coprod.right_unitor X).hom) (𝟙 Y) :=
by tidy
end
section prod_functor
variables {C} [has_binary_products C]
/-- The binary product functor. -/
@[simps]
def prod.functor : C ⥤ C ⥤ C :=
{ obj := λ X, { obj := λ Y, X ⨯ Y, map := λ Y Z, prod.map (𝟙 X) },
map := λ Y Z f, { app := λ T, prod.map f (𝟙 T) }}
/-- The product functor can be decomposed. -/
def prod.functor_left_comp (X Y : C) :
prod.functor.obj (X ⨯ Y) ≅ prod.functor.obj Y ⋙ prod.functor.obj X :=
nat_iso.of_components (prod.associator _ _) (by tidy)
end prod_functor
section coprod_functor
variables {C} [has_binary_coproducts C]
/-- The binary coproduct functor. -/
@[simps]
def coprod.functor : C ⥤ C ⥤ C :=
{ obj := λ X, { obj := λ Y, X ⨿ Y, map := λ Y Z, coprod.map (𝟙 X) },
map := λ Y Z f, { app := λ T, coprod.map f (𝟙 T) }}
/-- The coproduct functor can be decomposed. -/
def coprod.functor_left_comp (X Y : C) :
coprod.functor.obj (X ⨿ Y) ≅ coprod.functor.obj Y ⋙ coprod.functor.obj X :=
nat_iso.of_components (coprod.associator _ _) (by tidy)
end coprod_functor
section prod_comparison
universe w
variables {C} {D : Type u₂} [category.{w} D]
variables (F : C ⥤ D) {A A' B B' : C}
variables [has_binary_product A B] [has_binary_product A' B']
variables [has_binary_product (F.obj A) (F.obj B)] [has_binary_product (F.obj A') (F.obj B')]
/--
The product comparison morphism.
In `category_theory/limits/preserves` we show this is always an iso iff F preserves binary products.
-/
def prod_comparison (F : C ⥤ D) (A B : C)
[has_binary_product A B] [has_binary_product (F.obj A) (F.obj B)] :
F.obj (A ⨯ B) ⟶ F.obj A ⨯ F.obj B :=
prod.lift (F.map prod.fst) (F.map prod.snd)
@[simp, reassoc]
lemma prod_comparison_fst :
prod_comparison F A B ≫ prod.fst = F.map prod.fst :=
prod.lift_fst _ _
@[simp, reassoc]
lemma prod_comparison_snd :
prod_comparison F A B ≫ prod.snd = F.map prod.snd :=
prod.lift_snd _ _
/-- Naturality of the prod_comparison morphism in both arguments. -/
@[reassoc] lemma prod_comparison_natural (f : A ⟶ A') (g : B ⟶ B') :
F.map (prod.map f g) ≫ prod_comparison F A' B' =
prod_comparison F A B ≫ prod.map (F.map f) (F.map g) :=
begin
rw [prod_comparison, prod_comparison, prod.lift_map, ← F.map_comp, ← F.map_comp,
prod.comp_lift, ← F.map_comp, prod.map_fst, ← F.map_comp, prod.map_snd]
end
/--
The product comparison morphism from `F(A ⨯ -)` to `FA ⨯ F-`, whose components are given by
`prod_comparison`.
-/
@[simps]
def prod_comparison_nat_trans [has_binary_products C] [has_binary_products D]
(F : C ⥤ D) (A : C) :
prod.functor.obj A ⋙ F ⟶ F ⋙ prod.functor.obj (F.obj A) :=
{ app := λ B, prod_comparison F A B,
naturality' := λ B B' f, by simp [prod_comparison_natural] }
@[reassoc]
lemma inv_prod_comparison_map_fst [is_iso (prod_comparison F A B)] :
inv (prod_comparison F A B) ≫ F.map prod.fst = prod.fst :=
by simp [is_iso.inv_comp_eq]
@[reassoc]
lemma inv_prod_comparison_map_snd [is_iso (prod_comparison F A B)] :
inv (prod_comparison F A B) ≫ F.map prod.snd = prod.snd :=
by simp [is_iso.inv_comp_eq]
/-- If the product comparison morphism is an iso, its inverse is natural. -/
@[reassoc]
lemma prod_comparison_inv_natural (f : A ⟶ A') (g : B ⟶ B')
[is_iso (prod_comparison F A B)] [is_iso (prod_comparison F A' B')] :
inv (prod_comparison F A B) ≫ F.map (prod.map f g) =
prod.map (F.map f) (F.map g) ≫ inv (prod_comparison F A' B') :=
by rw [is_iso.eq_comp_inv, category.assoc, is_iso.inv_comp_eq, prod_comparison_natural]
/--
The natural isomorphism `F(A ⨯ -) ≅ FA ⨯ F-`, provided each `prod_comparison F A B` is an
isomorphism (as `B` changes).
-/
@[simps {rhs_md := semireducible}]
def prod_comparison_nat_iso [has_binary_products C] [has_binary_products D]
(A : C) [∀ B, is_iso (prod_comparison F A B)] :
prod.functor.obj A ⋙ F ≅ F ⋙ prod.functor.obj (F.obj A) :=
{ hom := prod_comparison_nat_trans F A
..(@as_iso _ _ _ _ _ (nat_iso.is_iso_of_is_iso_app ⟨_, _⟩)) }
end prod_comparison
section coprod_comparison
universe w
variables {C} {D : Type u₂} [category.{w} D]
variables (F : C ⥤ D) {A A' B B' : C}
variables [has_binary_coproduct A B] [has_binary_coproduct A' B']
variables [has_binary_coproduct (F.obj A) (F.obj B)] [has_binary_coproduct (F.obj A') (F.obj B')]
/--
The coproduct comparison morphism.
In `category_theory/limits/preserves` we show
this is always an iso iff F preserves binary coproducts.
-/
def coprod_comparison (F : C ⥤ D) (A B : C)
[has_binary_coproduct A B] [has_binary_coproduct (F.obj A) (F.obj B)] :
F.obj A ⨿ F.obj B ⟶ F.obj (A ⨿ B) :=
coprod.desc (F.map coprod.inl) (F.map coprod.inr)
@[simp, reassoc]
lemma coprod_comparison_inl :
coprod.inl ≫ coprod_comparison F A B = F.map coprod.inl :=
coprod.inl_desc _ _
@[simp, reassoc]
lemma coprod_comparison_inr :
coprod.inr ≫ coprod_comparison F A B = F.map coprod.inr :=
coprod.inr_desc _ _
/-- Naturality of the coprod_comparison morphism in both arguments. -/
@[reassoc] lemma coprod_comparison_natural (f : A ⟶ A') (g : B ⟶ B') :
coprod_comparison F A B ≫ F.map (coprod.map f g) =
coprod.map (F.map f) (F.map g) ≫ coprod_comparison F A' B' :=
begin
rw [coprod_comparison, coprod_comparison, coprod.map_desc, ← F.map_comp, ← F.map_comp,
coprod.desc_comp, ← F.map_comp, coprod.inl_map, ← F.map_comp, coprod.inr_map]
end
/--
The coproduct comparison morphism from `FA ⨿ F-` to `F(A ⨿ -)`, whose components are given by
`coprod_comparison`.
-/
@[simps]
def coprod_comparison_nat_trans [has_binary_coproducts C] [has_binary_coproducts D]
(F : C ⥤ D) (A : C) :
F ⋙ coprod.functor.obj (F.obj A) ⟶ coprod.functor.obj A ⋙ F :=
{ app := λ B, coprod_comparison F A B,
naturality' := λ B B' f, by simp [coprod_comparison_natural] }
@[reassoc]
lemma map_inl_inv_coprod_comparison [is_iso (coprod_comparison F A B)] :
F.map coprod.inl ≫ inv (coprod_comparison F A B) = coprod.inl :=
by simp [is_iso.inv_comp_eq]
@[reassoc]
lemma map_inr_inv_coprod_comparison [is_iso (coprod_comparison F A B)] :
F.map coprod.inr ≫ inv (coprod_comparison F A B) = coprod.inr :=
by simp [is_iso.inv_comp_eq]
/-- If the coproduct comparison morphism is an iso, its inverse is natural. -/
@[reassoc]
lemma coprod_comparison_inv_natural (f : A ⟶ A') (g : B ⟶ B')
[is_iso (coprod_comparison F A B)] [is_iso (coprod_comparison F A' B')] :
inv (coprod_comparison F A B) ≫ coprod.map (F.map f) (F.map g) =
F.map (coprod.map f g) ≫ inv (coprod_comparison F A' B') :=
by rw [is_iso.eq_comp_inv, category.assoc, is_iso.inv_comp_eq, coprod_comparison_natural]
/--
The natural isomorphism `FA ⨿ F- ≅ F(A ⨿ -)`, provided each `coprod_comparison F A B` is an
isomorphism (as `B` changes).
-/
@[simps {rhs_md := semireducible}]
def coprod_comparison_nat_iso [has_binary_coproducts C] [has_binary_coproducts D]
(A : C) [∀ B, is_iso (coprod_comparison F A B)] :
F ⋙ coprod.functor.obj (F.obj A) ≅ coprod.functor.obj A ⋙ F :=
{ hom := coprod_comparison_nat_trans F A
..(@as_iso _ _ _ _ _ (nat_iso.is_iso_of_is_iso_app ⟨_, _⟩)) }
end coprod_comparison
end category_theory.limits
open category_theory.limits
namespace category_theory
variables {C : Type u} [category.{v} C]
/-- Auxiliary definition for `over.coprod`. -/
@[simps]
def over.coprod_obj [has_binary_coproducts C] {A : C} : over A → over A ⥤ over A := λ f,
{ obj := λ g, over.mk (coprod.desc f.hom g.hom),
map := λ g₁ g₂ k, over.hom_mk (coprod.map (𝟙 _) k.left) }
/-- A category with binary coproducts has a functorial `sup` operation on over categories. -/
@[simps]
def over.coprod [has_binary_coproducts C] {A : C} : over A ⥤ over A ⥤ over A :=
{ obj := λ f, over.coprod_obj f,
map := λ f₁ f₂ k,
{ app := λ g, over.hom_mk (coprod.map k.left (𝟙 _))
(by { dsimp, rw [coprod.map_desc, category.id_comp, over.w k] }),
naturality' := λ f g k, by ext; { dsimp, simp, }, },
map_id' := λ X, by ext; { dsimp, simp, },
map_comp' := λ X Y Z f g, by ext; { dsimp, simp, }, }.
end category_theory
|
14d6a84e4c7671b08e01e0c0dbb22d7c76f27b8a | 6432ea7a083ff6ba21ea17af9ee47b9c371760f7 | /tests/lean/2161.lean | 7330d12a6115f658aa88516ba86b0c2a240edeb7 | [
"Apache-2.0",
"LLVM-exception",
"NCSA",
"LGPL-3.0-only",
"LicenseRef-scancode-inner-net-2.0",
"BSD-3-Clause",
"LGPL-2.0-or-later",
"Spencer-94",
"LGPL-2.1-or-later",
"HPND",
"LicenseRef-scancode-pcre",
"ISC",
"LGPL-2.1-only",
"LicenseRef-scancode-other-permissive",
"SunPro",
"CMU-Mach"... | permissive | leanprover/lean4 | 4bdf9790294964627eb9be79f5e8f6157780b4cc | f1f9dc0f2f531af3312398999d8b8303fa5f096b | refs/heads/master | 1,693,360,665,786 | 1,693,350,868,000 | 1,693,350,868,000 | 129,571,436 | 2,827 | 311 | Apache-2.0 | 1,694,716,156,000 | 1,523,760,560,000 | Lean | UTF-8 | Lean | false | false | 617 | lean | structure Foo where num : Nat deriving DecidableEq
namespace Foo
instance : OfNat Foo n := ⟨⟨n⟩⟩
/-! # Example 1 -/
@[irreducible] def mul (a b : Foo) : Foo :=
let d := Nat.gcd a.num 1
⟨(a.num.div d) * (b.num.div d)⟩
-- should fail fast; exact heartbeat count at time of writing is 31
set_option maxHeartbeats 310
example : ((Foo.mul 4 1).mul 1).mul 1 = 4 := by decide
/-! # Example 2 -/
@[irreducible] def add (a b : Foo) : Foo := ⟨a.num * b.num⟩
-- should not succeed (and fail fast); exact heartbeat count at time of writing is 21
example : ((Foo.add 4 1).add 1).add 1 = 4 := by decide
|
fefe27b5f0406015555fa80dad0aa2b9739f6d4d | aa5a655c05e5359a70646b7154e7cac59f0b4132 | /stage0/src/Lean/Elab/Structure.lean | 3c21c569acc75bcdfe90ac12971c74534d642c09 | [
"Apache-2.0"
] | permissive | lambdaxymox/lean4 | ae943c960a42247e06eff25c35338268d07454cb | 278d47c77270664ef29715faab467feac8a0f446 | refs/heads/master | 1,677,891,867,340 | 1,612,500,005,000 | 1,612,500,005,000 | null | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 27,364 | lean | /-
Copyright (c) 2020 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Leonardo de Moura
-/
import Lean.Parser.Command
import Lean.Meta.Closure
import Lean.Meta.SizeOf
import Lean.Elab.Command
import Lean.Elab.DeclModifiers
import Lean.Elab.DeclUtil
import Lean.Elab.Inductive
import Lean.Elab.DeclarationRange
namespace Lean.Elab.Command
open Meta
/- Recall that the `structure command syntax is
```
parser! (structureTk <|> classTk) >> declId >> many Term.bracketedBinder >> optional «extends» >> Term.optType >> optional (" := " >> optional structCtor >> structFields)
```
-/
structure StructCtorView where
ref : Syntax
modifiers : Modifiers
inferMod : Bool -- true if `{}` is used in the constructor declaration
name : Name
declName : Name
structure StructFieldView where
ref : Syntax
modifiers : Modifiers
binderInfo : BinderInfo
inferMod : Bool
declName : Name
name : Name
binders : Syntax
type? : Option Syntax
value? : Option Syntax
structure StructView where
ref : Syntax
modifiers : Modifiers
scopeLevelNames : List Name -- All `universe` declarations in the current scope
allUserLevelNames : List Name -- `scopeLevelNames` ++ explicit universe parameters provided in the `structure` command
isClass : Bool
declName : Name
scopeVars : Array Expr -- All `variable` declaration in the current scope
params : Array Expr -- Explicit parameters provided in the `structure` command
parents : Array Syntax
type : Syntax
ctor : StructCtorView
fields : Array StructFieldView
inductive StructFieldKind where
| newField | fromParent | subobject
deriving Inhabited
structure StructFieldInfo where
name : Name
declName : Name -- Remark: this field value doesn't matter for fromParent fields.
fvar : Expr
kind : StructFieldKind
inferMod : Bool := false
value? : Option Expr := none
deriving Inhabited
def StructFieldInfo.isFromParent (info : StructFieldInfo) : Bool :=
match info.kind with
| StructFieldKind.fromParent => true
| _ => false
def StructFieldInfo.isSubobject (info : StructFieldInfo) : Bool :=
match info.kind with
| StructFieldKind.subobject => true
| _ => false
/- Auxiliary declaration for `mkProjections` -/
structure ProjectionInfo where
declName : Name
inferMod : Bool
structure ElabStructResult where
decl : Declaration
projInfos : List ProjectionInfo
projInstances : List Name -- projections (to parent classes) that must be marked as instances.
mctx : MetavarContext
lctx : LocalContext
localInsts : LocalInstances
defaultAuxDecls : Array (Name × Expr × Expr)
private def defaultCtorName := `mk
/-
The structure constructor syntax is
```
parser! try (declModifiers >> ident >> optional inferMod >> " :: ")
```
-/
private def expandCtor (structStx : Syntax) (structModifiers : Modifiers) (structDeclName : Name) : TermElabM StructCtorView := do
let useDefault := do
let declName := structDeclName ++ defaultCtorName
addAuxDeclarationRanges declName structStx[2] structStx[2]
pure { ref := structStx, modifiers := {}, inferMod := false, name := defaultCtorName, declName := declName }
if structStx[5].isNone then
useDefault
else
let optCtor := structStx[5][1]
if optCtor.isNone then
useDefault
else
let ctor := optCtor[0]
withRef ctor do
let ctorModifiers ← elabModifiers ctor[0]
checkValidCtorModifier ctorModifiers
if ctorModifiers.isPrivate && structModifiers.isPrivate then
throwError "invalid 'private' constructor in a 'private' structure"
if ctorModifiers.isProtected && structModifiers.isPrivate then
throwError "invalid 'protected' constructor in a 'private' structure"
let inferMod := !ctor[2].isNone
let name := ctor[1].getId
let declName := structDeclName ++ name
let declName ← applyVisibility ctorModifiers.visibility declName
addDocString' declName ctorModifiers.docString?
addAuxDeclarationRanges declName ctor[1] ctor[1]
pure { ref := ctor, name := name, modifiers := ctorModifiers, inferMod := inferMod, declName := declName }
def checkValidFieldModifier (modifiers : Modifiers) : TermElabM Unit := do
if modifiers.isNoncomputable then
throwError "invalid use of 'noncomputable' in field declaration"
if modifiers.isPartial then
throwError "invalid use of 'partial' in field declaration"
if modifiers.isUnsafe then
throwError "invalid use of 'unsafe' in field declaration"
if modifiers.attrs.size != 0 then
throwError "invalid use of attributes in field declaration"
if modifiers.isPrivate then
throwError "private fields are not supported yet"
/-
```
def structExplicitBinder := parser! atomic (declModifiers true >> "(") >> many1 ident >> optional inferMod >> optDeclSig >> optional Term.binderDefault >> ")"
def structImplicitBinder := parser! atomic (declModifiers true >> "{") >> many1 ident >> optional inferMod >> declSig >> "}"
def structInstBinder := parser! atomic (declModifiers true >> "[") >> many1 ident >> optional inferMod >> declSig >> "]"
def structSimpleBinder := parser! atomic (declModifiers true >> ident) >> optional inferMod >> optDeclSig >> optional Term.binderDefault
def structFields := parser! many (structExplicitBinder <|> structImplicitBinder <|> structInstBinder)
```
-/
private def expandFields (structStx : Syntax) (structModifiers : Modifiers) (structDeclName : Name) : TermElabM (Array StructFieldView) :=
let fieldBinders := if structStx[5].isNone then #[] else structStx[5][2][0].getArgs
fieldBinders.foldlM (init := #[]) fun (views : Array StructFieldView) fieldBinder => withRef fieldBinder do
let mut fieldBinder := fieldBinder
if fieldBinder.getKind == ``Parser.Command.structSimpleBinder then
fieldBinder := Syntax.node ``Parser.Command.structExplicitBinder
#[ fieldBinder[0], mkAtomFrom fieldBinder "(", mkNullNode #[ fieldBinder[1] ], fieldBinder[2], fieldBinder[3], fieldBinder[4], mkAtomFrom fieldBinder ")" ]
let k := fieldBinder.getKind
let binfo ←
if k == ``Parser.Command.structExplicitBinder then pure BinderInfo.default
else if k == ``Parser.Command.structImplicitBinder then pure BinderInfo.implicit
else if k == ``Parser.Command.structInstBinder then pure BinderInfo.instImplicit
else throwError "unexpected kind of structure field"
let fieldModifiers ← elabModifiers fieldBinder[0]
checkValidFieldModifier fieldModifiers
if fieldModifiers.isPrivate && structModifiers.isPrivate then
throwError "invalid 'private' field in a 'private' structure"
if fieldModifiers.isProtected && structModifiers.isPrivate then
throwError "invalid 'protected' field in a 'private' structure"
let inferMod := !fieldBinder[3].isNone
let (binders, type?) :=
if binfo == BinderInfo.default then
expandOptDeclSig fieldBinder[4]
else
let (binders, type) := expandDeclSig fieldBinder[4]
(binders, some type)
let value? :=
if binfo != BinderInfo.default then none
else
let optBinderDefault := fieldBinder[5]
if optBinderDefault.isNone then none
else
-- binderDefault := parser! " := " >> termParser
some optBinderDefault[0][1]
let idents := fieldBinder[2].getArgs
idents.foldlM (init := views) fun (views : Array StructFieldView) ident => withRef ident do
let name := ident.getId
if isInternalSubobjectFieldName name then
throwError! "invalid field name '{name}', identifiers starting with '_' are reserved to the system"
let declName := structDeclName ++ name
let declName ← applyVisibility fieldModifiers.visibility declName
addDocString' declName fieldModifiers.docString?
return views.push {
ref := ident,
modifiers := fieldModifiers,
binderInfo := binfo,
inferMod := inferMod,
declName := declName,
name := name,
binders := binders,
type? := type?,
value? := value?
}
private def validStructType (type : Expr) : Bool :=
match type with
| Expr.sort .. => true
| _ => false
private def checkParentIsStructure (parent : Expr) : TermElabM Name :=
match parent.getAppFn with
| Expr.const c _ _ => do
unless isStructure (← getEnv) c do
throwError! "'{c}' is not a structure"
pure c
| _ => throwError "expected structure"
private def findFieldInfo? (infos : Array StructFieldInfo) (fieldName : Name) : Option StructFieldInfo :=
infos.find? fun info => info.name == fieldName
private def containsFieldName (infos : Array StructFieldInfo) (fieldName : Name) : Bool :=
(findFieldInfo? infos fieldName).isSome
private partial def processSubfields (structDeclName : Name) (parentFVar : Expr) (parentStructName : Name) (subfieldNames : Array Name)
(infos : Array StructFieldInfo) (k : Array StructFieldInfo → TermElabM α) : TermElabM α :=
let rec loop (i : Nat) (infos : Array StructFieldInfo) := do
if h : i < subfieldNames.size then
let subfieldName := subfieldNames.get ⟨i, h⟩
if containsFieldName infos subfieldName then
throwError! "field '{subfieldName}' from '{parentStructName}' has already been declared"
let val ← mkProjection parentFVar subfieldName
let type ← inferType val
withLetDecl subfieldName type val fun subfieldFVar =>
/- The following `declName` is only used for creating the `_default` auxiliary declaration name when
its default value is overwritten in the structure. -/
let declName := structDeclName ++ subfieldName
let infos := infos.push { name := subfieldName, declName := declName, fvar := subfieldFVar, kind := StructFieldKind.fromParent }
loop (i+1) infos
else
k infos
loop 0 infos
private partial def withParents (view : StructView) (i : Nat) (infos : Array StructFieldInfo) (k : Array StructFieldInfo → TermElabM α) : TermElabM α := do
if h : i < view.parents.size then
let parentStx := view.parents.get ⟨i, h⟩
withRef parentStx do
let parent ← Term.elabType parentStx
let parentName ← checkParentIsStructure parent
let toParentName := Name.mkSimple $ "to" ++ parentName.eraseMacroScopes.getString! -- erase macro scopes?
if containsFieldName infos toParentName then
throwErrorAt! parentStx "field '{toParentName}' has already been declared"
let env ← getEnv
let binfo := if view.isClass && isClass env parentName then BinderInfo.instImplicit else BinderInfo.default
withLocalDecl toParentName binfo parent fun parentFVar =>
let infos := infos.push { name := toParentName, declName := view.declName ++ toParentName, fvar := parentFVar, kind := StructFieldKind.subobject }
let subfieldNames := getStructureFieldsFlattened env parentName
processSubfields view.declName parentFVar parentName subfieldNames infos fun infos => withParents view (i+1) infos k
else
k infos
private def elabFieldTypeValue (view : StructFieldView) (params : Array Expr) : TermElabM (Option Expr × Option Expr) := do
match view.type? with
| none =>
match view.value? with
| none => pure (none, none)
| some valStx =>
let value ← Term.elabTerm valStx none
let value ← mkLambdaFVars params value
pure (none, value)
| some typeStx =>
let type ← Term.elabType typeStx
match view.value? with
| none =>
let type ← mkForallFVars params type
pure (type, none)
| some valStx =>
let value ← Term.elabTermEnsuringType valStx type
let type ← mkForallFVars params type
let value ← mkLambdaFVars params value
pure (type, value)
private partial def withFields
(views : Array StructFieldView) (i : Nat) (infos : Array StructFieldInfo) (k : Array StructFieldInfo → TermElabM α) : TermElabM α := do
if h : i < views.size then
let view := views.get ⟨i, h⟩
withRef view.ref $
match findFieldInfo? infos view.name with
| none => do
let (type?, value?) ← Term.elabBinders view.binders.getArgs fun params => elabFieldTypeValue view params
match type?, value? with
| none, none => throwError "invalid field, type expected"
| some type, _ =>
withLocalDecl view.name view.binderInfo type fun fieldFVar =>
let infos := infos.push { name := view.name, declName := view.declName, fvar := fieldFVar, value? := value?,
kind := StructFieldKind.newField, inferMod := view.inferMod }
withFields views (i+1) infos k
| none, some value =>
let type ← inferType value
withLocalDecl view.name view.binderInfo type fun fieldFVar =>
let infos := infos.push { name := view.name, declName := view.declName, fvar := fieldFVar, value? := value,
kind := StructFieldKind.newField, inferMod := view.inferMod }
withFields views (i+1) infos k
| some info =>
match info.kind with
| StructFieldKind.newField => throwError! "field '{view.name}' has already been declared"
| StructFieldKind.fromParent =>
match view.value? with
| none => throwError! "field '{view.name}' has been declared in parent structure"
| some valStx => do
if let some type := view.type? then
throwErrorAt! type "omit field '{view.name}' type to set default value"
else
let mut valStx := valStx
if view.binders.getArgs.size > 0 then
valStx ← `(fun $(view.binders.getArgs)* => $valStx:term)
let fvarType ← inferType info.fvar
let value ← Term.elabTermEnsuringType valStx fvarType
let infos := infos.push { info with value? := value }
withFields views (i+1) infos k
| StructFieldKind.subobject => unreachable!
else
k infos
private def getResultUniverse (type : Expr) : TermElabM Level := do
let type ← whnf type
match type with
| Expr.sort u _ => pure u
| _ => throwError "unexpected structure resulting type"
private def collectUsed (params : Array Expr) (fieldInfos : Array StructFieldInfo) : StateRefT CollectFVars.State TermElabM Unit := do
params.forM fun p => do
let type ← inferType p
Term.collectUsedFVars type
fieldInfos.forM fun info => do
let fvarType ← inferType info.fvar
Term.collectUsedFVars fvarType
match info.value? with
| none => pure ()
| some value => Term.collectUsedFVars value
private def removeUnused (scopeVars : Array Expr) (params : Array Expr) (fieldInfos : Array StructFieldInfo)
: TermElabM (LocalContext × LocalInstances × Array Expr) := do
let (_, used) ← (collectUsed params fieldInfos).run {}
Term.removeUnused scopeVars used
private def withUsed {α} (scopeVars : Array Expr) (params : Array Expr) (fieldInfos : Array StructFieldInfo) (k : Array Expr → TermElabM α)
: TermElabM α := do
let (lctx, localInsts, vars) ← removeUnused scopeVars params fieldInfos
withLCtx lctx localInsts $ k vars
private def levelMVarToParamFVar (fvar : Expr) : StateRefT Nat TermElabM Unit := do
let type ← inferType fvar
discard <| Term.levelMVarToParam' type
private def levelMVarToParamFVars (fvars : Array Expr) : StateRefT Nat TermElabM Unit :=
fvars.forM levelMVarToParamFVar
private def levelMVarToParamAux (scopeVars : Array Expr) (params : Array Expr) (fieldInfos : Array StructFieldInfo)
: StateRefT Nat TermElabM (Array StructFieldInfo) := do
levelMVarToParamFVars scopeVars
levelMVarToParamFVars params
fieldInfos.mapM fun info => do
levelMVarToParamFVar info.fvar
match info.value? with
| none => pure info
| some value =>
let value ← Term.levelMVarToParam' value
pure { info with value? := value }
private def levelMVarToParam (scopeVars : Array Expr) (params : Array Expr) (fieldInfos : Array StructFieldInfo) : TermElabM (Array StructFieldInfo) :=
(levelMVarToParamAux scopeVars params fieldInfos).run' 1
private partial def collectUniversesFromFields (r : Level) (rOffset : Nat) (fieldInfos : Array StructFieldInfo) : TermElabM (Array Level) := do
fieldInfos.foldlM (init := #[]) fun (us : Array Level) (info : StructFieldInfo) => do
let type ← inferType info.fvar
let u ← getLevel type
let u ← instantiateLevelMVars u
accLevelAtCtor u r rOffset us
private def updateResultingUniverse (fieldInfos : Array StructFieldInfo) (type : Expr) : TermElabM Expr := do
let r ← getResultUniverse type
let rOffset : Nat := r.getOffset
let r : Level := r.getLevelOffset
match r with
| Level.mvar mvarId _ =>
let us ← collectUniversesFromFields r rOffset fieldInfos
let rNew := mkResultUniverse us rOffset
assignLevelMVar mvarId rNew
instantiateMVars type
| _ => throwError "failed to compute resulting universe level of structure, provide universe explicitly"
private def collectLevelParamsInFVar (s : CollectLevelParams.State) (fvar : Expr) : TermElabM CollectLevelParams.State := do
let type ← inferType fvar
let type ← instantiateMVars type
pure $ collectLevelParams s type
private def collectLevelParamsInFVars (fvars : Array Expr) (s : CollectLevelParams.State) : TermElabM CollectLevelParams.State :=
fvars.foldlM collectLevelParamsInFVar s
private def collectLevelParamsInStructure (structType : Expr) (scopeVars : Array Expr) (params : Array Expr) (fieldInfos : Array StructFieldInfo)
: TermElabM (Array Name) := do
let s := collectLevelParams {} structType
let s ← collectLevelParamsInFVars scopeVars s
let s ← collectLevelParamsInFVars params s
let s ← fieldInfos.foldlM (fun (s : CollectLevelParams.State) info => collectLevelParamsInFVar s info.fvar) s
pure s.params
private def addCtorFields (fieldInfos : Array StructFieldInfo) : Nat → Expr → TermElabM Expr
| 0, type => pure type
| i+1, type => do
let info := fieldInfos[i]
let decl ← Term.getFVarLocalDecl! info.fvar
let type ← instantiateMVars type
let type := type.abstract #[info.fvar]
match info.kind with
| StructFieldKind.fromParent =>
let val := decl.value
addCtorFields fieldInfos i (type.instantiate1 val)
| StructFieldKind.subobject =>
let n := mkInternalSubobjectFieldName $ decl.userName
addCtorFields fieldInfos i (mkForall n decl.binderInfo decl.type type)
| StructFieldKind.newField =>
addCtorFields fieldInfos i (mkForall decl.userName decl.binderInfo decl.type type)
private def mkCtor (view : StructView) (levelParams : List Name) (params : Array Expr) (fieldInfos : Array StructFieldInfo) : TermElabM Constructor :=
withRef view.ref do
let type := mkAppN (mkConst view.declName (levelParams.map mkLevelParam)) params
let type ← addCtorFields fieldInfos fieldInfos.size type
let type ← mkForallFVars params type
let type ← instantiateMVars type
let type := type.inferImplicit params.size !view.ctor.inferMod
pure { name := view.ctor.declName, type := type }
@[extern "lean_mk_projections"]
private constant mkProjections (env : Environment) (structName : Name) (projs : List ProjectionInfo) (isClass : Bool) : Except KernelException Environment
private def addProjections (structName : Name) (projs : List ProjectionInfo) (isClass : Bool) : TermElabM Unit := do
let env ← getEnv
match mkProjections env structName projs isClass with
| Except.ok env => setEnv env
| Except.error ex => throwKernelException ex
private def mkAuxConstructions (declName : Name) : TermElabM Unit := do
let env ← getEnv
let hasUnit := env.contains `PUnit
let hasEq := env.contains `Eq
let hasHEq := env.contains `HEq
mkRecOn declName
if hasUnit then mkCasesOn declName
if hasUnit && hasEq && hasHEq then mkNoConfusion declName
private def addDefaults (lctx : LocalContext) (defaultAuxDecls : Array (Name × Expr × Expr)) : TermElabM Unit := do
let localInsts ← getLocalInstances
withLCtx lctx localInsts do
defaultAuxDecls.forM fun (declName, type, value) => do
/- The identity function is used as "marker". -/
let value ← mkId value
discard <| mkAuxDefinition declName type value (zeta := true)
setReducibleAttribute declName
private def elabStructureView (view : StructView) : TermElabM Unit := do
view.fields.forM fun field => do
if field.declName == view.ctor.declName then
throwErrorAt! field.ref "invalid field name '{field.name}', it is equal to structure constructor name"
addAuxDeclarationRanges field.declName field.ref field.ref
let numExplicitParams := view.params.size
let type ← Term.elabType view.type
unless validStructType type do throwErrorAt view.type "expected Type"
withRef view.ref do
withParents view 0 #[] fun fieldInfos =>
withFields view.fields 0 fieldInfos fun fieldInfos => do
Term.synthesizeSyntheticMVarsNoPostponing
let u ← getResultUniverse type
let inferLevel ← shouldInferResultUniverse u
withUsed view.scopeVars view.params fieldInfos $ fun scopeVars => do
let numParams := scopeVars.size + numExplicitParams
let fieldInfos ← levelMVarToParam scopeVars view.params fieldInfos
let type ← withRef view.ref do
if inferLevel then
updateResultingUniverse fieldInfos type
else
checkResultingUniverse (← getResultUniverse type)
pure type
trace[Elab.structure]! "type: {type}"
let usedLevelNames ← collectLevelParamsInStructure type scopeVars view.params fieldInfos
match sortDeclLevelParams view.scopeLevelNames view.allUserLevelNames usedLevelNames with
| Except.error msg => withRef view.ref <| throwError msg
| Except.ok levelParams =>
let params := scopeVars ++ view.params
let ctor ← mkCtor view levelParams params fieldInfos
let type ← mkForallFVars params type
let type ← instantiateMVars type
let indType := { name := view.declName, type := type, ctors := [ctor] : InductiveType }
let decl := Declaration.inductDecl levelParams params.size [indType] view.modifiers.isUnsafe
Term.ensureNoUnassignedMVars decl
addDecl decl
let projInfos := (fieldInfos.filter fun (info : StructFieldInfo) => !info.isFromParent).toList.map fun (info : StructFieldInfo) =>
{ declName := info.declName, inferMod := info.inferMod : ProjectionInfo }
addProjections view.declName projInfos view.isClass
mkAuxConstructions view.declName
let instParents ← fieldInfos.filterM fun info => do
let decl ← Term.getFVarLocalDecl! info.fvar
pure (info.isSubobject && decl.binderInfo.isInstImplicit)
let projInstances := instParents.toList.map fun info => info.declName
Term.applyAttributesAt view.declName view.modifiers.attrs AttributeApplicationTime.afterTypeChecking
projInstances.forM fun declName => addInstance declName AttributeKind.global (evalPrio! default)
let lctx ← getLCtx
let fieldsWithDefault := fieldInfos.filter fun info => info.value?.isSome
let defaultAuxDecls ← fieldsWithDefault.mapM fun info => do
let type ← inferType info.fvar
pure (info.declName ++ `_default, type, info.value?.get!)
/- The `lctx` and `defaultAuxDecls` are used to create the auxiliary `_default` declarations
The parameters `params` for these definitions must be marked as implicit, and all others as explicit. -/
let lctx :=
params.foldl (init := lctx) fun (lctx : LocalContext) (p : Expr) =>
lctx.setBinderInfo p.fvarId! BinderInfo.implicit
let lctx :=
fieldInfos.foldl (init := lctx) fun (lctx : LocalContext) (info : StructFieldInfo) =>
if info.isFromParent then lctx -- `fromParent` fields are elaborated as let-decls, and are zeta-expanded when creating `_default`.
else lctx.setBinderInfo info.fvar.fvarId! BinderInfo.default
addDefaults lctx defaultAuxDecls
/-
parser! (structureTk <|> classTk) >> declId >> many Term.bracketedBinder >> optional «extends» >> Term.optType >> " := " >> optional structCtor >> structFields >> optDeriving
where
def «extends» := parser! " extends " >> sepBy1 termParser ", "
def typeSpec := parser! " : " >> termParser
def optType : Parser := optional typeSpec
def structFields := parser! many (structExplicitBinder <|> structImplicitBinder <|> structInstBinder)
def structCtor := parser! try (declModifiers >> ident >> optional inferMod >> " :: ")
-/
def elabStructure (modifiers : Modifiers) (stx : Syntax) : CommandElabM Unit := do
checkValidInductiveModifier modifiers
let isClass := stx[0].getKind == ``Parser.Command.classTk
let modifiers := if isClass then modifiers.addAttribute { name := `class } else modifiers
let declId := stx[1]
let params := stx[2].getArgs
let exts := stx[3]
let parents := if exts.isNone then #[] else exts[0][1].getSepArgs
let optType := stx[4]
let derivingClassViews ← getOptDerivingClasses stx[6]
let type ← if optType.isNone then `(Sort _) else pure optType[0][1]
let declName ←
runTermElabM none fun scopeVars => do
let scopeLevelNames ← Term.getLevelNames
let ⟨name, declName, allUserLevelNames⟩ ← Elab.expandDeclId (← getCurrNamespace) scopeLevelNames declId modifiers
addDeclarationRanges declName stx
Term.withDeclName declName do
let ctor ← expandCtor stx modifiers declName
let fields ← expandFields stx modifiers declName
Term.withLevelNames allUserLevelNames <| Term.withAutoBoundImplicitLocal <|
Term.elabBinders params (catchAutoBoundImplicit := true) fun params => do
let params ← Term.addAutoBoundImplicits params
let allUserLevelNames ← Term.getLevelNames
Term.withAutoBoundImplicitLocal (flag := false) do
elabStructureView {
ref := stx
modifiers := modifiers
scopeLevelNames := scopeLevelNames
allUserLevelNames := allUserLevelNames
declName := declName
isClass := isClass
scopeVars := scopeVars
params := params
parents := parents
type := type
ctor := ctor
fields := fields
}
unless isClass do
mkSizeOfInstances declName
return declName
derivingClassViews.forM fun view => view.applyHandlers #[declName]
builtin_initialize registerTraceClass `Elab.structure
end Lean.Elab.Command
|
43a98e916fcd02beac3fe4a888c55b7fd0bf10fc | 55c7fc2bf55d496ace18cd6f3376e12bb14c8cc5 | /src/category_theory/full_subcategory.lean | eec75206f3146b4b343b06778f7cf3fa19d96468 | [
"Apache-2.0"
] | permissive | dupuisf/mathlib | 62de4ec6544bf3b79086afd27b6529acfaf2c1bb | 8582b06b0a5d06c33ee07d0bdf7c646cae22cf36 | refs/heads/master | 1,669,494,854,016 | 1,595,692,409,000 | 1,595,692,409,000 | 272,046,630 | 0 | 0 | Apache-2.0 | 1,592,066,143,000 | 1,592,066,142,000 | null | UTF-8 | Lean | false | false | 3,852 | lean | /-
Copyright (c) 2017 Scott Morrison. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Scott Morrison, Reid Barton
-/
import category_theory.fully_faithful
import category_theory.groupoid
namespace category_theory
universes v u₁ u₂ -- declare the `v`'s first; see `category_theory.category` for an explanation
section induced
/- Induced categories.
Given a category D and a function F : C → D from a type C to the
objects of D, there is an essentially unique way to give C a
category structure such that F becomes a fully faithful functor,
namely by taking Hom_C(X, Y) = Hom_D(FX, FY). We call this the
category induced from D along F.
As a special case, if C is a subtype of D, this produces the full
subcategory of D on the objects belonging to C. In general the
induced category is equivalent to the full subcategory of D on the
image of F.
-/
/-
It looks odd to make D an explicit argument of `induced_category`,
when it is determined by the argument F anyways. The reason to make D
explicit is in order to control its syntactic form, so that instances
like `induced_category.has_forget₂` (elsewhere) refer to the correct
form of D. This is used to set up several algebraic categories like
def CommMon : Type (u+1) := induced_category Mon (bundled.map @comm_monoid.to_monoid)
-- not `induced_category (bundled monoid) (bundled.map @comm_monoid.to_monoid)`,
-- even though `Mon = bundled monoid`!
-/
variables {C : Type u₁} (D : Type u₂) [category.{v} D]
variables (F : C → D)
include F
/--
`induced_category D F`, where `F : C → D`, is a typeclass synonym for `C`,
which provides a category structure so that the morphisms `X ⟶ Y` are the morphisms
in `D` from `F X` to `F Y`.
-/
@[nolint has_inhabited_instance unused_arguments]
def induced_category : Type u₁ := C
variables {D}
instance induced_category.has_coe_to_sort [has_coe_to_sort D] :
has_coe_to_sort (induced_category D F) :=
⟨_, λ c, ↥(F c)⟩
instance induced_category.category : category.{v} (induced_category D F) :=
{ hom := λ X Y, F X ⟶ F Y,
id := λ X, 𝟙 (F X),
comp := λ _ _ _ f g, f ≫ g }
/--
The forgetful functor from an induced category to the original category,
forgetting the extra data.
-/
@[simps] def induced_functor : induced_category D F ⥤ D :=
{ obj := F, map := λ x y f, f }
instance induced_category.full : full (induced_functor F) :=
{ preimage := λ x y f, f }
instance induced_category.faithful : faithful (induced_functor F) := {}
end induced
instance induced_category.groupoid {C : Type u₁} (D : Type u₂) [groupoid.{v} D] (F : C → D) :
groupoid.{v} (induced_category D F) :=
{ inv := λ X Y f, groupoid.inv f,
inv_comp' := λ X Y f, groupoid.inv_comp f,
comp_inv' := λ X Y f, groupoid.comp_inv f,
.. induced_category.category F }
section full_subcategory
/- A full subcategory is the special case of an induced category with F = subtype.val. -/
variables {C : Type u₂} [category.{v} C]
variables (Z : C → Prop)
instance full_subcategory : category.{v} {X : C // Z X} :=
induced_category.category subtype.val
/--
The forgetful functor from a full subcategory into the original category
("forgetting" the condition).
-/
def full_subcategory_inclusion : {X : C // Z X} ⥤ C :=
induced_functor subtype.val
@[simp] lemma full_subcategory_inclusion.obj {X} :
(full_subcategory_inclusion Z).obj X = X.val := rfl
@[simp] lemma full_subcategory_inclusion.map {X Y} {f : X ⟶ Y} :
(full_subcategory_inclusion Z).map f = f := rfl
instance full_subcategory.full : full (full_subcategory_inclusion Z) :=
induced_category.full subtype.val
instance full_subcategory.faithful : faithful (full_subcategory_inclusion Z) :=
induced_category.faithful subtype.val
end full_subcategory
end category_theory
|
9facdeb8cf3205ed18eb31e4bd858f7541273de8 | 8cae430f0a71442d02dbb1cbb14073b31048e4b0 | /src/algebra/hom/iterate.lean | 4bd68c2cdae3cfdd7c28c8e5990897d7e2682e0d | [
"Apache-2.0"
] | permissive | leanprover-community/mathlib | 56a2cadd17ac88caf4ece0a775932fa26327ba0e | 442a83d738cb208d3600056c489be16900ba701d | refs/heads/master | 1,693,584,102,358 | 1,693,471,902,000 | 1,693,471,902,000 | 97,922,418 | 1,595 | 352 | Apache-2.0 | 1,694,693,445,000 | 1,500,624,130,000 | Lean | UTF-8 | Lean | false | false | 6,588 | lean | /-
Copyright (c) 2020 Yury Kudryashov. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yury Kudryashov
-/
import algebra.group_power.lemmas
import group_theory.group_action.opposite
/-!
# Iterates of monoid and ring homomorphisms
> THIS FILE IS SYNCHRONIZED WITH MATHLIB4.
> Any changes to this file require a corresponding PR to mathlib4.
Iterate of a monoid/ring homomorphism is a monoid/ring homomorphism but it has a wrong type, so Lean
can't apply lemmas like `monoid_hom.map_one` to `f^[n] 1`. Though it is possible to define
a monoid structure on the endomorphisms, quite often we do not want to convert from
`M →* M` to `monoid.End M` and from `f^[n]` to `f^n` just to apply a simple lemma.
So, we restate standard `*_hom.map_*` lemmas under names `*_hom.iterate_map_*`.
We also prove formulas for iterates of add/mul left/right.
## Tags
homomorphism, iterate
-/
open function
variables {M : Type*} {N : Type*} {G : Type*} {H : Type*}
/-- An auxiliary lemma that can be used to prove `⇑(f ^ n) = (⇑f^[n])`. -/
lemma hom_coe_pow {F : Type*} [monoid F] (c : F → M → M) (h1 : c 1 = id)
(hmul : ∀ f g, c (f * g) = c f ∘ c g) (f : F) : ∀ n, c (f ^ n) = (c f^[n])
| 0 := by { rw [pow_zero, h1], refl }
| (n + 1) := by rw [pow_succ, iterate_succ', hmul, hom_coe_pow]
namespace monoid_hom
section
variables [mul_one_class M] [mul_one_class N]
@[simp, to_additive]
theorem iterate_map_one (f : M →* M) (n : ℕ) : f^[n] 1 = 1 :=
iterate_fixed f.map_one n
@[simp, to_additive]
theorem iterate_map_mul (f : M →* M) (n : ℕ) (x y) :
f^[n] (x * y) = (f^[n] x) * (f^[n] y) :=
semiconj₂.iterate f.map_mul n x y
end
variables [monoid M] [monoid N] [group G] [group H]
@[simp, to_additive]
theorem iterate_map_inv (f : G →* G) (n : ℕ) (x) :
f^[n] (x⁻¹) = (f^[n] x)⁻¹ :=
commute.iterate_left f.map_inv n x
@[simp, to_additive]
theorem iterate_map_div (f : G →* G) (n : ℕ) (x y) :
f^[n] (x / y) = (f^[n] x) / (f^[n] y) :=
semiconj₂.iterate f.map_div n x y
theorem iterate_map_pow (f : M →* M) (n : ℕ) (a) (m : ℕ) : f^[n] (a^m) = (f^[n] a)^m :=
commute.iterate_left (λ x, f.map_pow x m) n a
theorem iterate_map_zpow (f : G →* G) (n : ℕ) (a) (m : ℤ) : f^[n] (a^m) = (f^[n] a)^m :=
commute.iterate_left (λ x, f.map_zpow x m) n a
lemma coe_pow {M} [comm_monoid M] (f : monoid.End M) (n : ℕ) : ⇑(f^n) = (f^[n]) :=
hom_coe_pow _ rfl (λ f g, rfl) _ _
end monoid_hom
lemma monoid.End.coe_pow {M} [monoid M] (f : monoid.End M) (n : ℕ) : ⇑(f^n) = (f^[n]) :=
hom_coe_pow _ rfl (λ f g, rfl) _ _
-- we define these manually so that we can pick a better argument order
namespace add_monoid_hom
variables [add_monoid M] [add_group G]
theorem iterate_map_smul (f : M →+ M) (n m : ℕ) (x : M) :
f^[n] (m • x) = m • (f^[n] x) :=
f.to_multiplicative.iterate_map_pow n x m
attribute [to_additive, to_additive_reorder 5] monoid_hom.iterate_map_pow
theorem iterate_map_zsmul (f : G →+ G) (n : ℕ) (m : ℤ) (x : G) :
f^[n] (m • x) = m • (f^[n] x) :=
f.to_multiplicative.iterate_map_zpow n x m
attribute [to_additive, to_additive_reorder 5] monoid_hom.iterate_map_zpow
end add_monoid_hom
lemma add_monoid.End.coe_pow {A} [add_monoid A] (f : add_monoid.End A) (n : ℕ) : ⇑(f^n) = (f^[n]) :=
hom_coe_pow _ rfl (λ f g, rfl) _ _
namespace ring_hom
section semiring
variables {R : Type*} [semiring R] (f : R →+* R) (n : ℕ) (x y : R)
lemma coe_pow (n : ℕ) : ⇑(f^n) = (f^[n]) :=
hom_coe_pow _ rfl (λ f g, rfl) f n
theorem iterate_map_one : f^[n] 1 = 1 := f.to_monoid_hom.iterate_map_one n
theorem iterate_map_zero : f^[n] 0 = 0 := f.to_add_monoid_hom.iterate_map_zero n
theorem iterate_map_add : f^[n] (x + y) = (f^[n] x) + (f^[n] y) :=
f.to_add_monoid_hom.iterate_map_add n x y
theorem iterate_map_mul : f^[n] (x * y) = (f^[n] x) * (f^[n] y) :=
f.to_monoid_hom.iterate_map_mul n x y
theorem iterate_map_pow (a) (n m : ℕ) : f^[n] (a^m) = (f^[n] a)^m :=
f.to_monoid_hom.iterate_map_pow n a m
theorem iterate_map_smul (n m : ℕ) (x : R) :
f^[n] (m • x) = m • (f^[n] x) :=
f.to_add_monoid_hom.iterate_map_smul n m x
end semiring
variables {R : Type*} [ring R] (f : R →+* R) (n : ℕ) (x y : R)
theorem iterate_map_sub : f^[n] (x - y) = (f^[n] x) - (f^[n] y) :=
f.to_add_monoid_hom.iterate_map_sub n x y
theorem iterate_map_neg : f^[n] (-x) = -(f^[n] x) :=
f.to_add_monoid_hom.iterate_map_neg n x
theorem iterate_map_zsmul (n : ℕ) (m : ℤ) (x : R) :
f^[n] (m • x) = m • (f^[n] x) :=
f.to_add_monoid_hom.iterate_map_zsmul n m x
end ring_hom
--what should be the namespace for this section?
section monoid
variables [monoid G] (a : G) (n : ℕ)
@[simp, to_additive] lemma smul_iterate [mul_action G H] :
((•) a : H → H)^[n] = (•) (a^n) :=
funext (λ b, nat.rec_on n (by rw [iterate_zero, id.def, pow_zero, one_smul])
(λ n ih, by rw [iterate_succ', comp_app, ih, pow_succ, mul_smul]))
@[simp, to_additive] lemma mul_left_iterate : ((*) a)^[n] = (*) (a^n) :=
smul_iterate a n
@[simp, to_additive] lemma mul_right_iterate : (* a)^[n] = (* a ^ n) :=
smul_iterate (mul_opposite.op a) n
@[to_additive]
lemma mul_right_iterate_apply_one : (* a)^[n] 1 = a ^ n :=
by simp [mul_right_iterate]
@[simp, to_additive]
lemma pow_iterate (n : ℕ) (j : ℕ) : ((λ (x : G), x^n)^[j]) = λ x, x^(n^j) :=
begin
letI : mul_action ℕ G :=
{ smul := λ n g, g^n,
one_smul := pow_one,
mul_smul := λ m n g, pow_mul' g m n },
exact smul_iterate n j,
end
end monoid
section group
variables [group G]
@[simp, to_additive]
lemma zpow_iterate (n : ℤ) (j : ℕ) : ((λ (x : G), x^n)^[j]) = λ x, x^(n^j) :=
begin
letI : mul_action ℤ G :=
{ smul := λ n g, g^n,
one_smul := zpow_one,
mul_smul := λ m n g, zpow_mul' g m n },
exact smul_iterate n j,
end
end group
section semigroup
variables [semigroup G] {a b c : G}
@[to_additive]
lemma semiconj_by.function_semiconj_mul_left (h : semiconj_by a b c) :
function.semiconj ((*)a) ((*)b) ((*)c) :=
λ j, by rw [← mul_assoc, h.eq, mul_assoc]
@[to_additive]
lemma commute.function_commute_mul_left (h : commute a b) :
function.commute ((*)a) ((*)b) :=
semiconj_by.function_semiconj_mul_left h
@[to_additive]
lemma semiconj_by.function_semiconj_mul_right_swap (h : semiconj_by a b c) :
function.semiconj (*a) (*c) (*b) :=
λ j, by simp_rw [mul_assoc, ← h.eq]
@[to_additive]
lemma commute.function_commute_mul_right (h : commute a b) :
function.commute (*a) (*b) :=
semiconj_by.function_semiconj_mul_right_swap h
end semigroup
|
91da59ba8777fcdc759589aeb46bea96ee18df4d | b00eb947a9c4141624aa8919e94ce6dcd249ed70 | /tests/lean/run/newfrontend1.lean | f1d7064b33ebfb965bde237b94f25ae648a32474 | [
"Apache-2.0"
] | permissive | gebner/lean4-old | a4129a041af2d4d12afb3a8d4deedabde727719b | ee51cdfaf63ee313c914d83264f91f414a0e3b6e | refs/heads/master | 1,683,628,606,745 | 1,622,651,300,000 | 1,622,654,405,000 | 142,608,821 | 1 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 8,784 | lean | def x := 1
#check x
variable {α : Type}
def f (a : α) : α :=
a
def tst (xs : List Nat) : Nat :=
xs.foldl (init := 10) (· + ·)
#check tst [1, 2, 3]
#check fun x y : Nat => x + y
#check tst
#check (fun stx => if True then let e := stx; Pure.pure e else Pure.pure stx : Nat → Id Nat)
#check let x : Nat := 1; x
def foo (a : Nat) (b : Nat := 10) (c : Bool := Bool.true) : Nat :=
a + b
set_option pp.all true
#check foo 1
#check foo 3 (c := false)
def Nat.boo (a : Nat) :=
succ a -- succ here is resolved as `Nat.succ`.
#check Nat.boo
#check true
-- apply is still a valid identifier name
def apply := "hello"
#check apply
theorem simple1 (x y : Nat) (h : x = y) : x = y :=
by {
assumption
}
theorem simple2 (x y : Nat) : x = y → x = y :=
by {
intro h;
assumption
}
syntax "intro2" : tactic
macro_rules
| `(tactic| intro2) => `(tactic| intro; intro )
theorem simple3 (x y : Nat) : x = x → x = y → x = y :=
by {
intro2;
assumption
}
macro "intro3" : tactic => `(intro; intro; intro)
macro "check2" x:term : command => `(#check $x #check $x)
macro "foo" x:term "," y:term : term => `($x + $y + $x)
set_option pp.all false
check2 0+1
check2 foo 0,1
theorem simple4 (x y : Nat) : y = y → x = x → x = y → x = y :=
by {
intro3;
assumption
}
theorem simple5 (x y z : Nat) : y = z → x = x → x = y → x = z :=
by {
intro h1; intro _; intro h3;
exact Eq.trans h3 h1
}
theorem simple6 (x y z : Nat) : y = z → x = x → x = y → x = z :=
by {
intro h1; intro _; intro h3;
refine Eq.trans ?_ h1;
assumption
}
theorem simple7 (x y z : Nat) : y = z → x = x → x = y → x = z :=
by {
intro h1; intro _; intro h3;
refine' Eq.trans ?pre ?post;
exact y;
{ exact h3 }
{ exact h1 }
}
theorem simple8 (x y z : Nat) : y = z → x = x → x = y → x = z := by
intro h1; intro _; intro h3
refine' Eq.trans ?pre ?post
case post => exact h1
case pre => exact h3
theorem simple9 (x y z : Nat) : y = z → x = x → x = y → x = z := by
intros h1 _ h3
traceState
focus
refine' Eq.trans ?pre ?post
first
| exact h1
assumption
| exact y
exact h3
assumption
theorem simple9b (x y z : Nat) : y = z → x = x → x = y → x = z := by
intros h1 _ h3
traceState
focus
refine' Eq.trans ?pre ?post
first
| exact h1
| exact y; exact h3
assumption
theorem simple9c (x y z : Nat) : y = z → x = x → x = y → x = z := by
intros h1 _ h3
solve
| exact h1
| refine' Eq.trans ?pre ?post; exact y; exact h3; assumption
| exact h3
theorem simple9d (x y z : Nat) : y = z → x = x → x = y → x = z := by
intros h1 _ h3
refine' Eq.trans ?pre ?post
solve
| exact h1
| exact y
| exact h3
solve
| exact h1
| exact h3
solve
| exact h1
| assumption
namespace Foo
def Prod.mk := 1
#check (⟨2, 3⟩ : Prod _ _)
end Foo
theorem simple10 (x y z : Nat) : y = z → x = x → x = y → x = z :=
by {
intro h1; intro h2; intro h3;
skip;
apply Eq.trans;
exact h3;
assumption
}
theorem simple11 (x y z : Nat) : y = z → x = x → x = y → x = z :=
by {
intro h1; intro h2; intro h3;
apply @Eq.trans;
traceState;
exact h3;
assumption
}
theorem simple12 (x y z : Nat) : y = z → x = x → x = y → x = z :=
by {
intro h1; intro h2; intro h3;
apply @Eq.trans;
try exact h1; -- `exact h1` fails
traceState;
try exact h3;
traceState;
try exact h1;
}
theorem simple13 (x y z : Nat) : y = z → x = x → x = y → x = z := by
intros h1 h2 h3
traceState
apply @Eq.trans
case b => exact y
traceState
repeat assumption
theorem simple13b (x y z : Nat) : y = z → x = x → x = y → x = z := by {
intros h1 h2 h3;
traceState;
apply @Eq.trans;
case b => exact y;
traceState;
repeat assumption
}
theorem simple14 (x y z : Nat) : y = z → x = x → x = y → x = z := by
intros
apply @Eq.trans
case b => exact y
repeat assumption
theorem simple15 (x y z : Nat) : y = z → x = x → x = y → x = z :=
by {
intros h1 h2 h3;
revert y;
intros y h1 h3;
apply Eq.trans;
exact h3;
exact h1
}
theorem simple16 (x y z : Nat) : y = z → x = x → x = y → x = z :=
by {
intros h1 h2 h3;
try clear x; -- should fail
clear h2;
traceState;
apply Eq.trans;
exact h3;
exact h1
}
macro "blabla" : tactic => `(assumption)
-- Tactic head symbols do not become reserved words
def blabla := 100
#check blabla
theorem simple17 (x : Nat) (h : x = 0) : x = 0 :=
by blabla
theorem simple18 (x : Nat) (h : x = 0) : x = 0 :=
by blabla
theorem simple19 (x y : Nat) (h₁ : x = 0) (h₂ : x = y) : y = 0 :=
by subst x; subst y; exact rfl
theorem tstprec1 (x y z : Nat) : x + y * z = x + (y * z) :=
rfl
theorem tstprec2 (x y z : Nat) : y * z + x = (y * z) + x :=
rfl
set_option pp.all true
#check fun {α} (a : α) => a
#check @(fun α (a : α) => a)
#check
let myid := fun {α} (a : α) => a;
myid [myid 1]
-- In the following example, we need `@` otherwise we will try to insert mvars for α and [Add α],
-- and will fail to generate instance for [Add α]
#check @(fun α (s : Add α) (a : α) => a + a)
def g1 {α} (a₁ a₂ : α) {β} (b : β) : α × α × β :=
(a₁, a₂, b)
def id1 : {α : Type} → α → α :=
fun x => x
def listId : List ({α : Type} → α → α) :=
(fun x => x) :: []
def id2 : {α : Type} → α → α :=
@(fun α (x : α) => id1 x)
def id3 : {α : Type} → α → α :=
@(fun α x => id1 x)
def id4 : {α : Type} → α → α :=
fun x => id1 x
def id5 : {α : Type} → α → α :=
fun {α} x => id1 x
def id6 : {α : Type} → α → α :=
@(fun {α} x => id1 x)
def id7 : {α : Type} → α → α :=
fun {α} x => @id α x
def id8 : {α : Type} → α → α :=
fun {α} x => id (@id α x)
def altTst1 {m σ} [Alternative m] [Monad m] : Alternative (StateT σ m) :=
⟨StateT.failure, StateT.orElse⟩
def altTst2 {m σ} [Alternative m] [Monad m] : Alternative (StateT σ m) :=
⟨@(fun α => StateT.failure), @(fun α => StateT.orElse)⟩
def altTst3 {m σ} [Alternative m] [Monad m] : Alternative (StateT σ m) :=
⟨fun {α} => StateT.failure, fun {α} => StateT.orElse⟩
#check_failure 1 + true
/-
universes u v
/-
MonadFunctorT.{u ?M_1 v} (λ (β : Type u), m α) (λ (β : Type u), m' α) n n'
-/
set_option pp.raw.maxDepth 100
set_option trace.Elab true
def adapt {m m' σ σ'} {n n' : Type → Type} [MonadFunctor m m' n n'] [MonadStateAdapter σ σ' m m'] : MonadStateAdapter σ σ' n n' :=
⟨fun split join => monadMap (adaptState split join : m α → m' α)⟩
-/
syntax "fn" (term:max)+ "=>" term : term
macro_rules
| `(fn $xs* => $b) => `(fun $xs* => $b)
set_option pp.all false
#check fn x => x+1
#check fn α (a : α) => a
def tst1 : {α : Type} → α → α :=
@(fn α a => a)
#check @tst1
syntax ident "==>" term : term
syntax "{" ident "}" "==>" term : term
macro_rules
| `($x:ident ==> $b) => `(fn $x => $b)
| `({$x:ident} ==> $b) => `(fun {$x:ident} => $b)
#check x ==> x+1
def tst2a : {α : Type} → α → α :=
@(α ==> a ==> a)
def tst2b : {α : Type} → α → α :=
{α} ==> a ==> a
#check @tst2a
#check @tst2b
def tst3a : {α : Type} → {β : Type} → α → β → α × β :=
@(α ==> @(β ==> a ==> b ==> (a, b)))
def tst3b : {α : Type} → {β : Type} → α → β → α × β :=
{α} ==> {β} ==> a ==> b ==> (a, b)
syntax "function" (term:max)+ "=>" term : term
macro_rules
| `(function $xs* => $b) => `(@(fun $xs* => $b))
def tst4 : {α : Type} → {β : Type} → α → β → α × β :=
function α β a b => (a, b)
theorem simple20 (x y z : Nat) : y = z → x = x → x = y → x = z :=
by intros h1 h2 h3;
try clear x; -- should fail
clear h2;
traceState;
apply Eq.trans;
exact h3;
exact h1
theorem simple21 (x y z : Nat) : y = z → x = x → y = x → x = z :=
fun h1 _ h3 =>
have : x = y := by { apply Eq.symm; assumption };
Eq.trans this (by assumption)
theorem simple22 (x y z : Nat) : y = z → y = x → id (x = z + 0) :=
fun h1 h2 => show x = z + 0 by
apply Eq.trans
exact h2.symm
assumption
skip
theorem simple23 (x y z : Nat) : y = z → x = x → y = x → x = z :=
fun h1 _ h3 =>
have : x = y := by apply Eq.symm; assumption
Eq.trans this (by assumption)
theorem simple24 (x y z : Nat) : y = z → x = x → y = x → x = z :=
fun h1 _ h3 =>
have h : x = y := by apply Eq.symm; assumption
Eq.trans h (by assumption)
def f1 (x : Nat) : Nat :=
let double x := x + x
let rec loop x :=
match x with
| 0 => 0
| x+1 => loop x + double x
loop x
#eval f1 5
def f2 (x : Nat) : String :=
let bad x : String := toString x
bad x
def f3 x y :=
x + y + 1
theorem f3eq x y : f3 x y = x + y + 1 :=
rfl
def f4 (x y : Nat) : String :=
if x > y + 1 then "hello" else "world"
|
b5d0acd97521dff115f3b7610e70e92a7549ad0c | 80cc5bf14c8ea85ff340d1d747a127dcadeb966f | /src/algebraic_geometry/sheafed_space.lean | 301b25c03d23f8e25dcc48a8671aae8f90f82065 | [
"Apache-2.0"
] | permissive | lacker/mathlib | f2439c743c4f8eb413ec589430c82d0f73b2d539 | ddf7563ac69d42cfa4a1bfe41db1fed521bd795f | refs/heads/master | 1,671,948,326,773 | 1,601,479,268,000 | 1,601,479,268,000 | 298,686,743 | 0 | 0 | Apache-2.0 | 1,601,070,794,000 | 1,601,070,794,000 | null | UTF-8 | Lean | false | false | 4,597 | lean | /-
Copyright (c) 2019 Scott Morrison. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Scott Morrison
-/
import algebraic_geometry.presheafed_space
import topology.sheaves.sheaf
/-!
# Sheafed spaces
Introduces the category of topological spaces equipped with a sheaf (taking values in an
arbitrary target category `C`.)
We further describe how to apply functors and natural transformations to the values of the
presheaves.
-/
universes v u
open category_theory
open Top
open topological_space
open opposite
open category_theory.limits
open category_theory.category category_theory.functor
variables (C : Type u) [category.{v} C] [limits.has_products C]
local attribute [tidy] tactic.op_induction'
namespace algebraic_geometry
/-- A `SheafedSpace C` is a topological space equipped with a sheaf of `C`s. -/
structure SheafedSpace extends PresheafedSpace C :=
(sheaf_condition : presheaf.sheaf_condition)
variables {C}
namespace SheafedSpace
instance coe_carrier : has_coe (SheafedSpace C) Top :=
{ coe := λ X, X.carrier }
/-- Extract the `sheaf C (X : Top)` from a `SheafedSpace C`. -/
def sheaf (X : SheafedSpace C) : sheaf C (X : Top.{v}) := ⟨X.presheaf, X.sheaf_condition⟩
@[simp] lemma as_coe (X : SheafedSpace C) : X.carrier = (X : Top.{v}) := rfl
@[simp] lemma mk_coe (carrier) (presheaf) (h) :
(({ carrier := carrier, presheaf := presheaf, sheaf_condition := h } : SheafedSpace.{v} C) : Top.{v}) = carrier :=
rfl
instance (X : SheafedSpace.{v} C) : topological_space X := X.carrier.str
/-- The trivial `punit` valued sheaf on any topological space. -/
noncomputable
def punit (X : Top) : SheafedSpace (discrete punit) :=
{ sheaf_condition := presheaf.sheaf_condition_punit _,
..@PresheafedSpace.const (discrete punit) _ X punit.star }
noncomputable
instance : inhabited (SheafedSpace (discrete _root_.punit)) := ⟨punit (Top.of pempty)⟩
instance : category (SheafedSpace C) :=
show category (induced_category (PresheafedSpace C) SheafedSpace.to_PresheafedSpace),
by apply_instance
/-- Forgetting the sheaf condition is a functor from `SheafedSpace C` to `PresheafedSpace C`. -/
def forget_to_PresheafedSpace : (SheafedSpace C) ⥤ (PresheafedSpace C) :=
induced_functor _
variables {C}
section
local attribute [simp] id comp presheaf.pushforward
@[simp] lemma id_base (X : SheafedSpace C) :
((𝟙 X) : X ⟶ X).base = (𝟙 (X : Top.{v})) := rfl
lemma id_c (X : SheafedSpace C) :
((𝟙 X) : X ⟶ X).c =
(((functor.left_unitor _).inv) ≫ (whisker_right (nat_trans.op (opens.map_id (X.carrier)).hom) _)) := rfl
@[simp] lemma id_c_app (X : SheafedSpace C) (U) :
((𝟙 X) : X ⟶ X).c.app U = eq_to_hom (by { op_induction U, cases U, refl }) :=
by { op_induction U, cases U, simp only [id_c], dsimp, simp, }
@[simp] lemma comp_base {X Y Z : SheafedSpace C} (f : X ⟶ Y) (g : Y ⟶ Z) :
(f ≫ g).base = f.base ≫ g.base := rfl
@[simp] lemma comp_c_app {X Y Z : SheafedSpace C} (α : X ⟶ Y) (β : Y ⟶ Z) (U) :
(α ≫ β).c.app U = (β.c).app U ≫ (α.c).app (op ((opens.map (β.base)).obj (unop U))) ≫
(Top.presheaf.pushforward.comp _ _ _).inv.app U := rfl
variables (C)
/-- The forgetful functor from `SheafedSpace` to `Top`. -/
def forget : SheafedSpace C ⥤ Top :=
{ obj := λ X, (X : Top.{v}),
map := λ X Y f, f.base }
end
open Top.presheaf
/--
The restriction of a sheafed space along an open embedding into the space.
-/
noncomputable
def restrict {U : Top} (X : SheafedSpace C)
(f : U ⟶ (X : Top.{v})) (h : open_embedding f) : SheafedSpace C :=
{ sheaf_condition := λ ι 𝒰, is_limit.of_iso_limit
((is_limit.postcompose_inv_equiv _ _).inv_fun (X.sheaf_condition _))
(sheaf_condition_equalizer_products.fork.iso_of_open_embedding h 𝒰).symm,
..X.to_PresheafedSpace.restrict f h }
/--
The global sections, notated Gamma.
-/
def Γ : (SheafedSpace C)ᵒᵖ ⥤ C :=
forget_to_PresheafedSpace.op ⋙ PresheafedSpace.Γ
lemma Γ_def : (Γ : _ ⥤ C) = forget_to_PresheafedSpace.op ⋙ PresheafedSpace.Γ := rfl
@[simp] lemma Γ_obj (X : (SheafedSpace C)ᵒᵖ) : Γ.obj X = (unop X).presheaf.obj (op ⊤) := rfl
lemma Γ_obj_op (X : SheafedSpace C) : Γ.obj (op X) = X.presheaf.obj (op ⊤) := rfl
@[simp] lemma Γ_map {X Y : (SheafedSpace C)ᵒᵖ} (f : X ⟶ Y) :
Γ.map f = f.unop.c.app (op ⊤) ≫ (unop Y).presheaf.map (opens.le_map_top _ _).op := rfl
lemma Γ_map_op {X Y : SheafedSpace C} (f : X ⟶ Y) :
Γ.map f.op = f.c.app (op ⊤) ≫ X.presheaf.map (opens.le_map_top _ _).op := rfl
end SheafedSpace
end algebraic_geometry
|
541196a681dd018f046bdb4d3ab84d719d4251c2 | 6432ea7a083ff6ba21ea17af9ee47b9c371760f7 | /tests/lean/run/extern.lean | 9e36419b29b240f8d8e2ec3687e89545eea10cba | [
"Apache-2.0",
"LLVM-exception",
"NCSA",
"LGPL-3.0-only",
"LicenseRef-scancode-inner-net-2.0",
"BSD-3-Clause",
"LGPL-2.0-or-later",
"Spencer-94",
"LGPL-2.1-or-later",
"HPND",
"LicenseRef-scancode-pcre",
"ISC",
"LGPL-2.1-only",
"LicenseRef-scancode-other-permissive",
"SunPro",
"CMU-Mach"... | permissive | leanprover/lean4 | 4bdf9790294964627eb9be79f5e8f6157780b4cc | f1f9dc0f2f531af3312398999d8b8303fa5f096b | refs/heads/master | 1,693,360,665,786 | 1,693,350,868,000 | 1,693,350,868,000 | 129,571,436 | 2,827 | 311 | Apache-2.0 | 1,694,716,156,000 | 1,523,760,560,000 | Lean | UTF-8 | Lean | false | false | 310 | lean | @[extern]
def foo (x : Nat) := x
@[extern "bla"]
def foo2 (x : Nat) := x
@[extern 2 "boo"]
def foo3 (x : Nat) := x
@[extern cpp "Lean::bla" llvm "lean_bla"]
def foo4 (x : Bool) := x
@[extern cpp inline "#1 && #2"]
def foo5 (x y : Bool) := x
-- @[extern cpp adhoc llvm "foo"]
-- def foo6 (x y : Bool) := x
|
bde1efbed4e4e491cd83f684568d8a5f72170cba | b7f22e51856f4989b970961f794f1c435f9b8f78 | /tests/lean/run/blast_cc_noconfusion.lean | 0e8c51c7402e3c988addb13e669e0677a2722979 | [
"Apache-2.0"
] | permissive | soonhokong/lean | cb8aa01055ffe2af0fb99a16b4cda8463b882cd1 | 38607e3eb57f57f77c0ac114ad169e9e4262e24f | refs/heads/master | 1,611,187,284,081 | 1,450,766,737,000 | 1,476,122,547,000 | 11,513,992 | 2 | 0 | null | 1,401,763,102,000 | 1,374,182,235,000 | C++ | UTF-8 | Lean | false | false | 1,284 | lean | import data.list
open nat
set_option blast.strategy "cc"
constant f : nat → nat
example (a b c d : nat) : f d = f b → succ a = f b → f d = succ c → a = c :=
by blast
example (a b c d e : nat) : f d = f b → f e = f b → succ a = f b → f e = succ c → a = c :=
by blast
example (a b c d e : nat) : f d = f b → f e = f b → succ a = f b → f e = zero → false :=
by blast
example (a b c d e : nat) : f d = f b → f e = f b → succ a = f b → f e = 0 → false :=
by blast
open list
example (a b c d e f : nat) (l1 l2 l3 l4 : list nat) : l1 = l2 → l2 = l3 → l4 = [a, b, succ c] → l1 = [c, d, succ e] → l3 = l4 → c = e :=
by blast
example (a b c d e f : nat) (l1 l2 l3 l4 : list nat) : l4 = [a, b, succ (succ c)] → l1 = [c, d, succ (succ e)] → l3 = l4 → l1 = l2 → l2 = l3 → c = e :=
by blast
example (a b c d e f : nat) (l1 l2 l3 l4 : list nat) : l4 = [a, b, succ c] → l1 = [c, d, 0] → l3 = l4 → l1 = l2 → l2 = l3 → false :=
by blast
example (a b c d e f : nat) (l1 l2 l3 l4 : list nat) : l4 = [a, b, succ c] → l1 = nil → l3 = l4 → l1 = l2 → l2 = l3 → false :=
by blast
example (a b c d e f : nat) (l1 l2 l3 l4 : list nat) : l1 = l2 → l2 = l3 → l4 = [a, b, succ c] → l1 = nil → l3 = l4 → false :=
by blast
|
e0a9faac7d835f4d867232dd3430875525238395 | 4ad6af7525e674c3cdc623c1495472954f3ce34c | /src/03_haskell.lean | ae2ab3d37079fd74813b71e735bbd32dd5a1b590 | [] | no_license | alcides/lean3_tutorial | 4bf48026f7cfa5ae80e9a75f46ca23364d455810 | 7a871e00c4fd5cb000929a59e1bd804a626ef277 | refs/heads/master | 1,663,719,613,974 | 1,591,141,389,000 | 1,591,141,389,000 | 268,600,781 | 5 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 4,448 | lean | /-
In a undergraduate class I have taught the past years, it was frequent to ask students
to prove some properties about their programs.
Here we follow the exercices students have been typically asked to do in pen and paper.
-/
/-
This is how you inductively define new types.
The haskell version:
data List a = Empty
| Cons a (List a)
Note: Lean provides a convient list structure with a few lemmas available. You should
use the default ones as much as possible, as they will save you time and trouble.
-/
inductive L (a:Type) : Type
| empty : L
| cons : a → L → L
/-
If you want to refer to the empty constructor, you have to use "L.empty".
While this allows you to have multiple constructors with the same name in
different types, it clutters the code.
To overcome it, we bring everything within L to the outer scope with:
-/
open L
/-
length :: [a] -> nat
length [] = 0
length (x:xs) = 1 + length xs
-/
def length {a:Type} : L a → nat
| empty := 0
| (cons head tail) := 1 + length tail
/-
map :: (a → b) → [a] → [b]
map _ [] = []
map f (x:xs) = f x : map f xs
-/
def map {a:Type} {b:Type} : (a → b) → L a → L b
| _ empty := empty
| f (cons head tail) := cons (f head) (map f tail)
/-
Now that we have defined the computable part, let us move into the second language
to prove some properties.
In this first example, we will show a particular example, not really a property. As such,
we will use example instead of lemma or theorem.
-/
example :
length (map id (cons 1 (cons 2 empty))) = 2
:=
begin
rewrite map,
rw map,
rw map,
rw length,
rw length,
rw length,
end
/-
rw stands for rewrite, a new tactic that replaces the ocurrent of that function, using its definition.
This is a very useful tactic.
The proof is very repetitive — nobody writes code/proofs like this. Let's see how to improve it in this level.
-/
/-
Next goal: prove that the length of the map of a list is equal to that of the original list.
-/
theorem length_map_is_the_same (a b:Type) (f:a→b) (xs:L a) :
length (map f xs) = length xs :=
begin
induction xs,
{
-- Base case: empty
rw length,
rw map,
rw length,
},
{
-- Recursive case: cons
rw map,
rw length,
rw length,
rw xs_ih,
}
end
/-
This is our first proof by induction on the structure of the list xs.
If you try to rw map or length before doing the induction, it will yield an error. If a function is
defined using equations, rewrite is only possible if it is clear which of the equations to use. For that
we need to rewrite empty or rewrite cons. By using induction, we can rewrite is knowing its structure.
The induction tactic leaves two goals to be solved instead of the original one. Now we need to prove both,
but they are hopefully easier. Despite not being necessary, we organize both goals using curly braces. To
each goal its block. (begin-end also work, but let us reserve those for the outer scope only. Despite having
editor support, it is considered polite to comment what each sub-goal refers to.
Typically in the recursive/inductive step, we are looking to advance one side of the equality to contain one
side of the inductive hypothisis. The default name in this case is (xs_ih). Always look at the context on the
side window and look for it.
-/
@[simp] /- Please ignore this line for now. -/
theorem map_id_is_the_same (a:Type) (xs:L a) :
map id xs = xs :=
begin
sorry, -- it is your turn again.
end
/-
Let us address the weird @[simp] address before the last theorem. Have you noticed how
you have never had to proe that 1+1 = 2 or any of those basic steps. Most tactics try
to simplify the result automatically, but you can do it manually using the "simp" tactic.
The annotation in the previous theorem is how the user can indicate that whenver Lean tries
to simplify a proposition, it can use that theorem automatically. It is how the Lean
standard library was written.
-/
example :
length (map id (cons 1 (cons 2 empty))) == 1 + 1 :=
begin
simp,
repeat {
rw length,
},
end
/-
The other new tactic in this example is the repeat tactic, that tries to repeat the inside tactics
as many times as possible until it fails, even if it fails at the first try.
This is how you can avoid the boilerplate in the first example in this file.
-/ |
14bf991342ea66f5bab678ccecee34ab450e372f | 037dba89703a79cd4a4aec5e959818147f97635d | /src/2020/peano/peano_practice_questions.lean | c07b204c789aa6acbf229c508d038ff6053aa1a3 | [] | no_license | ImperialCollegeLondon/M40001_lean | 3a6a09298da395ab51bc220a535035d45bbe919b | 62a76fa92654c855af2b2fc2bef8e60acd16ccec | refs/heads/master | 1,666,750,403,259 | 1,665,771,117,000 | 1,665,771,117,000 | 209,141,835 | 115 | 12 | null | 1,640,270,596,000 | 1,568,749,174,000 | Lean | UTF-8 | Lean | false | false | 2,562 | lean | /- MATH40001 : Introduction to university mathematics.
Peano Axioms - Extra Practice, October 2020.
These questions are based on Dr Lawn's Practice Questions
on Blackboard.
This is a Lean file. It can be read with the Lean theorem prover.
You can work on this file online at the following URL:
or you can install Lean and its maths library following the instructions at
https://leanprover-community.github.io/get_started.html
There are advantages to installing Lean on your own computer
(for example it's faster), but it's more hassle than just using it online.
Replace the sorries for the theorems you think are provable
with tactics which prove them.
Here, we use the function `succ` instead of `ν`.
-/
import data.nat.basic
open nat function
#check (succ : ℕ → ℕ)
#reduce succ 0
#reduce succ 36
theorem exists_succ_true : ∃ (ν : ℕ → ℕ), ν = succ :=
begin
sorry
end
theorem exists_succ_false : ¬ ∃ (ν : ℕ → ℕ), ν = succ :=
begin
sorry
end
theorem succ_injective_true : injective succ :=
begin
unfold injective,
sorry
end
theorem succ_injective_false : ¬ injective succ :=
begin
unfold injective,
sorry
end
theorem succ_surjective_true : surjective succ :=
begin
unfold surjective,
sorry
end
theorem succ_surjective_false : ¬ surjective succ :=
begin
unfold surjective,
sorry
end
theorem all_functions_are_succ_true : ∀ (ν : ℕ → ℕ), ν = succ :=
begin
sorry
end
theorem all_functions_are_succ_false : ¬ ∀ (ν : ℕ → ℕ), ν = succ :=
begin
sorry
end
theorem exists_unique_zero_true : ∃! n : ℕ, n = 0 :=
begin
sorry
end
theorem exists_unique_zero_false : ¬ ∃! n : ℕ, n = 0:=
begin
sorry
end
/-
The lemma
`funext_iff` : (f₁ = f₂) ↔ (∀ x, f₁ x = f₂ x)
might come in handy somewhere above.
Next, try writing down the Peano Axioms as given in the lectures/notes:
type `\forall`, `\exists`, `\nu`, `\in`, `\sub` and `\to`
and then SPACE or TAB for their respective symbols ∀ ∃ ν ∈ ⊆ →
-/
def N : set ℕ := {n | true} -- Let `N` be the set of all natural numbers
def Peano_Axiom_1 : Prop := 0 ∈ N -- as an example
def Peano_Axiom_2 : Prop := sorry
def Peano_Axiom_3 : Prop := sorry
def Peano_Axiom_4 : Prop := sorry
def Peano_Axiom_5 : Prop := sorry
-- Lean Fun Facts!
set_option pp.numerals false -- changes lean's pretty printer options
#reduce succ 5
#reduce 37
#check 6
#check 37
-- Compare Lean's recursor with (P5)
#check (@nat.rec : ∀ {C : ℕ → Sort*}, C 0 → (∀ n, C n → C (succ n)) → ∀ n, C n)
|
52fb4f53f5db8ce513556904575b10ee99be143c | d0f9af2b0ace5ce352570d61b09019c8ef4a3b96 | /hw3/dm_box.lean | 4bcf40f5a783fe64b01270ebab166ef22d7688d6 | [] | no_license | jngo13/Discrete-Mathematics | 8671540ef2da7c75915d32332dd20c02f001474e | bf674a866e61f60e6e6d128df85fa73819091787 | refs/heads/master | 1,675,615,657,924 | 1,609,142,011,000 | 1,609,142,011,000 | 267,190,341 | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 1,280 | lean | -- Justin Ngo
-- jmn4fms
-- 2/3/20
-- Sullivan 2102-001
/-
3. [30 points]
Define a polymorphic ADT called dm_box. This type
builder takes one type argument. The intuitive
idea is that a dm_box contains one value of the
type specified by the type argument. Define dm_box
to have one constructor, mk, that takes one value
of the specified type and that produces a dm_box
with that value stored "in" the box. Note: a box
is very much like an ordered pair but it contains
only one value, not two. Define one "inspector"
function, unbox, that takes a dm_box and returns
the value "inside" the box. Write unbox, unbox',
and unbox'', using respectively lambda, C-style,
and cases syntax. Put your definitions in a file,
dm_box.lean, and write a few test cases, using
values of different types, in dm_box_test.lean.
-/
inductive dm_box (value:Type): Type
| mk: value → dm_box --first type of dm_box
open dm_box --data type has its own namespace
--Lamda style
def unbox {value: Type}: dm_box value → value :=
λ (b: dm_box value),
match b with
| dm_box.mk x := x
end
-- C style
def unbox' {value: Type} (b: dm_box value):=
match b with
|(dm_box.mk x) := x
end
-- By case
def unbox'' {value: Type}: (dm_box value) → value
|(dm_box.mk x) := x |
b1f6a9f8040e24084827e8cb231fd805a7b9a4cb | cf39355caa609c0f33405126beee2739aa3cb77e | /tests/lean/run/record4.lean | 9454f3b9dd7817661e6827af4322c467110c24ab | [
"Apache-2.0"
] | permissive | leanprover-community/lean | 12b87f69d92e614daea8bcc9d4de9a9ace089d0e | cce7990ea86a78bdb383e38ed7f9b5ba93c60ce0 | refs/heads/master | 1,687,508,156,644 | 1,684,951,104,000 | 1,684,951,104,000 | 169,960,991 | 457 | 107 | Apache-2.0 | 1,686,744,372,000 | 1,549,790,268,000 | C++ | UTF-8 | Lean | false | false | 185 | lean | structure point (A : Type) (B : Type) :=
mk :: (x : A) (y : B)
inductive color
| red | green | blue
structure color_point (A : Type) (B : Type) extends point A B :=
mk :: (c : color)
|
8d9df4687eb5c0f939e1c3ffdf82c02d7f21eff3 | 5d166a16ae129621cb54ca9dde86c275d7d2b483 | /tests/lean/run/smt_tests3.lean | 7815a0371d6efac4810d0909a73dad2536a973f5 | [
"Apache-2.0"
] | permissive | jcarlson23/lean | b00098763291397e0ac76b37a2dd96bc013bd247 | 8de88701247f54d325edd46c0eed57aeacb64baf | refs/heads/master | 1,611,571,813,719 | 1,497,020,963,000 | 1,497,021,515,000 | 93,882,536 | 1 | 0 | null | 1,497,029,896,000 | 1,497,029,896,000 | null | UTF-8 | Lean | false | false | 680 | lean | def f : nat → nat
| 0 := 1
| (n+1) := f n + 1
lemma ex(a : nat) : f a ≠ 0 :=
begin
induction a,
dsimp [f], intro x, contradiction,
dsimp [f],
change nat.succ (f a_1) ≠ 0,
apply nat.succ_ne_zero
end
lemma ex2 (a : nat) : f a ≠ 0 :=
begin [smt]
induction a,
{ intros, ematch_using [f] },
{ repeat {ematch_using [f, nat.add_one_eq_succ, nat.succ_ne_zero]}}
end
lemma ex3 (a : nat) : f (a+1) = f a + 1 :=
begin [smt]
dsimp [f]
end
lemma ex4 (a : nat) : f (a+1) = f a + 1 :=
begin [smt]
simp [f]
end
lemma ex5 (a : nat) : f (a+1) = f a + 1 :=
begin [smt]
ematch_using [f]
end
lemma ex6 (a : nat) : f 0 = 1 :=
begin [smt]
ematch_using [f]
end
|
19a6a9c4898299777c3a6e3cfec401675e37fad1 | 947fa6c38e48771ae886239b4edce6db6e18d0fb | /src/field_theory/fixed.lean | 86caf68458c2013073913f3960a1e76ff6c17125 | [
"Apache-2.0"
] | permissive | ramonfmir/mathlib | c5dc8b33155473fab97c38bd3aa6723dc289beaa | 14c52e990c17f5a00c0cc9e09847af16fabbed25 | refs/heads/master | 1,661,979,343,526 | 1,660,830,384,000 | 1,660,830,384,000 | 182,072,989 | 0 | 0 | null | 1,555,585,876,000 | 1,555,585,876,000 | null | UTF-8 | Lean | false | false | 16,171 | lean | /-
Copyright (c) 2020 Kenny Lau. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kenny Lau
-/
import algebra.polynomial.group_ring_action
import field_theory.normal
import field_theory.separable
import field_theory.tower
/-!
# Fixed field under a group action.
This is the basis of the Fundamental Theorem of Galois Theory.
Given a (finite) group `G` that acts on a field `F`, we define `fixed_points G F`,
the subfield consisting of elements of `F` fixed_points by every element of `G`.
This subfield is then normal and separable, and in addition (TODO) if `G` acts faithfully on `F`
then `finrank (fixed_points G F) F = fintype.card G`.
## Main Definitions
- `fixed_points G F`, the subfield consisting of elements of `F` fixed_points by every element of
`G`, where `G` is a group that acts on `F`.
-/
noncomputable theory
open_locale classical big_operators
open mul_action finset finite_dimensional
universes u v w
variables {M : Type u} [monoid M]
variables (G : Type u) [group G]
variables (F : Type v) [field F] [mul_semiring_action M F] [mul_semiring_action G F] (m : M)
/-- The subfield of F fixed by the field endomorphism `m`. -/
def fixed_by.subfield : subfield F :=
{ carrier := fixed_by M F m,
zero_mem' := smul_zero m,
add_mem' := λ x y hx hy, (smul_add m x y).trans $ congr_arg2 _ hx hy,
neg_mem' := λ x hx, (smul_neg m x).trans $ congr_arg _ hx,
one_mem' := smul_one m,
mul_mem' := λ x y hx hy, (smul_mul' m x y).trans $ congr_arg2 _ hx hy,
inv_mem' := λ x hx, (smul_inv'' m x).trans $ congr_arg _ hx }
section invariant_subfields
variables (M) {F}
/-- A typeclass for subrings invariant under a `mul_semiring_action`. -/
class is_invariant_subfield (S : subfield F) : Prop :=
(smul_mem : ∀ (m : M) {x : F}, x ∈ S → m • x ∈ S)
variable (S : subfield F)
instance is_invariant_subfield.to_mul_semiring_action [is_invariant_subfield M S] :
mul_semiring_action M S :=
{ smul := λ m x, ⟨m • x, is_invariant_subfield.smul_mem m x.2⟩,
one_smul := λ s, subtype.eq $ one_smul M s,
mul_smul := λ m₁ m₂ s, subtype.eq $ mul_smul m₁ m₂ s,
smul_add := λ m s₁ s₂, subtype.eq $ smul_add m s₁ s₂,
smul_zero := λ m, subtype.eq $ smul_zero m,
smul_one := λ m, subtype.eq $ smul_one m,
smul_mul := λ m s₁ s₂, subtype.eq $ smul_mul' m s₁ s₂ }
instance [is_invariant_subfield M S] : is_invariant_subring M (S.to_subring) :=
{ smul_mem := is_invariant_subfield.smul_mem }
end invariant_subfields
namespace fixed_points
variable (M)
-- we use `subfield.copy` so that the underlying set is `fixed_points M F`
/-- The subfield of fixed points by a monoid action. -/
def subfield : subfield F :=
subfield.copy (⨅ (m : M), fixed_by.subfield F m) (fixed_points M F)
(by { ext z, simp [fixed_points, fixed_by.subfield, infi, subfield.mem_Inf] })
instance : is_invariant_subfield M (fixed_points.subfield M F) :=
{ smul_mem := λ g x hx g', by rw [hx, hx] }
instance : smul_comm_class M (fixed_points.subfield M F) F :=
{ smul_comm := λ m f f', show m • (↑f * f') = f * (m • f'), by rw [smul_mul', f.prop m] }
instance smul_comm_class' : smul_comm_class (fixed_points.subfield M F) M F :=
smul_comm_class.symm _ _ _
@[simp] theorem smul (m : M) (x : fixed_points.subfield M F) : m • x = x :=
subtype.eq $ x.2 m
-- Why is this so slow?
@[simp] theorem smul_polynomial (m : M) (p : polynomial (fixed_points.subfield M F)) : m • p = p :=
polynomial.induction_on p
(λ x, by rw [polynomial.smul_C, smul])
(λ p q ihp ihq, by rw [smul_add, ihp, ihq])
(λ n x ih, by rw [smul_mul', polynomial.smul_C, smul, smul_pow', polynomial.smul_X])
instance : algebra (fixed_points.subfield M F) F :=
by apply_instance
theorem coe_algebra_map :
algebra_map (fixed_points.subfield M F) F = subfield.subtype (fixed_points.subfield M F) :=
rfl
lemma linear_independent_smul_of_linear_independent {s : finset F} :
linear_independent (fixed_points.subfield G F) (λ i : (s : set F), (i : F)) →
linear_independent F (λ i : (s : set F), mul_action.to_fun G F i) :=
begin
haveI : is_empty ((∅ : finset F) : set F) := ⟨subtype.prop⟩,
refine finset.induction_on s (λ _, linear_independent_empty_type)
(λ a s has ih hs, _),
rw coe_insert at hs ⊢,
rw linear_independent_insert (mt mem_coe.1 has) at hs,
rw linear_independent_insert' (mt mem_coe.1 has), refine ⟨ih hs.1, λ ha, _⟩,
rw finsupp.mem_span_image_iff_total at ha, rcases ha with ⟨l, hl, hla⟩,
rw [finsupp.total_apply_of_mem_supported F hl] at hla,
suffices : ∀ i ∈ s, l i ∈ fixed_points.subfield G F,
{ replace hla := (sum_apply _ _ (λ i, l i • to_fun G F i)).symm.trans (congr_fun hla 1),
simp_rw [pi.smul_apply, to_fun_apply, one_smul] at hla,
refine hs.2 (hla ▸ submodule.sum_mem _ (λ c hcs, _)),
change (⟨l c, this c hcs⟩ : fixed_points.subfield G F) • c ∈ _,
exact submodule.smul_mem _ _ (submodule.subset_span $ mem_coe.2 hcs) },
intros i his g,
refine eq_of_sub_eq_zero (linear_independent_iff'.1 (ih hs.1) s.attach (λ i, g • l i - l i) _
⟨i, his⟩ (mem_attach _ _) : _),
refine (@sum_attach _ _ s _ (λ i, (g • l i - l i) • mul_action.to_fun G F i)).trans _,
ext g', dsimp only,
conv_lhs { rw sum_apply, congr, skip, funext, rw [pi.smul_apply, sub_smul, smul_eq_mul] },
rw [sum_sub_distrib, pi.zero_apply, sub_eq_zero],
conv_lhs { congr, skip, funext,
rw [to_fun_apply, ← mul_inv_cancel_left g g', mul_smul, ← smul_mul', ← to_fun_apply _ x] },
show ∑ x in s, g • (λ y, l y • mul_action.to_fun G F y) x (g⁻¹ * g') =
∑ x in s, (λ y, l y • mul_action.to_fun G F y) x g',
rw [← smul_sum, ← sum_apply _ _ (λ y, l y • to_fun G F y),
← sum_apply _ _ (λ y, l y • to_fun G F y)], dsimp only,
rw [hla, to_fun_apply, to_fun_apply, smul_smul, mul_inv_cancel_left]
end
variables [fintype G] (x : F)
/-- `minpoly G F x` is the minimal polynomial of `(x : F)` over `fixed_points G F`. -/
def minpoly : polynomial (fixed_points.subfield G F) :=
(prod_X_sub_smul G F x).to_subring (fixed_points.subfield G F).to_subring $ λ c hc g,
let ⟨n, hc0, hn⟩ := polynomial.mem_frange_iff.1 hc in hn.symm ▸ prod_X_sub_smul.coeff G F x g n
namespace minpoly
theorem monic : (minpoly G F x).monic :=
by { simp only [minpoly, polynomial.monic_to_subring], exact prod_X_sub_smul.monic G F x }
theorem eval₂ : polynomial.eval₂ (subring.subtype $ (fixed_points.subfield G F).to_subring) x
(minpoly G F x) = 0 :=
begin
rw [← prod_X_sub_smul.eval G F x, polynomial.eval₂_eq_eval_map],
simp only [minpoly, polynomial.map_to_subring],
end
theorem eval₂' :
polynomial.eval₂ (subfield.subtype $ (fixed_points.subfield G F)) x (minpoly G F x) = 0 :=
eval₂ G F x
theorem ne_one :
minpoly G F x ≠ (1 : polynomial (fixed_points.subfield G F)) :=
λ H, have _ := eval₂ G F x,
(one_ne_zero : (1 : F) ≠ 0) $ by rwa [H, polynomial.eval₂_one] at this
theorem of_eval₂ (f : polynomial (fixed_points.subfield G F))
(hf : polynomial.eval₂ (subfield.subtype $ fixed_points.subfield G F) x f = 0) :
minpoly G F x ∣ f :=
begin
erw [← polynomial.map_dvd_map' (subfield.subtype $ fixed_points.subfield G F),
minpoly, polynomial.map_to_subring _ (subfield G F).to_subring, prod_X_sub_smul],
refine fintype.prod_dvd_of_coprime
(polynomial.pairwise_coprime_X_sub_C $ mul_action.injective_of_quotient_stabilizer G x)
(λ y, quotient_group.induction_on y $ λ g, _),
rw [polynomial.dvd_iff_is_root, polynomial.is_root.def, mul_action.of_quotient_stabilizer_mk,
polynomial.eval_smul',
← subfield.to_subring.subtype_eq_subtype,
← is_invariant_subring.coe_subtype_hom' G (fixed_points.subfield G F).to_subring,
← mul_semiring_action_hom.coe_polynomial, ← mul_semiring_action_hom.map_smul,
smul_polynomial, mul_semiring_action_hom.coe_polynomial,
is_invariant_subring.coe_subtype_hom', polynomial.eval_map,
subfield.to_subring.subtype_eq_subtype, hf, smul_zero]
end
/- Why is this so slow? -/
theorem irreducible_aux (f g : polynomial (fixed_points.subfield G F))
(hf : f.monic) (hg : g.monic) (hfg : f * g = minpoly G F x) :
f = 1 ∨ g = 1 :=
begin
have hf2 : f ∣ minpoly G F x,
{ rw ← hfg, exact dvd_mul_right _ _ },
have hg2 : g ∣ minpoly G F x,
{ rw ← hfg, exact dvd_mul_left _ _ },
have := eval₂ G F x,
rw [← hfg, polynomial.eval₂_mul, mul_eq_zero] at this,
cases this,
{ right,
have hf3 : f = minpoly G F x,
{ exact polynomial.eq_of_monic_of_associated hf (monic G F x)
(associated_of_dvd_dvd hf2 $ @of_eval₂ G _ F _ _ _ x f this) },
rwa [← mul_one (minpoly G F x), hf3,
mul_right_inj' (monic G F x).ne_zero] at hfg },
{ left,
have hg3 : g = minpoly G F x,
{ exact polynomial.eq_of_monic_of_associated hg (monic G F x)
(associated_of_dvd_dvd hg2 $ @of_eval₂ G _ F _ _ _ x g this) },
rwa [← one_mul (minpoly G F x), hg3,
mul_left_inj' (monic G F x).ne_zero] at hfg }
end
theorem irreducible : irreducible (minpoly G F x) :=
(polynomial.irreducible_of_monic (monic G F x) (ne_one G F x)).2 (irreducible_aux G F x)
end minpoly
theorem is_integral : is_integral (fixed_points.subfield G F) x :=
⟨minpoly G F x, minpoly.monic G F x, minpoly.eval₂ G F x⟩
theorem minpoly_eq_minpoly :
minpoly G F x = _root_.minpoly (fixed_points.subfield G F) x :=
minpoly.eq_of_irreducible_of_monic (minpoly.irreducible G F x)
(minpoly.eval₂ G F x) (minpoly.monic G F x)
instance normal : normal (fixed_points.subfield G F) F :=
⟨λ x, (is_integral G F x).is_algebraic _, λ x, (polynomial.splits_id_iff_splits _).1 $
by { rw [← minpoly_eq_minpoly, minpoly,
coe_algebra_map, ← subfield.to_subring.subtype_eq_subtype,
polynomial.map_to_subring _ (fixed_points.subfield G F).to_subring, prod_X_sub_smul],
exact polynomial.splits_prod _ (λ _ _, polynomial.splits_X_sub_C _) }⟩
instance separable : is_separable (fixed_points.subfield G F) F :=
⟨λ x, is_integral G F x,
λ x, by
{ -- this was a plain rw when we were using unbundled subrings
erw [← minpoly_eq_minpoly,
← polynomial.separable_map (fixed_points.subfield G F).subtype,
minpoly, polynomial.map_to_subring _ ((subfield G F).to_subring) ],
exact polynomial.separable_prod_X_sub_C_iff.2 (injective_of_quotient_stabilizer G x) }⟩
lemma dim_le_card : module.rank (fixed_points.subfield G F) F ≤ fintype.card G :=
dim_le $ λ s hs, by simpa only [dim_fun', cardinal.mk_coe_finset, finset.coe_sort_coe,
cardinal.lift_nat_cast, cardinal.nat_cast_le]
using cardinal_lift_le_dim_of_linear_independent'
(linear_independent_smul_of_linear_independent G F hs)
instance : finite_dimensional (fixed_points.subfield G F) F :=
is_noetherian.iff_fg.1 $ is_noetherian.iff_dim_lt_aleph_0.2 $
lt_of_le_of_lt (dim_le_card G F) (cardinal.nat_lt_aleph_0 _)
lemma finrank_le_card : finrank (fixed_points.subfield G F) F ≤ fintype.card G :=
begin
rw [← cardinal.nat_cast_le, finrank_eq_dim],
apply dim_le_card,
end
end fixed_points
lemma linear_independent_to_linear_map (R : Type u) (A : Type v) (B : Type w)
[comm_semiring R] [ring A] [algebra R A]
[comm_ring B] [is_domain B] [algebra R B] :
linear_independent B (alg_hom.to_linear_map : (A →ₐ[R] B) → (A →ₗ[R] B)) :=
have linear_independent B (linear_map.lto_fun R A B ∘ alg_hom.to_linear_map),
from ((linear_independent_monoid_hom A B).comp
(coe : (A →ₐ[R] B) → (A →* B))
(λ f g hfg, alg_hom.ext $ monoid_hom.ext_iff.1 hfg) : _),
this.of_comp _
lemma cardinal_mk_alg_hom (K : Type u) (V : Type v) (W : Type w)
[field K] [field V] [algebra K V] [finite_dimensional K V]
[field W] [algebra K W] [finite_dimensional K W] :
cardinal.mk (V →ₐ[K] W) ≤ finrank W (V →ₗ[K] W) :=
cardinal_mk_le_finrank_of_linear_independent $ linear_independent_to_linear_map K V W
section alg_hom_fintype
/-- A technical finiteness result. -/
noncomputable def fintype.subtype_prod {E : Type*} {X : set E} (hX : X.finite) {L : Type*}
(F : E → multiset L) : fintype (Π x : X, {l : L // l ∈ F x}) :=
by { classical, letI : fintype X := set.finite.fintype hX, exact pi.fintype}
variables (E K : Type*) [field E] [field K] [algebra F E] [algebra F K] [finite_dimensional F E]
/-- Function from Hom_K(E,L) to pi type Π (x : basis), roots of min poly of x -/
-- Marked as `noncomputable!` since this definition takes multiple seconds to compile,
-- and isn't very computable in practice (since neither `finrank` nor `fin_basis` are).
noncomputable! def roots_of_min_poly_pi_type (φ : E →ₐ[F] K)
(x : set.range (finite_dimensional.fin_basis F E : _ → E)) :
{l : K // l ∈ (((minpoly F x.1).map (algebra_map F K)).roots : multiset K)} :=
⟨φ x, begin
rw [polynomial.mem_roots_map (minpoly.ne_zero_of_finite_field_extension F x.val),
← polynomial.alg_hom_eval₂_algebra_map, ← φ.map_zero],
exact congr_arg φ (minpoly.aeval F (x : E)),
end⟩
lemma aux_inj_roots_of_min_poly : function.injective (roots_of_min_poly_pi_type F E K) :=
begin
intros f g h,
suffices : (f : E →ₗ[F] K) = g,
{ rw linear_map.ext_iff at this,
ext x, exact this x },
rw function.funext_iff at h,
apply linear_map.ext_on (finite_dimensional.fin_basis F E).span_eq,
rintro e he,
have := (h ⟨e, he⟩),
apply_fun subtype.val at this,
exact this,
end
/-- Given field extensions `E/F` and `K/F`, with `E/F` finite, there are finitely many `F`-algebra
homomorphisms `E →ₐ[K] K`. -/
noncomputable instance alg_hom.fintype : fintype (E →ₐ[F] K) :=
let n := finite_dimensional.finrank F E in
begin
let B : basis (fin n) F E := finite_dimensional.fin_basis F E,
let X := set.range (B : fin n → E),
have hX : X.finite := set.finite_range ⇑B,
refine @fintype.of_injective _ _
(fintype.subtype_prod hX (λ e, ((minpoly F e).map (algebra_map F K)).roots)) _
(aux_inj_roots_of_min_poly F E K),
end
end alg_hom_fintype
noncomputable instance alg_equiv.fintype (K : Type u) (V : Type v)
[field K] [field V] [algebra K V] [finite_dimensional K V] :
fintype (V ≃ₐ[K] V) :=
fintype.of_equiv (V →ₐ[K] V) (alg_equiv_equiv_alg_hom K V).symm
lemma finrank_alg_hom (K : Type u) (V : Type v)
[field K] [field V] [algebra K V] [finite_dimensional K V] :
fintype.card (V →ₐ[K] V) ≤ finrank V (V →ₗ[K] V) :=
fintype_card_le_finrank_of_linear_independent $ linear_independent_to_linear_map K V V
namespace fixed_points
theorem finrank_eq_card (G : Type u) (F : Type v) [group G] [field F]
[fintype G] [mul_semiring_action G F] [has_faithful_smul G F] :
finrank (fixed_points.subfield G F) F = fintype.card G :=
le_antisymm (fixed_points.finrank_le_card G F) $
calc fintype.card G
≤ fintype.card (F →ₐ[fixed_points.subfield G F] F) :
fintype.card_le_of_injective _ (mul_semiring_action.to_alg_hom_injective _ F)
... ≤ finrank F (F →ₗ[fixed_points.subfield G F] F) : finrank_alg_hom (fixed_points G F) F
... = finrank (fixed_points.subfield G F) F : finrank_linear_map' _ _ _
/-- `mul_semiring_action.to_alg_hom` is bijective. -/
theorem to_alg_hom_bijective (G : Type u) (F : Type v) [group G] [field F]
[fintype G] [mul_semiring_action G F] [has_faithful_smul G F] :
function.bijective (mul_semiring_action.to_alg_hom _ _ : G → F →ₐ[subfield G F] F) :=
begin
rw fintype.bijective_iff_injective_and_card,
split,
{ exact mul_semiring_action.to_alg_hom_injective _ F },
{ apply le_antisymm,
{ exact fintype.card_le_of_injective _ (mul_semiring_action.to_alg_hom_injective _ F) },
{ rw ← finrank_eq_card G F,
exact has_le.le.trans_eq (finrank_alg_hom _ F) (finrank_linear_map' _ _ _) } },
end
/-- Bijection between G and algebra homomorphisms that fix the fixed points -/
def to_alg_hom_equiv (G : Type u) (F : Type v) [group G] [field F]
[fintype G] [mul_semiring_action G F] [has_faithful_smul G F] :
G ≃ (F →ₐ[fixed_points.subfield G F] F) :=
equiv.of_bijective _ (to_alg_hom_bijective G F)
end fixed_points
|
194c263c7fd81e02d6eb5d6a3af02644c6873707 | 8eeb99d0fdf8125f5d39a0ce8631653f588ee817 | /src/category_theory/category/pairwise.lean | 62efab647e67731dcc1af11a9419a5e22e147064 | [
"Apache-2.0"
] | permissive | jesse-michael-han/mathlib | a15c58378846011b003669354cbab7062b893cfe | fa6312e4dc971985e6b7708d99a5bc3062485c89 | refs/heads/master | 1,625,200,760,912 | 1,602,081,753,000 | 1,602,081,753,000 | 181,787,230 | 0 | 0 | null | 1,555,460,682,000 | 1,555,460,682,000 | null | UTF-8 | Lean | false | false | 4,356 | lean | /-
Copyright (c) 2020 Scott Morrison. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Scott Morrison
-/
import topology.sheaves.sheaf
import category_theory.limits.preserves.basic
/-!
# The category of "pairwise intersections".
Given `ι : Type v`, we build the diagram category `pairwise ι`
with objects `single i` and `pair i j`, for `i j : ι`,
whose only non-identity morphisms are
`left : single i ⟶ pair i j` and `right : single j ⟶ pair i j`.
We use this later in describing the sheaf condition.
Given any function `U : ι → α`, where `α` is some complete lattice (e.g. `opens X`),
we produce a functor `pairwise ι ⥤ αᵒᵖ` in the obvious way,
and show that `supr U` provides a limit cone over this functor.
-/
noncomputable theory
universes v u
open topological_space
open Top
open opposite
open category_theory
open category_theory.limits
namespace category_theory
/--
An inductive type representing either a single term of a type `ι`, or a pair of terms.
We use this as the objects of a category to describe the sheaf condition.
-/
inductive pairwise (ι : Type v)
| single : ι → pairwise
| pair : ι → ι → pairwise
variables {ι : Type v}
namespace pairwise
instance pairwise_inhabited [inhabited ι] : inhabited (pairwise ι) := ⟨single (default ι)⟩
/--
Morphisms in the category `pairwise ι`. The only non-identity morphisms are
`left i j : single i ⟶ pair i j` and `right i j : single j ⟶ pair i j`.
-/
inductive hom : pairwise ι → pairwise ι → Type v
| id_single : Π i, hom (single i) (single i)
| id_pair : Π i j, hom (pair i j) (pair i j)
| left : Π i j, hom (single i) (pair i j)
| right : Π i j, hom (single j) (pair i j)
open hom
instance hom_inhabited [inhabited ι] : inhabited (hom (single (default ι)) (single (default ι))) :=
⟨id_single (default ι)⟩
/--
The identity morphism in `pairwise ι`.
-/
def id : Π (o : pairwise ι), hom o o
| (single i) := id_single i
| (pair i j) := id_pair i j
/-- Composition of morphisms in `pairwise ι`. -/
def comp : Π {o₁ o₂ o₃ : pairwise ι} (f : hom o₁ o₂) (g : hom o₂ o₃), hom o₁ o₃
| _ _ _ (id_single i) g := g
| _ _ _ (id_pair i j) g := g
| _ _ _ (left i j) (id_pair _ _) := left i j
| _ _ _ (right i j) (id_pair _ _) := right i j
section
local attribute [tidy] tactic.case_bash
instance : category (pairwise ι) :=
{ hom := hom,
id := id,
comp := λ X Y Z f g, comp f g, }
end
variables {α : Type v} (U : ι → α)
section
variables [semilattice_inf α]
/-- Auxilliary definition for `diagram`. -/
@[simp]
def diagram_obj : pairwise ι → αᵒᵖ
| (single i) := op (U i)
| (pair i j) := op (U i ⊓ U j)
/-- Auxilliary definition for `diagram`. -/
@[simp]
def diagram_map : Π {o₁ o₂ : pairwise ι} (f : o₁ ⟶ o₂), diagram_obj U o₁ ⟶ diagram_obj U o₂
| _ _ (id_single i) := 𝟙 _
| _ _ (id_pair i j) := 𝟙 _
| _ _ (left i j) := (hom_of_le inf_le_left).op
| _ _ (right i j) := (hom_of_le inf_le_right).op
/--
Given a function `U : ι → α` for `[semilattice_inf α]`, we obtain a functor `pairwise ι ⥤ αᵒᵖ`,
sending `single i` to `op (U i)` and `pair i j` to `op (U i ⊓ U j)`,
and the morphisms to the obvious inequalities.
-/
@[simps]
def diagram : pairwise ι ⥤ αᵒᵖ :=
{ obj := diagram_obj U,
map := λ X Y f, diagram_map U f, }
end
section
-- `complete_lattice` is not really needed, as we only ever use `inf`,
-- but the appropriate structure has not been defined.
variables [complete_lattice α]
/-- Auxilliary definition for `cone`. -/
def cone_π_app : Π (o : pairwise ι), op (supr U) ⟶ diagram_obj U o
| (single i) := (hom_of_le (le_supr _ _)).op
| (pair i j) := (hom_of_le inf_le_left ≫ hom_of_le (le_supr U i)).op
/--
Given a function `U : ι → α` for `[complete_lattice α]`,
`supr U` provides a cone over `diagram U`.
-/
@[simps]
def cone : cone (diagram U) :=
{ X := op (supr U),
π := { app := cone_π_app U, } }
/--
Given a function `U : ι → α` for `[complete_lattice α]`,
`supr U` provides a limit cone over `diagram U`.
-/
def cone_is_limit : is_limit (cone U) :=
{ lift := λ s, op_hom_of_le
begin
apply complete_lattice.Sup_le,
rintros _ ⟨j, rfl⟩,
exact le_of_op_hom (s.π.app (single j))
end }
end
end pairwise
end category_theory
|
72abda189abab45befab4dc382765910f5bee5f8 | 6432ea7a083ff6ba21ea17af9ee47b9c371760f7 | /src/lake/Lake/Util/Error.lean | 5e353ad2fefb5181316015fa13d1d9cb5c1eac23 | [
"Apache-2.0",
"LLVM-exception",
"NCSA",
"LGPL-3.0-only",
"LicenseRef-scancode-inner-net-2.0",
"BSD-3-Clause",
"LGPL-2.0-or-later",
"Spencer-94",
"LGPL-2.1-or-later",
"HPND",
"LicenseRef-scancode-pcre",
"ISC",
"LGPL-2.1-only",
"LicenseRef-scancode-other-permissive",
"SunPro",
"CMU-Mach"... | permissive | leanprover/lean4 | 4bdf9790294964627eb9be79f5e8f6157780b4cc | f1f9dc0f2f531af3312398999d8b8303fa5f096b | refs/heads/master | 1,693,360,665,786 | 1,693,350,868,000 | 1,693,350,868,000 | 129,571,436 | 2,827 | 311 | Apache-2.0 | 1,694,716,156,000 | 1,523,760,560,000 | Lean | UTF-8 | Lean | false | false | 1,143 | lean | /-
Copyright (c) 2021 Mac Malone. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Mac Malone
-/
namespace Lake
class MonadError (m : Type u → Type v) where
error {α : Type u} : String → m α
export MonadError (error)
instance [MonadLift m n] [MonadError m] : MonadError n where
error msg := liftM (m := m) <| error msg
instance : MonadError IO where
error msg := throw <| IO.userError msg
instance : MonadError (EIO String) where
error msg := throw msg
instance : MonadError (Except String) where
error msg := throw msg
/--
Perform an EIO action.
If it throws an error, invoke `error` with its string representation.
-/
protected def MonadError.runEIO [Monad m]
[MonadError m] [MonadLiftT BaseIO m] [ToString ε] (x : EIO ε α) : m α := do
match (← x.toBaseIO) with
| Except.ok a => pure a
| Except.error e => error (toString e)
/--
Perform an IO action.
If it throws an error, invoke `error` with its string representation.
-/
@[inline] protected def MonadError.runIO
[Monad m] [MonadError m] [MonadLiftT BaseIO m] (x : IO α) : m α :=
MonadError.runEIO x
|
e1694d45f3f8f2a76c07d43cd57babb464a98a53 | 2c096fdfecf64e46ea7bc6ce5521f142b5926864 | /src/Lean/Widget/InteractiveDiagnostic.lean | 24d859d4b5b0679ce7c5542ceaef69c5e5ef9d8d | [
"Apache-2.0",
"LLVM-exception",
"NCSA",
"LGPL-3.0-only",
"LicenseRef-scancode-inner-net-2.0",
"BSD-3-Clause",
"LGPL-2.0-or-later",
"Spencer-94",
"LGPL-2.1-or-later",
"HPND",
"LicenseRef-scancode-pcre",
"ISC",
"LGPL-2.1-only",
"LicenseRef-scancode-other-permissive",
"SunPro",
"CMU-Mach"... | permissive | Kha/lean4 | 1005785d2c8797ae266a303968848e5f6ce2fe87 | b99e11346948023cd6c29d248cd8f3e3fb3474cf | refs/heads/master | 1,693,355,498,027 | 1,669,080,461,000 | 1,669,113,138,000 | 184,748,176 | 0 | 0 | Apache-2.0 | 1,665,995,520,000 | 1,556,884,930,000 | Lean | UTF-8 | Lean | false | false | 8,763 | lean | /-
Copyright (c) 2021 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Wojciech Nawrocki
-/
import Lean.Linter.UnusedVariables
import Lean.Server.Utils
import Lean.Widget.InteractiveGoal
namespace Lean.Widget
open Lsp Server
inductive StrictOrLazy (α β : Type) : Type
| strict : α → StrictOrLazy α β
| lazy : β → StrictOrLazy α β
deriving Inhabited, RpcEncodable
structure LazyTraceChildren where
indent : Nat
children : Array (WithRpcRef MessageData)
deriving TypeName
inductive MsgEmbed where
| expr : CodeWithInfos → MsgEmbed
| goal : InteractiveGoal → MsgEmbed
| trace (indent : Nat) (cls : Name) (msg : TaggedText MsgEmbed) (collapsed : Bool)
(children : StrictOrLazy (Array (TaggedText MsgEmbed)) (WithRpcRef LazyTraceChildren))
deriving Inhabited, RpcEncodable
/-- We embed objects in LSP diagnostics by storing them in the tag of an empty subtree (`text ""`).
In other words, we terminate the `MsgEmbed`-tagged tree at embedded objects and instead store
the pretty-printed embed (which can itself be a `TaggedText`) in the tag. -/
abbrev InteractiveDiagnostic := Lsp.DiagnosticWith (TaggedText MsgEmbed)
deriving instance RpcEncodable for Lsp.DiagnosticWith
namespace InteractiveDiagnostic
open MsgEmbed
def toDiagnostic (diag : InteractiveDiagnostic) : Lsp.Diagnostic :=
{ diag with message := prettyTt diag.message }
where
prettyTt (tt : TaggedText MsgEmbed) : String :=
let tt : TaggedText MsgEmbed := tt.rewrite fun
| .expr tt, _ => .text tt.stripTags
| .goal g, _ => .text (toString g.pretty)
| .trace .., _ => .text "(trace)"
tt.stripTags
end InteractiveDiagnostic
private def mkPPContext (nCtx : NamingContext) (ctx : MessageDataContext) : PPContext := {
env := ctx.env, mctx := ctx.mctx, lctx := ctx.lctx, opts := ctx.opts,
currNamespace := nCtx.currNamespace, openDecls := nCtx.openDecls
}
private inductive EmbedFmt
/-- Tags denote `Info` objects. -/
| expr (ctx : Elab.ContextInfo) (infos : RBMap Nat Elab.Info compare)
| goal (ctx : Elab.ContextInfo) (lctx : LocalContext) (g : MVarId)
/-- Some messages (in particular, traces) are too costly to print eagerly. Instead, we allow
the user to expand sub-traces interactively. -/
| trace (cls : Name) (msg : Format) (collapsed : Bool)
(children : StrictOrLazy (Array Format) (Array MessageData))
/-- Ignore any tags in this subtree. -/
| ignoreTags
deriving Inhabited
private abbrev MsgFmtM := StateT (Array EmbedFmt) IO
open MessageData in
/-- We first build a `Nat`-tagged `Format` with the most shallow tag, if any,
in every branch indexing into the array of embedded objects. -/
private partial def msgToInteractiveAux (msgData : MessageData) : IO (Format × Array EmbedFmt) :=
go { currNamespace := Name.anonymous, openDecls := [] } none msgData #[]
where
pushEmbed (e : EmbedFmt) : MsgFmtM Nat :=
modifyGet fun es => (es.size, es.push e)
withIgnoreTags (x : MsgFmtM Format) : MsgFmtM Format := do
let fmt ← x
let t ← pushEmbed EmbedFmt.ignoreTags
return Format.tag t fmt
mkContextInfo (nCtx : NamingContext) (ctx : MessageDataContext) : Elab.ContextInfo := {
env := ctx.env
mctx := ctx.mctx
fileMap := default
options := ctx.opts
currNamespace := nCtx.currNamespace
openDecls := nCtx.openDecls
-- Hack: to make sure unique ids created at `ppExprWithInfos` do not collide with ones in `ctx.mctx`
ngen := { namePrefix := `_diag }
}
go : NamingContext → Option MessageDataContext → MessageData → MsgFmtM Format
| _, _, ofFormat fmt => withIgnoreTags (pure fmt)
| _, _, ofLevel u => return format u
| _, _, ofName n => return format n
| nCtx, some ctx, ofSyntax s => withIgnoreTags (ppTerm (mkPPContext nCtx ctx) ⟨s⟩) -- HACK: might not be a term
| _, none, ofSyntax s => withIgnoreTags (pure s.formatStx)
| _, none, ofExpr e => return format (toString e)
| nCtx, some ctx, ofExpr e => do
let ci := mkContextInfo nCtx ctx
let (fmt, infos) ← ci.runMetaM ctx.lctx <| PrettyPrinter.ppExprWithInfos e
let t ← pushEmbed <| EmbedFmt.expr ci infos
return Format.tag t fmt
| _, none, ofGoal mvarId => pure $ "goal " ++ format (mkMVar mvarId)
| nCtx, some ctx, ofGoal mvarId =>
return .tag (← pushEmbed (.goal (mkContextInfo nCtx ctx) ctx.lctx mvarId)) "\n"
| nCtx, _, withContext ctx d => go nCtx ctx d
| _, ctx, withNamingContext nCtx d => go nCtx ctx d
| nCtx, ctx, tagged _ d => go nCtx ctx d
| nCtx, ctx, nest n d => Format.nest n <$> go nCtx ctx d
| nCtx, ctx, compose d₁ d₂ => do let d₁ ← go nCtx ctx d₁; let d₂ ← go nCtx ctx d₂; pure $ d₁ ++ d₂
| nCtx, ctx, group d => Format.group <$> go nCtx ctx d
| nCtx, ctx, .trace cls header children collapsed => do
let header := (← go nCtx ctx header).nest 4
let nodes ←
if collapsed && !children.isEmpty then
let children := children.map fun child =>
MessageData.withNamingContext nCtx <|
match ctx with
| some ctx => MessageData.withContext ctx child
| none => child
pure (.lazy children)
else
pure (.strict (← children.mapM (go nCtx ctx)))
let e := .trace cls header collapsed nodes
pure (.tag (← pushEmbed e) ".\n")
partial def msgToInteractive (msgData : MessageData) (hasWidgets : Bool) (indent : Nat := 0) : IO (TaggedText MsgEmbed) := do
if !hasWidgets then
return (TaggedText.prettyTagged (← msgData.format)).rewrite fun _ tt => .text tt.stripTags
let (fmt, embeds) ← msgToInteractiveAux msgData
/- Here we rewrite a `TaggedText Nat` corresponding to a whole `MessageData` into one where
the tags are `TaggedText MsgEmbed`s corresponding to embedded objects with their subtree
empty (`text ""`). In other words, we terminate the `MsgEmbed`-tagged -tree at embedded objects
and store the pretty-printed embed (which can itself be a `TaggedText`) in the tag. -/
let rec fmtToTT (fmt : Format) (indent : Nat) : IO (TaggedText MsgEmbed) :=
(TaggedText.prettyTagged fmt indent).rewriteM fun (n, col) tt =>
match embeds[n]! with
| .expr ctx infos =>
return .tag (.expr (tagExprInfos ctx infos tt)) default
| .goal ctx lctx g =>
ctx.runMetaM lctx do
return .tag (.goal (← goalToInteractive g)) default
| .trace cls msg collapsed children => do
let col := col + tt.stripTags.length - 2
let children ←
match children with
| .lazy children => pure <| .lazy ⟨{indent := col+2, children := children.map .mk}⟩
| .strict children => pure <| .strict (← children.mapM (fmtToTT · (col+2)))
return .tag (.trace indent cls (← fmtToTT msg col) collapsed children) default
| .ignoreTags => return .text tt.stripTags
fmtToTT fmt indent
/-- Transform a Lean Message concerning the given text into an LSP Diagnostic. -/
def msgToInteractiveDiagnostic (text : FileMap) (m : Message) (hasWidgets : Bool) : IO InteractiveDiagnostic := do
let low : Lsp.Position := text.leanPosToLspPos m.pos
let fullHigh := text.leanPosToLspPos <| m.endPos.getD m.pos
let high : Lsp.Position := match m.endPos with
| some endPos =>
/-
Truncate messages that are more than one line long.
This is a workaround to avoid big blocks of "red squiggly lines" on VS Code.
TODO: should it be a parameter?
-/
let endPos := if endPos.line > m.pos.line then { line := m.pos.line + 1, column := 0 } else endPos
text.leanPosToLspPos endPos
| none => low
let range : Range := ⟨low, high⟩
let fullRange : Range := ⟨low, fullHigh⟩
let severity? := some <| match m.severity with
| .information => .information
| .warning => .warning
| .error => .error
let source? := some "Lean 4"
let tags? :=
if m.data.isDeprecationWarning then some #[.deprecated]
else if m.data.isUnusedVariableWarning then some #[.unnecessary]
else none
let message ← try
msgToInteractive m.data hasWidgets
catch ex =>
pure <| TaggedText.text s!"[error when printing message: {ex.toString}]"
pure { range, fullRange? := some fullRange, severity?, source?, message, tags? }
end Lean.Widget
|
8cbd35b5dc5d6eeb5c068ca64ab42c937f5ba570 | fa02ed5a3c9c0adee3c26887a16855e7841c668b | /src/order/filter/bases.lean | 3263a60f1b22ffe99ff59a28ddd1f7fc1f3359e2 | [
"Apache-2.0"
] | permissive | jjgarzella/mathlib | 96a345378c4e0bf26cf604aed84f90329e4896a2 | 395d8716c3ad03747059d482090e2bb97db612c8 | refs/heads/master | 1,686,480,124,379 | 1,625,163,323,000 | 1,625,163,323,000 | 281,190,421 | 2 | 0 | Apache-2.0 | 1,595,268,170,000 | 1,595,268,169,000 | null | UTF-8 | Lean | false | false | 37,231 | lean | /-
Copyright (c) 2020 Yury Kudryashov. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yury Kudryashov, Johannes Hölzl, Mario Carneiro, Patrick Massot
-/
import order.filter.basic
import data.set.countable
/-!
# Filter bases
A filter basis `B : filter_basis α` on a type `α` is a nonempty collection of sets of `α`
such that the intersection of two elements of this collection contains some element of
the collection. Compared to filters, filter bases do not require that any set containing
an element of `B` belongs to `B`.
A filter basis `B` can be used to construct `B.filter : filter α` such that a set belongs
to `B.filter` if and only if it contains an element of `B`.
Given an indexing type `ι`, a predicate `p : ι → Prop`, and a map `s : ι → set α`,
the proposition `h : filter.is_basis p s` makes sure the range of `s` bounded by `p`
(ie. `s '' set_of p`) defines a filter basis `h.filter_basis`.
If one already has a filter `l` on `α`, `filter.has_basis l p s` (where `p : ι → Prop`
and `s : ι → set α` as above) means that a set belongs to `l` if and
only if it contains some `s i` with `p i`. It implies `h : filter.is_basis p s`, and
`l = h.filter_basis.filter`. The point of this definition is that checking statements
involving elements of `l` often reduces to checking them on the basis elements.
We define a function `has_basis.index (h : filter.has_basis l p s) (t) (ht : t ∈ l)` that returns
some index `i` such that `p i` and `s i ⊆ t`. This function can be useful to avoid manual
destruction of `h.mem_iff.mpr ht` using `cases` or `let`.
This file also introduces more restricted classes of bases, involving monotonicity or
countability. In particular, for `l : filter α`, `l.is_countably_generated` means
there is a countable set of sets which generates `s`. This is reformulated in term of bases,
and consequences are derived.
## Main statements
* `has_basis.mem_iff`, `has_basis.mem_of_superset`, `has_basis.mem_of_mem` : restate `t ∈ f`
in terms of a basis;
* `basis_sets` : all sets of a filter form a basis;
* `has_basis.inf`, `has_basis.inf_principal`, `has_basis.prod`, `has_basis.prod_self`,
`has_basis.map`, `has_basis.comap` : combinators to construct filters of `l ⊓ l'`,
`l ⊓ 𝓟 t`, `l ×ᶠ l'`, `l ×ᶠ l`, `l.map f`, `l.comap f` respectively;
* `has_basis.le_iff`, `has_basis.ge_iff`, has_basis.le_basis_iff` : restate `l ≤ l'` in terms
of bases.
* `has_basis.tendsto_right_iff`, `has_basis.tendsto_left_iff`, `has_basis.tendsto_iff` : restate
`tendsto f l l'` in terms of bases.
* `is_countably_generated_iff_exists_antimono_basis` : proves a filter is
countably generated if and only if it admis a basis parametrized by a
decreasing sequence of sets indexed by `ℕ`.
* `tendsto_iff_seq_tendsto ` : an abstract version of "sequentially continuous implies continuous".
## Implementation notes
As with `Union`/`bUnion`/`sUnion`, there are three different approaches to filter bases:
* `has_basis l s`, `s : set (set α)`;
* `has_basis l s`, `s : ι → set α`;
* `has_basis l p s`, `p : ι → Prop`, `s : ι → set α`.
We use the latter one because, e.g., `𝓝 x` in an `emetric_space` or in a `metric_space` has a basis
of this form. The other two can be emulated using `s = id` or `p = λ _, true`.
With this approach sometimes one needs to `simp` the statement provided by the `has_basis`
machinery, e.g., `simp only [exists_prop, true_and]` or `simp only [forall_const]` can help
with the case `p = λ _, true`.
-/
open set filter
open_locale filter classical
variables {α : Type*} {β : Type*} {γ : Type*} {ι : Type*} {ι' : Type*}
/-- A filter basis `B` on a type `α` is a nonempty collection of sets of `α`
such that the intersection of two elements of this collection contains some element
of the collection. -/
structure filter_basis (α : Type*) :=
(sets : set (set α))
(nonempty : sets.nonempty)
(inter_sets {x y} : x ∈ sets → y ∈ sets → ∃ z ∈ sets, z ⊆ x ∩ y)
instance filter_basis.nonempty_sets (B : filter_basis α) : nonempty B.sets := B.nonempty.to_subtype
/-- If `B` is a filter basis on `α`, and `U` a subset of `α` then we can write `U ∈ B` as
on paper. -/
@[reducible]
instance {α : Type*}: has_mem (set α) (filter_basis α) := ⟨λ U B, U ∈ B.sets⟩
-- For illustration purposes, the filter basis defining (at_top : filter ℕ)
instance : inhabited (filter_basis ℕ) :=
⟨{ sets := range Ici,
nonempty := ⟨Ici 0, mem_range_self 0⟩,
inter_sets := begin
rintros _ _ ⟨n, rfl⟩ ⟨m, rfl⟩,
refine ⟨Ici (max n m), mem_range_self _, _⟩,
rintros p p_in,
split ; rw mem_Ici at *,
exact le_of_max_le_left p_in,
exact le_of_max_le_right p_in,
end }⟩
/-- `is_basis p s` means the image of `s` bounded by `p` is a filter basis. -/
protected structure filter.is_basis (p : ι → Prop) (s : ι → set α) : Prop :=
(nonempty : ∃ i, p i)
(inter : ∀ {i j}, p i → p j → ∃ k, p k ∧ s k ⊆ s i ∩ s j)
namespace filter
namespace is_basis
/-- Constructs a filter basis from an indexed family of sets satisfying `is_basis`. -/
protected def filter_basis {p : ι → Prop} {s : ι → set α} (h : is_basis p s) : filter_basis α :=
{ sets := s '' set_of p,
nonempty := let ⟨i, hi⟩ := h.nonempty in ⟨s i, mem_image_of_mem s hi⟩,
inter_sets := by { rintros _ _ ⟨i, hi, rfl⟩ ⟨j, hj, rfl⟩,
rcases h.inter hi hj with ⟨k, hk, hk'⟩,
exact ⟨_, mem_image_of_mem s hk, hk'⟩ } }
variables {p : ι → Prop} {s : ι → set α} (h : is_basis p s)
lemma mem_filter_basis_iff {U : set α} : U ∈ h.filter_basis ↔ ∃ i, p i ∧ s i = U :=
iff.rfl
end is_basis
end filter
namespace filter_basis
/-- The filter associated to a filter basis. -/
protected def filter (B : filter_basis α) : filter α :=
{ sets := {s | ∃ t ∈ B, t ⊆ s},
univ_sets := let ⟨s, s_in⟩ := B.nonempty in ⟨s, s_in, s.subset_univ⟩,
sets_of_superset := λ x y ⟨s, s_in, h⟩ hxy, ⟨s, s_in, set.subset.trans h hxy⟩,
inter_sets := λ x y ⟨s, s_in, hs⟩ ⟨t, t_in, ht⟩,
let ⟨u, u_in, u_sub⟩ := B.inter_sets s_in t_in in
⟨u, u_in, set.subset.trans u_sub $ set.inter_subset_inter hs ht⟩ }
lemma mem_filter_iff (B : filter_basis α) {U : set α} : U ∈ B.filter ↔ ∃ s ∈ B, s ⊆ U :=
iff.rfl
lemma mem_filter_of_mem (B : filter_basis α) {U : set α} : U ∈ B → U ∈ B.filter:=
λ U_in, ⟨U, U_in, subset.refl _⟩
lemma eq_infi_principal (B : filter_basis α) : B.filter = ⨅ s : B.sets, 𝓟 s :=
begin
have : directed (≥) (λ (s : B.sets), 𝓟 (s : set α)),
{ rintros ⟨U, U_in⟩ ⟨V, V_in⟩,
rcases B.inter_sets U_in V_in with ⟨W, W_in, W_sub⟩,
use [W, W_in],
finish },
ext U,
simp [mem_filter_iff, mem_infi this]
end
protected lemma generate (B : filter_basis α) : generate B.sets = B.filter :=
begin
apply le_antisymm,
{ intros U U_in,
rcases B.mem_filter_iff.mp U_in with ⟨V, V_in, h⟩,
exact generate_sets.superset (generate_sets.basic V_in) h },
{ rw sets_iff_generate,
apply mem_filter_of_mem }
end
end filter_basis
namespace filter
namespace is_basis
variables {p : ι → Prop} {s : ι → set α}
/-- Constructs a filter from an indexed family of sets satisfying `is_basis`. -/
protected def filter (h : is_basis p s) : filter α := h.filter_basis.filter
protected lemma mem_filter_iff (h : is_basis p s) {U : set α} :
U ∈ h.filter ↔ ∃ i, p i ∧ s i ⊆ U :=
begin
erw [h.filter_basis.mem_filter_iff],
simp only [mem_filter_basis_iff h, exists_prop],
split,
{ rintros ⟨_, ⟨i, pi, rfl⟩, h⟩,
tauto },
{ tauto }
end
lemma filter_eq_generate (h : is_basis p s) : h.filter = generate {U | ∃ i, p i ∧ s i = U} :=
by erw h.filter_basis.generate ; refl
end is_basis
/-- We say that a filter `l` has a basis `s : ι → set α` bounded by `p : ι → Prop`,
if `t ∈ l` if and only if `t` includes `s i` for some `i` such that `p i`. -/
protected structure has_basis (l : filter α) (p : ι → Prop) (s : ι → set α) : Prop :=
(mem_iff' : ∀ (t : set α), t ∈ l ↔ ∃ i (hi : p i), s i ⊆ t)
section same_type
variables {l l' : filter α} {p : ι → Prop} {s : ι → set α} {t : set α} {i : ι}
{p' : ι' → Prop} {s' : ι' → set α} {i' : ι'}
lemma has_basis_generate (s : set (set α)) :
(generate s).has_basis (λ t, finite t ∧ t ⊆ s) (λ t, ⋂₀ t) :=
⟨begin
intro U,
rw mem_generate_iff,
apply exists_congr,
tauto
end⟩
/-- The smallest filter basis containing a given collection of sets. -/
def filter_basis.of_sets (s : set (set α)) : filter_basis α :=
{ sets := sInter '' { t | finite t ∧ t ⊆ s},
nonempty := ⟨univ, ∅, ⟨⟨finite_empty, empty_subset s⟩, sInter_empty⟩⟩,
inter_sets := begin
rintros _ _ ⟨a, ⟨fina, suba⟩, rfl⟩ ⟨b, ⟨finb, subb⟩, rfl⟩,
exact ⟨⋂₀ (a ∪ b), mem_image_of_mem _ ⟨fina.union finb, union_subset suba subb⟩,
by rw sInter_union⟩,
end }
/-- Definition of `has_basis` unfolded with implicit set argument. -/
lemma has_basis.mem_iff (hl : l.has_basis p s) : t ∈ l ↔ ∃ i (hi : p i), s i ⊆ t :=
hl.mem_iff' t
lemma has_basis.eq_of_same_basis (hl : l.has_basis p s) (hl' : l'.has_basis p s) : l = l' :=
begin
ext t,
rw [hl.mem_iff, hl'.mem_iff]
end
lemma has_basis_iff : l.has_basis p s ↔ ∀ t, t ∈ l ↔ ∃ i (hi : p i), s i ⊆ t :=
⟨λ ⟨h⟩, h, λ h, ⟨h⟩⟩
lemma has_basis.ex_mem (h : l.has_basis p s) : ∃ i, p i :=
let ⟨i, pi, h⟩ := h.mem_iff.mp univ_mem_sets in ⟨i, pi⟩
protected lemma has_basis.nonempty (h : l.has_basis p s) : nonempty ι :=
nonempty_of_exists h.ex_mem
protected lemma is_basis.has_basis (h : is_basis p s) : has_basis h.filter p s :=
⟨λ t, by simp only [h.mem_filter_iff, exists_prop]⟩
lemma has_basis.mem_of_superset (hl : l.has_basis p s) (hi : p i) (ht : s i ⊆ t) : t ∈ l :=
(hl.mem_iff).2 ⟨i, hi, ht⟩
lemma has_basis.mem_of_mem (hl : l.has_basis p s) (hi : p i) : s i ∈ l :=
hl.mem_of_superset hi $ subset.refl _
/-- Index of a basis set such that `s i ⊆ t` as an element of `subtype p`. -/
noncomputable def has_basis.index (h : l.has_basis p s) (t : set α) (ht : t ∈ l) :
{i : ι // p i} :=
⟨(h.mem_iff.1 ht).some, (h.mem_iff.1 ht).some_spec.fst⟩
lemma has_basis.property_index (h : l.has_basis p s) (ht : t ∈ l) : p (h.index t ht) :=
(h.index t ht).2
lemma has_basis.set_index_mem (h : l.has_basis p s) (ht : t ∈ l) : s (h.index t ht) ∈ l :=
h.mem_of_mem $ h.property_index _
lemma has_basis.set_index_subset (h : l.has_basis p s) (ht : t ∈ l) : s (h.index t ht) ⊆ t :=
(h.mem_iff.1 ht).some_spec.snd
lemma has_basis.is_basis (h : l.has_basis p s) : is_basis p s :=
{ nonempty := let ⟨i, hi, H⟩ := h.mem_iff.mp univ_mem_sets in ⟨i, hi⟩,
inter := λ i j hi hj, by simpa [h.mem_iff]
using l.inter_sets (h.mem_of_mem hi) (h.mem_of_mem hj) }
lemma has_basis.filter_eq (h : l.has_basis p s) : h.is_basis.filter = l :=
by { ext U, simp [h.mem_iff, is_basis.mem_filter_iff] }
lemma has_basis.eq_generate (h : l.has_basis p s) : l = generate { U | ∃ i, p i ∧ s i = U } :=
by rw [← h.is_basis.filter_eq_generate, h.filter_eq]
lemma generate_eq_generate_inter (s : set (set α)) :
generate s = generate (sInter '' { t | finite t ∧ t ⊆ s}) :=
by erw [(filter_basis.of_sets s).generate, ← (has_basis_generate s).filter_eq] ; refl
lemma of_sets_filter_eq_generate (s : set (set α)) : (filter_basis.of_sets s).filter = generate s :=
by rw [← (filter_basis.of_sets s).generate, generate_eq_generate_inter s] ; refl
lemma has_basis.to_has_basis' (hl : l.has_basis p s) (h : ∀ i, p i → ∃ i', p' i' ∧ s' i' ⊆ s i)
(h' : ∀ i', p' i' → s' i' ∈ l) : l.has_basis p' s' :=
begin
refine ⟨λ t, ⟨λ ht, _, λ ⟨i', hi', ht⟩, mem_sets_of_superset (h' i' hi') ht⟩⟩,
rcases hl.mem_iff.1 ht with ⟨i, hi, ht⟩,
rcases h i hi with ⟨i', hi', hs's⟩,
exact ⟨i', hi', subset.trans hs's ht⟩
end
lemma has_basis.to_has_basis (hl : l.has_basis p s) (h : ∀ i, p i → ∃ i', p' i' ∧ s' i' ⊆ s i)
(h' : ∀ i', p' i' → ∃ i, p i ∧ s i ⊆ s' i') : l.has_basis p' s' :=
hl.to_has_basis' h $ λ i' hi', let ⟨i, hi, hss'⟩ := h' i' hi' in hl.mem_iff.2 ⟨i, hi, hss'⟩
lemma has_basis.to_subset (hl : l.has_basis p s) {t : ι → set α} (h : ∀ i, p i → t i ⊆ s i)
(ht : ∀ i, p i → t i ∈ l) : l.has_basis p t :=
hl.to_has_basis' (λ i hi, ⟨i, hi, h i hi⟩) ht
lemma has_basis.eventually_iff (hl : l.has_basis p s) {q : α → Prop} :
(∀ᶠ x in l, q x) ↔ ∃ i, p i ∧ ∀ ⦃x⦄, x ∈ s i → q x :=
by simpa using hl.mem_iff
lemma has_basis.frequently_iff (hl : l.has_basis p s) {q : α → Prop} :
(∃ᶠ x in l, q x) ↔ ∀ i, p i → ∃ x ∈ s i, q x :=
by simp [filter.frequently, hl.eventually_iff]
lemma has_basis.exists_iff (hl : l.has_basis p s) {P : set α → Prop}
(mono : ∀ ⦃s t⦄, s ⊆ t → P t → P s) :
(∃ s ∈ l, P s) ↔ ∃ (i) (hi : p i), P (s i) :=
⟨λ ⟨s, hs, hP⟩, let ⟨i, hi, his⟩ := hl.mem_iff.1 hs in ⟨i, hi, mono his hP⟩,
λ ⟨i, hi, hP⟩, ⟨s i, hl.mem_of_mem hi, hP⟩⟩
lemma has_basis.forall_iff (hl : l.has_basis p s) {P : set α → Prop}
(mono : ∀ ⦃s t⦄, s ⊆ t → P s → P t) :
(∀ s ∈ l, P s) ↔ ∀ i, p i → P (s i) :=
⟨λ H i hi, H (s i) $ hl.mem_of_mem hi,
λ H s hs, let ⟨i, hi, his⟩ := hl.mem_iff.1 hs in mono his (H i hi)⟩
lemma has_basis.ne_bot_iff (hl : l.has_basis p s) :
ne_bot l ↔ (∀ {i}, p i → (s i).nonempty) :=
forall_sets_nonempty_iff_ne_bot.symm.trans $ hl.forall_iff $ λ _ _, nonempty.mono
lemma has_basis.eq_bot_iff (hl : l.has_basis p s) :
l = ⊥ ↔ ∃ i, p i ∧ s i = ∅ :=
not_iff_not.1 $ ne_bot_iff.symm.trans $ hl.ne_bot_iff.trans $
by simp only [not_exists, not_and, ← ne_empty_iff_nonempty]
lemma basis_sets (l : filter α) : l.has_basis (λ s : set α, s ∈ l) id :=
⟨λ t, exists_sets_subset_iff.symm⟩
lemma has_basis_self {l : filter α} {P : set α → Prop} :
has_basis l (λ s, s ∈ l ∧ P s) id ↔ ∀ t ∈ l, ∃ r ∈ l, P r ∧ r ⊆ t :=
begin
simp only [has_basis_iff, exists_prop, id, and_assoc],
exact forall_congr (λ s, ⟨λ h, h.1, λ h, ⟨h, λ ⟨t, hl, hP, hts⟩, mem_sets_of_superset hl hts⟩⟩)
end
/-- If `{s i | p i}` is a basis of a filter `l` and each `s i` includes `s j` such that
`p j ∧ q j`, then `{s j | p j ∧ q j}` is a basis of `l`. -/
lemma has_basis.restrict (h : l.has_basis p s) {q : ι → Prop}
(hq : ∀ i, p i → ∃ j, p j ∧ q j ∧ s j ⊆ s i) :
l.has_basis (λ i, p i ∧ q i) s :=
begin
refine ⟨λ t, ⟨λ ht, _, λ ⟨i, hpi, hti⟩, h.mem_iff.2 ⟨i, hpi.1, hti⟩⟩⟩,
rcases h.mem_iff.1 ht with ⟨i, hpi, hti⟩,
rcases hq i hpi with ⟨j, hpj, hqj, hji⟩,
exact ⟨j, ⟨hpj, hqj⟩, subset.trans hji hti⟩
end
/-- If `{s i | p i}` is a basis of a filter `l` and `V ∈ l`, then `{s i | p i ∧ s i ⊆ V}`
is a basis of `l`. -/
lemma has_basis.restrict_subset (h : l.has_basis p s) {V : set α} (hV : V ∈ l) :
l.has_basis (λ i, p i ∧ s i ⊆ V) s :=
h.restrict $ λ i hi, (h.mem_iff.1 (inter_mem_sets hV (h.mem_of_mem hi))).imp $
λ j hj, ⟨hj.fst, subset_inter_iff.1 hj.snd⟩
lemma has_basis.has_basis_self_subset {p : set α → Prop} (h : l.has_basis (λ s, s ∈ l ∧ p s) id)
{V : set α} (hV : V ∈ l) : l.has_basis (λ s, s ∈ l ∧ p s ∧ s ⊆ V) id :=
by simpa only [and_assoc] using h.restrict_subset hV
theorem has_basis.ge_iff (hl' : l'.has_basis p' s') : l ≤ l' ↔ ∀ i', p' i' → s' i' ∈ l :=
⟨λ h i' hi', h $ hl'.mem_of_mem hi',
λ h s hs, let ⟨i', hi', hs⟩ := hl'.mem_iff.1 hs in mem_sets_of_superset (h _ hi') hs⟩
theorem has_basis.le_iff (hl : l.has_basis p s) : l ≤ l' ↔ ∀ t ∈ l', ∃ i (hi : p i), s i ⊆ t :=
by simp only [le_def, hl.mem_iff]
theorem has_basis.le_basis_iff (hl : l.has_basis p s) (hl' : l'.has_basis p' s') :
l ≤ l' ↔ ∀ i', p' i' → ∃ i (hi : p i), s i ⊆ s' i' :=
by simp only [hl'.ge_iff, hl.mem_iff]
lemma has_basis.ext (hl : l.has_basis p s) (hl' : l'.has_basis p' s')
(h : ∀ i, p i → ∃ i', p' i' ∧ s' i' ⊆ s i)
(h' : ∀ i', p' i' → ∃ i, p i ∧ s i ⊆ s' i') : l = l' :=
begin
apply le_antisymm,
{ rw hl.le_basis_iff hl',
simpa using h' },
{ rw hl'.le_basis_iff hl,
simpa using h },
end
lemma has_basis.inf (hl : l.has_basis p s) (hl' : l'.has_basis p' s') :
(l ⊓ l').has_basis (λ i : ι × ι', p i.1 ∧ p' i.2) (λ i, s i.1 ∩ s' i.2) :=
⟨begin
intro t,
simp only [mem_inf_sets, exists_prop, hl.mem_iff, hl'.mem_iff],
split,
{ rintros ⟨t, ⟨i, hi, ht⟩, t', ⟨i', hi', ht'⟩, H⟩,
use [(i, i'), ⟨hi, hi'⟩, subset.trans (inter_subset_inter ht ht') H] },
{ rintros ⟨⟨i, i'⟩, ⟨hi, hi'⟩, H⟩,
use [s i, i, hi, subset.refl _, s' i', i', hi', subset.refl _, H] }
end⟩
lemma has_basis_principal (t : set α) : (𝓟 t).has_basis (λ i : unit, true) (λ i, t) :=
⟨λ U, by simp⟩
lemma has_basis.sup (hl : l.has_basis p s) (hl' : l'.has_basis p' s') :
(l ⊔ l').has_basis (λ i : ι × ι', p i.1 ∧ p' i.2) (λ i, s i.1 ∪ s' i.2) :=
⟨begin
intros t,
simp only [mem_sup_sets, hl.mem_iff, hl'.mem_iff, prod.exists, union_subset_iff, exists_prop,
and_assoc, exists_and_distrib_left],
simp only [← and_assoc, exists_and_distrib_right, and_comm]
end⟩
lemma has_basis.inf_principal (hl : l.has_basis p s) (s' : set α) :
(l ⊓ 𝓟 s').has_basis p (λ i, s i ∩ s') :=
⟨λ t, by simp only [mem_inf_principal, hl.mem_iff, subset_def, mem_set_of_eq,
mem_inter_iff, and_imp]⟩
lemma has_basis.inf_basis_ne_bot_iff (hl : l.has_basis p s) (hl' : l'.has_basis p' s') :
ne_bot (l ⊓ l') ↔ ∀ ⦃i⦄ (hi : p i) ⦃i'⦄ (hi' : p' i'), (s i ∩ s' i').nonempty :=
(hl.inf hl').ne_bot_iff.trans $ by simp [@forall_swap _ ι']
lemma has_basis.inf_ne_bot_iff (hl : l.has_basis p s) :
ne_bot (l ⊓ l') ↔ ∀ ⦃i⦄ (hi : p i) ⦃s'⦄ (hs' : s' ∈ l'), (s i ∩ s').nonempty :=
hl.inf_basis_ne_bot_iff l'.basis_sets
lemma has_basis.inf_principal_ne_bot_iff (hl : l.has_basis p s) {t : set α} :
ne_bot (l ⊓ 𝓟 t) ↔ ∀ ⦃i⦄ (hi : p i), (s i ∩ t).nonempty :=
(hl.inf_principal t).ne_bot_iff
lemma inf_ne_bot_iff :
ne_bot (l ⊓ l') ↔ ∀ ⦃s : set α⦄ (hs : s ∈ l) ⦃s'⦄ (hs' : s' ∈ l'), (s ∩ s').nonempty :=
l.basis_sets.inf_ne_bot_iff
lemma inf_principal_ne_bot_iff {s : set α} :
ne_bot (l ⊓ 𝓟 s) ↔ ∀ U ∈ l, (U ∩ s).nonempty :=
l.basis_sets.inf_principal_ne_bot_iff
lemma inf_eq_bot_iff {f g : filter α} :
f ⊓ g = ⊥ ↔ ∃ (U ∈ f) (V ∈ g), U ∩ V = ∅ :=
not_iff_not.1 $ ne_bot_iff.symm.trans $ inf_ne_bot_iff.trans $
by simp [← ne_empty_iff_nonempty]
protected lemma disjoint_iff {f g : filter α} :
disjoint f g ↔ ∃ (U ∈ f) (V ∈ g), U ∩ V = ∅ :=
disjoint_iff.trans inf_eq_bot_iff
lemma mem_iff_inf_principal_compl {f : filter α} {s : set α} :
s ∈ f ↔ f ⊓ 𝓟 sᶜ = ⊥ :=
begin
refine not_iff_not.1 ((inf_principal_ne_bot_iff.trans _).symm.trans ne_bot_iff),
exact ⟨λ h hs, by simpa [empty_not_nonempty] using h s hs,
λ hs t ht, inter_compl_nonempty_iff.2 $ λ hts, hs $ mem_sets_of_superset ht hts⟩,
end
lemma not_mem_iff_inf_principal_compl {f : filter α} {s : set α} :
s ∉ f ↔ ne_bot (f ⊓ 𝓟 sᶜ) :=
(not_congr mem_iff_inf_principal_compl).trans ne_bot_iff.symm
lemma mem_iff_disjoint_principal_compl {f : filter α} {s : set α} :
s ∈ f ↔ disjoint f (𝓟 sᶜ) :=
mem_iff_inf_principal_compl.trans disjoint_iff.symm
lemma le_iff_forall_disjoint_principal_compl {f g : filter α} :
f ≤ g ↔ ∀ V ∈ g, disjoint f (𝓟 Vᶜ) :=
forall_congr $ λ _, forall_congr $ λ _, mem_iff_disjoint_principal_compl
lemma le_iff_forall_inf_principal_compl {f g : filter α} :
f ≤ g ↔ ∀ V ∈ g, f ⊓ 𝓟 Vᶜ = ⊥ :=
forall_congr $ λ _, forall_congr $ λ _, mem_iff_inf_principal_compl
lemma inf_ne_bot_iff_frequently_left {f g : filter α} :
ne_bot (f ⊓ g) ↔ ∀ {p : α → Prop}, (∀ᶠ x in f, p x) → ∃ᶠ x in g, p x :=
by simpa only [inf_ne_bot_iff, frequently_iff, exists_prop, and_comm]
lemma inf_ne_bot_iff_frequently_right {f g : filter α} :
ne_bot (f ⊓ g) ↔ ∀ {p : α → Prop}, (∀ᶠ x in g, p x) → ∃ᶠ x in f, p x :=
by { rw inf_comm, exact inf_ne_bot_iff_frequently_left }
lemma has_basis.eq_binfi (h : l.has_basis p s) :
l = ⨅ i (_ : p i), 𝓟 (s i) :=
eq_binfi_of_mem_sets_iff_exists_mem $ λ t, by simp only [h.mem_iff, mem_principal_sets]
lemma has_basis.eq_infi (h : l.has_basis (λ _, true) s) :
l = ⨅ i, 𝓟 (s i) :=
by simpa only [infi_true] using h.eq_binfi
lemma has_basis_infi_principal {s : ι → set α} (h : directed (≥) s) [nonempty ι] :
(⨅ i, 𝓟 (s i)).has_basis (λ _, true) s :=
⟨begin
refine λ t, (mem_infi (h.mono_comp _ _) t).trans $
by simp only [exists_prop, true_and, mem_principal_sets],
exact λ _ _, principal_mono.2
end⟩
/-- If `s : ι → set α` is an indexed family of sets, then finite intersections of `s i` form a basis
of `⨅ i, 𝓟 (s i)`. -/
lemma has_basis_infi_principal_finite (s : ι → set α) :
(⨅ i, 𝓟 (s i)).has_basis (λ t : set ι, finite t) (λ t, ⋂ i ∈ t, s i) :=
begin
refine ⟨λ U, (mem_infi_finite _).trans _⟩,
simp only [infi_principal_finset, mem_Union, mem_principal_sets, exists_prop,
exists_finite_iff_finset, finset.set_bInter_coe]
end
lemma has_basis_binfi_principal {s : β → set α} {S : set β} (h : directed_on (s ⁻¹'o (≥)) S)
(ne : S.nonempty) :
(⨅ i ∈ S, 𝓟 (s i)).has_basis (λ i, i ∈ S) s :=
⟨begin
refine λ t, (mem_binfi _ ne).trans $ by simp only [mem_principal_sets],
rw [directed_on_iff_directed, ← directed_comp, (∘)] at h ⊢,
apply h.mono_comp _ _,
exact λ _ _, principal_mono.2
end⟩
lemma has_basis_binfi_principal'
(h : ∀ i, p i → ∀ j, p j → ∃ k (h : p k), s k ⊆ s i ∧ s k ⊆ s j) (ne : ∃ i, p i) :
(⨅ i (h : p i), 𝓟 (s i)).has_basis p s :=
filter.has_basis_binfi_principal h ne
lemma has_basis.map (f : α → β) (hl : l.has_basis p s) :
(l.map f).has_basis p (λ i, f '' (s i)) :=
⟨λ t, by simp only [mem_map, image_subset_iff, hl.mem_iff, preimage]⟩
lemma has_basis.comap (f : β → α) (hl : l.has_basis p s) :
(l.comap f).has_basis p (λ i, f ⁻¹' (s i)) :=
⟨begin
intro t,
simp only [mem_comap_sets, exists_prop, hl.mem_iff],
split,
{ rintros ⟨t', ⟨i, hi, ht'⟩, H⟩,
exact ⟨i, hi, subset.trans (preimage_mono ht') H⟩ },
{ rintros ⟨i, hi, H⟩,
exact ⟨s i, ⟨i, hi, subset.refl _⟩, H⟩ }
end⟩
lemma comap_has_basis (f : α → β) (l : filter β) :
has_basis (comap f l) (λ s : set β, s ∈ l) (λ s, f ⁻¹' s) :=
⟨λ t, mem_comap_sets⟩
lemma has_basis.prod_self (hl : l.has_basis p s) :
(l ×ᶠ l).has_basis p (λ i, (s i).prod (s i)) :=
⟨begin
intro t,
apply mem_prod_iff.trans,
split,
{ rintros ⟨t₁, ht₁, t₂, ht₂, H⟩,
rcases hl.mem_iff.1 (inter_mem_sets ht₁ ht₂) with ⟨i, hi, ht⟩,
exact ⟨i, hi, λ p ⟨hp₁, hp₂⟩, H ⟨(ht hp₁).1, (ht hp₂).2⟩⟩ },
{ rintros ⟨i, hi, H⟩,
exact ⟨s i, hl.mem_of_mem hi, s i, hl.mem_of_mem hi, H⟩ }
end⟩
lemma mem_prod_self_iff {s} : s ∈ l ×ᶠ l ↔ ∃ t ∈ l, set.prod t t ⊆ s :=
l.basis_sets.prod_self.mem_iff
lemma has_basis.sInter_sets (h : has_basis l p s) :
⋂₀ l.sets = ⋂ i ∈ set_of p, s i :=
begin
ext x,
suffices : (∀ t ∈ l, x ∈ t) ↔ ∀ i, p i → x ∈ s i,
by simpa only [mem_Inter, mem_set_of_eq, mem_sInter],
simp_rw h.mem_iff,
split,
{ intros h i hi,
exact h (s i) ⟨i, hi, subset.refl _⟩ },
{ rintros h _ ⟨i, hi, sub⟩,
exact sub (h i hi) },
end
variables [preorder ι] (l p s)
/-- `is_antimono_basis p s` means the image of `s` bounded by `p` is a filter basis
such that `s` is decreasing and `p` is increasing, ie `i ≤ j → p i → p j`. -/
structure is_antimono_basis extends is_basis p s : Prop :=
(decreasing : ∀ {i j}, p i → p j → i ≤ j → s j ⊆ s i)
(mono : monotone p)
/-- We say that a filter `l` has a antimono basis `s : ι → set α` bounded by `p : ι → Prop`,
if `t ∈ l` if and only if `t` includes `s i` for some `i` such that `p i`,
and `s` is decreasing and `p` is increasing, ie `i ≤ j → p i → p j`. -/
structure has_antimono_basis [preorder ι] (l : filter α) (p : ι → Prop) (s : ι → set α)
extends has_basis l p s : Prop :=
(decreasing : ∀ {i j}, p i → p j → i ≤ j → s j ⊆ s i)
(mono : monotone p)
end same_type
section two_types
variables {la : filter α} {pa : ι → Prop} {sa : ι → set α}
{lb : filter β} {pb : ι' → Prop} {sb : ι' → set β} {f : α → β}
lemma has_basis.tendsto_left_iff (hla : la.has_basis pa sa) :
tendsto f la lb ↔ ∀ t ∈ lb, ∃ i (hi : pa i), ∀ x ∈ sa i, f x ∈ t :=
by { simp only [tendsto, (hla.map f).le_iff, image_subset_iff], refl }
lemma has_basis.tendsto_right_iff (hlb : lb.has_basis pb sb) :
tendsto f la lb ↔ ∀ i (hi : pb i), ∀ᶠ x in la, f x ∈ sb i :=
by simp only [tendsto, hlb.ge_iff, mem_map, filter.eventually]
lemma has_basis.tendsto_iff (hla : la.has_basis pa sa) (hlb : lb.has_basis pb sb) :
tendsto f la lb ↔ ∀ ib (hib : pb ib), ∃ ia (hia : pa ia), ∀ x ∈ sa ia, f x ∈ sb ib :=
by simp [hlb.tendsto_right_iff, hla.eventually_iff]
lemma tendsto.basis_left (H : tendsto f la lb) (hla : la.has_basis pa sa) :
∀ t ∈ lb, ∃ i (hi : pa i), ∀ x ∈ sa i, f x ∈ t :=
hla.tendsto_left_iff.1 H
lemma tendsto.basis_right (H : tendsto f la lb) (hlb : lb.has_basis pb sb) :
∀ i (hi : pb i), ∀ᶠ x in la, f x ∈ sb i :=
hlb.tendsto_right_iff.1 H
lemma tendsto.basis_both (H : tendsto f la lb) (hla : la.has_basis pa sa)
(hlb : lb.has_basis pb sb) :
∀ ib (hib : pb ib), ∃ ia (hia : pa ia), ∀ x ∈ sa ia, f x ∈ sb ib :=
(hla.tendsto_iff hlb).1 H
lemma has_basis.prod (hla : la.has_basis pa sa) (hlb : lb.has_basis pb sb) :
(la ×ᶠ lb).has_basis (λ i : ι × ι', pa i.1 ∧ pb i.2) (λ i, (sa i.1).prod (sb i.2)) :=
(hla.comap prod.fst).inf (hlb.comap prod.snd)
lemma has_basis.prod' {la : filter α} {lb : filter β} {ι : Type*} {p : ι → Prop}
{sa : ι → set α} {sb : ι → set β}
(hla : la.has_basis p sa) (hlb : lb.has_basis p sb)
(h_dir : ∀ {i j}, p i → p j → ∃ k, p k ∧ sa k ⊆ sa i ∧ sb k ⊆ sb j) :
(la ×ᶠ lb).has_basis p (λ i, (sa i).prod (sb i)) :=
⟨begin
intros t,
rw mem_prod_iff,
split,
{ rintros ⟨u, u_in, v, v_in, huv⟩,
rcases hla.mem_iff.mp u_in with ⟨i, hi, si⟩,
rcases hlb.mem_iff.mp v_in with ⟨j, hj, sj⟩,
rcases h_dir hi hj with ⟨k, hk, ki, kj⟩,
use [k, hk],
calc
(sa k).prod (sb k) ⊆ (sa i).prod (sb j) : set.prod_mono ki kj
... ⊆ u.prod v : set.prod_mono si sj
... ⊆ t : huv, },
{ rintro ⟨i, hi, h⟩,
exact ⟨sa i, hla.mem_of_mem hi, sb i, hlb.mem_of_mem hi, h⟩ },
end⟩
end two_types
/-- `is_countably_generated f` means `f = generate s` for some countable `s`. -/
def is_countably_generated (f : filter α) : Prop :=
∃ s : set (set α), countable s ∧ f = generate s
/-- `is_countable_basis p s` means the image of `s` bounded by `p` is a countable filter basis. -/
structure is_countable_basis (p : ι → Prop) (s : ι → set α) extends is_basis p s : Prop :=
(countable : countable $ set_of p)
/-- We say that a filter `l` has a countable basis `s : ι → set α` bounded by `p : ι → Prop`,
if `t ∈ l` if and only if `t` includes `s i` for some `i` such that `p i`, and the set
defined by `p` is countable. -/
structure has_countable_basis (l : filter α) (p : ι → Prop) (s : ι → set α)
extends has_basis l p s : Prop :=
(countable : countable $ set_of p)
/-- A countable filter basis `B` on a type `α` is a nonempty countable collection of sets of `α`
such that the intersection of two elements of this collection contains some element
of the collection. -/
structure countable_filter_basis (α : Type*) extends filter_basis α :=
(countable : countable sets)
-- For illustration purposes, the countable filter basis defining (at_top : filter ℕ)
instance nat.inhabited_countable_filter_basis : inhabited (countable_filter_basis ℕ) :=
⟨{ countable := countable_range (λ n, Ici n),
..(default $ filter_basis ℕ),}⟩
lemma antimono_seq_of_seq (s : ℕ → set α) :
∃ t : ℕ → set α, (∀ i j, i ≤ j → t j ⊆ t i) ∧ (⨅ i, 𝓟 $ s i) = ⨅ i, 𝓟 (t i) :=
begin
use λ n, ⋂ m ≤ n, s m, split,
{ exact λ i j hij, bInter_mono' (Iic_subset_Iic.2 hij) (λ n hn, subset.refl _) },
apply le_antisymm; rw le_infi_iff; intro i,
{ rw le_principal_iff, refine (bInter_mem_sets (finite_le_nat _)).2 (λ j hji, _),
rw ← le_principal_iff, apply infi_le_of_le j _, apply le_refl _ },
{ apply infi_le_of_le i _, rw principal_mono, intro a, simp, intro h, apply h, refl },
end
lemma countable_binfi_eq_infi_seq [complete_lattice α] {B : set ι} (Bcbl : countable B)
(Bne : B.nonempty) (f : ι → α) :
∃ (x : ℕ → ι), (⨅ t ∈ B, f t) = ⨅ i, f (x i) :=
begin
rw countable_iff_exists_surjective_to_subtype Bne at Bcbl,
rcases Bcbl with ⟨g, gsurj⟩,
rw infi_subtype',
use (λ n, g n), apply le_antisymm; rw le_infi_iff,
{ intro i, apply infi_le_of_le (g i) _, apply le_refl _ },
{ intros a, rcases gsurj a with ⟨i, rfl⟩, apply infi_le }
end
lemma countable_binfi_eq_infi_seq' [complete_lattice α] {B : set ι} (Bcbl : countable B) (f : ι → α)
{i₀ : ι} (h : f i₀ = ⊤) :
∃ (x : ℕ → ι), (⨅ t ∈ B, f t) = ⨅ i, f (x i) :=
begin
cases B.eq_empty_or_nonempty with hB Bnonempty,
{ rw [hB, infi_emptyset],
use λ n, i₀,
simp [h] },
{ exact countable_binfi_eq_infi_seq Bcbl Bnonempty f }
end
lemma countable_binfi_principal_eq_seq_infi {B : set (set α)} (Bcbl : countable B) :
∃ (x : ℕ → set α), (⨅ t ∈ B, 𝓟 t) = ⨅ i, 𝓟 (x i) :=
countable_binfi_eq_infi_seq' Bcbl 𝓟 principal_univ
namespace is_countably_generated
/-- A set generating a countably generated filter. -/
def generating_set {f : filter α} (h : is_countably_generated f) :=
classical.some h
lemma countable_generating_set {f : filter α} (h : is_countably_generated f) :
countable h.generating_set :=
(classical.some_spec h).1
lemma eq_generate {f : filter α} (h : is_countably_generated f) :
f = generate h.generating_set :=
(classical.some_spec h).2
/-- A countable filter basis for a countably generated filter. -/
def countable_filter_basis {l : filter α} (h : is_countably_generated l) :
countable_filter_basis α :=
{ countable := (countable_set_of_finite_subset h.countable_generating_set).image _,
..filter_basis.of_sets (h.generating_set) }
lemma filter_basis_filter {l : filter α} (h : is_countably_generated l) :
h.countable_filter_basis.to_filter_basis.filter = l :=
begin
conv_rhs { rw h.eq_generate },
apply of_sets_filter_eq_generate,
end
lemma has_countable_basis {l : filter α} (h : is_countably_generated l) :
l.has_countable_basis (λ t, finite t ∧ t ⊆ h.generating_set) (λ t, ⋂₀ t) :=
⟨by convert has_basis_generate _ ; exact h.eq_generate,
countable_set_of_finite_subset h.countable_generating_set⟩
lemma exists_countable_infi_principal {f : filter α} (h : f.is_countably_generated) :
∃ s : set (set α), countable s ∧ f = ⨅ t ∈ s, 𝓟 t :=
begin
let B := h.countable_filter_basis,
use [B.sets, B.countable],
rw ← h.filter_basis_filter,
rw B.to_filter_basis.eq_infi_principal,
rw infi_subtype''
end
lemma exists_seq {f : filter α} (cblb : f.is_countably_generated) :
∃ x : ℕ → set α, f = ⨅ i, 𝓟 (x i) :=
begin
rcases cblb.exists_countable_infi_principal with ⟨B, Bcbl, rfl⟩,
exact countable_binfi_principal_eq_seq_infi Bcbl,
end
/-- If `f` is countably generated and `f.has_basis p s`, then `f` admits a decreasing basis
enumerated by natural numbers such that all sets have the form `s i`. More precisely, there is a
sequence `i n` such that `p (i n)` for all `n` and `s (i n)` is a decreasing sequence of sets which
forms a basis of `f`-/
lemma exists_antimono_subbasis {f : filter α} (cblb : f.is_countably_generated)
{p : ι → Prop} {s : ι → set α} (hs : f.has_basis p s) :
∃ x : ℕ → ι, (∀ i, p (x i)) ∧ f.has_antimono_basis (λ _, true) (λ i, s (x i)) :=
begin
rcases cblb.exists_seq with ⟨x', hx'⟩,
have : ∀ i, x' i ∈ f := λ i, hx'.symm ▸ (infi_le (λ i, 𝓟 (x' i)) i) (mem_principal_self _),
let x : ℕ → {i : ι // p i} := λ n, nat.rec_on n (hs.index _ $ this 0)
(λ n xn, (hs.index _ $ inter_mem_sets (this $ n + 1) (hs.mem_of_mem xn.coe_prop))),
have x_mono : ∀ n : ℕ, s (x n.succ) ⊆ s (x n) :=
λ n, subset.trans (hs.set_index_subset _) (inter_subset_right _ _),
replace x_mono : ∀ ⦃i j⦄, i ≤ j → s (x j) ≤ s (x i),
{ refine @monotone_of_monotone_nat (order_dual $ set α) _ _ _,
exact x_mono },
have x_subset : ∀ i, s (x i) ⊆ x' i,
{ rintro (_|i),
exacts [hs.set_index_subset _, subset.trans (hs.set_index_subset _) (inter_subset_left _ _)] },
refine ⟨λ i, x i, λ i, (x i).2, _⟩,
have : (⨅ i, 𝓟 (s (x i))).has_antimono_basis (λ _, true) (λ i, s (x i)) :=
⟨has_basis_infi_principal (directed_of_sup x_mono), λ i j _ _ hij, x_mono hij, monotone_const⟩,
convert this,
exact le_antisymm (le_infi $ λ i, le_principal_iff.2 $ by cases i; apply hs.set_index_mem)
(hx'.symm ▸ le_infi (λ i, le_principal_iff.2 $
this.to_has_basis.mem_iff.2 ⟨i, trivial, x_subset i⟩))
end
/-- A countably generated filter admits a basis formed by a monotonically decreasing sequence of
sets. -/
lemma exists_antimono_basis {f : filter α} (cblb : f.is_countably_generated) :
∃ x : ℕ → set α, f.has_antimono_basis (λ _, true) x :=
let ⟨x, hxf, hx⟩ := cblb.exists_antimono_subbasis f.basis_sets in ⟨x, hx⟩
end is_countably_generated
lemma has_countable_basis.is_countably_generated {f : filter α} {p : ι → Prop} {s : ι → set α}
(h : f.has_countable_basis p s) :
f.is_countably_generated :=
⟨{t | ∃ i, p i ∧ s i = t}, h.countable.image s, h.to_has_basis.eq_generate⟩
lemma is_countably_generated_seq (x : ℕ → set α) : is_countably_generated (⨅ i, 𝓟 $ x i) :=
begin
rcases antimono_seq_of_seq x with ⟨y, am, h⟩,
rw h,
use [range y, countable_range _],
rw (has_basis_infi_principal _).eq_generate,
{ simp [range] },
{ exact directed_of_sup am },
{ use 0 },
end
lemma is_countably_generated_of_seq {f : filter α} (h : ∃ x : ℕ → set α, f = ⨅ i, 𝓟 $ x i) :
f.is_countably_generated :=
let ⟨x, h⟩ := h in by rw h ; apply is_countably_generated_seq
lemma is_countably_generated_binfi_principal {B : set $ set α} (h : countable B) :
is_countably_generated (⨅ (s ∈ B), 𝓟 s) :=
is_countably_generated_of_seq (countable_binfi_principal_eq_seq_infi h)
lemma is_countably_generated_iff_exists_antimono_basis {f : filter α} :
is_countably_generated f ↔ ∃ x : ℕ → set α, f.has_antimono_basis (λ _, true) x :=
begin
split,
{ exact λ h, h.exists_antimono_basis },
{ rintros ⟨x, h⟩,
rw h.to_has_basis.eq_infi,
exact is_countably_generated_seq x },
end
lemma is_countably_generated_principal (s : set α) : is_countably_generated (𝓟 s) :=
begin
rw show 𝓟 s = ⨅ i : ℕ, 𝓟 s, by simp,
apply is_countably_generated_seq
end
namespace is_countably_generated
lemma inf {f g : filter α} (hf : is_countably_generated f) (hg : is_countably_generated g) :
is_countably_generated (f ⊓ g) :=
begin
rw is_countably_generated_iff_exists_antimono_basis at hf hg,
rcases hf with ⟨s, hs⟩,
rcases hg with ⟨t, ht⟩,
exact has_countable_basis.is_countably_generated
⟨hs.to_has_basis.inf ht.to_has_basis, set.countable_encodable _⟩
end
lemma inf_principal {f : filter α} (h : is_countably_generated f) (s : set α) :
is_countably_generated (f ⊓ 𝓟 s) :=
h.inf (filter.is_countably_generated_principal s)
lemma exists_antimono_seq' {f : filter α} (cblb : f.is_countably_generated) :
∃ x : ℕ → set α, (∀ i j, i ≤ j → x j ⊆ x i) ∧ ∀ {s}, (s ∈ f ↔ ∃ i, x i ⊆ s) :=
let ⟨x, hx⟩ := is_countably_generated_iff_exists_antimono_basis.mp cblb in
⟨x, λ i j, hx.decreasing trivial trivial, λ s, by simp [hx.to_has_basis.mem_iff]⟩
protected lemma comap {l : filter β} (h : l.is_countably_generated) (f : α → β) :
(comap f l).is_countably_generated :=
let ⟨x, hx_mono⟩ := h.exists_antimono_basis in
is_countably_generated_of_seq ⟨_, (hx_mono.to_has_basis.comap _).eq_infi⟩
end is_countably_generated
end filter
|
1465636578eaba1a0d9bedc33a54c0b268ce19a6 | d1a52c3f208fa42c41df8278c3d280f075eb020c | /stage0/src/Lean/Meta/GeneralizeVars.lean | 4ee1322c6cd2ac69a912928622a1cfcd2abe7c3c | [
"Apache-2.0",
"LLVM-exception",
"NCSA",
"LGPL-3.0-only",
"LicenseRef-scancode-inner-net-2.0",
"BSD-3-Clause",
"LGPL-2.0-or-later",
"Spencer-94",
"LGPL-2.1-or-later",
"HPND",
"LicenseRef-scancode-pcre",
"ISC",
"LGPL-2.1-only",
"LicenseRef-scancode-other-permissive",
"SunPro",
"CMU-Mach"... | permissive | cipher1024/lean4 | 6e1f98bb58e7a92b28f5364eb38a14c8d0aae393 | 69114d3b50806264ef35b57394391c3e738a9822 | refs/heads/master | 1,642,227,983,603 | 1,642,011,696,000 | 1,642,011,696,000 | 228,607,691 | 0 | 0 | Apache-2.0 | 1,576,584,269,000 | 1,576,584,268,000 | null | UTF-8 | Lean | false | false | 2,748 | lean | /-
Copyright (c) 2021 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Leonardo de Moura
-/
import Lean.Meta.Basic
import Lean.Util.CollectFVars
namespace Lean.Meta
/--
Add to `forbidden` all a set of `FVarId`s containing `targets` and all variables they depend on.
-/
partial def mkGeneralizationForbiddenSet (targets : Array Expr) (forbidden : FVarIdSet := {}) : MetaM FVarIdSet := do
let mut s := { fvarSet := forbidden }
let mut todo := #[]
for target in targets do
if target.isFVar then
todo := todo.push target.fvarId!
else
s := collectFVars s (← instantiateMVars (← inferType target))
loop todo.toList s.fvarSet
where
visit (fvarId : FVarId) (todo : List FVarId) (s : FVarIdSet) : MetaM (List FVarId × FVarIdSet) := do
let localDecl ← getLocalDecl fvarId
let mut s' := collectFVars {} (← instantiateMVars localDecl.type)
if let some val := localDecl.value? then
s' := collectFVars s' (← instantiateMVars val)
let mut todo := todo
let mut s := s
for fvarId in s'.fvarSet do
unless s.contains fvarId do
todo := fvarId :: todo
s := s.insert fvarId
return (todo, s)
loop (todo : List FVarId) (s : FVarIdSet) : MetaM FVarIdSet := do
match todo with
| [] => return s
| fvarId::todo =>
if s.contains fvarId then
loop todo s
else
let (todo, s) ← visit fvarId todo <| s.insert fvarId
loop todo s
/--
Collect variables to be generalized.
It uses the following heuristic
- Collect forward dependencies that are not in the forbidden set, and depend on some variable in `targets`.
- We use `mkForbiddenSet` to compute `forbidden`.
Remark: we *not* collect instance implicit arguments nor auxiliary declarations for compiling
recursive declarations.
-/
def getFVarSetToGeneralize (targets : Array Expr) (forbidden : FVarIdSet) : MetaM FVarIdSet := do
let mut s : FVarIdSet := targets.foldl (init := {}) fun s target => if target.isFVar then s.insert target.fvarId! else s
let mut r : FVarIdSet := {}
for localDecl in (← getLCtx) do
unless forbidden.contains localDecl.fvarId do
unless localDecl.isAuxDecl || localDecl.binderInfo.isInstImplicit do
if (← getMCtx).findLocalDeclDependsOn localDecl fun fvarId => s.contains fvarId then
r := r.insert localDecl.fvarId
s := s.insert localDecl.fvarId
return r
def getFVarsToGeneralize (targets : Array Expr) (forbidden : FVarIdSet := {}) : MetaM (Array FVarId) := do
let forbidden ← mkGeneralizationForbiddenSet targets forbidden
let s ← getFVarSetToGeneralize targets forbidden
sortFVarIds s.toArray
end Lean.Meta
|
f63a270d56a1044466062a27b7748ca2dae2a9d6 | cf39355caa609c0f33405126beee2739aa3cb77e | /tests/lean/extra/616b.hlean | 15cb89434be185461743518a0fc946b33910ad94 | [
"Apache-2.0"
] | permissive | leanprover-community/lean | 12b87f69d92e614daea8bcc9d4de9a9ace089d0e | cce7990ea86a78bdb383e38ed7f9b5ba93c60ce0 | refs/heads/master | 1,687,508,156,644 | 1,684,951,104,000 | 1,684,951,104,000 | 169,960,991 | 457 | 107 | Apache-2.0 | 1,686,744,372,000 | 1,549,790,268,000 | C++ | UTF-8 | Lean | false | false | 249 | hlean | import .f616a
open eq
definition my_elim {A P : Type*} {R : A → A → Type*} (Pc : A → P)
(Pp : Π⦃a a' : A⦄ (H : R a a'), Pc a = Pc a') (x : quotient R) : P :=
begin
induction x,
exact (Pc a),
refine (pathover_of_eq (Pp H))
end
|
4660162df34a48b00bead920ad30fa76c2af7794 | 4727251e0cd73359b15b664c3170e5d754078599 | /src/group_theory/index.lean | 79b83b7e5edc44938243d32e16299aed9dcddf4c | [
"Apache-2.0"
] | permissive | Vierkantor/mathlib | 0ea59ac32a3a43c93c44d70f441c4ee810ccceca | 83bc3b9ce9b13910b57bda6b56222495ebd31c2f | refs/heads/master | 1,658,323,012,449 | 1,652,256,003,000 | 1,652,256,003,000 | 209,296,341 | 0 | 1 | Apache-2.0 | 1,568,807,655,000 | 1,568,807,655,000 | null | UTF-8 | Lean | false | false | 11,214 | lean | /-
Copyright (c) 2021 Thomas Browning. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Thomas Browning
-/
import group_theory.quotient_group
import set_theory.cardinal.finite
/-!
# Index of a Subgroup
In this file we define the index of a subgroup, and prove several divisibility properties.
Several theorems proved in this file are known as Lagrange's theorem.
## Main definitions
- `H.index` : the index of `H : subgroup G` as a natural number,
and returns 0 if the index is infinite.
- `H.relindex K` : the relative index of `H : subgroup G` in `K : subgroup G` as a natural number,
and returns 0 if the relative index is infinite.
# Main results
- `card_mul_index` : `nat.card H * H.index = nat.card G`
- `index_mul_card` : `H.index * fintype.card H = fintype.card G`
- `index_dvd_card` : `H.index ∣ fintype.card G`
- `index_eq_mul_of_le` : If `H ≤ K`, then `H.index = K.index * (H.subgroup_of K).index`
- `index_dvd_of_le` : If `H ≤ K`, then `K.index ∣ H.index`
- `relindex_mul_relindex` : `relindex` is multiplicative in towers
-/
namespace subgroup
open_locale cardinal
variables {G : Type*} [group G] (H K L : subgroup G)
/-- The index of a subgroup as a natural number, and returns 0 if the index is infinite. -/
@[to_additive "The index of a subgroup as a natural number,
and returns 0 if the index is infinite."]
noncomputable def index : ℕ :=
nat.card (G ⧸ H)
/-- The relative index of a subgroup as a natural number,
and returns 0 if the relative index is infinite. -/
@[to_additive "The relative index of a subgroup as a natural number,
and returns 0 if the relative index is infinite."]
noncomputable def relindex : ℕ :=
(H.subgroup_of K).index
@[to_additive] lemma index_comap_of_surjective {G' : Type*} [group G'] {f : G' →* G}
(hf : function.surjective f) : (H.comap f).index = H.index :=
begin
letI := quotient_group.left_rel H,
letI := quotient_group.left_rel (H.comap f),
have key : ∀ x y : G', setoid.r x y ↔ setoid.r (f x) (f y) :=
λ x y, iff_of_eq (congr_arg (∈ H) (by rw [f.map_mul, f.map_inv])),
refine cardinal.to_nat_congr (equiv.of_bijective (quotient.map' f (λ x y, (key x y).mp)) ⟨_, _⟩),
{ simp_rw [←quotient.eq'] at key,
refine quotient.ind' (λ x, _),
refine quotient.ind' (λ y, _),
exact (key x y).mpr },
{ refine quotient.ind' (λ x, _),
obtain ⟨y, hy⟩ := hf x,
exact ⟨y, (quotient.map'_mk' f _ y).trans (congr_arg quotient.mk' hy)⟩ },
end
@[to_additive] lemma index_comap {G' : Type*} [group G'] (f : G' →* G) :
(H.comap f).index = H.relindex f.range :=
eq.trans (congr_arg index (by refl))
((H.subgroup_of f.range).index_comap_of_surjective f.range_restrict_surjective)
variables {H K L}
@[to_additive relindex_mul_index] lemma relindex_mul_index (h : H ≤ K) :
H.relindex K * K.index = H.index :=
((mul_comm _ _).trans (cardinal.to_nat_mul _ _).symm).trans
(congr_arg cardinal.to_nat (equiv.cardinal_eq (quotient_equiv_prod_of_le h))).symm
@[to_additive] lemma index_dvd_of_le (h : H ≤ K) : K.index ∣ H.index :=
dvd_of_mul_left_eq (H.relindex K) (relindex_mul_index h)
@[to_additive] lemma relindex_subgroup_of (hKL : K ≤ L) :
(H.subgroup_of L).relindex (K.subgroup_of L) = H.relindex K :=
((index_comap (H.subgroup_of L) (inclusion hKL)).trans (congr_arg _ (inclusion_range hKL))).symm
variables (H K L)
@[to_additive relindex_mul_relindex] lemma relindex_mul_relindex (hHK : H ≤ K) (hKL : K ≤ L) :
H.relindex K * K.relindex L = H.relindex L :=
begin
rw [←relindex_subgroup_of hKL],
exact relindex_mul_index (λ x hx, hHK hx),
end
@[to_additive] lemma inf_relindex_right : (H ⊓ K).relindex K = H.relindex K :=
begin
rw [←subgroup_of_map_subtype, relindex, relindex, subgroup_of, comap_map_eq_self_of_injective],
exact subtype.coe_injective,
end
@[to_additive] lemma inf_relindex_left : (H ⊓ K).relindex H = K.relindex H :=
by rw [inf_comm, inf_relindex_right]
@[to_additive relindex_inf_mul_relindex]
lemma relindex_inf_mul_relindex : H.relindex (K ⊓ L) * K.relindex L = (H ⊓ K).relindex L :=
by rw [←inf_relindex_right H (K ⊓ L), ←inf_relindex_right K L, ←inf_relindex_right (H ⊓ K) L,
inf_assoc, relindex_mul_relindex (H ⊓ (K ⊓ L)) (K ⊓ L) L inf_le_right inf_le_right]
@[to_additive]
lemma inf_relindex_eq_relindex_sup [K.normal] : (H ⊓ K).relindex H = K.relindex (H ⊔ K) :=
cardinal.to_nat_congr (quotient_group.quotient_inf_equiv_prod_normal_quotient H K).to_equiv
@[to_additive] lemma relindex_eq_relindex_sup [K.normal] : K.relindex H = K.relindex (H ⊔ K) :=
by rw [←inf_relindex_left, inf_relindex_eq_relindex_sup]
variables {H K}
@[to_additive] lemma relindex_dvd_of_le_left (hHK : H ≤ K) : K.relindex L ∣ H.relindex L :=
begin
apply dvd_of_mul_left_eq ((H ⊓ L).relindex (K ⊓ L)),
rw [←inf_relindex_right H L, ←inf_relindex_right K L],
exact relindex_mul_relindex (H ⊓ L) (K ⊓ L) L (inf_le_inf_right L hHK) inf_le_right,
end
variables (H K)
@[simp, to_additive] lemma index_top : (⊤ : subgroup G).index = 1 :=
cardinal.to_nat_eq_one_iff_unique.mpr ⟨quotient_group.subsingleton_quotient_top, ⟨1⟩⟩
@[simp, to_additive] lemma index_bot : (⊥ : subgroup G).index = nat.card G :=
cardinal.to_nat_congr (quotient_group.quotient_bot.to_equiv)
@[to_additive] lemma index_bot_eq_card [fintype G] : (⊥ : subgroup G).index = fintype.card G :=
index_bot.trans nat.card_eq_fintype_card
@[simp, to_additive] lemma relindex_top_left : (⊤ : subgroup G).relindex H = 1 :=
index_top
@[simp, to_additive] lemma relindex_top_right : H.relindex ⊤ = H.index :=
by rw [←relindex_mul_index (show H ≤ ⊤, from le_top), index_top, mul_one]
@[simp, to_additive] lemma relindex_bot_left : (⊥ : subgroup G).relindex H = nat.card H :=
by rw [relindex, bot_subgroup_of, index_bot]
@[to_additive] lemma relindex_bot_left_eq_card [fintype H] :
(⊥ : subgroup G).relindex H = fintype.card H :=
H.relindex_bot_left.trans nat.card_eq_fintype_card
@[simp, to_additive] lemma relindex_bot_right : H.relindex ⊥ = 1 :=
by rw [relindex, subgroup_of_bot_eq_top, index_top]
@[simp, to_additive] lemma relindex_self : H.relindex H = 1 :=
by rw [relindex, subgroup_of_self, index_top]
@[simp, to_additive card_mul_index]
lemma card_mul_index : nat.card H * H.index = nat.card G :=
by { rw [←relindex_bot_left, ←index_bot], exact relindex_mul_index bot_le }
@[to_additive] lemma index_map {G' : Type*} [group G'] (f : G →* G') :
(H.map f).index = (H ⊔ f.ker).index * f.range.index :=
by rw [←comap_map_eq, index_comap, relindex_mul_index (H.map_le_range f)]
@[to_additive] lemma index_map_dvd {G' : Type*} [group G'] {f : G →* G'}
(hf : function.surjective f) : (H.map f).index ∣ H.index :=
begin
rw [index_map, f.range_top_of_surjective hf, index_top, mul_one],
exact index_dvd_of_le le_sup_left,
end
@[to_additive] lemma dvd_index_map {G' : Type*} [group G'] {f : G →* G'}
(hf : f.ker ≤ H) : H.index ∣ (H.map f).index :=
begin
rw [index_map, sup_of_le_left hf],
apply dvd_mul_right,
end
@[to_additive] lemma index_map_eq {G' : Type*} [group G'] {f : G →* G'}
(hf1 : function.surjective f) (hf2 : f.ker ≤ H) : (H.map f).index = H.index :=
nat.dvd_antisymm (H.index_map_dvd hf1) (H.dvd_index_map hf2)
@[to_additive] lemma index_eq_card [fintype (G ⧸ H)] :
H.index = fintype.card (G ⧸ H) :=
nat.card_eq_fintype_card
@[to_additive index_mul_card] lemma index_mul_card [fintype G] [hH : fintype H] :
H.index * fintype.card H = fintype.card G :=
by rw [←relindex_bot_left_eq_card, ←index_bot_eq_card, mul_comm]; exact relindex_mul_index bot_le
@[to_additive] lemma index_dvd_card [fintype G] : H.index ∣ fintype.card G :=
begin
classical,
exact ⟨fintype.card H, H.index_mul_card.symm⟩,
end
variables {H K L}
@[to_additive]
lemma relindex_eq_zero_of_le_left (hHK : H ≤ K) (hKL : K.relindex L = 0) : H.relindex L = 0 :=
eq_zero_of_zero_dvd (hKL ▸ (relindex_dvd_of_le_left L hHK))
@[to_additive]
lemma relindex_eq_zero_of_le_right (hKL : K ≤ L) (hHK : H.relindex K = 0) : H.relindex L = 0 :=
cardinal.to_nat_apply_of_omega_le (le_trans (le_of_not_lt (λ h, cardinal.mk_ne_zero _
((cardinal.cast_to_nat_of_lt_omega h).symm.trans (cardinal.nat_cast_inj.mpr hHK))))
(quotient_subgroup_of_embedding_of_le H hKL).cardinal_le)
@[to_additive] lemma relindex_le_of_le_left (hHK : H ≤ K) (hHL : H.relindex L ≠ 0) :
K.relindex L ≤ H.relindex L :=
nat.le_of_dvd (nat.pos_of_ne_zero hHL) (relindex_dvd_of_le_left L hHK)
@[to_additive] lemma relindex_le_of_le_right (hKL : K ≤ L) (hHL : H.relindex L ≠ 0) :
H.relindex K ≤ H.relindex L :=
cardinal.to_nat_le_of_le_of_lt_omega (lt_of_not_ge (mt cardinal.to_nat_apply_of_omega_le hHL))
(cardinal.mk_le_of_injective (quotient_subgroup_of_embedding_of_le H hKL).2)
@[to_additive] lemma relindex_ne_zero_trans (hHK : H.relindex K ≠ 0) (hKL : K.relindex L ≠ 0) :
H.relindex L ≠ 0 :=
λ h, mul_ne_zero (mt (relindex_eq_zero_of_le_right (show K ⊓ L ≤ K, from inf_le_left)) hHK) hKL
((relindex_inf_mul_relindex H K L).trans (relindex_eq_zero_of_le_left inf_le_left h))
@[to_additive] lemma relindex_inf_ne_zero (hH : H.relindex L ≠ 0) (hK : K.relindex L ≠ 0) :
(H ⊓ K).relindex L ≠ 0 :=
begin
replace hH : H.relindex (K ⊓ L) ≠ 0 := mt (relindex_eq_zero_of_le_right inf_le_right) hH,
rw ← inf_relindex_right at hH hK ⊢,
rw inf_assoc,
exact relindex_ne_zero_trans hH hK,
end
@[to_additive] lemma index_inf_ne_zero (hH : H.index ≠ 0) (hK : K.index ≠ 0) : (H ⊓ K).index ≠ 0 :=
begin
rw ← relindex_top_right at hH hK ⊢,
exact relindex_inf_ne_zero hH hK,
end
@[to_additive] lemma relindex_inf_le : (H ⊓ K).relindex L ≤ H.relindex L * K.relindex L :=
begin
by_cases h : H.relindex L = 0,
{ exact (le_of_eq (relindex_eq_zero_of_le_left (by exact inf_le_left) h)).trans (zero_le _) },
rw [←inf_relindex_right, inf_assoc, ←relindex_mul_relindex _ _ L inf_le_right inf_le_right,
inf_relindex_right, inf_relindex_right],
exact mul_le_mul_right' (relindex_le_of_le_right inf_le_right h) (K.relindex L),
end
@[to_additive] lemma index_inf_le : (H ⊓ K).index ≤ H.index * K.index :=
by simp_rw [←relindex_top_right, relindex_inf_le]
@[simp, to_additive index_eq_one] lemma index_eq_one : H.index = 1 ↔ H = ⊤ :=
⟨λ h, quotient_group.subgroup_eq_top_of_subsingleton H (cardinal.to_nat_eq_one_iff_unique.mp h).1,
λ h, (congr_arg index h).trans index_top⟩
@[to_additive] lemma index_ne_zero_of_fintype [hH : fintype (G ⧸ H)] : H.index ≠ 0 :=
by { rw index_eq_card, exact fintype.card_ne_zero }
/-- Finite index implies finite quotient. -/
@[to_additive "Finite index implies finite quotient."]
noncomputable def fintype_of_index_ne_zero (hH : H.index ≠ 0) : fintype (G ⧸ H) :=
(cardinal.lt_omega_iff_fintype.mp (lt_of_not_ge (mt cardinal.to_nat_apply_of_omega_le hH))).some
@[to_additive one_lt_index_of_ne_top]
lemma one_lt_index_of_ne_top [fintype (G ⧸ H)] (hH : H ≠ ⊤) : 1 < H.index :=
nat.one_lt_iff_ne_zero_and_ne_one.mpr ⟨index_ne_zero_of_fintype, mt index_eq_one.mp hH⟩
end subgroup
|
b4ec897b5eb4324e3741e31942db711e08ca0ab1 | 9dd3f3912f7321eb58ee9aa8f21778ad6221f87c | /tests/lean/char_lits.lean | 110961ef5f20eb1eebefeaa3e3f9bee64400d391 | [
"Apache-2.0"
] | permissive | bre7k30/lean | de893411bcfa7b3c5572e61b9e1c52951b310aa4 | 5a924699d076dab1bd5af23a8f910b433e598d7a | refs/heads/master | 1,610,900,145,817 | 1,488,006,845,000 | 1,488,006,845,000 | null | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 199 | lean | import system.io
check #"a"
vm_eval #"a"
vm_eval #"\n"
vm_eval #"\\"
vm_eval put_str (list.cons #"\\" "aaa")
vm_eval put_str [#"\n"]
vm_eval put_str [#"\n"]
vm_eval put_str (list.cons #"\'" "aaa")
|
e9d66f1becfc811b6185596e8f4e7a4cb908c33c | 07c6143268cfb72beccd1cc35735d424ebcb187b | /test/library_search/basic.lean | 1a8320069cd66ba02c9f078dc11f730fe22bbec7 | [
"Apache-2.0"
] | permissive | khoek/mathlib | bc49a842910af13a3c372748310e86467d1dc766 | aa55f8b50354b3e11ba64792dcb06cccb2d8ee28 | refs/heads/master | 1,588,232,063,837 | 1,587,304,803,000 | 1,587,304,803,000 | 176,688,517 | 0 | 0 | Apache-2.0 | 1,553,070,585,000 | 1,553,070,585,000 | null | UTF-8 | Lean | false | false | 2,871 | lean | /-
Copyright (c) 2018 Scott Morrison. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Scott Morrison
-/
import data.nat.basic
/- Turn off trace messages so they don't pollute the test build: -/
set_option trace.silence_library_search true
/- For debugging purposes, we can display the list of lemmas: -/
-- set_option trace.suggest true
namespace test.library_search
-- Check that `library_search` fails if there are no goals.
example : true :=
begin
trivial,
success_if_fail { library_search },
end
-- Verify that `library_search` solves goals via `solve_by_elim` when the library isn't
-- even needed.
example (P : Prop) (p : P) : P :=
by library_search
example (P : Prop) (p : P) (np : ¬P) : false :=
by library_search
example (X : Type) (P : Prop) (x : X) (h : Π x : X, x = x → P) : P :=
by library_search
def lt_one (n : ℕ) := n < 1
lemma zero_lt_one (n : ℕ) (h : n = 0) : lt_one n := by subst h; dsimp [lt_one]; simp
-- Verify that calls to solve_by_elim to discharge subgoals use `rfl`
example : lt_one 0 :=
by library_search
example (α : Prop) : α → α :=
by library_search -- says: `exact id`
example (p : Prop) [decidable p] : (¬¬p) → p :=
by library_search -- says: `exact not_not.mp`
example (a b : Prop) (h : a ∧ b) : a :=
by library_search -- says: `exact h.left`
example (P Q : Prop) [decidable P] [decidable Q]: (¬ Q → ¬ P) → (P → Q) :=
by library_search -- says: `exact not_imp_not.mp`
example (a b : ℕ) : a + b = b + a :=
by library_search -- says: `exact add_comm a b`
example {a b : ℕ} : a ≤ a + b :=
by library_search -- says: `exact nat.le.intro rfl`
example (n m k : ℕ) : n * (m - k) = n * m - n * k :=
by library_search -- says: `exact nat.mul_sub_left_distrib n m k`
example (n m k : ℕ) : n * m - n * k = n * (m - k) :=
by library_search -- says: `exact eq.symm (nat.mul_sub_left_distrib n m k)`
example {n m : ℕ} (h : m < n) : m ≤ n - 1 :=
by library_search -- says: `exact nat.le_pred_of_lt h`
example {α : Type} (x y : α) : x = y ↔ y = x :=
by library_search -- says: `exact eq_comm`
example (a b : ℕ) (ha : 0 < a) (hb : 0 < b) : 0 < a + b :=
by library_search -- says: `exact add_pos ha hb`
example (a b : ℕ) : 0 < a → 0 < b → 0 < a + b :=
by library_search -- says: `exact add_pos`
example (a b : ℕ) (h : a ∣ b) (w : b > 0) : a ≤ b :=
by library_search -- says: `exact nat.le_of_dvd w h`
-- We even find `iff` results:
example : ∀ P : Prop, ¬(P ↔ ¬P) :=
by library_search -- says: `λ (a : Prop), (iff_not_self a).mp`
example {a b c : ℕ} (ha : a > 0) (w : b ∣ c) : a * b ∣ a * c :=
by library_search -- exact mul_dvd_mul_left a w
example {a b c : ℕ} (h₁ : a ∣ c) (h₂ : a ∣ b + c) : a ∣ b :=
by library_search -- says `exact (nat.dvd_add_left h₁).mp h₂`
end test.library_search
|
823cf48c12a6492b0f83b172d13a363e919a41e8 | 302c785c90d40ad3d6be43d33bc6a558354cc2cf | /src/computability/partrec_code.lean | 126327b13f4f3a3972583d61c617db2ff566022c | [
"Apache-2.0"
] | permissive | ilitzroth/mathlib | ea647e67f1fdfd19a0f7bdc5504e8acec6180011 | 5254ef14e3465f6504306132fe3ba9cec9ffff16 | refs/heads/master | 1,680,086,661,182 | 1,617,715,647,000 | 1,617,715,647,000 | null | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 38,586 | lean | /-
Copyright (c) 2018 Mario Carneiro. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Mario Carneiro
Godel numbering for partial recursive functions.
-/
import computability.partrec
open encodable denumerable
namespace nat.partrec
open nat (mkpair)
theorem rfind' {f} (hf : nat.partrec f) : nat.partrec (nat.unpaired (λ a m,
(nat.rfind (λ n, (λ m, m = 0) <$> f (mkpair a (n + m)))).map (+ m))) :=
partrec₂.unpaired'.2 $
begin
refine partrec.map
((@partrec₂.unpaired' (λ (a b : ℕ),
nat.rfind (λ n, (λ m, m = 0) <$> f (mkpair a (n + b))))).1 _)
(primrec.nat_add.comp primrec.snd $
primrec.snd.comp primrec.fst).to_comp.to₂,
have := rfind (partrec₂.unpaired'.2 ((partrec.nat_iff.2 hf).comp
(primrec₂.mkpair.comp
(primrec.fst.comp $ primrec.unpair.comp primrec.fst)
(primrec.nat_add.comp primrec.snd
(primrec.snd.comp $ primrec.unpair.comp primrec.fst))).to_comp).to₂),
simp at this, exact this
end
inductive code : Type
| zero : code
| succ : code
| left : code
| right : code
| pair : code → code → code
| comp : code → code → code
| prec : code → code → code
| rfind' : code → code
end nat.partrec
namespace nat.partrec.code
open nat (mkpair unpair)
open nat.partrec (code)
instance : inhabited code := ⟨zero⟩
protected def const : ℕ → code
| 0 := zero
| (n+1) := comp succ (const n)
theorem const_inj : Π {n₁ n₂}, nat.partrec.code.const n₁ = nat.partrec.code.const n₂ → n₁ = n₂
| 0 0 h := by simp
| (n₁+1) (n₂+1) h := by { dsimp [nat.partrec.code.const] at h,
injection h with h₁ h₂,
simp only [const_inj h₂] }
protected def id : code := pair left right
def curry (c : code) (n : ℕ) : code :=
comp c (pair (code.const n) code.id)
def encode_code : code → ℕ
| zero := 0
| succ := 1
| left := 2
| right := 3
| (pair cf cg) := bit0 (bit0 $ mkpair (encode_code cf) (encode_code cg)) + 4
| (comp cf cg) := bit0 (bit1 $ mkpair (encode_code cf) (encode_code cg)) + 4
| (prec cf cg) := bit1 (bit0 $ mkpair (encode_code cf) (encode_code cg)) + 4
| (rfind' cf) := bit1 (bit1 $ encode_code cf) + 4
def of_nat_code : ℕ → code
| 0 := zero
| 1 := succ
| 2 := left
| 3 := right
| (n+4) := let m := n.div2.div2 in
have hm : m < n + 4, by simp [m, nat.div2_val];
from lt_of_le_of_lt
(le_trans (nat.div_le_self _ _) (nat.div_le_self _ _))
(nat.succ_le_succ (nat.le_add_right _ _)),
have m1 : m.unpair.1 < n + 4, from lt_of_le_of_lt m.unpair_le_left hm,
have m2 : m.unpair.2 < n + 4, from lt_of_le_of_lt m.unpair_le_right hm,
match n.bodd, n.div2.bodd with
| ff, ff := pair (of_nat_code m.unpair.1) (of_nat_code m.unpair.2)
| ff, tt := comp (of_nat_code m.unpair.1) (of_nat_code m.unpair.2)
| tt, ff := prec (of_nat_code m.unpair.1) (of_nat_code m.unpair.2)
| tt, tt := rfind' (of_nat_code m)
end
private theorem encode_of_nat_code : ∀ n, encode_code (of_nat_code n) = n
| 0 := rfl
| 1 := rfl
| 2 := rfl
| 3 := rfl
| (n+4) := let m := n.div2.div2 in
have hm : m < n + 4, by simp [m, nat.div2_val];
from lt_of_le_of_lt
(le_trans (nat.div_le_self _ _) (nat.div_le_self _ _))
(nat.succ_le_succ (nat.le_add_right _ _)),
have m1 : m.unpair.1 < n + 4, from lt_of_le_of_lt m.unpair_le_left hm,
have m2 : m.unpair.2 < n + 4, from lt_of_le_of_lt m.unpair_le_right hm,
have IH : _ := encode_of_nat_code m,
have IH1 : _ := encode_of_nat_code m.unpair.1,
have IH2 : _ := encode_of_nat_code m.unpair.2,
begin
transitivity, swap,
rw [← nat.bit_decomp n, ← nat.bit_decomp n.div2],
simp [encode_code, of_nat_code, -add_comm],
cases n.bodd; cases n.div2.bodd;
simp [encode_code, of_nat_code, -add_comm, IH, IH1, IH2, m, nat.bit]
end
instance : denumerable code :=
mk' ⟨encode_code, of_nat_code,
λ c, by induction c; try {refl}; simp [
encode_code, of_nat_code, -add_comm, *],
encode_of_nat_code⟩
theorem encode_code_eq : encode = encode_code := rfl
theorem of_nat_code_eq : of_nat code = of_nat_code := rfl
theorem encode_lt_pair (cf cg) :
encode cf < encode (pair cf cg) ∧
encode cg < encode (pair cf cg) :=
begin
simp [encode_code_eq, encode_code, -add_comm],
have := nat.mul_le_mul_right _ (dec_trivial : 1 ≤ 2*2),
rw [one_mul, mul_assoc, ← bit0_eq_two_mul, ← bit0_eq_two_mul] at this,
have := lt_of_le_of_lt this (lt_add_of_pos_right _ (dec_trivial:0<4)),
exact ⟨
lt_of_le_of_lt (nat.le_mkpair_left _ _) this,
lt_of_le_of_lt (nat.le_mkpair_right _ _) this⟩
end
theorem encode_lt_comp (cf cg) :
encode cf < encode (comp cf cg) ∧
encode cg < encode (comp cf cg) :=
begin
suffices, exact (encode_lt_pair cf cg).imp
(λ h, lt_trans h this) (λ h, lt_trans h this),
change _, simp [encode_code_eq, encode_code]
end
theorem encode_lt_prec (cf cg) :
encode cf < encode (prec cf cg) ∧
encode cg < encode (prec cf cg) :=
begin
suffices, exact (encode_lt_pair cf cg).imp
(λ h, lt_trans h this) (λ h, lt_trans h this),
change _, simp [encode_code_eq, encode_code],
end
theorem encode_lt_rfind' (cf) : encode cf < encode (rfind' cf) :=
begin
simp [encode_code_eq, encode_code, -add_comm],
have := nat.mul_le_mul_right _ (dec_trivial : 1 ≤ 2*2),
rw [one_mul, mul_assoc, ← bit0_eq_two_mul, ← bit0_eq_two_mul] at this,
refine lt_of_le_of_lt (le_trans this _)
(lt_add_of_pos_right _ (dec_trivial:0<4)),
exact le_of_lt (nat.bit0_lt_bit1 $ le_of_lt $
nat.bit0_lt_bit1 $ le_refl _),
end
section
open primrec
theorem pair_prim : primrec₂ pair :=
primrec₂.of_nat_iff.2 $ primrec₂.encode_iff.1 $ nat_add.comp
(nat_bit0.comp $ nat_bit0.comp $
primrec₂.mkpair.comp
(encode_iff.2 $ (primrec.of_nat code).comp fst)
(encode_iff.2 $ (primrec.of_nat code).comp snd))
(primrec₂.const 4)
theorem comp_prim : primrec₂ comp :=
primrec₂.of_nat_iff.2 $ primrec₂.encode_iff.1 $ nat_add.comp
(nat_bit0.comp $ nat_bit1.comp $
primrec₂.mkpair.comp
(encode_iff.2 $ (primrec.of_nat code).comp fst)
(encode_iff.2 $ (primrec.of_nat code).comp snd))
(primrec₂.const 4)
theorem prec_prim : primrec₂ prec :=
primrec₂.of_nat_iff.2 $ primrec₂.encode_iff.1 $ nat_add.comp
(nat_bit1.comp $ nat_bit0.comp $
primrec₂.mkpair.comp
(encode_iff.2 $ (primrec.of_nat code).comp fst)
(encode_iff.2 $ (primrec.of_nat code).comp snd))
(primrec₂.const 4)
theorem rfind_prim : primrec rfind' :=
of_nat_iff.2 $ encode_iff.1 $ nat_add.comp
(nat_bit1.comp $ nat_bit1.comp $
encode_iff.2 $ primrec.of_nat code)
(const 4)
theorem rec_prim' {α σ} [primcodable α] [primcodable σ]
{c : α → code} (hc : primrec c)
{z : α → σ} (hz : primrec z)
{s : α → σ} (hs : primrec s)
{l : α → σ} (hl : primrec l)
{r : α → σ} (hr : primrec r)
{pr : α → code × code × σ × σ → σ} (hpr : primrec₂ pr)
{co : α → code × code × σ × σ → σ} (hco : primrec₂ co)
{pc : α → code × code × σ × σ → σ} (hpc : primrec₂ pc)
{rf : α → code × σ → σ} (hrf : primrec₂ rf) :
let PR (a) := λ cf cg hf hg, pr a (cf, cg, hf, hg),
CO (a) := λ cf cg hf hg, co a (cf, cg, hf, hg),
PC (a) := λ cf cg hf hg, pc a (cf, cg, hf, hg),
RF (a) := λ cf hf, rf a (cf, hf),
F (a c) : σ := nat.partrec.code.rec_on c
(z a) (s a) (l a) (r a) (PR a) (CO a) (PC a) (RF a) in
primrec (λ a, F a (c a)) :=
begin
intros,
let G₁ : (α × list σ) × ℕ × ℕ → option σ := λ p,
let a := p.1.1, IH := p.1.2, n := p.2.1, m := p.2.2 in
(IH.nth m).bind $ λ s,
(IH.nth m.unpair.1).bind $ λ s₁,
(IH.nth m.unpair.2).map $ λ s₂,
cond n.bodd
(cond n.div2.bodd
(rf a (of_nat code m, s))
(pc a (of_nat code m.unpair.1, of_nat code m.unpair.2, s₁, s₂)))
(cond n.div2.bodd
(co a (of_nat code m.unpair.1, of_nat code m.unpair.2, s₁, s₂))
(pr a (of_nat code m.unpair.1, of_nat code m.unpair.2, s₁, s₂))),
have : primrec G₁,
{ refine option_bind (list_nth.comp (snd.comp fst) (snd.comp snd)) _,
refine option_bind ((list_nth.comp (snd.comp fst)
(fst.comp $ primrec.unpair.comp (snd.comp snd))).comp fst) _,
refine option_map ((list_nth.comp (snd.comp fst)
(snd.comp $ primrec.unpair.comp (snd.comp snd))).comp $ fst.comp fst) _,
have a := fst.comp (fst.comp $ fst.comp $ fst.comp fst),
have n := fst.comp (snd.comp $ fst.comp $ fst.comp fst),
have m := snd.comp (snd.comp $ fst.comp $ fst.comp fst),
have m₁ := fst.comp (primrec.unpair.comp m),
have m₂ := snd.comp (primrec.unpair.comp m),
have s := snd.comp (fst.comp fst),
have s₁ := snd.comp fst,
have s₂ := snd,
exact (nat_bodd.comp n).cond
((nat_bodd.comp $ nat_div2.comp n).cond
(hrf.comp a (((primrec.of_nat code).comp m).pair s))
(hpc.comp a (((primrec.of_nat code).comp m₁).pair $
((primrec.of_nat code).comp m₂).pair $ s₁.pair s₂)))
(primrec.cond (nat_bodd.comp $ nat_div2.comp n)
(hco.comp a (((primrec.of_nat code).comp m₁).pair $
((primrec.of_nat code).comp m₂).pair $ s₁.pair s₂))
(hpr.comp a (((primrec.of_nat code).comp m₁).pair $
((primrec.of_nat code).comp m₂).pair $ s₁.pair s₂))) },
let G : α → list σ → option σ := λ a IH,
IH.length.cases (some (z a)) $ λ n,
n.cases (some (s a)) $ λ n,
n.cases (some (l a)) $ λ n,
n.cases (some (r a)) $ λ n,
G₁ ((a, IH), n, n.div2.div2),
have : primrec₂ G := (nat_cases
(list_length.comp snd) (option_some_iff.2 (hz.comp fst)) $
nat_cases snd (option_some_iff.2 (hs.comp (fst.comp fst))) $
nat_cases snd (option_some_iff.2 (hl.comp (fst.comp $ fst.comp fst))) $
nat_cases snd (option_some_iff.2 (hr.comp (fst.comp $ fst.comp $ fst.comp fst)))
(this.comp $
((fst.pair snd).comp $ fst.comp $ fst.comp $ fst.comp $ fst).pair $
snd.pair $ nat_div2.comp $ nat_div2.comp snd)),
refine ((nat_strong_rec
(λ a n, F a (of_nat code n)) this.to₂ $ λ a n, _).comp
primrec.id $ encode_iff.2 hc).of_eq (λ a, by simp),
simp,
iterate 4 {cases n with n, {refl}},
simp [G], rw [list.length_map, list.length_range],
let m := n.div2.div2,
show G₁ ((a, (list.range (n+4)).map (λ n, F a (of_nat code n))), n, m)
= some (F a (of_nat code (n+4))),
have hm : m < n + 4, by simp [nat.div2_val, m];
from lt_of_le_of_lt
(le_trans (nat.div_le_self _ _) (nat.div_le_self _ _))
(nat.succ_le_succ (nat.le_add_right _ _)),
have m1 : m.unpair.1 < n + 4, from lt_of_le_of_lt m.unpair_le_left hm,
have m2 : m.unpair.2 < n + 4, from lt_of_le_of_lt m.unpair_le_right hm,
simp [G₁], simp [list.nth_map, list.nth_range, hm, m1, m2],
change of_nat code (n+4) with of_nat_code (n+4),
simp [of_nat_code],
cases n.bodd; cases n.div2.bodd; refl
end
theorem rec_prim {α σ} [primcodable α] [primcodable σ]
{c : α → code} (hc : primrec c)
{z : α → σ} (hz : primrec z)
{s : α → σ} (hs : primrec s)
{l : α → σ} (hl : primrec l)
{r : α → σ} (hr : primrec r)
{pr : α → code → code → σ → σ → σ}
(hpr : primrec (λ a : α × code × code × σ × σ,
pr a.1 a.2.1 a.2.2.1 a.2.2.2.1 a.2.2.2.2))
{co : α → code → code → σ → σ → σ}
(hco : primrec (λ a : α × code × code × σ × σ,
co a.1 a.2.1 a.2.2.1 a.2.2.2.1 a.2.2.2.2))
{pc : α → code → code → σ → σ → σ}
(hpc : primrec (λ a : α × code × code × σ × σ,
pc a.1 a.2.1 a.2.2.1 a.2.2.2.1 a.2.2.2.2))
{rf : α → code → σ → σ}
(hrf : primrec (λ a : α × code × σ, rf a.1 a.2.1 a.2.2)) :
let F (a c) : σ := nat.partrec.code.rec_on c
(z a) (s a) (l a) (r a) (pr a) (co a) (pc a) (rf a) in
primrec (λ a, F a (c a)) :=
begin
intros,
let G₁ : (α × list σ) × ℕ × ℕ → option σ := λ p,
let a := p.1.1, IH := p.1.2, n := p.2.1, m := p.2.2 in
(IH.nth m).bind $ λ s,
(IH.nth m.unpair.1).bind $ λ s₁,
(IH.nth m.unpair.2).map $ λ s₂,
cond n.bodd
(cond n.div2.bodd
(rf a (of_nat code m) s)
(pc a (of_nat code m.unpair.1) (of_nat code m.unpair.2) s₁ s₂))
(cond n.div2.bodd
(co a (of_nat code m.unpair.1) (of_nat code m.unpair.2) s₁ s₂)
(pr a (of_nat code m.unpair.1) (of_nat code m.unpair.2) s₁ s₂)),
have : primrec G₁,
{ refine option_bind (list_nth.comp (snd.comp fst) (snd.comp snd)) _,
refine option_bind ((list_nth.comp (snd.comp fst)
(fst.comp $ primrec.unpair.comp (snd.comp snd))).comp fst) _,
refine option_map ((list_nth.comp (snd.comp fst)
(snd.comp $ primrec.unpair.comp (snd.comp snd))).comp $ fst.comp fst) _,
have a := fst.comp (fst.comp $ fst.comp $ fst.comp fst),
have n := fst.comp (snd.comp $ fst.comp $ fst.comp fst),
have m := snd.comp (snd.comp $ fst.comp $ fst.comp fst),
have m₁ := fst.comp (primrec.unpair.comp m),
have m₂ := snd.comp (primrec.unpair.comp m),
have s := snd.comp (fst.comp fst),
have s₁ := snd.comp fst,
have s₂ := snd,
exact (nat_bodd.comp n).cond
((nat_bodd.comp $ nat_div2.comp n).cond
(hrf.comp $ a.pair (((primrec.of_nat code).comp m).pair s))
(hpc.comp $ a.pair (((primrec.of_nat code).comp m₁).pair $
((primrec.of_nat code).comp m₂).pair $ s₁.pair s₂)))
(primrec.cond (nat_bodd.comp $ nat_div2.comp n)
(hco.comp $ a.pair (((primrec.of_nat code).comp m₁).pair $
((primrec.of_nat code).comp m₂).pair $ s₁.pair s₂))
(hpr.comp $ a.pair (((primrec.of_nat code).comp m₁).pair $
((primrec.of_nat code).comp m₂).pair $ s₁.pair s₂))) },
let G : α → list σ → option σ := λ a IH,
IH.length.cases (some (z a)) $ λ n,
n.cases (some (s a)) $ λ n,
n.cases (some (l a)) $ λ n,
n.cases (some (r a)) $ λ n,
G₁ ((a, IH), n, n.div2.div2),
have : primrec₂ G := (nat_cases
(list_length.comp snd) (option_some_iff.2 (hz.comp fst)) $
nat_cases snd (option_some_iff.2 (hs.comp (fst.comp fst))) $
nat_cases snd (option_some_iff.2 (hl.comp (fst.comp $ fst.comp fst))) $
nat_cases snd (option_some_iff.2 (hr.comp (fst.comp $ fst.comp $ fst.comp fst)))
(this.comp $
((fst.pair snd).comp $ fst.comp $ fst.comp $ fst.comp $ fst).pair $
snd.pair $ nat_div2.comp $ nat_div2.comp snd)),
refine ((nat_strong_rec
(λ a n, F a (of_nat code n)) this.to₂ $ λ a n, _).comp
primrec.id $ encode_iff.2 hc).of_eq (λ a, by simp),
simp,
iterate 4 {cases n with n, {refl}},
simp [G], rw [list.length_map, list.length_range],
let m := n.div2.div2,
show G₁ ((a, (list.range (n+4)).map (λ n, F a (of_nat code n))), n, m)
= some (F a (of_nat code (n+4))),
have hm : m < n + 4, by simp [nat.div2_val, m];
from lt_of_le_of_lt
(le_trans (nat.div_le_self _ _) (nat.div_le_self _ _))
(nat.succ_le_succ (nat.le_add_right _ _)),
have m1 : m.unpair.1 < n + 4, from lt_of_le_of_lt m.unpair_le_left hm,
have m2 : m.unpair.2 < n + 4, from lt_of_le_of_lt m.unpair_le_right hm,
simp [G₁], simp [list.nth_map, list.nth_range, hm, m1, m2],
change of_nat code (n+4) with of_nat_code (n+4),
simp [of_nat_code],
cases n.bodd; cases n.div2.bodd; refl
end
end
section
open computable
/- TODO(Mario): less copy-paste from previous proof -/
theorem rec_computable {α σ} [primcodable α] [primcodable σ]
{c : α → code} (hc : computable c)
{z : α → σ} (hz : computable z)
{s : α → σ} (hs : computable s)
{l : α → σ} (hl : computable l)
{r : α → σ} (hr : computable r)
{pr : α → code × code × σ × σ → σ} (hpr : computable₂ pr)
{co : α → code × code × σ × σ → σ} (hco : computable₂ co)
{pc : α → code × code × σ × σ → σ} (hpc : computable₂ pc)
{rf : α → code × σ → σ} (hrf : computable₂ rf) :
let PR (a) := λ cf cg hf hg, pr a (cf, cg, hf, hg),
CO (a) := λ cf cg hf hg, co a (cf, cg, hf, hg),
PC (a) := λ cf cg hf hg, pc a (cf, cg, hf, hg),
RF (a) := λ cf hf, rf a (cf, hf),
F (a c) : σ := nat.partrec.code.rec_on c
(z a) (s a) (l a) (r a) (PR a) (CO a) (PC a) (RF a) in
computable (λ a, F a (c a)) :=
begin
intros,
let G₁ : (α × list σ) × ℕ × ℕ → option σ := λ p,
let a := p.1.1, IH := p.1.2, n := p.2.1, m := p.2.2 in
(IH.nth m).bind $ λ s,
(IH.nth m.unpair.1).bind $ λ s₁,
(IH.nth m.unpair.2).map $ λ s₂,
cond n.bodd
(cond n.div2.bodd
(rf a (of_nat code m, s))
(pc a (of_nat code m.unpair.1, of_nat code m.unpair.2, s₁, s₂)))
(cond n.div2.bodd
(co a (of_nat code m.unpair.1, of_nat code m.unpair.2, s₁, s₂))
(pr a (of_nat code m.unpair.1, of_nat code m.unpair.2, s₁, s₂))),
have : computable G₁,
{ refine option_bind (list_nth.comp (snd.comp fst) (snd.comp snd)) _,
refine option_bind ((list_nth.comp (snd.comp fst)
(fst.comp $ computable.unpair.comp (snd.comp snd))).comp fst) _,
refine option_map ((list_nth.comp (snd.comp fst)
(snd.comp $ computable.unpair.comp (snd.comp snd))).comp $ fst.comp fst) _,
have a := fst.comp (fst.comp $ fst.comp $ fst.comp fst),
have n := fst.comp (snd.comp $ fst.comp $ fst.comp fst),
have m := snd.comp (snd.comp $ fst.comp $ fst.comp fst),
have m₁ := fst.comp (computable.unpair.comp m),
have m₂ := snd.comp (computable.unpair.comp m),
have s := snd.comp (fst.comp fst),
have s₁ := snd.comp fst,
have s₂ := snd,
exact (nat_bodd.comp n).cond
((nat_bodd.comp $ nat_div2.comp n).cond
(hrf.comp a (((computable.of_nat code).comp m).pair s))
(hpc.comp a (((computable.of_nat code).comp m₁).pair $
((computable.of_nat code).comp m₂).pair $ s₁.pair s₂)))
(computable.cond (nat_bodd.comp $ nat_div2.comp n)
(hco.comp a (((computable.of_nat code).comp m₁).pair $
((computable.of_nat code).comp m₂).pair $ s₁.pair s₂))
(hpr.comp a (((computable.of_nat code).comp m₁).pair $
((computable.of_nat code).comp m₂).pair $ s₁.pair s₂))) },
let G : α → list σ → option σ := λ a IH,
IH.length.cases (some (z a)) $ λ n,
n.cases (some (s a)) $ λ n,
n.cases (some (l a)) $ λ n,
n.cases (some (r a)) $ λ n,
G₁ ((a, IH), n, n.div2.div2),
have : computable₂ G := (nat_cases
(list_length.comp snd) (option_some_iff.2 (hz.comp fst)) $
nat_cases snd (option_some_iff.2 (hs.comp (fst.comp fst))) $
nat_cases snd (option_some_iff.2 (hl.comp (fst.comp $ fst.comp fst))) $
nat_cases snd (option_some_iff.2 (hr.comp (fst.comp $ fst.comp $ fst.comp fst)))
(this.comp $
((fst.pair snd).comp $ fst.comp $ fst.comp $ fst.comp $ fst).pair $
snd.pair $ nat_div2.comp $ nat_div2.comp snd)),
refine ((nat_strong_rec
(λ a n, F a (of_nat code n)) this.to₂ $ λ a n, _).comp
computable.id $ encode_iff.2 hc).of_eq (λ a, by simp),
simp,
iterate 4 {cases n with n, {refl}},
simp [G], rw [list.length_map, list.length_range],
let m := n.div2.div2,
show G₁ ((a, (list.range (n+4)).map (λ n, F a (of_nat code n))), n, m)
= some (F a (of_nat code (n+4))),
have hm : m < n + 4, by simp [nat.div2_val, m];
from lt_of_le_of_lt
(le_trans (nat.div_le_self _ _) (nat.div_le_self _ _))
(nat.succ_le_succ (nat.le_add_right _ _)),
have m1 : m.unpair.1 < n + 4, from lt_of_le_of_lt m.unpair_le_left hm,
have m2 : m.unpair.2 < n + 4, from lt_of_le_of_lt m.unpair_le_right hm,
simp [G₁], simp [list.nth_map, list.nth_range, hm, m1, m2],
change of_nat code (n+4) with of_nat_code (n+4),
simp [of_nat_code],
cases n.bodd; cases n.div2.bodd; refl
end
end
def eval : code → ℕ →. ℕ
| zero := pure 0
| succ := nat.succ
| left := ↑(λ n : ℕ, n.unpair.1)
| right := ↑(λ n : ℕ, n.unpair.2)
| (pair cf cg) := λ n, mkpair <$> eval cf n <*> eval cg n
| (comp cf cg) := λ n, eval cg n >>= eval cf
| (prec cf cg) := nat.unpaired (λ a n,
n.elim (eval cf a) (λ y IH, do i ← IH, eval cg (mkpair a (mkpair y i))))
| (rfind' cf) := nat.unpaired (λ a m,
(nat.rfind (λ n, (λ m, m = 0) <$>
eval cf (mkpair a (n + m)))).map (+ m))
instance : has_mem (ℕ →. ℕ) code := ⟨λ f c, eval c = f⟩
@[simp] theorem eval_const : ∀ n m, eval (code.const n) m = roption.some n
| 0 m := rfl
| (n+1) m := by simp! *
@[simp] theorem eval_id (n) : eval code.id n = roption.some n := by simp! [(<*>)]
@[simp] theorem eval_curry (c n x) : eval (curry c n) x = eval c (mkpair n x) :=
by simp! [(<*>)]
theorem const_prim : primrec code.const :=
(primrec.id.nat_iterate (primrec.const zero)
(comp_prim.comp (primrec.const succ) primrec.snd).to₂).of_eq $
λ n, by simp; induction n; simp [*, code.const, function.iterate_succ']
theorem curry_prim : primrec₂ curry :=
comp_prim.comp primrec.fst $
pair_prim.comp (const_prim.comp primrec.snd) (primrec.const code.id)
theorem curry_inj {c₁ c₂ n₁ n₂} (h : curry c₁ n₁ = curry c₂ n₂) : c₁ = c₂ ∧ n₁ = n₂ :=
⟨by injection h, by { injection h,
injection h with h₁ h₂,
injection h₂ with h₃ h₄,
exact const_inj h₃ }⟩
theorem smn : ∃ f : code → ℕ → code,
computable₂ f ∧ ∀ c n x, eval (f c n) x = eval c (mkpair n x) :=
⟨curry, primrec₂.to_comp curry_prim, eval_curry⟩
theorem exists_code {f : ℕ →. ℕ} : nat.partrec f ↔ ∃ c : code, eval c = f :=
⟨λ h, begin
induction h,
case nat.partrec.zero { exact ⟨zero, rfl⟩ },
case nat.partrec.succ { exact ⟨succ, rfl⟩ },
case nat.partrec.left { exact ⟨left, rfl⟩ },
case nat.partrec.right { exact ⟨right, rfl⟩ },
case nat.partrec.pair : f g pf pg hf hg {
rcases hf with ⟨cf, rfl⟩, rcases hg with ⟨cg, rfl⟩,
exact ⟨pair cf cg, rfl⟩ },
case nat.partrec.comp : f g pf pg hf hg {
rcases hf with ⟨cf, rfl⟩, rcases hg with ⟨cg, rfl⟩,
exact ⟨comp cf cg, rfl⟩ },
case nat.partrec.prec : f g pf pg hf hg {
rcases hf with ⟨cf, rfl⟩, rcases hg with ⟨cg, rfl⟩,
exact ⟨prec cf cg, rfl⟩ },
case nat.partrec.rfind : f pf hf {
rcases hf with ⟨cf, rfl⟩,
refine ⟨comp (rfind' cf) (pair code.id zero), _⟩,
simp [eval, (<*>), pure, pfun.pure, roption.map_id'] },
end, λ h, begin
rcases h with ⟨c, rfl⟩, induction c,
case nat.partrec.code.zero { exact nat.partrec.zero },
case nat.partrec.code.succ { exact nat.partrec.succ },
case nat.partrec.code.left { exact nat.partrec.left },
case nat.partrec.code.right { exact nat.partrec.right },
case nat.partrec.code.pair : cf cg pf pg { exact pf.pair pg },
case nat.partrec.code.comp : cf cg pf pg { exact pf.comp pg },
case nat.partrec.code.prec : cf cg pf pg { exact pf.prec pg },
case nat.partrec.code.rfind' : cf pf { exact pf.rfind' },
end⟩
def evaln : ∀ k : ℕ, code → ℕ → option ℕ
| 0 _ := λ m, none
| (k+1) zero := λ n, guard (n ≤ k) >> pure 0
| (k+1) succ := λ n, guard (n ≤ k) >> pure (nat.succ n)
| (k+1) left := λ n, guard (n ≤ k) >> pure n.unpair.1
| (k+1) right := λ n, guard (n ≤ k) >> pure n.unpair.2
| (k+1) (pair cf cg) := λ n, guard (n ≤ k) >>
mkpair <$> evaln (k+1) cf n <*> evaln (k+1) cg n
| (k+1) (comp cf cg) := λ n, guard (n ≤ k) >>
do x ← evaln (k+1) cg n, evaln (k+1) cf x
| (k+1) (prec cf cg) := λ n, guard (n ≤ k) >>
n.unpaired (λ a n,
n.cases (evaln (k+1) cf a) $ λ y, do
i ← evaln k (prec cf cg) (mkpair a y),
evaln (k+1) cg (mkpair a (mkpair y i)))
| (k+1) (rfind' cf) := λ n, guard (n ≤ k) >>
n.unpaired (λ a m, do
x ← evaln (k+1) cf (mkpair a m),
if x = 0 then pure m else
evaln k (rfind' cf) (mkpair a (m+1)))
theorem evaln_bound : ∀ {k c n x}, x ∈ evaln k c n → n < k
| 0 c n x h := by simp [evaln] at h; cases h
| (k+1) c n x h := begin
suffices : ∀ {o : option ℕ}, x ∈ guard (n ≤ k) >> o → n < k + 1,
{ cases c; rw [evaln] at h; exact this h },
simpa [(>>)] using nat.lt_succ_of_le
end
theorem evaln_mono : ∀ {k₁ k₂ c n x}, k₁ ≤ k₂ → x ∈ evaln k₁ c n → x ∈ evaln k₂ c n
| 0 k₂ c n x hl h := by simp [evaln] at h; cases h
| (k+1) (k₂+1) c n x hl h := begin
have hl' := nat.le_of_succ_le_succ hl,
have : ∀ {k k₂ n x : ℕ} {o₁ o₂ : option ℕ},
k ≤ k₂ → (x ∈ o₁ → x ∈ o₂) → x ∈ guard (n ≤ k) >> o₁ → x ∈ guard (n ≤ k₂) >> o₂,
{ simp [(>>)], introv h h₁ h₂ h₃, exact ⟨le_trans h₂ h, h₁ h₃⟩ },
simp at h ⊢,
induction c with cf cg hf hg cf cg hf hg cf cg hf hg cf hf generalizing x n;
rw [evaln] at h ⊢; refine this hl' (λ h, _) h,
iterate 4 {exact h},
{ -- pair cf cg
simp [(<*>)] at h ⊢,
exact h.imp (λ a, and.imp (hf _ _) $ Exists.imp $ λ b, and.imp_left (hg _ _)) },
{ -- comp cf cg
simp at h ⊢,
exact h.imp (λ a, and.imp (hg _ _) (hf _ _)) },
{ -- prec cf cg
revert h, simp,
induction n.unpair.2; simp,
{ apply hf },
{ exact λ y h₁ h₂, ⟨y, evaln_mono hl' h₁, hg _ _ h₂⟩ } },
{ -- rfind' cf
simp at h ⊢,
refine h.imp (λ x, and.imp (hf _ _) _),
by_cases x0 : x = 0; simp [x0],
exact evaln_mono hl' }
end
theorem evaln_sound : ∀ {k c n x}, x ∈ evaln k c n → x ∈ eval c n
| 0 _ n x h := by simp [evaln] at h; cases h
| (k+1) c n x h := begin
induction c with cf cg hf hg cf cg hf hg cf cg hf hg cf hf generalizing x n;
simp [eval, evaln, (>>), (<*>)] at h ⊢; cases h with _ h,
iterate 4 {simpa [pure, pfun.pure, eq_comm] using h},
{ -- pair cf cg
rcases h with ⟨y, ef, z, eg, rfl⟩,
exact ⟨_, hf _ _ ef, _, hg _ _ eg, rfl⟩ },
{ --comp hf hg
rcases h with ⟨y, eg, ef⟩,
exact ⟨_, hg _ _ eg, hf _ _ ef⟩ },
{ -- prec cf cg
revert h,
induction n.unpair.2 with m IH generalizing x; simp,
{ apply hf },
{ refine λ y h₁ h₂, ⟨y, IH _ _, _⟩,
{ have := evaln_mono k.le_succ h₁,
simp [evaln, (>>)] at this,
exact this.2 },
{ exact hg _ _ h₂ } } },
{ -- rfind' cf
rcases h with ⟨m, h₁, h₂⟩,
by_cases m0 : m = 0; simp [m0] at h₂,
{ exact ⟨0,
⟨by simpa [m0] using hf _ _ h₁,
λ m, (nat.not_lt_zero _).elim⟩,
by injection h₂ with h₂; simp [h₂]⟩ },
{ have := evaln_sound h₂, simp [eval] at this,
rcases this with ⟨y, ⟨hy₁, hy₂⟩, rfl⟩,
refine ⟨ y+1, ⟨by simpa [add_comm, add_left_comm] using hy₁, λ i im, _⟩,
by simp [add_comm, add_left_comm] ⟩,
cases i with i,
{ exact ⟨m, by simpa using hf _ _ h₁, m0⟩ },
{ rcases hy₂ (nat.lt_of_succ_lt_succ im) with ⟨z, hz, z0⟩,
exact ⟨z, by simpa [nat.succ_eq_add_one, add_comm, add_left_comm] using hz, z0⟩ } } }
end
theorem evaln_complete {c n x} : x ∈ eval c n ↔ ∃ k, x ∈ evaln k c n :=
⟨λ h, begin
suffices : ∃ k, x ∈ evaln (k+1) c n,
{ exact let ⟨k, h⟩ := this in ⟨k+1, h⟩ },
induction c generalizing n x;
simp [eval, evaln, pure, pfun.pure, (<*>), (>>)] at h ⊢,
iterate 4 { exact ⟨⟨_, le_refl _⟩, h.symm⟩ },
case nat.partrec.code.pair : cf cg hf hg {
rcases h with ⟨x, hx, y, hy, rfl⟩,
rcases hf hx with ⟨k₁, hk₁⟩, rcases hg hy with ⟨k₂, hk₂⟩,
refine ⟨max k₁ k₂, _⟩,
refine ⟨le_max_left_of_le $ nat.le_of_lt_succ $ evaln_bound hk₁,
_, evaln_mono (nat.succ_le_succ $ le_max_left _ _) hk₁,
_, evaln_mono (nat.succ_le_succ $ le_max_right _ _) hk₂, rfl⟩ },
case nat.partrec.code.comp : cf cg hf hg {
rcases h with ⟨y, hy, hx⟩,
rcases hg hy with ⟨k₁, hk₁⟩, rcases hf hx with ⟨k₂, hk₂⟩,
refine ⟨max k₁ k₂, _⟩,
exact ⟨le_max_left_of_le $ nat.le_of_lt_succ $ evaln_bound hk₁, _,
evaln_mono (nat.succ_le_succ $ le_max_left _ _) hk₁,
evaln_mono (nat.succ_le_succ $ le_max_right _ _) hk₂⟩ },
case nat.partrec.code.prec : cf cg hf hg {
revert h,
generalize : n.unpair.1 = n₁, generalize : n.unpair.2 = n₂,
induction n₂ with m IH generalizing x n; simp,
{ intro, rcases hf h with ⟨k, hk⟩,
exact ⟨_, le_max_left _ _,
evaln_mono (nat.succ_le_succ $ le_max_right _ _) hk⟩ },
{ intros y hy hx,
rcases IH hy with ⟨k₁, nk₁, hk₁⟩, rcases hg hx with ⟨k₂, hk₂⟩,
refine ⟨(max k₁ k₂).succ, nat.le_succ_of_le $ le_max_left_of_le $
le_trans (le_max_left _ (mkpair n₁ m)) nk₁, y,
evaln_mono (nat.succ_le_succ $ le_max_left _ _) _,
evaln_mono (nat.succ_le_succ $ nat.le_succ_of_le $ le_max_right _ _) hk₂⟩,
simp [evaln, (>>)],
exact ⟨le_trans (le_max_right _ _) nk₁, hk₁⟩ } },
case nat.partrec.code.rfind' : cf hf {
rcases h with ⟨y, ⟨hy₁, hy₂⟩, rfl⟩,
suffices : ∃ k, y + n.unpair.2 ∈ evaln (k+1) (rfind' cf)
(mkpair n.unpair.1 n.unpair.2), {simpa [evaln, (>>)]},
revert hy₁ hy₂, generalize : n.unpair.2 = m, intros,
induction y with y IH generalizing m; simp [evaln, (>>)],
{ simp at hy₁, rcases hf hy₁ with ⟨k, hk⟩,
exact ⟨_, nat.le_of_lt_succ $ evaln_bound hk, _, hk, by simp; refl⟩ },
{ rcases hy₂ (nat.succ_pos _) with ⟨a, ha, a0⟩,
rcases hf ha with ⟨k₁, hk₁⟩,
rcases IH m.succ
(by simpa [nat.succ_eq_add_one, add_comm, add_left_comm] using hy₁)
(λ i hi, by simpa [nat.succ_eq_add_one, add_comm, add_left_comm] using
hy₂ (nat.succ_lt_succ hi))
with ⟨k₂, hk₂⟩,
use (max k₁ k₂).succ,
rw [zero_add] at hk₁,
use (nat.le_succ_of_le $ le_max_left_of_le $ nat.le_of_lt_succ $ evaln_bound hk₁),
use a,
use evaln_mono (nat.succ_le_succ $ nat.le_succ_of_le $ le_max_left _ _) hk₁,
simpa [nat.succ_eq_add_one, a0, -max_eq_left, -max_eq_right, add_comm, add_left_comm] using
evaln_mono (nat.succ_le_succ $ le_max_right _ _) hk₂ } }
end, λ ⟨k, h⟩, evaln_sound h⟩
section
open primrec
private def lup (L : list (list (option ℕ))) (p : ℕ × code) (n : ℕ) :=
do l ← L.nth (encode p), o ← l.nth n, o
private lemma hlup : primrec (λ p:_×(_×_)×_, lup p.1 p.2.1 p.2.2) :=
option_bind
(list_nth.comp fst (primrec.encode.comp $ fst.comp snd))
(option_bind (list_nth.comp snd $ snd.comp $ snd.comp fst) snd)
private def G (L : list (list (option ℕ))) : option (list (option ℕ)) :=
option.some $
let a := of_nat (ℕ × code) L.length,
k := a.1, c := a.2 in
(list.range k).map (λ n,
k.cases none $ λ k',
nat.partrec.code.rec_on c
(some 0) -- zero
(some (nat.succ n))
(some n.unpair.1)
(some n.unpair.2)
(λ cf cg _ _, do
x ← lup L (k, cf) n,
y ← lup L (k, cg) n,
some (mkpair x y))
(λ cf cg _ _, do
x ← lup L (k, cg) n,
lup L (k, cf) x)
(λ cf cg _ _,
let z := n.unpair.1 in
n.unpair.2.cases
(lup L (k, cf) z)
(λ y, do
i ← lup L (k', c) (mkpair z y),
lup L (k, cg) (mkpair z (mkpair y i))))
(λ cf _,
let z := n.unpair.1, m := n.unpair.2 in do
x ← lup L (k, cf) (mkpair z m),
x.cases
(some m)
(λ _, lup L (k', c) (mkpair z (m+1)))))
private lemma hG : primrec G :=
begin
have a := (primrec.of_nat (ℕ × code)).comp list_length,
have k := fst.comp a,
refine option_some.comp
(list_map (list_range.comp k) (_ : primrec _)),
replace k := k.comp fst, have n := snd,
refine nat_cases k (const none) (_ : primrec _),
have k := k.comp fst, have n := n.comp fst, have k' := snd,
have c := snd.comp (a.comp $ fst.comp fst),
apply rec_prim c
(const (some 0))
(option_some.comp (primrec.succ.comp n))
(option_some.comp (fst.comp $ primrec.unpair.comp n))
(option_some.comp (snd.comp $ primrec.unpair.comp n)),
{ have L := (fst.comp fst).comp fst,
have k := k.comp fst, have n := n.comp fst,
have cf := fst.comp snd,
have cg := (fst.comp snd).comp snd,
exact option_bind
(hlup.comp $ L.pair $ (k.pair cf).pair n)
(option_map ((hlup.comp $
L.pair $ (k.pair cg).pair n).comp fst)
(primrec₂.mkpair.comp (snd.comp fst) snd)) },
{ have L := (fst.comp fst).comp fst,
have k := k.comp fst, have n := n.comp fst,
have cf := fst.comp snd,
have cg := (fst.comp snd).comp snd,
exact option_bind
(hlup.comp $ L.pair $ (k.pair cg).pair n)
(hlup.comp ((L.comp fst).pair $
((k.pair cf).comp fst).pair snd)) },
{ have L := (fst.comp fst).comp fst,
have k := k.comp fst, have n := n.comp fst,
have cf := fst.comp snd,
have cg := (fst.comp snd).comp snd,
have z := fst.comp (primrec.unpair.comp n),
refine nat_cases
(snd.comp (primrec.unpair.comp n))
(hlup.comp $ L.pair $ (k.pair cf).pair z)
(_ : primrec _),
have L := L.comp fst, have z := z.comp fst, have y := snd,
refine option_bind
(hlup.comp $ L.pair $
(((k'.pair c).comp fst).comp fst).pair
(primrec₂.mkpair.comp z y))
(_ : primrec _),
have z := z.comp fst, have y := y.comp fst, have i := snd,
exact hlup.comp ((L.comp fst).pair $
((k.pair cg).comp $ fst.comp fst).pair $
primrec₂.mkpair.comp z $ primrec₂.mkpair.comp y i) },
{ have L := (fst.comp fst).comp fst,
have k := k.comp fst, have n := n.comp fst,
have cf := fst.comp snd,
have z := fst.comp (primrec.unpair.comp n),
have m := snd.comp (primrec.unpair.comp n),
refine option_bind
(hlup.comp $ L.pair $ (k.pair cf).pair (primrec₂.mkpair.comp z m))
(_ : primrec _),
have m := m.comp fst,
exact nat_cases snd (option_some.comp m)
((hlup.comp ((L.comp fst).pair $
((k'.pair c).comp $ fst.comp fst).pair
(primrec₂.mkpair.comp (z.comp fst)
(primrec.succ.comp m)))).comp fst) }
end
private lemma evaln_map (k c n) :
(((list.range k).nth n).map (evaln k c)).bind (λ b, b) = evaln k c n :=
begin
by_cases kn : n < k,
{ simp [list.nth_range kn] },
{ rw list.nth_len_le,
{ cases e : evaln k c n, {refl},
exact kn.elim (evaln_bound e) },
simpa using kn }
end
theorem evaln_prim : primrec (λ (a : (ℕ × code) × ℕ), evaln a.1.1 a.1.2 a.2) :=
have primrec₂ (λ (_:unit) (n : ℕ),
let a := of_nat (ℕ × code) n in
(list.range a.1).map (evaln a.1 a.2)), from
primrec.nat_strong_rec _ (hG.comp snd).to₂ $
λ _ p, begin
simp [G],
rw (_ : (of_nat (ℕ × code) _).snd =
of_nat code p.unpair.2), swap, {simp},
apply list.map_congr (λ n, _),
rw (by simp : list.range p = list.range
(mkpair p.unpair.1 (encode (of_nat code p.unpair.2)))),
generalize : p.unpair.1 = k,
generalize : of_nat code p.unpair.2 = c,
intro nk,
cases k with k', {simp [evaln]},
let k := k'+1, change k'.succ with k,
simp [nat.lt_succ_iff] at nk,
have hg : ∀ {k' c' n},
mkpair k' (encode c') < mkpair k (encode c) →
lup ((list.range (mkpair k (encode c))).map (λ n,
(list.range n.unpair.1).map
(evaln n.unpair.1 (of_nat code n.unpair.2))))
(k', c') n = evaln k' c' n,
{ intros k₁ c₁ n₁ hl,
simp [lup, list.nth_range hl, evaln_map, (>>=)] },
cases c with cf cg cf cg cf cg cf;
simp [evaln, nk, (>>), (>>=), (<$>), (<*>), pure],
{ cases encode_lt_pair cf cg with lf lg,
rw [hg (nat.mkpair_lt_mkpair_right _ lf),
hg (nat.mkpair_lt_mkpair_right _ lg)],
cases evaln k cf n, {refl},
cases evaln k cg n; refl },
{ cases encode_lt_comp cf cg with lf lg,
rw hg (nat.mkpair_lt_mkpair_right _ lg),
cases evaln k cg n, {refl},
simp [hg (nat.mkpair_lt_mkpair_right _ lf)] },
{ cases encode_lt_prec cf cg with lf lg,
rw hg (nat.mkpair_lt_mkpair_right _ lf),
cases n.unpair.2, {refl},
simp,
rw hg (nat.mkpair_lt_mkpair_left _ k'.lt_succ_self),
cases evaln k' _ _, {refl},
simp [hg (nat.mkpair_lt_mkpair_right _ lg)] },
{ have lf := encode_lt_rfind' cf,
rw hg (nat.mkpair_lt_mkpair_right _ lf),
cases evaln k cf n with x, {refl},
simp,
cases x; simp [nat.succ_ne_zero],
rw hg (nat.mkpair_lt_mkpair_left _ k'.lt_succ_self) }
end,
(option_bind (list_nth.comp
(this.comp (const ()) (encode_iff.2 fst)) snd)
snd.to₂).of_eq $ λ ⟨⟨k, c⟩, n⟩, by simp [evaln_map]
end
section
open partrec computable
theorem eval_eq_rfind_opt (c n) :
eval c n = nat.rfind_opt (λ k, evaln k c n) :=
roption.ext $ λ x, begin
refine evaln_complete.trans (nat.rfind_opt_mono _).symm,
intros a m n hl, apply evaln_mono hl,
end
theorem eval_part : partrec₂ eval :=
(rfind_opt (evaln_prim.to_comp.comp
((snd.pair (fst.comp fst)).pair (snd.comp fst))).to₂).of_eq $
λ a, by simp [eval_eq_rfind_opt]
theorem fixed_point
{f : code → code} (hf : computable f) : ∃ c : code, eval (f c) = eval c :=
let g (x y : ℕ) : roption ℕ :=
eval (of_nat code x) x >>= λ b, eval (of_nat code b) y in
have partrec₂ g :=
(eval_part.comp ((computable.of_nat _).comp fst) fst).bind
(eval_part.comp ((computable.of_nat _).comp snd) (snd.comp fst)).to₂,
let ⟨cg, eg⟩ := exists_code.1 this in
have eg' : ∀ a n, eval cg (mkpair a n) = roption.map encode (g a n) :=
by simp [eg],
let F (x : ℕ) : code := f (curry cg x) in
have computable F :=
hf.comp (curry_prim.comp (primrec.const cg) primrec.id).to_comp,
let ⟨cF, eF⟩ := exists_code.1 this in
have eF' : eval cF (encode cF) = roption.some (encode (F (encode cF))),
by simp [eF],
⟨curry cg (encode cF), funext (λ n,
show eval (f (curry cg (encode cF))) n = eval (curry cg (encode cF)) n,
by simp [eg', eF', roption.map_id', g])⟩
theorem fixed_point₂
{f : code → ℕ →. ℕ} (hf : partrec₂ f) : ∃ c : code, eval c = f c :=
let ⟨cf, ef⟩ := exists_code.1 hf in
(fixed_point (curry_prim.comp
(primrec.const cf) primrec.encode).to_comp).imp $
λ c e, funext $ λ n, by simp [e.symm, ef, roption.map_id']
end
end nat.partrec.code
|
86f1cdc18581bb10820673dfc16698111c7e7007 | d450724ba99f5b50b57d244eb41fef9f6789db81 | /src/Submissions/hw7.lean | 2fe2fb61969bc07ec71deba5cfd4a41b4f08229f | [] | no_license | jakekauff/CS2120F21 | 4f009adeb4ce4a148442b562196d66cc6c04530c | e69529ec6f5d47a554291c4241a3d8ec4fe8f5ad | refs/heads/main | 1,693,841,880,030 | 1,637,604,848,000 | 1,637,604,848,000 | 399,946,698 | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 11,138 | lean | import data.set
import tactic.ring
namespace relation
-- Jakob Kauffmann (jgk2qq); github: jakekauff13
-- Collaborated with: Jumi Hall (jah5py) &
-- Connor McCaffrey (cam7qp)
-- PRELIMINARY SETUP
/-
Preliminary set up. For the rest of this file,
we specify an arbitrary binary relation, r, on
an arbitrary type, β, as a two-place predicate,
with infix notation x ≺ y for (r x y). One can
pronounce these expressions in English as "x is
related to y".
-/
variables {α β : Type} (r : β → β → Prop)
local infix `≺` : 50 := r
/-
The default Lean libraries are missing definitions
for the assympetric property of relations and for
the notion of a powerset. We define these terms for
use in the rest of this file.
-/
def asymmetric := ∀ ⦃x y⦄, x ≺ y → ¬ y ≺ x
def powerset (s : set β) := { s' | s' ⊆ s}
-- PROBLEMS
/-
#1: Give both a formal and an English-language proof. Then
answer the question, is the proposition true if you remove
the first condition, that β is inhabited? Briefly explain
your answer (in English).
-/
example : (∃ (b : β), true) → asymmetric r → ¬reflexive r :=
begin
assume e,
assume a,
assume x,
unfold asymmetric at a,
unfold reflexive at x,
cases e with w pf,
have rww := x w,
have c := a rww,
contradiction,
end
-- English-Language Proof:
/-
Proof: Suppose β is inhabited and r is asymmetric.
We now show r is not reflexive. We will prove by
negation, assuming that r is reflexive and then
we will show that this assumption leads to a contradiction
from which we can conclude r is not reflexive.
To derive the contradiction, we first expand the
definitions of asymmetric and reflexive. We will
now show that the following assumptions contradict
one another:
β: Type
r: β → β → Prop
e: ∃ (b : β), true
a: ∀ ⦃x y : β⦄, r x y → ¬r y x
x: ∀ (x : β), r x x
To show this by exists elimination we first infer
that there is a an object, w : β, of which we
have a proof of existence. Applying reflexivity (x),
to w, we deduce w ≺ w (r w w). Next, by applying
asymmetry (a), to w ≺ w we derive w ⊀ w, thus deriving
the aforementioned contradiction.
QED.
-/
/-
#2. Logic, like programming, is subtle. It's very easy for humans
to miss subtle corner cases. As an example, today I ran across
a problem in a textbook by Paul Traiger, a professor emeritus
of philosophy and cognitive science at Occidental College. He
asks students to prove that if a relation is both transitive and
reflexive that it cannot be anti-symmetric. See the question at
the very bottom of the page here:
https://sites.oxy.edu/traiger/logic/exercises/chapter13/properties_of_relations_exercise.html
Is the conjecture actually logically valid? If not, what condition
needs to be added to make it so? Try prove this/his version of the
conjecture, as articulated slightly differently below. If you get
stuck, then you need to figure out an additional condition that needs
to be added as a premise to make the proposition true. In that case,
add the premise and then show that the updated conjecture is true.
-/
example : (∃ (b : β), true) → transitive r → reflexive r → ¬ asymmetric r :=
begin
assume h,
unfold transitive reflexive asymmetric,
assume t r a,
cases h with b True,
have b_refl := r b,
have b_not_refl := a b_refl,
contradiction,
end
/-
#3: Prove that the subset relation on the powerset of any
set, s, is antisymmetric. Formally state and prove, and
then give an informal proof of, this proposition.
-/
example : ∀ (s : set β)
(s1 s2 ∈ powerset s),
s1 ⊆ s2 →
s2 ⊆ s1 →
s1 = s2 :=
begin
assume s s1 s2 s1ins s2ins s1ins2 s2ins1,
apply set.ext,
assume x,
split,
assume xins1,
exact s1ins2 xins1,
assume xins2,
exact s2ins1 xins2,
end
/-
Proof: Suppose that s is a set of type β and that s1 and s2
are in the powerset of s. We will prove that s1 = s2, assuming
the following: s1 ⊆ s2 and s2 ⊆ s1.
First, we equate the equals sign to an if and only if statement
under set extensionality. By application of our assumptions
on one another, we derive that s1 = s2.
QED.
-/
/-
Given two natural numbers, n and m, we will say that m divides n
if there is a natural number, k, such that n = k*m. Here's a formal
definition of this relation.
-/
def divides (m n : ℕ) := ∃ k, n = k * m
/-
#4: Formally and informally state and prove each of the following
propositions. Remember that the ring tactic is useful for producing
proofs of simple algebraic equalities involving + and *. You can use
the phrase, "by basic algebra" when translating the use of this tactic
into English. (Or if you wanted to be truly Hobbit-like you could say
"by the ring axioms!")
-/
-- A: For any n, 1 divides n.
example : ∀ n, divides 1 n :=
begin
assume n,
unfold divides,
cases n with p,
apply exists.intro 0,
refl,
apply exists.intro p.succ,
have mulone := mul_one p.succ,
rw mulone,
end
/-
Proof: We provide a proof that for any n, 1 divides n. In order
to provide this proof, we first assume n of type ℕ. Next, we
expand the definition of divides. We will then perform case analysis on
n to prove that there exists a k such that n = k * 1.
Case analysis yields two cases which we will prove, thus proving that
1 divides n. The first case is that in which n = 0. After application of
the exists introduction rule with the value 0, we now prove by simple algebra
that 0 = 0 * 1. The second case is that is which n > 0. Similarly, we show that
there exists a k such that n = k * 1, and that k is again equal to n.
QED.
-/
-- B. For any n, n divides n
example : ∀ n, divides n n :=
begin
assume n,
unfold divides,
apply exists.intro 1,
have mulone := one_mul n,
rw mulone,
end
/-
Proof: We provide a proof that for any n, n divides n. We first assume
n is of type ℕ, then we expand the definition of divides. After applying
the exists introduction rule with a value of 1, we must prove that
n = 1 * n, which is done by simple algebra.
QED.
-/
-- #C. prove that divides is reflexive
example : reflexive divides :=
begin
unfold reflexive divides,
assume n,
apply exists.intro 1,
have mulone := (one_mul n),
rw mulone,
end
/-
Proof: We will provide a proof that divides is reflexive. We first assume
n is of type ℕ, and then we expand the definition of divides and reflexive. After applying
the exists introduction rule with a value of 1, we must prove that
n = 1 * n, which is done by simple algebra.
-/
-- #D. prove that divides is transitive
example : transitive divides :=
begin
unfold transitive divides,
assume a b c,
assume ab bc,
cases ab with a1 p1,
cases bc with a2 p2,
apply exists.intro(a2*a1),
rw p2,
rw p1,
have mulassoc := mul_assoc a2 a1 a,
rw mulassoc,
end
/-
Proof: We will provide a proof that divides is transitive. We first expand
the definition of transitive and divides. We will then make the following
assumptions:
a b c : ℕ
ab : ∃ (k : ℕ), b = k * a
bc : ∃ (k : ℕ), c = k * b
Under these assumptions, we will prove that there exists a k such that
c = k * a, showing that divides is transitive. We begin by performing case
analysis on both ab and bc, yielding the following assumptions:
a b c a1 a2 : ℕ
p1 : b = a1 * a
p2 : c = a2 * b
We will use these assumptions to rewrite the final proposition c = k * a
to now be a2 * a1 * a = a2 * a1 * a. We do this by applying the exists
introduction rule for the value a2 * a1, converting the proposition into
c = a2 * a1 * a. Next, we have the proofs that c = a2 * b and b = a1 * a.
Using these, we can rewrite the final proposition as a2 * a1 * a = a2 * a1 * a,
which is true by reflexivity of equality.
QED.
-/
/-
E. Is divides symmetric? if yes, give a proof, otherwise
give a counterexample and a brief explanation to show that
it's not.
-/
example: symmetric divides :=
begin
end
-- Divides is NOT symmetric, as shown by the cases where 2 divides 4
-- (k = 2, which is a natural number), but 4 does not divide 2
-- (k = 1/2, which is not a natural number).
-- In order for a relation to be symmetric, the relation
-- must hold between the two values in both directions. However, with divides,
-- a natural number does not exist such that a number divides a larger number,
-- and that larger number divides the smaller number.
/-
#F. Prove that divides is antisymmetric.
-/
example : anti_symmetric divides :=
begin
unfold anti_symmetric divides,
assume x y xy yx,
apply exists.elim xy,
apply exists.elim yx,
assume a b c d,
rw b,
have : a = 1 := sorry,
rw this,
have mulone := one_mul y,
exact mulone,
end
/-
Proof: We will prove that divides is antisymmetric. First, we expand the
definitions of antisymmetric and divides. Then we perform case analysis on our
assumed exists statements, leaving us to rewrite the cases. It is obvious that the
value of a must be 1 by simple deduction from already present proofs, leaving us
again to simply rewrite our goal, giving us a new goal that 1 * y = y, which is
true by simple algebra.
QED.
-/
/- #5
Prove the following propositions. Remember that
throughout this file, each definition implicitly
includes β as a type and r as an arbitrary binary
relation on β. In addition to formal proofs, give
an English language proof of the last of the three
problems.
-/
-- A
example : asymmetric r → irreflexive r :=
begin
assume h x k,
have nk := h k,
contradiction,
end
/-
Proof: We will provide a proof that a relation is irreflexive, given
that the relation is asymmetric, by negation. We do this by assuming that
r x x is true and showing that ¬ r x x is true by applying the proof that
the relation is asymmetric to r x x, thus deriving a contradiction.
QED.
-/
-- B
example : irreflexive r → transitive r → asymmetric r :=
begin
unfold irreflexive transitive,
assume i t x y,
assume rxy,
assume nryx,
have f := t rxy nryx,
have nrxx := i x,
contradiction,
end
/-
Proof: We will provide a proof by negation that a relation is asymmetric,
given that the relation is irreflexive and transitive. We first expand the
definitions of irreflexive and transitive. Then we make the assumptions that
the relation r is irreflexive and transitive. Next, we assume r x y and ¬ r y x.
After this, we apply transitive to r x y and ¬ r y x to derive a proof of r x x.
Finally, we show a contradiction by applying irreflexive to x, which gives us ¬ r x x.
QED.
-/
-- C
example : transitive r → ¬ symmetric r → ¬ irreflexive r :=
begin
unfold transitive symmetric irreflexive,
assume trans symm irrefl,
end
/-
We do not believe that the proposition is provable or fixable. We tried to
add that β is inhabited, but this effort was futile. We were unable
to find a counter-example of a relation that shows the invalidity
of the proposition.
-/
end relation
|
1920c4de2eba0c24f88a9bed36d4555afdec1856 | cf39355caa609c0f33405126beee2739aa3cb77e | /tests/lean/run/coe_univ_bug.lean | bd2a219d406fe7af17b2b15be7e000e50a6d249b | [
"Apache-2.0"
] | permissive | leanprover-community/lean | 12b87f69d92e614daea8bcc9d4de9a9ace089d0e | cce7990ea86a78bdb383e38ed7f9b5ba93c60ce0 | refs/heads/master | 1,687,508,156,644 | 1,684,951,104,000 | 1,684,951,104,000 | 169,960,991 | 457 | 107 | Apache-2.0 | 1,686,744,372,000 | 1,549,790,268,000 | C++ | UTF-8 | Lean | false | false | 425 | lean | open nat
def below (n : nat) : nat → Prop :=
λ i, i < n
def f {n : nat} (v : subtype (below n)) : nat :=
v + 1
universe variable u
instance pred2subtype {A : Type u} : has_coe_to_sort (A → Prop) _ :=
⟨(λ p : A → Prop, subtype p)⟩
instance coesubtype {A : Type u} {p : A → Prop} : has_coe (@coe_sort _ _ pred2subtype p) A :=
⟨λ s, subtype.val s⟩
def g {n : nat} (v : below n) : nat :=
v + 1
#print g
|
d57a7b65f94690dc7f089f622a1aefbd59db81ed | e61a235b8468b03aee0120bf26ec615c045005d2 | /stage0/src/Init/Lean/Parser/Tactic.lean | 1f377b7e5584ed44ecf7faf61adb19589b0e6c36 | [
"Apache-2.0"
] | permissive | SCKelemen/lean4 | 140dc63a80539f7c61c8e43e1c174d8500ec3230 | e10507e6615ddbef73d67b0b6c7f1e4cecdd82bc | refs/heads/master | 1,660,973,595,917 | 1,590,278,033,000 | 1,590,278,033,000 | null | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 3,397 | lean | /-
Copyright (c) 2020 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Leonardo de Moura, Sebastian Ullrich
-/
prelude
import Init.Lean.Parser.Term
namespace Lean
namespace Parser
namespace Tactic
def underscoreFn : ParserFn :=
fun c s =>
let s := symbolFn "_" c s;
let stx := s.stxStack.back;
let s := s.popSyntax;
s.pushSyntax $ mkIdentFrom stx `_
@[inline] def underscore : Parser :=
{ fn := underscoreFn,
info := mkAtomicInfo "ident" }
def ident' : Parser := ident <|> underscore
@[builtinTacticParser] def «intro» := parser! nonReservedSymbol "intro " >> optional ident'
@[builtinTacticParser] def «intros» := parser! nonReservedSymbol "intros " >> many ident'
@[builtinTacticParser] def «revert» := parser! nonReservedSymbol "revert " >> many1 ident
@[builtinTacticParser] def «clear» := parser! nonReservedSymbol "clear " >> many1 ident
@[builtinTacticParser] def «subst» := parser! nonReservedSymbol "subst " >> many1 ident
@[builtinTacticParser] def «assumption» := parser! nonReservedSymbol "assumption"
@[builtinTacticParser] def «apply» := parser! nonReservedSymbol "apply " >> termParser
@[builtinTacticParser] def «exact» := parser! nonReservedSymbol "exact " >> termParser
@[builtinTacticParser] def «refine» := parser! nonReservedSymbol "refine " >> termParser
@[builtinTacticParser] def «case» := parser! nonReservedSymbol "case " >> ident >> tacticParser
@[builtinTacticParser] def «allGoals» := parser! nonReservedSymbol "allGoals " >> tacticParser
@[builtinTacticParser] def «skip» := parser! nonReservedSymbol "skip"
@[builtinTacticParser] def «traceState» := parser! nonReservedSymbol "traceState"
@[builtinTacticParser] def «failIfSuccess» := parser! nonReservedSymbol "failIfSuccess " >> tacticParser
@[builtinTacticParser] def «generalize» := parser! nonReservedSymbol "generalize" >> optional (try (ident >> " : ")) >> termParser 50 >> " = " >> ident
def majorPremise := parser! optional (try (ident >> " : ")) >> termParser
def inductionAlt : Parser := nodeWithAntiquot "inductionAlt" `Lean.Parser.Tactic.inductionAlt $ ident' >> many ident' >> darrow >> (Term.hole <|> Term.namedHole <|> tacticParser)
def inductionAlts : Parser := withPosition $ fun pos => "|" >> sepBy1 inductionAlt (checkColGe pos.column "alternatives must be indented" >> "|")
def withAlts : Parser := optional (" with " >> inductionAlts)
def usingRec : Parser := optional (" using " >> ident)
def generalizingVars := optional (" generalizing " >> many1 ident)
@[builtinTacticParser] def «induction» := parser! nonReservedSymbol "induction " >> majorPremise >> usingRec >> generalizingVars >> withAlts
@[builtinTacticParser] def «cases» := parser! nonReservedSymbol "cases " >> majorPremise >> withAlts
def withIds : Parser := optional (" with " >> many1 ident')
@[builtinTacticParser] def «injection» := parser! nonReservedSymbol "injection " >> termParser >> withIds
@[builtinTacticParser] def paren := parser! "(" >> nonEmptySeq >> ")"
@[builtinTacticParser] def nestedTacticBlock := parser! "begin " >> seq >> "end"
@[builtinTacticParser] def nestedTacticBlockCurly := parser! "{" >> seq >> "}"
@[builtinTacticParser] def orelse := tparser! " <|> " >> tacticParser 1
end Tactic
end Parser
end Lean
|
a3bf8a4287c8cd131921fa5e2fbb70b07247acba | f1b175e38ffc5cc1c7c5551a72d0dbaf70786f83 | /analysis/topology/uniform_space.lean | 4f2e00da544166ce956aed70716d580de6c51b66 | [
"Apache-2.0"
] | permissive | mjendrusch/mathlib | df3ae884dd5ce38c7edf452bcbfd3baf4e3a6214 | 5c209edb7eb616a26f64efe3500f2b1ba95b8d55 | refs/heads/master | 1,585,663,284,800 | 1,539,062,055,000 | 1,539,062,055,000 | null | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 85,522 | lean | /-
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
Theory of uniform spaces.
Uniform spaces are a generalization of metric spaces and topological groups. Many concepts directly
generalize to uniform spaces, e.g.
* completeness
* completion (on Cauchy filters instead of Cauchy sequences)
* extension of uniform continuous functions to complete spaces
* uniform contiunuity & embedding
* totally bounded
* totally bounded ∧ complete → compact
One reason to directly formalize uniform spaces is foundational: we define ℝ as a completion of ℚ.
The central concept of uniform spaces is its uniformity: a filter relating two elements of the
space. This filter is reflexive, symmetric and transitive. So a set (i.e. a relation) in this filter
represents a 'distance': it is reflexive, symmetric and the uniformity contains a set for which the
`triangular` rule holds.
The formalization is mostly based on the books:
N. Bourbaki: General Topology
I. M. James: Topologies and Uniformities
A major difference is that this formalization is heavily based on the filter library.
-/
import order.filter data.quot analysis.topology.topological_space analysis.topology.continuity
open set lattice filter classical
local attribute [instance] prop_decidable
set_option eqn_compiler.zeta true
universes u
section
variables {α : Type*} {β : Type*} {γ : Type*} {δ : Type*} {ι : Sort*}
/-- The identity relation, or the graph of the identity function -/
def id_rel {α : Type*} := {p : α × α | p.1 = p.2}
@[simp] theorem mem_id_rel {a b : α} : (a, b) ∈ @id_rel α ↔ a = b := iff.rfl
@[simp] theorem id_rel_subset {s : set (α × α)} : id_rel ⊆ s ↔ ∀ a, (a, a) ∈ s :=
by simp only [subset_def, prod.forall, mem_id_rel]; exact forall_congr (λ _, forall_eq')
/-- The composition of relations -/
def comp_rel {α : Type u} (r₁ r₂ : set (α×α)) := {p : α × α | ∃z:α, (p.1, z) ∈ r₁ ∧ (z, p.2) ∈ r₂}
@[simp] theorem mem_comp_rel {r₁ r₂ : set (α×α)}
{x y : α} : (x, y) ∈ comp_rel r₁ r₂ ↔ ∃ z, (x, z) ∈ r₁ ∧ (z, y) ∈ r₂ := iff.rfl
@[simp] theorem swap_id_rel : prod.swap '' id_rel = @id_rel α :=
set.ext $ assume ⟨a, b⟩, by rw [image_swap_eq_preimage_swap]; exact eq_comm
theorem monotone_comp_rel [preorder β] {f g : β → set (α×α)}
(hf : monotone f) (hg : monotone g) : monotone (λx, comp_rel (f x) (g x)) :=
assume a b h p ⟨z, h₁, h₂⟩, ⟨z, hf h h₁, hg h h₂⟩
lemma prod_mk_mem_comp_rel {a b c : α} {s t : set (α×α)} (h₁ : (a, c) ∈ s) (h₂ : (c, b) ∈ t) :
(a, b) ∈ comp_rel s t :=
⟨c, h₁, h₂⟩
@[simp] lemma id_comp_rel {r : set (α×α)} : comp_rel id_rel r = r :=
set.ext $ assume ⟨a, b⟩, by simp only [mem_comp_rel, mem_id_rel, exists_eq_left']
lemma comp_rel_assoc {r s t : set (α×α)} :
comp_rel (comp_rel r s) t = comp_rel r (comp_rel s t) :=
by ext p; cases p; simp only [mem_comp_rel]; tauto
/-- This core description of a uniform space is outside of the type class hierarchy. It is useful
for constructions of uniform spaces, when the topology is derived from the uniform space. -/
structure uniform_space.core (α : Type u) :=
(uniformity : filter (α × α))
(refl : principal id_rel ≤ uniformity)
(symm : tendsto prod.swap uniformity uniformity)
(comp : uniformity.lift' (λs, comp_rel s s) ≤ uniformity)
def uniform_space.core.mk' {α : Type u} (U : filter (α × α))
(refl : ∀ (r ∈ U.sets) x, (x, x) ∈ r)
(symm : ∀ r ∈ U.sets, {p | prod.swap p ∈ r} ∈ U.sets)
(comp : ∀ r ∈ U.sets, ∃ t ∈ U.sets, comp_rel t t ⊆ r) : uniform_space.core α :=
⟨U, λ r ru, id_rel_subset.2 (refl _ ru), symm,
begin
intros r ru,
rw [mem_lift'_sets],
exact comp _ ru,
apply monotone_comp_rel; exact monotone_id,
end⟩
/-- A uniform space generates a topological space -/
def uniform_space.core.to_topological_space {α : Type u} (u : uniform_space.core α) :
topological_space α :=
{ is_open := λs, ∀x∈s, { p : α × α | p.1 = x → p.2 ∈ s } ∈ u.uniformity.sets,
is_open_univ := λ _ _, by simp only [set.mem_univ, forall_true_iff]; exact univ_mem_sets,
is_open_inter :=
assume s t hs ht x ⟨xs, xt⟩, by filter_upwards [hs x xs, ht x xt] assume ⟨a, b⟩ ih1 ih2 h, ⟨ih1 h, ih2 h⟩,
is_open_sUnion :=
assume s hs x ⟨t, ts, xt⟩, by filter_upwards [hs t ts x xt] assume p ph h, ⟨t, ts, ph h⟩ }
lemma uniform_space.core_eq : ∀{u₁ u₂ : uniform_space.core α}, u₁.uniformity = u₂.uniformity → u₁ = u₂
| ⟨u₁, _, _, _⟩ ⟨u₂, _, _, _⟩ rfl := rfl
/-- A uniform space is a generalization of the "uniform" topological aspects of a
metric space. It consists of a filter on `α × α` called the "uniformity", which
satisfies properties analogous to the reflexivity, symmetry, and triangle properties
of a metric.
A metric space has a natural uniformity, and a uniform space has a natural topology.
A topological group also has a natural uniformity, even when it is not metrizable. -/
class uniform_space (α : Type u) extends topological_space α, uniform_space.core α :=
(is_open_uniformity : ∀s, is_open s ↔ (∀x∈s, { p : α × α | p.1 = x → p.2 ∈ s } ∈ uniformity.sets))
@[pattern] def uniform_space.mk' {α} (t : topological_space α)
(c : uniform_space.core α)
(is_open_uniformity : ∀s:set α, t.is_open s ↔
(∀x∈s, { p : α × α | p.1 = x → p.2 ∈ s } ∈ c.uniformity.sets)) :
uniform_space α := ⟨c, is_open_uniformity⟩
def uniform_space.of_core {α : Type u} (u : uniform_space.core α) : uniform_space α :=
{ to_core := u,
to_topological_space := u.to_topological_space,
is_open_uniformity := assume a, iff.refl _ }
def uniform_space.of_core_eq {α : Type u} (u : uniform_space.core α) (t : topological_space α)
(h : t = u.to_topological_space) : uniform_space α :=
{ to_core := u,
to_topological_space := t,
is_open_uniformity := assume a, h.symm ▸ iff.refl _ }
lemma uniform_space.to_core_to_topological_space (u : uniform_space α) :
u.to_core.to_topological_space = u.to_topological_space :=
topological_space_eq $ funext $ assume s,
by rw [uniform_space.core.to_topological_space, uniform_space.is_open_uniformity]
@[extensionality]
lemma uniform_space_eq : ∀{u₁ u₂ : uniform_space α}, u₁.uniformity = u₂.uniformity → u₁ = u₂
| (uniform_space.mk' t₁ u₁ o₁) (uniform_space.mk' t₂ u₂ o₂) h :=
have hu : u₁ = u₂, from uniform_space.core_eq h,
have ht : t₁ = t₂, from topological_space_eq $ funext $ assume s, by rw [o₁, o₂, hu],
by substs hu ht
lemma uniform_space.of_core_eq_to_core
(u : uniform_space α) (t : topological_space α) (h : t = u.to_core.to_topological_space) :
uniform_space.of_core_eq u.to_core t h = u :=
uniform_space_eq rfl
section uniform_space
variables [uniform_space α]
/-- The uniformity is a filter on α × α (inferred from an ambient uniform space
structure on α). -/
def uniformity : filter (α × α) := (@uniform_space.to_core α _).uniformity
lemma is_open_uniformity {s : set α} :
is_open s ↔ (∀x∈s, { p : α × α | p.1 = x → p.2 ∈ s } ∈ (@uniformity α _).sets) :=
uniform_space.is_open_uniformity s
lemma refl_le_uniformity : principal id_rel ≤ @uniformity α _ :=
(@uniform_space.to_core α _).refl
lemma refl_mem_uniformity {x : α} {s : set (α × α)} (h : s ∈ (@uniformity α _).sets) :
(x, x) ∈ s :=
refl_le_uniformity h rfl
lemma symm_le_uniformity : map (@prod.swap α α) uniformity ≤ uniformity :=
(@uniform_space.to_core α _).symm
lemma comp_le_uniformity : uniformity.lift' (λs:set (α×α), comp_rel s s) ≤ uniformity :=
(@uniform_space.to_core α _).comp
lemma tendsto_swap_uniformity : tendsto prod.swap (@uniformity α _) uniformity :=
symm_le_uniformity
lemma tendsto_const_uniformity {a : α} {f : filter β} : tendsto (λ_, (a, a)) f uniformity :=
assume s hs,
show {x | (a, a) ∈ s} ∈ f.sets,
from univ_mem_sets' $ assume b, refl_mem_uniformity hs
lemma comp_mem_uniformity_sets {s : set (α × α)} (hs : s ∈ (@uniformity α _).sets) :
∃t∈(@uniformity α _).sets, comp_rel t t ⊆ s :=
have s ∈ (uniformity.lift' (λt:set (α×α), comp_rel t t)).sets,
from comp_le_uniformity hs,
(mem_lift'_sets $ monotone_comp_rel monotone_id monotone_id).mp this
lemma symm_of_uniformity {s : set (α × α)} (hs : s ∈ (@uniformity α _).sets) :
∃t∈(@uniformity α _).sets, (∀a b, (a, b) ∈ t → (b, a) ∈ t) ∧ t ⊆ s :=
have preimage prod.swap s ∈ (@uniformity α _).sets, from symm_le_uniformity hs,
⟨s ∩ preimage prod.swap s, inter_mem_sets hs this, assume a b ⟨h₁, h₂⟩, ⟨h₂, h₁⟩, inter_subset_left _ _⟩
lemma comp_symm_of_uniformity {s : set (α × α)} (hs : s ∈ (@uniformity α _).sets) :
∃t∈(@uniformity α _).sets, (∀{a b}, (a, b) ∈ t → (b, a) ∈ t) ∧ comp_rel t t ⊆ s :=
let ⟨t, ht₁, ht₂⟩ := comp_mem_uniformity_sets hs in
let ⟨t', ht', ht'₁, ht'₂⟩ := symm_of_uniformity ht₁ in
⟨t', ht', ht'₁, subset.trans (monotone_comp_rel monotone_id monotone_id ht'₂) ht₂⟩
lemma uniformity_le_symm : uniformity ≤ (@prod.swap α α) <$> uniformity :=
by rw [map_swap_eq_comap_swap];
from map_le_iff_le_comap.1 tendsto_swap_uniformity
lemma uniformity_eq_symm : uniformity = (@prod.swap α α) <$> uniformity :=
le_antisymm uniformity_le_symm symm_le_uniformity
theorem uniformity_lift_le_swap {g : set (α×α) → filter β} {f : filter β} (hg : monotone g)
(h : uniformity.lift (λs, g (preimage prod.swap s)) ≤ f) : uniformity.lift g ≤ f :=
calc uniformity.lift g ≤ (filter.map prod.swap (@uniformity α _)).lift g :
lift_mono uniformity_le_symm (le_refl _)
... ≤ _ :
by rw [map_lift_eq2 hg, image_swap_eq_preimage_swap]; exact h
lemma uniformity_lift_le_comp {f : set (α×α) → filter β} (h : monotone f):
uniformity.lift (λs, f (comp_rel s s)) ≤ uniformity.lift f :=
calc uniformity.lift (λs, f (comp_rel s s)) =
(uniformity.lift' (λs:set (α×α), comp_rel s s)).lift f :
begin
rw [lift_lift'_assoc],
exact monotone_comp_rel monotone_id monotone_id,
exact h
end
... ≤ uniformity.lift f : lift_mono comp_le_uniformity (le_refl _)
lemma comp_le_uniformity3 :
uniformity.lift' (λs:set (α×α), comp_rel s (comp_rel s s)) ≤ uniformity :=
calc uniformity.lift' (λd, comp_rel d (comp_rel d d)) =
uniformity.lift (λs, uniformity.lift' (λt:set(α×α), comp_rel s (comp_rel t t))) :
begin
rw [lift_lift'_same_eq_lift'],
exact (assume x, monotone_comp_rel monotone_const $ monotone_comp_rel monotone_id monotone_id),
exact (assume x, monotone_comp_rel monotone_id monotone_const),
end
... ≤ uniformity.lift (λs, uniformity.lift' (λt:set(α×α), comp_rel s t)) :
lift_mono' $ assume s hs, @uniformity_lift_le_comp α _ _ (principal ∘ comp_rel s) $
monotone_comp (monotone_comp_rel monotone_const monotone_id) monotone_principal
... = uniformity.lift' (λs:set(α×α), comp_rel s s) :
lift_lift'_same_eq_lift'
(assume s, monotone_comp_rel monotone_const monotone_id)
(assume s, monotone_comp_rel monotone_id monotone_const)
... ≤ uniformity : comp_le_uniformity
lemma mem_nhds_uniformity_iff {x : α} {s : set α} :
(s ∈ (nhds x).sets) ↔ ({p : α × α | p.1 = x → p.2 ∈ s} ∈ (@uniformity α _).sets) :=
⟨ begin
simp only [mem_nhds_sets_iff, is_open_uniformity],
rintro ⟨t, ts, ht, xt⟩, filter_upwards [ht x xt] assume ⟨x', y⟩ h eq, ts $ h eq
end,
assume hs,
mem_nhds_sets_iff.mpr ⟨{x | {p : α × α | p.1 = x → p.2 ∈ s} ∈ (@uniformity α _).sets},
assume x' hx', refl_mem_uniformity hx' rfl,
is_open_uniformity.mpr $ assume x' hx',
let ⟨t, ht, tr⟩ := comp_mem_uniformity_sets hx' in
by filter_upwards [ht] assume ⟨a, b⟩ hp' (hax' : a = x'),
by filter_upwards [ht] assume ⟨a, b'⟩ hp'' (hab : a = b),
have hp : (x', b) ∈ t, from hax' ▸ hp',
have (b, b') ∈ t, from hab ▸ hp'',
have (x', b') ∈ comp_rel t t, from ⟨b, hp, this⟩,
show b' ∈ s,
from tr this rfl,
hs⟩⟩
lemma nhds_eq_comap_uniformity {x : α} : nhds x = uniformity.comap (prod.mk x) :=
by ext s; rw [mem_nhds_uniformity_iff, mem_comap_sets]; from iff.intro
(assume hs, ⟨_, hs, assume x hx, hx rfl⟩)
(assume ⟨t, h, ht⟩, uniformity.sets_of_superset h $
assume ⟨p₁, p₂⟩ hp (h : p₁ = x), ht $ by rwa h at hp)
lemma nhds_eq_uniformity {x : α} : nhds x = uniformity.lift' (λs:set (α×α), {y | (x, y) ∈ s}) :=
begin
ext s,
rw [mem_lift'_sets], tactic.swap, apply monotone_preimage,
rw [mem_nhds_uniformity_iff],
exact ⟨assume h, ⟨_, h, assume y h, h rfl⟩,
assume ⟨t, h₁, h₂⟩,
uniformity.sets_of_superset h₁ $
assume ⟨x', y⟩ hp (eq : x' = x), h₂ $
show (x, y) ∈ t, from eq ▸ hp⟩
end
lemma mem_nhds_left (x : α) {s : set (α×α)} (h : s ∈ (uniformity.sets : set (set (α×α)))) :
{y : α | (x, y) ∈ s} ∈ (nhds x).sets :=
have nhds x ≤ principal {y : α | (x, y) ∈ s},
by rw [nhds_eq_uniformity]; exact infi_le_of_le s (infi_le _ h),
le_principal_iff.1 this
lemma mem_nhds_right (y : α) {s : set (α×α)} (h : s ∈ (uniformity.sets : set (set (α×α)))) :
{x : α | (x, y) ∈ s} ∈ (nhds y).sets :=
mem_nhds_left _ (symm_le_uniformity h)
lemma tendsto_right_nhds_uniformity {a : α} : tendsto (λa', (a', a)) (nhds a) uniformity :=
assume s, mem_nhds_right a
lemma tendsto_left_nhds_uniformity {a : α} : tendsto (λa', (a, a')) (nhds a) uniformity :=
assume s, mem_nhds_left a
lemma lift_nhds_left {x : α} {g : set α → filter β} (hg : monotone g) :
(nhds x).lift g = uniformity.lift (λs:set (α×α), g {y | (x, y) ∈ s}) :=
eq.trans
begin
rw [nhds_eq_uniformity],
exact (filter.lift_assoc $ monotone_comp monotone_preimage $ monotone_comp monotone_preimage monotone_principal)
end
(congr_arg _ $ funext $ assume s, filter.lift_principal hg)
lemma lift_nhds_right {x : α} {g : set α → filter β} (hg : monotone g) :
(nhds x).lift g = uniformity.lift (λs:set (α×α), g {y | (y, x) ∈ s}) :=
calc (nhds x).lift g = uniformity.lift (λs:set (α×α), g {y | (x, y) ∈ s}) : lift_nhds_left hg
... = ((@prod.swap α α) <$> uniformity).lift (λs:set (α×α), g {y | (x, y) ∈ s}) : by rw [←uniformity_eq_symm]
... = uniformity.lift (λs:set (α×α), g {y | (x, y) ∈ image prod.swap s}) :
map_lift_eq2 $ monotone_comp monotone_preimage hg
... = _ : by rw [image_swap_eq_preimage_swap]; refl
lemma nhds_nhds_eq_uniformity_uniformity_prod {a b : α} :
filter.prod (nhds a) (nhds b) =
uniformity.lift (λs:set (α×α), uniformity.lift' (λt:set (α×α),
set.prod {y : α | (y, a) ∈ s} {y : α | (b, y) ∈ t})) :=
begin
rw [prod_def],
show (nhds a).lift (λs:set α, (nhds b).lift (λt:set α, principal (set.prod s t))) = _,
rw [lift_nhds_right],
apply congr_arg, funext s,
rw [lift_nhds_left],
refl,
exact monotone_comp (monotone_prod monotone_const monotone_id) monotone_principal,
exact (monotone_lift' monotone_const $ monotone_lam $
assume x, monotone_prod monotone_id monotone_const)
end
lemma nhds_eq_uniformity_prod {a b : α} :
nhds (a, b) =
uniformity.lift' (λs:set (α×α), set.prod {y : α | (y, a) ∈ s} {y : α | (b, y) ∈ s}) :=
begin
rw [nhds_prod_eq, nhds_nhds_eq_uniformity_uniformity_prod, lift_lift'_same_eq_lift'],
{ intro s, exact monotone_prod monotone_const monotone_preimage },
{ intro t, exact monotone_prod monotone_preimage monotone_const }
end
lemma nhdset_of_mem_uniformity {d : set (α×α)} (s : set (α×α)) (hd : d ∈ (@uniformity α _).sets) :
∃(t : set (α×α)), is_open t ∧ s ⊆ t ∧ t ⊆ {p | ∃x y, (p.1, x) ∈ d ∧ (x, y) ∈ s ∧ (y, p.2) ∈ d} :=
let cl_d := {p:α×α | ∃x y, (p.1, x) ∈ d ∧ (x, y) ∈ s ∧ (y, p.2) ∈ d} in
have ∀p ∈ s, ∃t ⊆ cl_d, is_open t ∧ p ∈ t, from
assume ⟨x, y⟩ hp, mem_nhds_sets_iff.mp $
show cl_d ∈ (nhds (x, y)).sets,
begin
rw [nhds_eq_uniformity_prod, mem_lift'_sets],
exact ⟨d, hd, assume ⟨a, b⟩ ⟨ha, hb⟩, ⟨x, y, ha, hp, hb⟩⟩,
exact monotone_prod monotone_preimage monotone_preimage
end,
have ∃t:(Π(p:α×α) (h:p ∈ s), set (α×α)),
∀p, ∀h:p ∈ s, t p h ⊆ cl_d ∧ is_open (t p h) ∧ p ∈ t p h,
by simpa only [exists_prop, classical.skolem] using this,
match this with
| ⟨t, ht⟩ :=
⟨(⋃ p:α×α, ⋃ h : p ∈ s, t p h : set (α×α)),
is_open_Union $ assume (p:α×α), is_open_Union $ assume hp, (ht p hp).right.left,
assume ⟨a, b⟩ hp, begin simp only [mem_Union]; exact ⟨(a, b), hp, (ht (a,b) hp).right.right⟩ end,
Union_subset $ assume p, Union_subset $ assume hp, (ht p hp).left⟩
end
lemma closure_eq_inter_uniformity {t : set (α×α)} :
closure t = (⋂ d∈(@uniformity α _).sets, comp_rel d (comp_rel t d)) :=
set.ext $ assume ⟨a, b⟩,
calc (a, b) ∈ closure t ↔ (nhds (a, b) ⊓ principal t ≠ ⊥) : by rw [closure_eq_nhds]; refl
... ↔ (((@prod.swap α α) <$> uniformity).lift'
(λ (s : set (α × α)), set.prod {x : α | (x, a) ∈ s} {y : α | (b, y) ∈ s}) ⊓ principal t ≠ ⊥) :
by rw [←uniformity_eq_symm, nhds_eq_uniformity_prod]
... ↔ ((map (@prod.swap α α) uniformity).lift'
(λ (s : set (α × α)), set.prod {x : α | (x, a) ∈ s} {y : α | (b, y) ∈ s}) ⊓ principal t ≠ ⊥) :
by refl
... ↔ (uniformity.lift'
(λ (s : set (α × α)), set.prod {y : α | (a, y) ∈ s} {x : α | (x, b) ∈ s}) ⊓ principal t ≠ ⊥) :
begin
rw [map_lift'_eq2],
simp only [image_swap_eq_preimage_swap]; refl,
exact monotone_prod monotone_preimage monotone_preimage
end
... ↔ (∀s∈(@uniformity α _).sets, ∃x, x ∈ set.prod {y : α | (a, y) ∈ s} {x : α | (x, b) ∈ s} ∩ t) :
begin
rw [lift'_inf_principal_eq, lift'_neq_bot_iff],
apply forall_congr, intro s, rw [ne_empty_iff_exists_mem],
exact monotone_inter (monotone_prod monotone_preimage monotone_preimage) monotone_const
end
... ↔ (∀s∈(@uniformity α _).sets, (a, b) ∈ comp_rel s (comp_rel t s)) :
forall_congr $ assume s, forall_congr $ assume hs,
⟨assume ⟨⟨x, y⟩, ⟨⟨hx, hy⟩, hxyt⟩⟩, ⟨x, hx, y, hxyt, hy⟩,
assume ⟨x, hx, y, hxyt, hy⟩, ⟨⟨x, y⟩, ⟨⟨hx, hy⟩, hxyt⟩⟩⟩
... ↔ _ : by simp only [mem_bInter_iff]
lemma uniformity_eq_uniformity_closure : (@uniformity α _) = uniformity.lift' closure :=
le_antisymm
(le_infi $ assume s, le_infi $ assume hs, le_principal_iff.2 $ by filter_upwards [hs] subset_closure)
(calc uniformity.lift' closure ≤ uniformity.lift' (λd, comp_rel d (comp_rel d d)) :
lift'_mono' (by intros s hs; rw [closure_eq_inter_uniformity]; exact bInter_subset_of_mem hs)
... ≤ uniformity : comp_le_uniformity3)
lemma uniformity_eq_uniformity_interior : (@uniformity α _) = uniformity.lift' interior :=
le_antisymm
(le_infi $ assume d, le_infi $ assume hd,
let ⟨s, hs, hs_comp⟩ := (mem_lift'_sets $
monotone_comp_rel monotone_id $ monotone_comp_rel monotone_id monotone_id).mp (comp_le_uniformity3 hd) in
let ⟨t, ht, hst, ht_comp⟩ := nhdset_of_mem_uniformity s hs in
have s ⊆ interior d, from
calc s ⊆ t : hst
... ⊆ interior d : (subset_interior_iff_subset_of_open ht).mpr $
assume x, assume : x ∈ t, let ⟨x, y, h₁, h₂, h₃⟩ := ht_comp this in hs_comp ⟨x, h₁, y, h₂, h₃⟩,
have interior d ∈ (@uniformity α _).sets, by filter_upwards [hs] this,
le_principal_iff.2 this)
(assume s hs, (uniformity.lift' interior).sets_of_superset (mem_lift' hs) interior_subset)
lemma interior_mem_uniformity {s : set (α × α)} (hs : s ∈ (@uniformity α _).sets) :
interior s ∈ (@uniformity α _).sets :=
by rw [uniformity_eq_uniformity_interior]; exact mem_lift' hs
lemma mem_uniformity_is_closed [uniform_space α] {s : set (α×α)} (h : s ∈ (@uniformity α _).sets) :
∃t∈(@uniformity α _).sets, is_closed t ∧ t ⊆ s :=
have s ∈ ((@uniformity α _).lift' closure).sets, by rwa [uniformity_eq_uniformity_closure] at h,
have ∃t∈(@uniformity α _).sets, closure t ⊆ s,
by rwa [mem_lift'_sets] at this; apply closure_mono,
let ⟨t, ht, hst⟩ := this in
⟨closure t, uniformity.sets_of_superset ht subset_closure, is_closed_closure, hst⟩
/- uniform continuity -/
def uniform_continuous [uniform_space β] (f : α → β) :=
tendsto (λx:α×α, (f x.1, f x.2)) uniformity uniformity
theorem uniform_continuous_def [uniform_space β] {f : α → β} :
uniform_continuous f ↔ ∀ r ∈ (@uniformity β _).sets,
{x : α × α | (f x.1, f x.2) ∈ r} ∈ (@uniformity α _).sets :=
iff.rfl
lemma uniform_continuous_id : uniform_continuous (@id α) :=
show tendsto (λ x:α×α, (x.1, x.2)) _ _, by simp only [prod.mk.eta]; exact tendsto_id
lemma uniform_continuous_const [uniform_space β] {b : β} : uniform_continuous (λa:α, b) :=
@tendsto_const_uniformity _ _ _ b uniformity
lemma uniform_continuous.comp [uniform_space β] [uniform_space γ] {f : α → β} {g : β → γ}
(hf : uniform_continuous f) (hg : uniform_continuous g) : uniform_continuous (g ∘ f) :=
hf.comp hg
def uniform_embedding [uniform_space β] (f : α → β) :=
function.injective f ∧
comap (λx:α×α, (f x.1, f x.2)) uniformity = uniformity
theorem uniform_embedding_def [uniform_space β] {f : α → β} :
uniform_embedding f ↔ function.injective f ∧ ∀ s, s ∈ (@uniformity α _).sets ↔
∃ t ∈ (@uniformity β _).sets, ∀ x y : α, (f x, f y) ∈ t → (x, y) ∈ s :=
by rw [uniform_embedding, eq_comm, filter.ext_iff]; simp only [filter.mem_comap_sets, subset_def, prod.forall]; refl
theorem uniform_embedding_def' [uniform_space β] {f : α → β} :
uniform_embedding f ↔ function.injective f ∧ uniform_continuous f ∧
∀ s, s ∈ (@uniformity α _).sets →
∃ t ∈ (@uniformity β _).sets, ∀ x y : α, (f x, f y) ∈ t → (x, y) ∈ s :=
by simp only [uniform_embedding_def]; exact
⟨λ ⟨I, H⟩, ⟨I, λ s su, (H _).2 ⟨s, su, λ x y, id⟩, λ s, (H s).1⟩,
λ ⟨I, H₁, H₂⟩, ⟨I, λ s, ⟨H₂ s,
λ ⟨t, tu, h⟩, sets_of_superset _ (H₁ tu) (λ ⟨a, b⟩, h a b)⟩⟩⟩
lemma uniform_embedding.uniform_continuous [uniform_space β] {f : α → β}
(hf : uniform_embedding f) : uniform_continuous f :=
(uniform_embedding_def'.1 hf).2.1
lemma uniform_embedding.uniform_continuous_iff [uniform_space β] [uniform_space γ] {f : α → β}
{g : β → γ} (hg : uniform_embedding g) : uniform_continuous f ↔ uniform_continuous (g ∘ f) :=
by unfold uniform_continuous tendsto; rw [← hg.2, ← map_le_iff_le_comap, filter.map_map]
lemma uniform_embedding.dense_embedding [uniform_space β] {f : α → β}
(h : uniform_embedding f) (hd : ∀x, x ∈ closure (range f)) : dense_embedding f :=
{ dense := hd,
inj := h.left,
induced :=
begin
intro a,
simp only [nhds_eq_uniformity],
rw [← h.2, comap_lift'_eq, comap_lift'_eq2],
refl,
exact monotone_preimage,
exact monotone_preimage
end }
lemma uniform_continuous.continuous [uniform_space β] {f : α → β}
(hf : uniform_continuous f) : continuous f :=
continuous_iff_tendsto.mpr $ assume a,
calc map f (nhds a) ≤
(map (λp:α×α, (f p.1, f p.2)) uniformity).lift' (λs:set (β×β), {y | (f a, y) ∈ s}) :
begin
rw [nhds_eq_uniformity, map_lift'_eq, map_lift'_eq2],
exact (lift'_mono' $ assume s hs b ⟨a', (ha' : (_, a') ∈ s), a'_eq⟩,
⟨(a, a'), ha', show (f a, f a') = (f a, b), from a'_eq ▸ rfl⟩),
exact monotone_preimage,
exact monotone_preimage
end
... ≤ nhds (f a) :
by rw [nhds_eq_uniformity]; exact lift'_mono hf (le_refl _)
lemma closure_image_mem_nhds_of_uniform_embedding
[uniform_space α] [uniform_space β] {s : set (α×α)} {e : α → β} (b : β)
(he₁ : uniform_embedding e) (he₂ : dense_embedding e) (hs : s ∈ (@uniformity α _).sets) :
∃a, closure (e '' {a' | (a, a') ∈ s}) ∈ (nhds b).sets :=
have s ∈ (comap (λp:α×α, (e p.1, e p.2)) $ uniformity).sets,
from he₁.right.symm ▸ hs,
let ⟨t₁, ht₁u, ht₁⟩ := this in
have ht₁ : ∀p:α×α, (e p.1, e p.2) ∈ t₁ → p ∈ s, from ht₁,
let ⟨t₂, ht₂u, ht₂s, ht₂c⟩ := comp_symm_of_uniformity ht₁u in
let ⟨t, htu, hts, htc⟩ := comp_symm_of_uniformity ht₂u in
have preimage e {b' | (b, b') ∈ t₂} ∈ (comap e $ nhds b).sets,
from preimage_mem_comap $ mem_nhds_left b ht₂u,
let ⟨a, (ha : (b, e a) ∈ t₂)⟩ := inhabited_of_mem_sets (he₂.comap_nhds_neq_bot) this in
have ∀b' (s' : set (β × β)), (b, b') ∈ t → s' ∈ (@uniformity β _).sets →
{y : β | (b', y) ∈ s'} ∩ e '' {a' : α | (a, a') ∈ s} ≠ ∅,
from assume b' s' hb' hs',
have preimage e {b'' | (b', b'') ∈ s' ∩ t} ∈ (comap e $ nhds b').sets,
from preimage_mem_comap $ mem_nhds_left b' $ inter_mem_sets hs' htu,
let ⟨a₂, ha₂s', ha₂t⟩ := inhabited_of_mem_sets (he₂.comap_nhds_neq_bot) this in
have (e a, e a₂) ∈ t₁,
from ht₂c $ prod_mk_mem_comp_rel (ht₂s ha) $ htc $ prod_mk_mem_comp_rel hb' ha₂t,
have e a₂ ∈ {b'':β | (b', b'') ∈ s'} ∩ e '' {a' | (a, a') ∈ s},
from ⟨ha₂s', mem_image_of_mem _ $ ht₁ (a, a₂) this⟩,
ne_empty_of_mem this,
have ∀b', (b, b') ∈ t → nhds b' ⊓ principal (e '' {a' | (a, a') ∈ s}) ≠ ⊥,
begin
intros b' hb',
rw [nhds_eq_uniformity, lift'_inf_principal_eq, lift'_neq_bot_iff],
exact assume s, this b' s hb',
exact monotone_inter monotone_preimage monotone_const
end,
have ∀b', (b, b') ∈ t → b' ∈ closure (e '' {a' | (a, a') ∈ s}),
from assume b' hb', by rw [closure_eq_nhds]; exact this b' hb',
⟨a, (nhds b).sets_of_superset (mem_nhds_left b htu) this⟩
/-- A filter `f` is Cauchy if for every entourage `r`, there exists an
`s ∈ f` such that `s × s ⊆ r`. This is a generalization of Cauchy
sequences, because if `a : ℕ → α` then the filter of sets containing
cofinitely many of the `a n` is Cauchy iff `a` is a Cauchy sequence. -/
def cauchy (f : filter α) := f ≠ ⊥ ∧ filter.prod f f ≤ uniformity
lemma cauchy_iff [uniform_space α] {f : filter α} :
cauchy f ↔ (f ≠ ⊥ ∧ (∀s∈(@uniformity α _).sets, ∃t∈f.sets, set.prod t t ⊆ s)) :=
and_congr (iff.refl _) $ forall_congr $ assume s, forall_congr $ assume hs, mem_prod_same_iff
lemma cauchy_downwards {f g : filter α} (h_c : cauchy f) (hg : g ≠ ⊥) (h_le : g ≤ f) : cauchy g :=
⟨hg, le_trans (filter.prod_mono h_le h_le) h_c.right⟩
lemma cauchy_nhds {a : α} : cauchy (nhds a) :=
⟨nhds_neq_bot,
calc filter.prod (nhds a) (nhds a) =
uniformity.lift (λs:set (α×α), uniformity.lift' (λt:set(α×α),
set.prod {y : α | (y, a) ∈ s} {y : α | (a, y) ∈ t})) : nhds_nhds_eq_uniformity_uniformity_prod
... ≤ uniformity.lift' (λs:set (α×α), comp_rel s s) :
le_infi $ assume s, le_infi $ assume hs,
infi_le_of_le s $ infi_le_of_le hs $ infi_le_of_le s $ infi_le_of_le hs $
principal_mono.mpr $
assume ⟨x, y⟩ ⟨(hx : (x, a) ∈ s), (hy : (a, y) ∈ s)⟩, ⟨a, hx, hy⟩
... ≤ uniformity : comp_le_uniformity⟩
lemma cauchy_pure {a : α} : cauchy (pure a) :=
cauchy_downwards cauchy_nhds
(show principal {a} ≠ ⊥, from mt principal_eq_bot_iff.1 (singleton_ne_empty a))
(pure_le_nhds a)
lemma le_nhds_of_cauchy_adhp {f : filter α} {x : α} (hf : cauchy f)
(adhs : f ⊓ nhds x ≠ ⊥) : f ≤ nhds x :=
have ∀s∈f.sets, x ∈ closure s,
begin
intros s hs,
simp only [closure_eq_nhds, inf_comm],
exact assume h', adhs $ bot_unique $ h' ▸ inf_le_inf (le_principal_iff.2 hs) (le_refl _)
end,
calc f ≤ f.lift' (λs:set α, {y | x ∈ closure s ∧ y ∈ closure s}) :
le_infi $ assume s, le_infi $ assume hs,
begin
rw [←forall_sets_neq_empty_iff_neq_bot] at adhs,
exact le_principal_iff.2 (mem_sets_of_superset hs (λ _ H, ⟨this s hs, subset_closure H⟩))
end
... ≤ f.lift' (λs:set α, {y | (x, y) ∈ closure (set.prod s s)}) :
by simp only [closure_prod_eq]; exact le_refl _
... = (filter.prod f f).lift' (λs:set (α×α), {y | (x, y) ∈ closure s}) :
begin
rw [prod_same_eq],
rw [lift'_lift'_assoc],
exact monotone_prod monotone_id monotone_id,
exact monotone_comp (assume s t h x h', closure_mono h h') monotone_preimage
end
... ≤ uniformity.lift' (λs:set (α×α), {y | (x, y) ∈ closure s}) : lift'_mono hf.right (le_refl _)
... = (uniformity.lift' closure).lift' (λs:set (α×α), {y | (x, y) ∈ s}) :
begin
rw [lift'_lift'_assoc],
exact assume s t h, closure_mono h,
exact monotone_preimage
end
... = uniformity.lift' (λs:set (α×α), {y | (x, y) ∈ s}) :
by rw [←uniformity_eq_uniformity_closure]
... = nhds x :
by rw [nhds_eq_uniformity]
lemma le_nhds_iff_adhp_of_cauchy {f : filter α} {x : α} (hf : cauchy f) :
f ≤ nhds x ↔ f ⊓ nhds x ≠ ⊥ :=
⟨assume h, (inf_of_le_left h).symm ▸ hf.left,
le_nhds_of_cauchy_adhp hf⟩
lemma cauchy_map [uniform_space β] {f : filter α} {m : α → β}
(hm : uniform_continuous m) (hf : cauchy f) : cauchy (map m f) :=
⟨have f ≠ ⊥, from hf.left, by simp; assumption,
calc filter.prod (map m f) (map m f) =
map (λp:α×α, (m p.1, m p.2)) (filter.prod f f) : filter.prod_map_map_eq
... ≤ map (λp:α×α, (m p.1, m p.2)) uniformity : map_mono hf.right
... ≤ uniformity : hm⟩
lemma cauchy_comap [uniform_space β] {f : filter β} {m : α → β}
(hm : comap (λp:α×α, (m p.1, m p.2)) uniformity ≤ uniformity)
(hf : cauchy f) (hb : comap m f ≠ ⊥) : cauchy (comap m f) :=
⟨hb,
calc filter.prod (comap m f) (comap m f) =
comap (λp:α×α, (m p.1, m p.2)) (filter.prod f f) : filter.prod_comap_comap_eq
... ≤ comap (λp:α×α, (m p.1, m p.2)) uniformity : comap_mono hf.right
... ≤ uniformity : hm⟩
/- separated uniformity -/
/-- The separation relation is the intersection of all entourages.
Two points which are related by the separation relation are "indistinguishable"
according to the uniform structure. -/
protected def separation_rel (α : Type u) [u : uniform_space α] :=
⋂₀ (@uniformity α _).sets
lemma separated_equiv : equivalence (λx y, (x, y) ∈ separation_rel α) :=
⟨assume x, assume s, refl_mem_uniformity,
assume x y, assume h (s : set (α×α)) hs,
have preimage prod.swap s ∈ (@uniformity α _).sets,
from symm_le_uniformity hs,
h _ this,
assume x y z (hxy : (x, y) ∈ separation_rel α) (hyz : (y, z) ∈ separation_rel α)
s (hs : s ∈ (@uniformity α _).sets),
let ⟨t, ht, (h_ts : comp_rel t t ⊆ s)⟩ := comp_mem_uniformity_sets hs in
h_ts $ show (x, z) ∈ comp_rel t t,
from ⟨y, hxy t ht, hyz t ht⟩⟩
protected def separation_setoid (α : Type u) [u : uniform_space α] : setoid α :=
⟨λx y, (x, y) ∈ separation_rel α, separated_equiv⟩
@[class] def separated (α : Type u) [uniform_space α] :=
separation_rel α = id_rel
theorem separated_def {α : Type u} [uniform_space α] :
separated α ↔ ∀ x y, (∀ r ∈ (@uniformity α _).sets, (x, y) ∈ r) → x = y :=
by simp only [separated, id_rel_subset.2 separated_equiv.1, subset.antisymm_iff, and_true];
simp only [subset_def, separation_rel, set.mem_sInter, prod.forall, mem_id_rel]
theorem separated_def' {α : Type u} [uniform_space α] :
separated α ↔ ∀ x y, x ≠ y → ∃ r ∈ (@uniformity α _).sets, (x, y) ∉ r :=
separated_def.trans $ forall_congr $ λ x, forall_congr $ λ y,
by rw ← not_imp_not; simp only [classical.not_forall]
instance separated_t2 [s : separated α] : t2_space α :=
⟨assume x y, assume h : x ≠ y,
let ⟨d, hd, (hxy : (x, y) ∉ d)⟩ := separated_def'.1 s x y h in
let ⟨d', hd', (hd'd' : comp_rel d' d' ⊆ d)⟩ := comp_mem_uniformity_sets hd in
have {y | (x, y) ∈ d'} ∈ (nhds x).sets,
from mem_nhds_left x hd',
let ⟨u, hu₁, hu₂, hu₃⟩ := mem_nhds_sets_iff.mp this in
have {x | (x, y) ∈ d'} ∈ (nhds y).sets,
from mem_nhds_right y hd',
let ⟨v, hv₁, hv₂, hv₃⟩ := mem_nhds_sets_iff.mp this in
have u ∩ v = ∅, from
eq_empty_of_subset_empty $
assume z ⟨(h₁ : z ∈ u), (h₂ : z ∈ v)⟩,
have (x, y) ∈ comp_rel d' d', from ⟨z, hu₁ h₁, hv₁ h₂⟩,
hxy $ hd'd' this,
⟨u, v, hu₂, hv₂, hu₃, hv₃, this⟩⟩
instance separated_regular [separated α] : regular_space α :=
{ regular := λs a hs ha,
have -s ∈ (nhds a).sets,
from mem_nhds_sets hs ha,
have {p : α × α | p.1 = a → p.2 ∈ -s} ∈ uniformity.sets,
from mem_nhds_uniformity_iff.mp this,
let ⟨d, hd, h⟩ := comp_mem_uniformity_sets this in
let e := {y:α| (a, y) ∈ d} in
have hae : a ∈ closure e, from subset_closure $ refl_mem_uniformity hd,
have set.prod (closure e) (closure e) ⊆ comp_rel d (comp_rel (set.prod e e) d),
begin
rw [←closure_prod_eq, closure_eq_inter_uniformity],
change (⨅d' ∈ uniformity.sets, _) ≤ comp_rel d (comp_rel _ d),
exact (infi_le_of_le d $ infi_le_of_le hd $ le_refl _)
end,
have e_subset : closure e ⊆ -s,
from assume a' ha',
let ⟨x, (hx : (a, x) ∈ d), y, ⟨hx₁, hx₂⟩, (hy : (y, _) ∈ d)⟩ := @this ⟨a, a'⟩ ⟨hae, ha'⟩ in
have (a, a') ∈ comp_rel d d, from ⟨y, hx₂, hy⟩,
h this rfl,
have closure e ∈ (nhds a).sets, from (nhds a).sets_of_superset (mem_nhds_left a hd) subset_closure,
have nhds a ⊓ principal (-closure e) = ⊥,
from (@inf_eq_bot_iff_le_compl _ _ _ (principal (- closure e)) (principal (closure e))
(by simp only [union_compl_self, sup_principal, principal_univ, union_comm])
(by simp only [compl_inter_self, inf_principal, principal_eq_bot_iff])).mpr
(le_principal_iff.2 this),
⟨- closure e, is_closed_closure, assume x h₁ h₂, @e_subset x h₂ h₁, this⟩,
..separated_t2 }
/-- A set `s` is totally bounded if for every entourage `d` there is a finite
set of points `t` such that every element of `s` is `d`-near to some element of `t`. -/
def totally_bounded (s : set α) : Prop :=
∀d ∈ (@uniformity α _).sets, ∃t : set α, finite t ∧ s ⊆ (⋃y∈t, {x | (x,y) ∈ d})
theorem totally_bounded_iff_subset {s : set α} : totally_bounded s ↔
∀d ∈ (@uniformity α _).sets, ∃t ⊆ s, finite t ∧ s ⊆ (⋃y∈t, {x | (x,y) ∈ d}) :=
⟨λ H d hd, begin
rcases comp_symm_of_uniformity hd with ⟨r, hr, rs, rd⟩,
rcases H r hr with ⟨k, fk, ks⟩,
let u := {y ∈ k | ∃ x, x ∈ s ∧ (x, y) ∈ r},
choose f this using assume x:u, x.2.2,
refine ⟨range f, _, _, _⟩,
{ exact range_subset_iff.2 (λ x, (this x).1) },
{ have : finite u := finite_subset fk (λ x h, h.1),
exact ⟨@set.fintype_range _ _ _ _ this.fintype⟩ },
{ intros x xs,
rcases mem_Union.1 (ks xs) with ⟨y, hy⟩,
rcases mem_Union.1 hy with ⟨hy, xy⟩,
let z : coe_sort u := ⟨y, hy, x, xs, xy⟩,
refine mem_Union.2 ⟨f z, mem_Union.2 ⟨mem_range_self z, _⟩⟩,
exact rd (mem_comp_rel.2 ⟨_, xy, rs (this z).2⟩) }
end,
λ H d hd, let ⟨t, _, ht⟩ := H d hd in ⟨t, ht⟩⟩
lemma totally_bounded_subset [uniform_space α] {s₁ s₂ : set α} (hs : s₁ ⊆ s₂)
(h : totally_bounded s₂) : totally_bounded s₁ :=
assume d hd, let ⟨t, ht₁, ht₂⟩ := h d hd in ⟨t, ht₁, subset.trans hs ht₂⟩
lemma totally_bounded_closure [uniform_space α] {s : set α} (h : totally_bounded s) :
totally_bounded (closure s) :=
assume t ht,
let ⟨t', ht', hct', htt'⟩ := mem_uniformity_is_closed ht, ⟨c, hcf, hc⟩ := h t' ht' in
⟨c, hcf,
calc closure s ⊆ closure (⋃ (y : α) (H : y ∈ c), {x : α | (x, y) ∈ t'}) : closure_mono hc
... = _ : closure_eq_of_is_closed $ is_closed_Union hcf $ assume i hi,
continuous_iff_is_closed.mp (continuous_id.prod_mk continuous_const) _ hct'
... ⊆ _ : bUnion_subset $ assume i hi, subset.trans (assume x, @htt' (x, i))
(subset_bUnion_of_mem hi)⟩
lemma totally_bounded_image [uniform_space α] [uniform_space β] {f : α → β} {s : set α}
(hf : uniform_continuous f) (hs : totally_bounded s) : totally_bounded (f '' s) :=
assume t ht,
have {p:α×α | (f p.1, f p.2) ∈ t} ∈ (@uniformity α _).sets,
from hf ht,
let ⟨c, hfc, hct⟩ := hs _ this in
⟨f '' c, finite_image f hfc, image_subset_iff.2 $ λ x hx,
let ⟨i, hi, ht⟩ := mem_bUnion_iff.1 (hct hx) in
mem_bUnion ⟨i, hi, rfl⟩ ht⟩
lemma totally_bounded_preimage [uniform_space α] [uniform_space β] {f : α → β} {s : set β}
(hf : uniform_embedding f) (hs : totally_bounded s) : totally_bounded (f ⁻¹' s) :=
λ t ht, begin
rw ← hf.2 at ht,
rcases mem_comap_sets.2 ht with ⟨t', ht', ts⟩,
rcases totally_bounded_iff_subset.1
(totally_bounded_subset (image_preimage_subset f s) hs) _ ht' with ⟨c, cs, hfc, hct⟩,
refine ⟨f ⁻¹' c, finite_preimage hf.1 hfc, λ x h, _⟩,
have := hct (mem_image_of_mem f h), rw [mem_bUnion_iff] at this ⊢,
rcases this with ⟨z, zc, zt⟩,
rcases cs zc with ⟨y, yc, rfl⟩,
exact ⟨y, zc, ts (by exact zt)⟩
end
lemma cauchy_of_totally_bounded_of_ultrafilter {s : set α} {f : filter α}
(hs : totally_bounded s) (hf : ultrafilter f) (h : f ≤ principal s) : cauchy f :=
⟨hf.left, assume t ht,
let ⟨t', ht'₁, ht'_symm, ht'_t⟩ := comp_symm_of_uniformity ht in
let ⟨i, hi, hs_union⟩ := hs t' ht'₁ in
have (⋃y∈i, {x | (x,y) ∈ t'}) ∈ f.sets,
from mem_sets_of_superset (le_principal_iff.mp h) hs_union,
have ∃y∈i, {x | (x,y) ∈ t'} ∈ f.sets,
from mem_of_finite_Union_ultrafilter hf hi this,
let ⟨y, hy, hif⟩ := this in
have set.prod {x | (x,y) ∈ t'} {x | (x,y) ∈ t'} ⊆ comp_rel t' t',
from assume ⟨x₁, x₂⟩ ⟨(h₁ : (x₁, y) ∈ t'), (h₂ : (x₂, y) ∈ t')⟩,
⟨y, h₁, ht'_symm h₂⟩,
(filter.prod f f).sets_of_superset (prod_mem_prod hif hif) (subset.trans this ht'_t)⟩
lemma totally_bounded_iff_filter {s : set α} :
totally_bounded s ↔ (∀f, f ≠ ⊥ → f ≤ principal s → ∃c ≤ f, cauchy c) :=
⟨assume : totally_bounded s, assume f hf hs,
⟨ultrafilter_of f, ultrafilter_of_le,
cauchy_of_totally_bounded_of_ultrafilter this
(ultrafilter_ultrafilter_of hf) (le_trans ultrafilter_of_le hs)⟩,
assume h : ∀f, f ≠ ⊥ → f ≤ principal s → ∃c ≤ f, cauchy c, assume d hd,
classical.by_contradiction $ assume hs,
have hd_cover : ∀{t:set α}, finite t → ¬ s ⊆ (⋃y∈t, {x | (x,y) ∈ d}),
by simpa only [not_exists, not_and] using hs,
let
f := ⨅t:{t : set α // finite t}, principal (s \ (⋃y∈t.val, {x | (x,y) ∈ d})),
⟨a, ha⟩ := @exists_mem_of_ne_empty α s
(assume h, hd_cover finite_empty $ h.symm ▸ empty_subset _)
in
have f ≠ ⊥,
from infi_neq_bot_of_directed ⟨a⟩
(assume ⟨t₁, ht₁⟩ ⟨t₂, ht₂⟩, ⟨⟨t₁ ∪ t₂, finite_union ht₁ ht₂⟩,
principal_mono.mpr $ diff_subset_diff_right $ Union_subset_Union $
assume t, Union_subset_Union_const or.inl,
principal_mono.mpr $ diff_subset_diff_right $ Union_subset_Union $
assume t, Union_subset_Union_const or.inr⟩)
(assume ⟨t, ht⟩, mt (diff_eq_empty.1 ∘ principal_eq_bot_iff.1) (hd_cover ht)),
have f ≤ principal s, from infi_le_of_le ⟨∅, finite_empty⟩ $ le_principal_iff.2 (diff_subset _ _),
let
⟨c, (hc₁ : c ≤ f), (hc₂ : cauchy c)⟩ := h f ‹f ≠ ⊥› this,
⟨m, hm, (hmd : set.prod m m ⊆ d)⟩ := (@mem_prod_same_iff α c d).mp $ hc₂.right hd
in
have c ≤ principal s, from le_trans ‹c ≤ f› this,
have m ∩ s ∈ c.sets, from inter_mem_sets hm $ le_principal_iff.mp this,
let ⟨y, hym, hys⟩ := inhabited_of_mem_sets hc₂.left this in
let ys := (⋃y'∈({y}:set α), {x | (x, y') ∈ d}) in
have m ⊆ ys,
from assume y' hy',
show y' ∈ (⋃y'∈({y}:set α), {x | (x, y') ∈ d}),
by rw bUnion_singleton; exact @hmd (y', y) ⟨hy', hym⟩,
have c ≤ principal (s - ys),
from le_trans hc₁ $ infi_le_of_le ⟨{y}, finite_singleton _⟩ $ le_refl _,
have (s - ys) ∩ (m ∩ s) ∈ c.sets,
from inter_mem_sets (le_principal_iff.mp this) ‹m ∩ s ∈ c.sets›,
have ∅ ∈ c.sets,
from c.sets_of_superset this $ assume x ⟨⟨hxs, hxys⟩, hxm, _⟩, hxys $ ‹m ⊆ ys› hxm,
hc₂.left $ empty_in_sets_eq_bot.mp this⟩
lemma totally_bounded_iff_ultrafilter {s : set α} :
totally_bounded s ↔ (∀f, ultrafilter f → f ≤ principal s → cauchy f) :=
⟨assume hs f, cauchy_of_totally_bounded_of_ultrafilter hs,
assume h, totally_bounded_iff_filter.mpr $ assume f hf hfs,
have cauchy (ultrafilter_of f),
from h (ultrafilter_of f) (ultrafilter_ultrafilter_of hf) (le_trans ultrafilter_of_le hfs),
⟨ultrafilter_of f, ultrafilter_of_le, this⟩⟩
lemma compact_of_totally_bounded_complete {s : set α}
(ht : totally_bounded s) (hc : ∀{f:filter α}, cauchy f → f ≤ principal s → ∃x∈s, f ≤ nhds x) :
compact s :=
begin
rw [compact_iff_ultrafilter_le_nhds],
rw [totally_bounded_iff_ultrafilter] at ht,
exact assume f hf hfs, hc (ht _ hf hfs) hfs
end
/-- A complete space is defined here using uniformities. A uniform space
is complete if every Cauchy filter converges. -/
class complete_space (α : Type u) [uniform_space α] : Prop :=
(complete : ∀{f:filter α}, cauchy f → ∃x, f ≤ nhds x)
theorem le_nhds_lim_of_cauchy {α} [uniform_space α] [complete_space α]
[inhabited α] {f : filter α} (hf : cauchy f) : f ≤ nhds (lim f) :=
lim_spec (complete_space.complete hf)
lemma complete_of_is_closed [complete_space α] {s : set α} {f : filter α}
(h : is_closed s) (hf : cauchy f) (hfs : f ≤ principal s) : ∃x∈s, f ≤ nhds x :=
let ⟨x, hx⟩ := complete_space.complete hf in
have x ∈ s, from is_closed_iff_nhds.mp h x $ neq_bot_of_le_neq_bot hf.left $
le_inf hx hfs,
⟨x, this, hx⟩
lemma compact_of_totally_bounded_is_closed [complete_space α] {s : set α}
(ht : totally_bounded s) (hc : is_closed s) : compact s :=
@compact_of_totally_bounded_complete α _ s ht $ assume f, complete_of_is_closed hc
lemma complete_space_extension [uniform_space β] {m : β → α}
(hm : uniform_embedding m)
(dense : ∀x, x ∈ closure (range m))
(h : ∀f:filter β, cauchy f → ∃x:α, map m f ≤ nhds x) :
complete_space α :=
⟨assume (f : filter α), assume hf : cauchy f,
let
p : set (α × α) → set α → set α := λs t, {y : α| ∃x:α, x ∈ t ∧ (x, y) ∈ s},
g := uniformity.lift (λs, f.lift' (p s))
in
have mp₀ : monotone p,
from assume a b h t s ⟨x, xs, xa⟩, ⟨x, xs, h xa⟩,
have mp₁ : ∀{s}, monotone (p s),
from assume s a b h x ⟨y, ya, yxs⟩, ⟨y, h ya, yxs⟩,
have f ≤ g, from
le_infi $ assume s, le_infi $ assume hs, le_infi $ assume t, le_infi $ assume ht,
le_principal_iff.mpr $
mem_sets_of_superset ht $ assume x hx, ⟨x, hx, refl_mem_uniformity hs⟩,
have g ≠ ⊥, from neq_bot_of_le_neq_bot hf.left this,
have comap m g ≠ ⊥, from comap_neq_bot $ assume t ht,
let ⟨t', ht', ht_mem⟩ := (mem_lift_sets $ monotone_lift' monotone_const mp₀).mp ht in
let ⟨t'', ht'', ht'_sub⟩ := (mem_lift'_sets mp₁).mp ht_mem in
let ⟨x, (hx : x ∈ t'')⟩ := inhabited_of_mem_sets hf.left ht'' in
have h₀ : nhds x ⊓ principal (range m) ≠ ⊥,
by rw [closure_eq_nhds] at dense; exact dense x,
have h₁ : {y | (x, y) ∈ t'} ∈ (nhds x ⊓ principal (range m)).sets,
from @mem_inf_sets_of_left α (nhds x) (principal (range m)) _ $ mem_nhds_left x ht',
have h₂ : range m ∈ (nhds x ⊓ principal (range m)).sets,
from @mem_inf_sets_of_right α (nhds x) (principal (range m)) _ $ subset.refl _,
have {y | (x, y) ∈ t'} ∩ range m ∈ (nhds x ⊓ principal (range m)).sets,
from @inter_mem_sets α (nhds x ⊓ principal (range m)) _ _ h₁ h₂,
let ⟨y, xyt', b, b_eq⟩ := inhabited_of_mem_sets h₀ this in
⟨b, b_eq.symm ▸ ht'_sub ⟨x, hx, xyt'⟩⟩,
have cauchy g, from
⟨‹g ≠ ⊥›, assume s hs,
let
⟨s₁, hs₁, (comp_s₁ : comp_rel s₁ s₁ ⊆ s)⟩ := comp_mem_uniformity_sets hs,
⟨s₂, hs₂, (comp_s₂ : comp_rel s₂ s₂ ⊆ s₁)⟩ := comp_mem_uniformity_sets hs₁,
⟨t, ht, (prod_t : set.prod t t ⊆ s₂)⟩ := mem_prod_same_iff.mp (hf.right hs₂)
in
have hg₁ : p (preimage prod.swap s₁) t ∈ g.sets,
from mem_lift (symm_le_uniformity hs₁) $ @mem_lift' α α f _ t ht,
have hg₂ : p s₂ t ∈ g.sets,
from mem_lift hs₂ $ @mem_lift' α α f _ t ht,
have hg : set.prod (p (preimage prod.swap s₁) t) (p s₂ t) ∈ (filter.prod g g).sets,
from @prod_mem_prod α α _ _ g g hg₁ hg₂,
(filter.prod g g).sets_of_superset hg
(assume ⟨a, b⟩ ⟨⟨c₁, c₁t, hc₁⟩, ⟨c₂, c₂t, hc₂⟩⟩,
have (c₁, c₂) ∈ set.prod t t, from ⟨c₁t, c₂t⟩,
comp_s₁ $ prod_mk_mem_comp_rel hc₁ $
comp_s₂ $ prod_mk_mem_comp_rel (prod_t this) hc₂)⟩,
have cauchy (filter.comap m g),
from cauchy_comap (le_of_eq hm.right) ‹cauchy g› (by assumption),
let ⟨x, (hx : map m (filter.comap m g) ≤ nhds x)⟩ := h _ this in
have map m (filter.comap m g) ⊓ nhds x ≠ ⊥,
from (le_nhds_iff_adhp_of_cauchy (cauchy_map hm.uniform_continuous this)).mp hx,
have g ⊓ nhds x ≠ ⊥,
from neq_bot_of_le_neq_bot this (inf_le_inf (assume s hs, ⟨s, hs, subset.refl _⟩) (le_refl _)),
⟨x, calc f ≤ g : by assumption
... ≤ nhds x : le_nhds_of_cauchy_adhp ‹cauchy g› this⟩⟩
/- separation space -/
section separation_space
local attribute [instance] separation_setoid
instance {α : Type u} [u : uniform_space α] : uniform_space (quotient (separation_setoid α)) :=
{ to_topological_space := u.to_topological_space.coinduced (λx, ⟦x⟧),
uniformity := map (λp:(α×α), (⟦p.1⟧, ⟦p.2⟧)) uniformity,
refl := assume s hs ⟨a, b⟩ (h : a = b),
have ∀a:α, (a, a) ∈ preimage (λ (p : α × α), (⟦p.fst⟧, ⟦p.snd⟧)) s,
from assume a, refl_mem_uniformity hs,
h ▸ quotient.induction_on a this,
symm := tendsto_map' $ tendsto_swap_uniformity.comp tendsto_map,
comp := calc (map (λ (p : α × α), (⟦p.fst⟧, ⟦p.snd⟧)) uniformity).lift' (λs, comp_rel s s) =
uniformity.lift' ((λs, comp_rel s s) ∘ image (λ (p : α × α), (⟦p.fst⟧, ⟦p.snd⟧))) :
map_lift'_eq2 $ monotone_comp_rel monotone_id monotone_id
... ≤ uniformity.lift' (image (λ (p : α × α), (⟦p.fst⟧, ⟦p.snd⟧)) ∘ (λs:set (α×α), comp_rel s (comp_rel s s))) :
lift'_mono' $ assume s hs ⟨a, b⟩ ⟨c, ⟨⟨a₁, a₂⟩, ha, a_eq⟩, ⟨⟨b₁, b₂⟩, hb, b_eq⟩⟩,
begin
clear_, cases a_eq, injection b_eq with h₁ h₂, simp only at h₂, subst h₂,
have h : (a₂, b₁) ∈ separation_rel α := quotient.exact h₁.symm,
exact ⟨(a₁, b₂), ⟨_, ha, ⟨_, h s hs, hb⟩⟩, rfl⟩
end
... = map (λp:(α×α), (⟦p.1⟧, ⟦p.2⟧)) (uniformity.lift' (λs:set (α×α), comp_rel s (comp_rel s s))) :
by rw [map_lift'_eq];
exact monotone_comp_rel monotone_id (monotone_comp_rel monotone_id monotone_id)
... ≤ map (λp:(α×α), (⟦p.1⟧, ⟦p.2⟧)) uniformity :
map_mono comp_le_uniformity3,
is_open_uniformity := assume s,
have ∀a, ⟦a⟧ ∈ s →
({p:α×α | p.1 = a → ⟦p.2⟧ ∈ s} ∈ (@uniformity α _).sets ↔
{p:α×α | p.1 ≈ a → ⟦p.2⟧ ∈ s} ∈ (@uniformity α _).sets),
from assume a ha,
⟨assume h,
let ⟨t, ht, hts⟩ := comp_mem_uniformity_sets h in
have hts : ∀{a₁ a₂}, (a, a₁) ∈ t → (a₁, a₂) ∈ t → ⟦a₂⟧ ∈ s,
from assume a₁ a₂ ha₁ ha₂, @hts (a, a₂) ⟨a₁, ha₁, ha₂⟩ rfl,
have ht' : ∀{a₁ a₂}, a₁ ≈ a₂ → (a₁, a₂) ∈ t,
from assume a₁ a₂ h, sInter_subset_of_mem ht h,
uniformity.sets_of_superset ht $ assume ⟨a₁, a₂⟩ h₁ h₂, hts (ht' $ setoid.symm h₂) h₁,
assume h, uniformity.sets_of_superset h $ λ p hp1 hp2, hp1 (hp2 ▸ setoid.refl _)⟩,
begin
simp only [topological_space.coinduced, u.is_open_uniformity, uniformity,
forall_quotient_iff, mem_map, mem_set_of_eq, quotient.eq],
exact ⟨λh a ha, (this a ha).mp $ h a ha, λh a ha, (this a ha).mpr $ h a ha⟩
end }
lemma uniform_continuous_quotient_mk :
uniform_continuous (quotient.mk : α → quotient (separation_setoid α)) :=
le_refl _
lemma comap_quotient_le_uniformity : comap (λ (p : α × α), (⟦p.fst⟧, ⟦p.snd⟧)) uniformity ≤ uniformity :=
assume t' ht',
let ⟨t, ht, tt_t'⟩ := comp_mem_uniformity_sets ht' in
let ⟨s, hs, ss_t⟩ := comp_mem_uniformity_sets ht in
⟨(λp:α×α, (⟦p.1⟧, ⟦p.2⟧)) '' s,
(@uniformity α _).sets_of_superset hs $ assume x hx, ⟨x, hx, rfl⟩,
assume ⟨a₁, a₂⟩ ⟨⟨b₁, b₂⟩, hb, ab_eq⟩,
have ⟦b₁⟧ = ⟦a₁⟧ ∧ ⟦b₂⟧ = ⟦a₂⟧, from prod.mk.inj ab_eq,
have b₁ ≈ a₁ ∧ b₂ ≈ a₂, from and.imp quotient.exact quotient.exact this,
have ab₁ : (a₁, b₁) ∈ t, from (setoid.symm this.left) t ht,
have ba₂ : (b₂, a₂) ∈ s, from this.right s hs,
tt_t' ⟨b₁, show ((a₁, a₂).1, b₁) ∈ t, from ab₁,
ss_t ⟨b₂, show ((b₁, a₂).1, b₂) ∈ s, from hb, ba₂⟩⟩⟩
lemma comap_quotient_eq_uniformity : comap (λ (p : α × α), (⟦p.fst⟧, ⟦p.snd⟧)) uniformity = uniformity :=
le_antisymm comap_quotient_le_uniformity le_comap_map
lemma complete_space_separation [h : complete_space α] :
complete_space (quotient (separation_setoid α)) :=
⟨assume f, assume hf : cauchy f,
have cauchy (comap (λx, ⟦x⟧) f), from
cauchy_comap comap_quotient_le_uniformity hf $
comap_neq_bot_of_surj hf.left $ assume b, quotient.exists_rep _,
let ⟨x, (hx : comap (λx, ⟦x⟧) f ≤ nhds x)⟩ := complete_space.complete this in
⟨⟦x⟧, calc f ≤ map (λx, ⟦x⟧) (comap (λx, ⟦x⟧) f) : le_map_comap $ assume b, quotient.exists_rep _
... ≤ map (λx, ⟦x⟧) (nhds x) : map_mono hx
... ≤ _ : continuous_iff_tendsto.mp uniform_continuous_quotient_mk.continuous _⟩⟩
lemma separated_separation [h : complete_space α] : separated (quotient (separation_setoid α)) :=
set.ext $ assume ⟨a, b⟩, quotient.induction_on₂ a b $ assume a b,
⟨assume h,
have a ≈ b, from assume s hs,
have s ∈ (comap (λp:(α×α), (⟦p.1⟧, ⟦p.2⟧)) uniformity).sets,
from comap_quotient_le_uniformity hs,
let ⟨t, ht, hts⟩ := this in
@hts (a, b) (h t ht),
show ⟦a⟧ = ⟦b⟧, from quotient.sound this,
assume heq : ⟦a⟧ = ⟦b⟧, assume h hs,
heq ▸ refl_mem_uniformity hs⟩
variables [uniform_space β] [uniform_space γ]
lemma uniform_continuous_quotient {f : quotient (separation_setoid α) → β}
(hf : uniform_continuous (λx, f ⟦x⟧)) : uniform_continuous f :=
hf
lemma uniform_continuous_quotient_lift
{f : α → β} {h : ∀a b, (a, b) ∈ separation_rel α → f a = f b}
(hf : uniform_continuous f) : uniform_continuous (λa, quotient.lift f h a) :=
uniform_continuous_quotient hf
lemma uniformity_quotient :
@uniformity (quotient (separation_setoid α)) _ = uniformity.map (λp:(α×α), (⟦p.1⟧, ⟦p.2⟧)) :=
rfl
lemma separated_of_uniform_continuous {f : α → β} (H : uniform_continuous f) {x y : α}
(h : x ≈ y) : f x ≈ f y :=
assume _ h', h _ (H h')
lemma eq_of_separated_of_uniform_continuous [separated β] {f : α → β} (H : uniform_continuous f) {x y : α}
(h : x ≈ y) : f x = f y :=
separated_def.1 (by apply_instance) _ _ $ separated_of_uniform_continuous H h
end separation_space
section uniform_extension
variables
[uniform_space β]
[uniform_space γ]
{e : β → α}
(h_e : uniform_embedding e)
(h_dense : ∀x, x ∈ closure (range e))
{f : β → γ}
(h_f : uniform_continuous f)
local notation `ψ` := (h_e.dense_embedding h_dense).extend f
lemma uniformly_extend_of_emb [cγ : complete_space γ] [sγ : separated γ] {b : β} :
ψ (e b) = f b :=
dense_embedding.extend_e_eq _ $ continuous_iff_tendsto.mp h_f.continuous b
lemma uniformly_extend_exists [complete_space γ] [sγ : separated γ] {a : α} :
∃c, tendsto f (comap e (nhds a)) (nhds c) :=
let de := (h_e.dense_embedding h_dense) in
have cauchy (nhds a), from cauchy_nhds,
have cauchy (comap e (nhds a)), from
cauchy_comap (le_of_eq h_e.right) this de.comap_nhds_neq_bot,
have cauchy (map f (comap e (nhds a))), from
cauchy_map h_f this,
complete_space.complete this
lemma uniformly_extend_spec [complete_space γ] [sγ : separated γ] {a : α} :
tendsto f (comap e (nhds a)) (nhds (ψ a)) :=
@lim_spec _ (id _) _ _ $ uniformly_extend_exists h_e h_dense h_f
lemma uniform_continuous_uniformly_extend [cγ : complete_space γ] [sγ : separated γ] :
uniform_continuous ψ :=
assume d hd,
let ⟨s, hs, hs_comp⟩ := (mem_lift'_sets $
monotone_comp_rel monotone_id $ monotone_comp_rel monotone_id monotone_id).mp (comp_le_uniformity3 hd) in
have h_pnt : ∀{a m}, m ∈ (nhds a).sets → ∃c, c ∈ f '' preimage e m ∧ (c, ψ a) ∈ s ∧ (ψ a, c) ∈ s,
from assume a m hm,
have nb : map f (comap e (nhds a)) ≠ ⊥,
from map_ne_bot (h_e.dense_embedding h_dense).comap_nhds_neq_bot,
have (f '' preimage e m) ∩ ({c | (c, ψ a) ∈ s } ∩ {c | (ψ a, c) ∈ s }) ∈ (map f (comap e (nhds a))).sets,
from inter_mem_sets (image_mem_map $ preimage_mem_comap $ hm)
(uniformly_extend_spec h_e h_dense h_f $ inter_mem_sets (mem_nhds_right _ hs) (mem_nhds_left _ hs)),
inhabited_of_mem_sets nb this,
have preimage (λp:β×β, (f p.1, f p.2)) s ∈ (@uniformity β _).sets,
from h_f hs,
have preimage (λp:β×β, (f p.1, f p.2)) s ∈ (comap (λx:β×β, (e x.1, e x.2)) uniformity).sets,
by rwa [h_e.right.symm] at this,
let ⟨t, ht, ts⟩ := this in
show preimage (λp:(α×α), (ψ p.1, ψ p.2)) d ∈ uniformity.sets,
from (@uniformity α _).sets_of_superset (interior_mem_uniformity ht) $
assume ⟨x₁, x₂⟩ hx_t,
have nhds (x₁, x₂) ≤ principal (interior t),
from is_open_iff_nhds.mp is_open_interior (x₁, x₂) hx_t,
have interior t ∈ (filter.prod (nhds x₁) (nhds x₂)).sets,
by rwa [nhds_prod_eq, le_principal_iff] at this,
let ⟨m₁, hm₁, m₂, hm₂, (hm : set.prod m₁ m₂ ⊆ interior t)⟩ := mem_prod_iff.mp this in
let ⟨a, ha₁, _, ha₂⟩ := h_pnt hm₁ in
let ⟨b, hb₁, hb₂, _⟩ := h_pnt hm₂ in
have set.prod (preimage e m₁) (preimage e m₂) ⊆ preimage (λp:(β×β), (f p.1, f p.2)) s,
from calc _ ⊆ preimage (λp:(β×β), (e p.1, e p.2)) (interior t) : preimage_mono hm
... ⊆ preimage (λp:(β×β), (e p.1, e p.2)) t : preimage_mono interior_subset
... ⊆ preimage (λp:(β×β), (f p.1, f p.2)) s : ts,
have set.prod (f '' preimage e m₁) (f '' preimage e m₂) ⊆ s,
from calc set.prod (f '' preimage e m₁) (f '' preimage e m₂) =
(λp:(β×β), (f p.1, f p.2)) '' (set.prod (preimage e m₁) (preimage e m₂)) : prod_image_image_eq
... ⊆ (λp:(β×β), (f p.1, f p.2)) '' preimage (λp:(β×β), (f p.1, f p.2)) s : mono_image this
... ⊆ s : image_subset_iff.mpr $ subset.refl _,
have (a, b) ∈ s, from @this (a, b) ⟨ha₁, hb₁⟩,
hs_comp $ show (ψ x₁, ψ x₂) ∈ comp_rel s (comp_rel s s),
from ⟨a, ha₂, ⟨b, this, hb₂⟩⟩
end uniform_extension
end uniform_space
end
/-- 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 Cauchy (α : Type u) [uniform_space α] : Type u := { f : filter α // cauchy f }
namespace Cauchy
section
parameters {α : Type u} [uniform_space α]
def gen (s : set (α × α)) : set (Cauchy α × Cauchy α) :=
{p | s ∈ (filter.prod (p.1.val) (p.2.val)).sets }
lemma monotone_gen : monotone gen :=
monotone_set_of $ assume p, @monotone_mem_sets (α×α) (filter.prod (p.1.val) (p.2.val))
private lemma symm_gen : map prod.swap (uniformity.lift' gen) ≤ uniformity.lift' gen :=
calc map prod.swap (uniformity.lift' gen) =
uniformity.lift' (λs:set (α×α), {p | s ∈ (filter.prod (p.2.val) (p.1.val)).sets }) :
begin
delta gen, rw map_lift'_eq (monotone_set_of (λ _, _)),
{ simp only [image_swap_eq_preimage_swap]; refl },
exact monotone_mem_sets
end
... ≤ uniformity.lift' gen :
uniformity_lift_le_swap
(monotone_comp (monotone_set_of $ assume p,
@monotone_mem_sets (α×α) ((filter.prod ((p.2).val) ((p.1).val)))) monotone_principal)
begin
have h := λ(p:Cauchy α×Cauchy α), @filter.prod_comm _ _ (p.2.val) (p.1.val),
simp only [h, mem_map, (∘), mem_preimage_eq, prod.swap_prod_mk, prod.mk.eta, set_of_mem],
exact le_refl _
end
private lemma comp_rel_gen_gen_subset_gen_comp_rel {s t : set (α×α)} : comp_rel (gen s) (gen t) ⊆
(gen (comp_rel s t) : set (Cauchy α × Cauchy α)) :=
assume ⟨f, g⟩ ⟨h, h₁, h₂⟩,
let ⟨t₁, (ht₁ : t₁ ∈ f.val.sets), t₂, (ht₂ : t₂ ∈ h.val.sets), (h₁ : set.prod t₁ t₂ ⊆ s)⟩ :=
mem_prod_iff.mp h₁ in
let ⟨t₃, (ht₃ : t₃ ∈ h.val.sets), t₄, (ht₄ : t₄ ∈ g.val.sets), (h₂ : set.prod t₃ t₄ ⊆ t)⟩ :=
mem_prod_iff.mp h₂ in
have t₂ ∩ t₃ ∈ h.val.sets,
from inter_mem_sets ht₂ ht₃,
let ⟨x, xt₂, xt₃⟩ :=
inhabited_of_mem_sets (h.property.left) this in
(filter.prod f.val g.val).sets_of_superset
(prod_mem_prod ht₁ ht₄)
(assume ⟨a, b⟩ ⟨(ha : a ∈ t₁), (hb : b ∈ t₄)⟩,
⟨x,
h₁ (show (a, x) ∈ set.prod t₁ t₂, from ⟨ha, xt₂⟩),
h₂ (show (x, b) ∈ set.prod t₃ t₄, from ⟨xt₃, hb⟩)⟩)
private lemma comp_gen :
(uniformity.lift' gen).lift' (λs, comp_rel s s) ≤ uniformity.lift' gen :=
calc (uniformity.lift' gen).lift' (λs, comp_rel s s) =
uniformity.lift' (λs, comp_rel (gen s) (gen s)) :
begin
rw [lift'_lift'_assoc],
exact monotone_gen,
exact (monotone_comp_rel monotone_id monotone_id)
end
... ≤ uniformity.lift' (λs, gen $ comp_rel s s) :
lift'_mono' $ assume s hs, comp_rel_gen_gen_subset_gen_comp_rel
... = (uniformity.lift' $ λs:set(α×α), comp_rel s s).lift' gen :
begin
rw [lift'_lift'_assoc],
exact (monotone_comp_rel monotone_id monotone_id),
exact monotone_gen
end
... ≤ uniformity.lift' gen : lift'_mono comp_le_uniformity (le_refl _)
instance completion_space : uniform_space (Cauchy α) :=
uniform_space.of_core
{ uniformity := uniformity.lift' gen,
refl := principal_le_lift' $ assume s hs ⟨a, b⟩ (a_eq_b : a = b),
a_eq_b ▸ a.property.right hs,
symm := symm_gen,
comp := comp_gen }
theorem mem_uniformity {s : set (Cauchy α × Cauchy α)} :
s ∈ (@uniformity (Cauchy α) _).sets ↔ ∃ t ∈ (@uniformity α _).sets, gen t ⊆ s :=
mem_lift'_sets monotone_gen
theorem mem_uniformity' {s : set (Cauchy α × Cauchy α)} :
s ∈ (@uniformity (Cauchy α) _).sets ↔ ∃ t ∈ (@uniformity α _).sets,
∀ f g : Cauchy α, t ∈ (filter.prod f.1 g.1).sets → (f, g) ∈ s :=
mem_uniformity.trans $ bex_congr $ λ t h, prod.forall
/-- Embedding of `α` into its completion -/
def pure_cauchy (a : α) : Cauchy α :=
⟨pure a, cauchy_pure⟩
lemma uniform_embedding_pure_cauchy : uniform_embedding (pure_cauchy : α → Cauchy α) :=
⟨assume a₁ a₂ h,
have (pure_cauchy a₁).val = (pure_cauchy a₂).val, from congr_arg _ h,
have {a₁} = ({a₂} : set α),
from principal_eq_iff_eq.mp this,
singleton_eq_singleton_iff.1 this,
have (preimage (λ (x : α × α), (pure_cauchy (x.fst), pure_cauchy (x.snd))) ∘ gen) = id,
from funext $ assume s, set.ext $ assume ⟨a₁, a₂⟩,
by simp only [pure_cauchy, mem_preimage_eq, gen, mem_set_of_eq, filter.pure_def, prod_principal_principal,
mem_principal_sets, prod_singleton_singleton, singleton_subset_iff, id],
calc comap (λ (x : α × α), (pure_cauchy (x.fst), pure_cauchy (x.snd))) (uniformity.lift' gen)
= uniformity.lift' (preimage (λ (x : α × α), (pure_cauchy (x.fst), pure_cauchy (x.snd))) ∘ gen) :
comap_lift'_eq monotone_gen
... = uniformity : by rw [this, lift'_id]⟩
lemma pure_cauchy_dense : ∀x, x ∈ closure (range pure_cauchy) :=
assume f,
have h_ex : ∀s∈(@uniformity (Cauchy α) _).sets, ∃y:α, (f, pure_cauchy y) ∈ s, from
assume s hs,
let ⟨t'', ht''₁, (ht''₂ : gen t'' ⊆ s)⟩ := (mem_lift'_sets monotone_gen).mp hs in
let ⟨t', ht'₁, ht'₂⟩ := comp_mem_uniformity_sets ht''₁ in
have t' ∈ (filter.prod (f.val) (f.val)).sets,
from f.property.right ht'₁,
let ⟨t, ht, (h : set.prod t t ⊆ t')⟩ := mem_prod_same_iff.mp this in
let ⟨x, (hx : x ∈ t)⟩ := inhabited_of_mem_sets f.property.left ht in
have t'' ∈ (filter.prod f.val (pure x)).sets,
from mem_prod_iff.mpr ⟨t, ht, {y:α | (x, y) ∈ t'},
assume y, begin rw mem_singleton_iff, rintro rfl, exact refl_mem_uniformity ht'₁ end,
assume ⟨a, b⟩ ⟨(h₁ : a ∈ t), (h₂ : (x, b) ∈ t')⟩,
ht'₂ $ prod_mk_mem_comp_rel (@h (a, x) ⟨h₁, hx⟩) h₂⟩,
⟨x, ht''₂ $ by exact this⟩,
begin
simp only [closure_eq_nhds, nhds_eq_uniformity, lift'_inf_principal_eq, set.inter_comm],
exact (lift'_neq_bot_iff $ monotone_inter monotone_const monotone_preimage).mpr
(assume s hs,
let ⟨y, hy⟩ := h_ex s hs in
have pure_cauchy y ∈ range pure_cauchy ∩ {y : Cauchy α | (f, y) ∈ s},
from ⟨mem_range_self y, hy⟩,
ne_empty_of_mem this)
end
instance : complete_space (Cauchy α) :=
complete_space_extension
uniform_embedding_pure_cauchy
pure_cauchy_dense $
assume f hf,
let f' : Cauchy α := ⟨f, hf⟩ in
have map pure_cauchy f ≤ uniformity.lift' (preimage (prod.mk f')),
from le_lift' $ assume s hs,
let ⟨t, ht₁, (ht₂ : gen t ⊆ s)⟩ := (mem_lift'_sets monotone_gen).mp hs in
let ⟨t', ht', (h : set.prod t' t' ⊆ t)⟩ := mem_prod_same_iff.mp (hf.right ht₁) in
have t' ⊆ { y : α | (f', pure_cauchy y) ∈ gen t },
from assume x hx, (filter.prod f (pure x)).sets_of_superset (prod_mem_prod ht' $ mem_pure hx) h,
f.sets_of_superset ht' $ subset.trans this (preimage_mono ht₂),
⟨f', by rwa [nhds_eq_uniformity]⟩
end
section
local attribute [instance] separation_setoid
lemma injective_separated_pure_cauchy {α : Type*} [uniform_space α] [s : separated α] :
function.injective (λa:α, ⟦pure_cauchy a⟧) | a b h :=
separated_def.1 s _ _ $ assume s hs,
let ⟨t, ht, hts⟩ :=
by rw [← (@uniform_embedding_pure_cauchy α _).right, filter.mem_comap_sets] at hs; exact hs in
have (pure_cauchy a, pure_cauchy b) ∈ t, from quotient.exact h t ht,
@hts (a, b) this
end
end Cauchy
instance nonempty_Cauchy {α : Type u} [h : nonempty α] [uniform_space α] : nonempty (Cauchy α) :=
h.rec_on $ assume a, nonempty.intro $ Cauchy.pure_cauchy a
instance inhabited_Cauchy {α : Type u} [inhabited α] [uniform_space α] : inhabited (Cauchy α) :=
⟨Cauchy.pure_cauchy $ default α⟩
section constructions
variables {α : Type*} {β : Type*} {γ : Type*} {δ : Type*} {ι : Sort*}
instance : partial_order (uniform_space α) :=
{ le := λt s, s.uniformity ≤ t.uniformity,
le_antisymm := assume t s h₁ h₂, uniform_space_eq $ le_antisymm h₂ h₁,
le_refl := assume t, le_refl _,
le_trans := assume a b c h₁ h₂, @le_trans _ _ c.uniformity b.uniformity a.uniformity h₂ h₁ }
instance : has_Sup (uniform_space α) :=
⟨assume s, uniform_space.of_core {
uniformity := (⨅u∈s, @uniformity α u),
refl := le_infi $ assume u, le_infi $ assume hu, u.refl,
symm := le_infi $ assume u, le_infi $ assume hu,
le_trans (map_mono $ infi_le_of_le _ $ infi_le _ hu) u.symm,
comp := le_infi $ assume u, le_infi $ assume hu,
le_trans (lift'_mono (infi_le_of_le _ $ infi_le _ hu) $ le_refl _) u.comp }⟩
private lemma le_Sup {tt : set (uniform_space α)} {t : uniform_space α} (h : t ∈ tt) :
t ≤ Sup tt :=
show (⨅u∈tt, @uniformity α u) ≤ t.uniformity,
from infi_le_of_le t $ infi_le _ h
private lemma Sup_le {tt : set (uniform_space α)} {t : uniform_space α} (h : ∀t'∈tt, t' ≤ t) :
Sup tt ≤ t :=
show t.uniformity ≤ (⨅u∈tt, @uniformity α u),
from le_infi $ assume t', le_infi $ assume ht', h t' ht'
instance : has_bot (uniform_space α) :=
⟨uniform_space.of_core { uniformity := ⊤, refl := le_top, symm := le_top, comp := le_top }⟩
instance : has_top (uniform_space α) :=
⟨{ to_topological_space := ⊤,
uniformity := principal id_rel,
refl := le_refl _,
symm := by simp only [tendsto, map_principal, swap_id_rel, le_principal_iff]; apply subset.refl,
comp :=
begin
rw [lift'_principal], {simp only [id_comp_rel, le_principal_iff, mem_principal_sets]},
exact monotone_comp_rel monotone_id monotone_id
end,
is_open_uniformity := λ s, by simp only [is_open_fold, is_open_top, true_iff]; intros x hx;
simp only [mem_principal_sets]; rintro ⟨a,b⟩ h rfl; cases h; exact hx } ⟩
instance : complete_lattice (uniform_space α) :=
{ sup := λa b, Sup {a, b},
le_sup_left := assume a b, le_Sup $ or.inr $ or.inl rfl,
le_sup_right := assume a b, le_Sup $ or.inl rfl,
sup_le := assume a b c h₁ h₂, Sup_le $ assume t' ht',
or.cases_on ht' (λ h, h.symm ▸ h₂)
(λ ht', or.cases_on ht' (λ h, h.symm ▸ h₁) false.elim),
inf := λa b, Sup {x | x ≤ a ∧ x ≤ b},
le_inf := assume a b c h₁ h₂, le_Sup ⟨h₁, h₂⟩,
inf_le_left := assume a b, Sup_le $ assume x ⟨ha, hb⟩, ha,
inf_le_right := assume a b, Sup_le $ assume x ⟨ha, hb⟩, hb,
top := ⊤,
le_top := assume u, u.refl,
bot := ⊥,
bot_le := assume a, show a.uniformity ≤ ⊤, from le_top,
Sup := Sup,
le_Sup := assume s u, le_Sup,
Sup_le := assume s u, Sup_le,
Inf := λtt, Sup {t | ∀t'∈tt, t ≤ t'},
le_Inf := assume s a hs, le_Sup hs,
Inf_le := assume s a ha, Sup_le $ assume u hs, hs _ ha,
..uniform_space.partial_order }
lemma supr_uniformity {ι : Sort*} {u : ι → uniform_space α} :
(supr u).uniformity = (⨅i, (u i).uniformity) :=
show (⨅a (h : ∃i:ι, a = u i), a.uniformity) = _, from
le_antisymm
(le_infi $ assume i, infi_le_of_le (u i) $ infi_le _ ⟨i, rfl⟩)
(le_infi $ assume a, le_infi $ assume ⟨i, (ha : a = u i)⟩, ha.symm ▸ infi_le _ _)
lemma sup_uniformity {u v : uniform_space α} :
(u ⊔ v).uniformity = u.uniformity ⊓ v.uniformity :=
have (u ⊔ v) = (⨆i (h : i = u ∨ i = v), i), by simp only [supr_or, supr_sup_eq, supr_supr_eq_left],
calc (u ⊔ v).uniformity = ((⨆i (h : i = u ∨ i = v), i) : uniform_space α).uniformity : by rw [this]
... = _ : by simp only [supr_uniformity, infi_or, infi_inf_eq, infi_infi_eq_left]
instance inhabited_uniform_space : inhabited (uniform_space α) := ⟨⊤⟩
/-- 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`. -/
def uniform_space.comap (f : α → β) (u : uniform_space β) : uniform_space α :=
{ uniformity := u.uniformity.comap (λp:α×α, (f p.1, f p.2)),
to_topological_space := u.to_topological_space.induced f,
refl := le_trans (by rw [comap_principal]; exact le_principal_iff.2
(assume ⟨a, b⟩ (h : a = b), h ▸ rfl)) (comap_mono u.refl),
symm := by simp only [tendsto_comap_iff, prod.swap, (∘)]; exact tendsto_comap.comp tendsto_swap_uniformity,
comp := le_trans
begin
rw [comap_lift'_eq, comap_lift'_eq2],
exact (lift'_mono' $ assume s hs ⟨a₁, a₂⟩ ⟨x, h₁, h₂⟩, ⟨f x, h₁, h₂⟩),
repeat { exact monotone_comp_rel monotone_id monotone_id }
end
(comap_mono u.comp),
is_open_uniformity := λ s, begin
change (@is_open α (u.to_topological_space.induced f) s ↔ _),
simp only [is_open_iff_nhds, nhds_induced_eq_comap, mem_nhds_uniformity_iff, comap, and_comm,
exists_prop, le_principal_iff],
refine ball_congr (λ x hx, ⟨_, _⟩),
{ rintro ⟨t, hts, ht⟩, refine ⟨_, ht, _⟩,
rintro ⟨x₁, x₂⟩ h rfl, exact hts (h rfl) },
{ rintro ⟨t, ht, hts⟩,
exact ⟨{y | (f x, y) ∈ t}, λ y hy, @hts (x, y) hy rfl,
mem_nhds_uniformity_iff.1 $ mem_nhds_left _ ht⟩ }
end }
lemma uniform_space_comap_id {α : Type*} : uniform_space.comap (id : α → α) = id :=
by ext u s; show s ∈ (comap (λ p:α×α, (p.1, p.2)) _).sets ↔ _; rw [prod.id_prod, filter.comap_id]
lemma uniform_space.comap_comap_comp {α β γ} [uγ : uniform_space γ] {f : α → β} {g : β → γ} :
uniform_space.comap (g ∘ f) uγ = uniform_space.comap f (uniform_space.comap g uγ) :=
by ext s; show _ ↔ s ∈ (comap _ (comap _ _)).sets; rw filter.comap_comap_comp; refl
lemma uniform_continuous_iff {α β} [uα : uniform_space α] [uβ : uniform_space β] (f : α → β) :
uniform_continuous f ↔ uβ.comap f ≤ uα :=
filter.map_le_iff_le_comap
lemma uniform_continuous_comap {f : α → β} [u : uniform_space β] :
@uniform_continuous α β (uniform_space.comap f u) u f :=
tendsto_comap
theorem to_topological_space_comap {f : α → β} {u : uniform_space β} :
@uniform_space.to_topological_space _ (uniform_space.comap f u) =
topological_space.induced f (@uniform_space.to_topological_space β u) :=
eq_of_nhds_eq_nhds $ assume a,
begin
simp only [nhds_induced_eq_comap, nhds_eq_uniformity, nhds_eq_uniformity],
change comap f (uniformity.lift' (preimage (λb, (f a, b)))) =
(u.uniformity.comap (λp:α×α, (f p.1, f p.2))).lift' (preimage (λa', (a, a'))),
rw [comap_lift'_eq monotone_preimage, comap_lift'_eq2 monotone_preimage],
exact rfl
end
lemma uniform_continuous_comap' {f : γ → β} {g : α → γ} [v : uniform_space β] [u : uniform_space α]
(h : uniform_continuous (f ∘ g)) : @uniform_continuous α γ u (uniform_space.comap f v) g :=
tendsto_comap_iff.2 h
lemma to_topological_space_mono {u₁ u₂ : uniform_space α} (h : u₁ ≤ u₂) :
@uniform_space.to_topological_space _ u₁ ≤ @uniform_space.to_topological_space _ u₂ :=
le_of_nhds_le_nhds $ assume a,
by rw [@nhds_eq_uniformity α u₁ a, @nhds_eq_uniformity α u₂ a]; exact (lift'_mono h $ le_refl _)
lemma to_topological_space_top : @uniform_space.to_topological_space α ⊤ = ⊤ := rfl
lemma to_topological_space_bot : @uniform_space.to_topological_space α ⊥ = ⊥ :=
bot_unique $ assume s hs, classical.by_cases
(assume : s = ∅, this.symm ▸ @is_open_empty _ ⊥)
(assume : s ≠ ∅,
let ⟨x, hx⟩ := exists_mem_of_ne_empty this in
have s = univ, from top_unique $ assume y hy, hs x hx (x, y) rfl,
this.symm ▸ @is_open_univ _ ⊥)
lemma to_topological_space_supr {ι : Sort*} {u : ι → uniform_space α} :
@uniform_space.to_topological_space α (supr u) = (⨆i, @uniform_space.to_topological_space α (u i)) :=
classical.by_cases
(assume h : nonempty ι,
eq_of_nhds_eq_nhds $ assume a,
begin
rw [nhds_supr, nhds_eq_uniformity],
change _ = (supr u).uniformity.lift' (preimage $ prod.mk a),
begin
rw [supr_uniformity, lift'_infi],
exact (congr_arg _ $ funext $ assume i, @nhds_eq_uniformity α (u i) a),
exact h,
exact assume a b, rfl
end
end)
(assume : ¬ nonempty ι,
le_antisymm
(have supr u = ⊥, from bot_unique $ supr_le $ assume i, (this ⟨i⟩).elim,
have @uniform_space.to_topological_space _ (supr u) = ⊥,
from this.symm ▸ to_topological_space_bot,
this.symm ▸ bot_le)
(supr_le $ assume i, to_topological_space_mono $ le_supr _ _))
lemma to_topological_space_Sup {s : set (uniform_space α)} :
@uniform_space.to_topological_space α (Sup s) = (⨆i∈s, @uniform_space.to_topological_space α i) :=
begin
rw [Sup_eq_supr, to_topological_space_supr],
apply congr rfl,
funext x,
exact to_topological_space_supr
end
lemma to_topological_space_sup {u v : uniform_space α} :
@uniform_space.to_topological_space α (u ⊔ v) =
@uniform_space.to_topological_space α u ⊔ @uniform_space.to_topological_space α v :=
ord_continuous_sup $ assume s, to_topological_space_Sup
instance : uniform_space empty := ⊤
instance : uniform_space unit := ⊤
instance : uniform_space bool := ⊤
instance : uniform_space ℕ := ⊤
instance : uniform_space ℤ := ⊤
instance {p : α → Prop} [t : uniform_space α] : uniform_space (subtype p) :=
uniform_space.comap subtype.val t
lemma uniformity_subtype {p : α → Prop} [t : uniform_space α] :
(@uniformity (subtype p) _) = comap (λq:subtype p × subtype p, (q.1.1, q.2.1)) uniformity :=
rfl
lemma uniform_continuous_subtype_val {p : α → Prop} [uniform_space α] :
uniform_continuous (subtype.val : {a : α // p a} → α) :=
uniform_continuous_comap
lemma uniform_continuous_subtype_mk {p : α → Prop} [uniform_space α] [uniform_space β]
{f : β → α} (hf : uniform_continuous f) (h : ∀x, p (f x)) :
uniform_continuous (λx, ⟨f x, h x⟩ : β → subtype p) :=
uniform_continuous_comap' hf
lemma tendsto_of_uniform_continuous_subtype
[uniform_space α] [uniform_space β] {f : α → β} {s : set α} {a : α}
(hf : uniform_continuous (λx:s, f x.val)) (ha : s ∈ (nhds a).sets) :
tendsto f (nhds a) (nhds (f a)) :=
by rw [(@map_nhds_subtype_val_eq α _ s a (mem_of_nhds ha) ha).symm]; exact
tendsto_map' (continuous_iff_tendsto.mp hf.continuous _)
instance [u₁ : uniform_space α] [u₂ : uniform_space β] : uniform_space (α × β) :=
uniform_space.of_core_eq
(u₁.comap prod.fst ⊔ u₂.comap prod.snd).to_core
prod.topological_space
(calc prod.topological_space = (u₁.comap prod.fst ⊔ u₂.comap prod.snd).to_topological_space :
by rw [to_topological_space_sup, to_topological_space_comap, to_topological_space_comap]; refl
... = _ : by rw [uniform_space.to_core_to_topological_space])
theorem uniformity_prod [uniform_space α] [uniform_space β] : @uniformity (α × β) _ =
uniformity.comap (λp:(α × β) × α × β, (p.1.1, p.2.1)) ⊓
uniformity.comap (λp:(α × β) × α × β, (p.1.2, p.2.2)) :=
sup_uniformity
lemma uniform_embedding_subtype_emb {α : Type*} {β : Type*} [uniform_space α] [uniform_space β]
(p : α → Prop) {e : α → β} (ue : uniform_embedding e) (de : dense_embedding e) :
uniform_embedding (de.subtype_emb p) :=
⟨(de.subtype p).inj,
by simp only [comap_comap_comp, (∘), dense_embedding.subtype_emb, uniformity_subtype, ue.right.symm]⟩
lemma uniform_extend_subtype {α : Type*} {β : Type*} {γ : Type*}
[uniform_space α] [uniform_space β] [uniform_space γ] [complete_space γ]
[inhabited γ] [separated γ]
{p : α → Prop} {e : α → β} {f : α → γ} {b : β} {s : set α}
(hf : uniform_continuous (λx:subtype p, f x.val))
(he : uniform_embedding e) (hd : ∀x:β, x ∈ closure (range e))
(hb : closure (e '' s) ∈ (nhds b).sets) (hs : is_closed s) (hp : ∀x∈s, p x) :
∃c, tendsto f (comap e (nhds b)) (nhds c) :=
have de : dense_embedding e,
from he.dense_embedding hd,
have de' : dense_embedding (de.subtype_emb p),
by exact de.subtype p,
have ue' : uniform_embedding (de.subtype_emb p),
from uniform_embedding_subtype_emb _ he de,
have b ∈ closure (e '' {x | p x}),
from (closure_mono $ mono_image $ hp) (mem_of_nhds hb),
let ⟨c, (hc : tendsto (f ∘ subtype.val) (comap (de.subtype_emb p) (nhds ⟨b, this⟩)) (nhds c))⟩ :=
uniformly_extend_exists ue' de'.dense hf in
begin
rw [nhds_subtype_eq_comap, comap_comap_comp] at hc,
change (tendsto (f ∘ @subtype.val α p) (comap (e ∘ @subtype.val α p) (nhds b)) (nhds c)) at hc,
rw [←comap_comap_comp] at hc,
existsi c,
apply tendsto_comap'' s _ _ hc,
exact ⟨_, hb, assume x,
begin
change e x ∈ (closure (e '' s)) → x ∈ s,
rw [←closure_induced, closure_eq_nhds],
simp only [nhds_induced_eq_comap, de.induced],
change x ∈ {x | nhds x ⊓ principal s ≠ ⊥} → x ∈ s,
rw [←closure_eq_nhds, closure_eq_of_is_closed hs],
exact id,
exact de.inj
end⟩,
exact (assume x hx, ⟨⟨x, hp x hx⟩, rfl⟩)
end
/- 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 -/
lemma uniformity_prod_eq_prod [uniform_space α] [uniform_space β] :
@uniformity (α×β) _ =
map (λp:(α×α)×(β×β), ((p.1.1, p.2.1), (p.1.2, p.2.2))) (filter.prod uniformity uniformity) :=
have map (λp:(α×α)×(β×β), ((p.1.1, p.2.1), (p.1.2, p.2.2))) =
comap (λp:(α×β)×(α×β), ((p.1.1, p.2.1), (p.1.2, p.2.2))),
from funext $ assume f, map_eq_comap_of_inverse
(funext $ assume ⟨⟨_, _⟩, ⟨_, _⟩⟩, rfl) (funext $ assume ⟨⟨_, _⟩, ⟨_, _⟩⟩, rfl),
by rw [this, uniformity_prod, filter.prod, comap_inf, comap_comap_comp, comap_comap_comp]
lemma mem_uniform_prod [t₁ : uniform_space α] [t₂ : uniform_space β] {a : set (α × α)} {b : set (β × β)}
(ha : a ∈ (@uniformity α _).sets) (hb : b ∈ (@uniformity β _).sets) :
{p:(α×β)×(α×β) | (p.1.1, p.2.1) ∈ a ∧ (p.1.2, p.2.2) ∈ b } ∈ (@uniformity (α × β) _).sets :=
by rw [uniformity_prod]; exact inter_mem_inf_sets (preimage_mem_comap ha) (preimage_mem_comap hb)
lemma tendsto_prod_uniformity_fst [uniform_space α] [uniform_space β] :
tendsto (λp:(α×β)×(α×β), (p.1.1, p.2.1)) uniformity uniformity :=
le_trans (map_mono (@le_sup_left (uniform_space (α×β)) _ _ _)) map_comap_le
lemma tendsto_prod_uniformity_snd [uniform_space α] [uniform_space β] :
tendsto (λp:(α×β)×(α×β), (p.1.2, p.2.2)) uniformity uniformity :=
le_trans (map_mono (@le_sup_right (uniform_space (α×β)) _ _ _)) map_comap_le
lemma uniform_continuous_fst [uniform_space α] [uniform_space β] : uniform_continuous (λp:α×β, p.1) :=
tendsto_prod_uniformity_fst
lemma uniform_continuous_snd [uniform_space α] [uniform_space β] : uniform_continuous (λp:α×β, p.2) :=
tendsto_prod_uniformity_snd
variables [uniform_space α] [uniform_space β] [uniform_space γ]
lemma uniform_continuous.prod_mk
{f₁ : α → β} {f₂ : α → γ} (h₁ : uniform_continuous f₁) (h₂ : uniform_continuous f₂) :
uniform_continuous (λa, (f₁ a, f₂ a)) :=
by rw [uniform_continuous, uniformity_prod]; exact
tendsto_inf.2 ⟨tendsto_comap_iff.2 h₁, tendsto_comap_iff.2 h₂⟩
lemma uniform_continuous.prod_mk_left {f : α × β → γ} (h : uniform_continuous f) (b) :
uniform_continuous (λ a, f (a,b)) :=
uniform_continuous.comp (uniform_continuous.prod_mk uniform_continuous_id uniform_continuous_const) h
lemma uniform_continuous.prod_mk_right {f : α × β → γ} (h : uniform_continuous f) (a) :
uniform_continuous (λ b, f (a,b)) :=
uniform_continuous.comp (uniform_continuous.prod_mk uniform_continuous_const uniform_continuous_id) h
instance complete_space.prod [complete_space α] [complete_space β] : complete_space (α × β) :=
{ complete := λ f hf,
let ⟨x1, hx1⟩ := complete_space.complete $ cauchy_map uniform_continuous_fst hf in
let ⟨x2, hx2⟩ := complete_space.complete $ cauchy_map uniform_continuous_snd hf in
⟨(x1, x2), by rw [nhds_prod_eq, filter.prod_def];
from filter.le_lift (λ s hs, filter.le_lift' $ λ t ht,
have H1 : prod.fst ⁻¹' s ∈ f.sets := hx1 hs,
have H2 : prod.snd ⁻¹' t ∈ f.sets := hx2 ht,
filter.inter_mem_sets H1 H2)⟩ }
lemma uniform_embedding.prod {α' : Type*} {β' : Type*}
[uniform_space α] [uniform_space β] [uniform_space α'] [uniform_space β']
{e₁ : α → α'} {e₂ : β → β'} (h₁ : uniform_embedding e₁) (h₂ : uniform_embedding e₂) :
uniform_embedding (λp:α×β, (e₁ p.1, e₂ p.2)) :=
⟨assume ⟨a₁, b₁⟩ ⟨a₂, b₂⟩,
λ h, prod.ext (h₁.left (prod.mk.inj h).1) (h₂.left (prod.mk.inj h).2),
by simp only [(∘), uniformity_prod, h₁.right.symm, h₂.right.symm, comap_inf, comap_comap_comp]⟩
lemma to_topological_space_prod [u : uniform_space α] [v : uniform_space β] :
@uniform_space.to_topological_space (α × β) prod.uniform_space =
@prod.topological_space α β u.to_topological_space v.to_topological_space := rfl
lemma to_topological_space_subtype [u : uniform_space α] {p : α → Prop} :
@uniform_space.to_topological_space (subtype p) subtype.uniform_space =
@subtype.topological_space α p u.to_topological_space := rfl
section separation_space
local attribute [instance] separation_setoid
lemma uniform_continuous_quotient_lift₂ [uniform_space γ]
{f : α → β → γ} {h : ∀a c b d, (a, b) ∈ separation_rel α → (c, d) ∈ separation_rel β → f a c = f b d}
(hf : uniform_continuous (λp:α×β, f p.1 p.2)) :
uniform_continuous (λp:_×_, quotient.lift₂ f h p.1 p.2) :=
begin
rw [uniform_continuous, uniformity_prod_eq_prod, uniformity_quotient, uniformity_quotient,
filter.prod_map_map_eq, filter.tendsto_map'_iff, filter.tendsto_map'_iff],
rwa [uniform_continuous, uniformity_prod_eq_prod, filter.tendsto_map'_iff] at hf
end
lemma separation_prod {a₁ a₂ : α} {b₁ b₂ : β} : (a₁, b₁) ≈ (a₂, b₂) ↔ a₁ ≈ a₂ ∧ b₁ ≈ b₂ :=
begin
split ; intro h,
{ exact ⟨separated_of_uniform_continuous uniform_continuous_fst h,
separated_of_uniform_continuous uniform_continuous_snd h⟩ },
{ rcases h with ⟨eqv_α, eqv_β⟩,
intros r r_in,
rw uniformity_prod at r_in,
rcases r_in with ⟨t_α, ⟨r_α, r_α_in, h_α⟩, t_β, ⟨r_β, r_β_in, h_β⟩, H⟩,
let p_α := λ (p : (α × β) × α × β), ((p.fst).fst, (p.snd).fst),
let p_β := λ (p : (α × β) × α × β), ((p.fst).snd, (p.snd).snd),
have key_α : p_α ((a₁, b₁), (a₂, b₂)) ∈ r_α, by simp only [p_α, eqv_α r_α r_α_in],
have key_β : p_β ((a₁, b₁), (a₂, b₂)) ∈ r_β, by simp only [p_β, eqv_β r_β r_β_in],
exact H ⟨h_α key_α, h_β key_β⟩ },
end
instance separated.prod [separated α] [separated β] : separated (α × β) :=
separated_def.2 $ assume x y H, prod.ext
(eq_of_separated_of_uniform_continuous uniform_continuous_fst H)
(eq_of_separated_of_uniform_continuous uniform_continuous_snd H)
end separation_space
end constructions
lemma lebesgue_number_lemma {α : Type u} [uniform_space α] {s : set α} {ι} {c : ι → set α}
(hs : compact s) (hc₁ : ∀ i, is_open (c i)) (hc₂ : s ⊆ ⋃ i, c i) :
∃ n ∈ (@uniformity α _).sets, ∀ x ∈ s, ∃ i, {y | (x, y) ∈ n} ⊆ c i :=
begin
let u := λ n, {x | ∃ i (m ∈ (@uniformity α _).sets), {y | (x, y) ∈ comp_rel m n} ⊆ c i},
have hu₁ : ∀ n ∈ (@uniformity α _).sets, is_open (u n),
{ refine λ n hn, is_open_uniformity.2 _,
rintro x ⟨i, m, hm, h⟩,
rcases comp_mem_uniformity_sets hm with ⟨m', hm', mm'⟩,
apply uniformity.sets_of_superset hm',
rintros ⟨x, y⟩ hp rfl,
refine ⟨i, m', hm', λ z hz, h (monotone_comp_rel monotone_id monotone_const mm' _)⟩,
change (x, z) ∈ comp_rel (comp_rel m' m') n,
rw comp_rel_assoc,
exact ⟨y, hp, hz⟩ },
have hu₂ : s ⊆ ⋃ n ∈ (@uniformity α _).sets, u n,
{ intros x hx,
rcases mem_Union.1 (hc₂ hx) with ⟨i, h⟩,
rcases comp_mem_uniformity_sets (is_open_uniformity.1 (hc₁ i) x h) with ⟨m', hm', mm'⟩,
exact mem_bUnion hm' ⟨i, _, hm', λ y hy, mm' hy rfl⟩ },
rcases compact_elim_finite_subcover_image hs hu₁ hu₂ with ⟨b, bu, b_fin, b_cover⟩,
refine ⟨_, Inter_mem_sets b_fin bu, λ x hx, _⟩,
rcases mem_bUnion_iff.1 (b_cover hx) with ⟨n, bn, i, m, hm, h⟩,
refine ⟨i, λ y hy, h _⟩,
exact prod_mk_mem_comp_rel (refl_mem_uniformity hm) (bInter_subset_of_mem bn hy)
end
lemma lebesgue_number_lemma_sUnion {α : Type u} [uniform_space α] {s : set α} {c : set (set α)}
(hs : compact s) (hc₁ : ∀ t ∈ c, is_open t) (hc₂ : s ⊆ ⋃₀ c) :
∃ n ∈ (@uniformity α _).sets, ∀ x ∈ s, ∃ t ∈ c, ∀ y, (x, y) ∈ n → y ∈ t :=
by rw sUnion_eq_Union at hc₂;
simpa only [set_coe.exists, exists_prop] using
lebesgue_number_lemma hs (by simpa only [set_coe.forall]) hc₂
|
cc2aab30842f43f566675f32b85aea79b1469706 | 4d2583807a5ac6caaffd3d7a5f646d61ca85d532 | /src/algebra/continued_fractions/computation/translations.lean | 90b9179c315121617a98bafe0b00b1659305b6ef | [
"Apache-2.0"
] | permissive | AntoineChambert-Loir/mathlib | 64aabb896129885f12296a799818061bc90da1ff | 07be904260ab6e36a5769680b6012f03a4727134 | refs/heads/master | 1,693,187,631,771 | 1,636,719,886,000 | 1,636,719,886,000 | null | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 10,459 | lean | /-
Copyright (c) 2020 Kevin Kappelmann. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kevin Kappelmann
-/
import algebra.continued_fractions.computation.basic
import algebra.continued_fractions.translations
/-!
# Basic Translation Lemmas Between Structures Defined for Computing Continued Fractions
## Summary
This is a collection of simple lemmas between the different structures used for the computation
of continued fractions defined in `algebra.continued_fractions.computation.basic`. The file consists
of three sections:
1. Recurrences and inversion lemmas for `int_fract_pair.stream`: these lemmas give us inversion
rules and recurrences for the computation of the stream of integer and fractional parts of
a value.
2. Translation lemmas for the head term: these lemmas show us that the head term of the computed
continued fraction of a value `v` is `⌊v⌋` and how this head term is moved along the structures
used in the computation process.
3. Translation lemmas for the sequence: these lemmas show how the sequences of the involved
structures (`int_fract_pair.stream`, `int_fract_pair.seq1`, and
`generalized_continued_fraction.of`) are connected, i.e. how the values are moved along the
structures and the termination of one sequence implies the termination of another sequence.
## Main Theorems
- `succ_nth_stream_eq_some_iff` gives as a recurrence to compute the `n + 1`th value of the sequence
of integer and fractional parts of a value in case of non-termination.
- `succ_nth_stream_eq_none_iff` gives as a recurrence to compute the `n + 1`th value of the sequence
of integer and fractional parts of a value in case of termination.
- `nth_of_eq_some_of_succ_nth_int_fract_pair_stream` and
`nth_of_eq_some_of_nth_int_fract_pair_stream_fr_ne_zero` show how the entries of the sequence
of the computed continued fraction can be obtained from the stream of integer and fractional
parts.
-/
namespace generalized_continued_fraction
open generalized_continued_fraction (of)
/- Fix a discrete linear ordered floor field and a value `v`. -/
variables {K : Type*} [linear_ordered_field K] [floor_ring K] {v : K}
namespace int_fract_pair
/-!
### Recurrences and Inversion Lemmas for `int_fract_pair.stream`
Here we state some lemmas that give us inversion rules and recurrences for the computation of the
stream of integer and fractional parts of a value.
-/
variable {n : ℕ}
lemma stream_eq_none_of_fr_eq_zero {ifp_n : int_fract_pair K}
(stream_nth_eq : int_fract_pair.stream v n = some ifp_n) (nth_fr_eq_zero : ifp_n.fr = 0) :
int_fract_pair.stream v (n + 1) = none :=
begin
cases ifp_n with _ fr,
change fr = 0 at nth_fr_eq_zero,
simp [int_fract_pair.stream, stream_nth_eq, nth_fr_eq_zero]
end
/--
Gives a recurrence to compute the `n + 1`th value of the sequence of integer and fractional
parts of a value in case of termination.
-/
lemma succ_nth_stream_eq_none_iff : int_fract_pair.stream v (n + 1) = none
↔ (int_fract_pair.stream v n = none ∨ ∃ ifp, int_fract_pair.stream v n = some ifp ∧ ifp.fr = 0) :=
begin
cases stream_nth_eq : (int_fract_pair.stream v n) with ifp,
case option.none : { simp [stream_nth_eq, int_fract_pair.stream] },
case option.some :
{ cases ifp with _ fr,
cases decidable.em (fr = 0);
finish [int_fract_pair.stream] }
end
/--
Gives a recurrence to compute the `n + 1`th value of the sequence of integer and fractional
parts of a value in case of non-termination.
-/
lemma succ_nth_stream_eq_some_iff {ifp_succ_n : int_fract_pair K} :
int_fract_pair.stream v (n + 1) = some ifp_succ_n
↔ ∃ (ifp_n : int_fract_pair K), int_fract_pair.stream v n = some ifp_n
∧ ifp_n.fr ≠ 0
∧ int_fract_pair.of ifp_n.fr⁻¹ = ifp_succ_n :=
begin
split,
{ assume stream_succ_nth_eq,
have : int_fract_pair.stream v (n + 1) ≠ none, by simp [stream_succ_nth_eq],
have : ¬int_fract_pair.stream v n = none
∧ ¬(∃ ifp, int_fract_pair.stream v n = some ifp ∧ ifp.fr = 0), by
{ have not_none_not_fract_zero,
from (not_iff_not_of_iff succ_nth_stream_eq_none_iff).elim_left this,
exact (not_or_distrib.elim_left not_none_not_fract_zero) },
cases this with stream_nth_ne_none nth_fr_ne_zero,
replace nth_fr_ne_zero : ∀ ifp, int_fract_pair.stream v n = some ifp → ifp.fr ≠ 0, by
simpa using nth_fr_ne_zero,
obtain ⟨ifp_n, stream_nth_eq⟩ : ∃ ifp_n, int_fract_pair.stream v n = some ifp_n, from
option.ne_none_iff_exists'.mp stream_nth_ne_none,
existsi ifp_n,
have ifp_n_fr_ne_zero : ifp_n.fr ≠ 0, from nth_fr_ne_zero ifp_n stream_nth_eq,
cases ifp_n with _ ifp_n_fr,
suffices : int_fract_pair.of ifp_n_fr⁻¹ = ifp_succ_n,
by simpa [stream_nth_eq, ifp_n_fr_ne_zero],
simp only [int_fract_pair.stream, stream_nth_eq, ifp_n_fr_ne_zero, option.some_bind, if_false]
at stream_succ_nth_eq,
injection stream_succ_nth_eq },
{ rintro ⟨⟨_⟩, ifp_n_props⟩, finish [int_fract_pair.stream, ifp_n_props] }
end
lemma exists_succ_nth_stream_of_fr_zero {ifp_succ_n : int_fract_pair K}
(stream_succ_nth_eq : int_fract_pair.stream v (n + 1) = some ifp_succ_n)
(succ_nth_fr_eq_zero : ifp_succ_n.fr = 0) :
∃ ifp_n : int_fract_pair K, int_fract_pair.stream v n = some ifp_n ∧ ifp_n.fr⁻¹ = ⌊ifp_n.fr⁻¹⌋ :=
begin
-- get the witness from `succ_nth_stream_eq_some_iff` and prove that it has the additional
-- properties
rcases (succ_nth_stream_eq_some_iff.elim_left stream_succ_nth_eq) with
⟨ifp_n, stream_nth_eq, nth_fr_ne_zero, _⟩,
existsi ifp_n,
cases ifp_n with _ ifp_n_fr,
suffices : ifp_n_fr⁻¹ = ⌊ifp_n_fr⁻¹⌋, by simpa [stream_nth_eq],
have : int_fract_pair.of ifp_n_fr⁻¹ = ifp_succ_n, by finish,
cases ifp_succ_n with _ ifp_succ_n_fr,
change ifp_succ_n_fr = 0 at succ_nth_fr_eq_zero,
have : int.fract ifp_n_fr⁻¹ = ifp_succ_n_fr, by injection this,
have : int.fract ifp_n_fr⁻¹ = 0, by rwa [succ_nth_fr_eq_zero] at this,
calc
ifp_n_fr⁻¹ = int.fract ifp_n_fr⁻¹ + ⌊ifp_n_fr⁻¹⌋ : by rw (int.fract_add_floor ifp_n_fr⁻¹)
... = ⌊ifp_n_fr⁻¹⌋ : by simp [‹int.fract ifp_n_fr⁻¹ = 0›]
end
end int_fract_pair
section head
/-!
### Translation of the Head Term
Here we state some lemmas that show us that the head term of the computed continued fraction of a
value `v` is `⌊v⌋` and how this head term is moved along the structures used in the computation
process.
-/
/-- The head term of the sequence with head of `v` is just the integer part of `v`. -/
@[simp]
lemma int_fract_pair.seq1_fst_eq_of : (int_fract_pair.seq1 v).fst = int_fract_pair.of v := rfl
lemma of_h_eq_int_fract_pair_seq1_fst_b : (of v).h = (int_fract_pair.seq1 v).fst.b :=
by { cases aux_seq_eq : (int_fract_pair.seq1 v), simp [of, aux_seq_eq] }
/-- The head term of the gcf of `v` is `⌊v⌋`. -/
@[simp]
lemma of_h_eq_floor : (of v).h = ⌊v⌋ :=
by simp [of_h_eq_int_fract_pair_seq1_fst_b, int_fract_pair.of]
end head
section sequence
/-!
### Translation of the Sequences
Here we state some lemmas that show how the sequences of the involved structures
(`int_fract_pair.stream`, `int_fract_pair.seq1`, and `generalized_continued_fraction.of`) are
connected, i.e. how the values are moved along the structures and how the termination of one
sequence implies the termination of another sequence.
-/
variable {n : ℕ}
lemma int_fract_pair.nth_seq1_eq_succ_nth_stream :
(int_fract_pair.seq1 v).snd.nth n = (int_fract_pair.stream v) (n + 1) := rfl
section termination
/-!
#### Translation of the Termination of the Sequences
Let's first show how the termination of one sequence implies the termination of another sequence.
-/
lemma of_terminated_at_iff_int_fract_pair_seq1_terminated_at :
(of v).terminated_at n ↔ (int_fract_pair.seq1 v).snd.terminated_at n :=
begin
rw [terminated_at_iff_s_none, of],
rcases (int_fract_pair.seq1 v) with ⟨head, ⟨st⟩⟩,
cases st_n_eq : st n;
simp [of, st_n_eq, seq.map, seq.nth, stream.map, seq.terminated_at, stream.nth]
end
lemma of_terminated_at_n_iff_succ_nth_int_fract_pair_stream_eq_none :
(of v).terminated_at n ↔ int_fract_pair.stream v (n + 1) = none :=
by rw [of_terminated_at_iff_int_fract_pair_seq1_terminated_at, seq.terminated_at,
int_fract_pair.nth_seq1_eq_succ_nth_stream]
end termination
section values
/-!
#### Translation of the Values of the Sequence
Now let's show how the values of the sequences correspond to one another.
-/
lemma int_fract_pair.exists_succ_nth_stream_of_gcf_of_nth_eq_some {gp_n : pair K}
(s_nth_eq : (of v).s.nth n = some gp_n) :
∃ (ifp : int_fract_pair K), int_fract_pair.stream v (n + 1) = some ifp ∧ (ifp.b : K) = gp_n.b :=
begin
obtain ⟨ifp, stream_succ_nth_eq, gp_n_eq⟩ :
∃ ifp, int_fract_pair.stream v (n + 1) = some ifp ∧ pair.mk 1 (ifp.b : K) = gp_n, by
{ unfold of int_fract_pair.seq1 at s_nth_eq,
rwa [seq.map_tail, seq.nth_tail, seq.map_nth, option.map_eq_some'] at s_nth_eq },
cases gp_n_eq,
injection gp_n_eq with _ ifp_b_eq_gp_n_b,
existsi ifp,
exact ⟨stream_succ_nth_eq, ifp_b_eq_gp_n_b⟩
end
/--
Shows how the entries of the sequence of the computed continued fraction can be obtained by the
integer parts of the stream of integer and fractional parts.
-/
lemma nth_of_eq_some_of_succ_nth_int_fract_pair_stream {ifp_succ_n : int_fract_pair K}
(stream_succ_nth_eq : int_fract_pair.stream v (n + 1) = some ifp_succ_n) :
(of v).s.nth n = some ⟨1, ifp_succ_n.b⟩ :=
begin
unfold of int_fract_pair.seq1,
rw [seq.map_tail, seq.nth_tail, seq.map_nth],
simp [seq.nth, stream_succ_nth_eq]
end
/--
Shows how the entries of the sequence of the computed continued fraction can be obtained by the
fractional parts of the stream of integer and fractional parts.
-/
lemma nth_of_eq_some_of_nth_int_fract_pair_stream_fr_ne_zero {ifp_n : int_fract_pair K}
(stream_nth_eq : int_fract_pair.stream v n = some ifp_n) (nth_fr_ne_zero : ifp_n.fr ≠ 0) :
(of v).s.nth n = some ⟨1, (int_fract_pair.of ifp_n.fr⁻¹).b⟩ :=
have int_fract_pair.stream v (n + 1) = some (int_fract_pair.of ifp_n.fr⁻¹), by
{ cases ifp_n, simp [int_fract_pair.stream, stream_nth_eq, nth_fr_ne_zero], refl },
nth_of_eq_some_of_succ_nth_int_fract_pair_stream this
end values
end sequence
end generalized_continued_fraction
|
974cdb6fceb9ac51b8baf0f27383dfca55039879 | d406927ab5617694ec9ea7001f101b7c9e3d9702 | /src/group_theory/group_action/sigma.lean | a7947d7f13176914fd4754379f87bb612827d846 | [
"Apache-2.0"
] | permissive | alreadydone/mathlib | dc0be621c6c8208c581f5170a8216c5ba6721927 | c982179ec21091d3e102d8a5d9f5fe06c8fafb73 | refs/heads/master | 1,685,523,275,196 | 1,670,184,141,000 | 1,670,184,141,000 | 287,574,545 | 0 | 0 | Apache-2.0 | 1,670,290,714,000 | 1,597,421,623,000 | Lean | UTF-8 | Lean | false | false | 2,272 | lean | /-
Copyright (c) 2022 Yaël Dillies. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yaël Dillies
-/
import group_theory.group_action.defs
/-!
# Sigma instances for additive and multiplicative actions
This file defines instances for arbitrary sum of additive and multiplicative actions.
## See also
* `group_theory.group_action.pi`
* `group_theory.group_action.prod`
* `group_theory.group_action.sum`
-/
variables {ι : Type*} {M N : Type*} {α : ι → Type*}
namespace sigma
section has_smul
variables [Π i, has_smul M (α i)] [Π i, has_smul N (α i)] (a : M) (i : ι) (b : α i)
(x : Σ i, α i)
@[to_additive sigma.has_vadd] instance : has_smul M (Σ i, α i) := ⟨λ a, sigma.map id $ λ i, (•) a⟩
@[to_additive] lemma smul_def : a • x = x.map id (λ i, (•) a) := rfl
@[simp, to_additive] lemma smul_mk : a • mk i b = ⟨i, a • b⟩ := rfl
@[to_additive] instance [has_smul M N] [Π i, is_scalar_tower M N (α i)] :
is_scalar_tower M N (Σ i, α i) :=
⟨λ a b x, by { cases x, rw [smul_mk, smul_mk, smul_mk, smul_assoc] }⟩
@[to_additive] instance [Π i, smul_comm_class M N (α i)] : smul_comm_class M N (Σ i, α i) :=
⟨λ a b x, by { cases x, rw [smul_mk, smul_mk, smul_mk, smul_mk, smul_comm] }⟩
@[to_additive] instance [Π i, has_smul Mᵐᵒᵖ (α i)] [Π i, is_central_scalar M (α i)] :
is_central_scalar M (Σ i, α i) :=
⟨λ a x, by { cases x, rw [smul_mk, smul_mk, op_smul_eq_smul] }⟩
/-- This is not an instance because `i` becomes a metavariable. -/
@[to_additive "This is not an instance because `i` becomes a metavariable."]
protected lemma has_faithful_smul' [has_faithful_smul M (α i)] : has_faithful_smul M (Σ i, α i) :=
⟨λ x y h, eq_of_smul_eq_smul $ λ a : α i, heq_iff_eq.1 (ext_iff.1 $ h $ mk i a).2⟩
@[to_additive] instance [nonempty ι] [Π i, has_faithful_smul M (α i)] :
has_faithful_smul M (Σ i, α i) :=
nonempty.elim ‹_› $ λ i, sigma.has_faithful_smul' i
end has_smul
@[to_additive] instance {m : monoid M} [Π i, mul_action M (α i)] : mul_action M (Σ i, α i) :=
{ mul_smul := λ a b x, by { cases x, rw [smul_mk, smul_mk, smul_mk, mul_smul] },
one_smul := λ x, by { cases x, rw [smul_mk, one_smul] } }
end sigma
|
4893f75988fb143e7ca12c0f8e6a8960e58cae23 | 4bcaca5dc83d49803f72b7b5920b75b6e7d9de2d | /src/Lean/Data/Position.lean | 3e1a0106e8b5cd2a91cfd459d104a0422b5cc3a4 | [
"Apache-2.0"
] | permissive | subfish-zhou/leanprover-zh_CN.github.io | 30b9fba9bd790720bd95764e61ae796697d2f603 | 8b2985d4a3d458ceda9361ac454c28168d920d3f | refs/heads/master | 1,689,709,967,820 | 1,632,503,056,000 | 1,632,503,056,000 | 409,962,097 | 1 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 2,500 | lean | /-
Copyright (c) 2018 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Leonardo de Moura, Sebastian Ullrich
-/
import Lean.Data.Format
namespace Lean
structure Position where
line : Nat
column : Nat
deriving Inhabited, DecidableEq, Repr
namespace Position
protected def lt : Position → Position → Bool
| ⟨l₁, c₁⟩, ⟨l₂, c₂⟩ => (l₁, c₁) < (l₂, c₂)
instance : ToFormat Position :=
⟨fun ⟨l, c⟩ => "⟨" ++ format l ++ ", " ++ format c ++ "⟩"⟩
instance : ToString Position :=
⟨fun ⟨l, c⟩ => "⟨" ++ toString l ++ ", " ++ toString c ++ "⟩"⟩
end Position
structure FileMap where
source : String
positions : Array String.Pos
lines : Array Nat
deriving Inhabited
class MonadFileMap (m : Type → Type) where
getFileMap : m FileMap
export MonadFileMap (getFileMap)
namespace FileMap
partial def ofString (s : String) : FileMap :=
let rec loop (i : String.Pos) (line : Nat) (ps : Array String.Pos) (lines : Array Nat) : FileMap :=
if s.atEnd i then { source := s, positions := ps.push i, lines := lines.push line }
else
let c := s.get i;
let i := s.next i;
if c == '\n' then loop i (line+1) (ps.push i) (lines.push (line+1))
else loop i line ps lines
loop 0 1 (#[0]) (#[1])
partial def toPosition (fmap : FileMap) (pos : String.Pos) : Position :=
match fmap with
| { source := str, positions := ps, lines := lines } =>
if ps.size >= 2 && pos <= ps.back then
let rec toColumn (i : String.Pos) (c : Nat) : Nat :=
if i == pos || str.atEnd i then c
else toColumn (str.next i) (c+1)
let rec loop (b e : Nat) :=
let posB := ps[b]
if e == b + 1 then { line := lines.get! b, column := toColumn posB 0 }
else
let m := (b + e) / 2;
let posM := ps.get! m;
if pos == posM then { line := lines.get! m, column := 0 }
else if pos > posM then loop m e
else loop b m
loop 0 (ps.size -1)
else if lines.isEmpty then
⟨0, 0⟩
else
-- Some systems like the delaborator use synthetic positions without an input file,
-- which would violate `toPositionAux`'s invariant.
-- Can also happen with EOF errors, which are not strictly inside the file.
⟨lines.back, pos - ps.back⟩
end FileMap
end Lean
def String.toFileMap (s : String) : Lean.FileMap :=
Lean.FileMap.ofString s
|
1012bb6b41be2014e3c7ed47787ba4ef51e48650 | 6432ea7a083ff6ba21ea17af9ee47b9c371760f7 | /tests/lean/run/congrThm.lean | b9934fd94652eb5f82afba6fa9010fdbf449bec7 | [
"Apache-2.0",
"LLVM-exception",
"NCSA",
"LGPL-3.0-only",
"LicenseRef-scancode-inner-net-2.0",
"BSD-3-Clause",
"LGPL-2.0-or-later",
"Spencer-94",
"LGPL-2.1-or-later",
"HPND",
"LicenseRef-scancode-pcre",
"ISC",
"LGPL-2.1-only",
"LicenseRef-scancode-other-permissive",
"SunPro",
"CMU-Mach"... | permissive | leanprover/lean4 | 4bdf9790294964627eb9be79f5e8f6157780b4cc | f1f9dc0f2f531af3312398999d8b8303fa5f096b | refs/heads/master | 1,693,360,665,786 | 1,693,350,868,000 | 1,693,350,868,000 | 129,571,436 | 2,827 | 311 | Apache-2.0 | 1,694,716,156,000 | 1,523,760,560,000 | Lean | UTF-8 | Lean | false | false | 339 | lean | import Lean
open Lean
open Lean.Meta
def test (f : Expr) : MetaM Unit := do
let some thm ← mkCongrSimp? f | unreachable!
check thm.type
check thm.proof
assert! (← isDefEq thm.type (← inferType thm.proof))
IO.println (← Meta.ppExpr thm.type)
#eval test (mkConst ``decide)
#eval test (mkConst ``Array.uget [levelZero])
|
62faf94a43fd84ed095c6185c4335fc54e03fd34 | e39f04f6ff425fe3b3f5e26a8998b817d1dba80f | /data/option.lean | ff0c53ce8a04e86bbf8fd96ac7c11a7c54beb9ba | [
"Apache-2.0"
] | permissive | kristychoi/mathlib | c504b5e8f84e272ea1d8966693c42de7523bf0ec | 257fd84fe98927ff4a5ffe044f68c4e9d235cc75 | refs/heads/master | 1,586,520,722,896 | 1,544,030,145,000 | 1,544,031,933,000 | null | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 7,735 | lean | /-
Copyright (c) 2017 Mario Carneiro. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Mario Carneiro
-/
import logic.basic data.bool init.data.option.instances
tactic.interactive
namespace option
variables {α : Type*} {β : Type*}
instance has_mem : has_mem α (option α) := ⟨λ a b, b = some a⟩
@[simp] theorem mem_def {a : α} {b : option α} : a ∈ b ↔ b = some a :=
iff.rfl
@[simp] theorem get_mem : ∀ {o : option α} (h : is_some o), option.get h ∈ o
| (some a) _ := rfl
theorem get_of_mem {a : α} : ∀ {o : option α} (h : is_some o), a ∈ o → option.get h = a
| _ _ rfl := rfl
theorem mem_unique {o : option α} {a b : α} (ha : a ∈ o) (hb : b ∈ o) : a = b :=
option.some.inj $ ha.symm.trans hb
theorem some_inj {a b : α} : some a = some b ↔ a = b := by simp
theorem injective_some (α : Type*) : function.injective (@some α) :=
λ _ _, some_inj.mp
@[extensionality] theorem ext : ∀ {o₁ o₂ : option α}, (∀ a, a ∈ o₁ ↔ a ∈ o₂) → o₁ = o₂
| none none H := rfl
| (some a) o H := ((H _).1 rfl).symm
| o (some b) H := (H _).2 rfl
theorem eq_none_iff_forall_not_mem {o : option α} :
o = none ↔ (∀ a, a ∉ o) :=
⟨λ e a h, by rw e at h; cases h, λ h, ext $ by simpa⟩
@[simp] theorem none_bind {α β} (f : α → option β) : none >>= f = none := rfl
@[simp] theorem some_bind {α β} (a : α) (f : α → option β) : some a >>= f = f a := rfl
@[simp] theorem none_bind' (f : α → option β) : none.bind f = none := rfl
@[simp] theorem some_bind' (a : α) (f : α → option β) : (some a).bind f = f a := rfl
@[simp] theorem bind_some : ∀ x : option α, x >>= some = x :=
@bind_pure α option _ _
@[simp] theorem bind_eq_some {α β} {x : option α} {f : α → option β} {b : β} : x >>= f = some b ↔ ∃ a, x = some a ∧ f a = some b :=
by cases x; simp
@[simp] theorem bind_eq_some' {x : option α} {f : α → option β} {b : β} : x.bind f = some b ↔ ∃ a, x = some a ∧ f a = some b :=
by cases x; simp
lemma bind_comm {α β γ} {f : α → β → option γ} (a : option α) (b : option β) :
a.bind (λx, b.bind (f x)) = b.bind (λy, a.bind (λx, f x y)) :=
by cases a; cases b; refl
@[simp] theorem map_none {α β} {f : α → β} : f <$> none = none := rfl
@[simp] theorem map_some {α β} {a : α} {f : α → β} : f <$> some a = some (f a) := rfl
@[simp] theorem map_none' {f : α → β} : option.map f none = none := rfl
@[simp] theorem map_some' {a : α} {f : α → β} : option.map f (some a) = some (f a) := rfl
@[simp] theorem map_eq_some {α β} {x : option α} {f : α → β} {b : β} : f <$> x = some b ↔ ∃ a, x = some a ∧ f a = b :=
by cases x; simp
@[simp] theorem map_eq_some' {x : option α} {f : α → β} {b : β} : x.map f = some b ↔ ∃ a, x = some a ∧ f a = b :=
by cases x; simp
@[simp] theorem map_id' : option.map (@id α) = id := map_id
@[simp] theorem seq_some {α β} {a : α} {f : α → β} : some f <*> some a = some (f a) := rfl
@[simp] theorem some_orelse' (a : α) (x : option α) : (some a).orelse x = some a := rfl
@[simp] theorem some_orelse (a : α) (x : option α) : (some a <|> x) = some a := rfl
@[simp] theorem none_orelse' (x : option α) : none.orelse x = x :=
by cases x; refl
@[simp] theorem none_orelse (x : option α) : (none <|> x) = x := none_orelse' x
@[simp] theorem orelse_none' (x : option α) : x.orelse none = x :=
by cases x; refl
@[simp] theorem orelse_none (x : option α) : (x <|> none) = x := orelse_none' x
@[simp] theorem is_some_none : @is_some α none = ff := rfl
@[simp] theorem is_some_some {a : α} : is_some (some a) = tt := rfl
theorem is_some_iff_exists {x : option α} : is_some x ↔ ∃ a, x = some a :=
by cases x; simp [is_some]; exact ⟨_, rfl⟩
@[simp] theorem is_none_none : @is_none α none = tt := rfl
@[simp] theorem is_none_some {a : α} : is_none (some a) = ff := rfl
@[simp] theorem not_is_some {a : option α} : is_some a = ff ↔ a.is_none = tt :=
by cases a; simp
theorem is_none_iff_eq_none {o : option α} : o.is_none = tt ↔ o = none :=
⟨option.eq_none_of_is_none, λ e, e.symm ▸ rfl⟩
instance decidable_eq_none {o : option α} : decidable (o = none) :=
decidable_of_bool _ is_none_iff_eq_none
instance decidable_forall_mem {p : α → Prop} [decidable_pred p] :
∀ o : option α, decidable (∀ a ∈ o, p a)
| none := is_true (by simp)
| (some a) := decidable_of_iff (p a) (by simp)
instance decidable_exists_mem {p : α → Prop} [decidable_pred p] :
∀ o : option α, decidable (∃ a ∈ o, p a)
| none := is_false (by simp)
| (some a) := decidable_of_iff (p a) (by simp)
/-- inhabited `get` function. Returns `a` if the input is `some a`,
otherwise returns `default`. -/
@[reducible] def iget [inhabited α] : option α → α
| (some x) := x
| none := default α
@[simp] theorem iget_some [inhabited α] {a : α} : (some a).iget = a := rfl
theorem iget_mem [inhabited α] : ∀ {o : option α}, is_some o → o.iget ∈ o
| (some a) _ := rfl
theorem iget_of_mem [inhabited α] {a : α} : ∀ {o : option α}, a ∈ o → o.iget = a
| _ rfl := rfl
@[simp] theorem guard_eq_some' {p : Prop} [decidable p] :
∀ u, guard p = some u ↔ p
| () := by by_cases p; simp [guard, h, pure]; intro; contradiction
/-- `guard p a` returns `some a` if `p a` holds, otherwise `none`. -/
def guard (p : α → Prop) [decidable_pred p] (a : α) : option α :=
if p a then some a else none
/-- `filter p o` returns `some a` if `o` is `some a`
and `p a` holds, otherwise `none`. -/
def filter (p : α → Prop) [decidable_pred p] (o : option α) : option α :=
o.bind (guard p)
@[simp] theorem guard_eq_some {p : α → Prop} [decidable_pred p] {a b : α} :
guard p a = some b ↔ a = b ∧ p a :=
by by_cases p a; simp [option.guard, h]; intro; contradiction
def to_list : option α → list α
| none := []
| (some a) := [a]
@[simp] theorem mem_to_list {a : α} {o : option α} : a ∈ to_list o ↔ a ∈ o :=
by cases o; simp [to_list, eq_comm]
def lift_or_get (f : α → α → α) : option α → option α → option α
| none none := none
| (some a) none := some a -- get a
| none (some b) := some b -- get b
| (some a) (some b) := some (f a b) -- lift f
instance lift_or_get_comm (f : α → α → α) [h : is_commutative α f] :
is_commutative (option α) (lift_or_get f) :=
⟨λ a b, by cases a; cases b; simp [lift_or_get, h.comm]⟩
instance lift_or_get_assoc (f : α → α → α) [h : is_associative α f] :
is_associative (option α) (lift_or_get f) :=
⟨λ a b c, by cases a; cases b; cases c; simp [lift_or_get, h.assoc]⟩
instance lift_or_get_idem (f : α → α → α) [h : is_idempotent α f] :
is_idempotent (option α) (lift_or_get f) :=
⟨λ a, by cases a; simp [lift_or_get, h.idempotent]⟩
instance lift_or_get_is_left_id (f : α → α → α) :
is_left_id (option α) (lift_or_get f) none :=
⟨λ a, by cases a; simp [lift_or_get]⟩
instance lift_or_get_is_right_id (f : α → α → α) :
is_right_id (option α) (lift_or_get f) none :=
⟨λ a, by cases a; simp [lift_or_get]⟩
theorem lift_or_get_choice {f : α → α → α} (h : ∀ a b, f a b = a ∨ f a b = b) :
∀ o₁ o₂, lift_or_get f o₁ o₂ = o₁ ∨ lift_or_get f o₁ o₂ = o₂
| none none := or.inl rfl
| (some a) none := or.inl rfl
| none (some b) := or.inr rfl
| (some a) (some b) := by simpa [lift_or_get] using h a b
section rel
inductive rel (r : α → β → Prop) : option α → option β → Prop
| some {a b} : r a b → rel (some a) (some b)
| none {} : rel none none
end rel
end option
|
dde06eac810c4340ee32a6da4e940d6b78f750ad | ebf7140a9ea507409ff4c994124fa36e79b4ae35 | /src/hints/category_theory/exercise3/hint4.lean | 4b5b895ac374ab671c9729c3313f7ec424e7cb22 | [] | no_license | fundou/lftcm2020 | 3e88d58a92755ea5dd49f19c36239c35286ecf5e | 99d11bf3bcd71ffeaef0250caa08ecc46e69b55b | refs/heads/master | 1,685,610,799,304 | 1,624,070,416,000 | 1,624,070,416,000 | null | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 430 | lean | import category_theory.equivalence
open category_theory
variables {C : Type*} [category C]
variables {D : Type*} [category D]
lemma equiv_reflects_mono {X Y : C} (f : X ⟶ Y) (e : C ≌ D)
(hef : mono (e.functor.map f)) : mono f :=
begin
split,
intros Z g h w,
apply e.functor.map_injective,
rw ← cancel_mono (e.functor.map f),
-- Now we're ready to push eveything back to `C`, using the same trick.
sorry
end
|
77df42cac3e0bdaa2479f20da040ba485e18f64d | 57aec6ee746bc7e3a3dd5e767e53bd95beb82f6d | /stage0/src/Init/System/IO.lean | 18e7a7f9693e6a12a94f0c49fb46fabc3eec6023 | [
"Apache-2.0"
] | permissive | collares/lean4 | 861a9269c4592bce49b71059e232ff0bfe4594cc | 52a4f535d853a2c7c7eea5fee8a4fa04c682c1ee | refs/heads/master | 1,691,419,031,324 | 1,618,678,138,000 | 1,618,678,138,000 | 358,989,750 | 0 | 0 | Apache-2.0 | 1,618,696,333,000 | 1,618,696,333,000 | null | UTF-8 | Lean | false | false | 19,636 | lean | /-
Copyright (c) 2017 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Luke Nelson, Jared Roesch, Leonardo de Moura, Sebastian Ullrich
-/
prelude
import Init.Control.EState
import Init.Control.Reader
import Init.Data.String
import Init.Data.ByteArray
import Init.System.IOError
import Init.System.FilePath
import Init.System.ST
import Init.Data.ToString.Macro
/-- Like https://hackage.haskell.org/package/ghc-Prim-0.5.2.0/docs/GHC-Prim.html#t:RealWorld.
Makes sure we never reorder `IO` operations.
TODO: mark opaque -/
def IO.RealWorld : Type := Unit
/- TODO(Leo): mark it as an opaque definition. Reason: prevent
functions defined in other modules from accessing `IO.RealWorld`.
We don't want action such as
```
def getWorld : IO (IO.RealWorld) := get
```
-/
def EIO (ε : Type) : Type → Type := EStateM ε IO.RealWorld
@[inline] def EIO.catchExceptions (x : EIO ε α) (h : ε → EIO Empty α) : EIO Empty α :=
fun s => match x s with
| EStateM.Result.ok a s => EStateM.Result.ok a s
| EStateM.Result.error ex s => h ex s
instance : Monad (EIO ε) := inferInstanceAs (Monad (EStateM ε IO.RealWorld))
instance : MonadFinally (EIO ε) := inferInstanceAs (MonadFinally (EStateM ε IO.RealWorld))
instance : MonadExceptOf ε (EIO ε) := inferInstanceAs (MonadExceptOf ε (EStateM ε IO.RealWorld))
instance : OrElse (EIO ε α) := ⟨MonadExcept.orelse⟩
instance [Inhabited ε] : Inhabited (EIO ε α) := inferInstanceAs (Inhabited (EStateM ε IO.RealWorld α))
open IO (Error) in
abbrev IO : Type → Type := EIO Error
@[inline] def EIO.toIO (f : ε → IO.Error) (x : EIO ε α) : IO α :=
x.adaptExcept f
@[inline] def EIO.toIO' (x : EIO ε α) : IO (Except ε α) :=
EIO.toIO (fun _ => unreachable!) (observing x)
@[inline] def IO.toEIO (f : IO.Error → ε) (x : IO α) : EIO ε α :=
x.adaptExcept f
/- After we inline `EState.run'`, the closed term `((), ())` is generated, where the second `()`
represents the "initial world". We don't want to cache this closed term. So, we disable
the "extract closed terms" optimization. -/
set_option compiler.extract_closed false in
@[inline] unsafe def unsafeEIO (fn : EIO ε α) : Except ε α :=
match fn.run () with
| EStateM.Result.ok a _ => Except.ok a
| EStateM.Result.error e _ => Except.error e
@[inline] unsafe def unsafeIO (fn : IO α) : Except IO.Error α :=
unsafeEIO fn
@[extern "lean_io_timeit"] constant timeit (msg : @& String) (fn : IO α) : IO α
@[extern "lean_io_allocprof"] constant allocprof (msg : @& String) (fn : IO α) : IO α
/- Programs can execute IO actions during initialization that occurs before
the `main` function is executed. The attribute `[init <action>]` specifies
which IO action is executed to set the value of an opaque constant.
The action `initializing` returns `true` iff it is invoked during initialization. -/
@[extern "lean_io_initializing"] constant IO.initializing : IO Bool
namespace IO
def ofExcept [ToString ε] (e : Except ε α) : IO α :=
match e with
| Except.ok a => pure a
| Except.error e => throw (IO.userError (toString e))
def lazyPure (fn : Unit → α) : IO α :=
pure (fn ())
/-- Monotonically increasing time since an unspecified past point in milliseconds. No relation to wall clock time. -/
@[extern "lean_io_mono_ms_now"] constant monoMsNow : IO Nat
def sleep (ms : UInt32) : IO Unit :=
-- TODO: add a proper primitive for IO.sleep
fun s => dbgSleep ms fun _ => EStateM.Result.ok () s
/--
Run `act` in a separate `Task`. This is similar to Haskell's [`unsafeInterleaveIO`](http://hackage.haskell.org/package/base-4.14.0.0/docs/System-IO-Unsafe.html#v:unsafeInterleaveIO),
except that the `Task` is started eagerly as usual. Thus pure accesses to the `Task` do not influence the impure `act`
computation.
Unlike with pure tasks created by `Task.mk`, tasks created by this function will be run even if the last reference
to the task is dropped. `act` should manually check for cancellation via `IO.checkCanceled` if it wants to react
to that. -/
@[extern "lean_io_as_task"]
constant asTask (act : IO α) (prio := Task.Priority.default) : IO (Task (Except IO.Error α))
/-- See `IO.asTask`. -/
@[extern "lean_io_map_task"]
constant mapTask (f : α → IO β) (t : Task α) (prio := Task.Priority.default) : IO (Task (Except IO.Error β))
/-- See `IO.asTask`. -/
@[extern "lean_io_bind_task"]
constant bindTask (t : Task α) (f : α → IO (Task (Except IO.Error β))) (prio := Task.Priority.default) : IO (Task (Except IO.Error β))
/-- Check if the task's cancellation flag has been set by calling `IO.cancel` or dropping the last reference to the task. -/
@[extern "lean_io_check_canceled"] constant checkCanceled : IO Bool
/-- Request cooperative cancellation of the task. The task must explicitly call `IO.checkCanceled` to react to the cancellation. -/
@[extern "lean_io_cancel"] constant cancel : @& Task α → IO Unit
/-- Check if the task has finished execution, at which point calling `Task.get` will return immediately. -/
@[extern "lean_io_has_finished"] constant hasFinished : @& Task α → IO Bool
/-- Wait for the task to finish, then return its result. -/
@[extern "lean_io_wait"] constant wait : Task α → IO α
/-- Wait until any of the tasks in the given list has finished, then return its result. -/
@[extern "lean_io_wait_any"] constant waitAny : @& List (Task α) → IO α
/-- Helper method for implementing "deterministic" timeouts. It is the numbe of "small" memory allocations performed by the current execution thread. -/
@[extern "lean_io_get_num_heartbeats"] constant getNumHeartbeats : EIO ε Nat
inductive FS.Mode where
| read | write | readWrite | append
constant FS.Handle : Type := Unit
/--
A pure-Lean abstraction of POSIX streams. We use `Stream`s for the standard streams stdin/stdout/stderr so we can
capture output of `#eval` commands into memory. -/
structure FS.Stream where
isEof : IO Bool
flush : IO Unit
read : USize → IO ByteArray
write : ByteArray → IO Unit
getLine : IO String
putStr : String → IO Unit
namespace Prim
open FS
@[extern "lean_get_stdin"] constant getStdin : IO FS.Stream
@[extern "lean_get_stdout"] constant getStdout : IO FS.Stream
@[extern "lean_get_stderr"] constant getStderr : IO FS.Stream
@[extern "lean_get_set_stdin"] constant setStdin : FS.Stream → IO FS.Stream
@[extern "lean_get_set_stdout"] constant setStdout : FS.Stream → IO FS.Stream
@[extern "lean_get_set_stderr"] constant setStderr : FS.Stream → IO FS.Stream
@[specialize] partial def iterate (a : α) (f : α → IO (Sum α β)) : IO β := do
let v ← f a
match v with
| Sum.inl a => iterate a f
| Sum.inr b => pure b
-- @[export lean_fopen_flags]
def fopenFlags (m : FS.Mode) (b : Bool) : String :=
let mode :=
match m with
| FS.Mode.read => "r"
| FS.Mode.write => "w"
| FS.Mode.readWrite => "r+"
| FS.Mode.append => "a" ;
let bin := if b then "b" else "t"
mode ++ bin
@[extern "lean_io_prim_handle_mk"] constant Handle.mk (s : @& String) (mode : @& String) : IO Handle
@[extern "lean_io_prim_handle_is_eof"] constant Handle.isEof (h : @& Handle) : IO Bool
@[extern "lean_io_prim_handle_flush"] constant Handle.flush (h : @& Handle) : IO Unit
@[extern "lean_io_prim_handle_read"] constant Handle.read (h : @& Handle) (bytes : USize) : IO ByteArray
@[extern "lean_io_prim_handle_write"] constant Handle.write (h : @& Handle) (buffer : @& ByteArray) : IO Unit
@[extern "lean_io_prim_handle_get_line"] constant Handle.getLine (h : @& Handle) : IO String
@[extern "lean_io_prim_handle_put_str"] constant Handle.putStr (h : @& Handle) (s : @& String) : IO Unit
@[extern "lean_io_getenv"] constant getEnv (var : @& String) : IO (Option String)
@[extern "lean_io_realpath"] constant realPath (fname : String) : IO String
@[extern "lean_io_is_dir"] constant isDir (fname : @& String) : IO Bool
@[extern "lean_io_file_exists"] constant fileExists (fname : @& String) : IO Bool
@[extern "lean_io_remove_file"] constant removeFile (fname : @& String) : IO Unit
@[extern "lean_io_app_dir"] constant appPath : IO String
@[extern "lean_io_current_dir"] constant currentDir : IO String
end Prim
namespace FS
variable [Monad m] [MonadLiftT IO m]
def Handle.mk (s : String) (Mode : Mode) (bin : Bool := true) : m Handle :=
liftM (Prim.Handle.mk s (Prim.fopenFlags Mode bin))
@[inline]
def withFile (fn : String) (mode : Mode) (f : Handle → m α) : m α :=
Handle.mk fn mode >>= f
/-- returns whether the end of the file has been reached while reading a file.
`h.isEof` returns true /after/ the first attempt at reading past the end of `h`.
Once `h.isEof` is true, the reading `h` raises `IO.Error.eof`.
-/
def Handle.isEof : Handle → m Bool := liftM ∘ Prim.Handle.isEof
def Handle.flush : Handle → m Unit := liftM ∘ Prim.Handle.flush
def Handle.read (h : Handle) (bytes : Nat) : m ByteArray := liftM (Prim.Handle.read h (USize.ofNat bytes))
def Handle.write (h : Handle) (s : ByteArray) : m Unit := liftM (Prim.Handle.write h s)
def Handle.getLine : Handle → m String := liftM ∘ Prim.Handle.getLine
def Handle.putStr (h : Handle) (s : String) : m Unit :=
liftM <| Prim.Handle.putStr h s
def Handle.putStrLn (h : Handle) (s : String) : m Unit :=
h.putStr (s.push '\n')
partial def Handle.readBinToEnd (h : Handle) : m ByteArray := do
let rec loop (acc : ByteArray) : m ByteArray := do
if ← h.isEof then
return acc
else
let buf ← h.read 1024
loop (acc ++ buf)
loop ByteArray.empty
partial def Handle.readToEnd (h : Handle) : m String := do
let rec read (s : String) := do
let line ← h.getLine
if line.length == 0 then pure s else read (s ++ line)
read ""
def readBinFile (fname : String) : m ByteArray := do
let h ← Handle.mk fname Mode.read true
h.readBinToEnd
def readFile (fname : String) : m String := do
let h ← Handle.mk fname Mode.read false
h.readToEnd
partial def lines (fname : String) : m (Array String) := do
let h ← Handle.mk fname Mode.read false
let rec read (lines : Array String) := do
let line ← h.getLine
if line.length == 0 then
pure lines
else if line.back == '\n' then
let line := line.dropRight 1
let line := if System.Platform.isWindows && line.back == '\x0d' then line.dropRight 1 else line
read <| lines.push line
else
pure <| lines.push line
read #[]
def writeBinFile (fname : String) (content : ByteArray) : m Unit := do
let h ← Handle.mk fname Mode.write true
h.write content
def writeFile (fname : String) (content : String) : m Unit := do
let h ← Handle.mk fname Mode.write false
h.putStr content
namespace Stream
def putStrLn (strm : FS.Stream) (s : String) : m Unit :=
liftM (strm.putStr (s.push '\n'))
end Stream
end FS
section
variable [Monad m] [MonadLiftT IO m]
def getStdin : m FS.Stream := liftM Prim.getStdin
def getStdout : m FS.Stream := liftM Prim.getStdout
def getStderr : m FS.Stream := liftM Prim.getStderr
/-- Replaces the stdin stream of the current thread and returns its previous value. -/
def setStdin : FS.Stream → m FS.Stream := liftM ∘ Prim.setStdin
/-- Replaces the stdout stream of the current thread and returns its previous value. -/
def setStdout : FS.Stream → m FS.Stream := liftM ∘ Prim.setStdout
/-- Replaces the stderr stream of the current thread and returns its previous value. -/
def setStderr : FS.Stream → m FS.Stream := liftM ∘ Prim.setStderr
def withStdin [MonadFinally m] (h : FS.Stream) (x : m α) : m α := do
let prev ← setStdin h
try x finally discard <| setStdin prev
def withStdout [MonadFinally m] (h : FS.Stream) (x : m α) : m α := do
let prev ← setStdout h
try
x
finally
discard <| setStdout prev
def withStderr [MonadFinally m] (h : FS.Stream) (x : m α) : m α := do
let prev ← setStderr h
try x finally discard <| setStderr prev
def print [ToString α] (s : α) : IO Unit := do
let out ← getStdout
out.putStr <| toString s
def println [ToString α] (s : α) : IO Unit :=
print ((toString s).push '\n')
def eprint [ToString α] (s : α) : IO Unit := do
let out ← getStderr
liftM <| out.putStr <| toString s
def eprintln [ToString α] (s : α) : IO Unit :=
eprint <| toString s |>.push '\n'
@[export lean_io_eprintln]
private def eprintlnAux (s : String) : IO Unit :=
eprintln s
def getEnv : String → m (Option String) := liftM ∘ Prim.getEnv
def realPath : String → m String := liftM ∘ Prim.realPath
def isDir : String → m Bool := liftM ∘ Prim.isDir
def fileExists : String → m Bool := liftM ∘ Prim.fileExists
def removeFile : String → m Unit := liftM ∘ Prim.removeFile
def appPath : m String := liftM Prim.appPath
def appDir : m String := do
let p ← appPath
let some p ← pure <| System.FilePath.parent p
| liftM (m := IO) <| throw <| IO.userError s!"System.IO.appDir: unexpected filename '{p}'"
realPath p
def currentDir : m String := liftM Prim.currentDir
end
namespace Process
inductive Stdio where
| piped
| inherit
| null
def Stdio.toHandleType : Stdio → Type
| Stdio.piped => FS.Handle
| Stdio.inherit => Unit
| Stdio.null => Unit
structure StdioConfig where
/- Configuration for the process' stdin handle. -/
stdin := Stdio.inherit
/- Configuration for the process' stdout handle. -/
stdout := Stdio.inherit
/- Configuration for the process' stderr handle. -/
stderr := Stdio.inherit
structure SpawnArgs extends StdioConfig where
/- Command name. -/
cmd : String
/- Arguments for the process -/
args : Array String := #[]
/- Working directory for the process. Inherit from current process if `none`. -/
cwd : Option String := none
/- Add or remove environment variables for the process. -/
env : Array (String × Option String) := #[]
-- TODO(Sebastian): constructor must be private
structure Child (cfg : StdioConfig) where
stdin : cfg.stdin.toHandleType
stdout : cfg.stdout.toHandleType
stderr : cfg.stderr.toHandleType
@[extern "lean_io_process_spawn"] constant spawn (args : SpawnArgs) : IO (Child args.toStdioConfig)
@[extern "lean_io_process_child_wait"] constant Child.wait {cfg : @& StdioConfig} : @& Child cfg → IO UInt32
structure Output where
exitCode : UInt32
stdout : String
stderr : String
/-- Run process to completion and capture output. -/
def output (args : SpawnArgs) : IO Output := do
let child ← spawn { args with stdout := Stdio.piped, stderr := Stdio.piped }
let stdout ← IO.asTask child.stdout.readToEnd Task.Priority.dedicated
let stderr ← child.stderr.readToEnd
let exitCode ← child.wait
let stdout ← IO.ofExcept stdout.get
pure { exitCode := exitCode, stdout := stdout, stderr := stderr }
/-- Run process to completion and return stdout on success. -/
def run (args : SpawnArgs) : IO String := do
let out ← output args
if out.exitCode != 0 then
throw <| IO.userError <| "process '" ++ args.cmd ++ "' exited with code " ++ toString out.exitCode;
pure out.stdout
end Process
structure AccessRight where
read : Bool := false
write : Bool := false
execution : Bool := false
def AccessRight.flags (acc : AccessRight) : UInt32 :=
let r : UInt32 := if acc.read then 0x4 else 0
let w : UInt32 := if acc.write then 0x2 else 0
let x : UInt32 := if acc.execution then 0x1 else 0
r.lor <| w.lor x
structure FileRight where
user : AccessRight := {}
group : AccessRight := {}
other : AccessRight := {}
def FileRight.flags (acc : FileRight) : UInt32 :=
let u : UInt32 := acc.user.flags.shiftLeft 6
let g : UInt32 := acc.group.flags.shiftLeft 3
let o : UInt32 := acc.other.flags
u.lor <| g.lor o
@[extern "lean_chmod"] constant Prim.setAccessRights (filename : @& String) (mode : UInt32) : IO Unit
def setAccessRights (filename : String) (mode : FileRight) : IO Unit :=
Prim.setAccessRights filename mode.flags
/- References -/
abbrev Ref (α : Type) := ST.Ref IO.RealWorld α
instance : MonadLift (ST IO.RealWorld) (EIO ε) := ⟨fun x s =>
match x s with
| EStateM.Result.ok a s => EStateM.Result.ok a s
| EStateM.Result.error ex _ => nomatch ex⟩
def mkRef [Monad m] [MonadLiftT (ST IO.RealWorld) m] (a : α) : m (IO.Ref α) :=
ST.mkRef a
namespace FS
namespace Stream
@[export lean_stream_of_handle]
def ofHandle (h : Handle) : Stream := {
isEof := Prim.Handle.isEof h,
flush := Prim.Handle.flush h,
read := Prim.Handle.read h,
write := Prim.Handle.write h,
getLine := Prim.Handle.getLine h,
putStr := Prim.Handle.putStr h,
}
structure Buffer where
data : ByteArray := ByteArray.empty
pos : Nat := 0
def ofBuffer (r : Ref Buffer) : Stream := {
isEof := do let b ← r.get; pure <| b.pos >= b.data.size,
flush := pure (),
read := fun n => r.modifyGet fun b =>
let data := b.data.extract b.pos (b.pos + n.toNat)
(data, { b with pos := b.pos + data.size }),
write := fun data => r.modify fun b =>
-- set `exact` to `false` so that repeatedly writing to the stream does not impose quadratic run time
{ b with data := data.copySlice 0 b.data b.pos data.size false, pos := b.pos + data.size },
getLine := r.modifyGet fun b =>
let pos := match b.data.findIdx? (start := b.pos) fun u => u == 0 || u = '\n'.toNat.toUInt8 with
-- include '\n', but not '\0'
| some pos => if b.data.get! pos == 0 then pos else pos + 1
| none => b.data.size
(String.fromUTF8Unchecked <| b.data.extract b.pos pos, { b with pos := pos }),
putStr := fun s => r.modify fun b =>
let data := s.toUTF8
{ b with data := data.copySlice 0 b.data b.pos data.size false, pos := b.pos + data.size },
}
end Stream
/-- Run action with `stdin` emptied and `stdout+stderr` captured into a `String`. -/
def withIsolatedStreams (x : IO α) : IO (String × Except IO.Error α) := do
let bIn ← mkRef { : Stream.Buffer }
let bOut ← mkRef { : Stream.Buffer }
let r ← withStdin (Stream.ofBuffer bIn) <|
withStdout (Stream.ofBuffer bOut) <|
withStderr (Stream.ofBuffer bOut) <|
observing x
let bOut ← bOut.get
let out := String.fromUTF8Unchecked bOut.data
pure (out, r)
end FS
end IO
universe u
namespace Lean
/-- Typeclass used for presenting the output of an `#eval` command. -/
class Eval (α : Type u) where
-- We default `hideUnit` to `true`, but set it to `false` in the direct call from `#eval`
-- so that `()` output is hidden in chained instances such as for some `m Unit`.
-- We take `Unit → α` instead of `α` because ‵α` may contain effectful debugging primitives (e.g., `dbg_trace`)
eval : (Unit → α) → forall (hideUnit : optParam Bool true), IO Unit
instance [ToString α] : Eval α :=
⟨fun a _ => IO.println (toString (a ()))⟩
instance [Repr α] : Eval α :=
⟨fun a _ => IO.println (repr (a ()))⟩
instance : Eval Unit :=
⟨fun u hideUnit => if hideUnit then pure () else IO.println (repr (u ()))⟩
instance [Eval α] : Eval (IO α) :=
⟨fun x _ => do let a ← x (); Eval.eval (fun _ => a)⟩
@[noinline, nospecialize] def runEval [Eval α] (a : Unit → α) : IO (String × Except IO.Error Unit) :=
IO.FS.withIsolatedStreams (Eval.eval a false)
end Lean
syntax "println! " (interpolatedStr(term) <|> term) : term
macro_rules
| `(println! $msg) =>
if msg.getKind == Lean.interpolatedStrKind then
`((IO.println (s! $msg) : IO Unit))
else
`((IO.println $msg : IO Unit))
|
5c12cfd0fdf60c13eaa543c2c2b8ed19a29f9c40 | fa02ed5a3c9c0adee3c26887a16855e7841c668b | /src/data/int/sqrt.lean | 829aa955bb9d2f9f7159b6732bd30f7e33ca1c86 | [
"Apache-2.0"
] | permissive | jjgarzella/mathlib | 96a345378c4e0bf26cf604aed84f90329e4896a2 | 395d8716c3ad03747059d482090e2bb97db612c8 | refs/heads/master | 1,686,480,124,379 | 1,625,163,323,000 | 1,625,163,323,000 | 281,190,421 | 2 | 0 | Apache-2.0 | 1,595,268,170,000 | 1,595,268,169,000 | null | UTF-8 | Lean | false | false | 1,052 | lean | /-
Copyright (c) 2018 Kenny Lau. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kenny Lau
-/
import data.nat.sqrt
/-!
# Square root of integers
This file defines the square root function on integers. `int.sqrt z` is the greatest integer `r`
such that `r * r ≤ z`. If `z ≤ 0`, then `int.sqrt z = 0`.
-/
namespace int
/-- `sqrt z` is the square root of an integer `z`. If `z` is positive, it returns the largest
integer `r` such that `r * r ≤ n`. If it is negative, it returns `0`. For example, `sqrt (-1) = 0`,
`sqrt 1 = 1`, `sqrt 2 = 1` -/
@[pp_nodot] def sqrt (z : ℤ) : ℤ :=
nat.sqrt $ int.to_nat z
theorem sqrt_eq (n : ℤ) : sqrt (n*n) = n.nat_abs :=
by rw [sqrt, ← nat_abs_mul_self, to_nat_coe_nat, nat.sqrt_eq]
theorem exists_mul_self (x : ℤ) :
(∃ n, n * n = x) ↔ sqrt x * sqrt x = x :=
⟨λ ⟨n, hn⟩, by rw [← hn, sqrt_eq, ← int.coe_nat_mul, nat_abs_mul_self],
λ h, ⟨sqrt x, h⟩⟩
theorem sqrt_nonneg (n : ℤ) : 0 ≤ sqrt n := coe_nat_nonneg _
end int
|
663aa400f06c0ed9eccb8dad777170220913e6c7 | 4727251e0cd73359b15b664c3170e5d754078599 | /src/algebra/lie/universal_enveloping.lean | c8bed4612a51d05c5f16da99bced444f2ce399e3 | [
"Apache-2.0"
] | permissive | Vierkantor/mathlib | 0ea59ac32a3a43c93c44d70f441c4ee810ccceca | 83bc3b9ce9b13910b57bda6b56222495ebd31c2f | refs/heads/master | 1,658,323,012,449 | 1,652,256,003,000 | 1,652,256,003,000 | 209,296,341 | 0 | 1 | Apache-2.0 | 1,568,807,655,000 | 1,568,807,655,000 | null | UTF-8 | Lean | false | false | 4,884 | lean | /-
Copyright (c) 2020 Oliver Nash. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Oliver Nash
-/
import algebra.lie.of_associative
import algebra.ring_quot
import linear_algebra.tensor_algebra.basic
/-!
# Universal enveloping algebra
Given a commutative ring `R` and a Lie algebra `L` over `R`, we construct the universal
enveloping algebra of `L`, together with its universal property.
## Main definitions
* `universal_enveloping_algebra`: the universal enveloping algebra, endowed with an
`R`-algebra structure.
* `universal_enveloping_algebra.ι`: the Lie algebra morphism from `L` to its universal
enveloping algebra.
* `universal_enveloping_algebra.lift`: given an associative algebra `A`, together with a Lie
algebra morphism `f : L →ₗ⁅R⁆ A`, `lift R L f : universal_enveloping_algebra R L →ₐ[R] A` is the
unique morphism of algebras through which `f` factors.
* `universal_enveloping_algebra.ι_comp_lift`: states that the lift of a morphism is indeed part
of a factorisation.
* `universal_enveloping_algebra.lift_unique`: states that lifts of morphisms are indeed unique.
* `universal_enveloping_algebra.hom_ext`: a restatement of `lift_unique` as an extensionality
lemma.
## Tags
lie algebra, universal enveloping algebra, tensor algebra
-/
universes u₁ u₂ u₃
variables (R : Type u₁) (L : Type u₂)
variables [comm_ring R] [lie_ring L] [lie_algebra R L]
local notation `ιₜ` := tensor_algebra.ι R
namespace universal_enveloping_algebra
/-- The quotient by the ideal generated by this relation is the universal enveloping algebra.
Note that we have avoided using the more natural expression:
| lie_compat (x y : L) : rel (ιₜ ⁅x, y⁆) ⁅ιₜ x, ιₜ y⁆
so that our construction needs only the semiring structure of the tensor algebra. -/
inductive rel : tensor_algebra R L → tensor_algebra R L → Prop
| lie_compat (x y : L) : rel (ιₜ ⁅x, y⁆ + (ιₜ y) * (ιₜ x)) ((ιₜ x) * (ιₜ y))
end universal_enveloping_algebra
/-- The universal enveloping algebra of a Lie algebra. -/
@[derive [inhabited, ring, algebra R]]
def universal_enveloping_algebra := ring_quot (universal_enveloping_algebra.rel R L)
namespace universal_enveloping_algebra
/-- The quotient map from the tensor algebra to the universal enveloping algebra as a morphism of
associative algebras. -/
def mk_alg_hom : tensor_algebra R L →ₐ[R] universal_enveloping_algebra R L :=
ring_quot.mk_alg_hom R (rel R L)
variables {L}
/-- The natural Lie algebra morphism from a Lie algebra to its universal enveloping algebra. -/
def ι : L →ₗ⁅R⁆ universal_enveloping_algebra R L :=
{ map_lie' := λ x y, by
{ suffices : mk_alg_hom R L (ιₜ ⁅x, y⁆ + (ιₜ y) * (ιₜ x)) = mk_alg_hom R L ((ιₜ x) * (ιₜ y)),
{ rw alg_hom.map_mul at this, simp [lie_ring.of_associative_ring_bracket, ← this], },
exact ring_quot.mk_alg_hom_rel _ (rel.lie_compat x y), },
..(mk_alg_hom R L).to_linear_map.comp ιₜ }
variables {A : Type u₃} [ring A] [algebra R A] (f : L →ₗ⁅R⁆ A)
/-- The universal property of the universal enveloping algebra: Lie algebra morphisms into
associative algebras lift to associative algebra morphisms from the universal enveloping algebra. -/
def lift : (L →ₗ⁅R⁆ A) ≃ (universal_enveloping_algebra R L →ₐ[R] A) :=
{ to_fun := λ f,
ring_quot.lift_alg_hom R ⟨tensor_algebra.lift R (f : L →ₗ[R] A),
begin
intros a b h, induction h with x y,
simp [lie_ring.of_associative_ring_bracket],
end⟩,
inv_fun := λ F, (F : universal_enveloping_algebra R L →ₗ⁅R⁆ A).comp (ι R),
left_inv := λ f, by { ext, simp [ι, mk_alg_hom], },
right_inv := λ F, by { ext, simp [ι, mk_alg_hom], } }
@[simp] lemma lift_symm_apply (F : universal_enveloping_algebra R L →ₐ[R] A) :
(lift R).symm F = (F : universal_enveloping_algebra R L →ₗ⁅R⁆ A).comp (ι R) :=
rfl
@[simp] lemma ι_comp_lift : (lift R f) ∘ (ι R) = f :=
funext $ lie_hom.ext_iff.mp $ (lift R).symm_apply_apply f
@[simp] lemma lift_ι_apply (x : L) : lift R f (ι R x) = f x :=
by rw [←function.comp_apply (lift R f) (ι R) x, ι_comp_lift]
lemma lift_unique (g : universal_enveloping_algebra R L →ₐ[R] A) :
g ∘ (ι R) = f ↔ g = lift R f :=
begin
refine iff.trans _ (lift R).symm_apply_eq,
split; {intro h, ext, simp [←h] },
end
/-- See note [partially-applied ext lemmas]. -/
@[ext] lemma hom_ext {g₁ g₂ : universal_enveloping_algebra R L →ₐ[R] A}
(h : (g₁ : universal_enveloping_algebra R L →ₗ⁅R⁆ A).comp (ι R) =
(g₂ : universal_enveloping_algebra R L →ₗ⁅R⁆ A).comp (ι R)) :
g₁ = g₂ :=
have h' : (lift R).symm g₁ = (lift R).symm g₂, { ext, simp [h], },
(lift R).symm.injective h'
end universal_enveloping_algebra
|
425744ad31f8d774e2c446cfa0c933bd3b5027d5 | 74addaa0e41490cbaf2abd313a764c96df57b05d | /Mathlib/algebra/lie/universal_enveloping.lean | 6ada08e97fa4508048863d9d96e3f1a847c81fce | [] | no_license | AurelienSaue/Mathlib4_auto | f538cfd0980f65a6361eadea39e6fc639e9dae14 | 590df64109b08190abe22358fabc3eae000943f2 | refs/heads/master | 1,683,906,849,776 | 1,622,564,669,000 | 1,622,564,669,000 | 371,723,747 | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 5,497 | lean | /-
Copyright (c) 2020 Oliver Nash. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Oliver Nash
-/
import Mathlib.PrePort
import Mathlib.Lean3Lib.init.default
import Mathlib.algebra.lie.basic
import Mathlib.algebra.ring_quot
import Mathlib.linear_algebra.tensor_algebra
import Mathlib.PostPort
universes u₁ u₂ u₃
namespace Mathlib
/-!
# Universal enveloping algebra
Given a commutative ring `R` and a Lie algebra `L` over `R`, we construct the universal
enveloping algebra of `L`, together with its universal property.
## Main definitions
* `universal_enveloping_algebra`: the universal enveloping algebra, endowed with an
`R`-algebra structure.
* `universal_enveloping_algebra.ι`: the Lie algebra morphism from `L` to its universal
enveloping algebra.
* `universal_enveloping_algebra.lift`: given an associative algebra `A`, together with a Lie
algebra morphism `f : L →ₗ⁅R⁆ A`, `lift R L f : universal_enveloping_algebra R L →ₐ[R] A` is the
unique morphism of algebras through which `f` factors.
* `universal_enveloping_algebra.ι_comp_lift`: states that the lift of a morphism is indeed part
of a factorisation.
* `universal_enveloping_algebra.lift_unique`: states that lifts of morphisms are indeed unique.
* `universal_enveloping_algebra.hom_ext`: a restatement of `lift_unique` as an extensionality
lemma.
## Tags
lie algebra, universal enveloping algebra, tensor algebra
-/
namespace universal_enveloping_algebra
/-- The quotient by the ideal generated by this relation is the universal enveloping algebra.
Note that we have avoided using the more natural expression:
| lie_compat (x y : L) : rel (ιₜ ⁅x, y⁆) ⁅ιₜ x, ιₜ y⁆
so that our construction needs only the semiring structure of the tensor algebra. -/
inductive rel (R : Type u₁) (L : Type u₂) [comm_ring R] [lie_ring L] [lie_algebra R L] : tensor_algebra R L → tensor_algebra R L → Prop
where
| lie_compat : ∀ (x y : L),
rel R L
(coe_fn (tensor_algebra.ι R) (has_bracket.bracket x y) +
coe_fn (tensor_algebra.ι R) y * coe_fn (tensor_algebra.ι R) x)
(coe_fn (tensor_algebra.ι R) x * coe_fn (tensor_algebra.ι R) y)
end universal_enveloping_algebra
/-- The universal enveloping algebra of a Lie algebra. -/
def universal_enveloping_algebra (R : Type u₁) (L : Type u₂) [comm_ring R] [lie_ring L] [lie_algebra R L] :=
ring_quot sorry
namespace universal_enveloping_algebra
/-- The quotient map from the tensor algebra to the universal enveloping algebra as a morphism of
associative algebras. -/
def mk_alg_hom (R : Type u₁) (L : Type u₂) [comm_ring R] [lie_ring L] [lie_algebra R L] : alg_hom R (tensor_algebra R L) (universal_enveloping_algebra R L) :=
ring_quot.mk_alg_hom R (rel R L)
/-- The natural Lie algebra morphism from a Lie algebra to its universal enveloping algebra. -/
def ι (R : Type u₁) {L : Type u₂} [comm_ring R] [lie_ring L] [lie_algebra R L] : lie_algebra.morphism R L (universal_enveloping_algebra R L) :=
lie_algebra.morphism.mk
(linear_map.to_fun (linear_map.comp (alg_hom.to_linear_map (mk_alg_hom R L)) (tensor_algebra.ι R))) sorry sorry sorry
/-- The universal property of the universal enveloping algebra: Lie algebra morphisms into
associative algebras lift to associative algebra morphisms from the universal enveloping algebra. -/
def lift (R : Type u₁) {L : Type u₂} [comm_ring R] [lie_ring L] [lie_algebra R L] {A : Type u₃} [ring A] [algebra R A] : lie_algebra.morphism R L A ≃ alg_hom R (universal_enveloping_algebra R L) A :=
equiv.mk
(fun (f : lie_algebra.morphism R L A) =>
coe_fn (ring_quot.lift_alg_hom R) { val := coe_fn (tensor_algebra.lift R) ↑f, property := sorry })
(fun (F : alg_hom R (universal_enveloping_algebra R L) A) =>
lie_algebra.morphism.comp (lie_algebra.of_associative_algebra_hom F) (ι R))
sorry sorry
@[simp] theorem lift_symm_apply (R : Type u₁) {L : Type u₂} [comm_ring R] [lie_ring L] [lie_algebra R L] {A : Type u₃} [ring A] [algebra R A] (F : alg_hom R (universal_enveloping_algebra R L) A) : coe_fn (equiv.symm (lift R)) F = lie_algebra.morphism.comp (lie_algebra.of_associative_algebra_hom F) (ι R) :=
rfl
@[simp] theorem ι_comp_lift (R : Type u₁) {L : Type u₂} [comm_ring R] [lie_ring L] [lie_algebra R L] {A : Type u₃} [ring A] [algebra R A] (f : lie_algebra.morphism R L A) : ⇑(coe_fn (lift R) f) ∘ ⇑(ι R) = ⇑f :=
funext (iff.mp lie_algebra.morphism.ext_iff (equiv.symm_apply_apply (lift R) f))
@[simp] theorem lift_ι_apply (R : Type u₁) {L : Type u₂} [comm_ring R] [lie_ring L] [lie_algebra R L] {A : Type u₃} [ring A] [algebra R A] (f : lie_algebra.morphism R L A) (x : L) : coe_fn (coe_fn (lift R) f) (coe_fn (ι R) x) = coe_fn f x := sorry
theorem lift_unique (R : Type u₁) {L : Type u₂} [comm_ring R] [lie_ring L] [lie_algebra R L] {A : Type u₃} [ring A] [algebra R A] (f : lie_algebra.morphism R L A) (g : alg_hom R (universal_enveloping_algebra R L) A) : ⇑g ∘ ⇑(ι R) = ⇑f ↔ g = coe_fn (lift R) f := sorry
/-- See note [partially-applied ext lemmas]. -/
theorem hom_ext (R : Type u₁) {L : Type u₂} [comm_ring R] [lie_ring L] [lie_algebra R L] {A : Type u₃} [ring A] [algebra R A] {g₁ : alg_hom R (universal_enveloping_algebra R L) A} {g₂ : alg_hom R (universal_enveloping_algebra R L) A} (h : ⇑g₁ ∘ ⇑(ι R) = ⇑g₂ ∘ ⇑(ι R)) : g₁ = g₂ := sorry
|
7b781718b519b4a2a97c84ef3ffa23ee9c246bb4 | e2fc96178628c7451e998a0db2b73877d0648be5 | /src/classes/context_free/basics/inclusion.lean | 25a5ff57fafc62a3df708049c38c4a281db814a3 | [
"BSD-2-Clause"
] | permissive | madvorak/grammars | cd324ae19b28f7b8be9c3ad010ef7bf0fabe5df2 | 1447343a45fcb7821070f1e20b57288d437323a6 | refs/heads/main | 1,692,383,644,884 | 1,692,032,429,000 | 1,692,032,429,000 | 453,948,141 | 7 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 3,892 | lean | import classes.context_free.basics.toolbox
import classes.context_sensitive.basics.inclusion
variables {T : Type}
def csg_of_cfg (g : CF_grammar T) : CS_grammar T :=
CS_grammar.mk g.nt g.initial (list.map (λ r : g.nt × (list (symbol T g.nt)),
csrule.mk [] r.fst [] r.snd) g.rules)
def grammar_of_cfg (g : CF_grammar T) : grammar T :=
grammar.mk g.nt g.initial (list.map (λ r : g.nt × (list (symbol T g.nt)),
grule.mk [] r.fst [] r.snd) g.rules)
lemma grammar_of_cfg_well_defined (g : CF_grammar T) :
grammar_of_csg (csg_of_cfg g) = grammar_of_cfg g :=
begin
unfold grammar_of_cfg,
delta csg_of_cfg,
delta grammar_of_csg,
simp only [list.map_map, eq_self_iff_true, heq_iff_eq, true_and],
ext1,
rw [list.nth_map, list.nth_map],
apply congr_fun,
ext1,
cases x,
{
refl,
},
apply congr_arg option.some,
simp [list.append_nil],
end
lemma grammar_of_csg_of_cfg :
grammar_of_csg ∘ csg_of_cfg = @grammar_of_cfg T :=
begin
ext,
apply grammar_of_cfg_well_defined,
end
lemma CF_language_eq_CS_language (g : CF_grammar T) :
CF_language g = CS_language (csg_of_cfg g) :=
begin
unfold CF_language,
unfold CS_language,
ext1 w,
change
CF_derives g [symbol.nonterminal g.initial] (list.map symbol.terminal w) =
CS_derives (csg_of_cfg g) [symbol.nonterminal (csg_of_cfg g).initial] (list.map symbol.terminal w),
rw eq_iff_iff,
split,
{
have indu :
∀ v : list (symbol T g.nt),
CF_derives g [symbol.nonterminal g.initial] v →
CS_derives (csg_of_cfg g) [symbol.nonterminal (csg_of_cfg g).initial] v,
{
clear w,
intros v h,
induction h with x y trash hyp ih,
{
apply CS_deri_self,
},
apply CS_deri_of_deri_tran,
{
exact ih,
},
unfold CF_transforms at hyp,
unfold CS_transforms,
delta csg_of_cfg,
dsimp only,
rcases hyp with ⟨r, rin, u, w, bef, aft⟩,
use csrule.mk [] r.fst [] r.snd,
split,
{
rw list.mem_map,
use r,
split,
{
exact rin,
},
{
refl,
},
},
use u,
use w,
split;
{
dsimp only,
rw list.append_nil,
rw list.append_nil,
assumption,
},
},
exact indu (list.map symbol.terminal w),
},
{
have indu :
∀ v : list (symbol T g.nt),
CS_derives (csg_of_cfg g) [symbol.nonterminal g.initial] v →
CF_derives g [symbol.nonterminal (csg_of_cfg g).initial] v,
{
clear w,
intros v h,
induction h with x y trash hyp ih,
{
apply CF_deri_self,
},
apply CF_deri_of_deri_tran,
{
exact ih,
},
unfold CS_transforms at hyp,
unfold CF_transforms,
delta csg_of_cfg at hyp,
dsimp only at hyp,
rcases hyp with ⟨r, rin, u, w, bef, aft⟩,
use (r.input_nonterminal, r.output_string),
split,
{
finish,
},
use u,
use w,
have cl_empty : r.context_left = list.nil,
{
finish,
},
have cr_empty : r.context_right = list.nil,
{
finish,
},
rw [cl_empty, cr_empty] at *,
repeat {
rw list.append_nil at *,
},
split;
assumption,
},
exact indu (list.map symbol.terminal w),
},
end
lemma CF_language_eq_grammar_language (g : CF_grammar T) :
CF_language g = grammar_language (grammar_of_cfg g) :=
begin
rw ←grammar_of_cfg_well_defined,
rw CF_language_eq_CS_language,
rw CS_language_eq_grammar_language,
end
theorem CF_subclass_CS {L : language T} :
is_CF L → is_CS L :=
begin
rintro ⟨g, eq_L⟩,
use csg_of_cfg g,
rw ←eq_L,
rw CF_language_eq_CS_language,
end
theorem CF_subclass_RE {L : language T} :
is_CF L → is_RE L :=
CS_subclass_RE ∘ CF_subclass_CS
|
140de7eaa32f93cf8a668d6e50dc463140718b96 | 36c7a18fd72e5b57229bd8ba36493daf536a19ce | /library/data/nat/bquant.lean | e16dd5f7cf27d049a6bce02ff9702c8aefb5efd9 | [
"Apache-2.0"
] | permissive | YHVHvx/lean | 732bf0fb7a298cd7fe0f15d82f8e248c11db49e9 | 038369533e0136dd395dc252084d3c1853accbf2 | refs/heads/master | 1,610,701,080,210 | 1,449,128,595,000 | 1,449,128,595,000 | null | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 5,747 | lean | /-
Copyright (c) 2014 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Author: Leonardo de Moura
Show that "bounded" quantifiers: (∃x, x < n ∧ P x) and (∀x, x < n → P x)
are decidable when P is decidable.
This module allow us to write if-then-else expressions such as
if (∀ x : nat, x < n → ∃ y : nat, y < n ∧ y * y = x) then t else s
without assuming classical axioms.
More importantly, they can be reduced inside of the Lean kernel.
-/
import data.nat.order data.nat.div
namespace nat
open subtype
definition bex [reducible] (n : nat) (P : nat → Prop) : Prop :=
∃ x, x < n ∧ P x
definition bsub [reducible] (n : nat) (P : nat → Prop) : Type₁ :=
{x | x < n ∧ P x}
definition ball [reducible] (n : nat) (P : nat → Prop) : Prop :=
∀ x, x < n → P x
lemma bex_of_bsub {n : nat} {P : nat → Prop} : bsub n P → bex n P :=
assume h, ex_of_sub h
theorem not_bex_zero (P : nat → Prop) : ¬ bex 0 P :=
λ H, obtain (w : nat) (Hw : w < 0 ∧ P w), from H,
and.rec_on Hw (λ h₁ h₂, absurd h₁ (not_lt_zero w))
theorem not_bsub_zero (P : nat → Prop) : bsub 0 P → false :=
λ H, absurd (bex_of_bsub H) (not_bex_zero P)
definition bsub_succ {P : nat → Prop} {n : nat} (H : bsub n P) : bsub (succ n) P :=
obtain (w : nat) (Hw : w < n ∧ P w), from H,
and.rec_on Hw (λ hlt hp, tag w (and.intro (lt.step hlt) hp))
theorem bex_succ {P : nat → Prop} {n : nat} (H : bex n P) : bex (succ n) P :=
obtain (w : nat) (Hw : w < n ∧ P w), from H,
and.rec_on Hw (λ hlt hp, exists.intro w (and.intro (lt.step hlt) hp))
definition bsub_succ_of_pred {P : nat → Prop} {a : nat} (H : P a) : bsub (succ a) P :=
tag a (and.intro (lt.base a) H)
theorem bex_succ_of_pred {P : nat → Prop} {a : nat} (H : P a) : bex (succ a) P :=
bex_of_bsub (bsub_succ_of_pred H)
theorem not_bex_succ {P : nat → Prop} {n : nat} (H₁ : ¬ bex n P) (H₂ : ¬ P n) : ¬ bex (succ n) P :=
λ H, obtain (w : nat) (Hw : w < succ n ∧ P w), from H,
and.rec_on Hw (λ hltsn hp, or.rec_on (nat.eq_or_lt_of_le (le_of_succ_le_succ hltsn))
(λ heq : w = n, absurd (eq.rec_on heq hp) H₂)
(λ hltn : w < n, absurd (exists.intro w (and.intro hltn hp)) H₁))
theorem not_bsub_succ {P : nat → Prop} {n : nat} (H₁ : ¬ bex n P) (H₂ : ¬ P n) : bsub (succ n) P → false :=
λ H, absurd (bex_of_bsub H) (not_bex_succ H₁ H₂)
theorem ball_zero (P : nat → Prop) : ball zero P :=
λ x Hlt, absurd Hlt !not_lt_zero
theorem ball_of_ball_succ {n : nat} {P : nat → Prop} (H : ball (succ n) P) : ball n P :=
λ x Hlt, H x (lt.step Hlt)
theorem ball_succ_of_ball {n : nat} {P : nat → Prop} (H₁ : ball n P) (H₂ : P n) : ball (succ n) P :=
λ (x : nat) (Hlt : x < succ n), or.elim (nat.eq_or_lt_of_le (le_of_succ_le_succ Hlt))
(λ heq : x = n, eq.rec_on (eq.rec_on heq rfl) H₂)
(λ hlt : x < n, H₁ x hlt)
theorem not_ball_of_not {n : nat} {P : nat → Prop} (H₁ : ¬ P n) : ¬ ball (succ n) P :=
λ (H : ball (succ n) P), absurd (H n (lt.base n)) H₁
theorem not_ball_succ_of_not_ball {n : nat} {P : nat → Prop} (H₁ : ¬ ball n P) : ¬ ball (succ n) P :=
λ (H : ball (succ n) P), absurd (ball_of_ball_succ H) H₁
end nat
section
open nat decidable
definition decidable_bex [instance] (n : nat) (P : nat → Prop) [H : decidable_pred P] : decidable (bex n P) :=
nat.rec_on n
(inr (not_bex_zero P))
(λ a ih, decidable.rec_on ih
(λ hpos : bex a P, inl (bex_succ hpos))
(λ hneg : ¬ bex a P, decidable.rec_on (H a)
(λ hpa : P a, inl (bex_succ_of_pred hpa))
(λ hna : ¬ P a, inr (not_bex_succ hneg hna))))
definition decidable_ball [instance] (n : nat) (P : nat → Prop) [H : decidable_pred P] : decidable (ball n P) :=
nat.rec_on n
(inl (ball_zero P))
(λ n₁ ih, decidable.rec_on ih
(λ ih_pos, decidable.rec_on (H n₁)
(λ p_pos, inl (ball_succ_of_ball ih_pos p_pos))
(λ p_neg, inr (not_ball_of_not p_neg)))
(λ ih_neg, inr (not_ball_succ_of_not_ball ih_neg)))
definition decidable_bex_le [instance] (n : nat) (P : nat → Prop) [H : decidable_pred P]
: decidable (∃ x, x ≤ n ∧ P x) :=
decidable_of_decidable_of_iff
(decidable_bex (succ n) P)
(exists_congr (λn, and_congr !lt_succ_iff_le !iff.refl))
definition decidable_ball_le [instance] (n : nat) (P : nat → Prop) [H : decidable_pred P]
: decidable (∀ x, x ≤ n → P x) :=
decidable_of_decidable_of_iff
(decidable_ball (succ n) P)
(forall_congr (λ n, imp_congr !lt_succ_iff_le !iff.refl))
end
namespace nat
open decidable
variable {P : nat → Prop}
variable [decP : decidable_pred P]
include decP
definition bsub_not_of_not_ball : ∀ {n : nat}, ¬ ball n P → {i | i < n ∧ ¬ P i}
| 0 h := absurd (ball_zero P) h
| (succ n) h := decidable.by_cases
(λ hp : P n,
have ¬ ball n P, from
assume b : ball n P, absurd (ball_succ_of_ball b hp) h,
have {i | i < n ∧ ¬ P i}, from bsub_not_of_not_ball this,
bsub_succ this)
(λ hn : ¬ P n, bsub_succ_of_pred hn)
theorem bex_not_of_not_ball {n : nat} (H : ¬ ball n P) : bex n (λ n, ¬ P n) :=
bex_of_bsub (bsub_not_of_not_ball H)
theorem ball_not_of_not_bex : ∀ {n : nat}, ¬ bex n P → ball n (λ n, ¬ P n)
| 0 h := ball_zero _
| (succ n) h := by_cases
(λ hp : P n, absurd (bex_succ_of_pred hp) h)
(λ hn : ¬ P n,
have ¬ bex n P, from
assume b : bex n P, absurd (bex_succ b) h,
have ball n (λ n, ¬ P n), from ball_not_of_not_bex this,
ball_succ_of_ball this hn)
end nat
|
7bf0df62316623a59029f65dae49167c77e95f1c | ec62863c729b7eedee77b86d974f2c529fa79d25 | /18/b.lean | 5fa05cd7dc8489369c729aacd82d1efc412b84ec | [] | no_license | rwbarton/advent-of-lean-4 | 2ac9b17ba708f66051e3d8cd694b0249bc433b65 | 417c7e2718253ba7148c0279fcb251b6fc291477 | refs/heads/main | 1,675,917,092,057 | 1,609,864,581,000 | 1,609,864,581,000 | 317,700,289 | 24 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 1,559 | lean | import Lean.Data.Json.Parser
open Lean Lean.Quickparse Lean.Json.Parser
inductive Node
| num : Int → Node
| add : Node → Node → Node
| mul : Node → Node → Node
instance : Inhabited Node := ⟨Node.num 0⟩
def Node.toString
| (Node.num n) => s!"{n}"
| (Node.add e₁ e₂) => "(" ++ e₁.toString ++ " + " ++ e₂.toString ++ ")"
| (Node.mul e₁ e₂) => "(" ++ e₁.toString ++ " * " ++ e₂.toString ++ ")"
instance : ToString Node := ⟨Node.toString⟩
partial def parseParens : Quickparse Node := do
let c ← peek!
if c.isDigit then Node.num <*> natMaybeZero
else if c == '(' then do
skip
let rec goSum : Quickparse Node := do
let n ← parseParens
match (← peek!) with
| '+' => do skip; Node.add n <*> goSum
| _ => n
let rec goProd : Quickparse Node := do
let n ← goSum
match (← peek!) with
| '*' => do skip; Node.mul n <*> goProd
| ')' => do skip; pure n
| _ => fail "bad parse"
goProd
else fail "bad parse"
def mungeString (s : String) : String :=
"(" ++ String.mk (s.toList.filter (· ≠ ' ')) ++ ")"
def parseLine (s : String) : Node :=
match (parseParens <* eoi) (mungeString s).mkIterator with
| Result.success _ n => n
| Result.error _ err => panic! err
def Node.eval
| (Node.num n) => n
| (Node.add e₁ e₂) => e₁.eval + e₂.eval
| (Node.mul e₁ e₂) => e₁.eval * e₂.eval
def main : IO Unit := do
let input ← IO.FS.lines "a.in"
let result := (input.map (λ l => (parseLine l).eval)).foldl (· + ·) 0
IO.print s!"{result}\n"
|
5fb56089f6d344c165ca06b8c3135d15e7b3673a | d406927ab5617694ec9ea7001f101b7c9e3d9702 | /src/algebra/module/equiv.lean | 7808fe6759225a1f7366488f341d0ba55eddd885 | [
"Apache-2.0"
] | permissive | alreadydone/mathlib | dc0be621c6c8208c581f5170a8216c5ba6721927 | c982179ec21091d3e102d8a5d9f5fe06c8fafb73 | refs/heads/master | 1,685,523,275,196 | 1,670,184,141,000 | 1,670,184,141,000 | 287,574,545 | 0 | 0 | Apache-2.0 | 1,670,290,714,000 | 1,597,421,623,000 | Lean | UTF-8 | Lean | false | false | 25,380 | lean | /-
Copyright (c) 2020 Anne Baanen. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Nathaniel Thomas, Jeremy Avigad, Johannes Hölzl, Mario Carneiro, Anne Baanen,
Frédéric Dupuis, Heather Macbeth
-/
import algebra.module.linear_map
/-!
# (Semi)linear equivalences
In this file we define
* `linear_equiv σ M M₂`, `M ≃ₛₗ[σ] M₂`: an invertible semilinear map. Here, `σ` is a `ring_hom`
from `R` to `R₂` and an `e : M ≃ₛₗ[σ] M₂` satisfies `e (c • x) = (σ c) • (e x)`. The plain
linear version, with `σ` being `ring_hom.id R`, is denoted by `M ≃ₗ[R] M₂`, and the
star-linear version (with `σ` being `star_ring_end`) is denoted by `M ≃ₗ⋆[R] M₂`.
## Implementation notes
To ensure that composition works smoothly for semilinear equivalences, we use the typeclasses
`ring_hom_comp_triple`, `ring_hom_inv_pair` and `ring_hom_surjective` from
`algebra/ring/comp_typeclasses`.
The group structure on automorphisms, `linear_equiv.automorphism_group`, is provided elsewhere.
## TODO
* Parts of this file have not yet been generalized to semilinear maps
## Tags
linear equiv, linear equivalences, linear isomorphism, linear isomorphic
-/
open function
open_locale big_operators
universes u u' v w x y z
variables {R : Type*} {R₁ : Type*} {R₂ : Type*} {R₃ : Type*}
variables {k : Type*} {S : Type*} {M : Type*} {M₁ : Type*} {M₂ : Type*} {M₃ : Type*}
variables {N₁ : Type*} {N₂ : Type*} {N₃ : Type*} {N₄ : Type*} {ι : Type*}
section
set_option old_structure_cmd true
/-- A linear equivalence is an invertible linear map. -/
@[nolint has_nonempty_instance]
structure linear_equiv {R : Type*} {S : Type*} [semiring R] [semiring S] (σ : R →+* S)
{σ' : S →+* R} [ring_hom_inv_pair σ σ'] [ring_hom_inv_pair σ' σ]
(M : Type*) (M₂ : Type*)
[add_comm_monoid M] [add_comm_monoid M₂] [module R M] [module S M₂]
extends linear_map σ M M₂, M ≃+ M₂
attribute [nolint doc_blame] linear_equiv.to_linear_map
attribute [nolint doc_blame] linear_equiv.to_add_equiv
notation M ` ≃ₛₗ[`:50 σ `] ` M₂ := linear_equiv σ M M₂
notation M ` ≃ₗ[`:50 R `] ` M₂ := linear_equiv (ring_hom.id R) M M₂
notation M ` ≃ₗ⋆[`:50 R `] ` M₂ := linear_equiv (star_ring_end R) M M₂
/-- `semilinear_equiv_class F σ M M₂` asserts `F` is a type of bundled `σ`-semilinear equivs
`M → M₂`.
See also `linear_equiv_class F R M M₂` for the case where `σ` is the identity map on `R`.
A map `f` between an `R`-module and an `S`-module over a ring homomorphism `σ : R →+* S`
is semilinear if it satisfies the two properties `f (x + y) = f x + f y` and
`f (c • x) = (σ c) • f x`. -/
class semilinear_equiv_class (F : Type*) {R S : out_param Type*} [semiring R] [semiring S]
(σ : out_param $ R →+* S) {σ' : out_param $ S →+* R}
[ring_hom_inv_pair σ σ'] [ring_hom_inv_pair σ' σ] (M M₂ : out_param Type*)
[add_comm_monoid M] [add_comm_monoid M₂] [module R M] [module S M₂]
extends add_equiv_class F M M₂ :=
(map_smulₛₗ : ∀ (f : F) (r : R) (x : M), f (r • x) = (σ r) • f x)
-- `R, S, σ, σ'` become metavars, but it's OK since they are outparams.
attribute [nolint dangerous_instance] semilinear_equiv_class.to_add_equiv_class
/-- `linear_equiv_class F R M M₂` asserts `F` is a type of bundled `R`-linear equivs `M → M₂`.
This is an abbreviation for `semilinear_equiv_class F (ring_hom.id R) M M₂`.
-/
abbreviation linear_equiv_class (F : Type*) (R M M₂ : out_param Type*)
[semiring R] [add_comm_monoid M] [add_comm_monoid M₂] [module R M] [module R M₂] :=
semilinear_equiv_class F (ring_hom.id R) M M₂
end
namespace semilinear_equiv_class
variables (F : Type*) [semiring R] [semiring S]
variables [add_comm_monoid M] [add_comm_monoid M₁] [add_comm_monoid M₂]
variables [module R M] [module S M₂] {σ : R →+* S} {σ' : S →+* R}
-- `σ'` becomes a metavariable, but it's OK since it's an outparam
@[priority 100, nolint dangerous_instance]
instance [ring_hom_inv_pair σ σ'] [ring_hom_inv_pair σ' σ] [s : semilinear_equiv_class F σ M M₂] :
semilinear_map_class F σ M M₂ :=
{ coe := (coe : F → M → M₂),
coe_injective' := @fun_like.coe_injective F _ _ _,
..s }
end semilinear_equiv_class
namespace linear_equiv
section add_comm_monoid
variables {M₄ : Type*}
variables [semiring R] [semiring S]
section
variables [add_comm_monoid M] [add_comm_monoid M₁] [add_comm_monoid M₂]
variables [module R M] [module S M₂] {σ : R →+* S} {σ' : S →+* R}
variables [ring_hom_inv_pair σ σ'] [ring_hom_inv_pair σ' σ]
include R
include σ'
instance : has_coe (M ≃ₛₗ[σ] M₂) (M →ₛₗ[σ] M₂) := ⟨to_linear_map⟩
-- see Note [function coercion]
instance : has_coe_to_fun (M ≃ₛₗ[σ] M₂) (λ _, M → M₂) := ⟨to_fun⟩
@[simp] lemma coe_mk {to_fun inv_fun map_add map_smul left_inv right_inv } :
⇑(⟨to_fun, map_add, map_smul, inv_fun, left_inv, right_inv⟩ : M ≃ₛₗ[σ] M₂) = to_fun :=
rfl
-- This exists for compatibility, previously `≃ₗ[R]` extended `≃` instead of `≃+`.
@[nolint doc_blame]
def to_equiv : (M ≃ₛₗ[σ] M₂) → M ≃ M₂ := λ f, f.to_add_equiv.to_equiv
lemma to_equiv_injective : function.injective (to_equiv : (M ≃ₛₗ[σ] M₂) → M ≃ M₂) :=
λ ⟨_, _, _, _, _, _⟩ ⟨_, _, _, _, _, _⟩ h, linear_equiv.mk.inj_eq.mpr (equiv.mk.inj h)
@[simp] lemma to_equiv_inj {e₁ e₂ : M ≃ₛₗ[σ] M₂} : e₁.to_equiv = e₂.to_equiv ↔ e₁ = e₂ :=
to_equiv_injective.eq_iff
lemma to_linear_map_injective :
injective (coe : (M ≃ₛₗ[σ] M₂) → (M →ₛₗ[σ] M₂)) :=
λ e₁ e₂ H, to_equiv_injective $ equiv.ext $ linear_map.congr_fun H
@[simp, norm_cast] lemma to_linear_map_inj {e₁ e₂ : M ≃ₛₗ[σ] M₂} :
(e₁ : M →ₛₗ[σ] M₂) = e₂ ↔ e₁ = e₂ :=
to_linear_map_injective.eq_iff
instance : semilinear_equiv_class (M ≃ₛₗ[σ] M₂) σ M M₂ :=
{ coe := linear_equiv.to_fun,
inv := linear_equiv.inv_fun,
coe_injective' := λ f g h₁ h₂, by { cases f, cases g, congr' },
left_inv := linear_equiv.left_inv,
right_inv := linear_equiv.right_inv,
map_add := map_add',
map_smulₛₗ := map_smul' }
lemma coe_injective :
@injective (M ≃ₛₗ[σ] M₂) (M → M₂) coe_fn :=
fun_like.coe_injective
end
section
variables [semiring R₁] [semiring R₂] [semiring R₃]
variables [add_comm_monoid M] [add_comm_monoid M₁] [add_comm_monoid M₂]
variables [add_comm_monoid M₃] [add_comm_monoid M₄]
variables [add_comm_monoid N₁] [add_comm_monoid N₂]
variables {module_M : module R M} {module_S_M₂ : module S M₂} {σ : R →+* S} {σ' : S →+* R}
variables {re₁ : ring_hom_inv_pair σ σ'} {re₂ : ring_hom_inv_pair σ' σ}
variables (e e' : M ≃ₛₗ[σ] M₂)
lemma to_linear_map_eq_coe : e.to_linear_map = (e : M →ₛₗ[σ] M₂) := rfl
@[simp, norm_cast] theorem coe_coe : ⇑(e : M →ₛₗ[σ] M₂) = e := rfl
@[simp] lemma coe_to_equiv : ⇑e.to_equiv = e := rfl
@[simp] lemma coe_to_linear_map : ⇑e.to_linear_map = e := rfl
@[simp] lemma to_fun_eq_coe : e.to_fun = e := rfl
section
variables {e e'}
@[ext] lemma ext (h : ∀ x, e x = e' x) : e = e' := fun_like.ext _ _ h
lemma ext_iff : e = e' ↔ ∀ x, e x = e' x := fun_like.ext_iff
protected lemma congr_arg {x x'} : x = x' → e x = e x' := fun_like.congr_arg e
protected lemma congr_fun (h : e = e') (x : M) : e x = e' x := fun_like.congr_fun h x
end
section
variables (M R)
/-- The identity map is a linear equivalence. -/
@[refl]
def refl [module R M] : M ≃ₗ[R] M := { .. linear_map.id, .. equiv.refl M }
end
@[simp] lemma refl_apply [module R M] (x : M) : refl R M x = x := rfl
include module_M module_S_M₂ re₁ re₂
/-- Linear equivalences are symmetric. -/
@[symm]
def symm (e : M ≃ₛₗ[σ] M₂) : M₂ ≃ₛₗ[σ'] M :=
{ to_fun := e.to_linear_map.inverse e.inv_fun e.left_inv e.right_inv,
inv_fun := e.to_equiv.symm.inv_fun,
map_smul' := λ r x, by rw map_smulₛₗ,
.. e.to_linear_map.inverse e.inv_fun e.left_inv e.right_inv,
.. e.to_equiv.symm }
omit module_M module_S_M₂ re₁ re₂
/-- See Note [custom simps projection] -/
def simps.symm_apply {R : Type*} {S : Type*} [semiring R] [semiring S] {σ : R →+* S}
{σ' : S →+* R} [ring_hom_inv_pair σ σ'] [ring_hom_inv_pair σ' σ]
{M : Type*} {M₂ : Type*} [add_comm_monoid M] [add_comm_monoid M₂] [module R M] [module S M₂]
(e : M ≃ₛₗ[σ] M₂) : M₂ → M := e.symm
initialize_simps_projections linear_equiv (to_fun → apply, inv_fun → symm_apply)
include σ'
@[simp] lemma inv_fun_eq_symm : e.inv_fun = e.symm := rfl
omit σ'
@[simp] lemma coe_to_equiv_symm : ⇑e.to_equiv.symm = e.symm := rfl
variables {module_M₁ : module R₁ M₁} {module_M₂ : module R₂ M₂} {module_M₃ : module R₃ M₃}
variables {module_N₁ : module R₁ N₁} {module_N₂ : module R₁ N₂}
variables {σ₁₂ : R₁ →+* R₂} {σ₂₃ : R₂ →+* R₃} {σ₁₃ : R₁ →+* R₃}
variables {σ₂₁ : R₂ →+* R₁} {σ₃₂ : R₃ →+* R₂} {σ₃₁ : R₃ →+* R₁}
variables [ring_hom_comp_triple σ₁₂ σ₂₃ σ₁₃]
variables [ring_hom_comp_triple σ₃₂ σ₂₁ σ₃₁]
variables {re₁₂ : ring_hom_inv_pair σ₁₂ σ₂₁} {re₂₃ : ring_hom_inv_pair σ₂₃ σ₃₂}
variables [ring_hom_inv_pair σ₁₃ σ₃₁] {re₂₁ : ring_hom_inv_pair σ₂₁ σ₁₂}
variables {re₃₂ : ring_hom_inv_pair σ₃₂ σ₂₃} [ring_hom_inv_pair σ₃₁ σ₁₃]
variables (e₁₂ : M₁ ≃ₛₗ[σ₁₂] M₂) (e₂₃ : M₂ ≃ₛₗ[σ₂₃] M₃)
include σ₃₁
/-- Linear equivalences are transitive. -/
-- Note: The linter thinks the `ring_hom_comp_triple` argument is doubled -- it is not.
@[trans, nolint unused_arguments]
def trans : M₁ ≃ₛₗ[σ₁₃] M₃ :=
{ .. e₂₃.to_linear_map.comp e₁₂.to_linear_map,
.. e₁₂.to_equiv.trans e₂₃.to_equiv }
omit σ₃₁
infixl ` ≪≫ₗ `:80 := @linear_equiv.trans _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
(ring_hom.id _) (ring_hom.id _) (ring_hom.id _)
(ring_hom.id _) (ring_hom.id _) (ring_hom.id _)
ring_hom_comp_triple.ids ring_hom_comp_triple.ids
ring_hom_inv_pair.ids ring_hom_inv_pair.ids ring_hom_inv_pair.ids
ring_hom_inv_pair.ids ring_hom_inv_pair.ids ring_hom_inv_pair.ids
variables {e₁₂} {e₂₃}
@[simp] lemma coe_to_add_equiv : ⇑(e.to_add_equiv) = e := rfl
/-- The two paths coercion can take to an `add_monoid_hom` are equivalent -/
lemma to_add_monoid_hom_commutes :
e.to_linear_map.to_add_monoid_hom = e.to_add_equiv.to_add_monoid_hom :=
rfl
include σ₃₁
@[simp] theorem trans_apply (c : M₁) :
(e₁₂.trans e₂₃ : M₁ ≃ₛₗ[σ₁₃] M₃) c = e₂₃ (e₁₂ c) := rfl
theorem coe_trans :
(e₁₂.trans e₂₃ : M₁ →ₛₗ[σ₁₃] M₃) = (e₂₃ : M₂ →ₛₗ[σ₂₃] M₃).comp (e₁₂ : M₁ →ₛₗ[σ₁₂] M₂) := rfl
omit σ₃₁
include σ'
@[simp] theorem apply_symm_apply (c : M₂) : e (e.symm c) = c := e.right_inv c
@[simp] theorem symm_apply_apply (b : M) : e.symm (e b) = b := e.left_inv b
omit σ'
include σ₃₁ σ₂₁ σ₃₂
@[simp] lemma trans_symm : (e₁₂.trans e₂₃ : M₁ ≃ₛₗ[σ₁₃] M₃).symm = e₂₃.symm.trans e₁₂.symm :=
rfl
lemma symm_trans_apply
(c : M₃) : (e₁₂.trans e₂₃ : M₁ ≃ₛₗ[σ₁₃] M₃).symm c = e₁₂.symm (e₂₃.symm c) := rfl
omit σ₃₁ σ₂₁ σ₃₂
@[simp] lemma trans_refl : e.trans (refl S M₂) = e := to_equiv_injective e.to_equiv.trans_refl
@[simp] lemma refl_trans : (refl R M).trans e = e := to_equiv_injective e.to_equiv.refl_trans
include σ'
lemma symm_apply_eq {x y} : e.symm x = y ↔ x = e y := e.to_equiv.symm_apply_eq
lemma eq_symm_apply {x y} : y = e.symm x ↔ e y = x := e.to_equiv.eq_symm_apply
omit σ'
lemma eq_comp_symm {α : Type*} (f : M₂ → α) (g : M₁ → α) :
f = g ∘ e₁₂.symm ↔ f ∘ e₁₂ = g := e₁₂.to_equiv.eq_comp_symm f g
lemma comp_symm_eq {α : Type*} (f : M₂ → α) (g : M₁ → α) :
g ∘ e₁₂.symm = f ↔ g = f ∘ e₁₂ := e₁₂.to_equiv.comp_symm_eq f g
lemma eq_symm_comp {α : Type*} (f : α → M₁) (g : α → M₂) :
f = e₁₂.symm ∘ g ↔ e₁₂ ∘ f = g := e₁₂.to_equiv.eq_symm_comp f g
lemma symm_comp_eq {α : Type*} (f : α → M₁) (g : α → M₂) :
e₁₂.symm ∘ g = f ↔ g = e₁₂ ∘ f := e₁₂.to_equiv.symm_comp_eq f g
variables [ring_hom_comp_triple σ₂₁ σ₁₃ σ₂₃] [ring_hom_comp_triple σ₃₁ σ₁₂ σ₃₂]
include module_M₃
lemma eq_comp_to_linear_map_symm (f : M₂ →ₛₗ[σ₂₃] M₃) (g : M₁ →ₛₗ[σ₁₃] M₃) :
f = g.comp e₁₂.symm.to_linear_map ↔ f.comp e₁₂.to_linear_map = g :=
begin
split; intro H; ext,
{ simp [H, e₁₂.to_equiv.eq_comp_symm f g] },
{ simp [←H, ←e₁₂.to_equiv.eq_comp_symm f g] }
end
lemma comp_to_linear_map_symm_eq (f : M₂ →ₛₗ[σ₂₃] M₃) (g : M₁ →ₛₗ[σ₁₃] M₃) :
g.comp e₁₂.symm.to_linear_map = f ↔ g = f.comp e₁₂.to_linear_map :=
begin
split; intro H; ext,
{ simp [←H, ←e₁₂.to_equiv.comp_symm_eq f g] },
{ simp [H, e₁₂.to_equiv.comp_symm_eq f g] }
end
lemma eq_to_linear_map_symm_comp (f : M₃ →ₛₗ[σ₃₁] M₁) (g : M₃ →ₛₗ[σ₃₂] M₂) :
f = e₁₂.symm.to_linear_map.comp g ↔ e₁₂.to_linear_map.comp f = g :=
begin
split; intro H; ext,
{ simp [H, e₁₂.to_equiv.eq_symm_comp f g] },
{ simp [←H, ←e₁₂.to_equiv.eq_symm_comp f g] }
end
lemma to_linear_map_symm_comp_eq (f : M₃ →ₛₗ[σ₃₁] M₁) (g : M₃ →ₛₗ[σ₃₂] M₂) :
e₁₂.symm.to_linear_map.comp g = f ↔ g = e₁₂.to_linear_map.comp f :=
begin
split; intro H; ext,
{ simp [←H, ←e₁₂.to_equiv.symm_comp_eq f g] },
{ simp [H, e₁₂.to_equiv.symm_comp_eq f g] }
end
omit module_M₃
@[simp] lemma refl_symm [module R M] : (refl R M).symm = linear_equiv.refl R M := rfl
include re₁₂ re₂₁ module_M₁ module_M₂
@[simp] lemma self_trans_symm (f : M₁ ≃ₛₗ[σ₁₂] M₂) :
f.trans f.symm = linear_equiv.refl R₁ M₁ :=
by { ext x, simp }
@[simp] lemma symm_trans_self (f : M₁ ≃ₛₗ[σ₁₂] M₂) :
f.symm.trans f = linear_equiv.refl R₂ M₂ :=
by { ext x, simp }
omit re₁₂ re₂₁ module_M₁ module_M₂
@[simp, norm_cast] lemma refl_to_linear_map [module R M] :
(linear_equiv.refl R M : M →ₗ[R] M) = linear_map.id :=
rfl
@[simp, norm_cast]
lemma comp_coe [module R M] [module R M₂] [module R M₃] (f : M ≃ₗ[R] M₂)
(f' : M₂ ≃ₗ[R] M₃) : (f' : M₂ →ₗ[R] M₃).comp (f : M →ₗ[R] M₂) = (f.trans f' : M ≃ₗ[R] M₃) :=
rfl
@[simp] lemma mk_coe (h₁ h₂ f h₃ h₄) :
(linear_equiv.mk e h₁ h₂ f h₃ h₄ : M ≃ₛₗ[σ] M₂) = e := ext $ λ _, rfl
protected theorem map_add (a b : M) : e (a + b) = e a + e b := map_add e a b
protected theorem map_zero : e 0 = 0 := map_zero e
-- TODO: `simp` isn't picking up `map_smulₛₗ` for `linear_equiv`s without specifying `map_smulₛₗ f`
@[simp] protected theorem map_smulₛₗ (c : R) (x : M) : e (c • x) = (σ c) • e x := e.map_smul' c x
include module_N₁ module_N₂
theorem map_smul (e : N₁ ≃ₗ[R₁] N₂) (c : R₁) (x : N₁) :
e (c • x) = c • e x := map_smulₛₗ e c x
omit module_N₁ module_N₂
@[simp] lemma map_sum {s : finset ι} (u : ι → M) : e (∑ i in s, u i) = ∑ i in s, e (u i) :=
e.to_linear_map.map_sum
@[simp] theorem map_eq_zero_iff {x : M} : e x = 0 ↔ x = 0 :=
e.to_add_equiv.map_eq_zero_iff
theorem map_ne_zero_iff {x : M} : e x ≠ 0 ↔ x ≠ 0 :=
e.to_add_equiv.map_ne_zero_iff
include module_M module_S_M₂ re₁ re₂
@[simp] theorem symm_symm (e : M ≃ₛₗ[σ] M₂): e.symm.symm = e :=
by { cases e, refl }
omit module_M module_S_M₂ re₁ re₂
lemma symm_bijective [module R M] [module S M₂] [ring_hom_inv_pair σ' σ]
[ring_hom_inv_pair σ σ'] : function.bijective (symm : (M ≃ₛₗ[σ] M₂) → (M₂ ≃ₛₗ[σ'] M)) :=
equiv.bijective ⟨(symm : (M ≃ₛₗ[σ] M₂) →
(M₂ ≃ₛₗ[σ'] M)), (symm : (M₂ ≃ₛₗ[σ'] M) → (M ≃ₛₗ[σ] M₂)), symm_symm, symm_symm⟩
@[simp] lemma mk_coe' (f h₁ h₂ h₃ h₄) : (linear_equiv.mk f h₁ h₂ ⇑e h₃ h₄ :
M₂ ≃ₛₗ[σ'] M) = e.symm :=
symm_bijective.injective $ ext $ λ x, rfl
@[simp] theorem symm_mk (f h₁ h₂ h₃ h₄) :
(⟨e, h₁, h₂, f, h₃, h₄⟩ : M ≃ₛₗ[σ] M₂).symm =
{ to_fun := f, inv_fun := e,
..(⟨e, h₁, h₂, f, h₃, h₄⟩ : M ≃ₛₗ[σ] M₂).symm } := rfl
@[simp] lemma coe_symm_mk [module R M] [module R M₂]
{to_fun inv_fun map_add map_smul left_inv right_inv} :
⇑((⟨to_fun, map_add, map_smul, inv_fun, left_inv, right_inv⟩ : M ≃ₗ[R] M₂).symm) = inv_fun :=
rfl
protected lemma bijective : function.bijective e := e.to_equiv.bijective
protected lemma injective : function.injective e := e.to_equiv.injective
protected lemma surjective : function.surjective e := e.to_equiv.surjective
protected lemma image_eq_preimage (s : set M) : e '' s = e.symm ⁻¹' s :=
e.to_equiv.image_eq_preimage s
protected lemma image_symm_eq_preimage (s : set M₂) : e.symm '' s = e ⁻¹' s :=
e.to_equiv.symm.image_eq_preimage s
end
/-- Interpret a `ring_equiv` `f` as an `f`-semilinear equiv. -/
@[simps]
def _root_.ring_equiv.to_semilinear_equiv (f : R ≃+* S) :
by haveI := ring_hom_inv_pair.of_ring_equiv f;
haveI := ring_hom_inv_pair.symm (↑f : R →+* S) (f.symm : S →+* R);
exact (R ≃ₛₗ[(↑f : R →+* S)] S) :=
by exact
{ to_fun := f,
map_smul' := f.map_mul,
.. f}
variables [semiring R₁] [semiring R₂] [semiring R₃]
variables [add_comm_monoid M] [add_comm_monoid M₁] [add_comm_monoid M₂]
/-- An involutive linear map is a linear equivalence. -/
def of_involutive {σ σ' : R →+* R} [ring_hom_inv_pair σ σ'] [ring_hom_inv_pair σ' σ]
{module_M : module R M} (f : M →ₛₗ[σ] M) (hf : involutive f) :
M ≃ₛₗ[σ] M :=
{ .. f, .. hf.to_perm f }
@[simp] lemma coe_of_involutive {σ σ' : R →+* R} [ring_hom_inv_pair σ σ']
[ring_hom_inv_pair σ' σ] {module_M : module R M} (f : M →ₛₗ[σ] M) (hf : involutive f) :
⇑(of_involutive f hf) = f :=
rfl
section restrict_scalars
variables (R) [module R M] [module R M₂] [module S M] [module S M₂]
[linear_map.compatible_smul M M₂ R S]
/-- If `M` and `M₂` are both `R`-semimodules and `S`-semimodules and `R`-semimodule structures
are defined by an action of `R` on `S` (formally, we have two scalar towers), then any `S`-linear
equivalence from `M` to `M₂` is also an `R`-linear equivalence.
See also `linear_map.restrict_scalars`. -/
@[simps]
def restrict_scalars (f : M ≃ₗ[S] M₂) : M ≃ₗ[R] M₂ :=
{ to_fun := f,
inv_fun := f.symm,
left_inv := f.left_inv,
right_inv := f.right_inv,
.. f.to_linear_map.restrict_scalars R }
lemma restrict_scalars_injective :
function.injective (restrict_scalars R : (M ≃ₗ[S] M₂) → (M ≃ₗ[R] M₂)) :=
λ f g h, ext (linear_equiv.congr_fun h : _)
@[simp]
lemma restrict_scalars_inj (f g : M ≃ₗ[S] M₂) :
f.restrict_scalars R = g.restrict_scalars R ↔ f = g :=
(restrict_scalars_injective R).eq_iff
end restrict_scalars
section automorphisms
variables [module R M]
instance automorphism_group : group (M ≃ₗ[R] M) :=
{ mul := λ f g, g.trans f,
one := linear_equiv.refl R M,
inv := λ f, f.symm,
mul_assoc := λ f g h, rfl,
mul_one := λ f, ext $ λ x, rfl,
one_mul := λ f, ext $ λ x, rfl,
mul_left_inv := λ f, ext $ f.left_inv }
/-- Restriction from `R`-linear automorphisms of `M` to `R`-linear endomorphisms of `M`,
promoted to a monoid hom. -/
@[simps]
def automorphism_group.to_linear_map_monoid_hom : (M ≃ₗ[R] M) →* (M →ₗ[R] M) :=
{ to_fun := coe,
map_one' := rfl,
map_mul' := λ _ _, rfl }
/-- The tautological action by `M ≃ₗ[R] M` on `M`.
This generalizes `function.End.apply_mul_action`. -/
instance apply_distrib_mul_action : distrib_mul_action (M ≃ₗ[R] M) M :=
{ smul := ($),
smul_zero := linear_equiv.map_zero,
smul_add := linear_equiv.map_add,
one_smul := λ _, rfl,
mul_smul := λ _ _ _, rfl }
@[simp] protected lemma smul_def (f : M ≃ₗ[R] M) (a : M) :
f • a = f a := rfl
/-- `linear_equiv.apply_distrib_mul_action` is faithful. -/
instance apply_has_faithful_smul : has_faithful_smul (M ≃ₗ[R] M) M :=
⟨λ _ _, linear_equiv.ext⟩
instance apply_smul_comm_class : smul_comm_class R (M ≃ₗ[R] M) M :=
{ smul_comm := λ r e m, (e.map_smul r m).symm }
instance apply_smul_comm_class' : smul_comm_class (M ≃ₗ[R] M) R M :=
{ smul_comm := linear_equiv.map_smul }
end automorphisms
section of_subsingleton
variables (M M₂) [module R M] [module R M₂] [subsingleton M] [subsingleton M₂]
/-- Any two modules that are subsingletons are isomorphic. -/
@[simps] def of_subsingleton : M ≃ₗ[R] M₂ :=
{ to_fun := λ _, 0,
inv_fun := λ _, 0,
left_inv := λ x, subsingleton.elim _ _,
right_inv := λ x, subsingleton.elim _ _,
.. (0 : M →ₗ[R] M₂)}
@[simp] lemma of_subsingleton_self : of_subsingleton M M = refl R M :=
by { ext, simp }
end of_subsingleton
end add_comm_monoid
end linear_equiv
namespace module
/-- `g : R ≃+* S` is `R`-linear when the module structure on `S` is `module.comp_hom S g` . -/
@[simps]
def comp_hom.to_linear_equiv {R S : Type*} [semiring R] [semiring S] (g : R ≃+* S) :
(by haveI := comp_hom S (↑g : R →+* S); exact (R ≃ₗ[R] S)) :=
by exact
{ to_fun := (g : R → S),
inv_fun := (g.symm : S → R),
map_smul' := g.map_mul,
..g }
end module
namespace distrib_mul_action
variables (R M) [semiring R] [add_comm_monoid M] [module R M]
variables [group S] [distrib_mul_action S M] [smul_comm_class S R M]
/-- Each element of the group defines a linear equivalence.
This is a stronger version of `distrib_mul_action.to_add_equiv`. -/
@[simps]
def to_linear_equiv (s : S) : M ≃ₗ[R] M :=
{ ..to_add_equiv M s,
..to_linear_map R M s }
/-- Each element of the group defines a module automorphism.
This is a stronger version of `distrib_mul_action.to_add_aut`. -/
@[simps]
def to_module_aut : S →* M ≃ₗ[R] M :=
{ to_fun := to_linear_equiv R M,
map_one' := linear_equiv.ext $ one_smul _,
map_mul' := λ a b, linear_equiv.ext $ mul_smul _ _ }
end distrib_mul_action
namespace add_equiv
section add_comm_monoid
variables [semiring R] [add_comm_monoid M] [add_comm_monoid M₂] [add_comm_monoid M₃]
variables [module R M] [module R M₂]
variable (e : M ≃+ M₂)
/-- An additive equivalence whose underlying function preserves `smul` is a linear equivalence. -/
def to_linear_equiv (h : ∀ (c : R) x, e (c • x) = c • e x) : M ≃ₗ[R] M₂ :=
{ map_smul' := h, .. e, }
@[simp] lemma coe_to_linear_equiv (h : ∀ (c : R) x, e (c • x) = c • e x) :
⇑(e.to_linear_equiv h) = e :=
rfl
@[simp] lemma coe_to_linear_equiv_symm (h : ∀ (c : R) x, e (c • x) = c • e x) :
⇑(e.to_linear_equiv h).symm = e.symm :=
rfl
/-- An additive equivalence between commutative additive monoids is a linear equivalence between
ℕ-modules -/
def to_nat_linear_equiv : M ≃ₗ[ℕ] M₂ :=
e.to_linear_equiv $ λ c a, by { erw e.to_add_monoid_hom.map_nsmul, refl }
@[simp] lemma coe_to_nat_linear_equiv :
⇑(e.to_nat_linear_equiv) = e := rfl
@[simp] lemma to_nat_linear_equiv_to_add_equiv :
e.to_nat_linear_equiv.to_add_equiv = e := by { ext, refl }
@[simp] lemma _root_.linear_equiv.to_add_equiv_to_nat_linear_equiv
(e : M ≃ₗ[ℕ] M₂) : e.to_add_equiv.to_nat_linear_equiv = e := fun_like.coe_injective rfl
@[simp] lemma to_nat_linear_equiv_symm :
(e.to_nat_linear_equiv).symm = e.symm.to_nat_linear_equiv := rfl
@[simp] lemma to_nat_linear_equiv_refl :
((add_equiv.refl M).to_nat_linear_equiv) = linear_equiv.refl ℕ M := rfl
@[simp] lemma to_nat_linear_equiv_trans (e₂ : M₂ ≃+ M₃) :
(e.to_nat_linear_equiv).trans (e₂.to_nat_linear_equiv) = (e.trans e₂).to_nat_linear_equiv := rfl
end add_comm_monoid
section add_comm_group
variables [add_comm_group M] [add_comm_group M₂] [add_comm_group M₃]
variable (e : M ≃+ M₂)
/-- An additive equivalence between commutative additive groups is a linear
equivalence between ℤ-modules -/
def to_int_linear_equiv : M ≃ₗ[ℤ] M₂ :=
e.to_linear_equiv $ λ c a, e.to_add_monoid_hom.map_zsmul a c
@[simp] lemma coe_to_int_linear_equiv :
⇑(e.to_int_linear_equiv) = e := rfl
@[simp] lemma to_int_linear_equiv_to_add_equiv :
e.to_int_linear_equiv.to_add_equiv = e := by { ext, refl }
@[simp] lemma _root_.linear_equiv.to_add_equiv_to_int_linear_equiv
(e : M ≃ₗ[ℤ] M₂) : e.to_add_equiv.to_int_linear_equiv = e := fun_like.coe_injective rfl
@[simp] lemma to_int_linear_equiv_symm :
(e.to_int_linear_equiv).symm = e.symm.to_int_linear_equiv := rfl
@[simp] lemma to_int_linear_equiv_refl :
((add_equiv.refl M).to_int_linear_equiv) = linear_equiv.refl ℤ M := rfl
@[simp] lemma to_int_linear_equiv_trans (e₂ : M₂ ≃+ M₃) :
(e.to_int_linear_equiv).trans (e₂.to_int_linear_equiv) = (e.trans e₂).to_int_linear_equiv :=
rfl
end add_comm_group
end add_equiv
|
f7bbcccb7b459bdbdeb58fc554bad417b24d6339 | 097294e9b80f0d9893ac160b9c7219aa135b51b9 | /instructor/include/includer.lean | 87d25e584c31a317ce451c42fe8141cd2cfc57bd | [] | no_license | AbigailCastro17/CS2102-Discrete-Math | cf296251be9418ce90206f5e66bde9163e21abf9 | d741e4d2d6a9b2e0c8380e51706218b8f608cee4 | refs/heads/main | 1,682,891,087,358 | 1,621,401,341,000 | 1,621,401,341,000 | 368,749,959 | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 42 | lean | import .includee
#check x
#check bor tt ff |
abeac8eefdd278a6d84d54a00fbdd2c834bad38b | 947fa6c38e48771ae886239b4edce6db6e18d0fb | /src/data/finite/basic.lean | cd984fca51e8361f3cf3ecb90e29f4efc3e26e0e | [
"Apache-2.0"
] | permissive | ramonfmir/mathlib | c5dc8b33155473fab97c38bd3aa6723dc289beaa | 14c52e990c17f5a00c0cc9e09847af16fabbed25 | refs/heads/master | 1,661,979,343,526 | 1,660,830,384,000 | 1,660,830,384,000 | 182,072,989 | 0 | 0 | null | 1,555,585,876,000 | 1,555,585,876,000 | null | UTF-8 | Lean | false | false | 5,137 | lean | /-
Copyright (c) 2022 Kyle Miller. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kyle Miller
-/
import data.fintype.basic
/-!
# Finite types
In this file we prove some theorems about `finite` and provide some instances. This typeclass is a
`Prop`-valued counterpart of the typeclass `fintype`. See more details in the file where `finite` is
defined.
## Main definitions
* `fintype.finite`, `finite.of_fintype` creates a `finite` instance from a `fintype` instance. The
former lemma takes `fintype α` as an explicit argument while the latter takes it as an instance
argument.
* `fintype.of_finite` noncomputably creates a `fintype` instance from a `finite` instance.
* `finite_or_infinite` is that every type is either `finite` or `infinite`.
## Implementation notes
There is an apparent duplication of many `fintype` instances in this module,
however they follow a pattern: if a `fintype` instance depends on `decidable`
instances or other `fintype` instances, then we need to "lower" the instance
to be a `finite` instance by removing the `decidable` instances and switching
the `fintype` instances to `finite` instances. These are precisely the ones
that cannot be inferred using `finite.of_fintype`. (However, when using
`open_locale classical` or the `classical` tactic the instances relying only
on `decidable` instances will give `finite` instances.) In the future we might
consider writing automation to create these "lowered" instances.
## Tags
finiteness, finite types
-/
noncomputable theory
open_locale classical
variables {α β γ : Type*}
lemma finite_or_infinite (α : Type*) :
finite α ∨ infinite α :=
begin
rw ← not_finite_iff_infinite,
apply em
end
namespace finite
@[priority 100] -- see Note [lower instance priority]
instance of_subsingleton {α : Sort*} [subsingleton α] : finite α :=
of_injective (function.const α ()) $ function.injective_of_subsingleton _
@[nolint instance_priority] -- Higher priority for `Prop`s
instance prop (p : Prop) : finite p := finite.of_subsingleton
instance [finite α] [finite β] : finite (α × β) :=
by { haveI := fintype.of_finite α, haveI := fintype.of_finite β, apply_instance }
instance {α β : Sort*} [finite α] [finite β] : finite (pprod α β) :=
of_equiv _ equiv.pprod_equiv_prod_plift.symm
lemma prod_left (β) [finite (α × β)] [nonempty β] : finite α :=
of_surjective (prod.fst : α × β → α) prod.fst_surjective
lemma prod_right (α) [finite (α × β)] [nonempty α] : finite β :=
of_surjective (prod.snd : α × β → β) prod.snd_surjective
instance [finite α] [finite β] : finite (α ⊕ β) :=
by { haveI := fintype.of_finite α, haveI := fintype.of_finite β, apply_instance }
lemma sum_left (β) [finite (α ⊕ β)] : finite α :=
of_injective (sum.inl : α → α ⊕ β) sum.inl_injective
lemma sum_right (α) [finite (α ⊕ β)] : finite β :=
of_injective (sum.inr : β → α ⊕ β) sum.inr_injective
instance {β : α → Type*} [finite α] [Π a, finite (β a)] : finite (Σ a, β a) :=
by { letI := fintype.of_finite α, letI := λ a, fintype.of_finite (β a), apply_instance }
instance {ι : Sort*} {π : ι → Sort*} [finite ι] [Π i, finite (π i)] : finite (Σ' i, π i) :=
of_equiv _ (equiv.psigma_equiv_sigma_plift π).symm
instance [finite α] : finite (set α) := by { casesI nonempty_fintype α, apply_instance }
end finite
/-- This instance also provides `[finite s]` for `s : set α`. -/
instance subtype.finite {α : Sort*} [finite α] {p : α → Prop} : finite {x // p x} :=
finite.of_injective coe subtype.coe_injective
instance pi.finite {α : Sort*} {β : α → Sort*} [finite α] [∀ a, finite (β a)] : finite (Π a, β a) :=
begin
haveI := fintype.of_finite (plift α),
haveI := λ a, fintype.of_finite (plift (β a)),
exact finite.of_equiv (Π (a : plift α), plift (β (equiv.plift a)))
(equiv.Pi_congr equiv.plift (λ _, equiv.plift)),
end
instance vector.finite {α : Type*} [finite α] {n : ℕ} : finite (vector α n) :=
by { haveI := fintype.of_finite α, apply_instance }
instance quot.finite {α : Sort*} [finite α] (r : α → α → Prop) : finite (quot r) :=
finite.of_surjective _ (surjective_quot_mk r)
instance quotient.finite {α : Sort*} [finite α] (s : setoid α) : finite (quotient s) :=
quot.finite _
instance function.embedding.finite {α β : Sort*} [finite β] : finite (α ↪ β) :=
begin
casesI is_empty_or_nonempty (α ↪ β) with _ h,
{ apply_instance, },
{ refine h.elim (λ f, _),
haveI : finite α := finite.of_injective _ f.injective,
exact finite.of_injective _ fun_like.coe_injective },
end
instance equiv.finite_right {α β : Sort*} [finite β] : finite (α ≃ β) :=
finite.of_injective equiv.to_embedding $ λ e₁ e₂ h, equiv.ext $
by convert fun_like.congr_fun h
instance equiv.finite_left {α β : Sort*} [finite α] : finite (α ≃ β) :=
finite.of_equiv _ ⟨equiv.symm, equiv.symm, equiv.symm_symm, equiv.symm_symm⟩
instance [finite α] {n : ℕ} : finite (sym α n) :=
by { haveI := fintype.of_finite α, apply_instance }
|
7454fbf44f322b92b7ed505ad833130e6237478c | 8cae430f0a71442d02dbb1cbb14073b31048e4b0 | /src/probability/independence/basic.lean | 7223f9b23c01e1217b282b34cafc08b32763eb6c | [
"Apache-2.0"
] | permissive | leanprover-community/mathlib | 56a2cadd17ac88caf4ece0a775932fa26327ba0e | 442a83d738cb208d3600056c489be16900ba701d | refs/heads/master | 1,693,584,102,358 | 1,693,471,902,000 | 1,693,471,902,000 | 97,922,418 | 1,595 | 352 | Apache-2.0 | 1,694,693,445,000 | 1,500,624,130,000 | Lean | UTF-8 | Lean | false | false | 45,062 | lean | /-
Copyright (c) 2021 Rémy Degenne. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Rémy Degenne
-/
import measure_theory.constructions.pi
/-!
# Independence of sets of sets and measure spaces (σ-algebras)
> THIS FILE IS SYNCHRONIZED WITH MATHLIB4.
> Any changes to this file require a corresponding PR to mathlib4.
* A family of sets of sets `π : ι → set (set Ω)` is independent with respect to a measure `μ` if for
any finite set of indices `s = {i_1, ..., i_n}`, for any sets `f i_1 ∈ π i_1, ..., f i_n ∈ π i_n`,
`μ (⋂ i in s, f i) = ∏ i in s, μ (f i) `. It will be used for families of π-systems.
* A family of measurable space structures (i.e. of σ-algebras) is independent with respect to a
measure `μ` (typically defined on a finer σ-algebra) if the family of sets of measurable sets they
define is independent. I.e., `m : ι → measurable_space Ω` is independent with respect to a
measure `μ` if for any finite set of indices `s = {i_1, ..., i_n}`, for any sets
`f i_1 ∈ m i_1, ..., f i_n ∈ m i_n`, then `μ (⋂ i in s, f i) = ∏ i in s, μ (f i)`.
* Independence of sets (or events in probabilistic parlance) is defined as independence of the
measurable space structures they generate: a set `s` generates the measurable space structure with
measurable sets `∅, s, sᶜ, univ`.
* Independence of functions (or random variables) is also defined as independence of the measurable
space structures they generate: a function `f` for which we have a measurable space `m` on the
codomain generates `measurable_space.comap f m`.
## Main statements
* `Indep_sets.Indep`: if π-systems are independent as sets of sets, then the
measurable space structures they generate are independent.
* `indep_sets.indep`: variant with two π-systems.
## Implementation notes
We provide one main definition of independence:
* `Indep_sets`: independence of a family of sets of sets `pi : ι → set (set Ω)`.
Three other independence notions are defined using `Indep_sets`:
* `Indep`: independence of a family of measurable space structures `m : ι → measurable_space Ω`,
* `Indep_set`: independence of a family of sets `s : ι → set Ω`,
* `Indep_fun`: independence of a family of functions. For measurable spaces
`m : Π (i : ι), measurable_space (β i)`, we consider functions `f : Π (i : ι), Ω → β i`.
Additionally, we provide four corresponding statements for two measurable space structures (resp.
sets of sets, sets, functions) instead of a family. These properties are denoted by the same names
as for a family, but without a capital letter, for example `indep_fun` is the version of `Indep_fun`
for two functions.
The definition of independence for `Indep_sets` uses finite sets (`finset`). An alternative and
equivalent way of defining independence would have been to use countable sets.
TODO: prove that equivalence.
Most of the definitions and lemma in this file list all variables instead of using the `variables`
keyword at the beginning of a section, for example
`lemma indep.symm {Ω} {m₁ m₂ : measurable_space Ω} [measurable_space Ω] {μ : measure Ω} ...` .
This is intentional, to be able to control the order of the `measurable_space` variables. Indeed
when defining `μ` in the example above, the measurable space used is the last one defined, here
`[measurable_space Ω]`, and not `m₁` or `m₂`.
## References
* Williams, David. Probability with martingales. Cambridge university press, 1991.
Part A, Chapter 4.
-/
open measure_theory measurable_space
open_locale big_operators measure_theory ennreal
namespace probability_theory
variables {Ω ι : Type*}
section definitions
/-- A family of sets of sets `π : ι → set (set Ω)` is independent with respect to a measure `μ` if
for any finite set of indices `s = {i_1, ..., i_n}`, for any sets
`f i_1 ∈ π i_1, ..., f i_n ∈ π i_n`, then `μ (⋂ i in s, f i) = ∏ i in s, μ (f i) `.
It will be used for families of pi_systems. -/
def Indep_sets [measurable_space Ω] (π : ι → set (set Ω)) (μ : measure Ω . volume_tac) :
Prop :=
∀ (s : finset ι) {f : ι → set Ω} (H : ∀ i, i ∈ s → f i ∈ π i), μ (⋂ i ∈ s, f i) = ∏ i in s, μ (f i)
/-- Two sets of sets `s₁, s₂` are independent with respect to a measure `μ` if for any sets
`t₁ ∈ p₁, t₂ ∈ s₂`, then `μ (t₁ ∩ t₂) = μ (t₁) * μ (t₂)` -/
def indep_sets [measurable_space Ω] (s1 s2 : set (set Ω)) (μ : measure Ω . volume_tac) : Prop :=
∀ t1 t2 : set Ω, t1 ∈ s1 → t2 ∈ s2 → μ (t1 ∩ t2) = μ t1 * μ t2
/-- A family of measurable space structures (i.e. of σ-algebras) is independent with respect to a
measure `μ` (typically defined on a finer σ-algebra) if the family of sets of measurable sets they
define is independent. `m : ι → measurable_space Ω` is independent with respect to measure `μ` if
for any finite set of indices `s = {i_1, ..., i_n}`, for any sets
`f i_1 ∈ m i_1, ..., f i_n ∈ m i_n`, then `μ (⋂ i in s, f i) = ∏ i in s, μ (f i) `. -/
def Indep (m : ι → measurable_space Ω) [measurable_space Ω] (μ : measure Ω . volume_tac) :
Prop :=
Indep_sets (λ x, {s | measurable_set[m x] s}) μ
/-- Two measurable space structures (or σ-algebras) `m₁, m₂` are independent with respect to a
measure `μ` (defined on a third σ-algebra) if for any sets `t₁ ∈ m₁, t₂ ∈ m₂`,
`μ (t₁ ∩ t₂) = μ (t₁) * μ (t₂)` -/
def indep (m₁ m₂ : measurable_space Ω) [measurable_space Ω] (μ : measure Ω . volume_tac) :
Prop :=
indep_sets {s | measurable_set[m₁] s} {s | measurable_set[m₂] s} μ
/-- A family of sets is independent if the family of measurable space structures they generate is
independent. For a set `s`, the generated measurable space has measurable sets `∅, s, sᶜ, univ`. -/
def Indep_set [measurable_space Ω] (s : ι → set Ω) (μ : measure Ω . volume_tac) : Prop :=
Indep (λ i, generate_from {s i}) μ
/-- Two sets are independent if the two measurable space structures they generate are independent.
For a set `s`, the generated measurable space structure has measurable sets `∅, s, sᶜ, univ`. -/
def indep_set [measurable_space Ω] (s t : set Ω) (μ : measure Ω . volume_tac) : Prop :=
indep (generate_from {s}) (generate_from {t}) μ
/-- A family of functions defined on the same space `Ω` and taking values in possibly different
spaces, each with a measurable space structure, is independent if the family of measurable space
structures they generate on `Ω` is independent. For a function `g` with codomain having measurable
space structure `m`, the generated measurable space structure is `measurable_space.comap g m`. -/
def Indep_fun [measurable_space Ω] {β : ι → Type*} (m : Π (x : ι), measurable_space (β x))
(f : Π (x : ι), Ω → β x) (μ : measure Ω . volume_tac) : Prop :=
Indep (λ x, measurable_space.comap (f x) (m x)) μ
/-- Two functions are independent if the two measurable space structures they generate are
independent. For a function `f` with codomain having measurable space structure `m`, the generated
measurable space structure is `measurable_space.comap f m`. -/
def indep_fun {β γ} [measurable_space Ω] [mβ : measurable_space β] [mγ : measurable_space γ]
(f : Ω → β) (g : Ω → γ) (μ : measure Ω . volume_tac) : Prop :=
indep (measurable_space.comap f mβ) (measurable_space.comap g mγ) μ
end definitions
section indep
@[symm] lemma indep_sets.symm {s₁ s₂ : set (set Ω)} [measurable_space Ω] {μ : measure Ω}
(h : indep_sets s₁ s₂ μ) :
indep_sets s₂ s₁ μ :=
by { intros t1 t2 ht1 ht2, rw [set.inter_comm, mul_comm], exact h t2 t1 ht2 ht1, }
@[symm] lemma indep.symm {m₁ m₂ : measurable_space Ω} [measurable_space Ω] {μ : measure Ω}
(h : indep m₁ m₂ μ) :
indep m₂ m₁ μ :=
indep_sets.symm h
lemma indep_bot_right (m' : measurable_space Ω) {m : measurable_space Ω}
{μ : measure Ω} [is_probability_measure μ] :
indep m' ⊥ μ :=
begin
intros s t hs ht,
rw [set.mem_set_of_eq, measurable_space.measurable_set_bot_iff] at ht,
cases ht,
{ rw [ht, set.inter_empty, measure_empty, mul_zero], },
{ rw [ht, set.inter_univ, measure_univ, mul_one], },
end
lemma indep_bot_left (m' : measurable_space Ω) {m : measurable_space Ω}
{μ : measure Ω} [is_probability_measure μ] :
indep ⊥ m' μ :=
(indep_bot_right m').symm
lemma indep_set_empty_right {m : measurable_space Ω} {μ : measure Ω} [is_probability_measure μ]
(s : set Ω) :
indep_set s ∅ μ :=
by { simp only [indep_set, generate_from_singleton_empty], exact indep_bot_right _, }
lemma indep_set_empty_left {m : measurable_space Ω} {μ : measure Ω} [is_probability_measure μ]
(s : set Ω) :
indep_set ∅ s μ :=
(indep_set_empty_right s).symm
lemma indep_sets_of_indep_sets_of_le_left {s₁ s₂ s₃: set (set Ω)} [measurable_space Ω]
{μ : measure Ω} (h_indep : indep_sets s₁ s₂ μ) (h31 : s₃ ⊆ s₁) :
indep_sets s₃ s₂ μ :=
λ t1 t2 ht1 ht2, h_indep t1 t2 (set.mem_of_subset_of_mem h31 ht1) ht2
lemma indep_sets_of_indep_sets_of_le_right {s₁ s₂ s₃: set (set Ω)} [measurable_space Ω]
{μ : measure Ω} (h_indep : indep_sets s₁ s₂ μ) (h32 : s₃ ⊆ s₂) :
indep_sets s₁ s₃ μ :=
λ t1 t2 ht1 ht2, h_indep t1 t2 ht1 (set.mem_of_subset_of_mem h32 ht2)
lemma indep_of_indep_of_le_left {m₁ m₂ m₃: measurable_space Ω} [measurable_space Ω]
{μ : measure Ω} (h_indep : indep m₁ m₂ μ) (h31 : m₃ ≤ m₁) :
indep m₃ m₂ μ :=
λ t1 t2 ht1 ht2, h_indep t1 t2 (h31 _ ht1) ht2
lemma indep_of_indep_of_le_right {m₁ m₂ m₃: measurable_space Ω} [measurable_space Ω]
{μ : measure Ω} (h_indep : indep m₁ m₂ μ) (h32 : m₃ ≤ m₂) :
indep m₁ m₃ μ :=
λ t1 t2 ht1 ht2, h_indep t1 t2 ht1 (h32 _ ht2)
lemma indep_sets.union [measurable_space Ω] {s₁ s₂ s' : set (set Ω)} {μ : measure Ω}
(h₁ : indep_sets s₁ s' μ) (h₂ : indep_sets s₂ s' μ) :
indep_sets (s₁ ∪ s₂) s' μ :=
begin
intros t1 t2 ht1 ht2,
cases (set.mem_union _ _ _).mp ht1 with ht1₁ ht1₂,
{ exact h₁ t1 t2 ht1₁ ht2, },
{ exact h₂ t1 t2 ht1₂ ht2, },
end
@[simp] lemma indep_sets.union_iff [measurable_space Ω] {s₁ s₂ s' : set (set Ω)}
{μ : measure Ω} :
indep_sets (s₁ ∪ s₂) s' μ ↔ indep_sets s₁ s' μ ∧ indep_sets s₂ s' μ :=
⟨λ h, ⟨indep_sets_of_indep_sets_of_le_left h (set.subset_union_left s₁ s₂),
indep_sets_of_indep_sets_of_le_left h (set.subset_union_right s₁ s₂)⟩,
λ h, indep_sets.union h.left h.right⟩
lemma indep_sets.Union [measurable_space Ω] {s : ι → set (set Ω)} {s' : set (set Ω)}
{μ : measure Ω} (hyp : ∀ n, indep_sets (s n) s' μ) :
indep_sets (⋃ n, s n) s' μ :=
begin
intros t1 t2 ht1 ht2,
rw set.mem_Union at ht1,
cases ht1 with n ht1,
exact hyp n t1 t2 ht1 ht2,
end
lemma indep_sets.bUnion [measurable_space Ω] {s : ι → set (set Ω)} {s' : set (set Ω)}
{μ : measure Ω} {u : set ι} (hyp : ∀ n ∈ u, indep_sets (s n) s' μ) :
indep_sets (⋃ n ∈ u, s n) s' μ :=
begin
intros t1 t2 ht1 ht2,
simp_rw set.mem_Union at ht1,
rcases ht1 with ⟨n, hpn, ht1⟩,
exact hyp n hpn t1 t2 ht1 ht2,
end
lemma indep_sets.inter [measurable_space Ω] {s₁ s' : set (set Ω)} (s₂ : set (set Ω))
{μ : measure Ω} (h₁ : indep_sets s₁ s' μ) :
indep_sets (s₁ ∩ s₂) s' μ :=
λ t1 t2 ht1 ht2, h₁ t1 t2 ((set.mem_inter_iff _ _ _).mp ht1).left ht2
lemma indep_sets.Inter [measurable_space Ω] {s : ι → set (set Ω)} {s' : set (set Ω)}
{μ : measure Ω} (h : ∃ n, indep_sets (s n) s' μ) :
indep_sets (⋂ n, s n) s' μ :=
by {intros t1 t2 ht1 ht2, cases h with n h, exact h t1 t2 (set.mem_Inter.mp ht1 n) ht2 }
lemma indep_sets.bInter [measurable_space Ω] {s : ι → set (set Ω)} {s' : set (set Ω)}
{μ : measure Ω} {u : set ι} (h : ∃ n ∈ u, indep_sets (s n) s' μ) :
indep_sets (⋂ n ∈ u, s n) s' μ :=
begin
intros t1 t2 ht1 ht2,
rcases h with ⟨n, hn, h⟩,
exact h t1 t2 (set.bInter_subset_of_mem hn ht1) ht2,
end
lemma indep_sets_singleton_iff [measurable_space Ω] {s t : set Ω} {μ : measure Ω} :
indep_sets {s} {t} μ ↔ μ (s ∩ t) = μ s * μ t :=
⟨λ h, h s t rfl rfl,
λ h s1 t1 hs1 ht1, by rwa [set.mem_singleton_iff.mp hs1, set.mem_singleton_iff.mp ht1]⟩
end indep
/-! ### Deducing `indep` from `Indep` -/
section from_Indep_to_indep
lemma Indep_sets.indep_sets {s : ι → set (set Ω)} [measurable_space Ω] {μ : measure Ω}
(h_indep : Indep_sets s μ) {i j : ι} (hij : i ≠ j) :
indep_sets (s i) (s j) μ :=
begin
classical,
intros t₁ t₂ ht₁ ht₂,
have hf_m : ∀ (x : ι), x ∈ {i, j} → (ite (x=i) t₁ t₂) ∈ s x,
{ intros x hx,
cases finset.mem_insert.mp hx with hx hx,
{ simp [hx, ht₁], },
{ simp [finset.mem_singleton.mp hx, hij.symm, ht₂], }, },
have h1 : t₁ = ite (i = i) t₁ t₂, by simp only [if_true, eq_self_iff_true],
have h2 : t₂ = ite (j = i) t₁ t₂, by simp only [hij.symm, if_false],
have h_inter : (⋂ (t : ι) (H : t ∈ ({i, j} : finset ι)), ite (t = i) t₁ t₂)
= (ite (i = i) t₁ t₂) ∩ (ite (j = i) t₁ t₂),
by simp only [finset.set_bInter_singleton, finset.set_bInter_insert],
have h_prod : (∏ (t : ι) in ({i, j} : finset ι), μ (ite (t = i) t₁ t₂))
= μ (ite (i = i) t₁ t₂) * μ (ite (j = i) t₁ t₂),
by simp only [hij, finset.prod_singleton, finset.prod_insert, not_false_iff,
finset.mem_singleton],
rw h1,
nth_rewrite 1 h2,
nth_rewrite 3 h2,
rw [← h_inter, ← h_prod, h_indep {i, j} hf_m],
end
lemma Indep.indep {m : ι → measurable_space Ω} [measurable_space Ω] {μ : measure Ω}
(h_indep : Indep m μ) {i j : ι} (hij : i ≠ j) :
indep (m i) (m j) μ :=
begin
change indep_sets ((λ x, measurable_set[m x]) i) ((λ x, measurable_set[m x]) j) μ,
exact Indep_sets.indep_sets h_indep hij,
end
lemma Indep_fun.indep_fun {m₀ : measurable_space Ω} {μ : measure Ω} {β : ι → Type*}
{m : Π x, measurable_space (β x)} {f : Π i, Ω → β i} (hf_Indep : Indep_fun m f μ)
{i j : ι} (hij : i ≠ j) :
indep_fun (f i) (f j) μ :=
hf_Indep.indep hij
end from_Indep_to_indep
/-!
## π-system lemma
Independence of measurable spaces is equivalent to independence of generating π-systems.
-/
section from_measurable_spaces_to_sets_of_sets
/-! ### Independence of measurable space structures implies independence of generating π-systems -/
lemma Indep.Indep_sets [measurable_space Ω] {μ : measure Ω} {m : ι → measurable_space Ω}
{s : ι → set (set Ω)} (hms : ∀ n, m n = generate_from (s n))
(h_indep : Indep m μ) :
Indep_sets s μ :=
λ S f hfs, h_indep S $ λ x hxS,
((hms x).symm ▸ measurable_set_generate_from (hfs x hxS) : measurable_set[m x] (f x))
lemma indep.indep_sets [measurable_space Ω] {μ : measure Ω} {s1 s2 : set (set Ω)}
(h_indep : indep (generate_from s1) (generate_from s2) μ) :
indep_sets s1 s2 μ :=
λ t1 t2 ht1 ht2, h_indep t1 t2 (measurable_set_generate_from ht1) (measurable_set_generate_from ht2)
end from_measurable_spaces_to_sets_of_sets
section from_pi_systems_to_measurable_spaces
/-! ### Independence of generating π-systems implies independence of measurable space structures -/
private lemma indep_sets.indep_aux {m2 : measurable_space Ω}
{m : measurable_space Ω} {μ : measure Ω} [is_probability_measure μ] {p1 p2 : set (set Ω)}
(h2 : m2 ≤ m) (hp2 : is_pi_system p2) (hpm2 : m2 = generate_from p2)
(hyp : indep_sets p1 p2 μ) {t1 t2 : set Ω} (ht1 : t1 ∈ p1) (ht2m : measurable_set[m2] t2) :
μ (t1 ∩ t2) = μ t1 * μ t2 :=
begin
let μ_inter := μ.restrict t1,
let ν := (μ t1) • μ,
have h_univ : μ_inter set.univ = ν set.univ,
by rw [measure.restrict_apply_univ, measure.smul_apply, smul_eq_mul, measure_univ, mul_one],
haveI : is_finite_measure μ_inter := @restrict.is_finite_measure Ω _ t1 μ ⟨measure_lt_top μ t1⟩,
rw [set.inter_comm, ← measure.restrict_apply (h2 t2 ht2m)],
refine ext_on_measurable_space_of_generate_finite m p2 (λ t ht, _) h2 hpm2 hp2 h_univ ht2m,
have ht2 : measurable_set[m] t,
{ refine h2 _ _,
rw hpm2,
exact measurable_set_generate_from ht, },
rw [measure.restrict_apply ht2, measure.smul_apply, set.inter_comm],
exact hyp t1 t ht1 ht,
end
lemma indep_sets.indep {m1 m2 : measurable_space Ω} {m : measurable_space Ω}
{μ : measure Ω} [is_probability_measure μ] {p1 p2 : set (set Ω)} (h1 : m1 ≤ m) (h2 : m2 ≤ m)
(hp1 : is_pi_system p1) (hp2 : is_pi_system p2) (hpm1 : m1 = generate_from p1)
(hpm2 : m2 = generate_from p2) (hyp : indep_sets p1 p2 μ) :
indep m1 m2 μ :=
begin
intros t1 t2 ht1 ht2,
let μ_inter := μ.restrict t2,
let ν := (μ t2) • μ,
have h_univ : μ_inter set.univ = ν set.univ,
by rw [measure.restrict_apply_univ, measure.smul_apply, smul_eq_mul, measure_univ, mul_one],
haveI : is_finite_measure μ_inter := @restrict.is_finite_measure Ω _ t2 μ ⟨measure_lt_top μ t2⟩,
rw [mul_comm, ← measure.restrict_apply (h1 t1 ht1)],
refine ext_on_measurable_space_of_generate_finite m p1 (λ t ht, _) h1 hpm1 hp1 h_univ ht1,
have ht1 : measurable_set[m] t,
{ refine h1 _ _,
rw hpm1,
exact measurable_set_generate_from ht, },
rw [measure.restrict_apply ht1, measure.smul_apply, smul_eq_mul, mul_comm],
exact indep_sets.indep_aux h2 hp2 hpm2 hyp ht ht2,
end
lemma indep_sets.indep' {m : measurable_space Ω}
{μ : measure Ω} [is_probability_measure μ] {p1 p2 : set (set Ω)}
(hp1m : ∀ s ∈ p1, measurable_set s) (hp2m : ∀ s ∈ p2, measurable_set s)
(hp1 : is_pi_system p1) (hp2 : is_pi_system p2) (hyp : indep_sets p1 p2 μ) :
indep (generate_from p1) (generate_from p2) μ :=
hyp.indep (generate_from_le hp1m) (generate_from_le hp2m) hp1 hp2 rfl rfl
variables {m0 : measurable_space Ω} {μ : measure Ω}
lemma indep_sets_pi_Union_Inter_of_disjoint [is_probability_measure μ]
{s : ι → set (set Ω)} {S T : set ι}
(h_indep : Indep_sets s μ) (hST : disjoint S T) :
indep_sets (pi_Union_Inter s S) (pi_Union_Inter s T) μ :=
begin
rintros t1 t2 ⟨p1, hp1, f1, ht1_m, ht1_eq⟩ ⟨p2, hp2, f2, ht2_m, ht2_eq⟩,
classical,
let g := λ i, ite (i ∈ p1) (f1 i) set.univ ∩ ite (i ∈ p2) (f2 i) set.univ,
have h_P_inter : μ (t1 ∩ t2) = ∏ n in p1 ∪ p2, μ (g n),
{ have hgm : ∀ i ∈ p1 ∪ p2, g i ∈ s i,
{ intros i hi_mem_union,
rw finset.mem_union at hi_mem_union,
cases hi_mem_union with hi1 hi2,
{ have hi2 : i ∉ p2 := λ hip2, set.disjoint_left.mp hST (hp1 hi1) (hp2 hip2),
simp_rw [g, if_pos hi1, if_neg hi2, set.inter_univ],
exact ht1_m i hi1, },
{ have hi1 : i ∉ p1 := λ hip1, set.disjoint_right.mp hST (hp2 hi2) (hp1 hip1),
simp_rw [g, if_neg hi1, if_pos hi2, set.univ_inter],
exact ht2_m i hi2, }, },
have h_p1_inter_p2 : ((⋂ x ∈ p1, f1 x) ∩ ⋂ x ∈ p2, f2 x)
= ⋂ i ∈ p1 ∪ p2, (ite (i ∈ p1) (f1 i) set.univ ∩ ite (i ∈ p2) (f2 i) set.univ),
{ ext1 x,
simp only [set.mem_ite_univ_right, set.mem_inter_iff, set.mem_Inter, finset.mem_union],
exact ⟨λ h i _, ⟨h.1 i, h.2 i⟩,
λ h, ⟨λ i hi, (h i (or.inl hi)).1 hi, λ i hi, (h i (or.inr hi)).2 hi⟩⟩, },
rw [ht1_eq, ht2_eq, h_p1_inter_p2, ← h_indep _ hgm], },
have h_μg : ∀ n, μ (g n) = (ite (n ∈ p1) (μ (f1 n)) 1) * (ite (n ∈ p2) (μ (f2 n)) 1),
{ intro n,
simp_rw g,
split_ifs,
{ exact absurd rfl (set.disjoint_iff_forall_ne.mp hST _ (hp1 h) _ (hp2 h_1)), },
all_goals { simp only [measure_univ, one_mul, mul_one, set.inter_univ, set.univ_inter], }, },
simp_rw [h_P_inter, h_μg, finset.prod_mul_distrib,
finset.prod_ite_mem (p1 ∪ p2) p1 (λ x, μ (f1 x)),
finset.union_inter_cancel_left, finset.prod_ite_mem (p1 ∪ p2) p2 (λ x, μ (f2 x)),
finset.union_inter_cancel_right, ht1_eq, ← h_indep p1 ht1_m, ht2_eq, ← h_indep p2 ht2_m],
end
lemma Indep_set.indep_generate_from_of_disjoint [is_probability_measure μ] {s : ι → set Ω}
(hsm : ∀ n, measurable_set (s n)) (hs : Indep_set s μ) (S T : set ι) (hST : disjoint S T) :
indep (generate_from {t | ∃ n ∈ S, s n = t}) (generate_from {t | ∃ k ∈ T, s k = t}) μ :=
begin
rw [← generate_from_pi_Union_Inter_singleton_left,
← generate_from_pi_Union_Inter_singleton_left],
refine indep_sets.indep'
(λ t ht, generate_from_pi_Union_Inter_le _ _ _ _ (measurable_set_generate_from ht))
(λ t ht, generate_from_pi_Union_Inter_le _ _ _ _ (measurable_set_generate_from ht))
_ _ _,
{ exact λ k, generate_from_le $ λ t ht, (set.mem_singleton_iff.1 ht).symm ▸ hsm k, },
{ exact λ k, generate_from_le $ λ t ht, (set.mem_singleton_iff.1 ht).symm ▸ hsm k, },
{ exact is_pi_system_pi_Union_Inter _ (λ k, is_pi_system.singleton _) _, },
{ exact is_pi_system_pi_Union_Inter _ (λ k, is_pi_system.singleton _) _, },
{ classical,
exact indep_sets_pi_Union_Inter_of_disjoint (Indep.Indep_sets (λ n, rfl) hs) hST, },
end
lemma indep_supr_of_disjoint [is_probability_measure μ] {m : ι → measurable_space Ω}
(h_le : ∀ i, m i ≤ m0) (h_indep : Indep m μ) {S T : set ι} (hST : disjoint S T) :
indep (⨆ i ∈ S, m i) (⨆ i ∈ T, m i) μ :=
begin
refine indep_sets.indep (supr₂_le (λ i _, h_le i)) (supr₂_le (λ i _, h_le i)) _ _
(generate_from_pi_Union_Inter_measurable_set m S).symm
(generate_from_pi_Union_Inter_measurable_set m T).symm _,
{ exact is_pi_system_pi_Union_Inter _ (λ n, @is_pi_system_measurable_set Ω (m n)) _, },
{ exact is_pi_system_pi_Union_Inter _ (λ n, @is_pi_system_measurable_set Ω (m n)) _ , },
{ classical,
exact indep_sets_pi_Union_Inter_of_disjoint h_indep hST, },
end
lemma indep_supr_of_directed_le {Ω} {m : ι → measurable_space Ω}
{m' m0 : measurable_space Ω} {μ : measure Ω} [is_probability_measure μ]
(h_indep : ∀ i, indep (m i) m' μ) (h_le : ∀ i, m i ≤ m0) (h_le' : m' ≤ m0)
(hm : directed (≤) m) :
indep (⨆ i, m i) m' μ :=
begin
let p : ι → set (set Ω) := λ n, {t | measurable_set[m n] t},
have hp : ∀ n, is_pi_system (p n) := λ n, @is_pi_system_measurable_set Ω (m n),
have h_gen_n : ∀ n, m n = generate_from (p n),
from λ n, (@generate_from_measurable_set Ω (m n)).symm,
have hp_supr_pi : is_pi_system (⋃ n, p n) := is_pi_system_Union_of_directed_le p hp hm,
let p' := {t : set Ω | measurable_set[m'] t},
have hp'_pi : is_pi_system p' := @is_pi_system_measurable_set Ω m',
have h_gen' : m' = generate_from p' := (@generate_from_measurable_set Ω m').symm,
-- the π-systems defined are independent
have h_pi_system_indep : indep_sets (⋃ n, p n) p' μ,
{ refine indep_sets.Union _,
simp_rw [h_gen_n, h_gen'] at h_indep,
exact λ n, (h_indep n).indep_sets, },
-- now go from π-systems to σ-algebras
refine indep_sets.indep (supr_le h_le) h_le' hp_supr_pi hp'_pi _ h_gen' h_pi_system_indep,
exact (generate_from_Union_measurable_set _).symm,
end
lemma Indep_set.indep_generate_from_lt [preorder ι] [is_probability_measure μ]
{s : ι → set Ω} (hsm : ∀ n, measurable_set (s n)) (hs : Indep_set s μ) (i : ι) :
indep (generate_from {s i}) (generate_from {t | ∃ j < i, s j = t}) μ :=
begin
convert hs.indep_generate_from_of_disjoint hsm {i} {j | j < i}
(set.disjoint_singleton_left.mpr (lt_irrefl _)),
simp only [set.mem_singleton_iff, exists_prop, exists_eq_left, set.set_of_eq_eq_singleton'],
end
lemma Indep_set.indep_generate_from_le [linear_order ι] [is_probability_measure μ]
{s : ι → set Ω} (hsm : ∀ n, measurable_set (s n)) (hs : Indep_set s μ)
(i : ι) {k : ι} (hk : i < k) :
indep (generate_from {s k}) (generate_from {t | ∃ j ≤ i, s j = t}) μ :=
begin
convert hs.indep_generate_from_of_disjoint hsm {k} {j | j ≤ i}
(set.disjoint_singleton_left.mpr hk.not_le),
simp only [set.mem_singleton_iff, exists_prop, exists_eq_left, set.set_of_eq_eq_singleton'],
end
lemma Indep_set.indep_generate_from_le_nat [is_probability_measure μ]
{s : ℕ → set Ω} (hsm : ∀ n, measurable_set (s n)) (hs : Indep_set s μ) (n : ℕ):
indep (generate_from {s (n + 1)}) (generate_from {t | ∃ k ≤ n, s k = t}) μ :=
hs.indep_generate_from_le hsm _ n.lt_succ_self
lemma indep_supr_of_monotone [semilattice_sup ι] {Ω} {m : ι → measurable_space Ω}
{m' m0 : measurable_space Ω} {μ : measure Ω} [is_probability_measure μ]
(h_indep : ∀ i, indep (m i) m' μ) (h_le : ∀ i, m i ≤ m0) (h_le' : m' ≤ m0) (hm : monotone m) :
indep (⨆ i, m i) m' μ :=
indep_supr_of_directed_le h_indep h_le h_le' (monotone.directed_le hm)
lemma indep_supr_of_antitone [semilattice_inf ι] {Ω} {m : ι → measurable_space Ω}
{m' m0 : measurable_space Ω} {μ : measure Ω} [is_probability_measure μ]
(h_indep : ∀ i, indep (m i) m' μ) (h_le : ∀ i, m i ≤ m0) (h_le' : m' ≤ m0) (hm : antitone m) :
indep (⨆ i, m i) m' μ :=
indep_supr_of_directed_le h_indep h_le h_le' (directed_of_inf hm)
lemma Indep_sets.pi_Union_Inter_of_not_mem {π : ι → set (set Ω)} {a : ι} {S : finset ι}
(hp_ind : Indep_sets π μ) (haS : a ∉ S) :
indep_sets (pi_Union_Inter π S) (π a) μ :=
begin
rintros t1 t2 ⟨s, hs_mem, ft1, hft1_mem, ht1_eq⟩ ht2_mem_pia,
rw [finset.coe_subset] at hs_mem,
classical,
let f := λ n, ite (n = a) t2 (ite (n ∈ s) (ft1 n) set.univ),
have h_f_mem : ∀ n ∈ insert a s, f n ∈ π n,
{ intros n hn_mem_insert,
simp_rw f,
cases (finset.mem_insert.mp hn_mem_insert) with hn_mem hn_mem,
{ simp [hn_mem, ht2_mem_pia], },
{ have hn_ne_a : n ≠ a, by { rintro rfl, exact haS (hs_mem hn_mem), },
simp [hn_ne_a, hn_mem, hft1_mem n hn_mem], }, },
have h_f_mem_pi : ∀ n ∈ s, f n ∈ π n, from λ x hxS, h_f_mem x (by simp [hxS]),
have h_t1 : t1 = ⋂ n ∈ s, f n,
{ suffices h_forall : ∀ n ∈ s, f n = ft1 n,
{ rw ht1_eq,
congr' with n x,
congr' with hns y,
simp only [(h_forall n hns).symm], },
intros n hnS,
have hn_ne_a : n ≠ a, by { rintro rfl, exact haS (hs_mem hnS), },
simp_rw [f, if_pos hnS, if_neg hn_ne_a], },
have h_μ_t1 : μ t1 = ∏ n in s, μ (f n), by rw [h_t1, ← hp_ind s h_f_mem_pi],
have h_t2 : t2 = f a, by { simp_rw [f], simp, },
have h_μ_inter : μ (t1 ∩ t2) = ∏ n in insert a s, μ (f n),
{ have h_t1_inter_t2 : t1 ∩ t2 = ⋂ n ∈ insert a s, f n,
by rw [h_t1, h_t2, finset.set_bInter_insert, set.inter_comm],
rw [h_t1_inter_t2, ← hp_ind (insert a s) h_f_mem], },
have has : a ∉ s := λ has_mem, haS (hs_mem has_mem),
rw [h_μ_inter, finset.prod_insert has, h_t2, mul_comm, h_μ_t1],
end
/-- The measurable space structures generated by independent pi-systems are independent. -/
theorem Indep_sets.Indep [is_probability_measure μ] (m : ι → measurable_space Ω)
(h_le : ∀ i, m i ≤ m0) (π : ι → set (set Ω)) (h_pi : ∀ n, is_pi_system (π n))
(h_generate : ∀ i, m i = generate_from (π i)) (h_ind : Indep_sets π μ) :
Indep m μ :=
begin
classical,
refine finset.induction _ _,
{ simp only [measure_univ, implies_true_iff, set.Inter_false, set.Inter_univ, finset.prod_empty,
eq_self_iff_true], },
intros a S ha_notin_S h_rec f hf_m,
have hf_m_S : ∀ x ∈ S, measurable_set[m x] (f x) := λ x hx, hf_m x (by simp [hx]),
rw [finset.set_bInter_insert, finset.prod_insert ha_notin_S, ← h_rec hf_m_S],
let p := pi_Union_Inter π S,
set m_p := generate_from p with hS_eq_generate,
have h_indep : indep m_p (m a) μ,
{ have hp : is_pi_system p := is_pi_system_pi_Union_Inter π h_pi S,
have h_le' : ∀ i, generate_from (π i) ≤ m0 := λ i, (h_generate i).symm.trans_le (h_le i),
have hm_p : m_p ≤ m0 := generate_from_pi_Union_Inter_le π h_le' S,
exact indep_sets.indep hm_p (h_le a) hp (h_pi a) hS_eq_generate (h_generate a)
(h_ind.pi_Union_Inter_of_not_mem ha_notin_S), },
refine h_indep.symm (f a) (⋂ n ∈ S, f n) (hf_m a (finset.mem_insert_self a S)) _,
have h_le_p : ∀ i ∈ S, m i ≤ m_p,
{ intros n hn,
rw [hS_eq_generate, h_generate n],
exact le_generate_from_pi_Union_Inter S hn, },
have h_S_f : ∀ i ∈ S, measurable_set[m_p] (f i) := λ i hi, (h_le_p i hi) (f i) (hf_m_S i hi),
exact S.measurable_set_bInter h_S_f,
end
end from_pi_systems_to_measurable_spaces
section indep_set
/-! ### Independence of measurable sets
We prove the following equivalences on `indep_set`, for measurable sets `s, t`.
* `indep_set s t μ ↔ μ (s ∩ t) = μ s * μ t`,
* `indep_set s t μ ↔ indep_sets {s} {t} μ`.
-/
variables {s t : set Ω} (S T : set (set Ω))
lemma indep_set_iff_indep_sets_singleton {m0 : measurable_space Ω}
(hs_meas : measurable_set s) (ht_meas : measurable_set t)
(μ : measure Ω . volume_tac) [is_probability_measure μ] :
indep_set s t μ ↔ indep_sets {s} {t} μ :=
⟨indep.indep_sets, λ h, indep_sets.indep
(generate_from_le (λ u hu, by rwa set.mem_singleton_iff.mp hu))
(generate_from_le (λ u hu, by rwa set.mem_singleton_iff.mp hu)) (is_pi_system.singleton s)
(is_pi_system.singleton t) rfl rfl h⟩
lemma indep_set_iff_measure_inter_eq_mul {m0 : measurable_space Ω}
(hs_meas : measurable_set s) (ht_meas : measurable_set t)
(μ : measure Ω . volume_tac) [is_probability_measure μ] :
indep_set s t μ ↔ μ (s ∩ t) = μ s * μ t :=
(indep_set_iff_indep_sets_singleton hs_meas ht_meas μ).trans indep_sets_singleton_iff
lemma indep_sets.indep_set_of_mem {m0 : measurable_space Ω} (hs : s ∈ S) (ht : t ∈ T)
(hs_meas : measurable_set s) (ht_meas : measurable_set t) (μ : measure Ω . volume_tac)
[is_probability_measure μ] (h_indep : indep_sets S T μ) :
indep_set s t μ :=
(indep_set_iff_measure_inter_eq_mul hs_meas ht_meas μ).mpr (h_indep s t hs ht)
lemma indep.indep_set_of_measurable_set {m₁ m₂ m0 : measurable_space Ω} {μ : measure Ω}
(h_indep : indep m₁ m₂ μ) {s t : set Ω} (hs : measurable_set[m₁] s) (ht : measurable_set[m₂] t) :
indep_set s t μ :=
begin
refine λ s' t' hs' ht', h_indep s' t' _ _,
{ refine generate_from_induction (λ u, measurable_set[m₁] u) {s} _ _ _ _ hs',
{ simp only [hs, set.mem_singleton_iff, set.mem_set_of_eq, forall_eq], },
{ exact @measurable_set.empty _ m₁, },
{ exact λ u hu, hu.compl, },
{ exact λ f hf, measurable_set.Union hf, }, },
{ refine generate_from_induction (λ u, measurable_set[m₂] u) {t} _ _ _ _ ht',
{ simp only [ht, set.mem_singleton_iff, set.mem_set_of_eq, forall_eq], },
{ exact @measurable_set.empty _ m₂, },
{ exact λ u hu, hu.compl, },
{ exact λ f hf, measurable_set.Union hf, },},
end
lemma indep_iff_forall_indep_set (m₁ m₂ : measurable_space Ω) {m0 : measurable_space Ω}
(μ : measure Ω) :
indep m₁ m₂ μ ↔ ∀ s t, measurable_set[m₁] s → measurable_set[m₂] t → indep_set s t μ :=
⟨λ h, λ s t hs ht, h.indep_set_of_measurable_set hs ht,
λ h s t hs ht, h s t hs ht s t (measurable_set_generate_from (set.mem_singleton s))
(measurable_set_generate_from (set.mem_singleton t))⟩
end indep_set
section indep_fun
/-! ### Independence of random variables
-/
variables {β β' γ γ' : Type*} {mΩ : measurable_space Ω} {μ : measure Ω} {f : Ω → β} {g : Ω → β'}
lemma indep_fun_iff_measure_inter_preimage_eq_mul
{mβ : measurable_space β} {mβ' : measurable_space β'} :
indep_fun f g μ
↔ ∀ s t, measurable_set s → measurable_set t
→ μ (f ⁻¹' s ∩ g ⁻¹' t) = μ (f ⁻¹' s) * μ (g ⁻¹' t) :=
begin
split; intro h,
{ refine λ s t hs ht, h (f ⁻¹' s) (g ⁻¹' t) ⟨s, hs, rfl⟩ ⟨t, ht, rfl⟩, },
{ rintros _ _ ⟨s, hs, rfl⟩ ⟨t, ht, rfl⟩, exact h s t hs ht, },
end
lemma Indep_fun_iff_measure_inter_preimage_eq_mul {ι : Type*} {β : ι → Type*}
(m : Π x, measurable_space (β x)) (f : Π i, Ω → β i) :
Indep_fun m f μ
↔ ∀ (S : finset ι) {sets : Π i : ι, set (β i)} (H : ∀ i, i ∈ S → measurable_set[m i] (sets i)),
μ (⋂ i ∈ S, (f i) ⁻¹' (sets i)) = ∏ i in S, μ ((f i) ⁻¹' (sets i)) :=
begin
refine ⟨λ h S sets h_meas, h _ (λ i hi_mem, ⟨sets i, h_meas i hi_mem, rfl⟩), _⟩,
intros h S setsΩ h_meas,
classical,
let setsβ : (Π i : ι, set (β i)) := λ i,
dite (i ∈ S) (λ hi_mem, (h_meas i hi_mem).some) (λ _, set.univ),
have h_measβ : ∀ i ∈ S, measurable_set[m i] (setsβ i),
{ intros i hi_mem,
simp_rw [setsβ, dif_pos hi_mem],
exact (h_meas i hi_mem).some_spec.1, },
have h_preim : ∀ i ∈ S, setsΩ i = (f i) ⁻¹' (setsβ i),
{ intros i hi_mem,
simp_rw [setsβ, dif_pos hi_mem],
exact (h_meas i hi_mem).some_spec.2.symm, },
have h_left_eq : μ (⋂ i ∈ S, setsΩ i) = μ (⋂ i ∈ S, (f i) ⁻¹' (setsβ i)),
{ congr' with i x,
simp only [set.mem_Inter],
split; intros h hi_mem; specialize h hi_mem,
{ rwa h_preim i hi_mem at h, },
{ rwa h_preim i hi_mem, }, },
have h_right_eq : (∏ i in S, μ (setsΩ i)) = ∏ i in S, μ ((f i) ⁻¹' (setsβ i)),
{ refine finset.prod_congr rfl (λ i hi_mem, _),
rw h_preim i hi_mem, },
rw [h_left_eq, h_right_eq],
exact h S h_measβ,
end
lemma indep_fun_iff_indep_set_preimage {mβ : measurable_space β} {mβ' : measurable_space β'}
[is_probability_measure μ] (hf : measurable f) (hg : measurable g) :
indep_fun f g μ ↔ ∀ s t, measurable_set s → measurable_set t → indep_set (f ⁻¹' s) (g ⁻¹' t) μ :=
begin
refine indep_fun_iff_measure_inter_preimage_eq_mul.trans _,
split; intros h s t hs ht; specialize h s t hs ht,
{ rwa indep_set_iff_measure_inter_eq_mul (hf hs) (hg ht) μ, },
{ rwa ← indep_set_iff_measure_inter_eq_mul (hf hs) (hg ht) μ, },
end
@[symm] lemma indep_fun.symm {mβ : measurable_space β} {f g : Ω → β} (hfg : indep_fun f g μ) :
indep_fun g f μ :=
hfg.symm
lemma indep_fun.ae_eq {mβ : measurable_space β} {f g f' g' : Ω → β}
(hfg : indep_fun f g μ) (hf : f =ᵐ[μ] f') (hg : g =ᵐ[μ] g') :
indep_fun f' g' μ :=
begin
rintro _ _ ⟨A, hA, rfl⟩ ⟨B, hB, rfl⟩,
have h1 : f ⁻¹' A =ᵐ[μ] f' ⁻¹' A := hf.fun_comp A,
have h2 : g ⁻¹' B =ᵐ[μ] g' ⁻¹' B := hg.fun_comp B,
rw [← measure_congr h1, ← measure_congr h2, ← measure_congr (h1.inter h2)],
exact hfg _ _ ⟨_, hA, rfl⟩ ⟨_, hB, rfl⟩
end
lemma indep_fun.comp {mβ : measurable_space β} {mβ' : measurable_space β'}
{mγ : measurable_space γ} {mγ' : measurable_space γ'} {φ : β → γ} {ψ : β' → γ'}
(hfg : indep_fun f g μ) (hφ : measurable φ) (hψ : measurable ψ) :
indep_fun (φ ∘ f) (ψ ∘ g) μ :=
begin
rintro _ _ ⟨A, hA, rfl⟩ ⟨B, hB, rfl⟩,
apply hfg,
{ exact ⟨φ ⁻¹' A, hφ hA, set.preimage_comp.symm⟩ },
{ exact ⟨ψ ⁻¹' B, hψ hB, set.preimage_comp.symm⟩ }
end
/-- If `f` is a family of mutually independent random variables (`Indep_fun m f μ`) and `S, T` are
two disjoint finite index sets, then the tuple formed by `f i` for `i ∈ S` is independent of the
tuple `(f i)_i` for `i ∈ T`. -/
lemma Indep_fun.indep_fun_finset [is_probability_measure μ]
{ι : Type*} {β : ι → Type*} {m : Π i, measurable_space (β i)}
{f : Π i, Ω → β i} (S T : finset ι) (hST : disjoint S T) (hf_Indep : Indep_fun m f μ)
(hf_meas : ∀ i, measurable (f i)) :
indep_fun (λ a (i : S), f i a) (λ a (i : T), f i a) μ :=
begin
-- We introduce π-systems, build from the π-system of boxes which generates `measurable_space.pi`.
let πSβ := (set.pi (set.univ : set S) ''
(set.pi (set.univ : set S) (λ i, {s : set (β i) | measurable_set[m i] s}))),
let πS := {s : set Ω | ∃ t ∈ πSβ, (λ a (i : S), f i a) ⁻¹' t = s},
have hπS_pi : is_pi_system πS := is_pi_system_pi.comap (λ a i, f i a),
have hπS_gen : measurable_space.pi.comap (λ a (i : S), f i a) = generate_from πS,
{ rw [generate_from_pi.symm, comap_generate_from],
{ congr' with s,
simp only [set.mem_image, set.mem_set_of_eq, exists_prop], },
{ apply_instance } },
let πTβ := (set.pi (set.univ : set T) ''
(set.pi (set.univ : set T) (λ i, {s : set (β i) | measurable_set[m i] s}))),
let πT := {s : set Ω | ∃ t ∈ πTβ, (λ a (i : T), f i a) ⁻¹' t = s},
have hπT_pi : is_pi_system πT := is_pi_system_pi.comap (λ a i, f i a),
have hπT_gen : measurable_space.pi.comap (λ a (i : T), f i a) = generate_from πT,
{ rw [generate_from_pi.symm, comap_generate_from],
{ congr' with s,
simp only [set.mem_image, set.mem_set_of_eq, exists_prop], },
{ apply_instance } },
-- To prove independence, we prove independence of the generating π-systems.
refine indep_sets.indep (measurable.comap_le (measurable_pi_iff.mpr (λ i, hf_meas i)))
(measurable.comap_le (measurable_pi_iff.mpr (λ i, hf_meas i))) hπS_pi hπT_pi hπS_gen hπT_gen _,
rintros _ _ ⟨s, ⟨sets_s, hs1, hs2⟩, rfl⟩ ⟨t, ⟨sets_t, ht1, ht2⟩, rfl⟩,
simp only [set.mem_univ_pi, set.mem_set_of_eq] at hs1 ht1,
rw [← hs2, ← ht2],
classical,
let sets_s' : (Π i : ι, set (β i)) := λ i, dite (i ∈ S) (λ hi, sets_s ⟨i, hi⟩) (λ _, set.univ),
have h_sets_s'_eq : ∀ {i} (hi : i ∈ S), sets_s' i = sets_s ⟨i, hi⟩,
{ intros i hi, simp_rw [sets_s', dif_pos hi], },
have h_sets_s'_univ : ∀ {i} (hi : i ∈ T), sets_s' i = set.univ,
{ intros i hi, simp_rw [sets_s', dif_neg (finset.disjoint_right.mp hST hi)], },
let sets_t' : (Π i : ι, set (β i)) := λ i, dite (i ∈ T) (λ hi, sets_t ⟨i, hi⟩) (λ _, set.univ),
have h_sets_t'_univ : ∀ {i} (hi : i ∈ S), sets_t' i = set.univ,
{ intros i hi, simp_rw [sets_t', dif_neg (finset.disjoint_left.mp hST hi)], },
have h_meas_s' : ∀ i ∈ S, measurable_set (sets_s' i),
{ intros i hi, rw h_sets_s'_eq hi, exact hs1 _, },
have h_meas_t' : ∀ i ∈ T, measurable_set (sets_t' i),
{ intros i hi, simp_rw [sets_t', dif_pos hi], exact ht1 _, },
have h_eq_inter_S : (λ (ω : Ω) (i : ↥S), f ↑i ω) ⁻¹' set.pi set.univ sets_s
= ⋂ i ∈ S, (f i) ⁻¹' (sets_s' i),
{ ext1 x,
simp only [set.mem_preimage, set.mem_univ_pi, set.mem_Inter],
split; intro h,
{ intros i hi, rw [h_sets_s'_eq hi], exact h ⟨i, hi⟩, },
{ rintros ⟨i, hi⟩, specialize h i hi, rw [h_sets_s'_eq hi] at h, exact h, }, },
have h_eq_inter_T : (λ (ω : Ω) (i : ↥T), f ↑i ω) ⁻¹' set.pi set.univ sets_t
= ⋂ i ∈ T, (f i) ⁻¹' (sets_t' i),
{ ext1 x,
simp only [set.mem_preimage, set.mem_univ_pi, set.mem_Inter],
split; intro h,
{ intros i hi, simp_rw [sets_t', dif_pos hi], exact h ⟨i, hi⟩, },
{ rintros ⟨i, hi⟩, specialize h i hi, simp_rw [sets_t', dif_pos hi] at h, exact h, }, },
rw Indep_fun_iff_measure_inter_preimage_eq_mul at hf_Indep,
rw [h_eq_inter_S, h_eq_inter_T, hf_Indep S h_meas_s', hf_Indep T h_meas_t'],
have h_Inter_inter : (⋂ i ∈ S, (f i) ⁻¹' (sets_s' i)) ∩ (⋂ i ∈ T, (f i) ⁻¹' (sets_t' i))
= ⋂ i ∈ (S ∪ T), (f i) ⁻¹' (sets_s' i ∩ sets_t' i),
{ ext1 x,
simp only [set.mem_inter_iff, set.mem_Inter, set.mem_preimage, finset.mem_union],
split; intro h,
{ intros i hi,
cases hi,
{ rw h_sets_t'_univ hi, exact ⟨h.1 i hi, set.mem_univ _⟩, },
{ rw h_sets_s'_univ hi, exact ⟨set.mem_univ _, h.2 i hi⟩, }, },
{ exact ⟨λ i hi, (h i (or.inl hi)).1, λ i hi, (h i (or.inr hi)).2⟩, }, },
rw [h_Inter_inter, hf_Indep (S ∪ T)],
swap, { intros i hi_mem,
rw finset.mem_union at hi_mem,
cases hi_mem,
{ rw [h_sets_t'_univ hi_mem, set.inter_univ], exact h_meas_s' i hi_mem, },
{ rw [h_sets_s'_univ hi_mem, set.univ_inter], exact h_meas_t' i hi_mem, }, },
rw finset.prod_union hST,
congr' 1,
{ refine finset.prod_congr rfl (λ i hi, _),
rw [h_sets_t'_univ hi, set.inter_univ], },
{ refine finset.prod_congr rfl (λ i hi, _),
rw [h_sets_s'_univ hi, set.univ_inter], },
end
lemma Indep_fun.indep_fun_prod [is_probability_measure μ]
{ι : Type*} {β : ι → Type*} {m : Π i, measurable_space (β i)}
{f : Π i, Ω → β i} (hf_Indep : Indep_fun m f μ) (hf_meas : ∀ i, measurable (f i))
(i j k : ι) (hik : i ≠ k) (hjk : j ≠ k) :
indep_fun (λ a, (f i a, f j a)) (f k) μ :=
begin
classical,
have h_right : f k = (λ p : (Π j : ({k} : finset ι), β j), p ⟨k, finset.mem_singleton_self k⟩)
∘ (λ a (j : ({k} : finset ι)), f j a) := rfl,
have h_meas_right : measurable
(λ p : (Π j : ({k} : finset ι), β j), p ⟨k, finset.mem_singleton_self k⟩),
from measurable_pi_apply ⟨k, finset.mem_singleton_self k⟩,
let s : finset ι := {i, j},
have h_left : (λ ω, (f i ω, f j ω))
= (λ p : (Π l : s, β l), (p ⟨i, finset.mem_insert_self i _⟩,
p ⟨j, finset.mem_insert_of_mem (finset.mem_singleton_self _)⟩))
∘ (λ a (j : s), f j a),
{ ext1 a,
simp only [prod.mk.inj_iff],
split; refl, },
have h_meas_left : measurable (λ p : (Π l : s, β l), (p ⟨i, finset.mem_insert_self i _⟩,
p ⟨j, finset.mem_insert_of_mem (finset.mem_singleton_self _)⟩)),
from measurable.prod (measurable_pi_apply ⟨i, finset.mem_insert_self i {j}⟩)
(measurable_pi_apply ⟨j, finset.mem_insert_of_mem (finset.mem_singleton_self j)⟩),
rw [h_left, h_right],
refine (hf_Indep.indep_fun_finset s {k} _ hf_meas).comp h_meas_left h_meas_right,
rw finset.disjoint_singleton_right,
simp only [finset.mem_insert, finset.mem_singleton, not_or_distrib],
exact ⟨hik.symm, hjk.symm⟩,
end
@[to_additive]
lemma Indep_fun.mul [is_probability_measure μ]
{ι : Type*} {β : Type*} {m : measurable_space β} [has_mul β] [has_measurable_mul₂ β]
{f : ι → Ω → β} (hf_Indep : Indep_fun (λ _, m) f μ) (hf_meas : ∀ i, measurable (f i))
(i j k : ι) (hik : i ≠ k) (hjk : j ≠ k) :
indep_fun (f i * f j) (f k) μ :=
begin
have : indep_fun (λ ω, (f i ω, f j ω)) (f k) μ := hf_Indep.indep_fun_prod hf_meas i j k hik hjk,
change indep_fun ((λ p : β × β, p.fst * p.snd) ∘ (λ ω, (f i ω, f j ω))) (id ∘ (f k)) μ,
exact indep_fun.comp this (measurable_fst.mul measurable_snd) measurable_id,
end
@[to_additive]
lemma Indep_fun.indep_fun_finset_prod_of_not_mem [is_probability_measure μ]
{ι : Type*} {β : Type*} {m : measurable_space β} [comm_monoid β] [has_measurable_mul₂ β]
{f : ι → Ω → β} (hf_Indep : Indep_fun (λ _, m) f μ) (hf_meas : ∀ i, measurable (f i))
{s : finset ι} {i : ι} (hi : i ∉ s) :
indep_fun (∏ j in s, f j) (f i) μ :=
begin
classical,
have h_right : f i = (λ p : (Π j : ({i} : finset ι), β), p ⟨i, finset.mem_singleton_self i⟩)
∘ (λ a (j : ({i} : finset ι)), f j a) := rfl,
have h_meas_right : measurable
(λ p : (Π j : ({i} : finset ι), β), p ⟨i, finset.mem_singleton_self i⟩),
from measurable_pi_apply ⟨i, finset.mem_singleton_self i⟩,
have h_left : (∏ j in s, f j) = (λ p : (Π j : s, β), ∏ j, p j) ∘ (λ a (j : s), f j a),
{ ext1 a,
simp only [function.comp_app],
have : (∏ (j : ↥s), f ↑j a) = (∏ (j : ↥s), f ↑j) a, by rw finset.prod_apply,
rw [this, finset.prod_coe_sort], },
have h_meas_left : measurable (λ p : (Π j : s, β), ∏ j, p j),
from finset.univ.measurable_prod (λ (j : ↥s) (H : j ∈ finset.univ), measurable_pi_apply j),
rw [h_left, h_right],
exact (hf_Indep.indep_fun_finset s {i} (finset.disjoint_singleton_left.mpr hi).symm hf_meas).comp
h_meas_left h_meas_right,
end
@[to_additive]
lemma Indep_fun.indep_fun_prod_range_succ [is_probability_measure μ]
{β : Type*} {m : measurable_space β} [comm_monoid β] [has_measurable_mul₂ β]
{f : ℕ → Ω → β} (hf_Indep : Indep_fun (λ _, m) f μ) (hf_meas : ∀ i, measurable (f i))
(n : ℕ) :
indep_fun (∏ j in finset.range n, f j) (f n) μ :=
hf_Indep.indep_fun_finset_prod_of_not_mem hf_meas finset.not_mem_range_self
lemma Indep_set.Indep_fun_indicator [has_zero β] [has_one β] {m : measurable_space β}
{s : ι → set Ω} (hs : Indep_set s μ) :
Indep_fun (λ n, m) (λ n, (s n).indicator (λ ω, 1)) μ :=
begin
classical,
rw Indep_fun_iff_measure_inter_preimage_eq_mul,
rintro S π hπ,
simp_rw set.indicator_const_preimage_eq_union,
refine @hs S (λ i, ite (1 ∈ π i) (s i) ∅ ∪ ite ((0 : β) ∈ π i) (s i)ᶜ ∅) (λ i hi, _),
have hsi : measurable_set[generate_from {s i}] (s i),
from measurable_set_generate_from (set.mem_singleton _),
refine measurable_set.union (measurable_set.ite' (λ _, hsi) (λ _, _))
(measurable_set.ite' (λ _, hsi.compl) (λ _, _)),
{ exact @measurable_set.empty _ (generate_from {s i}), },
{ exact @measurable_set.empty _ (generate_from {s i}), },
end
end indep_fun
end probability_theory
|
f1518a47a485b093ba5b1aab19c270bffeebdcf1 | 969dbdfed67fda40a6f5a2b4f8c4a3c7dc01e0fb | /src/computability/turing_machine.lean | 7dee8011654626d3c4b9ca322813a6fa1e9b28b1 | [
"Apache-2.0"
] | permissive | SAAluthwela/mathlib | 62044349d72dd63983a8500214736aa7779634d3 | 83a4b8b990907291421de54a78988c024dc8a552 | refs/heads/master | 1,679,433,873,417 | 1,615,998,031,000 | 1,615,998,031,000 | null | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 109,916 | lean | /-
Copyright (c) 2018 Mario Carneiro. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Author: Mario Carneiro
-/
import algebra.order
import data.fintype.basic
import data.pfun
import tactic.apply_fun
import logic.function.iterate
/-!
# Turing machines
This file defines a sequence of simple machine languages, starting with Turing machines and working
up to more complex languages based on Wang B-machines.
## Naming conventions
Each model of computation in this file shares a naming convention for the elements of a model of
computation. These are the parameters for the language:
* `Γ` is the alphabet on the tape.
* `Λ` is the set of labels, or internal machine states.
* `σ` is the type of internal memory, not on the tape. This does not exist in the TM0 model, and
later models achieve this by mixing it into `Λ`.
* `K` is used in the TM2 model, which has multiple stacks, and denotes the number of such stacks.
All of these variables denote "essentially finite" types, but for technical reasons it is
convenient to allow them to be infinite anyway. When using an infinite type, we will be interested
to prove that only finitely many values of the type are ever interacted with.
Given these parameters, there are a few common structures for the model that arise:
* `stmt` is the set of all actions that can be performed in one step. For the TM0 model this set is
finite, and for later models it is an infinite inductive type representing "possible program
texts".
* `cfg` is the set of instantaneous configurations, that is, the state of the machine together with
its environment.
* `machine` is the set of all machines in the model. Usually this is approximately a function
`Λ → stmt`, although different models have different ways of halting and other actions.
* `step : cfg → option cfg` is the function that describes how the state evolves over one step.
If `step c = none`, then `c` is a terminal state, and the result of the computation is read off
from `c`. Because of the type of `step`, these models are all deterministic by construction.
* `init : input → cfg` sets up the initial state. The type `input` depends on the model;
in most cases it is `list Γ`.
* `eval : machine → input → roption output`, given a machine `M` and input `i`, starts from
`init i`, runs `step` until it reaches an output, and then applies a function `cfg → output` to
the final state to obtain the result. The type `output` depends on the model.
* `supports : machine → finset Λ → Prop` asserts that a machine `M` starts in `S : finset Λ`, and
can only ever jump to other states inside `S`. This implies that the behavior of `M` on any input
cannot depend on its values outside `S`. We use this to allow `Λ` to be an infinite set when
convenient, and prove that only finitely many of these states are actually accessible. This
formalizes "essentially finite" mentioned above.
-/
open relation
open nat (iterate)
open function (update iterate_succ iterate_succ_apply iterate_succ'
iterate_succ_apply' iterate_zero_apply)
namespace turing
/-- The `blank_extends` partial order holds of `l₁` and `l₂` if `l₂` is obtained by adding
blanks (`default Γ`) to the end of `l₁`. -/
def blank_extends {Γ} [inhabited Γ] (l₁ l₂ : list Γ) : Prop :=
∃ n, l₂ = l₁ ++ list.repeat (default Γ) n
@[refl] theorem blank_extends.refl {Γ} [inhabited Γ] (l : list Γ) : blank_extends l l :=
⟨0, by simp⟩
@[trans] theorem blank_extends.trans {Γ} [inhabited Γ] {l₁ l₂ l₃ : list Γ} :
blank_extends l₁ l₂ → blank_extends l₂ l₃ → blank_extends l₁ l₃ :=
by rintro ⟨i, rfl⟩ ⟨j, rfl⟩; exact ⟨i+j, by simp [list.repeat_add]⟩
theorem blank_extends.below_of_le {Γ} [inhabited Γ] {l l₁ l₂ : list Γ} :
blank_extends l l₁ → blank_extends l l₂ →
l₁.length ≤ l₂.length → blank_extends l₁ l₂ :=
begin
rintro ⟨i, rfl⟩ ⟨j, rfl⟩ h, use j - i,
simp only [list.length_append, add_le_add_iff_left, list.length_repeat] at h,
simp only [← list.repeat_add, nat.add_sub_cancel' h, list.append_assoc],
end
/-- Any two extensions by blank `l₁,l₂` of `l` have a common join (which can be taken to be the
longer of `l₁` and `l₂`). -/
def blank_extends.above {Γ} [inhabited Γ] {l l₁ l₂ : list Γ}
(h₁ : blank_extends l l₁) (h₂ : blank_extends l l₂) :
{l' // blank_extends l₁ l' ∧ blank_extends l₂ l'} :=
if h : l₁.length ≤ l₂.length then
⟨l₂, h₁.below_of_le h₂ h, blank_extends.refl _⟩
else
⟨l₁, blank_extends.refl _, h₂.below_of_le h₁ (le_of_not_ge h)⟩
theorem blank_extends.above_of_le {Γ} [inhabited Γ] {l l₁ l₂ : list Γ} :
blank_extends l₁ l → blank_extends l₂ l →
l₁.length ≤ l₂.length → blank_extends l₁ l₂ :=
begin
rintro ⟨i, rfl⟩ ⟨j, e⟩ h, use i - j,
refine list.append_right_cancel (e.symm.trans _),
rw [list.append_assoc, ← list.repeat_add, nat.sub_add_cancel],
apply_fun list.length at e,
simp only [list.length_append, list.length_repeat] at e,
rwa [← add_le_add_iff_left, e, add_le_add_iff_right]
end
/-- `blank_rel` is the symmetric closure of `blank_extends`, turning it into an equivalence
relation. Two lists are related by `blank_rel` if one extends the other by blanks. -/
def blank_rel {Γ} [inhabited Γ] (l₁ l₂ : list Γ) : Prop :=
blank_extends l₁ l₂ ∨ blank_extends l₂ l₁
@[refl] theorem blank_rel.refl {Γ} [inhabited Γ] (l : list Γ) : blank_rel l l :=
or.inl (blank_extends.refl _)
@[symm] theorem blank_rel.symm {Γ} [inhabited Γ] {l₁ l₂ : list Γ} :
blank_rel l₁ l₂ → blank_rel l₂ l₁ := or.symm
@[trans] theorem blank_rel.trans {Γ} [inhabited Γ] {l₁ l₂ l₃ : list Γ} :
blank_rel l₁ l₂ → blank_rel l₂ l₃ → blank_rel l₁ l₃ :=
begin
rintro (h₁|h₁) (h₂|h₂),
{ exact or.inl (h₁.trans h₂) },
{ cases le_total l₁.length l₃.length with h h,
{ exact or.inl (h₁.above_of_le h₂ h) },
{ exact or.inr (h₂.above_of_le h₁ h) } },
{ cases le_total l₁.length l₃.length with h h,
{ exact or.inl (h₁.below_of_le h₂ h) },
{ exact or.inr (h₂.below_of_le h₁ h) } },
{ exact or.inr (h₂.trans h₁) },
end
/-- Given two `blank_rel` lists, there exists (constructively) a common join. -/
def blank_rel.above {Γ} [inhabited Γ] {l₁ l₂ : list Γ} (h : blank_rel l₁ l₂) :
{l // blank_extends l₁ l ∧ blank_extends l₂ l} :=
begin
refine if hl : l₁.length ≤ l₂.length
then ⟨l₂, or.elim h id (λ h', _), blank_extends.refl _⟩
else ⟨l₁, blank_extends.refl _, or.elim h (λ h', _) id⟩,
exact (blank_extends.refl _).above_of_le h' hl,
exact (blank_extends.refl _).above_of_le h' (le_of_not_ge hl)
end
/-- Given two `blank_rel` lists, there exists (constructively) a common meet. -/
def blank_rel.below {Γ} [inhabited Γ] {l₁ l₂ : list Γ} (h : blank_rel l₁ l₂) :
{l // blank_extends l l₁ ∧ blank_extends l l₂} :=
begin
refine if hl : l₁.length ≤ l₂.length
then ⟨l₁, blank_extends.refl _, or.elim h id (λ h', _)⟩
else ⟨l₂, or.elim h (λ h', _) id, blank_extends.refl _⟩,
exact (blank_extends.refl _).above_of_le h' hl,
exact (blank_extends.refl _).above_of_le h' (le_of_not_ge hl)
end
theorem blank_rel.equivalence (Γ) [inhabited Γ] : equivalence (@blank_rel Γ _) :=
⟨blank_rel.refl, @blank_rel.symm _ _, @blank_rel.trans _ _⟩
/-- Construct a setoid instance for `blank_rel`. -/
def blank_rel.setoid (Γ) [inhabited Γ] : setoid (list Γ) := ⟨_, blank_rel.equivalence _⟩
/-- A `list_blank Γ` is a quotient of `list Γ` by extension by blanks at the end. This is used to
represent half-tapes of a Turing machine, so that we can pretend that the list continues
infinitely with blanks. -/
def list_blank (Γ) [inhabited Γ] := quotient (blank_rel.setoid Γ)
instance list_blank.inhabited {Γ} [inhabited Γ] : inhabited (list_blank Γ) := ⟨quotient.mk' []⟩
instance list_blank.has_emptyc {Γ} [inhabited Γ] : has_emptyc (list_blank Γ) := ⟨quotient.mk' []⟩
/-- A modified version of `quotient.lift_on'` specialized for `list_blank`, with the stronger
precondition `blank_extends` instead of `blank_rel`. -/
@[elab_as_eliminator, reducible]
protected def list_blank.lift_on {Γ} [inhabited Γ] {α} (l : list_blank Γ) (f : list Γ → α)
(H : ∀ a b, blank_extends a b → f a = f b) : α :=
l.lift_on' f $ by rintro a b (h|h); [exact H _ _ h, exact (H _ _ h).symm]
/-- The quotient map turning a `list` into a `list_blank`. -/
def list_blank.mk {Γ} [inhabited Γ] : list Γ → list_blank Γ := quotient.mk'
@[elab_as_eliminator]
protected lemma list_blank.induction_on {Γ} [inhabited Γ]
{p : list_blank Γ → Prop} (q : list_blank Γ)
(h : ∀ a, p (list_blank.mk a)) : p q := quotient.induction_on' q h
/-- The head of a `list_blank` is well defined. -/
def list_blank.head {Γ} [inhabited Γ] (l : list_blank Γ) : Γ :=
l.lift_on list.head begin
rintro _ _ ⟨i, rfl⟩,
cases a, {cases i; refl}, refl
end
@[simp] theorem list_blank.head_mk {Γ} [inhabited Γ] (l : list Γ) :
list_blank.head (list_blank.mk l) = l.head := rfl
/-- The tail of a `list_blank` is well defined (up to the tail of blanks). -/
def list_blank.tail {Γ} [inhabited Γ] (l : list_blank Γ) : list_blank Γ :=
l.lift_on (λ l, list_blank.mk l.tail) begin
rintro _ _ ⟨i, rfl⟩,
refine quotient.sound' (or.inl _),
cases a; [{cases i; [exact ⟨0, rfl⟩, exact ⟨i, rfl⟩]}, exact ⟨i, rfl⟩]
end
@[simp] theorem list_blank.tail_mk {Γ} [inhabited Γ] (l : list Γ) :
list_blank.tail (list_blank.mk l) = list_blank.mk l.tail := rfl
/-- We can cons an element onto a `list_blank`. -/
def list_blank.cons {Γ} [inhabited Γ] (a : Γ) (l : list_blank Γ) : list_blank Γ :=
l.lift_on (λ l, list_blank.mk (list.cons a l)) begin
rintro _ _ ⟨i, rfl⟩,
exact quotient.sound' (or.inl ⟨i, rfl⟩),
end
@[simp] theorem list_blank.cons_mk {Γ} [inhabited Γ] (a : Γ) (l : list Γ) :
list_blank.cons a (list_blank.mk l) = list_blank.mk (a :: l) := rfl
@[simp] theorem list_blank.head_cons {Γ} [inhabited Γ] (a : Γ) :
∀ (l : list_blank Γ), (l.cons a).head = a :=
quotient.ind' $ by exact λ l, rfl
@[simp] theorem list_blank.tail_cons {Γ} [inhabited Γ] (a : Γ) :
∀ (l : list_blank Γ), (l.cons a).tail = l :=
quotient.ind' $ by exact λ l, rfl
/-- The `cons` and `head`/`tail` functions are mutually inverse, unlike in the case of `list` where
this only holds for nonempty lists. -/
@[simp] theorem list_blank.cons_head_tail {Γ} [inhabited Γ] :
∀ (l : list_blank Γ), l.tail.cons l.head = l :=
quotient.ind' begin
refine (λ l, quotient.sound' (or.inr _)),
cases l, {exact ⟨1, rfl⟩}, {refl},
end
/-- The `cons` and `head`/`tail` functions are mutually inverse, unlike in the case of `list` where
this only holds for nonempty lists. -/
theorem list_blank.exists_cons {Γ} [inhabited Γ] (l : list_blank Γ) :
∃ a l', l = list_blank.cons a l' :=
⟨_, _, (list_blank.cons_head_tail _).symm⟩
/-- The n-th element of a `list_blank` is well defined for all `n : ℕ`, unlike in a `list`. -/
def list_blank.nth {Γ} [inhabited Γ] (l : list_blank Γ) (n : ℕ) : Γ :=
l.lift_on (λ l, list.inth l n) begin
rintro l _ ⟨i, rfl⟩,
simp only [list.inth],
cases lt_or_le _ _ with h h, {rw list.nth_append h},
rw list.nth_len_le h,
cases le_or_lt _ _ with h₂ h₂, {rw list.nth_len_le h₂},
rw [list.nth_le_nth h₂, list.nth_le_append_right h, list.nth_le_repeat]
end
@[simp] theorem list_blank.nth_mk {Γ} [inhabited Γ] (l : list Γ) (n : ℕ) :
(list_blank.mk l).nth n = l.inth n := rfl
@[simp] theorem list_blank.nth_zero {Γ} [inhabited Γ] (l : list_blank Γ) : l.nth 0 = l.head :=
begin
conv {to_lhs, rw [← list_blank.cons_head_tail l]},
exact quotient.induction_on' l.tail (λ l, rfl)
end
@[simp] theorem list_blank.nth_succ {Γ} [inhabited Γ] (l : list_blank Γ) (n : ℕ) :
l.nth (n + 1) = l.tail.nth n :=
begin
conv {to_lhs, rw [← list_blank.cons_head_tail l]},
exact quotient.induction_on' l.tail (λ l, rfl)
end
@[ext] theorem list_blank.ext {Γ} [inhabited Γ] {L₁ L₂ : list_blank Γ} :
(∀ i, L₁.nth i = L₂.nth i) → L₁ = L₂ :=
list_blank.induction_on L₁ $ λ l₁, list_blank.induction_on L₂ $ λ l₂ H,
begin
wlog h : l₁.length ≤ l₂.length using l₁ l₂,
swap, { exact (this $ λ i, (H i).symm).symm },
refine quotient.sound' (or.inl ⟨l₂.length - l₁.length, _⟩),
refine list.ext_le _ (λ i h h₂, eq.symm _),
{ simp only [nat.add_sub_of_le h, list.length_append, list.length_repeat] },
simp at H,
cases lt_or_le i l₁.length with h' h',
{ simpa only [list.nth_le_append _ h',
list.nth_le_nth h, list.nth_le_nth h', option.iget] using H i },
{ simpa only [list.nth_le_append_right h', list.nth_le_repeat,
list.nth_le_nth h, list.nth_len_le h', option.iget] using H i },
end
/-- Apply a function to a value stored at the nth position of the list. -/
@[simp] def list_blank.modify_nth {Γ} [inhabited Γ] (f : Γ → Γ) : ℕ → list_blank Γ → list_blank Γ
| 0 L := L.tail.cons (f L.head)
| (n+1) L := (L.tail.modify_nth n).cons L.head
theorem list_blank.nth_modify_nth {Γ} [inhabited Γ] (f : Γ → Γ) (n i) (L : list_blank Γ) :
(L.modify_nth f n).nth i = if i = n then f (L.nth i) else L.nth i :=
begin
induction n with n IH generalizing i L,
{ cases i; simp only [list_blank.nth_zero, if_true,
list_blank.head_cons, list_blank.modify_nth, eq_self_iff_true,
list_blank.nth_succ, if_false, list_blank.tail_cons] },
{ cases i,
{ rw if_neg (nat.succ_ne_zero _).symm,
simp only [list_blank.nth_zero, list_blank.head_cons, list_blank.modify_nth] },
{ simp only [IH, list_blank.modify_nth, list_blank.nth_succ, list_blank.tail_cons],
congr } }
end
/-- A pointed map of `inhabited` types is a map that sends one default value to the other. -/
structure {u v} pointed_map (Γ : Type u) (Γ' : Type v)
[inhabited Γ] [inhabited Γ'] : Type (max u v) :=
(f : Γ → Γ') (map_pt' : f (default _) = default _)
instance {Γ Γ'} [inhabited Γ] [inhabited Γ'] : inhabited (pointed_map Γ Γ') :=
⟨⟨λ _, default _, rfl⟩⟩
instance {Γ Γ'} [inhabited Γ] [inhabited Γ'] : has_coe_to_fun (pointed_map Γ Γ') :=
⟨_, pointed_map.f⟩
@[simp] theorem pointed_map.mk_val {Γ Γ'} [inhabited Γ] [inhabited Γ']
(f : Γ → Γ') (pt) : (pointed_map.mk f pt : Γ → Γ') = f := rfl
@[simp] theorem pointed_map.map_pt {Γ Γ'} [inhabited Γ] [inhabited Γ']
(f : pointed_map Γ Γ') : f (default _) = default _ := pointed_map.map_pt' _
@[simp] theorem pointed_map.head_map {Γ Γ'} [inhabited Γ] [inhabited Γ']
(f : pointed_map Γ Γ') (l : list Γ) : (l.map f).head = f l.head :=
by cases l; [exact (pointed_map.map_pt f).symm, refl]
/-- The `map` function on lists is well defined on `list_blank`s provided that the map is
pointed. -/
def list_blank.map {Γ Γ'} [inhabited Γ] [inhabited Γ']
(f : pointed_map Γ Γ') (l : list_blank Γ) : list_blank Γ' :=
l.lift_on (λ l, list_blank.mk (list.map f l)) begin
rintro l _ ⟨i, rfl⟩, refine quotient.sound' (or.inl ⟨i, _⟩),
simp only [pointed_map.map_pt, list.map_append, list.map_repeat],
end
@[simp] theorem list_blank.map_mk {Γ Γ'} [inhabited Γ] [inhabited Γ']
(f : pointed_map Γ Γ') (l : list Γ) : (list_blank.mk l).map f = list_blank.mk (l.map f) := rfl
@[simp] theorem list_blank.head_map {Γ Γ'} [inhabited Γ] [inhabited Γ']
(f : pointed_map Γ Γ') (l : list_blank Γ) : (l.map f).head = f l.head :=
begin
conv {to_lhs, rw [← list_blank.cons_head_tail l]},
exact quotient.induction_on' l (λ a, rfl)
end
@[simp] theorem list_blank.tail_map {Γ Γ'} [inhabited Γ] [inhabited Γ']
(f : pointed_map Γ Γ') (l : list_blank Γ) : (l.map f).tail = l.tail.map f :=
begin
conv {to_lhs, rw [← list_blank.cons_head_tail l]},
exact quotient.induction_on' l (λ a, rfl)
end
@[simp] theorem list_blank.map_cons {Γ Γ'} [inhabited Γ] [inhabited Γ']
(f : pointed_map Γ Γ') (l : list_blank Γ) (a : Γ) : (l.cons a).map f = (l.map f).cons (f a) :=
begin
refine (list_blank.cons_head_tail _).symm.trans _,
simp only [list_blank.head_map, list_blank.head_cons, list_blank.tail_map, list_blank.tail_cons]
end
@[simp] theorem list_blank.nth_map {Γ Γ'} [inhabited Γ] [inhabited Γ']
(f : pointed_map Γ Γ') (l : list_blank Γ) (n : ℕ) : (l.map f).nth n = f (l.nth n) :=
l.induction_on begin
intro l, simp only [list.nth_map, list_blank.map_mk, list_blank.nth_mk, list.inth],
cases l.nth n, {exact f.2.symm}, {refl}
end
/-- The `i`-th projection as a pointed map. -/
def proj {ι : Type*} {Γ : ι → Type*} [∀ i, inhabited (Γ i)] (i : ι) :
pointed_map (∀ i, Γ i) (Γ i) := ⟨λ a, a i, rfl⟩
theorem proj_map_nth {ι : Type*} {Γ : ι → Type*} [∀ i, inhabited (Γ i)] (i : ι)
(L n) : (list_blank.map (@proj ι Γ _ i) L).nth n = L.nth n i :=
by rw list_blank.nth_map; refl
theorem list_blank.map_modify_nth {Γ Γ'} [inhabited Γ] [inhabited Γ']
(F : pointed_map Γ Γ') (f : Γ → Γ) (f' : Γ' → Γ')
(H : ∀ x, F (f x) = f' (F x)) (n) (L : list_blank Γ) :
(L.modify_nth f n).map F = (L.map F).modify_nth f' n :=
by induction n with n IH generalizing L; simp only [*,
list_blank.head_map, list_blank.modify_nth, list_blank.map_cons, list_blank.tail_map]
/-- Append a list on the left side of a list_blank. -/
@[simp] def list_blank.append {Γ} [inhabited Γ] : list Γ → list_blank Γ → list_blank Γ
| [] L := L
| (a :: l) L := list_blank.cons a (list_blank.append l L)
@[simp] theorem list_blank.append_mk {Γ} [inhabited Γ] (l₁ l₂ : list Γ) :
list_blank.append l₁ (list_blank.mk l₂) = list_blank.mk (l₁ ++ l₂) :=
by induction l₁; simp only [*,
list_blank.append, list.nil_append, list.cons_append, list_blank.cons_mk]
theorem list_blank.append_assoc {Γ} [inhabited Γ] (l₁ l₂ : list Γ) (l₃ : list_blank Γ) :
list_blank.append (l₁ ++ l₂) l₃ = list_blank.append l₁ (list_blank.append l₂ l₃) :=
l₃.induction_on $ by intro; simp only [list_blank.append_mk, list.append_assoc]
/-- The `bind` function on lists is well defined on `list_blank`s provided that the default element
is sent to a sequence of default elements. -/
def list_blank.bind {Γ Γ'} [inhabited Γ] [inhabited Γ']
(l : list_blank Γ) (f : Γ → list Γ')
(hf : ∃ n, f (default _) = list.repeat (default _) n) : list_blank Γ' :=
l.lift_on (λ l, list_blank.mk (list.bind l f)) begin
rintro l _ ⟨i, rfl⟩, cases hf with n e, refine quotient.sound' (or.inl ⟨i * n, _⟩),
rw [list.bind_append, mul_comm], congr,
induction i with i IH, refl,
simp only [IH, e, list.repeat_add, nat.mul_succ, add_comm, list.repeat_succ, list.cons_bind],
end
@[simp] lemma list_blank.bind_mk {Γ Γ'} [inhabited Γ] [inhabited Γ']
(l : list Γ) (f : Γ → list Γ') (hf) :
(list_blank.mk l).bind f hf = list_blank.mk (l.bind f) := rfl
@[simp] lemma list_blank.cons_bind {Γ Γ'} [inhabited Γ] [inhabited Γ']
(a : Γ) (l : list_blank Γ) (f : Γ → list Γ') (hf) :
(l.cons a).bind f hf = (l.bind f hf).append (f a) :=
l.induction_on $ by intro; simp only [list_blank.append_mk,
list_blank.bind_mk, list_blank.cons_mk, list.cons_bind]
/-- The tape of a Turing machine is composed of a head element (which we imagine to be the
current position of the head), together with two `list_blank`s denoting the portions of the tape
going off to the left and right. When the Turing machine moves right, an element is pulled from the
right side and becomes the new head, while the head element is consed onto the left side. -/
structure tape (Γ : Type*) [inhabited Γ] :=
(head : Γ)
(left : list_blank Γ)
(right : list_blank Γ)
instance tape.inhabited {Γ} [inhabited Γ] : inhabited (tape Γ) :=
⟨by constructor; apply default⟩
/-- A direction for the turing machine `move` command, either
left or right. -/
@[derive decidable_eq, derive inhabited]
inductive dir | left | right
/-- The "inclusive" left side of the tape, including both `left` and `head`. -/
def tape.left₀ {Γ} [inhabited Γ] (T : tape Γ) : list_blank Γ := T.left.cons T.head
/-- The "inclusive" right side of the tape, including both `right` and `head`. -/
def tape.right₀ {Γ} [inhabited Γ] (T : tape Γ) : list_blank Γ := T.right.cons T.head
/-- Move the tape in response to a motion of the Turing machine. Note that `T.move dir.left` makes
`T.left` smaller; the Turing machine is moving left and the tape is moving right. -/
def tape.move {Γ} [inhabited Γ] : dir → tape Γ → tape Γ
| dir.left ⟨a, L, R⟩ := ⟨L.head, L.tail, R.cons a⟩
| dir.right ⟨a, L, R⟩ := ⟨R.head, L.cons a, R.tail⟩
@[simp] theorem tape.move_left_right {Γ} [inhabited Γ] (T : tape Γ) :
(T.move dir.left).move dir.right = T :=
by cases T; simp [tape.move]
@[simp] theorem tape.move_right_left {Γ} [inhabited Γ] (T : tape Γ) :
(T.move dir.right).move dir.left = T :=
by cases T; simp [tape.move]
/-- Construct a tape from a left side and an inclusive right side. -/
def tape.mk' {Γ} [inhabited Γ] (L R : list_blank Γ) : tape Γ := ⟨R.head, L, R.tail⟩
@[simp] theorem tape.mk'_left {Γ} [inhabited Γ] (L R : list_blank Γ) :
(tape.mk' L R).left = L := rfl
@[simp] theorem tape.mk'_head {Γ} [inhabited Γ] (L R : list_blank Γ) :
(tape.mk' L R).head = R.head := rfl
@[simp] theorem tape.mk'_right {Γ} [inhabited Γ] (L R : list_blank Γ) :
(tape.mk' L R).right = R.tail := rfl
@[simp] theorem tape.mk'_right₀ {Γ} [inhabited Γ] (L R : list_blank Γ) :
(tape.mk' L R).right₀ = R := list_blank.cons_head_tail _
@[simp] theorem tape.mk'_left_right₀ {Γ} [inhabited Γ] (T : tape Γ) :
tape.mk' T.left T.right₀ = T :=
by cases T; simp only [tape.right₀, tape.mk',
list_blank.head_cons, list_blank.tail_cons, eq_self_iff_true, and_self]
theorem tape.exists_mk' {Γ} [inhabited Γ] (T : tape Γ) :
∃ L R, T = tape.mk' L R := ⟨_, _, (tape.mk'_left_right₀ _).symm⟩
@[simp] theorem tape.move_left_mk' {Γ} [inhabited Γ] (L R : list_blank Γ) :
(tape.mk' L R).move dir.left = tape.mk' L.tail (R.cons L.head) :=
by simp only [tape.move, tape.mk', list_blank.head_cons, eq_self_iff_true,
list_blank.cons_head_tail, and_self, list_blank.tail_cons]
@[simp] theorem tape.move_right_mk' {Γ} [inhabited Γ] (L R : list_blank Γ) :
(tape.mk' L R).move dir.right = tape.mk' (L.cons R.head) R.tail :=
by simp only [tape.move, tape.mk', list_blank.head_cons, eq_self_iff_true,
list_blank.cons_head_tail, and_self, list_blank.tail_cons]
/-- Construct a tape from a left side and an inclusive right side. -/
def tape.mk₂ {Γ} [inhabited Γ] (L R : list Γ) : tape Γ :=
tape.mk' (list_blank.mk L) (list_blank.mk R)
/-- Construct a tape from a list, with the head of the list at the TM head and the rest going
to the right. -/
def tape.mk₁ {Γ} [inhabited Γ] (l : list Γ) : tape Γ :=
tape.mk₂ [] l
/-- The `nth` function of a tape is integer-valued, with index `0` being the head, negative indexes
on the left and positive indexes on the right. (Picture a number line.) -/
def tape.nth {Γ} [inhabited Γ] (T : tape Γ) : ℤ → Γ
| 0 := T.head
| (n+1:ℕ) := T.right.nth n
| -[1+ n] := T.left.nth n
@[simp] theorem tape.nth_zero {Γ} [inhabited Γ] (T : tape Γ) : T.nth 0 = T.1 := rfl
theorem tape.right₀_nth {Γ} [inhabited Γ] (T : tape Γ) (n : ℕ) : T.right₀.nth n = T.nth n :=
by cases n; simp only [tape.nth, tape.right₀, int.coe_nat_zero,
list_blank.nth_zero, list_blank.nth_succ, list_blank.head_cons, list_blank.tail_cons]
@[simp] theorem tape.mk'_nth_nat {Γ} [inhabited Γ] (L R : list_blank Γ) (n : ℕ) :
(tape.mk' L R).nth n = R.nth n :=
by rw [← tape.right₀_nth, tape.mk'_right₀]
@[simp] theorem tape.move_left_nth {Γ} [inhabited Γ] :
∀ (T : tape Γ) (i : ℤ), (T.move dir.left).nth i = T.nth (i-1)
| ⟨a, L, R⟩ -[1+ n] := (list_blank.nth_succ _ _).symm
| ⟨a, L, R⟩ 0 := (list_blank.nth_zero _).symm
| ⟨a, L, R⟩ 1 := (list_blank.nth_zero _).trans (list_blank.head_cons _ _)
| ⟨a, L, R⟩ ((n+1:ℕ)+1) := begin
rw add_sub_cancel,
change (R.cons a).nth (n+1) = R.nth n,
rw [list_blank.nth_succ, list_blank.tail_cons]
end
@[simp] theorem tape.move_right_nth {Γ} [inhabited Γ] (T : tape Γ) (i : ℤ) :
(T.move dir.right).nth i = T.nth (i+1) :=
by conv {to_rhs, rw ← T.move_right_left}; rw [tape.move_left_nth, add_sub_cancel]
@[simp] theorem tape.move_right_n_head {Γ} [inhabited Γ] (T : tape Γ) (i : ℕ) :
((tape.move dir.right)^[i] T).head = T.nth i :=
by induction i generalizing T; [refl, simp only [*,
tape.move_right_nth, int.coe_nat_succ, iterate_succ]]
/-- Replace the current value of the head on the tape. -/
def tape.write {Γ} [inhabited Γ] (b : Γ) (T : tape Γ) : tape Γ := {head := b, ..T}
@[simp] theorem tape.write_self {Γ} [inhabited Γ] : ∀ (T : tape Γ), T.write T.1 = T :=
by rintro ⟨⟩; refl
@[simp] theorem tape.write_nth {Γ} [inhabited Γ] (b : Γ) :
∀ (T : tape Γ) {i : ℤ}, (T.write b).nth i = if i = 0 then b else T.nth i
| ⟨a, L, R⟩ 0 := rfl
| ⟨a, L, R⟩ (n+1:ℕ) := rfl
| ⟨a, L, R⟩ -[1+ n] := rfl
@[simp] theorem tape.write_mk' {Γ} [inhabited Γ] (a b : Γ) (L R : list_blank Γ) :
(tape.mk' L (R.cons a)).write b = tape.mk' L (R.cons b) :=
by simp only [tape.write, tape.mk', list_blank.head_cons, list_blank.tail_cons,
eq_self_iff_true, and_self]
/-- Apply a pointed map to a tape to change the alphabet. -/
def tape.map {Γ Γ'} [inhabited Γ] [inhabited Γ'] (f : pointed_map Γ Γ') (T : tape Γ) : tape Γ' :=
⟨f T.1, T.2.map f, T.3.map f⟩
@[simp] theorem tape.map_fst {Γ Γ'} [inhabited Γ] [inhabited Γ']
(f : pointed_map Γ Γ') : ∀ (T : tape Γ), (T.map f).1 = f T.1 :=
by rintro ⟨⟩; refl
@[simp] theorem tape.map_write {Γ Γ'} [inhabited Γ] [inhabited Γ'] (f : pointed_map Γ Γ') (b : Γ) :
∀ (T : tape Γ), (T.write b).map f = (T.map f).write (f b) :=
by rintro ⟨⟩; refl
@[simp] theorem tape.write_move_right_n {Γ} [inhabited Γ] (f : Γ → Γ) (L R : list_blank Γ) (n : ℕ) :
((tape.move dir.right)^[n] (tape.mk' L R)).write (f (R.nth n)) =
((tape.move dir.right)^[n] (tape.mk' L (R.modify_nth f n))) :=
begin
induction n with n IH generalizing L R,
{ simp only [list_blank.nth_zero, list_blank.modify_nth, iterate_zero_apply],
rw [← tape.write_mk', list_blank.cons_head_tail] },
simp only [list_blank.head_cons, list_blank.nth_succ, list_blank.modify_nth,
tape.move_right_mk', list_blank.tail_cons, iterate_succ_apply, IH]
end
theorem tape.map_move {Γ Γ'} [inhabited Γ] [inhabited Γ']
(f : pointed_map Γ Γ') (T : tape Γ) (d) : (T.move d).map f = (T.map f).move d :=
by cases T; cases d; simp only [tape.move, tape.map,
list_blank.head_map, eq_self_iff_true, list_blank.map_cons, and_self, list_blank.tail_map]
theorem tape.map_mk' {Γ Γ'} [inhabited Γ] [inhabited Γ'] (f : pointed_map Γ Γ')
(L R : list_blank Γ) : (tape.mk' L R).map f = tape.mk' (L.map f) (R.map f) :=
by simp only [tape.mk', tape.map, list_blank.head_map,
eq_self_iff_true, and_self, list_blank.tail_map]
theorem tape.map_mk₂ {Γ Γ'} [inhabited Γ] [inhabited Γ'] (f : pointed_map Γ Γ')
(L R : list Γ) : (tape.mk₂ L R).map f = tape.mk₂ (L.map f) (R.map f) :=
by simp only [tape.mk₂, tape.map_mk', list_blank.map_mk]
theorem tape.map_mk₁ {Γ Γ'} [inhabited Γ] [inhabited Γ'] (f : pointed_map Γ Γ')
(l : list Γ) : (tape.mk₁ l).map f = tape.mk₁ (l.map f) := tape.map_mk₂ _ _ _
/-- Run a state transition function `σ → option σ` "to completion". The return value is the last
state returned before a `none` result. If the state transition function always returns `some`,
then the computation diverges, returning `roption.none`. -/
def eval {σ} (f : σ → option σ) : σ → roption σ :=
pfun.fix (λ s, roption.some $ (f s).elim (sum.inl s) sum.inr)
/-- The reflexive transitive closure of a state transition function. `reaches f a b` means
there is a finite sequence of steps `f a = some a₁`, `f a₁ = some a₂`, ... such that `aₙ = b`.
This relation permits zero steps of the state transition function. -/
def reaches {σ} (f : σ → option σ) : σ → σ → Prop :=
refl_trans_gen (λ a b, b ∈ f a)
/-- The transitive closure of a state transition function. `reaches₁ f a b` means there is a
nonempty finite sequence of steps `f a = some a₁`, `f a₁ = some a₂`, ... such that `aₙ = b`.
This relation does not permit zero steps of the state transition function. -/
def reaches₁ {σ} (f : σ → option σ) : σ → σ → Prop :=
trans_gen (λ a b, b ∈ f a)
theorem reaches₁_eq {σ} {f : σ → option σ} {a b c}
(h : f a = f b) : reaches₁ f a c ↔ reaches₁ f b c :=
trans_gen.head'_iff.trans (trans_gen.head'_iff.trans $ by rw h).symm
theorem reaches_total {σ} {f : σ → option σ}
{a b c} : reaches f a b → reaches f a c →
reaches f b c ∨ reaches f c b :=
refl_trans_gen.total_of_right_unique ⟨λ _ _ _, option.mem_unique⟩
theorem reaches₁_fwd {σ} {f : σ → option σ}
{a b c} (h₁ : reaches₁ f a c) (h₂ : b ∈ f a) : reaches f b c :=
begin
rcases trans_gen.head'_iff.1 h₁ with ⟨b', hab, hbc⟩,
cases option.mem_unique hab h₂, exact hbc
end
/-- A variation on `reaches`. `reaches₀ f a b` holds if whenever `reaches₁ f b c` then
`reaches₁ f a c`. This is a weaker property than `reaches` and is useful for replacing states with
equivalent states without taking a step. -/
def reaches₀ {σ} (f : σ → option σ) (a b : σ) : Prop :=
∀ c, reaches₁ f b c → reaches₁ f a c
theorem reaches₀.trans {σ} {f : σ → option σ} {a b c : σ}
(h₁ : reaches₀ f a b) (h₂ : reaches₀ f b c) : reaches₀ f a c
| d h₃ := h₁ _ (h₂ _ h₃)
@[refl] theorem reaches₀.refl {σ} {f : σ → option σ} (a : σ) : reaches₀ f a a
| b h := h
theorem reaches₀.single {σ} {f : σ → option σ} {a b : σ}
(h : b ∈ f a) : reaches₀ f a b
| c h₂ := h₂.head h
theorem reaches₀.head {σ} {f : σ → option σ} {a b c : σ}
(h : b ∈ f a) (h₂ : reaches₀ f b c) : reaches₀ f a c :=
(reaches₀.single h).trans h₂
theorem reaches₀.tail {σ} {f : σ → option σ} {a b c : σ}
(h₁ : reaches₀ f a b) (h : c ∈ f b) : reaches₀ f a c :=
h₁.trans (reaches₀.single h)
theorem reaches₀_eq {σ} {f : σ → option σ} {a b}
(e : f a = f b) : reaches₀ f a b
| d h := (reaches₁_eq e).2 h
theorem reaches₁.to₀ {σ} {f : σ → option σ} {a b : σ}
(h : reaches₁ f a b) : reaches₀ f a b
| c h₂ := h.trans h₂
theorem reaches.to₀ {σ} {f : σ → option σ} {a b : σ}
(h : reaches f a b) : reaches₀ f a b
| c h₂ := h₂.trans_right h
theorem reaches₀.tail' {σ} {f : σ → option σ} {a b c : σ}
(h : reaches₀ f a b) (h₂ : c ∈ f b) : reaches₁ f a c :=
h _ (trans_gen.single h₂)
/-- (co-)Induction principle for `eval`. If a property `C` holds of any point `a` evaluating to `b`
which is either terminal (meaning `a = b`) or where the next point also satisfies `C`, then it
holds of any point where `eval f a` evaluates to `b`. This formalizes the notion that if
`eval f a` evaluates to `b` then it reaches terminal state `b` in finitely many steps. -/
@[elab_as_eliminator] def eval_induction {σ}
{f : σ → option σ} {b : σ} {C : σ → Sort*} {a : σ} (h : b ∈ eval f a)
(H : ∀ a, b ∈ eval f a →
(∀ a', b ∈ eval f a' → f a = some a' → C a') → C a) : C a :=
pfun.fix_induction h (λ a' ha' h', H _ ha' $ λ b' hb' e, h' _ hb' $
roption.mem_some_iff.2 $ by rw e; refl)
theorem mem_eval {σ} {f : σ → option σ} {a b} :
b ∈ eval f a ↔ reaches f a b ∧ f b = none :=
⟨λ h, begin
refine eval_induction h (λ a h IH, _),
cases e : f a with a',
{ rw roption.mem_unique h (pfun.mem_fix_iff.2 $ or.inl $
roption.mem_some_iff.2 $ by rw e; refl),
exact ⟨refl_trans_gen.refl, e⟩ },
{ rcases pfun.mem_fix_iff.1 h with h | ⟨_, h, h'⟩;
rw e at h; cases roption.mem_some_iff.1 h,
cases IH a' h' (by rwa e) with h₁ h₂,
exact ⟨refl_trans_gen.head e h₁, h₂⟩ }
end, λ ⟨h₁, h₂⟩, begin
refine refl_trans_gen.head_induction_on h₁ _ (λ a a' h _ IH, _),
{ refine pfun.mem_fix_iff.2 (or.inl _),
rw h₂, apply roption.mem_some },
{ refine pfun.mem_fix_iff.2 (or.inr ⟨_, _, IH⟩),
rw show f a = _, from h,
apply roption.mem_some }
end⟩
theorem eval_maximal₁ {σ} {f : σ → option σ} {a b}
(h : b ∈ eval f a) (c) : ¬ reaches₁ f b c | bc :=
let ⟨ab, b0⟩ := mem_eval.1 h, ⟨b', h', _⟩ := trans_gen.head'_iff.1 bc in
by cases b0.symm.trans h'
theorem eval_maximal {σ} {f : σ → option σ} {a b}
(h : b ∈ eval f a) {c} : reaches f b c ↔ c = b :=
let ⟨ab, b0⟩ := mem_eval.1 h in
refl_trans_gen_iff_eq $ λ b' h', by cases b0.symm.trans h'
theorem reaches_eval {σ} {f : σ → option σ} {a b}
(ab : reaches f a b) : eval f a = eval f b :=
roption.ext $ λ c,
⟨λ h, let ⟨ac, c0⟩ := mem_eval.1 h in
mem_eval.2 ⟨(or_iff_left_of_imp $ by exact
λ cb, (eval_maximal h).1 cb ▸ refl_trans_gen.refl).1
(reaches_total ab ac), c0⟩,
λ h, let ⟨bc, c0⟩ := mem_eval.1 h in mem_eval.2 ⟨ab.trans bc, c0⟩,⟩
/-- Given a relation `tr : σ₁ → σ₂ → Prop` between state spaces, and state transition functions
`f₁ : σ₁ → option σ₁` and `f₂ : σ₂ → option σ₂`, `respects f₁ f₂ tr` means that if `tr a₁ a₂` holds
initially and `f₁` takes a step to `a₂` then `f₂` will take one or more steps before reaching a
state `b₂` satisfying `tr a₂ b₂`, and if `f₁ a₁` terminates then `f₂ a₂` also terminates.
Such a relation `tr` is also known as a refinement. -/
def respects {σ₁ σ₂}
(f₁ : σ₁ → option σ₁) (f₂ : σ₂ → option σ₂) (tr : σ₁ → σ₂ → Prop) :=
∀ ⦃a₁ a₂⦄, tr a₁ a₂ → (match f₁ a₁ with
| some b₁ := ∃ b₂, tr b₁ b₂ ∧ reaches₁ f₂ a₂ b₂
| none := f₂ a₂ = none
end : Prop)
theorem tr_reaches₁ {σ₁ σ₂ f₁ f₂} {tr : σ₁ → σ₂ → Prop}
(H : respects f₁ f₂ tr) {a₁ a₂} (aa : tr a₁ a₂) {b₁} (ab : reaches₁ f₁ a₁ b₁) :
∃ b₂, tr b₁ b₂ ∧ reaches₁ f₂ a₂ b₂ :=
begin
induction ab with c₁ ac c₁ d₁ ac cd IH,
{ have := H aa,
rwa (show f₁ a₁ = _, from ac) at this },
{ rcases IH with ⟨c₂, cc, ac₂⟩,
have := H cc,
rw (show f₁ c₁ = _, from cd) at this,
rcases this with ⟨d₂, dd, cd₂⟩,
exact ⟨_, dd, ac₂.trans cd₂⟩ }
end
theorem tr_reaches {σ₁ σ₂ f₁ f₂} {tr : σ₁ → σ₂ → Prop}
(H : respects f₁ f₂ tr) {a₁ a₂} (aa : tr a₁ a₂) {b₁} (ab : reaches f₁ a₁ b₁) :
∃ b₂, tr b₁ b₂ ∧ reaches f₂ a₂ b₂ :=
begin
rcases refl_trans_gen_iff_eq_or_trans_gen.1 ab with rfl | ab,
{ exact ⟨_, aa, refl_trans_gen.refl⟩ },
{ exact let ⟨b₂, bb, h⟩ := tr_reaches₁ H aa ab in
⟨b₂, bb, h.to_refl⟩ }
end
theorem tr_reaches_rev {σ₁ σ₂ f₁ f₂} {tr : σ₁ → σ₂ → Prop}
(H : respects f₁ f₂ tr) {a₁ a₂} (aa : tr a₁ a₂) {b₂} (ab : reaches f₂ a₂ b₂) :
∃ c₁ c₂, reaches f₂ b₂ c₂ ∧ tr c₁ c₂ ∧ reaches f₁ a₁ c₁ :=
begin
induction ab with c₂ d₂ ac cd IH,
{ exact ⟨_, _, refl_trans_gen.refl, aa, refl_trans_gen.refl⟩ },
{ rcases IH with ⟨e₁, e₂, ce, ee, ae⟩,
rcases refl_trans_gen.cases_head ce with rfl | ⟨d', cd', de⟩,
{ have := H ee, revert this,
cases eg : f₁ e₁ with g₁; simp only [respects, and_imp, exists_imp_distrib],
{ intro c0, cases cd.symm.trans c0 },
{ intros g₂ gg cg,
rcases trans_gen.head'_iff.1 cg with ⟨d', cd', dg⟩,
cases option.mem_unique cd cd',
exact ⟨_, _, dg, gg, ae.tail eg⟩ } },
{ cases option.mem_unique cd cd',
exact ⟨_, _, de, ee, ae⟩ } }
end
theorem tr_eval {σ₁ σ₂ f₁ f₂} {tr : σ₁ → σ₂ → Prop}
(H : respects f₁ f₂ tr) {a₁ b₁ a₂} (aa : tr a₁ a₂)
(ab : b₁ ∈ eval f₁ a₁) : ∃ b₂, tr b₁ b₂ ∧ b₂ ∈ eval f₂ a₂ :=
begin
cases mem_eval.1 ab with ab b0,
rcases tr_reaches H aa ab with ⟨b₂, bb, ab⟩,
refine ⟨_, bb, mem_eval.2 ⟨ab, _⟩⟩,
have := H bb, rwa b0 at this
end
theorem tr_eval_rev {σ₁ σ₂ f₁ f₂} {tr : σ₁ → σ₂ → Prop}
(H : respects f₁ f₂ tr) {a₁ b₂ a₂} (aa : tr a₁ a₂)
(ab : b₂ ∈ eval f₂ a₂) : ∃ b₁, tr b₁ b₂ ∧ b₁ ∈ eval f₁ a₁ :=
begin
cases mem_eval.1 ab with ab b0,
rcases tr_reaches_rev H aa ab with ⟨c₁, c₂, bc, cc, ac⟩,
cases (refl_trans_gen_iff_eq
(by exact option.eq_none_iff_forall_not_mem.1 b0)).1 bc,
refine ⟨_, cc, mem_eval.2 ⟨ac, _⟩⟩,
have := H cc, cases f₁ c₁ with d₁, {refl},
rcases this with ⟨d₂, dd, bd⟩,
rcases trans_gen.head'_iff.1 bd with ⟨e, h, _⟩,
cases b0.symm.trans h
end
theorem tr_eval_dom {σ₁ σ₂ f₁ f₂} {tr : σ₁ → σ₂ → Prop}
(H : respects f₁ f₂ tr) {a₁ a₂} (aa : tr a₁ a₂) :
(eval f₂ a₂).dom ↔ (eval f₁ a₁).dom :=
⟨λ h, let ⟨b₂, tr, h, _⟩ := tr_eval_rev H aa ⟨h, rfl⟩ in h,
λ h, let ⟨b₂, tr, h, _⟩ := tr_eval H aa ⟨h, rfl⟩ in h⟩
/-- A simpler version of `respects` when the state transition relation `tr` is a function. -/
def frespects {σ₁ σ₂} (f₂ : σ₂ → option σ₂) (tr : σ₁ → σ₂) (a₂ : σ₂) : option σ₁ → Prop
| (some b₁) := reaches₁ f₂ a₂ (tr b₁)
| none := f₂ a₂ = none
theorem frespects_eq {σ₁ σ₂} {f₂ : σ₂ → option σ₂} {tr : σ₁ → σ₂} {a₂ b₂}
(h : f₂ a₂ = f₂ b₂) : ∀ {b₁}, frespects f₂ tr a₂ b₁ ↔ frespects f₂ tr b₂ b₁
| (some b₁) := reaches₁_eq h
| none := by unfold frespects; rw h
theorem fun_respects {σ₁ σ₂ f₁ f₂} {tr : σ₁ → σ₂} :
respects f₁ f₂ (λ a b, tr a = b) ↔ ∀ ⦃a₁⦄, frespects f₂ tr (tr a₁) (f₁ a₁) :=
forall_congr $ λ a₁, by cases f₁ a₁; simp only [frespects, respects, exists_eq_left', forall_eq']
theorem tr_eval' {σ₁ σ₂}
(f₁ : σ₁ → option σ₁) (f₂ : σ₂ → option σ₂) (tr : σ₁ → σ₂)
(H : respects f₁ f₂ (λ a b, tr a = b))
(a₁) : eval f₂ (tr a₁) = tr <$> eval f₁ a₁ :=
roption.ext $ λ b₂,
⟨λ h, let ⟨b₁, bb, hb⟩ := tr_eval_rev H rfl h in
(roption.mem_map_iff _).2 ⟨b₁, hb, bb⟩,
λ h, begin
rcases (roption.mem_map_iff _).1 h with ⟨b₁, ab, bb⟩,
rcases tr_eval H rfl ab with ⟨_, rfl, h⟩,
rwa bb at h
end⟩
/-!
## The TM0 model
A TM0 turing machine is essentially a Post-Turing machine, adapted for type theory.
A Post-Turing machine with symbol type `Γ` and label type `Λ` is a function
`Λ → Γ → option (Λ × stmt)`, where a `stmt` can be either `move left`, `move right` or `write a`
for `a : Γ`. The machine works over a "tape", a doubly-infinite sequence of elements of `Γ`, and
an instantaneous configuration, `cfg`, is a label `q : Λ` indicating the current internal state of
the machine, and a `tape Γ` (which is essentially `ℤ →₀ Γ`). The evolution is described by the
`step` function:
* If `M q T.head = none`, then the machine halts.
* If `M q T.head = some (q', s)`, then the machine performs action `s : stmt` and then transitions
to state `q'`.
The initial state takes a `list Γ` and produces a `tape Γ` where the head of the list is the head
of the tape and the rest of the list extends to the right, with the left side all blank. The final
state takes the entire right side of the tape right or equal to the current position of the
machine. (This is actually a `list_blank Γ`, not a `list Γ`, because we don't know, at this level
of generality, where the output ends. If equality to `default Γ` is decidable we can trim the list
to remove the infinite tail of blanks.)
-/
namespace TM0
section
parameters (Γ : Type*) [inhabited Γ] -- type of tape symbols
parameters (Λ : Type*) [inhabited Λ] -- type of "labels" or TM states
/-- A Turing machine "statement" is just a command to either move
left or right, or write a symbol on the tape. -/
inductive stmt
| move : dir → stmt
| write : Γ → stmt
instance stmt.inhabited : inhabited stmt := ⟨stmt.write (default _)⟩
/-- A Post-Turing machine with symbol type `Γ` and label type `Λ`
is a function which, given the current state `q : Λ` and
the tape head `a : Γ`, either halts (returns `none`) or returns
a new state `q' : Λ` and a `stmt` describing what to do,
either a move left or right, or a write command.
Both `Λ` and `Γ` are required to be inhabited; the default value
for `Γ` is the "blank" tape value, and the default value of `Λ` is
the initial state. -/
@[nolint unused_arguments] -- [inhabited Λ]: this is a deliberate addition, see comment
def machine := Λ → Γ → option (Λ × stmt)
instance machine.inhabited : inhabited machine := by unfold machine; apply_instance
/-- The configuration state of a Turing machine during operation
consists of a label (machine state), and a tape, represented in
the form `(a, L, R)` meaning the tape looks like `L.rev ++ [a] ++ R`
with the machine currently reading the `a`. The lists are
automatically extended with blanks as the machine moves around. -/
structure cfg :=
(q : Λ)
(tape : tape Γ)
instance cfg.inhabited : inhabited cfg := ⟨⟨default _, default _⟩⟩
parameters {Γ Λ}
/-- Execution semantics of the Turing machine. -/
def step (M : machine) : cfg → option cfg
| ⟨q, T⟩ := (M q T.1).map (λ ⟨q', a⟩, ⟨q',
match a with
| stmt.move d := T.move d
| stmt.write a := T.write a
end⟩)
/-- The statement `reaches M s₁ s₂` means that `s₂` is obtained
starting from `s₁` after a finite number of steps from `s₂`. -/
def reaches (M : machine) : cfg → cfg → Prop :=
refl_trans_gen (λ a b, b ∈ step M a)
/-- The initial configuration. -/
def init (l : list Γ) : cfg :=
⟨default Λ, tape.mk₁ l⟩
/-- Evaluate a Turing machine on initial input to a final state,
if it terminates. -/
def eval (M : machine) (l : list Γ) : roption (list_blank Γ) :=
(eval (step M) (init l)).map (λ c, c.tape.right₀)
/-- The raw definition of a Turing machine does not require that
`Γ` and `Λ` are finite, and in practice we will be interested
in the infinite `Λ` case. We recover instead a notion of
"effectively finite" Turing machines, which only make use of a
finite subset of their states. We say that a set `S ⊆ Λ`
supports a Turing machine `M` if `S` is closed under the
transition function and contains the initial state. -/
def supports (M : machine) (S : set Λ) :=
default Λ ∈ S ∧ ∀ {q a q' s}, (q', s) ∈ M q a → q ∈ S → q' ∈ S
theorem step_supports (M : machine) {S}
(ss : supports M S) : ∀ {c c' : cfg},
c' ∈ step M c → c.q ∈ S → c'.q ∈ S
| ⟨q, T⟩ c' h₁ h₂ := begin
rcases option.map_eq_some'.1 h₁ with ⟨⟨q', a⟩, h, rfl⟩,
exact ss.2 h h₂,
end
theorem univ_supports (M : machine) : supports M set.univ :=
⟨trivial, λ q a q' s h₁ h₂, trivial⟩
end
section
variables {Γ : Type*} [inhabited Γ]
variables {Γ' : Type*} [inhabited Γ']
variables {Λ : Type*} [inhabited Λ]
variables {Λ' : Type*} [inhabited Λ']
/-- Map a TM statement across a function. This does nothing to move statements and maps the write
values. -/
def stmt.map (f : pointed_map Γ Γ') : stmt Γ → stmt Γ'
| (stmt.move d) := stmt.move d
| (stmt.write a) := stmt.write (f a)
/-- Map a configuration across a function, given `f : Γ → Γ'` a map of the alphabets and
`g : Λ → Λ'` a map of the machine states. -/
def cfg.map (f : pointed_map Γ Γ') (g : Λ → Λ') : cfg Γ Λ → cfg Γ' Λ'
| ⟨q, T⟩ := ⟨g q, T.map f⟩
variables (M : machine Γ Λ)
(f₁ : pointed_map Γ Γ') (f₂ : pointed_map Γ' Γ) (g₁ : Λ → Λ') (g₂ : Λ' → Λ)
/-- Because the state transition function uses the alphabet and machine states in both the input
and output, to map a machine from one alphabet and machine state space to another we need functions
in both directions, essentially an `equiv` without the laws. -/
def machine.map : machine Γ' Λ'
| q l := (M (g₂ q) (f₂ l)).map (prod.map g₁ (stmt.map f₁))
theorem machine.map_step {S : set Λ}
(f₂₁ : function.right_inverse f₁ f₂)
(g₂₁ : ∀ q ∈ S, g₂ (g₁ q) = q) :
∀ c : cfg Γ Λ, c.q ∈ S →
(step M c).map (cfg.map f₁ g₁) =
step (M.map f₁ f₂ g₁ g₂) (cfg.map f₁ g₁ c)
| ⟨q, T⟩ h := begin
unfold step machine.map cfg.map,
simp only [turing.tape.map_fst, g₂₁ q h, f₂₁ _],
rcases M q T.1 with _|⟨q', d|a⟩, {refl},
{ simp only [step, cfg.map, option.map_some', tape.map_move f₁], refl },
{ simp only [step, cfg.map, option.map_some', tape.map_write], refl }
end
theorem map_init (g₁ : pointed_map Λ Λ') (l : list Γ) :
(init l).map f₁ g₁ = init (l.map f₁) :=
congr (congr_arg cfg.mk g₁.map_pt) (tape.map_mk₁ _ _)
theorem machine.map_respects
(g₁ : pointed_map Λ Λ') (g₂ : Λ' → Λ)
{S} (ss : supports M S)
(f₂₁ : function.right_inverse f₁ f₂)
(g₂₁ : ∀ q ∈ S, g₂ (g₁ q) = q) :
respects (step M) (step (M.map f₁ f₂ g₁ g₂))
(λ a b, a.q ∈ S ∧ cfg.map f₁ g₁ a = b)
| c _ ⟨cs, rfl⟩ := begin
cases e : step M c with c'; unfold respects,
{ rw [← M.map_step f₁ f₂ g₁ g₂ f₂₁ g₂₁ _ cs, e], refl },
{ refine ⟨_, ⟨step_supports M ss e cs, rfl⟩, trans_gen.single _⟩,
rw [← M.map_step f₁ f₂ g₁ g₂ f₂₁ g₂₁ _ cs, e], exact rfl }
end
end
end TM0
/-!
## The TM1 model
The TM1 model is a simplification and extension of TM0 (Post-Turing model) in the direction of
Wang B-machines. The machine's internal state is extended with a (finite) store `σ` of variables
that may be accessed and updated at any time.
A machine is given by a `Λ` indexed set of procedures or functions. Each function has a body which
is a `stmt`. Most of the regular commands are allowed to use the current value `a` of the local
variables and the value `T.head` on the tape to calculate what to write or how to change local
state, but the statements themselves have a fixed structure. The `stmt`s can be as follows:
* `move d q`: move left or right, and then do `q`
* `write (f : Γ → σ → Γ) q`: write `f a T.head` to the tape, then do `q`
* `load (f : Γ → σ → σ) q`: change the internal state to `f a T.head`
* `branch (f : Γ → σ → bool) qtrue qfalse`: If `f a T.head` is true, do `qtrue`, else `qfalse`
* `goto (f : Γ → σ → Λ)`: Go to label `f a T.head`
* `halt`: Transition to the halting state, which halts on the following step
Note that here most statements do not have labels; `goto` commands can only go to a new function.
Only the `goto` and `halt` statements actually take a step; the rest is done by recursion on
statements and so take 0 steps. (There is a uniform bound on many statements can be executed before
the next `goto`, so this is an `O(1)` speedup with the constant depending on the machine.)
The `halt` command has a one step stutter before actually halting so that any changes made before
the halt have a chance to be "committed", since the `eval` relation uses the final configuration
before the halt as the output, and `move` and `write` etc. take 0 steps in this model.
-/
namespace TM1
section
parameters (Γ : Type*) [inhabited Γ] -- Type of tape symbols
parameters (Λ : Type*) -- Type of function labels
parameters (σ : Type*) -- Type of variable settings
/-- The TM1 model is a simplification and extension of TM0
(Post-Turing model) in the direction of Wang B-machines. The machine's
internal state is extended with a (finite) store `σ` of variables
that may be accessed and updated at any time.
A machine is given by a `Λ` indexed set of procedures or functions.
Each function has a body which is a `stmt`, which can either be a
`move` or `write` command, a `branch` (if statement based on the
current tape value), a `load` (set the variable value),
a `goto` (call another function), or `halt`. Note that here
most statements do not have labels; `goto` commands can only
go to a new function. All commands have access to the variable value
and current tape value. -/
inductive stmt
| move : dir → stmt → stmt
| write : (Γ → σ → Γ) → stmt → stmt
| load : (Γ → σ → σ) → stmt → stmt
| branch : (Γ → σ → bool) → stmt → stmt → stmt
| goto : (Γ → σ → Λ) → stmt
| halt : stmt
open stmt
instance stmt.inhabited : inhabited stmt := ⟨halt⟩
/-- The configuration of a TM1 machine is given by the currently
evaluating statement, the variable store value, and the tape. -/
structure cfg :=
(l : option Λ)
(var : σ)
(tape : tape Γ)
instance cfg.inhabited [inhabited σ] : inhabited cfg := ⟨⟨default _, default _, default _⟩⟩
parameters {Γ Λ σ}
/-- The semantics of TM1 evaluation. -/
def step_aux : stmt → σ → tape Γ → cfg
| (move d q) v T := step_aux q v (T.move d)
| (write a q) v T := step_aux q v (T.write (a T.1 v))
| (load s q) v T := step_aux q (s T.1 v) T
| (branch p q₁ q₂) v T := cond (p T.1 v) (step_aux q₁ v T) (step_aux q₂ v T)
| (goto l) v T := ⟨some (l T.1 v), v, T⟩
| halt v T := ⟨none, v, T⟩
/-- The state transition function. -/
def step (M : Λ → stmt) : cfg → option cfg
| ⟨none, v, T⟩ := none
| ⟨some l, v, T⟩ := some (step_aux (M l) v T)
/-- A set `S` of labels supports the statement `q` if all the `goto`
statements in `q` refer only to other functions in `S`. -/
def supports_stmt (S : finset Λ) : stmt → Prop
| (move d q) := supports_stmt q
| (write a q) := supports_stmt q
| (load s q) := supports_stmt q
| (branch p q₁ q₂) := supports_stmt q₁ ∧ supports_stmt q₂
| (goto l) := ∀ a v, l a v ∈ S
| halt := true
open_locale classical
/-- The subterm closure of a statement. -/
noncomputable def stmts₁ : stmt → finset stmt
| Q@(move d q) := insert Q (stmts₁ q)
| Q@(write a q) := insert Q (stmts₁ q)
| Q@(load s q) := insert Q (stmts₁ q)
| Q@(branch p q₁ q₂) := insert Q (stmts₁ q₁ ∪ stmts₁ q₂)
| Q := {Q}
theorem stmts₁_self {q} : q ∈ stmts₁ q :=
by cases q; apply_rules [finset.mem_insert_self, finset.mem_singleton_self]
theorem stmts₁_trans {q₁ q₂} :
q₁ ∈ stmts₁ q₂ → stmts₁ q₁ ⊆ stmts₁ q₂ :=
begin
intros h₁₂ q₀ h₀₁,
induction q₂ with _ q IH _ q IH _ q IH;
simp only [stmts₁] at h₁₂ ⊢;
simp only [finset.mem_insert, finset.mem_union, finset.mem_singleton] at h₁₂,
iterate 3 {
rcases h₁₂ with rfl | h₁₂,
{ unfold stmts₁ at h₀₁, exact h₀₁ },
{ exact finset.mem_insert_of_mem (IH h₁₂) } },
case TM1.stmt.branch : p q₁ q₂ IH₁ IH₂ {
rcases h₁₂ with rfl | h₁₂ | h₁₂,
{ unfold stmts₁ at h₀₁, exact h₀₁ },
{ exact finset.mem_insert_of_mem (finset.mem_union_left _ $ IH₁ h₁₂) },
{ exact finset.mem_insert_of_mem (finset.mem_union_right _ $ IH₂ h₁₂) } },
case TM1.stmt.goto : l {
subst h₁₂, exact h₀₁ },
case TM1.stmt.halt {
subst h₁₂, exact h₀₁ }
end
theorem stmts₁_supports_stmt_mono {S q₁ q₂}
(h : q₁ ∈ stmts₁ q₂) (hs : supports_stmt S q₂) : supports_stmt S q₁ :=
begin
induction q₂ with _ q IH _ q IH _ q IH;
simp only [stmts₁, supports_stmt, finset.mem_insert, finset.mem_union,
finset.mem_singleton] at h hs,
iterate 3 { rcases h with rfl | h; [exact hs, exact IH h hs] },
case TM1.stmt.branch : p q₁ q₂ IH₁ IH₂ {
rcases h with rfl | h | h, exacts [hs, IH₁ h hs.1, IH₂ h hs.2] },
case TM1.stmt.goto : l { subst h, exact hs },
case TM1.stmt.halt { subst h, trivial }
end
/-- The set of all statements in a turing machine, plus one extra value `none` representing the
halt state. This is used in the TM1 to TM0 reduction. -/
noncomputable def stmts (M : Λ → stmt) (S : finset Λ) : finset (option stmt) :=
(S.bUnion (λ q, stmts₁ (M q))).insert_none
theorem stmts_trans {M : Λ → stmt} {S q₁ q₂}
(h₁ : q₁ ∈ stmts₁ q₂) : some q₂ ∈ stmts M S → some q₁ ∈ stmts M S :=
by simp only [stmts, finset.mem_insert_none, finset.mem_bUnion,
option.mem_def, forall_eq', exists_imp_distrib];
exact λ l ls h₂, ⟨_, ls, stmts₁_trans h₂ h₁⟩
variable [inhabited Λ]
/-- A set `S` of labels supports machine `M` if all the `goto`
statements in the functions in `S` refer only to other functions
in `S`. -/
def supports (M : Λ → stmt) (S : finset Λ) :=
default Λ ∈ S ∧ ∀ q ∈ S, supports_stmt S (M q)
theorem stmts_supports_stmt {M : Λ → stmt} {S q}
(ss : supports M S) : some q ∈ stmts M S → supports_stmt S q :=
by simp only [stmts, finset.mem_insert_none, finset.mem_bUnion,
option.mem_def, forall_eq', exists_imp_distrib];
exact λ l ls h, stmts₁_supports_stmt_mono h (ss.2 _ ls)
theorem step_supports (M : Λ → stmt) {S}
(ss : supports M S) : ∀ {c c' : cfg},
c' ∈ step M c → c.l ∈ S.insert_none → c'.l ∈ S.insert_none
| ⟨some l₁, v, T⟩ c' h₁ h₂ := begin
replace h₂ := ss.2 _ (finset.some_mem_insert_none.1 h₂),
simp only [step, option.mem_def] at h₁, subst c',
revert h₂, induction M l₁ with _ q IH _ q IH _ q IH generalizing v T;
intro hs,
iterate 3 { exact IH _ _ hs },
case TM1.stmt.branch : p q₁' q₂' IH₁ IH₂ {
unfold step_aux, cases p T.1 v,
{ exact IH₂ _ _ hs.2 },
{ exact IH₁ _ _ hs.1 } },
case TM1.stmt.goto { exact finset.some_mem_insert_none.2 (hs _ _) },
case TM1.stmt.halt { apply multiset.mem_cons_self }
end
variable [inhabited σ]
/-- The initial state, given a finite input that is placed on the tape starting at the TM head and
going to the right. -/
def init (l : list Γ) : cfg :=
⟨some (default _), default _, tape.mk₁ l⟩
/-- Evaluate a TM to completion, resulting in an output list on the tape (with an indeterminate
number of blanks on the end). -/
def eval (M : Λ → stmt) (l : list Γ) : roption (list_blank Γ) :=
(eval (step M) (init l)).map (λ c, c.tape.right₀)
end
end TM1
/-!
## TM1 emulator in TM0
To prove that TM1 computable functions are TM0 computable, we need to reduce each TM1 program to a
TM0 program. So suppose a TM1 program is given. We take the following:
* The alphabet `Γ` is the same for both TM1 and TM0
* The set of states `Λ'` is defined to be `option stmt₁ × σ`, that is, a TM1 statement or `none`
representing halt, and the possible settings of the internal variables.
Note that this is an infinite set, because `stmt₁` is infinite. This is okay because we assume
that from the initial TM1 state, only finitely many other labels are reachable, and there are
only finitely many statements that appear in all of these functions.
Even though `stmt₁` contains a statement called `halt`, we must separate it from `none`
(`some halt` steps to `none` and `none` actually halts) because there is a one step stutter in the
TM1 semantics.
-/
namespace TM1to0
section
parameters {Γ : Type*} [inhabited Γ]
parameters {Λ : Type*} [inhabited Λ]
parameters {σ : Type*} [inhabited σ]
local notation `stmt₁` := TM1.stmt Γ Λ σ
local notation `cfg₁` := TM1.cfg Γ Λ σ
local notation `stmt₀` := TM0.stmt Γ
parameters (M : Λ → stmt₁)
include M
/-- The base machine state space is a pair of an `option stmt₁` representing the current program
to be executed, or `none` for the halt state, and a `σ` which is the local state (stored in the TM,
not the tape). Because there are an infinite number of programs, this state space is infinite, but
for a finitely supported TM1 machine and a finite type `σ`, only finitely many of these states are
reachable. -/
@[nolint unused_arguments] -- [inhabited Λ] [inhabited σ] (M : Λ → stmt₁): We need the M assumption
-- because of the inhabited instance, but we could avoid the inhabited instances on Λ and σ here.
-- But they are parameters so we cannot easily skip them for just this definition.
def Λ' := option stmt₁ × σ
instance : inhabited Λ' := ⟨(some (M (default _)), default _)⟩
open TM0.stmt
/-- The core TM1 → TM0 translation function. Here `s` is the current value on the tape, and the
`stmt₁` is the TM1 statement to translate, with local state `v : σ`. We evaluate all regular
instructions recursively until we reach either a `move` or `write` command, or a `goto`; in the
latter case we emit a dummy `write s` step and transition to the new target location. -/
def tr_aux (s : Γ) : stmt₁ → σ → Λ' × stmt₀
| (TM1.stmt.move d q) v := ((some q, v), move d)
| (TM1.stmt.write a q) v := ((some q, v), write (a s v))
| (TM1.stmt.load a q) v := tr_aux q (a s v)
| (TM1.stmt.branch p q₁ q₂) v := cond (p s v) (tr_aux q₁ v) (tr_aux q₂ v)
| (TM1.stmt.goto l) v := ((some (M (l s v)), v), write s)
| TM1.stmt.halt v := ((none, v), write s)
local notation `cfg₀` := TM0.cfg Γ Λ'
/-- The translated TM0 machine (given the TM1 machine input). -/
def tr : TM0.machine Γ Λ'
| (none, v) s := none
| (some q, v) s := some (tr_aux s q v)
/-- Translate configurations from TM1 to TM0. -/
def tr_cfg : cfg₁ → cfg₀
| ⟨l, v, T⟩ := ⟨(l.map M, v), T⟩
theorem tr_respects : respects (TM1.step M) (TM0.step tr)
(λ c₁ c₂, tr_cfg c₁ = c₂) :=
fun_respects.2 $ λ ⟨l₁, v, T⟩, begin
cases l₁ with l₁, {exact rfl},
unfold tr_cfg TM1.step frespects option.map function.comp option.bind,
induction M l₁ with _ q IH _ q IH _ q IH generalizing v T,
case TM1.stmt.move : d q IH { exact trans_gen.head rfl (IH _ _) },
case TM1.stmt.write : a q IH { exact trans_gen.head rfl (IH _ _) },
case TM1.stmt.load : a q IH { exact (reaches₁_eq (by refl)).2 (IH _ _) },
case TM1.stmt.branch : p q₁ q₂ IH₁ IH₂ {
unfold TM1.step_aux, cases e : p T.1 v,
{ exact (reaches₁_eq (by simp only [TM0.step, tr, tr_aux, e]; refl)).2 (IH₂ _ _) },
{ exact (reaches₁_eq (by simp only [TM0.step, tr, tr_aux, e]; refl)).2 (IH₁ _ _) } },
iterate 2 {
exact trans_gen.single (congr_arg some
(congr (congr_arg TM0.cfg.mk rfl) (tape.write_self T))) }
end
theorem tr_eval (l : list Γ) : TM0.eval tr l = TM1.eval M l :=
(congr_arg _ (tr_eval' _ _ _ tr_respects ⟨some _, _, _⟩)).trans begin
rw [roption.map_eq_map, roption.map_map, TM1.eval],
congr' with ⟨⟩, refl
end
variables [fintype σ]
/-- Given a finite set of accessible `Λ` machine states, there is a finite set of accessible
machine states in the target (even though the type `Λ'` is infinite). -/
noncomputable def tr_stmts (S : finset Λ) : finset Λ' :=
(TM1.stmts M S).product finset.univ
open_locale classical
local attribute [simp] TM1.stmts₁_self
theorem tr_supports {S : finset Λ} (ss : TM1.supports M S) :
TM0.supports tr (↑(tr_stmts S)) :=
⟨finset.mem_product.2 ⟨finset.some_mem_insert_none.2
(finset.mem_bUnion.2 ⟨_, ss.1, TM1.stmts₁_self⟩),
finset.mem_univ _⟩,
λ q a q' s h₁ h₂, begin
rcases q with ⟨_|q, v⟩, {cases h₁},
cases q' with q' v', simp only [tr_stmts, finset.mem_coe,
finset.mem_product, finset.mem_univ, and_true] at h₂ ⊢,
cases q', {exact multiset.mem_cons_self _ _},
simp only [tr, option.mem_def] at h₁,
have := TM1.stmts_supports_stmt ss h₂,
revert this, induction q generalizing v; intro hs,
case TM1.stmt.move : d q {
cases h₁, refine TM1.stmts_trans _ h₂,
unfold TM1.stmts₁,
exact finset.mem_insert_of_mem TM1.stmts₁_self },
case TM1.stmt.write : b q {
cases h₁, refine TM1.stmts_trans _ h₂,
unfold TM1.stmts₁,
exact finset.mem_insert_of_mem TM1.stmts₁_self },
case TM1.stmt.load : b q IH {
refine IH (TM1.stmts_trans _ h₂) _ h₁ hs,
unfold TM1.stmts₁,
exact finset.mem_insert_of_mem TM1.stmts₁_self },
case TM1.stmt.branch : p q₁ q₂ IH₁ IH₂ {
change cond (p a v) _ _ = ((some q', v'), s) at h₁,
cases p a v,
{ refine IH₂ (TM1.stmts_trans _ h₂) _ h₁ hs.2,
unfold TM1.stmts₁,
exact finset.mem_insert_of_mem (finset.mem_union_right _ TM1.stmts₁_self) },
{ refine IH₁ (TM1.stmts_trans _ h₂) _ h₁ hs.1,
unfold TM1.stmts₁,
exact finset.mem_insert_of_mem (finset.mem_union_left _ TM1.stmts₁_self) } },
case TM1.stmt.goto : l {
cases h₁, exact finset.some_mem_insert_none.2
(finset.mem_bUnion.2 ⟨_, hs _ _, TM1.stmts₁_self⟩) },
case TM1.stmt.halt { cases h₁ }
end⟩
end
end TM1to0
/-!
## TM1(Γ) emulator in TM1(bool)
The most parsimonious Turing machine model that is still Turing complete is `TM0` with `Γ = bool`.
Because our construction in the previous section reducing `TM1` to `TM0` doesn't change the
alphabet, we can do the alphabet reduction on `TM1` instead of `TM0` directly.
The basic idea is to use a bijection between `Γ` and a subset of `vector bool n`, where `n` is a
fixed constant. Each tape element is represented as a block of `n` bools. Whenever the machine
wants to read a symbol from the tape, it traverses over the block, performing `n` `branch`
instructions to each any of the `2^n` results.
For the `write` instruction, we have to use a `goto` because we need to follow a different code
path depending on the local state, which is not available in the TM1 model, so instead we jump to
a label computed using the read value and the local state, which performs the writing and returns
to normal execution.
Emulation overhead is `O(1)`. If not for the above `write` behavior it would be 1-1 because we are
exploiting the 0-step behavior of regular commands to avoid taking steps, but there are
nevertheless a bounded number of `write` calls between `goto` statements because TM1 statements are
finitely long.
-/
namespace TM1to1
open TM1
section
parameters {Γ : Type*} [inhabited Γ]
theorem exists_enc_dec [fintype Γ] :
∃ n (enc : Γ → vector bool n) (dec : vector bool n → Γ),
enc (default _) = vector.repeat ff n ∧ ∀ a, dec (enc a) = a :=
begin
rcases fintype.exists_equiv_fin Γ with ⟨n, ⟨F⟩⟩,
let G : fin n ↪ fin n → bool := ⟨λ a b, a = b,
λ a b h, of_to_bool_true $ (congr_fun h b).trans $ to_bool_tt rfl⟩,
let H := (F.to_embedding.trans G).trans
(equiv.vector_equiv_fin _ _).symm.to_embedding,
classical,
let enc := H.set_value (default _) (vector.repeat ff n),
exact ⟨_, enc, function.inv_fun enc,
H.set_value_eq _ _, function.left_inverse_inv_fun enc.2⟩
end
parameters {Λ : Type*} [inhabited Λ]
parameters {σ : Type*} [inhabited σ]
local notation `stmt₁` := stmt Γ Λ σ
local notation `cfg₁` := cfg Γ Λ σ
/-- The configuration state of the TM. -/
inductive Λ' : Type (max u_1 u_2 u_3)
| normal : Λ → Λ'
| write : Γ → stmt₁ → Λ'
instance : inhabited Λ' := ⟨Λ'.normal (default _)⟩
local notation `stmt'` := stmt bool Λ' σ
local notation `cfg'` := cfg bool Λ' σ
/-- Read a vector of length `n` from the tape. -/
def read_aux : ∀ n, (vector bool n → stmt') → stmt'
| 0 f := f vector.nil
| (i+1) f := stmt.branch (λ a s, a)
(stmt.move dir.right $ read_aux i (λ v, f (tt ::ᵥ v)))
(stmt.move dir.right $ read_aux i (λ v, f (ff ::ᵥ v)))
parameters {n : ℕ} (enc : Γ → vector bool n) (dec : vector bool n → Γ)
/-- A move left or right corresponds to `n` moves across the super-cell. -/
def move (d : dir) (q : stmt') : stmt' := (stmt.move d)^[n] q
/-- To read a symbol from the tape, we use `read_aux` to traverse the symbol,
then return to the original position with `n` moves to the left. -/
def read (f : Γ → stmt') : stmt' :=
read_aux n (λ v, move dir.left $ f (dec v))
/-- Write a list of bools on the tape. -/
def write : list bool → stmt' → stmt'
| [] q := q
| (a :: l) q := stmt.write (λ _ _, a) $ stmt.move dir.right $ write l q
/-- Translate a normal instruction. For the `write` command, we use a `goto` indirection so that
we can access the current value of the tape. -/
def tr_normal : stmt₁ → stmt'
| (stmt.move d q) := move d $ tr_normal q
| (stmt.write f q) := read $ λ a, stmt.goto $ λ _ s, Λ'.write (f a s) q
| (stmt.load f q) := read $ λ a, stmt.load (λ _ s, f a s) $ tr_normal q
| (stmt.branch p q₁ q₂) := read $ λ a, stmt.branch (λ _ s, p a s) (tr_normal q₁) (tr_normal q₂)
| (stmt.goto l) := read $ λ a, stmt.goto $ λ _ s, Λ'.normal (l a s)
| stmt.halt := stmt.halt
theorem step_aux_move (d q v T) :
step_aux (move d q) v T =
step_aux q v ((tape.move d)^[n] T) :=
begin
suffices : ∀ i,
step_aux (stmt.move d^[i] q) v T =
step_aux q v (tape.move d^[i] T), from this n,
intro, induction i with i IH generalizing T, {refl},
rw [iterate_succ', step_aux, IH, iterate_succ]
end
theorem supports_stmt_move {S d q} :
supports_stmt S (move d q) = supports_stmt S q :=
suffices ∀ {i}, supports_stmt S (stmt.move d^[i] q) = _, from this,
by intro; induction i generalizing q; simp only [*, iterate]; refl
theorem supports_stmt_write {S l q} :
supports_stmt S (write l q) = supports_stmt S q :=
by induction l with a l IH; simp only [write, supports_stmt, *]
theorem supports_stmt_read {S} : ∀ {f : Γ → stmt'},
(∀ a, supports_stmt S (f a)) → supports_stmt S (read f) :=
suffices ∀ i (f : vector bool i → stmt'),
(∀ v, supports_stmt S (f v)) → supports_stmt S (read_aux i f),
from λ f hf, this n _ (by intro; simp only [supports_stmt_move, hf]),
λ i f hf, begin
induction i with i IH, {exact hf _},
split; apply IH; intro; apply hf,
end
parameter (enc0 : enc (default _) = vector.repeat ff n)
section
parameter {enc}
include enc0
/-- The low level tape corresponding to the given tape over alphabet `Γ`. -/
def tr_tape' (L R : list_blank Γ) : tape bool :=
begin
refine tape.mk'
(L.bind (λ x, (enc x).to_list.reverse) ⟨n, _⟩)
(R.bind (λ x, (enc x).to_list) ⟨n, _⟩);
simp only [enc0, vector.repeat,
list.reverse_repeat, bool.default_bool, vector.to_list_mk]
end
/-- The low level tape corresponding to the given tape over alphabet `Γ`. -/
def tr_tape (T : tape Γ) : tape bool := tr_tape' T.left T.right₀
theorem tr_tape_mk' (L R : list_blank Γ) : tr_tape (tape.mk' L R) = tr_tape' L R :=
by simp only [tr_tape, tape.mk'_left, tape.mk'_right₀]
end
parameters (M : Λ → stmt₁)
/-- The top level program. -/
def tr : Λ' → stmt'
| (Λ'.normal l) := tr_normal (M l)
| (Λ'.write a q) := write (enc a).to_list $ move dir.left $ tr_normal q
/-- The machine configuration translation. -/
def tr_cfg : cfg₁ → cfg'
| ⟨l, v, T⟩ := ⟨l.map Λ'.normal, v, tr_tape T⟩
parameter {enc}
include enc0
theorem tr_tape'_move_left (L R) :
(tape.move dir.left)^[n] (tr_tape' L R) =
(tr_tape' L.tail (R.cons L.head)) :=
begin
obtain ⟨a, L, rfl⟩ := L.exists_cons,
simp only [tr_tape', list_blank.cons_bind, list_blank.head_cons, list_blank.tail_cons],
suffices : ∀ {L' R' l₁ l₂}
(e : vector.to_list (enc a) = list.reverse_core l₁ l₂),
tape.move dir.left^[l₁.length]
(tape.mk' (list_blank.append l₁ L') (list_blank.append l₂ R')) =
tape.mk' L' (list_blank.append (vector.to_list (enc a)) R'),
{ simpa only [list.length_reverse, vector.to_list_length]
using this (list.reverse_reverse _).symm },
intros, induction l₁ with b l₁ IH generalizing l₂,
{ cases e, refl },
simp only [list.length, list.cons_append, iterate_succ_apply],
convert IH e,
simp only [list_blank.tail_cons, list_blank.append, tape.move_left_mk', list_blank.head_cons]
end
theorem tr_tape'_move_right (L R) :
(tape.move dir.right)^[n] (tr_tape' L R) =
(tr_tape' (L.cons R.head) R.tail) :=
begin
suffices : ∀ i L, (tape.move dir.right)^[i] ((tape.move dir.left)^[i] L) = L,
{ refine (eq.symm _).trans (this n _),
simp only [tr_tape'_move_left, list_blank.cons_head_tail,
list_blank.head_cons, list_blank.tail_cons] },
intros, induction i with i IH, {refl},
rw [iterate_succ_apply, iterate_succ_apply', tape.move_left_right, IH]
end
theorem step_aux_write (q v a b L R) :
step_aux (write (enc a).to_list q) v (tr_tape' L (list_blank.cons b R)) =
step_aux q v (tr_tape' (list_blank.cons a L) R) :=
begin
simp only [tr_tape', list.cons_bind, list.append_assoc],
suffices : ∀ {L' R'} (l₁ l₂ l₂' : list bool)
(e : l₂'.length = l₂.length),
step_aux (write l₂ q) v (tape.mk' (list_blank.append l₁ L') (list_blank.append l₂' R')) =
step_aux q v (tape.mk' (L'.append (list.reverse_core l₂ l₁)) R'),
{ convert this [] _ _ ((enc b).2.trans (enc a).2.symm);
rw list_blank.cons_bind; refl },
clear a b L R, intros,
induction l₂ with a l₂ IH generalizing l₁ l₂',
{ cases list.length_eq_zero.1 e, refl },
cases l₂' with b l₂'; injection e with e,
dunfold write step_aux,
convert IH _ _ e using 1,
simp only [list_blank.head_cons, list_blank.tail_cons,
list_blank.append, tape.move_right_mk', tape.write_mk']
end
parameters (encdec : ∀ a, dec (enc a) = a)
include encdec
theorem step_aux_read (f v L R) :
step_aux (read f) v (tr_tape' L R) =
step_aux (f R.head) v (tr_tape' L R) :=
begin
suffices : ∀ f,
step_aux (read_aux n f) v (tr_tape' enc0 L R) =
step_aux (f (enc R.head)) v
(tr_tape' enc0 (L.cons R.head) R.tail),
{ rw [read, this, step_aux_move, encdec, tr_tape'_move_left enc0],
simp only [list_blank.head_cons, list_blank.cons_head_tail, list_blank.tail_cons] },
obtain ⟨a, R, rfl⟩ := R.exists_cons,
simp only [list_blank.head_cons, list_blank.tail_cons,
tr_tape', list_blank.cons_bind, list_blank.append_assoc],
suffices : ∀ i f L' R' l₁ l₂ h,
step_aux (read_aux i f) v
(tape.mk' (list_blank.append l₁ L') (list_blank.append l₂ R')) =
step_aux (f ⟨l₂, h⟩) v
(tape.mk' (list_blank.append (l₂.reverse_core l₁) L') R'),
{ intro f, convert this n f _ _ _ _ (enc a).2; simp },
clear f L a R, intros, subst i,
induction l₂ with a l₂ IH generalizing l₁, {refl},
transitivity step_aux
(read_aux l₂.length (λ v, f (a ::ᵥ v))) v
(tape.mk' ((L'.append l₁).cons a) (R'.append l₂)),
{ dsimp [read_aux, step_aux], simp, cases a; refl },
rw [← list_blank.append, IH], refl
end
theorem tr_respects : respects (step M) (step tr)
(λ c₁ c₂, tr_cfg c₁ = c₂) :=
fun_respects.2 $ λ ⟨l₁, v, T⟩, begin
obtain ⟨L, R, rfl⟩ := T.exists_mk',
cases l₁ with l₁, {exact rfl},
suffices : ∀ q R, reaches (step (tr enc dec M))
(step_aux (tr_normal dec q) v (tr_tape' enc0 L R))
(tr_cfg enc0 (step_aux q v (tape.mk' L R))),
{ refine trans_gen.head' rfl _, rw tr_tape_mk', exact this _ R },
clear R l₁, intros,
induction q with _ q IH _ q IH _ q IH generalizing v L R,
case TM1.stmt.move : d q IH {
cases d; simp only [tr_normal, iterate, step_aux_move, step_aux,
list_blank.head_cons, tape.move_left_mk',
list_blank.cons_head_tail, list_blank.tail_cons,
tr_tape'_move_left enc0, tr_tape'_move_right enc0];
apply IH },
case TM1.stmt.write : f q IH {
simp only [tr_normal, step_aux_read dec enc0 encdec, step_aux],
refine refl_trans_gen.head rfl _,
obtain ⟨a, R, rfl⟩ := R.exists_cons,
rw [tr, tape.mk'_head, step_aux_write, list_blank.head_cons,
step_aux_move, tr_tape'_move_left enc0, list_blank.head_cons,
list_blank.tail_cons, tape.write_mk'],
apply IH },
case TM1.stmt.load : a q IH {
simp only [tr_normal, step_aux_read dec enc0 encdec],
apply IH },
case TM1.stmt.branch : p q₁ q₂ IH₁ IH₂ {
simp only [tr_normal, step_aux_read dec enc0 encdec, step_aux],
cases p R.head v; [apply IH₂, apply IH₁] },
case TM1.stmt.goto : l {
simp only [tr_normal, step_aux_read dec enc0 encdec, step_aux, tr_cfg, tr_tape_mk'],
apply refl_trans_gen.refl },
case TM1.stmt.halt {
simp only [tr_normal, step_aux, tr_cfg, step_aux_move,
tr_tape'_move_left enc0, tr_tape'_move_right enc0, tr_tape_mk'],
apply refl_trans_gen.refl }
end
omit enc0 encdec
open_locale classical
parameters [fintype Γ]
/-- The set of accessible `Λ'.write` machine states. -/
noncomputable def writes : stmt₁ → finset Λ'
| (stmt.move d q) := writes q
| (stmt.write f q) := finset.univ.image (λ a, Λ'.write a q) ∪ writes q
| (stmt.load f q) := writes q
| (stmt.branch p q₁ q₂) := writes q₁ ∪ writes q₂
| (stmt.goto l) := ∅
| stmt.halt := ∅
/-- The set of accessible machine states, assuming that the input machine is supported on `S`,
are the normal states embedded from `S`, plus all write states accessible from these states. -/
noncomputable def tr_supp (S : finset Λ) : finset Λ' :=
S.bUnion (λ l, insert (Λ'.normal l) (writes (M l)))
theorem tr_supports {S} (ss : supports M S) :
supports tr (tr_supp S) :=
⟨finset.mem_bUnion.2 ⟨_, ss.1, finset.mem_insert_self _ _⟩,
λ q h, begin
suffices : ∀ q, supports_stmt S q →
(∀ q' ∈ writes q, q' ∈ tr_supp M S) →
supports_stmt (tr_supp M S) (tr_normal dec q) ∧
∀ q' ∈ writes q, supports_stmt (tr_supp M S) (tr enc dec M q'),
{ rcases finset.mem_bUnion.1 h with ⟨l, hl, h⟩,
have := this _ (ss.2 _ hl) (λ q' hq,
finset.mem_bUnion.2 ⟨_, hl, finset.mem_insert_of_mem hq⟩),
rcases finset.mem_insert.1 h with rfl | h,
exacts [this.1, this.2 _ h] },
intros q hs hw, induction q,
case TM1.stmt.move : d q IH {
unfold writes at hw ⊢,
replace IH := IH hs hw, refine ⟨_, IH.2⟩,
cases d; simp only [tr_normal, iterate, supports_stmt_move, IH] },
case TM1.stmt.write : f q IH {
unfold writes at hw ⊢,
simp only [finset.mem_image, finset.mem_union, finset.mem_univ,
exists_prop, true_and] at hw ⊢,
replace IH := IH hs (λ q hq, hw q (or.inr hq)),
refine ⟨supports_stmt_read _ $ λ a _ s,
hw _ (or.inl ⟨_, rfl⟩), λ q' hq, _⟩,
rcases hq with ⟨a, q₂, rfl⟩ | hq,
{ simp only [tr, supports_stmt_write, supports_stmt_move, IH.1] },
{ exact IH.2 _ hq } },
case TM1.stmt.load : a q IH {
unfold writes at hw ⊢,
replace IH := IH hs hw,
refine ⟨supports_stmt_read _ (λ a, IH.1), IH.2⟩ },
case TM1.stmt.branch : p q₁ q₂ IH₁ IH₂ {
unfold writes at hw ⊢,
simp only [finset.mem_union] at hw ⊢,
replace IH₁ := IH₁ hs.1 (λ q hq, hw q (or.inl hq)),
replace IH₂ := IH₂ hs.2 (λ q hq, hw q (or.inr hq)),
exact ⟨supports_stmt_read _ (λ a, ⟨IH₁.1, IH₂.1⟩),
λ q, or.rec (IH₁.2 _) (IH₂.2 _)⟩ },
case TM1.stmt.goto : l {
refine ⟨_, λ _, false.elim⟩,
refine supports_stmt_read _ (λ a _ s, _),
exact finset.mem_bUnion.2 ⟨_, hs _ _, finset.mem_insert_self _ _⟩ },
case TM1.stmt.halt {
refine ⟨_, λ _, false.elim⟩,
simp only [supports_stmt, supports_stmt_move, tr_normal] }
end⟩
end
end TM1to1
/-!
## TM0 emulator in TM1
To establish that TM0 and TM1 are equivalent computational models, we must also have a TM0 emulator
in TM1. The main complication here is that TM0 allows an action to depend on the value at the head
and local state, while TM1 doesn't (in order to have more programming language-like semantics).
So we use a computed `goto` to go to a state that performes the desired action and then returns to
normal execution.
One issue with this is that the `halt` instruction is supposed to halt immediately, not take a step
to a halting state. To resolve this we do a check for `halt` first, then `goto` (with an
unreachable branch).
-/
namespace TM0to1
section
parameters {Γ : Type*} [inhabited Γ]
parameters {Λ : Type*} [inhabited Λ]
/-- The machine states for a TM1 emulating a TM0 machine. States of the TM0 machine are embedded
as `normal q` states, but the actual operation is split into two parts, a jump to `act s q`
followed by the action and a jump to the next `normal` state. -/
inductive Λ'
| normal : Λ → Λ'
| act : TM0.stmt Γ → Λ → Λ'
instance : inhabited Λ' := ⟨Λ'.normal (default _)⟩
local notation `cfg₀` := TM0.cfg Γ Λ
local notation `stmt₁` := TM1.stmt Γ Λ' unit
local notation `cfg₁` := TM1.cfg Γ Λ' unit
parameters (M : TM0.machine Γ Λ)
open TM1.stmt
/-- The program. -/
def tr : Λ' → stmt₁
| (Λ'.normal q) :=
branch (λ a _, (M q a).is_none) halt $
goto (λ a _, match M q a with
| none := default _ -- unreachable
| some (q', s) := Λ'.act s q'
end)
| (Λ'.act (TM0.stmt.move d) q) := move d $ goto (λ _ _, Λ'.normal q)
| (Λ'.act (TM0.stmt.write a) q) := write (λ _ _, a) $ goto (λ _ _, Λ'.normal q)
/-- The configuration translation. -/
def tr_cfg : cfg₀ → cfg₁
| ⟨q, T⟩ := ⟨cond (M q T.1).is_some (some (Λ'.normal q)) none, (), T⟩
theorem tr_respects : respects (TM0.step M) (TM1.step tr)
(λ a b, tr_cfg a = b) :=
fun_respects.2 $ λ ⟨q, T⟩, begin
cases e : M q T.1,
{ simp only [TM0.step, tr_cfg, e]; exact eq.refl none },
cases val with q' s,
simp only [frespects, TM0.step, tr_cfg, e, option.is_some, cond, option.map_some'],
have : TM1.step (tr M) ⟨some (Λ'.act s q'), (), T⟩ =
some ⟨some (Λ'.normal q'), (), TM0.step._match_1 T s⟩,
{ cases s with d a; refl },
refine trans_gen.head _ (trans_gen.head' this _),
{ unfold TM1.step TM1.step_aux tr has_mem.mem,
rw e, refl },
cases e' : M q' _,
{ apply refl_trans_gen.single,
unfold TM1.step TM1.step_aux tr has_mem.mem,
rw e', refl },
{ refl }
end
end
end TM0to1
/-!
## The TM2 model
The TM2 model removes the tape entirely from the TM1 model, replacing it with an arbitrary (finite)
collection of stacks, each with elements of different types (the alphabet of stack `k : K` is
`Γ k`). The statements are:
* `push k (f : σ → Γ k) q` puts `f a` on the `k`-th stack, then does `q`.
* `pop k (f : σ → option (Γ k) → σ) q` changes the state to `f a (S k).head`, where `S k` is the
value of the `k`-th stack, and removes this element from the stack, then does `q`.
* `peek k (f : σ → option (Γ k) → σ) q` changes the state to `f a (S k).head`, where `S k` is the
value of the `k`-th stack, then does `q`.
* `load (f : σ → σ) q` reads nothing but applies `f` to the internal state, then does `q`.
* `branch (f : σ → bool) qtrue qfalse` does `qtrue` or `qfalse` according to `f a`.
* `goto (f : σ → Λ)` jumps to label `f a`.
* `halt` halts on the next step.
The configuration is a tuple `(l, var, stk)` where `l : option Λ` is the current label to run or
`none` for the halting state, `var : σ` is the (finite) internal state, and `stk : ∀ k, list (Γ k)`
is the collection of stacks. (Note that unlike the `TM0` and `TM1` models, these are not
`list_blank`s, they have definite ends that can be detected by the `pop` command.)
Given a designated stack `k` and a value `L : list (Γ k)`, the initial configuration has all the
stacks empty except the designated "input" stack; in `eval` this designated stack also functions
as the output stack.
-/
namespace TM2
section
parameters {K : Type*} [decidable_eq K] -- Index type of stacks
parameters (Γ : K → Type*) -- Type of stack elements
parameters (Λ : Type*) -- Type of function labels
parameters (σ : Type*) -- Type of variable settings
/-- The TM2 model removes the tape entirely from the TM1 model,
replacing it with an arbitrary (finite) collection of stacks.
The operation `push` puts an element on one of the stacks,
and `pop` removes an element from a stack (and modifying the
internal state based on the result). `peek` modifies the
internal state but does not remove an element. -/
inductive stmt
| push : ∀ k, (σ → Γ k) → stmt → stmt
| peek : ∀ k, (σ → option (Γ k) → σ) → stmt → stmt
| pop : ∀ k, (σ → option (Γ k) → σ) → stmt → stmt
| load : (σ → σ) → stmt → stmt
| branch : (σ → bool) → stmt → stmt → stmt
| goto : (σ → Λ) → stmt
| halt : stmt
open stmt
instance stmt.inhabited : inhabited stmt := ⟨halt⟩
/-- A configuration in the TM2 model is a label (or `none` for the halt state), the state of
local variables, and the stacks. (Note that the stacks are not `list_blank`s, they have a definite
size.) -/
structure cfg :=
(l : option Λ)
(var : σ)
(stk : ∀ k, list (Γ k))
instance cfg.inhabited [inhabited σ] : inhabited cfg := ⟨⟨default _, default _, default _⟩⟩
parameters {Γ Λ σ K}
/-- The step function for the TM2 model. -/
@[simp] def step_aux : stmt → σ → (∀ k, list (Γ k)) → cfg
| (push k f q) v S := step_aux q v (update S k (f v :: S k))
| (peek k f q) v S := step_aux q (f v (S k).head') S
| (pop k f q) v S := step_aux q (f v (S k).head') (update S k (S k).tail)
| (load a q) v S := step_aux q (a v) S
| (branch f q₁ q₂) v S :=
cond (f v) (step_aux q₁ v S) (step_aux q₂ v S)
| (goto f) v S := ⟨some (f v), v, S⟩
| halt v S := ⟨none, v, S⟩
/-- The step function for the TM2 model. -/
@[simp] def step (M : Λ → stmt) : cfg → option cfg
| ⟨none, v, S⟩ := none
| ⟨some l, v, S⟩ := some (step_aux (M l) v S)
/-- The (reflexive) reachability relation for the TM2 model. -/
def reaches (M : Λ → stmt) : cfg → cfg → Prop :=
refl_trans_gen (λ a b, b ∈ step M a)
/-- Given a set `S` of states, `support_stmt S q` means that `q` only jumps to states in `S`. -/
def supports_stmt (S : finset Λ) : stmt → Prop
| (push k f q) := supports_stmt q
| (peek k f q) := supports_stmt q
| (pop k f q) := supports_stmt q
| (load a q) := supports_stmt q
| (branch f q₁ q₂) := supports_stmt q₁ ∧ supports_stmt q₂
| (goto l) := ∀ v, l v ∈ S
| halt := true
open_locale classical
/-- The set of subtree statements in a statement. -/
noncomputable def stmts₁ : stmt → finset stmt
| Q@(push k f q) := insert Q (stmts₁ q)
| Q@(peek k f q) := insert Q (stmts₁ q)
| Q@(pop k f q) := insert Q (stmts₁ q)
| Q@(load a q) := insert Q (stmts₁ q)
| Q@(branch f q₁ q₂) := insert Q (stmts₁ q₁ ∪ stmts₁ q₂)
| Q@(goto l) := {Q}
| Q@halt := {Q}
theorem stmts₁_self {q} : q ∈ stmts₁ q :=
by cases q; apply_rules [finset.mem_insert_self, finset.mem_singleton_self]
theorem stmts₁_trans {q₁ q₂} :
q₁ ∈ stmts₁ q₂ → stmts₁ q₁ ⊆ stmts₁ q₂ :=
begin
intros h₁₂ q₀ h₀₁,
induction q₂ with _ _ q IH _ _ q IH _ _ q IH _ q IH;
simp only [stmts₁] at h₁₂ ⊢;
simp only [finset.mem_insert, finset.mem_singleton, finset.mem_union] at h₁₂,
iterate 4 {
rcases h₁₂ with rfl | h₁₂,
{ unfold stmts₁ at h₀₁, exact h₀₁ },
{ exact finset.mem_insert_of_mem (IH h₁₂) } },
case TM2.stmt.branch : f q₁ q₂ IH₁ IH₂ {
rcases h₁₂ with rfl | h₁₂ | h₁₂,
{ unfold stmts₁ at h₀₁, exact h₀₁ },
{ exact finset.mem_insert_of_mem (finset.mem_union_left _ (IH₁ h₁₂)) },
{ exact finset.mem_insert_of_mem (finset.mem_union_right _ (IH₂ h₁₂)) } },
case TM2.stmt.goto : l {
subst h₁₂, exact h₀₁ },
case TM2.stmt.halt {
subst h₁₂, exact h₀₁ }
end
theorem stmts₁_supports_stmt_mono {S q₁ q₂}
(h : q₁ ∈ stmts₁ q₂) (hs : supports_stmt S q₂) : supports_stmt S q₁ :=
begin
induction q₂ with _ _ q IH _ _ q IH _ _ q IH _ q IH;
simp only [stmts₁, supports_stmt, finset.mem_insert, finset.mem_union,
finset.mem_singleton] at h hs,
iterate 4 { rcases h with rfl | h; [exact hs, exact IH h hs] },
case TM2.stmt.branch : f q₁ q₂ IH₁ IH₂ {
rcases h with rfl | h | h, exacts [hs, IH₁ h hs.1, IH₂ h hs.2] },
case TM2.stmt.goto : l { subst h, exact hs },
case TM2.stmt.halt { subst h, trivial }
end
/-- The set of statements accessible from initial set `S` of labels. -/
noncomputable def stmts (M : Λ → stmt) (S : finset Λ) : finset (option stmt) :=
(S.bUnion (λ q, stmts₁ (M q))).insert_none
theorem stmts_trans {M : Λ → stmt} {S q₁ q₂}
(h₁ : q₁ ∈ stmts₁ q₂) : some q₂ ∈ stmts M S → some q₁ ∈ stmts M S :=
by simp only [stmts, finset.mem_insert_none, finset.mem_bUnion,
option.mem_def, forall_eq', exists_imp_distrib];
exact λ l ls h₂, ⟨_, ls, stmts₁_trans h₂ h₁⟩
variable [inhabited Λ]
/-- Given a TM2 machine `M` and a set `S` of states, `supports M S` means that all states in
`S` jump only to other states in `S`. -/
def supports (M : Λ → stmt) (S : finset Λ) :=
default Λ ∈ S ∧ ∀ q ∈ S, supports_stmt S (M q)
theorem stmts_supports_stmt {M : Λ → stmt} {S q}
(ss : supports M S) : some q ∈ stmts M S → supports_stmt S q :=
by simp only [stmts, finset.mem_insert_none, finset.mem_bUnion,
option.mem_def, forall_eq', exists_imp_distrib];
exact λ l ls h, stmts₁_supports_stmt_mono h (ss.2 _ ls)
theorem step_supports (M : Λ → stmt) {S}
(ss : supports M S) : ∀ {c c' : cfg},
c' ∈ step M c → c.l ∈ S.insert_none → c'.l ∈ S.insert_none
| ⟨some l₁, v, T⟩ c' h₁ h₂ := begin
replace h₂ := ss.2 _ (finset.some_mem_insert_none.1 h₂),
simp only [step, option.mem_def] at h₁, subst c',
revert h₂, induction M l₁ with _ _ q IH _ _ q IH _ _ q IH _ q IH generalizing v T;
intro hs,
iterate 4 { exact IH _ _ hs },
case TM2.stmt.branch : p q₁' q₂' IH₁ IH₂ {
unfold step_aux, cases p v,
{ exact IH₂ _ _ hs.2 },
{ exact IH₁ _ _ hs.1 } },
case TM2.stmt.goto { exact finset.some_mem_insert_none.2 (hs _) },
case TM2.stmt.halt { apply multiset.mem_cons_self }
end
variable [inhabited σ]
/-- The initial state of the TM2 model. The input is provided on a designated stack. -/
def init (k) (L : list (Γ k)) : cfg :=
⟨some (default _), default _, update (λ _, []) k L⟩
/-- Evaluates a TM2 program to completion, with the output on the same stack as the input. -/
def eval (M : Λ → stmt) (k) (L : list (Γ k)) : roption (list (Γ k)) :=
(eval (step M) (init k L)).map $ λ c, c.stk k
end
end TM2
/-!
## TM2 emulator in TM1
To prove that TM2 computable functions are TM1 computable, we need to reduce each TM2 program to a
TM1 program. So suppose a TM2 program is given. This program has to maintain a whole collection of
stacks, but we have only one tape, so we must "multiplex" them all together. Pictorially, if stack
1 contains `[a, b]` and stack 2 contains `[c, d, e, f]` then the tape looks like this:
```
bottom: ... | _ | T | _ | _ | _ | _ | ...
stack 1: ... | _ | b | a | _ | _ | _ | ...
stack 2: ... | _ | f | e | d | c | _ | ...
```
where a tape element is a vertical slice through the diagram. Here the alphabet is
`Γ' := bool × ∀ k, option (Γ k)`, where:
* `bottom : bool` is marked only in one place, the initial position of the TM, and represents the
tail of all stacks. It is never modified.
* `stk k : option (Γ k)` is the value of the `k`-th stack, if in range, otherwise `none` (which is
the blank value). Note that the head of the stack is at the far end; this is so that push and pop
don't have to do any shifting.
In "resting" position, the TM is sitting at the position marked `bottom`. For non-stack actions,
it operates in place, but for the stack actions `push`, `peek`, and `pop`, it must shuttle to the
end of the appropriate stack, make its changes, and then return to the bottom. So the states are:
* `normal (l : Λ)`: waiting at `bottom` to execute function `l`
* `go k (s : st_act k) (q : stmt₂)`: travelling to the right to get to the end of stack `k` in
order to perform stack action `s`, and later continue with executing `q`
* `ret (q : stmt₂)`: travelling to the left after having performed a stack action, and executing
`q` once we arrive
Because of the shuttling, emulation overhead is `O(n)`, where `n` is the current maximum of the
length of all stacks. Therefore a program that takes `k` steps to run in TM2 takes `O((m+k)k)`
steps to run when emulated in TM1, where `m` is the length of the input.
-/
namespace TM2to1
-- A displaced lemma proved in unnecessary generality
theorem stk_nth_val {K : Type*} {Γ : K → Type*} {L : list_blank (∀ k, option (Γ k))} {k S} (n)
(hL : list_blank.map (proj k) L = list_blank.mk (list.map some S).reverse) :
L.nth n k = S.reverse.nth n :=
begin
rw [← proj_map_nth, hL, ← list.map_reverse, list_blank.nth_mk, list.inth, list.nth_map],
cases S.reverse.nth n; refl
end
section
parameters {K : Type*} [decidable_eq K]
parameters {Γ : K → Type*}
parameters {Λ : Type*} [inhabited Λ]
parameters {σ : Type*} [inhabited σ]
local notation `stmt₂` := TM2.stmt Γ Λ σ
local notation `cfg₂` := TM2.cfg Γ Λ σ
/-- The alphabet of the TM2 simulator on TM1 is a marker for the stack bottom,
plus a vector of stack elements for each stack, or none if the stack does not extend this far. -/
@[nolint unused_arguments] -- [decidable_eq K]: Because K is a parameter, we cannot easily skip
-- the decidable_eq assumption, and this is a local definition anyway so it's not important.
def Γ' := bool × ∀ k, option (Γ k)
instance Γ'.inhabited : inhabited Γ' := ⟨⟨ff, λ _, none⟩⟩
instance Γ'.fintype [fintype K] [∀ k, fintype (Γ k)] : fintype Γ' :=
prod.fintype _ _
/-- The bottom marker is fixed throughout the calculation, so we use the `add_bottom` function
to express the program state in terms of a tape with only the stacks themselves. -/
def add_bottom (L : list_blank (∀ k, option (Γ k))) : list_blank Γ' :=
list_blank.cons (tt, L.head) (L.tail.map ⟨prod.mk ff, rfl⟩)
theorem add_bottom_map (L) : (add_bottom L).map ⟨prod.snd, rfl⟩ = L :=
begin
simp only [add_bottom, list_blank.map_cons]; convert list_blank.cons_head_tail _,
generalize : list_blank.tail L = L',
refine L'.induction_on _, intro l, simp,
rw (_ : _ ∘ _ = id), {simp},
funext a, refl
end
theorem add_bottom_modify_nth (f : (∀ k, option (Γ k)) → (∀ k, option (Γ k))) (L n) :
(add_bottom L).modify_nth (λ a, (a.1, f a.2)) n = add_bottom (L.modify_nth f n) :=
begin
cases n; simp only [add_bottom,
list_blank.head_cons, list_blank.modify_nth, list_blank.tail_cons],
congr, symmetry, apply list_blank.map_modify_nth, intro, refl
end
theorem add_bottom_nth_snd (L n) : ((add_bottom L).nth n).2 = L.nth n :=
by conv {to_rhs, rw [← add_bottom_map L, list_blank.nth_map]}; refl
theorem add_bottom_nth_succ_fst (L n) : ((add_bottom L).nth (n+1)).1 = ff :=
by rw [list_blank.nth_succ, add_bottom, list_blank.tail_cons, list_blank.nth_map]; refl
theorem add_bottom_head_fst (L) : (add_bottom L).head.1 = tt :=
by rw [add_bottom, list_blank.head_cons]; refl
/-- A stack action is a command that interacts with the top of a stack. Our default position
is at the bottom of all the stacks, so we have to hold on to this action while going to the end
to modify the stack. -/
inductive st_act (k : K)
| push : (σ → Γ k) → st_act
| peek : (σ → option (Γ k) → σ) → st_act
| pop : (σ → option (Γ k) → σ) → st_act
instance st_act.inhabited {k} : inhabited (st_act k) := ⟨st_act.peek (λ s _, s)⟩
section
open st_act
/-- The TM2 statement corresponding to a stack action. -/
@[nolint unused_arguments] -- [inhabited Λ]: as this is a local definition it is more trouble than
-- it is worth to omit the typeclass assumption without breaking the parameters
def st_run {k : K} : st_act k → stmt₂ → stmt₂
| (push f) := TM2.stmt.push k f
| (peek f) := TM2.stmt.peek k f
| (pop f) := TM2.stmt.pop k f
/-- The effect of a stack action on the local variables, given the value of the stack. -/
def st_var {k : K} (v : σ) (l : list (Γ k)) : st_act k → σ
| (push f) := v
| (peek f) := f v l.head'
| (pop f) := f v l.head'
/-- The effect of a stack action on the stack. -/
def st_write {k : K} (v : σ) (l : list (Γ k)) : st_act k → list (Γ k)
| (push f) := f v :: l
| (peek f) := l
| (pop f) := l.tail
/-- We have partitioned the TM2 statements into "stack actions", which require going to the end
of the stack, and all other actions, which do not. This is a modified recursor which lumps the
stack actions into one. -/
@[elab_as_eliminator] def {l} stmt_st_rec
{C : stmt₂ → Sort l}
(H₁ : Π k (s : st_act k) q (IH : C q), C (st_run s q))
(H₂ : Π a q (IH : C q), C (TM2.stmt.load a q))
(H₃ : Π p q₁ q₂ (IH₁ : C q₁) (IH₂ : C q₂), C (TM2.stmt.branch p q₁ q₂))
(H₄ : Π l, C (TM2.stmt.goto l))
(H₅ : C TM2.stmt.halt) : ∀ n, C n
| (TM2.stmt.push k f q) := H₁ _ (push f) _ (stmt_st_rec q)
| (TM2.stmt.peek k f q) := H₁ _ (peek f) _ (stmt_st_rec q)
| (TM2.stmt.pop k f q) := H₁ _ (pop f) _ (stmt_st_rec q)
| (TM2.stmt.load a q) := H₂ _ _ (stmt_st_rec q)
| (TM2.stmt.branch a q₁ q₂) := H₃ _ _ _ (stmt_st_rec q₁) (stmt_st_rec q₂)
| (TM2.stmt.goto l) := H₄ _
| TM2.stmt.halt := H₅
theorem supports_run (S : finset Λ) {k} (s : st_act k) (q) :
TM2.supports_stmt S (st_run s q) ↔ TM2.supports_stmt S q :=
by rcases s with _|_|_; refl
end
/-- The machine states of the TM2 emulator. We can either be in a normal state when waiting for the
next TM2 action, or we can be in the "go" and "return" states to go to the top of the stack and
return to the bottom, respectively. -/
inductive Λ' : Type (max u_1 u_2 u_3 u_4)
| normal : Λ → Λ'
| go (k) : st_act k → stmt₂ → Λ'
| ret : stmt₂ → Λ'
open Λ'
instance Λ'.inhabited : inhabited Λ' := ⟨normal (default _)⟩
local notation `stmt₁` := TM1.stmt Γ' Λ' σ
local notation `cfg₁` := TM1.cfg Γ' Λ' σ
open TM1.stmt
/-- The program corresponding to state transitions at the end of a stack. Here we start out just
after the top of the stack, and should end just after the new top of the stack. -/
def tr_st_act {k} (q : stmt₁) : st_act k → stmt₁
| (st_act.push f) := write (λ a s, (a.1, update a.2 k $ some $ f s)) $ move dir.right q
| (st_act.peek f) := move dir.left $ load (λ a s, f s (a.2 k)) $ move dir.right q
| (st_act.pop f) :=
branch (λ a _, a.1)
( load (λ a s, f s none) q )
( move dir.left $
load (λ a s, f s (a.2 k)) $
write (λ a s, (a.1, update a.2 k none)) q )
/-- The initial state for the TM2 emulator, given an initial TM2 state. All stacks start out empty
except for the input stack, and the stack bottom mark is set at the head. -/
def tr_init (k) (L : list (Γ k)) : list Γ' :=
let L' : list Γ' := L.reverse.map (λ a, (ff, update (λ _, none) k a)) in
(tt, L'.head.2) :: L'.tail
theorem step_run {k : K} (q v S) : ∀ s : st_act k,
TM2.step_aux (st_run s q) v S =
TM2.step_aux q (st_var v (S k) s) (update S k (st_write v (S k) s))
| (st_act.push f) := rfl
| (st_act.peek f) := by unfold st_write; rw function.update_eq_self; refl
| (st_act.pop f) := rfl
/-- The translation of TM2 statements to TM1 statements. regular actions have direct equivalents,
but stack actions are deferred by going to the corresponding `go` state, so that we can find the
appropriate stack top. -/
def tr_normal : stmt₂ → stmt₁
| (TM2.stmt.push k f q) := goto (λ _ _, go k (st_act.push f) q)
| (TM2.stmt.peek k f q) := goto (λ _ _, go k (st_act.peek f) q)
| (TM2.stmt.pop k f q) := goto (λ _ _, go k (st_act.pop f) q)
| (TM2.stmt.load a q) := load (λ _, a) (tr_normal q)
| (TM2.stmt.branch f q₁ q₂) := branch (λ a, f) (tr_normal q₁) (tr_normal q₂)
| (TM2.stmt.goto l) := goto (λ a s, normal (l s))
| TM2.stmt.halt := halt
theorem tr_normal_run {k} (s q) : tr_normal (st_run s q) = goto (λ _ _, go k s q) :=
by rcases s with _|_|_; refl
open_locale classical
/-- The set of machine states accessible from an initial TM2 statement. -/
noncomputable def tr_stmts₁ : stmt₂ → finset Λ'
| Q@(TM2.stmt.push k f q) := {go k (st_act.push f) q, ret q} ∪ tr_stmts₁ q
| Q@(TM2.stmt.peek k f q) := {go k (st_act.peek f) q, ret q} ∪ tr_stmts₁ q
| Q@(TM2.stmt.pop k f q) := {go k (st_act.pop f) q, ret q} ∪ tr_stmts₁ q
| Q@(TM2.stmt.load a q) := tr_stmts₁ q
| Q@(TM2.stmt.branch f q₁ q₂) := tr_stmts₁ q₁ ∪ tr_stmts₁ q₂
| _ := ∅
theorem tr_stmts₁_run {k s q} : tr_stmts₁ (st_run s q) = {go k s q, ret q} ∪ tr_stmts₁ q :=
by rcases s with _|_|_; unfold tr_stmts₁ st_run
theorem tr_respects_aux₂
{k q v} {S : Π k, list (Γ k)} {L : list_blank (∀ k, option (Γ k))}
(hL : ∀ k, L.map (proj k) = list_blank.mk ((S k).map some).reverse) (o) :
let v' := st_var v (S k) o,
Sk' := st_write v (S k) o,
S' := update S k Sk' in
∃ (L' : list_blank (∀ k, option (Γ k))),
(∀ k, L'.map (proj k) = list_blank.mk ((S' k).map some).reverse) ∧
TM1.step_aux (tr_st_act q o) v
((tape.move dir.right)^[(S k).length] (tape.mk' ∅ (add_bottom L))) =
TM1.step_aux q v'
((tape.move dir.right)^[(S' k).length] (tape.mk' ∅ (add_bottom L'))) :=
begin
dsimp only, simp, cases o;
simp only [st_write, st_var, tr_st_act, TM1.step_aux],
case TM2to1.st_act.push : f {
have := tape.write_move_right_n (λ a : Γ', (a.1, update a.2 k (some (f v)))),
dsimp only at this,
refine ⟨_, λ k', _, by rw [
tape.move_right_n_head, list.length, tape.mk'_nth_nat, this,
add_bottom_modify_nth (λ a, update a k (some (f v))),
nat.add_one, iterate_succ']⟩,
refine list_blank.ext (λ i, _),
rw [list_blank.nth_map, list_blank.nth_modify_nth, proj, pointed_map.mk_val],
by_cases h' : k' = k,
{ subst k', split_ifs; simp only [list.reverse_cons,
function.update_same, list_blank.nth_mk, list.inth, list.map],
{ rw [list.nth_le_nth, list.nth_le_append_right];
simp only [h, list.nth_le_singleton, list.length_map, list.length_reverse, nat.succ_pos',
list.length_append, lt_add_iff_pos_right, list.length] },
rw [← proj_map_nth, hL, list_blank.nth_mk, list.inth],
cases decidable.lt_or_gt_of_ne h with h h,
{ rw list.nth_append, simpa only [list.length_map, list.length_reverse] using h },
{ rw [list.nth_len_le, list.nth_len_le];
simp only [nat.add_one_le_iff, h, list.length, le_of_lt,
list.length_reverse, list.length_append, list.length_map] } },
{ split_ifs; rw [function.update_noteq h', ← proj_map_nth, hL],
rw function.update_noteq h' } },
case TM2to1.st_act.peek : f {
rw function.update_eq_self,
use [L, hL], rw [tape.move_left_right], congr,
cases e : S k, {refl},
rw [list.length_cons, iterate_succ', tape.move_right_left, tape.move_right_n_head,
tape.mk'_nth_nat, add_bottom_nth_snd, stk_nth_val _ (hL k), e,
list.reverse_cons, ← list.length_reverse, list.nth_concat_length], refl },
case TM2to1.st_act.pop : f {
cases e : S k,
{ simp only [tape.mk'_head, list_blank.head_cons, tape.move_left_mk',
list.length, tape.write_mk', list.head', iterate_zero_apply, list.tail_nil],
rw [← e, function.update_eq_self], exact ⟨L, hL, by rw [add_bottom_head_fst, cond]⟩ },
{ refine ⟨_, λ k', _, by rw [
list.length_cons, tape.move_right_n_head, tape.mk'_nth_nat, add_bottom_nth_succ_fst,
cond, iterate_succ', tape.move_right_left, tape.move_right_n_head, tape.mk'_nth_nat,
tape.write_move_right_n (λ a:Γ', (a.1, update a.2 k none)),
add_bottom_modify_nth (λ a, update a k none),
add_bottom_nth_snd, stk_nth_val _ (hL k), e,
show (list.cons hd tl).reverse.nth tl.length = some hd,
by rw [list.reverse_cons, ← list.length_reverse, list.nth_concat_length]; refl,
list.head', list.tail]⟩,
refine list_blank.ext (λ i, _),
rw [list_blank.nth_map, list_blank.nth_modify_nth, proj, pointed_map.mk_val],
by_cases h' : k' = k,
{ subst k', split_ifs; simp only [
function.update_same, list_blank.nth_mk, list.tail, list.inth],
{ rw [list.nth_len_le], {refl}, rw [h, list.length_reverse, list.length_map] },
rw [← proj_map_nth, hL, list_blank.nth_mk, list.inth, e, list.map, list.reverse_cons],
cases decidable.lt_or_gt_of_ne h with h h,
{ rw list.nth_append, simpa only [list.length_map, list.length_reverse] using h },
{ rw [list.nth_len_le, list.nth_len_le];
simp only [nat.add_one_le_iff, h, list.length, le_of_lt,
list.length_reverse, list.length_append, list.length_map] } },
{ split_ifs; rw [function.update_noteq h', ← proj_map_nth, hL],
rw function.update_noteq h' } } },
end
parameters (M : Λ → stmt₂)
include M
/-- The TM2 emulator machine states written as a TM1 program.
This handles the `go` and `ret` states, which shuttle to and from a stack top. -/
def tr : Λ' → stmt₁
| (normal q) := tr_normal (M q)
| (go k s q) :=
branch (λ a s, (a.2 k).is_none) (tr_st_act (goto (λ _ _, ret q)) s)
(move dir.right $ goto (λ _ _, go k s q))
| (ret q) :=
branch (λ a s, a.1) (tr_normal q)
(move dir.left $ goto (λ _ _, ret q))
local attribute [pp_using_anonymous_constructor] turing.TM1.cfg
/-- The relation between TM2 configurations and TM1 configurations of the TM2 emulator. -/
inductive tr_cfg : cfg₂ → cfg₁ → Prop
| mk {q v} {S : ∀ k, list (Γ k)} (L : list_blank (∀ k, option (Γ k))) :
(∀ k, L.map (proj k) = list_blank.mk ((S k).map some).reverse) →
tr_cfg ⟨q, v, S⟩ ⟨q.map normal, v, tape.mk' ∅ (add_bottom L)⟩
theorem tr_respects_aux₁ {k} (o q v) {S : list (Γ k)} {L : list_blank (∀ k, option (Γ k))}
(hL : L.map (proj k) = list_blank.mk (S.map some).reverse) (n ≤ S.length) :
reaches₀ (TM1.step tr)
⟨some (go k o q), v, (tape.mk' ∅ (add_bottom L))⟩
⟨some (go k o q), v, (tape.move dir.right)^[n] (tape.mk' ∅ (add_bottom L))⟩ :=
begin
induction n with n IH, {refl},
apply (IH (le_of_lt H)).tail,
rw iterate_succ_apply', simp only [TM1.step, TM1.step_aux, tr,
tape.mk'_nth_nat, tape.move_right_n_head, add_bottom_nth_snd,
option.mem_def],
rw [stk_nth_val _ hL, list.nth_le_nth], refl, rwa list.length_reverse
end
theorem tr_respects_aux₃ {q v} {L : list_blank (∀ k, option (Γ k))} (n) :
reaches₀ (TM1.step tr)
⟨some (ret q), v, (tape.move dir.right)^[n] (tape.mk' ∅ (add_bottom L))⟩
⟨some (ret q), v, (tape.mk' ∅ (add_bottom L))⟩ :=
begin
induction n with n IH, {refl},
refine reaches₀.head _ IH,
rw [option.mem_def, TM1.step, tr, TM1.step_aux, tape.move_right_n_head, tape.mk'_nth_nat,
add_bottom_nth_succ_fst, TM1.step_aux, iterate_succ', tape.move_right_left], refl,
end
theorem tr_respects_aux {q v T k} {S : Π k, list (Γ k)}
(hT : ∀ k, list_blank.map (proj k) T = list_blank.mk ((S k).map some).reverse)
(o : st_act k)
(IH : ∀ {v : σ} {S : Π (k : K), list (Γ k)} {T : list_blank (∀ k, option (Γ k))},
(∀ k, list_blank.map (proj k) T = list_blank.mk ((S k).map some).reverse) →
(∃ b, tr_cfg (TM2.step_aux q v S) b ∧
reaches (TM1.step tr) (TM1.step_aux (tr_normal q) v (tape.mk' ∅ (add_bottom T))) b)) :
∃ b, tr_cfg (TM2.step_aux (st_run o q) v S) b ∧
reaches (TM1.step tr) (TM1.step_aux (tr_normal (st_run o q))
v (tape.mk' ∅ (add_bottom T))) b :=
begin
simp only [tr_normal_run, step_run],
have hgo := tr_respects_aux₁ M o q v (hT k) _ (le_refl _),
obtain ⟨T', hT', hrun⟩ := tr_respects_aux₂ hT o,
have hret := tr_respects_aux₃ M _,
have := hgo.tail' rfl,
rw [tr, TM1.step_aux, tape.move_right_n_head, tape.mk'_nth_nat, add_bottom_nth_snd,
stk_nth_val _ (hT k), list.nth_len_le (le_of_eq (list.length_reverse _)),
option.is_none, cond, hrun, TM1.step_aux] at this,
obtain ⟨c, gc, rc⟩ := IH hT',
refine ⟨c, gc, (this.to₀.trans hret c (trans_gen.head' rfl _)).to_refl⟩,
rw [tr, TM1.step_aux, tape.mk'_head, add_bottom_head_fst],
exact rc,
end
local attribute [simp] respects TM2.step TM2.step_aux tr_normal
theorem tr_respects : respects (TM2.step M) (TM1.step tr) tr_cfg :=
λ c₁ c₂ h, begin
cases h with l v S L hT, clear h,
cases l, {constructor},
simp only [TM2.step, respects, option.map_some'],
suffices : ∃ b, _ ∧ reaches (TM1.step (tr M)) _ _,
from let ⟨b, c, r⟩ := this in ⟨b, c, trans_gen.head' rfl r⟩,
rw [tr],
revert v S L hT, refine stmt_st_rec _ _ _ _ _ (M l); intros,
{ exact tr_respects_aux M hT s @IH },
{ exact IH _ hT },
{ unfold TM2.step_aux tr_normal TM1.step_aux,
cases p v; [exact IH₂ _ hT, exact IH₁ _ hT] },
{ exact ⟨_, ⟨_, hT⟩, refl_trans_gen.refl⟩ },
{ exact ⟨_, ⟨_, hT⟩, refl_trans_gen.refl⟩ }
end
theorem tr_cfg_init (k) (L : list (Γ k)) :
tr_cfg (TM2.init k L) (TM1.init (tr_init k L)) :=
begin
rw (_ : TM1.init _ = _),
{ refine ⟨list_blank.mk (L.reverse.map $ λ a, update (default _) k (some a)), λ k', _⟩,
refine list_blank.ext (λ i, _),
rw [list_blank.map_mk, list_blank.nth_mk, list.inth, list.map_map, (∘),
list.nth_map, proj, pointed_map.mk_val],
by_cases k' = k,
{ subst k', simp only [function.update_same],
rw [list_blank.nth_mk, list.inth, ← list.map_reverse, list.nth_map] },
{ simp only [function.update_noteq h],
rw [list_blank.nth_mk, list.inth, list.map, list.reverse_nil, list.nth],
cases L.reverse.nth i; refl } },
{ rw [tr_init, TM1.init], dsimp only, congr; cases L.reverse; try {refl},
simp only [list.map_map, list.tail_cons, list.map], refl }
end
theorem tr_eval_dom (k) (L : list (Γ k)) :
(TM1.eval tr (tr_init k L)).dom ↔ (TM2.eval M k L).dom :=
tr_eval_dom tr_respects (tr_cfg_init _ _)
theorem tr_eval (k) (L : list (Γ k)) {L₁ L₂}
(H₁ : L₁ ∈ TM1.eval tr (tr_init k L))
(H₂ : L₂ ∈ TM2.eval M k L) :
∃ (S : ∀ k, list (Γ k)) (L' : list_blank (∀ k, option (Γ k))),
add_bottom L' = L₁ ∧
(∀ k, L'.map (proj k) = list_blank.mk ((S k).map some).reverse) ∧
S k = L₂ :=
begin
obtain ⟨c₁, h₁, rfl⟩ := (roption.mem_map_iff _).1 H₁,
obtain ⟨c₂, h₂, rfl⟩ := (roption.mem_map_iff _).1 H₂,
obtain ⟨_, ⟨q, v, S, L', hT⟩, h₃⟩ := tr_eval (tr_respects M) (tr_cfg_init M k L) h₂,
cases roption.mem_unique h₁ h₃,
exact ⟨S, L', by simp only [tape.mk'_right₀], hT, rfl⟩
end
/-- The support of a set of TM2 states in the TM2 emulator. -/
noncomputable def tr_supp (S : finset Λ) : finset Λ' :=
S.bUnion (λ l, insert (normal l) (tr_stmts₁ (M l)))
theorem tr_supports {S} (ss : TM2.supports M S) :
TM1.supports tr (tr_supp S) :=
⟨finset.mem_bUnion.2 ⟨_, ss.1, finset.mem_insert.2 $ or.inl rfl⟩,
λ l' h, begin
suffices : ∀ q (ss' : TM2.supports_stmt S q)
(sub : ∀ x ∈ tr_stmts₁ q, x ∈ tr_supp M S),
TM1.supports_stmt (tr_supp M S) (tr_normal q) ∧
(∀ l' ∈ tr_stmts₁ q, TM1.supports_stmt (tr_supp M S) (tr M l')),
{ rcases finset.mem_bUnion.1 h with ⟨l, lS, h⟩,
have := this _ (ss.2 l lS) (λ x hx,
finset.mem_bUnion.2 ⟨_, lS, finset.mem_insert_of_mem hx⟩),
rcases finset.mem_insert.1 h with rfl | h;
[exact this.1, exact this.2 _ h] },
clear h l', refine stmt_st_rec _ _ _ _ _; intros,
{ -- stack op
rw TM2to1.supports_run at ss',
simp only [TM2to1.tr_stmts₁_run, finset.mem_union,
finset.mem_insert, finset.mem_singleton] at sub,
have hgo := sub _ (or.inl $ or.inl rfl),
have hret := sub _ (or.inl $ or.inr rfl),
cases IH ss' (λ x hx, sub x $ or.inr hx) with IH₁ IH₂,
refine ⟨by simp only [tr_normal_run, TM1.supports_stmt]; intros; exact hgo, λ l h, _⟩,
rw [tr_stmts₁_run] at h,
simp only [TM2to1.tr_stmts₁_run, finset.mem_union,
finset.mem_insert, finset.mem_singleton] at h,
rcases h with ⟨rfl | rfl⟩ | h,
{ unfold TM1.supports_stmt TM2to1.tr,
rcases s with _|_|_,
{ exact ⟨λ _ _, hret, λ _ _, hgo⟩ },
{ exact ⟨λ _ _, hret, λ _ _, hgo⟩ },
{ exact ⟨⟨λ _ _, hret, λ _ _, hret⟩, λ _ _, hgo⟩ } },
{ unfold TM1.supports_stmt TM2to1.tr,
exact ⟨IH₁, λ _ _, hret⟩ },
{ exact IH₂ _ h } },
{ -- load
unfold TM2to1.tr_stmts₁ at ss' sub ⊢,
exact IH ss' sub },
{ -- branch
unfold TM2to1.tr_stmts₁ at sub,
cases IH₁ ss'.1 (λ x hx, sub x $ finset.mem_union_left _ hx) with IH₁₁ IH₁₂,
cases IH₂ ss'.2 (λ x hx, sub x $ finset.mem_union_right _ hx) with IH₂₁ IH₂₂,
refine ⟨⟨IH₁₁, IH₂₁⟩, λ l h, _⟩,
rw [tr_stmts₁] at h,
rcases finset.mem_union.1 h with h | h;
[exact IH₁₂ _ h, exact IH₂₂ _ h] },
{ -- goto
rw tr_stmts₁, unfold TM2to1.tr_normal TM1.supports_stmt,
unfold TM2.supports_stmt at ss',
exact ⟨λ _ v, finset.mem_bUnion.2 ⟨_, ss' v, finset.mem_insert_self _ _⟩, λ _, false.elim⟩ },
{ exact ⟨trivial, λ _, false.elim⟩ } -- halt
end⟩
end
end TM2to1
end turing
|
6bf69ccc7644d568a9a159b4e6410f77da059446 | 6dc0c8ce7a76229dd81e73ed4474f15f88a9e294 | /src/Lean/Data/Lsp/Diagnostics.lean | d2744731da5b990027123078b7749da901d9f650 | [
"Apache-2.0"
] | permissive | williamdemeo/lean4 | 72161c58fe65c3ad955d6a3050bb7d37c04c0d54 | 6d00fcf1d6d873e195f9220c668ef9c58e9c4a35 | refs/heads/master | 1,678,305,356,877 | 1,614,708,995,000 | 1,614,708,995,000 | null | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 3,247 | lean | /-
Copyright (c) 2020 Marc Huisinga. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Marc Huisinga, Wojciech Nawrocki
-/
import Lean.Data.Json
import Lean.Data.Lsp.Basic
import Lean.Data.Lsp.Utf16
import Lean.Message
/-! Definitions and functionality for emitting diagnostic information
such as errors, warnings and #command outputs from the LSP server. -/
namespace Lean
namespace Lsp
open Json
inductive DiagnosticSeverity where
| error | warning | information | hint
deriving Inhabited, BEq
instance : FromJson DiagnosticSeverity := ⟨fun j =>
match j.getNat? with
| some 1 => DiagnosticSeverity.error
| some 2 => DiagnosticSeverity.warning
| some 3 => DiagnosticSeverity.information
| some 4 => DiagnosticSeverity.hint
| _ => none⟩
instance : ToJson DiagnosticSeverity := ⟨fun
| DiagnosticSeverity.error => 1
| DiagnosticSeverity.warning => 2
| DiagnosticSeverity.information => 3
| DiagnosticSeverity.hint => 4⟩
inductive DiagnosticCode where
| int (i : Int)
| string (s : String)
deriving Inhabited, BEq
instance : FromJson DiagnosticCode := ⟨fun
| num (i : Int) => DiagnosticCode.int i
| str s => DiagnosticCode.string s
| _ => none⟩
instance : ToJson DiagnosticCode := ⟨fun
| DiagnosticCode.int i => i
| DiagnosticCode.string s => s⟩
inductive DiagnosticTag where
| unnecessary
| deprecated
deriving Inhabited, BEq
instance : FromJson DiagnosticTag := ⟨fun j =>
match j.getNat? with
| some 1 => DiagnosticTag.unnecessary
| some 2 => DiagnosticTag.deprecated
| _ => none⟩
instance : ToJson DiagnosticTag := ⟨fun
| DiagnosticTag.unnecessary => (1 : Nat)
| DiagnosticTag.deprecated => (2 : Nat)⟩
structure DiagnosticRelatedInformation where
location : Location
message : String
deriving Inhabited, BEq, ToJson, FromJson
structure Diagnostic where
range : Range
severity? : Option DiagnosticSeverity := none
code? : Option DiagnosticCode := none
source? : Option String := none
message : String
tags? : Option (Array DiagnosticTag) := none
relatedInformation? : Option (Array DiagnosticRelatedInformation) := none
deriving Inhabited, BEq, ToJson, FromJson
structure PublishDiagnosticsParams where
uri : DocumentUri
version? : Option Int := none
diagnostics: Array Diagnostic
deriving Inhabited, BEq, ToJson, FromJson
/-- Transform a Lean Message concerning the given text into an LSP Diagnostic. -/
def msgToDiagnostic (text : FileMap) (m : Message) : IO Diagnostic := do
let low : Lsp.Position := text.leanPosToLspPos m.pos
let high : Lsp.Position := match m.endPos with
| some endPos => text.leanPosToLspPos endPos
| none => low
let range : Range := ⟨low, high⟩
let severity := match m.severity with
| MessageSeverity.information => DiagnosticSeverity.information
| MessageSeverity.warning => DiagnosticSeverity.warning
| MessageSeverity.error => DiagnosticSeverity.error
let source := "Lean 4 server"
let message ← m.data.toString
pure {
range := range,
severity? := severity,
source? := source,
message := message
}
end Lsp
end Lean
|
654ccbc89b5bd94c0bdd6b74fe165be9166e8c5b | 8cae430f0a71442d02dbb1cbb14073b31048e4b0 | /src/data/set/enumerate.lean | 78fe97525dd956ee515b9d61f170f9a0a5537fda | [
"Apache-2.0"
] | permissive | leanprover-community/mathlib | 56a2cadd17ac88caf4ece0a775932fa26327ba0e | 442a83d738cb208d3600056c489be16900ba701d | refs/heads/master | 1,693,584,102,358 | 1,693,471,902,000 | 1,693,471,902,000 | 97,922,418 | 1,595 | 352 | Apache-2.0 | 1,694,693,445,000 | 1,500,624,130,000 | Lean | UTF-8 | Lean | false | false | 3,061 | lean | /-
Copyright (c) 2017 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl
-/
import data.set.lattice
import data.nat.order.basic
import tactic.wlog
/-!
# Set enumeration
> THIS FILE IS SYNCHRONIZED WITH MATHLIB4.
> Any changes to this file require a corresponding PR to mathlib4.
This file allows enumeration of sets given a choice function.
The definition does not assume `sel` actually is a choice function, i.e. `sel s ∈ s` and
`sel s = none ↔ s = ∅`. These assumptions are added to the lemmas needing them.
-/
noncomputable theory
open function
namespace set
section enumerate
parameters {α : Type*} (sel : set α → option α)
/-- Given a choice function `sel`, enumerates the elements of a set in the order
`a 0 = sel s`, `a 1 = sel (s \ {a 0})`, `a 2 = sel (s \ {a 0, a 1})`, ... and stops when
`sel (s \ {a 0, ..., a n}) = none`. Note that we don't require `sel` to be a choice function. -/
def enumerate : set α → ℕ → option α
| s 0 := sel s
| s (n + 1) := do a ← sel s, enumerate (s \ {a}) n
lemma enumerate_eq_none_of_sel {s : set α} (h : sel s = none) : ∀ {n}, enumerate s n = none
| 0 := by simp [h, enumerate]; refl
| (n + 1) := by simp [h, enumerate]; refl
lemma enumerate_eq_none : ∀ {s n₁ n₂}, enumerate s n₁ = none → n₁ ≤ n₂ → enumerate s n₂ = none
| s 0 m := λ h _, enumerate_eq_none_of_sel h
| s (n + 1) m := λ h hm,
begin
cases hs : sel s,
{ exact enumerate_eq_none_of_sel sel hs },
{ cases m,
case nat.zero
{ have : n + 1 = 0, from nat.eq_zero_of_le_zero hm,
contradiction },
case nat.succ : m'
{ simp [hs, enumerate] at h ⊢,
have hm : n ≤ m', from nat.le_of_succ_le_succ hm,
exact enumerate_eq_none h hm } }
end
lemma enumerate_mem (h_sel : ∀ s a, sel s = some a → a ∈ s) :
∀ {s n a}, enumerate s n = some a → a ∈ s
| s 0 a := h_sel s a
| s (n+1) a :=
begin
cases h : sel s,
case none { simp [enumerate_eq_none_of_sel, h] },
case some : a'
{ simp [enumerate, h],
exact λ h' : enumerate _ (s \ {a'}) n = some a,
have a ∈ s \ {a'}, from enumerate_mem h',
this.left }
end
lemma enumerate_inj {n₁ n₂ : ℕ} {a : α} {s : set α} (h_sel : ∀ s a, sel s = some a → a ∈ s)
(h₁ : enumerate s n₁ = some a) (h₂ : enumerate s n₂ = some a) : n₁ = n₂ :=
begin
wlog hn : n₁ ≤ n₂,
{ cases le_total n₁ n₂ with H H; [skip, symmetry]; apply_assumption; assumption },
{ rcases nat.le.dest hn with ⟨m, rfl⟩, clear hn,
induction n₁ generalizing s,
case nat.zero
{ cases m,
case nat.zero { refl },
case nat.succ : m
{ have : enumerate sel (s \ {a}) m = some a, { simp [enumerate, *] at * },
have : a ∈ s \ {a}, from enumerate_mem _ h_sel this,
by simpa } },
case nat.succ { cases h : sel s; simp [enumerate, nat.add_succ, add_comm, *] at *; tauto } }
end
end enumerate
end set
|
63d513891cfd7d64a09fad1fc9be849e3a18b864 | 9be442d9ec2fcf442516ed6e9e1660aa9071b7bd | /tests/lean/interactive/completion7.lean | 2c2abc6a514da962509d8772fa899dab33d29bac | [
"Apache-2.0",
"LLVM-exception",
"NCSA",
"LGPL-3.0-only",
"LicenseRef-scancode-inner-net-2.0",
"BSD-3-Clause",
"LGPL-2.0-or-later",
"Spencer-94",
"LGPL-2.1-or-later",
"HPND",
"LicenseRef-scancode-pcre",
"ISC",
"LGPL-2.1-only",
"LicenseRef-scancode-other-permissive",
"SunPro",
"CMU-Mach"... | permissive | EdAyers/lean4 | 57ac632d6b0789cb91fab2170e8c9e40441221bd | 37ba0df5841bde51dbc2329da81ac23d4f6a4de4 | refs/heads/master | 1,676,463,245,298 | 1,660,619,433,000 | 1,660,619,433,000 | 183,433,437 | 1 | 0 | Apache-2.0 | 1,657,612,672,000 | 1,556,196,574,000 | Lean | UTF-8 | Lean | false | false | 96 | lean | #check And
--^ textDocument/completion
#check And.
--^ textDocument/completion
|
081a452cb23e590d31b0f3fde06427261ab67329 | 35677d2df3f081738fa6b08138e03ee36bc33cad | /test/library_search/basic.lean | 2722c04970cdd16071c2432aaa7afa4a5e77b16d | [
"Apache-2.0"
] | permissive | gebner/mathlib | eab0150cc4f79ec45d2016a8c21750244a2e7ff0 | cc6a6edc397c55118df62831e23bfbd6e6c6b4ab | refs/heads/master | 1,625,574,853,976 | 1,586,712,827,000 | 1,586,712,827,000 | 99,101,412 | 1 | 0 | Apache-2.0 | 1,586,716,389,000 | 1,501,667,958,000 | Lean | UTF-8 | Lean | false | false | 2,569 | lean | /-
Copyright (c) 2018 Scott Morrison. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Scott Morrison
-/
import data.nat.basic
/- Turn off trace messages so they don't pollute the test build: -/
set_option trace.silence_library_search true
/- For debugging purposes, we can display the list of lemmas: -/
-- set_option trace.suggest true
namespace test.library_search
-- Check that `library_search` fails if there are no goals.
example : true :=
begin
trivial,
success_if_fail { library_search },
end
-- Verify that `library_search` solves goals via `solve_by_elim` when the library isn't
-- even needed.
example (P : Prop) (p : P) : P :=
by library_search
example (P : Prop) (p : P) (np : ¬P) : false :=
by library_search
example (X : Type) (P : Prop) (x : X) (h : Π x : X, x = x → P) : P :=
by library_search
def lt_one (n : ℕ) := n < 1
lemma zero_lt_one (n : ℕ) (h : n = 0) : lt_one n := by subst h; dsimp [lt_one]; simp
-- Verify that calls to solve_by_elim to discharge subgoals use `rfl`
example : lt_one 0 :=
by library_search
example (a b : ℕ) : a + b = b + a :=
by library_search -- says: `exact add_comm a b`
example {a b : ℕ} : a ≤ a + b :=
by library_search -- says: `exact nat.le.intro rfl`
example (n m k : ℕ) : n * (m - k) = n * m - n * k :=
by library_search -- says: `exact nat.mul_sub_left_distrib n m k`
-- TODO this doesn't work yet, and would require `library_search` to use `symmetry`
-- example (n m k : ℕ) : n * m - n * k = n * (m - k) :=
-- by library_search -- says: `exact eq.symm (nat.mul_sub_left_distrib n m k)`
example {n m : ℕ} (h : m < n) : m ≤ n - 1 :=
by library_search -- says: `exact nat.le_pred_of_lt h`
example {α : Type} (x y : α) : x = y ↔ y = x :=
by library_search -- says: `exact eq_comm`
example (a b : ℕ) (ha : 0 < a) (hb : 0 < b) : 0 < a + b :=
by library_search -- says: `exact add_pos ha hb`
example (a b : ℕ) : 0 < a → 0 < b → 0 < a + b :=
by library_search -- says: `exact add_pos`
example (a b : ℕ) (h : a ∣ b) (w : b > 0) : a ≤ b :=
by library_search -- says: `exact nat.le_of_dvd w h`
-- We even find `iff` results:
example : ∀ P : Prop, ¬(P ↔ ¬P) :=
by library_search -- says: `λ (a : Prop), (iff_not_self a).mp`
example {a b c : ℕ} (ha : a > 0) (w : b ∣ c) : a * b ∣ a * c :=
by library_search -- exact mul_dvd_mul_left a w
example {a b c : ℕ} (h₁ : a ∣ c) (h₂ : a ∣ b + c) : a ∣ b :=
by library_search -- says `exact (nat.dvd_add_left h₁).mp h₂`
end test.library_search
|
2fb848f2da23ba190370959c5c386323ade7f269 | 63abd62053d479eae5abf4951554e1064a4c45b4 | /src/topology/separation.lean | 8dd71dfa17655c4cf5e360a1279486744c9f8018 | [
"Apache-2.0"
] | permissive | Lix0120/mathlib | 0020745240315ed0e517cbf32e738d8f9811dd80 | e14c37827456fc6707f31b4d1d16f1f3a3205e91 | refs/heads/master | 1,673,102,855,024 | 1,604,151,044,000 | 1,604,151,044,000 | 308,930,245 | 0 | 0 | Apache-2.0 | 1,604,164,710,000 | 1,604,163,547,000 | null | UTF-8 | Lean | false | false | 23,700 | lean | /-
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
Separation properties of topological spaces.
-/
import topology.subset_properties
open set filter
open_locale topological_space filter
local attribute [instance] classical.prop_decidable -- TODO: use "open_locale classical"
universes u v
variables {α : Type u} {β : Type v} [topological_space α]
section separation
/-- A T₀ space, also known as a Kolmogorov space, is a topological space
where for every pair `x ≠ y`, there is an open set containing one but not the other. -/
class t0_space (α : Type u) [topological_space α] : Prop :=
(t0 : ∀ x y, x ≠ y → ∃ U:set α, is_open U ∧ (xor (x ∈ U) (y ∈ U)))
theorem exists_open_singleton_of_open_finset [t0_space α] (s : finset α) (sne : s.nonempty)
(hso : is_open (↑s : set α)) :
∃ x ∈ s, is_open ({x} : set α):=
begin
induction s using finset.strong_induction_on with s ihs,
by_cases hs : set.subsingleton (↑s : set α),
{ rcases sne with ⟨x, hx⟩,
refine ⟨x, hx, _⟩,
have : (↑s : set α) = {x}, from hs.eq_singleton_of_mem hx,
rwa this at hso },
{ dunfold set.subsingleton at hs,
push_neg at hs,
rcases hs with ⟨x, hx, y, hy, hxy⟩,
rcases t0_space.t0 x y hxy with ⟨U, hU, hxyU⟩,
wlog H : x ∈ U ∧ y ∉ U := hxyU using [x y, y x],
obtain ⟨z, hzs, hz⟩ : ∃ z ∈ s.filter (λ z, z ∈ U), is_open ({z} : set α),
{ refine ihs _ (finset.filter_ssubset.2 ⟨y, hy, H.2⟩) ⟨x, finset.mem_filter.2 ⟨hx, H.1⟩⟩ _,
rw [finset.coe_filter],
exact is_open_inter hso hU },
exact ⟨z, (finset.mem_filter.1 hzs).1, hz⟩ }
end
theorem exists_open_singleton_of_fintype [t0_space α] [f : fintype α] [ha : nonempty α] :
∃ x:α, is_open ({x}:set α) :=
begin
refine ha.elim (λ x, _),
have : is_open (↑(finset.univ : finset α) : set α), { simp },
rcases exists_open_singleton_of_open_finset _ ⟨x, finset.mem_univ x⟩ this with ⟨x, _, hx⟩,
exact ⟨x, hx⟩
end
instance subtype.t0_space [t0_space α] {p : α → Prop} : t0_space (subtype p) :=
⟨λ x y hxy, let ⟨U, hU, hxyU⟩ := t0_space.t0 (x:α) y ((not_congr subtype.ext_iff_val).1 hxy) in
⟨(coe : subtype p → α) ⁻¹' U, is_open_induced hU, hxyU⟩⟩
/-- A T₁ space, also known as a Fréchet space, is a topological space
where every singleton set is closed. Equivalently, for every pair
`x ≠ y`, there is an open set containing `x` and not `y`. -/
class t1_space (α : Type u) [topological_space α] : Prop :=
(t1 : ∀x, is_closed ({x} : set α))
lemma is_closed_singleton [t1_space α] {x : α} : is_closed ({x} : set α) :=
t1_space.t1 x
lemma is_open_ne [t1_space α] {x : α} : is_open {y | y ≠ x} :=
compl_singleton_eq x ▸ is_open_compl_iff.2 (t1_space.t1 x)
instance subtype.t1_space {α : Type u} [topological_space α] [t1_space α] {p : α → Prop} :
t1_space (subtype p) :=
⟨λ ⟨x, hx⟩, is_closed_induced_iff.2 $ ⟨{x}, is_closed_singleton, set.ext $ λ y,
by simp [subtype.ext_iff_val]⟩⟩
@[priority 100] -- see Note [lower instance priority]
instance t1_space.t0_space [t1_space α] : t0_space α :=
⟨λ x y h, ⟨{z | z ≠ y}, is_open_ne, or.inl ⟨h, not_not_intro rfl⟩⟩⟩
lemma compl_singleton_mem_nhds [t1_space α] {x y : α} (h : y ≠ x) : {x}ᶜ ∈ 𝓝 y :=
mem_nhds_sets is_closed_singleton $ by rwa [mem_compl_eq, mem_singleton_iff]
@[simp] lemma closure_singleton [t1_space α] {a : α} :
closure ({a} : set α) = {a} :=
is_closed_singleton.closure_eq
lemma is_closed_map_const {α β} [topological_space α] [topological_space β] [t1_space β] {y : β} :
is_closed_map (function.const α y) :=
begin
apply is_closed_map.of_nonempty, intros s hs h2s, simp_rw [h2s.image_const, is_closed_singleton]
end
/-- A T₂ space, also known as a Hausdorff space, is one in which for every
`x ≠ y` there exists disjoint open sets around `x` and `y`. This is
the most widely used of the separation axioms. -/
class t2_space (α : Type u) [topological_space α] : Prop :=
(t2 : ∀x y, x ≠ y → ∃u v : set α, is_open u ∧ is_open v ∧ x ∈ u ∧ y ∈ v ∧ u ∩ v = ∅)
lemma t2_separation [t2_space α] {x y : α} (h : x ≠ y) :
∃u v : set α, is_open u ∧ is_open v ∧ x ∈ u ∧ y ∈ v ∧ u ∩ v = ∅ :=
t2_space.t2 x y h
@[priority 100] -- see Note [lower instance priority]
instance t2_space.t1_space [t2_space α] : t1_space α :=
⟨λ x, is_open_iff_forall_mem_open.2 $ λ y hxy,
let ⟨u, v, hu, hv, hyu, hxv, huv⟩ := t2_separation (mt mem_singleton_of_eq hxy) in
⟨u, λ z hz1 hz2, (ext_iff.1 huv x).1 ⟨mem_singleton_iff.1 hz2 ▸ hz1, hxv⟩, hu, hyu⟩⟩
lemma eq_of_nhds_ne_bot [ht : t2_space α] {x y : α} (h : ne_bot (𝓝 x ⊓ 𝓝 y)) : x = y :=
classical.by_contradiction $ assume : x ≠ y,
let ⟨u, v, hu, hv, hx, hy, huv⟩ := t2_space.t2 x y this in
absurd huv $ (inf_ne_bot_iff.1 h (mem_nhds_sets hu hx) (mem_nhds_sets hv hy)).ne_empty
lemma t2_iff_nhds : t2_space α ↔ ∀ {x y : α}, ne_bot (𝓝 x ⊓ 𝓝 y) → x = y :=
⟨assume h, by exactI λ x y, eq_of_nhds_ne_bot,
assume h, ⟨assume x y xy,
have 𝓝 x ⊓ 𝓝 y = ⊥ := classical.by_contradiction (mt h xy),
let ⟨u', hu', v', hv', u'v'⟩ := empty_in_sets_eq_bot.mpr this,
⟨u, uu', uo, hu⟩ := mem_nhds_sets_iff.mp hu',
⟨v, vv', vo, hv⟩ := mem_nhds_sets_iff.mp hv' in
⟨u, v, uo, vo, hu, hv, disjoint.eq_bot $ disjoint.mono uu' vv' u'v'⟩⟩⟩
lemma t2_iff_ultrafilter :
t2_space α ↔ ∀ f {x y : α}, is_ultrafilter f → f ≤ 𝓝 x → f ≤ 𝓝 y → x = y :=
t2_iff_nhds.trans
⟨assume h f x y u fx fy, h $ u.1.mono (le_inf fx fy),
assume h x y xy,
let ⟨f, hf, uf⟩ := @@exists_ultrafilter _ xy in
h f uf (le_trans hf inf_le_left) (le_trans hf inf_le_right)⟩
lemma is_closed_diagonal [t2_space α] : is_closed (diagonal α) :=
is_closed_iff_cluster_pt.mpr $ assume ⟨a₁, a₂⟩ h, eq_of_nhds_ne_bot $ assume : 𝓝 a₁ ⊓ 𝓝 a₂ = ⊥, h $
let ⟨t₁, ht₁, t₂, ht₂, (h' : t₁ ∩ t₂ ⊆ ∅)⟩ :=
by rw [←empty_in_sets_eq_bot, mem_inf_sets] at this; exact this in
begin
change t₁ ∈ 𝓝 a₁ at ht₁,
change t₂ ∈ 𝓝 a₂ at ht₂,
rw [nhds_prod_eq, ←empty_in_sets_eq_bot],
apply filter.sets_of_superset,
apply inter_mem_inf_sets (prod_mem_prod ht₁ ht₂) (mem_principal_sets.mpr (subset.refl _)),
exact assume ⟨x₁, x₂⟩ ⟨⟨hx₁, hx₂⟩, (heq : x₁ = x₂)⟩,
show false, from @h' x₁ ⟨hx₁, heq.symm ▸ hx₂⟩
end
lemma t2_iff_is_closed_diagonal : t2_space α ↔ is_closed (diagonal α) :=
begin
split,
{ introI h,
exact is_closed_diagonal },
{ intro h,
constructor,
intros x y hxy,
have : (x, y) ∈ (diagonal α)ᶜ, by rwa [mem_compl_iff],
obtain ⟨t, t_sub, t_op, xyt⟩ : ∃ t ⊆ (diagonal α)ᶜ, is_open t ∧ (x, y) ∈ t :=
is_open_iff_forall_mem_open.mp h _ this,
rcases is_open_prod_iff.mp t_op x y xyt with ⟨U, V, U_op, V_op, xU, yV, H⟩,
use [U, V, U_op, V_op, xU, yV],
have := subset.trans H t_sub,
rw eq_empty_iff_forall_not_mem,
rintros z ⟨zU, zV⟩,
have : ¬ (z, z) ∈ diagonal α := this (mk_mem_prod zU zV),
exact this rfl },
end
@[simp] lemma nhds_eq_nhds_iff {a b : α} [t2_space α] : 𝓝 a = 𝓝 b ↔ a = b :=
⟨assume h, eq_of_nhds_ne_bot $ by rw [h, inf_idem]; exact nhds_ne_bot, assume h, h ▸ rfl⟩
@[simp] lemma nhds_le_nhds_iff {a b : α} [t2_space α] : 𝓝 a ≤ 𝓝 b ↔ a = b :=
⟨assume h, eq_of_nhds_ne_bot $ by rw [inf_of_le_left h]; exact nhds_ne_bot, assume h, h ▸ le_refl _⟩
lemma tendsto_nhds_unique [t2_space α] {f : β → α} {l : filter β} {a b : α}
[ne_bot l] (ha : tendsto f l (𝓝 a)) (hb : tendsto f l (𝓝 b)) : a = b :=
eq_of_nhds_ne_bot $ ne_bot_of_le $ le_inf ha hb
lemma tendsto_nhds_unique' [t2_space α] {f : β → α} {l : filter β} {a b : α}
(hl : ne_bot l) (ha : tendsto f l (𝓝 a)) (hb : tendsto f l (𝓝 b)) : a = b :=
eq_of_nhds_ne_bot $ ne_bot_of_le $ le_inf ha hb
section lim
variables [t2_space α] {f : filter α}
/-!
### Properties of `Lim` and `lim`
In this section we use explicit `nonempty α` instances for `Lim` and `lim`. This way the lemmas
are useful without a `nonempty α` instance.
-/
lemma Lim_eq {a : α} [ne_bot f] (h : f ≤ 𝓝 a) :
@Lim _ _ ⟨a⟩ f = a :=
tendsto_nhds_unique (le_nhds_Lim ⟨a, h⟩) h
lemma Lim_eq_iff [ne_bot f] (h : ∃ (a : α), f ≤ nhds a) {a} : @Lim _ _ ⟨a⟩ f = a ↔ f ≤ 𝓝 a :=
⟨λ c, c ▸ le_nhds_Lim h, Lim_eq⟩
lemma is_ultrafilter.Lim_eq_iff_le_nhds [compact_space α] (x : α) (F : ultrafilter α) :
@Lim _ _ ⟨x⟩ F.1 = x ↔ F.1 ≤ 𝓝 x :=
⟨λ h, h ▸ is_ultrafilter.le_nhds_Lim _, Lim_eq⟩
lemma is_open_iff_ultrafilter' [compact_space α] (U : set α) :
is_open U ↔ (∀ F : ultrafilter α, F.Lim ∈ U → U ∈ F.1) :=
begin
rw is_open_iff_ultrafilter,
refine ⟨λ h F hF, h _ hF _ F.2 (is_ultrafilter.le_nhds_Lim _), _⟩,
intros cond x hx f hf h,
let F : ultrafilter α := ⟨f, hf⟩,
change F.1 ≤ _ at h,
rw ←is_ultrafilter.Lim_eq_iff_le_nhds at h,
rw ←h at *,
exact cond _ hx
end
lemma filter.tendsto.lim_eq {a : α} {f : filter β} [ne_bot f] {g : β → α} (h : tendsto g f (𝓝 a)) :
@lim _ _ _ ⟨a⟩ f g = a :=
Lim_eq h
lemma filter.lim_eq_iff {f : filter β} [ne_bot f] {g : β → α} (h : ∃ a, tendsto g f (𝓝 a)) {a} :
@lim _ _ _ ⟨a⟩ f g = a ↔ tendsto g f (𝓝 a) :=
⟨λ c, c ▸ tendsto_nhds_lim h, filter.tendsto.lim_eq⟩
lemma continuous.lim_eq [topological_space β] {f : β → α} (h : continuous f) (a : β) :
@lim _ _ _ ⟨f a⟩ (𝓝 a) f = f a :=
(h.tendsto a).lim_eq
@[simp] lemma Lim_nhds (a : α) : @Lim _ _ ⟨a⟩ (𝓝 a) = a :=
Lim_eq (le_refl _)
@[simp] lemma lim_nhds_id (a : α) : @lim _ _ _ ⟨a⟩ (𝓝 a) id = a :=
Lim_nhds a
@[simp] lemma Lim_nhds_within {a : α} {s : set α} (h : a ∈ closure s) :
@Lim _ _ ⟨a⟩ (𝓝[s] a) = a :=
by haveI : ne_bot (𝓝[s] a) := mem_closure_iff_cluster_pt.1 h;
exact Lim_eq inf_le_left
@[simp] lemma lim_nhds_within_id {a : α} {s : set α} (h : a ∈ closure s) :
@lim _ _ _ ⟨a⟩ (𝓝[s] a) id = a :=
Lim_nhds_within h
end lim
@[priority 100] -- see Note [lower instance priority]
instance t2_space_discrete {α : Type*} [topological_space α] [discrete_topology α] : t2_space α :=
{ t2 := assume x y hxy, ⟨{x}, {y}, is_open_discrete _, is_open_discrete _, rfl, rfl,
eq_empty_iff_forall_not_mem.2 $ by intros z hz;
cases eq_of_mem_singleton hz.1; cases eq_of_mem_singleton hz.2; cc⟩ }
private lemma separated_by_f {α : Type*} {β : Type*}
[tα : topological_space α] [tβ : topological_space β] [t2_space β]
(f : α → β) (hf : tα ≤ tβ.induced f) {x y : α} (h : f x ≠ f y) :
∃u v : set α, is_open u ∧ is_open v ∧ x ∈ u ∧ y ∈ v ∧ u ∩ v = ∅ :=
let ⟨u, v, uo, vo, xu, yv, uv⟩ := t2_separation h in
⟨f ⁻¹' u, f ⁻¹' v, hf _ ⟨u, uo, rfl⟩, hf _ ⟨v, vo, rfl⟩, xu, yv,
by rw [←preimage_inter, uv, preimage_empty]⟩
instance {α : Type*} {p : α → Prop} [t : topological_space α] [t2_space α] : t2_space (subtype p) :=
⟨assume x y h,
separated_by_f subtype.val (le_refl _) (mt subtype.eq h)⟩
instance {α : Type*} {β : Type*} [t₁ : topological_space α] [t2_space α]
[t₂ : topological_space β] [t2_space β] : t2_space (α × β) :=
⟨assume ⟨x₁,x₂⟩ ⟨y₁,y₂⟩ h,
or.elim (not_and_distrib.mp (mt prod.ext_iff.mpr h))
(λ h₁, separated_by_f prod.fst inf_le_left h₁)
(λ h₂, separated_by_f prod.snd inf_le_right h₂)⟩
instance Pi.t2_space {α : Type*} {β : α → Type v} [t₂ : Πa, topological_space (β a)] [Πa, t2_space (β a)] :
t2_space (Πa, β a) :=
⟨assume x y h,
let ⟨i, hi⟩ := not_forall.mp (mt funext h) in
separated_by_f (λz, z i) (infi_le _ i) hi⟩
variables [topological_space β]
lemma is_closed_eq [t2_space α] {f g : β → α}
(hf : continuous f) (hg : continuous g) : is_closed {x:β | f x = g x} :=
continuous_iff_is_closed.mp (hf.prod_mk hg) _ is_closed_diagonal
/-- If two continuous maps are equal on `s`, then they are equal on the closure of `s`. -/
lemma set.eq_on.closure [t2_space α] {s : set β} {f g : β → α} (h : eq_on f g s)
(hf : continuous f) (hg : continuous g) :
eq_on f g (closure s) :=
closure_minimal h (is_closed_eq hf hg)
/-- If two continuous functions are equal on a dense set, then they are equal. -/
lemma continuous.ext_on [t2_space α] {s : set β} (hs : dense s) {f g : β → α}
(hf : continuous f) (hg : continuous g) (h : eq_on f g s) :
f = g :=
funext $ λ x, h.closure hf hg (hs x)
lemma diagonal_eq_range_diagonal_map {α : Type*} : {p:α×α | p.1 = p.2} = range (λx, (x,x)) :=
ext $ assume p, iff.intro
(assume h, ⟨p.1, prod.ext_iff.2 ⟨rfl, h⟩⟩)
(assume ⟨x, hx⟩, show p.1 = p.2, by rw ←hx)
lemma prod_subset_compl_diagonal_iff_disjoint {α : Type*} {s t : set α} :
set.prod s t ⊆ {p:α×α | p.1 = p.2}ᶜ ↔ s ∩ t = ∅ :=
by rw [eq_empty_iff_forall_not_mem, subset_compl_comm,
diagonal_eq_range_diagonal_map, range_subset_iff]; simp
lemma compact_compact_separated [t2_space α] {s t : set α}
(hs : is_compact s) (ht : is_compact t) (hst : s ∩ t = ∅) :
∃u v : set α, is_open u ∧ is_open v ∧ s ⊆ u ∧ t ⊆ v ∧ u ∩ v = ∅ :=
by simp only [prod_subset_compl_diagonal_iff_disjoint.symm] at ⊢ hst;
exact generalized_tube_lemma hs ht is_closed_diagonal hst
/-- In a `t2_space`, every compact set is closed. -/
lemma is_compact.is_closed [t2_space α] {s : set α} (hs : is_compact s) : is_closed s :=
is_open_compl_iff.mpr $ is_open_iff_forall_mem_open.mpr $ assume x hx,
let ⟨u, v, uo, vo, su, xv, uv⟩ :=
compact_compact_separated hs (compact_singleton : is_compact {x})
(by rwa [inter_comm, ←subset_compl_iff_disjoint, singleton_subset_iff]) in
have v ⊆ sᶜ, from
subset_compl_comm.mp (subset.trans su (subset_compl_iff_disjoint.mpr uv)),
⟨v, this, vo, by simpa using xv⟩
lemma is_compact.inter [t2_space α] {s t : set α} (hs : is_compact s) (ht : is_compact t) :
is_compact (s ∩ t) :=
hs.inter_right $ ht.is_closed
/-- If a compact set is covered by two open sets, then we can cover it by two compact subsets. -/
lemma is_compact.binary_compact_cover [t2_space α] {K U V : set α} (hK : is_compact K)
(hU : is_open U) (hV : is_open V) (h2K : K ⊆ U ∪ V) :
∃ K₁ K₂ : set α, is_compact K₁ ∧ is_compact K₂ ∧ K₁ ⊆ U ∧ K₂ ⊆ V ∧ K = K₁ ∪ K₂ :=
begin
rcases compact_compact_separated (compact_diff hK hU) (compact_diff hK hV)
(by rwa [diff_inter_diff, diff_eq_empty]) with ⟨O₁, O₂, h1O₁, h1O₂, h2O₁, h2O₂, hO⟩,
refine ⟨_, _, compact_diff hK h1O₁, compact_diff hK h1O₂,
by rwa [diff_subset_comm], by rwa [diff_subset_comm], by rw [← diff_inter, hO, diff_empty]⟩
end
section
open finset function
/-- For every finite open cover `Uᵢ` of a compact set, there exists a compact cover `Kᵢ ⊆ Uᵢ`. -/
lemma is_compact.finite_compact_cover [t2_space α] {s : set α} (hs : is_compact s) {ι} (t : finset ι)
(U : ι → set α) (hU : ∀ i ∈ t, is_open (U i)) (hsC : s ⊆ ⋃ i ∈ t, U i) :
∃ K : ι → set α, (∀ i, is_compact (K i)) ∧ (∀i, K i ⊆ U i) ∧ s = ⋃ i ∈ t, K i :=
begin
classical,
induction t using finset.induction with x t hx ih generalizing U hU s hs hsC,
{ refine ⟨λ _, ∅, λ i, compact_empty, λ i, empty_subset _, _⟩, simpa only [subset_empty_iff,
finset.not_mem_empty, Union_neg, Union_empty, not_false_iff] using hsC },
simp only [finset.bUnion_insert] at hsC,
simp only [finset.mem_insert] at hU,
have hU' : ∀ i ∈ t, is_open (U i) := λ i hi, hU i (or.inr hi),
rcases hs.binary_compact_cover (hU x (or.inl rfl)) (is_open_bUnion hU') hsC
with ⟨K₁, K₂, h1K₁, h1K₂, h2K₁, h2K₂, hK⟩,
rcases ih U hU' h1K₂ h2K₂ with ⟨K, h1K, h2K, h3K⟩,
refine ⟨update K x K₁, _, _, _⟩,
{ intros i, by_cases hi : i = x,
{ simp only [update_same, hi, h1K₁] },
{ rw [← ne.def] at hi, simp only [update_noteq hi, h1K] }},
{ intros i, by_cases hi : i = x,
{ simp only [update_same, hi, h2K₁] },
{ rw [← ne.def] at hi, simp only [update_noteq hi, h2K] }},
{ simp only [bUnion_insert_update _ hx, hK, h3K] }
end
end
lemma locally_compact_of_compact_nhds [t2_space α] (h : ∀ x : α, ∃ s, s ∈ 𝓝 x ∧ is_compact s) :
locally_compact_space α :=
⟨assume x n hn,
let ⟨u, un, uo, xu⟩ := mem_nhds_sets_iff.mp hn in
let ⟨k, kx, kc⟩ := h x in
-- K is compact but not necessarily contained in N.
-- K \ U is again compact and doesn't contain x, so
-- we may find open sets V, W separating x from K \ U.
-- Then K \ W is a compact neighborhood of x contained in U.
let ⟨v, w, vo, wo, xv, kuw, vw⟩ :=
compact_compact_separated compact_singleton (compact_diff kc uo)
(by rw [singleton_inter_eq_empty]; exact λ h, h.2 xu) in
have wn : wᶜ ∈ 𝓝 x, from
mem_nhds_sets_iff.mpr
⟨v, subset_compl_iff_disjoint.mpr vw, vo, singleton_subset_iff.mp xv⟩,
⟨k \ w,
filter.inter_mem_sets kx wn,
subset.trans (diff_subset_comm.mp kuw) un,
compact_diff kc wo⟩⟩
@[priority 100] -- see Note [lower instance priority]
instance locally_compact_of_compact [t2_space α] [compact_space α] : locally_compact_space α :=
locally_compact_of_compact_nhds (assume x, ⟨univ, mem_nhds_sets is_open_univ trivial, compact_univ⟩)
/-- In a locally compact T₂ space, every point has an open neighborhood with compact closure -/
lemma exists_open_with_compact_closure [locally_compact_space α] [t2_space α] (x : α) :
∃ (U : set α), is_open U ∧ x ∈ U ∧ is_compact (closure U) :=
begin
rcases locally_compact_space.local_compact_nhds x set.univ filter.univ_mem_sets with
⟨K, h1K, _, h2K⟩,
rw [mem_nhds_sets_iff] at h1K, rcases h1K with ⟨t, h1t, h2t, h3t⟩,
exact ⟨t, h2t, h3t, compact_of_is_closed_subset h2K is_closed_closure $
closure_minimal h1t $ h2K.is_closed⟩
end
/-- In a locally compact T₂ space, every compact set is contained in the interior of a compact
set. -/
lemma exists_compact_superset [locally_compact_space α] [t2_space α] {K : set α}
(hK : is_compact K) : ∃ (K' : set α), is_compact K' ∧ K ⊆ interior K' :=
begin
choose U hU using λ x : K, exists_open_with_compact_closure (x : α),
rcases hK.elim_finite_subcover U (λ x, (hU x).1) (λ x hx, ⟨_, ⟨⟨x, hx⟩, rfl⟩, (hU ⟨x, hx⟩).2.1⟩) with
⟨s, hs⟩,
refine ⟨⋃ (i : K) (H : i ∈ s), closure (U i), _, _⟩,
exact (finite_mem_finset s).compact_bUnion (λ x hx, (hU x).2.2),
refine subset.trans hs _, rw subset_interior_iff_subset_of_open,
exact bUnion_subset_bUnion_right (λ x hx, subset_closure),
exact is_open_bUnion (λ x hx, (hU x).1)
end
end separation
section regularity
/-- A T₃ space, also known as a regular space (although this condition sometimes
omits T₂), is one in which for every closed `C` and `x ∉ C`, there exist
disjoint open sets containing `x` and `C` respectively. -/
class regular_space (α : Type u) [topological_space α] extends t1_space α : Prop :=
(regular : ∀{s:set α} {a}, is_closed s → a ∉ s → ∃t, is_open t ∧ s ⊆ t ∧ 𝓝[t] a = ⊥)
lemma nhds_is_closed [regular_space α] {a : α} {s : set α} (h : s ∈ 𝓝 a) :
∃t∈(𝓝 a), t ⊆ s ∧ is_closed t :=
let ⟨s', h₁, h₂, h₃⟩ := mem_nhds_sets_iff.mp h in
have ∃t, is_open t ∧ s'ᶜ ⊆ t ∧ 𝓝[t] a = ⊥,
from regular_space.regular (is_closed_compl_iff.mpr h₂) (not_not_intro h₃),
let ⟨t, ht₁, ht₂, ht₃⟩ := this in
⟨tᶜ,
mem_sets_of_eq_bot $ by rwa [compl_compl],
subset.trans (compl_subset_comm.1 ht₂) h₁,
is_closed_compl_iff.mpr ht₁⟩
lemma closed_nhds_basis [regular_space α] (a : α) :
(𝓝 a).has_basis (λ s : set α, s ∈ 𝓝 a ∧ is_closed s) id :=
⟨λ t, ⟨λ t_in, let ⟨s, s_in, h_st, h⟩ := nhds_is_closed t_in in ⟨s, ⟨s_in, h⟩, h_st⟩,
λ ⟨s, ⟨s_in, hs⟩, hst⟩, mem_sets_of_superset s_in hst⟩⟩
instance subtype.regular_space [regular_space α] {p : α → Prop} : regular_space (subtype p) :=
⟨begin
intros s a hs ha,
rcases is_closed_induced_iff.1 hs with ⟨s, hs', rfl⟩,
rcases regular_space.regular hs' ha with ⟨t, ht, hst, hat⟩,
refine ⟨coe ⁻¹' t, is_open_induced ht, preimage_mono hst, _⟩,
rw [nhds_within, nhds_induced, ← comap_principal, ← comap_inf, ← nhds_within, hat, comap_bot]
end⟩
variable (α)
@[priority 100] -- see Note [lower instance priority]
instance regular_space.t2_space [regular_space α] : t2_space α :=
⟨λ x y hxy,
let ⟨s, hs, hys, hxs⟩ := regular_space.regular is_closed_singleton
(mt mem_singleton_iff.1 hxy),
⟨t, hxt, u, hsu, htu⟩ := empty_in_sets_eq_bot.2 hxs,
⟨v, hvt, hv, hxv⟩ := mem_nhds_sets_iff.1 hxt in
⟨v, s, hv, hs, hxv, singleton_subset_iff.1 hys,
eq_empty_of_subset_empty $ λ z ⟨hzv, hzs⟩, htu ⟨hvt hzv, hsu hzs⟩⟩⟩
variable {α}
lemma disjoint_nested_nhds [regular_space α] {x y : α} (h : x ≠ y) :
∃ (U₁ V₁ ∈ 𝓝 x) (U₂ V₂ ∈ 𝓝 y), is_closed V₁ ∧ is_closed V₂ ∧ is_open U₁ ∧ is_open U₂ ∧
V₁ ⊆ U₁ ∧ V₂ ⊆ U₂ ∧ U₁ ∩ U₂ = ∅ :=
begin
rcases t2_separation h with ⟨U₁, U₂, U₁_op, U₂_op, x_in, y_in, H⟩,
rcases nhds_is_closed (mem_nhds_sets U₁_op x_in) with ⟨V₁, V₁_in, h₁, V₁_closed⟩,
rcases nhds_is_closed (mem_nhds_sets U₂_op y_in) with ⟨V₂, V₂_in, h₂, V₂_closed⟩,
use [U₁, V₁, mem_sets_of_superset V₁_in h₁, V₁_in,
U₂, V₂, mem_sets_of_superset V₂_in h₂, V₂_in],
tauto
end
end regularity
section normality
/-- A T₄ space, also known as a normal space (although this condition sometimes
omits T₂), is one in which for every pair of disjoint closed sets `C` and `D`,
there exist disjoint open sets containing `C` and `D` respectively. -/
class normal_space (α : Type u) [topological_space α] extends t1_space α : Prop :=
(normal : ∀ s t : set α, is_closed s → is_closed t → disjoint s t →
∃ u v, is_open u ∧ is_open v ∧ s ⊆ u ∧ t ⊆ v ∧ disjoint u v)
theorem normal_separation [normal_space α] (s t : set α)
(H1 : is_closed s) (H2 : is_closed t) (H3 : disjoint s t) :
∃ u v, is_open u ∧ is_open v ∧ s ⊆ u ∧ t ⊆ v ∧ disjoint u v :=
normal_space.normal s t H1 H2 H3
@[priority 100] -- see Note [lower instance priority]
instance normal_space.regular_space [normal_space α] : regular_space α :=
{ regular := λ s x hs hxs, let ⟨u, v, hu, hv, hsu, hxv, huv⟩ := normal_separation s {x} hs is_closed_singleton
(λ _ ⟨hx, hy⟩, hxs $ set.mem_of_eq_of_mem (set.eq_of_mem_singleton hy).symm hx) in
⟨u, hu, hsu, filter.empty_in_sets_eq_bot.1 $ filter.mem_inf_sets.2
⟨v, mem_nhds_sets hv (set.singleton_subset_iff.1 hxv), u, filter.mem_principal_self u, set.inter_comm u v ▸ huv⟩⟩ }
-- We can't make this an instance because it could cause an instance loop.
lemma normal_of_compact_t2 [compact_space α] [t2_space α] : normal_space α :=
begin
refine ⟨assume s t hs ht st, _⟩,
simp only [disjoint_iff],
exact compact_compact_separated hs.compact ht.compact st.eq_bot
end
end normality
|
e853ebad87359e95de315252b5a6e1a3c31705ae | 4727251e0cd73359b15b664c3170e5d754078599 | /src/tactic/linarith/lemmas.lean | d14c9a2497a22c006acc84571a797c520263c1a0 | [
"Apache-2.0"
] | permissive | Vierkantor/mathlib | 0ea59ac32a3a43c93c44d70f441c4ee810ccceca | 83bc3b9ce9b13910b57bda6b56222495ebd31c2f | refs/heads/master | 1,658,323,012,449 | 1,652,256,003,000 | 1,652,256,003,000 | 209,296,341 | 0 | 1 | Apache-2.0 | 1,568,807,655,000 | 1,568,807,655,000 | null | UTF-8 | Lean | false | false | 3,801 | lean | /-
Copyright (c) 2020 Robert Y. Lewis. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Robert Y. Lewis
-/
import algebra.order.ring
import data.int.basic
import tactic.norm_num
/-!
# Lemmas for `linarith`
This file contains auxiliary lemmas that `linarith` uses to construct proofs.
If you find yourself looking for a theorem here, you might be in the wrong place.
-/
namespace linarith
lemma int.coe_nat_bit0 (n : ℕ) : (↑(bit0 n : ℕ) : ℤ) = bit0 (↑n : ℤ) := by simp [bit0]
lemma int.coe_nat_bit1 (n : ℕ) : (↑(bit1 n : ℕ) : ℤ) = bit1 (↑n : ℤ) := by simp [bit1, bit0]
lemma int.coe_nat_bit0_mul (n : ℕ) (x : ℕ) : (↑(bit0 n * x) : ℤ) = (↑(bit0 n) : ℤ) * (↑x : ℤ) :=
by simp
lemma int.coe_nat_bit1_mul (n : ℕ) (x : ℕ) : (↑(bit1 n * x) : ℤ) = (↑(bit1 n) : ℤ) * (↑x : ℤ) :=
by simp
lemma int.coe_nat_one_mul (x : ℕ) : (↑(1 * x) : ℤ) = 1 * (↑x : ℤ) := by simp
lemma int.coe_nat_zero_mul (x : ℕ) : (↑(0 * x) : ℤ) = 0 * (↑x : ℤ) := by simp
lemma int.coe_nat_mul_bit0 (n : ℕ) (x : ℕ) : (↑(x * bit0 n) : ℤ) = (↑x : ℤ) * (↑(bit0 n) : ℤ) :=
by simp
lemma int.coe_nat_mul_bit1 (n : ℕ) (x : ℕ) : (↑(x * bit1 n) : ℤ) = (↑x : ℤ) * (↑(bit1 n) : ℤ) :=
by simp
lemma int.coe_nat_mul_one (x : ℕ) : (↑(x * 1) : ℤ) = (↑x : ℤ) * 1 := by simp
lemma int.coe_nat_mul_zero (x : ℕ) : (↑(x * 0) : ℤ) = (↑x : ℤ) * 0 := by simp
lemma nat_eq_subst {n1 n2 : ℕ} {z1 z2 : ℤ} (hn : n1 = n2) (h1 : ↑n1 = z1) (h2 : ↑n2 = z2) :
z1 = z2 :=
by simpa [eq.symm h1, eq.symm h2, int.coe_nat_eq_coe_nat_iff]
lemma nat_le_subst {n1 n2 : ℕ} {z1 z2 : ℤ} (hn : n1 ≤ n2) (h1 : ↑n1 = z1) (h2 : ↑n2 = z2) :
z1 ≤ z2 :=
by simpa [eq.symm h1, eq.symm h2, int.coe_nat_le]
lemma nat_lt_subst {n1 n2 : ℕ} {z1 z2 : ℤ} (hn : n1 < n2) (h1 : ↑n1 = z1) (h2 : ↑n2 = z2) :
z1 < z2 :=
by simpa [eq.symm h1, eq.symm h2, int.coe_nat_lt]
lemma eq_of_eq_of_eq {α} [ordered_semiring α] {a b : α} (ha : a = 0) (hb : b = 0) : a + b = 0 :=
by simp *
lemma le_of_eq_of_le {α} [ordered_semiring α] {a b : α} (ha : a = 0) (hb : b ≤ 0) : a + b ≤ 0 :=
by simp *
lemma lt_of_eq_of_lt {α} [ordered_semiring α] {a b : α} (ha : a = 0) (hb : b < 0) : a + b < 0 :=
by simp *
lemma le_of_le_of_eq {α} [ordered_semiring α] {a b : α} (ha : a ≤ 0) (hb : b = 0) : a + b ≤ 0 :=
by simp *
lemma lt_of_lt_of_eq {α} [ordered_semiring α] {a b : α} (ha : a < 0) (hb : b = 0) : a + b < 0 :=
by simp *
lemma mul_neg {α} [ordered_ring α] {a b : α} (ha : a < 0) (hb : 0 < b) : b * a < 0 :=
have (-b)*a > 0, from mul_pos_of_neg_of_neg (neg_neg_of_pos hb) ha,
neg_of_neg_pos (by simpa)
lemma mul_nonpos {α} [ordered_ring α] {a b : α} (ha : a ≤ 0) (hb : 0 < b) : b * a ≤ 0 :=
have (-b)*a ≥ 0, from mul_nonneg_of_nonpos_of_nonpos (le_of_lt (neg_neg_of_pos hb)) ha,
by simpa
-- used alongside `mul_neg` and `mul_nonpos`, so has the same argument pattern for uniformity
@[nolint unused_arguments]
lemma mul_eq {α} [ordered_semiring α] {a b : α} (ha : a = 0) (hb : 0 < b) : b * a = 0 :=
by simp *
lemma eq_of_not_lt_of_not_gt {α} [linear_order α] (a b : α) (h1 : ¬ a < b) (h2 : ¬ b < a) : a = b :=
le_antisymm (le_of_not_gt h2) (le_of_not_gt h1)
-- used in the `nlinarith` normalization steps. The `_` argument is for uniformity.
@[nolint unused_arguments]
lemma mul_zero_eq {α} {R : α → α → Prop} [semiring α] {a b : α} (_ : R a 0) (h : b = 0) :
a * b = 0 :=
by simp [h]
-- used in the `nlinarith` normalization steps. The `_` argument is for uniformity.
@[nolint unused_arguments]
lemma zero_mul_eq {α} {R : α → α → Prop} [semiring α] {a b : α} (h : a = 0) (_ : R b 0) :
a * b = 0 :=
by simp [h]
end linarith
|
db723153237dd8052ebf0deac9ef367af3637882 | 4727251e0cd73359b15b664c3170e5d754078599 | /src/analysis/box_integral/partition/subbox_induction.lean | 739d1b473f00f0377cfc2fc2d8e8819653c85a9a | [
"Apache-2.0"
] | permissive | Vierkantor/mathlib | 0ea59ac32a3a43c93c44d70f441c4ee810ccceca | 83bc3b9ce9b13910b57bda6b56222495ebd31c2f | refs/heads/master | 1,658,323,012,449 | 1,652,256,003,000 | 1,652,256,003,000 | 209,296,341 | 0 | 1 | Apache-2.0 | 1,568,807,655,000 | 1,568,807,655,000 | null | UTF-8 | Lean | false | false | 10,541 | lean | /-
Copyright (c) 2021 Yury Kudryashov. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yury Kudryashov
-/
import analysis.box_integral.box.subbox_induction
import analysis.box_integral.partition.tagged
/-!
# Induction on subboxes
In this file we prove (see
`box_integral.tagged_partition.exists_is_Henstock_is_subordinate_homothetic`) that for every box `I`
in `ℝⁿ` and a function `r : ℝⁿ → ℝ` positive on `I` there exists a tagged partition `π` of `I` such
that
* `π` is a Henstock partition;
* `π` is subordinate to `r`;
* each box in `π` is homothetic to `I` with coefficient of the form `1 / 2 ^ n`.
Later we will use this lemma to prove that the Henstock filter is nontrivial, hence the Henstock
integral is well-defined.
## Tags
partition, tagged partition, Henstock integral
-/
namespace box_integral
open set metric
open_locale classical topological_space
noncomputable theory
variables {ι : Type*} [fintype ι] {I J : box ι}
namespace prepartition
/-- Split a box in `ℝⁿ` into `2 ^ n` boxes by hyperplanes passing through its center. -/
def split_center (I : box ι) : prepartition I :=
{ boxes := finset.univ.map (box.split_center_box_emb I),
le_of_mem' := by simp [I.split_center_box_le],
pairwise_disjoint :=
begin
rw [finset.coe_map, finset.coe_univ, image_univ],
rintro _ ⟨s, rfl⟩ _ ⟨t, rfl⟩ Hne,
exact I.disjoint_split_center_box (mt (congr_arg _) Hne)
end }
@[simp] lemma mem_split_center : J ∈ split_center I ↔ ∃ s, I.split_center_box s = J :=
by simp [split_center]
lemma is_partition_split_center (I : box ι) : is_partition (split_center I) :=
λ x hx, by simp [hx]
lemma upper_sub_lower_of_mem_split_center (h : J ∈ split_center I) (i : ι) :
J.upper i - J.lower i = (I.upper i - I.lower i) / 2 :=
let ⟨s, hs⟩ := mem_split_center.1 h in hs ▸ I.upper_sub_lower_split_center_box s i
end prepartition
namespace box
open prepartition tagged_prepartition
/-- Let `p` be a predicate on `box ι`, let `I` be a box. Suppose that the following two properties
hold true.
* Consider a smaller box `J ≤ I`. The hyperplanes passing through the center of `J` split it into
`2 ^ n` boxes. If `p` holds true on each of these boxes, then it true on `J`.
* For each `z` in the closed box `I.Icc` there exists a neighborhood `U` of `z` within `I.Icc` such
that for every box `J ≤ I` such that `z ∈ J.Icc ⊆ U`, if `J` is homothetic to `I` with a
coefficient of the form `1 / 2 ^ m`, then `p` is true on `J`.
Then `p I` is true. See also `box_integral.box.subbox_induction_on'` for a version using
`box_integral.box.split_center_box` instead of `box_integral.prepartition.split_center`. -/
@[elab_as_eliminator]
lemma subbox_induction_on {p : box ι → Prop} (I : box ι)
(H_ind : ∀ J ≤ I, (∀ J' ∈ split_center J, p J') → p J)
(H_nhds : ∀ z ∈ I.Icc, ∃ (U ∈ 𝓝[I.Icc] z), ∀ (J ≤ I) (m : ℕ), z ∈ J.Icc → J.Icc ⊆ U →
(∀ i, J.upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) → p J) :
p I :=
begin
refine subbox_induction_on' I (λ J hle hs, H_ind J hle $ λ J' h', _) H_nhds,
rcases mem_split_center.1 h' with ⟨s, rfl⟩,
exact hs s
end
/-- Given a box `I` in `ℝⁿ` and a function `r : ℝⁿ → (0, ∞)`, there exists a tagged partition `π` of
`I` such that
* `π` is a Henstock partition;
* `π` is subordinate to `r`;
* each box in `π` is homothetic to `I` with coefficient of the form `1 / 2 ^ m`.
This lemma implies that the Henstock filter is nontrivial, hence the Henstock integral is
well-defined. -/
lemma exists_tagged_partition_is_Henstock_is_subordinate_homothetic (I : box ι)
(r : (ι → ℝ) → Ioi (0 : ℝ)) :
∃ π : tagged_prepartition I, π.is_partition ∧ π.is_Henstock ∧ π.is_subordinate r ∧
(∀ J ∈ π, ∃ m : ℕ, ∀ i, (J : _).upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) ∧
π.distortion = I.distortion :=
begin
refine subbox_induction_on I (λ J hle hJ, _) (λ z hz, _),
{ choose! πi hP hHen hr Hn Hd using hJ, choose! n hn using Hn,
have hP : ((split_center J).bUnion_tagged πi).is_partition,
from (is_partition_split_center _).bUnion_tagged hP,
have hsub : ∀ (J' ∈ (split_center J).bUnion_tagged πi), ∃ n : ℕ, ∀ i,
(J' : _).upper i - J'.lower i = (J.upper i - J.lower i) / 2 ^ n,
{ intros J' hJ',
rcases (split_center J).mem_bUnion_tagged.1 hJ' with ⟨J₁, h₁, h₂⟩,
refine ⟨n J₁ J' + 1, λ i, _⟩,
simp only [hn J₁ h₁ J' h₂, upper_sub_lower_of_mem_split_center h₁, pow_succ, div_div] },
refine ⟨_, hP, is_Henstock_bUnion_tagged.2 hHen, is_subordinate_bUnion_tagged.2 hr, hsub, _⟩,
refine tagged_prepartition.distortion_of_const _ hP.nonempty_boxes (λ J' h', _),
rcases hsub J' h' with ⟨n, hn⟩,
exact box.distortion_eq_of_sub_eq_div hn },
{ refine ⟨I.Icc ∩ closed_ball z (r z),
inter_mem_nhds_within _ (closed_ball_mem_nhds _ (r z).coe_prop), _⟩,
intros J Hle n Hmem HIcc Hsub,
rw set.subset_inter_iff at HIcc,
refine ⟨single _ _ le_rfl _ Hmem, is_partition_single _, is_Henstock_single _,
(is_subordinate_single _ _).2 HIcc.2, _, distortion_single _ _⟩,
simp only [tagged_prepartition.mem_single, forall_eq],
refine ⟨0, λ i, _⟩, simp }
end
end box
namespace prepartition
open tagged_prepartition finset function
/-- Given a box `I` in `ℝⁿ`, a function `r : ℝⁿ → (0, ∞)`, and a prepartition `π` of `I`, there
exists a tagged prepartition `π'` of `I` such that
* each box of `π'` is included in some box of `π`;
* `π'` is a Henstock partition;
* `π'` is subordinate to `r`;
* `π'` covers exactly the same part of `I` as `π`;
* the distortion of `π'` is equal to the distortion of `π`.
-/
lemma exists_tagged_le_is_Henstock_is_subordinate_Union_eq {I : box ι} (r : (ι → ℝ) → Ioi (0 : ℝ))
(π : prepartition I) :
∃ π' : tagged_prepartition I, π'.to_prepartition ≤ π ∧
π'.is_Henstock ∧ π'.is_subordinate r ∧ π'.distortion = π.distortion ∧
π'.Union = π.Union :=
begin
have := λ J, box.exists_tagged_partition_is_Henstock_is_subordinate_homothetic J r,
choose! πi πip πiH πir hsub πid, clear hsub,
refine ⟨π.bUnion_tagged πi, bUnion_le _ _, is_Henstock_bUnion_tagged.2 (λ J _, πiH J),
is_subordinate_bUnion_tagged.2 (λ J _, πir J), _, π.Union_bUnion_partition (λ J _, πip J)⟩,
rw [distortion_bUnion_tagged],
exact sup_congr rfl (λ J _, πid J)
end
/-- Given a prepartition `π` of a box `I` and a function `r : ℝⁿ → (0, ∞)`, `π.to_subordinate r`
is a tagged partition `π'` such that
* each box of `π'` is included in some box of `π`;
* `π'` is a Henstock partition;
* `π'` is subordinate to `r`;
* `π'` covers exactly the same part of `I` as `π`;
* the distortion of `π'` is equal to the distortion of `π`.
-/
def to_subordinate (π : prepartition I) (r : (ι → ℝ) → Ioi (0 : ℝ)) : tagged_prepartition I :=
(π.exists_tagged_le_is_Henstock_is_subordinate_Union_eq r).some
lemma to_subordinate_to_prepartition_le (π : prepartition I) (r : (ι → ℝ) → Ioi (0 : ℝ)) :
(π.to_subordinate r).to_prepartition ≤ π :=
(π.exists_tagged_le_is_Henstock_is_subordinate_Union_eq r).some_spec.1
lemma is_Henstock_to_subordinate (π : prepartition I) (r : (ι → ℝ) → Ioi (0 : ℝ)) :
(π.to_subordinate r).is_Henstock :=
(π.exists_tagged_le_is_Henstock_is_subordinate_Union_eq r).some_spec.2.1
lemma is_subordinate_to_subordinate (π : prepartition I) (r : (ι → ℝ) → Ioi (0 : ℝ)) :
(π.to_subordinate r).is_subordinate r :=
(π.exists_tagged_le_is_Henstock_is_subordinate_Union_eq r).some_spec.2.2.1
@[simp] lemma distortion_to_subordinate (π : prepartition I) (r : (ι → ℝ) → Ioi (0 : ℝ)) :
(π.to_subordinate r).distortion = π.distortion :=
(π.exists_tagged_le_is_Henstock_is_subordinate_Union_eq r).some_spec.2.2.2.1
@[simp] lemma Union_to_subordinate (π : prepartition I) (r : (ι → ℝ) → Ioi (0 : ℝ)) :
(π.to_subordinate r).Union = π.Union :=
(π.exists_tagged_le_is_Henstock_is_subordinate_Union_eq r).some_spec.2.2.2.2
end prepartition
namespace tagged_prepartition
/-- Given a tagged prepartition `π₁`, a prepartition `π₂` that covers exactly `I \ π₁.Union`, and
a function `r : ℝⁿ → (0, ∞)`, returns the union of `π₁` and `π₂.to_subordinate r`. This partition
`π` has the following properties:
* `π` is a partition, i.e. it covers the whole `I`;
* `π₁.boxes ⊆ π.boxes`;
* `π.tag J = π₁.tag J` whenever `J ∈ π₁`;
* `π` is Henstock outside of `π₁`: `π.tag J ∈ J.Icc` whenever `J ∈ π`, `J ∉ π₁`;
* `π` is subordinate to `r` outside of `π₁`;
* the distortion of `π` is equal to the maximum of the distortions of `π₁` and `π₂`.
-/
def union_compl_to_subordinate (π₁ : tagged_prepartition I) (π₂ : prepartition I)
(hU : π₂.Union = I \ π₁.Union) (r : (ι → ℝ) → Ioi (0 : ℝ)) :
tagged_prepartition I :=
π₁.disj_union (π₂.to_subordinate r)
(((π₂.Union_to_subordinate r).trans hU).symm ▸ disjoint_diff)
lemma is_partition_union_compl_to_subordinate (π₁ : tagged_prepartition I) (π₂ : prepartition I)
(hU : π₂.Union = I \ π₁.Union) (r : (ι → ℝ) → Ioi (0 : ℝ)) :
is_partition (π₁.union_compl_to_subordinate π₂ hU r) :=
prepartition.is_partition_disj_union_of_eq_diff ((π₂.Union_to_subordinate r).trans hU)
@[simp] lemma union_compl_to_subordinate_boxes (π₁ : tagged_prepartition I) (π₂ : prepartition I)
(hU : π₂.Union = I \ π₁.Union) (r : (ι → ℝ) → Ioi (0 : ℝ)) :
(π₁.union_compl_to_subordinate π₂ hU r).boxes = π₁.boxes ∪ (π₂.to_subordinate r).boxes :=
rfl
@[simp] lemma Union_union_compl_to_subordinate_boxes (π₁ : tagged_prepartition I)
(π₂ : prepartition I) (hU : π₂.Union = I \ π₁.Union) (r : (ι → ℝ) → Ioi (0 : ℝ)) :
(π₁.union_compl_to_subordinate π₂ hU r).Union = I :=
(is_partition_union_compl_to_subordinate _ _ _ _).Union_eq
@[simp] lemma distortion_union_compl_to_subordinate (π₁ : tagged_prepartition I)
(π₂ : prepartition I) (hU : π₂.Union = I \ π₁.Union) (r : (ι → ℝ) → Ioi (0 : ℝ)) :
(π₁.union_compl_to_subordinate π₂ hU r).distortion = max π₁.distortion π₂.distortion :=
by simp [union_compl_to_subordinate]
end tagged_prepartition
end box_integral
|
52be73894aa172181053749340bfb9b4b242f151 | 618003631150032a5676f229d13a079ac875ff77 | /src/algebra/char_zero.lean | 9a6c9ec552c24342070b7ef8ac4491f9a4fc4093 | [
"Apache-2.0"
] | permissive | awainverse/mathlib | 939b68c8486df66cfda64d327ad3d9165248c777 | ea76bd8f3ca0a8bf0a166a06a475b10663dec44a | refs/heads/master | 1,659,592,962,036 | 1,590,987,592,000 | 1,590,987,592,000 | 268,436,019 | 1 | 0 | Apache-2.0 | 1,590,990,500,000 | 1,590,990,500,000 | null | UTF-8 | Lean | false | false | 3,305 | lean | /-
Copyright (c) 2014 Mario Carneiro. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Mario Carneiro
Natural homomorphism from the natural numbers into a monoid with one.
-/
import algebra.field
import data.nat.cast
import tactic.wlog
/-- Typeclass for monoids with characteristic zero.
(This is usually stated on fields but it makes sense for any additive monoid with 1.) -/
class char_zero (α : Type*) [add_monoid α] [has_one α] : Prop :=
(cast_injective : function.injective (coe : ℕ → α))
theorem char_zero_of_inj_zero {α : Type*} [add_monoid α] [has_one α]
(add_left_cancel : ∀ a b c : α, a + b = a + c → b = c)
(H : ∀ n:ℕ, (n:α) = 0 → n = 0) : char_zero α :=
⟨λ m n, begin
assume h,
wlog hle : m ≤ n,
cases nat.le.dest hle with k e,
suffices : k = 0, by rw [← e, this, add_zero],
apply H, apply add_left_cancel n,
rw [← h, ← nat.cast_add, e, add_zero, h]
end⟩
-- We have no `left_cancel_add_monoid`, so we restate it for `add_group`
-- and `ordered_cancel_comm_monoid`.
theorem add_group.char_zero_of_inj_zero {α : Type*} [add_group α] [has_one α]
(H : ∀ n:ℕ, (n:α) = 0 → n = 0) : char_zero α :=
char_zero_of_inj_zero (@add_left_cancel _ _) H
theorem ordered_cancel_comm_monoid.char_zero_of_inj_zero {α : Type*}
[ordered_cancel_add_comm_monoid α] [has_one α]
(H : ∀ n:ℕ, (n:α) = 0 → n = 0) : char_zero α :=
char_zero_of_inj_zero (@add_left_cancel _ _) H
@[priority 100] -- see Note [lower instance priority]
instance linear_ordered_semiring.to_char_zero {α : Type*}
[linear_ordered_semiring α] : char_zero α :=
ordered_cancel_comm_monoid.char_zero_of_inj_zero $
λ n h, nat.eq_zero_of_le_zero $
(@nat.cast_le α _ _ _).1 (le_of_eq h)
namespace nat
variables {α : Type*} [add_monoid α] [has_one α] [char_zero α]
theorem cast_injective : function.injective (coe : ℕ → α) :=
char_zero.cast_injective
@[simp, norm_cast] theorem cast_inj {m n : ℕ} : (m : α) = n ↔ m = n :=
cast_injective.eq_iff
@[simp, norm_cast] theorem cast_eq_zero {n : ℕ} : (n : α) = 0 ↔ n = 0 :=
by rw [← cast_zero, cast_inj]
@[norm_cast] theorem cast_ne_zero {n : ℕ} : (n : α) ≠ 0 ↔ n ≠ 0 :=
not_congr cast_eq_zero
lemma cast_add_one_ne_zero (n : ℕ) : (n + 1 : α) ≠ 0 :=
by exact_mod_cast n.succ_ne_zero
end nat
@[field_simps] lemma two_ne_zero' {α : Type*} [add_monoid α] [has_one α] [char_zero α] : (2:α) ≠ 0 :=
have ((2:ℕ):α) ≠ 0, from nat.cast_ne_zero.2 dec_trivial,
by rwa [nat.cast_succ, nat.cast_one] at this
section
variables {α : Type*} [domain α] [char_zero α]
lemma add_self_eq_zero {a : α} : a + a = 0 ↔ a = 0 :=
by simp only [(two_mul a).symm, mul_eq_zero, two_ne_zero', false_or]
lemma bit0_eq_zero {a : α} : bit0 a = 0 ↔ a = 0 := add_self_eq_zero
end
section
variables {α : Type*} [division_ring α] [char_zero α]
@[simp] lemma half_add_self (a : α) : (a + a) / 2 = a :=
by rw [← mul_two, mul_div_cancel a two_ne_zero']
@[simp] lemma add_halves' (a : α) : a / 2 + a / 2 = a :=
by rw [← add_div, half_add_self]
lemma sub_half (a : α) : a - a / 2 = a / 2 :=
by rw [sub_eq_iff_eq_add, add_halves']
lemma half_sub (a : α) : a / 2 - a = - (a / 2) :=
by rw [← neg_sub, sub_half]
end
|
97179a2b0d718b8de4679a814369005734c7e48b | f5f7e6fae601a5fe3cac7cc3ed353ed781d62419 | /src/data/set/intervals.lean | 315f4bbf6f3f5b11f5878156c507e39c267f7357 | [
"Apache-2.0"
] | permissive | EdAyers/mathlib | 9ecfb2f14bd6caad748b64c9c131befbff0fb4e0 | ca5d4c1f16f9c451cf7170b10105d0051db79e1b | refs/heads/master | 1,626,189,395,845 | 1,555,284,396,000 | 1,555,284,396,000 | 144,004,030 | 0 | 0 | Apache-2.0 | 1,533,727,664,000 | 1,533,727,663,000 | null | UTF-8 | Lean | false | false | 10,622 | lean | /-
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
Intervals
Naming conventions:
`i`: infinite
`o`: open
`c`: closed
Each interval has the name `I` + letter for left side + letter for right side
TODO: This is just the beginning; a lot of rules are missing
-/
import data.set.lattice algebra.order algebra.order_functions
import tactic.linarith
namespace set
open set
section intervals
variables {α : Type*} [preorder α] {a a₁ a₂ b b₁ b₂ x : α}
/-- Left-open right-open interval -/
def Ioo (a b : α) := {x | a < x ∧ x < b}
/-- Left-closed right-open interval -/
def Ico (a b : α) := {x | a ≤ x ∧ x < b}
/-- Left-infinite right-open interval -/
def Iio (a : α) := {x | x < a}
/-- Left-closed right-closed interval -/
def Icc (a b : α) := {x | a ≤ x ∧ x ≤ b}
/-- Left-infinite right-closed interval -/
def Iic (b : α) := {x | x ≤ b}
/-- Left-open right-closed interval -/
def Ioc (a b : α) := {x | a < x ∧ x ≤ b}
/-- Left-closed right-infinite interval -/
def Ici (a : α) := {x | a ≤ x}
/-- Left-open right-infinite interval -/
def Ioi (a : α) := {x | a < x}
@[simp] lemma mem_Ioo : x ∈ Ioo a b ↔ a < x ∧ x < b := iff.rfl
@[simp] lemma mem_Ico : x ∈ Ico a b ↔ a ≤ x ∧ x < b := iff.rfl
@[simp] lemma mem_Iio : x ∈ Iio b ↔ x < b := iff.rfl
@[simp] lemma mem_Icc : x ∈ Icc a b ↔ a ≤ x ∧ x ≤ b := iff.rfl
@[simp] lemma mem_Iic : x ∈ Iic b ↔ x ≤ b := iff.rfl
@[simp] lemma mem_Ioc : x ∈ Ioc a b ↔ a < x ∧ x ≤ b := iff.rfl
@[simp] lemma mem_Ici : x ∈ Ici a ↔ a ≤ x := iff.rfl
@[simp] lemma mem_Ioi : x ∈ Ioi a ↔ a < x := iff.rfl
@[simp] lemma Ioo_eq_empty (h : b ≤ a) : Ioo a b = ∅ :=
eq_empty_iff_forall_not_mem.2 $ λ x ⟨h₁, h₂⟩, not_le_of_lt (lt_trans h₁ h₂) h
@[simp] lemma Ico_eq_empty (h : b ≤ a) : Ico a b = ∅ :=
eq_empty_iff_forall_not_mem.2 $ λ x ⟨h₁, h₂⟩, not_le_of_lt (lt_of_le_of_lt h₁ h₂) h
@[simp] lemma Icc_eq_empty (h : b < a) : Icc a b = ∅ :=
eq_empty_iff_forall_not_mem.2 $ λ x ⟨h₁, h₂⟩, not_lt_of_le (le_trans h₁ h₂) h
@[simp] lemma Ioc_eq_empty (h : b ≤ a) : Ioc a b = ∅ :=
eq_empty_iff_forall_not_mem.2 $ λ x ⟨h₁, h₂⟩, not_lt_of_le (le_trans h₂ h) h₁
@[simp] lemma Ioo_self (a : α) : Ioo a a = ∅ := Ioo_eq_empty $ le_refl _
@[simp] lemma Ico_self (a : α) : Ico a a = ∅ := Ico_eq_empty $ le_refl _
lemma Iio_ne_empty [no_bot_order α] (a : α) : Iio a ≠ ∅ :=
ne_empty_iff_exists_mem.2 (no_bot a)
lemma Ioi_ne_empty [no_top_order α] (a : α) : Ioi a ≠ ∅ :=
ne_empty_iff_exists_mem.2 (no_top a)
lemma Iic_ne_empty (b : α) : Iic b ≠ ∅ :=
ne_empty_iff_exists_mem.2 ⟨b, le_refl b⟩
lemma Ici_ne_empty (a : α) : Ici a ≠ ∅ :=
ne_empty_iff_exists_mem.2 ⟨a, le_refl a⟩
lemma Ioo_subset_Ioo (h₁ : a₂ ≤ a₁) (h₂ : b₁ ≤ b₂) :
Ioo a₁ b₁ ⊆ Ioo a₂ b₂ :=
λ x ⟨hx₁, hx₂⟩, ⟨lt_of_le_of_lt h₁ hx₁, lt_of_lt_of_le hx₂ h₂⟩
lemma Ioo_subset_Ioo_left (h : a₁ ≤ a₂) : Ioo a₂ b ⊆ Ioo a₁ b :=
Ioo_subset_Ioo h (le_refl _)
lemma Ioo_subset_Ioo_right (h : b₁ ≤ b₂) : Ioo a b₁ ⊆ Ioo a b₂ :=
Ioo_subset_Ioo (le_refl _) h
lemma Ico_subset_Ico (h₁ : a₂ ≤ a₁) (h₂ : b₁ ≤ b₂) :
Ico a₁ b₁ ⊆ Ico a₂ b₂ :=
λ x ⟨hx₁, hx₂⟩, ⟨le_trans h₁ hx₁, lt_of_lt_of_le hx₂ h₂⟩
lemma Ico_subset_Ico_left (h : a₁ ≤ a₂) : Ico a₂ b ⊆ Ico a₁ b :=
Ico_subset_Ico h (le_refl _)
lemma Ico_subset_Ico_right (h : b₁ ≤ b₂) : Ico a b₁ ⊆ Ico a b₂ :=
Ico_subset_Ico (le_refl _) h
lemma Icc_subset_Icc (h₁ : a₂ ≤ a₁) (h₂ : b₁ ≤ b₂) :
Icc a₁ b₁ ⊆ Icc a₂ b₂ :=
λ x ⟨hx₁, hx₂⟩, ⟨le_trans h₁ hx₁, le_trans hx₂ h₂⟩
lemma Icc_subset_Icc_left (h : a₁ ≤ a₂) : Icc a₂ b ⊆ Icc a₁ b :=
Icc_subset_Icc h (le_refl _)
lemma Icc_subset_Icc_right (h : b₁ ≤ b₂) : Icc a b₁ ⊆ Icc a b₂ :=
Icc_subset_Icc (le_refl _) h
lemma Ico_subset_Ioo_left (h₁ : a₁ < a₂) : Ico a₂ b ⊆ Ioo a₁ b :=
λ x, and.imp_left $ lt_of_lt_of_le h₁
lemma Icc_subset_Ico_right (h₁ : b₁ < b₂) : Icc a b₁ ⊆ Ico a b₂ :=
λ x, and.imp_right $ λ h₂, lt_of_le_of_lt h₂ h₁
lemma Ioo_subset_Ico_self : Ioo a b ⊆ Ico a b := λ x, and.imp_left le_of_lt
lemma Ico_subset_Icc_self : Ico a b ⊆ Icc a b := λ x, and.imp_right le_of_lt
lemma Ioo_subset_Icc_self : Ioo a b ⊆ Icc a b :=
subset.trans Ioo_subset_Ico_self Ico_subset_Icc_self
lemma Ico_subset_Iio_self : Ioo a b ⊆ Iio b := λ x, and.right
lemma Icc_subset_Icc_iff (h₁ : a₁ ≤ b₁) :
Icc a₁ b₁ ⊆ Icc a₂ b₂ ↔ a₂ ≤ a₁ ∧ b₁ ≤ b₂ :=
⟨λ h, ⟨(h ⟨le_refl _, h₁⟩).1, (h ⟨h₁, le_refl _⟩).2⟩,
λ ⟨h, h'⟩ x ⟨hx, hx'⟩, ⟨le_trans h hx, le_trans hx' h'⟩⟩
lemma Icc_subset_Ioo_iff (h₁ : a₁ ≤ b₁) :
Icc a₁ b₁ ⊆ Ioo a₂ b₂ ↔ a₂ < a₁ ∧ b₁ < b₂ :=
⟨λ h, ⟨(h ⟨le_refl _, h₁⟩).1, (h ⟨h₁, le_refl _⟩).2⟩,
λ ⟨h, h'⟩ x ⟨hx, hx'⟩, ⟨lt_of_lt_of_le h hx, lt_of_le_of_lt hx' h'⟩⟩
lemma Icc_subset_Ico_iff (h₁ : a₁ ≤ b₁) :
Icc a₁ b₁ ⊆ Ico a₂ b₂ ↔ a₂ ≤ a₁ ∧ b₁ < b₂ :=
⟨λ h, ⟨(h ⟨le_refl _, h₁⟩).1, (h ⟨h₁, le_refl _⟩).2⟩,
λ ⟨h, h'⟩ x ⟨hx, hx'⟩, ⟨le_trans h hx, lt_of_le_of_lt hx' h'⟩⟩
lemma Icc_subset_Ioc_iff (h₁ : a₁ ≤ b₁) :
Icc a₁ b₁ ⊆ Ioc a₂ b₂ ↔ a₂ < a₁ ∧ b₁ ≤ b₂ :=
⟨λ h, ⟨(h ⟨le_refl _, h₁⟩).1, (h ⟨h₁, le_refl _⟩).2⟩,
λ ⟨h, h'⟩ x ⟨hx, hx'⟩, ⟨lt_of_lt_of_le h hx, le_trans hx' h'⟩⟩
lemma Icc_subset_Iio_iff (h₁ : a₁ ≤ b₁) :
Icc a₁ b₁ ⊆ Iio b₂ ↔ b₁ < b₂ :=
⟨λ h, h ⟨h₁, le_refl _⟩, λ h x ⟨hx, hx'⟩, lt_of_le_of_lt hx' h⟩
lemma Icc_subset_Ioi_iff (h₁ : a₁ ≤ b₁) :
Icc a₁ b₁ ⊆ Ioi a₂ ↔ a₂ < a₁ :=
⟨λ h, h ⟨le_refl _, h₁⟩, λ h x ⟨hx, hx'⟩, lt_of_lt_of_le h hx⟩
lemma Icc_subset_Iic_iff (h₁ : a₁ ≤ b₁) :
Icc a₁ b₁ ⊆ Iic b₂ ↔ b₁ ≤ b₂ :=
⟨λ h, h ⟨h₁, le_refl _⟩, λ h x ⟨hx, hx'⟩, le_trans hx' h⟩
lemma Icc_subset_Ici_iff (h₁ : a₁ ≤ b₁) :
Icc a₁ b₁ ⊆ Ici a₂ ↔ a₂ ≤ a₁ :=
⟨λ h, h ⟨le_refl _, h₁⟩, λ h x ⟨hx, hx'⟩, le_trans h hx⟩
end intervals
section partial_order
variables {α : Type*} [partial_order α] {a b : α}
@[simp] lemma Icc_self (a : α) : Icc a a = {a} :=
set.ext $ by simp [Icc, le_antisymm_iff, and_comm]
lemma Ico_diff_Ioo_eq_singleton (h : a < b) : Ico a b \ Ioo a b = {a} :=
set.ext $ λ x, begin
simp, split,
{ rintro ⟨⟨ax, xb⟩, h⟩,
exact eq.symm (classical.by_contradiction
(λ ne, h (lt_of_le_of_ne ax ne) xb)) },
{ rintro rfl, exact ⟨⟨le_refl _, h⟩, (lt_irrefl x).elim⟩ }
end
lemma Icc_diff_Ico_eq_singleton (h : a ≤ b) : Icc a b \ Ico a b = {b} :=
set.ext $ λ x, begin
simp, split,
{ rintro ⟨⟨ax, xb⟩, h⟩,
exact classical.by_contradiction
(λ ne, h ax (lt_of_le_of_ne xb ne)) },
{ rintro rfl, exact ⟨⟨h, le_refl _⟩, λ _, lt_irrefl x⟩ }
end
end partial_order
section linear_order
variables {α : Type*} [linear_order α] {a a₁ a₂ b b₁ b₂ : α}
lemma Ioo_eq_empty_iff [densely_ordered α] : Ioo a b = ∅ ↔ b ≤ a :=
⟨λ eq, le_of_not_lt $ λ h,
let ⟨x, h₁, h₂⟩ := dense h in
eq_empty_iff_forall_not_mem.1 eq x ⟨h₁, h₂⟩,
Ioo_eq_empty⟩
lemma Ico_eq_empty_iff : Ico a b = ∅ ↔ b ≤ a :=
⟨λ eq, le_of_not_lt $ λ h, eq_empty_iff_forall_not_mem.1 eq a ⟨le_refl _, h⟩,
Ico_eq_empty⟩
lemma Icc_eq_empty_iff : Icc a b = ∅ ↔ b < a :=
⟨λ eq, lt_of_not_ge $ λ h, eq_empty_iff_forall_not_mem.1 eq a ⟨le_refl _, h⟩,
Icc_eq_empty⟩
lemma Ico_subset_Ico_iff (h₁ : a₁ < b₁) :
Ico a₁ b₁ ⊆ Ico a₂ b₂ ↔ a₂ ≤ a₁ ∧ b₁ ≤ b₂ :=
⟨λ h, have a₂ ≤ a₁ ∧ a₁ < b₂ := h ⟨le_refl _, h₁⟩,
⟨this.1, le_of_not_lt $ λ h', lt_irrefl b₂ (h ⟨le_of_lt this.2, h'⟩).2⟩,
λ ⟨h₁, h₂⟩, Ico_subset_Ico h₁ h₂⟩
lemma Ioo_subset_Ioo_iff [densely_ordered α] (h₁ : a₁ < b₁) :
Ioo a₁ b₁ ⊆ Ioo a₂ b₂ ↔ a₂ ≤ a₁ ∧ b₁ ≤ b₂ :=
⟨λ h, begin
rcases dense h₁ with ⟨x, xa, xb⟩,
split; refine le_of_not_lt (λ h', _),
{ have ab := lt_trans (h ⟨xa, xb⟩).1 xb,
exact lt_irrefl _ (h ⟨h', ab⟩).1 },
{ have ab := lt_trans xa (h ⟨xa, xb⟩).2,
exact lt_irrefl _ (h ⟨ab, h'⟩).2 }
end, λ ⟨h₁, h₂⟩, Ioo_subset_Ioo h₁ h₂⟩
lemma Ico_eq_Ico_iff (h : a₁ < b₁ ∨ a₂ < b₂) : Ico a₁ b₁ = Ico a₂ b₂ ↔ a₁ = a₂ ∧ b₁ = b₂ :=
⟨λ e, begin
simp [subset.antisymm_iff] at e, simp [le_antisymm_iff],
cases h; simp [Ico_subset_Ico_iff h] at e;
[ rcases e with ⟨⟨h₁, h₂⟩, e'⟩, rcases e with ⟨e', ⟨h₁, h₂⟩⟩ ];
have := (Ico_subset_Ico_iff (lt_of_le_of_lt h₁ $ lt_of_lt_of_le h h₂)).1 e';
tauto
end, λ ⟨h₁, h₂⟩, by rw [h₁, h₂]⟩
end linear_order
section decidable_linear_order
variables {α : Type*} [decidable_linear_order α] {a a₁ a₂ b b₁ b₂ : α}
@[simp] lemma Ico_diff_Iio {a b c : α} : Ico a b \ Iio c = Ico (max a c) b :=
set.ext $ by simp [Ico, Iio, iff_def, max_le_iff] {contextual:=tt}
@[simp] lemma Ico_inter_Iio {a b c : α} : Ico a b ∩ Iio c = Ico a (min b c) :=
set.ext $ by simp [Ico, Iio, iff_def, lt_min_iff] {contextual:=tt}
lemma Ioo_inter_Ioo {a b c d : α} : Ioo a b ∩ Ioo c d = Ioo (max a c) (min b d) :=
set.ext $ by simp [iff_def, Ioo, lt_min_iff, max_lt_iff] {contextual := tt}
end decidable_linear_order
section ordered_comm_group
variables {α : Type*} [ordered_comm_group α]
lemma image_neg_Iio (r : α) : image (λz, -z) (Iio r) = Ioi (-r) :=
begin
apply set.ext,
intros z,
apply iff.intro,
{ intros hz,
apply exists.elim hz,
intros z' hz',
rw [←hz'.2],
simp at *,
exact hz'.1 },
{ intros hz,
simp at *,
use -z,
simp [hz],
exact neg_lt.1 hz }
end
lemma image_neg_Iic (r : α) : image (λz, -z) (Iic r) = Ici (-r) :=
begin
apply set.ext,
intros z,
apply iff.intro,
{ intros hz,
apply exists.elim hz,
intros z' hz',
rw [←hz'.2],
simp at *,
exact hz'.1 },
{ intros hz,
simp at *,
use -z,
simp [hz],
exact neg_le.1 hz }
end
end ordered_comm_group
end set
|
80e11f8a4a3fb6789c9db529147f4f94c31987ba | 74addaa0e41490cbaf2abd313a764c96df57b05d | /Mathlib/tactic/scc.lean | 1c56014d8d57aac7a5242fc53dad56ae8744557a | [] | no_license | AurelienSaue/Mathlib4_auto | f538cfd0980f65a6361eadea39e6fc639e9dae14 | 590df64109b08190abe22358fabc3eae000943f2 | refs/heads/master | 1,683,906,849,776 | 1,622,564,669,000 | 1,622,564,669,000 | 371,723,747 | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 7,566 | lean | /-
Copyright (c) 2018 Simon Hudon All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Simon Hudon
Tactics based on the strongly connected components (SCC) of a graph where
the vertices are propositions and the edges are implications found
in the context.
They are used for finding the sets of equivalent propositions in a set
of implications.
-/
import Mathlib.PrePort
import Mathlib.Lean3Lib.init.default
import Mathlib.tactic.tauto
import Mathlib.data.sum
import Mathlib.PostPort
namespace Mathlib
/-!
# Strongly Connected Components
This file defines tactics to construct proofs of equivalences between a set of mutually equivalent
propositions. The tactics use implications transitively to find sets of equivalent propositions.
## Implementation notes
The tactics use a strongly connected components algorithm on a graph where propositions are
vertices and edges are proofs that the source implies the target. The strongly connected components
are therefore sets of propositions that are pairwise equivalent to each other.
The resulting strongly connected components are encoded in a disjoint set data structure to
facilitate the construction of equivalence proofs between two arbitrary members of an equivalence
class.
## Possible generalizations
Instead of reasoning about implications and equivalence, we could generalize the machinery to
reason about arbitrary partial orders.
## References
* Tarjan, R. E. (1972), "Depth-first search and linear graph algorithms",
SIAM Journal on Computing, 1 (2): 146–160, doi:10.1137/0201010
* Dijkstra, Edsger (1976), A Discipline of Programming, NJ: Prentice Hall, Ch. 25.
* <https://en.wikipedia.org/wiki/Disjoint-set_data_structure>
## Tags
graphs, tactic, strongly connected components, disjoint sets
-/
namespace tactic
/--
`closure` implements a disjoint set data structure using path compression
optimization. For the sake of the scc algorithm, it also stores the preorder
numbering of the equivalence graph of the local assumptions.
The `expr_map` encodes a directed forest by storing for every non-root
node, a reference to its parent and a proof of equivalence between
that node's expression and its parent's expression. Given that data
structure, checking that two nodes belong to the same tree is easy and
fast by repeatedly following the parent references until a root is reached.
If both nodes have the same root, they belong to the same tree, i.e. their
expressions are equivalent. The proof of equivalence can be formed by
composing the proofs along the edges of the paths to the root.
More concretely, if we ignore preorder numbering, the set
`{ {e₀,e₁,e₂,e₃}, {e₄,e₅} }` is represented as:
```
e₀ → ⊥ -- no parent, i.e. e₀ is a root
e₁ → e₀, p₁ -- with p₁ : e₁ ↔ e₀
e₂ → e₁, p₂ -- with p₂ : e₂ ↔ e₁
e₃ → e₀, p₃ -- with p₃ : e₃ ↔ e₀
e₄ → ⊥ -- no parent, i.e. e₄ is a root
e₅ → e₄, p₅ -- with p₅ : e₅ ↔ e₄
```
We can check that `e₂` and `e₃` are equivalent by seeking the root of
the tree of each. The parent of `e₂` is `e₁`, the parent of `e₁` is
`e₀` and `e₀` does not have a parent, and thus, this is the root of its tree.
The parent of `e₃` is `e₀` and it's also the root, the same as for `e₂` and
they are therefore equivalent. We can build a proof of that equivalence by using
transitivity on `p₂`, `p₁` and `p₃.symm` in that order.
Similarly, we can discover that `e₂` and `e₅` aren't equivalent.
A description of the path compression optimization can be found at:
<https://en.wikipedia.org/wiki/Disjoint-set_data_structure#Path_compression>
-/
namespace closure
/-- `with_new_closure f` creates an empty `closure` `c`, executes `f` on `c`, and then deletes `c`,
returning the output of `f`. -/
/-- `to_tactic_format cl` pretty-prints the `closure` `cl` as a list. Assuming `cl` was built by
`dfs_at`, each element corresponds to a node `pᵢ : expr` and is one of the folllowing:
- if `pᵢ` is a root: `"pᵢ ⇐ i"`, where `i` is the preorder number of `pᵢ`,
- otherwise: `"(pᵢ, pⱼ) : P"`, where `P` is `pᵢ ↔ pⱼ`.
Useful for debugging. -/
/-- `(n,r,p) ← root cl e` returns `r` the root of the tree that `e` is a part of (which might be
itself) along with `p` a proof of `e ↔ r` and `n`, the preorder numbering of the root. -/
/-- (Implementation of `merge`.) -/
/-- `merge cl p`, with `p` a proof of `e₀ ↔ e₁` for some `e₀` and `e₁`,
merges the trees of `e₀` and `e₁` and keeps the root with the smallest preorder
number as the root. This ensures that, in the depth-first traversal of the graph,
when encountering an edge going into a vertex whose equivalence class includes
a vertex that originated the current search, that vertex will be the root of
the corresponding tree. -/
/-- Sequentially assign numbers to the nodes of the graph as they are being visited. -/
/-- `prove_eqv cl e₀ e₁` constructs a proof of equivalence of `e₀` and `e₁` if
they are equivalent. -/
/-- `prove_impl cl e₀ e₁` constructs a proof of `e₀ -> e₁` if they are equivalent. -/
/-- `is_eqv cl e₀ e₁` checks whether `e₀` and `e₁` are equivalent without building a proof. -/
end closure
/-- mutable graphs between local propositions that imply each other with the proof of implication -/
/-- `with_impl_graph f` creates an empty `impl_graph` `g`, executes `f` on `g`, and then deletes
`g`, returning the output of `f`. -/
namespace impl_graph
/-- `add_edge g p`, with `p` a proof of `v₀ → v₁` or `v₀ ↔ v₁`, adds an edge to the implication
graph `g`. -/
/-- `merge_path path e`, where `path` and `e` forms a cycle with proofs of implication between
consecutive vertices. The proofs are compiled into proofs of equivalences and added to the closure
structure. `e` and the first vertex of `path` do not have to be the same but they have to be
in the same equivalence class. -/
/-- (implementation of `collapse`) -/
/-- `collapse path v`, where `v` is a vertex that originated the current search
(or a vertex in the same equivalence class as the one that originated the current search).
It or its equivalent should be found in `path`. Since the vertices following `v` in the path
form a cycle with `v`, they can all be added to an equivalence class. -/
/--
Strongly connected component algorithm inspired by Tarjan's and
Dijkstra's scc algorithm. Whereas they return strongly connected
components by enumerating them, this algorithm returns a disjoint set
data structure using path compression. This is a compact
representation that allows us, after the fact, to construct a proof of
equivalence between any two members of an equivalence class.
* Tarjan, R. E. (1972), "Depth-first search and linear graph algorithms",
SIAM Journal on Computing, 1 (2): 146–160, doi:10.1137/0201010
* Dijkstra, Edsger (1976), A Discipline of Programming, NJ: Prentice Hall, Ch. 25.
-/
/-- Use the local assumptions to create a set of equivalence classes. -/
end impl_graph
/--
`scc` uses the available equivalences and implications to prove
a goal of the form `p ↔ q`.
```lean
example (p q r : Prop) (hpq : p → q) (hqr : q ↔ r) (hrp : r → p) : p ↔ r :=
by scc
```
-/
/-- Collect all the available equivalences and implications and
add assumptions for every equivalence that can be proven using the
strongly connected components technique. Mostly useful for testing. -/
/--
`scc` uses the available equivalences and implications to prove
|
3a58f24d8ef41b7b7367bb9e96328bcf6e313429 | 92b50235facfbc08dfe7f334827d47281471333b | /library/theories/number_theory/prime_factorization.lean | d4f993f8846b2d5dce1f8be4606a5485cc78531b | [
"Apache-2.0"
] | permissive | htzh/lean | 24f6ed7510ab637379ec31af406d12584d31792c | d70c79f4e30aafecdfc4a60b5d3512199200ab6e | refs/heads/master | 1,607,677,731,270 | 1,437,089,952,000 | 1,437,089,952,000 | 37,078,816 | 0 | 0 | null | 1,433,780,956,000 | 1,433,780,955,000 | null | UTF-8 | Lean | false | false | 9,735 | lean | /-
Copyright (c) 2015 Jeremy Avigad. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Jeremy Avigad
Multiplicity and prime factors. We have:
mult p n := the greatest power of p dividing n if p > 1 and n > 0, and 0 otherwise.
prime_factors n := the finite set of prime factors of n, assuming n > 0
-/
import data.nat data.finset .primes
open eq.ops finset well_founded decidable
namespace nat
/- multiplicity -/
theorem mult_rec_decreasing {p n : ℕ} (Hp : p > 1) (Hn : n > 0) : n div p < n :=
have H' : n < n * p,
by rewrite [-mul_one n at {1}]; apply mul_lt_mul_of_pos_left Hp Hn,
div_lt_of_lt_mul H'
private definition mult.F (p : ℕ) (n : ℕ) (f: Π {m : ℕ}, m < n → ℕ) : ℕ :=
if H : (p > 1 ∧ n > 0) ∧ p ∣ n then
succ (f (mult_rec_decreasing (and.left (and.left H)) (and.right (and.left H))))
else 0
definition mult (p n : ℕ) : ℕ := fix (mult.F p) n
theorem mult_rec {p n : ℕ} (pgt1 : p > 1) (ngt0 : n > 0) (pdivn : p ∣ n) :
mult p n = succ (mult p (n div p)) :=
have H : (p > 1 ∧ n > 0) ∧ p ∣ n, from and.intro (and.intro pgt1 ngt0) pdivn,
eq.trans (well_founded.fix_eq (mult.F p) n) (dif_pos H)
private theorem mult_base {p n : ℕ} (H : ¬ ((p > 1 ∧ n > 0) ∧ p ∣ n)) :
mult p n = 0 :=
eq.trans (well_founded.fix_eq (mult.F p) n) (dif_neg H)
theorem mult_zero_right (p : ℕ) : mult p 0 = 0 :=
mult_base (assume H, !lt.irrefl (and.right (and.left H)))
theorem mult_eq_zero_of_not_dvd {p n : ℕ} (H : ¬ p ∣ n) : mult p n = 0 :=
mult_base (assume H', H (and.right H'))
theorem mult_eq_zero_of_le_one {p : ℕ} (n : ℕ) (H : p ≤ 1) : mult p n = 0 :=
mult_base (assume H', not_lt_of_ge H (and.left (and.left H')))
theorem mult_zero_left (n : ℕ) : mult 0 n = 0 :=
mult_eq_zero_of_le_one n !dec_trivial
theorem mult_one_left (n : ℕ) : mult 1 n = 0 :=
mult_eq_zero_of_le_one n !dec_trivial
theorem mult_pos_of_dvd {p n : ℕ} (pgt1 : p > 1) (npos : n > 0) (pdvdn : p ∣ n) : mult p n > 0 :=
by rewrite (mult_rec pgt1 npos pdvdn); apply succ_pos
theorem not_dvd_of_mult_eq_zero {p n : ℕ} (pgt1 : p > 1) (npos : n > 0) (H : mult p n = 0) :
¬ p ∣ n :=
assume pdvdn : p ∣ n,
ne_of_gt (mult_pos_of_dvd pgt1 npos pdvdn) H
theorem dvd_of_mult_pos {p n : ℕ} (H : mult p n > 0) : p ∣ n :=
by_contradiction (assume npdvdn : ¬ p ∣ n, ne_of_gt H (mult_eq_zero_of_not_dvd npdvdn))
/- properties of mult -/
theorem pow_mult_dvd (p n : ℕ) : p^(mult p n) ∣ n :=
begin
induction n using nat.strong_induction_on with [n, ih],
cases eq_zero_or_pos n with [nz, npos],
{rewrite nz, apply dvd_zero},
cases le_or_gt p 1 with [ple1, pgt1],
{rewrite [!mult_eq_zero_of_le_one ple1, pow_zero], apply one_dvd},
cases (or.swap (em (p ∣ n))) with [pndvdn, pdvdn],
{rewrite [mult_eq_zero_of_not_dvd pndvdn, pow_zero], apply one_dvd},
show p ^ (mult p n) ∣ n, from dvd.elim pdvdn
(take n',
assume Hn' : n = p * n',
have ppos : p > 0, from lt.trans zero_lt_one pgt1,
assert ndivpeq : n div p = n', from !div_eq_of_eq_mul_right ppos Hn',
assert ndivplt : n' < n,
by rewrite -ndivpeq; apply mult_rec_decreasing pgt1 npos,
begin
rewrite [mult_rec pgt1 npos pdvdn, ndivpeq, pow_succ', Hn'],
apply mul_dvd_mul !dvd.refl,
apply ih _ ndivplt
end)
end
theorem mult_one_right (p : ℕ) : mult p 1 = 0:=
assert H : p^(mult p 1) = 1, from eq_one_of_dvd_one !pow_mult_dvd,
or.elim (le_or_gt p 1)
(assume H1 : p ≤ 1, by rewrite [!mult_eq_zero_of_le_one H1])
(assume H1 : p > 1,
by_contradiction
assume H2 : mult p 1 ≠ 0,
have H3 : mult p 1 > 0, from pos_of_ne_zero H2,
assert H4 : p^(mult p 1) > 1, from pow_gt_one H1 H3,
show false, by rewrite H at H4; apply !lt.irrefl H4)
private theorem mult_pow_mul {p n : ℕ} (i : ℕ) (pgt1 : p > 1) (npos : n > 0) :
mult p (p^i * n) = i + mult p n :=
begin
induction i with [i, ih],
rewrite [pow_zero, one_mul, zero_add], -- strange: this fails with {brackets} around it
have ppos : p > 0, from lt.trans zero_lt_one pgt1,
have psin_pos : p^(succ i) * n > 0, from mul_pos (!pow_pos_of_pos ppos) npos,
have pdvd : p ∣ p^(succ i) * n, by rewrite [pow_succ', mul.assoc]; apply dvd_mul_right,
rewrite [mult_rec pgt1 psin_pos pdvd, pow_succ, mul.right_comm, !mul_div_cancel ppos, ih],
rewrite [add.comm i, add.comm (succ i)]
end
theorem mult_pow {p : ℕ} (i : ℕ) (pgt1 : p > 1) : mult p (p^i) = i :=
by rewrite [-(mul_one (p^i)), mult_pow_mul i pgt1 zero_lt_one, mult_one_right]
theorem le_mult {p i n : ℕ} (pgt1 : p > 1) (npos : n > 0) (pidvd : p^i ∣ n) : i ≤ mult p n :=
dvd.elim pidvd
(take m,
assume neq : n = p^i * m,
assert mpos : m > 0, from pos_of_mul_pos_left (neq ▸ npos),
by rewrite [neq, mult_pow_mul i pgt1 mpos]; apply le_add_right)
theorem not_dvd_div_pow_mult {p n : ℕ} (pgt1 : p > 1) (npos : n > 0) : ¬ p ∣ n div p^(mult p n) :=
assume pdvd : p ∣ n div p^(mult p n),
obtain m (H : n div p^(mult p n) = p * m), from exists_eq_mul_right_of_dvd pdvd,
assert neq : n = p^(succ (mult p n)) * m, from
calc
n = p^mult p n * (n div p^mult p n) : by rewrite (mul_div_cancel' !pow_mult_dvd)
... = p^(succ (mult p n)) * m : by rewrite [H, pow_succ, mul.assoc],
have H1 : p^(succ (mult p n)) ∣ n, by rewrite neq at {2}; apply dvd_mul_right,
have H2 : succ (mult p n) ≤ mult p n, from le_mult pgt1 npos H1,
show false, from !not_succ_le_self H2
theorem mult_mul {p m n : ℕ} (primep : prime p) (mpos : m > 0) (npos : n > 0) :
mult p (m * n) = mult p m + mult p n :=
let m' := m div p^mult p m, n' := n div p^mult p n in
assert pgt1 : p > 1, from gt_one_of_prime primep,
assert meq : m = p^mult p m * m', by rewrite (mul_div_cancel' !pow_mult_dvd),
assert neq : n = p^mult p n * n', by rewrite (mul_div_cancel' !pow_mult_dvd),
have m'pos : m' > 0, from pos_of_mul_pos_left (meq ▸ mpos),
have n'pos : n' > 0, from pos_of_mul_pos_left (neq ▸ npos),
have npdvdm' : ¬ p ∣ m', from !not_dvd_div_pow_mult pgt1 mpos,
have npdvdn' : ¬ p ∣ n', from !not_dvd_div_pow_mult pgt1 npos,
assert npdvdm'n' : ¬ p ∣ m' * n', from not_dvd_mul_of_prime primep npdvdm' npdvdn',
assert m'n'pos : m' * n' > 0, from mul_pos m'pos n'pos,
assert multm'n' : mult p (m' * n') = 0, from mult_eq_zero_of_not_dvd npdvdm'n',
calc
mult p (m * n) = mult p (p^(mult p m + mult p n) * (m' * n')) :
by rewrite [pow_add, mul.right_comm, -mul.assoc, -meq, mul.assoc,
mul.comm (n div _), -neq]
... = mult p m + mult p n :
by rewrite [!mult_pow_mul pgt1 m'n'pos, multm'n']
theorem dvd_of_forall_prime_mult_le {m n : ℕ} (mpos : m > 0)
(H : ∀ {p}, prime p → mult p m ≤ mult p n) :
m ∣ n :=
begin
revert H, revert n,
induction m using nat.strong_induction_on with [m, ih],
cases (decidable.em (m = 1)) with [meq, mneq],
{intros, rewrite meq, apply one_dvd},
have mgt1 : m > 1, from lt_of_le_of_ne (succ_le_of_lt mpos) (ne.symm mneq),
have mge2 : m ≥ 2, from succ_le_of_lt mgt1,
have hpd : ∃ p, prime p ∧ p ∣ m, from ex_prime_and_dvd mge2,
cases hpd with [p, H1],
cases H1 with [primep, pdvdm],
intro n,
cases (eq_zero_or_pos n) with [nz, npos],
{intros; rewrite nz; apply dvd_zero},
assume H : ∀ {p : ℕ}, prime p → mult p m ≤ mult p n,
obtain m' (meq : m = p * m'), from exists_eq_mul_right_of_dvd pdvdm,
assert pgt1 : p > 1, from gt_one_of_prime primep,
assert m'pos : m' > 0, from pos_of_ne_zero
(assume m'z, by revert mpos; rewrite [meq, m'z, mul_zero]; apply not_lt_zero),
have m'ltm : m' < m,
by rewrite [meq, -one_mul m' at {1}]; apply mul_lt_mul_of_lt_of_le m'pos pgt1 !le.refl,
have multpm : mult p m ≥ 1, from le_mult pgt1 mpos (by rewrite pow_one; apply pdvdm),
have multpn : mult p n ≥ 1, from le.trans multpm (H primep),
obtain n' (neq : n = p * n'),
from exists_eq_mul_right_of_dvd (dvd_of_mult_pos (lt_of_succ_le multpn)),
assert n'pos : n' > 0, from pos_of_ne_zero
(assume n'z, by revert npos; rewrite [neq, n'z, mul_zero]; apply not_lt_zero),
have H' : ∀q, prime q → mult q m' ≤ mult q n', from
(take q,
assume primeq : prime q,
have multqm : mult q m = mult q p + mult q m',
by rewrite [meq, mult_mul primeq (pos_of_prime primep) m'pos],
have multqn : mult q n = mult q p + mult q n',
by rewrite [neq, mult_mul primeq (pos_of_prime primep) n'pos],
show mult q m' ≤ mult q n', from le_of_add_le_add_left (multqm ▸ multqn ▸ H primeq)),
assert m'dvdn' : m' ∣ n', from ih m' m'ltm m'pos n' H',
show m ∣ n, by rewrite [meq, neq]; apply mul_dvd_mul !dvd.refl m'dvdn'
end
theorem eq_of_forall_prime_mult_eq {m n : ℕ} (mpos : m > 0) (npos : n > 0)
(H : ∀ {p}, prime p → mult p m = mult p n) : m = n :=
dvd.antisymm
(dvd_of_forall_prime_mult_le mpos (take p, assume primep, H primep ▸ !le.refl))
(dvd_of_forall_prime_mult_le npos (take p, assume primep, H primep ▸ !le.refl))
/- prime factors -/
definition prime_factors (n : ℕ) : finset ℕ := { p ∈ upto (succ n) | prime p ∧ p ∣ n }
theorem prime_of_mem_prime_factors {p n : ℕ} (H : p ∈ prime_factors n) : prime p :=
and.left (of_mem_filter H)
theorem dvd_of_mem_prime_factors {p n : ℕ} (H : p ∈ prime_factors n) : p ∣ n :=
and.right (of_mem_filter H)
theorem mem_prime_factors {p n : ℕ} (npos : n > 0) (primep : prime p) (pdvdn : p ∣ n) :
p ∈ prime_factors n :=
have plen : p ≤ n, from le_of_dvd npos pdvdn,
mem_filter_of_mem (mem_upto_of_lt (lt_succ_of_le plen)) (and.intro primep pdvdn)
end nat
|
038827b26bc957a9264141c72b2353871f3558e0 | 7d5ad87afb17e514aee234fcf0a24412eed6384f | /src/abel.lean | 7e972615828e11a8bd0e44c40d89f9750deeb637 | [] | no_license | digama0/flypitch | 764f849eaef59c045dfbeca142a0f827973e70c1 | 2ec14b8da6a3964f09521d17e51f363d255b030f | refs/heads/master | 1,586,980,069,651 | 1,547,078,141,000 | 1,547,078,283,000 | 164,965,135 | 1 | 0 | null | 1,547,082,858,000 | 1,547,082,857,000 | null | UTF-8 | Lean | false | false | 2,601 | lean | import .fol tactic.tidy
open fol
local notation h :: t := dvector.cons h t
local notation `[]` := dvector.nil
local notation `[` l:(foldr `, ` (h t, dvector.cons h t) dvector.nil `]`) := l
namespace abel
section
/- The language of abelian groups -/
inductive abel_functions : ℕ → Type
| zero : abel_functions 0
| plus : abel_functions 2
def L_abel : Language := ⟨abel_functions, λn, empty⟩
def L_abel_plus {n} (t₁ t₂ : bounded_term L_abel n) : bounded_term L_abel n :=
@bounded_term_of_function L_abel 2 n abel_functions.plus t₁ t₂
def zero {n} : bounded_term L_abel n := bd_const abel_functions.zero
infix ` +' `:100 := _root_.abel.L_abel_plus
def a_assoc : sentence L_abel := ∀' ∀' ∀' (((&2 +' &1) +' &0) ≃ (&2 +' (&1 +' &0)))
def a_zero_right : sentence L_abel := ∀' (&0 +' zero ≃ &0)
def a_zero_left : sentence L_abel := ∀'(zero +' &0 ≃ &0)
def a_inv : sentence L_abel := ∀' ∃' (&1 +' &0 ≃ zero ⊓ &0 +' &1 ≃ zero)
def a_comm : sentence L_abel := ∀' ∀' (&1 +' &0 ≃ &0 +' &1)
/- axioms of abelian groups -/
def T_ab : Theory L_abel := {a_assoc, a_zero_right, a_zero_left, a_inv, a_comm}
def L_abel_structure_of_int : Structure L_abel :=
begin
refine ⟨ℤ,_,_⟩,
{intros n f, induction f,
exact λ v, 0,
exact λ v, (v.nth 0 (by repeat{constructor})) + (v.nth 1 (by repeat{constructor}))},
{intros, cases a}
end
notation `ℤ'` := _root_.abel.L_abel_structure_of_int
@[simp]lemma ℤ'_ℤ : ↥(ℤ') = ℤ := by refl
@[reducible]instance has_zero_ℤ' : has_zero ℤ' := ⟨(0 : ℤ)⟩
@[reducible]instance has_add_ℤ' : has_add ℤ' := ⟨λx y, (x + y : ℤ)⟩
@[reducible]instance nonempty_ℤ' : nonempty ℤ' := by simp
@[simp]lemma zero_is_zero : @realize_bounded_term L_abel ℤ' _ [] _ zero [] = (0 : ℤ) := by refl
@[simp]lemma plus_is_plus_l : ∀ x y : ℤ', realize_bounded_term ([x,y]) (&0 +' &1) [] = x + y := by {intros, refl}
@[simp]lemma plus_is_plus_r : ∀ x y : ℤ', realize_bounded_term ([x,y]) (&1 +' &0) [] = y + x := by {intros, refl}
def presburger_arithmetic : Theory L_abel := Th ℤ'
theorem ℤ'_is_abelian_group : T_ab ⊆ presburger_arithmetic :=
begin
intros a H, repeat{cases H},
{tidy},
{intros x H, dsimp at H, unfold realize_bounded_formula, have : ∃ y : ℤ, x + y = 0,
by exact ⟨-x, by tidy⟩, rcases this with ⟨y, hy⟩, apply H y, simp[hy], refl},
{tidy, conv {to_lhs, change (0 : ℤ) + x, rw[zero_add]}, refl},
{tidy, conv {to_lhs, change x + 0, rw[add_zero]}, refl},
{tidy, conv {to_lhs, change x + x_1 + x_2}, finish}
end
end
end abel
|
412ef36bb150bac6bb4752d7fc86b9d92daaac68 | 94e33a31faa76775069b071adea97e86e218a8ee | /src/group_theory/specific_groups/dihedral.lean | e6c44a0b85319faeb21b995ab6b802179581516a | [
"Apache-2.0"
] | permissive | urkud/mathlib | eab80095e1b9f1513bfb7f25b4fa82fa4fd02989 | 6379d39e6b5b279df9715f8011369a301b634e41 | refs/heads/master | 1,658,425,342,662 | 1,658,078,703,000 | 1,658,078,703,000 | 186,910,338 | 0 | 0 | Apache-2.0 | 1,568,512,083,000 | 1,557,958,709,000 | Lean | UTF-8 | Lean | false | false | 5,859 | lean | /-
Copyright (c) 2020 Shing Tak Lam. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Shing Tak Lam
-/
import data.fintype.card
import data.zmod.basic
import group_theory.exponent
import data.int.parity
/-!
# Dihedral Groups
We define the dihedral groups `dihedral_group n`, with elements `r i` and `sr i` for `i : zmod n`.
For `n ≠ 0`, `dihedral_group n` represents the symmetry group of the regular `n`-gon. `r i`
represents the rotations of the `n`-gon by `2πi/n`, and `sr i` represents the reflections of the
`n`-gon. `dihedral_group 0` corresponds to the infinite dihedral group.
-/
/--
For `n ≠ 0`, `dihedral_group n` represents the symmetry group of the regular `n`-gon.
`r i` represents the rotations of the `n`-gon by `2πi/n`, and `sr i` represents the reflections of
the `n`-gon. `dihedral_group 0` corresponds to the infinite dihedral group.
-/
@[derive decidable_eq]
inductive dihedral_group (n : ℕ) : Type
| r : zmod n → dihedral_group
| sr : zmod n → dihedral_group
namespace dihedral_group
variables {n : ℕ}
/--
Multiplication of the dihedral group.
-/
private def mul : dihedral_group n → dihedral_group n → dihedral_group n
| (r i) (r j) := r (i + j)
| (r i) (sr j) := sr (j - i)
| (sr i) (r j) := sr (i + j)
| (sr i) (sr j) := r (j - i)
/--
The identity `1` is the rotation by `0`.
-/
private def one : dihedral_group n := r 0
instance : inhabited (dihedral_group n) := ⟨one⟩
/--
The inverse of a an element of the dihedral group.
-/
private def inv : dihedral_group n → dihedral_group n
| (r i) := r (-i)
| (sr i) := sr i
/--
The group structure on `dihedral_group n`.
-/
instance : group (dihedral_group n) :=
{ mul := mul,
mul_assoc :=
begin
rintros (a | a) (b | b) (c | c);
simp only [mul];
ring,
end,
one := one,
one_mul :=
begin
rintros (a | a),
exact congr_arg r (zero_add a),
exact congr_arg sr (sub_zero a),
end,
mul_one := begin
rintros (a | a),
exact congr_arg r (add_zero a),
exact congr_arg sr (add_zero a),
end,
inv := inv,
mul_left_inv := begin
rintros (a | a),
exact congr_arg r (neg_add_self a),
exact congr_arg r (sub_self a),
end }
@[simp] lemma r_mul_r (i j : zmod n) : r i * r j = r (i + j) := rfl
@[simp] lemma r_mul_sr (i j : zmod n) : r i * sr j = sr (j - i) := rfl
@[simp] lemma sr_mul_r (i j : zmod n) : sr i * r j = sr (i + j) := rfl
@[simp] lemma sr_mul_sr (i j : zmod n) : sr i * sr j = r (j - i) := rfl
lemma one_def : (1 : dihedral_group n) = r 0 := rfl
private def fintype_helper : (zmod n ⊕ zmod n) ≃ dihedral_group n :=
{ inv_fun := λ i, match i with
| (r j) := sum.inl j
| (sr j) := sum.inr j
end,
to_fun := λ i, match i with
| (sum.inl j) := r j
| (sum.inr j) := sr j
end,
left_inv := by rintro (x | x); refl,
right_inv := by rintro (x | x); refl }
/--
If `0 < n`, then `dihedral_group n` is a finite group.
-/
instance [fact (0 < n)] : fintype (dihedral_group n) := fintype.of_equiv _ fintype_helper
instance : nontrivial (dihedral_group n) := ⟨⟨r 0, sr 0, dec_trivial⟩⟩
/--
If `0 < n`, then `dihedral_group n` has `2n` elements.
-/
lemma card [fact (0 < n)] : fintype.card (dihedral_group n) = 2 * n :=
by rw [← fintype.card_eq.mpr ⟨fintype_helper⟩, fintype.card_sum, zmod.card, two_mul]
@[simp] lemma r_one_pow (k : ℕ) : (r 1 : dihedral_group n) ^ k = r k :=
begin
induction k with k IH,
{ rw nat.cast_zero, refl },
{ rw [pow_succ, IH, r_mul_r],
congr' 1,
norm_cast,
rw nat.one_add }
end
@[simp] lemma r_one_pow_n : (r (1 : zmod n))^n = 1 :=
begin
rw [r_one_pow, one_def],
congr' 1,
exact zmod.nat_cast_self _,
end
@[simp] lemma sr_mul_self (i : zmod n) : sr i * sr i = 1 := by rw [sr_mul_sr, sub_self, one_def]
/--
If `0 < n`, then `sr i` has order 2.
-/
@[simp] lemma order_of_sr (i : zmod n) : order_of (sr i) = 2 :=
begin
rw order_of_eq_prime _ _,
{ exact ⟨nat.prime_two⟩ },
rw [sq, sr_mul_self],
dec_trivial,
end
/--
If `0 < n`, then `r 1` has order `n`.
-/
@[simp] lemma order_of_r_one : order_of (r 1 : dihedral_group n) = n :=
begin
rcases n.eq_zero_or_pos with rfl | hn,
{ rw order_of_eq_zero_iff',
intros n hn,
rw [r_one_pow, one_def],
apply mt r.inj,
simpa using hn.ne' },
{ haveI := fact.mk hn,
apply (nat.le_of_dvd hn $ order_of_dvd_of_pow_eq_one $ @r_one_pow_n n).lt_or_eq.resolve_left,
intro h,
have h1 : (r 1 : dihedral_group n)^(order_of (r 1)) = 1,
{ exact pow_order_of_eq_one _ },
rw r_one_pow at h1,
injection h1 with h2,
rw [← zmod.val_eq_zero, zmod.val_nat_cast, nat.mod_eq_of_lt h] at h2,
exact absurd h2.symm (order_of_pos _).ne },
end
/--
If `0 < n`, then `i : zmod n` has order `n / gcd n i`.
-/
lemma order_of_r [fact (0 < n)] (i : zmod n) : order_of (r i) = n / nat.gcd n i.val :=
begin
conv_lhs { rw ←zmod.nat_cast_zmod_val i },
rw [←r_one_pow, order_of_pow, order_of_r_one]
end
lemma exponent : monoid.exponent (dihedral_group n) = lcm n 2 :=
begin
rcases n.eq_zero_or_pos with rfl | hn,
{ exact monoid.exponent_eq_zero_of_order_zero order_of_r_one },
haveI := fact.mk hn,
apply nat.dvd_antisymm,
{ apply monoid.exponent_dvd_of_forall_pow_eq_one,
rintro (m | m),
{ rw [←order_of_dvd_iff_pow_eq_one, order_of_r],
refine nat.dvd_trans ⟨gcd n m.val, _⟩ (dvd_lcm_left n 2),
{ exact (nat.div_mul_cancel (nat.gcd_dvd_left n m.val)).symm } },
{ rw [←order_of_dvd_iff_pow_eq_one, order_of_sr],
exact dvd_lcm_right n 2 } },
{ apply lcm_dvd,
{ convert monoid.order_dvd_exponent (r 1),
exact order_of_r_one.symm },
{ convert monoid.order_dvd_exponent (sr 0),
exact (order_of_sr 0).symm } }
end
end dihedral_group
|
033553f64b0dd3534382b4241c59ac5c5de7e4e1 | 0408d6ea582e97d5cc55ac8a0980d26df896ce66 | /src/padics/padic_numbers.lean | 60ff4839e6472f5770f5cf31395887dfb69a69ec | [] | no_license | lean-forward/coe_tactic | bba94535c7fb6ef65fcd81bedc28062b238a1594 | d5c30df244c3402de6323a538e99b5324779a2cb | refs/heads/master | 1,588,474,971,049 | 1,557,135,293,000 | 1,557,135,293,000 | 178,387,237 | 1 | 0 | null | 1,556,542,286,000 | 1,553,856,413,000 | Lean | UTF-8 | Lean | false | false | 30,070 | lean | /-
Copyright (c) 2018 Robert Y. Lewis. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Robert Y. Lewis
Define the p-adic numbers (rationals) ℚ_p as the completion of ℚ wrt the p-adic norm.
Show that the p-adic norm extends to ℚ_p, that ℚ is embedded in ℚ_p, and that ℚ_p is complete
-/
import data.real.cau_seq_completion topology.metric_space.cau_seq_filter
import algebra.archimedean analysis.normed_space.basic
import padics.padic_norm norm_cast
noncomputable theory
local attribute [instance, priority 1] classical.prop_decidable
open nat multiplicity padic_norm cau_seq cau_seq.completion metric
theorem nat.find_le {p q : ℕ → Prop} [decidable_pred p] [decidable_pred q]
(h : ∀ n, q n → p n) (hp : ∃ n, p n) (hq : ∃ n, q n) :
nat.find hp ≤ nat.find hq :=
nat.find_min' _ ((h _) (nat.find_spec hq))
@[norm_cast]
theorem int.coe_nat_multiplicity (a b : ℕ) :
multiplicity a b = multiplicity (a : ℤ) (b : ℤ) :=
begin
apply roption.ext',
{ repeat {rw [← finite_iff_dom, finite_def]},
norm_cast, simp },
{ intros h1 h2,
apply _root_.le_antisymm; { apply nat.find_le, norm_cast, simp }}
end
@[reducible] def padic_seq (p : ℕ) [p.prime] := cau_seq _ (padic_norm p)
namespace padic_seq
section
variables {p : ℕ} [nat.prime p]
lemma stationary {f : cau_seq ℚ (padic_norm p)} (hf : ¬ f ≈ 0) :
∃ N, ∀ m n, m ≥ N → n ≥ N → padic_norm p (f n) = padic_norm p (f m) :=
have ∃ ε > 0, ∃ N1, ∀ j ≥ N1, ε ≤ padic_norm p (f j),
from cau_seq.abv_pos_of_not_lim_zero $ not_lim_zero_of_not_congr_zero hf,
let ⟨ε, hε, N1, hN1⟩ := this,
⟨N2, hN2⟩ := cau_seq.cauchy₂ f hε in
⟨ max N1 N2,
λ n m hn hm,
have padic_norm p (f n - f m) < ε, from hN2 _ _ (max_le_iff.1 hn).2 (max_le_iff.1 hm).2,
have padic_norm p (f n - f m) < padic_norm p (f n),
from lt_of_lt_of_le this $ hN1 _ (max_le_iff.1 hn).1,
have padic_norm p (f n - f m) < max (padic_norm p (f n)) (padic_norm p (f m)),
from lt_max_iff.2 (or.inl this),
begin
by_contradiction hne,
rw ←padic_norm.neg p (f m) at hne,
have hnam := add_eq_max_of_ne p hne,
rw [padic_norm.neg, max_comm] at hnam,
rw ←hnam at this,
apply _root_.lt_irrefl _ (by simp at this; exact this)
end ⟩
def stationary_point {f : padic_seq p} (hf : ¬ f ≈ 0) : ℕ :=
classical.some $ stationary hf
lemma stationary_point_spec {f : padic_seq p} (hf : ¬ f ≈ 0) :
∀ {m n}, m ≥ stationary_point hf → n ≥ stationary_point hf →
padic_norm p (f n) = padic_norm p (f m) :=
classical.some_spec $ stationary hf
def norm (f : padic_seq p) : ℚ :=
if hf : f ≈ 0 then 0 else padic_norm p (f (stationary_point hf))
lemma norm_zero_iff (f : padic_seq p) : f.norm = 0 ↔ f ≈ 0 :=
begin
constructor,
{ intro h,
by_contradiction hf,
unfold norm at h, split_ifs at h,
apply hf,
intros ε hε,
existsi stationary_point hf,
intros j hj,
have heq := stationary_point_spec hf (le_refl _) hj,
simpa [h, heq] },
{ intro h,
simp [norm, h] }
end
end
section embedding
open cau_seq
variables {p : ℕ} [nat.prime p]
lemma equiv_zero_of_val_eq_of_equiv_zero {f g : padic_seq p}
(h : ∀ k, padic_norm p (f k) = padic_norm p (g k)) (hf : f ≈ 0) : g ≈ 0 :=
λ ε hε, let ⟨i, hi⟩ := hf _ hε in
⟨i, λ j hj, by simpa [h] using hi _ hj⟩
lemma norm_nonzero_of_not_equiv_zero {f : padic_seq p} (hf : ¬ f ≈ 0) :
f.norm ≠ 0 :=
hf ∘ f.norm_zero_iff.1
lemma norm_eq_norm_app_of_nonzero {f : padic_seq p} (hf : ¬ f ≈ 0) :
∃ k, f.norm = padic_norm p k ∧ k ≠ 0 :=
have heq : f.norm = padic_norm p (f $ stationary_point hf), by simp [norm, hf],
⟨f $ stationary_point hf, heq,
λ h, norm_nonzero_of_not_equiv_zero hf (by simpa [h] using heq)⟩
lemma not_lim_zero_const_of_nonzero {q : ℚ} (hq : q ≠ 0) : ¬ lim_zero (const (padic_norm p) q) :=
λ h', hq $ const_lim_zero.1 h'
lemma not_equiv_zero_const_of_nonzero {q : ℚ} (hq : q ≠ 0) : ¬ (const (padic_norm p) q) ≈ 0 :=
λ h : lim_zero (const (padic_norm p) q - 0), not_lim_zero_const_of_nonzero hq $ by simpa using h
lemma norm_nonneg (f : padic_seq p) : f.norm ≥ 0 :=
if hf : f ≈ 0 then by simp [hf, norm]
else by simp [norm, hf, padic_norm.nonneg]
lemma lift_index_left_left {f : padic_seq p} (hf : ¬ f ≈ 0) (v2 v3 : ℕ) :
padic_norm p (f (stationary_point hf)) = padic_norm p (f (max (stationary_point hf) (max v2 v3))) :=
let i := max (stationary_point hf) (max v2 v3) in
begin
apply stationary_point_spec hf,
{ apply le_max_left },
{ apply le_refl }
end
lemma lift_index_left {f : padic_seq p} (hf : ¬ f ≈ 0) (v1 v3 : ℕ) :
padic_norm p (f (stationary_point hf)) = padic_norm p (f (max v1 (max (stationary_point hf) v3))) :=
let i := max v1 (max (stationary_point hf) v3) in
begin
apply stationary_point_spec hf,
{ apply le_trans,
{ apply le_max_left _ v3 },
{ apply le_max_right } },
{ apply le_refl }
end
lemma lift_index_right {f : padic_seq p} (hf : ¬ f ≈ 0) (v1 v2 : ℕ) :
padic_norm p (f (stationary_point hf)) = padic_norm p (f (max v1 (max v2 (stationary_point hf)))) :=
let i := max v1 (max v2 (stationary_point hf)) in
begin
apply stationary_point_spec hf,
{ apply le_trans,
{ apply le_max_right v2 },
{ apply le_max_right } },
{ apply le_refl }
end
end embedding
end padic_seq
section
open padic_seq
meta def index_simp_core (hh hf hg : expr) (at_ : interactive.loc := interactive.loc.ns [none]) : tactic unit :=
do [v1, v2, v3] ← [hh, hf, hg].mmap
(λ n, tactic.mk_app ``stationary_point [n] <|> return n),
e1 ← tactic.mk_app ``lift_index_left_left [hh, v2, v3] <|> return `(true),
e2 ← tactic.mk_app ``lift_index_left [hf, v1, v3] <|> return `(true),
e3 ← tactic.mk_app ``lift_index_right [hg, v1, v2] <|> return `(true),
sl ← [e1, e2, e3].mfoldl (λ s e, simp_lemmas.add s e) simp_lemmas.mk,
when at_.include_goal (tactic.simp_target sl),
hs ← at_.get_locals, hs.mmap' (tactic.simp_hyp sl [])
/--
This is a special-purpose tactic that lifts padic_norm (f (stationary_point f)) to
padic_norm (f (max _ _ _)).
-/
meta def tactic.interactive.padic_index_simp (l : interactive.parse interactive.types.pexpr_list)
(at_ : interactive.parse interactive.types.location) : tactic unit :=
do [h, f, g] ← l.mmap tactic.i_to_expr,
index_simp_core h f g at_
end
namespace padic_seq
section embedding
open cau_seq
variables {p : ℕ} [hp : nat.prime p]
include hp
lemma norm_mul (f g : padic_seq p) : (f * g).norm = f.norm * g.norm :=
if hf : f ≈ 0 then
have hg : f * g ≈ 0, from mul_equiv_zero' _ hf,
by simp [hf, hg, norm]
else if hg : g ≈ 0 then
have hf : f * g ≈ 0, from mul_equiv_zero _ hg,
by simp [hf, hg, norm]
else
have hfg : ¬ f * g ≈ 0, by apply mul_not_equiv_zero; assumption,
begin
unfold norm,
split_ifs,
padic_index_simp [hfg, hf, hg],
apply padic_norm.mul
end
lemma eq_zero_iff_equiv_zero (f : padic_seq p) : mk f = 0 ↔ f ≈ 0 :=
mk_eq
lemma ne_zero_iff_nequiv_zero (f : padic_seq p) : mk f ≠ 0 ↔ ¬ f ≈ 0 :=
not_iff_not.2 (eq_zero_iff_equiv_zero _)
lemma norm_const (q : ℚ) : norm (const (padic_norm p) q) = padic_norm p q :=
if hq : q = 0 then
have (const (padic_norm p) q) ≈ 0,
by simp [hq]; apply setoid.refl (const (padic_norm p) 0),
by subst hq; simp [norm, this]
else
have ¬ (const (padic_norm p) q) ≈ 0, from not_equiv_zero_const_of_nonzero hq,
by simp [norm, this]
lemma norm_image (a : padic_seq p) (ha : ¬ a ≈ 0) :
(∃ (n : ℤ), a.norm = ↑p ^ (-n)) :=
let ⟨k, hk, hk'⟩ := norm_eq_norm_app_of_nonzero ha in
by simpa [hk] using padic_norm.image p hk'
lemma norm_one : norm (1 : padic_seq p) = 1 :=
have h1 : ¬ (1 : padic_seq p) ≈ 0, from one_not_equiv_zero _,
by simp [h1, norm, hp.gt_one]
private lemma norm_eq_of_equiv_aux {f g : padic_seq p} (hf : ¬ f ≈ 0) (hg : ¬ g ≈ 0) (hfg : f ≈ g)
(h : padic_norm p (f (stationary_point hf)) ≠ padic_norm p (g (stationary_point hg)))
(hgt : padic_norm p (f (stationary_point hf)) > padic_norm p (g (stationary_point hg))) :
false :=
begin
have hpn : padic_norm p (f (stationary_point hf)) - padic_norm p (g (stationary_point hg)) > 0,
from sub_pos_of_lt hgt,
cases hfg _ hpn with N hN,
let i := max N (max (stationary_point hf) (stationary_point hg)),
have hi : i ≥ N, from le_max_left _ _,
have hN' := hN _ hi,
padic_index_simp [N, hf, hg] at hN' h hgt,
have hpne : padic_norm p (f i) ≠ padic_norm p (-(g i)),
by rwa [ ←padic_norm.neg p (g i)] at h,
let hpnem := add_eq_max_of_ne p hpne,
have hpeq : padic_norm p ((f - g) i) = max (padic_norm p (f i)) (padic_norm p (g i)),
{ rwa padic_norm.neg at hpnem },
rw [hpeq, max_eq_left_of_lt hgt] at hN',
have : padic_norm p (f i) < padic_norm p (f i),
{ apply lt_of_lt_of_le hN', apply sub_le_self, apply padic_norm.nonneg },
exact lt_irrefl _ this
end
private lemma norm_eq_of_equiv {f g : padic_seq p} (hf : ¬ f ≈ 0) (hg : ¬ g ≈ 0) (hfg : f ≈ g) :
padic_norm p (f (stationary_point hf)) = padic_norm p (g (stationary_point hg)) :=
begin
by_contradiction h,
cases (decidable.em (padic_norm p (f (stationary_point hf)) >
padic_norm p (g (stationary_point hg))))
with hgt hngt,
{ exact norm_eq_of_equiv_aux hf hg hfg h hgt },
{ apply norm_eq_of_equiv_aux hg hf (setoid.symm hfg) (ne.symm h),
apply lt_of_le_of_ne,
apply le_of_not_gt hngt,
apply h }
end
theorem norm_equiv {f g : padic_seq p} (hfg : f ≈ g) : f.norm = g.norm :=
if hf : f ≈ 0 then
have hg : g ≈ 0, from setoid.trans (setoid.symm hfg) hf,
by simp [norm, hf, hg]
else have hg : ¬ g ≈ 0, from hf ∘ setoid.trans hfg,
by unfold norm; split_ifs; exact norm_eq_of_equiv hf hg hfg
private lemma norm_nonarchimedean_aux {f g : padic_seq p}
(hfg : ¬ f + g ≈ 0) (hf : ¬ f ≈ 0) (hg : ¬ g ≈ 0) : (f + g).norm ≤ max (f.norm) (g.norm) :=
begin
unfold norm, split_ifs,
padic_index_simp [hfg, hf, hg],
apply padic_norm.nonarchimedean
end
theorem norm_nonarchimedean (f g : padic_seq p) : (f + g).norm ≤ max (f.norm) (g.norm) :=
if hfg : f + g ≈ 0 then
have 0 ≤ max (f.norm) (g.norm), from le_max_left_of_le (norm_nonneg _),
by simpa [hfg, norm]
else if hf : f ≈ 0 then
have hfg' : f + g ≈ g,
{ change lim_zero (f - 0) at hf,
show lim_zero (f + g - g), by simpa using hf },
have hcfg : (f + g).norm = g.norm, from norm_equiv hfg',
have hcl : f.norm = 0, from (norm_zero_iff f).2 hf,
have max (f.norm) (g.norm) = g.norm,
by rw hcl; exact max_eq_right (norm_nonneg _),
by rw [this, hcfg]
else if hg : g ≈ 0 then
have hfg' : f + g ≈ f,
{ change lim_zero (g - 0) at hg,
show lim_zero (f + g - f), by simpa [add_sub_cancel'] using hg },
have hcfg : (f + g).norm = f.norm, from norm_equiv hfg',
have hcl : g.norm = 0, from (norm_zero_iff g).2 hg,
have max (f.norm) (g.norm) = f.norm,
by rw hcl; exact max_eq_left (norm_nonneg _),
by rw [this, hcfg]
else norm_nonarchimedean_aux hfg hf hg
lemma norm_eq {f g : padic_seq p} (h : ∀ k, padic_norm p (f k) = padic_norm p (g k)) :
f.norm = g.norm :=
if hf : f ≈ 0 then
have hg : g ≈ 0, from equiv_zero_of_val_eq_of_equiv_zero h hf,
by simp [hf, hg, norm]
else
have hg : ¬ g ≈ 0, from λ hg, hf $ equiv_zero_of_val_eq_of_equiv_zero (by simp [h]) hg,
begin
simp [hg, hf, norm],
let i := max (stationary_point hf) (stationary_point hg),
have hpf : padic_norm p (f (stationary_point hf)) = padic_norm p (f i),
{ apply stationary_point_spec, apply le_max_left, apply le_refl },
have hpg : padic_norm p (g (stationary_point hg)) = padic_norm p (g i),
{ apply stationary_point_spec, apply le_max_right, apply le_refl },
rw [hpf, hpg, h]
end
lemma norm_neg (a : padic_seq p) : (-a).norm = a.norm :=
norm_eq $ by simp
lemma norm_eq_of_add_equiv_zero {f g : padic_seq p} (h : f + g ≈ 0) : f.norm = g.norm :=
have lim_zero (f + g - 0), from h,
have f ≈ -g, from show lim_zero (f - (-g)), by simpa,
have f.norm = (-g).norm, from norm_equiv this,
by simpa [norm_neg] using this
lemma add_eq_max_of_ne {f g : padic_seq p} (hfgne : f.norm ≠ g.norm) :
(f + g).norm = max f.norm g.norm :=
have hfg : ¬f + g ≈ 0, from mt norm_eq_of_add_equiv_zero hfgne,
if hf : f ≈ 0 then
have lim_zero (f - 0), from hf,
have f + g ≈ g, from show lim_zero ((f + g) - g), by simpa,
have h1 : (f+g).norm = g.norm, from norm_equiv this,
have h2 : f.norm = 0, from (norm_zero_iff _).2 hf,
by rw [h1, h2]; rw max_eq_right (norm_nonneg _)
else if hg : g ≈ 0 then
have lim_zero (g - 0), from hg,
have f + g ≈ f, from show lim_zero ((f + g) - f), by rw [add_sub_cancel']; simpa,
have h1 : (f+g).norm = f.norm, from norm_equiv this,
have h2 : g.norm = 0, from (norm_zero_iff _).2 hg,
by rw [h1, h2]; rw max_eq_left (norm_nonneg _)
else
begin
unfold norm at ⊢ hfgne, split_ifs at ⊢ hfgne,
padic_index_simp [hfg, hf, hg] at ⊢ hfgne,
apply padic_norm.add_eq_max_of_ne,
simpa [hf, hg, norm] using hfgne
end
end embedding
end padic_seq
def padic (p : ℕ) [nat.prime p] := @cau_seq.completion.Cauchy _ _ _ _ (padic_norm p) _
notation `ℚ_[` p `]` := padic p
namespace padic
section completion
variables {p : ℕ} [nat.prime p]
instance discrete_field : discrete_field (ℚ_[p]) :=
cau_seq.completion.discrete_field
-- short circuits
instance : has_zero ℚ_[p] := by apply_instance
instance : has_one ℚ_[p] := by apply_instance
instance : has_add ℚ_[p] := by apply_instance
instance : has_mul ℚ_[p] := by apply_instance
instance : has_sub ℚ_[p] := by apply_instance
instance : has_neg ℚ_[p] := by apply_instance
instance : has_div ℚ_[p] := by apply_instance
instance : add_comm_group ℚ_[p] := by apply_instance
instance : comm_ring ℚ_[p] := by apply_instance
def mk : padic_seq p → ℚ_[p] := quotient.mk
end completion
section completion
variables (p : ℕ) [nat.prime p]
lemma mk_eq {f g : padic_seq p} : mk f = mk g ↔ f ≈ g := quotient.eq
def of_rat : ℚ → ℚ_[p] := cau_seq.completion.of_rat
@[simp] lemma of_rat_add : ∀ (x y : ℚ), of_rat p (x + y) = of_rat p x + of_rat p y :=
cau_seq.completion.of_rat_add
@[simp] lemma of_rat_neg : ∀ (x : ℚ), of_rat p (-x) = -of_rat p x :=
cau_seq.completion.of_rat_neg
@[simp] lemma of_rat_mul : ∀ (x y : ℚ), of_rat p (x * y) = of_rat p x * of_rat p y :=
cau_seq.completion.of_rat_mul
@[simp] lemma of_rat_sub : ∀ (x y : ℚ), of_rat p (x - y) = of_rat p x - of_rat p y :=
cau_seq.completion.of_rat_sub
@[simp] lemma of_rat_div : ∀ (x y : ℚ), of_rat p (x / y) = of_rat p x / of_rat p y :=
cau_seq.completion.of_rat_div
@[simp] lemma of_rat_one : of_rat p 1 = 1 := rfl
@[simp] lemma of_rat_zero : of_rat p 0 = 0 := rfl
@[simp] lemma cast_eq_of_rat_of_nat (n : ℕ) : (↑n : ℚ_[p]) = of_rat p n :=
begin
induction n with n ih,
{ refl },
{ simpa using ih }
end
-- without short circuits, this needs an increase of class.instance_max_depth
@[simp] lemma cast_eq_of_rat_of_int (n : ℤ) : ↑n = of_rat p n :=
by induction n; simp
lemma cast_eq_of_rat : ∀ (q : ℚ), (↑q : ℚ_[p]) = of_rat p q
| ⟨n, d, h1, h2⟩ :=
show ↑n / ↑d = _, from
have (⟨n, d, h1, h2⟩ : ℚ) = rat.mk n d, from rat.num_denom _,
by simp [this, rat.mk_eq_div, of_rat_div]
@[norm_cast] lemma coe_add : ∀ {x y : ℚ}, (↑(x + y) : ℚ_[p]) = ↑x + ↑y := by simp [cast_eq_of_rat]
@[norm_cast] lemma coe_neg : ∀ {x : ℚ}, (↑(-x) : ℚ_[p]) = -↑x := by simp [cast_eq_of_rat]
@[norm_cast] lemma coe_mul : ∀ {x y : ℚ}, (↑(x * y) : ℚ_[p]) = ↑x * ↑y := by simp [cast_eq_of_rat]
@[norm_cast] lemma coe_sub : ∀ {x y : ℚ}, (↑(x - y) : ℚ_[p]) = ↑x - ↑y := by simp [cast_eq_of_rat]
@[norm_cast] lemma coe_div : ∀ {x y : ℚ}, (↑(x / y) : ℚ_[p]) = ↑x / ↑y := by simp [cast_eq_of_rat]
@[simp_cast] lemma coe_one : (↑1 : ℚ_[p]) = 1 := rfl
@[simp_cast] lemma coe_zero : (↑1 : ℚ_[p]) = 1 := rfl
lemma const_equiv {q r : ℚ} : const (padic_norm p) q ≈ const (padic_norm p) r ↔ q = r :=
⟨ λ heq : lim_zero (const (padic_norm p) (q - r)),
eq_of_sub_eq_zero $ const_lim_zero.1 heq,
λ heq, by rw heq; apply setoid.refl _ ⟩
lemma of_rat_eq {q r : ℚ} : of_rat p q = of_rat p r ↔ q = r :=
⟨(const_equiv p).1 ∘ quotient.eq.1, λ h, by rw h⟩
@[norm_cast] lemma coe_inj {q r : ℚ} : (↑q : ℚ_[p]) = ↑r ↔ q = r := by simp [cast_eq_of_rat, of_rat_eq]
instance : char_zero ℚ_[p] :=
have ∀ n : ℕ, (↑(↑n : ℚ) : ℚ_[p]) = ↑n, by simp,
⟨λ m n, by {rw_mod_cast ← this, refl}⟩
end completion
end padic
def padic_norm_e {p : ℕ} [hp : nat.prime p] : ℚ_[p] → ℚ :=
quotient.lift padic_seq.norm $ @padic_seq.norm_equiv _ _
namespace padic_norm_e
section embedding
open padic_seq
variables {p : ℕ} [nat.prime p]
lemma defn (f : padic_seq p) {ε : ℚ} (hε : ε > 0) : ∃ N, ∀ i ≥ N, padic_norm_e (⟦f⟧ - f i) < ε :=
begin
simp only [padic.cast_eq_of_rat],
change ∃ N, ∀ i ≥ N, (f - const _ (f i)).norm < ε,
by_contradiction h,
cases cauchy₂ f hε with N hN,
have : ∀ N, ∃ i ≥ N, (f - const _ (f i)).norm ≥ ε,
by simpa [not_forall] using h,
rcases this N with ⟨i, hi, hge⟩,
have hne : ¬ (f - const (padic_norm p) (f i)) ≈ 0,
{ intro h, unfold padic_seq.norm at hge; split_ifs at hge, exact not_lt_of_ge hge hε },
unfold padic_seq.norm at hge; split_ifs at hge,
apply not_le_of_gt _ hge,
cases decidable.em ((stationary_point hne) ≥ N) with hgen hngen,
{ apply hN; assumption },
{ have := stationary_point_spec hne (le_refl _) (le_of_not_le hngen),
rw ←this,
apply hN,
apply le_refl, assumption }
end
protected lemma nonneg (q : ℚ_[p]) : padic_norm_e q ≥ 0 :=
quotient.induction_on q $ norm_nonneg
lemma zero_def : (0 : ℚ_[p]) = ⟦0⟧ := rfl
lemma zero_iff (q : ℚ_[p]) : padic_norm_e q = 0 ↔ q = 0 :=
quotient.induction_on q $
by simpa only [zero_def, quotient.eq] using norm_zero_iff
@[simp] protected lemma zero : padic_norm_e (0 : ℚ_[p]) = 0 :=
(zero_iff _).2 rfl
@[simp] protected lemma one' : padic_norm_e (1 : ℚ_[p]) = 1 :=
norm_one
@[simp] protected lemma neg (q : ℚ_[p]) : padic_norm_e (-q) = padic_norm_e q :=
quotient.induction_on q $ norm_neg
theorem nonarchimedean' (q r : ℚ_[p]) :
padic_norm_e (q + r) ≤ max (padic_norm_e q) (padic_norm_e r) :=
quotient.induction_on₂ q r $ norm_nonarchimedean
theorem add_eq_max_of_ne' {q r : ℚ_[p]} :
padic_norm_e q ≠ padic_norm_e r → padic_norm_e (q + r) = max (padic_norm_e q) (padic_norm_e r) :=
quotient.induction_on₂ q r $ λ _ _, padic_seq.add_eq_max_of_ne
lemma triangle_ineq (x y z : ℚ_[p]) :
padic_norm_e (x - z) ≤ padic_norm_e (x - y) + padic_norm_e (y - z) :=
calc padic_norm_e (x - z) = padic_norm_e ((x - y) + (y - z)) : by rw sub_add_sub_cancel
... ≤ max (padic_norm_e (x - y)) (padic_norm_e (y - z)) : padic_norm_e.nonarchimedean' _ _
... ≤ padic_norm_e (x - y) + padic_norm_e (y - z) :
max_le_add_of_nonneg (padic_norm_e.nonneg _) (padic_norm_e.nonneg _)
protected lemma add (q r : ℚ_[p]) : padic_norm_e (q + r) ≤ (padic_norm_e q) + (padic_norm_e r) :=
calc
padic_norm_e (q + r) ≤ max (padic_norm_e q) (padic_norm_e r) : nonarchimedean' _ _
... ≤ (padic_norm_e q) + (padic_norm_e r) :
max_le_add_of_nonneg (padic_norm_e.nonneg _) (padic_norm_e.nonneg _)
protected lemma mul' (q r : ℚ_[p]) : padic_norm_e (q * r) = (padic_norm_e q) * (padic_norm_e r) :=
quotient.induction_on₂ q r $ norm_mul
instance : is_absolute_value (@padic_norm_e p _) :=
{ abv_nonneg := padic_norm_e.nonneg,
abv_eq_zero := zero_iff,
abv_add := padic_norm_e.add,
abv_mul := padic_norm_e.mul' }
@[simp] lemma eq_padic_norm' (q : ℚ) : padic_norm_e (padic.of_rat p q) = padic_norm p q :=
norm_const _
protected theorem image' {q : ℚ_[p]} : q ≠ 0 → ∃ n : ℤ, padic_norm_e q = p ^ (-n) :=
quotient.induction_on q $ λ f hf,
have ¬ f ≈ 0, from (ne_zero_iff_nequiv_zero f).1 hf,
norm_image f this
lemma sub_rev (q r : ℚ_[p]) : padic_norm_e (q - r) = padic_norm_e (r - q) :=
by rw ←(padic_norm_e.neg); simp
end embedding
end padic_norm_e
namespace padic
section complete
open padic_seq padic
theorem rat_dense' {p : ℕ} [nat.prime p] (q : ℚ_[p]) {ε : ℚ} (hε : ε > 0) :
∃ r : ℚ, padic_norm_e (q - r) < ε :=
quotient.induction_on q $ λ q',
have ∃ N, ∀ m n ≥ N, padic_norm p (q' m - q' n) < ε, from cauchy₂ _ hε,
let ⟨N, hN⟩ := this in
⟨q' N,
begin
simp only [padic.cast_eq_of_rat],
change padic_seq.norm (q' - const _ (q' N)) < ε,
cases decidable.em ((q' - const (padic_norm p) (q' N)) ≈ 0) with heq hne',
{ simpa only [heq, padic_seq.norm, dif_pos] },
{ simp only [padic_seq.norm, dif_neg hne'],
change padic_norm p (q' _ - q' _) < ε,
have := stationary_point_spec hne',
cases decidable.em (N ≥ stationary_point hne') with hle hle,
{ have := eq.symm (this (le_refl _) hle),
simp at this, simpa [this] },
{ apply hN,
apply le_of_lt, apply lt_of_not_ge, apply hle, apply le_refl }}
end⟩
variables {p : ℕ} [nat.prime p] (f : cau_seq _ (@padic_norm_e p _))
open classical
private lemma div_nat_pos (n : ℕ) : (1 / ((n + 1): ℚ)) > 0 :=
div_pos zero_lt_one (by exact_mod_cast succ_pos _)
def lim_seq : ℕ → ℚ := λ n, classical.some (rat_dense' (f n) (div_nat_pos n))
lemma exi_rat_seq_conv {ε : ℚ} (hε : 0 < ε) :
∃ N, ∀ i ≥ N, padic_norm_e (f i - ((lim_seq f) i : ℚ_[p])) < ε :=
begin
refine (exists_nat_gt (1/ε)).imp (λ N hN i hi, _),
have h := classical.some_spec (rat_dense' (f i) (div_nat_pos i)),
refine lt_of_lt_of_le h (div_le_of_le_mul (by exact_mod_cast succ_pos _) _),
rw right_distrib,
apply le_add_of_le_of_nonneg,
{ exact le_mul_of_div_le hε (le_trans (le_of_lt hN) (by exact_mod_cast hi)) },
{ apply le_of_lt, simpa }
end
lemma exi_rat_seq_conv_cauchy : is_cau_seq (padic_norm p) (lim_seq f) :=
assume ε hε,
have hε3 : ε / 3 > 0, from div_pos hε (by norm_num),
let ⟨N, hN⟩ := exi_rat_seq_conv f hε3,
⟨N2, hN2⟩ := f.cauchy₂ hε3 in
begin
existsi max N N2,
intros j hj,
suffices : padic_norm_e ((↑(lim_seq f j) - f (max N N2)) + (f (max N N2) - lim_seq f (max N N2))) < ε,
{ ring at this ⊢,
rw [← padic_norm_e.eq_padic_norm', ← padic.cast_eq_of_rat],
exact_mod_cast this },
{ apply lt_of_le_of_lt,
{ apply padic_norm_e.add },
{ have : (3 : ℚ) ≠ 0, by norm_num,
have : ε = ε / 3 + ε / 3 + ε / 3,
{ apply eq_of_mul_eq_mul_left this, simp [left_distrib, mul_div_cancel' _ this ], ring },
rw this,
apply add_lt_add,
{ suffices : padic_norm_e ((↑(lim_seq f j) - f j) + (f j - f (max N N2))) < ε / 3 + ε / 3,
by simpa,
apply lt_of_le_of_lt,
{ apply padic_norm_e.add },
{ apply add_lt_add,
{ rw [padic_norm_e.sub_rev],
apply_mod_cast hN,
exact le_of_max_le_left hj },
{ apply hN2,
exact le_of_max_le_right hj,
apply le_max_right }}},
{ apply_mod_cast hN,
apply le_max_left }}}
end
private def lim' : padic_seq p := ⟨_, exi_rat_seq_conv_cauchy f⟩
private def lim : ℚ_[p] := ⟦lim' f⟧
theorem complete' : ∃ q : ℚ_[p], ∀ ε > 0, ∃ N, ∀ i ≥ N, padic_norm_e (q - f i) < ε :=
⟨ lim f,
λ ε hε,
let ⟨N, hN⟩ := exi_rat_seq_conv f (show ε / 2 > 0, from div_pos hε (by norm_num)),
⟨N2, hN2⟩ := padic_norm_e.defn (lim' f) (show ε / 2 > 0, from div_pos hε (by norm_num)) in
begin
existsi max N N2,
intros i hi,
suffices : padic_norm_e ((lim f - lim' f i) + (lim' f i - f i)) < ε,
{ ring at this; exact this },
{ apply lt_of_le_of_lt,
{ apply padic_norm_e.add },
{ have : ε = ε / 2 + ε / 2, by rw ←(add_self_div_two ε); simp,
rw this,
apply add_lt_add,
{ apply hN2, exact le_of_max_le_right hi },
{ rw_mod_cast [padic_norm_e.sub_rev],
apply hN,
exact le_of_max_le_left hi }}}
end ⟩
end complete
section normed_space
variables (p : ℕ) [nat.prime p]
instance : has_dist ℚ_[p] := ⟨λ x y, padic_norm_e (x - y)⟩
instance : metric_space ℚ_[p] :=
{ dist_self := by simp [dist],
dist_comm := λ x y, by unfold dist; rw ←padic_norm_e.neg (x - y); simp,
dist_triangle :=
begin
intros, unfold dist,
exact_mod_cast padic_norm_e.triangle_ineq _ _ _,
end,
eq_of_dist_eq_zero :=
begin
unfold dist, intros _ _ h,
apply eq_of_sub_eq_zero,
apply (padic_norm_e.zero_iff _).1,
exact_mod_cast h
end }
instance : has_norm ℚ_[p] := ⟨λ x, padic_norm_e x⟩
instance : normed_field ℚ_[p] :=
{ dist_eq := λ _ _, rfl,
norm_mul := by simp [has_norm.norm, padic_norm_e.mul'] }
instance : is_absolute_value (λ a : ℚ_[p], ∥a∥) :=
{ abv_nonneg := norm_nonneg,
abv_eq_zero := norm_eq_zero,
abv_add := norm_triangle,
abv_mul := by simp [has_norm.norm, padic_norm_e.mul'] }
theorem rat_dense {p : ℕ} {hp : p.prime} (q : ℚ_[p]) {ε : ℝ} (hε : ε > 0) :
∃ r : ℚ, ∥q - r∥ < ε :=
let ⟨ε', hε'l, hε'r⟩ := exists_rat_btwn hε,
⟨r, hr⟩ := rat_dense' q (by simpa using hε'l) in
⟨r, lt.trans (by simpa [has_norm.norm] using hr) hε'r⟩
end normed_space
end padic
namespace padic_norm_e
section normed_space
variables {p : ℕ} [hp : p.prime]
include hp
@[simp] protected lemma mul (q r : ℚ_[p]) : ∥q * r∥ = ∥q∥ * ∥r∥ :=
by simp [has_norm.norm, padic_norm_e.mul']
protected lemma is_norm (q : ℚ_[p]) : ↑(padic_norm_e q) = ∥q∥ := rfl
theorem nonarchimedean (q r : ℚ_[p]) : ∥q + r∥ ≤ max (∥q∥) (∥r∥) :=
begin
unfold has_norm.norm,
exact_mod_cast nonarchimedean' _ _
end
theorem add_eq_max_of_ne {q r : ℚ_[p]} (h : ∥q∥ ≠ ∥r∥) : ∥q+r∥ = max (∥q∥) (∥r∥) :=
begin
unfold has_norm.norm,
apply_mod_cast add_eq_max_of_ne',
intro h',
apply h,
unfold has_norm.norm,
exact_mod_cast h'
end
@[simp] lemma eq_padic_norm (q : ℚ) : ∥(↑q : ℚ_[p])∥ = padic_norm p q :=
begin
unfold has_norm.norm,
rw [← padic_norm_e.eq_padic_norm', ← padic.cast_eq_of_rat]
end
instance : nondiscrete_normed_field ℚ_[p] :=
{ non_trivial := ⟨padic.of_rat p (p⁻¹), begin
have h0 : p ≠ 0 := ne_of_gt (hp.pos),
have h1 : 1 < p := prime.gt_one hp,
rw [← padic.cast_eq_of_rat, eq_padic_norm],
simp only [padic_norm, inv_eq_zero],
rw if_neg,
swap, exact_mod_cast h0,
norm_cast,
rw padic_val_rat.inv,
swap, exact_mod_cast h0,
rw [neg_neg, padic_val_rat.padic_val_rat_self h1],
erw _root_.pow_one,
exact_mod_cast h1,
end⟩ }
protected theorem image {q : ℚ_[p]} : q ≠ 0 → ∃ n : ℤ, ∥q∥ = ↑((↑p : ℚ) ^ (-n)) :=
quotient.induction_on q $ λ f hf,
have ¬ f ≈ 0, from (padic_seq.ne_zero_iff_nequiv_zero f).1 hf,
let ⟨n, hn⟩ := padic_seq.norm_image f this in
⟨n, congr_arg rat.cast hn⟩
protected lemma is_rat (q : ℚ_[p]) : ∃ q' : ℚ, ∥q∥ = ↑q' :=
if h : q = 0 then ⟨0, by simp [h]⟩
else let ⟨n, hn⟩ := padic_norm_e.image h in ⟨_, hn⟩
def rat_norm (q : ℚ_[p]) : ℚ := classical.some (padic_norm_e.is_rat q)
lemma eq_rat_norm (q : ℚ_[p]) : ∥q∥ = rat_norm q := classical.some_spec (padic_norm_e.is_rat q)
theorem norm_rat_le_one : ∀ {q : ℚ} (hq : ¬ p ∣ q.denom), ∥(q : ℚ_[p])∥ ≤ 1
| ⟨n, d, hn, hd⟩ := λ hq : ¬ p ∣ d,
if hnz : n = 0 then
have (⟨n, d, hn, hd⟩ : ℚ) = 0,
from rat.zero_iff_num_zero.mpr hnz,
by norm_num [this]
else
begin
have hnz' : {rat . num := n, denom := d, pos := hn, cop := hd} ≠ 0, from mt rat.zero_iff_num_zero.1 hnz,
rw [padic_norm_e.eq_padic_norm],
norm_cast,
rw [padic_norm.eq_fpow_of_nonzero p hnz', padic_val_rat_def p hnz'],
have h : (multiplicity p d).get _ = 0, by simp [multiplicity_eq_zero_of_not_dvd, hq],
rw_mod_cast [h, sub_zero],
apply fpow_le_one_of_nonpos,
{ exact_mod_cast le_of_lt hp.gt_one, },
{ apply neg_nonpos_of_nonneg, norm_cast, simp, }
end
lemma eq_of_norm_add_lt_right {p : ℕ} {hp : p.prime} {z1 z2 : ℚ_[p]}
(h : ∥z1 + z2∥ < ∥z2∥) : ∥z1∥ = ∥z2∥ :=
by_contradiction $ λ hne,
not_lt_of_ge (by rw padic_norm_e.add_eq_max_of_ne hne; apply le_max_right) h
lemma eq_of_norm_add_lt_left {p : ℕ} {hp : p.prime} {z1 z2 : ℚ_[p]}
(h : ∥z1 + z2∥ < ∥z1∥) : ∥z1∥ = ∥z2∥ :=
by_contradiction $ λ hne,
not_lt_of_ge (by rw padic_norm_e.add_eq_max_of_ne hne; apply le_max_left) h
end normed_space
end padic_norm_e
namespace padic
variables {p : ℕ} [nat.prime p]
set_option eqn_compiler.zeta true
instance complete : cau_seq.is_complete ℚ_[p] norm :=
begin
split, intro f,
have cau_seq_norm_e : is_cau_seq padic_norm_e f, by {
intros ε hε,
let h := is_cau f ε (by exact_mod_cast hε),
unfold norm at h,
apply_mod_cast h,
},
cases padic.complete' ⟨f, cau_seq_norm_e⟩ with q hq,
existsi q,
intros ε hε,
cases exists_rat_btwn hε with ε' hε',
norm_cast at hε',
cases hq ε' hε'.1 with N hN, existsi N,
intros i hi, let h := hN i hi,
unfold norm,
rw_mod_cast [cau_seq.sub_apply, padic_norm_e.sub_rev],
refine lt.trans _ hε'.2,
exact_mod_cast hN i hi
end
lemma padic_norm_e_lim_le {f : cau_seq ℚ_[p] norm} {a : ℝ} (ha : a > 0)
(hf : ∀ i, ∥f i∥ ≤ a) : ∥f.lim∥ ≤ a :=
let ⟨N, hN⟩ := setoid.symm (cau_seq.equiv_lim f) _ ha in
calc ∥f.lim∥ = ∥f.lim - f N + f N∥ : by simp
... ≤ max (∥f.lim - f N∥) (∥f N∥) : padic_norm_e.nonarchimedean _ _
... ≤ a : max_le (le_of_lt (hN _ (le_refl _))) (hf _)
end padic
|
6870a839dc63e41586689783ef81518873e93735 | e151e9053bfd6d71740066474fc500a087837323 | /src/hott/types/nat/default.lean | a05f644c346f7004b77b9236f7154a11f1b0da4f | [
"Apache-2.0"
] | permissive | daniel-carranza/hott3 | 15bac2d90589dbb952ef15e74b2837722491963d | 913811e8a1371d3a5751d7d32ff9dec8aa6815d9 | refs/heads/master | 1,610,091,349,670 | 1,596,222,336,000 | 1,596,222,336,000 | 241,957,822 | 0 | 0 | Apache-2.0 | 1,582,222,839,000 | 1,582,222,838,000 | null | UTF-8 | Lean | false | false | 196 | lean | /-
Copyright (c) 2014 Floris van Doorn. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Floris van Doorn
-/
import .basic .order .sub .hott .div
|
434897738f06073bb538e833a24d7345f4615f6d | 69d4931b605e11ca61881fc4f66db50a0a875e39 | /src/topology/metric_space/pi_Lp.lean | a5ca82948f30e611c91d3fcc917db986f0d9a782 | [
"Apache-2.0"
] | permissive | abentkamp/mathlib | d9a75d291ec09f4637b0f30cc3880ffb07549ee5 | 5360e476391508e092b5a1e5210bd0ed22dc0755 | refs/heads/master | 1,682,382,954,948 | 1,622,106,077,000 | 1,622,106,077,000 | 149,285,665 | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 15,311 | lean | /-
Copyright (c) 2020 Sébastien Gouëzel. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Sébastien Gouëzel
-/
import analysis.mean_inequalities
/-!
# `L^p` distance on finite products of metric spaces
Given finitely many metric spaces, one can put the max distance on their product, but there is also
a whole family of natural distances, indexed by a real parameter `p ∈ [1, ∞)`, that also induce
the product topology. We define them in this file. The distance on `Π i, α i` is given by
$$
d(x, y) = \left(\sum d(x_i, y_i)^p\right)^{1/p}.
$$
We give instances of this construction for emetric spaces, metric spaces, normed groups and normed
spaces.
To avoid conflicting instances, all these are defined on a copy of the original Pi type, named
`pi_Lp p hp α`, where `hp : 1 ≤ p`. This assumption is included in the definition of the type
to make sure that it is always available to typeclass inference to construct the instances.
We ensure that the topology and uniform structure on `pi_Lp p hp α` are (defeq to) the product
topology and product uniformity, to be able to use freely continuity statements for the coordinate
functions, for instance.
## Implementation notes
We only deal with the `L^p` distance on a product of finitely many metric spaces, which may be
distinct. A closely related construction is the `L^p` norm on the space of
functions from a measure space to a normed space, where the norm is
$$
\left(\int ∥f (x)∥^p dμ\right)^{1/p}.
$$
However, the topology induced by this construction is not the product topology, this only
defines a seminorm (as almost everywhere zero functions have zero `L^p` norm), and some functions
have infinite `L^p` norm. All these subtleties are not present in the case of finitely many
metric spaces (which corresponds to the basis which is a finite space with the counting measure),
hence it is worth devoting a file to this specific case which is particularly well behaved.
The general case is not yet formalized in mathlib.
To prove that the topology (and the uniform structure) on a finite product with the `L^p` distance
are the same as those coming from the `L^∞` distance, we could argue that the `L^p` and `L^∞` norms
are equivalent on `ℝ^n` for abstract (norm equivalence) reasons. Instead, we give a more explicit
(easy) proof which provides a comparison between these two norms with explicit constants.
We also set up the theory for `pseudo_emetric_space` and `pseudo_metric_space`.
-/
open real set filter
open_locale big_operators uniformity topological_space nnreal ennreal
noncomputable theory
variables {ι : Type*}
/-- A copy of a Pi type, on which we will put the `L^p` distance. Since the Pi type itself is
already endowed with the `L^∞` distance, we need the type synonym to avoid confusing typeclass
resolution. Also, we let it depend on `p`, to get a whole family of type on which we can put
different distances, and we provide the assumption `hp` in the definition, to make it available
to typeclass resolution when it looks for a distance on `pi_Lp p hp α`. -/
@[nolint unused_arguments]
def pi_Lp {ι : Type*} (p : ℝ) (hp : 1 ≤ p) (α : ι → Type*) : Type* := Π (i : ι), α i
instance {ι : Type*} (p : ℝ) (hp : 1 ≤ p) (α : ι → Type*) [∀ i, inhabited (α i)] :
inhabited (pi_Lp p hp α) :=
⟨λ i, default (α i)⟩
namespace pi_Lp
variables (p : ℝ) (hp : 1 ≤ p) (α : ι → Type*) (β : ι → Type*)
/-- Canonical bijection between `pi_Lp p hp α` and the original Pi type. We introduce it to be able
to compare the `L^p` and `L^∞` distances through it. -/
protected def equiv : pi_Lp p hp α ≃ Π (i : ι), α i :=
equiv.refl _
section
/-!
### The uniformity on finite `L^p` products is the product uniformity
In this section, we put the `L^p` edistance on `pi_Lp p hp α`, and we check that the uniformity
coming from this edistance coincides with the product uniformity, by showing that the canonical
map to the Pi type (with the `L^∞` distance) is a uniform embedding, as it is both Lipschitz and
antiLipschitz.
We only register this emetric space structure as a temporary instance, as the true instance (to be
registered later) will have as uniformity exactly the product uniformity, instead of the one coming
from the edistance (which is equal to it, but not defeq). See Note [forgetful inheritance]
explaining why having definitionally the right uniformity is often important.
-/
variables [∀ i, emetric_space (α i)] [∀ i, pseudo_emetric_space (β i)] [fintype ι]
/-- Endowing the space `pi_Lp p hp β` with the `L^p` pseudoedistance. This definition is not
satisfactory, as it does not register the fact that the topology and the uniform structure coincide
with the product one. Therefore, we do not register it as an instance. Using this as a temporary
pseudoemetric space instance, we will show that the uniform structure is equal (but not defeq) to
the product one, and then register an instance in which we replace the uniform structure by the
product one using this pseudoemetric space and `pseudo_emetric_space.replace_uniformity`. -/
def pseudo_emetric_aux : pseudo_emetric_space (pi_Lp p hp β) :=
have pos : 0 < p := lt_of_lt_of_le zero_lt_one hp,
{ edist := λ f g, (∑ (i : ι), (edist (f i) (g i)) ^ p) ^ (1/p),
edist_self := λ f, by simp [edist, ennreal.zero_rpow_of_pos pos,
ennreal.zero_rpow_of_pos (inv_pos.2 pos)],
edist_comm := λ f g, by simp [edist, edist_comm],
edist_triangle := λ f g h, calc
(∑ (i : ι), edist (f i) (h i) ^ p) ^ (1 / p) ≤
(∑ (i : ι), (edist (f i) (g i) + edist (g i) (h i)) ^ p) ^ (1 / p) :
begin
apply ennreal.rpow_le_rpow _ (one_div_nonneg.2 $ le_of_lt pos),
refine finset.sum_le_sum (λ i hi, _),
exact ennreal.rpow_le_rpow (edist_triangle _ _ _) (le_trans zero_le_one hp)
end
... ≤
(∑ (i : ι), edist (f i) (g i) ^ p) ^ (1 / p) + (∑ (i : ι), edist (g i) (h i) ^ p) ^ (1 / p) :
ennreal.Lp_add_le _ _ _ hp }
/-- Endowing the space `pi_Lp p hp α` with the `L^p` edistance. This definition is not satisfactory,
as it does not register the fact that the topology and the uniform structure coincide with the
product one. Therefore, we do not register it as an instance. Using this as a temporary emetric
space instance, we will show that the uniform structure is equal (but not defeq) to the product one,
and then register an instance in which we replace the uniform structure by the product one using
this emetric space and `emetric_space.replace_uniformity`. -/
def emetric_aux : emetric_space (pi_Lp p hp α) :=
{ eq_of_edist_eq_zero := λ f g hfg,
begin
have pos : 0 < p := lt_of_lt_of_le zero_lt_one hp,
letI h := pseudo_emetric_aux p hp α,
have h : edist f g = (∑ (i : ι), (edist (f i) (g i)) ^ p) ^ (1/p) := rfl,
simp [h, ennreal.rpow_eq_zero_iff, pos, asymm pos, finset.sum_eq_zero_iff_of_nonneg] at hfg,
exact funext hfg
end,
..pseudo_emetric_aux p hp α }
local attribute [instance] pi_Lp.emetric_aux pi_Lp.pseudo_emetric_aux
lemma lipschitz_with_equiv : lipschitz_with 1 (pi_Lp.equiv p hp β) :=
begin
have pos : 0 < p := lt_of_lt_of_le zero_lt_one hp,
have cancel : p * (1/p) = 1 := mul_div_cancel' 1 (ne_of_gt pos),
assume x y,
simp only [edist, forall_prop_of_true, one_mul, finset.mem_univ, finset.sup_le_iff,
ennreal.coe_one],
assume i,
calc
edist (x i) (y i) = (edist (x i) (y i) ^ p) ^ (1/p) :
by simp [← ennreal.rpow_mul, cancel, -one_div]
... ≤ (∑ (i : ι), edist (x i) (y i) ^ p) ^ (1 / p) :
begin
apply ennreal.rpow_le_rpow _ (one_div_nonneg.2 $ le_of_lt pos),
exact finset.single_le_sum (λ i hi, (bot_le : (0 : ℝ≥0∞) ≤ _)) (finset.mem_univ i)
end
end
lemma antilipschitz_with_equiv :
antilipschitz_with ((fintype.card ι : ℝ≥0) ^ (1/p)) (pi_Lp.equiv p hp β) :=
begin
have pos : 0 < p := lt_of_lt_of_le zero_lt_one hp,
have nonneg : 0 ≤ 1 / p := one_div_nonneg.2 (le_of_lt pos),
have cancel : p * (1/p) = 1 := mul_div_cancel' 1 (ne_of_gt pos),
assume x y,
simp [edist, -one_div],
calc (∑ (i : ι), edist (x i) (y i) ^ p) ^ (1 / p) ≤
(∑ (i : ι), edist (pi_Lp.equiv p hp β x) (pi_Lp.equiv p hp β y) ^ p) ^ (1 / p) :
begin
apply ennreal.rpow_le_rpow _ nonneg,
apply finset.sum_le_sum (λ i hi, _),
apply ennreal.rpow_le_rpow _ (le_of_lt pos),
exact finset.le_sup (finset.mem_univ i)
end
... = (((fintype.card ι : ℝ≥0)) ^ (1/p) : ℝ≥0) *
edist (pi_Lp.equiv p hp β x) (pi_Lp.equiv p hp β y) :
begin
simp only [nsmul_eq_mul, finset.card_univ, ennreal.rpow_one, finset.sum_const,
ennreal.mul_rpow_of_nonneg _ _ nonneg, ←ennreal.rpow_mul, cancel],
have : (fintype.card ι : ℝ≥0∞) = (fintype.card ι : ℝ≥0) :=
(ennreal.coe_nat (fintype.card ι)).symm,
rw [this, ennreal.coe_rpow_of_nonneg _ nonneg]
end
end
lemma aux_uniformity_eq :
𝓤 (pi_Lp p hp β) = @uniformity _ (Pi.uniform_space _) :=
begin
have A : uniform_inducing (pi_Lp.equiv p hp β) :=
(antilipschitz_with_equiv p hp β).uniform_inducing
(lipschitz_with_equiv p hp β).uniform_continuous,
have : (λ (x : pi_Lp p hp β × pi_Lp p hp β),
((pi_Lp.equiv p hp β) x.fst, (pi_Lp.equiv p hp β) x.snd)) = id,
by ext i; refl,
rw [← A.comap_uniformity, this, comap_id]
end
end
/-! ### Instances on finite `L^p` products -/
instance uniform_space [∀ i, uniform_space (β i)] : uniform_space (pi_Lp p hp β) :=
Pi.uniform_space _
variable [fintype ι]
/-- pseudoemetric space instance on the product of finitely many pseudoemetric spaces, using the
`L^p` pseudoedistance, and having as uniformity the product uniformity. -/
instance [∀ i, pseudo_emetric_space (β i)] : pseudo_emetric_space (pi_Lp p hp β) :=
(pseudo_emetric_aux p hp β).replace_uniformity (aux_uniformity_eq p hp β).symm
/-- emetric space instance on the product of finitely many emetric spaces, using the `L^p`
edistance, and having as uniformity the product uniformity. -/
instance [∀ i, emetric_space (α i)] : emetric_space (pi_Lp p hp α) :=
(emetric_aux p hp α).replace_uniformity (aux_uniformity_eq p hp α).symm
protected lemma edist {p : ℝ} {hp : 1 ≤ p} {β : ι → Type*}
[∀ i, pseudo_emetric_space (β i)] (x y : pi_Lp p hp β) :
edist x y = (∑ (i : ι), (edist (x i) (y i)) ^ p) ^ (1/p) := rfl
/-- pseudometric space instance on the product of finitely many psuedometric spaces, using the
`L^p` distance, and having as uniformity the product uniformity. -/
instance [∀ i, pseudo_metric_space (β i)] : pseudo_metric_space (pi_Lp p hp β) :=
begin
/- we construct the instance from the pseudo emetric space instance to avoid checking again that
the uniformity is the same as the product uniformity, but we register nevertheless a nice formula
for the distance -/
have pos : 0 < p := lt_of_lt_of_le zero_lt_one hp,
refine pseudo_emetric_space.to_pseudo_metric_space_of_dist
(λf g, (∑ (i : ι), (dist (f i) (g i)) ^ p) ^ (1/p)) (λ f g, _) (λ f g, _),
{ simp [pi_Lp.edist, ennreal.rpow_eq_top_iff, asymm pos, pos,
ennreal.sum_eq_top_iff, edist_ne_top] },
{ have A : ∀ (i : ι), i ∈ (finset.univ : finset ι) → edist (f i) (g i) ^ p < ⊤ :=
λ i hi, by simp [lt_top_iff_ne_top, edist_ne_top, le_of_lt pos],
simp [dist, -one_div, pi_Lp.edist, ← ennreal.to_real_rpow,
ennreal.to_real_sum A, dist_edist] }
end
/-- metric space instance on the product of finitely many metric spaces, using the `L^p` distance,
and having as uniformity the product uniformity. -/
instance [∀ i, metric_space (α i)] : metric_space (pi_Lp p hp α) :=
begin
/- we construct the instance from the emetric space instance to avoid checking again that the
uniformity is the same as the product uniformity, but we register nevertheless a nice formula
for the distance -/
have pos : 0 < p := lt_of_lt_of_le zero_lt_one hp,
refine emetric_space.to_metric_space_of_dist
(λf g, (∑ (i : ι), (dist (f i) (g i)) ^ p) ^ (1/p)) (λ f g, _) (λ f g, _),
{ simp [pi_Lp.edist, ennreal.rpow_eq_top_iff, asymm pos, pos,
ennreal.sum_eq_top_iff, edist_ne_top] },
{ have A : ∀ (i : ι), i ∈ (finset.univ : finset ι) → edist (f i) (g i) ^ p < ⊤ :=
λ i hi, by simp [lt_top_iff_ne_top, edist_ne_top, le_of_lt pos],
simp [dist, -one_div, pi_Lp.edist, ← ennreal.to_real_rpow,
ennreal.to_real_sum A, dist_edist] }
end
protected lemma dist {p : ℝ} {hp : 1 ≤ p} {β : ι → Type*}
[∀ i, pseudo_metric_space (β i)] (x y : pi_Lp p hp β) :
dist x y = (∑ (i : ι), (dist (x i) (y i)) ^ p) ^ (1/p) := rfl
/-- seminormed group instance on the product of finitely many normed groups, using the `L^p`
norm. -/
instance semi_normed_group [∀i, semi_normed_group (β i)] : semi_normed_group (pi_Lp p hp β) :=
{ norm := λf, (∑ (i : ι), norm (f i) ^ p) ^ (1/p),
dist_eq := λ x y, by { simp [pi_Lp.dist, dist_eq_norm, sub_eq_add_neg] },
.. pi.add_comm_group }
/-- normed group instance on the product of finitely many normed groups, using the `L^p` norm. -/
instance normed_group [∀i, normed_group (α i)] : normed_group (pi_Lp p hp α) :=
{ ..pi_Lp.semi_normed_group p hp α }
lemma norm_eq {p : ℝ} {hp : 1 ≤ p} {β : ι → Type*}
[∀i, semi_normed_group (β i)] (f : pi_Lp p hp β) :
∥f∥ = (∑ (i : ι), ∥f i∥ ^ p) ^ (1/p) := rfl
lemma norm_eq_of_nat {p : ℝ} {hp : 1 ≤ p} {β : ι → Type*}
[∀i, semi_normed_group (β i)] (n : ℕ) (h : p = n) (f : pi_Lp p hp β) :
∥f∥ = (∑ (i : ι), ∥f i∥ ^ n) ^ (1/(n : ℝ)) :=
by simp [norm_eq, h, real.sqrt_eq_rpow, ←real.rpow_nat_cast]
variables (𝕜 : Type*) [normed_field 𝕜]
/-- The product of finitely many seminormed spaces is a seminormed space, with the `L^p` norm. -/
instance semi_normed_space [∀i, semi_normed_group (β i)] [∀i, semi_normed_space 𝕜 (β i)] :
semi_normed_space 𝕜 (pi_Lp p hp β) :=
{ norm_smul_le :=
begin
assume c f,
have : p * (1 / p) = 1 := mul_div_cancel' 1 (ne_of_gt (lt_of_lt_of_le zero_lt_one hp)),
simp only [pi_Lp.norm_eq, norm_smul, mul_rpow, norm_nonneg, ←finset.mul_sum, pi.smul_apply],
rw [mul_rpow (rpow_nonneg_of_nonneg (norm_nonneg _) _), ← rpow_mul (norm_nonneg _),
this, rpow_one],
exact finset.sum_nonneg (λ i hi, rpow_nonneg_of_nonneg (norm_nonneg _) _)
end,
.. pi.module ι β 𝕜 }
/-- The product of finitely many normed spaces is a normed space, with the `L^p` norm. -/
instance normed_space [∀i, normed_group (α i)] [∀i, normed_space 𝕜 (α i)] :
normed_space 𝕜 (pi_Lp p hp α) :=
{ ..pi_Lp.semi_normed_space p hp α 𝕜 }
/- Register simplification lemmas for the applications of `pi_Lp` elements, as the usual lemmas
for Pi types will not trigger. -/
variables {𝕜 p hp α}
[∀i, semi_normed_group (β i)] [∀i, semi_normed_space 𝕜 (β i)] (c : 𝕜) (x y : pi_Lp p hp β) (i : ι)
@[simp] lemma add_apply : (x + y) i = x i + y i := rfl
@[simp] lemma sub_apply : (x - y) i = x i - y i := rfl
@[simp] lemma smul_apply : (c • x) i = c • x i := rfl
@[simp] lemma neg_apply : (-x) i = - (x i) := rfl
end pi_Lp
|
0328172ddbae8a6f3951beac7e39004b46ca2a5a | e898bfefd5cb60a60220830c5eba68cab8d02c79 | /uexp/src/uexp/rules/ex2sigmod92.lean | 8827760e641faebe3a8648b2dd5c9023cbaf89d2 | [
"BSD-2-Clause"
] | permissive | kkpapa/Cosette | 9ed09e2dc4c1ecdef815c30b5501f64a7383a2ce | fda8fdbbf0de6c1be9b4104b87bbb06cede46329 | refs/heads/master | 1,584,573,128,049 | 1,526,370,422,000 | 1,526,370,422,000 | null | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 2,139 | lean | import ..sql
import ..tactics
import ..u_semiring
import ..extra_constants
import ..UDP
import ..canonize
import ..cosette_tactics
set_option profiler true
open Expr
open Proj
open Pred
open SQL
variable i1000 : const datatypes.int
theorem rule :
forall (Γ scm_itm scm_itp : Schema)
(rel_itm : relation scm_itm)
(rel_itp : relation scm_itp)
(itm_itemno : Column datatypes.int scm_itm)
(itm_type : Column datatypes.int scm_itm)
(itp_itemno : Column datatypes.int scm_itp)
(itp_np : Column datatypes.int scm_itp)
(ik : isKey itm_itemno rel_itm),
denoteSQL
(SELECT1 (combine (right⋅left⋅right)
(combine (right⋅right⋅itm_type)
(right⋅right⋅itm_itemno)))
FROM1 (product (DISTINCT (SELECT1 (combine (right⋅itp_itemno)
(right⋅itp_np))
FROM1 (table rel_itp)
WHERE (castPred (combine (right⋅itp_np)
(e2p (constantExpr i1000)))
predicates.gt)))
(table rel_itm))
WHERE (equal (uvariable (right⋅left⋅left))
(uvariable (right⋅right⋅itm_itemno))) : SQL Γ _) =
denoteSQL
(DISTINCT (SELECT1 (combine (right⋅left⋅itp_np)
(combine (right⋅right⋅itm_type)
(right⋅right⋅itm_itemno)))
FROM1 (product (table rel_itp)
(table rel_itm))
WHERE (and (castPred (combine (right⋅left⋅itp_np)
(e2p (constantExpr i1000)))
predicates.gt)
(equal (uvariable (right⋅left⋅itp_itemno))
(uvariable (right⋅right⋅itm_itemno))))) : SQL Γ _) :=
begin
intros,
unfold_all_denotations,
funext,
simp,
canonize,
sorry
end |
7f12b22079631c2517cf7453074079c9a81b4b2d | 46125763b4dbf50619e8846a1371029346f4c3db | /src/ring_theory/localization.lean | 8834fc012acef7a28add664adc3c5581bf3d8693 | [
"Apache-2.0"
] | permissive | thjread/mathlib | a9d97612cedc2c3101060737233df15abcdb9eb1 | 7cffe2520a5518bba19227a107078d83fa725ddc | refs/heads/master | 1,615,637,696,376 | 1,583,953,063,000 | 1,583,953,063,000 | 246,680,271 | 0 | 0 | Apache-2.0 | 1,583,960,875,000 | 1,583,960,875,000 | null | UTF-8 | Lean | false | false | 27,092 | lean | /-
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, Johan Commelin
-/
import tactic.ring data.quot data.equiv.algebra ring_theory.ideal_operations group_theory.submonoid
universes u v
namespace localization
variables (α : Type u) [comm_ring α] (S : set α) [is_submonoid S]
def r (x y : α × S) : Prop :=
∃ t ∈ S, ((x.2 : α) * y.1 - y.2 * x.1) * t = 0
local infix ≈ := r α S
section
variables {α S}
theorem r_of_eq {a₀ a₁ : α × S} (h : (a₀.2 : α) * a₁.1 = a₁.2 * a₀.1) : a₀ ≈ a₁ :=
⟨1, is_submonoid.one_mem S, by rw [h, sub_self, mul_one]⟩
end
theorem refl (x : α × S) : x ≈ x := r_of_eq rfl
theorem symm (x y : α × S) : x ≈ y → y ≈ x :=
λ ⟨t, hts, ht⟩, ⟨t, hts, by rw [← neg_sub, ← neg_mul_eq_neg_mul, ht, neg_zero]⟩
theorem trans : ∀ (x y z : α × S), x ≈ y → y ≈ z → x ≈ z :=
λ ⟨r₁, s₁, hs₁⟩ ⟨r₂, s₂, hs₂⟩ ⟨r₃, s₃, hs₃⟩ ⟨t, hts, ht⟩ ⟨t', hts', ht'⟩,
⟨s₂ * t' * t, is_submonoid.mul_mem (is_submonoid.mul_mem hs₂ hts') hts,
calc (s₁ * r₃ - s₃ * r₁) * (s₂ * t' * t) =
t' * s₃ * ((s₁ * r₂ - s₂ * r₁) * t) + t * s₁ * ((s₂ * r₃ - s₃ * r₂) * t') : by ring
... = 0 : by simp only [subtype.coe_mk] at ht ht'; rw [ht, ht']; simp⟩
instance : setoid (α × S) :=
⟨r α S, refl α S, symm α S, trans α S⟩
end localization
/-- The localization of a ring at a submonoid:
the elements of the submonoid become invertible in the localization.-/
def localization (α : Type u) [comm_ring α] (S : set α) [is_submonoid S] :=
quotient $ localization.setoid α S
namespace localization
variables (α : Type u) [comm_ring α] (S : set α) [is_submonoid S]
instance : has_add (localization α S) :=
⟨quotient.lift₂
(λ x y : α × S, (⟦⟨x.2 * y.1 + y.2 * x.1, x.2 * y.2⟩⟧ : localization α S)) $
λ ⟨r₁, s₁, hs₁⟩ ⟨r₂, s₂, hs₂⟩ ⟨r₃, s₃, hs₃⟩ ⟨r₄, s₄, hs₄⟩ ⟨t₅, hts₅, ht₅⟩ ⟨t₆, hts₆, ht₆⟩,
quotient.sound ⟨t₆ * t₅, is_submonoid.mul_mem hts₆ hts₅,
calc (s₁ * s₂ * (s₃ * r₄ + s₄ * r₃) - s₃ * s₄ * (s₁ * r₂ + s₂ * r₁)) * (t₆ * t₅) =
s₁ * s₃ * ((s₂ * r₄ - s₄ * r₂) * t₆) * t₅ + s₂ * s₄ * ((s₁ * r₃ - s₃ * r₁) * t₅) * t₆ : by ring
... = 0 : by simp only [subtype.coe_mk] at ht₅ ht₆; rw [ht₆, ht₅]; simp⟩⟩
instance : has_neg (localization α S) :=
⟨quotient.lift (λ x : α × S, (⟦⟨-x.1, x.2⟩⟧ : localization α S)) $
λ ⟨r₁, s₁, hs₁⟩ ⟨r₂, s₂, hs₂⟩ ⟨t, hts, ht⟩,
quotient.sound ⟨t, hts,
calc (s₁ * -r₂ - s₂ * -r₁) * t = -((s₁ * r₂ - s₂ * r₁) * t) : by ring
... = 0 : by simp only [subtype.coe_mk] at ht; rw ht; simp⟩⟩
instance : has_mul (localization α S) :=
⟨quotient.lift₂
(λ x y : α × S, (⟦⟨x.1 * y.1, x.2 * y.2⟩⟧ : localization α S)) $
λ ⟨r₁, s₁, hs₁⟩ ⟨r₂, s₂, hs₂⟩ ⟨r₃, s₃, hs₃⟩ ⟨r₄, s₄, hs₄⟩ ⟨t₅, hts₅, ht₅⟩ ⟨t₆, hts₆, ht₆⟩,
quotient.sound ⟨t₆ * t₅, is_submonoid.mul_mem hts₆ hts₅,
calc ((s₁ * s₂) * (r₃ * r₄) - (s₃ * s₄) * (r₁ * r₂)) * (t₆ * t₅) =
t₆ * ((s₁ * r₃ - s₃ * r₁) * t₅) * r₂ * s₄ + t₅ * ((s₂ * r₄ - s₄ * r₂) * t₆) * r₃ * s₁ :
by ring
... = 0 : by simp only [subtype.coe_mk] at ht₅ ht₆; rw [ht₅, ht₆]; simp⟩⟩
variables {α S}
def mk (r : α) (s : S) : localization α S := ⟦(r, s)⟧
/-- The natural map from the ring to the localization.-/
def of (r : α) : localization α S := mk r 1
instance : comm_ring (localization α S) :=
by refine
{ add := has_add.add,
add_assoc := λ m n k, quotient.induction_on₃ m n k _,
zero := of 0,
zero_add := quotient.ind _,
add_zero := quotient.ind _,
neg := has_neg.neg,
add_left_neg := quotient.ind _,
add_comm := quotient.ind₂ _,
mul := has_mul.mul,
mul_assoc := λ m n k, quotient.induction_on₃ m n k _,
one := of 1,
one_mul := quotient.ind _,
mul_one := quotient.ind _,
left_distrib := λ m n k, quotient.induction_on₃ m n k _,
right_distrib := λ m n k, quotient.induction_on₃ m n k _,
mul_comm := quotient.ind₂ _ };
{ intros,
try {rcases a with ⟨r₁, s₁, hs₁⟩},
try {rcases b with ⟨r₂, s₂, hs₂⟩},
try {rcases c with ⟨r₃, s₃, hs₃⟩},
refine (quotient.sound $ r_of_eq _),
simp only [is_submonoid.coe_mul, is_submonoid.coe_one, subtype.coe_mk],
ring }
instance : inhabited (localization α S) := ⟨0⟩
instance of.is_ring_hom : is_ring_hom (of : α → localization α S) :=
{ map_add := λ x y, quotient.sound $ by simp [add_comm],
map_mul := λ x y, quotient.sound $ by simp [add_comm],
map_one := rfl }
variables {S}
instance : has_coe_t α (localization α S) := ⟨of⟩ -- note [use has_coe_t]
instance coe.is_ring_hom : is_ring_hom (coe : α → localization α S) :=
localization.of.is_ring_hom
/-- The natural map from the submonoid to the unit group of the localization.-/
def to_units (s : S) : units (localization α S) :=
{ val := s,
inv := mk 1 s,
val_inv := quotient.sound $ r_of_eq $ mul_assoc _ _ _,
inv_val := quotient.sound $ r_of_eq $ show s.val * 1 * 1 = 1 * (1 * s.val), by simp }
@[simp] lemma to_units_coe (s : S) :
((to_units s) : localization α S) = ((s : α) : localization α S) := rfl
section
variables (α S) (x y : α) (n : ℕ)
@[simp] lemma of_zero : (of 0 : localization α S) = 0 := rfl
@[simp] lemma of_one : (of 1 : localization α S) = 1 := rfl
@[simp] lemma of_add : (of (x + y) : localization α S) = of x + of y :=
by apply is_ring_hom.map_add
@[simp] lemma of_sub : (of (x - y) : localization α S) = of x - of y :=
by apply is_ring_hom.map_sub
@[simp] lemma of_mul : (of (x * y) : localization α S) = of x * of y :=
by apply is_ring_hom.map_mul
@[simp] lemma of_neg : (of (-x) : localization α S) = -of x :=
by apply is_ring_hom.map_neg
@[simp] lemma of_pow : (of (x ^ n) : localization α S) = (of x) ^ n :=
by apply is_semiring_hom.map_pow
@[simp] lemma of_is_unit' (s ∈ S) : is_unit (of s : localization α S) :=
is_unit_unit $ to_units ⟨s, ‹s ∈ S›⟩
@[simp] lemma of_is_unit (s : S) : is_unit (of s : localization α S) :=
is_unit_unit $ to_units s
@[simp] lemma coe_zero : ((0 : α) : localization α S) = 0 := rfl
@[simp] lemma coe_one : ((1 : α) : localization α S) = 1 := rfl
@[simp] lemma coe_add : (↑(x + y) : localization α S) = x + y := of_add _ _ _ _
@[simp] lemma coe_sub : (↑(x - y) : localization α S) = x - y := of_sub _ _ _ _
@[simp] lemma coe_mul : (↑(x * y) : localization α S) = x * y := of_mul _ _ _ _
@[simp] lemma coe_neg : (↑(-x) : localization α S) = -x := of_neg _ _ _
@[simp] lemma coe_pow : (↑(x ^ n) : localization α S) = x ^ n := of_pow _ _ _ _
@[simp] lemma coe_is_unit' (s ∈ S) : is_unit ((s : α) : localization α S) := of_is_unit' _ _ _ ‹s ∈ S›
@[simp] lemma coe_is_unit (s : S) : is_unit ((s : α) : localization α S) := of_is_unit _ _ _
end
lemma mk_self {x : α} {hx : x ∈ S} :
(mk x ⟨x, hx⟩ : localization α S) = 1 :=
quotient.sound ⟨1, is_submonoid.one_mem S,
by simp only [subtype.coe_mk, is_submonoid.coe_one, mul_one, one_mul, sub_self]⟩
lemma mk_self' {s : S} :
(mk s s : localization α S) = 1 :=
by cases s; exact mk_self
lemma mk_self'' {s : S} :
(mk s.1 s : localization α S) = 1 :=
mk_self'
-- This lemma does not apply with simp, since (mk r s) simplifies to (r * s⁻¹).
-- However, it could apply with dsimp.
@[simp, nolint simp_nf]
lemma coe_mul_mk (x y : α) (s : S) :
↑x * mk y s = mk (x * y) s :=
quotient.sound $ r_of_eq $ by rw one_mul
lemma mk_eq_mul_mk_one (r : α) (s : S) :
mk r s = r * mk 1 s :=
by rw [coe_mul_mk, mul_one]
-- This lemma does not apply with simp, since (mk r s) simplifies to (r * s⁻¹).
-- However, it could apply with dsimp.
@[simp, nolint simp_nf]
lemma mk_mul_mk (x y : α) (s t : S) :
mk x s * mk y t = mk (x * y) (s * t) := rfl
lemma mk_mul_cancel_left (r : α) (s : S) :
mk (↑s * r) s = r :=
by rw [mk_eq_mul_mk_one, mul_comm ↑s, coe_mul,
mul_assoc, ← mk_eq_mul_mk_one, mk_self', mul_one]
lemma mk_mul_cancel_right (r : α) (s : S) :
mk (r * s) s = r :=
by rw [mul_comm, mk_mul_cancel_left]
@[simp] lemma mk_eq (r : α) (s : S) :
mk r s = r * ((to_units s)⁻¹ : units _) :=
quotient.sound $ by simp
@[elab_as_eliminator]
protected theorem induction_on {C : localization α S → Prop} (x : localization α S)
(ih : ∀ r s, C (mk r s : localization α S)) : C x :=
by rcases x with ⟨r, s⟩; exact ih r s
section
variables {β : Type v} [comm_ring β] {T : set β} [is_submonoid T] (f : α → β) [is_ring_hom f]
@[elab_with_expected_type]
def lift' (g : S → units β) (hg : ∀ s, (g s : β) = f s) (x : localization α S) : β :=
quotient.lift_on x (λ p, f p.1 * ((g p.2)⁻¹ : units β)) $ λ ⟨r₁, s₁⟩ ⟨r₂, s₂⟩ ⟨t, hts, ht⟩,
show f r₁ * ↑(g s₁)⁻¹ = f r₂ * ↑(g s₂)⁻¹, from
calc f r₁ * ↑(g s₁)⁻¹
= (f r₁ * g s₂ + ((g s₁ * f r₂ - g s₂ * f r₁) * g ⟨t, hts⟩) * ↑(g ⟨t, hts⟩)⁻¹)
* ↑(g s₁)⁻¹ * ↑(g s₂)⁻¹ :
by simp only [hg, subtype.coe_mk, (is_ring_hom.map_mul f).symm, (is_ring_hom.map_sub f).symm,
ht, is_ring_hom.map_zero f, zero_mul, add_zero];
rw [is_ring_hom.map_mul f, ← hg, mul_right_comm,
mul_assoc (f r₁), ← units.coe_mul, mul_inv_self];
rw [units.coe_one, mul_one]
... = f r₂ * ↑(g s₂)⁻¹ :
by rw [mul_assoc, mul_assoc, ← units.coe_mul, mul_inv_self, units.coe_one,
mul_one, mul_comm ↑(g s₂), add_sub_cancel'_right];
rw [mul_comm ↑(g s₁), ← mul_assoc, mul_assoc (f r₂), ← units.coe_mul,
mul_inv_self, units.coe_one, mul_one]
instance lift'.is_ring_hom (g : S → units β) (hg : ∀ s, (g s : β) = f s) :
is_ring_hom (localization.lift' f g hg) :=
{ map_one := have g 1 = 1, from units.ext (by rw hg; exact is_ring_hom.map_one f),
show f 1 * ↑(g 1)⁻¹ = 1, by rw [this, one_inv, units.coe_one, mul_one, is_ring_hom.map_one f],
map_mul := λ x y, localization.induction_on x $ λ r₁ s₁,
localization.induction_on y $ λ r₂ s₂,
have g (s₁ * s₂) = g s₁ * g s₂,
from units.ext (by simp only [hg, units.coe_mul]; exact is_ring_hom.map_mul f),
show _ * ↑(g (_ * _))⁻¹ = (_ * _) * (_ * _),
by simp only [subtype.coe_mk, mul_one, one_mul, subtype.coe_eta, this, mul_inv_rev];
rw [is_ring_hom.map_mul f, units.coe_mul, ← mul_assoc, ← mul_assoc];
simp only [mul_right_comm],
map_add := λ x y, localization.induction_on x $ λ r₁ s₁,
localization.induction_on y $ λ r₂ s₂,
have g (s₁ * s₂) = g s₁ * g s₂,
from units.ext (by simp only [hg, units.coe_mul]; exact is_ring_hom.map_mul f),
show _ * ↑(g (_ * _))⁻¹ = _ * _ + _ * _,
by simp only [subtype.coe_mk, mul_one, one_mul, subtype.coe_eta, this, mul_inv_rev];
simp only [is_ring_hom.map_mul f, is_ring_hom.map_add f, add_mul, (hg _).symm];
simp only [mul_assoc, mul_comm, mul_left_comm, (units.coe_mul _ _).symm];
rw [mul_inv_cancel_left, mul_left_comm, ← mul_assoc, mul_inv_cancel_right, add_comm] }
noncomputable def lift (h : ∀ s ∈ S, is_unit (f s)) :
localization α S → β :=
localization.lift' f (λ s, classical.some $ h s.1 s.2)
(λ s, by rw [← classical.some_spec (h s.1 s.2)]; refl)
instance lift.is_ring_hom (h : ∀ s ∈ S, is_unit (f s)) :
is_ring_hom (lift f h) :=
lift'.is_ring_hom _ _ _
-- This lemma does not apply with simp, since (mk r s) simplifies to (r * s⁻¹).
-- However, it could apply with dsimp.
@[simp, nolint simp_nf]
lemma lift'_mk (g : S → units β) (hg : ∀ s, (g s : β) = f s) (r : α) (s : S) :
lift' f g hg (mk r s) = f r * ↑(g s)⁻¹ := rfl
@[simp] lemma lift'_of (g : S → units β) (hg : ∀ s, (g s : β) = f s) (a : α) :
lift' f g hg (of a) = f a :=
have g 1 = 1, from units.ext_iff.2 $ by simp [hg, is_ring_hom.map_one f],
by simp [lift', quotient.lift_on_beta, of, mk, this]
@[simp] lemma lift'_coe (g : S → units β) (hg : ∀ s, (g s : β) = f s) (a : α) :
lift' f g hg a = f a := lift'_of _ _ _ _
@[simp] lemma lift_of (h : ∀ s ∈ S, is_unit (f s)) (a : α) :
lift f h (of a) = f a := lift'_of _ _ _ _
@[simp] lemma lift_coe (h : ∀ s ∈ S, is_unit (f s)) (a : α) :
lift f h a = f a := lift'_of _ _ _ _
@[simp] lemma lift'_comp_of (g : S → units β) (hg : ∀ s, (g s : β) = f s) :
lift' f g hg ∘ of = f := funext $ λ a, lift'_of _ _ _ a
@[simp] lemma lift_comp_of (h : ∀ s ∈ S, is_unit (f s)) :
lift f h ∘ of = f := lift'_comp_of _ _ _
@[simp] lemma lift'_apply_coe (f : localization α S → β) [is_ring_hom f]
(g : S → units β) (hg : ∀ s, (g s : β) = f s) :
lift' (λ a : α, f a) g hg = f :=
have g = (λ s, (units.map' f : units (localization α S) → units β) (to_units s)),
from funext $ λ x, units.ext $ (hg x).symm ▸ rfl,
funext $ λ x, localization.induction_on x
(λ r s, by subst this; rw [lift'_mk, ← (units.map' f).map_inv, units.coe_map'];
simp [is_ring_hom.map_mul f])
@[simp] lemma lift_apply_coe (f : localization α S → β) [is_ring_hom f] :
lift (λ a : α, f a)
(λ s hs, is_unit.map' f (is_unit_unit (to_units ⟨s, hs⟩))) = f :=
by rw [lift, lift'_apply_coe]
/-- Function extensionality for localisations:
two functions are equal if they agree on elements that are coercions.-/
protected lemma funext (f g : localization α S → β) [is_ring_hom f] [is_ring_hom g]
(h : ∀ a : α, f a = g a) : f = g :=
begin
rw [← lift_apply_coe f, ← lift_apply_coe g],
congr' 1,
exact funext h
end
variables {α S T}
def map (hf : ∀ s ∈ S, f s ∈ T) : localization α S → localization β T :=
lift' (of ∘ f) (to_units ∘ subtype.map f hf) (λ s, rfl)
instance map.is_ring_hom (hf : ∀ s ∈ S, f s ∈ T) : is_ring_hom (map f hf) :=
lift'.is_ring_hom _ _ _
@[simp] lemma map_of (hf : ∀ s ∈ S, f s ∈ T) (a : α) :
map f hf (of a) = of (f a) := lift'_of _ _ _ _
@[simp] lemma map_coe (hf : ∀ s ∈ S, f s ∈ T) (a : α) :
map f hf a = (f a) := lift'_of _ _ _ _
@[simp] lemma map_comp_of (hf : ∀ s ∈ S, f s ∈ T) :
map f hf ∘ of = of ∘ f := funext $ λ a, map_of _ _ _
@[simp] lemma map_id : map id (λ s (hs : s ∈ S), hs) = id :=
localization.funext _ _ $ map_coe _ _
lemma map_comp_map {γ : Type*} [comm_ring γ] (hf : ∀ s ∈ S, f s ∈ T) (U : set γ)
[is_submonoid U] (g : β → γ) [is_ring_hom g] (hg : ∀ t ∈ T, g t ∈ U) :
map g hg ∘ map f hf = map (λ x, g (f x)) (λ s hs, hg _ (hf _ hs)) :=
localization.funext _ _ $ by simp
lemma map_map {γ : Type*} [comm_ring γ] (hf : ∀ s ∈ S, f s ∈ T) (U : set γ)
[is_submonoid U] (g : β → γ) [is_ring_hom g] (hg : ∀ t ∈ T, g t ∈ U) (x) :
map g hg (map f hf x) = map (λ x, g (f x)) (λ s hs, hg _ (hf _ hs)) x :=
congr_fun (map_comp_map _ _ _ _ _) x
def equiv_of_equiv (h₁ : α ≃+* β) (h₂ : h₁ '' S = T) :
localization α S ≃+* localization β T :=
{ to_fun := map h₁ $ λ s hs, h₂ ▸ set.mem_image_of_mem _ hs,
inv_fun := map h₁.symm $ λ t ht,
by simp [h₁.image_eq_preimage, set.preimage, set.ext_iff, *] at *,
left_inv := λ _, by simp only [map_map, h₁.symm_apply_apply]; erw map_id; refl,
right_inv := λ _, by simp only [map_map, h₁.apply_symm_apply]; erw map_id; refl,
map_mul' := λ _ _, is_ring_hom.map_mul _,
map_add' := λ _ _, is_ring_hom.map_add _ }
end
section away
variables {β : Type v} [comm_ring β] (f : α → β) [is_ring_hom f]
@[reducible] def away (x : α) := localization α (powers x)
@[simp] def away.inv_self (x : α) : away x :=
mk 1 ⟨x, 1, pow_one x⟩
@[elab_with_expected_type]
noncomputable def away.lift {x : α} (hfx : is_unit (f x)) : away x → β :=
localization.lift' f (λ s, classical.some hfx ^ classical.some s.2) $ λ s,
by rw [units.coe_pow, ← classical.some_spec hfx,
← is_semiring_hom.map_pow f, classical.some_spec s.2]; refl
instance away.lift.is_ring_hom {x : α} (hfx : is_unit (f x)) :
is_ring_hom (localization.away.lift f hfx) :=
lift'.is_ring_hom _ _ _
@[simp] lemma away.lift_of {x : α} (hfx : is_unit (f x)) (a : α) :
away.lift f hfx (of a) = f a := lift'_of _ _ _ _
@[simp] lemma away.lift_coe {x : α} (hfx : is_unit (f x)) (a : α) :
away.lift f hfx a = f a := lift'_of _ _ _ _
@[simp] lemma away.lift_comp_of {x : α} (hfx : is_unit (f x)) :
away.lift f hfx ∘ of = f := lift'_comp_of _ _ _
noncomputable def away_to_away_right (x y : α) : away x → away (x * y) :=
localization.away.lift coe $
is_unit_of_mul_one x (y * away.inv_self (x * y)) $
by rw [away.inv_self, coe_mul_mk, coe_mul_mk, mul_one, mk_self]
instance away_to_away_right.is_ring_hom (x y : α) :
is_ring_hom (away_to_away_right x y) :=
away.lift.is_ring_hom _ _
end away
section at_prime
variables (P : ideal α) [hp : ideal.is_prime P]
include hp
instance prime.is_submonoid :
is_submonoid (-P : set α) :=
{ one_mem := P.ne_top_iff_one.1 hp.1,
mul_mem := λ x y hnx hny hxy, or.cases_on (hp.2 hxy) hnx hny }
@[reducible] def at_prime := localization α (-P)
instance at_prime.local_ring : local_ring (at_prime P) :=
local_of_nonunits_ideal
(λ hze,
let ⟨t, hts, ht⟩ := quotient.exact hze in
hts $ have htz : t = 0, by simpa using ht,
suffices (0:α) ∈ P, by rwa htz,
P.zero_mem)
(begin
rintro ⟨⟨r₁, s₁, hs₁⟩⟩ ⟨⟨r₂, s₂, hs₂⟩⟩ hx hy hu,
rcases is_unit_iff_exists_inv.1 hu with ⟨⟨⟨r₃, s₃, hs₃⟩⟩, hz⟩,
rcases quotient.exact hz with ⟨t, hts, ht⟩,
simp at ht,
have : ∀ {r s hs}, (⟦⟨r, s, hs⟩⟧ : at_prime P) ∈ nonunits (at_prime P) → r ∈ P,
{ haveI := classical.dec,
exact λ r s hs, not_imp_comm.1 (λ nr,
is_unit_iff_exists_inv.2 ⟨⟦⟨s, r, nr⟩⟧,
quotient.sound $ r_of_eq $ by simp [mul_comm]⟩) },
have hr₃ := (hp.mem_or_mem_of_mul_eq_zero ht).resolve_right hts,
have := (ideal.add_mem_iff_left _ _).1 hr₃,
{ exact not_or (mt hp.mem_or_mem (not_or hs₁ hs₂)) hs₃ (hp.mem_or_mem this) },
{ exact P.neg_mem (P.mul_mem_right
(P.add_mem (P.mul_mem_left (this hy)) (P.mul_mem_left (this hx)))) }
end)
end at_prime
variable (α)
def non_zero_divisors : set α := {x | ∀ z, z * x = 0 → z = 0}
instance non_zero_divisors.is_submonoid : is_submonoid (non_zero_divisors α) :=
{ one_mem := λ z hz, by rwa mul_one at hz,
mul_mem := λ x₁ x₂ hx₁ hx₂ z hz,
have z * x₁ * x₂ = 0, by rwa mul_assoc,
hx₁ z $ hx₂ (z * x₁) this }
@[simp] lemma non_zero_divisors_one_val : (1 : non_zero_divisors α).val = 1 := rfl
/-- The field of fractions of an integral domain.-/
@[reducible] def fraction_ring := localization α (non_zero_divisors α)
namespace fraction_ring
open function
variables {β : Type u} [integral_domain β] [decidable_eq β]
lemma eq_zero_of_ne_zero_of_mul_eq_zero {x y : β} :
x ≠ 0 → y * x = 0 → y = 0 :=
λ hnx hxy, or.resolve_right (eq_zero_or_eq_zero_of_mul_eq_zero hxy) hnx
lemma mem_non_zero_divisors_iff_ne_zero {x : β} :
x ∈ non_zero_divisors β ↔ x ≠ 0 :=
⟨λ hm hz, zero_ne_one (hm 1 $ by rw [hz, one_mul]).symm,
λ hnx z, eq_zero_of_ne_zero_of_mul_eq_zero hnx⟩
variable (β)
def inv_aux (x : β × (non_zero_divisors β)) : fraction_ring β :=
if h : x.1 = 0 then 0 else ⟦⟨x.2, x.1, mem_non_zero_divisors_iff_ne_zero.mpr h⟩⟧
instance : has_inv (fraction_ring β) :=
⟨quotient.lift (inv_aux β) $
λ ⟨r₁, s₁, hs₁⟩ ⟨r₂, s₂, hs₂⟩ ⟨t, hts, ht⟩,
begin
have hrs : s₁ * r₂ = 0 + s₂ * r₁,
from sub_eq_iff_eq_add.1 (hts _ ht),
by_cases hr₁ : r₁ = 0;
by_cases hr₂ : r₂ = 0;
simp [hr₁, hr₂] at hrs;
simp only [inv_aux, hr₁, hr₂, dif_pos, dif_neg, not_false_iff, subtype.coe_mk, quotient.eq],
{ exfalso,
exact mem_non_zero_divisors_iff_ne_zero.mp hs₁ hrs },
{ exfalso,
exact mem_non_zero_divisors_iff_ne_zero.mp hs₂ hrs },
{ apply r_of_eq,
simpa [mul_comm] using hrs.symm }
end⟩
lemma mk_inv {r s} :
(mk r s : fraction_ring β)⁻¹ =
if h : r = 0 then 0 else ⟦⟨s, r, mem_non_zero_divisors_iff_ne_zero.mpr h⟩⟧ := rfl
lemma mk_inv' :
∀ (x : β × (non_zero_divisors β)), (⟦x⟧⁻¹ : fraction_ring β) =
if h : x.1 = 0 then 0 else ⟦⟨x.2.val, x.1, mem_non_zero_divisors_iff_ne_zero.mpr h⟩⟧
| ⟨r,s,hs⟩ := rfl
instance : decidable_eq (fraction_ring β) :=
@quotient.decidable_eq (β × non_zero_divisors β) (localization.setoid β (non_zero_divisors β)) $
λ ⟨r₁, s₁, hs₁⟩ ⟨r₂, s₂, hs₂⟩, show decidable (∃ t ∈ non_zero_divisors β, (s₁ * r₂ - s₂ * r₁) * t = 0),
from decidable_of_iff (s₁ * r₂ - s₂ * r₁ = 0)
⟨λ H, ⟨1, λ y, (mul_one y).symm ▸ id, H.symm ▸ zero_mul _⟩,
λ ⟨t, ht1, ht2⟩, or.resolve_right (mul_eq_zero.1 ht2) $ λ ht,
one_ne_zero (ht1 1 ((one_mul t).symm ▸ ht))⟩
instance : field (fraction_ring β) :=
by refine
{ inv := has_inv.inv,
zero_ne_one := λ hzo,
let ⟨t, hts, ht⟩ := quotient.exact hzo in
zero_ne_one (by simpa using hts _ ht : 0 = 1),
mul_inv_cancel := quotient.ind _,
inv_zero := dif_pos rfl,
.. localization.comm_ring };
{ intros x hnx,
rcases x with ⟨x, z, hz⟩,
have : x ≠ 0,
from assume hx, hnx (quotient.sound $ r_of_eq $ by simp [hx]),
simp only [has_inv.inv, inv_aux, quotient.lift_beta, dif_neg this],
exact (quotient.sound $ r_of_eq $ by simp [mul_comm]) }
@[simp, nolint simp_nf] -- takes a crazy amount of time simplify lhs
lemma mk_eq_div {r s} : (mk r s : fraction_ring β) = (r / s : fraction_ring β) :=
show _ = _ * dite (s.1 = 0) _ _, by rw [dif_neg (mem_non_zero_divisors_iff_ne_zero.mp s.2)];
exact localization.mk_eq_mul_mk_one _ _
variables {β}
@[simp] lemma mk_eq_div' (x : β × (non_zero_divisors β)) :
(⟦x⟧ : fraction_ring β) = ((x.1) / ((x.2).val) : fraction_ring β) :=
by erw ← mk_eq_div; cases x; refl
lemma eq_zero_of (x : β) (h : (of x : fraction_ring β) = 0) : x = 0 :=
begin
rcases quotient.exact h with ⟨t, ht, ht'⟩,
simpa [mem_non_zero_divisors_iff_ne_zero.mp ht] using ht'
end
lemma of.injective : function.injective (of : β → fraction_ring β) :=
(is_add_group_hom.injective_iff _).mpr eq_zero_of
section map
open function is_ring_hom
variables {A : Type u} [integral_domain A] [decidable_eq A]
variables {B : Type v} [integral_domain B] [decidable_eq B]
variables (f : A → B) [is_ring_hom f]
def map (hf : injective f) : fraction_ring A → fraction_ring B :=
localization.map f $ λ s h,
by rw [mem_non_zero_divisors_iff_ne_zero, ← map_zero f, ne.def, hf.eq_iff];
exact mem_non_zero_divisors_iff_ne_zero.1 h
@[simp] lemma map_of (hf : injective f) (a : A) : map f hf (of a) = of (f a) :=
localization.map_of _ _ _
@[simp] lemma map_coe (hf : injective f) (a : A) : map f hf a = f a :=
localization.map_coe _ _ _
@[simp] lemma map_comp_of (hf : injective f) :
map f hf ∘ (of : A → fraction_ring A) = (of : B → fraction_ring B) ∘ f :=
localization.map_comp_of _ _
instance map.is_ring_hom (hf : injective f) : is_ring_hom (map f hf) :=
localization.map.is_ring_hom _ _
def equiv_of_equiv (h : A ≃+* B) : fraction_ring A ≃+* fraction_ring B :=
localization.equiv_of_equiv h
begin
ext b,
rw [h.image_eq_preimage, set.preimage, set.mem_set_of_eq,
mem_non_zero_divisors_iff_ne_zero, mem_non_zero_divisors_iff_ne_zero, ne.def],
exact h.symm.map_ne_zero_iff
end
end map
end fraction_ring
section ideals
theorem map_comap (J : ideal (localization α S)) :
ideal.map coe (ideal.comap (coe : α → localization α S) J) = J :=
le_antisymm (ideal.map_le_iff_le_comap.2 (le_refl _)) $ λ x,
localization.induction_on x $ λ r s hJ, (submodule.mem_coe _).2 $
mul_one r ▸ coe_mul_mk r 1 s ▸ (ideal.mul_mem_right _ $ ideal.mem_map_of_mem $
have _ := @ideal.mul_mem_left (localization α S) _ _ s _ hJ,
by rwa [coe_coe, coe_mul_mk, mk_mul_cancel_left] at this)
def le_order_embedding :
((≤) : ideal (localization α S) → ideal (localization α S) → Prop) ≼o
((≤) : ideal α → ideal α → Prop) :=
{ to_fun := λ J, ideal.comap coe J,
inj := function.injective_of_left_inverse (map_comap α),
ord := λ J₁ J₂, ⟨ideal.comap_mono, λ hJ,
map_comap α J₁ ▸ map_comap α J₂ ▸ ideal.map_mono hJ⟩ }
end ideals
section module
/-! ### `module` section
Localizations form an algebra over `α` induced by the embedding `coe : α → localization α S`.
-/
set_option class.instance_max_depth 50
variables (α S)
instance : algebra α (localization α S) := algebra.of_ring_hom coe (is_ring_hom.of_semiring coe)
lemma of_smul (c x : α) : (of (c • x) : localization α S) = c • of x :=
by { simp, refl }
lemma coe_smul (c x : α) : (coe (c • x) : localization α S) = c • coe x :=
of_smul α S c x
lemma coe_mul_eq_smul (c : α) (x : localization α S) : coe c * x = c • x :=
rfl
lemma mul_coe_eq_smul (c : α) (x : localization α S) : x * coe c = c • x :=
mul_comm x (coe c)
/-- The embedding `coe : α → localization α S` induces a linear map. -/
def lin_coe : α →ₗ[α] localization α S := ⟨coe, coe_add α S, coe_smul α S⟩
@[simp] lemma lin_coe_apply (a : α) : lin_coe α S a = coe a := rfl
instance coe_submodules : has_coe (ideal α) (submodule α (localization α S)) :=
⟨submodule.map (lin_coe _ _)⟩
@[simp] lemma of_id (a : α) : (algebra.of_id α (localization α S) : α → localization α S) a = ↑a :=
rfl
end module
section is_integer
/-- `a : localization α S` is an integer if it is an element of the original ring `α` -/
def is_integer (S : set α) [is_submonoid S] (a : localization α S) : Prop :=
a ∈ set.range (coe : α → localization α S)
lemma is_integer_coe (a : α) : is_integer α S a :=
⟨a, rfl⟩
lemma is_integer_add {a b} (ha : is_integer α S a) (hb : is_integer α S b) :
is_integer α S (a + b) :=
begin
rcases ha with ⟨a', ha⟩,
rcases hb with ⟨b', hb⟩,
use a' + b',
rw [coe_add, ha, hb]
end
lemma is_integer_mul {a b} (ha : is_integer α S a) (hb : is_integer α S b) :
is_integer α S (a * b) :=
begin
rcases ha with ⟨a', ha⟩,
rcases hb with ⟨b', hb⟩,
use a' * b',
rw [coe_mul, ha, hb]
end
set_option class.instance_max_depth 50
lemma is_integer_smul {a : α} {b} (hb : is_integer α S b) :
is_integer α S (a • b) :=
begin
rcases hb with ⟨b', hb⟩,
use a * b',
rw [←hb, ←coe_smul, smul_eq_mul]
end
end is_integer
end localization
|
faa4d2cee94c8e6ef007e1b84e3d882c82efab86 | e151e9053bfd6d71740066474fc500a087837323 | /src/hott/algebra/ordered_ring.lean | 7a0df989b3bf0cb70b742f74e13b069c640f67d1 | [
"Apache-2.0"
] | permissive | daniel-carranza/hott3 | 15bac2d90589dbb952ef15e74b2837722491963d | 913811e8a1371d3a5751d7d32ff9dec8aa6815d9 | refs/heads/master | 1,610,091,349,670 | 1,596,222,336,000 | 1,596,222,336,000 | 241,957,822 | 0 | 0 | Apache-2.0 | 1,582,222,839,000 | 1,582,222,838,000 | null | UTF-8 | Lean | false | false | 30,298 | lean | /-
Copyright (c) 2014 Jeremy Avigad. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Jeremy Avigad
Here an "ordered_ring" is partially ordered ring, which is ordered with respect to both a weak
order and an associated strict order. Our numeric structures (int, rat, and real) will be instances
of "linear_ordered_comm_ring". This development is modeled after Isabelle's library.
-/
import .ordered_group .ring
universes u v w
hott_theory
set_option old_structure_cmd true
namespace hott
open algebra
variable {A : Type _}
namespace algebra
@[hott] private def absurd_a_lt_a {B : Type _} {a : A} [s : strict_order A] (H : a < a) : B :=
absurd H (lt.irrefl a)
/- semiring structures -/
@[hott] structure ordered_semiring (A : Type _)
extends semiring A, ordered_mul_cancel_comm_monoid A renaming
mul→add mul_assoc→add_assoc one→zero one_mul→zero_add mul_one→add_zero mul_comm→add_comm
mul_left_cancel→add_left_cancel mul_right_cancel→add_right_cancel mul_le_mul_left→add_le_add_left
mul_lt_mul_left→add_lt_add_left le_of_mul_le_mul_left→le_of_add_le_add_left
lt_of_mul_lt_mul_left→lt_of_add_lt_add_left :=
(mul_le_mul_of_nonneg_left: Πa b c, le a b → le zero c → le (mul c a) (mul c b))
(mul_le_mul_of_nonneg_right: Πa b c, le a b → le zero c → le (mul a c) (mul b c))
(mul_lt_mul_of_pos_left: Πa b c, lt a b → lt zero c → lt (mul c a) (mul c b))
(mul_lt_mul_of_pos_right: Πa b c, lt a b → lt zero c → lt (mul a c) (mul b c))
-- /- we make it a class now (and not as part of the structure) to avoid
-- ordered_semiring.to_ordered_mul_cancel_comm_monoid to be an instance -/
attribute [class] ordered_semiring
@[hott, instance, reducible] def add_ab_group_of_ordered_semiring (A : Type _)
[H : ordered_semiring A] : semiring A :=
@ordered_semiring.to_semiring A H
@[hott, instance, reducible] def monoid_of_ordered_semiring (A : Type _)
[H : ordered_semiring A] : ordered_cancel_comm_monoid A :=
@ordered_semiring.to_ordered_mul_cancel_comm_monoid A H
section
variable [s : ordered_semiring A]
variables (a b c d e : A)
include s
@[hott] def mul_le_mul_of_nonneg_left {a b c : A} (Hab : a ≤ b) (Hc : 0 ≤ c) :
c * a ≤ c * b :=
ordered_semiring.mul_le_mul_of_nonneg_left _ _ _ _ Hab Hc
@[hott] def mul_le_mul_of_nonneg_right {a b c : A} (Hab : a ≤ b) (Hc : 0 ≤ c) :
a * c ≤ b * c :=
ordered_semiring.mul_le_mul_of_nonneg_right _ _ _ _ Hab Hc
@[hott] theorem mul_le_mul {a b c d : A} (Hac : a ≤ c) (Hbd : b ≤ d) (nn_b : 0 ≤ b)
(nn_c : 0 ≤ c) :
a * b ≤ c * d :=
calc
a * b ≤ c * b : mul_le_mul_of_nonneg_right Hac nn_b
... ≤ c * d : mul_le_mul_of_nonneg_left Hbd nn_c
@[hott] theorem mul_nonneg {a b : A} (Ha : a ≥ 0) (Hb : b ≥ 0) : a * b ≥ 0 :=
begin
have H : 0 * b ≤ a * b, from mul_le_mul_of_nonneg_right Ha Hb,
rwr zero_mul at H,
exact H
end
@[hott] theorem mul_nonpos_of_nonneg_of_nonpos {a b : A} (Ha : a ≥ 0) (Hb : b ≤ 0) : a * b ≤ 0 :=
begin
have H : a * b ≤ a * 0, from mul_le_mul_of_nonneg_left Hb Ha,
rwr mul_zero at H,
exact H
end
@[hott] theorem mul_nonpos_of_nonpos_of_nonneg {a b : A} (Ha : a ≤ 0) (Hb : b ≥ 0) : a * b ≤ 0 :=
begin
have H : a * b ≤ 0 * b, from mul_le_mul_of_nonneg_right Ha Hb,
rwr zero_mul at H,
exact H
end
@[hott] def mul_lt_mul_of_pos_left {a b c : A} (Hab : a < b) (Hc : 0 < c) :
c * a < c * b :=
ordered_semiring.mul_lt_mul_of_pos_left _ _ _ _ Hab Hc
@[hott] def mul_lt_mul_of_pos_right {a b c : A} (Hab : a < b) (Hc : 0 < c) :
a * c < b * c :=
ordered_semiring.mul_lt_mul_of_pos_right _ _ _ _ Hab Hc
-- TODO: once again, there are variations
@[hott] theorem mul_lt_mul {a b c d : A} (Hac : a < c) (Hbd : b ≤ d) (pos_b : 0 < b)
(nn_c : 0 ≤ c) : a * b < c * d :=
calc
a * b < c * b : mul_lt_mul_of_pos_right Hac pos_b
... ≤ c * d : mul_le_mul_of_nonneg_left Hbd nn_c
@[hott] def mul_pos {a b : A} (Ha : a > 0) (Hb : b > 0) : a * b > 0 :=
begin
have H : 0 * b < a * b, from mul_lt_mul_of_pos_right Ha Hb,
rwr zero_mul at H,
exact H
end
@[hott] def mul_neg_of_pos_of_neg {a b : A} (Ha : a > 0) (Hb : b < 0) : a * b < 0 :=
begin
have H : a * b < a * 0, from mul_lt_mul_of_pos_left Hb Ha,
rwr mul_zero at H,
exact H
end
@[hott] def mul_neg_of_neg_of_pos {a b : A} (Ha : a < 0) (Hb : b > 0) : a * b < 0 :=
begin
have H : a * b < 0 * b, from mul_lt_mul_of_pos_right Ha Hb,
rwr zero_mul at H,
exact H
end
end
@[hott, class] structure linear_ordered_semiring (A : Type _)
extends ordered_semiring A, linear_strong_order_pair A :=
(zero_lt_one : lt zero one)
section
variable [s : linear_ordered_semiring A]
variables {a b c : A}
include s
@[hott] theorem zero_lt_one : 0 < (1:A) := linear_ordered_semiring.zero_lt_one A
@[hott] theorem lt_of_mul_lt_mul_left (H : c * a < c * b) (Hc : c ≥ 0) : a < b :=
lt_of_not_ge
(assume H1 : b ≤ a,
have H2 : c * b ≤ c * a, from mul_le_mul_of_nonneg_left H1 Hc,
not_lt_of_ge H2 H)
@[hott] theorem lt_of_mul_lt_mul_right (H : a * c < b * c) (Hc : c ≥ 0) : a < b :=
lt_of_not_ge
(assume H1 : b ≤ a,
have H2 : b * c ≤ a * c, from mul_le_mul_of_nonneg_right H1 Hc,
not_lt_of_ge H2 H)
@[hott] theorem le_of_mul_le_mul_left (H : c * a ≤ c * b) (Hc : c > 0) : a ≤ b :=
le_of_not_gt
(assume H1 : b < a,
have H2 : c * b < c * a, from mul_lt_mul_of_pos_left H1 Hc,
not_le_of_gt H2 H)
@[hott] theorem le_of_mul_le_mul_right (H : a * c ≤ b * c) (Hc : c > 0) : a ≤ b :=
le_of_not_gt
(assume H1 : b < a,
have H2 : b * c < a * c, from mul_lt_mul_of_pos_right H1 Hc,
not_le_of_gt H2 H)
@[hott] theorem le_iff_mul_le_mul_left (a b : A) {c : A} (H : c > 0) : a ≤ b ↔ c * a ≤ c * b :=
iff.intro
(assume H', mul_le_mul_of_nonneg_left H' (le_of_lt H))
(assume H', le_of_mul_le_mul_left H' H)
@[hott] theorem le_iff_mul_le_mul_right (a b : A) {c : A} (H : c > 0) : a ≤ b ↔ a * c ≤ b * c :=
iff.intro
(assume H', mul_le_mul_of_nonneg_right H' (le_of_lt H))
(assume H', le_of_mul_le_mul_right H' H)
@[hott] theorem pos_of_mul_pos_left (H : 0 < a * b) (H1 : 0 ≤ a) : 0 < b :=
lt_of_not_ge
(assume H2 : b ≤ 0,
have H3 : a * b ≤ 0, from mul_nonpos_of_nonneg_of_nonpos H1 H2,
not_lt_of_ge H3 H)
@[hott] theorem pos_of_mul_pos_right (H : 0 < a * b) (H1 : 0 ≤ b) : 0 < a :=
lt_of_not_ge
(assume H2 : a ≤ 0,
have H3 : a * b ≤ 0, from mul_nonpos_of_nonpos_of_nonneg H2 H1,
not_lt_of_ge H3 H)
@[hott] theorem nonneg_of_mul_nonneg_left (H : 0 ≤ a * b) (H1 : 0 < a) : 0 ≤ b :=
le_of_not_gt
(assume H2 : b < 0,
not_le_of_gt (mul_neg_of_pos_of_neg H1 H2) H)
@[hott] theorem nonneg_of_mul_nonneg_right (H : 0 ≤ a * b) (H1 : 0 < b) : 0 ≤ a :=
le_of_not_gt
(assume H2 : a < 0,
not_le_of_gt (mul_neg_of_neg_of_pos H2 H1) H)
@[hott] theorem neg_of_mul_neg_left (H : a * b < 0) (H1 : 0 ≤ a) : b < 0 :=
lt_of_not_ge
(assume H2 : b ≥ 0,
not_lt_of_ge (mul_nonneg H1 H2) H)
@[hott] theorem neg_of_mul_neg_right (H : a * b < 0) (H1 : 0 ≤ b) : a < 0 :=
lt_of_not_ge
(assume H2 : a ≥ 0,
not_lt_of_ge (mul_nonneg H2 H1) H)
@[hott] theorem nonpos_of_mul_nonpos_left (H : a * b ≤ 0) (H1 : 0 < a) : b ≤ 0 :=
le_of_not_gt
(assume H2 : b > 0,
not_le_of_gt (mul_pos H1 H2) H)
@[hott] theorem nonpos_of_mul_nonpos_right (H : a * b ≤ 0) (H1 : 0 < b) : a ≤ 0 :=
le_of_not_gt
(assume H2 : a > 0,
not_le_of_gt (mul_pos H2 H1) H)
end
@[hott, class] structure decidable_linear_ordered_semiring (A : Type _)
extends linear_ordered_semiring A, decidable_linear_order A
/- ring structures -/
@[hott] structure ordered_ring (A : Type _) extends ring A, ordered_mul_ab_group A renaming
mul→add mul_assoc→add_assoc one→zero one_mul→zero_add mul_one→add_zero inv→neg
mul_left_inv→add_left_inv mul_comm→add_comm mul_le_mul_left→add_le_add_left
mul_lt_mul_left→add_lt_add_left,
zero_ne_one_class A :=
(mul_nonneg : Πa b, le zero a → le zero b → le zero (mul a b))
(mul_pos : Πa b, lt zero a → lt zero b → lt zero (mul a b))
-- /- we make it a class now (and not as part of the structure) to avoid
-- ordered_ring.to_ordered_mul_ab_group to be an instance -/
attribute [class] ordered_ring
@[hott, instance, reducible] def add_ab_group_of_ordered_ring (A : Type _)
[H : ordered_ring A] : ring A :=
@ordered_ring.to_ring A H
@[hott, instance, reducible] def monoid_of_ordered_ring (A : Type _)
[H : ordered_ring A] : ordered_ab_group A :=
@ordered_ring.to_ordered_mul_ab_group A H
@[hott, instance, reducible] def zero_ne_one_class_of_ordered_ring (A : Type _)
[H : ordered_ring A] : zero_ne_one_class A :=
@ordered_ring.to_zero_ne_one_class A H
@[hott] def ordered_ring.mul_le_mul_of_nonneg_left [s : ordered_ring A] {a b c : A}
(Hab : a ≤ b) (Hc : 0 ≤ c) : c * a ≤ c * b :=
have H1 : 0 ≤ b - a, from sub_nonneg_of_le Hab,
have H2 : 0 ≤ c * (b - a), from ordered_ring.mul_nonneg _ _ _ Hc H1,
begin
rwr mul_sub_left_distrib at H2,
exact (iff.mp (sub_nonneg_iff_le _ _) H2)
end
@[hott] def ordered_ring.mul_le_mul_of_nonneg_right [s : ordered_ring A] {a b c : A}
(Hab : a ≤ b) (Hc : 0 ≤ c) : a * c ≤ b * c :=
have H1 : 0 ≤ b - a, from iff.elim_right (sub_nonneg_iff_le _ _) Hab,
have H2 : 0 ≤ (b - a) * c, from ordered_ring.mul_nonneg _ _ _ H1 Hc,
begin
rwr mul_sub_right_distrib at H2,
exact le_of_sub_nonneg H2
end
@[hott] def ordered_ring.mul_lt_mul_of_pos_left [s : ordered_ring A] {a b c : A}
(Hab : a < b) (Hc : 0 < c) : c * a < c * b :=
have H1 : 0 < b - a, from iff.elim_right (sub_pos_iff_lt _ _) Hab,
have H2 : 0 < c * (b - a), from ordered_ring.mul_pos _ _ _ Hc H1,
begin
rwr mul_sub_left_distrib at H2,
exact (iff.mp (sub_pos_iff_lt _ _) H2)
end
@[hott] def ordered_ring.mul_lt_mul_of_pos_right [s : ordered_ring A] {a b c : A}
(Hab : a < b) (Hc : 0 < c) : a * c < b * c :=
have H1 : 0 < b - a, from iff.elim_right (sub_pos_iff_lt _ _) Hab,
have H2 : 0 < (b - a) * c, from ordered_ring.mul_pos _ _ _ H1 Hc,
begin
rwr mul_sub_right_distrib at H2,
exact (lt_of_sub_pos H2)
end
@[hott, instance, reducible] def ordered_ring.to_ordered_semiring [s : ordered_ring A] :
ordered_semiring A :=
{ mul_zero := mul_zero,
zero_mul := zero_mul,
add_left_cancel := @add.left_cancel A _,
add_right_cancel := @add.right_cancel A _,
le_of_add_le_add_left := @le_of_add_le_add_left A _,
mul_le_mul_of_nonneg_left := @ordered_ring.mul_le_mul_of_nonneg_left A _,
mul_le_mul_of_nonneg_right := @ordered_ring.mul_le_mul_of_nonneg_right A _,
mul_lt_mul_of_pos_left := @ordered_ring.mul_lt_mul_of_pos_left A _,
mul_lt_mul_of_pos_right := @ordered_ring.mul_lt_mul_of_pos_right A _,
lt_of_add_lt_add_left := @lt_of_add_lt_add_left A _, ..s }
section
variable [s : ordered_ring A]
variables {a b c : A}
include s
@[hott] theorem mul_le_mul_of_nonpos_left (H : b ≤ a) (Hc : c ≤ 0) : c * a ≤ c * b :=
have Hc' : -c ≥ 0, from iff.mpr (neg_nonneg_iff_nonpos _) Hc,
have H1 : -c * b ≤ -c * a, from mul_le_mul_of_nonneg_left H Hc',
have H2 : -(c * b) ≤ -(c * a),
begin
rwr [←neg_mul_eq_neg_mul, ←neg_mul_eq_neg_mul] at H1,
exact H1
end,
le_of_neg_le_neg H2
@[hott] theorem mul_le_mul_of_nonpos_right (H : b ≤ a) (Hc : c ≤ 0) : a * c ≤ b * c :=
have Hc' : -c ≥ 0, from iff.mpr (neg_nonneg_iff_nonpos _) Hc,
have H1 : b * -c ≤ a * -c, from mul_le_mul_of_nonneg_right H Hc',
have H2 : -(b * c) ≤ -(a * c),
begin
rwr [←neg_mul_eq_mul_neg, ←neg_mul_eq_mul_neg] at H1,
exact H1
end,
le_of_neg_le_neg H2
@[hott] theorem mul_nonneg_of_nonpos_of_nonpos (Ha : a ≤ 0) (Hb : b ≤ 0) : 0 ≤ a * b :=
begin
have H : 0 * b ≤ a * b, from mul_le_mul_of_nonpos_right Ha Hb,
rwr zero_mul at H,
exact H
end
@[hott] def mul_lt_mul_of_neg_left (H : b < a) (Hc : c < 0) : c * a < c * b :=
have Hc' : -c > 0, from iff.mpr (neg_pos_iff_neg _) Hc,
have H1 : -c * b < -c * a, from mul_lt_mul_of_pos_left H Hc',
have H2 : -(c * b) < -(c * a),
begin
rwr [←neg_mul_eq_neg_mul, ←neg_mul_eq_neg_mul] at H1,
exact H1
end,
lt_of_neg_lt_neg H2
@[hott] def mul_lt_mul_of_neg_right (H : b < a) (Hc : c < 0) : a * c < b * c :=
have Hc' : -c > 0, from iff.mpr (neg_pos_iff_neg _) Hc,
have H1 : b * -c < a * -c, from mul_lt_mul_of_pos_right H Hc',
have H2 : -(b * c) < -(a * c),
begin
rwr [←neg_mul_eq_mul_neg, ←neg_mul_eq_mul_neg] at H1,
exact H1
end,
lt_of_neg_lt_neg H2
@[hott] def mul_pos_of_neg_of_neg (Ha : a < 0) (Hb : b < 0) : 0 < a * b :=
begin
have H : 0 * b < a * b, from mul_lt_mul_of_neg_right Ha Hb,
rwr zero_mul at H,
exact H
end
end
-- TODO: we can eliminate mul_pos_of_pos, but now it is not worth the effort to redeclare the
-- class instance
@[hott, class] structure linear_ordered_ring (A : Type _)
extends ordered_ring A, linear_strong_order_pair A :=
(zero_lt_one : lt zero one)
@[hott, instance, reducible] def linear_ordered_ring.to_linear_ordered_semiring
[s : linear_ordered_ring A] : linear_ordered_semiring A :=
{ mul_zero := mul_zero,
zero_mul := zero_mul,
add_left_cancel := @add.left_cancel A _,
add_right_cancel := @add.right_cancel A _,
le_of_add_le_add_left := @le_of_add_le_add_left A _,
mul_le_mul_of_nonneg_left := @mul_le_mul_of_nonneg_left A _,
mul_le_mul_of_nonneg_right := @mul_le_mul_of_nonneg_right A _,
mul_lt_mul_of_pos_left := @mul_lt_mul_of_pos_left A _,
mul_lt_mul_of_pos_right := @mul_lt_mul_of_pos_right A _,
le_total := linear_ordered_ring.le_total,
lt_of_add_lt_add_left := @lt_of_add_lt_add_left A _, ..s }
@[hott, class] structure linear_ordered_comm_ring (A : Type _) extends
linear_ordered_ring A, comm_monoid A
@[hott] def linear_ordered_comm_ring.eq_zero_sum_eq_zero_of_mul_eq_zero
[s : linear_ordered_comm_ring A] {a b : A} (H : a * b = 0) : a = 0 ⊎ b = 0 :=
lt.by_cases
(assume Ha : 0 < a,
lt.by_cases
(assume Hb : 0 < b,
begin
have H1 : 0 < a * b, from mul_pos Ha Hb,
rwr H at H1,
apply absurd_a_lt_a H1
end)
(assume Hb : 0 = b, sum.inr (Hb⁻¹))
(assume Hb : 0 > b,
begin
have H1 : 0 > a * b, from mul_neg_of_pos_of_neg Ha Hb,
rwr H at H1,
apply absurd_a_lt_a H1
end))
(assume Ha : 0 = a, sum.inl (Ha⁻¹))
(assume Ha : 0 > a,
lt.by_cases
(assume Hb : 0 < b,
begin
have H1 : 0 > a * b, from mul_neg_of_neg_of_pos Ha Hb,
rwr H at H1,
apply absurd_a_lt_a H1
end)
(assume Hb : 0 = b, sum.inr (Hb⁻¹))
(assume Hb : 0 > b,
begin
have H1 : 0 < a * b, from mul_pos_of_neg_of_neg Ha Hb,
rwr H at H1,
apply absurd_a_lt_a H1
end))
-- Linearity implies no zero divisors. Doesn't need commutativity.
@[hott, instance, reducible] def linear_ordered_comm_ring.to_integral_domain
[s : linear_ordered_comm_ring A] : integral_domain A :=
{ eq_zero_sum_eq_zero_of_mul_eq_zero :=
@linear_ordered_comm_ring.eq_zero_sum_eq_zero_of_mul_eq_zero A s, ..s }
section
variable [s : linear_ordered_ring A]
variables (a b c : A)
include s
@[hott] theorem mul_self_nonneg : a * a ≥ 0 :=
sum.elim (le.total 0 a)
(assume H : a ≥ 0, mul_nonneg H H)
(assume H : a ≤ 0, mul_nonneg_of_nonpos_of_nonpos H H)
@[hott] theorem zero_le_one : 0 ≤ (1:A) := by rwr [←one_mul (1 : A)]; exact mul_self_nonneg 1
@[hott] theorem pos_prod_pos_sum_neg_prod_neg_of_mul_pos {a b : A} (Hab : a * b > 0) :
(a > 0 × b > 0) ⊎ (a < 0 × b < 0) :=
lt.by_cases
(assume Ha : 0 < a,
lt.by_cases
(assume Hb : 0 < b, sum.inl (pair Ha Hb))
(assume Hb : 0 = b,
begin
rwr [←Hb, mul_zero] at Hab,
apply absurd_a_lt_a Hab
end)
(assume Hb : b < 0,
absurd Hab (lt.asymm (mul_neg_of_pos_of_neg Ha Hb))))
(assume Ha : 0 = a,
begin
rwr [←Ha, zero_mul] at Hab,
apply absurd_a_lt_a Hab
end)
(assume Ha : a < 0,
lt.by_cases
(assume Hb : 0 < b,
absurd Hab (lt.asymm (mul_neg_of_neg_of_pos Ha Hb)))
(assume Hb : 0 = b,
begin
rwr [←Hb, mul_zero] at Hab,
apply absurd_a_lt_a Hab
end)
(assume Hb : b < 0, sum.inr (pair Ha Hb)))
@[hott] theorem gt_of_mul_lt_mul_neg_left {a b c : A} (H : c * a < c * b) (Hc : c ≤ 0) : a > b :=
have nhc : -c ≥ 0, from neg_nonneg_of_nonpos Hc,
have H2 : -(c * b) < -(c * a), from iff.mpr (neg_lt_neg_iff_lt _ _) H,
have H3 : (-c) * b < (-c) * a, from calc
(-c) * b = - (c * b) : by rwr neg_mul_eq_neg_mul
... < -(c * a) : H2
... = (-c) * a : by rwr neg_mul_eq_neg_mul,
lt_of_mul_lt_mul_left H3 nhc
@[hott] theorem zero_gt_neg_one : - 1 < (0:A) :=
by rwr ←neg_zero; exact neg_lt_neg zero_lt_one
@[hott] theorem le_of_mul_le_of_ge_one {a b c : A} (H : a * c ≤ b) (Hb : b ≥ 0) (Hc : c ≥ 1) :
a ≤ b :=
have H' : a * c ≤ b * c, from calc
a * c ≤ b : H
... = b * 1 : by rwr mul_one
... ≤ b * c : mul_le_mul_of_nonneg_left Hc Hb,
le_of_mul_le_mul_right H' (lt_of_lt_of_le zero_lt_one Hc)
@[hott] theorem nonneg_le_nonneg_of_squares_le {a b : A} (Ha : a ≥ 0) (Hb : b ≥ 0)
(H : a * a ≤ b * b) : a ≤ b :=
begin
apply le_of_not_gt,
intro Hab,
let Hposa := lt_of_le_of_lt Hb Hab,
let H' := calc
b * b ≤ a * b : mul_le_mul_of_nonneg_right (le_of_lt Hab) Hb
... < a * a : mul_lt_mul_of_pos_left Hab Hposa,
apply (not_le_of_gt H') H
end
end
/- TODO: Isabelle's library has all kinds of cancelation rules for the simplifier.
Search on mult_le_cancel_right1 in Rings.thy. -/
@[hott] structure decidable_linear_ordered_comm_ring (A : Type _) extends linear_ordered_comm_ring A,
decidable_linear_ordered_mul_ab_group A renaming
mul→add mul_assoc→add_assoc one→zero one_mul→zero_add mul_one→add_zero inv→neg
mul_left_inv→add_left_inv mul_comm→add_comm mul_le_mul_left→add_le_add_left
mul_lt_mul_left→add_lt_add_left
/- we make it a class now (and not as part of the structure) to avoid
ordered_semiring.to_ordered_mul_cancel_comm_monoid to be an instance -/
attribute [class] decidable_linear_ordered_comm_ring
@[hott, instance, reducible] def linear_ordered_comm_ring_of_decidable_linear_ordered_comm_ring
(A : Type _) [H : decidable_linear_ordered_comm_ring A] : linear_ordered_comm_ring A :=
@decidable_linear_ordered_comm_ring.to_linear_ordered_comm_ring A H
@[hott, instance, reducible]
def decidable_linear_ordered_ab_group_of_decidable_linear_ordered_comm_ring
(A : Type _) [H : decidable_linear_ordered_comm_ring A] : decidable_linear_ordered_ab_group A :=
@decidable_linear_ordered_comm_ring.to_decidable_linear_ordered_mul_ab_group A H
section
variable [s : decidable_linear_ordered_comm_ring A]
variables {a b c : A}
include s
@[hott] def sign (a : A) : A := lt.cases a 0 (- 1) 0 1
@[hott] theorem sign_of_neg (H : a < 0) : sign a = - 1 := lt.cases_of_lt H
@[hott] theorem sign_zero : sign 0 = (0:A) := lt.cases_of_eq rfl
@[hott] theorem sign_of_pos (H : a > 0) : sign a = 1 := lt.cases_of_gt H
@[hott] theorem sign_one : sign 1 = (1:A) := sign_of_pos zero_lt_one
@[hott] theorem sign_neg_one : sign (- 1) = -(1:A) := sign_of_neg (neg_neg_of_pos zero_lt_one)
@[hott] theorem sign_sign (a : A) : sign (sign a) = sign a :=
lt.by_cases
(assume H : a > 0,
calc
sign (sign a) = sign 1 : by rwr (sign_of_pos H)
... = 1 : by rwr sign_one
... = sign a : by rwr (sign_of_pos H))
(assume H : 0 = a,
calc
sign (sign a) = sign (sign 0) : by rwr H
... = sign 0 : by rwr ap sign sign_zero
... = sign a : by rwr ←H)
(assume H : a < 0,
calc
sign (sign a) = sign (- 1) : by rwr (sign_of_neg H)
... = - 1 : by rwr sign_neg_one
... = sign a : by rwr (sign_of_neg H))
@[hott] theorem pos_of_sign_eq_one (H : sign a = 1) : a > 0 :=
lt.by_cases
(assume H1 : 0 < a, H1)
(assume H1 : 0 = a,
begin
rwr [←H1, sign_zero] at H,
apply absurd H zero_ne_one
end)
(assume H1 : 0 > a,
have H2 : - 1 = 1 :> A, from (sign_of_neg H1)⁻¹ ⬝ H,
absurd ((eq_zero_of_neg_eq H2)⁻¹ᵖ) zero_ne_one)
@[hott] theorem eq_zero_of_sign_eq_zero (H : sign a = 0) : a = 0 :=
lt.by_cases
(assume H1 : 0 < a,
absurd (H⁻¹ ⬝ sign_of_pos H1) zero_ne_one)
(assume H1 : 0 = a, H1⁻¹)
(assume H1 : 0 > a,
have H2 : 0 = - 1 :> A, from H⁻¹ ⬝ sign_of_neg H1,
have H3 : 1 = 0 :> A, from eq_neg_of_eq_neg H2 ⬝ neg_zero,
absurd (H3⁻¹) zero_ne_one)
@[hott] theorem neg_of_sign_eq_neg_one (H : sign a = - 1) : a < 0 :=
lt.by_cases
(assume H1 : 0 < a,
have H2 : - 1 = 1 :> A, from H⁻¹ ⬝ (sign_of_pos H1),
absurd ((eq_zero_of_neg_eq H2)⁻¹) zero_ne_one)
(assume H1 : 0 = a,
have H2 : 0 = - 1 :> A,
begin
rwr [←H1, sign_zero] at H,
exact H
end,
have H3 : 1 = 0 :> A, from eq_neg_of_eq_neg H2 ⬝ neg_zero,
absurd (H3⁻¹) zero_ne_one)
(assume H1 : 0 > a, H1)
@[hott] theorem sign_neg (a : A) : sign (-a) = -(sign a) :=
lt.by_cases
(assume H1 : 0 < a,
calc
sign (-a) = - 1 : sign_of_neg (neg_neg_of_pos H1)
... = -(sign a) : by rwr (sign_of_pos H1))
(assume H1 : 0 = a,
calc
sign (-a) = sign (-0) : by rwr ←H1
... = sign 0 : by rwr neg_zero
... = 0 : by rwr sign_zero
... = -0 : by rwr neg_zero
... = -(sign 0) : by rwr sign_zero
... = -(sign a) : by rwr ←H1)
(assume H1 : 0 > a,
calc
sign (-a) = 1 : sign_of_pos (neg_pos_of_neg H1)
... = -(- 1) : by rwr neg_neg
... = -(sign a) : by rwr sign_of_neg H1)
@[hott] theorem sign_mul (a b : A) : sign (a * b) = sign a * sign b :=
hott.algebra.lt.by_cases
(assume z_lt_a : 0 < a,
lt.by_cases
(assume z_lt_b : 0 < b,
by rwr [sign_of_pos z_lt_a, sign_of_pos z_lt_b,
sign_of_pos (mul_pos z_lt_a z_lt_b), one_mul])
(assume z_eq_b : 0 = b, by rwr [←z_eq_b, mul_zero, sign_zero, mul_zero])
(assume z_gt_b : 0 > b,
by rwr [sign_of_pos z_lt_a, sign_of_neg z_gt_b,
sign_of_neg (mul_neg_of_pos_of_neg z_lt_a z_gt_b), one_mul]))
(assume z_eq_a : 0 = a, by rwr [←z_eq_a, zero_mul, sign_zero, zero_mul])
(assume z_gt_a : 0 > a,
lt.by_cases
(assume z_lt_b : 0 < b,
by rwr [sign_of_neg z_gt_a, sign_of_pos z_lt_b,
sign_of_neg (mul_neg_of_neg_of_pos z_gt_a z_lt_b), mul_one])
(assume z_eq_b : 0 = b, by rwr [←z_eq_b, mul_zero, sign_zero, mul_zero])
(assume z_gt_b : 0 > b,
by rwr [sign_of_neg z_gt_a, sign_of_neg z_gt_b,
sign_of_pos (mul_pos_of_neg_of_neg z_gt_a z_gt_b),
neg_mul_neg, one_mul]))
@[hott] theorem abs_eq_sign_mul (a : A) : abs a = sign a * a :=
lt.by_cases
(assume H1 : 0 < a,
calc
abs a = a : abs_of_pos H1
... = 1 * a : by rwr one_mul
... = sign a * a : by rwr (sign_of_pos H1))
(assume H1 : 0 = a,
calc
abs a = abs 0 : by rwr ←H1
... = 0 : abs_zero
... = 0 * a : by rwr zero_mul
... = sign 0 * a : by rwr sign_zero
... = sign a * a : by rwr ←H1)
(assume H1 : a < 0,
calc
abs a = -a : abs_of_neg H1
... = - 1 * a : by rwr neg_eq_neg_one_mul
... = sign a * a : by rwr (sign_of_neg H1))
@[hott] theorem eq_sign_mul_abs (a : A) : a = sign a * abs a :=
lt.by_cases
(assume H1 : 0 < a,
calc
a = abs a : by rwr abs_of_pos H1
... = 1 * abs a : by rwr one_mul
... = sign a * abs a : by rwr (sign_of_pos H1))
(assume H1 : 0 = a,
calc
a = 0 : H1⁻¹
... = 0 * abs a : by rwr zero_mul
... = sign 0 * abs a : by rwr sign_zero
... = sign a * abs a : by rwr H1)
(assume H1 : a < 0,
calc
a = -(-a) : by rwr neg_neg
... = -abs a : by rwr (abs_of_neg H1)
... = - 1 * abs a : by rwr neg_eq_neg_one_mul
... = sign a * abs a : by rwr (sign_of_neg H1))
-- @[hott] theorem abs_dvd_iff (a b : A) : abs a ∣ b ↔ a ∣ b :=
-- abs.by_cases iff.rfl (neg_dvd_iff_dvd _ _)
-- @[hott] theorem abs_dvd_of_dvd {a b : A} : a ∣ b → abs a ∣ b :=
-- iff.mpr !abs_dvd_iff
-- @[hott] theorem dvd_abs_iff (a b : A) : a ∣ abs b ↔ a ∣ b :=
-- abs.by_cases iff.rfl !dvd_neg_iff_dvd
-- @[hott] theorem dvd_abs_of_dvd {a b : A} : a ∣ b → a ∣ abs b :=
-- iff.mpr !dvd_abs_iff
-- @[hott] theorem abs_mul (a b : A) : abs (a * b) = abs a * abs b :=
-- sum.elim (le.total 0 a)
-- (assume H1 : 0 ≤ a,
-- sum.elim (le.total 0 b)
-- (assume H2 : 0 ≤ b,
-- calc
-- abs (a * b) = a * b : abs_of_nonneg (mul_nonneg H1 H2)
-- ... = abs a * b : by rwr (abs_of_nonneg H1)
-- ... = abs a * abs b : by rwr (abs_of_nonneg H2))
-- (assume H2 : b ≤ 0,
-- calc
-- abs (a * b) = -(a * b) : abs_of_nonpos (mul_nonpos_of_nonneg_of_nonpos H1 H2)
-- ... = a * -b : by rwr neg_mul_eq_mul_neg
-- ... = abs a * -b : by rwr (abs_of_nonneg H1)
-- ... = abs a * abs b : by rwr (abs_of_nonpos H2)))
-- (assume H1 : a ≤ 0,
-- sum.elim (le.total 0 b)
-- (assume H2 : 0 ≤ b,
-- calc
-- abs (a * b) = -(a * b) : abs_of_nonpos (mul_nonpos_of_nonpos_of_nonneg H1 H2)
-- ... = -a * b : by rwr neg_mul_eq_neg_mul
-- ... = abs a * b : by rwr (abs_of_nonpos H1)
-- ... = abs a * abs b : by rwr (abs_of_nonneg H2))
-- (assume H2 : b ≤ 0,
-- calc
-- abs (a * b) = a * b : abs_of_nonneg (mul_nonneg_of_nonpos_of_nonpos H1 H2)
-- ... = -a * -b : by rwr neg_mul_neg
-- ... = abs a * -b : by rwr (abs_of_nonpos H1)
-- ... = abs a * abs b : by rwr (abs_of_nonpos H2)))
-- @[hott] theorem abs_mul_abs_self (a : A) : abs a * abs a = a * a :=
-- abs.by_cases rfl !neg_mul_neg
-- @[hott] theorem abs_mul_self (a : A) : abs (a * a) = a * a :=
-- by rwr [abs_mul, abs_mul_abs_self]
-- @[hott] theorem sub_le_of_abs_sub_le_left (H : abs (a - b) ≤ c) : b - c ≤ a :=
-- if Hz : 0 ≤ a - b then
-- (calc
-- a ≥ b : (iff.mp (sub_nonneg_iff_le _ _)) Hz
-- ... ≥ b - c : sub_le_of_nonneg _ (le.trans !abs_nonneg H))
-- else
-- (have Habs : b - a ≤ c, by rwr [abs_of_neg (lt_of_not_ge Hz), neg_sub] at H; apply H,
-- have Habs' : b ≤ c + a, from (iff.mpr !le_add_iff_sub_right_le) Habs,
-- (iff.mp !le_add_iff_sub_left_le) Habs')
-- @[hott] theorem sub_le_of_abs_sub_le_right (H : abs (a - b) ≤ c) : a - c ≤ b :=
-- sub_le_of_abs_sub_le_left (!abs_sub ▸ H)
-- @[hott] theorem sub_lt_of_abs_sub_lt_left (H : abs (a - b) < c) : b - c < a :=
-- if Hz : 0 ≤ a - b then
-- (calc
-- a ≥ b : (iff.mp (sub_nonneg_iff_le _ _)) Hz
-- ... > b - c : sub_lt_of_pos _ (lt_of_le_of_lt !abs_nonneg H))
-- else
-- (have Habs : b - a < c, by rwr [abs_of_neg (lt_of_not_ge Hz), neg_sub] at H; apply H,
-- have Habs' : b < c + a, from lt_add_of_sub_lt_right Habs,
-- sub_lt_left_of_lt_add Habs')
-- @[hott] theorem sub_lt_of_abs_sub_lt_right (H : abs (a - b) < c) : a - c < b :=
-- sub_lt_of_abs_sub_lt_left (!abs_sub ▸ H)
-- @[hott] theorem abs_sub_square (a b : A) : abs (a - b) * abs (a - b) = a * a + b * b - (1 + 1) * a * b :=
-- begin
-- rwr [abs_mul_abs_self, *mul_sub_left_distrib, *mul_sub_right_distrib,
-- sub_eq_add_neg (a*b), sub_add_eq_sub_sub, sub_neg_eq_add, *right_distrib, sub_add_eq_sub_sub, *one_mul,
-- *add.assoc, {_ + b * b}add.comm, *sub_eq_add_neg],
-- rwr [{a*a + b*b}add.comm],
-- rwr [mul.comm b a, *add.assoc]
-- end
-- @[hott] theorem abs_abs_sub_abs_le_abs_sub (a b : A) : abs (abs a - abs b) ≤ abs (a - b) :=
-- begin
-- apply nonneg_le_nonneg_of_squares_le,
-- repeat apply abs_nonneg,
-- rwr [*abs_sub_square, *abs_abs, *abs_mul_abs_self],
-- apply sub_le_sub_left,
-- rwr *mul.assoc,
-- apply mul_le_mul_of_nonneg_left,
-- rwr ←abs_mul,
-- apply le_abs_self,
-- apply le_of_lt,
-- apply add_pos,
-- apply zero_lt_one,
-- apply zero_lt_one
-- end
end
/- TODO: Multiplication and one, starting with mult_right_le_one_le. -/
-- namespace norm_num
-- @[hott] theorem pos_bit0_helper [s : linear_ordered_semiring A] (a : A) (H : a > 0) : bit0 a > 0 :=
-- by rwr ↑bit0; apply add_pos H H
-- @[hott] theorem nonneg_bit0_helper [s : linear_ordered_semiring A] (a : A) (H : a ≥ 0) : bit0 a ≥ 0 :=
-- by rwr ↑bit0; apply add_nonneg H H
-- @[hott] theorem pos_bit1_helper [s : linear_ordered_semiring A] (a : A) (H : a ≥ 0) : bit1 a > 0 :=
-- begin
-- rwr ↑bit1,
-- apply add_pos_of_nonneg_of_pos,
-- apply nonneg_bit0_helper _ H,
-- apply zero_lt_one
-- end
-- @[hott] theorem nonneg_bit1_helper [s : linear_ordered_semiring A] (a : A) (H : a ≥ 0) : bit1 a ≥ 0 :=
-- by apply le_of_lt; apply pos_bit1_helper _ H
-- @[hott] theorem nonzero_of_pos_helper [s : linear_ordered_semiring A] (a : A) (H : a > 0) : a ≠ 0 :=
-- ne_of_gt H
-- @[hott] theorem nonzero_of_neg_helper [s : linear_ordered_ring A] (a : A) (H : a ≠ 0) : -a ≠ 0 :=
-- begin intro Ha, apply H, apply eq_of_neg_eq_neg, rwr neg_zero, exact Ha end
-- end norm_num
end algebra
end hott
|
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/-
POINTS: Welcome to the first CS2102 exam. The exam has 12
questions. Points for each question are as indicated, for a
total of 100 points.
READ CAREFULLY: If you are unable to answer a question in
a way that Lean accepts as syntactically correct, *comment
out your malformed answer*. Otherwise an error in your answer
can cause Lean not to recognize correct answers to other
questions. If you are sure an answer is correct but Lean is
not accepting it, look for problems in the preceding logic.
Do not change or delete any of the questions.
WHAT TO DO: Complete the exam by following the instructions
for each question. Save your file then upload the completed
and saved file to Collab. You have 75 minutes from the start
of the exam to the time where it must be uploaded to Collab.
OPEN NOTES: You may use the class notes for this exam, whether
provided to you by the instructors or taken by you (or for you).
STRICTLY INDIVIDUAL EFFORT: This is a strictly individual exam,
taken under the honor system. Do not communicate with anyone except
for the instructor about the content of this exam, by any means,
until you are sure that each person you are communicating with
has already completed the test.
-/
/- 1. (5 points)
What is the type of function1 (just below)? Give you answer by
replacing the hole (underscore) in the subsequent definition
with your answer.
-/
def function1 (f: ℕ → ℕ) (g: ℕ → ℕ) :=
λ (x: ℕ), 3
#check function1
def function1_type : Type :=
(ℕ → ℕ) → (ℕ → ℕ) → ℕ → ℕ
/- 2. (10 points)
Define three equivalent functions, called product1,
product2, and product3. Each must take two natural
numbers as its arguments and return their product.
Define the first version using C-style notation,
the second using a lambda abstraction, and the third
using a tactic script.
-/
-- Answer below:
-- ANSWER
-- C-style here
def product1 (n m : ℕ) : ℕ := n * m
-- Lambda abstraction here
def product2: ℕ → ℕ → ℕ :=
λ n m, n * m
-- Tactic script here
def product3: ℕ → ℕ → ℕ :=
begin
intros n m,
exact n * m,
end
/- 3. (5 points)
Given the definition of product1, what function
is (product1 5)? Answer by replacing the hole in
the following definition with a lambda abstraction.
-/
def product1_5 := λ m, 5 * m
/- 4. (5 points)
Which of the following properties does "product1_5" have?
Answer by placing a Y (for yes, it has this property), or
N (for no, it doesn't have this property), BEFORE the name
of each property, just after the dash.
-- ANSWER
- Y injective
- N surjective
- N one-to-many
- N strictly partial
- N bijective
-/
/- 5. (5 points)
Complete the proof of the following conjecture, that
(product1 4 6) = 24. Fill in the proposition to be
proved in the first hole (underscore) and a proof in
the second hole.
-/
-- ANSWER
example : (product1 4 6) = 24 := rfl
/- 6. (10 points)
State and prove the proposition that, for any natural
numbers, a, b, and c, if b = a, then if c = b, then a = c.
Fill in the holes in the following example accordingly,
replacing the underscores first with a formal statement
of the proposition, and then a proof of it, respectively.
-/
-- Complete by replacing the hole with a proof:
example: ∀ a b c: ℕ, b = a → c = b → a = c :=
begin
intros a b c,
assume ba cb,
have ab := eq.symm ba,
have bc := eq.symm cb,
exact eq.trans ab bc
end
/- 7. (10 points)
In the context of the following assumptions, use
"example" to formally state and prove the proposition
that "Jane is nice."
-/
axiom Person : Type
axioms Jill Jane : Person
axiom IsNice : Person → Prop
axiom JillIsNice : IsNice Jill
axiom JillIsJane : Jill = Jane
-- Fill in the holes with your proposition and proof
example : IsNice Jane :=
eq.subst JillIsJane JillIsNice
/- 8. (10 points)
Use "example" to prove that true ∧ true is true. Give two proofs, the first using a term-style
proof, the second using a tactic script.
-/
-- Your answers here
-- either one of the following would be ok
example : true ∧ true → true :=
λ tt, tt.left
example : true ∧ true :=
and.intro true.intro true.intro
/- 9. (10 points)
Define a function, called exfalso, that takes a proof
of false as an argument, and that returns a proof of
3 = 7 as a result.
-/
-- ANSWER
def exfalse (f : false) : 3 = 7 := false.elim f
/- 10. (10 points)
Formally state and prove the proposition,
that, for any propositions, A, B, and C,
A ∧ B ∧ C → C ∧ A ∧ B. You may write the
proof in any style you wish. One way to do it
would be to define a function that takes the
propositions, A, B, and C, and a proof of the
premise as its arguments and that returns a
proof of the conclusion as a result. You
might also use a tactic script.
-/
-- ANSWER
example : ∀ A B C : Prop, A ∧ B ∧ C → C ∧ A ∧ B :=
begin
intros A B C,
assume h,
have a := h.left,
have bc := h.right,
have b := bc.left,
have c := bc.right,
have ab := and.intro a b,
exact and.intro c ab,
end
/- 11. (10 points)
Formally (in Lean), prove that if A, B, and C
are any propositions, and if C is true, then
A ∧ B ∧ C → B ∧ A.
-/
-- Complete the following by replacing _ with a proof:
example: ∀(A B C: Prop), C → (A ∧ B ∧ C → B ∧ A) :=
begin
intros A B C,
assume c,
assume abc,
have a := abc.left,
have b := abc.right.left,
exact and.intro b a,
end
/- 12. (10 points)
Define a predicate, gt5, that is true for all and only for
natural numbers greater than 5. You may use the expression,
n > 5, in your answer. Then fill in the hole in the following
definition with the type of the term (gt5 4).
-/
-- ANSWER
def gt5 : ℕ → Prop :=
λ n, n > 5
-- ANSWER
#check gt5 4
def type_of_gt5_4 := Prop
/- 13. EXTRA CREDIT 5 points
Give brief natural-language (in English) rendition
of the following formal propositions.
∃ n, m : ℕ, isPrime n ∧ isPrime m ∧ m = n + 2
Answer: There are natural numbers, n and m, such that both
n and m are prime and m is just two larger than n. (Note:
such a pair of prime numbers is called a "prime pair" in
the mathematical literature.)
If by isPrime we mean the ordinary concept of primeness
from basic arithmetic, then the second proposition is true.
Prove it by giving values for n and m that satisfy the
predicate along with a very brief argument that the two
numbers do actually satisfy the predicate.
Answer:
n = 5
m = 7
Argument: Both 5 and 7 are prime (obvious) and 7 is two larger
than 5 (also trivial).
-/
|
d57d51d563f2928bc93181db56f9e78e450aaffa | 968e2f50b755d3048175f176376eff7139e9df70 | /examples/prop_logic_theory/unnamed_1813.lean | 1e1f1071f861e77e2ccb9c9904e4b1c2b96a751e | [] | no_license | gihanmarasingha/mth1001_sphinx | 190a003269ba5e54717b448302a27ca26e31d491 | 05126586cbf5786e521be1ea2ef5b4ba3c44e74a | refs/heads/master | 1,672,913,933,677 | 1,604,516,583,000 | 1,604,516,583,000 | 309,245,750 | 1 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 466 | lean | variables p q r : Prop
-- BEGIN
example (h : p ∨ q) (k₁ : p → r) (k₂ : q → r) : r :=
begin
-- By or elim. on `h`, it suffices
-- 1. to show `r` on the assumption `h₁ : p` and
-- 2. to show `r` on the assumption `h₂ : q`.
cases h with h₁ h₂,
{ show r, from k₁ h₁, }, -- We show `r` by implication elimination on `k₁` and `h₁`.
{ show r, from k₂ h₂, }, -- We show `r` by implication elimination on `k₂` and `h₂`.
end
-- END |
0f67e9cf62304bccba0bb8ef5154beb082ad19e3 | ce6917c5bacabee346655160b74a307b4a5ab620 | /src/ch5/ex0603.lean | 7da401961e49710a3ba3efbe56bbfd37c0f047b7 | [] | no_license | Ailrun/Theorem_Proving_in_Lean | ae6a23f3c54d62d401314d6a771e8ff8b4132db2 | 2eb1b5caf93c6a5a555c79e9097cf2ba5a66cf68 | refs/heads/master | 1,609,838,270,467 | 1,586,846,743,000 | 1,586,846,743,000 | 240,967,761 | 1 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 113 | lean | variables (f : ℕ → ℕ) (k : ℕ)
example (h₁ : f 0 = 0) (h₂ : k = 0) : f k = 0 :=
by rw [h₂, h₁]
|
5efa5cb3946a1618e0cab6b9d5a92ebe8e8f718c | 94e33a31faa76775069b071adea97e86e218a8ee | /src/tactic/congrm.lean | 887620cf228d6c1bd888b4878b7640a70e21a830 | [
"Apache-2.0"
] | permissive | urkud/mathlib | eab80095e1b9f1513bfb7f25b4fa82fa4fd02989 | 6379d39e6b5b279df9715f8011369a301b634e41 | refs/heads/master | 1,658,425,342,662 | 1,658,078,703,000 | 1,658,078,703,000 | 186,910,338 | 0 | 0 | Apache-2.0 | 1,568,512,083,000 | 1,557,958,709,000 | Lean | UTF-8 | Lean | false | false | 5,084 | lean | /-
Copyright (c) 2022 Damiano Testa. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Gabriel Ebner, Damiano Testa
-/
import tactic.interactive
/-! `congrm`: `congr` with pattern-matching
`congrm e` gives to the use the functionality of using `congr` with an expression `e` "guiding"
`congr` through the matching. This allows more flexibility than `congr' n`, which enters uniformly
through `n` iterations. Instead, we can guide the matching deeper on some parts of the expression
and stop earlier on other parts.
-/
namespace tactic
/--
For each element of `list congr_arg_kind` that is `eq`, add a pair `(g, pat)` to the
final list. Otherwise, discard an appropriate number of initial terms from each list
(possibly none from the first) and repeat.
`pat` is the given pattern-piece at the appropriate location, extracted from the last `list expr`.
It appears to be the list of arguments of a function application.
`g` is possibly the proof of an equality? It is extracted from the first `list expr`.
-/
private meta def extract_subgoals : list expr → list congr_arg_kind → list expr →
tactic (list (expr × expr))
| (_ :: _ :: g :: prf_args) (congr_arg_kind.eq :: kinds) (pat :: pat_args) :=
(λ rest, (g, pat) :: rest) <$> extract_subgoals prf_args kinds pat_args
| (_ :: prf_args) (congr_arg_kind.fixed :: kinds) (_ :: pat_args) :=
extract_subgoals prf_args kinds pat_args
| prf_args (congr_arg_kind.fixed_no_param :: kinds) (_ :: pat_args) :=
extract_subgoals prf_args kinds pat_args
| (_ :: _ :: prf_args) (congr_arg_kind.cast :: kinds) (_ :: pat_args) :=
extract_subgoals prf_args kinds pat_args
| _ _ [] := pure []
| _ _ _ := fail "unsupported congr lemma"
/--
`equate_with_pattern_core pat` solves a single goal of the form `lhs = rhs`
(assuming that `lhs` and `rhs` are unifiable with `pat`)
by applying congruence lemmas until `pat` is a metavariable.
Returns the list of metavariables for the new subgoals at the leafs.
Calls `set_goals []` at the end.
-/
meta def equate_with_pattern_core : expr → tactic (list expr) | pat :=
(applyc ``subsingleton.elim >> pure []) <|>
(applyc ``rfl >> pure []) <|>
if pat.is_mvar || pat.get_delayed_abstraction_locals.is_some then do
try $ applyc ``_root_.propext,
get_goals <* set_goals []
else match pat with
| expr.app _ _ := do
cl ← mk_specialized_congr_lemma pat,
H_congr_lemma ← assertv `H_congr_lemma cl.type cl.proof,
[prf] ← get_goals,
apply H_congr_lemma <|> fail "could not apply congr_lemma",
all_goals' $ try $ clear H_congr_lemma, -- given the `set_goals []` that follows, is this needed?
set_goals [],
prf ← instantiate_mvars prf,
subgoals ← extract_subgoals prf.get_app_args cl.arg_kinds pat.get_app_args,
subgoals ← subgoals.mmap (λ ⟨subgoal, subpat⟩, do
set_goals [subgoal],
equate_with_pattern_core subpat),
pure subgoals.join
| expr.lam _ _ _ body := do
applyc ``_root_.funext,
x ← intro pat.binding_name,
equate_with_pattern_core $ body.instantiate_var x
| expr.pi _ _ _ codomain := do
applyc ``_root_.pi_congr,
x ← intro pat.binding_name,
equate_with_pattern_core $ codomain.instantiate_var x
| _ := do
pat ← pp pat,
fail $ to_fmt "unsupported pattern:\n" ++ pat
end
/--
`equate_with_pattern pat` solves a single goal of the form `lhs = rhs`
(assuming that `lhs` and `rhs` are unifiable with `pat`)
by applying congruence lemmas until `pat` is a metavariable.
The subgoals for the leafs are prepended to the goals.
--/
meta def equate_with_pattern (pat : expr) : tactic unit := do
congr_subgoals ← solve1 (equate_with_pattern_core pat),
gs ← get_goals,
set_goals $ congr_subgoals ++ gs
end tactic
namespace tactic.interactive
open tactic interactive
setup_tactic_parser
/--
Assume that the goal is of the form `lhs = rhs` or `lhs ↔ rhs`.
`congrm e` takes an expression `e` containing placeholders `_` and scans `e, lhs, rhs` in parallel.
It matches both `lhs` and `rhs` to the pattern `e`, and produces one goal for each placeholder,
stating that the corresponding subexpressions in `lhs` and `rhs` are equal.
Examples:
```lean
example {a b c d : ℕ} :
nat.pred a.succ * (d + (c + a.pred)) = nat.pred b.succ * (b + (c + d.pred)) :=
begin
congrm nat.pred (nat.succ _) * (_ + _),
/- Goals left:
⊢ a = b
⊢ d = b
⊢ c + a.pred = c + d.pred
-/
sorry,
sorry,
sorry,
end
example {a b : ℕ} (h : a = b) : (λ y : ℕ, ∀ z, a + a = z) = (λ x, ∀ z, b + a = z) :=
begin
congrm λ x, ∀ w, _ + a = w,
-- produces one goal for the underscore: ⊢ a = b
exact h,
end
```
-/
meta def congrm (arg : parse texpr) : tactic unit := do
try $ applyc ``_root_.eq.to_iff,
`(@eq %%ty _ _) ← target | fail "congrm: goal must be an equality or iff",
ta ← to_expr ``((%%arg : %%ty)) tt ff,
equate_with_pattern ta
add_tactic_doc
{ name := "congrm",
category := doc_category.tactic,
decl_names := [`tactic.interactive.congrm],
tags := ["congruence"] }
end tactic.interactive
|
3248d740ddaf2c208c1ac4df146814c87f9f1ad8 | 9be442d9ec2fcf442516ed6e9e1660aa9071b7bd | /src/Lean/Elab/Import.lean | 002c8a8d45c93202bfd73bfcda177928d64332f0 | [
"Apache-2.0",
"LLVM-exception",
"NCSA",
"LGPL-3.0-only",
"LicenseRef-scancode-inner-net-2.0",
"BSD-3-Clause",
"LGPL-2.0-or-later",
"Spencer-94",
"LGPL-2.1-or-later",
"HPND",
"LicenseRef-scancode-pcre",
"ISC",
"LGPL-2.1-only",
"LicenseRef-scancode-other-permissive",
"SunPro",
"CMU-Mach"... | permissive | EdAyers/lean4 | 57ac632d6b0789cb91fab2170e8c9e40441221bd | 37ba0df5841bde51dbc2329da81ac23d4f6a4de4 | refs/heads/master | 1,676,463,245,298 | 1,660,619,433,000 | 1,660,619,433,000 | 183,433,437 | 1 | 0 | Apache-2.0 | 1,657,612,672,000 | 1,556,196,574,000 | Lean | UTF-8 | Lean | false | false | 2,517 | lean | /-
Copyright (c) 2019 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Leonardo de Moura, Sebastian Ullrich
-/
import Lean.Parser.Module
import Lean.Data.Json
namespace Lean.Elab
def headerToImports (header : Syntax) : List Import :=
let imports := if header[0].isNone then [{ module := `Init : Import }] else []
imports ++ header[1].getArgs.toList.map fun stx =>
-- `stx` is of the form `(Module.import "import" "runtime"? id)
let runtime := !stx[1].isNone
let id := stx[2].getId
{ module := id, runtimeOnly := runtime }
def processHeader (header : Syntax) (opts : Options) (messages : MessageLog) (inputCtx : Parser.InputContext) (trustLevel : UInt32 := 0)
: IO (Environment × MessageLog) := do
try
let env ← importModules (headerToImports header) opts trustLevel
pure (env, messages)
catch e =>
let env ← mkEmptyEnvironment
let spos := header.getPos?.getD 0
let pos := inputCtx.fileMap.toPosition spos
pure (env, messages.add { fileName := inputCtx.fileName, data := toString e, pos := pos })
def parseImports (input : String) (fileName : Option String := none) : IO (List Import × Position × MessageLog) := do
let fileName := fileName.getD "<input>"
let inputCtx := Parser.mkInputContext input fileName
let (header, parserState, messages) ← Parser.parseHeader inputCtx
pure (headerToImports header, inputCtx.fileMap.toPosition parserState.pos, messages)
@[export lean_print_imports]
def printImports (input : String) (fileName : Option String) : IO Unit := do
let (deps, _, _) ← parseImports input fileName
for dep in deps do
let fname ← findOLean dep.module
IO.println fname
deriving instance ToJson for Import
structure PrintImportResult where
imports? : Option (Array Import) := none
errors : Array String := #[]
deriving ToJson
structure PrintImportsResult where
imports : Array PrintImportResult
deriving ToJson
@[export lean_print_imports_json]
def printImportsJson (fileNames : Array String) : IO Unit := do
let rs ← fileNames.mapM fun fn => do
try
let (deps, _, msgs) ← parseImports (← IO.FS.readFile ⟨fn⟩) fn
if msgs.hasErrors then
return { errors := (← msgs.toList.toArray.mapM (·.toString)) }
else
return { imports? := some deps.toArray }
catch e => return { errors := #[e.toString] }
IO.println (toJson { imports := rs : PrintImportsResult })
end Lean.Elab
|
9c800a8f39f7bb67c2d1c867718ec6ee50ff4bc2 | ad0c7d243dc1bd563419e2767ed42fb323d7beea | /analysis/topology/uniform_space.lean | 710833c9e4b7d9f8b207bf50e9480e916d0e0203 | [
"Apache-2.0"
] | permissive | sebzim4500/mathlib | e0b5a63b1655f910dee30badf09bd7e191d3cf30 | 6997cafbd3a7325af5cb318561768c316ceb7757 | refs/heads/master | 1,585,549,958,618 | 1,538,221,723,000 | 1,538,221,723,000 | 150,869,076 | 0 | 0 | Apache-2.0 | 1,538,229,323,000 | 1,538,229,323,000 | null | UTF-8 | Lean | false | false | 84,405 | lean | /-
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
Theory of uniform spaces.
Uniform spaces are a generalization of metric spaces and topological groups. Many concepts directly
generalize to uniform spaces, e.g.
* completeness
* completion (on Cauchy filters instead of Cauchy sequences)
* extension of uniform continuous functions to complete spaces
* uniform contiunuity & embedding
* totally bounded
* totally bounded ∧ complete → compact
One reason to directly formalize uniform spaces is foundational: we define ℝ as a completion of ℚ.
The central concept of uniform spaces is its uniformity: a filter relating two elements of the
space. This filter is reflexive, symmetric and transitive. So a set (i.e. a relation) in this filter
represents a 'distance': it is reflexive, symmetric and the uniformity contains a set for which the
`triangular` rule holds.
The formalization is mostly based on the books:
N. Bourbaki: General Topology
I. M. James: Topologies and Uniformities
A major difference is that this formalization is heavily based on the filter library.
-/
import order.filter data.quot analysis.topology.topological_space analysis.topology.continuity
open set lattice filter classical
local attribute [instance] prop_decidable
set_option eqn_compiler.zeta true
universes u
section
variables {α : Type*} {β : Type*} {γ : Type*} {δ : Type*} {ι : Sort*}
/-- The identity relation, or the graph of the identity function -/
def id_rel {α : Type*} := {p : α × α | p.1 = p.2}
@[simp] theorem mem_id_rel {a b : α} : (a, b) ∈ @id_rel α ↔ a = b := iff.rfl
@[simp] theorem id_rel_subset {s : set (α × α)} : id_rel ⊆ s ↔ ∀ a, (a, a) ∈ s :=
by simp [subset_def]; exact forall_congr (λ a, by simp)
/-- The composition of relations -/
def comp_rel {α : Type u} (r₁ r₂ : set (α×α)) := {p : α × α | ∃z:α, (p.1, z) ∈ r₁ ∧ (z, p.2) ∈ r₂}
@[simp] theorem mem_comp_rel {r₁ r₂ : set (α×α)}
{x y : α} : (x, y) ∈ comp_rel r₁ r₂ ↔ ∃ z, (x, z) ∈ r₁ ∧ (z, y) ∈ r₂ := iff.rfl
@[simp] theorem swap_id_rel : prod.swap '' id_rel = @id_rel α :=
set.ext $ assume ⟨a, b⟩, by simp [image_swap_eq_preimage_swap]; exact eq_comm
theorem monotone_comp_rel [preorder β] {f g : β → set (α×α)}
(hf : monotone f) (hg : monotone g) : monotone (λx, comp_rel (f x) (g x)) :=
assume a b h p ⟨z, h₁, h₂⟩, ⟨z, hf h h₁, hg h h₂⟩
lemma prod_mk_mem_comp_rel {a b c : α} {s t : set (α×α)} (h₁ : (a, c) ∈ s) (h₂ : (c, b) ∈ t) :
(a, b) ∈ comp_rel s t :=
⟨c, h₁, h₂⟩
@[simp] lemma id_comp_rel {r : set (α×α)} : comp_rel id_rel r = r :=
set.ext $ assume ⟨a, b⟩, by simp
lemma comp_rel_assoc {r s t : set (α×α)} :
comp_rel (comp_rel r s) t = comp_rel r (comp_rel s t) :=
by ext p; cases p; simp only [mem_comp_rel]; tauto
/-- This core description of a uniform space is outside of the type class hierarchy. It is useful
for constructions of uniform spaces, when the topology is derived from the uniform space. -/
structure uniform_space.core (α : Type u) :=
(uniformity : filter (α × α))
(refl : principal id_rel ≤ uniformity)
(symm : tendsto prod.swap uniformity uniformity)
(comp : uniformity.lift' (λs, comp_rel s s) ≤ uniformity)
def uniform_space.core.mk' {α : Type u} (U : filter (α × α))
(refl : ∀ (r ∈ U.sets) x, (x, x) ∈ r)
(symm : ∀ r ∈ U.sets, {p | prod.swap p ∈ r} ∈ U.sets)
(comp : ∀ r ∈ U.sets, ∃ t ∈ U.sets, comp_rel t t ⊆ r) : uniform_space.core α :=
⟨U, λ r ru, id_rel_subset.2 (refl _ ru), symm,
begin
intros r ru,
rw [mem_lift'_sets],
exact comp _ ru,
apply monotone_comp_rel; exact monotone_id,
end⟩
/-- A uniform space generates a topological space -/
def uniform_space.core.to_topological_space {α : Type u} (u : uniform_space.core α) :
topological_space α :=
{ is_open := λs, ∀x∈s, { p : α × α | p.1 = x → p.2 ∈ s } ∈ u.uniformity.sets,
is_open_univ := by simp; intro; exact univ_mem_sets,
is_open_inter :=
assume s t hs ht x ⟨xs, xt⟩, by filter_upwards [hs x xs, ht x xt]; simp {contextual := tt},
is_open_sUnion :=
assume s hs x ⟨t, ts, xt⟩, by filter_upwards [hs t ts x xt] assume p ph h, ⟨t, ts, ph h⟩ }
lemma uniform_space.core_eq : ∀{u₁ u₂ : uniform_space.core α}, u₁.uniformity = u₂.uniformity → u₁ = u₂
| ⟨u₁, _, _, _⟩ ⟨u₂, _, _, _⟩ h := have u₁ = u₂, from h, by simp [*]
/-- A uniform space is a generalization of the "uniform" topological aspects of a
metric space. It consists of a filter on `α × α` called the "uniformity", which
satisfies properties analogous to the reflexivity, symmetry, and triangle properties
of a metric.
A metric space has a natural uniformity, and a uniform space has a natural topology.
A topological group also has a natural uniformity, even when it is not metrizable. -/
class uniform_space (α : Type u) extends topological_space α, uniform_space.core α :=
(is_open_uniformity : ∀s, is_open s ↔ (∀x∈s, { p : α × α | p.1 = x → p.2 ∈ s } ∈ uniformity.sets))
@[pattern] def uniform_space.mk' {α} (t : topological_space α)
(c : uniform_space.core α)
(is_open_uniformity : ∀s:set α, t.is_open s ↔
(∀x∈s, { p : α × α | p.1 = x → p.2 ∈ s } ∈ c.uniformity.sets)) :
uniform_space α := ⟨c, is_open_uniformity⟩
def uniform_space.of_core {α : Type u} (u : uniform_space.core α) : uniform_space α :=
{ to_core := u,
to_topological_space := u.to_topological_space,
is_open_uniformity := assume a, iff.refl _ }
def uniform_space.of_core_eq {α : Type u} (u : uniform_space.core α) (t : topological_space α)
(h : t = u.to_topological_space) : uniform_space α :=
{ to_core := u,
to_topological_space := t,
is_open_uniformity := assume a, h.symm ▸ iff.refl _ }
lemma uniform_space.to_core_to_topological_space (u : uniform_space α) :
u.to_core.to_topological_space = u.to_topological_space :=
topological_space_eq $ funext $ assume s,
by rw [uniform_space.core.to_topological_space, uniform_space.is_open_uniformity]
@[extensionality]
lemma uniform_space_eq : ∀{u₁ u₂ : uniform_space α}, u₁.uniformity = u₂.uniformity → u₁ = u₂
| (uniform_space.mk' t₁ u₁ o₁) (uniform_space.mk' t₂ u₂ o₂) h :=
have u₁ = u₂, from uniform_space.core_eq h,
have t₁ = t₂, from topological_space_eq $ funext $ assume s, by rw [o₁, o₂]; simp [this],
by simp [*]
lemma uniform_space.of_core_eq_to_core
(u : uniform_space α) (t : topological_space α) (h : t = u.to_core.to_topological_space) :
uniform_space.of_core_eq u.to_core t h = u :=
uniform_space_eq rfl
section uniform_space
variables [uniform_space α]
/-- The uniformity is a filter on α × α (inferred from an ambient uniform space
structure on α). -/
def uniformity : filter (α × α) := (@uniform_space.to_core α _).uniformity
lemma is_open_uniformity {s : set α} :
is_open s ↔ (∀x∈s, { p : α × α | p.1 = x → p.2 ∈ s } ∈ (@uniformity α _).sets) :=
uniform_space.is_open_uniformity s
lemma refl_le_uniformity : principal id_rel ≤ @uniformity α _ :=
(@uniform_space.to_core α _).refl
lemma refl_mem_uniformity {x : α} {s : set (α × α)} (h : s ∈ (@uniformity α _).sets) :
(x, x) ∈ s :=
refl_le_uniformity h rfl
lemma symm_le_uniformity : map (@prod.swap α α) uniformity ≤ uniformity :=
(@uniform_space.to_core α _).symm
lemma comp_le_uniformity : uniformity.lift' (λs:set (α×α), comp_rel s s) ≤ uniformity :=
(@uniform_space.to_core α _).comp
lemma tendsto_swap_uniformity : tendsto prod.swap (@uniformity α _) uniformity :=
symm_le_uniformity
lemma tendsto_const_uniformity {a : α} {f : filter β} : tendsto (λ_, (a, a)) f uniformity :=
assume s hs,
show {x | (a, a) ∈ s} ∈ f.sets,
from univ_mem_sets' $ assume b, refl_mem_uniformity hs
lemma comp_mem_uniformity_sets {s : set (α × α)} (hs : s ∈ (@uniformity α _).sets) :
∃t∈(@uniformity α _).sets, comp_rel t t ⊆ s :=
have s ∈ (uniformity.lift' (λt:set (α×α), comp_rel t t)).sets,
from comp_le_uniformity hs,
(mem_lift'_sets $ monotone_comp_rel monotone_id monotone_id).mp this
lemma symm_of_uniformity {s : set (α × α)} (hs : s ∈ (@uniformity α _).sets) :
∃t∈(@uniformity α _).sets, (∀a b, (a, b) ∈ t → (b, a) ∈ t) ∧ t ⊆ s :=
have preimage prod.swap s ∈ (@uniformity α _).sets, from symm_le_uniformity hs,
⟨s ∩ preimage prod.swap s, inter_mem_sets hs this, assume a b ⟨h₁, h₂⟩, ⟨h₂, h₁⟩, inter_subset_left _ _⟩
lemma comp_symm_of_uniformity {s : set (α × α)} (hs : s ∈ (@uniformity α _).sets) :
∃t∈(@uniformity α _).sets, (∀{a b}, (a, b) ∈ t → (b, a) ∈ t) ∧ comp_rel t t ⊆ s :=
let ⟨t, ht₁, ht₂⟩ := comp_mem_uniformity_sets hs in
let ⟨t', ht', ht'₁, ht'₂⟩ := symm_of_uniformity ht₁ in
⟨t', ht', ht'₁, subset.trans (monotone_comp_rel monotone_id monotone_id ht'₂) ht₂⟩
lemma uniformity_le_symm : uniformity ≤ (@prod.swap α α) <$> uniformity :=
by rw [map_swap_eq_comap_swap];
from map_le_iff_le_comap.1 tendsto_swap_uniformity
lemma uniformity_eq_symm : uniformity = (@prod.swap α α) <$> uniformity :=
le_antisymm uniformity_le_symm symm_le_uniformity
theorem uniformity_lift_le_swap {g : set (α×α) → filter β} {f : filter β} (hg : monotone g)
(h : uniformity.lift (λs, g (preimage prod.swap s)) ≤ f) : uniformity.lift g ≤ f :=
calc uniformity.lift g ≤ (filter.map prod.swap (@uniformity α _)).lift g :
lift_mono uniformity_le_symm (le_refl _)
... ≤ _ :
by rw [map_lift_eq2 hg, image_swap_eq_preimage_swap]; exact h
lemma uniformity_lift_le_comp {f : set (α×α) → filter β} (h : monotone f):
uniformity.lift (λs, f (comp_rel s s)) ≤ uniformity.lift f :=
calc uniformity.lift (λs, f (comp_rel s s)) =
(uniformity.lift' (λs:set (α×α), comp_rel s s)).lift f :
begin
rw [lift_lift'_assoc],
exact monotone_comp_rel monotone_id monotone_id,
exact h
end
... ≤ uniformity.lift f : lift_mono comp_le_uniformity (le_refl _)
lemma comp_le_uniformity3 :
uniformity.lift' (λs:set (α×α), comp_rel s (comp_rel s s)) ≤ uniformity :=
calc uniformity.lift' (λd, comp_rel d (comp_rel d d)) =
uniformity.lift (λs, uniformity.lift' (λt:set(α×α), comp_rel s (comp_rel t t))) :
begin
rw [lift_lift'_same_eq_lift'],
exact (assume x, monotone_comp_rel monotone_const $ monotone_comp_rel monotone_id monotone_id),
exact (assume x, monotone_comp_rel monotone_id monotone_const),
end
... ≤ uniformity.lift (λs, uniformity.lift' (λt:set(α×α), comp_rel s t)) :
lift_mono' $ assume s hs, @uniformity_lift_le_comp α _ _ (principal ∘ comp_rel s) $
monotone_comp (monotone_comp_rel monotone_const monotone_id) monotone_principal
... = uniformity.lift' (λs:set(α×α), comp_rel s s) :
lift_lift'_same_eq_lift'
(assume s, monotone_comp_rel monotone_const monotone_id)
(assume s, monotone_comp_rel monotone_id monotone_const)
... ≤ uniformity : comp_le_uniformity
lemma mem_nhds_uniformity_iff {x : α} {s : set α} :
(s ∈ (nhds x).sets) ↔ ({p : α × α | p.1 = x → p.2 ∈ s} ∈ (@uniformity α _).sets) :=
⟨ begin
simp [mem_nhds_sets_iff, is_open_uniformity],
exact assume t ts ht xt, by filter_upwards [ht x xt] assume ⟨x', y⟩ h eq, ts $ h eq
end,
assume hs,
mem_nhds_sets_iff.mpr ⟨{x | {p : α × α | p.1 = x → p.2 ∈ s} ∈ (@uniformity α _).sets},
assume x' hx', refl_mem_uniformity hx' rfl,
is_open_uniformity.mpr $ assume x' hx',
let ⟨t, ht, tr⟩ := comp_mem_uniformity_sets hx' in
by filter_upwards [ht] assume ⟨a, b⟩ hp' (hax' : a = x'),
by filter_upwards [ht] assume ⟨a, b'⟩ hp'' (hab : a = b),
have hp : (x', b) ∈ t, from hax' ▸ hp',
have (b, b') ∈ t, from hab ▸ hp'',
have (x', b') ∈ comp_rel t t, from ⟨b, hp, this⟩,
show b' ∈ s,
from tr this rfl,
hs⟩⟩
lemma nhds_eq_comap_uniformity {x : α} : nhds x = uniformity.comap (prod.mk x) :=
by ext s; rw [mem_nhds_uniformity_iff, mem_comap_sets]; from iff.intro
(assume hs, ⟨_, hs, assume x hx, hx rfl⟩)
(assume ⟨t, h, ht⟩, uniformity.sets_of_superset h $
assume ⟨p₁, p₂⟩ hp (h : p₁ = x), ht $ by simp [h.symm, hp])
lemma nhds_eq_uniformity {x : α} : nhds x = uniformity.lift' (λs:set (α×α), {y | (x, y) ∈ s}) :=
begin
ext s,
rw [mem_lift'_sets], tactic.swap, apply monotone_preimage,
simp [mem_nhds_uniformity_iff],
exact ⟨assume h, ⟨_, h, assume y h, h rfl⟩,
assume ⟨t, h₁, h₂⟩,
uniformity.sets_of_superset h₁ $
assume ⟨x', y⟩ hp (eq : x' = x), h₂ $
show (x, y) ∈ t, from eq ▸ hp⟩
end
lemma mem_nhds_left (x : α) {s : set (α×α)} (h : s ∈ (uniformity.sets : set (set (α×α)))) :
{y : α | (x, y) ∈ s} ∈ (nhds x).sets :=
have nhds x ≤ principal {y : α | (x, y) ∈ s},
by rw [nhds_eq_uniformity]; exact infi_le_of_le s (infi_le _ h),
by simp at this; assumption
lemma mem_nhds_right (y : α) {s : set (α×α)} (h : s ∈ (uniformity.sets : set (set (α×α)))) :
{x : α | (x, y) ∈ s} ∈ (nhds y).sets :=
mem_nhds_left _ (symm_le_uniformity h)
lemma tendsto_right_nhds_uniformity {a : α} : tendsto (λa', (a', a)) (nhds a) uniformity :=
assume s, mem_nhds_right a
lemma tendsto_left_nhds_uniformity {a : α} : tendsto (λa', (a, a')) (nhds a) uniformity :=
assume s, mem_nhds_left a
lemma lift_nhds_left {x : α} {g : set α → filter β} (hg : monotone g) :
(nhds x).lift g = uniformity.lift (λs:set (α×α), g {y | (x, y) ∈ s}) :=
eq.trans
begin
rw [nhds_eq_uniformity],
exact (filter.lift_assoc $ monotone_comp monotone_preimage $ monotone_comp monotone_preimage monotone_principal)
end
(congr_arg _ $ funext $ assume s, filter.lift_principal hg)
lemma lift_nhds_right {x : α} {g : set α → filter β} (hg : monotone g) :
(nhds x).lift g = uniformity.lift (λs:set (α×α), g {y | (y, x) ∈ s}) :=
calc (nhds x).lift g = uniformity.lift (λs:set (α×α), g {y | (x, y) ∈ s}) : lift_nhds_left hg
... = ((@prod.swap α α) <$> uniformity).lift (λs:set (α×α), g {y | (x, y) ∈ s}) : by rw [←uniformity_eq_symm]
... = uniformity.lift (λs:set (α×α), g {y | (x, y) ∈ image prod.swap s}) :
map_lift_eq2 $ monotone_comp monotone_preimage hg
... = _ : by simp [image_swap_eq_preimage_swap]
lemma nhds_nhds_eq_uniformity_uniformity_prod {a b : α} :
filter.prod (nhds a) (nhds b) =
uniformity.lift (λs:set (α×α), uniformity.lift' (λt:set (α×α),
set.prod {y : α | (y, a) ∈ s} {y : α | (b, y) ∈ t})) :=
begin
rw [prod_def],
show (nhds a).lift (λs:set α, (nhds b).lift (λt:set α, principal (set.prod s t))) = _,
rw [lift_nhds_right],
apply congr_arg, funext s,
rw [lift_nhds_left],
refl,
exact monotone_comp (monotone_prod monotone_const monotone_id) monotone_principal,
exact (monotone_lift' monotone_const $ monotone_lam $
assume x, monotone_prod monotone_id monotone_const)
end
lemma nhds_eq_uniformity_prod {a b : α} :
nhds (a, b) =
uniformity.lift' (λs:set (α×α), set.prod {y : α | (y, a) ∈ s} {y : α | (b, y) ∈ s}) :=
begin
rw [nhds_prod_eq, nhds_nhds_eq_uniformity_uniformity_prod, lift_lift'_same_eq_lift'],
{ intro s, exact monotone_prod monotone_const monotone_preimage },
{ intro t, exact monotone_prod monotone_preimage monotone_const }
end
lemma nhdset_of_mem_uniformity {d : set (α×α)} (s : set (α×α)) (hd : d ∈ (@uniformity α _).sets) :
∃(t : set (α×α)), is_open t ∧ s ⊆ t ∧ t ⊆ {p | ∃x y, (p.1, x) ∈ d ∧ (x, y) ∈ s ∧ (y, p.2) ∈ d} :=
let cl_d := {p:α×α | ∃x y, (p.1, x) ∈ d ∧ (x, y) ∈ s ∧ (y, p.2) ∈ d} in
have ∀p ∈ s, ∃t ⊆ cl_d, is_open t ∧ p ∈ t, from
assume ⟨x, y⟩ hp, mem_nhds_sets_iff.mp $
show cl_d ∈ (nhds (x, y)).sets,
begin
rw [nhds_eq_uniformity_prod, mem_lift'_sets],
exact ⟨d, hd, assume ⟨a, b⟩ ⟨ha, hb⟩, ⟨x, y, ha, hp, hb⟩⟩,
exact monotone_prod monotone_preimage monotone_preimage
end,
have ∃t:(Π(p:α×α) (h:p ∈ s), set (α×α)),
∀p, ∀h:p ∈ s, t p h ⊆ cl_d ∧ is_open (t p h) ∧ p ∈ t p h,
by simp [classical.skolem] at this; simp; assumption,
match this with
| ⟨t, ht⟩ :=
⟨(⋃ p:α×α, ⋃ h : p ∈ s, t p h : set (α×α)),
is_open_Union $ assume (p:α×α), is_open_Union $ assume hp, (ht p hp).right.left,
assume ⟨a, b⟩ hp, begin simp; exact ⟨a, b, hp, (ht (a,b) hp).right.right⟩ end,
Union_subset $ assume p, Union_subset $ assume hp, (ht p hp).left⟩
end
lemma closure_eq_inter_uniformity {t : set (α×α)} :
closure t = (⋂ d∈(@uniformity α _).sets, comp_rel d (comp_rel t d)) :=
set.ext $ assume ⟨a, b⟩,
calc (a, b) ∈ closure t ↔ (nhds (a, b) ⊓ principal t ≠ ⊥) : by simp [closure_eq_nhds]
... ↔ (((@prod.swap α α) <$> uniformity).lift'
(λ (s : set (α × α)), set.prod {x : α | (x, a) ∈ s} {y : α | (b, y) ∈ s}) ⊓ principal t ≠ ⊥) :
by rw [←uniformity_eq_symm, nhds_eq_uniformity_prod]
... ↔ ((map (@prod.swap α α) uniformity).lift'
(λ (s : set (α × α)), set.prod {x : α | (x, a) ∈ s} {y : α | (b, y) ∈ s}) ⊓ principal t ≠ ⊥) :
by refl
... ↔ (uniformity.lift'
(λ (s : set (α × α)), set.prod {y : α | (a, y) ∈ s} {x : α | (x, b) ∈ s}) ⊓ principal t ≠ ⊥) :
begin
rw [map_lift'_eq2],
simp [image_swap_eq_preimage_swap, function.comp],
exact monotone_prod monotone_preimage monotone_preimage
end
... ↔ (∀s∈(@uniformity α _).sets, ∃x, x ∈ set.prod {y : α | (a, y) ∈ s} {x : α | (x, b) ∈ s} ∩ t) :
begin
rw [lift'_inf_principal_eq, lift'_neq_bot_iff],
apply forall_congr, intro s, rw [ne_empty_iff_exists_mem],
exact monotone_inter (monotone_prod monotone_preimage monotone_preimage) monotone_const
end
... ↔ (∀s∈(@uniformity α _).sets, (a, b) ∈ comp_rel s (comp_rel t s)) :
forall_congr $ assume s, forall_congr $ assume hs,
⟨assume ⟨⟨x, y⟩, ⟨⟨hx, hy⟩, hxyt⟩⟩, ⟨x, hx, y, hxyt, hy⟩,
assume ⟨x, hx, y, hxyt, hy⟩, ⟨⟨x, y⟩, ⟨⟨hx, hy⟩, hxyt⟩⟩⟩
... ↔ _ : by simp
lemma uniformity_eq_uniformity_closure : (@uniformity α _) = uniformity.lift' closure :=
le_antisymm
(le_infi $ assume s, le_infi $ assume hs, by simp; filter_upwards [hs] subset_closure)
(calc uniformity.lift' closure ≤ uniformity.lift' (λd, comp_rel d (comp_rel d d)) :
lift'_mono' (by intros s hs; rw [closure_eq_inter_uniformity]; exact bInter_subset_of_mem hs)
... ≤ uniformity : comp_le_uniformity3)
lemma uniformity_eq_uniformity_interior : (@uniformity α _) = uniformity.lift' interior :=
le_antisymm
(le_infi $ assume d, le_infi $ assume hd,
let ⟨s, hs, hs_comp⟩ := (mem_lift'_sets $
monotone_comp_rel monotone_id $ monotone_comp_rel monotone_id monotone_id).mp (comp_le_uniformity3 hd) in
let ⟨t, ht, hst, ht_comp⟩ := nhdset_of_mem_uniformity s hs in
have s ⊆ interior d, from
calc s ⊆ t : hst
... ⊆ interior d : (subset_interior_iff_subset_of_open ht).mpr $
assume x, assume : x ∈ t, let ⟨x, y, h₁, h₂, h₃⟩ := ht_comp this in hs_comp ⟨x, h₁, y, h₂, h₃⟩,
have interior d ∈ (@uniformity α _).sets, by filter_upwards [hs] this,
by simp [this])
(assume s hs, (uniformity.lift' interior).sets_of_superset (mem_lift' hs) interior_subset)
lemma interior_mem_uniformity {s : set (α × α)} (hs : s ∈ (@uniformity α _).sets) :
interior s ∈ (@uniformity α _).sets :=
by rw [uniformity_eq_uniformity_interior]; exact mem_lift' hs
lemma mem_uniformity_is_closed [uniform_space α] {s : set (α×α)} (h : s ∈ (@uniformity α _).sets) :
∃t∈(@uniformity α _).sets, is_closed t ∧ t ⊆ s :=
have s ∈ ((@uniformity α _).lift' closure).sets, by rwa [uniformity_eq_uniformity_closure] at h,
have ∃t∈(@uniformity α _).sets, closure t ⊆ s,
by rwa [mem_lift'_sets] at this; apply closure_mono,
let ⟨t, ht, hst⟩ := this in
⟨closure t, uniformity.sets_of_superset ht subset_closure, is_closed_closure, hst⟩
/- uniform continuity -/
def uniform_continuous [uniform_space β] (f : α → β) :=
tendsto (λx:α×α, (f x.1, f x.2)) uniformity uniformity
theorem uniform_continuous_def [uniform_space β] {f : α → β} :
uniform_continuous f ↔ ∀ r ∈ (@uniformity β _).sets,
{x : α × α | (f x.1, f x.2) ∈ r} ∈ (@uniformity α _).sets :=
iff.rfl
lemma uniform_continuous_id : uniform_continuous (@id α) :=
by simp [uniform_continuous]; exact tendsto_id
lemma uniform_continuous_const [uniform_space β] {b : β} : uniform_continuous (λa:α, b) :=
@tendsto_const_uniformity _ _ _ b uniformity
lemma uniform_continuous.comp [uniform_space β] [uniform_space γ] {f : α → β} {g : β → γ}
(hf : uniform_continuous f) (hg : uniform_continuous g) : uniform_continuous (g ∘ f) :=
hf.comp hg
def uniform_embedding [uniform_space β] (f : α → β) :=
function.injective f ∧
comap (λx:α×α, (f x.1, f x.2)) uniformity = uniformity
theorem uniform_embedding_def [uniform_space β] {f : α → β} :
uniform_embedding f ↔ function.injective f ∧ ∀ s, s ∈ (@uniformity α _).sets ↔
∃ t ∈ (@uniformity β _).sets, ∀ x y : α, (f x, f y) ∈ t → (x, y) ∈ s :=
by rw [uniform_embedding, eq_comm, filter.ext_iff]; simp [subset_def]
theorem uniform_embedding_def' [uniform_space β] {f : α → β} :
uniform_embedding f ↔ function.injective f ∧ uniform_continuous f ∧
∀ s, s ∈ (@uniformity α _).sets →
∃ t ∈ (@uniformity β _).sets, ∀ x y : α, (f x, f y) ∈ t → (x, y) ∈ s :=
by simp [uniform_embedding_def, uniform_continuous_def]; exact
⟨λ ⟨I, H⟩, ⟨I, λ s su, (H _).2 ⟨s, su, λ x y, id⟩, λ s, (H s).1⟩,
λ ⟨I, H₁, H₂⟩, ⟨I, λ s, ⟨H₂ s,
λ ⟨t, tu, h⟩, sets_of_superset _ (H₁ t tu) (λ ⟨a, b⟩, h a b)⟩⟩⟩
lemma uniform_embedding.uniform_continuous [uniform_space β] {f : α → β}
(hf : uniform_embedding f) : uniform_continuous f :=
(uniform_embedding_def'.1 hf).2.1
lemma uniform_embedding.uniform_continuous_iff [uniform_space β] [uniform_space γ] {f : α → β}
{g : β → γ} (hg : uniform_embedding g) : uniform_continuous f ↔ uniform_continuous (g ∘ f) :=
by simp [uniform_continuous, tendsto]; rw [← hg.2, ← map_le_iff_le_comap, filter.map_map]
lemma uniform_embedding.dense_embedding [uniform_space β] {f : α → β}
(h : uniform_embedding f) (hd : ∀x, x ∈ closure (range f)) : dense_embedding f :=
{ dense := hd,
inj := h.left,
induced :=
begin
intro a,
simp [h.right.symm, nhds_eq_uniformity],
rw [comap_lift'_eq, comap_lift'_eq2],
refl,
exact monotone_preimage,
exact monotone_preimage
end }
lemma uniform_continuous.continuous [uniform_space β] {f : α → β}
(hf : uniform_continuous f) : continuous f :=
continuous_iff_tendsto.mpr $ assume a,
calc map f (nhds a) ≤
(map (λp:α×α, (f p.1, f p.2)) uniformity).lift' (λs:set (β×β), {y | (f a, y) ∈ s}) :
begin
rw [nhds_eq_uniformity, map_lift'_eq, map_lift'_eq2],
exact (lift'_mono' $ assume s hs b ⟨a', (ha' : (_, a') ∈ s), a'_eq⟩,
⟨(a, a'), ha', show (f a, f a') = (f a, b), from a'_eq ▸ rfl⟩),
exact monotone_preimage,
exact monotone_preimage
end
... ≤ nhds (f a) :
by rw [nhds_eq_uniformity]; exact lift'_mono hf (le_refl _)
lemma closure_image_mem_nhds_of_uniform_embedding
[uniform_space α] [uniform_space β] {s : set (α×α)} {e : α → β} (b : β)
(he₁ : uniform_embedding e) (he₂ : dense_embedding e) (hs : s ∈ (@uniformity α _).sets) :
∃a, closure (e '' {a' | (a, a') ∈ s}) ∈ (nhds b).sets :=
have s ∈ (comap (λp:α×α, (e p.1, e p.2)) $ uniformity).sets,
from he₁.right.symm ▸ hs,
let ⟨t₁, ht₁u, ht₁⟩ := this in
have ht₁ : ∀p:α×α, (e p.1, e p.2) ∈ t₁ → p ∈ s, from ht₁,
let ⟨t₂, ht₂u, ht₂s, ht₂c⟩ := comp_symm_of_uniformity ht₁u in
let ⟨t, htu, hts, htc⟩ := comp_symm_of_uniformity ht₂u in
have preimage e {b' | (b, b') ∈ t₂} ∈ (comap e $ nhds b).sets,
from preimage_mem_comap $ mem_nhds_left b ht₂u,
let ⟨a, (ha : (b, e a) ∈ t₂)⟩ := inhabited_of_mem_sets (he₂.comap_nhds_neq_bot) this in
have ∀b' (s' : set (β × β)), (b, b') ∈ t → s' ∈ (@uniformity β _).sets →
{y : β | (b', y) ∈ s'} ∩ e '' {a' : α | (a, a') ∈ s} ≠ ∅,
from assume b' s' hb' hs',
have preimage e {b'' | (b', b'') ∈ s' ∩ t} ∈ (comap e $ nhds b').sets,
from preimage_mem_comap $ mem_nhds_left b' $ inter_mem_sets hs' htu,
let ⟨a₂, ha₂s', ha₂t⟩ := inhabited_of_mem_sets (he₂.comap_nhds_neq_bot) this in
have (e a, e a₂) ∈ t₁,
from ht₂c $ prod_mk_mem_comp_rel (ht₂s ha) $ htc $ prod_mk_mem_comp_rel hb' ha₂t,
have e a₂ ∈ {b'':β | (b', b'') ∈ s'} ∩ e '' {a' | (a, a') ∈ s},
from ⟨ha₂s', mem_image_of_mem _ $ ht₁ (a, a₂) this⟩,
ne_empty_of_mem this,
have ∀b', (b, b') ∈ t → nhds b' ⊓ principal (e '' {a' | (a, a') ∈ s}) ≠ ⊥,
begin
intros b' hb',
rw [nhds_eq_uniformity, lift'_inf_principal_eq, lift'_neq_bot_iff],
exact assume s, this b' s hb',
exact monotone_inter monotone_preimage monotone_const
end,
have ∀b', (b, b') ∈ t → b' ∈ closure (e '' {a' | (a, a') ∈ s}),
from assume b' hb', by rw [closure_eq_nhds]; exact this b' hb',
⟨a, (nhds b).sets_of_superset (mem_nhds_left b htu) this⟩
/-- A filter `f` is Cauchy if for every entourage `r`, there exists an
`s ∈ f` such that `s × s ⊆ r`. This is a generalization of Cauchy
sequences, because if `a : ℕ → α` then the filter of sets containing
cofinitely many of the `a n` is Cauchy iff `a` is a Cauchy sequence. -/
def cauchy (f : filter α) := f ≠ ⊥ ∧ filter.prod f f ≤ uniformity
lemma cauchy_iff [uniform_space α] {f : filter α} :
cauchy f ↔ (f ≠ ⊥ ∧ (∀s∈(@uniformity α _).sets, ∃t∈f.sets, set.prod t t ⊆ s)) :=
and_congr (iff.refl _) $ forall_congr $ assume s, forall_congr $ assume hs, mem_prod_same_iff
lemma cauchy_downwards {f g : filter α} (h_c : cauchy f) (hg : g ≠ ⊥) (h_le : g ≤ f) : cauchy g :=
⟨hg, le_trans (filter.prod_mono h_le h_le) h_c.right⟩
lemma cauchy_nhds {a : α} : cauchy (nhds a) :=
⟨nhds_neq_bot,
calc filter.prod (nhds a) (nhds a) =
uniformity.lift (λs:set (α×α), uniformity.lift' (λt:set(α×α),
set.prod {y : α | (y, a) ∈ s} {y : α | (a, y) ∈ t})) : nhds_nhds_eq_uniformity_uniformity_prod
... ≤ uniformity.lift' (λs:set (α×α), comp_rel s s) :
le_infi $ assume s, le_infi $ assume hs,
infi_le_of_le s $ infi_le_of_le hs $ infi_le_of_le s $ infi_le_of_le hs $
principal_mono.mpr $
assume ⟨x, y⟩ ⟨(hx : (x, a) ∈ s), (hy : (a, y) ∈ s)⟩, ⟨a, hx, hy⟩
... ≤ uniformity : comp_le_uniformity⟩
lemma cauchy_pure {a : α} : cauchy (pure a) :=
cauchy_downwards cauchy_nhds
(show principal {a} ≠ ⊥, by simp)
(pure_le_nhds a)
lemma le_nhds_of_cauchy_adhp {f : filter α} {x : α} (hf : cauchy f)
(adhs : f ⊓ nhds x ≠ ⊥) : f ≤ nhds x :=
have ∀s∈f.sets, x ∈ closure s,
begin
intros s hs,
simp [closure_eq_nhds, inf_comm],
exact assume h', adhs $ bot_unique $ h' ▸ inf_le_inf (by simp; exact hs) (le_refl _)
end,
calc f ≤ f.lift' (λs:set α, {y | x ∈ closure s ∧ y ∈ closure s}) :
le_infi $ assume s, le_infi $ assume hs,
begin
rw [←forall_sets_neq_empty_iff_neq_bot] at adhs,
simp [this s hs],
exact mem_sets_of_superset hs subset_closure
end
... ≤ f.lift' (λs:set α, {y | (x, y) ∈ closure (set.prod s s)}) :
by simp [closure_prod_eq]; exact le_refl _
... = (filter.prod f f).lift' (λs:set (α×α), {y | (x, y) ∈ closure s}) :
begin
rw [prod_same_eq],
rw [lift'_lift'_assoc],
exact monotone_prod monotone_id monotone_id,
exact monotone_comp (assume s t h x h', closure_mono h h') monotone_preimage
end
... ≤ uniformity.lift' (λs:set (α×α), {y | (x, y) ∈ closure s}) : lift'_mono hf.right (le_refl _)
... = (uniformity.lift' closure).lift' (λs:set (α×α), {y | (x, y) ∈ s}) :
begin
rw [lift'_lift'_assoc],
exact assume s t h, closure_mono h,
exact monotone_preimage
end
... = uniformity.lift' (λs:set (α×α), {y | (x, y) ∈ s}) :
by rw [←uniformity_eq_uniformity_closure]
... = nhds x :
by rw [nhds_eq_uniformity]
lemma le_nhds_iff_adhp_of_cauchy {f : filter α} {x : α} (hf : cauchy f) :
f ≤ nhds x ↔ f ⊓ nhds x ≠ ⊥ :=
⟨assume h, (inf_of_le_left h).symm ▸ hf.left,
le_nhds_of_cauchy_adhp hf⟩
lemma cauchy_map [uniform_space β] {f : filter α} {m : α → β}
(hm : uniform_continuous m) (hf : cauchy f) : cauchy (map m f) :=
⟨have f ≠ ⊥, from hf.left, by simp; assumption,
calc filter.prod (map m f) (map m f) =
map (λp:α×α, (m p.1, m p.2)) (filter.prod f f) : filter.prod_map_map_eq
... ≤ map (λp:α×α, (m p.1, m p.2)) uniformity : map_mono hf.right
... ≤ uniformity : hm⟩
lemma cauchy_comap [uniform_space β] {f : filter β} {m : α → β}
(hm : comap (λp:α×α, (m p.1, m p.2)) uniformity ≤ uniformity)
(hf : cauchy f) (hb : comap m f ≠ ⊥) : cauchy (comap m f) :=
⟨hb,
calc filter.prod (comap m f) (comap m f) =
comap (λp:α×α, (m p.1, m p.2)) (filter.prod f f) : filter.prod_comap_comap_eq
... ≤ comap (λp:α×α, (m p.1, m p.2)) uniformity : comap_mono hf.right
... ≤ uniformity : hm⟩
/- separated uniformity -/
/-- The separation relation is the intersection of all entourages.
Two points which are related by the separation relation are "indistinguishable"
according to the uniform structure. -/
protected def separation_rel (α : Type u) [u : uniform_space α] :=
⋂₀ (@uniformity α _).sets
lemma separated_equiv : equivalence (λx y, (x, y) ∈ separation_rel α) :=
⟨assume x, assume s, refl_mem_uniformity,
assume x y, assume h (s : set (α×α)) hs,
have preimage prod.swap s ∈ (@uniformity α _).sets,
from symm_le_uniformity hs,
h _ this,
assume x y z (hxy : (x, y) ∈ separation_rel α) (hyz : (y, z) ∈ separation_rel α)
s (hs : s ∈ (@uniformity α _).sets),
let ⟨t, ht, (h_ts : comp_rel t t ⊆ s)⟩ := comp_mem_uniformity_sets hs in
h_ts $ show (x, z) ∈ comp_rel t t,
from ⟨y, hxy t ht, hyz t ht⟩⟩
protected def separation_setoid (α : Type u) [u : uniform_space α] : setoid α :=
⟨λx y, (x, y) ∈ separation_rel α, separated_equiv⟩
@[class] def separated (α : Type u) [uniform_space α] :=
separation_rel α = id_rel
theorem separated_def {α : Type u} [uniform_space α] :
separated α ↔ ∀ x y, (∀ r ∈ (@uniformity α _).sets, (x, y) ∈ r) → x = y :=
by simp [separated, id_rel_subset.2 separated_equiv.1, subset.antisymm_iff];
simp [subset_def, separation_rel]
theorem separated_def' {α : Type u} [uniform_space α] :
separated α ↔ ∀ x y, x ≠ y → ∃ r ∈ (@uniformity α _).sets, (x, y) ∉ r :=
separated_def.trans $ forall_congr $ λ x, forall_congr $ λ y,
by rw ← not_imp_not; simp [classical.not_forall]
instance separated_t2 [s : separated α] : t2_space α :=
⟨assume x y, assume h : x ≠ y,
let ⟨d, hd, (hxy : (x, y) ∉ d)⟩ := separated_def'.1 s x y h in
let ⟨d', hd', (hd'd' : comp_rel d' d' ⊆ d)⟩ := comp_mem_uniformity_sets hd in
have {y | (x, y) ∈ d'} ∈ (nhds x).sets,
from mem_nhds_left x hd',
let ⟨u, hu₁, hu₂, hu₃⟩ := mem_nhds_sets_iff.mp this in
have {x | (x, y) ∈ d'} ∈ (nhds y).sets,
from mem_nhds_right y hd',
let ⟨v, hv₁, hv₂, hv₃⟩ := mem_nhds_sets_iff.mp this in
have u ∩ v = ∅, from
eq_empty_of_subset_empty $
assume z ⟨(h₁ : z ∈ u), (h₂ : z ∈ v)⟩,
have (x, y) ∈ comp_rel d' d', from ⟨z, hu₁ h₁, hv₁ h₂⟩,
hxy $ hd'd' this,
⟨u, v, hu₂, hv₂, hu₃, hv₃, this⟩⟩
instance separated_regular [separated α] : regular_space α :=
{ regular := λs a hs ha,
have -s ∈ (nhds a).sets,
from mem_nhds_sets hs ha,
have {p : α × α | p.1 = a → p.2 ∈ -s} ∈ uniformity.sets,
from mem_nhds_uniformity_iff.mp this,
let ⟨d, hd, h⟩ := comp_mem_uniformity_sets this in
let e := {y:α| (a, y) ∈ d} in
have hae : a ∈ closure e, from subset_closure $ refl_mem_uniformity hd,
have set.prod (closure e) (closure e) ⊆ comp_rel d (comp_rel (set.prod e e) d),
begin
rw [←closure_prod_eq, closure_eq_inter_uniformity],
change (⨅d' ∈ uniformity.sets, _) ≤ comp_rel d (comp_rel _ d),
exact (infi_le_of_le d $ infi_le_of_le hd $ le_refl _)
end,
have e_subset : closure e ⊆ -s,
from assume a' ha',
let ⟨x, (hx : (a, x) ∈ d), y, ⟨hx₁, hx₂⟩, (hy : (y, _) ∈ d)⟩ := @this ⟨a, a'⟩ ⟨hae, ha'⟩ in
have (a, a') ∈ comp_rel d d, from ⟨y, hx₂, hy⟩,
h this rfl,
have closure e ∈ (nhds a).sets, from (nhds a).sets_of_superset (mem_nhds_left a hd) subset_closure,
have nhds a ⊓ principal (-closure e) = ⊥,
from (@inf_eq_bot_iff_le_compl _ _ _ (principal (- closure e)) (principal (closure e))
(by simp [principal_univ, union_comm]) (by simp)).mpr (by simp [this]),
⟨- closure e, is_closed_closure, assume x h₁ h₂, @e_subset x h₂ h₁, this⟩,
..separated_t2 }
/-- A set `s` is totally bounded if for every entourage `d` there is a finite
set of points `t` such that every element of `s` is `d`-near to some element of `t`. -/
def totally_bounded (s : set α) : Prop :=
∀d ∈ (@uniformity α _).sets, ∃t : set α, finite t ∧ s ⊆ (⋃y∈t, {x | (x,y) ∈ d})
theorem totally_bounded_iff_subset {s : set α} : totally_bounded s ↔
∀d ∈ (@uniformity α _).sets, ∃t ⊆ s, finite t ∧ s ⊆ (⋃y∈t, {x | (x,y) ∈ d}) :=
⟨λ H d hd, begin
rcases comp_symm_of_uniformity hd with ⟨r, hr, rs, rd⟩,
rcases H r hr with ⟨k, fk, ks⟩,
let u := {y ∈ k | ∃ x, x ∈ s ∧ (x, y) ∈ r},
let f : u → α := λ x, classical.some x.2.2,
have : ∀ x : u, f x ∈ s ∧ (f x, x.1) ∈ r := λ x, classical.some_spec x.2.2,
refine ⟨range f, _, _, _⟩,
{ exact range_subset_iff.2 (λ x, (this x).1) },
{ have : finite u := finite_subset fk (λ x h, h.1),
exact ⟨@set.fintype_range _ _ _ _ this.fintype⟩ },
{ intros x xs,
have := ks xs, simp at this,
rcases this with ⟨y, hy, xy⟩,
let z : coe_sort u := ⟨y, hy, x, xs, xy⟩,
simp, exact ⟨_, ⟨_, z.2, rfl⟩, rd $ mem_comp_rel.2 ⟨_, xy, rs (this z).2⟩⟩ }
end,
λ H d hd, let ⟨t, _, ht⟩ := H d hd in ⟨t, ht⟩⟩
lemma totally_bounded_subset [uniform_space α] {s₁ s₂ : set α} (hs : s₁ ⊆ s₂)
(h : totally_bounded s₂) : totally_bounded s₁ :=
assume d hd, let ⟨t, ht₁, ht₂⟩ := h d hd in ⟨t, ht₁, subset.trans hs ht₂⟩
lemma totally_bounded_closure [uniform_space α] {s : set α} (h : totally_bounded s) :
totally_bounded (closure s) :=
assume t ht,
let ⟨t', ht', hct', htt'⟩ := mem_uniformity_is_closed ht, ⟨c, hcf, hc⟩ := h t' ht' in
⟨c, hcf,
calc closure s ⊆ closure (⋃ (y : α) (H : y ∈ c), {x : α | (x, y) ∈ t'}) : closure_mono hc
... = _ : closure_eq_of_is_closed $ is_closed_Union hcf $ assume i hi,
continuous_iff_is_closed.mp (continuous_id.prod_mk continuous_const) _ hct'
... ⊆ _ : bUnion_subset $ assume i hi, subset.trans (assume x, @htt' (x, i))
(subset_bUnion_of_mem hi)⟩
lemma totally_bounded_image [uniform_space α] [uniform_space β] {f : α → β} {s : set α}
(hf : uniform_continuous f) (hs : totally_bounded s) : totally_bounded (f '' s) :=
assume t ht,
have {p:α×α | (f p.1, f p.2) ∈ t} ∈ (@uniformity α _).sets,
from hf ht,
let ⟨c, hfc, hct⟩ := hs _ this in
⟨f '' c, finite_image f hfc,
begin
simp [image_subset_iff],
simp [subset_def] at hct,
intros x hx, simp [-mem_image],
exact let ⟨i, hi, ht⟩ := hct x hx in ⟨f i, mem_image_of_mem f hi, ht⟩
end⟩
lemma totally_bounded_preimage [uniform_space α] [uniform_space β] {f : α → β} {s : set β}
(hf : uniform_embedding f) (hs : totally_bounded s) : totally_bounded (f ⁻¹' s) :=
λ t ht, begin
rw ← hf.2 at ht,
rcases mem_comap_sets.2 ht with ⟨t', ht', ts⟩,
rcases totally_bounded_iff_subset.1
(totally_bounded_subset (image_preimage_subset f s) hs) _ ht' with ⟨c, cs, hfc, hct⟩,
refine ⟨f ⁻¹' c, finite_preimage hf.1 hfc, λ x h, _⟩,
have := hct (mem_image_of_mem f h), simp at this ⊢,
rcases this with ⟨z, zc, zt⟩,
rcases cs zc with ⟨y, yc, rfl⟩,
exact ⟨y, zc, ts (by exact zt)⟩
end
lemma cauchy_of_totally_bounded_of_ultrafilter {s : set α} {f : filter α}
(hs : totally_bounded s) (hf : ultrafilter f) (h : f ≤ principal s) : cauchy f :=
⟨hf.left, assume t ht,
let ⟨t', ht'₁, ht'_symm, ht'_t⟩ := comp_symm_of_uniformity ht in
let ⟨i, hi, hs_union⟩ := hs t' ht'₁ in
have (⋃y∈i, {x | (x,y) ∈ t'}) ∈ f.sets,
from mem_sets_of_superset (le_principal_iff.mp h) hs_union,
have ∃y∈i, {x | (x,y) ∈ t'} ∈ f.sets,
from mem_of_finite_Union_ultrafilter hf hi this,
let ⟨y, hy, hif⟩ := this in
have set.prod {x | (x,y) ∈ t'} {x | (x,y) ∈ t'} ⊆ comp_rel t' t',
from assume ⟨x₁, x₂⟩ ⟨(h₁ : (x₁, y) ∈ t'), (h₂ : (x₂, y) ∈ t')⟩,
⟨y, h₁, ht'_symm h₂⟩,
(filter.prod f f).sets_of_superset (prod_mem_prod hif hif) (subset.trans this ht'_t)⟩
lemma totally_bounded_iff_filter {s : set α} :
totally_bounded s ↔ (∀f, f ≠ ⊥ → f ≤ principal s → ∃c ≤ f, cauchy c) :=
⟨assume : totally_bounded s, assume f hf hs,
⟨ultrafilter_of f, ultrafilter_of_le,
cauchy_of_totally_bounded_of_ultrafilter this
(ultrafilter_ultrafilter_of hf) (le_trans ultrafilter_of_le hs)⟩,
assume h : ∀f, f ≠ ⊥ → f ≤ principal s → ∃c ≤ f, cauchy c, assume d hd,
classical.by_contradiction $ assume hs,
have hd_cover : ∀{t:set α}, finite t → ¬ s ⊆ (⋃y∈t, {x | (x,y) ∈ d}),
by simpa using hs,
let
f := ⨅t:{t : set α // finite t}, principal (s \ (⋃y∈t.val, {x | (x,y) ∈ d})),
⟨a, ha⟩ := @exists_mem_of_ne_empty α s
(assume h, hd_cover finite_empty $ h.symm ▸ empty_subset _)
in
have f ≠ ⊥,
from infi_neq_bot_of_directed ⟨a⟩
(assume ⟨t₁, ht₁⟩ ⟨t₂, ht₂⟩, ⟨⟨t₁ ∪ t₂, finite_union ht₁ ht₂⟩,
principal_mono.mpr $ diff_subset_diff_right $ Union_subset_Union $
assume t, Union_subset_Union_const or.inl,
principal_mono.mpr $ diff_subset_diff_right $ Union_subset_Union $
assume t, Union_subset_Union_const or.inr⟩)
(assume ⟨t, ht⟩, by simp [diff_eq_empty]; exact hd_cover ht),
have f ≤ principal s, from infi_le_of_le ⟨∅, finite_empty⟩ $ by simp; exact subset.refl s,
let
⟨c, (hc₁ : c ≤ f), (hc₂ : cauchy c)⟩ := h f ‹f ≠ ⊥› this,
⟨m, hm, (hmd : set.prod m m ⊆ d)⟩ := (@mem_prod_same_iff α c d).mp $ hc₂.right hd
in
have c ≤ principal s, from le_trans ‹c ≤ f› this,
have m ∩ s ∈ c.sets, from inter_mem_sets hm $ le_principal_iff.mp this,
let ⟨y, hym, hys⟩ := inhabited_of_mem_sets hc₂.left this in
let ys := (⋃y'∈({y}:set α), {x | (x, y') ∈ d}) in
have m ⊆ ys,
from assume y' hy',
show y' ∈ (⋃y'∈({y}:set α), {x | (x, y') ∈ d}),
by simp; exact @hmd (y', y) ⟨hy', hym⟩,
have c ≤ principal (s - ys),
from le_trans hc₁ $ infi_le_of_le ⟨{y}, finite_singleton _⟩ $ le_refl _,
have (s - ys) ∩ (m ∩ s) ∈ c.sets,
from inter_mem_sets (le_principal_iff.mp this) ‹m ∩ s ∈ c.sets›,
have ∅ ∈ c.sets,
from c.sets_of_superset this $ assume x ⟨⟨hxs, hxys⟩, hxm, _⟩, hxys $ ‹m ⊆ ys› hxm,
hc₂.left $ empty_in_sets_eq_bot.mp this⟩
lemma totally_bounded_iff_ultrafilter {s : set α} :
totally_bounded s ↔ (∀f, ultrafilter f → f ≤ principal s → cauchy f) :=
⟨assume hs f, cauchy_of_totally_bounded_of_ultrafilter hs,
assume h, totally_bounded_iff_filter.mpr $ assume f hf hfs,
have cauchy (ultrafilter_of f),
from h (ultrafilter_of f) (ultrafilter_ultrafilter_of hf) (le_trans ultrafilter_of_le hfs),
⟨ultrafilter_of f, ultrafilter_of_le, this⟩⟩
lemma compact_of_totally_bounded_complete {s : set α}
(ht : totally_bounded s) (hc : ∀{f:filter α}, cauchy f → f ≤ principal s → ∃x∈s, f ≤ nhds x) :
compact s :=
begin
rw [compact_iff_ultrafilter_le_nhds],
rw [totally_bounded_iff_ultrafilter] at ht,
exact assume f hf hfs, hc (ht _ hf hfs) hfs
end
/-- A complete space is defined here using uniformities. A uniform space
is complete if every Cauchy filter converges. -/
class complete_space (α : Type u) [uniform_space α] : Prop :=
(complete : ∀{f:filter α}, cauchy f → ∃x, f ≤ nhds x)
theorem le_nhds_lim_of_cauchy {α} [uniform_space α] [complete_space α]
[inhabited α] {f : filter α} (hf : cauchy f) : f ≤ nhds (lim f) :=
lim_spec (complete_space.complete hf)
lemma complete_of_is_closed [complete_space α] {s : set α} {f : filter α}
(h : is_closed s) (hf : cauchy f) (hfs : f ≤ principal s) : ∃x∈s, f ≤ nhds x :=
let ⟨x, hx⟩ := complete_space.complete hf in
have x ∈ s, from is_closed_iff_nhds.mp h x $ neq_bot_of_le_neq_bot hf.left $
le_inf hx hfs,
⟨x, this, hx⟩
lemma compact_of_totally_bounded_is_closed [complete_space α] {s : set α}
(ht : totally_bounded s) (hc : is_closed s) : compact s :=
@compact_of_totally_bounded_complete α _ s ht $ assume f, complete_of_is_closed hc
lemma complete_space_extension [uniform_space β] {m : β → α}
(hm : uniform_embedding m)
(dense : ∀x, x ∈ closure (range m))
(h : ∀f:filter β, cauchy f → ∃x:α, map m f ≤ nhds x) :
complete_space α :=
⟨assume (f : filter α), assume hf : cauchy f,
let
p : set (α × α) → set α → set α := λs t, {y : α| ∃x:α, x ∈ t ∧ (x, y) ∈ s},
g := uniformity.lift (λs, f.lift' (p s))
in
have mp₀ : monotone p,
from assume a b h t s ⟨x, xs, xa⟩, ⟨x, xs, h xa⟩,
have mp₁ : ∀{s}, monotone (p s),
from assume s a b h x ⟨y, ya, yxs⟩, ⟨y, h ya, yxs⟩,
have f ≤ g, from
le_infi $ assume s, le_infi $ assume hs, le_infi $ assume t, le_infi $ assume ht,
le_principal_iff.mpr $
mem_sets_of_superset ht $ assume x hx, ⟨x, hx, refl_mem_uniformity hs⟩,
have g ≠ ⊥, from neq_bot_of_le_neq_bot hf.left this,
have comap m g ≠ ⊥, from comap_neq_bot $ assume t ht,
let ⟨t', ht', ht_mem⟩ := (mem_lift_sets $ monotone_lift' monotone_const mp₀).mp ht in
let ⟨t'', ht'', ht'_sub⟩ := (mem_lift'_sets mp₁).mp ht_mem in
let ⟨x, (hx : x ∈ t'')⟩ := inhabited_of_mem_sets hf.left ht'' in
have h₀ : nhds x ⊓ principal (range m) ≠ ⊥,
by simp [closure_eq_nhds] at dense; exact dense x,
have h₁ : {y | (x, y) ∈ t'} ∈ (nhds x ⊓ principal (range m)).sets,
from @mem_inf_sets_of_left α (nhds x) (principal (range m)) _ $ mem_nhds_left x ht',
have h₂ : range m ∈ (nhds x ⊓ principal (range m)).sets,
from @mem_inf_sets_of_right α (nhds x) (principal (range m)) _ $ subset.refl _,
have {y | (x, y) ∈ t'} ∩ range m ∈ (nhds x ⊓ principal (range m)).sets,
from @inter_mem_sets α (nhds x ⊓ principal (range m)) _ _ h₁ h₂,
let ⟨y, xyt', b, b_eq⟩ := inhabited_of_mem_sets h₀ this in
⟨b, b_eq.symm ▸ ht'_sub ⟨x, hx, xyt'⟩⟩,
have cauchy g, from
⟨‹g ≠ ⊥›, assume s hs,
let
⟨s₁, hs₁, (comp_s₁ : comp_rel s₁ s₁ ⊆ s)⟩ := comp_mem_uniformity_sets hs,
⟨s₂, hs₂, (comp_s₂ : comp_rel s₂ s₂ ⊆ s₁)⟩ := comp_mem_uniformity_sets hs₁,
⟨t, ht, (prod_t : set.prod t t ⊆ s₂)⟩ := mem_prod_same_iff.mp (hf.right hs₂)
in
have hg₁ : p (preimage prod.swap s₁) t ∈ g.sets,
from mem_lift (symm_le_uniformity hs₁) $ @mem_lift' α α f _ t ht,
have hg₂ : p s₂ t ∈ g.sets,
from mem_lift hs₂ $ @mem_lift' α α f _ t ht,
have hg : set.prod (p (preimage prod.swap s₁) t) (p s₂ t) ∈ (filter.prod g g).sets,
from @prod_mem_prod α α _ _ g g hg₁ hg₂,
(filter.prod g g).sets_of_superset hg
(assume ⟨a, b⟩ ⟨⟨c₁, c₁t, hc₁⟩, ⟨c₂, c₂t, hc₂⟩⟩,
have (c₁, c₂) ∈ set.prod t t, from ⟨c₁t, c₂t⟩,
comp_s₁ $ prod_mk_mem_comp_rel hc₁ $
comp_s₂ $ prod_mk_mem_comp_rel (prod_t this) hc₂)⟩,
have cauchy (filter.comap m g),
from cauchy_comap (le_of_eq hm.right) ‹cauchy g› (by assumption),
let ⟨x, (hx : map m (filter.comap m g) ≤ nhds x)⟩ := h _ this in
have map m (filter.comap m g) ⊓ nhds x ≠ ⊥,
from (le_nhds_iff_adhp_of_cauchy (cauchy_map hm.uniform_continuous this)).mp hx,
have g ⊓ nhds x ≠ ⊥,
from neq_bot_of_le_neq_bot this (inf_le_inf (assume s hs, ⟨s, hs, subset.refl _⟩) (le_refl _)),
⟨x, calc f ≤ g : by assumption
... ≤ nhds x : le_nhds_of_cauchy_adhp ‹cauchy g› this⟩⟩
/- separation space -/
section separation_space
local attribute [instance] separation_setoid
instance {α : Type u} [u : uniform_space α] : uniform_space (quotient (separation_setoid α)) :=
{ to_topological_space := u.to_topological_space.coinduced (λx, ⟦x⟧),
uniformity := map (λp:(α×α), (⟦p.1⟧, ⟦p.2⟧)) uniformity,
refl := assume s hs ⟨a, b⟩ (h : a = b),
have ∀a:α, (a, a) ∈ preimage (λ (p : α × α), (⟦p.fst⟧, ⟦p.snd⟧)) s,
from assume a, refl_mem_uniformity hs,
h ▸ quotient.induction_on a this,
symm := tendsto_map' $
by simp [prod.swap, (∘)]; exact tendsto_swap_uniformity.comp tendsto_map,
comp := calc (map (λ (p : α × α), (⟦p.fst⟧, ⟦p.snd⟧)) uniformity).lift' (λs, comp_rel s s) =
uniformity.lift' ((λs, comp_rel s s) ∘ image (λ (p : α × α), (⟦p.fst⟧, ⟦p.snd⟧))) :
map_lift'_eq2 $ monotone_comp_rel monotone_id monotone_id
... ≤ uniformity.lift' (image (λ (p : α × α), (⟦p.fst⟧, ⟦p.snd⟧)) ∘ (λs:set (α×α), comp_rel s (comp_rel s s))) :
lift'_mono' $ assume s hs ⟨a, b⟩ ⟨c, ⟨⟨a₁, a₂⟩, ha, a_eq⟩, ⟨⟨b₁, b₂⟩, hb, b_eq⟩⟩,
begin
simp at a_eq,
simp at b_eq,
have h : ⟦a₂⟧ = ⟦b₁⟧, { rw [a_eq.right, b_eq.left] },
have h : (a₂, b₁) ∈ separation_rel α := quotient.exact h,
simp [function.comp, set.image, comp_rel, and.comm, and.left_comm, and.assoc],
exact ⟨a₁, a_eq.left, b₂, b_eq.right, a₂, ha, b₁, h s hs, hb⟩
end
... = map (λp:(α×α), (⟦p.1⟧, ⟦p.2⟧)) (uniformity.lift' (λs:set (α×α), comp_rel s (comp_rel s s))) :
by rw [map_lift'_eq];
exact monotone_comp_rel monotone_id (monotone_comp_rel monotone_id monotone_id)
... ≤ map (λp:(α×α), (⟦p.1⟧, ⟦p.2⟧)) uniformity :
map_mono comp_le_uniformity3,
is_open_uniformity := assume s,
have ∀a, ⟦a⟧ ∈ s →
({p:α×α | p.1 = a → ⟦p.2⟧ ∈ s} ∈ (@uniformity α _).sets ↔
{p:α×α | p.1 ≈ a → ⟦p.2⟧ ∈ s} ∈ (@uniformity α _).sets),
from assume a ha,
⟨assume h,
let ⟨t, ht, hts⟩ := comp_mem_uniformity_sets h in
have hts : ∀{a₁ a₂}, (a, a₁) ∈ t → (a₁, a₂) ∈ t → ⟦a₂⟧ ∈ s,
from assume a₁ a₂ ha₁ ha₂, @hts (a, a₂) ⟨a₁, ha₁, ha₂⟩ rfl,
have ht' : ∀{a₁ a₂}, a₁ ≈ a₂ → (a₁, a₂) ∈ t,
from assume a₁ a₂ h, sInter_subset_of_mem ht h,
uniformity.sets_of_superset ht $ assume ⟨a₁, a₂⟩ h₁ h₂, hts (ht' $ setoid.symm h₂) h₁,
assume h, uniformity.sets_of_superset h $ by simp {contextual := tt}⟩,
begin
simp [topological_space.coinduced, u.is_open_uniformity, uniformity, forall_quotient_iff],
exact ⟨λh a ha, (this a ha).mp $ h a ha, λh a ha, (this a ha).mpr $ h a ha⟩
end }
lemma uniform_continuous_quotient_mk :
uniform_continuous (quotient.mk : α → quotient (separation_setoid α)) :=
le_refl _
lemma comap_quotient_le_uniformity : comap (λ (p : α × α), (⟦p.fst⟧, ⟦p.snd⟧)) uniformity ≤ uniformity :=
assume t' ht',
let ⟨t, ht, tt_t'⟩ := comp_mem_uniformity_sets ht' in
let ⟨s, hs, ss_t⟩ := comp_mem_uniformity_sets ht in
⟨(λp:α×α, (⟦p.1⟧, ⟦p.2⟧)) '' s,
(@uniformity α _).sets_of_superset hs $ assume x hx, ⟨x, hx, rfl⟩,
assume ⟨a₁, a₂⟩ ⟨⟨b₁, b₂⟩, hb, ab_eq⟩,
have ⟦b₁⟧ = ⟦a₁⟧ ∧ ⟦b₂⟧ = ⟦a₂⟧, from prod.mk.inj ab_eq,
have b₁ ≈ a₁ ∧ b₂ ≈ a₂, from and.imp quotient.exact quotient.exact this,
have ab₁ : (a₁, b₁) ∈ t, from (setoid.symm this.left) t ht,
have ba₂ : (b₂, a₂) ∈ s, from this.right s hs,
tt_t' ⟨b₁, show ((a₁, a₂).1, b₁) ∈ t, from ab₁,
ss_t ⟨b₂, show ((b₁, a₂).1, b₂) ∈ s, from hb, ba₂⟩⟩⟩
lemma comap_quotient_eq_uniformity : comap (λ (p : α × α), (⟦p.fst⟧, ⟦p.snd⟧)) uniformity = uniformity :=
le_antisymm comap_quotient_le_uniformity le_comap_map
lemma complete_space_separation [h : complete_space α] :
complete_space (quotient (separation_setoid α)) :=
⟨assume f, assume hf : cauchy f,
have cauchy (comap (λx, ⟦x⟧) f), from
cauchy_comap comap_quotient_le_uniformity hf $
comap_neq_bot_of_surj hf.left $ assume b, quotient.exists_rep _,
let ⟨x, (hx : comap (λx, ⟦x⟧) f ≤ nhds x)⟩ := complete_space.complete this in
⟨⟦x⟧, calc f ≤ map (λx, ⟦x⟧) (comap (λx, ⟦x⟧) f) : le_map_comap $ assume b, quotient.exists_rep _
... ≤ map (λx, ⟦x⟧) (nhds x) : map_mono hx
... ≤ _ : continuous_iff_tendsto.mp uniform_continuous_quotient_mk.continuous _⟩⟩
lemma separated_separation [h : complete_space α] : separated (quotient (separation_setoid α)) :=
set.ext $ assume ⟨a, b⟩, quotient.induction_on₂ a b $ assume a b,
⟨assume h,
have a ≈ b, from assume s hs,
have s ∈ (comap (λp:(α×α), (⟦p.1⟧, ⟦p.2⟧)) uniformity).sets,
from comap_quotient_le_uniformity hs,
let ⟨t, ht, hts⟩ := this in
hts begin dsimp, exact h t ht end,
show ⟦a⟧ = ⟦b⟧, from quotient.sound this,
assume heq : ⟦a⟧ = ⟦b⟧, assume h hs,
heq ▸ refl_mem_uniformity hs⟩
variables [uniform_space β] [uniform_space γ]
lemma uniform_continuous_quotient {f : quotient (separation_setoid α) → β}
(hf : uniform_continuous (λx, f ⟦x⟧)) : uniform_continuous f :=
hf
lemma uniform_continuous_quotient_lift
{f : α → β} {h : ∀a b, (a, b) ∈ separation_rel α → f a = f b}
(hf : uniform_continuous f) : uniform_continuous (λa, quotient.lift f h a) :=
uniform_continuous_quotient hf
lemma uniformity_quotient :
@uniformity (quotient (separation_setoid α)) _ = uniformity.map (λp:(α×α), (⟦p.1⟧, ⟦p.2⟧)) :=
rfl
lemma separated_of_uniform_continuous {f : α → β} (H : uniform_continuous f) {x y : α}
(h : x ≈ y) : f x ≈ f y :=
assume _ h', h _ (H h')
lemma eq_of_separated_of_uniform_continuous [separated β] {f : α → β} (H : uniform_continuous f) {x y : α}
(h : x ≈ y) : f x = f y :=
separated_def.1 (by apply_instance) _ _ $ separated_of_uniform_continuous H h
end separation_space
section uniform_extension
variables
[uniform_space β]
[uniform_space γ]
{e : β → α}
(h_e : uniform_embedding e)
(h_dense : ∀x, x ∈ closure (range e))
{f : β → γ}
(h_f : uniform_continuous f)
local notation `ψ` := (h_e.dense_embedding h_dense).extend f
lemma uniformly_extend_of_emb [cγ : complete_space γ] [sγ : separated γ] {b : β} :
ψ (e b) = f b :=
dense_embedding.extend_e_eq _ $ continuous_iff_tendsto.mp h_f.continuous b
lemma uniformly_extend_exists [complete_space γ] [sγ : separated γ] {a : α} :
∃c, tendsto f (comap e (nhds a)) (nhds c) :=
let de := (h_e.dense_embedding h_dense) in
have cauchy (nhds a), from cauchy_nhds,
have cauchy (comap e (nhds a)), from
cauchy_comap (le_of_eq h_e.right) this de.comap_nhds_neq_bot,
have cauchy (map f (comap e (nhds a))), from
cauchy_map h_f this,
complete_space.complete this
lemma uniformly_extend_spec [complete_space γ] [sγ : separated γ] {a : α} :
tendsto f (comap e (nhds a)) (nhds (ψ a)) :=
@lim_spec _ (id _) _ _ $ uniformly_extend_exists h_e h_dense h_f
lemma uniform_continuous_uniformly_extend [cγ : complete_space γ] [sγ : separated γ] :
uniform_continuous ψ :=
assume d hd,
let ⟨s, hs, hs_comp⟩ := (mem_lift'_sets $
monotone_comp_rel monotone_id $ monotone_comp_rel monotone_id monotone_id).mp (comp_le_uniformity3 hd) in
have h_pnt : ∀{a m}, m ∈ (nhds a).sets → ∃c, c ∈ f '' preimage e m ∧ (c, ψ a) ∈ s ∧ (ψ a, c) ∈ s,
from assume a m hm,
have nb : map f (comap e (nhds a)) ≠ ⊥,
from map_ne_bot (h_e.dense_embedding h_dense).comap_nhds_neq_bot,
have (f '' preimage e m) ∩ ({c | (c, ψ a) ∈ s } ∩ {c | (ψ a, c) ∈ s }) ∈ (map f (comap e (nhds a))).sets,
from inter_mem_sets (image_mem_map $ preimage_mem_comap $ hm)
(uniformly_extend_spec h_e h_dense h_f $ inter_mem_sets (mem_nhds_right _ hs) (mem_nhds_left _ hs)),
inhabited_of_mem_sets nb this,
have preimage (λp:β×β, (f p.1, f p.2)) s ∈ (@uniformity β _).sets,
from h_f hs,
have preimage (λp:β×β, (f p.1, f p.2)) s ∈ (comap (λx:β×β, (e x.1, e x.2)) uniformity).sets,
by rwa [h_e.right.symm] at this,
let ⟨t, ht, ts⟩ := this in
show preimage (λp:(α×α), (ψ p.1, ψ p.2)) d ∈ uniformity.sets,
from (@uniformity α _).sets_of_superset (interior_mem_uniformity ht) $
assume ⟨x₁, x₂⟩ hx_t,
have nhds (x₁, x₂) ≤ principal (interior t),
from is_open_iff_nhds.mp is_open_interior (x₁, x₂) hx_t,
have interior t ∈ (filter.prod (nhds x₁) (nhds x₂)).sets,
by rwa [nhds_prod_eq, le_principal_iff] at this,
let ⟨m₁, hm₁, m₂, hm₂, (hm : set.prod m₁ m₂ ⊆ interior t)⟩ := mem_prod_iff.mp this in
let ⟨a, ha₁, _, ha₂⟩ := h_pnt hm₁ in
let ⟨b, hb₁, hb₂, _⟩ := h_pnt hm₂ in
have set.prod (preimage e m₁) (preimage e m₂) ⊆ preimage (λp:(β×β), (f p.1, f p.2)) s,
from calc _ ⊆ preimage (λp:(β×β), (e p.1, e p.2)) (interior t) : preimage_mono hm
... ⊆ preimage (λp:(β×β), (e p.1, e p.2)) t : preimage_mono interior_subset
... ⊆ preimage (λp:(β×β), (f p.1, f p.2)) s : ts,
have set.prod (f '' preimage e m₁) (f '' preimage e m₂) ⊆ s,
from calc set.prod (f '' preimage e m₁) (f '' preimage e m₂) =
(λp:(β×β), (f p.1, f p.2)) '' (set.prod (preimage e m₁) (preimage e m₂)) : prod_image_image_eq
... ⊆ (λp:(β×β), (f p.1, f p.2)) '' preimage (λp:(β×β), (f p.1, f p.2)) s : mono_image this
... ⊆ s : image_subset_iff.mpr $ subset.refl _,
have (a, b) ∈ s, from @this (a, b) ⟨ha₁, hb₁⟩,
hs_comp $ show (ψ x₁, ψ x₂) ∈ comp_rel s (comp_rel s s),
from ⟨a, ha₂, ⟨b, this, hb₂⟩⟩
end uniform_extension
end uniform_space
end
/-- 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 Cauchy (α : Type u) [uniform_space α] : Type u := { f : filter α // cauchy f }
namespace Cauchy
section
parameters {α : Type u} [uniform_space α]
def gen (s : set (α × α)) : set (Cauchy α × Cauchy α) :=
{p | s ∈ (filter.prod (p.1.val) (p.2.val)).sets }
lemma monotone_gen : monotone gen :=
monotone_set_of $ assume p, @monotone_mem_sets (α×α) (filter.prod (p.1.val) (p.2.val))
private lemma symm_gen : map prod.swap (uniformity.lift' gen) ≤ uniformity.lift' gen :=
calc map prod.swap (uniformity.lift' gen) =
uniformity.lift' (λs:set (α×α), {p | s ∈ (filter.prod (p.2.val) (p.1.val)).sets }) :
begin
delta gen,
simp [map_lift'_eq, monotone_set_of, monotone_mem_sets,
function.comp, image_swap_eq_preimage_swap]
end
... ≤ uniformity.lift' gen :
uniformity_lift_le_swap
(monotone_comp (monotone_set_of $ assume p,
@monotone_mem_sets (α×α) ((filter.prod ((p.2).val) ((p.1).val)))) monotone_principal)
begin
have h := λ(p:Cauchy α×Cauchy α), @filter.prod_comm _ _ (p.2.val) (p.1.val),
simp [function.comp, h],
exact le_refl _
end
private lemma comp_rel_gen_gen_subset_gen_comp_rel {s t : set (α×α)} : comp_rel (gen s) (gen t) ⊆
(gen (comp_rel s t) : set (Cauchy α × Cauchy α)) :=
assume ⟨f, g⟩ ⟨h, h₁, h₂⟩,
let ⟨t₁, (ht₁ : t₁ ∈ f.val.sets), t₂, (ht₂ : t₂ ∈ h.val.sets), (h₁ : set.prod t₁ t₂ ⊆ s)⟩ :=
mem_prod_iff.mp h₁ in
let ⟨t₃, (ht₃ : t₃ ∈ h.val.sets), t₄, (ht₄ : t₄ ∈ g.val.sets), (h₂ : set.prod t₃ t₄ ⊆ t)⟩ :=
mem_prod_iff.mp h₂ in
have t₂ ∩ t₃ ∈ h.val.sets,
from inter_mem_sets ht₂ ht₃,
let ⟨x, xt₂, xt₃⟩ :=
inhabited_of_mem_sets (h.property.left) this in
(filter.prod f.val g.val).sets_of_superset
(prod_mem_prod ht₁ ht₄)
(assume ⟨a, b⟩ ⟨(ha : a ∈ t₁), (hb : b ∈ t₄)⟩,
⟨x,
h₁ (show (a, x) ∈ set.prod t₁ t₂, from ⟨ha, xt₂⟩),
h₂ (show (x, b) ∈ set.prod t₃ t₄, from ⟨xt₃, hb⟩)⟩)
private lemma comp_gen :
(uniformity.lift' gen).lift' (λs, comp_rel s s) ≤ uniformity.lift' gen :=
calc (uniformity.lift' gen).lift' (λs, comp_rel s s) =
uniformity.lift' (λs, comp_rel (gen s) (gen s)) :
begin
rw [lift'_lift'_assoc],
exact monotone_gen,
exact (monotone_comp_rel monotone_id monotone_id)
end
... ≤ uniformity.lift' (λs, gen $ comp_rel s s) :
lift'_mono' $ assume s hs, comp_rel_gen_gen_subset_gen_comp_rel
... = (uniformity.lift' $ λs:set(α×α), comp_rel s s).lift' gen :
begin
rw [lift'_lift'_assoc],
exact (monotone_comp_rel monotone_id monotone_id),
exact monotone_gen
end
... ≤ uniformity.lift' gen : lift'_mono comp_le_uniformity (le_refl _)
instance completion_space : uniform_space (Cauchy α) :=
uniform_space.of_core
{ uniformity := uniformity.lift' gen,
refl := principal_le_lift' $ assume s hs ⟨a, b⟩ (a_eq_b : a = b),
a_eq_b ▸ a.property.right hs,
symm := symm_gen,
comp := comp_gen }
theorem mem_uniformity {s : set (Cauchy α × Cauchy α)} :
s ∈ (@uniformity (Cauchy α) _).sets ↔ ∃ t ∈ (@uniformity α _).sets, gen t ⊆ s :=
mem_lift'_sets monotone_gen
theorem mem_uniformity' {s : set (Cauchy α × Cauchy α)} :
s ∈ (@uniformity (Cauchy α) _).sets ↔ ∃ t ∈ (@uniformity α _).sets,
∀ f g : Cauchy α, t ∈ (filter.prod f.1 g.1).sets → (f, g) ∈ s :=
mem_uniformity.trans $ bex_congr $ λ t h, prod.forall
/-- Embedding of `α` into its completion -/
def pure_cauchy (a : α) : Cauchy α :=
⟨pure a, cauchy_pure⟩
lemma uniform_embedding_pure_cauchy : uniform_embedding (pure_cauchy : α → Cauchy α) :=
⟨assume a₁ a₂ h,
have (pure_cauchy a₁).val = (pure_cauchy a₂).val, from congr_arg _ h,
have {a₁} = ({a₂} : set α),
from principal_eq_iff_eq.mp this,
by simp at this; assumption,
have (preimage (λ (x : α × α), (pure_cauchy (x.fst), pure_cauchy (x.snd))) ∘ gen) = id,
from funext $ assume s, set.ext $ assume ⟨a₁, a₂⟩,
by simp [preimage, gen, pure_cauchy, prod_principal_principal],
calc comap (λ (x : α × α), (pure_cauchy (x.fst), pure_cauchy (x.snd))) (uniformity.lift' gen)
= uniformity.lift' (preimage (λ (x : α × α), (pure_cauchy (x.fst), pure_cauchy (x.snd))) ∘ gen) :
comap_lift'_eq monotone_gen
... = uniformity : by simp [this]⟩
lemma pure_cauchy_dense : ∀x, x ∈ closure (range pure_cauchy) :=
assume f,
have h_ex : ∀s∈(@uniformity (Cauchy α) _).sets, ∃y:α, (f, pure_cauchy y) ∈ s, from
assume s hs,
let ⟨t'', ht''₁, (ht''₂ : gen t'' ⊆ s)⟩ := (mem_lift'_sets monotone_gen).mp hs in
let ⟨t', ht'₁, ht'₂⟩ := comp_mem_uniformity_sets ht''₁ in
have t' ∈ (filter.prod (f.val) (f.val)).sets,
from f.property.right ht'₁,
let ⟨t, ht, (h : set.prod t t ⊆ t')⟩ := mem_prod_same_iff.mp this in
let ⟨x, (hx : x ∈ t)⟩ := inhabited_of_mem_sets f.property.left ht in
have t'' ∈ (filter.prod f.val (pure x)).sets,
from mem_prod_iff.mpr ⟨t, ht, {y:α | (x, y) ∈ t'},
assume y, begin simp, intro h, simp [h], exact refl_mem_uniformity ht'₁ end,
assume ⟨a, b⟩ ⟨(h₁ : a ∈ t), (h₂ : (x, b) ∈ t')⟩,
ht'₂ $ prod_mk_mem_comp_rel (@h (a, x) ⟨h₁, hx⟩) h₂⟩,
⟨x, ht''₂ $ by dsimp [gen]; exact this⟩,
begin
simp [closure_eq_nhds, nhds_eq_uniformity, lift'_inf_principal_eq, set.inter_comm],
exact (lift'_neq_bot_iff $ monotone_inter monotone_const monotone_preimage).mpr
(assume s hs,
let ⟨y, hy⟩ := h_ex s hs in
have pure_cauchy y ∈ range pure_cauchy ∩ {y : Cauchy α | (f, y) ∈ s},
from ⟨mem_range_self y, hy⟩,
ne_empty_of_mem this)
end
instance : complete_space (Cauchy α) :=
complete_space_extension
uniform_embedding_pure_cauchy
pure_cauchy_dense $
assume f hf,
let f' : Cauchy α := ⟨f, hf⟩ in
have map pure_cauchy f ≤ uniformity.lift' (preimage (prod.mk f')),
from le_lift' $ assume s hs,
let ⟨t, ht₁, (ht₂ : gen t ⊆ s)⟩ := (mem_lift'_sets monotone_gen).mp hs in
let ⟨t', ht', (h : set.prod t' t' ⊆ t)⟩ := mem_prod_same_iff.mp (hf.right ht₁) in
have t' ⊆ { y : α | (f', pure_cauchy y) ∈ gen t },
from assume x hx, (filter.prod f (pure x)).sets_of_superset (prod_mem_prod ht' $ mem_pure hx) h,
f.sets_of_superset ht' $ subset.trans this (preimage_mono ht₂),
⟨f', by simp [nhds_eq_uniformity]; assumption⟩
end
section
local attribute [instance] separation_setoid
lemma injective_separated_pure_cauchy {α : Type*} [uniform_space α] [s : separated α] :
function.injective (λa:α, ⟦pure_cauchy a⟧) | a b h :=
separated_def.1 s _ _ $ assume s hs,
let ⟨t, ht, hts⟩ :=
by rw [← (@uniform_embedding_pure_cauchy α _).right, filter.mem_comap_sets] at hs; exact hs in
have (pure_cauchy a, pure_cauchy b) ∈ t, from quotient.exact h t ht,
@hts (a, b) this
end
end Cauchy
instance nonempty_Cauchy {α : Type u} [h : nonempty α] [uniform_space α] : nonempty (Cauchy α) :=
h.rec_on $ assume a, nonempty.intro $ Cauchy.pure_cauchy a
instance inhabited_Cauchy {α : Type u} [inhabited α] [uniform_space α] : inhabited (Cauchy α) :=
⟨Cauchy.pure_cauchy $ default α⟩
section constructions
variables {α : Type*} {β : Type*} {γ : Type*} {δ : Type*} {ι : Sort*}
instance : partial_order (uniform_space α) :=
{ le := λt s, s.uniformity ≤ t.uniformity,
le_antisymm := assume t s h₁ h₂, uniform_space_eq $ le_antisymm h₂ h₁,
le_refl := assume t, le_refl _,
le_trans := assume a b c h₁ h₂, @le_trans _ _ c.uniformity b.uniformity a.uniformity h₂ h₁ }
instance : has_Sup (uniform_space α) :=
⟨assume s, uniform_space.of_core {
uniformity := (⨅u∈s, @uniformity α u),
refl := le_infi $ assume u, le_infi $ assume hu, u.refl,
symm := le_infi $ assume u, le_infi $ assume hu,
le_trans (map_mono $ infi_le_of_le _ $ infi_le _ hu) u.symm,
comp := le_infi $ assume u, le_infi $ assume hu,
le_trans (lift'_mono (infi_le_of_le _ $ infi_le _ hu) $ le_refl _) u.comp }⟩
private lemma le_Sup {tt : set (uniform_space α)} {t : uniform_space α} (h : t ∈ tt) :
t ≤ Sup tt :=
show (⨅u∈tt, @uniformity α u) ≤ t.uniformity,
from infi_le_of_le t $ infi_le _ h
private lemma Sup_le {tt : set (uniform_space α)} {t : uniform_space α} (h : ∀t'∈tt, t' ≤ t) :
Sup tt ≤ t :=
show t.uniformity ≤ (⨅u∈tt, @uniformity α u),
from le_infi $ assume t', le_infi $ assume ht', h t' ht'
instance : has_bot (uniform_space α) :=
⟨uniform_space.of_core { uniformity := ⊤, refl := le_top, symm := le_top, comp := le_top }⟩
instance : has_top (uniform_space α) :=
⟨{ to_topological_space := ⊤,
uniformity := principal id_rel,
refl := le_refl _,
symm := by simp [tendsto]; apply subset.refl,
comp :=
begin
rw [lift'_principal], {simp},
exact monotone_comp_rel monotone_id monotone_id
end,
is_open_uniformity := by simp [is_open_fold, subset_def, id_rel] {contextual := tt } } ⟩
instance : complete_lattice (uniform_space α) :=
{ sup := λa b, Sup {a, b},
le_sup_left := assume a b, le_Sup $ by simp,
le_sup_right := assume a b, le_Sup $ by simp,
sup_le := assume a b c h₁ h₂, Sup_le $ assume t',
begin simp, intro h, cases h with h h, repeat { subst h; assumption } end,
inf := λa b, Sup {x | x ≤ a ∧ x ≤ b},
le_inf := assume a b c h₁ h₂, le_Sup ⟨h₁, h₂⟩,
inf_le_left := assume a b, Sup_le $ assume x ⟨ha, hb⟩, ha,
inf_le_right := assume a b, Sup_le $ assume x ⟨ha, hb⟩, hb,
top := ⊤,
le_top := assume u, u.refl,
bot := ⊥,
bot_le := assume a, show a.uniformity ≤ ⊤, from le_top,
Sup := Sup,
le_Sup := assume s u, le_Sup,
Sup_le := assume s u, Sup_le,
Inf := λtt, Sup {t | ∀t'∈tt, t ≤ t'},
le_Inf := assume s a hs, le_Sup hs,
Inf_le := assume s a ha, Sup_le $ assume u hs, hs _ ha,
..uniform_space.partial_order }
lemma supr_uniformity {ι : Sort*} {u : ι → uniform_space α} :
(supr u).uniformity = (⨅i, (u i).uniformity) :=
show (⨅a (h : ∃i:ι, a = u i), a.uniformity) = _, from
le_antisymm
(le_infi $ assume i, infi_le_of_le (u i) $ infi_le _ ⟨i, rfl⟩)
(le_infi $ assume a, le_infi $ assume ⟨i, (ha : a = u i)⟩, ha.symm ▸ infi_le _ _)
lemma sup_uniformity {u v : uniform_space α} :
(u ⊔ v).uniformity = u.uniformity ⊓ v.uniformity :=
have (u ⊔ v) = (⨆i (h : i = u ∨ i = v), i), by simp [supr_or, supr_sup_eq],
calc (u ⊔ v).uniformity = ((⨆i (h : i = u ∨ i = v), i) : uniform_space α).uniformity : by rw [this]
... = _ : by simp [supr_uniformity, infi_or, infi_inf_eq]
instance inhabited_uniform_space : inhabited (uniform_space α) := ⟨⊤⟩
/-- 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`. -/
def uniform_space.comap (f : α → β) (u : uniform_space β) : uniform_space α :=
{ uniformity := u.uniformity.comap (λp:α×α, (f p.1, f p.2)),
to_topological_space := u.to_topological_space.induced f,
refl := le_trans (by simp; exact assume ⟨a, b⟩ (h : a = b), h ▸ rfl) (comap_mono u.refl),
symm := by simp [tendsto_comap_iff, prod.swap, (∘)]; exact tendsto_comap.comp tendsto_swap_uniformity,
comp := le_trans
begin
rw [comap_lift'_eq, comap_lift'_eq2],
exact (lift'_mono' $ assume s hs ⟨a₁, a₂⟩ ⟨x, h₁, h₂⟩, ⟨f x, h₁, h₂⟩),
repeat { exact monotone_comp_rel monotone_id monotone_id }
end
(comap_mono u.comp),
is_open_uniformity := λ s, begin
change (@is_open α (u.to_topological_space.induced f) s ↔ _),
simp [is_open_iff_nhds, nhds_induced_eq_comap, mem_nhds_uniformity_iff, filter.comap, and_comm],
refine ball_congr (λ x hx, ⟨_, _⟩),
{ rintro ⟨t, hts, ht⟩, refine ⟨_, ht, _⟩,
rintro ⟨x₁, x₂⟩ h rfl, exact hts (h rfl) },
{ rintro ⟨t, ht, hts⟩,
exact ⟨{y | (f x, y) ∈ t}, λ y hy, @hts (x, y) hy rfl,
mem_nhds_uniformity_iff.1 $ mem_nhds_left _ ht⟩ }
end }
lemma uniform_space_comap_id {α : Type*} : uniform_space.comap (id : α → α) = id :=
by ext u ; dsimp [uniform_space.comap] ; rw [prod.id_prod, filter.comap_id]
lemma uniform_space.comap_comap_comp {α β γ} [uγ : uniform_space γ] {f : α → β} {g : β → γ} :
uniform_space.comap (g ∘ f) uγ = uniform_space.comap f (uniform_space.comap g uγ) :=
by ext ; dsimp [uniform_space.comap] ; rw filter.comap_comap_comp
lemma uniform_continuous_iff {α β} [uα : uniform_space α] [uβ : uniform_space β] (f : α → β) :
uniform_continuous f ↔ uβ.comap f ≤ uα :=
filter.map_le_iff_le_comap
lemma uniform_continuous_comap {f : α → β} [u : uniform_space β] :
@uniform_continuous α β (uniform_space.comap f u) u f :=
tendsto_comap
theorem to_topological_space_comap {f : α → β} {u : uniform_space β} :
@uniform_space.to_topological_space _ (uniform_space.comap f u) =
topological_space.induced f (@uniform_space.to_topological_space β u) :=
eq_of_nhds_eq_nhds $ assume a,
begin
simp [nhds_induced_eq_comap, nhds_eq_uniformity, nhds_eq_uniformity],
change comap f (uniformity.lift' (preimage (λb, (f a, b)))) =
(u.uniformity.comap (λp:α×α, (f p.1, f p.2))).lift' (preimage (λa', (a, a'))),
rw [comap_lift'_eq monotone_preimage, comap_lift'_eq2 monotone_preimage],
exact rfl
end
lemma uniform_continuous_comap' {f : γ → β} {g : α → γ} [v : uniform_space β] [u : uniform_space α]
(h : uniform_continuous (f ∘ g)) : @uniform_continuous α γ u (uniform_space.comap f v) g :=
tendsto_comap_iff.2 h
lemma to_topological_space_mono {u₁ u₂ : uniform_space α} (h : u₁ ≤ u₂) :
@uniform_space.to_topological_space _ u₁ ≤ @uniform_space.to_topological_space _ u₂ :=
le_of_nhds_le_nhds $ assume a,
by rw [@nhds_eq_uniformity α u₁ a, @nhds_eq_uniformity α u₂ a]; exact (lift'_mono h $ le_refl _)
lemma to_topological_space_top : @uniform_space.to_topological_space α ⊤ = ⊤ := rfl
lemma to_topological_space_bot : @uniform_space.to_topological_space α ⊥ = ⊥ :=
bot_unique $ assume s hs, classical.by_cases
(assume : s = ∅, this.symm ▸ @is_open_empty _ ⊥)
(assume : s ≠ ∅,
let ⟨x, hx⟩ := exists_mem_of_ne_empty this in
have s = univ, from top_unique $ assume y hy, hs x hx (x, y) rfl,
this.symm ▸ @is_open_univ _ ⊥)
lemma to_topological_space_supr {ι : Sort*} {u : ι → uniform_space α} :
@uniform_space.to_topological_space α (supr u) = (⨆i, @uniform_space.to_topological_space α (u i)) :=
classical.by_cases
(assume h : nonempty ι,
eq_of_nhds_eq_nhds $ assume a,
begin
rw [nhds_supr, nhds_eq_uniformity],
change _ = (supr u).uniformity.lift' (preimage $ prod.mk a),
begin
rw [supr_uniformity, lift'_infi],
exact (congr_arg _ $ funext $ assume i, @nhds_eq_uniformity α (u i) a),
exact h,
exact assume a b, rfl
end
end)
(assume : ¬ nonempty ι,
le_antisymm
(have supr u = ⊥, from bot_unique $ supr_le $ assume i, (this ⟨i⟩).elim,
have @uniform_space.to_topological_space _ (supr u) = ⊥,
from this.symm ▸ to_topological_space_bot,
this.symm ▸ bot_le)
(supr_le $ assume i, to_topological_space_mono $ le_supr _ _))
lemma to_topological_space_Sup {s : set (uniform_space α)} :
@uniform_space.to_topological_space α (Sup s) = (⨆i∈s, @uniform_space.to_topological_space α i) :=
begin
rw [Sup_eq_supr, to_topological_space_supr],
apply congr rfl,
funext x,
exact to_topological_space_supr
end
lemma to_topological_space_sup {u v : uniform_space α} :
@uniform_space.to_topological_space α (u ⊔ v) =
@uniform_space.to_topological_space α u ⊔ @uniform_space.to_topological_space α v :=
ord_continuous_sup $ assume s, to_topological_space_Sup
instance : uniform_space empty := ⊤
instance : uniform_space unit := ⊤
instance : uniform_space bool := ⊤
instance : uniform_space ℕ := ⊤
instance : uniform_space ℤ := ⊤
instance {p : α → Prop} [t : uniform_space α] : uniform_space (subtype p) :=
uniform_space.comap subtype.val t
lemma uniformity_subtype {p : α → Prop} [t : uniform_space α] :
(@uniformity (subtype p) _) = comap (λq:subtype p × subtype p, (q.1.1, q.2.1)) uniformity :=
rfl
lemma uniform_continuous_subtype_val {p : α → Prop} [uniform_space α] :
uniform_continuous (subtype.val : {a : α // p a} → α) :=
uniform_continuous_comap
lemma uniform_continuous_subtype_mk {p : α → Prop} [uniform_space α] [uniform_space β]
{f : β → α} (hf : uniform_continuous f) (h : ∀x, p (f x)) :
uniform_continuous (λx, ⟨f x, h x⟩ : β → subtype p) :=
uniform_continuous_comap' hf
lemma tendsto_of_uniform_continuous_subtype
[uniform_space α] [uniform_space β] {f : α → β} {s : set α} {a : α}
(hf : uniform_continuous (λx:s, f x.val)) (ha : s ∈ (nhds a).sets) :
tendsto f (nhds a) (nhds (f a)) :=
by rw [(@map_nhds_subtype_val_eq α _ s a (mem_of_nhds ha) ha).symm]; exact
tendsto_map' (continuous_iff_tendsto.mp hf.continuous _)
instance [u₁ : uniform_space α] [u₂ : uniform_space β] : uniform_space (α × β) :=
uniform_space.of_core_eq
(u₁.comap prod.fst ⊔ u₂.comap prod.snd).to_core
prod.topological_space
(calc prod.topological_space = (u₁.comap prod.fst ⊔ u₂.comap prod.snd).to_topological_space :
by rw [to_topological_space_sup, to_topological_space_comap, to_topological_space_comap]; refl
... = _ : by rw [uniform_space.to_core_to_topological_space])
theorem uniformity_prod [uniform_space α] [uniform_space β] : @uniformity (α × β) _ =
uniformity.comap (λp:(α × β) × α × β, (p.1.1, p.2.1)) ⊓
uniformity.comap (λp:(α × β) × α × β, (p.1.2, p.2.2)) :=
sup_uniformity
lemma uniform_embedding_subtype_emb {α : Type*} {β : Type*} [uniform_space α] [uniform_space β]
(p : α → Prop) {e : α → β} (ue : uniform_embedding e) (de : dense_embedding e) :
uniform_embedding (de.subtype_emb p) :=
⟨(de.subtype p).inj,
by simp [comap_comap_comp, (∘), dense_embedding.subtype_emb, uniformity_subtype, ue.right.symm]⟩
lemma uniform_extend_subtype {α : Type*} {β : Type*} {γ : Type*}
[uniform_space α] [uniform_space β] [uniform_space γ] [complete_space γ]
[inhabited γ] [separated γ]
{p : α → Prop} {e : α → β} {f : α → γ} {b : β} {s : set α}
(hf : uniform_continuous (λx:subtype p, f x.val))
(he : uniform_embedding e) (hd : ∀x:β, x ∈ closure (range e))
(hb : closure (e '' s) ∈ (nhds b).sets) (hs : is_closed s) (hp : ∀x∈s, p x) :
∃c, tendsto f (comap e (nhds b)) (nhds c) :=
have de : dense_embedding e,
from he.dense_embedding hd,
have de' : dense_embedding (de.subtype_emb p),
by exact de.subtype p,
have ue' : uniform_embedding (de.subtype_emb p),
from uniform_embedding_subtype_emb _ he de,
have b ∈ closure (e '' {x | p x}),
from (closure_mono $ mono_image $ hp) (mem_of_nhds hb),
let ⟨c, (hc : tendsto (f ∘ subtype.val) (comap (de.subtype_emb p) (nhds ⟨b, this⟩)) (nhds c))⟩ :=
uniformly_extend_exists ue' de'.dense hf in
begin
rw [nhds_subtype_eq_comap] at hc,
simp [comap_comap_comp] at hc,
change (tendsto (f ∘ @subtype.val α p) (comap (e ∘ @subtype.val α p) (nhds b)) (nhds c)) at hc,
rw [←comap_comap_comp] at hc,
existsi c,
apply tendsto_comap'' s _ _ hc,
exact ⟨_, hb, assume x,
begin
change e x ∈ (closure (e '' s)) → x ∈ s,
rw [←closure_induced, closure_eq_nhds],
dsimp,
rw [nhds_induced_eq_comap, de.induced],
change x ∈ {x | nhds x ⊓ principal s ≠ ⊥} → x ∈ s,
rw [←closure_eq_nhds, closure_eq_of_is_closed hs],
exact id,
exact de.inj
end⟩,
exact (assume x hx, ⟨⟨x, hp x hx⟩, rfl⟩)
end
/- 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 -/
lemma uniformity_prod_eq_prod [uniform_space α] [uniform_space β] :
@uniformity (α×β) _ =
map (λp:(α×α)×(β×β), ((p.1.1, p.2.1), (p.1.2, p.2.2))) (filter.prod uniformity uniformity) :=
have map (λp:(α×α)×(β×β), ((p.1.1, p.2.1), (p.1.2, p.2.2))) =
comap (λp:(α×β)×(α×β), ((p.1.1, p.2.1), (p.1.2, p.2.2))),
from funext $ assume f, map_eq_comap_of_inverse
(funext $ assume ⟨⟨_, _⟩, ⟨_, _⟩⟩, rfl) (funext $ assume ⟨⟨_, _⟩, ⟨_, _⟩⟩, rfl),
by rw [this, uniformity_prod, filter.prod, comap_inf, comap_comap_comp, comap_comap_comp]
lemma mem_uniform_prod [t₁ : uniform_space α] [t₂ : uniform_space β] {a : set (α × α)} {b : set (β × β)}
(ha : a ∈ (@uniformity α _).sets) (hb : b ∈ (@uniformity β _).sets) :
{p:(α×β)×(α×β) | (p.1.1, p.2.1) ∈ a ∧ (p.1.2, p.2.2) ∈ b } ∈ (@uniformity (α × β) _).sets :=
by rw [uniformity_prod]; exact inter_mem_inf_sets (preimage_mem_comap ha) (preimage_mem_comap hb)
lemma tendsto_prod_uniformity_fst [uniform_space α] [uniform_space β] :
tendsto (λp:(α×β)×(α×β), (p.1.1, p.2.1)) uniformity uniformity :=
le_trans (map_mono (@le_sup_left (uniform_space (α×β)) _ _ _)) map_comap_le
lemma tendsto_prod_uniformity_snd [uniform_space α] [uniform_space β] :
tendsto (λp:(α×β)×(α×β), (p.1.2, p.2.2)) uniformity uniformity :=
le_trans (map_mono (@le_sup_right (uniform_space (α×β)) _ _ _)) map_comap_le
lemma uniform_continuous_fst [uniform_space α] [uniform_space β] : uniform_continuous (λp:α×β, p.1) :=
tendsto_prod_uniformity_fst
lemma uniform_continuous_snd [uniform_space α] [uniform_space β] : uniform_continuous (λp:α×β, p.2) :=
tendsto_prod_uniformity_snd
variables [uniform_space α] [uniform_space β] [uniform_space γ]
lemma uniform_continuous.prod_mk
{f₁ : α → β} {f₂ : α → γ} (h₁ : uniform_continuous f₁) (h₂ : uniform_continuous f₂) :
uniform_continuous (λa, (f₁ a, f₂ a)) :=
by rw [uniform_continuous, uniformity_prod]; exact
tendsto_inf.2 ⟨tendsto_comap_iff.2 h₁, tendsto_comap_iff.2 h₂⟩
lemma uniform_continuous.prod_mk_left {f : α × β → γ} (h : uniform_continuous f) (b) :
uniform_continuous (λ a, f (a,b)) :=
uniform_continuous.comp (uniform_continuous.prod_mk uniform_continuous_id uniform_continuous_const) h
lemma uniform_continuous.prod_mk_right {f : α × β → γ} (h : uniform_continuous f) (a) :
uniform_continuous (λ b, f (a,b)) :=
uniform_continuous.comp (uniform_continuous.prod_mk uniform_continuous_const uniform_continuous_id) h
instance complete_space.prod [complete_space α] [complete_space β] : complete_space (α × β) :=
{ complete := λ f hf,
let ⟨x1, hx1⟩ := complete_space.complete $ cauchy_map uniform_continuous_fst hf in
let ⟨x2, hx2⟩ := complete_space.complete $ cauchy_map uniform_continuous_snd hf in
⟨(x1, x2), by rw [nhds_prod_eq, filter.prod_def];
from filter.le_lift (λ s hs, filter.le_lift' $ λ t ht,
have H1 : prod.fst ⁻¹' s ∈ f.sets := hx1 hs,
have H2 : prod.snd ⁻¹' t ∈ f.sets := hx2 ht,
filter.inter_mem_sets H1 H2)⟩ }
lemma uniform_embedding.prod {α' : Type*} {β' : Type*}
[uniform_space α] [uniform_space β] [uniform_space α'] [uniform_space β']
{e₁ : α → α'} {e₂ : β → β'} (h₁ : uniform_embedding e₁) (h₂ : uniform_embedding e₂) :
uniform_embedding (λp:α×β, (e₁ p.1, e₂ p.2)) :=
⟨assume ⟨a₁, b₁⟩ ⟨a₂, b₂⟩,
by simp [prod.mk.inj_iff]; exact assume eq₁ eq₂, ⟨h₁.left eq₁, h₂.left eq₂⟩,
by simp [(∘), uniformity_prod, h₁.right.symm, h₂.right.symm, comap_inf, comap_comap_comp]⟩
lemma to_topological_space_prod [u : uniform_space α] [v : uniform_space β] :
@uniform_space.to_topological_space (α × β) prod.uniform_space =
@prod.topological_space α β u.to_topological_space v.to_topological_space := rfl
lemma to_topological_space_subtype [u : uniform_space α] {p : α → Prop} :
@uniform_space.to_topological_space (subtype p) subtype.uniform_space =
@subtype.topological_space α p u.to_topological_space := rfl
section separation_space
local attribute [instance] separation_setoid
lemma uniform_continuous_quotient_lift₂ [uniform_space γ]
{f : α → β → γ} {h : ∀a c b d, (a, b) ∈ separation_rel α → (c, d) ∈ separation_rel β → f a c = f b d}
(hf : uniform_continuous (λp:α×β, f p.1 p.2)) :
uniform_continuous (λp:_×_, quotient.lift₂ f h p.1 p.2) :=
begin
rw [uniform_continuous, uniformity_prod_eq_prod, uniformity_quotient, uniformity_quotient,
filter.prod_map_map_eq, filter.tendsto_map'_iff, filter.tendsto_map'_iff],
rwa [uniform_continuous, uniformity_prod_eq_prod, filter.tendsto_map'_iff] at hf
end
lemma separation_prod {a₁ a₂ : α} {b₁ b₂ : β} : (a₁, b₁) ≈ (a₂, b₂) ↔ a₁ ≈ a₂ ∧ b₁ ≈ b₂ :=
begin
split ; intro h,
{ exact ⟨separated_of_uniform_continuous uniform_continuous_fst h,
separated_of_uniform_continuous uniform_continuous_snd h⟩ },
{ rcases h with ⟨eqv_α, eqv_β⟩,
intros r r_in,
rw uniformity_prod at r_in,
rcases r_in with ⟨t_α, ⟨r_α, r_α_in, h_α⟩, t_β, ⟨r_β, r_β_in, h_β⟩, H⟩,
let p_α := λ (p : (α × β) × α × β), ((p.fst).fst, (p.snd).fst),
let p_β := λ (p : (α × β) × α × β), ((p.fst).snd, (p.snd).snd),
have key_α : p_α ((a₁, b₁), (a₂, b₂)) ∈ r_α, by simp[p_α, eqv_α r_α r_α_in],
have key_β : p_β ((a₁, b₁), (a₂, b₂)) ∈ r_β, by simp[p_β, eqv_β r_β r_β_in],
exact H ⟨h_α key_α, h_β key_β⟩ },
end
instance separated.prod [separated α] [separated β] : separated (α × β) :=
separated_def.2 $ assume x y H, prod.ext
(eq_of_separated_of_uniform_continuous uniform_continuous_fst H)
(eq_of_separated_of_uniform_continuous uniform_continuous_snd H)
end separation_space
end constructions
lemma lebesgue_number_lemma {α : Type u} [uniform_space α] {s : set α} {ι} {c : ι → set α}
(hs : compact s) (hc₁ : ∀ i, is_open (c i)) (hc₂ : s ⊆ ⋃ i, c i) :
∃ n ∈ (@uniformity α _).sets, ∀ x ∈ s, ∃ i, {y | (x, y) ∈ n} ⊆ c i :=
begin
let u := λ n, {x | ∃ i (m ∈ (@uniformity α _).sets), {y | (x, y) ∈ comp_rel m n} ⊆ c i},
have hu₁ : ∀ n ∈ (@uniformity α _).sets, is_open (u n),
{ refine λ n hn, is_open_uniformity.2 _,
rintro x ⟨i, m, hm, h⟩,
rcases comp_mem_uniformity_sets hm with ⟨m', hm', mm'⟩,
apply uniformity.sets_of_superset hm',
rintros ⟨x, y⟩ hp rfl,
refine ⟨i, m', hm', λ z hz, h (monotone_comp_rel monotone_id monotone_const mm' _)⟩,
dsimp at hz ⊢, rw comp_rel_assoc,
exact ⟨y, hp, hz⟩ },
have hu₂ : s ⊆ ⋃ n ∈ (@uniformity α _).sets, u n,
{ intros x hx,
rcases mem_Union.1 (hc₂ hx) with ⟨i, h⟩,
rcases comp_mem_uniformity_sets (is_open_uniformity.1 (hc₁ i) x h) with ⟨m', hm', mm'⟩,
exact mem_bUnion hm' ⟨i, _, hm', λ y hy, mm' hy rfl⟩ },
rcases compact_elim_finite_subcover_image hs hu₁ hu₂ with ⟨b, bu, b_fin, b_cover⟩,
refine ⟨_, Inter_mem_sets b_fin bu, λ x hx, _⟩,
rcases mem_bUnion_iff.1 (b_cover hx) with ⟨n, bn, i, m, hm, h⟩,
refine ⟨i, λ y hy, h _⟩,
exact prod_mk_mem_comp_rel (refl_mem_uniformity hm) (bInter_subset_of_mem bn hy)
end
lemma lebesgue_number_lemma_sUnion {α : Type u} [uniform_space α] {s : set α} {c : set (set α)}
(hs : compact s) (hc₁ : ∀ t ∈ c, is_open t) (hc₂ : s ⊆ ⋃₀ c) :
∃ n ∈ (@uniformity α _).sets, ∀ x ∈ s, ∃ t ∈ c, ∀ y, (x, y) ∈ n → y ∈ t :=
by rw sUnion_eq_Union at hc₂;
simpa using lebesgue_number_lemma hs (by simpa) hc₂
|
6460a4d8023b24cb8e53203a11f4422ababb194b | b7f22e51856f4989b970961f794f1c435f9b8f78 | /tests/lean/run/blast_rec_eq.lean | 35354ceb66d7f14ad0415d52b716441a6dc41a15 | [
"Apache-2.0"
] | permissive | soonhokong/lean | cb8aa01055ffe2af0fb99a16b4cda8463b882cd1 | 38607e3eb57f57f77c0ac114ad169e9e4262e24f | refs/heads/master | 1,611,187,284,081 | 1,450,766,737,000 | 1,476,122,547,000 | 11,513,992 | 2 | 0 | null | 1,401,763,102,000 | 1,374,182,235,000 | C++ | UTF-8 | Lean | false | false | 402 | lean | open nat
lemma addz [simp] : ∀ a : nat, a + 0 = a := sorry
lemma zadd [simp] : ∀ a : nat, 0 + a = a := sorry
lemma adds [simp] : ∀ a b : nat, a + succ b = succ (a + b) := sorry
lemma sadd [simp] : ∀ a b : nat, succ a + b = succ (a + b) := sorry
definition comm : ∀ a b : nat, a + b = b + a
| a 0 := by simp
| a (succ n) :=
assert a + n = n + a, from !comm,
by simp
|
dd73aa562d84ac4df669c66b43a6f363f60c054e | 2c41ae31b2b771ad5646ad880201393f5269a7f0 | /Lean/Qualities/CyberCapable.lean | 7add5735fc9e649fb4ae4bd0be7aa5dc847570d6 | [] | no_license | kevinsullivan/Boehm | 926f25bc6f1a8b6bd47d333d936fdfc278228312 | 55208395bff20d48a598b7fa33a4d55a2447a9cf | refs/heads/master | 1,586,127,134,302 | 1,488,252,326,000 | 1,488,252,326,000 | 32,836,930 | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 689 | lean | -- Cyber Capable
/-
[CyberCapable] is parameterized by an instance of type [SystemType], and it's a sub-attribute to [MissionEffective].
An instance of type [SystemType] is deemed [CyberCapable] if and only if all the requirements are satisfied.
-/
import SystemModel.System
inductive CyberCapable (sys_type: SystemType): Prop
| intro : (exists cyberCapable: sys_type ^.Contexts -> sys_type ^.Phases -> sys_type ^.Stakeholders -> @SystemInstance sys_type -> Prop,
forall c: sys_type ^.Contexts, forall p: sys_type ^.Phases,
forall s: sys_type ^.Stakeholders, forall st: @SystemInstance sys_type, cyberCapable c p s st) ->
CyberCapable
|
d598b82fd8f3a831b598c62f5930047af3fb08a3 | 618003631150032a5676f229d13a079ac875ff77 | /src/ring_theory/polynomial.lean | 283d52c3b9ef28c7eba000d6cc10531b01131164 | [
"Apache-2.0"
] | permissive | awainverse/mathlib | 939b68c8486df66cfda64d327ad3d9165248c777 | ea76bd8f3ca0a8bf0a166a06a475b10663dec44a | refs/heads/master | 1,659,592,962,036 | 1,590,987,592,000 | 1,590,987,592,000 | 268,436,019 | 1 | 0 | Apache-2.0 | 1,590,990,500,000 | 1,590,990,500,000 | null | UTF-8 | Lean | false | false | 18,587 | lean | /-
Copyright (c) 2019 Kenny Lau. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kenny Lau
Ring-theoretic supplement of data.polynomial.
Main result: Hilbert basis theorem, that if a ring is noetherian then so is its polynomial ring.
-/
import data.mv_polynomial
import ring_theory.noetherian
noncomputable theory
local attribute [instance, priority 100] classical.prop_decidable
universes u v w
namespace polynomial
variables (R : Type u) [comm_ring R]
/-- The `R`-submodule of `R[X]` consisting of polynomials of degree ≤ `n`. -/
def degree_le (n : with_bot ℕ) : submodule R (polynomial R) :=
⨅ k : ℕ, ⨅ h : ↑k > n, (lcoeff R k).ker
/-- The `R`-submodule of `R[X]` consisting of polynomials of degree < `n`. -/
def degree_lt (n : ℕ) : submodule R (polynomial R) :=
⨅ k : ℕ, ⨅ h : k ≥ n, (lcoeff R k).ker
variable {R}
theorem mem_degree_le {n : with_bot ℕ} {f : polynomial R} :
f ∈ degree_le R n ↔ degree f ≤ n :=
by simp only [degree_le, submodule.mem_infi, degree_le_iff_coeff_zero, linear_map.mem_ker]; refl
@[mono] theorem degree_le_mono {m n : with_bot ℕ} (H : m ≤ n) :
degree_le R m ≤ degree_le R n :=
λ f hf, mem_degree_le.2 (le_trans (mem_degree_le.1 hf) H)
theorem degree_le_eq_span_X_pow {n : ℕ} :
degree_le R n = submodule.span R ↑((finset.range (n+1)).image (λ n, X^n) : finset (polynomial R)) :=
begin
apply le_antisymm,
{ intros p hp, replace hp := mem_degree_le.1 hp,
rw [← finsupp.sum_single p, finsupp.sum],
refine submodule.sum_mem _ (λ k hk, _),
show monomial _ _ ∈ _,
have := with_bot.coe_le_coe.1 (finset.sup_le_iff.1 hp k hk),
rw [single_eq_C_mul_X, C_mul'],
refine submodule.smul_mem _ _ (submodule.subset_span $ finset.mem_coe.2 $
finset.mem_image.2 ⟨_, finset.mem_range.2 (nat.lt_succ_of_le this), rfl⟩) },
rw [submodule.span_le, finset.coe_image, set.image_subset_iff],
intros k hk, apply mem_degree_le.2,
apply le_trans (degree_X_pow_le _) (with_bot.coe_le_coe.2 $ nat.le_of_lt_succ $ finset.mem_range.1 hk)
end
theorem mem_degree_lt {n : ℕ} {f : polynomial R} :
f ∈ degree_lt R n ↔ degree f < n :=
by { simp_rw [degree_lt, submodule.mem_infi, linear_map.mem_ker, degree,
finset.sup_lt_iff (with_bot.bot_lt_coe n), finsupp.mem_support_iff, with_bot.some_eq_coe,
with_bot.coe_lt_coe, lt_iff_not_ge', ne, not_imp_not], refl }
@[mono] theorem degree_lt_mono {m n : ℕ} (H : m ≤ n) :
degree_lt R m ≤ degree_lt R n :=
λ f hf, mem_degree_lt.2 (lt_of_lt_of_le (mem_degree_lt.1 hf) $ with_bot.coe_le_coe.2 H)
theorem degree_lt_eq_span_X_pow {n : ℕ} :
degree_lt R n = submodule.span R ↑((finset.range n).image (λ n, X^n) : finset (polynomial R)) :=
begin
apply le_antisymm,
{ intros p hp, replace hp := mem_degree_lt.1 hp,
rw [← finsupp.sum_single p, finsupp.sum],
refine submodule.sum_mem _ (λ k hk, _),
show monomial _ _ ∈ _,
have := with_bot.coe_lt_coe.1 ((finset.sup_lt_iff $ with_bot.bot_lt_coe n).1 hp k hk),
rw [single_eq_C_mul_X, C_mul'],
refine submodule.smul_mem _ _ (submodule.subset_span $ finset.mem_coe.2 $
finset.mem_image.2 ⟨_, finset.mem_range.2 this, rfl⟩) },
rw [submodule.span_le, finset.coe_image, set.image_subset_iff],
intros k hk, apply mem_degree_lt.2,
exact lt_of_le_of_lt (degree_X_pow_le _) (with_bot.coe_lt_coe.2 $ finset.mem_range.1 hk)
end
/-- Given a polynomial, return the polynomial whose coefficients are in
the ring closure of the original coefficients. -/
def restriction (p : polynomial R) : polynomial (ring.closure (↑p.frange : set R)) :=
⟨p.support, λ i, ⟨p.to_fun i,
if H : p.to_fun i = 0 then H.symm ▸ is_add_submonoid.zero_mem
else ring.subset_closure $ finsupp.mem_frange.2 ⟨H, i, rfl⟩⟩,
λ i, finsupp.mem_support_iff.trans (not_iff_not_of_iff ⟨λ H, subtype.eq H, subtype.mk.inj⟩)⟩
@[simp] theorem coeff_restriction {p : polynomial R} {n : ℕ} : ↑(coeff (restriction p) n) = coeff p n := rfl
@[simp] theorem coeff_restriction' {p : polynomial R} {n : ℕ} : (coeff (restriction p) n).1 = coeff p n := rfl
@[simp] theorem degree_restriction {p : polynomial R} : (restriction p).degree = p.degree := rfl
@[simp] theorem nat_degree_restriction {p : polynomial R} : (restriction p).nat_degree = p.nat_degree := rfl
@[simp] theorem monic_restriction {p : polynomial R} : monic (restriction p) ↔ monic p :=
⟨λ H, congr_arg subtype.val H, λ H, subtype.eq H⟩
@[simp] theorem restriction_zero : restriction (0 : polynomial R) = 0 := rfl
@[simp] theorem restriction_one : restriction (1 : polynomial R) = 1 :=
ext $ λ i, subtype.eq $ by rw [coeff_restriction', coeff_one, coeff_one]; split_ifs; refl
variables {S : Type v} [comm_ring S] {f : R → S} {x : S}
theorem eval₂_restriction {p : polynomial R} :
eval₂ f x p = eval₂ (f ∘ subtype.val) x p.restriction :=
rfl
section to_subring
variables (p : polynomial R) (T : set R) [is_subring T]
/-- Given a polynomial `p` and a subring `T` that contains the coefficients of `p`,
return the corresponding polynomial whose coefficients are in `T. -/
def to_subring (hp : ↑p.frange ⊆ T) : polynomial T :=
⟨p.support, λ i, ⟨p.to_fun i,
if H : p.to_fun i = 0 then H.symm ▸ is_add_submonoid.zero_mem
else hp $ finsupp.mem_frange.2 ⟨H, i, rfl⟩⟩,
λ i, finsupp.mem_support_iff.trans (not_iff_not_of_iff ⟨λ H, subtype.eq H, subtype.mk.inj⟩)⟩
variables (hp : ↑p.frange ⊆ T)
include hp
@[simp] theorem coeff_to_subring {n : ℕ} : ↑(coeff (to_subring p T hp) n) = coeff p n := rfl
@[simp] theorem coeff_to_subring' {n : ℕ} : (coeff (to_subring p T hp) n).1 = coeff p n := rfl
@[simp] theorem degree_to_subring : (to_subring p T hp).degree = p.degree := rfl
@[simp] theorem nat_degree_to_subring : (to_subring p T hp).nat_degree = p.nat_degree := rfl
@[simp] theorem monic_to_subring : monic (to_subring p T hp) ↔ monic p :=
⟨λ H, congr_arg subtype.val H, λ H, subtype.eq H⟩
omit hp
@[simp] theorem to_subring_zero : to_subring (0 : polynomial R) T (set.empty_subset _) = 0 := rfl
@[simp] theorem to_subring_one : to_subring (1 : polynomial R) T
(set.subset.trans (finset.coe_subset.2 finsupp.frange_single)
(finset.singleton_subset_set_iff.2 is_submonoid.one_mem)) = 1 :=
ext $ λ i, subtype.eq $ by rw [coeff_to_subring', coeff_one, coeff_one]; split_ifs; refl
end to_subring
variables (T : set R) [is_subring T]
/-- Given a polynomial whose coefficients are in some subring, return
the corresponding polynomial whose coefificents are in the ambient ring. -/
def of_subring (p : polynomial T) : polynomial R :=
⟨p.support, subtype.val ∘ p.to_fun,
λ n, finsupp.mem_support_iff.trans (not_iff_not_of_iff
⟨λ h, congr_arg subtype.val h, λ h, subtype.eq h⟩)⟩
@[simp] theorem frange_of_subring {p : polynomial T} :
↑(p.of_subring T).frange ⊆ T :=
λ y H, let ⟨hy, x, hx⟩ := finsupp.mem_frange.1 H in hx ▸ (p.to_fun x).2
end polynomial
variables {R : Type u} {σ : Type v} [comm_ring R]
namespace ideal
open polynomial
/-- Transport an ideal of `R[X]` to an `R`-submodule of `R[X]`. -/
def of_polynomial (I : ideal (polynomial R)) : submodule R (polynomial R) :=
{ carrier := I.carrier,
zero := I.zero_mem,
add := λ _ _, I.add_mem,
smul := λ c x H, by rw [← C_mul']; exact submodule.smul_mem _ _ H }
variables {I : ideal (polynomial R)}
theorem mem_of_polynomial (x) : x ∈ I.of_polynomial ↔ x ∈ I := iff.rfl
variables (I)
/-- Given an ideal `I` of `R[X]`, make the `R`-submodule of `I`
consisting of polynomials of degree ≤ `n`. -/
def degree_le (n : with_bot ℕ) : submodule R (polynomial R) :=
degree_le R n ⊓ I.of_polynomial
/-- Given an ideal `I` of `R[X]`, make the ideal in `R` of
leading coefficients of polynomials in `I` with degree ≤ `n`. -/
def leading_coeff_nth (n : ℕ) : ideal R :=
(I.degree_le n).map $ lcoeff R n
theorem mem_leading_coeff_nth (n : ℕ) (x) :
x ∈ I.leading_coeff_nth n ↔ ∃ p ∈ I, degree p ≤ n ∧ leading_coeff p = x :=
begin
simp only [leading_coeff_nth, degree_le, submodule.mem_map, lcoeff_apply, submodule.mem_inf, mem_degree_le],
split,
{ rintro ⟨p, ⟨hpdeg, hpI⟩, rfl⟩,
cases lt_or_eq_of_le hpdeg with hpdeg hpdeg,
{ refine ⟨0, I.zero_mem, bot_le, _⟩,
rw [leading_coeff_zero, eq_comm],
exact coeff_eq_zero_of_degree_lt hpdeg },
{ refine ⟨p, hpI, le_of_eq hpdeg, _⟩,
rw [leading_coeff, nat_degree, hpdeg], refl } },
{ rintro ⟨p, hpI, hpdeg, rfl⟩,
have : nat_degree p + (n - nat_degree p) = n,
{ exact nat.add_sub_cancel' (nat_degree_le_of_degree_le hpdeg) },
refine ⟨p * X ^ (n - nat_degree p), ⟨_, I.mul_mem_right hpI⟩, _⟩,
{ apply le_trans (degree_mul_le _ _) _,
apply le_trans (add_le_add' (degree_le_nat_degree) (degree_X_pow_le _)) _,
rw [← with_bot.coe_add, this],
exact le_refl _ },
{ rw [leading_coeff, ← coeff_mul_X_pow p (n - nat_degree p), this] } }
end
theorem mem_leading_coeff_nth_zero (x) :
x ∈ I.leading_coeff_nth 0 ↔ C x ∈ I :=
(mem_leading_coeff_nth _ _ _).trans
⟨λ ⟨p, hpI, hpdeg, hpx⟩, by rwa [← hpx, leading_coeff,
nat.eq_zero_of_le_zero (nat_degree_le_of_degree_le hpdeg),
← eq_C_of_degree_le_zero hpdeg],
λ hx, ⟨C x, hx, degree_C_le, leading_coeff_C x⟩⟩
theorem leading_coeff_nth_mono {m n : ℕ} (H : m ≤ n) :
I.leading_coeff_nth m ≤ I.leading_coeff_nth n :=
begin
intros r hr,
simp only [submodule.mem_coe, mem_leading_coeff_nth] at hr ⊢,
rcases hr with ⟨p, hpI, hpdeg, rfl⟩,
refine ⟨p * X ^ (n - m), I.mul_mem_right hpI, _, leading_coeff_mul_X_pow⟩,
refine le_trans (degree_mul_le _ _) _,
refine le_trans (add_le_add' hpdeg (degree_X_pow_le _)) _,
rw [← with_bot.coe_add, nat.add_sub_cancel' H],
exact le_refl _
end
/-- Given an ideal `I` in `R[X]`, make the ideal in `R` of the
leading coefficients in `I`. -/
def leading_coeff : ideal R :=
⨆ n : ℕ, I.leading_coeff_nth n
theorem mem_leading_coeff (x) :
x ∈ I.leading_coeff ↔ ∃ p ∈ I, polynomial.leading_coeff p = x :=
begin
rw [leading_coeff, submodule.mem_supr_of_directed],
simp only [mem_leading_coeff_nth],
{ split, { rintro ⟨i, p, hpI, hpdeg, rfl⟩, exact ⟨p, hpI, rfl⟩ },
rintro ⟨p, hpI, rfl⟩, exact ⟨nat_degree p, p, hpI, degree_le_nat_degree, rfl⟩ },
intros i j, exact ⟨i + j, I.leading_coeff_nth_mono (nat.le_add_right _ _),
I.leading_coeff_nth_mono (nat.le_add_left _ _)⟩
end
theorem is_fg_degree_le [is_noetherian_ring R] (n : ℕ) :
submodule.fg (I.degree_le n) :=
is_noetherian_submodule_left.1 (is_noetherian_of_fg_of_noetherian _
⟨_, degree_le_eq_span_X_pow.symm⟩) _
end ideal
/-- Hilbert basis theorem: a polynomial ring over a noetherian ring is a noetherian ring. -/
protected theorem polynomial.is_noetherian_ring [is_noetherian_ring R] : is_noetherian_ring (polynomial R) :=
⟨assume I : ideal (polynomial R),
let L := I.leading_coeff in
let M := well_founded.min (is_noetherian_iff_well_founded.1 (by apply_instance))
(set.range I.leading_coeff_nth) ⟨_, ⟨0, rfl⟩⟩ in
have hm : M ∈ set.range I.leading_coeff_nth := well_founded.min_mem _ _ _,
let ⟨N, HN⟩ := hm, ⟨s, hs⟩ := I.is_fg_degree_le N in
have hm2 : ∀ k, I.leading_coeff_nth k ≤ M := λ k, or.cases_on (le_or_lt k N)
(λ h, HN ▸ I.leading_coeff_nth_mono h)
(λ h x hx, classical.by_contradiction $ λ hxm,
have ¬M < I.leading_coeff_nth k, by refine well_founded.not_lt_min
(well_founded_submodule_gt _ _) _ _ _; exact ⟨k, rfl⟩,
this ⟨HN ▸ I.leading_coeff_nth_mono (le_of_lt h), λ H, hxm (H hx)⟩),
have hs2 : ∀ {x}, x ∈ I.degree_le N → x ∈ ideal.span (↑s : set (polynomial R)),
from hs ▸ λ x hx, submodule.span_induction hx (λ _ hx, ideal.subset_span hx) (ideal.zero_mem _)
(λ _ _, ideal.add_mem _) (λ c f hf, f.C_mul' c ▸ ideal.mul_mem_left _ hf),
⟨s, le_antisymm (ideal.span_le.2 $ λ x hx, have x ∈ I.degree_le N, from hs ▸ submodule.subset_span hx, this.2) $ begin
change I ≤ ideal.span ↑s,
intros p hp, generalize hn : p.nat_degree = k,
induction k using nat.strong_induction_on with k ih generalizing p,
cases le_or_lt k N,
{ subst k, refine hs2 ⟨polynomial.mem_degree_le.2
(le_trans polynomial.degree_le_nat_degree $ with_bot.coe_le_coe.2 h), hp⟩ },
{ have hp0 : p ≠ 0,
{ rintro rfl, cases hn, exact nat.not_lt_zero _ h },
have : (0 : R) ≠ 1,
{ intro h, apply hp0, ext i, refine (mul_one _).symm.trans _,
rw [← h, mul_zero], refl },
haveI : nonzero R := ⟨this⟩,
have : p.leading_coeff ∈ I.leading_coeff_nth N,
{ rw HN, exact hm2 k ((I.mem_leading_coeff_nth _ _).2
⟨_, hp, hn ▸ polynomial.degree_le_nat_degree, rfl⟩) },
rw I.mem_leading_coeff_nth at this,
rcases this with ⟨q, hq, hdq, hlqp⟩,
have hq0 : q ≠ 0,
{ intro H, rw [← polynomial.leading_coeff_eq_zero] at H,
rw [hlqp, polynomial.leading_coeff_eq_zero] at H, exact hp0 H },
have h1 : p.degree = (q * polynomial.X ^ (k - q.nat_degree)).degree,
{ rw [polynomial.degree_mul_eq', polynomial.degree_X_pow],
rw [polynomial.degree_eq_nat_degree hp0, polynomial.degree_eq_nat_degree hq0],
rw [← with_bot.coe_add, nat.add_sub_cancel', hn],
{ refine le_trans (polynomial.nat_degree_le_of_degree_le hdq) (le_of_lt h) },
rw [polynomial.leading_coeff_X_pow, mul_one],
exact mt polynomial.leading_coeff_eq_zero.1 hq0 },
have h2 : p.leading_coeff = (q * polynomial.X ^ (k - q.nat_degree)).leading_coeff,
{ rw [← hlqp, polynomial.leading_coeff_mul_X_pow] },
have := polynomial.degree_sub_lt h1 hp0 h2,
rw [polynomial.degree_eq_nat_degree hp0] at this,
rw ← sub_add_cancel p (q * polynomial.X ^ (k - q.nat_degree)),
refine (ideal.span ↑s).add_mem _ ((ideal.span ↑s).mul_mem_right _),
{ by_cases hpq : p - q * polynomial.X ^ (k - q.nat_degree) = 0,
{ rw hpq, exact ideal.zero_mem _ },
refine ih _ _ (I.sub_mem hp (I.mul_mem_right hq)) rfl,
rwa [polynomial.degree_eq_nat_degree hpq, with_bot.coe_lt_coe, hn] at this },
exact hs2 ⟨polynomial.mem_degree_le.2 hdq, hq⟩ }
end⟩⟩
attribute [instance] polynomial.is_noetherian_ring
namespace mv_polynomial
lemma is_noetherian_ring_fin_0 [is_noetherian_ring R] :
is_noetherian_ring (mv_polynomial (fin 0) R) :=
is_noetherian_ring_of_ring_equiv R
((mv_polynomial.pempty_ring_equiv R).symm.trans
(mv_polynomial.ring_equiv_of_equiv _ fin_zero_equiv'.symm))
theorem is_noetherian_ring_fin [is_noetherian_ring R] :
∀ {n : ℕ}, is_noetherian_ring (mv_polynomial (fin n) R)
| 0 := is_noetherian_ring_fin_0
| (n+1) :=
@is_noetherian_ring_of_ring_equiv (polynomial (mv_polynomial (fin n) R)) _ _ _
(mv_polynomial.fin_succ_equiv _ n).symm
(@polynomial.is_noetherian_ring (mv_polynomial (fin n) R) _ (is_noetherian_ring_fin))
/-- The multivariate polynomial ring in finitely many variables over a noetherian ring
is itself a noetherian ring. -/
instance is_noetherian_ring [fintype σ] [is_noetherian_ring R] :
is_noetherian_ring (mv_polynomial σ R) :=
trunc.induction_on (fintype.equiv_fin σ) $ λ e,
@is_noetherian_ring_of_ring_equiv (mv_polynomial (fin (fintype.card σ)) R) _ _ _
(mv_polynomial.ring_equiv_of_equiv _ e.symm) is_noetherian_ring_fin
lemma is_integral_domain_fin_zero (R : Type u) [comm_ring R] (hR : is_integral_domain R) :
is_integral_domain (mv_polynomial (fin 0) R) :=
ring_equiv.is_integral_domain R hR
((ring_equiv_of_equiv R fin_zero_equiv').trans (mv_polynomial.pempty_ring_equiv R))
/-- Auxilliary lemma:
Multivariate polynomials over an integral domain
with variables indexed by `fin n` form an integral domain.
This fact is proven inductively,
and then used to prove the general case without any finiteness hypotheses.
See `mv_polynomial.integral_domain` for the general case. -/
lemma is_integral_domain_fin (R : Type u) [comm_ring R] (hR : is_integral_domain R) :
∀ (n : ℕ), is_integral_domain (mv_polynomial (fin n) R)
| 0 := is_integral_domain_fin_zero R hR
| (n+1) :=
ring_equiv.is_integral_domain
(polynomial (mv_polynomial (fin n) R))
(is_integral_domain_fin n).polynomial
(mv_polynomial.fin_succ_equiv _ n)
lemma is_integral_domain_fintype (R : Type u) (σ : Type v) [comm_ring R] [fintype σ]
(hR : is_integral_domain R) : is_integral_domain (mv_polynomial σ R) :=
trunc.induction_on (fintype.equiv_fin σ) $ λ e,
@ring_equiv.is_integral_domain _ (mv_polynomial (fin $ fintype.card σ) R) _ _
(mv_polynomial.is_integral_domain_fin _ hR _)
(ring_equiv_of_equiv R e)
/-- Auxilliary definition:
Multivariate polynomials in finitely many variables over an integral domain form an integral domain.
This fact is proven by transport of structure from the `mv_polynomial.integral_domain_fin`,
and then used to prove the general case without finiteness hypotheses.
See `mv_polynomial.integral_domain` for the general case. -/
def integral_domain_fintype (R : Type u) (σ : Type v) [integral_domain R] [fintype σ] :
integral_domain (mv_polynomial σ R) :=
@is_integral_domain.to_integral_domain _ _ $ mv_polynomial.is_integral_domain_fintype R σ $
integral_domain.to_is_integral_domain R
protected theorem eq_zero_or_eq_zero_of_mul_eq_zero {R : Type u} [integral_domain R] {σ : Type v}
(p q : mv_polynomial σ R) (h : p * q = 0) : p = 0 ∨ q = 0 :=
begin
obtain ⟨s, p, rfl⟩ := exists_finset_rename p,
obtain ⟨t, q, rfl⟩ := exists_finset_rename q,
have : p.rename (subtype.map id (finset.subset_union_left s t) : {x // x ∈ s} → {x // x ∈ s ∪ t}) *
q.rename (subtype.map id (finset.subset_union_right s t)) = 0,
{ apply injective_rename _ subtype.val_injective, simpa using h },
letI := mv_polynomial.integral_domain_fintype R {x // x ∈ (s ∪ t)},
rw mul_eq_zero at this,
cases this; [left, right],
all_goals { simpa using congr_arg (rename subtype.val) this }
end
/-- The multivariate polynomial ring over an integral domain is an integral domain. -/
instance {R : Type u} {σ : Type v} [integral_domain R] :
integral_domain (mv_polynomial σ R) :=
{ eq_zero_or_eq_zero_of_mul_eq_zero := mv_polynomial.eq_zero_or_eq_zero_of_mul_eq_zero,
zero_ne_one :=
begin
intro H,
have : eval₂ id (λ s, (0:R)) (0 : mv_polynomial σ R) =
eval₂ id (λ s, (0:R)) (1 : mv_polynomial σ R),
{ congr, exact H },
simpa,
end,
.. (by apply_instance : comm_ring (mv_polynomial σ R)) }
end mv_polynomial
|
713d51a190af02c8f306fcbefadc8c97c9921a81 | b7f22e51856f4989b970961f794f1c435f9b8f78 | /tests/lean/slow/list_elab2.lean | cfd3d20ab185de003c255a81cdd12a7e94de7afb | [
"Apache-2.0"
] | permissive | soonhokong/lean | cb8aa01055ffe2af0fb99a16b4cda8463b882cd1 | 38607e3eb57f57f77c0ac114ad169e9e4262e24f | refs/heads/master | 1,611,187,284,081 | 1,450,766,737,000 | 1,476,122,547,000 | 11,513,992 | 2 | 0 | null | 1,401,763,102,000 | 1,374,182,235,000 | C++ | UTF-8 | Lean | false | false | 6,590 | lean | ----------------------------------------------------------------------------------------------------
--- 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
----------------------------------------------------------------------------------------------------
-- Theory list
-- ===========
--
-- Basic properties of lists.
import logic data.nat
-- import congr
open nat algebra
-- open congr
open eq.ops eq
inductive list (T : Type) : Type :=
| nil {} : list T
| cons : T → list T → list T
definition refl := @eq.refl
namespace list
-- Type
-- ----
infixr `::` := cons
section
variable {T : Type}
theorem list_induction_on {P : list T → Prop} (l : list T) (Hnil : P nil)
(Hind : forall x : T, forall l : list T, forall H : P l, P (cons x l)) : P l :=
list.rec Hnil Hind l
theorem list_cases_on {P : list T → Prop} (l : list T) (Hnil : P nil)
(Hcons : forall x : T, forall l : list T, P (cons x l)) : P l :=
list_induction_on l Hnil (take x l IH, Hcons x l)
notation `[` l:(foldr `,` (h t, cons h t) nil) `]` := l
-- Concat
-- ------
definition concat (s t : list T) : list T :=
list.rec t (fun x : T, fun l : list T, fun u : list T, cons x u) s
infixl `++` := concat
theorem nil_concat (t : list T) : nil ++ t = t := refl _
theorem cons_concat (x : T) (s t : list T) : (x :: s) ++ t = x :: (s ++ t) := refl _
theorem concat_nil (t : list T) : t ++ nil = t :=
list_induction_on t (refl _)
(take (x : T) (l : list T) (H : concat l nil = l),
H ▸ (refl (cons x (concat l nil))))
attribute concat [reducible]
theorem concat_nil2 (t : list T) : t ++ nil = t :=
list_induction_on t (refl _)
(take (x : T) (l : list T) (H : concat l nil = l),
-- H ▸ (refl (cons x (concat l nil))))
H ▸ (refl (concat (cons x l) nil)))
theorem concat_assoc (s t u : list T) : s ++ t ++ u = s ++ (t ++ u) :=
list_induction_on s (refl _)
(take x l,
assume H : concat (concat l t) u = concat l (concat t u),
H ▸ refl _)
theorem concat_assoc2 (s t u : list T) : s ++ t ++ u = s ++ (t ++ u) :=
list_induction_on s (refl _)
(take x l,
assume H : concat (concat l t) u = concat l (concat t u),
calc concat (concat (cons x l) t) u = cons x (concat (concat l t) u) : refl _
... = concat (cons x l) (concat t u) : { H })
theorem concat_assoc3 (s t u : list T) : s ++ t ++ u = s ++ (t ++ u) :=
list_induction_on s (refl _)
(take x l,
assume H : concat (concat l t) u = concat l (concat t u),
calc concat (concat (cons x l) t) u = cons x (concat l (concat t u)) : { H }
... = concat (cons x l) (concat t u) : refl _)
theorem concat_assoc4 (s t u : list T) : s ++ t ++ u = s ++ (t ++ u) :=
list_induction_on s (refl _)
(take x l,
assume H : concat (concat l t) u = concat l (concat t u),
calc
concat (concat (cons x l) t) u = cons x (concat (concat l t) u) : refl _
... = cons x (concat l (concat t u)) : { H }
... = concat (cons x l) (concat t u) : refl _)
-- Length
-- ------
definition length : list T → ℕ := list.rec 0 (fun x l m, succ m)
-- TODO: cannot replace zero by 0
theorem length_nil : length (@nil T) = zero := refl _
theorem length_cons (x : T) (t : list T) : length (x :: t) = succ (length t) := refl _
theorem length_concat (s t : list T) : length (s ++ t) = length s + length t :=
list_induction_on s
(calc
length (concat nil t) = length t : refl _
... = 0 + length t : {symm !zero_add}
... = length (@nil T) + length t : refl _)
(take x s,
assume H : length (concat s t) = length s + length t,
calc
length (concat (cons x s) t ) = succ (length (concat s t)) : refl _
... = succ (length s + length t) : { H }
... = succ (length s) + length t : {symm !succ_add}
... = length (cons x s) + length t : refl _)
-- Reverse
-- -------
definition reverse : list T → list T := list.rec nil (fun x l r, r ++ [x])
theorem reverse_nil : reverse (@nil T) = nil := refl _
theorem reverse_cons (x : T) (l : list T) : reverse (x :: l) = (reverse l) ++ (cons x nil) := refl _
-- opaque_hint (hiding reverse)
theorem reverse_concat (s t : list T) : reverse (s ++ t) = (reverse t) ++ (reverse s) :=
list_induction_on s
(calc
reverse (concat nil t) = reverse t : { nil_concat _ }
... = concat (reverse t) nil : symm (concat_nil _)
... = concat (reverse t) (reverse nil) : {symm (reverse_nil)})
(take x l,
assume H : reverse (concat l t) = concat (reverse t) (reverse l),
calc
reverse (concat (cons x l) t) = concat (reverse (concat l t)) (cons x nil) : refl _
... = concat (concat (reverse t) (reverse l)) (cons x nil) : { H }
... = concat (reverse t) (concat (reverse l) (cons x nil)) : concat_assoc _ _ _
... = concat (reverse t) (reverse (cons x l)) : refl _)
-- -- add_rewrite length_nil length_cons
theorem reverse_reverse (l : list T) : reverse (reverse l) = l :=
list_induction_on l (refl _)
(take x l',
assume H: reverse (reverse l') = l',
show reverse (reverse (cons x l')) = cons x l', from
calc
reverse (reverse (cons x l')) =
concat (reverse (cons x nil)) (reverse (reverse l')) : {reverse_concat _ _}
... = cons x l' : {H})
-- Append
-- ------
-- TODO: define reverse from append
definition append (x : T) : list T → list T := list.rec (x :: nil) (fun y l l', y :: l')
theorem append_nil (x : T) : append x nil = [x] := refl _
theorem append_cons (x : T) (y : T) (l : list T) : append x (y :: l) = y :: (append x l) := refl _
theorem append_eq_concat (x : T) (l : list T) : append x l = l ++ [x] :=
list_induction_on l (refl _)
(take y l,
assume P : append x l = concat l [x],
P ▸ refl _)
theorem append_eq_reverse_cons (x : T) (l : list T) : append x l = reverse (x :: reverse l) :=
list_induction_on l
(calc
append x nil = [x] : (refl _)
... = concat nil [x] : {symm (nil_concat _)}
... = concat (reverse nil) [x] : {symm (reverse_nil)}
... = reverse [x] : {symm (reverse_cons _ _)}
... = reverse (x :: (reverse nil)) : {symm (reverse_nil)})
(take y l',
assume H : append x l' = reverse (x :: reverse l'),
calc
append x (y :: l') = (y :: l') ++ [ x ] : append_eq_concat _ _
... = concat (reverse (reverse (y :: l'))) [ x ] : {symm (reverse_reverse _)}
... = reverse (x :: (reverse (y :: l'))) : refl _)
end
end list
|
309e2f0616ac14684155a07f1b0eb171e998a8ec | 618003631150032a5676f229d13a079ac875ff77 | /src/algebra/category/Group/images.lean | 32c082b6430a4dfce7ecb433fc1111e355e6df30 | [
"Apache-2.0"
] | permissive | awainverse/mathlib | 939b68c8486df66cfda64d327ad3d9165248c777 | ea76bd8f3ca0a8bf0a166a06a475b10663dec44a | refs/heads/master | 1,659,592,962,036 | 1,590,987,592,000 | 1,590,987,592,000 | 268,436,019 | 1 | 0 | Apache-2.0 | 1,590,990,500,000 | 1,590,990,500,000 | null | UTF-8 | Lean | false | false | 2,647 | lean | /-
Copyright (c) 2020 Scott Morrison. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Scott Morrison
-/
import algebra.category.Group
/-!
# The category of commutative additive groups has images.
-/
open category_theory
open category_theory.limits
universe u
namespace AddCommGroup
variables {G H : AddCommGroup.{0}} (f : G ⟶ H)
local attribute [ext] subtype.eq'
section -- implementation details of `has_image` for AddCommGroup; use the API, not these
/-- the image of a morphism in AddCommGroup is just the bundling of `set.range f` -/
def image : AddCommGroup := AddCommGroup.of (set.range f)
/-- the inclusion of `image f` into the target -/
def image.ι : image f ⟶ H := f.range_subtype_val
instance : mono (image.ι f) := concrete_category.mono_of_injective (image.ι f) subtype.val_injective
/-- the corestriction map to the image -/
def factor_thru_image : G ⟶ image f := add_monoid_hom.range_factorization f
lemma image.fac : factor_thru_image f ≫ image.ι f = f :=
by { ext, refl, }
local attribute [simp] image.fac
variables {f}
/-- the universal property for the image factorisation -/
noncomputable def image.lift (F' : mono_factorisation f) : image f ⟶ F'.I :=
{ to_fun :=
(λ x, F'.e (classical.indefinite_description _ x.2).1 : image f → F'.I),
map_zero' :=
begin
haveI := F'.m_mono,
apply injective_of_mono F'.m,
change (F'.e ≫ F'.m) _ = _,
rw [F'.fac, add_monoid_hom.map_zero],
convert (classical.indefinite_description (λ y, f y = 0) _).2,
end,
map_add' :=
begin
intros x y,
haveI := F'.m_mono,
apply injective_of_mono F'.m,
rw [add_monoid_hom.map_add],
change (F'.e ≫ F'.m) _ = (F'.e ≫ F'.m) _ + (F'.e ≫ F'.m) _,
rw [F'.fac],
rw (classical.indefinite_description (λ z, f z = _) _).2,
rw (classical.indefinite_description (λ z, f z = _) _).2,
rw (classical.indefinite_description (λ z, f z = _) _).2,
refl,
end,
}
lemma image.lift_fac (F' : mono_factorisation f) : image.lift F' ≫ F'.m = image.ι f :=
begin
ext x,
change (F'.e ≫ F'.m) _ = _,
rw [F'.fac, (classical.indefinite_description _ x.2).2],
refl,
end
end
/-- the factorisation of any morphism in AddCommGroup through a mono. -/
def mono_factorisation : mono_factorisation f :=
{ I := image f,
m := image.ι f,
e := factor_thru_image f }
noncomputable instance : has_image f :=
{ F := mono_factorisation f,
is_image :=
{ lift := image.lift,
lift_fac' := image.lift_fac } }
noncomputable instance : has_images.{0} AddCommGroup.{0} :=
{ has_image := infer_instance }
end AddCommGroup
|
a26c04e96c8da586cf995e0b99bc0f63d4f471ff | 7b681d6cc18477cf6b60470d9782923d3ea63915 | /W3-proof.lean | dd3d7c01cc945d670e640bd7b7dc447b3990d73a | [] | no_license | osoulim/LEAN | a7458f597abbe5c36ebbb3f36eab29a4c60f5140 | 5e0dc240e86e392fdab4b2ffdcc3174c0cce7b66 | refs/heads/master | 1,591,850,481,195 | 1,561,547,647,000 | 1,561,547,647,000 | 193,852,039 | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 313 | lean | -- ∀x A(x) -> (∀x B(x) -> ∀y(A(y) ∧ B(y)))
variable U: Type
variables A B: U -> Prop
example : (∀ x, A x) -> (∀ x, B x) -> (∀ x, A x ∧ B x) :=
assume hA: ∀ x, A x,
assume hB: ∀ x, B x,
assume y,
have pAy: A y, from hA y,
have pBy: B y, from hB y,
show A y ∧ B y, from and.intro pAy pBy |
de25a6bf5475c2e818f4a2f127edea9383877a08 | 1b8f093752ba748c5ca0083afef2959aaa7dace5 | /src/category_theory/examples/TopRing.lean | 62d1b93018e45270cbf9d95f739884a188ebfcc5 | [] | no_license | khoek/lean-category-theory | 7ec4cda9cc64a5a4ffeb84712ac7d020dbbba386 | 63dcb598e9270a3e8b56d1769eb4f825a177cd95 | refs/heads/master | 1,585,251,725,759 | 1,539,344,445,000 | 1,539,344,445,000 | 145,281,070 | 0 | 0 | null | 1,534,662,376,000 | 1,534,662,376,000 | null | UTF-8 | Lean | false | false | 927 | lean | import category_theory.category
import analysis.topology.topological_structures
universes u
open category_theory
namespace category_theory.examples
structure TopRing :=
{β : Type u}
[Ring : comm_ring β]
[Top : topological_space β]
[TopRing : topological_ring β]
instance TopRing_comm_ring (R : TopRing) : comm_ring R.β := R.Ring
instance TopRing_topological_space (R : TopRing) : topological_space R.β := R.Top
instance TopRing_topological_ring (R : TopRing) : topological_ring R.β := R.TopRing
instance : category TopRing :=
{ hom := λ R S, {f : R.β → S.β // is_ring_hom f ∧ continuous f },
id := λ R, ⟨id, by obviously⟩,
comp := λ R S T f g, ⟨g.val ∘ f.val,
begin -- TODO automate
cases f, cases g, cases f_property, cases g_property, split,
dsimp, resetI, apply_instance,
dsimp, apply continuous.comp ; assumption
end⟩ }
end category_theory.examples
|
1d9c443a67a07a614414da22ba271dc6b6adb502 | ecea1a568b8a7bdfef1206845f7dc2e62b85b6b3 | /tests/lean/run/check_constants.lean | d437e202ccddd256aa568c47445e7cf3c19e8728 | [
"Apache-2.0"
] | permissive | ndcroos/lean | b1b6de42ee4d3ded05829373e505e09614d4acdf | 6919d231413705c892eec02bdacd7d7d916524c8 | refs/heads/master | 1,625,911,732,192 | 1,507,549,407,000 | 1,507,549,407,000 | 106,106,359 | 0 | 0 | null | 1,507,388,410,000 | 1,507,388,410,000 | null | UTF-8 | Lean | false | false | 15,025 | lean | -- DO NOT EDIT, automatically generated file, generator scripts/gen_constants_cpp.py
import smt system.io
open tactic
meta def script_check_id (n : name) : tactic unit :=
do env ← get_env, (env^.get n >> return ()) <|> (guard $ env^.is_namespace n) <|> (attribute.get_instances n >> return ()) <|> fail ("identifier '" ++ to_string n ++ "' is not a constant, namespace nor attribute")
run_cmd script_check_id `abs
run_cmd script_check_id `absurd
run_cmd script_check_id `acc.cases_on
run_cmd script_check_id `acc.rec
run_cmd script_check_id `add_comm_group
run_cmd script_check_id `add_comm_semigroup
run_cmd script_check_id `add_group
run_cmd script_check_id `add_monoid
run_cmd script_check_id `and
run_cmd script_check_id `and.elim_left
run_cmd script_check_id `and.elim_right
run_cmd script_check_id `and.intro
run_cmd script_check_id `and.rec
run_cmd script_check_id `and.cases_on
run_cmd script_check_id `auto_param
run_cmd script_check_id `bit0
run_cmd script_check_id `bit1
run_cmd script_check_id `bin_tree.empty
run_cmd script_check_id `bin_tree.leaf
run_cmd script_check_id `bin_tree.node
run_cmd script_check_id `bool
run_cmd script_check_id `bool.ff
run_cmd script_check_id `bool.tt
run_cmd script_check_id `combinator.K
run_cmd script_check_id `cast
run_cmd script_check_id `cast_heq
run_cmd script_check_id `char
run_cmd script_check_id `char.of_nat
run_cmd script_check_id `char.of_nat_ne_of_ne
run_cmd script_check_id `classical.prop_decidable
run_cmd script_check_id `classical.type_decidable_eq
run_cmd script_check_id `coe
run_cmd script_check_id `coe_fn
run_cmd script_check_id `coe_sort
run_cmd script_check_id `coe_to_lift
run_cmd script_check_id `congr
run_cmd script_check_id `congr_arg
run_cmd script_check_id `congr_fun
run_cmd script_check_id `decidable
run_cmd script_check_id `decidable.to_bool
run_cmd script_check_id `distrib
run_cmd script_check_id `dite
run_cmd script_check_id `id
run_cmd script_check_id `empty
run_cmd script_check_id `Exists
run_cmd script_check_id `eq
run_cmd script_check_id `eq.cases_on
run_cmd script_check_id `eq.drec
run_cmd script_check_id `eq.mp
run_cmd script_check_id `eq.mpr
run_cmd script_check_id `eq.rec
run_cmd script_check_id `eq.refl
run_cmd script_check_id `eq.subst
run_cmd script_check_id `eq.symm
run_cmd script_check_id `eq.trans
run_cmd script_check_id `eq_of_heq
run_cmd script_check_id `eq_rec_heq
run_cmd script_check_id `eq_true_intro
run_cmd script_check_id `eq_false_intro
run_cmd script_check_id `eq_self_iff_true
run_cmd script_check_id `expr
run_cmd script_check_id `expr.subst
run_cmd script_check_id `format
run_cmd script_check_id `false
run_cmd script_check_id `false_of_true_iff_false
run_cmd script_check_id `false_of_true_eq_false
run_cmd script_check_id `true_eq_false_of_false
run_cmd script_check_id `false.rec
run_cmd script_check_id `field
run_cmd script_check_id `fin.mk
run_cmd script_check_id `fin.ne_of_vne
run_cmd script_check_id `forall_congr
run_cmd script_check_id `forall_congr_eq
run_cmd script_check_id `forall_not_of_not_exists
run_cmd script_check_id `funext
run_cmd script_check_id `ge
run_cmd script_check_id `gt
run_cmd script_check_id `has_add
run_cmd script_check_id `has_add.add
run_cmd script_check_id `andthen
run_cmd script_check_id `has_bind.and_then
run_cmd script_check_id `has_bind.bind
run_cmd script_check_id `has_bind.seq
run_cmd script_check_id `has_div
run_cmd script_check_id `has_div.div
run_cmd script_check_id `has_emptyc.emptyc
run_cmd script_check_id `has_mod.mod
run_cmd script_check_id `has_mul
run_cmd script_check_id `has_mul.mul
run_cmd script_check_id `has_insert.insert
run_cmd script_check_id `has_inv
run_cmd script_check_id `has_inv.inv
run_cmd script_check_id `has_le
run_cmd script_check_id `has_le.le
run_cmd script_check_id `has_lt
run_cmd script_check_id `has_lt.lt
run_cmd script_check_id `has_neg
run_cmd script_check_id `has_neg.neg
run_cmd script_check_id `has_one
run_cmd script_check_id `has_one.one
run_cmd script_check_id `has_orelse.orelse
run_cmd script_check_id `has_sep.sep
run_cmd script_check_id `has_sizeof
run_cmd script_check_id `has_sizeof.mk
run_cmd script_check_id `has_sub
run_cmd script_check_id `has_sub.sub
run_cmd script_check_id `has_to_format
run_cmd script_check_id `has_repr
run_cmd script_check_id `has_well_founded
run_cmd script_check_id `has_well_founded.r
run_cmd script_check_id `has_well_founded.wf
run_cmd script_check_id `has_zero
run_cmd script_check_id `has_zero.zero
run_cmd script_check_id `has_coe_t
run_cmd script_check_id `heq
run_cmd script_check_id `heq.refl
run_cmd script_check_id `heq.symm
run_cmd script_check_id `heq.trans
run_cmd script_check_id `heq_of_eq
run_cmd script_check_id `hole_command
run_cmd script_check_id `id_locked
run_cmd script_check_id `id_rhs
run_cmd script_check_id `if_neg
run_cmd script_check_id `if_pos
run_cmd script_check_id `iff
run_cmd script_check_id `iff_false_intro
run_cmd script_check_id `iff.intro
run_cmd script_check_id `iff.mp
run_cmd script_check_id `iff.mpr
run_cmd script_check_id `iff.refl
run_cmd script_check_id `iff.symm
run_cmd script_check_id `iff.trans
run_cmd script_check_id `iff_true_intro
run_cmd script_check_id `imp_congr
run_cmd script_check_id `imp_congr_eq
run_cmd script_check_id `imp_congr_ctx
run_cmd script_check_id `imp_congr_ctx_eq
run_cmd script_check_id `implies
run_cmd script_check_id `implies_of_if_neg
run_cmd script_check_id `implies_of_if_pos
run_cmd script_check_id `int
run_cmd script_check_id `int.has_add
run_cmd script_check_id `int.has_mul
run_cmd script_check_id `int.has_sub
run_cmd script_check_id `int.has_div
run_cmd script_check_id `int.has_le
run_cmd script_check_id `int.has_lt
run_cmd script_check_id `int.has_neg
run_cmd script_check_id `int.has_mod
run_cmd script_check_id `int.bit0_nonneg
run_cmd script_check_id `int.bit1_nonneg
run_cmd script_check_id `int.one_nonneg
run_cmd script_check_id `int.zero_nonneg
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|
cac5b74cde7f8bf6a16206ee36bdd59613953aa5 | 4727251e0cd73359b15b664c3170e5d754078599 | /src/data/real/ennreal.lean | 6c3306acf2d9a9ee82914a04ff10ba68f38df24d | [
"Apache-2.0"
] | permissive | Vierkantor/mathlib | 0ea59ac32a3a43c93c44d70f441c4ee810ccceca | 83bc3b9ce9b13910b57bda6b56222495ebd31c2f | refs/heads/master | 1,658,323,012,449 | 1,652,256,003,000 | 1,652,256,003,000 | 209,296,341 | 0 | 1 | Apache-2.0 | 1,568,807,655,000 | 1,568,807,655,000 | null | UTF-8 | Lean | false | false | 76,937 | lean | /-
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 data.real.nnreal
/-!
# Extended non-negative reals
We define `ennreal = ℝ≥0∞ := with_top ℝ≥0` to be the type of extended nonnegative real numbers,
i.e., the interval `[0, +∞]`. This type is used as the codomain of a `measure_theory.measure`,
and of the extended distance `edist` in a `emetric_space`.
In this file we define some algebraic operations and a linear order on `ℝ≥0∞`
and prove basic properties of these operations, order, and conversions to/from `ℝ`, `ℝ≥0`, and `ℕ`.
## Main definitions
* `ℝ≥0∞`: the extended nonnegative real numbers `[0, ∞]`; defined as `with_top ℝ≥0`; it is
equipped with the following structures:
- coercion from `ℝ≥0` defined in the natural way;
- the natural structure of a complete dense linear order: `↑p ≤ ↑q ↔ p ≤ q` and `∀ a, a ≤ ∞`;
- `a + b` is defined so that `↑p + ↑q = ↑(p + q)` for `(p q : ℝ≥0)` and `a + ∞ = ∞ + a = ∞`;
- `a * b` is defined so that `↑p * ↑q = ↑(p * q)` for `(p q : ℝ≥0)`, `0 * ∞ = ∞ * 0 = 0`, and `a *
∞ = ∞ * a = ∞` for `a ≠ 0`;
- `a - b` is defined as the minimal `d` such that `a ≤ d + b`; this way we have
`↑p - ↑q = ↑(p - q)`, `∞ - ↑p = ∞`, `↑p - ∞ = ∞ - ∞ = 0`; note that there is no negation, only
subtraction;
- `a⁻¹` is defined as `Inf {b | 1 ≤ a * b}`. This way we have `(↑p)⁻¹ = ↑(p⁻¹)` for
`p : ℝ≥0`, `p ≠ 0`, `0⁻¹ = ∞`, and `∞⁻¹ = 0`.
- `a / b` is defined as `a * b⁻¹`.
The addition and multiplication defined this way together with `0 = ↑0` and `1 = ↑1` turn
`ℝ≥0∞` into a canonically ordered commutative semiring of characteristic zero.
* Coercions to/from other types:
- coercion `ℝ≥0 → ℝ≥0∞` is defined as `has_coe`, so one can use `(p : ℝ≥0)` in a context that
expects `a : ℝ≥0∞`, and Lean will apply `coe` automatically;
- `ennreal.to_nnreal` sends `↑p` to `p` and `∞` to `0`;
- `ennreal.to_real := coe ∘ ennreal.to_nnreal` sends `↑p`, `p : ℝ≥0` to `(↑p : ℝ)` and `∞` to `0`;
- `ennreal.of_real := coe ∘ real.to_nnreal` sends `x : ℝ` to `↑⟨max x 0, _⟩`
- `ennreal.ne_top_equiv_nnreal` is an equivalence between `{a : ℝ≥0∞ // a ≠ 0}` and `ℝ≥0`.
## Implementation notes
We define a `can_lift ℝ≥0∞ ℝ≥0` instance, so one of the ways to prove theorems about an `ℝ≥0∞`
number `a` is to consider the cases `a = ∞` and `a ≠ ∞`, and use the tactic `lift a to ℝ≥0 using ha`
in the second case. This instance is even more useful if one already has `ha : a ≠ ∞` in the
context, or if we have `(f : α → ℝ≥0∞) (hf : ∀ x, f x ≠ ∞)`.
## Notations
* `ℝ≥0∞`: the type of the extended nonnegative real numbers;
* `ℝ≥0`: the type of nonnegative real numbers `[0, ∞)`; defined in `data.real.nnreal`;
* `∞`: a localized notation in `ℝ≥0∞` for `⊤ : ℝ≥0∞`.
-/
open classical set
open_locale classical big_operators nnreal
variables {α : Type*} {β : Type*}
/-- The extended nonnegative real numbers. This is usually denoted [0, ∞],
and is relevant as the codomain of a measure. -/
@[derive [
has_zero, add_comm_monoid,
canonically_ordered_comm_semiring, complete_linear_order, densely_ordered, nontrivial,
canonically_linear_ordered_add_monoid, has_sub, has_ordered_sub,
linear_ordered_add_comm_monoid_with_top]]
def ennreal := with_top ℝ≥0
localized "notation `ℝ≥0∞` := ennreal" in ennreal
localized "notation `∞` := (⊤ : ennreal)" in ennreal
namespace ennreal
variables {a b c d : ℝ≥0∞} {r p q : ℝ≥0}
-- TODO: why are the two covariant instances necessary? why aren't they inferred?
instance covariant_class_mul_le : covariant_class ℝ≥0∞ ℝ≥0∞ (*) (≤) :=
canonically_ordered_comm_semiring.to_covariant_mul_le
instance covariant_class_add_le : covariant_class ℝ≥0∞ ℝ≥0∞ (+) (≤) :=
ordered_add_comm_monoid.to_covariant_class_left ℝ≥0∞
instance : inhabited ℝ≥0∞ := ⟨0⟩
instance : has_coe ℝ≥0 ℝ≥0∞ := ⟨ option.some ⟩
instance : can_lift ℝ≥0∞ ℝ≥0 :=
{ coe := coe,
cond := λ r, r ≠ ∞,
prf := λ x hx, ⟨option.get $ option.ne_none_iff_is_some.1 hx, option.some_get _⟩ }
@[simp] lemma none_eq_top : (none : ℝ≥0∞) = ∞ := rfl
@[simp] lemma some_eq_coe (a : ℝ≥0) : (some a : ℝ≥0∞) = (↑a : ℝ≥0∞) := rfl
/-- `to_nnreal x` returns `x` if it is real, otherwise 0. -/
protected def to_nnreal : ℝ≥0∞ → ℝ≥0
| (some r) := r
| none := 0
/-- `to_real x` returns `x` if it is real, `0` otherwise. -/
protected def to_real (a : ℝ≥0∞) : real := coe (a.to_nnreal)
/-- `of_real x` returns `x` if it is nonnegative, `0` otherwise. -/
protected noncomputable def of_real (r : real) : ℝ≥0∞ := coe (real.to_nnreal r)
@[simp, norm_cast] lemma to_nnreal_coe : (r : ℝ≥0∞).to_nnreal = r := rfl
@[simp] lemma coe_to_nnreal : ∀{a:ℝ≥0∞}, a ≠ ∞ → ↑(a.to_nnreal) = a
| (some r) h := rfl
| none h := (h rfl).elim
@[simp] lemma of_real_to_real {a : ℝ≥0∞} (h : a ≠ ∞) : ennreal.of_real (a.to_real) = a :=
by simp [ennreal.to_real, ennreal.of_real, h]
@[simp] lemma to_real_of_real {r : ℝ} (h : 0 ≤ r) : ennreal.to_real (ennreal.of_real r) = r :=
by simp [ennreal.to_real, ennreal.of_real, real.coe_to_nnreal _ h]
lemma to_real_of_real' {r : ℝ} : ennreal.to_real (ennreal.of_real r) = max r 0 := rfl
lemma coe_to_nnreal_le_self : ∀{a:ℝ≥0∞}, ↑(a.to_nnreal) ≤ a
| (some r) := by rw [some_eq_coe, to_nnreal_coe]; exact le_rfl
| none := le_top
lemma coe_nnreal_eq (r : ℝ≥0) : (r : ℝ≥0∞) = ennreal.of_real r :=
by { rw [ennreal.of_real, real.to_nnreal], cases r with r h, congr, dsimp, rw max_eq_left h }
lemma of_real_eq_coe_nnreal {x : ℝ} (h : 0 ≤ x) :
ennreal.of_real x = @coe ℝ≥0 ℝ≥0∞ _ (⟨x, h⟩ : ℝ≥0) :=
by { rw [coe_nnreal_eq], refl }
@[simp] lemma of_real_coe_nnreal : ennreal.of_real p = p := (coe_nnreal_eq p).symm
@[simp, norm_cast] lemma coe_zero : ↑(0 : ℝ≥0) = (0 : ℝ≥0∞) := rfl
@[simp, norm_cast] lemma coe_one : ↑(1 : ℝ≥0) = (1 : ℝ≥0∞) := rfl
@[simp] lemma to_real_nonneg {a : ℝ≥0∞} : 0 ≤ a.to_real := by simp [ennreal.to_real]
@[simp] lemma top_to_nnreal : ∞.to_nnreal = 0 := rfl
@[simp] lemma top_to_real : ∞.to_real = 0 := rfl
@[simp] lemma one_to_real : (1 : ℝ≥0∞).to_real = 1 := rfl
@[simp] lemma one_to_nnreal : (1 : ℝ≥0∞).to_nnreal = 1 := rfl
@[simp] lemma coe_to_real (r : ℝ≥0) : (r : ℝ≥0∞).to_real = r := rfl
@[simp] lemma zero_to_nnreal : (0 : ℝ≥0∞).to_nnreal = 0 := rfl
@[simp] lemma zero_to_real : (0 : ℝ≥0∞).to_real = 0 := rfl
@[simp] lemma of_real_zero : ennreal.of_real (0 : ℝ) = 0 :=
by simp [ennreal.of_real]; refl
@[simp] lemma of_real_one : ennreal.of_real (1 : ℝ) = (1 : ℝ≥0∞) :=
by simp [ennreal.of_real]
lemma of_real_to_real_le {a : ℝ≥0∞} : ennreal.of_real (a.to_real) ≤ a :=
if ha : a = ∞ then ha.symm ▸ le_top else le_of_eq (of_real_to_real ha)
lemma forall_ennreal {p : ℝ≥0∞ → Prop} : (∀a, p a) ↔ (∀r:ℝ≥0, p r) ∧ p ∞ :=
⟨assume h, ⟨assume r, h _, h _⟩,
assume ⟨h₁, h₂⟩ a, match a with some r := h₁ _ | none := h₂ end⟩
lemma forall_ne_top {p : ℝ≥0∞ → Prop} : (∀ a ≠ ∞, p a) ↔ ∀ r : ℝ≥0, p r :=
option.ball_ne_none
lemma exists_ne_top {p : ℝ≥0∞ → Prop} : (∃ a ≠ ∞, p a) ↔ ∃ r : ℝ≥0, p r :=
option.bex_ne_none
lemma to_nnreal_eq_zero_iff (x : ℝ≥0∞) : x.to_nnreal = 0 ↔ x = 0 ∨ x = ∞ :=
⟨begin
cases x,
{ simp [none_eq_top] },
{ rintro (rfl : x = 0),
exact or.inl rfl },
end,
by rintro (h | h); simp [h]⟩
lemma to_real_eq_zero_iff (x : ℝ≥0∞) : x.to_real = 0 ↔ x = 0 ∨ x = ∞ :=
by simp [ennreal.to_real, to_nnreal_eq_zero_iff]
@[simp] lemma coe_ne_top : (r : ℝ≥0∞) ≠ ∞ := with_top.coe_ne_top
@[simp] lemma top_ne_coe : ∞ ≠ (r : ℝ≥0∞) := with_top.top_ne_coe
@[simp] lemma of_real_ne_top {r : ℝ} : ennreal.of_real r ≠ ∞ := by simp [ennreal.of_real]
@[simp] lemma of_real_lt_top {r : ℝ} : ennreal.of_real r < ∞ := lt_top_iff_ne_top.2 of_real_ne_top
@[simp] lemma top_ne_of_real {r : ℝ} : ∞ ≠ ennreal.of_real r := by simp [ennreal.of_real]
@[simp] lemma zero_ne_top : 0 ≠ ∞ := coe_ne_top
@[simp] lemma top_ne_zero : ∞ ≠ 0 := top_ne_coe
@[simp] lemma one_ne_top : 1 ≠ ∞ := coe_ne_top
@[simp] lemma top_ne_one : ∞ ≠ 1 := top_ne_coe
@[simp, norm_cast] lemma coe_eq_coe : (↑r : ℝ≥0∞) = ↑q ↔ r = q := with_top.coe_eq_coe
@[simp, norm_cast] lemma coe_le_coe : (↑r : ℝ≥0∞) ≤ ↑q ↔ r ≤ q := with_top.coe_le_coe
@[simp, norm_cast] lemma coe_lt_coe : (↑r : ℝ≥0∞) < ↑q ↔ r < q := with_top.coe_lt_coe
lemma coe_mono : monotone (coe : ℝ≥0 → ℝ≥0∞) := λ _ _, coe_le_coe.2
@[simp, norm_cast] lemma coe_eq_zero : (↑r : ℝ≥0∞) = 0 ↔ r = 0 := coe_eq_coe
@[simp, norm_cast] lemma zero_eq_coe : 0 = (↑r : ℝ≥0∞) ↔ 0 = r := coe_eq_coe
@[simp, norm_cast] lemma coe_eq_one : (↑r : ℝ≥0∞) = 1 ↔ r = 1 := coe_eq_coe
@[simp, norm_cast] lemma one_eq_coe : 1 = (↑r : ℝ≥0∞) ↔ 1 = r := coe_eq_coe
@[simp, norm_cast] lemma coe_nonneg : 0 ≤ (↑r : ℝ≥0∞) ↔ 0 ≤ r := coe_le_coe
@[simp, norm_cast] lemma coe_pos : 0 < (↑r : ℝ≥0∞) ↔ 0 < r := coe_lt_coe
lemma coe_ne_zero : (r : ℝ≥0∞) ≠ 0 ↔ r ≠ 0 := not_congr coe_eq_coe
@[simp, norm_cast] lemma coe_add : ↑(r + p) = (r + p : ℝ≥0∞) := with_top.coe_add
@[simp, norm_cast] lemma coe_mul : ↑(r * p) = (r * p : ℝ≥0∞) := with_top.coe_mul
@[simp, norm_cast] lemma coe_bit0 : (↑(bit0 r) : ℝ≥0∞) = bit0 r := coe_add
@[simp, norm_cast] lemma coe_bit1 : (↑(bit1 r) : ℝ≥0∞) = bit1 r := by simp [bit1]
lemma coe_two : ((2:ℝ≥0) : ℝ≥0∞) = 2 := by norm_cast
protected lemma zero_lt_one : 0 < (1 : ℝ≥0∞) :=
canonically_ordered_comm_semiring.zero_lt_one
@[simp] lemma one_lt_two : (1 : ℝ≥0∞) < 2 :=
coe_one ▸ coe_two ▸ by exact_mod_cast (@one_lt_two ℕ _ _)
lemma one_le_two : (1 : ℝ≥0∞) ≤ 2 := one_lt_two.le
@[simp] lemma zero_lt_two : (0:ℝ≥0∞) < 2 := lt_trans ennreal.zero_lt_one one_lt_two
lemma two_ne_zero : (2:ℝ≥0∞) ≠ 0 := (ne_of_lt zero_lt_two).symm
lemma two_ne_top : (2:ℝ≥0∞) ≠ ∞ := coe_two ▸ coe_ne_top
/-- `(1 : ℝ≥0∞) ≤ 1`, recorded as a `fact` for use with `Lp` spaces. -/
instance _root_.fact_one_le_one_ennreal : fact ((1 : ℝ≥0∞) ≤ 1) := ⟨le_rfl⟩
/-- `(1 : ℝ≥0∞) ≤ 2`, recorded as a `fact` for use with `Lp` spaces. -/
instance _root_.fact_one_le_two_ennreal : fact ((1 : ℝ≥0∞) ≤ 2) :=
⟨ennreal.coe_le_coe.2 (show (1 : ℝ≥0) ≤ 2, by norm_num)⟩
/-- `(1 : ℝ≥0∞) ≤ ∞`, recorded as a `fact` for use with `Lp` spaces. -/
instance _root_.fact_one_le_top_ennreal : fact ((1 : ℝ≥0∞) ≤ ∞) := ⟨le_top⟩
/-- The set of numbers in `ℝ≥0∞` that are not equal to `∞` is equivalent to `ℝ≥0`. -/
def ne_top_equiv_nnreal : {a | a ≠ ∞} ≃ ℝ≥0 :=
{ to_fun := λ x, ennreal.to_nnreal x,
inv_fun := λ x, ⟨x, coe_ne_top⟩,
left_inv := λ ⟨x, hx⟩, subtype.eq $ coe_to_nnreal hx,
right_inv := λ x, to_nnreal_coe }
lemma cinfi_ne_top [has_Inf α] (f : ℝ≥0∞ → α) : (⨅ x : {x // x ≠ ∞}, f x) = ⨅ x : ℝ≥0, f x :=
eq.symm $ ne_top_equiv_nnreal.symm.surjective.infi_congr _$ λ x, rfl
lemma infi_ne_top [complete_lattice α] (f : ℝ≥0∞ → α) : (⨅ x ≠ ∞, f x) = ⨅ x : ℝ≥0, f x :=
by rw [infi_subtype', cinfi_ne_top]
lemma csupr_ne_top [has_Sup α] (f : ℝ≥0∞ → α) : (⨆ x : {x // x ≠ ∞}, f x) = ⨆ x : ℝ≥0, f x :=
@cinfi_ne_top αᵒᵈ _ _
lemma supr_ne_top [complete_lattice α] (f : ℝ≥0∞ → α) : (⨆ x ≠ ∞, f x) = ⨆ x : ℝ≥0, f x :=
@infi_ne_top αᵒᵈ _ _
lemma infi_ennreal {α : Type*} [complete_lattice α] {f : ℝ≥0∞ → α} :
(⨅ n, f n) = (⨅ n : ℝ≥0, f n) ⊓ f ∞ :=
le_antisymm
(le_inf (le_infi $ assume i, infi_le _ _) (infi_le _ _))
(le_infi $ forall_ennreal.2 ⟨λ r, inf_le_of_left_le $ infi_le _ _, inf_le_right⟩)
lemma supr_ennreal {α : Type*} [complete_lattice α] {f : ℝ≥0∞ → α} :
(⨆ n, f n) = (⨆ n : ℝ≥0, f n) ⊔ f ∞ :=
@infi_ennreal αᵒᵈ _ _
@[simp] lemma add_top : a + ∞ = ∞ := add_top _
@[simp] lemma top_add : ∞ + a = ∞ := top_add _
/-- Coercion `ℝ≥0 → ℝ≥0∞` as a `ring_hom`. -/
def of_nnreal_hom : ℝ≥0 →+* ℝ≥0∞ :=
⟨coe, coe_one, λ _ _, coe_mul, coe_zero, λ _ _, coe_add⟩
@[simp] lemma coe_of_nnreal_hom : ⇑of_nnreal_hom = coe := rfl
section actions
/-- A `mul_action` over `ℝ≥0∞` restricts to a `mul_action` over `ℝ≥0`. -/
noncomputable instance {M : Type*} [mul_action ℝ≥0∞ M] : mul_action ℝ≥0 M :=
mul_action.comp_hom M of_nnreal_hom.to_monoid_hom
lemma smul_def {M : Type*} [mul_action ℝ≥0∞ M] (c : ℝ≥0) (x : M) :
c • x = (c : ℝ≥0∞) • x := rfl
instance {M N : Type*} [mul_action ℝ≥0∞ M] [mul_action ℝ≥0∞ N] [has_scalar M N]
[is_scalar_tower ℝ≥0∞ M N] : is_scalar_tower ℝ≥0 M N :=
{ smul_assoc := λ r, (smul_assoc (r : ℝ≥0∞) : _)}
instance smul_comm_class_left {M N : Type*} [mul_action ℝ≥0∞ N] [has_scalar M N]
[smul_comm_class ℝ≥0∞ M N] : smul_comm_class ℝ≥0 M N :=
{ smul_comm := λ r, (smul_comm (r : ℝ≥0∞) : _)}
instance smul_comm_class_right {M N : Type*} [mul_action ℝ≥0∞ N] [has_scalar M N]
[smul_comm_class M ℝ≥0∞ N] : smul_comm_class M ℝ≥0 N :=
{ smul_comm := λ m r, (smul_comm m (r : ℝ≥0∞) : _)}
/-- A `distrib_mul_action` over `ℝ≥0∞` restricts to a `distrib_mul_action` over `ℝ≥0`. -/
noncomputable instance {M : Type*} [add_monoid M] [distrib_mul_action ℝ≥0∞ M] :
distrib_mul_action ℝ≥0 M :=
distrib_mul_action.comp_hom M of_nnreal_hom.to_monoid_hom
/-- A `module` over `ℝ≥0∞` restricts to a `module` over `ℝ≥0`. -/
noncomputable instance {M : Type*} [add_comm_monoid M] [module ℝ≥0∞ M] : module ℝ≥0 M :=
module.comp_hom M of_nnreal_hom
/-- An `algebra` over `ℝ≥0∞` restricts to an `algebra` over `ℝ≥0`. -/
noncomputable instance {A : Type*} [semiring A] [algebra ℝ≥0∞ A] : algebra ℝ≥0 A :=
{ smul := (•),
commutes' := λ r x, by simp [algebra.commutes],
smul_def' := λ r x, by simp [←algebra.smul_def (r : ℝ≥0∞) x, smul_def],
to_ring_hom := ((algebra_map ℝ≥0∞ A).comp (of_nnreal_hom : ℝ≥0 →+* ℝ≥0∞)) }
-- verify that the above produces instances we might care about
noncomputable example : algebra ℝ≥0 ℝ≥0∞ := infer_instance
noncomputable example : distrib_mul_action ℝ≥0ˣ ℝ≥0∞ := infer_instance
lemma coe_smul {R} (r : R) (s : ℝ≥0) [has_scalar R ℝ≥0] [has_scalar R ℝ≥0∞]
[is_scalar_tower R ℝ≥0 ℝ≥0] [is_scalar_tower R ℝ≥0 ℝ≥0∞] :
(↑(r • s) : ℝ≥0∞) = r • ↑s :=
by rw [←smul_one_smul ℝ≥0 r (s: ℝ≥0∞), smul_def, smul_eq_mul, ←ennreal.coe_mul, smul_mul_assoc,
one_mul]
end actions
@[simp, norm_cast] lemma coe_indicator {α} (s : set α) (f : α → ℝ≥0) (a : α) :
((s.indicator f a : ℝ≥0) : ℝ≥0∞) = s.indicator (λ x, f x) a :=
(of_nnreal_hom : ℝ≥0 →+ ℝ≥0∞).map_indicator _ _ _
@[simp, norm_cast] lemma coe_pow (n : ℕ) : (↑(r^n) : ℝ≥0∞) = r^n :=
of_nnreal_hom.map_pow r n
@[simp] lemma add_eq_top : a + b = ∞ ↔ a = ∞ ∨ b = ∞ := with_top.add_eq_top
@[simp] lemma add_lt_top : a + b < ∞ ↔ a < ∞ ∧ b < ∞ := with_top.add_lt_top
lemma to_nnreal_add {r₁ r₂ : ℝ≥0∞} (h₁ : r₁ ≠ ∞) (h₂ : r₂ ≠ ∞) :
(r₁ + r₂).to_nnreal = r₁.to_nnreal + r₂.to_nnreal :=
by { lift r₁ to ℝ≥0 using h₁, lift r₂ to ℝ≥0 using h₂, refl }
lemma not_lt_top {x : ℝ≥0∞} : ¬ x < ∞ ↔ x = ∞ := by rw [lt_top_iff_ne_top, not_not]
lemma add_ne_top : a + b ≠ ∞ ↔ a ≠ ∞ ∧ b ≠ ∞ :=
by simpa only [lt_top_iff_ne_top] using add_lt_top
lemma mul_top : a * ∞ = (if a = 0 then 0 else ∞) :=
begin split_ifs, { simp [h] }, { exact with_top.mul_top h } end
lemma top_mul : ∞ * a = (if a = 0 then 0 else ∞) :=
begin split_ifs, { simp [h] }, { exact with_top.top_mul h } end
@[simp] lemma top_mul_top : ∞ * ∞ = ∞ := with_top.top_mul_top
lemma top_pow {n:ℕ} (h : 0 < n) : ∞^n = ∞ :=
nat.le_induction (pow_one _) (λ m hm hm', by rw [pow_succ, hm', top_mul_top])
_ (nat.succ_le_of_lt h)
lemma mul_eq_top : a * b = ∞ ↔ (a ≠ 0 ∧ b = ∞) ∨ (a = ∞ ∧ b ≠ 0) :=
with_top.mul_eq_top_iff
lemma mul_lt_top : a ≠ ∞ → b ≠ ∞ → a * b < ∞ :=
with_top.mul_lt_top
lemma mul_ne_top : a ≠ ∞ → b ≠ ∞ → a * b ≠ ∞ :=
by simpa only [lt_top_iff_ne_top] using mul_lt_top
lemma lt_top_of_mul_ne_top_left (h : a * b ≠ ∞) (hb : b ≠ 0) : a < ∞ :=
lt_top_iff_ne_top.2 $ λ ha, h $ mul_eq_top.2 (or.inr ⟨ha, hb⟩)
lemma lt_top_of_mul_ne_top_right (h : a * b ≠ ∞) (ha : a ≠ 0) : b < ∞ :=
lt_top_of_mul_ne_top_left (by rwa [mul_comm]) ha
lemma mul_lt_top_iff {a b : ℝ≥0∞} : a * b < ∞ ↔ (a < ∞ ∧ b < ∞) ∨ a = 0 ∨ b = 0 :=
begin
split,
{ intro h, rw [← or_assoc, or_iff_not_imp_right, or_iff_not_imp_right], intros hb ha,
exact ⟨lt_top_of_mul_ne_top_left h.ne hb, lt_top_of_mul_ne_top_right h.ne ha⟩ },
{ rintro (⟨ha, hb⟩|rfl|rfl); [exact mul_lt_top ha.ne hb.ne, simp, simp] }
end
lemma mul_self_lt_top_iff {a : ℝ≥0∞} : a * a < ⊤ ↔ a < ⊤ :=
by { rw [ennreal.mul_lt_top_iff, and_self, or_self, or_iff_left_iff_imp], rintro rfl, norm_num }
lemma mul_pos_iff : 0 < a * b ↔ 0 < a ∧ 0 < b := canonically_ordered_comm_semiring.mul_pos
lemma mul_pos (ha : a ≠ 0) (hb : b ≠ 0) : 0 < a * b :=
mul_pos_iff.2 ⟨pos_iff_ne_zero.2 ha, pos_iff_ne_zero.2 hb⟩
@[simp] lemma pow_eq_top_iff {n : ℕ} : a ^ n = ∞ ↔ a = ∞ ∧ n ≠ 0 :=
begin
induction n with n ihn, { simp },
rw [pow_succ, mul_eq_top, ihn],
fsplit,
{ rintro (⟨-,rfl,h0⟩|⟨rfl,h0⟩); exact ⟨rfl, n.succ_ne_zero⟩ },
{ rintro ⟨rfl, -⟩, exact or.inr ⟨rfl, pow_ne_zero n top_ne_zero⟩ }
end
lemma pow_eq_top (n : ℕ) (h : a ^ n = ∞) : a = ∞ :=
(pow_eq_top_iff.1 h).1
lemma pow_ne_top (h : a ≠ ∞) {n:ℕ} : a^n ≠ ∞ :=
mt (pow_eq_top n) h
lemma pow_lt_top : a < ∞ → ∀ n:ℕ, a^n < ∞ :=
by simpa only [lt_top_iff_ne_top] using pow_ne_top
@[simp, norm_cast] lemma coe_finset_sum {s : finset α} {f : α → ℝ≥0} :
↑(∑ a in s, f a) = (∑ a in s, f a : ℝ≥0∞) :=
of_nnreal_hom.map_sum f s
@[simp, norm_cast] lemma coe_finset_prod {s : finset α} {f : α → ℝ≥0} :
↑(∏ a in s, f a) = ((∏ a in s, f a) : ℝ≥0∞) :=
of_nnreal_hom.map_prod f s
section order
@[simp] lemma bot_eq_zero : (⊥ : ℝ≥0∞) = 0 := rfl
@[simp] lemma coe_lt_top : coe r < ∞ := with_top.coe_lt_top r
@[simp] lemma not_top_le_coe : ¬ ∞ ≤ ↑r := with_top.not_top_le_coe r
@[simp, norm_cast] lemma one_le_coe_iff : (1:ℝ≥0∞) ≤ ↑r ↔ 1 ≤ r := coe_le_coe
@[simp, norm_cast] lemma coe_le_one_iff : ↑r ≤ (1:ℝ≥0∞) ↔ r ≤ 1 := coe_le_coe
@[simp, norm_cast] lemma coe_lt_one_iff : (↑p : ℝ≥0∞) < 1 ↔ p < 1 := coe_lt_coe
@[simp, norm_cast] lemma one_lt_coe_iff : 1 < (↑p : ℝ≥0∞) ↔ 1 < p := coe_lt_coe
@[simp, norm_cast] lemma coe_nat (n : ℕ) : ((n : ℝ≥0) : ℝ≥0∞) = n := with_top.coe_nat n
@[simp] lemma of_real_coe_nat (n : ℕ) : ennreal.of_real n = n := by simp [ennreal.of_real]
@[simp] lemma nat_ne_top (n : ℕ) : (n : ℝ≥0∞) ≠ ∞ := with_top.nat_ne_top n
@[simp] lemma top_ne_nat (n : ℕ) : ∞ ≠ n := with_top.top_ne_nat n
@[simp] lemma one_lt_top : 1 < ∞ := coe_lt_top
@[simp, norm_cast] lemma to_nnreal_nat (n : ℕ) : (n : ℝ≥0∞).to_nnreal = n :=
by conv_lhs { rw [← ennreal.coe_nat n, ennreal.to_nnreal_coe] }
@[simp, norm_cast] lemma to_real_nat (n : ℕ) : (n : ℝ≥0∞).to_real = n :=
by conv_lhs { rw [← ennreal.of_real_coe_nat n, ennreal.to_real_of_real (nat.cast_nonneg _)] }
lemma le_coe_iff : a ≤ ↑r ↔ (∃p:ℝ≥0, a = p ∧ p ≤ r) := with_top.le_coe_iff
lemma coe_le_iff : ↑r ≤ a ↔ (∀p:ℝ≥0, a = p → r ≤ p) := with_top.coe_le_iff
lemma lt_iff_exists_coe : a < b ↔ (∃p:ℝ≥0, a = p ∧ ↑p < b) := with_top.lt_iff_exists_coe
lemma to_real_le_coe_of_le_coe {a : ℝ≥0∞} {b : ℝ≥0} (h : a ≤ b) : a.to_real ≤ b :=
show ↑a.to_nnreal ≤ ↑b,
begin
have : ↑a.to_nnreal = a := ennreal.coe_to_nnreal (lt_of_le_of_lt h coe_lt_top).ne,
rw ← this at h,
exact_mod_cast h
end
@[simp, norm_cast] lemma coe_finset_sup {s : finset α} {f : α → ℝ≥0} :
↑(s.sup f) = s.sup (λ x, (f x : ℝ≥0∞)) :=
finset.comp_sup_eq_sup_comp_of_is_total _ coe_mono rfl
lemma pow_le_pow {n m : ℕ} (ha : 1 ≤ a) (h : n ≤ m) : a ^ n ≤ a ^ m :=
begin
cases a,
{ cases m,
{ rw eq_bot_iff.mpr h,
exact le_rfl },
{ rw [none_eq_top, top_pow (nat.succ_pos m)],
exact le_top } },
{ rw [some_eq_coe, ← coe_pow, ← coe_pow, coe_le_coe],
exact pow_le_pow (by simpa using ha) h }
end
lemma one_le_pow_of_one_le (ha : 1 ≤ a) (n : ℕ) : 1 ≤ a ^ n :=
by simpa using pow_le_pow ha (zero_le n)
@[simp] lemma max_eq_zero_iff : max a b = 0 ↔ a = 0 ∧ b = 0 :=
by simp only [nonpos_iff_eq_zero.symm, max_le_iff]
@[simp] lemma max_zero_left : max 0 a = a := max_eq_right (zero_le a)
@[simp] lemma max_zero_right : max a 0 = a := max_eq_left (zero_le a)
@[simp] lemma sup_eq_max : a ⊔ b = max a b :=
rfl
protected lemma pow_pos : 0 < a → ∀ n : ℕ, 0 < a^n :=
canonically_ordered_comm_semiring.pow_pos
protected lemma pow_ne_zero : a ≠ 0 → ∀ n : ℕ, a^n ≠ 0 :=
by simpa only [pos_iff_ne_zero] using ennreal.pow_pos
@[simp] lemma not_lt_zero : ¬ a < 0 := by simp
protected lemma le_of_add_le_add_left : a ≠ ∞ → a + b ≤ a + c → b ≤ c :=
with_top.le_of_add_le_add_left
protected lemma le_of_add_le_add_right : a ≠ ∞ → b + a ≤ c + a → b ≤ c :=
with_top.le_of_add_le_add_right
protected lemma add_lt_add_left : a ≠ ∞ → b < c → a + b < a + c := with_top.add_lt_add_left
protected lemma add_lt_add_right : a ≠ ∞ → b < c → b + a < c + a := with_top.add_lt_add_right
protected lemma add_le_add_iff_left : a ≠ ∞ → (a + b ≤ a + c ↔ b ≤ c) :=
with_top.add_le_add_iff_left
protected lemma add_le_add_iff_right : a ≠ ∞ → (b + a ≤ c + a ↔ b ≤ c) :=
with_top.add_le_add_iff_right
protected lemma add_lt_add_iff_left : a ≠ ∞ → (a + b < a + c ↔ b < c) :=
with_top.add_lt_add_iff_left
protected lemma add_lt_add_iff_right : a ≠ ∞ → (b + a < c + a ↔ b < c) :=
with_top.add_lt_add_iff_right
protected lemma add_lt_add_of_le_of_lt : a ≠ ∞ → a ≤ b → c < d → a + c < b + d :=
with_top.add_lt_add_of_le_of_lt
protected lemma add_lt_add_of_lt_of_le : c ≠ ∞ → a < b → c ≤ d → a + c < b + d :=
with_top.add_lt_add_of_lt_of_le
instance contravariant_class_add_lt : contravariant_class ℝ≥0∞ ℝ≥0∞ (+) (<) :=
with_top.contravariant_class_add_lt
lemma lt_add_right (ha : a ≠ ∞) (hb : b ≠ 0) : a < a + b :=
by rwa [← pos_iff_ne_zero, ←ennreal.add_lt_add_iff_left ha, add_zero] at hb
lemma le_of_forall_pos_le_add : ∀{a b : ℝ≥0∞}, (∀ε : ℝ≥0, 0 < ε → b < ∞ → a ≤ b + ε) → a ≤ b
| a none h := le_top
| none (some a) h :=
have ∞ ≤ ↑a + ↑(1:ℝ≥0), from h 1 zero_lt_one coe_lt_top,
by rw [← coe_add] at this; exact (not_top_le_coe this).elim
| (some a) (some b) h :=
by simp only [none_eq_top, some_eq_coe, coe_add.symm, coe_le_coe, coe_lt_top, true_implies_iff]
at *; exact nnreal.le_of_forall_pos_le_add h
lemma lt_iff_exists_rat_btwn :
a < b ↔ (∃q:ℚ, 0 ≤ q ∧ a < real.to_nnreal q ∧ (real.to_nnreal q:ℝ≥0∞) < b) :=
⟨λ h,
begin
rcases lt_iff_exists_coe.1 h with ⟨p, rfl, _⟩,
rcases exists_between h with ⟨c, pc, cb⟩,
rcases lt_iff_exists_coe.1 cb with ⟨r, rfl, _⟩,
rcases (nnreal.lt_iff_exists_rat_btwn _ _).1 (coe_lt_coe.1 pc) with ⟨q, hq0, pq, qr⟩,
exact ⟨q, hq0, coe_lt_coe.2 pq, lt_trans (coe_lt_coe.2 qr) cb⟩
end,
λ ⟨q, q0, qa, qb⟩, lt_trans qa qb⟩
lemma lt_iff_exists_real_btwn :
a < b ↔ (∃r:ℝ, 0 ≤ r ∧ a < ennreal.of_real r ∧ (ennreal.of_real r:ℝ≥0∞) < b) :=
⟨λ h, let ⟨q, q0, aq, qb⟩ := ennreal.lt_iff_exists_rat_btwn.1 h in
⟨q, rat.cast_nonneg.2 q0, aq, qb⟩,
λ ⟨q, q0, qa, qb⟩, lt_trans qa qb⟩
lemma lt_iff_exists_nnreal_btwn :
a < b ↔ (∃r:ℝ≥0, a < r ∧ (r : ℝ≥0∞) < b) :=
with_top.lt_iff_exists_coe_btwn
lemma lt_iff_exists_add_pos_lt : a < b ↔ (∃ r : ℝ≥0, 0 < r ∧ a + r < b) :=
begin
refine ⟨λ hab, _, λ ⟨r, rpos, hr⟩, lt_of_le_of_lt (le_self_add) hr⟩,
cases a, { simpa using hab },
rcases lt_iff_exists_real_btwn.1 hab with ⟨c, c_nonneg, ac, cb⟩,
let d : ℝ≥0 := ⟨c, c_nonneg⟩,
have ad : a < d,
{ rw of_real_eq_coe_nnreal c_nonneg at ac,
exact coe_lt_coe.1 ac },
refine ⟨d-a, tsub_pos_iff_lt.2 ad, _⟩,
rw [some_eq_coe, ← coe_add],
convert cb,
have : real.to_nnreal c = d,
by { rw [← nnreal.coe_eq, real.coe_to_nnreal _ c_nonneg], refl },
rw [add_comm, this],
exact tsub_add_cancel_of_le ad.le
end
lemma coe_nat_lt_coe {n : ℕ} : (n : ℝ≥0∞) < r ↔ ↑n < r := ennreal.coe_nat n ▸ coe_lt_coe
lemma coe_lt_coe_nat {n : ℕ} : (r : ℝ≥0∞) < n ↔ r < n := ennreal.coe_nat n ▸ coe_lt_coe
@[simp, norm_cast] lemma coe_nat_lt_coe_nat {m n : ℕ} : (m : ℝ≥0∞) < n ↔ m < n :=
ennreal.coe_nat n ▸ coe_nat_lt_coe.trans nat.cast_lt
lemma coe_nat_ne_top {n : ℕ} : (n : ℝ≥0∞) ≠ ∞ := ennreal.coe_nat n ▸ coe_ne_top
lemma coe_nat_mono : strict_mono (coe : ℕ → ℝ≥0∞) := λ _ _, coe_nat_lt_coe_nat.2
@[simp, norm_cast] lemma coe_nat_le_coe_nat {m n : ℕ} : (m : ℝ≥0∞) ≤ n ↔ m ≤ n :=
coe_nat_mono.le_iff_le
instance : char_zero ℝ≥0∞ := ⟨coe_nat_mono.injective⟩
protected lemma exists_nat_gt {r : ℝ≥0∞} (h : r ≠ ∞) : ∃n:ℕ, r < n :=
begin
lift r to ℝ≥0 using h,
rcases exists_nat_gt r with ⟨n, hn⟩,
exact ⟨n, coe_lt_coe_nat.2 hn⟩,
end
lemma add_lt_add (ac : a < c) (bd : b < d) : a + b < c + d :=
begin
lift a to ℝ≥0 using ne_top_of_lt ac,
lift b to ℝ≥0 using ne_top_of_lt bd,
cases c, { simp }, cases d, { simp },
simp only [← coe_add, some_eq_coe, coe_lt_coe] at *,
exact add_lt_add ac bd
end
@[norm_cast] lemma coe_min : ((min r p:ℝ≥0):ℝ≥0∞) = min r p :=
coe_mono.map_min
@[norm_cast] lemma coe_max : ((max r p:ℝ≥0):ℝ≥0∞) = max r p :=
coe_mono.map_max
lemma le_of_top_imp_top_of_to_nnreal_le {a b : ℝ≥0∞} (h : a = ⊤ → b = ⊤)
(h_nnreal : a ≠ ⊤ → b ≠ ⊤ → a.to_nnreal ≤ b.to_nnreal) :
a ≤ b :=
begin
by_cases ha : a = ⊤,
{ rw h ha,
exact le_top, },
by_cases hb : b = ⊤,
{ rw hb,
exact le_top, },
rw [←coe_to_nnreal hb, ←coe_to_nnreal ha, coe_le_coe],
exact h_nnreal ha hb,
end
end order
section complete_lattice
lemma coe_Sup {s : set ℝ≥0} : bdd_above s → (↑(Sup s) : ℝ≥0∞) = (⨆a∈s, ↑a) := with_top.coe_Sup
lemma coe_Inf {s : set ℝ≥0} : s.nonempty → (↑(Inf s) : ℝ≥0∞) = (⨅a∈s, ↑a) := with_top.coe_Inf
@[simp] lemma top_mem_upper_bounds {s : set ℝ≥0∞} : ∞ ∈ upper_bounds s :=
assume x hx, le_top
lemma coe_mem_upper_bounds {s : set ℝ≥0} :
↑r ∈ upper_bounds ((coe : ℝ≥0 → ℝ≥0∞) '' s) ↔ r ∈ upper_bounds s :=
by simp [upper_bounds, ball_image_iff, -mem_image, *] {contextual := tt}
end complete_lattice
section mul
@[mono] lemma mul_le_mul : a ≤ b → c ≤ d → a * c ≤ b * d :=
mul_le_mul'
@[mono] lemma mul_lt_mul (ac : a < c) (bd : b < d) : a * b < c * d :=
begin
rcases lt_iff_exists_nnreal_btwn.1 ac with ⟨a', aa', a'c⟩,
lift a to ℝ≥0 using ne_top_of_lt aa',
rcases lt_iff_exists_nnreal_btwn.1 bd with ⟨b', bb', b'd⟩,
lift b to ℝ≥0 using ne_top_of_lt bb',
norm_cast at *,
calc ↑(a * b) < ↑(a' * b') :
coe_lt_coe.2 (mul_lt_mul' aa'.le bb' (zero_le _) ((zero_le a).trans_lt aa'))
... = ↑a' * ↑b' : coe_mul
... ≤ c * d : mul_le_mul a'c.le b'd.le
end
lemma mul_left_mono : monotone ((*) a) := λ b c, mul_le_mul le_rfl
lemma mul_right_mono : monotone (λ x, x * a) := λ b c h, mul_le_mul h le_rfl
lemma pow_strict_mono {n : ℕ} (hn : n ≠ 0) : strict_mono (λ (x : ℝ≥0∞), x^n) :=
begin
assume x y hxy,
obtain ⟨n, rfl⟩ := nat.exists_eq_succ_of_ne_zero hn,
induction n with n IH,
{ simp only [hxy, pow_one] },
{ simp only [pow_succ _ n.succ, mul_lt_mul hxy (IH (nat.succ_pos _).ne')] }
end
lemma max_mul : max a b * c = max (a * c) (b * c) :=
mul_right_mono.map_max
lemma mul_max : a * max b c = max (a * b) (a * c) :=
mul_left_mono.map_max
lemma mul_eq_mul_left : a ≠ 0 → a ≠ ∞ → (a * b = a * c ↔ b = c) :=
begin
cases a; cases b; cases c;
simp [none_eq_top, some_eq_coe, mul_top, top_mul, -coe_mul, coe_mul.symm,
nnreal.mul_eq_mul_left] {contextual := tt},
end
lemma mul_eq_mul_right : c ≠ 0 → c ≠ ∞ → (a * c = b * c ↔ a = b) :=
mul_comm c a ▸ mul_comm c b ▸ mul_eq_mul_left
lemma mul_le_mul_left : a ≠ 0 → a ≠ ∞ → (a * b ≤ a * c ↔ b ≤ c) :=
begin
cases a; cases b; cases c;
simp [none_eq_top, some_eq_coe, mul_top, top_mul, -coe_mul, coe_mul.symm] {contextual := tt},
assume h, exact mul_le_mul_left (pos_iff_ne_zero.2 h)
end
lemma mul_le_mul_right : c ≠ 0 → c ≠ ∞ → (a * c ≤ b * c ↔ a ≤ b) :=
mul_comm c a ▸ mul_comm c b ▸ mul_le_mul_left
lemma mul_lt_mul_left : a ≠ 0 → a ≠ ∞ → (a * b < a * c ↔ b < c) :=
λ h0 ht, by simp only [mul_le_mul_left h0 ht, lt_iff_le_not_le]
lemma mul_lt_mul_right : c ≠ 0 → c ≠ ∞ → (a * c < b * c ↔ a < b) :=
mul_comm c a ▸ mul_comm c b ▸ mul_lt_mul_left
end mul
section cancel
/-- An element `a` is `add_le_cancellable` if `a + b ≤ a + c` implies `b ≤ c` for all `b` and `c`.
This is true in `ℝ≥0∞` for all elements except `∞`. -/
lemma add_le_cancellable_iff_ne {a : ℝ≥0∞} : add_le_cancellable a ↔ a ≠ ∞ :=
begin
split,
{ rintro h rfl, refine ennreal.zero_lt_one.not_le (h _), simp, },
{ rintro h b c hbc, apply ennreal.le_of_add_le_add_left h hbc }
end
/-- This lemma has an abbreviated name because it is used frequently. -/
lemma cancel_of_ne {a : ℝ≥0∞} (h : a ≠ ∞) : add_le_cancellable a :=
add_le_cancellable_iff_ne.mpr h
/-- This lemma has an abbreviated name because it is used frequently. -/
lemma cancel_of_lt {a : ℝ≥0∞} (h : a < ∞) : add_le_cancellable a :=
cancel_of_ne h.ne
/-- This lemma has an abbreviated name because it is used frequently. -/
lemma cancel_of_lt' {a b : ℝ≥0∞} (h : a < b) : add_le_cancellable a :=
cancel_of_ne h.ne_top
/-- This lemma has an abbreviated name because it is used frequently. -/
lemma cancel_coe {a : ℝ≥0} : add_le_cancellable (a : ℝ≥0∞) :=
cancel_of_ne coe_ne_top
lemma add_right_inj (h : a ≠ ∞) : a + b = a + c ↔ b = c :=
(cancel_of_ne h).inj
lemma add_left_inj (h : a ≠ ∞) : b + a = c + a ↔ b = c :=
(cancel_of_ne h).inj_left
end cancel
section sub
lemma sub_eq_Inf {a b : ℝ≥0∞} : a - b = Inf {d | a ≤ d + b} :=
le_antisymm (le_Inf $ λ c, tsub_le_iff_right.mpr) $ Inf_le le_tsub_add
/-- This is a special case of `with_top.coe_sub` in the `ennreal` namespace -/
lemma coe_sub : (↑(r - p) : ℝ≥0∞) = ↑r - ↑p :=
with_top.coe_sub
/-- This is a special case of `with_top.top_sub_coe` in the `ennreal` namespace -/
lemma top_sub_coe : ∞ - ↑r = ∞ :=
with_top.top_sub_coe
/-- This is a special case of `with_top.sub_top` in the `ennreal` namespace -/
lemma sub_top : a - ∞ = 0 :=
with_top.sub_top
lemma sub_eq_top_iff : a - b = ∞ ↔ a = ∞ ∧ b ≠ ∞ :=
by { cases a; cases b; simp [← with_top.coe_sub] }
lemma sub_ne_top (ha : a ≠ ∞) : a - b ≠ ∞ :=
mt sub_eq_top_iff.mp $ mt and.left ha
protected lemma sub_eq_of_eq_add (hb : b ≠ ∞) : a = c + b → a - b = c :=
(cancel_of_ne hb).tsub_eq_of_eq_add
protected lemma eq_sub_of_add_eq (hc : c ≠ ∞) : a + c = b → a = b - c :=
(cancel_of_ne hc).eq_tsub_of_add_eq
protected lemma sub_eq_of_eq_add_rev (hb : b ≠ ∞) : a = b + c → a - b = c :=
(cancel_of_ne hb).tsub_eq_of_eq_add_rev
lemma sub_eq_of_add_eq (hb : b ≠ ∞) (hc : a + b = c) : c - b = a :=
ennreal.sub_eq_of_eq_add hb hc.symm
@[simp] protected lemma add_sub_cancel_left (ha : a ≠ ∞) : a + b - a = b :=
(cancel_of_ne ha).add_tsub_cancel_left
@[simp] protected lemma add_sub_cancel_right (hb : b ≠ ∞) : a + b - b = a :=
(cancel_of_ne hb).add_tsub_cancel_right
protected lemma lt_add_of_sub_lt_left (h : a ≠ ∞ ∨ b ≠ ∞) : a - b < c → a < b + c :=
begin
obtain rfl | hb := eq_or_ne b ∞,
{ rw [top_add, lt_top_iff_ne_top],
exact λ _, h.resolve_right (not_not.2 rfl) },
{ exact (cancel_of_ne hb).lt_add_of_tsub_lt_left }
end
protected lemma lt_add_of_sub_lt_right (h : a ≠ ∞ ∨ c ≠ ∞) : a - c < b → a < b + c :=
add_comm c b ▸ ennreal.lt_add_of_sub_lt_left h
lemma le_sub_of_add_le_left (ha : a ≠ ∞) : a + b ≤ c → b ≤ c - a :=
(cancel_of_ne ha).le_tsub_of_add_le_left
lemma le_sub_of_add_le_right (hb : b ≠ ∞) : a + b ≤ c → a ≤ c - b :=
(cancel_of_ne hb).le_tsub_of_add_le_right
protected lemma sub_lt_of_lt_add (hac : c ≤ a) (h : a < b + c) : a - c < b :=
((cancel_of_lt' $ hac.trans_lt h).tsub_lt_iff_right hac).mpr h
protected lemma sub_lt_iff_lt_right (hb : b ≠ ∞) (hab : b ≤ a) : a - b < c ↔ a < c + b :=
(cancel_of_ne hb).tsub_lt_iff_right hab
protected lemma sub_lt_self (ha : a ≠ ∞) (ha₀ : a ≠ 0) (hb : b ≠ 0) : a - b < a :=
(cancel_of_ne ha).tsub_lt_self (pos_iff_ne_zero.2 ha₀) (pos_iff_ne_zero.2 hb)
protected lemma sub_lt_self_iff (ha : a ≠ ∞) : a - b < a ↔ 0 < a ∧ 0 < b :=
(cancel_of_ne ha).tsub_lt_self_iff
lemma sub_lt_of_sub_lt (h₂ : c ≤ a) (h₃ : a ≠ ∞ ∨ b ≠ ∞) (h₁ : a - b < c) : a - c < b :=
ennreal.sub_lt_of_lt_add h₂ (add_comm c b ▸ ennreal.lt_add_of_sub_lt_right h₃ h₁)
lemma sub_sub_cancel (h : a ≠ ∞) (h2 : b ≤ a) : a - (a - b) = b :=
(cancel_of_ne $ sub_ne_top h).tsub_tsub_cancel_of_le h2
lemma sub_right_inj {a b c : ℝ≥0∞} (ha : a ≠ ∞) (hb : b ≤ a) (hc : c ≤ a) :
a - b = a - c ↔ b = c :=
(cancel_of_ne ha).tsub_right_inj (cancel_of_ne $ ne_top_of_le_ne_top ha hb)
(cancel_of_ne $ ne_top_of_le_ne_top ha hc) hb hc
lemma sub_mul (h : 0 < b → b < a → c ≠ ∞) : (a - b) * c = a * c - b * c :=
begin
cases le_or_lt a b with hab hab, { simp [hab, mul_right_mono hab] },
rcases eq_or_lt_of_le (zero_le b) with rfl|hb, { simp },
exact (cancel_of_ne $ mul_ne_top hab.ne_top (h hb hab)).tsub_mul
end
lemma mul_sub (h : 0 < c → c < b → a ≠ ∞) : a * (b - c) = a * b - a * c :=
by { simp only [mul_comm a], exact sub_mul h }
end sub
section sum
open finset
/-- A product of finite numbers is still finite -/
lemma prod_lt_top {s : finset α} {f : α → ℝ≥0∞} (h : ∀ a ∈ s, f a ≠ ∞) : (∏ a in s, f a) < ∞ :=
with_top.prod_lt_top h
/-- A sum of finite numbers is still finite -/
lemma sum_lt_top {s : finset α} {f : α → ℝ≥0∞} (h : ∀ a ∈ s, f a ≠ ∞) : ∑ a in s, f a < ∞ :=
with_top.sum_lt_top h
/-- A sum of finite numbers is still finite -/
lemma sum_lt_top_iff {s : finset α} {f : α → ℝ≥0∞} :
∑ a in s, f a < ∞ ↔ (∀ a ∈ s, f a < ∞) :=
with_top.sum_lt_top_iff
/-- A sum of numbers is infinite iff one of them is infinite -/
lemma sum_eq_top_iff {s : finset α} {f : α → ℝ≥0∞} :
(∑ x in s, f x) = ∞ ↔ (∃ a ∈ s, f a = ∞) :=
with_top.sum_eq_top_iff
lemma lt_top_of_sum_ne_top {s : finset α} {f : α → ℝ≥0∞} (h : (∑ x in s, f x) ≠ ∞) {a : α}
(ha : a ∈ s) : f a < ∞ :=
sum_lt_top_iff.1 h.lt_top a ha
/-- seeing `ℝ≥0∞` as `ℝ≥0` does not change their sum, unless one of the `ℝ≥0∞` is
infinity -/
lemma to_nnreal_sum {s : finset α} {f : α → ℝ≥0∞} (hf : ∀a∈s, f a ≠ ∞) :
ennreal.to_nnreal (∑ a in s, f a) = ∑ a in s, ennreal.to_nnreal (f a) :=
begin
rw [← coe_eq_coe, coe_to_nnreal, coe_finset_sum, sum_congr rfl],
{ intros x hx, exact (coe_to_nnreal (hf x hx)).symm },
{ exact (sum_lt_top hf).ne }
end
/-- seeing `ℝ≥0∞` as `real` does not change their sum, unless one of the `ℝ≥0∞` is infinity -/
lemma to_real_sum {s : finset α} {f : α → ℝ≥0∞} (hf : ∀ a ∈ s, f a ≠ ∞) :
ennreal.to_real (∑ a in s, f a) = ∑ a in s, ennreal.to_real (f a) :=
by { rw [ennreal.to_real, to_nnreal_sum hf, nnreal.coe_sum], refl }
lemma of_real_sum_of_nonneg {s : finset α} {f : α → ℝ} (hf : ∀ i, i ∈ s → 0 ≤ f i) :
ennreal.of_real (∑ i in s, f i) = ∑ i in s, ennreal.of_real (f i) :=
begin
simp_rw [ennreal.of_real, ←coe_finset_sum, coe_eq_coe],
exact real.to_nnreal_sum_of_nonneg hf,
end
theorem sum_lt_sum_of_nonempty {s : finset α} (hs : s.nonempty)
{f g : α → ℝ≥0∞} (Hlt : ∀ i ∈ s, f i < g i) :
∑ i in s, f i < ∑ i in s, g i :=
begin
induction hs using finset.nonempty.cons_induction with a a s as hs IH,
{ simp [Hlt _ (finset.mem_singleton_self _)] },
{ simp only [as, finset.sum_cons, not_false_iff],
exact ennreal.add_lt_add (Hlt _ (finset.mem_cons_self _ _))
(IH (λ i hi, Hlt _ (finset.mem_cons.2 $ or.inr hi))) }
end
theorem exists_le_of_sum_le {s : finset α} (hs : s.nonempty)
{f g : α → ℝ≥0∞} (Hle : ∑ i in s, f i ≤ ∑ i in s, g i) :
∃ i ∈ s, f i ≤ g i :=
begin
contrapose! Hle,
apply ennreal.sum_lt_sum_of_nonempty hs Hle,
end
end sum
section interval
variables {x y z : ℝ≥0∞} {ε ε₁ ε₂ : ℝ≥0∞} {s : set ℝ≥0∞}
protected lemma Ico_eq_Iio : (Ico 0 y) = (Iio y) := Ico_bot
lemma mem_Iio_self_add : x ≠ ∞ → ε ≠ 0 → x ∈ Iio (x + ε) :=
assume xt ε0, lt_add_right xt ε0
lemma mem_Ioo_self_sub_add : x ≠ ∞ → x ≠ 0 → ε₁ ≠ 0 → ε₂ ≠ 0 → x ∈ Ioo (x - ε₁) (x + ε₂) :=
assume xt x0 ε0 ε0', ⟨ennreal.sub_lt_self xt x0 ε0, lt_add_right xt ε0'⟩
end interval
section bit
@[simp] lemma bit0_inj : bit0 a = bit0 b ↔ a = b :=
⟨λh, begin
rcases (lt_trichotomy a b) with h₁| h₂| h₃,
{ exact (absurd h (ne_of_lt (add_lt_add h₁ h₁))) },
{ exact h₂ },
{ exact (absurd h.symm (ne_of_lt (add_lt_add h₃ h₃))) }
end,
λh, congr_arg _ h⟩
@[simp] lemma bit0_eq_zero_iff : bit0 a = 0 ↔ a = 0 :=
by simpa only [bit0_zero] using @bit0_inj a 0
@[simp] lemma bit0_eq_top_iff : bit0 a = ∞ ↔ a = ∞ :=
by rw [bit0, add_eq_top, or_self]
@[simp] lemma bit1_inj : bit1 a = bit1 b ↔ a = b :=
⟨λh, begin
unfold bit1 at h,
rwa [add_left_inj, bit0_inj] at h,
simp [lt_top_iff_ne_top]
end,
λh, congr_arg _ h⟩
@[simp] lemma bit1_ne_zero : bit1 a ≠ 0 :=
by unfold bit1; simp
@[simp] lemma bit1_eq_one_iff : bit1 a = 1 ↔ a = 0 :=
by simpa only [bit1_zero] using @bit1_inj a 0
@[simp] lemma bit1_eq_top_iff : bit1 a = ∞ ↔ a = ∞ :=
by unfold bit1; rw add_eq_top; simp
end bit
section inv
noncomputable theory
instance : has_inv ℝ≥0∞ := ⟨λa, Inf {b | 1 ≤ a * b}⟩
instance : div_inv_monoid ℝ≥0∞ :=
{ inv := has_inv.inv,
.. (infer_instance : monoid ℝ≥0∞) }
@[simp] lemma inv_zero : (0 : ℝ≥0∞)⁻¹ = ∞ :=
show Inf {b : ℝ≥0∞ | 1 ≤ 0 * b} = ∞, by simp; refl
@[simp] lemma inv_top : ∞⁻¹ = 0 :=
bot_unique $ le_of_forall_le_of_dense $ λ a (h : a > 0), Inf_le $ by simp [*, ne_of_gt h, top_mul]
@[simp, norm_cast] lemma coe_inv (hr : r ≠ 0) : (↑r⁻¹ : ℝ≥0∞) = (↑r)⁻¹ :=
le_antisymm
(le_Inf $ assume b (hb : 1 ≤ ↑r * b), coe_le_iff.2 $
by rintros b rfl; rwa [← coe_mul, ← coe_one, coe_le_coe, ← nnreal.inv_le hr] at hb)
(Inf_le $ by simp; rw [← coe_mul, mul_inv_cancel hr]; exact le_refl 1)
lemma coe_inv_le : (↑r⁻¹ : ℝ≥0∞) ≤ (↑r)⁻¹ :=
if hr : r = 0 then by simp only [hr, inv_zero, coe_zero, le_top]
else by simp only [coe_inv hr, le_rfl]
@[norm_cast] lemma coe_inv_two : ((2⁻¹ : ℝ≥0) : ℝ≥0∞) = 2⁻¹ :=
by rw [coe_inv (ne_of_gt _root_.zero_lt_two), coe_two]
@[simp, norm_cast] lemma coe_div (hr : r ≠ 0) : (↑(p / r) : ℝ≥0∞) = p / r :=
by rw [div_eq_mul_inv, div_eq_mul_inv, coe_mul, coe_inv hr]
lemma div_zero (h : a ≠ 0) : a / 0 = ∞ := by simp [div_eq_mul_inv, h]
@[simp] lemma inv_one : (1 : ℝ≥0∞)⁻¹ = 1 :=
by simpa only [coe_inv one_ne_zero, coe_one] using coe_eq_coe.2 inv_one
@[simp] lemma div_one {a : ℝ≥0∞} : a / 1 = a :=
by rw [div_eq_mul_inv, inv_one, mul_one]
protected lemma inv_pow {n : ℕ} : (a^n)⁻¹ = (a⁻¹)^n :=
begin
by_cases a = 0; cases a; cases n; simp [*, none_eq_top, some_eq_coe,
zero_pow, top_pow, nat.zero_lt_succ] at *,
rw [← coe_inv h, ← coe_pow, ← coe_inv (pow_ne_zero _ h), ← inv_pow₀, coe_pow]
end
instance : has_involutive_inv ℝ≥0∞ :=
{ inv := has_inv.inv,
inv_inv := λ a, by
by_cases a = 0; cases a; simp [*, none_eq_top, some_eq_coe, -coe_inv, (coe_inv _).symm] at * }
@[simp] lemma inv_eq_top : a⁻¹ = ∞ ↔ a = 0 :=
inv_zero ▸ inv_inj
lemma inv_ne_top : a⁻¹ ≠ ∞ ↔ a ≠ 0 := by simp
@[simp] lemma inv_lt_top {x : ℝ≥0∞} : x⁻¹ < ∞ ↔ 0 < x :=
by { simp only [lt_top_iff_ne_top, inv_ne_top, pos_iff_ne_zero] }
lemma div_lt_top {x y : ℝ≥0∞} (h1 : x ≠ ∞) (h2 : y ≠ 0) : x / y < ∞ :=
mul_lt_top h1 (inv_ne_top.mpr h2)
@[simp] lemma inv_eq_zero : a⁻¹ = 0 ↔ a = ∞ :=
inv_top ▸ inv_inj
lemma inv_ne_zero : a⁻¹ ≠ 0 ↔ a ≠ ∞ := by simp
lemma mul_inv {a b : ℝ≥0∞} (ha : a ≠ 0 ∨ b ≠ ∞) (hb : a ≠ ∞ ∨ b ≠ 0) :
(a * b)⁻¹ = a⁻¹ * b⁻¹ :=
begin
induction b using with_top.rec_top_coe,
{ simp at ha, simp [ha], },
induction a using with_top.rec_top_coe,
{ simp at hb, simp [hb] },
by_cases h'a : a = 0,
{ simp only [h'a, with_top.top_mul, ennreal.inv_zero, ennreal.coe_ne_top, zero_mul, ne.def,
not_false_iff, ennreal.coe_zero, ennreal.inv_eq_zero] },
by_cases h'b : b = 0,
{ simp only [h'b, ennreal.inv_zero, ennreal.coe_ne_top, with_top.mul_top, ne.def, not_false_iff,
mul_zero, ennreal.coe_zero, ennreal.inv_eq_zero] },
rw [← ennreal.coe_mul, ← ennreal.coe_inv, ← ennreal.coe_inv h'a, ← ennreal.coe_inv h'b,
← ennreal.coe_mul, nnreal.mul_inv, mul_comm],
simp [h'a, h'b],
end
@[simp] lemma inv_pos : 0 < a⁻¹ ↔ a ≠ ∞ :=
pos_iff_ne_zero.trans inv_ne_zero
@[simp] lemma inv_lt_inv : a⁻¹ < b⁻¹ ↔ b < a :=
begin
cases a; cases b; simp only [some_eq_coe, none_eq_top, inv_top],
{ simp only [lt_irrefl] },
{ exact inv_pos.trans lt_top_iff_ne_top.symm },
{ simp only [not_lt_zero, not_top_lt] },
{ cases eq_or_lt_of_le (zero_le a) with ha ha,
{ subst a, simp },
cases eq_or_lt_of_le (zero_le b) with hb hb,
{ subst b, simp [pos_iff_ne_zero, lt_top_iff_ne_top, inv_ne_top] },
{ rw [← coe_inv (ne_of_gt ha), ← coe_inv (ne_of_gt hb), coe_lt_coe, coe_lt_coe],
simp only [nnreal.coe_lt_coe.symm] at *,
exact inv_lt_inv ha hb } }
end
lemma inv_lt_iff_inv_lt : a⁻¹ < b ↔ b⁻¹ < a :=
by simpa only [inv_inv] using @inv_lt_inv a b⁻¹
lemma lt_inv_iff_lt_inv : a < b⁻¹ ↔ b < a⁻¹ :=
by simpa only [inv_inv] using @inv_lt_inv a⁻¹ b
@[simp, priority 1100] -- higher than le_inv_iff_mul_le
lemma inv_le_inv : a⁻¹ ≤ b⁻¹ ↔ b ≤ a :=
by simp only [le_iff_lt_or_eq, inv_lt_inv, inv_inj, eq_comm]
lemma inv_le_iff_inv_le : a⁻¹ ≤ b ↔ b⁻¹ ≤ a :=
by simpa only [inv_inv] using @inv_le_inv a b⁻¹
lemma le_inv_iff_le_inv : a ≤ b⁻¹ ↔ b ≤ a⁻¹ :=
by simpa only [inv_inv] using @inv_le_inv a⁻¹ b
@[simp] lemma inv_le_one : a⁻¹ ≤ 1 ↔ 1 ≤ a :=
inv_le_iff_inv_le.trans $ by rw inv_one
lemma one_le_inv : 1 ≤ a⁻¹ ↔ a ≤ 1 :=
le_inv_iff_le_inv.trans $ by rw inv_one
@[simp] lemma inv_lt_one : a⁻¹ < 1 ↔ 1 < a :=
inv_lt_iff_inv_lt.trans $ by rw [inv_one]
/-- The inverse map `λ x, x⁻¹` is an order isomorphism between `ℝ≥0∞` and its `order_dual` -/
@[simps apply]
def _root_.order_iso.inv_ennreal : ℝ≥0∞ ≃o ℝ≥0∞ᵒᵈ :=
{ to_fun := λ x, x⁻¹,
inv_fun := λ x, x⁻¹,
map_rel_iff' := λ a b, ennreal.inv_le_inv,
..equiv.inv ℝ≥0∞ }
@[simp]
lemma _root_.order_iso.inv_ennreal_symm_apply : order_iso.inv_ennreal.symm a = a⁻¹ := rfl
lemma pow_le_pow_of_le_one {n m : ℕ} (ha : a ≤ 1) (h : n ≤ m) : a ^ m ≤ a ^ n :=
begin
rw [←inv_inv a, ← ennreal.inv_pow, ← @ennreal.inv_pow a⁻¹, inv_le_inv],
exact pow_le_pow (one_le_inv.2 ha) h
end
@[simp] lemma div_top : a / ∞ = 0 := by rw [div_eq_mul_inv, inv_top, mul_zero]
@[simp] lemma top_div_coe : ∞ / p = ∞ := by simp [div_eq_mul_inv, top_mul]
lemma top_div_of_ne_top (h : a ≠ ∞) : ∞ / a = ∞ :=
by { lift a to ℝ≥0 using h, exact top_div_coe }
lemma top_div_of_lt_top (h : a < ∞) : ∞ / a = ∞ :=
top_div_of_ne_top h.ne
lemma top_div : ∞ / a = if a = ∞ then 0 else ∞ :=
by by_cases a = ∞; simp [top_div_of_ne_top, *]
@[simp] lemma zero_div : 0 / a = 0 := zero_mul a⁻¹
lemma div_eq_top : a / b = ∞ ↔ (a ≠ 0 ∧ b = 0) ∨ (a = ∞ ∧ b ≠ ∞) :=
by simp [div_eq_mul_inv, ennreal.mul_eq_top]
lemma le_div_iff_mul_le (h0 : b ≠ 0 ∨ c ≠ 0) (ht : b ≠ ∞ ∨ c ≠ ∞) :
a ≤ c / b ↔ a * b ≤ c :=
begin
cases b,
{ simp at ht,
split,
{ assume ha, simp at ha, simp [ha] },
{ contrapose,
assume ha,
simp at ha,
have : a * ∞ = ∞, by simp [ennreal.mul_eq_top, ha],
simp [this, ht] } },
rcases eq_or_ne b 0 with (rfl | hb),
{ simp at h0,
have : c / 0 = ∞, by simp [div_eq_top, h0],
simp [this] },
{ have : (b : ℝ≥0∞) ≠ 0, by simp [hb],
rw [← ennreal.mul_le_mul_left this coe_ne_top],
suffices : ↑b * a ≤ (↑b * ↑b⁻¹) * c ↔ a * ↑b ≤ c,
{ simpa [some_eq_coe, div_eq_mul_inv, hb, mul_left_comm, mul_comm, mul_assoc] },
rw [← coe_mul, mul_inv_cancel hb, coe_one, one_mul, mul_comm] },
end
lemma div_le_iff_le_mul (hb0 : b ≠ 0 ∨ c ≠ ∞) (hbt : b ≠ ∞ ∨ c ≠ 0) : a / b ≤ c ↔ a ≤ c * b :=
begin
suffices : a * b⁻¹ ≤ c ↔ a ≤ c / b⁻¹, by simpa [div_eq_mul_inv],
refine (le_div_iff_mul_le _ _).symm; simpa
end
lemma lt_div_iff_mul_lt (hb0 : b ≠ 0 ∨ c ≠ ∞) (hbt : b ≠ ∞ ∨ c ≠ 0) : c < a / b ↔ c * b < a :=
lt_iff_lt_of_le_iff_le (div_le_iff_le_mul hb0 hbt)
lemma div_le_of_le_mul (h : a ≤ b * c) : a / c ≤ b :=
begin
by_cases h0 : c = 0,
{ have : a = 0, by simpa [h0] using h, simp [*] },
by_cases hinf : c = ∞, by simp [hinf],
exact (div_le_iff_le_mul (or.inl h0) (or.inl hinf)).2 h
end
lemma div_le_of_le_mul' (h : a ≤ b * c) : a / b ≤ c :=
div_le_of_le_mul $ mul_comm b c ▸ h
lemma mul_le_of_le_div (h : a ≤ b / c) : a * c ≤ b :=
begin
rcases _root_.em (c = 0 ∧ b = 0 ∨ c = ∞ ∧ b = ∞) with (⟨rfl, rfl⟩|⟨rfl, rfl⟩)|H,
{ rw [mul_zero], exact le_rfl },
{ exact le_top },
{ simp only [not_or_distrib, not_and_distrib] at H,
rwa ← le_div_iff_mul_le H.1 H.2 }
end
lemma mul_le_of_le_div' (h : a ≤ b / c) : c * a ≤ b :=
mul_comm a c ▸ mul_le_of_le_div h
protected lemma div_lt_iff (h0 : b ≠ 0 ∨ c ≠ 0) (ht : b ≠ ∞ ∨ c ≠ ∞) :
c / b < a ↔ c < a * b :=
lt_iff_lt_of_le_iff_le $ le_div_iff_mul_le h0 ht
lemma mul_lt_of_lt_div (h : a < b / c) : a * c < b :=
by { contrapose! h, exact ennreal.div_le_of_le_mul h }
lemma mul_lt_of_lt_div' (h : a < b / c) : c * a < b := mul_comm a c ▸ mul_lt_of_lt_div h
lemma inv_le_iff_le_mul : (b = ∞ → a ≠ 0) → (a = ∞ → b ≠ 0) → (a⁻¹ ≤ b ↔ 1 ≤ a * b) :=
begin
cases a; cases b; simp [none_eq_top, some_eq_coe, mul_top, top_mul] {contextual := tt},
by_cases a = 0; simp [*, -coe_mul, coe_mul.symm, -coe_inv, (coe_inv _).symm, nnreal.inv_le]
end
@[simp] lemma le_inv_iff_mul_le : a ≤ b⁻¹ ↔ a * b ≤ 1 :=
begin
cases b, { by_cases a = 0; simp [*, none_eq_top, mul_top] },
by_cases b = 0; simp [*, some_eq_coe, le_div_iff_mul_le],
suffices : a ≤ 1 / b ↔ a * b ≤ 1, { simpa [div_eq_mul_inv, h] },
exact le_div_iff_mul_le (or.inl (mt coe_eq_coe.1 h)) (or.inl coe_ne_top)
end
lemma div_le_div {a b c d : ℝ≥0∞} (hab : a ≤ b) (hdc : d ≤ c) : a / c ≤ b / d :=
div_eq_mul_inv b d ▸ div_eq_mul_inv a c ▸ ennreal.mul_le_mul hab (ennreal.inv_le_inv.mpr hdc)
lemma mul_inv_cancel (h0 : a ≠ 0) (ht : a ≠ ∞) : a * a⁻¹ = 1 :=
begin
lift a to ℝ≥0 using ht,
norm_cast at *,
exact mul_inv_cancel h0
end
lemma inv_mul_cancel (h0 : a ≠ 0) (ht : a ≠ ∞) : a⁻¹ * a = 1 :=
mul_comm a a⁻¹ ▸ mul_inv_cancel h0 ht
lemma eq_inv_of_mul_eq_one_left (h : a * b = 1) : a = b⁻¹ :=
begin
rcases eq_or_ne b ∞ with rfl|hb,
{ have : false, by simpa [left_ne_zero_of_mul_eq_one h] using h,
exact this.elim },
{ rw [← mul_one a, ← mul_inv_cancel (right_ne_zero_of_mul_eq_one h) hb, ← mul_assoc, h, one_mul] }
end
lemma mul_le_iff_le_inv {a b r : ℝ≥0∞} (hr₀ : r ≠ 0) (hr₁ : r ≠ ∞) : (r * a ≤ b ↔ a ≤ r⁻¹ * b) :=
by rw [← @ennreal.mul_le_mul_left _ a _ hr₀ hr₁, ← mul_assoc, mul_inv_cancel hr₀ hr₁, one_mul]
lemma le_of_forall_nnreal_lt {x y : ℝ≥0∞} (h : ∀ r : ℝ≥0, ↑r < x → ↑r ≤ y) : x ≤ y :=
begin
refine le_of_forall_ge_of_dense (λ r hr, _),
lift r to ℝ≥0 using ne_top_of_lt hr,
exact h r hr
end
lemma le_of_forall_pos_nnreal_lt {x y : ℝ≥0∞} (h : ∀ r : ℝ≥0, 0 < r → ↑r < x → ↑r ≤ y) : x ≤ y :=
le_of_forall_nnreal_lt $ λ r hr, (zero_le r).eq_or_lt.elim (λ h, h ▸ zero_le _) (λ h0, h r h0 hr)
lemma eq_top_of_forall_nnreal_le {x : ℝ≥0∞} (h : ∀ r : ℝ≥0, ↑r ≤ x) : x = ∞ :=
top_unique $ le_of_forall_nnreal_lt $ λ r hr, h r
lemma add_div : (a + b) / c = a / c + b / c := right_distrib a b (c⁻¹)
lemma div_add_div_same {a b c : ℝ≥0∞} : a / c + b / c = (a + b) / c :=
add_div.symm
lemma div_self (h0 : a ≠ 0) (hI : a ≠ ∞) : a / a = 1 :=
mul_inv_cancel h0 hI
-- *TODO* this should surely be called div_mul_cancel?
lemma mul_div_cancel (h0 : a ≠ 0) (hI : a ≠ ∞) : (b / a) * a = b :=
by rw [div_eq_mul_inv, mul_assoc, inv_mul_cancel h0 hI, mul_one]
lemma mul_div_cancel' (h0 : a ≠ 0) (hI : a ≠ ∞) : a * (b / a) = b :=
by rw [mul_comm, mul_div_cancel h0 hI]
lemma mul_div_le : a * (b / a) ≤ b :=
begin
by_cases h0 : a = 0, { simp [h0] },
by_cases hI : a = ∞, { simp [hI] },
rw mul_div_cancel' h0 hI, exact le_refl b
end
lemma inv_two_add_inv_two : (2:ℝ≥0∞)⁻¹ + 2⁻¹ = 1 :=
by rw [← two_mul, ← div_eq_mul_inv, div_self two_ne_zero two_ne_top]
lemma inv_three_add_inv_three : (3 : ℝ≥0∞)⁻¹ + 3⁻¹ +3⁻¹ = 1 :=
begin
rw [show (3 : ℝ≥0∞)⁻¹ + 3⁻¹ + 3⁻¹ = 3 * 3⁻¹, by ring, ← div_eq_mul_inv, ennreal.div_self];
simp,
end
@[simp]
lemma add_halves (a : ℝ≥0∞) : a / 2 + a / 2 = a :=
by rw [div_eq_mul_inv, ← mul_add, inv_two_add_inv_two, mul_one]
@[simp]
lemma add_thirds (a : ℝ≥0∞) : a / 3 + a / 3 + a / 3 = a :=
by rw [div_eq_mul_inv, ← mul_add, ← mul_add, inv_three_add_inv_three, mul_one]
@[simp] lemma div_zero_iff : a / b = 0 ↔ a = 0 ∨ b = ∞ :=
by simp [div_eq_mul_inv]
@[simp] lemma div_pos_iff : 0 < a / b ↔ a ≠ 0 ∧ b ≠ ∞ :=
by simp [pos_iff_ne_zero, not_or_distrib]
lemma half_pos {a : ℝ≥0∞} (h : a ≠ 0) : 0 < a / 2 :=
by simp [h]
lemma one_half_lt_one : (2⁻¹:ℝ≥0∞) < 1 := inv_lt_one.2 $ one_lt_two
lemma half_lt_self {a : ℝ≥0∞} (hz : a ≠ 0) (ht : a ≠ ∞) : a / 2 < a :=
begin
lift a to ℝ≥0 using ht,
have h : (2 : ℝ≥0∞) = ((2 : ℝ≥0) : ℝ≥0∞), from rfl,
have h' : (2 : ℝ≥0) ≠ 0, from _root_.two_ne_zero',
rw [h, ← coe_div h', coe_lt_coe], -- `norm_cast` fails to apply `coe_div`
norm_cast at hz,
exact nnreal.half_lt_self hz
end
lemma half_le_self : a / 2 ≤ a := le_add_self.trans_eq (add_halves _)
lemma sub_half (h : a ≠ ∞) : a - a / 2 = a / 2 :=
begin
lift a to ℝ≥0 using h,
exact sub_eq_of_add_eq (mul_ne_top coe_ne_top $ by simp) (add_halves a)
end
@[simp] lemma one_sub_inv_two : (1:ℝ≥0∞) - 2⁻¹ = 2⁻¹ :=
by simpa only [div_eq_mul_inv, one_mul] using sub_half one_ne_top
lemma exists_inv_nat_lt {a : ℝ≥0∞} (h : a ≠ 0) :
∃n:ℕ, (n:ℝ≥0∞)⁻¹ < a :=
inv_inv a ▸ by simp only [inv_lt_inv, ennreal.exists_nat_gt (inv_ne_top.2 h)]
lemma exists_nat_pos_mul_gt (ha : a ≠ 0) (hb : b ≠ ∞) :
∃ n > 0, b < (n : ℕ) * a :=
begin
have : b / a ≠ ∞, from mul_ne_top hb (inv_ne_top.2 ha),
refine (ennreal.exists_nat_gt this).imp (λ n hn, _),
have : 0 < (n : ℝ≥0∞), from (zero_le _).trans_lt hn,
refine ⟨coe_nat_lt_coe_nat.1 this, _⟩,
rwa [← ennreal.div_lt_iff (or.inl ha) (or.inr hb)]
end
lemma exists_nat_mul_gt (ha : a ≠ 0) (hb : b ≠ ∞) :
∃ n : ℕ, b < n * a :=
(exists_nat_pos_mul_gt ha hb).imp $ λ n, Exists.snd
lemma exists_nat_pos_inv_mul_lt (ha : a ≠ ∞) (hb : b ≠ 0) :
∃ n > 0, ((n : ℕ) : ℝ≥0∞)⁻¹ * a < b :=
begin
rcases exists_nat_pos_mul_gt hb ha with ⟨n, npos, hn⟩,
have : (n : ℝ≥0∞) ≠ 0 := nat.cast_ne_zero.2 npos.lt.ne',
use [n, npos],
rwa [← one_mul b, ← inv_mul_cancel this coe_nat_ne_top,
mul_assoc, mul_lt_mul_left (inv_ne_zero.2 coe_nat_ne_top) (inv_ne_top.2 this)]
end
lemma exists_nnreal_pos_mul_lt (ha : a ≠ ∞) (hb : b ≠ 0) :
∃ n > 0, ↑(n : ℝ≥0) * a < b :=
begin
rcases exists_nat_pos_inv_mul_lt ha hb with ⟨n, npos : 0 < n, hn⟩,
use (n : ℝ≥0)⁻¹,
simp [*, npos.ne', zero_lt_one]
end
lemma exists_inv_two_pow_lt (ha : a ≠ 0) :
∃ n : ℕ, 2⁻¹ ^ n < a :=
begin
rcases exists_inv_nat_lt ha with ⟨n, hn⟩,
simp only [← ennreal.inv_pow],
refine ⟨n, lt_trans (inv_lt_inv.2 _) hn⟩,
norm_cast,
exact n.lt_two_pow
end
@[simp, norm_cast] lemma coe_zpow (hr : r ≠ 0) (n : ℤ) : (↑(r^n) : ℝ≥0∞) = r^n :=
begin
cases n,
{ simp only [int.of_nat_eq_coe, coe_pow, zpow_coe_nat] },
{ have : r ^ n.succ ≠ 0 := pow_ne_zero (n+1) hr,
simp only [zpow_neg_succ_of_nat, coe_inv this, coe_pow] }
end
lemma zpow_pos (ha : a ≠ 0) (h'a : a ≠ ∞) (n : ℤ) : 0 < a ^ n :=
begin
cases n,
{ exact ennreal.pow_pos ha.bot_lt n },
{ simp only [h'a, pow_eq_top_iff, zpow_neg_succ_of_nat, ne.def, not_false_iff,
inv_pos, false_and] }
end
lemma zpow_lt_top (ha : a ≠ 0) (h'a : a ≠ ∞) (n : ℤ) : a ^ n < ∞ :=
begin
cases n,
{ exact ennreal.pow_lt_top h'a.lt_top _ },
{ simp only [ennreal.pow_pos ha.bot_lt (n + 1), zpow_neg_succ_of_nat, inv_lt_top] }
end
lemma exists_mem_Ico_zpow
{x y : ℝ≥0∞} (hx : x ≠ 0) (h'x : x ≠ ∞) (hy : 1 < y) (h'y : y ≠ ⊤) :
∃ n : ℤ, x ∈ Ico (y ^ n) (y ^ (n + 1)) :=
begin
lift x to ℝ≥0 using h'x,
lift y to ℝ≥0 using h'y,
have A : y ≠ 0, by simpa only [ne.def, coe_eq_zero] using (ennreal.zero_lt_one.trans hy).ne',
obtain ⟨n, hn, h'n⟩ : ∃ n : ℤ, y ^ n ≤ x ∧ x < y ^ (n + 1),
{ refine nnreal.exists_mem_Ico_zpow _ (one_lt_coe_iff.1 hy),
simpa only [ne.def, coe_eq_zero] using hx },
refine ⟨n, _, _⟩,
{ rwa [← ennreal.coe_zpow A, ennreal.coe_le_coe] },
{ rwa [← ennreal.coe_zpow A, ennreal.coe_lt_coe] }
end
lemma exists_mem_Ioc_zpow
{x y : ℝ≥0∞} (hx : x ≠ 0) (h'x : x ≠ ∞) (hy : 1 < y) (h'y : y ≠ ⊤) :
∃ n : ℤ, x ∈ Ioc (y ^ n) (y ^ (n + 1)) :=
begin
lift x to ℝ≥0 using h'x,
lift y to ℝ≥0 using h'y,
have A : y ≠ 0, by simpa only [ne.def, coe_eq_zero] using (ennreal.zero_lt_one.trans hy).ne',
obtain ⟨n, hn, h'n⟩ : ∃ n : ℤ, y ^ n < x ∧ x ≤ y ^ (n + 1),
{ refine nnreal.exists_mem_Ioc_zpow _ (one_lt_coe_iff.1 hy),
simpa only [ne.def, coe_eq_zero] using hx },
refine ⟨n, _, _⟩,
{ rwa [← ennreal.coe_zpow A, ennreal.coe_lt_coe] },
{ rwa [← ennreal.coe_zpow A, ennreal.coe_le_coe] }
end
lemma Ioo_zero_top_eq_Union_Ico_zpow {y : ℝ≥0∞} (hy : 1 < y) (h'y : y ≠ ⊤) :
Ioo (0 : ℝ≥0∞) (∞ : ℝ≥0∞) = ⋃ (n : ℤ), Ico (y^n) (y^(n+1)) :=
begin
ext x,
simp only [mem_Union, mem_Ioo, mem_Ico],
split,
{ rintros ⟨hx, h'x⟩,
exact exists_mem_Ico_zpow hx.ne' h'x.ne hy h'y },
{ rintros ⟨n, hn, h'n⟩,
split,
{ apply lt_of_lt_of_le _ hn,
exact ennreal.zpow_pos (ennreal.zero_lt_one.trans hy).ne' h'y _ },
{ apply lt_trans h'n _,
exact ennreal.zpow_lt_top (ennreal.zero_lt_one.trans hy).ne' h'y _ } }
end
lemma zpow_le_of_le {x : ℝ≥0∞} (hx : 1 ≤ x) {a b : ℤ} (h : a ≤ b) : x ^ a ≤ x ^ b :=
begin
induction a with a a; induction b with b b,
{ simp only [int.of_nat_eq_coe, zpow_coe_nat],
apply pow_le_pow hx (int.le_of_coe_nat_le_coe_nat h), },
{ apply absurd h (not_le_of_gt _),
exact lt_of_lt_of_le (int.neg_succ_lt_zero _) (int.of_nat_nonneg _) },
{ simp only [zpow_neg_succ_of_nat, int.of_nat_eq_coe, zpow_coe_nat],
refine le_trans (inv_le_one.2 _) _;
apply ennreal.one_le_pow_of_one_le hx, },
{ simp only [zpow_neg_succ_of_nat],
apply inv_le_inv.2,
{ apply pow_le_pow hx,
have : -(↑(a+1) : ℤ) ≤ -(↑(b+1) : ℤ), from h,
have h' := le_of_neg_le_neg this,
apply int.le_of_coe_nat_le_coe_nat h' },
repeat { apply pow_pos (lt_of_lt_of_le zero_lt_one hx) } }
end
lemma monotone_zpow {x : ℝ≥0∞} (hx : 1 ≤ x) : monotone ((^) x : ℤ → ℝ≥0∞) :=
λ a b h, zpow_le_of_le hx h
lemma zpow_add {x : ℝ≥0∞} (hx : x ≠ 0) (h'x : x ≠ ∞) (m n : ℤ) :
x ^ (m + n) = x ^ m * x ^ n :=
begin
lift x to ℝ≥0 using h'x,
replace hx : x ≠ 0, by simpa only [ne.def, coe_eq_zero] using hx,
simp only [← coe_zpow hx, zpow_add₀ hx, coe_mul]
end
end inv
section real
lemma to_real_add (ha : a ≠ ∞) (hb : b ≠ ∞) : (a+b).to_real = a.to_real + b.to_real :=
begin
lift a to ℝ≥0 using ha,
lift b to ℝ≥0 using hb,
refl
end
lemma to_real_sub_of_le {a b : ℝ≥0∞} (h : b ≤ a) (ha : a ≠ ∞):
(a - b).to_real = a.to_real - b.to_real :=
begin
lift b to ℝ≥0 using ne_top_of_le_ne_top ha h,
lift a to ℝ≥0 using ha,
simp only [← ennreal.coe_sub, ennreal.coe_to_real, nnreal.coe_sub (ennreal.coe_le_coe.mp h)],
end
lemma le_to_real_sub {a b : ℝ≥0∞} (hb : b ≠ ∞) : a.to_real - b.to_real ≤ (a - b).to_real :=
begin
lift b to ℝ≥0 using hb,
cases a,
{ simp },
{ simp only [some_eq_coe, ←coe_sub, nnreal.sub_def, real.coe_to_nnreal', coe_to_real],
exact le_max_left _ _ }
end
lemma to_real_add_le : (a+b).to_real ≤ a.to_real + b.to_real :=
if ha : a = ∞ then by simp only [ha, top_add, top_to_real, zero_add, to_real_nonneg]
else if hb : b = ∞ then by simp only [hb, add_top, top_to_real, add_zero, to_real_nonneg]
else le_of_eq (to_real_add ha hb)
lemma of_real_add {p q : ℝ} (hp : 0 ≤ p) (hq : 0 ≤ q) :
ennreal.of_real (p + q) = ennreal.of_real p + ennreal.of_real q :=
by rw [ennreal.of_real, ennreal.of_real, ennreal.of_real, ← coe_add,
coe_eq_coe, real.to_nnreal_add hp hq]
lemma of_real_add_le {p q : ℝ} : ennreal.of_real (p + q) ≤ ennreal.of_real p + ennreal.of_real q :=
coe_le_coe.2 real.to_nnreal_add_le
@[simp] lemma to_real_le_to_real (ha : a ≠ ∞) (hb : b ≠ ∞) : a.to_real ≤ b.to_real ↔ a ≤ b :=
begin
lift a to ℝ≥0 using ha,
lift b to ℝ≥0 using hb,
norm_cast
end
lemma to_real_mono (hb : b ≠ ∞) (h : a ≤ b) : a.to_real ≤ b.to_real :=
(to_real_le_to_real (h.trans_lt (lt_top_iff_ne_top.2 hb)).ne hb).2 h
@[simp] lemma to_real_lt_to_real (ha : a ≠ ∞) (hb : b ≠ ∞) : a.to_real < b.to_real ↔ a < b :=
begin
lift a to ℝ≥0 using ha,
lift b to ℝ≥0 using hb,
norm_cast
end
lemma to_real_strict_mono (hb : b ≠ ∞) (h : a < b) : a.to_real < b.to_real :=
(to_real_lt_to_real (h.trans (lt_top_iff_ne_top.2 hb)).ne hb).2 h
lemma to_nnreal_mono (hb : b ≠ ∞) (h : a ≤ b) : a.to_nnreal ≤ b.to_nnreal :=
by simpa [←ennreal.coe_le_coe, hb, (h.trans_lt hb.lt_top).ne]
@[simp] lemma to_nnreal_le_to_nnreal (ha : a ≠ ∞) (hb : b ≠ ∞) :
a.to_nnreal ≤ b.to_nnreal ↔ a ≤ b :=
begin
refine ⟨_, to_nnreal_mono hb⟩,
{ intro h,
have key := ennreal.coe_le_coe.mpr h,
rwa [coe_to_nnreal ha, coe_to_nnreal hb] at key, },
end
lemma to_nnreal_strict_mono (hb : b ≠ ∞) (h : a < b) : a.to_nnreal < b.to_nnreal :=
by simpa [←ennreal.coe_lt_coe, hb, (h.trans hb.lt_top).ne]
@[simp] lemma to_nnreal_lt_to_nnreal (ha : a ≠ ∞) (hb : b ≠ ∞) :
a.to_nnreal < b.to_nnreal ↔ a < b :=
begin
refine ⟨_, to_nnreal_strict_mono hb⟩,
{ intro h,
have key := ennreal.coe_lt_coe.mpr h,
rwa [coe_to_nnreal ha, coe_to_nnreal hb] at key, },
end
lemma to_real_max (hr : a ≠ ∞) (hp : b ≠ ∞) :
ennreal.to_real (max a b) = max (ennreal.to_real a) (ennreal.to_real b) :=
(le_total a b).elim
(λ h, by simp only [h, (ennreal.to_real_le_to_real hr hp).2 h, max_eq_right])
(λ h, by simp only [h, (ennreal.to_real_le_to_real hp hr).2 h, max_eq_left])
lemma to_nnreal_pos_iff : 0 < a.to_nnreal ↔ (0 < a ∧ a < ∞) :=
begin
cases a,
{ simp [none_eq_top] },
{ simp [some_eq_coe] }
end
lemma to_nnreal_pos {a : ℝ≥0∞} (ha₀ : a ≠ 0) (ha_top : a ≠ ∞) : 0 < a.to_nnreal :=
to_nnreal_pos_iff.mpr ⟨bot_lt_iff_ne_bot.mpr ha₀, lt_top_iff_ne_top.mpr ha_top⟩
lemma to_real_pos_iff : 0 < a.to_real ↔ (0 < a ∧ a < ∞):=
(nnreal.coe_pos).trans to_nnreal_pos_iff
lemma to_real_pos {a : ℝ≥0∞} (ha₀ : a ≠ 0) (ha_top : a ≠ ∞) : 0 < a.to_real :=
to_real_pos_iff.mpr ⟨bot_lt_iff_ne_bot.mpr ha₀, lt_top_iff_ne_top.mpr ha_top⟩
lemma of_real_le_of_real {p q : ℝ} (h : p ≤ q) : ennreal.of_real p ≤ ennreal.of_real q :=
by simp [ennreal.of_real, real.to_nnreal_le_to_nnreal h]
lemma of_real_le_of_le_to_real {a : ℝ} {b : ℝ≥0∞} (h : a ≤ ennreal.to_real b) :
ennreal.of_real a ≤ b :=
(of_real_le_of_real h).trans of_real_to_real_le
@[simp] lemma of_real_le_of_real_iff {p q : ℝ} (h : 0 ≤ q) :
ennreal.of_real p ≤ ennreal.of_real q ↔ p ≤ q :=
by rw [ennreal.of_real, ennreal.of_real, coe_le_coe, real.to_nnreal_le_to_nnreal_iff h]
@[simp] lemma of_real_lt_of_real_iff {p q : ℝ} (h : 0 < q) :
ennreal.of_real p < ennreal.of_real q ↔ p < q :=
by rw [ennreal.of_real, ennreal.of_real, coe_lt_coe, real.to_nnreal_lt_to_nnreal_iff h]
lemma of_real_lt_of_real_iff_of_nonneg {p q : ℝ} (hp : 0 ≤ p) :
ennreal.of_real p < ennreal.of_real q ↔ p < q :=
by rw [ennreal.of_real, ennreal.of_real, coe_lt_coe, real.to_nnreal_lt_to_nnreal_iff_of_nonneg hp]
@[simp] lemma of_real_pos {p : ℝ} : 0 < ennreal.of_real p ↔ 0 < p :=
by simp [ennreal.of_real]
@[simp] lemma of_real_eq_zero {p : ℝ} : ennreal.of_real p = 0 ↔ p ≤ 0 :=
by simp [ennreal.of_real]
@[simp] lemma zero_eq_of_real {p : ℝ} : 0 = ennreal.of_real p ↔ p ≤ 0 :=
eq_comm.trans of_real_eq_zero
alias ennreal.of_real_eq_zero ↔ _ ennreal.of_real_of_nonpos
lemma of_real_sub (p : ℝ) (hq : 0 ≤ q) :
ennreal.of_real (p - q) = ennreal.of_real p - ennreal.of_real q :=
begin
obtain h | h := le_total p q,
{ rw [of_real_of_nonpos (sub_nonpos_of_le h), tsub_eq_zero_of_le (of_real_le_of_real h)] },
refine ennreal.eq_sub_of_add_eq of_real_ne_top _,
rw [←of_real_add (sub_nonneg_of_le h) hq, sub_add_cancel],
end
lemma of_real_le_iff_le_to_real {a : ℝ} {b : ℝ≥0∞} (hb : b ≠ ∞) :
ennreal.of_real a ≤ b ↔ a ≤ ennreal.to_real b :=
begin
lift b to ℝ≥0 using hb,
simpa [ennreal.of_real, ennreal.to_real] using real.to_nnreal_le_iff_le_coe
end
lemma of_real_lt_iff_lt_to_real {a : ℝ} {b : ℝ≥0∞} (ha : 0 ≤ a) (hb : b ≠ ∞) :
ennreal.of_real a < b ↔ a < ennreal.to_real b :=
begin
lift b to ℝ≥0 using hb,
simpa [ennreal.of_real, ennreal.to_real] using real.to_nnreal_lt_iff_lt_coe ha
end
lemma le_of_real_iff_to_real_le {a : ℝ≥0∞} {b : ℝ} (ha : a ≠ ∞) (hb : 0 ≤ b) :
a ≤ ennreal.of_real b ↔ ennreal.to_real a ≤ b :=
begin
lift a to ℝ≥0 using ha,
simpa [ennreal.of_real, ennreal.to_real] using real.le_to_nnreal_iff_coe_le hb
end
lemma to_real_le_of_le_of_real {a : ℝ≥0∞} {b : ℝ} (hb : 0 ≤ b) (h : a ≤ ennreal.of_real b) :
ennreal.to_real a ≤ b :=
have ha : a ≠ ∞, from ne_top_of_le_ne_top of_real_ne_top h,
(le_of_real_iff_to_real_le ha hb).1 h
lemma lt_of_real_iff_to_real_lt {a : ℝ≥0∞} {b : ℝ} (ha : a ≠ ∞) :
a < ennreal.of_real b ↔ ennreal.to_real a < b :=
begin
lift a to ℝ≥0 using ha,
simpa [ennreal.of_real, ennreal.to_real] using real.lt_to_nnreal_iff_coe_lt
end
lemma of_real_mul {p q : ℝ} (hp : 0 ≤ p) :
ennreal.of_real (p * q) = (ennreal.of_real p) * (ennreal.of_real q) :=
by { simp only [ennreal.of_real, coe_mul.symm, coe_eq_coe], exact real.to_nnreal_mul hp }
lemma of_real_pow {p : ℝ} (hp : 0 ≤ p) (n : ℕ) :
ennreal.of_real (p ^ n) = ennreal.of_real p ^ n :=
by rw [of_real_eq_coe_nnreal hp, ← coe_pow, ← of_real_coe_nnreal, nnreal.coe_pow, nnreal.coe_mk]
lemma of_real_inv_of_pos {x : ℝ} (hx : 0 < x) :
(ennreal.of_real x)⁻¹ = ennreal.of_real x⁻¹ :=
by rw [ennreal.of_real, ennreal.of_real, ←@coe_inv (real.to_nnreal x) (by simp [hx]), coe_eq_coe,
real.to_nnreal_inv.symm]
lemma of_real_div_of_pos {x y : ℝ} (hy : 0 < y) :
ennreal.of_real (x / y) = ennreal.of_real x / ennreal.of_real y :=
by rw [div_eq_inv_mul, div_eq_mul_inv, of_real_mul (inv_nonneg.2 hy.le), of_real_inv_of_pos hy,
mul_comm]
lemma to_real_of_real_mul (c : ℝ) (a : ℝ≥0∞) (h : 0 ≤ c) :
ennreal.to_real ((ennreal.of_real c) * a) = c * ennreal.to_real a :=
begin
cases a,
{ simp only [none_eq_top, ennreal.to_real, top_to_nnreal, nnreal.coe_zero, mul_zero, mul_top],
by_cases h' : c ≤ 0,
{ rw [if_pos], { simp }, { convert of_real_zero, exact le_antisymm h' h } },
{ rw [if_neg], refl, rw [of_real_eq_zero], assumption } },
{ simp only [ennreal.to_real, ennreal.to_nnreal],
simp only [some_eq_coe, ennreal.of_real, coe_mul.symm, to_nnreal_coe, nnreal.coe_mul],
congr, apply real.coe_to_nnreal, exact h }
end
@[simp] lemma to_nnreal_mul_top (a : ℝ≥0∞) : ennreal.to_nnreal (a * ∞) = 0 :=
begin
by_cases h : a = 0,
{ rw [h, zero_mul, zero_to_nnreal] },
{ rw [mul_top, if_neg h, top_to_nnreal] }
end
@[simp] lemma to_nnreal_top_mul (a : ℝ≥0∞) : ennreal.to_nnreal (∞ * a) = 0 :=
by rw [mul_comm, to_nnreal_mul_top]
@[simp] lemma to_real_mul_top (a : ℝ≥0∞) : ennreal.to_real (a * ∞) = 0 :=
by rw [ennreal.to_real, to_nnreal_mul_top, nnreal.coe_zero]
@[simp] lemma to_real_top_mul (a : ℝ≥0∞) : ennreal.to_real (∞ * a) = 0 :=
by { rw mul_comm, exact to_real_mul_top _ }
lemma to_real_eq_to_real (ha : a ≠ ∞) (hb : b ≠ ∞) :
ennreal.to_real a = ennreal.to_real b ↔ a = b :=
begin
lift a to ℝ≥0 using ha,
lift b to ℝ≥0 using hb,
simp only [coe_eq_coe, nnreal.coe_eq, coe_to_real],
end
lemma to_real_smul (r : ℝ≥0) (s : ℝ≥0∞) :
(r • s).to_real = r • s.to_real :=
begin
induction s using with_top.rec_top_coe,
{ rw [show r • ∞ = (r : ℝ≥0∞) * ∞, by refl],
simp only [ennreal.to_real_mul_top, ennreal.top_to_real, smul_zero] },
{ rw [← coe_smul, ennreal.coe_to_real, ennreal.coe_to_real],
refl }
end
protected lemma trichotomy (p : ℝ≥0∞) : p = 0 ∨ p = ∞ ∨ 0 < p.to_real :=
begin
rcases eq_or_lt_of_le (bot_le : 0 ≤ p) with (rfl : 0 = p) | (hp : 0 < p),
{ simp },
rcases eq_or_lt_of_le (le_top : p ≤ ⊤) with rfl | hp',
{ simp },
simp [ennreal.to_real_pos_iff, hp, hp'],
end
protected lemma trichotomy₂ {p q : ℝ≥0∞} (hpq : p ≤ q) :
(p = 0 ∧ q = 0) ∨ (p = 0 ∧ q = ∞) ∨ (p = 0 ∧ 0 < q.to_real) ∨ (p = ∞ ∧ q = ∞)
∨ (0 < p.to_real ∧ q = ∞) ∨ (0 < p.to_real ∧ 0 < q.to_real ∧ p.to_real ≤ q.to_real) :=
begin
rcases eq_or_lt_of_le (bot_le : 0 ≤ p) with (rfl : 0 = p) | (hp : 0 < p),
{ simpa using q.trichotomy },
rcases eq_or_lt_of_le (le_top : q ≤ ∞) with rfl | hq,
{ simpa using p.trichotomy },
repeat { right },
have hq' : 0 < q := lt_of_lt_of_le hp hpq,
have hp' : p < ∞ := lt_of_le_of_lt hpq hq,
simp [ennreal.to_real_le_to_real hp'.ne hq.ne, ennreal.to_real_pos_iff, hpq, hp, hp', hq', hq],
end
protected lemma dichotomy (p : ℝ≥0∞) [fact (1 ≤ p)] : p = ∞ ∨ 1 ≤ p.to_real :=
begin
have : p = ⊤ ∨ 0 < p.to_real ∧ 1 ≤ p.to_real,
{ simpa using ennreal.trichotomy₂ (fact.out _ : 1 ≤ p) },
exact this.imp_right (λ h, h.2)
end
/-- `ennreal.to_nnreal` as a `monoid_hom`. -/
def to_nnreal_hom : ℝ≥0∞ →* ℝ≥0 :=
{ to_fun := ennreal.to_nnreal,
map_one' := to_nnreal_coe,
map_mul' := by rintro (_|x) (_|y); simp only [← coe_mul, none_eq_top, some_eq_coe,
to_nnreal_top_mul, to_nnreal_mul_top, top_to_nnreal, mul_zero, zero_mul, to_nnreal_coe] }
lemma to_nnreal_mul {a b : ℝ≥0∞}: (a * b).to_nnreal = a.to_nnreal * b.to_nnreal :=
to_nnreal_hom.map_mul a b
lemma to_nnreal_pow (a : ℝ≥0∞) (n : ℕ) : (a ^ n).to_nnreal = a.to_nnreal ^ n :=
to_nnreal_hom.map_pow a n
lemma to_nnreal_prod {ι : Type*} {s : finset ι} {f : ι → ℝ≥0∞} :
(∏ i in s, f i).to_nnreal = ∏ i in s, (f i).to_nnreal :=
to_nnreal_hom.map_prod _ _
lemma to_nnreal_inv (a : ℝ≥0∞) : (a⁻¹).to_nnreal = (a.to_nnreal)⁻¹ :=
begin
rcases eq_or_ne a ∞ with rfl|ha, { simp },
lift a to ℝ≥0 using ha,
rcases eq_or_ne a 0 with rfl|ha, { simp },
rw [← coe_inv ha, to_nnreal_coe, to_nnreal_coe]
end
lemma to_nnreal_div (a b : ℝ≥0∞) : (a / b).to_nnreal = a.to_nnreal / b.to_nnreal :=
by rw [div_eq_mul_inv, to_nnreal_mul, to_nnreal_inv, div_eq_mul_inv]
/-- `ennreal.to_real` as a `monoid_hom`. -/
def to_real_hom : ℝ≥0∞ →* ℝ :=
(nnreal.to_real_hom : ℝ≥0 →* ℝ).comp to_nnreal_hom
lemma to_real_mul : (a * b).to_real = a.to_real * b.to_real :=
to_real_hom.map_mul a b
lemma to_real_pow (a : ℝ≥0∞) (n : ℕ) : (a ^ n).to_real = a.to_real ^ n :=
to_real_hom.map_pow a n
lemma to_real_prod {ι : Type*} {s : finset ι} {f : ι → ℝ≥0∞} :
(∏ i in s, f i).to_real = ∏ i in s, (f i).to_real :=
to_real_hom.map_prod _ _
lemma to_real_inv (a : ℝ≥0∞) : (a⁻¹).to_real = (a.to_real)⁻¹ :=
by { simp_rw ennreal.to_real, norm_cast, exact to_nnreal_inv a, }
lemma to_real_div (a b : ℝ≥0∞) : (a / b).to_real = a.to_real / b.to_real :=
by rw [div_eq_mul_inv, to_real_mul, to_real_inv, div_eq_mul_inv]
lemma of_real_prod_of_nonneg {s : finset α} {f : α → ℝ} (hf : ∀ i, i ∈ s → 0 ≤ f i) :
ennreal.of_real (∏ i in s, f i) = ∏ i in s, ennreal.of_real (f i) :=
begin
simp_rw [ennreal.of_real, ←coe_finset_prod, coe_eq_coe],
exact real.to_nnreal_prod_of_nonneg hf,
end
@[simp] lemma to_nnreal_bit0 {x : ℝ≥0∞} : (bit0 x).to_nnreal = bit0 (x.to_nnreal) :=
begin
by_cases hx_top : x = ∞,
{ simp [hx_top, bit0_eq_top_iff.mpr rfl], },
exact to_nnreal_add hx_top hx_top,
end
@[simp] lemma to_nnreal_bit1 {x : ℝ≥0∞} (hx_top : x ≠ ∞) :
(bit1 x).to_nnreal = bit1 (x.to_nnreal) :=
by simp [bit1, bit1, to_nnreal_add (by rwa [ne.def, bit0_eq_top_iff]) ennreal.one_ne_top]
@[simp] lemma to_real_bit0 {x : ℝ≥0∞} : (bit0 x).to_real = bit0 (x.to_real) :=
by simp [ennreal.to_real]
@[simp] lemma to_real_bit1 {x : ℝ≥0∞} (hx_top : x ≠ ∞) :
(bit1 x).to_real = bit1 (x.to_real) :=
by simp [ennreal.to_real, hx_top]
@[simp] lemma of_real_bit0 {r : ℝ} (hr : 0 ≤ r) :
ennreal.of_real (bit0 r) = bit0 (ennreal.of_real r) :=
of_real_add hr hr
@[simp] lemma of_real_bit1 {r : ℝ} (hr : 0 ≤ r) :
ennreal.of_real (bit1 r) = bit1 (ennreal.of_real r) :=
(of_real_add (by simp [hr]) zero_le_one).trans (by simp [real.to_nnreal_one, bit1, hr])
end real
section infi
variables {ι : Sort*} {f g : ι → ℝ≥0∞}
lemma infi_add : infi f + a = ⨅i, f i + a :=
le_antisymm
(le_infi $ assume i, add_le_add (infi_le _ _) $ le_rfl)
(tsub_le_iff_right.1 $ le_infi $ assume i, tsub_le_iff_right.2 $ infi_le _ _)
lemma supr_sub : (⨆i, f i) - a = (⨆i, f i - a) :=
le_antisymm
(tsub_le_iff_right.2 $ supr_le $ assume i, tsub_le_iff_right.1 $ le_supr _ i)
(supr_le $ assume i, tsub_le_tsub (le_supr _ _) (le_refl a))
lemma sub_infi : a - (⨅i, f i) = (⨆i, a - f i) :=
begin
refine (eq_of_forall_ge_iff $ λ c, _),
rw [tsub_le_iff_right, add_comm, infi_add],
simp [tsub_le_iff_right, sub_eq_add_neg, add_comm],
end
lemma Inf_add {s : set ℝ≥0∞} : Inf s + a = ⨅b∈s, b + a :=
by simp [Inf_eq_infi, infi_add]
lemma add_infi {a : ℝ≥0∞} : a + infi f = ⨅b, a + f b :=
by rw [add_comm, infi_add]; simp [add_comm]
lemma infi_add_infi (h : ∀i j, ∃k, f k + g k ≤ f i + g j) : infi f + infi g = (⨅a, f a + g a) :=
suffices (⨅a, f a + g a) ≤ infi f + infi g,
from le_antisymm (le_infi $ assume a, add_le_add (infi_le _ _) (infi_le _ _)) this,
calc (⨅a, f a + g a) ≤ (⨅ a a', f a + g a') :
le_infi $ assume a, le_infi $ assume a',
let ⟨k, h⟩ := h a a' in infi_le_of_le k h
... = infi f + infi g :
by simp [add_infi, infi_add]
lemma infi_sum {f : ι → α → ℝ≥0∞} {s : finset α} [nonempty ι]
(h : ∀(t : finset α) (i j : ι), ∃k, ∀a∈t, f k a ≤ f i a ∧ f k a ≤ f j a) :
(⨅i, ∑ a in s, f i a) = ∑ a in s, ⨅i, f i a :=
finset.induction_on s (by simp) $ assume a s ha ih,
have ∀ (i j : ι), ∃ (k : ι), f k a + ∑ b in s, f k b ≤ f i a + ∑ b in s, f j b,
from assume i j,
let ⟨k, hk⟩ := h (insert a s) i j in
⟨k, add_le_add (hk a (finset.mem_insert_self _ _)).left $ finset.sum_le_sum $
assume a ha, (hk _ $ finset.mem_insert_of_mem ha).right⟩,
by simp [ha, ih.symm, infi_add_infi this]
/-- If `x ≠ 0` and `x ≠ ∞`, then right multiplication by `x` maps infimum to infimum.
See also `ennreal.infi_mul` that assumes `[nonempty ι]` but does not require `x ≠ 0`. -/
lemma infi_mul_of_ne {ι} {f : ι → ℝ≥0∞} {x : ℝ≥0∞} (h0 : x ≠ 0) (h : x ≠ ∞) :
infi f * x = ⨅ i, f i * x :=
le_antisymm
mul_right_mono.map_infi_le
((div_le_iff_le_mul (or.inl h0) $ or.inl h).mp $ le_infi $
λ i, (div_le_iff_le_mul (or.inl h0) $ or.inl h).mpr $ infi_le _ _)
/-- If `x ≠ ∞`, then right multiplication by `x` maps infimum over a nonempty type to infimum. See
also `ennreal.infi_mul_of_ne` that assumes `x ≠ 0` but does not require `[nonempty ι]`. -/
lemma infi_mul {ι} [nonempty ι] {f : ι → ℝ≥0∞} {x : ℝ≥0∞} (h : x ≠ ∞) :
infi f * x = ⨅ i, f i * x :=
begin
by_cases h0 : x = 0,
{ simp only [h0, mul_zero, infi_const] },
{ exact infi_mul_of_ne h0 h }
end
/-- If `x ≠ ∞`, then left multiplication by `x` maps infimum over a nonempty type to infimum. See
also `ennreal.mul_infi_of_ne` that assumes `x ≠ 0` but does not require `[nonempty ι]`. -/
lemma mul_infi {ι} [nonempty ι] {f : ι → ℝ≥0∞} {x : ℝ≥0∞} (h : x ≠ ∞) :
x * infi f = ⨅ i, x * f i :=
by simpa only [mul_comm] using infi_mul h
/-- If `x ≠ 0` and `x ≠ ∞`, then left multiplication by `x` maps infimum to infimum.
See also `ennreal.mul_infi` that assumes `[nonempty ι]` but does not require `x ≠ 0`. -/
lemma mul_infi_of_ne {ι} {f : ι → ℝ≥0∞} {x : ℝ≥0∞} (h0 : x ≠ 0) (h : x ≠ ∞) :
x * infi f = ⨅ i, x * f i :=
by simpa only [mul_comm] using infi_mul_of_ne h0 h
/-! `supr_mul`, `mul_supr` and variants are in `topology.instances.ennreal`. -/
end infi
section supr
@[simp] lemma supr_eq_zero {ι : Sort*} {f : ι → ℝ≥0∞} : (⨆ i, f i) = 0 ↔ ∀ i, f i = 0 :=
supr_eq_bot
@[simp] lemma supr_zero_eq_zero {ι : Sort*} : (⨆ i : ι, (0 : ℝ≥0∞)) = 0 :=
by simp
lemma sup_eq_zero {a b : ℝ≥0∞} : a ⊔ b = 0 ↔ a = 0 ∧ b = 0 := sup_eq_bot_iff
lemma supr_coe_nat : (⨆n:ℕ, (n : ℝ≥0∞)) = ∞ :=
(supr_eq_top _).2 $ assume b hb, ennreal.exists_nat_gt (lt_top_iff_ne_top.1 hb)
end supr
end ennreal
|
e58edee57e542719c3d631c5ece1c39fd63364c3 | 74addaa0e41490cbaf2abd313a764c96df57b05d | /Mathlib/category_theory/conj.lean | e708cbaf67d6f96c3a63291bd472c70121781656 | [] | no_license | AurelienSaue/Mathlib4_auto | f538cfd0980f65a6361eadea39e6fc639e9dae14 | 590df64109b08190abe22358fabc3eae000943f2 | refs/heads/master | 1,683,906,849,776 | 1,622,564,669,000 | 1,622,564,669,000 | 371,723,747 | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 7,153 | lean | /-
Copyright (c) 2019 Yury Kudryashov. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yury Kudryashov
-/
import Mathlib.PrePort
import Mathlib.Lean3Lib.init.default
import Mathlib.category_theory.endomorphism
import Mathlib.algebra.group_power.default
import Mathlib.PostPort
universes u v v₁ u₁
namespace Mathlib
/-!
# Conjugate morphisms by isomorphisms
An isomorphism `α : X ≅ Y` defines
- a monoid isomorphism `conj : End X ≃* End Y` by `α.conj f = α.inv ≫ f ≫ α.hom`;
- a group isomorphism `conj_Aut : Aut X ≃* Aut Y` by `α.conj_Aut f = α.symm ≪≫ f ≪≫ α`.
For completeness, we also define `hom_congr : (X ≅ X₁) → (Y ≅ Y₁) → (X ⟶ Y) ≃ (X₁ ⟶ Y₁)`, cf. `equiv.arrow_congr`.
-/
namespace category_theory
namespace iso
/-- If `X` is isomorphic to `X₁` and `Y` is isomorphic to `Y₁`, then
there is a natural bijection between `X ⟶ Y` and `X₁ ⟶ Y₁`. See also `equiv.arrow_congr`. -/
def hom_congr {C : Type u} [category C] {X : C} {Y : C} {X₁ : C} {Y₁ : C} (α : X ≅ X₁) (β : Y ≅ Y₁) : (X ⟶ Y) ≃ (X₁ ⟶ Y₁) :=
equiv.mk (fun (f : X ⟶ Y) => inv α ≫ f ≫ hom β) (fun (f : X₁ ⟶ Y₁) => hom α ≫ f ≫ inv β) sorry sorry
@[simp] theorem hom_congr_apply {C : Type u} [category C] {X : C} {Y : C} {X₁ : C} {Y₁ : C} (α : X ≅ X₁) (β : Y ≅ Y₁) (f : X ⟶ Y) : coe_fn (hom_congr α β) f = inv α ≫ f ≫ hom β :=
rfl
theorem hom_congr_comp {C : Type u} [category C] {X : C} {Y : C} {Z : C} {X₁ : C} {Y₁ : C} {Z₁ : C} (α : X ≅ X₁) (β : Y ≅ Y₁) (γ : Z ≅ Z₁) (f : X ⟶ Y) (g : Y ⟶ Z) : coe_fn (hom_congr α γ) (f ≫ g) = coe_fn (hom_congr α β) f ≫ coe_fn (hom_congr β γ) g := sorry
@[simp] theorem hom_congr_refl {C : Type u} [category C] {X : C} {Y : C} (f : X ⟶ Y) : coe_fn (hom_congr (refl X) (refl Y)) f = f := sorry
@[simp] theorem hom_congr_trans {C : Type u} [category C] {X₁ : C} {Y₁ : C} {X₂ : C} {Y₂ : C} {X₃ : C} {Y₃ : C} (α₁ : X₁ ≅ X₂) (β₁ : Y₁ ≅ Y₂) (α₂ : X₂ ≅ X₃) (β₂ : Y₂ ≅ Y₃) (f : X₁ ⟶ Y₁) : coe_fn (hom_congr (α₁ ≪≫ α₂) (β₁ ≪≫ β₂)) f = coe_fn (equiv.trans (hom_congr α₁ β₁) (hom_congr α₂ β₂)) f := sorry
@[simp] theorem hom_congr_symm {C : Type u} [category C] {X₁ : C} {Y₁ : C} {X₂ : C} {Y₂ : C} (α : X₁ ≅ X₂) (β : Y₁ ≅ Y₂) : equiv.symm (hom_congr α β) = hom_congr (symm α) (symm β) :=
rfl
/-- An isomorphism between two objects defines a monoid isomorphism between their
monoid of endomorphisms. -/
def conj {C : Type u} [category C] {X : C} {Y : C} (α : X ≅ Y) : End X ≃* End Y :=
mul_equiv.mk (equiv.to_fun (hom_congr α α)) (equiv.inv_fun (hom_congr α α)) sorry sorry sorry
theorem conj_apply {C : Type u} [category C] {X : C} {Y : C} (α : X ≅ Y) (f : End X) : coe_fn (conj α) f = inv α ≫ f ≫ hom α :=
rfl
@[simp] theorem conj_comp {C : Type u} [category C] {X : C} {Y : C} (α : X ≅ Y) (f : End X) (g : End X) : coe_fn (conj α) (f ≫ g) = coe_fn (conj α) f ≫ coe_fn (conj α) g :=
mul_equiv.map_mul (conj α) g f
@[simp] theorem conj_id {C : Type u} [category C] {X : C} {Y : C} (α : X ≅ Y) : coe_fn (conj α) 𝟙 = 𝟙 :=
mul_equiv.map_one (conj α)
@[simp] theorem refl_conj {C : Type u} [category C] {X : C} (f : End X) : coe_fn (conj (refl X)) f = f := sorry
@[simp] theorem trans_conj {C : Type u} [category C] {X : C} {Y : C} (α : X ≅ Y) {Z : C} (β : Y ≅ Z) (f : End X) : coe_fn (conj (α ≪≫ β)) f = coe_fn (conj β) (coe_fn (conj α) f) :=
hom_congr_trans α α β β f
@[simp] theorem symm_self_conj {C : Type u} [category C] {X : C} {Y : C} (α : X ≅ Y) (f : End X) : coe_fn (conj (symm α)) (coe_fn (conj α) f) = f :=
eq.mpr (id (Eq._oldrec (Eq.refl (coe_fn (conj (symm α)) (coe_fn (conj α) f) = f)) (Eq.symm (trans_conj α (symm α) f))))
(eq.mpr (id (Eq._oldrec (Eq.refl (coe_fn (conj (α ≪≫ symm α)) f = f)) (self_symm_id α)))
(eq.mpr (id (Eq._oldrec (Eq.refl (coe_fn (conj (refl X)) f = f)) (refl_conj f))) (Eq.refl f)))
@[simp] theorem self_symm_conj {C : Type u} [category C] {X : C} {Y : C} (α : X ≅ Y) (f : End Y) : coe_fn (conj α) (coe_fn (conj (symm α)) f) = f :=
symm_self_conj (symm α) f
@[simp] theorem conj_pow {C : Type u} [category C] {X : C} {Y : C} (α : X ≅ Y) (f : End X) (n : ℕ) : coe_fn (conj α) (f ^ n) = coe_fn (conj α) f ^ n :=
monoid_hom.map_pow (mul_equiv.to_monoid_hom (conj α)) f n
/-- `conj` defines a group isomorphisms between groups of automorphisms -/
def conj_Aut {C : Type u} [category C] {X : C} {Y : C} (α : X ≅ Y) : Aut X ≃* Aut Y :=
mul_equiv.trans (mul_equiv.symm (Aut.units_End_equiv_Aut X))
(mul_equiv.trans (units.map_equiv (conj α)) (Aut.units_End_equiv_Aut Y))
theorem conj_Aut_apply {C : Type u} [category C] {X : C} {Y : C} (α : X ≅ Y) (f : Aut X) : coe_fn (conj_Aut α) f = symm α ≪≫ f ≪≫ α := sorry
@[simp] theorem conj_Aut_hom {C : Type u} [category C] {X : C} {Y : C} (α : X ≅ Y) (f : Aut X) : hom (coe_fn (conj_Aut α) f) = coe_fn (conj α) (hom f) :=
rfl
@[simp] theorem trans_conj_Aut {C : Type u} [category C] {X : C} {Y : C} (α : X ≅ Y) {Z : C} (β : Y ≅ Z) (f : Aut X) : coe_fn (conj_Aut (α ≪≫ β)) f = coe_fn (conj_Aut β) (coe_fn (conj_Aut α) f) := sorry
@[simp] theorem conj_Aut_mul {C : Type u} [category C] {X : C} {Y : C} (α : X ≅ Y) (f : Aut X) (g : Aut X) : coe_fn (conj_Aut α) (f * g) = coe_fn (conj_Aut α) f * coe_fn (conj_Aut α) g :=
mul_equiv.map_mul (conj_Aut α) f g
@[simp] theorem conj_Aut_trans {C : Type u} [category C] {X : C} {Y : C} (α : X ≅ Y) (f : Aut X) (g : Aut X) : coe_fn (conj_Aut α) (f ≪≫ g) = coe_fn (conj_Aut α) f ≪≫ coe_fn (conj_Aut α) g :=
conj_Aut_mul α g f
@[simp] theorem conj_Aut_pow {C : Type u} [category C] {X : C} {Y : C} (α : X ≅ Y) (f : Aut X) (n : ℕ) : coe_fn (conj_Aut α) (f ^ n) = coe_fn (conj_Aut α) f ^ n :=
monoid_hom.map_pow (mul_equiv.to_monoid_hom (conj_Aut α)) f n
@[simp] theorem conj_Aut_gpow {C : Type u} [category C] {X : C} {Y : C} (α : X ≅ Y) (f : Aut X) (n : ℤ) : coe_fn (conj_Aut α) (f ^ n) = coe_fn (conj_Aut α) f ^ n :=
monoid_hom.map_gpow (mul_equiv.to_monoid_hom (conj_Aut α)) f n
end iso
namespace functor
theorem map_hom_congr {C : Type u} [category C] {D : Type u₁} [category D] (F : C ⥤ D) {X : C} {Y : C} {X₁ : C} {Y₁ : C} (α : X ≅ X₁) (β : Y ≅ Y₁) (f : X ⟶ Y) : map F (coe_fn (iso.hom_congr α β) f) = coe_fn (iso.hom_congr (map_iso F α) (map_iso F β)) (map F f) := sorry
theorem map_conj {C : Type u} [category C] {D : Type u₁} [category D] (F : C ⥤ D) {X : C} {Y : C} (α : X ≅ Y) (f : End X) : map F (coe_fn (iso.conj α) f) = coe_fn (iso.conj (map_iso F α)) (map F f) :=
map_hom_congr F α α f
theorem map_conj_Aut {C : Type u} [category C] {D : Type u₁} [category D] (F : C ⥤ D) {X : C} {Y : C} (α : X ≅ Y) (f : Aut X) : map_iso F (coe_fn (iso.conj_Aut α) f) = coe_fn (iso.conj_Aut (map_iso F α)) (map_iso F f) := sorry
|
c06687fba9914f38611ab665bda67ac63aaf7fd2 | 55c7fc2bf55d496ace18cd6f3376e12bb14c8cc5 | /src/data/matrix/basic.lean | eec3b8ff4664fea7498e751b004b2e6b2ac2d18f | [
"Apache-2.0"
] | permissive | dupuisf/mathlib | 62de4ec6544bf3b79086afd27b6529acfaf2c1bb | 8582b06b0a5d06c33ee07d0bdf7c646cae22cf36 | refs/heads/master | 1,669,494,854,016 | 1,595,692,409,000 | 1,595,692,409,000 | 272,046,630 | 0 | 0 | Apache-2.0 | 1,592,066,143,000 | 1,592,066,142,000 | null | UTF-8 | Lean | false | false | 28,197 | lean | /-
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 algebra.big_operators.pi
import algebra.module.pi
import algebra.big_operators.ring
/-!
# Matrices
-/
universes u v w
open_locale big_operators
@[nolint unused_arguments]
def matrix (m n : Type u) [fintype m] [fintype n] (α : Type v) : Type (max u v) :=
m → n → α
variables {l m n o : Type u} [fintype l] [fintype m] [fintype n] [fintype o]
variables {α : Type v}
namespace matrix
section ext
variables {M N : matrix m n α}
theorem ext_iff : (∀ i j, M i j = N i j) ↔ M = N :=
⟨λ h, funext $ λ i, funext $ h i, λ h, by simp [h]⟩
@[ext] theorem ext : (∀ i j, M i j = N i j) → M = N :=
ext_iff.mp
end ext
/-- Apply a function to each matrix entry. -/
def map (M : matrix m n α) {β : Type w} (f : α → β) : matrix m n β := λ i j, f (M i j)
@[simp]
lemma map_apply {M : matrix m n α} {β : Type w} {f : α → β} {i : m} {j : n} :
M.map f i j = f (M i j) := rfl
def transpose (M : matrix m n α) : matrix n m α
| x y := M y x
localized "postfix `ᵀ`:1500 := matrix.transpose" in matrix
def col (w : m → α) : matrix m punit α
| x y := w x
def row (v : n → α) : matrix punit n α
| x y := v y
instance [inhabited α] : inhabited (matrix m n α) := pi.inhabited _
instance [has_add α] : has_add (matrix m n α) := pi.has_add
instance [add_semigroup α] : add_semigroup (matrix m n α) := pi.add_semigroup
instance [add_comm_semigroup α] : add_comm_semigroup (matrix m n α) := pi.add_comm_semigroup
instance [has_zero α] : has_zero (matrix m n α) := pi.has_zero
instance [add_monoid α] : add_monoid (matrix m n α) := pi.add_monoid
instance [add_comm_monoid α] : add_comm_monoid (matrix m n α) := pi.add_comm_monoid
instance [has_neg α] : has_neg (matrix m n α) := pi.has_neg
instance [add_group α] : add_group (matrix m n α) := pi.add_group
instance [add_comm_group α] : add_comm_group (matrix m n α) := pi.add_comm_group
@[simp] theorem zero_val [has_zero α] (i j) : (0 : matrix m n α) i j = 0 := rfl
@[simp] theorem neg_val [has_neg α] (M : matrix m n α) (i j) : (- M) i j = - M i j := rfl
@[simp] theorem add_val [has_add α] (M N : matrix m n α) (i j) : (M + N) i j = M i j + N i j := rfl
@[simp] lemma map_zero [has_zero α] {β : Type w} [has_zero β] {f : α → β} (h : f 0 = 0) :
(0 : matrix m n α).map f = 0 :=
by { ext, simp [h], }
lemma map_add [add_monoid α] {β : Type w} [add_monoid β] (f : α →+ β)
(M N : matrix m n α) : (M + N).map f = M.map f + N.map f :=
by { ext, simp, }
end matrix
/-- The `add_monoid_hom` between spaces of matrices induced by an `add_monoid_hom` between their
coefficients. -/
def add_monoid_hom.map_matrix [add_monoid α] {β : Type w} [add_monoid β] (f : α →+ β) :
matrix m n α →+ matrix m n β :=
{ to_fun := λ M, M.map f,
map_zero' := by simp,
map_add' := matrix.map_add f, }
@[simp] lemma add_monoid_hom.map_matrix_apply [add_monoid α] {β : Type w} [add_monoid β]
(f : α →+ β) (M : matrix m n α) : f.map_matrix M = M.map f := rfl
open_locale matrix
namespace matrix
section diagonal
variables [decidable_eq n]
/-- `diagonal d` is the square matrix such that `(diagonal d) i i = d i` and `(diagonal d) i j = 0`
if `i ≠ j`. -/
def diagonal [has_zero α] (d : n → α) : matrix n n α := λ i j, if i = j then d i else 0
@[simp] theorem diagonal_val_eq [has_zero α] {d : n → α} (i : n) : (diagonal d) i i = d i :=
by simp [diagonal]
@[simp] theorem diagonal_val_ne [has_zero α] {d : n → α} {i j : n} (h : i ≠ j) :
(diagonal d) i j = 0 := by simp [diagonal, h]
theorem diagonal_val_ne' [has_zero α] {d : n → α} {i j : n} (h : j ≠ i) :
(diagonal d) i j = 0 := diagonal_val_ne h.symm
@[simp] theorem diagonal_zero [has_zero α] : (diagonal (λ _, 0) : matrix n n α) = 0 :=
by simp [diagonal]; refl
@[simp] lemma diagonal_transpose [has_zero α] (v : n → α) :
(diagonal v)ᵀ = diagonal v :=
begin
ext i j,
by_cases h : i = j,
{ simp [h, transpose] },
{ simp [h, transpose, diagonal_val_ne' h] }
end
@[simp] theorem diagonal_add [add_monoid α] (d₁ d₂ : n → α) :
diagonal d₁ + diagonal d₂ = diagonal (λ i, d₁ i + d₂ i) :=
by ext i j; by_cases h : i = j; simp [h]
@[simp] lemma diagonal_map {β : Type w} [has_zero α] [has_zero β]
{f : α → β} (h : f 0 = 0) {d : n → α} :
(diagonal d).map f = diagonal (λ m, f (d m)) :=
by { ext, simp only [diagonal, map_apply], split_ifs; simp [h], }
section one
variables [has_zero α] [has_one α]
instance : has_one (matrix n n α) := ⟨diagonal (λ _, 1)⟩
@[simp] theorem diagonal_one : (diagonal (λ _, 1) : matrix n n α) = 1 := rfl
theorem one_val {i j} : (1 : matrix n n α) i j = if i = j then 1 else 0 := rfl
@[simp] theorem one_val_eq (i) : (1 : matrix n n α) i i = 1 := diagonal_val_eq i
@[simp] theorem one_val_ne {i j} : i ≠ j → (1 : matrix n n α) i j = 0 :=
diagonal_val_ne
theorem one_val_ne' {i j} : j ≠ i → (1 : matrix n n α) i j = 0 :=
diagonal_val_ne'
@[simp] lemma one_map {β : Type w} [has_zero β] [has_one β]
{f : α → β} (h₀ : f 0 = 0) (h₁ : f 1 = 1) :
(1 : matrix n n α).map f = (1 : matrix n n β) :=
by { ext, simp only [one_val, map_apply], split_ifs; simp [h₀, h₁], }
end one
section numeral
@[simp] lemma bit0_val [has_add α] (M : matrix m m α) (i : m) (j : m) :
(bit0 M) i j = bit0 (M i j) := rfl
variables [add_monoid α] [has_one α]
lemma bit1_val (M : matrix n n α) (i : n) (j : n) :
(bit1 M) i j = if i = j then bit1 (M i j) else bit0 (M i j) :=
by dsimp [bit1]; by_cases h : i = j; simp [h]
@[simp]
lemma bit1_val_eq (M : matrix n n α) (i : n) :
(bit1 M) i i = bit1 (M i i) :=
by simp [bit1_val]
@[simp]
lemma bit1_val_ne (M : matrix n n α) {i j : n} (h : i ≠ j) :
(bit1 M) i j = bit0 (M i j) :=
by simp [bit1_val, h]
end numeral
end diagonal
section dot_product
/-- `dot_product v w` is the sum of the entrywise products `v i * w i` -/
def dot_product [has_mul α] [add_comm_monoid α] (v w : m → α) : α :=
∑ i, v i * w i
lemma dot_product_assoc [semiring α] (u : m → α) (v : m → n → α) (w : n → α) :
dot_product (λ j, dot_product u (λ i, v i j)) w = dot_product u (λ i, dot_product (v i) w) :=
by simpa [dot_product, finset.mul_sum, finset.sum_mul, mul_assoc] using finset.sum_comm
lemma dot_product_comm [comm_semiring α] (v w : m → α) :
dot_product v w = dot_product w v :=
by simp_rw [dot_product, mul_comm]
@[simp] lemma dot_product_punit [add_comm_monoid α] [has_mul α] (v w : punit → α) :
dot_product v w = v ⟨⟩ * w ⟨⟩ :=
by simp [dot_product]
@[simp] lemma dot_product_zero [semiring α] (v : m → α) : dot_product v 0 = 0 :=
by simp [dot_product]
@[simp] lemma dot_product_zero' [semiring α] (v : m → α) : dot_product v (λ _, 0) = 0 :=
dot_product_zero v
@[simp] lemma zero_dot_product [semiring α] (v : m → α) : dot_product 0 v = 0 :=
by simp [dot_product]
@[simp] lemma zero_dot_product' [semiring α] (v : m → α) : dot_product (λ _, (0 : α)) v = 0 :=
zero_dot_product v
@[simp] lemma add_dot_product [semiring α] (u v w : m → α) :
dot_product (u + v) w = dot_product u w + dot_product v w :=
by simp [dot_product, add_mul, finset.sum_add_distrib]
@[simp] lemma dot_product_add [semiring α] (u v w : m → α) :
dot_product u (v + w) = dot_product u v + dot_product u w :=
by simp [dot_product, mul_add, finset.sum_add_distrib]
@[simp] lemma diagonal_dot_product [decidable_eq m] [semiring α] (v w : m → α) (i : m) :
dot_product (diagonal v i) w = v i * w i :=
have ∀ j ≠ i, diagonal v i j * w j = 0 := λ j hij, by simp [diagonal_val_ne' hij],
by convert finset.sum_eq_single i (λ j _, this j) _; simp
@[simp] lemma dot_product_diagonal [decidable_eq m] [semiring α] (v w : m → α) (i : m) :
dot_product v (diagonal w i) = v i * w i :=
have ∀ j ≠ i, v j * diagonal w i j = 0 := λ j hij, by simp [diagonal_val_ne' hij],
by convert finset.sum_eq_single i (λ j _, this j) _; simp
@[simp] lemma dot_product_diagonal' [decidable_eq m] [semiring α] (v w : m → α) (i : m) :
dot_product v (λ j, diagonal w j i) = v i * w i :=
have ∀ j ≠ i, v j * diagonal w j i = 0 := λ j hij, by simp [diagonal_val_ne hij],
by convert finset.sum_eq_single i (λ j _, this j) _; simp
@[simp] lemma neg_dot_product [ring α] (v w : m → α) : dot_product (-v) w = - dot_product v w :=
by simp [dot_product]
@[simp] lemma dot_product_neg [ring α] (v w : m → α) : dot_product v (-w) = - dot_product v w :=
by simp [dot_product]
@[simp] lemma smul_dot_product [semiring α] (x : α) (v w : m → α) :
dot_product (x • v) w = x * dot_product v w :=
by simp [dot_product, finset.mul_sum, mul_assoc]
@[simp] lemma dot_product_smul [comm_semiring α] (x : α) (v w : m → α) :
dot_product v (x • w) = x * dot_product v w :=
by simp [dot_product, finset.mul_sum, mul_assoc, mul_comm, mul_left_comm]
end dot_product
protected def mul [has_mul α] [add_comm_monoid α] (M : matrix l m α) (N : matrix m n α) :
matrix l n α :=
λ i k, dot_product (λ j, M i j) (λ j, N j k)
localized "infixl ` ⬝ `:75 := matrix.mul" in matrix
theorem mul_val [has_mul α] [add_comm_monoid α] {M : matrix l m α} {N : matrix m n α} {i k} :
(M ⬝ N) i k = ∑ j, M i j * N j k := rfl
instance [has_mul α] [add_comm_monoid α] : has_mul (matrix n n α) := ⟨matrix.mul⟩
@[simp] theorem mul_eq_mul [has_mul α] [add_comm_monoid α] (M N : matrix n n α) :
M * N = M ⬝ N := rfl
theorem mul_val' [has_mul α] [add_comm_monoid α] {M N : matrix n n α} {i k} :
(M ⬝ N) i k = dot_product (λ j, M i j) (λ j, N j k) := rfl
section semigroup
variables [semiring α]
protected theorem mul_assoc (L : matrix l m α) (M : matrix m n α) (N : matrix n o α) :
(L ⬝ M) ⬝ N = L ⬝ (M ⬝ N) :=
by { ext, apply dot_product_assoc }
instance : semigroup (matrix n n α) :=
{ mul_assoc := matrix.mul_assoc, ..matrix.has_mul }
end semigroup
@[simp] theorem diagonal_neg [decidable_eq n] [add_group α] (d : n → α) :
-diagonal d = diagonal (λ i, -d i) :=
by ext i j; by_cases i = j; simp [h]
section semiring
variables [semiring α]
@[simp] protected theorem mul_zero (M : matrix m n α) : M ⬝ (0 : matrix n o α) = 0 :=
by { ext i j, apply dot_product_zero }
@[simp] protected theorem zero_mul (M : matrix m n α) : (0 : matrix l m α) ⬝ M = 0 :=
by { ext i j, apply zero_dot_product }
protected theorem mul_add (L : matrix m n α) (M N : matrix n o α) : L ⬝ (M + N) = L ⬝ M + L ⬝ N :=
by { ext i j, apply dot_product_add }
protected theorem add_mul (L M : matrix l m α) (N : matrix m n α) : (L + M) ⬝ N = L ⬝ N + M ⬝ N :=
by { ext i j, apply add_dot_product }
@[simp] theorem diagonal_mul [decidable_eq m]
(d : m → α) (M : matrix m n α) (i j) : (diagonal d).mul M i j = d i * M i j :=
diagonal_dot_product _ _ _
@[simp] theorem mul_diagonal [decidable_eq n]
(d : n → α) (M : matrix m n α) (i j) : (M ⬝ diagonal d) i j = M i j * d j :=
by { rw ← diagonal_transpose, apply dot_product_diagonal }
@[simp] protected theorem one_mul [decidable_eq m] (M : matrix m n α) : (1 : matrix m m α) ⬝ M = M :=
by ext i j; rw [← diagonal_one, diagonal_mul, one_mul]
@[simp] protected theorem mul_one [decidable_eq n] (M : matrix m n α) : M ⬝ (1 : matrix n n α) = M :=
by ext i j; rw [← diagonal_one, mul_diagonal, mul_one]
instance [decidable_eq n] : monoid (matrix n n α) :=
{ one_mul := matrix.one_mul,
mul_one := matrix.mul_one,
..matrix.has_one, ..matrix.semigroup }
instance [decidable_eq n] : semiring (matrix n n α) :=
{ mul_zero := matrix.mul_zero,
zero_mul := matrix.zero_mul,
left_distrib := matrix.mul_add,
right_distrib := matrix.add_mul,
..matrix.add_comm_monoid,
..matrix.monoid }
@[simp] theorem diagonal_mul_diagonal [decidable_eq n] (d₁ d₂ : n → α) :
(diagonal d₁) ⬝ (diagonal d₂) = diagonal (λ i, d₁ i * d₂ i) :=
by ext i j; by_cases i = j; simp [h]
theorem diagonal_mul_diagonal' [decidable_eq n] (d₁ d₂ : n → α) :
diagonal d₁ * diagonal d₂ = diagonal (λ i, d₁ i * d₂ i) :=
diagonal_mul_diagonal _ _
lemma map_mul {L : matrix m n α} {M : matrix n o α}
{β : Type w} [semiring β] {f : α →+* β} :
(L ⬝ M).map f = L.map f ⬝ M.map f :=
by { ext, simp [mul_val, ring_hom.map_sum], }
lemma is_add_monoid_hom_mul_left (M : matrix l m α) :
is_add_monoid_hom (λ x : matrix m n α, M ⬝ x) :=
{ to_is_add_hom := ⟨matrix.mul_add _⟩, map_zero := matrix.mul_zero _ }
lemma is_add_monoid_hom_mul_right (M : matrix m n α) :
is_add_monoid_hom (λ x : matrix l m α, x ⬝ M) :=
{ to_is_add_hom := ⟨λ _ _, matrix.add_mul _ _ _⟩, map_zero := matrix.zero_mul _ }
protected lemma sum_mul {β : Type*} (s : finset β) (f : β → matrix l m α)
(M : matrix m n α) : (∑ a in s, f a) ⬝ M = ∑ a in s, f a ⬝ M :=
(@finset.sum_hom _ _ _ _ _ s f (λ x, x ⬝ M)
/- This line does not type-check without `id` and `: _`. Lean did not recognize that two different
`add_monoid` instances were def-eq -/
(id (@is_add_monoid_hom_mul_right l _ _ _ _ _ _ _ M) : _)).symm
protected lemma mul_sum {β : Type*} (s : finset β) (f : β → matrix m n α)
(M : matrix l m α) : M ⬝ ∑ a in s, f a = ∑ a in s, M ⬝ f a :=
(@finset.sum_hom _ _ _ _ _ s f (λ x, M ⬝ x)
/- This line does not type-check without `id` and `: _`. Lean did not recognize that two different
`add_monoid` instances were def-eq -/
(id (@is_add_monoid_hom_mul_left _ _ n _ _ _ _ _ M) : _)).symm
@[simp]
lemma row_mul_col_val (v w : m → α) (i j) : (row v ⬝ col w) i j = dot_product v w :=
rfl
end semiring
end matrix
/-- The `ring_hom` between spaces of square matrices induced by a `ring_hom` between their
coefficients. -/
def ring_hom.map_matrix [decidable_eq m] [semiring α] {β : Type w} [semiring β] (f : α →+* β) :
matrix m m α →+* matrix m m β :=
{ to_fun := λ M, M.map f,
map_one' := by simp,
map_mul' := λ L M, matrix.map_mul,
..(f.to_add_monoid_hom).map_matrix }
@[simp] lemma ring_hom.map_matrix_apply [decidable_eq m] [semiring α] {β : Type w} [semiring β]
(f : α →+* β) (M : matrix m m α) : f.map_matrix M = M.map f := rfl
open_locale matrix
namespace matrix
section ring
variables [ring α]
@[simp] theorem neg_mul (M : matrix m n α) (N : matrix n o α) :
(-M) ⬝ N = -(M ⬝ N) :=
by { ext, apply neg_dot_product }
@[simp] theorem mul_neg (M : matrix m n α) (N : matrix n o α) :
M ⬝ (-N) = -(M ⬝ N) :=
by { ext, apply dot_product_neg }
end ring
instance [decidable_eq n] [ring α] : ring (matrix n n α) :=
{ ..matrix.semiring, ..matrix.add_comm_group }
instance [semiring α] : has_scalar α (matrix m n α) := pi.has_scalar
instance {β : Type w} [semiring α] [add_comm_monoid β] [semimodule α β] :
semimodule α (matrix m n β) := pi.semimodule _ _ _
@[simp] lemma smul_val [semiring α] (a : α) (A : matrix m n α) (i : m) (j : n) : (a • A) i j = a * A i j := rfl
section semiring
variables [semiring α]
lemma smul_eq_diagonal_mul [decidable_eq m] (M : matrix m n α) (a : α) :
a • M = diagonal (λ _, a) ⬝ M :=
by { ext, simp }
@[simp] lemma smul_mul (M : matrix m n α) (a : α) (N : matrix n l α) : (a • M) ⬝ N = a • M ⬝ N :=
by { ext, apply smul_dot_product }
@[simp] lemma mul_mul_left (M : matrix m n α) (N : matrix n o α) (a : α) :
(λ i j, a * M i j) ⬝ N = a • (M ⬝ N) :=
begin
simp only [←smul_val],
simp,
end
/--
The ring homomorphism `α →+* matrix n n α`
sending `a` to the diagonal matrix with `a` on the diagonal.
-/
def scalar (n : Type u) [fintype n] [decidable_eq n] : α →+* matrix n n α :=
{ to_fun := λ a, a • 1,
map_zero' := by simp,
map_add' := by { intros, ext, simp [add_mul], },
map_one' := by simp,
map_mul' := by { intros, ext, simp [mul_assoc], }, }
section scalar
variable [decidable_eq n]
@[simp] lemma coe_scalar : (scalar n : α → matrix n n α) = λ a, a • 1 := rfl
lemma scalar_apply_eq (a : α) (i : n) :
scalar n a i i = a :=
by simp only [coe_scalar, mul_one, one_val_eq, smul_val]
lemma scalar_apply_ne (a : α) (i j : n) (h : i ≠ j) :
scalar n a i j = 0 :=
by simp only [h, coe_scalar, one_val_ne, ne.def, not_false_iff, smul_val, mul_zero]
end scalar
end semiring
section comm_semiring
variables [comm_semiring α]
lemma smul_eq_mul_diagonal [decidable_eq n] (M : matrix m n α) (a : α) :
a • M = M ⬝ diagonal (λ _, a) :=
by { ext, simp [mul_comm] }
@[simp] lemma mul_smul (M : matrix m n α) (a : α) (N : matrix n l α) : M ⬝ (a • N) = a • M ⬝ N :=
by { ext, apply dot_product_smul }
@[simp] lemma mul_mul_right (M : matrix m n α) (N : matrix n o α) (a : α) :
M ⬝ (λ i j, a * N i j) = a • (M ⬝ N) :=
begin
simp only [←smul_val],
simp,
end
end comm_semiring
section semiring
variables [semiring α]
def vec_mul_vec (w : m → α) (v : n → α) : matrix m n α
| x y := w x * v y
def mul_vec (M : matrix m n α) (v : n → α) : m → α
| i := dot_product (λ j, M i j) v
def vec_mul (v : m → α) (M : matrix m n α) : n → α
| j := dot_product v (λ i, M i j)
instance mul_vec.is_add_monoid_hom_left (v : n → α) :
is_add_monoid_hom (λM:matrix m n α, mul_vec M v) :=
{ map_zero := by ext; simp [mul_vec]; refl,
map_add :=
begin
intros x y,
ext m,
apply add_dot_product
end }
lemma mul_vec_diagonal [decidable_eq m] (v w : m → α) (x : m) :
mul_vec (diagonal v) w x = v x * w x :=
diagonal_dot_product v w x
lemma vec_mul_diagonal [decidable_eq m] (v w : m → α) (x : m) :
vec_mul v (diagonal w) x = v x * w x :=
dot_product_diagonal' v w x
@[simp] lemma mul_vec_one [decidable_eq m] (v : m → α) : mul_vec 1 v = v :=
by { ext, rw [←diagonal_one, mul_vec_diagonal, one_mul] }
@[simp] lemma vec_mul_one [decidable_eq m] (v : m → α) : vec_mul v 1 = v :=
by { ext, rw [←diagonal_one, vec_mul_diagonal, mul_one] }
@[simp] lemma mul_vec_zero (A : matrix m n α) : mul_vec A 0 = 0 :=
by { ext, simp [mul_vec] }
@[simp] lemma vec_mul_zero (A : matrix m n α) : vec_mul 0 A = 0 :=
by { ext, simp [vec_mul] }
@[simp] lemma vec_mul_vec_mul (v : m → α) (M : matrix m n α) (N : matrix n o α) :
vec_mul (vec_mul v M) N = vec_mul v (M ⬝ N) :=
by { ext, apply dot_product_assoc }
@[simp] lemma mul_vec_mul_vec (v : o → α) (M : matrix m n α) (N : matrix n o α) :
mul_vec M (mul_vec N v) = mul_vec (M ⬝ N) v :=
by { ext, symmetry, apply dot_product_assoc }
lemma vec_mul_vec_eq (w : m → α) (v : n → α) :
vec_mul_vec w v = (col w) ⬝ (row v) :=
by { ext i j, simp [vec_mul_vec, mul_val], refl }
variables [decidable_eq m] [decidable_eq n]
/--
`std_basis_matrix i j a` is the matrix with `a` in the `i`-th row, `j`-th column,
and zeroes elsewhere.
-/
def std_basis_matrix (i : m) (j : n) (a : α) : matrix m n α :=
(λ i' j', if i' = i ∧ j' = j then a else 0)
@[simp] lemma smul_std_basis_matrix (i : m) (j : n) (a b : α) :
b • std_basis_matrix i j a = std_basis_matrix i j (b • a) :=
by { unfold std_basis_matrix, ext, dsimp, simp }
@[simp] lemma std_basis_matrix_zero (i : m) (j : n) :
std_basis_matrix i j (0 : α) = 0 :=
by { unfold std_basis_matrix, ext, simp }
lemma std_basis_matrix_add (i : m) (j : n) (a b : α) :
std_basis_matrix i j (a + b) = std_basis_matrix i j a + std_basis_matrix i j b :=
begin
unfold std_basis_matrix, ext,
split_ifs with h; simp [h],
end
lemma matrix_eq_sum_std_basis (x : matrix n m α) :
x = ∑ (i : n) (j : m), std_basis_matrix i j (x i j) :=
begin
ext, iterate 2 {rw finset.sum_apply},
rw ← finset.sum_subset, swap 4, exact {i},
{ norm_num [std_basis_matrix] },
{ simp },
intros, norm_num at a, norm_num,
convert finset.sum_const_zero,
ext, norm_num [std_basis_matrix],
rw if_neg, tauto!,
end
-- TODO: tie this up with the `basis` machinery of linear algebra
-- this is not completely trivial because we are indexing by two types, instead of one
-- TODO: add `std_basis_vec`
lemma std_basis_eq_basis_mul_basis (i : m) (j : n) :
std_basis_matrix i j 1 = vec_mul_vec (λ i', ite (i = i') 1 0) (λ j', ite (j = j') 1 0) :=
begin
ext, norm_num [std_basis_matrix, vec_mul_vec],
split_ifs; tauto,
end
@[elab_as_eliminator] protected lemma induction_on'
{X : Type*} [semiring X] {M : matrix n n X → Prop} (m : matrix n n X)
(h_zero : M 0)
(h_add : ∀p q, M p → M q → M (p + q))
(h_std_basis : ∀ i j x, M (std_basis_matrix i j x)) :
M m :=
begin
rw [matrix_eq_sum_std_basis m, ← finset.sum_product'],
apply finset.sum_induction _ _ h_add h_zero,
{ intros, apply h_std_basis, }
end
@[elab_as_eliminator] protected lemma induction_on
[nonempty n] {X : Type*} [semiring X] {M : matrix n n X → Prop} (m : matrix n n X)
(h_add : ∀p q, M p → M q → M (p + q))
(h_std_basis : ∀ i j x, M (std_basis_matrix i j x)) :
M m :=
matrix.induction_on' m
begin
have i : n := classical.choice (by assumption),
simpa using h_std_basis i i 0,
end
h_add h_std_basis
end semiring
section ring
variables [ring α]
lemma neg_vec_mul (v : m → α) (A : matrix m n α) : vec_mul (-v) A = - vec_mul v A :=
by { ext, apply neg_dot_product }
lemma vec_mul_neg (v : m → α) (A : matrix m n α) : vec_mul v (-A) = - vec_mul v A :=
by { ext, apply dot_product_neg }
lemma neg_mul_vec (v : n → α) (A : matrix m n α) : mul_vec (-A) v = - mul_vec A v :=
by { ext, apply neg_dot_product }
lemma mul_vec_neg (v : n → α) (A : matrix m n α) : mul_vec A (-v) = - mul_vec A v :=
by { ext, apply dot_product_neg }
end ring
section transpose
open_locale matrix
/--
Tell `simp` what the entries are in a transposed matrix.
Compare with `mul_val`, `diagonal_val_eq`, etc.
-/
@[simp] lemma transpose_val (M : matrix m n α) (i j) : M.transpose j i = M i j := rfl
@[simp] lemma transpose_transpose (M : matrix m n α) :
Mᵀᵀ = M :=
by ext; refl
@[simp] lemma transpose_zero [has_zero α] : (0 : matrix m n α)ᵀ = 0 :=
by ext i j; refl
@[simp] lemma transpose_one [decidable_eq n] [has_zero α] [has_one α] : (1 : matrix n n α)ᵀ = 1 :=
begin
ext i j,
unfold has_one.one transpose,
by_cases i = j,
{ simp only [h, diagonal_val_eq] },
{ simp only [diagonal_val_ne h, diagonal_val_ne (λ p, h (symm p))] }
end
@[simp] lemma transpose_add [has_add α] (M : matrix m n α) (N : matrix m n α) :
(M + N)ᵀ = Mᵀ + Nᵀ :=
by { ext i j, simp }
@[simp] lemma transpose_sub [add_group α] (M : matrix m n α) (N : matrix m n α) :
(M - N)ᵀ = Mᵀ - Nᵀ :=
by { ext i j, simp }
@[simp] lemma transpose_mul [comm_semiring α] (M : matrix m n α) (N : matrix n l α) :
(M ⬝ N)ᵀ = Nᵀ ⬝ Mᵀ :=
begin
ext i j,
apply dot_product_comm
end
@[simp] lemma transpose_smul [semiring α] (c : α) (M : matrix m n α) :
(c • M)ᵀ = c • Mᵀ :=
by { ext i j, refl }
@[simp] lemma transpose_neg [has_neg α] (M : matrix m n α) :
(- M)ᵀ = - Mᵀ :=
by ext i j; refl
lemma transpose_map {β : Type w} {f : α → β} {M : matrix m n α} : Mᵀ.map f = (M.map f)ᵀ :=
by { ext, refl }
end transpose
def minor (A : matrix m n α) (row : l → m) (col : o → n) : matrix l o α :=
λ i j, A (row i) (col j)
@[reducible]
def sub_left {m l r : nat} (A : matrix (fin m) (fin (l + r)) α) : matrix (fin m) (fin l) α :=
minor A id (fin.cast_add r)
@[reducible]
def sub_right {m l r : nat} (A : matrix (fin m) (fin (l + r)) α) : matrix (fin m) (fin r) α :=
minor A id (fin.nat_add l)
@[reducible]
def sub_up {d u n : nat} (A : matrix (fin (u + d)) (fin n) α) : matrix (fin u) (fin n) α :=
minor A (fin.cast_add d) id
@[reducible]
def sub_down {d u n : nat} (A : matrix (fin (u + d)) (fin n) α) : matrix (fin d) (fin n) α :=
minor A (fin.nat_add u) id
@[reducible]
def sub_up_right {d u l r : nat} (A: matrix (fin (u + d)) (fin (l + r)) α) :
matrix (fin u) (fin r) α :=
sub_up (sub_right A)
@[reducible]
def sub_down_right {d u l r : nat} (A : matrix (fin (u + d)) (fin (l + r)) α) :
matrix (fin d) (fin r) α :=
sub_down (sub_right A)
@[reducible]
def sub_up_left {d u l r : nat} (A : matrix (fin (u + d)) (fin (l + r)) α) :
matrix (fin u) (fin (l)) α :=
sub_up (sub_left A)
@[reducible]
def sub_down_left {d u l r : nat} (A: matrix (fin (u + d)) (fin (l + r)) α) :
matrix (fin d) (fin (l)) α :=
sub_down (sub_left A)
section row_col
/-!
### `row_col` section
Simplification lemmas for `matrix.row` and `matrix.col`.
-/
open_locale matrix
@[simp] lemma col_add [semiring α] (v w : m → α) : col (v + w) = col v + col w := by { ext, refl }
@[simp] lemma col_smul [semiring α] (x : α) (v : m → α) : col (x • v) = x • col v := by { ext, refl }
@[simp] lemma row_add [semiring α] (v w : m → α) : row (v + w) = row v + row w := by { ext, refl }
@[simp] lemma row_smul [semiring α] (x : α) (v : m → α) : row (x • v) = x • row v := by { ext, refl }
@[simp] lemma col_val (v : m → α) (i j) : matrix.col v i j = v i := rfl
@[simp] lemma row_val (v : m → α) (i j) : matrix.row v i j = v j := rfl
@[simp]
lemma transpose_col (v : m → α) : (matrix.col v).transpose = matrix.row v := by {ext, refl}
@[simp]
lemma transpose_row (v : m → α) : (matrix.row v).transpose = matrix.col v := by {ext, refl}
lemma row_vec_mul [semiring α] (M : matrix m n α) (v : m → α) :
matrix.row (matrix.vec_mul v M) = matrix.row v ⬝ M := by {ext, refl}
lemma col_vec_mul [semiring α] (M : matrix m n α) (v : m → α) :
matrix.col (matrix.vec_mul v M) = (matrix.row v ⬝ M)ᵀ := by {ext, refl}
lemma col_mul_vec [semiring α] (M : matrix m n α) (v : n → α) :
matrix.col (matrix.mul_vec M v) = M ⬝ matrix.col v := by {ext, refl}
lemma row_mul_vec [semiring α] (M : matrix m n α) (v : n → α) :
matrix.row (matrix.mul_vec M v) = (M ⬝ matrix.col v)ᵀ := by {ext, refl}
end row_col
section update
/-- Update, i.e. replace the `i`th row of matrix `A` with the values in `b`. -/
def update_row [decidable_eq n] (M : matrix n m α) (i : n) (b : m → α) : matrix n m α :=
function.update M i b
/-- Update, i.e. replace the `i`th column of matrix `A` with the values in `b`. -/
def update_column [decidable_eq m] (M : matrix n m α) (j : m) (b : n → α) : matrix n m α :=
λ i, function.update (M i) j (b i)
variables {M : matrix n m α} {i : n} {j : m} {b : m → α} {c : n → α}
@[simp] lemma update_row_self [decidable_eq n] : update_row M i b i = b :=
function.update_same i b M
@[simp] lemma update_column_self [decidable_eq m] : update_column M j c i j = c i :=
function.update_same j (c i) (M i)
@[simp] lemma update_row_ne [decidable_eq n] {i' : n} (i_ne : i' ≠ i) :
update_row M i b i' = M i' := function.update_noteq i_ne b M
@[simp] lemma update_column_ne [decidable_eq m] {j' : m} (j_ne : j' ≠ j) :
update_column M j c i j' = M i j' := function.update_noteq j_ne (c i) (M i)
lemma update_row_val [decidable_eq n] {i' : n} :
update_row M i b i' j = if i' = i then b j else M i' j :=
begin
by_cases i' = i,
{ rw [h, update_row_self, if_pos rfl] },
{ rwa [update_row_ne h, if_neg h] }
end
lemma update_column_val [decidable_eq m] {j' : m} : update_column M j c i j' = if j' = j then c i else M i j' :=
begin
by_cases j' = j,
{ rw [h, update_column_self, if_pos rfl] },
{ rwa [update_column_ne h, if_neg h] }
end
lemma update_row_transpose [decidable_eq m] : update_row Mᵀ j c = (update_column M j c)ᵀ :=
begin
ext i' j,
rw [transpose_val, update_row_val, update_column_val],
refl
end
lemma update_column_transpose [decidable_eq n] : update_column Mᵀ i b = (update_row M i b)ᵀ :=
begin
ext i' j,
rw [transpose_val, update_row_val, update_column_val],
refl
end
end update
end matrix
namespace ring_hom
variables {β : Type*} [semiring α] [semiring β]
lemma map_matrix_mul (M : matrix m n α) (N : matrix n o α) (i : m) (j : o) (f : α →+* β) :
f (matrix.mul M N i j) = matrix.mul (λ i j, f (M i j)) (λ i j, f (N i j)) i j :=
by simp [matrix.mul_val, ring_hom.map_sum]
end ring_hom
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eef0f2611c77e7193a7ed01cf49ba918a665577e | 432d948a4d3d242fdfb44b81c9e1b1baacd58617 | /src/topology/algebra/group.lean | 5934c1069656c67904c4551df8d2d321c4188c30 | [
"Apache-2.0"
] | permissive | JLimperg/aesop3 | 306cc6570c556568897ed2e508c8869667252e8a | a4a116f650cc7403428e72bd2e2c4cda300fe03f | refs/heads/master | 1,682,884,916,368 | 1,620,320,033,000 | 1,620,320,033,000 | null | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 28,716 | lean | /-
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 order.filter.pointwise
import group_theory.quotient_group
import topology.algebra.monoid
import topology.homeomorph
/-!
# Theory of topological groups
This file defines the following typeclasses:
* `topological_group`, `topological_add_group`: multiplicative and additive topological groups,
i.e., groups with continuous `(*)` and `(⁻¹)` / `(+)` and `(-)`;
* `has_continuous_sub G` means that `G` has a continuous subtraction operation.
There is an instance deducing `has_continuous_sub` from `topological_group` but we use a separate
typeclass because, e.g., `ℕ` and `ℝ≥0` have continuous subtraction but are not additive groups.
We also define `homeomorph` versions of several `equiv`s: `homeomorph.mul_left`,
`homeomorph.mul_right`, `homeomorph.inv`, and prove a few facts about neighbourhood filters in
groups.
## Tags
topological space, group, topological group
-/
open classical set filter topological_space function
open_locale classical topological_space filter
universes u v w x
variables {α : Type u} {β : Type v} {G : Type w} {H : Type x}
section continuous_mul_group
/-!
### Groups with continuous multiplication
In this section we prove a few statements about groups with continuous `(*)`.
-/
variables [topological_space G] [group G] [has_continuous_mul G]
/-- Multiplication from the left in a topological group as a homeomorphism. -/
@[to_additive "Addition from the left in a topological additive group as a homeomorphism."]
protected def homeomorph.mul_left (a : G) : G ≃ₜ G :=
{ continuous_to_fun := continuous_const.mul continuous_id,
continuous_inv_fun := continuous_const.mul continuous_id,
.. equiv.mul_left a }
@[simp, to_additive]
lemma homeomorph.coe_mul_left (a : G) : ⇑(homeomorph.mul_left a) = (*) a := rfl
@[to_additive]
lemma homeomorph.mul_left_symm (a : G) : (homeomorph.mul_left a).symm = homeomorph.mul_left a⁻¹ :=
by { ext, refl }
@[to_additive]
lemma is_open_map_mul_left (a : G) : is_open_map (λ x, a * x) :=
(homeomorph.mul_left a).is_open_map
@[to_additive]
lemma is_closed_map_mul_left (a : G) : is_closed_map (λ x, a * x) :=
(homeomorph.mul_left a).is_closed_map
/-- Multiplication from the right in a topological group as a homeomorphism. -/
@[to_additive "Addition from the right in a topological additive group as a homeomorphism."]
protected def homeomorph.mul_right (a : G) :
G ≃ₜ G :=
{ continuous_to_fun := continuous_id.mul continuous_const,
continuous_inv_fun := continuous_id.mul continuous_const,
.. equiv.mul_right a }
@[to_additive]
lemma is_open_map_mul_right (a : G) : is_open_map (λ x, x * a) :=
(homeomorph.mul_right a).is_open_map
@[to_additive]
lemma is_closed_map_mul_right (a : G) : is_closed_map (λ x, x * a) :=
(homeomorph.mul_right a).is_closed_map
@[to_additive]
lemma is_open_map_div_right (a : G) : is_open_map (λ x, x / a) :=
by simpa only [div_eq_mul_inv] using is_open_map_mul_right (a⁻¹)
@[to_additive]
lemma is_closed_map_div_right (a : G) : is_closed_map (λ x, x / a) :=
by simpa only [div_eq_mul_inv] using is_closed_map_mul_right (a⁻¹)
@[to_additive]
lemma discrete_topology_of_open_singleton_one (h : is_open ({1} : set G)) : discrete_topology G :=
begin
rw ← singletons_open_iff_discrete,
intro g,
suffices : {g} = (λ (x : G), g⁻¹ * x) ⁻¹' {1},
{ rw this, exact (continuous_mul_left (g⁻¹)).is_open_preimage _ h, },
simp only [mul_one, set.preimage_mul_left_singleton, eq_self_iff_true,
inv_inv, set.singleton_eq_singleton_iff],
end
end continuous_mul_group
section topological_group
/-!
### Topological groups
A topological group is a group in which the multiplication and inversion operations are
continuous. Topological additive groups are defined in the same way. Equivalently, we can require
that the division operation `λ x y, x * y⁻¹` (resp., subtraction) is continuous.
-/
/-- A topological (additive) group is a group in which the addition and negation operations are
continuous. -/
class topological_add_group (G : Type u) [topological_space G] [add_group G]
extends has_continuous_add G : Prop :=
(continuous_neg : continuous (λa:G, -a))
/-- A topological group is a group in which the multiplication and inversion operations are
continuous. -/
@[to_additive]
class topological_group (G : Type*) [topological_space G] [group G]
extends has_continuous_mul G : Prop :=
(continuous_inv : continuous (has_inv.inv : G → G))
variables [topological_space G] [group G] [topological_group G]
export topological_group (continuous_inv)
export topological_add_group (continuous_neg)
@[to_additive]
lemma continuous_on_inv {s : set G} : continuous_on has_inv.inv s :=
continuous_inv.continuous_on
@[to_additive]
lemma continuous_within_at_inv {s : set G} {x : G} : continuous_within_at has_inv.inv s x :=
continuous_inv.continuous_within_at
@[to_additive]
lemma continuous_at_inv {x : G} : continuous_at has_inv.inv x :=
continuous_inv.continuous_at
@[to_additive]
lemma tendsto_inv (a : G) : tendsto has_inv.inv (𝓝 a) (𝓝 (a⁻¹)) :=
continuous_at_inv
/-- If a function converges to a value in a multiplicative topological group, then its inverse
converges to the inverse of this value. For the version in normed fields assuming additionally
that the limit is nonzero, use `tendsto.inv'`. -/
@[to_additive]
lemma filter.tendsto.inv {f : α → G} {l : filter α} {y : G} (h : tendsto f l (𝓝 y)) :
tendsto (λ x, (f x)⁻¹) l (𝓝 y⁻¹) :=
(continuous_inv.tendsto y).comp h
variables [topological_space α] {f : α → G} {s : set α} {x : α}
@[continuity, to_additive]
lemma continuous.inv (hf : continuous f) : continuous (λx, (f x)⁻¹) :=
continuous_inv.comp hf
attribute [continuity] continuous.neg -- TODO
@[to_additive]
lemma continuous_on.inv (hf : continuous_on f s) : continuous_on (λx, (f x)⁻¹) s :=
continuous_inv.comp_continuous_on hf
@[to_additive]
lemma continuous_within_at.inv (hf : continuous_within_at f s x) :
continuous_within_at (λ x, (f x)⁻¹) s x :=
hf.inv
@[instance, to_additive]
instance [topological_space H] [group H] [topological_group H] :
topological_group (G × H) :=
{ continuous_inv := continuous_inv.prod_map continuous_inv }
@[to_additive]
instance pi.topological_group {C : β → Type*} [∀ b, topological_space (C b)]
[∀ b, group (C b)] [∀ b, topological_group (C b)] : topological_group (Π b, C b) :=
{ continuous_inv := continuous_pi (λ i, (continuous_apply i).inv) }
variable (G)
/-- Inversion in a topological group as a homeomorphism. -/
@[to_additive "Negation in a topological group as a homeomorphism."]
protected def homeomorph.inv : G ≃ₜ G :=
{ continuous_to_fun := continuous_inv,
continuous_inv_fun := continuous_inv,
.. equiv.inv G }
@[to_additive]
lemma nhds_one_symm : comap has_inv.inv (𝓝 (1 : G)) = 𝓝 (1 : G) :=
((homeomorph.inv G).comap_nhds_eq _).trans (congr_arg nhds one_inv)
/-- The map `(x, y) ↦ (x, xy)` as a homeomorphism. This is a shear mapping. -/
@[to_additive "The map `(x, y) ↦ (x, x + y)` as a homeomorphism.
This is a shear mapping."]
protected def homeomorph.shear_mul_right : G × G ≃ₜ G × G :=
{ continuous_to_fun := continuous_fst.prod_mk continuous_mul,
continuous_inv_fun := continuous_fst.prod_mk $ continuous_fst.inv.mul continuous_snd,
.. equiv.prod_shear (equiv.refl _) equiv.mul_left }
@[simp, to_additive]
lemma homeomorph.shear_mul_right_coe :
⇑(homeomorph.shear_mul_right G) = λ z : G × G, (z.1, z.1 * z.2) :=
rfl
@[simp, to_additive]
lemma homeomorph.shear_mul_right_symm_coe :
⇑(homeomorph.shear_mul_right G).symm = λ z : G × G, (z.1, z.1⁻¹ * z.2) :=
rfl
variable {G}
@[to_additive]
lemma inv_closure (s : set G) : (closure s)⁻¹ = closure s⁻¹ :=
(homeomorph.inv G).preimage_closure s
/-- The (topological-space) closure of a subgroup of a space `M` with `has_continuous_mul` is
itself a subgroup. -/
@[to_additive "The (topological-space) closure of an additive subgroup of a space `M` with
`has_continuous_add` is itself an additive subgroup."]
def subgroup.topological_closure (s : subgroup G) : subgroup G :=
{ carrier := closure (s : set G),
inv_mem' := λ g m, by simpa [←mem_inv, inv_closure] using m,
..s.to_submonoid.topological_closure }
@[to_additive]
instance subgroup.topological_closure_topological_group (s : subgroup G) :
topological_group (s.topological_closure) :=
{ continuous_inv :=
begin
apply continuous_induced_rng,
change continuous (λ p : s.topological_closure, (p : G)⁻¹),
continuity,
end
..s.to_submonoid.topological_closure_has_continuous_mul}
lemma subgroup.subgroup_topological_closure (s : subgroup G) :
s ≤ s.topological_closure :=
subset_closure
lemma subgroup.is_closed_topological_closure (s : subgroup G) :
is_closed (s.topological_closure : set G) :=
by convert is_closed_closure
lemma subgroup.topological_closure_minimal
(s : subgroup G) {t : subgroup G} (h : s ≤ t) (ht : is_closed (t : set G)) :
s.topological_closure ≤ t :=
closure_minimal h ht
@[to_additive exists_nhds_half_neg]
lemma exists_nhds_split_inv {s : set G} (hs : s ∈ 𝓝 (1 : G)) :
∃ V ∈ 𝓝 (1 : G), ∀ (v ∈ V) (w ∈ V), v / w ∈ s :=
have ((λp : G × G, p.1 * p.2⁻¹) ⁻¹' s) ∈ 𝓝 ((1, 1) : G × G),
from continuous_at_fst.mul continuous_at_snd.inv (by simpa),
by simpa only [div_eq_mul_inv, nhds_prod_eq, mem_prod_self_iff, prod_subset_iff, mem_preimage]
using this
@[to_additive]
lemma nhds_translation_mul_inv (x : G) : comap (λ y : G, y * x⁻¹) (𝓝 1) = 𝓝 x :=
((homeomorph.mul_right x⁻¹).comap_nhds_eq 1).trans $ show 𝓝 (1 * x⁻¹⁻¹) = 𝓝 x, by simp
@[simp, to_additive] lemma map_mul_left_nhds (x y : G) : map ((*) x) (𝓝 y) = 𝓝 (x * y) :=
(homeomorph.mul_left x).map_nhds_eq y
@[to_additive] lemma map_mul_left_nhds_one (x : G) : map ((*) x) (𝓝 1) = 𝓝 x := by simp
@[to_additive]
lemma topological_group.ext {G : Type*} [group G] {t t' : topological_space G}
(tg : @topological_group G t _) (tg' : @topological_group G t' _)
(h : @nhds G t 1 = @nhds G t' 1) : t = t' :=
eq_of_nhds_eq_nhds $ λ x, by
rw [← @nhds_translation_mul_inv G t _ _ x , ← @nhds_translation_mul_inv G t' _ _ x , ← h]
@[to_additive]
lemma topological_group.of_nhds_aux {G : Type*} [group G] [topological_space G]
(hinv : tendsto (λ (x : G), x⁻¹) (𝓝 1) (𝓝 1))
(hleft : ∀ (x₀ : G), 𝓝 x₀ = map (λ (x : G), x₀ * x) (𝓝 1))
(hconj : ∀ (x₀ : G), map (λ (x : G), x₀ * x * x₀⁻¹) (𝓝 1) ≤ 𝓝 1) : continuous (λ x : G, x⁻¹) :=
begin
rw continuous_iff_continuous_at,
rintros x₀,
have key : (λ x, (x₀*x)⁻¹) = (λ x, x₀⁻¹*x) ∘ (λ x, x₀*x*x₀⁻¹) ∘ (λ x, x⁻¹),
by {ext ; simp[mul_assoc] },
calc map (λ x, x⁻¹) (𝓝 x₀)
= map (λ x, x⁻¹) (map (λ x, x₀*x) $ 𝓝 1) : by rw hleft
... = map (λ x, (x₀*x)⁻¹) (𝓝 1) : by rw filter.map_map
... = map (((λ x, x₀⁻¹*x) ∘ (λ x, x₀*x*x₀⁻¹)) ∘ (λ x, x⁻¹)) (𝓝 1) : by rw key
... = map ((λ x, x₀⁻¹*x) ∘ (λ x, x₀*x*x₀⁻¹)) _ : by rw ← filter.map_map
... ≤ map ((λ x, x₀⁻¹ * x) ∘ λ x, x₀ * x * x₀⁻¹) (𝓝 1) : map_mono hinv
... = map (λ x, x₀⁻¹ * x) (map (λ x, x₀ * x * x₀⁻¹) (𝓝 1)) : filter.map_map
... ≤ map (λ x, x₀⁻¹ * x) (𝓝 1) : map_mono (hconj x₀)
... = 𝓝 x₀⁻¹ : (hleft _).symm
end
@[to_additive]
lemma topological_group.of_nhds_one' {G : Type*} [group G] [topological_space G]
(hmul : tendsto (uncurry ((*) : G → G → G)) ((𝓝 1) ×ᶠ 𝓝 1) (𝓝 1))
(hinv : tendsto (λ x : G, x⁻¹) (𝓝 1) (𝓝 1))
(hleft : ∀ x₀ : G, 𝓝 x₀ = map (λ x, x₀*x) (𝓝 1))
(hright : ∀ x₀ : G, 𝓝 x₀ = map (λ x, x*x₀) (𝓝 1)) : topological_group G :=
begin
refine { continuous_mul := (has_continuous_mul.of_nhds_one hmul hleft hright).continuous_mul,
continuous_inv := topological_group.of_nhds_aux hinv hleft _ },
intros x₀,
suffices : map (λ (x : G), x₀ * x * x₀⁻¹) (𝓝 1) = 𝓝 1, by simp [this, le_refl],
rw [show (λ x, x₀ * x * x₀⁻¹) = (λ x, x₀ * x) ∘ λ x, x*x₀⁻¹, by {ext, simp [mul_assoc] },
← filter.map_map, ← hright, hleft x₀⁻¹, filter.map_map],
convert map_id,
ext,
simp
end
@[to_additive]
lemma topological_group.of_nhds_one {G : Type u} [group G] [topological_space G]
(hmul : tendsto (uncurry ((*) : G → G → G)) ((𝓝 1) ×ᶠ 𝓝 1) (𝓝 1))
(hinv : tendsto (λ x : G, x⁻¹) (𝓝 1) (𝓝 1))
(hleft : ∀ x₀ : G, 𝓝 x₀ = map (λ x, x₀*x) (𝓝 1))
(hconj : ∀ x₀ : G, tendsto (λ x, x₀*x*x₀⁻¹) (𝓝 1) (𝓝 1)) : topological_group G :=
{ continuous_mul := begin
rw continuous_iff_continuous_at,
rintros ⟨x₀, y₀⟩,
have key : (λ (p : G × G), x₀ * p.1 * (y₀ * p.2)) =
((λ x, x₀*y₀*x) ∘ (uncurry (*)) ∘ (prod.map (λ x, y₀⁻¹*x*y₀) id)),
by { ext, simp [uncurry, prod.map, mul_assoc] },
specialize hconj y₀⁻¹, rw inv_inv at hconj,
calc map (λ (p : G × G), p.1 * p.2) (𝓝 (x₀, y₀))
= map (λ (p : G × G), p.1 * p.2) ((𝓝 x₀) ×ᶠ 𝓝 y₀)
: by rw nhds_prod_eq
... = map (λ (p : G × G), x₀ * p.1 * (y₀ * p.2)) ((𝓝 1) ×ᶠ (𝓝 1))
: by rw [hleft x₀, hleft y₀, prod_map_map_eq, filter.map_map]
... = map (((λ x, x₀*y₀*x) ∘ (uncurry (*))) ∘ (prod.map (λ x, y₀⁻¹*x*y₀) id))((𝓝 1) ×ᶠ (𝓝 1))
: by rw key
... = map ((λ x, x₀*y₀*x) ∘ (uncurry (*))) ((map (λ x, y₀⁻¹*x*y₀) $ 𝓝 1) ×ᶠ (𝓝 1))
: by rw [← filter.map_map, ← prod_map_map_eq', map_id]
... ≤ map ((λ x, x₀*y₀*x) ∘ (uncurry (*))) ((𝓝 1) ×ᶠ (𝓝 1))
: map_mono (filter.prod_mono hconj $ le_refl _)
... = map (λ x, x₀*y₀*x) (map (uncurry (*)) ((𝓝 1) ×ᶠ (𝓝 1))) : by rw filter.map_map
... ≤ map (λ x, x₀*y₀*x) (𝓝 1) : map_mono hmul
... = 𝓝 (x₀*y₀) : (hleft _).symm
end,
continuous_inv := topological_group.of_nhds_aux hinv hleft hconj}
@[to_additive]
lemma topological_group.of_comm_of_nhds_one {G : Type*} [comm_group G] [topological_space G]
(hmul : tendsto (uncurry ((*) : G → G → G)) ((𝓝 1) ×ᶠ 𝓝 1) (𝓝 1))
(hinv : tendsto (λ x : G, x⁻¹) (𝓝 1) (𝓝 1))
(hleft : ∀ x₀ : G, 𝓝 x₀ = map (λ x, x₀*x) (𝓝 1)) : topological_group G :=
topological_group.of_nhds_one hmul hinv hleft (by simpa using tendsto_id)
end topological_group
section quotient_topological_group
variables [topological_space G] [group G] [topological_group G] (N : subgroup G) (n : N.normal)
@[to_additive]
instance {G : Type*} [group G] [topological_space G] (N : subgroup G) :
topological_space (quotient_group.quotient N) :=
quotient.topological_space
open quotient_group
@[to_additive]
lemma quotient_group.is_open_map_coe : is_open_map (coe : G → quotient N) :=
begin
intros s s_op,
change is_open ((coe : G → quotient N) ⁻¹' (coe '' s)),
rw quotient_group.preimage_image_coe N s,
exact is_open_Union (λ n, is_open_map_mul_right n s s_op)
end
@[to_additive]
instance topological_group_quotient [N.normal] : topological_group (quotient N) :=
{ continuous_mul := begin
have cont : continuous ((coe : G → quotient N) ∘ (λ (p : G × G), p.fst * p.snd)) :=
continuous_quot_mk.comp continuous_mul,
have quot : quotient_map (λ p : G × G, ((p.1:quotient N), (p.2:quotient N))),
{ apply is_open_map.to_quotient_map,
{ exact (quotient_group.is_open_map_coe N).prod (quotient_group.is_open_map_coe N) },
{ exact continuous_quot_mk.prod_map continuous_quot_mk },
{ exact (surjective_quot_mk _).prod_map (surjective_quot_mk _) } },
exact (quotient_map.continuous_iff quot).2 cont,
end,
continuous_inv := begin
have : continuous ((coe : G → quotient N) ∘ (λ (a : G), a⁻¹)) :=
continuous_quot_mk.comp continuous_inv,
convert continuous_quotient_lift _ this,
end }
attribute [instance] topological_add_group_quotient
end quotient_topological_group
/-- A typeclass saying that `λ p : G × G, p.1 - p.2` is a continuous function. This property
automatically holds for topological additive groups but it also holds, e.g., for `ℝ≥0`. -/
class has_continuous_sub (G : Type*) [topological_space G] [has_sub G] : Prop :=
(continuous_sub : continuous (λ p : G × G, p.1 - p.2))
@[priority 100] -- see Note [lower instance priority]
instance topological_add_group.to_has_continuous_sub [topological_space G] [add_group G]
[topological_add_group G] :
has_continuous_sub G :=
⟨by { simp only [sub_eq_add_neg], exact continuous_fst.add continuous_snd.neg }⟩
export has_continuous_sub (continuous_sub)
section has_continuous_sub
variables [topological_space G] [has_sub G] [has_continuous_sub G]
lemma filter.tendsto.sub {f g : α → G} {l : filter α} {a b : G} (hf : tendsto f l (𝓝 a))
(hg : tendsto g l (𝓝 b)) :
tendsto (λx, f x - g x) l (𝓝 (a - b)) :=
(continuous_sub.tendsto (a, b)).comp (hf.prod_mk_nhds hg)
variables [topological_space α] {f g : α → G} {s : set α} {x : α}
@[continuity] lemma continuous.sub (hf : continuous f) (hg : continuous g) :
continuous (λ x, f x - g x) :=
continuous_sub.comp (hf.prod_mk hg : _)
lemma continuous_within_at.sub (hf : continuous_within_at f s x) (hg : continuous_within_at g s x) :
continuous_within_at (λ x, f x - g x) s x :=
hf.sub hg
lemma continuous_on.sub (hf : continuous_on f s) (hg : continuous_on g s) :
continuous_on (λx, f x - g x) s :=
λ x hx, (hf x hx).sub (hg x hx)
end has_continuous_sub
lemma nhds_translation [topological_space G] [add_group G] [topological_add_group G] (x : G) :
comap (λy:G, y - x) (𝓝 0) = 𝓝 x :=
by simpa only [sub_eq_add_neg] using nhds_translation_add_neg x
/-- additive group with a neighbourhood around 0.
Only used to construct a topology and uniform space.
This is currently only available for commutative groups, but it can be extended to
non-commutative groups too.
-/
class add_group_with_zero_nhd (G : Type u) extends add_comm_group G :=
(Z [] : filter G)
(zero_Z : pure 0 ≤ Z)
(sub_Z : tendsto (λp:G×G, p.1 - p.2) (Z ×ᶠ Z) Z)
namespace add_group_with_zero_nhd
variables (G) [add_group_with_zero_nhd G]
local notation `Z` := add_group_with_zero_nhd.Z
@[priority 100] -- see Note [lower instance priority]
instance : topological_space G :=
topological_space.mk_of_nhds $ λa, map (λx, x + a) (Z G)
variables {G}
lemma neg_Z : tendsto (λa:G, - a) (Z G) (Z G) :=
have tendsto (λa, (0:G)) (Z G) (Z G),
by refine le_trans (assume h, _) zero_Z; simp [univ_mem_sets'] {contextual := tt},
have tendsto (λa:G, 0 - a) (Z G) (Z G), from
sub_Z.comp (tendsto.prod_mk this tendsto_id),
by simpa
lemma add_Z : tendsto (λp:G×G, p.1 + p.2) (Z G ×ᶠ Z G) (Z G) :=
suffices tendsto (λp:G×G, p.1 - -p.2) (Z G ×ᶠ Z G) (Z G),
by simpa [sub_eq_add_neg],
sub_Z.comp (tendsto.prod_mk tendsto_fst (neg_Z.comp tendsto_snd))
lemma exists_Z_half {s : set G} (hs : s ∈ Z G) : ∃ V ∈ Z G, ∀ (v ∈ V) (w ∈ V), v + w ∈ s :=
begin
have : ((λa:G×G, a.1 + a.2) ⁻¹' s) ∈ Z G ×ᶠ Z G := add_Z (by simpa using hs),
rcases mem_prod_self_iff.1 this with ⟨V, H, H'⟩,
exact ⟨V, H, prod_subset_iff.1 H'⟩
end
lemma nhds_eq (a : G) : 𝓝 a = map (λx, x + a) (Z G) :=
topological_space.nhds_mk_of_nhds _ _
(assume a, calc pure a = map (λx, x + a) (pure 0) : by simp
... ≤ _ : map_mono zero_Z)
(assume b s hs,
let ⟨t, ht, eqt⟩ := exists_Z_half hs in
have t0 : (0:G) ∈ t, by simpa using zero_Z ht,
begin
refine ⟨(λx:G, x + b) '' t, image_mem_map ht, _, _⟩,
{ refine set.image_subset_iff.2 (assume b hbt, _),
simpa using eqt 0 t0 b hbt },
{ rintros _ ⟨c, hb, rfl⟩,
refine (Z G).sets_of_superset ht (assume x hxt, _),
simpa [add_assoc] using eqt _ hxt _ hb }
end)
lemma nhds_zero_eq_Z : 𝓝 0 = Z G := by simp [nhds_eq]; exact filter.map_id
@[priority 100] -- see Note [lower instance priority]
instance : has_continuous_add G :=
⟨ continuous_iff_continuous_at.2 $ assume ⟨a, b⟩,
begin
rw [continuous_at, nhds_prod_eq, nhds_eq, nhds_eq, nhds_eq, filter.prod_map_map_eq,
tendsto_map'_iff],
suffices : tendsto ((λx:G, (a + b) + x) ∘ (λp:G×G,p.1 + p.2)) (Z G ×ᶠ Z G)
(map (λx:G, (a + b) + x) (Z G)),
{ simpa [(∘), add_comm, add_left_comm] },
exact tendsto_map.comp add_Z
end ⟩
@[priority 100] -- see Note [lower instance priority]
instance : topological_add_group G :=
⟨continuous_iff_continuous_at.2 $ assume a,
begin
rw [continuous_at, nhds_eq, nhds_eq, tendsto_map'_iff],
suffices : tendsto ((λx:G, x - a) ∘ (λx:G, -x)) (Z G) (map (λx:G, x - a) (Z G)),
{ simpa [(∘), add_comm, sub_eq_add_neg] using this },
exact tendsto_map.comp neg_Z
end⟩
end add_group_with_zero_nhd
section filter_mul
section
variables [topological_space G] [group G] [topological_group G]
@[to_additive]
lemma is_open.mul_left {s t : set G} : is_open t → is_open (s * t) := λ ht,
begin
have : ∀a, is_open ((λ (x : G), a * x) '' t) :=
assume a, is_open_map_mul_left a t ht,
rw ← Union_mul_left_image,
exact is_open_Union (λa, is_open_Union $ λha, this _),
end
@[to_additive]
lemma is_open.mul_right {s t : set G} : is_open s → is_open (s * t) := λ hs,
begin
have : ∀a, is_open ((λ (x : G), x * a) '' s),
assume a, apply is_open_map_mul_right, exact hs,
rw ← Union_mul_right_image,
exact is_open_Union (λa, is_open_Union $ λha, this _),
end
variables (G)
lemma topological_group.t1_space (h : @is_closed G _ {1}) : t1_space G :=
⟨assume x, by { convert is_closed_map_mul_right x _ h, simp }⟩
lemma topological_group.regular_space [t1_space G] : regular_space G :=
⟨assume s a hs ha,
let f := λ p : G × G, p.1 * (p.2)⁻¹ in
have hf : continuous f := continuous_fst.mul continuous_snd.inv,
-- a ∈ -s implies f (a, 1) ∈ -s, and so (a, 1) ∈ f⁻¹' (-s);
-- and so can find t₁ t₂ open such that a ∈ t₁ × t₂ ⊆ f⁻¹' (-s)
let ⟨t₁, t₂, ht₁, ht₂, a_mem_t₁, one_mem_t₂, t_subset⟩ :=
is_open_prod_iff.1 ((is_open_compl_iff.2 hs).preimage hf) a (1:G) (by simpa [f]) in
begin
use [s * t₂, ht₂.mul_left, λ x hx, ⟨x, 1, hx, one_mem_t₂, mul_one _⟩],
rw [nhds_within, inf_principal_eq_bot, mem_nhds_sets_iff],
refine ⟨t₁, _, ht₁, a_mem_t₁⟩,
rintros x hx ⟨y, z, hy, hz, yz⟩,
have : x * z⁻¹ ∈ sᶜ := (prod_subset_iff.1 t_subset) x hx z hz,
have : x * z⁻¹ ∈ s, rw ← yz, simpa,
contradiction
end⟩
local attribute [instance] topological_group.regular_space
lemma topological_group.t2_space [t1_space G] : t2_space G := regular_space.t2_space G
end
section
/-! Some results about an open set containing the product of two sets in a topological group. -/
variables [topological_space G] [group G] [topological_group G]
/-- Given a compact set `K` inside an open set `U`, there is a open neighborhood `V` of `1`
such that `KV ⊆ U`. -/
@[to_additive "Given a compact set `K` inside an open set `U`, there is a open neighborhood `V` of
`0` such that `K + V ⊆ U`."]
lemma compact_open_separated_mul {K U : set G} (hK : is_compact K) (hU : is_open U) (hKU : K ⊆ U) :
∃ V : set G, is_open V ∧ (1 : G) ∈ V ∧ K * V ⊆ U :=
begin
let W : G → set G := λ x, (λ y, x * y) ⁻¹' U,
have h1W : ∀ x, is_open (W x) := λ x, hU.preimage (continuous_mul_left x),
have h2W : ∀ x ∈ K, (1 : G) ∈ W x := λ x hx, by simp only [mem_preimage, mul_one, hKU hx],
choose V hV using λ x : K, exists_open_nhds_one_mul_subset (mem_nhds_sets (h1W x) (h2W x.1 x.2)),
let X : K → set G := λ x, (λ y, (x : G)⁻¹ * y) ⁻¹' (V x),
obtain ⟨t, ht⟩ : ∃ t : finset ↥K, K ⊆ ⋃ i ∈ t, X i,
{ refine hK.elim_finite_subcover X (λ x, (hV x).1.preimage (continuous_mul_left x⁻¹)) _,
intros x hx, rw [mem_Union], use ⟨x, hx⟩, rw [mem_preimage], convert (hV _).2.1,
simp only [mul_left_inv, subtype.coe_mk] },
refine ⟨⋂ x ∈ t, V x, is_open_bInter (finite_mem_finset _) (λ x hx, (hV x).1), _, _⟩,
{ simp only [mem_Inter], intros x hx, exact (hV x).2.1 },
rintro _ ⟨x, y, hx, hy, rfl⟩, simp only [mem_Inter] at hy,
have := ht hx, simp only [mem_Union, mem_preimage] at this, rcases this with ⟨z, h1z, h2z⟩,
have : (z : G)⁻¹ * x * y ∈ W z := (hV z).2.2 (mul_mem_mul h2z (hy z h1z)),
rw [mem_preimage] at this, convert this using 1, simp only [mul_assoc, mul_inv_cancel_left]
end
/-- A compact set is covered by finitely many left multiplicative translates of a set
with non-empty interior. -/
@[to_additive "A compact set is covered by finitely many left additive translates of a set
with non-empty interior."]
lemma compact_covered_by_mul_left_translates {K V : set G} (hK : is_compact K)
(hV : (interior V).nonempty) : ∃ t : finset G, K ⊆ ⋃ g ∈ t, (λ h, g * h) ⁻¹' V :=
begin
obtain ⟨t, ht⟩ : ∃ t : finset G, K ⊆ ⋃ x ∈ t, interior (((*) x) ⁻¹' V),
{ refine hK.elim_finite_subcover (λ x, interior $ ((*) x) ⁻¹' V) (λ x, is_open_interior) _,
cases hV with g₀ hg₀,
refine λ g hg, mem_Union.2 ⟨g₀ * g⁻¹, _⟩,
refine preimage_interior_subset_interior_preimage (continuous_const.mul continuous_id) _,
rwa [mem_preimage, inv_mul_cancel_right] },
exact ⟨t, subset.trans ht $ bUnion_subset_bUnion_right $ λ g hg, interior_subset⟩
end
/-- Every locally compact separable topological group is σ-compact.
Note: this is not true if we drop the topological group hypothesis. -/
@[priority 100] instance separable_locally_compact_group.sigma_compact_space
[separable_space G] [locally_compact_space G] : sigma_compact_space G :=
begin
obtain ⟨L, hLc, hL1⟩ := exists_compact_mem_nhds (1 : G),
refine ⟨⟨λ n, (λ x, x * dense_seq G n) ⁻¹' L, _, _⟩⟩,
{ intro n, exact (homeomorph.mul_right _).compact_preimage.mpr hLc },
{ refine Union_eq_univ_iff.2 (λ x, _),
obtain ⟨_, ⟨n, rfl⟩, hn⟩ : (range (dense_seq G) ∩ (λ y, x * y) ⁻¹' L).nonempty,
{ rw [← (homeomorph.mul_left x).apply_symm_apply 1] at hL1,
exact (dense_range_dense_seq G).inter_nhds_nonempty
((homeomorph.mul_left x).continuous.continuous_at $ hL1) },
exact ⟨n, hn⟩ }
end
end
section
variables [topological_space G] [comm_group G] [topological_group G]
@[to_additive]
lemma nhds_mul (x y : G) : 𝓝 (x * y) = 𝓝 x * 𝓝 y :=
filter_eq $ set.ext $ assume s,
begin
rw [← nhds_translation_mul_inv x, ← nhds_translation_mul_inv y, ← nhds_translation_mul_inv (x*y)],
split,
{ rintros ⟨t, ht, ts⟩,
rcases exists_nhds_one_split ht with ⟨V, V1, h⟩,
refine ⟨(λa, a * x⁻¹) ⁻¹' V, (λa, a * y⁻¹) ⁻¹' V,
⟨V, V1, subset.refl _⟩, ⟨V, V1, subset.refl _⟩, _⟩,
rintros a ⟨v, w, v_mem, w_mem, rfl⟩,
apply ts,
simpa [mul_comm, mul_assoc, mul_left_comm] using h (v * x⁻¹) v_mem (w * y⁻¹) w_mem },
{ rintros ⟨a, c, ⟨b, hb, ba⟩, ⟨d, hd, dc⟩, ac⟩,
refine ⟨b ∩ d, inter_mem_sets hb hd, assume v, _⟩,
simp only [preimage_subset_iff, mul_inv_rev, mem_preimage] at *,
rintros ⟨vb, vd⟩,
refine ac ⟨v * y⁻¹, y, _, _, _⟩,
{ rw ← mul_assoc _ _ _ at vb, exact ba _ vb },
{ apply dc y, rw mul_right_inv, exact mem_of_nhds hd },
{ simp only [inv_mul_cancel_right] } }
end
@[to_additive]
lemma nhds_is_mul_hom : is_mul_hom (λx:G, 𝓝 x) := ⟨λ_ _, nhds_mul _ _⟩
end
end filter_mul
instance additive.topological_add_group {G} [h : topological_space G]
[group G] [topological_group G] : @topological_add_group (additive G) h _ :=
{ continuous_neg := @continuous_inv G _ _ _ }
instance multiplicative.topological_group {G} [h : topological_space G]
[add_group G] [topological_add_group G] : @topological_group (multiplicative G) h _ :=
{ continuous_inv := @continuous_neg G _ _ _ }
namespace units
variables [monoid α] [topological_space α] [has_continuous_mul α]
instance : topological_group (units α) :=
{ continuous_inv := continuous_induced_rng ((continuous_unop.comp (continuous_snd.comp
(@continuous_embed_product α _ _))).prod_mk (continuous_op.comp continuous_coe)) }
end units
|
b6cd9379ca6413395c2cc2818bdc98d2ba94cdd7 | 32025d5c2d6e33ad3b6dd8a3c91e1e838066a7f7 | /tests/lean/run/generalizeTelescope.lean | 8949d90c4e786ef024fc6360a729c2b4d0373e96 | [
"Apache-2.0"
] | permissive | walterhu1015/lean4 | b2c71b688975177402758924eaa513475ed6ce72 | 2214d81e84646a905d0b20b032c89caf89c737ad | refs/heads/master | 1,671,342,096,906 | 1,599,695,985,000 | 1,599,695,985,000 | null | 0 | 0 | null | null | null | null | UTF-8 | Lean | false | false | 1,393 | lean | import Lean
open Lean
open Lean.Meta
inductive Vec (α : Type) : Nat → Type
| nil : Vec 0
| cons {n} : α → Vec n → Vec (n+1)
set_option trace.Meta.debug true
def nat := mkConst `Nat
def succ := mkConst `Nat.succ
def tst1 : MetaM Unit :=
withLocalDeclD `n nat $ fun n => do
let n1 := mkApp succ n;
let vecN1 := mkApp2 (mkConst `Vec) nat n1;
withLocalDeclD `xs vecN1 $ fun xs => do
generalizeTelescope #[n1, xs] `aux $ fun ys => do
t ← mkLambdaFVars ys ys.back;
trace! `Meta.debug t;
pure ()
#eval tst1
set_option pp.all true
def tst2 : MetaM Unit :=
withLocalDeclD `n nat $ fun n => do
let n1 := mkApp succ n;
let vecN1 := mkApp2 (mkConst `Vec) nat n1;
withLocalDeclD `xs vecN1 $ fun xs => do
e ← mkEqRefl xs;
generalizeTelescope #[n1, xs, e] `aux $ fun ys => do
t ← mkLambdaFVars ys ys.back;
trace! `Meta.debug t;
pure ()
#eval tst2
def failIfSuccess (x : MetaM Unit) : MetaM Unit :=
whenM (catch (x *> pure true) (fun _ => pure false)) $
throwError "unexpected success"
def tst3 : MetaM Unit :=
withLocalDeclD `n nat $ fun n => do
let n1 := mkApp succ n;
let vecN1 := mkApp2 (mkConst `Vec) nat n1;
withLocalDeclD `xs vecN1 $ fun xs => do
e ← mkEqRefl xs;
failIfSuccess $ do {
generalizeTelescope #[n1, e] `aux $ fun ys => do
t ← mkLambdaFVars ys ys.back;
trace! `Meta.debug t;
pure ()
};
trace! `Meta.debug "failed as expected"
#eval tst3
|
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