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import Mathlib
import OAI.Computability.VertexCover.Machines.Codec
import OAI.Computability.VertexCover.Machines.LCData

namespace OAI

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section

namespace VertexCover.Machine

noncomputable def Poly.finFunction {α β : Type} [Fintype β]
    (ea : α → List Bool) : (n : ℕ) → (f : α → Fin n → β) →
    (∀ i, Poly ea (finiteCode β) (fun a => f a i)) →
    Poly ea (finiteCode (Fin n → β)) f
  | 0,f,_ => (Poly.const ea (finiteCode (Fin 0 → β)) (fun i => Fin.elim0 i)).congr
    (fun a => by funext i; exact Fin.elim0 i)
  | n+1,f,cf =>
    (((cf 0).pair (Poly.finFunction ea n (fun a i => f a i.succ) (fun i => cf i.succ))).comp
      (Poly.finite _ _ (prodBits_injective (finiteCode_injective β) (finiteCode_injective (Fin n → β)))
        (fun p : β × (Fin n → β) => Fin.cons p.1 p.2))).congr
          (fun a => by funext i; refine Fin.cases ?_ (fun j => ?_) i <;> rfl)

noncomputable def Poly.finiteFunction {α β ι : Type} [Fintype β] [Fintype ι] [DecidableEq ι]
    (ea : α → List Bool) (f : α → ι → β)
    (cf : ∀ i, Poly ea (finiteCode β) (fun a => f a i)) :
    Poly ea (finiteCode (ι → β)) f := by
  let E := Fintype.equivFin ι
  exact ((Poly.finFunction ea (Fintype.card ι) (fun a i => f a (E.symm i))
    (fun i => cf (E.symm i))).comp
      (Poly.finite _ _ (finiteCode_injective _) (fun g : Fin (Fintype.card ι) → β => fun i => g (E i)))).congr
        (fun a => by funext i; exact congrArg (f a) (E.symm_apply_apply i))

noncomputable def Poly.finiteRecode {α : Type} [Fintype α] (ea : α → List Bool)
    (ha : Function.Injective ea) : Poly ea (finiteCode α) id :=
  Poly.finite ea (finiteCode α) ha id

noncomputable def Poly.fixedSum {α ι : Type} (ea : α → List Bool)
    (f : α → ι → ℕ) (cf : ∀ i, Poly ea natBits (fun a => f a i)) :
    (xs : List ι) → Poly ea natBits (fun a => (xs.map (f a)).sum)
  | [] => (Poly.const ea natBits 0).congr (fun _ => rfl)
  | i::xs => (((cf i).pair (Poly.fixedSum ea f cf xs)).comp Poly.natAdd).congr
    (fun a => by simp only [Function.comp_apply,List.map_cons,List.sum_cons])

noncomputable def Poly.finiteSum {α ι : Type} [Fintype ι] (ea : α → List Bool)
    (f : α → ι → ℕ) (cf : ∀ i, Poly ea natBits (fun a => f a i)) :
    Poly ea natBits (fun a => ∑ i, f a i) := by
  classical
  exact (Poly.fixedSum ea f cf Finset.univ.toList).congr (fun a => by simp)
end VertexCover.Machine
end


end
end
end
end
end
end
end
end
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end
end
end
end
end
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end
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end
end
end
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end
end
end

end OAI