mirror of https://github.com/nmvdw/HITs-Examples
396 lines
6.6 KiB
Coq
396 lines
6.6 KiB
Coq
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Require Import HoTT.
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Require Export HoTT.
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Theorem useful :
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forall (A B : Type)
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(f g : A -> B)
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(a a' : A)
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(p : a = a')
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(q : f a = g a),
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transport (fun x => f x = g x) p q = (ap f p)^ @ q @ (ap g p).
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Proof.
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intros.
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induction p.
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rewrite transport_1.
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rewrite ap_1.
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rewrite ap_1.
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rewrite concat_p1.
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simpl.
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rewrite concat_1p.
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reflexivity.
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Qed.
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Module Export modulo.
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Private Inductive Mod2 : Type0 :=
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| Z : Mod2
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| succ : Mod2 -> Mod2.
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Axiom mod : Z = succ(succ Z).
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Fixpoint Mod2_ind
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(P : Mod2 -> Type)
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(a : P Z)
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(s : forall (n : Mod2), P n -> P (succ n))
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(mod' : mod # a = s (succ Z) (s Z a))
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(x : Mod2)
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{struct x}
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: P x
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:=
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(match x return _ -> P x with
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| Z => fun _ => a
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| succ n => fun _ => s n ((Mod2_ind P a s mod') n)
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end) mod'.
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Axiom Mod2_ind_beta_mod : forall
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(P : Mod2 -> Type)
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(a : P Z)
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(s : forall (n : Mod2), P n -> P (succ n))
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(mod' : mod # a = s (succ Z) (s Z a))
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, apD (Mod2_ind P a s mod') mod = mod'.
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Fixpoint Mod2_rec
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(P : Type)
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(a : P)
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(s : P -> P)
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(mod' : a = s (s a))
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(x : Mod2)
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{struct x}
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: P
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:=
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(match x return _ -> P with
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| Z => fun _ => a
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| succ n => fun _ => s ((Mod2_rec P a s mod') n)
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end) mod'.
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Axiom Mod2_rec_beta_mod : forall
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(P : Type)
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(a : P)
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(s : P -> P)
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(mod' : a = s (s a))
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, ap (Mod2_rec P a s mod') mod = mod'.
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End modulo.
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Module Export moduloAlt.
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Private Inductive Mod2A : Type0 :=
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| ZA : Mod2A
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| succA : Mod2A -> Mod2A.
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Axiom modA : forall n : Mod2A, n = succA(succA n).
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Fixpoint Mod2A_ind
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(P : Mod2A -> Type)
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(z : P ZA)
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(s : forall n : Mod2A, P n -> P (succA n))
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(mod' : forall (n : Mod2A) (a : P n),
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modA n # a = s (succA n) (s n a))
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(x : Mod2A)
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{struct x}
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: P x
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:=
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(match x return _ -> P x with
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| ZA => fun _ => z
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| succA n => fun _ => s n ((Mod2A_ind P z s mod') n)
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end) mod'.
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Axiom Mod2A_ind_beta_mod : forall
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(P : Mod2A -> Type)
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(z : P ZA)
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(s : forall n : Mod2A, P n -> P (succA n))
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(mod' : forall (n : Mod2A) (a : P n),
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modA n # a = s (succA n) (s n a))
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(n : Mod2A)
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, apD (Mod2A_ind P z s mod') (modA n) = mod' n (Mod2A_ind P z s mod' n).
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Fixpoint Mod2A_rec
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(P : Type)
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(z : P)
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(s : P -> P)
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(mod' : forall (a : P),
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a = s (s a))
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(x : Mod2A)
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{struct x}
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: P
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:=
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(match x return _ -> P with
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| ZA => fun _ => z
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| succA n => fun _ => s ((Mod2A_rec P z s mod') n)
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end) mod'.
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Axiom Mod2A_rec_beta_mod : forall
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(P : Type)
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(z : P)
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(s : P -> P)
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(mod' : forall (a : P),
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a = s (s a))
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(n : Mod2A)
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, ap (Mod2A_rec P z s mod') (modA n) = mod' (Mod2A_rec P z s mod' n).
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End moduloAlt.
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Definition negate : Mod2 -> Mod2.
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Proof.
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refine (Mod2_ind _ _ _ _).
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Unshelve.
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Focus 2.
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apply (succ Z).
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Focus 2.
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intros.
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apply (succ H).
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simpl.
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rewrite transport_const.
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rewrite <- mod.
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reflexivity.
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Defined.
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Theorem modulo2 : forall n : Mod2, n = succ(succ n).
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Proof.
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refine (Mod2_ind _ _ _ _).
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Unshelve.
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Focus 2.
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apply mod.
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Focus 2.
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intro n.
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intro p.
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apply (ap succ p).
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simpl.
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rewrite useful.
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rewrite ap_idmap.
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rewrite concat_Vp.
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rewrite concat_1p.
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rewrite ap_compose.
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reflexivity.
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Defined.
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Definition plus : Mod2 -> Mod2 -> Mod2.
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Proof.
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intro n.
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refine (Mod2_ind _ _ _ _).
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Unshelve.
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Focus 2.
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apply n.
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Focus 2.
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intro m.
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intro k.
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apply (succ k).
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simpl.
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rewrite transport_const.
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apply modulo2.
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Defined.
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Definition Bool_to_Mod2 : Bool -> Mod2.
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Proof.
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intro b.
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destruct b.
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apply (succ Z).
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apply Z.
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Defined.
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Definition Mod2_to_Bool : Mod2 -> Bool.
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Proof.
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refine (Mod2_ind _ _ _ _).
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Unshelve.
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Focus 2.
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apply false.
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Focus 2.
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intro n.
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apply negb.
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Focus 1.
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simpl.
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apply transport_const.
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Defined.
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Theorem eq1 : forall n : Bool, Mod2_to_Bool (Bool_to_Mod2 n) = n.
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Proof.
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intro b.
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destruct b.
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Focus 1.
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compute.
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reflexivity.
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compute.
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reflexivity.
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Qed.
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Theorem Bool_to_Mod2_negb : forall x : Bool,
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succ (Bool_to_Mod2 x) = Bool_to_Mod2 (negb x).
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Proof.
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intros.
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destruct x.
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compute.
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apply mod^.
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compute.
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apply reflexivity.
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Defined.
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Theorem eq2 : forall n : Mod2, Bool_to_Mod2 (Mod2_to_Bool n) = n.
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Proof.
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refine (Mod2_ind _ _ _ _).
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Unshelve.
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Focus 2.
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compute.
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reflexivity.
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Focus 2.
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intro n.
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intro IHn.
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symmetry.
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transitivity (succ (Bool_to_Mod2 (Mod2_to_Bool n))).
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Focus 1.
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symmetry.
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apply (ap succ IHn).
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transitivity (Bool_to_Mod2 (negb (Mod2_to_Bool n))).
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apply Bool_to_Mod2_negb.
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enough (negb (Mod2_to_Bool n) = Mod2_to_Bool (succ n)).
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apply (ap Bool_to_Mod2 X).
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compute.
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reflexivity.
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simpl.
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rewrite concat_p1.
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rewrite concat_1p.
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rewrite useful.
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rewrite concat_p1.
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rewrite ap_idmap.
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rewrite ap_compose.
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enough (ap Mod2_to_Bool mod = reflexivity false).
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rewrite X.
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simpl.
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rewrite concat_1p.
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rewrite inv_V.
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reflexivity.
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enough (IsHSet Bool).
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apply axiomK_hset.
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apply X.
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apply hset_bool.
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Defined.
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Theorem adj :
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forall x : Mod2, eq1 (Mod2_to_Bool x) = ap Mod2_to_Bool (eq2 x).
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Proof.
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intro x.
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enough (IsHSet Bool).
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apply set_path2.
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apply hset_bool.
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Defined.
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Definition isomorphism : IsEquiv Mod2_to_Bool.
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Proof.
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apply (BuildIsEquiv Mod2 Bool Mod2_to_Bool Bool_to_Mod2 eq1 eq2 adj).
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Qed.
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Definition Mod2ToMod2A : Mod2 -> Mod2A.
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Proof.
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refine (Mod2_rec _ _ _ _).
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Unshelve.
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Focus 2.
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apply ZA.
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Focus 2.
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apply succA.
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Focus 1.
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simpl.
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apply modA.
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Defined.
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Definition Mod2AToMod2 : Mod2A -> Mod2.
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Proof.
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refine (Mod2A_rec _ _ _ _).
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Unshelve.
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Focus 1.
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apply Z.
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Focus 2.
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apply succ.
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Focus 1.
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intro a.
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apply (modulo2 a).
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Defined.
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Lemma Mod2AToMod2succA :
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forall (n : Mod2A), Mod2AToMod2(succA n) = succ (Mod2AToMod2 n).
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Proof.
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reflexivity.
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Defined.
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Lemma Mod2ToMod2Asucc :
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forall (n : Mod2), Mod2ToMod2A(succ n) = succA (Mod2ToMod2A n).
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Proof.
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reflexivity.
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Defined.
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Theorem eqI1 : forall (n : Mod2), n = Mod2AToMod2(Mod2ToMod2A n).
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Proof.
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refine (Mod2_ind _ _ _ _).
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Unshelve.
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Focus 2.
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reflexivity.
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Focus 2.
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intro n.
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intro H.
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rewrite Mod2ToMod2Asucc.
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rewrite Mod2AToMod2succA.
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rewrite <- H.
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reflexivity.
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simpl.
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rewrite useful.
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rewrite ap_idmap.
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rewrite concat_p1.
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rewrite ap_compose.
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rewrite Mod2_rec_beta_mod.
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rewrite Mod2A_rec_beta_mod.
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simpl.
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simpl.
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enough (modulo2 Z = mod).
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rewrite X.
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apply concat_Vp.
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compute.
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reflexivity.
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Defined.
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Theorem eqI2 : forall (n : Mod2A), n = Mod2ToMod2A(Mod2AToMod2 n).
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Proof.
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refine (Mod2A_ind _ _ _ _).
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Focus 1.
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reflexivity.
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Unshelve.
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Focus 2.
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intros.
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rewrite Mod2AToMod2succA.
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rewrite Mod2ToMod2Asucc.
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rewrite <- X.
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reflexivity.
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intros.
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simpl.
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rewrite useful.
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rewrite ap_idmap.
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rewrite ap_compose.
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rewrite Mod2A_rec_beta_mod.
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