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(************************************************************************)
(* v * The Coq Proof Assistant / The Coq Development Team *)
(* <O___,, * INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2010 *)
(* \VV/ **************************************************************)
(* // * This file is distributed under the terms of the *)
(* * GNU Lesser General Public License Version 2.1 *)
(************************************************************************)
(** This defines the functor that build consequences of proof-irrelevance *)
Require Export EqdepFacts.
Module Type ProofIrrelevance.
Axiom proof_irrelevance : forall (P:Prop) (p1 p2:P), p1 = p2.
End ProofIrrelevance.
Module ProofIrrelevanceTheory (M:ProofIrrelevance).
(** Proof-irrelevance implies uniqueness of reflexivity proofs *)
Module Eq_rect_eq.
Lemma eq_rect_eq :
forall (U:Type) (p:U) (Q:U -> Type) (x:Q p) (h:p = p),
x = eq_rect p Q x p h.
Proof.
intros; rewrite M.proof_irrelevance with (p1:=h) (p2:=refl_equal p).
reflexivity.
Qed.
End Eq_rect_eq.
(** Export the theory of injective dependent elimination *)
Module EqdepTheory := EqdepTheory(Eq_rect_eq).
Export EqdepTheory.
Scheme eq_indd := Induction for eq Sort Prop.
(** We derive the irrelevance of the membership property for subsets *)
Lemma subset_eq_compat :
forall (U:Set) (P:U->Prop) (x y:U) (p:P x) (q:P y),
x = y -> exist P x p = exist P y q.
Proof.
intros.
rewrite M.proof_irrelevance with (p1:=q) (p2:=eq_rect x P p y H).
elim H using eq_indd.
reflexivity.
Qed.
Lemma subsetT_eq_compat :
forall (U:Type) (P:U->Prop) (x y:U) (p:P x) (q:P y),
x = y -> existT P x p = existT P y q.
Proof.
intros.
rewrite M.proof_irrelevance with (p1:=q) (p2:=eq_rect x P p y H).
elim H using eq_indd.
reflexivity.
Qed.
End ProofIrrelevanceTheory.
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