Merge PR#318: Providing a file in the Logic library to work with extensional choice

1 files changed, 22 insertions, 0 deletions

diff --git a/theories/Logic/PropExtensionality.v b/theories/Logic/PropExtensionality.v
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+++ b/theories/Logic/PropExtensionality.v
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+(************************************************************************)
+(*  v      *   The Coq Proof Assistant  /  The Coq Development Team     *)
+(* <O___,, *   INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2016     *)
+(*   \VV/  **************************************************************)
+(*    //   *      This file is distributed under the terms of the       *)
+(*         *       GNU Lesser General Public License Version 2.1        *)
+(************************************************************************)
+
+(** This module states propositional extensionality and draws
+    consequences of it *)
+
+Axiom propositional_extensionality :
+  forall (P Q : Prop), (P <-> Q) -> P = Q.
+
+Require Import ClassicalFacts.
+
+Theorem proof_irrelevance : forall (P:Prop) (p1 p2:P), p1 = p2.
+Proof.
+  apply ext_prop_dep_proof_irrel_cic.
+  exact propositional_extensionality.
+Qed.
+