Ajout infos de débogage de "universe inconsistency" quand option Set

  Printing Universes est active.
Ajout de l'option "using" à la tactique non documentée "auto decomp".
Ajout de la base "extcore" pour étendre "auto decomp" avec des
  principes élémentaires tels que le dépliage de "iff".
Quelques extensions/raffinements dans ChoiceFacts et ClassicalFacts.


git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@10156 85f007b7-540e-0410-9357-904b9bb8a0f7

1 files changed, 21 insertions, 0 deletions

diff --git a/theories/Logic/ClassicalFacts.v b/theories/Logic/ClassicalFacts.v
index ad9171843..f3f177a73 100644
--- a/theories/Logic/ClassicalFacts.v
+++ b/theories/Logic/ClassicalFacts.v
@@ -91,6 +91,17 @@ Proof.
     right; apply (Ext A False); split; [ exact H | apply False_ind ].
 Qed.
 
+(** A weakest form of propositional extensionality: extensionality for
+    provable propositions only *)
+
+Definition provable_prop_extensionality := forall A:Prop, A -> A = True.
+
+Lemma provable_prop_ext :
+  prop_extensionality -> provable_prop_extensionality.
+Proof.
+  intros Ext A Ha; apply Ext; split; trivial.
+Qed.
+
 (************************************************************************)
 (** * Classical logic and proof-irrelevance *)
 
@@ -105,6 +116,7 @@ Qed.
         (just take the identity), which
      implies the existence of a fixpoint operator in [A]
         (e.g. take the Y combinator of lambda-calculus)
+
 *)
 
 Definition inhabited (A:Prop) := A.
@@ -143,6 +155,10 @@ Proof.
   reflexivity.
 Qed.
 
+(** Remark: [prop_extensionality] can be replaced in lemma [ext_prop_fixpoint]
+    by the weakest property [provable_prop_extensionality].
+*)
+
 (************************************************************************)
 (** ** CC |- prop_ext /\ dep elim on bool -> proof-irrelevance  *)
 
@@ -230,6 +246,11 @@ Section Proof_irrelevance_Prop_Ext_CC.
 
 End Proof_irrelevance_Prop_Ext_CC.
 
+(** Remark: [prop_extensionality] can be replaced in lemma
+    [ext_prop_dep_proof_irrel_gen] by the weakest property
+    [provable_prop_extensionality].  
+*)
+
 (************************************************************************)
 (** ** CIC |- prop. ext. -> proof-irrelevance                   *)