- Another bug in get_sort_family_of (sort-polymorphism of constants and

  inductive types was not taken into account).
- Virtually extended tauto to 
  - support arbitrary-length disjunctions and conjunctions,
  - support arbitrary complex forms of disjunctions and
    conjunctions when in the contravariant of an implicative hypothesis,
  - stick with the purely propositional fragment and not apply reflexivity.
  This is virtual in the sense that it is not activated since it breaks 
  compatibility with the existing tauto.
- Modified the notion of conjunction and unit type used in hipattern in a 
  way that is closer to the intuitive meaning (forbid dependencies 
  between parameters in conjunction; forbid indices in unit types).
- Investigated how far "iff" could be turned into a direct inductive
  definition; modified tauto.ml4 so that it works with the current and
  the alternative definition.
- Fixed a bug in the error message from lookup_eliminator.
- Other minor changes.



git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@11721 85f007b7-540e-0410-9357-904b9bb8a0f7

1 files changed, 7 insertions, 0 deletions

diff --git a/theories/Logic/Decidable.v b/theories/Logic/Decidable.v
index 6f793ce2f..6129128de 100644
--- a/theories/Logic/Decidable.v
+++ b/theories/Logic/Decidable.v
@@ -80,6 +80,13 @@ Proof.
 unfold decidable; tauto.
 Qed.
 
+Theorem not_iff : 
+  forall A B:Prop, decidable A -> decidable B -> 
+    ~ (A <-> B) -> (A /\ ~ B) \/ (~ A /\ B).
+Proof.
+unfold decidable; tauto.
+Qed.
+
 (** Results formulated with iff, used in FSetDecide. 
     Negation are expanded since it is unclear whether setoid rewrite 
     will always perform conversion. *)