Improve error handling and messages for typeclasses.

Add definitions of relational algebra in Classes/RelationClasses
including equivalence, inclusion, conjunction and disjunction. Add
PartialOrder class and show that we have a partial order on relations. 
Change SubRelation to subrelation for consistency with the standard
library. The caracterization of PartialOrder is a bit original: we
require an equivalence and a preorder so that the equivalence relation
is equivalent to the conjunction of the order relation and its
inverse. We can derive antisymmetry and appropriate morphism instances 
from this. Also add a fully general heterogeneous definition of
respectful from which we can build the non-dependent respectful
combinator.


git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@10728 85f007b7-540e-0410-9357-904b9bb8a0f7

1 files changed, 2 insertions, 0 deletions

diff --git a/theories/Program/Tactics.v b/theories/Program/Tactics.v
index f31115d99..f2dcdd0e0 100644
--- a/theories/Program/Tactics.v
+++ b/theories/Program/Tactics.v
@@ -27,9 +27,11 @@ Ltac destruct_pairs := repeat (destruct_one_pair).
 
 Ltac destruct_one_ex :=
   let tac H := let ph := fresh "H" in destruct H as [H ph] in
+  let tacT H := let ph := fresh "X" in destruct H as [H ph] in
     match goal with
       | [H : (ex _) |- _] => tac H
       | [H : (sig ?P) |- _ ] => tac H
+      | [H : (sigT ?P) |- _ ] => tacT H
       | [H : (ex2 _) |- _] => tac H
     end.