FSet/OrderedType now includes an eq_dec, and hence become an extension of DecidableType

 After lots of hesitations, OrderedType now requires this "eq_dec" field, which
 is redundant (can be deduced from "compare"), but allows the subtyping relation
 DecidableType <= OrderedType, and hence WS <= S : ordered sets are now truly
 extensions of weak sets. Of course this change introduces a last-minute
 incompatibility, but:

  - There is a clear gain in term of functionnality / simplicity.
  - FSets 8.2 already needs some adaptations when compared with 8.1, so it's
    the right time to push such incompatible changes.
  - Transition shouldn't be too hard: the old OrderedType still exists under
    the name MiniOrderedType, and functor MOT_to_OT allows to convert from
    one to the other.

 Beware, for a FSetInterface.WS (resp. S) to be coercible to a DecidableType
 (resp. OrderedType), an eq_dec on sets is now required in these interfaces
 and in the implementations. In pratice, it is really easy to build from
 equal and equal_1 and equal_2.

 Some name changes : in FSetFacts, old WFacts now correspond to WFacts_fun,
 while WFacts now expects only one argument (WFacts M := WFacts_fun M.E M).
 Idem with WDecide, WProperties and WEqProperties.

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@11693 85f007b7-540e-0410-9357-904b9bb8a0f7

1 files changed, 2 insertions, 6 deletions

diff --git a/theories/FSets/FMapInterface.v b/theories/FSets/FMapInterface.v
index 917534e19..ebc99933b 100644
--- a/theories/FSets/FMapInterface.v
+++ b/theories/FSets/FMapInterface.v
@@ -55,11 +55,7 @@ Definition Cmp (elt:Type)(cmp:elt->elt->bool) e1 e2 := cmp e1 e2 = true.
     No requirements for an ordering on keys nor elements, only decidability
     of equality on keys. First, a functorial signature: *)
 
-Module Type WSfun (E : EqualityType).
-
-  (** The module E of base objects is meant to be a [DecidableType]
-     (and used to be so). But requiring only an [EqualityType] here
-     allows subtyping between weak and ordered maps. *)
+Module Type WSfun (E : DecidableType).
 
   Definition key := E.t.
 
@@ -261,7 +257,7 @@ End WSfun.
     Similar to [WSfun] but expressed in a self-contained way. *)
 
 Module Type WS. 
-  Declare Module E : EqualityType.
+  Declare Module E : DecidableType.
   Include Type WSfun E.
 End WS.