[project @ 2001-01-25 17:12:34 by simonpj]

Tidy up intersectsVarSet and subVarSet

diff --git a/ghc/compiler/basicTypes/VarSet.lhs b/ghc/compiler/basicTypes/VarSet.lhs
index e90ed25..a3c55f4 100644 (file)
--- a/ghc/compiler/basicTypes/VarSet.lhs
+++ b/ghc/compiler/basicTypes/VarSet.lhs
@@ -37,7 +37,6 @@ type TyVarSet   = UniqSet TyVar
 
 emptyVarSet    :: VarSet
 intersectVarSet        :: VarSet -> VarSet -> VarSet
-intersectsVarSet:: VarSet -> VarSet -> Bool    -- True if non-empty intersection
 unionVarSet    :: VarSet -> VarSet -> VarSet
 unionVarSets   :: [VarSet] -> VarSet
 varSetElems    :: VarSet -> [Var]
@@ -55,7 +54,6 @@ lookupVarSet  :: VarSet -> Var -> Maybe Var
 mapVarSet      :: (Var -> Var) -> VarSet -> VarSet
 sizeVarSet     :: VarSet -> Int
 filterVarSet   :: (Var -> Bool) -> VarSet -> VarSet
-subVarSet      :: VarSet -> VarSet -> Bool
 extendVarSet_C  :: (Var->Var->Var) -> VarSet -> Var -> VarSet
 
 delVarSetByKey :: VarSet -> Unique -> VarSet
@@ -64,7 +62,12 @@ emptyVarSet  = emptyUniqSet
 unitVarSet     = unitUniqSet
 extendVarSet   = addOneToUniqSet
 intersectVarSet        = intersectUniqSets
-intersectsVarSet s1 s2 = not (isEmptyVarSet (s1 `intersectVarSet` s2))
+
+intersectsVarSet:: VarSet -> VarSet -> Bool    -- True if non-empty intersection
+       -- (s1 `intersectsVarSet` s2) doesn't compute s2 if s1 is empty
+subVarSet      :: VarSet -> VarSet -> Bool     -- True if first arg is subset of second
+       -- (s1 `subVarSet` s2) doesn't compute s2 if s1 is empty
+
 unionVarSet    = unionUniqSets
 unionVarSets   = unionManyUniqSets
 varSetElems    = uniqSetToList
@@ -79,11 +82,16 @@ mapVarSet   = mapUniqSet
 sizeVarSet     = sizeUniqSet
 filterVarSet   = filterUniqSet
 extendVarSet_C combine s x = addToUFM_C combine s x x
-a `subVarSet` b = isEmptyVarSet (a `minusVarSet` b)
 delVarSetByKey = delFromUFM_Directly   -- Can't be bothered to add this to UniqSet
 \end{code}
 
 \begin{code}
+-- See comments with type signatures
+intersectsVarSet s1 s2 = not (isEmptyVarSet (s1 `intersectVarSet` s2))
+a `subVarSet` b = isEmptyVarSet (a `minusVarSet` b)
+\end{code}
+
+\begin{code}
 seqVarSet :: VarSet -> ()
 seqVarSet s = sizeVarSet s `seq` ()
 \end{code}