X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2FbasicTypes%2FVarSet.lhs;h=6f03aad1bf05c1ce4c051fee1688969a98d166e5;hb=5e54b553bbb112167412ee9164135d56b06f5721;hp=67a3dbf4c2eb3d08c62dde6ffa187b53fb1d3a85;hpb=6084fb5517da34f65034370a3695e2af3b85ce2b;p=ghc-hetmet.git

diff --git a/compiler/basicTypes/VarSet.lhs b/compiler/basicTypes/VarSet.lhs
index 67a3dbf..6f03aad 100644
--- a/compiler/basicTypes/VarSet.lhs
+++ b/compiler/basicTypes/VarSet.lhs
@@ -15,7 +15,7 @@ module VarSet (
 	unionVarSet, unionVarSets,
 	intersectVarSet, intersectsVarSet, disjointVarSet,
 	isEmptyVarSet, delVarSet, delVarSetList, delVarSetByKey,
-	minusVarSet, foldVarSet, filterVarSet,
+	minusVarSet, foldVarSet, filterVarSet, fixVarSet,
 	lookupVarSet, mapVarSet, sizeVarSet, seqVarSet,
 	elemVarSetByKey
     ) where
@@ -63,6 +63,7 @@ extendVarSet_C  :: (Var->Var->Var) -> VarSet -> Var -> VarSet
 
 delVarSetByKey	:: VarSet -> Unique -> VarSet
 elemVarSetByKey :: Unique -> VarSet -> Bool
+fixVarSet       :: (VarSet -> VarSet) -> VarSet -> VarSet
 
 emptyVarSet	= emptyUniqSet
 unitVarSet	= unitUniqSet
@@ -100,6 +101,12 @@ elemVarSetByKey	= elemUniqSet_Directly
 intersectsVarSet s1 s2 = not (s1 `disjointVarSet` s2)
 disjointVarSet   s1 s2 = isEmptyVarSet (s1 `intersectVarSet` s2)
 subVarSet        s1 s2 = isEmptyVarSet (s1 `minusVarSet` s2)
+
+-- Iterate f to a fixpoint
+fixVarSet f s | new_s `subVarSet` s = s
+	      | otherwise	    = fixVarSet f new_s 
+	      where
+		new_s = f s
 \end{code}
 
 \begin{code}