X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2FbasicTypes%2FVarSet.lhs;h=6f03aad1bf05c1ce4c051fee1688969a98d166e5;hb=4623207393db41c970e713c326e9b54aa017dc3a;hp=f73bf1feba9ef225d7ebf7d451b73c64cb7e5d32;hpb=debbe39a1780f7dd02e54b0e846b79027ed2a20e;p=ghc-hetmet.git

diff --git a/compiler/basicTypes/VarSet.lhs b/compiler/basicTypes/VarSet.lhs
index f73bf1f..6f03aad 100644
--- a/compiler/basicTypes/VarSet.lhs
+++ b/compiler/basicTypes/VarSet.lhs
@@ -15,14 +15,14 @@ module VarSet (
 	unionVarSet, unionVarSets,
 	intersectVarSet, intersectsVarSet, disjointVarSet,
 	isEmptyVarSet, delVarSet, delVarSetList, delVarSetByKey,
-	minusVarSet, foldVarSet, filterVarSet,
+	minusVarSet, foldVarSet, filterVarSet, fixVarSet,
 	lookupVarSet, mapVarSet, sizeVarSet, seqVarSet,
 	elemVarSetByKey
     ) where
 
 #include "HsVersions.h"
 
-import Var
+import Var      ( Var, TyVar, Id )
 import Unique
 import UniqSet
 \end{code}
@@ -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}