+ Environments
+%* *
+%************************************************************************
+
+OccEnvs are used mainly for the envts in ModIfaces.
+
+They are efficient, because FastStrings have unique Int# keys. We assume
+this key is less than 2^24, so we can make a Unique using
+ mkUnique ns key :: Unique
+where 'ns' is a Char reprsenting the name space. This in turn makes it
+easy to build an OccEnv.
+
+\begin{code}
+instance Uniquable OccName where
+ getUnique (OccName ns fs)
+ = mkUnique char (I# (uniqueOfFS fs))
+ where -- See notes above about this getUnique function
+ char = case ns of
+ VarName -> 'i'
+ DataName -> 'd'
+ TvName -> 'v'
+ TcClsName -> 't'
+
+type OccEnv a = UniqFM a
+
+emptyOccEnv :: OccEnv a
+unitOccEnv :: OccName -> a -> OccEnv a
+extendOccEnv :: OccEnv a -> OccName -> a -> OccEnv a
+extendOccEnvList :: OccEnv a -> [(OccName, a)] -> OccEnv a
+lookupOccEnv :: OccEnv a -> OccName -> Maybe a
+mkOccEnv :: [(OccName,a)] -> OccEnv a
+elemOccEnv :: OccName -> OccEnv a -> Bool
+foldOccEnv :: (a -> b -> b) -> b -> OccEnv a -> b
+occEnvElts :: OccEnv a -> [a]
+extendOccEnv_C :: (a->a->a) -> OccEnv a -> OccName -> a -> OccEnv a
+plusOccEnv :: OccEnv a -> OccEnv a -> OccEnv a
+plusOccEnv_C :: (a->a->a) -> OccEnv a -> OccEnv a -> OccEnv a
+
+emptyOccEnv = emptyUFM
+unitOccEnv = unitUFM
+extendOccEnv = addToUFM
+extendOccEnvList = addListToUFM
+lookupOccEnv = lookupUFM
+mkOccEnv = listToUFM
+elemOccEnv = elemUFM
+foldOccEnv = foldUFM
+occEnvElts = eltsUFM
+plusOccEnv = plusUFM
+plusOccEnv_C = plusUFM_C
+extendOccEnv_C = addToUFM_C
+
+
+type OccSet = UniqFM OccName
+
+emptyOccSet :: OccSet
+unitOccSet :: OccName -> OccSet
+mkOccSet :: [OccName] -> OccSet
+extendOccSet :: OccSet -> OccName -> OccSet
+extendOccSetList :: OccSet -> [OccName] -> OccSet
+unionOccSets :: OccSet -> OccSet -> OccSet
+unionManyOccSets :: [OccSet] -> OccSet
+minusOccSet :: OccSet -> OccSet -> OccSet
+elemOccSet :: OccName -> OccSet -> Bool
+occSetElts :: OccSet -> [OccName]
+foldOccSet :: (OccName -> b -> b) -> b -> OccSet -> b
+isEmptyOccSet :: OccSet -> Bool
+intersectOccSet :: OccSet -> OccSet -> OccSet
+intersectsOccSet :: OccSet -> OccSet -> Bool
+
+emptyOccSet = emptyUniqSet
+unitOccSet = unitUniqSet
+mkOccSet = mkUniqSet
+extendOccSet = addOneToUniqSet
+extendOccSetList = addListToUniqSet
+unionOccSets = unionUniqSets
+unionManyOccSets = unionManyUniqSets
+minusOccSet = minusUniqSet
+elemOccSet = elementOfUniqSet
+occSetElts = uniqSetToList
+foldOccSet = foldUniqSet
+isEmptyOccSet = isEmptyUniqSet
+intersectOccSet = intersectUniqSets
+intersectsOccSet s1 s2 = not (isEmptyOccSet (s1 `intersectOccSet` s2))
+\end{code}
+
+
+%************************************************************************
+%* *