[project @ 2005-01-05 15:28:39 by simonpj]

[ghc-hetmet.git] / ghc / compiler / types / Type.lhs

diff --git a/ghc/compiler/types/Type.lhs b/ghc/compiler/types/Type.lhs
index d4bc995..c7613ab 100644 (file)
--- a/ghc/compiler/types/Type.lhs
+++ b/ghc/compiler/types/Type.lhs
@@ -63,9 +63,9 @@ module Type (
        seqType, seqTypes,
 
        -- Type substitutions
-       TvSubst(..),    -- Representation visible to a few friends
-       TvSubstEnv, emptyTvSubst,
-       mkTvSubst, zipTvSubst, zipTopTvSubst, mkTopTvSubst,
+       TvSubstEnv, emptyTvSubstEnv,    -- Representation widely visible
+       TvSubst(..), emptyTvSubst,      -- Representation visible to a few friends
+       mkTvSubst, zipTvSubst, zipTopTvSubst, mkTopTvSubst, notElemTvSubst,
        getTvSubstEnv, setTvSubstEnv, getTvInScope, extendTvInScope,
        extendTvSubst, extendTvSubstList, isInScope, composeTvSubst,
 
@@ -1025,6 +1025,8 @@ type TvSubstEnv = TyVarEnv Type
        -- in the middle of matching, and unification (see Types.Unify)
        -- So you have to look at the context to know if it's idempotent or
        -- apply-once or whatever
+emptyTvSubstEnv :: TvSubstEnv
+emptyTvSubstEnv = emptyVarEnv
 
 composeTvSubst :: InScopeSet -> TvSubstEnv -> TvSubstEnv -> TvSubstEnv
 -- (compose env1 env2)(x) is env1(env2(x)); i.e. apply env2 then env1
@@ -1051,6 +1053,9 @@ getTvInScope (TvSubst in_scope _) = in_scope
 isInScope :: Var -> TvSubst -> Bool
 isInScope v (TvSubst in_scope _) = v `elemInScopeSet` in_scope
 
+notElemTvSubst :: TyVar -> TvSubst -> Bool
+notElemTvSubst tv (TvSubst _ env) = not (tv `elemVarEnv` env)
+
 setTvSubstEnv :: TvSubst -> TvSubstEnv -> TvSubst
 setTvSubstEnv (TvSubst in_scope _) env = TvSubst in_scope env