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-rw-r--r--Term.hs35
1 files changed, 19 insertions, 16 deletions
diff --git a/Term.hs b/Term.hs
index f8f1b84..f351714 100644
--- a/Term.hs
+++ b/Term.hs
@@ -16,7 +16,7 @@ module Term (
-import Data.List
+import qualified Data.Set as Set
import TypeVar
@@ -100,7 +100,7 @@ substitute (tymap,vmap) term =
(TVar v) -> if (v == (fst x))
then snd x
else TVar v
- (TAbs v a) -> let safe = rename (TAbs v a) (union [fst x] (containsVars . snd $ x))
+ (TAbs v a) -> let safe = rename (TAbs v a) (freeVars . snd $ x)
in case safe of
(TAbs m n) -> TAbs m (varsub x n))
tydone = foldl' (\x y -> typesub y x) term tymap
@@ -108,19 +108,22 @@ substitute (tymap,vmap) term =
in vdone
-containsVars :: Term -> [Var]
-containsVars t =
- let f = (\term list ->
- case term of
- (TConst a b) -> list
- (TApp a b) -> union list ((f a list) ++ (f b list))
- (TVar a) -> union list [a]
- (TAbs a b) -> union list ([tVar a] ++ (f b list)))
- in f t []
+boundVars :: Term -> Set Var
+boundVars (TConst a b) = Set.empty
+boundVars (TApp a b) = Set.union (boundVars a) (boundVars b)
+boundVars (TVar a) = Set.empty
+boundVars (TAbs a b) = Set.insert a (boundVars b)
-rename :: Term -> [Var] -> Term
-rename (TAbs (TVar v) t) varlist =
+freeVars :: Term -> Set Var
+freeVars (TConst a b) = Set.empty
+freeVars (TApp a b) = Set.union (freeVars a) (freeVars b)
+freeVars (TVar a) = Set.singleton a
+freeVars (TAbs a b) = Set.delete a (freeVars b)
+
+
+rename :: Term -> Set Var -> Term
+rename (TAbs (TVar v) t) vars =
let doRename =
(\x y z -> case x of
(TAbs (TVar a) b) -> if (a == y)
@@ -132,14 +135,14 @@ rename (TAbs (TVar v) t) varlist =
then TVar z
else TVar a)
findSafe =
- (\x y -> if (x `elem` y)
+ (\x y -> if (Set.member x y)
then case x of
(Var a b) ->
case a of
(Name c d) -> findSafe (Var (Name c (d ++ "'")) b) y
else x)
- in if (v `elem` varlist)
- then doRename (TAbs (TVar v) t) v (findSafe v varlist)
+ in if (Set.member v vars)
+ then doRename (TAbs (TVar v) t) v (findSafe v vars)
else TAbs (TVar v) t