added pushAndPop function to push and pop the scope

diff --git a/Interpret.hs b/Interpret.hs
index 5a792b9b2bbbe27be026d99096d17df1ef5cffa2..8ac65bf247c9acf10699573d40669e65ca43782b 100644 (file)
--- a/Interpret.hs
+++ b/Interpret.hs
@@ -89,6 +89,11 @@ updateVariable :: Ident -> Value -> Variables -> Variables
 updateVariable _ _ [] = []
 updateVariable i v (m:ms) = if member i m then insert i v m:ms else m:updateVariable i v ms
 
+pushAndPop :: (MonadState Variables m) => m a -> m ()
+pushAndPop s = do
+       modify (empty:)
+       s
+       modify tail
 
 -- execute :: (MonadState Variables m) => Stm -> m ()
 execute :: Stm -> StateT Variables IO ()
@@ -96,17 +101,14 @@ execute (SNoop) = return ()
 execute (SExp e) = eval e >> return ()
 execute (SIf b s s') = do
        (VBool b') <- eval b
-       if b' then execute s else execute s'
+       pushAndPop $ if b' then execute s else execute s'
 execute (SPrint e) = do
        e' <- eval e
        lift $ print e'
-execute (SBlock ss) = do
-       modify (empty:)
-       mapM execute ss
-       modify tail
+execute (SBlock ss) = pushAndPop $ mapM execute ss
 execute (SWhile e s) = do
        (VBool b) <- eval e
-       if b then execute s >> execute (SWhile e s) else return ()
+       if b then pushAndPop (execute s) >> execute (SWhile e s) else return ()
 execute (SDecl t i e) =do
        e' <- eval e
        (m:ms) <- get