support for scope

diff --git a/Typecheck.hs b/Typecheck.hs
index 52f9816b07fdc277cdb385a70ed5c3b3588b849b..691b79b269350f18a31e463fc04d72c106502609 100644 (file)
--- a/Typecheck.hs
+++ b/Typecheck.hs
@@ -5,7 +5,7 @@ import Control.Monad.State
 import Data.Map as Map
 import Prelude hiding (lookup)
 
-type Types = Map Ident Type
+type Types = [Map Ident Type]
 
 inList :: Eq a => a -> [a] -> Bool
 inList _ [] = False
@@ -23,16 +23,16 @@ typeCheckExp (BiOpExp e o e') = do
                                        else return TBool
 typeCheckExp (EVar i) = typeCheckVar i
 typeCheckExp (EAss i e) = do
-       a <- typeCheckVar i
-       b <- typeCheckExp e
-       if a == b then return a else fail "FEL!"
+       t <- typeCheckVar i
+       t2 <- typeCheckExp e
+       if t == t2 then return t else fail $ "Illegal to assign an expression of type "++show t2++" to variable "++show i++" of type "++show t 
 typeCheckExp (EInt i) = return TInt
 typeCheckExp (EBool b) = return TBool
 typeCheckExp EReadI = return TInt
 typeCheckExp EReadB = return TBool
 typeCheckExp (ExpT t e) = do
        t2 <- typeCheckExp e
-       if t == t2 then return t else fail "FEL!"
+       if t == t2 then return t else fail "Something went wrong ExpT is created with the wrong type"
 typeCheckExp EDefault = return NoType
 typeCheckExp (EPost i op) = do
        TInt <- typeCheckVar i
@@ -46,8 +46,12 @@ typeCheckExp (ENot e) = do
 
 typeCheckVar :: (MonadState Types m) => Ident -> m Type 
 typeCheckVar i = do
-       e <- get
-       lookup i e
+       ms <- get
+       findVariable i ms
+
+findVariable :: (MonadState Types m) => Ident -> Types -> m Type
+findVariable i [] = fail $ "Variable "++show i++" not found in any scope."
+findVariable i (m:ms) = if member i m then lookup i m else findVariable i ms
 
 typeCheckStm :: (MonadState Types m) => Stm -> m Type 
 typeCheckStm SNoop = return NoType
@@ -55,7 +59,9 @@ typeCheckStm (SExp e) = do
        typeCheckExp e
        return NoType
 typeCheckStm (SBlock ss) = do 
+       modify (empty:)
        mapM typeCheckStm ss
+       modify tail
        return NoType
 typeCheckStm (SIf e s s') = do
        TBool <- typeCheckExp e
@@ -69,9 +75,9 @@ typeCheckStm (SWhile e s) = do
 typeCheckStm (SDecl t i e) = do
        t2 <- typeCheckExp e
        if t == t2 || t2 == NoType then do
-               m <- get
+               (m:ms) <- get
                case insertLookupWithKey (\k a1 a2 -> a1) i t m of 
-                       (Nothing,m') -> put m'
+                       (Nothing,m') -> put (m':ms)
                        _ -> fail $ "Duplicate variable declaration: "++show i
                return NoType
                else fail $ "Illegal to assign an expression of type "++show t2++" to variable "++show i++" of type "++show t

diff --git a/Typechecker.hs b/Typechecker.hs
index 2e205b7d0d516554e7d6909e9bbcf31d066898ee..87054767c896ee26b405b0af976f0b4bd09f5050 100644 (file)
--- a/Typechecker.hs
+++ b/Typechecker.hs
@@ -39,7 +39,7 @@ run v p s = let ts = myLLexer s in case p ts of
        Ok (Program s) -> do
                putStrLn "\nParse Successful!"
                showTree v (Program s)
-               runStateT (mapM typeCheckStm s) empty
+               runStateT (mapM typeCheckStm s) [empty]
                return ()
 
 showTree :: (Show a, Print a) => Int -> a -> IO ()

diff --git a/examples/scope b/examples/scope
new file mode 100644 (file)
index 0000000..8e90e04
--- /dev/null
+++ b/examples/scope
@@ -0,0 +1,7 @@
+int a = 3;
+
+if (a == 3){
+       bool a = true;
+       if (a) print a ;
+}
+print (a+5);