some restructuring

[proglang.git] / Typecheck.hs

diff --git a/Typecheck.hs b/Typecheck.hs
index 6e845ba2cb56b9625570676c65e6354da53eb4ba..2414203d7d81441d89080f3c3dc8d5486f140600 100644 (file)
--- a/Typecheck.hs
+++ b/Typecheck.hs
@@ -16,13 +16,12 @@ typeCheckExp :: (MonadState Types m) => Exp -> m Type
 typeCheckExp (BiOpExp e o e') = do
        t1 <- typeCheckExp e
        t2 <- typeCheckExp e'
-       if not(t1 == t2) then fail "" 
-               else case inList o [Eq,NEq] of
-                       True -> return TBool
-                       False -> if not(t1 == TInt) then fail "" 
-                               else case inList o [Plus,Minus,Times,Div] of
-                                       True -> return TInt
-                                       False -> return TBool
+       if not(t1 == t2) then fail "The parameters for the binary operator aren't equal" 
+               else if inList o [Eq,NEq] then return TBool
+                       else if not(t1 == TInt) then fail "The parameters need to be of type int" 
+                               else if inList o [Plus,Minus,Times,Div]
+                                       then return TInt
+                                       else return TBool
 typeCheckExp (EVar i) = typeCheckVar i
 typeCheckExp (EAss i e) = do
        a <- typeCheckVar i
@@ -70,7 +69,9 @@ typeCheckStm (SDecl t i e) = do
        t2 <- typeCheckExp e
        if t == t2 || t2 == NoType then do
                m <- get
-               put (insert i t m)
+               case insertLookupWithKey (\k a1 a2 -> a1) i t m of 
+                       (Nothing,m') -> put m'
+                       _ -> 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
 typeCheckStm (SPrint e) = do