initial commit of interpreter

[proglang.git] / Typecheck.hs

diff --git a/Typecheck.hs b/Typecheck.hs
index ec40b1f0bc7dc8e249e6e95b738ac3a85bbb2077..6f65d6e2f538d18d554787225c4aa138918a586f 100644 (file)
--- a/Typecheck.hs
+++ b/Typecheck.hs
@@ -1,12 +1,12 @@
 module Typecheck (typeCheckExp, typeCheckStm, typeCheckVar) where 
 
+
 import Abssyntax
 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
@@ -16,25 +16,24 @@ 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
-       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
@@ -42,12 +41,18 @@ typeCheckExp (EPost i op) = do
 typeCheckExp (ENeg e) = do
        TInt <- typeCheckExp e
        return TInt
-
+typeCheckExp (ENot e) = do
+       TBool <- typeCheckExp e
+       return TBool
 
 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 +60,9 @@ 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
@@ -69,13 +76,12 @@ typeCheckStm (SWhile e s) = do
 typeCheckStm (SDecl t i e) = do
        t2 <- typeCheckExp e
        if t == t2 || t2 == NoType then do
-               m <- get
-               case insertLookupWithKey (\k a1 a2 -> a1) i t m of 
-                       (Nothing,m') -> put m'
+               (m:ms) <- get
+               case insertLookupWithKey (\k a1 a2 -> a1) i t m of
+                       (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
 typeCheckStm (SPrint e) = do
        typeCheckExp e
        return NoType
-