eval (EInt n) = return (VInt n)
eval (EVar i) = getVariableValue i
eval (EAss i e) = setVariableValue i e
-eval EDefault = return (VInt 0) --FIXME!!!
+eval EDefault = error "EDefault called from an illegal place"
eval (BiOpExp e o e') = do
v <- eval e
v'<- eval e'
if inList o [Eq,NEq] then return $ opE o v v'
else let (VInt n1) = v in let (VInt n2) = v' in return $ op o n1 n2
-typeCheckExp (EPost i op) = do
+eval (EPost i o) = do
(VInt n) <- getVariableValue i
- setVariableValue i $ EInt $ n+1
+ let (VInt n') = op o n 1 in setVariableValue i $ EInt n'
return $ VInt n
+eval (ENeg e) = do
+ (VInt n) <- eval e
+ return $ VInt $ -n
+eval (ENot e) = do
+ (VBool b) <- eval e
+ return $ VBool $ not b
+eval EReadI = do
+ s <- lift $ getWord
+ return $ VInt $ read s
+eval EReadB = do
+ s <- lift $ getWord
+ return $ VBool $ read s
+
+getWord :: IO String
+getWord = do
+ c <- getChar
+ if inList c ['\n','\r',' ', '\t']
+ then return ""
+ else do
+ l <- getWord
+ return (c:l)
-- op :: Op -> (a -> a -> Value)
opE Eq = \e e' -> VBool $ e == e'
op Minus = \e e' -> VInt $ e - e'
op Times = \e e' -> VInt $ e * e'
op Div = \e e' -> VInt $ e `div` e'
+op Lt = \e e' -> VBool $ e < e'
+op ELt = \e e' -> VBool $ e <= e'
+op Gt = \e e' -> VBool $ e > e'
+op EGt = \e e' -> VBool $ e >= e'
getVariableValue :: (MonadState Variables m) => Ident -> m Value
getVariableValue i = do
ms <- get
findVariable i ms
+findVariable :: (MonadState Variables m) => Ident -> Variables -> m Value
+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
+
--setVariableValue :: (MonadState Variables m) => Ident -> Exp -> m Value
-setVariableValue :: Ident -> Exp -> StateT Variables IO Value
-setVariableValue i e = do
+--setVariableValue :: (MonadState Variables m) => Ident -> Exp -> m Value
+addVariable :: Ident -> Exp -> StateT Variables IO ()
+addVariable i e = do
e' <- eval e
(m:ms) <- get
put $ (insert i e' m):ms
- return e'
-findVariable :: (MonadState Variables m) => Ident -> Variables -> m Value
-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
+setVariableValue :: Ident -> Exp -> StateT Variables IO Value
+setVariableValue i e = do
+ v <- eval e
+ ms <- get
+ put $ updateVariable i v ms
+ return v
+
+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
+
-- execute :: (MonadState Variables m) => Stm -> m ()
execute :: Stm -> StateT Variables IO ()
+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'
execute (SPrint e) = do
e' <- eval e
lift $ print e'
-execute (SNoop) = return ()
execute (SBlock ss) = do
modify (empty:)
mapM execute ss
modify tail
execute (SWhile e s) = do
(VBool b) <- eval e
- if b then execute (SWhile e s) else return ()
+ if b then execute s >> execute (SWhile e s) else return ()
execute (SDecl t i EDefault) = do
case t of
- TInt -> setVariableValue i (EInt 0)
- TBool -> setVariableValue i (EBool False)
+ TInt -> addVariable i (EInt 0)
+ TBool -> addVariable i (EBool False)
return ()
-execute (SDecl t i e) = setVariableValue i e >> return ()
+execute (SDecl t i e) = addVariable i e >> return ()