import Data.Map as Map
import Prelude hiding (lookup)
-emptyState = State{variables=[empty], functions=(empty)}
+emptyState = State{variables=[empty], functions=(empty), ret=(VInt 0)}
data Value = VInt Integer | VBool Bool deriving Eq
type Variables = [Map Ident Value]
type Function = ([Decl],[Stm])
-data State = State {variables::Variables,functions::(Map Ident Function),ret::(MVar Value)}
+data State = State {variables::Variables,functions::(Map Ident Function),ret::Value}
+
+type EvalM = ErrorT String (StateT State IO)
interpret :: [Func] -> [Stm] -> IO ()
interpret fun st = do
- mv <- newEmptyMVar
- runStateT (do mapM Interpret.addFunction fun; mapM execute st) emptyState{ret=mv}
+ runStateT (runErrorT (do mapM Interpret.addFunction fun; mapM_ execute st)) emptyState
return ()
--eval :: (MonadState Variables m) => Exp -> m Value
-eval :: Exp -> StateT State IO Value
+eval :: Exp -> EvalM Value
eval (EBool b) = return (VBool b)
eval (EInt n) = return (VInt n)
eval (EVar i) = getVariableValue i
(VBool b) <- eval e
return $ VBool $ not b
eval EReadI = do
- s <- lift $ getWord
+ s <- liftIO $ getWord
return $ VInt $ read s
eval EReadB = do
- s <- lift $ getWord
+ s <- liftIO $ getWord
return $ VBool $ if (read s == 0) then False else True
eval (EFunc i as) = do
vs <- mapM eval as
let m = foldr (\((Decl t i),v) m -> insert i v m) empty $ zip ds vs
in modify (\s -> s{variables=[m]})
mapM_ execute ss `catchError` (\_ -> return ())
- v <- lift $ takeMVar $ ret state
+ s <- get
put state
- return v
+ return $ ret s
getWord :: IO String
getWord = do
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 :: (MonadState Variables m) => Ident -> Exp -> m Value
-
-setVariableValue :: Ident -> Exp -> StateT State IO Value
+setVariableValue :: Ident -> Exp -> EvalM Value
setVariableValue i e = do
v <- eval e
state <- get
modify (\s -> s { variables = tail $ variables s})
-- execute :: (MonadState Variables m) => Stm -> m ()
-execute :: Stm -> StateT State IO ()
+execute :: Stm -> EvalM ()
execute (SNoop) = return ()
execute (SExp e) = eval e >> return ()
execute (SIf b s s') = do
pushAndPop $ if b' then execute s else execute s'
execute (SPrint e) = do
e' <- eval e
- lift $ print e'
+ liftIO $ print e'
execute (SBlock ss) = pushAndPop $ mapM execute ss
execute (SWhile e s) = do
(VBool b) <- eval e
let (m:ms) = variables state in modify (\s -> s{variables=insert i v m:ms })
execute (SReturn e) = do
v <- eval e
- s <- get
- lift $ putMVar (ret s) v
- throwError $ userError "Returning.."
+ modify (\s -> s{ret=v})
+ throwError "Returning.."
addFunction :: (MonadState State m) => Func -> m ()
addFunction (Func _ i d ss) = modify (\s -> s{functions=insert i (d,ss) (functions s) })