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 m = ErrorT String m
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 addFunction fun; mapM_ execute st)) emptyState
return ()
---eval :: (MonadState Variables m) => Exp -> m Value
-eval :: Exp -> StateT State IO Value
+eval :: (MonadState State m, MonadIO m) => Exp -> EvalM m Value
eval (EBool b) = return (VBool b)
eval (EInt n) = return (VInt n)
eval (EVar i) = getVariableValue i
-eval (EAss i e) = setVariableValue i e
+eval (EAss i e) = do
+ v <- eval e
+ setVariableValue i v
eval (BiOpExp e o e') = do
v <- eval e
v'<- eval e'
if elem 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
+ else let (VInt n1) = v in let (VInt n2) = v' in return $! op o n1 n2
eval (EPost i o) = do
(VInt n) <- getVariableValue i
- let (VInt n') = op o n 1 in setVariableValue i $ EInt n'
+ setVariableValue i $ op o n 1
return $ VInt n
eval (ENeg e) = do
(VInt n) <- eval e
(VBool b) <- eval e
return $ VBool $ not b
eval EReadI = do
- s <- lift $ getWord
+ s <- liftIO $ getNumber
return $ VInt $ read s
eval EReadB = do
- s <- lift $ getWord
+ s <- liftIO $ getNumber
return $ VBool $ if (read s == 0) then False else True
eval (EFunc i as) = do
vs <- mapM eval as
(ds,ss) <- lookup i $ functions state
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
+ (mapM_ execute ss >> (fail $ "Function "++show i++" didn't return anything."))
+ `catchError` (\_ ->return ()) --Only errors thrown in ErrorT can be caught here, runtime errors pass through, so no need to check the error
+ v <- liftM ret get
put state
return v
-getWord :: IO String
-getWord = do
+--Stricter evaluation of the input
+getNumber :: IO String
+getNumber = do
+ c <- getChar
+ if elem c $ '-':['0'..'9']
+ then do
+ l <- getNumber2
+ return (c:l)
+ else fail "Non integer input."
+
+getNumber2 :: IO String
+getNumber2 = do
c <- getChar
- if elem c [' ', '\n', '\t', '\r']
- then return ""
- else do
- l <- getWord
+ if elem c ['0'..'9']
+ then do
+ l <- getNumber2
return (c:l)
+ else return ""
-- op :: Op -> (a -> a -> Value)
-opE Eq = \e e' -> VBool $ e == e'
-opE NEq = \e e' -> VBool $ not (e == e')
-op Plus = \e e' -> VInt $ 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'
+opE Eq e e' = VBool $ e == e'
+opE NEq e e' = VBool $ not (e == e')
+op Plus e e' =VInt $ e + e'
+op Minus e e' = VInt $ e - e'
+op Times e e' = VInt $ e * e'
+op Div _ 0 = error "Division by zero"
+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 State m) => Ident -> m Value
getVariableValue i = do
s <- get
findVariable i $ variables s
-findVariable :: (MonadState State m) => Ident -> Variables -> m Value
+findVariable :: (Monad 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 :: (MonadState Variables m) => Ident -> Exp -> m Value
-
-setVariableValue :: Ident -> Exp -> StateT State IO Value
-setVariableValue i e = do
- v <- eval e
- state <- get
- modify (\s -> s{variables= updateVariable i v $ variables state} )
+setVariableValue :: (MonadState State m) => Ident -> Value -> EvalM m Value
+setVariableValue i v = do
+ modify (\s -> s{variables= updateVariable i v $ variables s} )
return v
updateVariable :: Ident -> Value -> Variables -> Variables
s
modify (\s -> s { variables = tail $ variables s})
--- execute :: (MonadState Variables m) => Stm -> m ()
-execute :: Stm -> StateT State IO ()
+execute :: (MonadState State m, MonadIO m) => Stm -> EvalM m ()
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
TBool -> EBool False
execute (SDecl t i e) =do
v <- eval e
- state <- get
- let (m:ms) = variables state in modify (\s -> s{variables=insert i v m:ms })
+ (m:ms) <- liftM variables get
+ 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) })
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