runStateT (runErrorT (do mapM addFunction fun; mapM_ execute st)) emptyState
return ()
---eval :: (MonadState State m, MonadError String m, MonadIO m) => Exp -> m Value
eval :: (MonadState State m, MonadIO m) => Exp -> EvalM m Value
eval (EBool b) = return (VBool b)
eval (EInt n) = return (VInt n)
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
setVariableValue i $ op o n 1
in modify (\s -> s{variables=[m]})
(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
- state' <- get
+ v <- liftM ret get
put state
- return $ ret state'
+ return v
--Stricter evaluation of the input
getNumber :: IO String
getNumber = do
c <- getChar
- if elem c ['-','0'..'9']
+ 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
modify (\s -> s { variables = tail $ variables s})
--- execute :: (MonadState Variables m) => Stm -> m ()
execute :: (MonadState State m, MonadIO m) => Stm -> EvalM m ()
execute (SNoop) = return ()
execute (SExp e) = eval e >> return ()
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
modify (\s -> s{ret=v})