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implementation module WhileCommon
import StdBool, StdInt, StdList, StdClass, StdString
from StdFunc import o
from GenEq import generic gEq
import Common
import WhileLexer
import Yard
derive gEq AExpr, Operator, BExpr, Comparator
instance zero State where zero = \v -> Left (Runtime "Undefined variable")
instance toString AExpr
where
toString (Var v) = v
toString (Lit i) = toString i
toString (Op a1 op a2) = "(" <+ a1 <+ " " <+ op <+ " " <+ a2 <+ ")"
instance toString Operator
where
toString Add = "+"; toString Sub = "-"
toString Mul = "*"; toString Div = "/"
instance toString BExpr
where
toString (Bool b) = if b "true" "false"
toString (Not b) = "~" <+ b
toString (And b1 b2) = "(" <+ b1 <+ " & " <+ b2 <+ ")"
toString (Or b1 b2) = "(" <+ b1 <+ " | " <+ b2 <+ ")"
toString (Comp a1 cmp a2) = a1 <+ " " <+ cmp <+ " " <+ a2
instance toString Comparator
where
toString Eq = "="; toString Ne = "<>"
toString Le = "<="; toString Lt = "<"
toString Ge = ">="; toString Gt = ">"
instance eval AExpr Int
where
eval (Var v) st = st v
eval (Lit i) st = pure i
eval (Op a1 op a2) st = eval a1 st >>= \r1 -> eval a2 st >>= toOp op r1
where
toOp :: Operator -> Int Int -> Either Error Int
toOp Add = \i j -> pure (i + j)
toOp Sub = \i j -> pure (i - j)
toOp Mul = \i j -> pure (i * j)
toOp Div = \i j ->
if (j == 0) (Left (Runtime "Division by 0")) (pure (i / j))
instance eval BExpr Bool
where
eval (Bool b) st = pure b
eval (Not b) st = eval b st >>= pure o not
eval (And b1 b2) st = liftM2 (&&) (eval b1 st) (eval b2 st)
eval (Or b1 b2) st = liftM2 (||) (eval b1 st) (eval b2 st)
eval (Comp a1 cmp a2) st = liftM2 (toCmp cmp) (eval a1 st) (eval a2 st)
where
toCmp :: Comparator -> Int Int -> Bool
toCmp Eq = \i j -> i == j
toCmp Ne = \i j -> i <> j
toCmp Le = \i j -> i <= j
toCmp Lt = \i j -> i < j
toCmp Ge = \i j -> i >= j
toCmp Gt = \i j -> i > j
pbexpr :: Parser Token BExpr
pbexpr = liftM2 Or pbconj (item OrToken *> pbexpr) <|> pbconj
pbconj = liftM2 And pbnot (item AndToken *> pbconj) <|> pbnot
pbnot = item NotToken *> pbnot <|> pbcomp
pbcomp = liftM3 Comp paexpr (toComp <$> satisfy isCompToken) paexpr <|> pbconst
pbconst = toBool <$> satisfy isBoolToken
<|> item ParenOpen *> pbexpr <* item ParenClose
paexpr :: Parser Token AExpr
paexpr = liftOp Add pasub (item AddToken *> paexpr) <|> pasub
pasub = liftM2 (foldl (\r->Op r Sub)) pamul (many (item SubToken *> pamul))
pamul = liftOp Mul padiv (item MulToken *> pamul) <|> padiv
padiv = liftM2 (foldl (\r->Op r Div)) paref (many (item DivToken *> paref))
paref = Var o toVar <$> satisfy isVarToken
<|> (\(LiteralToken i) -> Lit i) <$> satisfy isLiteralToken
<|> item ParenOpen *> paexpr <* item ParenClose
toComp EqToken = Eq; toComp NeToken = Ne
toComp LeToken = Le; toComp LtToken = Lt
toComp GeToken = Ge; toComp GtToken = Gt
isCompToken t = isMember t [EqToken,NeToken,LeToken,LtToken,GeToken,GtToken]
toBool (BoolToken b) = Bool b
isBoolToken (BoolToken _) = True; isBoolToken _ = False
toVar (VarToken v) = v
isVarToken (VarToken _) = True; isVarToken _ = False
isLiteralToken (LiteralToken _) = True; isLiteralToken _ = False
liftOp :: Operator (m AExpr) (m AExpr) -> m AExpr | Monad m
liftOp op a1 a2 = a1 >>= \r1 -> a2 >>= \r2 -> pure (Op r1 op r2)
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