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|
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE TupleSections #-}
module Language.SimpleShell.Parser.Expr
( exprP
)
where
import Language.SimpleShell.Parser (Parser, lexeme, lookupVar, lookupFun)
import Language.SimpleShell.AST.Expr (Expr(..), TypedExpr, VarName, FunName)
import Language.SimpleShell.AST.SimpleType (SimpleType(..))
import Control.Monad.Combinators.FailExpr
( Associativity(..)
, makeExprParser
, Operator(..)
)
import Control.Applicative ((<|>))
import Control.Monad.Combinators (manyTill)
import Data.Char (isAlpha)
import Data.Foldable (asum)
import Data.Text (Text)
import Text.Megaparsec (takeWhile1P)
import Text.Megaparsec.Char (string, char)
import qualified Text.Megaparsec.Char.Lexer as L (charLiteral, decimal)
exprP :: Parser TypedExpr
exprP
= makeExprParser weakTermP binaryOperatorTable
weakTermP :: Parser TypedExpr
weakTermP
= strongTermP
<|> unaryOpP
<|> builtinUnaryFunP
<|> funP
strongTermP :: Parser TypedExpr
strongTermP
= literalP
<|> varP
<|> lexeme (char '(') *> exprP <* lexeme (char ')')
-- | Parse "strong" term with fixed type.
strongTermP' :: String -> SimpleType -> Parser Expr
strongTermP' errMsg t = do
(t', e) <- strongTermP
if t == t'
then return e
else fail errMsg
literalP :: Parser TypedExpr
literalP
= (IntType,) . IntLiteral <$> lexeme L.decimal
<|> (StrType,) . StrLiteral <$> lexeme strLitP
<|> (BoolType,) . BoolLiteral <$> lexeme boolLitP
where
strLitP = char '"' *> manyTill L.charLiteral (char '"')
boolLitP
= True <$ string "true"
<|> False <$ string "false"
varP :: Parser TypedExpr
varP = lexeme $ do
_ <- char '$'
x <- varNameP
t <- lookupVar x
return (t, Var x)
funP :: Parser TypedExpr
funP = do
fname <- lexeme funNameP
(t', ts) <- lookupFun fname
args <- mapM (strongTermP' "Type mismatch with function signature.") ts
return (t', FunCall fname args)
-- TODO
varNameP :: Parser VarName
varNameP = takeWhile1P Nothing isAlpha
-- TODO
funNameP :: Parser FunName
funNameP = takeWhile1P Nothing isAlpha
-- Binary operators.
type BinaryFun = Expr -> Expr -> Expr
type BinarySig = SimpleType -> SimpleType -> Maybe SimpleType
binaryOperatorTable :: [[Operator Parser TypedExpr]]
binaryOperatorTable =
[ [ binary AssocR "||" Or $ sameSig BoolType
]
, [ binary AssocR "&&" And $ sameSig BoolType
]
, [ binary AssocN "==" Eq $ anyCmpSig
, binary AssocN "!=" Neq $ anyCmpSig
, binary AssocN "<=" Le $ intCmpSig
, binary AssocN "<" Lt $ intCmpSig
, binary AssocN ">=" Ge $ intCmpSig
, binary AssocN ">" Gt $ intCmpSig
]
, [ Binary AssocL addP
, binary AssocL "-" Sub $ sameSig IntType
]
, [ binary AssocL "*" Mul $ sameSig IntType
, binary AssocL "/" Div $ sameSig IntType
]
]
where
sameSig :: SimpleType -> BinarySig
sameSig t t1 t2 = if t == t1 && t == t2 then Just t else Nothing
anyCmpSig t t'
| t == t' = Just BoolType
| otherwise = Nothing
intCmpSig IntType IntType = Just BoolType
intCmpSig _ _ = Nothing
addP :: Parser (TypedExpr -> TypedExpr -> Maybe TypedExpr)
addP = do
_ <- lexeme $ char '+'
return $ \(t1, x1) (t2, x2) ->
if t1 == t2
then
case t1 of
StrType -> Just (StrType, Concat x1 x2)
IntType -> Just (IntType, Add x1 x2)
_ -> Nothing
else Nothing
binary
:: Associativity -> Text -> BinaryFun -> BinarySig
-> Operator Parser TypedExpr
binary assoc symbol op sig = Binary assoc $ do
_ <- lexeme $ string symbol
return $ \(t1, e1) (t2, e2) -> fmap (, op e1 e2) $ sig t1 t2
-- Unary operators and builtin unary functions.
type UnaryFun = Expr -> Expr
type UnarySig = SimpleType -> Maybe SimpleType
type UnaryParser = Parser (TypedExpr -> Maybe TypedExpr)
unaryOperators, builtinUnaryFuns :: [UnaryParser]
(unaryOperators, builtinUnaryFuns) =
( [ unary "!" Not $ uniqueSig BoolType BoolType
, unary "-" UMinus $ uniqueSig IntType IntType
]
, [ unary "length" Length $ uniqueSig StrType IntType
, unary "int" IntCast $ uniqueSig StrType IntType
, unary "str" StrCast $ uniqueSig IntType StrType
]
)
where
uniqueSig :: SimpleType -> SimpleType -> UnarySig
uniqueSig t1 t2 t1'
| t1 == t1' = Just t2
| otherwise = Nothing
unary :: Text -> UnaryFun -> UnarySig -> UnaryParser
unary symbol op sig = do
_ <- lexeme $ string symbol
return $ \(t, e) -> fmap (, op e) $ sig t
unaryOpP, builtinUnaryFunP :: Parser TypedExpr
(unaryOpP, builtinUnaryFunP) =
( asum $ map (aux "unary operator" weakTermP ) unaryOperators
, asum $ map (aux "builtin unary function" strongTermP) builtinUnaryFuns
)
where
aux :: String -> Parser TypedExpr -> UnaryParser -> Parser TypedExpr
aux desc argP p = do
f <- p
x <- argP
case f x of
Just x' -> return x'
Nothing -> fail $ "Mismatching " ++ desc ++ " signature."
|
