{-# LANGUAGE Rank2Types, DeriveDataTypeable #-}
module Data.Parser (
Parser, Result(..),
parse, parseMaybe, parseEither
) where
import Prelude ()
import Prelude.Compat
import Control.Applicative
import Control.DeepSeq (NFData(..))
import Control.Monad.State.Strict
import Data.Typeable (Typeable)
data Result a = Error String
| Success a
deriving (Eq, Show, Typeable)
instance (NFData a) => NFData (Result a) where
rnf (Success a) = rnf a
rnf (Error err) = rnf err
instance Functor Result where
fmap f (Success a) = Success (f a)
fmap _ (Error err) = Error err
{-# INLINE fmap #-}
instance Monad Result where
return = Success
{-# INLINE return #-}
Success a >>= k = k a
Error err >>= _ = Error err
{-# INLINE (>>=) #-}
instance Applicative Result where
pure = return
{-# INLINE pure #-}
(<*>) = ap
{-# INLINE (<*>) #-}
instance MonadPlus Result where
mzero = fail "mzero"
{-# INLINE mzero #-}
mplus a@(Success _) _ = a
mplus _ b = b
{-# INLINE mplus #-}
instance Alternative Result where
empty = mzero
{-# INLINE empty #-}
(<|>) = mplus
{-# INLINE (<|>) #-}
instance Monoid (Result a) where
mempty = fail "mempty"
{-# INLINE mempty #-}
mappend = mplus
{-# INLINE mappend #-}
type Failure f r = String -> f r
type Success a f r = a -> f r
newtype Parser a = Parser {
runParser :: forall f r.
Failure f r
-> Success a f r
-> f r
}
instance Monad Parser where
m >>= g = Parser $ \kf ks -> let ks' a = runParser (g a) kf ks
in runParser m kf ks'
{-# INLINE (>>=) #-}
return a = Parser $ \_kf ks -> ks a
{-# INLINE return #-}
fail msg = Parser $ \kf _ks -> kf msg
{-# INLINE fail #-}
instance Functor Parser where
fmap f m = Parser $ \kf ks -> let ks' a = ks (f a)
in runParser m kf ks'
{-# INLINE fmap #-}
instance Applicative Parser where
pure = return
{-# INLINE pure #-}
(<*>) = apP
{-# INLINE (<*>) #-}
instance Alternative Parser where
empty = fail "empty"
{-# INLINE empty #-}
(<|>) = mplus
{-# INLINE (<|>) #-}
instance MonadPlus Parser where
mzero = fail "mzero"
{-# INLINE mzero #-}
mplus a b = Parser $ \kf ks -> let kf' _ = runParser b kf ks
in runParser a kf' ks
{-# INLINE mplus #-}
instance Monoid (Parser a) where
mempty = fail "mempty"
{-# INLINE mempty #-}
mappend = mplus
{-# INLINE mappend #-}
apP :: Parser (a -> b) -> Parser a -> Parser b
apP d e = do
b <- d
a <- e
return (b a)
{-# INLINE apP #-}
parse :: (a -> Parser b) -> a -> Result b
parse m v = runParser (m v) Error Success
parseMaybe :: (a -> Parser b) -> a -> Maybe b
parseMaybe m v = runParser (m v) (const Nothing) Just
parseEither :: (a -> Parser b) -> a -> Either String b
parseEither m v = runParser (m v) Left Right