{-# LANGUAGE Trustworthy #-}
{-# LANGUAGE NoImplicitPrelude #-}
module Text.ParserCombinators.ReadPrec
(
ReadPrec,
Prec,
minPrec,
lift,
prec,
step,
reset,
get,
look,
(+++),
(<++),
pfail,
choice,
readPrec_to_P,
readP_to_Prec,
readPrec_to_S,
readS_to_Prec,
)
where
import Text.ParserCombinators.ReadP
( ReadP
, ReadS
, readP_to_S
, readS_to_P
)
import qualified Text.ParserCombinators.ReadP as ReadP
( get
, look
, (+++), (<++)
, pfail
)
import GHC.Num( Num(..) )
import GHC.Base
import qualified Control.Monad.Fail as MonadFail
newtype ReadPrec a = P (Prec -> ReadP a)
instance Functor ReadPrec where
fmap h (P f) = P (\n -> fmap h (f n))
instance Applicative ReadPrec where
pure x = P (\_ -> pure x)
(<*>) = ap
liftA2 = liftM2
instance Monad ReadPrec where
fail s = P (\_ -> fail s)
P f >>= k = P (\n -> do a <- f n; let P f' = k a in f' n)
instance MonadFail.MonadFail ReadPrec where
fail s = P (\_ -> MonadFail.fail s)
instance MonadPlus ReadPrec
instance Alternative ReadPrec where
empty = pfail
(<|>) = (+++)
type Prec = Int
minPrec :: Prec
minPrec = 0
lift :: ReadP a -> ReadPrec a
lift m = P (\_ -> m)
step :: ReadPrec a -> ReadPrec a
step (P f) = P (\n -> f (n+1))
reset :: ReadPrec a -> ReadPrec a
reset (P f) = P (\_ -> f minPrec)
prec :: Prec -> ReadPrec a -> ReadPrec a
prec n (P f) = P (\c -> if c <= n then f n else ReadP.pfail)
get :: ReadPrec Char
get = lift ReadP.get
look :: ReadPrec String
look = lift ReadP.look
(+++) :: ReadPrec a -> ReadPrec a -> ReadPrec a
P f1 +++ P f2 = P (\n -> f1 n ReadP.+++ f2 n)
(<++) :: ReadPrec a -> ReadPrec a -> ReadPrec a
P f1 <++ P f2 = P (\n -> f1 n ReadP.<++ f2 n)
pfail :: ReadPrec a
pfail = lift ReadP.pfail
choice :: [ReadPrec a] -> ReadPrec a
choice ps = foldr (+++) pfail ps
readPrec_to_P :: ReadPrec a -> (Int -> ReadP a)
readPrec_to_P (P f) = f
readP_to_Prec :: (Int -> ReadP a) -> ReadPrec a
readP_to_Prec f = P f
readPrec_to_S :: ReadPrec a -> (Int -> ReadS a)
readPrec_to_S (P f) n = readP_to_S (f n)
readS_to_Prec :: (Int -> ReadS a) -> ReadPrec a
readS_to_Prec f = P (\n -> readS_to_P (f n))