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|
{-# LANGUAGE CPP #-}
-----------------------------------------------------------------------------
-- A Parser monad with access to the 'DynFlags'.
--
-- The 'P' monad only has access to the subset of of 'DynFlags'
-- required for parsing Haskell.
-- The parser for C-- requires access to a lot more of the 'DynFlags',
-- so 'PD' provides access to 'DynFlags' via a 'HasDynFlags' instance.
-----------------------------------------------------------------------------
module GHC.Cmm.Monad (
PD(..)
, liftP
) where
import GhcPrelude
import Control.Monad
import qualified Control.Monad.Fail as MonadFail
import DynFlags
import Lexer
newtype PD a = PD { unPD :: DynFlags -> PState -> ParseResult a }
instance Functor PD where
fmap = liftM
instance Applicative PD where
pure = returnPD
(<*>) = ap
instance Monad PD where
(>>=) = thenPD
#if !MIN_VERSION_base(4,13,0)
fail = MonadFail.fail
#endif
instance MonadFail.MonadFail PD where
fail = failPD
liftP :: P a -> PD a
liftP (P f) = PD $ \_ s -> f s
returnPD :: a -> PD a
returnPD = liftP . return
thenPD :: PD a -> (a -> PD b) -> PD b
(PD m) `thenPD` k = PD $ \d s ->
case m d s of
POk s1 a -> unPD (k a) d s1
PFailed s1 -> PFailed s1
failPD :: String -> PD a
failPD = liftP . fail
instance HasDynFlags PD where
getDynFlags = PD $ \d s -> POk s d
|
