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Merged
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Apr 24, 2017
Merged

Add mapParserT #54

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11 changes: 9 additions & 2 deletions src/Text/Parsing/Parser.purs
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Original file line number Diff line number Diff line change
Expand Up @@ -25,7 +25,7 @@ import Control.MonadPlus (class Alternative, class MonadZero, class MonadPlus, c
import Data.Either (Either(..))
import Data.Identity (Identity)
import Data.Monoid (class Monoid, mempty)
import Data.Newtype (class Newtype, unwrap)
import Data.Newtype (class Newtype, unwrap, over)
import Data.Tuple (Tuple(..))
import Text.Parsing.Parser.Pos (Position, initialPos)

Expand Down Expand Up @@ -69,7 +69,14 @@ runParser :: forall s a. s -> Parser s a -> Either ParseError a
runParser s = unwrap <<< runParserT s

hoistParserT :: forall s m n a. (m ~> n) -> ParserT s m a -> ParserT s n a
hoistParserT f (ParserT m) = ParserT (mapExceptT (mapStateT f) m)
hoistParserT = mapParserT

-- | Change the underlying monad action and data type in a ParserT monad action.
mapParserT :: forall b n s a m.
( m (Tuple (Either ParseError a) (ParseState s))
-> n (Tuple (Either ParseError b) (ParseState s))
) -> ParserT s m a -> ParserT s n b
mapParserT = over ParserT <<< mapExceptT <<< mapStateT

instance lazyParserT :: Lazy (ParserT s m a) where
defer f = ParserT (ExceptT (defer (runExceptT <<< unwrap <<< f)))
Expand Down