primula-bot-0.0.1: ApplicativeParsec.hs

-- | ApplicativeParsec.hs
-- A module (from 16th chapter of RWH) which add some applicative and
-- alternative functionality to Parsec.

module ApplicativeParsec (
    module Control.Applicative,
    module Text.ParserCombinators.Parsec
) where

import Control.Applicative
import Control.Monad (MonadPlus(..), ap)
-- Hide a few names that are provided by Applicative.
import Text.ParserCombinators.Parsec hiding (many, optional, (<|>))

-- The Applicative instance for every Monad looks like this.
instance Applicative (GenParser s a) where
    pure  = return
    (<*>) = ap

-- The Alternative instance for every MonadPlus looks like this.
instance Alternative (GenParser s a) where
    empty = mzero
    (<|>) = mplus