Helpers.hs

-----------------------------------------------------------------------------
-- |
-- Module      :  Lentil.Helpers
-- Copyright   :  © 2015 Francesco Ariis
-- License     :  GPLv3 (see the LICENSE file)
--
-- Ancillaries for other modules
-----------------------------------------------------------------------------

module Lentil.Helpers where

import Lentil.Types

import qualified System.IO as I
import qualified Text.Parsec as P
import qualified Text.Parsec.String as PS

import Control.Applicative hiding ( (<|>), optional, many )
import Prelude -- 7.8 hack

-- output errors
perr :: String -> IO ()
perr cs  = I.hPutStrLn I.stderr cs


-------------
-- PARSING --
-------------

-- like many1 for manyTill
manyTill1 :: PS.Parser a -> PS.Parser b -> PS.Parser [a]
manyTill1 p ed = (:) <$> p <*> P.manyTill p ed


-- parse an extension alias "aa->bc" -> Just ("aa", "bc")
aliasp :: String -> Maybe Alias
aliasp s = either (const Nothing) Just (P.parse p "" s)
    where
          p = manyTill1 P.anyChar (P.string aliasSign) >>= \a ->
              P.many P.anyChar                         >>= \b ->
              return ('.':a, '.':b)