import Text.ParserCombinators.ReadP

isNumericOrSep :: Char -> Bool
isNumericOrSep = flip elem $ "0123456789-, "

tuplify2 :: [Int] -> (Int, Int)
tuplify2 [x,y] = (x,y)

tupleAsIntPair :: ReadP (Int, Int)
tupleAsIntPair = fmap tuplify2 parsedList
    where   parsedList = fmap (map read) $ sepBy1 noparens sep
            noparens = between open close $ many1 (satisfy isNumericOrSep)
            open = char '('
            close = char ')'
            sep = char ','

isNumericOrSep :: Char -> Bool
isNumericOrSep = flip elem $ "0123456789- "

tupleAsIntPair :: ReadP (Int,Int)
tupleAsIntPair = fmap tuplify2 parsedList
 where
  parsedList = fmap (map read) $ between open close $ sepBy1 noparens sep
  noparens = many1 (satisfy isNumericOrSep)
  open = char '('
  close = char ')'
  sep = char ','

*Main> (readP_to_S tupleAsIntPair) "(3,4)"
 [((3,4),"")]

between :: ReadP open -> ReadP close -> ReadP a -> ReadP a
-- ^ @between open close p@ parses @open@, followed by @p@ and finally
--   @close@. Only the value of @p@ is returned.
between open close p = do _ <- open
                          x <- p
                          _ <- close
                         return x