module Hidden.Tools (
  isSymbol
, modifySnd
, guardEqual
) where

import Control.Monad.State( StateT(StateT, runStateT), lift, MonadTrans )
import Data.Char          ( isAlphaNum, isSpace, isPrint )
import Control.Monad      ( MonadPlus, guard )

isSymbol :: Char -> Bool
isSymbol = (not . isAlphaNum) &&& (not . isSpace) &&& isPrint

(&&&) :: (a -> Bool) -> (a -> Bool) -> a -> Bool
(p1 &&& p2) x = p1 x && p2 x

modifySnd :: (b -> c) -> (a, b) -> (a, c)
modifySnd f (x, y) = (x, f y)

guardEqual :: (MonadPlus m, Eq a) => m a -> m a -> m ()
guardEqual m1 m2 = do { x <- m1; y <- m2; guard (x == y) }