ifM :: Monad m => m Bool -> m a -> m a -> m a
ifM act t e = do
  b <- act
  if b then t else e

anAction    = return False
otherAction = return True

infixl 4 <?>

(<?>) :: Monad m => m Bool -> m a -> m a -> m a
(<?>) = ifM

main :: IO String
main =    anAction <?> do
			putStrLn "branch a"
			return "a"
		$ otherAction <?> do
			putStrLn "branch b"
			return "b"
		$ return "none"