Haskellでループみたいなん

gistfile1.hs

import Control.Monad
import Control.Monad.Trans
import Control.Monad.Trans.Loop

main :: IO ()
main = do
  putStrLn $ "Can you guess the number I have?"
  repeatLoopT $ do
    a <- liftIO $ readLn
    liftIO $ putStrLn $ "You said: " ++ show a
    when (a == 42) $ do
      liftIO $ putStrLn "That's right!"
      exit