Haskell I/O dialog sample

dialog2.hs

import System.IO

promptLine :: String -> IO String
promptLine prompt = do
    putStr prompt
    hFlush stdout
    getLine

doesQuit :: String -> Bool
doesQuit "" = True
doesQuit "quit" = True
doesQuit "koniec" = True
doesQuit "exit" = True
doesQuit _ = False

mainLoop :: IO()
mainLoop = do
  input <- promptLine "> "
  more <- processInput input
  if more
   then mainLoop 
   else return ()
  
main = mainLoop

processInput :: String -> IO Bool
processInput input = if doesQuit input then return False else do
  putStrLn $ "Powiedziales: " ++ input
  return True