http://stackoverflow.com/a/17503737/187663

Haskell code

import System.Random (randomRIO)

replies = ["Yes", "Signs point to yes", "It is certain", "It is decidedly so", "Without a doubt"
          , "Yes, definitely", "You may rely on it", "As I see it yes", "Most likely", "Outlook good"
          , "Reply hazy try again", "Ask again later", "Better not tell you now", "Cannot predict now"
          , "Concentrate and ask again", "Don't count on it", "My reply is no", "My sources say no"
          , "Outlook not so good", "Very doubtful"]

randomElem [] = error "Empty list"
randomElem xs = randomRIO (0, length xs - 1) >>= return . (xs !!)

main = do
  putStrLn "Type 'Exit' to end the program."
  putStrLn "Ask A Question: "

  u <- getLine
  if (u `elem` ["Exit", "exit"]) then return ()
  else randomElem replies >>= putStrLn >> main