職場の同僚に教えてもらったネタ

zndk-kiyoshi.hs

import System.Random (randomRIO)

zndk :: [String]
zndk = ["ズン", "ドコ"]

kiyoshi :: IO ()
kiyoshi = go 0
  where
    go  c = rand zndk >>= \v -> putStr v >> go' c v
    go' c "ズン" = go (c + 1)
    go' c "ドコ"
        | c < 4     = go 0
        | otherwise = putStrLn "きよし"

rand :: [a] -> IO a
rand xs = (!!) xs <$> randomRIO (0, length xs - 1)