starman example from futururelearn.com

starman.hs

-- main function
starman :: String -> Int -> IO ()
starman word n = turn word ['-' | x <- word] n

-- 
check :: String -> String -> Char -> (Bool, String)
check word display c = (c `elem` word, 
    [if x == c  then c 
        else y | 
    (x,y) <- zip word display])

-- count the turn
turn :: String -> String -> Int -> IO ()
turn word display n =
            do if n == 0
                then putStrLn "You lose"
                    else if word==display
                        then putStrLn "You win!"
                        else mkguess word display n

-- read a user response
mkguess :: String -> String -> Int -> IO() 
mkguess word display n =
  do putStrLn (display ++ "  " ++ take n (repeat '*'))
     putStr "  Enter your guess (or type 1 to exit) : "
     q <- getLine
     let q' = head q
     let (correct, display') = check word display q' 
     let n' = checkN correct q' n                                    
     turn word display' n'

-- check for special character to exit 
checkN :: Bool -> Char -> Int -> Int
checkN x '1' n  = 0
checkN True c n = n
checkN x  c  n  = n-1