Starman extended

starman.hs

import System.Random

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])

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

mkguess :: String -> String -> Int -> IO ()
mkguess word display n =
  do
    putStrLn (display ++ "  " ++ replicate n '*')
    putStr "  Enter your guess: "
    q <- getLine
    if length q == 1
      then do
        let (correct, display') = check word display (head q)
        let n' = if correct then n else n -1
        turn word display' n'
      else do
        putStrLn "  \n  Please enter one letter at a time\n"
        turn word display n

randomword :: IO String
randomword =
  do
    file <- readFile "/usr/share/dict/words"
    let linesOfFile = lines file
    index <- randomRIO (0, length linesOfFile - 1)
    return (linesOfFile !! index)

starman :: IO ()
starman =
  do
    word <- randomword
    let len = length word
    let n
          | len <= 5 = 5
          | len `elem` [6,7] = 6
          | len `elem` [8,9] = 7
          | len `elem` [10..12] = 8
          | otherwise = 9
    turn word ['-' | x <- word] n