Starman game from Functional Programming in Haskell Course at U of Glasgow, Slightly Improved

starman-improved.hs

import           System.IO
import           System.Random

-- The game

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])

outcome :: String -> String -> String
outcome word x = "You " ++ x ++ "! The word was " ++ word

turn :: String -> String -> Int -> IO ()
turn word display n
  | n == 0 = putStrLn $ outcome word "lose"
  | word == display = putStrLn $ outcome word "win"
  | otherwise =
    mkguess word display n

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

starman :: String -> Int -> IO ()
starman word = turn word ['-' | _ <- word]

-- IO

main :: IO ()
main = do
  handle <- openFile "dictionary.txt" ReadMode
  dict <- hGetContents handle
  let size = length $ lines dict
  idx <- getStdRandom (randomR (0, size))
  let word = lines dict !! idx
  starman (head (words word)) 5