Hi, I'm interested in learning how to program games. Since I have to start somewhere, I decided to write a simple Hangman game. I'm wondering if anyone can look at my code and give me some feedback. Thank you. -- Hangman game module Main where import Data.Char import Data.List import System.IO import System.Random import Control.Monad.State data GameState = GameState { gsAnswer :: String, -- the answer gsKnown :: [Maybe Char], -- partial answer known to the user gsGuesses :: [Char], -- incorrect letters guessed so far gsWrong :: Int, -- number of incorrect guesses gsWonLost :: Maybe Bool -- Just true = won, Just false = lost } deriving (Show) newGameState :: String -> GameState newGameState answer = GameState{ gsAnswer = map toUpper answer, gsKnown = (map (filt $ not . isAlpha) answer), gsGuesses = [], gsWrong = 0, gsWonLost = Nothing} data UserInput = UIGuess Char | UIQuit | UINewGame | UIRefresh deriving (Show) main :: IO () main = do hSetBuffering stdout NoBuffering putStr "Welcome to Hangman!\n\n" putStr instructions runStateT startNewGame undefined return () startNewGame :: StateT GameState IO () startNewGame = do nWord <- liftIO $ getStdRandom (randomR (0,length wordList - 1)) let word = wordList !! nWord let gs = newGameState word put gs liftIO $ putStrLn $ renderGameState gs gameLoop gameLoop :: StateT GameState IO () gameLoop = do ui <- liftIO getUserInput case ui of UIGuess c -> do modify $ handleGuess c gs <- get liftIO $ putStrLn $ renderGameState gs case (gsWonLost gs) of Nothing -> gameLoop Just True -> do liftIO $ putStrLn "Congratulations, you won!" startNewGame Just False -> do liftIO $ putStrLn "You've been hanged!" liftIO $ putStrLn $ "The word was \'" ++ (gsAnswer gs) ++ "\'." startNewGame UIQuit -> do gs <- get liftIO $ putStrLn $ "The word was \'" ++ (gsAnswer gs) ++ "\'." liftIO $ putStrLn "Thank you for playing!" UINewGame -> do gs <- get liftIO $ putStrLn $ "The word was \'" ++ (gsAnswer gs) ++ "\'." startNewGame UIRefresh -> do gs <- get liftIO $ putStrLn $ renderGameState gs gameLoop getUserInput :: IO UserInput getUserInput = do putStr "Hangman> " response <- getLine if null response then getUserInput else do let c:cs = response if isAlpha c then return $ UIGuess $ toUpper c else if c == ':' && not (null cs) then case toLower (head cs) of 'q' -> return UIQuit 'n' -> return UINewGame 'r' -> return UIRefresh '?' -> do putStr instructions getUserInput otherwise -> do putStrLn $ "Unknown command \'" ++ cs ++ "\'" putStrLn $ "Use \':?\' for help." getUserInput else do putStrLn $ "Invalid input \'" ++ response ++ "\'" putStrLn $ "Use \':?\' for help." getUserInput instructions :: String instructions = "Instructions:\n" ++ "To guess a letter, type the letter and press enter.\n" ++ "To quit or restart the game, use the following commands:\n" ++ " :q = quit\n" ++ " :n = new game\n" ++ " :r = re-display the game state\n" ++ " :? = show instructions\n" ++ "\n" filt :: (a -> Bool) -> a -> Maybe a filt pred x = if pred x then Just x else Nothing handleGuess :: Char -> GameState -> GameState handleGuess ch state = if (elem ch $ gsGuesses state) then state else if (elem ch $ gsAnswer state) then let revealed = map (filt (== ch)) (gsAnswer state) known = zipWith mplus (gsKnown state) revealed won = all (maybe False (const True)) known in state{gsKnown = known, gsWonLost = filt id won} else let wrong = 1 + (gsWrong state) in state{gsGuesses = ch:(gsGuesses state), gsWrong = wrong, gsWonLost = filt not (wrong < 7)} wordList :: [String] wordList = ["alligator", "angelfish", "ant", "bear", "buffalo", "butterfly", "canary", "chameleon", "crab", "dinosaur", "dog", "dolphin", "eel", "elephant", "flamingo", "frog", "giraffe", "goldfish", "grasshopper", "hedgehog", "hippopotamus", "horse", "iguana", "jaguar", "jellyfish", "kangaroo", "kinkajou", "lemur", "lizard", "llama", "meerkat", "moose", "mouse", "narwhal", "nautilus", "nuthatch", "ostrich", "owl", "panda", "pelican", "quail", "quokka", "raccoon", "rhinoceros", "salamander", "sea horse", "sea urchin", "snail", "tiger", "toucan", "uakari", "unicorn", "vampire bat", "vulture", "walrus", "wildebeest", "worm", "xenops", "yak", "yellow jacket", "zebra"] renderGameState :: GameState -> String renderGameState gs = let noose = renderNoose $ gsWrong gs report = ["","The Word:","",word,"","Your Guesses:","",guessed] word = intersperse ' ' $ map (maybe '_' id) (gsKnown gs) guessed = gsGuesses gs in (concat $ zipWith (++) noose $ map (++ "\n") report) renderNoose :: Int -> [String] renderNoose n | n <= 0 = [ " ___ ", " / | ", " | ", " | ", " | ", " | ", " | ", " -+- "] renderNoose 1 = [ " ___ ", " / | ", " | O ", " | ", " | ", " | ", " | ", " -+- "] renderNoose 2 = [ " ___ ", " / | ", " | O ", " | | ", " | ", " | ", " | ", " -+- "] renderNoose 3 = [ " ___ ", " / | ", " | O ", " | --| ", " | ", " | ", " | ", " -+- "] renderNoose 4 = [ " ___ ", " / | ", " | O ", " | --|-- ", " | ", " | ", " | ", " -+- "] renderNoose 5 = [ " ___ ", " / | ", " | O ", " | --|-- ", " | | ", " | ", " | ", " -+- "] renderNoose 6 = [ " ___ ", " / | ", " | O ", " | --|-- ", " | | ", " | / ", " | ", " -+- "] renderNoose n | n >= 7 = [ " ___ ", " / | ", " | O ", " | --|-- ", " | | ", " | / \\ ", " | ", " -+- "]