# Haskell Quiz/Yahtzee/Solution Bobstopper

### From HaskellWiki

This is a bit longer than the ruby solution but is a bit more featureful.

import Control.Arrow (first, second, (&&&)) import Control.Monad import Control.Monad.State import Data.List import Data.Maybe import qualified Data.Map as Map import System.Exit import System.Random -- Possible values of a 6 sided dice roll data DiceRoll = One | Two | Three | Four | Five | Six deriving (Eq, Ord, Enum, Bounded, Show) value = (1+) . fromEnum -- Some Random Utilities instance Random DiceRoll where randomR (min,max) g = first toEnum $ randomR (fromEnum min,fromEnum max) g random = randomR (minBound,maxBound) randomIOs :: Random a => IO [a] randomIOs = fmap randoms newStdGen rollDice = randomIO :: IO DiceRoll -- Generates n random dice rollNDice :: Int -> IO [DiceRoll] rollNDice n = (take n) `fmap` randomIOs -- reRollDice ns dice returns a new set of dice with dices at positions -- given by ns replaced with newly generated dice reRollDice :: [Int] -> [DiceRoll] -> IO [DiceRoll] reRollDice [] dice = return dice reRollDice (n:ns) dice = do next <- fmap (replace dice n) $ rollDice reRollDice ns next replace :: [a] -> Int -> a -> [a] replace xs i x = (take i xs) ++ [x] ++ (drop (i+1) xs) -- Scoring logic -- Yahtzee categories which can be scored against data Category = Ones | Twos | Threes | Fours | Fives | Sixes | ThreeOfAKind | FourOfAKind | FullHouse | SmallStraight | LargeStraight | Chance | Yahtzee deriving (Show, Read, Ord, Eq) -- Small Mapping just for counting type Count = Map.Map DiceRoll Int initCount = Map.fromAscList [ (One, 0), (Two, 0), (Three, 0) , (Four, 0), (Five, 0), (Six, 0)] -- Count how many of each DiceRoll there is in a hand countDice :: [DiceRoll] -> Count countDice = foldr (Map.adjust (+1)) initCount -- Count how many of a specific DiceRoll there is in a hand numberMatching :: DiceRoll -> [DiceRoll] -> Int numberMatching = (length .) . filter . (==) -- Test if a list is ascending incrementally isStraight :: (Bounded a, Enum a, Eq a) => [a] -> Bool isStraight [] = True isStraight xs = and $ zipWith isSucc xs (tail xs) where isSucc x y | x == maxBound = False | otherwise = y == succ x -- Determine a hand's score against a specific category score :: [DiceRoll] -> Category -> Int score dice Ones = numberMatching One dice score dice Twos = (numberMatching Two dice) * 2 score dice Threes = (numberMatching Three dice) * 3 score dice Fours = (numberMatching Four dice) * 4 score dice Fives = (numberMatching Five dice) * 5 score dice Sixes = (numberMatching Six dice) * 6 score dice ThreeOfAKind | Map.null $ Map.filter (>=3) $ countDice dice = 0 | otherwise = sum (map value dice) score dice FourOfAKind | Map.null $ Map.filter (>=4) $ countDice dice = 0 | otherwise = sum (map value dice) score dice Yahtzee | Map.null $ Map.filter (==5) $ countDice dice = 0 | otherwise = 50 score dice FullHouse | Map.size gt2 == 1 && head (Map.elems gt2) == 5 = 25 | Map.size gt2 == 2 && (not $ Map.null $ Map.filter (==3) gt2) = 25 | otherwise = 0 where gt2 = Map.filter (>=2) $ countDice dice score dice SmallStraight | (isStraight $ tail $ sort dice) || (isStraight $ take 4 $ sort dice) = 30 | otherwise = 0 score dice LargeStraight | isStraight $ sort dice = 40 | otherwise = 0 score dice Chance = sum $ map value dice -- The Game Logic type PlayerName = String type PlayerTotal = (PlayerName, Int) type ScoreCard = Map.Map Category (Maybe Int) maxReRolls = 2 -- An initial score with all categories unscored clearScore = Map.fromAscList [ (Ones, Nothing), (Twos, Nothing) , (Threes, Nothing), (Fours, Nothing) , (Fives, Nothing), (Sixes, Nothing) , (ThreeOfAKind, Nothing), (FourOfAKind, Nothing) , (FullHouse, Nothing), (SmallStraight, Nothing) , (LargeStraight, Nothing), (Chance, Nothing) , (Yahtzee, Nothing) ] data GameState = GameState { playerQueue :: [ PlayerName ] , players :: Map.Map PlayerName ScoreCard , reRolls :: Int } -- Generate a new game using the player names given newGame :: [PlayerName] -> GameState newGame [] = error "Need to define at least one player" newGame ps = GameState { playerQueue = cycle ps , players = Map.fromList $ zip ps (repeat clearScore) , reRolls = maxReRolls } -- Change a specific player's score by scoring the given hand against -- the given category adjustScore :: PlayerName -> Category -> [DiceRoll] -> GameState -> GameState adjustScore n c ds g = g { players = Map.adjust (adjustCategory c (score ds c)) n (players g) } -- Adjust the score for a specific category in a scorecard adjustCategory :: Category -> Int -> ScoreCard -> ScoreCard adjustCategory Yahtzee x s = Map.adjust (maybe (Just 50) (Just . (+x))) Yahtzee s adjustCategory c x s = Map.adjust (maybe (Just x) (error "Category already used")) c s currentPlayer :: GameState -> PlayerName currentPlayer = head . playerQueue -- Get the current scorecard of the given player playerScore :: PlayerName -> GameState -> ScoreCard playerScore n g = Map.findWithDefault err n (players g) where err = error $ "Couldn't find Player " ++ n ++ " in game!" -- Get the current scorecard for the current player currentPlayerScore :: GameState -> ScoreCard currentPlayerScore g = playerScore (currentPlayer g) g -- Uses up one of the available rerolls useReRoll :: GameState -> GameState useReRoll g = g { reRolls = (reRolls g)-1 } -- Reset the game for the next player newRound :: GameState -> GameState newRound g = g { reRolls = maxReRolls , playerQueue = tail $ playerQueue g } -- Returns the number of rounds in a game gameLength :: GameState -> Int gameLength = (13*) . Map.size . players -- Look up the score of the given category from a scorecard category :: Category -> ScoreCard -> Maybe Int category c s = Map.findWithDefault err c s where err = error $ "Couldn't find Category " ++ (show c) ++ " in player's score!" -- Determines whether it is ok to place a score against the category -- This function should always be used prior to scoring a category categoryOK :: Category -> ScoreCard -> Bool categoryOK Yahtzee _ = True categoryOK c s = isNothing $ category c s -- Calculates the "upper" total of the scorecard scoreUpper :: ScoreCard -> Int scoreUpper s = sum $ mapMaybe ((flip category) s) [Ones,Twos,Threes,Fours,Fives,Sixes] -- Calculates the "lower" total of the scorecard scoreLower :: ScoreCard -> Int scoreLower s = sum $ mapMaybe ((flip category) s) [ ThreeOfAKind, FourOfAKind, FullHouse , SmallStraight, LargeStraight, Yahtzee, Chance ] -- Calculates the grand total of the scorecard scoreTotal :: ScoreCard -> Int scoreTotal = (uncurry (+)) . (scoreUpper &&& scoreLower) -- Data structure to account for draws as well as outright winners data GameOutcome = Winner PlayerTotal | Draw [PlayerTotal] -- Determines the winner between two players winner :: PlayerTotal -> GameOutcome -> GameOutcome winner y (Winner x) | (snd x) > (snd y) = Winner x | (snd x) < (snd y) = Winner y | otherwise = Draw [x,y] winner y (Draw xs@(x:_)) | (snd x) > (snd y) = Draw xs | (snd x) < (snd y) = Winner y | otherwise = Draw $ y:xs -- Score printing utilities -- Prints the player's score printScore :: PlayerName -> Yahtzee () printScore p = do score <- gets (playerScore p) liftIO $ putStrLn $ show score -- Prints the player's final score totals printFinalScore :: PlayerName -> ScoreCard -> IO () printFinalScore n s = do putStrLn $ "*** Final Score for " ++ n ++ " ***" putStrLn $ "Lower Score: " ++ (show $ scoreLower s) putStrLn $ "Upper Score: " ++ (show $ scoreUpper s) newline putStrLn $ "TOTAL Score: " ++ (show $ scoreTotal s) -- Print the overall winner(s) and their score(s) printWinner :: GameOutcome -> IO () printWinner (Winner (n,s)) = putStrLn $ n++ " is the winner with " ++ (show s) ++ "!" printWinner (Draw ws) = do putStrLn "The game is a Draw!" mapM_ (\(n,s) -> putStrLn $ n++ "with " ++ (show s)) ws -- The Interface -- Valid user input types data Input = Accept Category | ShowScore | ReRoll [Int] | ReRollAll | Quit | Help | CategoryHelp deriving Read -- The game monad type Yahtzee a = StateT GameState IO a newline = putStrLn "" -- Persists in asking the given question until a valid answer is given. -- Valid answers are determined and returned by the given function ask :: String -> (String -> Maybe a) -> IO a ask question f = do putStr (question ++ "> ") x <- fmap f getLine case x of (Just answer) -> return answer Nothing -> putStrLn "Invalid input. Try again" >> ask question f -- Attempts to read a string. Returns Nothing if it fails maybeRead :: Read a => String -> Maybe a maybeRead s = case r of [] -> Nothing ((x,_):_) -> Just x where r = reads s -- The Game start and completion main :: IO () main = do playerNames <- getPlayerNames let game = newGame playerNames gameOver <- execStateT (replicateM_ (gameLength game) playerUp) game let scores = Map.toList $ players gameOver mapM_ (uncurry printFinalScore) scores let topScore = foldr winner (Winner ("Nobody",0)) (map (second scoreTotal) scores) printWinner topScore -- Ask for each player names until a blank line is reached getPlayerNames :: IO [PlayerName] getPlayerNames = do name <- ask "Enter player name (blank line to finish)" Just if null name then return [] else fmap (name:) getPlayerNames -- Start a round for the next player playerUp :: Yahtzee () playerUp = do player <- gets currentPlayer liftIO $ newline liftIO $ putStrLn "Next Round" liftIO $ newline printScore player liftIO $ newline liftIO $ putStrLn $ player ++ ", you're up!" (liftIO $ rollNDice 5) >>= userAction modify newRound -- Interact with the user during the round userAction :: [DiceRoll] -> Yahtzee () userAction dice = do liftIO $ putStrLn $ "Your roll is " ++ (show dice) input <- liftIO $ ask "Input Action (type Help for help)" maybeRead processInput input dice -- Process a user's input processInput :: Input -> [DiceRoll] -> Yahtzee () processInput (Accept c) ds = do player <- gets currentPlayer playerScore <- gets $ playerScore player if categoryOK c playerScore then do modify $ adjustScore player c ds printScore player else do (liftIO $ putStrLn ("Category " ++ (show c) ++ " already used")) userAction ds processInput ShowScore ds = gets currentPlayer >>= printScore >> userAction ds processInput (ReRoll is) ds = maybeReRoll ds $ modify useReRoll >> (liftIO $ reRollDice is ds) processInput ReRollAll ds = maybeReRoll ds $ modify useReRoll >> (liftIO $ rollNDice 5) processInput Quit _ = liftIO $ exitWith ExitSuccess processInput Help ds = do liftIO $ putStrLn "* Command List *" liftIO $ putStrLn "Accept category: Accept this roll and score against category" liftIO $ putStrLn "Score: Print your current score" liftIO $ putStrLn "ReRoll indexes: reroll the dice specified by the Haskell list of Ints in indexes" liftIO $ putStrLn "ReRollAll: discard all dice and roll a fresh set" liftIO $ putStrLn "Quit: Exit the game" liftIO $ putStrLn "Help: Display this help" liftIO $ putStrLn "CategoryHelp: Display available categories" liftIO $ newline userAction ds processInput CategoryHelp ds = do liftIO $ putStrLn "* Category List *" liftIO $ putStrLn "Ones | Twos | Threes | Fours | Fives | Sixes" liftIO $ putStrLn "| ThreeOfAKind | FourOfAKind | FullHouse" liftIO $ putStrLn "| SmallStraight | LargeStraight | Yahtzee | Chance" userAction ds -- takes a current diceroll and a command to reroll. -- Performs the reroll action only if the player has rerolls left. -- Otherwise tells the player no rerolls are left maybeReRoll :: [DiceRoll] -> Yahtzee [DiceRoll] -> Yahtzee () maybeReRoll dice cmd = do nextRound <- gets ((<=0) . reRolls) if nextRound then (liftIO $ putStrLn "No rolls left. Accept a category") >> userAction dice else cmd >>= userAction