第4回 スタートHaskell2 数当てゲーム解答

guessnumber.hs

import System.IO
import Data.List
import System.Random

main = do
        gen <- getStdGen
        let answer = take 4 (randomRs ('1', '4') gen)
        putStrLn "Hello, guess the number!"
        guessNumber answer

guessNumber::String->IO ()
guessNumber answer = do
        putStr "> "
        hFlush stdout
        line <- getLine
        if line == answer
            then putStrLn "correct!"
            else do
                if ((length line) == (length answer))
                then do
                    print $ countSamePos answer line
                    print $ countSameNum (sort answer) (sort line)
                else
                    putStrLn "input 4 numbers!"
                guessNumber answer

countSamePos xs ys = length . filter id $ zipWith (==) xs ys
countSameNum xss@(x:xs) yss@(y:ys)
                        | x == y = 1 + countSameNum xs ys
                        | x < y = countSameNum xs yss
                        | otherwise = countSameNum xss ys
countSameNum _ _ = 0