Hit & Blow

HitBlow.hs

module HitBlow where

import System.Random
import Control.Monad
import Data.List

decideNums :: IO [Int]
decideNums = do
  ixs <- forM [0..3] $ \i -> randomRIO (0,9-i)
  return $ fst $ foldl (\(a,a') i -> ((a'!!i):a,delete i a')) ([],[0..9]) ixs

countHitBlow :: [Int] -> [Int] -> (Int, Int)
countHitBlow ns ks = (hit, blow) where
  hit = length $ filter (\(n,k) -> n == k) $ zip ns ks
  blow = length (intersect ns ks) - hit

runGame ns = do
  putStr "number>"
  ks <- fmap ((read :: String -> Int) . return) <$> getLine

  if ks == ns
    then putStrLn "Exactly!"
    else do
      let (h,b) = countHitBlow ns ks
      putStrLn $ "hit: " ++ show h ++ " blow: " ++ show b
      runGame ns

main = do
  ns <- decideNums
  runGame ns