http://qiita.com/items/ebd8a56b41711ba459f9 の問題をhaskellで解いてみた

baseball.hs

import Data.Char
import System.Environment

main = do
  args <- getArgs
  print . process. head $ args

process = foldl (\acc x -> cal acc x) []

cal acc x = acc ++ [r x]
  where
    now = if acc == [] then [] else last acc
    r 's' = strike now
    r 'b' = ball now
    r 'h' = hit now
    r 'p' = pitcher now
    r 'f' = foul now

strike :: String -> String
strike [] = strike "000"
strike (o:s:b)
  | si < 2 = o : intToDigit(si + 1) : b
  | si >= 2 = if oi == 2 then "000" else intToDigit (oi + 1): "00"
  where
    si = digitToInt s
    oi = digitToInt o

ball :: String -> String
ball [] = ball "000"
ball (o:s:b)
  | bi < 3 = o:s:intToDigit(bi + 1): []
  | bi == 3 = o: "00"
  where
    bi = digitToInt . head $ b

hit :: String -> String
hit [] = hit "000"
hit (o:_) = o: "00"

pitcher :: String -> String
pitcher [] = pitcher "000"
pitcher (o:s:b)
  | oi < 2 = intToDigit(oi + 1) : "00"
  | oi == 2 = "000"
  where
    oi = digitToInt o

foul :: String -> String
foul [] = "000"
foul x@(o:s:b)
  | si < 2 = o : intToDigit(si + 1) : b
  | si == 2 = x
  where
    si = digitToInt s