Hadoopテスト reducer

reducer.hs

import System.IO
import Control.Applicative
import Control.Monad
import Text.Parsec
import Text.Parsec.String
import Data.Map
import Data.Char


wordCount' :: Parser (String, Int)
wordCount' = do
  word <- many1 letter
  skipMany1 space
  nstr <- digit
  return (word, c2i nstr)
  where
    c2i c = ord c - ord '0'

wordCount :: Parser (String, Int)
wordCount = (\x y -> (x, (read y))) <$> ((many1 letter) <* spaces) <*> (many1 digit)
  

updateMap :: (Ord k, Num v) => k -> v -> Map k v -> Map k v
updateMap k v m | Data.Map.member k m = adjust (+ v) k m
                | otherwise           = insert k v m

loop :: Map String Int -> IO (Map String Int)
loop m = do
  isEnd <- isEOF
  if isEnd then
    return m
    else do
    str    <- getLine
    case parse wordCount "" str of
      Right (k, v) -> loop $ updateMap k v m
      _            -> loop m

main = do
  m <- loop $ fromList []
  forM_ (toList m) $ \(s,n) -> putStrLn (s ++ "\t" ++  (show n))