practice of using enumerator

gistfile1.hs

{-# LANGUAGE OverloadedStrings #-}

-- http://d.hatena.ne.jp/kazu-yamamoto/20110216/1297845048

import Control.Monad.IO.Class (liftIO)
import qualified Data.ByteString as BS
import qualified Data.ByteString.Char8 as B -- for OverloadedString
import Data.Enumerator (($$), (<==<), ($=), (=$))
import qualified Data.Enumerator as E
import Data.Enumerator.Binary as EB
import qualified Data.Enumerator.List as EL
import Data.Maybe

consumer :: E.Iteratee BS.ByteString IO ()
consumer = do
  mw <- EB.head
  case mw of
    Nothing -> return ()
    Just w -> do
             liftIO . putStr $ "XXX "
             liftIO . BS.putStrLn . BS.singleton $ w
             consumer

listFeeder :: E.Enumerator BS.ByteString IO a
listFeeder = E.enumList 1 ["12", "34"]

fileFeeder :: E.Enumerator BS.ByteString IO a
fileFeeder = EB.enumFile "FILE"

consumer2 :: E.Iteratee BS.ByteString IO ()
consumer2 = do
  mw <- EB.head
  case mw of
    Nothing -> return ()
    Just w -> do
              liftIO . putStr $ "YYY "
              liftIO . BS.putStrLn . BS.singleton $ w