practice: Channel

tchan.hs

import Control.Monad (forM_)
import Control.Concurrent
import Control.Concurrent.Chan
import Control.Concurrent.STM
import System.Random

postString :: Int -> IO ()
postString num = do
  ch <- atomically newTChan
  forM_ [1..num] $ forkIO . worker ch
  putStrLn "start..."
  loopMain ch

worker :: TChan String -> Int -> IO ()
worker chan idx = do
  randomDelay 5
  atomically $ writeTChan chan $ "thread-" ++ show idx -- とりあえず文字列

-- 取り切ったらブロックしちゃうけど...
loopMain :: TChan String -> IO ()
loopMain chan = (atomically $ readTChan chan) >>= putStrLn >> loopMain chan

randomDelay :: Int -> IO ()
randomDelay max = (getStdRandom $ randomR (1, max)) >>= threadDelay . (*1000000)