Example of closable channels using forkJoin and random sleeps.

Closable Chan Example.hs

import Closable
import ForkJoin
import Control.Concurrent
import System.Random
import Control.Monad

main = do
  c <- newChan :: IO (Chan (Maybe String))

  forkIO $ getChanWhileJust c >>= mapM_ print

  forkJoin [ foo c "test_a.txt"
           , foo c "test_b.txt"]

  writeChan c Nothing

foo c f = do
  text  <- fmap lines (readFile f)
  rands <- fmap (randomRs (0::Float, 0.5)) newStdGen
  zipWithM_ (bar c) rands text

bar c x y = do
  threadDelay . floor . (* 10^6) $ x
  writeChan c $ Just y