broadcast by STM

bc.hs

import Control.Concurrent(forkIO,threadDelay)
import qualified Control.Concurrent.STM.TChan as TChan
import qualified Control.Monad.STM as STM

main = do
  rp <- TChan.newTChanIO
  bc <- TChan.newBroadcastTChanIO
  forkIO $ broadcast bc
  forkIO $ receive 0 rp bc
  forkIO $ receive 1 rp bc
  forkIO $ receive 2 rp bc
  forkIO $ receive 3 rp bc
  forkIO $ receive 4 rp bc
  forkIO $ receive 5 rp bc
  forkIO $ receive 6 rp bc
  forkIO $ receive 7 rp bc
  forkIO $ receive 8 rp bc
  forkIO $ receive 9 rp bc
  report rp
    
broadcast :: TChan.TChan Int -> IO()
broadcast c = loop 0
  where
    loop n = do
      STM.atomically $ TChan.writeTChan c n 
      threadDelay 10000
      loop $ n+1
      
receive :: Int -> TChan.TChan String -> TChan.TChan Int -> IO()
receive id rp bc = do
  dc <- STM.atomically $ TChan.dupTChan bc
  loop dc
  where
    loop dc = do
      n <- STM.atomically $ TChan.readTChan dc
      STM.atomically $ TChan.writeTChan rp $ "receive:" ++ (show id) ++ ":" ++ (show n)
      loop dc

report :: TChan.TChan String -> IO()
report c = loop
  where
    loop = do
      msg <- STM.atomically $ TChan.readTChan c
      putStrLn msg
      loop