Chinese Whisper

gistfile1.hs

import Control.Monad
import Control.Concurrent

chans = sequence $ replicate 100001 newEmptyMVar

whisper chans = do
  forM_ (zip chans (tail chans)) $ \(left,right) -> forkIO $ do
    msg <- readMVar right
    putMVar left (msg + 1)
  forkIO $ putMVar (last chans) 1
  takeMVar $ head chans


main = chans >>=  whisper >>= print