Hi there,
2008/10/9 David Leimbach
see writeTChan and readTChan. I assume readTChan is synchronous :-). writeTChan may be asynchronous for all I can tell (haven't looked deeply).
writeTChan is asynchronous, i.e. channels in this case are unbounded buffers.
But I did write a concurrent prime sieve with it:
I did the same, with the one-place-buffers (the MVars implemented over STM). Be warned that there is no stop condition, this just keeps printing primes forever. import Control.Concurrent (forkIO) import Control.Concurrent.STM -- MVars from the STM paper type MVar a = TVar (Maybe a) newEmptyMVar :: STM (MVar a) newEmptyMVar = newTVar Nothing takeMVar :: MVar a -> STM a takeMVar mv = do v <- readTVar mv case v of Nothing -> retry Just val -> do writeTVar mv Nothing return val putMVar :: MVar a -> a -> STM () putMVar mv val = do v <- readTVar mv case v of Nothing -> writeTVar mv (Just val) Just _ -> retry -- Sieve forever a = do a; forever a pfilter :: Int -> MVar Int -> MVar Int -> IO () pfilter p in_ out = forever $ do atomically $ do v <- takeMVar in_ if v `mod` p /= 0 then putMVar out v else return () sieve :: MVar Int -> MVar Int -> IO () sieve in_ out = do p <- atomically $ takeMVar in_ atomically $ putMVar out p ch <- atomically $ newEmptyMVar forkIO $ pfilter p in_ ch sieve ch out feeder :: MVar Int -> IO () feeder out = feed' 2 where feed' i = do atomically $ putMVar out i feed' (i+1) printer :: MVar Int -> IO () printer in_ = forever $ do v <- atomically $ takeMVar in_ putStrLn $ show v main :: IO () main = do in_ <- atomically newEmptyMVar out <- atomically newEmptyMVar forkIO $ feeder in_ forkIO $ printer out forkIO $ sieve in_ out return () cheers, Arnar