On Fri, Jan 07, 2005 at 02:57:19PM +0100, Tomasz Zielonka wrote:
My guess is it would be something like this, however you may want to do it differently to get better compositionality (withTimeout returns an IO action, not a STM action):
Maybe this will suffice, but I don't know if the delay thread will be garbage collected. import Control.Concurrent import Control.Concurrent.STM import Monad (when) makeDelay :: Int -> IO (STM ()) makeDelay time = do v <- atomically (newTVar False) forkIO $ do threadDelay time atomically (writeTVar v True) return $ readTVar v >>= \b -> when (not b) retry withTimeout :: Int -> STM a -> IO (Maybe a) withTimeout time fun = do delay <- makeDelay time atomically (fmap Just fun `orElse` (delay >> return Nothing)) Best regards, Tomasz