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
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