While we are waiting for ghc 6.6, could the same effect be achieved
by launching the computation that writes to t with forkIO?
On Nov 29, 2005, at 12:00 PM, Simon Marlow wrote:
threadDelay is IO-only; there's no way to use threadDelay in an STM
transaction. For example, if you want to wait for a TVar to go from
Nothing to Just x with a timeout, you could do this:
readOrTimeout :: TVar (Maybe a) -> Int -> STM (Maybe a)
readOrTimeout t secs = do
timeout <- registerTimeout secs
let check_timeout = do
b <- readTVar timeout
if b then return Nothing else retry
check_t = do
m <- readTVar t
case m of
Nothing -> retry
Just x -> return x
atomically $ check_timeout `orElse` check_t
--
http://wagerlabs.com/
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