darcs patch: forkChild, waitForChild, parIO, timeout
taralx at gmail.com
Tue Nov 7 11:04:24 EST 2006
On 11/7/06, Simon Marlow <simonmarhaskell at gmail.com> wrote:
> So 'timeout N E' should behave exactly the same as E as long as E doesn't time
> out. Three difficulties with this:
> 1. if E raises an exception, you want the exception propagated to the parent.
> 2. if another thread throws an exception to this thread, E should receive the
> 3. E should get the same result from myThreadId.
I think 2 and 3 go together, and require an exception. Here's my try:
data Timeout = Timeout deriving Typeable
timeout n f
| n < 0 = fmap Just f
| n == 0 = return Nothing
| otherwise = do
pt <- myThreadId
bracket (forkIO (threadDelay n >> throwDynTo pt Timeout))
(fmap Just f) `catchDyn` \Timeout -> return Nothing
Taral <taralx at gmail.com>
"You can't prove anything."
-- Gödel's Incompetence Theorem
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