On 29 November 2005 06:29, Tomasz Zielonka wrote: > On Mon, Nov 28, 2005 at 11:27:46PM +0000, Joel Reymont wrote: >> Folks, >> >> How would you implement a timed read from a channel with STM? I would >> like to return Timeout if nothing was read from a TChan in X ms. >> >> Is this a basic two-thread timeout implementation or is there a more >> elegant way of implementing this using `orElse`? > > Here is a basic two-thread implementation: > > http://www.haskell.org/pipermail/haskell-cafe/2005-January/008303.html > > The other approach I see is to create a TVar that would be updated > with current time every 0.1 s (or something like that), but that would > be rather inefficient. > > You could also create a time-out manager thread (with a priority > queue, etc), so you don't have to spawn a thread for every timeout.
Interestingly, GHC already has a timeout thread - the I/O manager thread handles threadDelay too. It wouldn't be too hard to adapt it to do STM timeouts too, with a function like registerTimeout :: Int -> STM (TVar Bool) and you wait for your timeout by waiting for the TVar to contain True. Cheers, Simon _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe