As for the producer/consumer scheme with the higher-order channel, it works in the single-producer case:
https://gist.github.com/michalmarczyk/5980097 (Actually this is simplified a bit in that it's also single consumer, but that's not a feature of the approach, but rather my quick & dirty poc.) Multi-producer, single-consumer could be done dually. On 12 July 2013 00:53, Michał Marczyk <michal.marc...@gmail.com> wrote: > I think you could pass the producer a higher-order (chan 1) with the > actual communication channel placed in the buffer. > > Then at each step the producer would do > > (when-let [c (<! communication-channel)] > (>! c (rand)) > (>! communication-channel c)) > > Once you close communication-channel, the put succeeds, but then the > take on communication-channel returns nil and the producer stops. > > Cheers, > M. > > > On 12 July 2013 00:37, Alex Miller <a...@puredanger.com> wrote: >> I haven't been in any discussions about this with the team, so it's entirely >> possible I am ignorant of some established future direction... but >> >> - "closed?" seems useful to me. (It may also be useful to ask "drained?" >> (closed + empty).) >> - >! returning an indicator of success also seems useful. However, since it >> executes asynchronously, I suspect adding that functionality may not be >> feasible (or may be feasible but incur a synchronization or complexity cost >> that is unacceptable). >> >> If you'd like to file a ticket at http://dev.clojure.org/jira/browse/ASYNC >> that would help to track the request. >> >> With respect to other strategies for dealing with this: >> >> 1) You could simply ignore the producer. If no one is requesting new values, >> the producer will not be run and no thread time should be consumed (there is >> of course heap being used). Not really recommending this but it's an option! >> >> 2) You could create a control channel for the producer (and other interested >> processes) that could transmit a stop message. Then alts! on the control >> channel in combination with the >! so that you're waiting on either the need >> to stop or the ability to put a new value in the channel. >> >> Alex >> >> >> On Thursday, July 11, 2013 7:16:56 AM UTC-5, vemv wrote: >>> >>> Consider a happy, oblivious producer of values: >>> >>> (def c (chan 42)) >>> >>> (go (while true (>! c (rand)))) >>> >>> It doesn't know where/now the channel is consumed (which part of the point >>> of channels/queues). However, we do know that at some point, nobody will >>> need the result of our producing, so we should stop our activity. >>> >>> It seems to me that a natural way to tell the producer to stop is to close >>> the channel. However: >>> >>> * there's nothing like a clojure.core.async/chan-closed? fn, AFAICT >>> * The >! fn unconditionally returns nil, whether the channel is open or >>> not. Only the blocking nature of the call can potentially vary - which is >>> not particularly useful for the purpose. >>> >>> What would be an adequate way to indicate termination? Just telling the >>> producer to stop (e.g. (reset! keep-producing false)) would break the >>> indirection one gains by using channels. >>> >>> What if >! returned true/false depending on whether the value was put >>> (because the channel was open)? >> >> -- >> -- >> You received this message because you are subscribed to the Google >> Groups "Clojure" group. >> To post to this group, send email to clojure@googlegroups.com >> Note that posts from new members are moderated - please be patient with your >> first post. >> To unsubscribe from this group, send email to >> clojure+unsubscr...@googlegroups.com >> For more options, visit this group at >> http://groups.google.com/group/clojure?hl=en >> --- >> You received this message because you are subscribed to the Google Groups >> "Clojure" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to clojure+unsubscr...@googlegroups.com. >> For more options, visit https://groups.google.com/groups/opt_out. >> >> -- -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
