Thank you for calling my attention to this possibility! e
On Wed, Dec 3, 2014 at 2:49 PM, Dylan Butman <dbut...@gmail.com> wrote: > Erik that's pretty! But be careful about go-loops and closed channels. > This will recur infinitely if events-ch is closed (it will continuously > return nil) > > (defn invoke-after-uninterrupted-delay > > ([period events-ch f] > > (invoke-after-uninterrupted-delay period events-ch f [])) > > ([period events-ch f & args] > > (async/go-loop [] > > (let [[v p] (async/alts! [(async/timeout period) events-ch])] > > (when v > > (if (= p events-ch) > > (recur) > > (apply f args))))))) > will allow the go-loop to return when the channel is closed. > > > On Monday, December 1, 2014 8:33:10 PM UTC-5, Erik Price wrote: >> >> Coincidentally, we recently wrote code to do something very similar. The >> following function will invoke f after period milliseconds, unless a >> value is sent on events-ch, in which case the timeout is reset (and >> starts counting down again): >> >> (defn invoke-after-uninterrupted-delay >> ([period events-ch f] >> (invoke-after-uninterrupted-delay period events-ch f [])) >> ([period events-ch f & args] >> (async/go-loop [] >> (let [[_ p] (async/alts! [(async/timeout period) events-ch])] >> (if (= p events-ch) >> (recur) >> (apply f args)))))) >> >> e >> >> >> On Mon, Dec 1, 2014 at 6:50 PM, Brian Craft <craft...@gmail.com> wrote: >> >>> That version has the unfortunate behavior that (func) can be interrupted >>> if (event) is called while it is running. Here's another version using an >>> agent: >>> >>> (defn queue-with-delay2 [period func] >>> (let [q (agent nil)] >>> (fn [] >>> (send-off q (fn [t] >>> (when t >>> (future-cancel t)) >>> (future (Thread/sleep period) (send-off q (fn [_] >>> (func) nil)))))))) >>> >>> Running with a sleep to see that (func) is not canceled by subsequence >>> (event) calls: >>> >>> (def event (queue-with-delay2 2000 #(do (println "running") >>> (Thread/sleep 2000) (println "ending")))) >>> >>> Oddly, if calling (event) between "running" and "ending" messages, the >>> repl will stack-overflow on the return value. No idea what that's about. >>> But, running like this is fine: >>> >>> (do (event) nil) >>> >>> >>> >>> >>> >>> On Monday, December 1, 2014 1:37:56 PM UTC-8, Brian Craft wrote: >>>> >>>> I have need to perform an action when a series of events is quiet for >>>> some period. That is, if one event arrives an action is queued to execute >>>> after some timeout. If a second event arrives the timeout is reset, and >>>> so-forth. >>>> >>>> The following code seems to work, however I'm wondering if calling >>>> 'future' from 'swap!' is a bad idea (side effecting), and if there's a >>>> better way. >>>> >>>> (defn queue-with-delay [period func] >>>> (let [f (atom nil)] >>>> (fn [] >>>> (when @f >>>> (future-cancel @f)) >>>> (swap! f (fn [_] (future (Thread/sleep period) (func))))))) >>>> >>>> >>>> Use like >>>> >>>> (def event (queue-with-delay 2000 #(println "running"))) >>>> (event) >>>> (event) >>>> (event) ; pause 2 sec >>>> "running" >>>> >>>> >>>> >>>> -- >>> You received this message because you are subscribed to the Google >>> Groups "Clojure" group. >>> To post to this group, send email to clo...@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+u...@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+u...@googlegroups.com. >>> For more options, visit https://groups.google.com/d/optout. >>> >> >> -- > 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/d/optout. > -- You received this message because you are subscribed to the Google Groups "Clojure" group. 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