(chan 0) is not actually valid (should just be (chan)) - I have a ticket to error on this more visibly. http://dev.clojure.org/jira/browse/ASYNC-143
Trasducers may produce more than one value (per things like the mapcat transducer) and thus a buffer is required so that there is somewhere to put those values when they are produced. This is mentioned in the docstring for chan: http://clojure.github.io/core.async/#clojure.core.async/chan "If a transducer is supplied a buffer must be specified." On Sunday, May 15, 2016 at 4:56:03 AM UTC-5, JvJ wrote: > > > I don't have much experience with core.async, and I recently tried using > channels with transducers. Strangely, I found that you need a buffer with > a size > of at least one in order for the transducer to be applied. > > I have a few toy functions: > > (defn push-nums > "Push a few numbers on a channel." > [n c] > (go (loop [i 0] > (when (< i n) > (>! c i) > (recur (inc i)))) > (>! c :end))) > > (defn print-nums > "Take the numbers from the channel and print them." > [c] > (go > (loop [] > (let [n (<! c)] > (when (not= :end n) > (println "A num: " n) > (recur)))) > (println "Finished with nums!!"))) > > > I used them in two different scenarios: > > > (let [c (chan 0 (map inc))] (push-nums 5 c) (print-nums c)) > ;=> A num: 0 > ;=> A num: 1 > ;=> A num: 2 > ;=> A num: 3 > ;=> A num: 4 > ;=> Finished with nums!! > > (let [c (chan 1 (map inc))] (push-nums 5 c) (print-nums c)) > ;=> A num: 1 > ;=> A num: 2 > ;=> A num: 3 > ;=> A num: 4 > ;=> A num: 5 > > > The transducer only gets applied when the argument 1 is passed in. I > assume this is by design, but I don't like the fact that > using transducers effectively limits certain options with channels. > > Does anyone know if there's a type of buffer that can be used to get > around this? > > > > -- 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.
