That's the case with clojure.core.map as well, don't consume the lazy seq the side effects aren't run...in short, map is not for side effects.
On Mon, Apr 7, 2014 at 11:32 AM, Alejandro Ciniglio <skiae...@gmail.com>wrote: > Yeah, that seems to be the best practice that's promoted as well. Another > gotcha with this implementation is that since it's done via extending the > channel protocol (specifically take!), it doesn't actually apply the > functions effects unless someone is reading from the channel. This could be > an issue if you want side-effects only from the map< call. > > > On Monday, April 7, 2014 11:36:21 AM UTC-4, James Reeves wrote: > >> This looks like a bug to me. A lot of the internal core.async functions >> rely on nil values indicating the channel is closed. >> >> - James >> >> >> On 7 April 2014 16:26, Alejandro Ciniglio <skia...@gmail.com> wrote: >> >>> Using core.async, I've understood the convention to be that if you take >>> nil from a channel, that channel is closed. This seems to hold for most >>> cases, but I've found a corner case when using map< that lets you pull nil >>> from a channel that is not closed. >>> >>> (def a (chan)) >>> (def c (map< seq a)) >>> (go (prn (<! c))) >>> (>!! a []) >>> ; => nil nil ;; [one nil is printed, one is returned] >>> (go (prn (<! c))) >>> (>!! a [1]) >>> ; => nil (1) >>> >>> This can be chained as well (e.g. (map< identity (map< seq a)) ), and >>> nils just flow through. >>> >>> From looking at the implementation, it's apparent that this happens >>> because the function application of map happens when taking from the output >>> channel so nil is not technically on the channel, (unless it flows through >>> to another map). >>> >>> Is this a bug or is my mental model of nil => closed incorrect? >>> >>> Thanks, >>> Alejandro >>> >>> -- >>> 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. > -- "One of the main causes of the fall of the Roman Empire was that-lacking zero-they had no way to indicate successful termination of their C programs." (Robert Firth) -- 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.
