It's worth knowing that the "moment" is implemented via a compare-and-set, and if the value has been changed (by another thread), the fn you passed to swap! will be called again with the atom's new value. On Jun 28, 2013 11:57 PM, "Greg" <g...@kinostudios.com> wrote:
> OK, I've found something that shows how these two work when used in the > implementation of a generator: > > https://gist.github.com/daveray/1263503 > > I think I understand what the problem is now: > > (reset! id (inc @id)) > > There's a "time gap" in between the dereference of 'id' and its assignment > back to 'id' (after being incremented). > > With swap!, no such problem exists, because it's an atomic operation where > there is no such "time gap" between dereferencing, applying a function, and > setting the new value. That all takes place in on magical atomic moment. > > If I've got this wrong, please let me know! > > Cheers, > Greg > > On Jun 28, 2013, at 11:19 PM, Greg <g...@kinostudios.com> wrote: > > Can anyone explain the relationship between swap! and reset! ? > > Why is using swap! in this example "safe" and using reset! not? > > I've tried searching google for comparisons of the two but can't find > anything, and the documentation doesn't help much. > > Thanks, > Greg > > On Jan 21, 2013, at 6:22 PM, Stephen Compall <stephen.comp...@gmail.com> > wrote: > > On Jan 21, 2013 3:28 PM, "Jim - FooBar();" <jimpil1...@gmail.com> wrote: > > ...or you can go all the way, skipping reset! completely: > > > > (swap! game-objects (fn [objects] (reduce-kv #(assoc % %2 (update-object > %3)) {} objects) )) > > Which also has the benefit of being safe, unlike any reset!-based update. > > -- > Stephen Compall > If anyone in the MSA is online, you should watch this flythrough. > > -- > 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 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. > > > -- -- 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.
