See my reply to Ken. I recommend against writing swap-meta! in your own code, except maybe as a shorthand for (swap! foo vary-meta); certainly don't implement it from the ground up when the language already gives you the function you want.
On Dec 12, 2:22 am, Alexander Yakushev <yakushev.a...@gmail.com> wrote: > On Dec 12, 12:36 am, Ken Wesson <kwess...@gmail.com> wrote: > > > > > You can "change" the metadata on the object held by the atom (if that > > object supports metadata) via (swap! a with-meta ...). > > > One thing a bit annoying is if you want to alter the metadata in an > > incremental way. To do that atomically requires a closure. Or defining > > a swap-meta! function, like so: > > > (defn swap-meta! [a f & args] > > (swap! a > > (fn [x] > > (with-meta x (apply f (meta x) args))))) > > I still very often mix up the state and identity in Clojure. What I > tried to do is to add metadata to the atom itself, not to the value it > holds. Now I see that it was kind of stupid:). > Your swap-meta! function is of great use, from now on I will use in > such cases. Thank you! > Your swap-meta! -- 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
