Thanks, man! I ended up using atoms.
On Tuesday, March 20, 2012 2:13:18 PM UTC-7, Cedric Greevey wrote: > > On Tue, Mar 20, 2012 at 11:16 AM, Tom Krestle <tom.kres...@gmail.com> > wrote: > > Greetings, > > > > I've stumbled across the following problem, which I believe is common and > > should have some sort of generic solution. Imagine I have > > > > ... ;; code inside defn > > ;; I extract some information out of my atom in closure: > > (swap! my-atom > > (fn [val] > > (let [extracted-info1 (extract-something-from val) > > extracted-info2 (extract-something-else-from val)] > > ;; update the atom > > (-> val > > (assoc ...) (assoc))))) ;; out of swap! > > > > ;; still code inside defn > > ;; now, here I need to use those extracted-info1, extracted-info2 that I > got > > out of atom inside swap! operation > > ;; What would be the common way to pass that information here? Using vals > > doesn't sound right. > > > > Have a beer! > > Tom > > The ugly way, as you noted, is to change the atom from some-map to > [some-map extracted-info-from-last-swap]. > > A less ugly way might be > > (let [ei (atom nil)] > (swap! my-atom > ... > (reset! ei extracted-info1) > ...) > (do-things-with ei)) > > If the swap! is retried, the ei atom will be reset! more than once, > but it will after the swap! contain the extracted-info1 from the > successful swap! of my-atom. > > The most functional way would be to see if you couldn't do the work > with ei *inside* the closure. However, if it's expensive or > side-effecty that doesn't play nice with swap! retrying. In that > instance, you might want to think of replacing my-atom with my-ref and > doing something like > > (dosync > (alter my-ref > ... > (send-off ei-agent ei-do-things-func extracted-info1) > ...)) > > Agent sends are held until a transaction commits, so the > ei-do-things-func will be called only once for each transaction on > my-ref. > > -- 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
