On Tue, Nov 30, 2010 at 5:27 PM, Robert McIntyre <r...@mit.edu> wrote: > Why not use good old runonce from lancet? > > (defn runonce > "Create a function that will only run once. All other invocations > return the first calculated value. The function can have side effects. > Returns a [has-run-predicate, reset-fn, once-fn]" > [function] > (let [sentinel (Object.) > result (atom sentinel) > reset-fn (fn [] (reset! result sentinel) nil) > has-run? #(not= @result sentinel)] > [has-run? > reset-fn > (fn [& args] > (locking sentinel > (if (= @result sentinel) > (reset! result (function)) > @result)))]))
Eww. Why (locking ...)? Why not just (swap! result #(if (= % sentinel) (function) %))? -- 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
