On Tue, Nov 30, 2010 at 7:23 PM, Alex Osborne <a...@meshy.org> wrote: >> Eww. Why (locking ...)? Why not just (swap! result #(if (= % sentinel) >> (function) %))? > > From the doc string: "The function can have side effects." > > Sometimes a lock is the right tool for the job.
I put a println in a swap! function once and the world didn't end. It just seems to me that the code that was posted more or less reinvents a (weak) form of swap! using reset! and locking. The requirements for runonce seem clear enough: the thing should run only once, so, you should check if it has already been run and if not run it and the check-and-maybe-run needs to be done atomically. And the original code even uses an atom to represent the has-it-run-yet? state. And swap!s on a single atom are supposed to be atomic, any given swap! definitely happening before or after any other given swap! on the same atom. So... -- 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
