On 21 February 2010 12:55, Jarkko Oranen <chous...@gmail.com> wrote: >> >> But surely in this case you could do: >> >> (defn print-info [] >> (let [[src dst] (dosync [...@source-account @dest-account])] >> (println src) >> (println dst))) >> >> or maybe: >> >> (defn print-info [] >> (let [[src dst] (dosync >> (ensure source-account) >> (ensure dest-account) >> [...@source-account @dest-account])] >> (println src) >> (println dst))) >> >> I suspect the ensures are necessary, but I would appreciate it if >> someone could explain why they are (or are not) necessary in this >> case. > > As far as I know, dosync guarantees that the derefs are consistent > with each other. That is, no other transaction can affect the return > value of the deref while the transaction is running. However, deref > doesn't guarantee that the values read are still current when the > transaction finishes. Some other transaction might have been committed > first. If you absolutely need the most recent values, not just > consistent ones, you need to use ensure.
OK, so ensure is not necessary in this case. Thanks. -- Michael Wood <esiot...@gmail.com> -- 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
