> > 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. -- 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
