> > > Most of the cache implementations in core.cache have no side-effects. They > simply return a new cache rather than overwriting the old one. The memoize > library places the cache in an atom, so it's guaranteed to change > atomically. >
I tried to read the cache code (btw an excellent exercise) , and I think I understand how persistent data structure/atom is employed here in case we deal with side effects free functions. > You could write this as a function. There's nothing in there that requires > a macro. > > (defn when-map-future-swap! [a k f] > (locking a > (when-not (contains? @a k) > (swap! a assoc k nil) > (future (swap! a assoc k (f k)))))) > I realized that later too ... But I'd personally just use a delay rather than "locking" for this purpose. > It is not that I like locking at all. However I still fail to see, how in a multithreaded context memoize/cache prevents executing a given function more than once (which I want to avoid at any cost here) since cache lookup and swap! does not seem to be atomic : https://github.com/clojure/core.cache/blob/master/src/main/clojure/clojure/core/cache.clj#L52 . Best regards, Andy -- 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 --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
