Looking through my recent work I see that a number of atoms, swap! and reset! calls have snuck into my work, usually when there's an expensive operation like reading and parsing a large file or connecting to a database. I find I'm doing things like
(def conf (atom nil)) (defn config [] (if (nil? @conf) (reset! conf (read-and-expensively-parse "somefile.xml")) @conf)) So that the first time (config) is called it will do the operation, but future attempts will simply deref the atom. Recent discussions here alerted me to memoize which will do this without the atom, but the documentation mentions that the functions that are memoized should be referentially transparent. Although I'm pretty sure that while my server is running, the config will not change - it can't be guaranteed in a formal sense. Reading a file or connecting to an external process is doing io of course, in theory someone could change the file while my back was turned. Questions: if I was prepared to live with the consequences of having to restart the server if the conf file had been changed, would it be more idiomatic to use use memoize to avoid mutating state? If I really had to change a conf file while the server was running, is there any way a memoized function could have it's cache cleared? I suspect the answer to that one is no - but you never know.... -- 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.
