On 8 March 2010 05:31, Eugen Dück <eu...@dueck.org> wrote: > And here's a variant that evicts elements when the size of the cache > exceeds some limit. In that case, the first item that was put in it > will be dissoc'ed. I'm using an array-map to accomplish this:
I don't think this will work as you expect it to. There are two reasons: (1) Array maps are transparently converted to hash maps when they grow beyond a certain size: user> (class (array-map :a 1 :b 2 :c 3 :d 4 :e 5 :f 6 :g 7 :h 8)) clojure.lang.PersistentArrayMap user> (class (assoc (array-map :a 1 :b 2 :c 3 :d 4 :e 5 :f 6 :g 7 :h 8) :i 9)) clojure.lang.PersistentArrayMap user> (class (assoc (array-map :a 1 :b 2 :c 3 :d 4 :e 5 :f 6 :g 7 :h 8) :i 9 :j 10)) clojure.lang.PersistentHashMap (2) More importantly, if you dissoc the first key from an array map, then assoc a new key onto the array map, the newly assoc key will take the first slot: user> (first (assoc (dissoc (array-map :a 1 :b 2 :c 3) :a) :d 4)) [:d 4] I'd suggest a vector instead; they're countable in constant time and you can use, say, conj and rest for add to end of queue / eject from front of queue. The idea is certainly a good one, though, so with the above mentioned issues fixed, this will be a nice utility function. Thanks for sharing! Sincerely, Michał -- 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
