The recent changes to iterate come with an interesting consequence: reducing an iterate multiple times will cause the entire chain of x, (f x), (f (f x)) .. to be recalculated every time.
I'd argue that this is not desiderable and a regression (even though probably one considered by design), and that this change in behaviour is going to produce a degradation in performance when the function to iterate actually does some computation rather than being a trivial function like the one used in the benchmarks in the CLJ-1603 ticket (inc) since its result won't be cached. If changing the new behaviour is out of the question I'd suggest to at least document this new behaviour. The docstring of iterate talks about returning a lazy-seq while when used with reduce it is actually a generator. To show what I mean here's a silly example using Threa/sleep to simulate computation: Clojure 1.7.0-alpha5 user=> (def a (iterate #(do (Thread/sleep 2) (inc %)) 0)) #'user/a user=> (time (reduce (fn [_ x] (if (= 50 x) (reduced nil))) nil a)) "Elapsed time: 106.385891 msecs" nil user=> (time (reduce (fn [_ x] (if (= 50 x) (reduced nil))) nil a)) "Elapsed time: 0.560275 msecs" nil Clojure 1.7.0-master-SNAPSHOT user=> (def a (iterate #(do (Thread/sleep 2) (inc %)) 0)) #'user/a user=> (time (reduce (fn [_ x] (if (= 50 x) (reduced nil))) nil a)) "Elapsed time: 109.088477 msecs" nil user=> (time (reduce (fn [_ x] (if (= 50 x) (reduced nil))) nil a)) "Elapsed time: 109.51494 msecs" nil -- 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.
