Hmm. (time isn't that reliable here. my lazy-shuffle might be quite slow after all.
On Jan 26, 10:46 pm, bOR_ <boris.sch...@gmail.com> wrote: > In addition to the functional shuffle thread (can't seem to post to > that one anymore, might be too old?), I've written alazy shuffle. Not > sure if it is the best way to write it, but I needed alazy shuffle > primarily because I wanted to randomly pair a few agents from a large > vector of agents without agents occurring one more than once. > > http://groups.google.com/group/clojure/browse_thread/thread/180842eb5... > > (defnlazy-shuffle > [coll] > (let [rand-pos (rand-int (count coll)) > [prior remainder] (split-at rand-pos coll)] > (lazy-cons (nth coll rand-pos) (lazy-shuffle(concat prior (rest > remainder)))))) > > user=> (time (take 50 (lazy-shuffle(range 10000)))) > > "Elapsed time: 0.246 msecs" > user=> (time (take 50 (shuffle-java (range 10000)))) > > "Elapsed time: 0.573 msecs" > > (defn frequencies > "Returns a map from distinct items in coll to the number > of times they appear." > [coll] > (reduce (fn [counts x] > (merge-with + counts {x 1})) > {} coll)) > > (frequencies (map (fn [n] (take 3 (lazy-shuffle(list 1 2 3)))) (range > 1000000))) > {(3 1 2) 166687, (1 2 3) 166126, (1 3 2) 167246, (3 2 1) 166918, (2 3 > 1) 166687, (2 1 3) 166336} --~--~---------~--~----~------------~-------~--~----~ 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 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 -~----------~----~----~----~------~----~------~--~---
