Filter the set in Clojure clojure.set / select vs. clojure.core / filter

Question

I would like to filter out a set, something like:

(filter-set even? #{1 2 3 4 5}) ; => #{2 4} 

If I use clojure.core/filter , I get seq, which is not a set:

 (filter even? #{1 2 3 4 5}) ; => (2 4) 

So, the best I came with is:

 (set (filter even? #{1 2 3 4 5})) 

But I don’t like it, it doesn’t look optimal to go from set to list back to set. What will be the method of Kladura for this?

UPDATE

I did the following to compare @ A.Webb and @Beyamor approaches. Interestingly, both have almost identical performance, but clojure.set/select slightly better.

 (defn set-bench [] (let [big-set (set (take 1000000 (iterate (fn [x] (int (rand 1000000000))) 1)))] (time (set (filter even? big-set))) ; "Elapsed time: 422.989 msecs" (time (clojure.set/select even? big-set))) ; "Elapsed time: 345.287 msecs" nil) ; don't break my REPL ! 

Answer 1

clojure.set is a convenient API for regular typing operations.

In this case, clojure.set / select is an installation-specific filter. It works by dissociating elements that do not match a predicate from a given set.

 (require 'clojure.set) (clojure.set/select even? #{1 2 3 4 5}) ; => #{2 4}