counted?

functionsince v0.0-927 clojure.core/counted?Edit
(counted? x)

Details:

Returns true if x executes count in constant time, false otherwise.

Lists, maps, sets, strings, and vectors can be counted in constant time.


Source docstring:
Returns true if coll implements count in constant time
Source code @ clojurescript:src/main/cljs/cljs/core.cljs
(defn ^boolean counted?
  [x] (satisfies? ICounted x))