`count`在Clojure集合上的性能是什么？ [英] What is the performance of `count` on a Clojure set?

问题描述

所以，我看到对于Clojure向量，列表和映射， count 操作是 O（1）。

So, I read that the count operation is O(1) for a Clojure vectors, lists and maps.

(count [1 2 3]) ;=> 3

但是对于Clojure集合，它还是 O（1）我想象它可能是，但我不知道如何找到。我快速阅读了 http://clojure.org/data_structures#Data%20Structures-Sets

But is it also O(1) for a Clojure set? I imagine it probably is, but I'm not really sure how to find out. I had a quick read of http://clojure.org/data_structures#Data%20Structures-Sets, but couldn't see the info there.

推荐答案

这是 O（1）

您可以通过观察 clojure.lang.PersistentSet c $ c> _count 字段：

You can verify this by observing that clojure.lang.PersistentSet maintains a _count field in the Java source code:

https://github.com/clojure/clojure/blob/master/src/jvm/clojure/lang/PersistentList.java

这篇关于`count`在Clojure集合上的性能是什么？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！