const_iterator和iterator之间有什么区别？ [英] what is the difference between const_iterator and iterator?

问题描述

这两个有关STL中的实现有什么区别。
关于性能有什么区别？
我想当它是只读，我们喜欢const_iterator。

谢谢。

解决方案

。

const_iterator 返回对常量值的引用（ const T& code>）并阻止修改引用的值：它强制执行 const -correctness 。

当你有一个const引用容器时，你只能得到一个 const_iterator 。

已编辑：我提到 const_iterator 返回常量指针

编辑：对于COW对象，获取非const迭代器（或取消引用）它）可能会触发副本。 （一些过时的，现在不允许的 std :: string 的实现使用COW。）

What is difference between these two regarding implementation inside STL. what is the difference regarding performance? I guess when it is read only, we prefer const_iterator. right?

Thank you.

解决方案

There is no performance difference.

The const_iterator returns a reference to a constant value (const T&) and prevents modification of the referenced value: it enforces const-correctness.

When you have a const reference to the container, you can only get a const_iterator.

Edited: I mentionned "The const_iterator returns constant pointers" which is not accurate, thanks to Brandon for pointing it out.

Edit: For COW objects, getting a non-const iterator (or dereferencing it) will probably trigger the copy. (Some obsolete and now disallowed implementations of std::string use COW.)

这篇关于const_iterator和iterator之间有什么区别？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！