为什么operator =返回引用而不是const引用 [英] Why operator= returns reference not const reference

问题描述

原来的问题是与重载operator =相关，我喜欢分享我的发现，因为对我来说这是非常重要的。
我不能想象合理的例子使用（a = b）作为左值。
在IRC和google的帮助下，我发现了下一篇文章：
http://msdn.microsoft.com/en-us/magazine/cc301415.aspx

The original question is related to overloading operator= and I like to share my findings as it was nontrivial for me to find them. I cannot imagine reasonable example to use (a=b) as lvalue. With the help of IRC and google I've found the next article: http://msdn.microsoft.com/en-us/magazine/cc301415.aspx

它提供了两个例子。

  (a=b)=c

  f(T& );
  f(a=b)

但两者都不好，我相信是不好的做法。
第二个给我相同的感觉。

but both a bit not good, and I believe that it is bad practice. The second one give me the same feeling. Could you provide more good examples why it should be non constant?

推荐答案

一个很好的理由是，其中一个标准中要求在标准容器中可用的类 X 的要求是，表达式 a = b 类型 X& （其中 a 是类型 X 和 b 是类型 X 的右值。

One good reason is that one of the requirements in the standard for a class X to be useable in the standard containers is that the expression a = b must have type X& (where a is an lvalue of type X and b is an rvalue of type X).

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