什么时候超载逗号运算符？

问题描述

我会在C ++中看到关于重载逗号运算符的问题（主要与重载本身无关，但是类似序列点的概念），这让我想到：

当应时，您的逗号超载了吗？它的实际用途是什么？

我只是想不到任何例子在我的头顶部，我看到或需要的东西像

  foo，bar; 
  

在现实世界的代码，所以我很好奇，

解决方案

让我们将重点改为：

答案：永不。

例外：如果你正在进行模板元编程，运算符放置在运算符优先级列表的最底部，这对于构造SFINAE-guard等可以派上用场。

我看到的只有两个实际用途运算符都位于中：

• –它的根本在于它允许Phoenix lambdas支持多个语句

I see questions on SO every so often about overloading the comma operator in C++ (mainly unrelated to the overloading itself, but things like the notion of sequence points), and it makes me wonder:

When should you overload the comma? What are some examples of its practical uses?

I just can't think of any examples off the top of my head where I've seen or needed to something like

foo, bar;

in real-world code, so I'm curious as to when (if ever) this is actually used.

解决方案

Let's change the emphasis a bit to:

The answer: Never.

The exception: If you're doing template metaprogramming, operator, has a special place at the very bottom of the operator precedence list, which can come in handy for constructing SFINAE-guards, etc.

The only two practical uses I've seen of overloading operator, are both in Boost:

• Boost.Assign
• Boost.Phoenix – it's fundamental here in that it allows Phoenix lambdas to support multiple statements

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