問題描述

我經(jīng)常看到關(guān)于在 C++ 中重載逗號(hào)運(yùn)算符的問題(主要與重載本身無關(guān)，但與序列點(diǎn)的概念有關(guān))，這讓我感到疑惑:

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:

什么時(shí)候應(yīng)該重載逗號(hào)?它的實(shí)際用途有哪些例子?

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

我只是想不出任何我見過或需要的例子

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;

在現(xiàn)實(shí)世界的代碼中，所以我很好奇何時(shí)(如果有的話)實(shí)際使用它.

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

推薦答案

讓我們稍微改變一下重點(diǎn):

Let's change the emphasis a bit to:

什么時(shí)候你應(yīng)該重載逗號(hào)?

When should you overload the comma?

答案:從不.

例外:如果你在做模板元編程，operator, 在運(yùn)算符優(yōu)先級(jí)列表的最底部有一個(gè)特殊的位置，它可以派上用場(chǎng)，用于構(gòu)建 SFINAE-guards 等.

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.

我見過的重載 operator, 的僅有的兩個(gè)實(shí)際用途都在 Boost:

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

• Boost.Assign
• Boost.Phoenix這里的基礎(chǔ)在于它允許 Phoenix lambdas 支持多個(gè)語句

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

這篇關(guān)于什么時(shí)候重載逗號(hào)運(yùn)算符?的文章就介紹到這了，希望我們推薦的答案對(duì)大家有所幫助，也希望大家多多支持html5模板網(wǎng)！