为什么在C ++ 0x中有一个sizeof ...运算符？ [英] Why is there a sizeof... operator in C++0x?

问题描述

我看到@GMan实施了 a版本的 sizeof ... 可变参数模板（据我所知）相当于内置的 sizeof .. 。。这不符合第二个设计原则： 更喜欢图书馆

std.org/jtc1/sc22/wg21/docs/papers/2006/n2080.pdfrel =nofollow>变化模板（版本3）
（N2080 = 06-0150），第6页：

虽然不是绝对必要的（我们可以实现 count 检查参数包的长度是一种常见的操作，值得一个简单的语法。此外，当可变参数模板与概念结合时，这种操作对于类型检查原因可能变得必要;见第3.3节。

（第3.3节谈到现在无关的概念。）

I saw that @GMan implemented a version of sizeof... for variadic templates which (as far as I can tell) is equivalent to the built in sizeof.... Doesn't this go against the second design principle: prefer libraries to language extensions?

解决方案

From Variadic Templates (Revision 3) (N2080=06-0150), page 6:

Although not strictly necessary (we can implement count without this feature), checking the length of a parameter pack is a common operation that deserves a simple syntax. Moreover, this operation may become necessary for type-checking reasons when variadic templates are combined with concepts; see Section 3.3.

(Section 3.3 talks about concepts which is irrelevant now.)

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