c++ - 标准关于可变参数模板的措辞

Question

14.5.3 [temp.variadic], paragraph 5

For the purpose of determining whether a parameter pack satisfies a rule regarding entities other than parameter packs, the parameter pack is considered to be the entity that would result from an instantiation of the pattern in which it appears. [Example:

template<class ... Types> void f(Types ... rest);
template<class ... Types> void g(Types ... rest) {
    f(&rest ...); // “&rest ...” is a pack expansion; “&rest” is its pattern
}

—end example]

委员会将实体的标题赋予参数包，这样lambda表达式就可以找到它的标识符而无需明确捕获它——参见this .话虽如此，我希望看到一个与使用参数包的 lambda 表达式相关的示例，但实际情况与我的预期相去甚远。我看不出上面的示例与措辞有何关系(我认为它应该与名称查找或其他内容有关)。此外，“实体”旁边的粗体文字的目的是什么(我几乎不明白它的意思......)？

Answer 1

我认为这是标准中的一个[小]编辑问题(我提交了一个关于它的问题)。有问题的文本是核心问题 1662 的结果, 建议在第 4 段末尾添加该文本，在这种情况下，整个文本将显示为:

A pack expansion consists of a pattern and an ellipsis, the instantiation of which produces zero or more instantiations of the pattern in a list (described below). The form of the pattern depends on the context in which the expansion occurs. Pack expansions can occur in the following contexts:
— In a function parameter pack [...]
— In a template parameter pack [...]
[...]
— In a fold-expression [...]
For the purpose of determining whether a parameter pack satisfies a rule regarding entities other than parameter packs, the parameter pack is considered to be the entity that would result from an instantiation of the pattern in which it appears.[Example:

template<class ... Types> void f(Types ... rest);
template<class ... Types> void g(Types ... rest) {
    f(&rest ...); // “&rest ...” is a pack expansion; “&rest” is its pattern
}

-end example]

这里的例子只是一个包扩展的例子——这是上一段介绍的术语。事实上，“For the purpose of...”部分已经成为自己的段落，而不是第 4 段的扩展，这使得示例的位置非常奇怪。

也就是说，示例无论如何都不是规范的，重要的是文本。