是否可以在可变参数模板函数中扩展非变量参数？ [英] Is it possible to expand non-variadic arguments in a variadic template function?

问题描述

通过一个例子来解释我的意思可能更容易。想象以下模板：

It is probably easier to explain what I mean by an example. Imagine a following template:

template <class... Args>
std::tuple<Args...> foo();

例如可以这样调用：

auto ret = foo<int, bool>();

但是，如果我想根据可变参数模板参数的数量将其他参数传递给函数，该怎么办？例如，假设我要为每个Args传递字符串文字：

But what if I want to pass additional arguments to the function, based on the number of variadic template arguments? For example, let's say I want to pass a character string literal for every Args:

auto ret = foo<int, bool>("a", "b");

此问题在于，似乎不可能扩展非变量论证，因此以下显然无法编译：

The problem with this, is that it does not seem possible to expand non-variadic arguments, so the following obviously doesn't compile:

template <class... Args>
std::tuple<Args...> foo(const char*... names);

是否有任何明智的实现方法？

Is there any sensible way to implement this?

推荐答案

您可以使用

template <class... Args>
std::tuple<Args...> foo(proxy<Args, const char*>... names);

其中 proxy 是

template<class T, class E>
using proxy = E;

您可以在此处看到以下内容： https://godbolt.org/g/SHBYzy

You can see this in action here: https://godbolt.org/g/SHBYzy

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