Is it possible to expand non-variadic arguments in a variadic template function?

Question

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

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

It can be invoked, for example, like this:

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

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"); 

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); 

Is there any sensible way to implement this?

Answer 1

You can do this with something like

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

where proxy is

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

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