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?
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
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