How to make a function that accepts another one with variadic arguments-CodePudding

I need a function My_func that works like this

   auto f = [](string s, double c) { return c; };
    assert(My_func(f)(std::make_tuple("Hello", 8.5)) == f("Hello", 8.5'));

Now i have

template <class T>
auto My_func(T&& f) {
    return [f = std::forward<T>(f)](auto&& value) {

    };
}

What should i add?

CodePudding user response：

I believe you are looking for std::apply

#include <cassert>
#include <string>
#include <tuple>

template <class F>
constexpr auto My_func(F&& f) {
    return [f = std::forward<F>(f)](auto&& tuple) mutable {
        return std::apply(std::forward<decltype(f)>(f),
                          std::forward<decltype(tuple)>(tuple));
    };
}
int main() {
    auto f = [](std::string s, double c) { return c; };
    assert(My_func(f)(std::make_tuple("Hello", 8.5)) == f("Hello", 8.5));
}

This is essentially just a functor wrapper for std::apply, that is still useful because it would not be possible to pass it around due to it being a template.