How Can I Pass a Tuple of Values as Arguments to a Variadic Template Function in C ?

Variadic Template Function Argument Expansion from Tuples

Consider a templated function with variadic template parameters:

template<typename Tret, typename... T> Tret func(const T&... t);

How can you call func() using a tuple of values as the arguments?

Modern C Solution (C 17 and Later)

In C 17, the std::apply() function provides an elegant solution:

std::apply(the_function, the_tuple);

Clang 3.9 Workaround

If you're using Clang 3.9, you can use the std::experimental::apply function instead.

Handling Templated Functions

If the_function is templated, you can use the following workaround:

#include <tuple>

template <typename T, typename U> void my_func(T &&t, U &&u) {}

int main() {

  std::tuple<int, float&> my_tuple;

  std::apply([](auto &&... args) { my_func(args...); }, my_tuple);

  return 0;
}

Generalized Overload Set Invocation

For a more versatile solution that can handle overload sets and function templates, refer to the comprehensive explanation at https://blog.tartanllama.xyz/passing-overload-sets/.

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