Unpacking arguments of a functional parameter to a C++ template class

Question

I have a question involving functional template arguments to template classes in C++.

I\'d like to define a template class Foo taking a single template

Answer 1

Declare a primary template and leave it unimplemented.

template
struct foo;     // unimplemented primary template

Then provide a partial specialization that matches function types as the template argument.

template
struct foo
{
    using args_t = std::tuple;
};

You can access the nested type as

foo::args_t

Live demo