Modern C++ Programming Cookbook

How to do it...

The std::invoke() function is a variadic function template that takes the callable object as the first argument and a variable list of arguments that are passed to the call. std::invoke() can be used to call the following:

• Free functions:

        auto a1 = std::invoke(add, 1, 2);   // a1 = 3

• Free functions through pointer to function:

        auto a2 = std::invoke(&add, 1, 2);  // a2 = 3         int(*fadd)(int const, int const) = &add;         auto a3 = std::invoke(fadd, 1, 2);  // a3 = 3

• Member functions through pointer to member function:

        foo f;         std::invoke(&foo::increment_by, f, 10);

• Data members:

        foo f;         auto x1 = std::invoke(&foo::x, f);  // x1 = 0

• Function objects:

        foo f;         auto x3 = std::invoke(std::plus<>(),   std::invoke(&foo::x, ...