How can I cleanly specify which arguments I am passing and which remain default?

Question

Asked because of this: Default argument in c++

Say I have a function such as this: void f(int p1=1, int p2=2, int p3=3, int p4=4);

And

Answer 1

This isn't really an answer, but...

In C++ Template Metaprogramming by David Abrahams and Aleksey Gurtovoy (published in 2004!) the authors talk about this:

While writing this book, we reconsidered the interface used for named function parameter support. With a little experimentation we discovered that it’s possible to provide the ideal syntax by using keyword objects with overloaded assignment operators:

f(slew = .799, name = "z");

They go on to say:

We’re not going to get into the implementation details of this named parameter library here; it’s straightforward enough that we suggest you try implementing it yourself as an exercise.

This was in the context of template metaprogramming and Boost::MPL. I'm not too sure how their "straighforward" implementation would jive with default parameters, but I assume it would be transparent.