What to do with private member functions when turning static class to namespace in C++?

Question

I have a class that has 5 static public functions and 1 static private function (called from one of the public functions). The class doesn't have any member variables. It seems to me that it should be a namespace and not a class. But what to do with the private function? I prefer it not to be accessible by every namespace user, but there is no access control in namespaces.

Answer 1

There are two ways i know of

Don't declare them in the header

One way is to not declare those functions inside the header. They can be placed into unnamed namespaces within the implementation file, only.

Indeed, you will then have to implement any function that accesses this private function in the implementation file (not inline in the header).

Put them into a detail namespace

Preferably, you put them in a different header, and include them. So the code of them won't disturb your interface header. This is how boost does it, too:

#include "detail/destroy.hpp"

namespace orbit {
  void destroy() {
    detail::destroy_planets();
    detail::destroy_stars();
  }
}

Answer 2

I don't think there is a solution to this :)

One -different- solution, would be to separate these functions into a separate compilation unit, then declare the private functions inside an anonymous namespace.

Answer 3

Keep the public declaration in the header file. Move the implementations to a cpp file. Mark previously private methods as static. This will make them unaccessible from a different linker objects (compilation units) and effectively hide them.