Possible to wrap or merge separate namespaces?

Question

I seem to recall seeing notes somewhere on a way to combine multiple namespaces into one.

Now, looking for said notes I am not finding them -- even searching using s

Answer 1

You can do this:

namespace c
{
    using namespace a;
    using namespace b;
}

But if a and b have elements with the same names, you won't be able to use them from namespace c.