friend functions of a class inside a namespace

Question

I\'ve two question about this code bellow:

namespace A { class window; }

void f(A::window);

namespace A
{
    class window
    {
    private:
       int a;         


        

Answer 1

As for 1), your function is not in the namespace, so you must use :: to tell the compiler to search it outside the namespace.

Otherwise, it will only look for function inside the namespace (that's why they exist). Koenig lookup doesn't apply here, as window class is inside the namespace.

not too sure about 2) though, but i bet it is related to 1).