namespaces and friends

Say you have two classes A and B that live in different namespaces. How would you make A's class be a friend of B's. The obvious solution does not seem to work.

Code:

---

namespace a {
      class b::B;
      class A {  friend class b::B; };
}

namespace b {
      class B {
           
      };
}

---

I pretty much fixed the problem with the code that I was working with by redesigning class A so that the variables were in protected space. Basically something like this

Code:

---

namespace a {
      class A { /* allow vars to be accessed as protected */ };
}

namespace b {
      class B;
      class C : public A { 
              friend class B;
      };

      class B  {
           
      };
}

---

However, I was wondering if this was something that C++ does not allow.

Your forward declaration of b::B isn't right....
You can have a forward decl. of a class that the compiler hasn't seen yet, but you can't have a forward decl. of a namespace that the compiler hasn't seen yet.

Code:

---

namespace b
{
    class B; // forward decl. of B in b
}

namespace a
{
    class A { friend class b::B; };
}

namespace b
{
    class B { };
}

---

gg