Thread: Finding friends

I am trying to decipher the following paragraph from chapter 11.5.1 of Bjarne Stroustrup's The C++ Programming Language:

"A friend class must be previously declared in an enclosing scope or defined in the non-class scope immediately enclosing the class that is declaring it a friend. Scopes outside the innermost enclosing namespace scope are not considered."

The following compliles and runs fine with Code::Blocks GCC, so I presume that the word "previously" relates only to "declared" and not to "defined", since the definition of class Y comes after that of class X:

Code:

#include <iostream>

using namespace std;

namespace out
{
class X
{
    int i;
    public:
    X(int j = 0):i(j){}
    friend class Y;
};

 class Y
{
    public:
    void f(X x){cout << x.i;}
};

}

int main()
{
    out::X x(101);
    out::Y y;
    y.f(x);
}

Likewise, the following compliles and runs fine with the same compiler, so I presume the second sentence relates only to definition and not to declaration, since the declaration of class Y is outside the innermost enclosing namespace and yet it is evidently being considered:

Code:

#include <iostream>

using namespace std;

class Y;

namespace out
{
class X
{
    int i;
    public:
    X(int j = 0):i(j){}
    friend class Y;
};
}

 class Y
{
    public:
    void f(out::X x){cout << x.i;}
};

int main()
{
    out::X x(101);
    Y y;
    y.f(x);
}

To sum up, I would interpret the text to mean the following:

A friend class must be declared previously in an enclosing scope or defined somewhere in the non-class scope immediately enclosing the class that is declaring it a friend. In the latter case, scopes outside the innermost namespace scope or not considered.

Is that right?