How to have a template class as friend?

[Chris Dams]

Dear all,

I would like to have a template class as friend of another class. If I write

class c
{ friend class t;
};

template <class T> class t
{
};

then this is not allowed and on my g++ version 4.0.2. It says that
"t is not a template type". Apparently this is because of the friend
declaration, because if I comment it out, the code compiles without errors.
But I want t to be a friend of c no matter what the template argument
of t is. Can anyone tell me how to do this?

Many thanks,
Chris

 

[Victor Bazarov]

I would like to have a template class as friend of another class. If
I write

class c
{ friend class t;
};

template <class T> class t
{
};

then this is not allowed and on my g++ version 4.0.2. It says that
"t is not a template type". Apparently this is because of the friend
declaration, because if I comment it out, the code compiles without
errors. But I want t to be a friend of c no matter what the template
argument
of t is. Can anyone tell me how to do this?

class c
{
void foo(); // private
template<class T> friend class t; // 't' is a template
};

template<class T> class t {
public:
void bar(c& cc) { cc.foo(); }
};

int main() {
t<int> tt;
c cc;
tt.bar(cc);
}


V

 

[Howard]

class c
{
void foo(); // private
template<class T> friend class t; // 't' is a template
};

template<class T> class t {
public:
void bar(c& cc) { cc.foo(); }
};

int main() {
t<int> tt;
c cc;
tt.bar(cc);
}

I was just wondering that myself. Thanks, Victor.

(P.S., "tt.bar"? Haven't been to one of those in a while...)

 

[Victor Bazarov]

[..]
(P.S., "tt.bar"? Haven't been to one of those in a while...)

I've never been to any of those! I just heard about them on t.vee()

V

 

[Chris Dams]

Dear Victor,

template<class T> friend class t; // 't' is a template

Thanks!

I had instead been trying variations of

friend template<class T> class t;

and that didn't work.

Best wishes,
Chris