partially specialized friend

[er]

hi,

here's my problem:

template<class T,unsigned int I> class A;

template<unsigned int I>
class B{

// how 2 make A<T,I> a friend, with T as a template parameter?

};

 

[jason.cipriani]

hi,

here's my problem:

template<class T,unsigned int I> class A;

template<unsigned int I>
class B{

// how 2 make A<T,I> a friend, with T as a template parameter?

};

You will either have to specify the type T in the friend declaration:

template<class T,unsigned int I> class A;

template<unsigned int I>
class B {
friend class A<int,I>; // T is int
};

Or you will have to provide another template parameter to B to use for
T:

template<class T,unsigned int I> class A;

template<class T,unsigned int I>
class B {
friend class A<T,I>;
}

AFAIK there is no way to say "declare all A<T,I> as friends of B<I>
for any T". C++03 [14.5.3/9] reads:

Friend declarations shall not declare partial specializations.
[Example:
template<class T> class A { };
class X {
template<class T> friend class A<T*>; // error
};
--end example]

As a sanity check I tested the following:

template<class T,unsigned int I> A;

template<unsigned int I>
class B {
template<class T> friend class A<T,I>;
};

And it fails with the expected error:

"ComeauTest.c", line 11: error: a friend declaration may not declare a
partial
specialization
template <class T> friend class A<T,I>;

So I do not think it is possible.

Jason

 

[er]

hi,

here's my problem:

template<class T,unsigned int I> class A;

template<unsigned int I>
class B{

// how 2 make A<T,I> a friend, with T as a template parameter?

};

You will either have to specify the type T in the friend declaration:

template<class T,unsigned int I> class A;

template<unsigned int I>
class B {
friend class A<int,I>; // T is int

};

Or you will have to provide another template parameter to B to use for
T:

template<class T,unsigned int I> class A;

template<class T,unsigned int I>
class B {
friend class A<T,I>;

}

AFAIK there is no way to say "declare all A<T,I> as friends of B<I>
for any T". C++03 [14.5.3/9] reads:

Friend declarations shall not declare partial specializations.
[Example:
template<class T> class A { };
class X {
template<class T> friend class A<T*>; // error};

--end example]

As a sanity check I tested the following:

template<class T,unsigned int I> A;

template<unsigned int I>
class B {
template<class T> friend class A<T,I>;

};

And it fails with the expected error:

"ComeauTest.c", line 11: error: a friend declaration may not declare a
partial
specialization
template <class T> friend class A<T,I>;

So I do not think it is possible.

Jason

Thanks much. Adding a template parameter would B would be really
inconvenient in my case, as I'd have to do so for its clients as well.
I take it i'll just have to do without friend.

 

[er]

You will either have to specify the type T in the friend declaration:

template<class T,unsigned int I> class A;

template<unsigned int I>
class B {
friend class A<int,I>; // T is int

Or you will have to provide another template parameter to B to use for
T:

template<class T,unsigned int I> class A;

template<class T,unsigned int I>
class B {
friend class A<T,I>;

}

AFAIK there is no way to say "declare all A<T,I> as friends of B<I>
for any T". C++03 [14.5.3/9] reads:

Friend declarations shall not declare partial specializations.
[Example:
template<class T> class A { };
class X {
template<class T> friend class A<T*>; // error};

--end example]

As a sanity check I tested the following:

template<class T,unsigned int I> A;

template<unsigned int I>
class B {
template<class T> friend class A<T,I>;

And it fails with the expected error:

"ComeauTest.c", line 11: error: a friend declaration may not declare a
partial
specialization
template <class T> friend class A<T,I>;

So I do not think it is possible.

Jason

Thanks much. Adding a template parameter would B would be really
inconvenient in my case, as I'd have to do so for its clients as well.
I take it i'll just have to do without friend.

.... or dont' specialize: template<class,unsigned int> friend class A;

 

[jason.cipriani]

... or dont' specialize: template<class,unsigned int> friend class A;

Ha... I guess that works, too. <g>