Templated friends?

Templated friends?

[Richard Guenther]

Hi!

Are we supposed to accept something like

template <class X>
class A {
        void bar() const;
        template <class Y>
        void foo(const A<Y>& a) const {
                a.bar();
        }
        template <class Y>
        friend class A;
};

int main(int argc, char **argv)
{
        A<int> a;
        A<double> b;
        a.foo(b);
        return 0;
}

The above gives

templatedfirends.cpp:5: error: `void A<X>::foo(const A<Y>&) const [with Y
= double, X = int]' is private
templatedfirends.cpp:16: error: within this context

which is incorrect(?)

Thanks, Richard.

--
Richard Guenther <richard.guenther@uni-tuebingen.de>
WWW: http://www.tat.physik.uni-tuebingen.de/~rguenth/

Re: Templated friends?

[Volker Reichelt]

Hi,

> template <class X>
> class A {
>         void bar() const;
>         template <class Y>
>         void foo(const A<Y>& a) const {
>                 a.bar();
>         }
>         template <class Y>
>         friend class A;
> };
>
> int main(int argc, char **argv)
> {
>         A<int> a;
>         A<double> b;
>         a.foo(b);
>         return 0;
> }

Your code is ill-formed. "foo" is a private member of "A" and therefore
can be called only inside member functions or friends. But "main" does not
belong to this category. You have to declare "foo" as a public member
to make the code compile.

Regards,
Volker