TITLE: Templates and friends

PROBLEM: tim@cometric.COM (Tim Sampson)

I have
a template class (kid) with a function (sound) which would like to call a
private function (oink) of a a non-template class (wanta).  As hard as I
try I cannot figure out how to make the template class a friend of the
non-template class.

    class wanta
	{
	friend class kid;			// does no good.
	private: void oink ();
	};
     ...
    template <int i> class kid: public pa
	{
	public: void sound () {be->oink ();}
	};


RESPONSE: steve@taumet.com (Steve Clamage)

The problem is that there is no class "kid" in your program;
there is a template class kid<something>, which is a shorthand
for an unbounded set of different classes with different names.

You can make individual template instantiations friends of class wanta,
but I don't think there is a way to make all possible instantiations
into friends of wanta.

For example:

	template <int i> class kid; // forward declaration

	class wanta { ... friend kid<10>; friend kid<39>; ... };

In this case, it might make sense to make the int a parameter of the
constructors of a non-template class kid, rather than a template
parameter.  I can't tell from the posted code whether this would be
a good solution or not.

Otherwise, you could make wanta::oink into a public function, or
provide a public function which provides what you want from oink
without making it completely public.