Re: Template<void>

The name "callbackbase" is used for the base class,
just to factor out the non-template parts. Other than that
it is never used. I wondered if we couldn't use an
otherwise-unused version of the template instead. Is this
legal (or could it be made legal with relatively few changes)?

(Untested code):

[begin]
template < class T >
class callback;

template<>
class callback<void> {
public:
    virtual void operator()() const { };
    virtual ~callback() = 0;
};
callback<void>::~callback() { }

template < class T >
class callback : public callback<void> {
public:
    typedef void (T::*Func)();
    callback( T& t, Func func ) : object(&t), f(func) { }
    void operator()() const { (object->*f)(); }
private:
    T* object;
    Func f;
};
[end]