class AnInterface_var : public _var {
protected:

    AnInterface_ptr ptr;

public:

    AnInterface_var () { ptr = AnInterface::_nil (); }
    AnInterface_var (AnInterface_ptr p) { ptr = p; }

    ...

    ~AnInterface_var () {
        release (ptr);
    }

    AnInterface_var &operator = (AnInterface_ptr p) {
        release (ptr);
        ptr = p;
        return (*this);
    }

    AnInterface_var &operator = (const AnInterface_var &var) {
        if (this != &var) {
            release (ptr);
            ptr = AnInterface::_duplicate (AnInterface_ptr (var));
        }
        return (*this);
    }

    operator AnInterface_ptr & () { return (ptr); }
    AnInterface _ptr operator -> () const { return (ptr); }

    ...
}