5 template <class T> struct B
9 B(T x, T y) : a(x), b(y) {}
10 template <class U> operator B<U> () const
11 { return B<U>((U)(this->a), (U)(this->b)); }
14 template <class T> struct C : public B<int>
17 inline T & operator *() { return *c; }
20 template <class T> struct D : virtual public C<T> { };