  void print_vector(std::ostream& out, const CGAL::Vector_3<R>& v) {
    print_vector_impl(out, Nef_3_internal::get_vector(v) );
  }
  void print_vector(std::ostream& out, const CGAL::Vector_3<R>& v) {
    print_vector_impl(out, Nef_3_internal::get_vector(v) );
  }