  void print_vector_impl(std::ostream& out, const CGAL::Vector_3<R> v, Null_functor)
  {
    out << v.x() << " " << v.y() << " " << v.z() << " " << 1;
  }
  void print_vector_impl(std::ostream& out, const CGAL::Vector_3<R> v, Null_functor)
  {
    out << v.x() << " " << v.y() << " " << v.z() << " " << 1;
  }