std::ostream& operator<<
 (std::ostream& os, const Nef_polyhedron_2<T,Items,Mark>& NP)
{
  os << "Nef_polyhedron_2<" << NP.EK.output_identifier() << ">\n";
  typedef typename Nef_polyhedron_2<T,Items,Mark>::Decorator Decorator;
  CGAL::PM_io_parser<Decorator> O(os, NP.pm()); O.print();
  return os;
}
std::ostream& operator<<
 (std::ostream& os, const Nef_polyhedron_2<T,Items,Mark>& NP)
{
  os << "Nef_polyhedron_2<" << NP.EK.output_identifier() << ">\n";
  typedef typename Nef_polyhedron_2<T,Items,Mark>::Decorator Decorator;
  CGAL::PM_io_parser<Decorator> O(os, NP.pm()); O.print();
  return os;
}