void PM_io_parser<PMDEC>::print_hedge(Halfedge_handle e) const
{ // syntax: index { opposite, prev, next, vertex, face, mark }
  out << index(e) << " { "
      << index(twin(e)) << ", "
      << index(previous(e)) << ", " << index(next(e)) << ", "
      << index(target(e)) << ", " <<   index(face(e)) << ", "
      << mark(e) << " }\n";
}
void PM_io_parser<PMDEC>::print_hedge(Halfedge_handle e) const
{  
  out << index(e) << " { "
      << index(twin(e)) << ", "
      << index(previous(e)) << ", " << index(next(e)) << ", "
      << index(target(e)) << ", " <<   index(face(e)) << ", "
      << mark(e) << " }\n";
}