void SM_io_parser<Decorator_>::print_loop(SHalfloop_const_handle l) const
{ // syntax: index { twin, face, mark, circle }
  out << index(l) << " { "
      << index(l->twin()) << ", "
      << index(l->incident_sface()) << ", "
      << l->mark() << ", " << l->circle() << " }\n";
}
void SM_io_parser<Decorator_>::print_loop(SHalfloop_const_handle l) const
{  
  out << index(l) << " { "
      << index(l->twin()) << ", "
      << index(l->incident_sface()) << ", "
      << l->mark() << ", " << l->circle() << " }\n";
}