*operation* void get_single_vertex(Vertex*& v)
  *wrapper* Vertex_selector
    *prefix*
    (@
    @)
  *wrapper* Any_term
    *prefix*
    (@
       derror('i',1," unexpected visit at Any_term::get_single_vertex\n");
       abort();
    @)
  *wrapper* Vertex_set
    *prefix*
    (@
       derror('i',1," unexpected visit at Vertex_set::get_single_vertex\n");
       abort();
    @)
  *wrapper* Vertex_set_comp
    *prefix*
    (@
       derror('i',1," unexpected visit at Vertex_set_comp::get_single_vertex\n");
       abort();
    @)
  *wrapper* Class_set_inst
    *prefix*
    (@
       derror('i',1," unexpected visit at Class_set_inst::get_single_vertex\n");
       abort();
    @)
  *wrapper* Late_selected_terms
    *prefix*
    (@
       derror('i',1," unexpected visit at Late_selected_terms::get_single_vertex\n");
       abort();
    @)
  *wrapper* Fixed_term
    *prefix*
    (@
      vertex->get_single_vertex(v);
    @)
  *wrapper* Vertex_set_sim
    *prefix*
    (@
       derror('i',1," unexpected visit at Vertex_set_sim::get_single_vertex\n");
       abort();
    @)
  *wrapper* Term
    *prefix*
    (@
       if (this->isTerminal())
         {
           derror('e',1," illegal vertex used in propagation directive: '");
           this->g_print(cout);
           cout << "' on line " << this->get_vertex()->get_vertex_name()->get_line_number() << endl;
           exit(-1);
         }

       v = (Vertex*)this->get_vertex()->g_copy();
    @)