// Check that a class does not inherit from itself either directly
// or indirectly.
*operation* int check_cycle_free()
  *init* (@ 1 @)

  *traverse* *from*      Cd_graph
             *through*   ->Alternat_ns,*,Term_Bar_list 
             *to-stop*   Term

  *carry* *in*    Vertex* src = (@ this->get_source() @)
          *along* *from* Adjacency 
                  *to*   Term

  *carry* *in*    Cd_graph* graph = (@ this @)
          *along* *from* Cd_graph 
                  *to*   Term

  *wrapper* Cd_graph
    *prefix* (@ cout << endl << "Checking inheritance cycles ..." << endl;
              @)

  *wrapper* Term
    *prefix* (@ Adjacency* adjclass = graph->find_adjacency(this->get_vertex());
                if (adjclass != NULL) {
                  if ((return_val) &&
                      (adjclass->check_cycle1(graph, src))) {
                    if (!src->g_equal(this->get_vertex())) {
                      cout << "\tto   ";
                      this->get_vertex()->g_print();
                      cout << endl;
                    }
                    cout << "\tto   ";
                    src->g_print();
                    cout << endl;
                    return_val = 0;
                  } 
                }
              @)


*operation* int check_cycle1(Cd_graph* graph, Vertex* src)
  *init* (@ 0 @)

  *traverse* *from*      Adjacency  
             *through*   ->Alternat_ns,*,Term_Bar_list
             *to-stop*   Term

  *wrapper* Term
    *prefix* (@ if (this->get_vertex()->g_equal(src)) {
                  cout << "sem-check: error: on line "
                       << this->find_line_number()
                       << " find inheritance cycle 1 :" << endl;
                  cout << endl << endl << "\tfrom ";
                  src->g_print();
                  cout << endl;
                  return_val = 1;
                }
                else {
                  Adjacency* adjclass = graph->find_adjacency(this->get_vertex());
                  if (adjclass != NULL) 
                    if (adjclass->check_cycle1(graph, src)) {
                      cout << "\tto   ";
                      this->g_print();
                      cout << endl;
                      return_val = 1;
                    }
                }
              @)