docs: public String stateName(
      int      state)
    {
      String name = "Unknown state = " + state;
      switch(state)
      {
        case NodeStack.VISIT_LEFT:
          name = "VISIT_LEFT";
          break;
        case NodeStack.PROCESS_CURRENT:
          name = "PROCESS_CURRENT";
          break;
        case NodeStack.VISIT_RIGHT:
          name = "VISIT_RIGHT";
          break;
        case NodeStack.DONE_VISITS:
          name = "DONE_VISITS";
          break;
      }
      return name;
    }