/* Verify compliance with rule 1. */
if (node->trb_color == TRB_RED)
  {
    if (node->trb_tag[0] == TRB_CHILD
        && node->trb_link[0]->trb_color == TRB_RED)
      {
        printf (" Red node %d has red left child %d\n",
                d, *(int *) node->trb_link[0]->trb_data);
        *okay = 0;
      }

    if (node->trb_tag[1] == TRB_CHILD
        && node->trb_link[1]->trb_color == TRB_RED)
      {
        printf (" Red node %d has red right child %d\n",
                d, *(int *) node->trb_link[1]->trb_data);
        *okay = 0;
      }
  }