if (min > max)
  {
    printf (" Parents of node %d constrain it to empty range %d...%d.\n",
            d, min, max);
    *okay = 0;
  }
else if (d < min || d > max)
  {
    printf (" Node %d is not in range %d...%d implied by its parents.\n",
            d, min, max);
    *okay = 0;
  }