@Override
  public int hc() {
    int hc = myHC;
    if (hc == -1) {
      hc = 0;
      TreeElement child = firstChild;
      while (child != null) {
        hc += child.hc();
        child = child.getTreeNext();
      }
      myHC = hc;
    }
    return hc;
  }
@Override
  public int hc()