docs: private void balance12(
      NodeStack     stack,
      GBSNode       bparent,         /* Parent of fringe balance point        */
      GBSNode       fpoint,          /* Fringe balance point                  */
      int           fpidx,           /* Index within stack of fpoint          */
      int           maxBal)          /* Maximum allowed fringe imbalance      */
    {
      /*
          k = 12,     2k-1 = 23,     k-1 = 11
  
                  [A-B-C-D-E-F-G-H-I-J-K]              [11 children]
  
                         becomes:
  
                  *-------F-------*
                  |               |
               *--C--*         *--I--*
               |     |         |     |
             *-B     D-*     *-H     J-*
             |         |     |         |
             A         E     G         K
  
    --------------------------------------------------------
  
                  *-------F-------*
                  |               |
               *--C--*         *--I--*
               |     |         |     |
             *-B     D-*     *-H     J-*          [14 children]
             |         |     |         |
             A         E     G         K - L-M-N-O-P-Q-R-S-T-U-V-W
  
  
                         becomes:
  
  
                *-----------L-----------*
                |                       |
          *-----F-----*           *-----R-----*
          |           |           |           |
        *-C-*       *-I-*       *-O-*       *-U-*
        |   |       |   |       |   |       |   |
      *-B   D-*   *-H   J-*   *-N   P*-   *-T   V-*
      |       |   |       |   |       |   |       |
      A       E   G       K   M       Q   S       W                     */
  
      if (maxBal == 11)
        {
          GBSNode a = fpoint;
          GBSNode b = a.rightChild();
          GBSNode c = b.rightChild();
          GBSNode d = c.rightChild();
          GBSNode e = d.rightChild();
          GBSNode f = e.rightChild();
          GBSNode g = f.rightChild();
          GBSNode h = g.rightChild();
          GBSNode i = h.rightChild();
          f.setLeftChild(c);
          f.setRightChild(i);
          c.setLeftChild(b);
          b.setLeftChild(a);
          b.clearRightChild();
          a.clearRightChild();
          e.clearRightChild();
          i.setLeftChild(h);
          h.setLeftChild(g);
          h.clearRightChild();
          g.clearRightChild();
          if (bparent.rightChild() == a)
            bparent.setRightChild(f);
          else
            bparent.setLeftChild(f);
        }
      else
        {
          if (maxBal != 14)
            error("fringeBalance12: maxBal != 14, maxBal = " + maxBal);
          GBSNode t0_top = stack.node(fpidx-3);
          GBSNode f = stack.node(fpidx-2);
          GBSNode j = fpoint;
          GBSNode k = j.rightChild();
          GBSNode l = k.rightChild();
          GBSNode m = l.rightChild();
          GBSNode n = m.rightChild();
          GBSNode o = n.rightChild();
          GBSNode p = o.rightChild();
          GBSNode q = p.rightChild();
          GBSNode r = q.rightChild();
          GBSNode s = r.rightChild();
          GBSNode t = s.rightChild();
          GBSNode u = t.rightChild();
          if (t0_top.rightChild() == f)
            t0_top.setRightChild(l);
          else
            t0_top.setLeftChild(l);
          l.setLeftChild(f);
          l.setRightChild(r);
          r.setLeftChild(o);
          r.setRightChild(u);
          o.setLeftChild(n);
          n.setLeftChild(m);
          n.clearRightChild();
          m.clearRightChild();
          q.clearRightChild();
          u.setLeftChild(t);
          t.setLeftChild(s);
          t.clearRightChild();
          s.clearRightChild();
          k.clearRightChild();
          if ((fpidx > 3) && (stack.balancePointIndex() > -1))
            {
              GBSNode qpoint = l;
              stack.setNode(fpidx-2, qpoint);
              GBSInsertHeight.singleInstance().balance(stack, qpoint);
            }
        }
    }