code: private void rightDepth(
      DeleteStack.FringeNote      xx,
      int           fbalance)
    {
      switch (fbalance)              /* Original father balance factor        */
      {
        case  1:                     /* Have deleted from right of right-heavy*/
                                     /*  Is now balanced but depth has        */
          xx.depthDecrease = true;   /*  decreased.                           */
          break;
        case  0:                     /* Both sides are t0                     */
          /* G has lost one from whichever side.                              */
          /*   UNLESS lastFringe does an insert fringe re-balancing.          */
          /* In which case it remains balanced and no height change           */
          xx.conditionalDecrease = true;
          xx.conditionalBalance = 0;
          break;
        case -1:                     /* Left side has more than one t0        */
          /* Is now balanced.                                                 */
          /* G has lost one from whichever side.                              */
          /*   UNLESS lastFringe does an insert fringe re-balancing.          */
          /* If true, stack.node(ntop).balance = +1,  G has not lost anything */
          xx.conditionalDecrease = true;
          xx.conditionalBalance = 1;
          break;
        default:
          throw new RuntimeException("Help!  fbalance = " + fbalance);
      }
    }
docs: Given the original balance factor from the original parent of
  the t0 sub-tree from which we deleted from the right side,
  determine the possible new balance factor and depth decrease
  indicator.