docs: protected List<EquPart> negatize(final List<EquPart> equParts)
      {
          int left = 0;
  
          for (int right = 1; right < equParts.size(); right++)
          {
              left = right - 1;
              if (equParts.get(left) instanceof OpSubtract)
                  if (left == 0)
                      equParts.set(left, new OpNegate(equParts.get(left)));
                  else
                  {
                      if (equParts.get(left - 1).negatize(equParts.get(right)))
                          equParts.set(left, new OpNegate(equParts.get(left)));
                  }
          }
          return equParts;
      }