docs: private void optimalRoot() {
  		NatureTerm to = end[0];
  		NatureTerm from;
  		int index = natureTermTable.length - 1;
  		while ((from = to.from) != null && index > 0) {
  			terms.get(--index).setNature(from.termNature.nature);
  			to = from;
  		}
  	}