protected void buildRangeFrag(Character start, Character end, Fragment newFrag) {
        if (end.compareTo((Character) start) < 0) {
            throw new IllegalArgumentException("invalid range " + start + "-" + end);
        }
        for (char i = (Character) start; i <= end; i++) {
            newFrag.getStart().addTransfer(i, newFrag.getEnd());
        }
    }