class Region {

    public Number length() {
        if(cachedLength == null) {
            Number l = getMax() == null || getMin() == null ?
                   null : getMax().doubleValue() - getMin().doubleValue();
            if(l != null) {
                cachedLength = FastNumber.orNull(l);
            }
        }
        return cachedLength;
    }

    public  Region();
    public  Region(Number v1, Number v2);

}