If you define it more generally: younger_person >= (older_person / 2) + 7 it has the added advantage that it proscribes anyone younger than 14 ever having

If you define it more generally: younger_person >= (older_person / 2) + 7 it has the added advantage that it proscribes anyone younger than 14 ever having sex (with anyone of any age) since the inequality could never be satisfied. For example if the older person was 12, then the younger person would have to be at least 13, which is impossible. http://en.wikipedia.org/wiki/Half_your_age_plus_seven http://en.wikipedia.org/wiki/Half_your_age_plus_seven