That's funny -- I work in genealogy software, and loops ("being your own grandpa") happen all the time, due to data entry errors. To avoid infinite recursion, w

That's funny -- I work in genealogy software, and loops ("being your own grandpa") happen all the time, due to data entry errors. To avoid infinite recursion, we always keep track of what records we've processed already, check whether "I've been there before", and bail out if the answer is affirmative.