Those are all fine to me, and I'll follow up with a "how do you know that's right?" if needed. Looping over all valid values in one interval, testing for membe

Those are all fine to me, and I'll follow up with a "how do you know that's right?" if needed. Looping over all valid values in one interval, testing for membership in the other, is kind of a red flag. A predicate that is incorrect and not caught by testing might be a very bad sign.