the bugs that try men's souls

[Sean McIlroy]

<later>
Wow again. I had a real "V8 moment" when I looked at your solution
(smacking my forhead, groaning ruefully, etc). You were right: my
intention was simply to hide the trivial cases from view; I completely
missed the fact that I was now testing for membership in a different
set. I should have remembered that python "plays fair", and looked a
little harder to find my mistake.

Thanks again,
Sean