Terry Jones wrote:

See also this thread:

http://mail.python.org/pipermail/python-dev/2006-May/064977.html

I implemented some of what I was proposing there (in Python though, not C), and am happy to send people the code if there's any interest.

These things can't be 100% clean (e.g., what happens when you call len on an infinite set), but you can still get a lot of useful functionality if what's provided matches your use case. Having efficient support for very large sets via complements, having a Universal set, etc., would all be nice.

Anyway, see the above thread for more discussion / opinions.

Did you register a module with PyPI? In any case, it seems to me that adding a 'universal set' to the set class does not work. On the otherhand, a separate set-complement class (which I am guessing is what you did) should work fine as far as it goes. Each instance would have normal set as its data member, and operations on complements and mixed operations would be defined in terms of operations on sets. A universal set would then be an instance with an empty set for a complement. I think the OP should look in this direction, possibly building on your existing code. Terry Jan Reedy