What's a good mathematical sets implementation in JavaScript?

Question

Where is a good mathematical sets implementation for JavaScript? It should include efficient implementations of intersection, union, complement, and (for bonus points) the Carte

Answer 1

In the program that sparked this question, a set is an Array and intersect is

s = [1,2,3];
q = [3,4,5];
sq = s.filter(function(x) {
    return q.indexOf(x) >= 0;
});

Of course it doesn't work in ie.