thanks fglock. the use of bitsets is important because theoretically i can unions, intersections etc a little faster, in a little less space - and the sets can be large, and it needs to be *fast*, or i will spend all my time answering 'why did you do it this way when it is soooo slow' type questions.

for 'sparse' sets, the approach your Set::Infinite takes is much more sensible, allowing it to do clever things with more complicated set types. i particularly like it's connection with dates, which seems a good idea. Quantum::Superpositions is something i should check out too, I guess.

...wufnik

-- in the world of the mules there are no rules --