# [plt-scheme] Is there a set data-type?

David Van Horn wrote:
>* On 2/5/10 11:03 AM, Paulo J. Matos wrote:
*>>* Thanks for the thoughts on performance.
*>>* Another thing I will have to think about is computing the cardinality of
*>>* the set which might return +inf.0 of course. I am not even sure this
*>>* representation allows the computation of cardinality in a finite amount
*>>* of time.
*>*
*>* When you're in the world of infinite sets there are all kinds of
*>* questions that are not decidable, that just comes with the territory.
*>*
*>* It's fun, for example, to construct the representation of Russell's
*>* paradoxical set: the set of all sets that don't contain themself.
*>*
*>* (define R (lambda (x) (not (x x))))
*>*
*>* Now is R a member of the set R? Well just run it and find out: (R R).
*>*
*>* David
*
I agree but my case is constrained to sets of Integers. What I will have
to work out is a way to implement all the set operations on possibly
infinite sets of integers. Fortunately I don't have to touch the case of
general sets! :)