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

On Fri, Feb 5, 2010 at 15:12, Matthias Felleisen <matthias at ccs.neu.edu> wrote:
>
> On Feb 5, 2010, at 8:29 AM, Todd O'Bryan wrote:
>
>> What do people use for a set data-type? If there isn't one built-in,
>> we're going to use a hash-table with #t as all the values.
>
> Just a tease: how would you use hashtable to represent infinite sets?

>From the top of my head, though that does probably not fit to the
definition of an infinite set:

(define towards-infinity-and-beyond (make-hash))
(hash-set! towards-infinity-and-beyond 'zero '())
(hash-set! 'me towards-infinity-and-beyond)