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

On Fri, Feb 5, 2010 at 15:41, Laurent <laurent.orseau at gmail.com> wrote:
> On Fri, Feb 5, 2010 at 15:40, Laurent <laurent.orseau at gmail.com> wrote:
>> 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)
>
> oops, please read on the last line:
> (hash-set! towards-infinity-and-beyond) 'me towards-infinity-and-beyond)

rahhh, well you got the idea... (and I'm going to get some sleep)