[racket] Take an element from a set

On 9/7/11 11:36 PM, Shriram Krishnamurthi wrote:
> A better design would be to use a different signature:
>
>    get-one/rest : (forall (A) (Set A) ->  (values A (Set A)))
>
> This performs the split "atomically", so it can ensure that the
> combination of "one" and "rest" is the same as the original set.

This should be provided by Racket.  I've written it locally multiple times.

David