On Monday 22 August 2016 at 15:46:41, Dianne Skoll wrote:
> On Mon, 22 Aug 2016 06:04:49 -0700
>
> Marc Perkel <[email protected]> wrote:
> > Set A - a finite set - has some members,
> > Set B - an infinite set - is everything that is NOT in Set A
>
> Set B is a very special case of an infinite set. We're talking about
> infinite sets in general.
>
> Also, you have to realize that although set B is in principle infinite,
> in practice it is not. Computers have finite memory, and although the
> number of email tokens representable in the memory of a computer is very,
> very, very large, it's not infinite.
I do not think that Marc is proposing to actually store set B in a computer
(or anywhere else).
Set B is simply a theoretical construct, defined as the inverse of Set A, and
to discover whether something is a member of it, you do not search through the
infinite set B for a match, you instead check all members of finite set A for a
non-match.
If nothing in Set A matches X, then X is a member of Set B.
Antony.
--
I have an excellent memory.
I can't think of a single thing I've forgotten.
Please reply to the list;
please *don't* CC me.
