On Monday 22 August 2016 at 15:46:41, Dianne Skoll wrote: > On Mon, 22 Aug 2016 06:04:49 -0700 > > Marc Perkel <supp...@junkemailfilter.com> 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.