Usefulness of the "not in" operator

[Roy Smith]

In article 
<acd018ad-8428-4c3d-8aa0-15c4a410fcf5 at x31g2000prd.googlegroups.com>,
 rusi <rustompmody at gmail.com> wrote:

> On Oct 8, 6:31 pm, Roy Smith <r... at panix.com> wrote:
> > In article <87ehyn8xlp.... at dpt-info.u-strasbg.fr>,
> >  Alain Ketterlin <al... at dpt-info.u-strasbg.fr> wrote:
> >
> > > Sure, but note that you can also reformulate != using not and ==, <
> > > using not and >=, etc. Operators like "not in" and "is not" should
> > > really be considered single tokens, even though they seem to use "not".
> > > And I think they are really convenient.
> >
> > If you want to take it one step further, all the boolean operators can
> > be derived from nand (the dualists would insist on using nor).
>                         ^^^^^^^^^^^^
> ????

Dualist (noun): a made up word referring to wrong-thinking people who 
have rejected the teachings of the Prophet Nand and believe the nor is 
the One True Operation on which all over operations can be constructed.