[NOT
====

Syntax: [not <predication>]

[NOT is a compound predication. It negates the truth
value of the predication.
All the variables that are used in the formula have
to be bound before [NOT starts checking. In particular
it should be made sure, that all the formulas, in which
not is used, are internally converted into a simple
predication, before not starts checking them. It is 
possible to negate composed formulas too if the internal
conversion is taken into account.
The rules of deMorgan are used for the conversion:
   not(A or B) == (not A) and (not B)
   not(A and B) == (not A) or (not B)
[NOT returns the negated value and an unusable
value.

Example: >(ask [and
                [computer _x]
                [not [harddisk _x]]]
               (kb-format "~%~A" (name-of _x)))
         RAM
         CD-ROM
         NIL

The interpreter searches for all components that are
not a harddisk.