not [Function]

not x => boolean

Arguments and Values::

x---a generalized boolean (i.e., any object).

boolean---a boolean.

Description::

Returns t if x is false; otherwise, returns nil.

Examples::

 (not nil) =>  T
 (not '()) =>  T
 (not (integerp 'sss)) =>  T
 (not (integerp 1)) =>  NIL
 (not 3.7) =>  NIL
 (not 'apple) =>  NIL

See Also::

section null [Function]

Notes::

not is intended to be used to invert the `truth value' of a boolean (or generalized boolean) whereas null is intended to be used to test for the empty list. Operationally, not and null compute the same result; which to use is a matter of style.

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