Syntax:

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

Side Effects: None.

Affected By: None.

Exceptional Situations: None.

See Also:

null

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.

• NOT-AND-NULL-RETURN-VALUE:X3J13-MAR-93