Function not

Syntax:

Arguments and Values:

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

boolean—a boolean.

Description:

6.4.0 3Returns 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:

\code (not x) \EQ (null x) \endcode

6.4.0 $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.