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  ANSI Common Lisp   5 Data and Control Flow   5.3 Dictionary of Data and Control Flow

5.3.31 not Function

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

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.

Allegro CL Implementation Details:
None.

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