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  ANSI Common Lisp   14 Conses   14.2 Dictionary of Conses

14.2.24 null Function

Syntax:
null object    boolean

Arguments and Values:
object - an object.

boolean - a boolean.

Description:
Returns t if object is the empty list; otherwise, returns nil.

Examples:
 (null '())   T
 (null nil)   T
 (null t)   NIL
 (null 1)   NIL

See Also:
not

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

 (null object) ==(typep object 'null) ==(eq object '())

Allegro CL Implementation Details:
None.

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