null

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 ’())

Expanded Reference: null

tip

TODO: Please contribute to this page by adding explanations and examples

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