null (Function)

Syntax:

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 (Function)

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 '())