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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

Side Effects: None.

Affected By: None.

Exceptional Situations: None.

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 '())

The following X3J13 cleanup issue, not part of the specification, applies to this section: