14.2.24 null [Function]

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 '())