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 '())