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::

section 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 '())

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