null (ANSI and GNU Common Lisp Document)

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#### 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 '())