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null (Function)

— Function: null object boolean
Arguments and Values:

object—an object.

boolean—a boolean.


Returns t if object is the empty list; otherwise, returns nil.

 (null '())  T
 (null nil)  T
 (null t)  NIL
 (null 1)  NIL
See Also:

not (Function)


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 '())