#### 5.3.31 not [Function] ¶

`not` x ⇒ boolean

#### Arguments and Values:: ¶

x—a generalized boolean (i.e., any object).

boolean—a boolean.

#### Description:: ¶

Returns t if x is false; otherwise, returns nil.

#### Examples:: ¶

     (not nil) ⇒  T
     (not '()) ⇒  T
     (not (integerp 'sss)) ⇒  T
     (not (integerp 1)) ⇒  NIL
     (not 3.7) ⇒  NIL
     (not 'apple) ⇒  NIL

#### See Also:: ¶

null [Function]

#### Notes:: ¶

not is intended to be used to invert the ‘truth value’ of a boolean (or generalized boolean) whereas null is intended to be used to test for the empty list. Operationally, not and null compute the same result; which to use is a matter of style.