R4RS 6.1  (not object)  ==>  boolean

NOT returns #T if OBJECT is false, and returns #F otherwise.

(not #t)        ==>  #f
(not 3)         ==>  #f
(not (list 3))  ==>  #f
(not #f)        ==>  #t
(not '())       ==>  #f
(not (list))    ==>  #f
(not 'nil)      ==>  #f
