Null
Recognizer for the empty list
Null is the function that checks whether its argument is
nil. For recursive definitions it is often preferable to test for the
end of a list using endp instead of null; see endp.
Null is a Common Lisp function. See any Common Lisp documentation for
more information.
Function: null
(defun null (x)
(declare (xargs :guard t))
(eq x nil))
