atom? - Get it right.

Since Google seems to be having a hard time finding it the right definition, I'd like to point out for the record that in Scheme, atom? should be defined so:

(define atom?
  (lambda (x)
    (and (not (pair? x)) (not (null? x)))))

Other definitions should be stoned to death or at least given a very dirty look.

Thank you for your attention to this matter.