Re: doc elisp intro cross reference fixes

[Luc Teirlinck]

Per Abrahamsen wrote:

   (let (found)
     (mapatoms (lambda (sym) 
                 (let ((group (get sym 'custom-group)))
                   (setq found (append group found)))))
     (mapatoms (lambda (sym)
                 (and (boundp sym)
                       (get sym 'standard-value)
                      (not (assq sym found))
                      (insert (format "%S\n" sym))))))

This lists all kinds of variables that _do_ have a :group.  (Actually,
I believe it lists all customizable variables.)

   > 2. A variable defined using a defcustom without a :group _is_ in a
   >    group, the `nil' group:

   Nope.

Why does `M-x customize-group RET nil RET' work then?  If you evaluate:

(defcustom a 4 "c")

then the customizable variable `a' winds up listed there, together
with the other four.

What about nil's plist?

Sincerely,

Luc.