Re: Symbol's function definition is void: remove-if-not

[Katsumi Yamaoka <yamaoka@jpl.org>]

Ted Zlatanov wrote:
[...]
>>> It looks like `remove-if-not' is used in several places actually:

>>> gnus-art.el:   (remove-if-not pred (mailcap-mime-types))
>>> gnus-group.el:                    (remove-if-not 'symbolp collection)))
>>> gnus-score.el:                                      (remove-if-not

> Those three should be able to use `gnus-remove-if' with the predicate
> inverted, I think.

No, gnus-group.el is not.  `gnus-group-completing-read' takes a hash
table as an argument, in addition to `gnus-read-move-group-name' in
gnus-sum.el.

>>> gnus-sum.el: (remove-if-not 'gnus-valid-move-group-p gnus-active-hashtb)
>>> gnus-sum.el: prom (remove-if-not 'gnus-valid-move-group-p gnus-active-hashtb)

KY> The use of `remove-if-not' in gnus-sum.el is a wrong approach since
[...]

> So it's potentially a bug.  I am no expert on ELisp data types,
> especially between Emacs and XEmacs.  Should we take this to emacs-devel
> or does someone know a good solution?

> I think it's acceptable to simply provide `gnus-remove-hashtb-keys-if'
> rather than try to reimplement CL.  So maybe that's the right way.

I'd like to try it (maybe tomorrow).

BTW, as you know `mapatoms' is the only means to access elements
of a hash table:

,---- (info "(elisp)Creating Symbols") ----
| there is no way to find all the symbols in an obarray except
| using `mapatoms' (below).
`----

It doesn't care of non-interned symbols in a hash table, so the
code `(remove-if-not 'symbolp collection)' used in gnus-group.el
is useless:

(let ((hashtable (make-vector 4096 0)))
  hashtable)
 => [0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ...

(let ((hashtable (make-vector 4096 0))
      rest)
  (intern "foo" hashtable)
  (intern "bar" hashtable)
  (mapatoms (lambda (symbol) (push symbol rest)) hashtable)
  rest)
 => (bar foo)