Re: functions to download mailing list archives

[GH]

Óscar Fuentes <ofv@wanadoo.es> writes:

> Instead of a recursive function use a recursive data structure: a list.

> The outer function puts in the list the initial URL, and then, in a
> loop, pops from the list a URL, downloads it, adds to the list the
> referenced URLs and repeats until the list is empty or some other
> condition is met.

> Some complications may remain: for instance, you need to detect cycles
> (the failure on your posted code probably comes from that). A list also
> comes handy for that, if you walk the list with dolist instead of
> popping elements and add new ones with add-to-list, which omits elements
> which are already in the list.

I dont know how. Maybe some like:

#+begin_src elisp

(defun lists-mbox-recursive-url-list (url-head id date)
  (with-current-buffer "*eww*"
    (shr-next-link)
    (let ((url (thing-at-point 'url)))
      (if (string-match (format "%s/archive/mbox/%s/%s\\(.+\\)" url-head id 
date)
                        url)
          (add-to-list url-list url)))
    (if (save-excursion (shr-next-link))
        (lists-mbox-recursive-url-list url-head id date)
      url-list)))


(let ((url-list '()))
  (with-current-buffer "*eww*"
    (beginning-of-buffer)
    (lists-mbox-recursive-url-list "https://lists.gnu.org"; "help-gnu-emacs" 
201)))

#+end_src

But return an error that I dont understand:

Debugger entered--Lisp error: (setting-constant nil)
  add-to-list(nil "https://lists.gnu.org/archive/mbox/help-gnu-emacs/...";)
  (if (string-match (format "%s/archive/mbox/%s/%s\\(.+\\)" url-head id date) 
url) (add-to-list url-list url))
  (let ((url (thing-at-point 'url))) (if (string-match (format 
"%s/archive/mbox/%s/%s\\(.+\\)" url-head id date) url) (add-to-list url-list 
url)))
  (save-current-buffer (set-buffer "*eww*") (shr-next-link) (let ((url 
(thing-at-point 'url))) (if (string-match (format 
"%s/archive/mbox/%s/%s\\(.+\\)" url-head id date) url) (add-to-list url-list 
url))) (if (save-excursion (shr-next-link)) (lists-mbox-recursive-url-list 
url-head id date) url-list))
  lists-mbox-recursive-url-list("https://lists.gnu.org"; "help-gnu-emacs" 201)

...

What mean "error: (setting-constant nil)"