At Fri, 17 Jun 2011 21:30:51 +0400,
Евгений Курбатов wrote:
> 
> Hello!
> 
> I do some elisp code to download the latest RSS feeds from some resource:
> 
> (setq debug-on-error t)
> (org-mode)
> (org-feed-update
>  '("arxiv"
>    "http://export.arxiv.org/rss/astro-ph"
>    (concat "~/org/arxiv-" (format-time-string "%Y-%m-%d.org"))
>    "arXiv.org"
>    )
>  )
> 
> The goal is to get an unique Org file for feeds per day. However, the error is rising:
> 
> Debugger entered--Lisp error: (wrong-type-argument stringp (concat "~/org/arxiv-" (format-time-string "%Y-%m-%d.org")))
>   expand-file-name((concat "~/org/arxiv-" (format-time-string "%Y-%m-%d.org")))
>   find-file-noselect((concat "~/org/arxiv-" (format-time-string "%Y-%m-%d.org")) nil nil nil)
>   find-file((concat "~/org/arxiv-" (format-time-string "%Y-%m-%d.org")))
>   org-feed-goto-inbox-internal((concat "~/org/arxiv-" (format-time-string "%Y-%m-%d.org")) "arXiv.org")
>   byte-code("\306   \"\307\n\"\310\311
> \"\211\312+\211,\203]
> 
> When I hardcode a string instead of (concat ...) everything is
> ok. The subject is also not in format-time-string, it is exactly in
> concat. The type returned by concat is the stringp, so the situation
> is very strange. I also tried to use org-feed-alist, and local
> variable instead of calling concat, nothing helps.

The quote in front of ("arxiv"

>  '("arxiv"

"quotes" the following list, i.e. Emacs does not evaluate the Lisp
expressions inside the list but processes it as pure data. 

To calculate the file name each time you call `org-feed-update' either
leave out the quotes like:

(org-feed-update (list "arxiv" "http://export.arxiv.org/rss/astro-ph" (concat … )))

-or-

Use backquotes:

http://www.gnu.org/s/emacs/manual/html_node/elisp/Backquote.html

(org-feed-update
 `("arxiv"
   "http://export.arxiv.org/rss/astro-ph"
   ,(concat "~/org/arxiv-" (format-time-string "%Y-%m-%d.org"))
   "arXiv.org"
  )
)

The ` means: The following structure is data except the parts with the
backquote ,.

Best,
  -- David
-- 
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Jabber.... dmjena@jabber.org
Email..... dmaus@ictsoc.de