Re: Get list of top-level headings

[Jonathan Gregory <jgrg@autistici.org>]

Hello Florian

On 19 May 2021, Florian Lindner wrote:

> Hello,
>
> I, an Emacs Lisp newbie, want to get a list of all top-level 
> headings
> of the current buffer. My approach so far is:
>
> (defun test-org-map()
>   (interactive)
>   (setq headings '())
>   (org-map-entries (lambda ()
>                      (setq current-header-item 
>                      (org-element-property :
> title (org-element-at-point))
>                      (message "Header: %s" current-header-item)
>                      (message "Is String: %s" (stringp
> (org-element-property :title (org-element-at-point))))
>                      (setq headings (append current-header-item
> headings))
>                      )
>                    "LEVEL=1"
>                    )
>   (dolist (heading headings)
>     (message "Header Item: %s" heading)
>     )
>   )
>
> This gives the otput:
>
> Header: AAA
> Is String: t
> Header: BBB
> Is String: t
> Header Item: 66 [3 times]
> Header Item: 65 [3 times]
>
> so basically the (org-element-property :title 
> (org-element-at-point)
> does exactly what I want, but building the list does not what I 
> want.
> I suppose that comes from a fundamental misunderstanding of how
> strings work in elisp.
>
> I would appreciate a short explanation (or pointers) why this 
> does not
> work. And of course, I am very open to completely different, 
> likely
> better, approches to that simply problem!
>
> Thanks,
> Florian

The org-map-entries function calls FUNC at each headline, so you 
have to (1) find the headline/title and (2) add it to your list. 
One way to do this is with the push macro.

--8<---------------cut here---------------start------------->8---
(defun test-org-map ()
  (interactive)
  (let (headlines)
    (org-map-entries
     (lambda ()
       (let* ((element (org-element-at-point))
	      (headline (org-element-property :title element)))
	 (push headline headlines)))
     "LEVEL=1")
    (print (nreverse headlines))))
--8<---------------cut here---------------end--------------->8---
    
Or by searching the buffer:

--8<---------------cut here---------------start------------->8---
(defun test-org-map ()
  (interactive)
  (let (headlines)
    (save-excursion
      (goto-char (point-max))
      (while (re-search-backward org-complex-heading-regexp nil t)
	(let ((headline (match-string-no-properties 4)))
	  (when (= (org-current-level) 1)
	    (push headline headlines))))
      (print headlines))))
--8<---------------cut here---------------end--------------->8---

BTW you're missing a closing parenthesis in:

 (setq current-header-item (org-element-property :title 
 (org-element-at-point)))

Maybe that's why you're getting errors.

-- 
Jonathan