Get list of top-level headings

Get list of top-level headings

[Florian Lindner]

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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
 

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Re: Get list of top-level headings

[John Kitchin]

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I think this is all you need to get a list of titles of level 1 headings as
strings

(org-map-entries (lambda () (fifth (org-heading-components))) "LEVEL=1")

this also works for me:

#+BEGIN_SRC emacs-lisp
(org-map-entries (lambda () (org-element-property :title
(org-element-at-point)) ) "LEVEL=1")
#+END_SRC




John

-----------------------------------
Professor John Kitchin (he/him/his)
Doherty Hall A207F
Department of Chemical Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
412-268-7803
@johnkitchin
http://kitchingroup.cheme.cmu.edu



On Wed, May 19, 2021 at 3:51 AM Florian Lindner <mailinglists@xgm.de> 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
>

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Re: Get list of top-level headings

[Jonathan Gregory]

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

Re: Get list of top-level headings

[Jonathan Gregory]

Hi

On 19 May 2021, John Kitchin wrote:

> I think this is all you need to get a list of titles of level 1
> headings as strings
>
> (org-map-entries (lambda () (fifth (org-heading-components)))
> "LEVEL=1")
>
> this also works for me:
>
> #+BEGIN_SRC emacs-lisp
> (org-map-entries (lambda () (org-element-property :title
> (org-element-at-point)) ) "LEVEL=1")
> #+END_SRC

This is a better approach indeed. No need to create a new list, 
although I get faster results using:

 (while (re-search-backward org-complex-heading-regexp nil t)


-- 
Jonathan

Re: Get list of top-level headings

[John Kitchin]

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that is often true, especially with large buffers, but you have to add a
bunch of code to go to point-max, and check the level with this.

#+BEGIN_SRC emacs-lisp
(save-excursion
  (goto-char (point-max))
  (let (components
(headings '()))
    (while (re-search-backward org-complex-heading-regexp nil t)
      (setq components (org-heading-components))
      (when (= (first components) 1)
(push (fifth components) headings)))
    headings))
#+END_SRC

This takes about 0.04 ms on a small example. The org-map-entries approach
takes 0.6ms on the same example. In a big buffer that might be noticeable!

John

-----------------------------------
Professor John Kitchin (he/him/his)
Doherty Hall A207F
Department of Chemical Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
412-268-7803
@johnkitchin
http://kitchingroup.cheme.cmu.edu



On Wed, May 19, 2021 at 10:19 AM Jonathan Gregory <jgrg@autistici.org>
wrote:

> Hi
>
> On 19 May 2021, John Kitchin wrote:
>
> > I think this is all you need to get a list of titles of level 1
> > headings as strings
> >
> > (org-map-entries (lambda () (fifth (org-heading-components)))
> > "LEVEL=1")
> >
> > this also works for me:
> >
> > #+BEGIN_SRC emacs-lisp
> > (org-map-entries (lambda () (org-element-property :title
> > (org-element-at-point)) ) "LEVEL=1")
> > #+END_SRC
>
> This is a better approach indeed. No need to create a new list,
> although I get faster results using:
>
>  (while (re-search-backward org-complex-heading-regexp nil t)
>
>
> --
> Jonathan
>
>

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