org-map-entries and org-map-continue-from

org-map-entries and org-map-continue-from

[Richard Lawrence]

Hi all,

Bastien had advised me [1] to use

(setq org-map-continue-from (outline-next-heading))

in a function called by org-map-entries in order to map that function
across just the /children/ of the current entry (i.e., to exclude the
current `parent' entry itself).  This works great, but I have now found
that it has a weird side-effect: it calls the function twice on the last
child.

For a simple example, suppose I write:
#+BEGIN_SRC emacs-lisp
(defun get-export-filenames ()
  (interactive)
  (setq export-files '())
  (progn
    (org-map-entries
     (lambda ()
       (setq org-map-continue-from (outline-next-heading))
       (let ((org-trust-scanner-tags t))
	 (push (org-entry-get (point) "EXPORT_FILE_NAME") export-files)))
     nil 'tree)
    (message export-files))) ; errors, but lets me see the list of collected values
#+END_SRC

And I call this function from a buffer that looks like:

* Top
<point is here when I call get-export-filenames>
** One
   :PROPERTIES:
   :EXPORT_FILE_NAME: one
   :END:
** Two
   :PROPERTIES:
   :EXPORT_FILE_NAME: two
   :END:
** Three
   :PROPERTIES:
   :EXPORT_FILE_NAME: three
   :END:
** Four
   :PROPERTIES:
   :EXPORT_FILE_NAME: four
   :END:

Then the list that I get back (the value of export-files) looks like:

("four" "four" "three" "two" "one")

Whereas I would like it to be just:

("four" "three" "two" "one")

Can anyone see what I need to do to achieve that? [Apart from just using
(cdr export-files), I mean -- I'd like to know the /right/ way.]  I'm
puzzled because outline-next-heading, if called interactively from the
last child, does indeed put point at the end of that child or at the
next (parent-level) heading, so it doesn't seem that the problem is that
it somehow loops back when there is no next child-level entry.

Many thanks if you catch something I've missed!

Best,
Richard

[1] http://article.gmane.org/gmane.emacs.orgmode/37244/

Re: org-map-entries and org-map-continue-from

[Nick Dokos]

Richard Lawrence <richard.lawrence@berkeley.edu> wrote:


> For a simple example, suppose I write:
> #+BEGIN_SRC emacs-lisp
> (defun get-export-filenames ()
>   (interactive)
>   (setq export-files '())
>   (progn
>     (org-map-entries
>      (lambda ()
>        (setq org-map-continue-from (outline-next-heading))
>        (let ((org-trust-scanner-tags t))
> 	 (push (org-entry-get (point) "EXPORT_FILE_NAME") export-files)))
>      nil 'tree)
>     (message export-files))) ; errors, but lets me see the list of collected values
> #+END_SRC
> 

As you point out below, everything works as it should: outline-next-heading
steps you through the headlines and eventually returns nil
correctly. The problem is that org-entry-get does not just look forward:
it looks *around* and finds the property when point is both at the
beginning and at the end of the headline "Four", so you get "four"
twice.

But I'm not sure what the right way to deal with it is.

Nick

> And I call this function from a buffer that looks like:
> 
> * Top
> <point is here when I call get-export-filenames>
> ** One
>    :PROPERTIES:
>    :EXPORT_FILE_NAME: one
>    :END:
> ** Two
>    :PROPERTIES:
>    :EXPORT_FILE_NAME: two
>    :END:
> ** Three
>    :PROPERTIES:
>    :EXPORT_FILE_NAME: three
>    :END:
> ** Four
>    :PROPERTIES:
>    :EXPORT_FILE_NAME: four
>    :END:
> 
> Then the list that I get back (the value of export-files) looks like:
> 
> ("four" "four" "three" "two" "one")
> 
> Whereas I would like it to be just:
> 
> ("four" "three" "two" "one")
> 
> Can anyone see what I need to do to achieve that? [Apart from just using
> (cdr export-files), I mean -- I'd like to know the /right/ way.]  I'm
> puzzled because outline-next-heading, if called interactively from the
> last child, does indeed put point at the end of that child or at the
> next (parent-level) heading, so it doesn't seem that the problem is that
> it somehow loops back when there is no next child-level entry.
> 
> Many thanks if you catch something I've missed!
> 
> Best,
> Richard
> 
> [1] http://article.gmane.org/gmane.emacs.orgmode/37244/
> 

Re: org-map-entries and org-map-continue-from

[Nick Dokos]

Nick Dokos <nicholas.dokos@hp.com> wrote:

> Richard Lawrence <richard.lawrence@berkeley.edu> wrote:
> 
> 
> > For a simple example, suppose I write:
> > #+BEGIN_SRC emacs-lisp
> > (defun get-export-filenames ()
> >   (interactive)
> >   (setq export-files '())
> >   (progn
> >     (org-map-entries
> >      (lambda ()
> >        (setq org-map-continue-from (outline-next-heading))
> >        (let ((org-trust-scanner-tags t))
> > 	 (push (org-entry-get (point) "EXPORT_FILE_NAME") export-files)))
> >      nil 'tree)
> >     (message export-files))) ; errors, but lets me see the list of collected values
> > #+END_SRC
> > 
> 

> But I'm not sure what the right way to deal with it is.
> 

Maybe this?

--8<---------------cut here---------------start------------->8---
#+BEGIN_SRC emacs-lisp
  (defun get-export-filenames ()
    (interactive)
    (setq export-files '())
    (progn
      (org-map-entries
       (lambda ()
         (setq org-map-continue-from (outline-next-heading))
         (if org-map-continue-from
             (let ((org-trust-scanner-tags t))
               (push (org-entry-get (point) "EXPORT_FILE_NAME") export-files))))
         nil 'tree)
       (message export-files))) ; errors, but lets me see the list of collected values
  
#+END_SRC
--8<---------------cut here---------------end--------------->8---


Nick

Re: org-map-entries and org-map-continue-from

[Richard Lawrence]

Nick Dokos <nicholas.dokos@hp.com> writes:

> The problem is that org-entry-get does not just look forward: it looks
> *around* and finds the property when point is both at the beginning
> and at the end of the headline "Four", so you get "four" twice.

Ah, so that's the culprit.  Thanks!

> Maybe this?
>
> #+BEGIN_SRC emacs-lisp
>   (defun get-export-filenames ()
>     (interactive)
>     (setq export-files '())
>     (progn
>       (org-map-entries
>        (lambda ()
>          (setq org-map-continue-from (outline-next-heading))
>          (if org-map-continue-from
>              (let ((org-trust-scanner-tags t))
>                (push (org-entry-get (point) "EXPORT_FILE_NAME") export-files))))
>          nil 'tree)
>        (message export-files))) ; errors, but lets me see the list of collected values
>   
> #+END_SRC

Indeed, that does seem to work: outline-next-heading returns nil if it
doesn't find a next heading, and a buffer location otherwise (at least
that's the way it looks based on some tests; the documentation doesn't
say, and I didn't crack open the code).  So wrapping the rest of the
lambda body in (if org-map-continue-from ...) prevents it from executing
that one last time.

Thanks for your help, Nick!

Best,
Richard