Re: [O] New feature: loop over siblings for some commands

[David Maus]

Hi Bastien,

At Wed, 27 Jul 2011 17:28:36 +0200,
Bastien wrote:
>
> Hi David,
>
> David Maus <address@hidden> writes:
>
> > I highly recommend to not use this macro but to build the intended
> > functionality with separate building blocks: Factor out the flesh of
> > the respective functions (e.g. org-schedule) and use org-map-entries
> > to map. As far as I can see, the latter provides all we need:
>
> I took this road.
>
>
> The first patch manually reverts the commit you are commenting.
>
> The third patch implements the "loop" functionality by just using
> `org-map-entries', not a macro.
>
> I'm sure we could have an `org-loop' macro factoring out the duplicate
> code in the new `org-schedule' and `org-deadline'.  If you have time to
> look at this, that will greatly help.

My vacation starts saturday so I do have time and really like to get
my hands dirty with some Lisp hacking.

Now for the macro (2 iterations later): It might not be necessary to
factor out the functions if the function that invokes the looping
can be called recursively.

E.g.

#+begin_src emacs-lisp
  (defmacro org-with-headline-siblings (function)
    "Apply function to siblings of current headline."
    `(org-map-entries ,function 'siblings))

  (defun org-schedule ()
    (...)
    (if (or (not (org-region-active-p))
            (not org-loop-over-siblings))
        (let ((org-loop-over-siblings nil))
          (org-with-headline-siblings 'org-schedule))))
#+end_src

If the function takes arguments, we need to wrap the function call at
the end in a lambda.

And if this works out, we are almost there:

#+begin_src emacs-lisp
  (defmacro org-with-headline-siblings-maybe (predicate &rest body)
    "Execute body on current headline's siblings if PREDICATE."
    `(progn
       ,@body
       (if ,predicate
           (org-map-entries '(lambda () (progn ,@body)) 'siblings))))
#+end_src

>
> > Another abstraction: Instead
> > 'org-loop-over-siblings-with-active-region' something like:
> > 'org-loop-over-headlines-with-active-region' that can be set to a
> > symbol or a list of symbols indicating which headings to loop over
> > (e.g. 'siblings, 'children, ...).
>
> The variable is now called `org-loop-over-headlines-in-active-region'
> and understand these kind of values:
>
> - nil: don't loop
> - t: loop over all headlines
> - "MATCH": a tag/property/todo match to loop over matching headlines
>

Nice. These values can fit into org-map-entries MATCH argument, can't
they?

We would have:
                 org-loop-over-headlines-in-active-region
                                  /
(org-map-entries FUNC &optional MATCH SCOPE &rest SKIP)
                 /                      \
           our function            region is active

I'm not quite sure, but

a/ we move the check for an active region to org-map-entries: If
SCOPE is 'region but no region is active, org-map-entries simply
returns.

b/ we modify org-map-entries, so that a MATCH of nil means: No
match.

This way we can express the predicate as a condition of map.

#+begin_src emacs-lisp
  (defmacro org-loop-over-headlines (&rest body)
    `(progn
       ,@body
       (org-map-entries '(lambda () (progn ,@body)) 
org-loop-over-headlines-in-active-region 'region)))
#+end_src

> If you can test these patches and send some feedback, that'd be nice!

Scheduled for Sunday.

Best,
  -- David
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