Nick,
Thanks very much!  Excellent description.
Cheers.
Fil

On 13 April 2012 00:35, Nick Dokos <nicholas.dokos@hp.com> wrote:

> Filippo A. Salustri <salustri@ryerson.ca> wrote:
>
> > Hi all,
> > I'm looking for a little coding help.
> >
> > I want to try to a task's priority automatically, based on the
> priorities of its subtasks.
> > Specifically, I'd like to set the priority of the task to the priority
> of the highest-priority
> > subtask.
> > And I'd like that task priority to be updated (if necessary)
> automatically any time I change the
> > priority of one of its subtasks.
> >
>
> The basic idea in all of these situations is to use org-map-entries
> from the mapping API:
>
>     (info "(org) Using the mapping API")
>
> to walk the entries, applying a function on each.
>
> The function to apply on each entry is frequently a specialization
> of one of the functions provided by the property API:
>
>     (info "(org) Using the property API")
>
> In this case, you need a function to get the priority of each entry:
>
> (def fas/task-priority ()
>     (org-entry-get (point) "PRIORITY"))
>
> which you can then give to org-map-entries:
>
>     (org-map-entries (function fas/task-priority) t 'tree)
>
> The assumption here is that we are at the head node and we have
> an arbitrary number of subnodes. The call above will accumulate
> the priorities of each subnode in a list (if a subnode does not
> have a priority assigned, the priority will be nil).
>
> For example, applying
>
> * section
> ** [#B] subsection
> *** [#C] subsubsection
> **** paragraph
> ***** [#B] subparagraph
>
> will return the list
>
> (nil "B" "C" nil "B")
>
> It is then just a matter of finding the highest priority and applying
> it to the top node. Assuming that "A" is higher priority than "B" etc,
> something like this will do:
>
> --8<---------------cut here---------------start------------->8---
> (defun fas/task-priority ()
>  (org-entry-get (point) "PRIORITY"))
>
> (defun fas/set-task-priority ()
>  (interactive)
>  (let* ((priorities (org-map-entries (function fas/task-priority) t 'tree))
>         (sortedpriorities (sort (delq nil priorities) (function
> string-lessp))))
>    (if sortedpriorities
>        (org-priority (aref (car sortedpriorities) 0)))))
> --8<---------------cut here---------------end--------------->8---
>
> org-priority wants a character, but sortedpriorities is a list of
> strings, hence the aref rigmarole. It should work even if *no*
> priorities are set at all: sortedpriorities will be nil, so nothing will
> be done.
>
> Nick
>
>


-- 
\V/_
Filippo A. Salustri, Ph.D., P.Eng.
Mechanical and Industrial Engineering
Ryerson University
350 Victoria St, Toronto, ON
M5B 2K3, Canada
Tel: 416/979-5000 ext 7749
Fax: 416/979-5265
Email: salustri@ryerson.ca
http://deseng.ryerson.ca/~fil/