Re: understanding the function outline-level

[Carsten Dominik <carsten.dominik@gmail.com>]

On Jun 7, 2011, at 8:33 PM, Niels Giesen wrote:

> Hi Michael,
> 
> match data get set by searches. One can inhibit match-data being
> cluttered by using the `save-match-data' macro (you should probably do
> so when using searches in a lisp program).
> 
> Outline.el seems to make very frequent use of this 'global' data;
> instead of passing this data on via function arguments or so, it
> depends on this dynamically set data, which makes it very hard to see
> who does what.
> 
> Some prodding about led me to believe the searching in
> `outline-back-to-heading' is your suspect (but I have not investigated
> this further). At least
> 
> (progn
>  (outline-back-to-heading)
>  (outline-level))

Or, alternatively, if you are already at the beginning of the headline

(and (looking-at outline-regexp)
     (funcall 'outline-level))

So outline-level needs to just have matched when calling that function.

IMPORTANT:

Using (funcall 'outline-level) is more general as major modes are allowed
to set their own function for level calculation. In fact, calling (outline-level)
in Org-mode will give the wrong result, because the regexp also
matches the space character after the stars, so the level is one less than the
length of the match string.

- Carsten


> 
> Returns a reasonable answer each time I run it.
> 
> (info "(Elisp)Match Data")
> 
> May be of interest to you.
> 
> On Tue, Jun 7, 2011 at 6:23 PM, Michael Brand
> <michael.ch.brand@gmail.com> wrote:
>> Hi all
>> 
>> I am on the way of tracking down an (Org?) buglet and now
>> outline-level tries to strike me with my lack of experience with
>> "Match Data" of Emacs search and I would like to ask for some help to
>> understand.
>> 
>> M-: (outline-level) returns a value that I don't understand yet. The
>> number does not correspond to the amount of stars and is independent
>> of at the beginning of which line the point was before. And when I
>> look at the implementation of outline-level I am missing a function
>> that initializes the "Match Data". Where is that last search or match
>> operation?
>> 
>> Michael
>> 
>> 
> 
> 
> 
> -- 
> http://pft.github.com
> 

- Carsten