Re: Special hilighting for comments

[tomas]

On Sun, Dec 11, 2022 at 07:33:19AM +0000, Heime wrote:
> 
> ------- Original Message -------
> On Sunday, December 11th, 2022 at 7:24 AM, tomas@tuxteam.de 
> <tomas@tuxteam.de> wrote:
> 
> 
> > On Sun, Dec 11, 2022 at 06:59:32AM +0000, Heime wrote:
> > 
> > > ------- Original Message -------
> > > On Sunday, December 11th, 2022 at 6:54 AM, tomas@tuxteam.de 
> > > tomas@tuxteam.de wrote:
> > > 
> > > > On Sun, Dec 11, 2022 at 02:37:38AM +0000, Heime wrote:
> > > > 
> > > > > Would you know the problem with the following regexp
> > > > > 
> > > > > "^;; \\[.+\\].*$"
> > > > > 
> > > > > It fails to match
> > > > > 
> > > > > ;; [something] other things
> > > > 
> > > > Worksforme. At least if the first semicolon is actually at the
> > > > start of a line, that is.
> > > > 
> > > > Cheers
> > > > --
> > > > t
> > > 
> > > Yes it works. I am trying to use subexp in highlight-regexp.
> > > To match "^;; \\[.+\\].*$" but highlight only the "\\[.+\\]" part.
> > 
> > 
> > Aha. Read again the documentation string of `hightlight-regexp'.
> > Is there any part in there you don't understand? What about
> > SUBEXP?
> 
> Right.  Have done 
> 
>   (highlight-regexp "^;; \\[.+\\].*$" 'elf-face "\\[.+\\]")
> 
> which does not get the highlighting.

[...]

Ah. There's your misunderstanding. Read the section about
"grouping constructs" in regular expressions. The short
version is that this argument SUBGROUP refers to the count
number of that subexpression, starting with 1.

So you need to group the part you are interested in in
your regexp (the subexpression) with \(...\) (don't forget
the extra backslash for the string syntax) like so:

  "^;; \\(\\[.+\\]\\).*$"

Now this is the first subgroup in your regexp (actually, the
only one). You refer to it with 1. This might work

   (highlight-regexp "^;; \\(\\[.+\\]\\).*$" 'elf-face 1)

Now read the section on "\( ... \)" in the chapter "Backslash
constructs in Regular Expressions". The others are useful,
too :)

Cheers
-- 
t

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