Re: Matching labels with buttons

[Heime <heimeborgia@protonmail.com>]

On Tuesday, July 16th, 2024 at 1:42 AM, Stephen Berman <stephen.berman@gmx.net> wrote:

> On Mon, 15 Jul 2024 12:58:05 +0000 Heime heimeborgia@protonmail.com wrote:
> 
> > Sent with Proton Mail secure email.
> > 
> > On Tuesday, July 16th, 2024 at 12:52 AM, Stephen Berman
> > stephen.berman@gmx.net wrote:
> > 
> > > On Mon, 15 Jul 2024 12:35:53 +0000 Heime heimeborgia@protonmail.com wrote:
> > > 
> > > > On Monday, July 15th, 2024 at 11:56 PM, Stephen Berman
> > > > stephen.berman@gmx.net wrote:
> > > > 
> > > > > On Mon, 15 Jul 2024 11:25:28 +0000 Heime heimeborgia@protonmail.com wrote:
> > > > > 
> > > > > > Sent with Proton Mail secure email.
> > > > > > 
> > > > > > On Monday, July 15th, 2024 at 11:17 PM, Heime
> > > > > > heimeborgia@protonmail.com wrote:
> > > > > > 
> > > > > > > I want to match cases such as
> > > > > > > 
> > > > > > > Label [-]
> > > > > > > 
> > > > > > > Have constructed the following regexp, but it does not match the above
> > > > > > > 
> > > > > > > "\\(.\\)\\(\\s-\\[\\-\\]\\s-\\)"
> > > > > > > 
> > > > > > > I aw using
> > > > > > > 
> > > > > > > (when (string-match "\\(.\\)\\(\\s-\\[\\-\\]\\s-\\)" text)
> > > > > > 
> > > > > > In the code I have
> > > > > > 
> > > > > > (if (string-match "\\(\\s-\\[\\-\\]\\s-\\)\\(.*\\)" label) ; [-] LB
> > > > > > 
> > > > > > (progn
> > > > > > (setq bt (match-string 1 label))
> > > > > > (setq lb (match-string 2 label))
> > > > > > (setq result
> > > > > > (concat bt (propertize lb 'face '(:foreground "red")))))
> > > > > > 
> > > > > > (when (string-match "\\(.\\)\\(\\s-\\[\\-\\]\\s-*\\)" label) ; LB [-]
> > > > > > 
> > > > > > (setq lb (match-string 1 label))
> > > > > > (setq bt (match-string 2 label))
> > > > > > (setq result
> > > > > > (concat (propertize lb 'face '(:foreground "red")) bt)))
> > > > > > 
> > > > > > Doing some tests with
> > > > > > 
> > > > > > "OFF [-]"
> > > > > > 
> > > > > > keeps matching the first string-match
> > > > > 
> > > > > That's because your regexp isn't anchored, so string-match succeeds if
> > > > > it finds a match anywhere in the string passed to it. To avoid this,
> > > > > start the regexp with "\\`", which anchors it to the start of the string
> > > > > being matched against; see (info "(elisp) Regexp Backslash").
> > > > > 
> > > > > Steve Berman
> > > > 
> > > > I would like to have two regex expressions, one to match only " [-] LABEL " and
> > > > another to match only " LABEL [-] ". With any number of whitespace.
> > > > 
> > > > Can one use "^" ? Or is "\\`" preferred ?
> > > 
> > > If you are always matching against a string, e.g. just using
> > > string-match, then IIUC "^" and "\\`" give the same results. If you are matching against test in a buffer, e.g. with re-search-forward, looking-at etc., then they can differ: "^" matches the beginning the the line containing the matched string, "\\\\\\\\`" the beginning of the string
> > > itself, regardless of where in the line it is (at point-min the results
> > > are the same).
> > > 
> > > > And can one use "[[:space:]]" rather
> > > > than "\\s-" ? Which is preferred ?
> > > 
> > > IIUC these both give the same results.
> > > 
> > > Steve Berman
> > 
> > Would I introduce \\` before the first grouping
> > 
> > "\\`\\(\\s-\\[\\-\\]\\s-\\)\\(.*\\)"
> 
> 
> Since "\\`" matches the empty string, I don't think it matters whether
> it's inside or outside of the group. But since in this case it's
> anchoring the entire regexp, it seems conceptually preferable to keep it
> outside (in contrast, e.g., to the case where the regexp is a
> disjunction and you only want to anchor one of the disjuncts).
> 
> > How would I print \\` in a docstring ?
> 
> 
> You have to escape the "`": \\\\\\\\=` (not \\=\\`).
> 
> Steve Berman


I also have to handle the case of " LABEL [-] " with a different regex, so I can
distinguish between " [-] LABEL " and " LABEL [-] ".