Re: Matching labels with buttons

[Stephen Berman <stephen.berman@gmx.net>]

On Mon, 15 Jul 2024 17:25:42 +0000 Heime <heimeborgia@protonmail.com> wrote:

> On Tuesday, July 16th, 2024 at 4:24 AM, Heime <heimeborgia@protonmail.com> wrote:
>
>> 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 [-] ".
>
> In the latter case I want to match [-] at the end with any trailing spaces.

With your original code amended by anchoring the first regexp as I
suggested, I think it handles both cases you want; at least the brief
tests I tried worked.  If you don't get the results you want, please
show the complete code you're using and examples where it fails.

Steve Berman