[External] : Use the characters "+" and "-" in regular expressions

[Christopher Dimech]

Try this one instead, which should match strings containing 0 or more 
whitespace characters.

(string-match "^[\s]*$" s)


> Sent: Thursday, May 20, 2021 at 11:40 PM
> From: steve-humphreys@gmx.com
> To: "Christopher Dimech" <dimech@gmx.com>
> Cc: "help-gnu-emacs@gnu.org" <help-gnu-emacs@gnu.org>
> Subject: [External] :  Use the characters "+" and "-" in regular expressions
>
>
>
> > Sent: Thursday, May 20, 2021 at 11:31 PM
> > From: "Christopher Dimech" <dimech@gmx.com>
> > To: steve-humphreys@gmx.com
> > Cc: "help-gnu-emacs@gnu.org" <help-gnu-emacs@gnu.org>
> > Subject: [External] :  Use the characters "+" and "-" in regular expressions
> >
> > This could be what you need
> >
> >   (string-match "[\s]+ " s)
> >
> > Matches any white-space character.
>
> That would actually match a sentence, which I don't want.
>
> What I like to match is a string composed only of whitespace.
>
> > > Sent: Thursday, May 20, 2021 at 11:19 PM
> > > From: steve-humphreys@gmx.com
> > > To: tomas@tuxteam.de
> > > Cc: "help-gnu-emacs@gnu.org" <help-gnu-emacs@gnu.org>
> > > Subject: Re: [External] :  Use the characters "+" and "-" in regular 
> > > expressions
> > >
> > > This is a string of blanks, a string composed of whitespace of any length.
> > >
> > > "                     "
> > >
> > >
> > >
> > > > Sent: Thursday, May 20, 2021 at 10:50 PM
> > > > From: tomas@tuxteam.de
> > > > To: steve-humphreys@gmx.com
> > > > Cc: "help-gnu-emacs@gnu.org" <help-gnu-emacs@gnu.org>
> > > > Subject: Re: [External] :  Use the characters "+" and "-" in regular 
> > > > expressions
> > > >
> > > > On Thu, May 20, 2021 at 12:37:17PM +0200, steve-humphreys@gmx.com wrote:
> > > >
> > > > [...]
> > > >
> > > > > Done some tests and got some strange results that thought would not 
> > > > > match.  Then things
> > > > > made more sense after your clarification because when I looked at 
> > > > > some of the strings,
> > > > > there was a comma in them.
> > > >
> > > > OK. Glad I could help.
> > > >
> > > > > Am seeing how to match strings of blank lines
> > > >
> > > > What is "a string of blank lines"?
> > > >
> > > > I know strings of characters. But a line is not a character.
> > > >
> > > > Do you mean "several blank lines next to each other"? I don't
> > > > think so. But what do you mean?
> > > >
> > > > > But " +" does not do the job.
> > > >
> > > > Again: you know by now that this will match "one or more spaces". Is
> > > > that for you a "string of blanks" (huh: where did you leave the
> > > > "line" from above?) or not?
> > > >
> > > > >                  I know why, but how can one match strings of blanks?
> > > >
> > > > To even have a chance to do that, you'll have to get hold of a more
> > > > or less precise idea of what "a string of blanks" is. This is work.
> > > >
> > > > Begin with:
> > > >
> > > >   (string-match " +" "A summer full of butterflies")
> > > >   => 1
> > > >
> > > > Bingo: the first run of one-or-more spaces is at the position 1
> > > > (the first position in the string is 0, the "A"). So it's working
> > > > as it should.
> > > >
> > > > So what is /your/ idea of "a string of blank lines" or "a string
> > > > of blanks"? Only you can find out.
> > > >
> > > > If you feel you are stuck in that task, it sometimes help to collect
> > > > a couple of examples and counter-examples (they'll come in handy
> > > > when you try to test your attempts).
> > > >
> > > > Cheers
> > > >  - t
> > > >
> > >
> > >
> >
> >
>
>