Anchoring a RE in a string

Anchoring a RE in a string

[Doug Lewan]

Currently I'm trying to check the /beginning/ of a multi-line string with a regular expression.
The scenario looks like this:

(string-match "^\\s-+ABCD"
              "qwer\n    zxcv\n    ABCD")
                                            ^ Matches here.

I want it to fail because the beginning doesn't match.
I hadn't expected the anchor (^) to match inside the string.

I can't be the only one to have wanted to do this.
What's the right way.

Thanks.

,Douglas
Douglas Lewan
Shubert Ticketing
(201) 489-8600 ext 224

RE: Anchoring a RE in a string

[Doug Lewan]

I've found the /adequate/ solution.

(setq s (delete ?\n s))
(string-match "^\\s-+ABCD" s)

Still, is there no way of truly anchoring at the beginning of a string?

> -----Original Message-----
> From: help-gnu-emacs-bounces+dougl=shubertticketing.com@gnu.org
> [mailto:help-gnu-emacs-bounces+dougl=shubertticketing.com@gnu.org] On
> Behalf Of Doug Lewan
> Sent: Friday, 2012 June 08 14:49
> To: help-gnu-emacs@gnu.org
> Subject: Anchoring a RE in a string
> 
> Currently I'm trying to check the /beginning/ of a multi-line string
> with a regular expression.
> The scenario looks like this:
> 
> (string-match "^\\s-+ABCD"
>               "qwer\n    zxcv\n    ABCD")
>                                             ^ Matches here.
> 
> I want it to fail because the beginning doesn't match.
> I hadn't expected the anchor (^) to match inside the string.
> 
> I can't be the only one to have wanted to do this.
> What's the right way.
> 
> Thanks.
> 
> ,Douglas
> Douglas Lewan
> Shubert Ticketing
> (201) 489-8600 ext 224
> 
> 

Re: Anchoring a RE in a string

[jpkotta]

On Friday, June 8, 2012 2:08:24 PM UTC-5, Doug Lewan wrote:
> I've found the /adequate/ solution.
> 
> (setq s (delete ?\n s))
> (string-match "^\\s-+ABCD" s)
> 
> Still, is there no way of truly anchoring at the beginning of a string?
> 
> > -----Original Message-----
> > From: help-gnu-emacs-bounces+dougl=shubertticketing.com@gnu.org
> > [mailto:help-gnu-emacs-bounces+dougl=shubertticketing.com@gnu.org] On
> > Behalf Of Doug Lewan
> > Sent: Friday, 2012 June 08 14:49
> > To: help-gnu-emacs@gnu.org
> > Subject: Anchoring a RE in a string
> > 
> > Currently I'm trying to check the /beginning/ of a multi-line string
> > with a regular expression.
> > The scenario looks like this:
> > 
> > (string-match "^\\s-+ABCD"
> >               "qwer\n    zxcv\n    ABCD")
> >                                             ^ Matches here.
> > 
> > I want it to fail because the beginning doesn't match.
> > I hadn't expected the anchor (^) to match inside the string.
> > 
> > I can't be the only one to have wanted to do this.
> > What's the right way.
> > 
> > Thanks.
> > 
> > ,Douglas
> > Douglas Lewan
> > Shubert Ticketing
> > (201) 489-8600 ext 224
> > 
> >

Use \\` instead of ^.  See "34.3.1.1 Special Characters in Regular Expressions" in the Elisp manual.

RE: Anchoring a RE in a string

[Doug Lewan]

\` -- empty string at the beginning of buffer

Fantastic!

In fact, I'd found my first use for \' just recently. I don't know why it didn't strike me.

I will never run out of things to learn in emacs. As a video game, I still feel like I'm on level 2.

> -----Original Message-----
> From: help-gnu-emacs-bounces+dougl=shubertticketing.com@gnu.org
> [mailto:help-gnu-emacs-bounces+dougl=shubertticketing.com@gnu.org] On
> Behalf Of jpkotta
> Sent: Friday, 2012 June 08 15:19
> To: gnu.emacs.help@googlegroups.com
> Cc: help-gnu-emacs@gnu.org
> Subject: Re: Anchoring a RE in a string
> 
> On Friday, June 8, 2012 2:08:24 PM UTC-5, Doug Lewan wrote:
> > I've found the /adequate/ solution.
> >
> > (setq s (delete ?\n s))
> > (string-match "^\\s-+ABCD" s)
> >
> > Still, is there no way of truly anchoring at the beginning of a
> string?
> >
> > > -----Original Message-----
> > > From: help-gnu-emacs-bounces+dougl=shubertticketing.com@gnu.org
> > > [mailto:help-gnu-emacs-bounces+dougl=shubertticketing.com@gnu.org]
> On
> > > Behalf Of Doug Lewan
> > > Sent: Friday, 2012 June 08 14:49
> > > To: help-gnu-emacs@gnu.org
> > > Subject: Anchoring a RE in a string
> > >
> > > Currently I'm trying to check the /beginning/ of a multi-line
> string
> > > with a regular expression.
> > > The scenario looks like this:
> > >
> > > (string-match "^\\s-+ABCD"
> > >               "qwer\n    zxcv\n    ABCD")
> > >                                             ^ Matches here.
> > >
> > > I want it to fail because the beginning doesn't match.
> > > I hadn't expected the anchor (^) to match inside the string.
> > >
> > > I can't be the only one to have wanted to do this.
> > > What's the right way.
> > >
> > > Thanks.
> > >
> > > ,Douglas
> > > Douglas Lewan
> > > Shubert Ticketing
> > > (201) 489-8600 ext 224
> > >
> > >
> 
> Use \\` instead of ^.  See "34.3.1.1 Special Characters in Regular
> Expressions" in the Elisp manual.

Re: Anchoring a RE in a string

[Philipp Haselwarter]

`rx' is cool when you're too lazy to look up special symbols


-- 
Philipp Haselwarter

Re: Anchoring a RE in a string

[rusi]

On Jun 10, 12:28 am, Philipp Haselwarter <phil...@haselwarter.org>
wrote:
> `rx' is cool when you're too lazy to look up special symbols
>
> --
> Philipp Haselwarter

Interesting!! Cant find an info page.

Re: Anchoring a RE in a string

[Philipp Haselwarter]

On Sun, Jun 10 2012 07:38 (@1339306698), rusi wrote:

> On Jun 10, 12:28 am, Philipp Haselwarter <phil...@haselwarter.org>
> wrote:
>> `rx' is cool when you're too lazy to look up special symbols
>>
>> --
>> Philipp Haselwarter
>
> Interesting!! Cant find an info page.
>

Unfortunately, its only mention in emacs or elisp info is Gerd
Moellmann's authorship notice: "[...] `rx.el', a regular expression
constructor. ".

Take a look at C-h f rx RET

-- 
Philipp Haselwarter

RE: Anchoring a RE in a string

[Drew Adams]

> Unfortunately, its only mention in emacs or elisp info is Gerd
> Moellmann's authorship notice: "[...] `rx.el', a regular expression
> constructor. ".  Take a look at C-h f rx RET

If you cannot find something in the manuals, try searching for it at EmacsWiki
(or Google after that).  Entering "rx" in the wiki search field shows this page
as the first search hit: http://emacswiki.org/emacs/rx.

(That of course is not intended to mean that something should not also be
mentioned in the manuals.  It's just intended to help you find information.  The
wiki is another resource, like help-gnu-emacs@gnu.org.)