Re: RegExp problem

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From	Thomas 'PointedEars' Lahn <PointedEars@web.de>
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Subject	Re: RegExp problem
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John English wrote:

> I have this string in JavaScript:
> 
>   var s = "</p><ol><li>First\n</li><li>Second\n</li></ol><p>";
> 
> Then I do this (to remove the outer "</p>...<p>"):

One wonders how it got there in the first place, since it is not Valid.
One also wonders why you think you need to (or could, trivially) fix that.

>   s = s.replace(/^<\/([^> ]+)[^>]*>(.*)<\1>$/,"$2");

  <strong title="You did not expect that x > y, did you?"
          style="color: red; font-weight: bold; text-transform: uppercase"
          >wrong</strong>

This expression does _not_ accurately match HTML tags or elements, or XML 
tags or elements for that matter.  See HTML5 (CR) and XHTML 1.0/1.1 (REC) 
for details.

> Nothing happens (s is unchanged, and if I use match() instead of replace
> it returns false), but if I go try it at
> http://www.regular-expressions.info/javascriptexample.html, it works!
> 
> I've tried all sorts of things (creating a separate regExp object, using
> //g, taking out the ^$, replacing [^> ]+ with [a-z0-9]*...) but nothing
> makes any difference.
> 
> It's driving me nuts. Can anyone tell me what I'm doing wrong here?

You are using “.” which does not match "\n", so that expression matches as 
far as 

   </p><ol><li>First\n</li><li>Second\n</li></ol><p>  
  `---'`-----------'
    :        :
    :        '-------.
    :                :
  ,----------------.,--.   
  ^<\/([^> ]+)[^>]*>(.*)<\1>$

(use a fixed-width font).  Then it fails, because "\n" is not matched by 
“<”.

That said, like so many other people before you, you are trying to apply an 
expression describing a Chomsky type-3 language to match a sentence of a 
text in a Chomsky type-2 language, which usually *must* fail.

-- 
PointedEars

Twitter: @PointedEars2
Please do not Cc: me. / Bitte keine Kopien per E-Mail.

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Thread

RegExp problem John English <john.foreign@gmail.com> - 2013-03-14 04:56 -0700
  Re: RegExp problem "Jukka K. Korpela" <jkorpela@cs.tut.fi> - 2013-03-14 14:22 +0200
    Re: RegExp problem "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2013-03-14 14:52 +0100
      Re: RegExp problem "Jukka K. Korpela" <jkorpela@cs.tut.fi> - 2013-03-14 16:08 +0200
      Re: RegExp problem Stefan Weiss <krewecherl@gmail.com> - 2013-03-14 15:25 +0100
        Re: RegExp problem Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-03-14 16:47 +0100
          Re: RegExp problem Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-03-14 21:11 +0100
        Re: RegExp problem "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2013-03-14 19:54 +0100
  Re: RegExp problem "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2013-03-14 13:26 +0100
  Re: RegExp problem Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-03-14 17:31 +0100

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