[thelist] Regular Expression - Is it a bug or am I missing something very obvious?

VOLKAN ÖZÇELİK volkan.ozcelik at gmail.com
Thu Mar 10 05:20:56 CST 2005


I think I am beginning to understand.

I'll post my final thoughts when I am clear on the subject.

Thank you for all for your help.

Cheers.


On Thu, 10 Mar 2005 13:12:24 +0200, VOLKAN ÖZÇELİK
<volkan.ozcelik at gmail.com> wrote:
> sorry. I looked at my posting, my original reg ex was wrong.
> 
> pardon me.
> 
> Could you please consider the following and discard my previous post.
> 
> sorry for the confusion.
> 
> ----
> 
> I minimized the problem further.
> 
> /<\/(?!p)[\s\S]*?>/ig   matches "</p>"
> 
> but neither
> 
> /<\/?(?!p)[\s\S]*?>/ig
> 
> nor
> 
> /<\/{0,1}(?!p)[\s\S]*?>/ig
> 
> matches "</p>". Imho the three expressions above should match "</p>".
> 
> So it is repetition-related. (the ? or {0,1} makes it fail.
> 
> Is it a problem with javascript regexp's lookahead assertion?
> 
> ---
> 
> On Thu, 10 Mar 2005 12:27:32 +0200, VOLKAN ÖZÇELİK
> <volkan.ozcelik at gmail.com> wrote:
> > /<\/?(?!p)[\s\S]*?>/ig
> >
> > what about the last ">" ?
> >
> > you tested it as
> >
> > '</p>'.match(/<\/?(?!p)/)
> >
> > but it should be
> >
> > '</p>'.match(/<\/?(?!p)>/)
> >
> > If the last ">" weren't there you were right. But now it should
> > account for the final ">" as well isn't it?
> >
> > Cheers,
> > Volkan.
> >
> >
> > ---------- Forwarded message ----------
> > From: Jeffery To <jeffery.to at gmx.net>
> > Date: Thu, 10 Mar 2005 04:50:07 -0500
> > Subject: Re: [thelist]  Regular Expression - Is it a bug or am I
> > missing something very obvious?
> > To: "thelist at lists.evolt.org" <thelist at lists.evolt.org>
> >
> > It's matching what you're telling it to match:
> >
> > '</p>'.match(/<\/?(?!p)/) returns '<' because the string '<' contains
> > the character '<', zero occurrences of the character '/' and is not
> > followed by the character 'p' in the source string. (It is followed by
> > the character '/'.)
> >
> > HTH,
> > Jeff
> >
> > VOLKAN ÖZÇELİK wrote:
> > > Hi Community, hi RegExp lovers!
> > >
> > > Regarding the following js reg exp.
> > >
> > > /<\/?(?!(p))/ig;   (It's a simplified version of what I'm working on)
> > >
> > > I think what it is supposed to do is:
> > >
> > > 1. match character < literally
> > > 2. match craracter / literally (zero or one times)
> > > 3. If there is a p immediately after do not match anything, just
> > > rollback (i.e. negative lookahead)
> > >
> > > so the code below
> > >
> > > var strTest1 = "</p>";
> > > var regEx1 = /<\/?(?!(p))/ig;
> > > strTest1 = strTest1.replace(regEx1,"")
> > > alert(strTest1);
> > >
> > > should alert "</p>".
> > > Well it doesn't. It alerts "p/>". Which means that it has found a match.
> > >
> > > I need to swap things around to make it work:
> > >
> > > var strTest2 = "</p>";
> > > regEx2 = /<(?!(\/p|p))/ig;
> > > strTest2 = strTest2.replace(regEx2,"")
> > > alert(strTest2);
> > >
> > > but why on earth do I need to make things unnecessarily complicated ?!
> > > The first one should work at least according to my humble logic!
> > >
> > > Is it a bug? Or am I missing a really simple thing?
> > >
> > > Please help me before I split this PC with an axe.
> > >
> > > TIA,
> > > Volkan.
> > --
> >
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