From: Josh Cheek <josh.cheek@...>
Date: 2011-02-01T17:55:44+09:00
Subject: Re: Recursive regular expressions in Ruby?

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On Tue, Feb 1, 2011 at 2:50 AM, Jarmo Pertman <jarmo.p@gmail.com> wrote:

> Thanks!
>
> It seems that you've given wrong link as i've unable to find anything
> regarding "regular expressions" in that pdf.
>
> Jarmo
>
> On Feb 1, 5:34 am, Josh Cheek <josh.ch...@gmail.com> wrote:
> > On Mon, Jan 31, 2011 at 5:05 PM, Jarmo Pertman <jarm...@gmail.com>
> wrote:
> > > Hi!
> >
> > > I was just wondering if there is possible to write recursive regular
> > > expressions in Ruby? As i'm understanding at this moment then there
> > > isn't. Prove me wrong.
> >
> > > If you're not aware of such possibility in Perl for example then here
> > > is one good blog post about it
> > >http://www.catonmat.net/blog/recursive-regular-expressions
> >
> > > It seems that also PHP has such a functionality.
> >
> > > Jarmo
> >
> > 1.9.2 has it, here is an example:
> >
> > regex = /^(?<bracketed>\[(\g<bracketed>|\d)\])$/
> >        '1'.match regex # => nil
> >      '[1]'.match regex # => #<MatchData "[1]" bracketed:"[1]">
> >    '[[1]]'.match regex # => #<MatchData "[[1]]" bracketed:"[[1]]">
> >  '[[[1]]]'.match regex # => #<MatchData "[[[1]]]" bracketed:"[[[1]]]">
> >
> > I found it in the Christmas edition of PragPub (
> http://pragprog.com/magazines/download/19.PDF) they talk about it more in
> > depth, as well, if you want more info.
>
>
You're right, that was the January edition. Here is the one I meant to link
to, Dec 2010 http://pragprog.com/magazines/download/18.PDF

It is in section "what's new in Ruby 1.9.2" on page 24

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