From: "Wolfgang Nádasi-Donner" <wonado@...>
Date: 2007-02-03T18:25:05+09:00
Subject: Re: Named groups in regexp matches?

Paddy3118 schrieb:
> On Jan 29, 10:14 pm, Wolfgang N�dasi-Donner <won...@donnerweb.de>
>> irb(main):001:0> md="abba".match(/(?<a1>.)(?<a2>.)\k<a2>\k<a1>/)
> Hi Wolfgang,
> I was going to ask why you did not use the syntax of (?P<name>...) as
> used in Python, but found that, according to http://www.amk.ca/python/
> howto/regex/regex.html#SECTION000530000000000000000, the P is for
> Python extensions.

It's not that easy. The regular expression engine used in Ruby 1.9 is not 
integral part or ruby. It is a stand alone regular expression engine called 
"Oniguruma" (http://www.geocities.jp/kosako3/oniguruma/).

Oniguruma is actually existent in tree variants, "2.x.y" can be used in Ruby 1.6 
and 1.8, but it is not the standard engine of Ruby 1.6/1.8, "4.x.y" will be used 
in Ruby 1.9ff, and "5.x.y" is not related to Ruby.

The syntax of the regular expressions are not defined by Ruby, they are defined 
by Oniguruma.

Wolfgang N�dasi-Donner