Allow back reference with nest level in Oniguruma for Ruby a

Ruby
1

Hello dear Ruby folks!

Nearly one year ago I asked K. Kosako for a new Oniguruma feature which
will
help to recognize plindrome sentences. It was an idea for an article
series in
Ruby-Mine, a german Ruby blog site, about pattern matching with Ruby
using
regular expressions.

K. Kosako built a special new element, which is described in the
History…

2006/07/18: Version 4.2.0

2006/07/18: [test] success in ruby 1.9.0 (2006-03-01) [i686-linux].
2006/07/18: [new] (thanks Wolfgang Nadasi-Donner)
add back reference with nest level.
\k<name+n>, \k

…and in the Oniguruma description…

back reference with nest level

 \k<name+n>     n: 0, 1, 2, ...
 \k<name-n>     n: 0, 1, 2, ...
 \k'name+n'     n: 0, 1, 2, ...
 \k'name-n'     n: 0, 1, 2, ...

 Destinate relative nest level from back reference position.

 ex 1.

   /\A(?<a>|.|(?:(?<b>.)\g<a>\k<b+0>))\z/.match("reer")

 ex 2.

   r = Regexp.compile(<<'__REGEXP__'.strip, Regexp::EXTENDED)
   (?<element> \g<stag> \g<content>* \g<etag> ){0}
   (?<stag> < \g<name> \s* > ){0}
   (?<name> [a-zA-Z_:]+ ){0}
   (?<content> [^<&]+ (\g<element> | [^<&]+)* ){0}
   (?<etag> </ \k<name+1> >){0}
   \g<element>
   __REGEXP__

   p r.match('<foo>f<bar>bbb</bar>f</foo>').captures

This feature disapeared for Ruby later on…

2006/08/11: Version 4.2.3

…
2006/08/07: [spec] move definition of USE_BACKREF_AT_LEVEL into
NOT_RUBY.

!!!
My question is now - WHY???

I would like to see it workable for Ruby again, it can be useful - and -
it is
already there!
!!!

Wolfgang Nádasi-Donner

2

I have one question, because there is no reaction to this post:

Is this here (comp.lang.ruby) the right place for discussions and
“change
proposals” for Oniguruma usage in Ruby 1.9?

If this is not the case, please give me a hint where to place these
texts.

Thanks in advance, Wolfgang Nádasi-Donner

3

Hi,

In message “Re: [Minor Change Proposal]Allow back reference with nest
level in Oniguruma for Ruby again”
on Wed, 16 May 2007 00:15:04 +0900, Wolfgang Nádasi-Donner
[email protected] writes:

|Is this here (comp.lang.ruby) the right place for discussions and “change
|proposals” for Oniguruma usage in Ruby 1.9?

ruby-core list is the better place.

          matz.
4

Yukihiro M. schrieb:

ruby-core list is the better place.

          matz.

I see - but how to place texts there? - Via “http://www.ruby-forum.com/”
there
is a read-only access only.

Wolfgang Nádasi-Donner

5

Yukihiro M. schrieb:

ruby-core list is the better place.

          matz.

Thank you for the hint - I copied it there and close the question in
comp.lang.ruby.