From: Tanaka Akira <akr@...17n.org>
Date: 2004-03-24T22:48:29+09:00
Subject: Re: GString and XSS (Re: groovy)

In article <pan.2004.03.24.13.22.04.276639@adslhome.dk>,
  Simon Strandgaard <neoneye@adslhome.dk> writes:

> With oniguruma (Rubys new regexp engine) you can use named backreferences.

For named capture, "...#{:foo}..." can be used as
gsub(/...(?<foo>...).../, "...#{:foo}...").  Anyway it avoids
backslash escape in the argument.

> But that is not what you ask for.

Yes.  This is another issue.  However I considered it too.

> Another possibility would be to pass a block to gsub
>
> str.gsub!(/(\s\w)(\w+)(\w\s)/) do |m|
>     $3 + $2 + $1
> end
>
> And then use $1..$9, but it seems more complex.

Yes.  gsub's block avoids the confusion.
However, people tends to gsub without block because it seems simpler.

> BTW: Why is 'm' of class String.  It would be nice if it were
> an instance of MatchData.  If it had been a MatchData object,
> then the following piece would have worked.
>
> str.gsub!(/(\s\w)(\w+)(\w\s)/) do |m|
>     m[3] + m[2] + m[1]
> end

I think a regexp with named capture should binds local variables.
It makes possible to describe your example as follows.

str.gsub!(/(?<a>\s\w)(?<b>\w+)(?<c>\w\s)/) { a + b + c }

Note that embedded regexp by #{} shouldn't bind local variables.
-- 
Tanaka Akira