From: Ronald Fischer <ronald.fischer@...>
Date: 2007-09-10T22:44:30+09:00
Subject: Re: gsub! and quoting question

> > data=%q(')
> > puts ":"+data+" replace quotes by "+%q(\\')
> >         data.gsub!(/'/,%q(\\'))
> > puts "data length now #{data.length}"
> >
> > This produced as output:
> >
> > :' replace quotes by \'
> > data length now 0
> >
> > From this I conclude that the gsub! had shortened the 
> string to length
> > zero.
> > Any explanation for this? How do I solve my problem in a proper way?
> 
> This comes up frequently. 

I'm sorry if I posted a question which has been answered already :-(

> You need to be aware that there are several
> levels of interpretation involved and so you need multiple levels of
> escaping.  This is sometimes obscured by the fact that '\1' works
> although it should read '\\1'.  These levels are: 1. string escaping,
> 2. regexp replacement string escaping. 

Hmmm... I would understand your argument if I had a digit following
a backslash (which would mean a backreference to the n-th group in
the pattern), but here we have \', and this is not a back reference,
isn't it? At least the discussion of String#gsub at
http://www.ruby-doc.org/core/
mentions only \1,\2,... etc. as back references.

Ronald
-- 
Ronald Fischer <ronald.fischer@venyon.com>
Phone: +49-89-452133-162