From: Ibraheem Umaru-Mohammed <umarumohammed@...>
Date: 2002-10-19T00:50:50+09:00
Subject: Re: gsub and Backslashes

* nico <n1k0@rogers.com> [2002-10-17 00:19]:
> On Wed, 16 Oct 2002 23:03:10 +0900
> William Djaja Tjokroaminata <billtj@y.glue.umd.edu> wrote:
> 
> > Hi Christian,
> > 
> > Can you give an example of how it may be tricky (causing
> > subtle/unnoticable bug) for a newcomer?
> > 
> > Regards,
> > 
> > Bill
> 
> I'm assuming he was referring to Botp's wish list not the ruby newcomers list (my mail reader thinks he was replying to that post).
> 

ibz@ignoramus:$ irb
Reading config file... done.
ruby-1.7.3 on i686-pc-linux with irb 0.9(02/07/03)
Type 'help' for more information.
>>> str = 'a\b\c'
... >>> puts str
a\b\c
nil
>>> puts str.gsub(/\\/,'\\\\')
a\b\c
nil
>>> puts str.gsub(/\\/,'\\\\\\')
a\\b\\c
nil
>>> puts str.gsub(/\\/,'\\\\\\\\')
a\\b\\c
nil
>>> puts str.gsub(/\\/) { '\\\\' }
a\\b\\c
nil
>>> puts str.gsub(/\\/, '\&\&')
a\\b\\c
nil
>>>

,---- [ Programming Ruby, p.64 ]
| When the substitution occurs, the regular expression 
| engine performs another pass through the string, converting 
| "\\" to "\", so the net effect is to replace each single 
| backslash with another single backslash.
`----

Kindest regards,


				--ibz.