From: Robert Klemme <shortcutter@...>
Date: 2009-03-25T06:11:56+09:00
Subject: Re: gsub and single quote issue

On 24.03.2009 21:32, Raj Singh wrote:
> a = " Ruby's gem "
> 
> puts a.gsub(/[']/, "") #=> 1. Rubys gem
> 
> puts a.gsub(/[']/, "'") #=> 2. Ruby's gem
> 
> puts a.gsub(/[']/, "\'") #=> 3. Ruby's gem
> 
> puts a.gsub(/[']/, "\\'") #=> 4. Rubys gem s gem
> 
> puts a.gsub(/[']/, "\\\'") #=> 5. Rubys gem s gem
> 
> puts a.gsub(/[']/, "\\\\'") #=> 6. Ruby\'s gem
> 
> puts " "
> 
> 
> I couldn't understand the result for #4 and #5. Any explanation is
> appreciated.

The sequence \' in a replacement string is interpreted as the post 
match.  That's why you see the duplication.  You'll see this nicely by 
bracketing the replacement:

irb(main):012:0> a = " Ruby's gem "
=> " Ruby's gem "
irb(main):013:0> a.gsub /'/, "<\\'>"
=> " Ruby<s gem >s gem "

There is also pre match:

irb(main):014:0> a.gsub /'/, "<\\`>"
=> " Ruby< Ruby>s gem "

Kind regards

	robert


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