From: Paul Rubel <prubel@...>
Date: 2004-11-04T05:03:02+09:00
Subject: Re: escaping single quotes in a string with gsub

David,

David A. Black writes:
 > Hi --
 > 
 > On Thu, 4 Nov 2004, Paul Rubel wrote:

 > I admit I get confused by escaping and stuff... but I can't quite
 > picture the case you're describing.  If a string contains a single
 > quote:
 > 
 >   "abc'def"
 > 
 > that's the same as:
 > 
 >   "abc\'def"
 > 
 > So I don't think you'll actually see that backslash before the single
 > quote when you scan the string.  

Insightful. I suspect you're right and that I made things needlessly
complicated (at least at this point). When my code sees the string the
escaping should already have occurred.

 > 
 > If you do see a slash -- i.e., if the string is:
 > 
 >   abc\'def
 > 
 > then that would probably be generated with "abc\\'def", which would be
 > equivalent to:
 > 
 >   "abc\\\'def"
 > 
 > I'm afraid I didn't quite follow the Summer's Day example.  Can you
 > give another?


The context that I saw the problem was the following:

The code takes in a name and a value and then evals them. If the
var_value has an unescaped single quote it would give an error that
the string was malformed.

   to_eval = "#{var_name} = '#{var_value}'";
   eval(to_eval, binding)

Looking at it now I expect that a backslash in the var_value will
cause problems most of the time as the strings contents get
interpolated a second time during the eval. Is there a better way to
set a value in a binding? The implementation has the option to set
values in a hash rather than in the binding but I'd like to keep both
if possible.

        thank you,
          Paul