From: Daniel DeLorme <dan-ml@...42.com>
Date: 2007-08-08T08:35:45+09:00
Subject: Re: Alternate Regular Expressions?

Kenneth McDonald wrote:
> Speaking as someone who has actually written and used (in Python) a more 
> abstract regex library,
> the biggest problem with regular expressions in most languages isn't the 
> syntax, but rather
> the inability to easily compose small REs into larger REs. Which is why 
> so many programs end
> up with huge, unreadable REs. As a small example, it's really nice (and 
> obvious) to be able to say
> 
>    re3 = re1 + re2

I agree with this and that's why I have the following add-on in my 
standard lib:

class Regexp
   def +(other)
     if other.is_a?(Regexp)
       if self.options == other.options
         Regexp.new(source + other.source, options)
       else
         Regexp.new(source + other.to_s, options)
       end
     else
       Regexp.new(source + Regexp.escape(other.to_s), options)
     end
   end
end

It could easily be improved so that, for example, a range would get 
appended as a character class, etc.

Daniel