From: Florian Gross <flgr@...>
Date: 2005-03-24T08:24:52+09:00
Subject: Re: Any guides for good coding in Ruby?

Josef 'Jupp' Schugt wrote:

> Here is the HOW IT IS DONE:
> 
> def threepack(x)
>   return x unless x.class == String
>   if /^[-+]?\d+\.\d+$/.match(x)
>     match  = /((\d\d\d)+)(?=\.)/.match(x)
>   elsif /^[-+]?\d+$/.match(x)
>     match  = /((\d\d\d)+)$/.match(x)
>   end
>   return x if match.nil?
>   result = match.pre_match
>   temp   = match[1]
>   until temp.empty?
>     result << ',' unless ['', '-', '+'].member?(result)
>     result << temp[0..2]
>     temp = temp[3..-1]
>   end
>   result << match.post_match unless match.post_match.nil?
>   result
> end

Nifty code, though I wonder if it could be simplified by using 
String#rindex? It's a nice method that's not commonly used, but very 
nifty when needing to work from the end to the beginning.