From: Josef 'Jupp' Schugt <jupp@...>
Date: 2005-03-26T06:27:14+09:00
Subject: Re: Any guides for good coding in Ruby?

Florian Gross wrote:
> Nifty code, though I wonder if it could be simplified by using 
> String#rindex?

I do not see any use of String#rindex that would simplify the code but
String#scan can do something for us:

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
   result << ',' unless ['', '-', '+'].member?(result)
   result << match[1].scan(/.../).join(',')
   result << match.post_match unless match.post_match.nil?
   result
end

An alternative solution using a complex Regexp is:

def threepack(x)
   return x unless x.class == String
   match = /^([-+]?)((\d{1,2})?)((\d{3})+)((\.\d+)?)$/.match(x)
   return x if match.nil?
   result = match[2].empty? ? match[1] : match[1] + match[2] + ','
   result + match[4].scan(/.../).join(',') + match[6]
end

match[1] is the sign, match[2] is the digits before the three-digit
blocks, match[4] is the concatenation of all three-digit blocks,
match[6] is what follows the three-digit blocks. The strings are empty
if the given part is absent.

Josef 'Jupp' Schugt
-- 
Damnant quod non intelligunt.