From: Gregory Millam <walker@...>
Date: 2003-12-09T04:49:07+09:00
Subject: Re: format money

Received: Tue, 9 Dec 2003 04:37:54 +0900
And lo Peter wrote:

> > Yes, there is.  I'm sure that there's a module in the RAA for this,
> > although I can't find it at the moment.  It's not too hard to do manually,
> > though:
> >
> > irb(main):001:0> balance = 2111000.5756
> > => 2111000.5756
> > irb(main):002:0>  balance = (balance * 100).round/100.0
> > => 2111000.58
> > irb(main):003:0> balance.to_s.reverse.gsub(/\d{3}/, '\&,').reverse
> > => "2,111,000.58"
> 
> This would turn 111000.5756 into ,111,000.58
> I assume that's not the intention?
> 

# Here's my try:

balance.to_s.reverse.gsub(/(\d{3})(?=\d)/,'\1,').reverse

examples:
irb(main):007:0> "123456789".reverse.gsub(/(\d{3})(?=\d)/,'\1,').reverse
=> "123,456,789"
irb(main):008:0> "1234567890".reverse.gsub(/(\d{3})(?=\d)/,'\1,').reverse
=> "1,234,567,890"

(?=\d) is a lookahead assertion that checks to see if there's a digit ahead of the current pattern without capturing it (which is the important thing).

- Greg Millam