From: Michael campbell <michael_s_campbell@...>
Date: 2004-02-01T07:23:22+09:00
Subject: Re: No difference between .. and ... flip/flop operators?

>    http://sean.chittenden.org/programming/ruby/programming_ruby/ 
> language.html
> 
> Search for "Ranges in Boolean Expressions" (this was missing from the  
> online pickaxe at rubycentral.com - not sure why).
> 
> If someone can explain the difference in a meaningful way, I'd be  
> grateful... I have enough trouble with the flip-flop as it is, and now  
> this!

The 2 dot form evaluates the end condition at the same time as the beginning one, so will flip to "on" then "off" if both are true.  The 3 dot form does not.