From: Sander Land <sander.land@...>
Date: 2008-01-06T05:54:52+09:00
Subject: Re: Fixnums can have instance variables? Cool.

On Jan 5, 2008 4:32 PM, Gary Wright <gwtmp01@mac.com> wrote:
> Actually it is a bit different.  Monkey patching is just adding
> methods to classes. Fixnum and String in your examples.
>
> Instance variables on Fixnums (or Symbols or Nil) is different.
> It is a good example of uniformity in Ruby but I'm hard pressed
> to think of a nice use case for the feature.
>
> Gary Wright
You can use it to cache the result of method calls.

class Fixnum
 def factorial
  @factorial ||= self * (self-1).factorial
 end
end
0.instance_variable_set('@factorial',1)