From: "David A. Black" <dblack@...>
Date: 2007-11-16T20:32:07+09:00
Subject: Re: meta-class subclass relationships

Hi --

On Fri, 16 Nov 2007, Greg Weeks wrote:

> PS: I just realized that my (erroneous) expectation
>
>    $Meta_A.superclass == $Meta_B
>    $Meta_B.superclass == $Meta_Object
>
> is asserted in Figure 24.2 of the Pickaxe book (2nd edition).  Eg, for
> the second equality, just replace "Guitar" with "B".  So why, I wonder,
> isn't it true?

It will be :-) It worked in 1.8.2, doesn't work in 1.8.6, works again
in 1.9. I don't know what the rationale was for changing the model,
but it's changed back.

rubypal:~$ cat super.rb
class Object
   def singleton_class
     class << self; self; end
   end
end
p String.singleton_class.superclass == Object.singleton_class

rubypal:~$ /usr/local/lib/ruby-1.8.2/bin/ruby -v super.rb 
ruby 1.8.2 (2004-12-25) [i686-linux]
true
rubypal:~$ ruby -v super.rb
ruby 1.8.6 (2007-03-13 patchlevel 0) [i686-linux]
false
rubypal:~$ /usr/local/lib/ruby-svn/bin/ruby -v super.rb 
ruby 1.9.0 (2007-11-07 patchlevel 0) [i686-linux]
true


David

-- 
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