From: Ilias Lazaridis <ilias@...>
Date: 2005-04-19T13:59:34+09:00
Subject: Re: - E03c - The Ruby Object Model (Revised Documentation)

Jim Weirich wrote:
> On Monday 18 April 2005 11:34 pm, Ilias Lazaridis wrote:
> 
>>>There is another evident mistake in your UML diagram. Object doesn't
>>>inherit from nil, nil is a literal and an instance of NilClass which
>>>inherit from Object.
>>
>>you are wrong:
>>
>>irb(main):001:0> Object.superclass
>>=> nil
> 
> The documentation for superclass clearly states that it returns the superclass 
> of its target, or nil.
> 
> In this case it returns nil because Object does not have a superclass, i.e. it 
> does not inherit from anything.

In context of an Language Object Model:

Object inherits from "nil".

"nil" is represented by an _instance_ of class "NilClass".

I've drawn this instance "nil" into the diagram.

[possibly it will be removed with the next revision]

-

Nil is a terribly confusing topic, thus I would prefere to keep is out 
of the currect topic.

You can review an old thread about smalltalk's Nil:

comp.lang.smalltalk > ST - The Loneliness of Nil
http://groups-beta.google.com/group/comp.lang.smalltalk/msg/f7f017a49e6268e1

..

-- 
http://lazaridis.com