From: Robert Dober <robert.dober@...>
Date: 2009-05-08T03:27:56+09:00
Subject: Re: Superclass of eigenclass

On Thu, May 7, 2009 at 7:17 PM, Danny O cuiv <danny.ocuiv@gmail.com> wrote:
> Hi Rick,
>
> I suspect that you're right that the text is incorrect. I doubt that
> it's a typo (in the sense of something that was fat-fingered) as the
> three sentences, taken together, are consistent in what they express. As
> such, it seems mistaken, which makes me curious to know what they were
> intending to say.
>
> Your investigation of the issue corresponds with mine. I would, however,
> take issue with an aspect of your revised wording, specifically the
> following:
>
>> The eigenclass of an ordinary object can have neither a subclass,
>> nor any other instance except that single ordinary object.
>
> The ordinary object is not an instance of the eigenclass. In your
> example, the ordinary object is an instance of TestClass, not of any
> eigenclass. Indeed, there would be a bootstrapping problem if you
> regarded the ordinary object as an instance of the eigenclass. (You can
> only have an eigenclass in the context of an existing object, so you
> couldn't have created that object in the first place by instantiating
> the eigenclass.)
I did not read that Rick said anything about instantiating, but for
what I am concerned he sure is right
because of this:

irb(main):006:0> a=Object::new
=> #<Object:0x872e658>
irb(main):007:0> s=class << a; self end
=> #<Class:#<Object:0x872e658>>
irb(main):008:0> a.is_a? s
=> true
irb(main):009:0> s::new
TypeError: can't create instance of singleton class
	from (irb):9:in `new'
	from (irb):9
	from /usr/local/bin/irb:12:in `<main>'

Cheers
R.