From: Ara.T.Howard@...
Date: 2005-05-05T04:45:01+09:00
Subject: Re: [RCR] Object#inside_metaclass?

On Thu, 5 May 2005, David A. Black wrote:

>> There is a difference in meaning between the word singleton class and
>> metaclass.  The original poster was using the correct terminology and
>> substituting the term "singleton class" would be incorrect.
>
> I disagree; I think Ara was using the term "metaclass" to mean "singleton
> class".  I'm taking my cue from his sample code:
>
>   # (top level code)
>
>   p inside_metaclass?     # false
>
>   class << self
>     p inside_metaclass?   # true
>   end
>
> So his concept of "inside a metaclass" includes "inside a non-class object's
> singleton class" (since top-level self is not a class).

it does - but inadvertently.  the only requirement i have is to determine
'inside_metaclass?' as in

   class C
     class << self
       p inside_metaclass? # true
     end
   end

the singleton meaning accreted itself into my impl in a moment of stupidity
;-(

> He then predicates that his code only works iff "all metaclasses descend
> from the metaclass of Object", but if he's using "metaclass" to mean the
> same thing he meant it to mean in "inside_metaclass?", then this means
> singleton class (and the statement is false).

you are right.  i didn't mean it - honest!  my need to is to have context
sensitive class methods

   class C
     method # does something
     class << self
       method # does another thing
     end
   end

and that's all.

> (I'm working in the dark a little here as the examples all print 'false' for
> me in 1.8.2 and slightly old 1.9.  I guess Ara's using a recent 1.9 -- ?)

hmm.  here's mine:

   jib:~/eg/ruby > cat a.rb
   class Class
     def inside_metaclass?
       inspect =~ %r/^#<Class:/ ? true : false
     end
   end

   class << self
     p inside_metaclass?
   end
   class C
     p inside_metaclass?
     class << self
       p inside_metaclass?
       class << self
         p inside_metaclass?
       end
     end
   end

   jib:~/eg/ruby > ruby a.rb
   true
   false
   true
   true

but this has been pointed out to break for anonymous classes.  arggh.

-a
-- 
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| that they pass away. --aitken roshi
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