From: matz@... (Yukihiro Matsumoto)
Date: 2002-02-08T01:23:56+09:00
Subject: Re: Class variable bug

Hi,

In message "Class variable bug"
    on 02/02/08, "Chr. Rippel" <chr_news@gmx.net> writes:

|It seems that the following class variable bug feel through the
|reporting cracks -  the problem is that the two different class method
|definition styles potentially effect the visibility of class variables
|in conjunction with mixins in subclasses.

First of all, if you put '-v' option to the interpeter, it warns you
about class variables, that means it might not work as you expected.

Second of all, the behavior difference comes from structure
difference, i.e.

|class A 
|    class <<  self
|        def first_form; @@var end
|    end
|end

In this case "@@var" is a class variable of surrounding class (unnamed
singleton class attached to A), whereas

|class A 
|    def A.first_form; @@var end
|end

"@@var" is a class variable of surrounding class (A).

This behavior difference is arguable.  Since "class << self" form can
be considered as short hand of singleton methods definitions, you can
say it is better to have same behavior to singleton methods.  It can
be implemented by simply removing one line from eval.c.  I'm open to
discussion.

							matz.