From: Yukihiro Matsumoto <matz@...>
Date: 2005-07-29T13:54:17+09:00
Subject: Re: What's so special about operators, built-in classes and modules?

Hi,

In message "Re: What's so special about operators, built-in classes and modules?"
    on Fri, 29 Jul 2005 11:00:47 +0900, Daniel Brockman <daniel@brockman.se> writes:

|Mathieu Bouchard replied[1],
|
|>>> module A; end
|>>> module B; include A; end
|>>> module C; include A; end
|>>> class D; include C,B; end
|>>>
|>>> This is a diamond inheritance pattern.
|
|but you never replied back to him.
|
|I'd appreciate it if someone could clarify once and for all
|how the diamond inheritance problem doesn't exist in Ruby.

The relationship figure should be the following:

         Object
           |
       A-C | B-A
          \|/
           D

I want to mixin behave more like traits.  The precedence should be
[D, C, A, B, A, Object] in the future.

This is a drawback I mentioned in [ruby-talk:149778]:
>I know there's some drawbacks in the current implementation of Ruby's
>mixin inheritance, when a module is included repeatedly.  I am willing
>to fix it.  I'm seeking the best way to fix.

Since repeated mixin inclusion is pretty rare case, this problem have
been there for long time.

							matz.