From: Joel VanderWerf <joelvanderwerf@...>
Date: 2010-04-21T05:53:21+09:00
Subject: [ruby-core:29675] Re: "include X; include Y" vs "include X, Y"

Caleb Clausen wrote:
> On 4/20/10, Daniel Berger <djberg96@gmail.com> wrote:
>> It seems that when including multiple modules with identical method
>> names there are different results when using multiple includes versus
>> a single include with multiple arguments. In the the former case we
>> get a "last method definition wins" but in the latter it's "first
>> method definition wins".
>>
>> Is this expected behavior? If so, where is it documented?
>>
>> module X
>>   def hello
>>     puts "hello"
>>   end
>> end
>>
>> module Y
>>   def hello
>>     puts "greetings"
>>   end
>> end
>>
>> class Foo
>>   include X
>>   include Y
>> end
>>
>> class Bar
>>   include X, Y
>> end
>>
>> Foo.new.hello # => greetings
>> Bar.new.hello # => hello
> 
> I have seen this before as well. I would expect "include X, Y" to mean
> "include X", then "include Y". But instead it is equivalent to
> "include Y" then "include X".

What if you think of it this way:

  class Bar
    inhertance.insert X, Y   # pseudo-ruby
  end

IMHO, it's nice to read the inheritance chain from left to right, as 
with class inheritance (class A < B...).

Nevertheless, the doc does not match the current behavior:

--------------------------------------------------------- Module#include
      include(module, ...)    => self
------------------------------------------------------------------------
      Invokes Module.append_features on each parameter in turn.

It's clear from the source and the example above that rb_mod_include() 
iterates in reverse, but that isn't what "in turn" suggests.