From: "Ara.T.Howard" <Ara.T.Howard@...>
Date: 2005-07-28T02:11:09+09:00
Subject: Re: What's so special about operators, built-in classes and modules?

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On Thu, 28 Jul 2005, Daniel Brockman wrote:

> Hmm, for some reason this part of your message was left out
> of my reply buffer, so I forgot to reply to it!
>
> "Ara.T.Howard" <Ara.T.Howard@noaa.gov> writes:
>
>>>> That's not instantiating a module. It's cute, but it's
>>>> not instantiating a module.
>>>
>>> Of course it's not instantiating a module, but it's
>>> pretty much _as good as_ instantiating a module.  It lets
>>> you use modules instead of classes, which demonstrates
>>> that the distinction is superficial.
>>
>> does it?
>>
>> [Complicated way of saying module.new.class !=3D module.]
>
> As I trust you are already aware, that's easily fixed:
> Just redefine the =E2=80=98class=E2=80=99 method to return the module.

yes - just pointing out there's more to being a class than having a new
method...

>> and, of course, you still can't inherit from M - but i
>> realize this needed be so.
>
> Yes, you can:
>
>   module N
>     include M
>   end

the problem is a bit deeper than that and stem from the fact that including=
 a
module does not inject the included modules singleton methods into the
'includee'.  for example (note this has the fix suggested above):

   harp:~ > cat a.rb
   class Module
     def new(*a, &b)
       (@__klass__ ||=3D (m =3D self and Class::new{ include(@@m =3D m); de=
f class;@@m;end }))::new(*a, &b)
     end
   end
   module M
     class << self
       def class_method
         42
       end
     end
     def instance_method
       42
     end
   end

   module N
     include M
   end

   begin
     m =3D M::new
     p m.class
     p m.instance_method
     p m.class.class_method
   rescue =3D> e
     puts "#{ e.message } (#{ e.class }"
   end

   begin
     n =3D N::new
     p n.class
     p n.instance_method
     p n.class.class_method
   rescue =3D> e
     puts "#{ e.message } (#{ e.class }"
   end

   harp:~ > ruby a.rb
   M
   42
   42
   N
   42
   undefined method `class_method' for N:Module (NoMethodError

i'm not saying it's not possible - just that it's a bit more work than you'=
re
suggesting.  doing things consistently at an object, class, module, and
singleton_class level gets very confusing very quicky - just check out the =
code
for my traits lib to see just how.  ;-)

i personally often get around this detail by

   module M
     module ClassMethods
     end
     module InstanceMethods
     end
     include InstanceMethods
     self.extend ClassMethods
     def self::included other
       class << other
         include InstanceMethods
       end
       other.extend ClassMethods
     end
   end

or something similar - in otherwords factor out class methods so that can b=
e
added individually to other classes/modules when they are included there.
thus begins the trickiness...


(ps. for some reason the charset from your message is very odd - it may be =
on
my end but thought you might like to know.  it looks like some sort of esca=
pe
chars around '@' signs - coloring?)

cheers.

-a
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| email :: ara [dot] t [dot] howard [at] noaa [dot] gov
| phone :: 303.497.6469
| My religion is very simple.  My religion is kindness.
| --Tenzin Gyatso
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