From: "David A. Black" <dblack@...>
Date: 2003-12-17T23:42:29+09:00
Subject: Re: UnboundMethods Useless?

Hi --

On Wed, 17 Dec 2003, Peter wrote:

> > I don't know what you mean by (ir)reversible, but the point is that
> > it's meaningless to talk about arbitrary objects being able to do
> > arbitrary things.  For example (and Guy has already given some),
> > String#strip removes whitespace.  What would it mean to remove
> > whitespace from a Hash or a Fixnum or a MyThing?  And more to the
> > point, what would happen if
> >
> > I don't mean: "Could such objects have some method called 'strip'
> > which made sense for them?" because that's not what you're suggesting.
> > What you're suggesting is that String#strip, Array#join, Thread#join,
> > IO#readlines, Regexp.escape, MyThing#some_method, and every other
> > method written for any purpose in Ruby should, without change or
> > adaptation, work for any Ruby object.
> 
> By the same reasoning, Ruby is suggesting that any module makes sense in
> any class/object, because you can include a module in any class you'd
> like. With freedom comes the possibility of doing something wrong, but
> that doesn't make freedom wrong, now does it?

There's a difference between freedom and a free-for-all or chaos.  In
the case of module inclusion, of course you can do things that don't
work:

  module M
    def x; strip; end
  end

  class C
    include M
  end

  C.new.x      # undefined method strip

but you've got a mechanism -- a language design -- in place which
handles errors.  (And of course there's much more to that design.)  If
you simply cut-and-paste methods (including core methods) from one
object to another, you're bypassing this.


David

-- 
David A. Black
dblack@wobblini.net