From: Todd Benson <caduceass@...>
Date: 2007-11-07T18:52:56+09:00
Subject: Re: dragons and factorials (keyboard input)

On Nov 6, 2007 10:55 PM, Thufir <hawat.thufir@gmail.com> wrote:

>
> I think that factorial would best be a module, as module's cannot be
> instantiated.  However, I would also want to prevent factorial from
> being extended so that nothing "from" it can be instantiated.  The
> idea of a factorial "object", or an object which descends from it,
> strikes me as ludicrous.  Is this un-ruby-ish thinking?

No, not really.  But keep in mind you can always make a copy of a
method on the fly in Ruby (unless $SAFE level alters this behavior;
which I'm not sure of)...

module M
  def self.factorial n; (1..n).inject { |f,i| f * i }; end
end

class C; end

c.extend(M)
c.fact # will result in error, which is what you want
m = Math.method(:factorial)
m.call 3 # will result in 6
Math.method(:factorial) == Math.method(:factorial)
# will result in true
Math.method(:factorial).object_id == Math.method(:factorial).object_id
# will result in false on my machine, but that's what I expect

> -Thufir

Todd