gem idea

gistfile1.txt

require 'forwardable'
module Blah
  include ::Forwardable
  def self.extended(base)
    base.send :def_delegators, :@list, :<<, :length # and anything else
  end
end


class List
  extend Blah

  def initialize(list = [])
    @list = list
  end

  def reverse
    List.new(@list.reverse)
  end
end

l = List.new
l << 1
l << 2
puts l.reverse.class # => List