meta_ruby1_6.rb

module Printable
  def print
  end

  def prepare_cover
  end
end

module Document
  def print_to_screen
    prepare_cover
    format_for_screen
    print
  end

  def format_for_screen
  end

  def print
  end
end

class Book
  include Document
  include Printable
end

#上記のprint_to_screenは正しいprintメソッドを呼び出していない　なぜか？
p Book.ancestors

b = Book.new
b = print_to_screen