framallo

class LinkedListNode
  attr_accessor :value, :next_node
  def initialize(value, next_node=nil)
    @value = value
    @next_node = next_node
  end
end

def print_values(list_node)
  if list_node

framallo

class Fixnum
  def digits
    to_s.split('').map(&:to_i)
  end

  def luhn?
    luhn_checksum % 10 == 0
  end

  def luhn_checksum

framallo

class Image
  attr_accessor :original_image, :image

  def initialize(image)
    @original_image = image
  end

  def image
    @image ||= @original_image.dup
  end