Linked-list (cons list) implementation in Ruby

empty_list.rb

class EmptyList
  def prepend(value)
    List.new(value, self)
  end

  def inspect
    "()"
  end

  def map(&block)
    self
  end

  def each(&block)
  end

  def first
    nil
  end

  def rest
    nil
  end
end

list.rb

class List
  attr_reader :first, :rest

  def initialize(first, rest)
    @first = first
    @rest = rest
  end

  def prepend(value)
    List.new(value, self)
  end

  def map(&block)
    List.new(block.call(first), rest.map(&block))
  end

  def each(&block)
    block.call(first)
    rest.each(&block)
    self
  end

  def inspect
    "(#{first.inspect}, #{rest.inspect})"
  end

  def to_s
    inspect
  end
end