class Construct
  attr_reader :car, :cdr

  def initialize(car, cdr)
    @car, @cdr = car, cdr
  end

  def construct_list?
    cdr.construct_list?
  end

  def to_array
    construct_list? ? [car] + cdr.to_array : self
  end

  def lisp_eval(environment, forms)
    if forms.defined?(car)
      # TODO implement and test
    else
      car.lisp_eval(environment, forms).
        call(*cdr.to_array.map { |x| x.lisp_eval(environment, forms) })
    end
  end
end