module Virtual
  # So when an object calls a method, or sends a message, this is what it sends: a Message

  # A message contains the sender, return and exceptional return addresses,the arguments,
  #  and a slot for the frame.

  # As such it is a very run-time object, deep in the machinery as it were, and does not have
  # meaningful methods you could call at compile time.

  # The methods that are there, are nevertheless meant to be called at compile time and generate
  # code, rather than executing it.

  # The caller creates the Message and passes control to the receiver's method

  # The receiver create a new Frame to hold local and temporary variables and (later) creates
  # default values for arguments that were not passed

  # How the actual finding of the method takes place (acording to the ruby rules) is not simple,
  # but as there is a guaranteed result (be it method_missing) it does not matter to the passing
  #  mechanism described

  # During compilation Message and frame objects are created to do type analysis

  class Message

    SELF_REG = :r0
    MESSAGE_REG = :r1
    FRAME_REG = :r2
    NEW_MESSAGE_REG = :r3

    TMP_REG = :r4

    def initialize me , normal , exceptional
      @me = me
      @next_normal = normal
      @next_exception = exceptional
      @arguments = arguments
      # a frame represents the local and temporary variables at a point in the program.
      @frame = nil
    end
    attr_reader :me, :next_normal, :next_exception, :arguments , :frame

    #
  end
end