rubyx/lib/slot_machine/instructions/block_yield.rb

module SlotMachine

  # A BlockYield calls an argument block. All we need to know is the index
  # of the argument, and the rest is almost as simple as a SimpleCall

  class BlockYield < Instruction
    attr :arg_index

    # pass in the source (sol statement) and the index.
    # The index is the argument index of the block that we call
    def initialize(source , index)
      super(source)
      @arg_index = index
    end

    def to_s
      "BlockYield[#{arg_index}] "
    end

    # almost as simple as a SimpleCall, use a dynamic_jump to get there
    def to_risc(compiler)
      return_label = Risc.label("block_yield", "continue_#{object_id}")
      index = arg_index
      return_address = compiler.load_object return_label
      compiler.build(to_s) do
        message[:next_message][:return_address] << return_address

        block_reg = message["arg#{index}".to_sym].to_reg

        message << message[:next_message]
        add_code Risc::DynamicJump.new("block_yield", block_reg )
        add_code return_label
      end
    end
  end

end