gistfile1.txt

class Acceptor
  attr_reader :things
  def initialize
    @things = {}
    yield self
  end
  def method_missing(s, a)
    @things[s] = a
  end
end

def macro(name, &block)
  params = Acceptor.new(&block).things
  eval <<-EOC
    class #{name} < SyntaxNode
      def initialize
        #{params.map { |k,v| "@#{k} = @elements[#{v}]" }.join("\n")}
      end
    end
  EOC
end