# Collect alternatives to an array by pushing them onto an internal
# instance variable @__alternatives. We can then assemble all the alternatives
# (including self) into an Array. This is used for specifying alternative
# RightHandSides in a Rule in a Grammar.
class Array
  def __alternatives
    @__alternatives ||= Array.new
  end

  def /(other)
    self.__alternatives << other
    self
  end

  def assemble_alternatives
    alternatives = self.__alternatives
    alternatives.unshift self
    alternatives
  end
end