true_false_comparison.rb

module TrueFalseComparison
  # Enable TrueClass and FalseClass values to be comparable.
  # TrueClass values are valued higher than FalseClass values.
  #
  # See this article for more info:
  # http://grosser.it/2010/07/30/ruby-true-false-comparison-with/
  #
  # Yes, this is evil monkey-patching. The alternative is much, much worse:
  #
  # [false, true, false].sort {|a, b| a ? (b ? 0 : -1) : (b ? 1 : 0) }
  # => [true, false, false]
  #
  def <=>(other)
    unless [TrueClass, FalseClass].include? other.class
      raise ArgumentError, "comparison of #{self} with #{other} failed"
    end

    self ? (other ? 0 : -1) : (other ? 1 : 0)
  end
end