# File lib/spreadsheet/datatypes.rb, line 21
  def boolean *args
    args.each do |key|
      define_method key do
        name = "@#{key}"
        !!(instance_variable_get(name) if instance_variables.include?(name))
      end
      define_method "#{key}?" do
        send key
      end
      define_method "#{key}=" do |arg|
        arg = false if arg == 0
        instance_variable_set("@#{key}", !!arg)
      end
      define_method "#{key}!" do
        send "#{key}=", true
      end
    end
  end