# File lib/spreadsheet/datatypes.rb, line 80
  def boolean *args
    args.each do |key|
      define_method key do
        name = ivar_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(ivar_name(key), !!arg)
      end
      define_method "#{key}!" do
        send "#{key}=", true
      end
    end
  end