# File lib/html5/filters/validator.rb, line 472
  def check_token_list(tag_name, attr_name, attr_value)
    # The "token" in the method name refers to tokens in an attribute value
    # i.e. http://www.whatwg.org/specs/web-apps/current-work/#set-of
    # but the "token" parameter refers to the token generated from
    # HTMLTokenizer.  Sorry for the confusion.
    value_list = parse_token_list(attr_value)
    value_dict = {}
    for current_value in value_list
      if value_dict.has_key?(current_value)
        yield({:type => "ParseError",
             :data => "duplicate-value-in-token-list",
             :datavars => {"tagName" => tag_name,
                  "attributeName" => attr_name,
                  "attributeValue" => current_value}})
        break
      end
      value_dict[current_value] = 1
    end
  end