anchor.diff:          longitude[1] - LONGITUDE_MAX, code.length);
     }
   
  -/**
  -    Decode either a latitude or longitude sequence.
  -    This decodes the latitude or longitude sequence of a lat/lng pair encoding.
  -    Starting at the character at position offset, every second character is
  -    decoded and the value returned.
  -    Args:
  -    code: A valid OLC code, presumed to be full, with the separator removed.
  -    offset: The character to start from.
  -    Returns:
  -    A pair of the low and high values. The low value comes from decoding the
  -    characters. The high value is the low value plus the resolution of the
  -    last position. Both values are offset into positive ranges and will need
  -    to be corrected before use.
  - */
  +  /// Decode either a latitude or longitude sequence.
  +  ///
  +  /// This decodes the latitude or longitude sequence of a lat/lng pair
  +  /// encoding. Starting at the character at position offset, every second
  +  /// character is decoded and the value returned.
  +  ///
  +  /// Args:
  +  ///
  +  /// * [code]: A valid OLC code, presumed to be full, with the separator
  +  /// removed.
  +  /// * [offset]: The character to start from.
  +  ///
  +  /// It returns a pair of the low and high values. The low value comes from
  +  /// decoding the characters. The high value is the low value plus the
  +  /// resolution of the last position. Both values are offset into positive
  +  /// ranges and will need to be corrected before use.
     List<double> decodePairsSequence(String code, double offset) {
       int i = 0;
       num value = 0;
  
positive.code:     return code;
    }
  
    /**
        Decode an OLC code made up of lat/lng pairs.
        This decodes an OLC code made up of alternating latitude and longitude
        characters, encoded using base 20.
        Args:
        code: A valid OLC code, presumed to be full, but with the separator
        removed.
     */
    CodeArea decodePairs(String code) {
      // Get the latitude and longitude values. These will need correcting from
      // positive ranges.
  
negative.code:   double longitudeCenter;
    int codeLength;
  
    /// Create a [CodeArea].
    ///
    /// Args:
    ///
    /// *[latitude_lo]: The latitude of the SW corner in degrees.
    /// *[longitude_lo]: The longitude of the SW corner in degrees.
    /// *[latitude_hi]: The latitude of the NE corner in degrees.
    /// *[longitude_hi]: The longitude of the NE corner in degrees.
    /// *[latitude_center]: The latitude of the center in degrees.
    /// *[longitude_center]: The longitude of the center in degrees.
    /// *[code_length]: The number of significant characters that were in the code.
    /// This excludes the separator.
    CodeArea(this.latitudeLo, this.longitudeLo, this.latitudeHi, this.longitudeHi,
        this.codeLength) {
      latitudeCenter =
  