anchor.diff:    if (latitude == 90) {
       latitude = latitude - computeLatitudePrecision(codeLength).toDouble();
     }
  -  var code =
  -      encodePairs(latitude, longitude, min(codeLength, PAIR_CODE_LENGTH));
  +  var code = encodePairs(latitude, longitude, min(codeLength, pairCodeLength));
     // If the requested length indicates we want grid refined codes.
  -  if (codeLength > PAIR_CODE_LENGTH) {
  -    code += encodeGrid(latitude, longitude, codeLength - PAIR_CODE_LENGTH);
  +  if (codeLength > pairCodeLength) {
  +    code += encodeGrid(latitude, longitude, codeLength - pairCodeLength);
     }
     return code;
   }
  
positive.code:     return false;
    }
    // If there are less characters than expected before the SEPARATOR.
    if (code.indexOf(SEPARATOR) >= 0 &&
        code.indexOf(SEPARATOR) < SEPARATOR_POSITION) {
      return true;
    }
    return false;
  
negative.code:   if (codeLength <= 10) {
      return pow(20, (codeLength ~/ -2) + 2);
    }
    return pow(20, -3) ~/ pow(gridRows, codeLength - 10);
  }
  
  /// Normalize a [longitude] into the range -180 to 180, not including 180.
  