public static Double complexSum ( Double value1, Double value2 ) {
        if ( ( value1 >= 0.0 && value2 >= 0.0 ) || ( value1 <= 0.0 && value2 <= 0.0 ) ) {
            return value1 + value2;
        } else if ( ( value1 >= 0.0 && value2 <= 0.0 ) || ( value1 <= 0.0 && value2 >= 0.0 ) ) {
            return value2 - value1;
        }
        return 0.0;
    }