void MarkModel::save(const std::string &filename)
{
    std::ofstream file(filename);
    if(file.is_open()) {
        std::for_each(this->marks.cbegin(), this->marks.cend(),
                      [&file](double mark) { file << mark << std::endl; } );
        file.close();
    }
}

void MarkModel::load(const std::string &filename)
{
    std::ifstream file(filename);
    if(file.is_open()) {
        std::string line;
        double mark;
        while( std::getline(file, line) ) {
            mark = std::stod(line);
            this->addMark(mark);
        }
        file.close();
    }
}