Developing the idea of caching the result of calculations of heavy functions , I propose to write a small template class, which will take the function as an argument, namely the lambda function, as the most universal an instrument within which a heavy function will be performed.

In this case, the result of the function will not be calculated at the time of creation of the Functor, but at the time of calling the operator parentheses () . And at the same time, the result will be cached. That will allow not to call a heavy function more than once as part of the execution of a method.

Suppose we wrote a function that calculates some value or uses a function to calculate this value, while the function_ which calculates the value is quite expensive to calculate and works for a long time. In this case, we call the lambda function several times in some code.

To avoid multiple calls to the heavy function, we can cache the value that the heavy function returns.

Let's look at an interesting construction from the C++14 standard, which allows you to return the structure used in one place of the code, but you need to return an object with named fields.

Such a construction can serve as a replacement for std::tuple. At the same time, we will not need to declare any additional structures that we are not going to transfer anywhere, since we need to get only a set of data that we will somehow use immediately at the place of return and will not transfer further in the same form.

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Snippet program code. Task Get the number of milliseconds in the current minute of the day. Used operator remainder of division.

Алгоритм Дейкстры позволяет нам найти кратчайший путь между любыми двумя вершинами графа.

Он отличается от минимального остовного дерева тем, что кратчайшее расстояние между двумя вершинами может не включать все вершины графа.

I propose to consider the option of using variables declared in the CMakeLists.txt file in C ++ code.

To begin with, what is it for? For example, you want to specify the version of the program and some other auxiliary information that is set during the assembly of the program, but at the same time you want to use this information in your C ++ code? Is it possible to do this? For example, to make it look like the image shows.

Просмотр наименований топлива.

После обработки запросов на получение наименований, формируем таблицу для отображения информации пользователю.

Список АЗС с которыми будем производить дальнейшие действия мы получили.
Создаем слот вызываемый при нажатии на CheckBox на на GroupBox Действия.

void FuelNameDialog::on_groupBoxActions_clicked(bool checked)
{
    if(checked){
        //Очищаем список терминалов передаваемых для дальнейшей обработки
        listTerminals.clear();
        //Добавляем отмеченные терминалы в список
        int rowCount = ui->tableWidgetTerm->rowCount();
        for(int i=0; i<rowCount; ++i){
            QWidget *item = ui->tableWidgetTerm->cellWidget(i,0);
            QCheckBox *checkBox = qobject_cast<QCheckBox*>(item->layout()->itemAt(0)->widget());
            if(checkBox->isChecked()){
               listTerminals.append(ui->tableWidgetTerm->item(i,1)->data(Qt::DisplayRole).toInt());
            }
        }
        //Проверяем что список не пустой
        if(listTerminals.size()==0){
            QMessageBox::warning(this, "Ошибка ввода","Нет выбранных терминалов");
            ui->groupBoxActions->setChecked(false);
            return;
        }
    }
    ui->groupBoxFuel->setEnabled(!checked);
}

Диалог изменения наименований топлива.

Внешний вид диалога.

Диалог полностью создавался в Qt Designer.