Exer02_41_3.cpp

// Rewrite of Exer1.22
#include <iostream>
struct Sales_data {
    std::string bookNo;
    unsigned units_sold = 0;
    double revenue = 0.0;
};
int main()
{
    Sales_data book, total;
    double price = 0;
    if(std::cin >> total.bookNo >> total.units_sold >> price)
    {
        total.revenue = price * total.units_sold;
        while(std::cin >> book.bookNo >> book.units_sold >> price){
            book.revenue = price * book.units_sold;
            if(book.bookNo == total.bookNo)
            {
                total.units_sold += book.units_sold;
                total.revenue += book.revenue;
            }
            else{
                std::cerr << "Not the same book!" << std::endl;
                break;
            }
        }
    }
    std::cout << total.bookNo << " "
              << total.units_sold << " "
              << total.revenue << std::endl;
    return 0;
}