Sales_data class

Sales_data_h.cpp

#include <iostream> /// std::cout; std::endl; std::cerr;
#include "Sales_data.h" /// Sales_data; o.isbn();

int main ()
{
    Sales_data total;

    if (std::cin >> total) {
        Sales_data trans;

        while (std::cin >> trans) {
            if (total.isbn() == trans.isbn())
                total += trans;
            else {
                std::cout << total << std::endl;
                total = trans;
            }
        }
        std::cout << total << std::endl;
    } else {
        std::cerr << "No data?!" << std::endl;
        return -1;
    }

    return 0;
}