review for CppPrimer#104

Sales.cpp

#include <iostream>
#include <string>

class Sales_data {
public:
    friend std::istream& read(std::istream&, Sales_data&);

    Sales_data(std::istream &is = std::cin) { read(is, *this); }

    std::string bookNo;
    int units_sold;
    double revenue;
};

std::istream& read(std::istream& is, Sales_data& item)
{
    double price = 0;
    is >> item.bookNo >> item.units_sold >> price;
    item.revenue = price * item.units_sold;
    return is;
}

int main()
{
    Sales_data sales;
    std::cout << sales.bookNo << "_" << sales.units_sold << "_" << sales.revenue << std::endl;
}

X.cpp

#include <iostream>

struct X {
    X(int i, int j): base(i), rem(base % j) {}
    int base, rem;
};

int main()
{
    X x(10, 5);
    std::cout << x.base << "_" << x.rem << std::endl;
}