ex7_41.cpp

//
//  ex7_41.cpp
//  Exercise 7.41
//
//  Created by pezy on 11/20/14.
//
//  @Brief implementation of class Sales_data
//  @See ex7_41.h

#include "ex7_41.h"

// constructor
Sales_data::Sales_data(std::istream &is) : Sales_data()
{
    std::cout << "Sales_data(istream &is)" << std::endl;
    read(is, *this);
}

// member functions.
Sales_data& Sales_data::combine(const Sales_data& rhs)
{
    units_sold += rhs.units_sold;
    revenue += rhs.revenue;
    return *this;
}

// friend functions
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;
}

std::ostream &print(std::ostream &os, const Sales_data &item)
{
    os << item.isbn() << " " << item.units_sold << " " << item.revenue;
    return os;
}

Sales_data add(const Sales_data &lhs, const Sales_data &rhs)
{
    Sales_data sum = lhs;
    sum.combine(rhs);
    return sum;
}