Sales_data.cpp

#include "Sales_data.h"
using std::istream; using std::ostream;

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

double Sales_data::avg_price () const {
	if (units_sold)
		return revenue/units_sold;
	else
		return 0;
}

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

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

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

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