#ifndef SALESITEM_H#define SALESITEM_H#include <iostream>#include <string>class Sales_item{public: Sales_item(const std::string &book):isbn(book),units_sold(0),revenue(0.0){} Sales_item(std::istream &is){ is >> *this;} friend std::istream& operator>>(std::istream &,Sales_item &); friend std::ostream& operator<<(std::ostream &,const Sales_item &);public: Sales_item & operator+=(const Sales_item&);public: double avg_price() const; bool same_isbn(const Sales_item &rhs)const { return isbn == rhs.isbn; } Sales_item():units_sold(0),revenue(0.0){}public: std::string isbn; unsigned units_sold; double revenue;};using std::istream;using std::ostream;Sales_item operator+(const Sales_item &,const Sales_item &);inline bool operator==(const Sales_item &lhs,const Sales_item &rhs){ return lhs.units_sold == rhs.units_sold && lhs.revenue == rhs.revenue && lhs.same_isbn(rhs);}inline bool operator!=(const Sales_item &lhs,const Sales_item &rhs){ return !(lhs == rhs);}inline Sales_item & Sales_item::operator +=(const Sales_item &rhs){ units_sold += rhs.units_sold; revenue += rhs.revenue; return *this;}inline Sales_item operator+(const Sales_item &lhs,const Sales_item &rhs){ Sales_item ret(lhs); ret += rhs; return ret;}inline istream& operator>>(istream &in,Sales_item &s){ double price; in >> s.isbn >> s.units_sold >> price; if(in) s.revenue = s.units_sold * price; else s = Sales_item(); return in;}inline ostream& operator<<(ostream &out,const Sales_item &s){ out << s.isbn << "\t" <<s.units_sold << "\t" << s.revenue << "\t" << s.avg_price(); return out;}inline double Sales_item::avg_price() const{ if(units_sold) return revenue/units_sold; else return 0;}#endif
