《C++ Primer》第一章的 Sales_item.h头文件源码

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#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