C++ Primer 第4版中的Sales_item.h源码

       转载地址：C++ Primer 第四版

       Sales_item.h文件源码如下：

#ifndef SALESITEM_H
#define SALESITEM_H
#include 
#include 
 
 
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" <

    

      下面， 我们做一个简单的测试：

#include 
#include 
 
 
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" <> item1 >> item2;   // read a pair of transactions 
    std::cout << item1 + item2 << std::endl; // print their sum 

    return 0; 
} 

       输入 x   1    5     x    3    4   并按enter, 结果如下：

x 1 5 x 3 4
x       4       17      4.25