1 #include <iostream>
2 #include <string>
3
4 using namespace std;
5 //重载操作符
6 //定义的方式是operator*() 重载*运算符
7
8 class Sales_item
9 {
10 friend ostream &operator<<(ostream &out,const Sales_item &s);
11 friend istream &operator>>(istream &in,Sales_item &s);
12 friend bool operator==(const Sales_item &,const Sales_item &);
13 public:
14 Sales_item(string &book,unsigned units,double price):
15 isbn(book),
16 units_sold(units),
17 revenue(units*price){}
18 Sales_item():
19 units_sold(0),
20 revenue(0.0){}
21 //重载+=运算符 一般设置为成员函数 ，因为修改了当前对象
22 Sales_item &operator+=(const Sales_item &);
23 public:
24 double avg_price() const;
25 // bool same_isbn(const Sales_item &rsh)
26 // {
27 // return isbn==rsh.isbn;
28 // }
29 private:
30 string isbn;
31 unsigned units_sold;
32 double revenue;
33 };
34 //计算书的平均价格
35 inline double Sales_item::avg_price() const
36 {
37 if(units_sold)
38 {
39 return revenue/units_sold;
40 }else{
41 return 0;
42 }
43 }
44 //重载==和!=运算符
45 inline bool operator==(const Sales_item &lsh,const Sales_item &rsh)
46 {
47 return lsh.isbn==rsh.isbn && lsh.units_sold==rsh.units_sold && lsh.revenue==rsh.revenue;
48 }
49 bool operator!=(const Sales_item &lsh,const Sales_item &rsh)
50 {
51 //让一个操作符调用另外一个操作符
52 return !(lsh==rsh);
53 }
54 //重载+=操作符
55 Sales_item& Sales_item::operator+=(const Sales_item &s)
56 {
57 this->units_sold+=s.units_sold;
58 this->revenue+=s.revenue;
59 return *this;
60 }
61 //重载加法操作符 一把不设置为成员函数
62 Sales_item operator+(const Sales_item &s1,const Sales_item &s2)
63 {
64 //将第一个参数进行实现用于返回结果
65 Sales_item ret(s1);
66 ret+=s2;
67 return ret;
68
69 }
70 //重载输出操作符
71 ostream &operator<<(ostream &out,const Sales_item &s)
72 {
73 out<<s.isbn<<"--"<<s.units_sold<<"--"<<s.revenue;
74 return out;
75 }
76 //重载输入操作符
77 istream &operator>>(istream &in,Sales_item &s)
78 {
79 double price;
80 in>>s.isbn>>s.units_sold>>price;
81 //输入的时候进行错误检查 如果出错就创建一个新的订单
82 if(in)
83 {
84 s.revenue=s.units_sold*price;
85 }else{
86 s=Sales_item();
87 }
88
89 return in;
90 }
91
92 int main()
93 {
94 string s("1-001-2543");
95 // Sales_item item1(s,25,2.50);
96 // cout<<item1<<endl;
97 // cin>>item1;
98 // cout<<item1<<endl;
99 // Sales_item item2(s,10,120.0);
100 // Sales_item item3(s,20,200.0);
101 // Sales_item ret=item2+item3;
102 // cout<<ret<<endl;
103 //
104 // Sales_item item4(s,20,200);
105 // item4+=item4;
106 // cout<<item4<<endl;
107 // Sales_item a(s,10,120.0);
108 // Sales_item b(s,10,120.0);
109 // Sales_item c(s,20,110.0);
110 // if(a==b)
111 // {
112 // cout<<"a和b是一个订单"<<endl;
113 // }
114 // if(a!=c)
115 // {
116 // cout<<"a和c不是一个订单"<<endl;
117 // }
118
119
120 return 0;
121 }
