C++之操作符重载 

  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 }

 

posted @ 2020-04-10 08:57  萌萌~  阅读(188)  评论(0)    收藏  举报