1 //运算符重载:友元函数方式
 2 #include <iostream.h>
 3 
 4 class complex //复数类
 5 {
 6 public:
 7     complex(){ real = imag = 0;}
 8     complex(double r, double i)
 9     {
10         real = r;
11         imag = i;
12     }
13     friend complex operator + (const complex &c1, const complex &c2); //相比于成员函数方式,友元函数前面加friend，形参多一个，去掉类域
14     friend complex operator - (const complex &c1, const complex &c2); //成员函数方式有隐含参数，友元函数方式无隐含参数
15     friend complex operator * (const complex &c1, const complex &c2);
16     friend complex operator / (const complex &c1, const complex &c2);
17 
18     friend void print(const complex &c); //友元函数
19 
20 private:
21     double real; //实部
22     double imag; //虚部
23 
24 };
25 
26 complex operator + (const complex &c1, const complex &c2) 
27 {
28     return complex(c1.real + c2.real, c1.imag + c2.imag);
29 }
30 
31 complex operator - (const complex &c1, const complex &c2)
32 {
33     return complex(c1.real - c2.real, c1.imag - c2.imag);
34 }
35 
36 complex operator * (const complex &c1, const complex &c2)
37 {
38     return complex(c1.real * c2.real - c1.imag * c2.imag, c1.real * c2.real + c1.imag * c2.imag);
39 }
40 
41 complex operator / (const complex &c1, const complex &c2)
42 {
43     return complex( (c1.real * c2.real + c1.imag * c2. imag) / (c2.real * c2.real + c2.imag * c2.imag), 
44         (c1.imag * c2.real - c1.real * c2.imag) / (c2.real * c2.real + c2.imag * c2.imag) );
45 }
46 
47 void print(const complex &c) 
48 {
49     if(c.imag < 0)
50         cout<<c.real<<c.imag<<‘i‘<<endl;
51     else
52         cout<<c.real<<‘+‘<<c.imag<<‘i‘<<endl;
53 }
54 
55 int main()
56 {    
57     complex c1(2.0, 3.5), c2(6.7, 9.8), c3;
58     c3 = c1 + c2;
59     cout<<"c1 + c2 = ";
60     print(c3); //友元函数不是成员函数，只能采用普通函数调用方式,不能通过类的对象调用
61 
62     c3 = c1 - c2;
63     cout<<"c1 - c2 = ";
64     print(c3);
65 
66     c3 = c1 * c2;
67     cout<<"c1 * c2 = ";
68     print(c3);
69 
70     c3 = c1 / c2;
71     cout<<"c1 / c2 = ";
72     print(c3);
73     return 0;
74 }