C++：友元运算符重载函数

运算符重载函数：实现对象之间进行算数运算，(实际上是对象的属性之间做运算),包括+(加号)、-(减号)、*、/、=、++、--、-(负号)、+(正号)

运算符重载函数分为：友元运算符重载函数、成员运算符重载函数

运算符运算符重载函数按运算类型为：双目运算符重载函数，如加、减、乘、除、赋值；   单目运算符重载函数：自加、自减、取正负号

切记：成员运算符. 和->，sezeof等不能重载。运算符重载函数的参数至少有一个是类类型或引用类型，

下面为友元运算符重载函数举例：

 1 #include<iostream>
 2 using namespace std;
 3 class Complex
 4 {
 5 public:
 6     Complex(double r=0.0,double i=0.0);
 7     void print();
 8     friend Complex operator+(Complex &a,Complex &b);
 9     friend Complex operator-(Complex &a,Complex &b);
10 private:
11     double real;
12     double imag;
13 };
14 Complex::Complex(double r,double i)
15 {
16     real = r;
17     imag = i;
18 }
19 Complex operator+(Complex &a,Complex &b)
20 {
21     Complex temp;
22     temp.real = a.real + b.real;
23     temp.imag = a.imag + b.imag;
24     return temp;
25 }
26 Complex operator-(Complex &a,Complex &b)
27 {
28     Complex temp;
29     temp.real = a.real - b.real;
30     temp.imag = a.imag - b.imag;
31     return temp;
32 }
33 void Complex::print()
34 {
35     cout<<real;
36     if(imag>0) cout<<"+";
37     if(imag!=0) cout<<imag<<‘i‘<<endl;
38 }
39 int main(int agrs,const char *agrv[])
40 {
41     Complex A1(2.3,4.6),A2(3.6,2.8),A3,A4;
42     A3 = A1 + A2;//A3 = operator+(A1,A2);
43     A4 = A1 - A2;//A4 = operator-(A1-A2);
44     A1.print();
45     A2.print();
46     A3.print();
47     A4.print();
48
49     return 0;
50 }

运行结果：

2.3+4.6i
3.6+2.8i
5.9+7.4i
-1.3+1.8i
Program ended with exit code: 0