其实c++中各种运算符，都是很特殊的一类函数，运算符函数

不过还是和普通函数有区别的

函数意味着它们可以被重载，这样方便程序员重载一些运算符

说白了，就是你可以自定义这个运算规则

下面是复数类实现加减乘除的运算

加减 用普通成员函数实现

乘除 用友元类成员函数实现

1 #include
     
       2 using namespace std; 3 #define cp Complex 4  5 class Complex 6 { 7 private: 8     double r,i; 9 public:10     Complex(double R = 0,double I = 0):r(R),i(I){};11     //成员函数实现12     Complex operator+(Complex b);13 14     Complex operator-(Complex b);15 16     //友元函数实现17    friend Complex operator*(Complex a,Complex b);18 19    friend Complex operator/(Complex a,Complex b);20 21     void display();22 };23 24 //类外实现函数25 Complex Complex::operator+(Complex b)26 {27   return Complex(r + b.r,i + b.i);28 }29 30 Complex Complex::operator-(Complex b)31 {32     return Complex(r - b.r,i - b.i);33 }34 35 Complex operator*(Complex a,Complex b)36 {37     Complex t;38     t.r = a.r*b.r - a.i*b.i;39 40     t.i = a.r*b.i + b.r*a.i;41     return t;42 }43 44 Complex operator/(Complex a,Complex b)45 {46     Complex t;47     double fm = 1 / (b.r*b.r + b.i*b.i);48 49     t.r = (a.r*b.r + a.i*b.i)*fm;50     t.i = (a.i*b.r - a.r*b.i)*fm;51     return t;52 }53 54 void Complex::display()55 {56     if(i == 0) cout << r << endl;57     else cout << r <<  ((i > 0)?" + ":"") <<  i << "i" << endl;58 }59 60 void test()61 {62    cp c1(1,2),c2(3,4),c3,c4,c5,c6;63    c3 = c1 + c2;64    c4 = c1 - c2;65    c5 = c1 * c2;66    c6 = c1 / c2;67 68    c1.display();69    c2.display();70    c3.display();71    c4.display();72    c5.display();73    c6.display();74 }75 int main()76 {77     test();78     return 0;79 }