# 概念 用户自己定义的类型的数据,是不能直接用“>”来输出和输入的｡ 如果想用它们输出和输入自己声明的类型的数据,必须对它们重载｡ # 形式 ~~~ istream & operator >> (istream &,自定义类 &);     //流插入 ostream & operator << (ostream &,自定义类 &);     //流提取 ~~~ # 例子 ~~~ // 重载流插入运算符“<<” ​ #include <iostream> using namespace std; ​ class Complex {    public:   Complex()   {       real=0;imag=0;   }   Complex(double r,double i)   {     real=r;imag=i;   }   Complex operator + (Complex &c2);   friend ostream& operator << (ostream&,Complex&);    private:   double real;   double imag; }; Complex Complex::operator + (Complex &c2) {    return Complex(real+c2.real,imag+c2.imag); } ​ ostream& operator << (ostream& output,Complex& c) {    output<<"("<<c.real<<"+"<<c.imag<<"i) "        <<endl;    return output; } ​ int  main() {    Complex c1(2,4),c2(6,10),c3;    c3=c1+c2;    cout<<c3;    return 0; } ~~~