一.对下标运算符[]的重载：

重载的格式：返回类型 类名 operator [](参数)；

#include<iostream>

using namespace std;

class A

{

public:

A(int n);

~A();

int & operator [](int n);//返回类型为int & 引用类型


private:

int *p;

int size;

};

int & A::operator[](int n){

return p[n];//返回p[n]

}

A::A(int n)

{

p = new int[n];

}


A::~A()

{

delete[]p;

}

int main(){

A a(5);

a[3] = 4;//等价于a.operator[](3)=4，相当于4赋值给了p[3];

cout << "a[3]=" << a[3] << endl;

cin.get();

return 0;

}

二.对（）运算符的重载

#include<iostream>

using namespace std;

class A{

public:

float operator()(double a,double b);

};

float A::operator ()(double a,double b){

return a*b;

}

int main(){

A f;

float a=f(10.0,1.23);//默认double类型

cout<<a<<endl;

return 0;

}

三.对流输出运算符‘<<’和流输出‘>>’的重载

#include<iostream>

using namespace std;

class A

{

public:

A(int n);

~A();

int& operator[](int);//这里用返回值类型为引用类型，完全是效率问题。

friend ostream& operator <<(ostream &otput, A& a);//对<<的重载最好用友员函数

friend istream& operator >>(istream &input, A& b);

private:

int *p;

int size;

};

int& A::operator[](int a){

if (a<size&&a>=0)

return p[a];

cout << "out of size" << endl;

exit(0);

}

ostream& operator <<(ostream &otput, A& a){

for (int i = 0; i < a.size; i++)

otput << a.p[i]<<' ';

cout << endl;

return otput;

}

istream& operator >>(istream &input, A& b){

for (int i = 0; i < b.size; i++){

input >> b.p[i];

}

return input;//这里返回值为istream 类型变量是规定。

}


A::A(int n)

{

p = new int[n];

size = n;

}


A::~A()

{

delete[]p;

size = 0;

}

int main(){

A a(5);

cout << "input the elements of A a" << endl;

cin >> a;

//cout << "a[5]" << a[5]<<endl;//直接退出。

cout << "a[3]=" << a[3] << endl;

cout << a<<endl;

system("pause");

return 0;

}