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#include <iostream>
using namespace std;

class Base1 { //基类Base1定义
public:
void display() const { cout << "Base1::display()" << endl; }
};

class Base2: public Base1 { //公有派生类Base2声明定义
public:
void display() const { cout << "Base2::display()" << endl; }
};

class Derived: public Base2 { //公有派生类Derived声明定义
public:
void display() const { cout << "Derived::display()" << endl; }
};

void fun(Base1 *ptr) { //参数为指向基类对象的指针
ptr->display(); //"对象指针->成员名"
}

int main() { //主函数
Base1 base1; //声明Base1类对象
Base2 base2; //声明Base2类对象
Derived derived; //声明Derived类对象

fun(&base1); //用Base1对象的指针调用fun函数
fun(&base2); //用Base2对象的指针调用fun函数
fun(&derived); //用Derived对象的指针调用fun函数

return 0;
}