// 静态类型转换
#include <iostream>
#include <cstring>
#include <cstdlib>

using namespace std;

class A
{
public:
    int x;
    A(int x) : x(x) {}
};

class B : public A
{
public:
    int y;
    B(int x, int y) : A(x), y(y) {}
};

int main()
{
    A *a = new A(5);
    B *b = new B(10, 20);

    A *c = static_cast<A *>(b); // 静态上行转换，子类指针向父类指针转换
    // cout << "a.x = " << a->x << endl;
    // cout << "b.x = " << b->x << ", b.y = " << b->y << endl;
    // cout << "b = " << b << endl;
    // cout << "c = " << c << endl;
    // cout << "c.x = " << c->x << endl;

    // B *b2 = static_cast<B *>(a); // 下行转换，父类指针向子类指针转换
    // B *b2 = (B *)a; // 强制下行转换，不安全
    // cout << "b2.x = " << b2->x << ", b2.y = " << b2->y << endl;

    delete a;
    delete b;

    return 0;
}