抽象类 虚函数实现

注意点：

class base{protected://抽象类成员变量要用protected，而用private子类明显不可以调用

double x;

public: base(double a){x=a;}

virtual void s()=0;//加个const就不对了

virtual void v()=0;};

#include<iostream>
using namespace std;

class base
{
protected:
    double x;
public:    
                                        
    base(double a){x=a;}
    virtual void s()=0;//加个const就不对了
    virtual void v()=0;
};

class fang:public base
{
public:
    fang(double a):base(a){};
    void s(){cout<<"the surface of fang is:"<<x*x*6<<endl;}
    void v(){cout<<"the v of fang is:"<<x*x*base::x<<endl;}
};

class ball:public base
{
public:
    ball(double a):base(a){}
    void s(){cout<<"the surface of ball is:"<<x*x*3.14*4<<endl;}
    void v(){cout<<"the v of ball is:"<<x*x*x*3.14*x/3*4<<endl;}
};

void main()
{
    fang f(3.0);
    f.s();
    f.v();
    ball b(3.0);
    b.s();
    b.v();
    ///////也可以用虚函数的指针
    base *p;
    p=&f;
    p->s();
    p->v();
    p=&b;
    p->s();
    p->v();

}