纯虚函数和抽象类简单应用

/****************************************************************************************
* 文件名：
* 功能：纯虚函数和抽象类简单应用
* 说明：纯虚函数在基类中不用定义该函数，它的实现部分，即函数体在各派生类中完成。
        包含一个或多个纯属函数的类称为抽象类，抽象类不能定义对象，但可以声明抽象类的指针。
* 时间：2011-3-31                                                   --Lzy
*****************************************************************************************/
//纯属函数应用

#include <iostream.h>

class CPoint        //抽象基类

{
protected:
    long x, y;

public:
    CPoint(int xx = 0, int yy = 0){x = xx; y = yy;}
    virtual void display() = 0;            //纯虚函数成员

};

class CRctangle:public CPoint
{
private:
    double width, height;

public:
    CRctangle(long x, long y, long w, long h):CPoint(x, y){width = w; height = h;}
    void display()
    {
        cout<<"矩形"<<endl;
        cout<<"位置：（"<<x<<","<<y<<")"<<endl;
        cout<<"长 = "<<width<<" 宽 = "<<height<<endl;
    }
};

class CTriangle:public CPoint
{
private:
    double a,b,c;

public:
    CTriangle(long x, long y, long a1, long b1, long c1):CPoint(x, y)
    {a = a1; b = b1; c = c1;}

    void display()
    {
        cout<<"三角形"<<endl;
        cout<<"位置：（"<<x<<","<<y<<")"<<endl;
        cout<<"三边长"<<a<<" "<<b<<" "<<c<<endl;
    }
};

void main()
{
    CPoint *ptr[2];            //声明抽象基类指针

    CRctangle r1(10,10,120,60);
    CTriangle t1(50,50,345,456,567);

    ptr[0] = &r1;            //指针指向 r1对象

    ptr[0]->display();

    ptr[1] = &t1;            //指针指向 t1对象

    ptr[1]->display();
}