C++作业（第八章）8-6

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本文介绍了一个使用C++实现的抽象类Shape及从其派生的Rectangle和Circle类。Rectangle和Circle类实现了计算面积和周长的方法。通过指向基类的指针调用这些方法，展示了多态性的应用。

8-6定义一个Shape抽象类，在此基础上派生出Rectangle和Circle，二者都有getArea()函数计算对象的面积，getPerim()函数计算对象的周长。

#include <iostream>

using namespace std;

class Shape
{
public:
    Shape(){}
    ~Shape(){}
    virtual float getArea() = 0;
    virtual float getPerim() = 0;
};
class Rectangle : public Shape
{
public:
    Rectangle(float len,float wid):length(len),width(wid){}
    ~Rectangle(){}
    float getArea() {return length * width;}
    float getPerim(){return 2*(length + width);}
    virtual getlength(){return length;}
    virtual getwidth(){return width;}
private:
    float length;
    float width;
};
class Circle : public Shape
{
public:
    Circle(float ri):r(ri){}
    ~Circle(){}
    float getArea() {return 3.14 * r * r;}
    float getPerim(){return 2 * 3.14 * r;}
    virtual getr(){return r;}
private:
    float r;
};
int main()
{
    Shape *a;
    a =  new Rectangle(1,2);
    cout << "The area of the Rectangle is " << a->getArea() << endl;
    cout << "The perimeter of the Rectangle is " << a->getPerim () << endl;
    delete a;
    a = new Circle(2);
    cout << "The area of the Circle is " << a->getArea () << endl;
    cout << "The perimeter of the Circle is " << a->getPerim () << endl;
    delete a;
    return 0;
}