第十三周實驗報告 任務三

源程式：

#include<iostream>
#include<Cmath>
using namespace std;
const double P = 3.14;

class Shape//定義虛基類
{
public:
	virtual double area() const = 0;//定義純虛函數
};

class Circle:public Shape//定義圓類
{
public:
	Circle(double r);
	
	~Circle();
	
	double area() const;//不要忘記const
	
private:
	double rang;
};

class Rectangle:public Shape//定義矩形類
{
public:
	Rectangle(double l, double w);
	
	~Rectangle();
	
	double area() const;
	
private:
	double len;
	double wid;
};

class Triangle:public Shape//定義三角形類
{
public:
	Triangle(double dl, double h);
	
	~Triangle();
	
	double area() const;
	
private:
	double dlen;
	double high;
};

Circle::Circle(double r):rang(r){}

Circle::~Circle(){}

double Circle::area() const
{
	return P * rang * rang;
}

Rectangle::Rectangle(double l, double w):len(l),wid(w){}

Rectangle::~Rectangle(){}

double Rectangle::area() const
{
	return len * wid;
}

Triangle::Triangle(double dl, double h):dlen(dl),high(h){}

Triangle::~Triangle(){}

double Triangle::area() const
{
	return 0.5 * dlen * high;
}

int main()
{
	Circle c1(12.6), c2(4.9);    //建立Circle類對象c1,c2,參數為圓半徑
	Rectangle r1(4.5, 8.4), r2(5.0, 2.5);       //建立Rectangle類對象r1,r2,參數為矩形長、寬
	Triangle t1(4.5, 8.4),t2(3.4, 2.8);    //建立Triangle類對象t1,t2，參數為三角形底邊長與高
	Shape *pt[6] = {&c1, &c2, &r1, &r2, &t1, &t2}; //定義基類指針數組pt，各元素指向一個派生類對象
	double areas = 0.0;      //areas為總面積
	for(int i = 0; i < 6; i ++)
	{
		areas = areas + pt[i]->area();
	}
	cout << "totol of all areas=" << areas << endl;   //輸出總面積
	system("pause");
	return 0;
}
           

截圖：

程式量産化了···

一開始不了解，忘記寫上 const ， 結果老出錯誤···後來好不容易發現···就又覺得自己好傻了···