Geometric_shape

8.6 几何形体的派生关系如下：

对平面形体有长和面积，对立体有表面积和体积，对几何图形基类，周长、面积和体积应怎样计算（用什么函数）?对平面图形体积怎样计算（用什么函数）？对立体图形周长怎么计算（用什么函数）?要求实现运行时的多态性。请编程，并测试。
解：运行时的多态性要用指针

#include <iostream>
#include <cmath>
using namespace std;
const double PI=3.1415926535;
class Geometric_shape{//几何图形
public:
	virtual double perimeter()=0;	//周长
	virtual double area()=0;		//面积
	virtual double volume()=0;		//体积
	virtual void Show(){};
};
class Circle :public Geometric_shape{//圆
	double radius;
public:
	Circle(){radius = 0; }
	Circle(double vv){radius = vv;}
	double perimeter(){return 2.0*PI*radius;}	//周长
	double area(){return PI*radius*radius;}		//面积
	double volume(){return 0;}		//体积
	void Show(){cout<<"radius="<<radius<<endl;}
};
class Rectangle:public Geometric_shape{//矩形
	double width,length;
public:
	Rectangle(){width=0; length=0;}//长宽
	Rectangle(double wid,double len){
		width = wid;
		length= len;
	}
	Rectangle(Rectangle& rr){
		width = rr.width;
		length = rr.length;
	}
	double perimeter(){return 2.0*(width+length);}	//周长
	double area(){return width*length;}		//面积
	double volume(){return 0;}		//体积
	void Show(){cout<<"width="<<width<<'\t'<<"length="<<length<<endl;}
};
class Triangle:public Geometric_shape{//三角形
	double a,b,c;
public:
	Triangle(){a=0;b=0;c=0;}
	Triangle(double v1,double v2,double v3){a = v1;b = v2;c = v3;}
	double perimeter(){return a+b+c;}	//周长
	double area(){
		double s=(a+b+c)/2.0;
		return sqrt(s*(s-a)*(s-b)*(s-c));
	}		//面积
	double volume(){return 0;}		//体积
	void Show(){cout<<"a="<<a<<'\t'<<"b="<<b<<'\t'<<"c="<<c<<endl;}
};
class Box:public Rectangle{//长方体
	double height;
public:
	Box(){height=0;}
	Box(double wid,double len,double heg):Rectangle(wid,len){height=heg;}

	double volume(){return area()*height;}		//体积
};
class Cylinder:public Circle {//圆柱体
	double height;
public:
	Cylinder(){height=0;}
	Cylinder(double vv,double heg):Circle(vv){height=heg;}
	double volume(){return area()*height;}		//体积
};
class Cone: public Circle {//圆锥
	double height;
public:
	Cone(){height=0;}
	Cone(double vv,double heg):Circle(vv){height=heg;}
	double volume(){return area()*height/3;}		//体积
};
class T_pyramid:public Triangle{//三棱锥
	double height;
public:
	T_pyramid(){height=0;}
	T_pyramid(double v1,double v2,double v3,double heg):Triangle(v1,v2,v3){height=heg;}
	double volume(){return area()*height/3;}		//体积
};
class T_prism:public Triangle{//三棱柱
	double height;
public:
	T_prism(){height=0;}
	T_prism(double v1,double v2,double v3,double heg):Triangle(v1,v2,v3){height=heg;}
	double volume(){return area()*height;}		//体积
};
int main(){
	Geometric_shape * gs;
	Circle cc1(10);
	Rectangle rt1(6,8);
	Triangle tg1(3,4,5);
	Box bx1(6,8,3);
	Cylinder cl1(10,3);
	Cone cn1(10,3);
	T_pyramid tpy1(3,4,5,3);
	T_prism tpr1(3,4,5,3);

	cc1.Show();//静态
	cout<<"圆周长："<<cc1.perimeter()<<'\t';
	cout<<"圆面积："<<cc1.area()<<'\t';
	cout<<"圆体积："<<cc1.volume()<<endl;
	gs=&rt1;//动态
	gs->Show();
	cout<<"矩形周长："<<gs->perimeter()<<'\t';
	cout<<"矩形面积："<<gs->area()<<'\t';
	cout<<"矩形体积："<<gs->volume()<<endl;
	gs=&tg1;//动态
	gs->Show();
	cout<<"三角形周长："<<gs->perimeter()<<'\t';
	cout<<"三角形面积："<<gs->area()<<'\t';
	cout<<"三角形体积："<<gs->volume()<<endl;
	gs=&bx1;//动态
	gs->Show();
	cout<<"长方体底周长："<<gs->perimeter()<<'\t';
	cout<<"长方体底面积："<<gs->area()<<'\t';
	cout<<"长方体体积："<<gs->volume()<<endl;
	gs=&cl1;//动态
	gs->Show();
	cout<<"圆柱体底周长："<<gs->perimeter()<<'\t';
	cout<<"圆柱体底面积："<<gs->area()<<'\t';
	cout<<"圆柱体体积："<<gs->volume()<<endl;
	gs=&cn1;//动态
	gs->Show();
	cout<<"圆锥体底周长："<<gs->perimeter()<<'\t';
	cout<<"圆锥体底面积："<<gs->area()<<'\t';
	cout<<"圆锥体体积："<<gs->volume()<<endl;
	gs=&tpy1;//动态
	gs->Show();
	cout<<"三棱锥底周长："<<gs->perimeter()<<'\t';
	cout<<"三棱锥底面积："<<gs->area()<<'\t';
	cout<<"三棱锥体积："<<gs->volume()<<endl;
	gs=&tpr1;//动态
	gs->Show();
	cout<<"三棱柱底周长："<<gs->perimeter()<<'\t';
	cout<<"三棱柱底面积："<<gs->area()<<'\t';
	cout<<"三棱柱体积："<<gs->volume()<<endl;
	return 0;
}