用抽象类设计计算二维图形面积的程序，在基类TDshape中设计纯虚函数area（）和printName().are()用于计算图形的几何面积，printName()用于打印输出几何图形的类名

#include<iostream>

using namespace std;

class TDshape{

protected:

double Width,Heigth;

public:

void set(double a,double b) {Width=a;Heigth=b;};

virtual double area()=0;

virtual void printName()=0;

};

class Triangle:public TDshape{

public:

void area(double Witdh,double Heigth){cout<<"三角形的面积"<<0.5*Width*Heigth;};

void printName(){ cout<<"Triangle"<<endl;};

double getWitdth(){ return Width;};

double getHeigth(){ return Heigth;};

};

class Retangle:public TDshape{

public:

void area(double Witdth,double Heigth){cout<<"矩形的面积"<<Width*Heigth<<endl;};

void printName(){ cout<<"Retangle"<<endl;};

double getWidth(){ return Width;};

double getHeigth(){return Heigth;};

};

void main(){

TDshape *pF;

Triangle t;

t.set(10,20);

pF=&t;

pF->area();

}