C++之纯虚函数和抽象类

virtual 返回值类型 函数名（参数列表）= 0；

#include<iostream>
using namespace std;

class Line{
public:
    Line(float len);
    virtual float Area()=0;
    virtual float Volume()=0;
protected:
    float m_len;
};
Line::Line(float len):m_len(len){

}

class Rec:public Line{
public:
    Rec(float len,float width);
    float Area();
protected:
    float m_width;
};
Rec::Rec(float len,float width):Line(len),m_width(width){

}
float Rec::Area(){
    return m_len*m_width;
}

class Cuboid:public Rec{
public:
    Cuboid(float len,float width,float height);
    float Area();
    float Volume();
protected:
    float m_height;
};
Cuboid::Cuboid(float len,float width,float height):Rec(len,width),m_height(height){

}
float Cuboid::Area(){
    return 2*(m_len*m_width+m_len*m_height+m_width*m_height);
}
float Cuboid::Volume(){
    return m_len*m_width*m_height;
}

class Cube:public Cuboid{
public:
    Cube(float len);
    float Area();
    float Volume();
};
Cube::Cube(float len):Cuboid(len,len,len){

}
float Cube::Area(){
    return 6*m_len*m_len;
}
float Cube::Volume(){
    return m_len*m_len*m_len;
}

int main()
{
//    Line *pl=new Rec(2,5);
//    cout<<pl->Area()<<endl;
//    delete pl;
//    cout<<"---------------------"<<endl;
    Line *p2= new Cuboid(2,3,4);
    cout<<p2->Area()<<","<<p2->Volume()<<endl;
    delete p2;    
    cout<<"---------------------"<<endl;
    Line *pc = new Cube(2);
    cout<<pc->Area()<<","<<pc->Volume()<<endl;
    delete pc;
}