[c++]派生類的應用

在已有的Point類的基礎上，定義一個“Circle”派生類，要求：新增一個半徑成員；能計

算並輸出圓的周長及加圓面積

#ifndef __Dervide_circle__circle__
#define __Dervide_circle__circle__
#include
using namespace std;
#define PI 3.1415926
class point
{ private:
    float x,y;
public:
    point(void)
    {x=0;y=0;}
    point(float a,float b)
    {x=a ; y=b; }
    point(const point &ob)
    {x=ob.x;y=ob.y;}
    void set_point(float a,float b);
    float read_x(void);
    float read_y(void);
    float read_x(void) const;
    float read_y(void) const;
    void move(float a,float b);
    void move(float a,float b) const;
};
class circle :public point
{
public:
    circle(float a ,float b ,float c):point(a,b)
    {r = c;}
    void set_r(float a){r = a;}
    float Get_R(){return r;}
    void circumference();
    void squire();
private:
    float r;
};
void point::set_point(float a,float b)
{x=a ; y=b; }
float point::read_x(void)
{ return x;}
float point::read_y(void)
{ return y;}
void point::move (float a,float b)
{ x+=a;y+=b;}
float point::read_x(void) const
{ return x;}
float point::read_y(void) const
{ return y;}
//void point::move (float a,float b) const
// { x+=a;y+=b;}

void circle::circumference()
{
    float c = 2*PI*r;
    cout<<"周長＝"<
 
 
 
 
#include"circle.h"
int main()
{
    circle C(1.2,2.0,3.0);
    cout<