程序代码：

#include<iostream>
using namespace std;
class c
{
public:
    c(float _r){m_flr=_r;}
    c(c &p){m_flr=p.m_flr;}
    ~c(){}
    float getArea();
private:
    float m_flr;
};
float c::getArea()
{
    return 3.14*m_flr*m_flr;
}
void main()
{
    c r(3);
    cout << r.getArea() << endl;
    c r2(r);
    
    cout << r2.getArea() << endl;
}

程序代码：

#include<iostream>
using namespace std;
class c
{
public:
    c(float _r){m_flr=_r;}
    c(c &p){m_flr=p.m_flr;}
    c operator+(int n) { m_flr+=n; return *this; }
    ~c(){}
    float getArea();
private:
    float m_flr;
};
float c::getArea()
{
    return 3.14*m_flr*m_flr;
}
void main()
{
    c r(3);
    cout << r.getArea() << endl;
    c r2(r+3);
    
    cout << r2.getArea() << endl;
}