C++定义一个圆类、线类、点类,并依次表示,要用上拷贝函数.最终求得圆的的周长,面积.

#include
using namespace std;
const double pi=3.1415926;
class point
{
public:
point(float a=0,float b=0):x(a),y(b){}
point(const point &p)
{
x=p.x;
y=p.y;
}
private:
float x;
float y;
};
class line
{
public:
line(float a=0,float b=0,float x=0,float y=0):beginpoint(a,b),endpoint(x,y){}
line(const line & l)
{
beginpoint=l.beginpoint;
endpoint=l.endpoint;
}
private:
point beginpoint;
point endpoint;
};
class circle
{
public:
circle(float x=0,float y=0,float z=0):c(x,y),r(z){}
circle(const circle &ch)
{
c=ch.c;
r=ch.r;
}
float area()
{
return pi*r*r;
}
float leng()
{
return 2*pi*r;
}
private:
float r;
point c;
};
int main()
{
line l(2,3.12,5.21,21);
circle c(3.21,21.2,4);
cout