[c++]cylinder顯示每個對象的體積

#include<iostream>
using namespace std;
#define p   3.1415926
class Cylinder
{
private:
    double v;
public:
    Cylinder(double r = 0,double h = 0)
    {
        v = p * r * r * h;
    }
    double vol()
    {
        return v;
    }
    
};
int main()
{
    class Cylinder vr(1,1);
    cout<<"vr ="<< vr.vol();
    return 0;
}