这个是哪里的错误啦友友们

Question

#include
#define PI 3.1415936
using namespace std;
class circle
{private: double radious;
public: circle(double r=0){radious=r;}
double round(double radious){return 2PIradious;}
double area(double radious){return PIradiousradious;}
};
void main()
{ double r;
cin>>r;
class c(r);
cout<<"半径为"<<r<<"的周长为"<<c.round<<endl;
cout<<"半径为"<<r<<"的面积为"<<c.area<<endl;
};

Answer 1

说明写在注释里

#include <iostream>

#define PI 3.1415936
using namespace std;

class circle {
private:
    double radious;
public:
    circle(double r = 0)
    {
        radious = r;
    }

    double round(double radious) { return 2 * PI * radious; }

    double area(double radious) { return PI * radious * radious; }
};

int main() {
    double r;
    cin >> r;
    circle c(r);    // 创建类对象语法错误
    cout << "半径为" << r << "的周长为" << c.round(r) << endl;   // 调用函数忘记传参
    cout << "半径为" << r << "的面积为" << c.area(r) << endl;

    return 0;
}