// 函数的默认参数

#include <iostream>

using namespace std;

bool isSs(int n = 10) // 判断 n 是否为质数
{
    int i = 2;
    for (; i < n / 2; i++)
    {
        if (n % i == 0)
            return false; // 0 为假
    }
    return true; // 非 0 为真
}

double area(double r = 1.0) // 求面积
{
    return 3.14 * r * r;
}

int main()
{
    cout << "isSS(7) is " << isSs(7) << endl;
    cout << "isSS() is " << isSs() << endl;
    cout << "area() is " << area() << endl;
    cout << "area(2) is " << area(2) << endl;
    return 0;
}