构造函数（..）

#include<iostream>//下次实验题选做题
using namespace std;

const float FencePrice=35.0 , ConcretePrice=20.0;

class Circle
{
    private:
       float radius;

    public:
        Circle(float r);//构造函数的声明
        float area();
        float perimeter();
        void set_radius(float r);
        float get_radius();
};

Circle::Circle(float r)//构造函数的定义
{
    radius=r;
//    cout<<"构造函数被调用"<<endl;
}

float Circle::area()
{
    return radius*radius*3.14;
}

float Circle::perimeter()
{
    return 2.0*3.14*radius;
}

void Circle::set_radius(float r)
{
    radius=r;
}

float Circle::get_radius()
{
    return radius;
}


int main()
{
    Circle Pool(100.0) , PoolRim(100.0+3.0);//使用构造函数之后，可以直接在定义的变量名后面加括号赋上初始值；
    float FenceCost,ConcreteCost;
    
//    cout<<"Input radius: ";
//    float r; cin>>r;
//
//    Pool.set_radius(r);
//    PoolRim.set_radius(r+3);
    
    FenceCost=PoolRim.perimeter()*FencePrice;
    cout<<"FenceCost is: "<<FenceCost<<endl;
    
    ConcreteCost=(PoolRim.area()-Pool.area())*ConcretePrice;
    cout<<"ConcreteCost is: "<<ConcreteCost<<endl;
    
    
    return 0;
}

下次实验选做题，用完可删去