C++运算符重载

bin554385863

1. #include <iostream>
   
2. class Circle
   
3. {
   
4. private:
   
5.     double Radius; //半径
   
6. public:
   
7.     static const double PI;
   
8.     Circle(double r = 0) : Radius(r) //构造函数
   
9.     {
   
10.     }
    
11.     Circle(Circle &circle) //赋值构造
    
12.     {
    
13.         this->Radius = circle.Radius;
    
14.     }
    
15.     void setCircleRadius(double r) //设置半径
    
16.     {
    
17.         Radius = r;
    
18.     }
    
19.     double getCircleRadius() //获取半径
    
20.     {
    
21.         return Radius;
    
22.     }
    
23.     double getCirclePerimeter() //获取周长
    
24.     {
    
25.         return 2 * PI * Radius;
    
26.     }
    
27.     double getCircleArea() //获取面积
    
28.     {
    
29.         return PI * Radius * Radius;
    
30.     }
    
31.     /*扩大倍数*/
    
32.     Circle &operator*(int n)
    
33.     {
    
34.         this->Radius = this->Radius * n;
    
35.         return *this;
    
36.     }
    
37.     friend std::ostream &operator<<(std::ostream &os, Circle &circle) //重载<<运算符
    
38.     {
    
39.         os << "CircleRadius: " << circle.Radius << "\n"
    
40.            << "CirclePerimeter: " << circle.getCirclePerimeter() << "\n"
    
41.            << "CircleArea: " << circle.getCircleArea() << std::endl;
    
42.         return os;
    
43.     }
    
44.     ~Circle() {}
    
45. };
    
46. double const Circle::PI = 3.141592653;
    
47. int main(int argc, char const *argv[])
    
48. {
    
49.     Circle circle, ncircle;
    
50.     std::cout << circle << std::endl;
    
51.     circle.setCircleRadius(10);
    
52.     std::cout << circle << std::endl;
    
53.     ncircle = circle * 2;
    
54.     std::cout << ncircle;
    
55.     return 0;
    
56. }
    

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Microsoft Windows [版本 10.0.18363.476]
(c) 2019 Microsoft Corporation。保留所有权利。

E:\Users\admin\Documents\VScode>c:\Users\admin\.vscode\extensions\ms-vscode.cpptools-0.26.1\debugAdapters\bin\WindowsDebugLauncher.exe --stdin=Microsoft-MIEngine-In-q01elhji.d3w --stdout=Microsoft-MIEngine-Out-cvizs1af.xw1 --stderr=Microsoft-MIEngine-Error-i5s3bovj.1rj --pid=Microsoft-MIEngine-Pid-hxzv5xmu.hvn --dbgExe=D:\MinGW\bin\gdb.exe --interpreter=mi
CircleRadius: 0
CirclePerimeter: 0
CircleArea: 0

CircleRadius: 10
CirclePerimeter: 62.8319
CircleArea: 314.159

CircleRadius: 20
CirclePerimeter: 125.664
CircleArea: 1256.64

E:\Users\admin\Documents\VScode>  
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这是我写的一个简单求圆的周长和面积的类
第32行对*的重载使得ncircle = circle * 2成立, 怎么重载也让ncircle = 2*circle成立;
Circle &operator*(Circle &circle, int n)---总是报错参数过多

bin554385863

找到方法了

1. /*扩大倍数*/
   
2.     Circle &operator*(int n)
   
3.     {
   
4.         this->Radius = n*this->Radius;
   
5.         return *this;
   
6.     }
   
7.     friend Circle operator*(int n, Circle &circle)
   
8.     {
   
9.         return circle*n;
   
10.     }

复制代码

bin554385863

1. #include <iostream>
   
2. class Circle
   
3. {
   
4. private:
   
5.     double Radius; //半径
   
6. public:
   
7.     static const double PI;
   
8.     Circle(double r = 0) : Radius(r) //构造函数
   
9.     {
   
10.     }
    
11.     Circle(const Circle &circle) //赋值构造
    
12.     {
    
13.         this->Radius = circle.Radius;
    
14.     }
    
15.     void setCircleRadius(double r) //设置半径
    
16.     {
    
17.         Radius = r;
    
18.     }
    
19.     double getCircleRadius() const //获取半径
    
20.     {
    
21.         return Radius;
    
22.     }
    
23.     double getCirclePerimeter() const //获取周长
    
24.     {
    
25.         return 2 * PI * Radius;
    
26.     }
    
27.     double getCircleArea() const//获取面积
    
28.     {
    
29.         return PI * Radius * Radius;
    
30.     }
    
31.     /*扩大倍数*/
    
32.     Circle &operator*(int n)
    
33.     {
    
34.         static Circle circle;
    
35.         circle.Radius = n*this->Radius;
    
36.         return circle;
    
37.     }
    
38.     friend Circle operator*(int n, Circle &circle)
    
39.     {
    
40.         return circle*n;
    
41.     }
    
42.     friend std::ostream &operator<<(std::ostream &os, Circle &circle) //重载<<运算符
    
43.     {
    
44.         os << "CircleRadius: " << circle.Radius << "\n"
    
45.            << "CirclePerimeter: " << circle.getCirclePerimeter() << "\n"
    
46.            << "CircleArea: " << circle.getCircleArea() << std::endl;
    
47.         return os;
    
48.     }
    
49.     ~Circle() {}
    
50. };
    
51. double const Circle::PI = 3.141592653;
    
52. int main(int argc, char const *argv[])
    
53. {
    
54.     Circle circle0, circle1, circle2,circle3;
    
55.     circle1.setCircleRadius(5);
    
56.     circle2 = circle1*2;
    
57.     circle3 = 5*circle2;
    
58.     std::cout<<circle0<<std::endl;
    
59.     std::cout<<circle1<<std::endl;
    
60.     std::cout<<circle2<<std::endl;
    
61.     std::cout<<circle3<<std::endl;
    
62.     return 0;
    
63. }
    
64. 
    

复制代码

------------------------------------------------------------------------------
Microsoft Windows [版本 10.0.18363.476]
(c) 2019 Microsoft Corporation。保留所有权利。

E:\Users\admin\Documents\VScode>c:\Users\admin\.vscode\extensions\ms-vscode.cpptools-0.26.1\debugAdapters\bin\WindowsDebugLauncher.exe --stdin=Microsoft-MIEngine-In-bq53flzb.pdd --stdout=Microsoft-MIEngine-Out-0ezshnul.zpd --stderr=Microsoft-MIEngine-Error-dzndlmdf.zut --pid=Microsoft-MIEngine-Pid-xianufj3.alm --dbgExe=D:\MinGW\bin\gdb.exe --interpreter=mi
CircleRadius: 0
CirclePerimeter: 0      
CircleArea: 0

CircleRadius: 5
CirclePerimeter: 31.4159
CircleArea: 78.5398

CircleRadius: 10
CirclePerimeter: 62.8319
CircleArea: 314.159

CircleRadius: 50
CirclePerimeter: 314.159
CircleArea: 7853.98


E:\Users\admin\Documents\VScode>