无参构造函数、有参构造函数、容器array

 1 #include <iostream>
 2 #include <array>
 3 
 4 class Circle
 5 {
 6 private:
 7     double r = 1.0;//默认值
 8 public: 
 9     Circle() = default;//无参构造函数(默认构造函数)
10     Circle(double r){this->r = r;}//有参构造函数
11     double getArea() 
12     {
13         return 3.14*r*r;
14     }
15 };
16 int main()
17 {
18     double TotalArea = 0.0;    
19     //调试,看不到调用默认构造函数,少了默认构造函数还不可以
20     std::array<Circle,10> CircleArray = {1.0,2.0,3.0,4.0,5.0};
21 
22     for ( auto it = CircleArray.begin(); it != CircleArray.end(); ++it )
23     {    
24         TotalArea += (*it).getArea();
25     }    
26     std::cout<<TotalArea<<std::endl;                        
27     return 0;
28 }

 https://zh.cppreference.com/w/cpp/container/array