定义一个圆类（Circle），属性为半径（radius）、圆周长和面积，操作为输入半径并计算周长、面积，输出半径、周长和面积。要求定义构造函数（以半径为参数，缺省值为0，周长和面积在构造函数中生成）和拷贝构造函数。(Define a circle class (Circle), the attributes are radius (radius), circle perimeter and area, operation as input radius, and calculate perimeter, area, output radius, perimeter and area. Requires defining constructor (with radius as parameter, default value 0, perimeter and area generated in constructor) and copy constructor.)