circle2.cpp

用三个类来研究类的继承！类Point、Circle、Cylinder

//circle2.cpp
//定义类Circle的成员函数

#include <iostream.h>
#include <assert.h>
#include <iomanip.h>
#include "point2.h"
#include "circle2.h"

//构造函数用 成员初始化表调用类Point的构造函数 以及初始化半径
Circle:: Circle(float r, float a, float b)
 :Point(a, b)	//调用基类的构造函数
{radius=r;}

//设置半径的值
void Circle:: setRadius(float r) {radius=r;}

//读取半径的值
float Circle:: getRadius() const {return radius;}

//计算圆的面积
float Circle:: area() const
{return 3.14159*radius*radius;}

//输出圆，格式：Center=[x, y]; Radius=#.##
ostream &operator<< (ostream &output, const Circle &c)
{
	output<<"Center=["<<c.x<<", "<<c.y<<"]; Radius="<<setiosflags(ios:: showpoint)
		<<setprecision(3)<<c.radius;

	return output;	//使得能够连续输出
}