C++学习之继承：点和圆

/**************************************************************************/
/*
 * main.cpp
 *
 *  Created on: May 20, 2013
 *      Author: shiguang
 */

#include “point.h”
#include “circle.h”

using namespace std;

int main()
{
 Point a(4, 5);
 Circle c(a, 7);
 cout << "The point is: " << c.getPoint() << endl;
 cout << "The radius is: " << c.getRadius() << endl;
 cout << "The area is: " << c.getArea() << endl;
 cout << "The circumference is: " << c.getCircum() << endl;  c.moveTo(1, 2);
 c.modifyRadius(3);
 cout << "The point is: " << c.getPoint() << endl;
 cout << "The radius is: " << c.getRadius() << endl;
 cout << "The area is: " << c.getArea() << endl;
 cout << "The circumference is: " << c.getCircum() << endl;
}

/**************************************************************************/
/*
 * point.h
 *
 *  Created on: May 20, 2013
 *      Author: shiguang
 */

#ifndef POINT_H_
#define POINT_H_

#include

using namespace std;

class Point
{
protected:
 double x, y;
public:
 static double PI;
public:
 Point(double a, double b);
 double xOffset() const;
 double yOffset() const;
 double angle() const;
 double radius() const;
 Point operator+(const Point &d) const;
 Point &operator+=(const Point &d);
 void moveTo(double a, double b);
 friend inline ostream& operator<<(ostream& o, const Point&d)
 {
  return o << '(' << d.x << ',' << d.y << ')';
 }
 virtual ~Point();
};

#endif /* POINT_H_ */

/**************************************************************************/
/*
 * point.cpp
 *
 *  Created on: May 20, 2013
 *      Author: shiguang
 */

#include “point.h”
#include

double Point::PI = 3.141592654;

Point::Point(double a, double b) :
  x(a), y(b)
{
 // TODO Auto-generated constructor stub
}

double Point::xOffset() const
{
 return x;
}

double Point::yOffset() const
{
 return y;
}

double Point::angle() const
{
 return (180 / PI) * atan2(y, x);
}

void Point::moveTo(double a, double b)
{
 x = a;
 y = b;
}

Point Point::operator +(const Point& d) const
{
 return Point(x + d.x, y + d.y);
}

Point &Point::operator +=(const Point& d)
{
 x += d.x;
 y += d.y;
 return *this;
}

Point::~Point()
{
 // TODO Auto-generated destructor stub
}

/**************************************************************************/
/*
 * circle.h
 *
 *  Created on: May 20, 2013
 *      Author: shiguang
 */

#ifndef CIRCLE_H_
#define CIRCLE_H_

#include “point.h”

class Circle: public Point
{
private:
 double radius;
public:
 Circle(const Point& p = Point(0, 0), double r = 0);
 double getRadius() const;
 Point getPoint() const;
 double getArea() const;
 double getCircum() const;
 void moveTo(double a, double b);
 void modifyRadius(double r);
 virtual ~Circle();
};

#endif /* CIRCLE_H_ */

/**************************************************************************/
/*
 * circle.cpp
 *
 *  Created on: May 20, 2013
 *      Author: shiguang
 */

#include “circle.h”

Circle::Circle(const Point &p, double r) :
  Point(p), radius(r)
{
 // TODO Auto-generated constructor stub
}

double Circle::getRadius() const
{
 return radius;
}

Point Circle::getPoint() const
{
//return (*(static_castthis));
 return *this;
}

double Circle::getArea() const
{
 return Point::PI * radius * radius;
}

double Circle::getCircum() const
{
 return 2 * Point::PI * radius;
}

void Circle::moveTo(double a, double b)
{
 x = a;
 y = b;
}