旋转测试运算符重载

Question

我的旋转测试功能不符合学校的。请赐教在哪里我已经错了。一直在努力解决了这么久，但无济于事。谢谢！

**********我的旋转测试**********

点（-50.000，-50.000）旋转45.000度是（0.000,0.000）

点（-6.000，-6.000）旋转45.000度是（0.000,0.000）

**********学校的旋转测试**********

点（-50.000，-50.000）旋转45.000度为（0.000，-70.711）

点（-6.000，-6.000）旋转45.000度为（0.000，-8.485）

旋转测试功能：

   Point Point::operator%( double angle)
{
    Point p;
    double rad=angle * PI / 180.0;
    double s = sin(rad);
    double c = cos(rad);


    // rotate point
    double xnew = p.x * c - p.y * s;
    double ynew = p.x * s + p.y * c;

    p.x = xnew;
    p.y = ynew;
    return p;
    // return Point(cos(degree) * (p.x) - sin(degree) * (p.y),
              // sin(degree) * (p.x) - cos(degree) * (p.y));

    // return p;
}

驱动程序文件：

 void RotateTest(void)
{
cout << "\n********** Rotate test ********** " << endl;

Point pt1(-50, -50);
double angle = 45;

Point pt2 = pt1 % angle;

cout.setf(std::ios_base::fixed, std::ios::floatfield);
std::cout.precision(3);
cout << "Point " << pt1 << " rotated " << angle << " degrees is " << 
    pt2 << endl;

pt1 = Point(-6, -6);
angle = 45;

pt2 = pt1 % angle;
cout << "Point " << pt1 << " rotated " << angle << " degrees is " << 
    pt2 << endl;

cout << endl;
cout.unsetf(std::ios_base::fixed);
std::cout.precision(6);
 } 

list.h文件：

 class Point
  {
    public:
  // Point(double X, double Y);    // Constructors (2)
  explicit Point(double x, double y); 

  Point();

   double getX() const;

   double getY() const;

   Point operator+(const Point& other)const ;

   Point& operator+(double val)  ;


   Point operator*(double value) ;

   Point operator%(double angle);


   double operator-(const Point& other)const ;

   Point operator-(double val);

   Point operator^(const Point& other);

   Point& operator+=(double val);
   Point& operator+=(const Point& other) ;

   Point& operator++();
   Point operator++(int); 

   Point& operator--(); 
   Point operator--(int); 

   Point operator-() const;


        // Overloaded operators (14 member functions)
   friend std::ostream &operator<<( std::ostream &output, const Point 
  &point );
    friend std::istream &operator>>( std::istream  &input, Point 
  &point );

    // Overloaded operators (2 friend functions)

  private:
  double x; // The x-coordinate of a Point
  double y; // The y-coordinate of a Point

    // Helper functions
  double DegreesToRadians(double degrees) const;
  double RadiansToDegrees(double radians) const;
  };

Answer 1

问题我从您发布的代码中看到的是，您使用的是函数的局部点，p，用于计算变换点。据推测，其被初始化为（0,0）。旋转这一点不会改变它的位置。您需要使用this。

Point Point::operator%( double angle)
{
    Point p;
    double rad=angle * PI / 180.0;
    double s = sin(rad);
    double c = cos(rad);

    // rotate point
    double xnew = this->x * c - this->y * s;
    double ynew = this->x * s + this->y * c;

    p.x = xnew;
    p.y = ynew;
    return p;
}

或简化的版本：

Point Point::operator%( double angle)
{
    double rad=angle * PI / 180.0;
    double s = sin(rad);
    double c = cos(rad);

    // rotate point
    return Point(this->x * c - this->y * s,
                 this->x * s + this->y * c);
}