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c++ - 运算符一元重载函数

问题描述

我被一元运算符重载的问题困住了。所以在下面显示的代码中，我基本上没有得到与我学校匹配的预期结果。有关更多信息，请参见下文。函数有一些限制，我不能添加任何参数，否则它会给我一个编译错误。那么我该怎么办呢？如果您需要更多信息，请告诉我。谢谢！

    Point& Point::operator-() 
{

    x = -x;
    y = -y;
    return *this;

}

结果如下：

**********我的一元测试**********

pt1 = (3,4)

pt2 = -pt1

pt1 = (-3,-4)

pt2 = (-3,-4)

pt3 = (-3,4)

pt4 = - - -pt3

pt3 = (3,-4)

pt4 = (3,-4)

**********学校的一元测试**********

pt1 = (3, 4)

pt2 = -pt1

pt1 = (3, 4)//

pt2 = (-3, -4)

pt3 = (-3, 4)

pt4 = - - -pt3

pt3 = (-3, 4)//

pt4 = (3, -4)

驱动文件

  void UnaryTest(void)
{
cout << "\n********** Unary test ********** " << endl;

Point pt1(3, 4);
cout << "pt1 = " << pt1 << endl;
Point pt2 = -pt1;
cout << "pt2 = -pt1" << endl;

cout << "pt1 = " << pt1 << endl;
cout << "pt2 = " << pt2 << endl;

cout << endl;

Point pt3(-3, 4);
cout << "pt3 = " << pt3 << endl;
Point pt4 = - - -pt3;
cout << "pt4 = - - -pt3" << endl;

cout << "pt3 = " << pt3 << endl;
cout << "pt4 = " << pt4 << endl;
}

列表.h 文件

  class Point
  {
   public:

  explicit Point(double x, double y); 

  Point();

   double getX() const;

   double getY() const;

   Point operator+(const Point& other)const ;

   Point& operator+(double value);


   Point operator*(double value) ;

   Point operator%(double angle);


   double operator-(const Point& other)const ;

   Point operator-(double value);

   Point operator^(const Point& other);

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

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

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

   Point& operator-() ;


        // 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;
};

 // Point& Add(const Point& other); // Overloaded operators (2 non-member, 
 non-friend functions)
    // Point& Multiply(const Point& other);
    Point operator+( double value, const Point& other );
    Point operator*( double value, const Point& other );

标签： c++operator-overloading

解决方案

原型是：

Point operator-(double value);

但是你的实现是：

Point& Point::operator-()

这不起作用（注意参考和不同的论点！）。

此外，您不应修改此运算符的对象。相反，你应该有这个：

Point operator-() const;

进而：

Point Point::operator-() const
{
    return Point(-x, -y);
}

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