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Unary operators only one operand operation, the following are examples of unary operators:

Unary operator typically appears at the left of the object on which they operate, for example! Obj, -obj and ++ obj, but sometimes they can also be used as a suffix, such as obj ++ or obj--.

The following example demonstrates how overloaded unary minus operator (-).

```#include <iostream>
using namespace std;

class Distance
{
private:
int feet;             // 0 到无穷
int inches;           // 0 到 12
public:
// 所需的构造函数
Distance(){
feet = 0;
inches = 0;
}
Distance(int f, int i){
feet = f;
inches = i;
}
// 显示距离的方法
void displayDistance()
{
cout << "F: " << feet << " I:" << inches <<endl;
}
// 重载负运算符（ - ）
Distance operator- ()
{
feet = -feet;
inches = -inches;
return Distance(feet, inches);
}
};
int main()
{
Distance D1(11, 10), D2(-5, 11);

-D1;                     // 取相反数
D1.displayDistance();    // 距离 D1

-D2;                     // 取相反数
D2.displayDistance();    // 距离 D2

return 0;
}
```

When the above code is compiled and executed, it produces the following results:

```F: -11 I:-10
F: 5 I:-11
```