关系运算符重载

C++语言支持各种关系运算符重载(<,>,>=,<=,==)，他们可用于比较C++内置的数据类型。

支持重载任意一个关系运算符，重载后的关系运算符可以用于比较类的对象。

/***
overrealate.cpp
***/
#include<iostream>
using namespace std;

class Distance
{
    private:
        int feet;
        int inches;
    public:
        Distance()
        {
            feet = 0;
            inches = 0;
        }
        Distance(int f,int i)
        {
            feet = f;
            inches = i;
        }

        void displayDistance()
        {
            cout << "F: " << feet << " I: " << inches << endl; 
        }

        Distance operator- ()
        {
            feet = -feet;
            inches = -inches;
            return Distance(feet,inches);
        }
        bool operator <(const Distance& d)
        {
            if(feet < d.feet)
            {   
                return true;
            }
            if(feet == d.feet && inches < d.inches)
            {
                return true;
            }
            return false;
        }
};

int main()
{
    Distance D1(11,10), D2(5,11);

    if(D1 < D2)
    {
        cout << "D1 is less than D2 " << endl;
    }
    else
    {
        cout << "D2 is less than D1" << endl; 
    }
    return 0;
}

运行结果：

exbot@ubuntu:~/wangqinghe/C++/20190808$ ./overrelation

D2 is less than D1