O operator overloading

C ++ can be used to extract flow stream insertion operator >> and << operator to input and output data types built, may be overloaded operators and extracting stream insertion operator to manipulate objects and other user-defined data types.

We sometimes need to operator overloading function is declared as class friend function, so we can not construct the object and calling the function directly.

/***
inputOver.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;
        }

        friend ostream &operator<<(ostream &output,const Distance &D)
        {
            output << "F: " << D.feet << " I: " << D.inches;
            return output;
        }
        friend istream &operator>>(istream &input,Distance &D)
        {
            input >> D.feet >> D.inches ;
            return input;
        }
};

int main()
{
    Distance D1(11,10),D2(5,11),D3;
    cout << "Enter the value of object : " << endl;
    cin >> D3;
    cout << "First Distance : " << D1 << endl;
    cout << "Second Distance : " << D2 << endl;
    cout << "Third Distance : " << D3 << endl;
    return 0; 
}

operation result:

exbot ubuntu @: ~ / wangqinghe / C ++ / 20190808 $ g ++ inputOver.cpp -o inputOver

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

Enter the value of object :

70 10

First Distance : F: 11 I: 10

Second Distance : F: 5 I: 11

Third Distance : F: 70 I: 10

 

If you reload the program written in the functional form of the members, it will be in the form d1 << cout output data.

/***
memberOver.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;
        }

        ostream &operator<<(ostream &os)
        {
            os << "F: " << feet << " I: " << inches << endl;
            return os;
        }
};

int main()
{
    Distance d1(20,18);
    d1 << cout;
    return 0; 
}

operation result:

exbot@ubuntu:~/wangqinghe/C++/20190808$ g++ memberOver.cpp -o memberOver

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

F: 20 I: 18