Overloading Insertion and Extraction Operators

• In previous post, I had talked about overloading binary operators using member function as well as friend function.

• We know that insertion (<<) and extraction (>>) are operators in C++ and just like other operators we can also overload this insertion and extraction operators. In this post I will show you how to overload insertion and extraction operators just like other operators.

• Consider the example of class ‘Box’ in which we want to read and print the data members of class by overloading insertion and extraction operator.

// Program to overload insertion and extraction operator

#include "iostream.h"
#include "conio.h"

class Box
{
    double height;
    double width;
    double vol ;
	
    public :
	friend istream & operator >> (istream &, Box &);
	friend ostream & operator << (ostream &, Box &);
 };

 istream & operator >> (istream &din, Box &b)
 {
	clrscr();
	cout << "Enter Box Height: " ; din >> b.height ;
	cout << "Enter Box Width : " ; din >> b.width ;
	return (din) ;
}
ostream & operator << (ostream &dout, Box &b)
{
	dout << endl << endl;
	dout << "Box Height : " << b.height << endl ;
	dout << "Box Width  : " << b.width << endl ;
	
        b.vol = b.height * b.width ;
	
        dout << "The Volume of Box : " << b.vol << endl;
        getch() ;
       
        return(dout) ;
 }

 void main()
 {
       Box b1;

       cin >> b1;
       cout << b1;
}

• In above example we are overloading insertion and extraction operator using friend function.
• For insertion operator overloading we are passing two arguments.
• One is object (‘dout’) of class ‘ostream’ and another is object (‘b’) of class “Box”. Also that function returns the object of type ‘ostream’ as ‘dout’.
• You can use any name you like instead of dout.