Answer to Question #263801 in C++ for AB Agha

Question

What is operator overloading? Explain this concept and provide a suitable example.

Answer 1

/*Operator overloading is an important concept in C++. It is polymorphysm in which
an operator is overloaded to give user defined meaning to it. Overloaded operator
is used to perform operation on user-defined data type. Almost any operator can be 
overloaded in C++. Operator that are not be overloaded are follows
- member selector - .
- sizeof
- ternary operator - ?
- member pointer selector - *
- scope operator - ::
Operator overloading can be done by implementing a function which can be
member function, non-member function or friend function
Following are some restrictions to be kept in mind while implementing operator
operator overloading
- Precedence and Associativity of an operator cannot be changed
- Arity cannot be changed. Unary operator remains unary, binary remains binary etc.
- No new operators can be created, only existing operators can be overloaded
- Cannot redefine the meaning of a procedure. You cannot change how inetgers are added
Reference - studytonight.com */

#include<iostream>
using namespace std;
class TwoInt
{
	int a;
	int b;
public:
	//default constructor
	TwoInt():a(0),b(0){}
	//init constructor
	TwoInt(int _a, int _b):a(_a),b(_b){}
	//assign constructor
	TwoInt(TwoInt& x):a(x.a),b(x.b){}
	//member function operator++
	void operator++()
	{
		a++;b++;
	}
	//member function operator--
	void operator--()
	{
		a--;b--;
	}
	friend ostream& operator<<(ostream& os, TwoInt& tin);
	friend TwoInt operator+ (TwoInt& x, TwoInt& y);
};


//non-member friend function operator<<
ostream& operator<<(ostream& os, TwoInt& tin)
{
	return os<<tin.a<<" "<<tin.b;
}

//non-member friend function operator+
TwoInt operator+ (TwoInt& x, TwoInt& y)
{
	TwoInt z(x.a+y.a,x.b+y.b);	
	return z;
}


int main()
{
	TwoInt x(1,5);
	cout<<"Output of primary TwoInt x is: \n";
	cout<<x<<endl;
	++x;
	cout<<"Output of TwoInt x after operator++ is: \n";
	cout<<x<<endl;
	TwoInt y(12,15);
	cout<<"Output of primary TwoInt y is: \n";
	cout<<y<<endl;
	--y;
	cout<<"Output of TwoInt y after operator-- is: \n";
	cout<<y<<endl;
	TwoInt z;
	cout<<"Output of TwoInt z after operator+ with x and y is : \n";
	z=x+y;
	cout<<z;	
}