023OverloadingOperatorUsingFriendPr7_3.cpp

# include<iostream>
using namespace std;

const int size = 3;

class vector
{
	int v[size];
	public:
		vector();	//constructs null vector
		vector(int *x);	//constructs vector from array
		friend vector operator * (int a, vector b);	//friend 1
		friend vector operator * (vector b, int a);	//friend 2
		friend istream & operator >> (istream &, vector &);
		friend ostream & operator << (ostream &, vector &);
};

vector :: vector()
{
	for(int i=0; i<size;i++)
		v[i] = 0;
}

vector :: vector(int *x)
{
	for(int i=0; i<size;i++)
		v[i] = x[i];
}

vector operator *(int a, vector b)
{
	vector c;
	for(int i=0; i<size;i++)
		c.v[i] = b.v[i]*a;
	return c;
}

istream & operator >> (istream &din, vector &b)
{
	for(int i=0;i<size;i++)
		din >> b.v[i];
	return(din);
}

ostream & operator << (ostream &dout, vector &b)
{
	dout << "(" << b.v[0];
	for(int i =1;i<size;i++)
		dout << ", "<< b.v[i];
	dout << ")";
	return(dout);	
}

int x[size] = {2, 4 ,6};

int main()
{
	vector m;	//invokes constructor 1
	vector n =x;	//invokes constructor 2

	cout << "Enter elements of vector m "<< "\n";
	cin >> m;	//invokes operator>>() functions
	
	cout << "\n";
	cout<< "m= "<< m << "\n";
	
	vector p,q;
	
	p = 2 * m;	//invokes friend 1
	q = n * 2;	//invokes friend 2
	
	cout << "\n";
	cout<< "p =  "<< p << "\n";	//invokes operator<<()
	cout<< "q =  "<< q << "\n";
	return 0;
}