26friendfunc.cpp

#include <iostream>
using namespace std;

class complex
{
    int a, b;

public:
    friend complex sumofcomplex(complex o1, complex o2);
    /*This is called a friend function
    whenever a class function is created outside the class scope, it is nessecary to declare the function as part of the class
    or as a "friend" to access the private data
    It doesn't require any object to access it
    There is no difference if the friend call is written in public or private
    it usually contains objects as arguments */
    void setnum(int n1, int n2)
    {
        a = n1;
        b = n2;
    }
    void printnum()
    {
        cout << "z = " << a << " + " << b << "i" << endl;
    }
};

complex sumofcomplex(complex o1, complex o2)
{
    complex o3;
    o3.setnum((o1.a + o2.a), (o1.b + o2.b));
    return o3;
}
int main()
{
    complex c1, c2, compsum;
    c1.setnum(1, 5);
    c1.printnum();

    c2.setnum(4, 3);
    c2.printnum();

    compsum = sumofcomplex(c1, c2);
    compsum.printnum();
    return 0;
}