Difference between revisions of "Advanced-C++/C2/Friend-Function/English"

Friend function.

We will do this with the help of an example.

Ubuntu OS v. 11.10

g++ compiler v. 4.6.1

We know, the private data is not accessible outside the class.

To access the private data we use friend function.

A friend function is not a member of the class.

Friend function can be invoked without using an object.

The argument passed in the friend function is used as its object.

friend return_type function_name( class_name object)

friend keyword is used to declare a friend function.

Then we give the return_type.

function_name is the name of the function.

Then we pass arguments as class_name and object of the class.

I have already typed the code on the editor.

I will open it.

In this program we will perform addition operation.

frnd.cpp

Let me explain the code now.

#include<iostream>

using namespace std;

class frnd

{

private:

int a,b;

public:

void input()

In this we have declared variables a and b as private.

Here we have declared a function input as public

cout<<"Enter the value of a and b\n";

cin>>a>>b;

friend int compute(frnd f1);

};

Here, we have passed arguments as class_name frnd and object of the class f1.

Then we close the class.

Now we can access the private members of class frnd using the friend function.

int compPlease make a mention of the compute method.ute(frnd f1)

return int(f1.a+f1.b);

In this we will perform addition operation.

We add the variables.

And then return the value.

Here we access the private variables in non-member function using the object f1.

int main()

{

frnd f;

f.input();

cout << "The result is: " << compute(f)<<"\n";

Then we call the function input using the object f.

And here we call function compute and pass f as argument.

You can see that we have passed the argument as f in function compute.

This is done by using the method pass by value.

f is passed to the value of f1.

return 0;

Ctrl, Alt and T keys simultaneously

g++ frnd.cpp -o frnd

To execute

Type

./frnd

g++ frnd.cpp -o frnd

To execute type

./frnd

Press Enter

Output

Enter the value of a and b

I will enter as:

8

4

The output is displayed as:

The result is: 12

Let us move back to our slides.

Summary

In this tutorial we have seen

Friend function.

eg. friend int compute(frnd f1);

Assignment

Write a program to find out the square and cube of a number.

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