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

Polymorphism.

Virtual members.

We will do this through an example.

Ubuntu OS version 11.10

gcc and g++ compiler v. 4.6.1

Polymorphism is the ability to take different forms.

It is the mechanism to use a function with same name in different ways.

Virtual function is the member function of a class.

It can be overriden in its derived class.

It is declared with virtual keyword.

Virtual function call is resolved at run-time.

Point the cursor to the file name

I have already written the code.

Let us go through it.

Note that our filename is virtual.cpp

In this program:

We will calculate the area of a rectangle, parallelogram and traingle.

#include <iostream>

using namespace std;

Here we are using std namespace.

class Parallelogram

protected:

int width, height, ar;

This is the base class.

In this we have declared integer variables as width, height and ar.

These are declared protected.

public:

void set_values (int a, int b)

Here we have passed two arguments as a and b.

Then we access the protected members using the public members.

virtual int area ()

{

ar=width*height;

cout<< "Area of parallelogram is "<< ar<<"\n";

}

Here we calculate the area of parallelogram.

class Rectangle: public Parallelogram

It inherits the properties of base class parallelogram.

int area ()

{

ar=width * height;

cout<< "Area of rectangle is "<<ar <<"\n";

}

Then we calculate the area of the rectangle.

And print the value.

class Triangle: public Parallelogram

This also inherits properties of the base class parallelogram.

Here again we override the function area.

int area ()

{

ar=width * height / 2;

cout<< "Area of triangle is "<< ar<<"\n";

}

And print the value.

int main()

Parallelogram *parallel, p;

We can see here pointer parallel.

*parallel, p;

This is called as Base pointer.

Pointer of base class can point to the object of the derived class.

Rectangle rect;

Triangle trgl;

parallel=&p;

parallel->set_values(3,2);

Then we pass arguments as 3 and 2.

parallel->area();

parallel=&rect;

parallel->set_values(4,5);

parallel->area();

rect is the object of class Rectangle.

Again we pass arguments as 4 and 5.

And we call the function area.

parallel=&trgl;

parallel->set_values(6,5);

parallel->area();

trgl.

This is the object of class Triangle.

Here we pass arguments as 6 and 5.

And call function area.

return 0;

Ctrl, Alt and T keys simultaneously

g++ virtual.cpp -o vir

To execute

Type

./vir

g++ virtual.cpp -o vir

Press Enter

Type:

./vir

Press Enter

Output

Area of parallelogram is 6

Area of rectangle is 20

Area of triangle is 15

Let us summarize.

Summary

Polymorphism.

Virtual function.

Assignment

Calculate the perimeter of rectangle, square and triangle.

Create perimeter as a virtual function.

About the Spoken Tutorial Project

It summarizes the Spoken Tutorial project

If you do not have good bandwidth, you can download and watch it

Spoken Tutorial Workshops

Conducts workshops using spoken tutorials

Gives certificates to those who pass an online test

For more details, please write to,

contact@spoken-tutorial.org

Acknowledgement

It is supported by the National Mission on Education through ICT, MHRD, Government of Indiaabout:startpage

More information on this Mission is available at: http://spoken-tutorial.org\NMEICT-Intro

Thank You for joining.