DATA STRUCTURES AND ALGORITHMS

LAB 2

Bianca Tesila

FILS, Feb 2014

OBJECTIVES

Transition from C to C++ Struct vs. classes in C++ Templates

WHY C++?

C + + allows the implementation of data structures with generic data types via templates.

C follows the procedural programming paradigm while C++ can follow both procedural paradigm and OOP (Which are the OOP principles?)

TRANSITION FROM C TO C++

Any program written in C (“.c” extension) can be compiled by a C++ compiler (“.cpp” extension); not vice versa

In C we don’t have classes!!!

The NAMESPACE feature in C++ is absent in case of C: avoid name collisions (namespaces are similar to Java packages- you can look for differences & similarities for the next time)

Standard input & output functions differ in the two languages: in C, we have scanf and printf; in C++ we have cin>> and cout<<

TRANSITION FROM C TO C++

‼ Exercise: Implement a function to sort an array of 5 elements of type double. Use a swap mechanism, which has to be implemented in another function.

Hint: Pay attention to passing by value/ passing by reference!

Do you remember which is the difference between them?

STRUCTURES VS CLASSES: STRUCTURES IN C++

We can define functions inside a structure; we can access the structure’s fields by using this-><field_name>

C++ structures support inheritance Everything inside a structure is public by default

Example:typedef struct complex {

double re;double im;void complex_initialize(double param_re, double param_im) {this->re = param_re;

this->im = param_im; } struct complex complex_conjugate() {struct complex conjugate;conjugate.complex_initialize(this->re, -(this->im)); return conjugate;

}}complex;

STRUCTURES VS. CLASSES

‼ Exercise: Add to the complex structure new functions for the addition, division and multiplication of complex numbers.

STRUCTURES VS. CLASSES: CLASSES What is a class? What is an object? Replace the keyword struct with the keyword class in the last

exercise C++ structures behave like C++ classes, allowing functions,

contructors, destructors. The main diffrence between classes and C++ structures is that everything inside a structure is public, by default, while everything inside a class is private, by default

STRUCTURES VS. CLASSES: CLASSES

‼ Exercise: Make a Complex class using the previous exercise.

Hint:

Don’t forget about the fact that everything inside a class is private, by default.

Take into account the Encapsulation principle!

TEMPLATE CLASSES Templates are a feature of the C++ programming language

that allow functions and classes to operate with generic types. This allows a function or class to work on many different data types without being rewritten for each one.

Templates are of great utility to programmers in C++, especially when combined with multiple inheritance and operator overloading.

Similar to Java Generics

template<typename T> class class_name { ... } A normal class definition will be prefixed by template<typename

T> The type T can now be used as a valid type within the class

we can have variables, function arguments and function return values of type T

Everything happens at compile time, not runtime The compiler analyzes how you use the class

TEMPLATE CLASSES: EXAMPLE

template<typename T>

class KeyStorage

{

public:

int key;

T member; //a generic member: we don't know its type when creating the class

};

int main()

{

//Everything happens to compile time, not to run time

//The compiler analyses the way in which you use the class

KeyStorage<long> keyElement1;

KeyStorage<int> keyElement2;

return 0;

}

‼ Exercise: Make a constructor, a destructor, a getter and a setter for the template class KeyStorage.

HOMEWORK

Finish all the lab exercises.

Implement a template class for storing the coordinates of a point. Add corresponding methods for moving a point(along Ox, along Oy, along both Ox and Oy). Using the implemented class, develop an application for moving a point inside a rectangle of dimensions 1 x N, where N is given by the user. Start from the origin.

Implement a template class for bank accounts with corresponding methods(deposit, withdrawal, balance display, display owner etc). Develop an application that uses this class.

INTERVIEW:

Does overloading exist in C++? Do abstract classes exist in C++? When is it better to use abstract classes and

when templates? Do static classes exist in C++?