1. DATA STRUCTURES AND ALGORITHMS
LAB 2
Bianca Tesila
FILS, Feb 2014

2. OBJECTIVES
Transition from C to C++
 Struct vs. classes in C++
 Templates
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3. WHY C++?
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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?)

4. TRANSITION FROM C TO C++
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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<<

5. 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?

6. STRUCTURES VS CLASSES: STRUCTURES IN C++
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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;

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

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

9. 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!

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

11. 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.

12. HOMEWORK
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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.

13. 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++?
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