COMPLAB-Week 3 Solved

                                                                       C++ as an Object-Oriented Language.
                                                                               Classes and Objects
                                                                               
Computer programs usually model aspects of some real or abstract world (the domain). Because each 
class models a concept, classes provide a more natural way to create such models. Each class in the 
model represents a noun in the domain, and the methods of the class represent verbs that may apply to 
that noun. Classes allow a clear correspondence (mapping) between the model and the domain, 
making it easier to design, build, modify and understand these models. Classes provide some control 
over the often challenging complexity of such models.
Classes can accelerate development by reducing redundant program code, testing and bug fixing. If a 
class has been thoroughly tested and is known to be a 'solid work', it is usually true that using or 
extending the well-tested class will reduce the number of bugs - as compared to the use of freshly[1]developed or ad hoc code - in the final output. In addition, efficient class reuse means that many bugs 
need to be fixed in only one place when problems are discovered.


Task 1. 
Develop and implement a Rectangle class. Consider the following mandatory functions and 
restrictions:
a) Any rectangle can be defined by its sides. The sides should not be accessible from 
the outside of Rectangle class.
b) At initialization phase, it should be possible to define the rectangle by:
- two sides: we get a default rectangle with non-equal sides;
- one side: we get a square (all sides are equal); square is just a special rectangle.
- no values, or empty parameter list: in this case the sides are zeroes.
c) Insure the consistency of initial values; the class attributes should always represent 
a valid rectangle. Users can enter any values (even negative), and it is your task to 
check the input consistency.
d) The class should provide the following information about the rectangle:
- length of all sides one after another;
- its perimeter;
- its area.
e) Implement print() public class operation that prints all information about the 
rectangle: its sides, area and perimeter values.
Write a main() function that contains all necessary testing code to check the 
correctness of the Rectangle class implementation. Any kind of user input should take 
place only in main(), not in the Rectangle class. However, validity check of input data 
is in the responsibility of Rectangle class.
Decomposition of the program:
- rectangle.h file: class declaration header;
- rectangle.cpp: implementation of methods declared in the header;
- main.cpp: the main program with testing code.


Task 2. 
Based on the example above (see Task 1) develop and implement a Circle class. A circle can 
be defined by its radius R, which should be stored as a class attribute. Make sure that a radius 
is inaccessible from the outside of Circle class. Insure the consistency of objects: it should not 
be possible to bring any circle into inconsistent state. The Circle class should provide 
information about the radius, area and circumference (length) of the circle. Write a testing 
function (main) to test the correctness of your implementation. Follow the program 
decomposition from Task 1 (header, implementation, main program)