ch06 objects and classes (1)

7/31/2019 Ch06 Objects and Classes (1)

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Introduction

Previously, programmers starting a project would sit

down almost immediately and start writing code.

As programming projects became large and more

complicated, it was found that this approach did not

work very well. The problem was complexity. Large programs are probably the most complicated

entities ever created by humans.

Because of this complexity, programs are prone to error,

and software errors can be expensive and even life

threatening (in air traffic control, for example).

Three major innovations in programming have been

devised to cope with the problem of complexity. They are2



Introduction

Object-oriented programming (OOP)

The Unified Modeling Language (UML)

Improved software development processes

You will be taught the C++ language with these develop-

ments in mind. You will not only learn a computer language, but new

ways of conceptualizing software development.

Other famous Object Oriented languages are JAVA, C# (C

Charp), VB.NET (Visual Basic Dot Net), Paython3, PHP5.

3



Object Oriented Programming

Object Oriented Programming offers a new and powerful

way to cope with complexity.

Instead of viewing a program as a series of steps to be

carried out, it views it as a group of objects that have

certain properties and can take certain actions. This may sound obscure until you learn more about it,

but it results in programs that are clearer, more reliable,

and more easily maintained.

A major goal of this course is to teach object-oriented

programming using C++ and cover all its major features.

4



The Unified Modeling Language

The Unified Modeling Language (UML) is a graphical

language consisting of many kinds of diagrams.

It helps program analysts figure out what a program

should do, and helps programmers design and

understand how a program works. The UML is a powerful tool that can make programming

easier and more effective.

We introduce each UML feature where it will help to

clarify the OOP topic being discussed.

In this way you learn the UML painlessly at the same time

the UML helps you to learn C++.

5



Class

A class serves as a plan, or template. It specifies what

data and what functions will be included in objects of

that class.

Defining the class doesn’t create any objects, just as the

type int doesn’t create any variables. A class is thus a description of a number of similar

objects.

Prince, Sting, and Madonna are members of the class of

rock musicians.

There is no one person called “rock musician” but specific

people with specific names are members of this class if

they possess certain characteristics. 6



Class

Picture a programming object

just like any normal object in

the real world.

Each real world object has its

own properties and specificthings that you can do with it.

For example, a bow has specific

properties such as color,

number of arrows, and weightand specific capabilities such as

the ability to fire .

7



Class

two Bow objects are declared using the Bow class, the

Bow class describes the properties of a bow, each of the

two Bow objects has distinct values for these properties 8



A Simple Class

// smallobj.cpp demonstrates a small, simple object

#include <iostream> using namespace std;

class smallobj // define a class (a concept)

{

private:

int somedata; // class data (attributes)

public:

void setdata(int d){ // member function (method)to

somedata = d; // set data

}

void showdata(){ // member function to display data

cout << "Data is " << somedata << endl;

}

};

9



A Simple Class

int main()

{smallobj s1, s2; // define two objects of class smallobj

s1.setdata(1066); // call member function to set data

s2.setdata(1776);

s1.showdata(); // call member function to display data

s2.showdata();

system("PAUSE");

return 0;

}

10



Classes and Objects

An object has the same relationship to a class that a

variable has to a data type.

An object is said to be an instance of a class, in the same

way my 1954 Chevrolet is an instance of a vehicle.

In the program the class , whose name is smallobj, isdefined in the first part of the program.

In main(), we define two objects s1 and s2 that are

instances of that class.

Each of the two objects is given a value, and each displays

its value.

11



Defining the Class

Syntax for class definition 12



Defining the Class

The definition starts with the keyword class, followed by

the class name—smallobj in this Example.

The body of the class is delimited by braces and

terminated by a semicolon.

An object has the same relationship to a class that avariable has to a data type.

A key feature of object-oriented programming is data

hiding. it means that data is concealed within a class so

that it cannot be accessed mistakenly by functions

outside the class.

The primary mechanism for hiding data is to put it in a

class and make it private. 13



Defining the Class

Because setdata()

and showdata()

follow the keyword

public, they can be

accessed from

outside the class.

In a class the

functions do not

occupy memoryuntil an object of

the class is created.

15



Defining the Class

Remember that the definition of the class smallobj does

not create any objects. It only describes how they will

look when they are created.

Defining objects means creating them. This is also called

instantiating them, because an instance of the class iscreated. An object is an instance of a class.

s1.setdata(1066); This syntax is used to call a member

function that is associated with a specific object s1.

Member functions of a class can be accessed only by an

object of that class.

16



Widget Parts as Objects (1/2)

// objpart.cpp widget part as an object


class part{ // define class

private:

int modelnumber; // ID number of widget

int partnumber; // ID number of widget part

float cost; // cost of part

public:

void setpart(int mn, int pn, float c){ // set data

modelnumber = mn;

partnumber = pn;

cost = c;

}

void showpart(){ // display data

cout << "Model " << modelnumber;

17



Widget Parts as Objects (1/2)

cout << ", part " << partnumber;

cout << ", costs $" << cost << endl;}

};

int main(){

part part1; // define object of class part

part1.setpart(6244, 373, 217.55F); // call member function

part1.showpart(); // call member function

system("PAUSE"); return 0;

}

If you were designing an inventory program you might

actually want to create a class something like part.

It’s an example of a C++ object representing a physical

object in the real world—a widget part. 18



Circles as Objects

// circles.cpp circles as graphics objects

#include "msoftcon.h" // for graphics functionsclass circle{ // graphics circle

protected :

int xCo, yCo; // coordinates of center

int radius;

color fillcolor; // colorfstyle fillstyle; // fill pattern

public: // sets circle attributes

void set(int x, int y, int r, color fc, fstyle fs){

xCo = x; yCo = y; radius = r;

fillcolor = fc; fillstyle = fs;

}

void draw(){ // draws the circle

set_color(fillcolor); // set color

set_fill_style(fillstyle); // set fill

19



Circles as Objects

draw_circle(xCo, yCo, radius);// draw solid circle

}};

int main(){

init_graphics(); // initialize graphics system

circle c1, c2, c3; // create circles

//set circle attributesc1.set(15, 7, 5, cBLUE, X_FILL);

c2.set(41, 12, 7, cRED, O_FILL);

c3.set(65, 18, 4, cGREEN, MEDIUM_FILL);

c1.draw(); //draw circles

c2.draw();

c3.draw();

set_cursor_pos(1, 25); // lower left corner

system("PAUSE");

return 0;

} 20



Using Class to Represent Distances

// englobj.cpp objects using English measurements


class Distance{ // English Distance class

private:

int feet;

float inches; public:

void setdist(int ft, float in) // set Distance to args

{ feet = ft; inches = in; }

void getdist(){ // get length from user

cout << "\nEnter feet: "; cin >> feet;

cout << "Enter inches: "; cin >> inches;

}

void showdist() // display distance

{ cout << feet << "\’-" << inches << '\”'; }

}; 21



Using Class to Represent Distances

int main()

{Distance dist1, dist2; // define two lengths

dist1.setdist(11, 6.25); // set dist1

dist2.getdist(); // get dist2 from user

// display lengthscout << "\ndist1 = ";

dist1.showdist();

cout << "\ndist2 = ";

dist2.showdist();

cout << endl;

system("PAUSE");

return 0;

} 22



Constructors

We see that member functions can be used to give values

to the data items in an object .

Sometimes, however, it’s convenient if an object can

initialize itself when it’s first created, without requiring a

separate call to a member function. Automatic initialization is carried out using a special

member function called a constructor .

A constructor is a member function that is executed

automatically whenever an object is created.

Constructor has the same name of class and it has no

return type.

23



Constructors: Count Example (1/2)

// counter.cpp object represents a counter variable


class Counter{

private:

unsigned int count; // count

public:Counter() : count(0) // constructor

{ cout << "constructor has been called \n"; }

void inc_count() // increment count

{ count++; }

int get_count() // return count

{ return count; }

};

24



Constructors: Count Example (2/2)

int main()

{Counter c1, c2; // define and initialize

cout << "\nc1=" << c1.get_count(); // display

cout << "\nc2=" << c2.get_count();

c1.inc_count(); // increment c1

c2.inc_count(); // increment c2c2.inc_count(); // increment c2

cout << "\nc1=" << c1.get_count(); // display again

cout << "\nc2=" << c2.get_count();

cout << endl;

system("PAUSE");

return 0;

}

25



Circles using Constructor (1/2)

// circles.cpp circles as graphics objects

#include "msoftcon.h" // for graphics functionsclass circle{ // graphics circle

protected :

int xCo, yCo; // coordinates of center

int radius;

color fillcolor; // colorfstyle fillstyle; // fill pattern

public: // sets circle attributes

circle(int x, int y, int r, color fc, fstyle fs):

xCo(x), yCo(y), radius(r), fillcolor(fc), fillstyle(fs)

{ } // 3 argument constructor

void draw(){ // draws the circle

set_color(fillcolor); // set color

set_fill_style(fillstyle); // set fill

26



Circles using Constructor (2/2)

draw_circle(xCo, yCo, radius); //draw solid circle

}};

int main(){

init_graphics(); // initialize graphics system

//create circles

circle c1(15, 7, 5, cBLUE, X_FILL);circle c2(41, 12, 7, cRED, O_FILL);

circle c3(65, 18, 4, cGREEN, MEDIUM_FILL);

c1.draw(); // draw circles

c2.draw();

c3.draw();

set_cursor_pos(1, 25); // lower left corner

return 0;

}

27



Destructor

You might guess that another function is called

automatically when an object is destroyed. This is indeedthe case. Such a function is called a destructor .

A destructor also has the same name as the class name

but is preceded by a tilde (~) sign: Like constructors, destructors do not have a return value.

They also take no arguments.

The most common use of destructors is to de-allocate

memory that was allocated for the object by the

constructor.

28



Using Destructor

// foo.cpp demonstrates destructor


class Foo{

private:

int data;

public:Foo() : data(0) // constructor (same name as class)

{cout<< "Wakeup \n" ; }

~Foo() // destructor (same name with tilde)

{cout<< "ByeBye \n" ; }

};

int main(){

Foo s1, s2; // define two objects of class Foo

system( "PAUSE" ); // Foo *s3; s3 = new Foo; delete s3;

return 0;

} 29



Objects as Function Arguments

Next program demonstrates some new aspects of

classes, which are:

Constructor Overloading

Defining Member Functions Outside The Class

Objects as Function Arguments.

30



Objects as Function Arguments (1/3)

// englcon.cpp constructors, adds objects using member function


class Distance // English Distance class

{

private:

int feet;float inches;

public: // constructor (no args)

Distance() : feet(0), inches(0.0)

{ cout<< "No Arguments Constructor has been Called \n" ; }

//constructor (two args)

Distance(int ft, float in) : feet(ft), inches(in)

{ cout<< "Two Arguments Constructor has been Called \n" ; }

31





cout << "\nEnter feet: "; cin >> feet;cout << "Enter inches: "; cin >> inches;

}

void showdist(){ // display distance

cout << feet << "\'-" << inches << '\"';

}void add_dist( Distance, Distance ); // declaration

};

// member function is defined outside the class

void Distance::add_dist(Distance d2, Distance d3){

inches = d2.inches + d3.inches; // add the inches

feet = 0; // (for possible carry)

if(inches >= 12.0){ // if total exceeds 12.0,

inches -= 12.0; // then decrease inches by 12.0

feet++; // and increase feet by 1

} 32




feet += d2.feet + d3.feet; // add the feet

}int main(){

Distance dist1, dist3; // Calls no args. constructor

Distance dist2(11, 6.25); // Calls two args. constructor


dist3.add_dist(dist1, dist2); // dist3 = dist1 + dist2

// display all lengths

cout << "\ndist1 = "; dist1.showdist();



cout << endl;

return 0;

}

33



Constructors Overloading

Since there are now two explicit constructors with the

same name, Distance(), we say the constructor isoverloaded .

Which of the two constructors is executed when an

object is created depends on how many arguments areused in the definition:

Distance length; // calls first constructor

Distance width(11, 6.0); // calls second constructor

34



Member Functions Defined Outside the Class

void add_dist( Distance, Distance ); This tells the compiler

that this function is a member of the class but that it will

be defined outside the class declaration, someplace else

in the listing.

35



Objects as Arguments

Since add_dist() is a member function of the Distance

class, it can access the private data in any object of classDistance supplied to it as an argument, using names like

dist1.inches and dist2.feet.

In the following statement dist3.add_dist(dist1, dist2);add_dist() can access dist3, the object for which it was

called, it can also access dist1 and dist2, because they are

supplied as arguments.

When the variables feet and inches are referred to within

this function, they refer to dist3.feet and dist3.inches.

Notice that the result is not returned by the function. The

return type of add_dist() is void. 36



Objects as Arguments

The result is stored automatically in the dist3 object.

To summarize, every call to a member function is

associated with a particular object (unless it’s a static

function; we’ll get to that later).

Using the member names alone (feet and inches), thefunction has direct access to all the members, whether

private or public, of that object .

member functions also have indirect access, using the

object name and the member name, connected with thedot operator (dist1.inches or dist2.feet) to other object s

of the same class that are passed as arguments.

37



38

10

8

11

6.25

22

2.25



The Default Copy Constructor

We’ve seen two ways to initialize objects.

A no-argument constructor can initialize data members toconstant values

A multi-argument constructor can initialize data members to

values passed as arguments.

You can also initialize one object with another object of the same type. Surprisingly, you don’t need to create a

special constructor for this; one is already built into all

classes.

It’s called the default copy constructor . It’s a one

argument constructor whose argument is an object of

the same class as the constructor. The next program

shows how this constructor is used. 39



The Default Copy Constructor (1/2)

// ecopycon.cpp initialize objects using default copy constr.



private:

int feet; float inches;

public:

Distance() : feet(0), inches(0.0) // constructor (no args)



{ cout<< "Two Arguments Constructor has been Called \n" ; }void getdist(){ // get length from user



}

40



The Default Copy Constructor (2/2)

void showdist(){ //display distance

cout << feet << "\'-" << inches << '\"';}

};

int main(){

Distance dist1; // calls no arguments constructor

Distance dist2(11, 6.25); // calls two-arg constructorDistance dist3(dist2); // calls default copy constructor

Distance dist4 = dist2; // also calls default copy const.



cout << "\ndist2 = "; dist2.showdist();cout << "\ndist3 = "; dist3.showdist();


cout << endl; return 0;

}

41



Returning Objects from Functions (1/3)

// englret.cpp function returns value of type Distance



private:

int feet; float inches;

public:Distance() : feet(0), inches(0.0) // constructor (no args)


// constructor (two args)


{ cout<< "Two Arguments Constructor has been Called \n" ; }


cout << "Enter feet: "; cin >> feet;


} 42




void showdist(){ //display distance

cout << feet << "\'-" << inches << '\"';}

Distance add_dist(Distance); // add

};

// add this distance to d2, return the sum Distance Distance::add_dist(Distance d2){

Distance temp; // temporary variable

temp.inches = inches + d2.inches; // add the inches

if(temp.inches >= 12.0){ // if total exceeds 12.0,

temp.inches -= 12.0; // then decrease inches by 12.0 and temp.feet = 1; // increase feet by 1

}

temp.feet += feet + d2.feet; // add the feet

return temp;

} 43

O f 3 3




int main()


Distance dist2(11, 6.25); // define, initialize dist2


dist3 = dist1.add_dist(dist2); // dist3 = dist1 + dist2


cout << "\ndist1 = " ; dist1.showdist();



cout << endl;return 0;

}

44

R i Obj f F i



Returning Objects from Functions

To execute the statement dist3 = dist1.add_dist(dist2);

A temporary object of class Distance is created to store

the sum.

The sum is calculated by adding two distances.

The first is the object dist1, of which add_dist() is a member. Itsmember data is accessed in the function as feet and

inches.

The second is the object passed as an argument, dist2.

Its member data is accessed as d2.feet and d2.inches.

The result is stored in temp and accessed as temp.feet

and temp.inches.

45

R i Obj f F i



Returning Objects from Functions

The temp object is then returned by the function using

the statement return temp;

The statement in main() assigns it to dist3.

Notice that dist1 is not modified; it simply supplies data

to add_dist(). Figure 6.7 shows how this looks.

In Chapter 8, “Operator Overloading” we’ll see how to

use the arithmetic + operator to achieve the even more

natural expression dist3 = dist1 + dist2;

46



47

10

8

11

6.25

22

2.25

St t d Cl



Structures and Classes

In fact, you can use structures in almost exactly the same

way that you use classes. The only formal differencebetween class and struct is that in a class the members

are private by default, while in a structure they are public

by default. You can just as well write

class foo

{

int data1; public:

void func();

}; //and the data1 will still be private.

48

St t d Cl



Structures and Classes

If you want to use a structure to accomplish the same

thing as this class, you can dispense with the keywordpublic, provided you put the public members before the

private ones

struct foo{void func();

private:

int data1;

}; // since public is the default.

However, in most situations programmers don’t use a

struct this way. They use structures to group only data,

and classes to group both data and functions.49

Cl Obj t d M



Classes, Objects and Memory

you might have the impression that each object created

from a class contains separate copies of that class’s data and member functions.

It’s true that each object has its own separate data items

But all the objects in a given class use the same member functions.

The member functions are created and placed in memory

only once—when they are defined in the class definition.

Since the functions for each object are identical. The data

items, however, will hold different values.

50



51

St ti Cl D t



Static Class Data

If a data item in a class is declared as static, only one such

item is created for the entire class, no matter how manyobjects there are.

A static data item is useful when all objects of the same

class must share a common item of information.

A member variable defined as static has characteristics

similar to a normal static variable: It is visible only within

the class, but its lifetime is the entire program. It conti-

nues to exist even if there are no objects of the class. a normal static variable is used to retain information

between calls to a function, static class member data is

used to share information among the objects of a class.52

U f Stati Cla Data



Uses of Static Class Data

Why would you want to use static member data? As an

example, suppose an object needed to know how many other objects of its class were in the program.

In a road-racing game, for example, a race car might want

to know how many other cars are still in the race.

In this case a static variable Total_Cars could be included

as a member of the class. All the objects would have

access to this variable. It would be the same variable for

all of them; they would all see the same number of Total_Cars.

53

Static Data Class (1/2)




// statdata.cpp demonstrates a simple static data member


class Car{

private:

static int Total_Cars; // only one data item for all objects

// note: "declaration" only! public:

Car() // increments count when object created

{ Total_Cars++; }

int How_Many() // returns count

{ return Total_Cars; }~Car()

{ Total_Cars--; }

};

int Car::Total_Cars = 0; // *definition* of count

54





int main(){

Car Toyota, Honda, Suzuki; // create three objects

cout << Toyota.How_Many() << " Cars are in Race" << endl;

cout << Honda.How_Many() << " Cars are in Race" << endl;

// each object sees the same datacout << Suzuki.How_Many() << " Cars are in Race" << endl;

Car *Pajero = new Car;

cout << Suzuki.How_Many() << " Cars are in Race" << endl;

delete Pajero;

cout << Honda.How_Many() << " Cars are in Race" << endl;

return 0;

}

55

Static Class Data (S t D l ti d D fi iti )



Static Class Data (Separate Declaration and Definition)

Ordinary variables are usually declared (the compiler is

told about their name and type) and defined (thecompiler sets aside memory to hold the variable) in the

same statement. e.g. int a;

Static member data, on the other hand, requires two

separate statements.

The variable’s declaration appears in the class definition,

but the variable is actually defined outside the class, in much

the same way as a global variable. If static member data were defined inside the class, it

would violate the idea that a class definition is only a

blueprint and does not set aside any memory.56

const Members Functions



const Members Functions

A const member function guarantees that it will never

modify any of its class’s member data.

57

//constfu.cpp demonstrates const member functions

class aClass

{

private:int alpha;

public:

void nonFunc() // non-const member function

{ alpha = 99; } // OK

void conFunc() const // const member function

{ alpha = 99; } // ERROR: can’t modify a member

};

Distance Class and Use of const (1/3)




// const member functions & const arguments to member functions



private:

int feet;

float inches; public: // constructor (no args)

Distance() : feet(0), inches(0.0)

{ } // constructor (two args)


{ }void getdist(){ // get length from user



}

58





void showdist() const // display distance

{ cout << feet << "\'-" << inches << '\"'; }Distance add_dist(const Distance&) const; //add

};

//add this distance to d2, return the sum

Distance Distance::add_dist(const Distance& d2) const{

Distance temp; // temporary variable// feet = 0; // ERROR: can’t modify this

// d2.feet = 0; // ERROR: can’t modify d2

temp.inches = inches + d2.inches; // add the inches

if(temp.inches >= 12.0) // if total exceeds 12.0,

{ temp.inches -= 12.0; // then decrease inches by 12.0temp.feet = 1; // and increase feet

} // by 1

temp.feet += feet + d2.feet; // add the feet

return temp;

} 59





int main()


Distance dist2(11, 6.25); // define, initialize dist2


dist3 = dist1.add_dist(dist2); // dist3 = dist1 + dist2

//display all lengths




cout << endl;return 0;

}

60

const Member Function Arguments



const Member Function Arguments

if an argument is passed to an ordinary function by

reference, and you don’t want the function to modify it,the argument should be made const in the function

declaration (and definition). This is true of member

functions as well.Distance Distance::add_dist(const Distance& d2) const{

In above line, argument to add_dist() is passed by

reference, and we want to make sure that won’t modify

this variable, which is dist2 in main(). Therefore we make

the argument d2 to add_dist() const in both declaration

and definition.

61

const Objects



const Objects

In several example programs, we’ve seen that we can

apply const to variables of basic types such as int to keepthem from being modified.

In a similar way, we can apply const to objects of classes.

When an object is declared as const, you can’t modify it.

It follows that you can use only const member functions

with it, because they’re the only ones that guarantee not

to modify it. e.g. A football field (for American-style

football) is exactly 300 feet long. If we were to use thelength of a football field in a program, it would make

sense to make it const, because changing it would

represent the end of the world for football fans.62

const Objects (1/2)



const Objects (1/2)

// constObj.cpp constant Distance objects


class Distance // English Distance class

{

private:

int feet;float inches;

public: // 2-arg constructor


{ }

void getdist() // user input; non-const func{

cout << "\nEnter feet:" ; cin >> feet;

cout << "Enter inches:" ; cin >> inches;

}

63

const Objects (2/2)



const Objects (2/2)

void showdist() const // display distance; const func

{cout << feet << "\'-" << inches << '\"';

}

};

int main(){

const Distance football(300, 0);

// football.getdist(); // ERROR: getdist() not const

cout << "football = " ;

football.showdist(); // OKcout << endl;

return 0;

}

64

Assignment Number 1 Question 1




Create a class called time

that has separate int member data for hours, minutes, andseconds.

One constructor should initialize this data to 0, and another

constructor should initialize it to fixed values.

Make void print() to display time in 23:59:59 format.

Make void setHour( int ) to set hours.

Make void setminute (int ) to set minutes.

Make void setSecond( int ) to set seconds.

Make void setTime( int, int, int ) to set hour, minute, second

Make int getHour(); int getMinute(); int getSecond();

to return hours, minute and seconds respectively.

65





include a tick member function that increments the

time stored in a Time object by one second. An add member function should add two objects of

type time passed as arguments.

Be sure to test the following cases:1. Incrementing into the next minute.

2. Incrementing into the next hour.

3. Incrementing into the next day (i.e., 23:59:59 to 00:00:00).

Make 1000 times loop in a main function. Call tick and printTime

functions in that loop for an object. Also make two objects and

add them to a third object and print their values.

66





Create a class called date

that has separate int member data for year, month, and day. One constructor should initialize this date to 20-02-2010, and

another constructor should initialize it to fixed values given by user.

Make void print() to display date in dd-mm-yyyy format.

Make void setDate( int, int, int ) to set day, month, year perform error checking while setting the values for data members

month, day and year.

Make void nextDay() to increment the day by one.

Be sure to test the following cases:

Incrementing into the next month.

Incrementing into the next year.

in main() test function nextDay in a loop that prints the date during

each iteration to illustrate that nexTDay works correctly.67





Create a class called Rational for performing arithmetic

with fractions. Write a program to test your class. Use integer variables to represent the private data of

the class the numerator and the denominator.

Provide a constructor that enables an object of this classto be initialized when it is declared. The constructor

should contain default values in case no initializers are

provided and should store the fraction in reduced form.

For example, the fraction 2/4 would be stored in theobject as 1 in the numerator and 2 in the denominator.

Provide public member functions that perform each of

the following tasks:68





1. Adding two Rational numbers. The result should be

stored in reduced form.2. Subtracting two Rational numbers. The result should

be stored in reduced form.

3. Multiplying two Rational numbers. The result shouldbe stored in reduced form.

4. Dividing two Rational numbers. The result should be

stored in reduced form.

5. Printing Rational numbers in the form a/b, where a is

the numerator and b is the denominator.

6. Printing Rational numbers in floating-point format.

69





Implement a Circle class. Each object of this class will

represent a circle, storing its radius and the x and y coordinates of its center as floats.

One constructor should initialize it data to 0, and another

constructor should initialize it to fixed values given by user.

Make void setValues(float, float, float) functions to set x,y

and radius.

Make float area() function, and a float circumference()

function to return area and circumference.

Make void print() function to display xy coordinates and

radius of a circle.

Call these functions in main() to display their working.

ch06 objects and classes (1)

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