Object-Oriented Programming
Object-Oriented Programming (COM357)
Lab Week 7
Exercise 1: Array of Objects
//In week 6, you learnt how to define a class, methods and create objects. In this
exercise you will learn how to create an array of objects. It is just like any other
array you learnt to use in the previous weeks. //
class person
{
char name;
int account;
float balance;
public:
void getdata(void);
//define the method outside the class definition
void display(void);
//define the method outside the class definition
};
void person::getdata(void)
{
cout << "Enter name: ";
cin >> name;
cout << "Enter account no: ";
cin >> account;
cout << "Enter balance amount: ";
cin >> balance;
}
void person::display(void)
{
cout << "\nName: " << name;
cout << "\nAccount: " << account;
cout << "\nBalance: " << balance;
}
void main()
{
…………; //create an array of 3 objects of type person
for(int i=0;i<3;i++)
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Object-Oriented Programming
{
cout << "\nGet details of person " << (i+1) << ": \n";
……..; //call the member method getdata() here
}
cout<<"\n";
for(int i=0;i<3;i++)
{
cout << "\nDetails of person " << (i+1) << ": \n";
……..; //call the member method display()
}
cout<<"\n";
getche();
}
Exercise 2: Constructors
This exercise will give you the basic concepts of constructor. A constructor has
the name same as the class, constructor has no type and constructor can have
parameter.
class solution
{
int a; int b; int c;
public:
void indata(void) //inside declaration
{
cout << "Enter a: ";
cin >> a;
cout << "Enter b: ";
cin >> b;
cout << "Enter c: ";
cin >> c;
}
//Define a constructor for the method above
void outdata(void)
{cout<<a<<b<<c<<endl;}
};
void main()
{
solution x;
x.indata();
//create an object and initialize the constructor by replacing the two lines
//above
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Object-Oriented Programming
x.outdata();
getche();
}
Exercise 3: Friend Functions
Friend function has been discussed in week 6. Please read the section of lecture
once again. A friend function is not a member method of a class but have access
to the data. It is declared in a class and can be defined anywhere in the program
like any function. It can only access data via an object.
Write a friend function mean() which will have access to the data items of the class. The
method mean() should display the mean of the data values a and b in the class.
class sample
{
float a;
float b;
public:
void input()
{
a=25.00;
b=40.00;
}
friend float mean(sample s);
};
float mean(sample s)
{
……………………// Define the function here
}
void main()
{
//write main program here….
//See the example in exercise 5….
//Create object……….
//Call methods………..
}
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Object-Oriented Programming
Exercises 4-5 are for super-mouse team
Exercise 4: Friend Functions with quadratic equation
A complex number consists of two parts – real part and an imaginary part written
as x  jy , where x and y are real values. j is imaginary quantity defined as
j  1 .
/* Friend functions*/
class complex //a+jb
{
float a;
float b;
public:
void input(float x, float y)
{
a=x;
b=y;
}
friend complex sum(complex, complex);
void display(complex);
};
complex sum(complex c1, complex c2)
{
complex c3;
c3.a=c1.a+c2.a;
c3.b=c1.b+c2.b;
return (c3);
}
void complex::display(complex c)
{
if(c.b>0)
cout << c.a << "+j" << c.b <<"\n";
else
cout << c.a << "-j" << c.b <<"\n";
//There will be a problem here when you run the program. Find it and correct
it!
}
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Object-Oriented Programming
void main()
{
complex A,B,C;
//object of type complex
A.input(3.0,5.5);
…………………
//Enter the values of B
C=sum(A,B);
// See how it is called
//Calculate the sum of the complex no
cout << "\n A = "; A.display(A);
cout << "\n B = "; B.display(B);
…………………………………..
//Display the complex number C
cout<<"\n";
getche();
}
Exercise 5: This is an extension of the exercise from last week.
Two roots of the quadratic equation ax 2  bx  c  0 is calculated by using the
formula:
 b  b 2  4ac
2a
Where a, b and c are real values. The term (b 2  4ac) is called discriminant.
There can be three different situations for the discriminant such
as (b 2  4ac)  0 , (b 2  4ac)  0 and (b 2  4ac)  0 . If (b 2  4ac)  0 , we get
x
an imaginary number for the term b 2  4ac , thus leading to a complex
solution. A complex number consists of two parts – real part and an imaginary
part, written as x  jy , where x and y are real values. j is defined as j   1 .
For the discriminant (b 2  4ac)  0 , the imaginary part is derived as follows
b 2  4ac =
p =
 1. p = jy .
Define a class for the complex number. Define a function (with parameters and
return value) for calculation of the discriminant. Write further functions (with
parameters/no parameters and return value/no return value) for the solutions of
the quadratic equation for (b 2  4ac)  0 , (b 2  4ac)  0 and (b 2  4ac)  0 .
Test the program for given values of a, b, c as follows.
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Object-Oriented Programming
1 2 3 for (b 2  4ac)  0
1 2 1 for (b 2  4ac)  0
1 3 2 for (b 2  4ac)  0
Depending on the value of the discriminant, it will call different functions
described below:
If the discriminant (b 2  4ac)  0 , it will display two complex solutions in the
following form:
----------------------------------------------------Discriminant (b^2 – 4*a*c) = ?
Quadratic equation has two complex solutions
X1= (-b+ j [sqrt(b^2 – 4*a* c)]/2*a =
X2= (-b- j [sqrt(b^2 – 4*a* c)]/2*a =
----------------------------------------------------If the discriminant (b 2  4ac)  0 , it will display two identical solutions in the
following form:
-------------------------------------------------Discriminant (b^2 – 4*a*c) = 0
The two real solutions are:
X1= (-b+sqrt(b^2 – 4*a* c)/2*a =
X2= (-b-sqrt(b^2 – 4*a* c)/2*a =
-------------------------------------------------If the discriminant (b 2  4ac)  0 , it will display two real solutions in the
following form:
-------------------------------------------------Discriminant (b^2 – 4*a*c) = ?
The two real solutions are:
X1= (-b+sqrt(b^2 – 4*a* c)/2*a =
X2= (-b-sqrt(b^2 – 4*a* c)/2*a =
-------------------------------------------------Do the exercises 1-3, compile the programs and run it. Show any two
programs to the demonstrator and get signed in. Exercises 4-5 are for
super-mouse team. You can choose exercises 1-3 or exercises 4-5. You will
need the programs for the lab submission in week 11.
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