Friend function in object oriented programming. operator overloading. unary perator.

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5. Friend Function
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Example
class Sum
{
private:
int a, b;
public:
void get_num()
{
cout<<“Enter any two numbers:n”;
cin>>a>>b;
}
friend int add(); //Friend function
Declaration
};
int add() // Friend function Defination
{
Sum s;
int temp;
s.get_num();
temp=s.a+s.b; // accessing private data
return temp;
}
int main()
{
int result;
result=add();
cout<<“Sum=”<<result<<endl;
}
Output
Enter any two numbers:
7
3
Sum= 10

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Example
class B;
classA
{
private:
int a;
public:
void setdata(int x)
{a=x;}
friend void fun(A,B);
};
class B
{
private:
int b;
public:
void setdata(int y)
{b=y;}
friend void fun(A,B);
};
void fun(A o1,B o2)
{
cout<<“sum is:”<<o1.a+o2.b;
}
void main()
{
A obj1;
B obj2;
obj1.setdata(2);
obj2.setdata(7);
fun(obj1,obj2);
}
Output
Sum is: 9

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Example
class example
{
private:
static int sum; //Static data
int x;
public:
example() //Constructor of the class
{
sum=sum+1;
x=sum;
}
~example() //Destructor of the class
{
sum=sum-1;
}
static void exforsys()
//Static function exforsys( ) defined with keyword
static
{
cout << "nResult is: " << sum;
}
void number() //Normal member
function number( )
{
cout << "nNumber is: " << x;
}
};
int example::sum=0;
void main()
{
example e1;
example::exforsys();
//Static function exforsys() accessed
using class name example and the scope
resolution operator ::
example e2,e3,e4;
example::exforsys();
e1.number();

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//Normal member function accessed using
object e1 and the dot member access
operator.
e2.number();
e3.number();
e4.number();
}
OUTPUT:
Result is:1
Result is:4
Number is:1
Number is:2
Number is:3
Number is:4

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Example
using namespace std;
class Box{
private:
int l,b,h;
public:
void setDimension(int l,int b,int h)
{
this->l=l;
this->b=b;
this->h=h;
}
void showDimension()
{
cout<<"nl="<<l<<" b="<<b<<"
h="<<h;
}
};
int main(){
Box smallBox;
smallBox.setDimension(12,10,5);
smallBox.showDimension();
}
Output
l=12 b=10 h=5

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19. "many-shaped”.
many forms
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Example
#include<iostream>
using namespace std;
class shape{
public:
int height,width;
float area;
shape(){
height=5;width=8;
void area();
};
class triangle:shape{
public:
void area(){
area=2*height;
cout<<area;
};
class rectangle:shape{
public:
void area(){
area=height*width;
cout<<area;}
};
int main(){
triangle a;
rectangle b;
a.area();
b.area();
}

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Syntax:
return type class name :: operator op
(argument list)
{
Body of function
}

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Example
#include <iostream>
using namespace std;
classTest
{
private:
int count;
public:
Test(): count(5)
{ }
void operator ++()
{
count = count+1;
}
void Display()
{
cout<<"Count: "<<count;
}
};
int main()
{
Test t; // this calls "function void operator
++()" function
++t;
t.Display();
return 0;
}

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Example
#include<iostream>
using namespace std;
class num{
private:
int a,b,c,d;
public:
void input(void);
void show(void);
num operator+(num);
};
void num::input(){
cout<<“enter values for a,b,c,d:”;
cin>>a>>b>>c>>d;
}
void num::show(){
cout<<“a”<<a<<“b”<<b<<“c”<<c<<“d”<<d
;
}
num num::operator +(num t){
num tmp;
tmp.a=a+t.a;
tmp.b=b+t.b;
tmp.c=c+t.c;
tmp.d=d+t.d;
return (temp);
}
int main(){
num X,Y,Z;
cout<<“/n object X:”;
X.input();
cout<<“/n objectY:”;

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Y.input();
Z=X+Y;
cout<<“/n X:”;
X.show();
cout<<“/nY:”;
Y.show();
cout<<“/n z:”;
Z.show();
}
Output
Object X
Enter values for a b c d:1 4 2 1
ObjectY
Enter values for a b c d:2 5 4 2
X:a=1 b=4 c=2 d=1
Y:a=2 b=5 c=4 d=2
Z:a=3 b=9 c=6 d=3

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class num{
private:
int a,b,c,d;
public:
void input(void);
void show(void);
friend num operator*(int,num);
};
void num::input(){
cout<<“enter values for a,b,c,d:”;
cin>>a>>b>>c>>d;
}
void num::show(){
cout<<“a”<<a<<“b”<<b<<“c”<<c<<“d”<<d
;
}
num num::operator *(int a,num t){
num tmp;
tmp.a=a*t.a;
tmp.b=b*t.b;
tmp.c=c*t.c;
tmp.d=d*t.d;
return (temp);
}
int main(){
Num X,Z;
cout<<“/n object X:”;
X.input();
Z=3*X;
cout<<“/n X:”;
X.show();
cout<<“/n Z:”;
Z.show();}
Output
Object X
Enter values for a b c d:1 2 2 3
X:a=1 b=2 c=2 d=3
Y:a=3 b=6 c=6 d=9

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32. method overloading "sum()"
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Example
#include<iostream>
#include<conio.h>
class Addition
{
public:
void sum(int a, int b)
{
cout<<a+b;
}
void sum(int a, int b, int c)
{
cout<<a+b+c; }
};
main()
{
Addition obj;
obj.sum(10, 20);
cout<<endl;
obj.sum(10, 20, 30); }
Output
30
60

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Syntax:
class classname{
public :
virtual void
memberfunctionname ( ) //
this denotes the c++virtual
function
{ : }
};

36. Example
class vehicle
//base class of C++ virtual function
{
public:
virtual void make ( ) // C++ virtual
function
{ cout<<" member function of base class
vehicle accessed" <<endl;}
};
class fourwheeler : public vehicle
{
public:
void make ( )
{
cout <<" virtual member function of derived
class fourwheeler accessed"<< endl;}
};
int main ( )
{
vehicle *a, *b;
a = new vehicle ( );
a-> make ( );
b = new fourwheeler ( );
b-> make ( );
return 0;}
Output:
Member function of base class
vehicle accessed
virtual member function of derived
class fourwheeler accessed.
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Example
#include<iostream.h>
#include<conio.h>
class Base {
public:
void show() {
cout<<"Base class"; }
};
class Derived:public Base {
public: void show() {
cout<<"Derived Class"; }
};
int mian() {
Base b;
Derived d;
b.show();
d.show();
}
Output
Base class Derived Class

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