Post on 06-May-2015
I N T R O D U C T I O N
O P E R A T O R O V E R L O A D I N G R E S T R I C T I O N
G E N E R A L R U L E S F O R O V E R L O A D I N G O P E R A T O R
O V E R L O A D I N G U N A R Y O P E R A T O R
O V E R L O A D I N G B I N A R Y O P E R A T O R
Operator Overloading
Compiled By: Kamal Acharya
Introduction
It gives additional meaning to the C++ operator when applied to the user defined data types.
We can create our own language by using the concept of operator overloading appropriately.
It require great care when misused program became very difficult to understand
Compiled By: Kamal Acharya
Operator Overloading Restriction
Following C++ Operator can’t be overloaded
Class member access operators(. & .*)
Scope Resolution Operator(::)
Sizeof Operator(sizeof())
Conditional Operator(? :)
Precedence of an operator cannot be changed
Associativity of an operator cannot be changed
Arity (number of operands) cannot be changed
Unary operators remain unary, and binary operators remain binary
Operators &, *, + and - each have unary and binary versions
Unary and binary versions can be overloaded separately
Compiled By: Kamal Acharya
No new operators can be created Use only existing operators
No overloading operators for built-in types Cannot change how two integers are added
Compiled By: Kamal Acharya
General Rules for overloading Operator
Syntax:
returnType classname::operator op(arguments)
{
body;
}
Example
void Integer::operator op()
{
Body;
}
Compiled By: Kamal Acharya
Steps
1. Create a class that is to be used
2. Declare the operator function in the public part of the class. It may be either member function or friend function.
3. Define operator function to implement the operation required
4. Overloaded can be invoked using the syntax such as:
op x;
Compiled By: Kamal Acharya
Overloading Unary Operator
Unary operator are those operator which works only on the single operand. Eg. ++, --, - etc
Unary operator acts on only one operand and can be overloaded in two ways:
1. Using non-static member function with no arguments
2. Using friend function with one argument where the argument must be either an object of the class or an reference to an object of the class
Compiled By: Kamal Acharya
Using non static member function
Example
class Test
{
…………
public:
void operator op()
{……… }
};
Void main()
{
…….
…….
op obj1; /* Same as obj1.operator op()*/
………………..
}
Compiled By: Kamal Acharya
Sample Program
#include<iostream.h>
#include<conio.h>
class increment
{
int m,n;
public:
increment(int x, int y)
{
m=x;
n=y;
}
void display()
{
cout<<"m= "<<m<<
"n="<<n<<endl;
}
void operator ++()
{
m++;n++;
}
};
Compiled By: Kamal Acharya
void main()
{
clrscr();
increment in1(20,30);
in1.display();
++in1;
in1.display();
increment in2(1,2);
in2.display();
in2.operator ++();
in2.display();
getch();
}
Compiled By: Kamal Acharya
OUTPUT
Compiled By: Kamal Acharya
Using Friend Function
Example
class Test
{
…………
public:
friend void operator op(Test);
};
Void main()
{
…….
…….
op obj1; /* Same as operator op(obj1)*/
………………..
}
Compiled By: Kamal Acharya
Sample Program
#include<iostream.h>
#include<conio.h>
class increment
{
int m,n;
public:
increment(int x, int y)
{
m=x; n=y;
}
void display()
{
cout<<"m= "<<m<<
"n="<<n<<endl;
}
friend void operator ++(increment&);
};
Compiled By: Kamal Acharya
void operator ++(increment& x)
{
++x.m;
++x.n;
}
void main()
{
clrscr();
increment in1(20,30);
in1.display();
++in1;
in1.display();
increment in2(1,2);
in2.display();
operator ++(in2);
in2.display();
getch();
}
Compiled By: Kamal Acharya
OUTPUT
Compiled By: Kamal Acharya
Overloading Binary Operator
Binary operator are those operator which works on two operands. Eg. +, -,*,/ etc
Binary operator acts on two operands and can be overloaded in two ways:
1. Using non-static member function with single argument.
2. Using friend function with two arguments where the arguments must be either an object of the class or an reference to an object of the class.
Compiled By: Kamal Acharya
Using non static member function
Example
class Test
{
…………
public:
void operator op(Test)
{……… }
};
Void main()
{
…….
…….
obj1 op obj2; /* Same as obj1.operator op(obj2)*/
………………..
}
Compiled By: Kamal Acharya
Sample Program
#include<iostream.h>
#include<conio.h>
class add
{
int m,n;
public:
add(int x, int y)
{
m=x; n=y;
}
void display()
{
cout<<"m= "<<m<<" n="<<n<<endl;
}
void operator +(add);
};
Compiled By: Kamal Acharya
void add::operator +(add x)
{
m=m+x.m;
n=n+x.n;
}
void main()
{
clrscr();
add obj1(20,30),obj2(2,3);
obj1.display();
obj2.display();
obj1+obj2;
obj1.display();
getch();
}
Compiled By: Kamal Acharya
Compiled By: Kamal Acharya
Using Friend Function
Example
class Test
{
…………
public:
friend void operator op(Test, Test);
};
Void main()
{
…….
…….
obj1 op obj2; /* Same as operator op(obj1, obj2)*/
………………..
}
Compiled By: Kamal Acharya
Sample Program
#include<iostream.h>
#include<conio.h>
class add
{
int m,n;
public:
add(int x, int y)
{
m=x; n=y;
}
void display()
{
cout<<"m= "<<m<<" n="<<n<<endl;
}
friend void operator +(add&,add&);
};
Compiled By: Kamal Acharya
void operator +(add& x, add& y)
{
x.m=x.m+y.m;
x.n=x.n+y.n;
}
void main()
{
clrscr();
add obj1(20,30),obj2(2,3);
obj1.display();
obj2.display();
obj1+obj2;
obj1.display();
getch();
}
Compiled By: Kamal Acharya
Compiled By: Kamal Acharya