Operator overloading

Operator Overloading
INTRODUCTION
OPERATOR OVERLOADING RESTRICTION
GENERAL RULES FOR OVERLOADING OPERATOR
OVERLOADING UNARY OPERATOR
OVERLOADING BINARY OPERATOR

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


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



 No new operators can be created


Use only existing operators

 No overloading operators for built-in types


Cannot change how two integers are added


General Rules for overloading Operator
 Syntax:

returnType classname::operator op(arguments)
{
body;
}
 Example
void Integer::operator op()
{
Body;
}

Steps
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;
1.


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.

2.

Using non-static member function with no arguments
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


Using non static member function
 Example

class Test
{
…………
public:
void operator op()
{……… }
};


Void main()
{
…….
…….
op obj1; /* Same as
obj1.operator
op()*/
………………..
}

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++;
}
};

void main()
{
clrscr();
increment in1(20,30);
in1.display();
++in1;
in1.display();
increment in2(1,2);


in2.display();
in2.operator ++();
in2.display();
getch();
}

OUTPUT


Using Friend Function
 Example

class Test
{
…………
public:
friend void operator
op(Test);
};


Void main()
{
…….
…….
op obj1; /* Same as
operator op(obj1)*/
………………..
}

Sample Program
#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;
}
++(increment&);
};

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();
}

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.

2.

Using non-static member function with single argument.
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.


Using non static member function
 Example

class Test
{
…………
public:
void operator op(Test)
{……… }
};


Void main()
{
…….
…….
obj1 op obj2; /* Same as
obj1.operator op(obj2)*/
………………..
}

Sample Program
#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);
};

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();
}

Using Friend Function
 Example

class Test
{
…………
public:
op(Test, Test);
};


Void main()
{
…….
…….
obj1 op obj2; /* Same as
operator op(obj1, obj2)*/
………………..
}

Sample Program
#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;
}
+(add&,add&);
};

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();
}

Operator overloading

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