C++ Tutorial
C++ Overloading (Operator and Function)
C++ allows
you to specify more than one definition for a function name or an operator in the same scope, which is called function overloading and operator
overloading respectively.
An
overloaded declaration is a declaration that had been declared with the same
name as a previously declared declaration in the same scope, except that both
declarations have different arguments and obviously different definition
(implementation).
When you
call an overloaded function or operator,
the compiler determines the most appropriate definition to use by comparing the
argument types you used to call the function or operator with the parameter
types specified in the definitions. The process of selecting the most
appropriate overloaded function or operator is called overload resolution.
Function overloading in
C++:
You can
have multiple definitions for the same function name in the same scope. The definition
of the function must differ from each other by the types and/or the number of
arguments in the argument list. You can not overload function declarations that
differ only by return type.
Following
is the example where same function print() is being used to print different data
types:
#include <iostream>
using namespace std;
class printData
{
public:
void print(int i) {
cout << "Printing int: " << i << endl;
}
void print(double f) {
cout << "Printing float: " << f << endl;
}
void print(char* c) {
cout << "Printing character: " << c << endl;
}
};
int main(void)
{
printData pd;
// Call print to print integer
pd.print(5);
// Call print to print float
pd.print(500.263);
// Call print to print character
pd.print("Hello C++");
return 0;
}
When the
above code is compiled and executed, it produces the following result:
Printing int: 5
Printing float: 500.263
Printing character: Hello C++
Operators overloading
in C++:
You can
redefine or overload most of the built-in operators available in C++. Thus a
programmer can use operators with user-defined types as well.
Overloaded
operators are functions with special names the keyword operator followed by the
symbol for the operator being defined. Like any other function, an overloaded
operator has a return type and a parameter list.
Box operator+(const Box&);
declares
the addition operator that can be used to add two Box objects and returns final Box
object. Most overloaded operators may be defined as ordinary non-member
functions or as class member functions. In case we define above function as
non-member function of a class then we would have to pass two arguments for
each operand as follows:
Box operator+(const Box&, const Box&);
Following
is the example to show the concept of operator over loading using a member
function. Here an object is passed as an argument whose properties will be
accessed using this object, the object which will call this operator can be
accessed using this operator as explained below:
#include <iostream>
using namespace std;
class Box
{
public:
double getVolume(void)
{
return length * breadth * height;
}
void setLength( double len )
{
length = len;
}
void setBreadth( double bre )
{
breadth = bre;
}
void setHeight( double hei )
{
height = hei;
}
// Overload + operator to add two Box objects.
Box operator+(const Box& b)
{
Box box;
box.length = this->length + b.length;
box.breadth = this->breadth + b.breadth;
box.height = this->height + b.height;
return box;
}
private:
double length; // Length of a box
double breadth; // Breadth of a box
double height; // Height of a box
};
// Main function for the program
int main( )
{
Box Box1; // Declare Box1 of type Box
Box Box2; // Declare Box2 of type Box
Box Box3; // Declare Box3 of type Box
double volume = 0.0; // Store the volume of a box here
// box 1 specification
Box1.setLength(6.0);
Box1.setBreadth(7.0);
Box1.setHeight(5.0);
// box 2 specification
Box2.setLength(12.0);
Box2.setBreadth(13.0);
Box2.setHeight(10.0);
// volume of box 1
volume = Box1.getVolume();
cout << "Volume of Box1 : " << volume <<endl;
// volume of box 2
volume = Box2.getVolume();
cout << "Volume of Box2 : " << volume <<endl;
// Add two object as follows:
Box3 = Box1 + Box2;
// volume of box 3
volume = Box3.getVolume();
cout << "Volume of Box3 : " << volume <<endl;
return 0;
}
When the
above code is compiled and executed, it produces the following result:
Volume of Box1 : 210
Volume of Box2 : 1560
Volume of Box3 : 5400
Overloadable/Non-overloadableOperators:
Following
is the list of operators which can be overloaded:
|
+
|
-
|
*
|
/
|
%
|
^
|
|
&
|
|
|
~
|
!
|
,
|
=
|
|
<
|
>
|
<=
|
>=
|
++
|
--
|
|
<<
|
>>
|
==
|
!=
|
&&
|
||
|
|
+=
|
-=
|
/=
|
%=
|
^=
|
&=
|
|
|=
|
*=
|
<<=
|
>>=
|
[]
|
()
|
|
->
|
->*
|
new
|
new []
|
delete
|
delete []
|
Following
is the list of operators, which can not be overloaded:
|
::
|
.*
|
.
|
?:
|
Operator Overloading
Examples:
Here are
various operator overloading examples to help you in understanding the concept.
|
S.N.
|
Operators
and Example
|
|
1
|
Unary
operators overloading
|
|
2
|
Binary
operators overloading
|
|
3
|
Relational
operators overloading
|
|
4
|
Input/Output
operators overloading
|
|
5
|
++ and
-- operators overloading
|
|
6
|
Assignment
operators overloading
|
|
7
|
Function
call () operator overloading
|
|
8
|
Subscripting
[] operator overloading
|
|
9
|
Class
member access operator -> overloading
|
