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;
}
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When the above code is
compiled and executed, it produces following result:
Printing int: 5
Printing float: 500.263
Printing character: Hello C++
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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&);
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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&);
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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;
}
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When the above code is
compiled and executed, it produces following result:
Volume of Box1 : 210
Volume of Box2 : 1560
Volume of Box3 : 5400
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Overloadable/Non-overloadableOperators:
Following is the list of
operators which can be overloaded:
+
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-
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*
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/
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%
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^
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&
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|
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~
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!
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,
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=
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<
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>
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<=
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>=
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++
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--
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<<
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>>
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==
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!=
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&&
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||
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+=
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-=
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/=
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%=
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^=
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&=
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|=
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*=
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<<=
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>>=
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[]
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()
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->
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->*
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new
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new []
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delete
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delete []
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Following is the list of
operators which can not be overloaded:
::
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.*
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.
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?:
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Operator Overloading
Examples:
Here are various operator
overloading examples to help you in understanding the concept.
S.N.
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Operators and Example
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1
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2
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3
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4
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5
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6
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7
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8
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9
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