The word polymorphism means having many forms. In simple words, we can define polymorphism as the ability of a message to be displayed in more than one form.
Real life example of polymorphism, a person at a same time can have different characteristic. Like a man at a same time is a father, a husband, a employee. So a same person posses have different behavior in different situations. This is called polymorphism.
Polymorphism is considered as one of the important features of Object Oriented Programming.
In C++ polymorphism is mainly divided into two types:
- Compile time Polymorphism
- Runtime Polymorphism
-
Compile time polymorphism: This type of polymorphism is achieved by function overloading or operator overloading.
-
Function Overloading: When there are multiple functions with same name but different parameters then these functions are said to be overloaded. Functions can be overloaded by change in number of arguments or/and change in type of arguments.
Rules of Function Overloading// C++ program for function overloading
#include <bits/stdc++.h>
using
namespace
std;
class
Geeks
{
public
:
// function with 1 int parameter
void
func(
int
x)
{
cout <<
"value of x is "
<< x << endl;
}
// function with same name but 1 double parameter
void
func(
double
x)
{
cout <<
"value of x is "
<< x << endl;
}
// function with same name and 2 int parameters
void
func(
int
x,
int
y)
{
cout <<
"value of x and y is "
<< x <<
", "
<< y << endl;
}
};
int
main() {
Geeks obj1;
// Which function is called will depend on the parameters passed
// The first 'func' is called
obj1.func(7);
// The second 'func' is called
obj1.func(9.132);
// The third 'func' is called
obj1.func(85,64);
return
0;
}
Output:
value of x is 7 value of x is 9.132 value of x and y is 85, 64
In the above example, a single function named func acts differently in three different situations which is the property of polymorphism.
-
Operator Overloading: C++ also provide option to overload operators. For example, we can make the operator (‘+’) for string class to concatenate two strings. We know that this is the addition operator whose task is to add to operands. So a single operator ‘+’ when placed between integer operands , adds them and when placed between string operands, concatenates them.
Example:// CPP program to illustrate
// Operator Overloading
#include<iostream>
using
namespace
std;
class
Complex {
private
:
int
real, imag;
public
:
Complex(
int
r = 0,
int
i =0) {real = r; imag = i;}
// This is automatically called when '+' is used with
// between two Complex objects
Complex operator + (Complex
const
&obj) {
Complex res;
res.real = real + obj.real;
res.imag = imag + obj.imag;
return
res;
}
void
print() { cout << real <<
" + i"
<< imag << endl; }
};
int
main()
{
Complex c1(10, 5), c2(2, 4);
Complex c3 = c1 + c2;
// An example call to "operator+"
c3.print();
}
Output:
12 + i9
In the above example the operator ‘+’ is overloaded. The operator ‘+’ is an addition operator and can add two numbers(integers or floating point) but here the operator is made to perform addition of two imaginary or complex numbers. To learn operator overloading in details visit this link.
-
Function Overloading: When there are multiple functions with same name but different parameters then these functions are said to be overloaded. Functions can be overloaded by change in number of arguments or/and change in type of arguments.
-
Runtime polymorphism: This type of polymorphism is achieved by Function Overriding.
-
Function overriding on the other hand occurs when a derived class has a definition for one of the member functions of the base class. That base function is said to be overridden.
// C++ program for function overriding
#include <bits/stdc++.h>
using
namespace
std;
class
base
{
public
:
virtual
void
print ()
{ cout<<
"print base class"
<<endl; }
void
show ()
{ cout<<
"show base class"
<<endl; }
};
class
derived:
public
base
{
public
:
void
print ()
//print () is already virtual function in derived class, we could also declared as virtual void print () explicitly
{ cout<<
"print derived class"
<<endl; }
void
show ()
{ cout<<
"show derived class"
<<endl; }
};
//main function
int
main()
{
base *bptr;
derived d;
bptr = &d;
//virtual function, binded at runtime (Runtime polymorphism)
bptr->print();
// Non-virtual function, binded at compile time
bptr->show();
return
0;
}
Output:
print derived class show base class
To learn runtime polymorphism in details visit this link.
-
Function overriding on the other hand occurs when a derived class has a definition for one of the member functions of the base class. That base function is said to be overridden.
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