Examples of const objects and const member functions in C++

Examples of const objects and const member functions in C++

const objects can only call const member functions:

#include<iostream> 
using namespace std; 
class A  
{  
public:  
  void fun()const 
  { 
    cout<<"const  A member function !"<<endl; 
    } 
  void fun() 
  { 
    cout<<" non const A member function  !"<<endl; 
  } 
};  
int main() 
{ 
  const A a; 
  a.fun(); 
} 

Output: const member function!

However, if you comment out the first fun, you will make an error: error C2662: "A::fun" : you cannot convert the "this" pointer from "const A" to "A" & ".

However, const member functions can be called by non-const objects:

#include<iostream> 
using namespace std; 
class A  
{  
public:  
  void fun()const 
  { 
    cout<<"const  A member function !"<<endl; 
    }   
 
/* void fun() 
  { 
    cout<<" non const A member function  !"<<endl; 
  } 
  */ 
};  
int main() 
{ 
   A a; 
  a.fun(); 
} 

Output: const member function!

Of course, non-const objects can call non-const member functions.

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