Why we used const function???

We Used Const function why??

#include<iostream>

using namespace std;

class A

     {

           private:

                    int a=5;

           public:

                int func1() const;

     };

int A::func1() const

     {

           cout<<a;

     }

int main()

     {

          A const a;

          a.func1();

     }

Now here i have a small example of const function................

So, why we need const function 

because a const function can't able to modify the class member variable in it. For example we have 

a meter reading class which reads the value of meter in km in its member variable ""M" now we want to display it so we use use a show () const which is only able to read it and display it.

                                   Let's you want to modify a class member variable in const function so you can use mutable keyword ........

GCC Compiler Warning: extended initializer lists only available with c++0x

How do you remove the compilation warning : 

extended initializer lists only available with c++0x  ??

You can remove it by compiling your code with :-

g++ -std=c++0x test.cpp

Declaring a const variable outside the class ??? Why and How

class A

        {

                 const  int    a; 

                 a=5;/////////// error

                 static const int b =6 ; running

         }

now here we can see that const int  may causes error in some compiler because

const variable specifies whether a variable is modifiable or not. But  initializing anywhere other than constructor causes default initialization followed by assignment...

so a is a const and you can't assign value to it....
Now question is that how can you define a const variable outside the class:::
                            here you can do that
                                              A():a(5)
                                                {
                           
                                                 }
whenever constructor is called value of a is initialized by 5

Initilization and assignment

                                    Difference between initialization and assignment

                                            

*Initialization is about creating a object but assignment is about set some value to object.

 for example:

                      int x=5; ///////initialization

                          x=6; assignment

Signature vs Return Type

hey...............
Why we can't have different signature with different return type ?
look ...........
class A
       {
              public:
                    int name1 (int , int);
                    float name1(int, int, int);
                    char name1(int , int);
        }
int main()
   {
            cout<<"Coming to calll ";  
            int a;
            a = name1(5,6);        //////oops cause compiler error;
    };
int A::name1(int ,int)
   {
                  --------
   }
float A::name1(int ,int, int)
   {
                  --------
   }
char A::name1(int ,int)
   {
                  --------
   }


so we got compilation error when we different signature with different return type but WHY?????????
coz....... compiler unable to find the return type of called function ...........

* and &

                                         Difference Between Pass by Reference and Address

Let's we have two variable

one *p  (::) another   is &p \_

now see the difference 

just kidding.................................................

1. *p can be redirected means it can point to different address  but &p can't be redirected...

2. *p can directly access values using '.' or '->' operator but &p can't do it again man "shit happen with &".

3. *p can be initialized as NULL but f***k &p can't ......

Happy Reading.........................