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Sakshi
Sakshi

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Const in CPP

  • Declaration of const data member
    const int x = 10;

  • once you have initialized x you can not reassign its value

  • value can not be changed

  • initialization is not same as assignment
    const int x = 20; //initialization
    x = 20; // assignment

  • example of constant value is pi = 3.14

  • we can initialize const members from both inside and outside of class

  • We can initialize const variable from outside of the class also, like passing value from main as parameter

  • Initializer list is used to define const members from outside of the class

  • How to initialize const data member outside of a class

  • for that you must use initializer list

#include <iostream>

using namespace std;

class A{
    public:
    const int a;
    // A(int b){
    //     a = b;
    // }

      A(int b) : a(b) {}; //initializer list

    void show(){
        cout<<a;
    }

// void changename(){
  //   a = 45;   
    //}
//error: assignment of read-only member ‘A::a’
};

int main()
{
    A obj(5),obj2(6);
    obj2.show();
    obj.show();

    return 0;
}

//output : 65

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