const_cast in C++

The const_cast operator in C++ is used to add or remove the const qualifier from a variable. This can be useful when you need to pass a const variable to a function that expects a non-const parameter. However, it should be used with caution, as modifying a const variable after casting away its const qualifier results in undefined behavior.

Syntax:

const_cast<new_type>(expression)

Example:

`void func(int* p) { *p = 10; }

int main() { const int a = 5; func(const_cast<int*>(&a)); // Undefined behavior if func modifies a return 0; }`

const Values

A const value is a variable whose value cannot be changed after initialization. This is useful for defining constants and ensuring that certain variables remain immutable throughout the program.

Example:

const int x = 10;
x = 20; // Error: assignment of read-only variable 'x'

const Pointers

There are several variations of const pointers, each with different meanings:

1. Pointer to const Data:
   • The data pointed to by the pointer is const and cannot be modified through the pointer.
   • The pointer itself can be changed to point to another address.

Syntax:

const int* ptr;

Example:

   int a = 10;
   int b = 20;
   const int* ptr = &a;
   *ptr = 30; // Error: cannot modify const int
   ptr = &b;  // Allowed: pointer can point to another address

1. const Pointer to Data:
   • The pointer itself is const and cannot be changed to point to another address.
   • The data pointed to by the pointer can be modified.