std::add_cv in C++ with Examples

The std::add_cv template of C++ STL is present in the <type_traits> header file. The std::add_cv template of C++ STL is used to get the type T with const and volatile qualification. The function std::is_same::value is used to check whether T is a const and volatile qualification or not.

Header File:

#include<type_traits>

Template Class:

template< class T >
struct add_cv

Syntax:

std::add_const::type

Parameter: The template std::add_cv accepts a single parameter T(Trait class) to check whether T is const and volatile qualified or not.

Below is the program to demonstrate std::add_cv in C++:

Program:

// C++ program to illustrate
// std::add_cv
#include <bits/stdc++.h>
#include <type_traits>
using namespace std;

// Driver Code
int main()
{

    // Declare variables of int, const,
    // volatile, const volatile using add_cv
    typedef add_cv<int>::type A;
    typedef add_cv<const int>::type B;
    typedef add_cv<volatile int>::type C;
    typedef add_cv<const volatile int>::type D;

    cout << boolalpha;

    // Check the type of variable declared
    // above is volatile or not

    cout << "A: "
         << is_volatile<A>::value
         << endl;

    cout << "B: "
         << is_volatile<B>::value
         << endl;

    cout << "C: "
         << is_volatile<C>::value
         << endl;

    cout
        << "D: "
        << is_volatile<D>::value
        << endl;

    return 0;
}

Output:

typedefs of const volatile int:
A: true
B: true
C: true
D: true

Reference: http://www.cplusplus.com/reference/type_traits/add_cv/