# std::remove_cv, std::remove_const, std::remove_volatile

From cppreference.com
< cpp‎ | types

Defined in header `<type_traits>` |  |
template< class T > struct remove_cv; | (1) | (since C++11)
template< class T > struct remove_const; | (2) | (since C++11)
template< class T > struct remove_volatile; | (3) | (since C++11)

Provides the member typedef `type` which is the same as `T`, except that its topmost cv-qualifiers are removed.

1) Removes the topmost const, or the topmost volatile, or both, if present.
2) Removes the topmost const.
3) Removes the topmost volatile.

The behavior of a program that adds specializations for any of the templates described on this page is undefined.

### Member types

Name | Definition
`type` | the type `T` without cv-qualifier

### Helper types

template< class T > using remove_cv_t = typename remove_cv<T>::type; |  | (since C++14)
template< class T > using remove_const_t = typename remove_const<T>::type; |  | (since C++14)
template< class T > using remove_volatile_t = typename remove_volatile<T>::type; |  | (since C++14)

### Possible implementation

    template<class T> struct remove_cv { typedef T type; };
    template<class T> struct remove_cv<const T> { typedef T type; };
    template<class T> struct remove_cv<volatile T> { typedef T type; };
    template<class T> struct remove_cv<const volatile T> { typedef T type; };

    template<class T> struct remove_const { typedef T type; };
    template<class T> struct remove_const<const T> { typedef T type; };

    template<class T> struct remove_volatile { typedef T type; };
    template<class T> struct remove_volatile<volatile T> { typedef T type; };

### Example

Removing const/volatile from const volatile int* does not modify the type, because the pointer itself is neither const nor volatile.

Run this code

    #include <type_traits>

    template<typename U, typename V>
    constexpr bool same = std::is_same_v<U, V>;

    static_assert
    (
        same<std::remove_cv_t<int>, int> &&
        same<std::remove_cv_t<const int>, int> &&
        same<std::remove_cv_t<volatile int>, int> &&
        same<std::remove_cv_t<const volatile int>, int> &&
        // remove_cv only works on types, not on pointers
        not same<std::remove_cv_t<const volatile int*>, int*> &&
        same<std::remove_cv_t<const volatile int*>, const volatile int*> &&
        same<std::remove_cv_t<const int* volatile>, const int*> &&
        same<std::remove_cv_t<int* const volatile>, int*>
    );

    int main() {}

### See also

is_const (C++11) | checks if a type is const-qualified (class template)
is_volatile (C++11) | checks if a type is volatile-qualified (class template)
add_cv add_const add_volatile (C++11)(C++11)(C++11) | adds const and/or volatile specifiers to the given type (class template)
remove_cvref (C++20) | combines std::remove_cv and std::remove_reference (class template)

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/types/remove_cv&oldid=155271"