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

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remove_cv remove_const remove_volatile
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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 .

If the program adds specializations for any of the templates described on this page, the behavior 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

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