std::remove_cv, std::remove_const, std::remove_volatile - cppreference.com

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# 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, the topmost volatile, or both, if present.

2) removes the topmost const

3) removes the topmost volatile

### [edit] Member types

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

### [edit] 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)

### [edit] Possible implementation

    template< class T >
    struct remove_cv {
        typedef typename std::remove_volatile<typename std::remove_const<T>::type>::type 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; };

### [edit] 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 <iostream>
    #include <type_traits>

    int main() {
        typedef std::remove_cv<const int>::type type1;
        typedef std::remove_cv<volatile int>::type type2;
        typedef std::remove_cv<const volatile int>::type type3;
        typedef std::remove_cv<const volatile int*>::type type4;
        typedef std::remove_cv<int * const volatile>::type type5;

        std::cout << "test1 " << (std::is_same<int, type1>::value
            ? "passed" : "failed") << '\n';
        std::cout << "test2 " << (std::is_same<int, type2>::value
            ? "passed" : "failed") << '\n';
        std::cout << "test3 " << (std::is_same<int, type3>::value
            ? "passed" : "failed") << '\n';
        std::cout << "test4 " << (std::is_same<const volatile int*, type4>::value
            ? "passed" : "failed") << '\n';
        std::cout << "test5 " << (std::is_same<int*, type5>::value
            ? "passed" : "failed") << '\n';
    }

Output:

    test1 passed
    test2 passed
    test3 passed
    test4 passed
    test5 passed

### [edit] See also

is_const (C++11) | checks if a type is const-qualified (class template) [edit]
is_volatile (C++11) | checks if a type is volatile-qualified (class template) [edit]

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