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

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Type trait constants
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.

#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';


test1 passed
test2 passed
test3 passed
test4 passed
test5 passed

[edit] See also

checks if a type is const-qualified
(class template) [edit]
checks if a type is volatile-qualified
(class template) [edit]