std::remove_cv, std::remove_const, std::remove_volatile - cppreference.com (original) (raw)
| 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.
Removes the topmost const, or the topmost volatile, or both, if present.
Removes the topmost const.
Removes the topmost volatile.
If the program adds specializations for any of the templates described on this page, the behavior is undefined.
[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 struct remove_cv { typedef T type; }; template struct remove_cv { typedef T type; }; template struct remove_cv { typedef T type; }; template struct remove_cv { typedef T type; }; template struct remove_const { typedef T type; }; template struct remove_const { typedef T type; }; template struct remove_volatile { typedef T type; }; template struct remove_volatile { 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 template<typename U, typename V> constexpr bool same = std::is_same_v<U, V>; static_assert ( same<std::remove_cv_t, int> && same<std::remove_cv_t, int> && same<std::remove_cv_t, int> && same<std::remove_cv_t, 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() {}