| 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.
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 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; }; |
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';
}Output:
test1 passed test2 passed test3 passed test4 passed test5 passed
See also
| (C++11) | checks if a type is const-qualified (class template) |
| (C++11) | checks if a type is volatile-qualified (class template) |
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