std::add_cv, std::add_const, std::add_volatile
Defined in header <type_traits>
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||
template< class T > struct add_cv; |
(1) | (since C++11) |
template< class T > struct add_const; |
(2) | (since C++11) |
template< class T > struct add_volatile; |
(3) | (since C++11) |
Provides the member typedef type
which is the same as T
, except it has a cv-qualifier added (unless T
is a function, a reference, or already has this cv-qualifier)
1) adds both const and volatile
2) adds const
3) adds volatile
Member types
Name | Definition |
type
|
the type T with the cv-qualifier
|
Helper types
template< class T > using add_cv_t = typename add_cv<T>::type; |
(since C++14) | |
template< class T > using add_const_t = typename add_const<T>::type; |
(since C++14) | |
template< class T > using add_volatile_t = typename add_volatile<T>::type; |
(since C++14) | |
Possible implementation
template< class T > struct add_cv { typedef const volatile T type; }; template< class T> struct add_const { typedef const T type; }; template< class T> struct add_volatile { typedef volatile T type; }; |
Example
Run this code
#include <iostream> #include <type_traits> struct foo { void m() { std::cout << "Non-cv\n"; } void m() const { std::cout << "Const\n"; } void m() volatile { std::cout << "Volatile\n"; } void m() const volatile { std::cout << "Const-volatile\n"; } }; int main() { foo{}.m(); std::add_const<foo>::type{}.m(); std::add_volatile<foo>::type{}.m(); std::add_cv<foo>::type{}.m(); }
Output:
Non-cv Const Volatile Const-volatile
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) |
removes const or/and volatile specifiers from the given type (class template) |
(C++17) |
obtains a reference to const to its argument (function template) |