Defined in header <type_traits> | ||
---|---|---|
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 typename std::add_volatile<typename std::add_const<T>::type>::type type; }; template< class T> struct add_const { typedef const T type; }; template< class T> struct add_volatile { typedef volatile T type; }; |
Example
#include <iostream> #include <type_traits> struct foo { void m() { std::cout << "Non-cv\n"; } void m() const { std::cout << "Const\n"; } }; template <class T> void call_m() { T().m(); } int main() { call_m<foo>(); call_m<std::add_const<foo>::type>(); }
Output:
Non-cv Const
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) |
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