std::is_swappable_with, std::is_swappable, std::is_nothrow_swappable_with, std::is_nothrow_swappable
| Defined in header <type_traits>
|
||
| template< class T, class U > struct is_swappable_with; |
(1) | (since C++17) |
| template< class T > struct is_swappable; |
(2) | (since C++17) |
| template< class T, class U > struct is_nothrow_swappable_with; |
(3) | (since C++17) |
| template< class T > struct is_nothrow_swappable; |
(4) | (since C++17) |
value equal true. Otherwise, value is false.| Type trait | The value of the member constant value
| |
|---|---|---|
T is a referenceable type
|
T is not a referenceable type
| |
| (2) | std::is_swappable_with<T&, T&>::value | false |
| (4) | std::is_nothrow_swappable_with<T&, T&>::value | |
If T or U is not a complete type, (possibly cv-qualified) void, or an array of unknown bound, the behavior is undefined.
If an instantiation of a template above depends, directly or indirectly, on an incomplete type, and that instantiation could yield a different result if that type were hypothetically completed, the behavior is undefined.
If the program adds specializations for any of the templates described on this page, the behavior is undefined.
Helper variable templates
| template< class T, class U > inline constexpr bool is_swappable_with_v = is_swappable_with<T, U>::value; |
(since C++17) | |
| template< class T > inline constexpr bool is_swappable_v = is_swappable<T>::value; |
(since C++17) | |
| template< class T, class U > inline constexpr bool is_nothrow_swappable_with_v = |
(since C++17) | |
| template< class T > inline constexpr bool is_nothrow_swappable_v = |
(since C++17) | |
Inherited from std::integral_constant
Member constants
| value [static] |
true if T is swappable with U, false otherwise (public static member constant) |
Member functions
| operator bool |
converts the object to bool, returns value (public member function) |
| operator() (C++14) |
returns value (public member function) |
Member types
| Type | Definition |
value_type
|
bool |
type
|
std::integral_constant<bool, value> |
Notes
This trait does not check anything outside the immediate context of the swap expressions: if the use of T or U would trigger template specializations, generation of implicitly-defined special member functions etc, and those have errors, the actual swap may not compile even if std::is_swappable_with<T, U>::value compiles and evaluates to true.
Example
| This section is incomplete Reason: no example |
See also
| swaps the values of two objects (function template) | |
| (C++11)(C++11)(C++11) |
checks if a type has a move assignment operator (class template) |
| (C++20) |
specifies that a type can be swapped or that two types can be swapped with each other (concept) |