std::experimental::ranges::is_swappable_with, std::experimental::ranges::is_swappable, std::experimental::ranges::is_nothrow_swappable_with, std::experimental::ranges::is_nothrow_swappable

< cpp‎ | experimental‎ | ranges
Technical Specification
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tag specifiers
template< class T, class U >
struct is_swappable_with;
(1) (ranges TS)
template< class T >
struct is_swappable;
(2) (ranges TS)
template< class T, class U >
struct is_nothrow_swappable_with;
(3) (ranges TS)
template< class T >
struct is_nothrow_swappable;
(4) (ranges TS)
1) If the expressions ranges::swap(std::declval<T>(), std::declval<U>()) and ranges::swap(std::declval<U>(), std::declval<T>()) are both well-formed when treated as an unevaluated operand, provides the member constant value equal true. Otherwise, value is false. Access checks are performed as if from a context unrelated to either type.
2) If T is not a referenceable type (i.e., possibly cv-qualified void or a function type with a cv-qualifier-seq or a ref-qualifier), provides a member constant value equal to false. Otherwise, provides a member constant value equal to ranges::is_swappable_with<T&, T&>::value.
3) Same as (1), but evaluations of both expressions from (1) are known not to throw exceptions.
4) Same as (2), but uses is_nothrow_swappable_with.

T and U shall each be a complete type, (possibly cv-qualified) void, or an array of unknown bound. Otherwise, the behavior is undefined.


[edit] Helper variable templates

template< class T, class U >
constexpr bool is_swappable_with_v = is_swappable_with<T, U>::value;
(1) (ranges TS)
template< class T >
constexpr bool is_swappable_v = is_swappable<T>::value;
(2) (ranges TS)
template< class T, class U >
constexpr bool is_nothrow_swappable_with_v = is_nothrow_swappable_with<T, U>::value;
(3) (ranges TS)
template< class T >
constexpr bool is_nothrow_swappable_v = is_nothrow_swappable<T>::value;
(4) (ranges TS)

Inherited from std::integral_constant

Member constants

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)
returns value
(public member function)

Member types

Type Definition
value_type bool
type std::integral_constant<bool, value>

[edit] 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 ranges::is_swappable_with<T,U>::value compiles and evaluates to true.

[edit] Example

[edit] See also

specifies that a type can be swapped or that two types can be swapped with each other
(concept) [edit]
checks if objects of a type can be swapped with objects of same or different type
(class template) [edit]