NAME¶

std::is_swappable_with,std::is_swappable,std::is_nothrow_swappable_with, - std::is_swappable_with,std::is_swappable,std::is_nothrow_swappable_with,

Synopsis¶

Defined in header <type_traits>
template< class T, class U > (1) (since C++17)
struct is_swappable_with;
template< class T > (2) (since C++17)
struct is_swappable;
template< class T, class U > (3) (since C++17)
struct is_nothrow_swappable_with;
template< class T > (4) (since C++17)
struct is_nothrow_swappable;

1) If the expressions swap(std::declval<T>(), std::declval<U>()) and
swap(std::declval<U>(), std::declval<T>()) are both well-formed in unevaluated
context after using std::swap; (see Swappable), provides the member constant value
equal true. Otherwise, value is false.
Access checks are performed as if from a context unrelated to either type.
3) Same as (1), but evaluations of both expressions from (1) are known not to throw
exceptions.

The value of the member constant value
Type trait 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.

Member constants¶

value true if T is swappable with U, false otherwise
[static] (public static member constant)

Member functions¶

operator bool converts the object to bool, returns value
(public member function)
operator() returns value
(C++14) (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¶

swap swaps the values of two objects
(function template)
is_move_assignable
is_trivially_move_assignable
is_nothrow_move_assignable checks if a type has a move assignment operator
(C++11) (class template)
(C++11)
(C++11)
swappable specifies that a type can be swapped or that two types
swappable_with can be swapped with each other
(C++20) (concept)

Category:¶

* Todo no example