std:: is_swappable_with, std:: is_swappable, std:: is_nothrow_swappable_with, std:: is_nothrow_swappable

is_constructible is_trivially_constructible is_nothrow_constructible (C++11) (C++11) (C++11)
is_default_constructible is_trivially_default_constructible is_nothrow_default_constructible (C++11) (C++11) (C++11)
is_copy_constructible is_trivially_copy_constructible is_nothrow_copy_constructible (C++11) (C++11) (C++11)
is_move_constructible is_trivially_move_constructible is_nothrow_move_constructible (C++11) (C++11) (C++11)
is_assignable is_trivially_assignable is_nothrow_assignable (C++11) (C++11) (C++11)

is_copy_assignable is_trivially_copy_assignable is_nothrow_copy_assignable (C++11) (C++11) (C++11)
is_move_assignable is_trivially_move_assignable is_nothrow_move_assignable (C++11) (C++11) (C++11)
is_destructible is_trivially_destructible is_nothrow_destructible (C++11) (C++11) (C++11)
has_virtual_destructor (C++11)
is_swappable_with is_swappable is_nothrow_swappable_with is_nothrow_swappable (C++17) (C++17) (C++17) (C++17)

Relationships and property queries

is_same (C++11)
is_convertible is_nothrow_convertible (C++11) (C++20)
is_layout_compatible (C++20)
is_pointer_interconvertible_base_of (C++20)
is_pointer_interconvertible_with_class (C++20)
is_corresponding_member (C++20)
reference_constructs_from_temporary (C++23)
reference_converts_from_temporary (C++23)

is_base_of (C++11)
is_virtual_base_of (C++26)
alignment_of (C++11)
rank (C++11)
extent (C++11)
is_invocable is_invocable_r is_nothrow_invocable is_nothrow_invocable_r (C++17) (C++17) (C++17) (C++17)

Type modifications

remove_cv remove_const remove_volatile (C++11) (C++11) (C++11)
add_cv add_const add_volatile (C++11) (C++11) (C++11)
make_signed (C++11)
make_unsigned (C++11)

remove_reference (C++11)
add_lvalue_reference add_rvalue_reference (C++11) (C++11)
remove_pointer (C++11)
add_pointer (C++11)
remove_extent (C++11)
remove_all_extents (C++11)

Type transformations

aligned_storage (C++11) (deprecated in C++23)
aligned_union (C++11) (deprecated in C++23)
decay (C++11)
remove_cvref (C++20)
enable_if (C++11)
void_t (C++17)

conditional (C++11)
common_type (C++11)
common_reference (C++20)
underlying_type (C++11)
result_of invoke_result (C++11) ( until C++20* ) (C++17)
type_identity (C++20)

Compile-time rational arithmetic

Compile-time integer sequences

integer_sequence

(C++14)

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)

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.

Type trait	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	false

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 = is_nothrow_swappable_with < T, U > :: value ;		(since C++17)
template < class T > inline constexpr bool is_nothrow_swappable_v = is_nothrow_swappable < T > :: value ;		(since C++17)

Inherited from std:: integral_constant

Member constants

value

[static]

true if

is swappable with

, 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

Compiler support
Freestanding and hosted
Language
Standard library
Standard library headers
Named requirements
Feature test macros (C++20)
Language support library
Concepts library (C++20)
Metaprogramming library (C++11)
Diagnostics library
General utilities library
Strings library
Containers library
Iterators library
Ranges library (C++20)
Algorithms library
Numerics library
Localizations library
Input/output library
Filesystem library (C++17)
Regular expressions library (C++11)
Concurrency support library (C++11)
Execution support library (C++26)
Technical specifications
Symbols index
External libraries

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