std::is_move_assignable, std::is_trivially_move_assignable, std::is_nothrow_move_assignable

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is_move_assignableis_trivially_move_assignableis_nothrow_move_assignable
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Defined in header <type_traits>
template< class T >
struct is_move_assignable;
(1) (since C++11)
template< class T >
struct is_trivially_move_assignable;
(2) (since C++11)
template< class T >
struct is_nothrow_move_assignable;
(3) (since C++11)

1) Checks whether a type is MoveAssignable, i.e. has an accessible explicit or implicit move assignment operator. If the requirement is met, a member constant value equal true is provided, otherwise value is false.

2) same as 1), but evaluation of the move-assignment expression will not call any operation that is not trivial.

3) same as 1), but the evaluation of the move-assignment expression will not call any operation that is not noexcept.

Contents

Inherited from std::integral_constant

Member constants

value
[static]
true if T is move-assignable, false otherwise
(public static member constant)

Member functions

operator bool
converts the object to bool, returns value
(public member function)

Member types

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

[edit] Possible implementation

template< class T>
struct is_move_assignable
    : std::is_assignable< typename std::add_lvalue_reference<T>::type,
                          typename std::add_rvalue_reference<T>::type> {};
 
template< class T>
struct is_trivially_move_assignable
    : std::is_trivially_assignable< typename std::add_lvalue_reference<T>::type,
                                    typename std::add_rvalue_reference<T>::type> {};
 
template< class T>
struct is_nothrow_move_assignable
    : std::is_nothrow_assignable< typename std::add_lvalue_reference<T>::type,
                                  typename std::add_rvalue_reference<T>::type> {};

[edit] Example

#include <iostream>
#include <string>
#include <type_traits>
struct Foo { int n; };
int main() {
    std::cout << std::boolalpha
              << "std::string is nothrow move-assignable? "
              << std::is_nothrow_move_assignable<std::string>::value << '\n'
              << "int[2] is move-assignable? "
              << std::is_move_assignable<int[2]>::value << '\n'
              << "Foo is trivally move-assignable? "
              << std::is_trivially_move_assignable<Foo>::value << '\n';
}

Output:

std::string is nothrow move-assignable? true
int[2] is move-assignable? false
Foo is trivially move-assignable? true

[edit] See also

checks if a type has a assignment operator for a specific argument
(class template)
checks if a type has a copy assignment operator
(class template)