Пространства имён
Варианты
Действия

std::is_copy_assignable, std::is_trivially_copy_assignable, std::is_nothrow_copy_assignable

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C++
 
Утилиты библиотеки
 
Поддержка типов
Основные типы
Original:
Basic types
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Основные типы
Исправлены типы целых ширину (C++11)
Числовые пределы
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Numeric limits
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numeric_limits
С числовым ограничивает интерфейс
Время тип информации
Original:
Runtime type information
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Тип черты
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Type traits
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Первичные категории типа
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Primary type categories
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is_void(C++11)
is_array(C++11)
is_pointer(C++11)
is_enum(C++11)
is_union(C++11)
is_class(C++11)
is_function(C++11)
is_object(C++11)
is_scalar(C++11)
is_compound(C++11)
is_integral(C++11)
is_floating_point(C++11)
is_fundamental(C++11)
is_arithmetic(C++11)
is_reference(C++11)
is_lvalue_reference(C++11)
is_rvalue_reference(C++11)
is_member_pointer(C++11)
is_member_object_pointer(C++11)
is_member_function_pointer(C++11)
Тип свойства
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Type properties
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is_const(C++11)
is_volatile(C++11)
is_pod(C++11)
is_empty(C++11)
is_polymorphic(C++11)
is_abstract(C++11)
Поддерживаемые операции
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Supported operations
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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)
Отношения собственности и запросов
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Relationships and property queries
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is_same(C++11)
is_base_of(C++11)
is_convertible(C++11)
alignment_of(C++11)
rank(C++11)
extent(C++11)
Тип модификаций
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Type modifications
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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)
Тип преобразования
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Type transformations
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aligned_storage(C++11)
aligned_union(C++11)
decay(C++11)
enable_if(C++11)
conditional(C++11)
common_type(C++11)
underlying_type(C++11)
result_of(C++11)
Введите черта констант
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Type trait constants
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integral_constant(C++11)
 
Заголовочный файл <type_traits>
template< class T >
struct is_copy_assignable;
 (1) (начиная с C++11)
template< class T >
struct is_trivially_copy_assignable;
 (2) (начиная с C++11)
template< class T >
struct is_nothrow_copy_assignable;
 (3) (начиная с C++11)
1)
Проверяет, является ли тип CopyAssignable, т. е. имеет доступный явного или неявного копирования оператора присваивания. Если требование считается выполненным, член постоянной value равных true обеспечивается, в противном случае value является false.
Original:
Checks whether a type is CopyAssignable, i.e. has an accessible explicit or implicit copy assignment operator. If the requirement is met, a member constant value equal true is provided, otherwise value is false.
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2)
То же, 1), но оценка копирования выражения присваивания не буду называть любой операции, которая не является тривиальной.
Original:
Same as 1), but evaluation of the copy-assignment expression will not call any operation that is not trivial.
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3)
То же, 1), но оценки копирования выражения присваивания не буду называть любые операции, которые не noexcept.
Original:
Same as 1), but the evaluation of the copy-assignment expression will not call any operation that is not noexcept.
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Содержание

Унаследован от std::integral_constant

Member constants

value
[static]
true если T is copy-assignable, false иначе
Original:
true if T is copy-assignable, false otherwise
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(public static константа-член)

Member functions

operator bool
преобразует объект в bool, возвращает value
Original:
converts the object to bool, returns value
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(public функция-член)

Member types

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

[править] Возможная реализация

template< class T>
struct is_copy_assignable
    : std::is_assignable< typename std::add_lvalue_reference<T>::type,
                    const typename std::add_lvalue_reference<T>::type> {};
 
template< class T>
struct is_trivially_copy_assignable
    : std::is_trivially_assignable< typename std::add_lvalue_reference<T>::type,
                              const typename std::add_lvalue_reference<T>::type> {};
 
template< class T>
struct is_nothrow_copy_assignable
    : std::is_nothrow_assignable< typename std::add_lvalue_reference<T>::type,
                            const typename std::add_lvalue_reference<T>::type> {};

[править] Пример

#include <iostream>
#include <utility>
#include <type_traits>
struct Foo { int n; };
int main() {
    std::cout << std::boolalpha
              << "Foo is trivally copy-assignable? "
              << std::is_trivially_copy_assignable<Foo>::value << '\n'
              << "int[2] is copy-assignable? "
              << std::is_copy_assignable<int[2]>::value << '\n'
              << "int is nothrow copy-assignable? "
              << std::is_nothrow_copy_assignable<int>::value << '\n';
}

Вывод: 

Foo is trivally copy-assignable? true
int[2] is copy-assignable? false
int is nothrow copy-assignable? true

[править] См. также

(C++11)
(C++11)
(C++11)
проверяет, является ли тип имеет оператор присваивания для конкретного аргумента
Original:
checks if a type has a assignment operator for a specific argument
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(шаблон класса) [edit]
(C++11)
(C++11)
(C++11)
проверяет, является ли тип имеет оператор ход назначения
Original:
checks if a type has a move assignment operator
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(шаблон класса) [edit]
Источник — «http://ru.cppreference.com/mwiki/index.php?title=cpp/types/is_copy_assignable&oldid=31408»