std::is_move_constructible, std::is_trivially_move_constructible, std::is_nothrow_move_constructible
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Elemento definito nell'header <type_traits>
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template< class T > struct is_move_constructible; |
(1) | (dal C++11) |
template< class T > struct is_trivially_move_constructible; |
(2) | (dal C++11) |
template< class T > struct is_nothrow_move_constructible; |
(3) | (dal C++11) |
Verifica se un tipo è
2) MoveConstructible
, cioè ha un costruttore accessibile mossa esplicita o implicita. Se la condizione è soddisfatta, un membro costante value
true parità è previsto, in caso contrario è value
false.Original:
Checks whether a type is
MoveConstructible
, i.e. has an accessible explicit or implicit move constructor. If the requirement is met, a member constant value
equal true is provided, otherwise value
is false.The text has been machine-translated via Google Translate.
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You can help to correct and verify the translation. Click here for instructions.
Uguale a 1), ma l'espressione di costruzione mossa non richiede qualsiasi operazione che non è banale.
3) Original:
Same as 1), but the move constructor expression does not call any operation that is not trivial.
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Uguale a 1), ma l'espressione di costruzione mossa viene noexcept.
Original:
Same as 1), but the move constructor expression is noexcept.
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Indice |
Inherited from std::integral_constant
Member constants
value [statico] |
true se T is move-constructible , false altrimenti Original: true if T is move-constructible , false otherwise The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (pubblico membro statico costante) |
Member functions
operator bool |
converte l'oggetto in bool, restituisce value Original: converts the object to bool, returns value The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (metodo pubblico) |
Member types
Tipo
Original: Type The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
Definition |
value_type
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bool
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type
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std::integral_constant<bool, value> |
[modifica] Note
Spostare i costruttori di solito sono noexcept, in quanto altrimenti sono inutilizzabili in qualsiasi codice che fornisce garanzia forte eccezione.
Original:
Move constructors are usually noexcept, since otherwise they are unusable in any code that provides strong exception guarantee.
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[modifica] Possibile implementazione
template<class T> struct is_move_constructible : std::is_constructible<T, typename std::add_rvalue_reference<T>::type> {}; template<class T> struct is_trivially_move_constructible : std::is_trivially_constructible<T, typename std::add_rvalue_reference<T>::type> {}; template<class T> struct is_nothrow_move_constructible : std::is_nothrow_constructible<T, typename std::add_rvalue_reference<T>::type> {}; |
[modifica] Esempio
#include <iostream> #include <type_traits> struct Ex1 { std::string str; // member has a non-trivial but non-throwing move ctor }; struct Ex2 { int n; Ex2(Ex2&&) = default; // trivial and non-throwing }; int main() { std::cout << std::boolalpha << "Ex1 is move-constructible? " << std::is_move_constructible<Ex1>::value << '\n' << "Ex1 is trivially move-constructible? " << std::is_trivially_move_constructible<Ex1>::value << '\n' << "Ex1 is nothrow move-constructible? " << std::is_nothrow_move_constructible<Ex1>::value << '\n' << "Ex2 is trivially move-constructible? " << std::is_trivially_move_constructible<Ex2>::value << '\n' << "Ex2 is nothrow move-constructible? " << std::is_nothrow_move_constructible<Ex2>::value << '\n'; }
Output:
Ex1 is move-constructible? true Ex1 is trivially move-constructible? false Ex1 is nothrow move-constructible? true Ex2 is trivially move-constructible? true Ex2 is nothrow move-constructible? true
[modifica] Vedi anche
(C++11) (C++11) (C++11) |
Verifica se un tipo ha un costruttore per argomenti specifici Original: checks if a type has a constructor for specific arguments The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (classe template) |
Verifica se un tipo ha un costruttore di default Original: checks if a type has a default constructor The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (classe template) | |
(C++11) (C++11) (C++11) |
Verifica se un tipo ha un costruttore di copia Original: checks if a type has a copy constructor The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (classe template) |
(C++11) |
ottiene un riferimento rvalue se il costruttore mossa non genera Original: obtains an rvalue reference if the move constructor does not throw The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (funzione di modello) |