std::initializer_list
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| Defined in header <initializer_list>
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| template< class T > class initializer_list; |
(ya que C + +11) | |
Un objeto de
std::initializer_list<T> tipo es un objeto proxy de peso ligero, que proporciona acceso a un conjunto de objetos de tipo T, asignada por la aplicación en el almacenamiento no especificado (que puede ser automática, temporal, o memoria estática de sólo lectura, en función de la situación )Original:
An object of type
std::initializer_list<T> is a lightweight proxy object, which provides access to an array of objects of type T, allocated by the implementation in unspecified storage (which could be automatic, temporary, or static read-only memory, depending on the situation)The text has been machine-translated via Google Translate.
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Este array se inicializa y un objeto
std::initializer_list se construye cuando preparaba un-init-list se utiliza en lista de inicialización, incluyendo la inicialización lista de funciones de llamada y expresión de asignación (que no debe confundirse con constructor lista de inicialización), o cuando preparó-init-list está obligado a auto, incluido en un archivo. oscilaba bucle for .Original:
This array is initialized and a
std::initializer_list object is constructed when a braced-init-list is used in lista de inicialización, including function-call list initialization and assignment expression (not to be confused with constructor lista de inicialización), or when braced-init-list is bound to auto, including in a ranged for loop.The text has been machine-translated via Google Translate.
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Initializer lista puede ser implementado como un par de punteros o punteros y longitud. Copia de un
std::initializer_list no copia los objetos subyacentes del matriz subyacente no se garantiza que existe después de la vida útil del objeto inicializador lista original ha terminado .Original:
Initializer list may be implemented as a pair of pointers or pointer and length. Copying a
std::initializer_list does not copy the underlying objects. The underlying array is not guaranteed to exist after the lifetime of the original initializer list object has ended.The text has been machine-translated via Google Translate.
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[editar] Tipos de miembros
| Miembro de tipo
Original: Member 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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T |
reference
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const T& |
const_reference
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const T& |
size_type
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size_t |
iterator
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const T* |
const_iterator
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const T* |
[editar] Las funciones miembro
| crea una lista de inicializador vacías Original: creates an empty initializer list The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (miembro público función) | |
Original: Capacity The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. | |
| devuelve el número de elementos en la lista de inicialización Original: returns the number of elements in the initializer list The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (miembro público función) | |
Original: Iterators The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. | |
| devuelve un puntero al primer elemento Original: returns a pointer the first element The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (miembro público función) | |
| devuelve un puntero a un más allá del último elemento Original: returns a pointer to one past the last element The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (miembro público función) | |
[editar] Terceros funciones
| se especializa std::begin Original: specializes std::begin The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (función de plantilla) | |
| se especializa std::end Original: specializes std::end The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (función de plantilla) | |
[editar] Ejemplo
#include <iostream> #include <vector> #include <initializer_list> template<class T> struct S { std::vector<T> v; S(std::initializer_list<T> l) : v(l) { std::cout << "constructed with a " << l.size() << "-element list\n"; } void append(std::initializer_list<T> l) { v.insert(v.end(), l.begin(), l.end()); } std::pair<const int*, size_t> c_arr() const { return {&v[0], v.size()}; // list-initialization in return statement } }; template<typename T> void templated_fn(T) { } int main() { S<int> s = {1,2,3,4,5}; // direct list-initialization s.append({6,7,8}); // list-initialization in function call std::cout << "The vector size is now " << s.c_arr().second << " ints:\n"; for(auto n : s.v) std::cout << ' ' << n; std::cout << '\n'; std::cout << "range-for over brace-init-list: \n"; for(int x : {-1, -2, -3}) // the rule for auto makes this ranged for work std::cout << x << ' '; std::cout << '\n'; auto al = {10, 11, 12}; // special rule for auto std::cout << "The list bound to auto has size() = " << al.size() << '\n'; // templated_fn({1,2,3}); // compiler error! "{1,2,3}" is not an expression, // it has no type, and so T cannot be deduced templated_fn<std::initializer_list<int>>({1,2,3}); // OK templated_fn<std::vector<int>>({1,2,3}); // also OK }
Output:
The vector size is now 8 ints: 1 2 3 4 5 6 7 8 range-for over brace-init-list: -1 -2 -3 The list bound to auto has size() = 3
