std::extent
De cppreference.com
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<tbody> </tbody>| Definido no cabeçalho <type_traits>
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template< class T, unsigned N = 0> struct extent; |
(desde C++11) | |
If T is an array type, provides the member constant value equal to the number of elements along the Nth dimension of the array, if N is in [0, std::rank<T>::value). For any other type, or if T is array of unknown bound along its first dimension and N is 0, value is 0.
Herdado de std::integral_constant
Member constants
value [estática] |
the number of elements along the Nth dimension of T (membro estático público constante) |
Member functions
operator std::size_t |
converte o objeto em std::size_t, retorna value Original: converts the object to std::size_t, returns value The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (função pública membro) |
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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std::size_t
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type
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std::integral_constant<std::size_t, value>
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Possível implementação
template<class T, unsigned N = 0>
struct extent : std::integral_constant<std::size_t, 0> {};
template<class T>
struct extent<T[], 0> : std::integral_constant<std::size_t, 0> {};
template<class T, unsigned N>
struct extent<T[], N> : std::integral_constant<std::size_t, std::extent<T, N-1>::value> {};
template<class T, std::size_t N>
struct extent<T[N], 0> : std::integral_constant<std::size_t, N> {};
template<class T, std::size_t I, unsigned N>
struct extent<T[I], N> : std::integral_constant<std::size_t, std::extent<T, N-1>::value> {};
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Exemplo
#include <iostream>
#include <type_traits>
int main()
{
std::cout << std::extent<int[3]>::value << '\n';
std::cout << std::extent<int[3][4]>::value << '\n';
std::cout << std::extent<int[3][4],1>::value << '\n';
std::cout << std::extent<int[3][4],2>::value << '\n';
std::cout << std::extent<int[]>::value << '\n';
}
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