std::extent
From Cppreference
Defined in header <type_traits>
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template< class T, unsigned N = 0>
struct extent; |
(C++11 feature) | |
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.
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Inherited from std::integral_constant
Member constants
value | the number of elements along the Nth dimension of T (public static member constant) |
Member functions
operator std::size_t | converts the object to std::size_t, returns value (public member function) |
Member types
Type | Definition |
value_type | std::size_t |
type | std::integral_constant<std::size_t, value> |
[edit] Equivalent definition
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> {}; |
[edit] Example
#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'; }
Output:
3 3 4 0 0
[edit] See also
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checks if a type is an array type (class template) |
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obtains the number of dimensions of an array type (class template) |
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removes one extent from the given array type (class template) |
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removes all extents from the given array type (class template) |