std::extent
From Get docs
Cpp/docs/latest/types/extent
std::extent
Defined in header <type_traits>
|
||
---|---|---|
|
(since C++11) |
If T
is an array type, provides the member constant value
equal to the number of elements along the N
th 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.
Helper variable template
|
(since C++17) |
Inherited from std::integral_constant
Member constants
value [static] |
the number of elements along the N th 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) |
operator() (C++14) |
returns value (public member function) |
Member types
Type | Definition |
---|---|
value_type
|
std::size_t
|
type
|
std::integral_constant<std::size_t, value>
|
Possible implementation
|
Example
#include <iostream>
#include <type_traits>
int main()
{
std::cout << std::extent<int[3]>::value << '\n'; //< default dimension is 0
std::cout << std::extent<int[3][4], 0>::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';
const auto ext = std::extent<int[9]>{};
std::cout << ext << '\n'; //< implicit conversion to std::size_t
const int ints[] = {1,2,3,4};
std::cout << std::extent<decltype(ints)>::value << '\n'; //< array size
}
Output:
3
3
4
0
0
9
4
See also
(C++11) |
checks if a type is an array type (class template) |
(C++11) |
obtains the number of dimensions of an array type (class template) |
(C++11) |
removes one extent from the given array type (class template) |
(C++11) |
removes all extents from the given array type (class template) |
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