std::is_bounded_array - cppreference.com

From cppreference.com


`template< class T > struct is_bounded_array;`		(since C++20)

std::is_bounded_array is a UnaryTypeTrait.

Checks whether T is an array type of known bound. Provides the member constant value which is equal to true, if T is an array type of known bound. Otherwise, value is equal to false.

If the program adds specializations for std::is_bounded_array or std::is_bounded_array_v, the behavior is undefined.

Template parameters

Helper variable template

`template< class T > constexpr bool is_bounded_array_v = is_bounded_array<T>::value;`		(since C++20)

Inherited from std::integral_constant

Member constants

true if T is an array type of known bound, false otherwise
(public static member constant)

Member functions

	converts the object to `bool`, returns `value` (public member function)
	returns `value` (public member function)

Member types

Type	Definition
`value_type`	`bool`
`type`	`std::integral_constant<bool, value>`

Possible implementation

template<class T>
struct is_bounded_array : std::false_type {};

template<class T, std::size_t N>
struct is_bounded_array<T[N]> : std::true_type {};

Notes

Feature-test macro	Value	Std	Feature
`__cpp_lib_bounded_array_traits`	`201902L`	(C++20)	`std::is_bounded_array`, std::is_unbounded_array

Example

#include <iostream>
#include <type_traits>

#define OUT(...) std::cout << #__VA_ARGS__ << " : " << __VA_ARGS__ << '\n'

class A {};

int main()
{
    std::cout << std::boolalpha;
    OUT(std::is_bounded_array_v<A>);
    OUT(std::is_bounded_array_v<A[]>);
    OUT(std::is_bounded_array_v<A[3]>);
    OUT(std::is_bounded_array_v<float>);
    OUT(std::is_bounded_array_v<int>);
    OUT(std::is_bounded_array_v<int[]>);
    OUT(std::is_bounded_array_v<int[3]>);
}

Output:

std::is_bounded_array_v<A> : false
std::is_bounded_array_v<A[]> : false
std::is_bounded_array_v<A[3]> : true
std::is_bounded_array_v<float> : false
std::is_bounded_array_v<int> : false
std::is_bounded_array_v<int[]> : false
std::is_bounded_array_v<int[3]> : true

	checks if a type is an array type (class template) [edit]
	checks if a type is an array type of unknown bound (class template) [edit]
	obtains the size of an array type along a specified dimension (class template) [edit]