std:: is_bounded_array

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is_bounded_array
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Defined in header <type_traits>
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

T - a type to check

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

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

Member functions

operator bool
converts the object to bool , returns value
(public member function)
operator()
(C++14)
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

Run this code 
#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

See also

(C++11)
checks if a type is an array type
(class template)
(C++20)
checks if a type is an array type of unknown bound
(class template)
(C++11)
obtains the size of an array type along a specified dimension
(class template)
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