std::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

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