std::is_unbounded_array

Defined in header <type_traits>
template< class T >
struct is_unbounded_array;
(since C++20)

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

Template parameters

T - a type to check

Helper variable template

template< class T >
inline constexpr bool is_unbounded_array_v = is_unbounded_array<T>::value;
(since C++20)

Inherited from std::integral_constant

Member constants

value
[static]
true if T is an array type of unknown 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_unbounded_array: std::false_type {};
 
template<class T>
struct is_unbounded_array<T[]> : std::true_type {};

Example

#include <iostream>
#include <type_traits>
 
class A {};
 
int main() 
{
    std::cout << std::boolalpha;
    std::cout << std::is_unbounded_array_v<A> << '\n';
    std::cout << std::is_unbounded_array_v<A[]> << '\n';
    std::cout << std::is_unbounded_array_v<A[3]> << '\n';
    std::cout << std::is_unbounded_array_v<float> << '\n';
    std::cout << std::is_unbounded_array_v<int> << '\n';
    std::cout << std::is_unbounded_array_v<int[]> << '\n';
    std::cout << std::is_unbounded_array_v<int[3]> << '\n';
}

Output:

false
true
false
false
false
true
false

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 known bound
(class template)
(C++11)
obtains the size of an array type along a specified dimension
(class template)

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