NAME¶

std::is_unbounded_array - std::is_unbounded_array

Synopsis¶

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

std::is_unbounded_array is a UnaryTypeTrait.

Checks whether T is an arrays 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.

If the program adds specializations for std::is_unbounded_array or
std::is_unbounded_array_v, the behavior is undefined.

Template parameters¶

T - a type to check

Helper variable template

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

Inherited from std::integral_constant

Member constants¶

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

Member functions¶

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

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 <type_traits>

class A {};

static_assert
(""
&& std::is_unbounded_array_v<A> == false
&& std::is_unbounded_array_v<A[]> == true
&& std::is_unbounded_array_v<A[3]> == false
&& std::is_unbounded_array_v<float> == false
&& std::is_unbounded_array_v<int> == false
&& std::is_unbounded_array_v<int[]> == true
&& std::is_unbounded_array_v<int[3]> == false
);

int main() {}

See also¶

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