std::is_unbounded_array

 

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

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 > 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 {};

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