std::is_unbounded_array

From cppreference.com
< cpp‎ | types
C++
Metaprogramming library
Type traits
Type categories
(C++11)
(C++11)(DR*)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
Type properties
(C++11)
(C++11)
(C++11)
(C++11)
(C++14)
(C++11)
(C++17)
(C++23)
(C++11)(deprecated in C++26)
(C++11)
(C++11)
(C++11)(until C++20*)
(C++11)(deprecated in C++20)
(C++11)
(C++11)
(C++20)
is_unbounded_array
(C++20)
(C++23)
(C++17)
Type trait constants
(C++11) (C++17) (C++11) (C++11)
Metafunctions
(C++17)
(C++17)
(C++17)
Supported operations
Relationships and property queries
Type modifications
(C++11)(C++11)(C++11)
(C++11)(C++11)(C++11)
(C++11)
(C++11)
Type transformations
(C++11)(deprecated in C++23)
(C++11)(deprecated in C++23)
(C++11)
(C++20)
(C++11)(until C++20*)(C++17)

(C++11)
(C++11)
(C++20)
(C++11)
(C++20)
(C++11)
(C++17)
Compile-time rational arithmetic
Compile-time integer sequences
(C++14)
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

(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)
Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/types/is_unbounded_array&oldid=176466