NAME¶

std::is_array - std::is_array

Synopsis¶

Defined in header <type_traits>
template< class T > (since C++11)
struct is_array;

std::is_array is a UnaryTypeTrait.

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

If the program adds specializations for std::is_array or std::is_array_v, the
behavior is undefined.

Template parameters¶

T - a type to check

Helper variable template

template< class T > (since C++17)
inline constexpr bool is_array_v = is_array<T>::value;

Inherited from std::integral_constant

Member constants¶

value true if T is an array type, 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_array : std::false_type {};

template<class T>
struct is_array<T[]> : std::true_type {};

template<class T, std::size_t N>
struct is_array<T[N]> : std::true_type {};

Example¶

// Run this code

#include <array>
#include <iostream>
#include <type_traits>

class A {};

int main()
{
std::cout << std::boolalpha;
std::cout << std::is_array<A>::value << '\n';
std::cout << std::is_array<A[]>::value << '\n';
std::cout << std::is_array<A[3]>::value << '\n';
std::cout << std::is_array<float>::value << '\n';
std::cout << std::is_array<int>::value << '\n';
std::cout << std::is_array<int[]>::value << '\n';
std::cout << std::is_array<int[3]>::value << '\n';
std::cout << std::is_array<std::array<int, 3>>::value << '\n';
}

Output:¶

false
true
true
false
false
true
true
false

See also¶

is_bounded_array checks if a type is an array type of known bound
(C++20) (class template)
is_unbounded_array checks if a type is an array type of unknown bound
(C++20) (class template)
rank obtains the number of dimensions of an array type
(C++11) (class template)
extent obtains the size of an array type along a specified dimension
(C++11) (class template)
remove_extent removes one extent from the given array type
(C++11) (class template)
remove_all_extents removes all extents from the given array type
(C++11) (class template)