Docs4dev
Docs
cpp / latest / types / is_array.html

std::is_array

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

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.

The behavior of a program that adds specializations for std::is_array or std::is_array_v is undefined.

Template parameters

T - a type to check

Helper variable template

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

Inherited from std::integral_constant

Member constants

value
[static]
true if T is an array type, 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_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

#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

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

© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
https://en.cppreference.com/w/cpp/types/is_array