# std::is_array

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< cpp‎ | types

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

`std::is_array` is an 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` (since C++17) 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

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

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