std::is_array

Defined in header <type_traits>

template< class T >
struct is_array;

(since C++11)

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.

Template parameters

a type to check

Helper variable template

template< class T >
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 <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[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[3]>::value << '\n';
}

Output:

false
true
false
false
true

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)
std::experimental::is_array_v (library fundamentals TS)	variable template alias of `std::is_array::value` (variable template)

Links:

http://en.cppreference.com/w/cpp/types/is_array

doc_CPP

2025-01-10 15:47:30

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