std::array

 

C++

Language

Standard library headers

Concepts

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

 

Containers library

array (C++11)

vector

deque

forward_list (C++11)

list

set

multiset

map

multimap

unordered_set (C++11)

unordered_multiset (C++11)

unordered_map (C++11)

unordered_multimap (C++11)

stack

queue

priority_queue

 

std::array

Member functions

Element access

array::at

array::operator[]

array::front

array::back

array::data

Iterators

array::beginarray::cbegin

array::endarray::cend

array::rbeginarray::crbegin

array::rendarray::crend

Capacity

array::empty

array::size

array::max_size

Modifiers

array::fill

array::swap

Non-member functions

get

swap

operator==operator!=operator<operator>operator<=operator>=

Helper classes

tuple_size

tuple_element

 

Defined in header <array>
template<     class T,     std::size_t N > struct array;		(since C++11)

std::array is a container that encapsulates fixed size arrays.

This container is an aggregate type with the same semantics as a struct holding a C-style array T[N] as its only non-static data member. Unlike a C-style array, it doesn't decay to T* automatically. As an aggregate type, it can be initialized with aggregate-initialization given at most N initializers that are convertible to T: std::array<int, 3> a = {1,2,3};.

The struct combines the performance and accessibility of a C-style array with the benefits of a standard container, such as knowing its own size, supporting assignment, random access iterators, etc.

std::array satisfies the requirements of Container and ReversibleContainer except that default-constructed array is not empty and that the complexity of swapping is linear, satisfies the requirements of ContiguousContainer (since C++17) and partially satisfies the requirements of SequenceContainer.

There is a special case for a zero-length array (N == 0). In that case, array.begin() == array.end(), which is some unique value. The effect of calling front() or back() on a zero-sized array is undefined.

An array can also be used as a tuple of N elements of the same type.

Iterator invalidation

As a rule, iterators to an array are never invalidated throughout the lifetime of the array. One should take note, however, that during swap, the iterator will continue to point to the same array element, and will thus change its value.

Member types

Member type	Definition
value_type	T
size_type	std::size_t
difference_type	std::ptrdiff_t
reference	value_type&
const_reference	const value_type&
pointer	value_type*
const_pointer	const value_type*
iterator	RandomAccessIterator and LiteralType (since C++17)
const_iterator	Constant random access iterator and LiteralType (since C++17)
reverse_iterator	std::reverse_iterator<iterator>
const_reverse_iterator	std::reverse_iterator<const_iterator>

Member functions

Implicitly-defined member functions
(constructor) (implicitly declared)	initialized the array following the rules of aggregate initialization (note that default initialization may result in indeterminate values for non-class T) (public member function)
(destructor) (implicitly declared)	destroys every element of the array (public member function)
operator= (implicitly declared)	overwrites every element of the array with the corresponding element of another array (public member function)
Element access
at	access specified element with bounds checking (public member function)
operator[]	access specified element (public member function)
front	access the first element (public member function)
back	access the last element (public member function)
data	direct access to the underlying array (public member function)
Iterators
begin cbegin	returns an iterator to the beginning (public member function)
end cend	returns an iterator to the end (public member function)
rbegin crbegin	returns a reverse iterator to the beginning (public member function)
rend crend	returns a reverse iterator to the end (public member function)
Capacity
empty	checks whether the container is empty (public member function)
size	returns the number of elements (public member function)
max_size	returns the maximum possible number of elements (public member function)
Operations
fill	fill the container with specified value (public member function)
swap	swaps the contents (public member function)

Non-member functions

operator==operator!=operator<operator<=operator>operator>=	lexicographically compares the values in the array (function template)
std::get(std::array)	accesses an element of an array (function template)
std::swap(std::array) (C++11)	specializes the std::swap algorithm (function template)

Helper classes

std::tuple_size<std::array>	obtains the size of an array (class template specialization)
std::tuple_element<std::array>	obtains the type of the elements of array (class template specialization)

Example

Run this code

#include <string>
#include <iterator>
#include <iostream>
#include <algorithm>
#include <array>
 
int main()
{
    // construction uses aggregate initialization
    std::array<int, 3> a1{ {1, 2, 3} }; // double-braces required in C++11 (not in C++14)
    std::array<int, 3> a2 = {1, 2, 3};  // never required after =
    std::array<std::string, 2> a3 = { std::string("a"), "b" };
 
    // container operations are supported
    std::sort(a1.begin(), a1.end());
    std::reverse_copy(a2.begin(), a2.end(), 
                      std::ostream_iterator<int>(std::cout, " "));
 
    std::cout << '\n';
 
    // ranged for loop is supported
    for(const auto& s: a3)
        std::cout << s << ' ';
}

Output:

3 2 1 
a b

See also

make_array	Creates a std::array object whose size and optionally element type are deduced from the arguments (function template)
to_array	Creates a std::array object from a built-in array (function template)