std::array

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()

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

Template parameters

Member types

Member functions

Non-member functions

Helper classes

Example

#include <algorithm>
#include <array>
#include <iostream>
#include <iterator>
#include <string>
 
int main()
{
    // Construction uses aggregate initialization
    std::array<int, 3> a1{{1, 2, 3}}; // Double-braces required in C++11 prior to
                                      // the CWG 1270 revision (not needed in C++11
                                      // after the revision and in C++14 and beyond)
 
    std::array<int, 3> a2 = {1, 2, 3}; // Double braces never required after =
 
    // Container operations are supported
    std::sort(a1.begin(), a1.end());
    std::ranges::reverse_copy(a2, std::ostream_iterator<int>(std::cout, " "));
    std::cout << '\n';
 
    // Ranged for loop is supported
    std::array<std::string, 2> a3{"E", "\u018E"};
    for (const auto& s : a3)
        std::cout << s << ' ';
    std::cout << '\n';
 
    // Deduction guide for array creation (since C++17)
    [[maybe_unused]] std::array a4{3.0, 1.0, 4.0}; // std::array<double, 3>
 
    // Behavior of unspecified elements is the same as with built-in arrays
    [[maybe_unused]] std::array<int, 2> a5; // No list init, a5[0] and a5[1]
                                            // are default initialized
    [[maybe_unused]] std::array<int, 2> a6{}; // List init, both elements are value
                                              // initialized, a6[0] = a6[1] = 0
    [[maybe_unused]] std::array<int, 2> a7{1}; // List init, unspecified element is value
                                               // initialized, a7[0] = 1, a7[1] = 0
}

3 2 1
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See also