Difference between revisions of "cpp/container/array"

Revision as of 06:49, 29 December 2014

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. 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.

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 functions

Non-member functions

Helper classes

Example

#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 << ' ';
}

3 2 1 
a b