std::array swap() method

od C++20

// Non-const version only
constexpr void swap( array& other ) noexcept(/* see below */);

do C++20

// Non-const version only
void swap( array& other ) noexcept(/* see below */);

The noexcept specification for these two looks like follows:

do C++17

noexcept(noexcept(swap(std::declval<T&>(), std::declval<T&>())))

od C++17

noexcept(std::is_nothrow_swappable_v<T>)

Exchanges the contents of the container with those of other.

Parameters

• other - the other array to exchange the contents with

Return value

(none)

Complexity

Linear in the size of the container.

Example

#include <array>
#include <iostream>
 
template<class Os, class V> Os& operator<<(Os& os, const V& v) {
    os << "{";
    for (auto i : v) os << ' ' << i;
    return os << " } ";
}
 
int main()
{
    std::array<int, 3> a1{1, 2, 3}, a2{4, 5, 6};
 
    auto it1 = a1.begin();
    auto it2 = a2.begin();
    int& ref1 = a1[1];
    int& ref2 = a2[1];
 
    std::cout << a1 << a2 << *it1 << ' ' << *it2 << ' ' << ref1 << ' ' << ref2 << '\n';
    a1.swap(a2);
    std::cout << a1 << a2 << *it1 << ' ' << *it2 << ' ' << ref1 << ' ' << ref2 << '\n';
 
    // Note that after swap iterators and references stay associated with their original
    // array, e.g. `it1` still points to element a1[0], `ref1` still refers to a1[1].
}

Possible output

{ 1 2 3 } { 4 5 6 } 1 4 2 5
{ 4 5 6 } { 1 2 3 } 4 1 5 2