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std::deque swap() method

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

Exchanges the contents of the container with those of other. Does not invoke any move, copy, or swap operations on individual elements.

Invalidation

The past-the-end iterator is invalidated.
All iterators and references remain valid.

If std::allocator_traits<allocator_type>::propagate_on_container_swap::value is true, then the allocators are exchanged using an unqualified call to non-member swap().
Otherwise, they are not swapped (and if get_allocator() != other.get_allocator(), the behavior is undefined

).

Parameters

  • other - container to exchange the contents with

Return value

(none)

Complexity

Constant - O(1).

Exceptions

noexcept(std::allocator_traits<Allocator>::is_always_equal::value)

Example

Main.cpp
#include <iostream>
#include <deque>

template<class Os, class Co> Os& operator<<(Os& os, const Co& co) {
os << "{";
for (auto const& i : co) { os << ' ' << i; }
return os << " } ";
}

int main()
{
std::deque<int> a1{1, 2, 3}, a2{4, 5};

auto it1 = std::next(a1.begin());
auto it2 = std::next(a2.begin());

int& ref1 = a1.front();
int& ref2 = a2.front();

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 the iterators and references stay associated with their
// original elements, e.g. it1 that pointed to an element in 'a1' with value 2
// still points to the same element, though this element was moved into 'a2'.
}
Possible output
{ 1 2 3 } { 4 5 } 2 5 1 4
{ 4 5 } { 1 2 3 } 2 5 1 4
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Hover to see the original license.

std::deque swap() method

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

Exchanges the contents of the container with those of other. Does not invoke any move, copy, or swap operations on individual elements.

Invalidation

The past-the-end iterator is invalidated.
All iterators and references remain valid.

If std::allocator_traits<allocator_type>::propagate_on_container_swap::value is true, then the allocators are exchanged using an unqualified call to non-member swap().
Otherwise, they are not swapped (and if get_allocator() != other.get_allocator(), the behavior is undefined

).

Parameters

  • other - container to exchange the contents with

Return value

(none)

Complexity

Constant - O(1).

Exceptions

noexcept(std::allocator_traits<Allocator>::is_always_equal::value)

Example

Main.cpp
#include <iostream>
#include <deque>

template<class Os, class Co> Os& operator<<(Os& os, const Co& co) {
os << "{";
for (auto const& i : co) { os << ' ' << i; }
return os << " } ";
}

int main()
{
std::deque<int> a1{1, 2, 3}, a2{4, 5};

auto it1 = std::next(a1.begin());
auto it2 = std::next(a2.begin());

int& ref1 = a1.front();
int& ref2 = a2.front();

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 the iterators and references stay associated with their
// original elements, e.g. it1 that pointed to an element in 'a1' with value 2
// still points to the same element, though this element was moved into 'a2'.
}
Possible output
{ 1 2 3 } { 4 5 } 2 5 1 4
{ 4 5 } { 1 2 3 } 2 5 1 4
This article originates from this CppReference page. It was likely altered for improvements or editors' preference. Click "Edit this page" to see all changes made to this document.
Hover to see the original license.