NAME¶

std::queue::swap - std::queue::swap

Synopsis¶

void swap( queue& other ) noexcept(/* see below */); (since C++11)

Exchanges the contents of the container adaptor with those of other. Effectively
calls

using std::swap;
swap(c, other.c);

Parameters¶

other - container adaptor to exchange the contents with

Return value¶

(none)

Exceptions¶

noexcept specification:
noexcept(noexcept(swap(c, other.c))) (since C++11)
(until C++17)
In the expression above, the identifier swap is looked up in the same
manner as the one used by the C++17 std::is_nothrow_swappable trait.
noexcept specification: (since C++17)
noexcept(std::is_nothrow_swappable_v<Container>)

Complexity¶

Same as underlying container (typically constant).

Notes¶

Some implementations (e.g. libc++) provide the swap member function as an extension
to pre-C++11 modes.

Example¶

// Run this code

#include <iostream>
#include <concepts>
#include <queue>
#include <string>
#include <string_view>
#include <vector>

template<typename Adaptor>
requires (std::ranges::input_range<typename Adaptor::container_type>)
void print(std::string_view name, const Adaptor& adaptor)
{
struct Printer : Adaptor // to use protected Adaptor::Container c;
{
void print(std::string_view name) const
{
std::cout << name << " [" << std::size(this->c) << "]: ";
for (auto const& elem : this->c)
std::cout << elem << ' ';
std::cout << '\n';
}
};

static_cast<Printer const&>(adaptor).print(name);
}

int main()
{
std::vector<std::string> v1{"1","2","3","4"},
v2{"Ɐ","B","Ɔ","D","Ǝ"};

std::queue s1(std::move(v1));
std::queue s2(std::move(v2));

print("s1", s1);
print("s2", s2);

s1.swap(s2);

print("s1", s1);
print("s2", s2);
}

Output:¶

s1 [4]: 4 3 2 1
s2 [5]: Ǝ D Ɔ B Ɐ
s1 [5]: Ǝ D Ɔ B Ɐ
s2 [4]: 4 3 2 1

Defect reports

The following behavior-changing defect reports were applied retroactively to
previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 2456 C++11 the noexcept specification is ill-formed made to work

See also¶

std::swap(std::queue) specializes the std::swap algorithm
(C++11) (function template)

Category:¶

* conditionally noexcept