NAME¶

std::swap(std::queue) - std::swap(std::queue)

Synopsis¶

Defined in header <queue>
template< class T, class Container >
(since C++11)
void swap( std::queue<T, Container>& lhs, (until C++17)

std::queue<T, Container>& rhs );
template< class T, class Container >

void swap( std::queue<T, Container>& lhs, (since C++17)
std::queue<T, Container>& rhs )

noexcept(/* see below */);

Specializes the std::swap algorithm for std::queue. Swaps the contents of lhs and
rhs. Calls lhs.swap(rhs).

This overload participates in overload resolution only if (since C++17)
std::is_swappable_v<Container> is true.

Parameters¶

lhs, rhs - containers whose contents to swap

Return value¶

(none)

Complexity¶

Same as swapping the underlying container.

Exceptions¶

noexcept specification: (since C++17)
noexcept(noexcept(lhs.swap(rhs)))

Notes¶

Although the overloads of std::swap for container adaptors are introduced in C++11,
container adaptors can already be swapped by std::swap in C++98. Such calls to
std::swap usually have linear time complexity, but better complexity may be
provided.

Example¶

// Run this code

#include <algorithm>
#include <iostream>
#include <queue>

int main()
{
std::queue<int> alice;
std::queue<int> bob;

auto print = [](const auto& title, const auto& cont)
{
std::cout << title << " size=" << cont.size();
std::cout << " front=" << cont.front();
std::cout << " back=" << cont.back() << '\n';
};

for (int i = 1; i < 4; ++i)
alice.push(i);
for (int i = 7; i < 11; ++i)
bob.push(i);

// Print state before swap
print("Alice:", alice);
print("Bob :", bob);

std::cout << "-- SWAP\n";
std::swap(alice, bob);

// Print state after swap
print("Alice:", alice);
print("Bob :", bob);
}

Output:¶

Alice: size=3 front=1 back=3
Bob : size=4 front=7 back=10
-- SWAP
Alice: size=4 front=7 back=10
Bob : size=3 front=1 back=3

See also¶

swap swaps the contents
(C++11) (public member function)

Category:¶

* conditionally noexcept