std::swap(std::stack)

Since C++17

Header: <stack>

# Declarations

template< class T, class Container >
void swap( std::stack<T, Container>& lhs,
std::stack<T, Container>& rhs );

(since C++11) (until C++17)

template< class T, class Container >
void swap( std::stack<T, Container>& lhs,
std::stack<T, Container>& rhs )
noexcept(/* see below */);

(since C++17)

# Parameters

lhs, rhs: containers whose contents to swap

# Return value

(none)

# 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

#include <algorithm>
#include <iostream>
#include <stack>
 
int main()
{
    std::stack<int> alice;
    std::stack<int> bob;
 
    auto print = [](const auto& title, const auto& cont)
    {
        std::cout << title << " size=" << cont.size();
        std::cout << " top=" << cont.top() << '\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("Bobby:", bob);
 
    std::cout << "-- SWAP\n";
    std::swap(alice, bob);
 
    // Print state after swap
    print("Alice:", alice);
    print("Bobby:", bob);
}

# See also

swap