std::swap(std::map)

 

C++

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std::map

Member functions

map::map map::~map               map::operator= map::get_allocator

Element access map::at map::operator[] Iterators map::beginmap::cbegin (C++11) map::endmap::cend (C++11) map::rbeginmap::crbegin (C++11)      map::rendmap::crend (C++11) Capacity map::size map::max_size map::empty Observers map::key_comp map::value_comp Modifiers map::clear map::insert map::erase map::swap map::extract (C++17) map::merge (C++17) map::insert_range (C++23) map::insert_or_assign (C++17) map::emplace (C++11) map::emplace_hint (C++11) map::try_emplace (C++17) Lookup map::count map::find map::contains (C++20) map::equal_range map::lower_bound map::upper_bound

Non-member functions

operator==operator<=> (C++20) std::swap(std::map) erase_if(std::map) (C++20)   operator!=operator<operator>operator<=operator>= (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)

Deduction guides (C++17)

 

Defined in header <map>
template< class Key, class T, class Compare, class Alloc > void swap( std::map<Key, T, Compare, Alloc>& lhs,            std::map<Key, T, Compare, Alloc>& rhs );		(until C++17)
template< class Key, class T, class Compare, class Alloc > void swap( std::map<Key, T, Compare, Alloc>& lhs,            std::map<Key, T, Compare, Alloc>& rhs )     noexcept(/* see below */);		(since C++17) (constexpr since C++26)

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

Parameters

lhs, rhs

-

containers whose contents to swap

Complexity

Constant.

Exceptions

noexcept specification:   noexcept(noexcept(lhs.swap(rhs))

(since C++17)

Example

Run this code

#include <algorithm>
#include <iostream>
#include <map>
 
int main()
{
    std::map<int, char> alice{{1, 'a'}, {2, 'b'}, {3, 'c'};
    std::map<int, char> bob{{7, 'Z'}, {8, 'Y'}, {9, 'X'}, {10, 'W'};
 
    auto print = [](std::pair<const int, char>& n)
    {
        std::cout << ' ' << n.first << ':' << n.second;
    };
 
    / Print state before swap
    std::cout << "Alice:";
    std::for_each(alice.begin(), alice.end(), print);
    std::cout << "\nBobby:";
    std::for_each(bob.begin(), bob.end(), print);
    std::cout << '\n';
 
    std::cout << "-- SWAP\n";
    std::swap(alice, bob);
 
    / Print state after swap
    std::cout << "Alice:";
    std::for_each(alice.begin(), alice.end(), print);
    std::cout << "\nBobby:";
    std::for_each(bob.begin(), bob.end(), print);
    std::cout << '\n';
}

Output:

Alice: 1:a 2:b 3:c
Bobby: 7:Z 8:Y 9:X 10:W
-- SWAP
Alice: 7:Z 8:Y 9:X 10:W
Bobby: 1:a 2:b 3:c

See also

swap	swaps the contents (public member function)

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