std::swap(s...ordered_map)(3)

🎀 NAME 🎀

std::swap(std::unordered_map) — and yes bestie, the other side is also std::swap(std::unordered_map). That’s the whole name. Iconic.

Manual page vibes: std::swap(std::unordered_map)(3), from the C++ Standard Libary. 🫶

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✨ Synopsis ✨

Defined in header <unordered_map>

First overload, tagged (since C++11) and (until C++17):

template< class Key, class T, class Hash, class KeyEqual, class Alloc >
void swap( std::unordered_map<Key, T, Hash, KeyEqual, Alloc>& lhs,
           std::unordered_map<Key, T, Hash, KeyEqual, Alloc>& rhs );

Second overload, tagged (since C++17):

template< class Key, class T, class Hash, class KeyEqual, class Alloc >
void swap( std::unordered_map<Key, T, Hash, KeyEqual, Alloc>& lhs,
           std::unordered_map<Key, T, Hash, KeyEqual, Alloc>& rhs )
    noexcept(/* see below */);

This specializes the std::swap algorithm for std::unordered_map. It swaps the contents of lhs and rhs. And the way it does that? It calls lhs.swap(rhs). Slay. 💅

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🦋 Parameters 🦋

• lhs, rhs — containers whose contents to swap. Literally the two besties exchanging their whole vibe. 💖

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🌸 Return value 🌸

(none) — nothing comes back, bestie. It’s a void situation. 🙈

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⭐ Complexity ⭐

Constant. That’s the whole energy: constant. Lowkey perfect. 🔥

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💀 Exceptions 💀

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

No cap, that’s the exact spec. 🫶

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🧚 Example 🧚

// Run this code

#include <algorithm>
#include <iostream>
#include <unordered_map>

int main()
{
    std::unordered_map<int, char> alice{{1, 'a'}, {2, 'b'}, {3, 'c'}};
    std::unordered_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 << "\n" "Bob  :";
    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 << "\n" "Bob  :";
    std::for_each(bob.begin(), bob.end(), print);
    std::cout << '\n';
}

Possible output:

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

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🌈 See also 🌈

• swap swaps the contents — public member function. That’s the member-function bestie. 🫶

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👑 Category 👑

• * conditionally noexcept

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Source/version/date: http://cppreference.com, 2024.06.10, std::swap(s...ordered_map)(3) — bye bestie, go swap something iconic 💖✨