std::swap(std::deque)(3)

💅 std::swap(std::deque) — bestie edition

ok so this is a page straight out of the C++ Standard Libary man pages (yes that's how they spell it, no I will not be fixing it, we respect the source 🫶), and today's main character is std::swap(std::deque).

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✨ NAME ✨

std::swap(std::deque) — which is, and I cannot stress this enough, literally std::swap(std::deque) 💖

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🌸 SYNOPSIS 🌸

First things first, this whole situation lives in the header <deque>:

Defined in header <deque>

and here's the signature, in all its two-flavours-of-C++ glory:

template< class T, class Alloc >

void swap( std::deque<T, Alloc>& lhs,      (until C++17)

           std::deque<T, Alloc>& rhs );

template< class T, class Alloc >

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

               noexcept(/* see below */);

So what's the vibe? This is a specialization of the std::swap algorithm, but specifically for std::deque 👑. It swaps the contents of lhs and rhs, and the way it does that is by calling lhs.swap(rhs). That's it. That's the whole bit, and honestly? slay.

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🎀 Parameters 🎀

• lhs, rhs — the containers whose contents we're swapping. that's it, that's the parameter list, they're just two deques getting their whole thing rearranged 💫

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🦋 Return value 🦋

(none) — nothing, nada, zero, the void. it does the thing and gives you nothing back, and that's iconic behaviour ✨

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⭐ Complexity ⭐

Constant. lowkey the best complexity tier, no cap 🔥

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💀 Exceptions 💀

noexcept specification, and this bit is since C++17:

noexcept(noexcept(lhs.swap(rhs)))

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🌈 Example 🌈

Run this code 🧚

#include <algorithm>
#include <iostream>
#include <deque>

int main()
{
    std::deque<int> alice{1, 2, 3};
    std::deque<int> bob{7, 8, 9, 10};

    auto print = [](const int& n) { std::cout << ' ' << n; };

    // 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';
}

Output:

Alice: 1 2 3
Bob  : 7 8 9 10
-- SWAP
Alice: 7 8 9 10
Bob  : 1 2 3

and that's the swap. Alice and Bob traded whole personalities and the program is thriving 😭💖

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🔥 See also 🔥

• swap — swaps the contents (it's a public member function, iykyk 👑)

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💜 Category 💜

• * conditionally noexcept

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fr fr that's the whole page, nothing skipped, nothing invented. go swap your deques, bestie 🫶

made with love from http://cppreference.com, dated 2024.06.10, and yes it's the std::swap(std::deque)(3) page in the C++ Standard Libary, mwah 💅✨