std::multimap::emplace(3)

💅 std::multimap::emplace(3) 💅

okay bestie, welcome to the C++ Standard Libary manual — yes, that's literally the manual name here, and we're keeping it, no cap. This page is all about std::multimap::emplace, and it's lowkey iconic for constructing stuff directly in place. ✨

🎀 NAME 🎀

std::multimap::emplace - std::multimap::emplace

🌈 Synopsis 🌈

template< class... Args >            (since C++11)
iterator emplace( Args&&... args );

Inserts a new element into the container constructed in-place with the given args. 🫶

The constructor of the new element (i.e. std::pair<const Key, T>) is called with exactly the same arguments as supplied to emplace, forwarded via std::forward<Args>(args)....

Careful use of emplace allows the new element to be constructed while avoiding unnecessary copy or move operations. literally efficiency main character energy. 💅

No iterators or references are invalidated. ngl, that part ate. 🍓

🌸 Parameters 🌸

• args — arguments to forward to the constructor of the element.

💖 Return value 💖

An iterator to the inserted element.

🔥 Exceptions 🔥

If an exception is thrown for any reason, this function has no effect (strong exception safety guarantee).

📈 Complexity 📈

Logarithmic in the size of the container.

🦋 Example 🦋

okay so here's the code, run it and watch the multimap do its thing:

// Run this code

#include <iostream>
#include <string>
#include <utility>
#include <map>

int main()
{
    std::multimap<std::string, std::string> m;

    // uses pair's move constructor
    m.emplace(std::make_pair(std::string("a"), std::string("a")));

    // uses pair's converting move constructor
    m.emplace(std::make_pair("b", "abcd"));

    // uses pair's template constructor
    m.emplace("d", "ddd");

    // emplace with duplicate key
    m.emplace("d", "DDD");

    // uses pair's piecewise constructor
    m.emplace(std::piecewise_construct,
              std::forward_as_tuple("c"),
              std::forward_as_tuple(10, 'c'));

    for (const auto& p : m)
        std::cout << p.first << " => " << p.second << '\n';
}

🍓 Output: 🍓

a => a
b => abcd
c => cccccccccc
d => ddd
d => DDD

👀 See also 👀

• emplace_hint — constructs elements in-place using a hint (C++11) (public member function)
• try_emplace — inserts in-place if the key does not exist, does nothing if the key exists (public member function)
• insert — inserts elements or nodes (since C++17) (public member function)

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and that's the whole page, bestie! 🫶 source: http://cppreference.com · version/date: 2024.06.10 · page: std::multimap::emplace(3) — bye! 💖