std::priori...ue::emplace(3)

💅 NAME

std::priority_queue::emplace — like, the emplace of std::priority_queue, bestie 💖

(okay so this page lives in the C++ Standard Libary manual — yes, that's their spelling up top, not mine, don't come for me 🙈 — and it's the std::priori...ue::emplace(3) page, the title got cutely truncated by the header, love that for it ✨)

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✨ SYNOPSIS ✨

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

Okay so real talk: this bad boy pushes a new element to the priority queue. And the way it does it? The element is constructed in-place, which literally means no copy or move operations are performed — none, zero, nada 🌸. The constructor of the element gets called with exactly the same arguments you handed to the function, so it's giving "build it right where it lives" main character energy 👑

Effectively calls — i.e. under the hood it's doing this exact thing:

c.emplace_back(std::forward<Args>(args)...);
std::push_heap(c.begin(), c.end(), comp);

Slay. That's the whole magic trick 🎀

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🎀 PARAMETERS

• args — the arguments to forward to the constructor of the element. Like, you're basically handing the element's constructor its little starter pack 🫶

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🌸 RETURN VALUE

(none) — nothing, nope, void, she returns nothing and honestly? iconic 😌

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🦋 COMPLEXITY

Logarithmic number of comparisons 🔥 — plus the complexity of Container::emplace_back, so budget for that too, iykyk.

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🍓 EXAMPLE

// Run this code

#include <iostream>
#include <queue>

struct S
{
    int id;

    S(int i, double d, std::string s) : id{i}
    {
        std::cout << "S::S(" << i << ", " << d << ", \"" << s << "\");\n";
    }
    friend bool operator< (S const& x, S const& y) { return x.id < y.id; }
};

int main()
{
    std::priority_queue<S> queue;
    queue.emplace(42, 3.14, "C++");
    std::cout << "id: " << queue.top().id << '\n';
}

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🔥 OUTPUT

S::S(42, 3.14, "C++")
id = 42

That's literally what the page says, I'm just the messenger 🙈💀

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🫶 SEE ALSO

• push — inserts element and sorts the underlying container (public member function)
• pop — removes the top element (public member function)

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okay that's the whole page bestie, you ate that 🍓 source is http://cppreference.com, dated 2024.06.10 — mwah, go forth and emplace responsibly 💜✨🧚