std::flat_multimap::empty(3)

💅 std::flat_multimap::empty(3) — C++ Standard Library, bestie edition

okay so real talk, this page is from the C++ Standard Library manual (section 3, bestie, we're in the big leagues ✨) and it's literally about one tiny little function that answers one tiny little question: is my flat_multimap empty or not? that's it. that's the whole vibe check. 🫶

---

🌸 NAME 🌸

std::flat_multimap::empty — and yes bestie, the name of the function is literally std::flat_multimap::empty, no notes, iconic behavior, it does exactly what it says on the tin 💅

---

✨ Synopsis ✨

here's the signature, copy it exactly, do not freestyle it:

[[nodiscard]] bool empty() const noexcept;  (since C++23)

so what does it do? it checks if the underlying containers have no elements. like, zero. nada. empty empty. 🕳️

and it's equivalent to this:

return begin()

== end();

(yeah the original page line-wraps it like that, it's giving "my code got squished by the terminal" energy 😭 but that's the equivalence: return begin() == end();)

also note that [[nodiscard]] — the compiler will side-eye you HARD if you call this and just throw away the answer. don't do that. it's rude. 💀

---

🎀 Parameters 🎀

(none)

zero parameters. no args, no drama, she takes nothing and she gives everything. 👑

---

🦋 Return value 🦋

• true if the underlying containers are empty
• false otherwise

that's it. binary. black and white. no nuance, no "it depends", no <italic>maybe</italic>. 😌

---

🌈 Complexity 🌈

Constant. ⚡

like, instant. no loops, no scanning, no "let me think about it". just vibes and a comparison. ate and left no crumbs. 🔥

---

🍓 Example 🍓

the original page says: the following code uses empty to check if a std::flat_multimap<int, int> contains any elements. and honestly? great use of the function, 10/10, no notes.

// Run this code

#include <iostream>
#include <flat_map>
#include <utility>

int main()
{
    std::flat_multimap<int,int> numbers;
    std::cout << std::boolalpha;
    std::cout << "Initially, numbers.empty(): " << numbers.empty() << '\n';

    numbers.emplace(42, 13);
    numbers.insert(std::make_pair(13317, 123));
    std::cout << "After adding elements, numbers.empty(): " << numbers.empty() << '\n';
}

bestie look at those numbers though — 42, 13, 13317, 123 — someone was having fun in the test suite and i respect it 😭💖

and notice the std::boolalpha — that's the little sprinkle that makes true/false print as actual words instead of 1/0. we love a readable output. ✨

---

🧚 Output 🧚

Initially, numbers.empty(): true
After adding elements, numbers.empty(): false

she starts empty, she gets some elements shoved in via emplace and insert, and then she's not empty anymore. character development. 👑

---

💜 See also 💜

• size — returns the number of elements (public member function)
• empty — checks whether the container is empty (C++17) (function template)

iykyk, size is the "how many" girlie and empty is the "any at all?" girlie. two different questions, both valid, both slaying. 💅

---

ngl if you're calling empty() and then immediately calling size() to check if it's 0... bestie. that's the same question twice. pick a lane. 🫶

---

and that's the page!! source is cppreference.com, dated 2024.06.10 — go drink some water, go compile something with -std=c++23, and remember: [[nodiscard]] is not a suggestion, it's a lifestyle. mwah 💋✨🎀