std::erase_...::multiset)(3)

💖 NAME 💖

okay so this is std::erase_if(std::multiset) — and yes, the NAME line says std::erase_if(std::multiset) again, because it's extra like that 💅. We're in the C++ Standard Libary manual, page std::erase_...::multiset)(3), section 3, and it's giving "erase a bunch of matching elements" energy.

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🎀 Synopsis 🎀

Defined in header <set> ✨

template< class Key, class Compare, class Alloc,

          class Pred >
std::multiset<Key, Compare, Alloc>::size_type         (since C++20)
    erase_if( std::multiset<Key, Compare, Alloc>& c,

              Pred pred );

This bad boy erases every element in c that satisfies the predicate pred — all of them, bestie, not just one. 💅

Equivalent to:

auto old_size = c.size();
for (auto first = c.begin(), last = c.end(); first != last;)
{
    if (pred(*first))
        first = c.erase(first);
    else
        ++first;
}
return old_size - c.size();

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🧚 Parameters 🧚

• c — the container from which to erase 🫶
• pred — the predicate that returns true if the element should be erased 💅

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🦋 Return value 🦋

It returns the number of erased elements. That's the whole return value, no cap. ✨

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🌈 Complexity 🌈

Linear. ⭐

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🍓 Example 🍓

// Run this code — yes bestie, run it:

#include <iostream>
#include <set>

void println(auto rem, auto const& container)
{
    std::cout << rem << '{';
    for (char sep[]{0, ' ', 0}; const auto& item : container)
        std::cout << sep << item, *sep = ',';
    std::cout << "}\n";
}

int main()
{
    std::multiset data{3, 3, 4, 5, 5, 6, 6, 7, 2, 1, 0};
    println("Original:\n", data);

    auto divisible_by_3 = [](auto const& x) { return (x % 3) == 0; };

    const auto count = std::erase_if(data, divisible_by_3);

    println("Erase all items divisible by 3:\n", data);
    std::cout << count << " items erased.\n";
}

💅 Output: 💅

Original:
{0, 1, 2, 3, 3, 4, 5, 5, 6, 6, 7}
Erase all items divisible by 3:
{1, 2, 4, 5, 5, 7}
5 items erased.

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👑 See also 👑

• remove — removes elements satisfying specific criteria 👑
• remove_if — function template 🌈

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that's the whole page, bestie! source/version/date tea: http://cppreference.com 🌸 2024.06.10 🎀 and the page id is std::erase_...::multiset)(3) — byeee! 🫶