std::flat_map::replace(3)

💅 std::flat_map::replace(3) 💅

okay so bestie, welcome to the C++ Standard Libary page for std::flat_map::replace — yes the manual name is literally "C++ Standard Libary" (not a typo, that's just how it's spelled in the header, iykyk). this one's a member function that lets you swap out the whole underlying container situation in one move. no cap, it's giving main character energy for flat_map. ✨

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📛 NAME 📛

std::flat_map::replace — literally just std::flat_map::replace. that's the name. periodt. 💅

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✨ Synopsis ✨

the squad's signature, since C++23, fr fr:

void replace( key_container_type&& key_cont, mapped_container_type&& mapped_cont );

so what does it do? it replaces the underlying containers c. equivalent to this little move-move situation:

c.keys = std::move(key_cont);
c.values = std::move(mapped_cont);

but like, you gotta meet these conditions or it's a whole mess:

• the expression key_cont.size() == mapped_cont.size() is true (sizes gotta match, no cap)
• the elements of key_cont are sorted with respect to compare (sorted, bestie, sorted)
• key_cont does not contain equal elements (no duplicates, we don't do that here)

⚠️ Otherwise, the behavior is undefined. like, undefined undefined. don't play with this. 💀

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🎀 Parameters 🎀

• keys_cont — a sorted keys container of type KeyContainer, the contents of which will be moved into *this. it's the key VIP, literally. 🔑
• mapped_cont — a container of mapped values of type MappedContainer, the contents of which will be moved into *this. the plus-one to the key container, they're a package deal. 🫶

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🌸 Return value 🌸

(none). it's void, bestie. it does the thing and dips. no return, no drama. 🙈

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🦋 Complexity 🦋

equals to complexity of std::move applied to adapted containers. that's it. that's the tea. ☕

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🔥 Example 🔥

run this code, it's iconic:

#include <algorithm>
#include <cassert>
#include <flat_map>
#include <print>
#include <vector>

int main()
{
    std::vector<int> keys{1, 2, 3};
    assert(std::ranges::is_sorted(keys));
    std::vector<double> values{2.2, 3.3, 1.1};
    assert(keys.size() == values.size());

    std::flat_map<int, double> map;
    assert(map.empty());

    map.replace(keys, values);
    assert(map.size() == 3);
    assert(map.keys() == 3);
    assert(map.values() == 3);
    assert(keys.empty());
    assert(values.empty());

    std::println("{}", map);
}

Output:

{1: 2.2, 2: 3.3, 3: 1.1}

and that's on periodt. the map ate and left no crumbs. 💅🔥

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👑 See also 👑

• extract — extracts the underlying containers (public member function). it's the sibling function, also a vibe. go check it out. 🌈

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okay bestie, that's the whole page. we got the header info ("C++ Standard Libary" manual, the source is http://cppreference.com, version 2024.06.10, date 2024.06.10, and the page is std::flat_map::replace(3)). now go slay your flat_map containers. mwah. 💖✨🎀