std::map::clear(3)

hii bestie 💖 you just opened the std::map::clear page from the C++ Standard Libary (yes, “Libary” — that’s literally how the header spells it, and we respect the typo 💀). it’s manual-page time, but make it cute.

✨ NAME ✨

std::map::clear — std::map::clear. that’s the name. that’s it. iconic minimalism 💅

🦋 Synopsis 🦋

void clear();  (noexcept since C++11)

okay so what does it actually do? it erases all elements from the container 🧹✨. after this call, size() returns zero — like, completely empty, not a single element left. bye bestie 👋

and heads up: it invalidates any references, pointers, and iterators referring to contained elements 😭. but the good news? any past-the-end iterator remains valid 🫶.

🌸 Parameters 🌸

(none) — nothing to pass in. zero. nada. it’s a no-argument situation 🫶.

🎀 Return value 🎀

(none) — it doesn’t hand anything back, it just clears and dips ✨.

⭐ Complexity ⭐

Linear in the size of the container, i.e., the number of elements. so the more stuff you’re clearing, the more work it does. periodt.

🔥 Example 🔥

the original page says // Run this code — so go off, run it bestie 💅

#include <iostream>
#include <string_view>
#include <map>

void print_info(std::string_view rem, const std::map<int, char>& v)
{
    std::cout << rem << "{ ";
    for (const auto& [key, value] : v)
        std::cout << '[' << key << "]:" << value << ' ';
    std::cout << "}\n";
    std::cout << "Size=" << v.size() << '\n';
}

int main()
{
    std::map<int, char> container{{1, 'x'}, {2, 'y'}, {3, 'z'}};
    print_info("Before clear: ", container);
    container.clear();
    print_info("After clear: ", container);
}

🌈 Output 🌈

Before clear: { [1]:x [2]:y [3]:z }
Size=3
After clear: { }
Size=0

💀 Defect reports 💀

The following behavior-changing defect reports were applied retroactively to previously published C++ standards. (retroactively!! the committee really said “we’ll fix it later” and honestly same 🙈)

• DR LWG 224
• Applied to C++98
• Behavior as published the complexity was log(size()) + N, but N was not defined
• Correct behavior corrected to 'linear in size()'

👑 See also 👑

• erase — erases elements (public member function).

mwah 💋 this masterpiece lives at http://cppreference.com and is dated 2024.06.10. now go clear that map, bestie — you’re literally gonna slay 🫶✨