std::list::prepend_range(3)

🌸 NAME 🌸

okay bestie, you're on the std::list::prepend_range(3) page from the C++ Standard Libary manual 💅 — yes, that spelling is in the header, we keep it.

std::list::prepend_range - std::list::prepend_range (the NAME line is literally twins, iconic).

🦋 Synopsis 🦋

so the signature is giving:

template< container-compatible-range<T> R >  (since C++23)
void prepend_range( R&& rg );

What it does: inserts, in non-reversing order, copies of elements in rg before begin(). Each iterator in the range rg is dereferenced exactly once.

No iterators or references are invalidated. periodt.

💖 Parameters 💖

• rg — a container compatible range, that is, an input_range whose elements are convertible to T.

✨ Type requirements ✨

• T must be EmplaceConstructible into list from *ranges::begin(rg).

⚠️ Otherwise, the behavior is undefined — not a vibe, bestie. Do not test fate.

🎀 Return value 🎀

(none) — literally nothing comes back. it's giving void, and that's fine 💖

🔥 Complexity 🔥

Linear in size of rg. so yeah, it scales with the range, no surprises.

💅 Notes 💅

Feature-test macro tea 💅:

• Feature-test macro: __cpp_lib_containers_ranges
• Value: 202202L
• Std: (C++23)
• Feature: Ranges-aware construction and insertion

🌈 Example 🌈

// Run this code

#include <algorithm>
#include <cassert>
#include <list>
#include <vector>

int main()
{
    auto container = std::list{0, 1, 2, 3};
    const auto rg = std::vector{-3, -2, -1};

#if __cpp_lib_containers_ranges
    container.prepend_range(rg);
#else
    container.insert(container.begin(), rg.cbegin(), rg.cend());
#endif
    assert(std::ranges::equal(container, std::list{-3, -2, -1, 0, 1, 2, 3}));
}

👑 See also 👑

• append_range — adds a range of elements to the end; (C++23); public member function.
• insert_range — inserts a range of elements; (C++23); public member function.
• push_front — inserts an element to the beginning; public member function.
• emplace_front — constructs an element in-place at the beginning; (C++11); public member function.

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later, bestie 🫶 — source/version/date: http://cppreference.com · 2024.06.10 · std::list::prepend_range(3).