std::forwar...assign_range(3)

💖 NAME 💖

std::forward_list::assign_range - std::forward_list::assign_range — yes, that's the NAME line, and it's iconic in its redundancy. This is the std::forwar...assign_range(3) page from the C++ Standard Libary manual, bestie. Buckle up. 🎀

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✨ Synopsis ✨

Okay so this one is since C++23 and it's giving template energy:

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

What it does: replaces elements in the container with a copy of each element in rg. Like, full replacement, no cap. 💅

It invalidates all iterators, pointers and references to the elements. So any iterator, pointer or reference to the old elements is cooked. 💀

Each iterator in the range rg is dereferenced exactly once. One pass, one vibe, no double-dipping. 🦋

⚠️ The behavior is undefined if rg overlaps with the container. Not "undefined-ish", not "maybe fine" — undefined. Do not overlap, bestie. 🙈

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🎀 Parameters 🎀

• rg — an input_range with reference type convertible to the element type of the container. That's the whole parameter, and she's doing her job. 💖

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🌸 Type requirements 🌸

• std::assignable_from<T&, ranges::range_reference_t<R>> must be modeled. Otherwise, the program is ill-formed. Periodt.
• T must be EmplaceConstructible into the container from *ranges::begin(rg). Otherwise, the behavior is undefined. So like, respect the requirements or catch these consequences. 😭

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🦋 Return value 🦋

(none) — she returns nothing. No notes, no receipts, just vibes. 💅

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⭐ Notes ⭐

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

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🔥 Example 🔥

// Run this code

#include <algorithm>
#include <cassert>
#include <forward_list>
#include <list>

int main()
{
    const auto source = std::list{2, 7, 1};
    auto destination = std::forward_list{3, 1, 4};
#ifdef __cpp_lib_containers_ranges
    destination.assign_range(source);
#else
    destination.assign(source.cbegin(), source.cend());
#endif
    assert(std::ranges::equal(source, destination));
}

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👑 See also 👑

• insert_range_after — inserts a range of elements after an element (C++23) (public member function).
• prepend_range — adds a range of elements to the beginning (C++23) (public member function).
• assign — assigns values to the container (public member function).

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Alright bestie, that's the page. Source/version and date, folded into a cute sign-off: http://cppreference.com · 2024.06.10 · std::forwar...assign_range(3). Go forth and assign ranges responsibly. Mwah 💋✨