Adjoints to "Enabling list-initialization for algorithms": find_last (original) (raw)

Published Proposal, 2024-03-31

Author:

Audience:

LWG, LEWG

Project:

ISO/IEC 14882 Programming Languages — C++, ISO/IEC JTC1/SC22/WG21

Abstract

We extend the same changes that [P2248R8] applied to the rest of the find algorithms to std::ranges::find_last.

Table of Contents

  1. 1 Changelog
  2. 2 Motivation and scope
  3. 3 Proposed Wording
  4. 4 Acknowledgements
  5. References
    1. Informative References

1. Changelog

2. Motivation and scope

In the Tokyo 2024 meeting [P2248R8] was adopted. Due to an oversight (which is entirely our fault) std::ranges::find_last was accidentally excluded from the algorithms for which a default template type parameter for the "value" argument was provided.

We propose to modify find_last’s specification, so that it matches the post-P2248 one for the rest of the algorithms (especially find).

3. Proposed Wording

All the proposed changes are relative to [N4971], assuming that [P2248R8]'s wording has been merged already.

Modify [alg.find.last] as shown:

template<forward_iterator I, sentinel_for S, class T, class Proj = identity, class T = projected_value_t<I, Proj>> requires indirect_binary_predicate<ranges::equal_to, projected<I, Proj>, const T*> constexpr subrange ranges::find_last(I first, S last, const T& value, Proj proj = {});

template<forward_range R, class T, class Proj = identity, class T = projected_value_t<iterator_t, Proj>> requires indirect_binary_predicate<ranges::equal_to, projected<iterator_t, Proj>, const T*> constexpr borrowed_subrange_t ranges::find_last(R&& r, const T& value, Proj proj = {});

4. Acknowledgements

Thanks to Jens Maurer for pointing out this oversight of [P2248R8].

Thanks to KDAB for supporting this work.

All remaining errors are ours and ours only.

References

Informative References

[N4971]

Thomas Köppe. Working Draft, Programming Languages — C++. 18 December 2023. URL: https://wg21.link/n4971

[P2248R8]

Giuseppe D'Angelo. Enabling list-initialization for algorithms. URL: https://isocpp.org/files/papers/P2248R8.html