FR-013-020 26.6.5 [range.repeat] Replace `repeat` with `cycle`

[wg21bot]

ranges::repeat produces a range of a value repeated n times. While useful, this is not as generic as a range that would repeat a given range n time. There is extensive standard practice for such a view, such as range-v3's cycle_view. in the presence of cycle_view, repeat could just be single(value)| cycle(n)?

Please consider standardising a cycle view to cycle n times over a range, such that repeat can be respecified in terms of cycle_view

[brycelelbach]

This needs a paper before it can be considered properly.

[inbal2l]

Scheduled for SG9's meeting in Kona, second session (10:00-11:30): https://wiki.edg.com/bin/view/Wg21kona2022/SG9

[inbal2l]

Reviewed by SG9 at Kona2022 meeting (Full Minutes).

Polls

__POLL: We support applying the resolution of “FR#415: FR-013-020 26.6.5 (range.repeat) Replace ranges::repeat with cycle_view (duplicate: US#528)”, specify “repeat” in terms of cycle_view (cycle_view will require a paper)__

SF	F	N	A	SA
0	0	0	0	9

Attendance: 14 (on-site 7, online 7)

# of Authors: 0

Author’s position: n/a

Outcome: Strong consensus against

Summary

SG9 sees repeat as a separate utility than cycle (both desired), therefore does not support the proposed resolution.

The issue was forwarded to LEWG.

[brycelelbach]

2022-11-11 10:00 to 11:30 UTC-10 Kona Library Evolution Meeting

FR-013-020: Replace repeat with cycle

2022-11-11 10:00 to 11:30 UTC-10 Kona Library Evolution Minutes

Champion: Corentin Jabot (in-person)

Chair: Bryce Adelstein Lelbach & Robert Leahy

Minute Taker: Steve Downey

Start: 2022-11-11 10:56 UTC-10

We could express repeat as cycle, but there might be a performance cost to doing that.

POLL: Reject FR-013-020 (Replace repeat with cycle), to be confirmed by a Library Evolution electronic poll.

Strongly Favor	Weakly Favor	Neutral	Weakly Against	Strongly Against
6	12	0	0	0

Attendance: 16 (in-person) + 3 (remote)

# of Authors: 2

Author Position: 2xSF

Outcome: Unanimous consensus in favor.

End: 11:08

Summary

Two NB comments suggested that repeat could be expressed as cycle (which is not in C++ today). While this is indeed possible, since the filing of the NB comments the authors learned that there is a performance cost to doing so. Also, we do not have a proposal for cycle on hand, and even if we did, it would be challenging to add it this late. We had consensus to reject these NB comments.

Next Steps

Take an electronic poll to reject FR-013-020 (Replace repeat with cycle) and any duplicate comments, to be confirmed by a Library Evolution electronic poll.

[brycelelbach]

2022-11 Library Evolution Electronic Poll Outcomes

Poll 1.5: Reject C++23 National Body comment FR-013-020 Replace repeat With cycle and any duplicate comments.

Strongly Favor	Weakly Favor	Neutral	Weakly Against	Strongly Against
15	6	2	0	0

Outcome: Strong consensus in favor.

[jensmaurer]

Rejected. There was no consensus for a change.