FR-014-021 26.6 [range.factories] Add `views::enumerate`

[wg21bot]

Despite great new additions to the set of views available to c++23, a very fundamental facility, the ability to get an indexed range of value is missing. This often forces to use a raw loop, and the combination of zip + iota is not always correct and is more cumbersome that it should be for such a ubiquitous primitive.

Please consider adopting P2164 views::enumerate in C++23.

[brycelelbach]

Duplicate of #525

[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 would prefer the tuple solution for “P2164: views::enumerate” (which is the safer way).

SF	F	N	A	SA
7	5	0	0	0

Attendance: 15 (on-site 11, online 4)

# of Authors: 1

Author’s position: F

Outcome: Strong consensus in favor

POLL: We support applying the resolution of “FR#416: FR-014-021 26.6 (range.factories) Add views::enumerate (duplicate: US#525)”, and forward “P2164: views::enumerate” to C++23 with the proposed resolution.

SF	F	N	A	SA
4	5	0	1	0

Attendance: 15: 4 11

# of Authors: 1

Author’s position: SF

Outcome: Consensus in favor

A: Oppose to adding features by NB comments

Summary

The author has presented the paper. There was a design question - whether we want tuple (which was implemented and is the simpler solution) or an aggregate (which was not implemented, and expected to have difficulty in implementation). SG9 voted for tuple (the verified solution).

SG9 supports the resolution proposed in the NB comment - adopting P2164 to C++23 (with the design guidance - use tuple and not aggregate). Will be passed for LEWG's final decision.

The issue was forwarded to LEWG.

[inbal2l]

LEWG has discussed the topic in the Kona meeting (full minute will be updated).

Polls

POLL: We want the “aggregate” solution over the “tuple” solution for “P2164: views::enumerate”

SF	F	N	A	SA
1	2	2	6	8

Attendance: 25 (20 on-site, 5 online)

# of Authors: 1xSA

Author Position: Consensus against

POLL: Apply the resolution of NB comment: “FR#416: FR-014-021 26.6 (range.factories) Add views::enumerate” (duplicate of: “US 48-108 26 [ranges] Add views::enumerate”) (issue: https://github.com/cplusplus/nbballot/issues/416) for C++23

SF	F	N	A	SA
6	10	0	2	2

Attendance: 25 (20 on-site, 5 online)

# of Authors: 1xSF

Author Position: Consensus in favor

Summary

LEWG accepted the resolution proposed in the NB comments and supports forwarding "P2164 views::enumerate" for C++23

[jensmaurer]

Removing the SG9 label.

[jensmaurer]

Accepted.