P2165R1 Compatibility between tuple and tuple-like objects (Corentin Jabot)

Review summary:
Topics to be addressed in a future revision:

1. A request for additional clarification for the motivation - why does comparing a pair to a tuple desirable.
   The question of defining which types will be supported in more detail was raised.
   Comments include:

• use of T<UT...> as a parameter in the constructors rejects types with non-type template parameters, including std::array.

• Paper should address tuple<int, double> constructible from ptr_tuple<int, double> (will not compile).

  Author's replay: Some of the types were considered and support requires complex additions. I agree this needs to be stated explicitly in the paper.

2. A request to explore in more detail information regarding the implementation experience and expected implications.
   Comments include:

• Is the proposal implementable with backward support (and is it needed).
• Does the implementation pass the existing tests for tuple in a stdlib implementation.

Waiting for next Revision.

P2165R2 Compatibility between tuple, pair and tuple-like objects (Corentin Jabot)

Was seen by SG9 on 2021-09-23 (Minutes)

Polls

POLL: We like the direction of P2165R2 and encourage more work.

Outcome: Weak consensus in favor

Attendance: 9

IL: Please notice that encouraging of more work is easy (for the group) and is the default for most papers

Summary

Author asked for guidance, this will also effect P2164R5: views::enumerate

Few topics came up during the discussion:

• There were some concerns around dealing with the tuple-pair problems in the standard lib (breaking code / limiting users' ability on user-defined types, etc.)
• A request to consider design alternatives to the tuple-like concept proposed (for example - always convert to tuples)
• Consider the idea of supporting tuple only in new facilities (for example - zip)

Paper P2165R3 Was seen by SG9 on Dec 20th, 2021 (Minutes).
Forwarded to LEWG, with the request that the author will add more implementation info before it reaches LEWG's telecon (tentatively scheduled for Jan 4th, 2022).

Polls

Poll: Forward “D2165R3: Compatibility between tuple, pair and tuple-like objects” to LEWG for C++23.

Attendance: 13

Author(s) position: SF

Outcome: Consensus in favor

A: Needs more implementation experience.

Summery

SG9 has some concerns about breaking the current usage of tuple and pair (for example in conversion)
DR3 was forwarded, with a request to add the following changes:

• A table of content
• A feature test macro
• Preferably, wider implementation experience

P2165R3 Compatibility between tuple, pair and tuple-like objects (Corentin Jabot)

2022-01-18 Library Evolution Telecon

P2163R3: Compatibility between tuple and tuple-like objects

2022-01-18 Library Evolution Telecon Minutes

Chair: Bryce Adelstein Lelbach

Champion: Corentin Jabot

Minute Taker: Inbal Levi

Start: 2022-01-18 12:09 Eastern

Does this proposal have:

• Examples?
  • Yes.
• Implementation experience?
  • Yes, in a fork of libstdc++, with all tests passing in C++20 mode.
• Usage experience?
  • No.
• Deployment experience?
  • No.
• Performance considerations?
  • N/A.
• Discussion of prior art?
  • Yes.
• Changes Library Evolution previously requested?
  • N/A.
• Wording?
  • Yes.
• Feature test macro?
  • Yes.

POLL: Send P2165R3 (Compatibility between tuple and tuple-like objects) to LWG for C++23 classified as an improvement (priority B2), to be confirmed with a Library Evolution electronic poll.

Attendance: 22

# of Authors: 1

Author Position: 1xSF

Outcome: Strong consensus in favor.

End: 12:22

Outcome

Send P2165R3 (Compatibility between tuple and tuple-like objects) to LWG for C++23 classified as an improvement (priority B2), to be confirmed with a Library Evolution electronic poll.

2022-01 Library Evolution Electronic Poll Outcomes

Send [P2165R3] (Compatibility Between tuple, pair, And tuple-Like Objects) to Library Working Group for C++23, classified as an improvement of an existing feature ([P0592R4] bucket 2 item)

Consensus in favor.

P2165R4 Compatibility between tuple, pair and tuple-like objects (Corentin Jabot)

This has been applied.

For the record, D2165R4 was reviewed by LWG in the 2022-07-15 telecon with a poll "Include P2165r4 into C++23?" The result was 12 in favour, 0 against, 0 neutral.