P3019 R12 Vocabulary Types for Composite Class Design

[wg21bot]

P3019R0 Vocabulary Types for Composite Class Design (Jonathan Coe, Antony Peacock, Sean Parent)

[jbcoe]

Draft and reference implementation at https://github.com/jbcoe/value_types

[ben-craig]

Library Evolution Meeting Kona 2023-11-08

P3019R1: Vocabulary Types for Composite Class Design

2023-11-08 Library Evolution Kona Minutes

Champion: Jonathan Coe

Chair: Inbal Levi / Billy Baker

Minute Taker: Eddie Nolan, Andreas Weis

Summary

POLL: Add "operator()", "operator[]" to the proposed classes.

SF	F	N	A	SA
0	0	10	4	5

Attendance: 19 IP + 8 R

# of Authors: 2

Authors’ position: 1 SA 1 WA

Outcome: Consensus Agains

POLL: Add "emplace" to the proposed classes.

SF	F	N	A	SA
0	1	1	11	6

Attendance: 19 IP + 8 R

# of Authors: 2

Authors’ position: 2xA

Outcome: Consensus Against

Favor: Have to spell the type if emplace is not there.

POLL: We want to support types that have comparison operators incompatible with regularity

SF	F	N	A	SA
0	9	5	2	2

Attendance: 19 IP + 8 R

# of Authors: 2

Authors’ position: 2x WF

Outcome: Not consensus for a change

IL: We need to take the following poll next meeting (POLL: Remove "noexcept" from all the functions apart from *, ->, move CTOR, and move assignment)

Next Steps

The paper made progress. Authors are to provide a new revision which will be seen again during the Kona meeting.

Library Evolution Meeting Kona 2023-11-10

P3019R02: Vocabulary Types for Composite Class Design

2023-11-10 Library Evolution Kona Minutes

Champion: Jonathan Coe

Chair: Ben Craig, Inbal Levi

Minute Taker: Eddie Nolan, Andreas Weis

Summary

POLL: Remove preconditions for move, copy, swap, move assign, assign, comparisons, and std::hash for indirect and polymorphic_value as appropriate.

Strongly Favor	Weakly Favor	Neutral	Weakly Against	Strongly Against
3	5	0	8	10

Attendance: 32 IP + 6 R
# of Authors: 2
Author Position: 2xSA
Outcome: Weak consensus against

POLL: Require T of polymorphic to be a polymorphic base class (which will prevent the template parameter from being an incomplete type)_

Strongly Favor	Weakly Favor	Neutral	Weakly Against	Strongly Against
1	0	4	6	17

Attendance: 31 IP + 4 R
# of Authors: 2
Author Position: 2XSA
Outcome: Strong consensus against

SF: Seems we love polymorphic<int> too much

POLL: Approve design of P3019R2 (Vocabulary Types for Composite Class Design), except ensure the swap noexcept specification matches std::vector and remove the std::optional specialization.

Strongly Favor	Weakly Favor	Neutral	Weakly Against	Strongly Against
10	12	2	2	0

Attendance: 32 IP + 4 R
# of Authors: 2
Author Position: 2xSF
Outcome: Strong Consensus in favor

WA: Can't vote in favor of the approach that makes the valueless state unsafe

Next Steps

The design was approved with the proposed changes in the polls. Minor fixes are still required, authors will work on this and present the change log at the next meeting.

The paper wording and final design will be reviewed in a telecon.

[inbal2l]

Library Evolution Telecon 2023-11-21

P3019R3: Vocabulary Types for Composite Class Design

2023-11-21 Library Evolution Telecon

Champion: Jonathan Coe
Chair: Inbal Levi
Minute Taker: Ben Craig

Summary

We covered change log for R3 (and before). We will see the paper again with the resolution for the topics:

• Investigate “valueless” state, include suggestions on what are the alternatives for handling “valueless” (apart from the approach in the paper) and come back to LEWG with a resolution (options are: allow moving “valueless”, assignment operator, etc.)
• Explore: Comparison operators of “indirect” should return “bool” vs. comparison operator of “indirect” should return what the underlying type does (and regularity).

Next meeting we should also discuss on the topics (and weather they can be added later):

• Should there be a make_indirect?
• providing nontype constructors as alternatives to allocator_tag constructors

POLL: Investigate “explicitness” of the CTORS for “indirect” and “polymorphic”, and come back to LEWG with a resolution.

SF	F	N	A	SA
3	1	5	7	1

Outcome: Weak consensus against (no need for additional exploration from the authors)
# of Authors: 2
Authors’ position: 2xN
Attendance: 30

POLL: Indirect should accept any T which is Cpp17Destructible (relax the restrictions in the paper, to allow int, union and function pointers).

SF	F	N	A	SA
4	11	2	0	0

Outcome: Consensus in favor
# of Authors: 2
Authors’ position: 2xF
Attendance: 30

Next Steps

Once we have a detailed reasoning for the course of action for "valueless state”, send the paper to SG23. Come back to LEWG with an investigation of the topics above.

Please reach out to authors between meetings. If no major topic comes up, the next meeting should be devoted to wording review.

[wg21bot]

P3019R1 Vocabulary Types for Composite Class Design (Jonathan Coe, Antony Peacock, Sean Parent)

[wg21bot]

P3019R2 Vocabulary Types for Composite Class Design (Jonathan Coe, Antony Peacock, Sean Parent)

[wg21bot]

P3019R3 Vocabulary Types for Composite Class Design (Jonathan Coe, Antony Peacock, Sean Parent)

[wg21bot]

P3019R8 Vocabulary Types for Composite Class Design (Jonathan Coe, Antony Peacock, Sean Parent)

[wg21bot]

P3019R9 Vocabulary Types for Composite Class Design (Jonathan Coe, Antony Peacock, Sean Parent)

[wg21bot]

P3019R10 Vocabulary Types for Composite Class Design (Jonathan Coe, Antony Peacock, Sean Parent)

[bstamour]

LWG looked at this paper in Wroclaw on Wednesday. Meeting minutes: https://wiki.edg.com/bin/view/Wg21wroclaw2024/LWG20241120-P3019ea

[bstamour]

LWG polled this paper in Wroclaw on Friday: Poll: put p3019r11 (as reviewed by JG and JW) into C++26?

|F|A|N|
|9|0|1|

[jensmaurer]

The Project Editor has decided, after consultation with the LWG chair, that the paper is sufficiently unclear to be applied in its present form. See cplusplus/draft#7429 for details.

Removing the "plenary-approved" tag so that LWG can have another look.

[jbcoe]

I’ll work on a revised P3019r12 which will need to go back to LEWG to address some changes to constraints/mandates.

[wg21bot]

P3019R11 Vocabulary Types for Composite Class Design (Jonathan Coe, Antony Peacock, Sean Parent)

[wg21bot]

P3019R12 Vocabulary Types for Composite Class Design (Jonathan Coe, Antony Peacock, Sean Parent)