P2988 R9 std::optional<T&>

[wg21bot]

P2988R0 std::optional<T&> (Steve Downey)

[inbal2l]

2024-01-02 Library Evolution Telecon

P2988R0: std::optional<T&>

2024-01-02 Library Evolution Telecon Minutes

Champion: Steve Downey

Chair: Billy Baker

Minute Taker: Ben Craig

Summary

References mentioned during the discussion:
references mentioned above:

1. https://thephd.dev/to-bind-and-loose-a-reference-optional
2. https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p2070r0.pdf
3. https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1175r0.html

The author will explore and add information on:

1. Explore compiler failure vs. compiler error for assignment op
2. Add references to analysis of the discussion of “Assign-through” optional direction, and the “Rebind” optional direction (https://wg21.link/p1683r0)
3. Consider a separate name then std::optional to the "ref" version?
4. Explore named function for separating between the cases above.
5. Add a feature test macro.
6. Explore and add examples for "const" behaviour.

No polls were taken.

Next Steps

The room was generally supportive of the proposal but would like the author to come back with more rationale for the (already settled) design decisions and further exploration of the open topics mentioned above.
Ville and Barry volunteered to help the author.
We will see the paper again in LEWG.

[wg21bot]

P2988R1 std::optional<T&> (Steve Downey, Peter Sommerlad)

[wg21bot]

P2988R3 std::optional<T&> (Steve Downey, Peter Sommerlad)

[wg21bot]

P2988R5 std::optional<T&> (Steve Downey, Peter Sommerlad)

[wg21bot]

P2988R6 std::optional<T&> (Steve Downey, Peter Sommerlad)

[inbal2l]

2024-09-03 Library Evolution Telecon

P2988R6 std::optional<T&>

2024-09-03 Library Evolution Telecon Minutes

Champion: Steve Downey
Chair: Inbal Levi
Minute Taker: Eddie Nolan

Summary

POLL: We’re happy with the behaviour “P2988R6: std::optional <T&>” which leave the behaviour of make_optional<T&> as currently is in the standard (return optional<T> or in some cases it being ill-formed)

Attendance: 20
Outcome: No objection to unanimous consent

Next Steps

We will continue the review of R6 of the paper during the next telecon.

[FabioFracassi]

2024-09-10 Library Evolution Telecon

P2988R6: std::optional<T&>

2024-09-10 Library Evolution Telecon Minutes

Champion: Steve Downey
Chair: Fabio Fracassi
Minute Taker: Mark Hoemmen

Summary

Paper Forwarding Checklist

Checklist
Why should this utility go into the standard library?	extention of standard type
Examples?	yes
Discussion of prior art?	yes, extensive
Implementation experience?	yes
Usage experience?	yes, e.g. through boost
Deployment experience?	no
Performance considerations?	yes
Changes Library Evolution previously requested?	yes
Support in "std::format" and "hash" (if required)?	n/a
Feature test macro?	yes
Freestanding?	yes
Constexpr?	yes
Wording?	yes

ACTION: Strike =T from ctor and assignment:
template <class U = T> constexpr explicit(see below) optional(U&& u) noexcept;

POLL: Add optional& constructor and assigment
(allowing to to construct opt<int&> from opt<int>
(opt<int const&> from opt<int> already works)).

SF	F	N	A	SA
4	4	0	0	0

Attendance: 15
# of Authors: 1
Author's Position: SF
Outcome: Consensus in favour

POLL: We approve of the design in P2988R7 with the added optional& constructor and assignment operator.

SF	F	N	A	SA
5	4	0	0	0

Attendance: 15
# of Authors: 1
Author Position: SF
Outcome: Consensus in favour

Next Steps

Design is approved. We will look at the updated wording in a future meeting, with the goal to forward to LWG.

[wg21bot]

P2988R7 std::optional<T&> (Steve Downey, Peter Sommerlad)

[wg21bot]

P2988R8 std::optional<T&> (Steve Downey, Peter Sommerlad)

[wg21bot]

P2988R9 std::optional<T&> (Steve Downey, Peter Sommerlad)