P2846 R6 reserve_hint: Eagerly reserving memory for not-quite-sized lazy ranges

[wg21bot]

P2846R0 size_hint: Eagerly reserving memory for not-quite-sized lazy ranges (Corentin Jabot)

[inbal2l]

SG9 (Ranges) reviewed P846R0 during the Varna meeting on 2023-06-12 (Full Minutes).

Polls

POLL: The standard needs to clearly define where size_hint should be called

SF	F	N	A	SA
0	2	0	3	2

Outcome: Weak consensus against

# Of Authors: 1

Author’s Position: WF

Attendance: 9

WF: We’re unsure what’s the recommendation (both said “very weakly in favor”)

SA: Performance hints should be hints

POLL: Prefer approximate_size over size_hint (for consistency with the concept name, approximately_sized_range)

F	N	A
3	2	2

Outcome: No consensus

# Of Authors: 1

Author’s Position: F

Attendance: 9

POLL: Modify the paper to include suggested guidance, make sized_range to subsume approximately_sized_range (assuming non breaking change), and forward “P2846R0: size_hint: Eagerly reserving memory for not-quite-sized lazy ranges” to LEWG for C++26.

SF	F	N	A	SA
3	3	1	0	0

Attendance: 9

# of Authors: 1

Author Position: SF

Outcome: Strong Consensus in Favour

Summary

The paper needs to apply the following updates:

1. Capture the implementation options (includes: mandating a call to size_hint (taking side effects into consideration), defining loosened requirements without mandating the use, or allowing implementations to ignore size_hint) - to be determined by LEWG
2. rename size_hint to: approximately_sized_range

And move the revised paper to LEWG for C++26

[wg21bot]

P2846R1 size_hint: Eagerly reserving memory for not-quite-sized lazy ranges (Corentin Jabot)