P3732 R2 Numeric Range Algorithms

[wg21bot]

P3732R0 Numeric Range Algorithms (Ruslan Arutyunyan, Mark Hoemmen, Alexey Kukanov, Bryce Adelstein Lelbach, Abhilash Majumder)

[wg21bot]

P3732R1 Numeric Range Algorithms (Ruslan Arutyunyan, Mark Hoemmen, Alexey Kukanov, Bryce Adelstein Lelbach, Abhilash Majumder)

[rarutyun]

P3732R1 "Numeric Range Algorithms" _into optimization is valuable.

SF	F	N	A	SA
4	5	0	0	0

Unanimous Consent.
Attendance: 11

P3732R1 "Numeric Range Algorithms" operator identity optimization is valuable.

SF	F	N	A	SA
3	6	0	0	0

Unanimous Consent.
Attendance: 11

[foonathan]

We discussed this in SG9 in Kona on Thursday: https://wiki.edg.com/bin/view/Wg21kona2025/NotesSG9P3732R1

We want reduce(in, init, [](auto lhs, auto rhs) { ... }) to work without providing an identity for the binary operation. The algorithm then doesn't use an identity.

No objection to unanimous consent.
Attendance: 8

We want reduce(in, init, std::ranges::plus{}) (or multiplies, etc.) to work using the natural identity of the operation whenever that is possible (at least for built-in types, possible more in a TBD mechanism) (by augmenting the definition of the standard library function objects with the identity somehow).

No objection to unanimous consent.
Attendance: 8

To associate an ad-hoc lambda with an identity, we prefer the option reduce(in, init, binary_operation([](auto lhs, auto rhs) { ... }, identity)) over the options reduce(in, init, [](auto lhs, auto rhs) { ... }, op_identity(identity)) or reduce(in, init, [](auto lhs, auto rhs) { ... }, identity).

SF	F	N	A	SA
4	3	0	0	0

Unanimous consensus in favor.
Author: 2xSF
Attendance: 8

We want the serial version of reduce_into (and variants) for consistency now.

No objection to unanimous dissent.
Attendance: 8

We want (the parallel) reduce_into to take a range as output instead of an output iterator (like all the other parallel range algorithms).

No objection to unanimous consent.
Attendance: 8

We want projections for the algorithms proposed by P3732R1 "Numeric Range Algorithms".

SF	F	N	A	SA
0	0	2	4	2

Strong consensus against.
Attendance: 9
Author: A, SA

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Authors will come back with a new revision.

[rarutyun]

SG1 looked at P3732R2 in Croydon, March 2026

Poll: We forward the design of P3732R2 (the changes in R2 have addressed the SG1 concerns) to LEWG for C++29

SF	F	N	A	SA
5	4	0	0	0

Outcome: Unanimous consent

[wg21bot]

P3732R2 Numeric Range Algorithms (Ruslan Arutyunyan, Mark Hoemmen, Alexey Kukanov, Bryce Adelstein Lelbach, Abhilash Majumder)