P2302R0: Prefer std::ranges::contains over std::basic_string_view::contains

P2302R0: Prefer std::ranges::contains over std::basic_string_view::contains

2021-03-16 Library Evolution Telecon Minutes

Chair: Ben Craig

Champion: Christopher Di Bella

Minute Taker: Inbal Levi

SUMMARY:
Ease of use with std::string is important, and removing that would be a usability regression. String literal behavior is different, and would include the null terminator. The 'contains' proposal does make an overload of two algorithms, element containment and subsequence containment. std::path may make things ambiguous. Any type where a value type has a range could be ambiguous.

OUTCOME:

POLL: Request paper to create or update LEWG policy on when to prefer free functions over member functions.

Attendance: 29

# of Authors: 1

Author Position: SF

Outcome: Consensus in favor

A: Don't want to spend the time discussing policies that we will have many exceptions to.
A: Varies enough on a case-by-case basis. Not convinced by bloating argument.
A: Unconvinced that we have discussed enough on whether such a policy makes sense.

POLL: Add free function template algorithms that test for element containment and/or range containment

Attendance: 29

# of Authors: 1

Author Position: SF

Outcome: Consensus in favor

POLL: Remove contains member functions from basic_string

Outcome: Did not take, author conceded point

ACTION: Come back with a paper that is adding the algorithms, but leaves string containment as is.

R1 of the paper was seen by SG9 on 2021-11-8. (Full Minutes)
Fixes requested:

• Distinguish between "search" and "find" versions (the search is for subranges as well), the name suggested by the author and approved by SG9 is "contains_subrange".
• Add implementation experience info to the paper. (links in the chat)

Polls

POLL: Modify "P2302R1 std::ranges::contains" by changing the name to contains_subrange for the search versions, and adding implementation experience to the paper. Then send the revised paper to LEWG for C++23

Outcome: No Objection To Unanimous Consent

Attendance: 11

# of Authors: 1

Outcome

SG9 forwarded to LEWG for C++23, with the following changes:

• Have distinguished names for the "search" overloads (by author's proposal: contains_subrange)
• Add a section describing implementation experience to the paper (if partial, elaborate on what is implemented).

P2302R1 std::ranges::contains (Christopher Di Bella)

P2302R2 std::ranges::contains (Christopher Di Bella)

A Library Evolution motion was made to advance this paper directly to electronic polling on 2021-12-07. The motion passed as of 2022-01-17.

P2302R3 std::ranges::contains (Christopher Di Bella)

2022-01 Library Evolution Electronic Poll Outcomes

Send [P2302R2] (ranges::contains) to Library Working Group for C++23, classified as an addition ([P0592R4] bucket 3 item)

Unanimous consensus in favor.

LWG reviewed and approved 2022-04-15

https://wiki.edg.com/bin/view/Wg21telecons2022/P2303-20220415

poll: adopt P2302r4 std::ranges contains for C++23 (with Jeff checking minor update) -- checked 2022-04-17

P2302R4 std::ranges::contains (Christopher Di Bella)