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### 3774. `<flat_set>` should include `<compare>`

Section: 24.6.5 [flat.set.syn] Status: WP Submitter: Jiang An Opened: 2022-09-12 Last modified: 2022-11-17

Priority: Not Prioritized

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Discussion:

This was originally editorial PR #5789 which is considered not-editorial.

`std::flat_set` and `std::flat_multiset` have `operator<=>` so `<compare>` should be included in the corresponding header, in the spirit of LWG 3330. `#include <compare>` is also missing in the adopted paper P1222R4.

[2022-09-23; Reflector poll]

Set status to Tentatively Ready after eight votes in favour during reflector poll.

[2022-11-12 Approved at November 2022 meeting in Kona. Status changed: Voting → WP.]

Proposed resolution:

This wording is relative to N4917.

1. Modify the synopsis in 24.6.5 [flat.set.syn] as indicated:

   >     #include <compare>              // see 17.12.1 [compare.syn]
   >     #include <initializer_list>     // see 17.11.2 [initializer.list.syn]