Issue 3490: ranges::drop_while_view::begin() is missing a precondition

Title: ranges::drop_while_view::begin() is missing a precondition
Status: c++23
Section: [range.drop.while.view]
Submitter: Michael Schellenberger Costa

Created on 2020-10-13.00:00:00 last changed 5 months ago

Messages

msg11701 (view)

Date: 2021-02-26.17:31:29

Proposed resolution:

This wording is relative to N4868.

Modify [range.drop.while.view] as indicated:

Since we usually don't rely on implicit bool conversion in Preconditions: elements an explicit "is true" has been added. Editorial fixes of the referenced paragraph [range.drop.while.view] p3 and similar places have been requested separately.
```
constexpr auto begin();
```
-?- Preconditions: pred_.has_value() is true.
-3- Returns: ranges::find_if_not(base_, cref(*pred_)).
-4- […]

msg11529 (view)

Date: 2021-02-26.00:00:00

[ 2021-02-26 Approved at February 2021 virtual plenary. Status changed: Tentatively Ready → WP. ]

msg11518 (view)

Date: 2020-11-15.00:00:00

[ 2020-11-07; Reflector prioritization ]

Set priority to 0 and status to Tentatively Ready after six votes in favour during reflector discussions.

msg11517 (view)

Date: 2020-10-13.00:00:00

Similar to ranges::filter_view [range.filter.view] p3, ranges::drop_while_view should have a precondition on its begin() method that the predicate is set.

I propose to add as [range.drop.while.view] p3:

Preconditions: pred_.has_value().

History
Date	User	Action	Args
2023-11-22 15:47:43	admin	set	status: wp -> c++23
2021-02-26 17:31:29	admin	set	messages: + msg11701
2021-02-26 17:31:29	admin	set	status: ready -> wp
2020-11-07 19:23:15	admin	set	messages: + msg11529
2020-11-07 19:23:15	admin	set	status: new -> ready
2020-10-26 17:18:52	admin	set	messages: + msg11518
2020-10-13 00:00:00	admin	create