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Add Iterator::map_windows #94667

Merged
merged 1 commit into from
Aug 13, 2023
Merged

Add Iterator::map_windows #94667

merged 1 commit into from
Aug 13, 2023

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frank-king
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@frank-king frank-king commented Mar 6, 2022 •
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Tracking issue: #87155.

This is inherited from the old PR #82413.

Unlike #82413, this PR implements the MapWindows to be lazy: only when pulling from the outer iterator, .next() of the inner iterator will be called.

Implementaion Steps

  • Implement MapWindows to keep the iterators' Laziness contract.
  • Fix the known bug of memory access error.
  • Full specialization of iterator-related traits for MapWindows.
    • Iterator::size_hint,
    • Iterator::count,
    • ExactSizeIterator (when I: ExactSizeIterator),
    • TrustedLen (when I: TrustedLen),
    • FusedIterator,
    • Iterator::advance_by,
    • Iterator::nth,
    • ...
  • More tests and docs.

Unresolved Questions:

  • Is there any more iterator-related traits should be specialized?
  • Is the double-space buffer worth?
  • Should there be rmap_windows or something else?
  • Taking GAT for consideration, should the mapper function be FnMut(&[I::Item; N]) -> R or something like FnMut(ArrayView<'_, I::Item, N>) -> R? Where ArrayView is mentioned in Extending core::ops::Index to return non-references generic-associated-types-initiative#2.
    • It can save memory, only the same size as the array window is needed,
    • It is more efficient, which requires less data copies,
    • It is possibly compatible with the GATified version of LendingIterator::windows.
    • But it prevents the array pattern matching like iter.map_windows(|_arr: [_; N]| ()), unless we extend the array pattern to allow matching the ArrayView.

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Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @m-ou-se (or someone else) soon.

Please see the contribution instructions for more information.

@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Mar 6, 2022
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@frank-king frank-king force-pushed the feature/iter_map_windows branch 2 times, most recently from 455690c to 32bab75 Compare March 7, 2022 10:16
@frank-king frank-king marked this pull request as ready for review March 7, 2022 15:16
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r? @rust-lang/libs
r? @LukasKalbertodt
r? @dtolnay

@rust-highfive rust-highfive assigned yaahc and unassigned m-ou-se Mar 7, 2022
@yaahc yaahc added the T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. label Mar 18, 2022
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bors commented Apr 8, 2022

☔ The latest upstream changes (presumably #95798) made this pull request unmergeable. Please resolve the merge conflicts.

@frank-king frank-king marked this pull request as draft April 14, 2022 09:21
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bors commented Jun 10, 2022

☔ The latest upstream changes (presumably #91970) made this pull request unmergeable. Please resolve the merge conflicts.

@Mark-Simulacrum Mark-Simulacrum added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 24, 2022
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Going to mark as waiting-on-author since it's in draft and has some conflicts -- not really clear what the state of this PR is though. If you'd like a review, please leave a comment with @rustbot ready.

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Got busy recently.

Actually, I think there should be more tests, while I'm not sure what are the best ways to test it. Maybe a review could help.

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@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 24, 2022
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dtolnay commented Dec 23, 2022

Reassigning yaahc's reviews as she has stepped down from the review rotation.

r? rust-lang/libs-api

@rustbot rustbot assigned BurntSushi and unassigned yaahc Dec 23, 2022
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dtolnay commented Jan 22, 2023

Reassigning BurntSushi's reviews because based on git log -i --grep=r=burntsushi the last time they did rust-lang/rust reviews was over 3 years ago.

r? rust-lang/libs-api

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It failed in #111760. wasm doesn't support unwinding panics.

@bors r-

@bors bors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels May 19, 2023
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The fix for that is adding #[cfg(not(panic = "abort"))] to the tests that need unwinding

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@rustbot ready

@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels May 27, 2023
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r=me with a rebase

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@rustbot rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jun 3, 2023
@Easyoakland Easyoakland mentioned this pull request Aug 7, 2023
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frank-king commented Aug 10, 2023 •
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Didn't see that message, sorry for the long wait.

@rustbot ready.

r? @Mark-Simulacrum

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rustbot commented Aug 10, 2023

Could not assign reviewer from: Mark-Simulacrum.
User(s) Mark-Simulacrum are either the PR author, already assigned, or on vacation, and there are no other candidates.
Use r? to specify someone else to assign.

@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Aug 10, 2023
@frank-king @LukasKalbertodt
Add Iterator::map_windows
97c953f 
This is inherited from the old PR.

This method returns an iterator over mapped windows of the starting
iterator. Adding the more straight-forward `Iterator::windows` is not
easily possible right now as the items are stored in the iterator type,
meaning the `next` call would return references to `self`. This is not
allowed by the current `Iterator` trait design. This might change once
GATs have landed.

The idea has been brought up by @m-ou-se here:
https://rust-lang.zulipchat.com/#narrow/stream/219381-t-libs/topic/Iterator.3A.3A.7Bpairwise.2C.20windows.7D/near/224587771

Co-authored-by: Lukas Kalbertodt <[email protected]>
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@bors r+

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bors commented Aug 13, 2023

📌 Commit 97c953f has been approved by Mark-Simulacrum

It is now in the queue for this repository.

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Aug 13, 2023
@GuillaumeGomez GuillaumeGomez mentioned this pull request Aug 13, 2023
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bors added a commit to rust-lang-ci/rust that referenced this pull request Aug 13, 2023
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Auto merge of rust-lang#114786 - GuillaumeGomez:rollup-0cos5gn, r=Gui…
1b198b3 
…llaumeGomez

Rollup of 5 pull requests

Successful merges:

 - rust-lang#94667 (Add `Iterator::map_windows`)
 - rust-lang#114069 (Allow using external builds of the compiler-rt profile lib)
 - rust-lang#114354 (coverage: Store BCB counter info externally, not directly in the BCB graph)
 - rust-lang#114625 (CI: use smaller machines in PR runs)
 - rust-lang#114777 (Migrate GUI colors test to original CSS color format)

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit 7f787e3 into rust-lang:master Aug 13, 2023
@rustbot rustbot added this to the 1.73.0 milestone Aug 13, 2023
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bors commented Aug 13, 2023

⌛ Testing commit 97c953f with merge 1b198b3...

@dtolnay dtolnay self-assigned this Mar 24, 2024
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