[libc++][ranges] Implement `ranges::stride_view`. #65200

hawkinsw · 2023-09-02T06:55:25Z

Implement ranges::stride_view in libc++. Migrating to this GitHub from Phabricator (https://reviews.llvm.org/D156924).

Closes #105198

hawkinsw · 2023-09-02T23:47:21Z

Thank you all for the feedback on this work. I am really excited to get to participate. As I said, I have committed small amounts of code in the past but this is my first attempt at doing a significant amount of implementation. I have already learned a ton and look forward to learning more!

hawkinsw · 2023-09-04T14:21:51Z

I just used a fixup! commit to add some additional code. I followed the new best practices and I hope that I did it correctly. Please let me know if I did not follow the instructions properly!

hawkinsw · 2023-09-07T00:30:07Z

I know how busy you all must be with the transition to GitHub. I am going to continue to work on writing tests and look forward to any feedback you have!

hawkinsw · 2023-09-11T21:52:11Z

Removed the WIP tag (and added an amend fixup commit to accomplish the same thing with in the git realm). I can't wait to hear how I can improve the implementation!!

Will

EricWF · 2023-09-06T21:06:03Z

libcxx/include/__ranges/stride_view.h

+  using difference_type = range_difference_t<_Base>;
+  using value_type      = range_value_t<_Base>;
+  using iterator_concept =
+      _If<random_access_range<_Base>,


None of this needs the cost of lazy SFINAE. and that's a lot of instantiations. Can we reduce it some?

@EricWF Sorry to have to ask ... I know what each of the words "lazy" and "SFINAE" means but in combination I am not entirely sure to what you are referring. Could you point me to something that I use to educate myself so that I can fix this antipattern? Sorry again to have to ask!

@EricWF I now realized what you meant and believe that the fixup I am about to submit will resolve this! Thanks again for the feedback!

I won't be so presumptuous as to Resolve this conversation, but let me know if what I just changed seems better.

EricWF · 2023-09-06T21:06:24Z

libcxx/include/__ranges/stride_view.h

+                  forward_iterator_tag,
+                  /* else */ input_iterator_tag >>>;
+
+  _LIBCPP_NO_UNIQUE_ADDRESS iterator_t<_Base> __current_     = iterator_t<_Base>();


A stateless iterator... interesting....

I agree. Although the standard labels this default value as exposition only, I checked that other range adaptor implementations follow that "guidance" (see, e.g., transform_view).

This isn't just about empty types. This also compresses types with tail padding.

libcxx/include/__ranges/stride_view.h

JMazurkiewicz

Quick review of product code. Also, please rebase.

I'm not maintainer, but I've already implemented `views::stride` in microsoft/STL/pull/2981, so my comments might be useful :)

JMazurkiewicz · 2023-09-06T20:53:29Z

libcxx/modules/std/ranges.inc

+    // [range.stride], stride view
+    using std::ranges::stride_view;
+
+    namespace views {
+      using std::ranges::views::stride;
+    }
+


std module is available in C++20 as an extensions, we should add language guards:

Suggested change

// [range.stride], stride view

using std::ranges::stride_view;

namespace views {

using std::ranges::views::stride;

}

#if _LIBCPP_STD_VER >= 23

// [range.stride], stride view

using std::ranges::stride_view;

namespace views {

using std::ranges::views::stride;

}

#endif // _LIBCPP_STD_VER >= 23

I just want to make sure that I understand:

In C++20 there is an extension that would enable the use of this module. std::ranges::stride_view is only available as of C++23. So, in the case where this module was used as an extension in a C++20-compatible compiler, without this guard there would be a problem.

I hope that I am understanding correctly! Great catch!

In C++20 there is an extension that would enable the use of this module.

Yes, it is documented here: https://libcxx.llvm.org/Modules.html

std::ranges::stride_view is only available as of C++23. So, in the case where this module was used as an extension in a C++20-compatible compiler, without this guard there would be a problem.

Yes, I've got bitten by it too while implementing views::chunk_by.

Thank you! I appreciate you pointing this out and I am glad that I understood your point. I believe that I have addressed the comment. If so, would you mind if I marked the conversation resolved?

libcxx/include/module.modulemap.in

libcxx/include/__ranges/stride_view.h

hawkinsw · 2023-09-13T21:41:42Z

@JMazurkiewicz Thank you for your incredibly helpful comments. I have a few things to do at $dayjob but I will address them as soon as possible. Thank you again for taking the time to comment.

hawkinsw · 2023-09-22T19:18:37Z

Hello again and sorry to bother. I would love to make any changes to the implementation that you think are necessary. I have really enjoyed the opportunity to implement stride_view and I have already started on slide_view!

Zingam · 2023-09-29T05:25:06Z

Hello again and sorry to bother. I would love to make any changes to the implementation that you think are necessary. I have really enjoyed the opportunity to implement stride_view and I have already started on slide_view!

Please update the status page and any papers: libcxx/docs/Status/RangesViews.csv
Also this PR needs a lot more tests.

hawkinsw · 2023-09-29T06:15:58Z

Hello again and sorry to bother. I would love to make any changes to the implementation that you think are necessary. I have really enjoyed the opportunity to implement stride_view and I have already started on slide_view!

Please update the status page and any papers: libcxx/docs/Status/RangesViews.csv Also this PR needs a lot more tests.

Thank you for the feedback! Are you asking for an update to remove you as an implementer? Refer to the this URL for the PR? I believe that the paper listed in the CSV is the right one? I am sorry if I am missing something obvious.

Zingam · 2023-09-30T14:18:39Z

Thank you for the feedback! Are you asking for an update to remove you as an implementer? Refer to the this URL for the PR? I believe that the paper listed in the CSV is the right one? I am sorry if I am missing something obvious.

Please change the URL to point to this PR, also mark which papers this PR implements as complete. You probably need to add the paper to the release notes, when this PR is approved.

var-const

Sorry about the long delay! I only went through the stride_view.h header and haven't looked at the tests closely yet, but I wanted to give you the feedback I have so far. Thanks a lot for all the work on the patch!

libcxx/include/__ranges/stride_view.h

var-const · 2023-10-03T02:54:59Z

libcxx/include/__ranges/stride_view.h

+
+public:
+  _LIBCPP_HIDE_FROM_ABI constexpr explicit stride_view(_View __base, range_difference_t<_View> __stride)
+      : __base_(std::move(__base)), __stride_(__stride) {}


Can we test with a move-only __base?

I believe that I addressed this in a93fef8

libcxx/include/__ranges/stride_view.h

var-const · 2023-10-03T03:39:14Z

libcxx/include/__ranges/stride_view.h

+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr range_rvalue_reference_t<_Base>
+  iter_move(__iterator const& __it) noexcept(noexcept(ranges::iter_move(__it.__current_))) {
+    return ranges::iter_move(__it.__current_);


Question: do we have tests for the customization point (here and for iter_swap)?

I believe that this is addressed in 8405d877bc86bde51c4ec61ca7811065c69f1149.

libcxx/include/__ranges/stride_view.h

var-const · 2023-10-03T03:41:52Z

libcxx/include/__ranges/stride_view.h

+struct __fn {
+  template <viewable_range _Range>
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, range_difference_t<_Range> __n) const
+      noexcept(noexcept(stride_view{std::forward<_Range>(__range), __n}))


This would be slightly easier to read if the three repetitions of the expression were vertically aligned. I think the best way to achieve that is using a /* */ comment like this -- see e.g. as_rvalue_view.h for an example.

Clever use of the block comment! I believe that this is addressed in accfb24af355238748e22653b46ed3c08db2208d.

libcxx/include/__ranges/stride_view.h

github-actions · 2023-10-06T12:58:19Z

✅ With the latest revision this PR passed the C/C++ code formatter.

Fix formatting.

Fix dereference test unsupported tag.

@EricWF

Address feedback from @EricWF.

Fix issue with version file.

Updating tests based on feedback. Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

Add check for whether iterator::base is move/copy Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

clang-format Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

Add additional testing for sentinel mathematics. Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

Make sure that all nodiscard-marked member functions are checked. Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

Fix bad rebase. Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

Finish fixing bad rebase. Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

Format. Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

Begin splitting iterator tests into different files. Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

Clean up the iterator increment tests. Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

Fix minor format error. Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

Refactor and add additional tests. Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

Bring into line with updates to features like [[nodiscard]] vs _LIBCPP_NODISCARD

Discard accidental change to another range adaptor.

Make formatting happy.

Add stride view into the module map. Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

Rebase to main.

Clang format changes.

Add another operator (+) test.

Fix verifier error triggered by bad auto format.

Explicitly import vector where needed (for modules).

frederick-vs-ja · 2024-11-02T14:08:57Z

libcxx/test/libcxx/ranges/range.adaptors/range.stride.view/base.nodiscard.verify.cpp

+// Test that std::ranges::stride_view::base() is marked nodiscard.
+
+#include <ranges>
+


CI failure caused by missed inclusion.

Suggested change

#include <vector>

hawkinsw requested a review from a team as a code owner September 2, 2023 06:55

cor3ntin added libc++ libc++ C++ Standard Library. Not GNU libstdc++. Not libc++abi. ranges Issues related to `<ranges>` labels Sep 2, 2023

var-const self-assigned this Sep 2, 2023

hawkinsw changed the title ~~WIP: [libc++][ranges] Implement ranges::stride_view.~~ [libc++][ranges] Implement ranges::stride_view. Sep 11, 2023

EricWF reviewed Sep 12, 2023

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hawkinsw requested a review from EricWF September 13, 2023 15:46

JMazurkiewicz reviewed Sep 13, 2023

View reviewed changes

hawkinsw requested a review from JMazurkiewicz September 15, 2023 18:32

hawkinsw force-pushed the stride_view branch from f06de96 to a3279a3 Compare September 15, 2023 22:23

hawkinsw requested a review from a team as a code owner September 15, 2023 22:23

hawkinsw self-assigned this Sep 27, 2023

var-const requested changes Oct 3, 2023

View reviewed changes

var-const removed their assignment Oct 3, 2023

hawkinsw force-pushed the stride_view branch from 4e5b784 to 606879f Compare October 6, 2023 12:47

hawkinsw force-pushed the stride_view branch from edb49ee to afb9798 Compare October 13, 2023 18:14

hawkinsw force-pushed the stride_view branch 4 times, most recently from f33b89b to 861dbbb Compare October 31, 2023 22:13

hawkinsw added 23 commits November 1, 2024 21:59

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

ec09f4c

Fix formatting.

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

43885f5

Fix dereference test unsupported tag.

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

42ff236

Address feedback from @EricWF.

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

38612b7

Fix issue with version file.

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

753533a

Updating tests based on feedback. Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

f1c3e49

Add check for whether iterator::base is move/copy Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

9dd7333

clang-format Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

c31f40c

Add additional testing for sentinel mathematics. Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

ceab485

Make sure that all nodiscard-marked member functions are checked. Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

10b9de4

Fix bad rebase. Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

ba6d6e1

Finish fixing bad rebase. Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

52ba8c4

Format. Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

2b78b94

Format. Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

d319d4c

Format. Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

4b8c86f

Begin splitting iterator tests into different files. Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

c261d69

Clean up the iterator increment tests. Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

1621f9c

Fix minor format error. Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

34f401e

Refactor and add additional tests. Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

0b49bfe

Bring into line with updates to features like [[nodiscard]] vs _LIBCPP_NODISCARD

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

a05716f

Discard accidental change to another range adaptor.

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

5131b09

Make formatting happy.

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

1949ba8

Add stride view into the module map. Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

0b74e47

Rebase to main.

hawkinsw force-pushed the stride_view branch from 49b94bf to 0b74e47 Compare November 2, 2024 02:25

hawkinsw added 5 commits November 1, 2024 23:01

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

1b542a2

Clang format changes.

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

8585167

Clang format changes.

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

67a0a66

Add another operator (+) test.

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

abc3d18

Fix verifier error triggered by bad auto format.

fixup! WIP: [libc++][ranges] Implement ranges::stride_view.

b8946ac

Explicitly import vector where needed (for modules).

frederick-vs-ja reviewed Nov 2, 2024

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[libc++][ranges] Implement `ranges::stride_view`. #65200

[libc++][ranges] Implement `ranges::stride_view`. #65200

hawkinsw commented Sep 2, 2023 •

edited by ldionne

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		// Test that std::ranges::stride_view::base() is marked nodiscard.

		#include <ranges>

[libc++][ranges] Implement ranges::stride_view. #65200

Are you sure you want to change the base?

[libc++][ranges] Implement ranges::stride_view. #65200

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[libc++][ranges] Implement `ranges::stride_view`. #65200

[libc++][ranges] Implement `ranges::stride_view`. #65200

hawkinsw commented Sep 2, 2023 •

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