Tracking Issue for slice::array_chunks

The feature gate for the issue is #![feature(array_chunks)].

Also tracks as_(r)chunks(_mut) in #![feature(slice_as_chunks)] -- these were FCPed starting at #74985 (comment) below.

About tracking issues

Tracking issues are used to record the overall progress of implementation.
They are also uses as hubs connecting to other relevant issues, e.g., bugs or open design questions.
A tracking issue is however not meant for large scale discussion, questions, or bug reports about a feature.
Instead, open a dedicated issue for the specific matter and add the relevant feature gate label.

Auto merge of rust-lang#75021 - cuviper:array_chunks_mut, r=scottmcm

Rollup merge of rust-lang#75026 - JulianKnodt:array_windows, r=Amanieu

Rollup merge of rust-lang#76635 - scottmcm:slice-as-chunks, r=LukasKa…

Is there any intention of providing the reverse versions of these functions?

Is there any intention of providing the reverse versions of these functions?

What would that look like?

Same API, but iterating backwards. I have a use case in which I need to convert either a prefix or a suffix of a slice to an array reference. This API is perfect for the prefix use case, and I'd love to be able to use it for the suffix use case as well.

@joshlf

@joshlf
Both slice of arrays and custom iterator type would implement the DoubleEndedIterator, so your use case does not need a separate reverse method.

That's only true if N evenly divides the length of the slice (see array_chunks docs). Otherwise, the remaining elements are only accessible via the remainder method, and won't be iterated over in the DoubleEndedIterator implementation.

There's a nice version of that in the "remove array_chunks" PR above too:

-        if v.len() % 2 != 0 {
+        let (chunks, []) = v.as_chunks::<2>() else {
             return Err(FromUtf16Error(()));
-        }
+        };

So if there's no tail expected -- there's a bug somewhere if it happens -- then something like

let (rgba, []) = data.as_chunks() else { unreachable!() };

might be a nice (and fuzzable!) way to communicate and catch that expectation.

(And yes, this is a fine place for this conversation because it's in context of whether there's sufficient value in the array_chunks iterator in addition to the already-stable stuff.)

There's a case to be made that as_chuncks_exact should be added as shorthand for that. But I could also see not wanting to add all the combinations

let (rgba, []) = data.as_chunks() else { unreachable!() };

This doesn't work well with coverage reporting, currently: #143149.

There's a case to be made that as_chuncks_exact should be added as shorthand for that.

This is what I do, having as_chunks_exact return an Option<&[[T; N]]> until the coverage stuff is fixed, so that I can use .unwrap_or_else(|| unreachable!()) instead of else { unreachable!() }.

But I could also see not wanting to add all the combinations

As well as maybe a long debate on whether it should return Option<> or panic.

@scottmcm

as_chunks_exact would be nice to have if it returned Result where the error type contains the length of the trailing slice (preferably as NonZeroUsize). Because Option has the concise alternative @scottmcm suggested but if one wants to return Result with the information it requires one more line of code.

Rollup merge of rust-lang#143289 - scottmcm:remove-array-chunks, r=jh…

Auto merge of #143289 - scottmcm:remove-array-chunks, r=jhpratt

Auto merge of rust-lang#143289 - scottmcm:remove-array-chunks, r=jhpratt

Auto merge of #143289 - scottmcm:remove-array-chunks, r=jhpratt

Navigation Menu

Repository navigation

Tracking Issue for slice::array_chunks #74985

About tracking issues

Steps

Unresolved Questions

Implementation history

161 remaining items

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Tracking Issue for slice::array_chunks #74985

Description

About tracking issues

Steps

Unresolved Questions

Implementation history

Activity

joshlf commented on Feb 10, 2021

thomcc commented on Apr 25, 2021

joshlf commented on Apr 26, 2021

newpavlov commented on Apr 26, 2021

joshlf commented on Apr 26, 2021

161 remaining items

scottmcm commented on Jul 2, 2025

fintelia commented on Jul 2, 2025

briansmith commented on Jul 2, 2025

Kixunil commented on Jul 3, 2025

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions