array zip_map feature

[conradludgate]

As discussed on zulip.

Introduces a new zip method on arrays that is considerably faster than the existing methods.

[rust-highfive]

r? @m-ou-se

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[slanterns]

Would it be better if this zip_map can be extended to general iterators, not just arrays (the current implementation might prevent other iterators to implement zip_map)? Since it seems to be a public api, it feels more consistent to me if it can be used on all iterators (like zipWith in other languages).

[m-ou-se]

While this seems reasonable, I'm worried about this leading us on a path towards a large amount of iterator-like functions on the array type. What are other iterator-like functions that anybody might want on the array type? Is zip_map more important or special than those? Where should we draw the line?

[conradludgate]

Where should we draw the line?

That is certainly a valid point. I feel like we might have already crossed that line with the existing map and zip methods.

I'll try @slanterns suggestion and see how well it optimised with some iterator adapters. If it does optimise well, maybe we can push for array: IntoIterator more.

[conradludgate]

Alternatively, my goal was to provide some convenient Add, Sub, Mul, etc methods that would be based on this impl.

I thought getting this PR in would be easier than an RFC regarding implementing these traits onto arrays, but maybe I'll start the RFC now

[JohnCSimon]

@conradludgate
Ping from triage: Can you please post the status of this PR?
Thank you.

[conradludgate]

Can you please post the status of this PR?

Still waiting for me to attempt the iterator adapter form to see if they can meet similar optimisations

[bors]

☔ The latest upstream changes (presumably #95602) made this pull request unmergeable. Please resolve the merge conflicts.

[scottmcm]

Assuming this is worth doing, I think it should happen in try_collect_into_array instead (

rust/library/core/src/array/mod.rs

Line 794 in 9fbbe75

fn try_collect_into_array<I, T, R, const N: usize>(iter: &mut I) -> Option<R::TryType>

), so that the other functions can benefit from doing it too

[conradludgate]

Yeah, as I said in my other comment, it doesn't actually seem to do much here. Although my new private methods on IntoIter make this much simpler to implement and share the drop checking code

[conradludgate]

I finally got some time to look into this more. I attempted adding a ZipMap iterator adapter and tried to use the arrays with those but I didn't get the results I was looking for.

Similarly, adding the drop check skip code to try_collect_into_array didn't do the job either.

It's a little disappointing but I guess this isn't worth it then if it can't generalise better. I'll focus on maintaining my crate

[JohnCSimon]

@conradludgate
ping from triage - can you post your status on this PR? can this be closed?