Construction from negative strides?

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
25/100
Issue type
Feature
Clarity
Needs clarification
Activity status
Stale
Tech stack
rust
Domain
data

Research direction

Start with the linked PyO3/rust-numpy issue for the full context, then inspect the referenced ndarray src/impl_raw_views.rs debug assertion. Determine whether negative-stride construction should have a public unsafe API and why strides are represented as usize; done requires a decided, documented API direction rather than only a local workaround.

Written by the indexing model from the issue text.

Description

Hi, thank you for this great library.

I encountered a problem when creating an ArrayView with a pointer and negative strides (see https://github.com/PyO3/rust-numpy/issues/151 for the full context).
We can do this by converting &[isize] to &[usize], but this causes panic by a debug assertion when building without --release flag.
So,

  • How about adding some unsafe API to do this? It would be like a public new_. I'm happy to create a PR if you're willing to.
  • Why are strides internally usize? It can be negative by slicing and I don't think it's reasonable to use usize.
Dominant language
Rust
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