Trait for 1d to nd index conversion

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
30/100
Issue type
Feature
Clarity
Needs clarification
Activity status
Stale
Tech stack
rust
Domain
data

Research direction

Start with the generic shuffle example and inspect the Array, Array1, and Dimension indexing, flattening, and reshaping APIs mentioned in the issue. A complete contribution would establish whether a single usize can be converted safely for arbitrary dimensions and document or test the resulting behavior.

Written by the indexing model from the issue text.

Description

Given an array of arbitrary dimension, is it possible to index into it using a single usize?

fn shuffle1<E>(values: &mut Array1<E>) {
    let mut i = values.len();
    while i >= 2 {
        // invariant: elements with index >= i have been locked in place.
        i -= 1;
        // lock element i in place.
        values.swap(i, thread_rng().gen_range(0, i + 1));
    }
}

fn shuffle<E, D: Dimension>(values: &mut Array<E, D>) {
    let mut i = values.len();
    while i >= 2 {
        i -= 1;
        values.swap(i, thread_rng().gen_range(0, i + 1));
        // This won't work as a single usize is not necessarily a valid index,
       // the usize must be converted to a index of dimension D
    }
}

One possible solution is probably to flatten the array, then shuffle it, then reshape it back, although I do think a method for indexing into the array with a single integer could be useful in general.

Dominant language
Rust
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