#array #dimension #split #vector #items #accessor #safety

vec_split

Splits arrays of vectors into arrays of items

5 releases

0.1.4 May 18, 2023
0.1.3 May 18, 2023
0.1.2 May 18, 2023
0.1.1 May 18, 2023
0.1.0 May 18, 2023

#2018 in Rust patterns

38 downloads per month
Used in micro_ndarray

MIT license

25KB
547 lines

vec_split

vec_split is a library to work with arrays of vectors as if they were instead one array for each dimension of the vector.

Example

let mut array = [[0.0, 0.0]; 10];
let [mut x_array, mut y_array] = array.vec_split_fast_mut();
for (i, item) in x_array.iter_mut().enumerate() {
    *item = i as f64 / 10.0;
}
for (i, item) in y_array.iter_mut().enumerate() {
    *item = i as f64 * 2.0;
}
for item in x_array.iter() {
    println!("X {item}");
}
for item in y_array.iter() {
    println!("Y {item}");
}

Safety and Accessor types

As is visible in the example, vec_split allows multiple mutable references to what is technically all the same array. This is SAFE because each part of the split array cannot write where the others do, meaning they are effectively separate.

FastAccessor also uses unsafe code to do some pointer manipulation. Because we want it to still be safe, the SizedVector trait has some special requirements. If these are always ensured, FastAccessor IS SAFE.

SAFETY: MUST have no extra items before first dimension in memory, MUST not have padding between items!! This means Vec, for example, is NOT fit for this trait. [T; D], for example, works.

This is essentially just saying that the vector MUST be an array, just like [T; D]. Vec<T> however does not work for this, as it has a lot of extra room around the items. If this is the case SafeAccessor must be used, which may be a small bit slower.

SafeAccessor uses no memory manipulation, so it may be slower, but it also doesn't have any way to cause UB or some other weirdness if some trait is implemented wrongly.

No runtime deps