Function returning ndarray with given size

help
1

I am trying to implement a whole bunch of generic functions, using ndarray, that all should

  • take in an array size the same way Array::zeros() does, so as either a usize or an n-tuple of usize
  • return an array with the given size
    I can do this for, say, Array1, but since i'm translating MATLAB code I really need it to work for any size, so I guess something like -> Array<T, IxDyn>?
    I've looked at things like shape: S with S : Into<IxDyn>, but so far all my attempts have been rejected by the compiler.
2

What have you tried so far? Have you looked at the implementation of Array::zeros?
If you just want to copy its behavior, why write a new function at all? Just use Array::zeros() directly.

1 Like
3

Thank you for your response, i just mentioned Array::zeros() as a simple example of the kind of objects that are usually passed to represent an array dimension. A big difference is that Array::zeros() being a method of ArrayBase uses shape: Sh with Sh: ShapeBuilder<Dim = D> where D is given by the ArrayBase. I'm tyring to have a completely standalone function that returns an Array, I'm not trying to extend the functionality of ArrayBase. I hope that made sense, I'm pretty new to rust.

4

You can reference the associated type of the ShapeBuilder trait:

use ndarray::{Array, DataOwned, ShapeBuilder};
use num::Zero;

fn new_array<D, S>(shape: S) -> Array<D, S::Dim>
where
    D: DataOwned + Clone + Zero,
    S: ShapeBuilder,
{
    Array::zeros(shape)
}
1 Like
5

Thank you very much, I just had not understood how to use ShapeBuilder, the example let me implement all the versions i needed.