ndarray::Array support from_ptr

[xis19]

I have noticed that ArrayMutView or ArrayView has from_shape_ptr, which allows operations like

    let mut data = [[1.0, 2.0, 3.0], [4.0, 5.0, 6.0], [7.0, 8.0, 9.0]];
    let dim = ndarray::Dim((2, 2));
    let shape = dim.strides(ndarray::Dim((3, 2)));
    unsafe {
        let mut dataMutView = ndarray::ArrayViewMut::from_shape_ptr(shape, data.as_mut_ptr() as *mut f64);
        // Do sth
    }

I am wondering if it is possible to allow converting data into a standard ndarray::Array? So the array is not owning, but I still could apply arithmetic operations on them?

[jturner314]

Array always owns its data and deallocates when it's dropped.

Note that you can use arithmetic operations with ArrayViewMut, though. (More info here.)

For example, you can do in-place operations (+=, *=, etc.), e.g.:

use ndarray::prelude::*;
use ndarray::aview_mut2;

fn main() {
    let mut data = [[1.0, 2.0, 3.0], [4.0, 5.0, 6.0], [7.0, 8.0, 9.0]];
    let mut v: ArrayViewMut2<'_, f64> = aview_mut2(&mut data);
    v += 0.5;
    assert_eq!(v, array![[1.5, 2.5, 3.5], [4.5, 5.5, 6.5], [7.5, 8.5, 9.5]]);
}

and non-in-place operations, e.g.:

use ndarray::prelude::*;
use ndarray::aview_mut2;

fn main() {
    let mut data = [[1.0, 2.0, 3.0], [4.0, 5.0, 6.0], [7.0, 8.0, 9.0]];
    let v: ArrayViewMut2<'_, f64> = aview_mut2(&mut data);
    let o: Array2<f64> = &v + 0.5;
    assert_eq!(o, array![[1.5, 2.5, 3.5], [4.5, 5.5, 6.5], [7.5, 8.5, 9.5]]);
}

You can also call map_inplace, etc., e.g.:

use ndarray::prelude::*;
use ndarray::aview_mut2;

fn main() {
    let mut data = [[1.0, 2.0, 3.0], [4.0, 5.0, 6.0], [7.0, 8.0, 9.0]];
    let mut v: ArrayViewMut2<'_, f64> = aview_mut2(&mut data);
    v.map_inplace(|elem| *elem += 0.5);
    assert_eq!(v, array![[1.5, 2.5, 3.5], [4.5, 5.5, 6.5], [7.5, 8.5, 9.5]]);
}

Does that answer your question?