Trait IndexLonger

pub trait IndexLonger<I> {
    type Output;

    // Required methods
    fn index(self, index: I) -> Self::Output;
    fn get(self, index: I) -> Option<Self::Output>;
    unsafe fn uget(self, index: I) -> Self::Output;
}

Extra indexing methods for array views

These methods are very similar to regular indexing or calling of the get/get_mut methods that we can use on any array or array view. The difference here is in the length of lifetime in the resulting reference.

Note that the ArrayView (read-only) and ArrayViewMut (read-write) differ in how they are allowed implement this trait – ArrayView’s implementation is usual. If you put in a ArrayView<'a, T, D> here, you get references &'a T out.

For ArrayViewMut to obey the borrowing rules we have to consume the view if we call any of these methods. (The equivalent of reborrow is .view_mut() for read-write array views, but if you can use that, then the regular indexing / get_mut should suffice, too.)

use ndarray::IndexLonger;
use ndarray::ArrayView;

let data = [0.; 256];
let long_life_ref = {
    // make a 16 × 16 array view
    let view = ArrayView::from(&data[..]).into_shape((16, 16)).unwrap();

    // index the view and with `IndexLonger`.
    // Note here that we get a reference with a life that is derived from
    // `data`, the base data, instead of being derived from the view
    IndexLonger::index(&view, [0, 1])
};

// view goes out of scope

assert_eq!(long_life_ref, &0.);

Required Associated Types

type Output

The type of the reference to the element that is produced, including its lifetime.

Required Methods

fn index(self, index: I) -> Self::Output

Get a reference of a element through the view.

This method is like Index::index but with a longer lifetime (matching the array view); which we can only do for the array view and not in the Index trait.

See also the get method which works for all arrays and array views.

Panics if index is out of bounds.

fn get(self, index: I) -> Option<Self::Output>

Get a reference of a element through the view.

This method is like ArrayBase::get but with a longer lifetime (matching the array view); which we can only do for the array view and not in the Index trait.

See also the get method (and get_mut) which works for all arrays and array views.

Panics if index is out of bounds.

unsafe fn uget(self, index: I) -> Self::Output

Get a reference of a element through the view without boundary check

This method is like elem with a longer lifetime (matching the array view); which we can’t do for general arrays.

See also the uget method which works for all arrays and array views.

Note: only unchecked for non-debug builds of ndarray.

Safety

The caller must ensure that the index is in-bounds.

Implementors

impl<'a, 'b, I, A, D> IndexLonger<I> for &'b ArrayBase<ViewRepr<&'a A>, D>

where I: NdIndex<D>, D: Dimension,

type Output = &'a A

impl<'a, I, A, D> IndexLonger<I> for ArrayBase<ViewRepr<&'a mut A>, D>

where I: NdIndex<D>, D: Dimension,

type Output = &'a mut A