Commits on Oct 14, 2022

1. Move upcast broadcast helper to dimension mod …

   This will allow upcast to be reused in other functions, such as the
   upcoming ArrayView::broadcast_ref.

   

   roblabla committed Oct 14, 2022
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2. Impl a lifetime-relaxed broadcast for ArrayView …

   ArrayView::broadcast has a lifetime that depends on &self instead of its
   internal buffer. This prevents writing some types of functions in an
   allocation-free way. For instance, take the numpy `meshgrid` function:
   It could be implemented like so:
   
   ```rust
   fn meshgrid_2d<'a, 'b>(coords_x: ArrayView1<'a, X>, coords_y: ArrayView1<'b, X>) -> (ArrayView2<'a, X>, ArrayView2<'b, X>) {
       let x_len = coords_x.shape()[0];
       let y_len = coords_y.shape()[0];
   
       let coords_x_s = coords_x.into_shape((1, y_len)).unwrap();
       let coords_x_b = coords_x_s.broadcast((x_len, y_len)).unwrap();
       let coords_y_s = coords_y.into_shape((x_len, 1)).unwrap();
       let coords_y_b = coords_y_s.broadcast((x_len, y_len)).unwrap();
   
       (coords_x_b, coords_y_b)
   }
   ```
   
   Unfortunately, this doesn't work, because `coords_x_b` is bound to the
   lifetime of `coord_x_s`, instead of being bound to 'a.
   
   This commit introduces a new function, broadcast_ref, that does just
   that.

   

   roblabla committed Oct 14, 2022
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