FEAT: Port stack to using try_append_array supporting Clone

Author: bluss

src/stacking.rs

@@ -97,9 +97,11 @@ where
     res_dim.set_axis(axis, 0);
     let mut res;
     unsafe {
+        // create the axis so that 0 is outermost axis
         res_dim.slice_mut().swap(axis.index(), 0);
         res = Array::from_shape_vec_unchecked(res_dim, Vec::with_capacity(new_len));
-        res.swap_axes(axis.index(), 0);
+        // swap axes so that `axis` is outermost axis
+        res.swap_axes(0, axis.index());
     }
 
     for array in arrays {
@@ -139,7 +141,7 @@ pub fn stack_new_axis<A, D>(
     arrays: &[ArrayView<A, D>],
 ) -> Result<Array<A, D::Larger>, ShapeError>
 where
-    A: Copy,
+    A: Clone,
     D: Dimension,
     D::Larger: RemoveAxis,
 {
@@ -159,24 +161,25 @@ where
 
     res_dim.set_axis(axis, arrays.len());
 
-    // we can safely use uninitialized values here because we will
-    // overwrite every one of them.
-    let mut res = Array::uninit(res_dim);
-
-    res.axis_iter_mut(axis)
-        .zip(arrays.iter())
-        .for_each(|(assign_view, array)| {
-            // assign_view is D::Larger::Smaller which is usually == D
-            // (but if D is Ix6, we have IxD != Ix6 here; differing types
-            // but same number of axes).
-            let assign_view = assign_view.into_dimensionality::<D>()
-                .expect("same-dimensionality cast");
-            array.assign_to(assign_view);
-        });
+    let new_len = dimension::size_of_shape_checked(&res_dim)?;
 
+    // start with empty array with precomputed capacity
+    res_dim.set_axis(axis, 0);
+    let mut res;
     unsafe {
-        Ok(res.assume_init())
+        // create the axis so that 0 is outermost axis
+        res_dim.slice_mut().swap(axis.index(), 0);
+        res = Array::from_shape_vec_unchecked(res_dim, Vec::with_capacity(new_len));
+        // swap axes so that `axis` is outermost axis
+        res.swap_axes(0, axis.index());
     }
+
+    for array in arrays {
+        res.try_append_array(axis, array.clone().insert_axis(axis))?;
+    }
+
+    debug_assert_eq!(res.len_of(axis), arrays.len());
+    Ok(res)
 }
 
 /// Stack arrays along the new axis.