Add insert/remove_axis_inplace for IxDyn arrays

Without these methods, users must have ownership of
dynamic-dimensional arrays to insert/remove axes, which is
unnecessarily restrictive.

Author: jturner314

src/impl_dyn.rs

@@ -0,0 +1,58 @@
+// Copyright 2018 bluss and ndarray developers.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Methods for dynamic-dimensional arrays.
+use imp_prelude::*;
+
+/// # Methods for Dynamic-Dimensional Arrays
+impl<A, S> ArrayBase<S, IxDyn>
+where
+    S: Data<Elem = A>,
+{
+    /// Insert new array axis of length 1 at `axis`, modifying the shape and
+    /// strides in-place.
+    ///
+    /// **Panics** if the axis is out of bounds.
+    ///
+    /// ```
+    /// use ndarray::{Axis, arr2, arr3};
+    ///
+    /// let mut a = arr2(&[[1, 2, 3], [4, 5, 6]]).into_dyn();
+    /// assert_eq!(a.shape(), &[2, 3]);
+    ///
+    /// a.insert_axis_inplace(Axis(1));
+    /// assert_eq!(a, arr3(&[[[1, 2, 3]], [[4, 5, 6]]]).into_dyn());
+    /// assert_eq!(a.shape(), &[2, 1, 3]);
+    /// ```
+    pub fn insert_axis_inplace(&mut self, axis: Axis) {
+        assert!(axis.index() <= self.ndim());
+        self.dim = self.dim.insert_axis(axis);
+        self.strides = self.strides.insert_axis(axis);
+    }
+
+    /// Remove array axis `axis`, modifying the shape and strides in-place.
+    ///
+    /// **Panics** if the axis is out of bounds or its length is zero.
+    ///
+    /// ```
+    /// use ndarray::{Axis, arr1, arr2};
+    ///
+    /// let mut a = arr2(&[[1, 2, 3], [4, 5, 6]]).into_dyn();
+    /// assert_eq!(a.shape(), &[2, 3]);
+    ///
+    /// a.remove_axis_inplace(Axis(1));
+    /// assert_eq!(a, arr1(&[1, 4]).into_dyn());
+    /// assert_eq!(a.shape(), &[2]);
+    /// ```
+    pub fn remove_axis_inplace(&mut self, axis: Axis) {
+        let len = self.len_of(axis);
+        assert_ne!(len, 0, "Length of removed axis must be nonzero.");
+        self.dim = self.dim.remove_axis(axis);
+        self.strides = self.strides.remove_axis(axis);
+    }
+}

src/lib.rs

@@ -240,7 +240,7 @@ pub type Ixs = isize;
 /// + [Conversions Between Array Types](#conversions-between-array-types)
 /// + [Constructor Methods for Owned Arrays](#constructor-methods-for-owned-arrays)
 /// + [Methods For All Array Types](#methods-for-all-array-types)
-///
+/// + [Methods for Dynamic-Dimensional Arrays](#methods-for-dynamic-dimensional-arrays)
 ///
 /// ## `Array`
 ///
@@ -1108,6 +1108,7 @@ impl<A, S, D> ArrayBase<S, D>
 
 mod impl_1d;
 mod impl_2d;
+mod impl_dyn;
 
 mod numeric;