refactor: add support for ancillary ndarray arguments having trailing dimensions

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Author: kgryte

lib/node_modules/@stdlib/ndarray/base/unary-reduce-subarray-by/README.md

@@ -194,7 +194,11 @@ var count = ctx.count;
 
 ## Notes
 
--   The output ndarray and any additional ndarray arguments are expected to have the same dimensions as the non-reduced dimensions of the input ndarray. When calling the reduction function, any additional ndarray arguments are provided as zero-dimensional ndarray-like objects.
+-   The output ndarray is expected to have the same dimensions as the non-reduced dimensions of the input ndarray.
+
+-   Any additional ndarray arguments are expected to have the same leading dimensions as the non-reduced dimensions of the input ndarray.
+
+-   When calling the reduction function, any additional ndarray arguments are provided as k-dimensional subarrays, where `k = M - N` with `M` being the number of dimensions in an ndarray argument and `N` being the number of non-reduced dimensions in the input ndarray. For example, if an input ndarray has three dimensions, the number of reduced dimensions is two, and an additional ndarray argument has one dimension, thus matching the number of non-reduced dimensions in the input ndarray, the reduction function is provided a zero-dimensional subarray as an additional ndarray argument. In the same scenario but where an additional ndarray argument has two dimensions, thus exceeding the number of non-reduced dimensions in the input ndarray, the reduction function is provided a one-dimensional subarray as an additional ndarray argument.
 
 -   The reduction function is expected to have the following signature:
 
@@ -204,7 +208,7 @@ var count = ctx.count;
 
     where
 
-    -   **arrays**: array containing a subarray of the input ndarray and any additional ndarray arguments as zero-dimensional ndarrays.
+    -   **arrays**: array containing a subarray of the input ndarray and any additional ndarray arguments as subarrays.
     -   **options**: function options (_optional_).
     -   **wrappedCallback**: callback function. This function is a wrapper around a provided `clbk` argument.
 

lib/node_modules/@stdlib/ndarray/base/unary-reduce-subarray-by/docs/repl.txt

@@ -14,10 +14,24 @@
     - order: specifies whether an ndarray is row-major (C-style) or column-major
     (Fortran-style).
 
-    The output ndarray and any additional ndarray arguments are expected to have
-    the same dimensions as the non-reduced dimensions of the input ndarray. When
-    calling the reduction function, any additional ndarray arguments are
-    provided as zero-dimensional ndarray-like objects.
+    The output ndarray is expected to have the same dimensions as the non-
+    reduced dimensions of the input ndarray.
+
+    Any additional ndarray arguments are expected to have the same leading
+    dimensions as the non-reduced dimensions of the input ndarray.
+
+    When calling the reduction function, any additional ndarray arguments are
+    provided as k-dimensional subarrays, where `k = M - N` with `M` being the
+    number of dimensions in an ndarray argument and `N` being the number of non-
+    reduced dimensions in the input ndarray. For example, if an input ndarray
+    has three dimensions, the number of reduced dimensions is two, and an
+    additional ndarray argument has one dimension, thus matching the number of
+    non-reduced dimensions in the input ndarray, the reduction function is
+    provided a zero-dimensional subarray as an additional ndarray argument. In
+    the same scenario but where an additional ndarray argument has two
+    dimensions, thus exceeding the number of non-reduced dimensions in the input
+    ndarray, the reduction function is provided a one-dimensional subarray as an
+    additional ndarray argument.
 
     Parameters
     ----------
@@ -31,7 +45,7 @@
         where
 
         - arrays: array containing a subarray of the input ndarray and any
-        additional ndarray arguments as zero-dimensional ndarrays.
+        additional ndarray arguments as subarrays.
         - options: function options.
         - wrappedCallback: callback function. This function is a wrapper around
         a provided `clbk` argument.

lib/node_modules/@stdlib/ndarray/base/unary-reduce-subarray-by/lib/initialize_array_views.js

@@ -18,10 +18,15 @@
 
 'use strict';
 
+// MODULES //
+
+var slice = require( '@stdlib/array/base/slice' );
+
+
 // MAIN //
 
 /**
-* Initialize ndarray-like objects for representing zero-dimensional sub-array views of ancillary ndarray arguments.
+* Initialize ndarray-like objects for representing sub-array views of ancillary ndarray arguments.
 *
 * ## Notes
 *
@@ -30,20 +35,25 @@
 *
 * @private
 * @param {ArrayLikeObject<Object>} arrays - list of ndarray-like objects
+* @param {NonNegativeInteger} k - number of non-reduced dimensions
 * @param {Array<Object>} out - output array
 * @returns {Array<Object>} output array
 */
-function initializeViews( arrays, out ) {
+function initializeViews( arrays, k, out ) {
+	var sh;
+	var N;
 	var v;
 	var i;
 
 	for ( i = 2; i < arrays.length; i++ ) {
 		v = arrays[ i ];
+		sh = v.shape;
+		N = sh.length;
 		out.push({
 			'dtype': v.dtype,
 			'data': v.data,
-			'shape': [],
-			'strides': [ 0 ],
+			'shape': slice( sh, k, N ),
+			'strides': ( N === k ) ? [ 0 ] : slice( v.strides, k, N ),
 			'offset': v.offset,
 			'order': v.order
 		});

lib/node_modules/@stdlib/ndarray/base/unary-reduce-subarray-by/lib/main.js

@@ -392,10 +392,16 @@ function unaryReduceSubarrayBy( fcn, arrays, dims, options, clbk, thisArg ) { //
 	if ( M > ndims ) {
 		throw new RangeError( format( 'invalid argument. Number of specified dimensions cannot exceed the number of dimensions in the input array. Number of dimensions: %d. Value: [%s].', ndims, join( dims, ',' ) ) );
 	}
-	// Verify that provided ndarrays have the expected number of dimensions...
+	// Compute the number of non-reduced dimensions:
 	K = ndims - M;
-	for ( i = 1; i < N; i++ ) {
-		if ( arr[ i ].shape.length !== K ) {
+
+	// Verify that the output ndarray has the expected number of dimensions...
+	if ( arr[ 1 ].shape.length !== K ) {
+		throw new Error( format( 'invalid argument. Arrays which are not being reduced must have the same number of non-reduced dimensions. Input array shape: [%s]. Number of non-reduced dimensions: %d. Array shape: [%s] (index: %d).', join( shx, ',' ), K, join( arr[ 1 ].shape, ',' ), 1 ) );
+	}
+	// Verify that any ancillary ndarrays have at least the number of non-reduced dimensions...
+	for ( i = 2; i < N; i++ ) {
+		if ( arr[ i ].shape.length < K ) {
 			throw new Error( format( 'invalid argument. Arrays which are not being reduced must have the same number of non-reduced dimensions. Input array shape: [%s]. Number of non-reduced dimensions: %d. Array shape: [%s] (index: %d).', join( shx, ',' ), K, join( arr[ i ].shape, ',' ), i ) );
 		}
 	}
@@ -447,7 +453,7 @@ function unaryReduceSubarrayBy( fcn, arrays, dims, options, clbk, thisArg ) { //
 			'order': x.order
 		}
 	];
-	initializeViews( arr, views );
+	initializeViews( arr, K, views );
 
 	// Determine whether we only have one loop dimension and can thus readily perform one-dimensional iteration...
 	if ( K === 1 ) {