fix: compute singleton strides as if strides computed apriori

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---

Author: kgryte

lib/node_modules/@stdlib/ndarray/base/expand-dimensions/lib/main.js

@@ -20,6 +20,7 @@
 
 // MODULES //
 
+var isRowMajor = require( '@stdlib/ndarray/base/assert/is-row-major-string' );
 var isReadOnly = require( '@stdlib/ndarray/base/assert/is-read-only' );
 var normalizeIndex = require( '@stdlib/ndarray/base/normalize-index' );
 var getDType = require( '@stdlib/ndarray/base/dtype' );
@@ -75,6 +76,7 @@ var format = require( '@stdlib/string/format' );
 function expandDimensions( x, axis ) {
 	var strides;
 	var shape;
+	var isrm;
 	var ord;
 	var sh;
 	var st;
@@ -85,6 +87,8 @@ function expandDimensions( x, axis ) {
 	sh = getShape( x, false );
 	st = getStrides( x, false );
 	ord = getOrder( x );
+
+	isrm = isRowMajor( ord );
 	N = sh.length;
 
 	strides = [];
@@ -97,8 +101,11 @@ function expandDimensions( x, axis ) {
 	if ( d === 0 ) {
 		// Prepend singleton dimension...
 		shape.push( 1 );
-		strides.push( st[ 0 ] );
-
+		if ( isrm ) {
+			strides.push( sh[ 0 ] * st[ 0 ] );
+		} else {
+			strides.push( st[ 0 ] );
+		}
 		// Copy remaining dimensions...
 		for ( i = 0; i < N; i++ ) {
 			shape.push( sh[ i ] );
@@ -112,13 +119,17 @@ function expandDimensions( x, axis ) {
 		}
 		// Append singleton dimension...
 		shape.push( 1 );
-		strides.push( st[ N-1 ] );
+		if ( isrm ) {
+			strides.push( st[ N-1 ] );
+		} else {
+			strides.push( sh[ N-1 ] * st[ N-1 ] );
+		}
 	} else {
 		// Insert a singleton dimension...
 		for ( i = 0; i < N+1; i++ ) {
 			if ( i === d ) {
 				shape.push( 1 );
-				if ( ord === 'row-major' ) {
+				if ( isrm ) {
 					strides.push( st[ i-1 ] );
 				} else { // ord === 'column-major'
 					strides.push( st[ i ] );

lib/node_modules/@stdlib/ndarray/base/expand-dimensions/test/test.js

@@ -159,7 +159,7 @@ tape( 'the function prepends singleton dimensions (base; row-major)', function t
 
 	t.notEqual( y, x, 'returns expected value' );
 	t.deepEqual( y.shape, [ 1, 2, 2 ], 'returns expected value' );
-	t.deepEqual( y.strides, [ 2, 2, 1 ], 'returns expected value' );
+	t.deepEqual( y.strides, [ 4, 2, 1 ], 'returns expected value' );
 	t.strictEqual( y.data, x.data, 'returns expected value' );
 
 	t.end();
@@ -174,7 +174,7 @@ tape( 'the function prepends singleton dimensions (base; row-major; negative axi
 
 	t.notEqual( y, x, 'returns expected value' );
 	t.deepEqual( y.shape, [ 1, 2, 2 ], 'returns expected value' );
-	t.deepEqual( y.strides, [ 2, 2, 1 ], 'returns expected value' );
+	t.deepEqual( y.strides, [ 4, 2, 1 ], 'returns expected value' );
 	t.strictEqual( y.data, x.data, 'returns expected value' );
 
 	t.end();
@@ -249,7 +249,7 @@ tape( 'the function appends singleton dimensions (base; column-major)', function
 
 	t.notEqual( y, x, 'returns expected value' );
 	t.deepEqual( y.shape, [ 2, 2, 1 ], 'returns expected value' );
-	t.deepEqual( y.strides, [ 1, 2, 2 ], 'returns expected value' );
+	t.deepEqual( y.strides, [ 1, 2, 4 ], 'returns expected value' );
 	t.strictEqual( y.data, x.data, 'returns expected value' );
 
 	t.end();
@@ -264,7 +264,7 @@ tape( 'the function appends singleton dimensions (base; column-major; negative i
 
 	t.notEqual( y, x, 'returns expected value' );
 	t.deepEqual( y.shape, [ 2, 2, 1 ], 'returns expected value' );
-	t.deepEqual( y.strides, [ 1, 2, 2 ], 'returns expected value' );
+	t.deepEqual( y.strides, [ 1, 2, 4 ], 'returns expected value' );
 	t.strictEqual( y.data, x.data, 'returns expected value' );
 
 	t.end();