feat: add accessor arrays support to blas/ext/base/gapx

lib/node_modules/@stdlib/blas/ext/base/gapx/README.md

@@ -106,6 +106,7 @@ gapx.ndarray( 3, 5.0, x, 1, x.length-3 );
 ## Notes
 
 -   If `N <= 0`, both functions return `x` unchanged.
+-   Both functions support array-like objects having getter and setter accessors for array element access (e.g., [`@stdlib/array/base/accessor`][@stdlib/array/base/accessor])
 -   Depending on the environment, the typed versions ([`dapx`][@stdlib/blas/ext/base/dapx], [`sapx`][@stdlib/blas/ext/base/sapx], etc.) are likely to be significantly more performant.
 
 </section>
@@ -158,6 +159,8 @@ console.log( x );
 
 [mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray
 
+[@stdlib/array/base/accessor]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/base/accessor
+
 <!-- <related-links> -->
 
 [@stdlib/blas/ext/base/dapx]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/blas/ext/base/dapx

lib/node_modules/@stdlib/blas/ext/base/gapx/docs/types/index.d.ts

@@ -20,7 +20,12 @@
 
 /// <reference types="@stdlib/types"/>
 
-import { NumericArray } from '@stdlib/types/array';
+import { NumericArray, Collection, AccessorArrayLike } from '@stdlib/types/array';
+
+/**
+* Input array.
+*/
+type InputArray = NumericArray | Collection<number> | AccessorArrayLike<number>;
 
 /**
 * Interface describing `gapx`.
@@ -41,7 +46,7 @@ interface Routine {
 	* gapx( x.length, 5.0, x, 1 );
 	* // x => [ 3.0, 6.0, 8.0, 0.0, 9.0, 5.0, 4.0, 2.0 ]
 	*/
-	( N: number, alpha: number, x: NumericArray, strideX: number ): NumericArray;
+	( N: number, alpha: number, x: InputArray, strideX: number ): InputArray;
 
 	/**
 	* Adds a scalar constant to each element in a strided array using alternative indexing semantics.
@@ -59,7 +64,7 @@ interface Routine {
 	* gapx.ndarray( x.length, 5.0, x, 1, 0 );
 	* // x => [ 3.0, 6.0, 8.0, 0.0, 9.0, 5.0, 4.0, 2.0 ]
 	*/
-	ndarray( N: number, alpha: number, x: NumericArray, strideX: number, offsetX: number ): NumericArray;
+	ndarray( N: number, alpha: number, x: InputArray, strideX: number, offsetX: number ): InputArray;
 }
 
 /**

lib/node_modules/@stdlib/blas/ext/base/gapx/docs/types/test.ts

@@ -16,6 +16,7 @@
 * limitations under the License.
 */
 
+import AccessorArray = require( '@stdlib/array/base/accessor' );
 import gapx = require( './index' );
 
 
@@ -25,7 +26,8 @@ import gapx = require( './index' );
 {
 	const x = new Float64Array( 10 );
 
-	gapx( x.length, 5.0, x, 1 ); // $ExpectType NumericArray
+	gapx( x.length, 5.0, x, 1 ); // $ExpectType Float64Array
+	gapx( x.length, 5.0, new AccessorArray( x ), 1 ); // $ExpectType AccessorArray
 }
 
 // The compiler throws an error if the function is provided a first argument which is not a number...
@@ -100,7 +102,8 @@ import gapx = require( './index' );
 {
 	const x = new Float64Array( 10 );
 
-	gapx.ndarray( x.length, 5.0, x, 1, 0 ); // $ExpectType NumericArray
+	gapx.ndarray( x.length, 5.0, x, 1, 0 ); // $ExpectType Float64Array
+	gapx.ndarray( x.length, 5.0, new AccessorArray( x ), 1, 0 ); // $ExpectType AccessorArray
 }
 
 // The compiler throws an error if the `ndarray` method is provided a first argument which is not a number...

lib/node_modules/@stdlib/blas/ext/base/gapx/lib/accessors.js

@@ -0,0 +1,70 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2025 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*    http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+'use strict';
+
+// MAIN //
+
+/**
+* Adds a scalar constant to each element in a strided array.
+*
+* @private
+* @param {PositiveInteger} N - number of indexed elements
+* @param {number} alpha - scalar constant
+* @param {Object} x - input array object
+* @param {Collection} x.data - input array data
+* @param {Array<Function>} x.accessors - array element accessors
+* @param {integer} strideX - stride length
+* @param {NonNegativeInteger} offsetX - starting index
+* @returns {Object} input array object
+*
+* @example
+* var toAccessorArray = require( '@stdlib/array/base/to-accessor-array' );
+* var arraylike2object = require( '@stdlib/array/base/arraylike2object' );
+*
+* var x = toAccessorArray( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ] );
+*
+* var v = gapx( 4, 5.0, arraylike2object( x ), 2, 1 );
+* // returns {...}
+*/
+function gapx( N, alpha, x, strideX, offsetX ) {
+	var xbuf;
+	var get;
+	var set;
+	var ix;
+	var i;
+
+	// Cache reference to array data:
+	xbuf = x.data;
+
+	// Cache reference to the element accessors:
+	get = x.accessors[ 0 ];
+	set = x.accessors[ 1 ];
+
+	ix = offsetX;
+	for ( i = 0; i < N; i++ ) {
+		set( xbuf, ix, alpha + get( xbuf, ix ) );
+		ix += strideX;
+	}
+	return x;
+}
+
+
+// EXPORTS //
+
+module.exports = gapx;

lib/node_modules/@stdlib/blas/ext/base/gapx/lib/ndarray.js

@@ -18,6 +18,12 @@
 
 'use strict';
 
+// MODULES //
+
+var arraylike2object = require( '@stdlib/array/base/arraylike2object' );
+var accessors = require( './accessors.js' );
+
+
 // VARIABLES //
 
 var M = 5;
@@ -44,11 +50,16 @@ var M = 5;
 function gapx( N, alpha, x, strideX, offsetX ) {
 	var ix;
 	var m;
+	var o;
 	var i;
 
 	if ( N <= 0 || alpha === 0.0 ) {
 		return x;
 	}
+	o = arraylike2object( x );
+	if ( o.accessorProtocol ) {
+		return accessors( N, alpha, o, strideX, offsetX );
+	}
 	ix = offsetX;
 
 	// Use loop unrolling if the stride is equal to `1`...

lib/node_modules/@stdlib/blas/ext/base/gapx/test/test.main.js

@@ -22,6 +22,7 @@
 
 var tape = require( 'tape' );
 var Float64Array = require( '@stdlib/array/float64' );
+var toAccessorArray = require( '@stdlib/array/base/to-accessor-array' );
 var gapx = require( './../lib' );
 
 
@@ -75,6 +76,43 @@ tape( 'the function adds a constant to each element of a strided array', functio
 	t.end();
 });
 
+tape( 'the function adds a constant to each element of a strided array (accessors)', function test( t ) {
+	var expected;
+	var x;
+
+	x = [
+		4.0,
+		2.0,
+		-3.0,
+		5.0,
+		-1.0,
+		2.0,
+		-5.0,
+		6.0
+	];
+	expected = [
+		9.0,
+		7.0,
+		2.0,
+		10.0,
+		4.0,
+		7.0,
+		0.0,
+		11.0
+	];
+
+	gapx( x.length, 5.0, toAccessorArray( x ), 1 );
+	t.deepEqual( x, expected, 'returns expected value' );
+
+	x = [ 1.0, 2.0 ];
+	expected = [ 6.0, 7.0 ];
+
+	gapx( x.length, 5.0, toAccessorArray( x ), 1 );
+	t.deepEqual( x, expected, 'returns expected value' );
+
+	t.end();
+});
+
 tape( 'the function returns a reference to the input array', function test( t ) {
 	var out;
 	var x;
@@ -139,6 +177,30 @@ tape( 'the function supports specifying a stride', function test( t ) {
 	t.end();
 });
 
+tape( 'the function supports specifying a stride (accessors)', function test( t ) {
+	var expected;
+	var x;
+
+	x = [
+		2.0,  // 0
+		-3.0,
+		-5.0, // 1
+		7.0,
+		6.0   // 2
+	];
+	expected = [
+		7.0,  // 0
+		-3.0,
+		0.0,  // 1
+		7.0,
+		11.0  // 2
+	];
+
+	gapx( 3, 5.0, toAccessorArray( x ), 2 );
+	t.deepEqual( x, expected, 'returns expected value' );
+	t.end();
+});
+
 tape( 'the function supports specifying a negative stride', function test( t ) {
 	var expected;
 	var x;
@@ -163,6 +225,30 @@ tape( 'the function supports specifying a negative stride', function test( t ) {
 	t.end();
 });
 
+tape( 'the function supports specifying a negative stride (accessors)', function test( t ) {
+	var expected;
+	var x;
+
+	x = [
+		2.0,  // 2
+		-3.0,
+		-5.0, // 1
+		7.0,
+		6.0   // 0
+	];
+	expected = [
+		7.0,  // 2
+		-3.0,
+		0.0,  // 1
+		7.0,
+		11.0  // 0
+	];
+
+	gapx( 3, 5.0, toAccessorArray( x ), -2 );
+	t.deepEqual( x, expected, 'returns expected value' );
+	t.end();
+});
+
 tape( 'the function supports view offsets', function test( t ) {
 	var expected;
 	var x0;