npm package: @stdlib/strided-base-nullary-addon-dispatch
Description: Dispatch to a native add-on applying a nullary function.
Author: The Stdlib Authors
Latest version: 0.3.1

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# dispatch

[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] <!-- [![dependencies][dependencies-image]][dependencies-url] -->

> Dispatch to a native add-on applying a nullary function.

<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->

<section class="intro">

</section>

<!-- /.intro -->

<!-- Package usage documentation. -->

<section class="installation">

## Installation

```bash
npm install @stdlib/strided-base-nullary-addon-dispatch
```

</section>

<section class="usage">

## Usage

```javascript
var dispatch = require( '@stdlib/strided-base-nullary-addon-dispatch' );
```

#### dispatch( addon, fallback )

Returns a function which dispatches to a native add-on applying a nullary function.

```javascript
function addon( N, dtypeX, x, strideX ) {
    // Call into native add-on...
}

function fallback( N, dtypeX, x, strideX ) {
    // Fallback JavaScript implementation...
}

// Create a dispatch function:
var f = dispatch( addon, fallback );

// ...

// Invoke the dispatch function with strided array arguments:
f( 2, 'generic', [ 1, 2 ], 1 );
```

The returned function has the following signature:

```text
f( N, dtypeX, x, strideX )
```

where

-   **N**: number of indexed elements.
-   **dtypeX**: `x` data type.
-   **x**: output array.
-   **strideX**: `x` stride length.

The `addon` function should have the following signature:

```text
f( N, dtypeX, x, strideX )
```

where

-   **N**: number of indexed elements.
-   **dtypeX**: `x` data type (enumeration constant).
-   **x**: output array.
-   **strideX**: `x` stride length.

The `fallback` function should have the following signature:

```text
f( N, dtypeX, x, strideX )
```

where

-   **N**: number of indexed elements.
-   **dtypeX**: `x` data type.
-   **x**: output array.
-   **strideX**: `x` stride length.

#### dispatch.ndarray( addon, fallback )

Returns a function which dispatches to a native add-on applying a nullary function using alternative indexing semantics.

<!-- eslint-disable max-len -->

```javascript
function addon( N, dtypeX, x, strideX ) {
    // Call into native add-on...
}

function fallback( N, dtypeX, x, strideX, offsetX ) {
    // Fallback JavaScript implementation...
}

// Create a dispatch function:
var f = dispatch.ndarray( addon, fallback );

// ...

// Invoke the dispatch function with strided array arguments:
f( 2, 'generic', [ 1, 2 ], 1, 0 );
```

The returned function has the following signature:

```text
f( N, dtypeX, x, strideX, offsetX )
```

where

-   **N**: number of indexed elements.
-   **dtypeX**: `x` data type.
-   **x**: output array.
-   **strideX**: `x` stride length.
-   **offsetX**: starting `x` index.

The `addon` function should have the following signature:

```text
f( N, dtypeX, x, strideX )
```

where

-   **N**: number of indexed elements.
-   **dtypeX**: `x` data type (enumeration constant).
-   **x**: output array.
-   **strideX**: `x` stride length.

The `fallback` function should have the following signature:

```text
f( N, dtypeX, x, strideX, offsetX )
```

where

-   **N**: number of indexed elements.
-   **dtypeX**: `x` data type.
-   **x**: output array.
-   **strideX**: `x` stride length.
-   **offsetX**: starting `x` index.

</section>

<!-- /.usage -->

<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

## Notes

-   To determine whether to dispatch to the `addon` function, the returned dispatch function checks whether the provided arrays are typed arrays. If the provided arrays are typed arrays, the dispatch function invokes the `addon` function; otherwise, the dispatch function invokes the `fallback` function.

</section>

<!-- /.notes -->

<!-- Package usage examples. -->

<section class="examples">

## Examples

<!-- eslint-disable max-len -->

<!-- eslint no-undef: "error" -->

```javascript
var Float64Array = require( '@stdlib/array-float64' );
var dispatch = require( '@stdlib/strided-base-nullary-addon-dispatch' );

function addon( N, dtypeX, x, strideX ) {
    console.log( x );
    // => <Float64Array>[ 3, 4 ]
}

function fallback( N, dtypeX, x, strideX, offsetX ) {
    console.log( x );
    // => [ 1, 2, 3, 4 ]
}

// Create a dispatch function:
var f = dispatch.ndarray( addon, fallback );

// Create a strided array:
var x = new Float64Array( [ 1, 2, 3, 4 ] );

// Dispatch to the add-on function:
f( 2, 'float64', x, 1, 2 );

// Define a new strided array:
x = [ 1, 2, 3, 4 ];

// Dispatch to the fallback function:
f( 2, 'generic', x, 1, 2 );
```

</section>

<!-- /.examples -->

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* * *

## Notice

This package is part of [stdlib][stdlib], a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop [stdlib][stdlib], see the main project [repository][stdlib].

#### Community

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---

## License

See [LICENSE][stdlib-license].


## Copyright

Copyright &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

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