npm package: @stdlib/ndarray-dispatch-by
Description: Create an ndarray function interface which accepts a callback function and performs multiple dispatch.
Author: The Stdlib Authors
Latest version: 0.2.3

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<details>
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</details>

# dispatchBy

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

> Create an [ndarray][@stdlib/ndarray/ctor] function interface which performs multiple dispatch.

<section class="intro">

</section>

<!-- /.intro -->

<section class="installation">

## Installation

```bash
npm install @stdlib/ndarray-dispatch-by
```

</section>

<section class="usage">

## Usage

```javascript
var dispatchBy = require( '@stdlib/ndarray-dispatch-by' );
```

#### dispatchBy( fcns, types, data, nargs, nin, nout )

Returns an [ndarray][@stdlib/ndarray/ctor] function interface which performs multiple dispatch.

<!-- eslint-disable array-element-newline -->

```javascript
console.log( 'TODO' );
```

The function accepts the following arguments:

-   **fcns**: list of [ndarray][@stdlib/ndarray/ctor] functions.
-   **types**: one-dimensional list of [ndarray][@stdlib/ndarray/ctor] argument [data types][@stdlib/ndarray/dtypes]. The length of `types` must be the number of [ndarray][@stdlib/ndarray/ctor] functions multiplied by `nin+nout`. If `fcns` is a function, rather than a list, the number of [ndarray][@stdlib/ndarray/ctor] functions is computed as `types.length / (nin+nout)`.
-   **data**: [ndarray][@stdlib/ndarray/ctor] function data (e.g., callbacks). If a list, the length of `data` must equal the number of [ndarray][@stdlib/ndarray/ctor] functions. If `null`, a returned [ndarray][@stdlib/ndarray/ctor] function interface does **not** provide a `data` argument to an invoked [ndarray][@stdlib/ndarray/ctor] function.
-   **nargs**: total number of [ndarray][@stdlib/ndarray/ctor] function interface arguments.
-   **nin**: number of input [ndarrays][@stdlib/ndarray/ctor].
-   **nout**: number of output [ndarrays][@stdlib/ndarray/ctor].

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   A returned [ndarray][@stdlib/ndarray/ctor] function interface has the following signature:

    ```text
    f( x, y, ... )
    ```

    where

    -   **x**: [ndarray][@stdlib/ndarray/ctor].
    -   **y**: [ndarray][@stdlib/ndarray/ctor].
    -   **...**: additional [ndarrays][@stdlib/ndarray/ctor].

-   The number of [ndarray][@stdlib/ndarray/ctor] function interface parameters is derived from `nargs`, the number of input [ndarrays][@stdlib/ndarray/ctor] is derived from `nin`, and the number of output [ndarrays][@stdlib/ndarray/ctor] is derived from `nout`.

-   An [ndarray][@stdlib/ndarray/ctor] function (i.e., a value provided for the `fcns` argument) should have the following signature:

    ```text
    f( arrays[, data] )
    ```

    where

    -   **arrays**: array containing input and output [ndarrays][@stdlib/ndarray/ctor].
    -   **data**: [ndarray][@stdlib/ndarray/ctor] function data (e.g., a callback).

-   For convenience, a single [ndarray][@stdlib/ndarray/ctor] function may be provided which will be invoked whenever the [ndarray][@stdlib/ndarray/ctor] argument data types match a sequence of types in `types`. Providing a single [ndarray][@stdlib/ndarray/ctor] function is particularly convenient for the case where, regardless of array data types, traversing arrays remains the same, but the [ndarray][@stdlib/ndarray/ctor] function `data` differs (e.g., callbacks which differ based on the array data types). For example, the following

    <!-- eslint-disable array-element-newline -->

    ```javascript
    var unary = require( '@stdlib/ndarray-base-unary-by' );

    function foo( x ) {
        return x * 10.0;
    }

    function bar( x ) {
        return x * 5.0;
    }

    var fcns = [
        unary,
        unary
    ];
    var types = [
        'float64', 'float64',
        'float32', 'float32'
    ];
    var data = [
        foo,
        bar
    ];

    var fcn = dispatchBy( fcns, types, data, 2, 1, 1 );
    ```

    is equivalent to

    <!-- eslint-disable array-element-newline -->

    ```javascript
    var unary = require( '@stdlib/ndarray-base-unary-by' );

    function foo( x ) {
        return x * 10.0;
    }

    function bar( x ) {
        return x * 5.0;
    }

    var types = [
        'float64', 'float64',
        'float32', 'float32'
    ];
    var data = [
        foo,
        bar
    ];

    var fcn = dispatchBy( unary, types, data, 2, 1, 1 );
    ```

</section>

<!-- /.notes -->

<section class="examples">

## Examples

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

```javascript
console.log( 'TODO' );
```

</section>

<!-- /.examples -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/ndarray-array`][@stdlib/ndarray/array]</span><span class="delimiter">: </span><span class="description">multidimensional arrays.</span>
-   <span class="package-name">[`@stdlib/ndarray-ctor`][@stdlib/ndarray/ctor]</span><span class="delimiter">: </span><span class="description">multidimensional array constructor.</span>

</section>

<!-- /.related -->

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<section class="main-repo" >

* * *

## 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

[![Chat][chat-image]][chat-url]

---

## License

See [LICENSE][stdlib-license].


## Copyright

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

</section>

<!-- /.stdlib -->

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[umd]: https://github.com/umdjs/umd
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[umd-url]: https://github.com/stdlib-js/ndarray-dispatch-by/tree/umd
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[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/ndarray-dispatch-by/main/LICENSE

[@stdlib/ndarray/array]: https://www.npmjs.com/package/@stdlib/ndarray-array

[@stdlib/ndarray/ctor]: https://www.npmjs.com/package/@stdlib/ndarray-ctor

[@stdlib/ndarray/dtypes]: https://www.npmjs.com/package/@stdlib/ndarray-dtypes

<!-- <related-links> -->

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</section>

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