npm package: @stdlib/ndarray-base-output-dtype
Description: Resolve the output data type from a list of input ndarray data types.
Author: The Stdlib Authors
Latest version: 0.1.1

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# outputDataType

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> Resolve the output ndarray [data type][@stdlib/ndarray/dtypes] from a list of input ndarray [data types][@stdlib/ndarray/dtypes].

<!-- 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>

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<!-- Package usage documentation. -->

<section class="installation">

## Installation

```bash
npm install @stdlib/ndarray-base-output-dtype
```

</section>

<section class="usage">

## Usage

```javascript
var outputDataType = require( '@stdlib/ndarray-base-output-dtype' );
```

#### outputDataType( dtypes, policy )

Resolves the output ndarray [data type][@stdlib/ndarray/dtypes] from a list of input ndarray [data types][@stdlib/ndarray/dtypes] according to a [data type policy][@stdlib/ndarray/output-dtype-policies].

```javascript
var dt = outputDataType( [ 'int32', 'uint32' ], 'floating_point' );
// returns 'float64'
```

The function supports the following parameters:

-   **dtypes**: list of input ndarray [data types][@stdlib/ndarray/dtypes].
-   **policy**: output [data type policy][@stdlib/ndarray/output-dtype-policies].

If `policy` is a [data type][@stdlib/ndarray/dtypes], the function always returns the `policy` value (i.e., the second argument).

```javascript
var dt = outputDataType( [ 'float32', 'float32' ], 'float64' );
// returns 'float64'

dt = outputDataType( [ 'int32', 'complex128' ], 'float64' );
// returns 'float64'

// ...
```

</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

-   When provided more than [data type][@stdlib/ndarray/dtypes], the function **always** applies [type promotion][@stdlib/ndarray/promotion-rules] to the provided data types, except for the following [data type policies][@stdlib/ndarray/output-dtype-policies]:

    -   `default`
    -   `default_index`
    -   `same`
    -   `<dtype>`

</section>

<!-- /.notes -->

<!-- Package usage examples. -->

<section class="examples">

## Examples

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

```javascript
var naryFunction = require( '@stdlib/utils-nary-function' );
var unzip = require( '@stdlib/utils-unzip' );
var cartesianProduct = require( '@stdlib/array-base-cartesian-product' );
var dtypes = require( '@stdlib/ndarray-dtypes' );
var logEachMap = require( '@stdlib/console-log-each-map' );
var outputDataType = require( '@stdlib/ndarray-base-output-dtype' );

// Get the list of real-valued data types:
var dt = dtypes( 'real' );

// Define a list of output data type policies:
var policies = [
    'default',
    'real',
    'floating_point',
    'complex_floating_point',
    'promoted'
];

// Generate data type pairs:
var pairs = cartesianProduct( dt, dt );

// Generate argument pairs:
var args = cartesianProduct( pairs, policies );

// Unzip the argument pair array:
args = unzip( args );

// Resolve output data types:
logEachMap( 'dtypes: (%15s). policy: %-24s. output dtype: %s.', args[ 0 ], args[ 1 ], naryFunction( outputDataType, 2 ) );
```

</section>

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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].

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---

## License

See [LICENSE][stdlib-license].


## Copyright

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

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