npm package: @stdlib/ndarray-base-unary-input-casting-dtype
Description: Resolve the input ndarray casting data type for a unary function.
Author: The Stdlib Authors
Latest version: 0.1.1

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# unaryInputCastingDataType

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> Resolve the input ndarray casting [data type][@stdlib/ndarray/dtypes] for a unary function.

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</section>

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<section class="installation">

## Installation

```bash
npm install @stdlib/ndarray-base-unary-input-casting-dtype
```

</section>

<section class="usage">

## Usage

```javascript
var unaryInputCastingDataType = require( '@stdlib/ndarray-base-unary-input-casting-dtype' );
```

#### unaryInputCastingDataType( idtype, odtype, policy )

Resolves the input ndarray casting [data type][@stdlib/ndarray/dtypes] for a unary function according to a [data type policy][@stdlib/ndarray/input-casting-policies].

```javascript
var dt = unaryInputCastingDataType( 'int32', 'float64', 'promoted' );
// returns 'float64'
```

The function supports the following parameters:

-   **idtype**: input ndarray data type.
-   **odtype**: output ndarray data type.
-   **policy**: input ndarray [casting policy][@stdlib/ndarray/input-casting-policies].

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

```javascript
var dt = unaryInputCastingDataType( 'float32', 'float64', 'complex128' );
// returns 'complex128'

dt = unaryInputCastingDataType( 'int32', 'float64', 'complex128' );
// returns 'complex128'

// ...
```

</section>

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</section>

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<section class="examples">

## Examples

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

```javascript
var naryFunction = require( '@stdlib/utils-nary-function' );
var unzip = require( '@stdlib/utils-unzip' );
var nCartesianProduct = require( '@stdlib/array-base-n-cartesian-product' );
var dtypes = require( '@stdlib/ndarray-dtypes' );
var logEachMap = require( '@stdlib/console-log-each-map' );
var inputCastingDataType = require( '@stdlib/ndarray-base-unary-input-casting-dtype' );

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

// Define a list of casting policies:
var policies = [
    'none',
    'promoted',
    'accumulation',
    'output'
];

// Generate dtype-policy argument groups:
var args = nCartesianProduct( dt, dt, policies );

// Unzip the argument arrays:
args = unzip( args );

// Resolve casting data types:
logEachMap( 'dtypes: (%10s, %10s). policy: %20s. result: %10s.', args[ 0 ], args[ 1 ], args[ 2 ], naryFunction( inputCastingDataType, 3 ) );
```

</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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