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# factory

> Create a function for applying a unary function to each element in an input array.

<section class="usage">

## Usage

```javascript
var factory = require( '@stdlib/math/array/tools/unary-factory' );
```

#### factory( fcn, idtypes, odtypes, policy )

Returns a function for applying a unary function to each element in an input array.

```javascript
var abs = require( '@stdlib/math/base/special/abs' );

var dtypes = [ 'float64', 'float32', 'generic' ];
var policy = 'same';

var unary = factory( abs, dtypes, dtypes, policy );
```

The function has the following parameters:

-   **fcn**: unary function to apply.
-   **idtypes**: list of supported input data types.
-   **odtypes**: list of supported input data types.
-   **policy**: output data type policy.

#### unary( x\[, options] )

Applies a unary function to each element in a provided input array.

```javascript
var abs = require( '@stdlib/math/base/special/abs' );

var dtypes = [ 'float64', 'float32', 'generic' ];
var policy = 'same';

var unary = factory( abs, dtypes, dtypes, policy );

var v = unary( [ -1.0, 2.0, -3.0, 4.0 ] );
// returns [ 1.0, 2.0, 3.0, 4.0 ]
```

The function has the following parameters:

-   **x**: input array.
-   **options**: function options.

The function accepts the following options:

-   **dtype**: output array data type. Setting this option, overrides the output data type policy.

By default, the function returns an array having a data type determined by the output data type policy. To override the default behavior, set the `dtype` option.

```javascript
var abs = require( '@stdlib/math/base/special/abs' );

var dtypes = [ 'float64', 'float32', 'generic' ];
var policy = 'same';

var unary = factory( abs, dtypes, dtypes, policy );

var v = unary( [ -1.0, 2.0, -3.0, 4.0 ], {
    'dtype': 'float64'
});
// returns <Float64Array>[ 1.0, 2.0, 3.0, 4.0 ]
```

#### unary.assign( x, out )

Applies a unary function to each element in a provided input array and assigns results to a provided output array.

```javascript
var abs = require( '@stdlib/math/base/special/abs' );
var zeros = require( '@stdlib/array/zeros' );

var dtypes = [ 'float64', 'float32', 'generic' ];
var policy = 'same';

var unary = factory( abs, dtypes, dtypes, policy );

var out = zeros( 4, 'float64' );
// returns <Float64Array>[ 0.0, 0.0, 0.0, 0.0 ]

var v = unary.assign( [ -1.0, 2.0, -3.0, 4.0 ], out );
// returns <Float64Array>[ 1.0, 2.0, 3.0, 4.0 ]

var bool = ( v === out );
// returns true
```

The method has the following parameters:

-   **x**: input array.
-   **out**: output array.

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   The output data type policy only applies to the function returned by `factory`. For the `assign` method, the output array is allowed to be any array-like object, including [accessor arrays][@stdlib/array/base/accessor].

</section>

<!-- /.notes -->

<section class="examples">

## Examples

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

```javascript
var base = require( '@stdlib/math/base/special/sin' );
var uniform = require( '@stdlib/random/array/uniform' );
var dtypes = require( '@stdlib/array/dtypes' );
var dtype = require( '@stdlib/array/dtype' );
var logEach = require( '@stdlib/console/log-each' );
var factory = require( '@stdlib/math/array/tools/unary-factory' );

// Define the supported input and output data types:
var idt = dtypes( 'real_and_generic' );
var odt = dtypes( 'real_floating_point_and_generic' );

// Define the policy mapping an input data type to an output data type:
var policy = 'real_floating_point_and_generic';

// Create an interface for computing the element-wise sine:
var sin = factory( base, idt, odt, policy );

// Generate an array of random numbers:
var x = uniform( 10, -1.0, 1.0, {
    'dtype': 'generic'
});

// Compute the element-wise sine:
var y = sin( x );

// Resolve the output array data type:
var dt = dtype( y );
console.log( dt );

// Print the results:
logEach( 'sin(%0.5f) = %0.5f', x, y );
```

</section>

<!-- /.examples -->

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

<section class="related">

</section>

<!-- /.related -->

<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="links">

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

</section>

<!-- /.links -->
