npm package: @stdlib/blas-tools-swap-factory
Description: Return a function which interchanges two vectors.
Author: The Stdlib Authors
Latest version: 0.1.1

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</details>

# factory

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> Return a function which interchanges two vectors.

<section class="intro">

</section>

<!-- /.intro -->

<section class="installation">

## Installation

```bash
npm install @stdlib/blas-tools-swap-factory
```

</section>

<section class="usage">

## Usage

```javascript
var factory = require( '@stdlib/blas-tools-swap-factory' );
```

#### factory( base, dtype )

Returns a function which interchanges two vectors.

```javascript
var dswap = require( '@stdlib/blas-base-dswap' ).ndarray;

var swap = factory( dswap, 'float64' );
```

The function has the following parameters:

-   **base**: "base" function which interchanges two vectors. Must have an `ndarray` function signature (i.e., must support index offsets).
-   **dtype**: array data type. The function assumes that the data type of all provided arrays is the same.

#### swap( x, y\[, dim] )

Interchanges two vectors.

```javascript
var Float64Array = require( '@stdlib/array-float64' );
var array = require( '@stdlib/ndarray-array' );
var dswap = require( '@stdlib/blas-base-dswap' ).ndarray;

var swap = factory( dswap, 'float64' );

var x = array( new Float64Array( [ 4.0, 2.0, -3.0, 5.0, -1.0 ] ) );
var y = array( new Float64Array( [ 2.0, 6.0, -1.0, -4.0, 8.0 ] ) );

swap( x, y );

var xbuf = x.data;
// returns <Float64Array>[ 2.0, 6.0, -1.0, -4.0, 8.0 ]

var ybuf = y.data;
// returns <Float64Array>[ 4.0, 2.0, -3.0, 5.0, -1.0 ]
```

The returned function has the following parameters:

-   **x**: a non-zero-dimensional [`ndarray`][@stdlib/ndarray/ctor]. Must have the same shape as `y`.
-   **y**: a non-zero-dimensional [`ndarray`][@stdlib/ndarray/ctor]. Must have the same shape as `x`.
-   **dim**: dimension along which to interchange vectors. Must be a negative integer. Negative indices are resolved relative to the last array dimension, with the last dimension corresponding to `-1`. Default: `-1`.

For multi-dimensional input [`ndarrays`][@stdlib/ndarray/ctor], the function performs batched computation, such that the function interchanges each pair of vectors in `x` and `y` according to the specified dimension index.

```javascript
var Float64Array = require( '@stdlib/array-float64' );
var array = require( '@stdlib/ndarray-array' );
var dswap = require( '@stdlib/blas-base-dswap' ).ndarray;

var swap = factory( dswap, 'float64' );

var opts = {
    'shape': [ 2, 3 ]
};
var x = array( new Float64Array( [ 4.0, 2.0, -3.0, 5.0, -1.0, 3.0 ] ), opts );
var y = array( new Float64Array( [ 2.0, 6.0, -1.0, -4.0, 8.0, 2.0 ] ), opts );

var v1 = x.get( 0, 0 );
// returns 4.0

var v2 = y.get( 0, 0 );
// returns 2.0

swap( x, y );

v1 = x.get( 0, 0 );
// returns 2.0

v2 = y.get( 0, 0 );
// returns 4.0
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

For the returned function,

-   Both input [`ndarrays`][@stdlib/ndarray/ctor] must have the same shape.
-   Negative indices are resolved relative to the last [`ndarray`][@stdlib/ndarray/ctor] dimension, with the last dimension corresponding to `-1`.
-   For multi-dimensional [`ndarrays`][@stdlib/ndarray/ctor], batched computation effectively means swapping all of `x` with all of `y`; however, the choice of `dim` will significantly affect performance. For best performance, specify a `dim` which best aligns with the [memory layout][@stdlib/ndarray/orders] of provided [`ndarrays`][@stdlib/ndarray/ctor].

</section>

<!-- /.notes -->

<section class="examples">

## Examples

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

```javascript
var discreteUniform = require( '@stdlib/random-array-discrete-uniform' );
var ndarray2array = require( '@stdlib/ndarray-to-array' );
var array = require( '@stdlib/ndarray-array' );
var dswap = require( '@stdlib/blas-base-dswap' ).ndarray;
var factory = require( '@stdlib/blas-tools-swap-factory' );

var swap = factory( dswap, 'float64' );

var opts = {
    'dtype': 'float64'
};

var x = array( discreteUniform( 10, 0, 100, opts ), {
    'shape': [ 5, 2 ]
});
console.log( ndarray2array( x ) );

var y = array( discreteUniform( 10, 0, 10, opts ), {
    'shape': x.shape
});
console.log( ndarray2array( y ) );

swap( x, y );
console.log( ndarray2array( x ) );
console.log( ndarray2array( y ) );
```

</section>

<!-- /.examples -->

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

<section class="related">

</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].

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

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

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