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# gsort

> Sort a strided array.

<section class="usage">

## Usage

```javascript
var gsort = require( '@stdlib/blas/ext/base/gsort' );
```

#### gsort( N, order, x, strideX )

Sorts a strided array.

```javascript
var x = [ 1.0, -2.0, 3.0, -4.0 ];

gsort( x.length, 1.0, x, 1 );
// x => [ -4.0, -2.0, 1.0, 3.0 ]
```

The function has the following parameters:

-   **N**: number of indexed elements.
-   **order**: sort order. If `order < 0.0`, the input strided array is sorted in **decreasing** order. If `order > 0.0`, the input strided array is sorted in **increasing** order. If `order == 0.0`, the input strided array is left unchanged.
-   **x**: input [`Array`][mdn-array] or [`typed array`][mdn-typed-array].
-   **strideX**: stride length.

The `N` and stride parameters determine which elements in the strided array are accessed at runtime. For example, to sort every other element:

```javascript
var x = [ 1.0, -2.0, 3.0, -4.0 ];

gsort( 2, -1.0, x, 2 );
// x => [ 3.0, -2.0, 1.0, -4.0 ]
```

Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views.

```javascript
var Float64Array = require( '@stdlib/array/float64' );

// Initial array...
var x0 = new Float64Array( [ 1.0, 2.0, 3.0, 4.0 ] );

// Create an offset view...
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

// Sort every other element...
gsort( 2, -1.0, x1, 2 );
// x0 => <Float64Array>[ 1.0, 4.0, 3.0, 2.0 ]
```

#### gsort.ndarray( N, order, x, strideX, offsetX )

Sorts a strided array using alternative indexing semantics.

```javascript
var x = [ 1.0, -2.0, 3.0, -4.0 ];

gsort.ndarray( x.length, 1.0, x, 1, 0 );
// x => [ -4.0, -2.0, 1.0, 3.0 ]
```

The function has the following additional parameters:

-   **offsetX**: starting index.

While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying buffer, the offset parameter supports indexing semantics based on a starting index. For example, to access only the last three elements:

```javascript
var x = [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ];

gsort.ndarray( 3, 1.0, x, 1, x.length-3 );
// x => [ 1.0, -2.0, 3.0, -6.0, -4.0, 5.0 ]
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   If `N <= 0` or `order == 0.0`, both functions return `x` unchanged.
-   The algorithm distinguishes between `-0` and `+0`. When sorted in increasing order, `-0` is sorted before `+0`. When sorted in decreasing order, `-0` is sorted after `+0`.
-   The algorithm sorts `NaN` values to the end. When sorted in increasing order, `NaN` values are sorted last. When sorted in decreasing order, `NaN` values are sorted first.
-   The input strided array is sorted **in-place** (i.e., the input strided array is **mutated**).

</section>

<!-- /.notes -->

<section class="examples">

## Examples

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

```javascript
var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
var gsort = require( '@stdlib/blas/ext/base/gsort' );

var x = discreteUniform( 10, -100, 100, {
    'dtype': 'generic'
});
console.log( x );

gsort( x.length, -1.0, x, -1 );
console.log( x );
```

</section>

<!-- /.examples -->

<section class="references">

</section>

<!-- /.references -->

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<section class="related">

</section>

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<section class="links">

[mdn-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array

[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray

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

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</section>

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