npm package: @stdlib/blas-ext-base-glast-index-of
Description: Return the last index of a specified search element in a strided array.
Author: The Stdlib Authors
Latest version: 0.1.1

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# glastIndexOf

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> Return the last index of a specified search element in a strided array.

<!-- 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/blas-ext-base-glast-index-of
```

</section>

<section class="usage">

## Usage

```javascript
var glastIndexOf = require( '@stdlib/blas-ext-base-glast-index-of' );
```

#### glastIndexOf( N, searchElement, x, strideX )

Returns the last index of a specified search element in a strided array.

```javascript
var x = [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, 3.0, -1.0 ];

var idx = glastIndexOf( x.length, 3.0, x, 1 );
// returns 6
```

The function has the following parameters:

-   **N**: number of indexed elements.
-   **searchElement**: search element.
-   **x**: input array.
-   **strideX**: stride length.

If the function is unable to find a search element, the function returns `-1`.

```javascript
var x = [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, 3.0 ];

var idx = glastIndexOf( x.length, 8.0, x, 1 );
// returns -1
```

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

```javascript
var x = [ -2.0, -1.0, 3.0, -5.0, 3.0, 4.0, -1.0, 0.0 ];

var idx = glastIndexOf( 4, 3.0, x, 2 );
// returns 2
```

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( [ -2.0, 3.0, -6.0, -4.0, 5.0, 3.0 ] );

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

// Find index:
var idx = glastIndexOf( 3, 3.0, x1, 2 );
// returns 2
```

#### glastIndexOf.ndarray( N, searchElement, x, strideX, offsetX )

Returns the last index of a specified search element in a strided array using alternative indexing semantics.

```javascript
var x = [ -2.0, 1.0, 3.0, -5.0, 4.0, 3.0, -1.0, 0.0 ];

var idx = glastIndexOf.ndarray( x.length, 3.0, x, 1, 0 );
// returns 5
```

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 of the strided array

```javascript
var x = [ -2.0, 1.0, 0.0, -5.0, 4.0, 3.0, 3.0, -1.0 ];

var idx = glastIndexOf.ndarray( 3, 3.0, x, 1, x.length-3 );
// returns 1
```

</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 searching for a search element, the function checks for equality using the strict equality operator `===`. As a consequence, `NaN` values are considered distinct, and `-0` and `+0` are considered the same.
-   Both functions support array-like objects having getter and setter accessors for array element access (e.g., [`@stdlib/array-base/accessor`][@stdlib/array/base/accessor]).

</section>

<!-- /.notes -->

<!-- Package usage examples. -->

<section class="examples">

## Examples

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

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

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

var idx = glastIndexOf.ndarray( x.length, 80.0, x, 1, 0 );
console.log( idx );
```

</section>

<!-- /.examples -->

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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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