npm package: @stdlib/ndarray-base-normalize-index
Description: Normalize an index to the interval [0,max].
Author: The Stdlib Authors
Latest version: 0.2.3

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# normalizeIndex

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> Normalize an index to the interval `[0,max]`.

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<section class="intro">

</section>

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<!-- Package usage documentation. -->

<section class="installation">

## Installation

```bash
npm install @stdlib/ndarray-base-normalize-index
```

</section>

<section class="usage">

## Usage

```javascript
var normalizeIndex = require( '@stdlib/ndarray-base-normalize-index' );
```

#### normalizeIndex( idx, max )

Normalizes an index to the interval `[0,max]`.

```javascript
var idx = normalizeIndex( 2, 10 );
// returns 2

idx = normalizeIndex( -5, 10 );
// returns 6
```

If provided an out-of-bounds index, the function returns `-1`.

```javascript
var idx = normalizeIndex( 15, 10 );
// returns -1

idx = normalizeIndex( -15, 10 );
// returns -1
```

</section>

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<section class="notes">

## Notes

-   During normalization, a negative index is converted to a nonnegative index according to `max + idx + 1`. If, after normalization, the resolved index is still negative, the value is considered out-of-bounds.

</section>

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<!-- Package usage examples. -->

<section class="examples">

## Examples

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

```javascript
var discreteUniform = require( '@stdlib/random-base-discrete-uniform' );
var normalizeIndex = require( '@stdlib/ndarray-base-normalize-index' );

var idx;
var out;
var i;

for ( i = 0; i < 100; i++ ) {
    idx = discreteUniform( -20, 20 );
    out = normalizeIndex( idx, 15 );
    console.log( '%d => [%d,%d] => %d', idx, 0, 15, out );
}
```

</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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