npm package: @stdlib/ndarray-base-normalize-indices
Description: Normalize a list of indices to the interval [0,max].
Author: The Stdlib Authors
Latest version: 0.1.1

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# normalizeIndices

[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] <!-- [![dependencies][dependencies-image]][dependencies-url] -->

> Normalize a list of indices 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-indices
```

</section>

<section class="usage">

## Usage

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

#### normalizeIndices( indices, max )

Normalizes a list of indices to the interval `[0,max]`.

```javascript
var idx = normalizeIndices( [ 2, -5 ], 10 );
// returns [ 2, 6 ]
```

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

```javascript
var idx = normalizeIndices( [ 15, -15 ], 10 );
// returns null
```

</section>

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<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

## Notes

-   The function mutates the input array, even when provided an out-of-bounds index. If mutation is undesired, copy the input array before calling this function.
-   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-array-discrete-uniform' );
var normalizeIndices = require( '@stdlib/ndarray-base-normalize-indices' );

// Generate a list of random indices:
var idx1 = discreteUniform( 100, -20, 20, {
    'dtype': 'generic'
});

// Normalize each index to the interval `[0, 15]`:
var idx2 = idx1.slice();
var out = normalizeIndices( idx2, 15 );

// Check whether one or more indices was invalid:
if ( out === null ) {
    console.log( 'One or more indices was invalid.' );
}

// Print the results...
var i;
for ( i = 0; i < idx1.length; i++ ) {
    console.log( '%d => [%d, %d] => %d', idx1[ i ], 0, 15, idx2[ i ] );
}
```

</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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