npm package: @stdlib/ndarray-iter-stacks
Description: Create an iterator which iterates over each subarray in a stack of subarrays according to a list of specified stack dimensions.
Author: The Stdlib Authors
Latest version: 0.1.1

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# nditerStacks

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

> Create an iterator which iterates over each subarray in a stack of subarrays according to a list of specified stack dimensions.

<!-- 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>

<!-- /.intro -->

<!-- Package usage documentation. -->

<section class="installation">

## Installation

```bash
npm install @stdlib/ndarray-iter-stacks
```

</section>

<section class="usage">

## Usage

```javascript
var nditerStacks = require( '@stdlib/ndarray-iter-stacks' );
```

#### nditerStacks( x, dims\[, options] )

Returns an iterator which iterates over each subarray in a stack of subarrays according to a list of specified stack dimensions.

```javascript
var array = require( '@stdlib/ndarray-array' );
var ndarray2array = require( '@stdlib/ndarray-to-array' );

var x = array( [ [ [ 1, 2 ], [ 3, 4 ] ], [ [ 5, 6 ], [ 7, 8 ] ] ] );
// returns <ndarray>

var iter = nditerStacks( x, [ 1, 2 ] );

var v = iter.next().value;
// returns <ndarray>

var arr = ndarray2array( v );
// returns [ [ 1, 2 ], [ 3, 4 ] ]

v = iter.next().value;
// returns <ndarray>

arr = ndarray2array( v );
// returns [ [ 5, 6 ], [ 7, 8 ] ]

// ...
```

The function accepts the following `options`:

-   **readonly**: boolean indicating whether returned [`ndarray`][@stdlib/ndarray/ctor] views should be read-only. In order to return writable [`ndarray`][@stdlib/ndarray/ctor] views, the input [`ndarray`][@stdlib/ndarray/ctor] must be writable. If the input [`ndarray`][@stdlib/ndarray/ctor] is read-only, setting this option to `false` raises an exception. Default: `true`.

By default, the iterator returns [`ndarray`][@stdlib/ndarray/ctor] views which are **read-only**. To return writable [views][@stdlib/ndarray/slice], set the `readonly` option to `false`.

```javascript
var array = require( '@stdlib/ndarray-array' );
var ndarray2array = require( '@stdlib/ndarray-to-array' );

var x = array( [ [ [ 1, 2 ], [ 3, 4 ] ], [ [ 5, 6 ], [ 7, 8 ] ] ] );
// returns <ndarray>

var iter = nditerStacks( x, [ 1, 2 ], {
    'readonly': false
});

var v = iter.next().value;
// returns <ndarray>

var arr = ndarray2array( v );
// returns [ [ 1, 2 ], [ 3, 4 ] ]

v.set( 0, 0, 10 );

arr = ndarray2array( v );
// returns [ [ 10, 2 ], [ 3, 4 ] ]
```

The returned [iterator][mdn-iterator-protocol] protocol-compliant object has the following properties:

-   **next**: function which returns an [iterator][mdn-iterator-protocol] protocol-compliant object containing the next iterated value (if one exists) assigned to a `value` property and a `done` property having a `boolean` value indicating whether the [iterator][mdn-iterator-protocol] is finished.
-   **return**: function which closes an [iterator][mdn-iterator-protocol] and returns a single (optional) argument in an [iterator][mdn-iterator-protocol] protocol-compliant object.

</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

-   The input [`ndarray`][@stdlib/ndarray/ctor] must have at least `dims.length+1` dimensions.
-   The list of provided index dimensions must be unique and resolve to index dimensions sorted in ascending order (i.e., the function does **not** allow rearranging [`ndarray`][@stdlib/ndarray/ctor] dimensions by specifying an arbitrary index order).
-   If an environment supports `Symbol.iterator`, the returned iterator is iterable.
-   A returned iterator does **not** copy a provided [`ndarray`][@stdlib/ndarray/ctor]. To ensure iterable reproducibility, copy the input [`ndarray`][@stdlib/ndarray/ctor] **before** creating an iterator. Otherwise, any changes to the contents of input [`ndarray`][@stdlib/ndarray/ctor] will be reflected in the returned iterator.
-   In environments supporting `Symbol.iterator`, the function **explicitly** does **not** invoke an ndarray's `@@iterator` method, regardless of whether this method is defined.

</section>

<!-- /.notes -->

<!-- Package usage examples. -->

<section class="examples">

## Examples

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

```javascript
var array = require( '@stdlib/ndarray-array' );
var zeroTo = require( '@stdlib/array-base-zero-to' );
var ndarray2array = require( '@stdlib/ndarray-to-array' );
var nditerStacks = require( '@stdlib/ndarray-iter-stacks' );

// Define an input array:
var x = array( zeroTo( 27 ), {
    'shape': [ 3, 3, 3 ]
});

// Create an iterator for iterating over matrices:
var it = nditerStacks( x, [ 1, 2 ] );

// Perform manual iteration...
var v;
while ( true ) {
    v = it.next();
    if ( v.done ) {
        break;
    }
    console.log( ndarray2array( v.value ) );
}

// Create an iterator for iterating over matrices:
it = nditerStacks( x, [ 0, 2 ] );

// Perform manual iteration...
while ( true ) {
    v = it.next();
    if ( v.done ) {
        break;
    }
    console.log( ndarray2array( v.value ) );
}

// Create an iterator for iterating over matrices:
it = nditerStacks( x, [ 0, 1 ] );

// Perform manual iteration...
while ( true ) {
    v = it.next();
    if ( v.done ) {
        break;
    }
    console.log( ndarray2array( v.value ) );
}
```

</section>

<!-- /.examples -->

<!-- Section to include cited references. If references are included, add a horizontal rule *before* the section. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="references">

</section>

<!-- /.references -->

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

<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/ndarray-iter/columns`][@stdlib/ndarray/iter/columns]</span><span class="delimiter">: </span><span class="description">create an iterator which iterates over each column in a matrix (or stack of matrices).</span>
-   <span class="package-name">[`@stdlib/ndarray-iter/matrices`][@stdlib/ndarray/iter/matrices]</span><span class="delimiter">: </span><span class="description">create an iterator which iterates over each matrix in a stack of matrices.</span>
-   <span class="package-name">[`@stdlib/ndarray-iter/rows`][@stdlib/ndarray/iter/rows]</span><span class="delimiter">: </span><span class="description">create an iterator which iterates over each row in a matrix (or stack of matrices).</span>
-   <span class="package-name">[`@stdlib/ndarray-iter/subarrays`][@stdlib/ndarray/iter/subarrays]</span><span class="delimiter">: </span><span class="description">create an iterator which iterates over each subarray in a stack of subarrays.</span>
-   <span class="package-name">[`@stdlib/ndarray-slice`][@stdlib/ndarray/slice]</span><span class="delimiter">: </span><span class="description">return a read-only view of an input ndarray.</span>

</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].

</section>

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[umd]: https://github.com/umdjs/umd
[es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules

[deno-url]: https://github.com/stdlib-js/ndarray-iter-stacks/tree/deno
[deno-readme]: https://github.com/stdlib-js/ndarray-iter-stacks/blob/deno/README.md
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[esm-url]: https://github.com/stdlib-js/ndarray-iter-stacks/tree/esm
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[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/ndarray-iter-stacks/main/LICENSE

[mdn-iterator-protocol]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterator_protocol

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

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

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

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

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

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

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