npm package: @stdlib/random-iter-randu
Description: Create an iterator for generating uniformly distributed pseudorandom numbers between 0 and 1.
Author: The Stdlib Authors
Latest version: 0.2.2

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    About stdlib...
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# randu

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> Create an iterator for generating uniformly distributed pseudorandom numbers between `0` and `1`.

<section class="installation">

## Installation

```bash
npm install @stdlib/random-iter-randu
```

</section>

<section class="usage">

## Usage

```javascript
var iterator = require( '@stdlib/random-iter-randu' );
```

#### iterator( \[options] )

Returns an iterator for generating uniformly distributed pseudorandom numbers between `0` and `1`.

```javascript
var it = iterator();
// returns <Object>

var r = it.next().value;
// returns <number>

r = it.next().value;
// returns <number>

r = it.next().value;
// returns <number>

// ...
```

The function accepts the following `options`:

-   **name**: name of a supported pseudorandom number generator (PRNG), which will serve as the underlying source of pseudorandom numbers. The following generators are supported:

    -   [`mt19937`][@stdlib/random/base/mt19937]: 32-bit Mersenne Twister.
    -   [`minstd`][@stdlib/random/base/minstd]: linear congruential pseudorandom number generator (LCG) based on Park and Miller.
    -   [`minstd-shuffle`][@stdlib/random/base/minstd-shuffle]: linear congruential pseudorandom number generator (LCG) whose output is shuffled.

    Default: [`'mt19937'`][@stdlib/random/base/mt19937].

-   **seed**: pseudorandom number generator seed. Valid seed values vary according to the underlying PRNG.

-   **state**: pseudorandom number generator state. Valid state values vary according to the underlying PRNG. If provided, the function ignores the `seed` option.

-   **copy**: `boolean` indicating whether to copy a provided pseudorandom number generator state. Setting this option to `false` allows sharing state between two or more pseudorandom number generators. Setting this option to `true` ensures that a returned generator has exclusive control over its internal state. Default: `true`.

-   **iter**: number of iterations.

By default, the underlying pseudorandom number generator is [`mt19937`][@stdlib/random/base/mt19937]. To use a different PRNG, set the `name` option.

```javascript
var it = iterator({
    'name': 'minstd-shuffle'
});

var r = it.next().value;
// returns <number>
```

To return an iterator having a specific initial state, set the iterator `state` option.

```javascript
var bool;
var it1;
var it2;
var r;
var i;

it1 = iterator();

// Generate pseudorandom numbers, thus progressing the generator state:
for ( i = 0; i < 1000; i++ ) {
    r = it1.next().value;
}

// Create a new iterator initialized to the current state of `it1`:
it2 = iterator({
    'state': it1.state
});

// Test that the generated pseudorandom numbers are the same:
bool = ( it1.next().value === it2.next().value );
// returns true
```

To seed the iterator, set the `seed` option.

```javascript
var it1 = iterator({
    'seed': 7823
});

var r1 = it1.next().value;
// returns <number>

var it2 = iterator({
    'seed': 7823
});

var r2 = it2.next().value;
// returns <number>

var bool = ( r1 === r2 );
// returns true
```

To limit the number of iterations, set the `iter` option.

```javascript
var it = iterator({
    'iter': 2
});

var r = it.next().value;
// returns <number>

r = it.next().value;
// returns <number>

r = it.next().done;
// returns true
```

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

-   **next**: function which returns an iterator 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 is finished.
-   **return**: function which closes an iterator and returns a single (optional) argument in an iterator protocol-compliant object.
-   **seed**: pseudorandom number generator seed.
-   **seedLength**: length of generator seed.
-   **state**: writable property for getting and setting the generator state.
-   **stateLength**: length of generator state.
-   **byteLength**: size (in bytes) of generator state.
-   **PRNG**: underlying pseudorandom number generator.

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   If an environment supports `Symbol.iterator`, the returned iterator is iterable.
-   **Warning**: the default underlying source of pseudorandom numbers may **change** in the future. If exact reproducibility is required, either explicitly specify a PRNG via the `name` option or use an underlying PRNG directly.
-   If PRNG state is "shared" (meaning a state array was provided during iterator creation and **not** copied) and one sets the underlying generator state to a state array having a different length, the iterator does **not** update the existing shared state and, instead, points to the newly provided state array. In order to synchronize the output of the underlying generator according to the new shared state array, the state array for **each** relevant iterator and/or PRNG must be **explicitly** set.
-   If PRNG state is "shared" and one sets the underlying generator state to a state array of the same length, the PRNG state is updated (along with the state of all other iterator and/or PRNGs sharing the PRNG's state array).

</section>

<!-- /.notes -->

<section class="examples">

## Examples

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

```javascript
var iterator = require( '@stdlib/random-iter-randu' );

var it;
var r;

// Create a seeded iterator for generating pseudorandom numbers:
it = iterator({
    'seed': 1234,
    'iter': 10
});

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

</section>

<!-- /.examples -->

<!-- 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/random-base/randu`][@stdlib/random/base/randu]</span><span class="delimiter">: </span><span class="description">uniformly distributed pseudorandom numbers between 0 and 1.</span>
-   <span class="package-name">[`@stdlib/random-iter/randi`][@stdlib/random/iter/randi]</span><span class="delimiter">: </span><span class="description">create an iterator for generating pseudorandom numbers having integer values.</span>

</section>

<!-- /.related -->

<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->


<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>

<!-- /.stdlib -->

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[npm-url]: https://npmjs.org/package/@stdlib/random-iter-randu

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[test-url]: https://github.com/stdlib-js/random-iter-randu/actions/workflows/test.yml?query=branch:v0.2.2

[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/random-iter-randu/main.svg
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[stdlib]: https://github.com/stdlib-js/stdlib

[stdlib-authors]: https://github.com/stdlib-js/stdlib/graphs/contributors

[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/random-iter-randu/tree/deno
[deno-readme]: https://github.com/stdlib-js/random-iter-randu/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/random-iter-randu/tree/umd
[umd-readme]: https://github.com/stdlib-js/random-iter-randu/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/random-iter-randu/tree/esm
[esm-readme]: https://github.com/stdlib-js/random-iter-randu/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/random-iter-randu/blob/main/branches.md

[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/random-iter-randu/main/LICENSE

[@stdlib/random/base/mt19937]: https://www.npmjs.com/package/@stdlib/random-base-mt19937

[@stdlib/random/base/minstd]: https://www.npmjs.com/package/@stdlib/random-base-minstd

[@stdlib/random/base/minstd-shuffle]: https://www.npmjs.com/package/@stdlib/random-base-minstd-shuffle

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

[@stdlib/random/base/randu]: https://www.npmjs.com/package/@stdlib/random-base-randu

[@stdlib/random/iter/randi]: https://www.npmjs.com/package/@stdlib/random-iter-randi

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

</section>

<!-- /.links -->