https://github.com/smol-rs/fastrand

A simple and fast random number generator
https://github.com/smol-rs/fastrand

rust

Last synced: 7 days ago
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A simple and fast random number generator

• Host: GitHub
• URL: https://github.com/smol-rs/fastrand
• Owner: smol-rs
• License: apache-2.0
• Created: 2020-05-27T16:19:19.000Z (over 4 years ago)
• Default Branch: master
• Last Pushed: 2024-10-20T09:00:47.000Z (25 days ago)
• Last Synced: 2024-10-29T16:23:59.437Z (15 days ago)
• Topics: rust
• Language: Rust
• Homepage:
• Size: 101 KB
• Stars: 404
• Watchers: 8
• Forks: 35
• Open Issues: 7
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG.md
  • License: LICENSE-APACHE

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README

        
# fastrand

[![Build](https://github.com/smol-rs/fastrand/workflows/CI/badge.svg)](

https://github.com/smol-rs/fastrand/actions)

[![License](https://img.shields.io/badge/license-Apache--2.0_OR_MIT-blue.svg)](

https://github.com/smol-rs/fastrand)

[![Cargo](https://img.shields.io/crates/v/fastrand.svg)](

https://crates.io/crates/fastrand)

[![Documentation](https://docs.rs/fastrand/badge.svg)](

https://docs.rs/fastrand)

A simple and fast random number generator.

The implementation uses [Wyrand](https://github.com/wangyi-fudan/wyhash), a simple and fast

generator but **not** cryptographically secure.

## Examples

Flip a coin:

```rust

if fastrand::bool() {

    println!("heads");

} else {

    println!("tails");

}

```

Generate a random `i32`:

```rust

let num = fastrand::i32(..);

```

Choose a random element in an array:

```rust

let v = vec![1, 2, 3, 4, 5];

let i = fastrand::usize(..v.len());

let elem = v[i];

```

Sample values from an array with `O(n)` complexity (`n` is the length of array):

```rust

fastrand::choose_multiple(vec![1, 4, 5].iter(), 2);

fastrand::choose_multiple(0..20, 12);

```

Shuffle an array:

```rust

let mut v = vec![1, 2, 3, 4, 5];

fastrand::shuffle(&mut v);

```

Generate a random `Vec` or `String`:

```rust

use std::iter::repeat_with;

let v: Vec = repeat_with(|| fastrand::i32(..)).take(10).collect();

let s: String = repeat_with(fastrand::alphanumeric).take(10).collect();

```

To get reproducible results on every run, initialize the generator with a seed:

```rust

// Pick an arbitrary number as seed.

fastrand::seed(7);

// Now this prints the same number on every run:

println!("{}", fastrand::u32(..));

```

To be more efficient, create a new `Rng` instance instead of using the thread-local

generator:

```rust

use std::iter::repeat_with;

let rng = fastrand::Rng::new();

let mut bytes: Vec = repeat_with(|| rng.u8(..)).take(10_000).collect();

```

This crate aims to expose a core set of useful randomness primitives. For more niche algorithms, consider using the [`fastrand-contrib`] crate alongside this one.

# Features

- `std` (enabled by default): Enables the `std` library. This is required for the global

  generator and global entropy. Without this feature, [`Rng`] can only be instantiated using

  the [`with_seed`](https://docs.rs/fastrand/latest/fastrand/struct.Rng.html#method.with_seed) method.

- `js`: Assumes that WebAssembly targets are being run in a JavaScript environment.

[`fastrand-contrib`]: https://crates.io/crates/fastrand-contrib

## License

Licensed under either of

 * Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)

 * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)

at your option.

#### Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted

for inclusion in the work by you, as defined in the Apache-2.0 license, shall be

dual licensed as above, without any additional terms or conditions.