## fastrand

A simple and fast random number generator

### 20 stable releases

 1.9.0 Feb 14, 2023 Jul 23, 2022 Jan 22, 2022 Dec 19, 2021 Jul 7, 2020

#3 in Algorithms

Used in 12,154 crates (338 directly)

Apache-2.0 OR MIT

23KB
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# fastrand

A simple and fast random number generator.

The implementation uses Wyrand, a simple and fast generator but not cryptographically secure.

## Examples

Flip a coin:

``````if fastrand::bool() {
} else {
println!("tails");
}
``````

Generate a random `i32`:

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

Choose a random element in an array:

``````let v = vec![1, 2, 3, 4, 5];
let i = fastrand::usize(..v.len());
let elem = v[i];
``````

Shuffle an array:

``````let mut v = vec![1, 2, 3, 4, 5];
fastrand::shuffle(&mut v);
``````

Generate a random `Vec` or `String`:

``````use std::iter::repeat_with;

let v: Vec<i32> = 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:

``````// 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:

``````use std::iter::repeat_with;

let rng = fastrand::Rng::new();
let mut bytes: Vec<u8> = repeat_with(|| rng.u8(..)).take(10_000).collect();
``````