Crate fastrand

source ·
Expand description

A simple and fast random number generator.

The implementation uses PCG XSH RR 64/32, a simple and fast generator but not cryptographically secure.

Examples

Flip a coin:

if fastrand::bool() {
    println!("heads");
} 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();

Structs

A random number generator.

Functions

Generates a random char in ranges a-z and A-Z.
Generates a random char in ranges a-z, A-Z and 0-9.
Generates a random bool.
Generates a random digit in the given base.
Generates a random f32 in range 0..1.
Generates a random f64 in range 0..1.
Generates a random i8 in the given range.
Generates a random i16 in the given range.
Generates a random i32 in the given range.
Generates a random i64 in the given range.
Generates a random i128 in the given range.
Generates a random isize in the given range.
Generates a random char in range a-z.
Initializes the thread-local generator with the given seed.
Shuffles a slice randomly.
Generates a random u8 in the given range.
Generates a random u16 in the given range.
Generates a random u32 in the given range.
Generates a random u64 in the given range.
Generates a random u128 in the given range.
Generates a random char in range A-Z.
Generates a random usize in the given range.