There is built-in support for a random number generator (RNG) associated with each thread stored in thread-local storage. This RNG can be accessed via thread_rng, or used implicitly via random. This RNG is normally randomly seeded from an operating-system source of randomness, e.g. /dev/urandom on Unix systems, and will automatically reseed itself from this source after generating 32 KiB of random data.

let tuple = rand::random::<(f64, char)>();
println!("{:?}", tuple)

use rand::Rng;

let mut rng = rand::thread_rng();
if rng.gen() { // random bool
    println!("i32: {}, u32: {}", rng.gen::<i32>(), rng.gen::<u32>())
}

It is also possible to use other RNG types, which have a similar interface. The following uses the "ChaCha" algorithm instead of the default.

use rand::{Rng, ChaChaRng};

let mut rng = rand::ChaChaRng::new_unseeded();
println!("i32: {}, u32: {}", rng.gen::<i32>(), rng.gen::<u32>())

`derive(Rand)`

You can derive the Rand trait for your custom type via the #[derive(Rand)] directive. To use this first add this to your Cargo.toml:

rand = "0.3"
rand_derive = "0.3"

Next in your crate:

extern crate rand;
#[macro_use]
extern crate rand_derive;

#[derive(Rand, Debug)]
struct MyStruct {
    a: i32,
    b: u32,
}

fn main() {
    println!("{:?}", rand::random::<MyStruct>());
}

License

rand is primarily distributed under the terms of both the MIT license and the Apache License (Version 2.0).

See LICENSE-APACHE, and LICENSE-MIT for details.