A Rust library for random number generation.
Rand provides utilities to generate random numbers, to convert them to useful types and distributions, and some randomness-related algorithms.
The core random number generation traits of Rand live in the rand_core crate; this crate is most useful when implementing RNGs.
API reference: master branch, by release.
Add this to your Cargo.toml
:
[dependencies] rand = "0.5"
and this to your crate root:
extern crate rand; use rand::prelude::*; fn main() { // basic usage with random(): let x: u8 = random(); println!("{}", x); let y = random::<f64>(); println!("{}", y); if random() { // generates a boolean println!("Heads!"); } // normal usage needs both an RNG and a function to generate the appropriate // type, range, distribution, etc. let mut rng = thread_rng(); if rng.gen() { // random bool let x: f64 = rng.gen(); // random number in range [0, 1) println!("x is: {}", x); let ch = rng.gen::<char>(); // Sometimes you need type annotation println!("char is: {}", ch); println!("Number from 0 to 9: {}", rng.gen_range(0, 10)); } }
The Rand crate provides:
thread_rng
: an automatically seeded, crypto-grade generator stored in thread-local memory.StdRng
, SmallRng
, prng
module.FromEntropy
trait, and as sources of external randomness EntropyRng
, OsRng
and JitterRng
.rand_core
(re-exported): base random number generator traits and error-reporting types.Standard
distribution for integers, floats, and derived types including tuples, arrays and Option
Uniform
ranges.gen_bool
aka Bernoulli distribution.seq
-uence related functionality:Version 0.5 is the latest version and contains many breaking changes. See the Upgrade Guide for guidance on updating from previous versions.
Version 0.4 was released in December 2017. It contains almost no breaking changes since the 0.3 series.
For more details, see the changelog.
The 0.5 release of Rand requires Rustc version 1.22 or greater. Rand 0.4 and 0.3 (since approx. June 2017) require Rustc version 1.15 or greater. Subsets of the Rand code may work with older Rust versions, but this is not supported.
Travis CI always has a build with a pinned version of Rustc matching the oldest supported Rust release. The current policy is that this can be updated in any Rand release if required, but the change must be noted in the changelog.
Rand is built with only the std
feature enabled by default. The following optional features are available:
alloc
can be used instead of std
to provide Vec
and Box
.i128_support
enables support for generating u128
and i128
values.log
enables some logging via the log
crate.nightly
enables all unstable features (i128_support
).serde1
enables serialization for some types, via Serde version 1.stdweb
enables support for OsRng
on wasm-unknown-unknown
via stdweb
combined with cargo-web
.no_std
mode is activated by setting default-features = false
; this removes functionality depending on std
:
thread_rng()
, and random()
are not available, as they require thread-local storage and an entropy source.OsRng
and EntropyRng
are unavailable.JitterRng
code is still present, but a nanosecond timer must be provided via JitterRng::new_with_timer
FromEntropy
trait (user must provide a seed).exp
and log
functions are not provided in core
.seq
-uence module is unavailable, as it requires Vec
.Rand is distributed under the terms of both the MIT license and the Apache License (Version 2.0).
See LICENSE-APACHE and LICENSE-MIT for details.