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.
Add this to your
 = "0.5"
and this to your crate root:
extern crate rand; use *;
The Rand crate provides:
- A convenient to use default RNG,
thread_rng: an automatically seeded, crypto-grade generator stored in thread-local memory.
- Pseudo-random number generators:
- Functionality for seeding PRNGs: the
FromEntropytrait, and as sources of external randomness
- Most content from
rand_core(re-exported): base random number generator traits and error-reporting types.
- 'Distributions' producing many different types of random values:
Standarddistribution for integers, floats, and derived types including tuples, arrays and
- Unbiased sampling from specified
- Sampling from exponential/normal/gamma distributions.
- Sampling from binomial/poisson distributions.
gen_boolaka Bernoulli distribution.
seq-uence related functionality:
- Sampling a subset of elements.
- Randomly shuffling a list.
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.
Rust version requirements
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:
alloccan be used instead of
i128_supportenables support for generating
logenables some logging via the
nightlyenables all unstable features (
serde1enables serialization for some types, via Serde version 1.
stdwebenables support for
no_std mode is activated by setting
default-features = false; this removes
functionality depending on
random()are not available, as they require thread-local storage and an entropy source.
JitterRngcode is still present, but a nanosecond timer must be provided via
- Since no external entropy is available, it is not possible to create
generators with fresh seeds using the
FromEntropytrait (user must provide a seed).
- Exponential, normal and gamma type distributions are unavailable since
logfunctions are not provided in
seq-uence module is unavailable, as it requires
Rand is distributed under the terms of both the MIT license and the Apache License (Version 2.0).