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 but are also exposed here; RNG implementations should prefer to use
rand_core while most other users should depend on
Add this to your
[dependencies] rand = "0.7"
To get started using Rand, see The Book.
Rand libs have inter-dependencies and make use of the semver trick in order to make traits compatible across crate versions. (This is especially important for
SeedableRng.) A few crate releases are thus compatibility shims, depending on the next lib version (e.g.
0.3.1). This means, for example, that
rand_core_0_3_0::SeedableRng are distinct, incompatible traits, which can cause build errors. Usually, running
cargo update is enough to fix any issues.
The Rand lib is not yet stable, however we are careful to limit breaking changes and warn via deprecation wherever possible. Patch versions never introduce breaking changes. The following minor versions are supported:
SeedableRng, and many small changes and fixes.
seqmodule, moving most PRNGs to external crates, and many small changes.
rand_core, and deprecating
Randand the previous distribution traits).
A detailed changelog is available.
When upgrading to the next minor series (especially 0.4 → 0.5), we recommend reading the Upgrade Guide.
Some versions of Rand crates have been yanked (“unreleased”). Where this occurs, the crate's CHANGELOG should be updated with a rationale, and a search on the issue tracker with the keyword
yank should uncover the motivation.
Since version 0.8, Rand requires Rustc version 1.36 or greater. Rand 0.7 requires Rustc 1.32 or greater while versions 0.5 require Rustc 1.22 or greater, and 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 these features enabled by default:
stdenables functionality dependent on the
std) enables functionality requiring an allocator
std) is an optional dependency providing the code behind
std_rngenables inclusion of
random(the latter two also require that
Optionally, the following dependencies can be enabled:
logenables logging via the
Additionally, these features configure Rand:
small_rngenables inclusion of the
nightlyenables all experimental features
simd_support(experimental) enables sampling of SIMD values (uniformly random SIMD integers and floats)
Rand supports limited functionality in
no_std mode (enabled via
default-features = false). In this case,
from_entropy are unavailable (unless
getrandom is enabled), large parts of
seq are unavailable (unless
alloc is enabled), and
random are unavailable.
Rand is distributed under the terms of both the MIT license and the Apache License (Version 2.0).