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 rand
.
Documentation:
Add this to your Cargo.toml
:
[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 RngCore
and SeedableRng
.) A few crate releases are thus compatibility shims, depending on the next lib version (e.g. rand_core
versions 0.2.2
and 0.3.1
). This means, for example, that rand_core_0_4_0::SeedableRng
and 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:
from_entropy
to SeedableRng
, and many small changes and fixes.seq
module, moving most PRNGs to external crates, and many small changes.RngCore
and rand_core
, and deprecating Rand
and 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.
Since version 0.7, Rand requires Rustc version 1.32 or greater. Rand 0.5 requires Rustc 1.22 or greater while versions 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:
std
enables functionality dependent on the std
liballoc
(implied by std
) enables functionality requiring an allocator (when using this feature in no_std
, Rand requires Rustc version 1.36 or greater)getrandom
(implied by std
) is an optional dependency providing the code behind rngs::OsRng
Optionally, the following dependencies can be enabled:
log
enables logging via the log
cratestdweb
implies getrandom/stdweb
to enable getrandom
support on wasm32-unknown-unknown
(will be removed in rand 0.8; activate via getrandom
crate instead)wasm-bindgen
implies getrandom/wasm-bindgen
to enable getrandom
support on wasm32-unknown-unknown
(will be removed in rand 0.8; activate via getrandom
crate instead)Additionally, these features configure Rand:
small_rng
enables inclusion of the SmallRng
PRNGnightly
enables all experimental featuressimd_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, OsRng
and from_entropy
are unavailable (unless getrandom
is enabled), large parts of seq
are unavailable (unless alloc
is enabled), and thread_rng
and random
are unavailable.
Rand is distributed under the terms of both the MIT license and the Apache License (Version 2.0).
See LICENSE-APACHE and LICENSE-MIT, and COPYRIGHT for details.