A Rust library for random number generation, featuring:
Rng
, SliceRandom
and IteratorRandom
traitsgetrandom
crate and fast, convenient generation via thread_rng
rand_core
(see the book)distributions
modulerand_distr
and via the statrs
#[no_std]
compatibility (partial)It's also worth pointing out what rand
is not:
rand
and rand_distr
each contain a lot of functionality.Documentation:
Add this to your Cargo.toml
:
[dependencies] rand = "0.8.4"
To get started using Rand, see The Book.
Rand is mature (suitable for general usage, with infrequent breaking releases which minimise breakage) but not yet at 1.0. We maintain compatibility with pinned versions of the Rust compiler (see below).
Current Rand versions are:
from_entropy
to SeedableRng
, and many small changes and fixes.A detailed changelog is available for releases.
When upgrading to the next minor series (especially 0.4 → 0.5), we recommend reading the Upgrade Guide.
Rand has not yet reached 1.0 implying some breaking changes may arrive in the future (SemVer allows each 0.x.0 release to include breaking changes), but is considered mature: breaking changes are minimised and breaking releases are infrequent.
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.
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.
Continuous Integration (CI) will always test the minimum supported Rustc version (the MSRV). 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 allocatorgetrandom
(implied by std
) is an optional dependency providing the code behind rngs::OsRng
std_rng
enables inclusion of StdRng
, thread_rng
and random
(the latter two also require that std
be enabled)Optionally, the following dependencies can be enabled:
log
enables logging via the log
crateAdditionally, these features configure Rand:
small_rng
enables inclusion of the SmallRng
PRNGnightly
enables some optimizations requiring nightly Rustsimd_support
(experimental) enables sampling of SIMD values (uniformly random SIMD integers and floats), requiring nightly Rustmin_const_gen
enables generating random arrays of any size using min-const-generics, requiring Rust ≥ 1.51.Note that nightly features are not stable and therefore not all library and compiler versions will be compatible. This is especially true of Rand's experimental simd_support
feature.
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.
The WASM target wasm32-unknown-unknown
is not automatically supported by rand
or getrandom
. To solve this, either use a different target such as wasm32-wasi
or add a direct dependency on getrandom
with the js
feature (if the target supports JavaScript). See getrandom#WebAssembly support.
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.