Trait Distribution

pub trait Distribution<T> {
    // Required method
    fn sample<R>(&self, rng: &mut R) -> T
       where R: Rng + ?Sized;

    // Provided methods
    fn sample_iter<R>(self, rng: R) -> Iter<Self, R, T>
       where R: Rng,
             Self: Sized { ... }
    fn map<F, S>(self, func: F) -> Map<Self, F, T, S>
       where F: Fn(T) -> S,
             Self: Sized { ... }
}

Types (distributions) that can be used to create a random instance of T.

It is possible to sample from a distribution through both the Distribution and Rng traits, via distr.sample(&mut rng) and rng.sample(distr). They also both offer the sample_iter method, which produces an iterator that samples from the distribution.

All implementations are expected to be immutable; this has the significant advantage of not needing to consider thread safety, and for most distributions efficient state-less sampling algorithms are available.

Implementations are typically expected to be portable with reproducible results when used with a PRNG with fixed seed; see the portability chapter of The Rust Rand Book. In some cases this does not apply, e.g. the usize type requires different sampling on 32-bit and 64-bit machines.

Required Methods

fn sample<R>(&self, rng: &mut R) -> T

where R: Rng + ?Sized,

Generate a random value of T, using rng as the source of randomness.

Provided Methods

fn sample_iter<R>(self, rng: R) -> Iter<Self, R, T>

where R: Rng, Self: Sized,

Create an iterator that generates random values of T, using rng as the source of randomness.

Note that this function takes self by value. This works since Distribution<T> is impl’d for &D where D: Distribution<T>, however borrowing is not automatic hence distr.sample_iter(...) may need to be replaced with (&distr).sample_iter(...) to borrow or (&*distr).sample_iter(...) to reborrow an existing reference.

Example

use rand::distr::{Distribution, Alphanumeric, Uniform, StandardUniform};

let mut rng = rand::rng();

// Vec of 16 x f32:
let v: Vec<f32> = StandardUniform.sample_iter(&mut rng).take(16).collect();

// String:
let s: String = Alphanumeric
    .sample_iter(&mut rng)
    .take(7)
    .map(char::from)
    .collect();

// Dice-rolling:
let die_range = Uniform::new_inclusive(1, 6).unwrap();
let mut roll_die = die_range.sample_iter(&mut rng);
while roll_die.next().unwrap() != 6 {
    println!("Not a 6; rolling again!");
}

fn map<F, S>(self, func: F) -> Map<Self, F, T, S>

where F: Fn(T) -> S, Self: Sized,

Map sampled values to type S

Example

use rand::distr::{Distribution, Uniform};

let die = Uniform::new_inclusive(1, 6).unwrap();
let even_number = die.map(|num| num % 2 == 0);
while !even_number.sample(&mut rand::rng()) {
    println!("Still odd; rolling again!");
}

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementations on Foreign Types

impl Distribution<f32> for Exp1

fn sample<R>(&self, rng: &mut R) -> f32

where R: Rng + ?Sized,

impl Distribution<f32> for StandardNormal

fn sample<R>(&self, rng: &mut R) -> f32

where R: Rng + ?Sized,

impl Distribution<f64> for Exp1

fn sample<R>(&self, rng: &mut R) -> f64

where R: Rng + ?Sized,

impl Distribution<f64> for StandardNormal

fn sample<R>(&self, rng: &mut R) -> f64

where R: Rng + ?Sized,

impl Distribution<u64> for Binomial

fn sample<R>(&self, rng: &mut R) -> u64

where R: Rng + ?Sized,

impl Distribution<u64> for Geometric

fn sample<R>(&self, rng: &mut R) -> u64

where R: Rng + ?Sized,

impl Distribution<u64> for StandardGeometric

fn sample<R>(&self, rng: &mut R) -> u64

where R: Rng + ?Sized,

impl Distribution<u64> for Hypergeometric

fn sample<R>(&self, rng: &mut R) -> u64

where R: Rng + ?Sized,

impl<F> Distribution<[F; 2]> for UnitCircle

where F: Float + SampleUniform,

fn sample<R>(&self, rng: &mut R) -> [F; 2]

where R: Rng + ?Sized,

impl<F> Distribution<[F; 2]> for UnitDisc

where F: Float + SampleUniform,

fn sample<R>(&self, rng: &mut R) -> [F; 2]

where R: Rng + ?Sized,

impl<F> Distribution<[F; 3]> for UnitBall

where F: Float + SampleUniform,

fn sample<R>(&self, rng: &mut R) -> [F; 3]

where R: Rng + ?Sized,

impl<F> Distribution<[F; 3]> for UnitSphere

where F: Float + SampleUniform,

fn sample<R>(&self, rng: &mut R) -> [F; 3]

where R: Rng + ?Sized,

impl<F> Distribution<F> for Beta<F>

where F: Float, Open01: Distribution<F>,

fn sample<R>(&self, rng: &mut R) -> F

where R: Rng + ?Sized,

impl<F> Distribution<F> for Cauchy<F>

where F: Float + FloatConst, StandardUniform: Distribution<F>,

fn sample<R>(&self, rng: &mut R) -> F

where R: Rng + ?Sized,

impl<F> Distribution<F> for ChiSquared<F>

where F: Float, StandardNormal: Distribution<F>, Exp1: Distribution<F>, Open01: Distribution<F>,

fn sample<R>(&self, rng: &mut R) -> F

where R: Rng + ?Sized,

impl<F> Distribution<F> for Exp<F>

where F: Float, Exp1: Distribution<F>,

fn sample<R>(&self, rng: &mut R) -> F

where R: Rng + ?Sized,

impl<F> Distribution<F> for FisherF<F>

where F: Float, StandardNormal: Distribution<F>, Exp1: Distribution<F>, Open01: Distribution<F>,

fn sample<R>(&self, rng: &mut R) -> F

where R: Rng + ?Sized,

impl<F> Distribution<F> for Frechet<F>

where F: Float, OpenClosed01: Distribution<F>,

fn sample<R>(&self, rng: &mut R) -> F

where R: Rng + ?Sized,

impl<F> Distribution<F> for Gamma<F>

where F: Float, StandardNormal: Distribution<F>, Exp1: Distribution<F>, Open01: Distribution<F>,

fn sample<R>(&self, rng: &mut R) -> F

where R: Rng + ?Sized,

impl<F> Distribution<F> for Gumbel<F>

where F: Float, OpenClosed01: Distribution<F>,

fn sample<R>(&self, rng: &mut R) -> F

where R: Rng + ?Sized,

impl<F> Distribution<F> for InverseGaussian<F>

where F: Float, StandardNormal: Distribution<F>, StandardUniform: Distribution<F>,

fn sample<R>(&self, rng: &mut R) -> F

where R: Rng + ?Sized,

impl<F> Distribution<F> for LogNormal<F>

where F: Float, StandardNormal: Distribution<F>,

fn sample<R>(&self, rng: &mut R) -> F

where R: Rng + ?Sized,

impl<F> Distribution<F> for Normal<F>

where F: Float, StandardNormal: Distribution<F>,

fn sample<R>(&self, rng: &mut R) -> F

where R: Rng + ?Sized,

impl<F> Distribution<F> for NormalInverseGaussian<F>

where F: Float, StandardNormal: Distribution<F>, StandardUniform: Distribution<F>,

fn sample<R>(&self, rng: &mut R) -> F

where R: Rng + ?Sized,

impl<F> Distribution<F> for Pareto<F>

where F: Float, OpenClosed01: Distribution<F>,

fn sample<R>(&self, rng: &mut R) -> F

where R: Rng + ?Sized,

impl<F> Distribution<F> for Pert<F>

where F: Float, StandardNormal: Distribution<F>, Exp1: Distribution<F>, Open01: Distribution<F>,

fn sample<R>(&self, rng: &mut R) -> F

where R: Rng + ?Sized,

impl<F> Distribution<F> for Poisson<F>

where F: Float + FloatConst, StandardUniform: Distribution<F>, StandardNormal: Distribution<F>, Exp1: Distribution<F>,

fn sample<R>(&self, rng: &mut R) -> F

where R: Rng + ?Sized,

impl<F> Distribution<F> for SkewNormal<F>

where F: Float, StandardNormal: Distribution<F>,

fn sample<R>(&self, rng: &mut R) -> F

where R: Rng + ?Sized,

impl<F> Distribution<F> for StudentT<F>

where F: Float, StandardNormal: Distribution<F>, Exp1: Distribution<F>, Open01: Distribution<F>,

fn sample<R>(&self, rng: &mut R) -> F

where R: Rng + ?Sized,

impl<F> Distribution<F> for Triangular<F>

where F: Float, StandardUniform: Distribution<F>,

fn sample<R>(&self, rng: &mut R) -> F

where R: Rng + ?Sized,

impl<F> Distribution<F> for Weibull<F>

where F: Float, OpenClosed01: Distribution<F>,

fn sample<R>(&self, rng: &mut R) -> F

where R: Rng + ?Sized,

impl<F> Distribution<F> for Zeta<F>

where F: Float, StandardUniform: Distribution<F>, OpenClosed01: Distribution<F>,

fn sample<R>(&self, rng: &mut R) -> F

where R: Rng + ?Sized,

impl<F> Distribution<F> for Zipf<F>

where F: Float, StandardUniform: Distribution<F>,

fn sample<R>(&self, rng: &mut R) -> F

where R: Rng + ?Sized,

impl<F, const N: usize> Distribution<[F; N]> for Dirichlet<F, N>

where F: Float, StandardNormal: Distribution<F>, Exp1: Distribution<F>, Open01: Distribution<F>,

fn sample<R>(&self, rng: &mut R) -> [F; N]

where R: Rng + ?Sized,

impl<T, D> Distribution<T> for &D

where D: Distribution<T> + ?Sized,

fn sample<R>(&self, rng: &mut R) -> T

where R: Rng + ?Sized,

impl<W> Distribution<usize> for WeightedAliasIndex<W>

where W: AliasableWeight,

fn sample<R>(&self, rng: &mut R) -> usize

where R: Rng + ?Sized,

impl<W> Distribution<usize> for WeightedTreeIndex<W>

where W: Clone + PartialEq + PartialOrd + SampleUniform + SubAssign + Weight,

Samples a randomly selected index from the weighted distribution.

Caution: This method panics if there are no elements or all weights are zero. However, it is guaranteed that this method will not panic if a call to WeightedTreeIndex::is_valid returns true.

fn sample<R>(&self, rng: &mut R) -> usize

where R: Rng + ?Sized,

Implementors

impl Distribution<bool> for Bernoulli

impl Distribution<bool> for StandardUniform

impl Distribution<char> for StandardUniform

impl Distribution<f32> for Open01

impl Distribution<f32> for OpenClosed01

impl Distribution<f32> for StandardUniform

impl Distribution<f64> for Open01

impl Distribution<f64> for OpenClosed01

impl Distribution<f64> for StandardUniform

impl Distribution<i8> for StandardUniform

impl Distribution<i16> for StandardUniform

impl Distribution<i32> for StandardUniform

impl Distribution<i64> for StandardUniform

impl Distribution<i128> for StandardUniform

impl Distribution<u8> for Alphanumeric

impl Distribution<u8> for StandardUniform

impl Distribution<u16> for StandardUniform

impl Distribution<u32> for StandardUniform

impl Distribution<u64> for StandardUniform

impl Distribution<u128> for StandardUniform

impl Distribution<()> for StandardUniform

impl Distribution<__m128i> for StandardUniform

impl Distribution<__m256i> for StandardUniform

impl Distribution<NonZero<i8>> for StandardUniform

impl Distribution<NonZero<i16>> for StandardUniform

impl Distribution<NonZero<i32>> for StandardUniform

impl Distribution<NonZero<i64>> for StandardUniform

impl Distribution<NonZero<i128>> for StandardUniform

impl Distribution<NonZero<u8>> for StandardUniform

impl Distribution<NonZero<u16>> for StandardUniform

impl Distribution<NonZero<u32>> for StandardUniform

impl Distribution<NonZero<u64>> for StandardUniform

impl Distribution<NonZero<u128>> for StandardUniform

impl<'a, T> Distribution<&'a T> for Choose<'a, T>

impl<A> Distribution<(A,)> for StandardUniform

where StandardUniform: Distribution<A>,

impl<A, B> Distribution<(A, B)> for StandardUniform

where StandardUniform: Distribution<A> + Distribution<B>,

impl<A, B, C> Distribution<(A, B, C)> for StandardUniform

where StandardUniform: Distribution<A> + Distribution<B> + Distribution<C>,

impl<A, B, C, D> Distribution<(A, B, C, D)> for StandardUniform

where StandardUniform: Distribution<A> + Distribution<B> + Distribution<C> + Distribution<D>,

impl<A, B, C, D, E> Distribution<(A, B, C, D, E)> for StandardUniform

where StandardUniform: Distribution<A> + Distribution<B> + Distribution<C> + Distribution<D> + Distribution<E>,

impl<A, B, C, D, E, F> Distribution<(A, B, C, D, E, F)> for StandardUniform

where StandardUniform: Distribution<A> + Distribution<B> + Distribution<C> + Distribution<D> + Distribution<E> + Distribution<F>,

impl<A, B, C, D, E, F, G> Distribution<(A, B, C, D, E, F, G)> for StandardUniform

where StandardUniform: Distribution<A> + Distribution<B> + Distribution<C> + Distribution<D> + Distribution<E> + Distribution<F> + Distribution<G>,

impl<A, B, C, D, E, F, G, H> Distribution<(A, B, C, D, E, F, G, H)> for StandardUniform

where StandardUniform: Distribution<A> + Distribution<B> + Distribution<C> + Distribution<D> + Distribution<E> + Distribution<F> + Distribution<G> + Distribution<H>,

impl<A, B, C, D, E, F, G, H, I> Distribution<(A, B, C, D, E, F, G, H, I)> for StandardUniform

where StandardUniform: Distribution<A> + Distribution<B> + Distribution<C> + Distribution<D> + Distribution<E> + Distribution<F> + Distribution<G> + Distribution<H> + Distribution<I>,

impl<A, B, C, D, E, F, G, H, I, J> Distribution<(A, B, C, D, E, F, G, H, I, J)> for StandardUniform

where StandardUniform: Distribution<A> + Distribution<B> + Distribution<C> + Distribution<D> + Distribution<E> + Distribution<F> + Distribution<G> + Distribution<H> + Distribution<I> + Distribution<J>,

impl<A, B, C, D, E, F, G, H, I, J, K> Distribution<(A, B, C, D, E, F, G, H, I, J, K)> for StandardUniform

where StandardUniform: Distribution<A> + Distribution<B> + Distribution<C> + Distribution<D> + Distribution<E> + Distribution<F> + Distribution<G> + Distribution<H> + Distribution<I> + Distribution<J> + Distribution<K>,

impl<A, B, C, D, E, F, G, H, I, J, K, L> Distribution<(A, B, C, D, E, F, G, H, I, J, K, L)> for StandardUniform

where StandardUniform: Distribution<A> + Distribution<B> + Distribution<C> + Distribution<D> + Distribution<E> + Distribution<F> + Distribution<G> + Distribution<H> + Distribution<I> + Distribution<J> + Distribution<K> + Distribution<L>,

impl<D, F, T, S> Distribution<S> for Map<D, F, T, S>

where D: Distribution<T>, F: Fn(T) -> S,

impl<T> Distribution<Wrapping<T>> for StandardUniform

where StandardUniform: Distribution<T>,

impl<T, const N: usize> Distribution<[T; N]> for StandardUniform

where StandardUniform: Distribution<T>,

impl<X> Distribution<usize> for WeightedIndex<X>

where X: SampleUniform + PartialOrd,

impl<X> Distribution<X> for Uniform<X>

where X: SampleUniform,