rand::distributions

Trait Distribution

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

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

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§

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fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> T

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

Provided Methods§

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fn sample_iter<R>(self, rng: R) -> DistIter<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::thread_rng;
use rand::distributions::{Distribution, Alphanumeric, Uniform, Standard};

let mut rng = thread_rng();

// Vec of 16 x f32:
let v: Vec<f32> = Standard.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);
let mut roll_die = die_range.sample_iter(&mut rng);
while roll_die.next().unwrap() != 6 {
    println!("Not a 6; rolling again!");
}
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fn map<F, S>(self, func: F) -> DistMap<Self, F, T, S>
where F: Fn(T) -> S, Self: Sized,

Create a distribution of values of ‘S’ by mapping the output of Self through the closure F

§Example
use rand::thread_rng;
use rand::distributions::{Distribution, Uniform};

let mut rng = thread_rng();

let die = Uniform::new_inclusive(1, 6);
let even_number = die.map(|num| num % 2 == 0);
while !even_number.sample(&mut 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.

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impl<'a, T, D: Distribution<T>> Distribution<T> for &'a D

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fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> T

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impl Distribution<bool> for Bernoulli

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impl Distribution<bool> for Standard

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impl Distribution<char> for Standard

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impl Distribution<f32> for Open01

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impl Distribution<f32> for OpenClosed01

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impl Distribution<f32> for Standard

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impl Distribution<f64> for Open01

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impl Distribution<f64> for OpenClosed01

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impl Distribution<f64> for Standard

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impl Distribution<i8> for Standard

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impl Distribution<i16> for Standard

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impl Distribution<i32> for Standard

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impl Distribution<i64> for Standard

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impl Distribution<i128> for Standard

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impl Distribution<isize> for Standard

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impl Distribution<u8> for Alphanumeric

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impl Distribution<u8> for Standard

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impl Distribution<u16> for Standard

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impl Distribution<u32> for Standard

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impl Distribution<u64> for Standard

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impl Distribution<u128> for Standard

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impl Distribution<()> for Standard

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impl Distribution<usize> for Standard

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impl Distribution<NonZero<u8>> for Standard

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impl Distribution<NonZero<u16>> for Standard

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impl Distribution<NonZero<u32>> for Standard

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impl Distribution<NonZero<u64>> for Standard

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impl Distribution<NonZero<u128>> for Standard

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impl Distribution<NonZero<usize>> for Standard

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

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

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

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

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

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

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

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

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

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

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

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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 Standard

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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 Standard

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

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impl<T> Distribution<Option<T>> for Standard

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impl<T> Distribution<[T; 0]> for Standard

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impl<T> Distribution<[T; 1]> for Standard

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impl<T> Distribution<[T; 2]> for Standard

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impl<T> Distribution<[T; 3]> for Standard

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impl<T> Distribution<[T; 4]> for Standard

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impl<T> Distribution<[T; 5]> for Standard

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impl<T> Distribution<[T; 6]> for Standard

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impl<T> Distribution<[T; 7]> for Standard

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impl<T> Distribution<[T; 8]> for Standard

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impl<T> Distribution<[T; 9]> for Standard

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impl<T> Distribution<[T; 10]> for Standard

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impl<T> Distribution<[T; 11]> for Standard

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impl<T> Distribution<[T; 12]> for Standard

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impl<T> Distribution<[T; 13]> for Standard

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impl<T> Distribution<[T; 14]> for Standard

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impl<T> Distribution<[T; 15]> for Standard

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impl<T> Distribution<[T; 16]> for Standard

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impl<T> Distribution<[T; 17]> for Standard

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impl<T> Distribution<[T; 18]> for Standard

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impl<T> Distribution<[T; 19]> for Standard

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impl<T> Distribution<[T; 20]> for Standard

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impl<T> Distribution<[T; 21]> for Standard

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impl<T> Distribution<[T; 22]> for Standard

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impl<T> Distribution<[T; 23]> for Standard

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impl<T> Distribution<[T; 24]> for Standard

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impl<T> Distribution<[T; 25]> for Standard

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impl<T> Distribution<[T; 26]> for Standard

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impl<T> Distribution<[T; 27]> for Standard

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impl<T> Distribution<[T; 28]> for Standard

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impl<T> Distribution<[T; 29]> for Standard

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impl<T> Distribution<[T; 30]> for Standard

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impl<T> Distribution<[T; 31]> for Standard

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impl<T> Distribution<[T; 32]> for Standard

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impl<T> Distribution<Wrapping<T>> for Standard

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

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impl<X: SampleUniform> Distribution<X> for Uniform<X>