Struct rand::distributions::Slice

source ·
pub struct Slice<'a, T> { /* private fields */ }
Expand description

A distribution to sample items uniformly from a slice.

Slice::new constructs a distribution referencing a slice and uniformly samples references from the items in the slice. It may do extra work up front to make sampling of multiple values faster; if only one sample from the slice is required, SliceRandom::choose can be more efficient.

Steps are taken to avoid bias which might be present in naive implementations; for example slice[rng.gen() % slice.len()] samples from the slice, but may be more likely to select numbers in the low range than other values.

This distribution samples with replacement; each sample is independent. Sampling without replacement requires state to be retained, and therefore cannot be handled by a distribution; you should instead consider methods on SliceRandom, such as SliceRandom::choose_multiple.

Example

use rand::Rng;
use rand::distributions::Slice;

let vowels = ['a', 'e', 'i', 'o', 'u'];
let vowels_dist = Slice::new(&vowels).unwrap();
let rng = rand::thread_rng();

// build a string of 10 vowels
let vowel_string: String = rng
    .sample_iter(&vowels_dist)
    .take(10)
    .collect();

println!("{}", vowel_string);
assert_eq!(vowel_string.len(), 10);
assert!(vowel_string.chars().all(|c| vowels.contains(&c)));

For a single sample, SliceRandom::choose may be preferred:

use rand::seq::SliceRandom;

let vowels = ['a', 'e', 'i', 'o', 'u'];
let mut rng = rand::thread_rng();

println!("{}", vowels.choose(&mut rng).unwrap())

Implementations

Create a new Slice instance which samples uniformly from the slice. Returns Err if the slice is empty.

Trait Implementations

Returns a copy of the value. Read more
Performs copy-assignment from source. Read more
Formats the value using the given formatter. Read more
Generate a random value of T, using rng as the source of randomness.
Create an iterator that generates random values of T, using rng as the source of randomness. Read more
Create a distribution of values of ‘S’ by mapping the output of Self through the closure F Read more

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more
Immutably borrows from an owned value. Read more
Mutably borrows from an owned value. Read more

Returns the argument unchanged.

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

The type returned in the event of a conversion error.
Performs the conversion.
The type returned in the event of a conversion error.
Performs the conversion.