Struct rand::distributions::Slice

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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, IndexedRandom::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 IndexedRandom, such as IndexedRandom::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, IndexedRandom::choose may be preferred:

use rand::seq::IndexedRandom;

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

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

Implementations§

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impl<'a, T> Slice<'a, T>

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pub fn new(slice: &'a [T]) -> Result<Self, EmptySlice>

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

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pub fn num_choices(&self) -> NonZeroUsize

Returns the count of choices in this distribution

Trait Implementations§

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impl<'a, T: Clone> Clone for Slice<'a, T>

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fn clone(&self) -> Slice<'a, T>

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl<'a, T: Debug> Debug for Slice<'a, T>

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fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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impl<'a> DistString for Slice<'a, char>

Note: the String is potentially left with excess capacity; optionally the user may call string.shrink_to_fit() afterwards.

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fn append_string<R: Rng + ?Sized>( &self, rng: &mut R, string: &mut String, len: usize, )

Append len random chars to string
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fn sample_string<R: Rng + ?Sized>(&self, rng: &mut R, len: usize) -> String

Generate a String of len random chars
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impl<'a, T> Distribution<&'a T> for Slice<'a, T>

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fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> &'a T

Generate a random value of T, using rng as the source of randomness.
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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. Read more
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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 Read more
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impl<'a, T: Copy> Copy for Slice<'a, T>

Auto Trait Implementations§

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impl<'a, T> Freeze for Slice<'a, T>

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impl<'a, T> RefUnwindSafe for Slice<'a, T>
where T: RefUnwindSafe,

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impl<'a, T> Send for Slice<'a, T>
where T: Sync,

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impl<'a, T> Sync for Slice<'a, T>
where T: Sync,

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impl<'a, T> Unpin for Slice<'a, T>

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impl<'a, T> UnwindSafe for Slice<'a, T>
where T: RefUnwindSafe,

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> CloneToUninit for T
where T: Copy,

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unsafe fn clone_to_uninit(&self, dst: *mut T)

🔬This is a nightly-only experimental API. (clone_to_uninit)
Performs copy-assignment from self to dst. Read more
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impl<T> CloneToUninit for T
where T: Clone,

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default unsafe fn clone_to_uninit(&self, dst: *mut T)

🔬This is a nightly-only experimental API. (clone_to_uninit)
Performs copy-assignment from self to dst. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

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

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impl<T> ToOwned for T
where T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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impl<V, T> VZip<V> for T
where V: MultiLane<T>,

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fn vzip(self) -> V