# Slice in rand::distributions - Rust
A distribution to sample items uniformly from a slice.
Keywords: rust, rustlang, rust-lang, Slice

# 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, `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

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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.

## 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, 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>ⓘNotable traits for DistIter<D, R, T>`impl<D, R, T> Iterator for DistIter<D, R, T> where
D: Distribution<T>,
R: Rng, type Item = 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

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

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

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

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

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

## Blanket Implementations

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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,

const: unstable · source

#### 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,

const: unstable · source

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

Mutably borrows from an owned value. Read more

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### impl<T> From<T> for T

const: unstable · source

#### fn from(t: T) -> T

Returns the argument unchanged.

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

const: unstable · source

#### 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,

#### 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)

🔬 This is a nightly-only experimental API. (`toowned_clone_into`)

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>,

#### type Error = Infallible

The type returned in the event of a conversion error.

const: unstable · source

#### 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>,

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

The type returned in the event of a conversion error.

const: unstable · source

#### 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