Trait rand::seq::IteratorRandom

pub trait IteratorRandom: Iterator + Sized {
    fn choose<R: ?Sized>(self, rng: &mut R) -> Option<Self::Item>
    where
        R: Rng,
    { ... }
    fn choose_multiple_fill<R: ?Sized>(
        self, 
        rng: &mut R, 
        buf: &mut [Self::Item]
    ) -> usize
    where
        R: Rng,
    { ... }
    fn choose_multiple<R: ?Sized>(
        self, 
        rng: &mut R, 
        amount: usize
    ) -> Vec<Self::Item>
    where
        R: Rng,
    { ... }
}

Extension trait on iterators, providing random sampling methods.

This trait is implemented on all sized iterators, providing methods for choosing one or more elements. You must use this trait:

use rand::seq::IteratorRandom;
 
fn main() {
    let mut rng = rand::thread_rng();
     
    let faces = "😀😎😐😕😠😢";
    println!("I am {}!", faces.chars().choose(&mut rng).unwrap());
}

Example output (non-deterministic):

I am 😀!

Provided methods

fn choose<R: ?Sized>(self, rng: &mut R) -> Option<Self::Item> where
    R: Rng, 

Choose one element at random from the iterator.

Returns None if and only if the iterator is empty.

This method uses [Iterator::size_hint] for optimisation. With an accurate hint and where [Iterator::nth] is a constant-time operation this method can offer O(1) performance. Where no size hint is available, complexity is O(n) where n is the iterator length. Partial hints (where lower > 0) also improve performance.

For slices, prefer [SliceRandom::choose] which guarantees O(1) performance.

fn choose_multiple_fill<R: ?Sized>(
    self,
    rng: &mut R,
    buf: &mut [Self::Item]
) -> usize where
    R: Rng, 

Collects values at random from the iterator into a supplied buffer until that buffer is filled.

Although the elements are selected randomly, the order of elements in the buffer is neither stable nor fully random. If random ordering is desired, shuffle the result.

Returns the number of elements added to the buffer. This equals the length of the buffer unless the iterator contains insufficient elements, in which case this equals the number of elements available.

Complexity is O(n) where n is the length of the iterator. For slices, prefer [SliceRandom::choose_multiple].

fn choose_multiple<R: ?Sized>(
    self,
    rng: &mut R,
    amount: usize
) -> Vec<Self::Item> where
    R: Rng, 

Collects amount values at random from the iterator into a vector.

This is equivalent to choose_multiple_fill except for the result type.

Although the elements are selected randomly, the order of elements in the buffer is neither stable nor fully random. If random ordering is desired, shuffle the result.

The length of the returned vector equals amount unless the iterator contains insufficient elements, in which case it equals the number of elements available.

Complexity is O(n) where n is the length of the iterator. For slices, prefer [SliceRandom::choose_multiple].

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Implementors

impl<I> IteratorRandom for I where
    I: Iterator + Sized, 

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