successors in core::iter - Rust
Description: Creates an iterator which, starting from an initial item, computes each successive item from the preceding one.

# Function successors

1.34.0 · Source

    pub fn successors<T, F>(first: Option<T>, succ: F) -> Successors<T, F> ⓘwhere
        F: FnMut(&T) -> Option<T>,

Expand description

Creates an iterator which, starting from an initial item, computes each successive item from the preceding one.

This iterator stores an optional item (`Option<T>`) and a successor closure (`impl FnMut(&T) -> Option<T>`). Its `next` method returns the stored optional item and if it is `Some(val)` calls the stored closure on `&val` to compute and store its successor. The iterator will apply the closure successively to the stored option’s value until the option is `None`. This also means that once the stored option is `None` it will remain `None`, as the closure will not be called again, so the created iterator is a `FusedIterator`. The iterator’s items will be the initial item and all of its successors as calculated by the successor closure.

    use std::iter::successors;

    let powers_of_10 = successors(Some(1_u16), |n| n.checked_mul(10));
    assert_eq!(powers_of_10.collect::<Vec<_>>(), &[1, 10, 100, 1_000, 10_000]);