Struct Fuse 

pub struct Fuse<I> { /* private fields */ }

An iterator that yields None forever after the underlying iterator yields None once.

This struct is created by Iterator::fuse. See its documentation for more.

Trait Implementations

impl<I: Clone> Clone for Fuse<I>

fn clone(&self) -> Fuse<I>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

where Self:,

Performs copy-assignment from source.

impl<I: Debug> Debug for Fuse<I>

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

Formats the value using the given formatter.

impl<I: Default> Default for Fuse<I>

fn default() -> Self

Creates a Fuse iterator from the default value of I.

let iter: Fuse<slice::Iter<'_, u8>> = Default::default();
assert_eq!(iter.len(), 0);

This is equivalent to I::default().fuse()¹; e.g. if I::default() is not an empty iterator, then this will not be an empty iterator.

#[derive(Default)]
struct Fourever;

impl Iterator for Fourever {
    type Item = u32;
    fn next(&mut self) -> Option<u32> {
        Some(4)
    }
}

let mut iter: Fuse<Fourever> = Default::default();
assert_eq!(iter.next(), Some(4));

---

1. if I does not override Iterator::fuse’s default implementation ↩

impl<I> DoubleEndedIterator for Fuse<I>

where I: DoubleEndedIterator,

fn next_back(&mut self) -> Option<<I as Iterator>::Item>

Removes and returns an element from the end of the iterator.

fn nth_back(&mut self, n: usize) -> Option<<I as Iterator>::Item>

Returns the nth element from the end of the iterator.

fn try_rfold<Acc, Fold, R>(&mut self, acc: Acc, fold: Fold) -> R

where Self: Sized, Fold: FnMut(Acc, Self::Item) -> R, R: Try<Output = Acc>,

This is the reverse version of Iterator::try_fold(): it takes elements starting from the back of the iterator.

fn rfold<Acc, Fold>(self, acc: Acc, fold: Fold) -> Acc

where Fold: FnMut(Acc, Self::Item) -> Acc,

An iterator method that reduces the iterator’s elements to a single, final value, starting from the back.

fn rfind<P>(&mut self, predicate: P) -> Option<Self::Item>

where P: FnMut(&Self::Item) -> bool,

Searches for an element of an iterator from the back that satisfies a predicate.

fn next_chunk_back<const N: usize>( &mut self, ) -> Result<[Self::Item; N], IntoIter<Self::Item, N>>

where Self: Sized,

🔬This is a nightly-only experimental API. (iter_next_chunk #98326)

Advances from the back of the iterator and returns an array containing the next N values in sequence.

fn advance_back_by(&mut self, n: usize) -> Result<(), NonZero<usize>>

🔬This is a nightly-only experimental API. (iter_advance_by #77404)

Advances the iterator from the back by n elements.

impl<I> ExactSizeIterator for Fuse<I>

where I: ExactSizeIterator,

fn len(&self) -> usize

Returns the exact remaining length of the iterator.

fn is_empty(&self) -> bool

🔬This is a nightly-only experimental API. (exact_size_is_empty #35428)

Returns true if the iterator is empty.

impl<I> FusedIterator for Fuse<I>

where I: Iterator,

impl<I> Iterator for Fuse<I>

where I: Iterator,

type Item = <I as Iterator>::Item

The type of the elements being iterated over.

fn next(&mut self) -> Option<Self::Item>

Advances the iterator and returns the next value.

fn nth(&mut self, n: usize) -> Option<I::Item>

Returns the nth element of the iterator.

fn last(self) -> Option<Self::Item>

Consumes the iterator, returning the last element.

fn count(self) -> usize

Consumes the iterator, counting the number of iterations and returning it.

fn size_hint(&self) -> (usize, Option<usize>)

Returns the bounds on the remaining length of the iterator.

fn try_fold<Acc, Fold, R>(&mut self, acc: Acc, fold: Fold) -> R

where Self: Sized, Fold: FnMut(Acc, Self::Item) -> R, R: Try<Output = Acc>,

An iterator method that applies a function as long as it returns successfully, producing a single, final value.

fn fold<Acc, Fold>(self, acc: Acc, fold: Fold) -> Acc

where Fold: FnMut(Acc, Self::Item) -> Acc,

Folds every element into an accumulator by applying an operation, returning the final result.

fn find<P>(&mut self, predicate: P) -> Option<Self::Item>

where P: FnMut(&Self::Item) -> bool,

Searches for an element of an iterator that satisfies a predicate.

fn next_chunk<const N: usize>( &mut self, ) -> Result<[Self::Item; N], IntoIter<Self::Item, N>>

where Self: Sized,

🔬This is a nightly-only experimental API. (iter_next_chunk #98326)

Advances the iterator and returns an array containing the next N values.

fn advance_by(&mut self, n: usize) -> Result<(), NonZero<usize>>

🔬This is a nightly-only experimental API. (iter_advance_by #77404)

Advances the iterator by n elements.

fn step_by(self, step: usize) -> StepBy<Self>

where Self: Sized,

Creates an iterator starting at the same point, but stepping by the given amount at each iteration.

fn chain<U>(self, other: U) -> Chain<Self, U::IntoIter>

where Self: Sized, U: IntoIterator<Item = Self::Item>,

Takes two iterators and creates a new iterator over both in sequence.

fn zip<U>(self, other: U) -> Zip<Self, U::IntoIter>

where Self: Sized, U: IntoIterator,

‘Zips up’ two iterators into a single iterator of pairs.

fn intersperse(self, separator: Self::Item) -> Intersperse<Self>

where Self: Sized, Self::Item: Clone,

🔬This is a nightly-only experimental API. (iter_intersperse #79524)

Creates a new iterator which places a copy of separator between items of the original iterator.

fn intersperse_with<G>(self, separator: G) -> IntersperseWith<Self, G>

where Self: Sized, G: FnMut() -> Self::Item,

🔬This is a nightly-only experimental API. (iter_intersperse #79524)

Creates a new iterator which places an item generated by separator between items of the original iterator.

fn map<B, F>(self, f: F) -> Map<Self, F>

where Self: Sized, F: FnMut(Self::Item) -> B,

Takes a closure and creates an iterator which calls that closure on each element.

fn for_each<F>(self, f: F)

where Self: Sized, F: FnMut(Self::Item),

Calls a closure on each element of an iterator.

fn filter<P>(self, predicate: P) -> Filter<Self, P>

where Self: Sized, P: FnMut(&Self::Item) -> bool,

Creates an iterator which uses a closure to determine if an element should be yielded.

fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F>

where Self: Sized, F: FnMut(Self::Item) -> Option<B>,

Creates an iterator that both filters and maps.

fn enumerate(self) -> Enumerate<Self>

where Self: Sized,

Creates an iterator which gives the current iteration count as well as the next value.

fn peekable(self) -> Peekable<Self>

where Self: Sized,

Creates an iterator which can use the peek and peek_mut methods to look at the next element of the iterator without consuming it. See their documentation for more information.

fn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P>

where Self: Sized, P: FnMut(&Self::Item) -> bool,

Creates an iterator that skips elements based on a predicate.

fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P>

where Self: Sized, P: FnMut(&Self::Item) -> bool,

Creates an iterator that yields elements based on a predicate.

fn map_while<B, P>(self, predicate: P) -> MapWhile<Self, P>

where Self: Sized, P: FnMut(Self::Item) -> Option<B>,

Creates an iterator that both yields elements based on a predicate and maps.

fn skip(self, n: usize) -> Skip<Self>

where Self: Sized,

Creates an iterator that skips the first n elements.

fn take(self, n: usize) -> Take<Self>

where Self: Sized,

Creates an iterator that yields the first n elements, or fewer if the underlying iterator ends sooner.

fn scan<St, B, F>(self, initial_state: St, f: F) -> Scan<Self, St, F>

where Self: Sized, F: FnMut(&mut St, Self::Item) -> Option<B>,

An iterator adapter which, like fold, holds internal state, but unlike fold, produces a new iterator.

fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F>

where Self: Sized, U: IntoIterator, F: FnMut(Self::Item) -> U,

Creates an iterator that works like map, but flattens nested structure.

fn flatten(self) -> Flatten<Self>

where Self: Sized, Self::Item: IntoIterator,

Creates an iterator that flattens nested structure.

fn map_windows<F, R, const N: usize>(self, f: F) -> MapWindows<Self, F, N>

where Self: Sized, F: FnMut(&[Self::Item; N]) -> R,

🔬This is a nightly-only experimental API. (iter_map_windows #87155)

Calls the given function f for each contiguous window of size N over self and returns an iterator over the outputs of f. Like slice::windows(), the windows during mapping overlap as well.

fn fuse(self) -> Fuse<Self>

where Self: Sized,

Creates an iterator which ends after the first None.

fn inspect<F>(self, f: F) -> Inspect<Self, F>

where Self: Sized, F: FnMut(&Self::Item),

Does something with each element of an iterator, passing the value on.

fn by_ref(&mut self) -> &mut Self

where Self: Sized,

Creates a “by reference” adapter for this instance of Iterator.

fn collect<B: FromIterator<Self::Item>>(self) -> B

where Self: Sized,

Transforms an iterator into a collection.

fn try_collect<B>(&mut self) -> <Self::Item::Residual as Residual<B>>::TryType

where Self: Sized, Self::Item: Try<Residual: Residual<B>>, B: FromIterator<<Self::Item as Try>::Output>,

🔬This is a nightly-only experimental API. (iterator_try_collect #94047)

Fallibly transforms an iterator into a collection, short circuiting if a failure is encountered.

fn collect_into<E: Extend<Self::Item>>(self, collection: &mut E) -> &mut E

where Self: Sized,

🔬This is a nightly-only experimental API. (iter_collect_into #94780)

Collects all the items from an iterator into a collection.

fn partition<B, F>(self, f: F) -> (B, B)

where Self: Sized, B: Default + Extend<Self::Item>, F: FnMut(&Self::Item) -> bool,

Consumes an iterator, creating two collections from it.

fn partition_in_place<'a, T: 'a, P>(self, predicate: P) -> usize

where Self: Sized + DoubleEndedIterator<Item = &'a mut T>, P: FnMut(&T) -> bool,

🔬This is a nightly-only experimental API. (iter_partition_in_place #62543)

Reorders the elements of this iterator in-place according to the given predicate, such that all those that return true precede all those that return false. Returns the number of true elements found.

fn is_partitioned<P>(self, predicate: P) -> bool

where Self: Sized, P: FnMut(Self::Item) -> bool,

🔬This is a nightly-only experimental API. (iter_is_partitioned #62544)

Checks if the elements of this iterator are partitioned according to the given predicate, such that all those that return true precede all those that return false.

fn try_for_each<F, R>(&mut self, f: F) -> R

where Self: Sized, F: FnMut(Self::Item) -> R, R: Try<Output = ()>,

An iterator method that applies a fallible function to each item in the iterator, stopping at the first error and returning that error.

fn reduce<F>(self, f: F) -> Option<Self::Item>

where Self: Sized, F: FnMut(Self::Item, Self::Item) -> Self::Item,

Reduces the elements to a single one, by repeatedly applying a reducing operation.

fn try_reduce<R>( &mut self, f: impl FnMut(Self::Item, Self::Item) -> R, ) -> <R::Residual as Residual<Option<R::Output>>>::TryType

where Self: Sized, R: Try<Output = Self::Item, Residual: Residual<Option<Self::Item>>>,

🔬This is a nightly-only experimental API. (iterator_try_reduce #87053)

Reduces the elements to a single one by repeatedly applying a reducing operation. If the closure returns a failure, the failure is propagated back to the caller immediately.

fn all<F>(&mut self, f: F) -> bool

where Self: Sized, F: FnMut(Self::Item) -> bool,

Tests if every element of the iterator matches a predicate.

fn any<F>(&mut self, f: F) -> bool

where Self: Sized, F: FnMut(Self::Item) -> bool,

Tests if any element of the iterator matches a predicate.

fn find_map<B, F>(&mut self, f: F) -> Option<B>

where Self: Sized, F: FnMut(Self::Item) -> Option<B>,

Applies function to the elements of iterator and returns the first non-none result.

fn try_find<R>( &mut self, f: impl FnMut(&Self::Item) -> R, ) -> <R::Residual as Residual<Option<Self::Item>>>::TryType

where Self: Sized, R: Try<Output = bool, Residual: Residual<Option<Self::Item>>>,

🔬This is a nightly-only experimental API. (try_find #63178)

Applies function to the elements of iterator and returns the first true result or the first error.

fn position<P>(&mut self, predicate: P) -> Option<usize>

where Self: Sized, P: FnMut(Self::Item) -> bool,

Searches for an element in an iterator, returning its index.

fn rposition<P>(&mut self, predicate: P) -> Option<usize>

where P: FnMut(Self::Item) -> bool, Self: Sized + ExactSizeIterator + DoubleEndedIterator,

Searches for an element in an iterator from the right, returning its index.

fn max(self) -> Option<Self::Item>

where Self: Sized, Self::Item: Ord,

Returns the maximum element of an iterator.

fn min(self) -> Option<Self::Item>

where Self: Sized, Self::Item: Ord,

Returns the minimum element of an iterator.

fn max_by_key<B: Ord, F>(self, f: F) -> Option<Self::Item>

where Self: Sized, F: FnMut(&Self::Item) -> B,

Returns the element that gives the maximum value from the specified function.

fn max_by<F>(self, compare: F) -> Option<Self::Item>

where Self: Sized, F: FnMut(&Self::Item, &Self::Item) -> Ordering,

Returns the element that gives the maximum value with respect to the specified comparison function.

fn min_by_key<B: Ord, F>(self, f: F) -> Option<Self::Item>

where Self: Sized, F: FnMut(&Self::Item) -> B,

Returns the element that gives the minimum value from the specified function.

fn min_by<F>(self, compare: F) -> Option<Self::Item>

where Self: Sized, F: FnMut(&Self::Item, &Self::Item) -> Ordering,

Returns the element that gives the minimum value with respect to the specified comparison function.

fn