Struct std::iter::Enumerate

#[must_use = "iterators are lazy and do nothing unless consumed"]
pub struct Enumerate<I> { /* fields omitted */ }

An iterator that yields the current count and the element during iteration.

This struct is created by the enumerate method on Iterator. See its documentation for more.

Trait Implementations

impl<I> DoubleEndedIterator for Enumerate<I> where
    I: ExactSizeIterator + DoubleEndedIterator, 

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

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

fn try_rfold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R where
    Fold: FnMut(Acc, <Enumerate<I> as Iterator>::Item) -> R,
    R: Try<Ok = Acc>,
    Enumerate<I>: Sized, 

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

fn rfold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc where
    Fold: FnMut(Acc, <Enumerate<I> as Iterator>::Item) -> Acc, 

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

default fn nth_back(&mut self, n: usize) -> Option<Self::Item>

🔬 This is a nightly-only experimental API. (iter_nth_back #56995)

Returns the nth element from the end of the iterator.

default 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.

impl<I> Iterator for Enumerate<I> where
    I: Iterator, 

type Item = (usize, <I as Iterator>::Item)

The type of the elements being iterated over.

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

Overflow Behavior

The method does no guarding against overflows, so enumerating more than usize::MAX elements either produces the wrong result or panics. If debug assertions are enabled, a panic is guaranteed.

Panics

Might panic if the index of the element overflows a usize.

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

Returns the bounds on the remaining length of the iterator.

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

Returns the nth element of the iterator.

fn count(self) -> usize

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

fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R where
    Fold: FnMut(Acc, <Enumerate<I> as Iterator>::Item) -> R,
    R: Try<Ok = Acc>,
    Enumerate<I>: Sized, 

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

fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc where
    Fold: FnMut(Acc, <Enumerate<I> as Iterator>::Item) -> Acc, 

An iterator method that applies a function, producing a single, final value.

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

Consumes the iterator, returning the last element.

Important traits for StepBy<I>

impl<I> Iterator for StepBy<I> where
    I: Iterator,  type Item = <I as Iterator>::Item;

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

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

Important traits for Chain<A, B>

impl<A, B> Iterator for Chain<A, B> where
    A: Iterator,
    B: Iterator<Item = <A as Iterator>::Item>,  type Item = <A as Iterator>::Item;

default fn chain<U>(
    self,
    other: U
) -> Chain<Self, <U as IntoIterator>::IntoIter> where
    U: IntoIterator<Item = Self::Item>, 

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

Important traits for Zip<A, B>

impl<A, B> Iterator for Zip<A, B> where
    A: Iterator,
    B: Iterator,  type Item = (<A as Iterator>::Item, <B as Iterator>::Item);

default fn zip<U>(self, other: U) -> Zip<Self, <U as IntoIterator>::IntoIter> where
    U: IntoIterator, 

'Zips up' two iterators into a single iterator of pairs.

Important traits for Map<I, F>

impl<B, I, F> Iterator for Map<I, F> where
    F: FnMut(<I as Iterator>::Item) -> B,
    I: Iterator,  type Item = B;

default fn map<B, F>(self, f: F) -> Map<Self, F> where
    F: FnMut(Self::Item) -> B, 

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

default fn for_each<F>(self, f: F) where
    F: FnMut(Self::Item), 

Calls a closure on each element of an iterator.

Important traits for Filter<I, P>

impl<I, P> Iterator for Filter<I, P> where
    I: Iterator,
    P: FnMut(&<I as Iterator>::Item) -> bool,  type Item = <I as Iterator>::Item;

default fn filter<P>(self, predicate: P) -> Filter<Self, P> where
    P: FnMut(&Self::Item) -> bool, 

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

Important traits for FilterMap<I, F>

impl<B, I, F> Iterator for FilterMap<I, F> where
    F: FnMut(<I as Iterator>::Item) -> Option<B>,
    I: Iterator,  type Item = B;

default fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F> where
    F: FnMut(Self::Item) -> Option<B>, 

Creates an iterator that both filters and maps.

Important traits for Enumerate<I>

impl<I> Iterator for Enumerate<I> where
    I: Iterator,  type Item = (usize, <I as Iterator>::Item);

default fn enumerate(self) -> Enumerate<Self>

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

Important traits for Peekable<I>

impl<I> Iterator for Peekable<I> where
    I: Iterator,  type Item = <I as Iterator>::Item;

default fn peekable(self) -> Peekable<Self>

Creates an iterator which can use peek to look at the next element of the iterator without consuming it.

Important traits for SkipWhile<I, P>

impl<I, P> Iterator for SkipWhile<I, P> where
    I: Iterator,
    P: FnMut(&<I as Iterator>::Item) -> bool,  type Item = <I as Iterator>::Item;

default fn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P> where
    P: FnMut(&Self::Item) -> bool, 

Creates an iterator that [skip]s elements based on a predicate.

Important traits for TakeWhile<I, P>

impl<I, P> Iterator for TakeWhile<I, P> where
    I: Iterator,
    P: FnMut(&<I as Iterator>::Item) -> bool,  type Item = <I as Iterator>::Item;

default fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P> where
    P: FnMut(&Self::Item) -> bool, 

Creates an iterator that yields elements based on a predicate.

Important traits for Skip<I>

impl<I> Iterator for Skip<I> where
    I: Iterator,  type Item = <I as Iterator>::Item;

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

Creates an iterator that skips the first n elements.

Important traits for Take<I>

impl<I> Iterator for Take<I> where
    I: Iterator,  type Item = <I as Iterator>::Item;

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

Creates an iterator that yields its first n elements.

Important traits for Scan<I, St, F>

impl<B, I, St, F> Iterator for Scan<I, St, F> where
    F: FnMut(&mut St, <I as Iterator>::Item) -> Option<B>,
    I: Iterator,  type Item = B;

default fn scan<St, B, F>(self, initial_state: St, f: F) -> Scan<Self, St, F> where
    F: FnMut(&mut St, Self::Item) -> Option<B>, 

An iterator adaptor similar to [fold] that holds internal state and produces a new iterator.

Important traits for FlatMap<I, U, F>

impl<I, U, F> Iterator for FlatMap<I, U, F> where
    F: FnMut(<I as Iterator>::Item) -> U,
    I: Iterator,
    U: IntoIterator,  type Item = <U as IntoIterator>::Item;

default fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F> where
    F: FnMut(Self::Item) -> U,
    U: IntoIterator, 

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

Important traits for Flatten<I>

impl<I, U> Iterator for Flatten<I> where
    I: Iterator,
    U: Iterator,
    <I as Iterator>::Item: IntoIterator,
    <<I as Iterator>::Item as IntoIterator>::IntoIter == U,
    <<I as Iterator>::Item as IntoIterator>::Item == <U as Iterator>::Item,  type Item = <U as Iterator>::Item;

default fn flatten(self) -> Flatten<Self> where
    Self::Item: IntoIterator, 

Creates an iterator that flattens nested structure.

Important traits for Fuse<I>

impl<I> Iterator for Fuse<I> where
    I: FusedIterator, impl<I> Iterator for Fuse<I> where
    I: Iterator,  type Item = <I as Iterator>::Item;

default fn fuse(self) -> Fuse<Self>

Creates an iterator which ends after the first [None].

Important traits for Inspect<I, F>

impl<I, F> Iterator for Inspect<I, F> where
    F: FnMut(&<I as Iterator>::Item),
    I: Iterator,  type Item = <I as Iterator>::Item;

default fn inspect<F>(self, f: F) -> Inspect<Self, F> where
    F: FnMut(&Self::Item), 

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

Important traits for &'_ mut I

impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W

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

Borrows an iterator, rather than consuming it.

#[must_use = "if you really need to exhaust the iterator, consider `.for_each(drop)` instead"]

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

Transforms an iterator into a collection.

default fn partition<B, F>(self, f: F) -> (B, B) where
    B: Default + Extend<Self::Item>,
    F: FnMut(&Self::Item) -> bool, 

Consumes an iterator, creating two collections from it.

default fn try_for_each<F, R>(&mut self, f: F) -> R where
    F: FnMut(Self::Item) -> R,
    R: Try<Ok = ()>, 

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

default fn all<F>(&mut self, f: F) -> bool where
    F: FnMut(Self::Item) -> bool, 

Tests if every element of the iterator matches a predicate.

default fn any<F>(&mut self, f: F) -> bool where
    F: FnMut(Self::Item) -> bool, 

Tests if any element of the iterator matches a predicate.

default 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.

default fn find_map<B, F>(&mut self, f: F) -> Option<B> where
    F: FnMut(Self::Item) -> Option<B>, 

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

default fn position<P>(&mut self, predicate: P) -> Option<usize> where
    P: FnMut(Self::Item) -> bool, 

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

default fn rposition<P>(&mut self, predicate: P) -> Option<usize> where
    P: FnMut(Self::Item) -> bool,
    Self: ExactSizeIterator + DoubleEndedIterator, 

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

default fn max(self) -> Option<Self::Item> where
    Self::Item: Ord, 

Returns the maximum element of an iterator.

default fn min(self) -> Option<Self::Item> where
    Self::Item: Ord, 

Returns the minimum element of an iterator.

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

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

default fn max_by<F>(self, compare: F) -> Option<Self::Item> where
    F: FnMut(&Self::Item, &Self::Item) -> Ordering, 

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

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

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

default fn min_by<F>(self, compare: F) -> Option<Self::Item> where
    F: FnMut(&Self::Item, &Self::Item) -> Ordering, 

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

Important traits for Rev<I>

impl<I> Iterator for Rev<I> where
    I: DoubleEndedIterator,  type Item = <I as Iterator>::Item;

default fn rev(self) -> Rev<Self> where
    Self: DoubleEndedIterator, 

Reverses an iterator's direction.

default fn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB) where
    FromA: Default + Extend<A>,
    FromB: Default + Extend<B>,
    Self: Iterator<Item = (A, B)>, 

Converts an iterator of pairs into a pair of containers.

Important traits for Copied<I>

impl<'a, I, T> Iterator for Copied<I> where
    I: Iterator<Item = &'a T>,
    T: 'a + Copy,  type Item = T;

default fn copied<'a, T>(self) -> Copied<Self> where
    Self: Iterator<Item = &'a T>,
    T: 'a + Copy, 

🔬 This is a nightly-only experimental API. (iter_copied #57127)

Creates an iterator which copies all of its elements.

Important traits for Cloned<I>

impl<'a, I, T> Iterator for Cloned<I> where
    I: Iterator<Item = &'a T>,
    T: 'a + Clone,  type Item = T;

default fn cloned<'a, T>(self) -> Cloned<Self> where
    Self: Iterator<Item = &'a T>,
    T: 'a + Clone, 

Creates an iterator which [clone]s all of its elements.

Important traits for Cycle<I>

impl<I> Iterator for Cycle<I> where
    I: Clone + Iterator,  type Item = <I as Iterator>::Item;

default fn cycle(self) -> Cycle<Self> where
    Self: Clone, 

Repeats an iterator endlessly.

default fn sum<S>(self) -> S where
    S: Sum<Self::Item>, 

Sums the elements of an iterator.

default fn product<P>(self) -> P where
    P: Product<Self::Item>, 

Iterates over the entire iterator, multiplying all the elements

default fn cmp<I>(self, other: I) -> Ordering where
    I: IntoIterator<Item = Self::Item>,
    Self::Item: Ord, 

Lexicographically compares the elements of this Iterator with those of another.

default fn partial_cmp<I>(self, other: I) -> Option<Ordering> where
    I: IntoIterator,
    Self::Item: PartialOrd<<I as IntoIterator>::Item>, 

Lexicographically compares the elements of this Iterator with those of another.

default fn eq<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialEq<<I as IntoIterator>::Item>, 

Determines if the elements of this Iterator are equal to those of another.

default fn ne<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialEq<<I as IntoIterator>::Item>, 

Determines if the elements of this Iterator are unequal to those of another.

default fn lt<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialOrd<<I as IntoIterator>::Item>, 

Determines if the elements of this Iterator are lexicographically less than those of another.

default fn le<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialOrd<<I as IntoIterator>::Item>, 

Determines if the elements of this Iterator are lexicographically less or equal to those of another.

default fn gt<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialOrd<<I as IntoIterator>::Item>, 

Determines if the elements of this Iterator are lexicographically greater than those of another.

default fn ge<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialOrd<<I as IntoIterator>::Item>, 

Determines if the elements of this Iterator are lexicographically greater than or equal to those of another.

default fn is_sorted(self) -> bool where
    Self::Item: PartialOrd<Self::Item>, 

🔬 This is a nightly-only experimental API. (is_sorted #53485)

new API

Checks if the elements of this iterator are sorted.

default fn is_sorted_by<F>(self, compare: F) -> bool where
    F: FnMut(&Self::Item, &Self::Item) -> Option<Ordering>, 

🔬 This is a nightly-only experimental API. (is_sorted #53485)

new API

Checks if the elements of this iterator are sorted using the given comparator function.

default fn is_sorted_by_key<F, K>(self, f: F) -> bool where
    F: FnMut(&Self::Item) -> K,
    K: PartialOrd<K>, 

🔬 This is a nightly-only experimental API. (is_sorted #53485)

new API

Checks if the elements of this iterator are sorted using the given key extraction function.

impl<I> TrustedLen for Enumerate<I> where
    I: TrustedLen, 

impl<I> ExactSizeIterator for Enumerate<I> where
    I: ExactSizeIterator, 

fn len(&self) -> usize

Returns the exact number of times the iterator will iterate.

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 Enumerate<I> where
    I: FusedIterator, 

impl<I> Clone for Enumerate<I> where
    I: Clone, 

Important traits for Enumerate<I>

impl<I> Iterator for Enumerate<I> where
    I: Iterator,  type Item = (usize, <I as Iterator>::Item);

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

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<I> Debug for Enumerate<I> where
    I: Debug, 

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

Formats the value using the given formatter.