Struct CharIndices 

pub struct CharIndices<'a> { /* private fields */ }

An iterator over the chars of a string slice, and their positions.

This struct is created by the char_indices method on str. See its documentation for more.

Implementations

impl<'a> CharIndices<'a>

pub fn as_str(&self) -> &'a str

Views the underlying data as a subslice of the original data.

This has the same lifetime as the original slice, and so the iterator can continue to be used while this exists.

pub fn offset(&self) -> usize

Returns the byte position of the next character, or the length of the underlying string if there are no more characters.

This means that, when the iterator has not been fully consumed, the returned value will match the index that will be returned by the next call to next().

Examples

let mut chars = "a楽".char_indices();

// `next()` has not been called yet, so `offset()` returns the byte
// index of the first character of the string, which is always 0.
assert_eq!(chars.offset(), 0);
// As expected, the first call to `next()` also returns 0 as index.
assert_eq!(chars.next(), Some((0, 'a')));

// `next()` has been called once, so `offset()` returns the byte index
// of the second character ...
assert_eq!(chars.offset(), 1);
// ... which matches the index returned by the next call to `next()`.
assert_eq!(chars.next(), Some((1, '楽')));

// Once the iterator has been consumed, `offset()` returns the length
// in bytes of the string.
assert_eq!(chars.offset(), 4);
assert_eq!(chars.next(), None);

Trait Implementations

impl<'a> Clone for CharIndices<'a>

fn clone(&self) -> CharIndices<'a>

Returns a duplicate of the value.

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

where Self:,

Performs copy-assignment from source.

impl<'a> Debug for CharIndices<'a>

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

Formats the value using the given formatter.

impl<'a> DoubleEndedIterator for CharIndices<'a>

fn next_back(&mut self) -> Option<(usize, char)>

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

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.

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

Returns the nth element from the end of the iterator.

fn try_rfold<B, F, R>(&mut self, init: B, f: F) -> R

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

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

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

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

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

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

impl<'a> Iterator for CharIndices<'a>

type Item = (usize, char)

The type of the elements being iterated over.

fn next(&mut self) -> Option<(usize, char)>

Advances the iterator and returns the next value.

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 last(self) -> Option<(usize, char)>

Consumes the iterator, returning the last element.

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

Returns the nth element of the iterator.

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 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 enumerate(self) -> Enumerate<Self>

where Self: Sized,

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

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 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 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 fuse(self) -> Fuse<Self>

where Self: Sized,

Creates an iterator which ends after the first None.

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_fold<B, F, R>(&mut self, init: B, f: F) -> R

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

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

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 fold<B, F>(self, init: B, f: F) -> B

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

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

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

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

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

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 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 rev(self) -> Rev<Self>

where Self: Sized + DoubleEndedIterator,

Reverses an iterator’s direction.

fn copied<'a, T>(self) -> Copied<Self>

where T: Copy + 'a, Self: Sized + Iterator<Item = &'a T>,

Creates an iterator which copies all of its elements.

fn cloned<'a, T>(self) -> Cloned<Self>

where T: Clone + 'a, Self: Sized + Iterator<Item = &'a T>,

Creates an iterator which clones all of its elements.

fn sum<S>(self) -> S

where Self: Sized, S: Sum<Self::Item>,

Sums the elements of an iterator.

fn cmp_by<I, F>(self, other: I, cmp: F) -> Ordering

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

🔬This is a nightly-only experimental API. (iter_order_by #64295)

Lexicographically compares the elements of this Iterator with those of another with respect to the specified comparison function.

fn eq<I>(self, other: I) -> bool

where I: IntoIterator, Self::Item: PartialEq<I::Item>, Self: Sized,

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

fn eq_by<I, F>(self, other: I, eq: F) -> bool

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

🔬This is a nightly-only experimental API. (iter_order_by #64295)

Determines if the elements of this Iterator are equal to those of another with respect to the specified equality function.