Struct std::ops::Range

pub struct Range<Idx> {
    pub start: Idx,
    pub end: Idx,
}

A (half-open) range bounded inclusively below and exclusively above (start..end).

The range start..end contains all values with start <= x < end. It is empty if start >= end.

Examples

The start..end syntax is a Range:

assert_eq!((3..5), std::ops::Range { start: 3, end: 5 });
assert_eq!(3 + 4 + 5, (3..6).sum());

let arr = [0, 1, 2, 3, 4];
assert_eq!(arr[ ..  ], [0, 1, 2, 3, 4]);
assert_eq!(arr[ .. 3], [0, 1, 2      ]);
assert_eq!(arr[ ..=3], [0, 1, 2, 3   ]);
assert_eq!(arr[1..  ], [   1, 2, 3, 4]);
assert_eq!(arr[1.. 3], [   1, 2      ]); // This is a `Range`
assert_eq!(arr[1..=3], [   1, 2, 3   ]);

Fields

start: Idx

The lower bound of the range (inclusive).

end: Idx

The upper bound of the range (exclusive).

Implementations

impl<Idx> Range<Idx> where
    Idx: PartialOrd<Idx>, 

pub fn contains<U>(&self, item: &U) -> bool where
    Idx: PartialOrd<U>,
    U: PartialOrd<Idx> + ?Sized, 

Returns true if item is contained in the range.

Examples

assert!(!(3..5).contains(&2));
assert!( (3..5).contains(&3));
assert!( (3..5).contains(&4));
assert!(!(3..5).contains(&5));

assert!(!(3..3).contains(&3));
assert!(!(3..2).contains(&3));

assert!( (0.0..1.0).contains(&0.5));
assert!(!(0.0..1.0).contains(&f32::NAN));
assert!(!(0.0..f32::NAN).contains(&0.5));
assert!(!(f32::NAN..1.0).contains(&0.5));

pub fn is_empty(&self) -> bool

Returns true if the range contains no items.

Examples

assert!(!(3..5).is_empty());
assert!( (3..3).is_empty());
assert!( (3..2).is_empty());

The range is empty if either side is incomparable:

assert!(!(3.0..5.0).is_empty());
assert!( (3.0..f32::NAN).is_empty());
assert!( (f32::NAN..5.0).is_empty());

Trait Implementations

impl<Idx> Clone for Range<Idx> where
    Idx: Clone, 

fn clone(&self) -> Range<Idx>

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<Idx> Debug for Range<Idx> where
    Idx: Debug, 

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

Formats the value using the given formatter.

impl<Idx> Default for Range<Idx> where
    Idx: Default, 

fn default() -> Range<Idx>

Returns the “default value” for a type.

impl<A> DoubleEndedIterator for Range<A> where
    A: Step, 

fn next_back(&mut self) -> Option<A>

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

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

Returns the nth element from the end of the iterator.

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

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

Advances the iterator from the back by n elements.

fn try_rfold<B, F, R>(&mut self, init: B, f: F) -> R where
    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
    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
    P: FnMut(&Self::Item) -> bool, 

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

impl ExactSizeIterator for Range<i16>

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 ExactSizeIterator for Range<i32>

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 ExactSizeIterator for Range<i8>

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 ExactSizeIterator for Range<isize>

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 ExactSizeIterator for Range<u16>

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 ExactSizeIterator for Range<u32>

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 ExactSizeIterator for Range<u8>

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 ExactSizeIterator for Range<usize>

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<Idx> Hash for Range<Idx> where
    Idx: Hash, 

fn hash<__H>(&self, state: &mut __H) where
    __H: Hasher, 

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H) where
    H: Hasher, 

Feeds a slice of this type into the given Hasher.

impl Index<Range<usize>> for String

type Output = str

The returned type after indexing.

fn index(&self, index: Range<usize>) -> &str

Performs the indexing (container[index]) operation.

impl IndexMut<Range<usize>> for String

fn index_mut(&mut self, index: Range<usize>) -> &mut str

Performs the mutable indexing (container[index]) operation.

impl<A> Iterator for Range<A> where
    A: Step, 

type Item = A

The type of the elements being iterated over.

fn next(&mut self) -> Option<A>

Advances the iterator and returns the next value.

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

Returns the bounds on the remaining length of the iterator.

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

Returns the nth element of the iterator.

fn last(self) -> Option<A>

Consumes the iterator, returning the last element.

fn min(self) -> Option<A>

Returns the minimum element of an iterator.

fn max(self) -> Option<A>

Returns the maximum element of an iterator.

fn is_sorted(self) -> bool

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

Checks if the elements of this iterator are sorted.

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

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

Advances the iterator by n elements.

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

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

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

fn count(self) -> usize

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

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.

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.

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.

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

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

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

fn intersperse_with<G>(self, separator: G) -> IntersperseWith<Self, G> where
    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 adjacent items of the original iterator.

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.

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

Calls a closure on each element of an iterator.

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.

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.

fn enumerate(self) -> Enumerate<Self>

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

fn peekable(self) -> Peekable<Self>

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
    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
    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
    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>

Creates an iterator that skips the first n elements.

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

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

An iterator adapter similar to fold that holds internal state and produces a new iterator.

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

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

fn fuse(self) -> Fuse<Self>

Creates an iterator which ends after the first None.

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

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

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

Borrows an iterator, rather than consuming it.

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

Transforms an iterator into a collection.

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

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

Consumes an iterator, creating two collections from it.

fn partition_in_place<'a, T, P>(self, predicate: P) -> usize where
    T: 'a,
    Self: 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
    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_fold<B, F, R>(&mut self, init: B, f: F) -> R where
    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
    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
    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
    F: FnMut(Self::Item, Self::Item) -> Self::Item, 

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

fn try_reduce<F, R>(
    &mut self,
    f: F
) -> <<R as Try>::Residual as Residual<Option<<R as Try>::Output>>>::TryType where
    F: FnMut(Self::Item, Self::Item) -> R,
    R: Try<Output = Self::Item>,
    <R as Try>::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
    F: FnMut(Self::Item) -> bool, 

Tests if every element of the iterator matches a predicate.

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

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

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.

fn try_find<F, R>(
    &mut self,
    f: F
) -> <<R as Try>::Residual as Residual<Option<Self::Item>>>::TryType where
    F: FnMut(&Self::Item) -> R,
    R: Try<Output = bool>,
    <R as Try>::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
    P: FnMut(Self::Item) -> bool, 

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

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.

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.

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.

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.

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

Reverses an iterator’s direction.

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.

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

Creates an iterator which copies all of its elements.

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

Creates an iterator which clones all of its elements.

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

Repeats an iterator endlessly.

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

Sums the elements of an iterator.

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

Iterates over the entire iterator, multiplying all the elements

fn cmp_by<I, F>(self, other: I, cmp: F) -> Ordering where
    I: IntoIterator,
    F: FnMut(Self::Item, <I as IntoIterator>::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 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.

fn partial_cmp_by<I, F>(self, other: I, partial_cmp: F) -> Option<Ordering> where
    I: IntoIterator,
    F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Option<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 as IntoIterator>::Item>, 

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
    I: IntoIterator,
    F: FnMut(Self::Item, <I as IntoIterator>::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.

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.

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.

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.

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.

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.

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)

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

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)

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

impl<Idx> PartialEq<Range<Idx>> for Range<Idx> where
    Idx: PartialEq<Idx>, 

fn eq(&self, other: &Range<Idx>) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Range<Idx>) -> bool

This method tests for !=.

impl<T> RangeBounds<T> for Range<&T>

fn start_bound(&self) -> Bound<&T>

Start index bound.

fn end_bound(&self) -> Bound<&T>

End index bound.

fn contains<U>(&self, item: &U) -> bool where
    T: PartialOrd<U>,
    U: PartialOrd<T> + ?Sized, 

Returns true if item is contained in the range.

impl<T> RangeBounds<T> for Range<T>

fn start_bound(&self) -> Bound<&T>

Start index bound.

fn end_bound(&self) -> Bound<&T>

End index bound.

fn contains<U>(&self, item: &U) -> bool where
    T: PartialOrd<U>,
    U: PartialOrd<T> + ?Sized, 

Returns true if item is contained in the range.

impl<T> SliceIndex<[T]> for Range<usize>

type Output = [T]

The output type returned by methods.

fn get(self, slice: &[T]) -> Option<&[T]>

🔬 This is a nightly-only experimental API. (slice_index_methods)

Returns a shared reference to the output at this location, if in bounds.

fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]>

🔬 This is a nightly-only experimental API. (slice_index_methods)

Returns a mutable reference to the output at this location, if in bounds.

unsafe fn get_unchecked(self, slice: *const [T]) -> *const [T]

🔬 This is a nightly-only experimental API. (slice_index_methods)

Returns a shared reference to the output at this location, without performing any bounds checking. Calling this method with an out-of-bounds index or a dangling slice pointer is undefined behavior even if the resulting reference is not used.

unsafe fn get_unchecked_mut(self, slice: *mut [T]) -> *mut [T]

🔬 This is a nightly-only experimental API. (slice_index_methods)

Returns a mutable reference to the output at this location, without performing any bounds checking. Calling this method with an out-of-bounds index or a dangling slice pointer is undefined behavior even if the resulting reference is not used.

fn index(self, slice: &[T]) -> &[T]

🔬 This is a nightly-only experimental API. (slice_index_methods)

Returns a shared reference to the output at this location, panicking if out of bounds.

fn index_mut(self, slice: &mut [T]) -> &mut [T]

🔬 This is a nightly-only experimental API. (slice_index_methods)

Returns a mutable reference to the output at this location, panicking if out of bounds.

impl SliceIndex<str> for Range<usize>

Implements substring slicing with syntax &self[begin .. end] or &mut self[begin .. end].

Returns a slice of the given string from the byte range [begin, end).

This operation is O(1).

Prior to 1.20.0, these indexing operations were still supported by direct implementation of Index and IndexMut.

Panics

Panics if begin or end does not point to the starting byte offset of a character (as defined by is_char_boundary), if begin > end, or if end > len.

Examples

let s = "Löwe 老虎 Léopard";
assert_eq!(&s[0 .. 1], "L");

assert_eq!(&s[1 .. 9], "öwe 老");

// these will panic:
// byte 2 lies within `ö`:
// &s[2 ..3];

// byte 8 lies within `老`
// &s[1 .. 8];

// byte 100 is outside the string
// &s[3 .. 100];

type Output = str

The output type returned by methods.

fn get(self, slice: &str) -> Option<&<Range<usize> as SliceIndex<str>>::Output>

🔬 This is a nightly-only experimental API. (slice_index_methods)

Returns a shared reference to the output at this location, if in bounds.

fn get_mut(
    self,
    slice: &mut str
) -> Option<&mut <Range<usize> as SliceIndex<str>>::Output>

🔬 This is a nightly-only experimental API. (slice_index_methods)

Returns a mutable reference to the output at this location, if in bounds.

unsafe fn get_unchecked(
    self,
    slice: *const str
) -> *const <Range<usize> as SliceIndex<str>>::Output

🔬 This is a nightly-only experimental API. (slice_index_methods)

Returns a shared reference to the output at this location, without performing any bounds checking. Calling this method with an out-of-bounds index or a dangling slice pointer is undefined behavior even if the resulting reference is not used.

unsafe fn get_unchecked_mut(
    self,
    slice: *mut str
) -> *mut <Range<usize> as SliceIndex<str>>::Output

🔬 This is a nightly-only experimental API. (slice_index_methods)

Returns a mutable reference to the output at this location, without performing any bounds checking. Calling this method with an out-of-bounds index or a dangling slice pointer is undefined behavior even if the resulting reference is not used.

fn index(self, slice: &str) -> &<Range<usize> as SliceIndex<str>>::Output

🔬 This is a nightly-only experimental API. (slice_index_methods)

Returns a shared reference to the output at this location, panicking if out of bounds.

fn index_mut(
    self,
    slice: &mut str
) -> &mut <Range<usize> as SliceIndex<str>>::Output

🔬 This is a nightly-only experimental API. (slice_index_methods)

Returns a mutable reference to the output at this location, panicking if out of bounds.

impl<Idx> Eq for Range<Idx> where
    Idx: Eq, 

impl<A> FusedIterator for Range<A> where
    A: Step, 

impl<Idx> StructuralEq for Range<Idx>

impl<Idx> StructuralPartialEq for Range<Idx>

impl<A> TrustedLen for Range<A> where
    A: TrustedStep,