# [−][src]Enum itertools::Either

```pub enum Either<L, R> {
Left(L),
Right(R),
}```

The enum `Either` with variants `Left` and `Right` is a general purpose sum type with two cases.

The `Either` type is symmetric and treats its variants the same way, without preference. (For representing success or error, use the regular `Result` enum instead.)

## Variants

`Left(L)`

A value of type `L`.

`Right(R)`

A value of type `R`.

## Methods

### `impl<L, R> Either<L, R>`[src]

#### `pub fn is_left(&self) -> bool`[src]

Return true if the value is the `Left` variant.

```use either::*;

let values = [Left(1), Right("the right value")];
assert_eq!(values.is_left(), true);
assert_eq!(values.is_left(), false);```

#### `pub fn is_right(&self) -> bool`[src]

Return true if the value is the `Right` variant.

```use either::*;

let values = [Left(1), Right("the right value")];
assert_eq!(values.is_right(), false);
assert_eq!(values.is_right(), true);```

#### `pub fn left(self) -> Option<L>`[src]

Convert the left side of `Either<L, R>` to an `Option<L>`.

```use either::*;

let left: Either<_, ()> = Left("some value");
assert_eq!(left.left(),  Some("some value"));

let right: Either<(), _> = Right(321);
assert_eq!(right.left(), None);```

#### `pub fn right(self) -> Option<R>`[src]

Convert the right side of `Either<L, R>` to an `Option<R>`.

```use either::*;

let left: Either<_, ()> = Left("some value");
assert_eq!(left.right(),  None);

let right: Either<(), _> = Right(321);
assert_eq!(right.right(), Some(321));```

#### ⓘImportant traits for Either<L, R>### Important traits for Either<L, R> `impl<L, R> Iterator for Either<L, R> where    L: Iterator,    R: Iterator<Item = <L as Iterator>::Item>,  type Item = <L as Iterator>::Item;``pub fn as_ref(&self) -> Either<&L, &R>`[src]

Convert `&Either<L, R>` to `Either<&L, &R>`.

```use either::*;

let left: Either<_, ()> = Left("some value");
assert_eq!(left.as_ref(), Left(&"some value"));

let right: Either<(), _> = Right("some value");
assert_eq!(right.as_ref(), Right(&"some value"));```

#### ⓘImportant traits for Either<L, R>### Important traits for Either<L, R> `impl<L, R> Iterator for Either<L, R> where    L: Iterator,    R: Iterator<Item = <L as Iterator>::Item>,  type Item = <L as Iterator>::Item;``pub fn as_mut(&mut self) -> Either<&mut L, &mut R>`[src]

Convert `&mut Either<L, R>` to `Either<&mut L, &mut R>`.

```use either::*;

fn mutate_left(value: &mut Either<u32, u32>) {
if let Some(l) = value.as_mut().left() {
*l = 999;
}
}

let mut left = Left(123);
let mut right = Right(123);
mutate_left(&mut left);
mutate_left(&mut right);
assert_eq!(left, Left(999));
assert_eq!(right, Right(123));```

#### ⓘImportant traits for Either<L, R>### Important traits for Either<L, R> `impl<L, R> Iterator for Either<L, R> where    L: Iterator,    R: Iterator<Item = <L as Iterator>::Item>,  type Item = <L as Iterator>::Item;``pub fn flip(self) -> Either<R, L>`[src]

Convert `Either<L, R>` to `Either<R, L>`.

```use either::*;

let left: Either<_, ()> = Left(123);
assert_eq!(left.flip(), Right(123));

let right: Either<(), _> = Right("some value");
assert_eq!(right.flip(), Left("some value"));```

#### ⓘImportant traits for Either<L, R>### Important traits for Either<L, R> `impl<L, R> Iterator for Either<L, R> where    L: Iterator,    R: Iterator<Item = <L as Iterator>::Item>,  type Item = <L as Iterator>::Item;``pub fn map_left<F, M>(self, f: F) -> Either<M, R> where    F: FnOnce(L) -> M, `[src]

Apply the function `f` on the value in the `Left` variant if it is present rewrapping the result in `Left`.

```use either::*;

let left: Either<_, u32> = Left(123);
assert_eq!(left.map_left(|x| x * 2), Left(246));

let right: Either<u32, _> = Right(123);
assert_eq!(right.map_left(|x| x * 2), Right(123));```

#### ⓘImportant traits for Either<L, R>### Important traits for Either<L, R> `impl<L, R> Iterator for Either<L, R> where    L: Iterator,    R: Iterator<Item = <L as Iterator>::Item>,  type Item = <L as Iterator>::Item;``pub fn map_right<F, S>(self, f: F) -> Either<L, S> where    F: FnOnce(R) -> S, `[src]

Apply the function `f` on the value in the `Right` variant if it is present rewrapping the result in `Right`.

```use either::*;

let left: Either<_, u32> = Left(123);
assert_eq!(left.map_right(|x| x * 2), Left(123));

let right: Either<u32, _> = Right(123);
assert_eq!(right.map_right(|x| x * 2), Right(246));```

#### `pub fn either<F, G, T>(self, f: F, g: G) -> T where    F: FnOnce(L) -> T,    G: FnOnce(R) -> T, `[src]

Apply one of two functions depending on contents, unifying their result. If the value is `Left(L)` then the first function `f` is applied; if it is `Right(R)` then the second function `g` is applied.

```use either::*;

fn square(n: u32) -> i32 { (n * n) as i32 }
fn negate(n: i32) -> i32 { -n }

let left: Either<u32, i32> = Left(4);
assert_eq!(left.either(square, negate), 16);

let right: Either<u32, i32> = Right(-4);
assert_eq!(right.either(square, negate), 4);```

#### `pub fn either_with<Ctx, F, G, T>(self, ctx: Ctx, f: F, g: G) -> T where    F: FnOnce(Ctx, L) -> T,    G: FnOnce(Ctx, R) -> T, `[src]

Like `either`, but provide some context to whichever of the functions ends up being called.

```// In this example, the context is a mutable reference
use either::*;

let mut result = Vec::new();

let values = vec![Left(2), Right(2.7)];

for value in values {
value.either_with(&mut result,
|ctx, integer| ctx.push(integer),
|ctx, real| ctx.push(f64::round(real) as i32));
}

assert_eq!(result, vec![2, 3]);```

#### ⓘImportant traits for Either<L, R>### Important traits for Either<L, R> `impl<L, R> Iterator for Either<L, R> where    L: Iterator,    R: Iterator<Item = <L as Iterator>::Item>,  type Item = <L as Iterator>::Item;``pub fn left_and_then<F, S>(self, f: F) -> Either<S, R> where    F: FnOnce(L) -> Either<S, R>, `[src]

Apply the function `f` on the value in the `Left` variant if it is present.

```use either::*;

let left: Either<_, u32> = Left(123);
assert_eq!(left.left_and_then::<_,()>(|x| Right(x * 2)), Right(246));

let right: Either<u32, _> = Right(123);
assert_eq!(right.left_and_then(|x| Right::<(), _>(x * 2)), Right(123));```

#### ⓘImportant traits for Either<L, R>### Important traits for Either<L, R> `impl<L, R> Iterator for Either<L, R> where    L: Iterator,    R: Iterator<Item = <L as Iterator>::Item>,  type Item = <L as Iterator>::Item;``pub fn right_and_then<F, S>(self, f: F) -> Either<L, S> where    F: FnOnce(R) -> Either<L, S>, `[src]

Apply the function `f` on the value in the `Right` variant if it is present.

```use either::*;

let left: Either<_, u32> = Left(123);
assert_eq!(left.right_and_then(|x| Right(x * 2)), Left(123));

let right: Either<u32, _> = Right(123);
assert_eq!(right.right_and_then(|x| Right(x * 2)), Right(246));```

#### ⓘImportant traits for Either<L, R>### Important traits for Either<L, R> `impl<L, R> Iterator for Either<L, R> where    L: Iterator,    R: Iterator<Item = <L as Iterator>::Item>,  type Item = <L as Iterator>::Item;``pub fn into_iter(    self) -> Either<<L as IntoIterator>::IntoIter, <R as IntoIterator>::IntoIter> where    L: IntoIterator,    R: IntoIterator<Item = <L as IntoIterator>::Item>, `[src]

Convert the inner value to an iterator.

```use either::*;

let left: Either<_, Vec<u32>> = Left(vec![1, 2, 3, 4, 5]);
let mut right: Either<Vec<u32>, _> = Right(vec![]);
right.extend(left.into_iter());
assert_eq!(right, Right(vec![1, 2, 3, 4, 5]));```

#### `pub fn left_or(self, other: L) -> L`[src]

Return left value or given value

Arguments passed to `left_or` are eagerly evaluated; if you are passing the result of a function call, it is recommended to use `left_or_else`, which is lazily evaluated.

# Examples

```let left: Either<&str, &str> = Left("left");
assert_eq!(left.left_or("foo"), "left");

let right: Either<&str, &str> = Right("right");
assert_eq!(right.left_or("left"), "left");```

#### `pub fn left_or_default(self) -> L where    L: Default, `[src]

Return left or a default

# Examples

```let left: Either<String, u32> = Left("left".to_string());
assert_eq!(left.left_or_default(), "left");

let right: Either<String, u32> = Right(42);
assert_eq!(right.left_or_default(), String::default());```

#### `pub fn left_or_else<F>(self, f: F) -> L where    F: FnOnce(R) -> L, `[src]

Returns left value or computes it from a closure

# Examples

```let left: Either<String, u32> = Left("3".to_string());
assert_eq!(left.left_or_else(|_| unreachable!()), "3");

let right: Either<String, u32> = Right(3);
assert_eq!(right.left_or_else(|x| x.to_string()), "3");```

#### `pub fn right_or(self, other: R) -> R`[src]

Return right value or given value

Arguments passed to `right_or` are eagerly evaluated; if you are passing the result of a function call, it is recommended to use `right_or_else`, which is lazily evaluated.

# Examples

```let right: Either<&str, &str> = Right("right");
assert_eq!(right.right_or("foo"), "right");

let left: Either<&str, &str> = Left("left");
assert_eq!(left.right_or("right"), "right");```

#### `pub fn right_or_default(self) -> R where    R: Default, `[src]

Return right or a default

# Examples

```let left: Either<String, u32> = Left("left".to_string());
assert_eq!(left.right_or_default(), u32::default());

let right: Either<String, u32> = Right(42);
assert_eq!(right.right_or_default(), 42);```

#### `pub fn right_or_else<F>(self, f: F) -> R where    F: FnOnce(L) -> R, `[src]

Returns left value or computes it from a closure

# Examples

```let left: Either<String, u32> = Left("3".to_string());
assert_eq!(left.right_or_else(|x| x.parse().unwrap()), 3);

let right: Either<String, u32> = Right(3);
assert_eq!(right.right_or_else(|_| unreachable!()), 3);```

### `impl<T, L, R> Either<(T, L), (T, R)>`[src]

#### `pub fn factor_first(self) -> (T, Either<L, R>)`[src]

Factor out a homogeneous type from an either of pairs.

Here, the homogeneous type is the first element of the pairs.

```use either::*;
let left: Either<_, (u32, String)> = Left((123, vec!));
assert_eq!(left.factor_first().0, 123);

let right: Either<(u32, Vec<u8>), _> = Right((123, String::new()));
assert_eq!(right.factor_first().0, 123);```

### `impl<T, L, R> Either<(L, T), (R, T)>`[src]

#### `pub fn factor_second(self) -> (Either<L, R>, T)`[src]

Factor out a homogeneous type from an either of pairs.

Here, the homogeneous type is the second element of the pairs.

```use either::*;
let left: Either<_, (String, u32)> = Left((vec!, 123));
assert_eq!(left.factor_second().1, 123);

let right: Either<(Vec<u8>, u32), _> = Right((String::new(), 123));
assert_eq!(right.factor_second().1, 123);```

### `impl<T> Either<T, T>`[src]

#### `pub fn into_inner(self) -> T`[src]

Extract the value of an either over two equivalent types.

```use either::*;

let left: Either<_, u32> = Left(123);
assert_eq!(left.into_inner(), 123);

let right: Either<u32, _> = Right(123);
assert_eq!(right.into_inner(), 123);```

## Trait Implementations

### `impl<L, R> Ord for Either<L, R> where    L: Ord,    R: Ord, `[src]

#### `fn max(self, other: Self) -> Self`1.21.0[src]

Compares and returns the maximum of two values. Read more

#### `fn min(self, other: Self) -> Self`1.21.0[src]

Compares and returns the minimum of two values. Read more

#### `fn clamp(self, min: Self, max: Self) -> Self`[src]

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

Restrict a value to a certain interval. Read more

### `impl<L, R> Clone for Either<L, R> where    L: Clone,    R: Clone, `[src]

#### `fn clone_from(&mut self, source: &Self)`1.0.0[src]

Performs copy-assignment from `source`. Read more

### `impl<L, R> DoubleEndedIterator for Either<L, R> where    L: DoubleEndedIterator,    R: DoubleEndedIterator<Item = <L as Iterator>::Item>, `[src]

#### `fn nth_back(&mut self, n: usize) -> Option<Self::Item>`[src]

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

Returns the `n`th element from the end of the iterator. Read more

#### `fn try_rfold<B, F, R>(&mut self, init: B, f: F) -> R where    F: FnMut(B, Self::Item) -> R,    R: Try<Ok = B>, `1.27.0[src]

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

#### `fn rfold<B, F>(self, accum: B, f: F) -> B where    F: FnMut(B, Self::Item) -> B, `1.27.0[src]

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

#### `fn rfind<P>(&mut self, predicate: P) -> Option<Self::Item> where    P: FnMut(&Self::Item) -> bool, `1.27.0[src]

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

### `impl<L, R> Iterator for Either<L, R> where    L: Iterator,    R: Iterator<Item = <L as Iterator>::Item>, `[src]

`Either<L, R>` is an iterator if both `L` and `R` are iterators.

#### `type Item = <L as Iterator>::Item`

The type of the elements being iterated over.

#### `fn step_by(self, step: usize) -> StepBy<Self>`1.28.0[src]

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

#### `fn chain<U>(self, other: U) -> Chain<Self, <U as IntoIterator>::IntoIter> where    U: IntoIterator<Item = Self::Item>, `1.0.0[src]

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

#### `fn zip<U>(self, other: U) -> Zip<Self, <U as IntoIterator>::IntoIter> where    U: IntoIterator, `1.0.0[src]

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

#### `fn map<B, F>(self, f: F) -> Map<Self, F> where    F: FnMut(Self::Item) -> B, `1.0.0[src]

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

#### `fn for_each<F>(self, f: F) where    F: FnMut(Self::Item), `1.21.0[src]

Calls a closure on each element of an iterator. Read more

#### `fn filter<P>(self, predicate: P) -> Filter<Self, P> where    P: FnMut(&Self::Item) -> bool, `1.0.0[src]

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

#### `fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F> where    F: FnMut(Self::Item) -> Option<B>, `1.0.0[src]

Creates an iterator that both filters and maps. Read more

#### `fn enumerate(self) -> Enumerate<Self>`1.0.0[src]

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

#### `fn peekable(self) -> Peekable<Self>`1.0.0[src]

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

#### `fn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P> where    P: FnMut(&Self::Item) -> bool, `1.0.0[src]

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

#### `fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P> where    P: FnMut(&Self::Item) -> bool, `1.0.0[src]

Creates an iterator that yields elements based on a predicate. Read more

#### `fn skip(self, n: usize) -> Skip<Self>`1.0.0[src]

Creates an iterator that skips the first `n` elements. Read more

#### `fn take(self, n: usize) -> Take<Self>`1.0.0[src]

Creates an iterator that yields its first `n` elements. Read more

#### `fn scan<St, B, F>(self, initial_state: St, f: F) -> Scan<Self, St, F> where    F: FnMut(&mut St, Self::Item) -> Option<B>, `1.0.0[src]

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

#### `fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F> where    F: FnMut(Self::Item) -> U,    U: IntoIterator, `1.0.0[src]

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

#### `fn flatten(self) -> Flatten<Self> where    Self::Item: IntoIterator, `1.29.0[src]

Creates an iterator that flattens nested structure. Read more

#### `fn fuse(self) -> Fuse<Self>`1.0.0[src]

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

#### `fn inspect<F>(self, f: F) -> Inspect<Self, F> where    F: FnMut(&Self::Item), `1.0.0[src]

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

#### `fn by_ref(&mut self) -> &mut Self`1.0.0[src]

Borrows an iterator, rather than consuming it. Read more

#### `fn partition<B, F>(self, f: F) -> (B, B) where    B: Default + Extend<Self::Item>,    F: FnMut(&Self::Item) -> bool, `1.0.0[src]

Consumes an iterator, creating two collections from it. Read more

#### `fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R where    F: FnMut(B, Self::Item) -> R,    R: Try<Ok = B>, `1.27.0[src]

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

#### `fn try_for_each<F, R>(&mut self, f: F) -> R where    F: FnMut(Self::Item) -> R,    R: Try<Ok = ()>, `1.27.0[src]

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

#### `fn any<F>(&mut self, f: F) -> bool where    F: FnMut(Self::Item) -> bool, `1.0.0[src]

Tests if any element of the iterator matches a predicate. Read more

#### `fn find<P>(&mut self, predicate: P) -> Option<Self::Item> where    P: FnMut(&Self::Item) -> bool, `1.0.0[src]

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

#### `fn find_map<B, F>(&mut self, f: F) -> Option<B> where    F: FnMut(Self::Item) -> Option<B>, `1.30.0[src]

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

#### `fn position<P>(&mut self, predicate: P) -> Option<usize> where    P: FnMut(Self::Item) -> bool, `1.0.0[src]

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

#### `fn rposition<P>(&mut self, predicate: P) -> Option<usize> where    P: FnMut(Self::Item) -> bool,    Self: ExactSizeIterator + DoubleEndedIterator, `1.0.0[src]

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

#### `fn max(self) -> Option<Self::Item> where    Self::Item: Ord, `1.0.0[src]

Returns the maximum element of an iterator. Read more

#### `fn min(self) -> Option<Self::Item> where    Self::Item: Ord, `1.0.0[src]

Returns the minimum element of an iterator. Read more

#### `fn max_by_key<B, F>(self, f: F) -> Option<Self::Item> where    B: Ord,    F: FnMut(&Self::Item) -> B, `1.6.0[src]

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

#### `fn max_by<F>(self, compare: F) -> Option<Self::Item> where    F: FnMut(&Self::Item, &Self::Item) -> Ordering, `1.15.0[src]

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

#### `fn min_by_key<B, F>(self, f: F) -> Option<Self::Item> where    B: Ord,    F: FnMut(&Self::Item) -> B, `1.6.0[src]

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

#### `fn min_by<F>(self, compare: F) -> Option<Self::Item> where    F: FnMut(&Self::Item, &Self::Item) -> Ordering, `1.15.0[src]

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

#### `fn rev(self) -> Rev<Self> where    Self: DoubleEndedIterator, `1.0.0[src]

Reverses an iterator's direction. Read more

#### `fn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB) where    FromA: Default + Extend<A>,    FromB: Default + Extend<B>,    Self: Iterator<Item = (A, B)>, `1.0.0[src]

Converts an iterator of pairs into a pair of containers. Read more

#### `fn copied<'a, T>(self) -> Copied<Self> where    Self: Iterator<Item = &'a T>,    T: 'a + Copy, `1.36.0[src]

Creates an iterator which copies all of its elements. Read more

#### `fn cloned<'a, T>(self) -> Cloned<Self> where    Self: Iterator<Item = &'a T>,    T: 'a + Clone, `1.0.0[src]

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

#### `fn cycle(self) -> Cycle<Self> where    Self: Clone, `1.0.0[src]

Repeats an iterator endlessly. Read more

#### `fn sum<S>(self) -> S where    S: Sum<Self::Item>, `1.11.0[src]

Sums the elements of an iterator. Read more

#### `fn product<P>(self) -> P where    P: Product<Self::Item>, `1.11.0[src]

Iterates over the entire iterator, multiplying all the elements Read more

#### `fn cmp<I>(self, other: I) -> Ordering where    I: IntoIterator<Item = Self::Item>,    Self::Item: Ord, `1.5.0[src]

Lexicographically compares the elements of this `Iterator` with those of another. Read more

#### `fn partial_cmp<I>(self, other: I) -> Option<Ordering> where    I: IntoIterator,    Self::Item: PartialOrd<<I as IntoIterator>::Item>, `1.5.0[src]

Lexicographically compares the elements of this `Iterator` with those of another. Read more

#### `fn eq<I>(self, other: I) -> bool where    I: IntoIterator,    Self::Item: PartialEq<<I as IntoIterator>::Item>, `1.5.0[src]

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

#### `fn ne<I>(self, other: I) -> bool where    I: IntoIterator,    Self::Item: PartialEq<<I as IntoIterator>::Item>, `1.5.0[src]

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

#### `fn lt<I>(self, other: I) -> bool where    I: IntoIterator,    Self::Item: PartialOrd<<I as IntoIterator>::Item>, `1.5.0[src]

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

#### `fn le<I>(self, other: I) -> bool where    I: IntoIterator,    Self::Item: PartialOrd<<I as IntoIterator>::Item>, `1.5.0[src]

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

#### `fn gt<I>(self, other: I) -> bool where    I: IntoIterator,    Self::Item: PartialOrd<<I as IntoIterator>::Item>, `1.5.0[src]

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

#### `fn ge<I>(self, other: I) -> bool where    I: IntoIterator,    Self::Item: PartialOrd<<I as IntoIterator>::Item>, `1.5.0[src]

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

#### `fn is_sorted(self) -> bool where    Self::Item: PartialOrd<Self::Item>, `[src]

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

new API

Checks if the elements of this iterator are sorted. Read more

#### `fn is_sorted_by<F>(self, compare: F) -> bool where    F: FnMut(&Self::Item, &Self::Item) -> Option<Ordering>, `[src]

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

new API

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

#### `fn is_sorted_by_key<F, K>(self, f: F) -> bool where    F: FnMut(&Self::Item) -> K,    K: PartialOrd<K>, `[src]

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

new API

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

### `impl<L, R> Into<Result<R, L>> for Either<L, R>`[src]

Convert from `Either` to `Result` with `Right => Ok` and `Left => Err`.

### `impl<L, R> Hash for Either<L, R> where    L: Hash,    R: Hash, `[src]

#### `fn hash_slice<H>(data: &[Self], state: &mut H) where    H: Hasher, `1.3.0[src]

Feeds a slice of this type into the given [`Hasher`]. Read more

### `impl<L, R> ExactSizeIterator for Either<L, R> where    L: ExactSizeIterator,    R: ExactSizeIterator<Item = <L as Iterator>::Item>, `[src]

#### `fn len(&self) -> usize`1.0.0[src]

Returns the exact number of times the iterator will iterate. Read more

#### `fn is_empty(&self) -> bool`[src]

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

Returns `true` if the iterator is empty. Read more

### `impl<L, R> From<Result<R, L>> for Either<L, R>`[src]

Convert from `Result` to `Either` with `Ok => Right` and `Err => Left`.

### `impl<L, R> Deref for Either<L, R> where    L: Deref,    R: Deref<Target = <L as Deref>::Target>, `[src]

#### `type Target = <L as Deref>::Target`

The resulting type after dereferencing.

## Blanket Implementations

### `impl<T> Itertools for T where    T: Iterator + ?Sized, `[src]

#### ⓘImportant traits for Interleave<I, J>### Important traits for Interleave<I, J> `impl<I, J> Iterator for Interleave<I, J> where    I: Iterator,    J: Iterator<Item = I::Item>,  type Item = I::Item;``fn interleave<J>(self, other: J) -> Interleave<Self, J::IntoIter> where    J: IntoIterator<Item = Self::Item>,    Self: Sized, `[src]

Alternate elements from two iterators until both have run out. Read more

#### ⓘImportant traits for InterleaveShortest<I, J>### Important traits for InterleaveShortest<I, J> `impl<I, J> Iterator for InterleaveShortest<I, J> where    I: Iterator,    J: Iterator<Item = I::Item>,  type Item = I::Item;``fn interleave_shortest<J>(    self,     other: J) -> InterleaveShortest<Self, J::IntoIter> where    J: IntoIterator<Item = Self::Item>,    Self: Sized, `[src]

Alternate elements from two iterators until at least one of them has run out. Read more

#### ⓘImportant traits for Intersperse<I>### Important traits for Intersperse<I> `impl<I> Iterator for Intersperse<I> where    I: Iterator,    I::Item: Clone,  type Item = I::Item;``fn intersperse(self, element: Self::Item) -> Intersperse<Self> where    Self: Sized,    Self::Item: Clone, `[src]

An iterator adaptor to insert a particular value between each element of the adapted iterator. Read more

#### ⓘImportant traits for ZipLongest<T, U>### Important traits for ZipLongest<T, U> `impl<T, U> Iterator for ZipLongest<T, U> where    T: Iterator,    U: Iterator,  type Item = EitherOrBoth<T::Item, U::Item>;``fn zip_longest<J>(self, other: J) -> ZipLongest<Self, J::IntoIter> where    J: IntoIterator,    Self: Sized, `[src]

Create an iterator which iterates over both this and the specified iterator simultaneously, yielding pairs of two optional elements. Read more

#### ⓘImportant traits for ZipEq<I, J>### Important traits for ZipEq<I, J> `impl<I, J> Iterator for ZipEq<I, J> where    I: Iterator,    J: Iterator,  type Item = (I::Item, J::Item);``fn zip_eq<J>(self, other: J) -> ZipEq<Self, J::IntoIter> where    J: IntoIterator,    Self: Sized, `[src]

Create an iterator which iterates over both this and the specified iterator simultaneously, yielding pairs of elements. Read more

#### ⓘImportant traits for Batching<I, F>### Important traits for Batching<I, F> `impl<B, F, I> Iterator for Batching<I, F> where    I: Iterator,    F: FnMut(&mut I) -> Option<B>,  type Item = B;``fn batching<B, F>(self, f: F) -> Batching<Self, F> where    F: FnMut(&mut Self) -> Option<B>,    Self: Sized, `[src]

A “meta iterator adaptor”. Its closure receives a reference to the iterator and may pick off as many elements as it likes, to produce the next iterator element. Read more

#### `fn group_by<K, F>(self, key: F) -> GroupBy<K, Self, F> where    Self: Sized,    F: FnMut(&Self::Item) -> K,    K: PartialEq, `[src]

Return an iterable that can group iterator elements. Consecutive elements that map to the same key (“runs”), are assigned to the same group. Read more

#### `fn chunks(self, size: usize) -> IntoChunks<Self> where    Self: Sized, `[src]

Return an iterable that can chunk the iterator. Read more

#### ⓘImportant traits for TupleWindows<I, T>### Important traits for TupleWindows<I, T> `impl<I, T> Iterator for TupleWindows<I, T> where    I: Iterator<Item = T::Item>,    T: TupleCollect + Clone,    T::Item: Clone,  type Item = T;``fn tuple_windows<T>(self) -> TupleWindows<Self, T> where    Self: Sized + Iterator<Item = T::Item>,    T: TupleCollect,    T::Item: Clone, `[src]

Return an iterator over all contiguous windows producing tuples of a specific size (up to 4). Read more

#### ⓘImportant traits for Tuples<I, T>### Important traits for Tuples<I, T> `impl<I, T> Iterator for Tuples<I, T> where    I: Iterator<Item = T::Item>,    T: TupleCollect,  type Item = T;``fn tuples<T>(self) -> Tuples<Self, T> where    Self: Sized + Iterator<Item = T::Item>,    T: TupleCollect, `[src]

Return an iterator that groups the items in tuples of a specific size (up to 4). Read more

#### `fn tee(self) -> (Tee<Self>, Tee<Self>) where    Self: Sized,    Self::Item: Clone, `[src]

Split into an iterator pair that both yield all elements from the original iterator. Read more

#### ⓘImportant traits for Step<I>### Important traits for Step<I> `impl<I> Iterator for Step<I> where    I: Iterator,  type Item = I::Item;``fn step(self, n: usize) -> Step<Self> where    Self: Sized, `[src]

Deprecated since 0.8:

Use std .step_by() instead

Return an iterator adaptor that steps `n` elements in the base iterator for each iteration. Read more

#### ⓘImportant traits for MapInto<I, R>### Important traits for MapInto<I, R> `impl<I, R> Iterator for MapInto<I, R> where    I: Iterator,    I::Item: Into<R>,  type Item = R;``fn map_into<R>(self) -> MapInto<Self, R> where    Self: Sized,    Self::Item: Into<R>, `[src]

Convert each item of the iterator using the `Into` trait. Read more

#### ⓘImportant traits for MapResults<I, F>### Important traits for MapResults<I, F> `impl<I, F, T, U, E> Iterator for MapResults<I, F> where    I: Iterator<Item = Result<T, E>>,    F: FnMut(T) -> U,  type Item = Result<U, E>;``fn map_results<F, T, U, E>(self, f: F) -> MapResults<Self, F> where    Self: Iterator<Item = Result<T, E>> + Sized,    F: FnMut(T) -> U, `[src]

Return an iterator adaptor that applies the provided closure to every `Result::Ok` value. `Result::Err` values are unchanged. Read more

#### ⓘImportant traits for Merge<I, J>### Important traits for Merge<I, J> `impl<I, J> Iterator for Merge<I, J> where    I: Iterator,    J: Iterator<Item = I::Item>,    I::Item: PartialOrd,  type Item = I::Item;``fn merge<J>(self, other: J) -> Merge<Self, J::IntoIter> where    Self: Sized,    Self::Item: PartialOrd,    J: IntoIterator<Item = Self::Item>, `[src]

Return an iterator adaptor that merges the two base iterators in ascending order. If both base iterators are sorted (ascending), the result is sorted. Read more

#### ⓘImportant traits for MergeBy<I, J, F>### Important traits for MergeBy<I, J, F> `impl<I, J, F> Iterator for MergeBy<I, J, F> where    I: Iterator,    J: Iterator<Item = I::Item>,    F: FnMut(&I::Item, &I::Item) -> bool,  type Item = I::Item;``fn merge_by<J, F>(self, other: J, is_first: F) -> MergeBy<Self, J::IntoIter, F> where    Self: Sized,    J: IntoIterator<Item = Self::Item>,    F: FnMut(&Self::Item, &Self::Item) -> bool, `[src]

Return an iterator adaptor that merges the two base iterators in order. This is much like `.merge()` but allows for a custom ordering. Read more

#### ⓘImportant traits for MergeJoinBy<I, J, F>### Important traits for MergeJoinBy<I, J, F> `impl<I, J, F> Iterator for MergeJoinBy<I, J, F> where    I: Iterator,    J: Iterator,    F: FnMut(&I::Item, &J::Item) -> Ordering,  type Item = EitherOrBoth<I::Item, J::Item>;``fn merge_join_by<J, F>(    self,     other: J,     cmp_fn: F) -> MergeJoinBy<Self, J::IntoIter, F> where    J: IntoIterator,    F: FnMut(&Self::Item, &J::Item) -> Ordering,    Self: Sized, `[src]

Create an iterator that merges items from both this and the specified iterator in ascending order. Read more

#### ⓘImportant traits for KMerge<I>### Important traits for KMerge<I> `impl<I> Iterator for KMerge<I> where    I: Iterator,    I::Item: PartialOrd,  type Item = I::Item;``fn kmerge(self) -> KMerge<<Self::Item as IntoIterator>::IntoIter> where    Self: Sized,    Self::Item: IntoIterator,    <Self::Item as IntoIterator>::Item: PartialOrd, `[src]

Return an iterator adaptor that flattens an iterator of iterators by merging them in ascending order. Read more

#### ⓘImportant traits for KMergeBy<I, F>### Important traits for KMergeBy<I, F> `impl<I, F> Iterator for KMergeBy<I, F> where    I: Iterator,    F: FnMut(&I::Item, &I::Item) -> bool,  type Item = I::Item;``fn kmerge_by<F>(    self,     first: F) -> KMergeBy<<Self::Item as IntoIterator>::IntoIter, F> where    Self: Sized,    Self::Item: IntoIterator,    F: FnMut(&<Self::Item as IntoIterator>::Item, &<Self::Item as IntoIterator>::Item) -> bool, `[src]

Return an iterator adaptor that flattens an iterator of iterators by merging them according to the given closure. Read more

#### ⓘImportant traits for Product<I, J>### Important traits for Product<I, J> `impl<I, J> Iterator for Product<I, J> where    I: Iterator,    J: Clone + Iterator,    I::Item: Clone,  type Item = (I::Item, J::Item);``fn cartesian_product<J>(self, other: J) -> Product<Self, J::IntoIter> where    Self: Sized,    Self::Item: Clone,    J: IntoIterator,    J::IntoIter: Clone, `[src]

Return an iterator adaptor that iterates over the cartesian product of the element sets of two iterators `self` and `J`. Read more

#### ⓘImportant traits for MultiProduct<I>### Important traits for MultiProduct<I> `impl<I> Iterator for MultiProduct<I> where    I: Iterator + Clone,    I::Item: Clone,  type Item = Vec<I::Item>;``fn multi_cartesian_product(    self) -> MultiProduct<<Self::Item as IntoIterator>::IntoIter> where    Self: Iterator + Sized,    Self::Item: IntoIterator,    <Self::Item as IntoIterator>::IntoIter: Clone,    <Self::Item as IntoIterator>::Item: Clone, `[src]

Return an iterator adaptor that iterates over the cartesian product of all subiterators returned by meta-iterator `self`. Read more

#### ⓘImportant traits for Coalesce<I, F>### Important traits for Coalesce<I, F> `impl<I, F> Iterator for Coalesce<I, F> where    I: Iterator,    F: FnMut(I::Item, I::Item) -> Result<I::Item, (I::Item, I::Item)>,  type Item = I::Item;``fn coalesce<F>(self, f: F) -> Coalesce<Self, F> where    Self: Sized,    F: FnMut(Self::Item, Self::Item) -> Result<Self::Item, (Self::Item, Self::Item)>, `[src]

Return an iterator adaptor that uses the passed-in closure to optionally merge together consecutive elements. Read more

#### ⓘImportant traits for Dedup<I>### Important traits for Dedup<I> `impl<I> Iterator for Dedup<I> where    I: Iterator,    I::Item: PartialEq,  type Item = I::Item;``fn dedup(self) -> Dedup<Self> where    Self: Sized,    Self::Item: PartialEq, `[src]

Remove duplicates from sections of consecutive identical elements. If the iterator is sorted, all elements will be unique. Read more

#### ⓘImportant traits for Unique<I>### Important traits for Unique<I> `impl<I> Iterator for Unique<I> where    I: Iterator,    I::Item: Eq + Hash + Clone,  type Item = I::Item;``fn unique(self) -> Unique<Self> where    Self: Sized,    Self::Item: Clone + Eq + Hash, `[src]

Return an iterator adaptor that filters out elements that have already been produced once during the iteration. Duplicates are detected using hash and equality. Read more

#### ⓘImportant traits for UniqueBy<I, V, F>### Important traits for UniqueBy<I, V, F> `impl<I, V, F> Iterator for UniqueBy<I, V, F> where    I: Iterator,    V: Eq + Hash,    F: FnMut(&I::Item) -> V,  type Item = I::Item;``fn unique_by<V, F>(self, f: F) -> UniqueBy<Self, V, F> where    Self: Sized,    V: Eq + Hash,    F: FnMut(&Self::Item) -> V, `[src]

Return an iterator adaptor that filters out elements that have already been produced once during the iteration. Read more

#### ⓘImportant traits for PeekingTakeWhile<'a, I, F>### Important traits for PeekingTakeWhile<'a, I, F> `impl<'a, I, F> Iterator for PeekingTakeWhile<'a, I, F> where    I: PeekingNext,    F: FnMut(&I::Item) -> bool,  type Item = I::Item;``fn peeking_take_while<F>(&mut self, accept: F) -> PeekingTakeWhile<Self, F> where    Self: Sized + PeekingNext,    F: FnMut(&Self::Item) -> bool, `[src]

Return an iterator adaptor that borrows from this iterator and takes items while the closure `accept` returns `true`. Read more

#### ⓘImportant traits for TakeWhileRef<'a, I, F>### Important traits for TakeWhileRef<'a, I, F> `impl<'a, I, F> Iterator for TakeWhileRef<'a, I, F> where    I: Iterator + Clone,    F: FnMut(&I::Item) -> bool,  type Item = I::Item;``fn take_while_ref<F>(&mut self, accept: F) -> TakeWhileRef<Self, F> where    Self: Clone,    F: FnMut(&Self::Item) -> bool, `[src]

Return an iterator adaptor that borrows from a `Clone`-able iterator to only pick off elements while the predicate `accept` returns `true`. Read more

#### ⓘImportant traits for WhileSome<I>### Important traits for WhileSome<I> `impl<I, A> Iterator for WhileSome<I> where    I: Iterator<Item = Option<A>>,  type Item = A;``fn while_some<A>(self) -> WhileSome<Self> where    Self: Sized + Iterator<Item = Option<A>>, `[src]

Return an iterator adaptor that filters `Option<A>` iterator elements and produces `A`. Stops on the first `None` encountered. Read more

#### ⓘImportant traits for TupleCombinations<I, T>### Important traits for TupleCombinations<I, T> `impl<I, T> Iterator for TupleCombinations<I, T> where    I: Iterator,    T: HasCombination<I>,  type Item = T;``fn tuple_combinations<T>(self) -> TupleCombinations<Self, T> where    Self: Sized + Clone,    Self::Item: Clone,    T: HasCombination<Self>, `[src]

Return an iterator adaptor that iterates over the combinations of the elements from an iterator. Read more

#### ⓘImportant traits for Combinations<I>### Important traits for Combinations<I> `impl<I> Iterator for Combinations<I> where    I: Iterator,    I::Item: Clone,  type Item = Vec<I::Item>;``fn combinations(self, n: usize) -> Combinations<Self> where    Self: Sized,    Self::Item: Clone, `[src]

Return an iterator adaptor that iterates over the `n`-length combinations of the elements from an iterator. Read more

#### ⓘImportant traits for PadUsing<I, F>### Important traits for PadUsing<I, F> `impl<I, F> Iterator for PadUsing<I, F> where    I: Iterator,    F: FnMut(usize) -> I::Item,  type Item = I::Item;``fn pad_using<F>(self, min: usize, f: F) -> PadUsing<Self, F> where    Self: Sized,    F: FnMut(usize) -> Self::Item, `[src]

Return an iterator adaptor that pads the sequence to a minimum length of `min` by filling missing elements using a closure `f`. Read more

#### ⓘImportant traits for WithPosition<I>### Important traits for WithPosition<I> `impl<I: Iterator> Iterator for WithPosition<I> type Item = Position<I::Item>;``fn with_position(self) -> WithPosition<Self> where    Self: Sized, `[src]

Return an iterator adaptor that wraps each element in a `Position` to ease special-case handling of the first or last elements. Read more

#### ⓘImportant traits for Positions<I, F>### Important traits for Positions<I, F> `impl<I, F> Iterator for Positions<I, F> where    I: Iterator,    F: FnMut(I::Item) -> bool,  type Item = usize;``fn positions<P>(self, predicate: P) -> Positions<Self, P> where    Self: Sized,    P: FnMut(Self::Item) -> bool, `[src]

Return an iterator adaptor that yields the indices of all elements satisfying a predicate, counted from the start of the iterator. Read more

#### ⓘImportant traits for Update<I, F>### Important traits for Update<I, F> `impl<I, F> Iterator for Update<I, F> where    I: Iterator,    F: FnMut(&mut I::Item),  type Item = I::Item;``fn update<F>(self, updater: F) -> Update<Self, F> where    Self: Sized,    F: FnMut(&mut Self::Item), `[src]

Return an iterator adaptor that applies a mutating function to each element before yielding it. Read more

#### `fn next_tuple<T>(&mut self) -> Option<T> where    Self: Sized + Iterator<Item = T::Item>,    T: TupleCollect, `[src]

Advances the iterator and returns the next items grouped in a tuple of a specific size (up to 4). Read more

#### `fn collect_tuple<T>(self) -> Option<T> where    Self: Sized + Iterator<Item = T::Item>,    T: TupleCollect, `[src]

Collects all items from the iterator into a tuple of a specific size (up to 4). Read more

#### `fn find_position<P>(&mut self, pred: P) -> Option<(usize, Self::Item)> where    P: FnMut(&Self::Item) -> bool, `[src]

Find the position and value of the first element satisfying a predicate. Read more

#### `fn all_equal(&mut self) -> bool where    Self::Item: PartialEq, `[src]

Check whether all elements compare equal. Read more

#### `fn dropping(self, n: usize) -> Self where    Self: Sized, `[src]

Consume the first `n` elements from the iterator eagerly, and return the same iterator again. Read more

#### `fn dropping_back(self, n: usize) -> Self where    Self: Sized,    Self: DoubleEndedIterator, `[src]

Consume the last `n` elements from the iterator eagerly, and return the same iterator again. Read more

#### `fn foreach<F>(self, f: F) where    F: FnMut(Self::Item),    Self: Sized, `[src]

Deprecated since 0.8:

Use .for_each() instead

Run the closure `f` eagerly on each element of the iterator. Read more

#### `fn concat(self) -> Self::Item where    Self: Sized,    Self::Item: Extend<<Self::Item as IntoIterator>::Item> + IntoIterator + Default, `[src]

Combine all an iterator's elements into one element by using `Extend`. Read more

#### `fn collect_vec(self) -> Vec<Self::Item> where    Self: Sized, `[src]

`.collect_vec()` is simply a type specialization of `.collect()`, for convenience. Read more

#### `fn set_from<'a, A: 'a, J>(&mut self, from: J) -> usize where    Self: Iterator<Item = &'a mut A>,    J: IntoIterator<Item = A>, `[src]

Assign to each reference in `self` from the `from` iterator, stopping at the shortest of the two iterators. Read more

#### `fn join(&mut self, sep: &str) -> String where    Self::Item: Display, `[src]

Combine all iterator elements into one String, seperated by `sep`. Read more

#### `fn format(self, sep: &str) -> Format<Self> where    Self: Sized, `[src]

Format all iterator elements, separated by `sep`. Read more

#### `fn format_with<F>(self, sep: &str, format: F) -> FormatWith<Self, F> where    Self: Sized,    F: FnMut(Self::Item, &mut dyn FnMut(&dyn Display) -> Result) -> Result, `[src]

Format all iterator elements, separated by `sep`. Read more

#### `fn fold_results<A, E, B, F>(&mut self, start: B, f: F) -> Result<B, E> where    Self: Iterator<Item = Result<A, E>>,    F: FnMut(B, A) -> B, `[src]

Fold `Result` values from an iterator. Read more

#### `fn fold_options<A, B, F>(&mut self, start: B, f: F) -> Option<B> where    Self: Iterator<Item = Option<A>>,    F: FnMut(B, A) -> B, `[src]

Fold `Option` values from an iterator. Read more

#### `fn fold1<F>(self, f: F) -> Option<Self::Item> where    F: FnMut(Self::Item, Self::Item) -> Self::Item,    Self: Sized, `[src]

Accumulator of the elements in the iterator. Read more

#### `fn tree_fold1<F>(self, f: F) -> Option<Self::Item> where    F: FnMut(Self::Item, Self::Item) -> Self::Item,    Self: Sized, `[src]

Accumulate the elements in the iterator in a tree-like manner. Read more

#### `fn fold_while<B, F>(&mut self, init: B, f: F) -> FoldWhile<B> where    Self: Sized,    F: FnMut(B, Self::Item) -> FoldWhile<B>, `[src]

Deprecated since 0.8:

Use .try_fold() instead

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

#### `fn sorted(self) -> IntoIter<Self::Item> where    Self: Sized,    Self::Item: Ord, `[src]

Sort all iterator elements into a new iterator in ascending order. Read more

#### `fn sorted_by<F>(self, cmp: F) -> IntoIter<Self::Item> where    Self: Sized,    F: FnMut(&Self::Item, &Self::Item) -> Ordering, `[src]

Sort all iterator elements into a new iterator in ascending order. Read more

#### `fn sorted_by_key<K, F>(self, f: F) -> IntoIter<Self::Item> where    Self: Sized,    K: Ord,    F: FnMut(&Self::Item) -> K, `[src]

Sort all iterator elements into a new iterator in ascending order. Read more

#### `fn partition_map<A, B, F, L, R>(self, predicate: F) -> (A, B) where    Self: Sized,    F: Fn(Self::Item) -> Either<L, R>,    A: Default + Extend<L>,    B: Default + Extend<R>, `[src]

Collect all iterator elements into one of two partitions. Unlike `Iterator::partition`, each partition may have a distinct type. Read more

#### `fn into_group_map<K, V>(self) -> HashMap<K, Vec<V>> where    Self: Iterator<Item = (K, V)> + Sized,    K: Hash + Eq, `[src]

Return a `HashMap` of keys mapped to `Vec`s of values. Keys and values are taken from `(Key, Value)` tuple pairs yielded by the input iterator. Read more

#### `fn minmax(self) -> MinMaxResult<Self::Item> where    Self: Sized,    Self::Item: PartialOrd, `[src]

Return the minimum and maximum elements in the iterator. Read more

#### `fn minmax_by_key<K, F>(self, key: F) -> MinMaxResult<Self::Item> where    Self: Sized,    K: PartialOrd,    F: FnMut(&Self::Item) -> K, `[src]

Return the minimum and maximum element of an iterator, as determined by the specified function. Read more

#### `fn minmax_by<F>(self, compare: F) -> MinMaxResult<Self::Item> where    Self: Sized,    F: FnMut(&Self::Item, &Self::Item) -> Ordering, `[src]

Return the minimum and maximum element of an iterator, as determined by the specified comparison function. Read more

### `impl<T> ToOwned for T where    T: Clone, `[src]

#### `type Owned = T`

The resulting type after obtaining ownership.

### `impl<I> IntoIterator for I where    I: Iterator, `[src]

#### `type Item = <I as Iterator>::Item`

The type of the elements being iterated over.

#### `type IntoIter = I`

Which kind of iterator are we turning this into?

### `impl<T, U> TryFrom<U> for T where    U: Into<T>, `[src]

#### `type Error = Infallible`

The type returned in the event of a conversion error.

### `impl<T, U> TryInto<U> for T where    U: TryFrom<T>, `[src]

#### `type Error = <U as TryFrom<T>>::Error`

The type returned in the event of a conversion error.