Enum itertools::Either

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

Either represents an alternative holding one value out of either of the two possible values.

Either is a general purpose sum type of two parts. For representing success or error, use the regular Result<T, E> instead.

Variants

Left(L)

A value of type L.

Right(R)

A value of type R.

Methods

impl<L, R> Either<L, R>

fn is_left(&self) -> bool

Return true if the value is the Left variant.

use either::*;

let values = [Left(1), Right("the right value")];
assert_eq!(values[0].is_left(), true);
assert_eq!(values[1].is_left(), false);

fn is_right(&self) -> bool

Return true if the value is the Right variant.

use either::*;

let values = [Left(1), Right("the right value")];
assert_eq!(values[0].is_right(), false);
assert_eq!(values[1].is_right(), true);

fn left(self) -> Option<L>

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);

fn right(self) -> Option<R>

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));

fn as_ref(&self) -> Either<&L, &R>

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"));

fn as_mut(&mut self) -> Either<&mut L, &mut R>

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));

fn flip(self) -> Either<R, L>

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"));

fn map_left<F, M>(self, f: F) -> Either<M, R> where F: FnOnce(L) -> M

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.map_left(|x| x * 2), Left(246));

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

fn map_right<F, S>(self, f: F) -> Either<L, S> where F: FnOnce(R) -> S

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.map_right(|x| x * 2), Left(123));

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

fn either<F, G, T>(self, f: F, g: G) -> T where F: FnOnce(L) -> T, G: FnOnce(R) -> T

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);

Trait Implementations

impl<L, R> ExactSizeIterator for Either<L, R> where L: ExactSizeIterator, R: ExactSizeIterator<Item=L::Item>

fn len(&self) -> usize

Returns the exact number of times the iterator will iterate.

fn is_empty(&self) -> bool

Unstable (exact_size_is_empty)

Returns whether the iterator is empty.

impl<L, R> DerefMut for Either<L, R> where L: DerefMut, R: DerefMut<Target=L::Target>

fn deref_mut(&mut self) -> &mut Either<L, R>::Target

impl<L, R> From<Result<R, L>> for Either<L, R>

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

fn from(r: Result<R, L>) -> Either<L, R>

Performs the conversion.

impl<L, R> PartialOrd<Either<L, R>> for Either<L, R> where L: PartialOrd<L>, R: PartialOrd<R>

fn partial_cmp(&self, __arg_0: &Either<L, R>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, __arg_0: &Either<L, R>) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, __arg_0: &Either<L, R>) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, __arg_0: &Either<L, R>) -> bool

This method tests greater than (for self and other) and is used by the > operator.

fn ge(&self, __arg_0: &Either<L, R>) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<L, R> Display for Either<L, R> where L: Display, R: Display

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

Formats the value using the given formatter.

impl<L, R> DoubleEndedIterator for Either<L, R> where L: DoubleEndedIterator, R: DoubleEndedIterator<Item=L::Item>

fn next_back(&mut self) -> Option<L::Item>

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

impl<L, R, Target> AsRef<Target> for Either<L, R> where L: AsRef<Target>, R: AsRef<Target>

fn as_ref(&self) -> &Target

impl<L, R> Clone for Either<L, R> where L: Clone, R: Clone

fn clone(&self) -> Either<L, R>

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<L, R> Deref for Either<L, R> where L: Deref, R: Deref<Target=L::Target>

type Target = L::Target

fn deref(&self) -> &Either<L, R>::Target

impl<L, R> PartialEq<Either<L, R>> for Either<L, R> where L: PartialEq<L>, R: PartialEq<R>

fn eq(&self, __arg_0: &Either<L, R>) -> bool

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

fn ne(&self, __arg_0: &Either<L, R>) -> bool

This method tests for !=.

impl<L, R> Into<Result<R, L>> for Either<L, R>

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

fn into(self) -> Result<R, L>

impl<L, R> Ord for Either<L, R> where L: Ord, R: Ord

fn cmp(&self, __arg_0: &Either<L, R>) -> Ordering

This method returns an Ordering between self and other.

impl<L, R> Debug for Either<L, R> where L: Debug, R: Debug

fn fmt(&self, __arg_0: &mut Formatter) -> Result<(), Error>

Formats the value using the given formatter.

impl<L, R> Copy for Either<L, R> where L: Copy, R: Copy

impl<L, R> Hash for Either<L, R> where L: Hash, R: Hash

fn hash<__HLR>(&self, __arg_0: &mut __HLR) where __HLR: Hasher

Feeds this value into the state given, updating the hasher as necessary.

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

Feeds a slice of this type into the state provided.

impl<L, R> Eq for Either<L, R> where L: Eq, R: Eq

impl<L, R> Iterator for Either<L, R> where L: Iterator, R: Iterator<Item=L::Item>

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

type Item = L::Item

The type of the elements being iterated over.

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

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 fold<Acc, G>(self, init: Acc, f: G) -> Acc where G: FnMut(Acc, Either<L, R>::Item) -> Acc

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

fn count(self) -> usize

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

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

Consumes the iterator, returning the last element.

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

Consumes the n first elements of the iterator, then returns the next() one.

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

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

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 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 peek to look at the next element of the iterator without consuming it.

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.

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 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 its first n elements.

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.

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.

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) -> ()

Do 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 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 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 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 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.

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

Returns the maximum element of an iterator.

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

Returns the minimum element of an iterator.

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

Unstable (iter_max_by)

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

Unstable (iter_min_by)

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 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.

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<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.

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

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

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

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

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

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

impl<L, R, Target> AsMut<Target> for Either<L, R> where L: AsMut<Target>, R: AsMut<Target>

fn as_mut(&mut self) -> &mut Target

Performs the conversion.