Enum itertools::Either [] [src]

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

A value of type L.

A value of type R.

Methods

impl<L, R> Either<L, R>
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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);

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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);

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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);

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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));

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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"));

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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));

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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"));

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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));

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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));

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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);

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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]);

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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));

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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));

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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]));

Trait Implementations

impl<L, R> Iterator for Either<L, R> where
    L: Iterator,
    R: Iterator<Item = <L as Iterator>::Item>, 
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Either<L, R> is an iterator if both L and R are iterators.

The type of the elements being iterated over.

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Advances the iterator and returns the next value. Read more

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Returns the bounds on the remaining length of the iterator. Read more

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

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

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Consumes the iterator, returning the last element. Read more

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Returns the nth element of the iterator. Read more

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Transforms an iterator into a collection. Read more

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

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

unstable replacement of Range::step_by

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

1.0.0
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Takes two iterators and creates a new iterator over both in sequence. Read more

1.0.0
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'Zips up' two iterators into a single iterator of pairs. Read more

1.0.0
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Takes a closure and creates an iterator which calls that closure on each element. Read more

1.22.0
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Calls a closure on each element of an iterator. Read more

1.0.0
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Creates an iterator which uses a closure to determine if an element should be yielded. Read more

1.0.0
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Creates an iterator that both filters and maps. Read more

1.0.0
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Creates an iterator which gives the current iteration count as well as the next value. Read more

1.0.0
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Creates an iterator which can use peek to look at the next element of the iterator without consuming it. Read more

1.0.0
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Creates an iterator that [skip]s elements based on a predicate. Read more

1.0.0
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Creates an iterator that yields elements based on a predicate. Read more

1.0.0
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Creates an iterator that skips the first n elements. Read more

1.0.0
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Creates an iterator that yields its first n elements. Read more

1.0.0
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An iterator adaptor similar to [fold] that holds internal state and produces a new iterator. Read more

1.0.0
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Creates an iterator that works like map, but flattens nested structure. Read more

1.0.0
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Creates an iterator which ends after the first [None]. Read more

1.0.0
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Do something with each element of an iterator, passing the value on. Read more

1.0.0
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Borrows an iterator, rather than consuming it. Read more

1.0.0
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Consumes an iterator, creating two collections from it. Read more

1.0.0
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Tests if any element of the iterator matches a predicate. Read more

1.0.0
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Searches for an element of an iterator that satisfies a predicate. Read more

1.0.0
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Searches for an element in an iterator, returning its index. Read more

1.0.0
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Searches for an element in an iterator from the right, returning its index. Read more

1.0.0
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Returns the maximum element of an iterator. Read more

1.0.0
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Returns the minimum element of an iterator. Read more

1.6.0
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Returns the element that gives the maximum value from the specified function. Read more

1.15.0
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Returns the element that gives the maximum value with respect to the specified comparison function. Read more

1.6.0
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Returns the element that gives the minimum value from the specified function. Read more

1.15.0
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Returns the element that gives the minimum value with respect to the specified comparison function. Read more

1.0.0
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Reverses an iterator's direction. Read more

1.0.0
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Converts an iterator of pairs into a pair of containers. Read more

1.0.0
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Creates an iterator which [clone]s all of its elements. Read more

1.0.0
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Repeats an iterator endlessly. Read more

1.11.0
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Sums the elements of an iterator. Read more

1.11.0
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Iterates over the entire iterator, multiplying all the elements Read more

1.5.0
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Lexicographically compares the elements of this Iterator with those of another. Read more

1.5.0
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Lexicographically compares the elements of this Iterator with those of another. Read more

1.5.0
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Determines if the elements of this Iterator are equal to those of another. Read more

1.5.0
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Determines if the elements of this Iterator are unequal to those of another. Read more

1.5.0
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Determines if the elements of this Iterator are lexicographically less than those of another. Read more

1.5.0
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Determines if the elements of this Iterator are lexicographically less or equal to those of another. Read more

1.5.0
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Determines if the elements of this Iterator are lexicographically greater than those of another. Read more

1.5.0
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Determines if the elements of this Iterator are lexicographically greater than or equal to those of another. Read more

impl<L, R> PartialOrd<Either<L, R>> for Either<L, R> where
    L: PartialOrd<L>,
    R: PartialOrd<R>, 
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This method returns an ordering between self and other values if one exists. Read more

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

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

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

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

impl<L, R> DoubleEndedIterator for Either<L, R> where
    L: DoubleEndedIterator,
    R: DoubleEndedIterator<Item = <L as Iterator>::Item>, 
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Removes and returns an element from the end of the iterator. Read more

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

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

impl<L, R> Debug for Either<L, R> where
    L: Debug,
    R: Debug
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Formats the value using the given formatter.

impl<L, R> PartialEq<Either<L, R>> for Either<L, R> where
    L: PartialEq<L>,
    R: PartialEq<R>, 
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This method tests for self and other values to be equal, and is used by ==. Read more

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This method tests for !=.

impl<L, R> Into<Result<R, L>> for Either<L, R>
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Convert from Either to Result with Right => Ok and Left => Err.

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impl<L, R, A> Extend<A> for Either<L, R> where
    L: Extend<A>,
    R: Extend<A>, 
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Extends a collection with the contents of an iterator. Read more

impl<L, R> Deref for Either<L, R> where
    L: Deref,
    R: Deref<Target = <L as Deref>::Target>, 
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impl<L, R> Clone for Either<L, R> where
    L: Clone,
    R: Clone
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Returns a copy of the value. Read more

1.0.0
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Performs copy-assignment from source. Read more

impl<L, R> ExactSizeIterator for Either<L, R> where
    L: ExactSizeIterator,
    R: ExactSizeIterator<Item = <L as Iterator>::Item>, 
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1.0.0
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Returns the exact number of times the iterator will iterate. Read more

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

Returns whether the iterator is empty. Read more

impl<L, R, Target> AsMut<Target> for Either<L, R> where
    L: AsMut<Target>,
    R: AsMut<Target>, 
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Performs the conversion.

impl<L, R> Copy for Either<L, R> where
    L: Copy,
    R: Copy
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impl<L, R> Hash for Either<L, R> where
    L: Hash,
    R: Hash
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Feeds this value into the given [Hasher]. Read more

1.3.0
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Feeds a slice of this type into the given [Hasher]. Read more

impl<L, R, Target> AsRef<Target> for Either<L, R> where
    L: AsRef<Target>,
    R: AsRef<Target>, 
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Performs the conversion.

impl<L, R> Ord for Either<L, R> where
    L: Ord,
    R: Ord
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This method returns an Ordering between self and other. Read more

1.22.0
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Compares and returns the maximum of two values. Read more

1.22.0
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Compares and returns the minimum of two values. Read more

impl<L, R> From<Result<R, L>> for Either<L, R>
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Convert from Result to Either with Ok => Right and Err => Left.

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Performs the conversion.

impl<L, R> Eq for Either<L, R> where
    L: Eq,
    R: Eq
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impl<L, R> Display for Either<L, R> where
    L: Display,
    R: Display
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Formats the value using the given formatter. Read more

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