[−][src]Enum futures_util::future::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

A value of type L.

A value of type R.

Methods

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

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);

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);

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);

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>

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>

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>

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>

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>

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));

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);

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>

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>

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>

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]));

impl<T, L, R> Either<(T, L), (T, 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![0]));
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]

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![0], 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]

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<A, B> Stream for Either<A, B> where
    A: Stream,
    B: Stream<Item = <A as Stream>::Item, Error = <A as Stream>::Error>, 
[src]

Values yielded by the stream.

Errors yielded by the stream.

Attempt to pull out the next value of this stream, registering the current task for wakeup if the value is not yet available, and returning None if the stream is exhausted. Read more

impl<A, B> Future for Either<A, B> where
    A: Future,
    B: Future<Item = <A as Future>::Item, Error = <A as Future>::Error>, 
[src]

A successful value

An error

Attempt to resolve the future to a final value, registering the current task for wakeup if the value is not yet available. Read more

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

ⓘImportant traits for Either<L, R>

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

impl<L, R> PartialOrd<Either<L, R>> for Either<L, R> where
    L: PartialOrd<L>,
    R: PartialOrd<R>, 
[src]

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

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

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

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

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

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

Performs the conversion.

impl<L, R> Error for Either<L, R> where
    L: Error,
    R: Error, 
[src]

Either implements Error if both L and R implement it.

This method is soft-deprecated. Read more

Deprecating in 1.33.0

: replaced by Error::source, which can support downcasting

The lower-level cause of this error, if any. Read more

The lower-level source of this error, if any. Read more

impl<L, R> Copy for Either<L, R> where
    L: Copy,
    R: Copy, 
[src]

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

This method returns an Ordering between self and other. Read more

Compares and returns the maximum of two values. Read more

Compares and returns the minimum of two values. Read more

impl<L, R, A> Extend<A> for Either<L, R> where
    L: Extend<A>,
    R: Extend<A>, 
[src]

Extends a collection with the contents of an iterator. Read more

impl<L, R> Display for Either<L, R> where
    L: Display,
    R: Display, 
[src]

Formats the value using the given formatter. 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.

Performs the conversion.

impl<L, R> Read for Either<L, R> where
    L: Read,
    R: Read, 
[src]

Either<L, R> implements Read if both L and R do.

Requires crate feature "use_std"

Pull some bytes from this source into the specified buffer, returning how many bytes were read. Read more

Read all bytes until EOF in this source, placing them into buf. Read more

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

Determines if this Reader can work with buffers of uninitialized memory. Read more

Read all bytes until EOF in this source, appending them to buf. Read more

Read the exact number of bytes required to fill buf. Read more

Creates a "by reference" adaptor for this instance of Read. Read more

Transforms this Read instance to an [Iterator] over its bytes. Read more

Creates an adaptor which will chain this stream with another. Read more

Creates an adaptor which will read at most limit bytes from it. Read more

impl<L, R> Write for Either<L, R> where
    L: Write,
    R: Write, 
[src]

Either<L, R> implements Write if both L and R do.

Requires crate feature "use_std"

Write a buffer into this object, returning how many bytes were written. Read more

Flush this output stream, ensuring that all intermediately buffered contents reach their destination. Read more

Attempts to write an entire buffer into this write. Read more

Writes a formatted string into this writer, returning any error encountered. Read more

Creates a "by reference" adaptor for this instance of Write. Read more

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

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

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

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

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.

The type of the elements being iterated over.

Advances the iterator and returns the next value. Read more

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

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

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

Consumes the iterator, returning the last element. Read more

Returns the nth element of the iterator. Read more

Transforms an iterator into a collection. Read more

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

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

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

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

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

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

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

Creates an iterator that both filters and maps. Read more

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

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

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

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

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

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

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

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

Creates an iterator that flattens nested structure. Read more

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

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

Borrows an iterator, rather than consuming it. Read more

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

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

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

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

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

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

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

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

Returns the maximum element of an iterator. Read more

Returns the minimum element of an iterator. Read more

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

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

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

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

Reverses an iterator's direction. Read more

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

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

Repeats an iterator endlessly. Read more

Sums the elements of an iterator. Read more

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

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

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

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

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

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

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

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

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

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

Performs the conversion.

impl<L, R> Debug for Either<L, R> where
    L: Debug,
    R: Debug, 
[src]

Formats the value using the given formatter. Read more

impl<L, R> Eq for Either<L, R> where
    L: Eq,
    R: Eq, 
[src]

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

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

ⓘImportant traits for Either<L, R>

Performs the conversion.

impl<L, R> BufRead for Either<L, R> where
    L: BufRead,
    R: BufRead, 
[src]

Requires crate feature "use_std"

Returns the contents of the internal buffer, filling it with more data from the inner reader if it is empty. Read more

Tells this buffer that amt bytes have been consumed from the buffer, so they should no longer be returned in calls to read. Read more

Read all bytes into buf until the delimiter byte or EOF is reached. Read more

Read all bytes until a newline (the 0xA byte) is reached, and append them to the provided buffer. Read more

Returns an iterator over the contents of this reader split on the byte byte. Read more

Returns an iterator over the lines of this reader. Read more

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

The resulting type after dereferencing.

ⓘImportant traits for Either<L, R>

Dereferences the value.

impl<L, R> PartialEq<Either<L, R>> for Either<L, R> where
    L: PartialEq<L>,
    R: PartialEq<R>, 
[src]

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

This method tests for !=.

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

ⓘImportant traits for Either<L, R>

Mutably dereferences the value.

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

Feeds this value into the given [Hasher]. Read more

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]

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

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

Returns whether the iterator is empty. Read more

impl<A, B> Sink for Either<A, B> where
    A: Sink,
    B: Sink<SinkItem = <A as Sink>::SinkItem, SinkError = <A as Sink>::SinkError>, 
[src]

The type of value that the sink accepts.

The type of value produced by the sink when an error occurs.

Attempts to prepare the Sink to receive a value. Read more

Begin the process of sending a value to the sink. Each call to this function must be preceded by a successful call to poll_ready which returned Ok(Async::Ready(())). Read more

Flush any remaining output from this sink. Read more

Flush any remaining output and close this sink, if necessary. Read more

Auto Trait Implementations

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

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

Blanket Implementations

impl<T> FutureExt for T where
    T: Future + ?Sized, 
[src]

Map this future's result to a different type, returning a new future of the resulting type. Read more

Map this future's error to a different error, returning a new future. Read more

Map this future's error to a new error type using the Into trait. Read more

Chain on a computation for when a future finished, passing the result of the future to the provided closure f. Read more

Execute another future after this one has resolved successfully. Read more

Execute another future if this one resolves with an error. Read more

Waits for either one of two differently-typed futures to complete. Read more

Joins the result of two futures, waiting for them both to complete. Read more

Same as join, but with more futures.

Same as join, but with more futures.

Same as join, but with more futures.

ⓘImportant traits for Either<L, R>

Deprecated

: use left_future instead

Wrap this future in an Either future, making it the left-hand variant of that Either. Read more

ⓘImportant traits for Either<L, R>

Wrap this future in an Either future, making it the left-hand variant of that Either. Read more

ⓘImportant traits for Either<L, R>

Deprecated

: use right_future instead

Wrap this future in an Either future, making it the right-hand variant of that Either. Read more

ⓘImportant traits for Either<L, R>

Wrap this future in an Either future, making it the right-hand variant of that Either. Read more

Convert this future into a single element stream. Read more

Flatten the execution of this future when the successful result of this future is itself another future. Read more

Flatten the execution of this future when the successful result of this future is a sink. Read more

Flatten the execution of this future when the successful result of this future is a stream. Read more

Fuse a future such that poll will never again be called once it has completed. Read more

Do something with the item of a future, passing it on. Read more

Do something with the error of a future, passing it on. Read more

Catches unwinding panics while polling the future. Read more

Create a cloneable handle to this future where all handles will resolve to the same result. Read more

Handle errors generated by this future by converting them into Self::Item. Read more

Assigns the provided Executor to be used when spawning tasks from within the future. Read more

impl<T> StreamExt for T where
    T: Stream + ?Sized, 
[src]

Converts this stream into a Future. Read more

Converts a stream of type T to a stream of type U. Read more

Converts a stream of error type T to a stream of error type U. Read more

Filters the values produced by this stream according to the provided predicate. Read more

Filters the values produced by this stream while simultaneously mapping them to a different type. Read more

Chain on a computation for when a value is ready, passing the resulting item to the provided closure f. Read more

Chain on a computation for when a value is ready, passing the successful results to the provided closure f. Read more

Chain on a computation for when an error happens, passing the erroneous result to the provided closure f. Read more

Collect all of the values of this stream into a vector, returning a future representing the result of that computation. Read more

Concatenate all results of a stream into a single extendable destination, returning a future representing the end result. Read more

Execute an accumulating computation over a stream, collecting all the values into one final result. Read more

Flattens a stream of streams into just one continuous stream. Read more

Skip elements on this stream while the predicate provided resolves to true. Read more

Take elements from this stream while the predicate provided resolves to true. Read more

Runs this stream to completion, executing the provided closure for each element on the stream. Read more

Runs this stream to completion, executing the provided closure for each element on the stream. This is similar to for_each but may begin processing an element while previous elements are still being processed. Read more

Map this stream's error to a different type using the Into trait. Read more

Creates a new stream of at most amt items of the underlying stream. Read more

Creates a new stream which skips amt items of the underlying stream. Read more

Fuse a stream such that poll will never again be called once it has finished. Read more

Borrows a stream, rather than consuming it. Read more

Catches unwinding panics while polling the stream. Read more

An adaptor for creating a buffered list of pending futures. Read more

An adaptor for creating a buffered list of pending futures (unordered). Read more

An adapter for zipping two streams together. Read more

Adapter for chaining two stream. Read more

Creates a new stream which exposes a peek method. Read more

An adaptor for chunking up items of the stream inside a vector. Read more

Creates a stream that selects the next element from either this stream or the provided one, whichever is ready first. Read more

A future that completes after the given stream has been fully processed into the sink, including flushing. Read more

Splits this Stream + Sink object into separate Stream and Sink objects. Read more

Do something with each item of this stream, afterwards passing it on. Read more

Do something with the error of this stream, afterwards passing it on. Read more

Handle errors generated by this stream by converting them into Option<Self::Item>, such that a None value terminates the stream. Read more

ⓘImportant traits for Either<L, R>

Deprecated

: use left_stream instead

Wrap this stream in an Either stream, making it the left-hand variant of that Either. Read more

ⓘImportant traits for Either<L, R>

Deprecated

: use right_stream instead

Wrap this stream in an Either stream, making it the right-hand variant of that Either. Read more

ⓘImportant traits for Either<L, R>

Wrap this stream in an Either stream, making it the left-hand variant of that Either. Read more

ⓘImportant traits for Either<L, R>

Wrap this stream in an Either stream, making it the right-hand variant of that Either. Read more

impl<T> SinkExt for T where
    T: Sink + ?Sized, 
[src]

Composes a function in front of the sink. Read more

Composes a function in front of the sink. Read more

Transforms the error returned by the sink.

Map this sink's error to a different error type using the Into trait. Read more

Adds a fixed-size buffer to the current sink. Read more

Close the sink. Read more

Fanout items to multiple sinks. Read more

Flush the sync, processing all pending items. Read more

A future that completes after the given item has been fully processed into the sink, including flushing. Read more

A future that completes after the given stream has been fully processed into the sink, including flushing. Read more

ⓘImportant traits for Either<L, R>

Wrap this sink in an Either sink, making it the left-hand variant of that Either. Read more

ⓘImportant traits for Either<L, R>

Wrap this stream in an Either stream, making it the right-hand variant of that Either. Read more

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

The type of the elements being iterated over.

Which kind of iterator are we turning this into?

Creates an iterator from a value. Read more

impl<T, U> TryFrom for T where
    T: From<U>, 
[src]

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

The type returned in the event of a conversion error.

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

Performs the conversion.

impl<T> From for T
[src]

Performs the conversion.

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

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

The type returned in the event of a conversion error.

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

Performs the conversion.

impl<T, U> Into for T where
    U: From<T>, 
[src]

Performs the conversion.

impl<T> Borrow for T where
    T: ?Sized, 
[src]

Immutably borrows from an owned value. Read more

impl<T> BorrowMut for T where
    T: ?Sized, 
[src]

Mutably borrows from an owned value. Read more

impl<T> Any for T where
    T: 'static + ?Sized, 
[src]

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

this method will likely be replaced by an associated static

Gets the TypeId of self. Read more

impl<T> ToString for T where
    T: Display + ?Sized, 
[src]

Converts the given value to a String. Read more

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

Creates owned data from borrowed data, usually by cloning. Read more

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

recently added

Uses borrowed data to replace owned data, usually by cloning. Read more

impl<F> IntoFuture for F where
    F: Future, 
[src]

The future that this type can be converted into.

The item that the future may resolve with.

The error that the future may resolve with.

Consumes this object and produces a future.