pub enum Either<L, R> {
Left(L),
Right(R),
}Expand description
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§
Implementations§
Source§impl<L, R> Either<L, R>
impl<L, R> Either<L, R>
Sourcepub fn is_left(&self) -> bool
pub 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);Sourcepub fn is_right(&self) -> bool
pub 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);Sourcepub fn left(self) -> Option<L>
pub 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);Sourcepub fn right(self) -> Option<R>
pub 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));Sourcepub fn as_ref(&self) -> Either<&L, &R> ⓘ
pub 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"));Sourcepub fn as_mut(&mut self) -> Either<&mut L, &mut R> ⓘ
pub 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));Sourcepub fn flip(self) -> Either<R, L> ⓘ
pub 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"));Sourcepub fn map_left<F, M>(self, f: F) -> Either<M, R> ⓘwhere
F: FnOnce(L) -> M,
pub 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));Sourcepub fn map_right<F, S>(self, f: F) -> Either<L, S> ⓘwhere
F: FnOnce(R) -> S,
pub 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));Sourcepub fn either<F, G, T>(self, f: F, g: G) -> T
pub fn either<F, G, T>(self, f: F, g: G) -> 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§
Source§impl<L, R, Target> AsMut<Target> for Either<L, R>
impl<L, R, Target> AsMut<Target> for Either<L, R>
Source§fn as_mut(&mut self) -> &mut Target
fn as_mut(&mut self) -> &mut Target
Source§impl<L, R> BufRead for Either<L, R>
Requires crate feature "use_std"
impl<L, R> BufRead for Either<L, R>
Requires crate feature "use_std"
Source§fn fill_buf(&mut self) -> Result<&[u8]>
fn fill_buf(&mut self) -> Result<&[u8]>
Read methods, if empty. Read moreSource§fn consume(&mut self, amt: usize)
fn consume(&mut self, amt: usize)
amount of additional bytes from the internal buffer as having been read.
Subsequent calls to read only return bytes that have not been marked as read. Read moreSource§fn has_data_left(&mut self) -> Result<bool, Error>
fn has_data_left(&mut self) -> Result<bool, Error>
buf_read_has_data_left)read. Read more1.83.0 · Source§fn skip_until(&mut self, byte: u8) -> Result<usize, Error>
fn skip_until(&mut self, byte: u8) -> Result<usize, Error>
byte or EOF is reached. Read more1.0.0 · Source§fn read_line(&mut self, buf: &mut String) -> Result<usize, Error>
fn read_line(&mut self, buf: &mut String) -> Result<usize, Error>
0xA byte) is reached, and append
them to the provided String buffer. Read moreSource§impl<L, R> DoubleEndedIterator for Either<L, R>
impl<L, R> DoubleEndedIterator for Either<L, R>
Source§fn next_back(&mut self) -> Option<L::Item>
fn next_back(&mut self) -> Option<L::Item>
Source§fn advance_back_by(&mut self, n: usize) -> Result<(), NonZero<usize>>
fn advance_back_by(&mut self, n: usize) -> Result<(), NonZero<usize>>
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fn nth_back(&mut self, n: usize) -> Option<Self::Item>
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fn try_rfold<B, F, R>(&mut self, init: B, f: F) -> R
Iterator::try_fold(): it takes
elements starting from the back of the iterator. Read moreSource§impl<L, R> Error for Either<L, R>
Either implements Error if both L and R implement it.
impl<L, R> Error for Either<L, R>
Either implements Error if both L and R implement it.
Source§fn description(&self) -> &str
fn description(&self) -> &str
Source§fn cause(&self) -> Option<&dyn Error>
fn cause(&self) -> Option<&dyn Error>
Source§impl<L, R> ExactSizeIterator for Either<L, R>
impl<L, R> ExactSizeIterator for Either<L, R>
Source§impl<L, R> From<Result<R, L>> for Either<L, R>
Convert from Result to Either with Ok => Right and Err => Left.
impl<L, R> From<Result<R, L>> for Either<L, R>
Convert from Result to Either with Ok => Right and Err => Left.
Source§impl<L, R> Into<Result<R, L>> for Either<L, R>
Convert from Either to Result with Right => Ok and Left => Err.
impl<L, R> Into<Result<R, L>> for Either<L, R>
Convert from Either to Result with Right => Ok and Left => Err.
Source§impl<L, R> Iterator for Either<L, R>
Either<L, R> is an iterator if both L and R are iterators.
impl<L, R> Iterator for Either<L, R>
Either<L, R> is an iterator if both L and R are iterators.
Source§fn next(&mut self) -> Option<L::Item>
fn next(&mut self) -> Option<L::Item>
Source§fn size_hint(&self) -> (usize, Option<usize>)
fn size_hint(&self) -> (usize, Option<usize>)
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&mut self,
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&mut self,
) -> Result<[Self::Item; N], IntoIter<Self::Item, N>>where
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fn nth(&mut self, n: usize) -> Option<Self::Item>
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iter_map_windows)f for each contiguous window of size N over
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Iterator. Read moreSource§fn try_collect<B>(
&mut self,
) -> <<Self::Item as Try>::Residual as Residual<B>>::TryType
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fn partition<B, F>(self, f: F) -> (B, B)
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) -> <<R as Try>::Residual as Residual<Option<<R as Try>::Output>>>::TryType
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fn max(self) -> Option<Self::Item>
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fn min(self) -> Option<Self::Item>
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fn max_by_key<B, F>(self, f: F) -> Option<Self::Item>
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fn max_by<F>(self, compare: F) -> Option<Self::Item>
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fn min_by<F>(self, compare: F) -> Option<Self::Item>
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Self: Sized + DoubleEndedIterator,
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Self: Sized + DoubleEndedIterator,
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Source§fn array_chunks<const N: usize>(self) -> ArrayChunks<Self, N>where
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iter_array_chunks)N elements of the iterator at a time. Read more1.11.0 · Source§fn product<P>(self) -> P
fn product<P>(self) -> P
Source§fn cmp_by<I, F>(self, other: I, cmp: F) -> Ordering
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iter_order_by)Iterator with those
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fn partial_cmp<I>(self, other: I) -> Option<Ordering>
PartialOrd elements of
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Self: Sized,
fn max(self, other: Self) -> Selfwhere
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Source§impl<L: PartialOrd, R: PartialOrd> PartialOrd for Either<L, R>
impl<L: PartialOrd, R: PartialOrd> PartialOrd for Either<L, R>
Source§impl<L, R> Read for Either<L, R>
Either<L, R> implements Read if both L and R do.
impl<L, R> Read for Either<L, R>
Either<L, R> implements Read if both L and R do.
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