Package com.github.tonivade.purefun.type

Interface Either<L,R>

Type Parameters:

L - type of the left value, negative case

R - type of the right value, positive case

All Superinterfaces:

Applicable<Either<L,?>,R>, Bindable<Either<L,?>,R>, EitherOf<L,R>, Kind<Either<L,?>,R>, Mappable<Either<L,?>,R>

All Known Implementing Classes:

Either.Left, Either.Right

public sealed interface Either<L,R>
extends EitherOf<L,R>, Bindable<Either<L,?>,R>, Applicable<Either<L,?>,R>
permits Either.Left<L,R>, Either.Right<L,R>

This type represents two possible values, called left or right. In general left case is considered the negative case, and right case the positive case, so is right biased

• Either.left(value): left value
• Either.right(value): right value

Usually this type is used to represent a function return type. The left value represents when the function fails, and the right value when function returns normally. It's the functional alternative to exceptions.

Try<T> and Either<Throwable, T> are isomorphisms.

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static final record	Either.Left<L,R>
static final record	Either.Right<L,R>

Nested classes/interfaces inherited from interface com.github.tonivade.purefun.core.Applicable

Applicable.Map2<F extends Applicable<F,?>,A,B>, Applicable.Map3<F extends Applicable<F,?>,A,B,C>, Applicable.Map4<F extends Applicable<F,?>,A,B,C,D>, Applicable.Map5<F extends Applicable<F,?>,A,B,C,D,E>

Method Summary

Modifier and Type	Method	Description
default <T> Either<L,T>	ap(Kind<Either<L,?>,? extends Function1<? super R,? extends T>> apply)
default <T, U> Either<T,U>	bimap(Function1<? super L,? extends T> leftMapper, Function1<? super R,? extends U> rightMapper)
default Option<Either<L,R>>	filter(Matcher1<? super R> matcher)
default Option<Either<L,R>>	filterNot(Matcher1<? super R> matcher)
default Either<L,R>	filterOrElse(Matcher1<? super R> matcher, Producer<? extends Kind<Either<L,?>,R>> orElse)
default <T> Either<L,T>	flatMap(Function1<? super R,? extends Kind<Either<L,?>,? extends T>> map)
default <T> Either<T,R>	flatMapLeft(Function1<? super L,? extends Either<? extends T,R>> map)
default <T> T	fold(Function1<? super L,? extends T> leftMapper, Function1<? super R,? extends T> rightMapper)
default R	get()
L	getLeft()	Returns the left value if available.
default R	getOrElse(Producer<? extends R> orElse)
default R	getOrElse(R value)
default R	getOrElseNull()
R	getRight()	Returns the right value if available.
boolean	isLeft()
boolean	isRight()
default Option<L>	left()
static <L, R> Either<L,R>	left(L value)
default <T> Either<L,T>	map(Function1<? super R,? extends T> map)
static <L, A, B, Z> Either<L,Z>	map2(Either<L,? extends A> eitherA, Either<L,? extends B> eitherB, Function2<? super A,? super B,? extends Z> mapper)
default <T> Either<T,R>	mapLeft(Function1<? super L,? extends T> map)
static <A> A	merge(Either<A,A> either)
default Either<L,R>	or(Producer<Kind<Either<L,?>,R>> orElse)
default Either<L,R>	orElse(Kind<Either<L,?>,R> orElse)
default Option<R>	right()
static <L, R> Either<L,R>	right(R value)
default Sequence<R>	sequence()
default Stream<R>	stream()
default Either<R,L>	swap()
default Option<R>	toOption()
default Validation<L,R>	toValidation()

Methods inherited from interface com.github.tonivade.purefun.core.Applicable

zip, zipLeft, zipRight, zipWith

Methods inherited from interface com.github.tonivade.purefun.core.Bindable

andThen

Methods inherited from interface com.github.tonivade.purefun.Kind

fix, kind

Method Details

left

static <L,
R> Either<L,R> left(L value)

right

static <L,
R> Either<L,R> right(R value)

isLeft

boolean isLeft()

isRight

boolean isRight()

getLeft

L getLeft()

Returns the left value if available. If not, it throws NoSuchElementException

Returns:

the left value

Throws:

NoSuchElementException - if left value is not available

getRight

R getRight()

Returns the right value if available. If not, it throws NoSuchElementException

Returns:

the right value

Throws:

NoSuchElementException - if right value is not available

get

default R get()

left

default Option<L> left()

right

default Option<R> right()

swap

default Either<R,L> swap()

bimap

default <T,
U> Either<T,U> bimap(Function1<? super L,? extends T> leftMapper,
 Function1<? super R,? extends U> rightMapper)

map

default <T> Either<L,T> map(Function1<? super R,? extends T> map)

Specified by:

map in interface Applicable<L,R>

Specified by:

map in interface Bindable<L,R>

Specified by:

map in interface Mappable<L,R>

ap

default <T> Either<L,T> ap(Kind<Either<L,?>,? extends Function1<? super R,? extends T>> apply)

Specified by:

ap in interface Applicable<L,R>

mapLeft

default <T> Either<T,R> mapLeft(Function1<? super L,? extends T> map)

flatMap

default <T> Either<L,T> flatMap(Function1<? super R,? extends Kind<Either<L,?>,? extends T>> map)

Specified by:

flatMap in interface Bindable<L,R>

flatMapLeft

default <T> Either<T,R> flatMapLeft(Function1<? super L,? extends Either<? extends T,R>> map)

filter

default Option<Either<L,R>> filter(Matcher1<? super R> matcher)

filterNot

default Option<Either<L,R>> filterNot(Matcher1<? super R> matcher)

filterOrElse

default Either<L,R> filterOrElse(Matcher1<? super R> matcher,
 Producer<? extends Kind<Either<L,?>,R>> orElse)

or

default Either<L,R> or(Producer<Kind<Either<L,?>,R>> orElse)

orElse

default Either<L,R> orElse(Kind<Either<L,?>,R> orElse)

getOrElse

default R getOrElse(R value)

getOrElseNull

@Nullable
default R getOrElseNull()

getOrElse

default R getOrElse(Producer<? extends R> orElse)

fold

default <T> T fold(Function1<? super L,? extends T> leftMapper,
 Function1<? super R,? extends T> rightMapper)

stream

default Stream<R> stream()

sequence

default Sequence<R> sequence()

toOption

default Option<R> toOption()

toValidation

default Validation<L,R> toValidation()

merge

static <A> A merge(Either<A,A> either)

map2

static <L,
A,
B,
Z> Either<L,Z> map2(Either<L,? extends A> eitherA,
 Either<L,? extends B> eitherB,
 Function2<? super A,? super B,? extends Z> mapper)