Package com.github.nullterminated.trylambda

Class Either<A,B>

java.lang.Object

com.github.nullterminated.trylambda.Either<A,B>

Direct Known Subclasses:

Either.Left, Either.Right

public abstract class Either<A,B>
extends java.lang.Object

A Java implementation of the Either monad. The Either type represents values with two possibilities: a value of type Either a b is either Left a or Right b. The Either type is sometimes used to represent a value which is either correct or an error; by convention, the Left constructor is used to hold an error value and the Right constructor is used to hold a correct value (mnemonic: "right" also means "correct"). Pattern matching is accomplished using polymorphism.

Author:

Ramsey Gurley

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	Either.Left<A,B>
static class	Either.Right<A,B>

Method Summary

Modifier and Type	Method	Description
abstract Either<B,A>	flip()	Flip an Either<A,B> to a Either<B,A>.
abstract A	getLeft()
abstract B	getRight()
boolean	isLeft()
boolean	isRight()
static <A,B> Either<A,B>	left(A left)	Factory method for constructing lefts.
abstract <X,Y> Either<X,Y>	map(java.util.function.Function<A,X> leftFunction, java.util.function.Function<B,Y> rightFunction)	Map this Either<A,B> to a new Either<X,Y>.
abstract <T> T	reduce(java.util.function.Function<A,T> leftFunction, java.util.function.Function<B,T> rightFunction)	Reduce an Either<A,B> to a single value type T.
static <A,B> Either<A,B>	right(B right)	Factory method for constructing rights.
abstract void	use(java.util.function.Consumer<A> leftConsumer, java.util.function.Consumer<B> rightConsumer)	Pass the value of this either to a consumer.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

left

public static <A,B> Either<A,B> left(A left)

Factory method for constructing lefts.

Type Parameters:

A - the left type

B - the right type

Parameters:

left - the left value

Returns:

a new left

right

public static <A,B> Either<A,B> right(B right)

Factory method for constructing rights.

Type Parameters:

A - the left type

B - the right type

Parameters:

right - the right value

Returns:

a new right

isLeft

public final boolean isLeft()

Returns:

true if left

isRight

public final boolean isRight()

Returns:

true if right

getLeft

public abstract A getLeft()

Returns:

the left value

Throws:

java.lang.UnsupportedOperationException - if the receiver is right

getRight

public abstract B getRight()

Returns:

the right value

Throws:

java.lang.UnsupportedOperationException - if the receiver is left

use

public abstract void use(java.util.function.Consumer<A> leftConsumer,
                         java.util.function.Consumer<B> rightConsumer)

Pass the value of this either to a consumer.

Parameters:

leftConsumer - the consumer for lefts

rightConsumer - the consumer for rights

map

public abstract <X,Y> Either<X,Y> map(java.util.function.Function<A,X> leftFunction,
                                      java.util.function.Function<B,Y> rightFunction)

Map this Either<A,B> to a new Either<X,Y>.

Type Parameters:

X - the new left type

Y - the new right type

Parameters:

leftFunction - function to convert A to X

rightFunction - function to convert B to Y

Returns:

a new Either<X,Y>

reduce

public abstract <T> T reduce(java.util.function.Function<A,T> leftFunction,
                             java.util.function.Function<B,T> rightFunction)

Reduce an Either<A,B> to a single value type T.

Type Parameters:

T - the result type

Parameters:

leftFunction - function to convert A to T

rightFunction - function to convert B to T

Returns:

a value typed T

flip

public abstract Either<B,A> flip()

Flip an Either<A,B> to a Either<B,A>.

Returns:

a new either with types flipped