Class EitherT<M extends MonadRec<?,M>, L, R>

java.lang.Object

com.jnape.palatable.lambda.monad.transformer.builtin.EitherT<M,L,R>

Type Parameters:

M - the outer stack-safe monad

L - the left type

R - the right type

All Implemented Interfaces:

Applicative<R, EitherT<M,L,?>>, Bifunctor<L, R, EitherT<M,?,?>>, BoundedBifunctor<L, R, Object, Object, EitherT<M,?,?>>, Functor<R, EitherT<M,L,?>>, Monad<R, EitherT<M,L,?>>, MonadBase<M, R, EitherT<?,L,?>>, MonadError<L, R, EitherT<M,L,?>>, MonadRec<R, EitherT<M,L,?>>, MonadT<M, R, EitherT<M,L,?>, EitherT<?,L,?>>

public final class EitherT<M extends MonadRec<?,M>, L, R>
extends Object
implements Bifunctor<L, R, EitherT<M,?,?>>, MonadT<M, R, EitherT<M,L,?>, EitherT<?,L,?>>, MonadError<L, R, EitherT<M,L,?>>

A monad transformer for Either.

Field Summary

Fields

Modifier and Type	Field	Description
private final MonadRec<Either<L,R>, M>	melr

Constructor Summary

Constructors

Modifier	Constructor	Description
private	EitherT(MonadRec<Either<L,R>, M> melr)

Method Summary

Modifier and Type	Method	Description
<L2,R2> EitherT<M,L2,R2>	biMap(Fn1<? super L, ? extends L2> lFn, Fn1<? super R, ? extends R2> rFn)	Dually map covariantly over both the left and right parameters.
<L2> EitherT<M,L2,R>	biMapL(Fn1<? super L, ? extends L2> fn)	Covariantly map over the left parameter.
<R2> EitherT<M,L,R2>	biMapR(Fn1<? super R, ? extends R2> fn)	Covariantly map over the right parameter.
EitherT<M,L,R>	catchError(Fn1<? super L, ? extends Monad<R, EitherT<M,L,?>>> recoveryFn)	Catch any thrown errors inside the Monad and resume normal operations.
<R2> EitherT<M,L,R2>	discardL(Applicative<R2, EitherT<M,L,?>> appB)	Sequence both this Applicative and appB, discarding this Applicative's result and returning appB.
<B> EitherT<M,L,R>	discardR(Applicative<B, EitherT<M,L,?>> appB)	Sequence both this Applicative and appB, discarding appB's result and returning this Applicative.
static <M extends MonadRec<?,M>, L, R> EitherT<M,L,R>	eitherT(MonadRec<Either<L,R>, M> melr)	Static factory method for lifting a Monad<Either<L, R>, M> into an EitherT.
boolean	equals(Object other)
<R2> EitherT<M,L,R2>	flatMap(Fn1<? super R, ? extends Monad<R2, EitherT<M,L,?>>> f)	Chain dependent computations that may continue or short-circuit based on previous results.
<R2> EitherT<M,L,R2>	fmap(Fn1<? super R, ? extends R2> fn)	Covariantly transmute this functor's parameter using the given mapping function.
int	hashCode()
<R2> Lazy<EitherT<M,L,R2>>	lazyZip(Lazy<? extends Applicative<Fn1<? super R, ? extends R2>, EitherT<M,L,?>>> lazyAppFn)	Given a lazy instance of this applicative over a mapping function, "zip" the two instances together using whatever application semantics the current applicative supports.
<R2, N extends MonadRec<?,N>> EitherT<N,L,R2>	lift(MonadRec<R2,N> mb)	Lift a new argument MonadRec into this MonadBase.
static <L> Lift<EitherT<?,L,?>>	liftEitherT()	Lift for EitherT.
<R2> EitherT<M,L,R2>	pure(R2 r2)	Lift the value b into this applicative functor.
static <M extends MonadRec<?,M>, L> Pure<EitherT<M,L,?>>	pureEitherT(Pure<M> pureM)	The canonical Pure instance for EitherT.
<MELR extends MonadRec<Either<L,R>, M>> MELR	runEitherT()	Recover the full structure of the embedded Monad.
EitherT<M,L,R>	throwError(L l)	Throw an error value of type E into the monad.
String	toString()
<R2> EitherT<M,L,R2>	trampolineM(Fn1<? super R, ? extends MonadRec<RecursiveResult<R,R2>, EitherT<M,L,?>>> fn)	Given some operation yielding a RecursiveResult inside this MonadRec, internally trampoline the operation until it yields a termination instruction.
<R2> EitherT<M,L,R2>	zip(Applicative<Fn1<? super R, ? extends R2>, EitherT<M,L,?>> appFn)	Given another instance of this applicative over a mapping function, "zip" the two instances together using whatever application semantics the current applicative supports.

Methods inherited from class Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface Functor

coerce

Field Details

melr

private final MonadRec<Either<L,R>, M extends MonadRec<?,M>> melr

Constructor Details

EitherT

private EitherT(MonadRec<Either<L,R>, M> melr)

Method Details

runEitherT

public <MELR extends MonadRec<Either<L,R>, M>> MELR runEitherT()

Recover the full structure of the embedded Monad.

Type Parameters:

MELR - the witnessed target type

Returns:

the embedded Monad

lift

public <R2, N extends MonadRec<?,N>>
EitherT<N,L,R2> lift(MonadRec<R2,N> mb)

Lift a new argument MonadRec into this MonadBase.

Specified by:

lift in interface MonadBase<M extends MonadRec<?,M>, L, R>

Specified by:

lift in interface MonadT<M extends MonadRec<?,M>, R, EitherT<M extends MonadRec<?,M>, L, ?>, EitherT<?,L,?>>

Type Parameters:

R2 - the MonadRec carrier type

N - the argument MonadRec witness

Parameters:

mb - the argument MonadRec

Returns:

the new MonadBase

flatMap

public <R2> EitherT<M,L,R2> flatMap(Fn1<? super R, ? extends Monad<R2, EitherT<M,L,?>>> f)

Chain dependent computations that may continue or short-circuit based on previous results.

Specified by:

flatMap in interface Monad<M extends MonadRec<?,M>, L>

Specified by:

flatMap in interface MonadError<M extends MonadRec<?,M>, L, R>

Specified by:

flatMap in interface MonadRec<M extends MonadRec<?,M>, L>

Specified by:

flatMap in interface MonadT<M extends MonadRec<?,M>, R, EitherT<M extends MonadRec<?,M>, L, ?>, EitherT<?,L,?>>

Type Parameters:

R2 - the resulting monad parameter type

Parameters:

f - the dependent computation over A

Returns:

the new monad instance

pure

public <R2> EitherT<M,L,R2> pure(R2 r2)

Lift the value b into this applicative functor.

Specified by:

pure in interface Applicative<M extends MonadRec<?,M>, L>

Specified by:

pure in interface Monad<M extends MonadRec<?,M>, L>

Specified by:

pure in interface MonadError<M extends MonadRec<?,M>, L, R>

Specified by:

pure in interface MonadRec<M extends MonadRec<?,M>, L>

Specified by:

pure in interface MonadT<M extends MonadRec<?,M>, R, EitherT<M extends MonadRec<?,M>, L, ?>, EitherT<?,L,?>>

Type Parameters:

R2 - the type of the returned applicative's parameter

Parameters:

r2 - the value

Returns:

an instance of this applicative over b

fmap

public <R2> EitherT<M,L,R2> fmap(Fn1<? super R, ? extends R2> fn)

Covariantly transmute this functor's parameter using the given mapping function. Generally this method is specialized to return an instance of the class implementing Functor.

Specified by:

fmap in interface Applicative<M extends MonadRec<?,M>, L>

Specified by:

fmap in interface Functor<M extends MonadRec<?,M>, L>

Specified by:

fmap in interface Monad<M extends MonadRec<?,M>, L>

Specified by:

fmap in interface MonadError<M extends MonadRec<?,M>, L, R>

Specified by:

fmap in interface MonadRec<M extends MonadRec<?,M>, L>

Specified by:

fmap in interface MonadT<M extends MonadRec<?,M>, R, EitherT<M extends MonadRec<?,M>, L, ?>, EitherT<?,L,?>>

Type Parameters:

R2 - the new parameter type

Parameters:

fn - the mapping function

Returns:

a functor over B (the new parameter type)

zip

public <R2> EitherT<M,L,R2> zip(Applicative<Fn1<? super R, ? extends R2>, EitherT<M,L,?>> appFn)

Given another instance of this applicative over a mapping function, "zip" the two instances together using whatever application semantics the current applicative supports.

Specified by:

zip in interface Applicative<M extends MonadRec<?,M>, L>

Specified by:

zip in interface Monad<M extends MonadRec<?,M>, L>

Specified by:

zip in interface MonadError<M extends MonadRec<?,M>, L, R>

Specified by:

zip in interface MonadRec<M extends MonadRec<?,M>, L>

Specified by:

zip in interface MonadT<M extends MonadRec<?,M>, R, EitherT<M extends MonadRec<?,M>, L, ?>, EitherT<?,L,?>>

Type Parameters:

R2 - the resulting applicative parameter type

Parameters:

appFn - the other applicative instance

Returns:

the mapped applicative

lazyZip

public <R2> Lazy<EitherT<M,L,R2>> lazyZip(Lazy<? extends Applicative<Fn1<? super R, ? extends R2>, EitherT<M,L,?>>> lazyAppFn)

Given a lazy instance of this applicative over a mapping function, "zip" the two instances together using whatever application semantics the current applicative supports. This is useful for applicatives that support lazy evaluation and early termination.

Specified by:

lazyZip in interface Applicative<M extends MonadRec<?,M>, L>

Specified by:

lazyZip in interface Monad<M extends MonadRec<?,M>, L>

Specified by:

lazyZip in interface MonadError<M extends MonadRec<?,M>, L, R>

Specified by:

lazyZip in interface MonadRec<M extends MonadRec<?,M>, L>

Specified by:

lazyZip in interface MonadT<M extends MonadRec<?,M>, R, EitherT<M extends MonadRec<?,M>, L, ?>, EitherT<?,L,?>>

Type Parameters:

R2 - the resulting applicative parameter type

Parameters:

lazyAppFn - the lazy other applicative instance

Returns:

the mapped applicative

See Also:

• Maybe
• Either

discardL

public <R2> EitherT<M,L,R2> discardL(Applicative<R2, EitherT<M,L,?>> appB)

Sequence both this Applicative and appB, discarding this Applicative's result and returning appB. This is generally useful for sequentially performing side-effects.

Specified by:

discardL in interface Applicative<M extends MonadRec<?,M>, L>

Specified by:

discardL in interface Monad<M extends MonadRec<?,M>, L>

Specified by:

discardL in interface MonadError<M extends MonadRec<?,M>, L, R>

Specified by:

discardL in interface MonadRec<M extends MonadRec<?,M>, L>

Specified by:

discardL in interface MonadT<M extends MonadRec<?,M>, R, EitherT<M extends MonadRec<?,M>, L, ?>, EitherT<?,L,?>>

Type Parameters:

R2 - the type of the returned Applicative's parameter

Parameters:

appB - the other Applicative

Returns:

appB

discardR

public <B> EitherT<M,L,R> discardR(Applicative<B, EitherT<M,L,?>> appB)

Sequence both this Applicative and appB, discarding appB's result and returning this Applicative. This is generally useful for sequentially performing side-effects.

Specified by:

discardR in interface Applicative<M extends MonadRec<?,M>, L>

Specified by:

discardR in interface Monad<M extends MonadRec<?,M>, L>

Specified by:

discardR in interface MonadError<M extends MonadRec<?,M>, L, R>

Specified by:

discardR in interface MonadRec<M extends MonadRec<?,M>, L>

Specified by:

discardR in interface MonadT<M extends MonadRec<?,M>, R, EitherT<M extends MonadRec<?,M>, L, ?>, EitherT<?,L,?>>

Type Parameters:

B - the type of appB's parameter

Parameters:

appB - the other Applicative

Returns:

this Applicative

throwError

public EitherT<M,L,R> throwError(L l)

Throw an error value of type E into the monad.

Specified by:

throwError in interface MonadError<M extends MonadRec<?,M>, L, R>

Parameters:

l - the error type

Returns:

the monad

catchError

public EitherT<M,L,R> catchError(Fn1<? super L, ? extends Monad<R, EitherT<M,L,?>>> recoveryFn)

Catch any thrown errors inside the Monad and resume normal operations.

Specified by:

catchError in interface MonadError<M extends MonadRec<?,M>, L, R>

Parameters:

recoveryFn - the catch function

Returns:

the recovered Monad

trampolineM

public <R2> EitherT<M,L,R2> trampolineM(Fn1<? super R, ? extends MonadRec<RecursiveResult<R,R2>, EitherT<M,L,?>>> fn)

Given some operation yielding a RecursiveResult inside this MonadRec, internally trampoline the operation until it yields a termination instruction.

Stack-safety depends on implementations guaranteeing that the growth of the call stack is a constant factor independent of the number of invocations of the operation. For various examples of how this can be achieved in stereotypical circumstances, see the referenced types.

Specified by:

trampolineM in interface MonadRec<M extends MonadRec<?,M>, L>

Type Parameters:

R2 - the ultimate resulting carrier type

Parameters:

fn - the function to internally trampoline

Returns:

the trampolined MonadRec

See Also:

• for a basic implementation
• for a coproduct implementation
• for an implementation leveraging an already stack-safe Monad#flatMap(Fn1)
• for a monad transformer implementation

biMap

public <L2,R2> EitherT<M,L2,R2> biMap(Fn1<? super L, ? extends L2> lFn,
 Fn1<? super R, ? extends R2> rFn)

Dually map covariantly over both the left and right parameters. This is isomorphic to biMapL(lFn).biMapR(rFn).

Specified by:

biMap in interface Bifunctor<M extends MonadRec<?,M>, L, R>

Specified by:

biMap in interface BoundedBifunctor<L, R, Object, Object, EitherT<M extends MonadRec<?,M>, ?, ?>>

Type Parameters:

L2 - the new left parameter type

R2 - the new right parameter type

Parameters:

lFn - the left parameter mapping function

rFn - the right parameter mapping function

Returns:

a bifunctor over C (the new left parameter type) and D (the new right parameter type)

biMapL

public <L2> EitherT<M,L2,R> biMapL(Fn1<? super L, ? extends L2> fn)

Covariantly map over the left parameter.

Specified by:

biMapL in interface Bifunctor<M extends MonadRec<?,M>, L, R>

Specified by:

biMapL in interface BoundedBifunctor<L, R, Object, Object, EitherT<M extends MonadRec<?,M>, ?, ?>>

Type Parameters:

L2 - the new left parameter type

Parameters:

fn - the mapping function

Returns:

a bifunctor over C (the new left parameter) and B (the same right parameter)

biMapR

public <R2> EitherT<M,L,R2> biMapR(Fn1<? super R, ? extends R2> fn)

Covariantly map over the right parameter. For all bifunctors that are also functors, it should hold that biMapR(f) == fmap(f).

Specified by:

biMapR in interface Bifunctor<M extends MonadRec<?,M>, L, R>

Specified by:

biMapR in interface BoundedBifunctor<L, R, Object, Object, EitherT<M extends MonadRec<?,M>, ?, ?>>

Type Parameters:

R2 - the new right parameter type

Parameters:

fn - the mapping function

Returns:

a bifunctor over A (the same left parameter) and C (the new right parameter)

equals

public boolean equals(Object other)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object

eitherT

public static <M extends MonadRec<?,M>, L, R>
EitherT<M,L,R> eitherT(MonadRec<Either<L,R>, M> melr)

Static factory method for lifting a Monad<Either<L, R>, M> into an EitherT.

Type Parameters:

M - the outer Monad unification parameter

L - the left type

R - the right type

Parameters:

melr - the Monad<Either<L, R>, M>

Returns:

the EitherT

pureEitherT

public static <M extends MonadRec<?,M>, L>
Pure<EitherT<M,L,?>> pureEitherT(Pure<M> pureM)

The canonical Pure instance for EitherT.

Type Parameters:

M - the argument Monad witness

L - the left type

Parameters:

pureM - the argument Monad Pure

Returns:

the Pure instance

liftEitherT

public static <L> Lift<EitherT<?,L,?>> liftEitherT()

Lift for EitherT.

Type Parameters:

L - the left type

Returns:

the Monadlifted into EitherT