Package com.jnape.palatable.lambda.monad

Interface MonadError<E,A,M extends MonadError<E,?,M>>

Type Parameters:

E - the error type

M - the Monad witness

A - the carrier

All Superinterfaces:

Applicative<A,M>, Functor<A,M>, Monad<A,M>

All Known Implementing Classes:

Either, Either.Left, Either.Right, EitherT, IO, IO.Compose, Maybe, Maybe.Just, Maybe.Nothing, MaybeT, Try, Try.Failure, Try.Success

public interface MonadError<E,A,M extends MonadError<E,?,M>>
extends Monad<A,M>

An interface for monads that can be interrupted with some type of error. The type of error is fully dictated by the instance of MonadError and is not necessarily analogous to Java exceptions or even Throwable. For instance, IO can be thrown any Throwable, where as Either can only be "thrown" a value of its left type.

See Also:

IO, Either, Try, Maybe

Method Summary

Modifier and Type	Method	Description
MonadError<E,A,M>	catchError(Fn1<? super E,? extends Monad<A,M>> recoveryFn)	Catch any thrown errors inside the Monad and resume normal operations.
default <B> MonadError<E,B,M>	discardL(Applicative<B,M> appB)	Sequence both this Applicative and appB, discarding this Applicative's result and returning appB.
default <B> MonadError<E,A,M>	discardR(Applicative<B,M> appB)	Sequence both this Applicative and appB, discarding appB's result and returning this Applicative.
<B> MonadError<E,B,M>	flatMap(Fn1<? super A,? extends Monad<B,M>> f)	Chain dependent computations that may continue or short-circuit based on previous results.
default <B> MonadError<E,B,M>	fmap(Fn1<? super A,? extends B> fn)	Covariantly transmute this functor's parameter using the given mapping function.
default <B> Lazy<? extends MonadError<E,B,M>>	lazyZip(Lazy<? extends Applicative<Fn1<? super A,? extends B>,M>> 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.
<B> MonadError<E,B,M>	pure(B b)	Lift the value b into this applicative functor.
MonadError<E,A,M>	throwError(E e)	Throw an error value of type E into the monad.
default <B> MonadError<E,B,M>	zip(Applicative<Fn1<? super A,? extends B>,M> 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 interface com.jnape.palatable.lambda.functor.Functor

coerce

Method Detail

throwError

MonadError<E,A,M> throwError(E e)

Throw an error value of type E into the monad.

Parameters:

e - the error type

Returns:

the monad

catchError

MonadError<E,A,M> catchError(Fn1<? super E,? extends Monad<A,M>> recoveryFn)

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

Parameters:

recoveryFn - the catch function

Returns:

the recovered Monad

flatMap

<B> MonadError<E,B,M> flatMap(Fn1<? super A,? extends Monad<B,M>> f)

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

Specified by:

flatMap in interface Monad<E,A>

Type Parameters:

B - the resulting monad parameter type

Parameters:

f - the dependent computation over A

Returns:

the new monad instance

pure

<B> MonadError<E,B,M> pure(B b)

Lift the value b into this applicative functor.

Specified by:

pure in interface Applicative<E,A>

Specified by:

pure in interface Monad<E,A>

Type Parameters:

B - the type of the returned applicative's parameter

Parameters:

b - the value

Returns:

an instance of this applicative over b

fmap

default <B> MonadError<E,B,M> fmap(Fn1<? super A,? extends B> 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<E,A>

Specified by:

fmap in interface Functor<E,A>

Specified by:

fmap in interface Monad<E,A>

Type Parameters:

B - the new parameter type

Parameters:

fn - the mapping function

Returns:

a functor over B (the new parameter type)

zip

default <B> MonadError<E,B,M> zip(Applicative<Fn1<? super A,? extends B>,M> 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<E,A>

Specified by:

zip in interface Monad<E,A>

Type Parameters:

B - the resulting applicative parameter type

Parameters:

appFn - the other applicative instance

Returns:

the mapped applicative

lazyZip

default <B> Lazy<? extends MonadError<E,B,M>> lazyZip(Lazy<? extends Applicative<Fn1<? super A,? extends B>,M>> 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<E,A>

Specified by:

lazyZip in interface Monad<E,A>

Type Parameters:

B - the resulting applicative parameter type

Parameters:

lazyAppFn - the lazy other applicative instance

Returns:

the mapped applicative

See Also:

Maybe, Either

discardL

default <B> MonadError<E,B,M> discardL(Applicative<B,M> 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<E,A>

Specified by:

discardL in interface Monad<E,A>

Type Parameters:

B - the type of the returned Applicative's parameter

Parameters:

appB - the other Applicative

Returns:

appB

discardR

default <B> MonadError<E,A,M> discardR(Applicative<B,M> 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<E,A>

Specified by:

discardR in interface Monad<E,A>

Type Parameters:

B - the type of appB's parameter

Parameters:

appB - the other Applicative

Returns:

this Applicative