W - the accumulation typeA - the value typepublic final class Writer<W,A> extends Object implements MonadWriter<W,A,Writer<W,?>>, MonadRec<A,Writer<W,?>>
| Modifier and Type | Method and Description |
|---|---|
Writer<W,A> |
censor(Fn1<? super W,? extends W> fn)
Update the accumulated state.
|
<B> Writer<W,B> |
discardL(Applicative<B,Writer<W,?>> appB)
Sequence both this
Applicative and appB, discarding this Applicative's
result and returning appB. |
<B> Writer<W,A> |
discardR(Applicative<B,Writer<W,?>> appB)
Sequence both this
Applicative and appB, discarding appB's result and
returning this Applicative. |
<B> Writer<W,B> |
flatMap(Fn1<? super A,? extends Monad<B,Writer<W,?>>> f)
Chain dependent computations that may continue or short-circuit based on previous results.
|
<B> Writer<W,B> |
fmap(Fn1<? super A,? extends B> fn)
Covariantly transmute this functor's parameter using the given mapping function.
|
<B> Lazy<Writer<W,B>> |
lazyZip(Lazy<? extends Applicative<Fn1<? super A,? extends B>,Writer<W,?>>> 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. |
static <W,A> Writer<W,A> |
listen(A a)
Construct a
Writer from a value. |
<B> Writer<W,Tuple2<A,B>> |
listens(Fn1<? super W,? extends B> fn)
Map the accumulation into a value and pair it with the current output.
|
<B> Writer<W,B> |
pure(B b)
Lift the value
b into this applicative functor. |
static <W> Pure<Writer<W,?>> |
pureWriter()
|
Tuple2<A,W> |
runWriter(Monoid<W> monoid)
|
static <W> Writer<W,Unit> |
tell(W w)
Construct a
Writer from an accumulation. |
<B> Writer<W,B> |
trampolineM(Fn1<? super A,? extends MonadRec<RecursiveResult<A,B>,Writer<W,?>>> fn)
Given some operation yielding a
RecursiveResult inside this MonadRec, internally trampoline the
operation until it yields a termination instruction. |
static <W,A> Writer<W,A> |
writer(Tuple2<A,W> aw)
Construct a
Writer from an accumulation and a value. |
<B> Writer<W,B> |
zip(Applicative<Fn1<? super A,? extends B>,Writer<W,?>> appFn)
Given another instance of this applicative over a mapping function, "zip" the two instances together using
whatever application semantics the current applicative supports.
|
public Tuple2<A,W> runWriter(Monoid<W> monoid)
Monoid for the accumulation, run the computation represented by this Writer, accumulate
the written output in terms of the Monoid, and produce the accumulation and the value.monoid - the accumulation Monoidpublic <B> Writer<W,Tuple2<A,B>> listens(Fn1<? super W,? extends B> fn)
listens in interface MonadWriter<W,A,Writer<W,?>>B - the mapped outputfn - the mapping functionMonadWriterpublic Writer<W,A> censor(Fn1<? super W,? extends W> fn)
censor in interface MonadWriter<W,A,Writer<W,?>>fn - the update functionMonadWriterpublic <B> Writer<W,B> trampolineM(Fn1<? super A,? extends MonadRec<RecursiveResult<A,B>,Writer<W,?>>> fn)
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.
trampolineM in interface MonadRec<A,Writer<W,?>>B - the ultimate resulting carrier typefn - the function to internally trampolineMonadRecfor a basic implementation,
for a {@link CoProduct2 coproduct} implementation,
for an implementation leveraging an already stack-safe {@link Monad#flatMap(Fn1)},
for a {@link MonadT monad transformer} implementationpublic <B> Writer<W,B> flatMap(Fn1<? super A,? extends Monad<B,Writer<W,?>>> f)
flatMap in interface Monad<A,Writer<W,?>>flatMap in interface MonadRec<A,Writer<W,?>>flatMap in interface MonadWriter<W,A,Writer<W,?>>B - the resulting monad parameter typef - the dependent computation over Apublic <B> Writer<W,B> pure(B b)
b into this applicative functor.pure in interface Applicative<A,Writer<W,?>>pure in interface Monad<A,Writer<W,?>>pure in interface MonadRec<A,Writer<W,?>>pure in interface MonadWriter<W,A,Writer<W,?>>B - the type of the returned applicative's parameterb - the valuepublic <B> Writer<W,B> fmap(Fn1<? super A,? extends B> fn)
fmap in interface Applicative<A,Writer<W,?>>fmap in interface Functor<A,Writer<W,?>>fmap in interface Monad<A,Writer<W,?>>fmap in interface MonadRec<A,Writer<W,?>>fmap in interface MonadWriter<W,A,Writer<W,?>>B - the new parameter typefn - the mapping functionpublic <B> Writer<W,B> zip(Applicative<Fn1<? super A,? extends B>,Writer<W,?>> appFn)
zip in interface Applicative<A,Writer<W,?>>zip in interface Monad<A,Writer<W,?>>zip in interface MonadRec<A,Writer<W,?>>zip in interface MonadWriter<W,A,Writer<W,?>>B - the resulting applicative parameter typeappFn - the other applicative instancepublic <B> Lazy<Writer<W,B>> lazyZip(Lazy<? extends Applicative<Fn1<? super A,? extends B>,Writer<W,?>>> lazyAppFn)
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.lazyZip in interface Applicative<A,Writer<W,?>>lazyZip in interface Monad<A,Writer<W,?>>lazyZip in interface MonadRec<A,Writer<W,?>>lazyZip in interface MonadWriter<W,A,Writer<W,?>>B - the resulting applicative parameter typelazyAppFn - the lazy other applicative instanceMaybe,
Eitherpublic <B> Writer<W,B> discardL(Applicative<B,Writer<W,?>> appB)
Applicative and appB, discarding this Applicative's
result and returning appB. This is generally useful for sequentially performing side-effects.discardL in interface Applicative<A,Writer<W,?>>discardL in interface Monad<A,Writer<W,?>>discardL in interface MonadRec<A,Writer<W,?>>discardL in interface MonadWriter<W,A,Writer<W,?>>B - the type of the returned Applicative's parameterappB - the other Applicativepublic <B> Writer<W,A> discardR(Applicative<B,Writer<W,?>> appB)
Applicative and appB, discarding appB's result and
returning this Applicative. This is generally useful for sequentially performing side-effects.discardR in interface Applicative<A,Writer<W,?>>discardR in interface Monad<A,Writer<W,?>>discardR in interface MonadRec<A,Writer<W,?>>discardR in interface MonadWriter<W,A,Writer<W,?>>B - the type of appB's parameterappB - the other Applicativepublic static <W> Writer<W,Unit> tell(W w)
Writer from an accumulation.W - the accumulation typeWriterpublic static <W,A> Writer<W,A> listen(A a)
Writer from a value.W - the accumulation typeA - the value typeWriterpublic static <W,A> Writer<W,A> writer(Tuple2<A,W> aw)
Writer from an accumulation and a value.W - the accumulation typeA - the value typeWriterT