Class Writer<W,A>
- java.lang.Object
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- com.jnape.palatable.lambda.functor.builtin.Writer<W,A>
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- Type Parameters:
W
- the accumulation typeA
- the value type
- All Implemented Interfaces:
Applicative<A,Writer<W,?>>
,Functor<A,Writer<W,?>>
,Monad<A,Writer<W,?>>
,MonadRec<A,Writer<W,?>>
,MonadWriter<W,A,Writer<W,?>>
public final class Writer<W,A> extends java.lang.Object implements MonadWriter<W,A,Writer<W,?>>, MonadRec<A,Writer<W,?>>
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method 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 thisApplicative
andappB
, discarding thisApplicative's
result and returningappB
.<B> Writer<W,A>
discardR(Applicative<B,Writer<W,?>> appB)
Sequence both thisApplicative
andappB
, discardingappB's
result and returning thisApplicative
.<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 alazy
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 aWriter
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 valueb
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 aWriter
from an accumulation.<B> Writer<W,B>
trampolineM(Fn1<? super A,? extends MonadRec<RecursiveResult<A,B>,Writer<W,?>>> fn)
Given some operation yielding aRecursiveResult
inside thisMonadRec
, internally trampoline the operation until it yields atermination
instruction.static <W,A>
Writer<W,A>writer(Tuple2<A,W> aw)
Construct aWriter
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.
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Method Detail
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runWriter
public Tuple2<A,W> runWriter(Monoid<W> monoid)
Given aMonoid
for the accumulation, run the computation represented by thisWriter
, accumulate the written output in terms of theMonoid
, and produce the accumulation and the value.- Parameters:
monoid
- the accumulationMonoid
- Returns:
- the accumulation with the value
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listens
public <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.- Specified by:
listens
in interfaceMonadWriter<W,A,Writer<W,?>>
- Type Parameters:
B
- the mapped output- Parameters:
fn
- the mapping function- Returns:
- the updated
MonadWriter
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censor
public Writer<W,A> censor(Fn1<? super W,? extends W> fn)
Update the accumulated state.- Specified by:
censor
in interfaceMonadWriter<W,A,Writer<W,?>>
- Parameters:
fn
- the update function- Returns:
- the updated
MonadWriter
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trampolineM
public <B> Writer<W,B> trampolineM(Fn1<? super A,? extends MonadRec<RecursiveResult<A,B>,Writer<W,?>>> fn)
Given some operation yielding aRecursiveResult
inside thisMonadRec
, internally trampoline the operation until it yields atermination
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 interfaceMonadRec<W,A>
- Type Parameters:
B
- the ultimate resulting carrier type- Parameters:
fn
- the function to internally trampoline- Returns:
- the trampolined
MonadRec
- See Also:
for a basic implementation
,for a implementation
,for an implementation leveraging an already stack-safe
,for a implementation
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flatMap
public <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.- Specified by:
flatMap
in interfaceMonad<W,A>
- Specified by:
flatMap
in interfaceMonadRec<W,A>
- Specified by:
flatMap
in interfaceMonadWriter<W,A,Writer<W,?>>
- Type Parameters:
B
- the resulting monad parameter type- Parameters:
f
- the dependent computation over A- Returns:
- the new monad instance
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pure
public <B> Writer<W,B> pure(B b)
Lift the valueb
into this applicative functor.- Specified by:
pure
in interfaceApplicative<W,A>
- Specified by:
pure
in interfaceMonad<W,A>
- Specified by:
pure
in interfaceMonadRec<W,A>
- Specified by:
pure
in interfaceMonadWriter<W,A,Writer<W,?>>
- Type Parameters:
B
- the type of the returned applicative's parameter- Parameters:
b
- the value- Returns:
- an instance of this applicative over b
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fmap
public <B> Writer<W,B> 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 interfaceApplicative<W,A>
- Specified by:
fmap
in interfaceFunctor<W,A>
- Specified by:
fmap
in interfaceMonad<W,A>
- Specified by:
fmap
in interfaceMonadRec<W,A>
- Specified by:
fmap
in interfaceMonadWriter<W,A,Writer<W,?>>
- Type Parameters:
B
- the new parameter type- Parameters:
fn
- the mapping function- Returns:
- a functor over B (the new parameter type)
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zip
public <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.- Specified by:
zip
in interfaceApplicative<W,A>
- Specified by:
zip
in interfaceMonad<W,A>
- Specified by:
zip
in interfaceMonadRec<W,A>
- Specified by:
zip
in interfaceMonadWriter<W,A,Writer<W,?>>
- Type Parameters:
B
- the resulting applicative parameter type- Parameters:
appFn
- the other applicative instance- Returns:
- the mapped applicative
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lazyZip
public <B> Lazy<Writer<W,B>> lazyZip(Lazy<? extends Applicative<Fn1<? super A,? extends B>,Writer<W,?>>> lazyAppFn)
Given alazy
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 interfaceApplicative<W,A>
- Specified by:
lazyZip
in interfaceMonad<W,A>
- Specified by:
lazyZip
in interfaceMonadRec<W,A>
- Specified by:
lazyZip
in interfaceMonadWriter<W,A,Writer<W,?>>
- Type Parameters:
B
- the resulting applicative parameter type- Parameters:
lazyAppFn
- the lazy other applicative instance- Returns:
- the mapped applicative
- See Also:
Maybe
,Either
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discardL
public <B> Writer<W,B> discardL(Applicative<B,Writer<W,?>> appB)
Sequence both thisApplicative
andappB
, discarding thisApplicative's
result and returningappB
. This is generally useful for sequentially performing side-effects.- Specified by:
discardL
in interfaceApplicative<W,A>
- Specified by:
discardL
in interfaceMonad<W,A>
- Specified by:
discardL
in interfaceMonadRec<W,A>
- Specified by:
discardL
in interfaceMonadWriter<W,A,Writer<W,?>>
- Type Parameters:
B
- the type of the returned Applicative's parameter- Parameters:
appB
- the other Applicative- Returns:
- appB
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discardR
public <B> Writer<W,A> discardR(Applicative<B,Writer<W,?>> appB)
Sequence both thisApplicative
andappB
, discardingappB's
result and returning thisApplicative
. This is generally useful for sequentially performing side-effects.- Specified by:
discardR
in interfaceApplicative<W,A>
- Specified by:
discardR
in interfaceMonad<W,A>
- Specified by:
discardR
in interfaceMonadRec<W,A>
- Specified by:
discardR
in interfaceMonadWriter<W,A,Writer<W,?>>
- Type Parameters:
B
- the type of appB's parameter- Parameters:
appB
- the other Applicative- Returns:
- this Applicative
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tell
public static <W> Writer<W,Unit> tell(W w)
Construct aWriter
from an accumulation.- Type Parameters:
W
- the accumulation type- Parameters:
w
- the accumulation- Returns:
- the
Writer
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listen
public static <W,A> Writer<W,A> listen(A a)
Construct aWriter
from a value.- Type Parameters:
W
- the accumulation typeA
- the value type- Parameters:
a
- the output value- Returns:
- the
Writer
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writer
public static <W,A> Writer<W,A> writer(Tuple2<A,W> aw)
Construct aWriter
from an accumulation and a value.- Type Parameters:
W
- the accumulation typeA
- the value type- Parameters:
aw
- the output value and accumulation- Returns:
- the
WriterT
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