final case class Loop[T, +E](alterand: Endo[T, E]) extends Decorator[T, T, E] with Product with Serializable
A decorator that feeds the output of each successful step back as the input of the next, effectively looping the inner endomorphic stage until it stops.
The tail-recursive loop works as follows:
h8io.stages.Status.Success+h8io.stages.Yield.Some: the output becomes the new input and the loop continues with theonSuccesscontinuation.h8io.stages.Status.Success+h8io.stages.Yield.None: no output was produced; the loop stops and emitsYield.None(Success, Loop(onComplete)).h8io.stages.Status.Completewith no errors: the loop stops, converts the status back toSuccess, and selects theCompletecontinuation for the next outer invocation.h8io.stages.Status.Completewith errors: the loop stops, preserves the errors, and selects theCompletecontinuation for the next outer invocation.
This makes Loop suitable for in-process iterative computations (e.g., fixed-point iterations) where the result of
one step seeds the next.
- T
the value type (both input and output)
- E
the error type (covariant)
- alterand
the inner endomorphic stage
T → Tto loop
- Source
- Loop.scala
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- val alterand: Endo[T, E]
The wrapped stage whose behavior is modified by this operator.
- def andThen[A](g: (Yield[T, T, E]) => A): (T) => A
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- @unspecialized()
- def apply(in: T): Yield[T, T, E]
Applies this stage to the given input, producing a Yield.
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- def compose[A](g: (A) => T): (A) => Yield[T, T, E]
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- final def execute(in: T): Outcome[T, E]
Executes this stage end-to-end and returns a plain Outcome.
Executes this stage end-to-end and returns a plain Outcome.
Internally this method:
- Applies the stage to
in, obtaining a Yield. - Disposes the Evolution carried by the Yield — since
executeis a terminal operation, the continuation is not needed and the resources held by this stage must be released immediately. - Wraps the result in an Outcome.Some or Outcome.None.
Disposal failures do not prevent the result from being returned. Any non-fatal exception raised by Evolution.dispose is captured in Outcome.disposeFailure and the outcome is still produced. Fatal exceptions are not caught and will propagate.
- in
the input value
- returns
Outcome.Some if this stage produced an output, Outcome.None otherwise
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- Applies the stage to
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- def skip(): Evolution[T, T, E]
Returns the Evolution for this stage without processing any input.
Returns the Evolution for this stage without processing any input.
Any stage that participates in a pipeline run but does not process the current input must call
skip()instead ofapply. Common triggers: an upstream stage produced no output (Yield.None), or a non-inclusive binary operation excluded this branch. The stage must return its Evolution as it would have appeared had it run, but must not perform any side effects or consume input.See the Lifecycle section in Stage for the full contract.
- returns
the Evolution representing how the pipeline should continue from this stage
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- final def ~>[_O, _E >: E](that: Stage[T, _O, _E]): Stage[T, _O, _E]
Composes this stage with
that, producing a new stage that feeds the output of this stage intothat.Composes this stage with
that, producing a new stage that feeds the output of this stage intothat.The resulting Stage.AndThen feeds the output of this stage into
that. If this stage produces an output, the statuses and evolutions of both stages are merged; if it produces no output, only the evolutions are composed andthatis not invoked for the current input.- _O
the output type of the composed pipeline
- _E
the combined error type (must be a supertype of
E)- that
the stage to execute after this one
- returns
a composed stage
this ~> that
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- Deprecated
(Since version 9)