SAMStage

SAMStage (Single Abstract Method Stage) adds a sealed skip on top of Stagnation: skip returns this, making the stage its own evolution whether or not it was applied. apply is the only abstract method, but dispose remains open and can be overridden when the stage holds resources that must be released.

import h8io.stages.*
import h8io.stages.base.*

object ParseInt extends SAMStage[String, Int, String] {
  override def apply(in: String): Yield[String, Int, String] =
    in.toIntOption match {
      case Some(n) => Yield.Some(n, Status.Success, this)
      case None    => Yield.None(Status.error(s"not a number: $in"), this)
    }
}

ParseInt("42")
// res0: Yield[String, Int, String] = Some(
//   out = 42,
//   status = Success,
//   evolution = <function1>
// )
ParseInt("hello")
// res1: Yield[String, Int, String] = None(
//   status = Complete("not a number: hello"),
//   evolution = <function1>
// )