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Effectful Evaluation

Decisions4s allows evaluating a decision based on effectful inputs, e.g., when network call is required for a particular piece of data.

  • Inputs will be executed at most once (memoized).
  • Inputs will be executed only if required by the rule.
  • Input is considered not required if catchAll expression is used for matching.
  • Table needs to use HitPolicy.First because it's the only one for which lazy evaluation can be expected.

To use that feature, add an additional dependency.

"org.business4s" %% "decisions4s-cats-effect" % "0.1.0"
import cats.effect.IO
import decisions4s.*
import decisions4s.cats.effect.*

val decisionTable: DecisionTable[Input, Output, HitPolicy.First] = ???
val input: Input[IO]                                             = ???

decisionTable.evaluateFirstF(input).map(_.output)

Other Effect Systems​

As of now only cats-effect is supported, but the same can be achieved for any other effect system or even () => T. If you want to give it a try and need assistance, please reach out on Discord.