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Skutek has evolved to, and been superseded byTurbolift. Turbolift retains most of features and syntax of Skutek. But it internally, it's no longer based on Eff monad.

Skutek (pronounced:skoo-tech) is a framework implementing a monad of extensible effects(a.k.a.One monad to rule them all), based onFreer monad, adapted to leverage specifics of Scala's type system, with main differences being:

• Use of intersection types in lieu of union types (which Scala doesn't have), to model sets of effects.

• Use of classic OOP inheritence as the way of extending the monad with new operations.

importskutek.abstraction._importskutek.std_effects._objectMainextendsApp {// Declare some effects:caseobjectMyReaderextendsReader[Int]caseobjectMyStateextendsState[Int]caseobjectMyExceptextendsExcept[String]// Create a monadic computation using those effects:valcomputation=for {    a<-MyState.Get    b<-MyReader.Ask    c<- {if (b!=0)Return(a/ b)elseMyExcept.Raise(s"Tried to divide$a by zero")    }    _<-MyState.Put(c)  }yield ()// Create a handler for the above computation, by composing// individual handlers of each requested effect:valhandler=MyExcept.handler<<<!MyState.handler(100).exec<<<!MyReader.handler(3)// Execute the computation using the handler:valresult= handler.run(computation)  println(result)// prints "Right(33)"}

The inferred type ofcomputation above is equivalent to:

Unit!!MyState.typewithMyReader.typewithMyExcept.type

where!! is infix type alias forComputation monad:

Computation[Unit,MyState.typewithMyReader.typewithMyExcept.type]

More usage inexamples directory.

libraryDependencies+="com.github.marcinzh"%%"skutek-core"%"0.16.0"

Cross built Built for Scala 2.13.

Warning: contains links to partially outdated and somewhat embarrassing manual.

• Simplicity of use:

  • No need of defining the effect stack upfront.
  • No need of lifting of operations into the monad.
  • Effect subtyping.

• Simplicity of implementation:

  • No dependencies on external libraries.
  • No clever type-fu, no macros. Mostly immutable OOP style.

• Practical stuff:

  • Predefined set of basic effects (Reader,Writer, etc.).Read more.
  • Conflict proof: ability for multiple instances of the same type of effect, to coexist in the same effect stack (e.g.State[Int] andState[String]).
  • Potentially parallel execution of effects.Read more.
  • Support forfor comprehension guards, for effects compatible with filtering (e.g.Maybe,Choice).
  • Tested stack safety.

• Caveats and limitations:

  • General infancy of the project.
  • No Limited possiblity of adapting pre-existing monads as Skutek's effects.
  • Removing effects from the stack (local handling) isn't as easy as adding them.Read more.
  • Rare occurences of false positives by Scala's linter (i.e. "inferredAny").Read more.
  • Using patterns infor comprehensions can trigger surprising compiler errors. It can be mitigated byThis compiler plugin.
  • Lack of performance analysis.
  • Concurrency effect is ahack.

WIP. Partially outdated since many breaking chanches in 0.10.0

MANUAL.md