Epic success \/ failure, refactoring to *real* FP
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My presentation at LambdaJam 2014
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Epic success \/ failure, refactoring to *real* FP
- 1. Epic Success V Failure ? Refactoring to real FP Eric Torreborre
- 2. Why, oh why?
- 3. What now?
- 4. How hard can it be? HelloWorldSpec.scala
- 5. How hard can it be? TextText ExampleExample TextText TextText ExampleExample StepStep ExampleExample Filtering Filtering by name by name by previous by previous Execution Execution concurrent concurrent conditional conditional Reporting Reporting console console htmlhtml
- 6. How hard can it be? Configuration(s)Configuration(s)ResourcesResources FileSystemFileSystem “Flow”“Flow” StateState CompositionComposition ErrorsErrors
- 7. Problem?
- 8. Strategy
- 9. Strategy
- 11. Filtering by previous TextText ExampleExample ExampleExample TextText StatsStats resultresult resultresultresultresult resultresultresultresult
- 13. Monad stacks values AA ErrorError FutureFuture now(a: A) delay(a: =>A) AA ErrorError FutureFuture AA ErrorError FutureFuture fail(t: Throwable) and flatM ap! and flatM ap!
- 14. Action in action Action[A]Action[A] AA ErrorError AA ErrorError AA IOIO AA ErrorError IOIO ReaderReader Conf => IO[A] => IO[Error] Error = String | Throwable | (String, Throwable)
- 15. Action in action
- 17. Filtering by previous TextText ExampleExample ExampleExample TextText StatsStats resultresult resultresultresultresult resultresultresultresult
- 18. Filtering by previous TextText ExampleExample ExampleExample TextText StatsStats resultresult Action[Fragment] => Task[Fragment] Fragment => Action[Result] Action[Result] => Action[Fragment] mapmap Task[Fragment] => Process[Task, Fragment] evaleval
- 21. On stacks No big deal No big deal Specialise Specialise LibraryLibrary Composition? Composition? Integration? Integration?
- 22. Scalaz-stream
- 24. Concurrency with With state! With state! TextText ExampleExample ExampleExample StepStep ExampleExample stop herestop here
- 25. Flatmap with Online testing! Online testing!
- 26. Flatmap with Online testing! Online testing! Text1Text1 Example1Example1 Example2Example2 Example3Example3 Text1Text1 Example1Example1 Example2Example2 Example3Example3 Example2.1Example2.1 Example2.2Example2.2
- 27. Reporting with “duplicate” stream “duplicate” stream Write to console Write to console Accumulate state Accumulate state
- 28. Reporting with Text1Text1 Example1Example1 Example2Example2 Example3Example3 “t1”“t1” “e1”“e1” “e2”“e2” “e3”“e3” > Console statsstats statsstats statsstats
- 30. Reporting with and Folds!
- 31. Reporting with and Folds!
- 32. Reporting with and Folds! Opaque dependent typeOpaque dependent type
- 33. Reporting with and Folds! Fold Monoid! Fold Monoid!
- 34. Reporting with and Folds!
- 35. Conclusion
Editor's Notes
- 3 years of specs1, 4 years of specs2 Html output: I suck at html / javascript Open Source = find people! Clinton -> new design, new CSS But implementation: ugh… Simplification / Composition / extension What about being “pure”
- Lots of possibilities More knowledge What happened: Success or Failure? This is eventually looking good and possibly looking fantastic
- Simple structure: But complex execution model -> even not enough separation between declaration and run And several functionalities on top - by tag -> read command line - by previous -> read files Execution: - must respect steps! - must be fully concurrent Reporting: - console must flow! - statistics must be stored Memory? Thread pool?
- Interested by the Cake Pattern and the ability to “hide” the implementation + Daniel Spiewak presentation on parametrizing it with a Monad But how far can you go with small functions?
- Use an elaborate data structure right away
- Process[Task, T] is a stream of Ts produced by a Task Process1 is like a map or filter operation A Task is an Error/Future monad stack
- Use a for comprehension Can be a bit tedious to retrofit the code like that But this is mostly a mechanical transformation And this provides a benefit
- Liberally use the configuration to influence the behaviour of your programming That’s dependency injection!
- Better than I feared In Scala you need to build a special stack for what you are doing, Reader Writer State won’t work easily Build your own collection of operators to create values, fromIO, failure,… Question : can you keep Configuration modular? Question: how to operate with another stack like Action <-> Task
- Use an elaborate data structure right away
- Not composable because the fragments are going to be executed twice
- Use a Fold to accumulate state
- Stacks not too hard to use Streamz a very powerful model, but very recent library and might need to come up with Folds for additional composition Being Functional = Honest brings opportunities - inject anything anywhere - careful execution model + flatmap == better execution control