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Uploaded byEric Torreborre
Shoehorning dependency injection into a FP language, what does it take?
This talks shows why dependency injection is important and how to support it in a functional programming language like Unison where the only abstraction available is its effect system.
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Shoehorning dependency injection into a FP language, what does it take?
- 1. Shoehorning dependency injection intoa FP language, what does it take? Eric Torreborre
- 2. Dependency injection andFP? DON’T COME NEAR MY FUNCTIONS, YOU PUNK!
- 3.
- 4. What have wedone here? Interface Implementation implements Dependency depends on
- 5. Component Based Development Onefunction alone does not always make sense by itself! Interface
- 6.
- 7. Decomposition? Configuration detail? Different filteringlogic? Debug summary? Simplified discount rules?
- 8.
- 9. Large applications A transactionengine The logger is here!
- 10. Large data models Datagenerators? Encoders/decoders?
- 11. Large data models Howabout generating data for users in a given city with a specific price?
- 12. What did wetry? Service locator Annotations + reflection
- 13. What did wetry? Typeclasses / implicits Effect libraries
- 14. What did wetry? Declare dependencies Wire dependencies
- 15. What makes DI“good”? Locality Typechecking Incrementality Effects Targeted overrides
- 16. Locality Adding a dependencyis immediate And limited to the strict necessary!
- 17. Incrementality Modifying the wiringmust be possible without touching it Can I define a “dev” profile reusing that code as-is?
- 18. Typechecking The compiler musttell us if a dependency is missing Not this!
- 19. Targeted overrides Any partof the graph can be overridden The same component type can have different implementations Or all of this Just this
- 20. Targeted overrides Any partof the graph can be overridden The same component type can have different implementations Should this concrete implementation be specified here?
- 21. Effects Instantiation can beeffectful Instances can be singletons or not Singleton is the default Java = unrestricted effects 🤪
- 22. Code at ourfingertips! Expressivity Conciseness Fast, accurate feedback
- 23.
- 24. What is Unison? Strongly,statically typed Haskell-like but - Strict evaluation - No type-classes - No macros Functional programming language Immutable code - Content-hashed - Stored in a database With an effect system!
- 25. Unison Cloud No ORMfor persistence Deploy services with code! - Abstract notion of Location - Run locally for testing - Easy rollback / versioning Services communicating with no JSON Distributed code - Services / daemons - Pipelines, KLogs (distributed streaming)
- 26.
- 27.
- 28.
- 29. Unison abilities IO Abort, Exception,Throw Store Remote Stream Random Each
- 30. A client application Http Logger Configuration Authenticator Level Application Accounts Top-levellogic Accounts API Auth. logic Keys GET, POST info, debug, error,…
- 31. A component interface Runtimeeffects (abstract) Concrete effect
- 32.
- 33.
- 34. Wiring dependencies constructor expression initialconfiguration make the top-level application! result
- 35.
- 36. Wiring dependencies build orretrieve from the store Stateful creation of components
- 37. Constructors Build effect Built component Forwhich type/build effect? How to build a value? What’s provided? What the “common stack”?
- 38. Untyped internals provided components phantomtype for a list of abilities build a value store the built value runtime effects untyped values
- 39. User-side vs library-side 4declarations per component 1 line per component Profit?
- 40. Locality? Yes, But No simplecall anymore
- 41. Incremental? Yes just add anew value/constructor
- 42. Typechecked? Yes, all components and effectsare listed And only typechecks if the component is available!
- 43. Effectful creation? additional effects arereturned Yes, But Cycles are not statically typechecked!
- 44.
- 45. Can we dobetter?
- 46. Why does thiswork? Abilities / expression language Dynamic types Phantom types
- 47. Why does thiswork? Type-level sets of types / effects Abstract list of effects Inferred list of effects
- 48. Do better inUnison? Type aliases
- 49. Do better inUnison? Override component effects ➕ = Collect function types: parameters + effects
- 50. Do better inUnison? Full dynamic types It’s functions all the way down
- 51. Do better ideally Meta-programmingDecompose / apply functions Custom compiler errors Stack can become large (Efficient) type-level sets https://xkcd.com/303 Good inference options = if prod then … else …
- 52. Please PL designers, giveus just enough meta-programming!
- 53.