The FP ecosystem in Kotlin

Arrow is a Kotlin library that has brought support for HKTs and type classes into the language. On top of that we have ported a good chunk of the FP stack including comprehensions, lenses, recursion schemes, and a blazing fast effects system. This enables experimenting with Haskell papers that you can seamlessly run on your phone.

The other aspect of Arrow is that it’s already widespread in the industry and is being used by startups and banks. It works on top of the vanilla Kotlin toolset, so it is safe to bring into your JVM programs. Bring your favorite FP constructs onto your day-to-day job!

Transcript

1. @pacoworks Paco Estevez “Stop ****ing up our language” The FP ecosystem in Kotlin
2. @pacoworks Arrow: arrow-kt.io 2
3. @pacoworks Version 0.10 - Released this month! 2.5 years running 3
4. @pacoworks Stop 4 First interaction with Kotlin leadership
5. @pacoworks 5 Meme: “I’m Spanish but I haven’t come to talk about FP”
6. @pacoworks Funktionale + Kategory = Arrow 6
7. @pacoworks Tens of known Apps, as many backends Talks around the world Multiple books 3k Github stars 7
8. @pacoworks Consultancies 8 Legitimate now
9. @pacoworks What is in it? 9
10. @pacoworks Boring libraries 10 Prelude Effect system Optics Metaprogramming utils soon
11. @pacoworks Incubator libraries 11 Recursion Schemes MTL Free AQL Streams Collections
12. @pacoworks Most important contribution? 12
13. @pacoworks 13
14. @pacoworks 14
15. @pacoworks 15
16. @pacoworks 16
17. @pacoworks Arrow Docs 17
20. @pacoworks Arrow Fx 20
21. @pacoworks Principles 21 Based off existing research Uses coroutines Flattened IO combinators
22. @pacoworks Primitives 22 fx for syntax effect to wrap ! to compute
24. @pacoworks Future of Fx 24 Bifunctor IO Reader + Bifunctor IO Streams
25. @pacoworks Arrow Core 25
26. @pacoworks Prelude I 26 Anaemic stdlib Datatypes
27. @pacoworks Kind<F, A> 27
28. @pacoworks F 28
29. @pacoworks class ForList private constructor() 29
30. @pacoworks class ForSequence private constructor() class ForOption private constructor() class ForTry private constructor() class ForId private constructor() class ForSet private constructor() 30
31. @pacoworks Kind<ForOption, A> isomorphism Option<A> 31 <--- <---
32. @pacoworks class Option<A>: Kind<ForOption, A> 32
33. @pacoworks fun Kind<ForOption, A>.fix(): Option<A> = 33
34. @pacoworks Extension functions are checked at compile time 34
35. @pacoworks fun Kind<ForOption, A>.fix(): Option<A> = this as Option<A> 35 Safe! Pinkie promise Totally ok
36. @pacoworks Prelude II 36 Anaemic stdlib Datatypes Typeclasses
37. @pacoworks fun <F, A, B> Kind<F, A>.map( f: (A) -> B, ): Kind<F, B> 37
38. @pacoworks 38
40. @pacoworks Arrow Meta 40
41. @pacoworks Tinkering… 41 Quasiquoting Hacking the typechecker Purity checker Coherent typeclass implementation
42. @pacoworks …in the real world 42 Early days Lots of potential experiments Focus on industrial uses
43. @pacoworks Growing an ecosystem 43
44. @pacoworks Letting talent flourish 44 Optics - Simon Vergauwen Recursion Schemes - Aedan Smith Free - Pablo Guardiola
45. @pacoworks Sister projects 45 Ank Helios Kessel Hoplite KotlinTest
46. @pacoworks Papers in Practice 46 The Frank language: Do be do be do Selective Applicative Functors Build Systems a la Carte Defunctionalized Kind Projections
47. @pacoworks Come join us! 47
48. @pacoworks Community ❤ gitter.im/arrow-kt/ 48 138 github contributors Gitter.im chat Kotlinlang slack #arrow
49. @pacoworks Arrow: arrow-kt.io pacoworks.com @pacoworks github.com/pakoito Slides: tinyurl.com/ArrowAle19 49 Special thanks to all Arrow contributors & supporters!