The FP ecosystem in Kotlin

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@pacoworks Paco Estevez “Stop ****ing up our language” The FP ecosystem in Kotlin

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@pacoworks Arrow: arrow-kt.io 2

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@pacoworks Version 0.10 - Released this month! 2.5 years running 3

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@pacoworks Stop 4 First interaction with Kotlin leadership

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@pacoworks 5 Meme: “I’m Spanish but I haven’t come to talk about FP”

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@pacoworks Funktionale + Kategory = Arrow 6

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@pacoworks Tens of known Apps, as many backends Talks around the world Multiple books 3k Github stars 7

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@pacoworks Consultancies 8 Legitimate now

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@pacoworks What is in it? 9

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@pacoworks Boring libraries 10 Prelude Effect system Optics Metaprogramming utils soon

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@pacoworks Incubator libraries 11 Recursion Schemes MTL Free AQL Streams Collections

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@pacoworks Most important contribution? 12

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@pacoworks Arrow Docs 17

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@pacoworks Arrow Fx 20

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@pacoworks Principles 21 Based off existing research Uses coroutines Flattened IO combinators

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@pacoworks Primitives 22 fx for syntax effect to wrap ! to compute

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@pacoworks Future of Fx 24 Bifunctor IO Reader + Bifunctor IO Streams

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@pacoworks Arrow Core 25

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@pacoworks Prelude I 26 Anaemic stdlib Datatypes

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@pacoworks Kind 27

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@pacoworks F 28

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@pacoworks class ForList private constructor() 29

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@pacoworks class ForSequence private constructor() class ForOption private constructor() class ForTry private constructor() class ForId private constructor() class ForSet private constructor() 30

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@pacoworks Kind isomorphism Option 31 <--- <---

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@pacoworks class Option: Kind 32

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@pacoworks fun Kind.fix(): Option = 33

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@pacoworks Extension functions are checked at compile time 34

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@pacoworks fun Kind.fix(): Option = this as Option 35 Safe! Pinkie promise Totally ok

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@pacoworks Prelude II 36 Anaemic stdlib Datatypes Typeclasses

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@pacoworks fun Kind.map( f: (A) -> B, ): Kind 37

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@pacoworks Arrow Meta 40

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@pacoworks Tinkering… 41 Quasiquoting Hacking the typechecker Purity checker Coherent typeclass implementation

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@pacoworks …in the real world 42 Early days Lots of potential experiments Focus on industrial uses

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@pacoworks Growing an ecosystem 43

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@pacoworks Letting talent flourish 44 Optics - Simon Vergauwen Recursion Schemes - Aedan Smith Free - Pablo Guardiola

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@pacoworks Sister projects 45 Ank Helios Kessel Hoplite KotlinTest

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@pacoworks Papers in Practice 46 The Frank language: Do be do be do Selective Applicative Functors Build Systems a la Carte Defunctionalized Kind Projections

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@pacoworks Come join us! 47

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@pacoworks Community ❤ gitter.im/arrow-kt/ 48 138 github contributors Gitter.im chat Kotlinlang slack #arrow

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@pacoworks Arrow: arrow-kt.io pacoworks.com @pacoworks github.com/pakoito Slides: tinyurl.com/ArrowAle19 49 Special thanks to all Arrow contributors & supporters!