Kotlin + Arrow = Alchemy

What happens if we mix together Kotlin and Arrow?
The answer is simple: Alchemy.

In this talk, I will deepen the alchemy between Kotlin and Arrow, by taking a procedural program and incrementally refactor to a purely functional one.

Transcript

1. Carlo Corti | @araknoid
2. Not propaganda about Functional Programming
3. Not a Monad tutorial
5. Software Engineer Co-Organiser Ticino Software Craftsmanship Deliberate Learner CARLO CORTI /carlocorti @araknoid
6. Functional Programming
7. Why another paradigm?
8. Comfort Zone As an Object Oriented programmer... Functional Programming
9. High Order Functions Currying Data Types Category Theory
10. Does the Category Theory help me deliver working software?
11. Where to go now?
12. SOLID to the extreme → Functions
13. Principles not abstractions Pure Functions No Side Effects Immutable Data Lazy Evaluation Statelessnes
14. Refactoring “to restructure software by applying a series of refactorings without changing its observable behavior” Martin Fowler, Refactoring: Improving the Design of Existing Code
15. It’s code time!
16. Partial function (String → Int) “1” “42” “K” 1 42 ? String Int
17. Partial function (String → Int) “1” “42” “K” 1 42 ? String Int W<Int>
18. “1” “42” “K” 1 42 ? Total function (String → W<Int>) String Int W<Int>
19. Try<A> Represents a computation that can result in a value or in an exception if something has gone wrong. Two possible implementations: • operation has been successful → Success<A> • computation has failed with a Throwable → Failure https://arrow-kt.io/docs/apidocs/arrow-core-data/arrow.core/-try/
20. It’s an higher order functions that process a data structure in some order and build a return value. inline fun <B> fold(ifFailure: (Throwable) -> B, ifSuccess: (A) -> B): B = when (this) { is Failure -> ifFailure(exception) is Success -> ifSuccess(value) } https://arrow-kt.io/docs/apidocs/arrow-core-data/arrow.core/-try/fold.html Fold
21. IO https://arrow-kt.io/docs/effects/io/ Used to achieve referential transparency for: • side-effects • lazy operations that can fail Data type of choice when interacting with: databases, network, operative systems, files
22. flatMap https://arrow-kt.io/docs/apidocs/arrow-core-data/arrow.core/-option/flat-map.html fun <B> flatMap(f: (A) -> OptionOf<B>): Option<B> = when (this) { is None -> this is Some -> f(t).fix() } Returns the result of applying f to this option’s value if this option is nonempty. Returns none if this option is empty
23. Long Story Short Pure/Total functions Immutability Go for principles not abstractions Learn abstractions out of need Category Theory as plus
24. Charles Duhigg, The power of Habit “Not sharing an opportunity to learn is a cardinal sin”
25. TH N YOU