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Kotlin & Arrow the functional way
This document discusses Kotlin and the Arrow library. It provides an overview of Kotlin, describing it as an object-oriented, functional programming language that runs on the JVM and can be used for mobile, backend, and frontend development. It then covers functional programming concepts in Kotlin like higher-order functions, purity, immutability, and pattern matching. Finally, it introduces Arrow, an open source library that brings functional programming abstractions to Kotlin like data types for modeling absence, errors, and parallel errors to avoid nulls and exceptions.
In this document
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Introduction to Kotlin and the speaker, Noe Luaces, sharing personal background.
Kotlin is a versatile language that supports object-oriented, functional programming, and is suitable for various applications, including mobile development.
Kotlin was developed by JetBrains in 2011, inspired to combine Scala’s features with Java's compiling speed.
Function types enable first-class functions in Kotlin, making them versatile and parametric.
Higher order functions accept other functions or lambda expressions as parameters, enhancing flexibility.
Pure functions are deterministic and side-effect-free, making them easier to test and predict.
Immutable objects improve thread safety, code cleanliness, and are preferred in Kotlin with 'val' keyword.
The 'when' construct allows advanced pattern matching in Kotlin, enhancing control flow without boilerplate.
Currying is breaking down functions into a series of single argument functions, streamlining function handling.
Kotlin features extensive null safety mechanisms to prevent null pointer exceptions and enhance stability.
Challenges involve avoiding exceptions for predictable failures, aiming for cleaner error handling.
Arrow is an open source library that enhances functional programming in Kotlin, akin to tools for Scala and Java.
The Option type in Arrow helps avoid null pointer exceptions by encapsulating possible values.
The Fold method is used to deal with Option values, handling cases for both presence and absence.
The Try type captures exceptions, allowing structured error handling and combining with other constructs.
Either represents a value that can either be an error or a successful outcome, facilitating error handling.
Example implementations demonstrating how to work with Either data structure and managing success or failure.
Validated collects multiple errors, providing a comprehensive error management strategy.
Summarizes key concepts of Kotlin and Arrow including functional programming principles and data types.
Highlights benefits of using Kotlin and Arrow in development such as syntax conciseness and functional patterns.
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Kotlin & Arrow the functional way
- 1. Kotlin & Arrow: Thefunctional way Noe Luaces @noe_luaces
- 2. ● Galician sinceI have memory (now living in Barcelona) ● Avid comic book reader since I was a teenager ● Software Engineer since October 2007 ● Kotlin Developer since October 2018 > whoami
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- 4. Designed to interoperate fullywith other JVM-based languages Object Oriented Kotlin is...
- 5. Designed to interoperate fullywith other JVM-based languages Object Oriented Great introductory language to functional programming Functional Kotlin is...
- 6. Designed to interoperate fullywith other JVM-based languages Object Oriented Great introductory language to functional programming Can be used in backend, frontend or as a script language Functional General Purpose Kotlin is...
- 7. Designed to interoperate fullywith other JVM-based languages Object Oriented Great introductory language to functional programming Can be used in backend, frontend or as a script language Functional General Purpose Kotlin is... Android has officially adopted Kotlin as the supported language for mobile development services Mobile Standard
- 8. ● Developed byJetBrains in 2011 ● Its name comes from Kotlin island, Russia Kotlin background
- 9. ● JetBrains leadDmitry Jemerov said that they were looking for a language with the same features as Scala but with a compilation velocity similar to Java Kotlin background
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- 11. Function Type ● Functionsin Kotlin are first-class values ● They can be assigned to variables and passed around as parameters
- 12. Function Type (functionreference)
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- 17. Higher Order Functions ●Functions that accept parameters typed as a function ● Functions that accept lambda expressions as parameters
- 18. Higher Order Functions ●Scope functions like run, apply, let, with, also accept a lambda expression ● Other functions such as map, flatMap, filter, fold
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- 21. Pure Functions ● Dependonly on the input to produce the result, not on any hidden information or external state ● Have no observable side effects, like modifying a variable passed by reference. ● Hence, they are easy to test
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- 25. Immutable objects ● Remainin exactly the state in which they were created. Therefore, they are thread-safe ● Are easier to write, use and they make cleaner code ● Make easier to parallelize the program as there are no conflicts among objects
- 26. Immutable objects ● Arepreferred whenever possible in Kotlin ● Are defined with the keyword val and can be initialized only single time ● Data classes, that hold the state which they were created with
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- 29. The "when {}"block ● Advanced form of the switch-case statement known from Java ● No break statements are needed at the end of each case
- 30. The "when {}"block ● Due smartcast, we can access methods or properties of the type without extra checks ● Smartcast also works with subclasses providing a full pattern matching ● Could be used as an expression or a statement
- 31. The "when {}"block
- 32. The "when {}"block
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- 34. Currying ● Is amathematical technique ● Consists on breaking down a function that takes multiple arguments into a series of functions that each take only one argument
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- 37. Null safety ● Explicitnullable declarations ● Safe calls ● !! operator
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- 39. What is missing? InFunctional Programming, we try to avoid throwing exceptions: ● For methods which fail often and predictably, like parsing user input as a number, it’s costly and unnecessary to throw exceptions ● Handling checked exceptions can easily make the client’s code needlessly complicated
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- 41. Arrow background ● Opensource library sponsored by 47 Degrees ● Fusion between KATEGORY and funKTionale, the most relevant FP libraries for Kotling in 2017 ● First release was available in 2018 ● Equivalent to Cats for Scala and Vavr for Java
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- 43. Data Type: Option ●Avoids NullPointerException, without error detail ● Possible values: None or Some
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- 45. Dealing with Optionvalues: Fold {() -> "Nothing!"} {(Book) -> "Book.name found!"}
- 46. Dealing with Optionvalues: Fold
- 47. Dealing with Optionvalues: Fold
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- 49. Data type: Try ●Useful to handle Runtime Exceptions ● Failure or Success ● Can be combined with a when statement that uses smart cast
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- 52. Data type: Either ●Represents a value with two possibilities ● Left (error case) or Right (happy case) ● Allows to fail fast providing all the context
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- 55. Dealing with Eithervalues
- 56. {cat -> IsDeadFailure(cat)} {cat -> cat.name} Dealing with Either values: Bimap
- 57. Dealing with Eithervalues: Bimap
- 58. Dealing with Eithervalues: Bimap
- 59. Dealing with Eithervalues
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- 61. Data type: Validated ●Collect all errors at once ● Possible values: Valid or Invalid ● Often used the typealias ValidatedNel ( instead of Validated<Nel>)
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- 65. To sum up... KOTLINARROW HIGHER ORDER FUNCTIONS IMMUTABILITY PATTERN MATCHING CURRYING EITHER OPTION TRY VALIDATIONS
- 66. Why Kotlin? ● Concisesyntax ● Null safety ● Ease of transition from Java ● Interoperability with other JVM-based languages ● Introductory language to functional programming ● Android's adoption as the supported language
- 67. Why Arrow? ● Datatypes ● Type classes ● Effects ● Optics ● Other functional programming patterns as higher- level abstractions ready to use
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