DroidJam India '18 Arrow and functional programming for Kotlin developers

In this talk, I’ll be describing Functional Programming in Kotlin, and Arrow library for Android Developers, taking some extracts from my book Functional Kotlin. Functional Programming is the most trendy thing nowadays as well as the most evolved paradigm.

Transcript

1. Functional Programming in Kotlin -
   Android
   DroidJam India 2018
   Rivu Chakraborty
   

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2. Rivu Chakraborty
   • A learner
   • Sr. Software Engineer (Android) @ Indus Net Technologies Pvt. Ltd.
   • Community Lead: GDG Kolkata, Kotlin Kolkata
   • Instructor @ Caster.io
   • Author – Reactive Programming in Kotlin
   • Author – Functional Kotlin
   • Author – Coroutines for Android Developers (WIP)
   • Author – Hands on Data Structures & Algorithms in Kotlin (WIP)
   @rivuchakraborty
   

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3. 50% off on EBook
   15% off on Print Book
   RPKFK50
   RPKFK15
   https://www.packtpub.com/application-
   development/reactive-programming-kotlin
   https://www.packtpub.com/application-
   development/functional-kotlin
   

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4. What is Functional Programming?
   • Representation of Mathematical Function
   State
   Traditional / Imperative / Von
   Neuman Style
   Input Output
   

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5. Why Functional Programming
   • Modulation of code
   • FP encourages safe ways of programming through Immutability &
   Pure Functions
   • Testing becomes easier
   • Programs are easier to read.
   

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6. What are Functional Languages?
   • Any language that gives support to Functions as first class citizens
   are called Functional Language.
   

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7. Pure Functions
   • Same return value for same input, can be cached
   • Doesn’t modify anything outside function scope (No side effects)
   fun square(n:Int):Int {
   return n*n
   }
   

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8. Immutability
   • Immutability != Read Only
   • Kotlin doesn’t force Immutability, it encourages Immutability
   • The val keyword doesn’t guarantees immutability
   

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9. Lambda
   • To be generic, lambda or lambda expressions generally means anonymous functions,
   that is, functions without names, which can be assigned to variables, passed as
   arguments, or returned from another function
   fun invokeSomeStuff(doSomeStuff:()->Unit) {
   doSomeStuff()
   }
   fun main(args: Array) {
   invokeSomeStuff {
   println("doSomeStuff called");
   }
   }
   

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10. Arrow
    • Functional companion to Kotlin’s Standard Library
    

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11. Type Constructors
    • Type Constructors are mainly theoretical concept. It’s not a Kotlin
    class constructor building a type.
    • We can reference Generic Parameterised Types as Type
    Constructors
    List
    Map
    Option
    Either
    

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12. Type Constructors
    • Option
    • Either
    • Try
    

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13. Type Classes
    • Type classes encode behaviour
    • You can use typeclasses as a DSL to access new free functionality
    for an existing type, or treat them as an abstraction placeholder
    for any one type that can implement the typeclass. The extension
    functions are scoped within the typeclass so they do not pollute
    the global namespace!
    • Example: Monads, Functors, Applicatives
    

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14. Monads, Functors, Applicatives
    

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15. This Photo by Unknown Author is licensed under CC BY-NC-ND
    @rivuchakraborty
    Rivu Chakraborty
    

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