Scala 3 - A Quick Tour - Singapore Scala Programmers 2021

Scala 3 is just around the corner! But how can you give Scala 3 a try? What are some of its new exciting features? How do you migrate to Scala 3? Join us and you'll discover the answers to these questions ;)

Transcript

1. Scala 3
   A Quick Tour
   @DanielaSfregola
   Singapore Scala Programmers - May 2021
   

   View Slide

2. Hellooooo
   • Software Engineer 

   living in London UK
   
   • Scala Lover ❤
   
   • OS Maintainer
   
   • Author of 

   "Get Programming with Scala"
   by Manning

   

   35% OFF with code "scala3party"
   

   View Slide

3. Scala 3 is here!
   • After 8 years of work
   
   • 28,000 commits
   
   • 7,400 pull requests
   
   • 4,100 closed issues
   
   • ...released on May 13th, 2021!
   https://www.scala-lang.org/blog/2021/05/14/scala3-is-here.html
   

   View Slide

4. An overview
   • https://dotty.epfl.ch/docs/reference/overview.html
   

   View Slide

5. @main Annotation
   object HelloWorld extends App {
   println("Hello World!")
   }
   

   View Slide

6. @main Annotation
   object HelloWorld extends App {
   println("Hello World!")
   }
   object HelloWorld {
   @main def hello: Unit = {
   println("Hello world!")
   }
   }
   

   View Slide

7. @main Annotation
   object HelloWorld extends App {
   println("Hello World!")
   }
   object HelloWorld {
   @main def hello: Unit = {
   println("Hello world!")
   }
   }
   object Hello {
   @main def echo(n: Int, word: String): Unit = {
   println(word * n)
   }
   }
   

   View Slide

8. Parametrized Traits
   trait Nameable {
   def name: String
   }
   

   View Slide

9. Parametrized Traits
   trait Nameable {
   def name: String
   }
   trait Nameable(name: String)
   

   View Slide

10. Intersection Types
    class A
    class B
    def foo: A & B = ???
    

    View Slide

11. Union Types
    class A
    class B
    def foo: A | B = ???
    

    View Slide

12. Package Object
    // in file my/demo/package.scala
    package my
    package object demo {
    def customLog(msg: String) {
    println(s"Customised package log: $msg")
    }
    }
    

    View Slide

13. Package Object
    // in file my/demo/package.scala
    package my
    package object demo {
    def customLog(msg: String) {
    println(s"Customised package log: $msg")
    }
    }
    [ DROPPED ]
    

    View Slide

14. Enums
    sealed abstract class Color(val rgb: Int)

    case object Red extends Color(0xFF0000)
    case object Green extends Color(0x00FF00)
    case object Blue extends Color(0x0000FF)
    

    View Slide

15. Enums
    sealed abstract class Color(val rgb: Int)

    case object Red extends Color(0xFF0000)
    case object Green extends Color(0x00FF00)
    case object Blue extends Color(0x0000FF)
    enum Color(val rgb: Int):
    case Red extends Color(0xFF0000)
    case Green extends Color(0x00FF00)
    case Blue extends Color(0x0000FF)
    

    View Slide

16. Improved Type Inference
    Map("Scala" -> 3).map { (k, v) => s"$k$v" }
    

    View Slide

17. Improved Type Inference
    Map("Scala" -> 3).map { (k, v) => s"$k$v" }
    Scala 2.13.4
    

    View Slide

18. Improved Type Inference
    Map("Scala" -> 3).map { (k, v) => s"$k$v" }
    Scala 2.13.4
    

    View Slide

19. Improved Type Inference
    Map("Scala" -> 3).map { (k, v) => s"$k$v" }
    Scala 3.0.0
    

    View Slide

20. Improved Type Inference
    Map("Scala" -> 3).map { (k, v) => s"$k$v" }
    Scala 3.0.0
    Scala 2.13.4
    

    View Slide

21. Procedure Syntax
    def echo(str: String) {
    str
    }
    

    View Slide

22. Procedure Syntax
    def echo(str: String) {
    str
    }
    Scala 2.13.4
    

    View Slide

23. Procedure Syntax
    def echo(str: String) {
    str
    }
    Scala 2.13.4
    

    View Slide

24. Procedure Syntax
    def echo(str: String) {
    str
    }
    Scala 3
    

    View Slide

25. Procedure Syntax
    def echo(str: String) {
    str
    }
    Scala 3
    

    View Slide

26. Improved Error Messages
    Arrested Developers
    What the Scala Compiler & Lucille Bluth 

    Have In Common
    by Fiona Condon, NeScala 2017
    https://www.youtube.com/watch?v=78iIbiRwFTM
    

    View Slide

27. Improved Error Messages
    def echo(str: String): Unit = {
    str
    }
    def echoTwice(str: String): String = {
    echo(str) match {
    case x: String => s"$x$x"
    }
    }
    

    View Slide

28. Improved Error Messages
    Scala 2.13.4
    

    View Slide

29. Improved Error Messages
    Scala 2.13.4
    Scala 3
    

    View Slide

30. Strict Equality
    List("Scala", "3").headOption == "Scala"
    

    View Slide

31. Strict Equality
    List("Scala", "3").headOption == "Scala"
    Scala 2.13.4
    

    View Slide

32. Strict Equality
    List("Scala", "3").headOption == "Scala"
    Scala 2.13.4
    Scala 3
    

    View Slide

33. Compatibility with 2.13
    Migrating to Scala 3
    is easy* !
    * if you are using Scala 2.13
    * if you don't have macros in your code
    Scala 3 Migration Guide
    https://scalacenter.github.io/scala-3-migration-guide
    

    View Slide

34. Thank You!
    •Twitter: @DanielaSfregola
    
    •"Get Programming with Scala" 

    by Manning

    

    35% OFF with code "scala3party"
    

    View Slide