Scala 3 - A Quick Tour - Scala Italy 2021

Transcript

1. Scala 3
   
   
   A Quick Tour
   
   
   @DanielaSfregola
   
   
   Scala Italy - October 2021
   

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2. Hellooooo
   • Software Engineer 

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

   "Get Programming with Scala"
   by Manning

   

   35% OFF on EVERYTHING

   with code "ctwscalait21"
   

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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
   

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

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

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

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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
   )
   
   }
   
   }
   

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8. Parametrized Traits
   trait Nameable
   {
   
   def name: Strin
   g
   
   }
   
   

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

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

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

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

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

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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)
    

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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)
    

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

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

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

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

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

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

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

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

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

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

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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
    

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

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28. Improved Error Messages
    Scala 2.13.4
    

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29. Improved Error Messages
    Scala 2.13.4
    Scala 3
    

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

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

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

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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://docs.scala-lang.org/scala3/guides/migration
    

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

    by Manning

    

    35% OFF on EVERYTHING 

    with code "ctwscalait21"
    

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