Scala Reloaded

Updated version of my scala talk

Transcript

1. Scala Mac Liaw mac@cylatech.com twitter:wmacgyver Materials drawn from:Michael Galpin’s SFJUG Presentation
3. Scala?   Statically Typed Language on Java VM   Object Oriented Language   Functional Language   Scalable Language   Concurrency
4. Smart Type System var name:String = “Powerful the Dark Side is”;
5. Smart Type System var name = “Powerful the Dark Side is”;
6. Smart Type System var name = “Powerful the Dark Side is”; def makeList(a:String, b:String):List[String] = { return a :: b :: Nil; }
7. Smart Type System var name = “Powerful the Dark Side is”; def makeList(a:String, b:String):List[String] = { return a :: b :: Nil }
8. Smart Type System var name = “Powerful the Dark Side is”; def makeList(a:String, b:String):List[String] = { a :: b :: Nil }
9. Smart Type System var name = “Powerful the Dark Side is”; def makeList(a:String, b:String):List[String] = a :: b :: Nil
10. Smart Type System var name = “Powerful the Dark Side is”; def makeList(a:String, b:String) = a :: b :: Nil
11. Object Orieted   No primitives   No int, just Int   No String[], just Array[String]   No operators   + - * / ++ += are just names for methods
12. Scala Objects class SimpleGreeter { val greeting = "Hello, world!" def greet() = println(greeting) } val g = new SimpleGreeter g.greet()
13. Traits & Mixins trait Friendly { def greet()="Hi" } class Cat extends Friendly {} class HungryCat extends Friendly { override def greet() = "Meow" } trait HyperGreeter extends Friendly {override def greet() = super.greet() + "!!!!!!!" }
14. Traits & Mixins trait Friendly { def greet()="Hi" } class Cat extends Friendly {} class HungryCat extends Friendly { override def greet() = "Meow" } trait HyperGreeter extends Friendly {override def greet() = super.greet() + "!!!!!!!" } var pet = new Cat println(pet.greet()) //print Hi
15. Traits & Mixins trait Friendly { def greet()="Hi" } class Cat extends Friendly {} class HungryCat extends Friendly { override def greet() = "Meow" } trait HyperGreeter extends Friendly {override def greet() = super.greet() + "!!!!!!!" } var pet = new HungryCat println(pet.greet()) //print Meow
16. Traits & Mixins trait Friendly { def greet()="Hi" } class Cat extends Friendly {} class HungryCat extends Friendly { override def greet() = "Meow" } trait HyperGreeter extends Friendly {override def greet() = super.greet() + "!!!!!!!" } var pet = new HungryCat with HyperGreeter println(pet.greet()) // print Meow!!!!!!!
17. Domain Specific Language   Built-in support for two DSLS   XML   Actors
18. XML DSL import scala.xml._ object XMLSample { def main(args: Array[String]) { val df = java.text.DateFormat.getDateInstance() val dateString = df.format(new java.util.Date()) def theDate(name: String) = <dateMsg addressedTo={ name }> Hello, { name }! Today is { dateString } </dateMsg>; println(theDate("Mac").toString()) } }
19. XML DSL <dateMsg addressedTo="Mac"> Hello, Mac! Today is May 13, 2015 </dateMsg>
20. Actors   Actor Model: A Different Way to Implement Concurrency
21. Actors   Actor Model: A Different Way to Implement Concurrency   Each Object is an Actor
22. Actors   Actor Model: A Different Way to Implement Concurrency   Each Object is an Actor   Each Actor has a Mailbox
23. Actors   Actor Model: A Different Way to Implement Concurrency   Each Object is an Actor   Each Actor has a Mailbox   Actors (Asynchronously) Send Messages and Receive them in their Mailbox
24. Actors   Actor Model: A Different Way to Implement Concurrency   Each Object is an Actor   Each Actor has a Mailbox   Actors (Asynchronously) Send Messages and Receive them in their Mailbox   Shares NOTHING!
25. Why Erlang Is Right?   No code changes for Multi-threaded vs Single-threaded   No Mutable State   No Locking, thus no DEAD Locks.   Let it Crash
26. Actor Example import akka.actor._ class YodaActor extends Actor { def receive = { case _ => println("Yoda rules!") } } class VaderActor extends Actor { def receive = { case "luke" => println("No, I'm your father!") case _ => println("Darkside rules!") } }
27. Actor Example object Main { def main(args: Array[String]) { val system = ActorSystem("StarWarsSystem") val yodaActor = system.actorOf(Props[YodaActor], name = "yodaactor") val vaderActor = system.actorOf(Props[VaderActor], name = "vaderactor") yodaActor ! "yes?" vaderActor ! "jedi" vaderActor ! "luke" } }