Scala PasT, Present &

Future @mircodotta

Who am I?• Felt in love with Scala in 2005

• Open Source contributor: Scala compiler & IDE, Lagom, Play, etc.

• Recently co-founded a Scala tooling company!

• Available for trainings (Akka/Play/Scala/Spark) and consulting.

Whoever wishes to foresee the future must

consult the past Macchiavelli

Scala: The Past

• Scala first release in 2003

• But, what’s the story before Scala?

Pizza

• 1995-19981

• Superset of Java with generics, first-class functions, case classes and patter matching.

• Why the name?

• Java was hacker’s drink

• Hacker’s food was needed ;-)1. www.slideshare.net/Odersky/scala-evolution/3-Pre_History1980s_Modula2_Oberon199095_Functional

Java 1.5

• Pizza led to Martin Odersky working on the Java compiler (javac).

• Martin co-designed the first version of generics in Java, and has written the recent javac.

Scala origins

• Goal: unify object-oriented and functional paradigms.

• Java was too constraining, hence the motivation to start fresh.

2003

Scala Martin’s mantra

• A language with a small core, few constructs but high abstraction power.

• Fact: Scala has less keywords than Java!

Scala evolution

First release

2003

Twitter adoption

Scala 2.0released

2006

Akkafirst release

2009

Lightbend(formerly Typesafe)

commercialsupport

Scala 2.9released

&Scala project

movedto GitHub

2011

Scala evolution

2012

Scala 2.10released

Scala Actordeprecated

and replacedby Akka

2013

Scala.JSreleased

2014

Scala 2.11released

2016

Scala 2.12(currently RC2)

Scala CentreFoundation

created!

Scala 2.9 to 2.11

• Releases are mainly about stability.

• Only new features:

• Value classes

• Implicit classes

• String interpolation

• macros (experimental)

Scala 2.12

• No additions to the language.

• So… ?

Scala 2.12• Scala 2.12 requires Java8.

• trait compiled to Java8 interface.

• Binary compat & reduced bytecode!

• scalac λ bytecode mimics javac’s.

• scala.FunctionN compiles to SAM type (Java8 λ).

• New backend & optimiser11. https://dl.dropboxusercontent.com/u/4881107/website/scala-user-group-2016.pdf

New trait encoding

trait PriceAlgorithm[Item] { def apply(item: Item): Double = ??? }

Let’s compare Scala 2.11 vs 2.12 bytecode

trait PriceAlgorithm[Item] { def apply(item: Item): Double = ??? }

Compiled with Scala 2.11

interface PriceAlgorithm<Item> { abstract double apply(Item); }

abstract class PriceAlgorithm$class { static double apply(PriceAlgorithm, java.lang.Object);

static void $init$(PriceAlgorithm); }

Two classfiles

trait PriceAlgorithm[Item] { def apply(item: Item): Double = ??? }

Compiled with Scala 2.12

interface PriceAlgorithm<Item> { public double apply(Item);

static double apply$(PriceAlgorithm, java.lang.Object);

static void $init$(PriceAlgorithm); }

Only one classfile!

Java8 API from Scala

Scala λ assignable to Java 8 λ

scala> import java.util.stream.{Stream, IntStream} scala> import java.util.{Arrays, List}

scala> val myList = Arrays.asList("a1", "a2", "b1", "c2", "c1") myList: java.util.List[String] = [a1, a2, b1, c2, c1]

scala> myList.stream. filter(_.startsWith("c")). map(_.toUpperCase). sorted. forEach(println) C1 C2

Why an optimiser?

• Some well-known patterns are not optimised by HotSpot (Oracle JIT).

• Transform the code to please HotSpot.

• Inlining vs binary resilience.

• Optimiser is not a magic wand, but rather a tool for experts.

• Compile with the -optimise flag.

Scala future

2016

Scala 2.12 Scala 2.13 (Aida)Improve the

library!Smaller core & stabilise

Q1 2018

(Don Giovanni)Faster compilerImprove binary

compatibility (TASTY)

2020?

Dotty?

• Dotty is the new Scala compiler Martin is working on with his group at EPFL.

• It’s research work, but a first release should be available soon.

• https://github.com/lampepfl/dotty

• Goal is to simplify the language.

The future of Scala

on a A4 paper

Credit goes to @malweene

https://twitter.com/malweene/status/743117270948274176

Questions?

@mircodotta