n this introduction to Scala, I will demonstrate why I love Scala and why I think that you will too. You’ll learn why you don’t need to go from 0 to functions and how you can ease yourself into this language. I’ll show you some Scala, compare it to Java, and give you pointers on how to start your journey into this functional object-oriented language.

1. DR.
SCALA
LOVE
Dianne Marsh
Director of Engineering -- Cloud Tools, Netflix
ScalaBay Meetup, Sept 2013
OR
HOW
I
LEARNED
TO
STOP
WORRYING
AND
LOVE
FUNCTIONS

2. Dr. Strangelove, 1964
“If this thing turns out
to be half as important
as I think it will be, I
think you’ll all be in
line for some personal
citations and
promotions when this
thing is over.”

3. What is Scala?
Object-oriented + Functional
Runs on JVM
Build on Java expertise

4. Why Is it Scary?
Early adopters scared folks away
Lost elasticity of learning new programming
languages
Comfort zone

5. What’s the Gain?
Modern language features
Let compiler work for you!

6. REPL
Interactive Interpreter
Read Evaluate Print Loop

7. Type Inference
val x = 5
val y = "Once upon a time"
val l = List("This", "is", "a",
"List")

8. Methods
def squareIt(x: Int) = x*x

9. Anatomy of a Case Class
case class Camera(width: Int,
height: Int) {
def megapixels = (width * height)
/1000000.0
def HD = megapixels > 1.08
}
val camera = new Camera(1024, 768)
camera.megapixels is 0.786432
camera.HD is false
camera is "Camera(1024,768)"

10. Reducing Boilerplate
class Dimension(var height:Int,
var width:Int)
val c = new Dimension(5,7)
c.height is 5
c.height = 10
c.height is 10
c.width = 19
c.width is 19

11. Pattern Matching
def batteryIndicator(batteryLevel:
Int) =
batteryLevel match {
case l if (l > 60) => "GREEN"
case l if (l > 20) => "YELLOW"
case _ => "RED"
}

12. Traits
trait Digital {
def batteryIndicator(batteryLevel:
Int) = …
}
val d = new Camera(1024, 768) with
Digital
d.batteryIndicator(56) is "YELLOW"

13. Functions are Objects
val v = Vector(19, 1, 7, 3, 2, 14)
v.sorted is Vector(1, 2, 3, 7, 14, 19)
v.sortWith((i, j) => j < i) is
Vector(19, 14, 7, 3, 2, 1)

14. It’s OK
To use Scala as a Better Java

15. Reaching into Java
import org.apache.commons.math._
import stat.regression.SimpleRegression
val r = new SimpleRegression
r.addData(1, 1)
r.addData(2, 1.1)
r.addData(3, 0.9)
r.addData(4, 1.2)
r.getN is 4
r.predict(6) is 1.19

16. It’s OK
To be verbose

17. Verbose Version
// Euler1.scala
val nums = 3 until 1000
val somenums = nums.filter
(x => (x % 3 == 0 || x % 5 ==0))
var sum = 0
somenums.foreach(sum += _)

18. Find the Sweet Spot
// Euler2.scala
val nums = 3 until 1000
val somenums = nums filter
(x => (x % 3 == 0 || x % 5 ==0))
val sum = somenums reduceLeft
{(x:Int,y:Int) => x + y}

19. More than 1 way ...
// Euler3.scala
val nums = 3 until 1000
val somenums = nums filter
(x => (x % 3 == 0 || x % 5 ==0))
val sum = somenums.foldLeft(0)(_+_)

20. Back off if it’s too much
// Euler4.scala
val nums = 3 until 1000
val somenums = nums filter
(x => (x % 3 == 0 || x % 5 ==0))
(0/:somenums)(_+_)

21. Code should be readable
To your team
To your customers
To yourself, in 6 months

22. Killer Apps in Scala
Compute intensive
Concurrency
Reactive applications
● Resilient
● Scalable
● Interactive, single-page
● Event Driven

23. Learning
Scala Koans -- scalakoans.org
Case Studies at Typesafe
Blogs
Books

24. Practicing
Solve Euler problems
Use ScalaTest
Use for non-production code

25. Contact Info
@dmarsh
dmarsh@netflix.com
We are always hiring ...