The document is an introduction to Scala for Java experts, highlighting its statically typed nature, type inference, and support for both functional and object-oriented programming. It includes examples and concepts related to data structures, queries, and DSLs, showcasing Scala's capabilities in comparison to Java and emphasizing key features like implicit types and pattern matching. Additionally, it references practical applications, including interaction with APIs and data sources.

1. Scala
Introductie voor Java (7) kenners

2. Edwin de Jong
edwin.de.jong@topicus.nl

3. Martin Oderski

6. • Statically typed

7. • Statically typed
• Type inference

8. • Statically typed
• Type inference
• Functional / OOP

9. • Statically typed
• Type inference
• Functional / OOP
• Compiled naar JVM bytecode

10. • Statically typed
• Type inference
• Functional / OOP
• Compiled naar JVM bytecode
• én .NET

11. • Statically typed
• Type inference
• Functional / OOP
• Compiled naar JVM bytecode
• én .NET
• én Javascript (scalajs)

12. Static vs. Dynamic

13. Type chaos

14. Type chaos
<K, V> List<K> keysAsList(HashMap<K, V> aMap) {
List<K> result = new LinkedList<K>();
for (K key : aMap.keySet()) {
result.add(key);
}
return result;
}

15. Implicit types

16. Implicit types
def keysAsList[K, V](m: Map[K, V]) =
m.keySet.toList

17. Alles is een object

18. Overpass Query Model

19. Overpass Query Model
Node

20. Overpass Query Model
Node
Way

21. Overpass Query Model
Node
Way
Relation

22. node["addr:city"="Deventer"]["addr:housenumber"="25"]
["addr:street"="Singel"];out

23. node["addr:city"="Deventer"]["addr:housenumber"="25"]
["addr:street"="Singel"];out
Node(
"addr:city" === "Deventer" and
"addr:housenumber" === "25" and
"addr:street" === "Singel") | OutStatement

24. node(2678759904);way(around: 1000);(rel(bw)
["route"="bicycle"]["type"="route"];way(r);node(w););out

25. node(2678759904);way(around: 1000);(rel(bw)
["route"="bicycle"]["type"="route"];way(r);node(w););out
Node(Id(2678759904)) |
Way(Around(1.kilo[metre])) |
Union(
Relation(isPartOf(Ways) and
"route" === "bicycle" and
"type" === "route") |
Way(containedIn(Relations)) |
Node(containedIn(Ways))
) | OutStatement)

26. sealed trait Statement

27. sealed trait Statement
!
case object OutStatement extends Statement

28. sealed trait Statement
!
case object OutStatement extends Statement
!
sealed trait PipeableStatement extends Statement {
def |(other: Statement) = PipedStatement(this, other)
def into(variable: String) = IntoStatement(this, variable)
}

29. sealed trait Statement
!
case object OutStatement extends Statement
!
sealed trait PipeableStatement extends Statement {
def |(other: Statement) = PipedStatement(this, other)
def into(variable: String) = IntoStatement(this, variable)
}
!
case class PipedStatement(left: Statement, right: Statement)
extends PipeableStatement
!
case class IntoStatement(s: Statement, variable: String)
extends PipeableStatement

30. Pimp my types

31. Pimp my types
implicit class PimpedStringClause(str: String) {
def ===(other: String) = Eq(str, other)
def !==(other: String) = Neq(str, other)
def ==~(other: String) = Regex(str, other)
def !=~(other: String) = Regex(str, other)
}

32. Pimp my types
implicit class PimpedStringClause(str: String) {
def ===(other: String) = Eq(str, other)
def !==(other: String) = Neq(str, other)
def ==~(other: String) = Regex(str, other)
def !=~(other: String) = Regex(str, other)
}
val str = “addr:street”
new PimpedStringClause(str).===(“Singel 25”)

33. Pimp my types
implicit class PimpedStringClause(str: String) {
def ===(other: String) = Eq(str, other)
def !==(other: String) = Neq(str, other)
def ==~(other: String) = Regex(str, other)
def !=~(other: String) = Regex(str, other)
}
val str = “addr:street”
new PimpedStringClause(str).===(“Singel 25”)
Eq(
“addr:street”,
“Singel 25”)

34. Pimp my types
implicit class PimpedStringClause(str: String) {
def ===(other: String) = Eq(str, other)
def !==(other: String) = Neq(str, other)
def ==~(other: String) = Regex(str, other)
def !=~(other: String) = Regex(str, other)
}
val str = “addr:street”
new PimpedStringClause(str).===(“Singel 25”)
str.===(“Singel 25”)
Eq(
“addr:street”,
“Singel 25”)

35. Pimp my types
implicit class PimpedStringClause(str: String) {
def ===(other: String) = Eq(str, other)
def !==(other: String) = Neq(str, other)
def ==~(other: String) = Regex(str, other)
def !=~(other: String) = Regex(str, other)
}
val str = “addr:street”
new PimpedStringClause(str).===(“Singel 25”)
str.===(“Singel 25”)
str === “Singel 25”
Eq(
“addr:street”,
“Singel 25”)

36. Pattern matching
def ClauseShows[S <: Clause]: Show[S] = shows {
case Id(id) ⇒ s"($id)"
case Eq(tag, value) ⇒ s"""["$tag"="$value"]"""
case HasKey(tag) ⇒ """["$tag"]"""
case Regex(tag, value) ⇒ s"""["$tag"~"$value"]"""
…
}

37. Map, flatmap en filter

38. Type-safe DSLs

39. Type-safe DSLs
val avg: Option[Float] =
from(grades)(g =>
where(g.subjectId === mathId)
compute(avg(g.scoreInPercentage))
)

40. Running Demo:
OpenStreetMaps en
Buienradar

41. Buienradar API
http://gps.buienradar.nl/getrr.php?
lat=52.2560148&lon=6.160242
000|17:35 040|17:40 000|17:45 000|17:50 000|
17:55 000|18:00 000|18:05 063|18:10 000|18:15
000|18:20 000|18:25 000|18:30 000|18:35 000|
18:40 000|18:45 000|18:50 000|18:55 000|19:00
000|19:05 000|19:10 000|19:15 000|19:20 000|
19:25 000|19:30 000|19:35
GET

44. • Actors

45. • Actors
• Scalaz

46. • Actors
• Scalaz
• Higher-order types

47. • Actors
• Scalaz
• Higher-order types
• Parser Combinators

48. • Actors
• Scalaz
• Higher-order types
• Parser Combinators
• ScalaTest / ScalaCheck

49. Ik wil meer!