Short (1hr) introduction to Scala Programming given to Topicus at 23rd of september, 2014. Accompanied by github projects: https://github.com/gedejong/overpascala https://github.com/gedejong/pollardRho

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!