1.
1
Containers and Aggregates,
Mutators and Isolates
for Reactive Programming
Aleksandar Prokopec, Philipp Haller, Martin Odersky

2.
Reactive Collections
http://reactive-collections.com
2

3.
Reactive
3

4.
4

5.
5
Observables (event streams)

6.
6
Observables (event streams)
• declarative
val log = messages .filter(_.length < 100) .scan(_ + “n” + _)

7.
7
Observables (event streams)
• declarative
val log = messages .filter(_.length < 100) .scan(_ + “n” + _)
var log = “” def receive = { case s: String => if (s.length < 100) log = log + “n” + s }

8.
8
Actors
• encapsulate mutable state

9.
9
Actors
• encapsulate mutable state
var log = “” def receive = { case s: String => if (s.length < 100) log = log + “n” + s }

10.
10
Reactive collections
Isolate Reactive Channel
Actor ? ActorRef
?
Observable
Observable

11.
11
Reactive values

12.
Reactive[T]
12

13.
val ticks: Reactive[Long]
13
ticks
1
1
2
2
3
3
4
4
60
60
61
61

14.
ticks onEvent { x => log.debug(s”tick no.$x”) }
14
1
2
3
4
60
61
tick no.1
tick no.2
tick no.3
tick no.4
tick no.60
tick no.61
...

15.
ticks foreach { x => log.debug(s”tick no.$x”) }
15
1
2
3
4
60
61

16.
16
for (x <- ticks) { log.debug(s”tick no.$x”) }
Single-threaded!

17.
17
Reactive combinators

18.
for (x <- ticks) yield {
x / 60
}
18

19.
val seconds: Reactive[Long] = for (x <- ticks) yield { x / 60 }
19

20.
60
61
val seconds: Reactive[Long] = for (x <- ticks) yield { x / 60 }
20
ticks
1
1
2
2
3
3
60
61
seconds
0
0
0
1
1
ticks
seconds
0
1

21.
val days: Reactive[Long] = seconds.map(_ / 86400)
21

22.
val days: Reactive[Long] =
seconds.map(_ / 86400)
val secondsToday =
22

23.
val days: Reactive[Long] = seconds.map(_ / 86400) val secondsToday = (seconds zip days) { (s, d) => s – d * 86400 }
23

24.
val angle =
secondsInDay.map(angleFunc)
24

25.
val angle = secondsInDay.map(angleFunc) val light = secondsInDay.map(lightFunc)
25

26.
26

27.
27
val rotate = keys
a ↓
shift ↓
a ↑
shift ↑
pgup ↓
pgup ↑
keys

28.
28
val rotate = keys.filter(_ == PAGEUP)
a ↓
shift ↓
a ↑
shift ↑
pgup ↓
pgup ↑
keys
pgup ↓
pgup ↑
filter

29.
29
val rotate =
keys.filter(_ == PAGEUP)
.map(_.down)
a ↓
shift ↓
a ↑
shift ↑
pgup ↓
pgup ↑
keys
pgup ↓
pgup ↑
filter
true
false
map

30.
30
if (rotate()) viewAngle += 1
true
false
map

31.
31
Signals

32.
32
trait Signal[T] extends Reactive[T] { def apply(): T }

33.
33
val rotate =
keys.filter(_ == PAGEUP)
.map(_.down)
.signal(false)
true
false
map
signal

34.
34
val rotate: Signal[Boolean] = keys.filter(_ == PAGEUP) .map(_.down) .signal(false)
true
false
map
signal

35.
35
val rotate: Signal[Boolean] val ticks: Reactive[Long]
ticks

36.
36
val rotate: Signal[Boolean]
val ticks: Reactive[Long]
ticks
rotate

37.
37
val rotate: Signal[Boolean]
val ticks: Reactive[Long]
val viewAngle: Signal[Double] =
ticks
rotate
viewAngle

38.
38
val rotate: Signal[Boolean] val ticks: Reactive[Long] val viewAngle: Signal[Double] = ticks.scanPast(0.0)
ticks
rotate
viewAngle

39.
39
val rotate: Signal[Boolean] val ticks: Reactive[Long] val viewAngle: Signal[Double] = ticks.scanPast(0.0) { (a, _) => if (rotate()) a + 1 else a }
ticks
rotate
viewAngle

40.
40

41.
41
val velocity =
ticks.scanPast(0.0) {
(v, _) =>
}
val viewAngle =

42.
42
val velocity = ticks.scanPast(0.0) { (v, _) => if (rotate()) v + 1 } val viewAngle =

43.
43
val velocity =
ticks.scanPast(0.0) {
(v, _) =>
if (rotate()) v + 1
else v – 0.5 }
val viewAngle =

44.
44
val velocity = ticks.scanPast(0.0) { (v, _) => if (rotate()) v + 1 else v – 0.5 } val viewAngle = velocity.scanPast(0.0)(_ + _)

45.
45

46.
46
Reactive mutators

47.
47
class Matrix {
def apply(x: Int, y: Int): Double
def update(x: Int, y: Int, v: Double)
}

48.
48
val screenMat: Signal[Matrix] = (projMat zip viewMat)(_ * _) val invScreenMat = screenMat.map(_.inverse)

49.
49
Reactive[immutable.Matrix[T]]

50.
50
val screenMat: Signal[Matrix] = (projMat zip viewMat)(_ * _) val invScreenMat = screenMat.map(_.inverse)
(4*4*8 + 16 + 16)*4*100 = 64 kb/s

51.
51
val screenMat = Mutable(new Matrix) (projMat, viewMat).mutate(screenMat) { (p, v) => screenMat().assignMul(p, v) } val invScreenMat = Mutable(new Matrix) screenMat.mutate(invScreenMat) { m => invScreenMat().assignInv(m) }

52.
52
Reactive collections

53.
53

54.
54
val selected: Reactive[Set[Character]]

55.
55
val selected: ReactSet[Character]

56.
56
trait ReactSet[T] extends ReactContainer[T] { def apply(x: T): Boolean }

57.
57
trait ReactContainer[T] {
def inserts: Reactive[T]
def removes: Reactive[T]
}

58.
58
A reactive collection is a pair of reactive values

59.
59
val selected =
new ReactHashSet[Character]

60.
60

61.
61
val selected = new ReactHashSet[Character] val decorations = selected .map(c => (c, decoFor(c)))

62.
62
class ReactContainer[T] { self => def inserts: Reactive[T] def removes: Reactive[T] def map[S](f: T => S) = new ReactContainer[S] { def inserts: Reactive[T] = self.inserts.map(f) def removes: Reactive[T] = self.removes.map(f) } }

63.
63
val selected =
new ReactHashSet[Character]
val decorations = selected
.map(c => (c, decoFor(c)))
.to[ReactHashMap]

64.
64
val selected = new ReactHashSet[Character] val decorations = selected .map(c => (c, decoFor(c))) .to[ReactHashMap]

65.
65
val selected = new ReactHashSet[Character] val decorations = selected .map(c => (c, decoFor(c))) .to[ReactHashMap]

66.
66
val selected = new ReactHashSet[Character] val decorations = selected .map(c => (c, decoFor(c))) .to[ReactHashMap]

67.
67
val selected =
new ReactHashSet[Character]
val decorations = selected
.map(c => (c, decoFor(c)))
.react.to[ReactHashMap]

68.
68
val selected = new ReactHashSet[Character] val decorations = selected .map(c => (c, decoFor(c))) .react.to[ReactHashMap]

69.
69
val selected =
new ReactHashSet[Character]
val decorations = selected
.map(c => (c, decoFor(c)))
.react.to[ReactHashMap]

70.
70
val selected = new ReactHashSet[Character] val decorations = selected .map(c => (c, decoFor(c))) .react.to[ReactHashMap]

71.
71
Isolates

72.
72
UI isolate
class UI extends Isolate[UI.Message] { val frames = source.filter(_ == UI.Frame) val exit = source onCase { case UI.Exit => exit() } }
Source

73.
73
UI Isolate
Source
AI Isolate
Source
Channel[AI.Message] 
 Channel[UI.Message]

74.
74
Reactive collections
Isolate Reactive Channel
Actor ? ActorRef
? Observable Observable

75.
75
Thank you!