Funk%onale*Programmierung* op%mal*nutzen* Michael*Sperber*

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1 Funk%onale*Programmierung* op%mal*nutzen* Michael*Sperber* *

2 Individualso<ware* branchenunabhängig* funk%onale*programmierung* Schulungen,*Coaching* funk%onalecprogrammierung.de*

3 Objektorien%erte*Programmierung* Objekt* Nachricht* Objekt* Impera've) Programmierung) Instruk%onen* Methode*

4 UFOs*in*Java* public class UFO { int x, y; List<Shot> shots; *

5 UFOs*in*Java* public class Shot { final String description; public Shot(String description) { this.description = description; public String getdescription() { return public boolean equals(object o) { if (this == o) return true; if (o == null getclass() = o.getclass()) return false; Shot shot = (Shot) o; return public int hashcode() { return public String tostring() { return "Shot{" + "description='" + description + '\'' + '}';

6 GeJer*und*SeJer* public class UFO { int x, y; List<Shot> shots; public UFO(int x, int y, List<Shot> shots) { this.x = x; this.y = y; this.shots = shots; public int getx() { return x; public void setx(int x) { this.x = x; public int gety() { return y; public void sety(int y) { this.y = y; public List<Shot> getshots() { return shots; *

7 UFO*bewegen* public class UFO {... public void move(int deltax, int deltay) { this.x = this.x + deltax; this.y = this.y + deltay;

8 Schuss*abfeuern* public class UFO {... public Shot fireshot() { int size = this.shots.size(); Shot lastshot = this.shots.get(size - 1); this.shots.remove(size - 1); return lastshot;

9 Abrüsten* public class UFO {... public void disarm(string description) { Iterator<Shot> it = shots.iterator(); while (it.hasnext()) { Shot shot = it.next(); if (shot.getdescription().equals(description)) it.remove(); *

10 Iteratoren*

11 Scala*ist*das*neue*Java** class Shot { final var description: String = null def this(description: String) { this() this.description = description def getdescription: String = { return description... *

12 Scala*ist*das*neue*Java*...* class UFO { var x: Int = 0 var y: Int = 0 final var shots: List[Shot] = null def this(x: Int, y: Int, shots: List[Shot]) { this() this.x = x this.y = y this.shots = shots def getx: Int = { return x def setx(x: Int) { this.x = x def gety: Int = { return y def sety(y: Int) { this.y = y... *

13 Das*neue*Java*...* class UFO {... def move(deltax: Int, deltay: Int) { this.x = this.x + deltax this.y = this.y + deltay def fireshot: Shot = { val size = this.shots.size(); val lastshot = this.shots.get(size - 1); this.shots.remove(this.shots.size - 1) return lastshot *

14 Eine*Welt*von*Objekten* ( *Trustees*of*the*Bri%sh*Museum)*

15 Impera%ve*Programmierung* room1.exit(elephant) hallway.enter(elephant) hallway.exit(elephant) room2.enter(elephant)

16 Impera%ve*So<ware*

17 Gesharter*mu%erbarer*Zustand*

18 Realität*und*Schnappschuss*

19 Scala* case class Shot(description: String) *

20 UFOs*in*Scala* case class UFO(x: Int, y: Int, shots: List[Shot]) { def move(deltax: Int, deltay: Int): UFO = UFO(x+deltaX, y+deltay, shots)... *

21 Schuss*abfeuern* case class UFO(x: Int, y: Int, shots: List[Shot]) {... def fireshot(): (UFO, Shot) = (this.copy(shots = shots.dropright(1)), shots.last)... *

22 Abrüsten* case class UFO(x: Int, y: Int, shots: List[Shot]) {... def disarm(description: String) : UFO = this.copy(shots = shots.filter({ shot => shot.description == description })) *

23 Die*rein*funk%onale*Fab* Scheduler*+*Fab* Scheduler*+*Fab* Schnappschuss* Schnappschuss* Schnappschuss* %me*

24 Spekula%ve*Simula%on*mit*FP*...*kann*parallel*laufen*

25 FabCZustand*

26 Func%onal*Data*Structures* map*&*reconstruc%on* can*run*in*parallel*

27 Filter*gibt s*auch*in*java*8*...* public class UFO { public void disarm(string description) { this.shots = shots.stream().filter(shot -> shot.getdescription().equals(description)).collect(collectors.tolist()); *

28 Tests* class UFOSpec extends Specification { "Shooting works" >> { "such that it loses a shot" >> { val u1 = UFO(10, 10, List(Shot("laser"), Shot("torpedo"))) val (u2, _) = u1.fireshot() u1.shots.length 1 must_== u2.shots.length *

29 ScalaCheck* class UFOSpec extends Specification with ScalaCheck { "Shooting works" >> { "such that it always loses a shot" >> { prop { (u1: UFO) => u1.shots.length > 0 ==> { val (u2, _) = u1.fireshot() u1.shots.length 1 must_== u2.shots.length *

30 (Interna%onal*Conference*on*Func%onal*Programming,*2000)*

31 Algebra* "Disarming works" >> { "and is commutative" >> { prop{ (kind1: String, kind2: String, ufo: UFO) => ufo.disarm(kind1).disarm(kind2) must_== ufo.disarm(kind2).disarm(kind1) *

32 Algebra* a + b = b + a a +(b + c) =(a + b)+c a (b + c) =(a b)+(a c)

33 Algebra* a \ b = b \ a a \ (b \ c) =(a \ b) \ c a \ (b [ c) =(a \ b) [ (a \ c)

34 Algebra* a? b = b? a a? (b? c) =(a? b)? c a (b? c) =(a b)? (a c)

35 Associa%vität* a + b + c a/b/c?)

36 Algebra*vs.*impera%ve*Programmierung* f(x) =f(x) f(x) == f(x)?)

37 Algebra*vs.*Programme* f(x) (b + c) (f(x) b)+(f(x) c)?)

38 Der*Scheduler*und*die*Fab*

39 Hoffnung*in*der*Fab* Trackin*

40 Reine*Hoffnung* Lächle?*

41 Hoffnung*mit*Anweisungen* Lernen*

42 Hoffnung*mit*Wiedervorlage* Gesündere* Ernährung*

43 Wiederholte*Hoffnung* Gesündere* Ernährung*

44 Zerstörte*Hoffnung*

45 Hoffnung*ist*eine*Monade* (cafepress.com)*

46 Monadische*Berechnungen* m*

47 Monaden* trait Monad[M[_]] { def unit[a](a: => A): M[A] def flatmap[a, B] (fa: M[A]) (f: A => M[B]) : M[B]

48 UFOCgestützte*Berechnungen* case class UFOComputation[A] (run: UFO => (UFO, A)) *

49 UFOCMonade* object UFOMonad extends Monad[UFOComputation] { * override def unit[a](a: => A) : UFOComputation[A] = UFOComputation({ ufo => (ufo, a) })

50 UFOCMonade* object UFOMonad extends Monad[UFOComputation] { override def flatmap[a, B] (fa: UFOComputation[A]) (f: A => UFOComputation[B]) : UFOComputation[B] = UFOComputation({ ufo => { val (ufo1, a) = fa.run(ufo) f(a).run(ufo1) }})

51 Monadische*Opera%onen* def fireshot() : UFOComputation[Shot] = UFOComputation({ ufo => ufo.fireshot() }) def disarm(description: String) : UFOComputation[Unit] = UFOComputation({ ufo => (ufo.disarm(description), ()) }) *

52 Banale*Opera%onen* def getufo() : UFOComputation[UFO] = UFOComputation({ ufo => (ufo, ufo) }) def setufo(ufo: UFO) : UFOComputation[Unit] = UFOComputation({ ufo => (ufo, ()) }) *

53 Monadische*Syntax* def fireshot() : UFOComputation[Shot] = for { ufo <- getufo() (ufo1, shot) = ufo.fireshot() _ <- setufo(ufo1) } yield shot

54 ScalaCheckCGeneratoren*für*UFOs* val shotgenerator = for { desc <- Gen.alphaStr } yield Shot(desc) implicit lazy val arbshot: Arbitrary[Shot] = Arbitrary(shotGenerator) val ufogenerator = for { x <- Gen.choose(-100, 100) y <- Gen.choose(-100, 100) shots <- Gen.containerOf[List, Shot](shotGenerator) } yield UFO(x, y, shots) implicit lazy val arbufo: Arbitrary[UFO] = Arbitrary(ufoGenerator)

55 ZUSAMMEN) FASSUNG)

56

57 Daten*sind*Schnappschüsse*

58 Eigenscha<en*staJ*Beispiele*

59 Algebra*bringt s*

60 Abstrak%on,*Abstrak%on,*Abstrak%on* (Paul*Hudak,*1952C2015)** (Augste*Herbin,* Abstrac%on )*

61 Mehr*Infos* ac%vecgroup.de*