Scalaz talk

Berlin, April 17

Transcript

1. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . . . . . . . . Scalaz Learn You Yet Another Real World Gentle Haskell (LYYARWGH) ((c) sproingie) George Leon ev deltamethod GmbH April 17, 2013 (λx.folonexlambda-calcul.us)@ folone.info George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 1 / 29
2. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . This talk https://github.com/folone/scalaz-talk-berlin https://speakerdeck.com/folone/scalaz-talk George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 2 / 29
3. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . Agenda Some hotness without context, to draw a en on (Op on, Boolean, Memo) Typeclasses Monoid Functor, Applica ve, Monad Effects scalaz 6 vs seven typelevel.scala George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 3 / 29
4. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . What is scalaz Purely func onal datatypes (Fingertree, HList, DList, Trees, Zippers, Nel, ImmutableArray) Typeclasses Effects Concurrency George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 4 / 29
5. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . Examples -- typesafe equals s> "" == 5 res0: Boolean = false s> "" === 5 <console>:14: error: type mismatch; found : Int(5) required: java.lang.String "" === 5 ^ <spoiler>∀ stuff ∈ scalaz ≡ scala.stdlib | stuff is typesafe ∨ stuff is strict</spoiler> George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 5 / 29
6. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . Examples -- op ons s> some(5) getOrElse 0 res1: Int = 5 s> some(5) | 0 res2: Int = 5 s> some(1) getOrElse "ok" res3: Any = 1 s> some(1) | "ok" <console>:14: error: type mismatch; found : java.lang.String("ok") required: Int some(1) | "ok" ^ s> ~some(5) // Monoids res4: Int = 5 s> ~none[Int] // NB: Beware of unary_~ on Validations (swap res5: Int = 0 George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 6 / 29
7. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . Examples -- op ons II // Smart constructors s> :t Some(1) s> :t None Some[Int] None.type s> :t some(1) s> :t none[Int] Option[Int] Option[Int] s> List(Some(1),None).foldLeft(None){(_, v) => v} <console>:14: error: type mismatch; found : v.type (with underlying type Option[Int]) required: None.type List(Some(1),None).foldLeft(None){(_, v) => v} ^ s> List(Some(1),None).foldLeft(none[Int]){(_, v) => v} res11: Option[Int] = None George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 7 / 29
8. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . Examples -- booleans scala> true ? println("true") | println("false") true scala> true ?? 5 scala> true !? 5 res14: Int = 5 res15: Int = 0 scala> false ?? 5 scala> false !? 5 res15: Int = 0 res17: Int = 5 George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 8 / 29
9. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . Examples -- func on composi on val a = (_:Int) + 6 val b = (_:Int).toString val c = (_:String).length scala> 5 |> a |> b |> c res18: Int = 2 scala> //(c · b · a) apply 5 // contramap res19: Int = 2 scala> 5 |> //(a ◦ b ◦ c) // map res20: Int = 2 // contramap === flip . map George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 9 / 29
10. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . Examples -- Memo def func(s: String) = // Expensive computation scala> Memo.immutableHashMapMemo(func) res11: String => java.lang.String = <function1> // Different strategies mutableHashMapMemo arrayMemo // sized immutableListMemo immutableTreeMapMemo doubleArrayMemo // memoizing Double results != sentinel weakHashMapMemo // GC George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 10 / 29
11. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . Examples -- Trampoline def even(n: Int): Boolean = if (n == 0) true else odd(n - 1) def odd(n: Int): Boolean = if (n == 0) false else even(n - 1) scala> even(30000) George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 11 / 29
12. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . Examples -- Trampoline def even(n: Int): Trampoline[Boolean] = if (n == 0) done(true) else suspend(odd(n - 1)) def odd(n: Int): Trampoline[Boolean] = if (n == 0) done(false) else suspend(even(n - 1)) scala> even(30000).run George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 12 / 29
13. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . Examples -- Trampoline def fibRec(n: Int): Int = if (n < 2) n else fibRec(n - 1) + fibRec(n - 2) def fibTailrec(n: Int) = { def loop(n: Int, next: Int, result: Int) = n match { case 0 => result case _ => loop(n - 1, next + result, next) } loop(n, 1, 0) } George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 13 / 29
14. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . Examples -- Trampoline def fibTramp(n: Int): Trampoline[Int] = if (n < 2) done(n) else suspend { for { i <- fibTramp(n - 1) j <- fibTramp(n - 2) } yield i + j } // Continuation monad magic Consult @runarorama's paper "Stackless Scala with Free Monads" George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 14 / 29
15. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . Typeclasses George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 15 / 29
16. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . Typeclasses George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 16 / 29
17. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . Typeclasses http://www.haskell.org/haskellwiki/Typeclassopedia http://typeclassopedia.bitbucket.org/ George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 17 / 29
18. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . Typeclasses A monoid generalizes the (++) opera on. A functor generalises the map opera on. An applica ve functor generalizes the zip (or zipWith) opera on. A monad generalizes the concat opera on. http://stackoverflow.com/a/15727162/163423 George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 18 / 29
19. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . Monoids (S, ⊗, 1) ∀a, b ∈ S : a ⊗ b ∈ S ∀a, b, c ∈ S : (a ⊗ b) ⊗ c = a ⊗ (b ⊗ c) ∀a ∈ S : 1 ⊗ a = a ⊗ 1 = a trait Semigroup[F] { def append(a1: F, a2: F): F } trait Monoid[F] extends Semigroup[F] { def zero: F } // scalacheck-binding import scalaz.scalacheck.ScalazProperties._ semigroup.laws[Int] monoid.laws[String] George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 19 / 29
20. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . Monoids scala> 1 |+| 5 res2: Int = 6 scala> Multiplication(2) |+| Multiplication(3) res4: Int @@ Multiplication = 6 scala> some(1) |+| some(5) res5: Option[Int] = Some(6) // Monoids beget monoids scala> some(some((1, "OH ", 1 + (_:Int)))) |+| some(some((4, "HAI", 2 * (_:Int)))) res6: Option[Option[(Int, java.lang.String, Int => Int)]] = Some(Some((5, OH HAI, <function1>))) George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 20 / 29
21. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . Monoids scala> List(1,2,3).suml res16: Int = 6 scala> List("OH ", "HAI", "!").suml res17: java.lang.String = OH HAI! George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 21 / 29
22. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . Functors trait Functor[F[_]] { def fmap[A, B](f: A => B): F[A] => F[B] } scala> some(3) map(_.toString) res13: Option[java.lang.String] = Some(3) George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 22 / 29
23. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . Applica ves trait Applicative[T[_]] extends Functor[T] { def pure[A](a: A): T[A] def <*>[A, B](tf: T[A => B])(ta: T[A]): T[B] } scala> some(1) <*> some((_:Int) + 2) <*> some((_:Int) * 5 res10: Option[Int] = Some(15) scala> List(1,2) <*> List((_:Int) * 5, (_: Int) + 2) res12: List[Int] = List(5, 10, 3, 4) George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 23 / 29
24. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . Applica ves scala> List(some(1), some(2), some(3)) res21: List[Option[Int]] = List(Some(1), Some(2), Some(3)) scala> .sequence res22: Option[List[Int]] = Some(List(1, 2, 3)) scala> res21.traverse(x => some(x)) // sequence . map res23: Option[List[Int]] = Some(List(1, 2, 3)) George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 24 / 29
25. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . Monads trait Monad[M[_]] extends Applicative[M]{ def >>=[A, B](ma: M[A])(f: A => M[B]): M[B] } scala> for { | i <- List(1,2,3) | j <- List(4,5,6) | } yield i*j res15: List[Int] = List(4, 5, 6, 8, 10, 12, 12, 15, 18) George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 25 / 29
26. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . IO DEMO George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 26 / 29
27. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . Scalaz 6 vs seven a-la-carte imports typeclass instances separated from instances tags law checking via scalacheck Isomorphisms Adjunc ons etc. Consult examples and tests. http://www.folone.info/blog/Scalaz-sevenMigration/ George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 27 / 29
28. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . typelevel.scala scalaz spire shapeless http://typelevel.org/ George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 28 / 29
29. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . Links learning scalaz day n: http://eed3si9n.com/category/tags/scala/scalaz Runar's talk on the Strange Loop conf last year: http://www.infoq.com/presentations/ Scalaz-Functional-Programming-in-Scala lambda-cats: http://spl.smugmug.com/gallery/13227630_j2MHcg/ George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 29 / 29
30. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . .. . That's it Ques ons? George Leon ev (deltamethod GmbH) Scalaz April 17, 2013 30 / 29