kleisli

Scala Kleisli throws an error in IntelliJ

由 人盡茶涼 提交于 2021-02-13 12:27:55
问题 trying to implement Kleisli category for a made-up Partial type in Scala (reading Bartosz Milewski's "category theory for programmers", that's exersize for chapter 4) object Kleisli { type Partial[A, B] = A => Option[B] implicit class KleisliOps[A, B](f1: Partial[A, B]) { def >=>[C](f2: Partial[B, C]): Partial[A, C] = (x: A) => for { y <- f1(x) z <- f2(y) } yield z def identity(f: Partial[A, B]): Partial[A, B] = x => f(x) } val safeRecip: Partial[Double, Double] = { case 0d => None case x =>

Scala Kleisli throws an error in IntelliJ

由 為{幸葍}努か 提交于 2021-02-13 12:23:00
问题 trying to implement Kleisli category for a made-up Partial type in Scala (reading Bartosz Milewski's "category theory for programmers", that's exersize for chapter 4) object Kleisli { type Partial[A, B] = A => Option[B] implicit class KleisliOps[A, B](f1: Partial[A, B]) { def >=>[C](f2: Partial[B, C]): Partial[A, C] = (x: A) => for { y <- f1(x) z <- f2(y) } yield z def identity(f: Partial[A, B]): Partial[A, B] = x => f(x) } val safeRecip: Partial[Double, Double] = { case 0d => None case x =>

Scala Kleisli throws an error in IntelliJ

由 邮差的信 提交于 2021-02-13 12:22:54
问题 trying to implement Kleisli category for a made-up Partial type in Scala (reading Bartosz Milewski's "category theory for programmers", that's exersize for chapter 4) object Kleisli { type Partial[A, B] = A => Option[B] implicit class KleisliOps[A, B](f1: Partial[A, B]) { def >=>[C](f2: Partial[B, C]): Partial[A, C] = (x: A) => for { y <- f1(x) z <- f2(y) } yield z def identity(f: Partial[A, B]): Partial[A, B] = x => f(x) } val safeRecip: Partial[Double, Double] = { case 0d => None case x =>

Scala Kleisli throws an error in IntelliJ

由 我的未来我决定 提交于 2021-02-13 12:21:02
问题 trying to implement Kleisli category for a made-up Partial type in Scala (reading Bartosz Milewski's "category theory for programmers", that's exersize for chapter 4) object Kleisli { type Partial[A, B] = A => Option[B] implicit class KleisliOps[A, B](f1: Partial[A, B]) { def >=>[C](f2: Partial[B, C]): Partial[A, C] = (x: A) => for { y <- f1(x) z <- f2(y) } yield z def identity(f: Partial[A, B]): Partial[A, B] = x => f(x) } val safeRecip: Partial[Double, Double] = { case 0d => None case x =>

Composing functions that return an option

由 六眼飞鱼酱① 提交于 2019-12-24 04:26:11
问题 Suppose I have a few functions of type Int => Option[Int] : def foo(n: Int): Int => Option[Int] = {x => if (x == n) none else x.some} val f0 = foo(0) val f1 = foo(1) I can compose them with >=> as follows: val composed: Int => Option[Int] = Kleisli(f0) >=> Kleisli(f1) Suppose now I need to compose all functions from a list: val fs: List[Int => Option[Int]] = List(0, 1, 2).map(n => foo(n)) I can do it with map and reduce : val composed: Int => Option[Int] = fs.map(f => Kleisli(f)).reduce(_ >=>

Scalaz Kleisli usage benefits

由 别来无恙 提交于 2019-12-21 04:34:15
问题 In scalaz Kleisli[M[_], A, B] is a wrapper of A => M[B] , which allows composition of such functions. For instance, if M[_] is monad I can compose Kleisli[M, A, B] and Kleisli[M, B, C] with >=> to get Kleisli[M, A, C] . In a nutshell, Kleisli provides fancy andThens depending on M . Is it correct ? Are there other benefits of using Kleisli ? 回答1: Here are two benefits as examples—I'm sure you could come up with others. First, it can be useful to abstract over different arrows, such as Kleisli

How to fix this exercise with Endomorphic wrapper?

由 天大地大妈咪最大 提交于 2019-12-20 03:28:07
问题 This is a follow-up to my previous question. Suppose I need to find an XML node by path. I can write a function to get a child node by name import scala.xml.{Node => XmlNode} def child(name: String): XmlNode = Option[XmlNode] = _.child.find(_.label == name) I compose the child functions with kleisli; e.g. scala> val a = <a><a0><a1><a2/></a1></a0></a> a: scala.xml.Elem = <a><a0><a1><a2/></a1></a0></a> scala> val find01 = Kleisli(child("a0")) >=> Kleisli(child("a1")) findAB: scalaz.Kleisli

How to use >=> in Scala?

由 喜欢而已 提交于 2019-12-06 21:47:57
问题 I am trying to use >=> (Kleisli arrow) in Scala. As I understand, it composes functions returning monads. Now I am trying it as follows: scala> val f = {i:Int => Some(i + 1)} f: Int => Some[Int] = <function1> scala> val g = {i:Int => Some(i.toString)} g: Int => Some[String] = <function1> scala> val h = f >=> g <console>:15: error: value >=> is not a member of Int => Some[Int] val h = f >=> g ^ Why does not it compile ? How to compose f and g with >=> ? 回答1: There are two problems here. The

How to use >=> in Scala?

由 旧街凉风 提交于 2019-12-05 02:23:41
I am trying to use >=> (Kleisli arrow) in Scala. As I understand, it composes functions returning monads. Now I am trying it as follows: scala> val f = {i:Int => Some(i + 1)} f: Int => Some[Int] = <function1> scala> val g = {i:Int => Some(i.toString)} g: Int => Some[String] = <function1> scala> val h = f >=> g <console>:15: error: value >=> is not a member of Int => Some[Int] val h = f >=> g ^ Why does not it compile ? How to compose f and g with >=> ? There are two problems here. The first is that the inferred types of your functions are too specific. Option is a monad, but Some is not. In
订阅 kleisli