LukaJCB

Uniting the bifunctor and monofunctor hierarchies

With the rise of so-called bifunctor IO types, such as ZIO, questions have naturally arisen of how one could leverage the cats-effect type classes to make use of this new power. So far suggestions have mostly focused on duplicating the existing hierarchy into two distinct branches, one parameterized over F[_] and another parameterized over F[_, _]. To me this is not a great situation, as now library maintainers would have to write code for both of these hierarchies or choose one and leave the other one in the dust.

Instead we should find a way to unite the two shapes under a single hierarchy. This is a draft on how to enable this unification using polymorphic function types in Dotty.

ShaneDelmore

  /*_*/
  val 1 = "Hello"
  /*_*/

jastice

Installation instructions

1. Install bloop 1.0.0-M11 by following the Bloop installation instructions. Then, make sure you start up the bloop server on the background and to generate the configuration files by running bloopInstall in your build tool.
2. Install IntelliJ 2018.2 EAP and then enable the nightly version of the Scala Plugin by opening Preferences | Languages & Frameworks | Scala | Updates tab and selecting the Nightly plugin update channel:
3. check for updates and download the Scala plugin Nightly release.
4. Reboot IntelliJ. The Scala plugin should now have version 2018.2.277 or higher (check in Preferences | Plugins)
5. Open the "Find Action" search box (usual hotkey Shift+Ctrl+A or shift+cmd+A) and search for "bsp". The search box will show the full action name: "Enable experime

johnynek

object Monad {
  trait Monad[F[_]] {
    def pure[A](a: A): F[A]

    /**
     * We can have a default implementation in terms of tailRecM
     * and map
     */
    def flatMap[A, B](fa: F[A])(fn: A => F[B]): F[B] = {
      def step(first: Option[A]): F[Either[Option[A], B]] =

d1egoaz

If you want to learn Scala, I’d suggest:

• Install IntelliJ + Scala Plugin
• Don’t do the Coursera courses yet.
• Don’t do the “red book” Functional Programming in Scala yet.
• Do: http://underscore.io/books/
  • Essential Scala
  • Essential Play
  • Essential Slick
• Do Scala for the Impatient: https://www.amazon.com/Scala-Impatient-Cay-S-Horstmann/dp/0321774094
• The Neophyte’s Guide to Scala http://danielwestheide.com/scala/neophytes.html

sir-wabbit

sealed trait Decidable[+Proof]
final case class Yes[Proof](proof: Proof) extends Decidable[Proof]
final case object No extends Decidable[Nothing]

sealed trait List[+A] {
  def nonEmpty: Decidable[this.type <:< ::[A]]
  def ::[AA >: A](value: AA): ::[AA] = new ::[AA](value, this)
}
final case object Nil extends List[Nothing] {
  def nonEmpty: Decidable[this.type <:< ::[Nothing]] = No

lamdor

scalaVersion := "2.11.8"
scalaOrganization := "org.typelevel"

libraryDependencies ++= Seq(
  "org.typelevel" %% "cats" % "0.9.0",
  "org.atnos" %% "eff" % "4.0.0"
)

addCompilerPlugin("org.spire-math" %% "kind-projector" % "0.9.3")

OlivierBlanvillain

Revisiting Tagless Final Interpreters

Tageless Final interpreters are an alternative to the traditional Algebraic Data Type (and generalized ADT) based implementation of the interpreter pattern. This document presents the Tageless Final approach with Scala, and shows how Dotty with it's recently added implicits functions makes the approach even more appealing. All examples are direct translations of their Haskell version presented in the Typed Tagless Final Interpreters: Lecture Notes (section 2).

The interpreter pattern has recently received a lot of attention in the Scala community. A lot of efforts have been invested in trying to address the biggest shortcomings of ADT/GADT based solutions: extensibility. One can first look at cats' Inject typeclass for an implementation of [Data Type à la Carte](http://www.cs.ru.nl/~W.Swierstra/Publications/DataTypesA

Fristi

package data

import cats.Cartesian
import cats.data.{NonEmptyList, State, StateT, Validated}
import cats.functor.Invariant
import cats.implicits._
import eu.timepit.refined._
import eu.timepit.refined.api.{Refined, Validate}
import eu.timepit.refined.boolean._
import eu.timepit.refined.collection._

paulp

// These lines go in ~/.sbt/0.13/global.sbt
watchSources ++= (
     (baseDirectory.value * "*.sbt").get
  ++ (baseDirectory.value / "project" * "*.scala").get
  ++ (baseDirectory.value / "project" * "*.sbt").get
)

addCommandAlias("rtu", "; reload ; test:update")
addCommandAlias("rtc", "; reload ; test:compile")
addCommandAlias("ru", "; reload ; update")