Scala example source code file (Cobind.scala)

This example Scala source code file (Cobind.scala) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Scala by Example" ^TM.

Learn more about this Scala project at its project page.

Java - Scala tags/keywords

boolean, cobind, cobindlaws, cokleisli, equal, functor

The Cobind.scala Scala example source code

package scalaz

////
/**
 *
 */
////
trait Cobind[F[_]] extends Functor[F] { self =>
  ////
  /** Also know as `extend` */
  def cobind[A, B](fa: F[A])(f: F[A] => B): F[B]

  final def extend[A, B](fa: F[A])(f: F[A] => B): F[B] = cobind(fa)(f)

  /** Also known as `duplicate` */
  def cojoin[A](fa: F[A]): F[F[A]] =
    cobind(fa)(fa => fa)

  // derived functions

  trait CobindLaws {
    def cobindAssociative[A, B, C, D](fa: F[A], f: F[A] => B, g: F[B] => C, h: F[C] => D)(implicit F: Equal[D]): Boolean = {
      implicit val C = self
      val d1 = ((Cokleisli(f) =>= Cokleisli(g)) =>= Cokleisli(h)) run fa
      val d2 = (Cokleisli(f) =>= (Cokleisli(g) =>= Cokleisli(h))) run fa
      F.equal(d1, d2)
    }
  }

  def cobindLaw = new CobindLaws {}

  ////
  val cobindSyntax = new scalaz.syntax.CobindSyntax[F] { def F = Cobind.this }
}

object Cobind {
  @inline def apply[F[_]](implicit F: Cobind[F]): Cobind[F] = F

  ////

  ////
}