Scala example source code file (Associative.scala)

This example Scala source code file (Associative.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

associative, associativelaw, boolean, equal, isomorphism

The Associative.scala Scala example source code

package scalaz

////
/**
 *
 */
////
trait Associative[=>:[_, _]]  { self =>
  ////
  import Isomorphism.<=>

  def reassociateLeft[A, B, C](f: A =>: (B =>: C)): (A =>: B) =>: C

  def reassociateRight[A, B, C](f: (A =>: B) =>: C): A =>: (B =>: C)

  def reassociateIso[A, B, C]: ((A =>: B) =>: C) <=> (A =>: (B =>: C)) =
    new (((A =>: B) =>: C) <=> (A =>: (B =>: C))) {
      def from = reassociateLeft
      def to = reassociateRight
    }

  trait AssociativeLaw {
    /** Reassociating left and then right is a no-op. */
    def leftRight[A, B, C](fa: A =>: (B =>: C))(implicit FR: Equal[A =>: (B =>: C)]): Boolean =
      FR.equal(reassociateRight(reassociateLeft(fa)), fa)

    /** Reassociating right and then left is a no-op. */
    def rightLeft[A, B, C](fa: (A =>: B) =>: C)(implicit FL: Equal[(A =>: B) =>: C]): Boolean =
      FL.equal(reassociateLeft(reassociateRight(fa)), fa)
  }

  def associativeLaw = new AssociativeLaw {}
  ////
  val associativeSyntax = new scalaz.syntax.AssociativeSyntax[=>:] { def F = Associative.this }
}

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

  ////

  ////
}