Scala example source code file (ApplicativePlus.scala)

This example Scala source code file (ApplicativePlus.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

applicativeplus, compositionapplicativeplus, mutual, plusempty, productapplicativeplus

The ApplicativePlus.scala Scala example source code

package scalaz

////
/**
 * [[scalaz.Applicative]] combined with [[scalaz.PlusEmpty]].
 */
////
trait ApplicativePlus[F[_]] extends Applicative[F] with PlusEmpty[F] { self =>
  ////

  /**The composition of ApplicativePlus `F` and Applicative `G`, `[x]F[G[x]]`, is a ApplicativePlus */
  override def compose[G[_]](implicit G0: Applicative[G]): ApplicativePlus[λ[α => F[G[α]]]] =
    new CompositionApplicativePlus[F, G] {
      implicit def F = self
      implicit def G = G0
    }

  /**The product of ApplicativePlus `F` and `G`, `[x](F[x], G[x]])`, is a ApplicativePlus */
  def product[G[_]](implicit G0: ApplicativePlus[G]): ApplicativePlus[λ[α => (F[α], G[α])]] =
    new ProductApplicativePlus[F, G] {
      implicit def F = self
      implicit def G = G0
    }

  private[this] class Mutual[A](a: F[A]) {
    lazy val y: Free.Trampoline[F[List[A]]] = z map (plus(_, point(Nil)))
    lazy val z: Free.Trampoline[F[List[A]]] = y map (apply2(a, _)(_ :: _))
  }

  /** `empty` or a non-empty list of results acquired by repeating `a`. */
  def some[A](a: F[A]): F[List[A]] = new Mutual(a).z.run

  /** A list of results acquired by repeating `a`.  Never `empty`;
    * initial failure is an empty list instead.
    */
  def many[A](a: F[A]): F[List[A]] = new Mutual(a).y.run

  ////
  val applicativePlusSyntax = new scalaz.syntax.ApplicativePlusSyntax[F] { def F = ApplicativePlus.this }
}

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

  ////

  ////
}