Scala example source code file (Zip.scala)

This example Scala source code file (Zip.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

apply, equal, functor, zip, ziplaw

The Zip.scala Scala example source code

package scalaz

////
/**
 *
 */
////
trait Zip[F[_]]  { self =>
  ////
  def zip[A, B](a: => F[A], b: => F[B]): F[(A, B)]

  // derived functions

  /**The composition of Zip `F` and `G`, `[x]F[G[x]]`, is a Zip (if F is a Functor) */
  def compose[G[_]](implicit T0: Functor[F], G0: Zip[G]): Zip[λ[α => F[G[α]]]] =
    new CompositionZip[F, G] {
      implicit def T = T0
      implicit def F = self
      implicit def G = G0
    }

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

  def zipWith[A, B, C](fa: => F[A], fb: => F[B])(f: (A, B) => C)(implicit F: Functor[F]): F[C] =
    F.map(zip(fa, fb)) {
      case (a, b) => f(a, b)
    }

  def apzip[A, B](f: => F[A] => F[B], a: => F[A]): F[(A, B)] =
    zip(a, f(a))

  def apzipPL[A, B](f: => F[A] @?> F[B], a: => F[A])(implicit M: Monoid[F[B]]): F[(A, B)] =
    apzip(f.getOrZ(_), a)

  def ap(implicit F: Functor[F]): Apply[F] =
    new Apply[F] {
      def ap[A, B](fa: => F[A])(f: => F[A => B]) =
        zipWith(fa, f)((a, g) => g(a))
      def map[A, B](fa: F[A])(f: A => B) =
        F.map(fa)(f)
      override def apply2[A, B, C](fa: => F[A], fb: => F[B])(f: (A, B) => C) =
        zipWith(fa, fb)(f)
      override def tuple2[A, B](fa: => F[A], fb: => F[B]) =
        self.zip(fa, fb)
    }

  trait ZipLaw {
    /** Zipping preserves structure. */
    def zipPreservation[A](fa: F[A])(implicit FA: Equal[F[A]], F: Functor[F]): Boolean = {
      val fab = zip(fa, fa)
      FA.equal(F.map(fab)(_._1), fa) && FA.equal(F.map(fab)(_._2), fa)
    }

    def zipSymmetric[A, B](fa: F[A], fb: F[B])(implicit FA: Equal[F[A]], F: Functor[F]) =
      FA.equal(F.map(zip(fa, fb))(_._1), F.map(zip(fb, fa))(_._2))
  }
  def zipLaw = new ZipLaw {}

  ////
  val zipSyntax = new scalaz.syntax.ZipSyntax[F] { def F = Zip.this }
}

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

  ////

  def fzip[F[_], A, B](t: LazyTuple2[F[A], F[B]])(implicit F: Zip[F]): F[(A, B)] =
      F.zip(t._1, t._2)
  ////
}