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Scala example source code file (Bifunctor.scala)

This example Scala source code file (Bifunctor.scala) is included in the "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

bifunctor, leftfunctor, productbifunctor, rightfunctor

The Bifunctor.scala Scala example source code

package scalaz

 * A type giving rise to two unrelated [[scalaz.Functor]]s.
trait Bifunctor[F[_, _]]  { self =>

  /** `map` over both type parameters. */
  def bimap[A, B, C, D](fab: F[A, B])(f: A => C, g: B => D): F[C, D]

  /**The composition of Bifunctors `F` and `G`, `[x,y]F[G[x,y],G[x,y]]`, is a Bifunctor */
  def compose[G[_, _]](implicit G0: Bifunctor[G]): Bifunctor[λ[(α, β) => F[G[α, β], G[α, β]]]] =
    new CompositionBifunctor[F, G] {
      implicit def F = self
      implicit def G = G0

  /**The product of Bifunctors `F` and `G`, `[x,y](F[x,y], G[x,y])`, is a Bifunctor */
  def product[G[_, _]](implicit G0: Bifunctor[G]): Bifunctor[λ[(α, β) => (F[α, β], G[α, β])]] =
    new ProductBifunctor[F, G] {
      implicit def F = self
      implicit def G = G0

  /** Extract the Functor on the first param. */
  def leftFunctor[X]: Functor[F[?, X]] =
    new LeftFunctor[F, X] {val F = self}

  def leftMap[A, B, C](fab: F[A, B])(f: A => C): F[C, B] =
    bimap(fab)(f, z => z)

  /** Extract the Functor on the second param. */
  def rightFunctor[X]: Functor[F[X, ?]] =
    new RightFunctor[F, X] {val F = self}

  /** Unify the functor over both params. */
  def uFunctor: Functor[λ[α => F[α, α]]] =
    new UFunctor[F] {val F = self}

  def rightMap[A, B, D](fab: F[A, B])(g: B => D): F[A, D] =
    bimap(fab)(z => z, g)

  def umap[A, B](faa: F[A, A])(f: A => B): F[B, B] =
    bimap(faa)(f, f)

  /** Embed two Functors , one on each side */
  def embed[G[_],H[_]](implicit G0: Functor[G], H0: Functor[H]): Bifunctor[λ[(α, β) => F[G[α],H[β]]]] =
    new CompositionBifunctorFunctors[F,G,H] {
      def F = self
      def G = G0
      def H = H0

  /** Embed one Functor to the left */
  def embedLeft[G[_]](implicit G0: Functor[G]): Bifunctor[λ[(α, β) => F[G[α],β]]] =

  /** Embed one Functor to the right */
  def embedRight[H[_]](implicit H0: Functor[H]): Bifunctor[λ[(α, β) => F[α,H[β]]]] =

  /** Bifunctors are covariant by nature */
  def widen[A, B, C >: A, D >: B](fab: F[A, B]): F[C, D] =
    bimap(fab)(identity[C], identity[D])

  val bifunctorSyntax = new scalaz.syntax.BifunctorSyntax[F] { def F = Bifunctor.this }

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



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