Scala example source code file (ScalaCheckBinding.scala)

This example Scala source code file (ScalaCheckBinding.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

arbitrary, arbitrarymonad, gen, genmonad, invariantfunctor, monad, scalacheckbinding, shrink, shrinkfunctor

The ScalaCheckBinding.scala Scala example source code

package scalaz
package scalacheck

/**
 * Type class instances for types from [[https://github.com/rickynils/scalacheck Scalacheck]]
 */
object ScalaCheckBinding {
  import org.scalacheck.{Gen, Arbitrary, Shrink}
  import Gen.{sized, const}

  implicit val ArbitraryMonad: Monad[Arbitrary] = new Monad[Arbitrary] {
    def bind[A, B](fa: Arbitrary[A])(f: A => Arbitrary[B]) = Arbitrary(fa.arbitrary.flatMap(f(_).arbitrary))
    def point[A](a: => A) = Arbitrary(sized(_ => const(a)))
    override def map[A, B](fa: Arbitrary[A])(f: A => B) = Arbitrary(fa.arbitrary.map(f))
  }

  implicit val GenMonad: Monad[Gen] = new Monad[Gen] {
    def point[A](a: => A) = sized(_ => const(a))
    def bind[A, B](fa: Gen[A])(f: A => Gen[B]) = fa flatMap f
    override def map[A, B](fa: Gen[A])(f: A => B) = fa map f
  }

  implicit val ShrinkFunctor: InvariantFunctor[Shrink] =
    new InvariantFunctor[Shrink] {
      def xmap[A, B](ma: Shrink[A], f: A => B, g: B => A): Shrink[B] =
        Shrink{b => ma shrink g(b) map f}
    }
}

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