Scala example source code file (IndexedContsTTest.scala)

This example Scala source code file (IndexedContsTTest.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, bifunctor, cobind, comonad, conttliststringint, equal, functor, gen, indexedcontsttest

The IndexedContsTTest.scala Scala example source code

package scalaz

import org.scalacheck.{Arbitrary, Gen}
import scalaz.scalacheck.ScalaCheckBinding._
import scalaz.scalacheck.ScalazProperties._
import scalaz.std.list._
import scalaz.std.string._

object IndexedContsTTest extends SpecLite {

  type ContTListString[A] = ContT[List, String, A]
  type ContTListStringInt = ContTListString[Int]

  def contTListStringGen[A](implicit A: Arbitrary[A]): Gen[ContTListString[A]] = Gen.frequency(
    (1, Functor[Gen].map(Gen.containerOf[List, String](Gen.alphaStr))(l => ContT(f => l))),
    (1, Functor[Gen].map(A.arbitrary)(ContT.point(_))),
    (1, Functor[Gen].map(A.arbitrary)(i => ContT(f => {
      val l = f(i)
      val (a, b) = l.splitAt((l.size + 1) % 3)
      a ::: List("foo") ::: b
    })))
  )

  implicit def contTListStringIntArb: Arbitrary[ContTListStringInt] = Arbitrary(contTListStringGen[Int])
  implicit def contTListStringInt2Arb: Arbitrary[ContTListString[Int => Int]] = Arbitrary(contTListStringGen[Int => Int])
  implicit def contTListStringIntEqual: Equal[ContTListStringInt] = new Equal[ContTListStringInt] {
    def equal(a: ContTListStringInt, b: ContTListStringInt): Boolean = {
      val f: Int => List[String] = _.toString.toList.map(_.toString)
      Equal[List[String]].equal(a(f), b(f))
    }
  }

  checkAll(monadPlus.laws[ContTListString])

  object instances {
    def functorRight[W[_]: Functor, M[_], R, O] = Functor[IndexedContsT[W, M, R, O, ?]]
    def functorLeft[W[_], M[_]: Functor, O, A] = Functor[IndexedContsT[W, M, ?, O, A]]
    def contravariant[W[_]: Functor, M[_]: Functor, R, A] = Contravariant[IndexedContsT[W, M, R, ?, A]]
    def bifunctor[W[_]: Functor, M[_]: Functor, O] = Bifunctor[IndexedContsT[W, M, ?, O, ?]]
    def bind[W[_]: Cobind, M[_], R] = Bind[ContsT[W, M, R, ?]]
    def monad[W[_]: Comonad, M[_], R] = Monad[ContsT[W, M, R, ?]]

    // checking absence of ambiguity
    def functor[W[_]: Comonad, M[_], R] = Functor[ContsT[W, M, R, ?]]
    def functor[W[_]: Cobind, M[_], R] = Functor[ContsT[W, M, R, ?]]
    def bind[W[_]: Comonad, M[_], R] = Bind[ContsT[W, M, R, ?]]
  }
}