Scala example source code file (LazyEitherTTest.scala)

This example Scala source code file (LazyEitherTTest.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

bifoldable, bifunctor, bindrec, bitraverse, equal, foldable, functor, int, lazyeithert, monad, monoid, traverse

The LazyEitherTTest.scala Scala example source code

package scalaz

import scalaz.scalacheck.ScalazProperties._
import scalaz.scalacheck.ScalazArbitrary._
import std.AllInstances._

object LazyEitherTTest extends SpecLite {

  import LazyEitherTest.LazyEitherEqual

  implicit def lazyEitherTEqual[F[_], A, B](implicit F0: Equal[F[LazyEither[A, B]]]): Equal[LazyEitherT[F, A, B]] =
    F0.contramap((_: LazyEitherT[F, A, B]).run)

  type LazyEitherTList[A, B] = LazyEitherT[List, A, B]
  type LazyEitherTListInt[A] = LazyEitherT[List, Int, A]

  checkAll(equal.laws[LazyEitherTListInt[Int]])
  checkAll(monadPlus.laws[LazyEitherTListInt])
  checkAll(traverse.laws[LazyEitherTListInt])
  checkAll(bitraverse.laws[LazyEitherTList])
  checkAll(bindRec.laws[LazyEitherTListInt])
  checkAll(monadError.laws[LazyEitherTListInt, Int])

  "tail recursive tailrecM" in {
    import Scalaz.Id
    type LazyEitherId[A] = LazyEitherT[Id, Int, A]

    val times = 10000

    val result =
      BindRec[LazyEitherId].tailrecM[Int, Int] {
        i => LazyEitherT[Id, Int, Int \/ Int](LazyEither.lazyRight(if (i < 10000) \/.left(i + 1) else \/.right(i)))
      }(0)
    result.getOrElse(0) must_=== times
  }

  private def lazyEitherTUcompilationTest: Unit = {
    val a: String \/ LazyEither[Int, Boolean] = null
    LazyEitherT.lazyEitherTU(a)
  }

  object instances {
    def functor[F[_] : Functor, A] = Functor[LazyEitherT[F, A, ?]]
    def plus[F[_] : Monad, A: Semigroup] = Plus[LazyEitherT[F, A, ?]]
    def monad[F[_] : Monad, A] = Monad[LazyEitherT[F, A, ?]]
    def monadPlus[F[_] : Monad, A: Monoid] = MonadPlus[LazyEitherT[F, A, ?]]
    def bind[F[_] : Monad, A] = Bind[LazyEitherT[F, A, ?]]
    def foldable[F[_] : Foldable, A] = Foldable[LazyEitherT[F, A, ?]]
    def traverse[F[_] : Traverse, A] = Traverse[LazyEitherT[F, A, ?]]
    def bifunctor[F[_] : Functor] = Bifunctor[LazyEitherT[F, ?, ?]]
    def bifoldable[F[_] : Foldable] = Bifoldable[LazyEitherT[F, ?, ?]]
    def bitraverse[F[_] : Traverse] = Bitraverse[LazyEitherT[F, ?, ?]]

    // checking absence of ambiguity
    def functor[F[_] : Monad : Traverse, A] = Functor[LazyEitherT[F, A, ?]]
    def functor[F[_] : Monad : BindRec, A] = Functor[LazyEitherT[F, A, ?]]
    def functor[F[_] : BindRec: Traverse, A] = Functor[LazyEitherT[F, A, ?]]
    def functor[F[_] : Monad, A: Monoid] = Functor[LazyEitherT[F, A, ?]]
    def bind[F[_] : Monad : BindRec, A] = Bind[LazyEitherT[F, A, ?]]
    def monad[F[_] : Monad, A: Monoid] = Monad[LazyEitherT[F, A, ?]]
    def monadError[F[_] : Monad, A] = MonadError[LazyEitherT[F, A, ?], A]
    def foldable[F[_] : Traverse, A] = Foldable[LazyEitherT[F, A, ?]]
    def bifunctor[F[_] : Traverse] = Bifunctor[LazyEitherT[F, ?, ?]]
    def bifoldable[F[_] : Traverse] = Bifoldable[LazyEitherT[F, ?, ?]]
  }

}