Scala example source code file (IterateeUsage.scala)

This example Scala source code file (IterateeUsage.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

app, ioexceptionor, iteratees, iteratees\\nare\\ncomposable, iterateeusage, list, none, some, stringreader

The IterateeUsage.scala Scala example source code

package scalaz.example

object IterateeUsage extends App {
  import scalaz._, Scalaz._, MonadPartialOrder._
  import iteratee._, Iteratee._
  import effect._

  val stream123 = enumStream[Int, Id](Stream(1, 2, 3))

  ((head[Int, Id]   &= stream123).run) assert_=== Some(1)
  ((length[Int, Id] &= stream123).run) assert_=== 3
  ((peek[Int, Id]   &= stream123).run) assert_=== Some(1)
  ((head[Int, Id]   &= enumStream(Stream())).run) assert_=== None

  def iter123 = enumIterator[Int, IO](Iterator(1, 2, 3))

  ((head[Int, IO]   &= iter123).run unsafePerformIO()) assert_=== Some(1)
  ((length[Int, IO] &= iter123).run unsafePerformIO()) assert_=== 3
  ((peek[Int, IO]   &= iter123).run unsafePerformIO()) assert_=== Some(1)
  ((head[Int, IO]   &= enumIterator[Int, IO](Iterator())).run unsafePerformIO()) assert_=== None

  val stream1_10 = enumStream[Int, Id]((1 to 10).toStream)

  (take[Int, List](3) &= stream1_10).run assert_=== List(1, 2, 3)
  (takeWhile[Int, List](_ <= 5) &= stream1_10).run assert_=== (1 to 5).toList
  (takeUntil[Int, List](_ >  5) &= stream1_10).run assert_=== (1 to 5).toList

  val readLn = takeWhile[Char, List](_ != '\n') flatMap (ln => drop[Char, Id](1).map(_ => ln))
  (collect[List[Char], List] %= readLn.sequenceI &= enumStream("Iteratees\nare\ncomposable".toStream)).run assert_=== List("Iteratees".toList, "are".toList, "composable".toList)

  (collect[List[Int], List] %= splitOn(_ % 3 != 0) &= stream1_10).run assert_=== List(List(1, 2), List(4, 5), List(7, 8), List(10))

  (collect[Int, List] %= map((_:String).toInt) &= enumStream(Stream("1", "2", "3"))).run assert_=== List(1, 2, 3)
  (collect[Int, List] %= filter((_:Int) % 2 == 0) &= stream1_10).run assert_=== List(2, 4, 6, 8, 10)

  (collect[List[Int], List] %= group(3) &= enumStream((1 to 9).toStream)).run assert_=== List(List(1, 2, 3), List(4, 5, 6), List(7, 8, 9))

  import java.io._

  def r = enumReader[IO](new StringReader("file contents"))

  ((head[IoExceptionOr[Char], IO] &= r).map(_ flatMap (_.toOption)).run.unsafePerformIO()) assert_=== Some('f')
  ((length[ IoExceptionOr[Char], IO] &= r).run.unsafePerformIO()) assert_=== 13
  ((peek[IoExceptionOr[Char], IO]   &= r).map(_ flatMap (_.toOption)).run.unsafePerformIO()) assert_=== Some('f')
  ((head[IoExceptionOr[Char], IO]  &= enumReader[IO](new StringReader(""))).map(_ flatMap (_.toOption)).run unsafePerformIO()) assert_=== None

  // As a monad
  val m1 = head[Int, Id] flatMap (b => head[Int, Id] map (b2 => (b tuple b2)))
  (m1 &= stream123).run assert_=== Some(1 -> 2)

  // As a monad using for comprehension (same as 'm1' example above)
  val m2 = for{
    b <- head[Int, Id]
    b2 <- head[Int, Id]
  } yield b tuple b2
  (m2 &= stream123).run assert_=== Some(1 -> 2)

  val colc = takeWhile[IoExceptionOr[Char], List](_.fold(_ => false, _ != ' ')).up[IO]
  ((colc &= r).map(_ flatMap (_.toOption)).run unsafePerformIO()) assert_=== List('f', 'i', 'l', 'e')

  val take10And5ThenHead = take[Int, List](10) zip take[Int, List](5) flatMap (ab => head[Int, Id] map (h => (ab, h)))
  (take10And5ThenHead &= enumStream((1 to 20).toStream)).run assert_=== (((1 to 10).toList, (1 to 5).toList), Some(11))
}