Scala example source code file (IListUsage.scala)

This example Scala source code file (IListUsage.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, icons, ilist, ilistusage, inil, int, string

The IListUsage.scala Scala example source code

package scalaz
package example

import Scalaz._

object IListUsage extends App {

  // Construct using elements
  val ns = IList(1, 2, 3)

  // Construct using cells
  val ns2 = ICons(1, ICons(2, ICons(3, INil())))
  val ns3 = 1 :: 2 :: 3 :: INil()

  // Construct from something else
  val ns4 = IList.fromList(List(1,3,4))
  val ns5 = IList.fromOption(Some(2))

  // Empty IList
  val e1 = INil[String]()
  val e2 = IList.empty[String]

  // IList is invariant; these won't compile
  // "abc" :: ns
  // e1 ++ ns

  // You can widen explicitly if you want to accomplish the above
  val any = "abc" :: ns.widen[Any]

  // List operations are generally the same as stdlib List
  val rev = ns.reverse
  val sum = ns.foldLeft(0)(_ + _)

  // But they are all total
  val tail = ns.tailOption
  val prod = ns.reduceLeftOption(_ * _)

  // Destructure with uncons
  val s1 = ns.uncons("empty", (h, t) => "head is %s and tail is %s".format(h, t))

  // Destructure with matching
  val s2 = ns match {
    case INil() => "empty"
    case ICons(h, t) => "head is %s and tail is %s".format(h, t)
  }

  // Same typeclass instances as List
  val xprod = (IList(1, 2) |@| IList(true, false)).tupled
  val unit  = 33.point[IList]
  val less  = IList(1,2,3) < IList(1,2,4)
  val trav  = IList(1, 2, 3).traverse(_.some)

  // Turn into something more familiar
  val lst = ns.toList
  val vec = ns.toVector
  val str = ns.toStream

  // Or less familiar
  val estr = ns.toEphemeralStream
  val zmap = ns.map(n => (n, "x" * n)).toMap // Int ==>> String

}