Scala example source code file (TriState.scala)

This example Scala source code file (TriState.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

anyval, boolean, false, int, not, tristate, true, unknown

The TriState.scala Scala example source code

package scala
package reflect
package internal
package util

import scala.language.implicitConversions

import TriState._

/** A simple true/false/unknown value, for those days when
 *  true and false don't quite partition the space.
 */
final class TriState private (val value: Int) extends AnyVal {
  def isKnown = this != Unknown
  def booleanValue = this match {
    case True  => true
    case False => false
    case _     => sys.error("Not a Boolean value")
  }
}

object TriState {
  implicit def booleanToTriState(b: Boolean): TriState = if (b) True else False

  val Unknown = new TriState(-1)
  val False   = new TriState(0)
  val True    = new TriState(1)
}