Scala example source code file (AbstractPartialFunction.scala)

This example Scala source code file (AbstractPartialFunction.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

annotation, function1, partialfunction, r, t1

The AbstractPartialFunction.scala Scala example source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2013, LAMP/EPFL                  **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

package scala
package runtime

import scala.annotation.unspecialized

/** `AbstractPartialFunction` reformulates all operations of its supertrait `PartialFunction`
 *  in terms of `isDefinedAt` and `applyOrElse`.
 *
 *  This allows more efficient implementations in many cases:
 *  - optimized `orElse` method supports chained `orElse` in linear time,
 *    and with no slow-down if the `orElse` part is not needed.
 *  - optimized `lift` method helps to avoid double evaluation of pattern matchers & guards
 *    of partial function literals.
 *
 *  This trait is used as a basis for implementation of all partial function literals.
 *
 *  @author  Pavel Pavlov
 *  @since   2.10
 */
abstract class AbstractPartialFunction[@specialized(scala.Int, scala.Long, scala.Float, scala.Double) -T1, @specialized(scala.Unit, scala.Boolean, scala.Int, scala.Float, scala.Long, scala.Double) +R] extends Function1[T1, R] with PartialFunction[T1, R] { self =>
  // this method must be overridden for better performance,
  // for backwards compatibility, fall back to the one inherited from PartialFunction
  // this assumes the old-school partial functions override the apply method, though
  // override def applyOrElse[A1 <: T1, B1 >: R](x: A1, default: A1 => B1): B1 = ???

  // probably okay to make final since classes compiled before have overridden against the old version of AbstractPartialFunction
  // let's not make it final so as not to confuse anyone
  /*final*/ def apply(x: T1): R = applyOrElse(x, PartialFunction.empty)
}