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Scala example source code file (Breaks.scala)

This example Scala source code file (Breaks.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Scala tags/keywords

breakcontrol, breakcontrol, breaks, breaks, controlthrowable, tryblock, tryblock, unit, unit

The Scala Breaks.scala source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2003-2011, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */



package scala.util.control

/** A class that can be instantiated for the break control abstraction.
 *  Example usage:<pre>
 *
 *  val mybreaks = new Breaks
 *  import</b> mybreaks.{break, breakable}
 *
 *  breakable {
 *    <b>for (...) {
 *      <b>if (...) break
 *    }
 *  }</pre>
 *
 *  Calls to break from one instantiation of Breaks will never
 *  target breakable objects of some other instantion.
 */  
class Breaks {

  private val breakException = new BreakControl

  /** A block from which one can exit with a `break''. */
  def breakable(op: => Unit) {
    try {
      op
    } catch {
      case ex: BreakControl => 
        if (ex ne breakException) throw ex
    }
  }
  
  trait TryBlock {
    def catchBreak(onBreak: => Unit): Unit
  }
  
  def tryBreakable(op: => Unit) = new TryBlock {
    def catchBreak(onBreak: => Unit) = try {
      op
    } catch {
      case ex: BreakControl =>
        if (ex ne breakException) throw ex
        onBreak
    }
  }

  /* Break from dynamically closest enclosing breakable block
   * @note this might be different than the statically closest enclosing
   * block!
   */
  def break() { throw breakException }
} 

/** An object that can be used for the break control abstraction.
 *  Example usage:<pre>
 *
 *  <b>import Breaks.{break, breakable}
 *
 *  breakable {
 *    <b>for (...) {
 *      <b>if (...) break
 *    }
 *  }</pre>
 *
 */  
object Breaks extends Breaks

private class BreakControl extends ControlThrowable

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