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Standard library for the Scala Programming Language
/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2013, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
package scala.concurrent
/** A `DelayedLazyVal` is a wrapper for lengthy computations which have a
* valid partially computed result.
*
* The first argument is a function for obtaining the result at any given
* point in time, and the second is the lengthy computation. Once the
* computation is complete, the `apply` method will stop recalculating it
* and return a fixed value from that point forward.
*
* @param f the function to obtain the current value at any point in time
* @param body the computation to run to completion in another thread
*
* @author Paul Phillips
* @version 2.8
*/
class DelayedLazyVal[T](f: () => T, body: => Unit)(implicit exec: ExecutionContext){
@volatile private[this] var _isDone = false
private[this] lazy val complete = f()
/** Whether the computation is complete.
*
* @return true if the computation is complete.
*/
def isDone = _isDone
/** The current result of f(), or the final result if complete.
*
* @return the current value
*/
def apply(): T = if (isDone) complete else f()
exec.execute(new Runnable { def run = { body; _isDone = true } })
}