From 5d2acb2b3d6b2880ba36f039bbf98c583ce85a21 Mon Sep 17 00:00:00 2001
From: aleksandar <aleksandar@lampmac14.epfl.ch>
Date: Thu, 12 Jan 2012 19:55:50 +0100
Subject: Port of akka Future implementation in progress.

---
 src/library/scala/concurrent/Future.scala      |  75 +++++++++--
 src/library/scala/concurrent/Promise.scala     |  27 +++-
 src/library/scala/concurrent/akka/Future.scala | 177 ++++++++++++++++++++++++-
 src/library/scala/concurrent/package.scala     |   6 +
 4 files changed, 269 insertions(+), 16 deletions(-)

(limited to 'src/library')

diff --git a/src/library/scala/concurrent/Future.scala b/src/library/scala/concurrent/Future.scala
index 748d08be9f..d074dbfaaa 100644
--- a/src/library/scala/concurrent/Future.scala
+++ b/src/library/scala/concurrent/Future.scala
@@ -61,6 +61,9 @@ import scala.collection.generic.CanBuildFrom
  *  {{{
  *  f flatMap { (x: Int) => g map { (y: Int) => x + y } }
  *  }}}
+ *  
+ *  @define nonDeterministic
+ *  Note: using this method yields nondeterministic dataflow programs.
  */
 trait Future[+T] extends Awaitable[T] {
 self =>
@@ -113,11 +116,11 @@ self =>
   
   /** The execution context of the future.
    */
-  def executionContext: ExecutionContext
+  def executor: ExecutionContext
   
   /** Creates a new promise.
    */
-  def newPromise[S]: Promise[S] = executionContext promise
+  def newPromise[S]: Promise[S] = executor promise
   
   
   /* Projections */
@@ -135,7 +138,7 @@ self =>
    *  and throws a corresponding exception if the original future fails.
    */
   def failed: Future[Throwable] = new Future[Throwable] {
-    def executionContext = self.executionContext
+    def executor = self.executor
     def onComplete[U](func: Either[Throwable, Throwable] => U) = {
       self.onComplete {
         case Left(t) => func(Right(t))
@@ -242,8 +245,8 @@ self =>
    *  val f = future { 5 }
    *  val g = f filter { _ % 2 == 1 }
    *  val h = f filter { _ % 2 == 0 }
-   *  block on g // evaluates to 5
-   *  block on h // throw a NoSuchElementException
+   *  await(0) g // evaluates to 5
+   *  await(0) h // throw a NoSuchElementException
    *  }}}
    */
   def filter(pred: T => Boolean): Future[T] = {
@@ -258,7 +261,6 @@ self =>
   }
   
   /** Creates a new future by mapping the value of the current future if the given partial function is defined at that value.
-   *  
    *  
    *  If the current future contains a value for which the partial function is defined, the new future will also hold that value.
    *  Otherwise, the resulting future will fail with a `NoSuchElementException`.
@@ -274,8 +276,8 @@ self =>
    *  val h = f collect {
    *    case x if x > 0 => x * 2
    *  }
-   *  block on g // evaluates to 5
-   *  block on h // throw a NoSuchElementException
+   *  await(0) g // evaluates to 5
+   *  await(0) h // throw a NoSuchElementException
    *  }}}
    */
   def collect[S](pf: PartialFunction[T, S]): Future[S] = {
@@ -289,14 +291,68 @@ self =>
     p.future
   }
   
+  /** Creates a new future which holds the result of this future if it was completed successfully, or, if not,
+   *  the result of the `that` future if `that` is completed successfully.
+   *  If both futures are failed, the resulting future holds the throwable object of the first future.
+   *  
+   *  Example:
+   *  {{{
+   *  val f = future { sys.error("failed") }
+   *  val g = future { 5 }
+   *  val h = f orElse g
+   *  await(0) h // evaluates to 5
+   *  }}}
+   */
+  def orElse[U >: T](that: Future[U]): Future[U] = {
+    val p = newPromise[U]
+    
+    onComplete {
+      case Left(t) => that onComplete {
+        case Left(_) => p failure t
+        case Right(v) => p success v
+      }
+      case Right(v) => p success v
+    }
+    
+    p.future
+  }
+  
+  /** Creates a new future which holds the result of either this future or `that` future, depending on
+   *  which future was completed first.
+   *  
+   *  $nonDeterministic
+   *  
+   *  Example:
+   *  {{{
+   *  val f = future { sys.error("failed") }
+   *  val g = future { 5 }
+   *  val h = f orElse g
+   *  await(0) h // evaluates to either 5 or throws a runtime exception
+   *  }}}
+   */
+  def or[U >: T](that: Future[U]): Future[U] = {
+    val p = newPromise[U]
+    
+    val completePromise: PartialFunction[Either[Throwable, T], _] = {
+      case Left(t) => p tryFailure t
+      case Right(v) => p trySuccess v
+    }
+    this onComplete completePromise
+    this onComplete completePromise
+    
+    p.future
+  }
+  
 }
 
 
 object Future {
   
+  /*
+  // TODO make more modular by encoding this within the execution context
   def all[T, Coll[X] <: Traversable[X]](futures: Coll[Future[T]])(implicit cbf: CanBuildFrom[Coll[_], T, Coll[T]]): Future[Coll[T]] = {
     val builder = cbf(futures)
-    val p: Promise[Coll[T]] = executionContext.promise[Coll[T]]
+    val p: Promise[Coll[T]] = executor.promise[Coll[T]]
     
     if (futures.size == 1) futures.head onComplete {
       case Left(t) => p failure t
@@ -317,6 +373,7 @@ object Future {
     
     p.future
   }
+  */
   
   @inline def apply[T](body: =>T)(implicit executor: ExecutionContext): Future[T] = executor.future(body)
   
diff --git a/src/library/scala/concurrent/Promise.scala b/src/library/scala/concurrent/Promise.scala
index aae0135af4..f6ea252f73 100644
--- a/src/library/scala/concurrent/Promise.scala
+++ b/src/library/scala/concurrent/Promise.scala
@@ -25,6 +25,9 @@ import scala.util.Timeout
  *  If the throwable used to fail this promise is an error, a control exception
  *  or an interrupted exception, it will be wrapped as a cause within an
  *  `ExecutionException` which will fail the promise.
+ *  
+ *  @define nonDeterministic
+ *  Note: Using this method may result in non-deterministic concurrent programs.
  */
 trait Promise[T] {
   
@@ -38,7 +41,15 @@ trait Promise[T] {
    *  
    *  $promiseCompletion
    */
-  def success(value: T): Unit
+  def success(v: T): this.type = if (trySuccess(v)) this else throw new IllegalStateException("Promise already completed.")
+  
+  /** Tries to complete the promise with a value.
+   *  
+   *  $nonDeterministic
+   *  
+   *  @return    If the promise has already been completed returns `false`, or `true` otherwise.
+   */
+  def trySuccess(value: T): Boolean
   
   /** Completes the promise with an exception.
    *  
@@ -48,8 +59,16 @@ trait Promise[T] {
    *  
    *  $promiseCompletion
    */
-  def failure(t: Throwable): Unit
-
+  def failure(t: Throwable): this.type = if (tryFailure(t)) this else throw new IllegalStateException("Promise already completed.")
+  
+  /** Tries to complete the promise with an exception.
+   *  
+   *  $nonDeterministic
+   *  
+   *  @return    If the promise has already been completed returns `false`, or `true` otherwise.
+   */
+  def tryFailure(t: Throwable): Boolean
+  
   /** Wraps a `Throwable` in an `ExecutionException` if necessary.
    *
    *  $allowedThrowables
@@ -58,7 +77,7 @@ trait Promise[T] {
     case t: Throwable if isFutureThrowable(t) => t
     case _ => new ExecutionException(t)
   }
-
+  
 }
 
 
diff --git a/src/library/scala/concurrent/akka/Future.scala b/src/library/scala/concurrent/akka/Future.scala
index e359456736..2b41c0c62e 100644
--- a/src/library/scala/concurrent/akka/Future.scala
+++ b/src/library/scala/concurrent/akka/Future.scala
@@ -1,4 +1,4 @@
-/*                     __                                               *\
+/*/*                     __                                               *\
 **     ________ ___   / /  ___     Scala API                            **
 **    / __/ __// _ | / /  / _ |    (c) 2003-2011, LAMP/EPFL             **
 **  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
@@ -6,11 +6,182 @@
 **                          |/                                          **
 \*                                                                      */
 
-package scala.concurrent
-package akka
+package scala.concurrent.akka
 
 
 
 
 
 
+sealed trait Future[+T] extends scala.concurrent.Future with Awaitable[T] {
+  
+  implicit def executor: ExecutionContext
+  
+  /**
+   * For use only within a Future.flow block or another compatible Delimited Continuations reset block.
+   *
+   * Returns the result of this Future without blocking, by suspending execution and storing it as a
+   * continuation until the result is available.
+   */
+  def apply(): T @cps[Future[Any]] = shift(this flatMap (_: T ⇒ Future[Any]))
+  
+  /**
+   * Tests whether this Future has been completed.
+   */
+  final def isCompleted: Boolean = value.isDefined
+  
+  /**
+   * The contained value of this Future. Before this Future is completed
+   * the value will be None. After completion the value will be Some(Right(t))
+   * if it contains a valid result, or Some(Left(error)) if it contains
+   * an exception.
+   */
+  def value: Option[Either[Throwable, T]]
+  
+  def onComplete(func: Either[Throwable, T] => Unit): this.type
+  
+  /**
+   * Creates a Future that will be the result of the first completed Future of this and the Future that was passed into this.
+   * This is semantically the same as: Future.firstCompletedOf(Seq(this, that))
+   */
+  //FIXME implement as the result of any of the Futures, or if both failed, the first failure
+  def orElse[A >: T](that: Future[A]): Future[A] = Future.firstCompletedOf(List(this, that)) //TODO Optimize
+  
+  final def recover[A >: T](pf: PartialFunction[Throwable, A]): Future[A] = {
+    val future = Promise[A]()
+    onComplete {
+      case Left(e) if pf isDefinedAt e ⇒ future.complete(try { Right(pf(e)) } catch { case x: Exception ⇒ Left(x) })
+      case otherwise                   ⇒ future complete otherwise
+    }
+    future
+  }
+  
+  /**
+   * Creates a new Future by applying a function to the successful result of
+   * this Future. If this Future is completed with an exception then the new
+   * Future will also contain this exception.
+   * Example:
+   * <pre>
+   * val future1 = for {
+   *   a: Int    <- actor ? "Hello" // returns 5
+   *   b: String <- actor ? a       // returns "10"
+   *   c: String <- actor ? 7       // returns "14"
+   * } yield b + "-" + c
+   * </pre>
+   */
+  final def map[A](f: T ⇒ A): Future[A] = {
+    val future = Promise[A]()
+    onComplete {
+      case l: Left[_, _] ⇒ future complete l.asInstanceOf[Either[Throwable, A]]
+      case Right(res) ⇒
+        future complete (try {
+          Right(f(res))
+        } catch {
+          case e ⇒
+            logError("Future.map", e)
+            Left(e)
+        })
+    }
+    future
+  }
+
+  /**
+   * Creates a new Future[A] which is completed with this Future's result if
+   * that conforms to A's erased type or a ClassCastException otherwise.
+   */
+  final def mapTo[A](implicit m: Manifest[A]): Future[A] = {
+    val fa = Promise[A]()
+    onComplete {
+      case l: Left[_, _] ⇒ fa complete l.asInstanceOf[Either[Throwable, A]]
+      case Right(t) ⇒
+        fa complete (try {
+          Right(BoxedType(m.erasure).cast(t).asInstanceOf[A])
+        } catch {
+          case e: ClassCastException ⇒ Left(e)
+        })
+    }
+    fa
+  }
+
+  /**
+   * Creates a new Future by applying a function to the successful result of
+   * this Future, and returns the result of the function as the new Future.
+   * If this Future is completed with an exception then the new Future will
+   * also contain this exception.
+   * Example:
+   * <pre>
+   * val future1 = for {
+   *   a: Int    <- actor ? "Hello" // returns 5
+   *   b: String <- actor ? a       // returns "10"
+   *   c: String <- actor ? 7       // returns "14"
+   * } yield b + "-" + c
+   * </pre>
+   */
+  final def flatMap[A](f: T ⇒ Future[A]): Future[A] = {
+    val p = Promise[A]()
+
+    onComplete {
+      case l: Left[_, _] ⇒ p complete l.asInstanceOf[Either[Throwable, A]]
+      case Right(r) ⇒
+        try {
+          p completeWith f(r)
+        } catch {
+          case e ⇒
+            p complete Left(e)
+            logError("Future.flatMap", e)
+        }
+    }
+    p
+  }
+
+  /**
+   * Same as onSuccess { case r => f(r) } but is also used in for-comprehensions
+   */
+  final def foreach(f: T ⇒ Unit): Unit = onComplete {
+    case Right(r) ⇒ f(r)
+    case _        ⇒
+  }
+
+  /**
+   * Used by for-comprehensions
+   */
+  final def withFilter(p: T ⇒ Boolean) = new FutureWithFilter[T](this, p)
+
+  final class FutureWithFilter[+A](self: Future[A], p: A ⇒ Boolean) {
+    def foreach(f: A ⇒ Unit): Unit = self filter p foreach f
+    def map[B](f: A ⇒ B): Future[B] = self filter p map f
+    def flatMap[B](f: A ⇒ Future[B]): Future[B] = self filter p flatMap f
+    def withFilter(q: A ⇒ Boolean): FutureWithFilter[A] = new FutureWithFilter[A](self, x ⇒ p(x) && q(x))
+  }
+
+  /**
+   * Returns a new Future that will hold the successful result of this Future if it matches
+   * the given predicate, if it doesn't match, the resulting Future will be a failed Future
+   * with a MatchError, of if this Future fails, that failure will be propagated to the returned Future
+   */
+  final def filter(pred: T ⇒ Boolean): Future[T] = {
+    val p = Promise[T]()
+    onComplete {
+      case l: Left[_, _] ⇒ p complete l.asInstanceOf[Either[Throwable, T]]
+      case r @ Right(res) ⇒ p complete (try {
+        if (pred(res)) r else Left(new MatchError(res))
+      } catch {
+        case e ⇒
+          logError("Future.filter", e)
+          Left(e)
+      })
+    }
+    p
+  }
+
+  protected def logError(msg: String, problem: Throwable): Unit = {
+    executor match {
+      case m: MessageDispatcher ⇒ m.prerequisites.eventStream.publish(Error(problem, msg, problem.getMessage))
+      case other                ⇒ problem.printStackTrace()
+    }
+  }
+}
+
+
+
+*/
diff --git a/src/library/scala/concurrent/package.scala b/src/library/scala/concurrent/package.scala
index 666e12456d..c35ece5668 100644
--- a/src/library/scala/concurrent/package.scala
+++ b/src/library/scala/concurrent/package.scala
@@ -50,6 +50,12 @@ package object concurrent {
     case _ => true
   }
   
+  private[concurrent] def resolveThrowable[T](source: Either[Throwable, T]): Either[Throwable, T] = source match {
+    case Left(t: scala.runtime.NonLocalReturnControl[_]) => Right(t.value.asInstanceOf[T])
+    case Left(t: InterruptedException) => Left(new ExecutionException("Boxed InterruptedException", t))
+    case _ => source
+  }
+  
   /* concurrency constructs */
   
   def future[T](body: =>T)(implicit execCtx: ExecutionContext = executionContext): Future[T] =
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