From 074f7e7b405aef70c6bcc59b0037ca98b541e131 Mon Sep 17 00:00:00 2001
From: Jason Zaugg <jzaugg@gmail.com>
Date: Wed, 19 Dec 2012 13:49:13 +0100
Subject: Update README.md

---
 README.md | 171 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 171 insertions(+)

(limited to 'README.md')

diff --git a/README.md b/README.md
index 39332b6..2a18af5 100644
--- a/README.md
+++ b/README.md
@@ -161,3 +161,174 @@ http://www.scala-lang.org/sites/default/files/contributor_agreement.pdf
 Before submitting a pull-request, please make sure you have followed the guidelines
 outlined in our [Pull Request Policy](https://github.com/scala/scala/wiki/Pull-Request-Policy).
 
+### Generated Code examples
+
+```scala
+val future = async {                                     
+ val f1 = async { true }                                 
+ val x = 1                                               
+ def inc(t: Int) = t + x                                 
+ val t = 0                                               
+ val f2 = async { 42 }                                   
+ if (await(f1)) await(f2) else { val z = 1; inc(t + z) }
+}                                                                            
+```
+
+After ANF transform.
+
+ - await calls are moved to only appear on the LHS of an value definition.
+ - `if` is not used as an expression, instead each branch writes its result
+   to a synthetic `var`.
+
+```scala
+ {
+  ();
+  val f1: scala.concurrent.Future[Boolean] = {
+    scala.concurrent.Future.apply[Boolean](true)(scala.concurrent.ExecutionContext.Implicits.global)
+  };
+  val x: Int = 1;
+  def inc(t: Int): Int = t.+(x);
+  val t: Int = 0;
+  val f2: scala.concurrent.Future[Int] = {
+    scala.concurrent.Future.apply[Int](42)(scala.concurrent.ExecutionContext.Implicits.global)
+  };
+  val await$1: Boolean = scala.async.Async.await[Boolean](f1);
+  var ifres$1: Int = 0;
+  if (await$1)
+    {
+      val await$2: Int = scala.async.Async.await[Int](f2);
+      ifres$1 = await$2
+    }
+  else
+    {
+      ifres$1 = {
+        val z: Int = 1;
+        inc(t.+(z))
+      }
+    };
+  ifres$1
+}
+```
+
+After async transform:
+
+ - one class synthesized to act as the state machine. It's `apply()` method will
+   be used to start the computation (even the code before the first await call
+   is executed asynchronously), and the the `apply(tr: scala.util.Try[Any])` method
+   will continue after each completed background task.
+ - each chunk of code moved into the a branch of the pattern match in `resume$async`.
+ - value and method definitions accessed from multiple states are lifted to be
+   members of `class stateMachine`. Others remain local, e.g. `val z`.
+
+```scala
+ {
+  class stateMachine$7 extends StateMachine[scala.concurrent.Promise[Int], scala.concurrent.ExecutionContext] {
+    def <init>() = {
+      super.<init>();
+      ()
+    };
+    var state$async: Int = 0;
+    val result$async: scala.concurrent.Promise[Int] = scala.concurrent.Promise.apply[Int]();
+    val execContext$async = scala.concurrent.ExecutionContext.Implicits.global;
+    var x$1: Int = 0;
+    def inc$1(t: Int): Int = t.$plus(x$1);
+    var t$1: Int = 0;
+    var f2$1: scala.concurrent.Future[Int] = null;
+    var await$1: Boolean = false;
+    var ifres$1: Int = 0;
+    var await$2: Int = 0;
+    def resume$async(): Unit = try {
+      state$async match {
+        case 0 => {
+          ();
+          val f1 = {
+            scala.concurrent.Future.apply[Boolean](true)(scala.concurrent.ExecutionContext.Implicits.global)
+          };
+          x$1 = 1;
+          t$1 = 0;
+          f2$1 = {
+            scala.concurrent.Future.apply[Int](42)(scala.concurrent.ExecutionContext.Implicits.global)
+          };
+          f1.onComplete(this)(execContext$async)
+        }
+        case 1 => {
+          ifres$1 = 0;
+          if (await$1)
+            {
+              state$async = 2;
+              resume$async()
+            }
+          else
+            {
+              state$async = 3;
+              resume$async()
+            }
+        }
+        case 2 => {
+          f2$1.onComplete(this)(execContext$async);
+          ()
+        }
+        case 5 => {
+          ifres$1 = await$2;
+          state$async = 4;
+          resume$async()
+        }
+        case 3 => {
+          ifres$1 = {
+            val z = 1;
+            inc$1(t$1.$plus(z))
+          };
+          state$async = 4;
+          resume$async()
+        }
+        case 4 => {
+          result$async.complete(scala.util.Success.apply(ifres$1));
+          ()
+        }
+      }
+    } catch {
+      case NonFatal((tr @ _)) => {
+        {
+          result$async.complete(scala.util.Failure.apply(tr));
+          ()
+        };
+        ()
+      }
+    };
+    def apply(tr: scala.util.Try[Any]): Unit = state$async match {
+      case 0 => {
+        if (tr.isFailure)
+          {
+            result$async.complete(tr.asInstanceOf[scala.util.Try[Int]]);
+            ()
+          }
+        else
+          {
+            await$1 = tr.get.asInstanceOf[Boolean];
+            state$async = 1;
+            resume$async()
+          };
+        ()
+      }
+      case 2 => {
+        if (tr.isFailure)
+          {
+            result$async.complete(tr.asInstanceOf[scala.util.Try[Int]]);
+            ()
+          }
+        else
+          {
+            await$2 = tr.get.asInstanceOf[Int];
+            state$async = 5;
+            resume$async()
+          };
+        ()
+      }
+    };
+    def apply: Unit = resume$async()
+  };
+  val stateMachine$7: StateMachine[scala.concurrent.Promise[Int], scala.concurrent.ExecutionContext] = new stateMachine$7();
+  scala.concurrent.Future.apply(stateMachine$7.apply())(scala.concurrent.ExecutionContext.Implicits.global);
+  stateMachine$7.result$async.future
+}
+```
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