convert isolates to use Future

corelib/src/future.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // Dart core library.
 
 
 /**
  * A Future is used to obtain a value sometime in the
  * future.
@@ skipping 93 matching lines @@
   /**
    * Called when value is available.
    */
   void complete(T value);
 
   /**
    * Called if an exception occured while trying to produce value.
    */
   void completeException(Object exception);
 }
+
+
+class Futures {

[Siggi Cherem (dart-lang), 2011/11/04 16:57:33]

+ comment on this class

[mattsh, 2011/11/04 17:10:31]

Done.

+
+  /**
+   * Returns a future which will complete once all the futures in a
+   * list are complete.  (The value of the returned future will
+   * be a list of all the values that were produced.)
+   */
+  static Future<List> wait(List<Future> futures) {
+    Completer completer = new Completer<Object>();

[Siggi Cherem (dart-lang), 2011/11/04 16:57:33]

Compelter<Object> -> Completer<List>?

[mattsh, 2011/11/04 17:10:31]

Done.

+    int remaining = futures.length;
+    List<Object> values = new List(futures.length);

[Siggi Cherem (dart-lang), 2011/11/04 16:57:33]

List<Object> -> List (let it be dynamic)

[mattsh, 2011/11/04 17:10:31]

I think it should be List<Object> here because we don't care what the values are
and we don't need to call any methods on them, and we want to get a static error
here if we did try to call something.

+
+    // As each future completes, put its value into the corresponding
+    // position in the list of values.
+    for (int i = 0; i < futures.length; i++) {
+      int pos = i;

[Siggi Cherem (dart-lang), 2011/11/04 16:57:33]

add here a TODO to remove this once loop-var capture works also in this kind of
for-loops (as it does in for-in loops).

[mattsh, 2011/11/04 17:10:31]

Done.

+      futures[pos].then((Object value) {

[Siggi Cherem (dart-lang), 2011/11/04 16:57:33]

Object -> var, or remove the type annotation.

[mattsh, 2011/11/04 17:10:31]

See above.

+        values[pos] = value;
+        if (--remaining == 0) {
+          completer.complete(values);
+        }
+      });
+    }
+    return completer.future;
+  }

[Siggi Cherem (dart-lang), 2011/11/04 16:57:33]

to address Ben's concern, let's add here a method that does what [then] used to
do, we can call it [chain] or [after]. This is what I have in mind:

static Future chain(Future future, var action(var value)) {
  Completer completer = new Completer()
  future.then((value) { completer.complete(action(value)); });
  future.handleException((ex) { completer.completeException(ex); });
  return completer.future;
}

[mattsh, 2011/11/04 17:10:31]

Can do in follow up CL.

+}
+