Add Stream.fromIterable

sdk/lib/core/iterable.dart

Index: sdk/lib/core/iterable.dart
diff --git a/sdk/lib/core/iterable.dart b/sdk/lib/core/iterable.dart
index feb93184746be1d33a743102af8326e94241ccb8..a2cc9cd2eb74d7c8d86f0e804df5408e309f773a 100644
--- a/sdk/lib/core/iterable.dart
+++ b/sdk/lib/core/iterable.dart
@@ -19,6 +19,10 @@ part of dart.core;
 abstract class Iterable<E> {
   const Iterable();
 
+  factory Iterable.generate(int count, E generator(int index)) {

[Sean Eagan, 2013/01/09 14:15:20]

Once we have a some way to get a integer range, I don't think we will need this
constructor:

range(10).mappedBy(f);

and then for Streams:

new Stream.fromIterable(range(10).mappedBy(f)); // or
new Stream.fromIterable(range(10)).mappedBy(f);

+    return new _GeneratorIterable<E>(count, generator);
+  }
+
   /**
    * Returns an [Iterator] that iterates over this [Iterable] object.
    */
@@ -588,3 +592,35 @@ class SkipWhileIterator<E> extends Iterator<E> {
 
   E get current => _iterator.current;
 }
+
+
+typedef E _Generator<E>(int index);
+
+class _GeneratorIterable<E> extends Iterable<E> {
+  final int _count;
+  final _Generator<E> _generator;
+  _GeneratorIterable(this._count, this._generator);
+  Iterator<E> get iterator => new _GeneratorIterator(_count, _generator);
+}
+
+class _GeneratorIterator<E> implements Iterator<E> {
+  final int _count;
+  final _Generator<E> _generator;
+  int _index = 0;
+  E _current;
+
+  _GeneratorIterator(this._count, this._generator);
+
+  bool moveNext() {
+    if (_index < _count) {
+      _current = _generator(_index);
+      _index++;
+      return true;
+    } else {
+      _current = null;
+      return false;
+    }
+  }
+
+  E get current => _current;
+}