Add min and max to Iterable and Stream.

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 0f846397285b2dfa8e3cd49d8d1b5fc6d48b1159..4a98650c18ffba6f629ca5d7b9493abbb96a7384 100644
--- a/sdk/lib/core/iterable.dart
+++ b/sdk/lib/core/iterable.dart
@@ -148,6 +148,52 @@ abstract class Iterable<E> {
   }
 
   /**
+   * Find the least element in the iterable.
+   *
+   * Returns null if the iterable is empty.
+   * Otherwise returns an element [:x:] of this [Iterable] so that
+   * [:x:] is not greater than [:y:] (that is, [:compare(x, y) <= 0:]) for all
+   * other elements [:y:] in the iterable.
+   *
+   * The [compare] function must be a proper [Comparator<T>]. If a function is
+   * not provided, [compare] defaults to [Comparable.compare].
+   */
+  T min([int compare(T a, T b)]) {
+    if (compare == null) compare = Comparable.compare;
+    Iterator it = iterator;
+    if (!it.moveNext()) return null;
+    T min = it.current;
+    while (it.moveNext) {
+      T current = it.current;
+      if (compare(min, current) > 0) min = current;
+    }
+    return min;
+  }
+
+  /**
+   * Find the largest element in the iterable.
+   *
+   * Returns null if the iterable is empty.
+   * Otherwise returns an element [:x:] of this [Iterable] so that
+   * [:x:] is not smaller than [:y:] (that is, [:compare(x, y) >= 0:]) for all
+   * other elements [:y:] in the iterable.
+   *
+   * The [compare] function must be a proper [Comparator<T>]. If a function is
+   * not provided, [compare] defaults to [Comparable.compare].
+   */
+  T max([int compare(T a, T b)]) {
+    if (compare == null) compare = Comparable.compare;
+    Iterator it = iterator;
+    if (!it.moveNext()) return null;
+    T max = it.current;
+    while (it.moveNext) {
+      T current = it.current;
+      if (compare(max, current) < 0) max = current;
+    }
+    return max;
+  }
+
+  /**
    * Returns true if there is no element in this collection.
    */
   bool get isEmpty => !iterator.moveNext();