Add min and max to Iterable and Stream.

sdk/lib/collection/collections.dart

Index: sdk/lib/collection/collections.dart
diff --git a/sdk/lib/collection/collections.dart b/sdk/lib/collection/collections.dart
index 230cfaef786c8c4ac60e386e6d1214a3a447a136..4bd1fadb513ce5e84a36fbb51ae347e2db93af69 100644
--- a/sdk/lib/collection/collections.dart
+++ b/sdk/lib/collection/collections.dart
@@ -70,6 +70,32 @@ class Collections {
     return result;
   }
 
+  static dynamic min(Iterable iterable, [int compare(var a, var b)]) {
+    if (compare == null) compare = Comparable.compare;
+    Iterator it = iterable.iterator;
+    if (!it.moveNext()) {
+      return null;

[Anders Johnsen, 2013/01/02 11:04:05]

State error? [].min() -> null?

[Lasse Reichstein Nielsen, 2013/01/02 11:49:33]

It's deliberate. We can argue whether it's the right thing to do :).
What I *really* would want is the interface:
  min([int compare(a,b)], {var ifEmpty})
but until we get both optional positional and named arguments, I'll just default
to null.

+    }
+    var min = it.current;
+    while (it.moveNext()) {
+      if (compare(min, it.current) > 0) min = it.current;
+    }
+    return min;
+  }
+
+  static dynamic max(Iterable iterable, [int compare(var a, var b)]) {
+    if (compare == null) compare = Comparable.compare;
+    Iterator it = iterable.iterator;
+    if (!it.moveNext()) {
+      return null;
+    }
+    var max = it.current;
+    while (it.moveNext()) {
+      if (compare(max, it.current) < 0) max = it.current;
+    }
+    return max;
+  }
+
   static dynamic single(Iterable iterable) {
     Iterator it = iterable.iterator;
     if (!it.moveNext()) throw new StateError("No elements");