Add fromIterable(s) constructors in SplayTreeMap and LinkedHashMap.

sdk/lib/collection/maps.dart

Index: sdk/lib/collection/maps.dart
diff --git a/sdk/lib/collection/maps.dart b/sdk/lib/collection/maps.dart
index bd7d755a6343139193bc5f673e869717b421a59b..03448fa54f07aba7cd4477f6ff74cec239a940e6 100644
--- a/sdk/lib/collection/maps.dart
+++ b/sdk/lib/collection/maps.dart
@@ -77,4 +77,45 @@ class Maps {
    * simply return the results of this method applied to the collection.
    */
   static String mapToString(Map m) => ToString.mapToString(m);
+
+  static _id(x) => x;
+
+  /**
+   * Helper to fill a map with key/value pairs computed from [iterable].

[floitsch, 2013/06/27 16:04:32]

Fills a map ...

Since it's a private method it cannot be much else than a helper.

[zarah, 2013/06/27 17:00:07]

Done.

+   *
+   * This method is used by Map classes in the named constructor fromIterable.
+   */
+  static void _fillMapWithMappedIterable(Map<K,V> map, Iterable<K> iterable,

[floitsch, 2013/06/27 16:04:32]

Don't use named arguments for internal helper methods. Pass them directly. It's
cheaper.

[zarah, 2013/06/27 17:00:07]

Done.

+                                         {K key(element), V value(element)}) {
+    if (key == null) key = _id;
+    if (value == null) value = _id;
+
+    for (var element in iterable) {
+      map[key(element)] = value(element);
+    }
+  }
+
+  /**
+   * Helper to fill a map by associating the [keys] to [values].
+   *
+   * This method is used by Map classes in the named constructor fromIterables.
+   */
+  static void _fillMapWithIterables(Map<K,V> map, Iterable<K> keys,
+                                    Iterable<V> values) {
+    Iterator<K> keyIterator = keys.iterator;
+    Iterator<V> valueIterator = values.iterator;
+
+    bool hasNextKey = keyIterator.moveNext();
+    bool hasNextValue = valueIterator.moveNext();
+
+    while (hasNextKey && hasNextValue) {
+      map[keyIterator.current] = valueIterator.current;
+      hasNextKey = keyIterator.moveNext();
+      hasNextValue = valueIterator.moveNext();
+    }
+
+    if (hasNextKey || hasNextValue) {
+      throw new ArgumentError("Iterables do not have same length.");
+    }
+  }
 }