Add fromIterable(s) constructors in SplayTreeMap and LinkedHashMap.

sdk/lib/collection/linked_hash_map.dart

 // Copyright (c) 2013, 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.
 
 part of dart.collection;
 
 /**
  * A hash-table based implementation of [Map].
  *
  * Keys insertion order is remembered, and keys are iterated in insertion order.
  * Values are iterated in their corresponding key's order.
  *
  * The keys of a `HashMap` must have consistent [Object.operator==]
  * and [Object.hashCode] implementations. This means that the `==` operator
  * must define a stable equivalence relation on the keys (reflexive,
  * anti-symmetric, transitive, and consistent over time), and that `hashCode`
  * must be the same for objects that are considered equal by `==`.
  *
  * The map allows `null` as a key.
  */
 class LinkedHashMap<K, V> implements Map<K, V> {
   external LinkedHashMap();
 
+  static _id(x) => x;
+
   factory LinkedHashMap.from(Map<K, V> other) {
     return new LinkedHashMap<K, V>()..addAll(other);
   }
 
+  factory LinkedHashMap.fromIterable(Iterable iterable,
+      {K key(element), V value(element)}) {
+
+    LinkedHashMap<K, V> map = new LinkedHashMap<K, V>();

[floitsch, 2013/06/27 15:21:38]

We start to have too much code-duplication.
Let's move these functions out and share them.

_id(x) => x;
// (missing types, documentation, ...)
_fillMapWithMappedIterable(map, iterable, key, element) { ... }
_fillMapWithIterables(map, keys, values) { ... }

I would put it in maps.dart.

[zarah, 2013/06/27 15:58:52]

Agree! Done.

+
+    if (key == null) key = _id;
+    if (value == null) value = _id;
+
+    for (var element in iterable) {
+      map[key(element)] = value(element);
+    }
+
+    return map;
+  }
+
+  factory LinkedHashMap.fromIterables(Iterable<K> keys, Iterable<V> values) {
+    LinkedHashMap<K, V> map = new LinkedHashMap<K, V>();
+
+    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.");
+    }
+
+    return map;
+  }
+
   external bool containsKey(Object key);
 
   external bool containsValue(Object value);
 
   external void addAll(Map<K, V> other);
 
   external V operator [](Object key);
 
   external void operator []=(K key, V value);
 
@@ skipping 11 matching lines @@
   external Iterable<V> get values;
 
   external int get length;
 
   external bool get isEmpty;
 
   external bool get isNotEmpty;
 
   String toString() => Maps.mapToString(this);
 }