Add fromIterable(s) constructors in SplayTreeMap and LinkedHashMap.

sdk/lib/collection/linked_hash_map.dart

Index: sdk/lib/collection/linked_hash_map.dart
diff --git a/sdk/lib/collection/linked_hash_map.dart b/sdk/lib/collection/linked_hash_map.dart
index 3082ce0881a8b99736968e9a37839bb375c80bbb..12695d43073b8c89ff8a80eeafa573d4c20d7b60 100644
--- a/sdk/lib/collection/linked_hash_map.dart
+++ b/sdk/lib/collection/linked_hash_map.dart
@@ -21,10 +21,49 @@ part of dart.collection;
 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);