Add fromIterable(s) constructors in SplayTreeMap and LinkedHashMap.

sdk/lib/collection/splay_tree.dart

Index: sdk/lib/collection/splay_tree.dart
diff --git a/sdk/lib/collection/splay_tree.dart b/sdk/lib/collection/splay_tree.dart
index 84e61e10d4386e01a8e85514a643374b22ad59d9..a49164ff87b86d282cff005818efa1490eaa2ebb 100644
--- a/sdk/lib/collection/splay_tree.dart
+++ b/sdk/lib/collection/splay_tree.dart
@@ -245,12 +245,51 @@ class SplayTreeMap<K, V> extends _SplayTree<K> implements Map<K, V> {
   // checked mode. http://dartbug.com/7733
   Function /* Comparator<K> */_comparator;
 
+  static _id(x) => x;
+
   SplayTreeMap([int compare(K key1, K key2)])
       : _comparator = (compare == null) ? Comparable.compare : compare;
 
   factory SplayTreeMap.from(Map<K, V> other, [int compare(K key1, K key2)]) =>
       new SplayTreeMap(compare)..addAll(other);
 
+  factory SplayTreeMap.fromIterable(Iterable iterable,
+      {int compare(K key1, K key2), K key(element), V value(element)}) {

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

move compare last. It doesn't make any semantic difference, but for
documentation and consistency I prefer it there.

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

Done.

+    SplayTreeMap<K, V> map = new SplayTreeMap<K, V>(compare);
+
+    if (key == null) key = _id;
+    if (value == null) value = _id;
+
+    for (var element in iterable) {
+      map[key(element)] = value(element);
+    }
+
+    return map;
+  }
+
+  factory SplayTreeMap.fromIterables(Iterable<K> keys, Iterable<V> values,
+      [int compare(K key1, K key2)]) {
+    SplayTreeMap<K, V> map = new SplayTreeMap<K, V>(compare);
+
+    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;
+  }
+
   int _compare(K key1, K key2) => _comparator(key1, key2);
 
   SplayTreeMap._internal();