Better documentation on Sets and Maps, and more.

sdk/lib/collection/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].
+ *
+ * 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, trasnitive, and consistent over time), and that `hashCode`

[floitsch, 2013/06/06 14:00:53]

transitive

[Lasse Reichstein Nielsen, 2013/06/10 05:48:50]

But I changed that! Really!
Grumble!

+ * must be the same for objects that are considered equal by `==`.
+ *
+ * The map allows `null` as a key.

[floitsch, 2013/06/06 14:00:53]

Should we add that the equivalence relationship does not work for doubles if
"NaN" is used?

[Lasse Reichstein Nielsen, 2013/06/10 05:48:50]

That is a property of doubles, which should be noted on the double type:
"doesn't play well with hash maps".

+ */
 class HashMap<K, V> implements Map<K, V> {
   external HashMap();
 
   factory HashMap.from(Map<K, V> other) {
     return new HashMap<K, V>()..addAll(other);
   }
 
   external int get length;
   external bool get isEmpty;
   external bool get isNotEmpty;
@@ skipping 11 matching lines @@
 
   external V putIfAbsent(K key, V ifAbsent());
 
   external V remove(K key);
   external void clear();
 
   external void forEach(void action(K key, V value));
 
   String toString() => Maps.mapToString(this);
 }