Add a basic YAML processor. Much of the language is still unimplemented.

utils/yaml/deep_equals.dart

+// Copyright (c) 2012, 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.
+
+#library("deep_equals");
+
+/**
+ * Returns whether two objects are structurally equivalent. This considers NaN
+ * values to be equivalent. It also handles self-referential structures.
+ */
+bool deepEquals(obj1, obj2, [List parents1, List parents2]) {
+  if (obj1 === obj2) return true;
+  if (parents1 == null) {
+    parents1 = [];
+    parents2 = [];
+  }
+
+  // parents1 and parents2 are guaranteed to be the same size.
+  for (var i = 0; i < parents1.length; i++) {
+    var loop1 = obj1 === parents1[i];
+    var loop2 = obj2 === parents2[i];
+    // If both structures loop in the same place, they're equal at that point in
+    // the structure. If one loops and the other doesn't, they're not equal.
+    if (loop1 && loop2) return true;
+    if (loop1 || loop2) return false;
+  }
+
+  parents1.add(obj1);
+  parents2.add(obj2);
+  try {
+    if (obj1 is List && obj2 is List) {
+      return _listEquals(obj1, obj2, parents1, parents2);
+    } else if (obj1 is Map && obj2 is Map) {
+      return _mapEquals(obj1, obj2, parents1, parents2);
+    } else if (obj1 is double && obj2 is double) {
+      return _doubleEquals(obj1, obj2);
+    } else {
+      return obj1 == obj2;
+    }
+  } finally {
+    parents1.removeLast();
+    parents2.removeLast();
+  }
+}
+
+/** Returns whether [list1] and [list2] are structurally equal. */
+bool _listEquals(List list1, List list2, List parents1, List parents2) {
+  if (list1.length != list2.length) return false;
+
+  for (var i = 0; i < list1.length; i++) {
+    if (!deepEquals(list1[i], list2[i], parents1, parents2)) return false;
+  }
+
+  return true;
+}
+
+/** Returns whether [map1] and [map2] are structurally equal. */
+bool _mapEquals(Map map1, Map map2, List parents1, List parents2) {
+  if (map1.length != map2.length) return false;
+
+  for (var key in map1.getKeys()) {
+    if (!map2.containsKey(key)) return false;
+    if (!deepEquals(map1[key], map2[key], parents1, parents2)) return false;
+  }
+
+  return true;
+}
+
+/**
+ * Returns whether two doubles are equivalent. This differs from `d1 == d2` in
+ * that it considers NaN to be equal to itself.
+ */
+bool _doubleEquals(double d1, double d2) {
+  if (d1.isNaN() && d2.isNaN()) return true;
+  return d1 == d2;
+}