[mdv] implement Node.createBinding and Node.createBindings

pkg/mdv/lib/src/list_diff.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.
 
 library mdv.src.list_diff;
 
 import 'dart:math' as math;
 import 'package:observe/observe.dart' show ListChangeRecord;
 
 /**
@@ skipping 20 matching lines @@
 
   // TODO(jmesserly): freeze remove list before handing it out?
   /** The items removed, if any. Otherwise this will be an empty list. */
   List get removed => _removed;
 
   /** The number of items added. */
   int get addedCount => _addedCount;
 
   int get removedCount => _removed.length;
 
+  /** Returns true if the provided index was changed by this operation. */
+  bool changes(key) {
+    // If key isn't an int, or before the index, then it wasn't changed.
+    if (key is! int || key < index) return false;
+
+    // If this was a shift operation, anything after index is changed.
+    if (addedCount != removedCount) return true;
+
+    // Otherwise, anything in the update range was changed.
+    return key < index + addedCount;
+  }
+
   String toString() => '#<$runtimeType index: $index, '
       'removed: $removed, addedCount: $addedCount>';
 }
 
 // Note: This function is *based* on the computation of the Levenshtein
 // "edit" distance. The one change is that "updates" are treated as two
 // edits - not one. With List splices, an update is really a delete
 // followed by an add. By retaining this, we optimize for "keeping" the
 // maximum array items in the original array. For example:
 //
@@ skipping 196 matching lines @@
         oldIndex++;
         break;
     }
   }
 
   if (splice != null) {
     splices.add(splice);
   }
   return splices;
 }