Move toString() to collection classes.

sdk/lib/collection/maps.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.
 
 part of dart.collection;
 
 /*
  * Helper class which implements complex [Map] operations
  * in term of basic ones ([Map.keys], [Map.operator []],
  * [Map.operator []=] and [Map.remove].)  Not all methods are
@@ skipping 41 matching lines @@
 
   static Iterable getValues(Map map) {
     return map.keys.map((key) => map[key]);
   }
 
   static int length(Map map) => map.keys.length;
 
   static bool isEmpty(Map map) => map.keys.isEmpty;
 
   static bool isNotEmpty(Map map) => map.keys.isNotEmpty;
-
+  

[Lasse Reichstein Nielsen, 2013/07/09 06:15:44]

Extra spaces added.

[zarah, 2013/07/09 08:20:54]

Done.

+  // A list to identify cyclic maps during toString() calls. 
+  static List _toStringList = new List();
+  
   /**
    * Returns a string representing the specified map. The returned string
    * looks like this: [:'{key0: value0, key1: value1, ... keyN: valueN}':].
    * The value returned by its [toString] method is used to represent each
    * key or value.
    *
    * If the map collection contains a reference to itself, either
    * directly as a key or value, or indirectly through other collections
    * or maps, the contained reference is rendered as [:'{...}':]. This
    * prevents the infinite regress that would otherwise occur. So, for example,
    * calling this method on a map whose sole entry maps the string key 'me'
    * to a reference to the map would return [:'{me: {...}}':].
    *
    * A typical implementation of a map's [toString] method will
    * simply return the results of this method applied to the collection.
    */
-  static String mapToString(Map m) => ToString.mapToString(m);
+  static String mapToString(Map m) {
+    for (int i = 0; i < _toStringList.length; i++) {
+      if (identical(_toStringList[i], m)) { return '{...}'; }
+    }
+    
+    var result = new StringBuffer();
+    try {
+      _toStringList.add(m);      
+      result.write('{');
+      bool first = true;
+      m.forEach((k, v) {
+        if(!first) {
+          result.write(', ');
+        }
+        first = false;

[Lasse Reichstein Nielsen, 2013/07/09 06:15:44]

Consider moving this assignment into the condition.

I can't guarantee it will be faster, though.

[zarah, 2013/07/09 08:20:54]

Not done, as discussed.

+        result.write(k);
+        result.write(': ');
+        result.write(v);
+      });
+      result.write('}');
+    } finally {
+      assert(identical(_toStringList.last, m));
+      _toStringList.removeLast();       
+    }
+
+    return result.toString();
+  }
 
   static _id(x) => x;
 
   /**
    * Fills a map with key/value pairs computed from [iterable].
    *
    * This method is used by Map classes in the named constructor fromIterable.
    */
   static void _fillMapWithMappedIterable(Map map, Iterable iterable,
                                          key(element), value(element)) {
@@ skipping 22 matching lines @@
       map[keyIterator.current] = valueIterator.current;
       hasNextKey = keyIterator.moveNext();
       hasNextValue = valueIterator.moveNext();
     }
 
     if (hasNextKey || hasNextValue) {
       throw new ArgumentError("Iterables do not have same length.");
     }
   }
 }