Wrote functions to convert collections and maps to strings and invoked

corelib/src/implementation/maps.dart

-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// 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.
 
 /*
  * Helper class which implements complex [Map] operations
  * in term of basic ones ([Map.getKeys], [Map.operator []],
  * [Map.operator []=] and [Map.remove].)  Not all methods are
  * necessary to implement each particular operation.
  */
 class Maps {
@@ skipping 40 matching lines @@
     final result = [];
     for (final k in map.getKeys()) {
       result.add(map[k]);
     }
     return result;
   }
 
   static int length(Map map) => map.getKeys().length;
 
   static bool isEmpty(Map map) => length(map) == 0;
+
+  /**
+   * 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) {
+    var result = new StringBuffer();
+    _emitMap(m, result, new List());
+    return result.toString();
+  }
+
+  /**
+   * Appends a string representing the specified map to the specified
+   * string buffer. The string is formatted as per [mapToString].
+   * The [:visiting:] list contains references to all of the enclosing
+   * collections and maps (which are currently in the process of being
+   * emitted into [:result:]). The [:visiting:] parameter allows this method
+   * to generate a [:'[...]':] or [:'{...}':] where required. In other words,
+   * it allows this method and [_emitCollection] to identify recursive maps
+   * and collections.
+   */
+  static void _emitMap(Map m, StringBuffer result, List visiting) {
+    visiting.add(m);
+    result.add('{');
+
+    bool first = true;
+    m.forEach((k, v) {
+      if (!first) {
+        result.add(', ');
+      }
+      first = false;
+      Collections._emitObject(k, result, visiting);
+      result.add(': ');
+      Collections._emitObject(v, result, visiting);
+    });
+
+    result.add('}');
+    visiting.removeLast();
+  }
 }