 			var stream 			: VertexStream 	= _propertyToStream[propertyName];
 			
 			if (!(stream.usage & StreamUsage.WRITE))
-				throw new Error("Unable to write data into vertex stream.");
+				throw new Error('Unable to write data into vertex stream.');
 			
 			var format 			: VertexFormat 	= stream.format;
 			var index			: int			= _index * format.size

			var stream 			: VertexStream	= _propertyToStream[propertyName];
			
			if (!(stream.usage & StreamUsage.READ))
				throw new Error("Unable to read data from vertex stream.");
			
			var format 			: VertexFormat 	= stream.format;
			var index			: int			= _index * format.size


		public function toString() : String
		{
			var str : String	= 'Vertex(index=' + _index;

			for (var field : String in _propertyToStream)
				str += ', ' + field + '=' + getProperty(field);

			str += ')';

			return str;
		}
