public function addClass(&$class)
    {
        if (isset($this->_classes[$class->name()])) {
            $phpdoctor =& $this->_root->phpdoctor();
            echo "\n";
            $phpdoctor->warning('Found class '.$class->name().' again, overwriting previous version');
        }
        $this->_classes[$class->name()] =& $class;
    }