public function compress()
    {
        $current   = $this->lexer->lookahead['position'];
        $this->lexer->reset();
        $string = '';
        
        while($this->lexer->moveNext() && $this->lexer->lookahead['position'] <= $current) {
            $string .= $this->lexer->lookahead['value'];
        }
        
        return $string;
    }