Lisphp_Scope::_symbol PHP Method

    protected static function _symbol($symbol)
    {
        if ($symbol instanceof Lisphp_Symbol) {
            return $symbol->symbol;
        } else {
            if (is_string($symbol)) {
                return $symbol;
            }
        }
        $type = is_object($symbol) ? get_class($symbol) : gettype($symbol);
        throw new UnexpectedValueException("expected symbol, but {$type} given");
    }