public function isMdAsciiPunct($c) {
        $code = ord($c);
        if(
            ( $code >= 0x21 /* ! */  && $code <= 0x2F /* / */) ||
            ( $code >= 0x3A /* : */  && $code <= 0x40 /* @ */) ||
            ( $code >= 0x5B /* [ */  && $code <= 0x60 /* ` */) ||
            ( $code >= 0x7B /* { */  && $code <= 0x7E /* ~ */)
        ) return true;
        return false;
    }