27 regular expression?

    27 regular expression?

    28 

    28 

    29 \item Assume the concatenation operation of two strings is written as $s_1 @ s_2$. 

    29 \item Assume the concatenation operation of two strings is written as $s_1 @ s_2$. 

    30 Define the operation  of \emph{concatenating} two sets of strings.

    30 Define the operation  of \emph{concatenating} two sets of strings.

    31 

    31 

    32 \item How is the power of a language defined? (Hint: There are two rules, one for $\_\!\_^0$ and

    35 \item How is the power of a language defined? (Hint: There are two rules, one for $\_\!\_^0$ and

    33 one for $\_\!\_^{n+1}$.)

    36 one for $\_\!\_^{n+1}$.)

    34 

    37 

    35 

    38 

    36 \end{enumerate}

    39 \end{enumerate}