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16 \begin{enumerate} |
16 \begin{enumerate} |
17 \item Why is every finite set of strings a regular language? |
17 \item Why is every finite set of strings a regular language? |
18 |
18 |
19 \item What is the language recognised by the regular expressions $(\varnothing^*)^*$. |
19 \item What is the language recognised by the regular expressions $(\varnothing^*)^*$. |
20 |
20 |
21 \item If a regular expression $r$ does not contain any occurrence of $\varnothing$ |
21 \item If a regular expression $r$ does not contain any occurrence of $\varnothing$, |
22 is it possible for $L(r)$ to be empty? |
22 is it possible for $L(r)$ to be empty? |
23 |
23 |
24 \item Assume that $s^{-1}$ stands for the operation of reversing a |
24 \item Assume that $s^{-1}$ stands for the operation of reversing a |
25 string $s$. Given the following \emph{reversing} function on regular |
25 string $s$. Given the following \emph{reversing} function on regular |
26 expressions |
26 expressions |