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21 and returns an integer. The function should satisfy the following property: |
21 and returns an integer. The function should satisfy the following property: |
22 \begin{center} |
22 \begin{center} |
23 $zeroable(r)$ \;if and only if\; $L(r) = \varnothing$ |
23 $zeroable(r)$ \;if and only if\; $L(r) = \varnothing$ |
24 \end{center} |
24 \end{center} |
25 |
25 |
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26 \item Define the tokens and regular expressions for a language |
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27 consisting of numbers, left-parenthesis (, right-parenthesis ), |
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28 identifiers and the operations $+$, $-$ and $*$. Can the following strings |
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29 in this language be lexed? |
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30 |
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31 \begin{itemize} |
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32 \item \texttt{"}$(a + 3) * b$\texttt{"} |
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33 \item \texttt{"}$)()++ -33$\texttt{"} |
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34 \item \texttt{"}$(a / 3) * 3$\texttt{"} |
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35 \end{itemize} |
26 \end{enumerate} |
36 \end{enumerate} |
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37 |
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38 In case they can, can you give the corresponding token sequences. |
27 |
39 |
28 \end{document} |
40 \end{document} |
29 |
41 |
30 %%% Local Variables: |
42 %%% Local Variables: |
31 %%% mode: latex |
43 %%% mode: latex |