66 \item Parser combinators can directly be given a string as |
66 \item Parser combinators can directly be given a string as |
67 input, without the need of a lexer. What are the |
67 input, without the need of a lexer. What are the |
68 advantages to first lex a string and then feed a |
68 advantages to first lex a string and then feed a |
69 sequence of tokens as input to the parser? |
69 sequence of tokens as input to the parser? |
70 |
70 |
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71 \item The injection function for sequence regular expressions is defined |
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72 by three clauses: |
71 |
73 |
72 |
74 \begin{center} |
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75 \begin{tabular}{l@{\hspace{1mm}}c@{\hspace{1mm}}l} |
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76 $\inj\,(r_1 \cdot r_2)\,c\,\,Seq(v_1,v_2)$ & $\dn$ & $Seq(\inj\,r_1\,c\,v_1,v_2)$\\ |
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77 $\inj\,(r_1 \cdot r_2)\,c\,\,\Left(Seq(v_1,v_2))$ & $\dn$ & $Seq(\inj\,r_1\,c\,v_1,v_2)$\\ |
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78 $\inj\,(r_1 \cdot r_2)\,c\,\,Right(v)$ & $\dn$ & $Seq(\textit{mkeps}(r_1),\inj\,r_2\,c\,v)$\\ |
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79 \end{tabular} |
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80 \end{center} |
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81 |
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82 Explain why there are three cases in the injection function for sequence |
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83 regular expressions. |
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84 |
73 \item \POSTSCRIPT |
85 \item \POSTSCRIPT |
74 \end{enumerate} |
86 \end{enumerate} |
75 |
87 |
76 \end{document} |
88 \end{document} |
77 |
89 |