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118 Let $r_1$ be the regular expression $a\cdot a\cdot a$ and $r_2$ be $(a^{\{19,19\}}) \cdot (a^?)$. |
118 Let $r_1$ be the regular expression $a\cdot a\cdot a$ and $r_2$ be $(a^{\{19,19\}}) \cdot (a^?)$. |
119 Decide whether the following three strings consisting of $a$s only can be matched by $(r_1^+)^+$. |
119 Decide whether the following three strings consisting of $a$s only can be matched by $(r_1^+)^+$. |
120 Similarly test them with $(r_2^+)^+$. Again answer in all six cases with yes or no. \medskip |
120 Similarly test them with $(r_2^+)^+$. Again answer in all six cases with yes or no. \medskip |
121 |
121 |
122 \noindent |
122 \noindent |
123 These are strings entirely made up of $a$s. Be careful when |
123 These are strings are meant to be entirely made up of $a$s. Be careful when |
124 copy-and-pasting the strings so as to not forgetting any $a$ and to not introducing any |
124 copy-and-pasting the strings so as to not forgetting any $a$ and to not introducing any |
125 other character. |
125 other character. |
126 |
126 |
127 \begin{enumerate} |
127 \begin{enumerate} |
128 \item $"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\\ |
128 \item $"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\\ |