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\section*{Homework 1}+ −
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\item {\bf (Optional)} If you want to look at code presented in the lectures, install the + −
Scala programming language available (for free) from+ −
\begin{center}+ −
\url{http://www.scala-lang.org}+ −
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\item {\bf (Optional)} Have a look at the crawler programs. + −
Can you find a usage for them in your daily programming life?+ −
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\item In the context of the course, what is meant by the term \emph{language}?+ −
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\item Give the definition for regular expressions. What is the meaning of a + −
regular expression?+ −
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\item Assume the concatenation operation of two strings is written as $s_1 @ s_2$. + −
Define the operation of \emph{concatenating} two sets of strings.+ −
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\item How is the power of a language defined? (Hint: There are two rules, one for $\_\!\_^0$ and+ −
one for $\_\!\_^{n+1}$.)+ −
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\item Given the regular expressions $r_1 = \epsilon$ and $r_2 = \varnothing$ and $r_3 = a$.+ −
How many strings can the regular expressions $r_1^*$, $r_2^*$ and $r_3^*$ each match?+ −
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\end{document}+ −
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