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====== Lab ======



===== Lab-01 - Expresii regulate =====



Key insights:
  * more languages than regular expressions
  * we do not know how to write regular expressions for some languages (as a direct consequence of the above)
  * reg.exps. are unambiguous and FINITE language representations


Objectives:
  * Understand what is a language and a regular expression is, and the relation between them;
  * Write several regular expressions for designated languages
  * Identify languages described by some regular expressions (e.g. ?!)

Resources (tentative):
  * http://www.idt.mdh.se/kurser/cd5560/10_01/examination/KOMPENDIER/Regular/kompendium_eng.pdf

=== Exercises ===
**I. What is the regular expression for the following languages:**

  * $math[\Sigma=\{0, 1\}], $math[L=\{011\}]
//Solution:// $math[E=011] \\
//Obs:// By definition the correct expression is $math[E=((01)1)], but we won't write them when not needed and we use a precedence rule to reduce the number of parantheses in regular expressions as much as possible (Kleene Star > Concatenation > Union).
  * $math[\Sigma=\{a, b\}], $math[L=\{a, b\}]
//Solution:// $math[E=a \cup b] \\
//Obs:// By definition the correct expression is $math[E=(a \cup b)], but we can remove parentheses for the same reason as above.
  * $math[\Sigma=\{0, 1\}], $math[L=\{e, 0, 1, 00, 01, 10, 11, 000, ...\}]
//Solution:// $math[E=(0 \cup 1)^{*}] \\
  * $math[\Sigma=\{0, 1\}], $math[L=\{010010101000010, 010010101000011\}]
//Solution:// $math[E=01001010100001(0 \cup 1)] \\
  * $math[\Sigma=\{0, 1\}], $math[L=\{w \in \Sigma^{*} \mid w \text{ ends with } 0\}] \\
//Solution:// $math[E=(0 \cup 1)^{*}0] \\
  * $math[\Sigma=\{0, 1\}], $math[L=\{w \in \Sigma^{*} \mid w=w_101 \lor w=1w_1, w_1 \in \Sigma^{*}\}] \\
//Solution:// $math[E=(0 \cup 1)^{*}01 \cup 1(0 \cup 1)] \\
  * $math[\Sigma=\{x, y\}], $math[L=\{w \in \Sigma^{*} \mid \#_x(w) = 2\}] \\
//Solution:// $math[E=y^{*}xy^{*}xy^{*}] \\
//Obs:// $math[\#_x(w)] denotes number of $math[x] in $math[w].
  * $math[\Sigma=\{a, b\}], $math[L=\{w \in \Sigma^{*} \mid \#_a(w) \,\vdots\, 2\}] \\
//Solution:// $math[E=(b^{*}ab^{*}ab^{*})^{*}] \\
  * $math[\Sigma=\{x, y\}], $math[L=\{w \in \Sigma^{*} \mid \#_x(w) \ge 1\}] \\
//Solution:// $math[E=(x \cup y)^{*}x(x \cup y)^{*}] \\
  * $math[\Sigma=\{a, b, c\}], $math[L=\{w \in \Sigma^{*} \mid \#_a(w) \ge 1 \land \#_c(w) \ge 1\}] \\
//Solution:// $math[E=((a \cup b \cup c)^{*}a(a \cup b \cup c)^{*}b(a \cup b \cup c)^{*}) \cup ((a \cup b \cup c)^{*}b(a \cup b \cup c)^{*}a(a \cup b \cup c)^{*})] \\
  * $math[\Sigma=\{a, b\}], $math[L=\{w \in \Sigma^{*} \mid w \text{ does not contain } ba\}] \\
//Solution:// $math[E=a^{*}b^{*}] \\
  * $math[\Sigma=\{a, b\}], $math[L=\{w \in \Sigma^{*} \mid \#_a(w) + \#_b(w) = 0\}] \\
//Solution:// $math[E=\epsilon] \\
  * $math[\Sigma=\{a, b\}], $math[L=\{w \in \Sigma^{*} \mid \#_a(w) + \#_b(w) < 0\}] \\
//Solution:// $math[E=\emptyset] \\

===== Lab x - JFlex =====

==== Installing JFlex ====

A complete, platform-dependent set of installation instructions can be found [[http://jflex.de/installing.html| here]]

==== The structure of a flex file ====

==== Writing a Hello World project ====

==== Application - parsing lists ====