33 

    33 

    34 

    34 

    35 \subsection*{Disclaimer\alert}

    35 \subsection*{Disclaimer\alert}

    36 

    36 

    37 It should be understood that the work you submit represents

    37 It should be understood that the work you submit represents

    40 exception is the Scala code from KEATS and the code I showed

    42 exception is the Scala code from KEATS and the code I showed

    41 during the lectures, which you can both freely use. You can

    43 during the lectures, which you can both freely use. You can

    43 %But do not

    45 %But do not

    44 %be tempted to ask Github Copilot for help or do any other

    46 %be tempted to ask Github Copilot for help or do any other

    45 %shenanigans like this!

    47 %shenanigans like this!

    46 

    48 

    47 \subsection*{Task 1}

    49 \subsection*{Task 1}

   102 \item there are semicolons \texttt{;}

   104 \item there are semicolons \texttt{;}

   103 \item whitespaces are either \texttt{" "} (one or more) or \texttt{$\backslash$n} or

   105 \item whitespaces are either \texttt{" "} (one or more) or \texttt{$\backslash$n} or

   104   \texttt{$\backslash$t} or \texttt{$\backslash$r}

   106   \texttt{$\backslash$t} or \texttt{$\backslash$r}

   105 \item identifiers are letters followed by underscores \texttt{\_\!\_}, letters

   107 \item identifiers are letters followed by underscores \texttt{\_\!\_}, letters

   106   or digits  

   108   or digits  

   108 a regular expression that can recognise \pcode{0}, but not numbers 

   110 a regular expression that can recognise \pcode{0}, but not numbers 

   109 with leading zeroes, such as \pcode{001}

   111 with leading zeroes, such as \pcode{001}

   110 \item strings are enclosed by double quotes, like \texttt{"\ldots"}, and consisting of

   112 \item strings are enclosed by double quotes, like \texttt{"\ldots"}, and consisting of

   111   symbols, digits, parentheses, whitespaces and \texttt{$\backslash$n} (note the latter is not the escaped version but \texttt{$\backslash$} followed by \texttt{n}, otherwise we would not be able to indicate in our strings when to write a newline).

   113   symbols, digits, parentheses, whitespaces and \texttt{$\backslash$n} (note the latter is not the escaped version but \texttt{$\backslash$} followed by \texttt{n}, otherwise we would not be able to indicate in our strings when to write a newline).

   112 \item comments start with \texttt{//} and contain symbols, spaces, parentheses and digits until the end-of-the-line markers

   114 \item comments start with \texttt{//} and contain symbols, spaces, parentheses and digits until the end-of-the-line markers

   150 

   152 

   151 Implement the Sulzmann \& Lu lexer from the lectures. For

   153 Implement the Sulzmann \& Lu lexer from the lectures. For

   152 this you need to implement the functions $nullable$ and $der$

   154 this you need to implement the functions $nullable$ and $der$

   153 (you can use your code from CW~1), as well as $mkeps$ and

   155 (you can use your code from CW~1), as well as $mkeps$ and

   154 $inj$. These functions need to be appropriately extended for

   156 $inj$. These functions need to be appropriately extended for

   156 you need to create are:

   158 you need to create are:

   157 

   159 

   158 

   160 

   159 \begin{center}

   161 \begin{center}

   160 \begin{tabular}{@ {}l@ {\hspace{2mm}}c@ {\hspace{2mm}}l@ {}}

   162 \begin{tabular}{@ {}l@ {\hspace{2mm}}c@ {\hspace{2mm}}l@ {}}

   193 allows you to extract easily the tokens from a value in the next

   195 allows you to extract easily the tokens from a value in the next

   194 task).\medskip 

   196 task).\medskip 

   195 

   197 

   196 \noindent

   198 \noindent

   197 Finally make that the function \texttt{lexing\_simp} generates

   199 Finally make that the function \texttt{lexing\_simp} generates

   199 

   201 

   200 \begin{center}

   202 \begin{center}

   201 \code{"read n;"}

   203 \code{"read n;"}

   202 \end{center} 

   204 \end{center} 

   203 

   205 

   212 

   214 

   213 

   215 

   214 

   216 

   215 \subsection*{Task 3}

   217 \subsection*{Task 3}

   216 

   218 

   218 each derivation step and rectifies the computed values after each

   220 each derivation step and rectifies the computed values after each

   219 injection. Use this lexer to tokenise the six WHILE programs

   221 injection. Use this lexer to tokenise the six WHILE programs

   220 in the \texttt{examples} directory. Make sure that the \texttt{tokenise}

   222 in the \texttt{examples} directory. Make sure that the \texttt{tokenise}

   221 function filters out whitespaces and comments.\bigskip

   223 function filters out whitespaces and comments.\bigskip

   222 

   224