# HG changeset patch
# User Christian Urban <urbanc@in.tum.de>
# Date 1573082839 0
# Node ID 1ee523c4f09891922fa4f05cf4dd6d2fb504e1cc
# Parent  c6c79d21f8a8ea5c1cc530f4885bcef2ddc709c6
update

diff -r c6c79d21f8a8 -r 1ee523c4f098 coursework/cw03.pdf
Binary file coursework/cw03.pdf has changed
diff -r c6c79d21f8a8 -r 1ee523c4f098 coursework/cw03.tex
--- a/coursework/cw03.tex	Wed Nov 06 23:17:05 2019 +0000
+++ b/coursework/cw03.tex	Wed Nov 06 23:27:19 2019 +0000
@@ -46,12 +46,13 @@
 
 \subsection*{Question 2}
 
-You should implement a parser for the WHILE language using
-parser combinators. Be careful that the parser takes as input
-a stream, or list, of tokens generated by the tokenizer from
-the previous coursework. For this you might want to filter out 
-whitespaces and comments. Your parser should be able to handle
-the WHILE programs in Figures~\ref{fib} and \ref{loop}.
+You should implement a parser for the WHILE language using parser
+combinators. Be careful that the parser takes as input a stream, or
+list, of tokens generated by the tokenizer from the previous
+coursework. For this you might want to filter out whitespaces and
+comments. Your parser should be able to handle the WHILE programs in
+Figures~\ref{fib}, \ref{loop} and \ref{primes} (if your lexer cannot
+deal with comments you can delete them from the prime number program).
 In addition give the parse tree for the statement:
 
 \begin{lstlisting}[language=While,numbers=none]
@@ -118,6 +119,8 @@
 evaluates to \pcode{true}, otherwise the else-branch.
 Loops should be run as long as the boolean is \pcode{true}.
 
+
+
 Give some time measurements for your interpreter
 and the loop program in Figure~\ref{loop}. For example
 how long does your interpreter take when \pcode{start}
@@ -126,20 +129,21 @@
 1 Minute?
 
 \begin{figure}[p]
-\begin{center}
-\mbox{\lstinputlisting[language=while]{../progs/fib.while}}
-\end{center}
+\lstinputlisting[language=while,xleftmargin=20mm]{../progs/fib.while}
 \caption{Fibonacci program in the WHILE language.\label{fib}}
 \end{figure}
 
 \begin{figure}[p]
-\begin{center}
-\mbox{\lstinputlisting[language=while]{../progs/loops.while}}
-\end{center}
+\lstinputlisting[language=while,xleftmargin=20mm]{../progs/loops.while}
 \caption{The three-nested-loops program in the WHILE language. 
 Usually used for timing measurements.\label{loop}}
 \end{figure}
 
+\begin{figure}[p]
+\lstinputlisting[language=while,xleftmargin=0mm]{../progs/primes.while}
+\caption{Prime number program.\label{primes}}
+\end{figure}
+
 \end{document}
 
 %%% Local Variables: 
diff -r c6c79d21f8a8 -r 1ee523c4f098 progs/comb2.scala
--- a/progs/comb2.scala	Wed Nov 06 23:17:05 2019 +0000
+++ b/progs/comb2.scala	Wed Nov 06 23:27:19 2019 +0000
@@ -115,10 +115,10 @@
 
 // boolean expressions with some simple nesting
 lazy val BExp: Parser[String, BExp] = 
-   (AExp ~ "==" ~ AExp) ==> { case x ~ y ~ z => Bop("==", x, z): BExp } || 
-   (AExp ~ "!=" ~ AExp) ==> { case x ~ y ~ z => Bop("!=", x, z): BExp } || 
-   (AExp ~ "<" ~ AExp) ==> { case x ~ y ~ z => Bop("<", x, z): BExp } || 
-   (AExp ~ ">" ~ AExp) ==> { case x ~ y ~ z => Bop(">", x, z): BExp } ||
+   (AExp ~ "==" ~ AExp) ==> { case x ~ _ ~ z => Bop("==", x, z): BExp } || 
+   (AExp ~ "!=" ~ AExp) ==> { case x ~ _ ~ z => Bop("!=", x, z): BExp } || 
+   (AExp ~ "<" ~ AExp) ==> { case x ~ _ ~ z => Bop("<", x, z): BExp } || 
+   (AExp ~ ">" ~ AExp) ==> { case x ~ _ ~ z => Bop(">", x, z): BExp } ||
    ("(" ~ BExp ~ ")" ~ "&&" ~ BExp) ==> { case x ~ y ~ z ~ u ~ v => And(y, v): BExp } ||
    ("(" ~ BExp ~ ")" ~ "||" ~ BExp) ==> { case x ~ y ~ z ~ u ~ v => Or(y, v): BExp } ||
    ("true" ==> (_ => True: BExp )) ||