
diff -r 80c691a4caab -r 7a0735db4788 wsheets/wsh01.tex
--- a/wsheets/wsh01.tex	Thu Nov 10 20:10:20 2022 +0000
+++ b/wsheets/wsh01.tex	Mon Nov 14 12:04:21 2022 +0000
@@ -28,8 +28,8 @@
 \section*{Scala Worksheet 1}
 
 Please install Scala on your work-machine: You should have
-Scala up and running, and also an IDE that allows you to
-access the Scala REPL. Some instructions are given at
+Scala up and running after this week, and also have an IDE that allows you to
+access the Scala REPL. Some installation instructions are given at
 
 \begin{center}
 \url{https://www.scala-lang.org/download/2.13.10.html}
@@ -53,14 +53,14 @@
 
 \begin{itemize}
 \item[0)] (if needed) \texttt{sudo apt-get remove scala-library scala}
-\item[1)] {\fontsize{8.5}{8.5}\selectfont\texttt{sudo wget https://downloads.lightbend.com/scala/2.13.10/scala-2.13.7.deb}}
+\item[1)] {\fontsize{8.5}{8.5}\selectfont\texttt{sudo wget https://downloads.lightbend.com/scala/2.13.10/scala-2.13.10.deb}}
 \item[2)] \texttt{sudo dpkg -i scala-2.13.10.deb}  
 \end{itemize}
 
 \noindent
 Other Linux distros: \texttt{sudo apt-get scala}\bigskip
 
-\noindent In the end you should have something running like
+\noindent In the end you should have something running like in your terminal/shell:
 
 \begin{lstlisting}[language={},numbers=none,basicstyle=\ttfamily\small]
 $ scala
@@ -70,12 +70,20 @@
 scala>
 \end{lstlisting}%$
 
+\noindent
+If you want to use VS Code or Codium, you might want to also look into setting up
+a key-shortcut for ``Run‐Selected‐Text‐In‐Active‐Terminal'' and also set up
+syntax highlighting. Have a look at the Scala handout uploaded to KEATS for information.\bigskip
+
+\noindent
+Make sure you have checked out the template files for the Scala CWs and registered the
+Github repository on KEATS. See whether you receive a test report when pushing some code.
 \newpage
 
 \subsection*{Task 1}
 
-`Play' with the Scala REPL and try out the following querries. Observe
-what Scala responds.
+`Play' with the Scala REPL and try out the following queries. Observe
+what Scala responds. Does it make sense?
 
 \begin{lstlisting}[numbers=none]
 scala> 2 + 2
@@ -98,22 +106,86 @@
 
 \subsection*{Task 2 (Vals)}
 
+Type in the value declarations below and observe Scala's responses. Explain what
+is printed as the value for \texttt{x} in the last line. Is \texttt{z} re-assigned
+in the 4th line?
+
+\begin{lstlisting}[numbers=none]
 scala> val z = 42
 scala> z = z + 1
+scala> val x = 2 * z
 scala> val z = 466
+scala> println(x)
+\end{lstlisting}
 
-\subsection*{Task 3}
+
+\subsection*{Task 3 (Strings)}
+
+Get familiar with constructing strings and printing strings
+(i.e.~\texttt{println}, \texttt{mkString}, \texttt{toString}, \ldots)
 
 \begin{lstlisting}[numbers=none]
 scala> println("Hello " ++ "World")
-scala> 
+scala> List(1,2,3,4).mkString("\n")
+scala> List(1,2,3,4).mkString("(", "|", ")")
 \end{lstlisting}
 
+\subsection*{Task 4 (Functions)}
+
+Write a function \texttt{miles2meters} taking an integer as argument
+and generating an integer. You can assume that one mile is 1609 meters.
+Remember that functions in Scala do not use the \texttt{return}-keyword.
+
+\subsection*{Task 5 (If-Conditions)}
+
+Make sure you understand if-conditions in Scala: They are
+\emph{expressions}, meaning they need to calculate a result. For
+example an \texttt{if} without an else-branch is nearly always
+\emph{not} what you intend to write (because you are not meant to
+change any ``state'' outside the expression). Also, remember the quirks
+in Scala with if-conditions needing parentheses and there is no
+\texttt{then}-keyword.
+
 \begin{lstlisting}[numbers=none]
-scala> println("Hello " ++ "World")
-scala> 
+scala> val s1 = "foo"
+scala> val s2 = "bar"
+scala  val s3 = "foobar"
+scala> if (s1 == s2) print("equal") else print("unequal")
+scala> if (s1 ++ s2 == s3) print("equal") else print("unequal")
 \end{lstlisting}
 
+\subsection*{Task 6 (For-Comprehensions, Harder)}
+
+Write \texttt{for}-comprehensions that enumerate all triples containing the numbers 1 - 5. That is,
+print the list
+
+\[
+\texttt{(1,1,1)}, \texttt{(2,1,1)}, \texttt{(3,1,1)} \;\ldots\; \texttt{(5,5,5)}
+\]
+
+\noindent
+Modify the \texttt{for}-comprehensions such that only triples are
+printed where the sum is divisible by 3.  Then sort the list according
+to the middle element (for this use \texttt{sortBy}).
+
+\subsection*{Task 7 (Recursion, Advanced /Hard)}
+
+Write a pretty print function for lists of integers which
+``condenses'' elements in the list, meaning if there is a number
+several times in a row, then print out \mbox{\texttt{n x e}}, where
+\texttt{n} is the number of repetitions and \texttt{e} is the
+number. For example
+
+\begin{lstlisting}[numbers=none]
+  List(1,1,1,2,3,3)    =>   List(3 x 1, 2, 2 x 3)
+  List(1,2,3,4,4,4)    =>   List(1, 2, 3, 3 x 4)
+  List(1,1,1,1,1,1)    =>   List(6 x 1)
+  List(1,1,1,2,1,1)    =>   List(3 x 1, 2, 2 x 1)
+\end{lstlisting}
+
+You might like to define a separate function that first counts the occurences
+for each element and returns a list of (Int, Int)-pairs .
+
 \end{document}
 
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