
diff -r 5266495f4aad -r 94117c4f8b67 wsheets/wsh02.tex
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+++ b/wsheets/wsh02.tex	Thu Nov 17 11:34:50 2022 +0000
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+% !TEX program = xelatex
+\documentclass{article}
+\usepackage{../styles/style}
+\usepackage{../styles/langs}
+\usepackage{tikz}
+\usepackage{pgf}
+\usepackage{marvosym}
+\usepackage{boxedminipage}
+
+\lstset{escapeinside={/*!}{!*/}}
+\newcommand{\annotation}[1]{\hfill\footnotesize{}#1}
+
+\usepackage{menukeys}
+
+
+% Exact colors from NB
+\usepackage[breakable]{tcolorbox}
+\definecolor{incolor}{HTML}{303F9F}
+\definecolor{outcolor}{HTML}{D84315}
+\definecolor{cellborder}{HTML}{CFCFCF}
+\definecolor{cellbackground}{HTML}{F7F7F7}
+
+
+    
+\begin{document}
+\fnote{\copyright{} Christian Urban, King's College London, 2022}
+
+\section*{Scala Worksheet 2}
+
+
+
+\subsection*{Task 1 (Options)}
+
+Get familiar with constructing strings and printing strings
+(i.e.~\texttt{println}, \texttt{mkString}, \texttt{toString}, \ldots)
+
+\begin{lstlisting}[numbers=none]
+scala> List(7,2,3,4,5,6).find(_ < 4)
+scala> List(5,6,7,8,9).find(_ < 4)
+scala> 
+\end{lstlisting}
+
+\subsection*{Task 2 (URLs / Files)}
+
+ALso Try
+
+\begin{lstlisting}[numbers=none]
+scala> 
+scala> 
+scala> 
+\end{lstlisting}
+
+\subsection*{Task 3 (Higher-Order Functions)}
+
+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> 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 4 (Maps)}
+
+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 5 (Pattern-Matching)}
+
+\subsection*{Task 6 (Web-Crawler)}
+
+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}
+
+%%% Local Variables: 
+%%% mode: latex
+%%% TeX-master: t
+%%% End: 




