
diff -r e0a82c9f1d21 -r ea39bbc8d98d cws/pre_cw02.tex
--- a/cws/pre_cw02.tex	Thu Nov 04 12:20:12 2021 +0000
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,161 +0,0 @@
-% !TEX program = xelatex
-\documentclass{article}
-\usepackage{../style}
-\usepackage{disclaimer}
-\usepackage{../langs}
-
-\begin{document}
-
-
-%% should ask to lower case the words.
-
-\section*{Preliminary Part 2 (Scala, 3 Marks)}
-
-\mbox{}\hfill\textit{``What one programmer can do in one month,}\\
-\mbox{}\hfill\textit{two programmers can do in two months.''}\smallskip\\
-\mbox{}\hfill\textit{ --- Frederick P.~Brooks (author of The Mythical Man-Month)}\bigskip\medskip
-
-\IMPORTANT{You are asked to implement a Scala program for measuring similarity in
-  texts. The preliminary part is due on \cwSEVEN{} at 5pm and worth 3\%.
-  Any 1\% you achieve in the preliminary part counts as your ``weekly engagement''.}
-
-\noindent
-Also note that the running time of each part will be restricted to a
-maximum of 30 seconds on my laptop.
-
-\DISCLAIMER{}
-
-
-\subsection*{Reference Implementation}
-
-Like the C++ part, the Scala part works like this: you
-push your files to GitHub and receive (after sometimes a long delay) some
-automated feedback. In the end we will take a snapshot of the submitted files and
-apply an automated marking script to them.\medskip
-
-\noindent
-In addition, the Scala part comes with reference
-implementations in form of \texttt{jar}-files. This allows you to run
-any test cases on your own computer. For example you can call Scala on
-the command line with the option \texttt{-cp docdiff.jar} and then
-query any function from the template file. Say you want to find out
-what the function \texttt{occurrences} produces: for this you just need
-to prefix it with the object name \texttt{CW7a}.  If you want to find out what
-these functions produce for the list \texttt{List("a", "b", "b")},
-you would type something like:
-
-\begin{lstlisting}[language={},numbers=none,basicstyle=\ttfamily\small]
-$ scala -cp docdiff.jar
-  
-scala> CW7a.occurrences(List("a", "b", "b"))
-...
-\end{lstlisting}%$
-
-\subsection*{Hints}
-
-\noindent
-\textbf{For the Preliminary Part:} useful operations involving regular
-expressions:
-\[\texttt{reg.findAllIn(s).toList}\]
-\noindent finds all
-substrings in \texttt{s} according to a regular regular expression
-\texttt{reg}; useful list operations: \texttt{.distinct}
-removing duplicates from a list, \texttt{.count} counts the number of
-elements in a list that satisfy some condition, \texttt{.toMap}
-transfers a list of pairs into a Map, \texttt{.sum} adds up a list of
-integers, \texttt{.max} calculates the maximum of a list.\bigskip
-
-
-
-\newpage
-\subsection*{Preliminary Part (3 Marks, file docdiff.scala)}
-
-It seems source code plagiarism---stealing and submitting someone
-else's code---is a serious problem at other
-universities.\footnote{Surely, King's students, after all their
-  instructions and warnings, would never commit such an offence. Yes?}
-Detecting such plagiarism is time-consuming and disheartening for
-lecturers at those universities. To aid these poor souls, let's
-implement in this part a program that determines the similarity
-between two documents (be they source code or texts in English). A
-document will be represented as a list of strings.
-
-
-\subsection*{Tasks}
-
-\begin{itemize}
-\item[(1)] Implement a function that `cleans' a string by finding all
-  (proper) words in this string. For this use the regular expression
-  \texttt{\textbackslash{}w+} for recognising words and the library function
-  \texttt{findAllIn}. The function should return a document (a list of
-  strings).\\
-  \mbox{}\hfill [0.5 Marks]
-
-\item[(2)] In order to compute the overlap between two documents, we
-  associate each document with a \texttt{Map}. This Map represents the
-  strings in a document and how many times these strings occur in the
-  document. A simple (though slightly inefficient) method for counting
-  the number of string-occurrences in a document is as follows: remove
-  all duplicates from the document; for each of these (unique)
-  strings, count how many times they occur in the original document.
-  Return a Map associating strings with occurrences. For example
-
-  \begin{center}
-  \pcode{occurrences(List("a", "b", "b", "c", "d"))}
-  \end{center}
-
-  produces \pcode{Map(a -> 1, b -> 2, c -> 1, d -> 1)} and
-
-  \begin{center}
-  \pcode{occurrences(List("d", "b", "d", "b", "d"))}
-  \end{center}
-
-  produces \pcode{Map(d -> 3, b -> 2)}.\hfill[1 Mark]
-
-\item[(3)] You can think of the Maps calculated under (2) as memory-efficient
-  representations of sparse ``vectors''. In this subtask you need to
-  implement the \emph{product} of two such vectors, sometimes also called
-  \emph{dot product} of two vectors.\footnote{\url{https://en.wikipedia.org/wiki/Dot_product}}
-
-  For this dot product, implement a function that takes two documents
-  (\texttt{List[String]}) as arguments. The function first calculates
-  the (unique) strings in both. For each string, it multiplies the
-  corresponding occurrences in each document. If a string does not
-  occur in one of the documents, then the product for this string is zero. At the end
-  you need to add up all products. For the two documents in (2) the dot
-  product is 7, because
-
-  \[
-    \underbrace{1 * 0}_{"a"} \;\;+\;\;
-    \underbrace{2 * 2}_{"b"} \;\;+\;\;
-    \underbrace{1 * 0}_{"c"} \;\;+\;\;
-    \underbrace{1 * 3}_{"d"} \qquad = 7
-  \]  
-  
-  \hfill\mbox{[1 Mark]}
-
-\item[(4)] Implement first a function that calculates the overlap
-  between two documents, say $d_1$ and $d_2$, according to the formula
-
-  \[
-  \texttt{overlap}(d_1, d_2) = \frac{d_1 \cdot d_2}{max(d_1^2, d_2^2)}  
-  \]
-
-  where $d_1^2$ means $d_1 \cdot d_1$ and so on.
-  You can expect this function to return a \texttt{Double} between 0 and 1. The
-  overlap between the lists in (2) is $0.5384615384615384$.
-
-  Second, implement a function that calculates the similarity of
-  two strings, by first extracting the substrings using the clean
-  function from (1)
-  and then calculating the overlap of the resulting documents.\\
-  \mbox{}\hfill\mbox{[0.5 Marks]}
-\end{itemize}
-
-
-\end{document} 
-
-%%% Local Variables: 
-%%% mode: latex
-%%% TeX-master: t
-%%% End: 




