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--- a/cws/main_cw03.tex Thu Nov 10 20:10:20 2022 +0000
+++ b/cws/main_cw03.tex Mon Nov 14 12:04:21 2022 +0000
@@ -237,7 +237,7 @@
\end{center}
\noindent
-The alternative regular expressions comes in two versions: one is
+The alternative regular expression comes in two versions: one is
binary (+ / \texttt{ALT}) and the other is n-ary ($\sum$ /
\texttt{ALTs}). The latter takes a list of regular expressions as
argument. In what follows we shall use $rs$ to stand for lists of
Binary file cws/main_cw04.pdf has changed
--- a/cws/main_cw04.tex Thu Nov 10 20:10:20 2022 +0000
+++ b/cws/main_cw04.tex Mon Nov 14 12:04:21 2022 +0000
@@ -173,7 +173,7 @@
computer. For example you can call Scala on the command line with the
option \texttt{-cp knight1.jar} and then query any function from the
\texttt{knight1.scala} template file. As usual you have to
-prefix the calls with \texttt{M4a}, \texttt{M4b} and \texttt{M4c}.
+prefix the calls with \texttt{M4a}, \texttt{M4b}, \texttt{M4c} and \texttt{M4d}.
Since some of the calls are time sensitive, I included some timing
information. For example
Binary file cws/main_cw05.pdf has changed
--- a/progs/lecture1.scala Thu Nov 10 20:10:20 2022 +0000
+++ b/progs/lecture1.scala Mon Nov 14 12:04:21 2022 +0000
@@ -436,6 +436,7 @@
// - no mutable data-structures (no Arrays, no ListBuffers)
// But what the heck....lets try to count to 1 Mio in parallel
+import scala.collection.parallel.CollectionConverters._
var cnt = 0
@@ -452,7 +453,7 @@
def count_intersection(A: Set[Int], B: Set[Int]) : Int = {
var count = 0
- for (x <- A.par; if (B contains x)) count += 1
+ for (x <- A; if (B contains x)) count += 1
count
}
--- a/progs/mandelbrot.scala Thu Nov 10 20:10:20 2022 +0000
+++ b/progs/mandelbrot.scala Mon Nov 14 12:04:21 2022 +0000
@@ -3,7 +3,7 @@
//
// see https://en.wikipedia.org/wiki/Mandelbrot_set
//
-// under scala 2.13.1 needs to be called with
+// under scala 2.13.XX needs to be called with
//
// scala -cp scala-parallel-collections_2.13-0.2.0.jar mandelbrot.scala
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/wsheets/wsh01.scala Mon Nov 14 12:04:21 2022 +0000
@@ -0,0 +1,109 @@
+
+// Task 1
+
+2 + 2
+1 / 2
+1.0 / 2
+1 / 2.0
+1 / 0
+1.0 / 0.0
+true == false
+true && false
+1 > 1.0
+"12345".length
+List(1,2,1).size
+Set(1,2,1).size
+List(1) == List(1)
+Set(1,2,3) == Set(3,2,1)
+Array(1) == Array(1)
+Array(1).sameElements(Array(1))
+
+
+// Task 2
+
+val z = 42
+z = z + 1 . // error
+val x = 2 * z
+val z = 466 // old z not accessible anymore
+println(x)
+
+
+// Task 3
+println("Hello " ++ "World")
+List(1,2,3,4).mkString("\n")
+List(1,2,3,4).mkString("(", "|", ")")
+
+
+// Task 4
+def miles2meters(m: Int): Int = m * 1609
+
+
+// Task 5
+
+val s1 = "foo"
+val s2 = "bar"
+val s3 = "foobar"
+if (s1 == s2) print("equal") else print("unequal")
+if (s1 ++ s2 == s3) print("equal") else print("unequal")
+
+
+// Task 6
+for (x <- (1 to 5).toList;
+ y <- (1 to 5).toList;
+ z <- (1 to 5).toList) yield (x,y,z)
+
+for (x <- (1 to 5).toList;
+ y <- (1 to 5).toList;
+ z <- (1 to 5).toList;
+ if (x + y + z) % 3 == 0) yield (x,y,z)
+
+(for (x <- (1 to 5).toList;
+ y <- (1 to 5).toList;
+ z <- (1 to 5).toList;
+ if (x + y + z) % 3 == 0) yield (x,y,z)).sortBy(_._2)
+
+
+
+// Task 7
+
+// first version with using an accumulator
+
+def cnt(xs: List[Int], acc: List[(Int, Int)] = Nil) : List[(Int, Int)] =
+ (xs, acc) match {
+ case (Nil, acc) => acc.reverse
+ case (x::xs, Nil) => cnt(xs, (x, 1)::Nil)
+ case (x::xs, (y, n)::ys) =>
+ if (x == y) cnt(xs, (y, n + 1)::ys)
+ else cnt(xs, (x, 1)::(y, n)::ys)
+ }
+
+def toStr(p: (Int, Int)) =
+ if (p._2 == 1) s"${p._1}" else s"${p._2} x ${p._1}"
+
+def pp_list(xs: List[Int]) = {
+ cnt(xs).map(toStr)
+}
+
+pp_list(List(1,1,1,2,3,3)) // List(3 x 1, 2, 2 x 3)
+pp_list(List(1,2,3,4,4,4)) // List(1, 2, 3, 3 x 4)
+pp_list(List(1,1,1,1,1,1)) // List(6 x 1)
+pp_list(List(1,1,1,2,1,1)) // List(3 x 1, 2, 2 x 1)
+
+// second version with just a simple counter
+
+def cnt2(xs: List[Int], n : Int = 0) : List[(Int, Int)] = xs match {
+ case Nil => Nil
+ case x::Nil => (x, n + 1)::Nil
+ case x::y::tail =>
+ if (x == y) cnt2(y::tail, n + 1)
+ else (x, n + 1)::cnt2(y::tail, 0)
+}
+
+def pp_list2(xs: List[Int]) = {
+ cnt2(xs).map(toStr)
+}
+
+pp_list2(List(1,1,1,2,3,3)) // List(3 x 1, 2, 2 x 3)
+pp_list2(List(1,2,3,4,4,4)) // List(1, 2, 3, 3 x 4)
+pp_list2(List(1,1,1,1,1,1)) // List(6 x 1)
+pp_list2(List(1,1,1,2,1,1)) // List(3 x 1, 2, 2 x 1)
\ No newline at end of file
--- 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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