3 \usepackage{chessboard}

     3 %\usepackage{chessboard}

     4 \usepackage[LSBC4,T1]{fontenc}

     4 %\usepackage[LSBC4,T1]{fontenc}

     8 

     8 \usetikzlibrary{shapes}

    55   \frametitle{My Scala Version}

    62   \frametitle{Scala 2.13.1}

   115   ``Since we cant use \code{var}s I was wondering if we could use a stack?''

   122   ``Since we can't use \code{var}s I was wondering if we could use a stack?''

   378 

   385 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     

   379 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     

   386 \begin{frame}[c,fragile]

   380 \begin{frame}[t]

   387   %\frametitle{Option Type}

   388   

   389   Find something below 4 in a list. What do you think Scala answers?\bigskip\bigskip

   390   

   391   \begin{onlyenv}<1>

   392   \begin{lstlisting}[language=Scala, numbers=none, xleftmargin=-1mm]

   393   List(7,2,3,4,5,6).find(_ < 4)

   394        

   395   List(5,6,7,8,9).find(_ < 4)

   396   \end{lstlisting}

   397   \end{onlyenv}

   398   \begin{onlyenv}<2>

   399   \begin{lstlisting}[language=Scala, numbers=none, xleftmargin=-1mm]

   400   List(7,2,3,4,5,6).find(_ < 4)

   401   res: Option[Int] = Some(2)

   402    

   403   List(5,6,7,8,9).find(_ < 4)

   404   res: Option[Int] = None

   405   \end{lstlisting}

   406   \end{onlyenv}

   407   

   408   \end{frame}

   409 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   410  

   411 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     

   412 \begin{frame}[c]

   382 

   414     

   383 

   415 \begin{itemize}

   384   

   416 \item if the value is present, you use\bigskip

   385 \end{frame}

   417 \begin{center}\pcode{Some(value)}\end{center}\bigskip\bigskip

   386 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   418 

   387 

   419 \item if no value is present, you use\bigskip

   388 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     

   420 \begin{center}\pcode{None}\end{center}\bigskip\bigskip

   389 \begin{frame}[t]

   421 \end{itemize}

   422 

   423 \small e.g.~\code{Option[Int]}, then \code{Some(42)} and \code{None}\\

   424 good for error handling      

   425 \end{frame}

   426 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   427     

   428 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     

   429 \begin{frame}[c,fragile]

   430 \frametitle{Option Type}

   431 

   432 \small   

   433 \begin{onlyenv}<1>

   434 \begin{lstlisting}[language=Scala, numbers=none, xleftmargin=-1mm]

   435 Integer.parseInt("1234")

   436 

   437 // vs.

   438 

   439 def get_me_an_int(s: String) : Option[Int] = 

   440  Try(Some(Integer.parseInt(s))).getOrElse(None)

   441 \end{lstlisting}

   442 \end{onlyenv}\bigskip\bigskip\bigskip

   443  

   444 in the Scala code it is clear from the type I have to deal 

   445 with the \pcode{None}-case; no JavaDoc needed

   446   

   447 \end{frame}

   448 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   449  

   450 

   451 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     

   452 \begin{frame}[c,fragile]

   392   

   455 In Scala, functions can take other functions as arguments and can return 

   393     

   456 a function as a result.\bigskip\bigskip  

   394 \end{frame}

   457 

   395 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   458 \begin{lstlisting}[language=Scala, numbers=none, xleftmargin=1mm]

   396   

   459 List(7,2,3,4,5,6).find(_ < 4)

   460 \end{lstlisting}

   461     

   462 \UParrow{1}{10}{11}    

   463 \end{frame}

   464 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   465   

   466 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     

   467 \begin{frame}[c,fragile]

   468 \frametitle{Higher-Order Functions (2)}

   469   

   470 

   471 \begin{lstlisting}[language=Scala, numbers=none, xleftmargin=1mm]

   472 def even(x: Int) : Boolean = x % 2 == 0

   473 

   474 List(1, 2, 3, 4, 5).filter(even)

   475   res : List[Int] = List(2, 4)

   476 

   477 List(1, 2, 3, 4, 5).count(even)

   478   res : Int = 2

   479 

   480 List(1, 2, 3, 4, 5).find(even)

   481   res: Option[Int] = Some(2)

   482 \end{lstlisting}

   483     

   484 \end{frame}

   485 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   486     

   487 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     

   488 \begin{frame}[c,fragile]

   489 \frametitle{map (lower case)}

   490 

   491  applies a function to each element of a list (and more)

   492 

   493 \begin{center}

   494 \begin{tikzpicture}[scale=0.9]

   495                       

   496   \node (A0) at (1.2,0) {\texttt{List(\,}};

   497   \node (A1) at (2.0,0) {\texttt{1\makebox[0mm]{ ,}}};

   498   \node (A2) at (2.9,0) {\texttt{2\makebox[0mm]{ ,}}};

   499   \node (A3) at (3.8,0) {\texttt{3\makebox[0mm]{ ,}}};

   500   \node (A4) at (4.7,0) {\texttt{4\makebox[0mm]{ ,}}};

   501   \node (A5) at (5.6,0) {\texttt{5\makebox[0mm]{ ,}}};

   502   \node (A6) at (6.5,0) {\texttt{6\makebox[0mm]{ ,}}};

   503   \node (A7) at (7.4,0) {\texttt{7\makebox[0mm]{ ,}}};

   504   \node (A8) at (8.3,0) {\texttt{8)}};

   505 

   506   \node (B0) at (1.2,-3) {\texttt{List(\,}};

   507   \node (B1) at (2.0,-3) {\texttt{1\makebox[0mm]{ ,}}};

   508   \node (B2) at (3.0,-3) {\texttt{4\makebox[0mm]{ ,}}};

   509   \node (B3) at (4.1,-3) {\texttt{9\makebox[0mm]{ ,}}};

   510   \node (B4) at (5.2,-3) {\texttt{16\makebox[0mm]{ ,}}};

   511   \node (B5) at (6.3,-3) {\texttt{25\makebox[0mm]{ ,}}};

   512   \node (B6) at (7.4,-3) {\texttt{36\makebox[0mm]{ ,}}};

   513   \node (B7) at (8.4,-3) {\texttt{49\makebox[0mm]{ ,}}};

   514   \node (B8) at (9.4,-3) {\texttt{64\makebox[0mm]{ )}}};

   515 

   516   \draw [->,line width=1mm] (A1.south) -- (B1.north);

   517   \draw [->,line width=1mm] (A2.south) -- (B2.north);

   518   \draw [->,line width=1mm] (A3.south) -- (B3.north);

   519   \draw [->,line width=1mm] (A4.south) -- (B4.north);

   520   \draw [->,line width=1mm] (A5.south) -- (B5.north);

   521   \draw [->,line width=1mm] (A6.south) -- (B6.north);

   522   \draw [->,line width=1mm] (A7.south) -- (B7.north);

   523   \draw [->,line width=1mm] (A8.south) -- (B8.north);

   524 

   525   \node [red] (Q0) at (-0.5,-0.3) {\large\texttt{n}}; 

   526   \node (Q1) at (-0.5,-0.4) {};

   527   \node (Q2) at (-0.5,-2.5) {};

   528   \node [red] (Q3) at (-0.5,-2.65) {\large\texttt{n\,*\,n}};

   529   \draw [->,red,line width=1mm] (Q1.south) -- (Q2.north);

   530 

   531   \node [red] at (-1.5,-1.5) {\Large{}\it\textbf{map}};

   532  \end{tikzpicture}

   533 \end{center}\bigskip

   534 

   535 \begin{lstlisting}[language=Scala, numbers=none, xleftmargin=1mm]

   536 List(1,2,3,4,5,6,7,8).map(n => n * n)

   537 \end{lstlisting}

   538 \end{frame}

   539 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   540   

   541 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     

   542 \begin{frame}[c,fragile]

   543 \frametitle{For-Comprehensions are maps}

   544   

   545 \begin{lstlisting}[language=Scala, numbers=none, xleftmargin=1mm]

   546 for (n <- List(1,2,3,4,5,6,7,8)) 

   547   yield n * n

   548 

   549 

   550 // is just syntactic sugar for

   551 

   552 

   553 List(1,2,3,4,5,6,7,8).map(n => n * n)

   554 \end{lstlisting}

   555     

   556 \end{frame}

   557 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   558     

   559 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     

   560 \begin{frame}[c,fragile]

   561 \frametitle{Map (upper case)}

   562 

   563 a type, representing a key-value association datastructure\bigskip\bigskip

   564 

   565 \begin{lstlisting}[language=Scala, numbers=none, xleftmargin=-2mm]

   566 val ascii = 

   567      ('a' to 'z').map(c => (c, c.toInt))

   568 

   569 val ascii_Map = ascii.toMap

   570 

   571 ascii_Map.get('a')   // -> 97

   572 \end{lstlisting}

   573 \end{frame}

   574 

   575 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     

   576 \begin{frame}[c,fragile]

   577 \frametitle{Recursion}

   578 

   579 

   580 

   581 \begin{lstlisting}[language=Scala, numbers=none, xleftmargin=-2mm]

   582 def fib(n: Int) : Int = { 

   583   if (n == 0 || n == 1) 1

   584    else fib(n - 1) + fib(n - 2)

   585 }

   586 \end{lstlisting}

   587 \end{frame}

   588 

   589 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     

   590 \begin{frame}[c,fragile]

   591 \frametitle{Recursion}

   592 

   593 \small

   594 \begin{lstlisting}[language=Scala, numbers=none, xleftmargin=-4mm]

   595 def my_flatten(xs: List[Option[Int]]): List[Int] = 

   596  xs match {

   597    case Nil => Nil 

   598    case None :: rest => my_flatten(rest)

   599    case Some(v) :: rest => v :: my_flatten(rest)

   600  }

   601 \end{lstlisting}

   602 \end{frame}

   603 

   604 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%