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\renewcommand{\slidecaption}{PEP (Scala) 02, King's College London}

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\begin{document}

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\begin{frame}[t]

\frametitle{%

  \begin{tabular}{@ {}c@ {}}

  \\[5mm]

  \huge PEP Scala (2) 

  \end{tabular}}

  \normalsize

  \begin{center}

  \begin{tabular}{ll}

    Email:  & christian.urban at kcl.ac.uk\\

    %Office: & N\liningnums{7.07} (North Wing, Bush House)\bigskip\\

    Slides \& Code: & KEATS\bigskip\\

    %Office Hours: &  Thursdays 12:00 -- 14:00\\

    %Additionally: & (for Scala) Tuesdays 10:45 -- 11:45\\ 

  \end{tabular}

  \end{center}

\end{frame}

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% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     

% \begin{frame}[t,fragile]

% \frametitle{For-Comprehensions}

% %\small

% \begin{lstlisting}[language=Scala,numbers=none]

% for (n <- List(1, 2, 3, 4, 5)) yield n * n

% \end{lstlisting}

% \begin{textblock}{5}(2,6)

% \includegraphics[scale=0.3]{../pics/fun.png}

% \end{textblock}  

% \begin{textblock}{5}(9,6)

% \includegraphics[scale=0.3]{../pics/fun.png}

% \end{textblock}  

% \end{frame}

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\begin{frame}[t]

\frametitle{For-Comprehensions}

\begin{center}

  \begin{tikzpicture}[scale=1,

                      node/.style={

                      rectangle,rounded corners=3mm,

                      very thick,draw=black!50,

                      minimum height=18mm, minimum width=20mm,

                      top color=white,bottom color=black!20}]

  \node (A0) at (0.1,0) {\texttt{\textcolor{purple}{\textbf{for}} (\alert<2->{n} <- List(}};

  \node (A1) at (2.3,0) {\texttt{\phantom{,}1,}};

  \node (A2) at (3.2,0) {\texttt{\phantom{,}2,}};

  \node (A3) at (4.1,0) {\texttt{\phantom{,}3,}};

  \node (A4) at (5.0,0) {\texttt{\phantom{,}4,}};

  \node (A5) at (5.9,0) {\texttt{\phantom{))}5))}};

  \node (A6) at (8,0) {\texttt{\textcolor{purple}{\textbf{yield}} \alert<2->{n\,*\,n}}};

  \onslide<2->{

  \node (B0) at (1.4,-3) {\texttt{List(}};

  \node (B1) at (2.3,-3) {\texttt{\phantom{,}1,}};

  \node (B2) at (3.6,-3) {\texttt{\phantom{,}4,}};

  \node (B3) at (4.9,-3) {\texttt{\phantom{,}9,}};

  \node (B4) at (6.2,-3) {\texttt{\phantom{,}16,}};

  \node (B5) at (7.5,-3) {\texttt{\phantom{,}25)}};}

  \onslide<2->{

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

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

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  \node (Q2) at (-0.45,-2.8) {};

  \node (Q3) at (-0.45,-2.95) {\alert<2->{\texttt{n\,*\,n:}}};

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

 \end{tikzpicture}

\end{center}

\onslide<3>{This is for when the for-comprehension\\ \textbf{yields / produces} a result.}

\end{frame}

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% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     

% \begin{frame}[t]

% \frametitle{For-Comprehensions Again}

% \begin{center}

%   \begin{tikzpicture}[scale=1,

%                       node/.style={

%                       rectangle,rounded corners=3mm,

%                       very thick,draw=black!50,

%                       minimum height=18mm, minimum width=20mm,

%                       top color=white,bottom color=black!20}]

%   \node (A0) at (0,0)

%     {\texttt{\textcolor{purple}{\textbf{for}} (n <- List(1, 2, 3, 4, 5))

%              \textcolor{purple}{\textbf{yield}} n\,*\,n}};

%   \node (A1) at (0,-1.5) {\LARGE\textbf{vs}};       

%   \node (A2) at (0,-3)

%     {\texttt{\textcolor{purple}{\textbf{for}} (n <- List(1, 2, 3, 4, 5)) println(n)}};

%  \end{tikzpicture}

% \end{center}\bigskip

% The second version is in case the for \textbf{does not}

% produce any result.

% \end{frame}

% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     

\begin{frame}[c,fragile]

  %\frametitle{Option Type}

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

  \begin{onlyenv}<1>

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

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

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

  \end{lstlisting}

  \end{onlyenv}

  \begin{onlyenv}<2>

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

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

  res: Option[Int] = Some(2)

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

  res: Option[Int] = None

  \end{lstlisting}

  \end{onlyenv}

  \end{frame}

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\begin{frame}[c]

\frametitle{Option Type}

\begin{itemize}

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

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

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

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

\end{itemize}

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

good for error handling      

\end{frame}

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\begin{frame}[c,fragile]

\frametitle{Option Type}

\small   

\begin{onlyenv}<1>

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

Integer.parseInt("1234")

// vs.

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

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

\end{lstlisting}

\end{onlyenv}\bigskip\bigskip\bigskip

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

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

\end{frame}

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\begin{frame}[c,fragile]

\frametitle{Higher-Order Functions}

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

a function as a result.\bigskip\bigskip  

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

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

\end{lstlisting}

\UParrow{1}{8}{11}    

\end{frame}

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\begin{frame}[c,fragile]

\frametitle{Higher-Order Functions (2)}

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

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

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

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

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

  res : Int = 2

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

  res: Option[Int] = Some(2)

\end{lstlisting}

\end{frame}

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\begin{frame}[c,fragile]

\frametitle{Anonymous Functions}

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

def less4(x: Int) = x < 4

\end{lstlisting}

\begin{center}

vs

\end{center}  

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

      (x: Int) => x < 4

\end{lstlisting}

\end{frame}

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\begin{frame}[c,fragile]

\frametitle{map (lower case)}

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

\begin{center}

\begin{tikzpicture}[scale=0.9]

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

 \end{tikzpicture}

\end{center}\bigskip

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

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

\end{lstlisting}

\end{frame}

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\begin{frame}[c,fragile]

\frametitle{For-Comprehensions are maps}

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

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

  yield n * n

// is just syntactic sugar for

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

\end{lstlisting}

\end{frame}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

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\begin{frame}[c,fragile]

\frametitle{Map (upper case)}

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

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

val ascii = 

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

val ascii_Map = ascii.toMap

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

\end{lstlisting}

\end{frame}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     

\begin{frame}[c,fragile]

\frametitle{Pattern Matching}

\ldots on pairs:\bigskip

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

def fizz_buzz(n: Int) : String = 

 (n % 3, n % 5) match {

   case (0, 0) => "fizz buzz"

   case (0, _) => "fizz"

   case (_, 0) => "buzz"

   case _ => n.toString  

 }

\end{lstlisting}

\end{frame}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     

\begin{frame}[c,fragile]

\frametitle{Recursion}

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

def fib(n: Int) : Int = { 

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

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

}

\end{lstlisting}

\end{frame}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     

\begin{frame}[c,fragile]

\frametitle{Recursion}

\small

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

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

 xs match {

   case Nil => Nil 

   case None :: rest => my_flatten(rest)

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

 }

\end{lstlisting}

\end{frame}

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\begin{frame}[c]

\frametitle{\begin{tabular}{c}\\[0cm]\alert{Questions?}\end{tabular}}

\begin{center}

  \begin{tabular}[t]{@{}l@{}l@{}}

    \includegraphics[scale=0.1]{../pics/mand4.png} & \hspace{4mm}

    \raisebox{0mm}{\includegraphics[scale=0.1]{../pics/mand3.png}}      

  \end{tabular}     

\end{center}

\begin{center}

  My Office Hours: Thursdays 12 -- 14\\

  And specifically for Scala: Tuesdays 10:45 -- 11:45

\end{center}

\end{frame}

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% \begin{frame}[t]

%   \begin{center}  

%   \includegraphics[scale=0.3]{../pics/blow.png}

%   \end{center}

%   \begin{textblock}{14}(2,11.4)

%   \large\bf{}Mind-Blowing Programming Languages:\\ 

%   Overloading in any language is great but it makes a difference\; \code{10/3}

%   \;or\; \code{10.0/3}

%   \end{textblock}

%   \end{frame}

  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% \begin{frame}[t]

%   \begin{center}  

%   \includegraphics[scale=0.3]{../pics/blow.png}

%   \end{center}

%   \begin{textblock}{14}(2,11.4)

%   \large\bf{}Mind-Blowing Programming Languages:\\ 

%   \centering PHP \textcolor{gray}{(7.0)}

%   \end{textblock}

%   \end{frame}

%   %%%

  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 

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\begin{frame}[c]

\frametitle{Jumping Towers}

\begin{center}

\begin{tikzpicture}[scale=1.2]

  \draw[line width=1mm,cap=round] (0,0) -- (5,0);

  \draw[line width=1mm,cap=round] (0,1) -- (5,1);

  \draw[line width=1mm,cap=round] (0,0) -- (0,1);

  \node at (0.5,0.5) {\textbf{\Large 3}};

  \draw[line width=1mm,cap=round] (1,0) -- (1,1);

  \node at (1.5,0.5) {\textbf{\Large 4}};

  \draw[line width=1mm,cap=round] (2,0) -- (2,1);

  \node at (2.5,0.5) {\textbf{\Large 2}};

  \draw[line width=1mm,cap=round] (3,0) -- (3,1);

  \node at (3.5,0.5) {\textbf{\Large 0}};

  \draw[line width=1mm,cap=round] (4,0) -- (4,1);

  \node at (4.5,0.5) {\textbf{\Large 1}};