\documentclass{beamer}
%include lhs2TeX.fmt
\author{Piyush P Kurur\\
  Office no: 224\\
  Dept. of Comp. Sci. and Engg.\\
  IIT Kanpur}


\newcommand{\Token}[2][]{\node(#2#1)[token]{#2};}
\newcommand{\Symbol}[2][]{\node(#2#1)[symbol]{#2};}
\newcommand{\Point}[1]{\node(#1)[point]{#1};}

\usepackage{tikz}
\usetikzlibrary{positioning,shapes,chains,fit}
\usetikzlibrary{shapes.symbols}
\usetikzlibrary{matrix}
\usetikzlibrary{backgrounds}
\usetikzlibrary{shapes.geometric}
\usepackage{multicol}

\usepackage{algorithm2e}
\usepackage{pgfkeys}

\pgfkeys {%
  /tikz/redbox/.style={%
    shape=rectangle,%
    minimum size=1.5em,%
    top color = white, %
    bottom color=red!50!black!50,
    inner sep=0pt,
    draw=black
  },
  /tikz/greybox/.style={ 
    shape=rectangle,%
    minimum width=7em,%
    minimum height=1.5em,
    fill=black!20,
    inner sep=0pt,
    draw=black
  },
  /tikz/blackbox/.style={ 
    shape=rectangle,%
    minimum width=7em,%
    minimum height=1.5em,
    fill=black,
    inner sep=0pt,
    draw=black
  },
  /tikz/whitebox/.style={
    shape=rectangle,
    minimum width=7em,
    minimum height=1.5em,
    draw=black
  },
  /tikz/bluebox/.style={
    shape=rectangle,
    minimum width=7em,
    minimum height=1.5em,
    fill=blue!40,
    draw=black
  },
  /tikz/whitetape/.style={
    shape=rectangle,
    minimum width=4em,
    minimum height=1.5em,
    draw=black
  },
  /tikz/bluearr/.style={
    ->,
    line width=0.25em, 
    draw=blue!40
  },
  /tikz/greenarr/.style={
    ->,
    line width=0.25em, 
    draw=green!40!black!60
  }
}

    
\newcommand{\arraythree}[4]{
  \begin{tikzpicture}[node distance=0]
    \pgfsetstrokeopacity{#4};
    \node[#1](a0#3){#2};
    \node[#1, right=of a0#3](a1#3){#2};
    \node[#1, right=of a1#3](a1#3){#2};
  \end{tikzpicture}
}

\newcommand{\arraytwo}[4]{
  \begin{tikzpicture}[node distance=0]
    \pgfsetstrokeopacity{#4};
    \node[#1](a0#3){#2};
    \node[#1,right=of a0#3]{#2};
  \end{tikzpicture}
}
  
\newcommand{\Array}[0]{
  \arraythree{box}{}{a}{1}
}

\newcommand{\AArray}[0]{%
  \arraythree{bbox}{\Array}{b}{0.5}}
\newcommand{\AAArray}[0]{%
  \arraytwo{bbbox}{\AArray}{c}{0.25}}


\newcommand{\T}[1]{\ensuremath{T\left(#1\right)}}  
\newcommand{\BigOh}[1]{\ensuremath{O\left(#1\right)}}
\title{Fundamentals of Computing: Lecture 23}
\date{September 23, 2009}
\begin{document}
\begin{frame}
  \maketitle
\end{frame}

\begin{frame}
  \frametitle{Summary of last class}
  \pause
  \begin{enumerate}
  \item Allocating memory using the |malloc|,
    \pause
  \item Freeing memory using |free|,
    \pause
  \item Finding size of a type using |sizeof|,
    \pause
  \item Finding the length of an array |sizeof(a)/sizeof(a[0])|
  \end{enumerate}
\end{frame}

\begin{frame}
  \frametitle{Void pointers}
  \pause
  Void pointers are ``generic'' pointer,
  \pause
  \begin{itemize}
  \item Any pointer can be cast to a void pointer variable
    \pause

    \begin{spec}
      void *vptr;
      char *str = "hello";
      vprt = (void *) str;
    \end{spec}
    \pause
  \item If a void pointer varaible was assigend a pointer to type |T|
    then a pointer to |T| variable can be cast back from the void
    pointer.
    \pause
    \begin{spec}
      void *vptr;
      T t, *tptr;
      vptr = (void *) &t;
      ...
      tptr = (T *) vptr;
    \end{spec}
    \pause
  \item A void pointer cannot be dereference. Nor can pointer
    arithmetic be done on it. Reason dereferencing does not make
    sense and for arithmetic we need to know the size.
  \end{itemize}
\end{frame}

\end{document}

\begin{frame}
  \frametitle{Structures}
  \pause
  \begin{code}
    # line 170 "lecture23.lhs"
  
    struct Vector2D{
      double x;
      double y;
    };
    
    struct Vector2D origin = {0.0,0.0};

  \end{code}

  This declares that Point2D is a combination of 2 doubles.
  
  \pause
  \begin{block}{Accessing the fields}
    
    \begin{spec}
      struct Vector v;
      printf("v is the vector (%f,%f)", p.x, p.y );
    \end{spec}
  \end{block}
\end{frame}

\begin{frame}
  \frametitle{Fields are both l-values and r-values}
  \pause
  \begin{spec}
    Vector2D addVector(Vector2D u, Vector2D)
    {
      Vector2D w;
      w.x = u.x + v.x;
      w.y = u.y + v.y;
      return w;
    }
  \end{spec}
\end{frame}

\begin{frame}
  \frametitle{Java programmers please note}
  
  Structures are \emph{not} passed as reference to functions.
 \pause
  \begin{code}
    #line 214 "lecture23.lhs"
    #include <stdio.h>
    void printVector(struct Vector2D);
    void shiftByOneUnit(struct Vector2D u);
    int main () {
      printf("Before shift: ");printVector(origin);
      shiftByOneUnit(origin);
      printf("After shift: ");printVector(origin);
    }
    void shiftByOneUnit(struct Vector2D u){
      u.x = u.x + 1;
    }
    void printVector(struct Vector2D u){
      printf("(%f,%f)\n",u.x,u.y);
    }
  
  \end{code}
\end{frame}


\begin{frame}
  \begin{block}{Syntax}
    \begin{spec}
      struct name {
        declarations; /* field declarations */
      };
    \end{spec}
  \end{block}

  \begin{itemize}
  \item There should be no recursive definition, however
    \pause
  \item A structure Foo can have as field member a pointer to Foo.
  \end{itemize}
  
\end{frame}

\end{document}
\begin{frame}
  \frametitle{Abstract data type List}
  \pause
  A list is either
  \begin{itemize}
  \item An empty list
    or
    \pause
  \item A starting element, called the head of the list, followed by a
    list of integers, called the tail.
  \end{itemize}

  \pause

  \begin{spec}
    data List = EmptyList | Node Int List
  \end{spec}

  \pause

  Things are not so clean in |C|
  \pause
  \begin{spec}
    typedef struct Node Node;
    struct Node {
      int datum;
      struct Node *next;
    };
    typedef Node * List;
    Node emptyNode = {0, NULL};
    List emptyList = &emptyNode;
  \end{spec}

\end{frame}