24 

    24 \setmonofont{Consolas}

    98 

    98 	

   203 What is a perfect attack?}

   203 What is a \alert{perfect} attack?}\bigskip

   223   \node [below right] at (A.north west) {\footnotesize\begin{tabular}{@{}l@{}}clean\\compiler\end{tabular}};}

   224   \node [below right] at (A.north west) {\footnotesize\begin{tabular}{@{}l@{}}

   225   \only<1,2>{clean}\only<3->{\alert{hacked}}\\compiler\end{tabular}};}

   227   \node (B) at (0,3)  [draw=black, rectangle, very thick, minimum height=8mm, minimum width=12mm] {};

   229   \node (B) at (-2,2)  [draw=black, rectangle, very thick, minimum height=10mm, minimum width=12mm] {};

   228   \node [below right] at (B.north west) {\footnotesize login};

   230   \node [below right] at (B.north west) {\footnotesize\begin{tabular}{@{}l@{}}login\\(src)\end{tabular}};

   229   \node [above right] at (B.south west) {\footnotesize \alert{infected}};

   231   

   230   \node [right] at (B.east) {\ldots};

   232   \node (C) at (2,2)  [draw=black, rectangle, very thick, minimum height=10mm, minimum width=12mm] {};

   233   \node [below right] at (C.north west) {\footnotesize\begin{tabular}{@{}l@{}}login\\(bin)\end{tabular}};

   234 

   235   \draw[->, line width=2mm] (B) -- (C);

   232  

   237   

   233 

   238  \onslide<3->{\node [above left=-1.5mm] at (C.south east) {\footnotesize \alert{$\blacksquare$}};}

   234 

   239 

   235   

   239 

   243 \end{frame}}

   240 

   244 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   241 \end{frame}}

   245 

   242 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   246 

   243 

   247 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   244 

   248 \mode<presentation>{

   245 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   249 \begin{frame}[c]

   246 \mode<presentation>{

   247 \begin{frame}[c]

   248 

   284   \node at (9.8,2) {\ldots};}

   285   \node at (9.8,2) {\ldots};

   286   \node at (8,-2) {\textcolor{gray}{\begin{tabular}{@{}l@{}}no host language\\needed\end{tabular}}};

   287   }

   367                & $|$ & $\alert{\text{write}\; Id}$\medskip\\

   432                & $|$ & $\alert{\text{write}\; Id}$\\

   433                 & $|$ & $\alert{\text{read}\; Id}$\medskip\\

   381 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   447 

   382 \mode<presentation>{

   383 \begin{frame}[c]

   384 \frametitle{\begin{tabular}{c}Fibonacci Numbers\end{tabular}}

   385 

   386 \mbox{}\\[-18mm]\mbox{}

   387 

   388 {\lstset{language=While}\fontsize{10}{12}\selectfont

   389 \texttt{\lstinputlisting{../progs/fib.while}}}

   390 

   391 \end{frame}}

   392 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   440 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   495  

   441 \mode<presentation>{

   442 \begin{frame}[c]

   443 \frametitle{\begin{tabular}{c}Test Program\end{tabular}}

   444 

   445 \mbox{}\\[-18mm]\mbox{}

   446 

   447 {\lstset{language=While}\fontsize{10}{12}\selectfont

   448 \texttt{\lstinputlisting{../progs/loops.while}}}

   449 

   450 \end{frame}}

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

   452 

   453 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   454 \mode<presentation>{

   455 \begin{frame}[t]

   456 \frametitle{\begin{tabular}{c}Interpreted Code\end{tabular}}

   457 

   458 \begin{center}

   459 \begin{tikzpicture}

   460 \begin{axis}[axis x line=bottom, axis y line=left, xlabel=n, ylabel=secs, legend style=small]

   461 \addplot+[smooth] file {interpreted.data};

   462 \end{axis}

   463 \end{tikzpicture}

   464 \end{center}

   465 

   466 \end{frame}}

   467 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 

   468 

   469 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   470 \mode<presentation>{

   471 \begin{frame}[c]

   472 \frametitle{\begin{tabular}{c}Java Virtual Machine\end{tabular}}

   473 

   474 \begin{itemize}

   475 \item introduced in 1995

   476 \item is a stack-based VM (like Postscript, CLR of .Net)

   477 \item contains a JIT compiler

   478 \item many languages take advantage of JVM's infrastructure (JRE)

   479 \item is garbage collected $\Rightarrow$ no buffer overflows

   480 \item some languages compiled to the JVM: Scala, Clojure\ldots

   481 \end{itemize}

   482 

   483 \end{frame}}

   484 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   485 

   486 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   487 \mode<presentation>{

   488 \begin{frame}[t]

   489 \frametitle{\begin{tabular}{c}Compiling AExps\end{tabular}}

   490 

   491 {\Large\bl{1 + 2}}

   492 

   493 \begin{center}

   494 \bl{\begin{tabular}{l}

   495 ldc 1\\

   496 ldc 2\\

   497 iadd\\

   498 \end{tabular}}

   499 \end{center}\end{frame}}

   500 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   501 

   502 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   503 \mode<presentation>{

   504 \begin{frame}[t]

   505 \frametitle{\begin{tabular}{c}Compiling AExps\end{tabular}}

   506 

   507 {\Large\bl{1 + 2 + 3}}

   508 

   509 \begin{center}

   510 \bl{\begin{tabular}{l}

   511 ldc 1\\

   512 ldc 2\\

   513 iadd\\

   514 ldc 3\\

   515 iadd\\

   516 \end{tabular}}

   517 \end{center}

   518 

   519 \end{frame}}

   520 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   521 

   522 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   523 \mode<presentation>{

   524 \begin{frame}[t]

   525 \frametitle{\begin{tabular}{c}Compiling AExps\end{tabular}}

   526 

   527 {\Large\bl{1 + (2 + 3)}}

   528 

   529 \begin{center}

   530 \bl{\begin{tabular}{l}

   531 ldc 1\\

   532 ldc 2\\

   533 ldc 3\\

   534 iadd\\

   535 iadd\\

   536 \end{tabular}}

   537 \end{center}\bigskip\pause

   538 \vfill

   539 

   540 \bl{dadd, fadd, ladd, \ldots}

   541 

   542 \end{frame}}

   543 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   544 

   545 

   546 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   547 \mode<presentation>{

   548 \begin{frame}[t]

   549 \frametitle{\begin{tabular}{c}Compiling AExps\end{tabular}}

   550 

   551 \begin{center}

   552 \bl{\begin{tabular}{@{}lcl@{}}

   553 $\text{compile}(n)$ & $\dn$ & $\text{ldc}\;n$\\

   554 $\text{compile}(a_1 + a_2)$ & $\dn$\\ 

   555 \multicolumn{3}{l}{$\qquad\text{compile}(a_1) \;@\;\text{compile}(a_2)\;@\; \text{iadd}$}\smallskip\\

   556 $\text{compile}(a_1 - a_2)$ & $\dn$\\ 

   557 \multicolumn{3}{l}{$\qquad\text{compile}(a_1) \;@\; \text{compile}(a_2)\;@\; \text{isub}$}\smallskip\\

   558 $\text{compile}(a_1 * a_2)$ & $\dn$\\ 

   559 \multicolumn{3}{l}{$\qquad\text{compile}(a_1) \;@\; \text{compile}(a_2)\;@\; \text{imul}$}\smallskip\\

   560 \end{tabular}}

   561 \end{center}\pause

   562 

   563 \end{frame}}

   564 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 

   565 

   566 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   567 \mode<presentation>{

   568 \begin{frame}[t]

   569 \frametitle{\begin{tabular}{c}Compiling AExps\end{tabular}}

   570 

   571 {\Large\bl{1 + 2 * 3 + (4 - 3)}}

   572 

   573 \begin{center}

   574 \bl{\begin{tabular}{l}

   575 ldc 1\\

   576 ldc 2\\

   577 ldc 3\\

   578 imul\\

   579 ldc 4\\

   580 ldc 3\\

   581 isub\\

   582 iadd\\

   583 iadd\\

   584 \end{tabular}}

   585 \end{center}

   586 

   587 \end{frame}}

   588 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   589 

   590 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   591 \mode<presentation>{

   592 \begin{frame}[t]

   593 \frametitle{\begin{tabular}{c}Variables\end{tabular}}

   594 

   595 {\Large\bl{$x := 5 + y * 2$}}\bigskip\pause   

   596 

   597 \begin{itemize}

   598 \item lookup: \bl{$\text{iload}\; index$}

   599 \item store: \bl{$\text{istore}\; index$}

   600 \end{itemize}\bigskip\pause

   601 

   602 while compilating we have to maintain a map between our identifiers and the

   603 Java bytecode indices

   604 

   605 \begin{center}

   606 \bl{$\text{compile}(a, E)$}

   607 \end{center}

   608 

   609 \end{frame}}

   610 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   611 

   612 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   613 \mode<presentation>{

   614 \begin{frame}[t]

   615 \frametitle{\begin{tabular}{c}Compiling AExps\end{tabular}}

   616 

   617 \begin{center}

   618 \bl{\begin{tabular}{@{}lcl@{}}

   619 $\text{compile}(n, E)$ & $\dn$ & $\text{ldc}\;n$\\

   620 $\text{compile}(a_1 + a_2, E)$ & $\dn$\\ 

   621 \multicolumn{3}{l}{$\qquad\text{compile}(a_1, E) \;@\;\text{compile}(a_2. E)\;@\; \text{iadd}$}\smallskip\\

   622 $\text{compile}(a_1 - a_2, E)$ & $\dn$\\ 

   623 \multicolumn{3}{l}{$\qquad\text{compile}(a_1, E) \;@\; \text{compile}(a_2, E)\;@\; \text{isub}$}\smallskip\\

   624 $\text{compile}(a_1 * a_2, E)$ & $\dn$\\ 

   625 \multicolumn{3}{l}{$\qquad\text{compile}(a_1, E) \;@\; \text{compile}(a_2, E)\;@\; \text{imul}$}\bigskip\\

   626 $\text{compile}(x, E)$ & $\dn$ & $\text{iload}\;E(x)$\\

   627 \end{tabular}}

   628 \end{center}\pause

   629 

   630 \end{frame}}

   631 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 

   632 

   633 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   634 \mode<presentation>{

   635 \begin{frame}[t]

   636 \frametitle{\begin{tabular}{c}Compiling Statements\end{tabular}}

   637 

   638 We return a list of instructions and an environment for the variables

   639 

   640 \begin{center}

   641 \bl{\begin{tabular}{@{}l@{\hspace{1mm}}c@{\hspace{1mm}}l@{}}

   642 $\text{compile}(\text{skip}, E)$ & $\dn$ & $(N\!il, E)$\bigskip\\

   643 $\text{compile}(x := a, E)$ & $\dn$\\

   644 \multicolumn{3}{l}{$(\text{compile}(a, E) \;@\;\text{istore}\;index, E(x\mapsto index))$}\\

   645 \end{tabular}}

   646 \end{center}\medskip

   647 

   648 where \bl{$index$} is \bl{$E(x)$} if it is already defined, or if it is not then the largest index not yet seen

   649 

   650 \end{frame}}

   651 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 

   652 

   653 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   654 \mode<presentation>{

   655 \begin{frame}[t]

   656 \frametitle{\begin{tabular}{c}Compiling AExps\end{tabular}}

   657 

   658 {\Large\bl{$x := x + 1$}}

   659 

   660 \begin{center}

   661 \bl{\begin{tabular}{l}

   662 iload $n_x$\\

   663 ldc 1\\

   664 iadd\\

   665 istore $n_x$\\

   666 \end{tabular}}

   667 \end{center}

   668 

   669 where \bl{$n_x$} is the index corresponding to the variable \bl{$x$}

   670 

   671 \end{frame}}

   672 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   673 

   674 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   675 \mode<presentation>{

   676 \begin{frame}[t]

   677 \frametitle{\begin{tabular}{c}Compiling Ifs\end{tabular}}

   678 

   679 {\Large\bl{$\text{if}\;b\;\text{then}\;cs_1\;\text{else}\;cs_2$}}\bigskip\bigskip

   680 

   681 \onslide<2->{Case }\only<2>{{\bf True}:}\only<3>{{\bf False}:}

   682 

   683 \begin{center}

   684 \begin{tikzpicture}[node distance=2mm and 4mm,

   685  block/.style={rectangle, minimum size=1cm, draw=black, line width=1mm},

   686  point/.style={rectangle, inner sep=0mm, minimum size=0mm, fill=red},

   687  skip loop/.style={red, line width=1mm, to path={-- ++(0,-10mm) -| (\tikztotarget)}}]

   688 \node (A1) [point] {};

   689 \node (b) [block, right=of A1] {code of \bl{$b$}};

   690 \node (A2) [point, right=of b] {};

   691 \node (cs1) [block, right=of A2] {code of \bl{$cs_1$}};

   692 \node (A3) [point, right=of cs1] {};

   693 \node (cs2) [block, right=of A3] {code of \bl{$cs_2$}};

   694 \node (A4) [point, right=of cs2] {};

   695 

   696 \only<2>{

   697 \draw (A1) edge [->, red, line width=1mm] (b);

   698 \draw (b) edge [->, red, line width=1mm] (cs1);

   699 \draw (cs1) edge [->, red, line width=1mm] (A3);

   700 \draw (A3) edge [->,skip loop] (A4);

   701 \node [below=of cs2] {\raisebox{-5mm}{\small{}jump}};}

   702 \only<3>{

   703 \draw (A1) edge [->, red, line width=1mm] (b);

   704 \draw (b) edge [->, red, line width=1mm] (A2);

   705 \draw (A2) edge [skip loop] (A3);

   706 \draw (A3) edge [->, red, line width=1mm] (cs2);

   707 \draw (cs2) edge [->,red, line width=1mm] (A4);

   708 \node [below=of cs1] {\raisebox{-5mm}{\small{}conditional jump}};}

   709 \end{tikzpicture}

   710 \end{center}

   711 

   712 

   713 \end{frame}}

   714 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   715 

   716 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   717 \mode<presentation>{

   718 \begin{frame}[c]

   719 \frametitle{\begin{tabular}{c}Conditional Jumps\end{tabular}}

   720 

   721 \begin{minipage}{1.1\textwidth}

   722 \begin{itemize}

   723 \item \bl{if\_icmpeq $label$} if two ints are equal, then jump\medskip

   724 \item \bl{if\_icmpne $label$} if two ints aren't equal, then jump\medskip

   725 \item \bl{if\_icmpge $label$} if one int is greater or equal then another, then jump

   726 \item[]\ldots

   727 \end{itemize}

   728 \end{minipage}\pause

   729 

   730 

   731 \begin{center}

   732 \bl{\begin{tabular}{l}

   733 $L_1$:\\

   734 \hspace{5mm}if\_icmpeq\;$L_2$\\

   735 \hspace{5mm}iload 1\\

   736 \hspace{5mm}ldc 1\\

   737 \hspace{5mm}iadd\\

   738 \hspace{5mm}if\_icmpeq\;$L_1$\\

   739 $L_2$:

   740 \end{tabular}}

   741 \end{center}

   742 

   743 \begin{textblock}{3.5}(11,12)

   744 \only<3>{labels must be unique}

   745 \end{textblock}

   746 \end{frame}}

   747 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   748 

   749 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   750 \mode<presentation>{

   751 \begin{frame}[t]

   752 \frametitle{\begin{tabular}{c}Compiling BExps\end{tabular}}

   753 

   754 {\Large\bl{$a_1 = a_2$}}

   755 

   756 \begin{center}

   757 \bl{\begin{tabular}{lcl}

   758 $\text{compile}(a_1 = a_2, E, lab)$ & $\dn$\\ 

   759 \multicolumn{3}{l}{$\quad\text{compile}(a_1, E) \;@\;\text{compile}(a_2, E)\;@\; \text{if\_icmpne}\;lab$}

   760 \end{tabular}}

   761 \end{center}

   762 

   763 \end{frame}}

   764 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   765 

   766 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   767 \mode<presentation>{

   768 \begin{frame}[t]

   769 \frametitle{\begin{tabular}{c}Compiling Ifs\end{tabular}}

   770 

   771 {\Large\bl{if $b$ then $cs_1$ else $cs_2$}}

   772 

   773 \begin{center}

   774 \bl{\begin{tabular}{lcl}

   775 $\text{compile}(\text{if}\;b\;\text{then}\; cs_1\;\text{else}\; cs_2, E)$ & $\dn$\\ 

   776 \multicolumn{3}{l}{$\quad l_{ifelse}\;$ \textcolor{black}{(fresh label)}}\\

   777 \multicolumn{3}{l}{$\quad l_{ifend}\;$ \textcolor{black}{(fresh label)}}\\

   778 \multicolumn{3}{l}{$\quad (is_1, E') = \text{compile}(cs_1, E)$}\\

   779 \multicolumn{3}{l}{$\quad (is_2, E'') = \text{compile}(cs_2, E')$}\\

   780 \multicolumn{3}{l}{$\quad(\text{compile}(b, E, l_{ifelse})$}\\

   781 \multicolumn{3}{l}{$\quad\phantom{(}@\;is_1$}\\

   782 \multicolumn{3}{l}{$\quad\phantom{(}@\; \text{goto}\;l_{ifend}$}\\

   783 \multicolumn{3}{l}{$\quad\phantom{(}@\;l_{ifelse}:$}\\

   784 \multicolumn{3}{l}{$\quad\phantom{(}@\;is_2$}\\

   785 \multicolumn{3}{l}{$\quad\phantom{(}@\;l_{ifend}:, E'')$}\\

   786 \end{tabular}}

   787 \end{center}

   788 

   789 \end{frame}}

   790 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   791 

   792 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   793 \mode<presentation>{

   794 \begin{frame}[t]

   795 \frametitle{\begin{tabular}{c}Compiling Whiles\end{tabular}}

   796 

   797 {\Large\bl{$\text{while}\;b\;\text{do}\;cs$}}\bigskip\bigskip

   798 

   799 \onslide<2->{Case }\only<2>{{\bf True}:}\only<3>{{\bf False}:}

   800 

   801 \begin{center}

   802 \begin{tikzpicture}[node distance=2mm and 4mm,

   803  block/.style={rectangle, minimum size=1cm, draw=black, line width=1mm},

   804  point/.style={rectangle, inner sep=0mm, minimum size=0mm, fill=red},

   805  skip loop/.style={red, line width=1mm, to path={-- ++(0,-10mm) -| (\tikztotarget)}}]

   806 \node (A0) [point, left=of A1] {};

   807 \node (A1) [point] {};

   808 \node (b) [block, right=of A1] {code of \bl{$b$}};

   809 \node (A2) [point, right=of b] {};

   810 \node (cs1) [block, right=of A2] {code of \bl{$cs$}};

   811 \node (A3) [point, right=of cs1] {};

   812 \node (A4) [point, right=of A3] {};

   813 

   814 \only<2>{

   815 \draw (A0) edge [->, red, line width=1mm] (b);

   816 \draw (b) edge [->, red, line width=1mm] (cs1);

   817 \draw (cs1) edge [->, red, line width=1mm] (A3);

   818 \draw (A3) edge [->,skip loop] (A1);}

   819 \only<3>{

   820 \draw (A0) edge [->, red, line width=1mm] (b);

   821 \draw (b) edge [->, red, line width=1mm] (A2);

   822 \draw (A2) edge [skip loop] (A3);

   823 \draw (A3) edge [->, red, line width=1mm] (A4);}

   824 \end{tikzpicture}

   825 \end{center}

   826 

   827 

   828 \end{frame}}

   829 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   830 

   831 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   832 \mode<presentation>{

   833 \begin{frame}[t]

   834 \frametitle{\begin{tabular}{c}Compiling Whiles\end{tabular}}

   835 

   836 {\Large\bl{while $b$ do $cs$}}

   837 

   838 \begin{center}

   839 \bl{\begin{tabular}{lcl}

   840 $\text{compile}(\text{while}\; b\; \text{do} \;cs, E)$ & $\dn$\\ 

   841 \multicolumn{3}{l}{$\quad l_{wbegin}\;$ \textcolor{black}{(fresh label)}}\\

   842 \multicolumn{3}{l}{$\quad l_{wend}\;$ \textcolor{black}{(fresh label)}}\\

   843 \multicolumn{3}{l}{$\quad (is, E') = \text{compile}(cs_1, E)$}\\

   844 \multicolumn{3}{l}{$\quad(l_{wbegin}:$}\\

   845 \multicolumn{3}{l}{$\quad\phantom{(}@\;\text{compile}(b, E, l_{wend})$}\\

   846 \multicolumn{3}{l}{$\quad\phantom{(}@\;is$}\\

   847 \multicolumn{3}{l}{$\quad\phantom{(}@\; \text{goto}\;l_{wbegin}$}\\

   848 \multicolumn{3}{l}{$\quad\phantom{(}@\;l_{wend}:, E')$}\\

   849 \end{tabular}}

   850 \end{center}

   851 

   852 \end{frame}}

   853 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 

   854