|    137  |    163  | 
|    138   \normalsize |    164   \normalsize | 
|    139   \begin{center} |    165   \begin{center} | 
|    140   \begin{tabular}{ll} |    166   \begin{tabular}{ll} | 
|    141   Email:  & christian.urban at kcl.ac.uk\\ |    167   Email:  & christian.urban at kcl.ac.uk\\ | 
|    142   Of$\!$fice: & S1.27 (1st floor Strand Building)\\ |    168   Office: & S1.27 (1st floor Strand Building)\\ | 
|    143   Slides: & KEATS (also home work is there)\\ |    169   Slides: & KEATS (also home work is there)\\ | 
|    144   \end{tabular} |    170   \end{tabular} | 
|    145   \end{center} |    171   \end{center} | 
|    146  |    172  | 
|    147  |    173 \end{frame}} | 
|    148 \end{frame}} |    174 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%      | 
|    149  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%      |    175  | 
|    150  |    176 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|    151 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |    177 \mode<presentation>{ | 
|    152 \mode<presentation>{ |    178 \begin{frame}[c] | 
|    153 \begin{frame}[c] |    179  | 
|    154 \frametitle{\begin{tabular}{c}Building a ``Web Browser''\end{tabular}} |    180 Imagine the following situation: You talk to somebody | 
|    155  |    181 and you find out that she/he has implemented a compiler.\smallskip | 
|    156 Using a lexer: assume the following regular expressions |    182  | 
|         |    183 What is your reaction? \pause Check all that apply.\bigskip | 
|         |    184  | 
|         |    185  \begin{itemize} | 
|         |    186  \item[$\Box$] You think she/he is God | 
|         |    187  \item[$\Box$] \"Uberhacker | 
|         |    188  \item[$\Box$] superhuman | 
|         |    189  \item[$\Box$] wizard | 
|         |    190  \item[$\Box$] supremo | 
|         |    191  \end{itemize} | 
|         |    192  | 
|         |    193 \end{frame}} | 
|         |    194 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    | 
|         |    195  | 
|         |    196 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    197 \mode<presentation>{ | 
|         |    198 \begin{frame}[c] | 
|         |    199 \frametitle{Bird's Eye View} | 
|         |    200  | 
|         |    201 \begin{center} | 
|         |    202 \begin{tikzpicture} | 
|         |    203 \node (rexp)  {\bl{\bf Lexer}}; | 
|         |    204 \node (nfa) [right=of rexp] {\bl{\bf Parser}}; | 
|         |    205 \node (dfa) [right=of nfa] {\bl{\begin{tabular}{c}\bf Machine Code/\\\bf Byte Code\end{tabular}}}; | 
|         |    206 \path[->, red, line width=2mm] (rexp) edge node [above=4mm, black] {\begin{tabular}{c@{\hspace{9mm}}}token\\[-1mm] | 
|         |    207 sequence\end{tabular}} (nfa); | 
|         |    208 \path[->, red, line width=2mm] (nfa) edge node [above=4mm, black] {\begin{tabular}{c}parse\\[-1mm] tree\end{tabular}}(dfa); | 
|         |    209 \end{tikzpicture}\\ | 
|         |    210 \end{center} | 
|         |    211  | 
|         |    212 \end{frame}} | 
|         |    213 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    | 
|         |    214  | 
|         |    215 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    216 \mode<presentation>{ | 
|         |    217 \begin{frame}[c] | 
|         |    218  | 
|         |    219 \begin{center} | 
|         |    220 \includegraphics[scale=0.7]{../pics/machine_code.jpg} | 
|         |    221 \end{center} | 
|         |    222  | 
|         |    223 \end{frame}} | 
|         |    224  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    | 
|         |    225   | 
|         |    226  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    227 \mode<presentation>{ | 
|         |    228 \begin{frame}[c] | 
|         |    229 \frametitle{Assembly Code} | 
|         |    230 \mbox{}\\[-20mm]\mbox{} | 
|         |    231  | 
|         |    232 \begin{center} | 
|         |    233 \includegraphics[scale=0.7]{../pics/assembly.jpg} | 
|         |    234 \end{center} | 
|         |    235  | 
|         |    236 \end{frame}} | 
|         |    237  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    | 
|         |    238  | 
|         |    239  | 
|         |    240 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    241 \mode<presentation>{ | 
|         |    242 \begin{frame}[c] | 
|         |    243  | 
|         |    244 \begin{center} | 
|         |    245 \bl{\begin{tabular}{@{}lcl@{}} | 
|         |    246 \textit{Stmt} & $\rightarrow$ &  $\texttt{skip}$\\ | 
|         |    247               & $|$ & \textit{Id}\;\texttt{:=}\;\textit{AExp}\\ | 
|         |    248               & $|$ & \texttt{if}\; \textit{BExp} \;\texttt{then}\; \textit{Block} \;\texttt{else}\; \textit{Block}\\ | 
|         |    249               & $|$ & \texttt{while}\; \textit{BExp} \;\texttt{do}\; \textit{Block}\\ | 
|         |    250               & $|$ & \texttt{read}\;\textit{Id}\\ | 
|         |    251               & $|$ & \texttt{write}\;\textit{Id}\\ | 
|         |    252               & $|$ & \texttt{write}\;\textit{String}\medskip\\ | 
|         |    253 \textit{Stmts} & $\rightarrow$ &  \textit{Stmt} \;\texttt{;}\; \textit{Stmts}\\ | 
|         |    254               & $|$ & \textit{Stmt}\medskip\\ | 
|         |    255 \textit{Block} & $\rightarrow$ &  \texttt{\{}\,\textit{Stmts}\,\texttt{\}}\\ | 
|         |    256                 & $|$ & \textit{Stmt}\medskip\\ | 
|         |    257 \textit{AExp} & $\rightarrow$ & \ldots\\ | 
|         |    258 \textit{BExp} & $\rightarrow$ & \ldots\\ | 
|         |    259 \end{tabular}} | 
|         |    260 \end{center} | 
|         |    261  | 
|         |    262  | 
|         |    263 \end{frame}} | 
|         |    264 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    | 
|         |    265  | 
|         |    266 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    267 \mode<presentation>{ | 
|         |    268 \begin{frame}[c] | 
|         |    269 \frametitle{\begin{tabular}{c}Fibonacci Numbers\end{tabular}} | 
|         |    270  | 
|         |    271 \mbox{}\\[-18mm]\mbox{} | 
|         |    272  | 
|         |    273 {\lstset{language=While}\fontsize{10}{12}\selectfont | 
|         |    274 \texttt{\lstinputlisting{../progs/fib.while}}} | 
|         |    275  | 
|         |    276 \end{frame}} | 
|         |    277 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    | 
|         |    278  | 
|         |    279 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    280 \mode<presentation>{ | 
|         |    281 \begin{frame}[c] | 
|         |    282 \frametitle{\begin{tabular}{c}Interpreter\end{tabular}} | 
|         |    283  | 
|         |    284 \begin{center} | 
|         |    285 \bl{\begin{tabular}{@{}lcl@{}} | 
|         |    286 $\text{eval}(n, E)$ & $\dn$ & $n$\\ | 
|         |    287 $\text{eval}(x, E)$ & $\dn$ & $E(x)$ \;\;\;\textcolor{black}{lookup \bl{$x$} in \bl{$E$}}\\ | 
|         |    288 $\text{eval}(a_1 + a_2, E)$ & $\dn$ & $\text{eval}(a_1, E) + \text{eval}(a_2, E)$\\ | 
|         |    289 $\text{eval}(a_1 - a_2, E)$ & $\dn$ & $\text{eval}(a_1, E) - \text{eval}(a_2, E)$\\ | 
|         |    290 $\text{eval}(a_1 * a_2, E)$ & $\dn$ & $\text{eval}(a_1, E) * \text{eval}(a_2, E)$\bigskip\\ | 
|         |    291 $\text{eval}(a_1 = a_2, E)$ & $\dn$ & $\text{eval}(a_1, E) = \text{eval}(a_2, E)$\\ | 
|         |    292 $\text{eval}(a_1\,!\!= a_2, E)$ & $\dn$ & $\neg(\text{eval}(a_1, E) = \text{eval}(a_2, E))$\\ | 
|         |    293 $\text{eval}(a_1 < a_2, E)$ & $\dn$ & $\text{eval}(a_1, E) < \text{eval}(a_2, E)$\ | 
|         |    294 \end{tabular}} | 
|         |    295 \end{center} | 
|         |    296  | 
|         |    297 \end{frame}} | 
|         |    298 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    | 
|         |    299  | 
|         |    300 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    301 \mode<presentation>{ | 
|         |    302 \begin{frame}[c] | 
|         |    303 \frametitle{\begin{tabular}{c}Interpreter (2)\end{tabular}} | 
|         |    304  | 
|         |    305 \begin{center} | 
|         |    306 \bl{\begin{tabular}{@{}lcl@{}} | 
|         |    307 $\text{eval}(\text{skip}, E)$ & $\dn$ & $E$\\ | 
|         |    308 $\text{eval}(x:=a, E)$ & $\dn$ & \bl{$E(x \mapsto \text{eval}(a, E))$}\\ | 
|         |    309 \multicolumn{3}{@{}l@{}}{$\text{eval}(\text{if}\;b\;\text{then}\;cs_1\;\text{else}\;cs_2 , E) \dn$}\\ | 
|         |    310 \multicolumn{3}{@{}l@{}}{\hspace{2cm}$\text{if}\;\text{eval}(b,E)\;\text{then}\; | 
|         |    311 \text{eval}(cs_1,E)$}\\ | 
|         |    312 \multicolumn{3}{@{}l@{}}{\hspace{2cm}$\phantom{\text{if}\;\text{eval}(b,E)\;}\text{else}\;\text{eval}(cs_2,E)$}\\ | 
|         |    313 \multicolumn{3}{@{}l@{}}{$\text{eval}(\text{while}\;b\;\text{do}\;cs, E) \dn$}\\ | 
|         |    314 \multicolumn{3}{@{}l@{}}{\hspace{2cm}$\text{if}\;\text{eval}(b,E)$}\\ | 
|         |    315 \multicolumn{3}{@{}l@{}}{\hspace{2cm}$\text{then}\; | 
|         |    316 \text{eval}(\text{while}\;b\;\text{do}\;cs, \text{eval}(cs,E))$}\\ | 
|         |    317 \multicolumn{3}{@{}l@{}}{\hspace{2cm}$\text{else}\; E$}\\ | 
|         |    318 $\text{eval}(\text{write}\; x, E)$ & $\dn$ & $\{\;\text{println}(E(x))\; ;\;E\;\}$\\ | 
|         |    319 \end{tabular}} | 
|         |    320 \end{center} | 
|         |    321  | 
|         |    322 \end{frame}} | 
|         |    323 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    | 
|         |    324  | 
|         |    325 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    326 \mode<presentation>{ | 
|         |    327 \begin{frame}[c] | 
|         |    328 \frametitle{\begin{tabular}{c}Test Program\end{tabular}} | 
|         |    329  | 
|         |    330 \mbox{}\\[-18mm]\mbox{} | 
|         |    331  | 
|         |    332 {\lstset{language=While}\fontsize{10}{12}\selectfont | 
|         |    333 \texttt{\lstinputlisting{../progs/loops.while}}} | 
|         |    334  | 
|         |    335 \end{frame}} | 
|         |    336 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    | 
|         |    337  | 
|         |    338 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    339 \mode<presentation>{ | 
|         |    340 \begin{frame}[t] | 
|         |    341 \frametitle{\begin{tabular}{c}Interpreted Code\end{tabular}} | 
|         |    342  | 
|         |    343 \begin{center} | 
|         |    344 \begin{tikzpicture} | 
|         |    345 \begin{axis}[axis x line=bottom, axis y line=left, xlabel=n, ylabel=secs, legend style=small] | 
|         |    346 \addplot+[smooth] file {interpreted.data}; | 
|         |    347 \end{axis} | 
|         |    348 \end{tikzpicture} | 
|         |    349 \end{center} | 
|         |    350  | 
|         |    351 \end{frame}} | 
|         |    352 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  | 
|         |    353  | 
|         |    354 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    355 \mode<presentation>{ | 
|         |    356 \begin{frame}[c] | 
|         |    357 \frametitle{\begin{tabular}{c}Java Virtual Machine\end{tabular}} | 
|         |    358  | 
|         |    359 \begin{itemize} | 
|         |    360 \item introduced in 1995 | 
|         |    361 \item is a stack-based VM (like Postscript, CLR of .Net) | 
|         |    362 \item contains a JIT compiler | 
|         |    363 \item many languages take advantage of JVM's infrastructure (JRE) | 
|         |    364 \item is garbage collected $\Rightarrow$ no buffer overflows | 
|         |    365 \item some languages compiled to the JVM: Scala, Clojure\ldots | 
|         |    366 \end{itemize} | 
|         |    367  | 
|         |    368 \end{frame}} | 
|         |    369 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    | 
|         |    370  | 
|         |    371 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    372 \mode<presentation>{ | 
|         |    373 \begin{frame}[t] | 
|         |    374 \frametitle{\begin{tabular}{c}Compiling AExps\end{tabular}} | 
|         |    375  | 
|         |    376 {\Large\bl{1 + 2}} | 
|         |    377  | 
|         |    378 \begin{center} | 
|         |    379 \bl{\begin{tabular}{l} | 
|         |    380 ldc 1\\ | 
|         |    381 ldc 2\\ | 
|         |    382 iadd\\ | 
|         |    383 \end{tabular}} | 
|         |    384 \end{center}\end{frame}} | 
|         |    385 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    | 
|         |    386  | 
|         |    387 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    388 \mode<presentation>{ | 
|         |    389 \begin{frame}[t] | 
|         |    390 \frametitle{\begin{tabular}{c}Compiling AExps\end{tabular}} | 
|         |    391  | 
|         |    392 {\Large\bl{1 + 2 + 3}} | 
|         |    393  | 
|         |    394 \begin{center} | 
|         |    395 \bl{\begin{tabular}{l} | 
|         |    396 ldc 1\\ | 
|         |    397 ldc 2\\ | 
|         |    398 iadd\\ | 
|         |    399 ldc 3\\ | 
|         |    400 iadd\\ | 
|         |    401 \end{tabular}} | 
|         |    402 \end{center} | 
|         |    403  | 
|         |    404 \end{frame}} | 
|         |    405 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    | 
|         |    406  | 
|         |    407 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    408 \mode<presentation>{ | 
|         |    409 \begin{frame}[t] | 
|         |    410 \frametitle{\begin{tabular}{c}Compiling AExps\end{tabular}} | 
|         |    411  | 
|         |    412 {\Large\bl{1 + (2 + 3)}} | 
|         |    413  | 
|         |    414 \begin{center} | 
|         |    415 \bl{\begin{tabular}{l} | 
|         |    416 ldc 1\\ | 
|         |    417 ldc 2\\ | 
|         |    418 ldc 3\\ | 
|         |    419 iadd\\ | 
|         |    420 iadd\\ | 
|         |    421 \end{tabular}} | 
|         |    422 \end{center}\bigskip\pause | 
|         |    423 \vfill | 
|         |    424  | 
|         |    425 \bl{dadd, fadd, ladd, \ldots} | 
|         |    426  | 
|         |    427 \end{frame}} | 
|         |    428 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    | 
|         |    429  | 
|         |    430  | 
|         |    431 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    432 \mode<presentation>{ | 
|         |    433 \begin{frame}[t] | 
|         |    434 \frametitle{\begin{tabular}{c}Compiling AExps\end{tabular}} | 
|         |    435  | 
|         |    436 \begin{center} | 
|         |    437 \bl{\begin{tabular}{@{}lcl@{}} | 
|         |    438 $\text{compile}(n)$ & $\dn$ & $\text{ldc}\;n$\\ | 
|         |    439 $\text{compile}(a_1 + a_2)$ & $\dn$\\  | 
|         |    440 \multicolumn{3}{l}{$\qquad\text{compile}(a_1) \;@\;\text{compile}(a_2)\;@\; \text{iadd}$}\smallskip\\ | 
|         |    441 $\text{compile}(a_1 - a_2)$ & $\dn$\\  | 
|         |    442 \multicolumn{3}{l}{$\qquad\text{compile}(a_1) \;@\; \text{compile}(a_2)\;@\; \text{isub}$}\smallskip\\ | 
|         |    443 $\text{compile}(a_1 * a_2)$ & $\dn$\\  | 
|         |    444 \multicolumn{3}{l}{$\qquad\text{compile}(a_1) \;@\; \text{compile}(a_2)\;@\; \text{imul}$}\smallskip\\ | 
|         |    445 \end{tabular}} | 
|         |    446 \end{center}\pause | 
|         |    447  | 
|         |    448 \end{frame}} | 
|         |    449 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  | 
|         |    450  | 
|         |    451 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    452 \mode<presentation>{ | 
|         |    453 \begin{frame}[t] | 
|         |    454 \frametitle{\begin{tabular}{c}Compiling AExps\end{tabular}} | 
|         |    455  | 
|         |    456 {\Large\bl{1 + 2 * 3 + (4 - 3)}} | 
|         |    457  | 
|         |    458 \begin{center} | 
|         |    459 \bl{\begin{tabular}{l} | 
|         |    460 ldc 1\\ | 
|         |    461 ldc 2\\ | 
|         |    462 ldc 3\\ | 
|         |    463 imul\\ | 
|         |    464 ldc 4\\ | 
|         |    465 ldc 3\\ | 
|         |    466 isub\\ | 
|         |    467 iadd\\ | 
|         |    468 iadd\\ | 
|         |    469 \end{tabular}} | 
|         |    470 \end{center} | 
|         |    471  | 
|         |    472 \end{frame}} | 
|         |    473 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    | 
|         |    474  | 
|         |    475 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    476 \mode<presentation>{ | 
|         |    477 \begin{frame}[t] | 
|         |    478 \frametitle{\begin{tabular}{c}Variables\end{tabular}} | 
|         |    479  | 
|         |    480 {\Large\bl{$x := 5 + y * 2$}}\bigskip\pause    | 
|         |    481  | 
|         |    482 \begin{itemize} | 
|         |    483 \item lookup: \bl{$\text{iload}\; index$} | 
|         |    484 \item store: \bl{$\text{istore}\; index$} | 
|         |    485 \end{itemize}\bigskip\pause | 
|         |    486  | 
|         |    487 while compilating we have to maintain a map between our identifiers and the | 
|         |    488 Java bytecode indices | 
|         |    489  | 
|         |    490 \begin{center} | 
|         |    491 \bl{$\text{compile}(a, E)$} | 
|         |    492 \end{center} | 
|         |    493  | 
|         |    494 \end{frame}} | 
|         |    495 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    | 
|         |    496  | 
|         |    497 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    498 \mode<presentation>{ | 
|         |    499 \begin{frame}[t] | 
|         |    500 \frametitle{\begin{tabular}{c}Compiling AExps\end{tabular}} | 
|         |    501  | 
|         |    502 \begin{center} | 
|         |    503 \bl{\begin{tabular}{@{}lcl@{}} | 
|         |    504 $\text{compile}(n, E)$ & $\dn$ & $\text{ldc}\;n$\\ | 
|         |    505 $\text{compile}(a_1 + a_2, E)$ & $\dn$\\  | 
|         |    506 \multicolumn{3}{l}{$\qquad\text{compile}(a_1, E) \;@\;\text{compile}(a_2. E)\;@\; \text{iadd}$}\smallskip\\ | 
|         |    507 $\text{compile}(a_1 - a_2, E)$ & $\dn$\\  | 
|         |    508 \multicolumn{3}{l}{$\qquad\text{compile}(a_1, E) \;@\; \text{compile}(a_2, E)\;@\; \text{isub}$}\smallskip\\ | 
|         |    509 $\text{compile}(a_1 * a_2, E)$ & $\dn$\\  | 
|         |    510 \multicolumn{3}{l}{$\qquad\text{compile}(a_1, E) \;@\; \text{compile}(a_2, E)\;@\; \text{imul}$}\bigskip\\ | 
|         |    511 $\text{compile}(x, E)$ & $\dn$ & $\text{iload}\;E(x)$\\ | 
|         |    512 \end{tabular}} | 
|         |    513 \end{center}\pause | 
|         |    514  | 
|         |    515 \end{frame}} | 
|         |    516 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  | 
|         |    517  | 
|         |    518 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    519 \mode<presentation>{ | 
|         |    520 \begin{frame}[t] | 
|         |    521 \frametitle{\begin{tabular}{c}Compiling Statements\end{tabular}} | 
|         |    522  | 
|         |    523 We return a list of instructions and an environment for the variables | 
|         |    524  | 
|         |    525 \begin{center} | 
|         |    526 \bl{\begin{tabular}{@{}l@{\hspace{1mm}}c@{\hspace{1mm}}l@{}} | 
|         |    527 $\text{compile}(\text{skip}, E)$ & $\dn$ & $(N\!il, E)$\bigskip\\ | 
|         |    528 $\text{compile}(x := a, E)$ & $\dn$\\ | 
|         |    529 \multicolumn{3}{l}{$(\text{compile}(a, E) \;@\;\text{istore}\;index, E(x\mapsto index))$}\\ | 
|         |    530 \end{tabular}} | 
|         |    531 \end{center}\medskip | 
|         |    532  | 
|         |    533 where \bl{$index$} is \bl{$E(x)$} if it is already defined, or if it is not then the largest index not yet seen | 
|         |    534  | 
|         |    535 \end{frame}} | 
|         |    536 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  | 
|         |    537  | 
|         |    538 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    539 \mode<presentation>{ | 
|         |    540 \begin{frame}[t] | 
|         |    541 \frametitle{\begin{tabular}{c}Compiling AExps\end{tabular}} | 
|         |    542  | 
|         |    543 {\Large\bl{$x := x + 1$}} | 
|         |    544  | 
|         |    545 \begin{center} | 
|         |    546 \bl{\begin{tabular}{l} | 
|         |    547 iload $n_x$\\ | 
|         |    548 ldc 1\\ | 
|         |    549 iadd\\ | 
|         |    550 istore $n_x$\\ | 
|         |    551 \end{tabular}} | 
|         |    552 \end{center} | 
|         |    553  | 
|         |    554 where \bl{$n_x$} is the index corresponding to the variable \bl{$x$} | 
|         |    555  | 
|         |    556 \end{frame}} | 
|         |    557 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    | 
|         |    558  | 
|         |    559 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    560 \mode<presentation>{ | 
|         |    561 \begin{frame}[t] | 
|         |    562 \frametitle{\begin{tabular}{c}Compiling Ifs\end{tabular}} | 
|         |    563  | 
|         |    564 {\Large\bl{$\text{if}\;b\;\text{then}\;cs_1\;\text{else}\;cs_2$}}\bigskip\bigskip | 
|         |    565  | 
|         |    566 \onslide<2->{Case }\only<2>{{\bf True}:}\only<3>{{\bf False}:} | 
|         |    567  | 
|         |    568 \begin{center} | 
|         |    569 \begin{tikzpicture}[node distance=2mm and 4mm, | 
|         |    570  block/.style={rectangle, minimum size=1cm, draw=black, line width=1mm}, | 
|         |    571  point/.style={rectangle, inner sep=0mm, minimum size=0mm, fill=red}, | 
|         |    572  skip loop/.style={red, line width=1mm, to path={-- ++(0,-10mm) -| (\tikztotarget)}}] | 
|         |    573 \node (A1) [point] {}; | 
|         |    574 \node (b) [block, right=of A1] {code of \bl{$b$}}; | 
|         |    575 \node (A2) [point, right=of b] {}; | 
|         |    576 \node (cs1) [block, right=of A2] {code of \bl{$cs_1$}}; | 
|         |    577 \node (A3) [point, right=of cs1] {}; | 
|         |    578 \node (cs2) [block, right=of A3] {code of \bl{$cs_2$}}; | 
|         |    579 \node (A4) [point, right=of cs2] {}; | 
|         |    580  | 
|         |    581 \only<2>{ | 
|         |    582 \draw (A1) edge [->, red, line width=1mm] (b); | 
|         |    583 \draw (b) edge [->, red, line width=1mm] (cs1); | 
|         |    584 \draw (cs1) edge [->, red, line width=1mm] (A3); | 
|         |    585 \draw (A3) edge [->,skip loop] (A4); | 
|         |    586 \node [below=of cs2] {\raisebox{-5mm}{\small{}jump}};} | 
|         |    587 \only<3>{ | 
|         |    588 \draw (A1) edge [->, red, line width=1mm] (b); | 
|         |    589 \draw (b) edge [->, red, line width=1mm] (A2); | 
|         |    590 \draw (A2) edge [skip loop] (A3); | 
|         |    591 \draw (A3) edge [->, red, line width=1mm] (cs2); | 
|         |    592 \draw (cs2) edge [->,red, line width=1mm] (A4); | 
|         |    593 \node [below=of cs1] {\raisebox{-5mm}{\small{}conditional jump}};} | 
|         |    594 \end{tikzpicture} | 
|         |    595 \end{center} | 
|         |    596  | 
|         |    597  | 
|         |    598 \end{frame}} | 
|         |    599 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    | 
|         |    600  | 
|         |    601 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    602 \mode<presentation>{ | 
|         |    603 \begin{frame}[c] | 
|         |    604 \frametitle{\begin{tabular}{c}Conditional Jumps\end{tabular}} | 
|         |    605  | 
|         |    606 \begin{minipage}{1.1\textwidth} | 
|         |    607 \begin{itemize} | 
|         |    608 \item \bl{if\_icmpeq $label$} if two ints are equal, then jump\medskip | 
|         |    609 \item \bl{if\_icmpne $label$} if two ints aren't equal, then jump\medskip | 
|         |    610 \item \bl{if\_icmpge $label$} if one int is greater or equal then another, then jump | 
|         |    611 \item[]\ldots | 
|         |    612 \end{itemize} | 
|         |    613 \end{minipage}\pause | 
|         |    614  | 
|         |    615  | 
|         |    616 \begin{center} | 
|         |    617 \bl{\begin{tabular}{l} | 
|         |    618 $L_1$:\\ | 
|         |    619 \hspace{5mm}if\_icmpeq\;$L_2$\\ | 
|         |    620 \hspace{5mm}iload 1\\ | 
|         |    621 \hspace{5mm}ldc 1\\ | 
|         |    622 \hspace{5mm}iadd\\ | 
|         |    623 \hspace{5mm}if\_icmpeq\;$L_1$\\ | 
|         |    624 $L_2$: | 
|         |    625 \end{tabular}} | 
|         |    626 \end{center} | 
|         |    627  | 
|         |    628 \begin{textblock}{3.5}(11,12) | 
|         |    629 \only<3>{labels must be unique} | 
|         |    630 \end{textblock} | 
|         |    631 \end{frame}} | 
|         |    632 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    | 
|         |    633  | 
|         |    634 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    635 \mode<presentation>{ | 
|         |    636 \begin{frame}[t] | 
|         |    637 \frametitle{\begin{tabular}{c}Compiling BExps\end{tabular}} | 
|         |    638  | 
|         |    639 {\Large\bl{$a_1 = a_2$}} | 
|    157  |    640  | 
|    158 \begin{center} |    641 \begin{center} | 
|    159 \bl{\begin{tabular}{lcl} |    642 \bl{\begin{tabular}{lcl} | 
|    160 $SY\!M$ & $\dn$ & $(\text{a}..\text{zA}..\text{Z0}..\text{9}..)$\\ |    643 $\text{compile}(a_1 = a_2, E, lab)$ & $\dn$\\  | 
|    161 $W\!O\!RD$ & $\dn$ & $SY\!M^+$\\ |    644 \multicolumn{3}{l}{$\quad\text{compile}(a_1, E) \;@\;\text{compile}(a_2, E)\;@\; \text{if\_icmpne}\;lab$} | 
|    162 $BT\!AG$ & $\dn$ & $<\!W\!O\!RD\!>$\\ |    645 \end{tabular}} | 
|    163 $ET\!AG$ & $\dn$ & $<\!/W\!O\!RD\!>$\\ |    646 \end{center} | 
|    164 $W\!HIT\!E$ & $\dn$ & $\texttt{" "} + \texttt{"}\slash{}n\texttt{"}$\\ |    647  | 
|    165 \end{tabular}} |    648 \end{frame}} | 
|    166 \end{center} |    649 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    | 
|    167  |    650  | 
|    168 \end{frame}} |    651 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|    169 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    |    652 \mode<presentation>{ | 
|    170  |    653 \begin{frame}[t] | 
|    171 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |    654 \frametitle{\begin{tabular}{c}Compiling Ifs\end{tabular}} | 
|    172 \mode<presentation>{ |    655  | 
|    173 \begin{frame}[c] |    656 {\Large\bl{if $b$ then $cs_1$ else $cs_2$}} | 
|    174 \frametitle{\begin{tabular}{c}Interpreting a List of Tokens\end{tabular}} |    657  | 
|         |    658 \begin{center} | 
|         |    659 \bl{\begin{tabular}{lcl} | 
|         |    660 $\text{compile}(\text{if}\;b\;\text{then}\; cs_1\;\text{else}\; cs_2, E)$ & $\dn$\\  | 
|         |    661 \multicolumn{3}{l}{$\quad l_{ifelse}\;$ \textcolor{black}{(fresh label)}}\\ | 
|         |    662 \multicolumn{3}{l}{$\quad l_{ifend}\;$ \textcolor{black}{(fresh label)}}\\ | 
|         |    663 \multicolumn{3}{l}{$\quad (is_1, E') = \text{compile}(cs_1, E)$}\\ | 
|         |    664 \multicolumn{3}{l}{$\quad (is_2, E'') = \text{compile}(cs_2, E')$}\\ | 
|         |    665 \multicolumn{3}{l}{$\quad(\text{compile}(b, E, l_{ifelse})$}\\ | 
|         |    666 \multicolumn{3}{l}{$\quad\phantom{(}@\;is_1$}\\ | 
|         |    667 \multicolumn{3}{l}{$\quad\phantom{(}@\; \text{goto}\;l_{ifend}$}\\ | 
|         |    668 \multicolumn{3}{l}{$\quad\phantom{(}@\;l_{ifelse}:$}\\ | 
|         |    669 \multicolumn{3}{l}{$\quad\phantom{(}@\;is_2$}\\ | 
|         |    670 \multicolumn{3}{l}{$\quad\phantom{(}@\;l_{ifend}:, E'')$}\\ | 
|         |    671 \end{tabular}} | 
|         |    672 \end{center} | 
|         |    673  | 
|         |    674 \end{frame}} | 
|         |    675 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    | 
|         |    676  | 
|         |    677 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    678 \mode<presentation>{ | 
|         |    679 \begin{frame}[t] | 
|         |    680 \frametitle{\begin{tabular}{c}Compiling Whiles\end{tabular}} | 
|         |    681  | 
|         |    682 {\Large\bl{$\text{while}\;b\;\text{do}\;cs$}}\bigskip\bigskip | 
|         |    683  | 
|         |    684 \onslide<2->{Case }\only<2>{{\bf True}:}\only<3>{{\bf False}:} | 
|         |    685  | 
|         |    686 \begin{center} | 
|         |    687 \begin{tikzpicture}[node distance=2mm and 4mm, | 
|         |    688  block/.style={rectangle, minimum size=1cm, draw=black, line width=1mm}, | 
|         |    689  point/.style={rectangle, inner sep=0mm, minimum size=0mm, fill=red}, | 
|         |    690  skip loop/.style={red, line width=1mm, to path={-- ++(0,-10mm) -| (\tikztotarget)}}] | 
|         |    691 \node (A0) [point, left=of A1] {}; | 
|         |    692 \node (A1) [point] {}; | 
|         |    693 \node (b) [block, right=of A1] {code of \bl{$b$}}; | 
|         |    694 \node (A2) [point, right=of b] {}; | 
|         |    695 \node (cs1) [block, right=of A2] {code of \bl{$cs$}}; | 
|         |    696 \node (A3) [point, right=of cs1] {}; | 
|         |    697 \node (A4) [point, right=of A3] {}; | 
|         |    698  | 
|         |    699 \only<2>{ | 
|         |    700 \draw (A0) edge [->, red, line width=1mm] (b); | 
|         |    701 \draw (b) edge [->, red, line width=1mm] (cs1); | 
|         |    702 \draw (cs1) edge [->, red, line width=1mm] (A3); | 
|         |    703 \draw (A3) edge [->,skip loop] (A1);} | 
|         |    704 \only<3>{ | 
|         |    705 \draw (A0) edge [->, red, line width=1mm] (b); | 
|         |    706 \draw (b) edge [->, red, line width=1mm] (A2); | 
|         |    707 \draw (A2) edge [skip loop] (A3); | 
|         |    708 \draw (A3) edge [->, red, line width=1mm] (A4);} | 
|         |    709 \end{tikzpicture} | 
|         |    710 \end{center} | 
|         |    711  | 
|         |    712  | 
|         |    713 \end{frame}} | 
|         |    714 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    | 
|         |    715  | 
|         |    716 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    717 \mode<presentation>{ | 
|         |    718 \begin{frame}[t] | 
|         |    719 \frametitle{\begin{tabular}{c}Compiling Whiles\end{tabular}} | 
|         |    720  | 
|         |    721 {\Large\bl{while $b$ do $cs$}} | 
|         |    722  | 
|         |    723 \begin{center} | 
|         |    724 \bl{\begin{tabular}{lcl} | 
|         |    725 $\text{compile}(\text{while}\; b\; \text{do} \;cs, E)$ & $\dn$\\  | 
|         |    726 \multicolumn{3}{l}{$\quad l_{wbegin}\;$ \textcolor{black}{(fresh label)}}\\ | 
|         |    727 \multicolumn{3}{l}{$\quad l_{wend}\;$ \textcolor{black}{(fresh label)}}\\ | 
|         |    728 \multicolumn{3}{l}{$\quad (is, E') = \text{compile}(cs_1, E)$}\\ | 
|         |    729 \multicolumn{3}{l}{$\quad(l_{wbegin}:$}\\ | 
|         |    730 \multicolumn{3}{l}{$\quad\phantom{(}@\;\text{compile}(b, E, l_{wend})$}\\ | 
|         |    731 \multicolumn{3}{l}{$\quad\phantom{(}@\;is$}\\ | 
|         |    732 \multicolumn{3}{l}{$\quad\phantom{(}@\; \text{goto}\;l_{wbegin}$}\\ | 
|         |    733 \multicolumn{3}{l}{$\quad\phantom{(}@\;l_{wend}:, E')$}\\ | 
|         |    734 \end{tabular}} | 
|         |    735 \end{center} | 
|         |    736  | 
|         |    737 \end{frame}} | 
|         |    738 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  | 
|         |    739  | 
|         |    740 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    741 \mode<presentation>{ | 
|         |    742 \begin{frame}[t] | 
|         |    743 \frametitle{\begin{tabular}{c}Compiling Writes\end{tabular}} | 
|         |    744  | 
|         |    745 {\Large\bl{write $x$}} | 
|         |    746  | 
|         |    747 \begin{center} | 
|         |    748 \small\bl{\begin{tabular}{l} | 
|         |    749 .method public static write(I)V\hspace{1cm}\textcolor{black}{(library function)}\\  | 
|         |    750 \;\;    .limit locals 5 \\ | 
|         |    751 \;\;    .limit stack 5 \\ | 
|         |    752 \;\;    iload 0 \\ | 
|         |    753 \;\;    getstatic java/lang/System/out Ljava/io/PrintStream;\\  | 
|         |    754 \;\;    swap \\ | 
|         |    755 \;\;    invokevirtual java/io/PrintStream/println(I)V \\ | 
|         |    756 \;\;    return \\ | 
|         |    757 .end method\bigskip\bigskip\\ | 
|         |    758 % | 
|         |    759 \normalsize | 
|         |    760 iload $E(x)$\\ | 
|         |    761 invokestatic write(I)V\\ | 
|         |    762 \end{tabular}} | 
|         |    763 \end{center} | 
|         |    764  | 
|         |    765 \end{frame}} | 
|         |    766 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  | 
|         |    767  | 
|         |    768 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    769 \mode<presentation>{ | 
|         |    770 \begin{frame}[c] | 
|         |    771  | 
|         |    772 \begin{center} | 
|         |    773 \small\bl{\begin{tabular}{l} | 
|         |    774 .class public XXX.XXX\\ | 
|         |    775 .super java/lang/Object\\ | 
|         |    776 \\ | 
|         |    777 .method public <init>()V\\ | 
|         |    778 \;\;     aload\_0\\ | 
|         |    779 \;\;     invokenonvirtual java/lang/Object/<init>()V\\ | 
|         |    780  \;\;    return\\ | 
|         |    781 .end method\\ | 
|         |    782 \\ | 
|         |    783 .method public static main([Ljava/lang/String;)V\\ | 
|         |    784 \;\;   .limit locals 200\\ | 
|         |    785 \;\;     .limit stack 200\\ | 
|         |    786 \\ | 
|         |    787    \textcolor{black}{(here comes the compiled code)}\\ | 
|         |    788 \\ | 
|         |    789 \;\;     return\\ | 
|         |    790 .end method\\ | 
|         |    791 \end{tabular}} | 
|         |    792 \end{center} | 
|         |    793  | 
|         |    794 \end{frame}} | 
|         |    795 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   | 
|         |    796  | 
|         |    797 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    798 \mode<presentation>{ | 
|         |    799 \begin{frame}[c] | 
|         |    800 \frametitle{\begin{tabular}{c}Next Compiler Phases\end{tabular}} | 
|    175  |    801  | 
|    176 \begin{itemize} |    802 \begin{itemize} | 
|    177 \item the text should be formatted consistently up to a specified width, say 60 characters  |    803 \item assembly $\Rightarrow$ byte code (class file) | 
|    178 \item potential linebreaks are inserted by the formatter (not the input) |    804 \item labels $\Rightarrow$ absolute or relative jumps\bigskip\bigskip | 
|    179 \item repeated whitespaces are ``condensed'' to a single whitepace |    805 \item \texttt{javap} is a disassembler for class files | 
|    180 \item \bl{$<\!p\!>$} \bl{$<\!\slash{}p\!>$}  start/end paragraph |         | 
|    181 \item \bl{$<\!b\!>$} \bl{$<\!\slash{}b\!>$}  start/end bold |         | 
|    182 \item \bl{$<\!red\!>$} \bl{$<\!\slash{}red\!>$}  start/end red (cyan, etc) |         | 
|    183  |         | 
|    184  |         | 
|    185 \end{itemize} |    806 \end{itemize} | 
|    186  |    807  | 
|    187 \end{frame}} |    808 \end{frame}} | 
|    188 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    |    809 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   | 
|    189  |    810  | 
|    190 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |    811 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|    191 \mode<presentation>{ |    812 \mode<presentation>{ | 
|    192 \begin{frame}[c] |    813 \begin{frame}[t] | 
|    193 \frametitle{\begin{tabular}{c}Interpreting a List of Tokens\end{tabular}} |    814 \frametitle{\begin{tabular}{c}Compiled Code\end{tabular}} | 
|    194  |    815  | 
|    195 The lexer cannot prevent errors like |    816 \begin{center} | 
|    196  |    817 \begin{tikzpicture} | 
|    197 \begin{center} |    818 \begin{axis}[axis x line=bottom, axis y line=left, xlabel=n, ylabel=secs, legend style=small] | 
|    198 \bl{$<\!b\!>$} \ldots \bl{$<\!p\!>$} \ldots \bl{$<\!\slash{}b\!>$} \ldots \bl{$<\!\slash{}p\!>$}  |    819 \addplot+[smooth] file {compiled.data}; | 
|    199 \end{center} |    820 \end{axis} | 
|    200  |    821 \end{tikzpicture} | 
|    201 or |    822 \end{center} | 
|    202  |    823  | 
|    203 \begin{center} |    824 \end{frame}} | 
|    204 \bl{$<\!\slash{}b\!>$} \ldots \bl{$<\!b\!>$} |    825 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  | 
|    205 \end{center} |    826  | 
|    206  |    827  | 
|    207  |    828  | 
|    208 \end{frame}} |    829 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|    209 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    |    830 \mode<presentation>{ | 
|    210  |    831 \begin{frame}[t] | 
|    211 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |    832 \frametitle{\begin{tabular}{c}Compiler vs.~Interpreter\end{tabular}} | 
|    212 \mode<presentation>{ |    833  | 
|    213 \begin{frame}[c] |    834 \begin{center} | 
|    214 \frametitle{\begin{tabular}{c}Parser Combinators\end{tabular}} |    835 \begin{tikzpicture} | 
|    215  |    836 \begin{axis}[axis x line=bottom, axis y line=left, ylabel=secs, | 
|    216 Parser combinators: \bigskip |    837     xlabel=n, | 
|    217  |    838     enlargelimits=0.05, | 
|    218 \begin{minipage}{1.1\textwidth} |    839     ybar interval=0.7, legend style=small] | 
|    219 \begin{center} |    840 \addplot file {interpreted2.data}; | 
|    220 \mbox{}\hspace{-12mm}\mbox{}$\underbrace{\text{list of tokens}}_{\text{input}}$ \bl{$\Rightarrow$}  |    841 \addplot file {compiled2.data}; | 
|    221 $\underbrace{\text{set of (parsed input, unparsed input)}}_{\text{output}}$ |    842 %\legend{interpreted, compiled} | 
|    222 \end{center} |    843 \end{axis} | 
|    223 \end{minipage}\bigskip |    844 \end{tikzpicture} | 
|         |    845 \end{center} | 
|         |    846  | 
|         |    847 \end{frame}} | 
|         |    848 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   | 
|         |    849  | 
|         |    850  | 
|         |    851  | 
|         |    852 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | 
|         |    853 \mode<presentation>{ | 
|         |    854 \begin{frame}[t] | 
|         |    855 \frametitle{\begin{tabular}{c}What Next\end{tabular}} | 
|    224  |    856  | 
|    225 \begin{itemize} |    857 \begin{itemize} | 
|    226 \item sequencing |    858 \item register spilling | 
|    227 \item alternative |    859 \item dead code removal | 
|    228 \item semantic action |    860 \item loop optimisations | 
|         |    861 \item instruction selection | 
|         |    862 \item type checking | 
|         |    863 \item concurrency | 
|         |    864 \item fuzzy testing | 
|         |    865 \item verification\bigskip\\ | 
|         |    866  | 
|         |    867 \item GCC, LLVM, tracing JITs | 
|    229 \end{itemize} |    868 \end{itemize} | 
|    230  |    869  | 
|    231 \end{frame}} |    870 \end{frame}} | 
|    232 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    |         | 
|    233  |         | 
|    234 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |         | 
|    235 \mode<presentation>{ |         | 
|    236 \begin{frame}[c] |         | 
|    237  |         | 
|    238 Alternative parser (code \bl{$p\;||\;q$})\bigskip |         | 
|    239  |         | 
|    240 \begin{itemize} |         | 
|    241 \item apply \bl{$p$} and also \bl{$q$}; then combine the outputs |         | 
|    242 \end{itemize} |         | 
|    243  |         | 
|    244 \begin{center} |         | 
|    245 \large \bl{$p(\text{input}) \cup q(\text{input})$} |         | 
|    246 \end{center} |         | 
|    247  |         | 
|    248  |         | 
|    249 \end{frame}} |         | 
|    250 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    |         | 
|    251  |         | 
|    252 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |         | 
|    253 \mode<presentation>{ |         | 
|    254 \begin{frame}[c] |         | 
|    255  |         | 
|    256 Sequence parser (code \bl{$p\sim q$})\bigskip |         | 
|    257  |         | 
|    258 \begin{itemize} |         | 
|    259 \item apply first \bl{$p$} producing a set of pairs |         | 
|    260 \item then apply \bl{$q$} to the unparsed parts |         | 
|    261 \item then combine the results:\\ \mbox{}\;\;((output$_1$, output$_2$), unparsed part) |         | 
|    262 \end{itemize} |         | 
|    263  |         | 
|    264 \begin{center} |         | 
|    265 \begin{tabular}{l} |         | 
|    266 \large \bl{$\{((o_1, o_2), u_2) \;|\;$}\\[2mm]  |         | 
|    267 \large\mbox{}\hspace{15mm} \bl{$(o_1, u_1) \in p(\text{input}) \wedge$}\\[2mm] |         | 
|    268 \large\mbox{}\hspace{15mm} \bl{$(o_2, u_2) \in q(u_1)\}$} |         | 
|    269 \end{tabular} |         | 
|    270 \end{center} |         | 
|    271  |         | 
|    272  |         | 
|    273 \end{frame}} |         | 
|    274 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    |         | 
|    275  |         | 
|    276  |         | 
|    277 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |         | 
|    278 \mode<presentation>{ |         | 
|    279 \begin{frame}[c] |         | 
|    280  |         | 
|    281 Function parser (code \bl{$p \Longrightarrow f$})\bigskip |         | 
|    282  |         | 
|    283 \begin{itemize} |         | 
|    284 \item apply \bl{$p$} producing a set of pairs |         | 
|    285 \item then apply the function \bl{$f$} to each first component |         | 
|    286 \end{itemize} |         | 
|    287  |         | 
|    288 \begin{center} |         | 
|    289 \begin{tabular}{l} |         | 
|    290 \large \bl{$\{(f(o_1), u_1) \;|\; (o_1, u_1) \in p(\text{input})\}$} |         | 
|    291 \end{tabular} |         | 
|    292 \end{center}\bigskip\bigskip\pause |         | 
|    293  |         | 
|    294 \bl{$f$} is the semantic action (``what to do with the parsed input'') |         | 
|    295  |         | 
|    296 \end{frame}} |         | 
|    297 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  |         | 
|    298  |         | 
|    299  |         | 
|    300 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |         | 
|    301 \mode<presentation>{ |         | 
|    302 \begin{frame}[c] |         | 
|    303  |         | 
|    304 Token parser:\bigskip |         | 
|    305  |         | 
|    306 \begin{itemize} |         | 
|    307 \item if the input is |         | 
|    308  |         | 
|    309 \begin{center} |         | 
|    310 \large \bl{$tok_1:: tok_2 :: \ldots :: tok_n$} |         | 
|    311 \end{center} |         | 
|    312  |         | 
|    313 then return |         | 
|    314  |         | 
|    315 \begin{center} |         | 
|    316 \large \bl{$\{(tok_1,\; tok_2 :: \ldots :: tok_n)\}$} |         | 
|    317 \end{center} |         | 
|    318  |         | 
|    319 or |         | 
|    320  |         | 
|    321 \begin{center} |         | 
|    322 \large \bl{$\{\}$} |         | 
|    323 \end{center} |         | 
|    324  |         | 
|    325 if \bl{$tok_1$} is not the right token we are looking for |         | 
|    326 \end{itemize} |         | 
|    327  |         | 
|    328  |         | 
|    329  |         | 
|    330 \end{frame}} |         | 
|    331 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  |         | 
|    332  |         | 
|    333 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |         | 
|    334 \mode<presentation>{ |         | 
|    335 \begin{frame}[c] |         | 
|    336  |         | 
|    337 Number-Token parser:\bigskip |         | 
|    338  |         | 
|    339 \begin{itemize} |         | 
|    340 \item if the input is |         | 
|    341  |         | 
|    342 \begin{center} |         | 
|    343 \large \bl{$num\_tok(42):: tok_2 :: \ldots :: tok_n$} |         | 
|    344 \end{center} |         | 
|    345  |         | 
|    346 then return |         | 
|    347  |         | 
|    348 \begin{center} |         | 
|    349 \large \bl{$\{(42,\; tok_2 :: \ldots :: tok_n)\}$} |         | 
|    350 \end{center} |         | 
|    351  |         | 
|    352 or |         | 
|    353  |         | 
|    354 \begin{center} |         | 
|    355 \large \bl{$\{\}$} |         | 
|    356 \end{center} |         | 
|    357  |         | 
|    358 if \bl{$tok_1$} is not the right token we are looking for |         | 
|    359 \end{itemize}\pause |         | 
|    360  |         | 
|    361 \begin{center} |         | 
|    362 list of tokens \bl{$\Rightarrow$} set of (\alert{int}, list of tokens) |         | 
|    363 \end{center} |         | 
|    364  |         | 
|    365 \end{frame}} |         | 
|    366 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  |         | 
|    367  |         | 
|    368 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |         | 
|    369 \mode<presentation>{ |         | 
|    370 \begin{frame}[c] |         | 
|    371  |         | 
|    372 \begin{itemize} |         | 
|    373 \item if the input is |         | 
|    374  |         | 
|    375 \begin{center} |         | 
|    376 \begin{tabular}{l} |         | 
|    377 \large \bl{$num\_tok(42)::$}\\ |         | 
|    378 \hspace{7mm}\large \bl{$num\_tok(3) ::$}\\ |         | 
|    379 \hspace{14mm}\large \bl{$tok_3 :: \ldots :: tok_n$} |         | 
|    380 \end{tabular} |         | 
|    381 \end{center} |         | 
|    382  |         | 
|    383 and the parser is  |         | 
|    384  |         | 
|    385 \begin{center} |         | 
|    386 \bl{$ntp \sim ntp$} |         | 
|    387 \end{center} |         | 
|    388  |         | 
|    389 the successful output will be |         | 
|    390  |         | 
|    391 \begin{center} |         | 
|    392 \large \bl{$\{((42, 3),\; tok_2 :: \ldots :: tok_n)\}$} |         | 
|    393 \end{center}\pause |         | 
|    394  |         | 
|    395 Now we can form |         | 
|    396 \begin{center} |         | 
|    397 \bl{$(ntp \sim ntp) \Longrightarrow f$} |         | 
|    398 \end{center} |         | 
|    399  |         | 
|    400 where \bl{$f$} is the semantic action (``what to do with the pair'') |         | 
|    401  |         | 
|    402 \end{itemize} |         | 
|    403  |         | 
|    404 \end{frame}} |         | 
|    405 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  |         | 
|    406  |         | 
|    407 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |         | 
|    408 \mode<presentation>{ |         | 
|    409 \begin{frame}[c] |         | 
|    410 \frametitle{\begin{tabular}{c}Semantic Actions\end{tabular}} |         | 
|    411  |         | 
|    412 Addition |         | 
|    413  |         | 
|    414 \begin{center} |         | 
|    415 \bl{$T \sim + \sim E \Longrightarrow \underbrace{f((x,y), z) \Rightarrow x + z}_{\text{semantic action}}$} |         | 
|    416 \end{center}\pause |         | 
|    417  |         | 
|    418 Multiplication |         | 
|    419  |         | 
|    420 \begin{center} |         | 
|    421 \bl{$F \sim * \sim T \Longrightarrow f((x,y), z) \Rightarrow x * z$} |         | 
|    422 \end{center}\pause |         | 
|    423  |         | 
|    424 Parenthesis |         | 
|    425  |         | 
|    426 \begin{center} |         | 
|    427 \bl{$\text{(} \sim E \sim \text{)} \Longrightarrow f((x,y), z) \Rightarrow y$} |         | 
|    428 \end{center} |         | 
|    429  |         | 
|    430 \end{frame}} |         | 
|    431 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    |         | 
|    432  |         | 
|    433 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |         | 
|    434 \mode<presentation>{ |         | 
|    435 \begin{frame}[c] |         | 
|    436 \frametitle{\begin{tabular}{c}Types of Parsers\end{tabular}} |         | 
|    437  |         | 
|    438 \begin{itemize} |         | 
|    439 \item {\bf Sequencing}: if \bl{$p$} returns results of type \bl{$T$}, and \bl{$q$} results of type \bl{$S$}, |         | 
|    440 then \bl{$p \sim q$} returns results of type |         | 
|    441  |         | 
|    442 \begin{center} |         | 
|    443 \bl{$T \times S$} |         | 
|    444 \end{center}\pause |         | 
|    445  |         | 
|    446 \item {\bf Alternative}: if \bl{$p$} returns results of type \bl{$T$} then  \bl{$q$} \alert{must} also have results of type \bl{$T$}, |         | 
|    447 and \bl{$p \;||\; q$} returns results of type |         | 
|    448  |         | 
|    449 \begin{center} |         | 
|    450 \bl{$T$} |         | 
|    451 \end{center}\pause |         | 
|    452  |         | 
|    453 \item {\bf Semantic Action}: if \bl{$p$} returns results of type \bl{$T$} and \bl{$f$} is a function from |         | 
|    454 \bl{$T$} to \bl{$S$}, then |         | 
|    455 \bl{$p \Longrightarrow f$} returns results of type |         | 
|    456  |         | 
|    457 \begin{center} |         | 
|    458 \bl{$S$} |         | 
|    459 \end{center} |         | 
|    460  |         | 
|    461 \end{itemize} |         | 
|    462  |         | 
|    463 \end{frame}} |         | 
|    464 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   |    871 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   | 
|    465  |    872  | 
|    466 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |         | 
|    467 \mode<presentation>{ |         | 
|    468 \begin{frame}[c] |         | 
|    469 \frametitle{\begin{tabular}{c}Input Types of Parsers\end{tabular}} |         | 
|    470  |         | 
|    471 \begin{itemize} |         | 
|    472 \item input: \alert{list of tokens} |         | 
|    473 \item output: set of (output\_type, \alert{list of tokens}) |         | 
|    474 \end{itemize}\bigskip\pause |         | 
|    475  |         | 
|    476 actually it can be any input type as long as it is a kind of sequence |         | 
|    477 (for example a string) |         | 
|    478  |         | 
|    479 \end{frame}} |         | 
|    480 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   |         | 
|    481  |         | 
|    482  |         | 
|    483 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |         | 
|    484 \mode<presentation>{ |         | 
|    485 \begin{frame}[c] |         | 
|    486 \frametitle{\begin{tabular}{c}Scannerless Parsers\end{tabular}} |         | 
|    487  |         | 
|    488 \begin{itemize} |         | 
|    489 \item input: \alert{string} |         | 
|    490 \item output: set of (output\_type, \alert{string}) |         | 
|    491 \end{itemize}\bigskip |         | 
|    492  |         | 
|    493 but lexers are better when whitespaces or comments need to be filtered out |         | 
|    494  |         | 
|    495 \end{frame}} |         | 
|    496 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   |         | 
|    497  |         | 
|    498 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |         | 
|    499 \mode<presentation>{ |         | 
|    500 \begin{frame}[c] |         | 
|    501 \frametitle{\begin{tabular}{c}Successful Parses\end{tabular}} |         | 
|    502  |         | 
|    503 \begin{itemize} |         | 
|    504 \item input: string |         | 
|    505 \item output: \alert{set of} (output\_type, string) |         | 
|    506 \end{itemize}\bigskip |         | 
|    507  |         | 
|    508 a parse is successful whenever the input has been |         | 
|    509 fully ``consumed'' (that is the second component is empty) |         | 
|    510  |         | 
|    511  |         | 
|    512 \end{frame}} |         | 
|    513 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   |         | 
|    514  |         | 
|    515 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |         | 
|    516 \mode<presentation>{ |         | 
|    517 \begin{frame}[c] |         | 
|    518 {\lstset{language=Scala}\fontsize{10}{12}\selectfont |         | 
|    519 \texttt{\lstinputlisting{app7.scala}}} |         | 
|    520 \end{frame}} |         | 
|    521 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   |         | 
|    522  |         | 
|    523 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |         | 
|    524 \mode<presentation>{ |         | 
|    525 \begin{frame}[c] |         | 
|    526 {\lstset{language=Scala}\fontsize{10}{12}\selectfont |         | 
|    527 \texttt{\lstinputlisting{app7.scala}}} |         | 
|    528 \end{frame}} |         | 
|    529 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   |         | 
|    530  |         | 
|    531 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |         | 
|    532 \mode<presentation>{ |         | 
|    533 \begin{frame}[c] |         | 
|    534 {\lstset{language=Scala}\fontsize{10}{12}\selectfont |         | 
|    535 \texttt{\lstinputlisting{app8.scala}}} |         | 
|    536 \end{frame}} |         | 
|    537 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   |         | 
|    538  |         | 
|    539 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |         | 
|    540 \mode<presentation>{ |         | 
|    541 \begin{frame}[c] |         | 
|    542 \frametitle{\begin{tabular}{c}Two Grammars\end{tabular}} |         | 
|    543  |         | 
|    544 Which languages are recognised by the following two grammars? |         | 
|    545  |         | 
|    546 \begin{center} |         | 
|    547 \bl{\begin{tabular}{lcl} |         | 
|    548 $S$ & $\rightarrow$ &  $1 \cdot S \cdot S$\\ |         | 
|    549         & $|$ & $\epsilon$ |         | 
|    550 \end{tabular}} |         | 
|    551 \end{center}\bigskip |         | 
|    552  |         | 
|    553 \begin{center} |         | 
|    554 \bl{\begin{tabular}{lcl} |         | 
|    555 $U$ & $\rightarrow$ &  $1 \cdot U$\\ |         | 
|    556         & $|$ & $\epsilon$ |         | 
|    557 \end{tabular}} |         | 
|    558 \end{center} |         | 
|    559  |         | 
|    560 \end{frame}} |         | 
|    561 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    |         | 
|    562  |         | 
|    563  |         | 
|    564 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |         | 
|    565 \mode<presentation>{ |         | 
|    566 \begin{frame}[t] |         | 
|    567 \frametitle{\begin{tabular}{c}Ambiguous Grammars\end{tabular}} |         | 
|    568  |         | 
|    569 \mbox{}\\[-25mm]\mbox{} |         | 
|    570  |         | 
|    571 \begin{center} |         | 
|    572 \begin{tikzpicture}[y=.2cm, x=.009cm] |         | 
|    573  	%axis |         | 
|    574 	\draw (0,0) -- coordinate (x axis mid) (1000,0); |         | 
|    575     	\draw (0,0) -- coordinate (y axis mid) (0,30); |         | 
|    576     	%ticks |         | 
|    577     	\foreach \x in {0, 20, 100, 200,...,1000} |         | 
|    578      		\draw (\x,1pt) -- (\x,-3pt) |         | 
|    579 			node[anchor=north] {\small \x}; |         | 
|    580     	\foreach \y in {0,5,...,30} |         | 
|    581      		\draw (1pt,\y) -- (-3pt,\y)  |         | 
|    582      			node[anchor=east] {\small\y};  |         | 
|    583 	%labels       |         | 
|    584 	\node[below=0.6cm] at (x axis mid) {\bl{1}s}; |         | 
|    585 	\node[rotate=90, left=1.2cm] at (y axis mid) {secs}; |         | 
|    586  |         | 
|    587 	%plots |         | 
|    588 	\draw[color=blue] plot[mark=*, mark options={fill=white}]  |         | 
|    589 		file {s-grammar1.data}; |         | 
|    590          \only<2->{\draw[color=red] plot[mark=triangle*, mark options={fill=white} ]  |         | 
|    591                   file {s-grammar2.data};} |         | 
|    592 	%legend |         | 
|    593 	\begin{scope}[shift={(400,20)}]  |         | 
|    594 	\draw[color=blue] (0,0) --  |         | 
|    595 		plot[mark=*, mark options={fill=white}] (0.25,0) -- (0.5,0)  |         | 
|    596 		node[right]{\small unambiguous}; |         | 
|    597 	\only<2->{\draw[yshift=\baselineskip, color=red] (0,0) --  |         | 
|    598                 plot[mark=triangle*, mark options={fill=white}] (0.25,0) -- (0.5,0) |         | 
|    599                 node[right]{\small ambiguous};}   |         | 
|    600 	\end{scope} |         | 
|    601 \end{tikzpicture} |         | 
|    602 \end{center} |         | 
|    603  |         | 
|    604 \end{frame}} |         | 
|    605 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    |         | 
|    606  |         | 
|    607 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |         | 
|    608 \mode<presentation>{ |         | 
|    609 \begin{frame}[c] |         | 
|    610 \frametitle{\begin{tabular}{c}What about Left-Recursion?\end{tabular}} |         | 
|    611  |         | 
|    612 \begin{itemize} |         | 
|    613 \item we record when we recursively called a parser\bigskip |         | 
|    614 \item whenever the is a recursion, the parser must have consumed something --- so |         | 
|    615 we can decrease the input string/list of token by one (at the end) |         | 
|    616 \end{itemize} |         | 
|    617 \end{frame}} |         | 
|    618 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    |         | 
|    619  |         | 
|    620 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |         | 
|    621 \mode<presentation>{ |         | 
|    622 \begin{frame}[c] |         | 
|    623 \frametitle{\begin{tabular}{c}While-Language\end{tabular}} |         | 
|    624  |         | 
|    625  |         | 
|    626 \begin{center} |         | 
|    627 \bl{\begin{tabular}{@{}lcl@{}} |         | 
|    628 $Stmt$ & $\rightarrow$ &  $\text{skip}$\\ |         | 
|    629               & $|$ & $Id := AExp$\\ |         | 
|    630               & $|$ & $\text{if}\; B\!Exp \;\text{then}\; Block \;\text{else}\; Block$\\ |         | 
|    631               & $|$ & $\text{while}\; B\!Exp \;\text{do}\; Block$\medskip\\ |         | 
|    632 $Stmts$ & $\rightarrow$ &  $Stmt \;\text{;}\; Stmts$\\ |         | 
|    633               & $|$ & $Stmt$\medskip\\ |         | 
|    634 $Block$ & $\rightarrow$ &  $\{ Stmts \}$\\ |         | 
|    635                 & $|$ & $Stmt$\medskip\\ |         | 
|    636 $AExp$ & $\rightarrow$ & \ldots\\ |         | 
|    637 $BExp$ & $\rightarrow$ & \ldots\\ |         | 
|    638 \end{tabular}} |         | 
|    639 \end{center} |         | 
|    640  |         | 
|    641  |         | 
|    642 \end{frame}} |         | 
|    643 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    |         | 
|    644  |         | 
|    645 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |         | 
|    646 \mode<presentation>{ |         | 
|    647 \begin{frame}[c] |         | 
|    648 \frametitle{\begin{tabular}{c}An Interpreter\end{tabular}} |         | 
|    649  |         | 
|    650 \begin{center} |         | 
|    651 \bl{\begin{tabular}{l} |         | 
|    652 $\{$\\ |         | 
|    653 \;\;$x := 5 \text{;}$\\ |         | 
|    654 \;\;$y := x * 3\text{;}$\\ |         | 
|    655 \;\;$y := x * 4\text{;}$\\ |         | 
|    656 \;\;$x := u * 3$\\ |         | 
|    657 $\}$ |         | 
|    658 \end{tabular}} |         | 
|    659 \end{center} |         | 
|    660  |         | 
|    661 \begin{itemize} |         | 
|    662 \item the interpreter has to record the value of \bl{$x$} before assigning a value to \bl{$y$}\pause |         | 
|    663 \item \bl{\text{eval}(stmt, env)} |         | 
|    664 \end{itemize} |         | 
|    665  |         | 
|    666  |         | 
|    667 \end{frame}} |         | 
|    668 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    |         | 
|    669  |    873  | 
|    670 \end{document} |    874 \end{document} | 
|    671  |    875  | 
|    672 %%% Local Variables:   |    876 %%% Local Variables:   | 
|    673 %%% mode: latex |    877 %%% mode: latex |