
diff -r 409e5014edde -r c18b991eaad2 slides/slides05.tex
--- a/slides/slides05.tex	Fri Oct 30 01:45:03 2020 +0000
+++ b/slides/slides05.tex	Wed Nov 04 17:34:52 2020 +0000
@@ -572,6 +572,25 @@
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  
 
 
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c,fragile]
+  \begin{mybox3}{}\it 
+    "The C++ grammar is ambiguous, context-dependent and potentially
+    requires infinite lookahead to resolve some ambiguities."
+  \end{mybox3}\bigskip
+
+
+  \hfill from the \href{http://www.computing.surrey.ac.uk/research/dsrg/fog/FogThesis.pdf}{PhD thesis} by Willink (2001)
+  
+  \small
+  \begin{center}
+  \begin{lstlisting}[language={},numbers=none]
+    int(x), y, *const z;
+    int(x), y, new int;
+  \end{lstlisting}
+  \end{center}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \begin{frame}[c]
@@ -588,435 +607,11 @@
 
 \begin{center}
 \bl{$\meta{S} \rightarrow\ldots\rightarrow^? ababaa$}
-\end{center}\pause
-
-\begin{center}
-  \tt Time flies like an arrow;\\ 
-  fruit flies like bananas.
-  \end{center}  
+\end{center}
 
 \end{frame}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
-
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c]
-\frametitle{Parser Combinators}
-
-One of the simplest ways to implement a parser, see
-{\small\url{https://vimeo.com/142341803}}\bigskip
-
-Parser combinators: \bigskip
-
-\begin{minipage}{1.1\textwidth}
-\begin{center}
-\mbox{}\hspace{-12mm}\mbox{}$\underbrace{\text{list of tokens}}_{\text{input}}$ \bl{$\Rightarrow$} 
-$\underbrace{\text{set of (parsed input, unparsed input)}}_{\text{output}}$
-\end{center}
-\end{minipage}\bigskip
-
-\begin{itemize}
-\item atomic parsers
-\item sequencing
-\item alternative
-\item semantic action
-\end{itemize}
-
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
-
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c]
-
-Atomic parsers, for example, number tokens
-
-\begin{center}
-\bl{$\texttt{Num(123)}::rest \;\Rightarrow\; \{(\texttt{Num(123)}, rest)\}$} 
-\end{center}\bigskip
-
-\begin{itemize}
-\item you consume one or more token from the\\ 
-  input (stream)
-\item also works for characters and strings
-\end{itemize}
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
-
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c]
-
-Alternative parser (code \bl{$p\;||\;q$})\bigskip
-
-\begin{itemize}
-\item apply \bl{$p$} and also \bl{$q$}; then combine 
-  the outputs
-\end{itemize}
-
-\begin{center}
-\large \bl{$p(\text{input}) \cup q(\text{input})$}
-\end{center}
-
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
-
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c]
-
-Sequence parser (code \bl{$p\sim q$})\bigskip
-
-\begin{itemize}
-\item apply first \bl{$p$} producing a set of pairs
-\item then apply \bl{$q$} to the unparsed part
-\item then combine the results:\medskip 
-\begin{center}
-((output$_1$, output$_2$), unparsed part)
-\end{center}
-\end{itemize}
-
-\begin{center}
-\begin{tabular}{l}
-\large \bl{$\{((o_1, o_2), u_2) \;|\;$}\\[2mm] 
-\large\mbox{}\hspace{15mm} \bl{$(o_1, u_1) \in p(\text{input}) \wedge$}\\[2mm]
-\large\mbox{}\hspace{15mm} \bl{$(o_2, u_2) \in q(u_1)\}$}
-\end{tabular}
-\end{center}
-
-
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
-
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c]
-
-Function parser (code \bl{$p \Rightarrow f\;$})\bigskip
-
-\begin{itemize}
-\item apply \bl{$p$} producing a set of pairs
-\item then apply the function \bl{$f$} to each first component
-\end{itemize}
-
-\begin{center}
-\begin{tabular}{l}
-\large \bl{$\{(f(o_1), u_1) \;|\; (o_1, u_1) \in p(\text{input})\}$}
-\end{tabular}
-\end{center}\bigskip\bigskip\pause
-
-\bl{$f$} is the semantic action (``what to do with the parsed input'')
-
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
-
-
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\mode<presentation>{
-\begin{frame}[c]
-\frametitle{\begin{tabular}{c}Semantic Actions\end{tabular}}
-
-Addition
-
-\begin{center}
-\bl{$\meta{T} \sim + \sim \meta{E} \Rightarrow \underbrace{f\,((x,y), z) \Rightarrow x + z}_{\text{semantic action}}$}
-\end{center}\pause
-
-Multiplication
-
-\begin{center}
-\bl{$\meta{F} \sim * \sim \meta{T} \Rightarrow f\,((x,y), z) \Rightarrow x * z$}
-\end{center}\pause
-
-Parenthesis
-
-\begin{center}
-\bl{$\text{(} \sim \meta{E} \sim \text{)} \Rightarrow f\,((x,y), z) \Rightarrow y$}
-\end{center}
-
-\end{frame}}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
-
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c]
-\frametitle{Types of Parsers}
-
-\begin{itemize}
-\item {\bf Sequencing}: if \bl{$p$} returns results of type \bl{$T$}, and \bl{$q$} results of type \bl{$S$},
-then \bl{$p \sim q$} returns results of type
-
-\begin{center}
-\bl{$T \times S$}
-\end{center}\pause
-
-\item {\bf Alternative}: if \bl{$p$} returns results of type \bl{$T$} then  \bl{$q$} \alert{must} also have results of type \bl{$T$},
-and \bl{$p \;||\; q$} returns results of type
-
-\begin{center}
-\bl{$T$}
-\end{center}\pause
-
-\item {\bf Semantic Action}: if \bl{$p$} returns results of type \bl{$T$} and \bl{$f$} is a function from
-\bl{$T$} to \bl{$S$}, then
-\bl{$p \Rightarrow f$} returns results of type
-
-\begin{center}
-\bl{$S$}
-\end{center}
-
-\end{itemize}
-
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  
-
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c]
-\frametitle{Input Types of Parsers}
-
-\begin{itemize}
-\item input: \alert{token list}
-\item output: set of (output\_type, \alert{token list})
-\end{itemize}\bigskip\pause
-
-actually it can be any input type as long as it is a kind of
-sequence (for example a string)
-
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  
-
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c]
-\frametitle{Scannerless Parsers}
-
-\begin{itemize}
-\item input: \alert{string}
-\item output: set of (output\_type, \alert{string})
-\end{itemize}\bigskip\bigskip
-
-but using lexers is better because whitespaces or comments can be
-filtered out; then input is a sequence of tokens
-
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  
-
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c]
-\frametitle{Successful Parses}
-
-\begin{itemize}
-\item input: string
-\item output: \alert{set of} (output\_type, string)
-\end{itemize}\bigskip
-
-a parse is successful whenever the input has been fully
-``consumed'' (that is the second component is empty)
-
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  
-
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c]
-\frametitle{Abstract Parser Class}
-
-\small
-\lstinputlisting[language=Scala,xleftmargin=1mm]
- {../progs/app7.scala}
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  
-
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c]
-
-\small
-\fontsize{10}{12}\selectfont
-\lstinputlisting[language=Scala,xleftmargin=1mm]
-  {../progs/app8.scala}
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
-
-
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c]
-\frametitle{Two Grammars}
-
-Which languages are recognised by the following two grammars?
-
-\begin{center}
-\bl{\begin{tabular}{lcl}
-$\meta{S}$ & $\rightarrow$ &  $1 \cdot \meta{S} \cdot \meta{S}$\\
-        & $|$ & $\epsilon$
-\end{tabular}}
-\end{center}\bigskip
-
-\begin{center}
-\bl{\begin{tabular}{lcl}
-$\meta{U}$ & $\rightarrow$ &  $1 \cdot \meta{U}$\\
-        & $|$ & $\epsilon$
-\end{tabular}}
-\end{center}
-
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
-
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[t]
-\frametitle{Ambiguous Grammars}
-
-\begin{center}
-\begin{tikzpicture}
-\begin{axis}[xlabel={\pcode{1}s},ylabel={time in secs},
-    enlargelimits=false,
-    xtick={0,100,...,1000},
-    xmax=1050,
-    ymax=33,
-    ytick={0,5,...,30},
-    scaled ticks=false,
-    axis lines=left,
-    width=11cm,
-    height=7cm, 
-    legend entries={unambiguous,ambiguous},  
-    legend pos=north east,
-    legend cell align=left,
-    x tick label style={font=\small,/pgf/number format/1000 sep={}}]
-\addplot[blue,mark=*, mark options={fill=white}] 
-  table {s-grammar1.data};
-\only<2>{
-  \addplot[red,mark=triangle*, mark options={fill=white}] 
-  table {s-grammar2.data};}  
-\end{axis}
-\end{tikzpicture}
-\end{center}
-
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
-
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
-\begin{frame}
-\frametitle{While-Language}
-\mbox{}\\[-23mm]\mbox{}
-
-\bl{\begin{plstx}[rhs style=,one per line]: \meta{Stmt} ::= skip
-         | \meta{Id} := \meta{AExp}
-         | if \meta{BExp} then \meta{Block} else \meta{Block}
-         | while \meta{BExp} do \meta{Block}\\
-: \meta{Stmts} ::= \meta{Stmt} ; \meta{Stmts}
-          | \meta{Stmt}\\
-: \meta{Block} ::= \{ \meta{Stmts} \}
-          | \meta{Stmt}\\
-: \meta{AExp} ::= \ldots\\
-: \meta{BExp} ::= \ldots\\\end{plstx}}
-
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
-
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c]
-\frametitle{An Interpreter}
-
-\begin{center}
-\bl{\begin{tabular}{l}
-$\{$\\
-\;\;$x := 5 \text{;}$\\
-\;\;$y := x * 3\text{;}$\\
-\;\;$y := x * 4\text{;}$\\
-\;\;$x := u * 3$\\
-$\}$
-\end{tabular}}
-\end{center}
-
-\begin{itemize}
-\item the interpreter has to record the value of \bl{$x$} before assigning a value to \bl{$y$}\pause
-\item \bl{\texttt{eval(stmt, env)}}
-\end{itemize}
-
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
-
-
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\mode<presentation>{
-\begin{frame}[c]
-\frametitle{\begin{tabular}{c}Interpreter\end{tabular}}
-
-\begin{center}
-\bl{\begin{tabular}{@{}lcl@{}}
-$\text{eval}(n, E)$ & $\dn$ & $n$\\
-$\text{eval}(x, E)$ & $\dn$ & $E(x)$ \;\;\;\textcolor{black}{lookup \bl{$x$} in \bl{$E$}}\\
-$\text{eval}(a_1 + a_2, E)$ & $\dn$ & $\text{eval}(a_1, E) + \text{eval}(a_2, E)$\\
-$\text{eval}(a_1 - a_2, E)$ & $\dn$ & $\text{eval}(a_1, E) - \text{eval}(a_2, E)$\\
-$\text{eval}(a_1 * a_2, E)$ & $\dn$ & $\text{eval}(a_1, E) * \text{eval}(a_2, E)$\bigskip\\
-$\text{eval}(a_1 = a_2, E)$ & $\dn$ & $\text{eval}(a_1, E) = \text{eval}(a_2, E)$\\
-$\text{eval}(a_1\,!\!= a_2, E)$ & $\dn$ & $\neg(\text{eval}(a_1, E) = \text{eval}(a_2, E))$\\
-$\text{eval}(a_1 < a_2, E)$ & $\dn$ & $\text{eval}(a_1, E) < \text{eval}(a_2, E)$\
-\end{tabular}}
-\end{center}
-
-\end{frame}}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\mode<presentation>{
-\begin{frame}[c]
-\frametitle{\begin{tabular}{c}Interpreter (2)\end{tabular}}
-
-\begin{center}
-\bl{\begin{tabular}{@{}lcl@{}}
-$\text{eval}(\text{skip}, E)$ & $\dn$ & $E$\\
-$\text{eval}(x:=a, E)$ & $\dn$ & \bl{$E(x \mapsto \text{eval}(a, E))$}\\
-\multicolumn{3}{@{}l@{}}{$\text{eval}(\text{if}\;b\;\text{then}\;cs_1\;\text{else}\;cs_2 , E) \dn$}\\
-\multicolumn{3}{@{}l@{}}{\hspace{2cm}$\text{if}\;\text{eval}(b,E)\;\text{then}\;
-\text{eval}(cs_1,E)$}\\
-\multicolumn{3}{@{}l@{}}{\hspace{2cm}$\phantom{\text{if}\;\text{eval}(b,E)\;}\text{else}\;\text{eval}(cs_2,E)$}\\
-\multicolumn{3}{@{}l@{}}{$\text{eval}(\text{while}\;b\;\text{do}\;cs, E) \dn$}\\
-\multicolumn{3}{@{}l@{}}{\hspace{2cm}$\text{if}\;\text{eval}(b,E)$}\\
-\multicolumn{3}{@{}l@{}}{\hspace{2cm}$\text{then}\;
-\text{eval}(\text{while}\;b\;\text{do}\;cs, \text{eval}(cs,E))$}\\
-\multicolumn{3}{@{}l@{}}{\hspace{2cm}$\text{else}\; E$}\\
-$\text{eval}(\text{write}\; x, E)$ & $\dn$ & $\{\;\text{println}(E(x))\; ;\;E\;\}$\\
-\end{tabular}}
-\end{center}
-
-\end{frame}}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
-
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c]
-\frametitle{Test Program}
-
-\mbox{}\\[-18mm]\mbox{}
-
-??%{\lstset{language=While}%%\fontsize{10}{12}\selectfont
-%\texttt{\lstinputlisting{../progs/loops.while}}}
-
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
-
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\mode<presentation>{
-\begin{frame}[t]
-\frametitle{\begin{tabular}{c}Interpreted Code\end{tabular}}
-
-\begin{center}
-\begin{tikzpicture}
-\begin{axis}[axis x line=bottom, axis y line=left, xlabel=n, ylabel=secs, legend style=small]
-\addplot+[smooth] file {interpreted.data};
-\end{axis}
-\end{tikzpicture}
-\end{center}
-
-\end{frame}}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
-
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\mode<presentation>{
-\begin{frame}[c]
-\frametitle{\begin{tabular}{c}Java Virtual Machine\end{tabular}}
-
-\begin{itemize}
-\item introduced in 1995
-\item is a stack-based VM (like Postscript, CLR of .Net)
-\item contains a JIT compiler
-\item many languages take advantage of JVM's infrastructure (JRE)
-\item is garbage collected $\Rightarrow$ no buffer overflows
-\item some languages compile to the JVM: Scala, Clojure\ldots
-\end{itemize}
-
-\end{frame}}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
 
 \begin{frame}[t,fragile]




