--- a/handouts/ho05.tex Tue Oct 16 14:40:30 2018 +0100
+++ b/handouts/ho05.tex Mon Oct 22 23:37:11 2018 +0100
@@ -17,8 +17,8 @@
example for which there exists no regular expression is the
language of well-parenthesised expressions. In languages like
Lisp, which use parentheses rather extensively, it might be of
-interest whether the following two expressions are
-well-parenthesised (the left one is, the right one is not):
+interest to know whether the following two expressions are
+well-parenthesised or not (the left one is, the right one is not):
\begin{center}
$(((()()))())$ \hspace{10mm} $(((()()))()))$
@@ -29,7 +29,7 @@
problems, we need more powerful techniques than regular
expressions. We will in particular look at \emph{context-free
languages}. They include the regular languages as the picture
-below shows:
+below about language classes shows:
\begin{center}
@@ -46,10 +46,30 @@
\end{tikzpicture}
\end{center}
-\noindent Context-free languages play an important role in
-`day-to-day' text processing and in programming languages.
-Context-free languages are usually specified by grammars. For
-example a grammar for well-parenthesised expressions is
+\noindent Each ``bubble'' stands for sets of languages (remember
+languages are sets of strings). As indicated the set of regular
+languages are fully included inside the context-free languages,
+meaning every regular language is also context-free, but not vice
+versa. Below I will let you think for example what the context-free
+grammar is for the language corresponding to the regular expression
+$(aaa)^*a$.
+
+Because of their convenience, context-free languages play an important
+role in `day-to-day' text processing and in programming
+languages. Context-free in this setting means that ``words'' have one
+meaning only ansd this meaning is independend from in which context
+the ``words'' appear. For example ambiguity issues like
+
+\begin{center}
+\tt Time flies like an arrow; fruit flies like a banana.
+\end{center}
+
+\noindent
+from natural languages were the meaning of \emph{flies} depend on the
+surounding \emph{context} are avoided as much as possible.
+
+Context-free languages are usually specified by grammars. For example
+a grammar for well-parenthesised expressions can be given as follows:
\begin{plstx}[margin=3cm]
: \meta{P} ::= ( \cdot \meta{P} \cdot ) \cdot \meta{P}
@@ -66,7 +86,8 @@
In general grammars consist of finitely many rules built up
from \emph{terminal symbols} (usually lower-case letters) and
-\emph{non-terminal symbols} (upper-case letters inside \meta{\mbox{}}). Rules have
+\emph{non-terminal symbols} (upper-case letters written in
+bold like \meta{A}, \meta{N} and so on). Rules have
the shape
\begin{plstx}[margin=3cm]
--- a/slides/slides05.tex Tue Oct 16 14:40:30 2018 +0100
+++ b/slides/slides05.tex Mon Oct 22 23:37:11 2018 +0100
@@ -1,3 +1,4 @@
+
\documentclass[dvipsnames,14pt,t]{beamer}
\usepackage{../slides}
\usepackage{../graphics}
@@ -30,7 +31,7 @@
\begin{center}
\begin{tabular}{ll}
Email: & christian.urban at kcl.ac.uk\\
- Office: & N7.07 (North Wing, Bush House)\\
+ Office: & N\liningnums{7.07} (North Wing, Bush House)\\
Slides: & KEATS (also home work is there)\\
\end{tabular}
\end{center}
@@ -371,6 +372,29 @@
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{frame}[c]
+\frametitle{Coursework: PLs (16)}
+
+\begin{itemize}
+\item Java (16)
+\item C++, C, C\# (14)
+\item JavaScript (10)
+\item Scala (9)
+\item Python (9)
+\item PHP (6)
+\item Haskell (3)
+\item Ruby (4)
+\item Bash, Perl, Powershell (2)
+\item TypeScript (1)
+\item R (1)
+\item Coconut (1)
+\item Pascal (1)
+\end{itemize}
+
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c]
\frametitle{Coursework: Nullable}
\begin{center}
@@ -400,18 +424,18 @@
\bl{$der\, c\, (r^+)$} & \bl{$\dn$} & $?$\\
\bl{$der\, c\, (r^?)$} & \bl{$\dn$} & $?$\\
\bl{$der\, c\, (r^{\{n\}})$} & \bl{$\dn$} &
- \bl{$if\;n=0\;then\;\ZERO\;else\;(der\,c\,r)\cdot r^{\{n-1\}}$}\\
+ \bl{$if\;n=0\;then\;\ZERO\;else\;(der\,c\,r)\cdot r^{\{n-\liningnums{1}\}}$}\\
\bl{$der\, c\, (r^{\{n..\}})$} & \bl{$\dn$} &
\bl{$if\;n=0\;then (der\,c\,r)\cdot r^*$}\\
- & & \bl{$\phantom{if\;n=0\;}else \;(der\,c\,r)\cdot r^{\{n-1..\}}$}\\
+ & & \bl{$\phantom{if\;n=0\;}else \;(der\,c\,r)\cdot r^{\{n-\liningnums{1}..\}}$}\\
\bl{$der\, c\, (r^{\{..n\}})$} & \bl{$\dn$} &
- \bl{$if\;n=0\;then\;\ZERO\;else\;(der\,c\,r)\cdot r^{\{..n-1\}}$}\\
+ \bl{$if\;n=0\;then\;\ZERO\;else\;(der\,c\,r)\cdot r^{\{..n-\liningnums{1}\}}$}\\
\bl{$der\, c\, (r^{\{n..m\}})$} & \bl{$\dn$} &
\bl{$if\;n = 0 \wedge m = 0\;then\;\ZERO\; else$}\\
- \multicolumn{3}{l}{\bl{$if\;n = 0 \wedge m > 0\;then\;(der\,c\,r)\cdot r^{\{..m-1\}}$}}\\
+ \multicolumn{3}{l}{\bl{$if\;n = 0 \wedge m > 0\;then\;(der\,c\,r)\cdot r^{\{..m-\liningnums{1}\}}$}}\\
\multicolumn{3}{l}{\bl{$\phantom{if\;n = 0 \wedge m > 0\;}else
- \;(der\,c\,r)\cdot r^{\{n-1..m-1\}}$}}\\
+ \;(der\,c\,r)\cdot r^{\{n-\liningnums{1}..m-\liningnums{1}\}}$}}\\
\bl{$der\, c\, (\sim{}r)$} & \bl{$\dn$} & $?$\\
\end{tabular}
\end{center}
@@ -436,7 +460,7 @@
\end{frame}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-
+
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{frame}[t]
\frametitle{Lexer, Parser}
@@ -568,7 +592,7 @@
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c]
+\begin{frame}[t]
\frametitle{Palindromes}
A grammar for palindromes over the alphabet~\bl{$\{a,b\}$}:
@@ -616,7 +640,7 @@
\item Begin with a string containing only the start symbol, say \bl{\meta{S}}\bigskip
\item Replace any nonterminal \bl{\meta{X}} in the string by the
right-hand side of some production \bl{$\meta{X} ::= \textit{rhs}$}\bigskip
-\item Repeat 2 until there are no nonterminals
+\item Repeat 2 until there are no nonterminals left
\end{enumerate}
\begin{center}
@@ -726,7 +750,7 @@
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{frame}[t]
\frametitle{Parse Trees}
-\mbox{}\\[-16mm]
+\mbox{}\\[-12mm]
\bl{\begin{plstx}: \meta{E} ::= \meta{F} | \meta{T} \cdot + \cdot \meta{E} | \meta{T} \cdot - \cdot \meta{E}\\
: \meta{T} ::= \meta{F} | \meta{F} \cdot * \cdot \meta{T}\\
@@ -805,7 +829,7 @@
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{frame}[c]
-\frametitle{Dangling Else}
+\frametitle{`Dangling' Else}
Another ambiguous grammar:\bigskip
@@ -938,19 +962,19 @@
Addition
\begin{center}
-\bl{$T \sim + \sim E \Rightarrow \underbrace{f((x,y), z) \Rightarrow x + z}_{\text{semantic action}}$}
+\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{$F \sim * \sim T \Rightarrow f((x,y), z) \Rightarrow x * z$}
+\bl{$\meta{F} \sim * \sim \meta{T} \Rightarrow f\,((x,y), z) \Rightarrow x * z$}
\end{center}\pause
Parenthesis
\begin{center}
-\bl{$\text{(} \sim E \sim \text{)} \Rightarrow f((x,y), z) \Rightarrow y$}
+\bl{$\text{(} \sim \meta{E} \sim \text{)} \Rightarrow f\,((x,y), z) \Rightarrow y$}
\end{center}
\end{frame}}
@@ -1062,14 +1086,14 @@
\begin{center}
\bl{\begin{tabular}{lcl}
-$S$ & $\rightarrow$ & $1 \cdot S \cdot S$\\
+$\meta{S}$ & $\rightarrow$ & $1 \cdot \meta{S} \cdot \meta{S}$\\
& $|$ & $\epsilon$
\end{tabular}}
\end{center}\bigskip
\begin{center}
\bl{\begin{tabular}{lcl}
-$U$ & $\rightarrow$ & $1 \cdot U$\\
+$\meta{U}$ & $\rightarrow$ & $1 \cdot \meta{U}$\\
& $|$ & $\epsilon$
\end{tabular}}
\end{center}
@@ -1199,7 +1223,7 @@
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{frame}[c]
-\frametitle{\begin{tabular}{c}Test Program\end{tabular}}
+\frametitle{Test Program}
\mbox{}\\[-18mm]\mbox{}