-
-Fortunately, Sod is syntactically quite simple. The notation is slightly
-unusual in order to make the presentation shorter and easier to read.
-
-Anywhere a simple nonterminal name $x$ may appear in the grammar, an
-\emph{indexed} nonterminal $x[a_1, \ldots, a_n]$ may also appear. On the
-left-hand side of a production rule, the indices $a_1$, \ldots, $a_n$ are
-variables which vary over all nonterminal and terminal symbols, and the
-variables may also appear on the right-hand side in place of a nonterminal.
-Such a rule stands for a family of rules, in each variable is replaced by
-each possible simple nonterminal or terminal symbol.
-
-The letter $\epsilon$ denotes the empty nonterminal
-\begin{quote}
- \syntax{$\epsilon$ ::=}
-\end{quote}
-
-The following indexed productions are used throughout the grammar, some often
-enough that they deserve special notation.
-\begin{itemize}
-\item @[$x$@] abbreviates @<optional>$[x]$, denoting an optional occurrence
- of $x$:
- \begin{quote}
- \syntax{@[$x$@] ::= <optional>$[x]$ ::= $\epsilon$ @! $x$}
- \end{quote}
-\item $x^*$ abbreviates @<zero-or-more>$[x]$, denoting a sequence of zero or
- more occurrences of $x$:
- \begin{quote}
- \syntax{$x^*$ ::= <zero-or-more>$[x]$ ::=
- $\epsilon$ @! <zero-or-more>$[x]$ $x$}
- \end{quote}
-\item $x^+$ abbreviates @<one-or-more>$[x]$, denoting a sequence of zero or
- more occurrences of $x$:
- \begin{quote}
- \syntax{$x^+$ ::= <one-or-more>$[x]$ ::= <zero-or-more>$[x]$ $x$}
- \end{quote}
-\item @<list>$[x]$ denotes a sequence of one or more occurrences of $x$
- separated by commas:
- \begin{quote}
- \syntax{<list>$[x]$ ::= $x$ @! <list>$[x]$ "," $x$}
- \end{quote}
-\end{itemize}
-
-\subsection{Lexical syntax}
-\label{sec:syntax.lex}