doc/refintro.tex: Split the syntax notation into subsections.

[sod] / doc / refintro.tex

diff --git a/doc/refintro.tex b/doc/refintro.tex
index 6d93b65..6689505 100644 (file)
--- a/doc/refintro.tex
+++ b/doc/refintro.tex
@@ -90,11 +90,17 @@ manual describes the base system as provided in the distribution.
 Fortunately, Sod is syntactically quite simple.  The notation is slightly
 unusual in order to make the presentation shorter and easier to read.
 
+
+\subsection{Empty production}
+
 The letter $\epsilon$ denotes the empty nonterminal
 \begin{quote}
   \syntax{$\epsilon$ ::=}
 \end{quote}
 
+
+\subsection{Indexed nonterminals}
+
 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
@@ -107,15 +113,20 @@ As a notational convenience, where an indexed nonterminal appears on the
 right-hand side of a production rule, each actual argument may be a sequence
 of alternative right-hand sides, separated by `$|$', rather than a a simple
 terminal or nonterminal symbol.  A complex indexing of this form, say
-$x[\alpha_1 | \beta_1 | \cdots, \ldots, \alpha_n | \beta_n | \cdots]$ means
-exactly the same as $x[a_1, \ldots, a_n]$ with the additional rules
+\syntax{$x$@[$\alpha_1^1$ @! $\alpha_1^2$ $| \cdots |$ $\alpha_1^{m_1},
+\ldots,$ $\alpha_n^1$ @! $\alpha_n^2$ $| \cdots |$ $\alpha_n^{m_n}$@]}
+means exactly the same as \syntax{$x$@[$a_1, \ldots, a_n$@]} with the
+additional rules
 \begin{quote}
-  \syntax{$a_1$ ::= $\alpha_1$ @! $\beta_1$ @! $\cdots$} \\
-  \hbox{}\qquad $\vdots$ \\
-  \syntax{$a_n$ ::= $\alpha_n$ @! $\beta_n$ @! $\cdots$}
+  \syntax{$a_1$ ::= $\alpha_1^1$ @! $\alpha_1^2$ $| \cdots |$ $\alpha_1^{m_1}$} \\*
+  \hbox{}\qquad $\vdots$ \\*
+  \syntax{$a_n$ ::= $\alpha_n^1$ @! $\alpha_n^2$ $| \cdots |$ $\alpha_1^{m_n}$}
 \end{quote}
 where $a_1$, \ldots, $a_n$ are new nonterminal symbols.
 
+
+\subsection{Common indexed productions}
+
 The following indexed productions are used throughout the grammar, some often
 enough that they deserve special notation.
 \begin{itemize}