%<+package> [2003/08/25 1.08 Syntax typesetting (MDW)]
% \end{meta-comment}
%
-% \CheckSum{1616}
+% \CheckSum{1628}
%% \CharacterTable
%% {Upper-case \A\B\C\D\E\F\G\H\I\J\K\L\M\N\O\P\Q\R\S\T\U\V\W\X\Y\Z
%% Lower-case \a\b\c\d\e\f\g\h\i\j\k\l\m\n\o\p\q\r\s\t\u\v\w\x\y\z
% blank lines. You can use the normal |\\| command to perform line-breaking
% of a production rule. Note that a production rule must begin with a
% nonterminal name enclosed in angle brackets (|<| \dots |>|), followed by
-% whitespace, then some kind of production operator (usually `::=') and then
-% some more whitespace. You can control how this text is actually typeset,
-% however.
+% any decorative material, whitespace, some kind of production operator
+% (usually `::=') and then some more whitespace. You can control how this
+% text is actually typeset, however.
%
% \DescribeMacro{\[[}
% \DescribeMacro{\]]}
%
% You can modify the appearance of grammars using three length parameters:
%
-% \begin{description} \def\makelabel{\hskip\labelsep\cmd}
+% \begin{description} \setdescriptionlabel{\cmd{#1}}
%
% \item [\grammarparsep] is the amount of space inserted between production
% rules. It is a rubber length whose default value is 8\,pt, with
%
% \end{description}
%
-% \DescribeMacro\grammarlabel
+% \DescribeMacro\grammarlabelx
% You can also control how the `label' is typeset by redefining the
-% |\grammarlabel| command. The command is given two arguments: the name of
-% the nonterminal (which was enclosed in angle brackets), and the `production
-% operator'. The command is expected to produce the label. By default, it
-% typesets the nonterminal name using |\synt| and the operator at opposite
-% ends of the label, separated by an |\hfill|.
+% |\grammarlabelx| command. The command is given three arguments: the name
+% of the nonterminal (which was enclosed in angle brackets), the following
+% decorative material, and the `production operator'. The command is
+% expected to produce the label. By default, it typesets the nonterminal
+% name using |\synt| followed by the decoration, and the operator, at
+% opposite ends of the label, separated by an |\hfill|.
+%
+% \DescribeMacro\grammarlabel
+% For compatibility, if there is no decorative material, the macro
+% |\grammarlabel| is called instead, with just two arguments: the nonterminal
+% name and the operator. The default implementation of |\grammarlabel| just
+% calls |\grammarlabelx| with empty decoration.
%
% \subsection{Syntax diagrams}
%
% ^^A took to get the table below to look right: __6. Hmm... not as bad
% ^^A as I expected. Most of them were fine-tuning things.
%
-% \medskip ^^A Leave a vertical gap
-% \hbox to\columnwidth{\hfil\vbox{\tabskip=0pt ^^A Centre it horizontally
-% \sdsize \csname sd@setsize\endcsname ^^A Position syntdiag arrows
-% \halign to .5\columnwidth{ ^^A Set the table width
+% \medskip ^^A Leave a vertical gap
+% \hbox to\columnwidth{\hfil\vbox{\tabskip=0pt ^^A Centre it horizontally
+% \sdsize \csname sd@setsize\endcsname ^^A Position syntdiag arrows
+% \halign to .5\columnwidth{ ^^A Set the table width
% &\ttfamily\ignorespaces#\unskip\hfil\tabskip=0pt ^^A Typeset the name
-% &\quad\csname sd@arr@#\endcsname\hfil ^^A Typeset the arrow
-% &\setbox0=\hbox{#}\tabskip=0pt plus 1fil\cr ^^A Stretch between columns
+% &\quad\csname sd@arr@#\endcsname\hfil ^^A Typeset the arrow
+% &\setbox0=\hbox{#}\tabskip=0pt plus 1fil\cr ^^A Stretch between columns
% >>-&>>-& &>-&>-& &->&->\cr
% -><&-><& &...&...& &-&-\cr
-% }}\hfil} ^^A Close the boxing
-% \medskip ^^A And leave another gap
+% }}\hfil} ^^A Close the boxing
+% \medskip ^^A And leave another gap
%
% These declarations should be used only in the optional argument to the
% \env{syntdiag$*$} command. The second optional argument to the
%
% The following length parameters may be altered:
%
-% \begin{description} \def\makelabel{\hskip\labelsep\cmd}
+% \begin{description} \setdescriptionlabel{\cmd{#1}}
%
% \item [\sdstartspace] The length of the rule between the arrows which
% begin each line of the syntax diagram and the first item on the line.
% |\lit| and |\lit*|) has two style commands associated with it, as shown
% in the table below.
%
-% \begin{tab}{lll} \hline
-% \bf Syntax item & \bf Left command & \bf Right command \\ \hline
-% Nonterminals & |\syntleft| & |\syntright| \\
-% Quoted terminals & |\litleft| & |\litright| \\
-% Unquoted terminals & |\ulitleft| & |\ulitright| \\ \hline
+% \begin{tab}{lll} \hline
+% \bf Syntax item & \bf Left command & \bf Right command \\ \hline
+% Nonterminals & |\syntleft| & |\syntright| \\
+% Quoted terminals & |\litleft| & |\litright| \\
+% Unquoted terminals & |\ulitleft| & |\ulitright| \\ \hline
% \end{tab}
%
% It's not too hard to see how this works. For example, if you look at
\bgroup%
\verb@eol@error%
\let\do\@makeother\dospecials%
+ \@noligs%
#2%
\catcode`#1\active%
\lccode`\~`#1%
% commands. Well, almost \dots
%
% \begin{macrocode}
-\newcommand{\grammarlabel}[3][]{%
- \synt{#2}#1 \hfill#3%
-}
+\newcommand{\grammarlabel}[2]{\grammarlabelx{#1}{}{#2}}
+\newcommand{\grammarlabelx}[3]{\synt{#1}#2 \hfill#3}
% \end{macrocode}
%
% Now for a bit of hacking to make the item stuff work properly. This gets
%
% \begin{macrocode}
\def\gr@implitem<#1>#2 #3 {%
- \sbox\z@{\hskip\labelsep\grammarlabel[{#2}]{#1}{#3}}%
+ \sbox\z@{%
+ \hskip\labelsep%
+ \def\@tempa{#2}%
+ \ifx\@tempa\@empty\grammarlabel{#1}{#3}%
+ \else\grammarlabelx{#1}{#2}{#3}\fi%
+ }%
\strut\@@par%
\vskip-\parskip%
\vskip-\baselineskip%