X-Git-Url: https://git.distorted.org.uk/~mdw/mdwtools/blobdiff_plain/e1069af1e2771b20455999803846ee852d7e42d6..88ddb950817e0413117789eaaee3752e9630453d:/syntax.dtx

diff --git a/syntax.dtx b/syntax.dtx
index 1226067..cbe09df 100644
--- a/syntax.dtx
+++ b/syntax.dtx
@@ -35,7 +35,7 @@
 %<+package>                [2003/08/25 1.08 Syntax typesetting (MDW)]
 % \end{meta-comment}
 %
-% \CheckSum{1616}
+% \CheckSum{1627}
 %% \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
@@ -172,7 +172,7 @@
 % \begin{listing}
 %\def\<#1>{\synt{#1}}
 % \end{listing}
-% to allow you to type "\\<"<text>">" as an alternative to 
+% to allow you to type "\\<"<text>">" as an alternative to
 % "\\synt{"<text>"}".
 %
 % \DescribeMacro\lit
@@ -283,14 +283,14 @@
 % 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 use syntax diagrams (see below) instead of a straight piece of BNF
-% by enclosing it in a |\[[| \dots |\]]| pair.  Note that you can't mix 
+% by enclosing it in a |\[[| \dots |\]]| pair.  Note that you can't mix
 % syntax diagrams and BNF in a production rule, and you will get something
 % which looks very strange if you try.
 %
@@ -325,13 +325,20 @@
 %
 % \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}
 %
@@ -445,7 +452,7 @@
 %
 % \DescribeMacro\tok
 % You can also include text using the |\tok| command.  The argument of this
-% command is typeset in \LaTeX's LR~mode and inserted into the diagram. 
+% command is typeset in \LaTeX's LR~mode and inserted into the diagram.
 % Syntax abbreviations are allowed within the argument, so you can, for
 % example, include textual descriptions like
 % \begin{listing}
@@ -473,7 +480,7 @@
 %
 % Note that items on the backwards arrow of a \env{rep} construction should
 % be displayed \emph{backwards}.  You must put the individual items in
-% reverse order when building this part of your diagrams.  \syn\ will 
+% reverse order when building this part of your diagrams.  \syn\ will
 % correctly reverse the arrows on \env{rep} structures, but apart from
 % this, you must cope on your own.  You are recommended to keep these parts
 % of your diagrams as simple as possible to avoid confusing readers.
@@ -604,7 +611,7 @@
 %
 % You can also alter the appearance of \env{stack}s and \env{rep}s by using
 % their optional positioning arguments.  By default, \env{stack}s descend
-% below the main line of the diagram, and \env{rep}s extend above it.  
+% below the main line of the diagram, and \env{rep}s extend above it.
 % Specifying an optional argument of |[b]| for either environment reverses
 % this, putting \env{stack}s above and \env{rep}s below the line.
 %
@@ -1132,7 +1139,7 @@
 % characters through.  By default, we re-enable |\|, and make `\verb*" "'
 % typeset some space glue, rather than a space character.  A macro
 % `\verb*"\ "' is defined to actually print a space character, which yield
-% `\verb*" "' in the `|\tt|' font. 
+% `\verb*" "' in the `|\tt|' font.
 %
 % Finally, it defines a |\ch| command, which, given a single-character
 % control sequence as its argument, typesets the character.  This is useful,
@@ -1298,7 +1305,7 @@
   \addspecial\|%
   \addspecial\"%
   \catcode`\|\active%
-  \catcode`\<\active% 
+  \catcode`\<\active%
   \catcode`\"\active%
   \catcode`\`\active%
 }
@@ -1358,9 +1365,8 @@
 % commands.  Well, almost \dots
 %
 %    \begin{macrocode}
-\newcommand{\grammarlabel}[2]{%
-  \synt{#1} \hfill#2%
-}
+\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
@@ -1372,8 +1378,13 @@
 % strut just makes sure that I know exactly how high the line is.
 %
 %    \begin{macrocode}
-\def\gr@implitem<#1> #2 {%
-  \sbox\z@{\hskip\labelsep\grammarlabel{#1}{#2}}%
+\def\gr@implitem<#1>#2 #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%