X-Git-Url: https://git.distorted.org.uk/~mdw/sod/blobdiff_plain/2242bae8744c32179cd43ff3531f0f4843b28254..713805e5b8e4b3dca718e8ca4dd0b0faca4b812d:/doc/sod.sty

diff --git a/doc/sod.sty b/doc/sod.sty
index d3e7740..c35e110 100644
--- a/doc/sod.sty
+++ b/doc/sod.sty
@@ -25,9 +25,19 @@
 
 \ProvidesPackage{sod}
 
+%%%--------------------------------------------------------------------------
+%%% Basic style things.
+
 %% More reference types.
 \defxref{p}{part}
 
+%% A gadget to include in `\xref': call as
+%%
+%%      \xref[\instead{THING}]{LABEL}
+%%
+%% to replace the usual `section' or whatever with THING.
+\def\instead#1#2{#1}
+
 %% Other languages with special typesetting.
 \def\Cplusplus{C\kern-\p@++}
 \def\Csharp{C\#}
@@ -63,7 +73,8 @@
 %% Diagram settings.
 \tikzset{
   every picture/.style={>=stealth, thick},
-  lit/.style={font=\sffamily}
+  lit/.style={font=\sffamily},
+  dashed/.style={dash pattern=on 2.19pt off 2.19pt}
 }
 
 %% Metavariables are italics without decoration.
@@ -96,15 +107,15 @@
 
 %% Intercept grammar typesetting and replace the vertical bar with the
 %% maths-font version.
-\let\@@grammar\grammar
-\def\grammar{\def\textbar{\hbox{$|$}}\@@grammar}
+\let\@@syn@shorts\syn@shorts
+\def\syn@shorts{\def\textbar{\hbox{$|$}}\@@syn@shorts}
 
 %% Collect super- and subscripts.  (Note that underscores are active for the
 %% most part.)  When we're done, end maths mode if we entered it
 %% conditionally.
 \def\@scripts{\futurelet\@ch\@scripts@i}
 \begingroup\lccode`\~=`\_\lowercase{\endgroup
-\def\@scripts@i{\if1\ifx\@ch~1\else\ifx\@ch^1\else0\fi\fi%
+\def\@scripts@i{\if1\ifx\@ch~1\else\ifx\@ch_1\else\ifx\@ch^1\else0\fi\fi\fi%
   \expandafter\@scripts@ii\else\expandafter\m@maybe@end\fi}}
 \def\@scripts@ii#1#2{\m@maybe#1{#2}\@scripts}
 
@@ -114,6 +125,14 @@
   \expandafter\@firstoftwo\expandafter\@scripts%
   \else\@tempa\expandafter\@scripts\fi}
 
+%% Lookahead without eating spaces.
+\def\@ifnextchar@preserve#1#2#3{%
+  \let\want@= #1\def\@tempa{#2}\def\@tempb{#3}%
+  \futurelet\nch@\@ifnch@p%
+}
+\def\@ifnch@p{%
+  \ifx\want@\nch@\expandafter\@tempa\else\expandafter\@tempb\fi}
+
 %% Extra syntax for Lisp templates.  These produce the maths-font versions of
 %% characters, which should contrast well against the sans face used for
 %% literals.
@@ -124,29 +143,73 @@
 \atdef ({\m@maybe(\@scripts}
 \atdef ){\m@maybe)\@scripts}
 \atdef !{\m@maybe|\@scripts}
+
 \def\returns{\m@maybe\longrightarrow\m@maybe@end\hspace{0.5em}\ignorespaces}
+\def\nlret{\\\hspace{4em}\returns}
 \atdef >{\leavevmode\unskip\hspace{0.5em}\returns}
-\atdef -#1{\if>#1\hbox{--\raisebox{.4pt}{>}}\penalty200\relax\fi}
+
+%% Extra syntax for common tokens.
+\atdef ~{\textasciitilde}
+\atdef -{\leavevmode\hbox\bgroup\futurelet\ch@\@dash}
+\def\@dash{%
+  \ifx\ch@>%
+    --\raisebox{.4pt}{>}%
+    \def\next@{\@firstoftwo{\egroup\penalty200\relax}}%
+  \else\ifx\ch@-%
+    --\,%
+    \def\next@{\@firstoftwo{\futurelet\ch@\@dash}}%
+  \else%
+    --%
+    \let\next@\egroup%
+  \fi\fi
+  \next@%
+}
 
 %% Comment setting.
 \def\comment#1{\mbox{\normalfont\itshape\/#1\/}}
 \atdef /*#1*/{/*\comment{#1}*/}
-\def\@semis{\@ifnextchar;{;\@semis}\@semicomment}
+\def\@semis;{\@ifnextchar@preserve;{;\@semis}\@semicomment}
 \def\@semicomment#1\\{\comment{#1}\\}
-\atdef ;#1\\{;\@semis}
+\atdef ;{;\@semis;}
 
-%% Environment for setting programs.  Newlines are explicit, because
-%% otherwise I need comments in weird places to make the vertical spacing
-%% come out properly.  You can write `\obeylines' if you really want to.
-\def\@prog{\let\prog@@cr\@tabcr\let\@tabcr\@progcr\codeface\tabbing}
-\def\prog{\quote\@prog}
-\def\endprog{\endtabbing\endquote}
-\let\nprog\@prog
-\let\endnprog\endtabbing
-\def\ind{\quad\=\+\kill}
+%% Put a chunk of text in a box.
+\newenvironment{boxy}[1][\q@]{%
+  \savenotes%
+  \dimen@\linewidth\advance\dimen@-1.2pt\advance\dimen@-2ex%
+  \medskip%
+  \vbox\bgroup\hrule\hbox\bgroup\vrule%
+  \vbox\bgroup\vskip1ex\hbox\bgroup\hskip1ex\minipage\dimen@%
+  \def\@temp{#1}\ifx\@temp\q@\else\leavevmode{\headfam\bfseries#1\quad}\fi%
+}{%
+  \endminipage\hskip1ex\egroup\vskip1ex\egroup%
+  \vrule\egroup\hrule\egroup%
+  \medskip%
+  \spewnotes%
+}
+
+%%%--------------------------------------------------------------------------
+%%% Environment for setting programs.
+
+%% Save `\kill' so that `longtable' won't clobber it.
+\let\prog@@kill\kill
+
+%% Main guts of `prog' and `nprog'.
+\def\@prog{%
+  \let\prog@@cr\@tabcr%
+  \let\@tabcr\@progcr%
+  \let\kill\prog@@kill%
+  \codeface%
+  \tabbing%
+}
+
+%% Newlines: called by `\\' within a `prog'.
+%%
+%% \\           newline without following break
+%% \\[SKIP]     newline /with/ break and vertical glue
+%% \\*[SKIP]    newline without break, with optional glue
+%% \\+          newline with break and a vertical gap
+%% \\-          newline without break, with a tiny gap
 \def\@progcr{\futurelet\@tempa\@progcr@i}
-{\def\:{\gdef\@progcr@sp}\: {\@progcr}}
-\atdef~{\textasciitilde}
 \def\@progcr@i{%
   \ifx\@tempa\@sptoken\let\next@\@progcr@sp\else
   \if1\ifx\@tempa[1\else
@@ -163,90 +226,245 @@
 \def\@progcr@ii#1{\csname @progcr@#1\endcsname\ignorespaces}
 \@namedef{@progcr@+}{\prog@@cr[\medskipamount]}
 \@namedef{@progcr@-}{\prog@@cr*[\jot]}
+{\def\:{\gdef\@progcr@sp}\: {\@progcr}} % \@progcr@sp eats space and recurses
+
+%% Set a program in `codeface', with implicit tabbing and other toys.
+%% Newlines are explicit, because otherwise I need comments in weird places
+%% to make the vertical spacing come out properly.  You can write
+%% `\obeylines' if you really want to.
+\def\prog{\quote\@prog}
+\def\endprog{\endtabbing\endquote}
+
+%% Like `prog', but without indenting the code.  Use this within environments
+%% which already set their contents out from the body text in some
+%% distinctive way.
+\let\nprog\@prog
+\let\endnprog\endtabbing
+
+%% Indent the following material.  Cancel using `\-'.
+\def\ind{\quad\=\+\kill}
+
+%% Show a backslash by the right-hand margin; for multiline macros etc.
 \def\macsl{\`\textbackslash\hskip\leftmargin}
 
-%% Put a chunk of text in a box.
-\newenvironment{boxy}[1][\q@]{%
-  \savenotes
-  \dimen@\linewidth\advance\dimen@-1.2pt\advance\dimen@-2ex%
-  \medskip%
-  \vbox\bgroup\hrule\hbox\bgroup\vrule%
-  \vbox\bgroup\vskip1ex\hbox\bgroup\hskip1ex\minipage\dimen@%
-  \def\@temp{#1}\ifx\@temp\q@\else\leavevmode{\headfam\bfseries#1\quad}\fi%
-}{%
-  \endminipage\hskip1ex\egroup\vskip1ex\egroup%
-  \vrule\egroup\hrule\egroup%
-  \medskip%
-  \spewnotes%
+%% \maplist{THING}{{ITEM}...}: Invoke THING{ITEM} for each ITEM in turn.
+\def\maplist#1#2{\map@i{#1}#2\q@}
+\def\map@i#1{\def\next@{\map@ii{#1}}\futurelet\ch@\next@}
+\def\map@ii#1{\ifx\ch@\q@\expandafter\@gobble%
+  \else\def\next@{\map@iii{#1}}\expandafter\next@\fi}
+\def\map@iii#1#2{#1{#2}\map@i{#1}}
+
+%% \crossproduct{THING}{{LIST}...} where each LIST is {ITEM}...
+%% For each possible way of selecting one ITEM from each LIST, in order,
+%% invoke THING{{ITEM}...}
+\toksdef\cprod@new=0
+\toksdef\cprod@old=2
+\toksdef\cprod@head=4
+\toksdef\cprod@tail=6
+\def\crossproduct#1#2{%
+  \cprod@new{{}}%
+  \maplist{\cprod@f{#1}}{#2}%
+  \cprod@head{#1}%
+  \edef\next@{\noexpand\maplist{\the\cprod@head}{\the\cprod@new}}
+  \next@%
+}
+\def\cprod@f#1#2{%
+  \cprod@old\cprod@new\cprod@new{}%
+  \maplist\cprod@g{#2}%
+}
+\def\cprod@g#1{%
+  \cprod@head{#1}%
+  \expandafter\maplist\expandafter\cprod@h\expandafter{\the\cprod@old}%
+}
+\def\cprod@h#1{%
+  \cprod@tail{#1}%
+  \cprod@new\expandafter{\the\expandafter\cprod@new\expandafter{%
+      \the\expandafter\cprod@tail\the\cprod@head}}%
 }
 
-%% Lisp documentation machinery.
-\def\definedescribecategory#1#2{\@namedef{cat!#1}{#2}}
-\def\describecategoryname#1{%
-  \expandafter\let\expandafter\@tempa\csname cat!#1\endcsname%
-  \ifx\@tempa\relax#1\else\@tempa\fi}
-\definedescribecategory{sym}{symbol}
-\definedescribecategory{fun}{function}
-\definedescribecategory{gf}{generic function}
-\definedescribecategory{msg}{message}
-\definedescribecategory{var}{variable}
-\definedescribecategory{modvar}{module variable}
-\definedescribecategory{const}{constant}
-\definedescribecategory{meth}{primary method}
-\definedescribecategory{ar-meth}{around method}
-\definedescribecategory{be-meth}{before method}
-\definedescribecategory{af-meth}{after method}
-\definedescribecategory{cls}{class}
-\definedescribecategory{rst}{restart}
-\definedescribecategory{ty}{type}
-\definedescribecategory{type}{type}
-\definedescribecategory{mac}{macro}
-\definedescribecategory{lmac}{local macro}
-\definedescribecategory{parse}{parser spec}
-\definedescribecategory{parseform}{parser form}
-\definedescribecategory{opt}{option handler}
-\definedescribecategory{optmac}{option macro}
-\definedescribecategory{plug}{pluggable parser}
-\def\nlret{\\\hspace{4em}\returns}
+%%%--------------------------------------------------------------------------
+%%% Machinery for describing functions, etc.
+
+%% \definedescribecategory{CAT}[KIND]{NAME}
+%%
+%% Define a category of things to document.  CAT is a short label identifying
+%% the category to `\describe', `\descref', and friends.  The NAME is the
+%% text to show in the description headline; it is a macro body which is
+%% passed an argument `#1' that applies a modifier to some portion of the
+%% text.
+%%
+%% The KIND allows additional arguments to be collected, included in label
+%% strings, and mentioned in the index.  The default is `plain'.
+\def\definedescribecategory#1{%
+  \@ifnextchar[{\def@desc{#1}}{\def@desc{#1}[plain]}}
+\def\def@desc#1[#2]#3{\@namedef{cat!#1}##1{#3}\@namedef{catsw!#1}{#2}}
 
+%% \describecategoryname[MOD]{CAT}
+%%
+%% Typeset the category name for CAT, modified by MOD.
+\def\describecategoryname{\@ifnextchar[\@descname@i{\@descname@i[]}}
+\def\@descname@i[#1]#2{%
+  \expandafter\let\expandafter\@tempa\csname cat!#2\endcsname%
+  \expandafter\let\expandafter\@tempb\csname modcat/#1\endcsname%
+  \ifx\@tempa\relax\@tempb{#2}\else\@tempa\@tempb\fi}
+
+%% Call a modifier method.
+\def\@mod@dispatch#1#2{\csname #1/#2\endcsname}
+
+%% Call a description method given the category.
+\def\@desc@dispatch#1#2{%
+  \csname #1/%
+    \expandafter\ifx\csname catsw!#2\endcsname\relax plain%
+    \else \csname catsw!#2\endcsname \fi%
+  \endcsname%
+}
+
+%% Modifier methods for the default `plain' modifier.
+\@namedef{modcat/plain}#1{#1}
+\@namedef{modlabel/plain}#1{#1}
+\@namedef{modindex/plain}#1{#1@\noexpand\code{#1}}
+
+%% Modifier methods for `setf'.  The name text prefixes the relevant word
+%% with `setf-'.
+\@namedef{modcat/setf}#1{\code{setf}-#1}
+\@namedef{modlabel/setf}#1{setf/#1}
+\@namedef{modindex/setf}#1{#1@\noexpand\code{#1}}
+
+%% Modifier methods for words with *earmuffs*.  Sort into the index without
+%% the earmuffs.
+\@namedef{modcat/muffs}#1{#1}
+\@namedef{modlabel/muffs}#1{#1}
+\@namedef{modindex/muffs}#1{\@unmuff#1@\noexpand\code{#1}}
+\def\@unmuff*#1*{#1}
+
+%% Modifier methods for :keywords.  Sort into the index without the `:'.
+\@namedef{modcat/kwd}#1{#1}
+\@namedef{modlabel/kwd}#1{#1}
+\@namedef{modindex/kwd}#1{\@gobble#1@\noexpand\code{#1}}
+
+%% Category-kind methods for plain categories.
+\@namedef{descargs/plain}#1{#1{}}
+\@namedef{desclabel/plain}#1#2#3{#2:\@mod@dispatch{modlabel}{#1}{#3}}
+\@namedef{descindex/plain}#1#2#3{%
+  \@mod@dispatch{modindex}{#1}{#3}!%
+  \protect\describecategoryname[#1]{#2}%
+}
+
+%% Category-kind methods for `method' categories.  Collect an extra argument
+%% listing the specializers: include them in the label, and typeset them in
+%% the index.
+\def\fmtspecs#1#2{%
+  \if!#2!\else\count@\z@\toks@{}#1\fmtspecs@i#2,\q@,\fi}
+\def\fmtspecs@i#1,{%
+  \def\@tempa{#1}%
+  \ifx\@tempa\q@%
+    \ifcase\count@(no args?!)%
+    \or% nothin' doin
+    \or \space and %
+    \else, and %
+    \fi%
+    \the\toks@%
+  \else%
+    \ifnum\count@>\@ne, \fi%
+    \the\toks@%
+    \toks@{\code{#1}}\advance\count@\@ne%
+    \expandafter\fmtspecs@i%
+  \fi%
+}
+\@namedef{descargs/method}#1#2{#1{{#2}}}
+\@namedef{desclabel/method}#1#2#3#4%
+  {#2:\@mod@dispatch{modlabel}{#1}{#4}(#3)}
+\@namedef{descindex/method}#1#2#3#4{%
+  \@mod@dispatch{modindex}{#1}{#4}!%
+  \protect\describecategoryname[#1]{#2}%
+  \protect\fmtspecs{ specialized at }{#3}%
+}
+
+%% Some magic strings.
 \def\q@{\q@}
+\def\@setf{setf}
+\def\@starstar{**}
 
-%% \parse@dhd{NEXT}[NAME]{CAT}{SYNOPSIS}
-%% call NEXT{NAME}{CAT}{SYNOPSIS}
-%%            #1    #2     #3
+%% \parse@dhd{NEXT}[MOD]{CAT}{...}...[NAME]{SYNOPSIS}
+%%
+%% Parse the arguments for a description header, and call
+%%
+%%      NEXT{MOD}{CAT}{{...}...}{NAME}{SYNOPSIS}
+%%
+%% Here, {...}... represents the additional category-kind arguments.  See
+%% `describe' for what all of this means.
 \def\parse@dhd#1{%  {NEXT}
-  \@ifnextchar[{\parse@dhd@cc{#1}}{\parse@dhd@cd{#1}}}
-\def\parse@dhd@cc#1[#2]#3#4{%  {NEXT}[NAME]{CAT}{SYNOPSIS}
-  #1{#2}{#3}{#4}}
-\def\parse@dhd@cd#1#2#3{%  {NEXT}{CAT}{SYNOPSIS}
-  \parse@dhd@ce{#1}{#2}{#3}#3 \q@}
-\def\parse@dhd@ce#1#2#3#4 #5\q@{%
-  % {NEXT}{CAT}{SYNOPSIS}NAME [ARGS...]\q@
-  #1{#4}{#2}{#3}}
+  \@ifnextchar[{\parse@dhd@a{#1}}{\parse@dhd@c{#1}}}
+\def\parse@dhd@a#1[#2]#3{%  {NEXT}[MOD]{CAT}
+  \@desc@dispatch{descargs}{#3}{\parse@dhd@ab{#1}{#2}{#3}}}
+\def\parse@dhd@ab#1#2#3#4{%  {NEXT}{MOD}{CAT}{{...}...}
+  \@ifnextchar[{\parse@dhd@ac{#1}{#2}{#3}{#4}}{\parse@dhd@ad{#1}{#2}{#3}{#4}}}
+\def\parse@dhd@ac#1#2#3#4[#5]#6{%  {NEXT}{MOD}{CAT}{{...}...}[NAME]{SYNOPSIS}
+  #1{#2}{#3}{#4}{#5}{#6}}
+\def\parse@dhd@ad#1#2#3#4#5{%  {NEXT}{MOD}{CAT}{{...}...}{NAME [ARGS...]}
+  \parse@dhd@ae{#1}{#2}{#3}{#4}{#5}#5 \q@}
+\def\parse@dhd@ae#1#2#3#4#5#6 #7\q@{%
+  % {NEXT}{MOD}{CAT}{{...}...}{SYNSOPSIS}NAME [ARGS...]\q@
+  #1{#2}{#3}{#4}{#6}{#5}}
 
+\def\parse@dhd@c#1#2{%  {NEXT}{CAT}
+  \@desc@dispatch{descargs}{#2}{\parse@dhd@cb{#1}{#2}}}
+\def\parse@dhd@cb#1#2#3{%  {NEXT}{CAT}{{...}...}
+  \@ifnextchar[{\parse@dhd@cc{#1}{#2}{#3}}{\parse@dhd@cd{#1}{#2}{#3}}}
+\def\parse@dhd@cc#1#2#3[#4]#5{%  {NEXT}{CAT}{{...}...}[NAME]{SYNOPSIS}
+  #1{plain}{#2}{#3}{#4}{#5}}
+\def\parse@dhd@cd#1#2#3#4{%  {NEXT}{CAT}{{...}...}{SYNOPSIS}
+  \parse@dhd@ce{#1}{#2}{#3}{#4}#4 \q@}
+\def\parse@dhd@ce#1#2#3#4#5 #6\q@{%
+  % {NEXT}{CAT}{{...}...}{SYNOPSIS}NAME [ARGS...]\q@
+  \def\temp@{#5}%
+  \ifx\@setf\temp@\def\next@{\parse@dhd@csetf{#1}{#2}{#3}{#4}#6 \q@}%
+  \else\def\temp@##1##2*##3\q@{\def\temp@{##1##3}}\temp@#5*\q@%
+    \ifx\temp@\@starstar\def\next@{#1{muffs}{#2}{#3}{#5}{#4}}%
+    \else\def\temp@##1##2\q@{\def\temp@{##1}}\temp@#5\q@%
+      \if:\temp@\def\next@{#1{kwd}{#2}{#3}{#5}{#4}}%
+      \else\def\next@{#1{plain}{#2}{#3}{#5}{#4}}\fi\fi\fi%
+  \next@%
+}
+\def\parse@dhd@csetf#1#2#3#4(#5 #6\q@{%
+  % {NEXT}{CAT}{{...}...}{SYNOPSIS}(NAME [ARGS...])\q@
+  #1{setf}{#2}{#3}{#5}{#4}}
+
+%% \dhead[MOD]{CAT}{...}...[NAME]{SYNOPSIS}
+%% \dhead*[MOD]{CAT}{...}...[NAME]{SYNOPSIS}
+%%
+%% Typeset a description head.  Use this within the first argument of
+%% `describe*'; see `describe' for the details.
+%%
+%% With `*', don't set labels or add items to the index.
 \newif\if@dheadfirst
-\def\dhead{\parse@dhd\dhead@}
-\def\dhead@#1#2#3{%  {NAME}{CAT}{SYNOPSIS}
-  \if@dheadfirst\global\@dheadfirstfalse\else\relax\\[\smallskipamount]\fi%
-  {\let\protect\@empty\def\@uscore{_\@gobble}\message{#2:#1}%
-   \def\@uscore{-\@gobble}\edef\@tempa{\noexpand\label{#2:#1}}\@tempa}%
-  {\begingroup\lccode`\~=`\_\lowercase{\endgroup\def~{_}}%
-   \protected@edef\@tempa##1{%
-     \noexpand\index{%
-       #1@{\noexpand\code{#1}}!%
-       \csname cat!#2\endcsname%
-       ##1%
-     }%
-   }%
-   \@tempa{|(}%
-   \toks@\expandafter{\after@desc}%
-   \toks\tw@\expandafter{\@tempa{|)}}%
-   \xdef\after@desc{\the\toks@\the\toks\tw@}}%
+\newif\if@dheadindex
+\def\dhead{\@ifstar%
+  {\parse@dhd{\global\@dheadindexfalse\dhead@}}%
+  {\parse@dhd{\global\@dheadindextrue\dhead@}}}
+\def\dhead@#1#2#3#4#5{%  {MOD}{CAT}{{...}...}{NAME}{SYNOPSIS}
+  \if@dheadfirst\global\@dheadfirstfalse\else\relax\\*[\smallskipamount]\fi%
+  \if@dheadindex%
+    \phantomsection%
+    {\let\protect\@empty\let\@uscore\relax%
+     \edef\temp@{\@desc@dispatch{desclabel}{#2}{#1}{#2}#3{#4}}%
+     \def\@uscore{_\@gobble}\expandafter\message\expandafter{\temp@}%
+     \def\@uscore{-\@gobble}\expandafter\label\expandafter{\temp@}}%
+    {\begingroup\lccode`\~=`\_\lowercase{\endgroup\def~{_}}%
+     \protected@edef\@tempa##1{%
+       \noexpand\index{\@desc@dispatch{descindex}{#2}{#1}{#2}#3{#4}##1}}%
+     \toks@\expandafter{\@tempa{|)}}%
+     \toks\tw@\expandafter{\after@desc}%
+     \xdef\after@desc{\the\toks\tw@\the\toks@}%
+     \@tempa{|(}}%
+  \fi%
   \rlap{\hb@xt@\linewidth{\hfil\normalfont\bfseries
-      [\describecategoryname{#2}]}}%
-  #3%
+      [\describecategoryname[#1]{#2}]}}%
+  #5%
 }
 
+%% Main guts of a description environment.  The argument here typesets the
+%% header line(s).
 \def\desc@begin#1{%
   \let\saved@after@desc\after@desc%
   \gdef\after@desc{}%
@@ -263,20 +481,177 @@
 }
 \def\desc@end{\endlist\after@desc\global\let\after@desc\saved@after@desc}
 
-\@namedef{describe*}#1{\desc@begin{#1}}
-\expandafter\let\csname enddescribe*\endcsname\desc@end
+%% \begin{describe}[MOD]{CAT}{...}...[NAME]{SYNOPSIS}
+%%   ...
+%% \end{describe}
+%%
+%% Describe some kind of program object.  The CAT names the category of thing
+%% being described -- this will be shown in the header, and index.  The
+%% SYNOPSIS is an implicit `prog' environment in which invoking the thing can
+%% be summarized.
+%%
+%% The {...}... are any additional arguments required by the category's kind
+%% (e.g., method specializers).
+%%
+%% The NAME is the name of the thing, which ends up in the index and
+%% cross-reference label.  If omitted, it defaults to the first word of the
+%% SYNOPSIS, except that there are some special cases.
+%%
+%% The MOD is the modifier to apply.  If omitted, it will usually default to
+%% `plain', but in the absence of a NAME, some kinds of synopses are
+%% recognized specially:
+%%
+%%   * `setf (NAME ...) ...': selects NAME, and defaults MOD to `setf'.
+%%
+%%   * `*NAME*': defaults MOD to `muffs'.
+%%
+%%   * `:NAME': defaults MOD to `kwd'.
 \def\describe{\parse@dhd\desc@}
-\def\desc@#1#2#3{\desc@begin{\dhead@{#1}{#2}{#3}}}
+\def\desc@#1#2#3#4#5{%
+  \global\@dheadindextrue%
+  \desc@begin{\dhead@{#1}{#2}{#3}{#4}{#5}}%
+}
 \let\enddescribe\desc@end
 
-\def\descref#1{\@ifnextchar[{\descref@i{#1}}{\descref@ii{#1}{}}}
-\def\descref@i#1[#2]{\descref@ii{#1}{ #2}}
-\def\descref@ii#1#2#3{%
-  \code{#1}#2 (page~%
-  {\let\protect\@empty%
-   \def\@uscore{-\@gobble}\edef\@tempa{\noexpand\pageref{#3:#1}}\@tempa}%
-  )%
+%% \begin{describe*}
+%%     {\dhead[MOD]{CAT}{...}...[NAME]{SYNOPSIS}
+%%      ...}
+%%   ...
+%% \end{describe*}
+%%
+%% This is the fancy form of `describe' for describing several different
+%% things at once.
+\@namedef{describe*}#1{\desc@begin{#1}}
+\expandafter\let\csname enddescribe*\endcsname\desc@end
+
+%% \parse@dlbl{NEXT}[MOD]{CAT}{...}...{LABEL}
+%%
+%% Parse a description label, and call
+%%
+%%      NEXT{MOD}{CAT}{{...}...}{LABEL}
+%%
+%% This handles defaulting the MOD correctly, based on the LABEL text.  See
+%% `\descref' for the details.
+\def\parse@dlbl#1{\@ifnextchar[{\parse@dlbl@a{#1}}{\parse@dlbl@c{#1}}}
+\def\parse@dlbl@a#1[#2]#3{\@desc@dispatch{descargs}{#3}{#1{#2}{#3}}}
+\def\parse@dlbl@c#1#2%
+  {\@desc@dispatch{descargs}{#2}{\parse@dlbl@cb{#1}{#2}}}
+\def\parse@dlbl@cb#1#2#3#4{%
+  \def\temp@##1##2*##3\q@{\def\temp@{##1##3}}\temp@#4*\q@%
+    \ifx\temp@\@starstar\def\next@{#1{muffs}{#2}{#3}{#4}}%
+    \else\def\temp@##1##2\q@{\def\temp@{##1}}\temp@#4\q@%
+      \if:\temp@\def\next@{#1{kwd}{#2}{#3}{#4}}
+      \else\def\next@{#1{plain}{#2}{#3}{#4}}\fi\fi%
+  \next@%
+}
+
+%% \descref[MOD]{CAT}{...}...{LABEL}[TEXT]
+%% \descref*[MOD]{CAT}{...}...{LABEL}
+%%
+%% Typesets a cross-reference to a described thing.  The CAT names the
+%% category of thing being described, and the LABEL names the specific thing.
+%%
+%% The {...}... are any additional arguments required by the category's kind
+%% (e.g., method specializers).
+%%
+%% The MOD is the modifier to apply, similar (but subtly different from) to
+%% the `describe' environment.  If omitted, it will usually default to
+%% `plain', but in the absence of a NAME, some kinds of synopses are
+%% recognized specially:
+%%
+%%   * `*NAME*': defaults MOD to `muffs'.
+%%
+%%   * `:NAME': defaults MOD to `kwd'.
+%%
+%% (`setf' is /not/ specially detected here.  Write an explicit `setf'
+%% modifier if necessary, because it's no more typing.)
+%%
+%% Usually a page-number cross-reference is included, so as to help readers
+%% of a dead-tree copy; this is suppressed by the `*' version.
+\def\descref{\@ifstar%
+  {\parse@dlbl{\descref@i\relax\@gobble\relax}}%
+  {\parse@dlbl{\descref@i{ (}\autopageref)}}}
+\def\descref@i#1#2#3#4#5#6#7{\@ifnextchar@preserve[%
+  % {PGA}{PGB}{PGC}{MOD}{CAT}{{...}...}{LABEL}
+  {\descref@ii{#1}{#2}{#3}{#4}{#5}{#6}{#7}}%
+  {\descref@iii{#1}{#2}{#3}{#4}{#5}{#6}{#7}{}}}
+\def\descref@ii#1#2#3#4#5#6#7[#8]%
+  % {PGA}{PGB}{PGC}{MOD}{CAT}{{...}...}{LABEL}[AFTER]
+  {\descref@iii{#1}{#2}{#3}{#4}{#5}{#6}{#7}{ #8}}
+\def\descref@iii#1#2#3#4#5#6#7#8{%
+  % {PGA}{PGB}{PGC}{MOD}{CAT}{{...}...}{LABEL}{AFTER}
+  \begingroup%
+    \let\protect\@empty\def\@uscore{-\@gobble}%
+    \edef\temp@{\@desc@dispatch{desclabel}{#5}{#4}{#5}#6{#7}}%
+    \edef\next@##1##2##3{\endgroup%
+      \noexpand\hyperref[\temp@]{##1}##2{\temp@}##3}%
+  \next@{\code{#7}}{#8#1#2}{#3}%
+}
+
+%% \descindex[MOD]{CAT}{...}...{LABEL}[SUFFIX]
+%%
+%% Set a label and index entry here, as if for a description.  The CAT names
+%% the category of thing being described, and the LABEL names the specific
+%% thing, as for `\descref'.  The {...}... are any additional arguments
+%% required by the category's kind (e.g., method specializers).  The MOD is
+%% the modifier to apply; see `\descref' for the details.
+%%
+%% The SUFFIX is appended to the index-entry text; by default it is empty.
+%% Useful values are `|(' and `|)' to set ranges.
+\def\descindex{\parse@dlbl\descindex@i}
+\def\descindex@i#1#2#3#4{\@ifnextchar[%
+  {\descindex@ii{#1}{#2}{#3}{#4}}%
+  {\descindex@ii{#1}{#2}{#3}{#4}[]}}
+\def\descindex@ii#1#2#3#4[#5]{%
+  {\begingroup\lccode`\~=`\_\lowercase{\endgroup\def~{_}}%
+   \protected@edef\@tempa{%
+     \noexpand\index{\@desc@dispatch{descindex}{#2}{#1}{#2}#3{#4}#5}}%
+   \@tempa}%
+}
+
+%% \desclabel[MOD]{CAT}{...}...{LABEL}[INDEX-SUFFIX]
+%%
+%% Set a label and index entry here, as if for a description.  The CAT names
+%% the category of thing being described, and the LABEL names the specific
+%% thing, as for `\descref'.  The {...}... are any additional arguments
+%% required by the category's kind (e.g., method specializers).  The MOD is
+%% the modifier to apply; see `\descref' for the details.
+%%
+%% This will also add an index entry, as for `\descindex'; the INDEX-SUFFIX
+%% argument has the same effect as its SUFFIX argument.
+\def\desclabel{\parse@dlbl\desclabel@i}
+\def\desclabel@i#1#2#3#4{%
+  \begingroup%
+    \let\protect\@empty\def\@uscore{-\@gobble}%
+    \edef\@tempa{\@desc@dispatch{desclabel}{#2}{#1}{#2}#3{#4}}%
+    \phantomsection\label{\@tempa}%
+  \endgroup%
+  \descindex@i{#1}{#2}{#3}{#4}%
 }
 
+%% Description categories.
+\definedescribecategory{sym}{symbol}
+\definedescribecategory{fun}{#1{function}}
+\definedescribecategory{gf}{generic #1{function}}
+\definedescribecategory{msg}{message}
+\definedescribecategory{var}{variable}
+\definedescribecategory{modvar}{module variable}
+\definedescribecategory{const}{constant}
+\definedescribecategory{meth}[method]{primary #1{method}}
+\definedescribecategory{ar-meth}[method]{\code{:around} #1{method}}
+\definedescribecategory{be-meth}[method]{\code{:before} #1{method}}
+\definedescribecategory{af-meth}[method]{\code{:after} #1{method}}
+\definedescribecategory{cls}{class}
+\definedescribecategory{rst}{restart}
+\definedescribecategory{ty}{type}
+\definedescribecategory{mac}{#1{macro}}
+\definedescribecategory{feat}{feature macro}
+\definedescribecategory{lmac}{local #1{macro}}
+\definedescribecategory{parse}{parser spec}
+\definedescribecategory{parseform}{parser form}
+\definedescribecategory{opt}{option handler}
+\definedescribecategory{optmac}{option macro}
+\definedescribecategory{plug}{pluggable parser}
+
 %%%----- That's all, folks --------------------------------------------------
 \endinput
