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authorKarl Berry <karl@freefriends.org>2007-05-22 17:49:29 +0000
committerKarl Berry <karl@freefriends.org>2007-05-22 17:49:29 +0000
commitb7e7419f2fbc20f964ebd505f4c9d35c4b37d6e7 (patch)
tree81f166fc88d80a1bc49c16f7de6aff4d4250cdec /Master/texmf-dist/source/latex/xbase
parent51266997b22750d1cef71d44b0785cc31337f0d5 (diff)
new package xbase, subsuming some others?
git-svn-id: svn://tug.org/texlive/trunk@4337 c570f23f-e606-0410-a88d-b1316a301751
Diffstat (limited to 'Master/texmf-dist/source/latex/xbase')
-rw-r--r--Master/texmf-dist/source/latex/xbase/ldcsetup.dtx335
-rw-r--r--Master/texmf-dist/source/latex/xbase/template.dtx2446
-rw-r--r--Master/texmf-dist/source/latex/xbase/xbase.ins73
-rw-r--r--Master/texmf-dist/source/latex/xbase/xparse.dtx2167
4 files changed, 5021 insertions, 0 deletions
diff --git a/Master/texmf-dist/source/latex/xbase/ldcsetup.dtx b/Master/texmf-dist/source/latex/xbase/ldcsetup.dtx
new file mode 100644
index 00000000000..7ebb1d59830
--- /dev/null
+++ b/Master/texmf-dist/source/latex/xbase/ldcsetup.dtx
@@ -0,0 +1,335 @@
+% \iffalse
+%% File: ldcsetup.dtx (C) Copyright 1999 Frank Mittelbach, Chris Rowley, David Carlisle
+%% (C) Copyright 2004-2006 Frank Mittelbach, LaTeX3 Project
+%%
+%% It may be distributed and/or modified under the conditions of the
+%% LaTeX Project Public License (LPPL), either version 1.3c of this
+%% license or (at your option) any later version. The latest version
+%% of this license is in the file
+%%
+%% http://www.latex-project.org/lppl.txt
+%%
+%% This file is part of the ``xbase bundle'' (The Work in LPPL)
+%% and all files in that bundle must be distributed together.
+%%
+%% The released version of this bundle is available from CTAN.
+%%
+%% -----------------------------------------------------------------------
+%%
+%% The development version of the bundle can be found at
+%%
+%% http://www.latex-project.org/cgi-bin/cvsweb.cgi/
+%%
+%% for those people who are interested.
+%%
+%%%%%%%%%%%
+%% NOTE: %%
+%%%%%%%%%%%
+%%
+%% Snapshots taken from the repository represent work in progress and may
+%% not work or may contain conflicting material! We therefore ask
+%% people _not_ to put them into distributions, archives, etc. without
+%% prior consultation with the LaTeX Project Team.
+%%
+%% -----------------------------------------------------------------------
+%%
+%<package>\RequirePackage{l3names}
+%<*dtx>
+%\fi
+\def\GetIdInfo$Id: #1.dtx #2 #3-#4-#5 #6 #7$#8{%
+ \def\fileversion{#2}%
+ \def\filedate{#3/#4/#5}%
+ \ProvidesFile{#1.dtx}[#3/#4/#5 v#2 #8]%
+}
+%\iffalse
+%</dtx>
+%\fi
+\GetIdInfo$Id: ldcsetup.dtx 574 2006-08-21 23:30:10Z morten $
+ {coding conventions and stuff}
+%
+% \iffalse
+%<*driver>
+\documentclass{ltxdoc}
+\begin{document}
+\DocInput{ldcsetup.dtx}
+\end{document}
+%</driver>
+% \fi
+%
+% \CheckSum{0}
+%
+% \title{The \textsf{ldcsetup} package\thanks{This file
+% has version number \fileversion, last
+% revised \filedate.}}
+% \author{DPC, FMi}
+% \date{\filedate}
+% \maketitle
+%
+% \begin{abstract}
+% Basic code shared by several other packages currently under development.
+% \end{abstract}
+%
+% \StopEventually{}
+%
+% \begin{macrocode}
+%<*package>
+% \end{macrocode}
+% |\CodeStart| is in effect here so we better stop it again.
+% \begin{macrocode}
+\CodeStop
+\RequirePackage{keyval,calc}
+\makeatletter
+% \end{macrocode}
+%
+% \section{Ignoring White Space}
+% Within a package, or in a document preamble, you can use
+% |\IgnoreWhiteSpace| this makes white space ignored, and |@|
+% a letter, and |~| a space character. It lasts until the end of the
+% current package or preamble.
+%
+%% Puts an ignored space at the end of the line, so `|\ |' does the right
+% thing. (Perhaps should instead just change catcode of |^^M|)
+% \begin{macrocode}
+\def\IgnoreWhiteSpace{%
+ \edef\@tempa{%
+ \catcode`\noexpand\~=\the\catcode`\~\relax
+ \catcode`\noexpand\ =\the\catcode`\ \relax
+ \catcode`\noexpand\^^I=\the\catcode`\^^I\relax
+ \catcode`\noexpand\@=\the\catcode`\@\relax
+ \endlinechar=\the\endlinechar\relax
+ }%
+ \ifx\@currname\@empty
+ \expandafter\AtBeginDocument\expandafter{\@tempa}%
+ \else
+ \expandafter\AtEndOfPackage\expandafter{\@tempa}%
+ \fi
+ \catcode`\~=10\relax
+ \catcode`\ =9\relax
+ \catcode`\^^I=9\relax
+ \makeatletter
+ \endlinechar=` %
+ \relax
+}
+% \end{macrocode}
+% The new syntax requires |:| and |_| to be letters; instead of
+% putting that into |\IgnoreWhiteSpace| we make a new command which
+% helps to gradually change packages from old to new syntax.
+% \begin{macrocode}
+\def\InternalSyntaxOn{%
+ \edef\@tempa{%
+ \catcode`\noexpand\~=\the\catcode`\~\relax
+ \catcode`\noexpand\ =\the\catcode`\ \relax
+ \catcode`\noexpand\^^I=\the\catcode`\^^I\relax
+ \catcode`\noexpand\@=\the\catcode`\@\relax
+ \catcode`\noexpand\:=\the\catcode`\:\relax
+ \catcode`\noexpand\_=\the\catcode`\_\relax
+ \endlinechar=\the\endlinechar\relax
+%FMi fix is not properly reset
+ \endlinechar=13\relax
+ }%
+%%% ????
+% this needs further work, don't think it is working
+ \ifx\InternalSyntaxOff\relax
+ \expandafter\def\expandafter\InternalSyntaxOff\expandafter
+ {\@tempa\let\InternalSyntaxOff\relax}%
+ \fi
+ \ifx\@currname\@empty
+ \expandafter\AtBeginDocument\expandafter{\@tempa}%
+ \else
+ \expandafter\AtEndOfPackage\expandafter{\@tempa}%
+ \fi
+ \catcode`\~=10\relax
+ \catcode`\ =9\relax
+ \catcode`\^^I=9\relax
+ \makeatletter
+ \catcode`\_=11\relax
+ \catcode`\:=11\relax
+ \endlinechar=` %
+ \relax
+}
+\let\InternalSyntaxOff\relax
+% \end{macrocode}
+%
+% Do it for this package.
+% \begin{macrocode}
+\IgnoreWhiteSpace
+% \end{macrocode}
+%
+% \section{KV fixes}
+% Allow\footnote{Not needed now?} key names to start with |\|.
+% \begin{macrocode}
+\def\define@key#1#2{%
+ \@ifnextchar[
+ {\KV@def{#1}{\string#2}}
+ {\@namedef{KV@#1@\string#2}####1}}
+\def\setkeys#1#2{%
+ \def\KV@prefix{KV@#1@\expandafter\string}%
+ \KV@do#2,\relax,}
+% \end{macrocode}
+%
+% Make KV |#| safe.
+% \begin{macrocode}
+% \end{macrocode}
+%
+% \begin{macrocode}
+\newtoks\KV@toks
+% \end{macrocode}
+%
+% \begin{macrocode}
+\def\KV@@sp@c#1\@nil#2\relax#3{\KV@toks{#1}\edef#3{\the\KV@toks}}
+% \end{macrocode}
+%
+% Generate error messages on missing `,'.
+%
+% More exactly if two `=' appear after a key generate an error.
+% The current KV just silently ignores everything after the second `='.
+% \begin{macrocode}
+\def\KV@equal{=}
+% \end{macrocode}
+%
+% \begin{macrocode}
+\def\KV@split#1=#2=#3\relax{%
+ \KV@@sp@def\@tempa{#1}%
+ \def\@tempd{#3}%
+ \ifx\@tempa\@empty\else
+ \expandafter\let\expandafter\@tempc
+ \csname\KV@prefix\@tempa\endcsname
+ \ifx\@tempc\relax
+ \KV@error{\@tempa\space \expandafter\@gobbletwo\string\@undefined}\@eha
+ \else
+ \ifx\@tempd\@empty
+ \KV@default
+ \else
+ \KV@@sp@def\@tempb{#2}%
+ \ifx\@tempd\KV@equal
+ \expandafter\@tempc\expandafter{\@tempb}\relax
+ \else
+ \KV@error{Extra~=~ sign~ after~ `#1'}\KV@erry
+ \fi
+ \fi
+ \fi
+ \fi}
+% \end{macrocode}
+%
+% \begin{macrocode}
+\def\KV@erry{\expandafter\KV@errx\meaning\@tempd\relax ignored\MessageBreak
+ missing~comma~in~`\expandafter\strip@prefix\meaning\@tempb'~?}
+% \end{macrocode}
+%
+% \begin{macrocode}
+\def\KV@errx#1>#2==\relax{%
+ `#2' }
+% \end{macrocode}
+%
+% \begin{macrocode}
+\def\KV@default{%
+ \expandafter\let\expandafter\@tempb
+ \csname\KV@prefix\@tempa @default\endcsname
+ \ifx\@tempb\relax
+ \KV@error{No value specified for \@tempa}\@eha
+ \else
+ \@tempb\relax
+ \fi}
+% \end{macrocode}
+%
+% \LaTeX\ style error message.
+% \begin{macrocode}
+\def\KV@error#1#2{\PackageError{keyval}{#1}{#2}}
+% \end{macrocode}
+%
+% Instead of doing a full KV parse, and evaluating all the keys,
+% you might want to parse a parameter list, even for undefined keys,
+% removing spaces, splitting up the `,` and `=' and resolving cases
+% where no value is supplied. This is used in |\DeclareGenericFunction|
+% which \emph{defines} a set of keys via such a KV parse.
+%
+% A setting of |, key = value ,| will result in |\KV@elt{key}{value}|
+% being added to the list, a seting of |, key ,| will result in
+% |\KV@default@elt{key}| being added. At the end of the parse the list
+% is executed. No keys are checked at this stage (so no csnames are used
+% up) the two |\KV|\ldots|@elt| commands must be defined as appropriate.
+%
+% \begin{macrocode}
+\def\KV@parse#1{
+ \begingroup
+% \end{macrocode}
+%
+% Locally fudge |\KV@@def| to just add to a token register
+% rather than make a definition.
+% \begin{macrocode}
+\def\KV@@sp@c##1\@nil##2\relax##3{\addto@hook##3{{##1}}}
+% \end{macrocode}
+%
+% Locally fudge |\KV@split| to just add to a token register
+% rather than execute the code for the found keys.
+% \begin{macrocode}
+\def\KV@split##1=##2=##3\relax{%
+ \def\@tempd{##3}%
+ \expandafter\ifx\expandafter=\@firstofone##1=\else
+ \ifx\@tempd\@empty
+ \addto@hook\KV@toks\KV@default@elt
+ \KV@@sp@def\KV@toks{##1}%
+ \else
+ \ifx\@tempd\KV@equal
+ \addto@hook\KV@toks\KV@elt
+ \KV@@sp@def\KV@toks{##1}%
+ \KV@@sp@def\KV@toks{##2}%
+ \else
+ \KV@err{Extra `=' after `##1'}\@ehd
+ \fi
+ \fi
+ \fi}
+% \end{macrocode}
+%
+% Initialise
+% \begin{macrocode}
+ \KV@toks{}
+% \end{macrocode}
+% Do the parse
+% \begin{macrocode}
+ \KV@do#1,\relax,
+% \end{macrocode}
+% Evaluate the token register outside the group.
+% \begin{macrocode}
+ \expandafter
+ \endgroup
+ \the\KV@toks}
+% \end{macrocode}
+%
+% \section{Calc fixes}
+%
+% Count Register assignments via calc. Here we also provide some
+% global versions since a normal global prefix won't have any effect.
+% \begin{macrocode}
+\let\SetInternalCounter\calc@assign@count
+\def\GsetInternalCounter#1{\SetInternalCounter{\global#1}}
+\def\gsetlength#1{\setlength{\global#1}}
+% \end{macrocode}
+%
+%
+% \section{Misc code that is best collected in one place}
+%
+% This section will receive odd code that would be of potential use to
+% other packages and should eventually made it to the kernel
+% (perhaps).
+%
+% \begin{macro}{\UndeclareRobustCommand}
+% Remove a robust command from memory if it isn't used any
+% longer. Of course this doesn't free the hash table but at least
+% the space gets reclaimed.
+% \begin{macrocode}
+\def\UndeclareRobustCommand#1{%
+ \global\let#1\undefined
+ \global\expandafter
+ \let\csname\expandafter\@gobble\string#1~\endcsname\undefined
+}
+% \end{macrocode}
+% \end{macro}
+%
+%
+% \begin{macrocode}
+%</package>
+% \end{macrocode}
+%
+% \Finale
+%
diff --git a/Master/texmf-dist/source/latex/xbase/template.dtx b/Master/texmf-dist/source/latex/xbase/template.dtx
new file mode 100644
index 00000000000..3e6a4050454
--- /dev/null
+++ b/Master/texmf-dist/source/latex/xbase/template.dtx
@@ -0,0 +1,2446 @@
+% \iffalse
+%% File: template.dtx (C) Copyright 1999-2001 David Carlisle, Frank Mittelbach
+%% (C) Copyright 2004-2006 Frank Mittelbach, LaTeX3 Project
+%%
+%% It may be distributed and/or modified under the conditions of the
+%% LaTeX Project Public License (LPPL), either version 1.3c of this
+%% license or (at your option) any later version. The latest version
+%% of this license is in the file
+%%
+%% http://www.latex-project.org/lppl.txt
+%%
+%% This file is part of the ``xbase bundle'' (The Work in LPPL)
+%% and all files in that bundle must be distributed together.
+%%
+%% The released version of this bundle is available from CTAN.
+%%
+%% -----------------------------------------------------------------------
+%%
+%% The development version of the bundle can be found at
+%%
+%% http://www.latex-project.org/cgi-bin/cvsweb.cgi/
+%%
+%% for those people who are interested.
+%%
+%%%%%%%%%%%
+%% NOTE: %%
+%%%%%%%%%%%
+%%
+%% Snapshots taken from the repository represent work in progress and may
+%% not work or may contain conflicting material! We therefore ask
+%% people _not_ to put them into distributions, archives, etc. without
+%% prior consultation with the LaTeX Project Team.
+%%
+%% -----------------------------------------------------------------------
+%%
+%<package>\RequirePackage{l3names}
+%<*dtx>
+%\fi
+\def\GetIdInfo$Id: #1.dtx #2 #3-#4-#5 #6 #7$#8{%
+ \def\fileversion{#2}%
+ \def\filedate{#3/#4/#5}%
+ \ProvidesFile{#1.dtx}[#3/#4/#5 v#2 #8]%
+}
+%\iffalse
+%</dtx>
+%\fi
+\GetIdInfo$Id: template.dtx 584 2006-12-12 17:29:34Z morten $
+ {template}
+% \iffalse
+%
+%
+%<*driver>
+\documentclass{ltxdoc}
+\makeatletter
+ \newenvironment{decl}[1][]%
+ {\par\small\addvspace{4.5ex plus 1ex}%
+ \vskip -\parskip
+ \ifx\relax#1\relax
+ \def\@decl@date{}%
+ \else
+ \def\@decl@date{\NEWfeature{#1}}%
+ \fi
+ \noindent\hspace{-\leftmargini}%
+ \begin{tabular}{|l|}\hline\ignorespaces}%
+ {\\\hline\end{tabular}\nobreak\@decl@date\par\nobreak
+ \vspace{2.3ex}\vskip -\parskip\@afterheading}
+\makeatother
+
+ \begin{document}
+ \catcode`\_=11
+ \catcode`\:=11
+ \DocInput{template.dtx}
+ \end{document}
+%</driver>
+%
+%
+% \fi
+%
+%
+% \CheckSum{0}
+%
+% \title{The \textsf{template} package\thanks{This file
+% has version number \fileversion, last
+% revised \filedate.}}
+% \author{DPC, FMi}
+% \date{\filedate}
+% \maketitle
+%
+% \changes{0.06}{1998/12/17}{generic functions reborn as templates}
+%
+% \tableofcontents
+%
+% \section{Introduction}
+% A \emph{Template} is a named `function' that has a fixed number
+% of \emph{mandatory arguments} and an additional set of \emph{keys}
+% or `named attributes' that are set in a `key value list'. That is,
+% a comma separated set of assignments of the form:\\
+% \meta{key$_1$} |=| \meta{value$_1$} |,|
+% \meta{key$_2$} |=| \meta{value$_2$} \ldots
+%
+% More specific instances of the template may be declared by
+% specifying settings of the parameters. The key value list is parsed
+% at the time the instance is declared, and an `internal' set of
+% parameter assignments is passed to the template code. It is normally
+% not parsed at run-time, though it is possible to enforce this
+% behaviour.
+%
+% Templates have a \emph{type} and a \emph{name}. Templates
+% of the same type have the same argument and parameter
+% structure. That is, templates of the same type are expected to be
+% exchangeable semantically. (However, except for checking that
+% templates of the same type always have the same number of arguments
+% this is not enforced by the code.)
+%
+% A template type is declared via the |\DeclareTemplateType|
+% declaration which takes two arguments: the name for the type and the
+% number of arguments a template of this type requires.
+%
+% Templates are declared via the |\DeclareTemplate|
+% command which takes five arguments
+% \begin{itemize}
+% \item The \emph{type} of the template (no |\|).
+% \item The \emph{name} of the template (no |\|).
+% \item The number of arguments for the template (same as on type
+% declaration).
+% \item A list declaring the keys accepted by the template,
+% with information about the action to take when the key is specified
+% with a value.
+% \item The code for the template. This may be arbitrary \TeX\
+% code. At some point it should execute |\DoParameterAssignments|
+% to run the parameter assigments.
+%
+% The mandatory arguments are accessed via |#1|, |#2|, \ldots
+% \end{itemize}
+%
+%
+% Each element of the key specification list is of the form:
+% \begin{flushleft}
+% \meta{key name} |=|
+% \meta{key type} \meta{optional default} \meta{internal code}
+% \end{flushleft}
+%
+% The \meta{key types} are essentially specified by giving a symbolic
+% representation of the assignment function to be used by \TeX.
+%
+% Currently the possibilities are
+%
+% \begin{center}\catcode`|=12
+% \begin{tabular}{l|ll|l}
+% key type& letter& internal code& argument form\\\hline
+% Command & f\emph{n}&command name & command definition\\
+% name & n & command name & command definition\\
+% length & l & length register& calc length syntax\\
+% fake length & L & command name & calc length syntax\\
+% count & c & count register& calc count syntax\\
+% fake count & C & command name & calc count syntax\\
+% boolean & b & name of \verb|\newif| switch& true or false\\
+% switch & s & \marg{true code}\marg{false code}& true or false\\
+% instance& i\marg{type}& command name& instance of this \emph{type}\\
+% direct & x & Internal code& any\\
+% general & g & general code & any
+% \end{tabular}
+% \end{center}
+%
+% In addition, any of these types may be prefixed by |+| to
+% denote a global assignment (described below).
+% |f| takes a digit from 0--9 to denote the number of arguments.
+% |n| is in fact the same as |f0|. When an instance is declared
+% The value assigned to the key should be the definition of
+% the command, using |#1|\ldots|#9| to denote the specified arguments.
+%
+% |c| takes an internal form a count register,
+% not a \LaTeX\ counter name.
+%
+% For |f|, |n|, |l|, and |c|, the assignment is done twice, once
+% at the time an instance is \emph{declared}. (This may involve
+% using \textsf{calc} expresions. Then the `primitive assignment'
+% of the value (not using calc) is copied to the internal parameter
+% list, to be executed when an instance is run. Sometimes you need the
+% expression to be evaluated at the time an instance is run rather
+% than the time it is declared. For example it may be an expression
+% involving some values that are not fixed throughout a document.
+% In this case the instance declaration may give a value in the
+% form |\DelayedEvaluation|\marg{calc expression}. In this case
+% the value is not evaluated when the instance is declared, and
+% instead the entire expression is copied to the `internal parameter
+% list' and is evaluated whenever the instance is used.
+%
+% |L| and |C| take the same value types as |l| and |c| but the internal
+% assignments are to macros not registers.
+%
+% Keys declared with |b| and |s| each take values either \emph{true} or
+% \emph{false}. if the key zzz is declared with |b| then specifying
+% |zzz=true| will essentially pass |\zzztrue| to the internal parameter
+% list (although in fact |\zzztrue| need not be defined) . If instead
+% zzz had been declared via |s|, then |zzz=true| would pass the tokens
+% of the \marg{true code} to the internal parameter list.
+%
+% If a key is specified as |x|, then when used the \emph{internal code}
+% will be copied to the internal parameter lists. This code may use |#1|
+% to denote the value supplied to the key in the instance declaration.
+% Note that this code is \emph{only} copied at the time the instance is
+% declared. It is not executed at this time. It is executed when the
+% instance is executed.\footnote{Despite the question of whether or
+% not x and g are still necessary these days, they have the wrong
+% `names' since x is the one that is not executed during delcaration
+% while g is.}
+%
+% If a key is declared with |g| then the code is run at the time the
+% instance is declared. By default \emph{nothing} is passed to the
+% internal parameter list. This code may use |#1| to denote the
+% value that will be supplied when an instance is declared.
+% Any code that should be run when an instance is executed should
+% be explicitly passed to the internal parameter list using
+% |\toks_add_right:Nn\l_TP_KV_assignments_toks{|\ldots|}|
+%
+% A key declared with |i|\marg{type} takes as value the name of a
+% declared instance of that type. The command token associated with
+% the key will store a command essentially equivalent to a call
+% to |\UseInstance|\marg{type}\marg{name}, but in a slightly optimised
+% internal form.
+% As an exception to this rule the replacement code may be of the form
+% |\UseTemplate| followed by the key settings for the template
+% but without the mandatory arguments. In this case the `inner'
+% instance declaration is `pre compiled' and the token assigned to
+% the store the value assigned to this key will execute an instance
+% of the template directly, it will not re-parse the keyword settings
+% each time the instance is used.
+%
+% \section{Commands}
+%
+%
+% \subsection{Template declaration commands}
+%
+% \begin{decl}
+% |\DeclareTemplateType| \marg{type}\marg{num}
+% \end{decl}
+% Declare a template type.
+%
+% \begin{decl}
+% |\DeclareTemplate|
+% \marg{type}\marg{tname}\marg{num}\marg{keyspec}\marg{code}
+% \end{decl}
+% Declare a template \meta{tname} of type \meta{type} with the set of
+% keys as defined by \meta{keyspec}. From this template instances can
+% be declared using |\DeclareInstance| At runtime such instances will run
+% \meta{code} and expect \meta{num} mandatory arguments (same number
+% for all templates of one type).\footnote{The \meta{num} argument is
+% redundent as it can be deduced from the type. However, for practical
+% reasons it seems better to keep that information with each
+% individual template declaration.}
+%
+% \begin{decl}
+% |\DeclareRestrictedTemplate|
+% \marg{type}\marg{new-tname}\marg{old-tname}\marg{keyvals}
+% \end{decl}
+% Declare as new template \meta{new-tname} for type \meta{type} by
+% taking template \meta{old-tname} as the basis and setting one or
+% more of its keys to specific values.
+%
+% \begin{decl}
+% |\DoParameterAssignments|
+% \end{decl}
+% The list of key value assignments made (and saved) during template
+% declaration is evaluated at this point in the template code.
+%
+%
+% \subsection{Instance declaration commands}
+%
+% \begin{decl}
+% |\DeclareInstance| \marg{type}\marg{iname}\marg{tname}\marg{keyvals}
+% \end{decl}
+% Declare an instance of type \meta{type} named \meta{iname} build
+% from using template \meta{tname} with key settings as given by
+% \meta{keyvals}.
+%
+% \begin{decl}
+% |\DeclareCollectionInstance|
+% \marg{collection}\marg{type}\marg{iname}\marg{tname}\marg{keyvals}
+% \end{decl}
+% Same as |\DeclareInstance| except that this instance is only active
+% when for the type \meta{type} the collection \meta{collection} was
+% selected via |\UseCollection|. E.g., within the frontmatter one
+% could make all headings behave differently by defining collection
+% instances for template type `head'.
+%
+% \subsection{Key value commands}
+%
+% \begin{decl}
+% |\DelayEvaluation|\marg{code}
+% \end{decl}
+% Used in the value spec for an instance to declare that the value
+% \meta{code} should not be evaluated at declaration time but at
+% run-time. Can also be used in the defaults for keys (given in square
+% brackets) in the declaration of templates.
+%
+% \begin{decl}
+% |\MultiSelection| \meta{counter} \marg{cases} \marg{else}
+% \end{decl}
+% Used in the value spec for an instance key to declare that the value of
+% this key depends on the current setting of \meta{counter} at run-time.
+% The \meta{cases} argument is a comma-separated list of ``values'',
+% the \meta{else} argument a single ``value''. If at run-time
+% \meta{counter} has the value $i$ then the $i$-th element of the
+% \meta{cases} list is selected. If that does not exist the
+% \meta{else} case is returned.
+%
+%
+% \subsection{Processing commands}
+%
+% \begin{decl}
+% |\UseTemplate| \marg{type}\marg{tname}\marg{keyval}
+% \end{decl}
+% Execute a template \meta{tname} of type \meta{type} at run-time
+% using \meta{keyvals} as the value assignments for its keys. In this
+% case the keys are evaluated at run-time thus this method is far
+% slower than using a predeclared instance of this template (see
+% below). This command can also appear as the value for a key of type
+% `i' in which case the evaluation happens at declaration time of the
+% template that contains this key!
+%
+%
+% \begin{decl}
+% |\UseInstance| \marg{type}\marg{iname}
+% \end{decl}
+% Run the instance \meta{iname} of template type \meta{type}. If a
+% collection is in force see if there is a collection instance of name
+% \meta{iname} and if so run that instead.
+%
+% \begin{decl}
+% |\UseCollection| \marg{type}\marg{collection}
+% \end{decl}
+% Declare that from now on (normal scoping rules) the collection
+% \meta{collection} for template type \meta{type} is in force. This
+% means that a call to |\UseInstance| will first check if there is a
+% collection instance defined, and if so use that instance, otherwise
+% use the normal instance.
+%
+%
+% \subsection{Test commands}
+%
+% \begin{decl}
+% |\IfExistsInstanceTF| \marg{type}\marg{iname}\marg{true}\marg{false}
+% \end{decl}
+% Test if for template type \meta{type} an instance with name
+% \meta{iname} exists. Select \meta{true} or \meta{false} code
+% accordingly.
+%
+%
+%
+% \section{Examples of template key types}
+%
+% The general syntax for key specification in templates (fourth argument
+% of the command |\DeclareTemplate|) is:
+%\begin{flushleft}
+%| {| \\
+%| | \meta{key-name$_1$} |=|\meta{key-type$_1$}
+% \meta{optional-default$_1$} \meta{storage-bin$_1$}|,|\\
+%| | \meta{key-name$_2$} |=|\meta{key-type$_2$}
+% \meta{optional-default$_2$} \meta{storage-bin$_2$}|,|\\
+%| ...|\\
+%| }|
+%\end{flushleft}
+% In this section we look at all possible key types and give examples
+% for them.
+%
+%
+% \subsection{Attributes that receive names as values}
+%
+% The type |n| expects to receive a \LaTeX{} name as a value. Used,
+% for example, to specify the name of a \LaTeX{} counter to use.
+%\begin{verbatim}
+% heading-id =n \heading@id,
+% counter-id =n [\DelayEvaluation{\heading@id}] \heading@counter,
+%\end{verbatim}
+% Notice the use of |\DelayEvaluation| in the default of
+% |counter-id|. It is necessary to make the default the token
+% |\heading@id| if we want to inherit the value from the |heading-id|
+% key. Otherwise it gets value of |\heading@id| at the time the
+% instance is declared.
+%
+%
+% \subsection{Attributes that receive functions as values}
+%
+%
+% The type |f|\meta{num} expects a function with \meta{num} arguments
+% as a value. The arguments are denoted by |#1|, |#2|, etc. In most
+% cases either |f0| (for declarations) or |f1| (to format one argument) are
+% needed.
+%\begin{verbatim}
+% initial-font =f0 \initial@font,
+% initial-format =f1 [#1] \initial@boxhandling,
+%\end{verbatim}
+%
+% \subsection{Attributes that receive dimensions as values}
+%
+% As far as specifying instances the |l| and |L| type behave
+% identically. They differ only in the type of internal storage-bin
+% they need: |l| expects a length register while |L| expects an
+% ordinary macro name and assigns its value via |\def:Npn |.
+%\begin{verbatim}
+% pre-sep =l \topsep,
+% post-sep =L \botsep,
+%\end{verbatim}
+%
+%
+%
+% \subsection{Attributes that receive integers as values}
+%
+% The |c| and |C| type receive integers as values. Again either of
+% them can be transparently used. In case of |c| the
+% \meta{storage-bin} has to be a \TeX{} count register not a \LaTeX{}
+% counter name, i.e., set up via |\newcount|. (\LaTeX{} counters can
+% be used as well if they are accessed via their internal name, i.e.,
+% via |\c@|\meta{\LaTeX-counter})
+%\begin{verbatim}
+% pre-penalty =c \@beginparpenalty,
+% penalty =C \hmaterial@penalty,
+%\end{verbatim}
+%
+%
+%
+% \subsection{Attributes that receive template instances as values}
+%
+% The type |i|\marg{type} takes as value the name of a declared
+% instance of that type. The \meta{storage-bin} associated with the
+% key will store a command essentially equivalent to a call to
+% |\UseInstance|\marg{type}\marg{name}, but in a slightly optimised
+% internal form.
+%
+% As an exception to this rule the replacement code may be of the form
+% |\UseTemplate| followed by the key settings for the template but
+% without the mandatory arguments. In this case the `inner' instance
+% declaration is `pre compiled' and the token assigned to the store
+% the value assigned to this key will execute an instance of the
+% template directly, it will not re-parse the keyword settings each
+% time the instance is used.
+%\begin{verbatim}
+% justification-setup =i{justification} \list@justification,
+%\end{verbatim}
+%
+% Usage within an instance declaration is either
+%\begin{verbatim}
+% justification-setup = raggedright,
+%\end{verbatim}
+% i.e., name of a declared instance or a call to |\UseTemplate|
+%\begin{verbatim}
+% justification-setup = \UseTemplate{justification}{TeX}
+% { startskip = 0pt, ... },
+%\end{verbatim}
+%
+%
+%
+% \subsection{Attributes that receive true or false values}
+%
+% The type |s| expects the strings |true| or |false| as values. In
+% this case the declaration has no \meta{storage-bin}. Instead the
+% declaration consists of two brace groups containing code. Depending
+% on the value one of the groups gets copied verbatim into the
+% internal parameter list of the instance and gets executed at
+% run-time at the point where |\DoParameterAssignments| is seen.
+%\begin{verbatim}
+% item-implicit-boolean =s
+% { \def:Npn \item@implicit@code{\item\relax} }{},
+% numbered-boolean =b [true] @heading@nums,
+%\end{verbatim}
+%
+%
+% \subsection{Attributes that accept any value}
+%
+% The type |g| is a low-level specification which contains arbitrary
+% code in place of the \meta{storage-bin}. This code is evaluated at
+% declaration time of the instance and by default \emph{nothing} is
+% passed to the internal parameter list (this has to happen explicitly
+% from within the code). |#1| may be used to access the value
+% specified.
+
+% The main purpose for this type is of historical nature (originally
+% most of the other types have been implemented internally using |g|).
+%
+% The type |x| also requires code in place of the \meta{storage-bin}.
+% However with this type all of the code is copied unevaluated to the
+% internal parameter list. There are some applications for this type
+% when implementing customisable defaults. However, it is likely that
+% it will not survive a final release.
+%\begin{verbatim}
+% generic-key =g \typeout{#1},
+% extra-assigns =x \typeout{#1},
+%\end{verbatim}
+%
+%
+%
+%
+%
+%
+% \section{A complete example}
+%
+% The following example shows a sketch of a template for typesetting
+% captions to be used as part of a larger mechanism setting whole
+% floats.\footnote{I made it up while I went along so if you spot the
+% ``missing brace'' or some other blunder tell me, FMi.}
+%
+% We declare a template type \texttt{caption} then define an example
+% template for that type and finally produce some instances from that.
+%
+% \subsection{Declaring the template type}
+%
+% To define the template type we first have to ask ourselves what
+% information would be varying each time such a template is used? A
+% potential answer could be the following:
+% \begin{itemize}
+% \item
+% The float name, e.g., `Table' or `Fig.' etc.
+% \item
+% The float
+% number e.g., `10' or `3--c' etc.
+% \item
+% The actual caption text as specified in the document.
+% \end{itemize}
+% Since the above items would be differed in each instantiation of
+% such a template we would pass them as mandatory argument to the
+% template.
+%
+% Are there others? Possibly. Here are two more that seem to be
+% useful, at least in a number of cases:
+% \begin{itemize}
+% \item
+% The text of the legend in document classes that distinguish
+% between caption text (heading to the figure/table) and legend
+% (explanatory material)
+% \item
+% Measure to which the caption should be typeset.
+% \end{itemize}
+% The last one of these might need some extra explanation. Suppose a
+% design requires that the caption width is decided depending on the
+% width of the table of figure, e.g., the caption is supposed to
+% typeset below some illustration and should not be wider than that
+% illustration, or the caption is typeset aside to the illustration
+% using the remaining space. In that case the process that formats the
+% whole float needs to communicate with the current template to pass
+% that (varying) information along. Of course, that could happen by
+% using global variables, e.g., the outer process sets the measure as
+% desired before calling the caption formatting template. What makes
+% more sense is likely to be a matter of taste but it also has to do
+% with the precise semantics of the template type. Staying with our
+% example: if the the semantics of the template type \texttt{caption}
+% is supposed to produce a formatted box (in \TeX{} terms) then we
+% should pass the measure as an argument if we ever intend to allow
+% for variations. If on the other hand the semantics are to format a
+% certain set of text into the current galley (which has measure of
+% its own) then a measure argument would not belong to this template
+% type.
+%
+% Are there other variations sensible? Yes, for example, instead of
+% passing a fixed string like ``Fig.'' as the first argument one could
+% pass an abstract float type identifier and let the template worry to
+% deduce from that information what fixed string to produce.
+%
+% Another question: why should we pass the fixed text (or an abstract
+% identifier from which it can be deduced) and the number as separate
+% arguments to the template instead of passing a combined string (like
+% it is done in the |\@makecaption| command of \LaTeXe{})? Answer:
+% because this allows to build templates that can individually
+% manipulate both bits of information, e.g., to format the number in a
+% different font, etc.
+%
+% So what are the conclusions of this discussion? Defining the
+% semantics of a template type is difficult and often needs several
+% trials to come up with something that is covering the anticipated
+% use. There is clearly not a cardinal way for defining template
+% types; how the overall separation into smaller units is done is
+% partly a matter of taste and partly a matter of the major layout
+% characteristics that one tries to support.
+%
+% Returning to our example: let's assume we settle for the first four
+% arguments, i.e., the calling template is responsible for setting the
+% measure for the caption text if necessary.
+%
+% What we also have to do is to define (at least for ourselves) what
+% data the arguments accept and what their semantics are. An informal
+% summary of that could be the following:
+% \begin{center}
+% \begin{tabular}{rrl}
+% \textit{Arg} & \textit{Data Type} & \textit{Description} \\[3pt]
+% 1 & text & fixed float description
+% \\
+% 2 & text/|\NoValue| & float number
+% \\
+% 3 & text & caption text
+% \\
+% 4 & text/|\NoValue| & legend text
+% \\
+% \end{tabular}
+% \end{center}
+% The second and the fourth argument are allowed to be missing (i.e.,
+% can get |\NoValue| passed as a value). Note that the empty string in
+% case of a text argument is different from |\NoValue|.
+%
+% We further declare that it is permissible for a template of this
+% type to ignore the information provided by all arguments except 3,
+% i.e., the caption text.
+%
+% Finally the result of the template formatting should is to typeset
+% text into a current galley (paragraph mode in \LaTeX{} lingua).
+%
+% All the above is semantic information that (at least right now) is
+% not being enforced by declaring a template type (except for the
+% number of arguments) but each template of a certain type is supposed
+% to conform to this specification nonetheless.\footnote{To make this
+% even clearer we are thinking of extending the template type
+% declaration with another argument in which one has to formally or
+% informally (?) specifies information like the one in the table
+% above.}
+%
+% This finally leads to the following declaration:
+%\begin{verbatim}
+%\DeclareTemplateType{caption}{4}
+%\end{verbatim}
+%
+% \subsection{Defining a first template}
+%
+% We start by defining a simple template of type \texttt{caption}
+% which roughly formats a caption like those being presented in
+% \LaTeXe{}'s article class, i.e., the caption is typeset as a
+% paragraph if it is longer than a single line, otherwise it is
+% centered. The legend even if present is ignored. Above and below we
+% give the designer the possibility to add some space.
+%
+% In fact the examples is more or less identical in code to
+% |\@makecaption| except that if the second argument (i.e., the
+% number) is |\NoValue| it and its preceding space\footnote{For those
+% who wonder: spaces are by default ignored within definitions when
+% the new packages are used due to a command \texttt{\textbackslash
+% InternalSyntaxOn}, do get a normal space one has to use
+% \texttt{\textasciitilde} and to obtain an unbreakable space
+% \texttt{\textbackslash nobreakspace}.} gets ignored.
+%
+% We start by declaring the template \texttt{toosimple} of type
+% \texttt{caption} having four mandatory arguments (as described in
+% the discussion of the template type).
+%\begin{verbatim}
+%\DeclareTemplate{caption}{toosimple}{4}
+%\end{verbatim}
+% The next argument of |\DeclareTemplate| lists all keys for the
+% template. In this case we have keys for the vertical spaces above
+% and below. We make them type |L| to save on registers but with a bit
+% of care we could also have used scratch registers like |\@tempskipa|
+% etc. Their default values are both zero.
+%\begin{verbatim}
+% {
+% above-skip =L [0pt] \caption@above@skip ,
+% below-skip =L [0pt] \caption@below@skip ,
+% }
+%\end{verbatim}
+% The final argument of |\DeclareTemplate| contains the actual
+% processing code. We start with looking at the second mandatory
+% argument (caption number) to find out if it is |\NoValue| and
+% depending on the result define a helper command |\caption@start|.
+%\begin{verbatim}
+% {
+% \IfNoValueTF{#2}
+% { \def:Npn \caption@start{#1:~} }
+% { \def:Npn \caption@start{#1~#2:~} }
+%\end{verbatim}
+% Having dealt with the prelims we now run |\DoParameterAssigments| at
+% which point the keys of the template are made available, e.g., at
+% this point all those right hand containers such as
+% |\caption@above@skip| get assigned the value specified in an
+% instantiation of the template. (That scheme allows to do preliminary
+% processing up front, e.g., defaults for the keys could be assigned
+% prior to that point in which case they are overwritten if the
+% template instance specifies a different value. the use of specifying
+% defaults via the |[..]| syntax as done above is slightly faster at
+% run-time but needs more memory.)
+%\begin{verbatim}
+% \DoParameterAssigments
+%\end{verbatim}
+% The rest of the code should look familiar to anybody who ever looked
+% at \texttt{article.cls}. The only point worth mentioning are the
+% |\relax| commands after |\caption@above@skip| and
+% |\caption@below@skip|. Since we have decided to use |L| as key type
+% these commands are macros and not registers containing the
+% dimensions as strings. This means that we have to be careful to
+% ensure that \TeX{} knows where the dimension ends. In certain cases
+% text following such a command might be mistaken as being part of the
+% dimension (e.g., if followed by the word \texttt{plus}, etc.). In
+% the code below this could only happen for the second |\vskip| but it
+% is good practice to always add a terminating |\relax| to avoid such
+% hidden traps.
+%\begin{verbatim}
+% \vskip \caption@above@skip \relax
+% \sbox \@tempboxa {\caption@start #3}
+% \ifdim \wd\@tempboxa >\hsize
+% \caption@start #3\par
+% \else
+% \global \@minipagefalse
+% \hb@xt@\hsize{\hfil\box\@tempboxa\hfil}
+% \fi
+% \vskip \caption@below@skip \relax
+% }
+%\end{verbatim}
+%
+% Why is the above template of not much use? Simply because it doesn't
+% offer any flexibility to declare different designs. The only
+% alteration offered to the designer is to modify the space above and
+% below the caption, e.g., the following declaration would mimic the
+% definition within the \texttt{article.cls} class of \LaTeXe :
+%\begin{verbatim}
+%\DeclareInstance{caption}{article}{toosimple}
+% {
+% above-skip = 0pt,
+% below-skip = 10pt,
+% }
+%\end{verbatim}
+% And that's all that can be manipulated. All items that people asking
+% to change, e.g., not having a colon after the number, using
+% different fonts and font sizes, etc.\ are still hard-wired and thus
+% inaccessible. So we have to do better if we want to make use of the
+% power the template mechanism offers.
+%
+%
+%
+% \subsection{Defining a better template}
+%
+% First step in defining better templates is to ask ourselves a couple
+% of questions:
+% \begin{itemize}
+% \item What are the main characteristics of the layout the template
+% is supposed to support?
+% \item What are the elements that we want to allow (or can allow) the
+% designer to modify?
+% \end{itemize}
+%
+% Take the first question first: the layout supported by the template
+% of the previous section had as its main characteristics that it
+% would center the caption if it would fit in a single line in the
+% current measure. We could consider this being an unchangable
+% characteristic of the layout this template produces (and a designer
+% would need to use a different template of type \texttt{caption} if a
+% design compatible with this restriction is desired) or we could try
+% to make our template smarter by adding bells and wistles that allow
+% the designer to say stuff like:
+%\begin{verbatim}
+% one-line-format = \hfil #1 \hfil,
+%\end{verbatim}
+% or
+%\begin{verbatim}
+% one-line-action = center,
+%\end{verbatim}
+% depending on how we intend to offer changing the behavior of the
+% template. Like when trying to define sensible template types we have
+% no single road to heaven (and probably as many to hell) --- it has a
+% lot to do with how we think about design.
+%
+% My advice, after having tried to work with these concepts for a
+% while, is to keep templates simple in so far as that most of not all
+% attribute for a template should be relevant for the design. In other
+% words, if you have attributes that, depending on their setting, make
+% half of the other attributes not applicable then it may be
+% appropriate to think about providing several templates instead. To
+% give an example from \LaTeXe : instead of having |\@startsection|
+% deal with both vertical heads and run-in heads provide individual
+% templates. (|\@startsection| is this famous command where design
+% switches are build in by making dimensions negative to signal
+% something and afterwards use the absolute value.)
+% Another way to look at this is to say that a template should
+% normally not contain large amounts of code which is only selected in
+% a subset of attribute settings.
+%
+% As said before there are no golden rules, it is perfectly possible
+% to make hugely complicated templates that solve every possible
+% aspect of layout one could think of in one go --- it is just that
+% with keeping it more simple one can get the same functionality with
+% less headaches for the template writer as well as the template user
+% later on.
+%
+% Returning to our example: allowing to handle the case of a single
+% line caption specially could well be considered part of the
+% template. In contrast: layouts that would put the caption number
+% sideways, i.e., which would need totally different internal coding
+% should probably be coded as a separate template of type
+% \texttt{caption}.
+%
+% So for our next example template we settle for the fixed caption
+% text plus number (if any) being at the beginning of the variable
+% caption text (coming from the document) and being together formatted
+% as some sort of a pargraph. In case of the whole caption being a
+% single line we allow the designer to specify how to lay it out
+% (e.g., centered, flush left, etc.). If there is a legend it will get
+% formatted by a vertical space followed by the legend formatted as
+% another paragraph.
+%
+% More precisely we allow for the following bells and wistles:
+%\begin{verbatim}
+%\DeclareTemplate{caption}{lesssimple}{4}
+% {
+%\end{verbatim}
+% The designer can specify the space above and below the caption like
+% we did in our first example.
+%\begin{verbatim}
+% above-skip =L [0pt] \caption@above@skip ,
+% below-skip =L [0pt] \caption@below@skip ,
+%\end{verbatim}
+% Regarding the caption number we support the case where no number is
+% present (the value being |\NoValue|) as well as the number being
+% present. For both cases the designer has to specify what formatting
+% should be attached. By default all is being typeset in the font the
+% whole caption is presented but if there is a need for it the
+% designer can use the following keys to attach special formatting
+% devices to each particular item beside specifying special spacing
+% information or replacing the default colon after the number with
+% something else.
+%\begin{verbatim}
+% number-format =f2 [#1~#2:~] \caption@number@format,
+% nonumber-format =f1 [#1:~] \caption@nonumber@format,
+%\end{verbatim}
+% If the caption is fitting onto a single line we make it possible
+% for the designer to specify how this single line should be
+% positioned (the default is to center the line).
+%\begin{verbatim}
+% single-line-format =f1 [\hfil#1\hfil] \caption@single@line@format,
+%\end{verbatim}
+% The font for the caption (including the fixed text and the number
+% unless specified differently above) is going to be the one decided
+% by the next key.
+%\begin{verbatim}
+% caption-font =f0 [\normalfont] \caption@font,
+%\end{verbatim}
+% The next attribute deserves some extra explanation: here we make use
+% of an interface which is explained in more detail when we reveil the
+% support for galley formatting.\footnote{Guess I have to apologize
+% for the fact that i partly make use of that interface in this
+% example while on other occasions (like the use of vertical spacing)
+% within the example I do not---consistency around midnight is not my
+% strength I fear (FMi).} In a nutshell the template type \texttt{hj}
+% (hyphenation \& justification) allows one to define a) the
+% justification concepts applied to the upcoming paragraphs, e.g.,
+% whether they should be set flush left, adjusted, first line
+% centered, etc.\ b) the linebreaking strategy used and c) the
+% hyphenation rules which should apply. All this is done by selecting
+% an appropriate (predefined) instance of this type as will hopefully
+% become somewhat clearer in the example instances shown below.
+%\begin{verbatim}
+% caption-hj-setup =i {hj} [default] \caption@hj@instance,
+%\end{verbatim}
+% In case there is a legend to format we give the designer the
+% possibility to specify by how much vertical space it should be
+% separated from the preceding paragraph (i.e., the caption text). The
+% attributes for font and hj setup are comparable to those for the
+% caption text itself (except that they will only apply to the
+% legend). The only addition is the key \texttt{legend-text} which is
+% allowed to take a fixed text (plus any formating and spacing for it)
+% which will be added to the front of the legend in case it is
+% provided at all (by default it is empty).
+%\begin{verbatim}
+% legend-sep =L [0pt] \caption@legend@sep ,
+% legend-text =f0 [] \caption@legend@text,
+% legend-font =f0 [\normalfont] \caption@legend@font,
+% legend-hj-setup =i {hj} [default] \caption@legend@hj@instance,
+% }
+%\end{verbatim}
+% The actual code for the template should hold few if any
+% surprises. In fact it is more or less identical to the one of the
+% first template example, except that now we have now taken out some
+% of the hardwired decisions and placed them into attributes.
+%\begin{verbatim}
+% {
+% \IfNoValueTF{#2}
+% { \def:Npn \caption@start{\caption@number@format{#1}{#2}} }
+% { \def:Npn \caption@start{\caption@nonumber@format{#1}} }
+% \DoParameterAssigments
+% \vskip \caption@above@skip \relax
+%\end{verbatim}
+% To properly measure the caption to determine if it fits a single
+% line we have to set it in the right font, so here as well as below
+% we have to apply |\caption@font|.
+%\begin{verbatim}
+% \sbox \@tempboxa {\caption@font \caption@start #3}
+% \ifdim \wd\@tempboxa >\hsize
+% \begingroup
+% \caption@font \caption@hj@instance
+% \caption@start #3\par
+% \endgroup
+% \else
+% \global \@minipagefalse
+% \hb@xt@\hsize{\caption@single@line@format{\box\@tempboxa}}
+% \fi
+%\end{verbatim}
+% To decide whether or not we have to set any legend we have to test
+% |#4| for being |\NoValue|. This part of the code was not present in
+% the previous example but otherwise should be straight forward.
+%\begin{verbatim}
+% \IfNoValueF{#4}
+% {
+% \vskip \caption@legend@sep \relax
+% \begingroup
+% \caption@legend@font \caption@legend@hj@instance
+% \caption@legend@text
+% #4\par
+% \endgroup
+% }
+% \vskip \caption@below@skip \relax
+% }
+%\end{verbatim}
+%
+% I wouldn't claim the the above template is good or contains
+% everything that would be desired and I'm sure that in the end we
+% will have several such template for typesetting the caption part and
+% perhaps decide on a different template type in the first place. So
+% this is only to give a glimpse of how the template interface could
+% be applied and I hope that reading it can see a) how they can apply
+% it to other areas as well as see what is wrong with the example
+% itself.
+%
+% To just note one point that i thought of being wrong after writing
+% the above paragraphs: the key \texttt{single-line-format} was
+% declared to be a function with one argument with the idea that
+% besides specifying the single line should be centered (|\hfil|) on
+% both sides, or flush left, or flush right (|\hfil| on one side) one
+% could also specify something like
+%\begin{verbatim}
+% single-line-format = \hspace{10pt}#1\hfil,
+%\end{verbatim}
+% that is a fixed indentation on the left in case where the caption is
+% a single line. However, of course one can't. Or at least it is not
+% safe to do so since our test in the code tests the width of the line
+% without taking into account such a finite fixed space and guess what
+% might happen? So in summary, flexibility needs some thought and
+% often some afterthoughts as well --- happy thinking :-)
+%
+%
+%
+% \subsection{Defining a few instances}
+%
+% So let us conclude this example with a few sample instances. We
+% start with one that repeats what current \LaTeXe{} provides in the
+% article class. It shows all keys with values. However in fact only
+% the first key is actually needed since all others are the same as
+% the default values in the template (and of course a legend is not
+% specifiable in standard \LaTeX{} coding so those settings simply do
+% not apply anyway).
+%\begin{verbatim}
+%\DeclareInstance{caption}{article}{lesssimple}
+% {
+% above-skip = 10pt,
+% below-skip = 0pt,
+% number-format = #1~#2:~,
+% nonumber-format = #1:~,
+% single-line-format = \hfil#1\hfil,
+% caption-font = \normalfont,
+% caption-hj-setup = default,
+% legend-sep = 0pt,
+% legend-text = ,
+% legend-font = \normalfont,
+% legend-hj-setup = default,
+% }
+%\end{verbatim}
+%
+% The next examples are taken from books on the shelf essentially a
+% random selection I fear. This one is from \emph{Introduction to
+% Database Design} by C.~J.~Date and it uses Helvetica for the caption
+% text with the caption flush left, with the figure and the fixed
+% string (e.g., `Fig.' in bold face) separated by a quad of space. No
+% legend either so this is not set up. The \texttt{hj} instance
+% \texttt{noindentflushleft} is supposed to produce a ragged right paragraph
+% without any indentation. It would have to be set up elsewhere
+% (instance to the template of type \texttt{hj}).
+%\begin{verbatim}
+%\DeclareInstance{caption}{DATE}{lesssimple}
+% {
+% above-skip = 10pt,
+% below-skip = 0pt,
+% number-format = \textbf{#1~#2}\quad,
+% nonumber-format = \textbf{#1}\quad,
+% single-line-format = #1\hfil,
+% caption-font = \fontfamily{phv} \normalfont,
+% caption-hj-setup = noindentflushleft,
+% }
+%\end{verbatim}
+%
+% The final example is from the book ``Methods of Book Design'' by
+% H.~Williamson which sets the caption centered if it fits a single
+% line but adjusted as a paragraph without any indentation if longer
+% than a single line. It uses old style numerals followed by a period
+% for the number (though the example isn't quite right as i guess the
+% text font used already has oldstyle numerals as default, so
+% |\oldstylenums| is in fact not necessary).
+%\begin{verbatim}
+%\DeclareInstance{caption}{WILLIAMSON}{lesssimple}
+% {
+% above-skip = 10pt,
+% below-skip = 0pt,
+% number-format = #1~\oldstylenums{#2}.~,
+% nonumber-format = #1~,
+% single-line-format = \hfil#1\hfil,
+% caption-font = \normalfont,
+% caption-hj-setup = noindentadjusted,
+% }
+%\end{verbatim}
+%
+%
+%
+% \section{Notes}
+%
+% \subsection{Note on multi-valued parameters}
+%
+%
+% The following code\footnote{docu taken from trial implementation in
+% xlists.dtx, FMi} implements for registers (ie L,l,C,c keys) and
+% for names (ie n key) a multi-selection mechanism of the following
+% form:
+% \begin{verbatim}
+% key = \MultiSelection \ListDepth {
+% \DelayEvaluation {2.5em},
+% 20pt + 34pt }
+% { \DelayEvaluation {1em} },
+% \end{verbatim}
+% where the first argument to |\MultiSelection| is a counter, the
+% second argument is a comma separated list of values denoting the
+% values for the cases 1, 2,\ldots, and the third argument contains
+% the value for all other cases.
+%
+% The values are evaluated at declaration time in case of registers
+% and therefore can contain calc expressions as well as
+% |\DelayEvaluation|.
+%
+% Due to the implementation the case list is not allowed to have a
+% trailing comma! And of course no checks are made whatsoever :-(
+%
+% A probably much nicer syntax would be something like this:
+% \begin{verbatim}
+% key = \MultiSelection {
+% selector = \ListDepth,
+% 1 = \DelayEvaluation {2.5em},
+% 2 = 20pt + 34pt,
+% else = \DelayEvaluation {1em}
+% },
+% \end{verbatim}
+% but i found that too difficult to implement right now.
+%
+% I think it should also be considered if this kind of thing should be
+% a generally available feature on all key types especially on the
+% f\meta{number} ones.
+%
+% Anyway it is what i need for lists right now and as such it is
+% sufficient.
+%
+%
+% \subsection{Notes on template restriction}
+%
+% Possible semantics:
+%
+% a: just:-) changes the defaults ie the new template has as
+% defaults those of its source as modified by the supplied
+% keyvals;
+%
+% b: similar to a: but also removes some keywords ie the new template
+% will not accept the keywods whose values are set by the suppied
+% keyvals;
+%
+% c: plan C.
+%
+%
+% Towards an implementation of b: but without a restriction on what
+% keys appear where.
+%
+%
+%
+%
+% \subsection{Open issues}
+%
+% In this section unresolved issues or ideas to think about and
+% perhaps implement are collected. There is no particular order to
+% them.
+%
+% \begin{itemize}
+% \item The order of arguments in |\UseCollection| is illogical in my
+% eyes! A collection typically modifies the behavior of several
+% types and thus should perhaps be first (as it is in the
+% |\DeclareCollectionInstance| case). Or not, or what?
+%
+% \item How should |\IfExistsInstanceTF| behave for Collection
+% instances? Do we need a special check for those or a default
+% action? Or do we need an additional test for the existence of
+% collection instances?
+%
+% \item It was suggested that the template type declaration should get
+% another argument in which (in?)formally the semantics for the
+% template types are described, e.g., data type of arguments,
+% resulting output, \ldots{} (somewhat like the description arguments
+% for functions and variables in Emacs-Lisp). The advantage being
+% that this helps employing the templates better as well as perhaps
+% guiding context sensitive editors to support the work with such
+% templates (e.g., providing help texts).
+%
+% \item The same might be of interest for the keys of individual
+% templates though here syntax support is already available to some
+% extend by the declaration of key types.
+%
+% \item There might be a need to distinguish between \TeX's dimen and
+% skip registers. Right now this is not done and both |l| and |L|
+% accepts what \LaTeX{} calls ``rubber length'' specifications.
+%
+% \item The type |b| can probably vanish. It is equivalent to
+% specifying the mutators of a |\newif| command in the brace groups,
+% e.g.
+%\begin{verbatim}
+% numbered-boolean =b [true] @heading@nums,
+% numbered-boolean =s [true] {\@heading@numstrue}
+% {\@heading@numsfalse},
+%\end{verbatim}
+%
+% \item See issue raised about syntax (and semantics) for
+% |\Multiselection|.
+%
+% \item |f0| keys should perhaps support |\UseTemplate| by replacing
+% it with its internal form. or perhaps this is a rubbish idea?
+%
+% \item Marcin Wolinski suggested to use |\EvalOnUse| instead or in
+% addition to |\DelayEvalutation|.
+%
+% \end{itemize}
+%
+% \StopEventually{}
+%
+% \section{Implementation}
+% \begin{macrocode}
+%<*package>
+% \end{macrocode}
+%
+% \begin{macrocode}
+\RequirePackage{ldcsetup,xparse}
+\RequirePackage{l3toks,l3tlp,l3skip,l3int,l3clist,l3token}
+% \end{macrocode}
+%
+% Ignore white space in this package.
+% \begin{macrocode}
+\CodeStart
+% \end{macrocode}
+%
+% Declare a private token register for building parameter lists.
+% Having the number saves a few expandafters
+% (probably not needed in the end).
+% \begin{macrocode}
+\toks_new:N\l_TP_KV_assignments_toks
+\toks_new:N\l_TP_default_assignments_toks
+% \end{macrocode}
+%
+%
+%
+% \begin{macro}{\TP_declare_instance:Nnn}
+% \begin{macro}{\TP_declare_instance:cnn}
+% Declare a command name to be an instance of a template
+% ie with a particular setting of the parameters.\\
+% |#1| internal command name for instance to be (globally) declared\\
+% |#2| template type/template name\\
+% |#3| key value assignments for parameters of |#2|
+% \begin{macrocode}
+\def_new:NNn \TP_declare_instance:Nnn 3{
+ \group_begin:
+ \TP_instdecl_generate_assignments:nn {#2}{#3}
+ \gdef:Npx #1 {
+ \tlp_if_eq:cNTF { TP>/#2 } \c_TP_doparameterassignments_tlp
+% \end{macrocode}
+% If the body of the template consists only of the token
+% |\DoParameterAssignments|, then we insert the list of parameter
+% assignments directly. Otherwise we have push them onto the stack
+% and prepare to execute the body code (which in turn will pop them
+% again when it reaches |\DoParameterAssignments| inside).
+% \begin{macrocode}
+ { \toks_use:N \l_TP_KV_assignments_toks }
+ {
+ \exp_not:N \TP_push_assignments:n
+ {\toks_use:N\l_TP_KV_assignments_toks}
+ \exp_not:c {TP>/#2}
+ }
+ }
+ \group_end:}
+\def_new:Npn \TP_declare_instance:cnn{\exp_args:Nc\TP_declare_instance:Nnn}
+% \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\c_TP_doparameterassignments_tlp}
+% \begin{macrocode}
+\tlp_set:Nn \c_TP_doparameterassignments_tlp {\DoParameterAssignments}
+% \end{macrocode}
+% \end{macro}
+%
+%
+% \begin{macro}{\UseTemplate}
+% |{type}{templatename}{keyval}|
+% Directly use a template with a particular parameter setting.
+% This is also picked up if used in a nested fashion inside a parameter
+% list.\\
+% |#1| type of a template.\\
+% |#2| name of a template.\\
+% |#3| key value assignments for parameters of |#1|.
+% \begin{macrocode}
+\def_new:NNn \UseTemplate 3{
+ \TP_instdecl_generate_assignments:nn {#1/#2}{#3}
+ \TP_push_assignments:
+ \cs_use:c { TP>/#1/#2 }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\DoParameterAssignments}
+% Access the parameter assignment list that was once stored in
+% |\l_TP_KV_assignments_toks| and then moved onto the
+% |\g_TP_assignments_stack_toks|.
+% \begin{macrocode}
+\def_new:Npn \DoParameterAssignments{
+ \exp_after:NN
+ \TP_pop_and_execute_assignments:nw
+ \toks_use:N \g_TP_assignments_stack_toks \q_stop
+}
+% \end{macrocode}
+%
+% \end{macro}
+%
+% \begin{macro}{\TP_pop_and_execute_assignments:nw}
+% \begin{macrocode}
+\def_new:Npn \TP_pop_and_execute_assignments:nw#1#2\q_stop{
+ \toks_gset:Nn \g_TP_assignments_stack_toks {#2}
+ #1}
+% \end{macrocode}
+% \end{macro}
+%
+%
+% \begin{macro}{\g_TP_assignments_stack_toks}
+% \begin{macrocode}
+\toks_new:N \g_TP_assignments_stack_toks
+\toks_gset:Nn \g_TP_assignments_stack_toks {\scan_stop:}% avoid brace loss
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\TP_push_assignments:n}
+% Store a list of parameter assignments given as an argument
+% in |\l_TP_KV_assignments_toks| and
+% then push it
+% onto the |\g_TP_assignments_stack_toks|. (My assumption is that
+% the somewhat strange
+% way to do this is in fact neccesary to preserve the |#| marks
+% which would otherwise need doubling --- check).
+% \begin{macrocode}
+\def_new:Npn \TP_push_assignments:n{
+ \tex_afterassignment:D \TP_push_assignments:
+ \l_TP_KV_assignments_toks}
+% \end{macrocode}
+%
+% \end{macro}
+%
+% \begin{macro}{\TP_push_assignments:}
+% Pushes the parameter assignment list stored in
+% |\l_TV_KV_assignments_toks| onto the stack
+% |\g_TP_assignments_stack_toks|.
+% \begin{macrocode}
+\def_new:Npn \TP_push_assignments:{
+ \toks_gset:No \g_TP_assignments_stack_toks
+ {\exp_after:NN
+% \end{macrocode}
+% this misuses the fact that |\toks_use:N| is really |\the| so expands
+% a little strangely (fix).
+% \begin{macrocode}
+ {\toks_use:N\exp_after:NN\l_TP_KV_assignments_toks\exp_after:NN}
+ \toks_use:N\g_TP_assignments_stack_toks}}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\DeclareTemplateType}
+% |{type}{nofarg}|
+% \begin{macrocode}
+\def_new:NNn \DeclareTemplateType 2{
+ \tlp_set:cn {TP@<#1>} {{}#2}}
+% \end{macrocode}
+% \end{macro}
+%
+%
+% \begin{macro}{\TP_get_csname_prefix:n}
+% |{type}| returns prefix for csnames for template type,
+% based on current collection.
+% \begin{macrocode}
+\def_new:Npn \TP_get_csname_prefix:n#1{
+ <\exp_after:NN\exp_after:NN\exp_after:NN
+ \use_arg_i:nn
+ \cs:w TP@<#1>\cs_end:>#1/
+}
+% \end{macrocode}
+%
+% \end{macro}
+%
+% \begin{macro}{\TP_get_arg_count:n}
+% |{type}| returns arg count for the template type.
+% \begin{macrocode}
+\def_new:Npn \TP_get_arg_count:n#1{
+ \exp_after:NN\exp_after:NN\exp_after:NN
+ \use_arg_ii:nn
+ \cs:w TP@<#1>\cs_end:
+}
+% \end{macrocode}
+% \end{macro}
+%
+%
+% \begin{macro}{\DeclareTemplate}
+% |{type}{templatename}{nofarg}{keywordspec}{code}|
+% \begin{macrocode}
+\def_long_new:NNn\DeclareTemplate 5{
+ \cs_if_free:cTF{TP@<#1>}
+ {\undefinedtype\DeclareTemplateType{#1}#3}
+ {
+ \int_compare:nNnF{#3}={\TP_get_arg_count:n{#1}}
+ { \BadArgCount }
+ }
+% \end{macrocode}
+% Parse the key declaration, and execute the list with a suitable
+% definition of |\KV@elt|.
+% \begin{macrocode}
+ \let:NN \KV_elt:nn \TP_templdecl_process_KV:nn
+ \def:Npn \KV_default_elt:n##1{
+ \PackageError{template}{Missing~ =~ after~ ##1}\@ehd}
+ \let:NN\KV@elt\KV_elt:nn
+ \let:NN\KV@default@elt\KV_default_elt:n
+ \tlp_set:Nn \l_TP_curr_name_tlp {#1/#2}
+ \toks_clear:N\l_TP_default_assignments_toks
+% \end{macrocode}
+% At this point there should be a test for which catcode regime we are
+% in. We just test if spaces are ignored.
+% \begin{macrocode}
+ %\int_compare:nNnTF{\char_value_catcode:n{`\ }}=\c_nine
+ %\KV_parse_picky_no_space_removal_no_sanitize:n
+ %\KV_parse_picky_space_removal_no_sanitize:n
+ \KV@parse{#4}
+% \end{macrocode}
+%
+% Define the defaults: the setting for |TPD>/\l_TP_curr_name_tlp| is a
+% tricky since |\l_TP_default_assignments_toks| may contain |#|. We
+% have to use an |x| expansion rather than
+% |o| since that will hide those during the assignment.
+% \begin{macrocode}
+ \tlp_set:cx { TPD>/\l_TP_curr_name_tlp }
+ {\toks_use:N\l_TP_default_assignments_toks}
+
+ \tlp_clear:c {TPR>/\l_TP_curr_name_tlp}
+
+ \tlp_set_eq:cN {TPO>/\l_TP_curr_name_tlp}\l_TP_curr_name_tlp
+% \end{macrocode}
+%
+% Define the template (using |\def_new:Npn| means that one can't
+% redefine a template easily).
+% \begin{macrocode}
+ \def:cNn {TP>/\l_TP_curr_name_tlp}{#3}{#5}
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\TP_templdecl_process_KV:nn}
+% The list of undefined keys and values is put in the list of the form\\
+% |\KV_elt:nn|\marg{key1}\marg{val1}%^^A
+% |\KV_elt:nn|\marg{key2}\marg{val2}\ldots\\
+% So just need to give this macro a suitable definition. We just need
+% to look at the first token of the value, to see what sort of key
+% it is, so call a helper function to split that off.
+% \begin{macrocode}
+\def_new:Npn \TP_templdecl_process_KV:nn#1#2{%
+ \let:NN \TP_templdecl_add_global_or_nothing: \use_noop:
+ \bool_set_false:N\l_TP_global_assignment_bool
+ \tlp_set:Nn\l_TP_currkey_tlp{#1}
+ \TP_templdecl_parse_KV:N#2\q_stop}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\TP_templdecl_parse_KV:N}
+% Case switch on the possible key types.
+% \begin{macrocode}
+\def_new:Npn \TP_templdecl_parse_KV:N#1{
+% \end{macrocode}
+% In |#1| we have key, in |#2| the first character after the equal
+% sign and in |#3| the remainder of the line. We now have to parse
+% that remainder to find out if it contains a default value (in
+% brackets) and then set up the key declaration needed to parse
+% instance declarations. The method is similar in most cases: we call
+% |\TP_parse_optional_key_default:nw| which parses for the default
+% and pass it already found key name as first argument, what to do in
+% the end as second argument, and the remainder delimited by |\q_stop|
+% so that it becomes parseable.
+%
+% Note that the code in the second argument to
+% |\TP_parse_optional_key_default:nw| normally calls on a macro with
+% one more argument than actually provided: the reason being that the
+% missing argument will be the remainder of the line (added by
+% |\TP_parse_optional_key_default:nw| after the default has be
+% removed (if present)).
+% \begin{macrocode}
+ \cs_if_free:cTF{TP_use_arg_type_#1:w}
+ {\PackageError{template}{Unknown~key~type~ (#1)~for~\l_TP_currkey_tlp}\@eha}
+ {\cs_use:c{TP_use_arg_type_#1:w}}
+% \end{macrocode}
+% The |f| and |i| keys are somewhat different since there we first
+% have to parse for an additional argument (a digit in case of |f|
+% or an template type name in case of |i|):
+% \begin{macrocode}
+% \end{macrocode}
+% One more alternative: a |+| after the equal sign signals global
+% so we change |\TP_templdecl_add_global_or_nothing:| to append a
+% |\pref_global:D| to the assignment toks and then reparse the rest.
+% \begin{macrocode}
+% \def:Npn \TP_templdecl_add_global_or_nothing:
+% {\toks_put_right:Nn \l_TP_KV_assignments_toks {\pref_global:D} }
+% \TP_templdecl_parse_KV:nw{#1}#3\TP_templdecl_parse_KV:nnw
+}
+% \end{macrocode}
+% \end{macro}
+%
+%
+% \begin{macro}{\l_TP_global_assignment_bool}
+% For keeping track of the assignments.
+% \begin{macrocode}
+\bool_new:N \l_TP_global_assignment_bool
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\TP_use_arg_type_+:w}
+% The |+| does two things: Sets a boolean true to be used by the
+% types that can't simply be prefixed with |\pref_global:D| and
+% defines |\TP_templdecl_add_global_or_nothing:| to put the prefix
+% onto the list. After that we simply call the big switch
+% again.\footnote{It should probably all be changed to not rely on
+% the prefix working}.
+% \begin{macrocode}
+\def_new:cpn{TP_use_arg_type_+:w} {
+ \bool_set_true:N\l_TP_global_assignment_bool
+ \def:Npn \TP_templdecl_add_global_or_nothing:
+ {\toks_put_right:Nn \l_TP_KV_assignments_toks {\pref_global:D} }
+ \TP_templdecl_parse_KV:N
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\TP_use_arg_type_l:w}
+% The |l| sets a length register. We disable the prefix and insert
+% either |\gsetlength| or |\setlength| depending on whether a |+|
+% was seen or not.
+% \begin{macrocode}
+\def_new:Npn\TP_use_arg_type_l:w {
+ \TP_parse_optional_key_default:nw
+ {
+ \let:NN \TP_templdecl_add_global_or_nothing: \use_noop:
+ \bool_if:NTF \l_TP_global_assignment_bool
+ {\TP_templdecl_setup_register_key:Nn\gsetlength}
+ {\TP_templdecl_setup_register_key:Nn\setlength}
+ }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\TP_use_arg_type_L:w}
+% The |L| sets a fake length register.
+% \begin{macrocode}
+\def_new:Npn\TP_use_arg_type_L:w {
+ \TP_parse_optional_key_default:nw
+ {\TP_templdecl_setup_fakeregister_key:NNn\setlength\l_tmpa_skip}
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\TP_use_arg_type_c:w}
+% The |c| sets a count register.
+% \begin{macrocode}
+\def_new:Npn\TP_use_arg_type_c:w {
+ \TP_parse_optional_key_default:nw
+ {
+ \let:NN\TP_templdecl_add_global_or_nothing:\use_noop:
+ \bool_if:NTF \l_TP_global_assignment_bool
+ {\TP_templdecl_setup_register_key:Nn\GSetInternalCounter}
+ {\TP_templdecl_setup_register_key:Nn\SetInternalCounter}
+ }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\TP_use_arg_type_C:w}
+% The |C| sets a fake count register.
+% \begin{macrocode}
+\def_new:Npn\TP_use_arg_type_C:w {
+ \TP_parse_optional_key_default:nw
+ {\TP_templdecl_setup_fakeregister_key:NNn
+ \SetInternalCounter\l_tmpa_int}
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\TP_use_arg_type_n:w}
+% The |n| sets a token list pointer.
+% \begin{macrocode}
+\def_new:Npn\TP_use_arg_type_n:w {
+ \TP_parse_optional_key_default:nw
+ {\TP_templdecl_setup_n_key:N}
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\TP_use_arg_type_f:w}
+% \begin{macro}{\TP_templdecl_parse_f_arg:nw}
+% The |f| defines a command with between 0 and 9 arguments.
+% \begin{macrocode}
+\def_new:Npn\TP_use_arg_type_f:w #1{
+ %\TP_templdecl_parse_f_arg:nw {#1}
+ \TP_parse_optional_key_default:nw{\TP_templdecl_setup_f_key:Nn{#1}}
+}
+% \end{macrocode}
+% Helper for |\TP_templdecl_parse_KV:nnw|.
+% \begin{macrocode}
+\def_new:Npn \TP_templdecl_parse_f_arg:nw#1#2{
+% \end{macrocode}
+% The third argument of |\TP_templdecl_setup_f_key:Nn|, i.e., the
+% macro name, is the remaining data up to |\q_stop| which is picked up
+% by |\TP_parse_optional_key_default:nw|.
+% \begin{macrocode}
+ \TP_parse_optional_key_default:nw{\TP_templdecl_setup_f_key:Nn{#1}{#2}}
+}
+% \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+%
+% \begin{macro}{\TP_use_arg_type_b:w}
+% \begin{macro}{\TP_templdecl_setup_b_key:nn}
+% The |b| uses access to the |\if_true:| and |\if_false:|
+% primitives. Needed?
+% \begin{macrocode}
+\def_new:Npn\TP_use_arg_type_b:w {
+ \TP_parse_optional_key_default:nw
+ {\TP_templdecl_setup_b_key:n}
+}
+% \end{macrocode}
+%
+% \begin{macrocode}
+\def_new:Npn \TP_templdecl_setup_b_key:n#1{
+ \let:cN { if#1 } \if_true:
+ \TP_templdecl_define_key:n
+ { \TP_templdecl_eval_b_key_value:nn {#1}{##1} }
+}
+% \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\TP_templdecl_eval_b_key_value:nn}
+% Modify so the boolean does not need to have been
+% declared with |\newif|
+% \begin{macrocode}
+\def_new:Npn \TP_templdecl_eval_b_key_value:nn#1#2{
+ \cs_if_free:cTF {if#2}
+ { \PackageError{template}{Bad~boolean~setting~#1=#2}\@eha }
+ { \tlp_set_eq:cc {if_#1:}{if_#2:}
+ \toks_put_right:Nf \l_TP_KV_assignments_toks
+ { \tlp_set_eq:cc {if_#1:}{if_#2:} }
+ }
+}
+% \end{macrocode}
+%
+% \end{macro}
+%
+% \begin{macro}{\TP_use_arg_type_s:w}
+% \begin{macro}{\TP_templdecl_setup_s_key:n}
+% The |s| chooses between true and false.
+% \begin{macrocode}
+\def_new:Npn\TP_use_arg_type_s:w {
+ \TP_parse_optional_key_default:nw
+ {\TP_templdecl_setup_s_key:n}
+}
+% \end{macrocode}
+% \begin{macrocode}
+\def_new:Npn \TP_templdecl_setup_s_key:n #1 {
+ \TP_templdecl_define_key:n
+ { \TP_templdecl_eval_s_key_value:nnn{##1}#1 }
+}
+% \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+%
+%
+%
+%
+%
+%
+% \begin{macro}{\TP_use_arg_type_i:w}
+% The |i| expects an instance.
+% \begin{macrocode}
+\def_new:Npn\TP_use_arg_type_i:w #1{
+ \TP_parse_optional_key_default:nw{\TP_templdecl_setup_i_key:nnn{#1}}
+}
+% \end{macrocode}
+%
+% declaration |hd =i{head} \fooo| \\
+% use |hd = mine|\\
+% makes |\fooo| shorthand for |\UseInstance{head}{mine}|
+%
+% also allowed: |hd = \UseTemplate{head}{...}{...}|\\
+% in case you want to use an unnamed instance of type |head|
+% in this place.
+% \end{macro}
+%
+% \begin{macro}{\TP_templdecl_setup_i_key:nnn}
+% MH change: do either local or global.
+% \begin{macrocode}
+\def_new:Npn \TP_templdecl_setup_i_key:nnn#1#2{
+ \TP_templdecl_define_key:n
+ {
+ \TP_templdecl_eval_i_key_value:Nnn #2 {#1}{##1}
+ }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\TP_templdecl_eval_i_key_value:Nnn}
+% MH change: Add extra argument for local or global.
+% \begin{macrocode}
+\def_new:Npn \TP_templdecl_eval_i_key_value:Nnn #1#2#3 {
+ \tlist_if_head_eq_meaning:nNTF {#3.}\UseTemplate
+ {
+ \io_put_term:x{\token_to_string:N\UseTemplate\space seen}
+% \end{macrocode}
+%
+% Code below from |\TP_templdecl_setup_f_key:Nn| (should be
+% combined and cleaned up)
+% at this point one should also check if first arg of |\UseTemplate|
+% corresponds to |#2| and if not complain (not done)
+%
+% \begin{macrocode}
+ {\TP_templdecl_declare_tmp_instance:nnnn #3 }
+ \toks_put_right:No \l_TP_KV_assignments_toks
+ { \exp_after:NN \KV@toks \exp_after:NN {\g_tmpa_tlp} }
+ %\TP_templdecl_add_global_or_nothing:
+ %\toks_put_right:Nn \l_TP_KV_assignments_toks
+ % { \def:Npx #1{ \toks_use:N \KV@toks} }
+ \bool_if:NTF \l_TP_global_assignment_bool
+ {\toks_put_right:Nn \l_TP_KV_assignments_toks
+ {\gdef:Npx #1 { \toks_use:N \KV@toks}}
+ }
+ {\toks_put_right:Nn \l_TP_KV_assignments_toks
+ {\def:Npx #1 { \toks_use:N \KV@toks}}
+ }
+ }
+ {
+ \TP_let_instance:Nnn#1{#2}{#3}
+% \end{macrocode}
+% We want the |\let:Nc| hiding in |\TP_let_instance:Nnn| to expand
+% fully to two csnames so we put a |\tex_romannumeral:D 0| (which in
+% itself expands to nothing) in front. This expands the |\let:Nc| fully
+% before finding out that |\let:NwN| is not expandable.
+% \begin{macrocode}
+ \toks_put_right:Nf \l_TP_KV_assignments_toks
+ { \TP_let_instance:Nnn#1{#2}{#3} }
+ }
+}
+% \end{macrocode}
+% \end{macro}
+%
+%
+%
+%
+%
+%
+%
+%
+% \begin{macro}{\TP_use_arg_type_x:w}
+% \begin{macro}{\TP_templdecl_setup_x_key:nn}
+% The |x| runs internal code.
+% \begin{macrocode}
+\def_new:Npn\TP_use_arg_type_x:w {
+ \TP_parse_optional_key_default:nw
+ {\TP_templdecl_setup_x_key:n}
+}
+% \end{macrocode}
+%
+% \begin{macrocode}
+\def_new:Npn \TP_templdecl_setup_x_key:n#1{
+ \TP_templdecl_define_key:n
+ { \toks_put_right:Nn\l_TP_KV_assignments_toks{#1} }
+}
+% \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+%
+%
+%
+%
+% \begin{macro}{\TP_use_arg_type_g:w}
+% \begin{macro}{\TP_templdecl_setup_g_key:nn}
+% The |g| runs any code.
+% \begin{macrocode}
+\def_new:Npn\TP_use_arg_type_g:w {
+ \TP_parse_optional_key_default:nw
+ {\TP_templdecl_setup_g_key:n}
+}
+% \end{macrocode}
+%
+% \begin{macrocode}
+\def_new:Npn \TP_templdecl_setup_g_key:n #1 {
+ \TP_templdecl_define_key:n{#1}}
+% \end{macrocode}
+%
+% \end{macro}
+% \end{macro}
+%
+%
+%
+%
+% \begin{macro}{\TP_templdecl_define_key:n}
+% Here we define the key in the current template.
+% \begin{macrocode}
+\def_new:Npn \TP_templdecl_define_key:n#1{
+ \tlp_set:Nx \l_tmpa_tlp {
+ \exp_not:N \TP_templdecl_remove_from_default_assignments:N
+ \exp_not:c{KV@\l_TP_curr_name_tlp @\l_TP_currkey_tlp}
+ \exp_not:o {\TP_templdecl_add_global_or_nothing: }
+ }
+ \exp_args:NcNo \def:NNn {KV@\l_TP_curr_name_tlp @\l_TP_currkey_tlp} 1
+ { \l_tmpa_tlp #1 }
+}
+% \end{macrocode}
+% \end{macro}
+%
+%
+%
+%
+%
+%
+%
+%
+%
+%
+% \begin{macro}{\TP_parse_optional_key_default:nw}
+% Look for default value. The |t| argument type here is one we
+% define for template so we can change it easily. Currently I just
+% set it to be a regular optional argument in brackets. |#1| is what
+% we are carrying over, |#2| the optional argument.
+% \begin{macrocode}
+\def_long:Npn \TP_ignore_leading_space_in_arg_ii:nn#1#2{
+ \exp_args:Nf\TP_ignore_leading_space_in_arg_ii_aux:nn
+ {\exp_not:N #2}{#1}
+}
+\def_long:Npn \TP_ignore_leading_space_in_arg_ii_aux:nn#1#2{#2{#1}}
+
+
+\DeclareArgumentType t[{meaning}{}{\NoValue}{#1[#2]}{#2}
+\DeclareDocumentCommand\TP_parse_optional_key_default:nw{mt}{
+ \IfNoValueTF{#2}
+ {\TP_templdecl_finish_key_setup:nw{#1}}
+ {\TP_templdecl_finish_key_setup_with_default:nnw{#1}{#2}}
+}
+%\show\TP_parse_optional_key_default:nw
+%\exp_args:Nc\show{\string\TP_parse_optional_key_default:nw}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\TP_templdecl_finish_key_setup:nw}
+% After having parsed the line and not found any default value it
+% remains to actually define the key for the instance parsing by
+% executing the setup code (in |#1|) giving it |#2| (i.e., the
+% remainder of the line) as an argument.
+% \begin{macrocode}
+\def_new:Npn \TP_templdecl_finish_key_setup:nw#1#2\q_stop{
+ \TP_ignore_leading_space_in_arg_ii:nn{#1}{#2}
+ %%%#1{#2}
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\TP_templdecl_finish_key_setup_with_default:nnw}
+% If there is a default the situation is more complicated since we
+% not only have to set up the key for the instance but also have to
+% add the default value to |\l_TP_default_assignments_toks| in an
+% appropriate way.
+%
+% First set up the the key itself:
+% \begin{macrocode}
+\def_new:Npn \TP_templdecl_finish_key_setup_with_default:nnw#1#2#3\q_stop{
+ \TP_ignore_leading_space_in_arg_ii:nn{#1}{#3}
+ %%% #1 {#3}
+% \end{macrocode}
+% Now we run the new key code (which is stored in |\KV@...| hopefully)
+% and give it the default found. By doing this in a group and by
+% locally emptying |\l_TP_KV_assignments_toks| we will get the
+% resulting assignment code into that register.
+%
+% (We set |\TP_templdecl_remove_from_default_assignments:N| to
+% |\use_none:n| since this is a temporary operation and we don't want
+% to change the default really.)
+% \begin{macrocode}
+ \group_begin:
+ \toks_clear:N \l_TP_KV_assignments_toks
+ \let:NN \TP_templdecl_remove_from_default_assignments:N \use_none:n
+ \cs_use:c{KV@\l_TP_curr_name_tlp @\l_TP_currkey_tlp}{#2}
+% \end{macrocode}
+% And now for a final trick: before closing the group again and losing
+% our local changes we run |\exp_after:NN| several times to get the
+% value of |\l_TP_KV_assignments_toks| into
+% |\l_TP_default_assignments_toks| outside that group!
+% \begin{macrocode}
+ \exp_after:NN
+ \group_end:
+ \exp_after:NN
+ \toks_set:Nn
+ \exp_after:NN
+ \l_TP_default_assignments_toks
+ \exp_after:NN
+ { \cs:w KV@\l_TP_curr_name_tlp @\l_TP_currkey_tlp \exp_after:NN \cs_end:
+ \exp_after:NN
+ { \toks_use:N \exp_after:NN \l_TP_KV_assignments_toks
+ \exp_after:NN
+ }
+ \toks_use:N\l_TP_default_assignments_toks
+ }
+}
+% \end{macrocode}
+% \end{macro}
+%
+%
+%
+% \begin{macro}{\c_TP_true_tlp}
+% \begin{macrocode}
+\tlp_new:Nn \c_TP_true_tlp {true}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\TP_templdecl_eval_s_key_value:nnn}
+% \begin{macrocode}
+\def_new:Npn \TP_templdecl_eval_s_key_value:nnn#1#2#3 {
+% no error check on this yet.
+ \tlp_set:Nn \l_tmpa_tlp {#1}
+ \tlp_if_eq:NNTF \l_tmpa_tlp \c_TP_true_tlp
+ { \toks_put_right:Nn \l_TP_KV_assignments_toks {#2} }
+ { \toks_put_right:Nn \l_TP_KV_assignments_toks {#3} }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\TP_templdecl_setup_register_key:Nnn}
+% This is normally called automatically by |\DeclareTemplate|.
+%
+% Command for setting a template attribute whose name
+% corresponds directly to a \TeX{} count or length register\\
+% |#1| the function to set the value eg \setlength.\\
+% |#2| key name.\\
+% |#3| the register to set.
+%
+% This command \emph{fully evaluates} the argument at declare time,
+% and assigns the value to the register. It also passes an assignment
+% of the register to the final value into the parameter list for the
+% template.
+%
+% If the value is a call to |\DelayEvaluation|, don't evaluate it now,
+% just pass the whole assignment to the template. Remember to remove
+% the |\DelayEvaluation|.
+% \begin{macrocode}
+\def_new:Npn \TP_templdecl_setup_register_key:Nn #1#2{
+ \TP_templdecl_define_key:n{
+ \tlist_if_head_eq_meaning:nNTF{##1}\DelayEvaluation
+ {
+% \end{macrocode}
+% Old line commented out. Remove |\DelayEvaluation| and also remove
+% the braces surrounding its argument.
+% \begin{macrocode}
+ \toks_put_right:Nn \l_TP_KV_assignments_toks {#1#2{##1}}
+ %\toks_set:No\l_tmpa_toks{\use_arg_ii:nn ##1}
+ %\toks_put_right:Nx \l_TP_KV_assignments_toks
+ % {\exp_not:n{#1#2}{\toks_use:N \l_tmpa_toks}}
+ }
+% \end{macrocode}
+%
+%
+% check for |\MultiSelection| creeping up and if so add something like
+%
+% \begin{verbatim}
+% \setlength\register{\ifcase\selector \or value1 \or value2
+% ... \else valueotherwise \fi}
+% \end{verbatim}
+% to |\l_TP_KV_assignments_toks|.
+%
+% \begin{macrocode}
+ {
+ \tlist_if_head_eq_meaning:nNTF{##1..}\MultiSelection
+ {
+ \group_begin:
+ \TP_multiselection_add:nnnnnn #1#2##1
+ \group_end:
+% \end{macrocode}
+%
+%
+% there are probably better ways to do this (:-)
+%
+% \begin{macrocode}
+ \tlist_if_in:onTF{\toks_use:N\g_TP_multiselection_toks}\DelayEvaluation
+ {
+ \toks_put_right:No\l_TP_KV_assignments_toks
+ {
+ \exp_after:NN#1\exp_after:NN#2\exp_after:NN
+ {\toks_use:N\g_TP_multiselection_toks}
+ }
+ }
+ {
+ \toks_put_right:No\l_TP_KV_assignments_toks
+ {
+ \exp_after:NN #2
+ \exp_after:NN= \toks_use:N\g_TP_multiselection_toks\scan_stop:
+ }
+ }
+% \end{macrocode}
+%
+%
+% otherwise do as before
+%
+% \begin{macrocode}
+ }
+ {
+ #1#2{##1}
+ \toks_put_right:No\l_TP_KV_assignments_toks {
+ \exp_after:NN #2 \exp_after:NN = \tex_the:D #2\scan_stop:
+ }
+ }
+ }
+ }
+}
+% \end{macrocode}
+% \end{macro}
+%
+%
+%
+%
+%
+%
+% \begin{macro}{\DelayEvaluation}
+% \begin{macro}{\MultiSelection}
+% Since we are testing explicitly for |\DelayEvaluation| and
+% |\MultiSelection| a few places we better give them unique
+% meanings!
+% \begin{macrocode}
+\def_new:NNn\DelayEvaluation 1{\use_none:n{\DelayEvaluation}#1}
+\def_new:NNn\MultiSelection 1{\use_none:n{\MultiSelection}#1}
+% \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\TP_templdecl_remove_from_default_assignments:N}
+% Note: the toks register is more or less a plists and should
+% perhaps be implemented as such as this would make far more
+% readable code.
+% \begin{macrocode}
+\def_new:Npn \TP_templdecl_remove_from_default_assignments:N#1{
+ \def:Npn \tmp:w ##1#1##2##3#1##4\q_stop{
+ \l_TP_default_assignments_toks{##1##3}
+ }
+ \exp_after:NN \tmp:w
+ \toks_use:N\l_TP_default_assignments_toks #1\scan_stop:#1\q_stop}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\TP_templdecl_setup_f_key:Nn}
+% Same for macro names. Again usually called automatically when
+% declaring a new template.\\
+% |#1| Determines how many arguments the function should have.\\
+% |#2| The macro to be defined.
+%
+% If the `|##1|`, the value passed as the argument of the key
+% to the macro |#2| is invoked starts with |\FunctionInstance|, then a
+% special procedure is taken. Instead of defining a macro with the
+% specified number of arguments, the paramater list of the nested
+% function instance is parsed, and |#2| is defined to be a macro
+% expanding to that instance. In this case the specified template
+% is responsible for picking up the requested number of
+% arguments. (This is \emph{not} checked.)
+% \begin{macrocode}
+\def_new:Npn \TP_templdecl_setup_f_key:Nn#1#2{
+% \end{macrocode}
+%
+% |##1| can either be arbitrary inline code, in which case it will be
+% defined with something similar to |\newcommand[val]| so it needs to
+% use |#1| -- |#val|.
+%
+% define it locally here (why this, David???)
+% \begin{macrocode}
+ \TP_templdecl_define_key:n
+ { \TP_templdecl_define_function:NNn#1#2{##1} }
+}
+% \end{macrocode}
+% \end{macro}
+%
+%
+% \begin{macro}{\TP_templdecl_define_function:NNn}
+% |\def:Npn | setup with a latex style `number of arguments' argument.
+% \begin{macrocode}
+\def_new:Npn \TP_templdecl_define_function:NNn#1#2#3{
+ \def:NNn #2 #1 {#3}
+ \toks_put_right:Nf \l_TP_KV_assignments_toks { \def:NNn #2 #1 {#3} }
+}
+% \end{macrocode}
+% \end{macro}
+%
+%
+%
+% \begin{macro}{\TP_templdecl_setup_n_key:N}
+% Here is the extended version that tries to deal with
+% |\MultiSelection|.
+%
+% In case of `n' keys there is no evaluation at declaration time so it
+% is not sensible to look for |\DelayEvaluation|. For this reason as
+% well as for the fact that |\TP_multiselection_add:nnnnnn| above
+% assumes that it deals
+% with registers that can be accessed via |\toks_use:N| we have to use a
+% different command to handle the |\MultiSelection| args but
+% it is essentially doing the same.
+%
+% \begin{macrocode}
+\def_new:Npn \TP_templdecl_setup_n_key:N#1{
+ \TP_templdecl_define_key:n{
+ \tlist_if_head_eq_meaning:nNTF{##1..}\MultiSelection
+ {
+ \group_begin:
+ \TP_templdecl_multiselection:nnnn ##1
+ \group_end:
+ \toks_put_right:Nx\l_TP_KV_assignments_toks {
+ \exp_not:n{\tlp_set:No #1} { \toks_use:N \g_TP_multiselection_toks}
+ }
+ }
+ {
+ \def:Npn #1{##1} % setting it?
+ \toks_put_right:Nn \l_TP_KV_assignments_toks
+ { \tlp_set:Nn #1{##1} }
+ }
+ }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\TP_templdecl_multiselection:nnnn}
+% Start the |\if_case:w|
+% \begin{macrocode}
+\def_new:Npn \TP_templdecl_multiselection:nnnn #1#2#3#4{
+ \toks_gset:Nn \g_TP_multiselection_toks {\if_case:w #2}
+ \clist_map_inline:nn {#3}{ \TP_multiselection_add_or_case:n {##1} }
+ \toks_gput_right:Nn\g_TP_multiselection_toks { \else: #4\fi: }
+}
+% \end{macrocode}
+% \end{macro}
+%
+%
+%
+%
+%
+%
+%
+%
+% \begin{macro}{\DeclareInstance}
+% |{type}{instname}{templatename}{keyval}|
+% \begin{macrocode}
+\def_new:Npn \DeclareInstance { \DeclareCollectionInstance{} }
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\DeclareCollectionInstance}
+% |{collection}{type}{instname}{templatename}{keyval}|
+% The fifth argument is picked up implicitly.
+% \begin{macrocode}
+\def_long_new:Npn \DeclareCollectionInstance#1#2#3#4{
+ \TP_declare_instance:cnn { <#1>#2/#3 }{ #2/#4 }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\UseCollection}
+% |{type}{collection}|
+% \begin{macrocode}
+\def_new:Npn \UseCollection#1#2{
+ \tlp_set:cx { TP@<#1> }
+ { {#2} \TP_get_arg_count:n{#1} }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\TP_let_instance:Nnn}
+% |\internalcommand{type}{instname}|
+%
+% The way this macro is used, it must result in |\let:NwN| |<csname1>|
+% |<csname2>| after exactly two expansions as it is used this way
+% in |\TP_templdecl_eval_i_key_value:nnn|!
+% \begin{macrocode}
+\def_new:Npn \TP_let_instance:Nnn#1#2#3{
+ \let:Nc #1
+ {
+ \cs_if_free:cTF { \TP_get_csname_prefix:n{#2} #3 }
+ { <>#2/ }
+ { \TP_get_csname_prefix:n{#2} }
+ #3
+ }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\UseInstance}
+% |{type}{instname}|
+% \begin{macrocode}
+\def_new:Npn \UseInstance#1#2{
+ \TP_let_instance:Nnn \l_tmpa_tlp {#1}{#2}
+ \tlp_if_eq:NNTF \l_tmpa_tlp \scan_stop:
+ \INSTANCEundefined
+ \l_tmpa_tlp
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\TP_templdecl_declare_tmp_instance:nnnn}
+% This macro is called when we have seen a |\UseTemplate|
+% declaration as part of an |i| key value. Therefore the
+% first argument will be dropped (it contains the token
+% |\UseTemplate|) the second and third will be combined to refer to
+% the template and the fourth argument will be implictly picked up
+% by |\TP_declare_instance:Nnn|.
+% \begin{macrocode}
+\def_long_new:Npn \TP_templdecl_declare_tmp_instance:nnnn#1#2#3{%
+ \TP_declare_instance:Nnn \g_tmpa_tlp {#2/#3} }
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\ShowTemplate}
+% Some extension to |\ShowTemplate| so that we also get to see the
+% restrictions if any
+% \begin{macrocode}
+\def_new:Npn \ShowTemplate#1#2{
+ \io_put_term:x{*******~ Template:~ #1/#2~ *******}
+ \io_put_term:x{*}
+ \io_put_term:x{*~ Defaults:}
+ \io_put_term:x{*}
+ \io_put_term:x{\token_to_string:N\TPD>/#1/#2=
+ \cs_meaning:c{TPD>/#1/#2}}
+ \io_put_term:x{*}
+ \io_put_term:x{*~ Restrictions:}
+ \io_put_term:x{*}
+ \io_put_term:x{\token_to_string:N\TPR>/#1/#2=
+ \cs_meaning:c{TPR>/#1/#2}}
+ \io_put_term:x{*}
+ \io_put_term:x{*~ Body:}
+ \io_put_term:x{*}
+ \cs_show:c {TP>/#1/#2}}
+% \end{macrocode}
+% \end{macro}
+%
+%
+% \begin{macro}{\ShowCollectionInstance}
+% \begin{macrocode}
+\def_new:Npn \ShowCollectionInstance#1#2#3{
+ \io_put_term:x{*******~ Instance:~ <#1>#2/#3~ *******}
+ \io_put_term:x{*}
+ \cs_show:c {<#1>#2/#3}}
+\def_new:Npn \ShowInstance{\ShowCollectionInstance{}}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\TP_templdecl_setup_fakeregister_key:NNn}
+% |{setcomand}{privateregister}{key}{internalcode}|
+% \begin{macrocode}
+\def_new:Npn \TP_templdecl_setup_fakeregister_key:NNn#1#2#3{
+ \TP_templdecl_define_key:n{
+ \tlist_if_head_eq_meaning:nNTF{##1..}\DelayEvaluation
+ {
+% \end{macrocode}
+% In the v0.08 version of \texttt{template.dtx} a
+% |\DelayEvaluation| for a faked register would simply be equiv to
+% a |\def:Npn | (code is below commented out). The negative side effect
+% of this is that something like |=L| used with |\DelayEvaluation|
+% would not allow for calc syntax since it would end up as
+% |\def:Npn |\allowbreak|\foo|\allowbreak|{a+b}|. The code below changes
+% this to first assign to a scratch register (at runtime) and then
+% do an |\edef|. Could be coded differently to save space (at cost
+% of time)
+% \begin{macrocode}
+% \toks_put_right:Nn \l_TP_KV_assignments_toks {\def:Npn #3{##1}}
+% \toks_put_right:Nn \l_TP_KV_assignments_toks
+% {#1#2{##1}\def:Npx #3{\toks_use:N#2}}
+ \toks_set:No \l_tmpa_toks {\use_arg_ii:nn ##1}
+ \toks_put_right:Nx \l_TP_KV_assignments_toks {
+ {\exp_not:n{#1#2}{\toks_use:N \l_tmpa_toks}
+ \exp_not:n{ \def:Npx #3{\toks_use:N#2} }
+ }
+ }
+ }
+% \end{macrocode}
+%
+%
+% Otherwise same game for fake registers except that instead of
+% passing the register to |\TP_multiselection_add:nnnnnn| we pass a
+% temp fake one and
+% doing a def instead of using |\setlength| or |\setcounter|
+%
+% and i haven't done the |\DelayEvaluation| bit for that case! as
+% i'm not sure what the best approach is for those
+% things\footnote{we might disallow it for that case in general ---
+% not a nice rule but an explainable one}
+%
+% \begin{macrocode}
+ {
+ \tlist_if_head_eq_meaning:nNTF{##1..}\MultiSelection
+ {
+ \group_begin:
+ \TP_multiselection_add:nnnnnn#1#2##1
+ \group_end:
+ \toks_put_right:Nx\l_TP_KV_assignments_toks
+ {\exp_not:n{\def:Npn #3} {\toks_use:N\g_TP_multiselection_toks}}
+ }
+ {
+ #1#2{##1}
+ \toks_put_right:Nx\l_TP_KV_assignments_toks
+ {\exp_not:n{\def:Npn#3} {\toks_use:N#2}}
+ }
+ }
+ }
+}
+% \end{macrocode}
+% \end{macro}
+%
+%
+% \begin{macro}{\g_TP_multiselection_toks}
+% \begin{macrocode}
+\toks_new:N \g_TP_multiselection_toks
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\TP_multiselection_add:nnnnnn}
+% \marg{operation} \marg{register} |\MultiSelection|
+% \marg{selector} \marg{case-list} \marg{else-case}
+%
+% This command builds up the |\if_case:w| code from the three arguments
+% of |\MultiSelection| and stores it in
+% |\g_TP_multiselection_toks|. This code is supposed to be run in
+% a group so a) we don't have to initialise
+% |\g_TP_multiselection_toks| and b) all changes to the used
+% registers not affecting the outside.
+%
+% \begin{macrocode}
+\def_new:Npn \TP_multiselection_add:nnnnnn #1#2#3#4#5#6{
+ \toks_gset:Nn \g_TP_multiselection_toks {\if_case:w #4}
+ \clist_map_inline:nn {#5}{
+ \tlist_if_head_eq_meaning:nNTF{##1..}\DelayEvaluation
+ {
+ \TP_multiselection_add_or_case:n {##1}
+ }
+ {
+ #1#2{##1}
+ \TP_multiselection_add_or_case:n { \toks_use:N #2 }
+ }
+ }
+ \toks_gput_right:Nn \g_TP_multiselection_toks { \else: #6\fi: }
+}
+% \end{macrocode}
+%
+% \end{macro}
+%
+% \begin{macro}{\TP_multiselection_add_or_case:o}
+% Since we intend to add |\or:| to |\g_TP_multiselection_toks|
+% within the |\_for| loop we have to hide it carefully or else we
+% will get some unmatched conditionals.
+%
+% Actually the |:o| is a slight lie here since the expanion happens
+% when we add things to the toks register inside.
+% \begin{macrocode}
+\def_new:Npn \TP_multiselection_add_or_case:n #1 {
+ \toks_gput_right:Nn \g_TP_multiselection_toks { \or: #1 }
+}
+\def_new:Npn \TP_multiselection_add_or_case:o {
+ \exp_args:NNo \TP_multiselection_add_or_case:n
+}
+% \end{macrocode}
+% \end{macro}
+%
+% Since i like to set things like |item-label-text| using this
+% mechanism i need to handle the `n' key specially.
+%
+% Actually i could have probably extended
+% |\TP_templdecl_setup_f_key:nnN| thus making
+% this generally available to all f\meta{number} keys but was too lazy
+% (or too stupid) to get it right first time so settled for the simple
+% solution.
+%
+% So |\TP_templdecl_parse_KV:nnw| now calls
+% |\TP_templdecl_setup_n_key:nN| for the `n' key. looks like
+% this thus be fixed some time soon
+%
+%
+%
+%
+%
+%
+%
+% \begin{macro}{\IfExistsInstanceTF}
+% tests that there is a \emph{default} definition
+% taken from xinitials.dtx:
+% \begin{macrocode}
+\def_new:Npn \IfExistsInstanceTF#1#2{
+ \cs_if_exist:cTF{<>#1/#2}
+}
+% \end{macrocode}
+%
+% FMi: what happens if we are in collection FOO and there exists an
+% instance I for type T within this collection but there doesn't exist
+% an instance in the empty collection?
+%
+% What would happen if \ldots\ --- not clear to me what the sematics
+% really should be. The code below is not better only different( and
+% slower).\footnote{fix semantics}
+% \begin{macrocode}
+\def:Npn \IfExistsInstanceTF#1#2{
+ \TP_let_instance:Nnn \l_tmpa_tlp {#1}{#2}
+% next is not \tlp_if_eq:NNTF but ...FT so done manually
+ \if_meaning:NN\l_tmpa_tlp\scan_stop:
+ \exp_after:NN\use_arg_ii:nn
+ \else:
+ \exp_after:NN\use_arg_i:nn
+ \fi:}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\DeclareRestrictedTemplate}
+% Setting it up:
+%
+%| \DeclareRestrictedTemplate|\\
+% |{T-type} {new-T-name} {source-T-name} {keyvals}|
+%
+% This uses the same code as {T-type} {source-T-name} but adds
+% settings from {keyvals}
+% \begin{macrocode}
+\def_new:Npn \DeclareRestrictedTemplate#1#2#3#4{
+ % CCC do we need a group here??
+ \tlp_set_eq:cc { TPD>/#1/#2 } { TPD>/#1/#3 }
+ \tlp_set_eq:cc { TP>/#1/#2 } { TP>/#1/#3 }
+
+ \toks_set:Nd \l_TP_KV_assignments_toks
+ {\cs:w TPR>/#1/#3\cs_end:}
+
+% adds stuff to \l_TP_KV_assignments_toks
+ \setkeys {\cs:w TPO>/#1/#3\cs_end:}{#4}
+
+ \tlp_set:co { TPR>/#1/#2 }
+ { \toks_use:N \l_TP_KV_assignments_toks }
+ \cs_if_free:cTF { TPO>/#1/#3 }
+ { \tlp_set:cn {TPO>/#1/#2}{#1/#3} }
+ { \tlp_set_eq:cc {TPO>/#1/#2}{TPO>/#1/#3} }
+}
+% \end{macrocode}
+% \end{macro}
+%
+%
+% Internals:
+%
+% \begin{macro}{\TP_instdecl_generate_assignments:nn}
+% These could probably be inlined, even when they do something!
+%
+% Assumption: setkeys fully expands its first argument.
+%
+% \begin{macrocode}
+\def_new:Npn \TP_instdecl_generate_assignments:nn#1#2 {
+ % Returns to \l_TP_KV_assignments_toks
+ % the restrictions
+ % stored in the TP-structure (at present
+ % in YAM) of the template #1
+
+ \toks_set:Nd \l_TP_default_assignments_toks
+ {\cs:w TPD>/#1\cs_end:\scan_stop:\scan_stop:}
+
+ \toks_set:Nd \l_TP_KV_assignments_toks
+ {\cs:w TPR>/#1\cs_end:}
+
+ \setkeys { \cs:w TPO>/#1 \cs_end: }
+ { #2 } % adds stuff to \l_TP_KV_assignments_toks
+
+% prepends stuff to \l_TP_KV_assignments_toks :
+ \exp_after:NN\TP_instdecl_add_default_recurse:nn
+ \toks_use:N\l_TP_default_assignments_toks
+
+}
+% \end{macrocode}
+% \end{macro}
+%
+%
+% \begin{macro}{\TP_instdecl_add_default_recurse:nn}
+% [ 2001/06/10 Think about doing this properly with explicit plists! --- but
+% this means that one has to think about whether or not plists should be
+% implemented as token registers and not as tlps as they are now. ]
+% \begin{macrocode}
+\def_new:Npn \TP_instdecl_add_default_recurse:nn#1#2{
+ \token_if_eq_meaning:NNF #1\scan_stop:
+ {
+ \l_tmpa_toks{#2}
+ \tlp_set:Nx \l_tmpa_tlp {
+ {\toks_use:N \l_tmpa_toks \toks_use:N \l_TP_KV_assignments_toks}
+ }
+ \l_TP_KV_assignments_toks \l_tmpa_tlp
+ \TP_instdecl_add_default_recurse:nn
+ }
+}
+% \end{macrocode}
+% \end{macro}
+%
+%
+%
+% |TPD>/type/name| stores the default parameter assignments.
+%
+% |TPR>/type/name| stores the parameter assignments that have been
+% made for a restricted template otherwise it is undefined (or |\scan_stop:|).
+%
+%
+% |TPO>/type/name| stores the full name (i.e. as |type/name|)
+% of the template a restricted
+% template is coming from originally.
+%
+%
+%
+%
+% \begin{macro}{\TP_split_finite_skip_value:nnNN}
+% This macro is for use in error checking template values like
+% "text-float-sep" that can't contain infinite glue and needs the
+% shrink and/or stretch components. First argument is the skip
+% register (which is likely to be user input), second is a template
+% key name, and the last two are the \meta{dimen} registers that
+% stores the stretch and shrink components. Assignments are global.
+% \begin{macrocode}
+\def_new:Npn \TP_split_finite_skip_value:nnNN #1#2{
+ \skip_split_finite_else_action:nnNN {#1} {
+ \PackageError{template}{Value~ for~ key~ #2~ contains~ `fil(ll)'}
+ {Only~ finite~ minus~ or~ plus~ parts~ are~ allowed~ for~ this~ key.}
+ }
+}
+% \end{macrocode}
+% \end{macro}
+%
+%
+%
+%
+% \begin{macrocode}
+%</package>
+% \end{macrocode}
+%
+% \Finale
+%
diff --git a/Master/texmf-dist/source/latex/xbase/xbase.ins b/Master/texmf-dist/source/latex/xbase/xbase.ins
new file mode 100644
index 00000000000..742a1aa8dc3
--- /dev/null
+++ b/Master/texmf-dist/source/latex/xbase/xbase.ins
@@ -0,0 +1,73 @@
+% \iffalse
+%%
+%% This file will generate fast loadable files and documentation
+%% driver files from the dtx files in this package when run through
+%% LaTeX or TeX.
+%%
+%% (C) Copyright 2000-2005 LaTeX3 Project
+%%
+%% It may be distributed and/or modified under the conditions of the
+%% LaTeX Project Public License (LPPL), either version 1.3a of this
+%% license or (at your option) any later version. The latest version
+%% of this license is in the file
+%%
+%% http://www.latex-project.org/lppl.txt
+%%
+%% This file is part of the ``xbase bundle'' (The Work in LPPL)
+%% and all files in that bundle must be distributed together.
+%%
+%% The released version of this bundle is available from CTAN.
+%%
+%% -----------------------------------------------------------------------
+%%
+%% The development version of the bundle can be found at
+%%
+%% http://www.latex-project.org/cgi-bin/cvsweb.cgi/
+%%
+%% for those people who are interested.
+%%
+%%%%%%%%%%%
+%% NOTE: %%
+%%%%%%%%%%%
+%%
+%% Snapshots taken from the repository represent work in progress and may
+%% not work or may contain conflicting material! We therefore ask
+%% people _not_ to put them into distributions, archives, etc. without
+%% prior consultation with the LaTeX Project Team.
+%%
+%% -----------------------------------------------------------------------
+%%
+%% $Id: xbase.ins 302 2005-03-01 22:49:14Z morten $
+%%
+% \fi
+%
+
+\input docstrip
+\keepsilent
+\askforoverwritefalse
+
+\preamble
+
+(C) Copyright The LaTeX3 Project and any individual authors
+listed elsewhere in this file.
+
+This is a generated file.
+
+This file was generated from file(s) of the xbase bundle.
+---------------------------------------------------------
+
+This file may only be distributed together with a copy of this bundle.
+You may however distribute the bundle without such generated files.
+
+======================================================================
+
+\endpreamble
+
+
+\generate{%
+ \file{ldcsetup.sty}{\from{ldcsetup.dtx}{package}}
+ \file{template.sty}{\from{template.dtx}{package,trace}}
+ \file{xparse.sty}{\from{xparse.dtx}{package}}
+}
+
+\endbatchfile
diff --git a/Master/texmf-dist/source/latex/xbase/xparse.dtx b/Master/texmf-dist/source/latex/xbase/xparse.dtx
new file mode 100644
index 00000000000..90346556975
--- /dev/null
+++ b/Master/texmf-dist/source/latex/xbase/xparse.dtx
@@ -0,0 +1,2167 @@
+% \iffalse
+%% File: xparse.dtx (C) Copyright 1999 Frank Mittelbach, Chris Rowley, David Carlisle
+%% (C) Copyright 2004-2006 Frank Mittelbach, LaTeX3 Project
+%%
+%% It may be distributed and/or modified under the conditions of the
+%% LaTeX Project Public License (LPPL), either version 1.3c of this
+%% license or (at your option) any later version. The latest version
+%% of this license is in the file
+%%
+%% http://www.latex-project.org/lppl.txt
+%%
+%% This file is part of the ``xbase bundle'' (The Work in LPPL)
+%% and all files in that bundle must be distributed together.
+%%
+%% The released version of this bundle is available from CTAN.
+%%
+%% -----------------------------------------------------------------------
+%%
+%% The development version of the bundle can be found at
+%%
+%% http://www.latex-project.org/cgi-bin/cvsweb.cgi/
+%%
+%% for those people who are interested.
+%%
+%%%%%%%%%%%
+%% NOTE: %%
+%%%%%%%%%%%
+%%
+%% Snapshots taken from the repository represent work in progress and may
+%% not work or may contain conflicting material! We therefore ask
+%% people _not_ to put them into distributions, archives, etc. without
+%% prior consultation with the LaTeX Project Team.
+%%
+%% -----------------------------------------------------------------------
+%%
+%<package>\RequirePackage{l3names}
+%<*dtx>
+%\fi
+\def\GetIdInfo$Id: #1.dtx #2 #3-#4-#5 #6 #7$#8{%
+ \def\fileversion{#2}%
+ \def\filedate{#3/#4/#5}%
+ \ProvidesFile{#1.dtx}[#3/#4/#5 v#2 #8]%
+}
+%\iffalse
+%</dtx>
+%\fi
+\GetIdInfo$Id: xparse.dtx 574 2006-08-21 23:30:10Z morten $
+ {generic document command parser}
+% \iffalse
+%<*driver>
+ \documentclass{ltxdoc}
+ \usepackage[T1]{fontenc}
+ \usepackage{textcomp}
+ \makeatletter
+ \providecommand*\eTeX{%
+ \if b\expandafter\@car\f@series\@nil\boldmath\fi
+ $\m@th\varepsilon$-\TeX}
+ \makeatother
+% \usepackage{ldcdoc}
+ \begin{document}
+ \catcode`\_=11
+ \catcode`\:=11
+ \DocInput{xparse.dtx}
+ \end{document}
+%</driver>
+% \fi
+%
+% \CheckSum{621}
+%
+%
+% \title{The \textsf{xparse} package\thanks{This file
+% has version number \fileversion, last
+% revised \filedate.}}
+% \author{FMi, CAR, DPC, MH}
+% \date{\copyright~\filedate}
+% \maketitle
+%
+% \begin{abstract}
+% The interfaces described in this document are not meant to be final
+% but only as a basis for discussion. Building productive applications
+% using the current code is discouraged.
+% \end{abstract}
+%
+% \section{Interface}
+%
+% This package implements high-level interface commands for class file
+% writers which allows the separation of formatting commands
+% (typically instances of so-called `templates') and their arguments
+% from the signature of document-level commands.
+%
+% This works by declaration commands that provide a general
+% specification method for the typical \LaTeX{} syntax, e.g.,
+% star-form, optional arguments, and mandatory arguments. A command
+% (or environment) declared in this way parses the input according to
+% its spec and presents its findings in a normalized way for further
+% processing.
+%
+% \subsection{Argument spec}
+%
+%
+% An argument specification is a list of letters each representing a
+% type of argument, i.e., |m| is a mandatory argument (surrounded by
+% braces), |o| an optional argument (surrounded by brackets if
+% present), and |s| represents a star (which might be present or not).
+% Thus the argument spec for headings as implemented by
+% |\@startsection| in standard \LaTeX{} would be represented by the
+% three letters |som|. Other argument types are available and can be
+% added at will. For a complete list of built-in argument types see
+% the next section.
+%
+% There is one important argument specifier worth taking note of. The
+% |P| does not behave as a normal argument specifier but allows the
+% next argument to take an argument containing the |\par| token which
+% is not allowed by default.
+%
+%
+% \subsection{Parsing results}
+%
+% To normalise the result of parsing the input according to an
+% argument specification it is important to uniquely identify all
+% arguments found. For this reason each parsing operation initiated by
+% one of the argument spec letters will result in an identifiable
+% output as follows:
+% \begin{description}
+% \item[m] will return the parsed argument surrounded by a brace
+% pair, i.e., will normally be the identity;
+% \item[o] will return the parsed argument surrounded by a brace pair
+% if present. Otherwise it will return the token |\NoValue|;
+% \item[O\{default\}] will return the parsed argument surrounded by a
+% brace pair if present. Otherwise it will return the |{default}|
+% as specified above.
+% \item[S\{\meta{symbol}\}] will return either the token |\c_true| or
+% |\c_false| depending on whether or not the next token is
+% \meta{symbol}.
+% \item[s] will return either the token |\c_true| or |\c_false|
+% depending on whether or not a star was parsed. This is just a
+% shorthand for |S{*}|.
+% \item[c] will parse the syntax |(|\meta{x}|,|\meta{y}|)|, i.e., a
+% coordinate pair and will return |{{|\meta{x}|}{|\meta{y}|}}| as
+% the result. If no open parentheses is scanned an error is
+% signalled.
+% \item[C\{\{x-default\}\{y-default\}\}] behaves like |c|, i.e.,
+% parses a coordinate pair if present. If the coordinate pair is
+% missing it returns the default values instead.
+% \item[l] Reads everything up to the first left brace as the
+% argument.
+% \end{description}
+% For example, given the spec |soomO{default}| the input
+% |*[Foo]{Bar}| would be parsed as
+% |\c_true{Foo}\NoValue{Bar}{default}|. In other words there will be
+% always exactly the same number of brace groups or tokens as the
+% number of letters in the argument spec.
+%
+% There are a few exceptions to this rule as the r\^ole of following
+% letters is to affect how the next argument is read.
+% \begin{description}
+% \item[>] takes a mandatory argument like |{P}| or |{PW}| and
+% inserts these extra argument specifiers so that they act on the
+% next regular argument type. See below.
+% \item[P] will cause the next argument to allow |\par| in it's
+% argument. Thus the specification |m>{P}mm| will cause the command to
+% read three mandatory arguments but only the second can contain the
+% |\par| token.
+% \item[W] will cause the next argument to \emph{not} ignore a space
+% when trying to scan ahead for a special symbol such as a |*| or an
+% optional argument. This is mostly useful when the last argument(s)
+% of a document command are optional (see example later on).
+% \end{description}
+%
+%
+% \subsection{Applying the parsing results}
+%
+% Since the result of the parsing is a well defined number of tokens or
+% brace groups it is easy to pass them on in any order to any
+% processing function. To this end the tokens or brace groups are
+% associated with the standard argument specifiers in \TeX{} macros,
+% i.e., |#1|, |#2|, and so forth. This limits the argument
+% specification to a maximum number of 9 letters, but for practical
+% applications this should be sufficient.
+%
+% \subsection{The class designer interface}
+%
+% This package provides commands for declaring commands
+% and environments to be used within the document body.
+%
+% \DescribeMacro\DeclareDocumentCommand
+% The |\DeclareDocumentCommand| declaration takes three arguments. The
+% first argument is the name of the command to be declared, the second
+% is the argument specification in the syntax described above, and the
+% third is the action to be carried out once the arguments are
+% parsed. Within the third argument |#1|, |#2|, etc.\ denote the
+% result of the parsing, e.g.,
+% \begin{verbatim}
+% \DeclareDocumentCommand{\chapter}{som}
+% { \IfBooleanTF {#1}
+% { \typesetnormalchapter {#2}{#3} }
+% { \typesetstarchapter {#3} }
+% }
+% \end{verbatim}
+% would be a way to define a |\chapter| command which would
+% essentially behave like the current \LaTeX{} command (except that it
+% would accept an optional argument even when a |*| was parsed). The
+% |\typesetnormalchapter| could test its first argument for being
+% |\NoValue| to see if an optional argument was present.
+%
+% Of course something like the |\IfNoValueTF| test could also be
+% placed inside a function that would process all three arguments, thus
+% using the templates and their instances as provided by the
+% \texttt{template} package such a declaration would probably look
+% more like the following example:
+% \begin{verbatim}
+% \DeclareDocumentCommand{\chapter}{som}
+% { \UseInstance {head} {A-head-main} {#1} {#2} {#3} }
+% \end{verbatim}
+%
+% Using the |\DeclareDocumentCommand| interface it is easy to modify
+% the document-level syntax while still applying the same
+% layout-generating functions, e.g., a class that would not support
+% optional arguments or star forms for the heading commands could
+% define |\chapter| like this:
+% \begin{verbatim}
+% \DeclareDocumentCommand{\chapter}{m}
+% { \UseInstance {head} {A-head-main} \BooleanFalse \NoValue {#1} }
+% \end{verbatim}
+% while a class that would allow for an additional optional argument
+% (for whatever reason) could define it like that:
+% \begin{verbatim}
+% \DeclareDocumentCommand{\chapter}{somo}
+% { \doSomethingWithTheExtraOptionalArg {#4}
+% \UseInstance {head} {A-head-main} {#1} {#2} {#3} }
+% \end{verbatim}
+% \DescribeMacro\ReDeclareDocumentCommand
+% \DescribeMacro\ProvideDocumentCommand
+% The commands |\ReDeclareDocumentCommand| and
+% |\ProvideDocumentCommand| work just like |\DeclareDocumentCommand|
+% with the exception that |\Re..| can only redefine an existing
+% command and |\Provide...| will only define the command if it is
+% already free.
+%
+%
+% \DescribeMacro\DeclareDocumentEnvironment
+% \DescribeMacro\ReDeclareDocumentEnvironment
+% \DescribeMacro\ProvideDocumentEnvironment The
+% |\DeclareDocumentEnvironment| declaration is similar to
+% |\DeclareDocumentCommand| except that it takes four arguments: the
+% first being the environment name (without a backslash), the second
+% again the argument-spec, and the third and forth are the actions
+% taken at start aqnd end of the environment. The parsed arguments are
+% available to both the start and the finish as |#1|, |#2|, etc.
+%
+% All commands and environments defined with the above commands are
+% automatically robust.
+%
+%
+%
+% \subsection{A different interface (for class design?)}
+%
+% Combining signature and top-level definition of a command |\foo| as
+% in
+% \begin{verbatim}
+% \DeclareDocumentCommand \foo { m c m }
+% { \typeout{1:#1}
+% \typeout{2:#2}
+% \typeout{3:#3}
+% }
+% \end{verbatim}
+% is fine in certain cases, e.g., if the user wants to declare a few
+% commands this way in the preamble of a document. However in a class
+% file it probably better to completely separate signature (i.e.,
+% argument \#1 and \#2) from top-level implementation (i.e., argument
+% \#3).
+%
+%
+% \begin{verbatim}
+% \DeclareDocumentCommandInterface \foo {bar} { m c m }
+% \end{verbatim}
+% The above now declare only the signature of the command |\foo| and
+% states that the implementation is to be found under the label |bar|.
+%
+% A bunch of such statements would then for the first time clearly
+% define a document class (i.e., what a document class instance needs
+% to define to be compliant).
+%
+% An instance would then consist of a lot of declarations of the type
+% \begin{verbatim}
+% \DeclareDocumentCommandImplementation {bar} {3}
+% { \typeout{1:#1}
+% \typeout{2:#2}
+% \typeout{3:#3}
+% }
+% \end{verbatim}
+% i.e., defining how to format things being referenced as part of the
+% signature.
+%
+% The functions |\DeclareDocumentCommandInterface| and
+% |\DeclareDocumentCommandImplementation| are implemented for now but
+% it is not sure if they will stay. If a document command is defined
+% with |\DeclareDocumentCommandInterface| but there is no matching
+% interface it prints the label in quotes as |``bar''|.
+%
+%
+%
+%
+% \subsection{Checking for a value or boolean}
+%
+% It would make perfect sense to make |\NoValue| a \LaTeX3 quark but
+% as there is a real danger of it getting executed by accident it is
+% best not to as it would result in an infinite loop.
+%
+% \DescribeMacro\NoValue
+% For this reason |\NoValue| is defined to expand to the string
+% |-NoValue-| which would get typeset if ever executed thus clearly
+% indicating the type of error the writer made.
+%
+% However this makes testing for this token slightly complicated as in
+% that case the test
+% \begin{verbatim}
+% \tlp_set:Nn \l_seen_tlp {#1}
+% \tlp_set:Nn \l_hidden_novalue_tlp {\NoValue}
+% \tlp_if_eq:NNTF \l_seen_tlp \l_hidden_novalue_tlp
+% \end{verbatim}
+% will be true if |#1| was |\NoValue| but false if |#1| itself
+% contains a macro which contains |\NoValue|; a case that happens
+% unfortunately very often in practice. Using an unguarded |x| type
+% expansion to define |\l_seen_tlp| is out of the question as |#1| is
+% typically either |\NoValue| or arbitrary user input for which we
+% can't properly guard it unless we are sure people only use robust
+% commands. When running a pure \LaTeX3 format where all document
+% commands are robust this is perhaps something to be looked at again
+% but when running on top of \LaTeXe{} we have to be careful.
+%
+% Therefore we use a somewhat different procedure here, which goes
+% like this:
+% \begin{enumerate}
+% \item Store |#1| in a temporary variable and check if it equals a
+% variable containing |\NoValue|. If true, execute the \meta{true}
+% code, otherwise go to~2.
+% \item Peek at the first token in |#1|. If this is a macro taking no
+% arguments expand |#1| once and go to~1. Otherwise execute the
+% \meta{false} code.
+% \end{enumerate}
+% The reason for the careful peeking ahead is that |#1| may very well
+% be a macro taking arguments and it is not certain that these
+% arguments are present! Hence this could lead to the well-known
+% \begin{verbatim}
+% Argument of \XXX has an extra }
+% \end{verbatim}
+% and we wouldn't want that\dots{} Goes without saying that this
+% procedure is quite tedious but usually it will exit after the first
+% time |#1| has been inspected. One additional test could be added,
+% namely that |#1| should also contain exactly one token but I don't
+% think that is going to matter much.
+%
+% \DescribeMacro\IfNoValueTF
+% \DescribeMacro\IfNoValueT
+% \DescribeMacro\IfNoValueF
+% \DescribeMacro\IfValueTF
+% \DescribeMacro\IfValueT
+% \DescribeMacro\IfValueF
+% These macros are used for checking if an optional argument was
+% present as in the example below.
+% \begin{verbatim}
+% \DeclareDocumentCommand\testcmd{om}{
+% \IfNoValueTF{#1}{``#2''}{#1,#2}
+% }
+% \end{verbatim}
+%
+%
+%
+% \DescribeMacro\IfBooleanTF
+% \DescribeMacro\IfBooleanT
+% \DescribeMacro\IfBooleanF
+% As mentioned earlier, the parsing result for a symbol argument like
+% |s| or |S{+}| is represented as the one of the tokens |\c_true| or
+% |\c_false| respectively. To test for these values the macro
+% |\IfBooleanTF| can be used. It expects as its first argument either
+% |\c_true| or |\c_false| and executes its second or third argument
+% depending on this value. |\IfBooleanT| and |\IfBooleanF| are
+% obvious shortcuts.
+%
+% At one point in time I thought that one can represent everything
+% using |\NoValue|, e.g., for the star case either return |*| or
+% |\NoValue|. However, this slows down processing of commands like
+% |\\*| considerably since they would then have to use a slower
+% internal test instead of a fast two-way switch.
+%
+%
+% \subsection{New argument types and shorthands}
+%
+% New argument types can be added at in a fairly straight forward
+% manner with the command
+% |\DeclareArgumentType|\DescribeMacro\DeclareArgumentType. This
+% command takes seven arguments: |#1| is a symbol denoting the
+% argument type, |#2| is the token the scanner should look for, |#3|
+% is one of the words |meaning|, |charcode| or |catcode| which is
+% handed down to the underlying |\peek_meaning:NTF| or
+% |\peek_charcode:NTF| etc. functions. For instance you can use the
+% |charcode| version if you want to pick up a literal |*| and not
+% just something that has the same \emph{meaning} as a regular
+% |*|. |#4| is for executing a special action (like an error message)
+% if no argument is found, |#5| is the default value in case of a
+% missing argument, |#6| is what the scanner will encounter, and
+% finally |#7| is what the scanner grabs from the argument type. This
+% is perhaps clearer with an example\dots{} This is how the |o| type
+% is implemented:
+% \begin{verbatim}
+% \DeclareArgumentType o [ {meaning} {} {\NoValue} {#1[#2]} {#2}
+% \end{verbatim}
+% In a similar fashion a |b| type expecting its argument inside |<|
+% and |>| would be defined as
+% \begin{verbatim}
+% \DeclareArgumentType b < {meaning} {} {\NoValue} {#1<#2>} {#2}
+% \end{verbatim}
+%
+% \DescribeMacro\DeclareArgumentTypeWithDefault
+% |\DeclareArgumentTypeWithDefault| is even simpler as this type
+% expects the default value to be input at the time of argument
+% specification. Thus arguments |#3| and |#4| from above are
+% unnecessary and are simply absent. Thus the |O| type is
+% implemented\footnote{I would say it is at best wishful thinking
+% that the interface could be something like
+% \texttt{\cs{DeclareArgumentTypeWithDefault}
+% C\{2\}\{meaning\}\{(\#1,\#2)\}\{\{\#1\}\{\#2\}\}} as it would
+% be quite troublesome implementation-wise and the current syntax
+% isn't that difficult to use.} as
+% \begin{verbatim}
+% \DeclareArgumentTypeWithDefault O [ {meaning}{#1[#2]} {#2}
+% \end{verbatim}
+% and again a similar |B| type could be implemented as
+% \begin{verbatim}
+% \DeclareArgumentTypeWithDefault B < {meaning}{#1<#2>} {#2}
+% \end{verbatim}
+%
+%
+% There is also a possibility to define a shorthand for a specific
+% sequence of arguments with the command
+% \DescribeMacro\DeclareArgumentTypeShorthand
+% |\DeclareArgumentTypeShorthand|. As an example the |s| argument
+% type is just a different way of saying |S{*}| so it's simply
+% implemented as
+% \begin{verbatim}
+% \DeclareArgumentTypeShorthand s {S{*}}
+% \end{verbatim}
+% Similarly one could add a shorthand |M| for inserting five
+% mandatory arguments where the latter is allowed to take |\par| in
+% its argument:
+% \begin{verbatim}
+% \DeclareArgumentTypeShorthand M {mmmm>{P}m}
+% \end{verbatim}
+%
+% Finally there is also the command
+% \DescribeMacro\DeclareSymbolArgument|\DeclareSymbolArgument| which
+% defines the low level interface to looking ahead for specific
+% symbols and removing them. For instance the |S| type argument is
+% declared as
+% \begin{verbatim}
+% \DeclareSymbolArgument S{meaning}
+% \end{verbatim}
+% So symbols picked up by this type will compare the meaning of the
+% tokens. One could do a
+% \begin{verbatim}
+% \DeclareSymbolArgument A{charcode}
+% \end{verbatim}
+% and then the |A| type would compare character codes instead. For
+% instance a command which expects a |+| symbol would return
+% \meta{true} if a |+| of any catcode is detected, not just catcode
+% 12 as is usual.
+%
+% \subsection{Some comments on the need for the \texttt{O} specifier}
+%
+% With |\newcommand| there is the possibility of specifying a default
+% for an optional argument which is stored away in a more or less
+% efficient manner. For example below is the old definition of
+% |\linebreak| as can be found in the \LaTeX2e kernel:
+%\begin{verbatim}
+%\def\linebreak{\@testopt{\@no@lnbk-}4}
+%\def\@no@lnbk #1[#2]{%
+% \ifvmode
+% \@nolnerr
+% \else
+% \@tempskipa\lastskip
+% \unskip
+% \penalty #1\@getpen{#2}%
+% \ifdim\@tempskipa>\z@
+% \hskip\@tempskipa
+% \ignorespaces
+% \fi
+% \fi}
+%\end{verbatim}
+% Ignoring for the moment that the above is slightly optimised an
+% expansion of this code under |\tracingall| will result in about 90
+% lines of tracing output. If we reimplement this using
+% |\DeclarDocumentCommand\linebreak{o}| we have to use |\IfNoValueTF|
+% to find out if an argument was present which (because of the careful
+% expansion we do internally) results in about twice as much of
+% tracing lines. In contrast using |O{4}| as below we end up with 110
+% lines, which seems roughly the price we have to pay for the extra
+% generality available (though this could perhaps even be reduced by a
+% better implementation of the parsing machine as originally done by
+% David, before i talked him into adding support for arguments in the
+% end code of an environment).\footnote{These comments were made
+% before the extensive changes in expl3 and xparse in 2005.}
+%
+%\begin{verbatim}
+%\DeclareDocumentCommand\linebreak { O{4} }
+% {
+% \ifvmode
+% \@nolnerr
+% \else
+% \@tempskipa\lastskip
+% \unskip
+% % \IfNoValueTF{#1}
+% % {\break}
+% % {\penalty -\@getpen{#1}}
+% \penalty -\@getpen{#1}
+% \ifdim\@tempskipa>\z@
+% \hskip\@tempskipa
+% \ignorespaces
+% \fi
+% \fi
+% }
+%\end{verbatim}
+%
+%
+% \subsection{A somewhat complicated example}
+%
+% This example reimplements the |\makebox| and |\framebox| interface
+% of \LaTeX{} both of which are unfortunately quite overloaded
+% syntactically. For this reason the example isn't meant to show good
+% coding practice but to show the power of the interface even though
+% applied in a somewhat bad way.
+%
+% |\makebox| and |\framebox| support the following different document
+% syntax forms:
+% \begin{itemize}
+% \item
+% |\makebox{A}|: only a single mandatory argument.
+%
+% \item
+% |\makebox[20pt]{B}|: one optional argument specify the box width.
+%
+%
+% \item
+% |\makebox[30pt][r]{C}|: two optional arguments the second specifying
+% the text position within the box being made (l,c,r being allowed
+% with c being the default).
+%
+% \item
+% |\makebox(20,30){D}|: within picture mode the width is specified not
+% as an optional argument in brackets but as a coordinate pair.
+%
+% \item
+% |\makebox(0,0)[lt]{E}|: in that case an optional argument following
+% coordinate pair denotes the placement within the box which can have
+% different values compared to case C above.
+% \end{itemize}
+%
+% To cater for this overloaded structure we can define |\makebox| to
+% be something like the following:
+%\begin{verbatim}
+%\DeclareDocumentCommand \makebox { C{\NoValue} o O{c} m}
+% { \IfNoValueTF{#1}
+% { \ltx@maketextbox{#2}{#3}{#4} }
+% { \ltx@makepicbox #1 {#2}{#4} } }
+%\end{verbatim}
+% In other words: if we do not see a coordinate pair first (i.e.,
+% first argument is |\NoValue| then we expect up to two optional
+% arguments (the width of the box or |\NoValue| if not given and the
+% placement specifier with a default of |c| if not given) and one
+% mandatory one which is the text. In that case we pass argument 2 to
+% 4 to an internal function |\ltx@maketextbox| which builds the text
+% box.
+%
+% Otherwise, if the first argument is a coordinate pair we parse an
+% optional argument denoting the placement specifier. Since
+% \texttt{xparse} doesn't support variant syntax we actually parse for
+% another optional argument (which has no meaning in that case and is
+% in fact ignored if present) followed by a mandatory one containing
+% the box text. In that case we pass the coordinate pair (|#1|), the
+% specifier (|#2|), and the text (|#4|) to the function
+% |\ltx@makepicbox| which builds the picture box. Note the special
+% handling of the coordinatesD: which are passed without surrounding
+% braces to |\ltx@makepicbox|: since the coordinate argument looks
+% like |{x-val}{y-val}| the receiving function |\ltx@makepicbox| gets
+% the |x-val| as argument one and the |y-val| as argument two.
+%
+% A definition for |\framebox| would look more or less identical
+% except that we would need to pass the arguments to slightly
+% different internal functions. The alternative is to give the
+% internal functions an extra argument that controls whether or not a
+% frame is bying built.
+%
+% \begin{macro}{\ltx@makepicbox}
+% So here is a possible implementation of |\ltx@makepicbox| that
+% builds a picture box with or without frame. It takes the following
+% mandatory arguments:
+% \begin{enumerate}
+% \item x-part of coordinate
+% \item y-part of coordinate
+% \item placement specifier, e.g., |lt| or |\NoValue|
+% \item text of box
+% \item the token |\frame| (if a frame should surround the box) or the
+% token |\@firstofone| --- not pretty i agree
+% \end{enumerate}
+%\begin{verbatim}
+%\def\ltx@makepicbox#1#2#3#4#5
+% {
+% #5{
+% \vbox to#2\unitlength
+% {\let\mb@b\vss \let\mb@l\hss\let\mb@r\hss
+% \let\mb@t\vss
+% \IfNoValueF{#3}
+% {
+% \@tfor\reserved@a :=#3\do{
+% \if s\reserved@a
+% \let\mb@l\relax\let\mb@r\relax
+% \else
+% \expandafter\let\csname mb@\reserved@a\endcsname\relax
+% \fi}%
+% }
+% \mb@t
+% \hb@xt@ #1\unitlength{\mb@l #4\mb@r}
+% \mb@b
+% \kern\z@}
+% }
+% }
+%\end{verbatim}
+% \end{macro}
+%
+%
+%
+% \begin{macro}{\ltx@maketextbox}
+% For the text case the internal function could take the following
+% mandatory arguments:
+% \begin{enumerate}
+% \item width of the box or |\NoValue| (denoting to build the box at
+% natural width)
+% \item placement specifier, e.g., |l|. (No test for |\NoValue| being undertaken)
+% \item text of box
+% \item the token |\fbox| (if a frame should surround the box) or the
+% token |\mbox|
+% \end{enumerate}
+% The actual code is taken straight from the current \LaTeX{} kernel
+% and looks kind of scary.
+%\begin{verbatim}
+%\def\ltx@maketextbox#1#2#3#4
+% {
+% \IfNoValueTF{#1}
+% {#4{#3}}
+% {
+% \leavevmode
+% \@begin@tempboxa\hbox{#3}
+% \setlength\@tempdima{#1}
+% \ifx#4\fbox
+% \setbox\@tempboxa\hb@xt@\@tempdima
+% {\kern\fboxsep\csname bm@#2\endcsname\kern\fboxsep}
+% \@frameb@x{\kern-\fboxrule}
+% \else
+% \hb@xt@\@tempdima{\csname bm@#2\endcsname}
+% \fi
+% \@end@tempboxa
+% }
+% }
+%\end{verbatim}
+% \end{macro}
+%
+% \begin{macro}{\makebox}
+% \begin{macro}{\framebox}
+% Given the above internal functions the declarations of |\makebox|
+% and |\framebox| would then look like this:
+%\begin{verbatim}
+%\DeclareDocumentCommand \makebox { C{\NoValue} o O{c} m}
+% { \IfNoValueTF{#1}
+% { \ltx@maketextbox{#2}{#3}{#4}\mbox }
+% { \ltx@makepicbox #1 {#2}{#4}\@firstofone } }
+%
+%\DeclareDocumentCommand \framebox { C{\NoValue} o O{c} m}
+% { \IfNoValueTF{#1}
+% { \ltx@maketextbox{#2}{#3}{#4}\fbox }
+% { \ltx@makepicbox #1 {#2}{#4}\frame } }
+%\end{verbatim}
+% \end{macro}
+% \end{macro}
+%
+%
+%
+% Here's another example which shows how one can use the |W| specifier.
+% The \textsf{amsmath} environments use their own definition of |\\|
+% which goes under the name |\math@cr|. As there is a good chance the
+% next line of math begins with either an asterisk or something in
+% square brackets this often leads to errors. The following example
+% definition works (I \emph{did} try it).
+% \begin{verbatim}
+% \CodeStart
+% \cs_gundefine:N \math@cr
+% \DeclareDocumentCommand\math@cr{>{W}s >{W}O{\z@}}{
+% \IfBooleanTF{#1}
+% { \global\@eqpen\@M }{
+% \global\@eqpen
+% \ifnum\dspbrk@lvl <\z@
+% \interdisplaylinepenalty
+% \else
+% -\@getpen\dspbrk@lvl
+% \fi
+% }
+% \math@cr@@@
+% \noalign{\vskip#2\relax}
+% }
+% \CodeStop
+% \end{verbatim}
+% Note that this definition automatically avoids problems within the
+% alignments even if it is called as |\\&|.
+%
+%
+%
+%
+% \subsection{Open issues}
+%
+% In this section unresolved issues or ideas to think about and
+% perhaps implement are collected. There is no particular order to
+% them.
+%
+% \begin{itemize}
+% \item
+% Support for parsing verbatim type of arguments was considered (and
+% actually implemented at one stage. E.g.,
+% |g{|\meta{prepare-parsing}|}| where |g| first run
+% \meta{prepare-parsing} (which might involve |catcode|
+% changes)\footnote{urg horror!}, then look at the next token: if
+% that would be a |{| it would scan a brace delimited argument
+% (reverting catcodes of |{| and |}| if needed) otherwise would scan
+% for an argument delimited by that token so that something like
+% |\verb+%\+| would scan |%\| as its argument assuming that the
+% \meta{prepare-parsing} turned |%| and |\| into non-letters.
+%
+% All kind of nasty problems lurking especially no proper error
+% checks possible and of course as we all know such commands would
+% then not work inside arguments of other commands. At least they
+% would have some restrictions.
+%
+% Also no way to make the parsing smart by not accepting newlines as
+% part of the code (|\verb| does this right now and this is really
+% helpful as it catches runaways nicely).
+%
+%
+% \item
+% \textsf{xparse} should probably go into the \LaTeX3 kernel in which
+% case it should also provide the definitions of |\begin| and |\end|
+% and this raises a few questions: Will environments be defined as
+% control sequences |\foo| and |\endfoo|? If they are do we then want
+% to include support for a separate command |\foo| and if so what
+% about using the environment forms in special scanner mechanisms
+% where we \emph{can't} use |\begin{foo}|? In those cases one could
+% use a special command like what the \textsf{fancyvrb} package
+% provides with the command |\VerbatimEnvironment| and all packages
+% that define such special arguments should then also make sure that
+% the |\foo| command issued on its own should cause an error.
+% Another solution would be to simply define environments as
+% |\beginfoo| and |\endfoo| and then let |\begin| check if it was
+% used to call an environment or a command. If the latter is the
+% case then insert grouping as that could be handled by |\beginfoo|
+% itself. When |\end| is reached check if |\endfoo| exists. If it
+% does then use that, otherwise we were probably using a normal
+% command which should just close the group.
+% \end{itemize}
+%
+%
+% \subsection{Rejected ideas---and why}
+%
+% Let's say the document command |\testmo| has signature |mo|. If we
+% call it as |\testmo{arg} [opt]| a following space will be obeyed.
+% However calling it with the mandatory argument only as in
+% |\testmo{arg}| will gobble a following space because the peek ahead
+% in the |o| type ignores spaces. We can record that a space has been
+% gobbled when peeking ahead and we can also put it back in if needed
+% but I have only ever seen one request for this and in that case the
+% better solution was to use a signature |mWo| so that no spaces are
+% allowed between the mandatory and the optional argument. One could
+% even argue that this is the most appropriate thing to do if the user
+% is really that sensitive to spaces! In any case it is not
+% implemented here as it creates an unnecessary overhead for something
+% that is never used and a simple solution exists.
+%
+% \subsection{Experimental features}
+%
+% Experimental features in an experimental packages\dots{} Needless to
+% say that you can't rely on them staying!
+%
+%
+% One new feature is what I decided to call ``pseudo
+% arguments''. Strictly speaking these aren't real arguments but
+% instead read by removing a begin group token and then using
+% |\tex_aftergroup:D| to regain control. The definition of |\footnote|
+% in plain \TeX\ uses this so that people can use
+% |\verb| and the like inside the footnotes. The command
+% |\DeclarePseudoArgument|\DescribeMacro{\DeclarePseudoArgument} takes
+% four arguments: |#1| is a name for the pseudo argument, |#2| is the
+% number of arguments it takes, |#3| is the action to be taken right
+% before the left brace is removed and |#4| is what to be done when
+% the right brace has been read and we regain control. Note that both
+% |#3| and |#4| may use arguments! Here is a silly example:
+% \begin{verbatim}
+% \DeclarePseudoArgument{boxtest}{1}
+% {Before:~`#1',\hbox_set_inline_begin:N \l_tmpa_box }
+% {\hbox_set_inline_end: \text_put_sp: the~ box:~
+% \hbox_unpack_and_clear:N\l_tmpa_box ,~
+% After:~`#1'}
+% \end{verbatim}
+% Now when you want to use it, you simply call it with the macro
+% |\UsePseudoArgument|\DescribeMacro{\UsePseudoArgument}, which as its
+% first argument takes a name and the remaining depend on how many
+% arguments the pseudo argument was defined to have. Hence we could
+% use our |boxtest| definition like this:
+% \begin{verbatim}
+% \DeclareDocumentCommand\sillyboxtest{m}{
+% Testing~#1:~\UsePseudoArgument{boxtest}{#1}
+% }
+% \end{verbatim}
+% Then calling |\sillyboxtest{AB}{a\verb*+% $%&\+b}| produces
+% \begin{quote}
+% Testing AB: Before: `AB', the box:
+% a\verb*+% $%&\+b, After: `AB'
+% \end{quote}
+% |\UsePseudoArgument| should always come last in the document
+% command definition.
+%
+% \StopEventually{}
+%
+% \section{Implementation}
+%
+% Versions prior to and including 1.19 contained several different
+% implementations. These are gone now but can be looked at by
+% getting an older version of the package from the CVS repository.
+%
+% First the required packages.
+% \begin{macrocode}
+%<*package>
+\RequirePackage{l3tlp,l3num,l3toks,l3prg,l3int,l3seq,l3token}
+% \end{macrocode}
+%
+%
+%
+% \subsection{Error and warning messages}
+%
+% Here we define the error message we're going to use in this package.
+%
+% \begin{macro}{\xparse_already_defined_error_msg:N}
+% \begin{macro}{\xparse_not_yet_defined_error_msg:N}
+% \begin{macro}{\xparse_begins_with_end_error_msg:N}
+% \begin{macro}{\xparse_unknown_arg_type_error_msg:N}
+% \begin{macro}{\xparse_number_of_arguments_error_msg:Nn}
+% \begin{macro}{\xparse_no_command_implementation_warning:n}
+% The names should give the function's purpose away.
+% \begin{macrocode}
+\def_new:NNn \xparse_already_defined_error_msg:N 1 {
+ \xparse_error:x {
+ Command~name~`\token_to_string:N #1'~ already~defined!
+ }
+}
+\def_new:NNn \xparse_not_yet_defined_error_msg:N 1 {
+ \xparse_error:x {
+ Command~`\token_to_string:N #1'~ not~ yet~defined!
+ }
+}
+\def_new:NNn \xparse_begins_with_end_error_msg:N 1 {
+ \xparse_error:x {
+ Command~`\token_to_string:N #1'~begins~with~
+ `\token_to_string:N \end'!
+ }
+}
+% \end{macrocode}
+% This one is for when we've encountered an unknown argument type in
+% the argument specification. We can try to recover by putting in an
+% |m| type instead and hope for the best.
+% \begin{macrocode}
+\def_new:NNn \xparse_unknown_arg_type_error_msg:N 1{
+ \xparse_error:x {
+ Unknown~ argument~ type~ `#1'~
+ I'll~ substitute~ it~ with~ `m'~ for~ now.~ Fingers~ crossed...
+ }
+}
+% \end{macrocode}
+% A message for people using the wrong number of arguments.
+% \begin{macrocode}
+\def_new:NNn \xparse_no_command_implementation_warning:n 1 {
+ \xparse_warning:x {No~ implementation~ for~ `#1'~ defined}
+}
+% \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\xparse_error:x}
+% \begin{macro}{\xparse_warning:x}
+% Here's how we produce the error messages and warnings currently.
+% This awaits a proper error message module!
+% \begin{macrocode}
+\def_new:NNn \xparse_error:x 1{\tex_errmessage:D {xparse~error:~#1}}
+\def_new:NNn \xparse_warning:x 1{\io_put_term:x{xparse~warning:~#1}}
+% \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+%
+%
+% \subsection{Checking for valid command names}
+%
+%
+% \begin{macro}{\xparse_if_definable:NT}
+% \begin{macro}{\xparse_if_definable:cT}
+% A definable command is either |\c_undefined| or |\scan_stop:| and
+% furthermore we won't allow it to start with |\end|.
+% If the command is definable we do what was asked for otherwise
+% we give an appropriate error message.
+% \begin{macrocode}
+\def_new:NNn \xparse_if_definable:NTF 1 {
+% \end{macrocode}
+% First check if the control sequence is free.
+% \begin{macrocode}
+ \cs_free:NTF #1
+% \end{macrocode}
+% If free check if it begins with |\end|.
+% \begin{macrocode}
+ {
+ \xparse_begins_with_end:NTF #1
+ { \xparse_begins_with_end_error_msg:N #1 \use_arg_ii:nn }
+ \use_arg_i:nn
+ }
+% \end{macrocode}
+% If not free give an error message.
+% \begin{macrocode}
+ { \xparse_already_defined_error_msg:N #1 \use_arg_ii:nn }
+}
+\def_new:NNn \xparse_if_definable:cTF 0 {
+ \exp_args:Nc \xparse_if_definable:NTF
+}
+% \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \begin{macro}{\xparse_if_redefinable:NTF}
+% \begin{macro}{\xparse_if_redefinable:cTF}
+% A re-definable command is almost the same as above but here we
+% demand that it already exists.
+% \begin{macrocode}
+\def_new:NNn \xparse_if_redefinable:NTF 1 {
+ \cs_free:NTF #1
+ { \xparse_not_yet_defined_error_msg:N #1 \use_arg_ii:nn }
+ {
+ \xparse_begins_with_end:NTF #1
+ { \xparse_begins_with_end_error_msg:N #1 \use_arg_ii:nn }
+ \use_arg_i:nn
+ }
+}
+\def_new:NNn \xparse_if_redefinable:cTF 0 {
+ \exp_args:Nc \xparse_if_redefinable:NTF
+}
+% \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+%
+% \begin{macro}{\xparse_begins_with_end:NTF}
+% \begin{macro}{\xparse_begins_with_end_aux:N}
+% Finally we need the magic function for checking if the control
+% sequence begins with |\end|.
+% We wish to determine if the control sequence in question begins with
+% |\end| which is forbidden. The end goal is to get a control sequence
+% consisting of the first three letters to test against |\end| with
+% |\cs_if_eq_name_p:NN|. The function |\cs_to_str:N| will remove the |\|
+% from a command name and return the rest of the characters with
+% category code 12. Thus using an |f| type expansion to get the first
+% three characters is perfectly safe as it'll stop right there. Then
+% we turn these three letters into a control sequence with a simple
+% expansion which is then tested with |\xparse_begins_with_end_aux:N|.
+% \begin{macrocode}
+\def_new:NNn \xparse_begins_with_end:NTF 1 {
+% \end{macrocode}
+% We do it all in a group as there is no need to fill up the hash
+% table with weird three letter control sequences.
+% \begin{macrocode}
+ \group_begin:
+ \exp_args:Nc \xparse_begins_with_end_aux:N {
+ \tlist_head_iii:f { \cs_to_str:N #1 ??}
+ }
+}
+% \end{macrocode}
+% After the above expansion tricks we now have a real control sequence
+% to test against |\end|. We end the group again.
+% \begin{macrocode}
+\def_new:NNn \xparse_begins_with_end_aux:N 1 {
+ \if:w \cs_if_eq_name_p:NN #1 \end
+ \group_end:
+ \exp_after:NN \use_arg_i:nn
+ \else:
+ \group_end:
+ \exp_after:NN \use_arg_ii:nn
+ \fi:
+}
+% \end{macrocode}
+% Note that these definitions make no use of temporary variables.
+% \end{macro}
+% \end{macro}
+%
+%
+%
+% \subsection{The high level commands}
+%
+%
+% Here we set up the functions for defining and redefining document
+% commands and environments. It's all rather straight forward here so
+% I've saved on the comments.
+%
+% \begin{macro}{\DeclareDocumentCommand}
+% \begin{macro}{\ReDeclareDocumentCommand}
+% In case we can't do what the user wanted we gobble the next
+% arguments from the input stream. For commands there are two
+% arguments waiting.
+% \begin{macrocode}
+\def_new:NNn \DeclareDocumentCommand 1 {
+ \xparse_if_definable:NTF #1
+ { \xparse_declare_document_command:Nnn #1 }
+ \use_none:nn
+}
+\def_new:NNn \ReDeclareDocumentCommand 1 {
+ \xparse_if_redefinable:NTF #1
+ { \xparse_declare_document_command:Nnn #1 }
+ \use_none:nn
+}
+% \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\DeclareDocumentEnvironment}
+% \begin{macro}{\ReDeclareDocumentEnvironment}
+% Three arguments for environments.
+% \begin{macrocode}
+\def_new:NNn \DeclareDocumentEnvironment 1 {
+ \xparse_if_definable:cTF {#1}
+ { \xparse_declare_document_environment:nnnn {#1} }
+ \use_none:nnn
+}
+\def_new:NNn \ReDeclareDocumentEnvironment 1 {
+ \xparse_if_redefinable:cTF {#1}
+ { \xparse_declare_document_environment:nnnn {#1} }
+ \use_none:nnn
+}
+% \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\ProvideDocumentCommand}
+% \begin{macro}{\ProvideDocumentEnvironment}
+% When providing a command we just check if the control sequence is
+% free. If it is let |\DeclareDocument...| do the rest, otherwise
+% gobble the next arguments.
+% \begin{macrocode}
+\def_new:NNn \ProvideDocumentCommand 1{
+ \cs_free:NTF #1
+ { \DeclareDocumentCommand #1}
+ \use_none:nn
+}
+\def_new:NNn \ProvideDocumentEnvironment 1{
+ \cs_free:cTF {#1}
+ { \DeclareDocumentEnvironment {#1} }
+ \use_none:nnn
+}
+% \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+%
+%
+% \subsection{The low level definitions}
+%
+%
+% First some helper functions
+% \begin{macro}{\l_xparse_grabbed_args_toks}
+% \begin{macro}{\l_xparse_end_environment_args_toks}
+% \begin{macro}{\l_xparse_mandatory_args_int}
+% \begin{macro}{\l_xparse_total_args_int}
+% We need some \meta{token} registers to keep track of things. We also
+% allocate an \meta{int} register to keep track of the number of
+% arguments.
+% \begin{macrocode}
+\toks_new:N \l_xparse_grabbed_args_toks
+\toks_new:N \l_xparse_end_environment_args_toks
+\int_new:N \l_xparse_mandatory_args_int
+\int_new:N \l_xparse_total_args_int
+% \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+%
+% \begin{macro}{\xparse_declare_document_command:Nnn}
+% \begin{macro}{\xparse_declare_document_command:cnn}
+% |\xparse_declare_document_command:Nnn| is a two step procedure. The
+% user level command |\|\meta{cmd} contains the argument grabbers
+% while the internal command |\\|\meta{cmd} holds the actual
+% definition of what to do with the arguments. Naturally this calls
+% for every such user level command to be robust which is done using
+% the \eTeX{} protection feature.
+% \begin{macrocode}
+\def_long:NNn \xparse_declare_document_command:Nnn 3{
+% \end{macrocode}
+% First we prepare the signature.
+% \begin{macrocode}
+ \xparse_prepare_signature:n {#2}
+% \end{macrocode}
+% Now for the document command. Make it robust and make sure it starts
+% with |\toks_set:Nn \l_xparse_grabbed_args_toks {\\|\meta{cmd}|}|.
+% \begin{macrocode}
+ \def_protected:Npx #1 {
+ \exp_not:n { \toks_set:Nn \l_xparse_grabbed_args_toks }
+ {\exp_not:c {\token_to_string:N #1}}
+% \end{macrocode}
+% Then add the argument grabbers which contain code gathered when
+% preparing the signature.
+% \begin{macrocode}
+ \toks_use:N \l_xparse_grabbed_args_toks
+% \end{macrocode}
+% Finally execute |\toks_use:N \l_xparse_grabbed_args_toks| which now
+% holds the grabbed arguments enclosed in braces and starts with the
+% internal command |\\|\meta{cmd}.
+% \begin{macrocode}
+ \exp_not:n{ \toks_use:N \l_xparse_grabbed_args_toks}
+ }
+% \end{macrocode}
+% Define the internal command by making it a |\long| macro with number
+% of arguments equal to |\l_xparse_total_args_int| and definition as
+% given by |#3|. Even though this internal macro allows |\par| in its
+% argument the decision is left to the individual argument grabbers.
+% \begin{macrocode}
+ \def_long:cNn {\token_to_string:N #1}\l_xparse_total_args_int{#3}
+}
+\def_new:Npn \xparse_declare_document_command:cnn {
+ \exp_args:Nc \xparse_declare_document_command:Nnn
+}
+% \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\xparse_declare_document_environment:nnnn}
+% |\xparse_declare_document_environment:nnnn| is almost the same. In
+% order to use the grabbed arguments we take them from
+% |\l_xparse_grabbed_args_toks| just before they are executed. We
+% also insert a |\group_begin:| as it will otherwise fail miserably
+% in case a user tries to use it without |\begin ... \end|.
+% \begin{macrocode}
+\def_long_new:NNn \xparse_declare_document_environment:nnnn 4 {
+ \xparse_declare_document_command:cnn {#1}{#2}
+ { \group_begin:
+ \toks_set_eq:NN \l_xparse_end_environment_args_toks
+ \l_xparse_grabbed_args_toks
+ #3
+ }
+% \end{macrocode}
+% We let |\end|\meta{envir} equal to a standard version which will do
+% all the work.
+% \begin{macrocode}
+ \let:cN {end #1} \xparse_parsed_end_environment:
+% \end{macrocode}
+% Now define |\end\\|\meta{envir}.
+% \begin{macrocode}
+ \def_long:cNn {end \token_to_string:N \\ #1}
+ \l_xparse_total_args_int{#4}
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\xparse_parsed_end_environment:}
+% \begin{macro}{\xparse_parsed_end_environment_aux:N}
+% |\end|\meta{envir} is set equal to |\xparse_parsed_end_environment:|
+% which then executes |\end\\|\meta{envir}. The |\\|\meta{envir} comes
+% from the argument grabbing. The remainder of the token list is the
+% grabbed arguments. We better make this robust as well.
+% \begin{macrocode}
+\def_protected_new:NNn \xparse_parsed_end_environment: 0{
+ \exp_after:NN \xparse_parsed_end_environment_aux:N
+ \toks_use:N \l_xparse_end_environment_args_toks
+ \group_end:
+}
+\def_new:NNn \xparse_parsed_end_environment_aux:N 1{
+ \cs_use:c {end \token_to_string:N #1 }
+}
+% \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+%
+% \subsubsection{A class designer interface}
+%
+% Below is the implementation of |\DeclareDocumentCommandInterface|
+% and the close cousin |\DeclareDocumentCommandImplementation|.
+% It is an open issue whether this concept should be supported.
+%
+% \begin{macro}{\DeclareDocumentCommandInterface}
+% With this macro we define the document command |#1| to have
+% signature |#3| which does the argument grabbing. The arguments are
+% passed on to the internal command |\impl-#2|.
+% \begin{macrocode}
+\def_long_new:NNn \DeclareDocumentCommandInterface 3{
+ \xparse_prepare_signature:n {#3}
+ \def_protected:Npx #1 {
+ \exp_not:n { \toks_set:Nn \l_xparse_grabbed_args_toks }
+ {\exp_not:c {impl-#2}}
+ \toks_use:N\l_xparse_grabbed_args_toks
+ \exp_not:n{ \toks_use:N \l_xparse_grabbed_args_toks}
+ }
+% \end{macrocode}
+% Define the internal command by making it a |\long| macro as we did
+% for |\DeclareDocumentCommand| but give it just a default definition
+% instead (usually an error message).
+% \begin{macrocode}
+ \def_long:cNn {impl-#2} \l_xparse_total_args_int
+ {\xparse_undefined_command_implementation:n{#2}}
+}
+% \end{macrocode}
+% \end{macro}
+% \begin{macro}{\xparse_undefined_command_implementation:n}
+% What to do if no implementation is made and the command is
+% called. Let's just typeset the name in quotes indicating that
+% something is wrong.
+% \begin{macrocode}
+\def_new:NNn \xparse_undefined_command_implementation:n 1{
+ ``#1''
+% \ensuremath{\langle\textit{#1}\rangle}
+ \xparse_no_command_implementation_warning:n {#1}
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\DeclareDocumentCommandImplementation}
+% Defines the internal command |\impl-#1| with |#2| arguments
+% and definition |#3|.
+% \begin{macrocode}
+\def_long_new:NNn \DeclareDocumentCommandImplementation 3{
+ \def_long:cNn {impl-#1}#2{#3}
+}
+% \end{macrocode}
+% \end{macro}
+%
+%
+% \subsection{Creating the signature}
+%
+%
+% \begin{macro}{\xparse_prepare_signature:n}
+% The actual preparation of the signature is always the same but we
+% have different ways of handling it afterwards, so we make it a
+% separate function.
+% \begin{macrocode}
+\def_new:NNn \xparse_prepare_signature:n 1 {
+% \end{macrocode}
+% Initialize the counter taking care of the number of arguments. In
+% case we reach more than nine we will give an error message later on.
+% \begin{macrocode}
+ \int_zero:N \l_xparse_total_args_int
+% \end{macrocode}
+% Clear the token register we use when building the signature and the
+% number of ``normal'' mandatory arguments. Also clear out the special
+% markers and initialize the two booleans to \meta{false}.
+% \begin{macrocode}
+ \toks_clear:N \l_xparse_grabbed_args_toks
+ \int_zero:N \l_xparse_mandatory_args_int
+ \bool_gset_false:N \g_xparse_insert_marker_bool
+ \bool_gset_false:N \g_xparse_allow_par_bool
+ \tlp_gset_eq:NN \g_xparse_ignore_marker_tlp
+ \g_xparse_ignore_spaces_marker_tlp
+% \end{macrocode}
+% Then call |\xparse_parse_signature:n|.
+% \begin{macrocode}
+ \xparse_parse_signature:n #1 \q_nil
+}
+% \end{macrocode}
+% \end{macro}
+%
+%
+% \subsection{The argument types}
+%
+%
+%
+% All argument types must be denoted by single letters.\footnote{You
+% can use a multi-letter sequence to denote a shorthand but it
+% requires you to put two brace groups around it in the signature and
+% it's not officially supported.} We have three categories of letters:
+% Special markers, basic argument types, and shorthands.
+%
+% For certain argument types where we peek ahead in the token stream
+% we have a multitude of choices for how the macro should work:
+% Should it ignore spaces or other tokens? Which test should it use
+% for comparing tokens: meaning, catcode or charcode? Because of
+% these difficulties every argument that require peeking ahead must
+% be declared as one of the three test types.
+%
+% \subsubsection{Special markers}
+%
+% Since there are different markers that may be used at the same
+% time, we use the a special ``insert'' marker |>| to do this.
+%
+% \begin{macro}{\g_xparse_ignore_marker_tlp}
+% The current ignore marker is contained in this string.
+% \begin{macrocode}
+\tlp_new:Nn \g_xparse_ignore_marker_tlp {}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\g_xparse_ignore_marker_seq}
+% We start out by declaring a new sequence to contain all the
+% different types of ignore functions. Each element should be the
+% missing part of a |\peek_meaning|\meta{text}|:NTF| function.
+% \begin{macrocode}
+\seq_new:N \g_xparse_ignore_marker_seq
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\g_xparse_insert_marker_bool}
+% A boolean to check if we just saw an insert marker.
+% \begin{macrocode}
+\bool_new:N \g_xparse_insert_marker_bool
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\xparse_add_arg_type_>:}
+% The insert marker is called when this is seen. Is has a funny
+% definition but it works. |#1| is some test in the loop function
+% and |#2| is the list of markers.
+% \begin{macrocode}
+\def_new:cpn {xparse_add_arg_type_>:} #1
+ \xparse_read_arg_type_or_grab_default:n #2{
+% \end{macrocode}
+% Insert pending |m| args first.
+% \begin{macrocode}
+ \xparse_add_remaining_m_args:
+% \end{macrocode}
+% Then we set the boolean true and subtract one from the argument
+% count.
+% \begin{macrocode}
+ \bool_gset_true:N \g_xparse_insert_marker_bool
+ \int_decr:N \l_xparse_total_args_int
+% \end{macrocode}
+% Then go through the list and call each subtype if it exists.
+% \begin{macrocode}
+ \tlist_map_inline:nn{#2}{
+ \xparse_check_and_add_argument_type:N ##1
+ }
+% \end{macrocode}
+% Finally call the loop again.
+% \begin{macrocode}
+ \xparse_parse_signature:n
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\xparse_add_ignore_marker:Nnn}
+% A small function for adding a new ignore type marker.
+% \begin{macrocode}
+\def_new:NNn \xparse_add_ignore_marker:Nnn 3{
+ \tlp_new:cn {g_xparse #2 _marker_tlp}{#3}
+ \seq_gpush:NC \g_xparse_ignore_marker_seq {g_xparse #2 _marker_tlp}
+ \def_new:cpn {xparse_add_arg_type_#1:}{
+ \tlp_gset_eq:Nc \g_xparse_ignore_marker_tlp {g_xparse #2 _marker_tlp}
+ }
+}
+% \end{macrocode}
+% \end{macro}
+% Here we add some ignore markers.
+% \begin{macrocode}
+\xparse_add_ignore_marker:Nnn W{_ignore_nothing}{}
+\xparse_add_ignore_marker:Nnn i{_ignore_spaces}{_ignore_spaces}
+\xparse_add_ignore_marker:Nnn I{_ignore_pars}{_ignore_pars}
+% \end{macrocode}
+%
+% \begin{macro}{\xparse_add_arg_type_P:}
+% This is simple, just set a boolean.
+% \begin{macrocode}
+\def_new:NNn \xparse_add_arg_type_P: 0{
+ \bool_gset_true:N \g_xparse_allow_par_bool
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\g_xparse_allow_par_bool}
+% The boolean for allowing the |\par| token.
+% \begin{macrocode}
+\bool_new:N \g_xparse_allow_par_bool
+% \end{macrocode}
+% \end{macro}
+%
+%
+% \begin{macro}{\xparse_parse_signature:n}
+% |\xparse_parse_signature:n| reads the signature one token/brace
+% group at a time and builds a list of argument grabbers which is
+% stored in |\l_xparse_grabbed_args_toks|. The function is recursive
+% which is why we use a quark to delimit it.
+% \begin{macrocode}
+\def_new:NNn \xparse_parse_signature:n 1{
+% \end{macrocode}
+% Check if we reached the end of the signature.
+% \begin{macrocode}
+ \quark_if_nil:NTF #1
+% \end{macrocode}
+% If we did we may have pending |m| type arguments so we clear them
+% out here. Also check if the insert marker is true because if it is,
+% something is wrong. Otherwise we just continue.
+% \begin{macrocode}
+ {
+ \xparse_add_remaining_m_args:
+ }
+% \end{macrocode}
+% Then proceed with adding arguments.
+% \begin{macrocode}
+ {
+ \int_incr:N \l_xparse_total_args_int
+ \xparse_check_and_add_argument_type:N #1
+% \end{macrocode}
+% If the insert marker is true at this point we reset it again and
+% also disallow |\par| in arguments and make all |\peek| functions use
+% the |_ignore_spaces| versions.
+% \begin{macrocode}
+ \bool_if:NT \g_xparse_insert_marker_bool
+ {
+ \bool_gset_false:N \g_xparse_insert_marker_bool
+ \bool_gset_false:N \g_xparse_allow_par_bool
+ \tlp_gset_eq:NN \g_xparse_ignore_marker_tlp
+ \g_xparse_ignore_spaces_marker_tlp
+ }
+% \end{macrocode}
+% After adding arguments we better set the boolean false in case we
+% don't have an insert marker.
+% \begin{macrocode}
+% \end{macrocode}
+% First we add the remaining |m| arguments.
+% \begin{macrocode}
+% \end{macrocode}
+% Then we run the loop again.
+% \begin{macrocode}
+ \xparse_read_arg_type_or_grab_default:n
+ }
+}
+% \end{macrocode}
+% \end{macro}
+%
+%
+% \begin{macro}{\xparse_check_and_add_argument_type:N}
+% This function checks if the argument type actually exists and gives
+% an error if it doesn't.
+% \begin{macrocode}
+\def_new:NNn \xparse_check_and_add_argument_type:N 1 {
+ \cs_free:cTF {xparse_add_arg_type_#1:}
+ { \xparse_unknown_arg_type_error_msg:N #1
+ \int_incr:N \l_xparse_mandatory_args_int
+ }
+% \end{macrocode}
+% Otherwise we just add it with its dedicated function.
+% \begin{macrocode}
+ { \cs_use:c {xparse_add_arg_type_#1:} }
+}
+% \end{macrocode}
+% \end{macro}
+%
+%
+%
+% \begin{macro}{\xparse_read_arg_type_or_grab_default:n}
+% \begin{macro}{\xparse_grab_default_arg:n}
+% \begin{macro}{\xparse_grab_default_arg_allow_par:n}
+% The function for grabbing a default value. The default setting is
+% just to tun the loop again. However, some argument types need to
+% add a default argument so we add these as well.
+% \begin{macrocode}
+\let_new:NN \xparse_read_arg_type_or_grab_default:n
+ \xparse_parse_signature:n
+\def_new:NNn \xparse_grab_default_arg:n 1{
+ \toks_put_right:Nn \l_xparse_grabbed_args_toks {{#1}}
+ \let:NN \xparse_read_arg_type_or_grab_default:n
+ \xparse_parse_signature:n
+ \xparse_parse_signature:n
+}
+\def_long_new:NNn \xparse_grab_default_arg_allow_par:n 1{
+ \toks_put_right:Nn \l_xparse_grabbed_args_toks {{#1}}
+ \let:NN \xparse_read_arg_type_or_grab_default:n
+ \xparse_parse_signature:n
+ \xparse_parse_signature:n
+}
+% \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+%
+%
+%
+%
+%
+% \subsubsection{The default argument types}
+%
+%
+%
+% When scanning the signature we need to add the argument type which
+% is done by a function |\xparse_add_arg_type_|\meta{X}|:|, where
+% \meta{X} is the letter denoting the argument type. If not found an
+% error message is issued ny |\xparse_unknown_arg_type_error_msg:N|.
+%
+% By default the package implements the argument types |m|, |S|, |c|,
+% |C|, |o|, and |O| argument types as low level ones. The |s| type is
+% a shorthand as we shall see later.
+%
+% As we don't make every single |m| argument a separate grabber all
+% other types must clear out any pending |m|s.
+%
+% \paragraph{Mandatory arguments}
+%
+% Below follows the implementation of mandatory arguments.
+%
+% \begin{macro}{\xparse_add_arg_type_m:}
+% Check if the user asked for an |m| argument allowing |\par|
+% tokens and insert it. Otherwise increment the number of
+% non-|\long| argument grabbers.
+% \begin{macrocode}
+\def_new:Npn \xparse_add_arg_type_m: {
+ \bool_if:NTF \g_xparse_allow_par_bool
+ {
+ \toks_put_right:Nn \l_xparse_grabbed_args_toks {\xparse_allow_par_m:w}
+ }
+ { \int_incr:N \l_xparse_mandatory_args_int }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\xparse_add_remaining_m_args:}
+% And here is the function for clearing out normal pending |m|
+% arguments. There is little point in adding any arguments if none
+% are required.
+% \begin{macrocode}
+\def_new:Npn \xparse_add_remaining_m_args: {
+ \int_compare:nNnF \l_xparse_mandatory_args_int = \c_zero
+ {
+ \toks_put_right:Nx \l_xparse_grabbed_args_toks {
+ \exp_not:c{xparse_m
+ \int_use:N \l_xparse_mandatory_args_int
+ :w }
+ }
+ \int_zero:N \l_xparse_mandatory_args_int
+ }
+}
+% \end{macrocode}
+% \end{macro}
+%
+%
+% \begin{macro}{\xparse_m1:w}
+% \begin{macro}{\xparse_m2:w}
+% \begin{macro}{\xparse_m3:w}
+% \begin{macro}{\xparse_m4:w}
+% \begin{macro}{\xparse_m5:w}
+% \begin{macro}{\xparse_m6:w}
+% \begin{macro}{\xparse_m7:w}
+% \begin{macro}{\xparse_m8:w}
+% \begin{macro}{\xparse_m9:w}
+% Grabbing 1--9 mandatory arguments. The one grabbing nine arguments
+% will automatically end with
+% |\toks_use:N \l_xparse_grabbed_args_toks| anyway so we avoid
+% problems with that one.
+% \begin{macrocode}
+\def_new:cpn {xparse_m1:w} #1 \l_xparse_grabbed_args_toks#2{
+ \toks_put_right:Nn \l_xparse_grabbed_args_toks{{#2}}
+ #1 \l_xparse_grabbed_args_toks
+}
+\def_new:cpn {xparse_m2:w} #1 \l_xparse_grabbed_args_toks #2#3{
+ \toks_put_right:Nn \l_xparse_grabbed_args_toks{{#2}{#3}}
+ #1 \l_xparse_grabbed_args_toks
+}
+\def_new:cpn {xparse_m3:w} #1 \l_xparse_grabbed_args_toks #2#3#4{
+ \toks_put_right:Nn \l_xparse_grabbed_args_toks{{#2}{#3}{#4}}
+ #1 \l_xparse_grabbed_args_toks
+}
+\def_new:cpn {xparse_m4:w} #1 \l_xparse_grabbed_args_toks #2#3#4#5{
+ \toks_put_right:Nn \l_xparse_grabbed_args_toks{{#2}{#3}{#4}{#5}}
+ #1 \l_xparse_grabbed_args_toks
+}
+\def_new:cpn {xparse_m5:w} #1 \l_xparse_grabbed_args_toks #2#3#4#5#6{
+ \toks_put_right:Nn \l_xparse_grabbed_args_toks{{#2}{#3}{#4}{#5}{#6}}
+ #1 \l_xparse_grabbed_args_toks
+}
+\def_new:cpn {xparse_m6:w} #1 \l_xparse_grabbed_args_toks #2#3#4#5#6#7{
+ \toks_put_right:Nn \l_xparse_grabbed_args_toks
+ {{#2}{#3}{#4}{#5}{#6}{#7}}
+ #1 \l_xparse_grabbed_args_toks
+}
+\def_new:cpn {xparse_m7:w} #1 \l_xparse_grabbed_args_toks#2#3#4#5#6#7#8{
+ \toks_put_right:Nn \l_xparse_grabbed_args_toks
+ {{#2}{#3}{#4}{#5}{#6}{#7}{#8}}
+ #1 \l_xparse_grabbed_args_toks
+}
+\def_new:cpn {xparse_m8:w} #1\l_xparse_grabbed_args_toks
+ #2#3#4#5#6#7#8#9{
+ \toks_put_right:Nn \l_xparse_grabbed_args_toks
+ {{#2}{#3}{#4}{#5}{#6}{#7}{#8}{#9}}
+ #1 \l_xparse_grabbed_args_toks
+}
+\def_new:cpn {xparse_m9:w} \toks_use:N \l_xparse_grabbed_args_toks
+ #1#2#3#4#5#6#7#8#9{
+ \toks_put_right:Nn \l_xparse_grabbed_args_toks
+ {{#1}{#2}{#3}{#4}{#5}{#6}{#7}{#8}{#9}}
+ \toks_use:N \l_xparse_grabbed_args_toks
+}
+% \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\xparse_allow_par_m:w}
+% The |m| type allowing |\par| tokens. We only define one of them as
+% two in a row would be quite rare.
+% \begin{macrocode}
+\def_long_new:Npn \xparse_allow_par_m:w #1 \l_xparse_grabbed_args_toks#2{
+ \toks_put_right:Nn \l_xparse_grabbed_args_toks{{#2}}
+ #1 \l_xparse_grabbed_args_toks
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \paragraph{Arguments delimited by a left brace}
+%
+% \begin{macro}{\xparse_add_arg_type_l:}
+% \begin{macro}{\xparse_l:w}
+% \begin{macro}{\xparse_allow_par_l:w}
+% This is almost exactly the same as the |m| type except we read
+% everything up to the first left brace.
+% \begin{macrocode}
+\def_new:Npn \xparse_add_arg_type_l: {
+ \xparse_add_remaining_m_args:
+ \bool_if:NTF \g_xparse_allow_par_bool
+ {
+ \toks_put_right:Nn \l_xparse_grabbed_args_toks {\xparse_allow_par_l:w}
+ }
+ { \toks_put_right:Nn \l_xparse_grabbed_args_toks {\xparse_l:w} }
+}
+\def_new:Npn \xparse_l:w #1 \l_xparse_grabbed_args_toks#2#{
+ \toks_put_right:Nn \l_xparse_grabbed_args_toks{{#2}}
+ #1 \l_xparse_grabbed_args_toks
+}
+\def_long_new:Npn \xparse_allow_par_l:w #1 \l_xparse_grabbed_args_toks#2#{
+ \toks_put_right:Nn \l_xparse_grabbed_args_toks{{#2}}
+ #1 \l_xparse_grabbed_args_toks
+}
+% \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+% \paragraph{Adding a symbol argument type}
+%
+%
+% \begin{macro}{\DeclareSymbolArgument}
+% The actual grabber functions just issue a |\peek_meaning_remove:NTF|
+% or similar on the symbol chosen. If found, we put a |\c_true| on the
+% argument stack and |\c_false| otherwise.
+% \begin{macrocode}
+\def_new:NNn \DeclareSymbolArgument 2{
+ \seq_map_variable:NNn \g_xparse_ignore_marker_seq \l_tmpa_tlp {
+ \def:cpx {xparse \l_tmpa_tlp _#1:w}##1##2\l_xparse_grabbed_args_toks{
+ \exp_not:c{peek_ #2 _remove \l_tmpa_tlp :NTF} ##1
+ {
+ \exp_not:N \toks_put_right:Nn \exp_not:N
+ \l_xparse_grabbed_args_toks \exp_not:N \c_true
+ ##2 \exp_not:N\l_xparse_grabbed_args_toks
+ }
+ {
+ \exp_not:N \toks_put_right:Nn \exp_not:N
+ \l_xparse_grabbed_args_toks \exp_not:N \c_false
+ ##2 \exp_not:N\l_xparse_grabbed_args_toks
+ }
+ }
+ }
+% \end{macrocode}
+% Implementing a symbol type is fairly straight forward. It needs to
+% grab a default argument. First we must clear out any pending |m|
+% arguments.
+% \begin{macrocode}
+ \def:cpn {xparse_add_arg_type_#1:} {
+ \xparse_add_remaining_m_args:
+ \toks_put_right:Nx \l_xparse_grabbed_args_toks
+ { \exp_not:c {xparse \g_xparse_ignore_marker_tlp _#1:w } }
+% \end{macrocode}
+% Nothing special when building the signature: We always grab a single
+% default argument.
+% \begin{macrocode}
+ \let:NN \xparse_read_arg_type_or_grab_default:n \xparse_grab_default_arg:n
+ }
+}
+% \end{macrocode}
+% It is this easy now:
+% \begin{macrocode}
+\DeclareSymbolArgument S{meaning}
+% \end{macrocode}
+% \end{macro}
+%
+%
+% \paragraph{Adding delimited arguments}
+%
+%
+% \begin{macro}{\DeclareArgumentType}
+% Argument types that read their argument delimited as the |o| type
+% can be defined with this function. |#1| is the letter associated
+% with the type, |#3| is the test type we should use, i.e.,
+% meaning, charcode or catcode. |#2| is the left delimiter \LaTeX{}
+% will look for, |#4| can be used for an error message or such in
+% case of a missing value, and |#5| the value inserted in case the
+% optional argument is missing. The last two arguments control how
+% the arguments are picked up and parsed on to the inner parsing.
+% \begin{macrocode}
+\def_new:NNn \DeclareArgumentType 7{
+% \end{macrocode}
+% For instance, we want |\DeclareArgumentType a{charcode}[...| to
+% define the function |\xparse_ignore_spaces_a:w| with meaning
+% |\peek_charcode_ignore_spaces:NTF [{...}{...}|. We want to define a
+% series of functions for each of these delimited argument types. One
+% for each of the |ignore| types plus an identical version of each of
+% these allowing the |\par| token in the argument. All the different
+% ignore types are stored in the sequence
+% |\g_xparse_ignore_marker_seq| so we go through that when doing the
+% definitions.
+% \begin{macrocode}
+ \seq_map_variable:NNn \g_xparse_ignore_marker_seq \l_tmpa_tlp {
+ \def:cpx {xparse \l_tmpa_tlp _#1:w}##1\l_xparse_grabbed_args_toks{
+ \exp_not:c{peek_#3 \l_tmpa_tlp :NTF} \exp_not:N #2
+ { \exp_not:c{xparse_#1_#3_help:nw}{##1} }
+ {
+ \exp_not:n {
+ #4 \toks_put_right:Nn \l_xparse_grabbed_args_toks {#5}
+ }
+ ##1 \exp_not:N\l_xparse_grabbed_args_toks
+ }
+ }
+% \end{macrocode}
+% And now an almost identical version which allows the |\par| token.
+% \begin{macrocode}
+ \def_long:cpx {xparse_allow_par \l_tmpa_tlp _#1:w}##1
+ \l_xparse_grabbed_args_toks{
+ \exp_not:c{peek_#3 \l_tmpa_tlp :NTF} \exp_not:N #2
+ { \exp_not:c{xparse_allow_par_#1_#3_help:nw}{##1} }
+ {
+ \exp_not:n {
+ #4 \toks_put_right:Nn \l_xparse_grabbed_args_toks {#5}
+ }
+ ##1 \exp_not:N\l_xparse_grabbed_args_toks
+ }
+ }
+ }
+% \end{macrocode}
+% Here is the function for building the argument grabbing. We clear
+% out the remaining |m| arguments first.
+% \begin{macrocode}
+ \def:cpn {xparse_add_arg_type_#1:} {
+ \xparse_add_remaining_m_args:
+ \toks_put_right:Nx \l_xparse_grabbed_args_toks {
+ \exp_not:c {xparse
+% \end{macrocode}
+% Insert |_allow_par| in the csname if needed. This also applies to
+% the argument grabber (although this should probably just be the
+% default).
+% \begin{macrocode}
+ \bool_if:NT \g_xparse_allow_par_bool {_allow_par}
+ \g_xparse_ignore_marker_tlp
+ _#1:w
+ }
+ }
+ \let:NN \xparse_read_arg_type_or_grab_default:n \xparse_parse_signature:n
+ }
+% \end{macrocode}
+% Now all we need to do is to define the helper functions.
+% \begin{macrocode}
+ \xparse_define_helper:Nnnn #1{#3}{#6}{#7}
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\DeclareArgumentTypeDefaultValue}
+% The same as above but expects a default value in the signature.
+% Therefore it doesn't have the arguments of the default value and
+% what to do if it is missing like the above.
+% \begin{macrocode}
+\def_new:NNn \DeclareArgumentTypeDefaultValue 5{
+ \seq_map_variable:NNn \g_xparse_ignore_marker_seq \l_tmpa_tlp {
+ \def:cpx {xparse \l_tmpa_tlp _#1:w}##1##2\l_xparse_grabbed_args_toks{
+ \exp_not:c{peek_#3 \l_tmpa_tlp :NTF} \exp_not:N #2
+ { \exp_not:c{xparse_#1_#3_help:nw}{##2} }
+ {
+ \exp_not:N \toks_put_right:Nn
+ \exp_not:N \l_xparse_grabbed_args_toks {{##1}}
+ ##2 \exp_not:N \l_xparse_grabbed_args_toks
+ }
+ }
+% \end{macrocode}
+% And now an almost identical version which allows the |\par| token.
+% \begin{macrocode}
+ \def_long:cpx {xparse_allow_par \l_tmpa_tlp _#1:w}##1##2
+ \l_xparse_grabbed_args_toks{
+ \exp_not:c{peek_#3 \l_tmpa_tlp :NTF} \exp_not:N #2
+ { \exp_not:c{xparse_allow_par_#1_#3_help:nw}{##2} }
+ {
+ \exp_not:N \toks_put_right:Nn
+ \exp_not:N \l_xparse_grabbed_args_toks {{##1}}
+ ##2 \exp_not:N \l_xparse_grabbed_args_toks
+ }
+ }
+ }
+% \end{macrocode}
+% Here is the function for building the argument grabbing. We clear
+% out the remaining |m| arguments first.
+% \begin{macrocode}
+ \def:cpn {xparse_add_arg_type_#1:} {
+ \xparse_add_remaining_m_args:
+ \toks_put_right:Nx \l_xparse_grabbed_args_toks {
+ \exp_not:c {xparse
+% \end{macrocode}
+% Insert |_allow_par| in the csname if needed. This also applies to
+% the argument grabber (although this should probably just be the
+% default).
+% \begin{macrocode}
+ \bool_if:NT \g_xparse_allow_par_bool {_allow_par}
+ \g_xparse_ignore_marker_tlp
+ _#1:w
+ }
+ }
+ \let:Nc \xparse_read_arg_type_or_grab_default:n
+ {xparse_grab_default_arg
+ \bool_if:NT \g_xparse_allow_par_bool {_allow_par}
+ :n
+ }
+ }
+% \end{macrocode}
+% Now all we need to do is to define the helper functions.
+% \begin{macrocode}
+ \xparse_define_helper:Nnnn #1{#3}{#4}{#5}
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\xparse_define_helper:Nnnn}
+% All we need now is the helper functions. We define a generic
+% interface that should be fairly easy to use.
+% \begin{macrocode}
+\def_new:NNn \xparse_define_helper:Nnnn 4{
+ \toks_set:Nn \l_tmpa_toks
+ {
+ #3
+ {
+% \end{macrocode}
+% Remember to add an extra set of braces here.
+% \begin{macrocode}
+ \toks_put_right:Nn \l_xparse_grabbed_args_toks {{#4}}
+ ##1 \l_xparse_grabbed_args_toks
+ }
+ }
+% \end{macrocode}
+% The next bit looks a little ugly but that's life.
+% \begin{macrocode}
+ \toks_set:Nx \l_tmpa_toks {
+ \exp_not:n {\def:cpn{xparse_#1_#2_help:nw}}
+ \toks_use:N \l_tmpa_toks
+ \exp_not:n {\def:cpn{xparse_allow_par_#1_#2_help:nw}}
+ \toks_use:N\l_tmpa_toks
+ }
+ \toks_use:N \l_tmpa_toks
+}
+% \end{macrocode}
+% \end{macro}
+%
+% All the above may seem like an awful lot of trouble but it is
+% general and it allows the following simple definitions:
+% \begin{macrocode}
+\DeclareArgumentType o[{meaning}{}{\NoValue}{#1[#2]}{#2}
+% \end{macrocode}
+% For the |c| type we add give an error message.
+% \begin{macrocode}
+\DeclareArgumentType c({meaning}{
+ \xparse_error:x{
+ Missing~ coordinate~ argument.~ A~ value~ of~ (0,0)~ is~ assumed}
+ }
+ {{00}}
+ {#1(#2,#3)}{{#2}{#3}}
+\DeclareArgumentTypeDefaultValue O[{meaning}{#1[#2]}{#2}
+\DeclareArgumentTypeDefaultValue C({meaning}{#1(#2,#3)}{{#2}{#3}}
+% \end{macrocode}
+% One could also do
+% \begin{verbatim}
+% \DeclareArgumentTypeDefaultValue O[{charcode}{#1#2#3]}{#3}
+% \end{verbatim}
+% where argument |#2| is the bracket but not requiring it to have
+% catcode~12. However we can't use the same trick for reading the end
+% of the argument.
+%
+% Another interesting one could be
+% \begin{verbatim}
+% \DeclareArgumentType a\c_group_begin_token{catcode}{}{\NoValue}{#1#2}{#2}
+% \end{verbatim}
+% which would basically be an optional argument in braces.
+%
+%
+%
+% \subsubsection{Argument shorthands}
+%
+%
+% \begin{macro}{\DeclareArgumentTypeShorthand}
+% Letting a letter or symbol be a shorthand for a more complicated
+% structure is rather easy actually. All we need to do is to gobble
+% the remainder of the main loop in the signature creation until
+% |\xparse_parse_signature:n|, decrement the argument counter, put
+% in the replacement argument specifiers and start the loop
+% again. The disadvantage of this scheme is that we have to cheat
+% and give it the wrong name as it should have a |w| argument
+% specification but I hope you can forgive this little white lie.
+% \begin{macrocode}
+\def_new:NNn \DeclareArgumentTypeShorthand 2{
+ \def_new:cpn {xparse_add_arg_type_#1:}
+ ##1 \xparse_read_arg_type_or_grab_default:n {
+ \int_decr:N \l_xparse_total_args_int
+ \xparse_read_arg_type_or_grab_default:n #2
+ }
+}
+% \end{macrocode}
+% \end{macro}
+% \begin{macro}{\xparse_add_arg_type_s:}
+% Defining the |s| type is easy now since it really means |S{*}|.
+% \begin{macrocode}
+\DeclareArgumentTypeShorthand s {S{*}}
+% \end{macrocode}
+% \end{macro}
+%
+%
+% \subsection{Checking for optional values}
+%
+%
+% \begin{macro}{\IfBooleanTF}
+% \begin{macro}{\IfBooleanT}
+% \begin{macro}{\IfBooleanF}
+% The logical \meta{true} and \meta{false} statements are just our
+% normal |\c_true| and |\c_false| so testing for them is done with
+% our usual |\prg_if_predicate:nTF| functions from \textsf{l3prg}.
+% \begin{macrocode}
+\let_new:NN \IfBooleanTF \prg_if_predicate:nTF
+\let_new:NN \IfBooleanT \prg_if_predicate:nT
+\let_new:NN \IfBooleanF \prg_if_predicate:nF
+% \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\NoValue}
+% \begin{macro}{\c_xparse_hidden_no_value_tlp}
+% |\NoValue| is just a text string and we define it as a token list
+% pointer. However we will actually test for token list pointers
+% with \emph{meaning} |\NoValue|. Hence if an argument is really
+% |-NoValue-| it will not be detected but that shouldn't happen.
+% \begin{macrocode}
+\tlp_new:Nn \NoValue {-NoValue-}
+\tlp_new:Nn \c_xparse_hidden_no_value_tlp {\NoValue}
+% \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\xparse_if_no_value:nTF}
+% The test start by making a token list pointer out of the first
+% argument and then check if it is equal to
+% |\c_xparse_hidden_no_value_tlp| which contains |\NoValue|.
+% \begin{macrocode}
+\def_long_new:Npn \xparse_if_no_value:nTF #1{
+ \tlp_set:Nx \l_tmpa_tlp{\exp_not:n{#1}}
+ \tlp_if_eq:NNTF \l_tmpa_tlp \c_xparse_hidden_no_value_tlp
+% \end{macrocode}
+% If they are equal we just exit and execute the \meta{true} code.
+% \begin{macrocode}
+ { \use_arg_i:nn }
+% \end{macrocode}
+% If not, take a closer look at |#1|. Peek ahead at the first token in
+% |#1| and then call the function |\xparse_if_no_value_aux:| but only
+% if |#1| is not empty or a blank space: in that case we can execute
+% the \meta{false} code immediately. We must use this test at some
+% point otherwise the macros for checking tokens will break since the
+% argument may be empty.
+% \begin{macrocode}
+ { \tlist_if_blank:nTF {#1}
+ { \use_arg_ii:nn }
+ {\peek_after:NN \xparse_if_no_value_aux: #1 \q_nil {#1} }
+ }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\xparse_if_no_value_aux:}
+% Now we simply check the argument specification of the token. If
+% it is not a macro the function |\token_get_arg_spec:N| returns
+% |\scan_stop:|.
+% \begin{macrocode}
+\def_long_new:Npn \xparse_if_no_value_aux: {
+ \tlp_set:Nx \l_tmpa_tlp{\token_get_arg_spec:N \l_peek_token }
+% \end{macrocode}
+% Then check if |\l_tmpa_tlp| is empty, because this means we have a
+% macro taking zero arguments and we can expand it once
+% safely. Otherwise we just exit and execute the false code. Remember
+% that we have the sequence |{#1}| waiting after the |\q_nil| in
+% |\xparse_if_no_value:nTF| above.
+% \begin{macrocode}
+ \tlp_if_empty:NTF \l_tmpa_tlp
+ {\use_arg_i_delimit_by_q_nil:nw {\exp_args:No\xparse_if_no_value:nTF}}
+ {\use_arg_i_delimit_by_q_nil:nw {\use_arg_iii:nnn}}
+}
+% \end{macrocode}
+% \end{macro}
+%
+%
+% \begin{macro}{\IfNoValueTF}
+% \begin{macro}{\IfNoValueT}
+% \begin{macro}{\IfNoValueF}
+% \begin{macro}{\IfValueTF}
+% \begin{macro}{\IfValueT}
+% \begin{macro}{\IfValueF}
+% |\IfNoValueTF| and its varieties are implemented as subcases of
+% |\xparse_if_no_value:nTF|.
+% \begin{macrocode}
+\let_new:NN \IfNoValueTF \xparse_if_no_value:nTF
+\def_long_new:NNn \IfNoValueT 2 {\xparse_if_no_value:nTF{#1}{#2}{}}
+\def_long_new:NNn \IfNoValueF 1 {\xparse_if_no_value:nTF {#1}{}}
+% \end{macrocode}
+% For |\IfValueTF| we just reverse the arguments.
+% \begin{macrocode}
+\def_long_new:NNn \IfValueTF 3{\xparse_if_no_value:nTF {#1}{#3}{#2}}
+\let_new:NN \IfValueT \IfNoValueF
+\let_new:NN \IfValueF \IfNoValueT
+% \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+%
+% \subsection{Pseudo arguments}
+%
+% \begin{macro}{\l_xparse_pseudo_post_arg_tlp}
+% A temporary token list pointer to store the post-arguments.
+% \begin{macrocode}
+\tlp_new:Nn \l_xparse_pseudo_post_arg_tlp {}
+% \end{macrocode}
+% \end{macro}
+% \begin{macro}{\DeclarePseudoArgument}
+% Must be called at the end of the replacement text. Can use the
+% parameters picked up so far. |#1| is a name for it, |#2| is the
+% number of arguments, |#3| is the pre-argument definition, |#4| is
+% the post-argument definition. The idea here is to define two
+% functions: One to execute before the special pseudo argument is
+% found and one to to it afterwards. Hence we define such two
+% functions with |#2| arguments and definitions |#3| and |#4|
+% respectively.
+% \begin{macrocode}
+\def_long_new:NNn \DeclarePseudoArgument 4{
+ \def_long:cNn {xparse_pseudo_pre_arg_#1:\prg_replicate:nn{#2}{n}}#2{#3}
+ \def_long:cNn {xparse_pseudo_post_arg_#1:\prg_replicate:nn{#2}{n}}#2{#4}
+% \end{macrocode}
+% In case the user doesn't put the argument in braces, it must be a
+% single token which we just grab and then execute the
+% post-argument. Surely it won't be a |\par| token!
+% \begin{macrocode}
+ \def:cNn {xparse_pseudo_nobrace_arg_#1:N} 1 {
+ ##1 \l_xparse_pseudo_post_arg_tlp
+ }
+% \end{macrocode}
+% The regular version of the command is then this:
+% \begin{enumerate}
+% \item Execute the pre-code at level $n$.
+% \item Store the post-code in a token list pointer at level $n$.
+% \item Look for a begin-group token.
+% \item[4a] If found, remove it, start a group (level $n+1$) and make
+% sure the token list pointer from 2) is executed after the group
+% has ended (at level $n$).
+% \item[4b] If not found, call the |nobrace_arg| version which also
+% executes the token list pointer from 2) at level $n$.
+% \end{enumerate}
+% This scheme enables these commands to be nested since they all
+% appear at different grouping levels.
+%
+% Next we define the function. Also make sure that it gets all the
+% arguments carried over to the post-argument.
+% \begin{macrocode}
+ \def_long:cNx {xparse_pseudo_arg_#1:w} #2
+ {
+ \exp_not:c {
+ xparse_pseudo_pre_arg_#1: \prg_replicate:nn{#2}{n}
+ }
+ \cs_use:c{def_aux_use_\int_use:N \int_eval:n{#2}_parameter:}
+ \exp_not:n {\tlp_set:Nn \l_xparse_pseudo_post_arg_tlp}
+ {
+ \exp_not:c {xparse_pseudo_post_arg_#1:\prg_replicate:nn{#2}{n}}
+ \cs_use:c{def_aux_use_\int_use:N \int_eval:n{#2}_parameter:}
+ }
+ \exp_not:n{ \peek_catcode_remove_ignore_spaces:NTF \c_group_begin_token }
+ {
+% \end{macrocode}
+% Here we insert the left brace token which was removed removed.
+% In case you're wondering then yes, I know that |\c_group_begin_token|
+% and |\group_execute_after:N| are unexpandable but I prefer this method
+% because I don't want to remember which commands are expandable and
+% which are not.
+% \begin{macrocode}
+ \exp_not:n {
+ \c_group_begin_token
+ \group_execute_after:N \l_xparse_pseudo_post_arg_tlp
+ }
+ }
+ {
+ \exp_not:c{xparse_pseudo_nobrace_arg_#1:N}
+ }
+ }
+}
+% \end{macrocode}
+% \end{macro}
+% \begin{macro}{\UsePseudoArgument}
+% Just a nice wrapper for calling such an argument.
+% \begin{macrocode}
+\def_new:NNn \UsePseudoArgument 1{\cs_use:c{xparse_pseudo_arg_#1:w}}
+% \end{macrocode}
+% \end{macro}
+%
+%
+%
+%
+% \Finale
+%
+\endinput
+%
+% $Log$
+% Revision 1.25 2006/07/17 22:25:53 morten
+% Minor change to reflect change in l3basics.dtx
+%
+% Revision 1.24 2006/07/08 22:44:29 morten
+% Fixed two lurking problems in \xparse_if_no_value:nTF.
+%
+% Revision 1.23 2006/07/06 14:56:04 morten
+% Change to use new \def:NNn syntax
+%
+% Revision 1.22 2006/01/17 23:04:08 morten
+% Added `l' type argument for reading up to a left brace.
+%
+% Revision 1.21 2006/01/04 02:42:35 morten
+% Changed RCS information retrieval. Rewrote \DeclareArgumentType and
+% its relatives in order for them to work properly with the new \peek_
+% functions. Changed how special markers are inserted into the
+% signature. Added `pseudo arguments'. Updated documentation to reflect
+% all these changes. And more which I can't remember right now :-)
+%
+% Revision 1.20 2005/04/06 21:24:47 morten
+% Total rewrite - there is only one implementation in the package
+% now. Documentation updated to match the changes.
+%
+%
+%