new package xbase, subsuming some others?

git-svn-id: svn://tug.org/texlive/trunk@4337 c570f23f-e606-0410-a88d-b1316a301751

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.
+%
+%
+%