% \iffalse meta-comment
%
% File: expkv-def.dtx Copyright (C) 2020 Jonathan P. Spratte
%
% This work  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
%
% ------------------------------------------------------------------------------
%
%<*driver>^^A>>=
\def\nameofplainTeX{plain}
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\input l3docstrip.tex
\askforoverwritefalse
\preamble

--------------------------------------------------------------
expkv-def -- a key-defining frontend for expkv
E-mail: jspratte@yahoo.de
Released under the LaTeX Project Public License v1.3c or later
See http://www.latex-project.org/lppl.txt
--------------------------------------------------------------

Copyright (C) 2020 Jonathan P. Spratte

This  work 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 work is "maintained" (as per LPPL maintenance status) by
  Jonathan P. Spratte.

This work consists of the file  expkv-def.dtx
and the derived files           expkv-def.pdf
                                expkv-def.sty
                                expkv-def.tex

\endpreamble
% stop docstrip adding \endinput
\postamble
\endpostamble
\generate{\file{expkv-def.sty}{\from{expkv-def.dtx}{pkg}}}
\generate{\file{expkv-def.tex}{\from{expkv-def.dtx}{tex}}}
\ifx\fmtname\nameofplainTeX
  \expandafter\endbatchfile
\else
  \expandafter\endgroup
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%
\IfFileExists{expkv-def.tex}{\input{expkv-def.tex}}{}
\ProvidesFile{expkv-def.dtx}
  [\csname ekvdDate\endcsname\ a key-defining frontend for expkv]
\PassOptionsToPackage{full}{textcomp}
\documentclass{l3doc}
\RequirePackage[oldstylenums,nott]{kpfonts}
\input{glyphtounicode}
\pdfgentounicode=1
\RequirePackage{listings}
\RequirePackage{booktabs}
\RequirePackage{array}
\RequirePackage{collcell}
\RequirePackage{siunitx}
\RequirePackage{xcolor}
\RequirePackage{caption}
\RequirePackage{microtype}
\RequirePackage{accsupp}
\lstset
  {
    ,flexiblecolumns=false
    ,basewidth=.53em
    ,gobble=2
    ,basicstyle=\fontfamily{jkp}\itshape
    ,morekeywords=^^A
      {^^A
        \ekvdefinekeys
      }
    ,morecomment=[l]\%
    ,commentstyle=\color[gray]{0.4}
    ,literate={\{}{{\CodeSymbol\{}}{1}
              {\}}{{\CodeSymbol\}}}{1}
    ^^A,literate=*{<key>}{\key}{4}{<set>}{\set}{4}
  }
\newcommand*\CodeSymbol[1]{\textbf{#1}}
\RequirePackage{randtext}
\let\metaORIG\meta
\protected\def\meta #1{\texttt{\metaORIG{#1}}}
\renewcommand*\thefootnote{\fnsymbol{footnote}}
\definecolor{expkvred}{HTML}{9F393D}
\colorlet{expkvgrey}{black!75}
\makeatletter
\newcommand*\expkv
  {^^A
    \texorpdfstring
      {^^A
        \mbox
          {^^A
            \BeginAccSupp{ActualText=expkv}^^A
            \href{https://github.com/Skillmon/tex_expkv}
              {^^A
                \rmfamily
                \bfseries
                {\color{expkvgrey}e\kern-.05em x\kern-.05em}^^A
                \lower.493ex
                  \hbox{{\color{expkvgrey}P}\kern-.1em{\color{expkvred}k}}^^A
                \kern-.18em{\color{expkvred}v}^^A
              }^^A
            \EndAccSupp{}^^A
          }^^A
      }
      {expkv}^^A
  }
\newcommand*\expkvd
  {^^A
    \texorpdfstring
      {^^A
        \mbox
          {^^A
            \BeginAccSupp{ActualText=expkv-def}^^A
            \href{https://github.com/Skillmon/tex_expkv-def}
              {^^A
                \rmfamily
                \bfseries
                {\color{expkvgrey}e\kern-.05em x\kern-.05em}^^A
                \lower.493ex
                  \hbox{{\color{expkvgrey}P}\kern-.1em{\color{expkvred}k}}^^A
                \kern-.18em{\color{expkvred}v}^^A
                {\color{expkvgrey}^^A
                  \kern.05em\rule[-.1ex]{.08em}{1.2ex}\kern.05em\textsc{def}^^A
                }^^A
              }^^A
            \EndAccSupp{}^^A
          }^^A
      }
      {expkv-def}^^A
  }
\newcommand\kv{\meta{key}=\meta{value}}
\newcommand\key{\meta{key}}
\newcommand\val{\meta{value}}
\newcommand\set{\meta{set}}
\newcommand\enfprot{\textcolor{black}{protected}}
\newcommand\allprot{\textcolor{gray}{protected}}
\newcommand\notprot{\textcolor{red!80!black}{protected}}
\newcommand\enflong{\textcolor{black}{long}}
\newcommand\alllong{\textcolor{gray}{long}}
\newcommand\notlong{\textcolor{red!80!black}{long}}
\newcommand\prefixes[2]
  {^^A
    \hfill
    \ifcase\numexpr#1\relax\or
      \enfprot\or
      \allprot\or
      \notprot\fi\space
    \ifcase\numexpr#2\relax\or
      \enflong\or
      \alllong\or
      \notlong\fi
  }
\hypersetup{linkcolor=red!80!black,urlcolor=purple!80!black}
\DoNotIndex{\def,\edef,\,,\=,\begingroup,\catcode,\chardef,\csname,\endcsname}
\DoNotIndex{\endgroup,\endinput,\errmessage,\expandafter,\input,\let,\long}
\DoNotIndex{\noexpand,\protected,\ProvidesFile,\ProvidesPackage,\relax,\space}
\DoNotIndex{\@,\unexpanded,\string,\expanded,\dimexpr,\global,\glueexpr,\hbox}
\DoNotIndex{\numexpr,\RequirePackage,\setbox,\the,\unless,\xdef}
\DoNotIndex{\ifcsname}
\DoNotIndex{\ifx}
\DoNotIndex{\ifdefined}
\DoNotIndex{\iffalse}
\DoNotIndex{\iftrue}
\DoNotIndex{\else}
\DoNotIndex{\fi}
\@gobble\fi ^^A ignoring \ifx, \ifcsname, etc., but only one \fi
\@gobble\fi ^^A ignoring \ifx, \ifcsname, etc., but only one \fi
\@gobble\fi ^^A ignoring \ifx, \ifcsname, etc., but only one \fi
\@gobble\fi ^^A ignoring \ifx, \ifcsname, etc., but only one \fi
\@ifdefinable\gobbledocstriptag{\def\gobbledocstriptag#1>{}}
\makeatother
\begin{document}
  \title
    {^^A
      \texorpdfstring
        {^^A
          \huge\expkvd
          \\[\medskipamount]
          \Large a key-defining frontend for \expkv
        }{expkv-def - a key-defining frontend for expkv}^^A
    }
  \date{\ekvdDate\space v\ekvdVersion}
  \author{Jonathan P. Spratte\thanks{\protect\randomize{jspratte@yahoo.de}}}
  \DocInput{expkv-def.dtx}
\end{document}
%</driver>^^A=<<
% \fi
%
% \maketitle
% \renewcommand*\thefootnote{\arabic{footnote}}
%
% \begin{abstract}
% \noindent\parfillskip=0pt
% \expkvd\ provides a small \kv\ interface to define keys for \expkv. Key-types
% are declared using prefixes, similar to static typed languages. The stylised
% name is \expkvd\ but the files use \file{expkv-def}, this is due to CTAN-rules
% which don't allow \string| in package names since that is the pipe symbol in *nix
% shells.
% \end{abstract}
%
% \tableofcontents
%
% \begin{documentation}^^A>>=
%
% \section{Documentation}
%
% Since the trend for the last couple of years goes to defining keys for a \kv\
% interface using a \kv\ interface, I thought that maybe providing such an
% interface for \expkv\ will make it more attractive for actual use, besides its
% unique selling points of being fully expandable, and fast and reliable. But at
% the same time I don't want to widen \expkv's initial scope. So here it is
% \expkvd, go define \kv\ interfaces with \kv\ interfaces.
%
% Unlike many of the other established \kv\ interfaces to define keys, \expkvd\
% works using prefixes instead of suffixes (\emph{e.g.}, |.tl_set:N| of
% \pkg{l3keys}) or directory like handlers (\emph{e.g.}, |/.store in| of
% \pkg{pgfkeys}). This was decided as a personal preference, more over in \TeX\
% parsing for the first space is way easier than parsing for the last one.
% \expkvd's prefixes are sorted into two categories: |p|-type, which are
% equivalent to \TeX's prefixes like |\long|, and |t|-type defining the type of
% the key. For a description of the available |p|-prefixes take a look at
% \autoref{sec:prefix:p}, the |t|-prefixes are described in
% \autoref{sec:prefix:t}.
%
% \expkvd\ is usable as generic code and as a \LaTeX\ package. It'll
% automatically load \expkv\ in the same mode as well. To use it, just use one
% of
% \begin{lstlisting}
% \usepackage{expkv-def} % LaTeX
% \input expkv-def       % plainTeX
% \end{lstlisting}
%
% \subsection{Macros}
% Apart from version and date containers there is only a single user-facing
% macro, and that should be used to define keys.
%
% \begin{function}{\ekvdefinekeys}
%   \begin{syntax}
%     \cs{ekvdefinekeys}\marg{set}\{\kv, \ldots\}
%   \end{syntax}
%   In \set, define \key\ to have definition \val. The general syntax for \key\
%   should be
%   \begin{quote}\ttfamily\small
%     \meta{prefix} \meta{name}
%   \end{quote}
%   Where \meta{prefix} is a space separated list of optional |p|-type prefixes
%   followed by one |t|-type prefix. The syntax of \val\ is dependent on the
%   used |t|-prefix.
% \end{function}
%
% \begin{function}{\ekvdDate,\ekvdVersion}
%   These two macros store the version and date of the package.
% \end{function}
%
% \subsection{Prefixes}
% As already said there are |p|-prefixes and |t|-prefixes. Not every |p|-prefix
% is allowed for all |t|-prefixes.
%
% \subsubsection{\texttt{p}-Prefixes}\label{sec:prefix:p}
% The |p|-type prefixes are pretty simple by nature, so their description is
% pretty simple. They affect the \key\ at use-time, so omitting |long| doesn't
% mean that a \meta{definition} can't contain a |\par| token, only that the
% \key\ will not accept a |\par| in \val.
% \begin{function}{protected,protect}
%   The following key will be defined |\protected|. Note that key-types which
%   can't be defined expandable will always use |\protected|.
% \end{function}
%
% \begin{function}{long}
%   The following key will be defined |\long|.
% \end{function}
%
% \subsubsection{\texttt{t}-Prefixes}\label{sec:prefix:t}
% Since the |p|-type prefixes apply to some of the |t|-prefixes automatically
% but sometimes one might be disallowed we need some way to highlight this
% behaviour. In the following an enforced prefix will be printed black
% (\texttt{\enfprot}), allowed prefixes will be grey (\texttt{\allprot}), and
% disallowed prefixes will be red (\texttt{\notprot}). This will be put
% flush-right in the syntax showing line.
%
% \begin{function}{code,ecode}
%   \begin{syntax}
%     code \key\ = \marg{definition} \prefixes22
%   \end{syntax}
%   Define \key\ to expand to \meta{definition}. The \key\ will require a \val\
%   for which you can use |#1| inside \meta{definition}. The |ecode| variant
%   will fully expand \meta{definition} inside an |\edef|.
% \end{function}
%
% \begin{function}{noval,enoval}
%   \begin{syntax}
%     noval \key\ = \marg{definition} \prefixes23
%   \end{syntax}
%   The |noval| type defines \key\ to expand to \meta{definition}. The \key\
%   will not take a \val. |enoval| fully expands \meta{definition} inside an
%   |\edef|.
% \end{function}
%
% \begin{function}{default,qdefault,edefault}
%   \begin{syntax}
%     default \key\ = \marg{definition} \prefixes23
%   \end{syntax}
%   This serves to place a default \val\ for a \key\ that takes an argument, the
%   \key\ can be of any argument-grabbing kind, and when used without a \val\
%   it will be passed \meta{definition} instead. The |qdefault| variant will
%   expand the \key's code once, so will be slightly quicker, but not change if
%   you redefine \key. The |edefault| on the other hand fully expands the
%   \key-code with \meta{definition} as its argument inside of an |\edef|.
% \end{function}
%
% \begin{function}{initial}
%   \begin{syntax}
%     initial \key\ = \{\val\} \prefixes33
%   \end{syntax}
%   With |initial| you can set an initial \val\ for an already defined argument
%   taking \key. It'll just call the key-macro of \key\ and pass it \val.
% \end{function}
%
% \begin{function}{bool,gbool,boolTF,gboolTF}
%   \begin{syntax}
%     bool \key\ = \meta{cs} \prefixes23
%   \end{syntax}
%   The \meta{cs} should be a single control sequence, such as |\iffoo|.
%   This will define \key\ to be a boolean key, which only takes the values
%   |true| or |false| and will throw an error for other values. If the key is
%   used without a \val\ it'll have the same effect as if you use
%   \texttt{\key=true}. |bool| and |gbool| will behave like \TeX-ifs so either
%   be |\iftrue| or |\iffalse|. The |boolTF| and |gboolTF| variants will both
%   take two arguments and if true the first will be used else the second, so
%   they are always either |\@firstoftwo| or |\@secondoftwo|. The variants with
%   a leading |g| will set the control sequence globally, the others locally. If
%   \meta{cs} is not yet defined it'll be initialised as the |false| version.
%   Note that the initialisation is \emph{not} done with |\newif|, so you will
%   not be able to do |\footrue| outside of the \kv\ interface, but you could
%   use |\newif| yourself. Even if the \key\ will not be |\protected| the
%   commands which execute the |true| or |false| choice will be, so the usage
%   should be safe in an expansion context (\emph{e.g.}, you can use
%   \texttt{edefault \key\ = false} without an issue to change the default
%   behaviour to execute the |false| choice).
% \end{function}
%
% \begin{function}{store,estore,gstore,xstore}
%   \begin{syntax}
%     store \key\ = \meta{cs} \prefixes12
%   \end{syntax}
%   The \meta{cs} should be a single control sequence, such as |\foo|.
%   This will define \key\ to store \val\ inside of the control sequence. If
%   \meta{cs} isn't yet defined it will be initialised as empty. The variants
%   behave similarly to their |\def|, |\edef|, |\gdef|, and |\xdef|
%   counterparts, but |store| and |gstore| will allow you to store macro
%   parameters inside of them by using |\unexpanded|.
% \end{function}
%
% \begin{function}{int,eint,gint,xint}
%   \begin{syntax}
%     int \key\ = \meta{cs} \prefixes12
%   \end{syntax}
%   The \meta{cs} should be a single control sequence, such as |\foo|.
%   An |int| key will be a \TeX-count register. If \meta{cs} isn't defined yet,
%   |\newcount| will be used to initialise it. The |eint| and |xint| versions
%   will use |\numexpr| to allow basic computations in their \val. The |gint|
%   and |xint| variants set the register globally.
% \end{function}
%
% \begin{function}{dimen,edimen,gdimen,xdimen}
%   \begin{syntax}
%     dimen \key\ = \meta{cs} \prefixes12
%   \end{syntax}
%   The \meta{cs} should be a single control sequence, such as |\foo|.
%   This is just like |int| but uses a dimen register, |\newdimen| and
%   |\dimexpr| instead.
% \end{function}
%
% \begin{function}{skip,eskip,gskip,xskip}
%   \begin{syntax}
%     skip \key\ = \meta{cs} \prefixes12
%   \end{syntax}
%   The \meta{cs} should be a single control sequence, such as |\foo|.
%   This is just like |int| but uses a skip register, |\newskip| and |\glueexpr|
%   instead.
% \end{function}
%
% \begin{function}{toks,gtoks,apptoks,gapptoks}
%   \begin{syntax}
%     toks \key\ = \meta{cs} \prefixes12
%   \end{syntax}
%   The \meta{cs} should be a single control sequence, such as |\foo|. 
%   Store \val\ inside of a toks-register. The |g| variants use |\global|, the
%   |app| variants append \val\ to the contents of that register. If \meta{cs}
%   is not yet defined it will be initialised with |\newtoks|.
% \end{function}
%
% \begin{function}{box,gbox}
%   \begin{syntax}
%     box \key\ = \meta{cs} \prefixes12
%   \end{syntax}
%   The \meta{cs} should be a single control sequence, such as |\foo|.
%   Typesets \val\ into a |\hbox| and stores the result in a box register. The
%   boxes are colour safe. \expkvd\ doesn't provide a |vbox| type.
% \end{function}
%
% \begin{function}{meta}
%   \begin{syntax}
%     meta \key\ = \{\kv, \ldots\} \prefixes22
%   \end{syntax}
%   This key type can set other keys, you can access the \val\ which was passed
%   to \key\ inside the \kv\ list with |#1|. It works by calling a sub-|\ekvset|
%   on the \kv\ list, so a |set| key will only affect that \kv\ list and not the
%   current |\ekvset|.
% \end{function}
%
% \begin{function}{nmeta}
%   \begin{syntax}
%     nmeta \key\ = \{\kv, \ldots\} \prefixes23
%   \end{syntax}
%   This key type can set other keys, the difference to |meta| is, that this key
%   doesn't take a value, so the \kv\ list is static.
% \end{function}
%
% \begin{function}{smeta}
%   \begin{syntax}
%     smeta \key\ = \marg{set}\{\kv, \ldots\} \prefixes22
%   \end{syntax}
%   Yet another |meta| variant. An |smeta| key will take a \val\ which you can
%   access using |#1|, but it sets the \kv\ list inside of \set, so is equal to
%   \texttt{\cs[no-index]{ekvset}\marg{set}\{\kv, \ldots\}}.
% \end{function}
%
% \begin{function}{snmeta}
%   \begin{syntax}
%     snmeta \key\ = \marg{set}\{\kv, \ldots\} \prefixes23
%   \end{syntax}
%   And the last |meta| variant. |snmeta| is a combination of |smeta| and
%   |nmeta|. It doesn't take an argument and sets the \kv\ list inside of \set.
% \end{function}
%
% \begin{function}{set}
%   \begin{syntax}
%     set \key\ = \marg{set} \prefixes33
%   \end{syntax}
%   This will define \key\ to change the set of the current |\ekvset|
%   invocation to \set. You can omit \set\ (including the equals sign),
%   which is the same as using \texttt{set \key\ = \{\key\}}. The created |set|
%   key will not take a \val. Note that just like in \expkv\ it'll not be
%   checked whether \set\ is defined and you'll get a low-level \TeX\ error if
%   you use an undefined \set.
% \end{function}
%
% \begin{function}{choice}
%   \begin{syntax}
%     choice \key\ = \{\val=\meta{definition}, \ldots\} \prefixes23
%   \end{syntax}
%   Defines \key\ to be a |choice| key, meaning it will only accept a limited
%   set of values. You should define each possible \val\ inside of the
%   \val=\meta{definition} list. If a defined \val\ is passed to \key\ the
%   \meta{definition} will be left in the input stream. You can make
%   individual values |protected| inside the \val=\meta{definition} list. By
%   default a |choice| key is expandable, an undefined \val\ will throw an error
%   in an expandable way.
% \end{function}
%
% \subsection{Bugs}
% I don't think there are any (but every developer says that), if you find some
% please let me know, either via the email address on the first page or on
% GitHub:
% \url{https://github.com/Skillmon/tex_expkv-def}
%
% \subsection{Example}
% The following is an example code defining each base key-type once. Please
% admire the very creative key-name examples.
%
% \begin{lstlisting}
% \ekvdefinekeys{example}
%   {
%     ,long code keyA = #1
%     ,noval     keyA = NoVal given
%     ,bool      keyB = \keyB
%     ,boolTF    keyC = \keyC
%     ,store     keyD = \keyD
%     ,int       keyE = \keyE
%     ,dimen     keyF = \keyF
%     ,skip      keyG = \keyG
%     ,toks      keyH = \keyH
%     ,default   keyH = \empty test
%     ,box       keyI = \keyI
%     ,qdefault  keyI = text
%     ,choice    keyJ =
%       {
%         ,protected 1 = \texttt{a}
%         ,2 = b
%         ,3 = c
%         ,4 = d
%         ,5 = e
%       }
%     ,edefault  keyJ = 2
%     ,meta      keyK = {keyA={#1},keyB=false}
%     ,set       setB = B
%   }
% \end{lstlisting}
%
% \subsection{License}
%
% Copyright \textcopyright\ 2020\unless\ifnum\year=2020--\the\year\fi\
% Jonathan P. Spratte
%
% \medskip\noindent
% This work 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:
%
% \url{http://www.latex-project.org/lppl.txt}
%
% \noindent
% This work is ``maintained'' (as per LPPL maintenance status) by
%
% \mbox{Jonathan P. Spratte}.
%
% \end{documentation}^^A=<<
%
% \begin{implementation}^^A>>=
%
% \clearpage
%
% \section{Implementation}^^A>>=
%^^A the LaTeX package >>=
% \subsection{The \LaTeX\ Package}
% Just like for \expkv\ we provide a small \LaTeX\ package that sets up things
% such that we behave nicely on \LaTeX\ packages and files system. It'll
% |\input| the generic code which implements the functionality.
% \gobbledocstriptag
%<*pkg>
%    \begin{macrocode}
\RequirePackage{expkv}
\def\ekvd@tmp
  {%
    \ProvidesFile{expkv-def.tex}%
      [\ekvdDate\space v\ekvdVersion\space a key-defining frontend for expkv]%
  }
\input{expkv-def.tex}
\ProvidesPackage{expkv-def}%
  [\ekvdDate\space v\ekvdVersion\space a key-defining frontend for expkv]
%    \end{macrocode}
% \gobbledocstriptag
%</pkg>
%^^A=<<
%^^A main file >>=
% \subsection{The Generic Code}
% The rest of this implementation will be the generic code.
% \gobbledocstriptag
%<*tex>
%
% Load \expkv\ if the package didn't already do so -- since \expkv\ has
% safeguards against being loaded twice this does no harm and the overhead
% isn't that big. Also we reuse some of the internals of \expkv\ to save us from
% retyping them.
%    \begin{macrocode}
\input expkv
%    \end{macrocode}
%
% We make sure that \file{expkv-def.tex} is only input once:
%    \begin{macrocode}
\expandafter\ifx\csname ekvdVersion\endcsname\relax
\else
  \expandafter\endinput
\fi
%    \end{macrocode}
%
% \begin{macro}{\ekvdVersion,\ekvdDate}
% We're on our first input, so lets store the version and date in a macro.
%    \begin{macrocode}
\def\ekvdVersion{0.1a}
\def\ekvdDate{2020-02-29}
%    \end{macrocode}
% \end{macro}
%
% If the \LaTeX\ format is loaded we want to be a good file and report back who
% we are, for this the package will have defined |\ekvd@tmp| to use
% |\ProvidesFile|, else this will expand to a |\relax| and do no harm.
%    \begin{macrocode}
\csname ekvd@tmp\endcsname
%    \end{macrocode}
%
% Store the category code of |@| to later be able to reset it and change it to
% 11 for now.
%    \begin{macrocode}
\expandafter\chardef\csname ekvd@tmp\endcsname=\catcode`\@
\catcode`\@=11
%    \end{macrocode}
% |\ekvd@tmp| will be reused later to handle expansion during the key
% defining. But we don't need it to ever store information long-term after
% \expkvd\ was initialized.
%
% \begin{macro}[internal]
%   {\ekvd@long,\ekvd@prot,\ekvd@clear@prefixes,\ekvd@empty}
% \expkvd\ will use |\ekvd@long| and |\ekvd@prot| to store whether a key should
% be defined as |\long| or |\protected|, and we have to clear them for every new
% key. By default they'll just be empty.
%    \begin{macrocode}
\def\ekvd@empty{}
\protected\def\ekvd@clear@prefixes
  {%
    \let\ekvd@long\ekvd@empty
    \let\ekvd@prot\ekvd@empty
  }
\ekvd@clear@prefixes
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\ekvdefinekeys}
% This is the one front-facing macro which provides the interface to define
% keys. It's using |\ekvparse| to handle the \kv\ list, the interpretation will
% be done by |\ekvd@noarg| and |\ekvd@|. The \set\ for which the keys should be
% defined is stored in |\ekvd@set|.
%    \begin{macrocode}
\protected\def\ekvdefinekeys#1%
  {%
    \def\ekvd@set{#1}%
    \ekvparse\ekvd@noarg\ekvd@
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[internal]{\ekvd@noarg,\ekvd@}
% |\ekvd@noarg| just places a special marker and gives control to |\ekvd@|.
% |\ekvd@| has to test whether there is a space inside the key and if so calls
% the prefix grabbing routine, else we throw an error and ignore the key.
%    \begin{macrocode}
\protected\def\ekvd@noarg#1{\ekvd@{#1}\ekvd@noarg@mark}
\protected\long\def\ekvd@#1#2%
  {%
    \ekvd@clear@prefixes
    \ekvd@ifspace{#1}%
      {\ekvd@prefix\ekv@mark#1\ekv@stop{#2}}%
      {\ekvd@err@missing@prefix{#1}}%
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[internal]{\ekvd@prefix,\ekvd@prefix@}
% \expkvd\ separates prefixes into two groups, the first being prefixes in the
% \TeX\ sense (|long| and |protected|) which use |@p@| in their name, the other
% being key-types (|code|, |int|, \emph{etc.}) which use |@t@| instead.
% |\ekvd@prefix| splits at the first space and checks whether its a |@p@|
% or |@t@| type prefix. If it is neither throw an error and gobble the
% definition (the value).
%    \begin{macrocode}
\protected\def\ekvd@prefix#1 {\ekv@strip{#1}\ekvd@prefix@\ekv@mark}
\protected\def\ekvd@prefix@#1#2\ekv@stop
  {%
    \ekv@ifdefined{ekvd@t@#1}%
      {\ekv@strip{#2}{\csname ekvd@t@#1\endcsname}}%
      {%
        \ekv@ifdefined{ekvd@p@#1}%
          {\csname ekvd@p@#1\endcsname{#2}}%
          {\ekvd@err@undefined@prefix{#1}\@gobble}%
      }%
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[internal]{\ekvd@prefix@after@p}
% The |@p@| type prefixes are all just modifying a following |@t@| type, so they
% will need to search for another prefix. This is true for all of them, so we
% use a macro to handle this. It'll throw an error if there is no other prefix.
%    \begin{macrocode}
\protected\def\ekvd@prefix@after@p#1%
  {%
    \ekvd@ifspace{#1}%
      {\ekvd@prefix#1\ekv@stop}%
      {%
        \expandafter\ekvd@err@missing@prefix\expandafter{\ekv@gobble@mark#1}%
        \@gobble
      }%
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[internal]{\ekvd@p@long,\ekvd@p@protected,\ekvd@p@protect}
% Define the |@p@| type prefixes, they all just store some information in a
% temporary macro and call |\ekvd@prefix@after@p|.
%    \begin{macrocode}
\protected\def\ekvd@p@long{\let\ekvd@long\long\ekvd@prefix@after@p}
\protected\def\ekvd@p@protected{\let\ekvd@prot\protected\ekvd@prefix@after@p}
\let\ekvd@p@protect\ekvd@p@protected
%    \end{macrocode}
% \end{macro}
%
% \subsubsection{Key Types}
%
% \begin{macro}[internal]{\ekvd@t@set}
% The |set| type is quite straight forward, just define a |NoVal| key to call
% |\ekvchangeset|.
%    \begin{macrocode}
\protected\def\ekvd@t@set#1#2%
  {%
    \ekvd@assert@not@long{set #1}%
    \ekvd@assert@not@protected{set #1}%
    \ekvd@ifnoarg{#2}%
      {\ekvdefNoVal\ekvd@set{#1}{\ekvchangeset{#1}}}%
      {%
        \ekv@ifempty{#2}%
          {\ekvd@err@missing@definition{set #1}}%
          {\ekvdefNoVal\ekvd@set{#1}{\ekvchangeset{#2}}}%
      }%
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[internal]{\ekvd@type@noval,\ekvd@t@noval,\ekvd@t@enoval}
% Another pretty simple type, |noval| just needs to assert that there is a
% definition and that |long| wasn't specified.
% There are types where the difference in the variants is so small, that we
% define a common handler for them, those common handlers are named with
% |@type@|. |noval| and |enoval| are so similar that we can use such a |@type@|
% macro, even if we could've done |noval| in a slightly faster way without it.
%    \begin{macrocode}
\protected\long\def\ekvd@type@noval#1#2#3#4%
  {%
    \ekvd@assert@arg{#1noval #3}{#4}%
      {%
        \ekvd@assert@not@long{#1noval #3}%
        \ekvd@prot#2\ekvd@tmp{#4}%
        \ekvletNoVal\ekvd@set{#3}\ekvd@tmp
      }%
  }
\protected\def\ekvd@t@noval{\ekvd@type@noval{}\def}
\protected\def\ekvd@t@enoval{\ekvd@type@noval e\edef}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[internal]{\ekvd@type@code,\ekvd@t@code,\ekvd@t@ecode}
% |code| is simple as well, |ecode| has to use |\edef| on a temporary macro,
% since \expkv\ doesn't provide an |\ekvedef|.
%    \begin{macrocode}
\protected\long\def\ekvd@type@code#1#2#3#4%
  {%
    \ekvd@assert@arg{#1code #3}{#4}
      {%
        \ekvd@prot\ekvd@long#2\ekvd@tmp##1{#4}%
        \ekvlet\ekvd@set{#3}\ekvd@tmp
      }%
  }
\protected\def\ekvd@t@code{\ekvd@type@code{}\def}
\protected\def\ekvd@t@ecode{\ekvd@type@code e\edef}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[internal]{\ekvd@type@default,\ekvd@t@default,\ekvd@t@qdefault}
% |\ekvd@type@default| asserts there was an argument, also the key for which one
% wants to set a default has to be already defined (this is not so important for
% |default|, but |qdefault| requires is). If everything is good, |\edef| a
% temporary macro that expands |\ekvd@set| and the |\csname| for the key, and in
% the case of |qdefault| does the first expansion step of the key-macro.
%    \begin{macrocode}
\protected\long\def\ekvd@type@default#1#2#3#4%
  {%
    \ekvd@assert@arg{#1default #3}{#4}%
      {%
        \ekvifdefined\ekvd@set{#3}%
          {%
            \ekvd@assert@not@long{#1default #3}%
            \ekvd@prot\edef\ekvd@tmp
              {%
                \unexpanded\expandafter#2%
                  {\csname\ekv@name\ekvd@set{#3}\endcsname{#4}}%
              }%
            \ekvletNoVal\ekvd@set{#3}\ekvd@tmp
          }%
          {\ekvd@err@undefined@key{#3}}%
      }%
  }
\protected\def\ekvd@t@default{\ekvd@type@default{}{}}
\protected\def\ekvd@t@qdefault{\ekvd@type@default q{\expandafter\expandafter}}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[internal]{\ekvd@t@edefault}
% |edefault| is too different from |default| and |qdefault| to reuse the
% |@type@| macro, as it doesn't need |\unexpanded| inside of |\edef|.
%    \begin{macrocode}
\protected\long\def\ekvd@t@edefault#1#2%
  {%
    \ekvd@assert@arg{edefault #1}{#2}%
      {%
        \ekvifdefined\ekvd@set{#1}%
          {%
            \ekvd@assert@not@long{edefault #1}%
            \ekvd@prot\edef\ekvd@tmp
              {\csname\ekv@name\ekvd@set{#1}\endcsname{#2}}%
            \ekvletNoVal\ekvd@set{#1}\ekvd@tmp
          }%
          {\ekvd@err@undefined@key{#1}}%
      }%
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[internal]{\ekvd@t@initial}
%    \begin{macrocode}
\long\def\ekvd@t@initial#1#2%
  {%
    \ekvd@assert@arg{initial #1}{#2}%
      {%
        \ekvifdefined\ekvd@set{#1}%
          {%
            \ekvd@assert@not@long{initial #1}%
            \ekvd@assert@not@protected{initial #1}%
            \csname\ekv@name\ekvd@set{#1}\endcsname{#2}%
          }%
          {\ekvd@err@undefined@key{#1}}%
      }%
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[internal]
%   {\ekvd@type@bool,\ekvd@t@bool,\ekvd@t@gbool,\ekvd@t@boolTF,\ekvd@t@gboolTF}
% The boolean types are a quicker version of a |choice| that accept |true| and
% |false|, and set up the |NoVal| action to be identical to \texttt{\key=true}.
% The |true| and |false| actions are always just |\let|ting the macro in |#7| to
% some other macro (\emph{e.g.}, \cs[no-index]{iftrue}).
%    \begin{macrocode}
\protected\def\ekvd@type@bool#1#2#3#4#5#6#7%
  {%
    \ekvd@assert@filledarg{#1bool#2 #6}{#7}%
      {%
        \ekvd@newlet#7#5%
        \ekvd@type@choice{#1bool#2}{#6}%
        \protected\ekvdefNoVal\ekvd@set{#6}{#3\let#7#4}%
        \protected\expandafter\def
          \csname\ekvd@choice@name\ekvd@set{#6}{true}\endcsname
          {#3\let#7#4}%
        \protected\expandafter\def
          \csname\ekvd@choice@name\ekvd@set{#6}{false}\endcsname
          {#3\let#7#5}%
      }%
  }
\protected\def\ekvd@t@bool{\ekvd@type@bool{}{}{}\iftrue\iffalse}
\protected\def\ekvd@t@gbool{\ekvd@type@bool g{}\global\iftrue\iffalse}
\protected\def\ekvd@t@boolTF{\ekvd@type@bool{}{TF}{}\@firstoftwo\@secondoftwo}
\protected\def\ekvd@t@gboolTF
  {\ekvd@type@bool g{TF}\global\@firstoftwo\@secondoftwo}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[internal]{\ekvd@type@box,\ekvd@t@box,\ekvd@t@gbox}
% Set up our boxes. Though we're a generic package we want to be colour safe, so
% we put an additional grouping level inside the box contents, for the case that
% someone uses \pkg{color}. |\ekvd@newreg| is a small wrapper which tests
% whether the first argument is defined and if not does
% |\csname new#2\endcsname#1|.
%    \begin{macrocode}
\protected\def\ekvd@type@box#1#2#3#4%
  {%
    \ekvd@assert@filledarg{#1box #3}{#4}%
      {%
        \ekvd@newreg#4{box}%
        \protected\ekvd@long\ekvdef\ekvd@set{#3}%
          {#2\setbox#4\hbox{\begingroup##1\endgroup}}%
      }%
  }
\protected\def\ekvd@t@box{\ekvd@type@box{}{}}
\protected\def\ekvd@t@gbox{\ekvd@type@box g\global}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[internal]{\ekvd@type@toks,\ekvd@t@toks,\ekvd@t@gtoks}
% Similar to |box|, but set the |toks|.
%    \begin{macrocode}
\protected\def\ekvd@type@toks#1#2#3#4%
  {%
    \ekvd@assert@filledarg{#1toks #3}{#4}%
      {%
        \ekvd@newreg#4{toks}%
        \protected\ekvd@long\ekvdef\ekvd@set{#3}{#2#4{##1}}%
      }%
  }
\protected\def\ekvd@t@toks{\ekvd@type@toks{}{}}
\protected\def\ekvd@t@gtoks{\ekvd@type@toks{g}\global}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[internal]{\ekvd@type@apptoks,\ekvd@t@apptoks,\ekvd@t@gapptoks}
% Just like |toks|, but expand the current contents of the |toks| register to
% append the new contents.
%    \begin{macrocode}
\protected\def\ekvd@type@apptoks#1#2#3#4%
  {%
    \ekvd@assert@filledarg{#1apptoks #3}{#4}%
      {%
        \ekvd@newreg#4{toks}%
        \protected\ekvd@long\ekvdef\ekvd@set{#3}{#2#4\expandafter{\the#4##1}}%
      }%
  }
\protected\def\ekvd@t@apptoks{\ekvd@type@apptoks{}{}}
\protected\def\ekvd@t@gapptoks{\ekvd@type@apptoks{g}\global}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[internal]
%   {
%     \ekvd@type@reg,\ekvd@t@int,\ekvd@t@eint,\ekvd@t@gint,\ekvd@t@xint,
%     \ekvd@t@dimen,\ekvd@t@edimen,\ekvd@t@gdimen,\ekvd@t@xdimen,
%     \ekvd@t@skip,\ekvd@t@eskip,\ekvd@t@gskip,\ekvd@t@xskip
%   }
% The |\ekvd@type@reg| can handle all the types for which the assignment will
% just be \texttt{\meta{register}=\meta{value}}.
%    \begin{macrocode}
\protected\def\ekvd@type@reg#1#2#3#4#5#6#7%
  {%
    \ekvd@assert@filledarg{#1 #6}{#7}%
      {%
        \ekvd@newreg#7{#2}%
        \protected\ekvd@long\ekvdef\ekvd@set{#6}{#3#7=#4##1#5\relax}%
      }%
  }
\protected\def\ekvd@t@int{\ekvd@type@reg{int}{count}{}{}{}}
\protected\def\ekvd@t@eint{\ekvd@type@reg{eint}{count}{}\numexpr\relax}
\protected\def\ekvd@t@gint{\ekvd@type@reg{gint}{count}\global{}{}}
\protected\def\ekvd@t@xint{\ekvd@type@reg{xint}{count}\global\numexpr\relax}
\protected\def\ekvd@t@dimen{\ekvd@type@reg{dimen}{dimen}{}{}{}}
\protected\def\ekvd@t@edimen{\ekvd@type@reg{edimen}{dimen}{}\dimexpr\relax}
\protected\def\ekvd@t@gdimen{\ekvd@type@reg{gdimen}{dimen}\global{}{}}
\protected\def\ekvd@t@xdimen{\ekvd@type@reg{xdimen}{dimen}\global\dimexpr\relax}
\protected\def\ekvd@t@skip{\ekvd@type@reg{skip}{skip}{}{}{}}
\protected\def\ekvd@t@eskip{\ekvd@type@reg{eskip}{skip}{}\glueexpr\relax}
\protected\def\ekvd@t@gskip{\ekvd@type@reg{gskip}{skip}\global{}{}}
\protected\def\ekvd@t@xskip{\ekvd@type@reg{xskip}{skip}\global\glueexpr\relax}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[internal]{\ekvd@type@store,\ekvd@t@store,\ekvd@t@gstore}
% The none-expanding |store| types use an |\edef| or |\xdef| and |\unexpanded|
% to be able to also store |#| easily.
%    \begin{macrocode}
\protected\def\ekvd@type@store#1#2#3#4%
  {%
    \ekvd@assert@filledarg{#1store #3}{#4}%
      {%
        \unless\ifdefined#4\let#4\ekvd@empty\fi
        \protected\ekvd@long\ekvdef\ekvd@set{#3}{#2#4{\unexpanded{##1}}}%
      }%
  }
\protected\def\ekvd@t@store{\ekvd@type@store{}\edef}
\protected\def\ekvd@t@gstore{\ekvd@type@store{g}\xdef}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[internal]{\ekvd@type@estore,\ekvd@t@estore,\ekvd@t@xstore}
% And the straight forward |estore| types.
%    \begin{macrocode}
\protected\def\ekvd@type@estore#1#2#3#4%
  {%
    \ekvd@assert@filledarg{#1store #3}{#4}%
      {%
        \ekvd@newlet#4\ekvd@empty
        \protected\ekvd@long\ekvdef\ekvd@set{#3}{#2#4{##1}}%
      }%
  }
\protected\def\ekvd@t@estore{\ekvd@type@estore{e}\edef}
\protected\def\ekvd@t@xstore{\ekvd@type@estore{x}\xdef}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[internal]
%   {\ekvd@type@meta,\ekvd@type@meta@,\ekvd@t@meta,\ekvd@t@nmeta}
% |meta| sets up things such that another instance of |\ekvset| will be run on
% the argument, with the same \set.
%    \begin{macrocode}
\protected\long\def\ekvd@type@meta#1#2#3#4#5%
  {%
    \ekvd@assert@filledarg{#1meta #4}{#5}%
      {%
        \edef\ekvd@tmp{\ekvd@set}%
        \expandafter\ekvd@type@meta@\expandafter{\ekvd@tmp}{#3}{#5}%
        #2\ekvd@set{#4}\ekvd@tmp
      }%
  }
\protected\long\def\ekvd@type@meta@#1#2#3%
  {%
    \ekvd@prot\ekvd@long\def\ekvd@tmp#2{\ekvset{#1}{#3}}%
  }
\protected\def\ekvd@t@meta{\ekvd@type@meta{}\ekvlet{##1}}
\protected\long\def\ekvd@t@nmeta#1#2%
  {%
    \ekvd@assert@not@long{nmeta #1}%
    \ekvd@type@meta n\ekvletNoVal{}{#1}{#2}%
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[internal]
%   {\ekvd@type@smeta,\ekvd@type@smeta@,\ekvd@t@smeta,\ekvd@t@snmeta}
% |smeta| is pretty similar to |meta|, but needs two arguments inside of \val,
% such that the first is the \set\ for which the sub-|\ekvset| and the second is
% the \kv\ list.
%    \begin{macrocode}
\protected\long\def\ekvd@type@smeta#1#2#3#4#5%
  {%
    \ekvd@assert@twoargs{s#1meta #4}{#5}%
      {%
        \expandafter\ekvd@type@smeta@\expandafter{\@secondoftwo#5}{#5}{#3}
        #2\ekvd@set{#4}\ekvd@tmp
      }%
  }
\protected\long\def\ekvd@type@smeta@#1#2#3%
  {%
    \expandafter\ekvd@type@meta@\expandafter{\@firstoftwo#2}{#3}{#1}%
  }
\protected\def\ekvd@t@smeta{\ekvd@type@smeta{}\ekvlet{##1}}
\protected\long\def\ekvd@t@snmeta#1#2%
  {%
    \ekvd@assert@not@long{snmeta #1}%
    \ekvd@type@smeta n\ekvletNoVal{}{#1}{#2}%
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[internal]
%   {
%     \ekvd@type@choice,\ekvd@populate@choice,\ekvd@populate@choice@,
%     \ekvd@populate@choice@noarg,\ekvd@choice@prefix,\ekvd@choice@prefix@,
%     \ekvd@choice@p@protected,\ekvd@choice@p@protect,
%     \ekvd@choice@p@long,\ekvd@choice@p@long@,\ekvd@t@choice
%   }
% The |choice| type is by far the most complex type, as we have to run a
% sub-parser on the choice-definition list, which should support the |@p@| type
% prefixes as well (but |long| will always throw an error, as they are not
% allowed to be long). |\ekvd@type@choice| will just define the choice-key, the
% handling of the choices definition will be done by |\ekvd@populate@choice|.
%    \begin{macrocode}
\protected\def\ekvd@type@choice#1#2%
  {%
    \ekvd@assert@not@long{#1 #2}%
    \ekvd@prot\edef\ekvd@tmp##1%
      {%
        \unexpanded{\ekvd@h@choice}{\ekvd@choice@name\ekvd@set{#2}{##1}}%
      }%
    \ekvlet\ekvd@set{#2}\ekvd@tmp
  }
%    \end{macrocode}
% |\ekvd@populate@choice| just uses |\ekvparse| and then gives control to
% |\ekvd@populate@choice@noarg|, which throws an error, and
% |\ekvd@populate@choice@|.
%    \begin{macrocode}
\protected\def\ekvd@populate@choice
  {%
    \ekvparse\ekvd@populate@choice@noarg\ekvd@populate@choice@
  }
\protected\long\def\ekvd@populate@choice@noarg#1%
  {%
    \expandafter\ekvd@err@missing@definition\expandafter{\ekvd@set@choice : #1}%
  }
%    \end{macrocode}
% |\ekvd@populate@choice@| runs the prefix-test, if there is none we can
% directly define the choice, for that |\ekvd@set@choice| will expand to the
% current choice-key's name, which will have been defined by |\ekvd@t@choice|.
% If there is a prefix run the prefix grabbing routine, which was altered for
% |@type@choice|.
%    \begin{macrocode}
\protected\long\def\ekvd@populate@choice@#1#2%
  {%
    \ekvd@clear@prefixes
    \expandafter\ekvd@assert@arg\expandafter{\ekvd@set@choice : #1}{#2}%
      {%
        \ekvd@ifspace{#1}%
          {\ekvd@choice@prefix\ekv@mark#1\ekv@stop}%
          {%
            \expandafter\def
              \csname\ekvd@choice@name\ekvd@set\ekvd@set@choice{#1}\endcsname
          }%
          {#2}%
      }%
  }
\protected\def\ekvd@choice@prefix#1
  {%
    \ekv@strip{#1}\ekvd@choice@prefix@\ekv@mark
  }
\protected\def\ekvd@choice@prefix@#1#2\ekv@stop
  {%
    \ekv@ifdefined{ekvd@choice@p@#1}%
      {%
        \csname ekvd@choice@p@#1\endcsname
        \ekvd@ifspace{#2}%
          {\ekvd@choice@prefix#2\ekv@stop}%
          {%
            \ekvd@prot\expandafter\def
              \csname
                \ekv@strip{#2}{\ekvd@choice@name\ekvd@set\ekvd@set@choice}%
              \endcsname
          }%
      }%
      {\ekvd@err@undefined@prefix{#1}\@gobble}%
  }
\protected\def\ekvd@choice@p@protected{\let\ekvd@prot\protected}
\let\ekvd@choice@p@protect\ekvd@choice@p@protected
\protected\def\ekvd@choice@p@long\ekvd@ifspace#1%
  {%
    \expandafter\ekvd@choice@p@long@\expandafter{\ekv@gobble@mark#1}%
    \ekvd@ifspace{#1}%
  }
\protected\def\ekvd@choice@p@long@#1%
  {%
    \expandafter\ekvd@err@no@long\expandafter
      {\ekvd@set@choice : long #1}%
  }
%    \end{macrocode}
% Finally we're able to set up the |@t@choice| macro, which has to store the
% current choice-key's name, define the key, and parse the available choices.
%    \begin{macrocode}
\protected\long\def\ekvd@t@choice#1#2%
  {%
    \ekvd@assert@arg{choice #1}{#2}%
      {%
        \ekvd@type@choice{choice}{#1}%
        \def\ekvd@set@choice{#1}%
        \ekvd@populate@choice{#2}%
      }%
  }
%    \end{macrocode}
% \end{macro}
%
% \subsubsection{Key Type Helpers}
% There are some keys that might need helpers during their execution (not during
% their definition, which are gathered as |@type@| macros). These helpers are
% named |@h@|.
%
% \begin{macro}[internal]{\ekvd@h@choice,\ekvd@h@choice@}
% The |choice| helper will just test whether the given choice was defined, if
% not throw an error expandably, else call the macro which stores the code for
% this choice.
%    \begin{macrocode}
\def\ekvd@h@choice#1%
  {%
    \expandafter\ekvd@h@choice@
      \csname\ifcsname#1\endcsname#1\else relax\fi\endcsname
      {#1}%
  }
\def\ekvd@h@choice@#1#2%
  {%
    \ifx#1\relax
      \ekvd@err@choice@invalid{#2}%
      \expandafter\@gobble
    \fi
    #1%
  }
%    \end{macrocode}
% \end{macro}
%
% \subsubsection{Tests}
%
% \begin{macro}[internal]{\ekvd@noarg@mark}
% This macro serves as a flag for the case that no \val\ was specified for a
% key. As such it is not a test, but exists only for some tests.
%    \begin{macrocode}
\def\ekvd@noarg@mark{\ekvd@noarg@mark}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[internal]{\ekvd@fi@firstoftwo}
% While we can reuse many of the internals of \expkv\ the specific case for this
% branch wasn't needed by \expkv\ and hence isn't defined. We'll need it, so we
% define it.
%    \begin{macrocode}
\long\def\ekvd@fi@firstoftwo\fi\@secondoftwo#1#2{\fi#1}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[internal]{\ekvd@newlet,\ekvd@newreg}
% These macros test whether a control sequence is defined, if it isn't they
% define it, either via |\let| or via the correct \cs[no-index]{new\meta{reg}}.
%    \begin{macrocode}
\protected\def\ekvd@newlet#1#2%
  {%
    \unless\ifdefined#1\let#1#2\fi
  }
\protected\def\ekvd@newreg#1#2%
  {%
    \unless\ifdefined#1\csname new#2\endcsname#1\fi
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[internal]
%   {\ekvd@assert@twoargs,\ekvd@ifnottwoargs,\ekvd@ifempty@gtwo}
% A test for exactly two tokens can be reduced for an empty-test after gobbling
% two tokens, in the case that there are fewer tokens than two in the argument,
% only macros will be gobbled that are needed for the true branch, which doesn't
% hurt, and if there are more this will not be empty.
%    \begin{macrocode}
\long\def\ekvd@assert@twoargs#1#2%
  {%
    \ekvd@ifnottwoargs{#2}%
      {\ekvd@err@missing@definition{#1}}%
  }
\long\def\ekvd@ifnottwoargs#1%
  {%
    \ekvd@ifempty@gtwo#1\ekv@ifempty@B
      \ekv@ifempty@false\ekv@ifempty@A\ekv@ifempty@B\@firstoftwo
  }
\long\def\ekvd@ifempty@gtwo#1#2{\ekv@ifempty@\ekv@ifempty@A}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[internal]{\ekvd@assert@arg,\ekvd@ifnoarg}
% The test for an argument is just an |\ifx| comparison with our |noarg@mark|.
%    \begin{macrocode}
\long\def\ekvd@assert@arg#1#2%
  {%
    \ekvd@ifnoarg{#2}%
      {\ekvd@err@missing@definition{#1}}%
  }
\long\def\ekvd@ifnoarg#1%
  {%
    \ifx\ekvd@noarg@mark#1%
      \ekvd@fi@firstoftwo
    \fi
    \@secondoftwo
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[internal]{\ekvd@assert@filledarg,\ekvd@ifnoarg@or@empty}
%    \begin{macrocode}
\long\def\ekvd@assert@filledarg#1#2%
  {%
    \ekvd@ifnoarg@or@empty{#2}%
      {\ekvd@err@missing@definition{#1}}%
  }
\long\def\ekvd@ifnoarg@or@empty#1%
  {%
    \ekvd@ifnoarg{#1}%
      \@firstoftwo
      {\ekv@ifempty{#1}}%
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[internal]{\ekvd@assert@not@long,\ekvd@assert@not@protected}
% Some key-types don't want to be |\long| or |\protected|, so we provide macros
% to test this and throw an error, this could be silently ignored but now users
% will learn to not use unnecessary stuff which slows the compilation down.
%    \begin{macrocode}
\long\def\ekvd@assert@not@long#1%
  {%
    \ifx\ekvd@long\long\ekvd@err@no@long{#1}\fi
  }
\long\def\ekvd@assert@not@protected#1%
  {%
    \ifx\ekvd@prot\protected\ekvd@err@no@protected{#1}\fi
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[internal]{\ekvd@ifspace,\ekvd@ifspace@}
% Yet another test which can be reduced to an if-empty, this time by gobbling
% everything up to the first space.
%    \begin{macrocode}
\long\def\ekvd@ifspace#1%
  {%
    \ekvd@ifspace@#1 \ekv@ifempty@B
      \ekv@ifempty@false\ekv@ifempty@A\ekv@ifempty@B\@firstoftwo
  }
\long\def\ekvd@ifspace@#1 % keep this space
  {%
    \ekv@ifempty@\ekv@ifempty@A
  }
%    \end{macrocode}
% \end{macro}
%
% \subsubsection{Messages}
%
% Most messages of \expkvd\ are not expandable, since they only appear during
% key-definition, which is not expandable anyway.
%
% \begin{macro}[internal]
%   {
%     \ekvd@err@missing@definition,\ekvd@err@missing@prefix,
%     \ekvd@err@undefined@prefix,\ekvd@err@undefined@key,\ekvd@err@no@protected,
%     \ekvd@err@no@long
%   }
% The non-expandable error messages are boring, so here they are:
%    \begin{macrocode}
\protected\def\ekvd@err@missing@definition#1%
  {\errmessage{expkv-def Error: Missing definition for key `\unexpanded{#1}'}}
\protected\def\ekvd@err@missing@prefix#1%
  {\errmessage{expkv-def Error: Missing prefix for key `\unexpanded{#1}'}}
\protected\def\ekvd@err@undefined@prefix#1%
  {\errmessage{expkv-def Error: Undefined prefix `\unexpanded{#1}'}}
\protected\def\ekvd@err@undefined@key#1%
  {\errmessage{expkv-def Error: Undefined key `\unexpanded{#1}'}}
\protected\def\ekvd@err@no@protected#1%
  {%
    \errmessage
      {expkv-def Error: prefix `protected' not accepted for `\unexpanded{#1}'}%
  }
\protected\def\ekvd@err@no@long#1%
  {%
    \errmessage
      {expkv-def Error: prefix `long' not accepted for `\unexpanded{#1}'}%
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[internal]
%   {
%     \ekvd@err@choice@invalid,\ekvd@err@choice@invalid@,\ekvd@choice@name,
%     \ekvd@err
%   }
% The expandable error messages use |\ekvd@err|, which is just like |\ekv@err|
% from \expkv\ or the way \pkg{expl3} throws expandable error messages. It uses
% an undefined control sequence to start the error message.
% |\ekvd@err@choice@invalid| will have to use this mechanism to throw its
% message. Also we have to retrieve the name parts of the choice in an easy way,
% so we use parentheses of catcode 8 here, which should suffice in most cases to
% allow for a correct separation.
%    \begin{macrocode}
\def\ekvd@err@choice@invalid#1%
  {%
    \ekvd@err@choice@invalid@#1\ekv@stop
  }
\begingroup
\catcode40=8
\catcode41=8
\@firstofone{\endgroup
\def\ekvd@choice@name#1#2#3%
  {%
    ekvd#1(#2)#3%
  }
\def\ekvd@err@choice@invalid@ ekvd#1(#2)#3\ekv@stop%
  {%
    \ekvd@err{invalid choice `#3' (`#2', set `#1')}%
  }
}
\begingroup
\edef\ekvd@err
  {%
    \endgroup
    \unexpanded{\long\def\ekvd@err}##1%
      {%
        \unexpanded{\expandafter\ekv@err@\@firstofone}%
        {\expandafter\noexpand\csname ! expkv-def Error:\endcsname ##1.}%
        \unexpanded{\ekv@stop}%
      }%
  }
\ekvd@err
%    \end{macrocode}
% \end{macro}
%
% Now everything that's left is to reset the category code of |@|.
%    \begin{macrocode}
\catcode`\@=\ekvd@tmp
%    \end{macrocode}
%
% \gobbledocstriptag
%</tex>
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