% \CheckSum{755}
% \iffalse meta-comment
% forest-index.dtx
%% `forest-index' is an indexing system for the documentation of package
%% `forest', using the package itself.  (The derived `forest-index.sty' is not
%% needed to use the package.)
%%
%% Copyright (c) 2012-2017 Saso Zivanovic
%%                         (Sa\v{s}o \v{Z}ivanovi\'{c})
%% saso.zivanovic@guest.arnes.si
%%
%% This work may be distributed and/or modified under the
%% conditions of the LaTeX Project Public License, either version 1.3
%% of this license or (at your option) any later version.
%% The latest version of this license is in
%% 
%%   http://www.latex-project.org/lppl.txt
%%   
%% and version 1.3 or later is part of all distributions of LaTeX
%% version 2005/12/01 or later.
%%
%% This work has the LPPL maintenance status `author-maintained'.
%%
%% This file is a part of package `forest'. For the list of files
%% constituting the package see main source file of the package,
%% `forest.dtx', or the derived `forest.sty'.
%%
% \fi
%
% \newcommand\entry[1]{{``#1''}}
%
% \subsection{\protect{\texttt{forest-index}}}
% \label{sec:forest-index}
%
% The indexing system used to document the \foRest; package uses the
% package itself quite heavily.  While this might be a bit surprising
% at first sight, as indexing draws no trees, the indexing package
% illustrates the usage of some of the more exotic features and
% usage-cases of the \foRest; package, which is why its source is
% included in this documentation.\footnote{Indexing with this package
% makes the compilation very slow, so I cannot whole-heartedly
% recommend it, but I still hope that it will make a useful example.}
%
% This package has three main functions:
% \begin{itemize}
% \item It is possible to index subentries using a \emph{short form}
%   of their index key, i.e.\ without referring to their ancestor
%   entries.  For example, instead of writing |\index{option>content}|
%   one can simply write |\index{content}|.  (Obviously, the subentry
%   must \entry{content} be defined as belonging to entry
%   \entry{option} first. This is done using
%   |\indexdef{option>content}|.)  This works for all keys which are a
%   subentry of a single entry.
% \item All subentries are automatically entered as main entries as
%   well, with a qualificator of which entry they belong to.  So,
%   |\index{option>content}| produces two index entries: entry
%   \entry{option} with subentry \entry{content} and entry
%   \entry{content \scriptsize option}.  This works for an arbitrary
%   number of subentry levels.
% \item Entries can be given options that format the appearance of the
%   entry and/or its descendants in both text and index. (Entries that
%   format the appearance of their descendants are called categories
%   below.)
% \item If |hyperref| package is loaded, the following hyperlinks are
%   created besides the standard ones linking the page numbers in
%   index to text:
%   \begin{enumerate*}[(i)]
%   \item entries in text link to the definition in text,
%   \item definitions in the text link to the index entry,
%   \item categories in index are cross-linked.
%   \end{enumerate*}
% 
% \end{itemize}
%
% The \foRest; package mainly enters the picture with respect to the
% entry formatting. A simple (narrow) tree is built containing an entry
% and all its ancestors.  Formatting instructions are then processed
% using \foRest;'s option processing mechanisms.
%
% Finally, note that this package might change without retaining
% backwards compatibility, and that changes of this package will not
% be entered into the changelog.
% 
% Identification.
%    \begin{macrocode}
\ProvidesPackage{forest-index}
\RequirePackage{forest}
%    \end{macrocode}
% Remember the original \LaTeX's |\index| command.
%    \begin{macrocode}
\let\forestindex@LaTeX@index\index
%    \end{macrocode}
%    
% \subsubsection*{The user interface macros}
%
% \DescribeMacro{\index} is the general purpose macro.
% \DescribeMacro{\indexdef} and \DescribeMacro{\indexex} are
% shorthands for indexing definitions and
% examples. \DescribeMacro{\indexitem} is a combination of |\indexdef|
% and the |\item| of the |lstdoc| package. It automatically indexes
% the command being documented.  \DescribeMacro{\indexset} neither
% typesets or indexes the entry, but only configures it; it is usually
% used to configure categories.  All these macros parse their
% arguments using |xparse|. The arguments, listed in the reverse
% order:
% \begin{itemize}
% \item The final argument, which is the only mandatory argument, is a
%   comma-separated list of index keys.
% \item The boolean switch |>| just before the mandatory argument
%   signals that the keys are given in the full form. Otherwise, keys
%   without a level separator are considered short.
% \item Indexing options are given by the |[|optional |]| argument.
% \item The first |(|optional|)| argument of:
%   \begin{compactitem}
%   \item |\indexitem|: specifies the default value of the command.
%   \item |\index|: is used to
%     provide ``early'' options.
%   \end{compactitem}
% \end{itemize}
%
% Among the options of these commands, three keylists are of special
% importance: |index_key_format|, |index_form_format| and
% |print_format|.  These hold instructions on how to format the index
% key, the form of the entry in the index and the form of the entry in
% the main text.  They work by modifying the contents of an
% \indexex{autowrapped toks} register |result|.  
%
% An example: how macros are indexed in this documentation. Style
% |macro| defined below does everything needed to format a macro name:
% it detokenizes the given name (in case the name contains some funny
% characters), prefixes the backslash, wraps in in the typewriter
% font, adds color and hyperlink (the final two styles are defined in
% below this package).  Note the usage of |\protect|: it is needed
% because we want to use these styles to format entries not just in
% the main next, but also in the index.
% \lstinputregion{forest-doc.tex}{index_macro_style} Then, we
% configure the main level entry \entry{macro}: the child of this
% entry will be formatted (both in index and in the main text) using
% the previously defined style.
% \lstinputregion{forest-doc.tex}{index_macro_category} Usage is then
% simple: we write |\indexex{macro>forestoption}| (or simply
% |\indexex{forestoption}| to get \indexex{forestoption}.
% 
%    \begin{macrocode}
\DeclareDocumentCommand\indexdef{O{} t> m}{%
  \IfBooleanTF{#2}
    {\let\forestindex@resolvekey\forestindex@resolvekey@long}
    {\let\forestindex@resolvekey\forestindex@resolvekey@shortorlong}%
  \forestindex@index{definition}{#1}{#3}}
\DeclareDocumentCommand\indexex{O{} t> m}{%
  \IfBooleanTF{#2}
    {\let\forestindex@resolvekey\forestindex@resolvekey@long}
    {\let\forestindex@resolvekey\forestindex@resolvekey@shortorlong}%
  \forestindex@index{example}{#1}{#3}}
% \DeclareDocumentCommand\indexitem{D(){} O{} t> m}{%
%   \IfBooleanTF{#3}
%     {\let\forestindex@resolvekey\forestindex@resolvekey@long}
%     {\let\forestindex@resolvekey\forestindex@resolvekey@shortorlong}%
%   \forestindex@index{definition}{default={#1},print format=item,#2}{#4}}
\DeclareDocumentCommand\indexitem{D(){} O{} t> m}{%
  \let\forestindex@resolvekey\forestindex@resolvekey@long
  \forestindex@index{definition}{default={#1},#2,print format+=item}{#4}}
\DeclareDocumentCommand\indexset{O{} t> m}{%
  \IfBooleanTF{#2}
    {\let\forestindex@resolvekey\forestindex@resolvekey@long}
    {\let\forestindex@resolvekey\forestindex@resolvekey@shortorlong}%
  \forestindex@index{not print,not index,definition}{set={#1}}{#3}}
\DeclareDocumentCommand\index{D(){} O{} t> m}{%
  \IfBooleanTF{#3}
    {\let\forestindex@resolvekey\forestindex@resolvekey@long}
    {\let\forestindex@resolvekey\forestindex@resolvekey@shortorlong}%
  \forestindex@index{#1}{#2}{#4}%
}
%    \end{macrocode}
% All UI macros call this macro.
% \begin{arguments}
% \item early option keylist
% \item late option keylist
% \item a comma-sep list of forest index key (full or short form). A
%   key can be given an argument using |key=argument| syntax. How the
%   argument is used is up to the user.  For example, the
%   \entry{environment} entry of the \foRest; documentation uses it to
%   typeset the contents of the environment:
%   \lstinputregion{forest-doc.tex}{forest_environment_doc}
% \end{arguments}
%    \begin{macrocode}
\def\forestindex@index#1#2#3{%
%    \end{macrocode}
% Partition the index keylist into single keys.  And put it all in a group: the
% persistent stuff is saved globally.
%    \begin{macrocode}
  {\forcsvlist{\forestindex@forkey{#1}{#2}}{#3}}%
}
\def\forestindex@forkey#1#2#3{%
%    \end{macrocode}
% Short-key resolution. The result is stored into |\forestindex@fullkey|.
%    \begin{macrocode}
  \forestindex@resolvekey{#3}%
%    \end{macrocode}
% Manipulate arguments a bit, so that we can use our quick-and-dirty one-arg
% memoization.
%    \begin{macrocode}
  %\forestset{@index/.process={__o}{#1}{#2}{\forestindex@fullkey}}
  \edef\forest@marshal{%
    \noexpand\forestindex@index@{%
      {\unexpanded{#1}}%
      {\unexpanded{#2}}%
      {\expandonce{\forestindex@fullkey}}%
    }%
  }\forest@marshal
}
%    \end{macrocode}
% Call the central processing command, style |@index|. See how
% \indexex{handler>process} is used to expand (once) the last argument.
%    \begin{macrocode}
\def\forestindex@index@#1{\forestset{@index/.process={__o}#1}}
\forestset{
%    \end{macrocode}
% \subsubsection*{Declarations}
%
% Should we print and/or index the entry? For example,
% |\index[not_print]{...}| will index silently (as \LaTeX's |\index|
% command does).
%    \begin{macrocode}
  declare boolean register=print,
  declare boolean register=index,
  declare boolean register=short,
%    \end{macrocode}
% Options |name|, |content|, |key| and |argument| hold info about the
% current entry. We need to declare only the latter two, the former
% two we steal from \foRest;.
%    \begin{macrocode}
  declare toks={key}{},
  declare toks={argument}{},
%    \end{macrocode}
% These options will hold first the initial, and then the calculated
% values of the index key, index form and the form in text.  When
% (late) options are executed, these options are initialized to the
% value of option |key|; it is safe to modify them at this point.
% Afterwards, they will be further processed by keylists
% |index_key_format|, |index_form_format| and |print_format|,
% respectively.
%    \begin{macrocode}
  declare toks={index key}{},
  declare toks={index form}{},
  declare toks={print form}{},
%    \end{macrocode}
% The customization of entries' appearance is done by specifying the
% following three keylists.  The keylists work by modifying register
% |result|.
%    \begin{macrocode}
  declare keylist={index key format}{},
  declare keylist={index format}{},
  declare keylist={print format}{},
  declare autowrapped toks register=result,
%    \end{macrocode}
% Some shorthands.
%    \begin{macrocode}
  format'/.style={print format'={#1}, index format'={#1}},
  format/.style={print format={#1}, index format={#1}},
  format+/.style={print format+={#1}, index format+={#1}},
  +format/.style={+print format={#1}, +index format={#1}},
  form/.style={print form={#1},index form={#1}},
  form+/.style={print form+={#1},index form+={#1}},
  +form/.style={+print form={#1},+index form={#1}},
%    \end{macrocode}
% Entry types are normal (default), definition, example.  Only
% definitions are special, as their options are automatically saved.
%    \begin{macrocode}
  declare toks register=index entry type,
  definition/.style={index entry type=definition},
  normal/.style={index entry type=normal},
  example/.style={index entry type=example},
  normal,
%    \end{macrocode}
% This option is used internally to store the hyper ids.
%    \begin{macrocode}
  declare toks={index@hypertarget}{},
  every index begin/.style={},
  every index end/.style={},
%    \end{macrocode}
% Some formatting tools need to know whether we're typesetting text or
% index: this info is stored in the |stage| register.\indexex[margin]{declare toks register}
%    \begin{macrocode}
  declare toks register=stage,
%    \end{macrocode}
%    
% \subsubsection*{The central processing command}
% \begin{arguments}
% \item early option keylist (these are only used to define category
%   ``@unknown'' at the end of this package)
% \item late option keylist
% \item index key (full form)
% \end{arguments}
%    \begin{macrocode}
  @index/.style n args={3}{
%    \end{macrocode}
% Set the defaults.
%    \begin{macrocode}
    print, index, index entry type=normal, set'={}, short,
%    \end{macrocode}
% Create the tree structure:
% |[entry[subentry[subsubentry...]]]|. Three options of every node
% created:
% \begin{compactitem}
% \item |key| contains the key of the (sub)entry
% \item |name| contains the full path to the (sub)entry
% \item |arguments| contains the arguments given to the (sub)entry's key
% \item |content| contains the full key, with arguments for all but
%   the most deeply embedded subentry
% \end{compactitem}
% \indexex{for step=\indexex{nodewalk}} is used because
% |create@subentry@node| walks down the created tree. At |if n=0|
% below, we're thus positioned at the lowest node.\indexex[margin]{step>nodewalk}
%    \begin{macrocode}
    for nodewalk={
%    \end{macrocode}
% The components of the full key are separated using \indexex{split},
% with different keys being executed for the first component and the
% rest.
%    \begin{macrocode}
      split={#3}{>}{create@main@entry@node, create@subentry@node},
%    \end{macrocode}
% Remove the argument from the most deeply embedded subentry.
%    \begin{macrocode}
      if n=0{
        content/.option=key,
      }{
        content/.process={OOw2} {!parent.content} {key} {##1>##2},
      }
    }{},
    for root'={
%    \end{macrocode}
% Don't memoize if the key is of an unknown category.
%    \begin{macrocode}
      if strequal/.process={O}{!root.name}{@unknown}{TeX=\global\forest@memoizing@ok@false}{},
%    \end{macrocode}
% Option |print_form| is what will be typeset in the text.  Option
% |index_key| is the key that will be used for sorting the
% index. Option |index_form| is what will be typeset in the index. All
% these are initialized to the |key|.  See how
% \indexex{handler>option} is used to assign an option value to
% another option.
%    \begin{macrocode}
      for tree={
        print form/.option=key,
        index key/.option=key,
        index form/.option=key,
      },
%    \end{macrocode}
% Below, \indexex{node key>on invalid} is set to \indexex{value of=on invalid>fake} at four points.
% This is so we won't get in trouble when |\indexset|ting the
% categories: when the category formatting code will try to step into
% the child, it will fail as the child does not exist when |\indexset|
% is called for the category; but we ignore the failure.
%
% Go to the the most deeply embedded subentry.\indexex[margin]{first leaf'}
%    \begin{macrocode}
      for first leaf'={
%    \end{macrocode} 
% Execute every index options and the given early options.
%    \begin{macrocode}
        on invalid={fake}{
          every index begin,
          #1,
        },
%    \end{macrocode}
% Ancestors are walked in the \indexex{reverse} order (top down).  At
% every node, the saved configuration is executed (if it exists).
%    \begin{macrocode}
        for reverse={current and ancestors}{on invalid={fake}{@@index/\forestoption{name}/.try}},
%    \end{macrocode}
% We don't execute the saved configuration for definitions, as
% definitions are where the configuration is set.
%    \begin{macrocode}
        if index entry type={definition}{}{%
          on invalid={fake}{@@index/\forestoption{name}/.try},
        },
%    \end{macrocode}
% Execute late (well, normal) options. See the discussion about early
% options above.
%    \begin{macrocode}
        on invalid={fake}{
          #2,
          every index end
        },
%    \end{macrocode}
% Remember the given config for the rest of the document.
%    \begin{macrocode}
        if set={}{}{save@session},
%    \end{macrocode}
% If we're at a definition, save the config into the auxiliary file.
%    \begin{macrocode}
        if index entry type={definition}{save@foridx}{},
      },
      stage={},
%    \end{macrocode}
% Create hyperlink targets of the form |.entry.subentry.subsubentry...|.
%
% \FoRest; points:
% \begin{enumerate*}[(i)]
% \item the generic conditional \indexex{if},
% \item handler \index{handler>process},
% \end{enumerate*}
%    \begin{macrocode}
      if index={
        index@hypertarget/.process={OS_= ? l_ w2}
         {index key}
         {}
         {}{.}
         {##2##1},
        for descendants={
          index@hypertarget/.process={OO S _l1= ? w2 }
            {!parent.index@hypertarget}{index key}
            {}
            {##1}      % empty index key
            {##1.##2}  % otherwise
        },
      }{},
%    \end{macrocode}
% Index.
%    \begin{macrocode}
      if index={
        begingroup,
        stage=index,
%    \end{macrocode}
% For each (sub)entry, format the |index_key| using the instructions
% in |index_key_format|.
%    \begin{macrocode}
        for tree={
          result/.option=index key,
          process keylist'={index key format}{current},
          index key/.register=result,
        },
%    \end{macrocode}
% For each (sub)entry, format the |index_form| using the instructions
% in |index_form_format|.
%    \begin{macrocode}
        for tree={
          result/.option=index form,
          process keylist'={index format}{current},
          index form/.register=result,
        },
%    \end{macrocode}
% Create an index entry for all nodes where |index_form| is non-empty.
%    \begin{macrocode}
        where index form={}{}{
%    \end{macrocode}
% All the ancestor nodes with an non-empty |index_form| will be
% appended (in script size, as a hyperlink) to the |index_form| of the
% current node.
%    \begin{macrocode}
          if n=0{
            temptoksb={},
          }{
            temptoksc={},
            for ancestors={
              if index form={}{}{
                temptoksb+/.expanded={\forestregister{temptoksc}%
                  \noexpand\protect\noexpand\hyperlinknocolor{%
                    \forestoption{index@hypertarget}}{\forestoption{index form}}},
                temptoksc={,\space},
              },
            },
            if temptoksb={}{}{
              +temptoksb={\protect\space\begingroup\protect\scriptsize},
              temptoksb+={\endgroup},
            },
          },
          temptoksa={},
          result'={},
          if n children=0{tempboola}{not tempboola},
          where index form={}{}{
%    \end{macrocode}
% Create the hypertarget that the definitions in text and other index entries
% will point to.
%    \begin{macrocode}
            temptoksd/.expanded={\noexpand\protect\noexpand\hypertarget{%
                  \forestoption{index@hypertarget}}{}},
%    \end{macrocode}
% Add the (inner) current node to the index entry of the (outer) current node.
%    \begin{macrocode}
            result+/.expanded={%
              \forestregister{temptoksa}%
              \forestoption{index key}%
              =\forestoption{index form}%
              \forestregister{temptoksd}%
              \forestregister{temptoksb}%
            },
            temptoksa={>},
            temptoksb={},
          },
%    \end{macrocode}
% Do the actual indexing.
%    \begin{macrocode}
          result+/.expanded={|indexpagenumber\forestregister{index entry type}},
          TeX and memoize/.expanded={\noexpand\forestindex@LaTeX@index{\forestregister{result}}},
        },
        endgroup
      }{},
      if print={
        begingroup,
        stage=print,
%    \end{macrocode}
% For each (sub)entry, format the |print_form| using the instructions
% in |print_form_format|.
%    \begin{macrocode}
        for tree={
          result/.option=print form,
          process keylist'={print format}{current},
          print form/.register=result,
        },
%    \end{macrocode}
% Typeset the entry in the text.
%    \begin{macrocode}
        for first leaf'={TeX and memoize/.expanded={\forestoption{print form}}},
        endgroup,
      }{},
    }
  },
%    \end{macrocode}
% Create the main entry node and set to be the root.
%    \begin{macrocode}
  create@main@entry@node/.style={% #1 = subentry
    set root={[]},
    do dynamics, for root'={process delayed=tree},
    root',
    setup@entry@node={#1}
  },
%    \end{macrocode}
% Create a subentry node and move into it.
%    \begin{macrocode}
  create@subentry@node/.style={
    append={[]},
    do dynamics, for root'={process delayed=tree},
    n=1,
    setup@entry@node={#1}
  },
%    \end{macrocode}
% Parse \#1 into |key| and |argument|, and assign |name| and |content|.
%    \begin{macrocode}
  setup@entry@node/.style={
    options={
      split={#1}{=}{key,argument},
      if n=0{
        name'/.option=key,
        content={#1},
      }{
        name'/.process={OOw2} {!parent.name} {key} {##1>##2},
        content/.process={Ow1} {!parent.content} {##1>#1},
      },
    }
  },
}
%    \end{macrocode}
% \subsubsection*{Saving and loading the options}
%    \begin{macrocode}
\forestset{
%    \end{macrocode}
% This register holds whatever we need to remember.
%    \begin{macrocode}
  declare keylist register=set,
%    \end{macrocode}
% Besides storing the keylist in the register, also immediately
% execute it.\indexex[margin]{Autoforward register}.
%    \begin{macrocode}
  Autoforward register={set}{##1},
%    \end{macrocode}
% Remember things by saving them in a global style.
%    \begin{macrocode}
  save@session/.style={@@index/\forestoption{name}/.global style/.register=set},
%    \end{macrocode}
% Save thinks to the auxiliary file.
%    \begin{macrocode}
  save@foridx/.style={
%    \end{macrocode}
% Don't save entries of unknown category.
%    \begin{macrocode}
    if strequal/.process={O}{!root.name}{@unknown}{}{
%    \end{macrocode}
% Don't save if nothing is set.
%    \begin{macrocode}
      if set={}{}{
        TeX and memoize/.expanded={%
          \noexpand\immediate\noexpand\write\noexpand\forestindex@out{%
            \noexpand\string\noexpand\indexloadsettings\noexpand\unexpanded{{\forestoption{name}}{\forestregister{set}}}%
          }%
        },
      },
    },
%    \end{macrocode}
% Save the full form of the key in the auxiliary file. Obviously, do
% it only for subentries.  The full form contains whatever arguments
% were given to the non-last component.
%    \begin{macrocode}
    if key/.process={O}{content} {} {%
      if short={
        TeX and memoize/.expanded={%
          \noexpand\immediate\noexpand\write\noexpand\forestindex@out{%
            \noexpand\string\noexpand\indexdefineshortkey\noexpand\unexpanded{{\forestoption{key}}{\forestoption{content}}}%
          }%
        }%
      }{}
    }
  }
}
%    \end{macrocode}
% Load settings from the auxiliary file into the global style.  Warn
% if anything was configured more than once (e.g.\ by |\indexdef|ing
% the same key twice).
%    \begin{macrocode}
\def\indexloadsettings#1#2{%
  \pgfkeysifdefined{/forest/@@index/#1/.@cmd}{%
    \forestindex@loadsettings@warning{#1}%
  }{}%
  % #s in #2 are doubled; the following \def removes one layer of doubling
  \def\forest@temp{#2}%
  \forestset{@@index/#1/.global style/.expand once=\forest@temp}%
}
\def\forestindex@loadsettings@warning#1{%
  \PackageWarning{forest-index}{Forest index key "#1" was configured more than once!
    I'm using the last configuration.}%
}
%    \end{macrocode}
% Load the full form of a short key from the auxiliary file. Out of
% kindness for the end user, remember all the full keys corresponding
% to a short key: this will make a more informative warning below.
%    \begin{macrocode}
\def\indexdefineshortkey#1#2{%
  \def\forestindex@temp@short{#1}%
  \def\forestindex@temp@long{#2}%
  \ifx\forestindex@temp@short\forestindex@temp@long
  \else
    \ifcsdef{index@long@#1}{%
      \global\cslet{index@long@#1}\relax
      \csgappto{index@alllong@#1}{,#2}%
    }{%
      \global\csgdef{index@long@#1}{#2}%
      \global\csgdef{index@alllong@#1}{#2}%
    }%
  \fi
}
%    \end{macrocode}
% \subsubsection*{Short key resolution}
%
% Nothing to do for a long key.
%    \begin{macrocode}
\def\forestindex@resolvekey@long#1{\def\forestindex@fullkey{#1}}
%    \end{macrocode}
% Decide whether a key is short or long based on the absence or
% presence of the level separator |>|.
%    \begin{macrocode}
\def\forestindex@resolvekey@shortorlong#1{%
  \pgfutil@in@>{#1}%
  \ifpgfutil@in@
    \expandafter\def\expandafter\forestindex@fullkey
  \else
    \expandafter\forestindex@resolvekey@short
  \fi
  {#1}%
}
%    \end{macrocode}
% Before resolving the short key, we need to split the user input into
% the key and the argument. The latter is then appended to the full
% key (which can, in principle, contain arguments for other components
% as well).
%    \begin{macrocode}
\def\forestindex@resolvekey@short#1{%
  \forestset{split={#1}{=}{index@resolveshortkey@key,index@resolveshortkey@arg}}%
}
\forestset{
  index@resolveshortkey@key/.code={%
    \ifcsvoid{index@long@#1}{%
      \forestindex@resolveshortkey@warning{#1}%
      \def\forestindex@fullkey{@unknown>#1}%
    }{%
      \letcs\forestindex@fullkey{index@long@#1}%
    }%
  },
  index@resolveshortkey@arg/.code={%
    \appto\forestindex@fullkey{=#1}%
  },
}
\def\forestindex@resolveshortkey@warning#1{%
  \PackageWarning{forest-index}{Cannot resolve short forest index key "#1".
    These are the definitions I found (from the previous run):
    "\csuse{index@alllong@#1}"}%
}
%    \end{macrocode}
% \subsubsection*{Formatting styles}
% 
% Define default colors for index entry types and provide a style that
% typesets the entry in text (but not index) in the desired color.
%    \begin{macrocode}
\forestset{
  normal color/.initial=blue,
  definition color/.initial=red,
  example color/.initial=darkgreen,
  print in color/.style={if stage={print}{result/.expanded=\noexpand\protect\noexpand\textcolor{%
        \pgfkeysvalueof{/forest/#1 color}}{\unexpanded{##1}}}{}},
  print in color/.default=\forestregister{index entry type},
%    \end{macrocode}
% Use this style in |..._format| keylists if you want the index
% entries to be hyperlinks to the definition, and the definition to be
% a hyperlink to the index.
%    \begin{macrocode}
  hyper/.style={
    if stage={index}{}{
      if index entry type={definition}{
        result/.expanded={\noexpand\hypertarget{\forestoption{name}}%
          {\noexpand\hyperlink{\forestoption{index@hypertarget}}{\forestregister{result}}}}
      }{
        result/.expanded=\noexpand\hyperlink{\forestoption{name}}{\forestregister{result}}
      }
    }
  },
}
%    \end{macrocode}
% Color page numbers in the index, with or without |hyperref| package.
%    \begin{macrocode}
\ifdef\hyperpage{%
  \newcommand\indexpagenumbernormal[1]{{%
      \hypersetup{linkcolor=\pgfkeysvalueof{/forest/normal color}}\hyperpage{#1}}}
  \newcommand\indexpagenumberdefinition[1]{{%
      \hypersetup{linkcolor=\pgfkeysvalueof{/forest/definition color}}\hyperpage{#1}}}
  \newcommand\indexpagenumberexample[1]{{%
      \hypersetup{linkcolor=\pgfkeysvalueof{/forest/example color}}\hyperpage{#1}}}
}{
  \newcommand\indexpagenumbernormal[1]{%
    \textcolor{\pgfkeysvalueof{/forest/normal color}}{#1}}
  \newcommand\indexpagenumberdefinition[1]{%
    \textcolor{\pgfkeysvalueof{/forest/definition color}}{#1}}
  \newcommand\indexpagenumberexample[1]{%
    \textcolor{\pgfkeysvalueof{/forest/example color}}{#1}}
}
%    \end{macrocode}
% Provide dummy |\hyper...| commands if |hyperref| is not loaded.
%    \begin{macrocode}
\providecommand\hyperlink[2]{#2}
\providecommand\hypertarget[2]{#2}
\providecommand\hypersetup[1]{}
%    \end{macrocode}
% This is used by entry qualifiers: we want them to be hyperlinks, but black.
%    \begin{macrocode}
\newcommand\hyperlinknocolor[2]{{\hypersetup{linkcolor=black}\hyperlink{#1}{#2}}}
%    \end{macrocode}
%    
% Use style |item| to have the index entry (in text) function as the
% |\item| of a |lstdoc|'s |syntax| environment.
%    \begin{macrocode}
\forestset{
  declare toks register=default,
  default={},
  item/.style={
    result/.process= {_RORw4}
      {} {default} {!parent.print form} {result}
      {\item[,##2,##3]{##4}},
  },
}
%    \end{macrocode}
% 
% \subsubsection*{Utilities}
%    
% We will need a global version of several |pgfkeys| commands.
%    \begin{macrocode}
\pgfkeys{/handlers/.global style/.code=\pgfkeys{\pgfkeyscurrentpath/.global code=\pgfkeysalso{#1}}}
\pgfkeysdef{/handlers/.global code}{\pgfkeysglobaldef{\pgfkeyscurrentpath}{#1}}
\long\def\pgfkeysglobaldef#1#2{%
  \long\def\pgfkeys@temp##1\pgfeov{#2}%
  \pgfkeysgloballet{#1/.@cmd}{\pgfkeys@temp}%
  \pgfkeysglobalsetvalue{#1/.@body}{#2}%
}
\def\pgfkeysgloballet#1#2{%
  \expandafter\global\expandafter\let\csname pgfk@#1\endcsname#2%
}
\long\def\pgfkeysglobalsetvalue#1#2{%
  \pgfkeys@temptoks{#2}\expandafter\xdef\csname pgfk@#1\endcsname{\the\pgfkeys@temptoks}%
}
\forestset{
  % unlike pgfmath function strequal, |if strequal| does not expand the compared args!
  if strequal/.code n args={4}{\ifstrequal{#1}{#2}{\pgfkeysalso{#3}}{\pgfkeysalso{#4}}},
}
%    \end{macrocode}
% Begin and end group, \foRest;-style:
%    \begin{macrocode}
\forestset{
  begingroup/.code={\begingroup},
  endgroup/.code={\endgroup},
}
%    \end{macrocode}
%
% \subsubsection{Memoize}
%
% Quick and dirty memoization. Single argument macros only. Does not support nesting.
% 
%    \begin{macrocode}
\newtoks\forest@memo@key
\newtoks\forest@memo
\newif\ifforest@memoizing@now@
\newif\ifforest@memoizing@ok@
\newif\ifforest@execandmemoize@
\def\forest@memoize#1{% #1 = \cs
  \cslet{forest@memo@orig@\string#1}#1%
  \def#1##1{%
    \ifforest@memoizing@now@
      \forest@globalsaveandrestoreifcs{forest@execandmemoize@}{%
        \global\forest@execandmemoize@false
        \csname forest@memo@orig@\string#1\endcsname{##1}%
      }%
    \else
      \expandafter\global\expandafter\forest@memo@key\expandafter{\detokenize{forest@memo@#1{##1}}}%
      \ifcsname\the\forest@memo@key\endcsname
        \@escapeifif{\csname\the\forest@memo@key\endcsname}%
      \else
        \@escapeifif{%
          \global\forest@memo{}%
          \global\forest@memoizing@ok@true
          \global\forest@memoizing@now@true
          \global\forest@execandmemoize@true
          \csname forest@memo@orig@\string#1\endcsname{##1}%
          \global\forest@execandmemoize@false
          \global\forest@memoizing@now@false
          \ifforest@memoizing@ok@
            \csxdef{\the\forest@memo@key}{\the\forest@memo}%
            \immediate\write\forest@memo@out{%
              \noexpand\forest@memo@load{\the\forest@memo@key}{\the\forest@memo}%
            }%
          \fi
        }%
      \fi
    \fi
  }%
}
\def\forest@memo@load#1#2{%
%    \end{macrocode}
% The following two |\def|s remove one level of hash-doubling from the
% arguments, introduced by |\write|.
%    \begin{macrocode}
  \def\forest@temp@key{#1}%
  \def\forest@temp@value{#2}%
  \csxdef{\detokenize\expandafter{\forest@temp@key}}{\expandonce\forest@temp@value}%
  \immediate\write\forest@memo@out{%
    \noexpand\forest@memo@load{\detokenize\expandafter{\forest@temp@key}}{\detokenize\expandafter{\forest@temp@value}}%
  }%
}
\forestset{
  TeX and memoize/.code={\forest@execandmemoize{#1}},
}
\def\forest@execandmemoize#1{%
  \ifforest@execandmemoize@
    \let\forest@memo@next\forest@execandmemoize@
  \else
    \let\forest@memo@next\@gobble
  \fi
  \forest@memo@next{#1}%
  #1%
}
\def\forest@execandmemoize@#1{%
  \gapptotoks\forest@memo{#1}%
}
\def\forest@memo@filename{\jobname.memo}
\newwrite\forest@memo@out
\immediate\openout\forest@memo@out=\forest@memo@filename.tmp
\IfFileExists{\forest@memo@filename}{%
  \input\forest@memo@filename\relax
}{}%
\AtEndDocument{%
  \immediate\closeout\forest@memo@out
  \forest@file@copy{\forest@memo@filename.tmp}{\forest@memo@filename}%
}
%    \end{macrocode}
% Commenting the following line turns off memoization.
%    \begin{macrocode}
\forest@memoize\forestindex@index@
%    \end{macrocode}
%
% \subsubsection*{Initialize}
%
% Declare category ``@unknown''.
%    \begin{macrocode}
\index(not print,not index)[%
    set={
      index key=unknown,
      form={\textbf{unknown!!}},
      for first={format={result/.expanded=\noexpand\textbf{\forestregister{result}??}}}
    },
  ]>{@unknown}
%    \end{macrocode}
% Load the auxiliary file made in the previous compilation, and open
% it for writing to save data from this compilation.
%    \begin{macrocode}
\def\forestindex@filename{\jobname.foridx}
\IfFileExists{\forestindex@filename}{%
  \input\forestindex@filename\relax
}{}%
\newwrite\forestindex@out
\immediate\openout\forestindex@out=\forestindex@filename.tmp
\AtEndDocument{%
  \immediate\closeout\forestindex@out
  \forest@file@copy{\forestindex@filename.tmp}{\forestindex@filename}%
}
\endinput
%    \end{macrocode}
%    
%%% \iffalse
%%% Local Variables:
%%% mode: doctex
%%% TeX-master: "forest-doc"
%%% TeX-command-default: "sty"
%%% End:
%%% \fi