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+%D \module
+%D   [       file=syst-aux, % merge of syst-gen cum suis
+%D        version=1996.03.20,
+%D          title=\CONTEXT\ System Macros,
+%D       subtitle=General,
+%D         author=Hans Hagen,
+%D           date=\currentdate,
+%D      copyright={PRAGMA ADE \& \CONTEXT\ Development Team}]
+%C
+%C This module is part of the \CONTEXT\ macro||package and is
+%C therefore copyrighted by \PRAGMA. See mreadme.pdf for
+%C details.
+
+\registerctxluafile{syst-aux}{}
+
+%D This fils is a follow up in \type {syst-aux.mkii} and \type {syst-aux.mkiv}
+%D where you can find some more pure \TEX\ or \LUATEX| variants.
+
+\unprotect
+
+%D \macros
+%D   {unexpanded}
+%D
+%D Because we use this module only in \MKIV, we have removed the old protection
+%D code.
+%D
+%D \starttyping
+%D \unexpanded\def\somecommand{... ... ...}
+%D \stoptyping
+%D
+%D This overloads the \ETEX\ primitive but as we already had an \MKII\ solution we
+%D keep the same name for a similar mechanism.
+
+\let\unexpanded\normalprotected
+
+\ifcase\contextlmtxmode
+
+    \def\startlmtxmode#1\stoplmtxmode{}
+    \let\stoplmtxmode \relax
+    \let\startmkivmode\relax
+    \let\stopmkivmode \relax
+
+\else
+
+    \let\startlmtxmode\relax
+    \let\stoplmtxmode \relax
+    \def\startmkivmode#1\stopmkivmode{}
+    \let\stopmkivmode \relax
+
+\fi
+
+%D As we don't have namespace definers yet, we use a special one:
+
+\ifdefined\c_syst_helpers_n_of_namespaces
+
+    % lets plug in a better error message
+
+\else
+
+    \newcount\c_syst_helpers_n_of_namespaces \c_syst_helpers_n_of_namespaces\pluseight % 1-8 reserved for catcodes
+
+    \def\v_interfaces_prefix_template_system{\number    \c_syst_helpers_n_of_namespaces>>}
+    %def\v_interfaces_prefix_template_system{\characters\c_syst_helpers_n_of_namespaces>>} % no \characters yet
+
+\fi
+
+\unexpanded\def\installsystemnamespace#1% maybe move this to syst-ini
+  {\ifcsname ??#1\endcsname
+     \writestatus\m!system{duplicate system namespace '#1'}\wait
+   \else
+     \global\advance\c_syst_helpers_n_of_namespaces\plusone
+     \expandafter\edef\csname ??#1\endcsname{\v_interfaces_prefix_template_system}%
+   \fi}
+
+%D \macros
+%D   {normalspace}
+%D
+%D There is already \type{\space} but just to be sure we also provide:
+
+\def\normalspace{ }
+
+%D \macros
+%D   {!!count, !!toks, !!dimen, !!box,
+%D    !!width, !!height, !!depth, !!string, !!done}
+%D
+%D We define some more \COUNTERS\ and \DIMENSIONS. We also define some shortcuts to
+%D the local scatchregisters~0, 2, 4, 6 and~8.
+
+\newcount\!!counta \newtoks\!!toksa \newdimen\!!dimena \newbox\!!boxa
+\newcount\!!countb \newtoks\!!toksb \newdimen\!!dimenb \newbox\!!boxb
+\newcount\!!countc \newtoks\!!toksc \newdimen\!!dimenc \newbox\!!boxc
+\newcount\!!countd \newtoks\!!toksd \newdimen\!!dimend \newbox\!!boxd
+\newcount\!!counte \newtoks\!!tokse \newdimen\!!dimene \newbox\!!boxe
+\newcount\!!countf \newtoks\!!toksf \newdimen\!!dimenf \newbox\!!boxf
+                                    \newdimen\!!dimeng
+                                    \newdimen\!!dimenh
+                                    \newdimen\!!dimeni
+                                    \newdimen\!!dimenj
+                                    \newdimen\!!dimenk
+
+\let\!!stringa\empty \let\!!stringb\empty \let\!!stringc\empty
+\let\!!stringd\empty \let\!!stringe\empty \let\!!stringf\empty
+
+\newdimen\!!widtha \newdimen\!!heighta \newdimen\!!deptha
+\newdimen\!!widthb \newdimen\!!heightb \newdimen\!!depthb
+\newdimen\!!widthc \newdimen\!!heightc \newdimen\!!depthc
+\newdimen\!!widthd \newdimen\!!heightd \newdimen\!!depthd
+
+\newif\if!!donea   \newif\if!!doneb    \newif\if!!donec
+\newif\if!!doned   \newif\if!!donee    \newif\if!!donef
+
+\def\!!zerocount {0} % alongside \zerocount
+\def\!!minusone {-1} % ...
+\def\!!plusone   {1} % ...
+\def\!!plustwo   {2} % ...
+\def\!!plusthree {3} % ...
+\def\!!plusfour  {4} % ...
+\def\!!plusfive  {5} % ...
+\def\!!plussix   {6} % ...
+\def\!!plusseven {7} % ...
+\def\!!pluseight {8} % ...
+\def\!!plusnine  {9} % alongside \plusnine
+
+\setnewconstant   \uprotationangle    0
+\setnewconstant\rightrotationangle   90
+\setnewconstant \downrotationangle  180
+\setnewconstant \leftrotationangle  270
+
+\ifdefined\data \else \let\data \relax \fi % dep checker
+
+%D \macros
+%D   {s!,c!,e!,p!,v!,@@,??}
+%D
+%D To save memory, we use constants (sometimes called variables). Redefining these
+%D constants can have disastrous results.
+
+\def\v!prefix! {v!}
+\def\c!prefix! {c!}
+\def\s!prefix! {s!}
+
+\def\s!next    {next}
+\def\s!default {default}
+\def\s!dummy   {dummy}
+\def\s!unknown {unknown}
+
+\def\s!do      {do}
+\def\s!dodo    {dodo}
+
+\def\s!complex {complex}
+\def\s!start   {start}
+\def\s!simple  {simple}
+\def\s!stop    {stop}
+
+\def\s!empty   {empty}
+
+%D Sometimes we pass macros as arguments to commands that don't expand them
+%D before interpretation. Such commands can be enclosed with \type {\expanded},
+%D like:
+%D
+%D \starttyping
+%D \expanded{\setupsomething[\alfa]}
+%D \stoptyping
+%D
+%D Such situations occur for instance when \type{\alfa} is a commalist or when data
+%D stored in macros is fed to index of list commands. If needed, one should use
+%D \type{\noexpand} inside the argument. Later on we will meet some more clever
+%D alternatives to this command. Beware, only the simple one has \type {\noexpand}
+%D before its argument.
+
+\let\m_syst_helpers_expanded\empty
+
+\unexpanded\def\expanded#1%
+  {\xdef\m_syst_helpers_expanded{\noexpand#1}\m_syst_helpers_expanded}
+
+\unexpanded\def\startexpanded#1\stopexpanded
+  {\xdef\m_syst_helpers_expanded{#1}\m_syst_helpers_expanded}
+
+\let\stopexpanded\relax
+
+%D Recent \TEX\ engines have a primitive \type {\expanded} and we will use that when
+%D possible. After all, we can make not expandable macros now.
+
+% We cannot use the next variant as first we need to adapt \type {##}'s in callers:
+%
+% \def\expanded#1%
+%   {\normalexpanded{\noexpand#1}}
+%
+% \def\startexpanded#1\stopexpanded
+%   {\normalexpanded{#1}}
+
+%D \macros
+%D   {gobbleoneargument,gobble...arguments}
+%D
+%D The next set of macros just do nothing, except that they get rid of a number of
+%D arguments.
+
+\def\gobbleoneargument   #1{}
+\def\gobbletwoarguments  #1#2{}
+\def\gobblethreearguments#1#2#3{}
+\def\gobblefourarguments #1#2#3#4{}
+\def\gobblefivearguments #1#2#3#4#5{}
+\def\gobblesixarguments  #1#2#3#4#5#6{}
+\def\gobblesevenarguments#1#2#3#4#5#6#7{}
+\def\gobbleeightarguments#1#2#3#4#5#6#7#8{}
+\def\gobbleninearguments #1#2#3#4#5#6#7#8#9{}
+\def\gobbletenarguments  #1{\gobbleninearguments}
+
+\def\gobbleoneoptional   [#1]{}
+\def\gobbletwooptionals  [#1][#2]{}
+\def\gobblethreeoptionals[#1][#2][#3]{}
+\def\gobblefouroptionals [#1][#2][#3][#4]{}
+\def\gobblefiveoptionals [#1][#2][#3][#4][#5]{}
+
+%D Reserved macros for tests:
+
+\let\donothing\empty
+
+\let\m_syst_string_one  \empty
+\let\m_syst_string_two  \empty
+\let\m_syst_string_three\empty
+\let\m_syst_string_four \empty
+
+\let\m_syst_action_yes  \empty
+\let\m_syst_action_nop  \empty
+
+%D \macros
+%D   {doifnextcharelse}
+%D
+%D When we started using \TEX\ in the late eighties, our first experiences with
+%D programming concerned a simple shell around \LATEX. The commands probably use
+%D most at \PRAGMA, are the itemizing ones. One of those few shell commands took
+%D care of an optional argument, that enabled us to specify what kind of item symbol
+%D we wanted. Without understanding anything we were able to locate a \LATEX\ macro
+%D that could be used to inspect the next character.
+%D
+%D It's this macro that the ancester of the next one presented here. It executes one
+%D of two actions, dependant of the next character. Disturbing spaces and line
+%D endings, which are normally interpreted as spaces too, are skipped.
+%D
+%D \starttyping
+%D \doifnextcharelse {karakter} {then ...} {else ...}
+%D \stoptyping
+%D
+%D This macro differs from the original in the use of \type {\localnext} because we
+%D don't want clashes with \type {\next}.
+
+\let\next          \relax
+\let\nextnext      \relax
+\let\nextnextnext  \relax
+\let\nexttoken     \relax
+\let\charactertoken\relax
+
+\let\m_syst_action_yes\relax
+\let\m_syst_action_nop\relax
+
+% \def\syst_helpers_inspect_next_character
+%   {\ifx\nexttoken\blankspace
+%      \expandafter\syst_helpers_reinspect_next_character
+%    \else
+%      \expandafter\syst_helpers_inspect_next_character_indeed
+%    \fi}
+%
+% \def\syst_helpers_inspect_next_character_indeed
+%   {\ifx\nexttoken\charactertoken
+%      \expandafter\m_syst_action_yes
+%    \else
+%      \expandafter\m_syst_action_nop
+%    \fi}
+
+\unexpanded\def\doifelsenextchar#1#2#3% #1 should not be {} !
+  {\def\m_syst_action_yes{#2}%
+   \def\m_syst_action_nop{#3}%
+   \futureexpandis#1\m_syst_action_yes\m_syst_action_nop}
+
+\unexpanded\def\doifelsenextcharcs % #1#2#3% #1 should not be {} !
+  {\futureexpandis}
+
+\let\doifnextcharelse  \doifelsenextchar
+\let\doifnextcharcselse\doifelsenextcharcs
+
+%D Because we will mostly use this macro for testing if the next character is \type
+%D {[}, we also make a slightly faster variant as it is not uncommon to have tens of
+%D thousands of calls to this test in a run. Of course it also is more convenient to
+%D read a trace then.
+
+% \newif\if_next_blank_space_token
+
+% \let\syst_helpers_next_optional_character_token=[
+%
+% \def\syst_helpers_inspect_next_optional_character
+%   {\ifx\nexttoken\blankspace
+%      \expandafter\syst_helpers_reinspect_next_optional_character
+%    \else
+%      \expandafter\syst_helpers_inspect_next_optional_character_indeed
+%    \fi}
+%
+% \def\syst_helpers_inspect_next_optional_character_indeed
+%   {\ifx\nexttoken\syst_helpers_next_optional_character_token
+%      \expandafter\m_syst_action_yes
+%    \else
+%      \expandafter\m_syst_action_nop
+%    \fi}
+
+\unexpanded\def\doifelsenextoptional#1#2%
+  {\def\m_syst_action_yes{#1}%
+   \def\m_syst_action_nop{#2}%
+   \futureexpandis[\m_syst_action_yes\m_syst_action_nop}
+
+\unexpanded\def\doifelsenextoptionalcs
+  {\futureexpandis[}
+
+\let\doifnextoptionalelse  \doifelsenextoptional
+\let\doifnextoptionalcselse\doifelsenextoptionalcs
+
+% \let\syst_helpers_next_bgroup_character_token\bgroup
+%
+% \def\syst_helpers_inspect_next_bgroup_character
+%   {\ifx\nexttoken\blankspace
+%      \expandafter\syst_helpers_reinspect_next_bgroup_character
+%    \else
+%      \expandafter\syst_helpers_inspect_next_bgroup_character_indeed
+%    \fi}
+%
+% \def\syst_helpers_inspect_next_bgroup_character_indeed
+%   {\ifx\nexttoken\syst_helpers_next_bgroup_character_token
+%      \expandafter\m_syst_action_yes
+%    \else
+%      \expandafter\m_syst_action_nop
+%    \fi}
+
+\unexpanded\def\doifelsenextbgroup#1#2%
+  {\def\m_syst_action_yes{#1}%
+   \def\m_syst_action_nop{#2}%
+   \futureexpandis\bgroup\m_syst_action_yes\m_syst_action_nop}
+
+\unexpanded\def\doifelsenextbgroupcs % #1#2
+  {\futureexpandis\bgroup}
+
+\let\doifnextbgroupelse  \doifelsenextbgroup
+\let\doifnextbgroupcselse\doifelsenextbgroupcs
+
+% \let\syst_helpers_next_parenthesis_character_token(
+%
+% \def\syst_helpers_inspect_next_parenthesis_character
+%   {\ifx\nexttoken\blankspace
+%      \expandafter\syst_helpers_reinspect_next_parenthesis_character
+%    \else
+%      \expandafter\syst_helpers_inspect_next_parenthesis_character_indeed
+%    \fi}
+%
+% \def\syst_helpers_inspect_next_parenthesis_character_indeed
+%   {\ifx\nexttoken\syst_helpers_next_parenthesis_character_token
+%      \expandafter\m_syst_action_yes
+%    \else
+%      \expandafter\m_syst_action_nop
+%    \fi}
+
+\unexpanded\def\doifelsenextparenthesis#1#2%
+  {\def\m_syst_action_yes{#1}%
+   \def\m_syst_action_nop{#2}%
+   \futureexpandis(\m_syst_action_yes\m_syst_action_nop}
+
+\let\doifnextparenthesiselse\doifelsenextparenthesis
+
+%D The next one is handy in predictable situations:
+
+\def\syst_helpers_do_if_fast_optional_check_else
+  {\ifx\nexttoken\syst_helpers_next_optional_character_token
+     \expandafter\m_syst_action_yes
+   \else
+     \expandafter\m_syst_action_nop
+   \fi}
+
+\unexpanded\def\doifelsefastoptionalcheck#1#2%
+  {\def\m_syst_action_yes{#1}%
+   \def\m_syst_action_nop{#2}%
+   \futureexpandis[\m_syst_action_yes\m_syst_action_nop}
+
+\unexpanded\def\doifelsefastoptionalcheckcs
+  {\futureexpandis[}
+
+\let\doiffastoptionalcheckelse  \doifelsefastoptionalcheck
+\let\doiffastoptionalcheckcselse\doifelsefastoptionalcheckcs
+
+%D Here's one for skipping spaces and pars, handy for:
+%D
+%D \starttyping
+%D \hbox
+%D
+%D   {a few lines later}
+%D \stoptyping
+%D
+%D like:
+%D
+%D \starttyping
+%D \def\somecommand{\dowithnextbox{\box\nextbox}\ruledhbox}
+%D
+%D \assumelongusagecs\somecommand
+%D
+%D \bgroup
+%D     oeps
+%D \egroup
+%D \stoptyping
+
+%D The cumbersome original:
+
+% \unexpanded\def\assumelongusagecs#1%
+%   {\let\m_syst_action#1%
+%    \futurelet\nexttoken\syst_helpers_ignore_spacing}
+%
+% \def\syst_helpers_ignore_spacing
+%   {\ifx\nexttoken\blankspace
+%      \expandafter\syst_helpers_ignore_spacing_blankspace
+%    \orelse\ifx\nexttoken\par
+%      \expandafter\syst_helpers_ignore_spacing_partoken
+%    \else
+%      \expandafter\m_syst_action
+%    \fi}
+%
+% \def\syst_helpers_ignore_spacing_partoken\par
+%   {\futurelet\nexttoken\syst_helpers_ignore_spacing}
+
+%D A bit less tracing noise:
+
+% \def\assume_long_usage_cs
+%   {\futureexpandis\par\assume_long_usage_par\m_syst_action}
+%
+% \def\assume_long_usage_par\par%
+%   {\assume_long_usage_cs}
+%
+% \unexpanded\def\assumelongusagecs#1{\let\m_syst_action#1\assume_long_usage_cs}
+
+%D Ok, using \type {\futureexpandisap} is maybe feature creep but I'd like to experiment
+%D with more tolerant user input. It might go away in which case we use the above.
+
+\unexpanded\def\assumelongusagecs#1%
+  {\futureexpandisap\relax#1#1}
+
+% D These macros use some auxiliary macros. Although we were able to program quite
+% D complicated things, I only understood these after rereading the \TEX book. The
+% D trick is in using a command with a one character name. Such commands differ from
+% D the longer ones in the fact that trailing spaces are {\em not} skipped. This
+% D enables us to indirectly define a long named macro that gobbles a space. In the
+% D first line we define \type {\blankspace}. Next we make \type {\:} equivalent to
+% D \type {\reinspect...}. This one||character command is expanded before the next
+% D \type {\def} comes into action. This way the space after \type {\:} becomes a
+% D delimiter of the longer named \type {\reinspectnextcharacter}.
+
+\let\next\:
+
+\def\:{\let\blankspace= }  \:
+
+% \def\:{\syst_helpers_reinspect_next_character}
+% \expandafter\def\: {\let\if_next_blank_space_token\iftrue\futurelet\nexttoken\syst_helpers_inspect_next_character}
+%
+% \def\:{\syst_helpers_reinspect_next_optional_character}
+% \expandafter\def\: {\let\if_next_blank_space_token\iftrue\futurelet\nexttoken\syst_helpers_inspect_next_optional_character}
+%
+% \def\:{\syst_helpers_reinspect_next_bgroup_character}
+% \expandafter\def\: {\let\if_next_blank_space_token\iftrue\futurelet\nexttoken\syst_helpers_inspect_next_bgroup_character}
+%
+% \def\:{\syst_helpers_reinspect_next_parenthesis_character}
+% \expandafter\def\: {\let\if_next_blank_space_token\iftrue\futurelet\nexttoken\syst_helpers_inspect_next_parenthesis_character}
+%
+% \def\:{\syst_helpers_ignore_spacing_blankspace}
+% \expandafter\def\: {\futurelet\nexttoken\syst_helpers_ignore_spacing}
+
+\let\:\next
+
+%D \macros
+%D   {setvalue,setgvalue,setevalue,setxvalue,
+%D    letvalue,letgvalue,getvalue,resetvalue,
+%D    undefinevalue,ignorevalue}
+%D
+%D \TEX's primitive \type {\csname} can be used to construct all kind of commands
+%D that cannot be defined with \type {\def} and \type {\let}. Every macro programmer
+%D sooner or later wants macros like these.
+%D
+%D \starttyping
+%D \setvalue   {name}{...} = \def\name{...}
+%D \setgvalue  {name}{...} = \gdef\name{...}
+%D \setevalue  {name}{...} = \edef\name{...}
+%D \setxvalue  {name}{...} = \xdef\name{...}
+%D \letvalue   {name}=\... = \let\name=\...
+%D \letgvalue  {name}=\... = \glet\name=\...
+%D \getvalue   {name}      = \name
+%D \resetvalue {name}      = \def\name{}
+%D \stoptyping
+%D
+%D As we will see, \CONTEXT\ uses these commands many times, which is mainly due to
+%D its object oriented and parameter driven character.
+
+\def\setvalue     #1{\expandafter\def \csname#1\endcsname}
+\def\setgvalue    #1{\expandafter\gdef\csname#1\endcsname}
+\def\setevalue    #1{\expandafter\edef\csname#1\endcsname}
+\def\setxvalue    #1{\expandafter\xdef\csname#1\endcsname}
+\def\getvalue     #1{\csname#1\endcsname} % maybe: \begincsname#1\endcsname
+\def\letvalue     #1{\expandafter\let \csname#1\endcsname}
+\def\letgvalue    #1{\expandafter\glet\csname#1\endcsname}
+\def\resetvalue   #1{\expandafter\let \csname#1\endcsname\empty}
+\def\undefinevalue#1{\expandafter\let \csname#1\endcsname\undefined}
+\def\ignorevalue#1#2{\expandafter\let \csname#1\endcsname\empty}
+
+\def\setuvalue    #1{\normalprotected\expandafter \def\csname#1\endcsname}
+\def\setuevalue   #1{\normalprotected\expandafter\edef\csname#1\endcsname}
+\def\setugvalue   #1{\normalprotected\expandafter\gdef\csname#1\endcsname}
+\def\setuxvalue   #1{\normalprotected\expandafter\xdef\csname#1\endcsname}
+
+\unexpanded\def\getuvalue#1{\csname#1\endcsname}
+
+%D \macros
+%D   {globallet,glet}
+%D
+%D In \CONTEXT\ of May 2000 using \type {\globallet} instead of the two tokens will
+%D save us some $300\times4=1200$ bytes of format file on a 32~bit system. Not that
+%D it matters much today. This shortcut is already defined:
+
+\let\globallet\glet
+
+%D \macros
+%D   {doifundefined,doifdefined,
+%D    doifundefinedelse,doifdefinedelse,
+%D    doifalldefinedelse}
+%D
+%D The standard way of testing if a macro is defined is comparing its meaning with
+%D another undefined one, usually \type{\undefined}. To garantee correct working of
+%D the next set of macros, \type{\undefined} may never be defined!
+%D
+%D \starttyping
+%D \doifundefined      {string}    {...}
+%D \doifdefined        {string}    {...}
+%D \doifundefinedelse  {string}    {then ...} {else ...}
+%D \doifdefinedelse    {string}    {then ...} {else ...}
+%D \doifalldefinedelse {commalist} {then ...} {else ...}
+%D \stoptyping
+%D
+%D Every macroname that \TEX\ builds gets an entry in the hash table, which is of
+%D limited size. It is expected that \ETEX\ will offer a less memory||consuming
+%D alternative.
+
+%D Although it will probably never be a big problem, it is good to be aware of the
+%D difference between testing on a macro name to be build by using \type{\csname} and
+%D \type{\endcsname} and testing the \type{\name} directly.
+%D
+%D \starttyping
+%D \expandafter\ifx\csname NameA\endcsname\relax ... \else ... \fi
+%D
+%D \ifundefined\NameB ... \else ... \fi
+%D \stoptyping
+
+% \suppressifcsnameerror\plusone % already set
+
+\def\doifelseundefined#1%
+  {\ifcsname#1\endcsname
+     \expandafter\secondoftwoarguments\else\expandafter\firstoftwoarguments
+   \fi}
+
+\def\doifelsedefined#1%
+  {\ifcsname#1\endcsname
+     \expandafter\firstoftwoarguments\else\expandafter\secondoftwoarguments
+   \fi}
+
+\def\doifundefined#1%
+  {\ifcsname#1\endcsname
+     \expandafter\gobbleoneargument\else\expandafter\firstofoneargument
+   \fi}
+
+\def\doifdefined#1%
+  {\ifcsname#1\endcsname
+     \expandafter\firstofoneargument\else\expandafter\gobbleoneargument
+   \fi}
+
+\let\doifundefinedelse\doifelseundefined
+\let\doifdefinedelse  \doifelsedefined
+
+%D \macros
+%D   {letbeundefined}
+%D
+%D Testing for being undefined comes down to testing on \type {\relax} when we use
+%D \type {\csname}, but when using \type {\ifx}, we test on being \type
+%D {\undefined}! In \ETEX\ we have \type {\ifcsname} and that way of testing on
+%D existance is not the same as the one described here. Therefore we introduce:
+
+\unexpanded\def\letbeundefined#1% potential stack buildup when used \global
+  {\expandafter\let\csname#1\endcsname\undefined} % or use \undefinevalue to match \setvalue
+
+\unexpanded\def\localundefine#1% conditional
+  {\ifcsname#1\endcsname\expandafter\let\csname#1\endcsname\undefined\fi}
+
+\unexpanded\def\globalundefine#1% conditional
+  {\ifcsname#1\endcsname\expandafter\glet\csname#1\endcsname\undefined\fi}
+
+%D Beware, being \type {\undefined} in \ETEX\ means that the macro {\em is} defined!
+%D
+%D When we were developing the scientific units module, we encountered different
+%D behavior in text and math mode, which was due to this grouping subtilities. We
+%D therefore decided to use \type{\begingroup} instead of \type{\bgroup}.
+
+\unexpanded\def\doifelsealldefined#1%
+  {\begingroup
+   \donetrue % we could use a reserved one and avoid the group
+   \processcommalist[#1]\syst_helpers_do_if_all_defined_else
+   \ifdone
+     \endgroup\expandafter\firstoftwoarguments
+   \else
+     \endgroup\expandafter\secondoftwoarguments
+   \fi}
+
+\let\doifalldefinedelse\doifelsealldefined
+
+\def\syst_helpers_do_if_all_defined_else#1%
+  {\ifcsname#1\endcsname\else
+     \donefalse
+     \expandafter\quitcommalist % added
+   \fi}
+
+%D \macros
+%D   {doif,doifelse,doifnot}
+%D
+%D Programming in \TEX\ differs from programming in procedural languages like
+%D \MODULA. This means that one --- well, let me speek for myself --- tries to do
+%D the things in the well known way. Therefore the next set of \type{\ifthenelse}
+%D commands were between the first ones we needed. A few years later, the opposite
+%D became true: when programming in \MODULA, I sometimes miss handy things like
+%D grouping, runtime redefinition, expansion etc. While \MODULA\ taught me to
+%D structure, \TEX\ taught me to think recursive.
+%D
+%D \starttyping
+%D \doif     {string1} {string2} {...}
+%D \doifnot  {string1} {string2} {...}
+%D \doifelse {string1} {string2} {then ...}{else ...}
+%D \stoptyping
+
+\unexpanded\def\doifelse#1#2%
+  {\iftok{#1}{#2}%
+     \expandafter\firstoftwoarguments
+   \else
+     \expandafter\secondoftwoarguments
+   \fi}
+
+\unexpanded\def\doif#1#2%
+  {\iftok{#1}{#2}%
+     \expandafter\firstofoneargument
+   \else
+     \expandafter\gobbleoneargument
+   \fi}
+
+\unexpanded\def\doifnot#1#2%
+  {\iftok{#1}{#2}%
+     \expandafter\gobbleoneargument
+   \else
+     \expandafter\firstofoneargument
+   \fi}
+
+%D \macros
+%D   {doifempty,doifemptyelse,doifnotempty}
+%D
+%D We complete our set of conditionals with:
+%D
+%D \starttyping
+%D \doifempty     {string} {...}
+%D \doifnotempty  {string} {...}
+%D \doifemptyelse {string} {then ...} {else ...}
+%D \stoptyping
+%D
+%D This time, the string is not expanded.
+
+\unexpanded\def\doifelseempty#1%
+  {\def\m_syst_string_one{#1}%
+   \ifx\m_syst_string_one\empty
+     \expandafter\firstoftwoarguments
+   \else
+     \expandafter\secondoftwoarguments
+   \fi}
+
+\let\doifemptyelse\doifelseempty
+
+\unexpanded\def\doifempty#1%
+  {\def\m_syst_string_one{#1}%
+   \ifx\m_syst_string_one\empty
+     \expandafter\firstofoneargument
+   \else
+     \expandafter\gobbleoneargument
+   \fi}
+
+\unexpanded\def\doifnotempty#1%
+  {\def\m_syst_string_one{#1}%
+   \ifx\m_syst_string_one\empty
+     \expandafter\gobbleoneargument
+   \else
+     \expandafter\firstofoneargument
+   \fi}
+
+%D \macros
+%D   {doifinset,doifnotinset,doifinsetelse}
+%D
+%D We can check if a string is present in a comma separated set of strings.
+%D Depending on the result, some action is taken.
+%D
+%D \starttyping
+%D \doifinset     {string} {string,...} {...}
+%D \doifnotinset  {string} {string,...} {...}
+%D \doifinsetelse {string} {string,...} {then ...} {else ...}
+%D \stoptyping
+
+% !0nop=\doifinsetelse{ccc}{,}{yes}{nop}
+% !0nop=\doifinsetelse{ccc}{,,}{yes}{nop}
+% !0nop=\doifinsetelse{ccc}{,,,}{yes}{nop}
+
+% !1nop=\doifinsetelse{}{}{yes}{nop}
+% !2yes=\doifinsetelse{aaa}{bbb,ccc,ddd,aaa,eee}{yes}{nop}
+% !3nop=\doifinsetelse{aaa}{bbb}{yes}{nop}
+% !4yes=\doifinsetelse{aaa}{aaa}{yes}{nop}
+% !5nop=\doifinsetelse{aaaa}{bbb,ccc,ddd,aaa,eee}{yes}{nop}
+% !6nop=\doifinsetelse{}{}{yes}{nop}
+% !7nop=\doifinsetelse{}{aaa}{yes}{nop}
+% !8nop=\doifinsetelse{aaa}{}{yes}{nop}
+
+% !1=\doifinset{}{}{yes}
+% !2yes=\doifinset{aaa}{bbb,ccc,ddd,aaa,eee}{yes}
+% !3=\doifinset{aaa}{bbb}{yes}
+% !4yes=\doifinset{aaa}{aaa}{yes}
+% !5=\doifinset{}{}{yes}
+% !6=\doifinset{aaa}{}{yes}
+
+% !1yes=\doifnotinset{}{}{yes}
+% !2=\doifnotinset{aaa}{bbb,ccc,ddd,aaa,eee}{yes}
+% !3yes=\doifnotinset{aaa}{bbb}{yes}
+% !4=\doifnotinset{aaa}{aaa}{yes}
+% !5yes=\doifnotinset{}{}{yes}
+% !6yes=\doifnotinset{aaa}{}{yes}
+
+\unexpanded\def\doifelseinset#1#2{\clf_doifelseinset{#1}{#2}}
+\unexpanded\def\doifinset    #1#2{\clf_doifinset    {#1}{#2}}
+\unexpanded\def\doifnotinset #1#2{\clf_doifnotinset {#1}{#2}}
+         % \let\firstinset        \clf_firstinset
+
+\let\doifinsetelse\doifelseinset
+
+%D \macros
+%D   {doifcommon,doifnotcommon,doifcommonelse}
+%D
+%D Probably the most time consuming tests are those that test for overlap in sets
+%D of strings.
+%D
+%D \starttyping
+%D \doifcommon     {string,...} {string,...} {...}
+%D \doifnotcommon  {string,...} {string,...} {...}
+%D \doifcommonelse {string,...} {string,...} {then ...} {else ...}
+%D \stoptyping
+
+% !1yes=\doifcommonelse{aaa,bbb,ccc}{aaa,bbb,ccc}{yes}{nop}
+% !2nop=\doifcommonelse{aaa,bbb,ccc}{ddd,eee,fff}{yes}{nop}
+% !3nop=\doifcommonelse{aaa}{ddd,eee,fff}{yes}{nop}
+% !4yes=\doifcommonelse{aaa}{aaa}{yes}{nop}
+% !5nop=\doifcommonelse{bbb}{aaa}{yes}{nop}
+% !6nop=\doifcommonelse{}{aaa,bbb,ccc}{yes}{nop}
+% !7nop=\doifcommonelse{aaa,bbb,ccc}{}{yes}{nop}
+% !8nop=\doifcommonelse{}{}{yes}{nop}
+
+% !9nop=\doifcommonelse{,,}{,,}{yes}{nop}
+% !9yes=\doifcommonelse{,a,}{,a,}{yes}{nop}
+% !9yes=\doifcommonelse{,,a,}{,a,}{yes}{nop}
+% !9yes=\doifcommonelse{,a,}{,,a,}{yes}{nop}
+% !9yes=\doifcommonelse{,a,}{,,,a,}{yes}{nop}
+% !9yes=\doifcommonelse{,,a,}{,,,a,}{yes}{nop}
+
+\unexpanded\def\doifelsecommon#1#2{\clf_doifelsecommon{#1}{#2}}
+\unexpanded\def\doifcommon    #1#2{\clf_doifcommon    {#1}{#2}}
+\unexpanded\def\doifnotcommon #1#2{\clf_doifnotcommon {#1}{#2}}
+
+\let\doifcommonelse\doifelsecommon
+
+%D \macros
+%D   {processcommalist,processcommacommand,quitcommalist,
+%D    processcommalistwithparameters}
+%D
+%D We've already seen some macros that take care of comma separated lists. Such
+%D list can be processed with
+%D
+%D \starttyping
+%D \processcommalist[string,string,...]\commando
+%D \stoptyping
+%D
+%D The user supplied command \type{\commando} receives one argument: the string.
+%D This command permits nesting and spaces after commas are skipped. Empty sets
+%D are no problem.
+%D
+%D \startbuffer
+%D \def\dosomething#1{(#1)}
+%D
+%D 1: \processcommalist [\hbox{$a,b,c,d,e,f$}] \dosomething \par
+%D 2: \processcommalist [{a,b,c,d,e,f}]        \dosomething \par
+%D 3: \processcommalist [{a,b,c},d,e,f]        \dosomething \par
+%D 4: \processcommalist [a,b,{c,d,e},f]        \dosomething \par
+%D 5: \processcommalist [a{b,c},d,e,f]         \dosomething \par
+%D 6: \processcommalist [{a,b}c,d,e,f]         \dosomething \par
+%D 7: \processcommalist []                     \dosomething \par
+%D 8: \processcommalist [{[}]                  \dosomething \par
+%D \stopbuffer
+%D
+%D \typebuffer
+%D
+%D Before we show the result, we present the macro's:
+
+\newcount\commalevel
+
+\installsystemnamespace{nextcommalevel}
+
+\def\syst_helpers_do_do_do_process_comma_item
+  {\csname\??nextcommalevel\the\commalevel\endcsname}
+
+% \ifcase\contextlmtxmode
+
+    \def\syst_helpers_do_process_comma_item
+      {\futurelet\nexttoken\syst_helpers_do_do_process_comma_item}
+
+    \def\syst_helpers_do_do_process_comma_item
+      {\ifx\nexttoken\blankspace
+         \expandafter\syst_helpers_re_do_process_comma_item
+       \else
+         \expandafter\syst_helpers_do_do_process_comma_item_indeed
+       \fi}
+
+    \def\syst_helpers_do_do_process_comma_item_indeed
+      {\ifx\nexttoken]%
+         \expandafter\gobbleoneargument
+       \else
+         \expandafter\syst_helpers_do_do_do_process_comma_item
+       \fi}
+
+% \else
+%
+%     \def\syst_helpers_do_process_comma_item
+%       {\futureexpandis]\gobbleoneargument\syst_helpers_do_do_do_process_comma_item}
+%
+% \fi
+
+%D Empty arguments are not processed. Empty items (\type {,,}) however are
+%D treated. We have to check for the special case \type {[{a,b,c}]}.
+
+\unexpanded\def\processcommalist[%
+  {\futurelet\nexttoken\syst_helpers_do_check_comma_item}
+
+\def\syst_helpers_do_check_comma_item
+  {\ifx\nexttoken]%
+     \expandafter\gobblethreearguments
+   \else
+     \expandafter\syst_helpers_do_process_comma_list
+   \fi
+   \relax} % this one preserved the next {}
+
+\def\syst_helpers_do_process_comma_list#1]#2%
+  {\global\advance\commalevel \plusone
+   \expandafter\def\csname\??nextcommalevel\the\commalevel\endcsname##1,%
+     {#2{##1}\syst_helpers_do_process_comma_item}%
+   \syst_helpers_do_do_process_comma_item_gobble#1,]\relax
+   \global\advance\commalevel \minusone }
+
+\def\syst_helpers_do_do_process_comma_item_gobble#1{\syst_helpers_do_do_process_comma_item}
+
+%D One way of quitting a commalist halfway is:
+
+\unexpanded\def\quitcommalist
+  {\begingroup\let\syst_helpers_do_process_comma_item\syst_helpers_do_quit_comma_list}
+
+\def\syst_helpers_do_quit_comma_list#1]%
+  {\endgroup}
+
+\unexpanded\def\quitprevcommalist
+  {\begingroup\let\syst_helpers_do_process_comma_item\syst_helpers_do_quit_prev_comma_list}
+
+\def\syst_helpers_do_quit_prev_comma_list#1]%
+  {\let\syst_helpers_do_process_comma_item\syst_helpers_do_quit_comma_list}
+
+%D The hack we used for checking the next character \type {\doifnextcharelse}
+%D is also used here.
+
+% \ifcase\contextlmtxmode
+
+    \let\next\:
+
+    \def\:{\syst_helpers_re_do_process_comma_item} % \:not saved ?
+
+    \expandafter\def\: {\futurelet\nexttoken\syst_helpers_do_do_process_comma_item}
+
+    \let\:\next
+
+% \fi
+
+%D The previous examples lead to:
+%D
+%D \getbuffer
+
+%D When a list is saved in a macro, we can use a construction like:
+%D
+%D \starttyping
+%D \expandafter\processcommalist\expandafter[\list]\command
+%D \stoptyping
+%D
+%D Such solutions suit most situations, but we wanted a bit more.
+%D
+%D \starttyping
+%D \processcommacommand[string,\stringset,string]\commando
+%D \stoptyping
+%D
+%D where \type{\stringset} is a predefined set, like:
+%D
+%D \starttyping
+%D \def\first{aap,noot,mies}
+%D \def\second{laatste}
+%D
+%D \processcommacommand[\first]\message
+%D \processcommacommand[\first,second,third]\message
+%D \processcommacommand[\first,between,\second]\message
+%D \stoptyping
+%D
+%D Commands that are part of the list are expanded, so the use of this macro has its
+%D limits.
+
+\unexpanded\def\processcommacommand[#1]%
+  {\normalexpanded{\processcommalist[#1]}}
+
+%D The argument to \type{\command} is not delimited. Because we often use \type {[]}
+%D as delimiters, we also have:
+%D
+%D \starttyping
+%D \processcommalistwithparameters[string,string,...]\command
+%D \stoptyping
+%D
+%D where \type{\command} looks like:
+%D
+%D \starttyping
+%D \def\command[#1]{... #1 ...}
+%D \stoptyping
+
+\unexpanded\def\processcommalistwithparameters[#1]#2%
+  {\def\syst_helpers_do_process_comma_list_with_parameters##1{#2[##1]}%
+   \processcommalist[#1]\syst_helpers_do_process_comma_list_with_parameters}
+
+%D \macros
+%D   {startprocesscommalist,startprocesscommacommand}
+%D
+%D Two more:
+
+\let\syst_helpers_comma_list_step\relax
+
+\unexpanded\def\startprocesscommalist[#1]#2\stopprocesscommalist
+  {\def\syst_helpers_comma_list_step##1{\def\currentcommalistitem{##1}#2}%
+   \processcommalist[#1]\syst_helpers_comma_list_step}
+
+\unexpanded\def\startprocesscommacommand[#1]#2\stopprocesscommacommand
+  {\def\syst_helpers_comma_list_step##1{\def\currentcommalistitem{##1}#2}%
+   \normalexpanded{\processcommalist[#1]}\syst_helpers_comma_list_step}
+
+\let\stopprocesscommalist   \relax
+\let\stopprocesscommacommand\relax
+
+%D \macros
+%D   {processaction,
+%D    processfirstactioninset,
+%D    processallactionsinset}
+%D
+%D \CONTEXT\ makes extensive use of a sort of case or switch command. Depending of
+%D the presence of one or more provided items, some actions is taken. These macros
+%D can be nested without problems.
+%D
+%D \starttyping
+%D \processaction           [x]     [a=>\a,b=>\b,c=>\c]
+%D \processfirstactioninset [x,y,z] [a=>\a,b=>\b,c=>\c]
+%D \processallactionsinset  [x,y,z] [a=>\a,b=>\b,c=>\c]
+%D \stoptyping
+%D
+%D We can supply both a \type {default} action and an action to be undertaken when
+%D an \type {unknown} value is met:
+%D
+%D \starttyping
+%D \processallactionsinset
+%D   [x,y,z]
+%D   [      a=>\a,
+%D          b=>\b,
+%D          c=>\c,
+%D    default=>\default,
+%D    unknown=>\unknown{... \commalistelement ...}]
+%D \stoptyping
+%D
+%D When \type {#1} is empty, this macro scans list \type {#2} for the keyword \type
+%D {default} and executed the related action if present. When \type {#1} is non
+%D empty and not in the list, the action related to \type {unknown} is executed.
+%D Both keywords must be at the end of list \type{#2}. Afterwards, the actually
+%D found keyword is available in \type {\commalistelement}. An advanced example of
+%D the use of this macro can be found in \PPCHTEX, where we completely rely on \TEX\
+%D for interpreting user supplied keywords like \type {SB}, \type {SB1..6}, \type
+%D {SB125} etc.
+
+\newcount\processlevel
+
+\unexpanded\def\syst_helpers_do_compare_process_action_a[#1=>#2][#3]%
+  {\edef\m_syst_string_two{#1}%
+   \ifx\m_syst_string_two\s!default
+     \let\commalistelement\empty
+     #2%
+   \fi}
+
+% met \quitcommalist tot meer dan 25\% sneller
+
+\unexpanded\def\syst_helpers_do_compare_process_action_b[#1=>#2][#3]%
+  {\edef\m_syst_string_two{#1}%
+   \ifx\m_syst_string_one\m_syst_string_two
+     \def\commalistelement{#3}%
+     #2%
+     \expandafter\quitcommalist
+   \orelse\ifx\m_syst_string_two\s!unknown
+     \def\commalistelement{#3}% beware of loops
+     #2%
+   \fi}
+
+\unexpanded\def\processaction[#1]#2[%
+  {\edef\m_syst_string_one{#1}%
+   \ifx\m_syst_string_one\empty
+     \let\syst_helpers_do_compare_process_action\syst_helpers_do_compare_process_action_a
+   \else
+     \let\syst_helpers_do_compare_process_action\syst_helpers_do_compare_process_action_b
+   \fi
+   \edef\syst_helpers_do_process_action##1{\syst_helpers_do_compare_process_action[##1][#1]}% expands #1
+   \processnextcommalist\relax\relax\syst_helpers_do_process_action[}
+
+\unexpanded\def\syst_helpers_do_compare_process_action_c[#1=>#2][#3]%
+  {\edef\m_syst_string_one{#1}%
+   \edef\m_syst_string_two{#3}%
+   \ifx\m_syst_string_one\m_syst_string_two
+     \def\commalistelement{#3}%
+     #2%
+     \expandafter\quitprevcommalist
+   \else
+     \edef\m_syst_string_one{#1}%
+     \ifx\m_syst_string_one\s!unknown
+       \def\commalistelement{#3}%
+       #2%
+     \fi
+   \fi}
+
+\unexpanded\def\processfirstactioninset[#1]%
+  {\edef\m_syst_string_one{#1}%
+   \ifx\m_syst_string_one\empty
+     \expandafter\processaction
+   \else
+     \expandafter\syst_helpers_process_first_action_in_set_indeed
+   \fi
+   [#1]}
+
+\unexpanded\def\syst_helpers_process_first_action_in_set_indeed[#1]#2[#3]%
+  {\def\syst_helpers_do_process_action##1%
+     {\def\syst_helpers_do_do_process_action####1{\syst_helpers_do_compare_process_action_c[####1][##1]}%
+      \processcommalist[#3]\syst_helpers_do_do_process_action}%
+   \normalexpanded{\processcommalist[#1]}\syst_helpers_do_process_action}
+
+\unexpanded\def\syst_helpers_do_compare_process_action_d[#1=>#2][#3]%
+  {\edef\m_syst_string_one{#1}%
+   \edef\m_syst_string_two{#3}%
+   \ifx\m_syst_string_one\m_syst_string_two
+     \def\commalistelement{#3}%
+     #2%
+     \expandafter\quitcommalist
+   \else
+     \edef\m_syst_string_one{#1}%
+     \ifx\m_syst_string_one\s!unknown
+       \def\commalistelement{#3}%
+       #2%
+     \fi
+   \fi}
+
+\installsystemnamespace{nextactionlevel}
+
+\unexpanded\def\syst_helpers_do_process_all_actions_in_set
+  {\csname\??nextactionlevel\the\processlevel\endcsname}
+
+\unexpanded\def\processallactionsinset[#1]%
+  {\edef\m_syst_string_one{#1}%
+   \ifx\m_syst_string_one\empty
+     \expandafter\processaction
+   \else
+     \expandafter\syst_helpers_process_all_actions_in_set_indeed
+   \fi
+   [#1]}
+
+\unexpanded\def\syst_helpers_process_all_actions_in_set_indeed[#1]#2[#3]%
+  {\advance\processlevel \plusone
+   \expandafter\def\csname\??nextactionlevel\the\processlevel\endcsname##1%
+     {\def\syst_helpers_do_do_process_action####1{\syst_helpers_do_compare_process_action_d[####1][##1]}%
+      \processcommalist[#3]\syst_helpers_do_do_process_action}%
+   \normalexpanded{\processcommalist[#1]}\syst_helpers_do_process_all_actions_in_set
+   \advance\processlevel\minusone}
+
+%D These macros use:
+
+\unexpanded\def\processnextcommalist#1#2#3[#4#5]%
+  {#1%
+   \let\nexttoken#4%
+   \global\advance\commalevel \plusone
+   \expandafter\def\csname\??nextcommalevel\the\commalevel\endcsname##1,%
+     {#3{##1}\syst_helpers_do_process_comma_item}%
+   \syst_helpers_do_do_process_comma_item#4#5,]\relax
+   \global\advance\commalevel\minusone
+   #2}
+
+%D \macros
+%D   {getfirstcharacter, firstcharacter, remainingcharacters, doiffirstcharacter}
+%D
+%D Sometimes the action to be undertaken depends on the next character. This macro
+%D get this character and puts it in \type {\firstcharacter}.
+%D
+%D \starttyping
+%D \getfirstcharacter {string}
+%D \stoptyping
+%D
+%D A two step expansion is used to prevent problems with complicated arguments, for
+%D instance arguments that consist of two or more expandable tokens.
+
+\let\firstcharacter     \empty
+\let\remainingcharacters\empty
+
+\unexpanded\def\getfirstcharacter     #1{\clf_getfirstcharacter{#1}}
+\unexpanded\def\doifelsefirstchar   #1#2{\clf_doifelsefirstchar{#1}{#2}}
+\unexpanded\def\thefirstcharacter     #1{\clf_thefirstcharacter{#1}}
+\unexpanded\def\theremainingcharacters#1{\clf_theremainingcharacters{#1}}
+
+\let\doiffirstcharelse\doifelsefirstchar
+
+%D \macros
+%D   {doifinstringelse, doifincsnameelse}
+%D
+%D We can check for the presence of a substring in a given sequence of characters.
+%D
+%D \starttyping
+%D \doifinsetelse {substring} {string} {then ...} {else ...}
+%D \stoptyping
+
+\let\m_syst_sub_string\empty
+
+\unexpanded\def\doifelseinstring#1%
+  {\edef\m_syst_sub_string{#1}% expand #1 here
+   \ifx\m_syst_sub_string\empty
+     \expandafter\thirdofthreearguments
+   \else
+     \expandafter\syst_helpers_do_if_in_string_else_indeed
+   \fi}
+
+\let\doifinstringelse\doifelseinstring
+
+\unexpanded\def\syst_helpers_do_if_in_string_else_indeed#1%
+  {\syst_helpers_do_if_in_string_else\m_syst_sub_string{#1}%
+     \expandafter\firstoftwoarguments
+   \else
+     \expandafter\secondoftwoarguments
+   \fi}
+
+\unexpanded\def\doifinstring#1%%
+  {\edef\m_syst_sub_string{#1}% expand #1 here
+   \ifx\m_syst_sub_string\empty
+     \expandafter\gobbletwoarguments
+   \else
+     \expandafter\syst_helpers_do_if_in_string_indeed
+   \fi}
+
+\unexpanded\def\syst_helpers_do_if_in_string_indeed#1%
+  {\syst_helpers_do_if_in_string_else\m_syst_sub_string{#1}%
+     \expandafter\firstofoneargument
+   \else
+     \expandafter\gobbleoneargument
+   \fi}
+
+\unexpanded\def\doifnotinstring#1%%
+  {\edef\m_syst_sub_string{#1}% expand #1 here
+   \ifx\m_syst_sub_string\empty
+     \expandafter\gobbletwoarguments
+   \else
+     \expandafter\syst_helpers_do_if_not_in_string_indeed
+   \fi}
+
+\unexpanded\def\syst_helpers_do_if_not_in_string_indeed#1%
+  {\syst_helpers_do_if_in_string_else\m_syst_sub_string{#1}%
+     \expandafter\gobbleoneargument
+   \else
+     \expandafter\firstofoneargument
+   \fi}
+
+% replaces prev
+
+\unexpanded\def\syst_helpers_do_if_in_string_else#1#2% ##2 can be {abc}
+  {\expandafter\def\expandafter\syst_helpers_do_do_if_in_string_else
+     \expandafter##\expandafter1#1##2##3^^^^0004{\unless\if##2@}% expand #1 here
+   \expandafter\syst_helpers_do_do_if_in_string_else\normalexpanded{#2#1}@@^^^^0004} % expand #2 here
+
+%D The next alternative proved to be upto twice as fast on tasks like checking
+%D reserved words in pretty verbatim typesetting! This is mainly due to the fact
+%D that passing (expanded) strings is much slower that passing a macro.
+%D
+%D \starttyping
+%D \doifincsnameelse {substring} {\string} {then ...} {else ...}
+%D \stoptyping
+%D
+%D Where \type {\doifinstringelse} does as much expansion as possible, the latter
+%D alternative does minimal (one level) expansion.
+
+\unexpanded\def\syst_helpers_do_if_in_csname_else#1#2%
+  {\def\syst_helpers_do_do_if_in_csname_else##1#1##2##3^^^^0004%
+     {\unless\if##2@}%
+   \expandafter\syst_helpers_do_do_if_in_csname_else#2#1@@^^^^0004}
+
+\unexpanded\def\doifelseincsname#1#2%
+  {\normalexpanded{\syst_helpers_do_if_in_csname_else{#1}}{#2}%
+     \expandafter\firstoftwoarguments
+   \else
+     \expandafter\secondoftwoarguments
+   \fi}
+
+\let\doifincsnameelse\doifelseincsname
+
+%D \macros
+%D   {doifnumberelse,doifnumber,doifnotnumber}
+%D
+%D The next macro executes a command depending of the outcome of a test on numerals.
+%D This is probably one of the fastest test possible, exept from a less robust
+%D 10||step \type {\if}||ladder or some tricky \type {\lcode} checking.
+%D
+%D \starttyping
+%D \doifnumberelse {string} {then ...} {else ...}
+%D \stoptyping
+%D
+%D The macro accepts \type {123}, \type {abc}, \type {{}}, \type {\getal} and \type
+%D {\the\count...}. This macro is a rather dirty one.
+
+\def\doifelsenumber#1%
+  {\ifchknum#1\or
+     \expandafter\firstoftwoarguments
+   \else
+     \expandafter\secondoftwoarguments
+   \fi}
+
+\def\doifnumber#1%
+  {\ifchknum#1\or
+     \expandafter\firstoftwoarguments
+   \else
+     \expandafter\gobbleoneargument
+   \fi}
+
+\def\doifnotnumber#1%
+  {\ifchknum#1\or
+     \expandafter\gobbleoneargument
+   \else
+     \expandafter\firstofoneargument
+   \fi}
+
+\let\doifnumberelse\doifelsenumber
+
+%D \macros
+%D   {setpercentdimen}
+%D
+%D \starttyping
+%D \scratchdimen=100pt \setpercentdimen\scratchdimen{10\letterpercent}
+%D \scratchdimen=100pt \setpercentdimen\scratchdimen{5pt}
+%D \scratchdimen       \percentdimen   \hsize       {10\letterpercent}
+%D \stoptyping
+
+\def\percentdimen#1#2% dimen percentage (with %)
+  {\dimexpr\clf_percentageof{#2}\dimexpr#1\relax}
+
+\unexpanded\def\setpercentdimen#1#2% dimen percentage (with %)
+  {#1=\clf_percentageof{#2}\dimexpr#1\relax}
+
+%D \macros
+%D   {makerawcommalist,
+%D    rawdoinsetelse,
+%D    rawprocesscommalist,
+%D    rawprocessaction}
+%D
+%D Some of the commands mentioned earlier are effective but slow. When one is
+%D desperately in need of faster alternatives and when the conditions are
+%D predictable safe, the \type {\raw} alternatives come into focus. A major drawback
+%D is that they do not take \type {\c!constants} into account, simply because no
+%D expansion is done. This is no problem with \type {\rawprocesscommalist}, because
+%D this macro does not compare anything. Expandable macros are permitted as search
+%D string.
+%D
+%D \starttyping
+%D \makerawcommalist[string,string,...]\stringlist
+%D \rawdoifelseinset{string}{string,...}{...}{...}
+%D \rawprocesscommalist[string,string,...]\commando
+%D \rawprocessaction[x][a=>\a,b=>\b,c=>\c]
+%D \stoptyping
+%D
+%D Spaces embedded in the list, for instance after commas, spoil the search process.
+%D The gain in speed depends on the length of the argument (the longer the argument,
+%D the less we gain).
+
+\unexpanded\def\makerawcommalist[#1]#2% use \processnext ... here
+  {\def\syst_helpers_do_make_raw_comma_list##1% we don't expand ##1
+     {\ifx#2\empty
+        \def#2{##1}%
+      \else
+        \expandafter\def\expandafter#2\expandafter{#2,##1}%
+      \fi}%
+   \let#2\empty
+   \processcommalist[#1]\syst_helpers_do_make_raw_comma_list}
+
+\def\syst_helpers_raw_process_comma_item#1,#2% #2 eats up preceding space
+  {\if]#1\else
+     \csname\??nextcommalevel\the\commalevel\endcsname{#1}%
+     \expandafter\syst_helpers_raw_process_comma_item
+   \fi#2}
+
+\unexpanded\def\rawprocesscommalist[#1]#2% accepteert ook [\cs]
+  {\global\advance\commalevel \plusone
+   \expandafter\let\csname\??nextcommalevel\the\commalevel\endcsname#2%
+   \expandafter\syst_helpers_raw_process_comma_item#1,],% \relax
+   \global\advance\commalevel \minusone }
+
+\unexpanded\def\rawprocesscommacommand[#1]% not really needed
+  {\normalexpanded{\rawprocesscommalist[#1]}}
+
+%D Here is one without nesting:
+
+\unexpanded\def\syst_helpers_fast_process_comma_item#1,#2% #2 eats up preceding space
+  {\if]#1\else
+     \syst_helpers_fast_process_comma_command{#1}%
+     \expandafter\syst_helpers_fast_process_comma_item
+   \fi#2}
+
+\unexpanded\def\fastprocesscommalist[#1]#2% accepteert ook [\cs]
+  {\let\syst_helpers_fast_process_comma_command#2%
+   \expandafter\syst_helpers_fast_process_comma_item#1,],}% \relax
+
+\unexpanded\def\fastprocesscommacommand[#1]#2% accepteert ook [\cs]
+  {\let\syst_helpers_fast_process_comma_command#2%
+   \normalexpanded{\syst_helpers_fast_process_comma_item#1},],}% \relax
+
+% \def\rawdoifelseinset#1#2{\doifinstringelse{,#1,}{,#2,}}
+% \def\rawdoifinset    #1#2{\doifinstring    {,#1,}{,#2,}}
+
+\def\m_syst_two_commas{,,}
+
+\unexpanded\def\rawdoifelseinset#1%
+  {\edef\m_syst_sub_string{,#1,}% expand #1 here
+   \ifx\m_syst_sub_string\m_syst_two_commas
+     \expandafter\thirdofthreearguments
+   \else
+     \expandafter\syst_helpers_raw_do_if_in_set_else
+   \fi}
+
+\let\rawdoifinsetelse\rawdoifinsetelse
+
+\unexpanded\def\syst_helpers_raw_do_if_in_set_else#1%
+  {\syst_helpers_do_if_in_string_else\m_syst_sub_string{,#1,}%
+     \expandafter\firstoftwoarguments
+   \else
+     \expandafter\secondoftwoarguments
+   \fi}
+
+\unexpanded\def\rawdoifinset#1%
+  {\edef\m_syst_sub_string{,#1,}% expand #1 here
+   \ifx\m_syst_sub_string\m_syst_two_commas
+     \expandafter\gobbletwoarguments
+   \else
+     \expandafter\syst_helpers_raw_do_if_in_set
+   \fi}
+
+\unexpanded\def\syst_helpers_raw_do_if_in_set#1%%
+  {\syst_helpers_do_if_in_string_else\m_syst_sub_string{,#1,}%
+     \expandafter\firstofoneargument
+   \else
+     \expandafter\gobbleoneargument
+   \fi}
+
+%D Some more raw material:
+
+\def\syst_helpers_do_raw_process_action[#1][#2]%
+  {\def\syst_helpers_do_do_raw_process_action##1,#1=>##2,##3^^^^0004%
+     {\if##3@\else
+        \def\m_syst_helpers_process_action{##2}%
+      \fi}%
+   \syst_helpers_do_do_raw_process_action,#2,#1=>,@^^^^0004}
+
+\unexpanded\def\rawprocessaction[#1]#2[#3]%
+  {\edef\m_syst_string_one{#1}%
+   \edef\m_syst_string_two{undefined}% better \!!undefined
+   \let\m_syst_helpers_process_action\m_syst_string_two
+   \ifx\m_syst_string_one\empty
+     \expandafter\syst_helpers_do_raw_process_action\expandafter[\s!default][#3]%
+   \else
+      \expandafter\syst_helpers_do_raw_process_action\expandafter[\m_syst_string_one][#3]%
+      \ifx\m_syst_helpers_process_action\m_syst_string_two
+        \expandafter\syst_helpers_do_raw_process_action\expandafter[\s!unknown][#3]%
+      \fi
+   \fi
+   \ifx\m_syst_helpers_process_action\m_syst_string_two
+   \else
+     \m_syst_helpers_process_action
+   \fi}
+
+%D When we process the list \type {a,b,c,d,e}, the raw routine takes over 30\% less
+%D time, when we feed $20+$ character strings we gain about 20\%. Alternatives which
+%D use \type {\futurelet} perform worse. Part of the speedup is due to the \type
+%D {\let} and \type {\expandafter} in the test.
+%D
+%D \macros
+%D   {dosetvalue,dosetevalue,dosetgvalue,docopyvalue,doresetvalue,
+%D    dogetvalue}
+%D
+%D When we are going to do assignments, we have to take multi||linguality into account.
+%D For the moment we keep things simple and single||lingual.
+%D
+%D \starttyping
+%D \dosetvalue   {label}    {variable}   {value}
+%D \dosetevalue  {label}    {variable}   {value}
+%D \dosetgvalue  {label}    {variable}   {value}
+%D \docopyvalue  {to label} {from label} {variable}
+%D \doresetvalue {label}    {variable}
+%D \stoptyping
+%D
+%D These macros are in fact auxiliary ones and are not meant for use outside the
+%D assignment macros.
+
+\def\dosetvalue#1#2% #3
+  {\expandafter\def\csname#1#2\endcsname} % {#3}}
+
+\def\dosetevalue#1#2% #3
+  {\expandafter\edef\csname#1#2\endcsname} % {#3}}
+
+\def\dosetgvalue#1#2% #3
+  {\expandafter\gdef\csname#1#2\endcsname} % {#3}}
+
+\def\doresetvalue#1#2%
+  {\expandafter\let\csname#1#2\endcsname\empty}
+
+\def\doignorevalue#1#2#3%
+  {\expandafter\let\csname#1#2\endcsname\empty}
+
+\def\docopyvalue#1#2#3%
+  {\expandafter\def\csname#1#3\endcsname{\csname#2#3\endcsname}}
+
+%D \macros
+%D   {doassign,undoassign,doassignempty}
+%D
+%D Assignments are the backbone of \CONTEXT. Abhorred by the concept of style file
+%D hacking, we took a considerable effort in building a parameterized system.
+%D Unfortunately there is a price to pay in terms of speed. Compared to other
+%D packages and taking the functionality of \CONTEXT\ into account, the total size
+%D of the format file is still very acceptable. Now how are these assignments done.
+%D
+%D Assignments can be realized with:
+%D
+%D \starttyping
+%D \doassign[label][variable=value]
+%D \undoassign[label][variable=value]
+%D \stoptyping
+%D
+%D and:
+%D
+%D \starttyping
+%D \doassignempty[label][variable=value]
+%D \stoptyping
+%D
+%D Assignments like \type{\doassign} are compatible with:
+%D
+%D \starttyping
+%D \def\labelvariable{value}
+%D \stoptyping
+%D
+%D We do check for the presence of an \type{=} and loudly complain of it's missed. We
+%D will redefine this macro later on, when a more advanced message mechanism is
+%D implemented.
+
+\newif\iferrorisfatal
+
+\unexpanded\def\waitonfatalerror
+  {\iferrorisfatal\wait\fi}
+
+\unexpanded\def\showassignerror#1#2%
+  {\writestatus{setup}{missing or ungrouped '=' after '#1' in line #2}%
+   \waitonfatalerror}
+
+\unexpanded\def\doassignempty[#1][#2=#3]%
+  {\ifcsname#1#2\endcsname\else\dosetvalue{#1}{#2}{#3}\fi}
+
+%D \macros
+%D   {getparameters,geteparameters,getgparameters,
+%D    forgetparameters}
+%D
+%D Using the assignment commands directly is not our ideal of user friendly interfacing,
+%D so we take some further steps.
+%D
+%D \starttyping
+%D \getparameters    [label] [...=...,...=...]
+%D \forgetparameters [label] [...=...,...=...]
+%D \stoptyping
+%D
+%D Again, the label identifies the category a variable belongs to. The second argument
+%D can be a comma separated list of assignments.
+%D
+%D \starttyping
+%D \getparameters
+%D   [demo]
+%D   [alfa=1,
+%D    beta=2]
+%D \stoptyping
+%D
+%D is equivalent to
+%D
+%D \starttyping
+%D \def\demoalfa{1}
+%D \def\demobeta{2}
+%D \stoptyping
+%D
+%D
+%D In the pre||multi||lingual stadium \CONTEXT\ took the next approach. With
+%D
+%D \starttyping
+%D \def\??demo {@@demo}
+%D \def\!!alfa {alfa}
+%D \def\!!beta {beta}
+%D \stoptyping
+%D
+%D calling
+%D
+%D \starttyping
+%D \getparameters
+%D   [\??demo]
+%D   [\!!alfa=1,
+%D    \!!beta=2]
+%D \stoptyping
+%D
+%D lead to:
+%D
+%D \starttyping
+%D \def\@@demoalfa{1}
+%D \def\@@demobeta{2}
+%D \stoptyping
+%D
+%D Because we want to be able to distinguish the \type{!!} pre||tagged user supplied
+%D variables from internal counterparts, we will introduce a slightly different tag
+%D in the multi||lingual modules. There we will use \type{c!} or \type{v!},
+%D depending on the context.
+%D
+%D By calling \type{doassign} directly, we save ourselves some argument passing
+%D and gain some speed. Whatever optimizations we do, this command will always be
+%D one of the bigger bottlenecks. The alternative \type{\geteparameters} --- it's
+%D funny to see that this alternative saw the light so lately --- can be used to do
+%D expanded assigments.
+
+\let\currentvalue\empty
+
+\unexpanded\def\getparameters   {\dogetparameters\dosetvalue}
+\unexpanded\def\geteparameters  {\dogetparameters\dosetevalue}
+\unexpanded\def\getgparameters  {\dogetparameters\dosetgvalue}
+\unexpanded\def\getxparameters  {\dogetparameters\dosetxvalue}
+\unexpanded\def\forgetparameters{\dogetparameters\doignorevalue}
+
+\let\getexpandedparameters\geteparameters
+
+\unexpanded\def\dogetparameters#1[#2]#3[#4%
+  {\if\noexpand#4]%
+     \expandafter\gobbleoneargument
+   \else
+     \let\setsomevalue#1%
+     \def\syst_helpers_get_parameters_assign{\syst_helpers_get_parameters_assign_indeed#2}%
+     \expandafter\syst_helpers_get_parameters
+   \fi#4}
+
+\def\syst_helpers_get_parameters#1]%
+  {\xprocesscommaitem#1,],^^^^0004}
+
+\def\syst_helpers_process_comma_item#1,#2% #2 takes space before ,
+  {\if,#1,% dirty trick for testing #1=empty
+     \expandafter\syst_helpers_process_comma_item
+   \orelse\if]#1%
+     \expandafter\gobbleoneargument
+   \else
+     \syst_helpers_get_parameters_assign^^^^0004#1==\empty^^^^0004%
+     \expandafter\syst_helpers_process_comma_item
+   \fi#2}
+
+\def\syst_helpers_assign_error#1#2#3%
+  {\showassignerror{#2}{\the\inputlineno\space(#1)}}
+
+\def\syst_helpers_get_parameters_assign_normal#1^^^^0004#2=#3=#4#5^^^^0004%
+  {\ifx\empty#2\empty
+     \expandafter\syst_helpers_assign_error
+   \orelse\ifx#4\empty
+     \expandafter\syst_helpers_assign_error
+   \else
+     \expandafter\setsomevalue
+   \fi
+   {#1}{#2}{#3}}
+
+\def\syst_helpers_get_parameters_assign_error#1^^^^0004#2=#3=#4#5^^^^0004%
+  {\ifx\empty#2\empty
+     \expandafter\syst_helpers_assign_error
+   \orelse\ifx#4\empty
+     \expandafter\syst_helpers_assign_error
+   \orelse\ifcsname#1#2\endcsname
+     \expandafter\let\expandafter\currentvalue\csname#1#2\endcsname
+     \expandafter\setsomevalue
+   \else
+     \let\currentvalue\empty
+     \expandafter\setsomevalue
+   \fi
+   {#1}{#2}{#3}}
+
+\let\syst_helpers_get_parameters_assign_indeed\syst_helpers_get_parameters_assign_normal
+
+\unexpanded\def\doassign  [#1][#2]{\let\setsomevalue\dosetvalue  \syst_helpers_get_parameters_assign_indeed#1^^^^0004#2==\empty^^^^0004}
+\unexpanded\def\doeassign [#1][#2]{\let\setsomevalue\dosetevalue \syst_helpers_get_parameters_assign_indeed#1^^^^0004#2==\empty^^^^0004}
+\unexpanded\def\undoassign[#1][#2]{\let\setsomevalue\doresetvalue\syst_helpers_get_parameters_assign_indeed#1^^^^0004#2==\empty^^^^0004}
+
+%D \macros
+%D   {processassignmentlist,processassignmentcommand,
+%D    startprocessassignmentlist,startprocessassignmentcommand}
+%D
+%D For Wolfgang:
+%D
+%D \starttyping
+%D \def\showpair#1#2{key:#1, value:#2\par}
+%D \processassignmentlist[a=1,b=2]\showpair
+%D \stoptyping
+%D
+%D We can optimize this one if needed but it's not a core macro so hardly worth the
+%D trouble and tokens.
+
+\unexpanded\def\processassignmentlist[#1]#2% #2 == \command{key}{value]
+  {\def\syst_helpers_process_assignment_entry##1{#2}% {##2}{##3} % namespace is ignored
+   \dogetparameters\syst_helpers_process_assignment_entry[][#1]}
+
+\unexpanded\def\processassignmentcommand[#1]%
+  {\normalexpanded{\processassignmentlist[#1]}}
+
+\unexpanded\def\startprocessassignmentlist[#1]#2\stopprocessassignmentlist
+  {\def\currentassignmentlistcommand##1##2{\def\currentassignmentlistkey{##1}\def\currentassignmentlistvalue{##2}#2}%
+   \processassignmentlist[#1]\currentassignmentlistcommand}
+
+\unexpanded\def\startprocessassignmentcommand[#1]#2\stopprocessassignmentcommand
+  {\def\currentassignmentlistcommand##1##2{\def\currentassignmentlistkey{##1}\def\currentassignmentlistvalue{##2}#2}%
+   \normalexpanded{\processassignmentlist[#1]}\currentassignmentlistcommand}
+
+%D \macros{currentvalue}
+%D
+%D Just in case a \type{\getparameter} argument itself ends up inside a \type
+%D {\write} or other expandable location, our new macro needs a default value.
+%D
+%D \starttyping
+%D \getparameters[xxx][aaa=bbb]\par
+%D \getparameters[xxx][=bbb]\par
+%D \getparameters[xxx][aaa=]\par
+%D \getparameters[xxx][=]\par
+%D \getparameters[xxx][aaa]\par
+%D \stoptyping
+
+%D \macros
+%D   {expandparameters}
+%D
+%D Example usage:
+%D
+%D \startbuffer
+%D \getparameters[taco][name=taco]
+%D \convertcommand\taconame\to\ascii \ascii
+%D \expandparameters \getparameters[taco][name=\currentvalue\space hoekwater]
+%D \convertcommand\taconame\to\ascii \ascii
+%D \getparameters[taco][name=\currentvalue\space hoekwater]
+%D \convertcommand\taconame\to\ascii \ascii
+%D \stopbuffer
+%D
+%D \typebuffer
+%D \startlines
+%D \getbuffer
+%D \stoplines
+%D
+%D Here we hook in the code (beware, this is the optimized get **):
+
+\def\syst_helpers_get_parameters_normal#1]%
+  {\syst_helpers_process_comma_item#1,],^^^^0004}
+
+\def\syst_helpers_get_parameters_expanded#1]%
+  {\let\dosetnvalue\setsomevalue
+   \let\setsomevalue\dosetevalue
+   \let\syst_helpers_get_parameters_assign_indeed\syst_helpers_get_parameters_assign_error
+   \let\setsomevalue\dosetevalue
+   \syst_helpers_process_comma_item#1,],^^^^0004%
+   \let\syst_helpers_get_parameters_assign_indeed\syst_helpers_get_parameters_assign_normal
+   \let\setsomevalue\dosetnvalue
+   \let\syst_helpers_get_parameters\syst_helpers_get_parameters_normal
+   \let\currentvalue\empty}
+
+\let\syst_helpers_get_parameters\syst_helpers_get_parameters_normal % **
+
+\unexpanded\def\expandparameters
+  {\let\syst_helpers_get_parameters\syst_helpers_get_parameters_expanded}
+
+%D \macros
+%D   {getemptyparameters}
+%D
+%D Sometimes we explicitly want variables to default to an empty string, so we
+%D welcome:
+%D
+%D \starttyping
+%D \getemptyparameters [label] [...=...,...=...]
+%D \stoptyping
+
+\unexpanded\def\getemptyparameters[#1]#2[#3]%
+  {\def\syst_helpers_get_empty_parameters##1{\doassignempty[#1][##1]}%
+   \processcommalist[#3]\syst_helpers_get_empty_parameters}
+
+%D \macros
+%D   {copyparameters}
+%D
+%D Some \CONTEXT\ commands take their default setups from others. All commands that
+%D are able to provide backgounds or rules around some content, for instance default
+%D to the standard command for ruled boxes. Is situations like this we can use:
+%D
+%D \starttyping
+%D \copyparameters [to-label] [from-label] [name1,name2,...]
+%D \stoptyping
+%D
+%D For instance
+%D
+%D \starttyping
+%D \copyparameters
+%D   [internal][external]
+%D   [alfa,beta]
+%D \stoptyping
+%D
+%D Leads to:
+%D
+%D \starttyping
+%D \def\internalalfa {\externalalfa}
+%D \def\internalbeta {\externalbeta}
+%D \stoptyping
+%D
+%D By using \type {\docopyvalue} we've prepared this command for use in a
+%D multi||lingual environment.
+
+\unexpanded\def\copyparameters[#1]#2[#3]#4[#5]%
+  {\doifnot{#1}{#3}
+     {\def\syst_helpers_copy_parameter{\docopyvalue{#1}{#3}}% ##1
+      \processcommalist[#5]\syst_helpers_copy_parameter}}
+
+%D \macros
+%D   {ifparameters,checkparameters}
+%D
+%D A slightly different one is \type {\checkparameters}, which also checks on the
+%D presence of a~\type {=}.
+%D
+%D The boolean \type {\ifparameters} can be used afterwards. Combining both in one
+%D \type {\if}||macro would lead to problems with nested \type {\if}'s.
+%D
+%D \starttyping
+%D \checkparameters[argument]
+%D \stoptyping
+
+\newif\ifparameters
+
+\def\syst_helpers_check_parameters#1=#2#3^^^^0004%
+  {\if#2^^^^0003\parametersfalse\else\parameterstrue\fi}
+
+\unexpanded\def\checkparameters[#1]%
+  {\syst_helpers_check_parameters#1=^^^^0003^^^^0003^^^^0004}
+
+%D \macros
+%D   {getfromcommalist,getfromcommacommand,
+%D    commalistelement,
+%D    getcommalistsize,getcommacommandsize}
+%D
+%D It's possible to get an element from a commalist or a command representing
+%D a commalist.
+%D
+%D \starttyping
+%D \getfromcommalist    [string] [n]
+%D \getfromcommacommand [string,\strings,string,...] [n]
+%D \stoptyping
+%D
+%D The difference betwee the two of them is the same as the difference between
+%D \type {\processcomma...}. The found string is stored in \type
+%D {\commalistelement}.
+%D
+%D We can calculate the size of a comma separated list by using:
+%D
+%D \starttyping
+%D \getcommalistsize    [string,string,...]
+%D \getcommacommandsize [string,\strings,string,...]
+%D \stoptyping
+%D
+%D Afterwards, the length is available in the macro \type {\commalistsize}
+%D (not a \COUNTER).
+
+\newcount\commalistcounter
+
+\def\commalistsize{0}
+
+\def\syst_helpers_get_comma_list_size#1%
+  {\advance\commalistcounter\plusone}
+
+\unexpanded\def\getcommalistsize#1]% don't loose [{#1}]
+  {\commalistcounter\zerocount
+   \processcommalist#1]\syst_helpers_get_comma_list_size   % was [{#1}]
+   \edef\commalistsize{\the\commalistcounter}}
+
+% \def\getcommacommandsize[#1]%
+%   {\edef\commacommand{#1}%
+%    \scratchtoks\expandafter{\expandafter[\commacommand]}%
+%    \expandafter\getcommalistsize\the\scratchtoks }
+
+\unexpanded\def\getcommacommandsize[#1]%
+  {\normalexpanded{\getcommalistsize[#1]}}
+
+\def\syst_helpers_get_from_comma_list#1%
+  {\advance\commalistcounter \minusone
+   \ifcase\commalistcounter
+     \def\commalistelement{#1}%
+     \expandafter\quitcommalist
+   \fi}
+
+\unexpanded\def\getfromcommalist[#1]#2[#3]%
+  {\let\commalistelement\empty
+   \commalistcounter#3\relax
+   \processcommalist[#1]\syst_helpers_get_from_comma_list}
+
+\unexpanded\def\getfromcommacommand[#1]%
+  {\normalexpanded{\getfromcommalist[#1]}}
+
+%D Watertight (and efficient) solutions are hard to find, due to the handling of
+%D braces during parameters passing and scanning. Nevertheless:
+%D
+%D \startbuffer
+%D \def\dosomething#1{(#1=\commalistsize) }
+%D
+%D \getcommalistsize [\hbox{$a,b,c,d,e,f$}] \dosomething 1
+%D \getcommalistsize [{a,b,c,d,e,f}]        \dosomething 1
+%D \getcommalistsize [{a,b,c},d,e,f]        \dosomething 4
+%D \getcommalistsize [a,b,{c,d,e},f]        \dosomething 4
+%D \getcommalistsize [a{b,c},d,e,f]         \dosomething 4
+%D \getcommalistsize [{a,b}c,d,e,f]         \dosomething 4
+%D \getcommalistsize []                     \dosomething 0
+%D \getcommalistsize [{[}]                  \dosomething 1
+%D \stopbuffer
+%D
+%D \typebuffer
+%D
+%D reports:
+%D
+%D \getbuffer
+
+%D \macros
+%D   {dogetcommalistelement,dogetcommacommandelement}
+%D
+%D For low level (fast) purposes, we can also use the next alternative, which can
+%D handle 8~elements at most.
+%D
+%D \starttyping
+%D \dogetcommalistelement1\from a,b,c\to\commalistelement
+%D \stoptyping
+
+\def\syst_helpers_get_comma_list_element#1\from#2,#3,#4,#5,#6,#7,#8\to#9%
+  {\edef#9{\ifcase#1\relax\or#2\or#3\or#4\or#5\or#6\or#7\or#8\fi}}
+
+\def\dogetcommacommandelement#1\from#2\to%
+  {\expandafter\syst_helpers_get_comma_list_element\expandafter#1\expandafter\from#2,,,,,,\to}
+
+%D \macros
+%D   {dosingleargument,dodoubleargument,dotripleargument,
+%D    doquadrupleargument,doquintupleargument,dosixtupleargument,
+%D    doseventupleargument}
+%D
+%D When working with delimited arguments, spaces and lineendings can interfere. The
+%D next set of macros uses \TEX' internal scanner for grabbing everything between
+%D arguments. Forgive me the funny names.
+%D
+%D \starttyping
+%D \dosingleargument\commando    = \commando[#1]
+%D \dodoubleargument\commando    = \commando[#1][#2]
+%D \dotripleargument\commando    = \commando[#1][#2][#3]
+%D \doquadrupleargument\commando = \commando[#1][#2][#3][#4]
+%D \doquintupleargument\commando = \commando[#1][#2][#3][#4][#5]
+%D \dosixtupleargument\commando  = \commando[#1][#2][#3][#4][#5][#6]
+%D \doseventupleargument\command = \commando[#1][#2][#3][#4][#5][#6][#7]
+%D \stoptyping
+%D
+%D These macros are used in the following way:
+%D
+%D \starttyping
+%D \def\dosetupsomething[#1][#2]%
+%D   {... #1 ... #2 ...}
+%D
+%D \unexpanded\def\setupsomething
+%D   {\dodoubleargument\dosetupsomething}
+%D \stoptyping
+%D
+%D The implementation can be surprisingly simple and needs no
+%D further explanation, like:
+%D
+%D \starttyping
+%D \def\dosingleargument#1[#2]%
+%D   {#1[#2]}
+%D \def\dotripleargument#1[#2]#3[#4]#5[#6]%
+%D   {#1[#2][#4][#6]}
+%D \def\doquintupleargument#1%
+%D   {\def\dodoquintupleargument[##1]##2[##3]##4[##5]##6[##7]##8[##9]%
+%D      {#1[##1][##3][##5][##7][##9]}%
+%D    \dodoquintupleargument}
+%D \stoptyping
+%D
+%D Because \TEX\ accepts 9~arguments at most, we have to use two||step solution when
+%D getting five or more arguments.
+%D
+%D When developing more and more of the real \CONTEXT, we started using some
+%D alternatives that provided empty arguments (in fact optional ones) whenever the
+%D user failed to supply them. Because this more complicated macros enable us to do
+%D some checking, we reimplemented the non||empty ones.
+
+%D \macros
+%D   {iffirstagument,ifsecondargument,ifthirdargument,
+%D    iffourthargument,iffifthargument,ifsixthargument,
+%D    ifseventhargument}
+%D
+%D We use some signals for telling the calling macros if all wanted arguments are
+%D indeed supplied by the user.
+
+\newif\iffirstargument
+\newif\ifsecondargument
+\newif\ifthirdargument
+\newif\iffourthargument
+\newif\iffifthargument
+\newif\ifsixthargument
+\newif\ifseventhargument
+
+%D \macros
+%D   {dosingleempty,dodoubleempty,dotripleempty,
+%D    doquadrupleempty,doquintupleempty,dosixtupeempty,
+%D    doseventupleempty}
+%D
+%D The empty argument supplying macros mentioned before, look like:
+%D
+%D \starttyping
+%D \dosingleempty    \command
+%D \dodoubleempty    \command
+%D \dotripleempty    \command
+%D \doquadrupleempty \command
+%D \doquintupleempty \command
+%D \dosixtuple_empty  \command
+%D \doseventupleempty\command
+%D \stoptyping
+%D
+%D So \type{\dodoubleempty} leads to:
+%D
+%D \starttyping
+%D \command[#1][#2]
+%D \command[#1][]
+%D \command[][]
+%D \stoptyping
+%D
+%D Depending of the generousity of the user. Afterwards one can use the \type
+%D {\if...argument} boolean. For novice: watch the stepwise doubling of \type {#}'s.
+
+%D Common:
+
+\newtoks\t_syst_aux
+
+\def\syst_helpers_single_empty_one_yes      {\firstargumenttrue  \the\t_syst_aux}
+\def\syst_helpers_double_empty_two_yes      {\secondargumenttrue \the\t_syst_aux}
+\def\syst_helpers_triple_empty_three_yes    {\thirdargumenttrue  \the\t_syst_aux}
+\def\syst_helpers_quadruple_empty_four_yes  {\fourthargumenttrue \the\t_syst_aux}
+\def\syst_helpers_quintuple_empty_five_yes  {\fifthargumenttrue  \the\t_syst_aux}
+\def\syst_helpers_sixtuple_empty_six_yes    {\sixthargumenttrue  \the\t_syst_aux}
+\def\syst_helpers_seventuple_empty_seven_yes{\seventhargumenttrue\the\t_syst_aux}
+
+%D Single:
+
+\unexpanded\def\dosingleempty#1%
+  {%syst_helpers_argument_reset
+   \t_syst_aux{#1}%
+   \futureexpand[\syst_helpers_single_empty_one_yes\syst_helpers_single_empty_one_nop}
+
+\def\syst_helpers_single_empty_one_nop
+  {\firstargumentfalse
+   \the\t_syst_aux[]}
+
+%D Double
+
+\unexpanded\def\dodoubleempty#1%
+  {%syst_helpers_argument_reset
+   \t_syst_aux{#1}%
+   \futureexpand[\syst_helpers_double_empty_one_yes\syst_helpers_double_empty_one_nop}
+
+\def\syst_helpers_double_empty_one_yes[#1]%
+  {\firstargumenttrue
+   \toksapp\t_syst_aux{[{#1}]}%
+   \futureexpand[\syst_helpers_double_empty_two_yes\syst_helpers_double_empty_two_nop}
+
+\def\syst_helpers_double_empty_one_nop
+  {\firstargumentfalse
+   \secondargumentfalse
+   \the\t_syst_aux[][]}
+
+\def\syst_helpers_double_empty_two_nop
+  {\secondargumentfalse
+   \the\t_syst_aux[]}
+
+% Triple
+
+\unexpanded\def\dotripleempty#1%
+  {%syst_helpers_argument_reset
+   \t_syst_aux{#1}%
+   \futureexpand[\syst_helpers_triple_empty_one_yes\syst_helpers_triple_empty_one_nop}
+
+\def\syst_helpers_triple_empty_one_yes[#1]%
+  {\firstargumenttrue
+   \toksapp\t_syst_aux{[{#1}]}%
+   \futureexpand[\syst_helpers_triple_empty_two_yes\syst_helpers_triple_empty_two_nop}
+
+\def\syst_helpers_triple_empty_two_yes[#1]%
+  {\secondargumenttrue
+   \toksapp\t_syst_aux{[{#1}]}%
+   \futureexpand[\syst_helpers_triple_empty_three_yes\syst_helpers_triple_empty_three_nop}
+
+\def\syst_helpers_triple_empty_one_nop
+  {\firstargumentfalse
+   \secondargumentfalse
+   \thirdargumentfalse
+   \the\t_syst_aux[][][]}
+
+\def\syst_helpers_triple_empty_two_nop
+  {\secondargumentfalse
+   \thirdargumentfalse
+   \the\t_syst_aux[][]}
+
+\def\syst_helpers_triple_empty_three_nop
+  {\thirdargumentfalse
+   \the\t_syst_aux[]}
+
+%D Quadruple:
+
+\unexpanded\def\doquadrupleempty#1%
+  {%syst_helpers_argument_reset
+   \t_syst_aux{#1}%
+   \futureexpand[\syst_helpers_quadruple_empty_one_yes\syst_helpers_quadruple_empty_one_nop}
+
+\def\syst_helpers_quadruple_empty_one_yes[#1]%
+  {\firstargumenttrue
+   \toksapp\t_syst_aux{[{#1}]}%
+   \futureexpand[\syst_helpers_quadruple_empty_two_yes\syst_helpers_quadruple_empty_two_nop}
+
+\def\syst_helpers_quadruple_empty_two_yes[#1]%
+  {\secondargumenttrue
+   \toksapp\t_syst_aux{[{#1}]}%
+   \futureexpand[\syst_helpers_quadruple_empty_three_yes\syst_helpers_quadruple_empty_three_nop}
+
+\def\syst_helpers_quadruple_empty_three_yes[#1]%
+  {\thirdargumenttrue
+   \toksapp\t_syst_aux{[{#1}]}%
+   \futureexpand[\syst_helpers_quadruple_empty_four_yes\syst_helpers_quadruple_empty_four_nop}
+
+\def\syst_helpers_quadruple_empty_one_nop
+  {\firstargumentfalse
+   \secondargumentfalse
+   \thirdargumentfalse
+   \fourthargumentfalse
+   \the\t_syst_aux[][][][]}
+
+\def\syst_helpers_quadruple_empty_two_nop
+  {\secondargumentfalse
+   \thirdargumentfalse
+   \fourthargumentfalse
+   \the\t_syst_aux[][][]}
+
+\def\syst_helpers_quadruple_empty_three_nop
+  {\thirdargumentfalse
+   \fourthargumentfalse
+   \the\t_syst_aux[][]}
+
+\def\syst_helpers_quadruple_empty_four_nop
+  {\fourthargumentfalse
+   \the\t_syst_aux[]}
+
+%D Quintuple:
+
+\unexpanded\def\doquintupleempty#1%
+  {%syst_helpers_argument_reset
+   \t_syst_aux{#1}%
+   \futureexpand[\syst_helpers_quintuple_empty_one_yes\syst_helpers_quintuple_empty_one_nop}
+
+\def\syst_helpers_quintuple_empty_one_yes[#1]%
+  {\firstargumenttrue
+   \toksapp\t_syst_aux{[{#1}]}%
+   \futureexpand[\syst_helpers_quintuple_empty_two_yes\syst_helpers_quintuple_empty_two_nop}
+
+\def\syst_helpers_quintuple_empty_two_yes[#1]%
+  {\secondargumenttrue
+   \toksapp\t_syst_aux{[{#1}]}%
+   \futureexpand[\syst_helpers_quintuple_empty_three_yes\syst_helpers_quintuple_empty_three_nop}
+
+\def\syst_helpers_quintuple_empty_three_yes[#1]%
+  {\thirdargumenttrue
+   \toksapp\t_syst_aux{[{#1}]}%
+   \futureexpand[\syst_helpers_quintuple_empty_four_yes\syst_helpers_quintuple_empty_four_nop}
+
+\def\syst_helpers_quintuple_empty_four_yes[#1]%
+  {\fourthargumenttrue
+   \toksapp\t_syst_aux{[{#1}]}%
+   \futureexpand[\syst_helpers_quintuple_empty_five_yes\syst_helpers_quintuple_empty_five_nop}
+
+\def\syst_helpers_quintuple_empty_one_nop
+  {\firstargumentfalse
+   \secondargumentfalse
+   \thirdargumentfalse
+   \fourthargumentfalse
+   \fifthargumentfalse
+   \the\t_syst_aux[][][][][]}
+
+\def\syst_helpers_quintuple_empty_two_nop
+  {\secondargumentfalse
+   \thirdargumentfalse
+   \fourthargumentfalse
+   \fifthargumentfalse
+   \the\t_syst_aux[][][][]}
+
+\def\syst_helpers_quintuple_empty_three_nop
+  {\thirdargumentfalse
+   \fourthargumentfalse
+   \fifthargumentfalse
+   \the\t_syst_aux[][][]}
+
+\def\syst_helpers_quintuple_empty_four_nop
+  {\fourthargumentfalse
+   \fifthargumentfalse
+   \the\t_syst_aux[][]}
+
+\def\syst_helpers_quintuple_empty_five_nop
+  {\fifthargumentfalse
+   \the\t_syst_aux[]}
+
+%D Sixtuple:
+
+\unexpanded\def\dosixtupleempty#1%
+  {%syst_helpers_argument_reset
+   \t_syst_aux{#1}%
+   \futureexpand[\syst_helpers_sixtuple_empty_one_yes\syst_helpers_sixtuple_empty_one_nop}
+
+\def\syst_helpers_sixtuple_empty_one_yes[#1]%
+  {\firstargumenttrue
+   \toksapp\t_syst_aux{[{#1}]}%
+   \futureexpand[\syst_helpers_sixtuple_empty_two_yes\syst_helpers_sixtuple_empty_two_nop}
+
+\def\syst_helpers_sixtuple_empty_two_yes[#1]%
+  {\secondargumenttrue
+   \toksapp\t_syst_aux{[{#1}]}%
+   \futureexpand[\syst_helpers_sixtuple_empty_three_yes\syst_helpers_sixtuple_empty_three_nop}
+
+\def\syst_helpers_sixtuple_empty_three_yes[#1]%
+  {\thirdargumenttrue
+   \toksapp\t_syst_aux{[{#1}]}%
+   \futureexpand[\syst_helpers_sixtuple_empty_four_yes\syst_helpers_sixtuple_empty_four_nop}
+
+\def\syst_helpers_sixtuple_empty_four_yes[#1]%
+  {\fourthargumenttrue
+   \toksapp\t_syst_aux{[{#1}]}%
+   \futureexpand[\syst_helpers_sixtuple_empty_five_yes\syst_helpers_sixtuple_empty_five_nop}
+
+\def\syst_helpers_sixtuple_empty_five_yes[#1]%
+  {\fifthargumenttrue
+   \toksapp\t_syst_aux{[{#1}]}%
+   \futureexpand[\syst_helpers_sixtuple_empty_six_yes\syst_helpers_sixtuple_empty_six_nop}
+
+\def\syst_helpers_sixtuple_empty_one_nop
+  {\firstargumentfalse
+   \secondargumentfalse
+   \thirdargumentfalse
+   \fourthargumentfalse
+   \fifthargumentfalse
+   \sixthargumentfalse
+   \the\t_syst_aux[][][][][][]}
+
+\def\syst_helpers_sixtuple_empty_two_nop
+  {\secondargumentfalse
+   \thirdargumentfalse
+   \fourthargumentfalse
+   \fifthargumentfalse
+   \sixthargumentfalse
+   \the\t_syst_aux[][][][][]}
+
+\def\syst_helpers_sixtuple_empty_three_nop
+  {\thirdargumentfalse
+   \fourthargumentfalse
+   \fifthargumentfalse
+   \sixthargumentfalse
+   \the\t_syst_aux[][][][]}
+
+\def\syst_helpers_sixtuple_empty_four_nop
+  {\fourthargumentfalse
+   \fifthargumentfalse
+   \sixthargumentfalse
+   \the\t_syst_aux[][][]}
+
+\def\syst_helpers_sixtuple_empty_five_nop
+  {\fifthargumentfalse
+   \sixthargumentfalse
+   \the\t_syst_aux[][]}
+
+\def\syst_helpers_sixtuple_empty_six_nop
+  {\sixthargumentfalse
+   \the\t_syst_aux[]}
+
+%D Seventuple:
+
+\unexpanded\def\doseventupleempty#1%
+  {%syst_helpers_argument_reset
+   \t_syst_aux{#1}%
+   \futureexpand[\syst_helpers_seventuple_empty_one_yes\syst_helpers_seventuple_empty_one_nop}
+
+\def\syst_helpers_seventuple_empty_one_yes[#1]%
+  {\firstargumenttrue
+   \toksapp\t_syst_aux{[{#1}]}%
+   \futureexpand[\syst_helpers_seventuple_empty_two_yes\syst_helpers_seventuple_empty_two_nop}
+
+\def\syst_helpers_seventuple_empty_two_yes[#1]%
+  {\secondargumenttrue
+   \toksapp\t_syst_aux{[{#1}]}%
+   \futureexpand[\syst_helpers_seventuple_empty_three_yes\syst_helpers_seventuple_empty_three_nop}
+
+\def\syst_helpers_seventuple_empty_three_yes[#1]%
+  {\thirdargumenttrue
+   \toksapp\t_syst_aux{[{#1}]}%
+   \futureexpand[\syst_helpers_seventuple_empty_four_yes\syst_helpers_seventuple_empty_four_nop}
+
+\def\syst_helpers_seventuple_empty_four_yes[#1]%
+  {\fourthargumenttrue
+   \toksapp\t_syst_aux{[{#1}]}%
+   \futureexpand[\syst_helpers_seventuple_empty_five_yes\syst_helpers_seventuple_empty_five_nop}
+
+\def\syst_helpers_seventuple_empty_five_yes[#1]%
+  {\fifthargumenttrue
+   \toksapp\t_syst_aux{[{#1}]}%
+   \futureexpand[\syst_helpers_seventuple_empty_six_yes\syst_helpers_seventuple_empty_six_nop}
+
+\def\syst_helpers_seventuple_empty_six_yes[#1]%
+  {\sixthargumenttrue
+   \toksapp\t_syst_aux{[{#1}]}%
+   \futureexpand[\syst_helpers_seventuple_empty_seven_yes\syst_helpers_seventuple_empty_seven_nop}
+
+\def\syst_helpers_seventuple_empty_one_nop
+  {\firstargumentfalse
+   \secondargumentfalse
+   \thirdargumentfalse
+   \fourthargumentfalse
+   \fifthargumentfalse
+   \sixthargumentfalse
+   \seventhargumentfalse
+   \the\t_syst_aux[][][][][][][]}
+
+\def\syst_helpers_seventuple_empty_two_nop
+  {\secondargumentfalse
+   \thirdargumentfalse
+   \fourthargumentfalse
+   \fifthargumentfalse
+   \sixthargumentfalse
+   \seventhargumentfalse
+   \the\t_syst_aux[][][][][][]}
+
+\def\syst_helpers_seventuple_empty_three_nop
+  {\thirdargumentfalse
+   \fourthargumentfalse
+   \fifthargumentfalse
+   \sixthargumentfalse
+   \seventhargumentfalse
+   \the\t_syst_aux[][][][][]}
+
+\def\syst_helpers_seventuple_empty_four_nop
+  {\fourthargumentfalse
+   \fifthargumentfalse
+   \sixthargumentfalse
+   \seventhargumentfalse
+   \the\t_syst_aux[][][][]}
+
+\def\syst_helpers_seventuple_empty_five_nop
+  {\fifthargumentfalse
+   \sixthargumentfalse
+   \seventhargumentfalse
+   \the\t_syst_aux[][][]}
+
+\def\syst_helpers_seventuple_empty_six_nop
+  {\sixthargumentfalse
+   \seventhargumentfalse
+   \the\t_syst_aux[][]}
+
+\def\syst_helpers_seventuple_empty_seven_nop
+  {\seventhargumentfalse
+   \the\t_syst_aux[]}
+
+%D Aliases:
+
+\let\dosingleargument    \dosingleempty
+\let\dodoubleargument    \dodoubleempty
+\let\dotripleargument    \dotripleempty
+\let\doquadrupleargument \doquadrupleempty
+\let\doquintupleargument \doquintupleempty
+\let\dosixtupleargument  \dosixtupleempty
+\let\doseventupleargument\doseventupleempty
+
+%D \macros
+%D   {strippedcsname}
+%D
+%D The next macro can be very useful when using \type{\csname} like in:
+%D
+%D \starttyping
+%D \csname if\strippedcsname\something\endcsname
+%D \stoptyping
+%D
+%D This expands to \type{\ifsomething}.
+
+% \def\strippedcsname
+%   {\expandafter\gobbleoneargument\string}
+
+\let\strippedcsname\csstring
+
+%D \macros
+%D   {complexorsimple,complexorsimpleempty}
+%D
+%D Setups can be optional. A command expecting a setup is prefixed by \type
+%D {\complex}, a command without one gets the prefix \type {\simple}. Commands like
+%D this can be defined by:
+%D
+%D \starttyping
+%D \complexorsimple\command
+%D \stoptyping
+%D
+%D When \type{\command} is followed by a \type{[setup]}, then
+%D
+%D \starttyping
+%D \complexcommand [setup]
+%D \stoptyping
+%D
+%D executes, else we get
+%D
+%D \starttyping
+%D \simplecommand
+%D \stoptyping
+%D
+%D An alternative for \type{\complexorsimple} is:
+%D
+%D \starttyping
+%D \complexorsimpleempty {command}
+%D \stoptyping
+%D
+%D Depending on the presence of \type{[setup]}, this one leads to one of:
+%D
+%D \starttyping
+%D \complexcommando [setup]
+%D \complexcommando []
+%D \stoptyping
+%D
+%D Many \CONTEXT\ commands started as complex or simple ones, but changed into more
+%D versatile (more object oriented) ones using the \type {\get..argument} commands.
+
+\unexpanded\def\complexorsimple#1%
+  {% \relax % prevents lookahead, brrr
+   \doifelsenextoptional
+     {\firstargumenttrue \csname\s!complex\csstring#1\endcsname}
+     {\firstargumentfalse\csname\s!simple \csstring#1\endcsname}}
+
+\unexpanded\def\complexorsimpleempty#1%
+  {% \relax % prevents lookahead, brrr
+   \doifelsenextoptional
+     {\firstargumenttrue \csname\s!complex\csstring#1\endcsname}
+     {\firstargumentfalse\csname\s!complex\csstring#1\endcsname[]}}
+
+%D \macros
+%D   {definecomplexorsimple,definecomplexorsimpleempty}
+%D
+%D The previous commands are used that often that we found it worthwile to offer two
+%D more alternatives. Watch the build in protection.
+
+\unexpanded\def\syst_helpers_complex_or_simple#1#2%
+  {\doifelsenextoptional{\firstargumenttrue#1}{\firstargumentfalse#2}}
+
+\unexpanded\def\syst_helpers_complex_or_simple_empty#1%
+  {\doifelsenextoptional{\firstargumenttrue#1}{\firstargumentfalse#1[]}}
+
+\unexpanded\def\definecomplexorsimple#1%
+  {\unexpanded\edef#1{\syst_helpers_complex_or_simple
+     \expandafter\noexpand\csname\s!complex\csstring#1\endcsname
+     \expandafter\noexpand\csname\s!simple \csstring#1\endcsname}}
+
+\unexpanded\def\definecomplexorsimpleempty#1%
+  {\unexpanded\edef#1{\syst_helpers_complex_or_simple_empty
+     \expandafter\noexpand\csname\s!complex\csstring#1\endcsname}}
+
+%D These commands are called as:
+%D
+%D \starttyping
+%D \definecomplexorsimple\command
+%D \stoptyping
+%D
+%D Of course, we must have available
+%D
+%D \starttyping
+%D \def\complexcommand[#1]{...}
+%D \def\simplecommand     {...}
+%D \stoptyping
+%D
+%D Using this construction saves a few string now and then.
+
+%D \macros
+%D   {dosinglegroupempty,dodoublegroupempty,dotriplegroupempty,
+%D    doquadruplegroupempty, doquintuplegroupempty}
+%D
+%D We've already seen some commands that take care of
+%D optional arguments between \type{[]}. The next two commands
+%D handle the ones with \type{{}}. They are called as:
+%D
+%D \starttyping
+%D \dosinglegroupempty    \ineedONEargument
+%D \dodoublegroupempty    \ineedTWOarguments
+%D \dotriplegroupempty    \ineedTHREEarguments
+%D \doquadruplegroupempty \ineedFOURarguments
+%D \doquintuplegroupempty \ineedFIVEarguments
+%D \stoptyping
+%D
+%D We can add additional definitions later when we have defined \type {\appendtoks}.
+
+\newconditional\c_syst_helpers_permit_spaces_between_groups
+
+\unexpanded\def    \permitspacesbetweengroups{\settrue \c_syst_helpers_permit_spaces_between_groups}
+\unexpanded\def\dontpermitspacesbetweengroups{\setfalse\c_syst_helpers_permit_spaces_between_groups}
+
+\dontpermitspacesbetweengroups
+
+%D We can avoid the nasty if handling in \type {syst-gen} by splitting the lot in
+%D pieces so that we have no nested \type {\nextarguments} potentially being an
+%D \type {conditional} token. Okay, these macros are not called that often but it
+%D saves crap when tracing.
+
+\unexpanded\def\dosinglegroupempty#1%
+  {\t_syst_aux{#1}%
+   \futureexpand\bgroup\syst_helpers_single_empty_one_yes\syst_helpers_single_group_empty_one_nop}
+
+\def\syst_helpers_single_group_empty_one_nop
+  {\firstargumentfalse
+   \the\t_syst_aux{}}
+
+\unexpanded\def\dodoublegroupempty#1%
+  {\t_syst_aux{#1}%
+   \futureexpand\bgroup\syst_helpers_group_double_empty_one_yes\syst_helpers_group_double_empty_one_nop}
+
+\def\syst_helpers_group_double_empty_one_yes#1%
+  {\firstargumenttrue
+   \toksapp\t_syst_aux{{#1}}%
+   \futureexpand\bgroup\syst_helpers_double_empty_two_yes\syst_helpers_group_double_empty_two_nop}
+
+\def\syst_helpers_group_double_empty_one_nop
+  {\firstargumentfalse
+   \secondargumentfalse
+   \the\t_syst_aux{}{}}
+
+\def\syst_helpers_group_double_empty_two_nop
+  {\secondargumentfalse
+   \the\t_syst_aux{}}
+
+\unexpanded\def\dotriplegroupempty#1%
+  {\t_syst_aux{#1}%
+   \futureexpand\bgroup\syst_helpers_group_triple_empty_one_yes\syst_helpers_group_triple_empty_one_nop}
+
+\def\syst_helpers_group_triple_empty_one_yes#1%
+  {\firstargumenttrue
+   \toksapp\t_syst_aux{{#1}}%
+   \futureexpand\bgroup\syst_helpers_group_triple_empty_two_yes\syst_helpers_group_triple_empty_two_nop}
+
+\def\syst_helpers_group_triple_empty_two_yes#1%
+  {\secondargumenttrue
+   \toksapp\t_syst_aux{{#1}}%
+   \futureexpand\bgroup\syst_helpers_triple_empty_three_yes\syst_helpers_group_triple_empty_three_nop}
+
+\def\syst_helpers_group_triple_empty_one_nop
+  {\firstargumentfalse
+   \secondargumentfalse
+   \thirdargumentfalse
+   \the\t_syst_aux{}{}{}}
+
+\def\syst_helpers_group_triple_empty_two_nop
+  {\secondargumentfalse
+   \thirdargumentfalse
+   \the\t_syst_aux{}{}}
+
+\def\syst_helpers_group_triple_empty_three_nop
+  {\thirdargumentfalse
+   \the\t_syst_aux{}}
+
+\unexpanded\def\doquadruplegroupempty#1%
+  {\t_syst_aux{#1}%
+   \futureexpand\bgroup\syst_helpers_group_quadruple_empty_one_yes\syst_helpers_group_quadruple_empty_one_nop}
+
+\def\syst_helpers_group_quadruple_empty_one_yes#1%
+  {\firstargumenttrue
+   \toksapp\t_syst_aux{{#1}}%
+   \futureexpand\bgroup\syst_helpers_group_quadruple_empty_two_yes\syst_helpers_group_quadruple_empty_two_nop}
+
+\def\syst_helpers_group_quadruple_empty_two_yes#1%
+  {\secondargumenttrue
+   \toksapp\t_syst_aux{{#1}}%
+   \futureexpand\bgroup\syst_helpers_group_quadruple_empty_three_yes\syst_helpers_group_quadruple_empty_three_nop}
+
+\def\syst_helpers_group_quadruple_empty_three_yes#1%
+  {\thirdargumenttrue
+   \toksapp\t_syst_aux{{#1}}%
+   \futureexpand\bgroup\syst_helpers_quadruple_empty_four_yes\syst_helpers_group_quadruple_empty_four_nop}
+
+\def\syst_helpers_group_quadruple_empty_one_nop
+  {\firstargumentfalse
+   \secondargumentfalse
+   \thirdargumentfalse
+   \fourthargumentfalse
+   \the\t_syst_aux{}{}{}{}}
+
+\def\syst_helpers_group_quadruple_empty_two_nop
+  {\secondargumentfalse
+   \thirdargumentfalse
+   \fourthargumentfalse
+   \the\t_syst_aux{}{}{}}
+
+\def\syst_helpers_group_quadruple_empty_three_nop
+  {\thirdargumentfalse
+   \fourthargumentfalse
+   \the\t_syst_aux{}{}}
+
+\def\syst_helpers_group_quadruple_empty_four_nop
+  {\fourthargumentfalse
+   \the\t_syst_aux{}}
+
+\unexpanded\def\doquintuplegroupempty#1%
+  {\t_syst_aux{#1}%
+   \futureexpand\bgroup\syst_helpers_group_quintuple_empty_one_yes\syst_helpers_group_quintuple_empty_one_nop}
+
+\def\syst_helpers_group_quintuple_empty_one_yes#1%
+  {\firstargumenttrue
+   \toksapp\t_syst_aux{{#1}}%
+   \futureexpand\bgroup\syst_helpers_group_quintuple_empty_two_yes\syst_helpers_group_quintuple_empty_two_nop}
+
+\def\syst_helpers_group_quintuple_empty_two_yes#1%
+  {\secondargumenttrue
+   \toksapp\t_syst_aux{{#1}}%
+   \futureexpand\bgroup\syst_helpers_group_quintuple_empty_three_yes\syst_helpers_group_quintuple_empty_three_nop}
+
+\def\syst_helpers_group_quintuple_empty_three_yes#1%
+  {\thirdargumenttrue
+   \toksapp\t_syst_aux{{#1}}%
+   \futureexpand\bgroup\syst_helpers_group_quintuple_empty_four_yes\syst_helpers_group_quintuple_empty_four_nop}
+
+\def\syst_helpers_group_quintuple_empty_four_yes#1%
+  {\fourthargumenttrue
+   \toksapp\t_syst_aux{{#1}}%
+   \futureexpand\bgroup\syst_helpers_quintuple_empty_five_yes\syst_helpers_group_quintuple_empty_five_nop}
+
+\def\syst_helpers_group_quintuple_empty_one_nop
+  {\firstargumentfalse
+   \secondargumentfalse
+   \thirdargumentfalse
+   \fourthargumentfalse
+   \fifthargumentfalse
+   \the\t_syst_aux{}{}{}{}{}}
+
+\def\syst_helpers_group_quintuple_empty_two_nop
+  {\secondargumentfalse
+   \thirdargumentfalse
+   \fourthargumentfalse
+   \fifthargumentfalse
+   \the\t_syst_aux{}{}{}{}}
+
+\def\syst_helpers_group_quintuple_empty_three_nop
+  {\thirdargumentfalse
+   \fourthargumentfalse
+   \fifthargumentfalse
+   \the\t_syst_aux{}{}{}}
+
+\def\syst_helpers_group_quintuple_empty_four_nop
+  {\fourthargumentfalse
+   \fifthargumentfalse
+   \the\t_syst_aux{}{}}
+
+\def\syst_helpers_group_quintuple_empty_five_nop
+  {\fifthargumentfalse
+   \the\t_syst_aux{}}
+
+%D These macros can explictly take care of spaces, which means that the next
+%D definition and calls are valid:
+%D
+%D \starttyping
+%D \def\test#1#2#3{[#1#2#3]}
+%D
+%D \dotriplegroupempty\test {a}{b}{c}
+%D \dotriplegroupempty\test {a}{b}
+%D \dotriplegroupempty\test {a}
+%D \dotriplegroupempty\test
+%D \dotriplegroupempty\test {a} {b} {c}
+%D \dotriplegroupempty\test {a} {b}
+%D \dotriplegroupempty\test
+%D   {a}
+%D   {b}
+%D \stoptyping
+%D
+%D And alike.
+
+%D \macros
+%D   {firstofoneargument, firstoftwoarguments, firstofthreearguments
+%D    secondoftwoarguments, secondofthreearguments,
+%D    thirdofthreearguments}
+%D
+%D The next six macros (dedicated to Taco) can conveniently used to select
+%D arguments. Their names explain their functionality.
+
+\def\firstofoneargument            #1{#1}
+
+\def\firstoftwoarguments         #1#2{#1}
+\def\secondoftwoarguments        #1#2{#2}
+
+\def\firstofthreearguments     #1#2#3{#1}
+\def\secondofthreearguments    #1#2#3{#2}
+\def\thirdofthreearguments     #1#2#3{#3}
+
+\def\firstoffourarguments    #1#2#3#4{#1}
+\def\secondoffourarguments   #1#2#3#4{#2}
+\def\thirdoffourarguments    #1#2#3#4{#3}
+\def\fourthoffourarguments   #1#2#3#4{#4}
+
+\def\firstoffivearguments  #1#2#3#4#5{#1}
+\def\secondoffivearguments #1#2#3#4#5{#2}
+\def\thirdoffivearguments  #1#2#3#4#5{#3}
+\def\fourthoffivearguments #1#2#3#4#5{#4}
+\def\fifthoffivearguments  #1#2#3#4#5{#5}
+
+\def\firstofsixarguments #1#2#3#4#5#6{#1}
+\def\secondofsixarguments#1#2#3#4#5#6{#2}
+\def\thirdofsixarguments #1#2#3#4#5#6{#3}
+\def\fourthofsixarguments#1#2#3#4#5#6{#4}
+\def\fifthofsixarguments #1#2#3#4#5#6{#5}
+\def\sixthofsixarguments #1#2#3#4#5#6{#6}
+
+\unexpanded\def\firstofoneunexpanded       #1{#1}
+
+\unexpanded\def\firstoftwounexpanded     #1#2{#1}
+\unexpanded\def\secondoftwounexpanded    #1#2{#2}
+
+\unexpanded\def\firstofthreeunexpanded #1#2#3{#1}
+\unexpanded\def\secondofthreeunexpanded#1#2#3{#2}
+\unexpanded\def\thirdofthreeunexpanded #1#2#3{#3}
+
+%D \macros
+%D   {globalletempty,letempty,
+%D    letvalueempty,letgvalueempty,
+%D    letvaluerelax,letgvaluerelax}
+%D
+%D Trivial:
+
+\unexpanded\def\letempty      #1{\let #1\empty}
+\unexpanded\def\globalletempty#1{\glet#1\empty}
+
+\unexpanded\def\letvalueempty #1{\expandafter\let \csname#1\endcsname\empty}
+\unexpanded\def\letgvalueempty#1{\expandafter\glet\csname#1\endcsname\empty}
+\unexpanded\def\letvaluerelax #1{\expandafter\let \csname#1\endcsname\relax}
+\unexpanded\def\letgvalurelax #1{\expandafter\glet\csname#1\endcsname\relax}
+
+\unexpanded\def\relaxvalueifundefined#1%
+  {\ifcsname#1\endcsname \else
+     \expandafter\let\csname#1\endcsname\relax
+   \fi}
+
+%D \macros
+%D   {wait}
+%D
+%D The next macro hardly needs explanation. Because no nesting is to be expected, we
+%D can reuse \type {\wait} within \type {\wait} itself.
+
+\unexpanded\def\wait
+  {\begingroup
+   \read16 to \wait
+   \endgroup}
+
+%D \macros
+%D   {writestring,writeline,
+%D    writestatus,statuswidth,normalwritestatus}
+%D
+%D Maybe one didn't notice, but we've already introduced a macro for showing
+%D messages. In the multi||lingual modules, we will also introduce a mechanism for
+%D message passing. For the moment we stick to the core macros:
+%D
+%D \starttyping
+%D \writestring {string}
+%D \writeline
+%D \writestatus {category} {message}
+%D \stoptyping
+%D
+%D Messages are formatted. One can provide the maximum with of the identification
+%D string with the macro \type {\statuswidth}.
+
+\setnewconstant\statuswidth  15
+\setnewconstant\statuswrite 128 % \pluscxxviii
+
+\ifdefined\writestring \else
+
+    \unexpanded\def\writestring{\immediate\write\statuswrite}
+    \unexpanded\def\writeline  {\writestring{}}
+
+\fi
+
+\unexpanded\def\normalwritestatus#1#2%
+  {\writestring{\expandafter\syst_helpers_split_status_yes\expandafter\statuswidth#1%
+     \space\space\space\space\space\space\space
+     \space\space\space\space\space\space\space
+     \space\space\space\space\space\space\end
+     \space:\space#2}}
+
+\def\syst_helpers_split_status_yes#1#2%
+  {\ifcase#1 \expandafter\syst_helpers_split_status_nop\fi#2%
+   \expandafter\syst_helpers_split_status_yes\expandafter{\the\numexpr#1+\minusone\relax}}
+
+\def\syst_helpers_split_status_nop#1\end
+  {}
+
+%D \macros
+%D   {immediatemessage}
+%D
+%D A fully expandable message:
+
+\let\immediatemessage\clf_immediatemessage % {} mandate
+
+%D \macros
+%D   {rawgetparameters}
+%D
+%D A raw and dirty alternative for \type {\getparameters}; no checking is done!
+
+\unexpanded\def\rawsetparameter#1=#2,%
+  {\if]#1\else
+     \expandafter\def\csname\rawparameterprefix#1\endcsname{#2}%
+     \expandafter\rawsetparameter
+   \fi}
+
+\unexpanded\def\rawgetparameters[#1][#2% some 5-10% faster
+  {\ifx#2]% test is needed, else bomb on [#1][]
+     \expandafter\gobbleoneargument
+   \else
+     \def\rawparameterprefix{#1}%
+     \expandafter\dorawgetparameters
+   \fi#2}
+
+\def\dorawgetparameters#1]%
+  {\expandafter\rawsetparameter#1,]=,}
+
+%D \macros
+%D   {doglobal,
+%D    redoglobal,dodoglobal,resetglobal}
+%D
+%D The two macros \type {\redoglobal} and \type{\dodoglobal} are used in this and
+%D some other modules to enforce a user specified \type {\doglobal} action. The last
+%D and often only global assignment in a macro is done with \type {\dodoglobal}, but
+%D all preceding ones with \type {\redoglobal}. When using only alternatives, one
+%D can reset this mechanism with \type {\resetglobal}.
+
+\unexpanded\def\resetglobal
+  {\let\redoglobal\relax
+   \let\dodoglobal\relax}
+
+\resetglobal
+
+\unexpanded\def\doglobal
+  {\ifx\redoglobal\relax
+     \let\redoglobal\global
+     \let\dodoglobal\syst_helpers_dodo_global
+   \fi}
+
+\def\syst_helpers_dodo_global
+  {\resetglobal\global}
+
+\def\saveglobal
+  {\let\syst_helpers_dodo_global\dodoglobal
+   \let\syst_helpers_redo_global\redoglobal}
+
+\def\restoreglobal
+  {\let\redoglobal\syst_helpers_redo_global
+   \let\dodoglobal\syst_helpers_dodo_global}
+
+%D A very useful application of this macro is \type {\newif}, \TEX's fake boolean
+%D type. Not being a primitive, \type {\global} hopelessly fails here. But a slight
+%D adaption of Knuth's original macro permits:
+%D
+%D \starttyping
+%D \doglobal\newif\iftest
+%D \stoptyping
+%D
+%D Of course one can still say:
+%D
+%D \starttyping
+%D \global\testtrue
+%D \global\testfalse
+%D \stoptyping
+%D
+%D Apart from the prefixes, a few more \type {\expandafters} are needed:
+
+% \unexpanded\def\newif#1% uses the original plain \@if
+%   {\privatescratchcounter\escapechar
+%    \escapechar\minusone
+%    \expandafter\expandafter\expandafter
+%      \redoglobal\expandafter\expandafter\expandafter
+%        \edef\@if#1{true}{\let\noexpand#1\noexpand\iftrue}%
+%    \expandafter\expandafter\expandafter
+%      \redoglobal\expandafter\expandafter\expandafter
+%        \edef\@if#1{false}{\let\noexpand#1\noexpand\iffalse}%
+%    \dodoglobal\@if#1{false}%
+%    \escapechar\privatescratchcounter}
+
+\normalprotected\def\newif#1% see syst-ini.mkiv
+  {\let\new_if_saved\newif
+   \let\newif\new_if_check
+   \expandafter\redoglobal\expandafter\def\csname\expandafter\newif\csstring#1true\endcsname {\let#1\iftrue }%
+   \expandafter\redoglobal\expandafter\def\csname\expandafter\newif\csstring#1false\endcsname{\let#1\iffalse}%
+   \dodoglobal\csname\expandafter\newif\csstring#1false\endcsname
+   \let\newif\new_if_saved}
+
+%D Also new:
+
+\unexpanded\def\define#1%
+  {\ifdefined#1%
+     \message{[\noexpand#1is already defined]}%
+     \unexpanded\expandafter\def\expandafter\gobbleddefinition
+   \else
+     \unexpanded\expandafter\def
+   \fi#1}
+
+\unexpanded\def\redefine#1%
+  {\ifdefined#1%
+     \message{[\noexpand#1is redefined]}%
+   \fi
+   \unexpanded\def#1}
+
+\unexpanded\def\definemacro#1%
+  {\ifdefined#1%
+     \message{[\noexpand#1is already defined]}%
+     \unexpanded\expandafter\def\expandafter\gobbleddefinition
+   \else
+     \unexpanded\expandafter\def
+   \fi#1}
+
+% \define\hans{hans}
+% \redefine\hans{hans}
+% \define\hans#1[]#2#3{hans}
+
+%D The next variant fits nicely in the setups syntax:
+%D
+%D \starttyping
+%D \starttexdefinition bagger [#1] #2
+%D     oeps
+%D     #1
+%D     oeps
+%D \stoptexdefinition
+%D
+%D \bagger [a] {b}
+%D \stoptyping
+
+% \starttexdefinition test
+% oeps
+% \stoptexdefinition
+%
+% [\test]
+
+\def\s!unexpanded{unexpanded}
+
+\bgroup \obeylines
+
+\glet\stoptexdefinition\relax
+
+\unexpanded\gdef\starttexdefinition%
+  {\bgroup%
+   \obeylines%
+   \syst_helpers_start_tex_definition}
+
+\gdef\syst_helpers_start_tex_definition#1
+  {\catcode\endoflineasciicode\ignorecatcode%
+   \clf_texdefinition_one{#1}}
+
+\gdef\dostarttexdefinition#1\stoptexdefinition%
+  {\egroup%
+   \clf_texdefinition_two{#1}}
+
+\egroup
+
+% \unexpanded\def\texdefinition#1{\csname\ifcsname#1\endcsname#1\else donothing\fi\endcsname} % todo: a nop cs: char 0 or some corenamespace
+
+\unexpanded\def\texdefinition#1{\begincsname#1\endcsname}
+
+% This is a first variant, more might be added:
+
+\unexpanded\def\starttexcode{\unprotect}
+\unexpanded\def\stoptexcode {\protect}
+
+%D \macros
+%D   {newcounter,
+%D    increment,decrement}
+%D
+%D Unfortunately the number of \COUNTERS\ in \TEX\ is limited, but fortunately we
+%D can store numbers in a macro. We can increment such pseudo \COUNTERS\ with \type
+%D {\increment}.
+%D
+%D \starttyping
+%D \increment(\counter,20)
+%D \increment(\counter,-4)
+%D \increment(\counter)
+%D \increment\counter
+%D \stoptyping
+%D
+%D After this sequence of commands, the value of \type {\counter} is 20, 16, 17
+%D and~18. Of course there is also the complementary command \type {\decrement}.
+%D
+%D Global assignments are possible too, using \type{\doglobal}:
+%D
+%D \starttyping
+%D \doglobal\increment\counter
+%D \stoptyping
+%D
+%D When \type {\counter} is undefined, it's value is initialized at~0. It is
+%D nevertheless better to define a \COUNTER\ explicitly. One reason could be that
+%D the \COUNTER\ can be part of a test with \type {\ifnum} and this conditional does
+%D not accept undefined macro's. The \COUNTER\ in our example can for instance be
+%D defined with:
+%D
+%D \starttyping
+%D \newcounter\counter
+%D \stoptyping
+%D
+%D The command \type {\newcounter} must not be confused with \type {\newcount}! Of
+%D course this mechanism is much slower than using \TEX's \COUNTERS\ directly. In
+%D practice \COUNTERS\ (and therefore our pseudo counters too) are seldom the
+%D bottleneck in the processing of a text. Apart from some other incompatilities we
+%D want to mention a pitfal when using \type {\ifnum}.
+%D
+%D \starttyping
+%D \ifnum\normalcounter=\pseudocounter \doif \else \doelse \fi
+%D \ifnum\pseudocounter=\normalcounter \doif \else \doelse \fi
+%D \stoptyping
+%D
+%D In the first test, \TEX\ continues it's search for the second number after
+%D reading \type {\pseudocounter}, while in the second test, it stops reading after
+%D having encountered a real one. Tests like the first one therefore can give
+%D unexpected results, for instance execution of \type {\doif} even if both numbers
+%D are unequal.
+
+\def\zerocountervalue{0}
+
+\unexpanded\def\newcounter#1%
+  {\dodoglobal\let#1\zerocountervalue}
+
+%D Nowadays we don't mind a few more tokens if we can gain a bit of speed.
+
+\def\syst_helpers_do_increment#1{\dodoglobal\edef#1{\the\numexpr\ifdefined#1\ifx#1\relax\else#1\fi\fi+\plusone \relax}}
+\def\syst_helpers_do_decrement#1{\dodoglobal\edef#1{\the\numexpr\ifdefined#1\ifx#1\relax\else#1\fi\fi+\minusone\relax}}
+
+\def\syst_helpers_do_do_do_increment#1,#2){\dodoglobal\edef#1{\the\numexpr\ifdefined#1\ifx#1\relax\else#1\fi\fi+#2\relax}}
+\def\syst_helpers_do_do_do_decrement#1,#2){\dodoglobal\edef#1{\the\numexpr\ifdefined#1\ifx#1\relax\else#1\fi\fi-#2\relax}}
+
+\def\syst_helpers_do_do_increment(#1%
+  {\def\m_syst_action_yes{\syst_helpers_do_do_do_increment#1}%
+   \def\m_syst_action_nop{\syst_helpers_do_do_do_increment#1,\plusone}%
+   \doifelsenextcharcs,\m_syst_action_yes\m_syst_action_nop}
+
+\def\syst_helpers_do_do_decrement(#1%
+  {\def\m_syst_action_yes{\syst_helpers_do_do_do_decrement#1}%
+   \def\m_syst_action_nop{\syst_helpers_do_do_do_decrement#1,\plusone}%
+   \doifelsenextcharcs,\m_syst_action_yes\m_syst_action_nop}
+
+\unexpanded\def\increment{\doifelsenextcharcs(\syst_helpers_do_do_increment\syst_helpers_do_increment}
+\unexpanded\def\decrement{\doifelsenextcharcs(\syst_helpers_do_do_decrement\syst_helpers_do_decrement}
+
+\unexpanded\def\fastincrement#1{\dodoglobal\edef#1{\the\numexpr#1+\plusone \relax}}
+\unexpanded\def\fastdecrement#1{\dodoglobal\edef#1{\the\numexpr#1+\minusone\relax}}
+
+\unexpanded\def\incrementvalue#1{\expandafter\increment\csname#1\endcsname}
+\unexpanded\def\decrementvalue#1{\expandafter\decrement\csname#1\endcsname}
+
+%D \macros
+%D  {newsignal}
+%D
+%D When writing advanced macros, we cannot do without signaling. A signal is a small
+%D (invisible) kern or penalty that signals the next macro that something just
+%D happened. This macro can take any action depending on the previous signal.
+%D Signals must be unique and the next macro takes care of that.
+%D
+%D \starttyping
+%D \newsignal\somesignal
+%D \stoptyping
+%D
+%D Signals old dimensions and can be used in skips, kerns and tests like \type
+%D {\ifdim}.
+
+\newdimen\maximumsignal % step is about 0.00025pt
+
+\unexpanded\def\newsignal#1%
+  {\ifdefined#1\else
+     \advance\maximumsignal 2\scaledpoint % to be save in rounding
+     \edef#1{\the\maximumsignal}%
+   \fi}
+
+%D \macros
+%D   {strippedcsname}
+%D
+%D The next macro can be very useful when using \type {\csname} like in:
+%D
+%D \starttyping
+%D \csname if\strippedcsname\something\endcsname
+%D \stoptyping
+
+\let\checkedstrippedcsname\csstring
+
+%D \macros
+%D   {savenormalmeaning}
+%D
+%D We will use this one in:
+
+\unexpanded\def\savenormalmeaning#1%
+  {\ifcsname normal\csstring#1\endcsname \else
+     \expandafter\let\csname normal\csstring#1\endcsname#1%
+   \fi}
+
+%D \macros
+%D   {dorecurse,recurselevel,recursedepth,
+%D    dostepwiserecurse}
+%D
+%D \TEX\ does not offer us powerfull for||loop mechanisms. On the other hand its
+%D recursion engine is quite unique. We therefore identify the for||looping macros
+%D by this method. The most simple alternative is the one that only needs a number.
+%D
+%D \starttyping
+%D \dorecurse {n} {whatever we want}
+%D \stoptyping
+%D
+%D This macro can be nested without problems and therefore be used in situations
+%D where \PLAIN\ \TEX's \type {\loop} macro ungracefully fails. The current value of
+%D the counter is available in \type {\recurselevel}, before as well as after the
+%D \typ {whatever we wat} stuff.
+%D
+%D \starttyping
+%D \dorecurse               % inner loop
+%D   {10}
+%D   {\recurselevel:          % outer value
+%D      \dorecurse          % inner loop
+%D        {\recurselevel}     % outer value
+%D        {\recurselevel}     % inner value
+%D      \dorecurse          % inner loop
+%D        {\recurselevel}     % outer value
+%D        {\recurselevel}     % inner value
+%D    \endgraf}
+%D \stoptyping
+%D
+%D In this example the first, second and fourth \type {\recurselevel} concern the
+%D outer loop, while the third and fifth one concern the inner loop. The depth of
+%D the nesting is available for inspection in \type {\recursedepth}.
+%D
+%D Both \type {\recurselevel} and \type {\recursedepth} are macros. The real
+%D \COUNTERS\ are hidden from the user because we don't want any interference.
+
+\newcount\outerrecurse
+\newcount\innerrecurse
+
+\def\recursedepth{\the\outerrecurse}
+\def\recurselevel{0}
+
+\let\syst_helpers_stepwise_next\relax
+
+\installsystemnamespace{recurseindex}
+\installsystemnamespace{recurseaction}
+
+\unexpanded\def\dostepwiserecurse#1#2#3#4% can be made faster by postponing #4
+  {\global\advance\outerrecurse \plusone
+   \expandafter\gdef\csname\??recurseaction\the\outerrecurse\endcsname{#4}%
+   \expandafter\glet\csname\??recurseindex \the\outerrecurse\endcsname\recurselevel
+   \ifnum#3>\zerocount\relax
+     \ifnum#2<#1\relax
+       \let\syst_helpers_stepwise_next\syst_helpers_stepwise_exit
+     \else
+       \let\syst_helpers_stepwise_next\syst_helpers_stepwise_recurse
+     \fi
+   \orelse\ifnum#3<\zerocount\relax
+     \ifnum#1<#2\relax
+       \let\syst_helpers_stepwise_next\syst_helpers_stepwise_exit
+     \else
+       \let\syst_helpers_stepwise_next\syst_helpers_stepwise_reverse
+     \fi
+   \else
+     \let\syst_helpers_stepwise_next\syst_helpers_stepwise_exit
+   \fi\normalexpanded{\syst_helpers_stepwise_next{\number#1}{\number#2}{\number#3}}}
+
+\unexpanded\def\syst_helpers_stepwise_recurse#1#2#3% from to step
+  {\ifnum#1>#2\relax
+     \expandafter\syst_helpers_stepwise_recurse_nop
+   \else
+     \def\recurselevel{#1}%
+     \doubleexpandafter\syst_helpers_stepwise_recurse_yes\expandafter
+   \fi\expandafter{\the\numexpr\recurselevel+#3\relax}{#2}{#3}}
+
+\unexpanded\def\syst_helpers_recurse_content
+  {\csname\??recurseaction\the\outerrecurse\endcsname}
+
+\unexpanded\def\syst_helpers_stepwise_recurse_yes
+  {\syst_helpers_recurse_content
+   \syst_helpers_stepwise_recurse}
+
+\unexpanded\def\syst_helpers_stepwise_reverse#1#2#3% from to step
+  {\ifnum#1<#2\relax
+     \expandafter\syst_helpers_stepwise_recurse_nop
+   \else
+     \def\recurselevel{#1}%
+     \innerrecurse#1\relax
+     \advance\innerrecurse#3\relax
+     \doubleexpandafter\syst_helpers_stepwise_reverse_yes\expandafter
+   \fi\expandafter{\the\innerrecurse}{#2}{#3}}
+
+\unexpanded\def\syst_helpers_stepwise_reverse_yes
+  {\syst_helpers_recurse_content
+   \syst_helpers_stepwise_reverse}
+
+\unexpanded\def\syst_helpers_stepwise_exit
+  {\syst_helpers_stepwise_recurse_nop\relax}
+
+\unexpanded\def\syst_helpers_stepwise_recurse_nop#1#2#3#4%
+  {\expandafter\let\expandafter\recurselevel\csname\??recurseindex\the\outerrecurse\endcsname
+   \global\advance\outerrecurse\minusone}
+
+\unexpanded\def\dorecurse#1%
+  {\dostepwiserecurse\plusone{#1}\plusone}
+
+\def\doexpandedrecurse#1#2% user macro (also was \doxprecurse)
+  {\ifnum#1>\zerocount
+     #2\expandafter\doexpandedrecurse\expandafter{\the\numexpr#1-\plusone\relax}{#2}%
+   \fi}
+
+%D As we can see here, the simple command \type{\dorecurse} is a special case of the
+%D more general:
+%D
+%D \starttyping
+%D \dostepwiserecurse {from} {to} {step} {action}
+%D \stoptyping
+%D
+%D This commands accepts positive and negative steps. Illegal values are handles as
+%D good as possible and the macro accepts numbers and \COUNTERS.
+%D
+%D \starttyping
+%D \dostepwiserecurse  {1} {10}  {2} {...}
+%D \dostepwiserecurse {10}  {1} {-2} {...}
+%D \stoptyping
+%D
+%D Because the simple case is used often, we implement it more efficiently:
+
+\unexpanded\def\dorecurse#1%
+  {\ifcase#1\relax
+     \expandafter\gobbletwoarguments
+   \or
+     \expandafter\syst_helpers_recurse_y
+   \else
+     \expandafter\syst_helpers_recurse_x
+   \fi{#1}}
+
+\unexpanded\def\syst_helpers_recurse_x#1#2%
+  {\global\advance\outerrecurse \plusone
+   \expandafter\gdef\csname\??recurseaction\the\outerrecurse\endcsname{#2}%
+   \expandafter\glet\csname\??recurseindex \the\outerrecurse\endcsname\recurselevel
+   \expandafter\syst_helpers_recurse_indeed\expandafter1\expandafter{\number#1}}
+
+\unexpanded\def\syst_helpers_recurse_y#1#2%
+  {\global\advance\outerrecurse \plusone
+   \expandafter\glet\csname\??recurseindex\the\outerrecurse\endcsname\recurselevel
+   \let\recurselevel\!!plusone
+   #2%
+   \expandafter\let\expandafter\recurselevel\csname\??recurseindex\the\outerrecurse\endcsname
+   \global\advance\outerrecurse \minusone}
+
+\unexpanded\def\syst_helpers_recurse_indeed#1#2% from to
+  {\ifnum#1>#2\relax
+     \expandafter\syst_helpers_recurse_indeed_nop
+   \else
+     \def\recurselevel{#1}%
+     \doubleexpandafter\syst_helpers_recurse_indeed_yes
+   \fi\expandafter{\the\numexpr\recurselevel+\plusone\relax}{#2}}
+
+\unexpanded\def\syst_helpers_recurse_indeed#1#2% from to
+  {\ifnum#1>#2\relax
+     \expandafter\syst_helpers_recurse_indeed_nop
+   \else
+     \def\recurselevel{#1}%
+     \innerrecurse#1\advance\innerrecurse\plusone
+     \doubleexpandafter\syst_helpers_recurse_indeed_yes
+   \fi\expandafter{\the\innerrecurse}{#2}}
+
+\unexpanded\def\syst_helpers_recurse_indeed_yes
+  {\syst_helpers_recurse_content
+   \syst_helpers_recurse_indeed}
+
+\unexpanded\def\syst_helpers_recurse_indeed_nop#1#2#3%
+  {\expandafter\let\expandafter\recurselevel\csname\??recurseindex\the\outerrecurse\endcsname
+   \global\advance\outerrecurse \minusone }
+
+%D \macros
+%D   {dowith}
+%D
+%D Here's a loop over whatever is in a list:
+%D
+%D \starttyping
+%D \dowith{a,b,c}{[#1]}
+%D \stoptyping
+
+\unexpanded\def\dowith#1#2%
+  {\def\syst_helpers_with##1{#2}%
+   \normalexpanded{\processcommalist[#1]}\syst_helpers_with}
+
+%D \macros
+%D   {doloop,exitloop}
+%D
+%D Sometimes loops are not determined by counters, but by (a combinations of)
+%D conditions. We therefore implement a straightforward loop, which can only be left
+%D when we explictly exit it. Nesting is supported. First we present a more
+%D extensive alternative.
+%D
+%D \starttyping
+%D \doloop
+%D   {Some kind of typesetting punishment \par
+%D    \ifnum\pageno>100 \exitloop \fi}
+%D \stoptyping
+%D
+%D When needed, one can call for \type {\looplevel} and \type {\loopdepth}.
+
+\let\endofloop\donothing % maybe \syst_helpers_loop_end
+
+\unexpanded\def\doloop#1%
+  {\global\advance\outerrecurse \plusone
+   \expandafter\gdef\csname\??recurseaction\the\outerrecurse\endcsname{#1}%
+   \expandafter\glet\csname\??recurseindex \the\outerrecurse\endcsname\recurselevel
+   \let\endofloop\syst_helpers_loop
+   \syst_helpers_loop1} % no \plusone else \recurselevel wrong
+
+\unexpanded\def\syst_helpers_loop#1%
+  {\def\recurselevel{#1}%
+   \expandafter\syst_helpers_loop_yes\expandafter{\the\numexpr\recurselevel+\plusone\relax}}
+
+\unexpanded\def\syst_helpers_loop_yes
+  {\syst_helpers_recurse_content
+   \endofloop}
+
+\unexpanded\def\syst_helpers_loop_nop#1%
+  {\let\endofloop\syst_helpers_loop % new, permits nested \doloop's
+   \expandafter\let\expandafter\recurselevel\csname\??recurseindex\the\outerrecurse\endcsname
+   \global\advance\outerrecurse\minusone}
+
+\unexpanded\def\exitloop                     % \exitloop quits at end
+  {\let\endofloop\syst_helpers_loop_nop}
+
+\unexpanded\def\exitloopnow#1\endofloop % \exitloopnow quits directly
+  {\syst_helpers_loop_nop}
+
+%D The loop is executed at least once, so beware of situations
+%D like:
+%D
+%D \starttyping
+%D \doloop {\exitloop some commands}
+%D \stoptyping
+%D
+%D It's just a matter of putting the text into the \type {\if} statement that should
+%D be there anyway, like in:
+%D
+%D \starttyping
+%D \doloop {\ifwhatever \exitloop \else some commands\fi}
+%D \stoptyping
+%D
+%D You can also quit a loop immediately, by using \type
+%D {\exitloopnow} instead. Beware, this is more sensitive
+%D for conditional errors.
+
+%D Krzysztof Leszczynski suggested to provide access to the level by means of a
+%D \type {#1}. I decided to pass the more frequently used level as \type {#1} and
+%D the less favoured depth as \type {#2}. The intended usage is:
+%D
+%D \starttyping
+%D \dorecurse{3}{\definesymbol[test-#1][xx-#1]}
+%D
+%D \def\test{\dorecurse{3}{\definesymbol[test-##1][xx-##1]}} \test
+%D
+%D \symbol[test-1]\quad\symbol[test-2]\quad\symbol[test-3]
+%D \stoptyping
+%D
+%D Since the hashed arguments are expanded, we don't need tricky expansion here.
+%D
+%D \starttyping
+%D \dorecurse{3}{\expanded{\definesymbol[test-\recurselevel][xx-\recurselevel]}}
+%D \stoptyping
+
+\def\syst_helpers_recurse_content
+  {\csname\??recurseaction\the\outerrecurse\expandafter\expandafter\expandafter\endcsname
+     \expandafter\expandafter\expandafter{\expandafter\recurselevel\expandafter}\expandafter{\the\outerrecurse}}
+
+\unexpanded\def\syst_helpers_recurse_x#1#2%
+  {\global\advance\outerrecurse \plusone
+   \expandafter\gdef\csname\??recurseaction\the\outerrecurse\endcsname##1##2{#2}%
+   \expandafter\glet\csname\??recurseindex \the\outerrecurse\endcsname\recurselevel
+   \expandafter\syst_helpers_recurse_indeed\expandafter1\expandafter{\number#1}}
+
+\unexpanded\def\syst_helpers_recurse_y#1#2%
+  {\global\advance\outerrecurse \plusone
+   \expandafter\glet\csname\??recurseindex \the\outerrecurse\endcsname\recurselevel
+   \let\recurselevel\!!plusone
+   \expandafter\gdef\csname\??recurseaction\the\outerrecurse\endcsname##1##2{#2}%
+   \syst_helpers_recurse_content
+   \expandafter\let\expandafter\recurselevel\csname\??recurseindex\the\outerrecurse\endcsname
+   \global\advance\outerrecurse \minusone}
+
+\unexpanded\def\doloop#1%
+  {\global\advance\outerrecurse \plusone
+   \expandafter\gdef\csname\??recurseaction\the\outerrecurse\endcsname##1##2{#1}%
+   \expandafter\glet\csname\??recurseindex \the\outerrecurse\endcsname\recurselevel
+   \let\endofloop\syst_helpers_loop
+   \syst_helpers_loop1} % no \plusone else \recurselevel wrong
+
+\installsystemnamespace{recursestepwise}
+
+\unexpanded\def\dostepwiserecurse#1#2#3#4% can be made faster by postponing #4
+  {\global\advance\outerrecurse \plusone
+   \expandafter\gdef\csname\??recurseaction\the\outerrecurse\endcsname##1##2{#4}%
+   \expandafter\glet\csname\??recurseindex \the\outerrecurse\endcsname\recurselevel
+   \csname\??recursestepwise
+     % we need the x in order to avoid the \relax that tex adds
+     \ifnum#3>\zerocount
+       \ifnum#2<#1x\else d\fi
+     \orelse\ifnum#3<\zerocount
+       \ifnum#1<#2x\else r\fi
+     \fi
+   \expandafter\endcsname\normalexpanded{{\number#1}{\number#2}{\number#3}}}
+ % \expandafter\endcsname\expandafter{\number#1\expandafter}\expandafter{\number#2\expandafter}\expandafter{\number#3}}
+
+\letvalue{\??recursestepwise x}\syst_helpers_stepwise_exit
+\letvalue{\??recursestepwise d}\syst_helpers_stepwise_recurse
+\letvalue{\??recursestepwise r}\syst_helpers_stepwise_reverse
+
+\newcount\fastloopindex
+\newcount\fastloopfinal
+
+\let\m_syst_helpers_fast_loop_cs\relax
+
+\unexpanded\def\dofastloopcs#1%
+  {\fastloopfinal#1\relax
+   \ifcase\fastloopfinal
+     \expandafter\gobbleoneargument
+   \else
+     \expandafter\syst_helpers_fast_loop_cs
+   \fi}
+
+\unexpanded\def\syst_helpers_fast_loop_cs#1%
+  {\let\m_syst_helpers_fast_loop_cs#1%
+   \fastloopindex\plusone
+   \syst_helpers_fast_loop_cs_step}
+
+\unexpanded\def\syst_helpers_fast_loop_cs_step
+  {\ifnum\fastloopindex>\fastloopfinal
+     \let\m_syst_helpers_fast_loop_cs\relax
+   \else
+     \m_syst_helpers_fast_loop_cs
+     \advance\fastloopindex\plusone
+     \expandafter\syst_helpers_fast_loop_cs_step
+   \fi}
+
+% Helper:
+
+\unexpanded\def\resetrecurselevel{\let\recurselevel\!!zerocount}
+
+\let\recurselevel\!!zerocount
+
+% \appendtoks \resetrecurselevel \to \everydump
+
+%D \macros
+%D   {doloopoverlist}
+%D
+%D \starttyping
+%D \doloopoverlist {red,green,blue} {
+%D      \setuppalet[\recursestring]
+%D      \doloopoverlist {light,normal,dark} {
+%D          \blackrule[color=\recursestring,width=20cm,height=2cm,depth=0cm]\par
+%D      }
+%D  }
+%D \stoptyping
+%D
+%D or:
+%D
+%D \starttyping
+%D \doloopoverlist {red,green,blue} {
+%D      \setuppalet[#1]
+%D      \doloopoverlist {light,normal,dark} {
+%D          \blackrule[color=##1,width=20cm,height=2cm,depth=0cm]\par
+%D      }
+%D  }
+%D \stoptyping
+
+\unexpanded\def\doloopoverlist#1#2%
+  {\global\advance\outerrecurse\plusone
+   \expandafter\gdef\csname\??recurseaction\the\outerrecurse\endcsname##1{\edef\recursestring{##1}#2}%
+   \expandafter\glet\csname\??recurseindex \the\outerrecurse\endcsname\recursestring
+   \normalexpanded{\processcommalist[#1]{\expandafter\noexpand\csname\??recurseaction\the\outerrecurse\endcsname}}%
+   \expandafter\let\expandafter\recursestring\csname\??recurseindex\the\outerrecurse\endcsname
+   \global\advance\outerrecurse\minusone}
+
+%D \macros
+%D   {newevery,everyline,EveryLine,EveryPar}
+%D
+%D Lets skip to something quite different. It's common use to use \type {\everypar}
+%D for special purposes. In \CONTEXT\ we use this primitive for locating sidefloats.
+%D This means that when user assignments to \type {\everypar} can interfere with
+%D those of the package. We therefore introduce \type {\EveryPar}.
+%D
+%D The same goes for \type {\EveryLine}. Because \TEX\ offers no \type {\everyline}
+%D primitive, we have to call for \type {\everyline} when we are working on a line
+%D by line basis. Just by calling \type {\EveryPar{}} and \type {\EveryLine{}} we
+%D restore the old situation.
+
+% \dorecurse{2}{
+%     \expanded{\everypar{before \recurselevel\space}}
+%     \EveryPar{x } [before \recurselevel\space x] \par
+%     \EveryPar{y } [before \recurselevel\space y] \par
+%     \EveryPar{}   [before \recurselevel]   \par
+%     \EveryPar{x } \EveryPar{y } \EveryPar{} [before \recurselevel] \par
+%     \EveryPar{y } \everypar{before } [before] \par
+% }
+
+\installsystemnamespace{extraevery}
+
+\unexpanded\def\newevery#1#2%
+  {\ifx#1\everypar\else\newtoks#1\fi% we test for redefinition elsewhere
+   \ifx#2\relax\orelse\ifdefined#2\else
+     \expandafter\newtoks\csname\??extraevery\csstring#1\endcsname
+     \edef#2{\syst_helpers_every#1\csname\??extraevery\csstring#1\endcsname}%
+   \fi}
+
+\unexpanded\def\syst_helpers_every#1#2%
+  {\removetoks\the#2\from#1%
+   \appendtoks\the#2\to  #1%
+   #2}
+
+%D This one permits definitions like:
+
+\newevery \everypar  \EveryPar  % we get a warning which is ok
+\newevery \everyline \EveryLine
+
+%D and how about:
+
+\newtoks \neverypar
+
+\unexpanded\def\forgeteverypar
+  {\everypar{\the\neverypar}}
+
+%D Which we're going to use indeed! When the second argument equals \type {\relax},
+%D the first token list is created unless it is already defined.
+%D
+%D Technically spoken we could have used the method we are going to present in the
+%D visual debugger. First we save the primitive \type{\everypar}:
+%D
+%D \starttyping
+%D \let\normaleverypar=\everypar
+%D \stoptyping
+%D
+%D Next we allocate a \TOKENLIST\ named \type{\everypar}, which means that
+%D \type{\everypar} is no longer a primitive but something like \type{\toks44}.
+%D
+%D \starttyping
+%D \newtoks\everypar
+%D \stoptyping
+%D
+%D Because \TEX\ now executes \type{\normaleverypar} instead of \type{\everypar}, we
+%D are ready to assign some tokens to this internally known and used \TOKENLIST.
+%D
+%D \starttyping
+%D \normaleverypar={all the things the system wants to do \the\everypar}
+%D \stoptyping
+%D
+%D Where the user can provide his own tokens to be expanded every time he expects
+%D them to expand.
+%D
+%D \starttyping
+%D \everypar={something the user wants to do}
+%D \stoptyping
+%D
+%D We don't use this method because it undoubtly leads to confusing situations,
+%D especially when other packages are used, but it's this kind of tricks that make
+%D \TEX\ so powerful.
+
+%D \macros
+%D   {convertargument,convertcommand,convertvalue}
+%D
+%D Some persistent experimenting led us to the next macro. This macro converts a
+%D parameter or an expanded macro to it's textual meaning.
+%D
+%D \starttyping
+%D \convertargument ... \to \command
+%D \stoptyping
+%D
+%D For example,
+%D
+%D \starttyping
+%D \convertargument{one \two \three{four}}\to\ascii
+%D \stoptyping
+%D
+%D The resulting macro \type{\ascii} can be written to a file or the terminal
+%D without problems. In \CONTEXT\ we use this macro for generating registers and
+%D tables of contents.
+%D
+%D The second conversion alternative accepts a command:
+%D
+%D \starttyping
+%D \convertcommand\command\to\ascii
+%D \stoptyping
+%D
+%D Both commands accept the prefix \type{\doglobal} for global assignments.
+
+\unexpanded\def\convertvalue#1\to
+  {\expandafter\convertcommand\csname#1\endcsname\to}
+
+\unexpanded\def\defconvertedvalue#1#2% less sensitive for \to
+  {\expandafter\defconvertedcommand\expandafter#1\csname#2\endcsname}
+
+%D \macros
+%D   {doifassignmentelse}
+%D
+%D A lot of \CONTEXT\ commands take optional arguments, for instance:
+%D
+%D \starttyping
+%D \dothisorthat[alfa,beta]
+%D \dothisorthat[first=foo,second=bar]
+%D \dothisorthat[alfa,beta][first=foo,second=bar]
+%D \stoptyping
+%D
+%D Although a combined solution is possible, we prefer a seperation. The next
+%D command takes care of propper handling of such multi||faced commands.
+%D
+%D \starttyping
+%D \doifassignmentelse {...} {then ...} {else ...}
+%D \stoptyping
+
+\def\syst_helpers_check_if_assignment_else#1=#2#3^^^^0004{\if#2^^^^0003}%
+\def\syst_helpers_check_else_assignment_if#1=#2#3^^^^0004{\unless\if#2^^^^0003}%
+
+\unexpanded\def\doifelseassignment#1%
+  {\expandafter\syst_helpers_check_if_assignment_else\detokenize{#1}=^^^^0003^^^^0003^^^^0004%
+     \expandafter\secondoftwoarguments
+   \else
+     \expandafter\firstoftwoarguments
+   \fi}
+
+\unexpanded\def\doifelseassignmentcs#1#2#3%
+  {\expandafter\syst_helpers_check_if_assignment_else\detokenize{#1}=^^^^0003^^^^0003^^^^0004%
+     \expandafter#3%
+   \else
+     \expandafter#2%
+   \fi}
+
+\let\doifassignmentelse  \doifelseassignment
+\let\doifassignmentelsecs\doifelseassignmentcs
+
+\newif\ifassignment
+
+\unexpanded\def\docheckassignment#1%
+  {\expandafter\syst_helpers_check_if_assignment_else\detokenize{#1}=^^^^0003^^^^0003^^^^0004%
+     \assignmentfalse
+   \else
+     \assignmenttrue
+   \fi}
+
+%D These can be used for cases where we want less tracing noise.
+
+\unexpanded\def\validassignment#1%
+  {\expandafter\syst_helpers_check_else_assignment_if\detokenize{#1}=^^^^0003^^^^0003^^^^0004}
+
+\unexpanded\def\novalidassignment#1%
+  {\expandafter\syst_helpers_check_if_assignment_else\detokenize{#1}=^^^^0003^^^^0003^^^^0004}
+
+%D In \ETEX\ we can use \type {\detokenize} and gain some speed, but in general far
+%D less that 1\% for \type {\convertargument} and nil for \type {\convertcommand}.
+%D This macro is more robust than the pure \TEX\ one, something I found out when
+%D primitives like \type {\jobname} were fed (or something undefined).
+
+\unexpanded\def\convertargument#1\to#2{\dodoglobal\edef#2{\detokenize{#1}}}
+\unexpanded\def\convertcommand #1\to#2{\dodoglobal\edef#2{\expandafter\detokenize\expandafter{#1}}} % hm, only second is also ok
+
+\unexpanded\def\defconvertedargument #1#2{\edef#1{\detokenize{#2}}}
+\unexpanded\def\defconvertedcommand  #1#2{\edef#1{\detokenize\expandafter{#2}}}
+\unexpanded\def\edefconvertedargument#1#2{\edef#1{#2}%
+                                          \edef#1{\detokenize\expandafter{#1}}}
+\unexpanded\def\gdefconvertedargument#1#2{\xdef#1{\detokenize{#2}}}
+\unexpanded\def\gdefconvertedcommand #1#2{\xdef#1{\detokenize\expandafter{#2}}}
+\unexpanded\def\xdefconvertedargument#1#2{\xdef#1{#2}%
+                                          \xdef#1{\detokenize\expandafter{#1}}}
+
+%D When you try to convert a primitive command, you'll find out that the \ETEX\
+%D method fails on for instance \type {\jobname} in the sense that it returns the
+%D filename instead of just \type {\jobname}. So far this does not give real
+%D problems.
+
+%D This is typically a macro that one comes to after reading the \TEX book
+%D carefully. Even then, the definite solution was found after rereading the \TEX
+%D book. The first implementation was:
+%D
+%D \starttyping
+%D \def\doconvertargument#1->#2\\\\{#2}
+%D \stoptyping
+%D
+%D The \type {-}, the delimiter \type {\\\\} and the the second argument are
+%D completely redundant.
+
+%D \macros
+%D   {showvalue}
+%D
+%D Ahandy macro, for testing purposes only:
+
+\unexpanded\def\showvalue#1%
+  {\ifcsname#1\endcsname
+     \expandafter\show\csname#1\endcsname
+   \else
+     \show\undefined
+   \fi}
+
+%D \macros
+%D   {doifmeaningelse}
+%D
+%D We can use both commands in testing, but alas, not all meanings expand to
+%D something \type {->}. This is no problem in the \ETEX\ implementation, but since
+%D we want compatibility, we need:
+%D
+%D \starttyping
+%D \doifmeaningelse {\next} {\something} {true} {false}
+%D \stoptyping
+%D
+%D Watch the one level expansion of the second argument.
+
+\unexpanded\def\doifelsemeaning#1#2%
+  {\edef\m_syst_string_one{\normalmeaning#1}%
+   \def \m_syst_string_two{#2}%
+   \edef\m_syst_string_two{\normalmeaning\m_syst_string_two}%
+   \ifx\m_syst_string_one\m_syst_string_two
+     \expandafter\firstoftwoarguments
+   \else
+     \expandafter\secondoftwoarguments
+   \fi}
+
+\let\doifmeaningelse\doifelsemeaning
+
+%D \macros
+%D   {doifsamestringselse,doifsamestring,doifnotsamestring}
+%D
+%D The next comparison macro converts the arguments into expanded strings. This
+%D command can be used to compare for instance \type {\jobname} with a name stored
+%D in a macro.
+%D
+%D \starttyping
+%D \doifelse          {\jobname}{oeps}{YES}{NO}
+%D \doifsamestringelse{\jobname}{oeps}{YES}{NO}
+%D \stoptyping
+
+\def\syst_helpers_if_samestring_else#1#2#3#4%
+  {\edef\m_syst_string_one{\detokenize\expandafter{\normalexpanded{#3}}}%
+   \edef\m_syst_string_two{\detokenize\expandafter{\normalexpanded{#4}}}%
+   \ifx\m_syst_string_one\m_syst_string_two\expandafter#1\else\expandafter#2\fi}
+
+\unexpanded\def\doifelsesamestring{\syst_helpers_if_samestring_else\firstoftwoarguments\secondoftwoarguments}
+\unexpanded\def\doifsamestring    {\syst_helpers_if_samestring_else\firstofoneargument \gobbleoneargument   }
+\unexpanded\def\doifnotsamestring {\syst_helpers_if_samestring_else\gobbleoneargument  \firstofoneargument  }
+
+\let\doifsamestringelse\doifelsesamestring
+
+%D \macros
+%D   {ConvertToConstant,ConvertConstantAfter}
+%D
+%D When comparing arguments with a constant, we can get into trouble when this
+%D argument consists of tricky expandable commands. One solution for this is
+%D converting the argument to a string of unexpandable characters. To make
+%D comparison possible, we have to convert the constant too.
+%D
+%D \starttyping
+%D \ConvertToConstant\doifelse {...} {...} {then ...} {else ...}
+%D \stoptyping
+%D
+%D This construction is only needed when the first argument can give troubles.
+%D Misuse can slow down processing.
+%D
+%D \starttyping
+%D \ConvertToConstant\doifelse{\c!alfa}        {\c!alfa}{...}{...}
+%D \ConvertToConstant\doifelse{alfa}           {\c!alfa}{...}{...}
+%D \ConvertToConstant\doifelse{alfa}           {alfa}   {...}{...}
+%D \ConvertToConstant\doifelse{alfa \alfa test}{\c!alfa}{...}{...}
+%D \stoptyping
+%D
+%D In examples~2 and~3 both arguments equal, in~1 and~4 they differ.
+
+\unexpanded\def\ConvertToConstant#1#2#3%
+  {\edef\m_syst_string_one{\expandafter\detokenize\expandafter{#2}}%
+   \edef\m_syst_string_two{\expandafter\detokenize\expandafter{#3}}%
+   #1{\m_syst_string_one}{\m_syst_string_two}}
+
+%D When the argument \type{#1} consists of commands, we had better use
+%D
+%D \starttyping
+%D \ConvertConstantAfter\processaction[#1][...]
+%D \ConvertConstantAfter\doifelse{#1}{\v!something}{}{}
+%D \stoptyping
+%D
+%D This commands accepts things like:
+%D
+%D \starttyping
+%D \v!constant
+%D constant
+%D \hbox to \hsize{\rubish}
+%D \stoptyping
+%D
+%D As we will see in the core modules, this macro permits constructions like:
+%D
+%D \starttyping
+%D \setupfootertexts[...][...]
+%D \setupfootertexts[margin][...][...]
+%D \setupfootertexts[\v!margin][...][...]
+%D \stoptyping
+%D
+%D where \type {...} can be anything legally \TEX.
+
+\unexpanded\def\CheckConstantAfter#1#2%
+  {\expandafter\convertargument\v!prefix!\to\ascii
+   \convertargument#1\to#2\relax
+   \doifelseinstring\ascii{#2}
+     {\expandafter\convertargument#1\to#2}
+     {}}
+
+\unexpanded\def\ConvertConstantAfter#1#2#3%
+  {\CheckConstantAfter{#2}\asciia
+   \CheckConstantAfter{#3}\asciib
+   #1{\asciia}{\asciib}}
+
+%D \macros
+%D   {assignifempty}
+%D
+%D We can assign a default value to an empty macro using:
+%D
+%D \starttyping
+%D \assignifempty \macros {default value}
+%D \stoptyping
+%D
+%D We don't explicitly test if the macro is defined.
+
+\unexpanded\def\assignifempty#1#2% can be sped up
+  {\doifsomething{#1}{\def#1{#2}}} % {\doifnot{#1}{}{\def#1{#2}}}
+
+%D \macros
+%D   {gobbleuntil,grabuntil,gobbleuntilrelax,
+%D    processbetween,processuntil}
+%D
+%D In \TEX\ gobbling usually stand for skipping arguments, so here are our gobbling
+%D macros.
+%D
+%D In \CONTEXT\ we use a lot of \type {\start}||\type {\stop} like constructions.
+%D Sometimes, the \type {\stop} is used as a hard coded delimiter like in: %D
+%D \starttyping
+%D \unexpanded\def\startcommand#1\stopcommand%
+%D   {... #1 ...}
+%D \stoptyping
+%D
+%D In many cases the \type {\start}||\type {\stop} pair is defined at format
+%D generation time or during a job. This means that we cannot hardcode the \type
+%D {\stop} criterium. Only after completely understanding \type {\csname} and \type
+%D {\expandafter} I was able to to implement a solution, starting with:
+%D
+%D \starttyping
+%D \grabuntil{stop}\command
+%D \stoptyping
+%D
+%D This commands executes, after having encountered \type {\stop} the command \type
+%D {\command}. This command receives as argument the text preceding the \type
+%D {\stop}. This means that:
+%D
+%D \starttyping
+%D \unexpanded\def\starthello%
+%D   {\grabuntil{stophello}\message}
+%D
+%D \starthello Hello world!\stophello
+%D \stoptyping
+%D
+%D results in: \type{\message{Hello world!}}.
+
+\let\syst_helpers_grab_indeed\relax
+
+\unexpanded\def\syst_helpers_grab#1#2%
+  {\def\syst_helpers_grab_indeed##1#1{#2{##1}}\syst_helpers_grab_indeed}
+
+\unexpanded\def\grabuntil#1%
+  {\expandafter\syst_helpers_grab\expandafter{\csname#1\endcsname}}
+
+%D The next command build on this mechanism:
+%D
+%D \starttyping
+%D \processbetween{string}\command
+%D \stoptyping
+%D
+%D Here:
+%D
+%D \starttyping
+%D \processbetween{hello}\message
+%D \starthello Hello again!\stophello
+%D \stoptyping
+%D
+%D leads to: \type{\message{Hello again!}}. The command
+%D
+%D \starttyping
+%D \gobbleuntil{sequence}
+%D \stoptyping
+%D
+%D is related to these commands. This one simply throws away
+%D everything preceding \type{\command}.
+
+\let\syst_helpers_gobble_indeed\relax
+
+\unexpanded\def\processbetween#1#2%
+  {\setvalue{\s!start#1}{\grabuntil{\s!stop#1}{#2}}}
+
+\unexpanded\def\gobbleuntil#1%
+  {\def\syst_helpers_gobble_indeed##1#1{}\syst_helpers_gobble_indeed}
+
+\unexpanded\def\gobbleuntilrelax#1\relax
+  {}
+
+%D The next one simply expands the pickup up tokens.
+%D
+%D \starttyping
+%D \processuntil{sequence}
+%D \stoptyping
+
+\let\syst_helpers_until_indeed\relax
+
+\unexpanded\def\processuntil#1%
+  {\def\syst_helpers_until_indeed##1#1{##1}\syst_helpers_until_indeed}
+
+%D \macros
+%D   {groupedcommand}
+%D
+%D Commands often manipulate argument as in:
+%D
+%D \starttyping
+%D \def\doezomaarwat#1{....#1....}
+%D \stoptyping
+%D
+%D A disadvantage of this approach is that the tokens that form \type{#1} are fixed
+%D the the moment the argument is read in. Normally this is no problem, but for
+%D instance verbatim environments adapt the \CATCODES\ of characters and therefore
+%D are not always happy with already fixed tokens.
+%D
+%D Another problem arises when the argument is grouped not by \type {{}} but by
+%D \type {\bgroup} and \type {\egroup}. Such an argument fails, because the \type
+%D {\bgroup} is een as the argument (which is quite normal).
+%D
+%D The next macro offers a solution for both unwanted situations:
+%D
+%D \starttyping
+%D \groupedcommand {before} {after}
+%D \stoptyping
+%D
+%D Which can be used like:
+%D
+%D \starttyping
+%D \def\cite%
+%D   {\groupedcommand{\rightquote\rightquote}{\leftquote\leftquote}}
+%D \stoptyping
+%D
+%D This command is equivalent to, but more 'robust' than:
+%D
+%D \starttyping
+%D \def\cite#1%
+%D   {\rightquote\rightquote#1\leftquote\leftquote}
+%D \stoptyping
+%D
+%D \starttyping
+%D \def\rightword%
+%D   {\groupedcommand{\hfill\hbox}{\parfillskip\zeropoint}}
+%D
+%D .......... \rightword{the right way}
+%D \stoptyping
+%D
+%D Here \TEX\ typesets \type {\bf the right way} unbreakable at the end of the line.
+%D The solution mentioned before does not work here. We also handle
+%D
+%D \starttyping
+%D to be \bold{bold} or not, that's the question
+%D \stoptyping
+%D
+%D and
+%D
+%D \starttyping
+%D to be {\bold bold} or not, that's the question
+%D \stoptyping
+%D
+%D This alternative checks for a \type {\bgroup} token first. The internal
+%D alternative does not accept the box handling mentioned before, but further
+%D nesting works all right. The extra \type {\bgroup}||\type {\egroup} is needed to
+%D keep \type {\m_syst_helpers_handle_group_after} both into sight and local.
+
+\let\m_syst_helpers_handle_group_after \relax
+\let\m_syst_helpers_handle_group_before\relax
+
+\unexpanded\def\syst_helpers_handle_group_nop
+  {\ifnum\currentgrouptype=\semisimplegroupcode
+     \expandafter\syst_helpers_handle_group_nop_a
+   \else
+     \expandafter\syst_helpers_handle_group_nop_b
+   \fi}
+
+\def\syst_helpers_handle_group_nop_a
+  {\begingroup
+   \aftergroup\m_syst_helpers_handle_group_a
+   \aftergroup\endgroup
+   \m_syst_helpers_handle_group_b}
+
+\def\syst_helpers_handle_group_nop_b
+  {\bgroup
+   \aftergroup\m_syst_helpers_handle_group_a
+   \aftergroup\egroup
+   \m_syst_helpers_handle_group_b}
+
+\unexpanded\def\syst_helpers_handle_group_normal
+  {\bgroup
+   \afterassignment\m_syst_helpers_handle_group_normal_before
+   \let\next=}
+
+\def\m_syst_helpers_handle_group_normal_before
+  {\bgroup
+   \m_syst_helpers_handle_group_b
+   \bgroup
+   \aftergroup\m_syst_helpers_handle_group_a
+   \aftergroup\egroup
+   \aftergroup\egroup}
+
+\unexpanded\def\syst_helpers_handle_group_simple% no inner group (so no kerning interference)
+  {\bgroup
+   \afterassignment\m_syst_helpers_handle_group_simple_before
+   \let\next=}
+
+\def\m_syst_helpers_handle_group_simple_before
+  {\bgroup
+   \aftergroup\m_syst_helpers_handle_group_simple_after
+   \m_syst_helpers_handle_group_b}
+
+\def\m_syst_helpers_handle_group_simple_after
+  {\m_syst_helpers_handle_group_a
+   \egroup}%
+
+\unexpanded\def\syst_helpers_handle_group_pickup% no inner group (so no kerning interference)
+  {\bgroup
+   \afterassignment\m_syst_helpers_handle_group_pickup_before
+   \let\next=}
+
+\def\m_syst_helpers_handle_group_pickup_before
+  {\bgroup
+   \aftergroup\m_syst_helpers_handle_group_a
+   \aftergroup\egroup
+   \aftergroup\m_syst_helpers_handle_group_p
+   \m_syst_helpers_handle_group_b}
+
+\unexpanded\def\syst_helpers_handle_group_nop_x
+  {\ifnum\currentgrouptype=\semisimplegroupcode
+     \begingroup
+     \aftergroup\endgroup
+   \else
+     \bgroup
+     \aftergroup\egroup
+   \fi
+   \m_syst_helpers_handle_group_b}
+
+\unexpanded\def\syst_helpers_handle_group_normal_x
+  {\bgroup
+   \afterassignment\m_syst_helpers_handle_group_normal_before_x
+   \let\next=}
+
+\def\m_syst_helpers_handle_group_normal_before_x
+  {\bgroup
+   \m_syst_helpers_handle_group_b
+   \bgroup
+   \aftergroup\egroup
+   \aftergroup\egroup}
+
+%D I considered it a nuisance that
+%D
+%D \starttyping
+%D \color[green]
+%D   {as grass}
+%D \stoptyping
+%D
+%D was not interpreted as one would expect. This is due to the fact that \type
+%D {\futurelet} obeys blank spaces, and a line||ending token is treated as a blank
+%D space. So the final implementation became:
+
+\unexpanded\def\groupedcommand#1#2%
+  {\def\m_syst_helpers_handle_group_b{#1}%
+   \def\m_syst_helpers_handle_group_a{#2}%
+   \futureexpandis\bgroup\syst_helpers_handle_group_normal\syst_helpers_handle_group_nop}
+
+\unexpanded\def\groupedcommandcs#1#2%
+  {\let\m_syst_helpers_handle_group_b#1%
+   \let\m_syst_helpers_handle_group_a#2%
+   \futureexpandis\bgroup\syst_helpers_handle_group_normal\syst_helpers_handle_group_nop}
+
+\unexpanded\def\simplegroupedcommand#1#2%
+  {\def\m_syst_helpers_handle_group_b{#1}%
+   \def\m_syst_helpers_handle_group_a{#2}%
+   \futureexpandis\bgroup\syst_helpers_handle_group_simple\syst_helpers_handle_group_nop}
+
+\unexpanded\def\pickupgroupedcommand#1#2#3%
+  {\def\m_syst_helpers_handle_group_b{#1}%
+   \def\m_syst_helpers_handle_group_a{#2}%
+   \def\m_syst_helpers_handle_group_p{#2}%
+   \futureexpandis\bgroup\syst_helpers_handle_group_pickup\syst_helpers_handle_group_nop}
+
+\unexpanded\def\triggergroupedcommand#1%
+  {\def\m_syst_helpers_handle_group_b{#1}%
+   \futureexpandis\bgroup\syst_helpers_handle_group_normal_x\syst_helpers_handle_group_nop_x}
+
+\unexpanded\def\triggergroupedcommandcs#1%
+  {\let\m_syst_helpers_handle_group_b#1%
+   \futureexpandis\bgroup\syst_helpers_handle_group_normal_x\syst_helpers_handle_group_nop_x}
+
+%D Users should be aware of the fact that grouping can interfere with ones paragraph
+%D settings that are executed after the paragraph is closed. One should therefore
+%D explictly close the paragraph with \type {\par}, else the settings will be
+%D forgotten and not applied. So it's:
+%D
+%D \starttyping
+%D \def\BoldRaggedCenter%
+%D   {\groupedcommand{\raggedcenter\bf}{\par}}
+%D \stoptyping
+
+%D \macros
+%D   {checkdefined}
+%D
+%D The bigger the system, the greater the change that user defined commands collide
+%D with those that are part of the system. The next macro gives a warning when a
+%D command is already defined. We considered blocking the definition, but this is
+%D not always what we want.
+%D
+%D \starttyping
+%D \checkdefined {category} {class} {command}
+%D \stoptyping
+%D
+%D The user is warned with the suggestion to use \type {CAPITALS}. This suggestion
+%D is feasible, because \CONTEXT only defines lowcased macros.
+
+\unexpanded\def\showdefinederror#1#2%
+  {\writestatus\m!system{#1 #2 replaces a macro, use CAPITALS!}}
+
+\unexpanded\def\checkdefined#1#2#3%
+  {\doifdefined{#3}{\showdefinederror{#2}{#3}}}
+
+%D \macros
+%D   {GotoPar,GetPar}
+%D
+%D Typesetting a paragraph in a special way can be done by first grabbing the
+%D contents of the paragraph and processing this contents grouped. The next macro
+%D for instance typesets a paragraph in boldface.
+%D
+%D \starttyping
+%D \def\remark#1\par%
+%D   {\bgroup\bf#1\egroup}
+%D \stoptyping
+%D
+%D This macro has to be called like
+%D
+%D \starttyping
+%D \remark some text ... ending with \par
+%D \stoptyping
+%D
+%D Instead of \type {\par} we can of course use an empty line. When we started
+%D typesetting with \TEX, we already had produced lots of text in plain \ASCII. In
+%D producing such simple formatted texts, we adopted an open layout, and when
+%D switching to \TEX, we continued this open habit. Although \TEX\ permits a cramped
+%D and badly formatted source, it adds to confusion and sometimes introduces errors.
+%D So we prefer:
+%D
+%D \starttyping
+%D \remark
+%D
+%D some text ... ending with an empty line
+%D \stoptyping
+%D
+%D We are going to implement a mechanism that allows such open specifications. The
+%D definition of the macro handling \type {\remark} becomes:
+%D
+%D \starttyping
+%D \def\remark%
+%D   {\BeforePar{\bgroup\bf}%
+%D    \AfterPar{\egroup}%
+%D    \GetPar}
+%D \stoptyping
+%D
+%D A macro like \type {\GetPar} can be defined in several ways. The recent version,
+%D the fourth one in a row, originally was far more complicated, but some
+%D functionality has been moved to other macros.
+%D
+%D We start with the more simple but in some cases more appropriate alternative is
+%D \type {\GotoPar}. This one leaves \type {\par} unchanged and is therefore more
+%D robust. On the other hand, \type {\AfterPar} is not supported.
+
+\newtoks\BeforePar
+\newtoks\AfterPar
+
+\def\redowithpar\par
+  {\doifelsenextchar\par\redowithpar\dodowithpar}%
+
+\def\dowithpar#1#2%
+  {\def\dodowithpar##1\par{#1##1#2}%
+   \redowithpar\par}
+
+\def\redogotopar\par
+  {\doifelsenextchar\par\redogotopar\dodogotopar}%
+
+\def\dogotopar#1%
+  {\def\dodogotopar{#1}%
+   \redogotopar\par}
+
+\def\dogotoparcs#1%
+  {\let\dodogotopar#1%
+   \redogotopar\par}
+
+\unexpanded\def\GetPar
+  {\expanded
+     {\dowithpar
+        {\the\BeforePar
+         \BeforePar\emptytoks}
+        {\the\AfterPar
+         \BeforePar\emptytoks
+         \AfterPar\emptytoks}}}
+
+\unexpanded\def\GotoPar
+  {\expanded
+     {\dogotopar
+        {\the\BeforePar
+         \BeforePar\emptytoks}}}
+
+%D \macros
+%D   {dowithpargument,dowithwargument}
+%D
+%D The next macros are a variation on \type {\GetPar}. When macros expect an
+%D argument, it interprets a grouped sequence of characters a one token. While this
+%D adds to robustness and less ambiguous situations, we sometimes want to be a bit
+%D more flexible, or at least want to be a bit more tolerant to user input.
+%D
+%D We start with a commands that acts on paragraphs. This
+%D command is called as:
+%D
+%D \starttyping
+%D \dowithpargument\command
+%D \dowithpargument{\command ... }
+%D \stoptyping
+%D
+%D In \CONTEXT\ we use this one to read in the titles of chapters, sections etc. The
+%D commands responsible for these activities accept several alternative ways of
+%D argument passing. In these examples, the \type {\par} can be omitted when an
+%D empty line is present.
+%D
+%D \starttyping
+%D \command{...}
+%D \command ... \par
+%D \command
+%D   {...}
+%D \command
+%D   ... \par
+%D \stoptyping
+
+\let\syst_helpers_next_par\relax
+\let\syst_helpers_next_arg\relax
+
+\unexpanded\def\dowithpargument#1%
+  {\def\syst_helpers_next_par##1 \par{#1{##1}}%
+   \def\syst_helpers_next_arg##1{#1{##1}}%
+   \doifelsenextbgroup\syst_helpers_next_arg{\doifelsenextchar\par{#1{}}\syst_helpers_next_par}}
+
+%D The \type {p} in the previous command stands for paragraph. When we want to act
+%D upon words we can use the \type{w} alternative.
+%D
+%D \starttyping
+%D \dowithwargument\command
+%D \dowithwargument{... \command ...}
+%D \stoptyping
+%D
+%D The main difference bwteen two alternatives is in the handling of \type {\par}'s.
+%D This time the space token acts as a delimiter.
+%D
+%D \starttyping
+%D \command{...}
+%D \command ...
+%D \command
+%D   {...}
+%D \command
+%D   ...
+%D \stoptyping
+
+\let\syst_helpers_next_war\relax
+\let\syst_helpers_next_arg\relax
+
+\unexpanded\def\dowithwargument#1%
+  {\def\syst_helpers_next_war##1 {#1{##1}}%
+   \def\syst_helpers_next_arg##1{#1{##1}}%
+   \doifelsenextbgroup\syst_helpers_next_arg\syst_helpers_next_war}
+
+%D \macros
+%D   {dorepeat,dorepeatwithcommand}
+%D
+%D When doing repetitive tasks, we stromgly advice to use \type {\dorecurse}. The
+%D next alternative however, suits better some of the \CONTEXT\ interface commands.
+%D
+%D \starttyping
+%D \dorepeat[n*\command]
+%D \stoptyping
+%D
+%D The value of the used \COUNTER\ can be called within
+%D \type{\command} by \type{\repeater}.
+%D
+%D A slightly different alternative is:
+%D
+%D \starttyping
+%D \dorepeatwithcommand[n*{...}]\command
+%D \stoptyping
+%D
+%D When we call for something like:
+%D
+%D \starttyping
+%D \dorepeatwithcommand[3*{Hello}]\message
+%D \stoptyping
+%D
+%D we get ourselves three \type {\message{Hello}} messages in a row. In both
+%D commands, the \type {n*} is optional. When this specification is missing, the
+%D command executes once.
+
+\unexpanded\def\dorepeatwithcommand[#1]%
+  {\syst_helpers_repeat_with_command#1*\empty*\relax}
+
+\def\syst_helpers_repeat_with_command#1*#2#3*#4\relax#5%
+  {\ifx#2\empty\syst_helpers_repeat_with_command_again[#1]#5\else\syst_helpers_repeat_with_command_indeed{#1}{#2}{#3}#5\fi}
+
+\def\syst_helpers_repeat_with_command_indeed#1#2#3#4%
+  {\ifx#2\empty % redundant but gives cleaner extensions
+     #4{#1}%
+   \orelse\ifnum#1<\zerocount
+    %\normalexpanded{\dorecurse{\number-\number#1}}{#4{-#2#3}}%
+     \dorecurse{-#1}{#4{-#2#3}}%
+   \orelse\ifx#2+%
+     \dorecurse{#1}{#4{#3}}%
+   \else
+     \dorecurse{#1}{#4{#2#3}}%
+   \fi}
+
+\def\syst_helpers_repeat_with_command_again[#1]#2%
+  {#2{#1}}
+
+%D The extension hook permits something like:
+%D
+%D \starttyping
+%D \bgroup
+%D
+%D \catcode`\*=\superscriptcatcode
+%D
+%D \gdef\syst_helpers_repeat_with_command_again[#1]%
+%D   {\redodorepeatwithcommand#1*\empty*\relax}
+%D
+%D \gdef\redodorepeatwithcommand#1*#2#3*#4\relax#5%
+%D   {\syst_helpers_repeat_with_command_indeed{#1}{#2}{#3}#5}
+%D
+%D \egroup
+%D \stoptyping
+%D
+%D although one may wonder if changing the catcode of \type {*} is wise.
+
+%D \macros
+%D   {doifstringinstringelse}
+%D
+%D The next macro is meant for situations where both strings are macros. This save
+%D some unneeded expansion.
+%D
+%D \starttyping
+%D \def\doifstringinstringelse#1#2%
+%D   {\syst_helpers_do_if_in_string_else#1#2%
+%D      \expandafter\firstoftwoarguments
+%D    \else
+%D      \expandafter\secondoftwoarguments
+%D    \fi}
+%D \stoptyping
+%D
+%D A bit faster is:
+
+\def\syst_helpers_if_instring_else_indeed#1%
+  {\if#1@%
+     \expandafter\secondoftwoarguments
+   \else
+     \expandafter\firstoftwoarguments
+   \fi}
+
+\def\doifelsestringinstring#1#2%
+  {\expandafter\def\expandafter\syst_helpers_if_instring_else\expandafter##\expandafter1#1##2##3^^^^0004%
+     {\syst_helpers_if_instring_else_indeed##2}%
+   \expandafter\expandafter\expandafter\syst_helpers_if_instring_else\expandafter#2#1@@^^^^0004}
+
+\let\doifstringinstringelse\doifelsestringinstring
+
+%D \macros
+%D   {appendtoks,prependtoks,appendtoksonce,prependtoksonce,
+%D    doifintokselse,flushtoks,dotoks}
+%D
+%D We use tokenlists sparsely within \CONTEXT, because the comma separated lists are
+%D more suitable for the user interface. Nevertheless we have:
+%D
+%D \starttyping
+%D (\doglobal) \appendtoks ... \to\tokenlist
+%D (\doglobal) \prependtoks ... \to\tokenlist
+%D (\doglobal) \flushtoks\tokenlist
+%D             \dotoks\tokenlist
+%D \stoptyping
+%D
+%D These macros are clones of the ones implemented in page~378 of Knuth's \TEX book.
+
+\newtoks\t_syst_helpers_scratch
+\let    \m_syst_helpers_scratch\empty
+
+\unexpanded\def\appendtoks#1\to#2%
+  {\ifx\dodoglobal\relax
+     \expandafter\toksapp
+   \else
+     \resetglobal
+     \expandafter\gtoksapp
+   \fi#2{#1}}
+
+\unexpanded\def\prependtoks#1\to#2%
+  {\ifx\dodoglobal\relax
+     \expandafter\tokspre
+   \else
+     \resetglobal
+     \expandafter\gtokspre
+   \fi#2{#1}}
+
+\def\syst_helpers_append_toks_indeed
+  {\ifx\dodoglobal\relax
+     \expandafter\toksapp
+   \else
+     \resetglobal
+     \expandafter\gtoksapp
+   \fi\m_syst_helpers_scratch\t_syst_helpers_scratch}
+
+\def\syst_helpers_prepend_toks_indeed
+  {\ifx\dodoglobal\relax
+     \expandafter\tokspre
+   \else
+     \resetglobal
+     \expandafter\gtokspre
+   \fi\m_syst_helpers_scratch\t_syst_helpers_scratch}
+
+\unexpanded\def\appendtoksonce#1\to#2%
+  {\let\m_syst_helpers_scratch#2%
+   \t_syst_helpers_scratch{#1}%
+   \doifelseintoks\t_syst_helpers_scratch\m_syst_helpers_scratch
+     \donothing
+     \syst_helpers_append_toks_indeed}
+
+\unexpanded\def\prependtoksonce#1\to#2%
+  {\let\m_syst_helpers_scratch#2%
+   \t_syst_helpers_scratch{#1}%
+   \doifelseintoks\t_syst_helpers_scratch\m_syst_helpers_scratch
+     \donothing
+     \syst_helpers_prepend_toks_indeed}
+
+%D The test macro:
+
+\unexpanded\def\doifelseintoks#1#2% #1 en #2 zijn toks
+  {\edef\asciia{\detokenize\expandafter{\the#1}}%
+   \edef\asciib{\detokenize\expandafter{\the#2}}%
+   \doifelsestringinstring\asciia\asciib}
+
+\let\doifintokselse\doifelseintoks
+
+%D Moved from \type {lxml-ini.tex} to here. This one is for generators that collect
+%D stuff piecewise, which is sometimes hard on mechanisms that grab content using
+%D delimiters:
+%D
+%D \starttyping
+%D \startcollecting
+%D \startcollect \bTABLE \stopcollect
+%D     \startcollect \bTR \stopcollect
+%D         \startcollect \bTD \stopcollect
+%D         \startcollect   foo\stopcollect
+%D         \startcollect \eTD \stopcollect
+%D         \startcollect \bTD \stopcollect
+%D         \startcollect   bar\stopcollect
+%D         \startcollect \eTD \stopcollect
+%D     \startcollect \eTR \stopcollect
+%D \startcollect \eTABLE \stopcollect
+%D \stopcollecting
+%D \stoptyping
+
+\newtoks \collectingtoks
+
+\unexpanded\def\startcollect        #1\stopcollect        {\toksapp \collectingtoks{#1}}
+\unexpanded\def\startexpandedcollect#1\stopexpandedcollect{\etoksapp\collectingtoks{#1}}
+
+\unexpanded\def\startcollecting{\collectingtoks\emptytoks}
+\unexpanded\def\stopcollecting {\the\collectingtoks}
+
+\unexpanded\def\collect        {\toksapp \collectingtoks}
+\unexpanded\def\collectexpanded{\etoksapp\collectingtoks}
+
+%D A nice one too:
+
+% {\scratchtoks{abc} \removetoks b\from\scratchtoks [\the\scratchtoks]}
+% {\scratchtoks{abc} \removetoks x\from\scratchtoks [\the\scratchtoks]}
+% {\scratchtoks{} \removetoks x\from\scratchtoks [\the\scratchtoks]}
+% {\scratchtoks{xaa} \removetoks x\from\scratchtoks [\the\scratchtoks]}
+% {\scratchtoks{a\relax b} \removetoks \relax\from\scratchtoks [\showthe\scratchtoks]}
+
+\unexpanded\def\removetoks#1\from#2%
+  {\def\syst_helpers_remove_toks##1#1##2\empty\empty\empty##3^^^^0004%
+     {\def\m_syst_string_one{##3}%
+      \ifx\m_syst_string_one\empty#2{##1}\else#2{##1##2}\fi}%
+   \expandafter\syst_helpers_remove_toks\the#2\empty\empty\empty#1\empty\empty\empty^^^^0004}
+
+%D Also:
+
+\unexpanded\def\appendetoks#1\to#2%
+  {\ifx\dodoglobal\relax
+     \expandafter\etoksapp
+   \else
+     \resetglobal
+     \expandafter\xtoksapp
+   \fi#2{#1}}
+
+\unexpanded\def\prependetoks#1\to#2%
+  {\ifx\dodoglobal\relax
+     \expandafter\etokspre
+   \else
+     \resetglobal
+     \expandafter\xtokspre
+   \fi#2{#1}}
+
+%D Hm.
+
+\unexpanded\def\flushtoks#1% nb: can reassign to #1 again, hence the indirectness
+  {\t_syst_helpers_scratch#1\relax
+   \dodoglobal#1\emptytoks
+   \the\t_syst_helpers_scratch\relax}
+
+\let\dotoks\the
+
+%D \macros
+%D   {beforesplitstring,aftersplitstring}
+%D
+%D These both commands split a string at a given point in two
+%D parts, so \type{x.y} becomes \type{x} or \type{y}.
+%D
+%D \starttyping
+%D \beforesplitstring test.tex\at.\to\filename
+%D \aftersplitstring  test.tex\at.\to\extension
+%D \stoptyping
+%D
+%D The first routine looks (and is indeed) a bit simpler than the second one. The
+%D alternative looking more or less like the first one did not always give the
+%D results we needed. Both implementations show some insight in the manipulation of
+%D arguments.
+
+\let\syst_helpers_split_string\relax
+
+\unexpanded\def\beforesplitstring#1\at#2\to#3%
+  {\def\syst_helpers_split_string##1#2##2#2##3\\%
+     {\def#3{##1}}%
+   \expandafter\syst_helpers_split_string#1#2#2\\}
+
+\unexpanded\def\aftersplitstring#1\at#2\to#3%
+  {\def\syst_helpers_split_string##1#2##2@@@##3\\%
+     {\def#3{##2}}%
+   \expandafter\syst_helpers_split_string#1@@@#2@@@\\}
+
+%D \macros
+%D   {splitstring,greedysplitstring}
+%D
+%D A bonus macro.
+
+\unexpanded\def\splitstring#1\at#2\to#3\and#4%
+  {\def\syst_helpers_split_string##1#2##2\empty\empty\empty##3\\%
+     {\def#3{##1}%
+      \def\syst_helpers_split_string{##3}%
+      \ifx\syst_helpers_split_string\empty
+        \let#4\empty
+      \else
+        \def#4{##2}%
+      \fi}%
+   \expandafter\syst_helpers_split_string#1\empty\empty\empty#2\empty\empty\empty\\}
+
+\unexpanded\def\greedysplitstring#1\at#2\to#3\and#4%
+  {\edef\asciib{#1}%
+   \let\asciic\asciib
+   \let#3\empty
+   \let#4\empty
+   \doloop
+     {\expandafter\splitstring\asciib\at#2\to\asciia\and\asciib
+      \ifx\asciib\empty
+        \exitloop
+      \else
+        % not \edef#3{\ifx#3\empty\else#3#2\fi\asciia} else
+        % /root/path fails because then #3==empty
+        \edef#3{\ifcase\recurselevel\or\else#3#2\fi\asciia}%
+        \let#4\asciib
+      \fi}%
+  \ifx#3\empty\let#3\asciic\fi}
+
+%D \macros
+%D   {beforetestandsplitstring,
+%D    aftertestandsplitstring,
+%D    testandsplitstring}
+
+\unexpanded\def\beforetestandsplitstring#1\at#2\to#3%
+  {\def\syst_helpers_split_string##1#2##2#2##3##4\\%
+     {\ifx##3\empty\let#3\empty\else\def#3{##1}\fi}%
+   \expandafter\syst_helpers_split_string#1#2#2\empty\\}
+
+\unexpanded\def\aftertestandsplitstring#1\at#2\to#3%
+  {\def\syst_helpers_split_string ##1#2##2@@@##3##4\\%
+     {\ifx##3\empty\let#3\empty\else\def#3{##2}\fi}%
+   \expandafter\syst_helpers_split_string #1@@@#2@@@\empty\\}
+
+\def\testandsplitstring#1\at#2\to#3\and#4%
+  {\def\syst_helpers_split_string##1#2##2#2##3##4\\%
+     {\ifx##3\empty\let#3\empty\let#4\empty\else\def#3{##1}\def#4{##2}\fi}%
+   \expandafter\syst_helpers_split_string#1#2#2\empty\\}
+
+%D \macros
+%D   {splitatperiod,
+%D   {splitatcomma,
+%D    splitatasterisk,
+%D    splitatcolon,
+%D    splitatcolons}
+
+\unexpanded\def\splitatperiod  #1{\normalexpanded{\syst_helpers_splitatperiod  #1}..\relax}
+\unexpanded\def\splitatcomma   #1{\normalexpanded{\syst_helpers_splitatcomma   #1},,\relax}    % not at ", "
+\unexpanded\def\splitatasterisk#1{\normalexpanded{\syst_helpers_splitatasterisk#1}**\relax}
+\unexpanded\def\splitatcolon   #1{\normalexpanded{\syst_helpers_splitatcolon   #1}::\relax}
+\unexpanded\def\splitatcolons  #1{\normalexpanded{\syst_helpers_splitatcolons  #1}::::\relax}
+
+\unexpanded\def\syst_helpers_splitatperiod    #1.#2.#3\relax#4#5{\def#4{#1}\def#5{#2}}
+\unexpanded\def\syst_helpers_splitatcomma     #1,#2,#3\relax#4#5{\def#4{#1}\def#5{#2}}
+\unexpanded\def\syst_helpers_splitatasterisk  #1*#2*#3\relax#4#5{\def#4{#1}\def#5{#2}}
+\unexpanded\def\syst_helpers_splitatcolon     #1:#2:#3\relax#4#5{\def#4{#1}\def#5{#2}}
+\unexpanded\def\syst_helpers_splitatcolons  #1::#2::#3\relax#4#5{\edef#4{#1}\edef#5{#2}}
+
+%D \macros
+%D   {removesubstring}
+%D
+%D A first application of the two routines defined above is:
+%D
+%D \starttyping
+%D \removesubstring-\from first-last\to\nothyphenated
+%D \stoptyping
+%D
+%D Which in terms of \TEX\ looks like:
+
+\unexpanded\def\removesubstring#1\from#2\to#3%
+  {\splitstring#2\to\m_syst_string_one\and\m_syst_string_two
+   \dodoglobal#3{\m_syst_string_one\m_syst_string_two}}
+
+%D \macros
+%D   {appendtocommalist,prependtocommalist,
+%D    addtocommalist,removefromcommalist}
+%D
+%D When working with comma separated lists, one sooner or later want the tools to
+%D append or remove items from such a list. When we add an item, we first check if
+%D it's already there. This means that every item in the list is unique.
+%D
+%D \starttyping
+%D \addtocommalist      {alfa}  \name
+%D \addtocommalist      {beta}  \name
+%D \addtocommalist      {gamma} \name
+%D \removefromcommalist {beta}  \name
+%D \stoptyping
+%D
+%D These commands can be prefixed with \type {\doglobal}. The implementation of the
+%D second command is more complecated, because we have to take leading spaces into
+%D account. Keep in mind that users may provide lists with spaces after the commas.
+%D When one item is left, we also have to get rid of trailing spaces.
+%D
+%D \starttyping
+%D \def\words{alfa, beta, gamma, delta}
+%D \def\words{alfa,beta,gamma,delta}
+%D \stoptyping
+%D
+%D Removing an item takes more time than adding one. A fast appending alternative,
+%D without any testing, is also provided:
+%D
+%D \starttyping
+%D \appendtocommalist  {something} \name
+%D \prependtocommalist {something} \name
+%D \stoptyping
+%D
+%D This can be implemented as follows:
+%D
+%D \starttyping
+%D \def\appendtocommalist#1#2%
+%D   {\ifx#2\empty
+%D      \dodoglobal\edef#2{#1}%
+%D    \else % no test on empty
+%D      \dodoglobal\edef#2{#2,#1}%
+%D    \fi}
+%D
+%D \def\prependtocommalist#1#2%
+%D   {\ifx#2\empty
+%D      \dodoglobal\edef#2{#1}%
+%D    \else % no test on empty
+%D      \dodoglobal\edef#2{#1,#2}%
+%D    \fi}
+%D \stoptyping
+%D
+%D The faster alternatives are:
+
+\unexpanded\def\appendtocommalist#1#2%
+  {\dodoglobal\edef#2{\ifx#2\empty\else#2,\fi#1}}
+
+\unexpanded\def\prependtocommalist#1#2%
+  {\dodoglobal\edef#2{#1\ifx#2\empty\else,#2\fi}}
+
+\unexpanded\def\addtocommalist#1#2% {item} \cs
+  {\rawdoifelseinset{#1}#2\resetglobal
+     {\dodoglobal\edef#2{\ifx#2\empty\else#2,\fi#1}}}
+
+\unexpanded\def\pretocommalist#1#2% {item} \cs
+  {\rawdoifelseinset{#1}#2\resetglobal
+     {\dodoglobal\edef#2{#1\ifx#2\empty\else,#2\fi}}}
+
+\unexpanded\def\robustdoifelseinset#1#2%
+  {\edef\m_syst_string_one{\detokenize\expandafter{\normalexpanded{#1}}}%
+   \edef\m_syst_string_two{\detokenize\expandafter{\normalexpanded{#2}}}%
+   \rawdoifelseinset\m_syst_string_one\m_syst_string_two}
+
+\let\robustdoifinsetelse\robustdoifelseinset
+
+\unexpanded\def\robustaddtocommalist#1#2% {item} \cs
+  {\robustdoifelseinset{#1}#2\resetglobal
+     {\dodoglobal\edef#2{\ifx#2\empty\else#2,\fi#1}}}
+
+\unexpanded\def\robustpretocommalist#1#2% {item} \cs
+  {\robustdoifelseinset{#1}#2\resetglobal
+     {\dodoglobal\edef#2{#1\ifx#2\empty\else,#2\fi}}}
+
+\unexpanded\def\xsplitstring#1#2% \cs {str}
+  {\def\syst_helpers_split_string##1,#2,##2,#2,##3\\%
+     {\edef\m_syst_string_one{\bcleanedupcommalist##1\empty\empty\relax}%
+      \edef\m_syst_string_two{\acleanedupcommalist##2,,\relax}}%
+   \expandafter\syst_helpers_split_string\expandafter,#1,,#2,,#2,\\}
+
+\def\bcleanedupcommalist#1#2#3\relax{\if#1,\else#1\fi\if#2,\else#2\fi#3}
+\def\bcleanedupcommalist#1#2\relax{\if#1,\else#1\fi#2}
+\def\acleanedupcommalist#1,,#2\relax{#1}
+
+\unexpanded\def\removefromcommalist#1#2% to be sped up
+  {\rawdoifelseinset{#1}#2%
+     {\normalexpanded{\xsplitstring\noexpand#2{#1}}%
+      \dodoglobal\edef#2%
+        {\ifx\m_syst_string_one\empty
+           \m_syst_string_two
+         \else
+           \m_syst_string_one\ifx\m_syst_string_two\empty\else,\m_syst_string_two\fi
+         \fi}}
+     \resetglobal}
+
+%D \macros
+%D   {substituteincommalist}
+%D
+%D Slow but seldom used, so for the moment we stick to this implementation.
+%D
+%D \starttyping
+%D \substituteincommalist{old}{new}{list}
+%D \stoptyping
+
+\def\syst_helpers_substitute_in_comma_list_step#1%
+  {\edef\m_syst_string_three{#1}%
+   \ifx\m_syst_string_one\m_syst_string_three
+     \ifx\m_syst_string_two\empty \else
+       \edef\m_syst_string_four{\ifx\m_syst_string_four\empty\else\m_syst_string_four,\fi\m_syst_string_two}%
+     \fi
+   \else
+     \edef\m_syst_string_four{\ifx\m_syst_string_four\empty\else\m_syst_string_four,\fi#1}%
+   \fi}
+
+\unexpanded\def\substituteincommalist#1#2#3% old, new, list (slooow)
+  {\edef\m_syst_string_one{#1}%
+   \edef\m_syst_string_two{#2}%
+   \let\m_syst_string_four\empty
+   \normalexpanded{\rawprocesscommacommand[#3]}\syst_helpers_substitute_in_comma_list_step
+   \let#3\m_syst_string_four}
+
+%D \macros
+%D   {replaceincommalist}
+%D
+%D The next macro can be used to replace an indexed element in a commalist:
+%D
+%D \starttyping
+%D \replaceincommalist\MyList{2}
+%D \stoptyping
+%D
+%D Element~2 will be replaced by the current meaning of the macro \type
+%D {\newcommalistelement}. The old meaning is saved in \type {\commalistelement}.
+%D The replacement honors grouped items, like in:
+%D
+%D \starttyping
+%D \def\MyList{a,b,c,d,e,f}   \replaceincommalist\MyList{3}
+%D \def\MyList{a,b,c,d,e,f}   \replaceincommalist\MyList{3}
+%D \def\MyList{a,{b,c},d,e,f} \replaceincommalist\MyList{3}
+%D \def\MyList{a,b,c,{d,e,f}} \replaceincommalist\MyList{3}
+%D \stoptyping
+%D
+%D This macro was used in the bibtex code (and is probably no longer needed).
+
+\newcount\c_syst_helpers_comma_list_index
+\let     \m_syst_helpers_comma_list_target\empty
+
+\let\newcommalistelement\empty
+
+\def\syst_helpers_replace_in_comma_list_step#1%
+  {\ifnum\commalistcounter=\c_syst_helpers_comma_list_index\relax
+     \ifx\newcommalistelement\empty\else
+       \ifx\m_syst_helpers_comma_list_target\empty
+         \let\m_syst_helpers_comma_list_target\newcommalistelement
+       \else
+         \expandafter\expandafter\expandafter\def\expandafter\expandafter\expandafter
+           \m_syst_helpers_comma_list_target\expandafter\expandafter\expandafter
+             {\expandafter\m_syst_helpers_comma_list_target\expandafter,\newcommalistelement}%
+       \fi
+     \fi
+     \def\commalistelement{#1}%
+   \else
+     \ifx\m_syst_helpers_comma_list_target\empty
+       \ifx\nexttoken\bgroup % is known -)
+         \def\m_syst_helpers_comma_list_target{{#1}}%
+       \else
+         \def\m_syst_helpers_comma_list_target{#1}%
+       \fi
+     \else
+       \ifx\nexttoken\bgroup % is known -)
+         \expandafter\def\expandafter\m_syst_helpers_comma_list_target\expandafter{\m_syst_helpers_comma_list_target,{#1}}%
+       \else
+         \expandafter\def\expandafter\m_syst_helpers_comma_list_target\expandafter{\m_syst_helpers_comma_list_target,#1}%
+       \fi
+     \fi
+   \fi
+   \advance\commalistcounter\plusone}
+
+\unexpanded\def\replaceincommalist#1#2% #1 = commalistelement #2 = position starts at 1
+  {\c_syst_helpers_comma_list_index#2\relax
+   \let\m_syst_helpers_comma_list_target\empty
+   \let\commalistelement\empty
+   \commalistcounter\plusone
+   \expandafter\processcommalist\expandafter[#1]\syst_helpers_replace_in_comma_list_step
+   \dodoglobal\let#1\m_syst_helpers_comma_list_target}
+
+%D \macros
+%D   {globalprocesscommalist}
+%D
+%D The commalist processing commands are characterized by the fact that the way they
+%D handle expansion as well as the fact that they can be nested. This makes them
+%D kind of useless for handling comma lists in alignments. In these situations the
+%D next macro can be of use.
+
+\let\m_syst_helpers_comma_list_command_global\empty
+
+\def\syst_helpers_comma_list_command_global_step#1,%
+  {\if]#1\else
+     \m_syst_helpers_comma_list_command_global{#1}%
+     \expandafter\syst_helpers_comma_list_command_global_step
+   \fi}
+
+\unexpanded\def\globalprocesscommalist[#1]#2%
+  {\glet\m_syst_helpers_comma_list_command_global#2%
+   \expandafter\syst_helpers_comma_list_command_global_step#1,],}
+
+%D \macros
+%D   {withoutpt,PtToCm,
+%D    numberofpoints,dimensiontocount}
+%D
+%D We can convert point into centimeters with:
+%D
+%D \starttyping
+%D \PtToCm{dimension}
+%D \stoptyping
+
+{\catcode`\.=\othercatcode
+ \catcode`\p=\othercatcode
+ \catcode`\t=\othercatcode
+ \gdef\WITHOUTPT#1pt{#1}}
+
+\def\withoutpt#1%
+  {\expandafter\WITHOUTPT#1}
+
+%D The capitals are needed because \type {p} and \type {t} have catcode~12, while
+%D macronames only permit tokens with the catcode~11. As a result we cannot use the
+%D \type {.group} primitives. Those who want to know more about this kind of
+%D manipulations, we advice to study the \TEX book in detail. Because this macro
+%D does not do any assignment, we can use it in the following way too.
+
+\def\PtToCm#1%
+  {\withoutpt\the\dimexpr0.0351459804\dimexpr#1\relax\relax cm}
+
+%D We also support:
+%D
+%D \starttyping
+%D \numberofpoints   {dimension}
+%D \dimensiontocount {dimension} {\count}
+%D \stoptyping
+%D
+%D Both macros return a rounded number.
+
+% \dimensiontocount{10.49pt}\scratchcounter \the\scratchcounter / \numberofpoints{10.49pt}
+% \dimensiontocount{10.51pt}\scratchcounter \the\scratchcounter / \numberofpoints{10.51pt}
+
+\def\dimensiontocount#1#2{#2\numexpr\dimexpr#1\relax/\maxcard\relax}
+\def\numberofpoints    #1{\the\numexpr\dimexpr#1\relax/\maxcard\relax}
+
+%D \macros
+%D   {swapdimens,swapcounts,swapmacros,
+%D    globalswapdimens,globalswapcounts,globalswapmacros}
+%D
+%D Simple but effective are the next two macros. There name exactly states their
+%D purpose.
+
+\newdimen\d_syst_helpers_swapped
+\newcount\c_syst_helpers_swapped
+\let     \m_syst_helpers_swapped\relax
+
+\unexpanded\def\swapdimens#1#2{\d_syst_helpers_swapped    #1\relax#1#2\relax#2\d_syst_helpers_swapped}
+\unexpanded\def\swapcounts#1#2{\c_syst_helpers_swapped    #1\relax#1#2\relax#2\c_syst_helpers_swapped}
+\unexpanded\def\swapmacros#1#2{\let\m_syst_helpers_swapped#1\let  #1#2\let  #2\m_syst_helpers_swapped}
+
+\unexpanded\def\globalswapdimens#1#2{\d_syst_helpers_swapped    #1\global#1#2\global#2\d_syst_helpers_swapped}
+\unexpanded\def\globalswapcounts#1#2{\c_syst_helpers_swapped    #1\global#1#2\global#2\c_syst_helpers_swapped}
+\unexpanded\def\globalswapmacros#1#2{\let\m_syst_helpers_swapped#1\glet  #1#2\glet  #2\m_syst_helpers_swapped}
+
+%D \macros
+%D   {pushmacro,popmacro}
+%D
+%D Premature and a bit of beta, we offer:
+%D
+%D \starttyping
+%D \pushmacro\macro
+%D \popmacro\macro
+%D \stoptyping
+%D
+%D Beware: global!
+
+\installsystemnamespace{localpushedmacro}
+\installsystemnamespace{globalpushedmacro}
+
+\let\m_syst_helpers_push_macro\empty
+
+\newcount\c_syst_helpers_pop_count
+
+\def\syst_helpers_push_macro_new_global
+  {\expandafter\newcount\csname\??globalpushedmacro\m_syst_helpers_push_macro\endcsname
+   \global\advance\csname\??globalpushedmacro\m_syst_helpers_push_macro\endcsname\plusone}
+
+\def\syst_helpers_push_macro_new_local
+  {\expandafter\newcount\csname\??localpushedmacro\m_syst_helpers_push_macro\endcsname
+   \global\advance\csname\??localpushedmacro\m_syst_helpers_push_macro\endcsname\plusone}
+
+\unexpanded\def\globalpushmacro#1%
+  {\xdef\m_syst_helpers_push_macro{\csstring#1}%
+   \ifcsname\??globalpushedmacro\m_syst_helpers_push_macro\endcsname
+     \global\advance\lastnamedcs\plusone
+   \else
+     \syst_helpers_push_macro_new_global
+   \fi
+   \expandafter\glet\csname\the\lastnamedcs\m_syst_helpers_push_macro\endcsname#1}
+
+\unexpanded\def\localpushmacro#1% this one can be used to push a value over an \egroup
+  {\xdef\m_syst_helpers_push_macro{\csstring#1}%
+   \ifcsname\??localpushedmacro\m_syst_helpers_push_macro\endcsname
+     \global\advance\lastnamedcs\plusone
+   \else
+     \syst_helpers_push_macro_new_local
+   \fi
+   \expandafter\glet\csname\the\lastnamedcs\m_syst_helpers_push_macro\endcsname#1}
+
+\unexpanded\def\globalpopmacro#1%
+  {\xdef\m_syst_helpers_push_macro{\csstring#1}%
+   \c_syst_helpers_pop_count\csname\??globalpushedmacro\m_syst_helpers_push_macro\endcsname
+   \global\advance\lastnamedcs \minusone
+   \expandafter\glet\expandafter#1\csname\the\c_syst_helpers_pop_count\m_syst_helpers_push_macro\endcsname}
+
+\unexpanded\def\localpopmacro#1%
+  {\xdef\m_syst_helpers_push_macro{\csstring#1}%
+   \c_syst_helpers_pop_count\csname\??localpushedmacro\m_syst_helpers_push_macro\endcsname
+   \global\advance\lastnamedcs \minusone
+   \expandafter\let\expandafter#1\csname\the\c_syst_helpers_pop_count\m_syst_helpers_push_macro\endcsname}
+
+\let\pushmacro\localpushmacro
+\let\popmacro \localpopmacro
+
+%D \macros
+%D   {setlocalhsize,distributedhsize}
+%D
+%D Sometimes we need to work with the \type{ \hsize} that is corrected for
+%D indentation and left and right skips. The corrected value is available in \type
+%D {\localhsize}, which needs to be calculated with \type {\setlocalhsize} first. %D
+%D
+%D \starttyping
+%D \setlocalhsize        \hbox to \localhsize{...}
+%D \setlocalhsize[-1em]  \hbox to \localhsize{...}
+%D \setlocalhsize[.5ex]  \hbox to \localhsize{...}
+%D \stoptyping
+%D
+%D These examples show us that an optional can be used. The value provided is added
+%D to \type {\localhsize}.
+
+\newdimen\localhsize
+
+\unexpanded\def\setlocalhsize % don't change !
+  {\doifelsenextoptional
+     \syst_helpers_set_local_hsize_yes
+     \syst_helpers_set_local_hsize_nop}
+
+\def\syst_helpers_set_local_hsize_nop
+  {\localhsize\availablehsize}
+
+\def\syst_helpers_set_local_hsize_yes[#1]%
+  {\syst_helpers_set_local_hsize_nop
+   \advance\localhsize#1\relax}
+
+\def\availablehsize
+  {\dimexpr
+     \hsize-\leftskip-\rightskip
+     \ifnum\hangafter<\zerocount
+       \ifdim\hangindent>\zeropoint-\else+\fi\hangindent
+     \fi
+   \relax}
+
+\def\distributedhsize#1#2#3%
+  {\dimexpr(#1-\numexpr#3-1\relax\dimexpr#2\relax)/#3\relax}
+
+\def\hsizefraction#1#2%
+  {\dimexpr#1/#2\relax}
+
+%D \macros
+%D   {doifvalue,doifnotvalue,doifelsevalue,
+%D    doifnothing,doifsomething,doifelsenothing,
+%D    doifvaluenothing,doifvaluesomething,doifelsevaluenothing}
+%D
+%D These \type {\if} commands can be used to access macros (or variables) that are
+%D normally accessed by using \type {\getvalue}. Using these alternatives safes us
+%D three tokens per call. Anyone familiar with the not||values ones, can derive
+%D their meaning from the definitions.
+
+\unexpanded\def\doifvalue#1#2%
+  {\iftok{\csname#1\endcsname}{#2}%
+     \expandafter\firstofoneargument
+   \else
+     \expandafter\gobbleoneargument
+   \fi}
+
+\unexpanded\def\doifnotvalue#1#2%
+  {\iftok{\csname#1\endcsname}{#2}%
+     \expandafter\gobbleoneargument
+   \else
+     \expandafter\firstofoneargument
+   \fi}
+
+\unexpanded\def\doifelsevalue#1#2%
+  {\iftok{\csname#1\endcsname}{#2}%
+     \expandafter\firstoftwoarguments
+   \else
+     \expandafter\secondoftwoarguments
+   \fi}
+
+\unexpanded\def\doifnothing#1%
+  {\iftok{#1}\emptytoks
+     \expandafter\firstofoneargument
+   \else
+     \expandafter\gobbleoneargument
+   \fi}
+
+\unexpanded\def\doifsomething#1%
+  {\iftok{#1}\emptytoks
+     \expandafter\gobbleoneargument
+   \else
+     \expandafter\firstofoneargument
+   \fi}
+
+\unexpanded\def\doifelsenothing#1%
+  {\iftok{#1}\emptytoks
+      \expandafter\firstoftwoarguments
+   \else
+     \expandafter\secondoftwoarguments
+   \fi}
+
+\unexpanded\def\doifelsesomething#1%
+  {\iftok{#1}\emptytoks
+     \expandafter\secondoftwoarguments
+   \else
+     \expandafter\firstoftwoarguments
+   \fi}
+
+\unexpanded\def\doifvaluenothing#1%
+  {\iftok{\csname#1\endcsname}\emptytoks
+     \expandafter\firstofoneargument
+   \else
+     \expandafter\gobbleoneargument
+   \fi}
+
+\unexpanded\def\doifvaluesomething#1%
+  {\iftok{\csname#1\endcsname}\emptytoks
+     \expandafter\gobbleoneargument
+   \else
+     \expandafter\firstofoneargument
+   \fi}
+
+\unexpanded\def\doifelsevaluenothing#1%
+  {\iftok{\csname#1\endcsname}\emptytoks
+     \expandafter\firstoftwoarguments
+   \else
+     \expandafter\secondoftwoarguments
+   \fi}
+
+\let\doifvalueelse       \doifelsevalue
+\let\doifnothingelse     \doifelsenothing
+\let\doifsomethingelse   \doifelsesomething
+\let\doifvaluenothingelse\doifelsevaluenothing
+
+%D \macros
+%D   {doifemptyelsevalue, doifemptyvalue, doifnotemptyvalue}
+%D
+%D Also handy:
+
+\def\doifelseemptyvalue#1%
+  {\expandafter\ifx\csname#1\endcsname\empty
+     \expandafter\firstoftwoarguments
+   \else
+     \expandafter\secondoftwoarguments
+   \fi}
+
+\let\doifemptyvalueelse\doifelseemptyvalue
+
+\def\doifemptyvalue#1%
+  {\expandafter\ifx\csname#1\endcsname\empty
+     \expandafter\firstofoneargument
+   \else
+     \expandafter\gobbleoneargument
+   \fi}
+
+\def\doifnotemptyvalue#1%
+  {\expandafter\ifx\csname#1\endcsname\empty
+     \expandafter\gobbleoneargument
+   \else
+     \expandafter\firstofoneargument
+   \fi}
+
+%D \macros
+%D   {doifallcommonelse}
+%D
+%D A complete match of two sets can be tested with \type {\doifallcommonelse}, where
+%D the first two arguments are sets.
+
+\def\syst_helpers_do_if_all_common_else#1#2#3#4% slow
+  {\def\syst_helpers_do_common_check_all##1%
+     {\doifnotinset{##1}{#4}\donefalse
+      \ifdone\else\expandafter\quitcommalist\fi}%
+   \donetrue
+   \processcommalist[#3]\syst_helpers_do_common_check_all
+   \ifdone\expandafter#1\else\expandafter#2\fi}
+
+\unexpanded\def\doifelseallcommon{\syst_helpers_do_if_all_common_else\firstoftwoarguments\secondoftwoarguments}
+\unexpanded\def\doifallcommon    {\syst_helpers_do_if_all_common_else\firstofonearguments\gobbleoneargument   }
+\unexpanded\def\doifnotallcommon {\syst_helpers_do_if_all_common_else\gobbleoneargument  \firstofonearguments }
+
+\let\doifallcommonelse\doifelseallcommon
+
+%D \macros
+%D   {DOIF,DOIFELSE,DOIFNOT}
+%D
+%D \TEX\ is case sensitive. When comparing arguments, this feature sometimes is less
+%D desirable, for instance when we compare filenames. The next three alternatives
+%D upcase their arguments before comparing them.
+%D
+%D \starttyping
+%D \DOIF     {string1} {string2} {...}
+%D \DOIFNOT  {string1} {string2} {...}
+%D \DOIFELSE {string1} {string2} {then ...}{else ...}
+%D \stoptyping
+%D
+%D We have to use a two||step implementation, because the
+%D expansion has to take place outside \type{\uppercase}.
+%D
+%D These might end up as \LUA based helpers (i.e. consider these
+%D obsolete:
+
+\unexpanded\def\syst_helpers_do_IF#1#2%
+  {\uppercase{\syst_helpers_do_if_in_string_else{$#1$}{$#2$}}%
+     \expandafter\firstofoneargument
+   \else
+     \expandafter\gobbleoneargument
+   \fi}
+
+\unexpanded\def\syst_helpers_do_IF_NOT#1#2%
+  {\uppercase{\syst_helpers_do_if_in_string_else{$#1$}{$#2$}}%
+     \expandafter\gobbleoneargument
+   \else
+     \expandafter\firstofoneargument
+   \fi}
+
+\unexpanded\def\syst_helpers_do_IF_ELSE#1#2%
+  {\uppercase{\syst_helpers_do_if_in_string_else{$#1$}{$#2$}}%
+     \expandafter\firstoftwoarguments
+   \else
+     \expandafter\secondoftwoarguments
+   \fi}
+
+\unexpanded\def\syst_helpers_do_IF_INSTRING_ELSE#1#2%
+  {\uppercase{\syst_helpers_do_if_in_string_else{$#1$}{$#2$}}%
+     \expandafter\firstoftwoarguments
+   \else
+     \expandafter\secondoftwoarguments
+   \fi}
+
+\unexpanded\def\DOIF             #1#2{\normalexpanded{\syst_helpers_do_IF              {#1}{#2}}}% will become obsolete
+\unexpanded\def\DOIFNOT          #1#2{\normalexpanded{\syst_helpers_do_IF_NOT          {#1}{#2}}}% will become obsolete
+\unexpanded\def\DOIFELSE         #1#2{\normalexpanded{\syst_helpers_do_IF_ELSE         {#1}{#2}}}% will become obsolete
+\unexpanded\def\DOIFINSTRINGELSE #1#2{\normalexpanded{\syst_helpers_do_IF_INSTRING_ELSE{#1}{#2}}}% will become obsolete
+
+%D \macros
+%D   {dosingleargumentwithset,
+%D    dodoubleargumentwithset,dodoubleemptywithset,
+%D    dotripleargumentwithset,dotripleemptywithset}
+%D
+%D These maybe too mysterious macros enable us to handle more than one setup at once.
+%D
+%D \starttyping
+%D \dosingleargumentwithset \command[#1]
+%D \dodoubleargumentwithset \command[#1][#2]
+%D \dotripleargumentwithset \command[#1][#2][#3]
+%D \dodoubleemptywithset    \command[#1][#2]
+%D \dotripleemptywithset    \command[#1][#2][#3]
+%D \stoptyping
+%D
+%D The first macro calls \type {\command[##1]} for each string in the set~\type
+%D {#1}. The second one calls for \typ {\command [##1][#2]} and the third, well one
+%D may guess. These commands support constructions like:
+%D
+%D \starttyping
+%D \def\dodefinesomething[#1][#2]%
+%D   {\getparameters[\??xx#1][#2]}
+%D
+%D \unexpanded\def\definesomething%
+%D   {\dodoubleargumentwithset\dodefinesomething}
+%D \stoptyping
+%D
+%D Which accepts calls like:
+%D
+%D \starttyping
+%D \definesomething[alfa,beta,...][variable=...,...]
+%D \stoptyping
+
+\let\m_syst_helpers_with_set_command\empty
+\let\syst_helpers_with_set_step     \relax
+
+\def\syst_helpers_with_set_double[#1][#2]%
+  {\doifsomething{#1}%
+     {\def\syst_helpers_with_set_step##1{\m_syst_helpers_with_set_command[##1][#2]}%
+      \processcommalist[#1]\syst_helpers_with_set_step}}
+
+\def\syst_helpers_with_set_triple[#1][#2][#3]%
+  {\doifsomething{#1}%
+     {\def\syst_helpers_with_set_step##1{\m_syst_helpers_with_set_command[##1][#2][#3]}%
+      \processcommalist[#1]\syst_helpers_with_set_step}}
+
+\def\dodoubleemptywithset   #1{\let\m_syst_helpers_with_set_command#1\dodoubleempty   \syst_helpers_with_set_double} % \command
+\def\dodoubleargumentwithset#1{\let\m_syst_helpers_with_set_command#1\dodoubleargument\syst_helpers_with_set_double} % \command
+
+\def\dotripleemptywithset   #1{\let\m_syst_helpers_with_set_command#1\dotripleempty   \syst_helpers_with_set_triple} % \command
+\def\dotripleargumentwithset#1{\let\m_syst_helpers_with_set_command#1\dotripleargument\syst_helpers_with_set_triple} % \command
+
+%D \macros
+%D   {stripcharacters,stripspaces}
+%D
+%D The next command was needed first when we implemented the \CONTEXT\ interactivity
+%D macros. When we use labeled destinations, we often cannot use all the characters
+%D we want. We therefore strip some of the troublemakers, like spaces, from the
+%D labels before we write them to the \DVI||file, which passes them to for instance
+%D a \POSTSCRIPT\ file.
+%D
+%D \starttyping
+%D \stripspaces\from\one\to\two
+%D \stoptyping
+%D
+%D Both the old string \type{\one} and the new one \type{\two}
+%D are expanded. This command is a special case of:
+%D
+%D \starttyping
+%D \stripcharacter\char\from\one\to\two
+%D \stoptyping
+%D
+%D As we can see below, spaces following a control sequence are to enclosed in \type
+%D {{}}.
+
+\let\m_syst_helpers_strip_character\empty
+
+\unexpanded\def\stripcharacter#1\from#2\to#3%
+  {\def\syst_helpers_strip_character##1#1##2\end
+     {\edef\m_syst_helpers_strip_character{\m_syst_helpers_strip_character##1}%
+      \doifnotempty{##2}{\syst_helpers_strip_character##2\end}}%
+   \let\m_syst_helpers_strip_character\empty
+   \edef\m_syst_string_one{#2}%
+   \expandafter\syst_helpers_strip_character\m_syst_string_one#1\end
+   \dodoglobal\let#3\m_syst_helpers_strip_character}
+
+\unexpanded\def\stripspaces\from#1\to#2% will become \unspacestring#1\from#2
+  {\stripcharacter{ }\from#1\to#2}
+
+%D \macros
+%D   {unspacestring}
+%D
+%D The next macro does the same but is more compatible with other macros, like \type
+%D {\convert...}.
+
+\unexpanded\def\unspacestring#1\to#2%
+  {\stripcharacter{ }\from#1\to#2}
+
+%D \macros
+%D   {executeifdefined}
+%D
+%D \CONTEXT\ uses one auxiliary file for all data concerning tables of contents,
+%D references, two||pass optimizations, sorted lists etc. This file is loaded as
+%D many times as needed. During such a pass we skip the commands thate are of no use
+%D at that moment. Because we don't want to come into trouble with undefined
+%D auxiliary commands, we call the macros in a way similar to \type {\getvalue}. The
+%D next macro take care of such executions and when not defined, gobbles the
+%D unwanted arguments.
+%D
+%D \starttyping
+%D \executeifdefined{name}\gobbleoneargument
+%D \stoptyping
+%D
+%D We can of course gobble more arguments using the appropriate gobbling command.
+
+\def\executeifdefined#1% #2 / never change this one again
+  {\ifcsname#1\endcsname
+   % \csname#1\expandafter\expandafter\expandafter\endcsname\expandafter\gobbleoneargument
+     \expandafter\expandafter\expandafter\lastnamedcs\expandafter\gobbleoneargument
+   \else
+     \expandafter\firstofoneargument
+   \fi}
+
+%D This one also has the advantage that it is fully expandable and that it can be
+%D used after an assignment.
+
+%D \macros
+%D   {doifsomespaceelse}
+%D
+%D The next command checks a string on the presence of a space and executed a
+%D command accordingly.
+%D
+%D \starttyping
+%D \doifsomespaceelse {tekst} {then ...} {else ...}
+%D \stoptyping
+%D
+%D We use this command in \CONTEXT\ for determing if an argument must be broken into
+%D words when made interactive. Watch the use of \type {\noexpand}.
+
+%D Is this one still needed?
+
+\def\syst_helpers_if_some_space_else#1 #2#3^^^^0004{\if\noexpand#2@}
+
+\def\doifelsesomespace#1%                     % #2#3%
+  {\syst_helpers_if_some_space_else#1 @ @^^^^0004% #3\else#2\fi}
+     \expandafter\secondoftwoarguments
+   \else
+     \expandafter\firstoftwoarguments
+   \fi}
+
+\let\doifsomespaceelse\doifelsesomespace
+
+%D \macros
+%D   {processseparatedlist}
+%D
+%D Maybe a bit late, but here is a more general version of the \type
+%D {\processcommalist} command. This time we don't handle nesting but accept
+%D arbitrary seperators.
+%D
+%D \starttyping
+%D \processseparatedlist[list][separator]\command
+%D \stoptyping
+%D
+%D One can think of things like:
+%D
+%D \starttyping
+%D \processseparatedlist[alfa+beta+gamma][+]\message
+%D \stoptyping
+%D
+%D We want to handle all situations, like:
+%D
+%D \startbuffer
+%D \processseparatedlist[{aap noot}]  [ ]{\def\xxx} \convertcommand\xxx\to\ascii {\tttf\ascii}
+%D \processseparatedlist[{aap} {noot}][ ]{\def\xxx} \convertcommand\xxx\to\ascii {\tttf\ascii}
+%D \processseparatedlist[aap {noot}]  [ ]{\def\xxx} \convertcommand\xxx\to\ascii {\tttf\ascii}
+%D \processseparatedlist[aap noot]    [ ]{\def\xxx} \convertcommand\xxx\to\ascii {\tttf\ascii}
+%D \stopbuffer
+%D
+%D \typebuffer \getbuffer
+%D
+%D Therefore we smuggle a \type {\relax} in front of the argument, which we remove
+%D afterwards.
+
+\let\syst_helpers_process_separated_list_step\relax
+
+\def\syst_helpers_process_separated_list#1]#2[#3]#4%
+   {\def\syst_helpers_process_separated_list_step##1##2#3%
+      {\def\m_syst_string_one{##2}% suggested by VZ
+       \if]##1%
+         \let\syst_helpers_process_separated_list_step\relax
+       \orelse\ifx\blankspace\m_syst_string_one
+         #4{##1}%
+       \orelse\if]##2%
+         \let\syst_helpers_process_separated_list_step\relax
+       \else
+         #4{##1##2}%
+       \fi
+       \syst_helpers_process_separated_list_step}%
+    \expandafter\syst_helpers_process_separated_list_step\gobbleoneargument#1#3]#3}
+
+\unexpanded\def\processseparatedlist[%
+  {\syst_helpers_process_separated_list\relax}
+
+%D \macros
+%D   {processlist}
+%D
+%D An even more general list processing macro is the following one:
+%D
+%D \starttyping
+%D \processlist{beginsym}{endsym}{separator}\docommand list
+%D \stoptyping
+%D
+%D This one supports arbitrary open and close symbols as well as user defined
+%D separators.
+%D
+%D \starttyping
+%D \processlist(){=>}\docommand(a=>b=>c=>d)
+%D \stoptyping
+
+\let\syst_helpers_process_any_list       \relax
+\let\syst_helpers_process_any_list_indeed\relax
+\let\syst_helpers_process_any_list_step  \relax
+
+\unexpanded\def\processlist#1#2#3#4% no blank skipping !
+  {\def\syst_helpers_process_any_list_indeed##1#2%
+     {\def\syst_helpers_process_any_list_step####1####2#3%
+        {\ifx#2####1%
+           \let\syst_helpers_process_any_list_step\relax
+         \orelse\ifx#2####2%
+           \let\syst_helpers_process_any_list_step\relax
+         \else
+           #4{####1####2}%
+         \fi
+         \syst_helpers_process_any_list_step}%
+      \expandafter\syst_helpers_process_any_list_step\gobbleoneargument##1#3#2#3}%
+   \def\syst_helpers_process_any_list#1%
+     {\syst_helpers_process_any_list_indeed\relax}%
+    \syst_helpers_process_any_list}
+
+%D \macros
+%D   {processassignlist}
+%D
+%D Is possible to combine an assignment list with one containing keywords.
+%D Assignments are treated accordingly, keywords are treated by \type {\command}.
+%D
+%D \starttyping
+%D \processassignlist[...=...,...=...,...]\commando
+%D \stoptyping
+%D
+%D This command can be integrated in \type {\getparameters}, but we decided best not
+%D to do so.
+
+\unexpanded\def\processassignlist#1[#2]#3%
+  {\def\syst_helpers_process_assign_list_assign[##1=##2=##3]%
+     {\doif{##3}\relax{#3{##1}}}%
+   \def\syst_helpers_process_assign_list_step##1%
+     {\syst_helpers_process_assign_list_assign[##1==\relax]}%
+   \processcommalist[#2]\syst_helpers_process_assign_list_step}
+
+%D \macros
+%D   {untextargument
+%D    untexcommand}
+%D
+%D When manipulating data(bases) and for instance generating index entries, the next
+%D three macros can be of help:
+%D
+%D \starttyping
+%D \untextargument{...}\to\name
+%D \untexcommand  {...}\to\name
+%D \stoptyping
+%D
+%D They remove braces and backslashes and give us something to sort.
+
+\let\m_syst_helpers_untexed\empty
+
+\unexpanded\def\untexsomething
+  {\begingroup
+   \catcode\leftbraceasciicode \ignorecatcode
+   \catcode\rightbraceasciicode\ignorecatcode
+   \escapechar\minusone
+   \syst_helpers_untex_something}
+
+\def\syst_helpers_untex_something#1#2\to#3%
+  {\doglobal#1#2\to\m_syst_helpers_untexed
+   \endgroup
+   \let#3\m_syst_helpers_untexed}
+
+\unexpanded\def\untexargument{\untexsomething\convertargument}
+\unexpanded\def\untexcommand {\untexsomething\convertcommand}
+
+%D \macros
+%D   {ScaledPointsToBigPoints,ScaledPointsToWholeBigPoints}
+%D
+%D One characteristic of \POSTSCRIPT\ and \PDF\ is that both used big points (\TEX's
+%D bp). The next macros convert points and scaled points into big points. The magic
+%D factor $72/72.27$ can be found in most \TEX\ related books.
+%D
+%D \starttyping
+%D \ScaledPointsToBigPoints      {number} \target
+%D \ScaledPointsToWholeBigPoints {number} \target
+%D \stoptyping
+
+\let\tobigpoints     \clf_tobigpoints
+\let\towholebigpoints\clf_towholebigpoints
+
+\unexpanded\def\PointsToBigPoints           #1#2{\edef#2{\tobigpoints     #1}}             % can be avoided
+\unexpanded\def\PointsToWholeBigPoints      #1#2{\edef#2{\towholebigpoints#1}}             % can be avoided
+\unexpanded\def\ScaledPointsToBigPoints     #1#2{\edef#2{\tobigpoints     #1\scaledpoint}} % obsolete
+\unexpanded\def\ScaledPointsToWholeBigPoints#1#2{\edef#2{\towholebigpoints#1\scaledpoint}} % obsolete
+
+%D \macros
+%D   {PointsToReal}
+%D
+%D Points can be stripped from their suffix by using \type {\withoutpt}. The next
+%D macro enveloppes this macro.
+%D
+%D \starttyping
+%D \PointsToReal {dimension} \target
+%D \stoptyping
+
+\unexpanded\def\PointsToReal#1#2%
+  {\edef#2{\withoutpt\the\dimexpr#1}}
+
+%D \macros
+%D  {dontleavehmode}
+%D
+%D Sometimes when we enter a paragraph with some command, the first token gets the
+%D whole first line. We can prevent this by saying:
+%D
+%D \starttyping
+%D \dontleavehmode
+%D \stoptyping
+%D
+%D This command is used in for instance the language module \type {lang-ini}. The
+%D first version was:
+%D
+%D \starttyping
+%D \def\dontleavehmode{\ifhmode\else\ifmmode\else$ $\fi\fi}
+%D \stoptyping
+%D
+%D Next, Taco came with a better alternative (using mathsurround):
+%D
+%D \starttyping
+%D \def\dontleavehmode
+%D   {\ifhmode\else \ifmmode\else
+%D      {\mathsurround\zeropoint\everymath\emptytoks$ $}%
+%D    \fi \fi}
+%D \stoptyping
+%D
+%D And finaly we got the following alternative, one that avoids interfering grouping
+%D at the cost of a box.
+%D
+%D \starttyping
+%D \newbox\b_syst_helpers_dlh
+%D
+%D \unexpanded\def\dontleavehmode
+%D   {\ifhmode\else \ifmmode\else
+%D      \setbox\b_syst_helpers_dlh\hbox{\mathsurround\zeropoint\everymath\emptytoks$ $}\unhbox\b_syst_helpers_dlh
+%D    \fi \fi}
+%D \stoptyping
+%D
+%D But, as we run a recent version of \TEX, we can use the new primitive:
+
+\ifdefined\normalquitvmode \let\dontleavehmode\normalquitvmode \fi
+
+%D \macros
+%D   {utfupper, utflower, uppercasestring, lowercasestring}
+%D
+%D The names tell what they do:
+%D
+%D \starttyping
+%D \uppercasestring somestring\to\somestring
+%D \lowercasestring somestring\to\somestring
+%D \stoptyping
+%D
+%D The first argument may be a \type{\macro}.
+%D
+%D These macros are sort of obsolete as we never use uppercase this way. But
+%D nevertheless we provide them:
+
+\def\utfupper#1{\clf_upper{#1}} % expandable
+\def\utflower#1{\clf_lower{#1}} % expandable
+
+\unexpanded\def\uppercasestring#1\to#2{\dodoglobal\edef#2{\clf_upper{#1}}}
+\unexpanded\def\lowercasestring#1\to#2{\dodoglobal\edef#2{\clf_lower{#1}}}
+
+%D \macros
+%D   {handletokens}
+%D
+%D With the next macro we enter a critical area of macro expansion. What we want is
+%D a macro that looks like:
+%D
+%D \starttyping
+%D \handletokens some tokens\with \somemacro
+%D \stoptyping
+%D
+%D A bonus example:
+%D
+%D \starttyping
+%D \hbox{\handletokens tekst en meer tekst\with\ruledhbox}
+%D
+%D \def\weetikveel#1{\if#1\blankspace\space\else\ruledhbox{#1}\fi}
+%D
+%D \hbox{\handletokens tekst en meer tekst\with\weetikveel}
+%D \stoptyping
+
+%D \macros
+%D   {counttoken,counttokens}
+%D
+%D For the few occasions that we want to know the number of specific tokens in a
+%D string, we can use:
+%D
+%D \starttyping
+%D \counttoken  token\in string\to \somecount
+%D \counttokens          string\to \somecount
+%D \stoptyping
+%D
+%D This macro, that for instance is used in \type {cont-tab}, takes a real counter.
+%D The macro can be preceded by \type {\doglobal}.
+
+\def\syst_helpers_count_token#1% obeys {}
+  {\def\m_syst_string_three{#1}%
+   \ifx\m_syst_string_two\m_syst_string_three \else
+     \ifx\m_syst_string_one\m_syst_string_three
+       \advance\privatescratchcounter\plusone
+     \fi
+     \expandafter\syst_helpers_count_token
+   \fi}
+
+\unexpanded\def\counttoken#1\in#2\to#3%
+  {\privatescratchcounter\zerocount
+   \def\m_syst_string_one{#1}%
+   \def\m_syst_string_two{\end}%
+   \syst_helpers_count_token#2\end
+   \dodoglobal#3\privatescratchcounter}
+
+\unexpanded\def\counttokens#1\to#2%
+  {\privatescratchcounter\zerocount
+   \def\syst_helpers_count_token##1{\advance\privatescratchcounter\plusone}%
+   \handletokens#1\with\syst_helpers_count_token
+   \dodoglobal#2\privatescratchcounter}
+
+%D \macros
+%D   {splitofftokens}
+%D
+%D Running this one not always gives the expected results. Consider for instance the
+%D macro for which I originally wrote this token handler.
+
+\unexpanded\def\splitofftokens#1\from#2\to#3% slow but hardly used
+  {\ifnum#1>\zerocount
+     \privatescratchcounter#1\relax
+     \def\syst_helpers_split_off_tokens##1%
+       {\ifnum\privatescratchcounter>\zerocount
+          \advance\privatescratchcounter \minusone
+          \edef#3{#3##1}%
+        \fi}%
+   % \let#3\empty % #3 can be #2, so:
+     \expandafter\let\expandafter#3\expandafter\empty
+     \expandafter\handletokens#2\with\syst_helpers_split_off_tokens
+   \else
+     \edef#3{#2}%
+   \fi}
+
+%D This macro can be called like:
+%D
+%D \startbuffer[example]
+%D \splitofftokens10\from01234567 890123456789\to\test [\test]
+%D \stopbuffer
+%D
+%D up there. The reason for this is not that logical but follows from \TEX's
+%D However, the characters that we expect to find in \type {\test} just don't show
+%D sometimes mysterious way of expanding. Look at this:
+%D
+%D \startbuffer[next]
+%D \def\next{a} \edef\test{\next}                                          [\test]
+%D \let\next=b  \edef\test{\test\next}                                     [\test]
+%D \let\next=c  \edef\test{\next}                                          [\test]
+%D \let\next=d  \edef\test{\test\next}                                     [\test]
+%D \let\next=e  \expandafter\edef\expandafter\test\expandafter{\test\next} [\test]
+%D \stopbuffer
+%D
+%D \typebuffer[next]
+%D
+%D Careful reading shows that inside an \type {\edef} macro's that are \type {\let}
+%D are not expanded!
+%D
+%D \unprotect\getbuffer[next]\protect
+%D
+%D That's why we finally end up with a macro that looks ahead by using an
+%D assignment, this time by using \type {\futurelet}, and grabbing an argument as
+%D well. That way we can handle the sentinal, a blank space and grouped tokens.
+
+\unexpanded\def\syst_helpers_handle_tokens % \nexthandledtoken is part of interface
+  {\futurelet\nexthandledtoken\syst_helpers_handle_tokens_indeed}
+
+\def\handletokens#1\with#2%
+  {\gdef\syst_helpers_handle_tokens_command{#2}% permits more complex #2's
+   \syst_helpers_handle_tokens#1\end}
+
+\def\syst_helpers_handle_tokens_indeed
+  {\ifx\nexthandledtoken\blankspace
+     \expandafter\syst_helpers_handle_tokens_indeed_one
+   \orelse\ifx\nexthandledtoken\end
+     \expandafter\gobbletwoarguments % also gobble the \end
+   \else
+     \expandafter\syst_helpers_handle_tokens_indeed_two
+   \fi *}
+
+\def\syst_helpers_handle_tokens_indeed_one * %
+  {\syst_helpers_handle_tokens_command{ }\syst_helpers_handle_tokens}
+
+\def\syst_helpers_handle_tokens_indeed_two *#1%
+  {\syst_helpers_handle_tokens_command{#1}\syst_helpers_handle_tokens}
+
+%D This macro is tested on:
+%D
+%D \def\xxx#1{[#1]}
+%D
+%D \startlines
+%D \handletokens         abc\with\xxx
+%D \handletokens       a b c\with\xxx
+%D \handletokens     a  b  c\with\xxx
+%D \handletokens      a{bc}d\with\xxx
+%D \handletokens a\space bc \with\xxx
+%D \stoplines
+%D
+%D And our previous example shows up as:
+%D
+%D \getbuffer[example]
+
+%D \macros
+%D   {iftrialtypesetting, ifvisible}
+%D
+%D The next boolean is at first sight a strange one. Sometimes one does a trial
+%D typesetting run, for instance to determine dimensions. Some mechanisms, like
+%D object inclusion, can fail on such trials. Temporary setting the next boolean to
+%D true, helps a lot. The second boolena can be used to inhibit processing
+%D completely.
+
+\newif\ifvisible \visibletrue
+
+\newtoks\everysettrialtypesetting
+\newtoks\everyresettrialtypesetting
+
+\unexpanded\def\settrialtypesetting  {\the\everysettrialtypesetting  } % obeys grouping so
+\unexpanded\def\resettrialtypesetting{\the\everyresettrialtypesetting} % this one is seldom needed
+
+\let\iftrialtypesetting\iffalse % so we have no \trialtypesettingtrue|false in mkiv !
+
+\appendtoks \let\iftrialtypesetting\iftrue  \to \everysettrialtypesetting
+\appendtoks \let\iftrialtypesetting\iffalse \to \everyresettrialtypesetting
+
+%D \macros
+%D   {twodigitrounding}
+%D
+%D When using \type {\special}s or \type {\pdfliteral}s, it sometimes makes sense to
+%D limit the precission. The next macro rounds a real number to two digits. It takes
+%D one argument and only works in \ETEX.
+
+\def\integerrounding   #1{\clf_rounded\zerocount\numexpr#1\relax}
+\def\onedigitrounding  #1{\clf_rounded\plusone  \numexpr#1\relax}
+\def\twodigitrounding  #1{\clf_rounded\plustwo  \numexpr#1\relax}
+\def\threedigitrounding#1{\clf_rounded\plusthree\numexpr#1\relax}
+
+%D \macros
+%D   {processcontent}
+%D
+%D This macro is first used in the tabulation macros.
+%D
+%D \starttyping
+%D \unexpanded\def\starthans%
+%D   {\processcontent{stophans}\test{\message{\test}\wait}}
+%D \stoptyping
+
+\unexpanded\def\processcontent#1%
+  {\begingroup\expandafter\syst_helpers_process_content\csname#1\endcsname}
+
+\unexpanded\def\syst_helpers_process_content#1#2#3%
+  {\unexpanded\def\syst_helpers_process_content##1#1%
+     {\endgroup\def#2{##1}#3}%
+   \syst_helpers_process_content}
+
+%D \macros
+%D   {dogobblesingleempty, dogobbledoubleempty}
+%D
+%D These two macros savely grab and dispose two arguments.
+
+\def\dogobblesingleempty{\dosingleempty\syst_helpers_gobble_single_empty}
+\def\dogobbledoubleempty{\dodoubleempty\syst_helpers_gobble_double_empty}
+
+\def\syst_helpers_gobble_single_empty    [#1]{}
+\def\syst_helpers_gobble_double_empty[#1][#2]{}
+
+\let\gobblesingleempty\dogobblesingleempty % also used
+\let\gobbledoubleempty\dogobbledoubleempty % also used
+
+%D \macros
+%D   {setdimensionwithunit, freezedimensionwithunit}
+%D
+%D The next assignments are all valid:
+%D
+%D \starttyping
+%D \setdimensionwithunit\scratchdimen{10}  {cm}
+%D \setdimensionwithunit\scratchdimen{10cm}{cm}
+%D \setdimensionwithunit\scratchdimen{10cm}{}
+%D \freezedimensionwithunit\SomeWidth{\textwidth}
+%D \freezedimensionwithunit\SomeDepth{\dp\strutbox}
+%D \stoptyping
+%D
+%D As an alternative for the next macro we can use a global assignment inside a box.
+%D The \type {\empty}'s permits gobbling while preventing spurious \type {\relax}'s.
+
+\unexpanded\def\setdimensionwithunit#1#2#3% number unit dimension / nice trick
+  {\afterassignment\gobblefourarguments#1=#2#3pt\relax\empty\empty\empty\empty}
+
+\unexpanded\def\freezedimensionwithunit#1#2%
+  {\setdimensionwithunit\privatescratchdimen#1{#2}\edef#1{\the\privatescratchdimen}}
+
+%D \macros
+%D   {doifsometokselse, doifsometoks}
+%D
+%D Not that fast I guess, but here's a way to test for token registers being empty.
+
+\unexpanded\def\doifelsesometoks#1%
+  {\iftok#1\emptytoks
+     \expandafter\secondoftwoarguments
+   \else
+     \expandafter\firstoftwoarguments
+   \fi}
+
+\unexpanded\def\doifsometoks#1%
+  {\iftok#1\emptytoks
+     \expandafter\gobbleoneargument
+   \else
+     \expandafter\firstofoneargument
+   \fi}
+
+\unexpanded\def\doifemptytoks#1%
+  {\iftok#1\emptytoks
+     \expandafter\firstofoneargument
+   \else
+     \expandafter\gobbleoneargument
+   \fi}
+
+\let\doifsometokselse\doifelsesometoks
+
+%D \macros
+%D   {startstrictinspectnextcharacter}
+%D
+%D This one is for the bibliography module (still?):
+
+\let\syst_helpers_strict_inspect_next_character[
+
+\def\syst_helpers_strict_inspect_next_character% no user macro !
+  {\ifx\nexttoken[%
+     \expandafter\m_syst_action_yes
+   \else
+     \expandafter\m_syst_action_nop
+   \fi}
+
+\unexpanded\def\strictdoifelsenextoptional#1#2%
+  {\def\m_syst_action_yes{#1}%
+   \def\m_syst_action_nop{#2}%
+   \futurelet\nexttoken\syst_helpers_strict_inspect_next_character}
+
+\let\strictdoifnextoptionalelse\strictdoifelsenextoptional
+
+%D \macros
+%D   {gobblespacetokens}
+%D
+%D This macro needs a speed-up!
+
+%\def\gobblespacetokens
+%  {\doifnextcharelse\empty\donothing\donothing} % no {}\do\do !
+
+\def\gobblespacetokens
+  {\afterassignment\nexttoken\let\nexttoken=}
+
+%D \macros
+%D   {verbatimargument}
+%D
+%D As the name says, this macro converts its argument to a (rather safe) string.
+
+\let\verbatimstring\detokenize
+
+%D These are needed in ordinal number conversions:
+
+\def\lastdigit#1%
+  {\expandafter\thelastdigit\number#1\relax}
+
+\def\thelastdigit#1#2%
+  {\ifx#2\relax#1\else\expandafter\thelastdigit\expandafter#2\fi}
+
+\def\lasttwodigits#1%
+  {\expandafter\thelasttwodigits\expandafter0\number#1\relax}
+
+\def\thelasttwodigits#1#2#3% 0 dig ... \relax
+  {\ifx#3\relax#1#2\else\expandafter\thelasttwodigits\expandafter#2\expandafter#3\fi}
+
+%D \macros
+%D   {serializecommalist}
+%D
+%D Concatenate commalists:
+
+\let\syst_helpers_serialize_comma_list_step\relax
+
+\def\syst_helpers_serialize_comma_list_step#1%
+  {\edef\serializedcommalist{\serializedcommalist#1}}
+
+\unexpanded\def\serializecommalist[#1]%
+  {\let\serializedcommalist\empty
+   \processcommacommand[#1]\syst_helpers_serialize_comma_list_step}
+
+%D \macros
+%D   {purenumber}
+%D
+%D Sometimes we need control over when \TEX\ stops reading a number, especially in
+%D full expandable macros where using \type {\relax} would lead to disasters.
+%D
+%D \starttyping
+%D \ifodd\purenumber{...}\space ... \else ... \fi
+%D \stoptyping
+%D
+%D Here we use a space as number delimiter in combination with a space- and
+%D relax-less \type {\purenumber}. This macro works ok with \type {\the}, \type
+%D {\number} as well as \ETEX's \type {\numexpr}.
+
+\def\purenumber#1{\expandafter\firstofoneargument\expandafter{\number#1}}
+
+%D \macros
+%D   {filterfromvalue}
+%D
+%D \starttyping
+%D \setvalue{xx}{{A}{B}{C}}
+%D
+%D \filterfromvalue{xx}{3}{3}
+%D \filterfromvalue{xx}{3}{2}
+%D \filterfromvalue{xx}{3}{1}
+%D \stoptyping
+%D
+%D An alternative is to store 'max' in the list, say:
+%D
+%D \starttyping
+%D \setvalue{xx}{3{A}{B}{C}}
+%D
+%D \filterfromvalues{3}{xx}{3}
+%D \filterfromvalues{3}{xx}{2}
+%D \filterfromvalues{3}{xx}{1}
+%D \stoptyping
+%D
+%D I'll implement this when I'm in \quotation {writing dirty macros mood}.
+
+\def\dofilterfromstr#1#2% max n % no need to be fast
+  {\expandafter \expandafter \expandafter \csstring
+   \ifcase#1\or \ifcase#2\or
+     \firstofoneargument     \else
+     \gobbleoneargument      \fi
+   \or \ifcase#2\or
+     \firstoftwoarguments    \or
+     \secondoftwoarguments   \else
+     \gobbletwoarguments     \fi
+   \or \ifcase#2\or
+     \firstofthreearguments  \or
+     \secondofthreearguments \or
+     \thirdofthreearguments  \else
+     \gobblethreearguments   \fi
+   \or \ifcase#2\or
+     \firstoffourarguments   \or
+     \secondoffourarguments  \or
+     \thirdoffourarguments   \or
+     \fourthoffourarguments  \else
+     \gobblefourarguments    \fi
+   \or \ifcase#2\or
+     \firstoffivearguments   \or
+     \secondoffivearguments  \or
+     \thirdoffivearguments   \or
+     \fourthoffivearguments  \or
+     \fifthoffivearguments   \else
+     \gobblefivearguments    \fi
+   \fi}
+
+\def\filterfromvalue#1#2#3% value max n
+  {\expandafter\doubleexpandafter\csname         % we use the fact that an
+     \expandafter\ifx\csname#1\endcsname\relax   % undefined cs has become \relax
+       \csstring\gobbleoneargument               % which we then gobble here
+     \else
+       \dofilterfromstr{#2}{#3}%
+     \fi
+     \endcsname\csname#1\endcsname}
+
+\def\filterfromnext#1#2% max n {..}{..}{..}{..}
+  {\csname\dofilterfromstr{#1}{#2}\endcsname}
+
+%D \macros
+%D   {definemeasure}
+%D
+%D \starttyping
+%D \definemeasure[mywidth][\dimexpr(\textwidth-1cm)]
+%D
+%D ... \measure{mywidth} ...
+%D \stoptyping
+
+\installsystemnamespace{measure}
+
+\unexpanded\def\definemeasure
+  {\dodoubleargument\syst_helpers_define_measure}
+
+\def\syst_helpers_define_measure[#1][#2]%
+  {\expandafter\def\csname\??measure#1\endcsname{#2}}
+
+\unexpanded\def\freezemeasure
+  {\dodoubleargument\syst_helpers_freeze_measure}
+
+\def\syst_helpers_freeze_measure[#1][#2]%
+  {\expandafter\edef\csname\??measure#1\endcsname{\the\dimexpr#2}}
+
+\unexpanded\def\setmeasure #1#2{\expandafter\def \csname\??measure#1\endcsname{#2}}             % quick way
+\unexpanded\def\setgmeasure#1#2{\expandafter\gdef\csname\??measure#1\endcsname{#2}}             % quick way
+\unexpanded\def\setemeasure#1#2{\expandafter\edef\csname\??measure#1\endcsname{\the\dimexpr#2}} % quick way
+\unexpanded\def\setxmeasure#1#2{\expandafter\xdef\csname\??measure#1\endcsname{\the\dimexpr#2}} % quick way
+
+\def\measure
+  {\the\measured}
+
+\def\measured#1%
+ %{\dimexpr\ifcsname\??measure#1\endcsname\csname\??measure#1\endcsname\else\zeropoint\fi\relax}
+  {\dimexpr\ifcsname\??measure#1\endcsname\lastnamedcs\else\zeropoint\fi\relax}
+
+% #2 could be omitted, but we want to support spaces
+%
+% \setmeasure {x}  {1cm}
+% \setmeasure {xx} {1cm}
+% \setmeasure {xxx}{1cm}
+
+%D \macros
+%D   {dividedsize}
+%D
+%D This one can be used inside a measure (used in m4all):
+%D
+%D \starttyping
+%D \definemeasure[columnwidth][\dividedsize\textwidth{1em}{3}]
+%D \stoptyping
+
+\def\dividedsize#1#2#3% size gap n
+  {\dimexpr
+     \ifnum\dimexpr#1\relax>\plusone
+       (\dimexpr#1\relax-\numexpr#3-\plusone\relax\dimexpr#2\relax)/#3\else#1%
+     \fi
+   \relax}
+
+%D \macros
+%D   {doifdimensionelse}
+%D
+%D This is a dirty one: we simply append a unit and discard it when needed.
+
+\def\doifelsedimension#1%
+  {\ifchkdim#1\or
+     \expandafter\firstoftwoarguments
+   \else
+     \expandafter\secondoftwoarguments
+   \fi}
+
+\let\doifdimensionelse\doifelsedimension
+
+%D Ok, here's another one, slower but seldom used. This one scans the text.
+%D
+%D \starttabulate[|Tc|Tc|]
+%D \NC pt      \NC  \doifdimenstringelse     {pt}{yes}{no} \NC \NR
+%D \NC 12pt    \NC  \doifdimenstringelse  {-12pt}{yes}{no} \NC \NR
+%D \NC 1pt     \NC  \doifdimenstringelse    {1pt}{yes}{no} \NC \NR
+%D \NC 12pt    \NC  \doifdimenstringelse   {12pt}{yes}{no} \NC \NR
+%D \NC 12.0pt  \NC  \doifdimenstringelse {12.0pt}{yes}{no} \NC \NR
+%D \NC -.12pt  \NC  \doifdimenstringelse {-.12pt}{yes}{no} \NC \NR
+%D \NC .12pt   \NC  \doifdimenstringelse  {.12pt}{yes}{no} \NC \NR
+%D \NC -12pt   \NC  \doifdimenstringelse  {-12pt}{yes}{no} \NC \NR
+%D \NC -12.0pt \NC  \doifdimenstringelse{-12.0pt}{yes}{no} \NC \NR
+%D \NC big     \NC  \doifdimenstringelse    {big}{yes}{no} \NC \NR
+%D \NC 10      \NC  \doifdimenstringelse     {10}{yes}{no} \NC \NR
+%D \NC 1       \NC  \doifdimenstringelse      {1}{yes}{no} \NC \NR
+%D \stoptabulate
+
+\let\doifelsedimenstring\doifelsedimension
+\let\doifdimenstringelse\doifelsedimenstring
+
+%D \macros
+%D   {comparedimension,comparedimensioneps}
+%D
+%D This is a dirty one: we simply append a unit and discard it when needed.
+
+\newdimen   \roundingeps \roundingeps=10sp
+\newconstant\compresult
+
+\def\comparedimension#1#2%
+  {\compresult
+     \ifdim#1<#2%
+       \zerocount
+     \orelse\ifdim#1<#2%
+       \plusone
+     \else
+       \plustwo
+     \fi}
+
+\def\comparedimensioneps#1#2% todo: use eps feature
+  {\compresult
+     \ifdim\dimexpr#1-#2\relax<\roudingeps
+       \zerocount
+     \orelse\ifdim\dimexpr#2-#1\relax<\roudingeps
+       \zerocount
+     \orelse\ifdim#1<#2%
+       \plusone
+     \else
+       \plustwo
+     \fi}
+
+% pretty ugly but fast
+
+% \copycsname xxx\endcsname\csname ..\endcsname
+
+\unexpanded\def\copycsname{\expandafter\expandafter\expandafter\let\expandafter\expandafter\csname}
+
+% \letcscsname    \crap               \csname ..\endcsname
+% \letcsnamecs    \csname ..\endcsname\crap
+% \letcsnamecsname\csname ..\endcsname\csname ..\endcsname
+
+\unexpanded\def\letcscsname    {\expandafter\let\expandafter}
+\unexpanded\def\letcsnamecs    {\expandafter\let}
+\unexpanded\def\letcsnamecsname{\expandafter\expandafter\expandafter\let\expandafter\expandafter}
+
+% another one, add an item to a commalist
+
+\unexpanded\def\addvalue#1#2% cs item
+  {\ifcsname#1\endcsname\else\expandafter\let\csname#1\endcsname\empty\fi
+   \normalexpanded{\noexpand\addtocommalist{#2}\expandafter\noexpand\csname#1\endcsname}}
+
+\def\unspaced#1%
+  {\syst_helpers_unspaced#1\end}
+
+\def\syst_helpers_unspaced#1%
+  {\ifx#1\end
+     \expandafter\gobbleoneargument
+   \orelse\ifx#1\blankspace
+     % go on
+   \else
+     #1%
+   \fi
+   \syst_helpers_unspaced}
+
+\unexpanded\def\unspaceargument#1\to#2%
+  {\privatescratchcounter\catcode\spaceasciicode
+   \catcode\spaceasciicode\ignorecatcode
+   \scantextokens{\edef#2{#1}}%
+   \catcode\spaceasciicode\privatescratchcounter}
+
+\unexpanded\def\unspaceafter#1#2%
+  {\unspaceargument#2\to\ascii
+   \expandafter#1\expandafter{\ascii}}
+
+% sometimes handy:
+
+\unexpanded\def\doifelsehasspace#1%
+  {\edef\m_syst_string_one{#1}%
+   \normalexpanded{\syst_helpers_if_has_space_else#1\space}\empty\relax}
+
+\let\doifhasspaceelse\doifelsehasspace
+
+\unexpanded\def\syst_helpers_if_has_space_else#1 #2#3\relax % \space\empty\relax
+  {\ifx\m_syst_string_one\space
+     \expandafter\firstoftwoarguments
+   \orelse\ifx#2\empty
+     \expandafter\secondoftwoarguments
+   \else
+     \expandafter\firstoftwoarguments
+   \fi}
+
+% this will replace loadfile once and alike !!! todo
+
+\installsystemnamespace{flag}
+
+\unexpanded\def\setflag  #1{\expandafter\dodoglobal\expandafter\let\csname\??flag#1\endcsname\zerocount}
+\unexpanded\def\resetflag#1{\expandafter\dodoglobal\expandafter\let\csname\??flag#1\endcsname\plusone}
+
+\def\flag#1{\csname\??flag#1\endcsname}
+
+\def\doifelseflagged#1%
+  {\expandafter\ifx\csname\??flag#1\endcsname\relax
+     \expandafter\secondoftwoarguments
+   \orelse\ifcase\csname\??flag#1\endcsname
+     \expandafter\firstoftwoarguments
+   \else
+     \expandafter\secondoftwoarguments
+   \fi}
+
+\let\doifflaggedelse\doifelseflagged
+
+\def\doifnotflagged#1%
+  {\expandafter\ifx\csname\??flag#1\endcsname\relax
+     \expandafter\firstofoneargument
+   \orelse\ifcase\csname\??flag#1\endcsname
+     \expandafter\gobbleoneargument
+   \else
+     \expandafter\firstofoneargument
+   \fi}
+
+\unexpanded\def\inheritparameter[#1]#2[#3]#4[#5]% tag tokey fromkey
+  {\expandafter\def\csname#1#3\expandafter\endcsname\expandafter{\csname#1#5\endcsname}}
+
+\def\syst_helpers_if_non_zero_positive_else#1#2\end % #3#4%
+  {\ifx#1\relax
+     \ifcase\privatescratchcounter
+       \endgroup
+       \doubleexpandafter\secondoftwoarguments
+     \else
+       \endgroup
+       \doubleexpandafter\firstoftwoarguments
+     \fi
+   \else
+      \endgroup
+      \expandafter\secondoftwoarguments
+   \fi}
+
+% used ?
+
+\def\doifelsenonzeropositive#1%
+  {\begingroup\afterassignment\syst_helpers_if_non_zero_positive_else\privatescratchcounter=0#1\relax\empty\end}
+
+\let\doifnonzeropositiveelse\doifelsenonzeropositive
+
+% here ?
+
+\unexpanded\def\dosetrawvalue #1#2#3{\expandafter \def\csname#1#2\endcsname{#3}}
+\unexpanded\def\dosetrawevalue#1#2#3{\expandafter\edef\csname#1#2\endcsname{#3}}
+\unexpanded\def\dosetrawgvalue#1#2#3{\expandafter\gdef\csname#1#2\endcsname{#3}}
+\unexpanded\def\dosetrawxvalue#1#2#3{\expandafter\xdef\csname#1#2\endcsname{#3}}
+
+\unexpanded\def\getrawparameters      {\dogetparameters\dosetrawvalue }
+\unexpanded\def\getraweparameters     {\dogetparameters\dosetrawevalue}
+\unexpanded\def\getrawgparameters     {\dogetparameters\dosetrawgvalue}
+\unexpanded\def\getrawxparameters     {\dogetparameters\dosetrawxvalue}
+
+\unexpanded\def\globalgetrawparameters{\dogetparameters\dosetrawgvalue} % obsolete
+
+%D Sort of obsolete:
+
+\newcount\c_syst_helpers_mod
+
+\unexpanded\def\dosetmodulo#1#2#3%
+  {\c_syst_helpers_mod#1\divide\c_syst_helpers_mod#2\multiply\c_syst_helpers_mod#2%
+   #3#1\advance#3-\c_syst_helpers_mod}
+
+\unexpanded\def\dosetdivision#1#2#3%
+  {#3#1\divide#3 #2\relax}
+
+\unexpanded\def\DoMod#1by#2to#3{\dosetmodulo  {#1}{#2}{#3}}
+\unexpanded\def\DoDiv#1by#2to#3{\dosetdivision{#1}{#2}{#3}}
+
+\def\syst_helpers_unprotected#1\par
+  {#1\protect}
+
+\unexpanded\def\unprotected
+  {\unprotect
+   \syst_helpers_unprotected}
+
+\let\resettimer    \clf_resettimer
+\let\elapsedtime   \clf_elapsedtime
+\let\elapsedseconds \elapsedtime
+
+\newcount\c_syst_helpers_test_feature_n
+\newcount\c_syst_helpers_test_feature_m
+
+\def\currentfeaturetest{\number\c_syst_helpers_test_feature_n}
+
+\unexpanded\def\testfeature#1#2%
+  {\c_syst_helpers_test_feature_m#1\relax
+   \def\syst_helpers_test_feature_yes
+     {\advance\c_syst_helpers_test_feature_n\plusone
+      \ifnum\c_syst_helpers_test_feature_n>\c_syst_helpers_test_feature_m\else
+        #2\expandafter\syst_helpers_test_feature_yes
+      \fi}%
+   \def\syst_helpers_test_feature_nop
+     {\advance\c_syst_helpers_test_feature_n\plusone
+      \ifnum\c_syst_helpers_test_feature_n>\c_syst_helpers_test_feature_m\else
+        \expandafter\syst_helpers_test_feature_nop
+      \fi}%
+   \retestfeature}
+
+\unexpanded\def\retestfeature % timer support is new per 10/5/2005
+  {\bgroup
+   \ifcase\interactionmode\let\wait\relax\fi
+   \clf_resettimer
+   \c_syst_helpers_test_feature_n\zerocount
+   \syst_helpers_test_feature_nop
+   \clf_benchmarktimer
+   \writestatus\m!system{starting feature test (n=\number\c_syst_helpers_test_feature_m)}\wait
+   \c_syst_helpers_test_feature_n\zerocount
+   \syst_helpers_test_feature_yes
+   \writestatus\m!system{\number\c_syst_helpers_test_feature_m\space feature tests done (\elapsedseconds s)}%
+   \wait
+   \egroup}
+
+\unexpanded\def\showtimer#1%
+  {\writestatus{runtime}{\elapsedseconds\space s / #1}}
+
+\unexpanded\def\testfeatureonce#1#2%
+  {\begingroup
+   \let\wait\relax
+   \testfeature{#1}{#2}%
+   \endgroup}
+
+%D \macros
+%D   {freezedimenmacro}
+%D
+%D This macro is use as:
+%D
+%D \starttyping
+%D \freezedimenmacro\leftmargindistance
+%D \stoptyping
+
+\unexpanded\def\freezedimenmacro#1%
+  {\edef#1{\the\dimexpr#1}}
+
+%D The next macro negates a macro (dimension or number, or actually, whatever. It's
+%D a typical example of \type {\if} usage:
+%D
+%D \starttyping
+%D \if-\whatever \else-\whatever\fi => else => -whatever
+%D \if--\whatever\else-\whatever\fi => then =>  whatever
+%D \stoptyping
+
+\def\negated#1{\if-#1\else-#1\fi} % does only work in macros or text
+
+\def\gobbleassigndimen#1\\{}
+
+\def\assigndimen#1#2%
+  {\afterassignment\gobbleassigndimen#1=#2\zeropoint\\}
+
+\unexpanded\def\appended#1#2#3{\expandafter#1\expandafter#2\expandafter{#2#3}}
+\unexpanded\def\appendvalue #1{\expandafter\appended\expandafter \def\csname#1\endcsname}
+\unexpanded\def\appendgvalue#1{\expandafter\appended\expandafter\gdef\csname#1\endcsname}
+
+\unexpanded\def\prepended#1#2#3%
+  {\t_syst_helpers_scratch{#3}%
+   \expandafter\expandafter\expandafter#1\expandafter\expandafter\expandafter#2\expandafter\expandafter\expandafter
+     {\expandafter\the\expandafter\t_syst_helpers_scratch#2}}
+
+\unexpanded\def\prependvalue #1{\expandafter\prepended\expandafter \def\csname#1\endcsname}
+\unexpanded\def\prependgvalue#1{\expandafter\prepended\expandafter\gdef\csname#1\endcsname}
+
+%D \macros
+%D   {dowithrange}
+%D
+%D This one is for Mojca Miklavec, who made me aware of the fact that \type
+%D {page-imp.tex} was not the best place to hide it.
+%D
+%D \startbuffer
+%D \def\DoSomething#1{ [item #1] }
+%D
+%D \processranges[1,4:5]\DoSomething \par
+%D \dowithrange  {1,4:5}\DoSomething \par
+%D \stopbuffer
+%D
+%D \typebuffer \blank \getbuffer \blank
+
+\def\syst_helpers_with_range#1%
+  {\splitstring#1\at:\to\m_syst_helpers_range_from\and\m_syst_helpers_range_to
+   \ifx\m_syst_helpers_range_to\empty\let\m_syst_helpers_range_to\m_syst_helpers_range_from\fi
+   \dostepwiserecurse\m_syst_helpers_range_from\m_syst_helpers_range_to\plusone{\m_helpers_range_action{##1}}}%
+
+\unexpanded\def\processranges[#1]#2% #1= n:m,p,q:r
+  {\def\m_helpers_range_action{#2}%
+   \processcommacommand[#1]\syst_helpers_with_range}
+
+\unexpanded\def\dowithrange#1#2%
+  {\def\m_helpers_range_action{#2}%
+   \processcommacommand[#1]\syst_helpers_with_range}
+
+% \def\DoSomething#1{ [item #1] }
+% \dowithrange[1,4:5]\DoSomething
+
+%D \macros
+%D   {ignoreimplicitspaces}
+%D
+%D \startbuffer
+%D \def\whatever[#1]{\expanded{\definedfont[#1 at 12pt]}\ignorespaces}
+%D {a\whatever[Serif]b a\whatever[Serif] b a\whatever[Serif]\space b}
+%D \def\whatever[#1]{\expanded{\definedfont[#1 at 12pt]}\ignoreimplicitspaces}
+%D {a\whatever[Serif]b a\whatever[Serif] b a\whatever[Serif]\space b}
+%D \stopbuffer
+%D
+%D \typebuffer \getbuffer
+
+\unexpanded\def\ignoreimplicitspaces
+  {\doifelsenextchar\relax\relax\relax}
+
+%D \macros
+%D   {processwords}
+%D
+%D Not that sophisticated but sometimes users (like in metafun).
+
+\def\syst_helpers_process_word#1 #2\_e_o_w_
+  {\doifsomething{#1}{\processword{#1} \syst_helpers_process_word#2 \_e_o_w_}}
+
+\def\processwords#1%
+  {\syst_helpers_process_word#1 \_e_o_w_}% no \unskip
+
+\let\processword\relax
+
+%D \macros
+%D   {startnointerference}
+%D
+%D \starttyping
+%D \startnointerference
+%D all kind of code
+%D \stopnointerference
+%D \stoptyping
+
+\newbox\b_syst_helpers_no_interference
+
+\unexpanded\def\startnointerference % not even grouped !
+  {\setbox\b_syst_helpers_no_interference\vbox
+   \bgroup}
+
+\unexpanded\def\stopnointerference
+  {\egroup
+   \setbox\b_syst_helpers_no_interference\emptybox}
+
+%D A variant for \type {\executeifdefined}:
+
+\def\expandcheckedcsname#1#2% #2 is often a \xxxparameter  so let's expand it once
+  {\normalexpanded{\noexpand\syst_helpers_expand_checked_csname{#1}{#2}}}
+
+\def\syst_helpers_expand_checked_csname#1#2#3%
+  {\csname#1\ifcsname#1#2\endcsname#2\else#3\fi\endcsname}
+
+%D Signal. Some fonts have a char0 rendering so we need to make sure that it is not
+%D set in the font! (This will be overloaded)
+
+\unexpanded\def\signalcharacter{\char\zerocount} % \zwj
+
+%D A few secial variants of commands defined here. Some more will be moved here (e.g.
+%D from table modules.
+
+\def\dodirectdoubleempty#1#2% used in math (lookahead issues)
+  {\ifx#2[%
+     \expandafter\syst_helpers_direct_double_empty_one_yes
+   \else
+     \expandafter\syst_helpers_direct_double_empty_one_nop
+   \fi#1#2}
+
+\def\syst_helpers_direct_double_empty_one_yes#1[#2]#3%
+  {\ifx#3[\else\expandafter\syst_helpers_direct_double_empty_two_nop\fi#1[#2]#3}
+
+\def\syst_helpers_direct_double_empty_one_nop#1{#1[][]}
+\def\syst_helpers_direct_double_empty_two_nop#1[#2]{#1[#2][]}
+
+%D Used in math definitions (in an \type {\edef}):
+
+%D \startbuffer
+%D [\docheckedpair{}]
+%D [\docheckedpair{a}]
+%D [\docheckedpair{a,b}]
+%D [\docheckedpair{a,b,c}]
+%D \stopbuffer
+%D
+%D \typebuffer \startlines \getbuffer \stoplines
+
+\def\docheckedpair#1%
+  {\syst_helpers_checked_pair#1,,\_o_e_p_}
+
+\def\syst_helpers_checked_pair#1,#2,#3\_o_e_p_
+  {#1,#2}
+
+%D Here are some nasty helpers. They can be used to fill often expanded token
+%D lists efficiently (see tabulate for an example).
+
+\def\constantnumber#1%
+  {\ifcase#1\zerocount
+   \or      \plusone
+   \or      \plustwo
+   \or      \plusthree
+   \or      \plusfour
+   \or      \plusfive
+   \or      \plussix
+   \or      \plusseven
+   \or      \pluseight
+   \or      \plusnine
+   \or      \plusten
+   \else    \number#1\relax\fi}
+
+\def\constantnumberargument#1%
+  {\ifcase#1\zerocount
+   \or      \plusone
+   \or      \plustwo
+   \or      \plusthree
+   \or      \plusfour
+   \or      \plusfive
+   \or      \plussix
+   \or      \plusseven
+   \or      \pluseight
+   \or      \plusnine
+   \or      \plusten
+   \else    {\number#1}\fi}
+
+\def\constantdimen#1%
+  {\ifdim#1=\zeropoint
+     \zeropoint
+   \else
+     \the#1\relax
+   \fi}
+
+\def\constantdimenargument#1%
+  {\ifdim#1=\zeropoint
+     \zeropoint
+   \else
+     {\the#1}%
+   \fi}
+
+\def\constantemptyargument#1%
+  {\ifx#1\empty
+     \noexpand\empty
+   \else
+     {#1}%
+   \fi}
+
+%D \macros
+%D   {getsubstring}
+%D \startbuffer
+%D
+%D \getsubstring{4}{}{Who Wants This}
+%D \getsubstring{4}{9}{Who Wants This}
+%D \getsubstring{9}{-2}{Who Wants This}
+%D \getsubstring{1}{5}{Who Wants This}
+%D \stopbuffer
+%D
+%D \typebuffer
+%D
+%D \startlines
+%D \getbuffer
+%D \stoplines
+
+% expandable:
+
+\def\getsubstring#1#2#3{\clf_getsubstring{#3}{#1}{#2}}
+
+%D Other dimensions than pt (used in mb-mp)
+
+\def\converteddimen#1#2{\clf_converteddimen\dimexpr#1\relax{#2}}
+
+%D Maybe (looks ugly):
+%D
+%D \starttyping
+%D \doifcase {foo}
+%D     {bar}     {BAR}
+%D     {foo}     {FOO}
+%D     {default} {DEFAULT}
+%D
+%D \doifcase {foo}
+%D     {bar}     {BAR}
+%D     {foo}     {\doifcase {bar}
+%D                     {bar}     {BAR}
+%D                     {foo}     {FOO}
+%D                     {default} {DEFAULT}
+%D               }
+%D     {default} {DEFAULT}
+%D \stoptyping
+
+% \doifcase {\btxfoundname{author}}
+%     {author}  {\btxflush{author}}
+%     {editor}  {\texdefinition{btx:apa:editor-or-editors}}
+%     {title}   {\texdefinition{btx:apa:title-subtitle-type}}
+%     {default} {\btxflush{author}}
+
+% \unexpanded\def\doifcase#1%
+%   {\edef\m_case_asked{#1}%
+%    \syst_aux_case}
+%
+% \def\syst_aux_case#1%
+%   {\edef\m_case_temp{#1}%
+%    \ifx\m_case_temp\m_case_asked
+%       \expandafter\syst_aux_case_yes
+%    \orelse\ifx\m_case_temp\s!default
+%       \expandafter\firstofoneargument
+%    \else
+%       \expandafter\syst_aux_case_nop
+%    \fi}
+%
+% \def\syst_aux_skip#1#2%
+%   {\edef\m_case_temp{#1}%
+%    \ifx\m_case_temp\s!default
+%      \expandafter\syst_aux_done
+%    \else
+%      \expandafter\syst_aux_skip
+%    \fi}
+%
+% \def\syst_aux_case_yes#1%
+%   {\def\syst_aux_done{#1}%
+%    \syst_aux_skip}
+%
+% \def\syst_aux_case_nop#1%
+%   {\syst_aux_case}
+
+%D \macros
+%D   {ntimes}
+%D
+%D some repetition:
+%D
+%D \startbuffer
+%D \ntimes{*}{20}
+%D \stopbuffer
+%D
+%D \typebuffer \blank gives: \getbuffer \blank
+%D
+%D This is not real fast but quite okay:
+
+%def\ntimes#1#2{\ifnum#2>\zerocount#1\ntimes{#1}{\numexpr#2-\plusone\relax}\fi} % 1.72
+\def\ntimes#1#2{\clf_ntimes{#1}\numexpr#2\relax}                                % 0.33
+
+%D Experiment (sometimes looks nicer in code):
+
+\unexpanded\def\sameargumentscondition#1#2%
+  {\edef\m_syst_string_one{#1}%
+   \edef\m_syst_string_two{#2}%
+   \ifx\m_syst_string_one\m_syst_string_two}
+
+\unexpanded\def\emptyargumentcondition#1%
+  {\edef\m_syst_string_one{#1}%
+   \ifx\m_syst_string_one\empty}
+
+\protect \endinput