%D \module
%D   [     file=m-chemie,
%D       versie=1996.10.16,
%D         naam=\PPCHTEX\ (Plain Pictex Context cHemie \TEX),
%D       auteur=J. Hagen,
%D        datum=\huidigedatum,
%D    copyright=J. Hagen, A.F. Otten]
%
% Copyright Notice / 1996
%
% This module is part of the ConTeXt distribution. This
% macropackage will be put in the public domain as soon as the
% source is fully documented.
%
% This module is to be used as a whole and may not be adapted
% without knowledge of the authors. No separate parts may be
% distributed.
%
% Non-commercial (educational) institutions are hereby granted
% to use this module. Commercial use is only permitted after
% written permission.
%
% Errors can be reported to the authors and will be solved as
% soon as possible. Suggestions are welcome.
%
% copyright : PRAGMA
% authors   : J. Hagen / A.F. Otten
% address   : Postbox 125
%             8000 AC Zwolle
%             The Netherlands
% telephone : 038 4 229 775
% e-mail    : pragma@pi.net

% Deze module ondersteunt het zetten van chemische
% (structuur)formules. Hoewel de macro' zijn afgestemd op
% CONTEXT, zijn ze ook buiten deze zetomgeving te gebruiken.
%
% Dit is, afgezien van updates, de definitieve versie van
% PPCHTEX. Gebruikersgemak, eenvoud, flexibiliteit, en
% snelheid zijn inmiddels redelijk geoptimaliseerd. Dit neemt
% niet weg dat hier en daar nog verbetering mogelijk is. Dit
% zal dan ook nog gebeuren.
%
% Volgende versies zullen tenminste dezelfde functionaliteit
% hebben. We houden ons natuurlijk het recht voor de kwaliteit
% van de output te verbeteren. Daarnaast staan nog op het
% wensenlijstje:
%
% -  optimaliseren in termen van proces-tijd
% -  aanpassen naamgeving van interne macro's
% -  toevoegen van functionaliteit
% -  in \!!-vorm omzetten van GIVES, TB enz.
%
% De mix tussen engels en nederlands lijkt soms verwarrend.
% Meestal zijn verborgen macro's engels en zichtbare macro's
% nederlands. Het gebruik van [ ] en { } sluit aan op andere
% Context-macro's. Hetzelfde geldt voor instellingen en
% \start-\stop-constructies.
%
% De schijnbaar overbodige \bgroup-\egroup constructie
% garandeert aansluiting bij de Context-macro's voor het
% plaatsen van figuren, tabellen en andere floats.
%
% Binnen Context worden de macro's geladen met
% \gebruikextras[chemie]. Daarbij wordt een passende melding
% getoont. Buiten Context genereren we een melding:

\doifundefined{gebruikextras}%
  {\writestatus{laden}{Context Chemie Macro's / 1996.3.1}}

% Er wordt gebruik gemaakt van PiCTeX, een macropakket dat
% is ontwikkeld door M.J. Wichura. Hieronder wordt PiCTeX
% geladen. Er wordt, zonodig, rekening gehouden met LaTeX.

\doifundefined{doinputonce}
  {\def\doinputonce#1{\input #1 \relax}}

\doifundefined{fiverm}  % In the more recent LaTeX versions
  {\font\fiverm=cmr5 }  % \fiverm is no longer (pre)defined.

\doifundefined{beginpicture}          % PiCTeX
  {\doifdefinedelse{newenvironment}%  % LaTeX
     {\doinputonce{prepictex}%
      \doinputonce{pictex}%
      \doinputonce{postpictex}}%
     {\doinputonce{pictex}}}

% De onderstaande help-informatie (%I) kan worden opgeroepen
% in TeXEdit. De daaropvolgende setup-informatie (%S) kan
% nadat zij is uit deze file is gefilterd met TeXUtil, in
% handleidingen worden gebruikt. In deze file opgenomen
% documentatie (%D en %M) kan worden gebruikt voor een
% technische handleiding. Met %T kunnen templates worden
% gedefinieerd voor TeXEdit.

%I n=Chemie
%I c=\stelchemiein,\chemie
%I
%I Chemische formules kunnen worden gezet met behulp van de
%I onderstaande commando's:
%I
%I buiten $ en $$ :
%I
%I   \chemie[segmenten][symbolen]
%I
%I   \startchemie[instellingen]
%I     \chemie...
%I     \chemie...
%I   \stopchemie
%I
%I en binnen $ en $$:
%I
%I   \chemie{}{}
%I
%I Voor tekst, uitleg en voorbeelde verwijzen we vooralsnog
%I naar de handleiding.
%P
%I Het gedrag van de macro's kan worden ingesteld met:
%I
%I   \stelchemiein[breedte=,hoogte=,links=,rechts=,boven=,
%I     onder=,korps=,schaal=,status=,assenstelsel=,kader=,
%I     variant=,optie=,formaat=,tekstformaat=,resolutie=,
%I     offset=,letter=]
%I
%I Structuren kunnen worden voorgedefinieerd met het commando
%I
%I   \definieerchemie[naam]{\chemie...}

%S \startsetup
%S   \command
%S     [stelchemiein]
%S   \type
%S     [\!!vars]
%S   \variable
%S     [\!!breedte]
%S     [\!!getal,\!!passend]
%S     [0]
%S   \variable
%S     [\!!hoogte]
%S     [\!!getal,\!!passend]
%S     [0]
%S   \variable
%S     [\!!links]
%S     [\!!getal]
%S     [0]
%S   \variable
%S     [\!!rechts]
%S     [\!!getal]
%S     [0]
%S   \variable
%S     [\!!boven]
%S     [\!!getal]
%S     [0]
%S   \variable
%S     [\!!onder]
%S     [\!!getal]
%S     [0]
%S   \variable
%S     [\!!resolutie]
%S     [\!!getal]
%S     [\systeemresolutie]
%S   \variable
%S     [\!!korps]
%S     [10pt,11pt,12pt]
%S     [\systeemkorps]
%S   \variable
%S     [\!!schaal]
%S     [\!!klein,\!!middel,\!!groot]
%S     [\!!middel]
%S   \variable
%S     [\!!formaat]
%S     [\!!klein,\!!middel,\!!groot]
%S     [\!!groot]
%S   \variable
%S     [\!!tekstformaat]
%S     [\!!klein,\!!middel,\!!groot]
%S     [\!!groot]
%S   \variable
%S     [\!!status]
%S     [\!!start,\!!stop]
%S     [\!!start]
%S   \variable
%S     [\!!kader]
%S     [\!!aan,\!!uit]
%S     [\!!uit]
%S   \variable
%S     [\!!assenstelsel]
%S     [\!!aan,\!!uit]
%S     [\!!uit]
%S   \variable
%S     [\!!optie]
%S     [\!!test]
%S     []
%S   \variable
%S     [\!!variant]
%S     [1,2]
%S     [1]
%S   \variable
%S     [\!!offset]
%S     [HIGH,LOW]
%S     [LOW]
%S   \variable
%S     [\!!letter]
%S     [\!!commando]
%S     [\rm]
%S \stopsetup

%S \startsetup
%S   \command
%S     [startchemie]
%S   \type
%S     [\!!vars\!!stp]
%S   \variable
%S     [\!!breedte]
%S     [\!!getal,\!!passend]
%S     [0]
%S   \variable
%S     [\!!hoogte]
%S     [\!!getal,\!!passend]
%S     [0]
%S   \variable
%S     [\!!links]
%S     [\!!getal]
%S     [0]
%S   \variable
%S     [\!!rechts]
%S     [\!!getal]
%S     [0]
%S   \variable
%S     [\!!boven]
%S     [\!!getal]
%S     [0]
%S   \variable
%S     [\!!onder]
%S     [\!!getal]
%S     [0]
%S   \variable
%S     [\!!korps]
%S     [10pt,11pt,12pt]
%S     [\systeemkorps]
%S   \variable
%S     [\!!schaal]
%S     [\!!klein,\!!middel,\!!groot]
%S     [\!!groot]
%S   \variable
%S     [\!!status]
%S     [\!!start,\!!stop]
%S     [\!!start]
%S   \variable
%S     [\!!kader]
%S     [\!!aan,\!!uit]
%S     [\!!uit]
%S   \variable
%S     [\!!assenstelsel]
%S     [\!!aan,\!!uit]
%S     [\!!uit]
%S   \variable
%S     [\!!optie]
%S     [\!!test]
%S     []
%S   \variable
%S     [\!!variant]
%S     [1,2]
%S     [1]
%S   \variable
%S     [\!!offset]
%S     [HIGH,LOW]
%S     [LOW]
%S   \variable
%S     [\!!letter]
%S     [\!!commando]
%S     [\rm]
%S \stopsetup

%S \startsetup
%S   \command
%S     [chemie]
%S   \type
%S     [\!!vals\!!vals]
%S   \value
%S     [\!!list]
%S     []
%S   \value
%S     [\!!list]
%S     []
%S \stopsetup

%S \startsetup
%S   \command
%S     [definieerchemie]
%S   \type
%S     [\!!val\!!arg]
%S   \value
%S     [\!!text]
%S     []
%S \stopsetup

\unprotect

% Om te voorkomen dat sub- en superscripts botsen passen we
% wat fontdimen's aan (Knuth, The TeXBook, p179). Helaas
% kunnen deze instellingen niet lokaal worden gehouden door
% groeperen, vandaar dat een en ander moet worden geset ‚n
% gereset.
%
% Er dient een relatie te worden gelegd met de afmetingen
% van de letters. In een eerdere versie werden daartoe de
% \fontdimen's opgehoogd. Omdat dit problemen gaf bij
% scaled fonts, is bij nader inzien gekozen voor de
% onderstaande oplossing, waarbij de nieuwe waarden worden
% afgeleid van de x-height (\fontdimen5). De factor 0.70
% is min of meer experimenteel vastgesteld. Soms worden de
% regels iets verder uit elkaar gezet. Jammer. Italic fonts
% hebben grotere cijfers en vallen min of meer uit de boot.

\newif\ifloweredsubscripts

% Due to some upward incompatibality of LaTeX to LaTeX2.09
% and/or LaTeX2e we had to force \@@chemieletter. Otherwise
% some weird \nullfont error comes up.

\def\beginlatexmathmodehack%
  {\ifmmode
     \let\endlatexmathmodehack=\relax
   \else
     \def\endlatexmathmodehack{$}$\@@chemieletter
   \fi}

\def\setsubscripts%
  {\beginlatexmathmodehack
   \def\dosetsubscript##1##2##3%
     {\dimen0=##3\fontdimen5##2%
      \setxvalue{@@\string##1\string##2}{\the##1##2\relax}%
      ##1##2=\dimen0\relax}%
   \def\dodosetsubscript##1##2%
     {\dosetsubscript{##1}{\textfont2}{##2}%
      \dosetsubscript{##1}{\scriptfont2}{##2}%
      \dosetsubscript{##1}{\scriptscriptfont2}{##2}}%
   %\dodosetsubscript{\fontdimen14}{?}%
   \dodosetsubscript{\fontdimen16}{.7}%
   \dodosetsubscript{\fontdimen17}{.7}%
   \global\loweredsubscriptstrue
   \endlatexmathmodehack}

\def\resetsubscripts%
  {\ifloweredsubscripts
     \beginlatexmathmodehack
     \def\doresetsubscript##1##2%
       {\dimen0=\getvalue{@@\string##1\string##2}\relax
        ##1##2=\dimen0}%
     \def\dodoresetsubscript##1%
       {\doresetsubscript{##1}{\textfont2}%
        \doresetsubscript{##1}{\scriptfont2}%
        \doresetsubscript{##1}{\scriptscriptfont2}}%
     %\dodoresetsubscript{\fontdimen14}%
     \dodoresetsubscript{\fontdimen16}%
     \dodoresetsubscript{\fontdimen17}%
     \global\loweredsubscriptsfalse
     \endlatexmathmodehack
   \fi}

\def\doresetsubscripts%
  {\resetsubscripts}

\def\sethighsubscripts%
  {\resetsubscripts
   \let\dosetsubscripts=\relax}

\def\setlowsubscripts%
  {\def\dosetsubscripts{\setsubscripts}}

\setlowsubscripts

\newcount\horchemical          % t.z.t. \newcounter
\newcount\verchemical          % t.z.t. \newcounter
\newcount\txtchemical          % t.z.t. \newcounter
\newcount\chemicalfile         % t.z.t. \newcounter

\newif\ifinchemical            \inchemicalfalse
\newif\iffixedchemical         \fixedchemicalfalse
\newif\ifsavechemical          \savechemicalfalse
\newif\ifloadchemical          \loadchemicalfalse

\newbox\chemicalsymbols

% Eigenlijk moeten de constanten en variabelen in cont-nl.tex
% staan. Dit pakket is echter relatief onafhankelijk van CONTEXT.

\def\!!chemie                  {chemie}
\def\??chemie                  {@@chemie}

\def\!!translate               {translate}
\def\!!distance                {distance}
\def\!!mirror                  {mirror}
\def\!!rotate                  {rotate}
\def\!!substitute              {substitute}

\def\!!executechemical         {executechemical}
\def\!!chemicaltextelement     {chemicaltext}
\def\!!chemicallinesegment     {chemicalline}
\def\!!chemicalcircsegment     {chemicalcirc}

\def\!!chemicalspace           {\quad}

% begin van experiment:
%
% De onderstaande twee macro's kunnen worden gebruikt voor
% bijvoorbeeld een interactiemechanisme.
%
% \gotochemical   {verwijzing} {tekst}
% \thisischemical {verwijzing}

\def\dowithchemical%
  {}

\doifdefinedelse{@@iastatus}
  {\def\gotochemical#1#2{\naar{#2}[#1]}%
   \def\thisischemical#1{\paginareferentie[#1]}}
  {\def\gotochemical#1{}%
   \def\thisischemical#1{}}

% eind van experiment

\def\setchemicalmaximum #1
  {\def\maxchemical{#1}}

\def\doifchemicalnumber#1#2#3%
  {\doifnumberelse{#1}
     {\ifnum#1>\maxchemical
        \writestatus{chemie}{nummer #1 wordt overgeslagen}%
      \else
        #3%
      \fi}
     {\unknownchemical{#2}}}%

\def\stelchemieformaatin[#1]%
  {\assignvalue
     {\dogetvalue{#1}{\!!formaat}}
     {\@@localchemieformaat}
     {\scriptscriptstyle}
     {\scriptstyle}
     {\textstyle}%
   \assignvalue
     {\dogetvalue{#1}{\!!tekstformaat}}
     {\chemicalstyle}
     {\scriptscriptstyle}
     {\scriptstyle}
     {\textstyle}%
   \assignvalue
     {\dogetvalue{#1}{\!!schaal}}
     {\@@localchemieschaal}
     {500}
     {625}
     {750}}

\def\dostelchemiein[#1]%
  {\getparameters[\??chemie\!!chemie][#1]%
   \doifelse{\@@chemiechemieoffset}{LOW}
     {\setlowsubscripts}
     {\sethighsubscripts}%
   \stelchemieformaatin[\??chemie\!!chemie]}

\def\stelchemiein%
  {\dosingleargument\dostelchemiein}

\def\@@chemieletter%        %  $inner-style$
  {\@@chemiechemieletter}   % $$outer-style$$

\def\doloadchemical%
  {\global\advance\chemicalfile by 1\relax
   \writestatus{chemie}{inlezen uit chem-\the\chemicalfile.tex}%
   \replot "chem-\the\chemicalfile.tex" }

\def\dosavechemical%
  {\global\advance\chemicalfile by 1\relax
   \writestatus{chemie}{wegschrijven naar chem-\the\chemicalfile.tex}%
   \savelinesandcurves on "chem-\the\chemicalfile.tex" }

\def\writetest#1#2%
  {}

\def\complexstartchemie[#1]%
  {\copyparameters
     [\??chemie][\??chemie\!!chemie]
     [\!!breedte,\!!hoogte,\!!links,\!!rechts,\!!boven,\!!onder,
      \!!korps,\!!formaat,\!!schaal,\!!status,\!!kader,\!!assenstelsel,
      \!!plaats,\!!optie,\!!variant,\!!file,\!!resolutie,\!!offset,
      \!!letter]%
   \getparameters
     [\??chemie]
     [#1]%
   \beginpicture
   %
   \stelchemieformaatin[\??chemie]%
   %
   \doif{\@@chemievariant}{2}
     {\!widtha=50.8mm
      \divide\!widtha by \@@chemieresolutie\relax
      \plotsymbolspacing=\!widtha
      \setplotsymbol({\vrule\!!!height\!widtha\!!!width\!widtha})}%
   %
   \!counta=250000
   \divide\!counta by \@@localchemieschaal
   \!widtha=\@@chemiekorps
   \divide\!widtha by \!counta
   \setcoordinatesystem units <\the\!widtha,\the\!widtha>%
   %
   % \!counta = -x     \!countc = -y
   % \!countb = +x     \!countd = +y
   %
   \def\calculateaxis##1##2##3##4##5%
     {##1=##3\relax
      ##2=##4\relax
      \ifnum##5=0
        \ifnum##3=0
          \ifnum##4=0
            ##1=2000
            ##2=2000
           \fi
        \fi
      \else
        \ifnum##3=0
          \ifnum##4=0
            ##1=##5\relax
            \divide##1 by 2
            ##2=##1\relax
          \else
            ##1=##5\relax
            \advance##1 by -##2\relax
          \fi
        \else
          \ifnum##4=0
            ##2=##5\relax
            \advance##2 by -##1\relax
          \fi
        \fi
      \fi}%
   \fixedchemicalfalse
   \doif{\@@chemiebreedte}{\!!passend}
     {\def\@@chemiebreedte{1}%
      \fixedchemicaltrue}%
   \doif{\@@chemiehoogte}{\!!passend}
     {\def\@@chemiehoogte{1}%
      \fixedchemicaltrue}%
   \calculateaxis
     {\!counta}{\!countb}
     {\@@chemielinks}{\@@chemierechts}{\@@chemiebreedte}%
   \calculateaxis
     {\!countc}{\!countd}
     {\@@chemieonder}{\@@chemieboven}{\@@chemiehoogte}%
   %
   \doifelse{\@@chemieplaats}{\!!intekst}
     {\accountingon
      \setplotarea
        x from 0 to 0,
        y from 0 to 0 }%
     {\setplotarea
        x from {-\the\!counta} to {\the\!countb},
        y from {-\the\!countc} to {\the\!countd} }%
   %
   \doifinset{\!!aan}{\@@chemiekader,\@@chemieassenstelsel}
     {\axis top /
      \axis bottom /
      \axis left /
      \axis right / }%
   \doif{\@@chemiestatus}{\!!start}
     {\doif{\@@chemieassenstelsel}{\!!aan}
        {\axis
           bottom shiftedto y=0
           ticks from {-\the\!counta} to {\the\!countb} by 500 /
         \axis
           left shiftedto x=0
           ticks from {-\the\!countc} to {\the\!countd} by 500 / }}%
   \iffixedchemical
     \accountingon
     \def\account##1##2%
       {\put {} at {##1} {##2} }%
   \else
     \accountingoff
     \def\account##1##2%
       {}%
   \fi
   \doifelse{\@@chemieoptie}{\!!test}
     {\def\writetest{\writestatus}}
     {\def\writetest##1##2{}}%
   \doif{\@@chemiefile}{load}         % experiment
     {\loadchemicaltrue               % experiment
      \doloadchemical}%               % experiment
   \doif{\@@chemiefile}{save}         % experiment
     {\savechemicaltrue               % experiment
      \dosavechemical}%               % experiment
   \ignorespaces}

\def\startchemie%
  {\bgroup                    %  t.b.v. ungrouped floats
   \catcode`\^=\@@superscript %  t.b.v. \enableduplication
   \catcode`\_=\@@subscript   %  t.b.v. de zekerheid
   \begingroup                %  t.b.v. symmetrietest: %% \endgroup
   \inchemicaltrue
   \def\@@chemicalpostponed{}%
   \setbox0=\vbox\bgroup
   \complexorsimpleempty{startchemie}}

\def\stopchemie%
  {\put {\box\chemicalsymbols} at 0 0 %
   \endpicture
   \egroup
   \!heighta=\ht0
   \advance\!heighta by \dp0
   \ht0=\!heighta
   \dp0=\!!zeropoint
   \box0
   \inchemicalfalse            %  t.b.v. symmetrietest: %% \begingroup
   \endgroup
   \egroup                     %  t.b.v. ungrouped floats
   \ignorespaces}

% \setchemicalcoordinates{#1}{#2}
%
% #1: verplaatsing in x-richting
% #2: verplaatsing in y-richting

\def\setchemicalcoordinates#1#2%
  {\advance\horchemical by #1\relax
   \advance\verchemical by #2\relax
   \setcoordinatesystem point at {\the\horchemical} {\the\verchemical} }

\def\resetchemicalcoordinates%
  {\horchemical=0
   \verchemical=0
   \setcoordinatesystem point at 0 0 }

\def\setchemicaltranslate #1 #2 #3
  {\setvalue{\!!translate#1}{\setchemicalcoordinates{#2}{#3}}}

\def\processchemicaltranslate#1%
  {\def\doprocess[##1##2]%
     {\doifchemicalnumber{##1}{MOV#1}
        {\ifnum##1=0
           \resetchemicalcoordinates
         \else
           \getvalue{\!!translate##1}%
           \dochemicaloffset{##1}%
           \def\chemicaloffset{0}%
           \def\chemicaloffsetfactor{1}%
         \fi}}%
   \doprocess[#1]}

\def\setchemicaldistance #1
  {\setvalue{\!!distance1}{\setchemicalcoordinates{-#1}{  0}}%
   \setvalue{\!!distance2}{\setchemicalcoordinates{  0}{ #1}}%
   \setvalue{\!!distance3}{\setchemicalcoordinates{ #1}{  0}}%
   \setvalue{\!!distance4}{\setchemicalcoordinates{  0}{-#1}}}

\def\processchemicaldistance#1%
  {\def\doprocess[##1##2]%
     {\doifchemicalnumber{##1}{ADJ#1}
        {\ifnum##1=0
           \resetchemicalcoordinates
         \else
           \def\@@chemicalpostponed{\getvalue{\!!distance##1}}%
           \@@chemicalpostponed
         \fi}}%
   \doprocess[#1]}

\def\setchemicalsubstitute #1
  {\setvalue{\!!substitute1}{\setchemicalcoordinates{-#1}{  0}}%
   \setvalue{\!!substitute2}{\setchemicalcoordinates{  0}{ #1}}%
   \setvalue{\!!substitute3}{\setchemicalcoordinates{ #1}{  0}}%
   \setvalue{\!!substitute4}{\setchemicalcoordinates{  0}{-#1}}}

\def\processchemicalsubstitute#1%
  {\def\doprocess[##1##2]%
     {\doifchemicalnumber{##1}{SUB#1}
        {\ifnum##1=0
           \resetchemicalcoordinates
         \else
           \def\@@chemicalpostponed{\getvalue{\!!substitute##1}}%
           \@@chemicalpostponed
         \fi}}%
   \doprocess[#1]}

% Het is mogelijk een offset of move meerdere malen uit te
% voeren, door een nummer voor het commando te plaatsen.

\def\chemicalrepeat       {1}

\def\doprocesschemical[#1#2]#3%
  {\doifnumberelse{#1}
     {\def\chemicalrepeat{#1}%
      \processchemical[#2]%
      \def\chemicalrepeat{1}}
     {#3}}

% \dochemicaloffset{#1}
%
% #1: binding

\def\chemicaloffsetfactor {1}
\def\chemicaloffset       {0}

\def\processchemicaloffset#1%
  {\def\doprocess[##1##2]%
     {\doifnumberelse{##1}
        {\let\chemicaloffsetfactor=\chemicalrepeat
         \def\chemicaloffset{##1}}
        {\unknownchemical{OFF#1}}}%
   \doprocess[#1]}

\def\dochemicaloffset#1%
  {\doifinsetelse{#1}{1,2,8}%
     {\!counta=200\relax
      \multiply\!counta by \chemicaloffset\relax
      \multiply\!counta by \chemicaloffsetfactor\relax
      \edef\currentchemicaloffset{\the\!counta}%
      \setchemicalcoordinates{-\currentchemicaloffset}{0}%
      \def\undochemicaloffset%
        {\setchemicalcoordinates{\currentchemicaloffset}{0}%
         \def\undochemicaloffset{}}}
     {\def\undochemicaloffset{}}}

% \dosetchemicalrotation{#1}{#2}
%
% #1: cos(phi)
% #2: sin(phi)

\def\chemicalrotation   {1}

\def\setchemicalmirror#1%
  {\setvalue{\!!mirror#1}{*}}

\def\resetchemicalmirror#1%
  {\resetvalue{\!!mirror#1}}

\def\togglechemicalmirror#1%
  {\doifelse{\getvalue{\!!mirror#1}}{*}
     {\resetchemicalmirror{#1}}
     {\setchemicalmirror{#1}}}

\def\dosetchemicalrotation#1#2%
 {\startrotation by {#1} {#2} }   %% \stoprotation (t.b.v. testen)

\def\chemicalrotate[#1]%
  {\doifdefinedelse{\!!mirror#1}
     {\getvalue{\!!rotate\chemicalrotation.#1\getvalue{\!!mirror#1}}}
     {\getvalue{\!!rotate\chemicalrotation.#1}}}

\def\setchemicalrotation #1 #2 #3 #4 #5 #6 #7 #8 #9
  {\setvalue{\!!rotate1.#1}{\dosetchemicalrotation{#2}{#3}}%
   \setvalue{\!!rotate2.#1}{\dosetchemicalrotation{#4}{#5}}%
   \setvalue{\!!rotate3.#1}{\dosetchemicalrotation{#6}{#7}}%
   \setvalue{\!!rotate4.#1}{\dosetchemicalrotation{#8}{#9}}}

\def\processchemicalrotation#1%
  {\def\doprocess[##1##2]%
     {\doifnumberelse{##1}
        {\def\chemicalrotation{##1}}
        {\unknownchemical{ROT#1}}}%
   \doprocess[#1]}

% \filtertextelement[#1][#2][#3][#4]
%
% #1: volgnummer
% #2: offset in uitlijningen
% #3: lijst met uitlijningen -> \chemicalloca
% #4: lijst met teksten      -> \chemicaltext

\def\filterchemicaltextelement[#1][#2][#3][#4]%
  {\ifnum#1=0\relax
     \edef\chemicalloca{}%
   \else
     \!counta=\chemicalrotation
     \advance\!counta by -1
     \multiply\!counta by #2
     \advance\!counta by #1
     \getfromcommalist[#3][\the\!counta]%
     \let\chemicalloca=\commalistelement
   \fi
   \advance\txtchemical by 1
   \getfromcommalist[#4][\txtchemical]%
   \let\chemicaltext=\commalistelement}

% \putchemicaltext{#1}{#2}
%
% #1 : x-coordinaat
% #2 : y-coordinaat
%
% \chemicaltext en \chemicalloca worden met \gettextelement
% opgehaald uit de tweede set bij \chemie
%
% Ten behoeve van testdoeleinden wordt gebruik gemaakt van
% \chemicalframe in plaats van het meer sjieke, maar tevens
% meer trage \omlijnd.

\def\chemicalframe#1%
  {\hbox{\vbox{\hrule\hbox{\vrule\vbox{#1}\vrule}\hrule}}}

\def\putchemicaltext#1#2%    % t.b.v. symmetrietest: %% \startrotation
  {\doifelse{\@@chemieoptie}{\!!test}
     {\def\@@chemieframe{\stoprotation\chemicalframe}}
     {\def\@@chemieframe{}}%
   \dosetsubscripts
   \setbox2=\hbox{$\@@chemieletter{\@@localchemieformaat \chemicaltext}$}%
   \setbox4=\hbox{$\@@chemieletter{\@@localchemieformaat C_2^2}$}%
   \setbox6=\hbox{$\@@chemieletter{\@@localchemieformaat O}$}%        % C
   \doresetsubscripts
   \doifnot{\@@chemieplaats}{\!!intekst}
     {\ht2=\ht4
      \dp2=\dp4}%
   \setbox2=\hbox{\@@chemieframe{\box2}}%
   \ifdim\wd2>\wd6
     \doifelse{#1#2}{00}
       {\wd2=\wd6}
       {\doifinset{\chemicalloca}{t,b}{\wd2=\wd6}}%
   \fi
   \put
     {\dowithchemical{\copy2}}     % per se \copy0 i.p.v. \box2
     [\chemicalloca]
     at {#1} {#2} }

\def\setchemicaltextelement #1 #2 #3
  {\setvalue{\!!chemicaltextelement#1}{\putchemicaltext{#2}{#3}}}

\def\getchemicaltextelement[#1][#2][#3][#4][#5]%
  {\filterchemicaltextelement[#2][#3][#4][#5]%
   \doifelse{#2}{0}
     {\putchemicaltext{0}{0}}
     {\chemicalrotate[#2]%
      \dochemicaloffset{#2}%
      \getvalue{\!!chemicaltextelement#1}%
      \undochemicaloffset}}

\def\processchemicaltextelement#1#2#3#4#5%
  {\def\doprocess[##1##2##3##4##5]%
     {\doifelse{##1}{?}
        {\doprocess[1..\maxchemical ????]}
        {\doifchemicalnumber{##1}{#1#2}
           {\doifelse{##2##3}{..}
              {\doifchemicalnumber{##4}{#1#2}
                 {\getchemicaltextelement[#1][##1][#4][#5][#3]%
                  \doifnot{##1}{##4}
                    {\!counta=##1\relax
                     \advance\!counta by 1
                     \edef\nextsegment{\the\!counta}%
                     \doprocess[\nextsegment..##4##5]}}}
              {\getchemicaltextelement[#1][##1][#4][#5][#3]%
               \doifnot{##2}{?}{\doprocess[##2##3##4##5]}}}}}%
   \doprocess[#2]}

% \plotchemicalline{#1}{#2}{#3}{#4}
%
% #1: x-coordinaat beginpunt
% #2: y-coordinaat beginpunt
% #3: x-coordinaat eindpunt
% #4: y-coordinaat eindpunt

\def\plotchemicalline#1#2#3#4%
  {\ifloadchemical
   \else
     \plot {#1} {#2} {#3} {#4} /
   \fi
   \account{#1}{#2}%
   \account{#3}{#4}}

\def\setchemicallinesegment #1 #2 #3 #4 #5
  {\setvalue{\!!chemicallinesegment#1}{\plotchemicalline{#2}{#3}{#4}{#5}}}

\def\getchemicallinesegment[#1][#2]%
  {\chemicalrotate[#1]%
   \dochemicaloffset{#1}%
   \getvalue{\!!chemicallinesegment#2}%
   \getvalue{\!!chemicallinesegment#21}%
   \getvalue{\!!chemicallinesegment#22}%
   \undochemicaloffset}

\def\getprivatechemicallinesegment[#1][#2]%
  {\chemicalrotate[#1]%
   \getvalue{\!!chemicallinesegment#2#1}}

\def\doprocesschemicallinesegment#1#2#3%
  {\def\doprocess[##1##2##3##4##5]%
     {\doifelse{##1}{?}
        {\doprocess[1..\maxchemical ????]}
        {\doifchemicalnumber{##1}{#2#3}
           {\doifelse{##2##3}{..}
              {\doifchemicalnumber{##4}{#2#3}
                 {#1[##1][#2]%
                  \doifnot{##1}{##4}
                    {\!counta=##1\relax
                     \advance\!counta by 1
                     \edef\nextsegment{\the\!counta}%
                     \doprocess[\nextsegment..##4##5]}}}
              {#1[##1][#2]%
               \doifnot{##2}{?}
                 {\doprocess[##2##3##4##5]}}}}}%
   \doprocess[#3]}

\def\processchemicallinesegment%
  {\doprocesschemicallinesegment\getchemicallinesegment}

\def\processprivatechemicallinesegment%
  {\doprocesschemicallinesegment\getprivatechemicallinesegment}

% \plotchemicalcircle{#1}{#2}{#3}{#4}
%
% #1: lengte van de boog in graden
% #2: x-coordinaat eindpunt
% #3: y-coordinaat eindpunt

\def\plotchemicalcircle#1#2#3%
  {\ifloadchemical
   \else
     \circulararc {#1} degrees from {#2} {#3} center at {0} {0} %
   \fi}

\def\setchemicalcircsegment #1 #2 #3 #4
  {\setvalue{\!!chemicalcircsegment#1}{\plotchemicalcircle{#2}{#3}{#4}}}

\def\getchemicalcircsegment[#1][#2]%
  {\chemicalrotate[#1]%
   \getvalue{\!!chemicalcircsegment#2}}

\def\processchemicalcircsegment#1#2%
  {\def\doprocess[##1##2##3##4##5]%
     {\doifelse{##1}{?}
        {\doprocess[1..\maxchemical ????]}
        {\doifchemicalnumber{##1}{#1#2}
           {\doifelse{##2##3}{..}
              {\doifchemicalnumber{##4}{#1#2}
                 {\getchemicalcircsegment[##1][#1]%
                  \doifnot{##1}{##4}
                    {\!counta=##1\relax
                     \advance\!counta by 1
                     \edef\nextsegment{\the\!counta}%
                     \doprocess[\nextsegment..##4##5]}}}
              {\getchemicalcircsegment[##1][#1]%
               \doifnot{##2}{?}
                 {\doprocess[##2##3##4##5]}}}}}%
   \doprocess[#2]}

\def\doskipchemie[#1][#2]%
  {{\tt[chemie]}}

\def\skipchemie%
  {\dodoubleargument\doskipchemie}

\def\complexchemie%
  {\ifinchemical
     \let\next=\dochemie
   \else
     \writestatus{chemie}{de [][]-vorm is hier niet toegestaan}%
     \let\next=\skipchemie
   \fi
   \next}

\newif\ifinnerchemical

\def\dosimplechemie#1#2%
  {\doifdefinedelse{@@chemieplaats}
     {\writestatus{chemie}{de {}{}-vorm is hier niet toegestaan}}
     {\ifinnerchemical
        \let\chemicalsign=\chemicalinnersign
        \let\chemicalmolecule=\chemicalinnermolecule
        \let\chemicalsinglearrow=\chemicalsingleinnerarrow
        \let\chemicaldoublearrow=\chemicaldoubleinnerarrow
      \else
        \let\chemicalsign=\chemicaloutersign
        \let\chemicalmolecule=\chemicaloutermolecule
        \let\chemicalsinglearrow=\chemicalsingleouterarrow
        \let\chemicaldoublearrow=\chemicaldoubleouterarrow
      \fi
      \processallactionsinset
        [#1]
        [       HIGH=>\sethighsubscripts,       % NIEUW
                 LOW=>\setlowsubscripts,        % NIEUW
                PLUS=>\chemicalsign{+},
               GIVES=>\chemicalsinglearrow{#2},
         EQUILIBRIUM=>\chemicaldoublearrow{#2},
              SINGLE=>\singlechemicalbond,
              DOUBLE=>\doublechemicalbond,
              TRIPLE=>\triplechemicalbond,
                   +=>\chemicalsign{+},
                  ->=>\chemicalsinglearrow{#2},
                 <->=>\chemicaldoublearrow{#2},
                   -=>\singlechemicalbond,
                  --=>\doublechemicalbond,
                 ---=>\triplechemicalbond,
         \!!!unknown=>\chemicalmolecule{\commalistelement}{#2}]}}

\def\dosimplechemieA#1%
  {\let\!!chemicalspace=\relax
   \def\dodosimplechemie##1%
     {\dosimplechemie{##1}{}}%
   \processcommalist[\@@chemiechemieoffset,#1]\dodosimplechemie
   \egroup}

\def\dosimplechemieB#1#2%
  {\dosimplechemie{#1}{#2}%
   \egroup}

\def\dosimplechemieC#1%
  {$\simplechemie{#1}{}$%
   \egroup} % erbij

\def\simplechemie%
  {\ifinner
     \innerchemicaltrue
   \else
     \innerchemicalfalse
   \fi
   \bgroup
   \catcode`\^=\@@superscript %  t.b.v. \enableduplication
   \catcode`\_=\@@subscript   %  t.b.v. de zekerheid
   \ifmmode
     \ifinnerchemical
       \let\next=\dosimplechemieA
     \else
       \let\next=\dosimplechemieB
     \fi
   \else
     \let\next=\dosimplechemieC
   \fi
   \next}

\def\chemie%
  {\complexorsimple{chemie}}

\def\donaarchemie[#1]%
  {\def\dowithchemical%                       % experiment
     {\gotochemical{#1}}%                     % experiment
   \chemie}                                   % experiment

\def\naarchemie%                              % experiment
  {\dosingleargument\donaarchemie}            % experiment

\def\dododochemie#1[#2][#3]%                  % experiment
  {\def\simpledododochemie%                   % experiment
     {#1[#2][#3]}%                            % experiment
   \def\complexdododochemie[##1]%             % experiment
     {\def\dowithchemical%                    % experiment
        {\thisischemical{#2}}%                % experiment
      #1[#3][##1]}%                           % experiment
   \complexorsimple{dododochemie}}%           % experiment

\def\dochemie[#1]%
  {\def\simpledochemie%
     {\writetest{chemie}{[#1][]}%
      \dodochemie[#1][]}%
   %
   \def\complexdochemie[##1]%
     {\writetest{chemie}{[#1][##1]}%
      \txtchemical=0%
      \dodochemie[#1][##1]}%
   %
   \def\complexdochemie[##1]%                 % experiment
     {\writetest{chemie}{[#1][##1]}%          % experiment
      \txtchemical=0%                         % experiment
      \dododochemie\dodochemie[#1][##1]}%     % experiment
   %
   \complexorsimple{dochemie}}

\def\dodochemie[#1][#2]%
  {\ignorespaces
   \ifinchemical
     \drawchemical[#1][#2]%
     \ignorespaces
   \else
     \startchemie[\!!plaats=\!!intekst]%
       \drawchemical[#1][#2]%
     \stopchemie
   \fi
   \ignorespaces}

% \reversechemical#1#2#3
%
% #1: prefix
% #2: volgnummer enz
% #3: tegengestelde volgnummers

\def\reversechemical#1#2#3%
  {\def\doprocess[##1##2]%
     {\doifchemicalnumber{##1}{#1#2}%
        {\getfromcommalist[#3][##1]%
         \let\reversechemicalaction=\commalistelement
         \processchemical[#1\reversechemicalaction##2]}}%
   \doprocess[#2]}

% \processunknownchemical[#1????][#2]
%
% #1: bindingen enz.
% #2: atomen enz.

\def\defaultchemical%
  {SIX}

\def\processunknownchemical[#1????][#2]%
  {\processaction
     [#1]
     [       SAVE=>\executechemicalSAVE,
          RESTORE=>\executechemicalRESTORE,
      \!!!default=>,
      \!!!unknown=>\doifdefinedelse{\!!executechemical#1}
                     {\def\chemicalrotation{1}%
                      \def\chemicaloffset{0}%
                      \doifdefined{\!!executechemical#1}
                        {\getvalue{\!!executechemical#1}[#2]}%
                      \@@chemicalpostponed}
                     {\getpredefinedchemical{#1}}]}

\setvalue{\!!chemie\!!x1}{0}
\setvalue{\!!chemie\!!y1}{0}

\def\executechemicalSAVE%
  {%\writestatus{chemie}{saving \the\horchemical,\the\verchemical}%
   \increment\chemicalstack
   \letvalue {\!!chemie n\chemicalstack}=\chemicalname
   %\letvalue {\!!chemie p\chemicalstack}=\@@chemicalpostponed
   \setevalue{\!!chemie x\chemicalstack}{\the\horchemical}%
   \setevalue{\!!chemie y\chemicalstack}{\the\verchemical}}

\def\restorechemicalvalues#1%
  {\let\oldprocesschemical=\processchemical
   \doifdefined{\!!executechemical#1}{\getvalue{\!!executechemical#1}[]}%
   \let\processchemical=\oldprocesschemical}

\def\executechemicalRESTORE%
  {\ifnum\chemicalstack=0\relax
     \horchemical=\getvalue{\!!chemie x1}\relax
     \verchemical=\getvalue{\!!chemie y1}\relax
   \else
     \restorechemicalvalues{\getvalue{\!!chemie n\chemicalstack}}%
     %\@EA\let\@EA\@@chemicalpostponed\@EA=\csname\!!chemie p\chemicalstack\endcsname
     \let\@@chemicalpostponed=\relax
     \horchemical=\getvalue{\!!chemie x\chemicalstack}\relax
     \verchemical=\getvalue{\!!chemie y\chemicalstack}\relax
     \decrement\chemicalstack
   \fi
   %\writestatus{chemie}{restoring \the\horchemical,\the\verchemical}%
   \setcoordinatesystem point at {\the\horchemical} {\the\verchemical} }

% \processlocalchemicals{#1}
%
% #1: commando's

\def\dodoprocesschemical#1%
  {\processchemical[#1????]}

\def\processlocalchemicals#1%
  {\processcommalist[#1]\dodoprocesschemical}

% \drawchemical[#1][#2]
%
% #1: bindingen enz.
% #2: atomen enz.

\newcounter\chemicalnesting

\def\localdodochemie[#1][#2]%
  {\writetest{chemie}{[#1][#2]}%
   %\bgroup     % koppelen en afmetingen gaat fout
   \increment\chemicalnesting
   \letvalue{\??chemie\!!!unknown\chemicalnesting}\unknownchemical
   \setevalue{\??chemie\!!tekst\chemicalnesting}{\the\txtchemical}%
   \txtchemical=0
   \dodochemie[#1][#2]%
   \@EA\txtchemical\@EA\csname\??chemie\!!tekst\chemicalnesting\endcsname
   \@EA\let\@EA\unknownchemical\csname\??chemie\!!!unknown\chemicalnesting\endcsname
   \decrement\chemicalnesting
   %\egroup     % koppelen en afmetingen gaat fout
   \ignorespaces}%

\def\drawchemical[#1][#2]%
  {\ignorespaces
   \def\dodochemie[##1][##2]%
     {\drawchemical[##1][##2]%
      \ignorespaces}%
   \def\dochemie[##1]%
     {\def\simpledochemie%
        {\writetest{chemie}{[##1][#2]}%
         \dodochemie[##1][#2]%
         \ignorespaces}%
      \def\complexdochemie[####1]%
        {\dododochemie\localdodochemie[##1][####1,#2]}% 
     \complexorsimple{dochemie}}%
   \doif{\@@chemiestatus}{\!!start}
     {\doif{\chemicalname}{\!!!unknown}
        {\getvalue{\!!executechemical\defaultchemical}[#2]}%
      \def\unknownchemical##1%
        {\processunknownchemical[##1][#2]}%
      \processcommalist[\@@chemieoffset,#1]\dodoprocesschemical}%
   \ignorespaces}

% De onderstaande macro's zijn verantwoordelijk voor het zetten
% van de + en pijlen. De +, en dus ook de pijlen, worden omhoog
% gehaald. Dit oogt m.i. fraaier.

\def\chemicalraise#1#2%
  {{\setbox0=\hbox{$#1+$}%
    \raise\dp0\hbox{$#1#2$}}}

\def\chemicalinnersign#1%
  {\chemicalraise{\chemicalstyle}{#1}}

\def\chemicaloutersign#1%
  {\chemicalraise{}{#1}}

\def\chemicalsingleinnerarrow#1%
  {\chemicalraise{\chemicalstyle}{\longrightarrow}}

\def\chemicalsingleouterarrow#1%
  {\chemicalraise{}{\hbox%
     {$\!!chemicalspace
       \buildrel
         \@@chemieletter{\scriptstyle\quad#1\quad}%
       \over{\overrightarrow
         {\hphantom{\@@chemieletter{\scriptstyle\quad#1\quad}}}}%
       \!!chemicalspace$}}}

\def\chemicalsinglepicturearrow#1%
  {\lower.5ex\hbox
      {$\!!chemicalspace
        \buildrel
          \@@chemieletter{\scriptstyle\quad#1\quad}%
        \over{\overrightarrow
          {\hphantom{\@chemieletter{\scriptstyle\quad#1\quad}}}}%
        \!!chemicalspace$}}

\def\chemicaldoubleinnerarrow#1%
  {\lower.2ex\hbox
     {\setbox2=\hbox{$\chemicalstyle\longrightarrow$}%
      \wd2=\!!zeropoint
      \raise\ht2\box2\hbox{$\chemicalstyle\longleftarrow$}}}

\def\chemicaldoubleouterarrow#1%
  {\lower.5ex\hbox
     {$\!!chemicalspace
       \buildrel
         \@@chemieletter{\scriptstyle\quad#1\quad}%
       \over{\overrightarrow{\overleftarrow
         {\hphantom{\@@chemieletter{\scriptstyle\quad#1\quad}}}}}%
       \!!chemicalspace$}}

\def\chemicaldoublepicturearrow#1%
  {\lower.5ex\hbox
     {$\!!chemicalspace
       \buildrel
         \@@chemieletter{\scriptstyle\quad#1\quad}%
       \over{\overrightarrow{\overleftarrow
         {\hphantom{\@@chemieletter{\scriptstyle\quad#1\quad}}}}}%
       \!!chemicalspace$}}

\def\chemicalinnermolecule#1#2%
  {\!!chemicalspace
   %\mathop   % onnodig, genereert trouwens een spatie
     {\dosetsubscripts
      \hbox{$\@@chemieletter{\chemicalstyle\strut#1}$}%
      \doresetsubscripts}%
   \!!chemicalspace}

\def\chemicaloutermolecule#1#2%
  {\!!chemicalspace
   \mathop
     {\dosetsubscripts
      \hbox{$\@@chemieletter{\strut#1}$}%
      \doresetsubscripts}%
   \doifnot{#2}{}
     {_{\@@chemieletter{\strut#2}}}%
   \!!chemicalspace}

% Bij de in-line bindingen wordt gebruik gemaakt van
% een \hrule. De maatvoering wordt bepaald door een
% kunstmatige em (\wd0).

\def\somechemicalbond%
  {\hrule width \wd0 height .4pt}

\def\dochemicalbonds#1#2#3%
  {{\setbox0=\hbox
      {$\@@chemieletter{\chemicalstyle M}$}%
    \vbox to \ht0
      {\hsize\wd0
       \vskip.1\wd0#1\vfill#2\vfill#3\vskip.1\wd0}}}

\def\singlechemicalbond%
  {\dochemicalbonds{}{\somechemicalbond}{}}

\def\doublechemicalbond%
  {\dochemicalbonds{\somechemicalbond}{}{\somechemicalbond}}

\def\triplechemicalbond%
  {\dochemicalbonds{\somechemicalbond}{\somechemicalbond}{\somechemicalbond}}

% In plaats van \def\naam{\chemie[...]...} kan beter gebruik
% worden gemaakt van het commando
%
%   \definieerchemie[naam]{commando's}
%
% De naam krijgt, om problemen met bestaande macro's te
% voorkomen, een prefix. Bij het ophalen van een commando
% worden beide definities afgehandeld.

\def\dodefinieerchemie[#1]#2%
  {\doifdefined{\??chemie#1}
     {\writestatus{chemie}{definitie #1 bestaat reeds}}%
   \setvalue{\??chemie#1}{#2}}

\def\definieerchemie
  {\dosingleargument\dodefinieerchemie}

\def\getpredefinedchemical#1%
  {\doifdefinedelse{\??chemie#1}
     {\getvalue{\??chemie#1}}
     {\doifdefinedelse{#1}
        {\getvalue{#1}}
        {\writestatus{chemie}{definitie #1 bestaat niet}}}}

% Hieronder zijn de definities van de structuren opgenomen. De
% naam van de structuur is als volgt opgebouwd:
%
%   \executechemicalNUMBER[#1]
%
% waarbij [#1] betrekking heeft op de tekstelementen van \chemie,
% de [tweede lijst] dus.
%
% De aan \chemie[#1][#2] meegegeven lijst van segmenten wordt
% deels door de in \execute gedefinieerde macro's afgehandeld,
% deels door algemene macro's. Segmenten hebben de vorm:
%
%   [+|-|]identifier[X|XYZ|X..Y]
%
% Voorbeelden van segmenten zijn:
%
%   R1
%   R1..4
%   R135
%   -R1
%   +R35

\setchemicalmaximum 0

\def\processchemical[#1]%
  {\unknownchemical{#1}}

\def\setchemicalname#1 %
  {\def\chemicalname{#1}}

\let\chemicalname=\!!!unknown

% Vooruitlopend op een gedetailleerde documentatie, zijn hier
% vast enkele gebruikte afmetingen:
%
% lengte radikalen          :  500
% afstand radikalen         :  100
% afstand dubbele radikalen :  260
% afstand substituenten     : +125

\def\executechemicalONE[#1]%
  {\setchemicalname ONE
   %
   \setchemicalmaximum      8
   \setchemicaldistance     0
   \setchemicalsubstitute 625
   %
   \setchemicalrotation 1  1      0      1      0      1      0      1      0
   \setchemicalrotation 2  0.707 -0.707  0.707 -0.707  0.707 -0.707  0.707 -0.707
   \setchemicalrotation 3  0     -1      0     -1      0     -1      0     -1
   \setchemicalrotation 4 -0.707 -0.707 -0.707 -0.707 -0.707 -0.707 -0.707 -0.707
   \setchemicalrotation 5 -1      0     -1      0     -1      0     -1      0
   \setchemicalrotation 6 -0.707  0.707 -0.707  0.707 -0.707  0.707 -0.707  0.707
   \setchemicalrotation 7  0      1      0      1      0      1      0      1
   \setchemicalrotation 8  0.707  0.707  0.707  0.707  0.707  0.707  0.707  0.707
   %
   \setchemicaltranslate 1 -1000     0
   \setchemicaltranslate 2 -1000  1000
   \setchemicaltranslate 3     0  1000
   \setchemicaltranslate 4  1000  1000
   \setchemicaltranslate 5  1000     0
   \setchemicaltranslate 6  1000 -1000
   \setchemicaltranslate 7     0 -1000
   \setchemicaltranslate 8 -1000 -1000
   %
   \setchemicallinesegment  SB   300     0   700     0
   \setchemicallinesegment DB1   300    50   700    50
   \setchemicallinesegment DB2   300   -50   700   -50
   %
   \setchemicaltextelement   Z   800     0
   \setchemicaltextelement  RZ   950     0
   %
   \def\processchemical[##1##2##3##4]%
     {\doprocesschemical[##1##2##3##4]
        {\processaction
           [##1##2##3##4]
           [    SUB##4=>\processchemicalsubstitute{##4},
                ADJ##4=>\processchemicaldistance{##4},
                MOV##4=>\processchemicaltranslate{##4},
                OFF##4=>\processchemicaloffset{##4},
              SB##3##4=>\processchemicallinesegment{SB}{##3##4},
              DB##3##4=>\processchemicallinesegment{DB}{##3##4},
              TB##3##4=>\processchemicallinesegment{SB}{##3##4}%
                        \processchemicallinesegment{DB}{##3##4},
              CZ##3##4=>\processchemicaltextelement{RZ}{##3##4}{#1}{0}
                          {},
            Z##2##3##4=>\processchemicaltextelement{Z}{##2##3##4}{#1}{0}
                          {l,l,t,r,r,r,b,l},
           \!!!unknown=>\unknownchemical{##1##2##3##4}]}}}

\def\executechemicalTHREE[#1]%
  {\setchemicalname THREE
   %
   \setchemicalmaximum      3
   \setchemicaldistance   289
   \setchemicalsubstitute 952
   %
   \setchemicalrotation 1  1    0      0     -1   -1    0      0      1
   \setchemicalrotation 2 -0.5 -0.866 -0.866  0.5  0.5  0.866  0.866 -0.5
   \setchemicalrotation 3 -0.5  0.866  0.866  0.5  0.5 -0.866 -0.866 -0.5
   %
   \setchemicaltranslate 1 -1000     0
   \setchemicaltranslate 2     0  1000
   \setchemicaltranslate 3  1000     0
   \setchemicaltranslate 4     0 -1000
   %
   \setchemicallinesegment   B   577     0  -289  -500
   \setchemicallinesegment  SB   352  -130   -64  -370
   \setchemicallinesegment -SB   352  -130  -289  -500
   \setchemicallinesegment +SB   577     0   -64  -370
   \setchemicallinesegment DB1   327   -87   -89  -327
   \setchemicallinesegment DB2   377  -172   -39  -413
   \setchemicallinesegment   R   577     0  1077     0
   \setchemicallinesegment  -R   577     0  1010   250
   \setchemicallinesegment  +R   577     0  1010  -250
   \setchemicallinesegment ER1   577    50  1077    50
   \setchemicallinesegment ER2   577   -50  1077   -50
   \setchemicallinesegment  SR   837     0  1077     0
   \setchemicallinesegment -SR   802   130  1010   250
   \setchemicallinesegment +SR   802  -130  1010  -250
   \setchemicallinesegment DR1   837    50  1077    50
   \setchemicallinesegment DR2   837   -50  1077   -50
   %
   \setchemicaltextelement   Z   577     0
   \setchemicaltextelement  RZ  1177     0
   \setchemicaltextelement -RZ  1097   300
   \setchemicaltextelement +RZ  1097  -300
   \setchemicaltextelement CRZ  1077     0
   %
   \def\processchemical[##1##2##3##4]%
     {\processaction
        [##1##2##3##4]
        [    ROT##4=>\processchemicalrotation{##4},
             MOV##4=>\processchemicaltranslate{##4},
             SUB##4=>\processchemicalsubstitute{##4},
             ADJ##4=>\processchemicaldistance{##4},
             -RZ##4=>\processchemicaltextelement{-RZ}{##4}{#1}{3}
                       {l,t,r, l,r,l, r,b,l, r,l,r},
             +RZ##4=>\processchemicaltextelement{+RZ}{##4}{#1}{3}
                       {l,r,b, r,r,l, r,l,t, l,l,r},
             -SB##4=>\processchemicallinesegment{-SB}{##4},
             +SB##4=>\processchemicallinesegment{+SB}{##4},
             -SR##4=>\processchemicallinesegment{-SR}{##4},
             +SR##4=>\processchemicallinesegment{+SR}{##4},
             CRZ##4=>\processchemicaltextelement{CRZ}{##4}{#1}{0}
                       {},
           DB##3##4=>\processchemicallinesegment{DB}{##3##4},
           DR##3##4=>\processchemicallinesegment{DR}{##3##4},
           RZ##3##4=>\processchemicaltextelement{RZ}{##3##4}{#1}{3}
                       {l,r,r, t,r,l, r,l,l, b,l,r},
           ER##3##4=>\processchemicallinesegment{ER}{##3##4},
           SB##3##4=>\processchemicallinesegment{SB}{##3##4},
           SR##3##4=>\processchemicallinesegment{SR}{##3##4},
           -R##3##4=>\processchemicallinesegment{-R}{##3##4},
           +R##3##4=>\processchemicallinesegment{+R}{##3##4},
         B##2##3##4=>\processchemicallinesegment{B}{##2##3##4},
         R##2##3##4=>\processchemicallinesegment{R}{##2##3##4},
         Z##2##3##4=>\processchemicaltextelement{Z}{##2##3##4}{#1}{0}
                       {},
        \!!!unknown=>\unknownchemical{##1##2##3##4}]}}

\def\executechemicalFOUR[#1]%
  {\setchemicalname FOUR
   %
   \setchemicalmaximum      4
   \setchemicaldistance   500
   \setchemicalsubstitute   0
   %
   \setchemicalrotation 1  1  0  0 -1 -1  0  0  1
   \setchemicalrotation 2  0 -1 -1  0  0  1  1  0
   \setchemicalrotation 3 -1  0  0  1  1  0  0 -1
   \setchemicalrotation 4  0  1  1  0  0 -1 -1  0
   %
   \setchemicaltranslate 1 -1000     0
   \setchemicaltranslate 2     0  1000
   \setchemicaltranslate 3  1000     0
   \setchemicaltranslate 4     0 -1000
   %
   \setchemicallinesegment   B   500   500   500  -500
   \setchemicallinesegment  SB   500   240   500  -240
   \setchemicallinesegment -SB   500   240   500  -500
   \setchemicallinesegment +SB   500   500   500  -240
   \setchemicallinesegment DB1   450   240   450  -240
   \setchemicallinesegment DB2   550   240   550  -240
   \setchemicallinesegment  EB   360   300   360  -300
   \setchemicallinesegment   R   500   500   854   854
   \setchemicallinesegment  -R   500   500   500  1000
   \setchemicallinesegment  +R   500   500  1000   500
   \setchemicallinesegment ER1   465   535   819   889
   \setchemicallinesegment ER2   535   465   889   819
   \setchemicallinesegment  SR   684   684   854   854
   \setchemicallinesegment -SR   500   760   500  1000
   \setchemicallinesegment +SR   760   500  1000   500
   \setchemicallinesegment DR1   649   719   819   889
   \setchemicallinesegment DR2   719   649   889   819
   %
   \setchemicaltextelement   Z   500   500
   \setchemicaltextelement  RZ   925   925
   \setchemicaltextelement -RZ   500  1100
   \setchemicaltextelement +RZ  1100   500
   \setchemicaltextelement CRZ  1038  1038
   %
   \def\processchemical[##1##2##3##4]%
     {\processaction
        [##1##2##3##4]
        [    ROT##4=>\processchemicalrotation{##4},
             SUB##4=>\processchemicalsubstitute{##4},
             ADJ##4=>\processchemicaldistance{##4},
             MOV##4=>\processchemicaltranslate{##4},
             -RZ##4=>\processchemicaltextelement{-RZ}{##4}{#1}{4}
                       {b,l,t,r, l,t,r,b, t,r,b,l, r,b,l,t},
             +RZ##4=>\processchemicaltextelement{+RZ}{##4}{#1}{4}
                       {l,t,r,b, t,r,b,l, r,b,l,t, b,l,t,r},
             -SB##4=>\processchemicallinesegment{-SB}{##4},
             +SB##4=>\processchemicallinesegment{+SB}{##4},
             -SR##4=>\processchemicallinesegment{-SR}{##4},
             +SR##4=>\processchemicallinesegment{+SR}{##4},
             CRZ##4=>\processchemicaltextelement{CRZ}{##4}{#1}{0}
                       {},
           DB##3##4=>\processchemicallinesegment{DB}{##3##4},
           DR##3##4=>\processchemicallinesegment{DR}{##3##4},
           EB##3##4=>\processchemicallinesegment{EB}{##3##4},
           ER##3##4=>\processchemicallinesegment{ER}{##3##4},
           RZ##3##4=>\processchemicaltextelement{RZ}{##3##4}{#1}{4}
                       {lb,lt,rt,rb, lt,rt,rb,lb, rt,rb,lb,lt, rb,lb,lt,rt},
           SB##3##4=>\processchemicallinesegment{SB}{##3##4},
           SR##3##4=>\processchemicallinesegment{SR}{##3##4},
           -R##3##4=>\processchemicallinesegment{-R}{##3##4},
           +R##3##4=>\processchemicallinesegment{+R}{##3##4},
         B##2##3##4=>\processchemicallinesegment{B}{##2##3##4},
         R##2##3##4=>\processchemicallinesegment{R}{##2##3##4},
         Z##2##3##4=>\processchemicaltextelement{Z}{##2##3##4}{#1}{0}
                       {},
        \!!!unknown=>\unknownchemical{##1##2##3##4}]}}

\def\executechemicalFIVE[#1]%
  {\setchemicalname FIVE
   %
   \setchemicalmaximum       5
   \setchemicaldistance    688
   \setchemicalsubstitute 1226
   %
   \setchemicalrotation 1  1      0      0     -1     -1      0      0      1
   \setchemicalrotation 2  0.309 -0.951 -0.951 -0.309 -0.309  0.940  0.951  0.309
   \setchemicalrotation 3 -0.809 -0.588 -0.588  0.809  0.809  0.588  0.588 -0.809
   \setchemicalrotation 4 -0.809  0.588  0.588  0.809  0.809 -0.588 -0.588 -0.809
   \setchemicalrotation 5  0.309  0.951  0.951 -0.309 -0.309 -0.951 -0.951  0.309
   %
   \setchemicaltranslate 1 -1376     0
   \setchemicaltranslate 2  -425  1304
   \setchemicaltranslate 3  1113   809
   \setchemicaltranslate 4  1113  -809
   \setchemicaltranslate 5  -425 -1304
   %
   \setchemicallinesegment   B   688   500   688  -500
   \setchemicallinesegment   S  -263   808   688  -500
   \setchemicallinesegment  SB   688   240   688  -240
   \setchemicallinesegment -SB   688   240   688  -500
   \setchemicallinesegment +SB   688   500   688  -240
   \setchemicallinesegment DB1   638   240   638  -240
   \setchemicallinesegment DB2   738   240   738  -240
   \setchemicallinesegment  EB   548   340   548  -340
   \setchemicallinesegment   R   688   500  1093   794
   \setchemicallinesegment  -R   688   500   688  1000
   \setchemicallinesegment  +R   688   500  1163   345
   \setchemicallinesegment ER1   659   540  1064   834
   \setchemicallinesegment ER2   727   460  1122   754
   \setchemicallinesegment  SR   898   653  1093   794
   \setchemicallinesegment -SR   688   760   688  1000
   \setchemicallinesegment +SR   935   420  1163   345
   \setchemicallinesegment DR1   869   693  1064   834
   \setchemicallinesegment DR2   927   613  1122   754
   %
   \setchemicaltextelement   Z   688   500
   \setchemicaltextelement  RZ  1188   863
   \setchemicaltextelement -RZ   688  1100
   \setchemicaltextelement +RZ  1258   315
   \setchemicaltextelement CRZ  1323   947
   %
   \setchemicalcircsegment   C    72   475  -345
   %
   \def\processchemical[##1##2##3##4]%
     {\processaction
        [##1##2##3##4]
        [    ROT##4=>\processchemicalrotation{##4},
             SUB##4=>\processchemicalsubstitute{##4},
             ADJ##4=>\processchemicaldistance{##4},
             MOV##4=>\processchemicaltranslate{##4},
             -RZ##4=>\processchemicaltextelement{-RZ}{##4}{#1}{5}
                       {b,l,t,r,r, l,t,r,r,l, t,r,r,l,l, r,b,l,t,r},
             +RZ##4=>\processchemicaltextelement{+RZ}{##4}{#1}{5}
                       {l,t,r,r,b, t,r,r,l,l, r,r,l,l,r, b,l,l,r,r},
             -SB##4=>\processchemicallinesegment{-SB}{##4},
             +SB##4=>\processchemicallinesegment{+SB}{##4},
             -SR##4=>\processchemicallinesegment{-SR}{##4},
             +SR##4=>\processchemicallinesegment{+SR}{##4},
             CRZ##4=>\processchemicaltextelement{CRZ}{##4}{#1}{0}
                       {},
           DB##3##4=>\processchemicallinesegment{DB}{##3##4},
           DR##3##4=>\processchemicallinesegment{DR}{##3##4},
           EB##3##4=>\processchemicallinesegment{EB}{##3##4},
           ER##3##4=>\processchemicallinesegment{ER}{##3##4},
           RZ##3##4=>\processchemicaltextelement{RZ}{##3##4}{#1}{5}
                       {l,l,r,r,r, l,r,r,b,l, r,r,b,l,t, r,l,l,t,r},
           SB##3##4=>\processchemicallinesegment{SB}{##3##4},
           SR##3##4=>\processchemicallinesegment{SR}{##3##4},
           -R##3##4=>\processchemicallinesegment{-R}{##3##4},
           +R##3##4=>\processchemicallinesegment{+R}{##3##4},
         B##2##3##4=>\processchemicallinesegment{B}{##2##3##4},
         C##2##3##4=>\processchemicalcircsegment{C}{##2##3##4},
         R##2##3##4=>\processchemicallinesegment{R}{##2##3##4},
         S##2##3##4=>\processchemicallinesegment{S}{##2##3##4},
         Z##2##3##4=>\processchemicaltextelement{Z}{##2##3##4}{#1}{0}
                       {},
        \!!!unknown=>\unknownchemical{##1##2##3##4}]}}

\def\executechemicalSIX[#1]%
  {\setchemicalname SIX
   %
   \setchemicalmaximum       6
   \setchemicalsubstitute 1375
   \setchemicaldistance    866
   %
   \setchemicalrotation 1  1    0   0 -1     -1    0    0      1
   \setchemicalrotation 2  0.5 -0.866 -0.866 -0.5 -0.5  0.866  0.866  0.5
   \setchemicalrotation 3 -0.5 -0.866 -0.866  0.5  0.5  0.866  0.866 -0.5
   \setchemicalrotation 4 -1    0      0      1    1    0      0     -1
   \setchemicalrotation 5 -0.5  0.866  0.866  0.5  0.5 -0.866 -0.866 -0.5
   \setchemicalrotation 6  0.5  0.866  0.866 -0.5 -0.5 -0.866 -0.866  0.5
   %
   \setchemicaltranslate     1 -1732     0
   \setchemicaltranslate     2  -866  1500
   \setchemicaltranslate     3   866  1500
   \setchemicaltranslate     4  1732     0
   \setchemicaltranslate     5   866 -1500
   \setchemicaltranslate     6  -866 -1500
   %
   \setchemicallinesegment   B   866   500   866  -500
   \setchemicallinesegment   S     0  1000   866  -500
   \setchemicallinesegment  SB   866   240   866  -240
   \setchemicallinesegment -SB   866   240   866  -500
   \setchemicallinesegment +SB   866   500   866  -240
   \setchemicallinesegment DB1   816   240   816  -240
   \setchemicallinesegment DB2   916   240   916  -240
   \setchemicallinesegment  EB   726   340   726  -340
   \setchemicallinesegment   R   866   500  1299   750
   \setchemicallinesegment  -R   866   500   866  1000
   \setchemicallinesegment  +R   866   500  1299   250
   \setchemicallinesegment ER1   841   543  1274   793
   \setchemicallinesegment ER2   891   457  1324   707
   \setchemicallinesegment  SR  1091   630  1299   750
   \setchemicallinesegment -SR   866   740   866  1000
   \setchemicallinesegment +SR  1091   370  1299   250
   \setchemicallinesegment DR1  1066   673  1274   793
   \setchemicallinesegment DR2  1116   588  1324   707
   %
   \setchemicalcircsegment   C   60  600 -346
   %
   \setchemicaltextelement   Z   866   500
   \setchemicaltextelement  RZ  1386   800
   \setchemicaltextelement -RZ   866  1100
   \setchemicaltextelement +RZ  1386   200
   \setchemicaltextelement CRZ  1524   880
   %
   \def\processchemical[##1##2##3##4]%
     {\processaction
        [##1##2##3##4]
        [    ROT##4=>\processchemicalrotation{##4},
             SUB##4=>\processchemicalsubstitute{##4},
             ADJ##4=>\processchemicaldistance{##4},
             MOV##4=>\processchemicaltranslate{##4},
             -RZ##4=>\processchemicaltextelement{-RZ}{##4}{#1}{6}
                       {b,l,l,t,r,r, l,l,r,r,r,l, t,r,r,b,l,l, r,r,l,l,l,r},
             +RZ##4=>\processchemicaltextelement{+RZ}{##4}{#1}{6}
                       {l,t,r,r,b,l, r,r,r,l,l,l, r,b,l,l,t,r, l,l,l,r,r,r},
             -SB##4=>\processchemicallinesegment{-SB}{##4},
             +SB##4=>\processchemicallinesegment{+SB}{##4},
             -SR##4=>\processchemicallinesegment{-SR}{##4},
             +SR##4=>\processchemicallinesegment{+SR}{##4},
             CRZ##4=>\processchemicaltextelement{CRZ}{##4}{#1}{0}
                       {},
           DB##3##4=>\processchemicallinesegment{DB}{##3##4},
           EB##3##4=>\processchemicallinesegment{EB}{##3##4},
           ER##3##4=>\processchemicallinesegment{ER}{##3##4},
           RZ##3##4=>\processchemicaltextelement{RZ}{##3##4}{#1}{6}
                       {l,l,t,r,r,b, l,r,r,r,l,l, r,r,b,l,l,t, r,l,l,l,r,r},
           SB##3##4=>\processchemicallinesegment{SB}{##3##4},
           SR##3##4=>\processchemicallinesegment{SR}{##3##4},
           DR##3##4=>\processchemicallinesegment{DR}{##3##4},
           -R##3##4=>\processchemicallinesegment{-R}{##3##4},
           +R##3##4=>\processchemicallinesegment{+R}{##3##4},
         B##2##3##4=>\processchemicallinesegment{B}{##2##3##4},
         C##2##3##4=>\processchemicalcircsegment{C}{##2##3##4},
         R##2##3##4=>\processchemicallinesegment{R}{##2##3##4},
         S##2##3##4=>\processchemicallinesegment{S}{##2##3##4},
         Z##2##3##4=>\processchemicaltextelement{Z}{##2##3##4}{#1}{0}
                       {},
        \!!!unknown=>\unknownchemical{##1##2##3##4}]}}

% 1  :    0
% 2  : -115
% 3* : -195
% 3  : -165
% 4  : -245

\def\executechemicalCARBON[#1]%
  {\setchemicalname CARBON
   %
   \setchemicalmaximum    4
   \setchemicaldistance   0
   \setchemicalsubstitute 0
   %
   \setchemicalrotation 1   1      0      0     -1     -1      0      0      1
   \setchemicalrotation 2  -0.423 -0.906 -0.906  0.423  0.423  0.906  0.906 -0.423
   \setchemicalrotation 3  -0.966 -0.259 -0.259  0.966  0.966  0.259  0.259 -0.966
   \setchemicalrotation 3* -0.966  0.259  0.259  0.966  0.966 -0.259 -0.259 -0.966
   \setchemicalrotation 4  -0.423  0.906  0.906  0.423  0.423 -0.906 -0.906 -0.423
   %
   \setchemicaltranslate 1 -1500     0
   \setchemicaltranslate 2     0  1500
   \setchemicaltranslate 3  1500     0
   \setchemicaltranslate 4     0 -1500
   %
   \setchemicallinesegment B1   500 0  1000 0
   \setchemicallinesegment B2   300 0  1000 0
   \setchemicallinesegment B3   500 0  1000 0
   \setchemicallinesegment B4   300 0  1000 0
   %
   \setchemicaltextelement  Z  1100 0
   %
   \setchemicalcircsegment  C   360 0  -500
   %
   \def\processchemical[##1##2##3##4##5]%
     {\processaction
        [##1##2##3##4##5]
        [      MIR????=>\setchemicalmirror{3},
              -MIR????=>\resetchemicalmirror{3},
              *MIR????=>\togglechemicalmirror{3},
                CB????=>\processlocalchemicals{B,C,Z},
                 C????=>\processchemicalcircsegment{C}{1????},
               -ROT##5=>\reversechemical{ROT}{##5}{3,4,1,2},
             ROT##4##5=>\processchemicalrotation{##4##5},
             MOV##4##5=>\processchemicaltranslate{##4##5},
           CB##3##4##5=>\processlocalchemicals
                          {ROT##3,C,B,Z2..4,
                           MOV##3,*MIR,-ROT##3,C,B,Z2..4},
         B##2##3##4##5=>\processprivatechemicallinesegment{B}{##2##3##4##5},
         Z##2##3##4##5=>\processchemicaltextelement{Z}{##2##3##4##5}{#1}{4}
                          {l,t,r,b, t,r,b,l, r,b,l,t, b,l,t,r},
           \!!!unknown=>\unknownchemical{##1##2##3##4##5}]}}

% 1:   45      2:  -90      3: -225
% 4:  -45      5: -135      6: -270

\def\executechemicalNEWMAN[#1]%
  {\setchemicalname NEWMAN
   %
   \setchemicalmaximum    6
   \setchemicaldistance   0
   \setchemicalsubstitute 0
   %
   \setchemicalrotation 1  0.707  0.707  0.707 -0.707 -0.707 -0.707 -0.707  0.707
   \setchemicalrotation 2  0     -1     -1      0      0      1      1      0
   \setchemicalrotation 3 -0.707  0.707  0.707  0.707  0.707 -0.707 -0.707 -0.707
   \setchemicalrotation 4  0.707 -0.707 -0.707 -0.707 -0.707  0.707  0.707  0.707
   \setchemicalrotation 5 -0.707 -0.707 -0.707  0.707  0.707  0.707  0.707 -0.707
   \setchemicalrotation 6  0      1      1      0      0     -1     -1      0
   %
   \setchemicaltranslate 1 -1500     0
   \setchemicaltranslate 2     0  1500
   \setchemicaltranslate 3  1500     0
   \setchemicaltranslate 4     0 -1500
   %
   \setchemicallinesegment B1    0 0  1000 0
   \setchemicallinesegment B2    0 0  1000 0
   \setchemicallinesegment B3    0 0  1000 0
   \setchemicallinesegment B4  500 0  1000 0
   \setchemicallinesegment B5  500 0  1000 0
   \setchemicallinesegment B6  500 0  1000 0
   %
   \setchemicaltextelement  Z 1100 0
   %
   \setchemicalcircsegment  C  360 0  -500
   %
   \def\processchemical[##1##2##3##4]%
     {\processaction
        [##1##2##3##4]
        [     B????=>\processlocalchemicals{B1..6},
             CB????=>\processlocalchemicals{B1..6,C,Z1..6},
              C????=>\processchemicalcircsegment{C}{1????},
             ROT##4=>\processchemicalrotation{##4},
             MOV##4=>\processchemicaltranslate{##4},
         B##2##3##4=>\processprivatechemicallinesegment{B}{##2##3##4},
         Z##2##3##4=>\processchemicaltextelement{Z}{##2##3##4}{#1}{6}
                       {l,t,r,l,r,b, l,r,l,r,r,l, r,b,l,r,l,t, r,l,r,l,l,r},
        \!!!unknown=>\unknownchemical{##1##2##3##4}]}}

\def\executechemicalarrow#1#2[#3]%
  {\getfromcommalist[#3][1]%
   \let\toptext=\commalistelement
   \getfromcommalist[#3][2]%
   \let\bottext=\commalistelement
   \def\dochemicaltext##1%
     {\dosetsubscripts%
      $\@@chemieletter{\@@localchemieformaat\strut##1}$%
      \doresetsubscripts}%
   \doifelse{\@@chemieplaats}{\!!intekst}%
     {#1{\dochemicaltext\toptext}}%
     {\setbox\chemicalsymbols=\hbox
        {\box\chemicalsymbols
         \vbox{\halign{##\cr
           \hbox to 3em{\hss\dochemicaltext{\toptext}\hss}\cr
           #2%
           \hbox to 3em{\hss\dochemicaltext{\bottext}\hss}\cr}}}}}

\def\executechemicalGIVES%
  {\executechemicalarrow
     {\chemicalsinglepicturearrow}% nodig
     {\rightarrowfill\cr}}

\def\executechemicalEQUILIBRIUM%
  {\executechemicalarrow
     {\chemicaldoublepicturearrow}%  nodig
     {\rightarrowfill\cr\leftarrowfill\cr}}

\def\executechemicalsign#1[#2]%
  {\doifelse{\@@chemieplaats}{\!!intekst}
     {\dosetsubscripts
      $\@@chemieletter{\@@localchemieformaat#1}$%
      \doresetsubscripts}
     {\setbox\chemicalsymbols=\hbox
        {\box\chemicalsymbols
         \dosetsubscripts
         $\@@chemieletter{\@@localchemieformaat#1}$%
         \doresetsubscripts}}}

\def\executechemicalPLUS%
  {\executechemicalsign{+}}

\def\executechemicalMINUS%
  {\executechemicalsign{-}}

\def\executechemicalSPACE[#1]%
  {\doifnot{\@@chemieplaats}{\!!intekst}%
     {\setbox\chemicalsymbols=\hbox
        {\box\chemicalsymbols
         \quad}}}

\def\executechemicalLOW[#1]%
  {\setlowsubscripts}

\def\executechemicalHIGH[#1]%
  {\sethighsubscripts}

\stelchemiein
  [\!!breedte=0,
   \!!hoogte=0,
   \!!links=0,
   \!!rechts=0,
   \!!boven=0,
   \!!onder=0,
   \!!korps=\systeemkorps,
   \!!resolutie=\systeemresolutie,
   \!!schaal=\!!middel,
   \!!formaat=\!!middel,
   \!!tekstformaat=\!!groot,
   \!!kader=\!!uit,
   \!!assenstelsel=\!!uit,
   \!!status=\!!start,
   \!!letter=\rm,
   \!!plaats=,
   \!!optie=,
   \!!file=,
   \!!offset=LOW,
   \!!variant=1]

% Tijdelijk plaatsen we deze extra macro's hier.
%
% mathontop: \mtop {} {}
% textontop: \ttop {} {}

\def\putontop#1#2%
  {\vbox
     {\halign
        {\strut\hss##\hss\cr
         #1\cr
         #2\cr}}}

\def\ttop#1#2%
  {\putontop{\tx#1}{#2}}

\def\mtop#1#2%
  {\vbox
     {\offinterlineskip
      \halign
        {\hss##\hss\cr
         $\scriptscriptstyle#1$\cr
         \noalign{\vskip.5ex}%
         $#2$\cr}}}

\def\ctop#1#2%
  {\vbox
     {\offinterlineskip
      \halign
        {\hss##\hss\cr
         $\@@chemieletter{\@@localchemieformaat\scriptscriptstyle#1}$\cr
         \noalign{\vskip.5ex}%
         $\@@chemieletter{\@@localchemieformaat#2}$\cr}}}

\protect