chemnum (12mar14)

git-svn-id: svn://tug.org/texlive/trunk@33161 c570f23f-e606-0410-a88d-b1316a301751

1 files changed, 1677 insertions, 1424 deletions

diff --git a/Master/texmf-dist/tex/latex/chemnum/chemnum.sty b/Master/texmf-dist/tex/latex/chemnum/chemnum.sty
index af6e6c07c8f..39578d42ec5 100644
--- a/Master/texmf-dist/tex/latex/chemnum/chemnum.sty
+++ b/Master/texmf-dist/tex/latex/chemnum/chemnum.sty
@@ -1,1389 +1,1669 @@
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-% - chemnum - chemnum.sty
-% - a comprehensive approach for the numbering of chemical compounds
-% -----------------------------------------------------------------------------
-% - Clemens NIEDERBERGER
-% - contact@mychemistry.eu
-% -----------------------------------------------------------------------------
-% - If you have any ideas, questions, suggestions or bugs to report, please
-% - feel free to contact me.
-% -----------------------------------------------------------------------------
-% - Copyright 2011-2013 Clemens Niederberger
-% -
-% - This work may be distributed and/or modified under the
-% - conditions of the LaTeX Project Public License, either version 1.3
-% - of this license or (at your option) any later version.
-% - The latest version of this license is in
-% -   http://www.latex-project.org/lppl.txt
-% - and version 1.3 or later is part of all distributions of LaTeX
-% - version 2005/12/01 or later.
-% -
-% - This work has the LPPL maintenance status `maintained'.
-% -
-% - The Current Maintainer of this work is Clemens Niederberger.
-% -
-% - This work consists of the files
-% -   chemnum.sty, chemnum_de.tex, chemnum_en.tex, chemnum_it.tex
-% -   scheme-tmp.ps, scheme-bla.ps,
-% -   README
-% -   chemnum_de.pdf, chemnum_en.pdf, chemnum_it.pdf
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\RequirePackage { expl3 , xparse , l3keys2e , etoolbox , psfrag }
-
-\ProvidesExplPackage
-  {chemnum}
-  {2013/06/05}
-  {0.6b}
-  {a comprehensive approach for the numbering of chemical compounds}
-
-% --------------------------------------------------------------------------
-% check expl3 version:
-\@ifpackagelater { expl3 } { 2012/11/21 }
-  { }
-  {
-    \PackageError { chemnum } { Support~package~expl3~too~old }
-      {
-        You~need~to~update~your~installation~of~the~bundles~'l3kernel'~and~
-        'l3packages'.\MessageBreak
-        Loading~chemnum~will~abort!
-      }
-    \tex_endinput:D
+% ----------------------------------------------------------------------------
+\def\chemnumdate{2014/03/12}
+\def\chemnumversion{1.0}
+\def\chemnuminfo{a comprehensive approach for the numbering of chemical compounds}
+
+\RequirePackage{expl3}[2013/07/14]
+\RequirePackage{xparse,l3keys2e}
+
+% ----------------------------------------------------------------------------
+% provide the package:
+\ProvidesExplPackage{chemnum}
+  {\chemnumdate}
+  {\chemnumversion}
+  {\chemnuminfo\space (CN)}
+
+% ----------------------------------------------------------------------------
+% required packages:
+% language support:
+\RequirePackage{translations}[2013/07/12]
+% greek alphabet for the labels matching to chemmacros' selection:
+\RequirePackage{chemgreek}[2013/07/13]
+\RequirePackage{psfrag}
+
+% ----------------------------------------------------------------------------
+% messages:
+\msg_new:nnn {chemnum} {missing-label}
+  { The~ key~ `#1'~ has~ no~ label~ associated~ \msg_line_context: }
+
+\msg_new:nnn {chemnum} {erroneous-argument-combination}
+  {
+    Apparently~ you've~ used~ both~ the~ `*'~ and~ the~ `+'~
+    argument.~ This~ does~ not~ make~ sense.~ I'm~ doing~
+    nothing~ \msg_line_context:
   }
 
-% --------------------------------------------------------------------------
-% error for missing packages
-\msg_set:nnnn { chemnum } { support-missing }
-  { Support~package~#1~missing. }
+\msg_new:nnn {chemnum} {unknown-counter-format}
   {
-    Support~package~#1~seems~to~be~missing. \\
-    Please~install~an~up~to~date~version~of~#1. \\
+    I~ do~ not~ know~ the~ counter~ format~ `#1'.~  I'll~ use~ `arabic'~
+    instead~ \msg_line_context:
   }
 
-% warning, if textgreek has already been loaded AND option
-% "textgreek = <value>" is used
-\msg_set:nnnn { chemnum } { textgreek-loaded }
+\msg_new:nnn {chemnum} {compound-not-initiated}
+  { The~ compound~ `#1'~ has~ not~ been~ initiated~ \msg_line_context: }
+
+\msg_new:nnn {chemnum} {subcompound-not-initiated}
   {
-    The~package~textgreek~has~already~been~loaded. \\
-    \tl_if_blank:nF { #1 } { Option~#1~will~not~be~used. }
+    The~ compound~ `#1\l__chemnum_compound_separator_tl #2'~ has~ not~ been~
+    initiated~ \msg_line_context:
   }
+
+\msg_new:nnn {chemnum} {log-compound-silent}
   {
-    The~package~textgreek~has~already~been~loaded. \\
-    \tl_if_blank:nF { #1 } { Option~#1~will~not~be~used. }
+    ................................................. \\
+    . ~ \msg_info_text:n {chemnum}: ~
+      defined~ new~ compound~ `#1'~with~output~
+      \chemnum_expandable_get_compound_property:nn {#1}
+        {counter-representation} . \\
+    .................................................
   }
 
-% textgreek support and package options:
-\bool_new:N \l__chemnum_textgreek_bool
-\bool_set_false:N \l__chemnum_textgreek_bool
+\msg_new:nnn {chemnum} {log-compound-verbose}
+  {
+    ................................................. \\
+    . ~ \msg_info_text:n {chemnum}: ~ defined~ new~ compound: \\
+    . \c_space_tl \c_space_tl \c_space_tl
+    ID ~=~ #1 \\
+    . \c_space_tl \c_space_tl \c_space_tl
+    internal~ number ~=~
+    \chemnum_expandable_get_compound_property:nn {#1} {number} \\
+    . \c_space_tl \c_space_tl \c_space_tl
+    label ~=~
+    \chemnum_expandable_get_compound_property:nn {#1}
+      {counter-representation}  \\
+    . \c_space_tl \c_space_tl \c_space_tl
+    pre~ label~ code ~=~
+    \chemnum_expandable_get_compound_property:nn {#1}
+      {pre-label-code}  \\
+    . \c_space_tl \c_space_tl \c_space_tl
+    post~ label~ code ~=~
+    \chemnum_expandable_get_compound_property:nn {#1}
+      {post-label-code}  \\
+    . \c_space_tl \c_space_tl \c_space_tl
+    pre~ main~ label~ code ~=~
+    \chemnum_expandable_get_compound_property:nn {#1}
+      {pre-main-label-code}  \\
+    . \c_space_tl \c_space_tl \c_space_tl
+    post~ main~ label~ code ~=~
+    \chemnum_expandable_get_compound_property:nn {#1}
+      {post-main-label-code}  \\
+    . \c_space_tl \c_space_tl \c_space_tl
+    format ~=~
+    \chemnum_expandable_get_compound_property:nn {#1}
+      {label-format}  \\
+    .................................................
+  }
 
-\cs_new_protected:Npn \__chemnum_load_textgreek:n #1
+\msg_new:nnn {chemnum} {log-subcompound-silent}
   {
-    \AtEndPreamble
-      {
-        \file_if_exist:nTF { textgreek . sty }
-          {
-            \@ifpackageloaded { textgreek }
-              { \msg_warning:nnx { chemnum } { textgreek-loaded } { #1 } }
-              { \RequirePackage [ #1 ] { textgreek } }
-            \bool_set_true:N \l__chemnum_textgreek_bool
-          }
-          {
-            \msg_warning:nnx { chemnum } { support-missing } { textgreek }
-            \bool_set_false:N \l__chemnum_textgreek_bool
-          }
-      }
+    ................................................. \\
+    . ~ \msg_info_text:n {chemnum}: ~
+      defined~ new~ subcompound~ `#2'~ with~ output~
+      \chemnum_expandable_get_subcompound_property:nnn {#1} {#2}
+        {counter-representation} \\
+    . ~ belonging~ to~ the~ main~ compound~ `#1'. \\
+    .................................................
   }
 
-\cs_new:Npn \__chemnum_package_options:n #1
-  { \keys_set:nn { chemnum / package } { #1 } }
-
-\keys_define:nn { chemnum / package } {
-  textgreek .choice: ,
-  textgreek / artemisia .code:n     = \__chemnum_load_textgreek:n { #1 } ,
-  textgreek / cbgreek   .code:n     = \__chemnum_load_textgreek:n { #1 } ,
-  textgreek / euler     .code:n     = \__chemnum_load_textgreek:n { #1 } ,
-  textgreek / false     .code:n     =
-    { \bool_set_false:N \l__chemnum_textgreek_bool } ,
-  textgreek             .default:n  = cbgreek
-}
-
-\ProcessKeysOptions { chemnum / package }
-
-\AtBeginDocument{
-\bool_if:NTF \l__chemnum_textgreek_bool
-  {
-    \cs_new_eq:NN \__chemnum_alpha:   \textalpha
-    \cs_new_eq:NN \__chemnum_beta:    \textbeta
-    \cs_new_eq:NN \__chemnum_gamma:   \textgamma
-    \cs_new_eq:NN \__chemnum_delta:   \textdelta
-    \cs_new_eq:NN \__chemnum_epsilon: \textepsilon
-    \cs_new_eq:NN \__chemnum_zeta:    \textzeta
-    \cs_new_eq:NN \__chemnum_eta:     \texteta
-    \cs_new_eq:NN \__chemnum_theta:   \texttheta
-    \cs_new_eq:NN \__chemnum_iota:    \textiota
-    \cs_new_eq:NN \__chemnum_kappa:   \textkappa
-    \cs_new_eq:NN \__chemnum_lambda:  \textlambda
-    \cs_new_eq:NN \__chemnum_mu:      \textmugreek
-    \cs_new_eq:NN \__chemnum_nu:      \textnu
-    \cs_new_eq:NN \__chemnum_xi:      \textxi
-    \cs_new_eq:NN \__chemnum_omikron: \textomikron
-    \cs_new_eq:NN \__chemnum_pi:      \textpi
-    \cs_new_eq:NN \__chemnum_rho:     \textrho
-    \cs_new_eq:NN \__chemnum_sigma:   \textsigma
-    \cs_new_eq:NN \__chemnum_tau:     \texttau
-    \cs_new_eq:NN \__chemnum_upsilon: \textupsilon
-    \cs_new_eq:NN \__chemnum_phi:     \textphi
-    \cs_new_eq:NN \__chemnum_chi:     \textchi
-    \cs_new_eq:NN \__chemnum_psi:     \textpsi
-    \cs_new_eq:NN \__chemnum_omega:   \textomega
-    \cs_new_eq:NN \__chemnum_Alpha:   \textAlpha
-    \cs_new_eq:NN \__chemnum_Beta:    \textBeta
-    \cs_new_eq:NN \__chemnum_Gamma:   \textGamma
-    \cs_new_eq:NN \__chemnum_Delta:   \textDelta
-    \cs_new_eq:NN \__chemnum_Epsilon: \textEpsilon
-    \cs_new_eq:NN \__chemnum_Zeta:    \textZeta
-    \cs_new_eq:NN \__chemnum_Eta:     \textEta
-    \cs_new_eq:NN \__chemnum_Theta:   \textTheta
-    \cs_new_eq:NN \__chemnum_Iota:    \textIota
-    \cs_new_eq:NN \__chemnum_Kappa:   \textKappa
-    \cs_new_eq:NN \__chemnum_Lambda:  \textLambda
-    \cs_new_eq:NN \__chemnum_Mu:      \textMugreek
-    \cs_new_eq:NN \__chemnum_Nu:      \textNu
-    \cs_new_eq:NN \__chemnum_Xi:      \textXi
-    \cs_new_eq:NN \__chemnum_Omikron: \textOmikron
-    \cs_new_eq:NN \__chemnum_Pi:      \textPi
-    \cs_new_eq:NN \__chemnum_Rho:     \textRho
-    \cs_new_eq:NN \__chemnum_Sigma:   \textSigma
-    \cs_new_eq:NN \__chemnum_Tau:     \textTau
-    \cs_new_eq:NN \__chemnum_Upsilon: \textUpsilon
-    \cs_new_eq:NN \__chemnum_Phi:     \textPhi
-    \cs_new_eq:NN \__chemnum_Chi:     \textChi
-    \cs_new_eq:NN \__chemnum_Psi:     \textPsi
-    \cs_new_eq:NN \__chemnum_Omega:   \textOmega
-  }
-  {
-    \RequirePackage { bm }% abhängig machen von textoption bold
-    \cs_new:Npn \__chemnum_bm:n #1
-      {
-        \bool_if:NTF \l__chemnum_cmpd_bold_bool
-          { \bm { #1 } }
-          { #1 }
-      }
-    \cs_new:Npn \__chemnum_alpha:   { \ensuremath { \__chemnum_bm:n { \mathrm { \alpha } } } }
-    \cs_new:Npn \__chemnum_beta:    { \ensuremath { \__chemnum_bm:n { \mathrm { \beta } } } }
-    \cs_new:Npn \__chemnum_gamma:   { \ensuremath { \__chemnum_bm:n { \mathrm { \gamma } } } }
-    \cs_new:Npn \__chemnum_delta:   { \ensuremath { \__chemnum_bm:n { \mathrm { \delta } } } }
-    \cs_new:Npn \__chemnum_epsilon: { \ensuremath { \__chemnum_bm:n { \mathrm { \varepsilon } } } }
-    \cs_new:Npn \__chemnum_zeta:    { \ensuremath { \__chemnum_bm:n { \mathrm { \zeta } } } }
-    \cs_new:Npn \__chemnum_eta:     { \ensuremath { \__chemnum_bm:n { \mathrm { \eta } } } }
-    \cs_new:Npn \__chemnum_theta:   { \ensuremath { \__chemnum_bm:n { \mathrm { \theta } } } }
-    \cs_new:Npn \__chemnum_iota:    { \ensuremath { \__chemnum_bm:n { \mathrm { \iota } } } }
-    \cs_new:Npn \__chemnum_kappa:   { \ensuremath { \__chemnum_bm:n { \mathrm { \kappa } } } }
-    \cs_new:Npn \__chemnum_lambda:  { \ensuremath { \__chemnum_bm:n { \mathrm { \lampda } } } }
-    \cs_new:Npn \__chemnum_mu:      { \ensuremath { \__chemnum_bm:n { \mathrm { \mu } } } }
-    \cs_new:Npn \__chemnum_nu:      { \ensuremath { \__chemnum_bm:n { \mathrm { \nu } } } }
-    \cs_new:Npn \__chemnum_xi:      { \ensuremath { \__chemnum_bm:n { \mathrm { \xi } } } }
-    \cs_new:Npn \__chemnum_omikron: { \ensuremath { \__chemnum_bm:n { \mathrm { o } } } }
-    \cs_new:Npn \__chemnum_pi:      { \ensuremath { \__chemnum_bm:n { \mathrm { \pi } } } }
-    \cs_new:Npn \__chemnum_rho:     { \ensuremath { \__chemnum_bm:n { \mathrm { \rho } } } }
-    \cs_new:Npn \__chemnum_sigma:   { \ensuremath { \__chemnum_bm:n { \mathrm { \sigma } } } }
-    \cs_new:Npn \__chemnum_tau:     { \ensuremath { \__chemnum_bm:n { \mathrm { \tau } } } }
-    \cs_new:Npn \__chemnum_upsilon: { \ensuremath { \__chemnum_bm:n { \mathrm { \upsilon } } } }
-    \cs_new:Npn \__chemnum_phi:     { \ensuremath { \__chemnum_bm:n { \mathrm { \varphi } } } }
-    \cs_new:Npn \__chemnum_chi:     { \ensuremath { \__chemnum_bm:n { \mathrm { \chi } } } }
-    \cs_new:Npn \__chemnum_psi:     { \ensuremath { \__chemnum_bm:n { \mathrm { \psi } } } }
-    \cs_new:Npn \__chemnum_omega:   { \ensuremath { \__chemnum_bm:n { \mathrm { \omega } } } }
-    \cs_new:Npn \__chemnum_Alpha:   { \ensuremath { \__chemnum_bm:n { \mathrm { A } } } }
-    \cs_new:Npn \__chemnum_Beta:    { \ensuremath { \__chemnum_bm:n { \mathrm { B } } } }
-    \cs_new:Npn \__chemnum_Gamma:   { \ensuremath { \__chemnum_bm:n { \mathrm { \Gamma } } } }
-    \cs_new:Npn \__chemnum_Delta:   { \ensuremath { \__chemnum_bm:n { \mathrm { \Delta } } } }
-    \cs_new:Npn \__chemnum_Epsilon: { \ensuremath { \__chemnum_bm:n { \mathrm { E } } } }
-    \cs_new:Npn \__chemnum_Zeta:    { \ensuremath { \__chemnum_bm:n { \mathrm { Z } } } }
-    \cs_new:Npn \__chemnum_Eta:     { \ensuremath { \__chemnum_bm:n { \mathrm { H } } } }
-    \cs_new:Npn \__chemnum_Theta:   { \ensuremath { \__chemnum_bm:n { \mathrm { \Theta } } } }
-    \cs_new:Npn \__chemnum_Iota:    { \ensuremath { \__chemnum_bm:n { \mathrm { I } } } }
-    \cs_new:Npn \__chemnum_Kappa:   { \ensuremath { \__chemnum_bm:n { \mathrm { K } } } }
-    \cs_new:Npn \__chemnum_Lambda:  { \ensuremath { \__chemnum_bm:n { \mathrm { \Lambda } } } }
-    \cs_new:Npn \__chemnum_Mu:      { \ensuremath { \__chemnum_bm:n { \mathrm { M } } } }
-    \cs_new:Npn \__chemnum_Nu:      { \ensuremath { \__chemnum_bm:n { \mathrm { N } } } }
-    \cs_new:Npn \__chemnum_Xi:      { \ensuremath { \__chemnum_bm:n { \mathrm { \Xi } } } }
-    \cs_new:Npn \__chemnum_Omikron: { \ensuremath { \__chemnum_bm:n { \mathrm { O } } } }
-    \cs_new:Npn \__chemnum_Pi:      { \ensuremath { \__chemnum_bm:n { \mathrm { \Pi } } } }
-    \cs_new:Npn \__chemnum_Rho:     { \ensuremath { \__chemnum_bm:n { \mathrm { P } } } }
-    \cs_new:Npn \__chemnum_Sigma:   { \ensuremath { \__chemnum_bm:n { \mathrm { \Sigma } } } }
-    \cs_new:Npn \__chemnum_Tau:     { \ensuremath { \__chemnum_bm:n { \mathrm { T } } } }
-    \cs_new:Npn \__chemnum_Upsilon: { \ensuremath { \__chemnum_bm:n { \mathrm { \Upsilon } } } }
-    \cs_new:Npn \__chemnum_Phi:     { \ensuremath { \__chemnum_bm:n { \mathrm { \Phi } } } }
-    \cs_new:Npn \__chemnum_Chi:     { \ensuremath { \__chemnum_bm:n { \mathrm { X } } } }
-    \cs_new:Npn \__chemnum_Psi:     { \ensuremath { \__chemnum_bm:n { \mathrm { \Psi } } } }
-    \cs_new:Npn \__chemnum_Omega:   { \ensuremath { \__chemnum_bm:n { \mathrm { \Omega } } } }
-  }
-}
-
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-% TOOLS
-\int_new:N   \g__chemnum_cmpd_main_int
-\prop_new:N  \g__chemnum_label_prop
-\int_new:N   \g__chemnum_cmpd_int
-\int_new:N   \l__chemnum_tmpa_int
-\tl_new:N    \l__chemnum_tmpa_tl
-\tl_new:N    \l__chemnum_tmpb_tl
-\tl_new:N    \l__chemnum_tmpc_tl
-\seq_new:N   \g__chemnum_cmpd_saved_seq
-
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-% READ FROM PREVIOUS RUN, SAVE FOR NEXT RUN
-% save all labels in a clist
-\cs_new_protected:Npn \chemnum_cmpd_save:n #1
-  { \seq_gput_right:Nn \g__chemnum_cmpd_saved_seq { #1 } }
-
-\msg_set:nnn { chemnum } { missing-cmpd-file }
-  {
-    The~file~ \c_job_name_tl .cmpd~hasn't~been~available~yet. \\
-    Please~rerun~to~get~referencing~compound~labels~right.
-  }
-
-\file_if_exist:nTF { ./ \c_job_name_tl . cmpd }
-  { \file_input:n { ./ \c_job_name_tl . cmpd } }
-  { \msg_warning:nn { chemnum }{ missing-cmpd-file } }
-
-% write ref commands for all labels in <jobname>.cmpd file to make them
-% available at the next run
-\AtEndDocument
-  {
-    \iow_new:N \__chemnum_aux_file:
-    \iow_open:Nn \__chemnum_aux_file: { ./ \c_job_name_tl . cmpd }
-    \seq_map_inline:Nn \g__chemnum_cmpd_saved_seq
+\msg_new:nnn {chemnum} {log-subcompound-verbose}
+  {
+    ................................................. \\
+    . ~ \msg_info_text:n {chemnum}: ~ defined~ new~ subcompound: \\
+    . \c_space_tl \c_space_tl \c_space_tl
+    ID ~=~ #2 \\
+    . \c_space_tl \c_space_tl \c_space_tl
+    main~ compound~ ID ~=~
+    \chemnum_expandable_get_subcompound_property:nnn {#1} {#2}
+      {main-compound} \\
+    . \c_space_tl \c_space_tl \c_space_tl
+    internal~ number ~=~
+    \chemnum_expandable_get_subcompound_property:nnn {#1} {#2} {number} \\
+    . \c_space_tl \c_space_tl \c_space_tl
+    label ~=~
+    \chemnum_expandable_get_subcompound_property:nnn {#1} {#2}
+      {counter-representation}  \\
+    .................................................
+  }
+
+\msg_new:nnn { chemnum } { deprecated-command }
+  {
+    The~ command~ `\token_to_str:N #1'~ \msg_line_context: \c_space_tl is~
+    deprecated.~ Use~ `\token_to_str:N #2'~ instead.~ `\token_to_str:N #1'~
+    may~ be~ removed~ in~ future~ versions.
+  }
+
+% ----------------------------------------------------------------------------
+% deprecated command names:
+%   #1: old name
+%   #2: new name
+\cs_new_protected:Npn \chemnum_deprecated_command:NN #1#2
+  {
+    \cs_new:Npn #1
       {
-        \iow_now:Nx \__chemnum_aux_file:
-          {
-            \use:c { cs_new:cpn } { chemnum_cmpd_ #1 _ref: }
-              { \exp_not:f { \use:c { chemnum_cmpd_ #1 : } } }
-          }
-        \cs_if_exist:cT { chemnum_cmpd_ #1 _min: }
-          {
-            \iow_now:Nx \__chemnum_aux_file:
-              {
-                \use:c { cs_new:cpn } { chemnum_cmpd_ #1 _min_ref: }
-                  { \exp_not:f { \use:c { chemnum_cmpd_ #1 _min: } } }
-              }
-          }
-        \cs_if_exist:cT { chemnum_cmpd_ #1 _max: }
-          {
-            \iow_now:Nx \__chemnum_aux_file:
-              {
-                \use:c { cs_new:cpn } { chemnum_cmpd_ #1 _max_ref: }
-                  { \exp_not:f { \use:c { chemnum_cmpd_ #1 _max: } } }
-              }
-          }
+        \msg_warning:nnnn { chemnum } { deprecated-command }
+          { #1 } { #2 }
+        #2
       }
-    \iow_close:N \__chemnum_aux_file:
   }
 
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-% COMPOUND LABELS
-% STYLE OF COMPOUND LABEL
-\tl_new:N \l__chemnum_style_tmp_tl
-\bool_new:N \l__chemnum_cmpd_style_is_macro_bool
-
-% default style
-\cs_new:Npn \chemnum_cmpd_style:n #1 { #1  }
+% ----------------------------------------------------------------------------
+% variants of kernel functions:
+\cs_generate_variant:Nn \prop_gput:Nnn         { Nnx , cnx , cnV }
+\cs_generate_variant:Nn \prop_put:Nnn          { NV , NVV , NVx }
+\cs_generate_variant:Nn \prop_if_in:NnTF       { NV }
+\cs_generate_variant:Nn \quark_if_no_value:nTF { V }
+\cs_generate_variant:Nn \quark_if_no_value:nF  { V }
+\cs_generate_variant:Nn \seq_set_split:Nnn     { NV , NVV }
+\cs_generate_variant:Nn \seq_use:Nnnn          { NVVV }
+\cs_generate_variant:Nn \tl_if_eq:nnF          { Vx }
+\cs_generate_variant:Nn \tl_if_in:nnTF         { VV }
+
+% ----------------------------------------------------------------------------
+% temporary variables:
+\tl_new:N \l__chemnum_tmpa_tl
+\tl_new:N \l__chemnum_tmpb_tl
+
+\seq_new:N \l__chemnum_tmpa_seq
+\seq_new:N \l__chemnum_tmpb_seq
+\seq_new:N \l__chemnum_tmpc_seq
+\seq_new:N \l__chemnum_tmpd_seq
+\seq_new:N \l__chemnum_tmpe_seq
+
+\int_new:N \l__chemnum_tmpa_int
+\int_new:N \l__chemnum_tmpb_int
+\int_new:N \l__chemnum_tmpc_int
+
+% ----------------------------------------------------------------------------
+% variables:
+\prop_new:N \l__chemnum_label_formats_prop
+
+% the main label counter:
+% not very expl3 like but allows `cmpdmain' to be added to the \cl@<ounter>
+% list, i.e., it can e.g. be reset for every chapter:
+\newcounter{cmpdmain}
+% counter for internal reference if needed. Will be a unique number in order
+% of declaration:
+\int_new:N \g__chemnum_main_int
+\int_new:N \l__chemnum_compound_replace_int
+
+\seq_new:N \g__chemnum_initiated_compounds_seq
+\seq_new:N \g__chemnum_defined_compounds_seq
+
+\tl_new:N     \l__chemnum_label_format_tl
+\tl_set:Nn    \l__chemnum_label_format_tl {\bfseries}
+\tl_new:N     \l__chemnum_local_label_format_tl
+\tl_set_eq:NN \l__chemnum_local_label_format_tl \l__chemnum_label_format_tl
+\tl_new:N     \l__chemnum_default_counter_representation_tl
+\tl_set:Nn    \l__chemnum_default_counter_representation_tl {arabic}
+\tl_new:N     \l__chemnum_default_subcounter_representation_tl
+\tl_set:Nn    \l__chemnum_default_subcounter_representation_tl {alph}
+\tl_new:N     \l__chemnum_pre_counter_default_tl
+\tl_new:N     \l__chemnum_post_counter_default_tl
+\tl_new:N     \l__chemnum_pre_label_default_tl
+\tl_new:N     \l__chemnum_post_label_default_tl
+\tl_new:N     \l__chemnum_pre_main_label_default_tl
+\tl_new:N     \l__chemnum_post_main_label_default_tl
+\tl_new:N     \l__chemnum_main_separator_tl
+\tl_set:Nn    \l__chemnum_main_separator_tl {,}
+\tl_new:N     \l__chemnum_sub_separator_tl
+\tl_set:Nn    \l__chemnum_sub_separator_tl {,}
+\tl_new:N     \l__chemnum_compound_separator_tl
+\tl_set:Nn    \l__chemnum_compound_separator_tl {.}
+
+\tl_new:N  \l__chemnum_sep_list_two_tl
+\tl_set:Nn \l__chemnum_sep_list_two_tl { \GetTranslation {chemnum-sep-two} }
+\tl_new:N  \l__chemnum_sep_list_more_tl
+\tl_set:Nn \l__chemnum_sep_list_more_tl {,~}
+\tl_new:N  \l__chemnum_sep_list_last_two_tl
+\tl_set:Nn \l__chemnum_sep_list_last_two_tl { \GetTranslation {chemnum-sep-last-two} }
+
+\tl_new:N  \l__chemnum_sep_sublist_two_tl
+\tl_set:Nn \l__chemnum_sep_sublist_two_tl {,}
+\tl_new:N  \l__chemnum_sep_sublist_more_tl
+\tl_set:Nn \l__chemnum_sep_sublist_more_tl {,}
+\tl_new:N  \l__chemnum_sep_sublist_last_two_tl
+\tl_set:Nn \l__chemnum_sep_sublist_last_two_tl {,}
+\tl_new:N  \l__chemnum_sep_sublist_range_tl
+\tl_set:Nn \l__chemnum_sep_sublist_range_tl {--}
+
+\tl_new:N  \l__chemnum_compound_replace_tl
+\tl_new:N  \l__chemnum_compound_replace_format_tl
+\tl_new:N  \l__chemnum_compound_replace_local_format_tl
+\tl_set:Nn \l__chemnum_compound_replace_format_tl { \sffamily }
+\tl_new:N  \l__chemnum_compound_replace_tag_tl
+\tl_set:Nn \l__chemnum_compound_replace_tag_tl { TMP }
+\tl_new:N  \l__chemnum_psfrag_texpos_tl
+\tl_new:N  \l__chemnum_psfrag_local_texpos_tl
+\tl_set:Nn \l__chemnum_psfrag_texpos_tl { b }
+\tl_new:N  \l__chemnum_psfrag_pspos_tl
+\tl_new:N  \l__chemnum_psfrag_local_pspos_tl
+\tl_set:Nn \l__chemnum_psfrag_pspos_tl { b }
 
-% set style
-\cs_new_protected:Npn \__chemnum_cmpd_set_style:n #1
-  { \cs_set:Npn \chemnum_cmpd_style:n { #1 } }
+\bool_new:N \l__chemnum_compound_local_bool
+\bool_new:N \g__chemnum_initiate_bool
+\bool_new:N \g__chemnum_initiate_strict_bool
+\bool_new:N \g__chemnum_initiate_sub_bool
+\bool_new:N \l__chemnum_log_bool
+\bool_set_true:N \l__chemnum_log_bool
+\bool_new:N \l__chemnum_log_verbose_bool
+\bool_new:N \l__chemnum_compress_subcompounds_bool
+\bool_set_true:N \l__chemnum_compress_subcompounds_bool
+\bool_new:N \l__chemnum_merge_list_bool
+\bool_new:N \l__chemnum_sub_only_bool
+\bool_new:N \l__chemnum_sub_all_bool
+\bool_new:N \l__chemnum_show_def_bool
+\bool_new:N \l__chemnum_show_ref_bool
+\bool_new:N \l__chemnum_compound_replace_auto_bool
+\bool_set_true:N \l__chemnum_compound_replace_auto_bool
+\bool_new:N \l__chemnum_compound_replace_auto_this_bool
+\bool_set_true:N \l__chemnum_compound_replace_auto_this_bool
+\bool_new:N \l__chemnum_replace_local_bool
+
+% ----------------------------------------------------------------------------
+% label formats:
+
+% #1: name
+% #2: function with 1 n-type argument that takes an integer
+\cs_new_protected:Npn \chemnum_add_label_format:nn #1#2
+  {
+    \cs_if_exist:cTF { __chemnum_#1_label_format:n }
+      { \cs_set:cpn { __chemnum_#1_label_format:n } ##1 { #2 { ##1 } } }
+      { \cs_new:cpn { __chemnum_#1_label_format:n } ##1 { #2 { ##1 } } }
+    \prop_put:Nnx \l__chemnum_label_formats_prop {#1}
+      { \exp_not:c { __chemnum_#1_label_format:n } }
+  }
 
-% use style
-\bool_new:N \l__chemnum_cmpd_bold_bool
-\bool_set_true:N \l__chemnum_cmpd_bold_bool
+% a user level command to add new formats
+\NewDocumentCommand \newcmpdcounterformat { mm }
+  { \chemnum_add_label_format:nn {#1} {#2} }
+
+\newcmpdcounterformat {arabic} { \int_to_arabic:n }
+\newcmpdcounterformat {alph  } { \int_to_alph:n }
+\newcmpdcounterformat {Alph  } { \int_to_Alph:n }
+\newcmpdcounterformat {roman } { \int_to_roman:n }
+\newcmpdcounterformat {Roman } { \int_to_Roman:n }
+\newcmpdcounterformat {greek } { \chemgreek_int_to_greek:n }
+\newcmpdcounterformat {Greek } { \chemgreek_int_to_Greek:n }
+
+% ----------------------------------------------------------------------------
+%%% options
+% options assigned to group `compound' are only setable with the \cmpd command
+% except they're _also_ asigned to the `general' group; likewise options that
+% are assigned to the group `general' can only be set with \setchemnum except
+% they're also assigned to the `compound' group.
+\keys_define:nn {chemnum}
+  {
+    local                 .bool_set:N = \l__chemnum_compound_local_bool ,
+    local                 .groups:n   = {compound} ,
+    % counter:
+    counter-within        .code:n     = \@addtoreset{cmpdmain}{#1} ,
+    counter-within        .groups:n   = {general} ,
+    counter-format        .code:n     =
+      \prop_if_in:NnTF \l__chemnum_label_formats_prop {#1}
+        {
+          \tl_set:Nn
+            \l__chemnum_default_counter_representation_tl
+            {#1}
+        }
+        {
+          \msg_warning:nnn {chemnum} {unknown-counter-format} {#1}
+          \tl_set:Nn
+            \l__chemnum_default_counter_representation_tl
+            {arabic}
+        } ,
+    counter-format        .groups:n   = {compound,general} ,
+    sub-counter-format    .code:n     =
+      \prop_if_in:NnTF \l__chemnum_label_formats_prop {#1}
+        {
+          \tl_set:Nn
+            \l__chemnum_default_subcounter_representation_tl
+            {#1}
+        }
+        {
+          \msg_warning:nnn {chemnum} {unknown-counter-format} {#1}
+          \tl_set:Nn
+            \l__chemnum_default_subcounter_representation_tl
+            {arabic}
+        } ,
+    sub-counter-format    .groups:n   = {compound,general} ,
+    % label:
+    pre-label-code        .tl_set:N   = \l__chemnum_pre_label_default_tl ,
+    pre-label-code        .groups:n   = {compound} ,
+    post-label-code       .tl_set:N   = \l__chemnum_post_label_default_tl ,
+    post-label-code       .groups:n   = {compound} ,
+    pre-main-label-code   .tl_set:N   = \l__chemnum_pre_main_label_default_tl ,
+    pre-main-label-code   .groups:n   = {compound} ,
+    post-main-label-code  .tl_set:N   = \l__chemnum_post_main_label_default_tl ,
+    post-main-label-code  .groups:n   = {compound} ,
+    main-sub-sep          .tl_set:N   = \l__chemnum_compound_separator_tl ,
+    main-sub-sep          .groups:n   = {general,list} ,
+    list-label-sep        .tl_set:N   = \l__chemnum_main_separator_tl ,
+    list-label-sep        .groups:n   = {general,list} ,
+    sub-list-label-sep    .tl_set:N   = \l__chemnum_sub_separator_tl ,
+    sub-list-label-sep    .groups:n   = {general,list} ,
+    format                .code:n     =
+      \tl_set:Nn \l__chemnum_local_label_format_tl {#1}
+      \bool_if:NF \l__chemnum_compound_local_bool
+        { \tl_set:Nn \l__chemnum_label_format_tl {#1} } ,
+    format                .groups:n   = {compound,general} ,
+    sub-only              .bool_set:N = \l__chemnum_sub_only_bool ,
+    sub-only              .groups:n   = {compound,sub-only} ,
+    sub-all               .bool_set:N = \l__chemnum_sub_all_bool ,
+    sub-all               .groups:n   = {compound} ,
+    compress              .bool_set:N =
+      \l__chemnum_compress_subcompounds_bool ,
+    compress              .groups:n   = {compound,general} ,
+    merge                 .bool_set:N =
+      \l__chemnum_merge_list_bool ,
+    merge                 .groups:n   = {general,list} ,
+    % initiation:
+    init                  .choice: ,
+    init / true           .code:n     =
+      \bool_set_true:N \g__chemnum_initiate_bool
+      \bool_set_true:N \g__chemnum_initiate_sub_bool
+      \bool_set_false:N \g__chemnum_initiate_strict_bool ,
+    init / main           .code:n     =
+      \bool_set_true:N \g__chemnum_initiate_bool
+      \bool_set_false:N \g__chemnum_initiate_sub_bool
+      \bool_set_false:N \g__chemnum_initiate_strict_bool ,
+    init / false          .code:n     =
+      \bool_set_false:N \g__chemnum_initiate_bool
+      \bool_set_false:N \g__chemnum_initiate_sub_bool
+      \bool_set_false:N \g__chemnum_initiate_strict_bool ,
+    init / strict         .code:n     =
+      \bool_set_true:N \g__chemnum_initiate_bool
+      \bool_set_true:N \g__chemnum_initiate_sub_bool
+      \bool_set_true:N \g__chemnum_initiate_strict_bool ,
+    init / main-strict    .code:n     =
+      \bool_set_true:N \g__chemnum_initiate_bool
+      \bool_set_false:N \g__chemnum_initiate_sub_bool
+      \bool_set_true:N \g__chemnum_initiate_strict_bool ,
+    init                  .default:n  = true ,
+    init                  .groups:n   = {general} ,
+    % list processing:
+    list-sep-two          .tl_set:N   = \l__chemnum_sep_list_two_tl ,
+    list-sep-two          .groups:n   = {general,list} ,
+    list-sep-more         .tl_set:N   = \l__chemnum_sep_list_more_tl ,
+    list-sep-more         .groups:n   = {general,list} ,
+    list-sep-last-two     .tl_set:N   = \l__chemnum_sep_list_last_two_tl ,
+    list-sep-last-two     .groups:n   = {general,list} ,
+    sub-list-sep-two      .tl_set:N   = \l__chemnum_sep_sublist_two_tl ,
+    sub-list-sep-two      .groups:n   = {compound,general} ,
+    sub-list-sep-more     .tl_set:N   = \l__chemnum_sep_sublist_more_tl ,
+    sub-list-sep-more     .groups:n   = {compound,general} ,
+    sub-list-sep-last-two .tl_set:N   = \l__chemnum_sep_sublist_last_two_tl ,
+    sub-list-sep-last-two .groups:n   = {compound,general} ,
+    sub-list-sep-range    .tl_set:N   = \l__chemnum_sep_sublist_range_tl ,
+    sub-list-sep-range    .groups:n   = {compound,general} ,
+    % logging and other information:
+    log                   .choice: ,
+    log / true            .code:n     =
+      \bool_set_true:N \l__chemnum_log_bool
+      \bool_set_false:N \l__chemnum_log_verbose_bool ,
+    log / silent          .code:n     =
+      \bool_set_true:N \l__chemnum_log_bool
+      \bool_set_false:N \l__chemnum_log_verbose_bool ,
+    log / false           .code:n     =
+      \bool_set_false:N \l__chemnum_log_bool
+      \bool_set_false:N \l__chemnum_log_verbose_bool ,
+    log / verbose         .code:n     =
+      \bool_set_true:N \l__chemnum_log_bool
+      \bool_set_true:N \l__chemnum_log_verbose_bool ,
+    log                   .default:n  = true ,
+    log                   .groups:n   = {general} ,
+    show-keys             .choice: ,
+    show-keys / true      .code:n     =
+      \bool_set_true:N \l__chemnum_show_def_bool
+      \bool_set_true:N \l__chemnum_show_ref_bool ,
+    show-keys / false     .code:n     =
+      \bool_set_false:N \l__chemnum_show_def_bool
+      \bool_set_false:N \l__chemnum_show_ref_bool ,
+    show-keys / def       .code:n     =
+      \bool_set_true:N \l__chemnum_show_def_bool
+      \bool_set_false:N \l__chemnum_show_ref_bool ,
+    show-keys / ref       .code:n     =
+      \bool_set_false:N \l__chemnum_show_def_bool
+      \bool_set_true:N \l__chemnum_show_ref_bool ,
+    show-keys             .default:n  = true ,
+    show-keys             .groups:n   = {general} ,
+    replace               .bool_set:N = \l__chemnum_replace_local_bool ,
+    replace               .groups:n   = {replace} ,
+    replace-auto          .bool_set:N = \l__chemnum_compound_replace_auto_bool ,
+    replace-tag           .tl_set:N   = \l__chemnum_compound_replace_tag_tl ,
+    replace-tag           .groups:n   = {general} ,
+    tag                   .code:n     =
+      \tl_set:Nn \l__chemnum_compound_replace_tag_tl {#1}
+      \bool_set_false:N \l__chemnum_compound_replace_auto_this_bool ,
+    tag                   .groups:n   = {replace} ,
+    replace-style         .tl_set:N   = \l__chemnum_compound_replace_format_tl ,
+    replace-style         .groups:n   = {general} ,
+    style                 .code:n     =
+      \tl_set:Nn \l__chemnum_compound_replace_local_format_tl {#1}
+      \bool_set_true:N \l__chemnum_replace_local_bool ,
+    style                 .groups:n   = {replace} ,
+    replace-pos           .code:n     = \__chemnum_set_psfrag_pos:nn #1 ,
+    replace-pos           .groups:n   = {general} ,
+    pos                   .code:n     =
+      \bool_set_true:N \l__chemnum_replace_local_bool
+      \__chemnum_set_psfrag_local_pos:nn #1 ,
+    pos                   .groups:n   = {replace}
+  }
 
-\cs_new_protected:Npn \__chemnum_cmpd_use_style:n #1
+% ----------------------------------------------------------------------------
+% #1: int variable that holds the value
+% #2: the chosen format
+% this command is expandable
+\cs_new:Npn \__chemnum_label_format:Nn #1#2
   {
-    \group_begin:
-      \bool_if:NT \l__chemnum_cmpd_bold_bool
-        { \bfseries }
-      \chemnum_cmpd_style:n { #1 }
-    \group_end:
+    \prop_if_in:NnTF \l__chemnum_label_formats_prop {#2}
+      { \use:c { __chemnum_#2_label_format:n } {#1} }
+      { \__chemnum_arabic_label_format:n {#1} }
   }
+\cs_generate_variant:Nn \__chemnum_label_format:Nn { NV , cV }
 
-%-----------------------------------------------------------------------------%
-% prefix, suffix, delimiters, format and separator of compound label
-\tl_new:N \l__chemnum_cmpd_prefix_tl
-\tl_new:N \l__chemnum_cmpd_suffix_tl
+% ----------------------------------------------------------------------------
+% auxiliary file -- we'll use the .aux file
+% first let's add dummy definitions so we can hopefully avoid error messages
+% if the `chemnum' package is removed from the preamble
+\AtBeginDocument
+  {
+    \if@filesw
+      \iow_now:Nn \@auxout
+        {
+          \providecommand\chemnum@cmpd[8]{} ^^J
+          \providecommand\chemnum@subcmpd[4]{} ^^J
+          \providecommand\chemnum@check{}
+        }
+    \fi
+  }
 
-\tl_new:N \l__chemnum_cmpd_space_tl
-\tl_set:Nn \l__chemnum_cmpd_space_tl { \penalty\@m\  }
+% we use this one to trigger a LaTeX rerun warning -- to be precise the
+% ``Label(s) may have changed'' warning:
+\cs_new_protected:Npn \__chemnum_rerun:
+  { \AtEndDocument { \def \chemnum@check { \@tempswatrue } } }
+
+% add the rerun check at the end:
+\AtEndDocument { \if@filesw \iow_now:Nn \@auxout { \chemnum@check } \fi }
+
+% ----------------------------------------------------------------------------
+% initiating new compounds
+% - property list that holds
+%   - ID
+%   - counter value
+%   - counter represetation
+%   - pre-counter-code
+%   - post-counter-code
+%   - pre-label-code
+%   - post-label-code
+%   - formatting code
+% - add to list of initiated compounds
+
+\cs_new_protected:Npn \chemnum_initiate_compound:n #1
+  {
+    \chemnum_compound_if_initiated:nF {#1}
+      { \seq_gput_right:Nn \g__chemnum_initiated_compounds_seq {#1} }
+  }
 
-\tl_new:N \l__chemnum_cmpd_separator_tl
+% #1: ID
+\cs_new_protected:Npn \chemnum_define_compound:n #1
+  {
+    \chemnum_initialize_compound:n {#1}
+    \chemnum_compound_declare_properties:nn {#1}
+      {
+        ID ,
+        number ,
+        counter-representation ,
+        pre-label-code ,
+        post-label-code ,
+        pre-main-label-code ,
+        post-main-label-code ,
+        label-format
+      }
+    \chemnum_compound_set_property:nnn {#1} {ID} {#1}
+    \chemnum_compound_set_property:nnx {#1} {number}
+      { \int_use:N \c@cmpdmain }
+    \chemnum_compound_set_property:nnx {#1} {counter-representation}
+      {
+        \tl_use:N \l__chemnum_pre_counter_default_tl
+        \__chemnum_label_format:NV
+          \c@cmpdmain % \g__chemnum_main_int
+          \l__chemnum_default_counter_representation_tl
+        \tl_use:N \l__chemnum_post_counter_default_tl
+      }
+    \chemnum_compound_set_property:nnV {#1} {pre-label-code}
+      \l__chemnum_pre_label_default_tl
+    \chemnum_compound_set_property:nnV {#1} {post-label-code}
+      \l__chemnum_post_label_default_tl
+    \chemnum_compound_set_property:nnV {#1} {pre-main-label-code}
+      \l__chemnum_pre_main_label_default_tl
+    \chemnum_compound_set_property:nnV {#1} {post-main-label-code}
+      \l__chemnum_post_main_label_default_tl
+    \chemnum_compound_set_property:nnV {#1} {label-format}
+      \l__chemnum_label_format_tl
+    \__chemnum_write_compound_to_auxfile:nnnVVVVV {#1}
+      { \int_use:N \g__chemnum_main_int }
+      {
+        \tl_use:N \l__chemnum_pre_counter_default_tl
+        \__chemnum_label_format:NV
+          \c@cmpdmain % \g__chemnum_main_int
+          \l__chemnum_default_counter_representation_tl
+        \tl_use:N \l__chemnum_post_counter_default_tl
+      }
+      \l__chemnum_pre_label_default_tl
+      \l__chemnum_post_label_default_tl
+      \l__chemnum_pre_main_label_default_tl
+      \l__chemnum_post_main_label_default_tl
+      \l__chemnum_label_format_tl
+    \chemnum_compound_update_properties:n {#1}
+    \chemnum_log_main:n {#1}
+  }
 
-\tl_new:N \l__chemnum_cmpd_odelim_tl
-\tl_new:N \l__chemnum_cmpd_cdelim_tl
+% TODO: keep? and if: what should it set?
+\cs_new_protected:Npn \chemnum_set_compound:n #1
+  {
+    % those should be done: however, they overwrite existing options in any
+    % case... this would overwrite options that really should stay set.
+    
+    % \chemnum_compound_set_property:nnV {#1} {pre-label-code}
+    %   \l__chemnum_pre_label_default_tl
+    % \chemnum_compound_set_property:nnV {#1} {post-label-code}
+    %   \l__chemnum_post_label_default_tl
+    % \chemnum_compound_set_property:nnV {#1} {post-main-label-code}
+    %   \l__chemnum_post_main_label_default_tl
+    % \chemnum_compound_set_property:nnV {#1} {label-format}
+    %   \l__chemnum_label_format_tl
+    % \__chemnum_write_compound_to_auxfile:nnnVVVV {#1}
+    %   { \int_use:N \g__chemnum_main_int }
+    %   {
+    %     \tl_use:N \l__chemnum_pre_counter_default_tl
+    %     \__chemnum_label_format:NV
+    %       \c@cmpdmain % \g__chemnum_main_int
+    %       \l__chemnum_default_counter_representation_tl
+    %     \tl_use:N \l__chemnum_post_counter_default_tl
+    %   }
+    %   \l__chemnum_pre_label_default_tl
+    %   \l__chemnum_post_label_default_tl
+    %   \l__chemnum_post_main_label_default_tl
+    %   \l__chemnum_label_format_tl
+    % \chemnum_compound_update_properties:n {#1}
+  }
 
-% error message for wrong argument length of delim-keys
-\msg_set:nnn { chemnum } { delimiters }
+\cs_new_protected:Npn \chemnum_initialize_compound:n #1
   {
-    "#1-delim~=~<odelim><cdelim>"~needs~two~tokens~or~token~groups~as~a~value~
-    \msg_line_context: .
+    \seq_gput_right:Nn \g__chemnum_defined_compounds_seq {#1}
+    \int_gincr:N \g__chemnum_main_int
+    \stepcounter{cmpdmain}
+    \seq_new:c { g__chemnum_#1_initiated_subcompounds_seq }
   }
 
-% set compound delimiters
-\cs_new_protected:Npn \__chemnum_cmpd_delim:n #1
+% #1: main ID
+% #2: sub ID
+\cs_new_protected:Npn \chemnum_define_subcompound:nn #1#2
   {
-    \tl_if_blank:nTF { #1 }
+    \chemnum_initialize_subcompound:nn {#1} {#2}
+    \chemnum_subcompound_declare_properties:nnn {#1} {#2}
       {
-        \tl_clear:N \l__chemnum_cmpd_odelim_tl
-        \tl_clear:N \l__chemnum_cmpd_cdelim_tl
+        ID ,
+        main-compound ,
+        number ,
+        counter-representation
       }
+    \chemnum_subcompound_set_property:nnnn {#1} {#2} {ID} {#2}
+    \chemnum_subcompound_set_property:nnnn {#1} {#2} {main-compound} {#1}
+    \chemnum_subcompound_set_property:nnnx {#1} {#2} {number}
+      { \int_use:c { g__chemnum_compound_#1_subcompound_int } }
+    \chemnum_subcompound_set_property:nnnx {#1} {#2} {counter-representation}
       {
-        \int_compare:nNnTF { \tl_count:n { #1 } } = 2
-          {
-            \tl_set:Nx \l__chemnum_cmpd_odelim_tl { \tl_head:n { #1 } }
-            \tl_set:Nx \l__chemnum_cmpd_cdelim_tl { \tl_tail:n { #1 } }
-          }
-          { \msg_error:nnx { chemnum } { delimiters } { cmpd } }
+        \__chemnum_label_format:cV
+          { g__chemnum_compound_#1_subcompound_int }
+          \l__chemnum_default_subcounter_representation_tl
       }
-  } 
-
-% format of numbering
-\cs_new:Npn \__chemnum_cmpd_kind:nn #1#2
-  { \cs:w int_to_#1:n \cs_end: #2 }
-
-% default format
-\tl_new:N  \l__chemnum_cmpd_kind_value_tl
-\tl_set:Nn \l__chemnum_cmpd_kind_value_tl { arabic }
-
-% format of sub-numbering
-\cs_new:Npn \__chemnum_cmpd_sub_kind:nn #1#2
-  { \cs:w int_to_ #1 :n \cs_end: #2 }
-\cs_generate_variant:Nn \__chemnum_cmpd_sub_kind:nn { Nc }
-
-% default format
-\tl_new:N  \l__chemnum_cmpd_sub_kind_value_tl
-\tl_set:Nn \l__chemnum_cmpd_sub_kind_value_tl { alph }
-
-%-----------------------------------------------------------------------------%
-% add greek letters and symbols as numbering format
-% define \int_to_greek function
-\cs_new:Npn \int_to_greek:n { }
-% \bool_if:NTF \l__chemnum_textgreek_bool
-%   {
-    \cs_set:Npn \int_to_greek:n #1
+    \__chemnum_write_subcompound_to_auxfile:nnnn {#1} {#2}
+      { \int_use:c { g__chemnum_compound_#1_subcompound_int } }
       {
-        \int_to_symbols:nnn {#1} { 24 }
-          {
-            {  1 } { \exp_not:o \__chemnum_alpha: }
-            {  2 } { \exp_not:o \__chemnum_beta: }
-            {  3 } { \exp_not:o \__chemnum_gamma: }
-            {  4 } { \exp_not:o \__chemnum_delta: }
-            {  5 } { \exp_not:o \__chemnum_epsilon: }
-            {  6 } { \exp_not:o \__chemnum_zeta: }
-            {  7 } { \exp_not:o \__chemnum_eta: }
-            {  8 } { \exp_not:o \__chemnum_theta: }
-            {  9 } { \exp_not:o \__chemnum_iota: }
-            { 10 } { \exp_not:o \__chemnum_kappa: }
-            { 11 } { \exp_not:o \__chemnum_lambda: }
-            { 12 } { \exp_not:o \__chemnum_mu: }
-            { 13 } { \exp_not:o \__chemnum_nu: }
-            { 14 } { \exp_not:o \__chemnum_xi: }
-            { 15 } { \exp_not:o \__chemnum_omikron: }
-            { 16 } { \exp_not:o \__chemnum_pi: }
-            { 17 } { \exp_not:o \__chemnum_rho: }
-            { 18 } { \exp_not:o \__chemnum_sigma: }
-            { 19 } { \exp_not:o \__chemnum_tau: }
-            { 20 } { \exp_not:o \__chemnum_upsilon: }
-            { 21 } { \exp_not:o \__chemnum_phi: }
-            { 22 } { \exp_not:o \__chemnum_chi: }
-            { 23 } { \exp_not:o \__chemnum_psi: }
-            { 24 } { \exp_not:o \__chemnum_omega: }
-          }
+        \__chemnum_label_format:cV
+          { g__chemnum_compound_#1_subcompound_int }
+          \l__chemnum_default_subcounter_representation_tl
       }
-%   }
-%   {
-%     \cs_set_eq:NN \int_to_greek:n \int_to_alph:n
-%   }
+    \chemnum_subcompound_update_properties:nn {#1} {#2}
+    \chemnum_log_sub:nn {#1} {#2}
+  }
 
-% define \int_to_Greek function
-\cs_new:Npn \int_to_Greek:n { }
-\bool_if:NTF \l__chemnum_textgreek_bool
+\cs_new_protected:Npn \chemnum_initialize_subcompound:nn #1#2
   {
-    \cs_set_protected:Npn \int_to_Greek:n #1
+    \int_if_exist:cF { g__chemnum_compound_#1_subcompound_int }
+      { \int_new:c { g__chemnum_compound_#1_subcompound_int } }
+    \int_gincr:c { g__chemnum_compound_#1_subcompound_int }
+    \seq_if_exist:cF { g__chemnum_compound_#1_subcompounds_seq }
+      { \seq_new:c { g__chemnum_compound_#1_subcompounds_seq } }
+    \prop_if_exist:cF { g__chemnum_compound_#1_subcompounds_prop }
+      { \prop_new:c { g__chemnum_compound_#1_subcompounds_prop } }
+    \seq_gput_right:cn { g__chemnum_compound_#1_subcompounds_seq } {#2}
+    \prop_gput:cnx { g__chemnum_compound_#1_subcompounds_prop } {#2}
       {
-        \int_to_symbols:nnn { #1 } { 24 }
-          {
-            {  1 } { \exp_not:o \__chemnum_Alpha: }
-            {  2 } { \exp_not:o \__chemnum_Beta: }
-            {  3 } { \exp_not:o \__chemnum_Gamma: }
-            {  4 } { \exp_not:o \__chemnum_Delta: }
-            {  5 } { \exp_not:o \__chemnum_Epsilon: }
-            {  6 } { \exp_not:o \__chemnum_Zeta: }
-            {  7 } { \exp_not:o \__chemnum_Eta: }
-            {  8 } { \exp_not:o \__chemnum_Theta: }
-            {  9 } { \exp_not:o \__chemnum_Iota: }
-            { 10 } { \exp_not:o \__chemnum_Kappa: }
-            { 11 } { \exp_not:o \__chemnum_Lambda: }
-            { 12 } { \exp_not:o \__chemnum_Mu: }
-            { 13 } { \exp_not:o \__chemnum_Nu: }
-            { 14 } { \exp_not:o \__chemnum_Xi: }
-            { 15 } { \exp_not:o \__chemnum_Omikron: }
-            { 16 } { \exp_not:o \__chemnum_Pi: }
-            { 17 } { \exp_not:o \__chemnum_Rho: }
-            { 18 } { \exp_not:o \__chemnum_Sigma: }
-            { 19 } { \exp_not:o \__chemnum_Tau: }
-            { 20 } { \exp_not:o \__chemnum_Upsilon: }
-            { 21 } { \exp_not:o \__chemnum_Phi: }
-            { 22 } { \exp_not:o \__chemnum_Chi: }
-            { 23 } { \exp_not:o \__chemnum_Psi: }
-            { 24 } { \exp_not:o \__chemnum_Omega: }
-          }
+        \int_use:c { g__chemnum_compound_#1_subcompound_int } :
+        \__chemnum_label_format:cV
+          { g__chemnum_compound_#1_subcompound_int }
+          \l__chemnum_default_subcounter_representation_tl
       }
   }
+
+% ----------------------------------------------------------------------------
+\cs_new_protected:Npn \chemnum_log_main:n #1
   {
-    \cs_set_eq:NN \int_to_Greek:n \int_to_Alph:n
+    \bool_if:NT \l__chemnum_log_bool
+      {
+        \bool_if:NTF \l__chemnum_log_verbose_bool
+          { \msg_log:nnn {chemnum} {log-compound-verbose} {#1} }
+          { \msg_log:nnn {chemnum} {log-compound-silent}  {#1} }
+      }
   }
 
-% define \int_to_Symbol function
-\cs_new_protected:Npn \int_to_Symbol:n #1
+\cs_new_protected:Npn \chemnum_log_sub:nn #1#2
   {
-    \int_to_symbols:nnn { #1 } { 9 }
+    \bool_if:NT \l__chemnum_log_bool
       {
-        { 1 } {\exp_not:o \textasteriskcentered }
-        { 2 } {\exp_not:o \textdagger}
-        { 3 } {\exp_not:o \textdaggerdbl}
-        { 4 } {\exp_not:o \textsection}
-        { 5 } {\exp_not:o \textparagraph}
-        { 6 } {\exp_not:o \textbardbl}
-        { 7 } {\exp_not:o \textasteriskcentered \textasteriskcentered}
-        { 8 } {\exp_not:o \textdagger \textdagger}
-        { 9 } {\exp_not:o \textdaggerdbl \textdaggerdbl}
+        \bool_if:NTF \l__chemnum_log_verbose_bool
+          { \msg_log:nnnn {chemnum} {log-subcompound-verbose} {#1} {#2} }
+          { \msg_log:nnnn {chemnum} {log-subcompound-silent}  {#1} {#2} }
       }
   }
 
-%-----------------------------------------------------------------------------%
-% lists of sublabels
-\clist_new:N \l__chemnum_sublabel_clist
-\tl_new:N    \l__chemnum_sublabel_list_sep_tl
-\tl_set:Nn   \l__chemnum_sublabel_list_sep_tl { , }
-\tl_new:N    \l__chemnum_cmpd_sublabel_list_tl
-\int_new:N   \l__chemnum_sublabel_list_current_int
-\int_new:N   \l__chemnum_sublabel_list_length_int
-\bool_new:N  \l__chemnum_sublabel_list_bool
+% ----------------------------------------------------------------------------
+% #1: ID
+\prg_new_protected_conditional:Npnn \chemnum_compound_if_initiated:n #1
+  { T,F,TF }
+  {
+    \seq_if_in:NnTF \g__chemnum_initiated_compounds_seq {#1}
+      { \prg_return_true: }
+      { \prg_return_false: }
+  }
+
+% #1: main ID
+% #2: sub ID
+\prg_new_protected_conditional:Npnn \chemnum_subcompound_if_initiated:nn #1#2
+  { T,F,TF }
+  {
+    \seq_if_in:cnTF { g__chemnum_#1_initiated_subcompounds_seq } {#2}
+      { \prg_return_true: }
+      { \prg_return_false: }
+  }
+
+% #1: ID
+\prg_new_protected_conditional:Npnn \chemnum_compound_if_defined:n #1
+  { T,F,TF }
+  {
+    \seq_if_in:NnTF \g__chemnum_defined_compounds_seq {#1}
+      { \prg_return_true: }
+      { \prg_return_false: }
+  }
+
+% #1: main ID
+% #2: sub ID
+\prg_new_protected_conditional:Npnn \chemnum_subcompound_if_defined:nn #1#2
+  { T,F,TF }
+  {
+    \seq_if_in:cnTF { g__chemnum_compound_#1_subcompounds_seq } {#2}
+      { \prg_return_true: }
+      { \prg_return_false: }
+  }
+
+% ----------------------------------------------------------------------------
+% #1: ID
+% #2: property to be defined
+\cs_new_protected:Npn \chemnum_compound_declare_property:nn #1#2
+  {
+    \seq_if_in:cnF { g__chemnum_compound_#1_properties_seq } {#2}
+      { \seq_gput_right:cn { g__chemnum_compound_#1_properties_seq } {#2} }
+  }
+
+% #1: ID
+% #2: properties to be defined
+\cs_new_protected:Npn \chemnum_compound_declare_properties:nn #1#2
+  {
+    \seq_if_exist:cF { g__chemnum_compound_#1_properties_seq }
+      { \seq_new:c { g__chemnum_compound_#1_properties_seq } }
+    \prop_if_exist:cF { g__chemnum_compound_#1_prop }
+      { \prop_new:c { g__chemnum_compound_#1_prop } }
+    \clist_map_inline:nn { #2 }
+      { \chemnum_compound_declare_property:nn {#1} {##1} }
+  }
+
+% #1: ID
+% #2: property to be set
+% #3: value of property
+\cs_new_protected:Npn \chemnum_compound_set_property:nnn #1#2#3
+  {
+    \seq_if_in:cnTF { g__chemnum_compound_#1_properties_seq } {#2}
+      { \prop_gput:cnn { g__chemnum_compound_#1_prop } {#2} {#3} }
+      { \ERROR }
+  }
+\cs_generate_variant:Nn \chemnum_compound_set_property:nnn { nnV , nnx }
 
-\cs_new_protected:Npn \__chemnum_cmpd_sublabel_list:nn #1#2
+% #1: ID
+% #2: property to be updated
+\cs_new_protected:Npn \chemnum_compound_update_property:nn #1#2
   {
-    \clist_clear:N \l__chemnum_sublabel_clist
-    \clist_set_eq:NN \l__chemnum_sublabel_clist #2
-    \int_set:Nn \l__chemnum_sublabel_list_length_int
-      { \clist_count:N \l__chemnum_sublabel_clist }
-    \clist_map_variable:NNn \l__chemnum_sublabel_clist \l__chemnum_tmpb_tl
+    \seq_if_in:cnTF { g__chemnum_compound_#1_properties_seq } {#2}
       {
-        \int_incr:N \l__chemnum_sublabel_list_current_int
-        \exp_after:wN \__chemnum_cmpd_sublabelsep:n \l__chemnum_tmpb_tl \q_stop
-        \use:c { chemnum_cmpd_#1_ \l__chemnum_cmpd_sub_one_label_tl _ref: }
-        \tl_if_blank:VF \l__chemnum_cmpd_sub_two_label_tl
+        \prop_get:cnN { g__chemnum_compound_#1_prop } {previous-#2}
+          \l__chemnum_tmpa_tl
+        \prop_get:cnN { g__chemnum_compound_#1_prop } {#2}
+          \l__chemnum_tmpb_tl
+        \tl_if_eq:NNF \l__chemnum_tmpb_tl \l__chemnum_tmpa_tl
           {
-            \tl_use:N \l__chemnum_sub_range_sep_tl
-            \use:c { chemnum_cmpd_#1_ \l__chemnum_cmpd_sub_two_label_tl _ref: }
+            \prop_gput:cnV { g__chemnum_compound_#1_prop }
+              {previous-#2}
+              \l__chemnum_tmpb_tl
           }
-        \int_compare:nT
+      }
+      { \ERROR }
+  }
+
+% #1: ID
+\cs_new_protected:Npn \chemnum_compound_update_properties:n #1
+  {
+    \seq_map_inline:cn { g__chemnum_compound_#1_properties_seq }
+      { \chemnum_compound_update_property:nn {#1} {##1} }
+  }
+
+% #1: main ID
+% #2. sub ID
+% #3: property to be defined
+\cs_new_protected:Npn \chemnum_subcompound_declare_property:nnn #1#2#3
+  {
+    \seq_if_in:cnF { g__chemnum_compound_#1_#2_properties_seq } {#3}
+      { \seq_gput_right:cn { g__chemnum_compound_#1_#2_properties_seq } {#3} }
+  }
+
+% #1: main ID
+% #2. sub ID
+% #3: properties to be defined
+\cs_new_protected:Npn \chemnum_subcompound_declare_properties:nnn #1#2#3
+  {
+    \seq_if_exist:cF { g__chemnum_compound_#1_#2_properties_seq }
+      { \seq_new:c { g__chemnum_compound_#1_#2_properties_seq } }
+    \prop_if_exist:cF { g__chemnum_compound_#1_#2_properties_prop }
+      { \prop_new:c { g__chemnum_compound_#1_#2_properties_prop } }
+    \clist_map_inline:nn { #3 }
+      { \chemnum_subcompound_declare_property:nnn {#1} {#2} {##1} }
+  }
+
+% #1: main ID
+% #2: sub ID
+% #3: property to be set
+% #4: value of property
+\cs_new_protected:Npn \chemnum_subcompound_set_property:nnnn #1#2#3#4
+  {
+    \seq_if_in:cnTF { g__chemnum_compound_#1_#2_properties_seq } {#3}
+      { \prop_gput:cnn { g__chemnum_compound_#1_#2_properties_prop } {#3} {#4} }
+      { \ERROR }
+  }
+\cs_generate_variant:Nn \chemnum_subcompound_set_property:nnnn { nnnV , nnnx }
+
+% #1: main ID
+% #2. sub ID
+% #3: property to be updated
+\cs_new_protected:Npn \chemnum_subcompound_update_property:nnn #1#2#3
+  {
+    \seq_if_in:cnTF { g__chemnum_compound_#1_#2_properties_seq }
+      {
+        \prop_get:cnN { g__chemnum_compound_#1_#2_properties_prop } {previous-#3}
+          \l__chemnum_tmpa_tl
+        \prop_get:cnN { g__chemnum_compound_#1_#2_properties_prop } {#3}
+          \l__chemnum_tmpb_tl
+        \tl_if_eq:NNF \l__chemnum_tmpb_tl \l__chemnum_tmpa_tl
           {
-            \l__chemnum_sublabel_list_current_int
-            <
-            \l__chemnum_sublabel_list_length_int
+            \prop_gput:cnV { g__chemnum_compound_#1_#2_properties_prop }
+              {previous-#3}
+              \l__chemnum_tmpb_tl
           }
-          { \tl_use:N \l__chemnum_sublabel_list_sep_tl }
       }
+      { \ERROR }
   }
 
-%-----------------------------------------------------------------------------%
-% variables
-\bool_new:N \l__chemnum_cmpd_name_bool
-\bool_set_false:N \l__chemnum_cmpd_name_bool
-\bool_new:N \l__chemnum_cmpd_all_bool
-\bool_set_false:N \l__chemnum_cmpd_all_bool
-\bool_new:N \l__chemnum_cmpd_range_bool
-\bool_set_false:N \l__chemnum_cmpd_range_bool
-\bool_new:N \l__chemnum_sub_label_only_bool
-\bool_set_false:N \l__chemnum_sub_label_only_bool
-
-\tl_new:N  \l__chemnum_cmpd_name_tl
-\tl_new:N  \l__chemnum_cmpd_labelsep_tl
-\tl_set:Nn \l__chemnum_cmpd_labelsep_tl { . }
-\tl_new:N  \l__chemnum_sublist_input_separator_tl
-\tl_set:Nn \l__chemnum_sublist_input_separator_tl { , }
-\tl_new:N  \l__chemnum_sublist_output_separator_tl
-\tl_set:Nn \l__chemnum_sublist_output_separator_tl { , }
-\tl_new:N  \l__chemnum_sublabel_range_marker_tl
-\tl_set:Nn \l__chemnum_sublabel_range_marker_tl { .. }
-\tl_new:N  \l__chemnum_sub_range_sep_tl
-\tl_set:Nn \l__chemnum_sub_range_sep_tl { -- }
-
-%-----------------------------------------------------------------------------%
-% hyperref support
-\tl_new:N \l__chemnum_cmpd_hyper_name_tl
-
-\bool_new:N \l__chemnum_use_hyperref_bool
-\bool_new:N \l__chemnum_hypertarget_bool
-\bool_new:N \l__chemnum_hyperlink_bool
-
-\cs_new_eq:NN \__chemnum_make_hyper:nn \use_ii:nn
-
-% #1: main label, #2: sub labels, #3: invisible
-\cs_new_protected:Npn \__chemnum_hyperref:nnn #1#2#3
-   {
-     \bool_if:nF { #3 || !\l__chemnum_use_hyperref_bool }
-       {
-         \bool_if:NT \l__chemnum_hypertarget_bool
-           {
-             \cs_set:Npn \__chemnum_make_hyper:nn ##1##2
-               {
-                 \raisebox { 3ex } [ 0pt ]
-                   { \hypertarget { ##1 } { } } ##2
-               }
-           }
-         \bool_if:NT \l__chemnum_hyperlink_bool
-           { \cs_set_eq:NN \__chemnum_make_hyper:nn \hyperlink }
-         \bool_if:nT
-           { !\l__chemnum_hypertarget_bool && !\l__chemnum_hyperlink_bool }
-           {
-             \tl_if_blank:nTF { #2 }
-               { % no sublabel
-                 \tl_set:Nn \l__chemnum_cmpd_hyper_name_tl
-                   { chemnum_cmpd_#1 }
-                 \cs_if_exist:cTF { chemnum_cmpd_#1_hyper: }
-                   {
-                     \bool_set_false:N \l__chemnum_hypertarget_bool
-                     \cs_set_eq:NN \__chemnum_make_hyper:nn \hyperlink
-                   }
-                   {
-                     \bool_set_true:N \l__chemnum_hypertarget_bool
-                     \cs_set:Npn \__chemnum_make_hyper:nn ##1##2
-                       {
-                         \raisebox { 3ex } [ 0pt ]
-                           { \hypertarget { ##1 } { } } ##2
-                       }
-                     \cs_new:cpn { chemnum_cmpd_#1_hyper: } { }
-                   }
-               }
-               {
-                 \__chemnum_cmpd_sublist:n { #2 }
-                 \int_compare:nT { \l__chemnum_cmpd_sublist_length_int < 2 }
-                   { % no sublabel list
-                     \__chemnum_cmpd_subrange_separate:n { #2 }
-                     \tl_if_blank:VT \l__chemnum_tmpc_tl
-                       { % no sublabel range
-                         \tl_set:Nn \l__chemnum_cmpd_hyper_name_tl
-                           { chemnum_cmpd_#1_ \l__chemnum_tmpb_tl }
-                         \cs_if_exist:cTF
-                           { chemnum_cmpd_#1_ \l__chemnum_tmpb_tl _hyper: }
-                           {
-                             \bool_set_false:N \l__chemnum_hypertarget_bool
-                             \cs_set_eq:NN \__chemnum_make_hyper:nn \hyperlink
-                           }
-                           {
-                             \bool_set_true:N \l__chemnum_hypertarget_bool
-                             \cs_set:Npn \__chemnum_make_hyper:nn ##1##2
-                               {
-                                 \raisebox { 3ex } [ 0pt ]
-                                   { \hypertarget { ##1 } { } } ##2
-                               }
-                             \cs_new:cpn
-                               { chemnum_cmpd_#1_ \l__chemnum_tmpb_tl _hyper: } { }
-                           }
-                       }
-                   }
-               }
-           }
-       }
-   }
-
-%-----------------------------------------------------------------------------%
-% property keys for compounds
-\keys_define:nn { chemnum } {
-  cmpd-style           .code:n             = \__chemnum_cmpd_set_style:n { #1 } ,
-  cmpd-weight          .choice: ,
-  cmpd-weight / bold   .code:n             =
-    \bool_set_true:N \l__chemnum_cmpd_bold_bool ,
-  cmpd-weight / normal .code:n             =
-    \bool_set_false:N \l__chemnum_cmpd_bold_bool ,
-  cmpd-label           .code:n             =
-    {
-      \bool_set_true:N \l__chemnum_cmpd_name_bool
-      \tl_set:Nn \l__chemnum_cmpd_name_tl { #1 }
-    } ,
-  cmpd-prefix          .tl_set:N           = \l__chemnum_cmpd_prefix_tl ,
-  cmpd-prefix          .default:n          = { } ,
-  cmpd-suffix          .tl_set:N           = \l__chemnum_cmpd_suffix_tl ,
-  cmpd-suffix          .default:n          = { } ,
-  cmpd-space           .tl_set:N           = \l__chemnum_cmpd_space_tl ,
-  cmpd-space           .default:n          = { \penalty\@m\  },
-  cmpd-delim           .code:n             = \__chemnum_cmpd_delim:n { #1 },
-  cmpd-delim           .default:n          = { ( } { ) } ,
-  cmpd-odelim          .tl_set:N           = \l__chemnum_cmpd_odelim_tl ,
-  cmpd-odelim          .default:n          = { } ,
-  cmpd-cdelim          .tl_set:N           = \l__chemnum_cmpd_cdelim_tl ,
-  cmpd-cdelim          .default:n          = { } ,
-  cmpd-all             .bool_set:N         = \l__chemnum_cmpd_all_bool ,
-  cmpd-all             .default:n          = true ,
-  cmpd-counter         .choice: ,
-  cmpd-counter         .choice_code:n      =
-    \tl_set_eq:NN \l__chemnum_cmpd_kind_value_tl \l_keys_choice_tl ,
-  cmpd-counter         .generate_choices:n =
-    { arabic , alph , Alph , greek, Greek , roman , Roman , Symbol } ,
-  cmpd-counter         .default:n          = arabic ,
-  hyper-use            .choice: ,
-  hyper-use / true     .code:n             =
-    {
-      \bool_set_true:N \l__chemnum_use_hyperref_bool
-      \bool_set_false:N \l__chemnum_hypertarget_bool
-      \bool_set_false:N \l__chemnum_hyperlink_bool
-    } ,
-  hyper-use / false    .code:n             =
-    {
-      \bool_set_false:N \l__chemnum_use_hyperref_bool
-      \bool_set_false:N \l__chemnum_hypertarget_bool
-      \bool_set_false:N \l__chemnum_hyperlink_bool
-    } ,
-  hyper-use            .default:n          = true ,
-  hyper-target         .code:n             =
-    {
-      \tl_set:Nn \l__chemnum_cmpd_hyper_name_tl { #1 }
-      \bool_set_true:N \l__chemnum_use_hyperref_bool
-      \bool_set_true:N \l__chemnum_hypertarget_bool
-      \bool_set_false:N \l__chemnum_hyperlink_bool
-    } ,
-  hyper-link           .code:n             =
-    {
-      \tl_set:Nn \l__chemnum_cmpd_hyper_name_tl { #1 }
-      \bool_set_true:N \l__chemnum_use_hyperref_bool
-      \bool_set_false:N \l__chemnum_hypertarget_bool
-      \bool_set_true:N \l__chemnum_hyperlink_bool
-    } ,
-  sub-counter          .choice: ,
-  sub-counter          .choice_code:n      =
-    \tl_set_eq:NN \l__chemnum_cmpd_sub_kind_value_tl \l_keys_choice_tl ,
-  sub-counter          .generate_choices:n =
-    { arabic , alph , Alph , greek , Greek , roman , Roman , Symbol } ,
-  sub-counter          .default:n          = alph ,
-  sub-input-sep        .code:n             = \__chemnum_subcmpdsep:n { #1 } ,
-  sub-input-sep        .default:n          = . ,
-  sub-output-sep       .tl_set:N           = \l__chemnum_cmpd_separator_tl ,
-  sub-output-sep       .default:n          = { } ,
-  sublist-input-sep    .tl_set:N           =
-    \l__chemnum_sublist_input_separator_tl ,
-  sublist-input-sep    .default:n          = { , } ,
-  sublist-output-sep   .tl_set:N           =
-    \l__chemnum_sublist_output_separator_tl ,
-  sublist-output-sep   .default:n          = { , } ,
-  sub-only             .bool_set:N         = \l__chemnum_sub_label_only_bool ,
-  sub-only             .default:n          = true ,
-  subrange-output-sep  .tl_set:N           = \l__chemnum_sub_range_sep_tl ,
-  subrange-output-sep  .default:n          = { -- } ,
-  subrange-input-sep   .code:n             =
-    \__chemnum_sublabel_range_marker:n { #1 } ,
-  subrange-input-sep   .default:n          = { .. }
-}
-
-%-----------------------------------------------------------------------------%
-% list separators, delimiters, prefix and suffix
-\bool_new:N \l__chemnum_no_serial_comma_bool
-\bool_set_false:N \l__chemnum_no_serial_comma_bool
-
-\tl_new:N  \l__chemnum_list_input_separator_tl
-\tl_set:Nn \l__chemnum_list_input_separator_tl { , }
-\tl_new:N  \l__chemnum_list_separator_tl
-\tl_set:Nn \l__chemnum_list_separator_tl { , }
-\tl_new:N  \l__chemnum_list_space_tl
-\tl_set:Nn \l__chemnum_list_space_tl { \penalty\@m\  }
-\tl_new:N  \l__chemnum_list_last_separator_lang_tl
-\tl_set:Nn \l__chemnum_list_last_separator_lang_tl { and }
-\tl_new:N  \l__chemnum_list_last_separator_tl
-\tl_set:Nn \l__chemnum_list_last_separator_tl
-  { \tl_use:N \l__chemnum_list_last_separator_lang_tl }
-\tl_new:N  \l__chemnum_list_prefix_tl { }
-\tl_set:Nn \l__chemnum_list_prefix_tl { }
-\tl_new:N  \l__chemnum_list_suffix_tl { }
-\tl_set:Nn \l__chemnum_list_suffix_tl { }
-\tl_new:N  \l__chemnum_list_odelim_tl { }
-\tl_new:N  \l__chemnum_list_cdelim_tl { }
-
-\cs_new_protected:Npn \__chemnum_list_delim:n #1 {
-  \tl_if_blank:nTF { #1 } {
-    \tl_clear:N \l__chemnum_list_odelim_tl
-    \tl_clear:N \l__chemnum_list_cdelim_tl
-  }{
-    \int_compare:nNnTF { \tl_count:n { #1 } } = 2 {
-      \tl_set:Nx \l__chemnum_list_odelim_tl { \tl_head:n { #1 } }
-      \tl_set:Nx \l__chemnum_list_cdelim_tl { \tl_tail:n { #1 } }
-    }{ \msg_error:nnx { chemnum } { delimiters } { list } }
-  }
-}
-
-%-----------------------------------------------------------------------------%
-% property keys for lists
-\keys_define:nn { chemnum } {
-  list-prefix        .tl_set:N   = \l__chemnum_list_prefix_tl ,
-  list-prefix        .default:n  = { } ,
-  list-suffix        .tl_set:N   = \l__chemnum_list_suffix_tl ,
-  list-suffix        .default:n  = { } ,
-  list-delim         .code:n     = \__chemnum_list_delim:n { #1 } ,
-  list-delim         .default:n  = { ( } { ) } ,
-  list-odelim        .tl_set:N   = \l__chemnum_list_odelim_tl ,
-  list-odelim        .default:n  = { } ,
-  list-cdelim        .tl_set:N   = \l__chemnum_list_cdelim_tl ,
-  list-cdelim        .default:n  = { } ,
-  list-space         .tl_set:N   = \l__chemnum_list_space_tl ,
-  list-space         .default:n  = { \penalty\@m\  } ,
-  list-input-sep     .tl_set:N   = \l__chemnum_list_input_separator_tl ,
-  list-input-sep     .default:n  = { , } ,
-  list-output-sep    .tl_set:N   = \l__chemnum_list_separator_tl ,
-  list-output-sep    .default:n  = { , } ,
-  list-last-sep      .tl_set:N   = \l__chemnum_list_last_separator_tl ,
-  list-last-sep      .default:n  = \l__chemnum_list_last_separator_lang_tl ,
-  list-serial-comma  .choice: ,
-  list-serial-comma / true .code:n =
-    \bool_set_false:N \l__chemnum_no_serial_comma_bool ,
-  list-serial-comma / false .code:n =
-    \bool_set_true:N \l__chemnum_no_serial_comma_bool ,
-  list-serial-comma  .default:n  = true ,
-  list-lang          .choice: ,
-  list-lang / US     .code:n     =
-    {
-      \bool_set_false:N \l__chemnum_no_serial_comma_bool
-      \tl_set:Nn \l__chemnum_list_last_separator_lang_tl { and }
-    } ,
-  list-lang / GB     .code:n     =
-    {
-      \bool_set_true:N \l__chemnum_no_serial_comma_bool
-      \tl_set:Nn \l__chemnum_list_last_separator_lang_tl { and }
-    } ,
-  list-lang / DE     .code:n     =
-    {
-      \bool_set_true:N \l__chemnum_no_serial_comma_bool
-      \tl_set:Nn \l__chemnum_list_last_separator_lang_tl { und }
-    } ,
-  list-lang / FR     .code:n     =
-    {
-      \bool_set_true:N \l__chemnum_no_serial_comma_bool
-      \tl_set:Nn \l__chemnum_list_last_separator_lang_tl { et }
-    } ,
-  list-lang / IT     .code:n     =
-    {
-      \bool_set_true:N \l__chemnum_no_serial_comma_bool
-      \tl_set:Nn \l__chemnum_list_last_separator_lang_tl { e }
-    } ,
-  list-lang / ES     .code:n     =
-    {
-      \bool_set_true:N \l__chemnum_no_serial_comma_bool
-      \tl_set:Nn \l__chemnum_list_last_separator_lang_tl { y }
-    } ,
-  list-lang          .default:n  = US
-}
-
-%-----------------------------------------------------------------------------%
-% label and sublabel declaration
-\cs_new_protected:Npn \__chemnum_cmpd_declare:n #1
-  {
-    \cs_if_exist:cF { chemnum_cmpd_#1: }
-      {
-        \int_gincr:N \g__chemnum_cmpd_main_int
-        \prop_gput:Nnx \g__chemnum_label_prop
-          { #1 }
-          { \int_use:N \g__chemnum_cmpd_main_int }
-        \chemnum_cmpd_save:n { #1 }
-        \bool_if:NF \l__chemnum_cmpd_name_bool
-          { \int_gincr:N \g__chemnum_cmpd_int }
-        \cs_new:cpx { chemnum_cmpd_#1: } {
-          \bool_if:NTF \l__chemnum_cmpd_name_bool
-            { \l__chemnum_cmpd_name_tl }
+% #1: main ID
+% #2: sub ID
+\cs_new_protected:Npn \chemnum_subcompound_update_properties:nn #1#2
+  {
+    \seq_map_inline:cn { g__chemnum_compound_#1_#2_properties_seq }
+      { \chemnum_subcompound_update_property:nnn {#1} {#2} {##1} }
+  }
+
+% #1: ID
+% #2: property
+\cs_new_protected:Npn \chemnum_get_compound_property:nn #1#2
+  { \chemnum_get_compound_property_or:nnn {#1} {#2} { } }
+
+\cs_new_protected:Npn \chemnum_get_compound_property_or:nnn #1#2#3
+  {
+    \prop_get:cnNTF { g__chemnum_compound_#1_prop } {#2}
+      \l__chemnum_tmpa_tl
+      { \tl_use:N \l__chemnum_tmpa_tl }
+      {#3}
+  }
+
+\cs_new:Npn \chemnum_expandable_get_compound_property:nn #1#2
+  { \prop_get:cn { g__chemnum_compound_#1_prop } {#2} }
+\cs_generate_variant:Nn \chemnum_expandable_get_compound_property:nn { V }
+
+% #1: main ID
+% #2: sub ID
+% #3: property
+\cs_new_protected:Npn \chemnum_get_subcompound_property:nnn #1#2#3
+  { \chemnum_get_subcompound_property_or:nnnn {#1} {#2} {#3} { } }
+
+\cs_new_protected:Npn \chemnum_get_subcompound_property_or:nnnn #1#2#3#4
+  {
+    \prop_get:cnNTF { g__chemnum_compound_#1_#2_properties_prop } {#3}
+      \l__chemnum_tmpa_tl
+      { \tl_use:N \l__chemnum_tmpa_tl }
+      {#4}
+  }
+
+\cs_new:Npn \chemnum_expandable_get_subcompound_property:nnn #1#2#3
+  { \prop_get:cn { g__chemnum_compound_#1_#2_properties_prop } {#3} }
+
+% ----------------------------------------------------------------------------
+\DeclareExpandableDocumentCommand \cmpdproperty { mm }
+  { \chemnum_expandable_get_compound_property:nn {#1} {#2} }
+
+\DeclareExpandableDocumentCommand \subcmpdproperty { mmm }
+  { \chemnum_expandable_get_subcompound_property:nnn {#1} {#2} {#3} }
+
+% ----------------------------------------------------------------------------
+% initiating subcompounds:
+
+% #1: main ID
+% #2: sub ID
+\cs_new_protected:Npn \chemnum_initiate_subcompound:nn #1#2
+  {
+    \chemnum_subcompound_if_initiated:nnF {#1} {#2}
+      { \seq_gput_right:cn { g__chemnum_#1_initiated_subcompounds_seq } {#2} }
+  }
+
+% ----------------------------------------------------------------------------
+
+% saving compounds to the auxilliary file:
+% #1: ID
+% #2: counter value
+% #3: counter representation
+% #4: pre label
+% #5: post label
+% #6: pre main label
+% #7: post main label
+% #8: label format
+\cs_new_protected:Npn \__chemnum_write_compound_to_auxfile:nnnnnnnn #1#2#3#4#5#6#7#8
+  {
+    \if@filesw
+      \token_if_eq_meaning:NNT \@nodocument \relax
+        {
+          \iow_now:Nx \@auxout
             {
-              \__chemnum_cmpd_kind:nn
-                \l__chemnum_cmpd_kind_value_tl
-                \g__chemnum_cmpd_int
+              \exp_not:N \chemnum@cmpd{#1}{#2}{#3}
+              \exp_not:n { {#4}{#5}{#6}{#7}{#8} }
             }
         }
-      }
+    \fi
   }
+\cs_generate_variant:Nn \__chemnum_write_compound_to_auxfile:nnnnnnnn { nnnVVVVV }
 
-\cs_new_protected:Npn \__chemnum_cmpd_sub_declare:nn #1#2
+% #1: main ID
+% #2: sub ID
+% #2: counter value
+% #3: counter representation
+\cs_new_protected:Npn \__chemnum_write_subcompound_to_auxfile:nnnn #1#2#3#4
   {
-    \cs_if_exist:cF { chemnum_cmpd_#1_#2: }
-      {
-        \chemnum_cmpd_save:n { #1 _ #2 }
-        \cs_new:cpx { chemnum_cmpd_#1_#2: } { }
-        \int_gincr:c { g_chemnum_cmpd_#1_int }
-        % why is the next line working when \cs_gset:cpx doesn't?
-        % (in case ":" is part of #1)
-        \exp_after:wN \cs_gset:Npx \cs:w chemnum_cmpd_#1_#2: \cs_end:
-          {
-            \__chemnum_cmpd_sub_kind:Nc
-              \l__chemnum_cmpd_sub_kind_value_tl
-              { g_chemnum_cmpd_#1_int }
-          }
-        \int_compare:nT { \int_use:c { g_chemnum_cmpd_#1_int } = 1 }
-          {
-            \cs_gset_eq:cc { chemnum_cmpd_#1_min: } { chemnum_cmpd_#1_#2: }
-          }
-        \cs_gset_eq:cc { chemnum_cmpd_#1_max: } { chemnum_cmpd_#1_#2: }
-      }
+    \if@filesw
+      \token_if_eq_meaning:NNT \@nodocument \relax
+        {
+          \iow_now:Nx \@auxout
+            { \exp_not:N \chemnum@subcmpd{#1}{#2}{#3}{#4} }
+        }
+    \fi
+  }
+
+% ----------------------------------------------------------------------------
+% #1: ID
+% #2: counter value
+% #3: counter representation
+% #4: pre label
+% #5: post label
+% #6: pre main label
+% #7: post main label
+% #8: label format
+\cs_new_protected:Npn \chemnum@cmpd #1#2#3#4#5#6#7#8
+  {
+    \prop_if_exist:cF { g__chemnum_compound_#1_prop }
+      { \prop_new:c { g__chemnum_compound_#1_prop } }
+    \prop_gput:cnn { g__chemnum_compound_#1_prop }
+      {previous-number} {#2}
+    \prop_gput:cnn { g__chemnum_compound_#1_prop }
+      {previous-counter-representation} {#3}
+    \prop_gput:cnn { g__chemnum_compound_#1_prop }
+      {previous-pre-label-code} {#4}
+    \prop_gput:cnn { g__chemnum_compound_#1_prop }
+      {previous-post-label-code} {#5}
+    \prop_gput:cnn { g__chemnum_compound_#1_prop }
+      {previous-pre-main-label-code} {#6}
+    \prop_gput:cnn { g__chemnum_compound_#1_prop }
+      {previous-post-main-label-code} {#7}
+    \prop_gput:cnn { g__chemnum_compound_#1_prop }
+      {previous-label-format} {#8}
+  }
+
+% #1: main ID
+% #2: sub ID
+% #3: counter value
+% #4: counter representation
+\cs_new_protected:Npn \chemnum@subcmpd #1#2#3#4
+  {
+    \prop_if_exist:cF { g__chemnum_compound_#1_#2_properties_prop }
+      { \prop_new:c { g__chemnum_compound_#1_#2_properties_prop } }
+    \prop_gput:cnn { g__chemnum_compound_#1_#2_properties_prop }
+      {previous-number} {#3}
+    \prop_gput:cnn { g__chemnum_compound_#1_#2_properties_prop }
+      {previous-counter-representation} {#4}
   }
-\cs_generate_variant:Nn \__chemnum_cmpd_sub_declare:nn { no }
 
-\cs_new_protected:Npn \__chemnum_cmpd_sub_initiate:nn #1#2
+% ----------------------------------------------------------------------------
+% declaring and writing compounds:
+
+% #1: options
+% #2: ID
+\cs_new_protected:Npn \chemnum_declare_compound:nn #1#2
   {
-    \cs_if_exist:cF { chemnum_cmpd_ #1 _ #2 _init: }
+    \tl_if_blank:nF {#1}
+      { \keys_set_groups:nnn {chemnum} {compound} { local=true , #1 } }
+    \chemnum_compound_if_initiated:nF {#2}
       {
-        \bool_if:NTF \l__chemnum_cmpd_init_strict_bool
-          {
-            \msg_error:nnx   { chemnum } { cmpd-init-sub }
-              { #1 \l__chemnum_cmpd_labelsep_tl #2 }
-          }
+        \bool_if:NT \g__chemnum_initiate_bool
           {
-            \msg_warning:nnx { chemnum } { cmpd-init-sub }
-               { #1 \l__chemnum_cmpd_labelsep_tl #2 }
+            \bool_if:NTF \g__chemnum_initiate_strict_bool
+              { \msg_error:nnn   {chemnum} {compound-not-initiated} {#2} }
+              { \msg_warning:nnn {chemnum} {compound-not-initiated} {#2} }
           }
+        \bool_if:NT \l__chemnum_show_def_bool
+          { \cmpdshowdef { #2 } }
+        \bool_set_false:N \l__chemnum_show_ref_bool
+        \chemnum_initiate_compound:n {#2}
       }
+    \chemnum_compound_if_defined:nTF {#2}
+      { \chemnum_set_compound:n {#2} }
+      { \chemnum_define_compound:n {#2} }
   }
 
-%-----------------------------------------------------------------------------%
-% label and sublabel initiation
-\cs_new_protected:Npn \__chemnum_cmpd_initiate:nn #1#2
+% #1: options
+% #2: main ID
+% #3: sub ID
+\cs_new_protected:Npn \chemnum_declare_subcompound:nnn #1#2#3
   {
-    \cs_if_exist:cTF { chemnum_cmpd_#1_init: }
+    % \keys_set:nn {chemnum} {#1}
+    \chemnum_subcompound_if_initiated:nnF {#2} {#3}
       {
-        \bool_if:NT \l__chemnum_cmpd_sub_init_bool
+        \bool_if:NT \g__chemnum_initiate_sub_bool
           {
-            \tl_if_blank:nF { #2 }
+            \bool_if:NTF \g__chemnum_initiate_strict_bool
               {
-                \__chemnum_cmpd_sublist:n { #2 }
-                \tl_map_inline:Nn  \l__chemnum_cmpd_sublist_tl
-                  {
-                    \__chemnum_cmpd_subrange_separate:n { ##1 }
-                    \__chemnum_cmpd_sub_initiate:nn { #1 } { \l__chemnum_tmpb_tl }
-                    \tl_if_blank:VF \l__chemnum_tmpc_tl
-                      { \__chemnum_cmpd_sub_initiate:nn { #1 } { \l__chemnum_tmpc_tl } }
-                  }
+                \msg_error:nnnn {chemnum} {subcompound-not-initiated}
+                  {#2} {#3}
+              }
+              {
+                \msg_warning:nnnn {chemnum} {subcompound-not-initiated}
+                  {#2} {#3}
               }
           }
+        \bool_if:NT \l__chemnum_show_def_bool
+          { \subcmpdshowdef { #2 } { #3 } }
+        \bool_set_false:N \l__chemnum_show_ref_bool
+        \chemnum_initiate_subcompound:nn {#2} {#3}
       }
+    \chemnum_subcompound_if_defined:nnF {#2} {#3}
+      { \chemnum_define_subcompound:nn {#2} {#3} }
+  }
+
+\cs_new_protected:Npn \chemnum_compound_start:n #1
+  {
+    \bool_if:NF \l__chemnum_sub_only_bool
+      { \chemnum_get_compound_property:nn {#1} {pre-label-code} }
+  }
+
+\cs_new:Npn \chemnum_expandable_compound_start:n #1
+  {
+    \bool_if:NF \l__chemnum_sub_only_bool
       {
-        \bool_if:NTF \l__chemnum_cmpd_init_strict_bool
-          { \msg_error:nnx { chemnum } { cmpd-init } { #1 } }
-          { \msg_warning:nnx { chemnum } { cmpd-init } { #1 } }
+        \chemnum_expandable_get_compound_property:nn {#1}
+          {previous-pre-label-code}
       }
   }
 
-%-----------------------------------------------------------------------------%
-% sub label separator
-% error message if no separator is chosen
-\msg_set:nnnn { chemnum } { sub-label-separator }
+\cs_new_protected:Npn \chemnum_compound_finish:n #1
   {
-    Missing~separator~token~as~value~for~the~key~sub-cmpd-sep \c_space_tl
-    \msg_line_context: !
+    \bool_if:NF \l__chemnum_sub_only_bool
+      { \chemnum_get_compound_property:nn {#1} {post-label-code} }
   }
+
+\cs_new:Npn \chemnum_expandable_compound_finish:n #1
   {
-    You~used~the~key~sub-cmpd-sep \c_space_tl \msg_line_context: ~but~left~the~
-    argument~empty.\\
-    This~can't~work.~Please~select~a~token~as~separator.
+    \bool_if:NF \l__chemnum_sub_only_bool
+      {
+        \chemnum_expandable_get_compound_property:nn {#1}
+          {previous-post-label-code}
+      }
   }
 
-%-----------------------------------------------------------------------------%
-% variables
-
-\tl_new:N \l__chemnum_cmpd_main_label_tl
-\tl_new:N \l__chemnum_cmpd_sub_label_tl
-\tl_new:N \l__chemnum_labelsep_tmp_tl
+% actively write a compound:
+% #1: ID
+\cs_new_protected:Npn \chemnum_compound_write:n #1
+  {
+    \chemnum_get_compound_property:nn {#1} {pre-main-label-code}
+    \group_begin:
+      \bool_if:NTF \l__chemnum_compound_local_bool
+        { \l__chemnum_local_label_format_tl }
+        { \chemnum_get_compound_property:nn {#1} {label-format} }
+      { \chemnum_get_compound_property:nn {#1} {counter-representation} }
+    \group_end:
+    \chemnum_get_compound_property:nn {#1} {post-main-label-code}
+  }
 
-% set sublabel-separator
-\cs_new_protected:Npn \__chemnum_subcmpdsep:n #1 {
-  \tl_if_blank:nTF { #1 }
-    { \msg_error:nn { chemnum } { sub-label-separator } }
-    { \tl_set:Nn \l__chemnum_cmpd_labelsep_tl { #1 } }
-}
+% actively write a subcompound:
+% #1: main ID
+% #2: sub ID
+\cs_new_protected:Npn \chemnum_subcompound_write:nn #1#2
+  {
+    \group_begin:
+      \bool_if:NTF \l__chemnum_compound_local_bool
+        { \l__chemnum_local_label_format_tl }
+        { \chemnum_get_compound_property:nn {#1} {label-format} }
+      {
+        \chemnum_get_subcompound_property:nnn {#1} {#2}
+          {counter-representation}
+      }
+    \group_end:
+  }
 
-\cs_new_protected:Npn \__chemnum_sublabel_range_marker:n #1 {
-  \tl_if_blank:nTF { #1 }
-    { \msg_error:nn { chemnum } { sub-label-range_sep } }
-    { \tl_set:Nn \l__chemnum_sublabel_range_marker_tl { #1 } }
-}
+% this is only provided for use in PDF strings:
+\cs_new:Npn \chemnum_expandable_compound_write:n #1
+  {
+    \chemnum_expandable_get_compound_property:nn {#1} {pre-main-label-code}
+    \chemnum_expandable_get_compound_property:nn {#1} {counter-representation}
+    \chemnum_expandable_get_compound_property:nn {#1} {post-main-label-code}
+  }
 
-% actual separating
-\cs_new_protected:Npn \__chemnum_cmpd_labelsep:n #1 \q_stop {
-  \tl_clear:N \l__chemnum_labelsep_tmp_tl
-  \tl_if_in:oVTF { #1 } \l__chemnum_cmpd_labelsep_tl
-    { 
-      \tl_set:Nn \l__chemnum_labelsep_tmp_tl { #1 }
-      \tl_replace_once:NVn \l__chemnum_labelsep_tmp_tl
-        \l__chemnum_cmpd_labelsep_tl
-        { \q_nil }
-      \exp_after:wN \__chemnum_cmpd_labelsep_aux_ii:n
-        \l__chemnum_labelsep_tmp_tl \q_stop
-    }
-    { \__chemnum_cmpd_labelsep_aux_i:n { #1 } }
-}
-\cs_generate_variant:Nn \tl_if_in:nnTF       { oV }
-\cs_generate_variant:Nn \tl_replace_once:Nnn { NV }
+\cs_new:Npn \chemnum_expandable_subcompound_write:nn #1#2
+  {
+    \chemnum_expandable_get_subcompound_property:nnn {#1} {#2}
+      {counter-representation}
+  }
 
-\cs_new_protected:Npn \__chemnum_cmpd_labelsep_aux_i:n #1
+% read and write saved values:
+% #1: ID
+\cs_new_protected:Npn \chemnum_compound_read:n #1
   {
-    \tl_set:Nn \l__chemnum_cmpd_main_label_tl { #1 }
-    \tl_clear:N \l__chemnum_cmpd_sub_label_tl
+    \chemnum_get_compound_property:nn {#1} {previous-pre-main-label-code}
+    \group_begin:
+      \chemnum_get_compound_property:nn {#1} {previous-label-format}
+      {
+        \chemnum_get_compound_property_or:nnn {#1}
+          { previous-counter-representation }
+          { ?? \__chemnum_rerun: }
+      }
+    \group_end:
+    \chemnum_get_compound_property:nn {#1} {previous-post-main-label-code}
+    
   }
 
-\cs_new_protected:Npn \__chemnum_cmpd_labelsep_aux_ii:n #1 \q_nil #2 \q_stop
+% #1: main ID
+% #2: sub ID
+\cs_new_protected:Npn \chemnum_subcompound_read:nn #1#2
   {
-    \tl_set:Nn \l__chemnum_cmpd_main_label_tl { #1 }
-    \tl_set:Nn \l__chemnum_cmpd_sub_label_tl { #2 }
+    \group_begin:
+      \bool_if:NTF \l__chemnum_compound_local_bool
+        { \l__chemnum_local_label_format_tl }
+        { \chemnum_get_compound_property:nn {#1} {previous-label-format} }
+      {
+        \chemnum_get_subcompound_property_or:nnnn {#1} {#2}
+          {previous-counter-representation}
+          { ?? \__chemnum_rerun: }
+      }
+    \group_end:
   }
 
-% sublabel separating to display a list and/or range
-\tl_new:N \l__chemnum_cmpd_sublist_tl
-\int_new:N \l__chemnum_cmpd_sublist_length_int
+% this is only provided for use in PDF strings:
+\cs_new:Npn \chemnum_expandable_compound_read:n #1
+  {
+    \chemnum_expandable_get_compound_property:nn {#1} {previous-pre-main-label-code}
+    \chemnum_expandable_get_compound_property:nn {#1} {previous-counter-representation}
+    \chemnum_expandable_get_compound_property:nn {#1} {previous-post-main-label-code}
+  }
 
-\NewDocumentCommand \__chemnum_cmpd_sublist:n
-  { > { \exp_args:No \SplitList { \l__chemnum_sublist_input_separator_tl } } m }
+\cs_new:Npn \chemnum_expandable_subcompound_read:nn #1#2
   {
-    \tl_set:Nn \l__chemnum_cmpd_sublist_tl { #1 }
-    \int_zero:N \l__chemnum_cmpd_sublist_length_int
-    \tl_map_inline:Nn \l__chemnum_cmpd_sublist_tl
-      { \int_incr:N \l__chemnum_cmpd_sublist_length_int }
+    \chemnum_expandable_get_subcompound_property:nnn {#1} {#2}
+      {previous-counter-representation}
   }
 
-\cs_new_protected:Npn \__chemnum_cmpd_subrange_separate:n #1
+% #1: boolean: if true register compound but don't write the label
+% #2: boolean: if true only read compound
+% #3: write == true and read == false
+% #4: write == true and read == true
+\cs_new:Npn \chemnum_if_write_and_or_read:NNTF #1#2
   {
-    \tl_clear:N \l__chemnum_tmpb_tl
-    \tl_clear:N \l__chemnum_tmpc_tl
-    \tl_if_in:noTF { #1 } { \l__chemnum_sublabel_range_marker_tl }
+    \bool_if:NTF #1
+      { \use_none:nn }
       {
-        \tl_set:Nn \l__chemnum_tmpb_tl { #1 }
-        \tl_replace_once:NVn \l__chemnum_tmpb_tl
-          \l__chemnum_sublabel_range_marker_tl
-          { \q_nil }
-        \exp_after:wN \__chemnum_cmpd_subrange_separate_aux:w \l__chemnum_tmpb_tl \q_stop
+        \bool_if:NTF #2
+          { \use_ii:nn }
+          { \use_i:nn }
       }
-      { \tl_set:Nn \l__chemnum_tmpb_tl { #1 } }
   }
 
-\cs_new_protected:Npn \__chemnum_cmpd_subrange_separate_aux:w #1 \q_nil #2 \q_stop
+% write a label from the entries of \cmpd:
+% #1: boolean: if true register compound but don't write the label
+% #2: boolean: if true only read compound
+% #3: options
+% #4: label specifications
+\cs_new_protected:Npn \chemnum_single_compound:NNnn #1#2#3#4
   {
-    \tl_set:Nn \l__chemnum_tmpb_tl { #1 }
-    \tl_set:Nn \l__chemnum_tmpc_tl { #2 }
+    \bool_if:NT #1 { \@bsphack }
+    \group_begin:
+      \chemnum_split_sub_from_main:VNNnn
+        \l__chemnum_compound_separator_tl
+        #1 #2 {#3} {#4}
+    \group_end:
+    \bool_if:NT {#1} { \@esphack }
   }
 
-%-----------------------------------------------------------------------------%
-% print compound label
-\cs_new_protected:Npn \__chemnum_cmpd_print:n #1
+% #1: label separator
+% #2: boolean: if true register compound but don't write the label
+% #3: boolean: if true only read compound
+% #4: options
+% #5: label spec
+\cs_new_protected:Npn \chemnum_split_sub_from_main:nNNnn #1#2#3#4#5
+  {
+    \cs_set:Npn \__chemnum_split_sub_from_main_aux:nnnw ##1##2##3##4#1##5#1##6 \q_stop
+      {
+        \bool_if:NF ##2 { \chemnum_declare_compound:nn {##3} {##4} }
+        \keys_set_groups:nnn {chemnum} {sub-only} {#4} 
+        \chemnum_if_write_and_or_read:NNTF #2 #3
+          { \chemnum_compound_start:n {##4} }
+          { \chemnum_expandable_compound_start:n {##4} }
+        % shis is in the compound_write command:
+        \chemnum_write_main:nnnn {##1} {##2} {##3} {##4}
+        \bool_if:nT
+          {
+            !\l__chemnum_sub_all_bool &&
+            !\tl_if_blank_p:n {##5}
+          }
+          { \chemnum_write_sublist:NNnnn ##1 ##2 {##3} {##4} {##5} }
+        \bool_if:NT \l__chemnum_sub_all_bool
+          {
+            \tl_clear:N \l__chemnum_tmpa_tl
+            \tl_set:Nx \l__chemnum_tmpa_tl
+              { \seq_use:cn { g__chemnum_compound_##4_subcompounds_seq } { , } }
+            \tl_if_blank:VF \l__chemnum_tmpa_tl
+              {
+                \chemnum_write_sublist:NNnnV ##1 ##2 {##3} {##4}
+                  \l__chemnum_tmpa_tl
+              }
+          }
+        \chemnum_if_write_and_or_read:NNTF #2 #3
+          { \chemnum_compound_finish:n {##4} }
+          { \chemnum_expandable_compound_finish:n {##4} }
+      }
+    \__chemnum_split_sub_from_main_aux:nnnw {#2} {#3} {#4} #5#1#1 \q_stop
+  }
+\cs_generate_variant:Nn \chemnum_split_sub_from_main:nNNnn { V }
+
+\cs_new:Npn \__chemnum_split_sub_from_main_aux:nnnw #1#2#3#4.#5.#6 \q_stop {}
+
+% \chemnum_write_main:nnnn will write the main label, either with saved
+% values (+ variant, boolean #2=true), or only register it (* variant, boolean
+% #1=true)
+% 
+% #1: boolean: if true register compound but don't write the label
+% #2: boolean: if true only read compound
+% #3: options
+% #4: label spec
+\cs_new_protected:Npn \chemnum_write_main:nnnn #1#2#3#4
   {
-    \tl_if_blank:VF \l__chemnum_cmpd_prefix_tl
+    \bool_if:NTF #2
       {
-        \tl_use:N \l__chemnum_cmpd_prefix_tl
-        \tl_use:N \l__chemnum_cmpd_space_tl
+        \chemnum_compound_read:n {#4}
+        \bool_if:NT #1
+          { \msg_error:nn {chemnum} { erroneous-argument-combination } }
       }
-    \tl_use:N \l__chemnum_cmpd_odelim_tl
-    \__chemnum_cmpd_use_style:n { #1 }
-    \tl_use:N \l__chemnum_cmpd_cdelim_tl
-    \tl_if_blank:VF \l__chemnum_cmpd_suffix_tl
       {
-        \tl_use:N \l__chemnum_cmpd_space_tl
-        \tl_use:N \l__chemnum_cmpd_suffix_tl
+        \bool_if:NT \l__chemnum_show_ref_bool
+          { \cmpdshowref { #4 } }
+        \bool_if:nF
+          { #1 || \l__chemnum_sub_only_bool }
+          { \chemnum_compound_write:n {#4} }
       }
   }
 
-%-----------------------------------------------------------------------------%
-% main internal compound label command
-% #1: <main label> #2: <sub label> #3: <invisible> #4: <no delim>
-% #2 may be a list of sublabels
-\cs_new_protected:Npn \__chemnum_cmpd_aux:nnnn #1#2#3#4
+% ----------------------------------------------------------------------------
+\cs_set_protected:Npn \chemnum_show_key_def:n #1
+  { \marginpar { \fbox { \normalfont \ttfamily #1 } } }
+
+\cs_set_protected:Npn \chemnum_show_key_ref:n #1
+  {
+    \group_begin:
+      \hbox_unpack:N \c_empty_box % this is \leavevmode
+      \vbox_to_zero:n
+        {
+          \tex_vss:D
+          \hbox_overlap_right:n
+            {
+              \tex_vrule:D \tex_raise:D .75em
+              \hbox:n
+                { \underbar { \normalfont \footnotesize \ttfamily #1 } }
+            }
+        }
+    \group_end:
+  }
+
+% ----------------------------------------------------------------------------
+\NewDocumentCommand \chemnumshowdef { m }
+  { \chemnum_show_key_def:n { #1 } }
+\NewDocumentCommand \chemnumshowref { m }
+  { \chemnum_show_key_ref:n { #1 } }
+
+\NewDocumentCommand \cmpdshowdef { m } { \chemnumshowdef { #1 } }
+\NewDocumentCommand \cmpdshowref { m } { \chemnumshowref { #1 } }
+\NewDocumentCommand \subcmpdshowdef { mm } { \chemnumshowdef { #2~(#1) } }
+\NewDocumentCommand \subcmpdshowref { mm } { \chemnumshowref { #2 } }
+
+% ----------------------------------------------------------------------------
+% #1: boolean: if true register compound but don't write the label
+% #2: boolean: if true only read compound
+% #3: options
+% #4: main label id
+% #5: sublabel list
+\cs_new_protected:Npn \chemnum_write_sublist:NNnnn #1#2#3#4#5
+  {
+    \seq_set_split:NVn
+      \l__chemnum_tmpc_seq
+      \l__chemnum_sub_separator_tl
+      {#5}
+    \seq_remove_duplicates:N \l__chemnum_tmpc_seq
+    \seq_map_inline:Nn \l__chemnum_tmpc_seq
+      {
+        \bool_if:NF #2
+          { \chemnum_declare_subcompound:nnn {#3} {#4} {##1} }
+      }
+    \seq_clear:N \l__chemnum_tmpd_seq
+    % puts the subcompounds ready to be printed in \l__chemnum_tmpd_seq :
+    \chemnum_sort_subcompounds:NNNnnNN #1#2
+      \l__chemnum_tmpc_seq
+      {#3}
+      {#4}
+      \l__chemnum_tmpd_seq % to write the uncompressed list
+      \l__chemnum_tmpe_seq % for compressing the list, holds the numbers
+    \bool_if:nTF
+      {
+        \l__chemnum_compress_subcompounds_bool
+        &&
+        \int_compare_p:n { \seq_count:N \l__chemnum_tmpe_seq > 2 }
+      }
+      {
+        % needs a seq with the associated /numbers/!
+        \chemnum_compress_subcompounds:NNN
+          \l__chemnum_tmpd_seq % holds the IDs
+          \l__chemnum_tmpe_seq % holds the numbers
+          \l__chemnum_tmpc_seq % the new sequence
+        \seq_use:Nn \l__chemnum_tmpc_seq {}
+      }
+      {
+        \seq_use:NVVV \l__chemnum_tmpd_seq
+          \l__chemnum_sep_sublist_two_tl
+          \l__chemnum_sep_sublist_more_tl
+          \l__chemnum_sep_sublist_last_two_tl
+      }
+  }
+\cs_generate_variant:Nn \chemnum_write_sublist:NNnnn { NNnnV }
+
+% #1: boolean: if true register compound but don't write the label
+% #2: boolean: if true only read compound
+% #3: options
+% #4: main ID
+% #5: sub ID
+\cs_new_protected:Npn \chemnum_write_subcompound:NNnnn #1#2#3#4#5
+  {
+    \bool_if:NTF #2
+      { \chemnum_subcompound_read:nn {#4} {#5} }
+      {
+        \chemnum_declare_subcompound:nnn {#3} {#4} {#5}
+        \bool_if:NT \l__chemnum_show_ref_bool
+          { \subcmpdshowref { #4 } { #5 } }
+        \bool_if:NF #1
+          { \chemnum_subcompound_write:nn {#4} {#5} }
+      }
+  }
+\cs_generate_variant:Nn \chemnum_write_subcompound:NNnnn { NNnnV }
+
+%%% The following command sorts the sequence according to the order in which
+%%% they've been declared
+% #1: boolean: if true register compound but don't write the label
+% #2: boolean: if true only read compound
+% #3: sub ID sequence
+% #4: options
+% #5: main ID
+% #6: seq variable
+% #7: seq variable
+\cs_new_protected:Npn \chemnum_sort_subcompounds:NNNnnNN #1#2#3#4#5#6#7
   {
-    \bool_if:NT \l__chemnum_cmpd_initiated_bool
-      { \__chemnum_cmpd_initiate:nn { #1 } { #2 } }
-    \bool_if:NF \l__chemnum_cmpd_ref_bool
-      { \__chemnum_cmpd_declare:n { #1 } }
-    \__chemnum_hyperref:nnn { #1 } { #2 } { #3 }
-    \tl_if_blank:nF { #2 }
+    \seq_clear:N #6
+    \seq_clear:N #7
+    \bool_if:NF #1
       {
-        \cs_if_exist:cF { g_chemnum_cmpd_#1_int }
-          { \int_new:c { g_chemnum_cmpd_#1_int } }
-        \__chemnum_cmpd_sublist:n { #2 }
-        \bool_if:NF \l__chemnum_cmpd_ref_bool
+        \seq_map_inline:cn { g__chemnum_compound_#5_subcompounds_seq }
           {
-            \tl_map_inline:Nn \l__chemnum_cmpd_sublist_tl
+            \seq_if_in:NnT #3 {##1}
               {
-                \__chemnum_cmpd_subrange_separate:n { ##1 }
-                \__chemnum_cmpd_sub_declare:no { #1 } { \l__chemnum_tmpb_tl }
-                \tl_if_blank:VF \l__chemnum_tmpc_tl
-                  { \__chemnum_cmpd_sub_declare:no { #1 } { \l__chemnum_tmpc_tl } }
+                \seq_put_right:Nn #6
+                  { \chemnum_write_subcompound:NNnnn #1 #2 {#4} {#5} {##1} }
+                \seq_put_right:Nx #7
+                  {
+                    \chemnum_expandable_get_subcompound_property:nnn
+                      { #5 } { ##1 } { number }
+                  }
               }
           }
       }
-    \bool_if:NTF #3
-      { \mode_if_horizontal:T { \tex_unskip:D } }
-      { 
-        \bool_if:NT #4
+  }
+
+% #1: sub ID sequence
+% #2: sub ID sequence that holds the numbers rather than the IDs
+% #3: seq variable
+\cs_new_protected:Npn \chemnum_compress_subcompounds:NNN #1#2#3
+  {
+    \int_zero:N \l__chemnum_tmpa_int
+    \int_zero:N \l__chemnum_tmpb_int
+    \seq_clear:N \l__chemnum_tmpa_seq
+    \seq_clear:N #3
+    \seq_map_inline:Nn #2
+      {
+        \int_incr:N \l__chemnum_tmpa_int
+        \int_compare:nTF { \l__chemnum_tmpa_int = 1 }
+          { \seq_put_right:Nn \l__chemnum_tmpa_seq { 1 } }
+          {
+            \seq_put_right:Nx \l__chemnum_tmpa_seq
+              { \int_eval:n { ##1 - \l__chemnum_tmpb_int } }
+          }
+        \int_set:Nn \l__chemnum_tmpb_int { ##1 }
+      }
+    \int_zero:N \l__chemnum_tmpa_int
+    \int_set:Nn \l__chemnum_tmpb_int { \seq_count:N #2 }
+    \int_zero:N \l__chemnum_tmpc_int
+    \seq_map_inline:Nn \l__chemnum_tmpa_seq
+      {
+        \int_incr:N \l__chemnum_tmpa_int
+        \int_compare:nTF { \l__chemnum_tmpa_int = 1 }
           {
-            \tl_clear:N \l__chemnum_cmpd_odelim_tl
-            \tl_clear:N \l__chemnum_cmpd_cdelim_tl
+            \int_add:Nn \l__chemnum_tmpc_int { ##1 }
+            \seq_put_right:Nx #3 { \seq_item:Nn #1 { 1 } }
           }
-        \__chemnum_make_hyper:nn { \l__chemnum_cmpd_hyper_name_tl }
           {
-            \__chemnum_cmpd_print:n
+            \int_compare:nTF { ##1 = 1 }
+              { \int_add:Nn \l__chemnum_tmpc_int { ##1 } }
               {
-                \bool_if:NF \l__chemnum_sub_label_only_bool
+                \int_compare:nTF { \l__chemnum_tmpc_int > 2 }
                   {
-                    \bool_if:NTF \l__chemnum_cmpd_ref_bool
-                      { \use:c { chemnum_cmpd_ #1 _ref: } }
-                      { \use:c { chemnum_cmpd_ #1 : } }
+                    \seq_put_right:NV #3 \l__chemnum_sep_sublist_range_tl
+                    \seq_put_right:Nx #3
+                      { \seq_item:Nn #1 { \l__chemnum_tmpa_int - 1 } }
+                    \seq_put_right:NV #3 \l__chemnum_sep_sublist_two_tl
+                    \seq_put_right:Nx #3
+                      { \seq_item:Nn #1 { \l__chemnum_tmpa_int } }
                   }
-                \bool_if:NTF \l__chemnum_cmpd_all_bool
                   {
-                    \tl_use:N \l__chemnum_cmpd_separator_tl
-                    \use:c { chemnum_cmpd_ #1 _min_ref: }
-                    \cs_if_eq:ccF
-                      { chemnum_cmpd_ #1 _min_ref: }
-                      { chemnum_cmpd_ #1 _max_ref: }
+                    \seq_get_right:NN #3 \l__chemnum_tmpa_tl
+                    \tl_if_eq:VxF
+                      \l__chemnum_tmpa_tl
+                      { \seq_item:Nn #1 { \l__chemnum_tmpa_int - 1 } }
                       {
-                        \tl_use:N \l__chemnum_sub_range_sep_tl
-                        \use:c { chemnum_cmpd_ #1 _max_ref: }
+                        \seq_put_right:NV #3 \l__chemnum_sep_sublist_two_tl
+                        \seq_put_right:Nx #3
+                          { \seq_item:Nn #1 { \l__chemnum_tmpa_int - 1 } }
                       }
+                    \seq_put_right:NV #3 \l__chemnum_sep_sublist_two_tl
+                    \seq_put_right:Nx #3
+                      { \seq_item:Nn #1 { \l__chemnum_tmpa_int } }
                   }
+                \int_set:Nn \l__chemnum_tmpc_int { 1 }
+              }
+            \int_compare:nT { \l__chemnum_tmpa_int = \l__chemnum_tmpb_int }
+              {
+                \seq_get_right:NN #3 \l__chemnum_tmpa_tl
+                \tl_if_eq:VxF
+                  \l__chemnum_tmpa_tl
+                  { \seq_item:Nn #1 { \l__chemnum_tmpa_int } }
                   {
-                    \bool_if:NTF \l__chemnum_sublabel_list_bool
-                      {
-                        \__chemnum_cmpd_sublabel_list:nn { #1 }
-                          { \l__chemnum_cmpd_sublabel_list_tl }
-                      }
-                      {
-                        \tl_if_blank:nF { #2 }
-                          {
-                            \tl_use:N \l__chemnum_cmpd_separator_tl
-                            \int_zero:N \l__chemnum_tmpa_int
-                            \tl_map_inline:Nn \l__chemnum_cmpd_sublist_tl
-                              {
-                                \int_incr:N \l__chemnum_tmpa_int
-                                \__chemnum_cmpd_subrange_separate:n { ##1 }
-                                \bool_if:NTF \l__chemnum_cmpd_ref_bool
-                                  { \use:c { chemnum_cmpd_ #1 _ \l__chemnum_tmpb_tl _ref: } }
-                                  { \use:c { chemnum_cmpd_ #1 _ \l__chemnum_tmpb_tl : } }
-                                \tl_if_blank:VF \l__chemnum_tmpc_tl
-                                  {
-                                    \tl_use:N \l__chemnum_sub_range_sep_tl
-                                    \bool_if:NTF \l__chemnum_cmpd_ref_bool
-                                      { \use:c { chemnum_cmpd_ #1 _ \l__chemnum_tmpc_tl _ref: } }
-                                      { \use:c { chemnum_cmpd_ #1 _ \l__chemnum_tmpc_tl : } }
-                                  }
-                                \int_compare:nF
-                                  { \l__chemnum_tmpa_int = \l__chemnum_cmpd_sublist_length_int }
-                                  { \l__chemnum_sublist_output_separator_tl }
-                              }
-                          }
-                      }
+                    \int_compare:nTF { \l__chemnum_tmpc_int > 2 }
+                      { \seq_put_right:NV #3 \l__chemnum_sep_sublist_range_tl }
+                      { \seq_put_right:NV #3 \l__chemnum_sep_sublist_last_two_tl }
+                    \seq_put_right:Nx #3
+                      { \seq_item:Nn #1 { \l__chemnum_tmpa_int } }
                   }
               }
           }
       }
   }
 
-\cs_generate_variant:Nn \__chemnum_cmpd_aux:nnnn { VV }
-
-%-----------------------------------------------------------------------------%
-% create compound label
-% #1: label name #2: star (invisible) #3: minus (no delimiters)
-\cs_new_protected:Npn \__chemnum_cmpd:nnn #1#2#3 {
-  \group_begin:
-    \tl_clear:N \l__chemnum_cmpd_main_label_tl
-    \tl_clear:N \l__chemnum_cmpd_sub_label_tl
-    \__chemnum_cmpd_labelsep:n #1 \q_stop
-    \tl_remove_all:Nn \l__chemnum_cmpd_sub_label_tl { ~ }
-    \__chemnum_cmpd_aux:VVnn
-      \l__chemnum_cmpd_main_label_tl
-      \l__chemnum_cmpd_sub_label_tl
-      { #2 }
-      { #3 }
-  \group_end:
-}
-
-\cs_generate_variant:Nn \__chemnum_cmpd:nnn { V }
-
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-% DOCUMENT COMMANDS
-% variables:
-\int_new:N \l__chemnum_list_items_int
-\int_new:N \l__chemnum_list_separate_int
-
-\tl_new:N  \l__chemnum_list_last_sep_empty_tl
-\tl_set:Nn \l__chemnum_list_last_sep_empty_tl { empty }
-
-\bool_new:N \l__chemnum_cmpd_ref_bool
-
-\msg_set:nnnn { chemnum } { fatal-combination }
-  {
-    You~can't~use \c_space_tl \token_to_str:N \cmpd \c_space_tl
-    with~star~and~#1 \c_space_tl \msg_line_context: .
-  }
-  {
-    You~used \c_space_tl \token_to_str:N \cmpd \c_space_tl
-    with~both~star~and~#1 \c_space_tl \msg_line_context: .\\
-    ~This~is~not~possible~since~it~doesn't~make~any~sense.
-  }
-
-%-----------------------------------------------------------------------------%
-% MAIN COMMAND
-% \cmpd*+-[<key-value-list>]{<(possibly comma separated list of) compound
-% label(s)>}
-\NewDocumentCommand \__chemnum_input_separator:n
-  { > { \exp_args:No \SplitList { \l__chemnum_list_input_separator_tl } } m }
-  { \tl_set:Nn \l__chemnum_tmpb_tl { #1 } }
-
-\NewDocumentCommand \cmpd { s t+ t- o m }
-  { \cmpd_main:nnnnn { #1 } { #2 } { #3 } { #4 } { #5 } }
-
-\cs_new_protected:Npn \cmpd_main:nnnnn #1#2#3#4#5
+% ----------------------------------------------------------------------------
+% the code level version of the main command:
+% #1: boolean: if true register compound but don't write the label
+% #2: boolean: if true only read compound
+% #3: options
+% #4: list of IDs
+\cs_new_protected:Npn \chemnum_cmpd:nnnn #1#2#3#4
   {
-    \IfBooleanT #2
-      {
-        \bool_set_true:N \l__chemnum_cmpd_ref_bool
-        \IfBooleanT #1
-          { \msg_error:nnx { chemnum } { fatal-combination } { plus } }
-      }
-    \tl_clear:N \l__chemnum_tmpa_tl
     \group_begin:
-      \int_zero:N \l__chemnum_list_items_int
-      \int_zero:N \l__chemnum_list_separate_int
-      \IfNoValueF { #4 }
-        { \keys_set:nn { chemnum } { #4 } }
-      \__chemnum_input_separator:n { #5 }
-      \tl_map_variable:NNn \l__chemnum_tmpb_tl \l__chemnum_tmpa_tl
+      \keys_set_groups:nnn {chemnum} {list} {#3}
+      \seq_set_split:NVn
+        \l__chemnum_tmpa_seq
+        \l__chemnum_main_separator_tl
+        {#4}
+      \seq_remove_duplicates:N \l__chemnum_tmpa_seq
+      \chemnum_sort_main_labels:N \l__chemnum_tmpa_seq
+      \seq_clear:N \l__chemnum_tmpb_seq
+      \seq_map_inline:Nn \l__chemnum_tmpa_seq
         {
-          \tl_if_blank:VF \l__chemnum_tmpa_tl
-            { \int_incr:N \l__chemnum_list_items_int }
+          \seq_put_right:Nn \l__chemnum_tmpb_seq
+            { \chemnum_single_compound:NNnn #1 #2 {#3} {##1} }
         }
-      \tl_map_variable:NNn \l__chemnum_tmpb_tl \l__chemnum_tmpa_tl
+      \bool_if:NTF #1 % starred call of \cmpd
+        { \seq_use:Nn \l__chemnum_tmpb_seq {} }
         {
-          \tl_remove_all:Nn \l__chemnum_tmpa_tl { ~ }
-          \tl_if_blank:VF \l__chemnum_tmpa_tl
-            {
-              \int_incr:N \l__chemnum_list_separate_int
-              \IfBooleanF #1
-                {
-                  \if_int_compare:w \l__chemnum_list_separate_int = 1
-                    \if_int_compare:w \l__chemnum_list_items_int = 1
-                    \else:
-                      \tl_use:N \l__chemnum_list_prefix_tl
-                      \tl_if_blank:VF { \l__chemnum_list_prefix_tl }
-                        { \l__chemnum_list_space_tl }
-                      \tl_use:N \l__chemnum_list_odelim_tl
-                    \fi:
-                  \fi:
-                }
-              \IfBooleanTF #1
-                {
-                  \__chemnum_cmpd:Vnn
-                    \l__chemnum_tmpa_tl
-                    { \BooleanTrue }
-                    { \BooleanFalse }
-                  \IfBooleanT #3
-                    {
-                      \msg_error:nnx { chemnum }
-                        { fatal-combination } { minus }
-                    }
-                }
-                { 
-                  \IfBooleanTF #3
-                    {
-                      \__chemnum_cmpd:Vnn
-                        \l__chemnum_tmpa_tl
-                        { \BooleanFalse }
-                        { \BooleanTrue }
-                    }
-                    {
-                      \__chemnum_cmpd:Vnn
-                        \l__chemnum_tmpa_tl
-                        { \BooleanFalse }
-                        { \BooleanFalse }
-                    }
-                  \int_compare:nTF
-                    { \l__chemnum_list_separate_int = \l__chemnum_list_items_int }
-                    {
-                      \int_compare:nNnF { \l__chemnum_list_items_int } = { 1 }
-                        {
-                          \tl_use:N \l__chemnum_list_cdelim_tl
-                          \tl_if_blank:VF
-                            { \l__chemnum_list_suffix_tl }
-                            { \l__chemnum_list_space_tl }
-                          \tl_use:N \l__chemnum_list_suffix_tl
-                        }
-                    }
-                    {
-                      \int_compare:nTF
-                        {
-                          \l__chemnum_list_separate_int
-                          =
-                          \int_eval:n { \l__chemnum_list_items_int - 1 }
-                        }
-                        {
-                          \tl_if_eq:NNTF
-                            \l__chemnum_list_last_separator_tl
-                            \l__chemnum_list_last_sep_empty_tl
-                            {
-                              \tl_use:N \l__chemnum_list_separator_tl
-                              \l__chemnum_list_space_tl
-                            }
-                            {
-                              \int_compare:nNnF
-                                { \l__chemnum_list_separate_int } = { 1 }
-                                {
-                                  \bool_if:NF \l__chemnum_no_serial_comma_bool
-                                    { \l__chemnum_list_separator_tl }
-                                }
-                              \tl_if_blank:VF \l__chemnum_list_last_separator_tl
-                                { \l__chemnum_list_space_tl }
-                              \tl_use:N \l__chemnum_list_last_separator_tl
-                              \l__chemnum_list_space_tl
-                            }
-                        }
-                        {
-                          \tl_use:N \l__chemnum_list_separator_tl
-                          \l__chemnum_list_space_tl
-                        }
-                  }
-                }
-            }
+          \seq_use:NVVV \l__chemnum_tmpb_seq
+            \l__chemnum_sep_list_two_tl
+            \l__chemnum_sep_list_more_tl
+            \l__chemnum_sep_list_last_two_tl
         }
     \group_end:
-    \bool_set_false:N \l__chemnum_cmpd_ref_bool
-  }
-
-%-----------------------------------------------------------------------------%
-% INITIALISING LABELS
-\bool_new:N \l__chemnum_cmpd_initiated_bool
-\bool_new:N \l__chemnum_cmpd_init_strict_bool
-\bool_new:N \l__chemnum_cmpd_sub_init_bool
-\bool_new:N \l__chemnum_cmpd_init_declare_bool
-
-\tl_new:N  \l__chemnum_cmpd_init_separator_tl
-\tl_set:Nn \l__chemnum_cmpd_init_separator_tl { , }
-
-% property keys for \cmpdinit command
-% strict=true will produce an error instead of a warning
-\keys_define:nn { chemnum } {
-  init-strict    .bool_set:N = \l__chemnum_cmpd_init_strict_bool ,
-  init-strict    .default:n  = true ,
-  init-sub       .bool_set:N = \l__chemnum_cmpd_sub_init_bool ,
-  init-sub       .default:n  = true ,
-  init-input-sep .tl_set:N   = \l__chemnum_cmpd_init_separator_tl ,
-  init-input-sep .default:n  = { , }
-}
-
-% warning/error messages
-\msg_set:nnn { chemnum } { cmpd-init }
-  {
-    You~used~\token_to_str:N \cmpdinit \c_space_tl but~didn't~initiate~
-    compound~"#1"~\msg_line_context: .
   }
 
-\msg_set:nnn { chemnum } { cmpd-init-sub }
+% #1: first variable
+% #2: second variable
+% #3: main/sub separator
+% #4: complete label
+\cs_new_protected:Npn \chemnum_separate_main_sub:NNnn #1#2#3#4
   {
-    You~used~\token_to_str:N \cmpdinit \c_space_tl and~"init-sub~=~true"~
-    but~didn't~initiate~sub-compound~"#1"~\msg_line_context: .
+    \cs_set:Npn \__chemnum_remove_sub:w ##1#3##2 \q_stop
+      { \exp_not:n { ##1 } }
+    \cs_set:Npn \__chemnum_get_sub:w ##1#3##2#3##3 \q_stop
+      {
+        \tl_if_blank:nF {##2} { \exp_not:n { ##2 } }
+      }
+    \tl_set:Nx #1 { \__chemnum_remove_sub:w #4#3 \q_stop }
+    \tl_set:Nx #2 { \__chemnum_get_sub:w #4#3#3 \q_stop }
   }
+\cs_generate_variant:Nn \chemnum_separate_main_sub:NNnn { NNV }
 
-% initialize (and maybe declare) labels
-\cs_new_protected:Npn \__chemnum_cmpd_init:n #1
+% sorting and merging of the main label list:
+% #1: seq that holds the label list
+\cs_new_protected:Npn \chemnum_sort_main_labels:N #1
   {
-    \tl_clear:N \l__chemnum_tmpa_tl
-    \tl_set:Nn \l__chemnum_tmpa_tl { #1 }
-    \tl_remove_all:Nn \l__chemnum_tmpa_tl { ~ }
-    \tl_clear:N \l__chemnum_cmpd_main_label_tl
-    \tl_clear:N \l__chemnum_cmpd_sub_label_tl
-    \exp_after:wN \__chemnum_cmpd_labelsep:n \l__chemnum_tmpa_tl \q_stop
-    \cs_if_exist:cF { chemnum_cmpd_ \l__chemnum_cmpd_main_label_tl  _init: }
+    \prop_clear:N \l__chemnum_tmpa_prop
+    \seq_clear:N \l__chemnum_tmpb_seq
+    \seq_clear:N \l__chemnum_tmpc_seq
+    % build property list that holds entries of #1:
+    \seq_map_inline:Nn #1
       {
-        \cs_new_protected:cpn
-          { chemnum_cmpd_ \l__chemnum_cmpd_main_label_tl _init: }
-          { }
+        \chemnum_separate_main_sub:NNVn
+          \l__chemnum_tmpa_tl % main part
+          \l__chemnum_tmpb_tl % sub part
+          \l__chemnum_compound_separator_tl
+          {##1}
+        \bool_if:NTF \l__chemnum_merge_list_bool
+          {
+            \prop_get:NVNTF \l__chemnum_tmpa_prop
+              \l__chemnum_tmpa_tl
+              \l__chemnum_tmpc_tl
+              {
+                \prop_put:NVx \l__chemnum_tmpa_prop
+                  \l__chemnum_tmpa_tl
+                  {
+                    \exp_not:V \l__chemnum_tmpc_tl
+                    \exp_not:V \l__chemnum_sub_separator_tl
+                    \exp_not:V \l__chemnum_tmpb_tl
+                  }
+              }
+              {
+                \prop_put:NVV \l__chemnum_tmpa_prop
+                  \l__chemnum_tmpa_tl
+                  \l__chemnum_tmpb_tl
+              }
+          }
+          {
+            \prop_get:NVNTF \l__chemnum_tmpa_prop
+              \l__chemnum_tmpa_tl
+              \l__chemnum_tmpc_tl
+              {
+                \prop_put:NVx \l__chemnum_tmpa_prop
+                  \l__chemnum_tmpa_tl
+                  {
+                    \exp_not:V \l__chemnum_tmpc_tl
+                    \exp_not:V \l__chemnum_main_separator_tl
+                    \exp_not:n {##1}
+                  }
+              }
+              {
+                \prop_put:NVn \l__chemnum_tmpa_prop
+                  \l__chemnum_tmpa_tl
+                  {##1}
+              }
+          }
       }
-    \bool_if:NT \l__chemnum_cmpd_sub_init_bool
+    % merge = true:
+    %   \l__chemnum_tmpa_prop now holds all main labels with possible sublabel
+    % lists
+    % merge = false
+    %   \l__chemnum_tmpa_prop now holds all main labels with all occurences of
+    %   the respective main label as property
+    %
+    % build sequence that holds entries of #1 in order of already defined
+    % labels:
+    \seq_map_inline:Nn \g__chemnum_defined_compounds_seq
       {
-        \tl_if_blank:VF \l__chemnum_cmpd_sub_label_tl
+        \bool_if:NTF \l__chemnum_merge_list_bool
           {
-            \__chemnum_cmpd_sublist:V \l__chemnum_cmpd_sub_label_tl
-            \tl_map_inline:Nn \l__chemnum_cmpd_sublist_tl
+            \prop_get:NnNT \l__chemnum_tmpa_prop {##1} \l__chemnum_tmpa_tl
               {
-                \cs_if_exist:cF
+                \tl_if_in:VVTF
+                  \l__chemnum_tmpa_tl
+                  \l__chemnum_sub_separator_tl
                   {
-                    chemnum_cmpd_ 
-                    \l__chemnum_cmpd_main_label_tl
-                    _
-                    ##1
-                    _init:
+                    \seq_put_right:Nx \l__chemnum_tmpb_seq
+                      {
+                        \exp_not:n { ##1 }
+                        \tl_if_blank:VF \l__chemnum_tmpa_tl
+                          {
+                            \exp_not:V \l__chemnum_compound_separator_tl
+                            { \exp_not:V \l__chemnum_tmpa_tl }
+                          }
+                      }
                   }
                   {
-                    \cs_new_protected:cpn
+                    \seq_put_right:Nx \l__chemnum_tmpb_seq
                       {
-                        chemnum_cmpd_
-                        \l__chemnum_cmpd_main_label_tl
-                        _
-                        ##1
-                        _init:
+                        \exp_not:n { ##1 }
+                        \tl_if_blank:VF \l__chemnum_tmpa_tl
+                          {
+                            \exp_not:V \l__chemnum_compound_separator_tl
+                            \exp_not:V \l__chemnum_tmpa_tl
+                          }
                       }
-                      { }
                   }
+                \seq_if_in:NnF \l__chemnum_tmpc_seq {##1}
+                  { \seq_put_right:Nn \l__chemnum_tmpc_seq {##1} }
+              }
+          }
+          {
+            \prop_get:NnNT \l__chemnum_tmpa_prop {##1} \l__chemnum_tmpa_tl
+              {
+                \tl_if_in:VVTF
+                  \l__chemnum_tmpa_tl
+                  \l__chemnum_main_separator_tl
+                  {
+                    \seq_set_split:NVV \l__chemnum_tmpc_seq
+                      \l__chemnum_main_separator_tl
+                      \l__chemnum_tmpa_tl
+                    \seq_map_inline:Nn \l__chemnum_tmpc_seq
+                      { \seq_put_right:Nn \l__chemnum_tmpb_seq {####1} }
+                  }
+                  { \seq_put_right:NV \l__chemnum_tmpb_seq \l__chemnum_tmpa_tl }
               }
           }
       }
-    \bool_if:NT \l__chemnum_cmpd_init_declare_bool
+    % \l__chemnum_tmpb_seq now holds all labels that are already defined
+    % merge = true :
+    %   the same \l__chemnum_tmpc_seq which only holds the /main/ labels
+    \bool_if:NTF \l__chemnum_merge_list_bool
       {
-        \__chemnum_cmpd:Vnn
-          \l__chemnum_tmpa_tl
-          { \BooleanTrue }
-          { \BooleanFalse }
+        \seq_map_inline:Nn #1
+          {
+            \chemnum_separate_main_sub:NNVn
+              \l__chemnum_tmpa_tl % main part
+              \l__chemnum_tmpb_tl % sub part
+              \l__chemnum_compound_separator_tl
+              {##1}
+            % check if existing main label is present, otherwise add entry
+            \seq_if_in:NVF \l__chemnum_tmpc_seq \l__chemnum_tmpa_tl
+              {
+                \prop_get:NVNT \l__chemnum_tmpa_prop
+                  \l__chemnum_tmpa_tl
+                  \l__chemnum_tmpc_tl
+                  {
+                    \seq_put_right:Nx \l__chemnum_tmpb_seq
+                      {
+                        \exp_not:V \l__chemnum_tmpa_tl
+                        \tl_if_blank:VF \l__chemnum_tmpc_tl
+                          {
+                            \exp_not:V \l__chemnum_compound_separator_tl
+                            \exp_not:V \l__chemnum_tmpc_tl
+                          }
+                      }
+                    \seq_put_right:NV \l__chemnum_tmpc_seq \l__chemnum_tmpa_tl
+                  }
+              }
+          }
+      }
+      {
+        \seq_map_inline:Nn #1
+          {
+            \seq_if_in:NnF \l__chemnum_tmpb_seq {##1}
+              { \seq_put_right:Nn \l__chemnum_tmpb_seq {##1} }
+          }
       }
+    \seq_set_eq:NN #1 \l__chemnum_tmpb_seq
   }
-\cs_generate_variant:Nn \__chemnum_cmpd_sublist:n { V }
-
-% \cmpdinit*[strict=<bool>]{<comma separated list of label names>}
-\NewDocumentCommand \cmpdinit { s o m }
-  {
-    \bool_set_true:N \l__chemnum_cmpd_initiated_bool
-    \IfBooleanTF #1
-      { \bool_set_false:N \l__chemnum_cmpd_init_declare_bool }
-      { \bool_set_true:N \l__chemnum_cmpd_init_declare_bool }
-    \IfNoValueF { #2 } { \keys_set:nn { chemnum } { #2 } }
-    \__chemnum_input_separator:n { #3 }
-    \tl_map_function:NN \l__chemnum_tmpb_tl \__chemnum_cmpd_init:n
-  }
-
-%-----------------------------------------------------------------------------%
-% RESET LABEL NUMBERS
-% \cmpdreset[<number>]
-\NewDocumentCommand \cmpdreset { o }
-  {
-    \IfNoValueTF { #1 }
-      { \int_zero:N \g__chemnum_cmpd_int }
-      { \int_set:Nn \g__chemnum_cmpd_int { #1 - 1 } }
-  }
-
-%-----------------------------------------------------------------------------%
-% CHEMNUM SETUP COMMAND
-% \cmpdsetup{<key-value-list>}
-\NewDocumentCommand \cmpdsetup { m }
-  { \keys_set:nn { chemnum } { #1 } \tex_ignorespaces:D }
-
-%-----------------------------------------------------------------------------%
-% REPLACE TAG IN EPS PICTURE WITH LABEL
-% works similar to \schemeref command of the chemscheme package
-% \cmpdref-[<keyval>][<tag>]{<label name>}
-\tl_new:N  \l__chemnum_cmpdref_tl
-\tl_new:N  \l__chemnum_cmpdref_style_tl
-\tl_set:Nn \l__chemnum_cmpdref_style_tl { \sffamily }
-\tl_new:N  \l__chemnum_cmpdref_marker_tl
-\tl_set:Nn \l__chemnum_cmpdref_marker_tl { TMP }
-\tl_new:N  \l__chemnum_psfrag_texpos_tl
-\tl_new:N  \l__chemnum_psfrag_texpos_current_tl
-\tl_set:Nn \l__chemnum_psfrag_texpos_tl { b }
-\tl_new:N  \l__chemnum_psfrag_pspos_tl
-\tl_new:N  \l__chemnum_psfrag_pspos_current_tl
-\tl_set:Nn \l__chemnum_psfrag_pspos_tl { b }
 
-\int_new:N \l__chemnum_cmpdref_int
+% %-----------------------------------------------------------------------------%
+% % REPLACE TAG IN EPS PICTURE WITH LABEL
+% % works similar to \schemeref command of the chemscheme package
+% % \cmpdref-[<keyval>][<tag>]{<label name>}
 
 \cs_new_protected:Npn \__chemnum_set_psfrag_pos:nn #1#2
   {
@@ -1391,240 +1671,213 @@
     \tl_set:Nn \l__chemnum_psfrag_pspos_tl { #2 }
   }
 
+\cs_new_protected:Npn \__chemnum_set_psfrag_local_pos:nn #1#2
+  {
+    \tl_set:Nn \l__chemnum_psfrag_local_texpos_tl { #1 }
+    \tl_set:Nn \l__chemnum_psfrag_local_pspos_tl { #2 }
+  }
+\cs_generate_variant:Nn \__chemnum_set_psfrag_local_pos:nn { VV }
+
 \cs_new_protected:Npn \__chemnum_psfrag:nnnn #1#2#3#4
   { \psfrag { #1 } [ #2 ] [ #3 ] { #4 } }
-\cs_generate_variant:Nn \__chemnum_psfrag:nnnn { VVVn }
+\cs_generate_variant:Nn \__chemnum_psfrag:nnnn { VVVx }
 
-\cs_new_protected:Npn \__chemnum_set_psfrag_pos_local:w #1 ref-pos #2 = #3#4 , #5 \q_stop
+% #1: boolean: if true only read label
+% #2: options
+% #3: label spec
+\cs_new_protected:Npn \chemnum_cmpd_replace:nnn #1#2#3
   {
-    \tl_set_eq:NN \l__chemnum_psfrag_texpos_current_tl \l__chemnum_psfrag_texpos_tl
-    \tl_set_eq:NN \l__chemnum_psfrag_pspos_current_tl  \l__chemnum_psfrag_pspos_tl
-    \tl_set:Nn \l__chemnum_psfrag_texpos_tl { #3 }
-    \tl_set:Nn \l__chemnum_psfrag_pspos_tl { #4 }
+    % place the label
+    %   just in case it hasn't been declared:
+    \labelcmpd[{#2}]{#3}
+    % set specific replacement options
+    \keys_set_groups:nnn {chemnum} {replace} { replace=false, #2 }
+    \bool_if:nTF
+      {
+        \l__chemnum_compound_replace_auto_bool &&
+        \l__chemnum_compound_replace_auto_this_bool
+      }
+      {
+        \int_incr:N \l__chemnum_compound_replace_int
+        \tl_set:Nx \l__chemnum_compound_replace_tl
+          {
+            \exp_not:V \l__chemnum_compound_replace_tag_tl
+            \exp_not:V \l__chemnum_compound_replace_int
+          }
+      }
+      {
+        \tl_set_eq:NN
+          \l__chemnum_compound_replace_tl
+          \l__chemnum_compound_replace_tag_tl
+        \bool_set_true:N \l__chemnum_compound_replace_auto_this_bool
+      }
+    %   replace in EPS, this must not be in a group:
+    \bool_if:NTF \l__chemnum_replace_local_bool
+      {
+        \__chemnum_psfrag:VVVx
+          \l__chemnum_compound_replace_tl
+          \l__chemnum_psfrag_local_texpos_tl
+          \l__chemnum_psfrag_local_pspos_tl
+          {
+            \group_begin:
+              \exp_not:V \l__chemnum_compound_replace_local_format_tl
+              \exp_not:n
+                { \chemnum_cmpd:nnnn { \c_false_bool } { #1 } { #2 } { #3 } }
+            \group_end:
+          }
+      }
+      {
+        \__chemnum_psfrag:VVVx
+          \l__chemnum_compound_replace_tl
+          \l__chemnum_psfrag_texpos_tl
+          \l__chemnum_psfrag_pspos_tl
+          {
+            \group_begin:
+              \exp_not:V \l__chemnum_compound_replace_format_tl
+              \exp_not:n
+                { \chemnum_cmpd:nnnn { \c_false_bool } { #1 } { #2 } { #3 } }
+            \group_end:
+          }
+      }
+    % clean up local options:
+    \keys_set_groups:nnn {chemnum} {replace} { replace=false }
+    \__chemnum_set_psfrag_local_pos:VV
+      \l__chemnum_psfrag_texpos_tl
+      \l__chemnum_psfrag_pspos_tl
+    \tl_set_eq:NN
+      \l__chemnum_compound_replace_local_format_tl
+      \l__chemnum_compound_replace_format_tl
   }
 
-\keys_define:nn { chemnum }
+\NewDocumentCommand \replacecmpd { t+ o m }
+  { \chemnum_cmpd_replace:nnn { #1 } { #2 } { #3 } }
+
+\chemnum_deprecated_command:NN \cmpdref \replacecmpd
+
+% ----------------------------------------------------------------------------
+% the user level version of the main command:
+\NewDocumentCommand \cmpd { st+O{}m  }
+  { \chemnum_cmpd:nnnn {#1} {#2} {#3} {#4} }
+
+\NewDocumentCommand \refcmpd { O{}m  }
+  { \chemnum_cmpd:nnnn { \c_false_bool } { \c_true_bool } {#1} {#2} }
+
+\NewDocumentCommand \labelcmpd { O{}m  }
+  { \chemnum_cmpd:nnnn { \c_true_bool } { \c_false_bool } {#1} {#2} }
+
+\DeclareExpandableDocumentCommand \cmpdplain { m }
   {
-    ref-tag   .tl_set:N  = \l__chemnum_cmpdref_marker_tl ,
-    ref-tag   .default:n = { TMP } ,
-    ref-style .tl_set:N  = \l__chemnum_cmpdref_style_tl ,
-    ref-style .default:n = { } ,
-    ref-pos   .code:n    = \__chemnum_set_psfrag_pos:nn #1 ,
-    ref-pos   .default:n = bb
+    \chemnum_expandable_compound_start:n {#1}
+    \chemnum_expandable_compound_read:n {#1}
+    \chemnum_expandable_compound_finish:n {#1}
   }
 
-\NewDocumentCommand \cmpdref { t- t+ o o m }
-  { \cmpd_ref:nnnnn { #1 } { #2 } { #3 } { #4 } { #5 } }
+\DeclareExpandableDocumentCommand \subcmpdplain { mm }
+  { \chemnum_expandable_subcompound_read:nn {#1} {#2} }
 
-\cs_new_protected:Npn \cmpd_ref:nnnnn #1#2#3#4#5
+\DeclareExpandableDocumentCommand \submaincmpdplain { mm }
   {
-      \IfBooleanT { #1 }
-        { \keys_set:nn { chemnum } { cmpd-delim = } }
-      \IfNoValueTF { #3 }
-        {
-          \int_incr:N \l__chemnum_cmpdref_int
-          \tl_set:No \l__chemnum_cmpdref_tl
-            {
-              \tl_use:N \l__chemnum_cmpdref_marker_tl
-              \int_use:N \l__chemnum_cmpdref_int
-            }
-        }
-        {
-          \tl_if_blank:nTF { #3 }
-            {
-              \int_incr:N \l__chemnum_cmpdref_int
-              \tl_set:No \l__chemnum_cmpdref_tl
-                {
-                  \tl_use:N \l__chemnum_cmpdref_marker_tl
-                  \int_use:N \l__chemnum_cmpdref_int
-                }
-            }
-            { \tl_set:Nn \l__chemnum_cmpdref_tl { #3 } }
-        }
-    \IfNoValueTF { #4 }
-        {
-          % need to call it once invisible in case it's the first time the label
-          % is called. Somehow it otherwise “vanishes” inside \psfrag
-          \IfBooleanF { #2 }
-            { \cmpd * { #5 } }
-          \__chemnum_psfrag:VVVn
-            \l__chemnum_cmpdref_tl
-            \l__chemnum_psfrag_texpos_tl
-            \l__chemnum_psfrag_pspos_tl
-            {
-              \group_begin:
-                \keys_set:nn { chemnum }
-                  { cmpd-style = \l__chemnum_cmpdref_style_tl }
-                \IfBooleanTF { #2 }
-                  { \cmpd + { #5 } }
-                  { \cmpd { #5 } }
-              \group_end:
-            }
-        }
-        {
-          % TODO: set psfrag positions before \__chemnum_psfrag is called
-          % ?? hat sich erledigt, oder?
-          \IfBooleanF { #2 }
-            { \cmpd * [ #4 ] { #5 } }
-          \tl_if_in:nnT { #4 } { ref-pos }
-            { \__chemnum_set_psfrag_pos_local:w #4 , \q_stop }
-          \__chemnum_psfrag:VVVn
-            \l__chemnum_cmpdref_tl
-            \l__chemnum_psfrag_texpos_tl
-            \l__chemnum_psfrag_pspos_tl
-            {
-              \group_begin:
-                \keys_set:nn { chemnum }
-                  { cmpd-style = \l__chemnum_cmpdref_style_tl }
-                \IfBooleanTF { #2 }
-                  { \cmpd + [ #4 ] { #5 } }
-                  { \cmpd [ #4 ] { #5 } }
-              \group_end:
-            }
-          \tl_if_in:nnT { #4 } { ref-pos }
-            {
-              \tl_set_eq:NN
-                \l__chemnum_psfrag_texpos_tl \l__chemnum_psfrag_texpos_current_tl
-              \tl_set_eq:NN
-                \l__chemnum_psfrag_pspos_tl \l__chemnum_psfrag_pspos_current_tl
-            }
-        }
+    \chemnum_expandable_compound_start:n {#1}
+    \chemnum_expandable_compound_read:n {#1}
+    \chemnum_expandable_subcompound_read:nn {#1} {#2}
+    \chemnum_expandable_compound_finish:n {#1}
   }
 
-% --------------------------------------------------------------------------- %
-% one for the hackers: get the label numbers in an expandable way:
-\cs_new:Npn \cmpd@main #1 { \use:c { chemnum_cmpd_#1: } }
-\cs_new:Npn \cmpd@sub #1#2 { \use:c { chemnum_cmpd_#1_#2: } }
+% ----------------------------------------------------------------------------
+\cs_new_protected:Npn \chemnum_init:nn #1#2
+  {
+    \group_begin:
+      % this is semantically wrong!  The conflict: either I allow initiation
+      % to be set locally (which does not make sense, really) or I use wrong
+      % semantics at this very point in the package code...
+      \bool_set_false:N \g__chemnum_initiate_bool
+      \bool_set_false:N \g__chemnum_initiate_sub_bool
+      \chemnum_cmpd:nnnn { \c_true_bool } { \c_false_bool } {#1} {#2}
+    \group_end:
+  }
 
-% usage - main label of \cmpd{<label>.<sub>} => \cmpd@main{<label>}
-%       - sublabel   of \cmpd{<label>.<sub>} => \cmpd@aub{<label>}{<sub>}
-% Please be aware that this will _not_ be expandable when you use greek labels
+\NewDocumentCommand \initcmpd { O{}m }
+  { \chemnum_init:nn {#1} {#2} }
+\@onlypreamble\cmpdinit
 
-% --------------------------------------------------------------------------- %
-% language support:
+\chemnum_deprecated_command:NN \cmpdinit \initcmpd
 
-\RequirePackage { translations }
-\DeclareTranslationFallback     { and~(list~seperator) } { and }
-\DeclareTranslation { English } { and~(list~seperator) } { and }
-\DeclareTranslation { French  } { and~(list~seperator) } { et }
-\DeclareTranslation { German  } { and~(list~seperator) } { und }
-\DeclareTranslation { Italian } { and~(list~seperator) } { e }
-\DeclareTranslation { Spanish } { and~(list~seperator) } { y }
-\tl_set:Nn \l__chemnum_list_last_separator_lang_tl
-  { \GetTranslation { and~(list~seperator) } }
+% ----------------------------------------------------------------------------
+% resetting compound numbering
+\cs_new_protected:Npn \chemnum_reset_compounds:n #1
+  { \setcounter {cmpdmain} { \int_eval:n { #1 - 1 } } }
 
-\AtBeginDocument
+\NewDocumentCommand \resetcmpd { O{1} }
+  { \chemnum_reset_compounds:n {#1} }
+
+\chemnum_deprecated_command:NN \cmpdreset \resetcmpd
+
+% ----------------------------------------------------------------------------
+% language support:
+\DeclareTranslationFallback      {chemnum-sep-two} {~and~}
+\DeclareTranslation {English}    {chemnum-sep-two} {~and~}
+\DeclareTranslation {German}     {chemnum-sep-two} {~und~}
+\DeclareTranslation {French}     {chemnum-sep-two} {~et~}
+\DeclareTranslation {Spanish}    {chemnum-sep-two} {~y~}
+\DeclareTranslation {Italian}    {chemnum-sep-two} {~e~}
+\DeclareTranslation {Catalan}    {chemnum-sep-two} {~i~}
+\DeclareTranslation {Portuguese} {chemnum-sep-two} {~e~}
+\DeclareTranslation {Dutch}      {chemnum-sep-two} {~en~}
+\DeclareTranslation {Danish}     {chemnum-sep-two} {~og~}
+\DeclareTranslation {Swedish}    {chemnum-sep-two} {~och~}
+\DeclareTranslation {Finnish}    {chemnum-sep-two} {~ja~}
+\DeclareTranslation {Norwegian}  {chemnum-sep-two} {~og~}
+
+\DeclareTranslationFallback      {chemnum-sep-last-two} {~and~}
+\DeclareTranslation {English}    {chemnum-sep-last-two} {~and~}
+\DeclareTranslation {American}   {chemnum-sep-last-two} {,~and~}
+\DeclareTranslation {British}    {chemnum-sep-last-two} {~and~}
+\DeclareTranslation {German}     {chemnum-sep-last-two} {~und~}
+\DeclareTranslation {French}     {chemnum-sep-last-two} {~et~}
+\DeclareTranslation {Spanish}    {chemnum-sep-last-two} {~y~}
+\DeclareTranslation {Italian}    {chemnum-sep-last-two} {~e~}
+\DeclareTranslation {Catalan}    {chemnum-sep-last-two} {~i~}
+\DeclareTranslation {Portuguese} {chemnum-sep-last-two} {~e~}
+\DeclareTranslation {Dutch}      {chemnum-sep-last-two} {~en~}
+\DeclareTranslation {Danish}     {chemnum-sep-last-two} {~og~}
+\DeclareTranslation {Swedish}    {chemnum-sep-last-two} {~och~}
+\DeclareTranslation {Finnish}    {chemnum-sep-last-two} {~ja~}
+\DeclareTranslation {Norwegian}  {chemnum-sep-last-two} {~og~}
+
+% ----------------------------------------------------------------------------
+% TODO: add a warning for those options that can't be set with the setup
+%       command, i.e., those belonging to the `compound' group
+\cs_new_protected:Npn \chemnum_setup:n #1
   {
-    \@ifpackageloaded { babel }
-      {
-        \iflanguage { american }
-          { \bool_set_false:N \l__chemnum_no_serial_comma_bool }
-          { \bool_set_true:N  \l__chemnum_no_serial_comma_bool }
-        \cs_new_eq:NN \__chemnum_selectlanguage:n \selectlanguage
-        \cs_set:Npn \selectlanguage #1
-          {
-            \__chemnum_selectlanguage:n { #1 }
-            \iflanguage { american }
-              { \bool_set_false:N \l__chemnum_no_serial_comma_bool }
-              { \bool_set_true:N  \l__chemnum_no_serial_comma_bool }
-          }
-      }
-      {}
+    \keys_set_filter:nnn {chemnum} {compound,general} {#1}
+    \keys_set_groups:nnn {chemnum} {general} {#1}
   }
 
+\NewDocumentCommand \setchemnum { m }
+  { \chemnum_setup:n {#1} }
+
+\chemnum_deprecated_command:NN \cmpdsetup \setchemnum
+
 \tex_endinput:D
 
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% ----------------------------------------------------------------------------
+TODO:
+
+% ----------------------------------------------------------------------------
+new features in chemnum v1.0:
+- \cmpdplain{<id>} => reads label and writes it expandably without
+  formatting.  It is not able to parse a list.  Its sole purpose is usage in
+  pdfstrings (cf. \texorpdfstring{<tex>}{<pdfstring>}).
+- \refcmpd[<options>]{<id>} only reference a label, similar to \cmpdplain but
+  unexpandable and able to parse a list.  The same as \cmpd+
+- \cmpdproperty, \subcmpdproperty
+- \newcmpdcounterformat
+- logging messages
+- \cmpdshowdef, \cmpdshowref, \subcmpdshowdef, \subcmpdshowref
+- some options are grouped `compound': only those can be set with \cmpd
+- sub label list is sorted
+- sub label list is compressed when option `compress=true' is used
+
+% ----------------------------------------------------------------------------
 HISTORY:
- 2011/06/27 version 0.1
- 2011/06/29 version 0.1a - bugfixes
- 2011/07/17 version 0.2  - instead of two commands (\cmpd and \cmpdlist ) only 
-                         one (\cmpd) for both tasks
-                         - setup with a keyval system
-                         - possibility to initiate sublabels
-                         - choices "greek" and "Greek" for the cmpd-counter
-                         keys, choice "symbol" changed to "Symbol"
-                         - package option "textgreek = <value>" to control
-                         usage of the `textgreek' package
-                         - former \cmpd+ is now \cmpd-
-                         - new \cmpd+ added which reads label from
-                         <jobname>.cmpd
-                         - bugfix: wrong declaration in \cmpdinit and \cmpd
-                         when used with line break fixed
-                         - bugfix: error when \cmpd was used in vertical mode
-                         fixed
-                         - bugfix: corrected up to date support test
-                         - bugfix: wrong output in \cmpd* list removed
-                         - commented and cleaned up code
- 2011/08/02 version 0.3  - keys "cmpd-all", "sub-list", "sub-range-sep" and
-                         "sub-range-marker" added, key "cmpd-sub-counter"
-                         renamed into "sub-counter", key "sub-cmpd-sep"
-                         renamed into "sub-marker"
-                         - \cmpdref-[<keyval>][<tag>]{<label name>} added
-                         - key "ref-tag" added
-                         - cleaned up code
- 2011/09/03 version 0.3a - it is now impossible to use the (conflicting or 
-                         better: senseless) \cmpd*+ and \cmpd*- command
-                         versions. An error message is produced.
-                         - made sure code has no more than 80 tokens per line
-                         to improve readability on small screens
-                         - bug (unwanted whitespace) in \cmpdsetup fixed
- 2011/11/03 version 0.3b - key "sub-only" added, see schema 23 at
-                         http://www.arkat-usa.org/get-file/29257/ or scheme 4
-                         at http://www.arkat-usa.org/get-file/27301/ for
-                         reasons, why
- 2011/11/08 version 0.3c - localization via `babel' is now supported with the
-                         help of the `translator' package
-                         - key "list-serial-comma" added
- 2011/12/01 version 0.3d - greek letters without `textgreek' package
-                         - new key cmpd-weight = bold/normal
-                         - bugfix: sublabels are now possible, when main label
-                         name contains a colon
-                         - it is now possible to change the list input
-                         separator; this means the comma may be part of the
-                         label name
- 2011/12/01 version 0.3e - bugfix: labels have been saved in a wrong way, when
-                         "list-input-sep" had been changed. this is fixed
- 2011/12/09 version 0.4  - new input of sublabel lists and ranges
-                         - new key: "sublist-input-sep"
-                         - new key: "sublist-output-sep"
-                         - new key: "init-input-sep"
-                         - "sub-marker"       => "sub-input-sep"
-                         - "cmpd-sep"         => "sub-output-sep"
-                         - "sub-range-sep"    => "subrange-output-sep"
-                         - "sub-range-marker" => "subrange-input-sep"
-                         - "strict"           => "init-strict"
-                         - "sub-init"         => "init-sub"
-                         - key removed: "sub-list"
-                         - it is now possible, to mark the labels with
-                         \hypertarget and \hyperlink if `hyperref' is loaded
-                         - new key: "hyper-use"
-                         - new key: "hyper-target"
-                         - new key: "hyper-link"
-                         - new key: "ref-style"
-                         - documentation got an index
- 2012/02/22 version 0.4a - corrected outdated expl3 function
- 2012/04/15 version 0.4b - bugfix in \cmpdref
- 2012/04/20 version 0.5  - new option "ref-pos"
-                         - switched order of optional arguments of \cmpdref
- 2012/05/03 version 0.5a - corrected stupid typos in documentation
- 2012/05/17 version 0.5b - retrieve label numbers in an expandable (LaTeX2e) way
-                           see
-                           https://groups.google.com/d/topic/de.comp.text.tex/LF0knPIuqrM/discussio
-                           for possible reasons why
- 2012/07/24 version 0.5c - adapted to changes in l3kernel
- 2012/08/15 version 0.5d - fixed bug in \cmpdref
- 2012/09/17 version 0.5e - fixed bug in \cmpdinit
- 2012/12/29 version 0.5f - added Italian documentation, minor adjustment of `ref-pos'
- 2013/01/20 version 0.6  - added + argument to \cmpdref
-                         - changed internal syntax
- 2013/04/17 version 0.6a - adapted to deprecated l3 functions
-                         - protected functions that needed to be
- 2013/06/05 version 0.6b - internal changes to the code
- 
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-% TODO:
- - add a possibility to \ref{} the compounds
- - (rudimentäre) Unterstützung für hyperref und pdfstrings
- - provide expandable makro which gives the label and/or sublabel without any
-   formatting
+