LaTeX3 - Data structure to be reused

Question

I want to store several pieces of data, each of the following type, so that I can manipulate them both for formatting and for calculations. The number of lines analysed in the user's code is not fixed in advance.

I have already made the parser that extracts this values.

LINE: 1
    CTXT: xvals
    LABEL: t
    VAL: 1, 20, 300, 4000
LINE: 2
    CTXT: imgs
    LABEL: f(t)
    VAL: a , b, bb, ccc, dddd
LINE: 3
    CTXT: imgs
    LABEL: g(t)
    VAL: U, V, VV, WWW, XXXX

I will produce in this simple situation the following output, see the nicematrix table, but this is only the 1st functionality. I would like for example to compute the maximum of f later in the document. To do that, I need to recover the context imgs such as to find the label f(t) and its associated values.

\documentclass[11pt, a4paper]{article}
\usepackage{nicematrix}
\begin{document}
\section{What the user types}
\begin{verbatim}
\begin{functable}
    xvals =    t : 1 , 20 , 300 , 4000 ;
    imgs  = f(t) : a , bb , ccc , dddd ;
            g(t) : U , VV , WWW , XXXX
\end{functable}
\end{verbatim}
\section{What the user sees}
$\begin{NiceArray}[cell-space-limits = 3pt]{c*{4}{|c}}
    t    & 1 & 20 & 300 & 4000
\ \hline
    f(t) & a & bb & ccc & dddd
\ \hline
    g(t) & U & VV & VVV & WWW
\end{NiceArray}$
\section{What can be do after}
The user can ask for example to rebuild the 1st table 
with something like this.
\begin{verbatim}
\begin{functable}[rebuild=1]
\end{functable}
\end{verbatim}
The user can also ask to calculate the maximum value 
of $f(t)$ via something like \verb+\calcfunctable{max=f(t)}+.
\end{document}

I see two possibilities.

1. Either use the starray package, but I fear that this project will be not maintained in the long term.

2. Or I can try to implement a homemade solution which looks like a list of property lists.

JSON like structure expected [2024-03-09.v1]

The idea is to have a variable associated with each table, a variable that can be iterated dictionary by dictionary, and for each dictionary thus obtained, we will have access to the different types of values.

[
    {
        'CTX'  : 'xvals',
        'VAL'  : ['1', '20', '300', '4000'],
        'LABEL': 't',
        'LINE' : '1'
    },
    {
        'CTX'  : 'imgs',
        'VAL'  : ['a' , 'b', 'bb', 'ccc', 'dddd'],
        'LABEL': 'f(t)',
        'LINE' : '2'
    },
    {
        'CTX'  : 'imgs',
        'VAL'  : ['U', 'V', 'VV', 'WWW', 'XXXX'],
        'LABEL': 'g(t)',
        'LINE' : '3'
    }
]

Some additional information [2024-01-17.v1]

1. The parser gives l3-token lists.

2. The value of VAL keys can be used as comma separated lists, or as sequences by L3 functions. The second choice should be better.

3. The values will be used in different situations, sometimes to print a table, sometimes to perform calculations. This should be similar to what it is done in this answer.

Proof of Concept simplified [2024-03-09.v1]

\documentclass[12pt]{article}
\ExplSyntaxOn
% -- FUNCTABLE ENV. -- %
\NewDocumentEnvironment{ functable }{ b }{%
  \tns_functab_functable:n { #1 }
}{}
\cs_new:Npn \tns_functab_functable:n #1 {
  \tns_core_DSL_ctxt_parser:nn { functable } { #1 }
\bigskip\par
  NEW ~ DATA ~ \int_use:N \g_tns_functab_id_int
\par
  TODO
}
% -- DSL - L3 -- %
\tl_new:N   \g_tns_functab_semicolon_tl
\tl_gset:Nn \g_tns_functab_semicolon_tl { ; }
\tl_new:N   \g_tns_functab_colon_tl
\tl_gset:Nn \g_tns_functab_colon_tl { : }
\cs_generate_variant:Nn \seq_set_split:Nnn { NV }
\AtBeginDocument {
  \tl_gset_rescan:NnV \g_tns_functab_semicolon_tl
                      {}
                      \g_tns_functab_semicolon_tl
\tl_gset_rescan:NnV \g_tns_functab_colon_tl
                      {}
                      \g_tns_functab_colon_tl
}
% :: AGNOSTIC PARSERS :: %
\int_new:N   \g_tns_functab_id_int
\int_gset:Nn \g_tns_functab_id_int { 0 }
\int_new:N \l_tns_core_ctxt_nb_line_int
\seq_new:N \l_tns_core_ctxts_seq
\tl_new:N  \l_tns_core_current_ctxt_tl
\cs_new:Npn \tns_core_DSL_ctxt_parser:nn #1#2 {
% The ID nb. of the env.
  \int_gincr:N \g_tns_functab_id_int
% Line by line parsing.
%
% Lines are semi-colon separated.
  \seq_set_split:NVn \l_tns_core_ctxts_seq
                      \g_tns_functab_semicolon_tl
                      { #2 }
\int_zero:N \l_tns_core_ctxt_nb_line_int
\seq_map_inline:Nn \l_tns_core_ctxts_seq {
    \bigskip\par
\int_incr:N \l_tns_core_ctxt_nb_line_int

Line ~ \int_use:N \l_tns_core_ctxt_nb_line_int
\par


% Get the context and its content.
    \seq_set_split:Nnn \l_tmpa_seq { = } { ##1 }
\int_set:Nn \l_tmpa_int {\seq_count:N \l_tmpa_seq}

\quad
\int_case:nnF { \int_use:N \l_tmpa_int } {
  { 1 } {
    LAST - CTXT: ~
    (\tl_use:N \l_tns_core_current_ctxt_tl)
  }
  { 2 } {
    \seq_pop_left:NN \l_tmpa_seq \l_tns_core_current_ctxt_tl

    NEW - CTXT: ~
    (\tl_use:N \l_tns_core_current_ctxt_tl)
  }
}{
  ILLEGAL!
}


% Get the optional label and its content.
    \seq_pop_left:NN \l_tmpa_seq \l_tmpa_tl
\seq_set_split:NVV \l_tmpa_seq
                   \g_tns_functab_colon_tl
                   \l_tmpa_tl

\int_set:Nn \l_tmpa_int {\seq_count:N \l_tmpa_seq}

\par\quad
\int_case:nnF { \int_use:N \l_tmpa_int } {
  { 1 } {
    NO LABEL
  }
  { 2 } {
    \seq_pop_left:NN \l_tmpa_seq \l_tmpa_tl

    LABEL: ~
    $(\tl_use:N \l_tmpa_tl)$
  }
}{
  ILLEGAL!
}

\par\quad

\seq_pop_left:NN \l_tmpa_seq \l_tmpa_tl

VAL: ~
$(\tl_use:N \l_tmpa_tl)$

}
}
\ExplSyntaxOff
\begin{document}
\begin{functable}
    xvals =    t : 1 , 20 , 300 , 4000 ;
    imgs  = f(t) : a , bb , ccc , dddd ;
            g(t) : U , VV , WWW , XXXX
\end{functable}
\end{document}

Answer 1

Update

The code is split over an environment savefunctable and a command \usefunctable. Both take a name as the first argument. The contents of the environment savefunctable is stored internally and can be used later with the command \usefunctable by specifying the appropriate name.

\documentclass[border=6pt,varwidth]{standalone}
\usepackage{nicematrix}
\usepackage{pgfplots}
\pgfplotsset{compat=1.18}
\ExplSyntaxOn
\cs_generate_variant:Nn \seq_map_indexed_inline:Nn { cn }
\cs_generate_variant:Nn \seq_gset_from_clist:Nn { ce }
\seq_new:N \l__projetmbc_functable_seq
\seq_new:N \l__projetmbc_key_name_list_seq
\tl_new:N \l__projetmbc_coordinates_tl
\tl_new:N \l__projetmbc_key_tl
\tl_new:N \l__projetmbc_name_tl
\NewDocumentEnvironment { savefunctable } { m +b }
  {
    \seq_set_split:Nnn \l__projetmbc_functable_seq { ; } {#2}
    \seq_map_inline:Nn \l__projetmbc_functable_seq
      {
        \seq_set_split:Nnn \l__projetmbc_key_name_list_seq { = } {##1}
        \int_compare:nNnT { \seq_count:N \l__projetmbc_key_name_list_seq } = { 2 }
          {
            \seq_pop_left:NN \l__projetmbc_key_name_list_seq \l__projetmbc_key_tl
            \seq_gclear_new:c { g__projetmbc_#1_key_\l__projetmbc_key_tl _seq }
          }
        \seq_set_split:Nee \l__projetmbc_key_name_list_seq { \c_colon_str } { \seq_item:Nn \l__projetmbc_key_name_list_seq { 1 } }
        \seq_pop_left:NN \l__projetmbc_key_name_list_seq \l__projetmbc_name_tl
        \seq_gput_right:cV { g__projetmbc_#1_key_\l__projetmbc_key_tl _seq } \l__projetmbc_name_tl
        \seq_gclear_new:c { g__projetmbc_#1_key_\l__projetmbc_key_tl _name_\l__projetmbc_name_tl _seq }
        \seq_gset_from_clist:ce { g__projetmbc_#1_key_\l__projetmbc_key_tl _name_\l__projetmbc_name_tl _seq } { \seq_item:Nn \l__projetmbc_key_name_list_seq { 1 } }
      }
  }
  {}
\NewDocumentCommand \usefunctable { m m }
  {
    \str_case:nnF {#2}
      {
        { list~of~imgs }
          {
            \seq_use:cn { g__projetmbc_#1_key_imgs_seq } { , ~ }
          }
        { maximum~of~xvals }
          {
            \fp_eval:n { max ( \seq_use:cn { g__projetmbc_#1_key_xvals_name_\seq_item:cn { g__projetmbc_#1_key_xvals_seq } { 1 }_seq } { , } ) }
          }
        { NiceArray }
          {
            $
              \begin { NiceArray }
                [ cell-space-limits = 3pt ]
                { c * { \seq_count:c { g__projetmbc_#1_key_xvals_name_\seq_item:cn { g__projetmbc_#1_key_xvals_seq } { 1 }_seq } } { | c } }
                \seq_item:cn { g__projetmbc_#1_key_xvals_seq } { 1 } & \seq_use:cn { g__projetmbc_#1_key_xvals_name_\seq_item:cn { g__projetmbc_#1_key_xvals_seq } { 1 }_seq } { & } \\ \hline
                \seq_map_indexed_inline:cn { g__projetmbc_#1_key_imgs_seq }
                  {
                    ##2 & \seq_use:cn { g__projetmbc_#1_key_imgs_name_##2_seq } { & }
                    \int_compare:nNnF {##1} = { \seq_count:c { g__projetmbc_#1_key_imgs_seq } }
                      { \\ \hline }
                  }
              \end { NiceArray }
            $
          }
        { plot }
          {
            \tl_build_begin:N \l__projetmbc_coordinates_tl
            \seq_map_indexed_inline:cn { g__projetmbc_#1_key_xvals_name_\seq_item:cn { g__projetmbc_#1_key_xvals_seq } { 1 }_seq }
              {
                \tl_build_put_right:Ne \l__projetmbc_coordinates_tl
                  { ( ##2 , \seq_item:cn { g__projetmbc_#1_key_imgs_name_\seq_item:cn { g__projetmbc_#1_key_imgs_seq } { 1 }_seq } {##1} ) }
              }
            \tl_build_end:N \l__projetmbc_coordinates_tl
            \begin { tikzpicture }
              \begin { axis }
                [
                  ymin = 0
                ]
                \addplot coordinates
                  { \l__projetmbc_coordinates_tl }
                ;
              \end { axis }
            \end { tikzpicture }
          }
      }
      { \errmessage { wrong~option~for~functable~environment } }
  }
\ExplSyntaxOff
\begin{document}
\begin{savefunctable}{example 1}
    xvals =    t : 1 , 20 , 300 , 4000 ;
    imgs  = f(t) : a , bb , ccc , dddd ;
            g(t) : U , VV , WWW , XXXX
\end{savefunctable}
\begin{savefunctable}{example 2}
    xvals =    t : 1 , 2 , 3 , 4 ;
    imgs  = f(t) : 8 , 5 , 7 , 6 ;
\end{savefunctable}
Using \texttt{example 1} with \texttt{NiceArray}: \usefunctable{example 1}{NiceArray}
The maximum of the \texttt{xvals} of \texttt{example 2}: \usefunctable{example 2}{maximum of xvals}
The list of \texttt{imgs} of \texttt{example 1}: \usefunctable{example 1}{list of imgs}
A \texttt{plot} for \texttt{example 2}: \usefunctable{example 2}{plot}
\end{document}

Original answer

An environment functable is defined. It takes one mandatory argument and thereafter the body.

The body is first split over ; with \seq_set_split:Nnn. Then items are split over =. A key such as xvals or imgs is stored in \l__projetmbc_key_tl.

Similarly, a name such as t or f(t) is stored in \l__projetmbc_name_tl.

The environment functable depends on the first mandatory argument. Below are examples for NiceArray, maximum of xvals, list of imgs and plot.

\documentclass[border=6pt,varwidth]{standalone}
\usepackage{nicematrix}
\usepackage{pgfplots}
\pgfplotsset{compat=1.18}
\ExplSyntaxOn
\cs_generate_variant:Nn \seq_map_indexed_inline:Nn { cn }
\cs_generate_variant:Nn \seq_set_from_clist:Nn { ce }
\seq_new:N \l__projetmbc_functable_seq
\seq_new:N \l__projetmbc_key_name_list_seq
\tl_new:N \l__projetmbc_coordinates_tl
\tl_new:N \l__projetmbc_key_tl
\tl_new:N \l__projetmbc_name_tl
\NewDocumentEnvironment { functable } { m +b }
  {
    \seq_set_split:Nnn \l__projetmbc_functable_seq { ; } {#2}
    \seq_map_inline:Nn \l__projetmbc_functable_seq
      {
        \seq_set_split:Nnn \l__projetmbc_key_name_list_seq { = } {##1}
        \int_compare:nNnT { \seq_count:N \l__projetmbc_key_name_list_seq } = { 2 }
          {
            \seq_pop_left:NN \l__projetmbc_key_name_list_seq \l__projetmbc_key_tl
            \seq_clear_new:c { l__projetmbc_key_\l__projetmbc_key_tl _seq }
          }
        \seq_set_split:Nee \l__projetmbc_key_name_list_seq { \c_colon_str } { \seq_item:Nn \l__projetmbc_key_name_list_seq { 1 } }
        \seq_pop_left:NN \l__projetmbc_key_name_list_seq \l__projetmbc_name_tl
        \seq_put_right:cV { l__projetmbc_key_\l__projetmbc_key_tl _seq } \l__projetmbc_name_tl
        \seq_clear_new:c { l__projetmbc_key_\l__projetmbc_key_tl _name_\l__projetmbc_name_tl _seq }
        \seq_set_from_clist:ce { l__projetmbc_key_\l__projetmbc_key_tl _name_\l__projetmbc_name_tl _seq } { \seq_item:Nn \l__projetmbc_key_name_list_seq { 1 } }
      }
    \str_case:nnF {#1}
      {
        { list~of~imgs }
          {
            \seq_use:Nn \l__projetmbc_key_imgs_seq { , ~ }
          }
        { maximum~of~xvals }
          {
            \fp_eval:n { max ( \seq_use:cn { l__projetmbc_key_xvals_name_\seq_item:Nn \l__projetmbc_key_xvals_seq { 1 }_seq } { , } ) }
          }
        { NiceArray }
          {
            $
              \begin { NiceArray }
                [ cell-space-limits = 3pt ]
                { c * { \seq_count:c { l__projetmbc_key_xvals_name_\seq_item:Nn \l__projetmbc_key_xvals_seq { 1 }_seq } } { | c } }
                \seq_item:Nn \l__projetmbc_key_xvals_seq { 1 } & \seq_use:cn { l__projetmbc_key_xvals_name_\seq_item:Nn \l__projetmbc_key_xvals_seq { 1 }_seq } { & } \\ \hline
                \seq_map_indexed_inline:Nn \l__projetmbc_key_imgs_seq
                  {
                    ##2 & \seq_use:cn { l__projetmbc_key_imgs_name_##2_seq } { & }
                    \int_compare:nNnF {##1} = { \seq_count:N \l__projetmbc_key_imgs_seq }
                      { \\ \hline }
                  }
              \end { NiceArray }
            $
          }
        { plot }
          {
            \tl_build_begin:N \l__projetmbc_coordinates_tl
            \seq_map_indexed_inline:cn { l__projetmbc_key_xvals_name_\seq_item:Nn \l__projetmbc_key_xvals_seq { 1 }_seq }
              {
                \tl_build_put_right:Ne \l__projetmbc_coordinates_tl
                  { ( ##2 , \seq_item:cn { l__projetmbc_key_imgs_name_\seq_item:Nn \l__projetmbc_key_imgs_seq { 1 }_seq } {##1} ) }
              }
            \tl_build_end:N \l__projetmbc_coordinates_tl
            \begin { tikzpicture }
              \begin { axis }
                [
                  ymin = 0
                ]
                \addplot coordinates
                  { \l__projetmbc_coordinates_tl }
                ;
              \end { axis }
            \end { tikzpicture }
          }
      }
      { \errmessage { wrong~option~for~functable~environment } }
  }
  {}
\ExplSyntaxOff
\begin{document}
Using \texttt{NiceArray}:
\begin{functable}{NiceArray}
    xvals =    t : 1 , 20 , 300 , 4000 ;
    imgs  = f(t) : a , bb , ccc , dddd ;
            g(t) : U , VV , WWW , XXXX
\end{functable}
The maximum of the \texttt{xvals}:
\begin{functable}{maximum of xvals}
    xvals =    t : 1 , 20 , 300 , 4000 ;
    imgs  = f(t) : a , bb , ccc , dddd ;
            g(t) : U , VV , WWW , XXXX
\end{functable}
The list of \texttt{imgs}:
\begin{functable}{list of imgs}
    xvals =    t : 1 , 20 , 300 , 4000 ;
    imgs  = f(t) : a , bb , ccc , dddd ;
            g(t) : U , VV , WWW , XXXX
\end{functable}
A plot:
\begin{functable}{plot}
    xvals =    t : 1 , 2 , 3 , 4 ;
    imgs  = f(t) : 8 , 5 , 7 , 6 ;
\end{functable}
\end{document}