General ⇒ \ref with macro as parameter

[stridder]

Hello,
I would like to write a macro (using Latex3/expl3) that can automatically refer to say plot using several key-value parameters. Here is what I currently have:

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\keys_define:nn{label}{
	Re .tl_set:N = \l_label_Re_tl, 
	DOF .tl_set:N = \l_label_DOF_tl,
	statsName .tl_set:N = \l_label_statsName_tl,
}


\NewDocumentCommand{\getProjOneLabel}{m}{
	\keys_set:nn{label}{#1}
	\newcommand{\Stat}{\StrLeft{\l_label_statsName_tl}{3}} %1st 3 letters of
	fig:{\Stat}Re\l_label_Re_tl DOF\l_label_DOF_tl
}

when I test it with:

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label=\getProjOneLabel{statsName=Strouhal,DOF=4M, Re=50}

It shows:
label=fig:StrRe50DOF4M
which is correct. But when I use it for real referencing like this:

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\ref{\getProjOneLabel{statsName=Strouhal,DOF=4M, Re=50}}

instead of reference in the output this shown:
??fig:StrRe50DOF4M

I think this has smth to do with order of expansion, but I don't understand expansion process fully yet. Tried putting \expandafter many times, still fails. Could smbd please explain step by step what goes wrong here?
When I hardcode label as

Code: Select all

\ref{fig:StrRe50DOF4M}

it does work.

The goal is to write a macro say '\plotref' that will execute

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\ref{\getProjOneLabel{statsName=Strouhal,DOF=4M, Re=50}}

where all RHS values will be passed as key-valued parameters.
I am new to Latex3 and even to regular Latex/Tex, the more details the better.
Thank you very much.

[cgnieder]

Your macro is not expandable. Any time you make assignments like setting options or defining macros you have unexpandable operations. In \label and \ref I'd make sure only to use expandable tokens.

Unfortunately you're example was far from complete, so…

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\documentclass{article}
\usepackage{expl3,xparse}

\ExplSyntaxOn
\tl_new:N \l_my_label_Re_tl
\tl_new:N \l_my_label_DOF_tl
\tl_new:N \l_my_label_statsName_tl
\tl_new:N \l_my_label_stat_tl

\keys_define:nn {label}
  {
    Re        .tl_set:N = \l_my_label_Re_tl ,
    DOF       .tl_set:N = \l_my_label_DOF_tl ,
    statsName .tl_set:N = \l_my_label_statsName_tl
  }

\cs_new_protected:Npn \my_set_project_one_label:n #1
  {
    \group_begin:
      \keys_set:nn {label} {#1}
      \tl_set:Nx \l_my_label_stat_tl % this is *not* expandable!
        {
          \tl_item:Nn \l_my_label_statsName_tl {1}
          \tl_item:Nn \l_my_label_statsName_tl {2}
          \tl_item:Nn \l_my_label_statsName_tl {3}
        }
       \label {
         fig : \tl_use:N \l_my_label_stat_tl
         Re \tl_use:N \l_my_label_Re_tl
         DOF \tl_use:N \l_my_label_DOF_tl
       }
    \group_end:
  }

\cs_new_protected:Npn \my_ref_project_one_label:n #1
  {
    \group_begin:
      \keys_set:nn {label} {#1} % this is *not* expandable!
      \tl_set:Nx \l_my_label_stat_tl % this is *not* expandable!
        {
          \tl_item:Nn \l_my_label_statsName_tl {1}
          \tl_item:Nn \l_my_label_statsName_tl {2}
          \tl_item:Nn \l_my_label_statsName_tl {3}
        }
       \ref {
         fig : \tl_use:N \l_my_label_stat_tl
         Re \tl_use:N \l_my_label_Re_tl
         DOF \tl_use:N \l_my_label_DOF_tl
       }
    \group_end:
  }

\NewDocumentCommand {\setProjOneLabel} {m}
  { \my_set_project_one_label:n {#1} }

\NewDocumentCommand {\refProjOneLabel} {m}
  { \my_ref_project_one_label:n {#1} }

\begin{document}

\setProjOneLabel{statsName=Strouhal,DOF=4M, Re=50}

\refProjOneLabel{statsName=Strouhal,DOF=4M, Re=50}

\end{document}

Regards