How to pass comma-separated list as value to l3keys in LaTeX3

Question

I would like to do the following:

\mycmd{foo={a,b,c},baz={1,2,3}}

where {a,b,c} and {1,2,3} are arrays/sequences of data.

The MWE is this:

\documentclass[a4paper]{article}

\usepackage[english]{babel}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{expl3}
\usepackage{xparse}

\ExplSyntaxOn

\begin{document}

\keys_define:nn { mycmd }
{
  \foo .tl_set:N = \l_mycmd_foo_tl,
  \baz .tl_set:N = \l_mycmd_baz_tl
}

\NewDocumentCommand\mycmd{m}{
  \keys_set:nn { mycmd } { #1 }

  % iterate through `\l_mycmd_foo_tl` comma-separated list
  % iterate through `\l_mycmd_bar_tl` comma-separated list
}

\mycmd{foo={a,b,c},baz={1,2,3}}

\end{document}

Answer 1

If comma separated lists are mandatory, use foo .clist_set:N etc. in order to set expl3 clists and than iterate over them, e.g. with \clist_map_inline:Nn, where ##1 is replaced with the relevant entry of the list (assuming that \clist_map_inline:Nn is used within another macro).

\documentclass[a4paper]{article}

\usepackage[english]{babel}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{expl3}
\usepackage{xparse}

\ExplSyntaxOn



\begin{document}

\keys_define:nn { mycmd }
{
%  \foo .tl_set:N = \l_mycmd_foo_tl,
%  \baz .tl_set:N = \l_mycmd_baz_tl

  foo .clist_set:N = \l_mycmd_foo_clist,
  baz .clist_set:N = \l_mycmd_baz_clist
}

\NewDocumentCommand\mycmd{m}{
  \keys_set:nn { mycmd } { #1 }

  \clist_map_inline:Nn \l_mycmd_foo_clist {
    value\space##1\par
  }

  \clist_map_inline:Nn \l_mycmd_baz_clist {
    value\space##1\par
  }

  % iterate through `\l_mycmd_foo_tl` comma-separated list
  % iterate through `\l_mycmd_bar_tl` comma-separated list
}

\mycmd{foo={a,b,c},baz={1,2,3}}

\end{document}