new command for nested enumerate with variable arguments

Question

I have some text that I want to turn into a template which looks like this:

Extensions: 
\begin{enumerate}
    \item[2.a] xyz
        \begin{enumerate}[i.]
            \item a
            \item b
            \item c
        \end{enumerate}
    \item[5.b] abc
        \begin{enumerate}[i.]
            \item x
            \item y
        \end{enumerate}
\end{enumerate}\\

I want to make a new command that mimics the text above but that takes as arguments something like:

\ucextensions{[2.a] xyz, [5.b] abc}{{a, b, c}, {x, y}}

Please note that I will have variable numbers of arguments. I already have:

\newcommand{\ucextensions}[2]{
Extensions: 
\begin{enumerate}
    \forcsvlist{\item}{#1 \extensionsteps{#2}}
\end{enumerate}\\
}

\newcommand{\extensionsteps}[1]{
\begin{enumerate}[i.]
    \forcsvlist{\item}{#1}
\end{enumerate}
}

which gives output like:

1. [2.a] xyz
2. [5.b] abc
   • a, b, c
   • x, y

(except with i. and ii. instead of bullets). I would like instead to have output like:

1. [2.a] xyz
   • a
   • b
   • c
2. [5.b] abc
   • x
   • y

(again with i's instead of bullets). I am using the etoolbox package to do this. Is there a way to do something similar that would take either a nested csv, or a series of csv's to create the desired output?

Answer 1

I'd re-order the input a bit:

\documentclass{article}

\usepackage{enumerate}

\makeatletter
\def\ucextensions#1{%
\begin{enumerate}%
\@for\tmp:=#1\do{\expandafter\ucext\tmp}%
\end{enumerate}}

\newcommand\ucext[2]{%
\item\relax#1\begin{enumerate}[i]%
\@for\tmpb:=#2\do{\item\tmpb}%
\end{enumerate}}

\makeatletter

\begin{document}

\ucextensions{{[2.a] xyz}{a, b, c},
              {[5.b] abc}{x, y}
             }

\end{document}

Answer 2

I find this kind of input error prone, because the inner list related to an item is placed far from it.

It's possible to get what you want, but perhaps a different syntax can be better.

\documentclass{article}

\usepackage{xparse}

\ExplSyntaxOn
\NewDocumentCommand\ucextensions{mm}
 {
  \jani_ucextensions:nn { #1 } { #2 }
 }

\seq_new:N \l__jani_ucext_outer_seq
\seq_new:N \l__jani_ucext_inner_seq
\seq_new:N \l__jani_ucext_temp_seq
\int_new:N \l__jani_ucext_step_int

\cs_new_protected:Npn \jani_ucextensions:nn #1 #2
 {
  \seq_set_split:Nnn \l__jani_ucext_outer_seq { , } { #1 }
  \seq_set_split:Nnn \l__jani_ucext_inner_seq { , } { #2 }
  \int_zero:N \l__jani_ucext_step_int
  \par Extensions:
  \begin{enumerate}
  \seq_map_inline:Nn \l__jani_ucext_outer_seq
   {
    \item {##1}
    \int_incr:N \l__jani_ucext_step_int
    \seq_set_split:Nnx \l__jani_ucext_temp_seq { , }
     { \seq_item:Nn \l__jani_ucext_inner_seq { \l__jani_ucext_step_int } }
    \begin{itemize}
    \item \seq_use:Nn \l__jani_ucext_temp_seq { \item }
    \end{itemize}
   }
  \end{enumerate}
 }
\cs_generate_variant:Nn \seq_set_split:Nnn { Nnx }
\ExplSyntaxOff

\begin{document}

\ucextensions{[2.a] xyz, [5.b] abc}{{a, b, c}, {x, y}}

\end{document}

I define two sequences, storing the items in the first and second argument, split at commas.

An enumerate environment is opened, then I do a mapping on the first sequence, using the corresponding element in the second sequence, that I again split at commas for building the inner itemize.

A different syntax can be accommodated with a very similar macro for doing the job.

\documentclass{article}

\usepackage{xparse}

\ExplSyntaxOn

\NewDocumentCommand{\ucextensions}{m}
 {
  \group_begin:
  \jani_ucextensions:n { #1 }
  \group_end:
 }

\seq_new:N \l__jani_ucext_outer_seq
\seq_new:N \l__jani_ucext_inner_seq
\seq_new:N \l__jani_ucext_temp_seq
\int_new:N \l__jani_ucext_step_int

\keys_define:nn { jani/ucext }
 {
  ext  .code:n = \seq_put_right:Nn \l__jani_ucext_outer_seq { #1 },
  spec .code:n = \seq_put_right:Nn \l__jani_ucext_inner_seq { #1 },
 }

\cs_new_protected:Npn \jani_ucextensions:n #1
 {
  \keys_set:nn { jani/ucext } { #1 }
  \int_zero:N \l__jani_ucext_step_int
  \par Extensions:
  \begin{enumerate}
  \seq_map_inline:Nn \l__jani_ucext_outer_seq
   {
    \item {##1}
    \int_incr:N \l__jani_ucext_step_int
    \seq_set_split:Nnx \l__jani_ucext_temp_seq { \\ }
     { \seq_item:Nn \l__jani_ucext_inner_seq { \l__jani_ucext_step_int } }
    \begin{itemize}
    \item \seq_use:Nn \l__jani_ucext_temp_seq { \item }
    \end{itemize}
   }
  \end{enumerate}
 }
\cs_generate_variant:Nn \seq_set_split:Nnn { Nnx }
\ExplSyntaxOff

\begin{document}

\ucextensions{
  ext  = [2.a] xyz,
  spec =  a \\ b \\ c,
  ext  = [5.b] abc,
  spec = x \\ y
}

\end{document}

Each extension should be followed by its specifications, so it's impossible to forget something.

The output is exactly the same.