Efficiently Passing Multiple Arguments into a \newcommand

Question

Suppose I define a \newcommand with multiple arguments, such as in this example:

\documentclass{article}
\newcommand{\testing}[9]{#1,\ #2,\ #3,\ #4,\ #5,\ #6,\ #7,\ #8,\ #9}

\begin{document}
\title{Test}
\maketitle
\begin{equation}
    \testing{S_1}{S_2}{S_3}{S_4}{S_5}{S_6}{S_7}{S_8}{S_9}
\end{equation}
\end{document}

If I call the command \testings, I have to put each separate argument inside its own curly braces (to the best of my knowledge). Is there a more efficient way to pass these arguments into the command \testings? For example, something more along the lines of \testings{S_1,S_2,S_3,S_4,S_5,S_6,S_7,S_8,S_9}?

Note: The example above is very simple. A more realistic example might be something like \newcommand{\limset}[3]{\lim_{#1 \rightarrow #2^{#3}}.

Answer 1

The more realistic example can be easily dealt with by using xparse facilities:

\NewDocumentCommand{\limset}{>{\SplitArgument{2}{,}}m}{%
  \finallimset#1%
}
\NewDocumentCommand{\finallimset}{mmm}{%
  \lim_{#1\rightarrow #2\IfValueT{#3}{^{#3}}}%
}

Complete example:

\documentclass{article}
\usepackage{xparse}

\NewDocumentCommand{\limset}{>{\SplitArgument{2}{,}}m}{%
  \finallimset#1%
}
\NewDocumentCommand{\finallimset}{mmm}{%
  \lim_{#1\rightarrow #2\IfValueT{#3}{^{#3}}}%
}

\begin{document}

\[
\limset{x,0}f(x)
\qquad
\limset{x,0,+}g(x)
\]

\end{document}

With the preprocessor \SplitArgument{2}{,} you tell LaTeX to split the argument at commas, which should be at most two. Then #1 will effectively become {A}{B}{C}, where A, B and C stand for the three pieces. If the last is missing, it will receive the special value -NoValue- that can be tested with \IfValueT: if there is not -NoValue-, perform the stated action, otherwise ignore it.

The split argument is then passed to the auxiliary macro \finallimset which must have three arguments as stated.

Answer 2

\usepackage{xparse}
\NewDocumentCommand \testings { m }
 {
  \clist_set:Nn \l_tmpa_clist { #1 }
  \clist_use:Nn \l_tmpa_clist { ,\ }
 }
\NewDocumentCommand \limset { m }
 {
  \clist_set:Nn \l_tmpa_clist { #1 }
  \lim
  \sb % note \sb rather than _
   {
    \clist_item:Nn \l_tmpa_clist { 1 }
    \to
    \clist_item:Nn \l_tmpa_clist { 2 }
    ^ { \clist_item:Nn \l_tmpa_clist { 3 } }
   }
 }

And then: $\testings{S_1,S_2,S_3,S_4,S_5,S_6,S_7,S_8,S_9,S_{10},S_{11},S_{12}}$ and $\limset{t,0,+}$ should work.