taple.tex

\documentclass{jarticle}

\makeatletter

\def\tuple#1{%
	\begingroup
		\newcount\@fuck@i
		\newcount\@fuck@ii
		\@fuck@i = -1
		\@fuck@ii = 0
		\@for\mem:=#1\do{ \advance\@fuck@i by 1\relax }
		\left(
		\@for\mem:=#1\do{%
			\@tempcnta = \@fuck@i
			\@tempcntb = \@fuck@ii
			\ifnum \@fuck@ii<\@fuck@i\relax%
				%|\mem - \the\@fuck@ii|,%
				\mem,
				\advance\@tempcntb by 1%
			\else%
				%|\mem - \the\@fuck@ii|%
				\mem
			\fi%
			\@fuck@i = \@tempcnta
			\@fuck@ii = \@tempcntb
		}
		\right)
	\endgroup
}
\makeatother

\begin{document}
$ \tuple{ \tuple{a, b, 1, 2}, \tuple{d, i, a}, a, 1, 2, \tuple{1, 2}} $

\end{document}