\begin{diagram}{Set constructors}{setconstuctors}
\begin{mysyntdiag}
\synt{set\ constructor} \lit* [ 
\[
 \<[b] \synt{set\ group} \\ \lit* , \>
\]
\lit* ]
\end{mysyntdiag}
\begin{mysyntdiag}
\synt{set\ group} \synt{expression} 
\[
\lit* {..} \synt{expression}
\]
\end{mysyntdiag}
\end{diagram}