\begin{circus}
\circchannel a
\end{circus}
\begin{circus}
\circprocess P \circdef \circbegin \circspot a \then \Skip \circend \\
\circprocess Q \circdef P \lpar \lchanset a \rchanset \rpar P \\
\circprocess R \circdef Q \lpar \lchanset a \rchanset \rpar P \\
\end{circus}