&(\texttt{fold } (\rightarrow) \texttt{ } \alpha \texttt{ } \tau^*)
\unif \tau^e = \star_2
&\star = \star_2 \cdot \star_1
- &\texttt{fold apfs } \tau^e \textit{ fs}^* = \tau^r
+ &\texttt{fold apfs } \tau^{e \star} \textit{ fs}^* = \tau^r
}
}
\end{equation}