\begin{tabbing}
w{-}pred($w$;$e$)
\\[0ex]$\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$\=i\=f time($e$)=$_{2}$0$\rightarrow$ inr($\cdot$)\+\+
\\[0ex]; isnull(a(loc($e$);time($e$)$-$1))$\rightarrow$ w{-}pred($w$;$\langle$loc($e$)$,\,$time($e$)$-$1$\rangle$)
\-\\[0ex]else inl($\langle$loc($e$)$,\,$time($e$)$-$1$\rangle$) fi
\-\\[0ex]\emph{(recursive)}
\end{tabbing}