\begin{tabbing}
eventlist(${\it pred?}$; $e$)
\\[0ex]$\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$if first($e$) then cons($e$; []) else append(eventlist(${\it pred?}$; pred($e$)); cons($e$; [])) fi 
\\[0ex]
\\[0ex]{\em clarification:}
\\[0ex]
\\[0ex]eventlist(${\it pred?}$; $e$)
\\[0ex]$\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$\=if first(${\it pred?}$;$e$)\+
\\[0ex]then cons($e$; [])
\\[0ex]else append(eventlist(${\it pred?}$; pred(${\it pred?}$;$e$)); cons($e$; []))
\\[0ex]fi 
\-\\[0ex]\emph{(recursive)}
\end{tabbing}