Def before(e) == if first(e) nil else before(pred(e)) @ [pred(e)] fi
Def (recursive)

is mentioned by

Thm* the_es:ES, e',e:E. (e  before(e'))  (e <loc e')	[member-es-before]
Def [e, e'] == filter(ev.es-ble{i:l}(es;e;ev);before(e') @ [e'])	[es-interval]

Try larger context: EventSystems IF YOU CAN SEE THIS go to /sfa/Nuprl/Shared/Xindentation_hack_doc.html