mb event system 2 Sections EventSystems Search Doc
IF YOU CAN SEE THIS go to http://www.cs.cornell.edu/Info/People/sfa/Nuprl/Shared/Xindentation_hack_doc.html
Def rcvtype(e) == 1of(2of(2of(2of(2of(es)))))(lnk(e),tag(e))

is mentioned by

Def valtype(e) == if isrcv(e) rcvtype(e) else acttype(e) fi[es-valtype]

Try larger context: EventSystems IF YOU CAN SEE THIS go to http://www.cs.cornell.edu/Info/People/sfa/Nuprl/Shared/Xindentation_hack_doc.html

mb event system 2 Sections EventSystems Search Doc