Who Cites append?
append	Def as @ bs == Case of as; nil  bs ; a.as'  [a / (as' @ bs)]  (recursive)
	Thm* T:Type, as,bs:T List. (as @ bs)  T List

Syntax:

as @ bs

has structure:

append(as; bs)

About: IF YOU CAN SEE THIS go to /sfa/Nuprl/Shared/Xindentation_hack_doc.html