Some definitions of interest.
assert	Def b == if b True else False fi
	Thm* b:. b  Prop
isl	Def isl(x) == InjCase(x; y. true; z. false)
	Thm* A,B:Type, x:A+B. isl(x)
outl	Def outl(x) == InjCase(x; y. y; z. "???")
	Thm* A,B:Type, x:A+B. isl(x)  outl(x)  A

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