Some definitions of interest.
fact	Def fact(n) == if n=0 then 1 else nfact(n-1) fi   (recursive)
	Thm* n:. fact(n)
nat	Def  == {i:| 0i }
	Thm*   Type
	Thm*   S
not	Def A == A  False
	Thm* A:Prop. (A)  Prop

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