Some definitions of interest.
assert	Def b == if b True else False fi
	Thm* b:. b  Prop
kleene_minimize	Def mu(f) == if f(0) 0 else 1+mu(x.f(1+x)) fi  (recursive)
	Thm* mu  {f:()| x:. f(x) }
nat	Def  == {i:| 0i }
	Thm*   Type

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