Some definitions of interest.
absval	Def |i| == if 0i i else -i fi
	Thm* x:. |x|
le	Def AB == B<A
	Thm* i,j:. (ij)  Prop
nat_plus	Def  == {i:| 0<i }
	Thm*   Type
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