Some definitions of interest.
eq_int	Def  i=j == if i=j true ; false fi
	Thm*  i,j:. (i=j)
nat	Def   == {i:| 0i }
	Thm*    Type
nequal	Def  a  b  T == a = b  T
	Thm*  A:Type, x,y:A. (x  y)  Prop

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