Some definitions of interest.
decidable	Def Dec(P) == P  P
	Thm* A:Prop. Dec(A)  Prop
int_lower	Def {...i} == {j:| ji }
	Thm* i:. {...i}  Type
int_seg	Def {i..j} == {k:| i  k < j }
	Thm* m,n:. {m..n}  Type
le	Def AB == B<A
	Thm* i,j:. (ij)  Prop

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