Some definitions of interest.
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
nat	Def  == {i:| 0i }
	Thm*   Type
le	Def AB == B<A
	Thm* i,j:. (ij)  Prop
listify	Def f{m..n} == if nm nil else f(m).f{(m+1)..n} fi  (recursive)
	Thm* T:Type, m,n:, f:({m..n}T). f{m..n}  T List
select	Def l[i] == hd(nth_tl(i;l))
	Thm* A:Type, l:A List, n:. 0n  n<||l||  l[n]  A

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