Some definitions of interest.
array_append	Def arr1 @ arr2 == <arr1.l,arr2.u,(i.if i<arr1.u arr1[i] ; arr2[i] fi)>
	Thm* T:Type, i:, j:{i...}, k:{j...}, a:[T]Array{i..j}, b:[T]Array{j..k}. Thm* a @ b  [T]Array{i..k}
p_array	Def [T]Array{i..j} == {a:[T]Array | a.l = i & a.u = j }
	Thm* T:Type{i}, i:, j:{i...}. [T]Array{i..j}  Type{[i']}
int_upper	Def {i...} == {j:| ij }
	Thm* n:. {n...}  Type

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