Some definitions of interest.
firstn	Def firstn(n;as) Def == Case of as Def == Canil  nil Def == Caa.as'  if 0<n [a / firstn(n-1;as')] else nil fi Def (recursive)
	Thm* A:Type, as:A List, n:. firstn(n;as)  A List
int_seg	Def {i..j} == {k:| i  k < j }
	Thm* m,n:. {m..n}  Type
lt_int	Def i<j == if i<j true ; false fi
	Thm* i,j:. (i<j)
top	Def Top == Void given Void
	Thm* Top  Type

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