T:Type, as, bs:(T List). nth_tl(||as||;as @ bs) ~ bs 

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Definitions	i <z j, i z j, t  T, type List, s = t, Type, x:AB(x), s ~ t, x:A. B(x), as @ bs, ||as||, nth_tl(n;as), [car / cdr], #$n, n+m, , a < b, n - m, i  j , {T}, P  Q, SQType(T), ff, , b, b, True, A  B, tt, tl(l), x:A  B(x), P & Q, P  Q, T, P  Q, A, (i = j), x =a y, null(as), a < b, f(a), x f y, a < b, [d], p  q, p  q, p q, , Unit, left + right
Lemmas	eqtt to assert, assert of le int, iff transitivity, eqff to assert, iff wf, rev implies wf, squash wf, true wf, bnot of le int, assert of lt int, le int wf, length wf1, le wf, non neg length, bool wf, lt int wf, assert wf, bnot wf, append wf, nth tl wf, guard wf