L:(Top List), n:. (||L||  n)  (firstn(n;L) ~ L) 

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Definitions	x:A. B(x), P  Q, ||as||, firstn(n;as), Y, t  T, if b then t else f fi , tt, P  Q, , P & Q, P  Q, ff, T, True, , Unit,
Lemmas	le wf, top wf, lt int wf, bool wf, iff transitivity, assert wf, eqtt to assert, assert of lt int, le int wf, bnot wf, eqff to assert, squash wf, true wf, bnot of lt int, assert of le int, non neg length