Local Open Scope logic.
(*Require Import tweetnacl20140427.split_array_lemmas.*)
unfold Byte.max_unsigned, Int.max_unsigned. simpl. omega. Qed.

Lemma force_lengthn_mapN {A B} (f:A->B) n: forall l d fd,
(n < length l)%nat ->
force_lengthn n (map f l) fd =
map f (force_lengthn n l d).