proposition: Lemma Npow2_gt_zero: forall sz : nat, 0 < Npow2 sz.
proof: Proof. induction sz; try reflexivity. apply N.mul_pos_pos; auto || reflexivity. Qed.
imports: Fiat.Common.Coq__8_4__8_5__Compat List Bedrock.Word Coq.ZArith.ZArith Coq.micromega.Psatz NArith NArithRing