proposition: Lemma size_bitseq_of_nat i n : size (bitseq_of_nat i n) == n.
proof: Proof. by rewrite /bitseq_of_nat size_pad_seqL. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype tuple) BinPos BinNat PArith ssr_ext