proposition: Lemma shlB_dropmsb n (p: BITS n.+1) : shlB (dropmsb p) = dropmsb (shlB p).
proof: Proof. apply toNat_inj. rewrite toNat_shlB 2!toNat_dropmsb toNat_shlB. rewrite -(mul2n (toNat p)). rewrite (expnS 2 n). rewrite -muln_modr //. by rewrite mul2n. Qed.
imports: HB(structures) mathcomp.ssreflect.ssreflect mathcomp(ssrfun ssrbool eqtype ssrnat seq fintype tuple zmodp div) ssrextra.tuple ssrextra.nat spec spec.properties operations mathcomp(ssralg)